THE Franklin institute LIBRARY The Elihu Thomson Collection • Given by Mrs. Elihu Thomson CLASS 67/ BOOK ACCESSION /.^jfiX^L THE PRACTICAL METAL-WORKER'S ASSISTANT. THE PRACTICAL METAL-WORKER'S ASSISTANT: CONTAINING THE ARTS OF WORKING ALL METALS AND ALLOYS, FORGING OF IRON AND STEEL, HARDENING AND TEMPERING, MELTING AND MIXING, CASTING AND FOUNDING, WORKS IN SHEET METAL, THE PROCESSES DEPENDENT ON THE DUCTILITY OF THE METALS, SOLDERING, AND THE MOST IMPROVED PROCESSES, AND TOOLS EMPLOYED BY METAL-WORKERS. WITH THE APPLICATION OF THE ART OF ELECTRO-METALLURGY MANUFACTURING PROCESSES: COLLECTED FROM ORIGINAL SOURCES, AND FROM THE WORKS OF HOLTZAPFFEL, BERGERON, LEUPOLD, PLUMIER, NAPIER, AND OTHERS. THE ORIGINAL MATTER IS PURELY AMERICAN. THE WHOLE ARRANGED With Numerous Engravings on Wood, TO SUIT THE AMERICAN METAL WORKER. BY OLIYEE BYRNE, CIYIL, MILITARY, AND MECHANICAL ENGINEER; AUTHOR OF " THE PRACTICAL MODEL CALCULATOR j" COMPILER AND EDITOR OF THE " DICTIONARY OF MACHINES, MECHANICS, ENGINE- WORK AND ENGINEERING;" " THE PRACTICAL COTTON- SPINNER j" AUTHOR AND INVENTOR OF THE " CALCULUS OF FORM," A NEW SCIENCE, A SUBSTITUTE FOR THE DIFFERENTIAL AND INTEGRAL CALCULUS; ETC. ETC. PHILADELPHIA: HENRY CAREY BAIRD, SUCCESSOR TO E. L. CAREY. 1851. /&7 Entered according- to the Act of Congress, in the year 1851, by HENRY CARE\T BAIRD, in the Office of the Clerk of the District Court in and for the Eastern District of Pennsylvania. LIBRARY of ' ' THE * * FRANKLIN INSTITUTE PHILADELPHIA: T. K. AND P. G. COLLINS, PRINTERS. PREFACE. This work is designed to keep pace with the mechanical arts in this country, although they are in a rapid state of progression, and fast approaching to perfection. Any mechanic, previously unac- quainted with subjects treated of in this work, may, by following its pages as a text-book, succeed in his earliest attempts to accomplish even the most difficult processes described; hence the descriptions and directions-are of the most practical nature. Metallic materials are submitted to the greatest variety of pro- cesses, which mainly depend on their properties of fusibility, mal- leability, and ductility; consequently the formation and quali- ties of alloys are considered, as also the arts of founding and soldering ; those of forging works in iron and steel which are com- paratively thick, and the nearly analogous treatment of thin works, or those in sheet metals ; puddling, drawing tubes and wires, casting drop-shot, hardening and tempering, and a variety of correlative in- formation is also offered, for the particulars of which the reader is referred to the table of contents. The general principles upon which cutting tools are formed are explained. Although the prin- ciples are few and simple, the forms and proportions of cutting tools are extensively modified, to adapt them to the different materials, to the various shapes to be produced, and to the convenience of the opera- tor, or of the machine in which they are fixed. The remarks on the tools will inevitably be somewhat commingled with the account of their particular use, and the consideration of the machines with which they are allied, for it is difficult to say where the appellation tool ends, and where that of machine or engine begins. All sorts of metal workers' tools are treated of — planes, geer cutting tools, turn- ing tools, boring tools, screw-cutting tools, shears, punches, and so on — the various subdivisions of which are particularized in the table of contents. The extensive application of the art of Electro-Metallurgy to the vi PKEPACE. purposes of manufacture, and its general utility to all persons en- gaged in the multifarious processes into which the art has ramified, were sufficient recommendation to secure it a place, in a condensed form, in the present work. The grand and varied specimens of the products of the art of Electro-Metallurgy, everywhere displayed and admired, prove the immense importance of the art to the metal worker ; and it is hard to say how much may yet be expected from it, one of the most ingenious of modern applications of science, which subject the powers of nature to the use and pleasure of civil- ized man. Much of the matter introduced in this volume is highly honorable to the ingenuity and skill of American metal workers ; although our space is limited we shall particularize : the method of making wrought- iron directly from the ore, by Alexander Dickerson, of Newark, N. J. ; the machine for compressing and rolling puddlers' balls, invented by John F. Winslow, of Troy, New York; the type founding ma- chine ; the machine for making sheet metal pipes, invented by William Ostrander, of New York; the method of constructing me- tallic boats, invented by Mr. Francis, of New York; the machine for manufacturing lead pipe ; Hare's blowpipe ; the anti-friction engineering tools, invented by David Dick, of Meadville, Pennsyl- vania ; the slatting and paring machines ; universal drilling ma- chines ; geer cutting engines ; lathes ; and other engineers' tools, manufactured at the Lowell Machine Shop, Lowell, Mass. ; the mode of manufacturing drop shot, invented by David Smith, of the house of Le Eoy and Co., No. 263, Water Street, New York ; and other improvements and inventions of minor importance. Philadelphia, November 10th, 1851. CONTENTS. METALS. Antimony, bismuth, copper, gold, iron, lead, mercury Manufacture of cast-iron Smelting . . . • • • • Iron furnaces of the United States . Dickerson's method of making wrought-iron directly from the ore Manufacture of malleable iron .... Puddling Winslow's machine for compressing puddlers' balls Angle and T iron ...... Varieties of iron ...... MANUFACTURE OF STEEL. Blistered steel ...... Shear steel . . . . ... Cast-steel ....... FORGING IRON AND STEEL. Management of fires . . . The blast ....... Anchors, vertical hammer ..... Tongs and general tools ..... The small lift hammer ..... Degrees of heat ..... Management of the fire ..... Black-red heat . ...... Welding-heat . . . . . ORDINARY PRACTICE OF FORGING. Drawing down, jumping, building up, or welding Set-hammers, top- fullers ..... The ordinary hand hammer .... Smoothing off work ...... vm CONTENTS. PAGE Anvils 45 Round fullers ..... 45 Heading tools ..... 46 Making bolts and nuts ...... 47 Mortises ...... 49 Beak-iron, set-hammer ..... 49 GENERAL EXAMPLES OF WELDING. Shutting together, shutting up , . . . .51 The butt joint ...... 52 Wrought-iron hinges and conical sockets . . . . .53 Damascus twist ...... 54 Wrought-iron tubes, musket barrels . . . . .55 Chains, the wrought-iron wheels for locomotive engines . . .56 Hatchets ....... 57 CONCLUDING REMARKS ON FORGING; THE APPLICATIONS OF HEADING TOOLS, SWAGE TOOLS, PUNCHES, &c Heading tools ..... 60 Cut nails 60 The spring swage ..... 61 Trip and tilt hammers, manufactured at the Lowell Machine Shop . 62 HARDENING AND TEMPERING. Hammer hardening ...... 64 The quantity of carbon in cast-iron .... 64 Steel and glass, polarization .... 65 Practice of hardening and tempering steel . . . .66 Pinny steel ...... 68 Edge tools ...... 69 Making magnets ........... 70 Table of heat for tempering ..... 71 Examples of hardening and tempering .... 72 Razors, pen-knives, hatchets, adzes, cold chisels . . . .73 Composition used by experienced saw makers . . . .74 Watch springs ..... 75 Jacob Perkins' discovery ..... 76 File makers ...... 77 Reverberatory furnace ..... 78 Oldham's process ...... 79 HARDENING AND SOFTENING CAST-IRON. Chilled iron-casting ....... 81 Malleable iron-casting ....... 82 Case-hardening wrought and cast-iron . . . . .83 CONTENTS. ix THE METALS AND ALLOYS MOST COMMONLY USED. PAGE Antimony, bismuth 86 Description of the physical character and uses of the metals and alloys commonly used in the mechanical and useful arts . . 86 to 108 Table of the cohesive force of solid bodies .... 109 to 113 REMARKS ON THE CHARACTERS OF THE METALS AND ALLOYS. Hardness, fracture, and color of alloys ... . 114 Soft bronze . . . . • • • • .115 Malleability and ductility of alloys . . • « .116 Gold, silver, and copper H7 Strength and cohesion of alloys .. . • • • .117 Alloy-balance . . • • • • • • Table of decimal proportions . . • • • .119 Fusibility of alloys 120 M. Mallett's process . . . • • ■ • 121 Palladiumizing process . ..... 121 MELTING AND MIXING THE METALS. The various furnaces for melting ...... 123 Antimony, copper, gold, silver, and their alloys .... 124 The brass furnace 125 Observations on the management of the furnace and on mixing alloys . 126 Metal for printers' type 127 How to make the best brass . . . • • • 128 Vitreous fluxes 129 Copper and tin alloys 131 Barron's furnace . • • • • • • 132 CASTING AND FOUNDING. Metallic moulds . ' . . . • » • • 133 Earthen moulds 133 Complex moulds . . . • • • • .134 Metal moulds for pewter works ...... 135 Bearings for locomotive engines ...... 137 Type founding 138 Type founding machine ....... 139 Plaster of Paris moulds and sand moulds ..... 139 Stereotype founding 140 Moulding sand and flasks 140 Patterns, moulds, and moulding simple objects . . ... 141 Foundry patterns HI The cores of moulds 143 X CONTENTS. PAGE Picker out and loosening bar ...... 146 Moulding cored works . . . . . . , 147 Core-boxes ......... 148 False core and drawback . . . . . . .150 Reversing and figure casting . . . . . .151 Casting figures and busts ....... 152 Filling the moulds ....... . 154 Gun-metal and pot-metal ....... 155 Carbonaceous facings ....... 155 Green-sand and dry-sand moulds ...... 158 Moulds of various kinds ...... . 159 Runners ........ 159 Flasks for iron-founders . . . . . , 160 Three-part flasks . . . ... . . .161 Remarks on patterns for iron castings ..... 163 Contraction measures or rules ..... . 163 Equality of strength and thickness ...... 165 Loam moulding ........ 166 Crooked pipes, large bells, brass guns ..... 169 Reverberatory furnace ....... 170 Melting and pouring iron . . . . . .171 Cupolas ......... 172 Proportioning the change . . . . . . 173 Coating ladles . . . . . . . 174 Heavy castings, filling open moulds ..... 175 Cast-iron ornaments ........ 177 WORKS IN SHEET METAL, MADE BY JOINING. Malleability, and elasticity ....... 178 Terrestrial globes . . . . . . . .181 Works in sheet metal made by cutting, bending, and joining . . 181 Folded works with curved surfaces ...... 183 Polygonal works ........ 185 Tools for working in sheet metal . . . . . .186 Hammers, beak-irons, stakes, teests, hatchet-stakes, creases, &c. . 187 Modes of bending curved work ...... 189 Ostrander's metal pipe machine . . . . . .191 Angle and surface joints ....... 192 Rivet joints ......... 193 Roll joint ......... 194 Francis' life-boats ........ 195 Hydraulic press .... . . . . . . 196 Dick's anti-friction press ....... 198 Iron and copper boats ....... 199 CONTENTS. xi WORKS IN SHEET METAL MADE BY RAISING. * PAGE Circular works spun in the lathe ...... 200 Works raised by the hammer 202 Solid and hollow blows 203 Raising and hollowing ....... 205 Raising globes and ogees ....... 207 Hollowing tin-work 208 French horns, vases 209 Dovetail joints ........ 210 Jelly moulds ......... 211 Stamping . . . . . • • • 211 Peculiarities in tools • . . . . . • 212 Plated metals and works 213 Snarling-irons 213 The pitch-block . . 214 THE PRINCIPLES AND PRACTICE OF FLATTENING THIN PLATES OF METAL WITH THE HAMMER. Loose parts and bulges ....... 217 Works requiring great truth ...... 218 PROCESSES DEPENDENT ON DUCTILITY. Drawing wires 221 Straightening wire 223 Cylindrical shafts 224 Multiform wires, for various uses ...... 225 Double plates or swage-bits 225 Drawing metal tubes 226 Triangular, square, and rectangular brass tubes .... 227 Lead pipe machine 229 SOLDERING. General remarks on soldering ...... 230 Tabular view of the process of soldering . 231 Hard soldering . . • 231 Soft soldering 232 Soldering per se 233 Modes of applying heat in soldering ..... 233 The use of the blowpipe 235 Deoxidizing flame 236 Airo-hydrogen blowpipe ....... 237 Examples of hard soldering ...... 238 Examples of soft soldering 240 xii CONTENTS. PAGE The copper bit ....... 241 Thick metal works .. . . . . . . . 243 Pewterers' hot-air Blast ....... 244 Various modes of tinning . . . . . . . 245 Burning together ......... 246 Compensation balance ....... 247 Plumbers' work ........ 249 SHEARS. Cutting nippers for wires ....... 250 Cutting pliers . . . . . . . .251 Scissors and shears for soft flexible materials .... 252 Twitter bit . . . . . ' . . . .253 Button-hole scissors ........ 255 Pocket scissors ........ 255 Sliding shears . . . . . . . .256 Perpetual shears . . . . . . . .257 Shears for metal worked by manual power .... 258 Bench shears ........ 259 Purchase shears . . . . . . . 259 Different kinds of shears . . . . . . .261 Engineers' shearing tools, worked by steam power . . . 262 Boiler makers' shears ....... 263 Portable punching and shearing machine ..... 264 Vice to cut boiler plate ....... 265 Hydraulic machine for cutting off copper bolts .... 266 Dick's anti-friction press ...... . 267 PUNCHES. Punches used without guides ..... . 268 Confectioners' punches ...... . 269 Punches of arbitrary forms ....... 270 Army clothiers ....... . 270 Punches for red-hot iron ...... . 271 Harp makers' punch . . . . . . .271 Punches used with simple guides . . . . . . 272 Pen-making machine ..... . 272 The drop hammer ...... . . 273 Punches used in fly-presses ...... 274 The toggle joint press ..... . . 277 Punching large chains for machinery ..... 279 Chains for watches ...... . . 280 Lariviere's perforated plates . . . . . 281 Buhl works of Robert B. Henesey .... . . 283 Cut brads ......... 284 Punching machinery used by engineers ..... 285 CONTENTS. Xlll PAGE Slatting and paring machine ...... 286 Upright drill, Lowell Machine Shop . . . . .288 Universal drilling machine ....... 289 David Smith's new method of manufacturing drop shot . . . 289 DRILLS. Drills used hy hand ........ 291 O'Tool's pin drill ........ 295 Methods of working drills by hand power ..... 296 Drill stocks ......... 297 Pump-drill ......... 299 Expanding braces and lever drill ...... 301 O'Kelly's differential screw drill . . . . . . 303 Drilling and boring machines ...... 304 Portable hand drill ........ 308 D valves of a steam engine . . . . . . .311 Broaches for making taper holes ...... 311 Drills and broaches compared . . . . . .313 SCREW-CUTTING TOOLS. Originating screws ........ 315 Common screws ........ 317 Screws perfectly true . . . . . . .318 Cutting internal screws . . . . . . .319 The principle of chamfering ...... 320 Transverse sections of taps ...... 321 Ordinary tangent screw ....... 325 Diestocks . . . . . . . .327 Master taps ......... 329 Modification in dies ........ 331 Bolt screwing machines ....... 335 Shaping machine ........ 336 Geer cutting machine ....... 337 Screws cut by hand in the common lathe ..... 337 Cutting screws with traversing mandrels ..... 338 Earliest screw lathe ........ 340 Fixed slide-rest and change wheels ...... 345 Slide-lathe . 347 Modes of computing trains of wheels ..... 349 Screw tools for square threads . . . . . .351 Modes of originating and improving screws. .... 355 Fusee engine 357 Ramsden's screw-cutting engine . ... . . . 359 Engine for dividing circles and straight lines .... 360 Chucking and reaming lathe ...... 366 Engine lathe ......... 367 xiv CONTENTS. PAGE Screw threads considered in respect to their proportions, forms, and general characters 368 Strength of screws and nuts ...... 373 Different sections of screw threads ...... 377 Angular screw threads . . . • • • . * 380 Screws of standard measure ...... 385 ELECTRO-METALLURGY. Nomenclature ........ 387 Batteries ......... 388 Best kind of zinc ........ 389 Economy in amalgamation ....... 390 Different elements in batteries ...... 391 Properties of metals fit for batteries ..... 392 Copper and zinc plates ....... 395 Battery of eight cells ....... 399 ELECTROTYPE PROCESS. Forms of apparatus 403 Comparative value of existing solutions ..... 405 How often solutions should he changed and zinc amalgamated . . 405 Making of moulds 406 Moulds in wax and plaster, gutta percha/fusible alloys, &c. . . 407 To make busts and figures 410 Electrotypes from daguerreotypes . . . • • .411 Compound cell process ....... 413 Mode suspending objects for coating ..... 414 OTHER APPLICATIONS OF COATING WITH COPPER. .Coppered cloth 417 Calico printers' rollers ....... 417 Etching of rollers 418 Printing from electrotypes ....... 418 Copying of copperplate engravings ..... 418 Coating of glass and porcelain ...... 418 Galvanic soldering ........ 419 BRONZING Brown bronzes ........ 421 Black bronzes ........ 422 Green bronzes ........ 422 CONTENTS. XV DEPOSITION OF METALS UPON ONE ANOTHER, PAGE Coating of iron with copper ....... 423 Cyanide of potassium, its manufacture ..... 424 Cyanide of copper solution ....... 425 Peculiarities in working cyanide of copper solution . . . 426 Preparation of iron for coating with copper .... 427 Effects of conducting power in solutions and metals . . . 427 Illustrations of conduction ....... 428 Non-adherence of deposit ....... 429 Coating of iron with zinc ....... 429 Sulphate of zinc ........ 429 Use of zinc coating ........ 430 Influence of galvanism in protecting metals from destruction by oxida- tion and solution ........ 430 ELECTRO-PLATING. To make silvering solution ....... 432 Cyanide of silver dissolved in yellow prussiate of potash . . . 433 Solution made with oxide of silver ...... 434 Solution made with chloride of silver ..... 434 The best method of making silver solution .... 434 Hyposulphite of silver solution ...... 435 Sulphite of silver solution ....... 436 To recover silver from solutions ...... 437 Preparation of articles for plating ...... 437 Practical instructions in plating ...... 439 Taking Silver from Copper, first method ..... 440 — - — ■ second method .... 441 Cyanide of silver and potassium, its decomposition during the plating process ......... 441 Other effects produced in working ...... 442 Machine for moving goods while subjected to the electro-plating pro- cess . . ..' **. . . . . . 443 Deposit dissolving off in solution ...... 443 Opposite currents of electricity from vats ..... 444 Test for the quantity of free cyanide of potassium in solutions . . 445 Rate of depositing silver ....... 446 Bright deposit of silver ....... 446 Different metals for plating ....... 446 Electricity given off from sandy deposits ..... 447 The old method of plating . . . . . . .447 Advantages of electro-plating ...... 448 Objections to electro-plating ...... 449 Solid silver articles made by the battery . • . . . 450 xvi CONTENTS. Dead silver for medals Protection of silver surface . Cleaning of silver ELECTRO-GILDING Preparation of solution of gold Battery process for preparing gold solution Process of gilding Conditions required in gilding Method of maintaining the gold solution . Method of regulating the color of the gilding Coloring of gilding j . Method of dissolving gold from gilt articles Objections to electro-gilding Effects of cyanogen upon health Practical suggestions on gilding RESULTS OF EXPERIMENTS ON THE DEPOSITION OF OTHER METALS AS COATINGS. Coating with platinum . . . . . . 458 Coating with palladium ....... 459 Coating with nickel ........ 459 Deposition of antimony, arsenic, tin, iron, lead, bismuth, and cadmium . 459 Deposition of alloys ....... 460 Deposition of bronze ....... 460 THEORETICAL OBSERVATIONS. Action of sulphate of copper upon iron ..... 461 Faraday's theory of electrolysis ...... 462 Graham's theory of electrolysis ...... 462 Daniell's and Miller's views ...... 463 Proposed theory ........ 464 Dr. Medcalf s theory ....... 464 PAGE . 451 . 451 . 452 . 453 . 453 . 454 . 454 . 455 . 455 . 455 . 456 . 456 . 457 THE PRACTICAL METAL-WORKERS' ASSISTANT. METALS. The chemist enumerates forty-one different metals; of these many are entirely confined to the laboratory, part are only used in the chemical arts, and those to which I propose to refer as connected •with our subject, are but fourteen, namely, Antimony, Bismuth, Copper, Gold, Iron, Lead, Mercury, Nickel, Palladium, Platinum, Rhodium, Silver, Tin, and Zinc. Of these, mercury is always fluid in our latitudes, and antimony and bismuth are brittle metals, consequently they are not used alone in construction, and pure nickel, although malleable, is rarely so employed ; subtracting these, ten remain. Palladium, platinum, and rhodium are principally used on account of their infusibility and resistance to acids, for a few purposes con- nected with science : their abstraction reduces the number to seven. Gold and silver are mostly reserved for coin, and articles of luxury, so that taking away these also, the majority of the works of mechanical art fall exclusively on five, namely, copper, iron, lead, tin, and zinc. These five practical metals, if the term may be allowed, are again virtually extended by an infinitude of combina- tions^ or alloys, principally amongst themselves, although with the occasional introduction of the metals before named, and some few others. Of all the metals, however, iron is the one to which, from its manifold changes and adaptations, and from its abundance, the most importance is to be attached ; so much so, that were we compelled to the choice, it would be doubtless politic to sacrifice all the others for its possession. It is subjected to several of the methods of treat- ment common to the other ordinary metals, and to a variety of changes no less important peculiarly its own. . 0n * nese several grounds, therefore, the principal share of atten- tion will be devoted to iron and its several modifications, and it is intended as a general illustration, to commence with a slight sketch 18 METALS. of the manufacture of iron from the ore, into cast-iron, wrought iron, blistered, shear, and cast-steel ; and its part manufacture for the purpose of commerce, into ingot, bar, sheet and wire. This will be followed by its further preparation, by forging, into some of the elements of machinery and tools; the various changes of hardening and tempering, applied under a variety of circumstances, will be then described. It is proposed subsequently to consider the thirteen other metals, both in their simple and alloyed states, which will lead to a general outline of the methods of casting objects of various forms, and also of the practice of soldering, which is dependent on the fusible property of some of the metals. Manufacture of Cast Iron. — The ore having been raised, the first process to which it is subjected is called calcining or roasting; the iron-stone or raw-mine is intermixed with coal and thrown into heaps, commonly from thirty to sixty feet in length, ten to sixteen feet wide, and about five to ten feet high ; the heaps are ignited and allowed to burn themselves out, which takes place in three or four weeks. This calcines the ore, and drives off a portion of the water, sulphur, and other volatile matters, after which the ore is said to be torrified; this process is also performed in kilns. The smelting is generally performed in England and Wales with coke, and therefore another distinct part of the manufacture of iron is the preparation of the coke, which, like torrifying the ore, is also performed upon an enormous scale either in open heaps or in kilns, more generally the former. The smelting furnace used in South Wales is represented in Fig. 1 ; its height is about forty-five the filling place up an inclined plane, by means of the steam engine; a full barrow proceeds along the upper surface of the rail, arrived at the top it turns over, dis- Fig. 1. feet, its diameter at the largest part, or boshes, from twelve to eighteen feet, and it terminates at the bottom in the hearth, which is originally a cube of about a yard on every side, but soon becomes of an irregular form from the inten- sity of the heat. In mountainous countries the furnace is usually built by the side of a hill, upon the summit of which the coke and mine are pre- pared, so that they, along with the due proportion of limestone, may be wheeled in barrows along the bridge represented, into the mouth of the furnace. In level countries, the charge has to be dragged to MANUFACTURE OF CAST IRON. 19 charges its contents into the furnace and returns on the lower side, much the same as the buckets of a dredging machine ; there are two such barrows, and from their action they are called tipplers : the most general plan, however, and the best, is to fill the furnace by hand, a man being stationed at the top, on the plane provided for the purpose. The furnace requires, in addition to the solid materials, an enor- mous supply of air, which is driven in by blowing engines of various constructions, either at the ordinary temperature or in a heated state, and at one, two, or three sides of the cubical hearth through appro- priate pipes or tuyeres; the fourth or front side of the hearth being reserved for the dam stone, over which the cinder or scoria flows in a fluid state, and for the aperture through which the charge of melted iron is removed. When the charge arrives at the hottest part of the furnace, the carbon of the fuel is considered to unite with the oxygen of the ore, and to escape in the form of carbonic acid gas, and carbonic oxide. The lime serves as a flux to fuse the clay and silex of the iron-stone into an imperfect glass or scoria; and the particles of the metal now released, ooze out from the iron-stones, mix with some of the carbon of the fuel, fall in drops through the fiery mass, and collect on the bed or hearth of the furnace ;. whilst the scoria floats on the surface of the fluid metal, and defends it from the air. When the scoria has accumulated in sufficient quantity to reach a proper aperture in the front of the furnace, it flows away as a con- stant stream of liquid lava; and the furnace is tapped at intervals, to allow the charge of metal to run out into channels formed in a bed of sand for its reception: it now assumes the name of crude- iron, cast-iron, or the pig iron of commerce, which is a compound more or less pure, of iron and carbon in different proportions. The choice of the flux depends on the nature of the ore or mine. For argillaceous ores, lime is required; and frequently the cinders or slag from the fineries and forge are mixed with the lime. For calcareous ores, clay is added, in order to establish a similar train of affinities as regards the earthy matters of the ore. One of the main objects being to fuse all the earths into a glass, so fluid as not to detain the globules of metal, from descending through it to the general mass of fluid iron beneath. When the iron ores are very pure, clay is introduced into the furnace, but these pure ores are more commonly mixed in small quantities with the poorer of other districts, and are used without being calcined. It is fortunate that in this country nature has generally supplied the three materials, iron-stone, coal, and lime, at the same localities, as otherwise their transport would add materially to the cost of the production of this invaluable metal. The iron furnaces of the United States are, generally speaking, far superior to those of England or the rest of Europe. On this point we refer our readers to "Overman on Iron," and, as our space is limited, be contented to introduce one of the many American itn- 20 METALS. provements. This is a method of making wrought-iron directly from the ore, patented by Alexander Dickerson, of Newark, N. J., 22d July, 1850. We have seen some of the iron produced, it is of the best quality. Of this furnace, Fig. 2 represents a side view when complete. Fig. 3, a longitudinal section of the same. Fig. 4, top view of cylinders, partly open. Figs. 5, and 6, large and small water plates occupy- ing places F and E respectively, through which small jets of water Fig. 4. Fig. 2. Fig. 5. Fig. 6. Fig. 3. MANUFACTURE OF MALLEABLE IRON. 21 continually flow, to prevent the flame from burning the cylinders. L and M, two upright cylinders, standing on the water plates ; and between which cylinders in space B are placed in equal alternate layers, the pulverized ore and charcoal, or 25 per cent, in weight of anthracite if that is substituted for charcoal. The escape heat passes through an opening P in the arch freely through space C between the masonry work D and the outer cylin- der L, and also within the inner cylinder M through space A, whereby the ore mixed with the coal is completely and uniformly surrounded by the flame of heat and deoxydized, and yet perfectly protected from the air, flame and noxious gases. When thus deox- ydized, one charge of the ore, by elevating valve R, is readily pre- cipitated on the preparatory bottom G ; where it is stirred and freed from the small particles of coal that accompany it from the cylinders. It is then passed over on the puddling bottom G, where it is further stirred and made up into balls, when it is ready for the hammer or rolls. In the fire chamber 0, the heat and flame may be produced from wood, anthracite or bituminous coal. The whole furnace much resembles an elongated ordinary pud- dling furnace, with the addition of a preparatory bottom, over which are placed the cylinders and their appendages. While in operation, the cylinders are charged from the top with the ore and coal pulverized and mixed. The cylinders are kept at a red heat. The ore is thoroughly deoxydized in them, and deposited from them in successive charges on the preparatory and puddling bottoms, as rapidly as the balls are taken from the latter for the hammer or rolls. Thus the operation is continuous and economical, as only the escape heat of the furnace is employed in the cylinders. The whole is easily managed and worked, the operation is steady, and the product certain and uniform. The iron produced is ex- tremely pliable, ductile, and malleable, and applicable to all the arts. It is produced at a saving of about 40 per cent, of any other pro- cess — and in this way the best quality of wrought-iron is produced for about the same price as pig. A ton and a half of anthracite coal, and two and half to three tons of ore make a ton of blooms in twelve hours. A furnace complete costs from $1,200 to $1,500. Manufacture of Malleable Iron. — Formerly, wrought-iron was obtained either directly from the ore, or from cast iron, by a process still in extensive operation, in which wood charcoal is re- quired. Puddling. — The crude cast iron is remelted in quantities of from half a ton to one ton, in a furnace called the chafery, or refinery, blown with blast ; it is kept fluid for about half an hour, and then cast into a plate about four inches thick, which is purer, finer in the grain than pig metal, and also much harder and whiter ; it is then called refined metal. The plate when cold is broken up, and from two to four hundred weight of the fragments, with a certain propor- 22 METALS. tion of lime, are piled on the hearth of the puddling furnace, -which is a reverberatory furnace without blast. - In about half an hour the iron begins to melt, and whilst it is in the semi-fluid state, the workman stirs and turns it about with iron tools ; he also throws small ladles full of water upon it from time to time. In this condition the metal appears to ferment, and heaves about from some internal change ; this is considered to arise from the escape of the carbon in a volatilized form, which ignites at the sur- face with spirits of blue flame : in about twenty minutes the pasty condition gives way, and the iron takes a granulated form without any apparent disposition to cohesion ; the fire is now urged to the utmost, and before the metal becomes a stiff conglomerated mass, the workman divides it into lumps or balls of about fifty pounds in weight. These balls are taken out one at a time, and shingled, or worked under a massive helve or forge-hammer, that weighs six or eight tons, and is moved by the steam engine : this compresses the ball, squeezes out the loose fluid matter, and converts it into a bloom, or short rudely-formed bar. The bloom is then raised to the welding heat in a reheating furnace, and again passed under the hammer, or through grooved rollers, or it is submitted to both processes, by which it is elongated into a rough bar. The shingling is sometimes performed by large squeezers, somewhat like huge pliers, or by roughened rollers that also serve to compress the iron ; but the pon- derous flat-faced helve is considered the more effectively to expel the dross and foreign matters from the bloom, and to weld the same more perfectly at every point of its length. The machine for compressing and rolling puddler's balls, invented by John F. Winslow of Troy, New York, is very effective and pos- sesses many advantages, of which may be mentioned : 1. Great expedition in shingling puddler's iron, one of these machines being sufficient to do the work of twenty-five puddling furnaces. 2. The saving of shinglers' wages ; no waste of iron ; turning out the blooms while very hot, enabling the roller to reduce them to very sound bars. 3. The ends of the blooms are thoroughly upset, a very small amount of power operates the machine, and little or no expense for repairs. The nature of the first part of this invention consists in rolling and compressing puddler's balls or loops of iron into blooms, &c, by means of a rotating cam-formed compresser, combined with two or more rollers placed near to one another, and at the same distance from the axis of motion of the compresser, so that the compression and elongation of the loops will be due entirely to the eccentricity of the compresser, the whole being so geared that the rollers shall turn in the direction opposite to the motion of the compresser, that the loop may be rotated and retained between the rollers and the compresser : the surfaces of the rollers are formed with slight pro- jections to take hold of and turn the loop of iron, and the surface of the cam-formed compresser with teeth, which are very large at PUDDLING. 23 first, or on that part of the compresser which first acts on the loop, to squeeze out the impurities, and at the same time insure the turning of the loop, and then gradually diminished until the surface becomes quite or nearly smooth to finish the bloom. And the second part of this invention consists in combining with the compresser and rollers two cheeks, one on each side, and pro- vided with springs that force them towards one another that they may yield to the ends of the loop of iron as it is lengthened out by the action of the compresser and rollers, and at the same time to make sufficient resistance to give a proper form to the ends of the blooms, &c. And the third part of this invention consists in combining with the compressor and rollers, a feeder or sliding frame operated by a projection on the compresser or the shaft thereof, to carry in the ball of iron between the compresser and roller, as that part of the compresser which is recessed for that purpose comes round to the proper place for the introduction of the ball, and the discharge of the bloom ; and also in combining in like manner a follower for dis- charging the bloom after it has been completed. (a) represents the frame of the machine properly adapted to the intended purpose, but which may be varied at pleasure. In appro- priate boxes (bb) between the standards of this frame run the journals of an eccentric roller (c), the periphery of which is cam-formed and provided with cogs, for the purpose of squeezing the ball of iron and forcing out the impurities, and gradually reducing its diameter and elongating it. Below this squeezing roller are arranged two fluted rollers (dd) whose journals are fitted to appropriate boxes in the frame. These rollers constitute the concave on which the ball of iron rests during the operations of the squeezer; cogwheels (efg h) being employed to connect the shaft of the rollers with the shaft of the squeezer in such manner as that the peripheries of the two rol- lers (dd) shall turn in the same direction, and that of the squeezer in a reverse direction, and thus cause the ball or mass of iron, dur- ing the operation of squeezing, to rotate about its axis, or nearly so ; the requisite power for this purpose being communicated to the machine from some first mover in any efficient manner. One of the bottom rollers (d) has a strong flanch (i) on one side which pro- jects sufficiently to pass within the periphery of that part of the squeezer which acts on the iron, after it has been so much elongated as to have one of its ends approach the flanch, and therefore towards the end of the operation of the squeezer that end of the bloom or mass of iron which is towards this flanch will be upset by it and properly formed. On the side of the machine opposite to the flanch (i) is a hammer (j) on the end of the bar (k) which slides in collars (I). The face of this hammer is smooth, and made as hammers for working iron usually are, and its edges are adapted to the peripheries of the two rollers (dd) and to that part of the periphery of the squeezer which acts on the bloom at the time the hammer is to strike the ends of the bloom. A strong helical spring surrounds the bar 24 METALS. (k) of the hammer, one end bearing against one of the collars {T), and the other against the back of the hammer, so that its tension will always force the hammer towards the flanch (i) of the roller (d), and towards the outer end, the said bar (k) is provided with a spur (m), Fig. 7. the inner face of which is slightly rounded to bear against the face of a cam (n), so formed that at each revolution of the bottom rollers it gives the hammer two blows upon the bloom, and at every revolu- tion of the rollers the spring is liberated and the hammer strikes the PUDDLING. 25 bloom, and thus upsets the ends, the flanch (i) in this part of the operation performing the office of an anvil ; the face of the cam is then made in the form of an inclined plane to draw back the hammer preparatory to another operation. Instead of forcing the hammer towards the bloom by a spring and drawing it back by a cam, this arrangement may be reversed by making the spring simply of sufficient length to draw back the ham- mer, and reversing the cam that it may force the hammer towards the bloom at the required time. And if desired, a lever, operated m any desired manner, such as by a cam or crank, may be used to operate the hammer instead of a cam, and under this latter modifi- cation the spring may be dispensed with altogether by connecting the hammer bar with the lever. The bars are next cut into short pieces, and piled in groups of four to six ; they are again raised to the welding heat in a reheating fur- nace, and passed through other rollers to weld them throughout their length, and reduce them to the required sizes ; and sometimes the processes of cutting and welding are again repeated in the manufac- ture of still, superior kinds of iron. A similar process of manufacture is still carried on, partly with wood charcoal, in place of coals and coke ; the iron thus manufac- tured, called charcoal iron, is much purer, but it is also more ex- pensive in England ; it is sometimes, by way of distinction, left in ridges from the hammer, when it is called dented iron. The rollers or rolls of the iron works are turned of a variety of forms, according to the section of the iron that is to be produced ; in general one pair is used exclusively for each form of iron required; a i th , ou S h in the imaginary sketch, Fig. 8, it is supposed that the shaded portion represents the upper edge of the bottom roll ; and that the top roll, which is not drawn, almost exactly meets the bot- tom one, with the exception of the grooves, and which are in gene- ral turned partly in each roll, in the manner denoted by the black figures. Fig. 8. One pair will have a series of angular grooves for square iron gradually less and less, as a, b, c, Fig. 8, so that the bar may be ra- pidly reduced without the necessity for altering the adjustment of the rolls, which would lose much valuable time ; the flat bars are pre- pared square, and then flattened in grooves, such as that at d; round, or bolt iron, requires semicircular grooves, e ; but round iron often shows a seam down one side, from the thin waste spread out between the rolls being afterwards laid down without being welded, when the iron is turned one quarter round and sent again° through 26 METALS. the rollers : therefore the best round works are mostly forged from square bars. Figs. / and g are described as angle, and T iron ; these are par- ticularly used in making boilers, the ribs of iron steam-vessels ; also frames, sashes, and various works requiring strength with lightness. Plain cylindrical rollers serve for producing plate and sheet iron, which vary in thickness from one inch to that of writing-paper, and rolls turned like Fig. i, are employed for curvilinear ribbed plates, or the corrugated iron, an elegant application lately patented for roofs. Other rollers composed of two series of steeled discs, placed upon spindles, are used to slit thin plates of iron about six inches wide, into a number of small rods for the manufacture of nails, and similar rods are also made of larger sizes called slit iron, they always exhibit two ragged edges, and from being tied up in small parcels, are also known as bundle iron. Figs. 9. 10. 11. 12. Figs. 9, 10, 11 and 12, represent four amongst numerous other sections of railway iron ; these bars are produced in rollers turned with counterpart grooves ; as before, the shaded portions represent frag- ments of the lower rollers, and the upper rollers are supposed to occupy the spaces immediately adjoining the section of the rails. For these also, three, four, or more grooves, varying gradually from that of the roughly prepared bar, to that of the finished rail, are employed, and this in like manner saves the necessity for adjusting the distance between the rollers during the progress of the work. All the foregoing rolls are supposed to be concentric, and to pro- duce parallel bars and plates of the respective sections ; but in making fish-bellied railway bars, (no longer used,) taper plates for coach springs, and similar tapered works, the rollers, whether plain or grooved, are turned eccentrically, so as to make the works respect- ively thicker or deeper in the middle, as in Fig. 13; this requires additional dexterity on the part of the workman to introduce the material at the proper time of the revolution, upon which it is unne- cessary to enlarge. The general effect of the manufacture of malleable iron is to de- prive the cast-iron of its carbon; this is done in the puddling furnace ; the original crystaline structure gives way to the fibrous, from the working under the hammer and rollers, by which every individual particle or crystal is drawn out as it were into a thread, the multi- tude of which constitute the fibrous bar or metallic rope, to which it has some resemblance except in the absence of twist. The rod may now be bent in any direction without risk of fracture; and the supe- rior kinds, even when cold, may be absolutely tied in a knot, like a rope, when a sufficient force is applied. VARIETIES OF IRON. 27 Should it however occur that the first operation, or shingling pro- cess, were imperfectly performed, the error will be extended in a proportionaldegree throughout the mass, which will account for the general continuance of any imperfection throughout the bar of iron, or a considerable length of the wire in which the reduction or elon- gation are further extended; and to which evil all metals and alloys, subjected to these processes of elongation, are also liable. Malleable iron is divided into three principal varieties; first, red- short iron; secondly, cold-short iron; thirdly, iron partaking of neither of these evils; and which may be so far denominated pure malleable iron. The first kind is brittle when hot, but extremely soft and ductile whilst cold; this is considered to result from the presence of a little carbon. The cold-short withstands the greatest degree of heat with- out fusion, and may be forged under the heaviest hammers when hot, but it is brittle when cold; this is attributed to the presence of a little silex. The third kind is considered to be entirely free from either carbon or silex, &c, and to be the pure simple metal; but in the general way the characters of iron are intermediate between those described. From one and a half to two tons of pig-iron have been used to produce one ton of malleable iron ; but the average quantity is now from twenty-six to twenty-seven tons for each twenty tons of pro- duce.