TURNING

AND

MECHANICAL MANIPULATION.

BY THE LATE

CHARLES HOLTZAPFFEL,

ASSOCIATE OF THE INSTITUTION OP CIVIL ENGINEERS, LONDON J

HONORARY MEMBER OF THE ROYAL SCOTTISH SOCIETY OF ARTS, EDINBURGH J

CORRESPONDING MEMBER OF THE AMERICAN INSTITUTE OF NEW YORK J

ALSO OF THE AMERICAN INSTITUTE, PHILADELPHIA,

ETC., ETC.

a 2

VOL. 1.

MATERIALS ; THEIR DIFFERENCES, CHOICE, AND PREPARATION ; VARIOUS MODES OF WORKING THEM, GENERALLY WITHOUT CUTTING TOOLS.

VOL. II.

THE PRINCIPLES OF CONSTRUCTION, ACTION, AND APPLICATION, OF CUTTING

TOOLS USED BY HAND ; AND ALSO OF MACHINES DERIVED

FROM THE HAND TOOLS.

VOL. III.

ABRASIVE AND MISCELLANEOUS PROCESSES, WHICH CANNOT BE ACCOMPLISHED WITH CUTTING TOOLS.

VOL. IV. THE PRINCIPLES AND PRACTICE OF HAND OR SIMPLE TURNING.

VOL. V. THE PRINCIPLES AND PRACTICE OF ORNAMENTAL OR COMPLEX TURNING.

VOL. VI. THE PRINCIPLES AND PRACTICE OF AMATEUR MECHANICAL ENGINEERING.

TURNING

AND

MECHANICAL MANIPULATION.

INTENDED AS

WORK OF GENERAL REFERENCE AND PRACTICAL INSTRUCTION,

ON THE LATHE,

AND THE -VARIOUS MECHANICAL PURSUITS FOLLOWED BY AMATEURS-

BY THE LATE

CHARLES HOLTZAPFFEL,

ASSOCIATE OF THE INSTITUTION OF CIVIL ENGINEERS, LONDON ;

HONORARY MEMBER OF THE ROYAL SCOTTISH SOCIETY OF ARTS, EDINBURGH

CORRESPONDING MEMBER OF THE AMERICAN INSTITUTE OF NEW YORK ;

ALSO OF THE FRANKLIN INSTITUTE, PHILADELPHIA,

ETC., ETC.

TO BE COMPRISED IN SIX VOLUMES.

VOL. III.

ABRASIVE AND MISCELLANEOUS PROCESSES, WHICH CANNOT BE ACCOMPLISHED WITH CUTTING TOOLS.

Illustrated by upwards of One Hundred and Eighty Wood Cuts. .

i it \

LONDON:

RELISHED EY HOLTZAPFFEL & Co., 64, CHARING CROSS, AND 127 LONG ACRE.

And to be had of all Booksellers. 1850.

LONDON : BRADBURY AND EVANS, PRINTERS, WHITEPUIARS.

PREFACE TO THE THIRD VOLUME.

LN offering to the public the third volume of the late Mr. Charles HoltzapffeFs work on Turning and Mechanical Manipulation, some explanation is required of the circumstances under which the work has been continued. On the premature and lamented death of the highly talented author, it became necessary either to abandon the work, or to endeavour to realize the views with which it had been undertaken. In deciding on the latter course, Holtzapffel & Co. were influenced partly by the circum- stance, mentioned in the preface to the first volume, of the absence of any general treatise in the English language for the guidance of amateurs of mechanical pursuits, but principally by desire of fulfilling the intentions of the author, and of pre- iting disappointment to his kind and numerous patrons, who lave most strenuously urged the importance of completing the /ork, more especially as the first two volumes had been so ivourably received by the public.

The arrangement of the subjects to be treated on in the >resent and succeeding volumes had been determined on by the ite author, many notes had been written, and considerable jress made in the advancement of the work. The third )lume being now completed, it is respectfully submitted to ie public, with humble confidence that it will be received with leniency.

Vlll

In compiling the present volume every endeavour has been made to follow, as closely as possible, the course indicated by the late Mr. C. Holtzapffel, and it is trusted that these efforts have been in great measure successful; but notwithstanding that every care has been taken to render this part of the work as complete and correct as possible, imperfections, omissions, and errors, have doubtless arisen ; it is hoped that these defects will be viewed with liberal kindness, and pointed out for future correction.

In conclusion, it may be permitted to mention that the delay in the completion of the present volume has been considerably increased by the interruptions of ordinary business, and other circumstances wholly unavoidable. It is, however, fully expected that the fourth volume will be published within a much more limited period, as the late author's notes on its subjects are more complete, and upwards of one hundred and fifty pages had been printed under his personal superintendence.

CHARING CROSS, LONDON, December 5, 1850.

GENERAL SKETCH

OF THE

CONTENTS OF THE .WORK.

VOL. I. [ATERIALS, THEIR DIFFERENCES, CHOICE, AND PREPARATION; VARIOUS

MODES OF WORKING THEM, GENERALLY WITHOUT CUTTING TOOLS, itroduction— Materials from the Vegetable, the Animal, and the Mineral Kingdoms.— Their uses in the Mechanical Arts depend on their structural differences, and physical characters. The modes of severally preparing, working, and joining the materials, with the practical descrip- tion of a variety of Processes, which do not, generally, require the use of Tools with cutting edges.

VOL. II.

IE PRINCIPLES OF CONSTRUCTION, ACTION, AND APPLICATION, OF CUTTING TOOLS USED BY HAND ; AND ALSO OF MACHINES DERIVED

FROM THE HAND TOOLS, le principles and descriptions of Cutting Tools generally — namely, Chisels and Planes, Turning Tools, Boring Tools, Screw-cutting Tools, Saws, Files, Shears, and Punches. The hand tools and their modes of use are first described ; and subsequently various machines in which the hand processes are more or less closely followed.

VOL. III.

ABRASIVE AND MISCELLANEOUS PROCESSES, WHICH CANNOT BE ACCOM- PLISHED WITH CUTTING TOOLS.

Grinding and Polishing, viewed as extremes of the same process, and as applied both to the pro- duction of form, and the embellishment of surface, in numerous cases to which, from the nature of the materials operated upon, and other causes, Cutting Tools are altogether inappli- cable. Preparation and Application of Varnishes, Lackers, &c. .

VOL. IV.

THE PRINCIPLES AND PRACTICE OF HAND OR SIMPLE TURNING. Descriptions of various Lathes ; — applications of numerous Chucks, or apparatus for fixing works in the Lathe. Elementary instructions in turning the soft and hard woods, ivory and metals , and also in Screw-cutting. With numerous Practical Examples, some plain and simple, others difficult and complex, to show how much may be done with hand tools alone.

VOL. V.

PRINCIPLES AND PRACTICE OF ORNAMENTAL OR COMPLEX TURNING. Sliding Rest with Fixed Tools— Revolving Cutters, used in the Sliding Rest with the Division Plate and Overhead Motion. Various kinds of Eccentric, Oval, Spherical, Right-line and other Chucks. Ibbetson's Geometric Chuck. The Rose Engine, and analogous contrivances, &c. With numerous Practical Examples.

VOL. VI.

THE PRINCIPLES AND PRACTICE OF AMATEUR MECHANICAL ENGINEERING. Lathes with Sliding Rests for metal turning, Self-acting and Screw- cutting Lathes— Drilling Machines — Planing Engines — Key-groove, Slotting and Paring Machines — Wheel-cutting and Shaping Engines, &c.

With numerous Practical Examples.

%* The First, Second, and Third Volumes of this worli, are written as accompanying books, and have one Index in common, so as to constitute a general and preliminary work, the addition to which of any of the other volumes, will render the subject complete for the three classes of Amateurs referred to in the Introductory Chapter.

A few additional copies of the Index have been printed for the convenience of those who may desire to bind the Index with Vols. I. and II.

TABLE OF CONTENTS OF THE TRIED VOLUME.

CHAP. XXXI.— GENERAL REMARKS UPON ABRASIVE PROCESSES.

PAGE

INTRODUCTION — Comparison of abrasive and cutting processes . 1026

1. Preliminary observations on grinding and polishing — First, on the substances that are to be ground and polished — Secondly, on the materials, or abrasive powders, by the successive employment of which different substances are polished — Thirdly, on the tools or apparatus by the agency of which abrasive substances are applied to the objects to be ground and polished . . . 1028

SECT. 2. Descriptive Catalogue of the apparatus, materials, and processes, for grinding and polishing, commonly employed in the mechanical and useful arts — Including bobs, bouldering stones, brushes — buff leather ; polishers, sticks, and wheels — burnishers of various kinds — caps — cloth ; polishers, rubbers, and wheels — emery ; cake, cloth, paper, powders, sticks, and wheels — Fayrer's swing hone — glass paper, glazers — leather; polishers, rubbers, and wheels — mills — moslings; oil- stones— polishers and rubbers of various forms and materials— rumble or shaking machine— skive — slicer — Wheels of natural stone, as grind- stones ; different methods of mounting these ; driven by manual and steam power; hacking, jarring, roving, straggling, and turning grind- stones, to keep them in order. General methods of application to works of large and small size, dry and wet stones— Wheels, of factitious stone or composition wheelsj of crocus, corundum, and emery — Wheels of metal, or metallic laps, constructions and applications of those used by cutlers, diamond polishers, engineers, glass-grinders, lapidaries, and mechanists generally — Wheels of wood or glaze wheels, used by cutlers, glass-cutters, and lapidaries — Wheels of leather or buff wheels, glazers and polishers; general construction, action, and appli- cation, for polishing cutlery, lapidary, and metal works — Wheels of cloth, for ivory-workers, lapidaries, &c. — Wheels of bristles or wire, for curved, chased, and pierced works.

Preparation and application of grinding and polishing materials — chalk, charcoal, corundum, diamond, Dutch rush, emery, fish-skin— Flanders brick, flint, gannister stone, glass, gritstones, and hone slates of various kinds — lime, loam, oilstone, oxides of iron, lead, and tin — pumice-stone, putty-powder, rottenstone, sand, sawdust, Tripoli, and whiting.

General methods of grinding and polishing — albata — brass; cast, filed, stamped, and turned works — Britannia and bronze metals- braziers' and coppersmiths' works— cutlery and edge tools; best and

TABLE OF CONTENTS OF VOL. III.

ordinary — electrum, enamels, fluor-spar, glass, gold, and granite — horn, ivory and bone ; carved, flat and turned works— Lapidary works, general routine illustrated by the three different modes of cutting, grinding, and polishing, alabaster, carnelian, and sapphire — lists of materials treated in a similar manner, with remarks upon the pecu- liarities of working all the principal substances employed by the , lapidary — Polishing lithographic stones— machinery, large and small ; flat and turned works, in iron and steel — marble ; flat, ornamented, sculptured, and turned works — marquetry works in wood and metal —mineral substances, painted works, porphyry, platinum, and scag- liola— shells, nacreous and porcellaneous— carving shell cameos — Polishing silversmiths' works — slate, tortoiseshell, and varnished works — whalebone — woods ; hard and soft, flat and turned — wrought- iron and zinc .... ... 1033

CHAP. XXXII.— GRINDING AND SHARPENING CUTTING TOOLS.

SECT. 1 . Grinding cutting tools on the ordinary grindstone — Importance of the grindstone — various arrangements of frames for grindstones driven by handles and treadles — Grinding and polishing lathe for amateurs — General remarks on grinding tools — Examples : grinding carpen- ters' bench plane-irons, chisels, gouges, and moulding plane-irons ; turners' chisels and gouges — flat, side, triangular, and square tools — Gravers, drills, and point tools — Round and heel tools — Slide rest- tools and cutters . . . . .1127

SECT. 2. Sharpening cutting tools on the oilstone — General remarks on oil- stones, and angles at which the tools are held — Examples : carpen- ters' tools, bench plane-irons, chisels, gouges, and moulding plane-irons —Turners' chisels, gouges, flat, moulding, and other tools for wood, ivory, and brass . . . .1141

SECT. 3. Setting razors — Proportions and sections of razors, various modes in which they are ground — Tests for keenness of edge — Faulty con- ditions of razors — Whetstones usually employed — Setting edge of razors — Razor strops . . . . . . .1146

SECT. 4. Sfiarpening cutting tools with artificial grinders — Horizontal grinding machine — Guides for grinding tools to definite angles — Instrument for grinding and setting ordinary turning tools — Instrument for setting rose-engine tools — Instrument for sharpening straight and angular tools for ornamental turning — Vertical lap, mounted on lathe, for setting tools — Sharpening tools with concave edges — Conical grinders for bead tools and drills — Sharpening ornamental drills and cutters — Sharpening moulding tools, figured punches, &c. — Sir J. Robison's instrument for setting the edges of pen-knives, razors, and surgical instruments . 1156

CHAP. XXXIII.— THE FIGURATION OF MATERIALS BY ABRASION.

SECT. 1 . The production of plane surfaces by abrasion — General remarks, principal dependence for accuracy of form placed upon that of the abrasive tool, or on the relative motions of the grinder and work —

TABLE OF CONTENTS OF VOL. in.

PAGE

Revolving laps for flat works in metal — Lapping flat surfaces — Cut- ting facets on steel jewellery, facetting gold and silver works — Watch- makers' Geneva tool for polishing flat heads of small screws — Grinding large flat works in metal— Nasmyth's machine for flat sur- faces— General methods pursued in the figuration of materials by abrasion illustrated by the modes of working stone and marble — saws for soft stone — saws for hard stone and marble — setting out and sawing blocks of marble and slabs — grub-saws for narrow slips and small works— grinding and polishing plane and figured surfaces by hand, inlaid works — Application of machinery to working marble — machine for large blocks — Tulloch's sawing machine for slabs — cir- cular sawing machine for narrow slips — sawing circular works — revolving laps for grinding plane surfaces — grinding machine for large slabs — machine for working mouldings — polishing machine — Manufacture of plate-glass — grinding machines — smoothing by hand — polishing machines — Manufacture of sheet-glass — grinding and polishing machines— Grinding accurate plane surfaces, illustrated by methods pursued for optical purposes — grinding parallel disks of glass for sextants — plane specula . . . . . .1179

SECT. 2. The production of cylindrical surfaces ly abrasion — Grinding external cylindrical surfaces in metal — Clamps used by hand, or in the lathe, for rods, lathe mandrels, gages, rollers, &c. — Fixed and revolving grinders, mounted in the lathe for accurate works — Grinding accurate cylindrical rollers for paper-making with water only — Grinding cylin- drical rims of pulleys — Mr. J. Whitelaw's and Messrs. Randolph & Elliott's machines — Grinding internal cylindrical surfaces — Solid and expanding grinders for cylindrical holes — Fitting together external and internal cylinders ....... 1232

SECT. 3. The production of conical surfaces by abrasion — Grinding external conical surfaces in metal ; grinders similar to these employed for cylinders — Clamps for short cones, lathe mandrels, &c. — Fixed and revolving grinders — Grinding conical holes — Solid and spring grinders for axletree-boxes, collars for lathe mandrels, &c. . . . 1252

SECT. 4. The production of spherical surfaces by abrasion — Guy's method of grinding accurate spheres in hardened steel, glass, &c. ; one of the most unexceptionable examples of the production of form by abrasion — Grinding spherical surfaces for lenses — formation of the grinding tools— motions given to the tool, correction of curvature— preparation of the glass — rough and smooth grinding — Polishing lenses — cloth polisher for lenses of ordinary accuracy — grinding the edges circular — Varley's lathe for grinding and polishing lenses and specula — machinery for grinding common lenses — Grinding and polishing best lenses for object glasses — silk polisher — accuracy of radius of curva- ture, Ross's sphereometer — Grinding and polishing lenses for micro- scopes— Grinding and polishing specula for reflecting telescopes — Small specula ground and polished by hand — rough grinding with emery, smoothing with bed of hones, polishing tools — preparation of pitch polisher— manipulation and sources of error in the hand process

TABLE OF CONTENTS OF VOL. Ill,

PAGE

— The Earl of Rosse's machine for grinding and polishing three-foot speculum — management of the resinous composition for the polisher — modifications adopted in grinding and polishing the six-foot spe- culum— Methods of supporting specula in telescopes, and while being figured — Mr. W. Lassell's machine for polishing specula — Dr. R. Greene's machine for grinding and polishing specula and lenses — Rev. W. Hodgson's temporary apparatus for polishing small specula — Grinding machine for spherical stoppers of air-tight jars . 1257

SECT. 5. Glass-cutting — Glass-cutters' wheels, mills, and polishers — rough grinding flutes, splits, and pillars, on iron wheels fed with sand — smooth-grinding on fine grit stones — Polishing on willow wheels, and wheel brushes — Fitting stoppers into glass bottles— cutting glass drops 1296

CHAP. XXXIV.— LAPIDARY WORK.

SECT. 1. Slitting, cutting, and polishing flat and rounded works — General remarks on various apparatus — Ordinary lapidaries' bench, gim peg, slitting mill — Mortars for crushing and grinding diamond powder — Charging the slicer, slicing gems and small stones — Crane for slicing large stones — Flatting mill, rough and smooth grinding flat surfaces — Cutting the edges of stones to definite forms — cutting convex sur- faces— cutting concave surfaces and mouldings — cutting seal handles — Drilling large and small holes . . . . . 1 302

SECT. 2. Cutting facets — Different forms of facetting — Preparation of stones for receiving facets — Facetting trap or square cut stone — Brilliant cut— Half brilliant cut— Full brilliant cut— Trap brilliant cut— Double brilliant or Lisbon cut — Rose cut — Star cut — and dental cut — Geneva tool for facetting — Fictitious gems — Action of heat on carnelian, &c. — Pastes. — Metallic foils — Painted stones and doublets . . .1321

SECT. 3. Lapidary apparatus for amateurs — Driven by foot- wheel and treadle — Crane for slicing smaller large stones— Apparatus for cutting facets mechanically — Table of settings for the instrument — Application to facetting . .... 1341

CHAP. XXXV.— GEM AND GLASS ENGRAVING.

SFXT. 1. Introduction — Seal and gem engraving — Seal engraver's engine — Preparation of tools, or small grinding wheels of different forms- Charging the tools with diamond powder — Preparing the stones — Engraving shield with quarterings — Colour lines — Succession of the tools in gem and seal engraving — Position of the hands — Cutting curved lines — Sinking flat surfaces — Position of the stone — Difficulties of manipulation — Mr. H. Weigal on the comparative abilities of English and Foreign gem engravers— Polishing engraved surfaces — Qualities of different stones — Taking proof impressions of seals . 1348

SECT. 2. Cameo cutting — Effected by the same general methods and tools as those employed in engraving in intaglio — Selection of the stones — Onyx, gem engraver's application of the term — Adaptation of the

TABLE OF CONTENTS OF VOL. III.

PAGE

design to the stone — Succession of the processes — Spade for smoothing ........ 1365

SECT. 3. Glass engraving — Effected in the same general manner as seal engraving, but with larger apparatus — Glass engraver's tool and wheels — Engraving works of different kinds . . . . 3 369

CHAP. XXXVI.— VARNISHING AND LACKERING.

SECT. 1 . Preparation of the varnishes — General qualities of the resins com- monly used hi making varnishes, Anime, amber, copal, lac, saudarac, mastic, damar, and common resin — Vehicles for varnishes — Clarifying and boiling linseed oil— Oil of turpentine — Alcohol, common tests for strength, and methods of concentrating — Preparation of oil varnishes — Apparatus employed in making small quantities — General routine of the process — Fine copal varnishes — Cabinet, carriage, and wainscot varnishes — Amber varnish — Preparation of spirit and turpentine varnishes, with and without the employment of heat — White and brown hard spirit varnishes — Hardwood lacker — French polish — Bleaching lac varnishes — Lackers for brass — methods of colouring — Mastic and turpentine varnishes — Crystal, paper, water, sealing wax, and black varnishes ....... 1374

SECT. 2. Application of varnishes — Spirit varnishing — necessity of dry and warm atmosphere — varnishing flat surfaces — polishing and painting varnished works — Japanning, black, brown, and ornamented works — Lackering brass, &c. — methods of heating — Lackering flat works — management of the brush — Lackering circular works in the lathe — Dipping and bronzing ornamental brass works — Lackering or polishing hardwood turned works — French polishing — Indian varnishes for Burmese ware, palanquins, and furniture .... 1399

GENERAL INDEX of Vols. I. to III. 1420

ERRATA,

Page

1027, line 10 from bottom, for This, read Thus.

1067, line 12 from bottom, for Chap. XXXIII., Sect. 2, read Chap. XXXIL,

Sect. 3.

1078, line 11 from bottom, for Durbec, read Purbec. 1 151, line 4 from top, for off, read of. 1224, line 1 at top, for leve, read level. 1368, line 14 from bottom, for soft iron, read soft iron wire.

TURNING

MECHANICAL MANIPULATION.

VOL. III.

ABRASIVE AND MISCELLANEOUS PROCESSES, WHICH CANNOT BE ACCOMPLISHED WITH CUTTING TOOLS.

CHAPTER XXXI.

GENERAL REMARKS UPON ABRASIVE PROCESSES. INTRODUCTION.

THE third volume, which is now to be commenced, refers to a class of operations entirely dissimilar to those which have been described in the foregoing pages; as the former descriptions and instructions have referred alone to the treatment of such mate- rials as admit of being cut with steel tools. In page 12 of the Introduction to the first volume of this work, it is stated that —

" The third volume will be devoted to the explanation of abrasive processes ; namely, those for restoring or sharpening the edges of cutting tools ; those for working upon substances to which, from their hardness or crystalline structure, the cutting tools, (made of hardened and tempered steel,) are quite inap- plicable ; and also to the modes of polishing, which may be viewed as a delicate and extreme application of the abrasive process, and the final operation after the cutting tools, and lastly, to the ordinary modes of staining, lackering, varnishing, and other miscellaneous subjects/'

1027 COMPARISON OF ABRASIVE AND CUTTING PROCESSES.

In addition to the broad distinction between the processes which have been hitherto described, and that are performed with cutting tools of steel, there is another conspicuous difference, namely, that in works executed by cutting, the material is mostly removed in chips and fragments, which in the case of woods may be burned as fuel, or in metals usually admit of being reunited by fusion, and again converted into ingots, bars, or sheets, for sub- sequent use in the arts, — whereas in the second class of effects now to be considered, or those of abrasion by various frictional processes, the removed materials are ground to powder, and are mostly unsuited to further use.