^ The forge pig, ballast, and white cast-iron, is the kind principally used, as it contains least carbon, the whole of which should be expelled in the conversion of the cast metal into wrought iron. It appears to be unnecessary to attempt any minute description of the different marks and qualities of iron; first, as these descrip- tions have been minutely given in many works, some of which are alluded to at the end of this chapter ; and secondly, as in common with most other articles, the quality of iron governs the price. The quantity used by the amateur will be comparatively inconsiderable; he will be therefore disposed to ask for the best article, and to pay the best price. I will only add, that little can be known of the character of iron from its outside appearance, beyond that of its having been well or ill manufactured, so far as regards its formation into bars. The smith is principally guided by the fracture when he breaks down the iron, that is, when the bar is nicked on opposite sides with the cold chisel, laid across the anvil upon a strip of iron near to the cut that it may stand hollow, and the blows of the pane of the sledge-hammer are directed upon the cut. The judgment will be partly formed upon the force thus required in breaking the iron; the weakest and worse kinds will yield very readily; when small, sometimes even to the blow of the chisel alone, and will then show a coarse and brilliant appearance, entirely granu- lar or crystaline; this iron would be called very common and bad. If, on the other hand, the iron breaks with difficulty, and the line of 28 METALS. separation, instead of being moderately flat, is irregular, or presents what may be called a hilly surface, the sides of which have a fibrous structure and a sort of lead-colored or a dull gray hue, this kind will have a large proportion of fibre, and it will be called excellent tough iron. Other kinds will be intermediate, and present partly the crystal- ine and partly the fibrous appearance, and their relative values will depend upon how nearly they approach the one or other character. Another trial is the extent to which iron, when slightly nicked, may be bent to and fro without breaking; the coarse brittle kind will scarcely bend even once, whereas superior kinds, especially stub, charcoal, and dented irons, will often endure many deflections before fracture, and when nicked on the outside only and doubled flat together, will bend as an arch and partly split open through the centre of the bar, somewhere near the bottom of the cut made with the chisel, the entire fracture presenting the beautiful fibrous appear- ance and dull leaden hue before described. Manufacture of Steel. — Steel is manufactured from pure mal- leable iron by the process called cementation; the Swedish iron from the Dannemora mines marked with the letter L in the centre of a circle, and called "Hoop L," is generally used ; irons of a few other marks are also used for second-rate kinds of steel. The bars are arranged in a furnace that consists of two troughs, about fourteen feet long, and two feet square ; a layer of charcoal powder is spread over the bottom, then a layer of bars, and so on alternately ; the full charge is about ten tons; the top is covered over first with char- coal, then sand, and lastly with the waste or slush from the grind- stone trough, applied wet, so as to cement the whole closely down, for the entire exclusion of the air. A coal fire is now lighted below and between the troughs; and at the end of about seven days, the bars are found to have increased in weight the one hundred and fiftieth part, by an absorption of carbon, and to present, when broken, a fracture more crystaline, although less shining than before. The bars, when thus converted, are also covered with blisters, apparently from the expansion of the minute bubbles of air within them; this gives rise to the appellation blistered- steel. The continuance of the process of cementation introduces more and more carbon, and renders the bars more fusible, and would ulti- mately cause them to run into a mass, if the heat were not checked ; to avoid this mischief a bar is occasionally withdrawn and broken to watch the progress; and the work is complete when the cementa- tion has extended to the centre of the bars ; the conversion occupies, with the time for charging and emptying the furnace, about fourteen days. A very small quantity of steel is employed in the blistered state, for welding to iron for certain parts of mechanism, but not for edge tools ; the bulk of the blistered steel is passed through one of the two following processes, by which it is made either into shear-steel, or cast-steel. MANUFACTUKE OP STEEL. 29 Shear-steel is produced by piling together six or eight pieces of blistered-steel, about thirty inches long, and securing the ends within an iron nng, terminating in a bar about five feet long by way of a handle. ^ They are then brought to a welding heat in a 'furnace and submitted to the helve or tilt hammer, which unites and extends them into a bar called shear-steel, from its having been much used in the manufacture of shears for cloth mills, and also German steel trom having been in former years procured from that country bometimes the bars are again cut and welded, and called double-shear steel, trom the repetition. This process of working, as in the manufacture of iron, restores the fibrous character, and retains the property of welding: the shear steel is close, hard and elastic; it is much used for tool?, composed jointly of steel and iron; its superior elasticity also adapts it to the formation of springs, and some kinds are prepared expressly for the same under the name of spring-steel. In making cast-steel about twenty-six or twenty-eight pounds of fragments of blistered-steel, selected from different varieties, are placed in a crucible made of clay, shaped like a barrel, and fitted with a cover, which is cemented down with a fusible lute that melts after a time the better to secure the joining. Either one or two pots are ex- posed to a vivid heat in a furnace like the brass-founders' air-furnace m which the bhstered-steel is thoroughly melted in the course of three or four hours ; it is then removed by the workman in a glowing state, and poured into a mould of iron, either two inches square for bars or about six by eighteen inches, for rolling into sheet-steel. For large ingots the contents of two or more pots are run together in the same mould, but it requires extremely great care in managing the very intense temperature, that it shall be alike in both or all The pots. lhe mgots are reheated in an open fire much like that of the com- mon forge, and are passed under a heavy hammer weighing several tons, such as those of iron-works; the blows are given gently at first, owing to the crystaline nature of the mass, but as the fibre is eliminated the strength of the blows is increased Steel is reduced under the heavy hammer to sizes as small as three-quarters of an inch square. Smaller bars are finished under tilt hammers, which are much lighter than the preceding, move con- siderab y quicker, and are actuated by springs instead of gravity alone ; these condense the steel to the utmost. Rollers are also used, ST \ ^ Steel ° f r ° Un 1 d ' half - round > ^d triangular sections out the tilt hammer is greatly preferred. J? St ;! tee K iS * th ? m ° S i Uni , f ° m in the har aest, and alto- gether the best adapted to the formation of cutting tools, especially those made entirely of steel ; butmuch of the cast-steel will not endur^ the ordinary process of welding, but will fly in pieces under the ham- mer when struck. In respect to steel, the same general remarks offered upon iron may be repeated, namely, that price in a great measure governs quality, feteel when broken does not show the fibrous character of 30 METALS. iron, and in general the harder or harsher the steel, the more irregu- lar or the less nearly flat will be its fracture. The blistered-steel should appear throughout its substance of an uniform appearance, namely, crystaline and coarse, much like infe- rior iron, but with less lustre and less of the bluish tint ; when but partially converted, the film of iron will be readily distinguished in the centre. The blistered-steel when it has been once passed through the fire and well hammered, assumes as may be supposed a much finer grain, as in fact the operation converts it (although in the small way), into shear steel. Shear steel breaks with a much finer fracture, but the ^crystaline appearance is still readily distinguished. Cast-steel is in general the finest of all in its fracture, and unless closely inspected, its sepa- rate crystals or granulations should be scarcely observable, but the appearance should be that of a fine, light, slaty-gray tint, almost without lustre. The quality of steel is considerably improved, especially as regards cutting tools, when after being forged it is hammer-hardened, or well worked with the hammer until quite cold, as this tends to close the "pores" and to make the material more dense; above all things excess of heat should be avoided, as it makes the grain coarse and shining, almost like that of bad iron, and which deterioration can be only partially restored, by good sound hammering under a pecu- liar management. The particular degrees of heat at which different samples of iron and steel, bearing the same name, should be worked, can only be found by trial; and it would be hardly possible to de- scribe the shades of difference. It would have been incompatible with the nature of this work to have entered more largely into the manufacture of iron and steel, or to have attempted the notice of the various alloys of steel which have received many attractive denominations, especially when so much has been already written on the subject. Of all the works published on the manufacture of iron and steel, those of the most importance, are Overman on Iron, and the collec- tion of Mushet's papers, which have appeared in the "Philosophical Magazine" at various times subsequent to 1798, and were collected and published by himself under the title " Papers on Iron and Steel;" the labor and research therein recorded are very great. Of the more brief and popular accounts of this subject, perhaps the best is that given in Oliver Byrne's Dictionary, published by Appletons, New York. Aikin's Dictionary of Chemistry and Mine- ralogy; three volumes on the Manufactures in Metal, in Lardner's Cyclopedia ; and Ure's Dictionary of Manufactures and Mines, con- tain likewise a very large store of information on the metals gene- rally. The reader will also consult with advantage, Aikin's " Illustra- tions of Arts and Manufactures," and various articles in the Ency- clopedias. FORGING LARGE PADDLE-SHAFTS. 31 FORGING IRON AND STEEL. In entering upon this subject, which performs so important and indispensable a part in every branch of mechanical industry, it is proposed first to notice some of the general methods pursued, com- mencing with the heaviest works, and gradually proceeding to those of the smallest proportions. This arrangement is principally adopted that the apparatuses, which undergo a corresponding change in their kind and dimensions, may be adverted to. After this, the management of the fire, and the degrees of heat required for various purposes, will be described ; and then the ele- mentary practice of forging will be attempted : those works made principally in one piece will be first treated of, and afterwards such as are composed of two or more parts, and which require the opera- tion of welding. The heaviest works of all, are generally heated in air furnaces of various descriptions, some of which resemble but greatly exceed in size those employed in the works where iron is manufactured, and m which the process of forging may be truly considered to commence with the very first blow given upon the ball, as it leaves the puddling furnace for being converted into a bloom. At these works, in addition to the ordinary manufactures of bar, plate, and hoop iron in all their varieties, the hammer-men are em- ployed in preparing masses, technically called "uses," which mean pieces to he used in the construction of certain large works, by the combination or welding of several of these masses. A square shaft, to be used at an iron-works, was made by laying together sixteen square, pieces, measuring collectively about twenty-six inches square, and six feet long. These were bound together, and put into a power- ful air furnace, and the ends of the group were welded into a solid mass under the heavy hammer weighing five tons; the weld was afterwards extended throughout the length. The paddle-shafts of the largest steam-ships are wrought by successive additions at the one end, as follows : A slab or use is welded on one side close to the end, and when drawn down to the common thickness, the addi- tional matter becomes thrown into the length ; the next use is then placed on the adjoining side of the as yet square shaft, and also drawn into the length, and so on until the full measure is attained. These ponderous masses are managed with far more facility than might be expected by those who have never witnessed such interest- ing proceedings. First, the "heat" has a long iron rod attached to it in continuation of its axis, to serve as a "porter" or guide rod; the mass is suspended under a traversing crane at that point where it is nearly equipoised : the crane not only serves to swing it round from the fire to the hammer, but the traverse motion also moves the work endways upon the anvil, and small changes of elevation are some- times effected by a screw adjustment in the suspending chain. The circular form is obtained by shifting the work round upon its axis 32 FORGING IRON AND STEEL. by means of a cross lever fixed upon the porter, and moved by one or two men, so as to expose each part of the circumference to the action of the helve; this is readily done, as the crane terminates in a pulley, around which an endless band of chain is placed, and the work lies within the chain, which shifts round when the work is turned upon the anvil : the precision of the forgings produced by these means is very surprising. A similar mode of work is adopted on a smaller scale for many of the spindles, shafts, and other parts of ordinary mechanism, which are forged under the great hammer, often of several bars piled to- gether and fagoted; a suitable term, as they are frequently made of a round bar in the centre, and a group of bars of angular section, called mitre iron, around the same, which are temporarily wedged within a hoop, somewhat after the manner of a fagot of wood. Such ■works are likewise made of scrap-iron, which consists of a strange heterogeneous medley of odd scraps and refuse from a thousand works, scarcely two pieces of which are alike. A number of these fragments are enveloped in an old piece of sheet iron, and held together by a hoop, the mass is raised to the welding heat in a blast or air furnace, and the whole is consolidated and drawn down under the tilt-hammer ; one long bar that serves as the porter being welded on by the first blow. The mingling of the fibres in the scrap-iron is considered highly favorable to the strength of the bar produced. The scrap-iron is sometimes twisted during the process of manufacture, to lay all the filaments like a rope, and prevent the formation of spills, or the longitudinal dirty seams found on the surface of inferior iron. Sometimes the formation of the scrap-iron is immediately fol- lowed by the production of the shafts and other heavy works for which it is required ; at other times the masses are elongated into bars sold under the name of scrap-iron, although it is very question- able if all the iron that is so named is produced in the manner im- plied. The long furnaces are particularly well suited to straight works and bars, but when the objects get shorter and of more complex figures, the open fire or ordinary smith's hearth is employed. This, when of the largest kind, is a trough or pit of brickwork about six feet square, elevated only about six inches from the ground ; the one side of the hearth is extended into a vertical wall leading to the chimney, the lower end of which terminates in a hood usually of stout plate iron, which serves to collect the smoke from the fire. The back wall of the forge is fitted with a large cast-iron plate, or a back, in the centre of which is a very thick projecting nozzle also of iron, perforated for admitting the wind used to urge the fire ; the aperture is called the tuyere. The blast is sometimes supplied from ordinary bellows of various forms ; at other times, by three enormous air-pumps, which lead into a fourth cylinder or regulator, the piston of which is loaded with weights, so as to force the air through pipes all over the smithy, and anchors; vertical hammer. 33 every fire has a valve to regulate its individual blast; but the more modern and general plan is the revolving fan, also worked by the engine, the blast from which is similarly distributed. In some cases the cast-iron forge back is made hollow, that a stream of water may circulate through it from a small cistern ; the water-back is thereby prevented from becoming so hot as the others, and its durability is much increased. In other cases the air, in its passage from the blowing apparatus, flows through chambers in the back plate so as to become heated in its progress, and thus to urge the fire with hot Mast, which is by many considered to effect a very great economy in the fuel. Some heavy works of rather complex form, such as anchors, are most conveniently managed by hand forging ; many of these require two gangs of men with heavy sledge-hammers, each consisting of six to twelve men, who relieve each other at short intervals, as the work is exceedingly laborious. Their hammers are swung round and made to fall upon one particular spot with great uniformity ; the conduc- tor of this noisy, although dumb concert so far as relates to voice, stands at a respectful distance, and directs the blows of his assistants with a long wooden wand. The Hercules, or crane, used for trans- ferring the work from the fire to the anvil, which is at about the same elevation as the fire itself, is still retained. The square shanks of anchors are partly forged under a vertical hammer of very simple construction, called a "monkey." It con- sists of a long iron bar running very loosely through an eye or aper- ture several feet above the anvil, and terminating at foot in a mass of iron, or the ram. The hammer is elevated by means of a chain, attached to the rod and also to a drum overhead, which is put into gear with the engine, and suddenly released by a simple contrivance, when the hammer has reached the height of from two to five feet, according to circumstances. The ram is made to fall upon any pre- cise spot indicated by the wand of the foreman, as it has a horizon- tal range of some twenty inches from the central position, and is guided by two slight guy rods, hooked to the ram and placed at right angles ; the guys are held by two men, who watch the direc- tions given. This contrivance is far more effective than the blows of the sledge-hammers, and although now but little used is perhaps more suitable to such purposes than the helve or lift-hammer, which always ascends to one height, and falls upon one fixed spot. The square shank of the anchor, and works of the same section, ;are readily shifted the exact quarter circle, as the sling-chain is imade with flat links, each a trifle longer than the side of the (square of the work, which, therefore, bears quite flat upon one link, ;and, when twisted, it shifts the chain the space of a link, and rests ;as before. Many implements and tools, such as shovels, spades, mattocks, ;and cleavers, are partly forged under the tilt-hammer; the prepara- tory processes, called moulding, which include the insertion of the ffiteel, are done by ordinary hand forging. The objects are then 34 FORGING IRON AND STEEL. spread out under the broad face of the tilt-hammer, the workman in such cases being sometimes seated on a chair suspended from the ceiling, and, by paddling about with his feet, he places himself with great dexterity in front or on either side of the anvil with the pro- gressive changes of the work: the concluding processes are mostly done by hand with the usual tools. A similar arrangement is also adopted in tilting small-sized steel. With the reduction of size in the objects to be forged, the num- ber of hands is also lessened, and the crane required for heavy work is abandoned for a chain or sling from the ceiling ; but, for the ma- jority of purposes, two men only are required, when the work is said to be two-handed. The principal, or the fireman, takes the manage- ment of the work both in the fire and upon the anvil; he directs and assists with a small hammer of from two to four pounds weight ; the duty of his assistant is to blow the bellows and wield the sledge- hammer, that weighs from about ten to fourteen pounds, although sometimes more, and from which he derives his name of hammer- man. As the works to be forged become smaller, the hearth is gradually lessened in size, and more elevated, so as to stand about two and a half feet from the ground; it is now built hollow, with an arch beneath serving as the ash-pit to receive the cinders and clinkers. The single hearths are made about a yard square, and those forges which have two fires under the same hood, measure about two yards by one ; a double trough, to contain water in the one compartment and coals in the other, is usually added, and the ordinary double bellows is used. In proportion as the hearth is more elevated, so is the anvil likewise, that in ordinary use standing about two feet or two and a half feet from the ground, its weight being from two to four hundred-weight. Numerous small works are forged at once from the end of the bar of iron, which then also serves the office of the porter required for heavy masses; but when the small objects are cut off from the bar, or the pieces are too short to be held in the hand, tongs of different forms are needful to grasp the work. These are made of various shapes, magnitudes, and length, according to circumstances ; but the annexed figures will serve to explain some of the most general kinds, although variations are continually made in their form to meet peculiar cases. Figs. 14 and 15 are called fiat-hit tongs ; these are either made to fit very close, as in Fig. 15, for thin works, or to stand more open, as in Fig. 14, for thicker bars, but always parallel ; and a ring, or coupler, is put upon the handles, or reins, to maintain the grip upon the work ; others of the same general form are made with hollow, half-round bits ; but it is much better they should be angular, like the ends of Fig. 16, as then they serve equally well for round bars, or for square bars held upon their opposite angles. Tongs that are made long, and swelled open behind, as in Fig. 16, are very excel- lent for general purposes, and also serve for bolts and similar objects TONGS AND GENERAL TOOLS. 35 with the heads placed inwards. The pincer tongs, Fig. 17, are also applied to similar uses, and serve for shorter bolts. Fig. 18, represents tongs much used at Sheffield, amongst the cutlers; they are called crook-bit tongs ; their jaws overhang the side so as to allow the bar of iron or steel to pass down beside the rivet, and the nib at the end prevents the rod from being displaced by the jar of hammering; these are very convenient. Fig. 19, or the hammer tongs, are used for managing works punched with holes, such as hammers and hatchets : as the pins enter the holes, and maintain the grasp, they should be made stout and long, so as to ad- mit of being repaired from time to time, as the bits get destroved by the fire. Figs. 15. 16. 17. 18. 19. 20. Fig. 14. Fig. 20, or hoop tongs, are very much used by ship-smiths, for grasping hoops and rings, which may be then worked either on the edge, when laid flat on the anvil, or on the side when upon the beak- iron : and lastly, Fig. 21 represents the smith's pliers, or light tongs, used for picking up little pieces of iron, or small tools and punches, many of which are continually driven out upon the ground in the ordinary course of work; they are also convenient in hardening small tools. In addition to the hearth, anvil, and tongs, the smithy contains a number of chisels, punches, and swages or striking tools, called also top and bottom tools, of a variety of suitable forms and generally in pairs; these may be considered as reduced copies of the grooves turned in the rollers, and occasionally made on the faces of the tilt- hammers of the iron-works for the production of square, flat, round, T form iron, angle iron, and railway bars, as referred to. The bottom tools of the ordinary smith's shop, have square tangs to fit the large hole in the anvil ; in using them the fireman holds the work upon the bottom tool, and above the work he places the top or rod tool, which is then struck by the sledge-hammer of his as- sistant. 86 FORGING IRON AND STEEL. In fitting the hazel rods to the top tools, the rods are alternately wetted in the middle of their length, and wormed over the fire to soften them, that portion is then twisted like a rope, and the rod is wound once round the head of the tool, and retained by an iron ferrule or coupler ; a rigid iron handle would jar the hand. When these tools are used for large works, a square plate of sheet- iron, with a hole punched in the middle of it, is put on the rod to- wards the tool, to shield the hand of the workman from the heat ; and it not unfrequently happens with such large works that the rod catches fire, and the tool is then dipped at short intervals in the slake trough to extinguish it. The smith who works without any helpmate is much more circum- scribed as to tools, and he is from necessity compelled to abandon all those used in pairs, unless the upper tools have some mechanical guide to support and direct them. In addition to the anvil he only uses the fixed cutter and heading tools ; he may occasionally support the end of the tongs in a hook attached to his apron-string, or suspended from his neck, whilst he applies a hand-chisel, a punch, or a name-mark in the left hand, and strikes with the hammer held in the right. The method is however ample for a variety of small works, such as cutlery, tools, nails, and small ironmongery, which are wrought almost exclusively by the hand-hammer. Attempts to work small tilt-hammers with the foot have been found generally ineffective, as the attention of the individual is too much subdivided in managing the whole, neither is his strength sufficient for a continued exertion at such work; but the "Oliver," which we shall now describe, is one of the best tools of this class. The Oliver, or Small Lift-Hammer. — Fig. 22 represents a species of lift-hammer worked by the foot. The hammer-head is about two and a half inches square and ten long, with a swage tool having a conical crease attached to it, and a corresponding swage is fixed in a square cast-iron anvil block, about twelve inches square, and six deep, with one or two round holes for punching, &c. The hammer handle is about two to two and a half feet long, and mounted in a cross spindle nearly as long, supported in a wooden frame be- tween end screws, to adjust the groove in the hammer-face to that in the anvil block. A short arm, five or six inches long, is attached to the right end of the hammer axis, and from this arm proceeds a cord to a spring pole overhead, and also a chain to a treadle a little above the floor of the smithy. When left to itself the hammer handle is raised to nearly a verti- cal position by the spring, and it is brought down very readily with the foot, so as to give good hard blows at the commencement of moulding the objects, and then light blows for finishing them. The machine was used when the author first saw it, in making long stout nails, intended for fixing the tires of wheels, secured within the fel- loes by washers and riveting ; the nails were made very nicely round and taper, and were forged expeditiously. MANAGEMENT OF THE FIRE, ETC. 37 Fig. 22. ^ For single hand-forging, the fire becomes still further reduced in size, and proportionally elevated from the ground ; and this being the scale of work most commonly followed by the amateur, a port- able forge of suitable dimensions, and made entirely of iron, is re- presented in Fig. 23; the bellows are placed beneath the hearth and worked by a treadle. This forge is also occasionally fitted with a furnace for melting small quantities of metal, and with various apparatus for other ap- plications of heat, such as soldering, either with a small charcoal fire, or a lamp and blowpipe, which are likewise urged with the bellows. These applications, and also that of hardening and tempering tools, which will be severally returned to at their respective places, are much facilitated by the bellows being worked with the foot, as it leaves both hands at liberty for the management either of the work or fire, with the so-called fire-irons, which include a poker, a slice or shovel, and a rake, in addition to the supply of tongs of some of the former shown. The forge represented is sufficiently powerful for a moderate share of those works which require the use of the sledge-hammer ; but, when the latter tool is used, the anvil should not fall short of one hundred pounds in weight ; and the heavier it is the less it will re- bound under the hammer. Management of the fire; the degrees of heat. — The ordi- nary fuel for the smith's forge is coal, and the kinds to be preferred are such as are dense and free from metallic matters, as these are generally accompanied with sulphur, which is highly detrimental. 38 FORGING IRON AND STEEL. Copper is usually forged in a coke fire ; silver and gold in those made of charcoal; but the hearths do not materially differ from those used for iron. Compressed peat charcoal has been strongly recom- mended on account of its freedom from sulphur — one of the greatest enemies in nearly all metallurgic operations. Fig. 23. The fire is sometimes made open, at other times hollow, or like a tunnel; and the larger the fire is required to be, so much the more distant is it situated from the tuyere iron. Before lighting the fire, the useful cinders are first turned back on the hearth, and the ex- hausted dust or slack is cleared away from the iron back and thrown into the ash-pit ; a fair-sized heap of shavings is then lighted, and allowed to burn until the flame is nearly extinguished, when the embers are covered over with the cinders, and the bellows are urged. A dense white smoke first rises, and, in two or three minutes, the flame bursts forth, unless the fire be choked, when the poker is care- fully passed into the mouth of the tuyere. The work is now laid on the fire, and covered over with green or fresh coals, which are beaten around the tuyere and the work, the blast being continued all the while; the whole mass will soon be in a state of ignition. A MANAGEMENT OF THE EIRE, ETC. 39 heap of fresh coals is always kept at the outside wall of the fire, and they are gradually advanced at intervals into the centre of the flame to make up for those consumed. In making a large hollow fire, after a good-sized fire has been lighted in the ordinary way, the ignited fuel is brought forward on the hearth to expose the tuyere iron, into the central aperture of which the poker is introduced. A mass of small wetted coal is beaten hard round the poker to constitute the stock, the magnitude of which will depend on the distance at which the fire is required to stand off, and a second stock is also made opposite the first, the two resembling two hills with the lighted fuel lying between them. The durability of the fire will depend on the stocks being hard rammed, which, for large works, is often done with the sledge-hammer. The work is now laid in the hollow just opposite the blast-pipe, and covered on its two sides and top with thin pieces of wood, and a heap of wetted coals is carefully banked up around the same and beaten down with the slice or shovel ; when carefully done, the heap is made to assume the smooth form of an embankment of earthwork. The bellows are blown gently all the time, and the work is not with- drawn until the wood is consumed, and the flame peeps through at each end of the aperture, so as to cake the coals well together into a hard mass; after which the work may be removed or shifted about without any risk of breaking down the fire. In localities where wood is scarce, small iron rods are placed around the principal mass, often designated the heat ; the small rods are first withdrawn when the fire has burned up, to allow room for the removal of the work. Sometimes when a fire is required only for hardening, the center- ing of the arch is made entirely of wood, either in one or several pieces : and in this manner it may be built of any required form, as angular for knees, circular for hoops, and so on (although such works are usually done in open fires, which resemble the above in all respects, except the covering-in or roof) : small coal is thrown at intervals into the hollow fire to replace that which is burned, and by careful management, one of these combustible edifices will last half a day, or even the entire day, without renewal. Occasionally, the stock around the tuyere iron will serve with a little repair for a second day, if when the fire is turned back at night, that part is allowed to remain, and the fire is extinguished with water. When a small hollow fire is required, the same general methods are less carefully followed, and an iron tube introduced amidst the coals, makes a very convenient muffle or oven for some purposes. In forging, the iron or steel is in almost every case heated to a greater or less degree, to make it softer and more malleable by lessening its cohesion ; the softening goes on increasing with the accession of temperature, until it arrives at a point beyond that which can be usefully employed, or at which the material, whether iron or steel, falls in pieces under the blows of the hammer, but 40 FORGING IRON AND STEEL. which degree is very different with various materials, and even witfo varieties bearing the same name. Pure iron will bear an almost unlimited degree of heat, the hot short iron bears much less, and is in fact very brittle when heated ; other kinds are intermediate: of steel, the shear-steel will generally bear the highest temperature, the blistered-steel the next, and the cast-steel the least of all ; but all these kinds, especially cast-steel, differ very much according to the processes of manufacture, as some cast-steel may be readily welded, but it is then somewhat less certain to harden perfectly. Without attempting any refined division, I may add, the smith commonly speaks of five degrees of temperature; namely: — The black-red heat, just visible by daylight ; The low-red heat ; The bright-red heat, when the black scales may be seen ; The white-heat, when the scales are scarcely visible ; The welding-heat, when the iron begins to burn with vivid sparks. Steel requires on the whole very much more precaution as to the degree of heat than iron ; the temperature of cast-steel should not generally exceed a bright-red heat, that of blistered and shear-steel that of a moderate white-heat. Although steel cannot in conse- quence be so far softened in the fire as iron, and is therefore always more dense and harder to forge, still from its superior cohesion it bears a much greater amount of hard work under the hammer, when it is not over-heated or burned ; but the smallest available tempera- ture should be always employed with this material, as in fact with all others. It has been recommended to try by experiment the lowest degree of heat at which every sample of steel will harden, and in forging, always to keep a trifle below that point. This proposal however is rarely tried, and still less followed, as the usual attempt is to lessen the labor of forging, by softening the steel so far as it is safely practicable. Iron is more commonly worked at the bright-red and the white- heats, the welding-heat being reserved for those cases in which welding is required ; or others in which, from the great extension or working of the iron, there is risk of separating its fibres or laminae, so as to cause the work to become unsound or hollow, from the dis- rupture of its substance ; whereas these same processes being carried on at the welding temperature, the work would be kept sound, as every blow would effect the operation of welding rather than that of separation. The cracks and defects in iron are generally very plainly shown by a difference in colour at the parts when they are heated to a dull-red ; this method of trial is often had recourse to in examining the soundness both of new and old forgings. When a piece of forged work is required to be particularly sound, it is a common practice to subject every part of the material in suc- cession to a welding heat, and to work it well under the hammer, as a repetition of the process of manufacture to insure the perfection ORDINARY PRACTICE OP FORGING. 41 of-the iron; this is technically called talcing a heat over it — in fact, a heat is generally understood to imply the welding heat. For a two-inch shaft of the soundest quality, two and a half inch iron would be selected, to allow for the reduction in the fire and the lathe. Some also twist the iron before the hammering to prevent it from becoming " spilly." The use of sand sprinkled upon the iron is to preserve it from abso- lute contact with the air, which would cause it to waste away from the oxidation of its surface, and fall off in scales around the anvil. If the sand is thrown on when the metal is only at the full red heat it falls off without adhering ; but, when the white heat is approached, the sand begins to adhere to the iron ; it next melts on its surface, over which it then runs like fluid glass, and defends it from the air. When this point has been rather exceeded, so that the metal never- theless begins to burn with vivid sparks and a hissing noise like fire- works, the welding temperature is arrived at, and which should not be exceeded. The sparks are, however, considered a sign of a dirty fire or bad iron, as the purer the iron the less it is subject to waste or oxidation, in the course of work. In welding two pieces of iron together, care must be taken that both arrive at the welding heat at the same moment; it may be ne- cessary to keep one of the pieces a little on one side of the most intense part of the fire (which is just opposite the blast), should the one be in advance of the other. In all cases, a certain amount of time is essential, otherwise, if the fire be unnecessarily urged, the outer case of the iron may be at the point of ignition before the centre has exceeded the red heat. In welding iron to steel, the latter must be heated in a considerably less degree than the iron, the welding heat of steel being lower from its greater fusibility. But the process of welding will be separately considered under a few of its most general applications, when the ordinary practice of forg- ing has been discussed, and to which we will now proceed. Ordinary practice op porging. — The general practice of forging works from the bar of iron or steel are, for the most part, included in the three following modes; the first two occur in almost every case, and frequently all three together, namely : — By drawing-down, or reduction ; By jumping, or up-setting ; otherwise, thickening and shortening; By building-up, or welding. When it is desired to reduce the general thickness of the object, both in length and width, then the flat face of the hammer is made to fall level upon the work; but, where the length or breadth alone is to be extended, the pane or narrow edge of the hammer is first used, and its blows are directed at right angles to the direction in which the iron is to be spread. To meet the variety of cases which occur, the smith has hammers in which the panes are made in different ways — either at right angles to the handle, parallel with the same, or oblique. In order to obtain the same results with more precision and effect, 42 FORGING IRON AND STEEL. tools of the same characters, but which are struck with the sledge- hammer, are also commonly used. Those with flat faces are made like hammers, and usually with similar handles, except that, for the convenience of reversing them, they are not wedged in; these are called set-hammers; others, which have very broad faces, are called flatters ; and the top tools, with narrow round edges like the pane of the hammer, are called top-fullers. They all have the ordinary hazel rods. When the sides of the object are required to be parallel, and it is to be reduced both in width and thickness, the flat face of the ham- mer is made to fall parallel with the anvil, as represented in Fig. 24, or oblique, for producing taper pieces, as in Fig. 25, and, action and reaction being equal, the lower face of the work receives the same absolute blow from the anvil as that applied above by the hammer itself. It is not requisite, therefore, to present every one of the four sides to the hammer, but any two at right angles to each other. This is only true for works of modern dimensions ; in large masses, such as anchors, the soft doughy state of the metal acts as a cushion, and greatly lessens the recoil of the anvil, and on this account such works are presented to the hammer on all four sides. It is also very injudicious in such cases to continue the exterior finish, or battering-off, too long, as this extends the outer case of the metal more than the inner part, and sometimes separates the two. When imperfect forgings are broken in the act of being proved, the inner bars are sometimes found not to be even welded together, and the outside part is a detached sheath, almost like the rind or bark of a tree. In twisting the work round the quarter circle, some practice is called for, in order to retain the rectangular section, and not to al- low it to degenerate into the lozenge or rhomboidal form, which error it is difficult to retrace. This indeed may be considered the first stumbling-block in forg- ing, and one for which it is difficult to provide written rules. Of course in converting a round bar into a square with the hammer, the accuracy will depend almost entirely upon the change of exactly ninety degrees being given to the work, and this the experienced smith will accomplish with that same degree of feeling, or intuition, which teaches the exact distances required upon the finger-board of a violin, which is defined by habit alone. In the original manufacture of the iron, the carefully turned grooves, a, b, c, of the rollers, page 25, produce the square figure with great truth and facility ; and under the tilt-hammer the two op- posite sides are sure to be parallel, from the respective parallelism of the faces of the hammer and anvil ; and the tilters, from constant practice, apply the work with great truth in its second position. So that under ordinary circumstances th'e prepared materials are true and square, and the smith has principally to avoid losing that ac- curacy. First, he must acquire the habit of feeling when the bar lies per- ORDINARY PRACTICE OF FORGING. 43 fectly flat upon the anvil, by holding it slenderly, leaving it almost to rotate in his grasp, or in fact to place itself. Next, he must cause the hammer to fall flat upon the work ; with which view he will neither grasp its handle close against the head of the hammer, nor at the extreme end of the handle, but at that intermediate point where he finds it comfortably to rebound from the anvil, with the least effort of, or jar to his wrist. And the height of the wrist must also be such as not to allow either the front or back edge of the hammer-face to strike the work first, which would indent it, but it must fall fair and parallel, and without bruising the work. Figs. 24. 25. 26. It would be desirable practice to hammer a bar of cold iron, or still better one of steel, as there would be more leisure for observa- tion, the indentations of the hammer could be easily noticed ; and if the work, especially steel, were held too tightly, or without resting fairly on the anvil, it would indicate the error by additional noise and by jarring the wrist ; whereas, when hot, the false blows or positions would cause the work to get out of shape, without such indications. As to the best form of the hammer, there is much of habit and something of fancy. The ordinary hand-hammer is represented in Figs. 24 and 25, but most tool makers prefer the hammer without a pane, and with the handle quite at the top, the two forming almost a right angle, or from that to about eighty degrees ; and sometimes the head is bent like a portion of a circle. Similar but much heavier hand-hammers, occasionally of the weight of twelve or fourteen pounds, are used by the spade-makers for planishing ; but the work being thin and cold, the hammer rises almost exclusively by the re- action, and requires little more than guidance. Again, the farriers prefer for some parts of their work, a hammer the head of which is almost a sphere ; it has two flat faces, one rounded face for the inside of the shoe, and one very stunted pane at right angles to the handle, used for drawing down the clip in front of the horse-shoe ; in fact, nearly a small volume might be written upon all the varieties of hammers. To return to the forging ; the flat face of the hammer should not only fall flat, but also centrally upon the work ; that is, the centre of the hammer, in which point the principal force of the blow is con- centrated, should fall on the centre of the bar, otherwise that edge of the work to which the hammer might lean would be the more re- 44 FORGING IRON AND STEEL. duced, and consequently the parallelism of the work would be lost. It would also be bent in respect to length, as the thinned edge would become more elongated, and thence convex ; and when the blows were irregularly scattered, the work would become twisted or put in winding, which would be a still worse error. I will suppose it required to draw down (the technical term for reduction), six inches of the end of a square or rectangular bar of iron or steel ; the smith will place the bar across the anvil with per- haps four inches overhanging, and not resting quite flat, but tilted up about a quarter or half an inch at the near side of the anvil, as in Fig. 25, but less in degree, and the hammer will be made to fall as there shown, except that it will be at a very small angle with the anvil. Having given one blow, he will as the only change, twist the work a quarter turn, and strike it again ; then he will draw the bar half an inch or an inch towards him, and give it two more similar blows, and so on until he arrives at the extreme end, when he will recom- mence ; but this will be done almost in the time of reading these words. The descent of the hammer, the drawing the work towards himself (whence perhaps the term), and the quarter turn backwards and forwards, all go on simultaneously and with some expedition. At other times the work is drawn down over the beak iron, in which case the curvature of this part of the anvil makes it less material at what angle the work is held or the blows given, provided the two posi- tions be alike. In smoothing off the work, the position of Fig. 24 is assumed ; the work is laid flat upon the anvil, and the hammer is made to fall as nearly as possible horizontally ; a series of blows are given all along the work between every quarter turn, the hammer being directed upon one spot, and the work drawn gradually beneath it. The circumstances are exactly the same as regards the sledge- hammer, which is used up-hand for light work ; the right hand being slid towards the head in the act of lifting the hammer from off the work, and slipped down again as the tool descends ; and the condi- tions are scarcely altered when the smith swings the hammer about in a circle, the signal for which is "about sledge;" whereas when, in either case, the blows of the sledge-hammer are to be discontinued, the fireman taps the anvil with his hand-hammer, which is, I believe, an universal language. In drawing down the tang or taper-point of a tool, the extreme end of the iron or steel is placed a little beyond the edge of the an- vil, as in Fig. 25, by which means the risk of indenting the anvil is entirely removed, and the small irregular piece in excess beyond the taper is not cut off until the tang is completed. Fig. 26 shows the position of the chisel in cutting off the finished object from the bar of which it formed a part ; that is, the work is placed betwixt the edge of the anvil, and that of the chisel immediately above the same ; the two resemble in effect a pair of shears. Sometimes the edge of the anvil alone is used for small objects, first to indent, and then to ORDINARY PRACTICE OF FORGING. 45 break off the work, but this is likely to injure the anvil, and is a bad practice. When it is required to make a set-off, it is done by placing the intended shoulder at the edge of the anvil : the blows of the ham- mer will be effective only where opposed to the anvil, but the remain- der of the bar will retain its full size and sink down, as represented in Fig. 27. Should it be necessary to make a shoulder on both sides, a Figs. 27. 28. 29. flat-ended set hammer, struck by the sledge, is used for setting down the upper shoulder, as in Fig. 28, as the direct blows of the hammer could not be given with so much precision. In each of these cases some precaution must be observed, as otherwise the tools, although so much more blunt than the chisel, Fig. 26, will resemble it in effect, and cripple or weaken the work in the corner ; on this account the smith's tools are rarely quite sharp at the angles : this mischief is almost removed when the round fullers, Fig. 29, are used for reducing the principal bulk, and the sharper tools are only employed for trim- ming the angles with moderate blows. When the iron is to be set down, and also spread laterally, as in Fig. 30, it is first nicked with a round fuller as upon the dotted line at a Fig. 30. a, and the piece at the end is spread by the same tool, upon the short lines of the object, or parallel with the length of the bar : the first notch greatly assists in keeping a good shoulder at the bottom of the part set down, and the lines are supposed to represent the rough indications of the round fuller before the work is trimmed up. There is often considerable choice of method in forging, and the skillful workman selects that method of proceeding which will pro- duce the result with the least portion of manual labor. Thus an ordinary screw-bolt, that I will suppose to measure five-eighths of an inch in diameter in the stem, and one inch square in the head, may be made in either of the three following ways adverted to in the outset : — First, by drawing-down: — A bar of iron is selected one inch 46 FORGING IRON AND STEEL. square, or of the size of the head of the bolt, and a short portion of the same is set down, according to Fig. 29, by a pair of fullers that are convex in profile as shown, and also slightly concave upon the line at right angles to the paper ; this prepares the shoulder or joining of the two dimensions; the bolt is made cylindrical, and of proper diameter between the rounding tools, Fig. 31 ; and lastly, it is cut off with the chisel, as in Fig. 26, so much of the original square bar as suffices for the thickness of the head being allowed to remain. Secondly, by jumping:— A piece of bolt-iron of five-eighths of an inch in diameter, or of the size of the stem of the bolt, is cut off somewhat longer than the intended length; "a short heat" is taken upon it, that is, the extreme end alone is made white-hot, then placed perpendicularly upon the anvil, and the cold end is struck with the hammer as in driving in a nail; this thickens the metal or upsets it, and makes a thick conical button. The head is completed, by driving the bolt into a heading tool with a circular hole of five-eighths diameter; the thickened part of the head prevents the piece from passing through, and the lump is flattened out by the hammer into an irregular button or disk, which is afterwards beaten square to com- plete the bolt. Figs. 32, 33, and 34, explain these processes; the latter is a single tool, but the heading tool, Fig. 35, with several holes, is also used. Figs. 31. 34. 33. 32. In upsetting the end of the work, if more convenient, it may b 4 e held horizontally across the anvil, and struck on the heated extrem- ity with the hand hammer ; or it can be jumped forcibly upon the anvil, when its own weight will supply the required momentum. If too considerable a portion of the work is heated, it will either bend, or it will swell generally ; and therefore to limit the enlargement to the required spot, should the heat be too long, the neighboring part is partially cooled by immersing it in the water-trough, as near to the heat as admissible. Thirdly, the same bolt may be made by building up or welding: — ORDINARY PRACTICE OF FORGING. 47 An eye is first made at the end of a small rod of square or flat iron; by bending it round the beak iron, as in Fig. 36, it is placed around the rod of five- eighths round iron, and the curled end is cut' off with the chisel, as in Fig. 37, enough iron being left in the ring, which is afterwards welded to the five-eighths inch rod to form the head of the bolt, by a few quick light blows given at the proper heat; the bolt is then completed by any of the tools already described, that may be preferred. A swage at the angle of sixty degrees, Fig. 38, will be found very convenient in forming hexagonal heads, as the horizontal blow of the hammer completes the equilateral triangle, and two posi- tions operate on every side of the hexagon; Fig. 38 is essential like- wise in forging triangular files and rods. Of these three modes of making a bolt, and which will apply to a multitude of objects somewhat analogous in form, the first is the most general for small and short bolts; the second for small but longer kinds ; and the third is perhaps the most common for large bolts, although the least secure ; it is used for bolts for ordinary building purposes, but is less generally employed for the parts of mechanism. For works of the same character, in which a considerable length of two different sections or magnitudes of iron are required, the method by drawing down from the large size would be too expensive ; the method by upsetting would be impracticable ; and therefore a more judicious use is made of the iron store, and the object is made in two parts, of bars of the exact sections respectively. The larger bar is reduced to the size of the smaller, generally upon the beak iron with top fullers, and with a gradual transition or taper extend- ing some few inches, as represented in Fig. 39; the two pieces are scarfed or prepared for welding, but which part of the subject is for the present deferred, in order that the different examples of welding may be given together. The Fig. 39 is also intended to explain two other proceedings very commonly required in forging. Bars are bent down at right angles as for the short end or corking of the piece, Fig. 39, by lay- ing the work on the anvil, and holding it down with the sledge-ham- mer, as in Fig. 40 ; the end is then bent with the hand-hammer, and trimmed square over the edge of the anvil; or when more precision is wanted, the work is screwed fast in the tail-vice, which is one of the tools of every smith's shop, and it is bent over the jaws of the vice. When the external angle, as well as the internal, is required to be sharp and square, the work is reduced with the fuller from a larger bar to the form of Fig. 41, to compensate for the great extension in length that occurs at the outer part, or heel of the bend, of which the inner angle forms as it were the centre. The holes in Fig. 39, for the cross bolts, are made with a rod-punch, which is driven a little more than half way through from the one side whilst the work lies upon the anvil, so that when turned over, the cooling effect of the punch may serve to show the place where the tool must be again applied for the completion of the hole ; the 48 FORGING IRON AND STEEL. little bit or burr is then driven out, either through the square hole in the anvil that is intended for the bottom tools, or else upon the bolster, Fig. 42, a tool faced with steel, and having an aperture of the same form and dimensions as the face of the punch. Figs. 40. 39. ggp^ ^- 7 45. Fig. 45 shows the ordinary mode of making the square nuts for bolts. A flat bar is first nicked on the sides with the chisel, then punched, and the rough nuts if small, are separated and strung upon the end of the poker (a slight round rod bent up at the end), for the convenience of managing them in the fire, from which they are removed one at a time when hot, and finished on the triblet, Fig. 46, which serves both as a handle, and also as the means of perfect- ing the holes. For making hexagon nuts, the flat bar is nicked on both edges with a narrow round fuller; this gives a nearer approach to the hexa- gon : the nuts are then flattened on the face, punched, and dressed on the triblet within the angular swage, Fig. 38, before adverted to. Thick circular collars are made precisely in the same way, with the exception that they are finished externally with the hammer, or between top and bottom rounding tools of corresponding diameter. It is usual in punching holes through thick pieces, to throw a little coal-dust into the hole when it is partly made, to prevent the punch sticking in so fast as it otherwise would: the punch generally gets red-hot in the process, and requires to be immediately cooled on removal from the hole. In making a socket, or a very deep hole in the one end of a bar, some difficulty is experienced in getting the hole in the axis of the bar, and in avoiding to burst open the iron ; such holes are produced differently, by sinking the hole as a groove in the centre of a flat bar by means of a fuller ; the piece is cut nearly through from the opposite side, folded together lengthways, and welded. The hole thus formed will only require to be perfected by the introduction of an appropriate punch, and to be worked on the outside, with those tools required for dressing off its exterior surface, whilst the punch remains in the hole to prevent its sides from being squeezed in : this method is very good. ORDINARY PRACTICE OF FORGING. 49 For_ punching square holes, square punches and bolsters are used, and Fig. 43, the split bolster, is employed for cutting out long rect- angular holes or mortises, which are often done at two or more cuts with an oblong punch. Mortises, when of still greater length, are usually made by punch- ing a hole of their full width at each end, and cutting out a strip of metal between them, by two long incisions made with the rod-chisel; at other times one cut only is made, and the mortise is opened out; this retains all the iron, but makes the ends narrower than the mid- dle. In finishing a mortise, a parallel plate or drift is inserted in the slit; the drift is laid across the chaps of the vice, whilst the bar of iron lies partly between its jaws, in order that the blows of the hammer may be effective, on the upper and under surfaces of the one rib at the^ same time. The drift serves as a temporary anvil ; the other rib is completed in the same manner, and the work is finally closed to its true width upon the anvil, the drift still lying in the mortise. When a thick lump is wanted at the end of a bar, it is often made by cutting the iron nearly through and doubling it backwards and forwards, as in Fig. 44 ; the whole is then welded into a solid mass as the preparatory step. Fig. 47. fig. 48 . A piece with three tails, such as Fig. 47, is made from a large square bar ; an elliptical hole is first punched through the bar, and the remainder is split with a chisel, as in Fig. 48, the work at the time being laid upon a soft iron cutting plate in order to shield the chisel from being driven against the hardened steel face of the an- vil; the end is afterwards opened into a fork, and moulded into shape over the beak-iron, as indicated by the dotted lines. The concave lines about the object are principally worked with the fuller, or half-round set-hammer ; and in making all the holes, narrow oval punches are used as described at the commencement, and the slits are enlarged into circular holes by conical mandrels ; these bulge the metal out, and the holes are more judiciously formed in this manner than if the metal were wasted by cutting out great circular holes, which would sever a large quantity of the fibres and reduce the strength. The mandrels are left in the holes whilst the parts around them are finished, which tends to the perfection of both parts ; as the holes more closely copy the mandrels, and the marginal parts are better finished when the apertures are for the time rendered solid. 4 50 FORGING IRON AND STEEL. Supposing a hole to be wanted in the cylindrical part of the work that should be finished between the rounding tools, the mandrel could not be allowed to remain in ; and therefore a short piece of iron is forged or drawn down to the size of the hole, cut off in length to the diameter of the part, and inserted in the hole to preserve it from being compressed, yet without interference with the completion of the cylindrical portion ; which accomplished, this little bit, called by the un-mechanical name of a devil, is driven out, unless by a very careless use of the welding temperature it should have been perma- nently fastened in. Towards the conclusion a long mandrel is passed through the two holes in the fork of Fig. 47, to show whether their common axis is at right angles to the main rod, otherwise the one or other arm is drawn out, or upset, according as the work may err in respect to deficiency or excess of length. Such a piece as Fig. 47, if of large dimensions, would be made in two separate parts, and welded through the central line or axis. Should it happen the two arms are not quite parallel, that is, when viewed edgeways should they stand oblique to each other, or to the central bar, an error that could scarcely be corrected by the hammer alone; the work would be fixed in the vice with the two tails upwards, and the one or other of these would be twisted to its true position by a hook wrench or set, made like the three sides of a square, but the one very long to serve as a lever ; it is applied exactly in the manner of a key, spanner, or screw wrench, in turn- ing round a bolt or screw. The hook wrench is constantly used for taking the twist out of work, or the error of winding, as the hammer can only be successfully employed for correcting the curvatures of length. Some bent objects, such as cranks and straps, are made from bar- iron, bent over specific moulds, which are sometimes made in pairs like dies, and pressed together by screw contrivances. When the moulds are single, the work is often retained in contact with the same, at some appropriate part, by means of straps and wedges ; whilst the work is bent to the form of the mould by top tools of suit- able kinds. Objects of more nearly rectilinear form are cut out of large plates and bars of iron with chisels ; for example, the cranks of locomotive engines are faggoted up of several bars or uses laid together, and pared to the shape ; they are sometimes forged in two separate parts, and welded between the cranks, at other times they are forged out of one parallel mass, and afterwards twisted with a hook-wrench, in the neck between the cranks, to place the latter at right angles. The notches are sometimes cut out on the anvil whilst the work is red- hot ; or otherwise by machinery when in the cold state. A very different method of making rectangular cranks and similar works is also recommended, by bending one or more straight bars of iron to the form, the angles, which are at first rounded, are perfected by welding on outer caps. In this case the fibre runs round the figure, whereas when the gap is cut out, a large proportion of the GENERAL EXAMPLES OF WELDING. £>1 fibres are cut into short lengths, and therefore a greater bulk must be allowed for equal strength : this method is however seldom used. All kinds of levers, arms, brackets and frames, are made after these several methods, partly by bending and welding, and partly by cut- ting and punching out ; and few branches of industry present a greater variety in the choice of methods, and which call the judg- ment of the smith continually into requisition. General Examples of Welding.— The former illustrations of forging have been principally descriptive of such works as could be made from a single bar of iron, on purpose that the examples to be advanced in welding or joining together two pieces of iron by heat, technically called "shutting together" or "shutting up" might be collected at one place. There are several ways of accomplishing this operation, and which bear some little analogy to the joints employed in carpentry ; more particularly that called scarfing, used in the construction of long beams and girders by joining two shorter pieces together endways, with sloping joints, which in carpentry are interlaced or mortised together in various ways, and then secured by iron straps or bolts. In smith's work, likewise, the joinings are called scarfs, but from the adhesive nature of the iron when at a suitable temperature, the ac- cessories called for in carpentry, such as glue, bolts, straps and pins, are no longer wanted. The example, Fig. 39, was left unfinished, but we will proceed to show the mode of joining the two cylindrical ends of the work. The scarfs required for the 6 shut,' are made by first upsetting or thicken- ing the iron by blows upon its extremity, to prepare it for the loss it will sustain from scaling off, both in the fire and upon the anvil, and also in the subsequent working upon the joint. It is next rudely tapered off to the form of a flight of steps, as shown in Figs. 49 and 50, and the sides are slightly beveled or pointed, as in Fig. 50, the proportions being somewhat exceeded to render the forms more ap- parent. 1) a c The two extremities are next heated to the point of ignition ; and •when this is approached, a little sand is strewed upon each part, •which fuses and spreads something like a varnish, and partially de- jfends them from the air ; the heat is proper when, notwithstanding 52 FORGING IRON AND STEEL. the sand, the iron begins to burn away with vivid sparks. The two men then take each one piece, strike them forcibly across the_ anvil to remove any loose cinders, place them in their true positions, exactly as in Fig. 49, and two or three blows of the small hammer of the principal or fireman stick them together ; the assistant then quickly joins in with the sledge-hammer, and the smoothing off and completion of the work are soon accomplished. It is of course necessary to perform the work with rapidity, and literally "to strike whilst the iron is hot;" the smith afterwards jumps the end of the rod upon the anvil, or strikes it endways with the hammer ; this proves the soundness of the joint, but it is mostly done to enlarge the part, should it during the process have become accidentally reduced below the general size. The sand appears to be quite essential to the process of welding, as although the heat might be arrived at without its agency, the surfaces of the metal would become foul and covered with oxide when unprotected from the air — at all events common experience shows that it is always required. The scarf joint, shown in Figs. 49 and 50, is commonly used for all straight bars, whether flat, square or round, when of medium size. In very heavy works the welding is principally accomplished within the fire : the two parts are previously prepared either to the form of the tongue or split joint, Fig. 51, or to that of the butt joint, Fig. 52, and placed in their relative positions in a large hollow fire. When the two parts are at the proper heat, they are jumped together endways, which is greatly facilitated by their suspension from the crane, and they are afterwards struck on the ends with sledge-ham- mers, a heavy mass being in some cases held against the opposite extremity to sustain the blows ; the heat is kept up, and the work is ultimately withdrawn from the fire, and finished upon the anvil. The butt joint, Fig. 52, is materially strengthened, when, as it is usually the case for the paddle shafts of steam vessels and similar works, the joint whilst still large is notched in on three or four sides, and pieces called stick-in pieces, dowels, or charlins, one of which is represented by the dotted lines, are prepared at another fire, and laid in the notches; the whole, when raised to the^welding heat, is well worked together and reduced to the intended size ; this mingles all the parts in a very substantial manner. For the majority of works, however, the scarf joint, Fig. 49, is used, but the stick-in pieces are also occasionally employed, especially when any accidental deficiency of iron is to be feared. When two bars are required to form a T joint, the transverse piece is thinned down as at a, in Fig. 53 ; for an angle or corner the form of b may be adopted ; but c, in which each part is cut off ob- liquely, is to be preferred. The pieces a, b, e, are ^ represented upside down, in order that the ridges set down on their lower sur- faces may be seen. In most cases when two separate bars are to be joined, whatever the nature of the joint, the metal should be first upset, and then set down in ridges on the edge of the anvil, or with GENERAL EXAMPLES OP WELDING. 53 a set hammer, as the plain chamfered or sloping surfaces are ant to W ^rTirn e " mT ^ h « ] a * d ^ ^ ^n. vvnen a T joint is made of square or th ck iron the one ^Vr-A ;« upset, and moulded with the fuller much in the Cm of the leSe • s then welded against the flat side of the bar : such works are some times Wded with dowel or tenon joints, but all the varieties of method cannot be noticed. eiies 01 There are many works in which the opposite edges, or the ends of the same piece, require to be welded ; in these the risk of ?he two parts sliding asunder scarcely exists, and the scarfs are made with a plain chamfer, or simply to overlap or fold together witTout any particular preparation. g wunout Of the last kind Fig. 44 may be taken as an example, in which he' smi h 7 dlSP ,L id0n t0 ^r te 5 in this and --ilar ca e, \Z Z« w leaVes 1 * he P arts sll S h % ^en, in order that the very last process before welding may be the striking the whole edgeways upon the anvi , to drive out any loose scales, cinders or sand sSed between the joints- which if allowed to remain would be either ~t°Se r ^ S ° Und ° f ^ ™ k > ° r ™** P^iali; Fe- In works that have accidentally broken in the welded part the fracture will be frequently seen to have arisen from some dirty matter having been allowed to remain between them, on which LTount sttrVthTn A„r? eXt ^ ing ° Ver , a krge sirfaCe are °^ ™» secure than those of smaller area, from the greater risk of their becoming foul In fact, throwing a little small coal between the and ZZ Sm ' &C l S t W ° rk n0t int6nded t0 be ™ ited > is a common b£>Zg welded " 7 t0 them from «f^o 0 U Cal i S?Cke i te ° f S ° Cket Chisel8 ' S arden s P uds > and a variety of agricultural implements, are formed out of a bar of flat iron hammer Tdtn <* to an angle, with the pane of the hammer, and then bent within a semi-circular bottom tool also, by the pane of the hammer, to the form of Fig. 54; after which the Figs. 54. sockets are still more curled up by blows on the edges, and are perfected upon a taper pointed mandrel, so that th? two edges slightly overlap at the mouth of the socket, and meet pretty uni- tnel J dt ^iT^ Fig - 55 ' ? d la8tl * ab0Ut an inch °r "ore at the 1 welded. Sometimes the welding is continued throughout the length, but more commonly only a small portion of the extremity withThir ' Tl ^ remainder of th o edges are drawn together with the pane of the hammer. In making wrought iron hinges, two short slits are cut length- 54 FORGING IRON AND STEEL. ways and nearly through the bar, towards its extremity; the iron is then folded round a mandrel, set down close in the corner, and the two ends are welded together. To complete the hinge, it only remains to cut away transversely, either the central piece or the two external pieces to form the knuckles, and the addition of the pin or pivot finishes the work. ' . , Musket barrels, when made entirely by hand, were forged in the form of long strips about a yard long and four inches wide but taper both in length and width, which were bent round a cylmdrical mandrel until their edges slightly overlapped; they were then welded at three or four heats, by introducing the mandrel within them in- stantly on their removal from the fire at the proper heat, m order to prevent the sides of the tube from being pressed together by the blows of the hammer. . „ They have been subsequently, and are now almost universally welded by machinery at one heat, and whilst of the length of only one foot, as on removal from the fire the mandrel is quickly intro- duced, and the two are passed through a pair of grooved rollers: they are afterwards extended to the full length by similar means but at a lower temperature, so that the iron is not so much injured as when thrice heated to the welding point. The twisted barrels are made out of long ribands of iron wound spirally around a mandrel, and welded on their edges by jumping them upon the ground or rather on an anvil embedded therein. Ihe plain stub barrels are made in this manner, from iron manufactured from a bundle of stub-nails, welded together and drawn out into ribands to insure the possession of a material most thoroughly and intimately worked. The Damascus barrels are made from a mij^re of stub-nails and clippings of steel in given proportions, puddled together, made into a bloom, and subsequently passed through all the stages of the manufacture of iron already explained; to obtain an iron that shall be of unequal quality and hardness, and therefore display different colors and markings when oxidized or brined. Other twisted barrels are made in the like manner, except that the bars to form the ribands are twisted whilst red-hot like ropes, some to the right, others to the left, and which are sometimes again lami- nated together for greater diversity; they are subsequently again drawn into the ribands and wound upon the mandrel, and frequently two or three differently prepared pieces are placed side by side to form the complex and ornamental figures for the barrels of lowlmg- pieces, described as " stub-twist wire-twist, Damascus-twist, &c. A method amongst others of the formation of the Damascus gun barrels ; by arranging twenty-five thin bars of iron and mild steel in alternate layers, welding the whole together, drawing it downfall, twisting it like a rope, and again welding three such ropes, lor the formation of the riband which is then spirally twisted to form a barrel, that exhibits, when finished and acted upon by acids, a di- versified laminated structure, resembling when properly managed an ostrich feather. GENERAL EXAMPLES OF WELDING. 55 When the illumination by gas was first introduced in the large way, the old musket-barrels, laid by in quiet retirement from the fatigues of war, were employed for the conveyance of gas ; and by a curious coincidence, various iron foundries desisted in a great mea- sure from the manufacture of iron ordnance, and took up the peaceful employment of casting pipes for gas and water. The breech ends of the musket-barrels were broached and tapped, and the muzzles were screwed externally, to connect the two without detached sockets. From the rapid increase of gas illumination, the old gun- barrels soon became scarce, and new tubes with detached sockets, made by the old barrel-forgers, were first resorted to. This led to a series of valuable contrivances for the manufacture of the wrought-iron tubes, under which the tubes were first bent up by hand hammers and swages, to bring the edges near together ; and they were welded between semi-circular swages, fixed respectively in the anvil, and the face of a small tilt-hammer worked by ma- chinery, by a series of blows along the tube, either with or without a mandrel. The tube was completed on being passed between rol- lers with half-round grooves, which forced it over a conical or egg- shaped piece at the end of a long bar, to perfect the interior sur- face. Various steps of improvement have been since made; for instance, the skelps were bent at two squeezes, first to the semi-cylindrical, and then to the tubular form (preparatory to welding), between a swage-tool five feet long worked by machinery. The whole pro- cess was afterwards carried on by rollers, but abandoned on account of the unequal velocity at which the greatest and least diameters of the rollers traveled. In the present method of manufacturing the patent welded tube, the end of the skelp is bent to the circular form, its entire length is raised to the welding heat in an appropriate furnace, and as it leaves the furnace almost at the point of fusion, it is dragged by the chain of a draw-bench, after the manner of wire, through a pair of tongs with two bell-mouthed jaws; these are opened at the moment of in- troducing the end of a skelp, which is welded without the agency of a mandrel. By this ingenious arrangement, wrought-iron tubes may be made from the diameter of six inches internally and about one-eighth to three-eighths of an inch thick, to as small as one-quarter of an inch diameter and one-tenth bore; and so admirably is the joining effected in those of the best description, that they will withstand the great- est pressures of gas, steam or water, to which they have been sub- jected, and they admit of being bent both in the heated and cold state almost with impunity. Sometimes the tubes are made one upon the other when greater thickness is required ; but these stout pipes, and those larger than three inches, are comparatively but little used. The wrought-iron tubes of hydrostatic presses, which measure about half an inch internally, and one-fourth to three-eighths of an inch 5G FORGING IRON AND STEEL. thick in the metal, are frequently subjected to a pressure equal to four tons on each square inch. Various articles with large apertures are made, not by punching or cutting out the holes, but by folding the metal around the beak iron, and finishing them upon a triblet of the appropriate figure; thus the complete smithy is generally furnished with a series of cones turned in the lathe, for making rings the ends of which are folded together and welded, such as Fig. 56. The same rings when made of such cast-steel as does not admit of being welded, are first punched with a small hole, and gradually thinned out by blows around the margin, until they reach the diameter sought ; but this, like numerous other works, requires considerable forethought to pro- portion the quantity of the material to its ultimate form and bulk, so that the work may not in the end become either too slight or too heavy. Chains may be taken as another familiar example of welding; in these the iron is cut off with a plain chamfer, as from the annular form of the links their extremities cannot slide asunder when struck ; every succeeding link is bent, introduced, and finally welded. _ In some of these welded chains the links are no more than half an inch long, and the iron wire one-eighth of an inch diameter; several inches of such chain are required to weigh one pound : these are made with great dexterity by a man and a boy at a small fire. The curbed chains are welded in the ordinary form and twisted after- wards, a few links being made red-hot at a time for the purpose. The massive cable-chains are made much in the same manner, although partly by aid of machinery : the bar of iron now one, one and a half, or even two inches in diameter, is heated, and the scarf is made as a plain chamfer by a cutting machine ; the link is then formed by inserting the end of the heated bar within a loop in the edge of an oval disk which may be compared to a chuck fixed on the end of a lathe mandrel. The disk is put in gear with the steam-engine ; it makes exactly one revolution, and throws itself out of motion ; this bends the heated extremity of the iron into an oval figure, afterwards it is detached from the rod with a chamfered cut by the cutting machine, which at one stroke makes the second scarf of the detached link, and the first of that next to be curled up. The link is now threaded to the extremity of the chain, closed together, and transferred to the fire, the loose end being carried by a traverse crane ; when the link is at the proper heat, it is returned to the anvil, welded, and dressed off between top and bottom tools, after which the cast-iron transverse stay is inserted, and the link having been closed upon the stay, the routine is recommenced. The work commonly requires three men, and the scarf is placed at the side of the oval link, and flatway through the same. In similar chains made by hand it is perhaps more customary to weld the link at the crown, or small end. The tires of wrought-iron wheels for locomotive engines and car- riages, are in general bent to the circle by somewhat analogous GENERAL EXAMPLES OF WELDING. 