On examination of the various abrasive processes, and of which grinding for the production of form, and polishing for the production of surface, may be considered as the extremes, it will be seen there are in every case of abrasion three distinct points to be considered.

First, the substances that are to be ground or polished. Secondly, the materials or abrasive powders by the successive employment of which different substances are polished.

Thirdly, the tools or apparatus by the agency of which abrasive substances are applied to the objects to be ground or polished.

Much variety necessarily exists under all three of these heads, and sometimes the very same substance may be referred to all of them ; for example — glass is frequently polished, as in plate glass, cut glass, and lenses. — Glass is frequently used as a polish- ing material when pulverized and glued upon paper. — And glass is also frequently used by watchmakers and some other artizans, as a tool or rubber through the medium of which, some of the polishing powders are applied to metal works in the act of polish- ing them.

The same thing may be observed of iron. — This metal in its various metallic forms is continually ground and polished. — An iron disk is used with diamond powder under the name of a skive, as the lap whereby diamonds for jewellery are polished, — and iron when reduced to the form of the peroxide or crocus, is used for very many purposes in the arts, and amongst others for polishing the specula of reflecting telescopes.

By way of condensing the numerous particulars that are to be offered under these several heads and rendering them easy of access and comparison, they will be arranged in alphabetical

PRELIMINARY OBSERVATIONS ON GRINDING AND POLISHING. 1028

form in a " Descriptive Catalogue of the Apparatus Materials and Processes for Grinding and Polishing, commonly employed in the Mechanical and Useful arts."

The catalogue will be found to contain much general infor- mation upon, and many practical examples of abrasive processes, and will be followed by one chapter on the grinding and sharpen- ing of tools of various kinds ; — one chapter on the figuration of materials by abrasion, — in which will be described under distinct sections, some of the modes of producing plane surfaces, cylin- drical and conical surfaces, spheres and spherical surfaces, and various mixed and arbitrary forms. After which, two other chapters will relate respectively to the art of the lapidary, and those of the engravers on glass and gems, — which several chap- ters will be materially assisted by the matter contained in the alphabetical' catalogue, — before proceeding to which it is pro- posed to add a few explanatory remarks on the three classes of information contained in the catalogue.

SECT. I. PRELIMINARY OBSERVATIONS ON GRINDING AND POLISHING.

First, on the substances that are to be ground and polished.

The objects or substances the grinding and polishing of which are described, will be found to include nearly all those materials from tbe vegetable, animal, and mineral kingdoms, which are commonly used in the mechanical arts ; those especially of which mention has been made in the first volume of this work in reference to their preparation and figuration by means of cutting tools, so far as regards the substances which admit of being subsequently polished. To these will be added the cutting, grinding and polishing of various hard and crystalline bodies on which cutting tools are ineffective.

Part of these materials such as the woods, ivory, and some of the metals and alloys, marble, glass, &c., receive dissimilar treat- ment from different classes of artizans, the principal variations of practice will be respectively noticed and contrasted under their respective heads : but it will be readily imagined that many unimportant variations are made, that are based rather on pre- judice than necessity, and the insertion of which would tend

B 2

1029

ANALYSES OF POLISHING MATERIALS.

perhaps to confuse rather than assist, and therefore the ordinary routines will be alone adverted to.

Secondly, on .the materials or abrasive powders, by the suc- cessive employment of which different substances are polished.

The grinding and polishing materials used in the arts will be found principally to consist of carbon, alumina, and silex, in various degrees of crystallization and admixture, and usually combined with the oxide of iron and some other substances as may be seen by their comparative analyses given in the annexed table.

TABLE OF THE ANALYSES OF POLISHING MATERIALS.

	Carbon.	Alumine.	Silex.	Lime.	Iron.	Authorities, &c.
(1)
Diamond . .	100-
(2)
Sapphire . . .		98-5		0-5	1-0	Klaproth.
Ruby .... Corundum	...	90-0 86-5	7-0 7-0		1-2 4-0	Chenevix. Chenevix.
Emery of Naxos		86-5	3-0		4-0	Tennant.
Emery of Jersey Rottenstone . .	ib-b	53-83 86-0	12-66 4-0	1-66	24-66	Vauquelin. R. Phillips.
(3)
Flint ....		0-25	98-0	0-5	0-25	Water 1-0. Klaproth.
Tripoli . . .		10-0	90-0			Trace of Iron and Lime.
Tripoli . . .	...	1-5	81-0	...	8-0	/ Water & Sulp. Acid 8-5. 1 Bucholz.
Polishing Slate .		4-0	83-5	8-5	1-6	Water 9-0. Bucholz.
Polishing Slate .		7-0	66-5	1-25	2-5	J Water 19. Magnesia 1-5. 1 Klaproth.
Bohemian Stone		1-0	79-0	1-0	4-0	Water 14-0 Bucholz.
Turkey Hone .	...	3-33	72-0	1333	...	Carbonic Acid 10-33. Holme.
Pumice Stone .		16-0	70-0	2-5	0-5	("Potash 6-5, Water 3-0. \ Berthier.
CO
Oxide of Iron .j				69-22	Oxygen 30-78. Berzelius.
Oxide of Tin .' ...					/Tin 78-34. Oxygen 21 -66. 1 J.Davy.
Chalk ....		...		56-5		f Carbonic Acid 43-0. \ Water 0-5. Bucholz.

Carbon in its purest and most crystalline form constitutes the diamond, the hardest substance in nature, and which in the

PRINCIPAL COMPONENTS OF POLISHING MATERIALS. 1030

pulverized state is variously employed, as, for example, in the polishing of diamonds for jewellery ; in the configuration of the rubies and sapphires used for the pivot holes of watches and chronometers ; diamond powder is also used by the lapidary in slitting all stones, of course including even those which admit of being polished by abrasive powders of inferior hardness to the diamond. Carbon, in another of its conditions, also constitutes charcoal, and which, probably from the minute particles of silex disseminated throughout its substance, is employed in polishing copper and others of the softer metals.

Alumina when highly crystallized is the basis of the ruby, sapphire, and other gems which are next in hardness -to the dia- mond. This earth, with the addition of a little silex and iron, constitutes the principal part of corundum, emery, and rotten- stone ; abrasive materials that are largely employed in grinding and polishing the harder metals and mineral substances. Alu- mina, when decomposed, is the basis of most of the clays and loams, some of which, under different names, are likewise used in abrasive processes. It is fortunate for the mechanical arts, that emery, which is nearly the hardest and most useful of all abrasive substances, is also found in sufficient abundance to serve for every required application.

Silex, in its crystalline form, and variously coloured, assumes the names of quartz, amethyst, rock crystal, flint, agate, and when in a disentegrated state, that of sand. Silex, with the addition of a little alumina and foreign matters, constitutes also the major part of the abrasive materials known as grit or grind- stones, rubstones, hones and slaty stones, pumice stone, tripoli, and some others, all of which are softer than those mineral sub- stances which are composed principally of alumina.

Of the siliceous abrasives, the gritty and slaty stones are very largely employed in the formation and sharpening of tools ; pumice-stone, tripoli, and others for polishing metallic and other substances, softer than those which, from their superior hardness, require the employment of emery and rottenstone, abrasives that have alumina for their common base.

To those abrasive materials of which carbon, alumina, and silex form the base, may be added the oxide of iron used under the names of crocus and rouge, and the oxides of tin and lead, or putty powders, these are artificially prepared ; and a few mineral

1031 APPLICATION OF ABRASIVE MATERIALS.

substances of no great importance as abrasives are used without any preparation, such as lime and chalk.

Thirdly, on the tools or apparatus, by the agency of which abrasive substances are applied to the objects to be ground or polished.

Some of the abrasive substances are employed in the solid forms in which they are first obtained, as the grindstone, oil- stone, hones, charcoal, Dutch rush, and fish skin ; a few are pulverized and mixed with various cements, thus the effective grindstone and razor hone of the Hindoo are corundum mixed with melted gum lac, and moulded into form ; wax and crocus similarly mixed are used in optical works amongst ourselves ; and of late years emery has been reunited into factitious stones. But metal, wood, paper, leather, cloth, or bristles, are the more common implements or vehicles, by aid of which the several powders are applied in a variety of ways, after the powders have been carefully separated into grains of similar magnitude, the sizes of which must be proportioned to the perfection of the surface to be produced, and with a gradual transition from coarse to fine. This succession is adopted upon the same principle as that in filing a coarse file is first used, because it may be made to act rapidly; but as the form of the work becomes gradually developed, a second cut file, a smooth, and lastly, a superfine file is used, and which progressive mode of action is in no case more distinctly seen in works of polishing, than in the manu- facture of a highly finished razor, which is described under the head Cutlery in the following Catalogue.

The grinding powder is of course always harder than the substance to be ground, whereas the implement or grinding tool is softer, and generally agrees in form with the analogous cutting or moulding tools used for producing work of corresponding shapes in other substances, as practised in different branches of the mechanical arts. Thus turned works are often polished with blunt factitious turning tools of wood supplied with the powders; flat works require artificial saws, files, and planes ; a convex surface requires a concave grinding tool, and so on.

IMPORTANCE OF CLEANLINESS IN POLISHING. 1032

Cleanliness should be most scrupulously observed in polishing. This remark may appear misemployed as regards a process in which various dark-coloured powders, &c. are mingled with oil or water somewhat like the pigments used by artists, and are so employed, that the hands must almost inevitably become more or less soiled ; but that degree of care and order must at any rate be adhered to, which will entirely avoid the different powders and materials becoming mixed. The finest powder, if mingled with the coarse, would be comparatively inert and harmless, but a grain or two of the coarse powders, if accidentally present along with the fine, would inflict deep scratches, and completely nullify the efforts at obtaining a highly polished surface.

On this account it is desirable not only to keep the various polishing tools and powders carefully separated in boxes or bottles, but also before proceeding to each finer stage of the process, carefully to wipe or even to rinse the work in water, for the entire removal of all the previous materials employed in the earlier stages of polishing.

Having advanced these preliminary and general remarks, we shall at once proceed to the descriptive and general Catalogue, deferring until the subsequent chapters a variety of additional matters of a more specific character.

SECT. II.

DESCRIPTIVE CATALOGUE

OF THE

APPARATUS, MATERIALS, AND PROCESSES

FOR

GRINDING AND POLISHING,

COMMONLY EMPLOYED

IN THE

MECHANICAL AND USEFUL ARTS.

N.B.— The descriptions of the Mineral Substances, are for the most part extracted or modified from those given in Wm. Phillips's Mineralogy, 3rd edition, London, 1823.

AGATE. Some of the uses of Agate in the mechanical and useful arts are described in Vol. i. page 173, and this substance although much harder than Carnelian is cut and polished precisely after the same manner, and which process is fully described under the head CARNELIAN in this Catalogue.

ALABASTER. The general modes of working Alabaster with saws, chisels, files, and turning tools, as regards its configuration, are described in pages 164-5 of the first volume, but this substance is polished quite differently by the sculptor in chiselled or carved works, by the marble worker in turned works, and by the lapidary in small objects of bijouterie and vertu ; it is therefore proposed briefly to describe these three several modes.

1. — ALABASTER. — CHISELLED OR SCULPTURED WORKS. The dull or dead parts of sculpture, after having been carved with chisels, as more fully described under the head marble, are, 1st, smoothed with bent rasps and files, known as rifflers, and, 2ndly, are afterwards scraped with a triangular scraper. 3rdly, they are additionally smoothed with fish skin or glass paper, and, 4thly, with Dutch rush used^ with water.

In some few instances carved works are polished, or else the ground alone from which the figures are relieved is polished by way of contrast, in such cases after the four previous stages, the parts to be polished are wrought with the end of a stick of deal or other soft wood, supplied with Trent sand

APPARATUS, ETC., FOR GRINDING AND POLISHING. 1034

and water, and used as a pencil or brush with small circular strokes, and afterwards with a stick and putty powder with water, just the same as in corresponding works of marble, which are fully treated under that head in this Catalogue.

2. — ALABASTER. — TURNED AND POLISHED WORKS. Mr. Hall of Derby has kindly furnished the author with the following outline of his usual practice. " When the article is finished with the turning tool, take, 1st, a piece of very fine soft sandstone, (found in Derbyshire in thin beds in the red marl formation,) and apply it with water to the work, whilst it is in quick revolution moving the stone all over until there is worked up 'a body of mud ; 2ndly, take a wet rag and work this sludge well on the alabaster, then wash the work clean ; and 3rdly, apply a rag charged with putty powder and water, until there is a gloss upon the work. 4thly and lastly, apply another rag charged with a mixture of putty powder, and soap and water, for a short time and wipe the alabaster dry which completes the polish."

3. — ALABASTER AS TREATED BY THE LAPIDARY. Alabaster is far less frequently wrought by the lapidary than the sculptor, but as it is treated by the former in a manner somewhat different from the harder stones, it is made one of the three general examples of the lapidary's art, introduced into this cata- logue, namely, the working of Alabaster ; the working of Carnelian ; and the working of Sapphire ; which substances differ greatly in hardness. To these three descriptions are appended lists of the principal stones and other substances that are similarly treated, by Mr. Ward and other lapidaries, whom the author has consulted. In the Chapter on Lapidary Work these outlines will be filled up, and the general practice of this curious and interesting art will be considered somewhat more at length.

In working Alabaster to the required forms the lapidary first employs as usual the slitting mill, which is a thin plate of iron fixed on a vertical spindle, and made to revolve with moderate velocity, the edge of the slicer is charged with diamond powder, and lubricated with the Oil of Brick. This instru- ment which may be considered as the circular saw for small stones, is used with light pressure and plenty of brick oil.

Secondly the alabaster is roughed, or roughly ground on what the lapidary terms a roughing or lead mill, namely a flat circular plate of lead, fixed on "a spindle similar to that of the slicer, the milljor lap therefore travels in a horizontal plane, and is abundantly supplied with coarse emery and water by means of a brush. The stone is moved to and from the center of the rapidly revolving lap, until all the marks from the slitting mill are removed, and the stone is reduced to a flat surface.

Thirdly the alabaster is smoothed on the same lead mill with flour emery, but prior to smoothing the stone, the grains of the coarse emery previously used, and that remain on the lap, are rubbed down fine with a smooth lump of emery stone. It would apparently be a better practice to use two different laps, and together with them emery of two different sizes ; as in the first place, the operation of smoothing the mill, is tedious, it also tends to wear

1035 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

away the lap towards the edge, thus degenerating the plane or flat surface into an irregularly coned surface, with which it is impossible to grind works accurately flat ; and moreover if any coarse grains of emery are left in the lap, they greatly retard the smoothing, and consequently the polishing also. Indeed it will be found a most erroneous practice, to hurry over any one process with the intention of making up for it in the next, for as each stage of the work requires successively finer polishing powders, the various steps should be continued the proportional times, or ultimate success will be more tediously, if at all attained.

As it is difficult to polish alabaster and substances equally soft on the inelastic lead lap with rottenstone, (the means usually employed for harder stones,) the following is the course ordinarily followed. After the roughing mill has been used, the stone is smoothed on a wood mill or a disk of maho- gany used with flour emery and water ; on account of the greater elasticity of the wood mill, and the slight roughness of its face from the rubbing up of the fibres, it acts more quickly and satisfactorily than the metal tool.

Fourthly the earlier stage of the polishing is accomplished on a list mill with pumice-stone and water, but as the list which is wound on spirally is very elastic, flat works must be lightly applied, or they will sink into the soft face of the list mill and become rounded at the edges.

Fifthly the polishing is completed on a leather lap, or a thick piece of buff leather pasted securely on a wooden disk, and supplied with fine putty powder and water. Sometimes indeed the naked hand, and a little moistened putty powder are finally used for the last polish.

These several mills or laps are more particularly described under the article WHEELS in this Catalogue.

The following substances are worked by the lapidary in nearly or exactly the same manner as Alabaster, and descriptive articles are severally intro- duced in the Catalogue upon these particular substances, pointing out also any peculiarities of method pursued either by the lapidary or other artizan, as the case may be, in working them.

(Substances treated by the Lapidary like Alabaster.)

Amber. Cannel Coal. Coral. Enamels. Glass.

Jet. Lava. Malachite. Mother of Pearl. Nacreous Shells.

Opal.

Potstone.

Satinstone.

Steatite.

Turquoise.

4. — CLEANING ALABASTER. — Ornamental works in alabaster that have become soiled are sometimes cleaned hi the following simple manner : — The object is first immersed in plain spring water for four or five days, the water is then changed and a small quantity of lime is added, the alabaster is allowed to remain in this solution for a further period of four or five days, after which it is only necessary to thoroughly rinse the object, which is allowed to dry gradually in the open air, and the process of cleaning is completed. Should the alabaster

AND PROCESSES FOR GRINDING AND POLISHING. 1036

have been very much soiled, a single course of the above treatment may fail to restore the original whiteness ; hi this case the process is repeated, and in extreme instances a third application is sometimes necessary. Earthenware pans are the most suitable vessels to be employed, as wooden tubs, especially those of oak, are almost certain to stain the alabaster.

Objects that consist of several pieces will be separated by the above pro- cess ; they are, therefore, lastly, reunited with plaster of Paris, all the parts to which the plaster is to be applied being first moistened with water to ensure the adhesion of the plaster.

In the original working and finishing of the alabaster, all the pores or grain of the stone become filled with the fine powder produced in polishing, and which gives the alabaster a more compact surface than it would otherwise present. This powder is removed by the above treatment, and the alabaster then exhibits its natural granular and sparkling appearance : should this be objected to, the polish may be renewed by the employment of putty powder, applied upon a rag or stick as described hi article 1.

ALB AT A or BRITISH PLATE of the best kind is treated almost like silver work. In polishing spoons made of the inferior kinds of Albata, the 1st operation, which is called roughing, is done upon bobs (see WHEELS, article 51,) covered with sea-horse hide with a plentiful supply of Trent sand and oil ; 2ndly, rottenstone and oil is used ; and 3dly, the finishing is done upon bobs with oil and very finely powdered lime, materials that are of the cheapest kind, and require little or no preparation.

ALBATA or GERMAN SILVER is polished by the mathematical instrument makers the same as BRASS. See that article, paragraph 4.

ALUMINA, in a compact or crystalline form is the base of some very hard mineral substances used in the arts, namely, emery, corundum, sapphire and ruby, of which it constitutes from 86^ to 98 per cent.: these are only exceeded in hardness by the diamond. See the table, page 1029.

AMBER after having been filed, may be polished 1st with Trent sand, or scraped Flanders brick on flannel with water ; 2ndly, rottenstone with oil on flannel ; Srdly, rottenstone dry on the hand.

Turned works are generally polished first with glass paper, and then with rottenstone and oil.

The lapidary works amber just after the mode described under Alabaster, article 3, but necklaces and other ornaments in amber that are cut into facets, are more usually and better executed by the gold cutters, or those artizans who cut and polish facetted works, and by the same routine as that described in the article 3, under the head GOLD.

AMETHYST or violet quartz is cut and polished by the lapidary like CARNELIAN, which see.

1 037 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

AQUAMARINE, called also BERYL, and ANCIENT BERYL, is of various shades of pale yellow, green and blue, it was so named from its resemblance to sea water, and is worked like CARNELIAN.

ASTERIA. See SAPPHIRE.

AVANTURINE, a mineral which is found variously coloured and always enclosing particles of mica ; the most common colour of the base is brown or reddish brown. It is worked by the lapidary like Carnelian, but does not admit of so good a polish as the imitation.

2. — FACTITIOUS AVANTURINE, which is glass or paste enclosing particles of metal is generally more close and brilliant than the real stone, and was much used in common jewellery, the imitation avanturine is cut and polished like other pastes, as described under the head ALABASTER, article 3. The method of making this artificial avanturine which is now lost, is considered to have originated with the Italian artists, this substance is now very scarce and much valued.

3. — ARTIFICIAL AVANTURINE which is more brilliant than the last, and used as a microscopic object, is prepared from blue glass coloured by the oxide of copper, which is stirred with an iron rod. The oxygen from its superior affinity for the latter metal quits the copper, and unites itself to the iron, and in the act of resuming the metallic form, the copper partially crystallizes, and becomes entangled in the glass. From the striated condition the glass assumes on being stirred, the bright and metallic picture is irregular, and appears full of hills and dales, occasionally clouded with the dark coloured glass in which no copper is visible. The crystallization may be distinctly seen with a common lens of half an inch focus.

BERYL, a term that designates amongst lapidaries and virtuosi a very rich deep brown diaphanous carnelian ; it is frequently engraved into intaglios, just after the manner of carnelian generally.

BETEL-NUTS, when turned, are in general polished only with fine glass paper, and a few of their own shavings ; whiting and water may be used as for Ivory.

" BLOODSTONE is a very hard, compact variety of haematite iron ore, which when reduced to a suitable form, fixed into a handle, and well polished, forms the best description of burnisher for producing a higher lustre on gilt coat- buttons, which is performed in the turning lathe by the Birmingham manu- facturers. The gold on china ware is burnished by its means. Burnishers are likewise formed of agate and flint ; the former substance is preferred by bookbinders, and the latter for gilding on wood, as picture-frames, &c." —

BLOODSTONE, the appellation sometimes employed by the lapidary and jeweller, to distinguish a dark green stone usually containing red spots, whence its

AND PROCESSES FOR GRINDING AND POLISHING. 1038

popular name of bloodstone ; it is mineralogically known as the Heliotrope, and is considered as a variety of chalcedony : this stone is worked exactly like CARNELIAN, but is much harder and takes longer to polish.

BOB, a familiar name used at Birmingham, for small leather polishing wheels, with rounded edges, each made entirely of a thick piece of lull-neck, or sea-cow leather, perforated to receive the spindle, and used in polishing the insides of the bowls of spoons and other articles. See WHEELS, article 52.

BONE. — After the turning tool or scraper has been used, bone is polished, 1st, with glass paper, 2ndly, with Trent sand or Flanders' brick with water on flannel ; 3rdly, whiting and water on woollen rag ; 4thly, a small quantity of white wax is rubbed on the work with a very quick motion, the wax fills the minute pores, but only a very small quantity should be allowed to remain on the work. Common bone works, such as nail and tooth-brushes, are frequently polished only with slaked lime used wet on flannel or woollen cloth.