57 means to those employed in chain-making, as are likewise the skelps for the twisted barrels of guns : the latter only require a mandrel or spindle with a winch handle at the one extremity, and a loop for the end of the skelp, which is wound in contact with the mandrel by means of a fixed bar placed near the same ; such barrels are coiled up in three lengths, which are joined together after the spirals are welded. Wheels for railways display many curious examples of smithing ; thus some, except the nave, are made entirely by welding ; others are partly combined with rivets ; in all the nave or boss is a mass of cast-iron usually poured around the ends of the spokes. The common practice of welding the tires of railway wheels is now as follows : the tires are cut off with ridges in the centre, so as in meeting to form two angular notches, into which two thin iron wedges are subsequently welded radially ; the four parts thus united together in the form of a cross, make a very secure joint without the necessity for upsetting the iron, which would distort the form of the tire. The succeeding illustration of the practice of forging will be that of" the formation of a hatchet, Figs. 57 and 58, which like many similar tools is made by doubling the iron around a mandrel, to form the eye of the tool ; it will also permit the description of some other general proceedings, and likewise the introduction of the steel for the cutting edge. D H In making the hatchet, a piece of flat iron is selected of the width of A E, and twice the length of AD; it is thinned and extended sideways before it is folded together, to form the projections near B and F, by blows with the pane of the hammer or a round-edged ful- ler, on the lines A B to E F, but the metal must be preserved of the full thickness at the part A E, to form the poll of the hatchet, although a piece of steel is frequently welded on at that part as a previous step. The work is then bent round a mandrel, Figs. 59 and 60, exactly of the section of the eye as seen in Fig. 58, and the work is welded across the line B F ; the mandrel is again introduced, and the eye is perfected. A slip of shear-steel, equal in length to D H, is next inserted be- tween the two tails of the iron, as yet of their original size, up to the former weld, and all three are welded together between C, G, J), H : 58 FORGING IRON AND STEEL. the combined iron and steel are now drawn out sideways, by blows of the pane of the hammer on and between C D and G H, to extend them together to I J. The tool is then flattened and smoothed with the face of the hammer, and the edges are pared with straight or circular chisels to the particular pattern, and trimmed with a round- faced hammer, or a top fuller. In smoothing off the work, the smith pursues his common method of first removing with a file the hard black scales that appear like spots when the work is removed from the fire ; he then dips the ham- mer in the slake trough, and lets fall upon the anvil a few drops of the water it picks up, the explosion of which when the red-hot metal is struck upon it, makes a smart report and detaches the scales that would be otherwise indented in the work. It should be observed that the mandrel, Fig. 59, is purposely made very taper, and is intro- duced into the hole from both sides, so that the eye may be smaller in the middle ; when therefore the handle of the tool is carefully fitted and wedged in, the handle is, as it were, dove-tailed, and the tool can neither fly off nor slip down the handle ; the same mode is also adopted for the heads of hammers. In spades, and many similar implements, the steel is introduced between the two pieces of iron of which the tools are made ; in others, as plane irons and socket chisels, it is laid on the outside, and the two are afterwards extended in length or width to the re- quired size. The ordinary chisel for the smith's shop is made by inserting the steel in a cleft, as in Fig. 51, and so is also the pane of a hammer; but the flat face of the hammer is sometimes stuck on whilst it continues at the extremity of a flat bar of steel ; it is then cut off, and the welding is afterwards completed. At other times the face of the hammer is prepared like a nail, with a small spike and a very large head, so as to be driven into the iron to retain its position, until finally secured by the operation of welding. In putting a piece of steel into the end of an iron rod to serve for a centre, the bar is heated, fixed horizontally in the vice, and punched lengthways with a sharp square punch, for the reception of the steel, which is drawn down like a taper tang or thick nail, and driven in ; the whole is then returned to the fire, and when at the proper heat united by welding, the blows being first directed as for forming a very obtuse cone, to prevent the piece of steel from drop- ping out. For some few purposes the blistered steel is used for welding, either to itself or to iron ; it is true the first working under the ham- mer in a measure changes it to the condition of shear-steel, but less efficiently so than when the ordinary course of manufacture is pur- sued, as the hammering is found to improve steel in a remarkable and increasing degree. For the majority of works in which it is necessary to weld steel to iron, or steel to steel, the shear, or double shear, is exceedingly suitable ; it is used for welding upon various cutting tools, as the majority of cast-steel will not endure the heat without crumbling APPLICATIONS OF HEADING TOOLS, ETC. 59 ■under the hammer. Shear-steel is also used for various kinds of springs, and for some cutting tools requiring much elasticity. It is more usual to reserve the cast-steel for those works in -which the process of welding is not required, although of late years mild cast-steel, or welding cast-steel, containing a smaller proportion of carbon has been rather extensively used ; but in general the harder the steel the less easily will it admit of welding, and not unfrequently it is altogether inadmissible. The hard or harsh varieties of cast-steel, are somewhat more man- ageable when fused borax is used as a defence instead of sand, either sprinkled on in powder or rubbed on in a lump : and cast-steel other- wise intractable may be sometimes welded to iron by first heating the iron pretty smartly, then placing the cold steel beside it in the fire, and welding them the moment the steel has acquired its maxi- mum temperature, by which time the iron will be fully up to the welding heat. When both are put into the fire cold alike, the steel is often spoiled before the iron is nearly hot enough, and therefore it is generally usual to heat the iron and steel separately, and only to place them in contact towards the conclusion of the period of getting up the heat. In forging works either of iron or steel, the uniformity of the hammering tends greatly to increase and equalize the strength of each material ; and in steel, judicious and equal forg- ing greatly lessens also the after-risk in hardening. When cast-steel has been spoiled by overheating, it may be par- tially recovered by four or five reheatings and quenchings in water, each carried to an extent a little less and less than the first excess ; and lastly, the steel must have a good hammering at the ordinary red heat. Some go so far as to prefer for cutting tools the steel thus recovered, but this seems a most questionable policy, although the change wrought by this treatment is really remarkable ; as the fragment broken off from the bar in the spoiled state, and another from the same bar after part restoration and hardening, will exhibit the extreme characters of coarse and fine. The hammering I suspect to be the principal requisite, and in superior tools it should be continued until the work is nearly cold, to produce the maximum amount of condensation before hardening ; but no hammering will restore the loss of tenacity consequent upon the over-heating, or even the too frequent heating, of steel, without excess. Concluding Remarks on Forging ; and the Applications of Heading Tools, Swage Tools, Punches, etc. — With the utmost care and unlimited space, it would have been quite impossible to have conveyed the instructions called for, in forging the thousand varieties of tools, and parts of mechanism the smith is continually called upon to produce ; and all that could be reasonably attempted in this place, was to convey a few of the general features and prac- tices of this most useful and interesting branch of industry. It is hoped, that such combinations of these methods may be readily ar- rived at as will serve for the majority of ordinary wants. 60 FORGING IRON AND STEEL. The smith in all cases selects or prepares that particular form and magnitude of iron, and also adopts that order of proceeding, which experience points out as being the most exact, sound, and economi- cal. In this he is assisted by a large assortment of various tools and moulds for such parts of the work as are often repeated, or that are of a character sufficiently general to warrant the outlay, and to some of which I will advert. The heading tools, Figs. 34 and 35, are made of all sizes and varieties of form ; some with a square recess to produce a square beneath the head, to prevent the bolt from being turned round in the act of tightening its nut; others for countersunk and round-headed bolts, with and without square shoulders : many similar heading tools are used for all those parts of work which at all resemble bolts, in having any sudden enlargement from the stem or shaft. The holes in the swage block, Fig. 61, are used after the manner of heading tools for large objects ; the grooves and recesses around its margin, also serve in a variety of works as bot- tom swages beyond the size of those fitted to the anvil. At the oppo- site extreme of the heading tools, as to size, may be noticed those constantly employed in producing the smallest kinds of nails, brads and rivets, of various denomina- tions, some of which heading tools divide in two parts like a pair of spring forceps to release the nails after they have been forged. _ The forge used by the nail-makers is built as a circular pedestal with the fire in the centre and the chimney directly over it ; the rock-staff of the bellows extends entirely around the forge, so that one of the four or five persons who work at the same fire is continu- ally blowing it, whence the fire is always at the heat proper for weld- ing, and which keeps the nails sound and good. These kinds are called wrought nails and brads, in contradistinction to similar nails cut out of sheet-iron by various processes of shearing and punching, which latter kinds are known as cut brads and nails, and will be ad- verted to hereafter. The top and bottom rounding tools, Fig. 31, are made of all diam- eters for plain cylindrical works : and when they are used for objects the different parts of which are of various diameters, it requires much care to apply them equally on all parts of the work, that the several circles may be concentric and true one with the other, or possess one axis in common. To insure this condition some of these rounding tools are made of various and specific forms, for the heads of screws, for collars, flanges or enlargements, which are of continual occurrence in machinery ; for the ornamental swells or flanges about the iron APPLICATIONS OF HEADING TOOLS, ETC. 61 work' of carriages, and other works. Such tools, like the pair rep- resented in Figs. 62 and 63, are called swage or collar tools; they save labor in a most important degree, and are thus made. A solid mould, core or striker, exactly a copy of the work to be produced, is made of steel by hand-forging, and then turned in the lathe to the required form, as shown in Fig. 64. Figs. 62. 66. 69. 68. The top tool is first moulded to the general form in an appropriate aperture in the swage block, Fig. 61, it is faced with steel like a hammer, and the core, Fig. 64, is indented into it; the blows of the sledge-hammer not being given directly upon the core, but upon some hollow tool previously made; otherwise the core must be filed partly flat to present a plane surface to the hammer. The bottom tool, which is fitted to the anvil, is made in a similar manner, and some- times the two are finished at the same time whilst hot, with the cold striker between them ; their edges are carefully rounded with a file so as not to cut the work, and lastly they are hardened, under a stream of water. In preparing the work for the collar tools, when the projection is inconsiderable, the work is always drawn down rudely to the form between the top and bottom fullers, as in Fig. 29 ; but for greater economy, large works in iron are sometimes made by folding a ring around them as in Fig. 37. The metal for a large ring is occasion- ally moulded in a bottom tool, like Fig. 65, and coiled up to the shape of Fig. 66, after which it is closed upon the central rod be- tween the swages, and then welded within them. The tools are slightly greased, to prevent the work from hanging to them, and from the same motive their surfaces are not made quite flat or perpen- dicular, but slightly conical, and all the angles are obliterated and rounded. The spring swage tool, represented in Fig. 67, is used for some small manufacturing purposes; it differs in no respect from the former, except in the steel spring which connects the two parts ; it is employed for light single hand-forgings. Other workmen use swage tools, such as Fig. 68, in which there is a square recess in 62 FORGING IRON AND STEEL. the bottom tool to fit the margin of the top-tool so as to guide it exactly to its true position. In practice the recess in the bottom tool would be deeper, and taper or larger above to guide the tool more easily to its place ; but if so drawn the figure would have been less distinct. This kind also may be used for single hand works, and is particularly suited to those which are of rectangular section, as the shoulders of table-knives ; these do not admit of being twisted round, which movement furnishes the guide for the position of the top-tool in forging circular works. The smith has likewise a variety of punches of all shapes and sizes, for making holes of corresponding forms ; and also drifts or mandrels, used alone for finishing them, many of which, like the turned cones, are made from a small to a large size to serve for objects of various sizes. Two examples of the very dexterous use of punches, are in the hands of almost every person, namely, ordi- nary scissors and pliers. m The first are made from a small bar of flat steel ; the end is flat- tened and punched with a small round hole, which is gradually opened upon a beak-iron, Fig. 69, attached to the square hole of the anvil ; the beak-iron has a shallow groove (accidentally omitted) for rounding the inside of the bows. The remaining parts of the scissors are moulded jointly by the hammer, and bottom swage tools ; but the bows are mostly finished by the eye alone. In some pliers, the central half of the joint is first made; the aperture in the other part is then punched through sideways, and sufficiently bulged out to allow the middle joint to be passed through, after which the outsides are closed upon the centre. This proceed- ing exhibits, in the smallest kinds especially, a surprising degree of dexterity and dispatch, only to be arrived at by very great practice ; and which in this and numerous other instances of manufacture could be scarcely attained but for the enormous demand, which enables a great subdivision of labor to be successfully applied to their production. Figs. 70, 71, 72 and 73 represent the ordinary trip and tilt hammer used in this country. The drawings are taken from those manufactured Fig. 70. Fig. 71. at the Lowell Machine Shop, Lowell, Mass., of which TV. A. Burke is the superintendent. The smaller trip-hammers are mounted with HARDENING AND TEMPERING. 63 iron bed-piece& firmly bolted on large timber, furnished with a cast- iron stake, adapted to drawing and swaging spindles, bolts, and other Fig. 72. Fig. 73. small work, balance wheels on cam shaft, and a husk adjustable by bolts and screws ; the hammer-head weighing from thirty to one hundred and twenty-five pounds, driven by a belt. The heavy trip- hammer, manufactured in this shop, has a very heavy strong cast- iron frame, adjustable husk, cast-iron stake, driven by belt with balance-wheel on cam-shaft, and suited to a hammer-head weighing- from one hundred and twenty-five to four hundred pounds. HARDENING AND TEMPERING. General View of the Subject.— When the malleable metals are hammered, or rolled, they generally increase in hardness, in elas- ticity, and in density or specific gravity ; which effects are produced simply from the closer approximation of their particles, and in this respect steel may be perhaps considered to excel, as the process called hammer-hardening, which simply means hammering without heat, is frequently employed as the sole means of hardening some kinds of steel springs, and for which it answers remarkably well. After a certain degree of compression, the malleable metals as- sume their closest and most condensed states ; and it then becomes necessary to discontinue the compression or elongation, as it would cause the disunion or cracking of the sheet or wire, or else the metal must be softened by the process of annealing. The metals, lead, tin, and zinc, are by some considered to be per- ceptibly softened by immersion in boiling water ; but such of the metals as will bear it are generally heated to redness, the cohesion of the mass is for the time reduced, and the metal becomes as soft as at first, and the working and annealing may be thus alternately pursued, until the sheet metal, or the wire, reaches its limit of tenuity. The generality of the metals and alloys suffer no very observable change, whether or not they are suddenly quenched in water from the red heat. Pure hammered iron, like the rest, appears after an- 04 HARDENING AND TEMPERING. nealing, to be equally soft whether suddenly or slowly cooled ; some of the impure kinds of malleable iron harden by immersion, but only to an extent that is rather hurtful than useful, and which may be considered as an accidental quality. Steel however receives by sudden cooling that extreme degree of hardness combined with tenacity, which places it so incalculably be- yond every other material for the manufacture of cutting tools ; especially as it likewise admits of a regular gradation from extreme hardness to its softest state, when subsequently re-heated or tempered. Steel therefore assumes a place in the economy of manufactures un- approachable by any other material, consequently we may safely say that without it, it would be impossible to produce nearly all our finished works in metal and other hard substances ; for although some of the metallic alloys are remarkable for hardness, and were used for various implements of peaceful industry, and also those of war, before the invention of steel ; yet in point of absolute and en- during hardness, and equally so in respect to elasticity and tenacity, they fall exceedingly short of hardened steel. Hammer hardening renders the steel more fibrous and less crys- taline, and reduces it in bulk ; on the other hand, fire hardening makes steel more crystaline, and frequently of greater bulk ; but the elastic nature of hammer hardened steel, will not take so wide nor so efficient a range as that which is fire hardened. If we attempt to seek the remarkable difference between pure iron and steel in their chemical analyses, it appears to result from a mi- nute portion of carbon ; and cast-iron, which possesses a much larger share, presents, as we should expect, somewhat similar phenomena. Iron semi-steelified ..... contains one 150th of carbon. Soft cast-steel capable of welding . . . (i 120th Cast-steel for common purposes (i lUOth " Cast steel requiring more hardness (< 90th Steel capable of standing a few blows, but quite \ 50th " unfit for drawing ..... First approach to a steely granulated fracture u 30th to 40th. White cast-iron . . . . . . 25th " Mottled cast-iron \ ti 20th " Carbonated cast-iron . ... . . . 11 15th " Super-carbonated crude iron .... (1 12th For the mode of analysis for ascertaining the quantity of carbon in cast-iron and steel, invented by M. V. Regnault, Mining Engi- neer, see Annales de Qhimie et de Physique, for January, 1839 ; also Journal of the Franklin Institute, vol. xxv. p. 327. It is stated that the analysis is very easy and exact, and may be completed in half an hour. Moreover, as the hard and soft conditions of steel may be reversed backwards and forwards without any rapid chemical change in its substance, it has been pronounced to result from internal arrange- ment or crystalization, which may be in a degree illustrated and explained by similar changes observed in glass. A wine-glass, or other object recently blown, and plunged whilst GENERAL VIEW OF THE SUBJECT. 65 red hot into cold water, cracks in a thousand places, and even cooled in warm air it is very brittle, and will scarcely endure the slightest violence or sudden change of temperature; and visitors to the glass- house are often shown that a wineglass, or other article of irregular form, breaks in cooling in the open air from its unequal contraction at different parts. But the objects would have become useful, and less disposed to fracture,, if they had been allowed to arrange their particles gradually during their very slow passage through the long annealing oven or leer of the glass house, the end at which they enter being at the red heat, and the opposite extremity almost cold. To perfect the annealing, it is not unusual with lamp-glasses, tubes for steam-gages, and similar pieces exposed to sudden transitions of heat and cold, to place them in a vessel of cold water, which is slowly raised to the boiling temperature, kept for some hours at that heat and then allowed to cool very slowly : the effect thus produced is far from chimerical. For such pieces of flint glass intended for cutting, as are found to be insufficiently annealed, the boiling is some- times preferred to a second passage through the leer: lamp-glasses are also much less exposed to fracture when they have been once used, as the heat, if not too suddenly applied or checked, completes the annealing. Steel in like manner when suddenly cooled is disposed to crack in pieces, which is a constant source of anxiety ; the danger increases with the thickness in the same way as with glass, and the more es- pecially when the works are unequally thick and thin. Another ground of analogy between glass and steel appears to exist in the pieces of unannealed glass used for exhibiting the phe- nomena, formerly called double refraction, but now polarization of light ; an effect distinctly traced to its peculiar crystalline structure. In glass it is supposed to arise from the cooling of the external crust more rapidly than the internal mass ; the outer crust is there- fore^ a state of tension, or restraint, from an attempt to squeeze the inner mass into a smaller space than it seems to require ; and from the hasty arrangement of the unannealed glass the natural positions of its crystals are in a measure disturbed or dislocated. It has been shown experimentally, that a re-arrangement of the particles of glass occurs in the process of annealing, as, of two pieces of the same tube each 40 inches long, the one sent through the leer con- tracted one-sixteenth of an inch more than the other, which was cooled as usual in the open air. Tubes for philosophical purposes are not annealed, as their inner surfaces are apt to become soiled with the sulphur of the fuel ; they are in consequence very brittle and liable to accident. The unannealed glass, when cautiously heated and slowly cooled, ceases to present the polarizing effect, and the steel similarly treated ceases to be hard; and may we not therefore indulge in the specu- lation, that in both cases a peculiar crystalline structure is consequent upon the unannealed or hardened state ? In the process of hardening steel, water is by no means essential, 66 HARDENING AND TEMPERING. as the sole object is to extract its heat rapidly, and the following are examples, commencing with the condition of extreme hardness, and ending with the reverse condition. A thin heated blade placed between the cold hammer and anvil, or other good conductors of heat, becomes perfectly hard. Thicker pieces of steel, cooled by exposure to the air upon the anvil, become rather hard, but readily admit of being filed. They become softer when placed on cold cinders, or other bad conductors of heat. Still more soft when placed in hot cinders, or within the fire itself, and cooled by their gradual extinction. When the steel is encased in close boxes with charcoal powder, and it is raised to a red-heat and allowed to cool in the fire or furnace, it assumes its softest state ; unless, lastly, we proceed to its partial decomposition. This is done by enclosing the steel with iron turnings or filings, the scales from the smith's anvil, lime, or other matters that will abstract the car- bon from its surface ; by this mode it is superficially decarbonized, or reduced to. the condition of pure soft iron, in the manner practiced by Mr. Jacob Perkins, of Massachusetts, in his most ingenious and effective combination of processes, employed for producing in unlimited numbers absolutely identical impressions of bank notes and cheques, for the prevention of forgery. These methods of treating steel will be hereafter noticed. A nearly similar variety of conditions might be referred to as existing in cast-iron in its ordinary state, governed by the. magni- tude, quality, and management of the castings ; independently of which, by one particular method, some cast-iron may be rendered externally as hard as the hardest steel ; such are called chilled iron castings ; and, as the opposite extreme, by a method of annealing combined with partial decomposition, malleable iron castings may be obtained, so that cast-iron nails may be clenched. Again, the purest iron, and most varieties of cast-iron, may, by another proceeding, be superficially converted into steel, and then hardened, the operation being appropriately named case-hardening. I therefore propose to illustrate these phenomena collectively, under three divisions: first, the hardening and tempering of steel; secondly, the hardening and annealing of cast-iron; and thirdly, the process of case-hardening. Practice of hardening and tempering Steel. — It may perhaps be truly said, that upon no one subject connected with mechanical art does there exist such a contrariety of opinion, not unmixed with prejudice, as upon that of hardening and tempering steel ; which makes it often difficult to reconcile the practices followed by different individuals in order to arrive at exactly similar ends. The real diffi- culty of the subject occurs in part from the mysteriousness of the change ; and from the absence of defined measures, by which either the steps of the process itself, or the value of the results when obtained, may be satisfactorily measured; as each is determined almost alone by the unassisted senses of sight and touch, instead of by those phy- sical means by which numerous other matters may be strictly tested PRACTICE OF HARDENING AND TEMPERING STEEL. 67 and measured, nearly without reference to the judgment of the indi- vidual, which m its very nature is less to be relied upon The excellence of cutting tools, for instance, is pronounced upon their relative degrees of endurance, but many accidental circum- stances here interfere to vitiate the strict comparison : and in respect to the measure of simple hardness, nearly the only test is the resist- ance the objects offer to the file, a mode in two ways defective, as the hies differ amongst themselves in hardness; and they only serve to indicate in an imperfect manner to the touch of the individual a general notion without any distinct measure, so that when the opinion of half a dozen persons may be taken, upon as many pieces of steel differing but slightly in hardness, the want of uniformity in their decisions will show the vague nature of the proof. Under these circumstances, instead of recommending any parti- cular methods, I have determined to advance a variety of practical examples derived from various sources, which will serve in most cases to confirm, but in some to confute one another; leaving to every individual to follow those examples which may be the most nearly paralle with his own wants. There are, however, some few points upon which it may be said that all are agreed ; namely The temperature suitable to forging and hardening steel differs in some^ degree with its quality and its mode of manufacture; the heat that is required diminishes with the increase of carbon: m In every case the lowest available temperature should be employed m each process the hammering should be applied in the most equal manner throughout, and for cutting tools it should be continued until they are nearly cold: Coke or charcoal is much better as a fuel than fresh coal, the sul- phur of which is highly injurious: . ^he scale should be removed from the face of the work to expose it the more uniformly to the effect of the cooling medium : . Hardening a second time without the intervention of hammering is attended with increased risk; and the less frequently steel passes through the fire the better. In hardening and tempering steel there are three things to be con- sidered ; namely, the means of heating the objects to redness, the means of cooling the same, and the means of applying the heat for tempering or letting them down. I will speak of these separately, before giving examples of their application. The smallest works are heated with the flame of the blowpipe and are occasionally supported upon charcoal ; but' as the blowpipe is used to a far greater extent in soldering, its management will be described m the chapter devoted to that process. For objects that are too large to be heated by the blowpipe, and too small to be conveniently warmed in the naked fire, various pro- tective means are employed. Thus, an iron tube or sheet-iron box inserted in the midst of the ignited fuel is a safe and cleanly way it resembles the muffle employed in chemical works. The work is then managed with long forceps made of steel or iron wire, bent in 68 HARDENING AND TEMPERING. the form of the letter U, and flattened or hollowed at the ends. A crucible or an iron pot about four to six inches deep, filled with lead and heated to redness, is likewise excellent, but more particularly for long and thin tools, such as gravers for artists, and other slight instruments; several of these may be inserted at once, although to- wards the last they should be moved about to equalize the heat ; the weight of the lead makes it desirable to use a bridle or trevet for the support of the crucible. Some workmen place on the fire a pan of charcoal dust, and heat it to redness. Great numbers of tools, both of medium and large size, are heated in the ordinary forge fire, which should consist of cinders rather than fresh coals; coke and also charcoal are used, but far less generally; recourse is also had to hollow fires, the construction of which was explained at page 38 ; but the bellows should be very sparingly used, except in blowing up the fire before the introduction of the work, which should be allowed ample time to get hot, or, as it is called, to " soak*" Which method soever may be resorted to for heating the work, the greatest care should be given to communicate to all the parts requiring to be hardened a uniform temperature, and which is only to be arrived at by cautiously moving the work to and fro to expose all parts alike to the fire ; the difficulty of accomplishing this of course increases with long objects, for which fires of proportionate length are required. % It is far better to err on the side of deficiency than of excess ot heat ; the point is rather critical, and not alike in all varieties of steel.' Until the quality of the steel is familiarly known, it is a safe precaution to commence rather too low than otherwise, as then the extent of the mischief will be the necessity for a repetition of the process at a higher degree of heat ; but the steel, if burned or over- heated, will be covered with scales, and what is far worse, its quality will be permanently injured; a good hammering will, in a degree, restore it ; but this in finished works is generally impracticable. Less than a certain heat fails to produce hardness, and in the opinion of some workmen has quite the opposite effect, and they con- sequently resort to it as the means of rapid annealing; not, however, by plunging the steel into the water and allowing it to remain until cold, but dipping it quickly, holding it in the steam for a few mo- ments, dipping it again and so on, reducing it to the cold state m a hasty but intermittent manner. There is another opinion prevalent amongst workmen, that steel which is "pinny," or as if composed of a bundle of hard wires, is rendered uniform in its substance if it is first hardened and then annealed. ' ,.' . . , Secondly, the choice of the cooling medium has reference mainly to the relative powers of conducting heat they severally possess : the following have been at different times resorted to with various degrees of success : currents of cold air ; immersion in water in various states, in oil or wax, and in freezing mixtures; mercury, and flat metallic PRACTICE OF HARDENING AND TEMPERING STEEL. 69 surfaces have been also used. Plain water, at a temperature of 40° Fahrenheit, has been recommended. On the whole, however, there appears to be an opinion that mercury gives the greatest degree of hardness ; then cold salt and water, or water mixed with various " astringent and acidifying matters;" plain water follows; and lastly, oily mixtures. I find but one person who has commonly used the mercury ; many presume upon the good conducting power of the metal, and the non- formation of steam, which causes a separation betwixt the steel and water when the latter is employed as the cooling medium. I have failed to learn the reason of the advantage of salt and water, unless the fluid have, as well as a greater density, a superior conducting power. The file-makers medicate the water in other ways, but this is one of the questionable mysteries which is never divulged; although it is supposed that a small quantity of white arsenic is generally added to water saturated with salt. One thing, however, may be noticed, that articles hardened in salt and water are apt to rust, unless they are laid for a time in lime-water, or some neutralizing agent. With plain water an opinion very largely exists in favor of that which has been used over and over again even for years, provided it is not greasy : and when the steel is very harsh, the chill is taken off plain water to lessen the risk of cracking it ; oily mixtures impart to thin articles, such as springs, a sufficient and milder degree of hardness, with less danger of cracking, than from water ; and in some cases a medium course is pursued by covering the water with a thick film of oil, which is said to be adopted occasionally with scythes, reaping-hooks, and thin edge-tools. A so-called natural spring is made by a vessel with a true and a false bottom, the latter perforated with small holes; it is filled with water, and a copious supply is admitted beneath the partition ; it ascends through the holes, and pursues the same current as the heated portions, which also escape at the top. This was invented by the late John Oldham, of Dublin, Engineer to the Bank of Eng- land, and was used by him in hardening the rollers for transferring the impressions to the steel-plates for bank-notes. Sometimes when neighboring parts of works are required to be respectively hard and soft, metal tubes or collars are fitted tight upon the work, to protect the parts to be kept soft from the direct action of the water, at any rate for so long a period as they retain the temperature suitable to hardening. The process of hardening is generally one of anxiety, as the sudden transition from heat to cold often causes the works to become greatly distorted if not cracked. The last accident is much the most likely to occur with thick massive pieces, which are, as it were, hardened in layers, as although the external crust or shell may be perfectly hard, there is almost a certainty that towards the centre the parts are gradually less hard ; and when broken the inner por- tions will sometimes admit of being readily filed. 70 HARDENING AND TEMPERING. When in the fire the steel becomes altogether expanded, and in the water its outer crust is suddenly arrested, hut with a tendency to contract from the loss of heat, which cannot so rapidly occur at the central part ; it may be therefore presumed that the inner bulk continues to contract after the outer crust is fixed, and which tends to tear the two asunder, the more especially if there be any defective part in the steel itself. An external flake of greater or less extent not unfrequently shells off in hardening; and it often happens that works remain unbroken for hours after removal from the water, but eventually give way and crack with a loud report, from the rigid unequal tension produced by the violence of the process of harden- ing- The contiguity of thick and thin parts is also highly dangerous, as they can neither receive nor yield up heat, in the same times ; the mischief is sometimes lessened by binding pieces of metal around the thin parts with wire, to save them from the action of the cooling medium. Sharp angular notches are also fertile sources of mischief, and where practicable they should be rejected in favour of curved lines. As regards both cracks and distortions, it may perhaps be generally said, that their avoidance depends principally upon manipulation, or the successful management of every step; first the original manufac- ture of the steel, its being forged and wrought, so that it may be equally condensed on all sides with the hammer, otherwise, when the cohesion of the mass is lessened from its becoming red hot, it re- covers in part from any unequal state of density in which it may have been placed. Whilst red-hot, it is also in its weakest condition ; it is therefore prone to injury either from incautious handling with the tongs, or from meeting the sudden cooling action irregularly, and therefore it is generally best to plunge works vertically, as all parts are then exposed to equal circumstances, and less disturbance is risked than when the objects are immersed obliquely or sideways into the water; although for swords, and objects of similar form, it is found the best to dip them exactly as in making a vertical downward cut with a sabre, which for this weapon is its strongest direction. Occasionally objects are clamped between stubborn pieces of metal, as soft iron or copper, during their passage through the fire and water. Such plans can be seldom adopted, and are rarely fol- lowed, the success of the process being mostly allowed to depend ex- clusively upon good general management. In making the magnets for needles ten inches long, one-fourth of an inch wide, and the two-hundredth part of an inch thick, this precaution entirely failed ; and the needles assumed all sorts of dis- tortions when released from between the stiff bars within which they were hardened. The plan was eventually abandoned and the mag- nets were heated in the ordinary way within an iron tube, and were set straight with the hammer after being let down to a deep orange PRACTICE OF HARDENING AND TEMPERING STEEL. 71 or brown color. Steel, however, is in the best condition for the for- mation of good permanent magnets when perfectly hard. In all cases the thick unequal scale left from the forge should be ground off before hardening, in order to expose a clean metallic sur- face, otherwise the cooling medium cannot produce its due and equal effect throughout the instrument. The edges also should be left thick, that they may not be burned in the fire ; thus it will frequently happen that the extreme end or edge of a tool is inferior in quality to the part within, and that the instrument is much better after it has been a few times ground. Thirdly, the heat for tempering or letting down. Between the extreme conditions of hard and soft steel there are many interme- diate grades, the common index for which is the oxidation of the brightened surface, and it is quite sufficient for practice. These tints, and their respective approximate temperatures, are thus tabulated : — 1. Very pale straw yellow 2. A shade of darker yellow 3. Darker straw yellow 4. Still darker straw yellow 5. A brown yellow 6. A yellow, tinged slightly with 7. Light purple 8. Dark purple 9. Dark blue . 10. Paler blue . 11. Still paler blue 12. Still paler blue, with a tinge of green purple 430 450 470 490 500 520 530 550 570 590 610 630 Tools for metal. Tools for wood, and screw taps, &c. I Hatchets, chipping chisels, and other percussive tools, saws, &c. Springs. Too soft for the above pur- poses. The first tint arrives at about 430° F., but it is only seen by com- parison with a piece of steel not heated : the tempering colors differ slightly with the various qualities of steel. The heat for tempering being moderate, it is often supplied by the part of the tool not requiring to be hardened, and which is not there- fore cooled in the water. The workman first hastily tries with a file whether the work is hard ; he then partially brightens it at a few parts with a piece of grindstone or an emery stick, that he may be enabled to watch for the required color; which attained, the work is usually cooled in any convenient manner, lest the body of the tool should continue to supply heat. But when, on the contrary, the color does not otherwise appear, partial recurrence is had to the mode in which the work was heated, as the flame of the candle, or the surface of the clear fire applied, if possible, a little below the part where the color is to be observed, that it may not be soiled by the smoke. A very convenient and general manner of tempering small objects is to heat to redness a few inches of the end of a flat bar of iron about two feet long ; it is laid across the anvil, or fixed by its cold extremity in the vice ; and the work is placed on that part of its surface which is found by trial to be of the suitable temperature, by gradually sliding the work towards the heated extremity. In this manner many tools may be tempered at once, those at the hot part 72 HARDENING AND TEMPERING. being pushed off into a vessel of water or oil, as they severally show the required color, but it requires dexterity and quickness in thus managing many pieces. Vessels containing oil or fusible alloys carefully heated to the re- quired temperatures have also been used, and I shall have to describe a method called " blazing off," resorted to for many articles, such as springs and saws, by heating them over the naked fire until the oil, wax, or composition in which they have been hardened ignites ; this can only occur when they respectively reach their boiling tempera- tures and are also evaporated in the gaseous form. The period of letting down the works is also commonly chosen for correcting, by means of the hammer, those distortions which so com- monly occur in hardening ; this is done upon the anvil, either with the thin pane of an ordinary hammer, or else with a hack-hammer, a tool terminating at each end in an obtuse chisel edge which re- quires continual repair on the grindstone. The blows are given on the hollow side of the work, and at right angles to the length of the curve; they elongate the concave side, and gradually restore it to a plane surface, when the blows are dis- tributed consistently with the position of the erroneous parts. The hack-hammer unavoidably injures the surface of the work, but the blows should not be too violent, as they are then also more prone to break the work, the liability to which is materially lessened when it is kept at or near the tempering heat, and the edge of the hack- hammer is slightly rounded. Common Examples of Hardening and Tempering Steel. — Watchmakers' drills of the smallest kinds are heated in the blue part of the flame of the candle ; larger drills are heated with the blowpipe flame, applied very obliquely, and a little below the point ; when very thin they may be whisked in the air to cool them, but they are more generally thrust into the tallow of the candle or the oil of the lamp; they are tempered either by their own heat, or by immersion in the flame below the point of the tool. For tools between those suited to the action of the blowpipe and those proper for the open fire, there are many which require either the iron tube, or the bath of lead or charcoal described at page 68, but the greater number of works are hardened in the ordinary smith's fire, without such defences. Tools of moderate size, such as the majority of turning tools, carpenters' chisels and gouges, and so forth, are generally heated in the open fire; they require to be continually drawn backwards and forwards through the fire, to equalize the temperature applied, they are plunged vertically into the water, and then moved about sideways to expose them to the cooler portions of the fluid. If needful, they are only dipped to a certain depth, the remainder being left soft. Some persons use a shallow vessel filled only to the height of the portion to be hardened, and plunge the tools to the bottom; but this strict line of demarkation is sometimes dangerous, as the tools are apt to become cracked at the part, and therefore a small vertical COMMON EXAMPLES OF HARDENING AND TEMPERING STEEL. 73 movement is also generally given, that the transition from the hard to the soft part may occupy more length. Razors and penknives are too frequently hardened without the removal of the scale arising from the forging; this practice, which is not done with the best works, cannot be too much deprecated. The blades are heated in a coke or charcoal fire, and dipped into the water obliquely. In tempering razors, they are laid on their backs upon a clear fire, about half-a-dozen together, and they are removed one at a time, when the edges, which are as yet thick, come down to a pale straw color ; should the backs accidentally get heated beyond the straw color, the blades are cooled in water, but not otherwise. Penknife blades are tempered, a dozen or two at a time, on a plate of iron or copper about twelve inches long, three or four wide, and about a quarter of an inch thick; the blades are arranged close to- gether on their backs, and lean at an angle against each other. As they come down to the temper, they are picked out with small pliers and thrown into water if necessary; other blades are then thrust forward from the cooler parts of the plate to take their place. Hatchets, adzes, cold chisels, and numbers of similar tools, in which the total bulk is considerable compared with the part to be hardened, are only partially dipped; they are afterwards let down by the heat of the remainder of the tool, and when the color indicative of the temper is attained, they are entirely quenched. With the view of removing the loose scales, or the oxidation acquired in the fire, some workmen rub the objects hastily in dry salt before plunging them in the water, in order to give them a cleaner and whiter face. In hardening large dies, anvils, and other pieces of considerable size, by direct immersion, the rapid formation of steam at the sides of the metal prevents the free access of the water for the removal of the heat with the required expedition; in these cases, a copious stream of water from a reservoir above is allowed to fall on the sur- face to be hardened. This contrivance is frequently called a " float," and although the derivation of the name is not very clear, the prac- tice is excellent, as it supplies an abundance of cold water; and which, as it falls directly on the centre of the anvil, is sure to render that part hard. It is, however, rather dangerous to stand near such works at the time, as when the anvil face is not perfectly welded, it sometimes in part flies off with great violence and a loud report. Occasionally the object is partly immersed in a tank beneath the fall of water, by means of a crane and slings ; it is ultimately tem- pered with its own heat, and dropped in the water to become entirely cold. Oil, or various mixtures of oil, tallow, wax, and resin, are. used for many thin and elastic objects, such as needles, fish-hooks, steel pens and springs, which require a milder degree of hardness than is given by water. For example, steel pens are heated in large quantities in iron trays within a furnace, and are then hardened in an oily mixture; gene- rally they are likewise tempered in oil, or a composition the boiling 74 HARDENING AND TEMPERING. point of which is the same as the temperature suited to letting them down. This mode is particularly expeditious, as the temper cannot fall below the assigned degree. The dry heat of an oven is also used, and both the oil and oven may be made to serve for tempers harder than that given by boiling oil ; but more care and observa- tion are required for these lower temperatures. Saws and springs are generally hardened in various compositions of oil, suet, wax and other ingredients, which, however, lose their hardening property after a few weeks' constant use: the saws are heated in long furnaces, and then immersed horizontally and edge- ways in a long trough containing the composition; two troughs are commonly used, the one until it gets too warm, then the other for a period, and so on alternately. Part of the composition is wiped off the saws with a piece of leather, when they are removed from the trough, and they are heated one by one over a clear coke fire, until the grease inflames; this is called " blazing off." The composition used by an experienced saw-maker is two pounds of suet and a quarter of a pound of bees-wax to every gallon of whale-oil ; these are boiled together, and will serve for thin works and most kinds of steel. The addition of black resin, to the extent of about one pound to the gallon, makes it serve for thicker pieces and for those it refused to harden before ; but the resin should be addecf with judgment, or the works will become too hard and brittle. The composition is useless when it has been constantly employed for about a month ; the period depends, however, on the extent to which it is used, and the trough should be thoroughly cleaned out before new mixture is placed in it. The following recipe is recommended: — Twenty gallons of spermaceti oil; Twenty pounds of beef suet rendered ; One gallon of neat's-foot oil; One pound of pitch ; Three pounds of black resin. These last two articles must be previously melted together, and then added to the other ingredients ; when the whole must be heated in a proper iron vessel, with a close cover fitted to it, until the moist- ure is entirely evaporated, and the composition will take fire on a flaming body being presented to its surface, but which must be in- stantly extinguished again by putting on the cover of the vessel. When the saws are wanted to be rather hard, but little of the grease is burned off; when milder, a larger portion ; and for a spring temper, the whole is allowed to burn away. When the work is thick, or irregularly thick and thin, as in some springs, a second and third dose is burned off, to insure equality of temper at all parts alike. Gun-lock springs are sometimes literally fried in oil for a consider- able time over a fire in an iron tray ; the thick parts are then sure to be sufliciently reduced, and the thin parts do not become the more softened from the continuance of the blazing heat. Springs and saws appear to lose their elasticity, after hardening COMMON EXAMPLES. T5 and tempering, from the reduction and friction they undergo in grinding and polishing. Towards the conclusion of the manufacture, the elasticity of the saw is restored principally by hammering, and partly by heating it over a clear coke fire to a straw color : the tint is removed by very diluted muriatic acid, after which the saws are well washed in plain water and dried. Watch springs are hammered out of round steel wire, of suitable diameter, until they fill the gage for width, which at the same time insures equality of thickness; the holes are punched in their extremi- ties, and they are trimmed on the edge with a smooth file ; the springs are then tied up with binding-wire, in a loose open coil, and heated over a charcoal fire upon a perforated revolving plate, they are hard- ened in oil, and blazed off. The spring is now distended in a long metal frame, similar to that used for a saw blade, and ground and polished with emery and oil, between lead blocks ; by this time its elasticity appears quite lost, and it may be bent in any direction ; its elasticity is, however, en- tirely restored by a subsequent hammering on a very bright anvil, which " puts the nature into the spring." The coloring is done over a flat plate of iron, or hood, under which a little spirit-lamp is kept burning; the spring is continually drawn backwards and forwards, about two or three inches at a time, until it assumes the orange or deep blue tint throughout, according to the taste of the purchaser; by many the coloring is considered to be a matter of ornament, and not essential. The last process is to coil the spring into the spiral form, that it may enter the barrel in which it is to be contained ; this is done by a tool with a small axis and winch handle, and does not require heat. The balance-springs of marine chronometers, which are in the form of a screw, are wound into the square thread of a screw of the appropriate diameter and coarseness ; the two ends of the spring are retained by side-screws, and the whole is carefully enveloped in platinum-foil, and tightly bound with wire. The mass is next heated in a piece of gun barrel closed at the one end, and plunged into oil, which hardens the spring almost without discoloring it, owing to the exclusion of the air by the close platinum covering, which is now removed, and the spring is let down to the blue, before removal from the screwed block. The balance or hair-springs of common watches are frequently left soft; those of the best watches are hardened in the coil upon a plain cylinder, and are then curled into the spiral form between the edge of a blunt knife and the thumb, the same as in curling up a narrow ribbon of paper, or the filaments of an ostrich feather. Thirty-two hundred balance-springs weigh about one ounce. The soft springs are worth 60 cents each ; the hardened and tempered springs, $1 28 each. This raises the value of the steel, originally less than four cents, to $2000 and $8000 respectively. But springs also include the heaviest examples of hardened steel works uncom- bined with iron: for example, bow-springs for all kind of vehicles. 76 HARDENING AND TEMPERING. some intended for railway use, measure feet long, and weigh 50 pounds each piece; two of these are used in combination; other single springs are 6 feet long, and weigh seventy pounds. The principle of these bow-springs will be immediately seen, by conceiving the common archery bow fixed horizontally with its cord upwards ; the body of the carriage being attached to the cord sways both perpen- dicularly and sideways with perfect freedom. In hardening them they are heated by being drawn backwards and forwards through an ordinary forge fire, built hollow, and they are immersed in a trough of plain water: in tempering them they are heated until the black red is just visible at night; by daylight the heat is denoted by its making a piece of wood sparkle when rubbed on the spring, which is then allowed to cool in the air. The metal is nine-sixteenths of an inch thick, and some consider five-eighths the limits to which steel will harden properly, that is sufficiently alike to serve as a spring ; their elasticity is tested far beyond their intended range. Great diversity of opinion exists respecting the cause of elasticity in springs; by some it is referred to different states of electricity; by others the elasticity is considered to reside in the thin blue, oxi- dized surface, the removal of which is thought to destroy the elasti- city, much in the same manner that the elasticity of a cane is greatly lost by stripping off its silicious rind. The elasticity of a thick spring is certainly much impaired by grinding off a small quantity of its exterior metal, which is harder than the inner portion ; and perhaps thin springs sustain in the polishing a proportional loss, which is to them equally fatal. It has been stated that the bare removal of the blue tint from a pendulum spring, by its immersion in weak acid, caused the chrono- meter to lose nearly one minute each hour; a second and equal im- mersion scarcely caused any further loss. It is supposed springs get stronger, in a minute degree, during the first two or three years they are in use, from some atmospheric change; when the springs are coated with gold by the electrotype process, no such change is observable, and the covering, although perfect, may be so thin as not to compensate for the loss of the blue oxidized surface. Less Common Examples of Hardening, and Precautionary Measures. — English writers are famous all over the world for dis- tributing between themselves and their friends the inventions and discoveries of 'the rest of mankind. One of the leading points of Jacob Perkins' discovery is disposed of in an original manner in the following paragraph. I thought I was up to every mode in which they drag in their friends ; but this mode is new to me. One of the most serious evils in hardening steel, especially in thick blocks, or those which are unequally thick and thin, is their liability to crack, from the sudden transition; and in reference to hardening razors, a case in point; Mr. mentions it as the ob- servation and practice of one of his workmen, "that the charcoal PRECAUTIONARY MEASURES. 77 fire should be made up with shavings of leather ;" and upon being asked what good he supposed the leather could do, this workman replied, " that he could take upon him to say that he never had a razor crack in the hardening since he had used this method, though it was a frequent occurrence before." When brittle substances crack in cooling, it always happens from the outside contracting and becoming too small to contain the inte- rior parts. But it is known that hard steel occupies more space than when soft; and it may easily be inferred that the nearer the steel approaches to the state of iron, the less will be this increase of dimensions. If, then, we suppose a razor or any other piece of steel to be heated in an open fire with a current of air passing through it, the external part will, by the loss of carbon, become less steely than before : and when the whole piece comes to be hardened, the inside will be too large for the external part, which will probably crack. But if the piece of steel be wrapped up in the cementing mixture, or if the fire itself contain animal coal, and is put together so as to operate in the manner of that mixture, the external part, instead of being degraded by this heat, will be more carbonated than the internal part, in consequence of which it will be so far from splitting or bursting during its cooling, that it will be acted upon in a contrary direction, tending to render it more dense and solid. The cracking which so often occurs on the immersion of steel articles in water, does not appear to arise so much from any decar- bonization of the surface merely, as from the sudden condensation and contraction of a superficial portion of the metal, while the mass in- side remains swelled with the heat, and probably expands for a moment, on the outside coming in contact with the water. The file-makers, to save their works from clinking or cracking partly through in hardening, draw the files through yeast, beer- grounds, or any sticky material, and then through a mixture of com- mon salt and animal hoof roasted and pounded. This is corrobora- tive of the above, as in the like manner it supplies a little carbon to the outside, and also renders the steel somewhat harder and less dis- posed to crack ; the composition also renders the more important service of protecting the fine points of the teeth from being injured by the fire. An analogous method is now practiced in hardening Murphy's axletrees, which are of wrought iron, with two pieces of steel welded into the lower side, where they rest upon the wheels and sustain the load. The work is heated in an open forge fire, quite in the ordi- nary way, and when it is removed, a mixture, principally the prus- siate of potash, is laid upon the steel, the axletree is then immediately immersed in water, and additional water is allowed to fall upon it from a cistern. The steel is considered to become very materially harder for the treatment, and the iron around the same is also par- tially hardened. These are, in fact, applications of the case-hardening process, which is usually applied to wrought iron for giving it a steely exterior, 78 HARDENING AND TEMPERING. as the name very properly implies. Occasionally, steel which hard- ens but imperfectly, either from an original defect in the material, or from its having become deteriorated by bad treatment, or too frequent passage through the fire, is submitted to the case-hardening process in the ordinary way, by inclosing the objects in iron boxes, as will be explained. Jacob Perkins's admirable process of transfer engraving may be thus explained. A soft steel plate was first engraved with the re- quired subject in the most finished style of art, either by hand or mechanically, or the two combined, and the plate was then hardened. A decarbonized steel cylinder was next rolled over the hardened plate by powerful machinery until the engraved impression appear- ed in relief, the hollow lines of the original becoming ridges upon the cylinder. The roller was reconverted to the condition of ordi- nary steel and hardened, after which it served for returning the impression to any number of decarbonized plates, every one of which became absolutely a counterpart of the original; and every plate, when hardened, would yield the enormous number of 150,000 im- pressions without any perceptible difference between the first and the last. In the event of any accident occurring to the transfer roller, the original plate still existed, from which another or any required number of rollers could be made, and from these rollers any number of new plates, all capable of producing as many impressions as above cited. The present practice at the Bank of England, introduced by the late Mr. John Oldham, and now under the superintendence of his son, Mr. Thomas Oldham, is to anneal at one time four cast-iron boxes each containing from three to six steel plates, surrounded on all sides with fine charcoal mixed with an equal quantity of chalk and driven in hard. The reverberatory furnace employed, has a circular cast-iron plate or bed upon which the four boxes are fastened by wedges, and as the plate revolves very slowly and continually by the steam-engine employed in working the printing-presses and other machinery, the plates are exposed in the most equal manner to the heat, and when the proper temperature is attained all the apertures are carefully closed and luted to extend the cooling over a space of at least forty- eight hours. The surfaces of the cylinders and plates are thus rendered ex- ceedingly soft, to the depth of about the 32d of an inch, " so as to become more like lead than anything else," and thus much of their surfaces must be turned or planed off; the device is raised in the transfer-press upon the natural soft steel of the rollers, under a pressure of some tons, and these are hardened without any inten- tional application of the case-hardening process, as the simple steel is undoubtedly very superior in all respects to that which has been decarbonized and reconverted. The plates themselves are used in the soft state, as they then admit PRECAUTIONARY MEASURES. 79 of reparation by the transfer rollers ; and the process is found to be more economical, as the risk of warping is avoided, and they may be easily repaired. The dates and numbers are at present printed as a second process by letter-press printing, with the machines in- vented by the late Mr. Bramah, and which have been engraved and described in different books. In hardening engraved plates, rollers, dies, and similar works, it is of the greatest importance to preserve the surface unimpaired, and as steel is very liable to oxidation at the red heat if exposed to the air for even a few seconds, and which oxidized scale will in some cases nearly remove, or at any rate injure, the subject produced upon its surface ; it is of great importance to conduct the heating and cooling with the most complete exclusion of the air. Mr. Thomas Oldham has, within these few weeks, introduced a mode of proceeding which appears as near to perfection as possible, and by it, instead of the works acquiring the ordinary black and gray tints, and a minute roughness, like the surface of the finest emery paper, the steel comes out of the water as smooth to the touch as at first, and mottled with all the beautiful tints seen on case-hard- ened gun-locks. The method is simply as follows : — The work to be hardened is inclosed in a wrought-iron box with a loose cover, a false bottom, and with three ears projecting from its surface about midway ; the steel is surrounded on all sides with car- bon from leather, driven in hard, and the cover and bottom are carefully luted with moist clay. Thus prepared, the case is placed in the vertical position, in a bridle fixed across a great tub, which is then filled with water almost to touch the false bottom of the case. The latter is now heated in the furnace as quickly as will allow the uniform penetration of the heat. When sufficiently hot, it is removed to its place in the hardening tub, the cover of the iron box is removed, and the neck or gudgeon of the cylinder is grasped, beneath the surface of the carbon, with a long pair of tongs, upon which a coupler is dropped to secure the grasp. It only remains for the individual to hold the tongs with a glove whilst a smart tap of a hammer is given on their extremity ; this knocks out the false bottom of the case and the cylinder and tongs are instantly immersed in the water ; the tongs prevent the cylinder from falling on its side, and thus injuring its delicate but still hot surface. For square plates, a suitable frame is attached by four slight claws, and it is the frame which is seized by the tongs ; the lat- ter are sometimes held by a chain, which removes the risk of accident to the individual. In some cases, the work assumes a striated and mackled appearance, evident to the touch as well as the sight, and which is to be attributed to an imperfect manufacture of the steel. Mr. Oldham informs me that in the Paris Mint, the dies are in- closed in the soot of burnt wood ; and that in our own mint, the dies are hardened by a powerful jet of water. He also adds, that his workpeople have the impression that steel is reduced to its softest :state by enclosure with lime and ox-gall. 80 HARDENING AND TEMPERING. Various methods have been likewise attempted to prevent the dis- tortions to which work is liable in the operation of hardening, but without any very advantageous results ; for instance, it has been recommended to harden small cylindrical wires, by rolling them when heated between cold metallic surfaces to retain them perfectly straight. This might probably answer, but unfortunately cylindri- cal steel wires supply but a very insignificant portion of our wants. Another mode tried by Dr. Wollaston was to inclose the piece of steel in a tube filled with Newton's fusible alloy, the whole to be heated to redness and plunged in cold water : the object was released by immersion in boiling water, which melted the alloy, and the piece came out perfectly unaltered in form, and quite hard. This mode is too circuitous for common practice, and the reason why it is to be always successful is not very apparent. Is not this a base attempt to drag in Newton and Wollaston ? To these men the English attribute everything. Jacob Perkins was an American to whom all the credit is due. The two Oldhams were Irishmen, Brunei was a Frenchman, and Bramah was a German. Mr. Perkins resorted to a very simple practice with the view of less- ening the distortion of his engraved steel plates by boiling the water in which they were to be hardened to drive off the air, and plunging them vertically ; and as the plates were required to be tempered to a straw color, instead of allowing them to remain in the water until entirely cold, he removed them whilst the inside was still hot, and placed them on the top of a clear fire until the tallow with which they were rubbed, smoked ; the plate was then returned to the water for a few moments, and so on alternately until they were quite cold, the surface never being allowed to exceed the tempering heat. From various observations, it appears on the whole to be the best in thick works thus to combine the hardening and tempering pro- cesses, instead of allowing the objects to become entirely cold, and then to reheat them for tempering. To ascertain the time when the plate should be first removed from the water, Mr. Perkins heated a piece of steel to the straw color, and dipped it into water to learn the sound it made ; and when the hardened plate caused the same sound, it was considered to be cooled to the right degree, and was immediately withdrawn. I will conclude these numerous examples and remarks by one of a very curious, massive, and perfect kind, in which the hardening is sure to occur without loss of figure, unless the work break under the process. I refer to the locomotive wheels with hardened steel tires, which may be viewed as the most ponderous example of hardening, as the tires of the eight-foot wheels weigh about 10 cwt., and con- sist of about one-third steel, and there seems no reason why this dia- meter might not be greatly exceeded. The materials for the tires are first swaged separately, and then welded together under the heavy hammer at the steel-works, after which they are bent to the circle, welded, and turned to certain gages. The tire is now heated to redness in a circular furnace ; HARDENING AND SOFTENING CAST-IRON. 81 during the time it is getting hot, the iron wheel, previously turned to the right diameter, is bolted down upon a face-plate ; the tire ex- pands with the heat, and when at a cherry-red, it is dropped over the wheel, for which it was previously too small, and is also hastily bolted down to the surface plate, the whole load is quickly immersed by a swing crane into a tank of water about five feet deep, and hauled up and down until nearly cold ; the steel tires are not after- wards tempered. The spokes are forged out of flat bars with T formed heads; these are arranged radially in the founder's mould, whilst the cast-iron centre is poured around them : the ends of the T heads are then welded together to constitute the periphery of the wheel or inner tire, and little wedge-form pieces are inserted where there is any deficiency of iron. The wheel is then chucked on a lathe, bored, and turned on the edge, not cylindrically, but like the meeting of two cones, and about one quarter of an inch higher in the middle than on the two edges. The compound tire is turned to the corresponding form, and conse- quently larger within or under-cut, so that the shrinking secures the tire without the possibility of obliquity or derangement, and no rivets are required. It sometimes happens that the tire breaks in shrink- ing when by mismanagement the diameter of the wheel is in excess. Hardening and softening Cast-iron.— The similitude of che- mical constitution between steel, which usually contains about one per cent, of carbon, and cast-iron that has from three to six or seven per cent., naturally leads to the expectation of some correspondence in their characters, and which is found to exist. Thus some kinds of cast-iron will harden almost like steel, but they generally require a higher temperature ; and the majority of cast-iron, also like steel, assumes different degrees of hardness, according to the rapidity with which the pieces are allowed to cool. The casting left undisturbed in the mould, is softer than a similar one exposed to the air soon after it has been poured. Large cast- ings cannot cool very hastily, and are seldom so hard as the small pieces, some of which are hardened like steel by the moisture com- bined with the moulding sand, and cannot be filed until they have been annealed after the manner of steel, which renders them soft and easy to be worked. Chilled iron-castings present as difficult a problem as the harden- ing and tempering of steel; the fact is simply this, that iron cast- ings, made in iron moulds under particular circumstances, become on their outer surfaces perfectly hard, and resist the file almost like hardened steel ; the effect is however superficial, as the chilled ex- terior shows a distinct line of demarkation when the objects are broken. The production of chilled castings is always a matter of some un- certainty, and depends upon the united effect of several causes ; the quality of the iron, the thickness of the casting, the temperature of the iron at the time of pouring, and the condition or temperature of 82 HARDENING AND TEMPERING. the iron mould, which has a greater effect in " striking in" when the mould is heated than if quite cold : a very thin stratum of earthy- matter will almost entirely obviate the chilling effect. A cold mould does not generally chill so readily as one heated nearly to the extent called "black-hot:" but the reverse conditions occur with some cast- iron. The hard portion varies from less than one-sixteenth to more than one-fourth of an inch in thickness. There is this remarkable difference between cast-iron thus hard- ened, and steel hardened by plunging whilst hot into water ; that whereas the latter is softened again by a dull red-heat, the chilled castings on the contrary are turned out of the moulds as soon as the metal is set, and are allowed to cool in the air ; yet although the whole is at a bright red heat, no softening of the chilled part takes place. This material has been employed for punches for red-hot iron ; the punches were fixed in cast-iron sockets, from which they only projected sufficiently to perforate the wheel tires in the forma- tion of which they were used, and from retaining their hardness they were more efficient than those punches made of steel. Chilled castings are also commonly employed for axletree boxes, and naves of wheels, which are finished by grinding only ; also for cylinders for rolling metal, for the heavy hammers and anvils or stithies for iron works, the stamp-heads for pounding metallic ores, &c. Cannon balls, as well as ploughshares, are examples of chilled castings ; with balls the chilling is unimportant, and occurs alone from the method essential to giving the balls the required perfection of form and size. Malleable iron-castings are at the opposite extreme of the scale, and are rendered externally soft by the abstraction of their carbon, whereby they are nearly reduced to the condition of pure malleable . iron, but without the fibre which is due to the hammering and rolling employed at the forge. The malleable iron-castings are made from the rich iron, and are at first as brittle as glass or hardened steel ; they are enclosed in iron boxes of suitable size, and surrounded with pounded iron-stone, or some of the metallic oxides, as the scales from the iron forge, or with common lime, and various other absorbents of carbon, used either together or separately. The cases, which are sometimes as large as barrels, are luted, rolled into the ovens or furnaces, and submitted to a good heat for about five days, and are then allowed to cool very gradually within the furnaces. The time and other circumstances determine the depth of the ef- fect ; thin pieces become malleable entirely through; they are then readily bent, and may be slightly forged ; cast-iron nails and tacks thus treated admit of being clenched, thicker pieces retain a central portion of cast-iron, but in a softened state, and not brittle as at first ; on sawing them through, the skin or coat of soft iron is per- fectly distinct from the remainder. The mode is particularly useful for thin articles that can be more economically and correctly cast, than wrought at the forge, as bridle- CASE-HARDENING WROUGHT AND CAST-IRON. 83 bits, snuffers, parts of locks, culinary and other vessels, pokers and tongs, many of which are subsequently case-hardened and polished as will be explained, but malleable cast-iron should never be used for cutting-tools. Case-Hardening Wrought and Cast-Iron.— The property of hardening is not possessed by pure malleable iron ; but I have now to explain a rapid and partial process of cementation, bv which wrought-iron is first converted exteriorly into steel, and is subse- quently hardened to that particular depth; leaving the central parts m their original condition of soft fibrous iron. The process is very consistently called case-hardening, and is of great importance in the mechanical arts, as the pieces combine the economy, strength and internal flexibility of iron, with a thin casting of steel ; which al- though admirable as an armor of defence from wear or deteriora- tion as regards the surface, is unfit for the formation of cutting edges or tools, owing to the entire absence of hammering, subsequent to the cementation with the carbon. Cast-iron obtains in like man- ner a coating of steel, which surrounds the peculiar shape the metal may have assumed in the iron-foundry and workshop. The principal agents used for case-hardening are animal matters as the hoofs, horns, bones, and skins of animals ; these are nearly alike in chemical constitution ; they are mostly charred and coarsely pounded ; some persons also mix a little common salt with some of the above. The works should be surrounded on all sides with a layer from half an inch to one inch thick. The methods pursued by different individuals do not greatly dif- fer ; for example, the gunsmith inserts the iron work of the gun-lock in a sheet-iron case in the midst of bone-dust (often not burned)' the hd of the box is tied on with iron wire, and the joint is luted with clay ; it is then heated to redness as quickly as possible and retained at that heat from half an hour to an hour, and the contents are quickly immersed in cold water. The objects sought are a steely exterior, and a clean surface covered with the pretty mottled tints ap- parently caused by oxidation from the partial admission of air.' Some of the malleable iron castings, such as snuffers, are case- hardened to admit of a better polish ; it is usually done with burnt bone-dust, and at a dull red heat ; they remain in the fire about two or three hours, and should be immersed in oil, as it does not render them quite so brittle as when plunged into water. It must be re- membered they are sometimes changed throughout their substance into an inferior kind of steel, by a process that should in such in- stances be called cementation, and not case-hardening, consequently they will not endure violence. The mechanician and engineer use horns, hoofs, bone-dust, and ■leather, and allow the period to extend from two to eight hours, most generally four or five ; sometimes for its greater penetration, the pro- cess is repeated a second time with new carbonaceous materials. Some open the box and immerse the work in water direct from the furnace ; others, with the view to preserve a better surface, allow the 84 HARDENING AND TEMPERING. box to cool without being opened, and harden the pieces with the open fire as a subsequent operation ; the carbon once added, the work may be annealed and hardened much the same as ordinary steel. When the case-hardening is required to terminate at any particu- lar' part, as a shoulder, the object is left with a band or projection, the Avork is allowed to cool without being immersed in water, the band is turned off, and the work when hardened in the open fire is only effected so far as the original cemented surface remains. A new substance for the case-hardening process, but containing the same elements as those more commonly employed, has of late years been added, namely, the prussiate of potash (a salt consist- ing of two atoms of carbon and one of nitrogen), which is made from a variety of animal matters. It is a new application without any change of principle ; the time occupied in this steelifying process, is sometimes only minutes instead of hours and days, as for example when iron is heated in the open fire to a dull red, and the prussiate is either sprinkled upon it or rubbed on in the lump, it is returned to the fire for a few minutes and immersed in water ; but the process is then exceedingly super- ficial, and it may if needful be limited to any particular part upon which alone the prussiate is applied. The effect by many is thought to be partial or in spots, as if the salt refused to act uniformly ; in the same manner that water only moistens a greasy surface in places. The prussiate of potash has been used for case-hardening the bearings of wrought-iron shafts, but this seems scarcely worth the doing. In the general way, the conversion of the iron into steel, by case- hardening, is quite superficial, and does not exceed the sixteenth of an inch; if made to extend to one-quarter or three-eighths of an inch in depth, to say the least it would be generally useless, as the object is to obtain durability of surface, with strength of interior, and this would disproportionately encroach on the strong iron within. The steel obtained in this adventitious manner is not equal in strength to that converted and hammered in the usual way, and if sent in so deeply, the provision for wear would far exceed that which is re- quired. Let us compare the case-hardening process with the usual conver- sion of steel. The latter requires a period of about seven days, and a very pure carbon, namely wood charcoal, of which a minute por- tion only is absorbed ; and it being a simple body, when the access of air is prevented by the proper security of the troughs, the bulk of the charcoal remains unconsumed, and is reserved for future use, as it has undergone no change. The hasty and partial process of cementation is produced in a period commonly less than as many hours with the animal charcoal, or than as many minutes with the prussiate of potash ; but all these are compound bodies (which con- tain cyanogen, a body consisting of carbon and nitrogen), and are never used a second time, but on the contrary the process is often repeated with another dose. It would be, therefore, an interesting i METALS AND ALLOYS. 85 inquiry for the chemist, as to whether the cyanogen is absorbed after the same manner as carbon in ordinary steel, or whether the nitrogen assists in any way in hastening the admission of the carbon, by some as yet untraced affinity or decomposition. It may happen that the carbon is not essential, as the Indian steel or wootz is stated to contain alumine, silex, and manganese. This hasty supposition will apply less easily to cast-iron, which contains from three to seven times as much carbon as steel, and although not always hardened by simple immersion, is constantly under the influence of the case-hardening process ; unless we adopt the supposition, that the carbon in cast-iron which is mixed with the metal in the shape of cinder in the blast furnace, when all is in a fluid state, is in a less refined union than that instilled in a more aeriform condition in the acts of cementation and case-hardenino-. THE METALS AND ALLOYS MOST COMMONLY USED. The thirteen metals before referred to have now to be considered, namely, Antimony, Bismuth, Copper, Gold, Lead, Mercury, Nickel' Palladium, Platinum, Rhodium, Silver, Tin, and Zinc. Unlike iron and steel, they do not admit of being hardened beyond that degree which maybe produced by simple mechanical means, such as hammer- ing, rolling, &c, neither (with the exception of platinum), do they submit to the process of welding. On the other hand, their fusibility offers an easy means of uniting and combining many of these metals with great readiness, either singly, or in mixtures of two or several kinds, which are called alloys. By the process of founding, any required form may be given to the fusible metals and alloys ; their malleability and ducti- lity are also turned to most useful and varied accounts ; and by partial fusion neighboring metallic surfaces may be united, sometimes per se, but more generally by the interposition of a still more fusible metal or alloy called solder. The author intends therefore to commence with a brief notice of the physical characters and principal uses of the thirteen metals before named, and of their more important alloys. Tables of the cohesive force and of the general properties of metals will be next added to avoid the occasional necessity for reference to other works. These tables will be followed by some remarks on alloys, which as regards their utility in the arts, may be almost considered as so many distinct metals: this will naturally lead to the processes of melting, mixing and casting the metals ; a general notice and ex- planation of many works, taking their origin in the malleable and ductile properties, will then follow; and the consideration of the metals, and of materials from the three kingdoms, will be concluded by a descriptive account of the modes of soldering. 86 DESCRIPTION OF THE PHYSICAL CHAEACTER AND USES THE METALS AND ALLOYS COMMONLY EMPLOYED IN THE MECHANICAL AND USEFUL ARTS. ANTIMONY is of a silvery white color, brittle and crystaline in its ordinary texture. It fuses at about 800°, or at a dull red heat, and is volatile at a white heat. Its specific gravity is 6.712. Antimony expands on cooling ; it is scarcely used alone, except in combination with similar bars of other metals for producing thermo-electricity : but antimony, which in the me- tallic state is frequently called "regulus," is generally com- bined with a large portion of lead, and sometimes with tin, and other metals. See Lead and Tin. " Antimony and tin, mixed in equal proportions, form a moderately hard, brittle, and very brilliant alloy, capable of receiving an exquisite polish, and not easily tarnished by ex- posure to the air ; it has been occasionally manufactured into speculums for telescopes. Its s. g. is less than the mean of its constituent parts.'' BISMUTH is a brittle white metal with a slight tint of red : its specific gravity is 9.822. It fuses at 476° to 507°, and always crystalizes on cooling. According to Chaudet, pure bismuth is somewhat flexible. A cast bar of the metal, one-tenth of an inch diameter, supports, according to Muschenbroeck, a weight of forty-eight pounds. Bismuth is volatile at a high heat, may be distilled in close vessels. It transmits heat more slowly than most other metals, perhaps in consequence of its texture. Bismuth is scarcely used alone, but it is employed for im- parting fusibility to alloys, thus : 8 bismuth, 5 lead, 3 tin, constitute a fusible alloy, which melts at 212° F. 2 bismuth, 1 lead, 1 tin, a fusible alloy, which melts at 201° F. 5 bismuth, 3 lead, 2 tin, when combined melt at 199°. METALS AND ALLOYS. 87 8 bismuth, 5 lead, 4 tin, 1 type-metal, constitute the fusi- ble alloy used on the Continent for producing the beautiful casts of the French medals, by the eliehee process. The metals should be repeatedly melted and poured into drops until they are well mixed. 1 bismuth, and 2 tin, make an alloy found to be the most suitable for rose-engine and eccentric-turned patterns, to be printed from after the manner of letter-press. The thin plates are cast upon a cold surface of metal or stone, upon which a piece of smooth paper is placed, and then a metal ring ; the alloy should neither burr nor crumble ; if proper, it turns soft and silky ; when too crystaline, more tin should be added. 