BOULDERING STONE.— This name is applied by the Sheffield cutlers to the smooth translucent flint pebbles, found in gravel pits, with which they smooth down the faces of buff and wooden wheels, by abrading any large grains of emery, or other powder contained on their surfaces. See WHEELS, articles 43 and 44. The bouldering stones are usually selected of about the size of a hen's or pigeon's egg, and of a flattened form ; and the flat side becomes gradually worn down and smooth from its continual application. The term appears to be derived from the provincial use of the word boulder, to denote the round stones used in paving ; whence, also, boulder-setter or pavior.

Metal laps are " bouldered down ; " first, they are supplied with a little emery and oil, which is spread with the fingers, and then pressed into the metal and worn down fine and smooth with the bouldering stone, and wood laps are first anointed with flour emery or fine flour emery ; they are then well bouldered, and are lastly waxed by holding a small piece of wax against the revolving wheel ; these processes greatly reduce the cut of the powders ; and unless the bouldering stone is plentifully applied the colour or high gloss cannot be produced on the works.

BRASS is finished by different classes of artizans, by methods that are widely dissimilar, many of which are described ; and it may be considered that the same modes are also suited to the other alloys, consisting principally of copper, such as gun metal, electrum, or German silver, &c., particularly as regards parts of machinery and mathematical instruments.

1. — TURNED WORKS IN BRASS are frequently polished with emery paper alone, two sizes of which are mostly used with a little oil. For plane and cylin- drical surfaces, the emery paper is wrapped around a parallel piece of stick, and for internal plane surfaces it is applied by means of a small cubical block

1039 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

of wood ; these methods tend to preserve the external angles from being rounded. An additional lustre is given, if required, by woollen cloths with oil and rottenstone. When the work is not to be varnished, a minute quantity of the polishing oil is left on, which somewhat prevents tarnishing.

The sliding tubes of telescopes, after having been cleaned off with fine emery paper, are brushed with a revolving or wheel brush, with fine crocus and oil, and are finished with a woollen rag and rottenstone, nearly free from oil, and rubbed lengthways, the lathe being for the time at rest.

2. — COMMON FLAT WORKS, after they have been filed up, are frequently finished first with coarse and then with fine emery paper, which is often used dry or without oil, and wrapped around a file or wooden rubber. The gram is usually laid straight, or in one direction ; at other times the works are coarsely curled by a circulating motion of the hand.

3. SUPERIOR FLAT WORKS. — The brass plates for the mechanism of harps are

perhaps more carefully treated than any of this kind. The plates of the harp machinery are planed and scraped, the mechanism is then fitted, and the second axes or arbors are ground into their respective pivot -holes with fine oilstone powder. The plates are again carefully scraped, after which they are polished, 1st, with" charcoal in the stick, to remove all the marks made with the scraper and file. 2ndly, flour emery is dusted over the plate from a muslin bag, and rubbed with a piece of wood three or four inches square, covered with baize nailed around the edges, to serve as a rubber. 3rdly, rottenstone is similarly employed upon a rubber covered with two or three thicknesses of fine woollen cloth ; the plate is then washed quite clean and dried. 4thly, it is finished with a dry buff rubber and rottenstone ; the holes are then cleaned out with a feather slightly coated with dry whiting, and finally the plate is varnished. In all the processes it is necessary to follow the curvature of the plate, in order to lay the gram in accordance therewith.

Brass door-plates of the best kind are treated with nearly the same care, although immaterial variations are often made in the routine.

4. — FLAT WORKS IN MATHEMATICAL INSTRUMENTS. — Such of these as are in brass and gun metal, when left from a very smooth file are prepared first with a stick of water of ayr stone ; and are afterwards finished with water of ayr stone scraped to a fine powder, mixed with a little oil to the consistence of treacle, and applied with a smooth piece of white deal. If the work present lines from the grain of the wood, it is rubbed with the clean finger, or a buff stick smeared with oil, the polishing stuff that remains on the work being sufficient for the concluding step.

The edges of work, after having been drawfiled, are scraped with a sharp triangular scraper, applied almost without pressure, in order to avoid utters or indentations ; oilstone powder with oil is next used on a piece of maho- gany, then scraped water of ayr stone, as above, and lastly, a buff stick with dry rottenstone.

5. — FLAT WORKS CURLED. — These are filed, scraped, and stoned, as by the mathe-

AND PROCESSES FOR GRINDING AND POLISHING. 1040

matical instrument makers. The work is then clouded with a piece of charcoal and water, by means of which the entire surface is covered with large curly marks, which form the ground. The curls resemble an irregular cycloidal pattern, with loops of from one quarter to one inch diameter, according to the magnitude of the work. Similar, but much smaller marks are then made with a piece of snake-stone, blue-stone, or even common slate pencil, filed to a blunt point. The general effect of the work much depends upon the entire surface being uniformly covered, with which view the curls should be first regularly continued around the margin, the central parts are then filled in ; after which the work is ready to be varnished.

The curled surfaces are desirable, in so much as any little accidental injuries or rubbing, arising from the continued use of the articles, are less observable upon curled surfaces than upon similar pieces laid with an even grain ; and the curled parts mixed with the bright edges have a good effect. The mode was introduced by the author's father.

6. — WATCHWORK IN BRASS. — Flat works of medium character, after having been filed, are polished, 1st, with a stick of blue stone and water, and 2ndly, with a slip of box wood, with the unguent obtained by rubbing two pieces of blue-stone together with oil. The best and flattest watch works, after 1st, the blue-stone, are polished 2ndly with pewter and red stuff or crocus, and 3rdly with a piece of tortoiseshell, horn, or ivory, supplied with very fine red stuff and oil.

Tortoiseshell is preferred for the polisher, as it may be used nearly dry and leaves the fewest streaks or shades hi the work ; horn is next in estima- tion, and ivory the least of the three ; each of which materials, and also pewter, glass, &c., are used in flat pieces from one to two inches square, which are smeared with the powders mixed with oil ; the work is then rubbed on the surface with the fingers, as if it were the muller used in grinding paint ; this produces very flat surfaces. The burnisher is sometimes used after the powders.

Most of the brass work of watches is gilt by water gilding, to prevent it tarnishing from the effect of the atmosphere. The polishing of the steel part of watchwork is described under the head MACHINERY in iron and steel in this catalogue, article 1 3.

7. — BRAZIERS WORKS.— The coppersmiths and braziers adopt nearly the same treatment for brass as for copper. Subsequently to the brass work having been annealed for the last time, and before it is planished with the hammer, it is generally pickled with nitrous acid diluted with very little water, and then scoured with coarse red tripoli and water to remove the oxidation caused by the fire. The work when planished is cleaned 1st witfi crocus and oil ; 2ndly, the oil is rubbed off with whiting ; and 3rdly, the final polish is given with dry rottenstone usually applied on an old worsted stocking.

8. — STAMPED WORKS IN BRASS, for house furniture, such as finger plates for doors, and numerous other objects stamped out of sheet brass, are treated in a manner entirely different from all the preceding, as the sheet brass when

1041 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

carefully rolled is left very smooth and only requires to be made bright. The stamped works are 1st cut out, 2ndly figured between dies, in a fly press, or under a stamp hammer usually called a force, 3rdly they are annealed, 4thly coloured by immersion in an acid preparation, Sthly washed and dried in saw- dust. The entire surface is now of a rich yellow or gold colour but dead or dull, Gthly the parts desired to be bright are burnished with a steel burnisher which is lubricated with water alone, or with water having a trifling admix- ture of vinegar or beer, and 7thly the work is varnished. The methods of colouring, bronzing, and varnishing, stamped works and others of the same character, will be hereafter detailed.

9. — CAST WORKS IN BRASS FOR HOUSE FURNITURE, including lamp and gas fittings. These works receive little or no polishing by the ordinary methods of abrasion with powders, which would be too tedious and expensive a process. The smallest and commonest of the castings, after haring been cleaned by the brass founder, in the rumble, are coarsely filed and then scraped ; those pieces which are more carefully moulded, as described under fine casting, (vol. i. p. 341,) require only the removal of the rough edges or burrs, and the tubes employed in gas works, &c., are left sufficiently smooth from the draw-plate. The several parts after having been adapted together, by aid of the file, turning tool, screws or solder, are almost exclusively decorated by the processes of dipping, bronzing, burnishing and varnishing ; part of which processes, as noticed in the last article, will be treated of towards the end of this volume.

BRITANNIA METAL works, like those in hard pewter, which this alloy con- siderably resembles, after having been turned are in great measure finished by the steel burnisher with an abundance of oil ; the final lustre is usually given with rottenstone and oil on woollen rag. Frequently a very minute coat of oil is left as a defence to retard the action of the atmosphere, at other times the surfaces are thoroughly brightened with dry whiting, applied on wash leather.

Many workmen polish Britannia metal with Trent sand and oil, to the exclusion of all other applications. This sand is probably unequalled as to fineness.

BRONZE. — The Bronze metal, (copper and tin,) is now usually called gun-metal, or bell metal, according to its proportions, and is polished after the manner of BRASS, which see articles 1 to 5.

The colours of bronzes, imitative of those tints which occur on the metal from long exposure to the atmosphere, are sometimes produced chemically in the modes to be subsequently described.

BRUSH WHEELS, circular revolving brushes are used with various polishing materials, see WHEELS articles 65 and 66. Hand polishing brushes are also used, which are made almost like nail brushes, but many of them are longer,

AND PROCESSES FOR GRINDING AND POLISHING. 1042

narrower, and also softer, especially such as are used by watchmakers, jewellers, and others.

BUFF LEATHER is used in various ways for polishing ; thus it is glued on the circular edges or plane surfaces of wooden polishing wheels, and used with coarse emery, crocus, rottenstone, and other powders, see WHEELS, article 5.

BUFF STICKS are parallel rods of deal upon which strips of buff leather are fixed, either by means of glue, or by folding the leather around the ends, and securing it by iron tacks. The buff sticks are principally used with crocus and rottenstone, both with or without oil, and for most of the metals as well as various other substances ; in some few cases the buff stick is moistened with water, see TORTOISESHELL. BUFF WHEELS are described under the head WHEELS, articles 51 to 53.

BURNISHER. — This valuable instrument is in general a piece of hardened steel very highly polished, and when judiciously applied to the smooth surfaces of metals, it imparts to them, by means of friction, or intimate contact, a polish nearly equal to that which the burnisher itself possesses.

2. — THE ACTION OF THE BURNISHER appears to depend upon two circumstances ; first, that the harder the material to be polished the greater lustre it will receive, and the burnisher is commonly made of hardened steel, which exceeds in hardness nearly every metallic body. And secondly, its action de- pends on the intimacy of the contact, betwixt the burnisher and the work ; and the pressure of the brightened burnisher being, in reality, from its rounded or elliptical section, exerted upon only one mathematical line or point of the work at a time, it acts with great pressure and in a manner distantly analogous to the steel die used in making coin ; in which latter case, the dull but smooth blank, becomes instantly the bright and lustrous coin, in virtue of the intimate contact produced in the coining press, between the entire surface of the blank and that of the highly polished die.

It by no means follows however that the burnisher will produce highly finished surfaces, unless they have been previously rendered smooth, and proper for the application of this instrument ; as a rough surface having any file marks or scratches, will exhibit the original defects, notwithstanding that they may be glossed over with the burnisher which follows every irregularity ; and excessive pressure, which might be expected to correct the evil as in coining, only fills the work with furrows, or produces an irregular indented surface, which by workmen is said to loefull of utters.

Therefore, the greater the degree of excellence that is required in bur- nished' works, the more carefully should they be smoothed before the application of the burnisher, and which should be cleaned on a buff stick with crocus immediately before use ; and it should in general be applied with the least degree of friction that will suffice. Cutlers mostly consider that burnishers for steel are best rubbed on a buff stick with the finest flour

VOL. III. C

1043 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

emery ; for silver however they polish the burnisher with crocus as usual. Most of the metals previously to their being burnished are rubbed with oil to lessen the risk of tearing or scratching them, but for gold and silver, the burnisher is commonly used dry, unless soap and water or skimmed milk are employed ; and for brass furniture, water with or without a little vinegar, or else beer is preferred for lubricating the burnisher.

3.— THE MOST GENERAL FORMS OF BURNISHERS.— The burnisher used by mechani- cians generally, resembles in form a file of elliptical section without teeth ; it is made particularly hard and well polished. For engravers in line and mezzotint, the burnishers are sometimes crooked like the horn of a cow ; for watchmakers and others, they are flat so as to apply to pivots, and other burnishers for these artizans are nearly cylindrical for the interior surfaces of pivot holes, and which are applied as in using a polygonal broach. For ironmongery a narrow piece of steel is inlaid in a cross handle of wood, that is used almost like a spoke-shave, and the pressure is increased by a leather strap or bridle attached on both sides of the burnisher, in the bend of which the workman places his foot, to give the pressure. The same form of bur- nisher is employed in Sheffield for the springs of pocket knives, but the strap is generally omitted.

The burnisher is sometimes also fitted up with a handle at one end and a hook and staple at the other, somewhat like the paring knife used by clog makers and others (see fig. 18, vol. 1, page 26). This kind, which is called the clog burnisher, is much used at Sheffield, for the backs and squares of knife blades, which, after they have been made quite smooth, rare moistened with the tongue and burnished with the clog burnisher, then the work and tool are wiped quite dry with a clean linen cloth, and a very gentle dry bur- nishing completes the work.

Fender makers and others have the burnisher at the bottom end of a pole suspended from the ceiling, or rather from a long and strong spring like that of the pole lathe, or a straight coach spring ; this enables them- to take a very long and equal stroke. The same contrivance, (which is also used in calenc cloth by hand,) is nearly copied, but with a piece of leather and emery, laying a straight and dull grain on long works.

Burnishers made of flint, agate, and bloodstone are used by bookbinders and picture frame makers, also by silversmiths and jewellers, and other artizans, see BLOODSTONE.

CANNEL COAL. — In polishing flat works of this material, such as inkstands, water of ayr stone in the stick is 1st used with water ; 2ndly, charcoal dust soft soap on a flannel ; and although 3rdly, for fine works rottenstone on hand or flannel have been used, it is better to continue the second pro< until the completion, adding only additional soft soap with water as lubricator. For the working of cannel coal, see vol. 1, p. 162.

For objects turned in the lathe, the water of ayr stone is superseded emery paper.

Lllclli Ul

a very idering TV, for

AND PROCESSES FOR GRINDING AND POLISHING. 1044

The Lapidary works Cannel Coal just as he would Alabaster ; see Article 3 under that head.

CAP. — A term used by many of the Sheffield Cutlers to designate wooden wheels, capped or surrounded with a ring of metal to constitute laps, the edges only of which are used, see WHEELS, articles 37 to 47, where their construc- tion and application are described.

CARBON, when highly crystallized, as hi the diamond, is the hardest substance in nature, and cuts all others. Next in hardness to the diamond are those mineral substances having for their bases alumina, silex, and the metallic oxides of iron and tin. See also the articles on DIAMOND and CHARCOAL.

CARBUNCLE. — The stone that is considered to have obtained this name, in ancient as well as in modern times, is the Almandine, or Precious Garnet of mineralogy ; it is usually polished en cabochon, or with a rounded surface without facets, after the general manner of oriental jewellery, and is worked like CARNELIAN, as described in the following article.

CARNELIAN is the substance that has been selected as the example of the mode of cutting and polishing stones of a medium degree of hardness, the two other examples being Alabaster for the softest stones, and Sapphire for the hardest, excepting alone the diamond, which last is worked in a manner peculiar to itself, and is separately considered. As already observed, some of these subjects will be resumed more at length in Chapter XXXIV. on Lapidary work.

1. — CARNELIAN when operated upon by the Lapidary, is, 1st, slit with the thin iron slicer fed with diamond dust and moistened with brick oil ; 2ndly, it is rough ground on the lead mill with coarse emery and water ; and, 3rdly, it is smoothed either on the same lap rubbed down fine, or with a similar lap used with finer emery ; thus far the steps are precisely as explained with regard to Alabaster.

4thly. Carnelian and stones of similar or superior hardness, and which are not smaller than about one third of an inch in diameter, are in almost all cases polished on a lead mill plentifully supplied with rottenstone and water ; but this fine powder will scarcely adhere after the manner of the coarser and granular emery, or by simple pressure, and therefore to expe- dite the process the face of the polishing lap is hacked, or jarred, although in a manner quite different from that pursued by the cutler.

The Lapidary employs the blade of an old table knife which he holds slenderly between the thumb and finger, placed near the middle of the blade, while the front part of the edge rests on the lap, not perpendicularly, but slanted a little forwards, so as to meet the lap edge foremost during its revo- lution: the unstable position of the knife causes it to jump, vibrate, or chatter on the lap, and at each jump it makes a very slight furrow ; these fill the face of the mill with minute lines or grooves, that serve for the lodgement of

c 2

1045 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

the finely powdered rottenstone. It is however to be observed that the wheel should be made first to revolve in the one direction, and then in the opposite, that the marks of the hacking-knife may cross each other.

2. Smaller and harder stones are more commonly polished on a pewter than a

lead lap, and for the smallest and hardest stones a copper lap is preferred ; but all the polishing tools, of what metal soever they may be made, are hacked as above described, and used with rottenstone and water.

3. — ROUNDED OR CONVEX STONES, or those said to be cut en, cabochon, whether of Carnelian or even several of the harder stones, are in many cases succes- sively wrought by means of the wood mill with fine emery, the list mill with pumice-stone, and leather lap with putty powder, precisely as described under the head Alabaster. This is done on account of the greater elasticity of these apparatus, which enables them to ply more conveniently to the globular forms of the works to be polished, and avoid wearing them in ridges or flat places.

4. — FACETTED WORKS on all stones and hard substances, are for the most part cut by the Lapidary after one of three different modes. First, for pastes or arti- ficial stones, and many soft stones, as amber, carnelian, jet, &c., the facets are usually cut on a lead wheel with emery, and polished on pewter with rottenstone. — Secondly, for some of a harder kind but inferior in hardness to sapphires, the succession of tools is a pewter lap and fine emery for the cut- ting, and a copper lap with rottenstone for the polishing. — Thirdly, for sapphires, the chrysoberyl, and rarely for some few others likewise, a copper lap with diamond powder is used for cutting the facets, and a copper lap with rottenstone for polishing them. — And fourthly, with the diamond, two stones are rubbed in a peculiar manner the one against the other to cut the facets, and they are polished by means of the dop, and an iron lap or skive fed with diamond powder ; this process is more fully described in vol. 1, page 1 76.

5. — From the comparatively small size of the stones and gems that are cut into facets, they cannot generally be held unassistedly in the fingers, the stone is consequently cemented centrally upon the end of a round stick of wood nearly like a drawing pencil. The stick when held vertically, gives the posi tion for grinding the central facet or table of the stone, the stick is inclined to a certain angle for the eight, twelve, or more facets, contiguous to the table ; of which facets, two, three, or four series are commonly required at different inclinations, and, lastly, the horizontal position of the stick serves in cutting the girdle or central band around the exterior edge of the stones.

The several inclinations of the stick on which the stone is cemented, are easily determined by placing the upper end of the stick into one of several holes in a vertical post, fixed alongside the lap, and this retains the inclina- tion very accurately and simply, but all these matters will be further eluci- dated in the 34th chapter on Lapidary Work generally.

6. — The following substances are worked by the lapidary in nearly or exactly the same manner as carnelian, and descriptive articles are introduced in the catalogue upon each of these particular substances, pointing out their

!

AND PROCESSES FOR GRINDING AND POLISHING.

1046

principal external features, and also any peculiarities of method, pursued either by the lapidary or other artizan, as the case may be, in working them.

(SUBSTANCES TREATED BY THE LAPIDARY LIKE CARNELIAN.)
Agate	Elvans	Mina Nova
Amethyst	Emerald	Onyx
Aquamarine	Felspar	Opal
Beryl	Flint	Pastes
Bloodstone	Fluor Spar	Peridot
Brazilian Topaz	Garnet	Plasma
Carbuncle	Granite	Porphyry
Cat's-eye	Heliotrope	Quartz
Chalcedony	Jade	Sard
Chrysolite	Jasper	Sardonyx
Chrysoprase	Lapis Lazuli	Serpentine
Crystal	Marble	Topazes.

CAST-IRON. — When the parts of machinery that are made in cast-iron are polished they are treated as described in tlu's catalogue under the general article on MACHINERY made of iron and steel.

THE FRONT OF STOVES, and similar bright works in cast iron, are first ground on large grindstones, and then buffed on large revolving buffs upon which a coating of emery has been fixed by glue. They are sometimes finished by a hand rubber used as a spokeshave having a piece of leather supplied with fine emery and oil, but the rubbers suspended from the ceiling at the end of a powerful spring, are also very judiciously employed in these large works. See the end of the article BURNISHER.

FIRE IRONS are often cast in iron that is afterwards rendered malleable ; which is a rapid way of producing beautiful form, combined with strength and a certain measure of flexibility, see vol. 1, page 259, the works are afterwards case- hardened, that they may admit of a better lustre, and which is generally given by grindstones, glazers, buffs and brushwheels, much the same as in cutlery but on a larger scale.

CAT'S-EYE, a mineral consisting of quartz enclosing amianthus or asbestos, and thence possessing the property emphatically described by the French as chatoyant ; the cat's-eye is polished just like AGATE or CARNELIAN.

CHALCEDONY, a name applied to many siliceous minerals including as varieties the onyx, sard, sardonyx, plasma, heliotrope, and chrysoprase : they are wrought like CARNELIAN, which see.

CHALK when simply scraped, or else crushed under the hammer, is occasionally used in polishing bone, ivory, and some few soft substances, it cuts much

1045 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

the finely powdered rottenstone. It is however to be observed that the wheel should be made first to revolve in the one direction, and then hi the opposite, that the marks of the hacking-knife may cross each other.

2. Smaller and harder stones are more commonly polished on a pewter than a

lead lap, and for the smallest and hardest stones a copper lap is preferred ; but all the polishing tools, of what metal soever they may be made, are hacked as above described, and used with rottenstone and water.

3. — ROUNDED OR CONVEX STONES, or those said to be cut en cabochon, whether of Carnelian or even several of the harder stones, are in many cases succes- sively wrought by means of the wood mill with fine emery, the list mill with pumice-stone, and leather lap with putty powder, precisely as described under the head Alabaster. This is done on account of the greater elasticity of these apparatus, which enables them to ply more conveniently to the globular forms of the works to be polished, and avoid wearing them in ridges or flat places.

4.— FACETTED WORKS on all stones and hard substances, are for the most part cut by the Lapidary after one of three different modes. First, for pastes or arti- ficial stones, and many soft stones, as amber, carnelian, jet, &c., the facets are usually cut on a lead wheel with emery, and polished on pewter with rottenstone. — Secondly, for some of a harder kind but inferior in hardness to sapphires, the succession of tools is a pewter lap and fine emery for the cut- ting, and a copper lap with rottenstone for the polishing. — Thirdly, for sapphires, the chrysoberyl, and rarely for some few others likewise, a copper lap with diamond powder is used for cutting the facets, and a copper lap with rottenstone for polishing them. — And fourthly, with the diamond, two stones are rubbed in a peculiar manner the one against the other to cut the facets, and they are polished by means of the dop, and an iron lap or skive fed with diamond powder ; this process is more fully described in vol. 1, page 176.

5. — From the comparatively small size of the stones and gems that are cut into facets, they cannot generally be held unassistedly in the fingers, the stone is consequently cemented centrally upon the end of a round stick of wood, nearly like a drawing pencil. The stick when held vertically) gives the posi- tion for grinding the central facet or table of the stone, the stick is inclined to a certain angle for the eight, twelve, or more facets, contiguous to the table ; of which facets, two, three, or four series are commonly required at different inclinations, and, lastly, the horizontal position of the stick serves in cutting the girdle or central band around the exterior edge of the stones.

The several inclinations of the stick on which the stone is cemented, are easily determined by placing the upper end of the stick into one of several holes in a vertical post, fixed alongside the lap, and this retains the inclina- tion very accurately and simply, but all these matters will be further eluci- dated in the 34th chapter on Lapidary Work generally.

6. — The following substances are worked by the lapidary in nearly or exactly the same manner as carnelian, and descriptive articles are introduced hi the catalogue upon each of these particular substances, pointing out their

AND PROCESSES FOR GRINDING AND POLISHING.

1046

Agate	Elvans
Amethyst	Emerald
Aquamarine	Felspar
Beryl	Flint
Bloodstone Fluor Spar
Brazilian Topaz Garnet
Carbuncle Granite
Cat's-eye	Heliotrope
Chalcedony	Jade
Chrysolite	Jasper
Chrysoprase	Lapis Lazuli
Crystal	Marble

principal external features, and also any peculiarities of method, pursued either by the lapidary or other artizan, as the case may be, in working them.

(SUBSTANCES TREATED BY THE LAPIDARY LIKE CARNELIAN.)

Mina Nova

Onyx

Opal

Pastes

Peridot

Plasma

Porphyry

Quartz

Sard

Sardonyx

Serpentine

Topazes.

CAST-IRON. — When the parts of machinery that are made in cast-iron are polished they are treated as described in this catalogue under the general article on MACHINERY made of iron and steel.

THE FRONT OF STOVES, and similar bright works in cast iron; are first ground on large grindstones, and then buffed on large revolving buffs upon which a coating of emery has been fixed by glue. They are sometimes finished by a hand rubber used as a spokeshave having a piece of leather supplied with fine emery and oil, but the rubbers suspended from the ceiling at the end of a powerful spring, are also very judiciously employed in these large works. See the end of the article BURNISHER.

FIRE IRONS are often cast in iron that is afterwards rendered malleable ; which is a rapid way of producing beautiful form, combined with strength and a certain measure of flexibility, see vol. 1, page 259, the works are afterwards case- hardened, that they may admit of a better lustre, and which is generally given by grindstones, glazers, buffs and brushwheels, much the same as in cutlery but on a larger scale.

CAT'S-EYE, a mineral consisting of quartz enclosing amianthus or asbestos, and thence possessing the property emphatically described by the French as chatoyant ; the cat's-eye is polished just like AGATE or CARNELIAN.

CHALCEDONY, a name applied to many siliceous minerals including as varieties the onyx, sard, sardonyx, plasma, heliotrope, and chrysoprase : they are wrought like CARNELIAN, which see.

CHALK when simply scraped, or else crushed under the hammer, is occasionally used in polishing bone, ivory, and some few soft substances, it cuts much

1047 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

more quickly in its natural state as above, than when manufactured into the well known article Whiting.

2. — WHITING is made by grinding the chalk under a runner, washing it for the removal of sand and other impurities, sometimes met with in chalk, and then drying it in lumps. In the prepared state the particles of the chalk are so smooth, as hardly to abrade any but very soft materials, therefore the principal use of whiting when applied to the metals seems to be the absorption of the grease, from works previously polished by other means.

3. — CHALK PREPARED BY DOUBLE DECOMPOSITION. — A recent mode of preparing this polishing material, so as to obtain it perfectly free from silex, (which sometimes accompanies the ordinary kind and is a very active polishing material,) is as follows. Mix filtered and transparent solutions of the muriate of lime, and the carbonate of soda, when these are thrown in contact, the muriatic acid quits the lime and combines with the soda, making common table salt, and the carbonic acid and lime unite and fall down as an impalpable precipitate, which may be collected by filtration. The pure carbonate of lime thus prepared, polishes quickly and smoothly, and nevertheless wears away the material so little as not in any perceptible degree to injure its form or sharpness, it seems rather to burnish than abrade the work.

CHARCOAL. — Sticks of this material are very extensively used for polishing several of the metals, and the action seems to depend on the silex dissemi- nated throughout the substance of the charcoal. Considerable discrimina- tion is required in the selection of pieces, from the bulk of that which is prepared from small green wood for metallurgical and domestic purposes, as but few pieces possess the requisite cutting quality ; the workmen gene- rally try it either on the teeth or finger nail.

The stick of charcoal is applied at an angle of about 40 or 50 degrees to the work, the position best suited to every piece being found by trial. Some pieces will cut rapidly and coarsely with water, others more slowly and smoothly with oil ; and pieces of good quality are very highly prized by workmen. Some artizans conceive that charcoal cuts more greedily when moistened with vinegar, but which fluid is objectionable as it stains the metals.

In the course of polishing, the charcoal picks up the abraded particles of metal, they sometimes enter its pores, and would scratch the work if allowed to remain on the charcoal, consequently two pieces are mostly used ; the one merely to clean the other by rubbing them together at their ends in the same manner that the painter rubs two lumps of pumice-stone together to clean their surfaces. In finishing delicate works, and laying the grain, abundance of oil or water should be used, so as to float off the minute particles of metal removed in the process.

The charcoal prepared from the wood of elder appears to have the decided preference especially for polishing the steel and copper plates used by

AND PROCESSES FOR GRINDING AND POLISHING. 1048

engravers, both in their first preparation, and in the removal of the burrs thrown up by the graver. To ensure the possession of the true sort, it is recommended to obtain the waste pieces of elder from the rule maker, to cut them into short pieces, and then to burn them in a crucible filled with sand, in order to exclude the air, otherwise the entire substance of the wood may be burned to ashes; the kitchen or forge fire may be used, and the crucible should be allowed to cool in the embers.

The charcoal made from willow truncheons, is described as being much in esteem by the manufacturers of copper plates for engravers ; and elm wood is also stated by Mr. Thomas Gill as being suitable for making the charcoal for polishing. See Tech. Repos. vol. ii. p. 264.

[ARNLEY FOREST STONE, See HONE SLATES, article 2.

[RYSOBERYL, a hard aluminous stone, of a green colour, and semi-trans- parent ; it is chiefly procured in Brazil, and is worked like the SAPPHIRE.

[RYSOLITE or PERIDOT, a yellow gem, sometimes tinged with green or brown, that is obtained principally from the Levant. It possesses a pecu- liarity, inasmuch as although it is slit and facetted just like Carnelian, it can scarcely be well polished, otherwise than by means of a copper lap with rottenstone, a few drops of sulphuric acid being used instead of water

to moisten the rottenstone.

•

CHRYSOPRASE, a variety of CHALCEDONY, of an apple green colour, and semi- opaque, which is much prized by jewellers. It is cut and polished after the mode of Carnelian, and frequently of a convex form, or en cdbochon.

CLAY, see LOAM.

CLOTH is extensively used as a vehicle for polishing powders of all kinds ; woollen and felted cloths are the most in requisition. Some of the felted cloths used for marble, glass, &c., and which are called nap, are upwards of half an inch thick. Thinner cloths, such as the stout cloths used for great coats and for the blankets of printing presses, are also employed, especially when discarded from their original purposes, and also ordinary woollen cloth, including the list, or selvedges, and so on.

Old worsted stockings are used hi many trades ; linen and cotton cloths and rags are also employed, but, from being thinner, are less generally used than woollen cloths. CLOTH WHEELS, see Wheels, articles 61 to 64.

)LCOTHAR OF VITRIOL, see OXIDE OF IRON.

>NES.— The principal modes of grinding cones will be explained in Chap. XXXIII., Sect. 3.

1049 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

COPPERSMITH'S WORK, subsequently to its having been annealed for the last tune, and before it is planished with the hammer, is generally pickled with sulphuric acid and water, in about equal parts, and scoured with coarse red tripoli and water, to remove the oxidation caused by the fire. The work when planished is cleaned, 1st, with crocus and oil, 2ndly, the oil is rubbed off with whiting, and 3rdly, the work is polished with dry crocus, the rubber being generally an old worsted stocking.

COQUILLA NUT receives a good natural polish by the following applications : — 1st, glass paper ; 2ndly, tripoli and oil on rag ; 3rdly, dry putty powder or rottenstone. This routine gives a more durable polish than hardwood lacker applied with friction, a mode of finish also employed.

Common turned and filed works are often finished with one or two coats of varnish, applied like paint with a brush, this gives them a coarse brightness.

Eccentric turned works hi coquilla nut are polished very slightly with putty powder or rottenstone and oil on a brush ; but the tools should be very sharp, so as to leave but little or no necessity for polishing at ah1.

CORAL. — The red variety of this singular substance is somewhat used hi jewellery, and admits of an excellent polish. When hi rounded pieces, it is polished after the routine followed by the lapidary with ALABASTER ; when coral is cut in facets as for beads, &c., it is worked like CARNELIAN.

COROSOS or the vegetable ivory nut, see vol. 1, page 112, is polished just the same as the ivory of the elephant, and other animals ; but the vegetable ivory, apparently from its facility of absorbing moisture, alters sensibly in size and form during the process of polishing.

CORUNDUM includes very dissimilar minerals, all consisting almost entirely of highly crystalline alumina, namely, — Precious Corundum, or the Sapphire and Ruby, — Common Corundum — and Emery. — The last two are the common abrasives of the Asiatics and Europeans respectively ; and all are separately described under their respective heads in this catalogue.

1. — COMMON CORUNDUM, says Phillips, probably from its texture, has received the name of imperfect Corundum ; and from its hardness, and from its occasional pearly lustre, Adamantine Spar : it occurs everywhere from China to Bengal, and is met with of various colours, but more often of a greyish or greenish tint. Corundum is much used in India for Corundum Wheels and Rubbers, the methods of constructing which are described in the following articles : —

2.— CORUNDUM WHEEL. — « This kind of lapidaries' wheel is called in the Tamul language Couroundum-sane. It is composed of corundum, more or less finely powdered, cemented together by lac-resin : the proportions, by volume, consisting of two-thirds of powdered corundum, and one-third of lac-resin. The corundum powder is put into an earthen vessel, and heated over a clear

AND PROCESSES FOR GRINDING AND POLISHING. 1050

fire ; and when of a sufficient heat, (which is ascertained by a small piece of the resin readily fusing,) the resin is added in portions, carefully stirring at the tune, to form an intimate mixture. When made into a mass, it is put upon a smooth slab of stone, and kneaded by beating it with a pestle ; it is then rolled upon a stick, reheated several times, continually kneading it until the mixture is perfectly uniform. It is afterwards separated from the stick, laid again upon a stone table which has been previously covered with very fine corundum powder, and flattened into the form of a wheel by an iron rolling pin. The wheel is then polished by a plate of iron and corundum powder ; and finally, a hole is made through the middle of it by a heated rod of copper or iron.

" These wheels are made with a grain more or less fine, as the coarser perform the first rough work, and the finer cut the stones. They are mounted on a horizontal axis, and the workman, sitting on the ground, makes them revolve with a spring-bow, which he moves with his right hand, at the same time holding the stone with his left against the wheel, the latter being, from time to time, carefully moistened and sprinkled with corundum powder. The polish is given by wheels of lead and very fine corundum powder."

3. — CORUNDUM RUBBERS. — " The proportions generally used in making the corun- dum rubbers are, for the coarse, lac, 8, corundum, 1 ; for the medium, lac, 12 to 16, and corundum 1, by weight. The fine rubber is made by mixing the grindings of agates, carnelians, and the like, with lac ; and as the lapidary's wheels, upon which they are ground are made of corundum and lac also, the grindings must contain a portion of those materials; their pro- portion, in composition, must vary according to the nature of the stone from which they are ground ; but 6 of lac to 1 of grindings, may be considered a good proportion generally.

" The lac is first melted, and the corundum, after it has been reduced to a powder, mixed intimately with it. The composition is then moulded in the shape of a brick about 6 x 4 X H inch, with a handle of wood about 6 inches at one end, having a rise of about 30 degrees for the convenience of working it."

Some dentists employ old files thinly coated with a cement of emery and shell lac, in finishing the enamel or mineral teeth. The incorporation of the materials is greatly assisted when the emery or corundum is heated to the melting point of the gum resin.

"HOCUS. See OXIDE OF IRON.

JRYSTAL, or ROCK CRYSTAL, is a popular name for Quartz, or pure crystalline silex, the finest and largest crystals of which are found in Madagascar Dauphin^, and the Alps ; the so called Bristol diamonds are nothing but fine specimens of quartz cut and polished.

The Brazilian pebbles for spectacles are lenses ground out of pure, trans-

1051 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,.

parent, colourless quartz, the stone is cut into slices by the lapidary, after- wards it is snipped into the form of the lenses, with nippers which resemble wide flat pliers, and are made of soft iron, in order that the quartz or glass may slightly imbed itself, to gain a hold, which could not take place with the hard steel faces of ordinary pliers ; lastly the pieces of crystal are ground into the form of lenses and polished by the optician, exactly in the same mode that he employs for glass lenses, and which will be described.

Many remarkable specimens of cups, tazzas, and other works of art have been formed by abrasion from the beautiful material rock crystal, or quartz ; some of these may be seen in the British Museum, and excite astonishment by the laborious perseverance they evince.

CUTLER'S GREEN HONE, see HONE SLATES, article 6.

CUTLERY is ground and polished with the various natural and artificial grinders, the constructions and applications of which are described under the article WHEELS in this Catalogue : the ordinary succession of the principal processes will be therefore alone adverted to in this place.

1. — FINE CUTLERY. — The manufacture of a razor blade of the best quality may be viewed as a suitable example of the mode of treating articles of fine cutlery : the succession of processes is as follows :— 1st, the blade is moulded ; 2ndly, forged ; 3rdly, ground into form and scorched, or the black scale ground off : this is done on a dry coarse Wickersley grit stone ; 4thly, the blade is drilled for the joint and stamped with the name ; 5thly, hardened and tem- pered (see vol. 1, page 248) ; Gthly, ground on a wet Wickersley grit stone from 4 to 8 inches diameter ; 7thly, the shoulders of the blade are sometimes ground on a fine dry stone ; for this purpose the edge of the stone is waxed up, or kept keen by rubbing bees-wax on the side near the periphery to hold the particles of the stone together ; the wax keeps the stone from crumbling away, but the dry stone should be sparingly used after hardening, as it is liable to soften the edge of the blade ; 8thly, the blade is lapped on a lead lap of a diameter a little smaller than the grindstone employed in the 6th process — the lap scarcely alters in course of use, and gives the true curve to the surfaces ; 9thly, the tang and back are glazed on a leather glazer ; 1 Othly, the razor blade is polished on a soft buff wheel fed with dry crocus and revolving very slowly. This completes the manufacture of the blade, which is then ready to be handled preparatory to the setting, which will be described in Chapter XXXII.

The best penknife blades and scissors are treated in a similar manner to the above.

2. — COMMON CUTLERY. — All work should be scorched or dry ground to remove the scale before hardening, but this is frequently omitted in common works, and the usual routine after hardening is, 1st, the coarse wet stone ; 2ndly, the fine wet stone ; and, Srdly, the buff with fine emery. Sometimes one or

AND PROCESSES FOR GRINDING AND POLISHING. 1052

more intermediate stages between the extremes of the common and best cutlery are resorted to, according to price. Common razors, after being hardened, are, 1st, ground on a wet stone from 12 to 15 inches diameter ; 2ndly, lapped ; and, 3rdly, polished. 3. — EDGE TOOLS are treated the same as common cutlery.

DEVONSHIRE OILSTONE, see HONE SLATES.

DIAMOND, this remarkable and most useful gem has been considered at some length in the first volume, pages 175 — 180 — first as regards the processes of splitting, cutting, and polishing diamonds for jewellery, — then its use in the hands of the glass-cutter and glazier — and lastly several of the uses of the diamond as tools, and which applications include the formation of the jewelled holes of ruby and sapphire for watches and chronometers, every process of which requires the intervention of the diamond.

In this place it is proposed to describe the three different modes in which the diamond powder is prepared for the use of various artizans, as the subsequent chapters will treat of its practical application by the lapidary, gem-engraver, and others.

1. — DIAMOND POWDER FOR LAPIDARIES' USE. — Lapidaries generally purchase small imperfect diamonds, and the fragments removed by splitting or cleavage, in preparing stones for jewellery. These fragments are crushed in a hardened steel mortar with a cylindrical hole about half an inch diameter, and nearly two inches deep, the bottom of the cavity is hemispherical or constitutes perhaps the third part only of the circle, the pestle almost fits the aperture of the mortar and is curved to the same degree, there is also a cover that fits a recess in the mortar to prevent the escape of any of the valuable dust.

The pestle is struck a few blows with a light hammer, and is twisted round between each blow, this readily crushes the diamond, which, although so incomparably hard, is brittle from its crystalline structure. The frag- ments are carefully collected, and mixed with a little of the oil of brick, in a small cup or any convenient vessel, which should have a cover to keep the prepared diamond from being wasted. When not wanted for immediate use, the prepared diamond is kept in a pasty condition between two very small watch glasses, cemented with soft wax around their edges.

2. — DIAMOND POWDER FOR SEAL ENGRAVERS. — This is required to be much more finely pulverized than for lapidary work, therefore having been crushed as above, the fragments are ground into a thick paste, with a few drops of olive oil, in another pestle and mortar of hardened steel, the surfaces of which are both exactly spherical with a curvature of from one to two inches radius ; this mortar has a tin cover that it may serve as the recipient for the powder which has been ground. Sometimes for reducing the powder after it has been crushed, flat grinders of hardened steel are employed, but these are less generally used than the spherical form. Rough diamonds of a dark steely colour are generally selected by the seal engravers, as these are con- sidered the hardest stones.

1053 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

3. — DIAMOND POWDER FOB WATCH JEWELLERS. — These artizans who use

larger quantities of diamond powder than the above, for cutting as well as for polishing rubies, sapphires, and topazes, pursue a different method. They purchase the fine dust, or diamond bort3 that is rubbed off stones used for jewellery hi the act of cutting them into facets, in which process two dia- monds are operated upon at once, and caused mutually to abrade each other in forming the one facet on each stone ; see vol. 1, page 176. The diamond bort is usually washed for its separation into two or three sizes, exactly after the manner of washing emery, except that the process is carried on upon a very much smaller scale, and the finest olive oil is used instead of water, the diamond powder is generally laid by under a stratum of oil to prevent waste ; oil is employed because of its viscidity, it does not allow the diamond to sub- side so quickly as water, and it is moreover the fluid always employed in the using and preservation of the diamond by these artizans.

4. — THE APPLICATION OF DIAMOND POWDER to the splitting or sawing of minerals will be described in the chapter XXXIV. on Lapidary work. The coarser diamond powder used for grinding or cutting is generally burnished into the surface of the iron lap or skive of the diamond worker, and frequently also into the iron, copper, or other laps used by different artizans : hi cutting sapphires the lapidary works the diamond powder into the copper lap, with a smooth piece of agate applied with gentle pressure. The finer diamond powder used for polishing, is simply applied on the surface of the tools, with the finger, or a small flattened wire used as a spatula. The gem engraver puts the diamond hi minute hollowed disks of tin, two of which hi fact are soldered to a strip of tin, and worn on the forefinger of the left hand as a ring : the one disk, of half an inch diameter, contains the mixed diamond paste, the other disk, one or two drops of the oil of brick, with which the tool is frequently lubricated.

5. — FICTITIOUS DIAMONDS. — The white sapphire is sometimes used hi jewellery as a substitute for the diamond, and the zircon is said also to be so employed when deprived of its colour by heat : the so-called Bristol diamonds are crystals of quartz cut and polished, but those imitations which are con- sidered to come the nearest to real diamonds, in point of lustre or colour, though not in hardness, are met with amongst the pastes of the first quality, which are made artificially, and polished on pewter wheels with rottenstone, and not on copper wheels, like most of the hard gems.

DUTCH RUSH, or the Equisetum Hyemale, is said to be a native of Scotland, and to thrive best in the marshy places in mountainous districts ; it is gathered in pieces two or three feet long, which are intersected by knots at distances of four to six niches. The rush is usually of the size of a writing quill, of a greenish-grey colour, with a groovy surface that feels rough like fine glass paper, from the quantity of silex disseminated throughout its exterior surface, and upon which circumstance depends its suitability to polishing hardwoods, alabaster, marbles, and some other substances. According to

AND PROCESSES FOR GRINDING AND POLISHING. 1054

the analysis of Sprengel, Dutch Rush, wheii dry, contains rather more than 13 per cent, of ashes, viz. Silex, 6-38, Garb. Lime, 5-51, Potash salts, -79, and Alumina -46.

For the application of Dutch Rush, see WOOD, article 5, and ALABASTER, article 1.

EDGE TOOLS are treated of under the head CUTLERY.

ELECTRUM or GERMAN SILVER. — See Silver, Albata, and Brass. The respective modes being used, according to the nature of the works made in this triple alloy, which differs greatly as to value and quality.

ELVANS, the modes of working and polishing porphyry and granite, and also the elvans, which are of intermediate character between these two, are described in pages 169 to 172 of the first volume. By the lapidary, the elvans and porphyries are wrought like CARNELIAN, the granite somewhat differently, on account of its unequal hardness, see GRANITE.

EMERY.