2 bismuth, 4 lead, 3 tin, ) , „ , , 1 bismuth, 1 lead, 2 tin, | constitute pewterers softsolders. All these alloys must be cooled quickly to avoid the separa- tion of the bismuth ; they are rendered more fusible by a small addition of mercury. COPPER, with the exception of titanium, is the only metal which has a red color : it has much lustre, is very malleable and ductile, and exhales a peculiar smell when warmed or rubbed. It melts at a bright-red or dull-white heat ; at a temperature intermediate between the fusing points of silver and gold = 1996° Fahr. Its specific gravity varies from 8.86 to 8.89 ; the former being the least density of cast copper, the latter the greatest of rolled or hammered copper. Copper is used alone for many important purposes, and very extensively for the following : namely, sheathing and bolts for ships, brewing, distilling, and culinary vessels. Some of the fire boxes for locomotive engines, boilers for marine engines, rollers for calico-printing and paper-making, plates for the use of engravers, &c. Copper is used in alloying gold and silver, for coin, plate, &c, and it enters with zinc and nickel into the composition of German silver. Copper alloyed with one-tenth of its weight of arsenic is so similar in appearance to silver, as to have been substituted for it. The alloys of copper, which are very numerous and im- portant, are principally included under the general name, Brass. In the more common acceptation, brass means the yellow alloy of copper, with about half its weight of zinc ; this is often called by engineers "yellow brass." Copper alloyed with about one-ninth its weight of tin, is the metal of brass ordnance, which is very generally called gun-metal; similar alloys used for the "brasses" or bearings of machinery, are called by engineers, hard brass, and also gun-metal; and such alloys when employed for statues and medaLs are called bronze. The further addition of tin leads METALS AND ALLOYS MOST COMMONLY USED. to bell metal, and speculum metal, which are named after their respective uses ; and when the proportion of copper is exceedingly small the alloy constitutes one kind of pewter. Copper, when alloyed with nearly half its weight of lead, forms an inferior alloy, resembling gun-metal in color, but very much softer and cheaper, lead being only about one- fourth the value of tin, and used in much larger proportion. This inferior alloy is called pot-metal, and also cock-metal, because it is used for large vessels and measures, for the large taps or cocks for brewers, dyers and distillers, and those of smaller kinds for household use. Generally, the copper is only alloyed with one of the metals, zinc, tin, or lead ; occasionally with two, and some- times with the three in various proportions. In many cases, the new metals are carefully weighed according to the qua- lities desired in the alloy, but random mixtures more frequent- ly occur, from the ordinary practice of filling the crucible in great part with various pieces of old metal, of unknown proportions, and adding a certain quantity of new metal to bring it up to the color and hardness required. This is not done solely from motives of economy, but also from an im- pression which appears to be very generally entertained, that such mixtures are more homogeneous than those composed entirely of new metals, fused together for the first time. The remarks I have to offer on these copper alloys will be arranged in the tabular form, in four groups ; and to make them as practical as possible, they will be stated in the terms commonly used in the brass-foundry. Thus, when the founder is asked the usual proportions of yellow brass, he will say, 6 to 8 oz. of zinc, (to every pound of copper being implied.) In speaking of gun-metal, he would not say, it had one-ninth, or 11 per cent, of tin, but simply that it was 1J, 2, or 1\ oz. (of tin), as the case might be ; so that the quantity and kind of the alloy, or the addition to the pound of copper, is usu- ally alone named : and to associate the various ways of stat- ing these proportions, many are transcribed in the forms in which they are elsewhere designated. Alloys of Copper and Zinc only. The marginal numbers denote the ounces of zinc added to every pound of copper. to I oz. Castings are seldom made of pure copper, as under or- dinary circumstances it does not cast soundly ; about half an ounce of zinc is usually added, frequently in the shape of 4 oz. of brass to every pound of copper ; and by others 4 oz. of brass are added to every two or three pounds of copper. to If oz. Gilding metal, for common jewelry : it is made by mixing 4 parts of copper with 1 of calamine brass ; or some- times 1 lb. of copper with 6 oz. of brass. The sheet gild- PHYSICAL CHARACTER AND USES. 89 ing-metal will be found to match pretty well in color with the cast gun-metal, which latter does not admit of being rolled ; they may be therefore used together when required. 3 oz. Red sheet brass, made at Hegermuhl, or 5J parts copper, 1 zinc. 3 to 4 oz. Bath metal, pinchbeck, Mannheim gold, similor, and alloys bearing various names, and resembling inferior jewel- er's gold greatly alloyed with copper, are of about this pro- portion: some of them contain a little tin ; now, however, they are scarcely used. 6 oz. Brass, that bears soldering well. 6 oz. Bristol brass is said to be of this proportion. 8 oz. Ordinary brass, the general proportion; less fit for solder- ing than 6 oz., it being more fusible. 8 oz. Is generally the ingot brass, made by simple fusion of the two metals. 9 oz. This proportion is the one extreme of Muntz's patent sheathing. See 10-f. lOf oz. Muntz's metal, or 40 zinc and 60 copper. "Any propor- tions,'' says the patentee, " between the extremes, 50 zinc and 50 copper, and 37 zinc 63 copper, will roll and work at the red-heat ;" but the first-named proportion, or 40 zinc to 60 copper is preferred. The metal is cast into ingots, heated to a red-heat, and rolled and worked at that heat into ships' bolts and other fastenings and sheathing. 12 oz. Spelter-solder for copper and iron is sometimes made in this proportion ; for brass work, the metals are generally mixed in equal parts. See 16 oz. 12 oz. Pale yellow metal, fit for dipping in acids, is often made in this proportion. 16 oz. Soft spelter-solder, suitable for ordinary brass work, is made of equal parts of copper and zinc. About 14 lbs. of each are melted together and poured into an ingot mould with cross ribs, which indents it into little squares of about 2 lbs. weight ; much of the zinc is lost. These lumps are after- wards heated nearly to redness upon a charcoal fire, and are broken up one at a time with great rapidity on an anvil or in an iron pestle and mortar. The heat is a critical point ; if too great, the solder is beaten into a cake or coarse lumps and becomes tarnished ; when the heat is proper, it is nicely granulated, and remains of a bright yellow color ; it is after- wards passed through a sieve. Of course the ultimate pro- portion is less than 16 oz. of zinc. 16 oz. Equal parts is the one extreme of Muntz's patent sheath- ing. See lOf . 16| oz. Mosaic gold, which is dark-colored when first cast, but on dipping assumes a beautiful golden tint. When cooled and broken, all yellowness must cease, and the tinge vary from reddish fawn or salmon color, to . a light purple or lilac, and 90 METALS AND ALLOYS MOST COMMONLY USED. from that to whiteness. The proportions are stated as from 52 to 58 zinc to 50 of copper, or 16 J to 17 oz. to the pound. 32 oz. or 2 zinc to 1 copper, a bluish-white, brittle alloy, very brilliant, and so crystaline that it may be pounded cold in a mortar. 128 oz. or 2 ounces of copper to every pound of zinc ; a hard crystal- ine metal differing but little from zinc, but more tenacious ; it has been used for laps or polishing disks. Remarks on the Alloys of Copper and Zinc. These metals seem to mix in all proportions. The addition of zinc continually increases the fusibility, but from the extremely volatile nature of zinc, these alloys cannot be arrived at with very strict regard to proportion. The red color of copper slides into that of yellow brass at about 4 or 5 oz. to the pound, and remains little altered unto about 8 or 10 oz. ; after this it becomes whiter, and when 32 oz. of zinc are added to 16 of copper, the mixture has the brilliant silvery color of speculum metal, but with a bluish tint. These alloys, from about 8 to 16 oz. to the pound of copper, are extensively used for dipping, as in an enormous variety of furniture work ; in all cases the metal is annealed before the application of the scouring or cleaning processes, and of the acids, bronzes and lackers subsequently used. The alloys with zinc retain their malleability and ductility well, unto about 8 or 10 ounces to the pound ; after this, the crystaline character slowly begins to prevail. The alloy of 2 zinc and 1 copper, before named, may be crumbled in a mortar when cold. The ordinary range of good yellow brass, that files and turns well, is from about to 9 oz. to the pound. With ad- ditional zinc, it is harder and more crystaline; with less, more tenacious, and it hangs to the file like copper ; the range is wide, and small differences are not perceived. Alloys of Copper and tin only. The marginal numbers denote the ounces of tin added to every pound of copper. Ancient Copper and Tin Alloys. Ancient bronze nails, flexible, or 20 copper, 1 tin. According to Pliny, as quoted by Wilkinson. Ancient weapons and tools, by various analyses, or 8 to 15 per cent, tin ; medals from 8 to 12 per cent, tin, with two parts zinc added to each 100, for ^improving the bronze color. f oz. If oz. Soft bronze, or . . 9 to 1 2 oz. Medium bronze, or 8 to 1 2 1 oz. Hard bronze, or . . 7 to 1 6 to 8 oz. Ancient mirrors. PHYSICAL CHARACTER AND USES. 91 Modern Copper and Tin Alloys. 1 oz. Soft gun-metal, that bears drifting, or stretching from a perforation. 1 J oz. A little harder alloy, fit for mathematical instruments; or 12 copper and 1 very pure grain tin. 1J oz. Still harder, fit for wheels to be cut with teeth. 1J to 2 oz. Brass ordnance, or 8 to 12 per cent, tin ; but the general proportion is one-ninth part of tin. 2 oz. Hard bearings for machinery. 1\ oz. Very hard bearings for machinery. By Muschenbroek's Tables it appears that the proportion 1 tin and 6 copper is the most tenacious alloy ; it is too brittle for general use, and con- tains oz. to the pound of copper. 3 oz. Soft musical bells. 3^ oz. Chinese gongs and cymbals, or 20 per cent. tin. 4 oz. House bells. 4| oz. Large bells. 5 oz. Largest bells. to oz. Speculum metal. Sometimes one ounce of brass is added to every pound as the means of introducing a trifling quantity of zinc, at other times small proportions of silver are added ; the employment of arsenic is by some recommended. The object agreed upon by all experimentalists appears to be the exact saturation of the copper with the tin, and the proportionate quantities differ very materially (in this and all other alloys), according to the respective degrees of purity of the metals : for the most perfect alloys to this group, Swedish copper, and grain tin, should be used. When the copper is in excess, it imparts a red tint easily detected ; when the tin is in excess, the fracture is granu- lated and also less white. The practice is to pour the melted tin into the fluid copper when it is at the lowest temperature that a mixture by stirring can be effected, then to pour the mixture into an ingot and to complete the combination by re- melting in the most gradual manner, by putting the metal into the furnace as soon almost as the fire is lighted : trial is made of a little piece taken from the pot immediately prior to pouring. 32 oz. of tin to one pound of copper, makes the alloy called by the pewterers "temper," which is added in small quantities to tin, for some kinds of pewter, called " tin and temper," in which the copper is much less than 1 per cent. Remarks on the Alloys of Copper and Tin only. These metals seem to mix in all proportions. The addition of tin continually increases the fusibility, although when it is added cOld it is apt to make the copper pasty, or even to set in a solid lump in the crucible. 92 METALS AND ALLOYS MOST COMMONLY USED. The red color of the copper is not greatly impaired in those proportions used by the engineer, namely, up to about 2| ounces to the pound ; it becomes grayish white at 6, the limit suitable for bells, and quite white at about 8, the speculum metal ; after this, the alloy becomes of a bluish cast. The tin alloy is scarcely malleable at 2 ounces, and soon becomes very hard, brittle, and sonorous ; and when it has ceased to serve for producing sound, it is employed for reflect- ing light. The tough tenacious character of copper under the tools rapidly gives way; alloys of 1\ cut easily, 2\ assume about the maximum hardness without being crystaline ; after this they yield to the file by crumbling in fragments rather than by ordinary abrasion in shreds, until the tin very greatly predominates, as in the pewters, when the alloys become the more flexible, soft, malleable, and ductile, the less copper they contain. Alloys of Copper and Lead only. The marginal numbers denote the ounces of lead added to every pound of copper. 2 oz. A red-colored and ductile alloy. 4 oz. Less red and ductile ; neither of these is so much used as the following, as the object is to employ as much lead as possible. 6 oz. Ordinary pot-metal, called dry pot-metal, as this quantity of lead will be taken up without separating on cooling ; this is brittle when warmed. 7 oz. This alloy is rather short, or disposed to break. 8 oz. Inferior pot-metal, called wet pot-metal, as the lead partly oozes out in cooling, especially when the new metals are mixed ; it is therefore always usual to fill the crucible in part with old metal, and to add new for the remainder. This alloy is very brittle when slightly warmed. More lead can scarcely be used, as it separates on cooling. Remarks on the Alloys of Copper and Lead only. These metals mix in all proportions until the lead amounts to nearly half, after this they separate in cooling. The addition of lead greatly increases the fusibility. The red color of the copper is soon deadened by the lead ; at about 4 ounces to the pound the work has a bluish leaden hue when first turned, but changes in an hour or so to that of a dull gun-metal character. When the lead does not exceed about 4 oz. the mixture is tolerably malleable, but with more lead it soon becomes very brittle and rotten : the alloy is greatly inferior to gun-metal, and is principally used on account of the cheapness of the mixture, and the facility with which it is turned and filed. PHYSICAL CHARACTER AND USES. 93 Alloys op Copper, Zinc, Tin, and Lead, &c. This group refers principally to gun-metal alloys, to which more or less zinc is added by many engineers; the quantity of tin in every pound of the alloy, which is expressed by the marginal numbers, principally determines the hardness. M. Keller's statues at Versailles are found, as the mean of four analyses, to consist of — Copper . . . 91.40 or about 14f ounces. Zinc . . . 5.53 " 1 ounce. Tin . . . . 1.70 " Of " Lead . . . 1.37 " 0J " In 100 parts or the 16 ounces. lj to 2i oz. tin to 1 lb. copper used for bronze medals, or 8 to 15 per cent, tin, with the addition of 2 parts in each 100 of zinc, to improve the color. The modern so-called bronze medals of our Mint are of pure copper, and are afterwards bronzed superficially. 1\ oz. tin, | zinc to 16 oz. copper. Pumps and works requiring great tenacity. 1A oz. tin, 2 oz. brass, 16 " ' ) t, , , is u £ " 16 " J or wheels to be cut into teeth. 2 4 " H " 16 « For turning work.. 2 i " H " 16 " For nuts of coarse threads, and bearings. The engineer who uses these five alloys recommends melt- ing the copper alone, the small quantity of brass is then melted in another crucible, and the tin in a ladle ; the two latter are added to the copper when it has been removed from the furnace, the whole are stirred together and poured into the moulds without being run into ingots. The real quantity of tin to every pound of copper is about one-eighth oz. less than the numbers stated, owing to the addition of the brass, which increases the proportion of copper. If oz. tin, If oz. zinc, to 1 lb. copper. This alloy, which is a tough, yellow, brassy, gun-metal, is used for general purposes ; it is made by mixing 1 \ lb. tin, 1| lb. zinc, and 10 lbs. of copper ; the alloy is first run into ingots. 2 1 oz. tin, I oz.^ zinc, to 1 lb. copper, used for bearings to sustain great weights. 2| oz. tin, 2|- oz. zinc, to 1 lb. copper, were mixed by Chantrey, and a razor was made from the alloy ; it proved nearly as hard as tempered steel, and exceedingly destructive to new files, and none others would touch it. 1 oz. tin, 2 oz. zinc, 16 oz. brass. Best hard white metal for but- tons. 2 oz - tin ? oz- zinc, 16 oz. brass. Common white metal for buttons. METALS AND ALLOYS MOST COMMONLY USED. 10 lbs. tin, 6 lbs. copper, 4 lbs. brass constitute white solder. The copper and brass are first melted together, the tin is added, and the whole stirred and poured through birch twigs into water to granulate it ; it is afterwards dried and pulver- ized cold in an iron pestle and mortar. This white solder was introduced as a substitute for silver solder in making gilt buttons. Another button solder consists of 10 parts copper, 8 of brass, and 12 of spelter or zinc. Remarks on Alloys op copper, Zinc, Tin, and Lead, &c. Ordinary Yellow Brass, (copper and zinc,) is rendered very sensibly harder, so as not to require to be hammered, by a small addition of tin, say J or \ oz. to the lb. On the other hand by the addition of \ to \ oz. of lead, it becomes more malleable and casts more sharply. Brass becomes a little whiter for the tin, and redder for the lead. The addition of nickel to copper and zinc constitutes the so-called German silver. Gun Metal (copper and tin) very commonly receives a small addition of zinc ; this makes the alloy mix better, and to lean to the character of brass by increasing the malleability without materially reducing the hardness. The zinc, which is sometimes added in the form of brass, also improves the color of the alloy, both in the recent and bronzed states. Lead in small quantity improves the ductility of gun-metal, but at the expense of its hardness and color ; it is seldom added. Nickel has been proposed as an addition to gun metal by O'Donovan of Dublin, and antimony bv his countryman Dr. Ure. Pot Metal (copper and lead) is improved by the addition of tin, and the three metals will mix in almost any proportions : when the tin predominates, the alloy so much the more nearly approaches the condition of gun metal. Zinc may be added to pot metal in very small quantity, but when the zinc be- comes a considerable amount, the copper takes up the zinc, forming a kind of brass, and leaves the lead at liberty, and which in great measure separates in cooling. Zinc and lead are also very indisposed to mix alone, although a little arsenic assists their union by " killing" the lead, as in shot metal. Antimony also facilitates the combination of pot-metal ; 7 lead, 1 antimony, and 16 copper, mixed perfectly well the first fusion, and the alloy was decidedly harder than 4 lead and 16 copper; and apparently a better metal. "Lead and antimony, though in small quantity, have a remarkable effect in diminishing the elasticity and sonorousness of the copper alloys." PHYSICAL CHARACTER AND USES. 95 GOLD is of a deep and peculiar yellow color. It melts at a bright red heat, equivalent to 2016° of Fahrenheit's scale, and when in fusion appears of a brilliant greenish color. Its specific gravity is 19.3. It is so malleable that it may be extended into leaves which do not exceed the one two hundred and eighty-two thousandth of an inch in thickness, or a single grain may be extended over 56 square inches of surface. This extensibility of the metal is well illustrated by gilt but- tons, 144 of which are gilt by 5 grains of gold, and less than even half that quantity is adequate to giving them a very thin coating. It is also so ductile that a grain may be drawn out into 500 feet of wire. The pure acids have no action upon gold. Gold in the pure or fine state is not employed in bulk for many purposes in the arts, as it is then too soft to be durable. The gold foil used by dentists for stopping decayed teeth is perhaps as nearly pure as the metal can be obtained; it con- tains about 6 grains of alloy in the pound troy, or the one- thousandth part. Every superficial inch of this gold foil or leaf weighs f of a grain, and is 42 times as thick as the leaf used for gilding. The wire for gold lace prepared by the refiners for gold- lace manufacturers, requires equally fine gold, as when alloy- ed it does not so well retain its brilliancy. The gold in the proportion of about 100 grains to the pound troy of silver, or of 140 grains for double-gilt wire, is beaten into sheets as thin as paper; it is then burnished upon a stout red-hot silver bar, the surface of which has been scraped perfectly clean. When extended by drawing, the gold still bearing the same relation as to quantity, namely, the 57th part of the weight becomes of only one-third the thickness of ordinary gold-leaf used for gilding. In water-gilding, fine gold is amalgamated with mercury, and washed over the gilding metal (copper and tin), the mercury attaches itself to the metal, and when evaporated by heat it leaves the gold behind in the dead or frosted state: it is brightened with the burnisher. By the electrotype process a still thinner covering of pure gold may be deposited on silver, steel, and other metals. French watch-makers introduced this method of protecting the steel pendulum springs of marine chronometers and other time- pieces from rust. Fine gold is also used for soldering chemical vessels made of platinum. Gold Alloys. Gold-leaf for gilding contains from 3 to 12 grains of alloy to the oz., but generally 6 grains. The gold used by re- spectable dentists, for plates, is nearly pure, but necessarily 96 METALS AND ALLOYS MOST COMMONLY USED. contains about 6 grains copper in the oz. troy, or one 80th part ; others use gold containing upwards of one-third of alloy; the copper is then very injurious. With copper, gold forms a ductile alloy of a deeper color, harder and more fusible than pure gold; this alloy, in the proportion of 11 of gold to 1 of copper, constitutes English standard gold; its density is 17.157, being a little below the mean, so that the metals slightly expand on combining. One troy pound of this alloy is coined into 46§§ English sovereigns, or 20 troy pounds into 934 sovereigns and a half. (The pound was formerly coined into 44 guineas and a half). The standard gold of France consists of 9 parts of gold and 1 of copper. For G-old Plate the French have three different standards : 92 parts gold, 8 copper; also 84 gold, 16 copper; and 75 gold, 25 copper. In England, the purity of gold is expressed by the terms 22, 18, 16, 12, 8, carats, &c. The pound troy is supposed to be divided into 24 parts, and the gold, if it could be ob- tained perfectly pure, might be called 24 carats fine. The "Old Standard Gold," or that of our present cur- rency, is called fine, there being 22 parts of pure gold to 2 of copper. The "New Standard," for watch-cases, &c. is 18 carats of fine gold, and 6 of alloy. No gold of inferior quality to 18 carats, or the " New Standard,'' can receive the Hall mark; and gold of lower quality is generally described by its com- mercial value, as $15 or $10 gold, &c. The alloy may be entirely silver, which will give a green color, or entirely copper for a red color, but the copper and silver are more usually mixed in the one alloy according to the taste and judgment of the jeweler. The following alloys of gold are transcribed from the memoranda of the proportions employed by a practical jeweler of considerable experience. When it is otherwise expressed, it will be understood all these alloys are made with fine gold, fine silver, and fine copper, obtained direct from the refiners. And to insure the standard gold passing the test of the Hall, 3 or 4 grains additional of gold are usually added to every ounce. First Group. Different kinds of gold that are finished by polish- ing, burnishing, &c. without necessarily requiring to be colored : — The gold of 22 carats fine is so little used, on account of its ex- pense and greater softness, that it has been purposely omit- ted. COLORED GOLD. 97 18 carats, or New Standard gold, of yellow tint: 15 dwt. 0 grs. gold. 2 dwt. 18 grs. silver. 2 dwt. 6 grs. copper. 20 dwt. 0 grs. 18 carats, of red tint : 15 dwt. 0 grs. gold. 1 dwt. 18 grs. silver. 3 dwt. 6 grs. copper. 20 dwt. 0 grs. 16 carats, or Spring gold : this, when drawn or rolled very hard, makes springs little in- ferior to those of steel. 1 oz. 16 dwt. gold. or 1.12 6 dwt. silver. — .4 12 dwt. copper. — .12 15 gold of yellow tint, or the fine gold of the jewelers; 16 carats nearly; 1 oz. 0 dwt. gold 7 dwt. silver. 5 dwt. copper. 2 oz. 14 dwt. 2. 8 1 oz. 12 dwt. gold of red tint, or carats : 1 oz. 0 dwt. gold. 2 dwt. silver 8 dwt. copper. 1 oz. 10 dwt. Second Group. Colored golds: these all require to be submitted to the process of wet-coloring, which will be explained ; they are used m much smaller quantities, and require to be very exactly pro- portioned. Full red gold : 5 dwt. gold. 5 dwt. copper. 10 dwt. Red gold: 10 dwt. gold. 1 dwt. silver. 4 dwt. copper. 15 dwt. Green gold: 5 dwt. 0 grs. gold. 21 grs. silver, 5 dwt. 21 grs. Gray gold: (Platinum is also called gray gold by jewel- ers.) 3 dwt. 15 grs. gold. 1 dwt. 9 grs. silver. 5 dwt. 0 grs. Blue gold: scarcely used: 5 dwt. gold. 5 dwt. steel filings. 10 dwt. Antique gold, of a fine green- ish-yellow color : 18 dwt. 9 grs. gold, or 18. 9 21 grs. silver, — 1. 3 18 grs. copper, — .12 20 dwt. 0 grs. 20. 0 7 98 METALS AND ALLOYS MOST COMMONLY USED. Third G-roup. Gold solders : these are generally made from gold of the same quality and value as they are intended for, with a small addition of silver and copper, thus : — Solder for 22 carat gold : 1 dwt. 0 grs of 22 carat gold. 2 grs. silver. 1 gr. copper. 1 dwt. 3 grs. Solder for 18 carat gold : 1 dwt. 0 grs. of 18 carat gold. 2 grs. silver. 1 gr. copper. 1 dwt. 3 grs. Solder for $15 gold :* 1 dwt. 0 grs. of $15 gold. 10 grs. silver. 8 grs. copper. 1 dwt. 18 grs. Solder for $10 gold: but mid- dling silver solder is more generally used. 1 dwt. fine gold. 1 dwt. silver. 2 dwt. copper. 4 dwt. Dr. Hermstadt's imitation of gold, which is stated not only to re- semble gold in color, but also in specific gravity and ductility, con- sists of 16 parts of platinum, 7 parts of copper, and 1 zinc, put in a crucible, covered with charcoal powder, and melted into a mass. Gold alloyed with platinum is also rather elastic, but the platinum whitens the alloy more rapidly than silver. LEAD appears to have been known in the earliest ages of the world. Its color is bluish white ; it has much brilliancy, is remarka- bly flexible and soft, and leaves a black streak on paper : when handled it exhales a peculiar odor. It melts at about 612°, and by the united action of heat and air, is readily converted into an oxide. Its specific gravity, when pure, is 11.445 ; but the lead of commerce seldom exceeds 11.35. Lead is used in a state of comparative purity for roofs, cisterns, pipes, vessels for sulphuric acid, &c. Ships were sheathed with lead and with wood, from before the Christian era to 1450, after which wood was more commonly employ- ed, and in 1790 to 1800 copper sheathing became general; of late years, lead with a little antimony has likewise been used, also an alloy of copper and zinc and galvanized sheet iron. The most important alloys of lead are those employ- ed for printers' type, namely, about 3 lead, 1 antimony, for the smallest, hardest and most brit- tle types. • By others, 4 grains of brass are added to the solder; it then fuses beautifully and is of good color. Zinc is sometimes added to other good solders to increase their fusibility, the" zinc (or brass when used) should be added at the last moment, to lessen the volatil- ization of the zinc. LEAD. 09 4 lead, 1 antimony, for small, hard, brittle types. 5 lead, 1 antimony, for types of medium size. 6 lead, 1 antimony, for large types. 7 lead, 1 antimony, for the largest and softest types. . The sma11 types generally contain from 4 to 6 per cent, of tin, and sometimes also 1 to 2 per cent, of copper; but as old metal is always used with the new, the proportions are not exactly known. Stereotype-plates contain about 4 to 8 parts of lead to 1 of antimony. Baron Wetterstedt's patent sheathing for ships, consists of lead with from 2 to 8 per cent, of antimony; about 3 per cent, is the usual quantity. The alloy is rolled into sheets. Similar alloys, and those of lead and tin in various prepa- rations, are much used for emery wheels and grinding-tools of various forms by the lapidary, engineer, and others. The latter also employs these readily-fused alloys for temporary bearings, guides, screw nuts, &c. Organ pipes consist of lead alloyed with about half its quan- tity of tin to harden it. The mottled or crystaline appear- ance so much admired shows an abundance of tin. Shot metal is said to consist of 40 lbs. of arsenic to one ton of lead. In casting sheet-lead, the metal was poured from a swing- trough upon a long and nearly horizontal table covered with a thin layer of coarse damp sand, previously leveled with a metal rule or strike. The thickness of the fluid metal was determined by running the strike along the table before the lead cooled, the excess being thus swept into a spill-trough at the lower end of the table; but the sheet-lead now more com- monly used, is cast in a thick slab, and reduced between laminating rollers ; it is known as " milled-lead." The metal for organ-pipes is prepared by allowing the me- tal to escape through the slit in a trough, as it is slid along a horizontal table, so as to leave a trail of metal behind it; the thickness of the metal is regulated by the width of the slit through which it runs, and the rapidity of the traverse ; a piece of cloth or ticken is stretched upon the casting table. The metal is planed to thickness, bent up and soldered into the pipes. Lead pipes are cast as hollow cylinders arid drawn out upon triblets ; they are also cast of indefinite length without drawing. A patent was taken out for casting a sheath of tin within the lead, but it has been abandoned. Lead shot are cast by letting the metal run through a nar- row slit, into a species of colander at the top of a lofty tower ; the metal escapes in drops, which for the most part assume the spherical form before they reach the tank of water into 100 METALS AND ALLOYS MOST COMMONLY USED. which they fall at the foot of the tower, and this prevents their being bruised. The more lofty the tower, the larger the shot that can be produced ; the good and the bad shot are separated by throwing small quantities at a time upon a smooth board nearly horizontal, which is slightly wriggled ; the true or round shot run to the bottom, the imperfect ones stop by the way, and are thrown aside to be re-melted ; the shot are afterwards riddled or sifted for size, and churned in a barrel with black lead. MERCURY is a brilliant white metal, having much of the color of silver, whence the terms hydrargyrum, argentum vivum, and quicksilver. It has been known from very remote ages. It is liquid at all common temperatures ; solid and malleable at 40° F., and contracts considerably at the moment of con- gelation. It boils and becomes vapor at about 670°. Its specific gravity at 60° is 13.5. In the solid state its density exceeds 14. The specific gravity of mercurial vapor is 6.976. Mercury is used in the fluid state for a variety of philo- sophical instruments, and for pressure gages for steam-en-- gines, &c. It is sometimes, although rarely, employed for rendering alloys more fusible ; it is used with tin-foil for sil- vering looking-glasses, and it has been employed as a substi- tute for water in hardening steel. Mercury forms amalgams with bismuth, copper, gold, lead, palladium, silver, tin, and zinc. Mercury is commonly used for the extraction of gold and silver from their ores by amalgamation, and also in water- gilding. NICKEL is a white brilliant metal, which acts upon the magnetic needle, and is itself capable of becoming a magnet. _ Its mag- netism is more feeble than that of iron, and vanishes at a heat somewhat below redness, 630°. It is ductile and malle- able. Its specific gravity varies from 8.27 to 8.40 when fused, and after hammering, from 8.69 to 9.00. It is not oxidized by exposure to air at common temperatures, but when heated in the air it acquires various tints like steel ; at a red-heat it becomes coated by a gray oxide. _ _ Nickel is scarcely used in the simple state, but principally used together with copper and zinc, in alloys that are rendered the harder and whiter the more nickel they contain ; they are known under the names of albata, British plate, electrum, German silver, pakfong, teutanag, &c. : the proportions differ much according to price ; thus the Commonest are 3 to 4 parts Nickel, 20 copper, and 16 zinc. Best . are 5 to 6 parts Nickel, 20 copper, and 8 to 10 zinc. About two-thirds of this metal is used for articles resembling PALLADIUM. PLATINUM. 101 plated goods, and some of which are also plated ; the remainder is employed for harness, furniture, drawing and mathematical instruments, spectacles, the tongues for accordions, and nume- rous other small works. The white copper of the Chinese, which is the same as the German silver of the present day, is composed of 31.6 partsof nickel, 40.4 of copper, 25.4 of zinc, and 2.6 of iron, 17.48 53.39 — 13.0 The white copper manufactured at Sutil in the duchy of Saxe Hildburghausen, is said by Keferstein, to consist of copper 88.000, nickel 8.753, sulphur with a little antimony 0.750, silex, clay, and iron, 1.75. The iron is considered to be accidentally introduced into these several alloys, along with the nickel, and a minute quantity is not prejudicial. Iron and steel have been alloyed with nickel ; the former (the same as the meteoric iron which always contains nickel) is little disposed to rust: whereas the alloy of steel with nickel is worse in that respect than steel not alloyed. PALLADIUM is of a dull-white color, malleable and ductile. Its specific gravity is about 11.3, or 11.86 when laminated. It fuses at a temperature above that required for the fusion of gold. Palladium is a soft metal, but its alloys are all harder than the pure metal. With silver it forms a very tough mal- leable alloy, fit for the graduations of mathematical instru- ments, and for^ dental surgery, for which it is much used by the French; with silver and copper, palladium makes a very springy alloy, used for the points of pencil-cases, inoculating lancets, tooth-picks or any purpose where elasticity and the property of not tarnishing are required; thus alloyed it takes a high polish. Pure palladium is not fusible at ordinary temperatures, (but at a high temperature) it agglutinates so as to be afterwards malleable and ductile. This useful metal has recently been found in some abun- dance^ the gold ores of the Minas Geraes district. Palla- dium is calculated thoroughly to fulfil many of the purposes to which platinum and gold are applied in the useful arts, and from its low specific gravity, it may be obtained at about half the price of an equal bulk of platinum, and at one-eighth that of gold ; and it equally resists the action of mineral acids and sulphureted hydrogen. Palladium was used in the construction of the balances for the United States' Mint. PLATINUM is a white metal extremely difficult -of fusion, and un- altered by the joint action of heat and air. It varies in den- sity from 21 to 21.5, according to the degree of mechanical METALS AND ALLOYS MOST COMMONLY USED. compression which it has sustained ; it is extremely ductile, but cannot be beaten into such thin leaves as gold and silver. The particles of the generality of the metals, when separated from the foreign matters with which they are combined, are joined into solid masses by simple fusion ; but platinum being nearly infusible when pure, requires a very different treatment. The platinum is first dissolved chemically, and it is then thrown down in the state of a precipitate; next it is partly agglutinated in the crucible into a spongy mass, and is then compressed whilst cold in a. rectangular mould by means of a powerful fly-press or other means, which in operating upon 500 ounces, converts the platinum into a dense block about 5 inches by 4, and 2f inches thick. This block is heated in a smith's forge, with two tuyeres meeting at an angle, at which spot the platinum is placed, amidst the charcoal fire ; when it has reached the welding point, or almost a, blue heat, it receives one blow under a heavy drop, or a vertical hammer somewhat like a pile-driving engine ; it then requires to be reheated, and it thus receives a fresh blow about every 20 minutes, and in a week or ten days, it is sufficiently welded- or consolidated on all sides to admit of being forged into bars, and converted into sheets, rods, or wires by the ordinary means. The motive for operating upon so great a quantity is for making the large pans for concentrating sulphuric acid, in only two or three pieces which are soldered together with fine gold. In France, 2,000 ounces are sometimes welded into one mass, so that the vessels may be absolutely entire. For small quantities the treatment is the same, but in place of the drop, the ordinary flatter and sledge-hammer are used. Platinum is exceedingly tough and tenacious, and "hangs to the file worse than copper," on which account, when it is used for the graduated limbs of mathematical instruments, the divisions should be cut with a. diamond point, which is the best instrument for fine graduations of all kinds, and for rul- ing grounds, or the lined surfaces for etching. Platinum is employed in Russia for coin. This valuable metal is also used for the touch-holes of fowling-pieces, and in various chemical and philosophical apparatus, in which resist- ance to fusion or to the acids is essential. The alloys of platinum are scarcely used in the arts; that with a small quantity of copper is employed in Paris for den- tal surgery. " Dr. Von Eckart's alloy contains platinum 2.40, silver 3.53, and copper 11.71. It is highly elastic, of the^ same specific gravity as silver, and not subject to tarnish ; it pan be drawn to the finest wire from \ of an inch diameter with- out annealing, and does not lose its elasticity by annealing. RHODIUM. SILVER. 103 It is highly sonorous, and bears hammering red-hot, rolling and polishing." _ Dr. Ryan added to silver, one-fourth of its weight of pla- tinum, and he considers that it took up one-tenth its weight. The alloy became much harder than silver, capable of resist- ing the tarnishing influences of sulphur and hydrogen, and was fit for graduations. An alloy of platinum with ten parts of arsenic is fusible at a heat a little above redness, and may therefore be cast in moulds. On exposing the alloy to a gradually-increasing temperature in open vessels, the arsenic is oxidized and ex- pelled, and the platinum recovers its purity and infusibility. Tin also so greatly increases the fusibility of platinum, that it is hazardous to solder the latter metal with tin-solder, al- though gold is so used. Platinum, as well as gold, silver and copper, are deposited by the electrotype process ; and silver plates thus platinized are employed in the Galvanic Battery. RHODIUM is a white metal very difficult of fusion; its specific gravity is about 11 : it is extremely hard. When pure the acids do not dissolve it. Rhodium has been long employed for the nibs of pens, which have been also made of ruby, mounted on shafts of spring gold ; these kinds have had to endure for the last seven or eight years the rivalry of "Hawkins's everlasting Pen," of which latter, the author from many months' constant use can speak most favorably. " The everlasting pen," says the in- ventor, "'is made of gold tipped with a natural alloy, which is as much harder than rhodium as steel is harder than lead ; will endure longer than the ruby ; yields ink as freely as the quill, is as easily wiped, and if left unwiped is not cor- roded." Mr. Hawkins employs the natural alloy of iridium and os- mium, two scarce metals discovered by Mr. Tennant of Bel- fast amongst the grains of platinum: the alloy is not malleable, and is so hard as to require to be worked with diamond pow- der. The metals rhodium, iridium, and osmium, are not other- wise employed in the arts than for pens ; although steel has been alloyed with rhodium. _ The inventor of the gold pen, Mr. Hawkins, is an Ame- rican. SILVER is of a more pure white than any other metal ; it has con- siderable brilliancy, and takes a high polish. Its specific gravity varies between 10.4, which is the density of cast sil- ver, and 10.5 to 10.6, which is the density of rolled or stamped silver. ^ It is so malleable and ductile, that it may be ex- tended into leaves not exceeding the ten-thousandth of an inch 104 METALS AND ALLOYS MOST COMMONLY USED. in thickness, and drawn into wire much finer than a human hair. Silver melts at a bright-red heat, at 1873° of Fahren- heit's scale, and when in fusion appears extremely brilliant. Silver is but little used in the pure unalloyed state on account of its extreme softness, but it is generally alloyed with copper in about the same proportion as in our coin, and none of inferior value can receive the "Hall mark." Dia- monds are set in fine silver, and in silver containing 3 to 12 grs. of copper in the ounce, the work is soldered with pure tin. The sheet metal for plated works is prepared by fitting to- gether very truly, a short stout bar of copper, and a thinner plate of silver ; when scraped perfectly clean they are tied strongly together with binding wire, and united by partial fusion without the aid of solder. The plated metal is then rolled out, and the silver always remains perfectly united and of the same proportional thickness as at first. Additional silver may be burnished on hot, when the surfaces are scraped clean as explained under gold ; this is done either to repair a defect, or to make any part thicker for engraving upon, and the uniformity of surface is restored with the hammer. In addition to its use for articles of luxury, the important service of copper plated with silver for the parabolic reflect- ors of lighthouses must not be overlooked ; these are worked to the curve with great perfection by the hammer alone. Plated spoons, forks, harness, and many other articles, are made of iron, copper, brass, and German silver either cast or stamped into shape ; the objects are then filed and scraped perfectly clean; and fine silver often little thicker than paper is attached with the aid of tin solder and heat : the silver is rubbed close upon every part with a burnisher. The electrotype process is also used for plating several of the metals with silver, which it does in the most uniform and perfect manner ; the silver added is charged by weight at about three times the price of the metal ; the German silver or albata is generally used for the interior substance, as when the silver is partially worn through, the white alloy is not so readily detected as iron or copper. Silver Alloys. The alloy with copper constitutes plate and coin ; by the addition of a small proportion of copper to silver, the metal is rendered harder and more sonorous, while its color is scarcely impaired. Even with equal weights of the two metals, the compound is white ; the maximum of hardness is obtained when the copper amounts to one-fifth of the silver. " For silver plate, the French proportions are, 9 J parts silver, J copper ; and for trinkets, 8 parts silver, 2 copper." TIN, AND ITS USES. 105 Silver solders are made in the following proportions : — Hardest silver solder, 4 parts fine silver, and one part cop- per ; this is difficult to fuse, but is occasionally employed for figures. Hard silver solder, 8 parts silver, and 1 part brass wire, which is added when the silver is melted, to avoid wasting the zinc. Soft silver solder for general use, 2 parts fine silver, and 1 part brass wire. By some few, f part of arsenic is added, to render the solder more fusible and white, but it becomes less malleable ; the arsenic must be introduced at the last moment, with care to avoid its fumes. Silver is also soldered with tin solder, (2 tin, 1 lead,) and with pure tin. Silver and Mercury are used in the plastic metallic stop- ping for teeth. TIN has a silvery-white color with a slight tint of yellow ; it is malleable, though sparingly ductile. Common tin-foil, which is obtained by beating out the metal, is not more than l-000th of an inch in thickness, and what is termed white JDuch metal is in much thinner leaves. Its specific gravity fluctuates from 7.28 to 7.6, the lightest being the purest metal. When bent it occasions a peculiar crackling noise, arising from the de- struction of cohesion amongst its particles. When a bar of tin is rapidly bent backwards and forwards, several times successively, it becomes so hot that it cannot be held in the hand. When rubbed, it exhales a peculiar odor. It melts at 442°, and, by exposure to heat and air, is gradu- ally converted into a protoxide. Pure tin is commonly used for dyers' kettles ; it is also some- times employed for the bearings of locomotive carriages and other machinery. This metal is beaten into very large sheets, some of which measure 200 by 100 inches, and are of about the thickness of an ordinary card; the small sized foil is stated not to exceed one thousandth of an inch in thickness. The metal is first laminated between rollers, and then spread one sheet at a time upon a large iron surface or anvil, by the direct blows of hammers with very long handles; great skill is required to avoid beating the sheets into holes. The large sheets of tin-foil are only used for silvering looking-glasses by amalgamation with mercury. ' Tin-foil is also used for electrical purposes. The amalgam used for electrical ma- chines, is 7 tin, 3 zinc, and 2 mercury. Tin is drawn into wire, which is soft and capable of being bent and unbent many times without breaking ; it is mode- rately tenacious and completely inelastic. Tin tube is ex- tensively used for gas fitting and many other purposes by Le Roy & Co., of New York ; it has been recently introduced METALS AND ALLOYS MOST COMMONLY USED. in an ingenious manner for the formation of very cheap vessels, for containing artists' and common colors, besides numerous other solid substances and fluids, required to be her- metically sealed, with the power of abstracting small quantities. Tin plate is an abbreviation of tinned iron plate ; the plates of charcoal iron are scoured bright, pickled, and immersed in a bath of melted tin covered with oil, or with a mixture of oil and common resin ; they come out thoroughly coated. Tinned iron wire is similarly prepared : there are several niceties in the manipulation of each of these processes, which cannot be noticed in this place. Tin is one of the most cleanly and sanatory of metals, and is largely consumed as a coating for culinary vessels, although the quantity taken up in the tinning is exceedingly small, and which was noticed by Pliny. Tin imparts hardness, whiteness and fusibility to many alloys, and is the basis of diiferent solders, and other import- ant alloys, all of which have a low power of conducting heat. Pewter is principally tin ; mostly lead is the only addition, at other times copper, but antimony, zinc, &c, are used with the above, as will be separately adverted to. The exact pro- portions are unknown even to those engaged in the manufac- ture of pewter, as it is found to be the better mixed when it contains a considerable portion of old metal to which new metal is added by trial. Some pewters are made very common ; when cast they are black, shining and soft ; when turned, dull and bluish. Other pewters only contain \ or \ of lead ; these when cast are white, without gloss and hard ; such are pronounced very good metal, and are but little darker than tin. The French legis- lature sanctions the employment of 18 per cent, of lead with 82 of tin as quite harmless in vessels for wine and vinegar. The finest pewter, frequently called "tin and temper," consists mostly of tin, with a very little copper, which makes it hard and somewhat sonorous, but the pewter becomes brown- colored when the copper is in excess. The copper is melted, and twice its weight of tin is added to it, and from about J to 7 lbs. of this alloy or the " temper," are added to every block of tin weighing from 360 to 390 pounds. Antimony is said to harden tin and to preserve a more silvery color, but is little used in pewter. Zinc is employed to cleanse the metal rather than as an ingredient; some stir the fluid pewter with a thin strip, half zinc and half tin ; others allow a small lump of zinc to float on the surface of the fluid metal whilst they are casting, to lessen the oxidation. White metal is said to consist of 3| cwt. of block tin, 28 lbs. antimony, 8 lbs. copper, and 8 lbs. brass ; it is cast into in- gots and rolled into very thin sheets Tin solders are very much used in the arts. ZINC. 107 1 tin 3 lead, the coarse plumber's solder, melts at about 500 F. 2 tin, Head, the ordinary or fine tin solder, melts at about 360 F. ZINC is a bluish-white metal, with considerable lustre, rather hard, of a specific gravity of about 6.8 in its usual state, but, when drawn into wire, or rolled into plates, its density is augment- ed to 7 or 7.2. In its ordinary state at common tempera- tures, it is tough, and with difficulty broken by blows of the hammer. It becomes very brittle when its temperature ap- proaches that of fusion, which is about 773° ; but at a tem- perature a little above 212°, and between that and 300°, it becomes ductile and malleable, and may be rolled into thin leaves, and drawn into moderately fine wire, which, however, possesses but little tenacity. When a mass of zinc, which has been fused, is slowly cooled, its fracture exhibits a lamel- lar and prismatic crystaline texture. Zinc, which is commercially known as " Spelter,'' although it is always brittle when cast, has of late years taken its place amongst the malleable metals ; the early stages of its manufacture into sheet, foil and wire are stated to be con- ducted at a temperature somewhat above that of boiling water ; and it may be afterwards bent and hammered cold, . but it returns to its original crystaline texture when reinelted. A_ It has |een applied to many of the purposes of iron, tinned- iron, and copper; it is less subject to oxidation from the eifects of the atmosphere than the iron, and much cheaper, although less tenacious, ductile, or durable than the copper. The sheet metals when bent lengthways of the sheet, (or like a roll of cloth,) are less disposed to crack than if bent sideways; in this respect zinc and sheet iron are the worst: the risk is less- ened when they are warmed. Zinc is applied as a coating to preserve iron from rust. Zinc mixed with one-twentieth its weight of speculum metal may be melted in an iron ladle, and made to serve for some of the purposes of brass, such as common chucks. The alloy is sufficient to modify the crystaline character, but reserves the toughness of the zinc; it will not, however, bear hammer- ing either hot or cold. Four atoms of zinc and one of tin, or 133.2 and 57.9, make a hard, malleable, and less crystal- ine alloy. Biddery ware, manufactured at Biddery, a large city, 60 miles N. W. o'f Hyderabad in the East Indies, and also at Benares, is said to consist of copper 16 oz., lead 4 oz., and tin 2 oz., melted together; and to every 3 oz. of this alloy, 16 oz. of spelter or zinc are added. The metal is used as an inferior substitute for silver, and resembles some sorts of pew- ter. 108 METALS AND ALLOYS MOST COMMONLY USED. The foregoing alloys are mostly derived from actual prac- tice, and although it has been abundantly shown that alloys are most perfect, when mixed according to atomic proportions, or by multiples of their chemical equivalents, yet this excel- lent method is little adopted, owing to various interferences. For example, it is in most cases necessary from an econo- mic view, to mix some of the old alloys (the proportions of which are uncertain), along with the new metals. In most cases also, unless the fusion and refusion of the alloys are conducted with considerably more care than ordinary practice ever attains, or really demands, the loss by oxidation completely invalidates any nice attempts at proportion ; and which pro- portions can be alone exactly arrived at, when the combined metals are nearly or quite pure. For the convenience, however, of those who may desire to pursue the scientific course, the chemical equivalents of the metals upon the hydrogen scale now most usually adopted, are appended to the list of metals. Thus, for mixtures of any metals, say tin and zinc ; instead of taking arbitrary quantites, one atom of tin, or 57.9 parts by weight, should be combined with 1, 2, 3, 4, or 5 atoms of zinc, or any multiple of 32.3 parts, and so with all other metals. The following table will be found of considerable service in all inquiries which regard the employment of the metals and alloys in sustaining loads. The first column of figures denotes the compara- tive strength of the metals, glass being considered as unity ; thus steel of razor temper is nearly 16 times as strong as glass of equal size ; and by the second column, it is seen that a bar of steel one inch square is pulled asunder by a load of 150,000 lbs. 109 TABLES OF THE COHESIVE FORCE OF SOLID BODIES. Table I. — Metals. (h) and (Z) mark the highest and lowest result which Muschenbroek obtained from each kind of iron. METALS. STEEL. Razor temper . Soft IRON. Wire German bar, mark BR (h) Swedish bar (h) . . . German bar, mark L (h) Wire Bar Liege bar (h) . . . . Spanish bar .... Bar Bar Oosement bar (h) . . Cable German bar, mark L (I) German bar, common Swedish bar ) Oosement bar J Bar of best quality Liege bar (I) . . German bar, mark BR (Z) Bar* Bar of good quality Cable Bar, fine-grained medium fineness coarse-grained CAST IRON. French t German . . . . . French, soft ... 4 English j French t — i English, soft ... 4 c.2 oq 15.927 12.739 12.004 9.880 9.445 9.119 9.1 8.964 8.794 8-685 8.581 8.492 8.142 7.752 7.382 7.339 7.296 7.006 6.621 6.514 6.480 5.839 5.787 5.306 3.618 2.172 7.470 7.250 6.754 5.520 5.412 4.540 4.334 C5 « o _ 150,000 120,000 113,077 93,069 88,972 85,000 85,797 84,443 82,839 81,901 80,833 80,000 76,697 73,024 69,538 69,133 68,728 66,000 62,369 61,361 61,041 55,000 54,513 49,982 34,081 20,460 70,367 68,295 63,622 52,000 50,981 42,666 40,824 m bo t 7.78 to 7.84 7.807 AUTHORITY. Muschenbroek, Encyclo. Brit., art Strength. Idem. Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Int. ad Phil. Nat. i. 426 Idem. Idem. Buffon, ffiuvres de Gauthey, ii. 153. Emerson, Mechanics, 115. Muschenb, Int. ad Phil. Nat. i. 426. Idem. Soufflot Rondelet's L'Art de Bitir, iv. 500. Edin. Encyclo., art. Bridge, 544. Muschenb. Intr. ad Phil. Nat. i. 426. Annals of Phil. vii. 320. Muschenb. Intr. ad Phil. Nat. i. 426. Idem. Idem. Rumford, Phil. Mag. x. 51. Muschenb. Intr. ad Phil. Nat. i. 426. Idem. Perronet. OZuv. de Gauthey, ii. 154. Rumford, Phil. Mag. x. 51. Annals of Phil. x. 311. Rondelet, L'Art. de Batir, iv. 502. Idem. Idem. Navier, ffiuv. de Gauthey, ii. 150. Muschenb. Intr. ad Phil. Nat. i. 417, Rondelet, L'Art. de Batir, iv. 514. Banks, Gregory's Mechan. i. 129, Ex. i. L'Ecole des Ponts, &c. Gaut. ii. 150 Gauthey, (Euvres, ii. 150. Banks, Greg. Mech. i. 148. Ex. iii. * This is the mean result of thirty-three experiments, t Kirwan, Elem. Miner, ii. 155. j Calculated from experiments on the transverse strength, by arts. 14 and 15. § Yielded to the file without difficulty. 110 TABLES OP THE COHESIVE FORCE OF SOLID BODIES. Table I. — Continued. METALS. Specific cohe- sion. Glass I. Coh. force of a square inch in lbs. avoir. Specific gravity. | Hardness. AUTHORITY. CAST IRON. Gray, of Cruzot, 2d fu- Gray, of Cruzot, 1st fu- 4.000 3 202 37,680 30,680 30,162 Rondelet, L'Art de Batir, iv. 514. Ramus, Gauthey, ii. 150. Idem.t COPPER. Wire 6.606 ?. 396 9, 152 61,228 22,570 20,272 8.182 8.726 st Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. Idem. PLATINUM. 5.995 5 625 56,473 52,987 20.847 8§ Morveau, Ann. de Chimie, xxv; 8. Sickingen, Ann. de Chimie, xxv. 9. SILVER. 4 090 4 342 38,257 40,902 11.091 7§ Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. GOLD. 3 279 30,888 20,450 19.238 6t Sickingen, Ann. de Chimie, xxv. 9. Muschenb. Intr. ad Phil. Nat. i. 417. TIN. Cast, English black . . idem Malacca . . . 0 7568 0.706 0.565 0.3906 0.342 7 129 6',650 5,322 3,679 3,211 ■ 7.295 7.2165 6.1256^ > 6} Morveau, Ann. de Chim. Ixxi. 194. Muschenb. Intr. ad Phil. Nat. i. 417. Idem. Idem. Idem. BISMUTH. 3,250 3,00S 9.810) 9.9265 7§ Muschenb. Intr. ad Phil. Nat. i. 417. Idem. i. 454. ZINC. Wire Cast, Goslar, from . . to . . . 2,394 0.3118 0.2855 22,551 16,616 2,937 2,689 1 7.215J* 6J Morveau, Ann. de Chim. Ixxi. 194. By my trial Muschenb. Intr. ad Phil. Nat. i. 417. LEAD. Milled Wire Wire Wire 0 3533 0 334 0.274 0 2704 0 094 3,328 3,146 2,581 2,547 885 11.407^ 11.348 11.282 11.479^ 5$ By my trial. Muschenb. Intr. ad Phil. Nat. i. 452. Idem. Morveau, Ann. de Chim. Ixxi. 194. Muschenb. Intr. ad Phil. Nat. i. 452. Antimony, cast . . . 0.1126 1,060 4.500 Gt Muschenb. Intr. ad Phil. Nat. i. 417. # Calculated from experiments on the transverse strength by arts. 14 and 15. I In the operation of casting, the surface of the iron always becomes much harder, and is more tenacious than the internal parts ; hence the strength of a small specimen is always greater than that of a large one. N. B . — AVhen the specific gravity is not referred to a separate authority, it is to be considered that of the specimen of which the cohesive force is given. J Kirwan's Miner, vol. ii. § Thomson's Chemistry, vol. i. Ill TABLES OF THE COHESIVE FORCE OF SOLID BODIES. Table II. — Alloys. ALLOY OF Specific cohesion. Glass I. Cohesion of square inch in lbs. avoir. Specific gravity. AUTHORITY. Parts. Parts. Gold . . . 2 Silver . . 1 2.972 28,000 Musch. Encyclop. Brit. art. Gold . . . 5 Copper . . 1 5.307 50,000 Idem. [Strength. Silver 5 Copper • • 1 5.14S 48,500 Idem. Silver . . 4 Tin . . . 1 4.352 41,000 Idem. Brass . . 4.870 45,882 Muschenb.j Colson, i. 242. Copper . . 10 Tin . . . 1 3.407 32.093 Musch. Intr. ad Phil. Nat. Copper . . 8 Tin . . . 1 3.831 36,088 Idem. [i. 428. Copper . 6 Tin . . . 1 4.687 44,071 Idem. Copper . . 4 Tin . . . 1 3.794 35,739 Idem. Copper . . 2 Tin . . . ] 0.108 1,017 Idem. Copper . . 1 Tin . . ] 0.077 725 Idem. Tin, English 10 Lead . . . 1 0.733 6,904 Musch. Intr. ad Phil. Nat. Tin, — 8 Lead . . . 1 0.841 7,922 Idem. [i. 438. Tin, — 6 ] 0.849 7,997 Idem. Tin, — 4 Lead 1 1.126 10,607 Idem. Tin, — 2 Lead 1 0.793 7,470 Idem. Tin, — 1 Lead . . . 1 0.751 7,074 Idem. Tin, Banca 10 Antimony • ] 1.187 11,181 7.359 Musch. Intr. ad Phil. Nat. Tin, — 8 Antimony . ] 1.049 9,881 7.276 Idem. [i. 442. Tin, — 6 Antimony . 1 1.341 12,632 7.228 Idem. Tin, — 4 Antimony . 1 1.431 13,480 7.192 Idem. Tin, — 2 Antimony • j 1 .277 12,029 7.105 Idem. Tin, — 1 Antimony • ] 0.338 3,1S4 7.060 Idem. Tin, — 10 Bismuth . . 1 1.347 12,688 7.576 Musch. Intr. ad Phil. Nat. Tin, — 4 Bismuth . . 1 1.772 16,692 7.613 Idem. [i. 443. Tin, — 2 Bismuth . 1 1.488 14,017 8.076 Idem. Tin, — 1 Bismuth . 1 1.276 12,020 8.146 Idem. Tin, — 1 Bismuth . 2 1.063 10,013 8.58 Idem. Tin, — 1 Bismuth . . 4 0.836 7,875 9.009 Idem. Tin, — 1 Bismuth . . 10 0.411 3,871 9.439 Idem. Tin, — 10 Zinc, Indian 1 1.371 12,914 7.288 Musch. Intr. ad Phil. Nat. Tin, — 2 Zinc . . . 1 1.595 15,025 7.000 Idem. [i. 444. Tin, — 1 Zinc . . . 1 1.682 15,844 7.321 Idem. Tin, — 1 Zinc . . . 2 1.701 16,023 7.100 Idem. Tin, — 1 Zinc . . . 10 0.602 5,671 7.130 Idem. Tin, English 1 Zinc, Goslar 1 0.958 9,024 Musch. Intr. ad Phil. Nat. Tin, — 2 Zinc . . . 1 1.164 10,964 Idem. [i. 446. Tin, — 4 Zinc . . . 1 1.089 10,258 Idem. Tin, — 8 Zinc . . . 1 1.126 10,607 Idem. Tin, — 1 Antimony . 1 0.154 1,450 7.000 Musch. Intr. ad Phil. Nat. Tin, — 3 Antimony . 2 0.338 3,184 Idem. [i. 448. Tin, — 4 Antimony . 1 1.202 11,323 Idem. Lead, Scotch 1 Bismuth . . 1 0.777 7,319 10.931 Musch. Intr. ad Phil. Nat. Lead, — 2 Bismuth . . 1 0.620 5,840 11.090 Idem. [i. 454. Lead, — 10 Bismuth . . 1 0.300 2,826 10.827 Idem. 112 TABULAR VIEW OF SOME OF THE PROPERTIES OF METALS. Specific gravity. Platinum 20.98 Gold 19.258 Indium 18.680 Tungsten 17.50 Mercury 13.568 Palladium 11.50 Lead 11.35 Rhodium 11.0 Silver 10.47 Bismuth 9.80 Uranium 9.00 Copper 8.89 Cadmium 8.60 Cobalt 8.53 Nickel 8.27 Iron 7.78 Molybdenum .... 7.40 Tin 7.30 Zinc 7.00 Manganese 6.85 Antimony 6.70 Tellurium 6.10 Arsenic 5.8 Titanium 5.3 Sodium 0.972 Potassium 0.865 Chemical equiva- lents. 98.8 199.2 98.8 99.7 202. 53.3 103.6 52.2 108. 71. 217. 31.6 55.8 29.5 29.5 28. 47.7 57.9 32.3 27.7 64.6 64.2 37.7 24.3 23.3 39.15 Alloys possessed of greater specific gra- vity than the mean of their components. Gold and Zinc. — Tin. — Bismuth. — Antimony. — Cobalt. Silver and Zinc. — Lead. — Tin. — Bismuth. — Antimony. Copper and Zinc. — Tin. — Palladium. — Bismuth. — Antimony. Lead and Bismuth. — Antimony. Platinum and Molybdenum. Palladium and Bismuth. FUSIBILITY. Fahrenheit /Mercury 39 deg. Potassium 136 " Sodium 190 " iTin 442 « iismuth 497 « jLead 612 « [ Tellurium, rather less fusible than lead. I Arsenic, undetermined. 'Zinc 773 " Antimony, a little below a red heat. \Cadmium, about .... 442 " /Silver 1873 deg. Copper 1996 " Gold 2016 « Cobalt, rather less fusible than iron. Iron, cast ...... 2786 " llron, malleable . ( re q" irin g &° h'gh" Manganese . A est . * ea < of a ° ( smith's forge. iNickel, nearly the same as Cobalt. 'Palladium Molybdenum \Uranium Tungsten JChromium JTitanium 'Cerium Osmium Iridium Rhodium Platinum \Columbium [Almost infusible and not to be procured in buttons by the heat of a smith's forge, but fusible before the oxyhy- drogen blowpipe. Alloys having a specific gravity inferior to the mean of their components. Gold and Silver. — Iron. — Lead. — Copper. — Iridium. — Nickel. Silver and Copper. Copper and Lead. Iron and Bismuth. — Antimony. — Lead. Tin and Lead. — Palladium. — Antimony. Nickel and Arsenic. Zinc and Antimony. TABULAR VIEW OF METALS. TABULAR VIEW OF METALS — Continued. 113 Titanium Manganese Platinum Palladium Copper Gold Silver . Tellurium Bismuth Cadmium Tin . Chromium Rhodium Nickel Cobalt Iron Antimony Zinc Lead . Potassium Sodium Mercury HARDNESS. I Harder than Steel Scratched by Calcspar. Scratch glass. I ^Scratched by glass. Scratched by the nail. Soft as wax (at 60 deg.) Liquid. BRITTLENESS. The following metals are brittle, and most of them may even be reduced to powder. Antimony. Arsenic. Bismuth. Cerium. Chromium. Cobalt. Columbium. Manganese. Molybdenum. Rhodium. Tellurium. Titanium. Tungsten. Uranium. MALLEABILITY, Or admit of being extended by the hammer. Gold. Silver. Copper. Tin. Cadmium. Platinum. Lead. Zinc. Iron. Nickel.. Palladium. Potassium. Sodium. Frozen Mercury. DUCTILITY, Or admit of being drawn into wires. Gold. Tin. Silver. Lead. Platinum. Nickel. Iron. Palladium. Copper. Cadmium. Zinc. TENACITY. Weights sustained by wires 0.787 of a line diameter. Iron , Copper Platinum Silver Gold Zinc . Tin . Lead 549 lbs. 250 dec. pts. 302 274 187 150 109 34 27 278 320 137 753 540 630 621 Elasticity and sonorousness belong to the hardest metals only, and are most evident in certain alloys. Odor and taste are most remarkable in copper, iron, and tin. LINEAR DILATATIONS BY HEAT. Dimensions which a bar takes at 212°, whose length at 32° is 1.000000; also its dilatation in vulgar fractions. Platinum .... 1.00091085 or one 1097th part. Palladium .... 1.00100000 " 1000th " Antimony .... 1.00108300 " 923d " Cast Iron .... 1.00111025 " 901st " Steel 1.00121286 " 824th " Wrought Iron. . . 1.00124860 " 801st " Bismuth 1.00139200 " 718th " Gold 1.00149824 « 667th " Copper 1.00179633 " 557th " Gun metal (C.8,T.l) 1.00181700 " 550th " Brass 1.00190663 " 524th « Speculum metal . . 1.00193300 " 517th « Silver 1.00200183 " 499th « Tin 1.00235840 « 424th " Lead 1.00285768 « 350th " Zinc 1.00297650 « 336th " The above are the mean proportions of the various examples of each metal, given in Ure's Dictionary of Chemistry and elsewhere. POWER OF CONDUCTING HEAT. From Despretz's Experiments.* Copducting power Gold 100 Platinum .... 98.1 Silver 97.3 Copper 89.82 Iron 37.41 Zinc 36.37 Tin 30.38 Lead 17.96 Marble 2.34 Porcelain .... 1.22 Brick earth .... 1.1 3t * Ann. de Chim. et de Phys. xix. 97. f Traite Elementaire de Phy- sique, par M. Despretz, p. 20, as quoted by Dr. Thomson, On Heat and Electricity, p. 103. 8 114 CHARACTERS OF THE METALS AND ALLOYS. REMARKS ON THE CHARACTERS OF THE METALS AND ALLOYS. Hardness, Fracture, and Color op Alloys. — The object of the present chapter is to explain in a general way some of the pe- culiarities and differences amongst alloys, prior to entering on the means of melting the metals, without which process alloys cannot be made : yet notwithstanding that the list contains the greater num- ber of the alloys in ordinary use, and many others, it is merely a small fraction of those which might be made. It is also stated that metals appear to unite with one another in every proportion, precisely in the same manner as sulphuric acid and water. Thus there is no limit to the number of alloys of gold and copper. The same might be said of many other metals, and when the alloys compounded of three, four, or more metals, are taken into account, the conceivable number of alloys becomes almost unlimited. It is certain, however, that metals have a tendency to combine in definite proportion ; for several atomic compounds of this kind occur native. It is indeed possible that the variety of proportions in al- loys is rather apparent than real, arising from the mixture of a few definite compounds with each other, or with uncombined metal; an opinion not only suggested by the mode in which alloys are prepared, but in some measure supported by observation. It appears to be scarcely possible to give any sufficiently general rules, by which the properties of alloys may be safely inferred from those of their constituents ; for although, in many cases, the work- ing qualities and appearance of an alloy, may be nearly a mean pro- portional between the nature and quantities of the metals composing it ; yet in other and frequent instances the deviations are excessive, as will be seen by several of the examples referred to. Thus, when lead, a soft and malleable metal, is combined with an- timony, which is hard, brittle, and crystaline, in the proportions of from twelve to fifty parts of lead to one of antimony ; a flexible alloy is obtained, resembling lead, but somewhat harder, and which is rolled into sheets for sheathing ships. Six parts of lead and one of antimony are used for the large soft printers' types, which will bend slightly, but are considerably harder than the foregoing ; and three parts of lead and one of antimony are employed for the smallest types, that are very hard and brittle, and will not bend at all ; an- timony being the more expensive metal, is used in the smallest quan- tity that will suffice. In this alloy the antimony fulfils another service besides that of imparting hardness : antimony somewhat expands on cooling, where- as lead contracts very much, and the antimony, therefore, within certain limits, compensates for this contraction, and causes the alloy to retain the full size of the moulds. Sometimes, from motives of economy, the neighboring parts of machinery are not wrought accurately to correspond one with the DISSIMILARITY OF THE COPPER ALLOYS. 115 other, but lead is poured in to fill up the intermediate space, and to make contact; as around the brass nuts in the heads of some screw presses, in the guides or followers for the same,* and some other parts of either temporary or permanent machinery. Antimony is quite essential in all these cases to prevent the contraction the lead alone would sustain, and which would defeat the intended object, as the metal would otherwise become smaller than the space to be filled. * A little tin is commonly introduced into types, and likewise copper in minute quantity; iron and bismuth are also spoken of; the last is said to be employed on account of its well-known property of expand- ing in cooling, so as to cause the types to swell in the mould, and copy the face of the letter more perfectly, but although I find bismuth to have been thus used, it appears to be neither common nor essen- tial in printing types. The difference in specific gravity between lead and antimony con- stantly interferes, and unless the type metal is frequently stirred, the lead, from being the heavier metal, sinks to the bottom, and the antimony is disproportionally used from the surface. In the above examples, the differences arising from the proportions appear intelligible enough, as when the soft lead prevails, the mix- ture is much like the lead; and as the hard, brittle antimony is in- creased, the alloy becomes hardened, and more brittle: with the pro- portion of four to one, the fracture is neither reluctant like that of lead, nor foliated like antimony, but assumes very nearly the grain and color of some kinds of steel and cast-iron. In like manner, when tin and lead are alloyed, the former metal imparts to the mixture some of its hardness, whiteness, and fusibility, in proportion to its quantity; as seen in the various qualities of pewter, in which how- ever copper, and sometimes zinc or antimony are found. The same agreement is not always met with; as nine parts of cop- per, which is red, and one part of tin, which is white, each very mal- leable and ductile metals, make the tough, rigid metal used in brass ordnance, from which it obtains its modern name of gun-metal, but which neither admits of rolling nor drawing into wire; the same alloy is described by Pliny as the soft bronze of his day. The continual addition of the tin, the softer metal, produces a gradual increase of hardness in the mixture; with about one-sixth of tin the alloy assumes its maximum hardness consistent with its application to mechanical uses; with one-fourth to one-third tin it becomes highly elastic and sonorous, and its brittleness rather than its hardness is greatly in- creased. When the copper becomes two, and the tin one part, the alloy is so hard as not to admit of being cut with steel tools, but crumbles under their action; when struck with a hammer or even suddenly warmed it flies in pieces like glass, and clearly shows a structure highly crystaline, instead of malleable. The alloy has no trace of the red color of the copper, but it is quite white, susceptible of an exquisite polish, and being little disposed to tarnish, it is most per- 116 CHARACTERS OF THE METALS AND ALLOYS. fectly adapted to the reflecting speculums of telescopes and other instruments, for which purpose it is alone used. Copper, when combined in the same proportions with a different metal, also light-colored and fusible, namely, two parts of copper, with one of zinc, (which latter metal is of a bluish-white, and crys- talline, whereas tin is very ductile,) makes an alloy of entirely oppo- site character to the speculum metal ; namely, the soft yellow brass, which becomes by hammering very elastic and ductile, and is very easily cut and filed. Again, the same proportions, namely, two parts of copper and one of lead, make a common inferior metal, called pot-metal, or cock- metal, from its employment in those respective articles. This alloy is much softer than brass, and hardly possesses malleability ; when, for example, the beer-tap is driven into the cask, immediately after it has been scalded, the blow occasionally breaks it in pieces, from its reduced cohesion. Another proof of the inferior attachment of the copper and lead exists in the fact that, if the moulds are opened before the castings are almost cold enough to be handled, the lead will ooze out and appear on the surface in globules. This also occurs to a less extent in gun-metal, which should not on that account be too rapidly ex- posed to the air ; or the tin strikes to the surface, as it is called, and makes it particularly hard at those parts, from the proportional in- crease of the tin. In casting large masses of gun-metal, it frequent- ly happens that little hard lumps, consisting of nearly half tin, work up to the surface of the runners or pouring places, during the time the metal is cooling. In brass, this separation scarcely happens, and these moulds may be opened whilst the castings are red hot, without such occurrence ; from which it appears that the copper and zinc are in more perfect chemical union than the alloys of copper with tin and with lead. Malleability and Ductility of Alloys. — The malleability and ductility of alloys are in a great measure referable to the degrees in which the metals of which they are respectively composed, possess these characters. Lead and tin are malleable, flexible, ductile, and inelastic whilst cold, but when their temperatures much exceed about half way to- wards their melting heats they are exceedingly brittle and tender, owing to their reduced cohesion. The alloys of lead and tin partake of the general nature of these two metals ; they are flexible when cold, even with certain additions of the brittle metals, antimony and bismuth, or of the fluid metal mercury ; but they crumble with a small elevation of temperature, as these alloys melt at a lower degree than either of their components, to which circumstance we are indebted for the tin solders. Zinc, when cast in thin cakes, is somewhat brittle when cold, but its toughness is so far increased when it is raised to about 300° F. that its manufacture into sheets by means of rollers is then admissi- ble ; it becomes the malleable zinc, and retains the malleable and STRENGTH OF ALLOYS. 117 ductile character, in a moderate degree, even when cold, hut in Trend- ing rather thick plates it is advisable to warm them to avoid frac- ture ; when zinc is remelted, it resumes its original crystaline con- dition. It is considered that most of the sheet zinc contains a very little lead. Zinc and lead will not combine without the assistance of arsenic, unless the lead is in very small quantity ; the arsenic makes this and other alloys very brittle, and it is besides dangerous to use. Zinc and tin make, as may be supposed, somewhat hard and brittle al- loys, but none of the zinc alloys, except that with copper to consti- tute brass, are much used. Gold, silver, and copper, which are greatly superior in strength to the fusible metals above named, may be forged either when red-hot or cold, as soon as they have been purified from their earthy mat- ters, and fused into ingots ; and the alloys of gold, silver, and cop- per are also malleable, either red-hot or cold. Fine, or pure gold and silver, are but little used alone ; the alloy is in many cases introduced less with the view of depreciating their value than of adding to their hardness, tenacity, and ductility; the processes which the most severely test these qualities, namely, draw- ing the finest wires, and beating gold and silver leaf, are not per- formed with the pure metals, but gold is alloyed with copper for the red tint, with silver for the green, and with both for intermediate shades. Silver is alloyed with copper only, and when the quantity is small its color suffers but slightly from the addition, although its working qualities are greatly improved, pure silver being little used. The alloys of similar metals having been considered, it only re- mains to observe that when dissimilar metals are combined, as those of the two opposite groups; namely, the fusible lead, tin, or zinc, with the less fusible copper, gold, and silver: the malleability of the alloys when cold, is less than that of the superior metal ; and when heated barely to redness, they fly in pieces under the hammer; and, therefore, brass, gun-metal, &c, when red-hot, must be treated with precaution and tenderness. It will be remembered the action of rollers is more regular than that of the hammer ; and soon gives rise to the fibrous character, which, so far as it exists in metals, is the very ele- ment of strength when it is uniformly distributed throughout their substance. This will be seen by the inspection of the relative de- grees of cohesion possessed by the same metal when in the conditions of the casting, sheet, or wire, shown by the table, and to which quality or the tenacity of the alloys we shall now devote a few lines. Strength or Cohesion of Alloys. — The strength or cohesion of the alloys, is in general greatly superior to that of any of the metals of which they are composed. For example, on comparing some of the numbers of the table, on pages 111 and 113, it will be seen that the relative weights, which tear asunder a bar one inch square of the several substances, stand as follows — all the numbers being selected from Muschenbroek's valuable investigations, so that it may be presumed the same metals, and also the same means of trial, were used in every case. 118 CHARACTERS OF THE METALS AND ALLOYS. Allovs. Cast Metals. 10 Copper, 1 Tin, 32,093 lbs. 8 — 1 — 36,088 " 6 — 1 — 44,071 « 4 — 1 — 35,739 " 2 — 1 — 1,017 « 1 — 1 — 725 " Barbary Copper, 22,570 lbs. Japan — 20,272 " English Block Tin, 6,650 Do. Banca Malacca 5,322 Tin, 3,679 — 3,211 The inspection of these numbers is highly conclusive, and it shows that the engineer agrees -with theory and experiment, in selecting the proportion 6 to 1 as the strongest alloy ; and that the philosopher, in choosing the most reflective mixture, employs the weakest but one ; its strength being only one-third to one-sixth that of the tin, or one- twentieth that of the copper, which latter constitutes two-thirds its amount. It is much to be regretted that the valuable labors of Muschen- broek have not been followed up by other experiments upon the alloys in more general use. One curious circumstance will be ob- served, however, in those which are given, namely, that in the follow- ing alloys, which are the strongest of their respective groups, the tin is always four times the quantity of the other metal; and they all confirm the circumstance, of the alloys having mostly a greater degree of cohesion than the stronger of their component metals. Alloys. Cast Metals. 4 English Tin, 4 Banca Tin, 4 — — 4 English Tin, Lead, Antimony, Bismuth, Goslar Zinc, Antimony, 10,607 lbs. 13,480 " 16,692 " 10,258 "* 11,323 " Lead, 885 lbs. Antimony, 1,060 " Zinc, 2,689 « Bismuth, 3,008 " Tin, 3,211 to 6,650 « * This, in truth, is an exception; it barely equals in strength the alloys with 8 and 2 parts of tin to 1 of zinc, but is superior to that of equal parts : it corroborates the great increase of strength in alloys generally. TABLE OF PROPORTIONS OF ALLOYS. 119 Fig. 74 represents a very ingenious instrument, denominated an alloy-balance. It is intended for weighing those metals the propor- tions of which are stated decimally: its principle, which is so simple as hardly to require explanation, depends upon the law that weights in equilibrium are inversely as their distances from the point of sup- port. For weighing out any precise number of pounds or ounces, in the common way, the arms of the ordinary scale-beam are made as nearly equal as possible; so that the weights, and the articles to be weighed, may be made to change places, in proof of the equality of the instru- ment. But to weigh out an alloy, say of 17 parts tin and 83 copper, unless the quantities were either 17 and 83 lbs. or ounces, would require a little calculation. This is obviated, if the point of suspension a, of the alloy-balance, which is hung from any fixed support b, is adjusted until the arms are respectively as 17 to 83 ; and for this purpose the half of the beam is divided into fifty equal parts numbered from the one end; and, prior to use, it only remains to adjust the weight, w, so as to place the empty balance in equilibrium. A quantity of copper, rudely estimated, having been suspended from the short arm of the balance, the proportionate quantity of the tin will be denoted with critical accuracy, when, by its gradual addition, the beam is exactly restored to the horizontal line; should the alloy consist of three or more parts, the process of weighing is somewhat more complex. The annexed table was calculated by the author, for converting the proportions of alloys stated decimally, into avoirdupois weight. It applies with equal facility to alloys containing two or many com- ponents, so as to bring them readily within the power of ordinary scales. TABLE FOR CONVERTING DECIMAL PROPORTIONS Into Divisions of the Pound Avoirdupois. Decimal. oz. dr. Decimal. oz. dr. Decimal. oz. dr. Decimal. oz. dr. .78 1 13.28 2 1 25.78 4 1 38.28 6 1 1.56 2 14.06 2 2 26.56 4 2 39.06 6 2 2.34 3 14.84 2 3 27.34 4 3 39.84 6 3 3.12 4 15.62 2 4 28.12 4 4 40.62 6 4 3.91 5 16.41 2 5 28.91 4 5 41.41 6 5 4.69 6 17.19 2 6 29.69 4 6 42.19 6 6 5.47 7 17.97 2 7 30.47 4 7 42.97 6 7 6.25 1 0 18.75 3 0 31.25 5 0 43.75 7 0 7.03 1 1 19.53 3 1 32.03 5 1 44.53 7 1 7.81 1 2 20.31 3 2 32.81 5 2 45.31 7 2 8.59 1 3 21.09 3 3 33.59 5 3 46.09 7 3 9.37 1 4 21.87 3 4 34.37 5 4 46.87 7 4 10.16 1 5 22.66 3 5 35.16 5 5 47.66 7 5 10.94 1 6 23.44 3 6 35.94 5 6 48.44 7 6 11.72 1 7 24.22 3 7 36.72 5 7 49.22 7 7 12.50 2 0 25.06 4 0 37.50 6 0 50 00 8 0 120 CHARACTERS OF THE METALS AND ALLOTS. Application of the Table. The Chinese Packfong, similar to our German silver, is said to consist of — 40.4 parts of Copper ] f 6 oz. 4 drams, nearly. 25.4 — Zinc ! . 14 — 0 — full. 31.6 - Nickel I e( l™ alent t0 \ 5 - 1 - nearly. 2.6 — Iron J (^0 — 3 — full. 100.0 parts 16 oz. 0 — Avoird's. All nice attempts at proportion are, however, entirely futile, un- less the metals are perfectly pure ; for example, it is a matter of common observation that for speculums a variable quantity of from seven and a half to eight and a half ounces of tin is required for the exact saturation of every pound of copper, and upon which satura- tion the efficiency of the compound depends ; bells of exactly similar quality sometimes thus require the dose of tin to vary from three and a half to five ounces to the pound of copper, according to the qualities of the metals. The variations in the purity of the metals obtained from different localities are abundantly demonstrated by the disagreement in the cohesive strengths of^the two in question, more particularly the tin, as seen on page 118, and which can be only ascribed to their re- spective amounts of impurity. Any other supposition than the pre- sence of foreign matter, would necessarily go to disprove the fact of the metals being simple bodies, and therefore strictly alike when absolutely pure, wheresoever they may have been obtained. Fusibility of Alloys. — In concluding this slight view of some of the general characters of alloys, it remains to consider the influence of heat, both as an agent in their formation and as regards the de- gree in which it is required for their after-fusion; the lowest avail- able temperature being the most desirable in every such case. Metals do not combine with each other in their solid state, owing to the influence of chemical affinity being counteracted by the force of cohesion. It is necessary to liquefy at least one of them, in which case they always unite, provided their mutual attraction is energetic Thus, brass is formed when pieces of copper are put into melted zinc ; and gold unites with mercury at common tempera- tures by mere contact. The agency of mercury in bringing about triple combinations of the metals, both with and without heat, is also very curious and ex- tensive. Thus, in water-gilding, the silver, copper, or gilding metal, when chemically clean, are rubbed over with an amalgam of gold containing about eight parts of mercury; this immediately attaches itself, and it is only necessary to evaporate the mercury, which re- quires a very moderate heat, and the gold is left behind. Water- silvering is similarly accomplished. mallett's zincing process. 121 Cast-iron, wrought-iron, and steel, as well as copper and many other metals, may be tinned in a similar manner. An amalgam of tin and mercury is made so as to be soft and just friable; the metal to be tinned is thoroughly cleaned, either by filing or turning, or if only tarnished by exposure, it is cleaned with a piece of emery-paper or otherwise, without oil, and then rubbed with a thick cloth moist- ened with a few drops of muriatic acid. A little of the amalgam then rubbed on with the same rag, thoroughly coats the cleaned parts of the metal by a process which is described as cold-tinning ; other pieces of metal may be attached to the tinned parts by the ordinary process of tin-soldering. In making the tinned iron plates, the scoured and cleaned iron plates are immersed is a bath of pure melted tin, covered with pure tallow, the tin then unites with every part of the surfaces; and in the ordinary practice of tinning culinary vessels of copper, pure tin is also used. The two metals, however, must then be raised to the melting heat of tin ; but the presence of a little mercury enables the process to be executed at the atmospheric temperature, as above ex- plained. In M. Mallett's recently patented processes for the protection of iron from oxidation and corrosion, and for the prevention of the foul- ing of ships, one proceeding consists in covering the iron with zinc. The ribs or plates for iron ships are immersed in a cleansing bath of equal parts of sulphuric or muriatic acid and water, used warm ; the works are then hammered, and scrubbed with emery or sand, to detach the scales and to thoroughly clean them; they are then im- mersed in a preparing bath of equal parts of saturated solutions of muriate of zinc and sal-ammoniac, from which the works are transferred to a fluid metallic bath, consisting of 202 parts of mercury and 1292 parts of zinc, both by weight (being in the proportion of one atom of mercury to forty atoms of zinc) ; to every ton weight of which alloy, is added about one pound of either potassium or sodium, (the metallic bases of potass and soda,) the latter being preferred. As soon as the cleaned iron works have attained the melting heat of the triple alloy, they are removed, having become thoroughly coated with zinc. The affinity of this alloy for iron is, however, so intense, and the peculiar circumstances of surface as induced upon the iron presented to it by the preparing bath are such, that care is requisite lest by too long an immersion the plates are not partially or wholly dissolved. Indeed where the articles to be covered are small, or their parts mi- nute, such as wire, nails or small chain, it is necessary before immers- ing them to permit the triple alloy to dissolve or combine with some wrought-iron, in order that its affinity for iron may be partially satis- fied and thus diminished. At the proper fusing temperature of this alloy, which is about 680° Fahr., it will dissolve a plate of wrought- iron of an eighth of an inch thick in a few seconds. The Palladiumizing Process. — The articles to be protected are to be first cleansed in the same way as in the case of zincing ; namely, by means of the double salts of zinc and ammonia, or of manganese 122 CHARACTERS OF THE METALS AND ALLOYS. and ammonia; and then to be thinly coated over with palladium, applied in a state of amalgam with mercury. In the opinion of eminent chemists and metallurgists, all the me- tals, even the most refractory, which nearly or quite refuse to melt in the crucible when alone, will gradually run down when surround- ed by some of the more fusible metals in the fluid state ; in a man- ner similar to the solution of the metals in mercury, as in the amal- gams, or the solutions of solid salts in water. The surfaces of the superior metals are, as it were, dissolved, washed down, or reduced to the state of alloys, layer by layer, until the entire mass is liquefied. Thus nickel, although it barely fuses alone, enters into the com- position of German silver by aid of the copper, and whilst it gives whiteness and hardness, it also renders the mixture less fusible. Pla- tinum combines very readily with zinc, arsenic, and also with tin and other metals; so much so that it is dangerous to melt either of those metals in a platinum spoon ; or to solder platinum with common tin solder, which fuses at a very low temperature : although platinum is constantly soldered with fine gold, the melting point of which is very high in the scale. Again, the circumstances that some of the fusible bismuth alloys melt below the temperature of boiling water, or at less than half the melting heat of tin, their most fusible ingre- dient, show that the points of fusion of alloys are equally as diffi- cult of explanation or generalization as many other of the anomalous circumstances concerning them. This much, however, may be safely advanced, that alloys, without exception, are more easily fused than the superior metal of which they are composed; and extending the same view to t\\e relative quan- tities of the components, it may be observed that the hard solders for the various metals and alloys, are in general made of the self- same material which they are intended to join, but with small ad- ditions of the more fusible metals. The solder should be, as nearly aa practicable, equal to the metal on which it is employed, in hardness, color, and every property except fusibility ; in which it must excel just to an extent that, when ordinary care is used, will avoid the risk of melting at the same time, both the object to be soldered and like- wise the softer alloy or solder by which it is intended to unite its parts. It would appear as if every example of soldering in which a more fusible alloy is interposed, were also one of superficial alloying. Thus, when two pieces of iron are united by copper, used as a sol- der, it seems to be a natural conclusion that each surface of the iron becomes alloyed with the copper : and that the two alloyed surfaces are held together from their particles having been fused in contact, and run into one film. It is much the same when brass or spelter solder is used, except that triple alloys are then formed at the sur- faces of the iron, and so with most other instances of soldering. And in cases where metallic surfaces are coated by other metals, the latter being at the time in a state of fusion, as in tinned-iron plates and silvered copper; may it not also be conceived, that be- FURNACES FOR MELTING THE METALS. 