1. — ORDINARY PREPARATION OF EMERY. — The following is the manufacturers' ordinary process ; the lumps of emery stone are broken up precisely after the manner of stone for repairing Macadamized roads, and into lumps of similar size. The lumps are then crushed under stampers such as are used for pounding metallic ores, and driven by water or steam power ; the stampers are considered to leave the particles more angular than they would be if ground under runners, a mode sometimes employed. The coarse powder is then sifted through sieves of wire cloth, which are generally cylindrical, like the bolting cylinders of corn mills, but the sieves are covered with wire cloth, having in general about 90 to 16 wires to the inch. The following table shows the numbers of wires usually contained in the sieves, and the names of the kinds respectively produced by them : —

16. Corn emery.

24. Coarse grinding

36. Grinding

46. Fine grinding

60. Coarse flour emery 70. Flour

80. Fine flour

90. Superfine flour

53. Super grinding

No. 16 sieve gives emery of about the size of mustard seed, and coarser fragments extending nearly to the size of peppercorns, are also occasionally prepared for the use of engineers.

The sieves have sometimes as many as 120 wires in the inch, the very fine sizes of emery are however more commonly sifted through lawn sieves; but the finest emery that is obtained from the manufacturers, is that which floats in the atmosphere of the stamping room, and is deposited on the beams and shelves, from which it is occasionally collected.

The manufacturers rarely or never wash the emery, which is mostly done

1055 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

by the glass workers, opticians, and such others as require a greater d( of precision than can be obtained by sifting. 2. — WASHING EMERY BY HAND. — Washing-over or elutriation, as the process is called by chemists, is a valuable application of the law of gravity to the chemical, metallurgical and mechanical arts. Thus the alluvial deposits of some of the tropical rivers are washed for the separation of the particles of gold they contain. A small portion of the mud of the river is stirred in a large quantity of water contained in a broad shallow basin, the gold being several times as heavy as the earthy particles quickly subsides, and the mud which remains suspended for a long period in the water, is removed by pour- ing off the water from the valuable sediment.

In a similar manner the particles of emery and other powders may be separated according to their magnitudes, in a more accurate manner than can be accomplished by sieves. A portion of emery, powder of uncertain size is thoroughly well mixed in a large quantity of water, as in a common wash hand basin, and at the end of 1 0 seconds the liquid is poured off from the sediment which has fallen down in that period ; the sediment is laid aside in a separate vessel. The bulk is again stirred and poured off at 1 0 seconds, and this second sediment added to the first, and which process is repeated until no further sediment is deposited in the period of 10 seconds ; the process requires watchfulness and a steady hand. A fresh deposit is similarly collected from the residue after a longer period of rest, say 20 seconds, until the whole quantity of emery is divided into grains of so many sizes, as may be required for the particular branch of manufacture for which it is intended ; thus — 3. — EMERY FOR THE CONSTRUCTION OF MECHANISM. — The author has been for many years in the habit of employing emery of twelve degrees of fineness, part of them prepared by himself by washing over, namely : No. 1. Corn emery of commerce prepared by sifting

„ 2. Grinding „

„ 3. Fine grinding „

,,4. Superfine grinding „

„ 5. Deposited at the end of 2 seconds,

» 6' n 5 »

» 7. „ 10 „

„ 8. „ 20 „

„ 9. „ 60 „

„ 10. „ 3 minutes.

,,H. „ 15 „

,,12. „ 60 „

The emeries of the sizes 5 to 12 are preserved in glass bottles, to prevent them from becoming accidentally mixed or contaminated with foreign substances.

4. — EMERY FOR OPTICAL PURPOSES. — Mr. Ross mixes four pounds of the flour emery of commerce, with 1 ounce of powdered gum arable, and then throws the powder into 2 gallons of clean water. He collects deposits, as above

AND PROCESSES FOR GRINDING AND POLISHING. 1056

described, at the end of 10 seconds, 30 seconds, 2 minutes, 10, 20, and 60 minutes, and that which is not deposited by one hour's subsidence is thrown away as useless for grinding lenses. The use of the gum arable, which renders the water slightly viscid, was recommended by Dr. Green for pre- paring red oxide of iron, for polishing specula. See Trans. Soc. of Arts. Vol. L. p. 152.

5. — WASHING EMERY IN THE LARGE WAY. — Washing emery by hand as above explained is far too tedious for those who require very large quantities of emery, ssuch as the manufacturers of plate glass and some others, who generally adopt the following mode : — Twelve or more cylinders of sneet copper, of the common height of about two feet, and varying from about 3, 5, 8 to 30 or 40 inches in diameter, are placed exactly level, and communicating at their upper edges, each to the next, by small troughs or channels ; the largest vessel has also a waste pipe near the top.

At the commencement of the process, the cylinders are all filled to the brim with clean water, the pulverised emery is then churned up, with abundance of water in another vessel, and allowed to run into the smallest or the three inch cylinder, through a tube opposite the gutter leading to the second cylinder. The water, during its short passage across the three inch cylinder, deposits hi that vessel, such of the coarsest emery as will not bear suspension for that limited time ; the particles next finer, are deposited hi the second or the five inch cylinder, during the somewhat longer time the mixed stream takes in passing the brim of that vessel and so on. Eventually the water forms a very languid eddy in the largest cylinder, and deposits therein the very fine particles that have remained in suspension until this period, and the water lastly escapes by the waste pipe nearly or entirely free from emery.

In this simple yet elegant arrangement, time is also the measure of the particles respectively deposited hi tthe 12 or more vessels, their number being determined by the quantity of sizes respectively required hi the manu- facture to which the emery is applied. When the vessels are to a certain degree filled with emery, the process is stopped, they are emptied, the emery is carefully dried and laid by, and the process is recommenced. 6. — EMERY PAPER is prepared like glass paper, and of about six degrees of coarseness. The powders sifted through the sieves with 30 and 90 meshes per linear inch being in general the coarsest and finest sizes employed. When used by artizans, the emery paper is commonly wrapped around a file or a slip of wood, and applied just like a file, with or without oil, according to circumstances. The emery paper cuts more smoothly with oil, but leaves the work dull.

7. — EMERY CLOTH only differs from emery paper in the employment of thin cotton cloth instead of paper, as the material upon which the emery is fixed by means of glue. The emery cloth, when folded around a file, does not ply so readily to it as emery paper, and is apt to unroll, therefore smiths, engineers and others, give the preference to the emery paper and emery

1057 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

sticks ; but for household and other purposes, where the hand alone is used, the greater durability of the cloth is advantageous. Edwards' patent for emery cloth was taken out in December 1 830.

8. — EMERY STICKS, are rods of deal about 8 to 12 inches long, planed up square, or with one side rounded like the half round file. Nails are driven into each end of the sticks as temporary handles, they are then brushed over one at a time, with thin glue, and dabbed at all parts in a heap of emery powder, and knocked on one end to shake of the excess, two coats of glue and emery are generally used. The emery sticks are much more economical than emery paper wrapped on a file, which is liable to be torn.

9. — EMERY CAKE consists of emery mixed with a little suet chopped small, rendered down, and mixed with a very little bees' wax, so as to constitute a solid lump, with which to dress the edges of buff and glaze wheels. The ingredients should be thoroughly incorporated by stirring the mixture whilst fluid, after which it is frequently poured into water, and thoroughly kneaded with the hands, and rolled into lumps before it has time to cool. The emery cake is sometimes applied to the wheels whilst they are revolving ; but the more usual course is to stop the wheel, and rub in the emery cake by hand, it is afterwards smoothed down with the thumb.

10. — EMERY PAPER, OR EDWARDS' PATENT RAZOR STROP PAPER, is a new article in which fine emery and glass are mixed with the paper pulp, and made into sheets as in making ordinary paper. The emery and glass are said to con- stitute together 60 per cent, of the weight of the paper, which resembles drawing paper except that it has a delicate fawn colour. This emery paper is directed to be pasted or glued upon a piece of wood, and when rubbed with a little oil to be used as a razor strop, of which it is by far the least expensive of any previously in use. The patent for this invention was granted to the Rev. Mr Edwards, in November 1843, and he was rewarded for the same by the Society of Arts, in June, 1846.

11. — BARCLAY'S ARTIFICIAL EMERY STONE. — The numerous articles already given on emery, and various ways in which it is prepared and used will be concluded by a description of the invention of a Mr. Henry Barclay, who took out letters patent in August, 1842, for a very efficient mode of combining powdered emery into disks and laps of different kinds, suitable to grinding, cutting, and polishing glass, enamels, metals, and other hard substances. The process of manufacture is as follows : —

Coarse Emery Powder is mixed with about half its weight of pulverized Stem-bridge loam, and a little water or other liquid, to make a thick paste, this is pressed into a metallic mould by means of a screw press, and after having been thoroughly dried, is baked or burned in a crucible, muffle, or close receiver, within a furnace, at a temperature considerably above a " red heat," and below the "full white heat."

In this case the clay or alumine serves as a bond, and unites the particles very completely in a solid substance, called A rtificial Emery Stone, which cuts very greedily, and yet seems hardly to suffer perceptible wear or destruction.

AND PROCESSES FOR GRINDING AND POLISHING. 1058

Superfine Grinding Emery, is formed into wheels exactly in the same manner as the above, but the proportion of loam is then only one-fourth, instead of one-half that of the emery : these emery stones, which are of medium fine- ness, cut less quickly but more smoothly than the above.

Flour Emery, when manufactured into artificial stones, requires no uniting substance, but the moistened flour emery is alone forced into the metal mould and fired, as some portions of the alumine present seem abundantly to suffice to unite the remainder. These fine wheels render the works sub- mitted to them exceedingly smooth, but they do not produce a high polish on account of the comparative coarseness of the flour emery.

Stourbridge loam is by no means the only ingredient used in uniting the particles of emery, as many other substances answer as well ; such as slate, Yorkshire gritstone, crocus, &c., and in this way the hardness and cut of the emery stone may be varied to a great extent.

Most of the grinders made of the Emery stone are formed with central holes, so as to admit of being attached to the lathe upon appropriate chucks or spindles ; and the substance is so porous as to absorb much water, which is gradually thrown to the surface by the centrifugal motion so as to keep the edge conveniently moist, or with excessive velocity, the water is thrown off as in trundling a mop. Mr. Barclay has made the disks of various dia- meters from £ inch to 8 or 10 inches diameter, but the difficulty increases with the size, as the large ones are liable to warp and crack in the firing.

When the emery stone laps are required to have plane surfaces, angular or convex edges, &c., that could not be readily moulded, the composition is partially fired at a low heat, then turned in a lathe to the specific form, and the firing at a nearly white-heat completes the manufacture.

The coarse emery stone has been tried in cutting glass, and is reported then to fulfil in itself the offices, first, of the iron disk fed with sand used in roughing, and secondly, of the Lancashire fine grit stone used in smoothing ; as when of proper consistence, the artificial emery stone cuts as quickly as the former, and as smoothly as the latter, and has the advantage of main- taining its form in an eminent degree.

Small fragments of these disks, spoiled in the firing, have been successfully used in scrubbing off the rough sand coat of door plates, mouldings, &c., cast in brass, &c., and indeed the Patent Emery Stone eminently deserves more extended use than it has, up to the present time, attained,

It remains to be observed that Mr. Barclay took up the subject of the Artificial Emery Stone from necessity, as in his professional employment of making artificial teeth and gums, of a kind of hard porcelain, he found the small grindstones, (tediously prepared by rubbing down waste flakes of the Yorkshire stone used for paving into flat plates, and which are afterwards drilled and turned to the requisite forms,) wore out amazingly quick, even when assisted by coarse sand and water ; but the present scheme fulfils the office of the grindstone in an admirable manner ; and some small artificial stones made as above have been in almost daily use for 3 or 4 years.

VOL. III. D

1059 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

.

The project bears an evident analogy to Mr. Prosser's Patent making buttons, various articles, and even fire bricks, out of dry clay in powder compressed in a mould and afterwards burned, and it offers certain advantages over the corundum wheels used in India, and described under the head CORUNDUM.

EMERALDS. — These valuable stones, the finest of which are found in Peru, are considered to be very soft gems, and in consequence they require more than ordinary care in their polishing, and still do not admit of such acute angles and edges being given to them as to many of the harder gems. The Emerald is worked just like CARNELIAN.

ENAMELS. — These are metallic surfaces covered with a thin coating of glass of various colours, and which is sometimes partially transparent, but generally opaque. The enamel or glass is ground to powder, mixed with some vehicle, such as turpentine, or oil of spike, and spread on as a thick coating of paint, and when dried, the whole is heated just sufficiently to fuse the enamel, and cause it to adhere to the metal.

The work is placed within a muffle, which is in many cases a miniature arched vault open at one end, placed in the midst of a small furnace, and surrounded by burning fuel, which keeps it at the red heat, although the fuel cannot possibly touch the work. In other cases the furnace is made of sheet iron ; it then measures externally about 20 inches long, 12 wide, and 10 deep, and is mounted on wrought iron legs that support it, so that the opening or door, which is at the one end, may be on the level with the eye of the artist, whilst from the opposite end proceeds the flue leading into a chimney. The whole apparatus bears some resemblance to a German stove, or rather, to a laundry stove considerably elevated, but the muffle, or a heated chamber corresponding therewith, is always provided for the reception of the work to be enamelled to protect the same from the flame and smoke of the fuel.

Many of the enamelled works can hardly be said to be polished artificially, as the lustre is produced simply by the process of fusion ; thus the enamelled faces of watches, when the ground has been fired, only require the figures to be added, as the vitreous surface is mostly smooth enough from the fusion without being polished ; and in less favourable cases the work is only ground to a level but dull surface, and afterwards just raised to the melting point, so as to fuse the surface, and thereby give it the polish.

The backs of gold watches and numerous articles of jewellery, including mourning rings, are so enamelled as to show various devices or inscriptions in gold, upon a ground or general surface of enamel ; in this case the work is engraved, all the parts where the enamel is to appear being cut away by the graver, and the spaces are afterwards filled in with the pulverised enamel, which is burnt in, and lastly, the whole is polished down to a uniform surface.

Formerly nearly all the enamelled works were polished by the lapidaries, who used, 1st, the horizontal lead mill with fine emery for grinding ; 2ndly,

AND PROCESSES FOR GRINDING AND POLISHING. 1060

lead with rottcnstone and water ; and 3rdly, the leather lap or buff wheel with putty powder. But the enamellers of the present day mostly polish their own work, and employ either an ordinary lathe with a mandrel upon which the laps are screwed like chucks, the cylindrical edges of the laps being alone used, or else they employ a polishing lathe similar to those of cutlers and others.

The French enamellers commonly select instead of emery, a hard white pulverised porcelain, called white emery, which is manufactured at the Royal Manufactory of Porcelain at Sevres, and they afterwards polish with yellow tripoli ; the first is applied on a lead or wooden wheel, and the latter on a buff.

When enamels are polished by hand, the work is first roughed down with slips of water of ayr stone and water, used after the manner of a file ; after which the different artists use slips of boxwood, mahogany, or metal, first, with pumice-stone, and then with crocus, nearly as for gold.

FACETS, a few words are given on the cutting of the facets or gems at the con- elusion of the article on Carnelian, but the subject will be considered more at length in the chapter on lapidary work.

FAYRER'S SWING HONE.— This is a flat and parallel slip of brass, in form like a hone, but with pivots at the ends by which it is suspended in two notches, so that this metal lap, or factitious hone, may accommodate itself to the angle at which the razor or other instrument is applied to it. The one side of the bi'ass is first used with fine oilstone powder and oil, afterwards the second side with pulverised water of ayr stone and oil, and the razor strop is afterwards resorted to, see Trans. Soc. of Arts, vol. 48, p. 248.

FELSPAR. — The fine varieties of this siliceous mineral, display most beautiful and varied iridescent colours ; namely, blues and greens in the Labrador Felspar, a beautiful apple green in the Amazon Stone, and a pearly white in the Adularia or Moonstone, the colours are best seen when the specimens are polished, which is effected as with Carnelian although Felspar is scarcely so hard.

FELT or Felted Cloth is very much used for polishing especially for marble. See CLOTH and MARBLE.

> FISH SKIN is the skin of the Dog Fish, and some others which is dried as its

only preparation. The scales of the skin are hard and pointed and stand up obliquely, so that they cut or abrade very effectually in the one direction, but not in the other. Fish skin is more durable but less generally con- venient than glass paper, to which it probably gave rise. It is however now but little used in polishing, although in clearing off rounded and irregular works, as in pattern making, from the fish skin being somewhat rigid, when bent round the finger it may be almost used as a file, and it has the further advantage of leaving nothing behind it, whereas, glass paper commonly deposits D 2

1061 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

some of the particles of glass in the surface of the wood, to the detriment of any tools subsequently employed. The fins should be selected for fine works.

FLANDERS BRICKS, these which are now equally or better known as Bath bricks, are made in large quantities of a clay found at Bridgewater, and which contains a considerable proportion of fine sand. Besides the extensive employment of these bricks for domestic purposes, and in making founders cores, they are sometimes employed when rubbed to powder, in polishing bone, ivory, and soft metals, and also in dressing cutlers dry buff wheels, boards for cleaning table knives, &c. Trent sand is preferable when it can be procured.

FLAT SURFACES. — The principal modes of grinding flat or plane surfaces, will be described in Chap. XXXIII. sect. 1.

FLINT is not frequently polished by the lapidary but is then treated like Carnelian. Until of late years one of the greatest uses of this substance was for procur- ing fire, but percussion caps and Congreve matches have nearly superseded this employment of flint, which still however enters largely into the composi- tion of porcelain, and has given the name to Flint Glass, although hi this manufacture it is now rejected in favor of the more available article, the pure sand obtained from Alum Bay, Isle of Wight, Maidstone, and elsewhere. Flint is employed in the mechanical arts, as the " louldering stone" for rubbing down to a smooth face the laps, buffs and glaze wheels of the cutler, and pulverized flint has also obtained the employment described in the succeeding article.

Flint. The late Mr. Larkin in finishing his beautiful wood models of crystals, employed calcined flint pulverized and glued upon wooden face wheels, as more fully described under the heads GLASS PAPER, and WHEELS, article 59.

FLUOR SPAR. — This substance from the confusion in the arrangement, and the frangibility of its crystals requires a peculiar and careful treatment whilst being turned into form, and which is described at page 168-9 of the first volume. The smoothing and polishing are conducted almost the same as in marble, but as fluor spar requires a longer continuance of the polishing process, it demands considerable care to preserve the square fillets of the work from being rounded in the polishing, and with which object the powders are sometimes applied on small square slips of metal or wood, the sides of which are used somewhat as a file so as to present a superior degree of definition and permanence in the form of the polishers, than would be obtained by the exclusive use of cloth applied with the fingers.

The lapidary pursues the same method in polishing fluor spar as carnelian, but he does not succeed so well as the Derbyshire workmen, and only pro- duces what may be termed "a greasy polish."

AND PROCESSES FOR GRINDING AND POLISHING. 1062

F REESTONES.- Few or none of these admit of being polished, but many of them are rubbed smooth ; the rubber being in general a smaller piece of the same kind of stone, sometimes used alone, at other times with a plentiful supply of sharp sand and water. In turned works, the stone rubber is smaller and held in the hand, the process being frequently conducted dry, and without additional sand.

GANNISTER STONE a species of slaty-stone somewhat resembling the Charnley Forest, or Mount Sorrel stone, and which is abundantly used in repairing the macadamized roads around Sheffield. When calcined, pulverized, sifted, and applied on a straight buff stick of the bull neck leather, the Gannister stone is preferred to most other materials, for smoothing the threaded shoul- ders of pocket knives after they have been filed, as it is considered better to preserve the keen threads or projecting ridges of the shoulders than other abrasive powders. The work is completed on a wheel brush fed with fine emery and oil, followed by another with crocus and oil.

GARNETS are worked by the lapidary just like Carnelian, so far as the succes- sion of the tools is concerned, the production of the facets is further noticed in the chapter on lapidary work. The fine large Garnets when cut en cabochon, or with a rounded face, are known as Carbuncles and are sup- posed to be the gems so designated also in the Scriptures.

GERMAN HONE.— See HONE SPATES, also the article on setting razors in Chap. XXXII.

GLASS is polished in various different manners, some of which are else- where particularized. Thus Plate Glass, is roughed with sand, smoothed with emery, and polished with crocus. See Chap. XXXIII. Sect. 1. Glass Lenses, are roughed out with sand, figured with emery, and polished with putty powder. See Chap. XXXIII. Sect. 4. Cut glass for household purposes and toys, is roughed with sand, smoothed on a Lancashire grit-stone, then with pumice-stone, and lastly is polished with putty or rottenstone see Chap. XXXIII. Sect. 5.

Lapidaries in cutting glass for jewellery adopt the mode described in this catalogue as used by them for alabaster, with the exception that they omit the wooden mill.

Glass is used as a vehicle for polishing powders by watchmakers, watch- jewellers, and some others. See BRASS, article 6, and MACHINERY, article 13.

GLASS PAPER. — In making this useful article, the fragments of broken wine bottles are carefully washed to remove all dirt, the glass is then crushed under a runner, and sifted into about six sizes as in manufacturing emery. The paper is brushed over with thin glue, and the pulverized glass is then dusted over it from a sieve, which completes the process. Sometimes two coats of glue and glass are applied, or Venetian red is mixed with the glue to

1063 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

give that tint to the glass and sand papers, and under Edward's Patent, thin cotton cloth is used instead of paper, as the vehicle for the glass.

See FLINT, an article recommended instead of glass for the above and other purposes.

GLAZERS, or GLAZING WHEELS. — Wooden wheels covered with leather when charged with fine emery receive the above names, but when supplied with crocus and used for finer purposes they are called polishers. Such wheels charged with emery cake, bouldered and waxed to deaden the emery are much used at Sheffield. See WHEELS, articles 50 and 51.

GOLD is in general polished much the same as silver although some variation is made as works in gold are in general much smaller and do not require such active means as those in silver.

1. — Gold is 1st polished with water of ayr stone in the stick used with water, 2ndly with slips of wood with coarse crocus, and 3dly with a buff stick and fine crocus or rouge. The black polish which is so much esteemed, is given with the naked hand and rouge, but the perfection of the polish depends on the peculiar texture of the skin, as the hands of some individuals do not at all answer the purpose.

2. — FLAT WORKS IN GOLD are treated by cutlers and others 1st with water of ayr stone in the stick with water, 2ndly charcoal in the stick with water, 3dly boxwood and rouge very nearly dry.

3. — CUT on FACETTED GOLD is wrought upon pewter laps with crocus, the process closely resembles the cutting of facets on gems, see Chap. XXXIV., but the work is guided by the fingers alone.

GRANITE, after having been worked into form with heavy dumpy picks, and then with the hammer and chisel or diamond point, is 1st ground to a moderately smooth surface with a heavy iron plate fed with sharp sand or coarse emery and water, and put into reciprocal motion, or in turned works the granite is put in quick circular revolution against the rubber. 2ndly the work is smoothed with another iron plate and coarse flour emery. 3dly it is further advanced by wooden rubbers with fine flour emery, the rubbers being made the end- way of the wood. 4thly and lastly crocus is used on thick felt laid on wood or metal. On account of the softness of the mica compared with the quartz and felspar, which together constitute the granite, the hard rubbers must be persevered in until near the conclusion, to keep the work flat, otherwise the mica is too quickly worn away, and leaves minute hollows. Sometimes lumps of granite are used as rubbers instead of the iron plates.

2. — GRANITE, when worked by the lapidary is slit and roughly ground in the com- mon mode adopted both with CARNELIAN and ALABASTER, namely the slicer with diamond powder and the roughing or lead mill with coarse emery ; afterwards it is found best to smooth it on a mahogany wheel with flour

AND PROCESSES FOR GRINDING AND POLISHING. 1064

emery, and to polish it on the lead wheel with rottenstone ; but it requires great care to prevent the soft mica from being unduly worn away.

GREENSTONE. — See HONE SLATES, also the article on setting razors, Chap. XXXII.

GRINDSTONE. — Grit Stones or Grinding Stones are varieties of sandstones, some

of which are described.

1. — t( NEWCASTLE GRINDSTONES abound in the coal districts of Northumberland, Durham, Yorkshire and Derbyshire ; and are selected of different degrees of density and coarseness, best suited to the various manufactures of Sheffield and Birmingham, for grinding and giving a smooth and polished surface to their different wares."

2.—" BILSTON GRINDSTONE is a similar description of stone, of great excellence, it is of a lighter colour, much finer and of a very sharp nature, and at the same time not too hard. It is confined to a very small spot of limited extent and thickness, in the immediate vicinity of Bilston, in Staffordshire, where it lies above the coal, and is now quarried entirely for the purpose of grind- stones."

3. — " CARPENTERS' RUBSTONE is a hard close variety, used as a portable stone for sharpening tools by rubbing them on the flat stone instead of grinding. It is also much employed for the purpose of giving a smooth and uniform surface to copper plates for the engraver."

A much softer variety of sandstone, is usually cut into a square form from eight to twelve inches long, in which state they are used dry by shoe-makers, pocket-book makers, cork-cutters, and others, for giving a sort of rough edge to their bladed knives and instruments of a similar description.

4. — " DEVONSHIRE BATTS. — A porous fine-grained sandstone hi considerable repute, from the quarries of Black Down Cliffs, near Collumpton."

5. — " YORKSHIRE GRIT is a variety not at all applied as a whetstone, but is in con- siderable use as a polisher of marble, and of copper plates for engravers."

6. — " CONGLETON GRIT is a very similar stone of a softer nature, and made use of by the same description of workmen."

7. — SHEFFIELD GRINDSTONE is a hard coarse grit stone used for grinding large files, and similar purposes, it is obtained from Hardsley which lies about 1 4 miles north of Sheffield.

8. — WICKERSLEY GRINDSTONES are very generally used in Sheffield for most pur- poses of grinding, as knives, scissors, razors, saws, and edge tools generally. Wickersley stones are quarried at a village of that name about 9 miles east of the town of Sheffield.

9. — SHEFFIELD BLUESTONEis a finer grained stone than either of the last two kinds, and is very generally used at Sheffield for finishing the grinding of articles of cutlery, that have been prepared on the Wickersley stones. The act of grinding on a blue stone is called "wkittening" and the blades of table and pocket knives are always-thus treated in Sheffield. The bluestones are found very abundantly in the neighbourhood of Sheffield at from i to H miles on the north and south sides of the town.

1065 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

GUM LAC. — See LAC ; also CORUNDUM.

GUN METAL is polished like brass, which see.

GYPSUM.— See ALABASTER.

HACKING, a process employed in dressing rough grindstones, by notching or checkering the high parts with a hack hammer, which resembles a small adze of from one to three pounds weight, fitted with a short handle. The process is fully described under WHEELS, article 15.

2. — The periphery or face of soft metal laps and wooden glaze wheels, are also in some cases hacked by the cutlers, with a very light sharp hammer, the edge of which should be as keen as a chisel, and used very delicately ; but by far the more usual course is to score the edges of the wheels while they are at rest, with a pointed knife, which injures these tools less and entirely avoids the risk of spoiling the edge or angle of the lap, which should be scrupulously preserved.

3. — Lapidaries employ an entirely different mode of hacking or jarring their leaden pewter and copper polishing wheels, which are used with rottenstone and water, as fully described under the head CARNELIAN.

HARDWOOD.— See WOOD.

HELIOTROPE. — See BLOODSTONE, and also the article on CARNELIAN.

HONE SLATES. — A mineralogical distinction for various slaty stones that are used in straight pieces or slabs for whetting or sharpening the edges of tools subsequently to their having been ground on revolving grindstones. The following quotations are from Mr. Knight's paper in the Trans, of the Society of Arts, vol 50, page 233.

1. — " NORWAY RAGSTONE. — This is the coarsest variety of the hone slates. It is imported in very considerable quantities from Norway in the form of square prisms, from nine to twelve inches long, and one to two inches diameter, gives a finer edge than the sandstones, and is in very general use."

2. — " CHARNLEY FOREST STONE is one of the best 'substitutes for the Turkey oil- stone, and much in request by joiners and others, for giving a fine edge to various tools and also penknives. It has hitherto been found only on Charnwood Forest, near Mount Sorrel, in Leicestershire." The best Charu- ley Forest Stone, is by some considered to come only from the Whittle Hill Quarry, the other stones from the neighbourhood are more pinny, or present hard places.

3. — <( AYR- STONE, SCOTCH-STONE, OR SNAKE-STONE, is most in request as a polish- ing stone for marble and copper-plates ; but the harder varieties have of late been employed as whetstones." These stones should always be kept damp or even wet, to prevent their becoming hard.

4. — " IDWALL OR WELSH OIL-STONE is generally harder, but in other respects

AND PROCESSES FOR GRINDING AND POLISHING. 1066

differs but little as a whetstone from the Charnley Forest. It is obtained from the vicinity of Llyn Idwall, in the Snowdon district of North Wales," and is now in more general use for small articles of cutlery than the Charnley Forest Stone.

5 "DEVONSHIRE OIL-STONE is an excellent variety for sharpening all kinds of

thin edged broad instruments, as plane-irons, chisels, &c.,and deserves to be better known. This stone was first brought into notice by Mr John Taylor, who met with it in the neighbourhood of Tavistock, and sent a small parcel to London for distribution ; but for want of a constant and regular supply, it is entirely out of use here."

6. — " CUTLERS' GREEN HONE is of so hard and close a nature, that it is only applicable to the purposes of cutlers and instrument makers, for giving the last edge to the lancet and other delicate surgical instruments. It has Tiitherto been only found in the Snowdon mountains of North Wales."

7. — " GERMAN RAZOR HONE. — This is universally known throughout Europe, and generally esteemed as the best whetstone for all kinds of the finer descriptions of cutlery. It is obtained from the slate mountains in the neigh- bourhood of Ratisbon, where it occurs in the form of a yellow vein running virtually into the blue slate, sometimes not more than an inch in thickness, and varying to twelve and sometimes eighteen inches, from whence it is quarried, and then sawed into thin slabs, which are usually cemented into a similar slab of the slate to serve as a support, and in that state sold for use. That which is obtained from the lowest part of the vein is esteemed the best and termed old rock." The German Hone is now used almost exclusively for razors, as being very soft, it is cut by any instrument applied at an angle, and not laid flat down as a razor invariably is.

8. — « BLUE POLISHING STONE is a dark slate of very uniform character ; in appear- ance not at all laminated ; is in considerable use among jewellers, clock- makers, and other workers in silver and metal, for polishing off their work, and for whose greater convenience it is cut into lengths of about six inches, and from a quarter of an inch to an inch or more wide, and packed up in small bundles of from six to sixteen in each, and secured by means of withes of osier, and in that state imported for use."

0. — " GREY POLISHING STONE is a stone of very similar properties to the blue, but of a somewhat coarser texture and paler colours. Its uses are the same and both kinds are manufactured near Ratisbon."

10. — " WELSH CLEARING-STONE is a soft variety of hone-slate, the use of which is confined to curriers, and by them employed to give a fine smooth edge to their broad and straight-edged knives for dressing leather. They are always cut of a circular form."

11. — PERUVIAN HONE has been recently introduced as a whetstone, and is said to be imported from South America. It cuts freely with either oil or water, and is suitable for sharpening large tools that do not require a very fine edge.

12. — WELSH HONE. See article 4.

13.— OILSTONE WHITE AND BLACK. These are varieties of the Turkey-stone. See OILSTONE.

1067 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

14. — ARKANSAS STONE, from N. AMERICA is of unequal texture and cuts slowly.

15. — BOHEMIAN STONES are imported from Germany, and are used by jewellers in the same manner as the blue and grey polishing stones for polishing small works, such as the settings around gems. The Bohemian stones cut well, and keep a good point for small work.

HORN handles for razors, knives, and similar works when moulded (see vol. 1, page 125) are scraped and then buffed with Trent sand and oil, and after- wards with rottenstone and oil as more fully explained under the head " Tortoiseshell ;" but upon which latter material the Trent sand is not used in its natural state, as it would be too coarse and vigorous in its action on that soft and expensive substance ; for buffing tortoiseshell therefore the Trent sand is first calcined and pounded, and then passed through a muslin sieve. See article TORTOISESHELL.

Horn is sometimes used by watchmakers as a vehicle for the application of polishing powders to flat works. See MACHINERY, article 1 3.

HYACINTH.— See ZIRCON.

IDWALL STONE.— See HONE SLATES, article 4.

IRON. — The modes of polishing the parts of machinery made in wrought and cast iron, are described in the general article MACHINERY in this Catalogue. See also WROUGHT-IRON and CAST-IRON.

IRON STONE. — A straight slab of the haematite iron ore, ground flat on the one face, is sometimes used by the Sheffield cutlers after the yellow German hone, in polishing the " cannell " or chamfers made by the German hone in setting razors. — The iron stone is very hard, and leaves a very smooth edge, almost fulfilling the purpose of the razor strop, but it must be used very lightly and sparingly. See the article on setting razors, Chap. XXXIII. Sect. 2.

IVORY. — The modes of polishing objects made of this useful and ornamental sub- stance, differ according to the nature of the works ; and although the remarks here offered refer especially to the ivory of the elephant, that of the tusks of other animals, also the corosos or vegetable ivory, and bone are treated nearly or quite the same, when applied to similar uses.

TURNED WORKS.

1. — TURNED WORKS with plain surfaces may in general be left so smooth from the tool as to require but very little polishing, a point always aimed at with superior workmen by the employment of sharp tools. In the polishing of turned works very fine glass paper or emery paper is 1st used, and it is rendered still finer and smoother by rubbing two pieces together face to face ; 2iidly, whiting and water as thick as cream is then applied on wash leather,

AND PROCESSES FOR GRINDING AND POLISHING. 1068

linen, or cotton rag, which should be thin that the fingers may the more readily feel and avoid the keen fillets and edges of the ivory work, that would be rounded by excessive polishing ; 3rdly, when the work feels smooth, or to hang less to the rag than at first, the work is washed with clean water on the same or another rag ; 4thly, it is rubbed with a clean dry cloth until all the moisture is absorbed, and lastly a very minute quantity of oil or tallow is put on the rag to give a gloss.

Scarcely any of the oil remains behind, and the apprehension of its being absorbed by the ivory and disposing it to turn yellow, may be discarded ; indeed the quantity of oil used is quite insignificant, and its main purpose is to keep the surface of the ivory slightly lubricated, so that the rag may not hang to it and wear it into rings or groovy marks. Putty powder is some- times used for polishing ivory work, but it is more expensive and scarcely better suited than whiting which is sufficiently hard for the purpose.

2. — TURNED WORKS .consisting of many parts are best polished separately, as they are then more accessible, and the whiting and water do not penetrate and clog the joinings of the several parts, and prevent their easy separation. Accurate workmen frequently polish screw threads, in order to make them move the more easily, and to endure the longer without wearing loose ; this is some- times done with screws in ivory and the woods, as well as those in the metals, and is to be highly recommended.

3. — TURNED WORKS ornamented with the eccentric chuck, revolving cutters, &c. also require to be cut with exceedingly sharp tools, in order that but little polishing may be necessary.

The polishing of irregular surfaces is generally done with a moderately hard nail brush, supplied with whiting and water, and lightly applied in all directions, to penetrate every interstice ; after a period the work is brushed with plain water and a clean brush, to remove every vestige of the whiting. The ivory is dried by wiping and pressing it with a clean linen or cotton rag, and is afterwards allowed to dry in the air, or at a good distance from the fire ; when dry a gloss is given with a clean brush on which a minute drop of oil is first applied.

It is better to do too little polishing at first, so as to need a repetition of the process, rather than by injudicious activity, to round and obliterate all the delicate points and edges of the works, upon the preservation of which their beauty mainly depends.

FLAT AND FILED WORKS.

4. — SUPERIOR FLAT WORKS are accurately filed and scraped, then cleaned with fine glass paper folded around a square stick, afterwards with whiting also on a stick of deal planed very flat and square and used as a file ; some workmen cover the wood with one or two layers of flannel or cloth, but the naked wood, although somewhat tedious, will produce more exact surfaces and better defined edges.

1069 DESCRIPTIVE CATALOGUE OP APPARATUS, MATERIALS,

5. — COMMON FILED AND CARVED WORKS are finished — 1st, with Trent sand and water on flannel or a brush ; 2ndly, scraped Flanders brick used in the like manner ; 3rdly, wet linen or woollen rag with powdered chalk, which soon rubs down smooth, and to the condition of ordinary whiting.

6. — RAZORS AND KNIFE HANDLES are most generally finished by shaving or scrap- ing, and 2ndly by buffing them on the wheels, as more fully explained under the head TORTOISESHELL ; but the following methods are by some preferred.

7. — COMMON RAZOR HANDLES. — These are sawn out and filed, then scraped with an old razor blade, called a shaving blade ; two razor handles or scales are then held at the one end in a pair of clamps in the vice, and rubbed lengthways — • 1st, with chalk and water on felt or cloth, which cuts very quickly ; and 2ndly with whiting and water for the finish.

8. — BEST RAZOR HANDLES. — Two scales are slightly rivetted together and buffed, 1st, on a buff wheel fed with Trent sand ; 2ndly, buffed with rottenstone ; 3rdly, they are handed up or polished with the naked hand and rotten- stone. Other workmen entirely omit the rottenstone, which requires oil, and conduct the work with chalk and whiting, so that water may be used through- out the work.

9. — UMBRELLA AND PARASOL HANDLES, and many similar pieces are polished first with sand, and then with whiting, on cloth wheels consisting of several circles of thick cloth or felt, clamped between two smaller disks of wood ; the cloth projects about an inch around the margin to make a soft elastic edge.

JACINTH or Hyacinth.— See ZIRCON.

JADE is polished by lapidaries like CARNELIAN but it only takes a greasy and not a brilliant polish.

JAPANNED WORKS.— Such of the japanned works as are baked hi ovens, for the evaporation of the solvent of the varnish, are 1st forwarded with pumice- stone powder applied with water on list or flannel ; 2ndly they are polished either with rottenstone or putty powder and oil, also on flannel ; and 3rdly with the dry hand and rottenstone.

JARGOON.— See ZIRCON.

JASPER obtains just the same treatment as Camelian in the Lapidary's art ; it occurs of numerous colours and varieties, and is nearly equal to Agate in point of hardness.

JET is a soft bituminous mineral, and, like Cannel Coal, receives in the hands of the lapidary the same routine as ALABASTER ; which see.

The articles on Jet and Cannel Coal (vol 1, page 162 — 3) describe an en- tirely different method of working these peculiar substances, and to which the reader is referred. See also CANNEL COAL in this Catalogue.

AND PROCESSES FOR GRINDING AND POLISHING. 1070

JEWELLERY. — See the articles on Gold, Silver, Enamels, and Saw-dust.

LAC or GUM LAC is used in India with powdered corundum in the formation of wheels and rubbers ; see CORUNDUM. It is somewhat used in the same manner hi England, but with emery instead of corundum.

LAPIS LAZULI " is used in jewellery, but is chiefly important as affording that beautiful pigment ultra-marine, so highly valued by painters on account of its great advantage in not changing by time or exposure." — In producing this pigment the mineral is simply calcined and then levigated. The lapis lazuli is difficult to polish on account of the irregularity of its substance, which abounds in soft parts that wear away more quickly than the remainder ; it is treated as CABNELIAN.

iPS, metal polishing wheels, see WHEELS, articles 37 to 47. . j|

jAVAS, which are occasionally arranged as specimens, do not in general admit of being well polished, because of their being irregularly hard and soft, and also scoriacious ; they are worked by the lapidary just like ALABASTER, which see.

LEAD is the basis of many of the laps, and is rendered sometimes harder by the addition of variable proportions of tin and antimony ; see WHEELS, articles, 37 to 47.

Lead may be readily worked with rasps, but it clogs files so much as to render it difficult to produce a smooth surface by those instruments ; in practice it is generally scraped for the smoothest surfaces. Lead is not often polished, it would require to be treated like pewter but with greater care, to prevent the formation of utters in the scraping or burnishing.

Lead when reduced to the white oxide, forms the commonest kind of putty powder, the process of manufacturing which is described under the head PUTTY POWDER.

LEATHER. — The leather principally used for polishing, hi the manufacturing towns of Sheffield and Birmingham, is the beast hide, or the leather of the ox as prepared for the soles of shoes, which is much softer and open in the grain before it is hammered as for the soles of shoes. The hide is usually cut into parallel pieces or strips, which are glued around the edges of wooden disks ; then constituting buff wheels if charged with emery, and polishers if dressed with crocus ; and the leather is also fixed on straight sticks known as buff sticks.

The leather varies much hi thickness, that about the neck of the hide being sometimes nearly an inch thick, and very soft, this part being designated as bull neck, a material for which the thick hide of the sea cow or sea horse ia frequently substituted.

Occasionally the curried hides of the horse, and other leathers used in making harness, are employed for buff wheels ; and in the metropolis in

1071 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

particular, the thick buff leather of old regimental belts is much employed for similar uses, but although cheaper it is softer and far less durable. Wash leather, prepared from sheep skins split in two, is also much used in polishing, but mostly after the manner of a dusting cloth, or to prevent the hand touching the goods.

LENSES.— fife* Chap. XXXIII. Sect. 4.

LIME is occasionally used as a polishing material on account of its cheapness, as the only preparation required is to slake the lime with a little water, it then falls to a fine powder and which is sometimes sifted. Lime is used for polishing the commonest works in bone, such as brushes, and also for Albata Spoons.

LIMESTONES. — The substances to which this name is applied differ greatly in hardness and compactness. Some are so soft as not to admit of being polished, and are treated much the same as the Freestones, (which see,) whereas, those limestones which do admit of being polished, are generally designated under the name marble, the mode of polishing which is minutely described under that head.

LITHOGRAPHIC STONES, are a fine oolite, a peculiar kind of fine granular lime- stone, principally obtained from the interior of Germany.

The surfaces of lithographic stones are required to possess different degrees of smoothness, according to the subject for which they are employed. When the drawing is to be made at once upon the stone, a certain amount of rough- ness or granulation is necessary, or it will not so well abrade the lithographic drawing chalk, and this granulation is required to be more or less fine according to the kind of drawing. But much smoother surfaces are required for those stones upon which the transfer process is to be employed, as for lithographic writing, which is first executed on paper, and then transferred to the stone, by passing them together through the press.

The stones are, 1st, rubbed smooth with another lump of lithographic stone, and silver sand applied with water, the sand is prepared of different degrees of fineness by sifting, as explained under the head Emery, the coarsest sieves employed have about 80 wires in the inch, the finest about 120. The stones for chalk drawing are left from the sand of appropriate fineness, but those required for the transfer process are, 2ndly, smoothed with a lump of pumice- stone and water, and 3rdly, polished with a piece of snake stone, also applied with water.

LOAM is used with water by some manufacturers as a cheap material with which to grind in the conical plugs of brass valves and cocks. Loam contains more silex than the generality of the clays, but which also are occasionally used for polishing common works.

AND PROCESSES FOR GRINDING AND POLISHING.

1072

MACHINERY COMPOSED OF WROUGHT-!RON, CAST-IRON AND STEEL.— The engineer and mechanist employ nearly the same routine for polishing these three materials, more particularly in turned works, in which the variations prin- cipally depend upon the degree of finish required. This general article is therefore intended to apply to each of the three materials ; and some parti- cular observations expressly suited to each of them, will be found under their respective heads of WROUGHT-!RON, CAST-IRON, and STEEL.

TURNED WORKS.

1 . — LARGE SIZED TURNED WORKS. — Such parts of machinery as come under this denomination, are in almost every case turned in self-acting lathes, which, under proper management, leave the surfaces very exact and smooth, so that many of them require no polishing whatever ; and which process is reserved for those exterior parts which meet the eye, when the machinery is erected.

Heavy works are made to revolve with considerably greater velocity than that proper for turning, and they are polished with a long stick of deal 1 to 2 inches thick, and 2 to 4 inches wide, the end of which is cut off square. The stick is dipped into a shallow vessel containing oil, then into another with dry emery after which it is pressed forcibly against the work, never being allowed to remain long hi one position upon the lathe rest. Occa- sionally, for additional purchase, a bent bar of iron is used, to the end of which is fixed a block of wood, in imitation of the hanging tools for turning iron, figs. 423 and 424, page 527, vol. ii. Sometimes on the end of the polishing stick is placed a thick piece of leather for the application of the emery, of which two or at most three different-sized grains are used, namely, corn emery, grinding, and fine grinding emery.

2. — MEDIUM SIZED TURNED WORKS. — Many of these which are turned in power lathes running at a proportionate velocity, with tools properly formed and lubricated with abundance of water from a small jet, are left so smooth as hardly to want any polishing, or at most an inconsiderable amount of polishing with fine emery powder or emery paper ; but in other works less skilfully turned by hand tools and with little or no water, it is usual to reduce any very trifling irregularities of surface to a general level, by means of a smooth file, slightly greased, which is rubbed lightly over the work as it revolves ; careless workmen are apt however to rely too much on this practice, and having left the work full of ridges from the turning tool, to begin with a coarse file ; this practice is detrimental to the production of good true work, and the preservation of the angles.

Works of medium size are polished nearly as above described, but with a deal stick chopped to a chisel edge, or to a square point and thrust against the work ; sometimes instead of the point the side of the stick near the end is used as a crow-bar for additional purchase.

Generally two, but occasionally three sizes of emery are used, varying

1073 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

from grinding to flour emery ; but it is necessary between the application of each powder, to wipe the work entirely clean, with rags, cotton-waste, saw- dust, nioslings, (or the curriers' shavings of leather), and also to use a fresh stick, or to chop a clean point, for every kind of emery.

3. — SMALL SIZED TURNED WORKS. — For these, emery sticks, (those with emery glued upon them,) and emery paper are much used ; but the loose powder applied as above although less cleanly, is in general somewhat quicker and also cheaper. For the plane surfaces and other parts of small-turned works, required to be particularly flat, emery paper folded around a smooth file or a flat piece of wood is used, or else flat pieces of mahogany, box- wood or metal, supplied with fine emery powder and oil are employed with still greater advantage.

In some few cases after the finest or flour emery has been used, fine crocus is applied similarly, or with a buff stick, but this is unusual as two sizes of emery are alone in general employed. Some parts of superior works in iron and steel, especially the rounded edges, are brightened with the burnisher, but such parts require to be previously polished quite smooth ; both the work and burnisher must be wiped thoroughly clean from emery or dust, the burnisher is then held against the work as it revolves, a little oil being interposed to lubricate the surfaces.

4. — SCREW THREADS that are required to fit accurately and smoothly, and also to sustain frequent unscrewing, should be polished with a pointed stick and emery ; as frequently the removal of the rough edges will make that screw enter which appeared to be too large, and the smooth screw present far less friction and disposition to wear out.

5, — THE HEADS OF SCREWS are often finished with the side of an emery stick as they revolve in the lathe ; and if they are to be burnished the emery must be carefully removed from the notch by folding the rag and drawing it through like a saw or the process will fail, and the burnisher will be injured.

6. — SMALL ROUND RODS used for inferior purposes and not requii'ing to be cylindrical, are often ground bright against the edges of large revolving grindstones driven by power. The rod is held rather loosely in the hands of the workman and at a small angle to the axis of the stone ; then without any great attention on the part of the individual, the grindstone causes the rod slowly to rotate in his hands, so as to act on every part of its circum- ference, and the obliquity of the two axes also causes the rod to traverse endlong through the hands like a screw, and thus every part of the rod is acted upon successively by the grindstone.

7. — CYLINDRICAL WORKS that require great accuracy are ground by methods that will be explained in Chap. XXXIII. Sect. 2, but other cylindrical rods of inferior kinds, used only as levers and for similar common purposes, are often polished between two sticks, (supplied with emery and oil,) placed trans- versely to the cylinder, grasped in both hands, and rubbed lengthways on the work as the lathe revolves. Considerable friction may thus be given "on

AND PROCESSES FOR GRINDING AND POLISHING. 1074

opposite sides, and therefore without bending the cylinder, the figure of which is materially improved by the treatment. Sometimes for greater purchase, the sticks are united at the one end by a loop of string or wire, and compressed at the other, like nut-crackers, with one or both hands. 8. — LATHES FOB POLISHING. — In large manufactories it is usual to perform the polishing on common lathes kept entirely apart from those used for turning, on account of the mischief that ensues when gritty matters find their way into the fittings of the mandrel or other part of the lathe ; and careful workmen who use the same lathe for turning and also for polishing, avoid with scrupulous care the scattering of the powders, and frequently employ a spare center for the popit head, in polishing spindles and pieces requiring support at both ends, as the grit is almost sure to deteriorate the center employed in polishing works.

FLAT WORKS.

9. — LARGE-SIZED FLAT WORKS. — These are in almost every case, castings in iron, wrought in the planing machine ; — a machine that produces its results with so much accuracy and precision, that polishing is not frequently required as the concluding step. When however large planed works are polished, it is with rubbers of various kinds applied with emery and oil. Sometimes a flat lump of lead is cast upon the center of an old file, or of a still longer bar of iron ; at other times a bar of wood serves as the handle, and to it is fixed by screws or nails a piece of lead or wood, or wood covered with thick leather ; such rubbers are generally held in the two hands much after the manner of the spokeshave or drawknife, or they are worked by one very long handle as in smoothing a large slab of stone or marble. When the rubbers are large they are occasionally loaded with heavy weights, so that the workmen have only to drag them to and fro on the works, the forms of which latter are in general too diversified to offer much inducement to the application of machinery to rectilinear polishing.

1 0. — MEDIUM-SIZED FLAT WORKS. — Such of these as are of cast-iron, are also for the most part worked in the planing machine, and if at all polished, it is done with emery rubbers nearly or precisely as above described ; most of the flat parts of mechanism that are made in wrought iron and steel, are too irregular in their forms to admit of being worked otherwise than with the file. The black oxidized surfaces of forged works are often removed on the grindstone prior to the application of the file ; this application of the grindstone is in general highly economical, it being comparatively, much more rapid in its action, and less costly in respect to wear and tear than the file.

Sometimes, indeed, the flat parts of iron works are reduced on the grind- stone to accurate plane surfaces, but this requires the assistance of mechanism, which is by no means common ; this subject, and also the application of revolving metallic laps to the production of flat works, will be noticed in the first section of Chap. XXXIII.

1075 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

The coarser and larger of the filed works are sometimes left from the file, or without being subsequently polished ; in which case the coarser marks left from the file when used in the customary manner, or from point to heel, are removed by the method known as draw-filing, in which the file is drawn sideways along the work ; draw-filing is particularly employed in narrow pieces. Large broad surfaces are occasionally finished by giving a circulating motion to the file, thereby producing curly marks. Each of these latter pro- cesses are more effectual when the file is moderately supplied with oil, which lessens its disposition to become pinny, or clogged, by particles which stick into it, and scratch the work ; but the reader is referred to the pre- vious chapter on the File, vol. ii., page 852, for more detailed particulars of these applications of this useful instrument.

Works requiring a finish superior to that of draw-filing, are rubbed with an emery stick, or with rubbers of the various kinds already noticed, and supplied with emery and oil.

11. — SMALL-SIZED FLAT WORKS, after having been draw-filed, are more usually finished with the emery stick, and often followed by emery paper of different degrees of coarseness wrapped on a file or a square stick. The emery is moistened with oil for the more finished works, the dry rubber gives however the brighter surface, and it is sometimes applied with a curling motion, so as to diversify the grain left on the work.

Buff sticks supplied with crocus are often used for the last gloss, but on small flat surfaces they must be cautiously applied for fear of rounding them, a defect that is easily distinguished, and very objectionable.

Still smaller works and those required to be very flat are finished with square slips of stone with oil, or slips of mahogany, brass or tin, any of which are used with fine flour emery or oilstone- powder and then with crocus.

12. — SMALL FLAT WORKS OF HARDENED STEEL. — As it commonly happens that in the process of hardening steel works they are more or less distorted from their intended figures, and as in many cases it is impossible or inadmissible to restore them to the plane figure by the hack hammer, (see vol. 1 , p. 247,) grinding is then resorted to, metal laps generally of lead with a little anti- mony, and laps of copper or of cast-iron are also employed with emery and water. When it is desired the works should present very true plane surfaces, the laps should be themselves very exact and flat. There is however a con- stant tendency to depreciate the figure of the lap, because the outer part or exterior diameter gets the more worn, on account of the greater rapidity of its action at that part. After the lap has been used, the mode of finishing described in the last article is also sometimes employed.

13. — WATCHWORKS IN STEEL.— Steel works of this diminutive kind are generally polished by the watchmakers, 1st with a steel rubber and oilstone powder, 2ndly, with a steel rubber and crocus of two degrees of coarseness, which is frequently called red stuff from its colour, and Srdly with gun metal or glass rubbers supplied with fine crocus. Some of the work is beautifully finished on tin or pewter revolving laps,

AND PROCESSES FOR GRINDING AND POLISHING. 1076

into which the red stuff is embedded, occasionally with the burnisher, they are used nearly or quite dry, and when the laps are carefully preserved, they themselves present, under the magnifier, a beautiful smooth surface and which they impart to the work.

Many of the grinders and rubbers for watchwork, are made from one to two inches square, and of steel, glass, gun-metal, tortoiseshell, horn, or ivory, &c., the small pieces are laid down upon the anointed grinders, and rubbed about with the fingers, as if the work were a muller used in grinding paint, this mode also preserves the flatness of the respective objects in a most admirable manner.

MALACHITE, or the massive green carbonate of copper, is much used for jewellery and articles of vertu, the finest malachite is from Russia, and as it is traversed by numerous circular fissures ; from the imperfect joinings of the botryoidal masses of which it may be considered to be composed ; it is difficult to polish, and requires great care and attention ; notwithstanding its hardness it is con- sidered by some lapidaries better to treat it as alabaster than carnelian, but each method is followed.

[ ARBLE is polished in different modes, which are jointly dependent on the nature of the marble, and the character of the work; some of the principal methods will be described.

Marble is generally worked by the lapidary after the manner of carnelian, sometimes of alabaster, but he is far less successful in this department of art than the sculptor and marble workers.

1 . — MARBLE ORNAMENTS and small works intended for close inspection, and which require the highest possible finish. — " After the marble is sawn into slab the first operation is to grind it down with a flat coarse sand-stone and water, or with an iron plate, fed with fine sand and water, until all the marks of the saw are perfectly removed ; 2ndly, a fine sandstone, (procured from Bilston,) is used with water, until the marks made by the first stone are removed ; 3rdly, a finer sandstone which is found near Congleton, is applied to work out the marks of the former ; 4thly, pumice-stone with water, and 5thly, snake stone is used, and the last finishes what is called the growiding.

" Next comes the polishing, which is principally performed with rollers of woollen cloth or list made to the size of about three inches diameter. As the 6th process a rubber is charged with flour emery and a moderate degree of moisture ; this rubber is worked uniformly over every part, until the marble acquires a kind of greasy polish ; 7thly, the work is completed with a similar roll of cloth charged with putty powder and water. Some prefer as the polisher, an old cotton stocking not made into a rubber, and in some few of the more delicate works, crocus is used intermediately between the emery and the putty-powder. It is necessary to wash the marble after each operation, so that not a particle of the previous polishing material may remain, otherwise the work will be scratched."

E2

1077 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

2.— MARBLE WORKS TURNED IN THE LATHE. — " Turned works are polished as above, excepting that for the rolls of cloth are substituted two or three thicknesses of cloth supplied with emery or putty powder, and held upon the work by the hand, which is constantly moved about."

For the above paragraphs, and also for the practical remarks on turning marble, the author is indebted to Mr. Hall of the Marble-works, Derby ; and for the subsequent particulars to Mr. Thomas Smith, sculptor, of London. 3.— STATUARY and large works in marble, which are dependent on their general design and effect, rather than on elaborate finish, are executed by a different class of artists, and require only part of the above proceses to be resorted to. By Statuaries the marble is rubbed with two qualities of gritstone, the coarse, which is somewhat finer than Bilston, is known as first grit, and the fine as second grit. Thirdly, the work is smoothed with snakestone, after which the white or statuary marble is finished with putty powder and water, on a wooden Uock covered with thick nap, or felted cloth. (See article RUBBER.)

The Irish black marble is by some considered harder than the Derbyshire, and after the snakestone has been used, it is polished with tripoli on felt as above, and finished with putty powder or crocus, but the rubber is then covered with three thicknesses of stout linen.

The finest Welsh black marble is esteemed still harder and blacker than the Irish, and after the snakestone, is polished by laying a thin plate of copper or lead on the wooden rubber, and using therewith tripoli and water, and finally putty powder or crocus on linen as before.

The Irish marble is less brittle than the Welsh, and better suited to carved ornaments. Marble has of late years been sawn, ground, and polished to a very great extent, by means of machinery, much of which took its rise from the comparatively old machinery used for the same purposes in Derbyshire.

SCULPTURE. — The dull parts of sculpture are finished in four different manners, or rather, the complete process of smoothing is discontinued at various stages, so as to form four gradations, denoted by the respective paragraphs.

The marble is First, sometimes left from the long and very slender statu- ary's chisel, the reverse end of which is formed with a sharp circular edge or ridge, just like a hollow center, in order that the metal hammer, which is of soft iron, tin, or zinc, may be slightly indented by the chisel, so as to avoid its glancing off ; the chisel marks leave the surface somewhat rough and matted, intermediate between the granular and crystalline character.

Secondly, For surfaces somewhat smoother, rasps are used to remove the ridges left by the chisel, the rasps leave a striated or lined effect suitable for draperies, and which is made more or less regular according to the uniformity of the strokes, or the reverse.

Thirdly, Files are employed for still smoother surfaces of the same character ; and it is to be observed that the files and rasps are generally curved at the ends, to adapt them to the curvilinear forms of the sculpture. See the article on RIFLERS, in the chapter on FILES, vol. 2, page 834.

AND PROCESSES FOR GRINDING AND POLISHING. 1078

Fourthly, For the smoothest of the dull or unpolished surfaces, the faint marks left by the file are rubbed out with Trent sand or silver sand and water, applied by means of a stick of deal cut to a point, and rubbed all over the work in little irregular circles, as a child would scribble on a slate, and if the end of the stick is covered with two or three thicknesses of cloth, the marble receives a still rounder or softer effect than from the naked stick, for which the cabbage wood or partridge wood is sometimes used, and the end of the stick is slightly bruised, so that the fibres of the wood may assume the character of the stiff brush, known by artists as a scrub.

Mr. Thomas Smith adds that he has successfully copied the minute rough- ness or granulation of the skin, by a kind of etching which lie was induced to try, by imagining that he could trace such a process to have been used in some of the most perfect of the ancient marbles that had not been exposed to open air. The work having been smoothed with sand as above, he takes a hard stubby brush, and therewith dots the marble with muriatic acid, and which quickly, yet partially, dissolves the surface. The stringency of the acid, which must not be excessive, is tested upon a piece of waste marble : the brush is hastily dipped in the acid, applied to the work, quickly rinsed in water, and then used for removing the acid from the marble. It is obvious the process calls for a certain admixture of dexterity and bold- ness, and sometimes requires several repetitions, the process occupying only a few minutes each time.

Fifthly, The bright parts of sculpture. Few of the works in sculpture are polished, and such as are, are required in the first instance to pass through the four stages already explained for producing the smooth but dull surface ; after which, slender square pieces of the second gritstone and of snakestone are used with water as a pencil, and then fine emery and putty powder on sticks of wood ; but the work is exceedingly tedious, and requires very great care, that the artistical character of the work, and any keen edges that may be required are not lost in the polishing. To avoid the tediousness and the risk of deterioration, it is not unusual in carved black marbles, and those of dark colours, after using the snakestone, to coat the work with varnish, by which a gloss is given without attrition. The pillars of the Temple Church, London, which are of Durbec marble, were in like manner French polished, after the manner of furniture, when that building was recently restored.

MARBLES FOR CHILDREN.— These are principally manufactured in Germany ; some are made of clay covered with a glaze and baked as in pottery ; others are made of alabaster and marble ; but the greater part are made of a hard stone found near Coburg in Saxony. The stone is first broken with the hammer into small cubical fragments, and about 100 to 150 of these are ground at one time in a mill, somewhat like a flour mill. The lower stone, and which remains at rest, has several concentric circular grooves or furrows ; the upper stone is of the same diameter as the lower, and is made to revolve

*

1079 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

by water or other power. Minute streams of water are directed into the furrows of the lower stone. The pressure of the runner on the little pieces rolls them over in all directions, and in about one quarter of an hour the whole of the rough fragments are reduced into nearly accurate spheres. Frequently a thick circular slab of oak or elm is used instead of the upper or revolving stone. — Extracted from Gill's Description. See Tech. Repos. for 1828, p. 219.

The late Mr. Henry Guy's method, by which spheres of metal and other hard substances, are produced with perfect accuracy, will be described in Chap. XXXIII. Sect. 4, of this volume.

MARQUETRY WORK.— This term, probably derived from the French definitions, marqueterie en bris and marqueterie en metal, (see foot note, page 732, vol. 2) has been selected to denote a variety of works, also known as buhl work, reisner work, parquetage, mosaic, &c., in which two or more woods, metals, and other materials, are united by various modes of inlaying, some of which are entirely executed with the saw, as described in pages 731 — 739. The methods of polishing these works depend on the materials of which they are respectively composed, and are generally as follows.

2. — MARQUETRY ENTIRELY OF WOOD. — This is reduced to a level surface with the toothing plane, and is then scraped with the joiner's scraper, which so far as possible is applied obliquely to the joints of the marquetry, as when the scraper is applied parallel with the joints, or broadside, it is liable to dig down, and if applied at right angles to the joints it does not cut so cleanly as in the inclined position, like the skew irons of some rebate planes. The scraper is sometimes employed with such good effect, that the work only requires to be rubbed with a few of its own shavings, as in many draftboards made of holly and ebony.

When the scraper is less successfully used, fine glass paper on a flat piece of cork is employed to smooth the work, and the paper is preferable, if it is worn until it almost ceases to cut, and has become uniformly choked or clogged with the fine dust from the work, but which must not be allowed to collect in hard partial lumps, a condition that may readily occur with resinous or greasy woods, as these lumps would scratch the work.

3. — MARQUETRY IN WOOD AND METAL, and also those which contain ivory, pearl shell, tortoiseshell, and metals, require to be levelled very carefully with flat files handled after the manner of figs. 8 1 6 to 8 1 8, page 834, vol. 2, ending with a very smooth flat file, after which the scraper should be used if practicable, and followed by glass or emery paper employed very sparingly as above directed. When the metal preponderates emery paper is much to be preferred, and really good sand paper, which is of an intermediate character between glass and emery paper, has also been used, but as stated above, the paper of which kind soever, should have but very little cut, should be applied dry, and allowed to become clogged, so as to act principally as a hard dry rubber or burnisher. If the polishing is at all in excess, the wood will inevitably be

AND PROCESSES FOR GRINDING AND POLISHING. 1080

worn down so as to allow the metal or harder material to project above the general surface.

It is always particularly hazardous to resort to wet polishing with inlaid works, as if the water is carelessly used, there is risk of its penetrating to the glue and loosening the pieces, 'and if the woods are only superficially wetted they are apt to curl up at the edges and become warped ; and besides the grain of the wood is almost certain to rise with the wet and leave a rough unsightly surface. Oil is preferable only so far as not dissolving the glue, but oil or water are alike inapplicable to light- coloured woods, which are almost sure to become stained by the polishing powders, and the fluids used in their lubrication.

4. — MARQUETRY ENTIRELY OP METAL, which is less common and more recent than the foregoing kinds, is first smoothed with a flat file, secondly it is very care fully scraped with a triangular or other scraper, thirdly it is rubbed with a stick of snakestone and water, fourthly with charcoal in the stick and oil, and it is finished with a coil of list or other rubber supplied with rotteustoue and oil.

5. — MARQUETRY WITH VARNISHED SURFACES. — Many of the modern marquetry works, instead of having their surfaces polished simply by attrition as above described, are covered with varnish either applied with friction as in the so- called French polish, or the varnish is laid on in several coats with a brush and polished off with pumice-stone and rottenstone. Previously to their being varnished, which processes will be hereafter described, the marquetry works are levelled with the file or scraper as the case may be, and smoothed with glass paper.

MEERSCHAUM is scraped to a smooth surface, but it is so soft as scarcely to admit of being polished, otherwise than by dipping the meerschaum into melted wax to fill up its pores, and rubbing it when dry with a flannel ; and which is the usual process. MILK MEERSCHAUM obtains a somewhat different treatment.

MILL a general termed used by lapidaries to represent their different wheels ; as roughing-mill, cloth-mill, etc. See the introductory article on WHEELS, also Chap. XXXIV. on LAPIDARY WORK.

MOSLINGS. — The thin shreds or shavings of leather shaved off by the currier in dressing cow, or calf skins. They are frequently used for removing oil from metals that are being polished and serve extremely well, being as bibu- lous as blotting paper. Cotton waste is similarly employed especially in the vicinity of cotton mills.

MOTHER OF PEARL.— See SHELLS. NACREOUS SHELLS.— Idem.

1081 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS, NORWAY RAGSTONE. See HONE SLATES, article 1.

OILSTONE. — The Turkey Oilstone can hardly be considered as a hone slate, having nothing of a lamellar or schistose appearance. As a whetstone, it surpasses every other known substance, and possesses, in an eminent degree, the property of abrading the hardest steel, and is at the same time of so compact and close a nature, as to resist the pressure necessary for sharpen- ing a graver, or other small instrument of that description. Little more is known of its natural history than that it is found in the interior of Asia Minor, and brought down to Smyrna for sale. The white and black varieties of Turkey oilstone, differ but little in their general characters, the black is, however, somewhat harder, and is imported in larger pieces than the white.

2. — OILSTONES FITTED IN CASES. — The rough irregular pieces of oilstone scarcely ever exceed about 3 inches square and 10 inches long, and are generally about one third smaller ; when cut into rectangular forms it is done with the lapidary's slitting mill and diamond powder, the blocks are then rubbed smooth with sand or emery on an iron plate. The piece of oilstone is generally inlaid in a block of wood, in which it is cemented with the putty used by glaziers, and to avoid the deposition of dust a wooden lid is usually added ; the lid is sometimes covered with a thick piece of buff leather which serves to absorb the oil from the tool and is used in the manner of a razor strop. The oil employed on the oilstone should be indisposed to dry or thicken, in this respect sperm oil is the best, but neats-foot oil is nearly as good, and has no offensive smell.

The joiner often puts three or more small points in the stock or bed of the stone, that it may take a firm hold of the work bench when dabbed down thereupon ; and the turner adds two fillets so that it may fit transversely on the bearers of the lathe.

3. — OILSTONE SLIPS, are small pieces of this useful stone cut into different forms by the lapidary. Some oilstone slips are wide thin pieces, the edges of which are rounded to adapt them to the curvatures of gouges, and such slips are usually cut wedge form, that the semicircular edges on the one slip may be of two sizes and curvatures ; these are used for gouges, for various figured tools used by turners, and also for plane irons for mouldings. Other Oil- stone slips for polishing are cut into pieces from \ to -| inches square and 3 to 6 inches long, to be used after the manner of files, by mechanicians, watchmakers and other artizans.

4. — OILSTONE POWDER. — Fragments of oilstone when pulverised sifted and washed, are much in request by mechanicians. This abrasive is generally preferred for grinding together those fittings of mathematical instruments and machinery, which are made wholly or in part of brass or gun metal ; for oilstone being softer and more pulverulent than emery, is less liable to become embedded in the metal than emery, which latter is then apt conti- nually to grind, and ultimately damage the accuracy of the fittings of brass works. In modern practice it is usual, however, as far as possible to discard

AND PROCESSES FOR GRINDING AND POLISHING. 1082

the grinding together of surfaces, with the view of producing accuracy of form or precision of contact.

Oilstone powder is preferred to pumice-stone powder for polishing supe- rior brass works, and it is also used by the watchmaker on rubbers of pewter in polishing steel.

ONYX, a variety of Chalcedony that is wrought by the lapidary like Carnelian.

OPAL. — This beautiful iridescent gem, although soft is very brittle and tender, on account of the numerous fissures by which it is traversed, and that apparently give rise to the splendid play of colours seen in precious opals of fine quality. Opals are always cut with rounded faces, and are more generally treated like alabaster than carnelian.

OXIDES OF IRON. — The red and black oxides of iron, and mixtures of them, are prepared by manufacturing chemists at Liverpool, Sheffield, Derby and elsewhere, as polishing powders, commercially known as crocus, rouge, red stuff, colcothar of vitriol, &c., and the same substances are also employed as pigments, under the names of red-brown, purple-brown, &c. The ordinary manufacture of crocus will be first noticed, and then the more exact method, required in the higher branches of scientific art, in order completely to avoid the accidental admixtures of silex and other impurities. As however these several matters have been elsewhere described with great exactness, it is conceived best to quote these passages, and it is to be observed that articles 1, 4, 6 and 7 are literal extracts from Mr. Thomas Gill's paper on the pre- paration of the metallic oxides, contained in Tech. Repos. vol. 1, pages 431-5.

1. — CROCUS AND ROUGE. — " These articles are manufactured at Liverpool," said the late Mr. Samuel Varley, " by persons who make it their sole occupation, in the following manner. They take crystals of sulphate of iron, (green vitriol or copperas,) immediately from the crystallising vessels, hi the copperas works there, so as to have them as clean as possible ; and in- stantly put them into crucibles or cast iron pots, and expose them to heat, without suffering the smallest particles of dust to get in, which would have a tendency to scratch the articles to be polished. Those portions which are least calcined, and are of a scarlet colour, are fit to make rouge for polishing gold or silver ; whilst those which are more calcined, or have become red, purple, or bluish purple, form crocus fit for polishing brass or steel. Of these, the bluish-purpled coloured part are the hardest, and are found nearest to the bottom of the vessels, and consequently have been exposed to the greatest degree of heat."

2. — MR. ANDREW Ross's MODE OF PREPARING OXIDES OF IRON. — "Dissolve crystals of sulpKate of iron in water ; filter the solution, to separate some particles of silex which are generally present and sometimes are abundant ; then precipitate from this filtered solution the protoxide of iron by the addi- tion of a saturated solution of soda, which must also be filtered. This gray

1083 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

oxide is to be repeatedly washed and then dried ; put it in this state into a crucible, and very gradually raise it to a dull red heat ; then pour it into a clean metal or earthen dish, and while cooling it will absorb oxygen from the atmosphere, and acquire a beautiful dark-red colour. In this state it is fit for polishing the softer metals, as silver and gold, but will scarcely make any impression on hardened steel or glass. For these latter purposes, I dis- covered that it is the black oxide that effected the polish, (and this gives to the red oxide a purple hue, which is used as the criterion of its cutting quality in ordinary,) therefore, for polishing the harder materials, the oxide must be heated to a bright red, and kept in that state until a sufficient quantity of it is converted into black oxide to give the mass a deep purple hue when exposed to the atmosphere. I have converted the whole into black oxide ; but this is liable to scratch, and does not work so pleasantly as when mixed with the softer material. The powder must now be levigated with a soft wrought iron spatula, upon a soft iron slab, and afterwards washed in a very weak solution of gum-arabic as recommended by Dr. Green in his paper on Specula. The oxide prepared in this manner is almost impalpable, and free from all extraneous matter, and has the requisite quality in an eminent degree for polishing steel, glass, the softer gems, &c. See EMERY, article 4.

3. — LORD ROSSE'S MODE OF PREPARING THE PEROXIDE OF IRON. — "I prepare the peroxide of iron by precipitation with water of ammonia from a pure dilute solution of sulphate of iron ; the precipitate is washed, pressed in a screw press till nearly dry, and exposed to a heat which in]the dark appears a dull low red. The only points of importance are, that the sulphate of iron should be pure, that the water of ammonia should be decidedly in excess, and that the heat should not exceed that I have described. The colour will be a bright crimson inclining to yellow. I have tried both potash and soda pure instead of water of ammonia, but after washing with some degree of care, a trace of the alkali still remained, and the peroxide was of an ochrey colour till overheated, and did not polish properly." See Phil. Trans., 1840, p. 521.

4. — JEWELLERS' ROUGE " Is prepared by persons in this metropolis, by decom- posing sulphate of iron with potash ; well washing the yellow oxide of iron, to free it from the sulphate of potash ; and slightly calcining it, till it acquires a scarlet colour."

5. — SPECULAR IRON ORE when finely pulverized and washed, makes a polishing powder which is greatly recommended by Mr. Heath for razor strops and other uses. It closely resembles both in appearance and effect the crocus artificially prepared from the sulphate of iron.

6. — ARTIFICIAL SPECULAR IRON ORE. — " This is made in the following manner. Equal parts of sulphate of iron and hydrochlorate of soda, (common salt,) are to be well mixed, by rubbing them together in a mortar : the mixture is then to be put into a shallow cupel or crucible, and exposed to a red-heat : a con- siderable quantity of vapour will be disengaged, and the matter will run into fusion. When vapours no longer arise, remove the vessel, and let it cool. " The mass will be of a violet-brown colour, covered with extremely brilliant

AND PROCESSES FOR GRINDING AND POLISHING. 1084

scales resembling mica, and perfectly like the specular iron-ore. This mass must be dissolved in water ; as well to separate the sulphate of soda which is formed by the decomposition of the two salts employed, as to wash over the lighter particles of uncrystallized oxide, which forms an excellent polishing powder.

" The fire must not be continued too long, nor be too violent ; for then the powder would become black, extremely hard, and produce no good effect. The artificial specular iron ore is the more preferred, the nearer it approxi- mates to the violet colour.

" The micaceous scales which subside after the washing over of the powdery part, afford an excellent material for razor strops, when applied to the strop with a little grease previously rubbed over it j as we can vouch, from our own experience in the use of it, for several months past."

It has been suggested to the author by an experienced chemist, that the atomic proportions of the sulphate of iron and common salt, should be taken for the last process, and when it is considered that, as noticed by the Earl of Rosse, the present limit of perfection hi the polishing of specula, depends mainly on the fineness and efficiency of the polishing material, it becomes evident that the subject demands every care hi its investigation, and which may apologize for the length of the foregoing articles.

7. — AN IMPROVED TRIPOLI, FOR POLISHING GOLD AND SILVER. — " The basis of this excellent Tripoli consists of a mineral substance, abundantly found in the coal and iron mines of Staffordshire, &c. &c. ; known by the name of dunch, or curl stone. It had formerly been employed for no other purpose than as a material for mending the roads. It is a compound of iron, alumine, lime, and silex." — Mr. Gill proposed this application of clunck from the external and chemical resemblance it bears to Septaria — the well-known basis of the Roman Cement, the employment of which in polishing he had previously advocated in the Annals of Philosophy. He goes on to say — "The polishing effects of the calcined and pulverized duncli are however still superior to that of the Septaria, when prepared in a similar manner ; and are, indeed, in point of quickness of action in producing the polish, and in the beautiful black lustre which it gives to the gold or silver, far beyond any thing I have ever met with."

OXIDES OF LEAD AND TIN.— See PUTTY POWDER.

PAINTED WORKS, such as the panels of carriages,are first grounded, or carefully painted three or four times in good oil colour, and when thoroughly dry and hard, the surface of the paint is rubbed smooth with a lump of pumice-stone plentifully supplied with water ; two pieces of pumice-stone are used and continually rubbed together to remove the paint accumulated on their sur- faces. The finishing colour, which is frequently ground up in varnish, instead of oil, is then laid on, and the panels after having had three or four coats of carriage varnish, (a description of copal varnish,) are carefully polished first with a rag supplied with pulverized pumice-stone and water,

1085 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

and then with rottenstone and oil on other rubbers : the worsted stocking being here likewise in great requisition for the purpose.

PALLADIUM. — Palladium, platinum and silver when inlaid in the limbs of mathe- matical instruments, are treated much the same as platinum, which see.

PASTES, or factitious gems made in coloured glass, are polished after the mode employed for the gems themselves, and the succession of the mills and pow- ders used by the lapidary for the purpose is nearly the same as that described under CARNELIAN. Facets on pastes, are cut on a lead mill with flour emery, and polished on pewter with rottenstone, but the particulars of this part of the lapidaries' art will be found in Chap. XXXIV. The description of the principal Factitious Diamonds will be found under DIAMOND, article 5.

PEARL SHELL, or Mother of Pearl. — See SHELLS.

PEBBLES. — Although these differ much in their colour and general appearance, they may be viewed as varieties of Agate, and are treated as such, or in the mode fully described under the head CARNELIAN.

PERIDOT.— See CHRYSOLITE.

PEWTER is seldom polished ; the articles when left from the turning tool or scraper, are burnished with plenty of oil, the oil is removed with a rag and whiting, and this is the only polish given. Pewter vessels are mostly cleaned with silver sand and water, or with liquids containing potash or soda, to remove the grease.

PEWTER is much used for laps and polishers by lapidaries, jewellers, watch- makers and many others. The metal of old pewter plates is preferred, but tin unalloyed appears to be nearly identical in effect.

PLASMA, which is a variety of Chalcedony, is polished like CARNELIAN.

PLASTER OF PARIS. — In removing the seams left from the mould a knife or scraper is first used and the work is then rubbed with Dutch rush, or fish skin previously softened in water. The cleaning off is best done before the plaster is dry.

PLASTER OF PARIS is made very closely to resemble ivory, by the following process, invented by Mr. Franchi, an Italian figure caster : — Plaster and colouring matter, are employed in the proportions of one pound of superfine plaster of Paris, to half an ounce of Italian yellow ochre reduced to the finest powder, they are intimately mixed by passing them together through a fine sieve, after which the plaster cast is made in the usual way. It is first allowed to dry in the open air, and is then carefully heated in an oven, (one that is used for culinary purposes will answer,) the hot plaster cast when thoroughly dry, is soaked for one quarter of an hour in a bath containing

AND PROCESSES FOR GRINDING AND POLISHING. 1086

equal parts of white wax, spermaceti, and stearine, heated just a little beyond the melting point. The cast on removal is set on edge that the superfluous composition may drain off, and before it cocls its surface is brushed with a brush like that known by house painters as a sash tool, to remove any wax which may have settled in the crevices, and finally when the plaster is entirely cold, its surface is polished by rubbing it with a tuft of cotton wool.

Mr. Franchi's specimens, some of which are very classical and in high relief, are cast in a peculiar manner in elastic moulds ; and although he states the above to be the usual proportions of the yellow ochre for a medium tint, the quantity may be reduced or increased for paler or darker shades. He adds that the brown discoloured parts in old carvings in ivory, are some- times imitated in water colours with a camel hair pencil before the works are dipped in the composition, which entirely defends them from the action of the air, and permits them to be washed with soap and water if so required.

Mr. Franchi was rewarded by the Society of Arts for this invention in 1846.

PLATE GLASS.— The polishing of this beautiful material is slightly noticed in Chap. XXXIII. Sect. 1.

PLATINUM is very difficult to file and polish, but these processes are not often required, as the great use of platinum is for chemical apparatus, which are wrought almost exclusively with the hammer and soldered with pure gold. Platinum is sometimes inlaid in the limbs of mathematical instruments to receive the graduations, and then in filing this peculiar metal, the file is generally moistened with oil to prevent it from tearing up ; and in polishing platinum the mathematical instrument makers use 1st, water of Ayr stone ; 2ndly, blue stone ; 3dly, charcoal, — all with water ; and 4thly, they lay the grain with charcoal and abundance of oil, in order that the metallic particles may be floated away. It is necessary to use two pieces of charcoal, and these are rubbed together at short intervals, in order to remove from the one, those minute particles of metal which become embedded in the other, and that if allowed to remain would scratch the work.

POLISHING SLATES.— See HONE SLATES, articles 8, 9, and 15. PORCELLANOUS SHELLS.— See SHELLS.

PORPHYRY is not much used in this country, but is successfully worked in Sweden, — first with the pick and chisels, and afterwards by grinding it into form with emery and water applied through the medium of heavy rubbers, also of porphyry. As in other cases it is needful to employ a gradual suc- cession of emery as to coarseness, It is probable the final polish is obtained by rubbers of wood with flour emery, and wood covered with buff or felt and fed with crocus, much the same as in the treatment known to be applied

1087 DESCRIPTIVE CATALOGUE OF APPARATUS, MATERIALS,

to granite. From the homogeneity of porphyry it is less difficult to manage than granite, but they each demand great time and patience.

The Elvans of Cornwall require similar treatment to porphyry and granite, between which they are systematically placed.

By the lapidary porphyry is treated like AGATE or CARNELIAN.

POTSTONE, a magnesian mineral, allied to Serpentine and Steatite, is very soft when first raised, and then admits of being very easily turned with chisels of various forms. See vol. 1, page 166. The common practice in Germany for polishing the Potstone, is to use first sand and water, and afterwards tripoli and water, occasionally also rottenstone and oil for the highest gloss, the whole are mostly applied on woollen cloths.

When the lapidary polishes the Potstone, is it usually by the process recommended for Alabaster, unless from long exposure it has become har- dened, and then it is worked as Carnelian.

" PUMICE-STONE is a volcanic product, and is obtained principally from the Campo Bianco, one of the Lipari islands, which is entirely composed of this substance. It is extensively employed in various branches of the arts, and particularly in the state of powder, for polishing the various articles of cut glass ; it is also extensively used in dressing leather, and in grinding and polishing the surface of metallic plates, &c."

Pumice-stone is ground or crushed under a runner, and sifted, and in this state it is used for brass and other metal works, and also for japanned, var- nished, and painted goods, for which latter purposes it is generally applied on woollen cloths with water.

PUTTY POWDER is the pulverised oxide of tin, or generally of tin and lead mixed hi various proportions, — the process of manufacture is alike in all cases. The metal is oxidized in an iron muffle, or a rectangular box, close on all sides, except a square hole in the front side. The retort is surrounded by fire and kept at the red heat, so that its contents are partially ignited, and they are continually stirred to expose fresh portions to the heated air ; the process is complete when the fluid metal entirely disappears, and the upper part of the oxide then produced, sparkles somewhat like particles of incandescent charcoal. The oxide is then removed with ladles and spread over the bottom of large iron cooling pans and allowed to cool. The lumps of oxide, which are as hard as marble, are then selected from the mass and ground dry under the runner, the putty powder is afterwards carefully sifted through lawn.

As a criterion of quality it may be said that the whitest putty powder is the purest provided it be heavy, some of the common kinds are brown and yellow, whilst others from the intentional admixture of a little ivory black are known as grey putty. The pure white putty, and which is used by marble workers, opticians, and some others, is the smoothest and most cutting ; it should consist of the oxide of tin alone, but to lessen the

AND PROCESSES FOR GRINDING AND POLISHING. 1088

difficulty of manufacture, a very little lead, (the linings of tea chests,) or else an alloy called shruff (prepared in ingots by the pewterers) is added to assist the oxidation.

The putty powder of commerce of good fair quality, is made of about equal parts of tin and lead, or tin and shruff ; the common dark coloured kinds are prepared of lead only, but these are much harsher to the touch and altogether inferior.

Perhaps the most extensive use of putty powder is in glass and marble works, but the best kind serves admirably as plate powder, and for the general purposes of polishing.

2. — PUTTY POWDER FOR FINE OPTICAL PURPOSES is prepared by Mr. A. Ross by the following method, which is the result of many experiments. Metallic tin is dissolved in nitro-muriatic acid, and precipitated from the filtered solution by liquid ammonia, both fluids being largely diluted with water. The per-oxide of tin is then washed in abundance of water, collected on a cloth filter, and sqvieezed as dry as possible in a piece of new clean linen ; the mass is now subjected to pressure in a screw press, or between lever boards, to make it as dry as possible. When the lump thus produced has been broken in pieces and dried in the air, it is finely levigated while dry, on a plate of glass with an iron spatula, and afterwards exposed in a crucible to a low white heat.

Before the per-oxide has been heated, or whilst it is in the levigated hydrous state, the putty powder possesses but little cutting quality, as under the microscope the particles then appear to have no determined form, or to be amorphous, and on being wetted to resume the gelatinous condition of the hydrous precipitate, so as to be useless for polishing ; whereas when the powder is heated, to render it anhydrous, most of the particles take their natural form, that of lamellar crystals, and act with far more energy, (yet without scratching,) than any of the ordinary polishing powders. The whole mass requires to be washed or elutriated in the usual manner after having been heated, in order to separate the coarser particles.

Mr. Ross usually adds a little crocus to the putty powder by way of colour- ing matter, as it is then easier to learn the quantity of powder that remains on the polishing tool ; and it may be added that this is the polishing powder employed by Mr. Ross in making his recently improved achromatic object glasses for astronomical purposes.

QUARTZ. — Pure silex, occurs both crystalline and amorphous and is polished after the mode described for CARNELIAN. The reader is also referred to the article CRYSTAL, by which name Quartz is very commonly known in the arts.

LGSTONE.— See HONE SLATES, article 1 .

RAGST

RED STUFF. — A name applied by watchmakers to some kinds of crocus, or the oxide of iron, the manufacture of which is described under the head OXIDE OF IRON.

1089 DESCRIPTIVE CATALOGUE OF APPABATUS, MATERIALS,

RHODIUM, which is an extremely hard metal, is generally figured and ground on an iron lap, into the surface of which fragments of diamond have been ham- mered. As a temporary expedient rhodium may be polished on a brass lap with oilstone powder and oil, using a high velocity.

ROCK CRYSTAL.— See CRYSTAL.

ROTTENSTONE is a variety of Tripoli, almost peculiar to England, and proves a most valuable material for giving polish and lustre to a great variety of articles, as silver, the metals, glass, and in the hands of the lapidary even to the hardest stones. It is found in considerable quantities both in Derby- shire and South Wales.

ROUGE. — See J)XIDE OF IRON, articles 1 and 4.

RUBBERS. — The rubbers used in polishing often follow very nearly the form of the plane, the file, or the turning tool, accordingly as the respective artizans use the plane, file, or turning tool in their several avocations. For instance, the carpenter wraps glass paper around a square flat piece of cork ; the smith and others using files, fold emery paper upon that instrument, or use, after the manner of the file, square pieces of wood and metal fed with the several powders mixed with oil, and they also employ either the sides or the sloping ends of square slips of the polishing stones.

Many of the turned works in the metals, &c. are polished with pointed sticks of deal, by the ends of which the gritty substances are forcibly applied as the work revolves.

2. — THE RUBBER USED BY MASONS AND STATUARIES is frequently a slab of grit stone, to which a handle is attached by means of an iron strap, or cement. Sometimes the handle is short and perpendicular, at other times long and horizontal, or inclined at a small angle or loosely attached by an eye bolt, and stones of two or three qualities, from coarse to fine, are used in succes- sion. The same forms are also given to the handles of flat plates of iron and lead that are fed with sharp sand for polishing stone, or with emery for metal ; and the plate may in this case be made of such a weight as to supply the required pressure, leaving to the workman alone to put it in movement to and fro upon the work, with strokes evenly distributed throughout its svirface.

3. — THE BLOCK OR CLOTH RUBBER USED FOR MARBLE, consists of a wooden block about 12 or 14 inches long, 3 to 6 wide, and 2 to 3 thick, a hole is bored through the wood at one end for a transverse stick or handle which projects, horizon tally on both sides, and there are fillets of wood on the top by which lumps of lead are temporarily affixed to give the required pressure. Felted cloth nearly half an inch thick, (called nap,} is fixed below the rubber by folding the cloth a little way up the ends and nailing it, or thinner woollen and also one or more layers of coarse linen cloth are also used according to the degree of hardness required.

4. — LARGE CLOTH RUBBERS for polishing marble are sometimes made of woollen

AND PROCESSES FOR GRINDING AND POLISHING. 1090

or other rags placed in a rectangular iron frame, connected by two side screws which compress the rags into a dense mass, the surface of which is allowed to wear itself flat or it is levelled with a red-hot iron ; sometimes the ring is entire and the rags are fixed by wedges, at other times the ring is in two parts and connected by side screws to produce the compression, and a socket is added for the attachment of the handle by which the rubber is moved.

5. — SMALL CLOTH RUBBERS OR ROLLERS, used for various purposes in polishing, are commonly made of a coil of list or the selvedge of woollen cloth, wound up spirally to the diameter of two to four inches and tied round tightly with string. They are usually covered with a cloth of some kind that may easily be renewed.

6. — RUBBERS FOR FRENCH POLISHING are made of little balls of wadding, (that used for ladies dresses,) covered with a linen rag. The rubber is placed on the open mouth of the bottle which is then turned up, the varnish thus collected is covered with a second rag, and moistened with one or two drops of linseed oil, the varnish gradually exudes according to the degree of pressure given to the ball, which is of about the size of a walnut, and is thrown away after four or five minutes' use, as it hardens from the accumulation of the varnish and then scratches instead of polishing the work.

RUBY. — See SAPPHIRE, of which it is considered to be a variety. For the preparation of ruby holes for the pivots of watches, see vol. 1, pages 178 — 9.

RUMBLE or Shaking Machine. — This is a contrivance sometimes used for polishing small articles principally by their attrition against each other. The rumble is a cylindrical vessel with a side door for the introduction of the work, and