123 tween the two exterior surfaces, which are doubtless the simple metals, a thin film of an alloy compounded of the two does in reality exist? And in those cases in which the coating is laid on by the aid of mercury, and without heat, the circumstances are very similar, as the fluidity of mercury is identical with the ordinary state of fusion of other metals, although the latter require higher temperatures than that of our atmosphere. When portions of the same metal are united by partial fusion, and without solder, as in the process decribed as burning together, and more recently known as the " autogenous" mode of soldering, no alloy is formed, as the metals simply fuse together at their sur- faces. Neither can it be supposed that any formation of alloy can occur, where the one metal is attached to the other by the act of burnish- ing on with heat, as in making gilt wire, but without a temperature sufficient to fuse either of the metals. The union in this case is pro- bably mechanical, and caused by the respective particles or crystals of the one metal being forced into the pores of the other, and be- coming attached by a species of entanglement, similar to that which may be conceived to exist throughout solid bodies. This process, almost more than any other in common use, requires that the metals should be perfectly or chemically clean ; for which purpose they are scraped quite bright before they are burnished together, so that the junction may be next approaching to that of solids generally. And, lastly, when metals are deposited upon other metals by. chemical or electrical means, the addition frequently appears to be a detached sheath, and which is easily removed ; indeed, unless the metal to be coated is chemically clean, and that various attendant circumstances are favorable, the sound and absolute union of the two does not always happen, even when carefully aimed at. It is time, however, that we proceed to the description of the methods of forming the ordinary alloys, the subject of the succeed- ing matter. MELTING AND MIXING THE METALS. The various Furnaces, etc., for Melting the Metals. — The subject upon which we have now to enter consists of two principal divisions, namely, the melting and combining of the metals, and the formation of the moulds into which the fluid metals are to be poured. In the foundry the two processes are generally carried on together, so that by the time the mould is completed, the metal may be ready to be poured into it; but as in conveying these several parti- culars the one process must have precedence, I propose to com- mence with the means ordinarily employed in melting and mixing the metals, in order to associate more closely all that concerns the alloys. In accordance with ordinary practice, the formation of the moulds will be described whilst the metals may be supposed to be in course of fusion ; the concluding remarks will be on pouring, or 124 MELTING AND MIXING THE METALS. filling the moulds, the act strickly speaking of casting, and which completes the work. The fusible metals, or those not requiring the red-heat, are melted when in small quantities in the ordinary plumber's ladle over the fire ; otherwise larger cast-iron ladles or pans are used, beneath which a fire is lighted ; for very large quantities and various manu- facturing purposes, such as casting sheet-lead, and lead pipe, and also for type-founding, the metals are melted in iron pans set in brickwork, with a fire-place and ash-pit beneath, much the same as an ordinary laundry copper, and the metals are removed from the pans with ladles. The pewterers and some others call the melting pan a pit, although it is erected entirely above the floor ; and as their meltings are made up in great part of old metal, which is sometimes wet or damp, they have iron doors to enclose the mouth of the pan, in case any of the metal should be splashed about from the moisture reaching the fluid metal. Antimony, copper, gold, silver, and their alloys, are for the most part melted in crucibles within furnaces similar to the kind used by the brass founders, which is represented at a, Fig. 75; the entire figure represents the imaginary section of a brass foundry, with the Fig. 75. moulding trough, h, for the sand on the side opposite the furnace, the pouring or spill trough, c, in the centre, and the core oven d, which is usually built in the wall close against one of the flues; but these matters will be described hereafter. The brass furnace is usually built within a cast-iron cylinder, about 20 to 24 inches diameter and 30 to 40 inches high, which is erected over an ash-pit arrived at through a loose grating on a level with the floor of the foundry. The mouth of the furnace stands about 8 or 10 inches above the floor, and its central aperture is closed with a plate now usually of iron, although still called a tile; the inside of the furnace is contracted to about 10 inches diameter by fire-bricks refiners' furnace, etc. 125 set in Stourbridge clay, except a small aperture at the back about 4 or 5 inches square, leading into the chimney. There are generally three or four such furnaces standing in a row, and separate flues proceed from all into the great chimney or stack, the height of which varies from about twenty to forty feet, and up- wards, the more lofty it is the greater the draught; every furnace has also a damper to regulate its individual fire. It is quite essential for constant work to have several furnaces, in order that one or two may be in use, whilst the others lie idle to allow of their being repaired, as they rapidly burn away, and when the space around the crucible exceeds about 2 or 3 inches, the fuel is consumed unnecessarily quick; the furnace is then contracted to its original size with a dressing of road drift and water applied like mortar, the fire is lighted immediately, and urged vigorously to glaze the lining. Road drift, or the scrapings of the ordinary turn- pike roads, principally silex and alumina, is often used for the entire lining of the furnace. The refuse sand from the glass grinders, which contains flint glass, is also used for repairing them. It is also convenient to have several furnaces for another reason, as when a single casting requires more than the usual charge of one furnace, namely, about 40 to 60 lbs., two or more fires can be used. When the quantity of brass to be melted exceeds the charge of three or four ordinary air furnaces, the common blast furnace for iron is sometimes used as a temporary expedient; the practice, however, is bad, as it causes great oxidation and waste. The greatest quantities of metal, as for large bells, statues, and ordnance, amounting some- times to several tons, are commonly melted in reverberatory furnaces. The furnaces used by the gold and silver refiners are in many re- spects similar to the brass furnace a, Fig. 75, but they are built as a stunted wall along one or more sides of the refinery, and entirely above the floor of the same. The several apertures for the fuel and crucible are from 9 to 16 inches square, or else cylindrical, and 12 to 20 inches deep; the front edge of the wall is horizontal, and stands about 30 inches from the ground, but from the mouth of the furnace backwards it is inclined at an angle of about 20 to 40 degrees, so that the tiles, or the iron covers of the furnace, lie at that angle. A narrow ledge cast in the solid with the iron plates covering the up- per surface of the wall, retains the tiles in their position. The small kinds of air furnaces are of easy construction, but as a temporary expedient almost any close fire may be used, including some of the German stoves and hot-air stoves, that is for melting brass, which is more fusible than copper ; although it is much the most convenient that the fire be open at the top, so that the contents of the crucible may be seen without the necessity for its removal from the fire. Such stoves, however, radiate heat in a somewhat in- convenient manner, and to a much greater extent than the various portable furnaces, most of which are lined with fire-brick or clay ; the lining concentrates the heat and economizes the fuel. Many of these portable furnaces answer not only for copper but also for iron, 126 MELTING AND MIXING THE METALS. when they have a good draft; it may happen, however, that the che- mical furnaces are equally as inaccessible to the amateur as those expressly constructed for the metals. Country blacksmiths, who are frequently called upon to practice many trades, sometimes melt from ten to fifteen pounds of brass in the ordinary forge fire, but there is considerable risk of cracking the earthen crucible at the point exposed to the blast ; a wrought iron pot is sometimes resorted to, but this is not very enduring, as the brass will soon cause it to burn into holes and leak. Observations on the Management of the Furnace, and on Mixing Alloys.— The fuel for the brass furnace is always hard coke, which is prepared in ovens and broken into lumps about the size of hens' eggs : in lighting the fire, a bundle of shavings, chips of cork, or any similar combustible, is first thrown in and ignited, and then some coke or charcoal is added. It is also usual to put the pot in the fire at an early stage, and with its mouth downwards : by this means the thin edge which admits the most easily of expansion gets hot first, and the heat plays within the crucible, so as to warm it gradually: it is not reversed until the whole is red hot: putting it in bottom downwards would be almost certain to cause it to crack. The pot is now bedded upon the fuel, and the brass-founder, whilst making up the fire, puts an iron cover with a long central handle over the mouth of the pot, to prevent the small cokes which are now thrown on from entering the same. Next, the charge of metal is put in the crucible, and three or four large pieces of coke are placed across the mouth of the pot ; the tile is put on the furnace, the damper is then adjusted to heat the crucible quickly, and the whole is left to itself until the metal is run down. The gold and silver refiners and jewelers manage their furnaces much in the same way, except that they support the crucible upon a hollow earthen stand placed on the fire-bars to catch any leakage, and also put an earthen cover over its mouth. They generally use coke, although charcoal is a purer fuel, and is laid upon the fluid metals to prevent oxidation. The above, and the so-called blue pots, or black-lead pots, are not burned until they are put into the fire for use ; but the Hessian pots, the English brown or clay pots, the Cornish and the Wedgwood crucibles, are all burned before use. It may be further observed, that the pots for brass are too porous for gold and silver, as they suck up too much of the same : the black-lead pots are closer and better for the precious metals, and they withstand change of temperature best of any kind ; they are however the most expensive, but cannot be safely used with fluxes. The Hessian crucibles resist the fluxes, and serve with care for seve- ral consecutive meltings ; the English clay pots, which resemble the Hessian, are safe for one or sometimes for more meltings, and their cost is trifling. The pots for gold and silver are occasionally coat- ed or luted externally with clay* as a protection. The generality of the metals are far more disposed to oxidation when in the melted condition than when solid : it is therefore usual, MIXING PEWTER, TYPE METAL, ETC. 127 whilst they are in the crucible, to protect their surfaces from the air with some flux, to lessen their disposition to oxidize. In the iron furnace, the slag from the lime floats on the metal and fulfils this end ; many brass-founders always throw broken glass, charcoal dust, sandiver, or sal-enixon, into the melting pot; by others these pecautionary measures are altogether neglected. The black and white fluxes, borax, and saltpetre are also used for the precious metals, and oil or resin for the more fusible, as lead or tin; but ex- cess of heat should be at all times avoided. The generality of the fusible metals may be mixed in all pro- portions. Those in which the melting points are tolerably similar may be easily combined, such as lead with tin, or gold with silver or copper ; these appear to call for no instructions beyond moderation in the heat employed, but the difficulty of making definite and uni- form alloys increases when the melting point of the metals, or their qualities or quantities, are widely dissimilar. In mixing alloys with new metals, it is usual to melt the less fusi- ble first, and subsequently to add the more fusible ; the mixture is then stirred well together, and common opinion seems to be in favor of running the metal into an ingot mould, as the second fusion is considered more thoroughly to incorporate the mixture. Sometimes, with the same view, the alloy is granulated, by pouring it from the crucible into water, either from a considerable height through a colander, or over a bundle of birch twigs, which subdivide it into small pieces ; others condemn such practices, and greatly prefer the first fusion, in order to avoid oxidation, and departure from the intended proportions. But in many, and perhaps in most cases, it is the practice to fill the melting pan, or the crucible, in part with old alloy, consisting of fragments of spoiled or worn-out work ; and to which is added, part- ly by calculation but principally by trial, a certain quantity of new metals. This is not always done from motives of economy alone, but from the opinion that such mixtures cast and work better than those made entirely of new metals. When small quantities of a metal of difficult fusion, are added to large proportions of others which are much more fusible, the whole quantities are not mixed at once. Thus in pewter, it would be scarcely possible to throw into the melted tin the half per cent, or the one per cent, of melted copper with any certainty of the two combining properly, and it is therefore usual to melt the copper in a crucible, and to add to it two or three times its weight of melted tin ; this, as it were, dilutes the copper, and makes the alloy known as temper, which may be fused in a ladle, and added in small quantities to the fluid pewter or to the tin, as the case may be, until on trying the mixture by the assay its proportions are considered suitable. The metal for printers' type is often mixed nearly in the same manner ; the copper is first melted alone in a crucible, the antimony is melted in another crucible, and is poured into the copper ; some- times a little lead is also added. The hard alloy and the tin are then 128 MELTING AND MIXING THE METALS. introduced to the mass of type-metal or lead, also in great measure by trial, as old metal mostly enters into the mixture. The composition of Britannia metal is as follows : 0% cwt. of best block tin; 28 lbs. of martial regulus of antimony; 8 lbs. of copper, and 8 lbs. of brass. The amalgamation of these metals is effected by melting the tin, and raising it just to a red heat in a stout cast- iron pot or trough, and then pouring into it, first the regulus, and afterwards the copper and brass, from the crucibles in which they have been respectively melted, the caster meanwhile stirring the mass about during this operation, in order that the mixture may be complete. It would appear, however, much more likely and consistent that a similar mode is adopted in making - this alloy, as in pewter and type- metal ; namely, that the copper and brass are melted together in one crucible, the antimony then added from another crucible, and perhaps also a little tin ; this would dilute the hard metals, and make a fusible compound, to be added to the remainder of the tin when raised a very little beyond its fusing point, so as to maintain fluidity when the whole were mixed and stirred together, previously to being poured into in- gots. By this treatment the tin would be much less exposed to waste. "When a very oxidizable or volatile metal, as zinc, is mixed with another metal the fusing point of which is greatly higher, as with copper for making the important alloy brass, whatever weight of each may be put into the crucible, it is scarcely possible to speak with anything like certainty of the proportions of the alloy produced, from the rapid and nearly uncontrollable manner in which the waste of the zinc occurs. Various means have been devised at different times for combining these two metals. Although the most direct way of forming the different kinds of brass is by immediately combining the metals together, one of them, which is most properly called brass, was manufactured long before zinc, one of its component parts, was known in its metallic form. The ore of the latter metal was cemented with sheets of copper, charcoal being present. The zinc was formed and united with the copper, without becoming visible in a distinct form. The same method is still practiced for making brass. The best way of uniting zinc with copper, in the first instance, will be to introduce the copper in thin slips into the melted zinc, till the alloy requires a tolerable heat to fuse it, and then to unite it with the melted copper. Some persons thrust the whole of the copper, in thin plates, into the melted zinc, which rapidly dissolves them; and the mass is kept in a pasty condition until within a few minutes of the time of pouring, when they augment the heat to the degree required for the casting process. But the plan which is the most expeditious, and now most usually adopted, is to thrust the broken lumps of zinc beneath the surface of the melted copper with the tongs, which mode will be more par- THE AUTHOR'S EXPERIMENTS ON ALLOYS OF COPPER. 129 ticularly described; but howsoever conducted, a considerable waste of the zinc will inevitably occur. It is also certain that every successive fusion wastes, in some degree, the more oxidizable metal, so that the original proportion is more and more departed from, especially with the least excess of heat; and when the metals are not well covered with flux. The loose oxide frequently mixes with the metal ; this in brass gives rise to the white- colored stains, and the little cavities filled with the white oxide of zinc ; and in gun-metal the stains and streaks are blacker, and the oxide of tin, (or putty powder,) being much harder than the former, is sadly destructive to the tools. The vitreous fluxes collect these oxides, and are therefore serviceable ; but when in excess, they are liable to run into the mould when the metal is poured. The chemist generally uses covers to the crucibles, to lessen the access of air, and therefore the oxidation ; but the brass-founder frequently leaves the metal entirely uncovered: no considerable waste occurs until the metal is entirely fused, and rather hotter than is required for pouring, which is indicated by the zinc beginning to burn at the surface with a blue flame. The loss which occurs in melting brass-filings is a proof that the granulation of the metals is not always desirable ; and unless the brass-filings are well drawn, by a group of magnets, to free them from particles of iron and steel, the latter often spoil the castings, as they become so exceedingly hard as to resist the file or turning tool and can be only removed by the hammer and cold-chisel. In collecting the several alloys given at pages 86 to 108, especially those of copper, I found great difficulty in reconciling many of the statements derived from books ; and therefore, to place the matter upon a surer basis, and also with some other views, I determined to mix a series of the copper alloys, in quantities of from one to two pounds each, pursuing, as nearly as possible, the common course of foundry work, to make the results practical and useful. My first intention was to weigh the metals into the crucible, and to find, by the weight of the product, the amount of loss in every case, as well as the quality of the alloy. Commencing^ with this view with copper and zinc, the several attempts entirely failed ; owing to the extremely volatile nature of the latter metal, especially when exposed to the high temperature of melted copper. The difficulty was greatly increased, owing to the very large extent of surface ex- posed to the air, compared with that which occurs when greater quantities are dealt with, and the increased rapidity with which the whole was cooled. The zinc was added to the melted copper in various ways; namely, in solid lumps, in thin sheets hammered into balls, poured in when melted in an iron ladle; and all these, both whilst the crucible was in the fire and after its removal from the same. The surface of the copper was in some cases covered with glass or charcoal, and in others uncovered, but all to no purpose ; as from one-eighth to one- 9 130 MELTING AND MIXING THE METALS. half the zinc was consumed with most vexatious brilliancy, according to the modes of treatment: and these methods were therefore aban- doned as hopeless. I was the more diverted from the above attempts, by the well known fact that the greatest loss always occurs in the first mixing of the two metals, and which the founder is in general anxious to avoid: thus when a very small quantity of zinc is required, as for the so-called copper casting, about 4 oz. of brass are added to every 2 or 3 lbs. of copper. And in ordinary work, a pot of brass weigh- ing 40 lbs., is made up of 10, 20, or 30 lbs. of old brass, and two- thirds of the remainder of copper, these are first melted : a short time before pouring, the one-third of the new metals, or the zinc is plunged in, when the temperature of the mass is such that it just avoids sticking to the iron rod with which it is stirred. In mixing the copper and zinc for my experiments on brass, an entirely different course was therefore determined upon, namely, to melt the metals on a large scale, and in the usual proportion, that is, 24 lbs. of copper to 12 lbs. of zinc, to learn the first loss of zinc when conducted with ordinary care. Then to remelt a quantity of the alloy over and over again, taking a trial bar every time, in order to ascertain the average loss of zinc in every fusion. From the residue of the original mixture, to make the alloys containing less zinc, by a proportional addition of copper; and those alloys containing more zinc, by a similar addition of zinc. And lastly, to have the whole of the bars assayed, to determine the absolute proportions of copper and zinc contained in all, and from these analyses to select my series of specimens, as nearly in agreement as I could with the proportions in common use. This method answered every expectation. Twenty-four pounds of copper, namely, clean ship's bolts, were first melted alone to ascertain the loss sustained by passing through the fire, which was found to be barely J oz. on the whole. A simi- lar weight of the same copper was weighed out, and also 12 lbs. of the best Hamburg zinc, in cakes about f inch thick, which were broken into pieces. The copper was first melted, and when the whole was nearly run down the coke was removed to expose the top of the pot, which was watched until the boiling of the copper, arising probably from es- cape of bubbles of air locked up at the lower part of the semi-fluid mass, ceased, and the copper assumed a bright red, but sluggish ap- pearance; the zinc was then added. Precaution is necessary in introducing the first quantity of zinc, not to set the copper, which is liable to occur if a large quantity of cold metal is thrown in, simply from the abstraction of heat ; and it is also necessary to warm the zinc that it may be perfectly dry, as the least moisture would drive the metal out of the pot with danger- ous violence. A small lump of zinc, therefore, was taken in the tongs, held beside the pot for a few moments, and then put in with the tongs with an action between a stir and a plunge, regardless of THE AUTHOR'S EXPERIMENTS ON ALLOYS OF COPPER. 131 the flare, and of the low crackling noise, just as if butter had been thrown in ; the zinc was absorbed, and the surface of the pot was clear from its fumes almost immediately. The remainder of the zinc was then directly added, in about eight pieces, one at a time, much in the same manner, but the danger of setting the copper nearly ceases when a small quantity of the spelter is introduced. After every addition the pot was free from flame in a few moments, a hand- ful of broken glass was then thrown in, the tile replaced, and the whole allowed to stand for about fifteen minutes to raise the metal to the proper heat for pouring, which is denoted by the commencement of the blue fumes of the zinc. The pot was then taken from the fire, well stirred for one minute, and poured ; the weight of the brass yielded was 34 lbs. 12£ oz., showing a loss of 1 lb. 3J oz., or one-tenth of the zinc, or the one- thirtieth part of the whole quantity. This experiment was repeated, and the loss was then 1 lb. 3 oz., the difference being only \ an oz. By analysis, the mean of the two brasses was 31£ per cent, zinc; or instead of being 8 oz. to the pound, it was only 7\ oz. Twelve pounds of each of these experimental mixtures were re- melted six times, a bar weighing about one pound and a half being taken every time ; the two series of trials were conducted in differ- ent foundries, by different men, and quite in the ordinary course of work ; but the loss per cent, of zinc was in the six experiments ^ ex- actly alike in each series, that is, each bar, after the sixth melting, contained 22J per cent, or 4f oz. to the pound of copper. The second fusion in each case sustained the greatest loss, (say nearly two-fold ;) and in the others, taking all the accidental circumstances into account, the loss might be pronounced nearly alike every fusion. In making the alloys with more zinc ; the calculated weight of the first alloy was melted, and the amount of zinc was warmed and plunged in with the tongs, whilst the pot was in the fire, the whole was stirred and quickly poured : the losses in weight were rather large, but this is common when the zinc is in great quantity. To make the alloys containing less zinc than the alloy, the calculated weight of copper was first made red-hot and the respective portion of the brass alloy was then put in the pot, by which means the two ran down nearly together: it being found that the copper, if entirely melted before the brass was added, incurred a risk of being set at the bottom of the pot ; and remelting the mass, wasted the zinc. These alloys came out much nearer to their intended weights. In making the tin and copper alloys, very little difficulty was ex- perienced. The copper was put into the pot together with a little charcoal, which was added to assist the fusion and also to cause the alloy to run clean out ; as in pouring gun-metal a small quantity is usually left on the lip of the crucible, which would have been an in- terference in these experiments. When the copper had ceased boil- ing, and was at a bright red heat, it was taken from the fire, and the 132 MELTING AND MIXING THE METALS. tin, previously melted in a ladle, was thrown in ; every mixture was well stirred and poured immediately. In the fourteen alloys thus formed, each weighing about a pound and a half, namely, J, 1, If, &c., up to 8 oz. of tin to the pound of copper, (missing the 6| and 7|,) no material loss was sustained in nine instances, and in the other five it never exceeded | oz., and that quantity was probably lost rather in fragments than by oxida- tion. Alloys of 2, 4, 6 and 8 ounces of lead to the pound of copper, were made exactly under the same circumstances as the last. Messrs. Barron and Brother, of New York, manufacture a very effective and economical furnace, which supplies the necessary quan- tity of air ; for in the combustion of fuel only a certain quantity of air is required, either an excess or deficiency is prejudicial to proper combustion. The metals are melted by this furnace in less time, and at a less expense of fuel than any that have fallen under my notice. In less than ten minutes, gold, silver, and copper can be melted by the furnace of Barron and Brother. The first size will melt from 4 to 12 ounces of gold with about a quart of coal ; the second size will melt 50 to 120 ounces with about two quarts ; and the third size will melt from 100 to 500 ounces with three or four quarts of coal. It is a difficulty of no ordinary description to ascertain the tem- perature^ of a furnace with sufficient accuracy. Every fire and every furnace is continually changing its temperature. When a furnace is charged with a fresh supply of fuel, its temperature is lowered by the absorption of heat which the cold fuel takes up when thrown upon the fire. The temperature is lowered by a rush of cold air through the open door. Experiments made by the pyrometer showing the mean tem- perature of the flues in a steam engine boiler, and the effects pro- duced by the admission of air through a permanent and regulated apparatus behind the bridge, indicate that in making the quantity of water evaporated by one pound of coal as the measure of economy, the mean of nearly the whole experiments is about 12J per cent, in favor of a regulated and continuous supply of air. In order to insure economy and effect in the combustion of fuel, a large supply of air must be admitted to the furnace, and that in the ratio of 10 volumes of air to 1 of coal gas. Perfect combustion is the prevention of smoke. And it is found that in order to render the residue of the products of combustion transparent or smokeless, a supply of air amounting to ten times the gases evolved must be admitted. PRINCIPLES OF MOULDING. 133 CASTING AND FOUNDING. Metallic Moulds — We are indebted to the fusibility of the metals, for the power of giving them with great facility and perfection, any required form, by pouring them whilst in the fluid state into moulds of various kinds, of which the castings become in general the exact counterparts. This property is of immeasurable value. Some few objects are cast in open moulds, so that the upper sur- face of the fluid metal assumes the horizontal position the same as other liquids, as in casting ingots, flat plates, and some few other objects; but in general the metals are cast in close moulds, so that it becomes necessary to provide one or more apertures or ingates for pouring in the metal, and for allowing the escape of the air which previously filled the moulds. When these moulds are made of metal, they must be sufficiently hot not to chill or solidify the fluid metal before it has time to adapt itself thoroughly to every part of the mould ; and when the moulds are made of earthy matters, although moisture is essential to their formation, little or none should remain at the time they are filled. The earthen moulds must be also sufficiently pervious to air, that any vapor or gases which may be formed, either at the moment of pouring in the metal or during its solidification, may have free vent to escape; otherwise, if these gases are rapidly formed, there is great danger of the metal being driven out of the mould with a violent explosion, or when more slowly formed and locked up without suffi- cient freedom for escape, the casting will be said to be blown, as some of the bubbles of air will displace the fluid metal and render it spongy or porous. It not unfrequently happens that castings which appear externally good and sound, are full of hidden defects, because the surface being first cooled, the bubbles of air will attempt to break their way through the central and still soft parts of the casting. Fig. 76. C b 3 A The explanatory diagram, Fig. 76, is intended to elucidate some of the circumstances concerning the construction of moulds, which in the greater number of cases are made only in two parts, but in 134 CASTING AND FOUNDING. other cases are divided into several. The figure to be moulded is supposed to be a rod of elliptical section, the mould for which might be divided into two parts through the line A, B, because no part of the figure projects beyond the lines a, b, drawn from the margin of the model at right angles to the line of divison, and in which direc- tion the half of the mould would be removed or lifted; the model could be afterwards drawn out from the second half of the mould in a similar manner. The mould could be also parted upon the line C, D, because in that direction likewise, no part of the model extends beyond the lines c, d, which show the direction in which the mould would be then lifted. The mould, however complex, could be also parted either upon A B or upon C D, provided no part of the model outstepped the rect- angle formed by the dotted lines b, c, or was undercut. But, considering the figure 76 to be turned bottom upwards, and with the line E, F, horizontal, the removal of the entire half of the mould upon the lines e, /, would be impossible, because in raising the mould perpendicularly to E, F, that portion of the mould situated within the one perpendicular e, would catch against the overhanging part of the oval towards A. Were the mould of metal, and therefore rigid, it would be entirely locked fast, or it would not "deliver;" were the mould of sand, and therefore yielding, it would break and leave behind that part between A and E which caused the obstruction. Con- sequently, in such a case, the mould would be made with a small loose part between A and E, so that when the principal portion, from A to F, had been lifted perpendicularly or in the direction of the line e, the small undercut piece, A to E, might be withdrawn sideways, on which account it would be designated by the iron founder a drawback, by the brass founder a false core. All the patterns in the mould, Fig. 77, could be extracted from Fig. 77. a * b c d e f g h each half of the mould, because none of them encroach beyond the perpendicular line, or that in which the mould is lifted ; a and b, could be laid in exactly upon the diagonal, or upon one flat side, or partly embedded ; and in like manner /, g, 7t, might be sunk more or less into the mould, their sides being perpendicular; but the pat- terns in Fig. 78 being undercut, the division of the mould into two METAL MOULDS FOR PEWTER WORKS. 135 parts only would be impracticable, and false cores or subdivisions would be required in the manner represented,, the construction of which will be hereafter detailed. Extending these same views to a more complex object, such as a bust, it will be conceived that the mould must be divided into so many- pieces, that none of them will be required to embrace any overhang- ing part of the figure. For instance, were it attempted to mould a human head, so that the parting might pass through the central line of the face and down the back, the two halves could not be sepa- rated if they were made each in a single piece ; as the inner angles of the eyes, the spaces behind the ears, and the curls of the hair would obstruct it, and the head could be only thus moulded by mak- ing false cores or loose pieces at these particular places, in the man- ner illustrated by the former figures. These would require to be accurately adapted to the surrounding parts, by pins or contrivances to ensure their re-taking their true positions. These remarks, how- ever, are only advanced by way of general illustration, as figure cast- m* is the most refined part of the art of moulding. Metal moulds are employed for many works in the easily-fused metals, which are required to be produced in large quantities, and with great similitude and economy : the examination of which moulds will serve to demonstrate many of the points of construction and pro- ceeding Thus the common bullet mould is made like a pair ot pliers, the jaws of which are conjointly pierced with a hole or passage leading into a spherical cavity ; the aperture is equally divided be- tween the two halves of the mould, so that in fact the division is truly upon the diametrical line both of the sphere and the runner or the largest part of each, otherwise the pliers could not be opened to remove the bullet when cast. Iron shot for great guns are like- wise cast in iron moulds, by which they also possess great accuracy of form and size. 136 CASTING AND POUNDING. Figs. 79 to 82 represent the moulds for casting pewter inkstands: these moulds are a little more complex? and are each made in four parts ; the black portions represent the sections of the inkstands to be cast. The moulds each consist of a top piece or cap t, a bottom or core 5,and two sides or cottles, s s; in Fig. 82, the one side is removed, in order to expose the casting, and the top piece t is sup- posed to be sawn through to make the whole more distinct. It will be seen, the top and bottom parts have each a rebate like the lid of a snuff-box, which embrace the external edges of the two side pieces 8 8, and the latter divide as in the bullet mould, exactly upon the diametrical line of the inkstand, which in a circular object is of course the largest part; the positions of the parts are therefore strictly maintained. When the mould has been put together, laid upon its side, and filled through x, the ingate, or as it is technically called, the tedge, it is allowed to stand about a minute or two, and then the top t, is knocked off by one or two light blows of a pewter mallet ; the mould is then held in the hand and the bottom part or core is knocked out of the casting by the edge ; lastly, the two sides are pulled asunder by their handles, and the casting is removed from the one in which it happens to stick fast ; but it requires cautious handling not to break it. The face of the mould is slightly coated with red ochre and white of egg, to prevent the casting adhering to the same, and to give the works a better face : the first few castings are generally spoiled, until in fact the mould becomes properly warmed. Most of the works made in the very useful material, pewter, are cast in gun-metal moulds, which require much skill in their construc- tion; thus a pewter tankard, with a hinged cover and spout, consists of six pieces, every one of which requires a different mould ; thus, 1. The body has a mould in four parts, like that for the inkstand, but it is filled in the erect position through two ingates, which are made through the top piece t, of the mould : 2. The bottom requires a mould in two parts, and is poured at the edge : 3. The cover is cast in the same manner ; and thus far the moulds are all made in the lathe, in which useful machine these castings are also finished before being sol- dered together : 4. The spout requires a mould in two parts : 5. The piece, Fig. 84, by which the cover is hinged to the handle, requires a much more complex mould, which divides in four parts, as shown in Fig. 83, and much resembles, except in external form, the remaining mould: namely, _ 6. For the handle, which mould, like the last, consists of four pieces fitted together with various ears and projections ; they are METAL MOULDS FOR PEWTER WORKS. 137 represented in their relative positions in Fig. 86, with the exception of the piece a, Fig. 87, which is detached and shown bottom upwards. Fig. 85 shows the pewter handle separately, with the three knuckles for joining on the cover ; and on reference to Fig. 86, of the five parts through which the pin p, is thrust, the two external pieces belong respectively to the sides c, and d, of the mould, the others are parts of the casting, and the two hollows are formed by the two solid knuckles fixed to the detached piece of the mould a, Fig. 87. At the time of pouring, the pin p, serves to connect the three parts a, c, d, together, and also to form the hole in the casting, for the pin of the joint. Figs. 85. 86. 87. Fig. 88 shows the section of the mould upon the dotted line s: by this it will be seen the handle is cast hollow, as almost immediate- ly the mould has been filled through t, all but the thin external shell is poured out again, and the weight is reduced to less than half. To extract the handle, the pin p, is first twisted out ; then the joint piece a, is removed ; next the back piece b ; and lastly the two sides c, d, are pulled asunder. Tin or pewter bearings for locomotive carriages, have been cast in appropriate metal moulds ; and such materials are very useful to the mechanist for many temporary purposes, such as collars, bearings, screws and nuts, either for difficult positions, or where no screw tap is at hand and the resistance is moderate ; in such cases the parts of the machine constitute one portion of the mould, the apertures being closed with moist loam : the processes are most successful when the parts can be made warm and the clay is nearly dry. The most important, exact, and interesting example of casting in metallic moulds is that of type-founding, the description of which, as well as drawings of the mould, have been repeatedly given; some of the peculiarities only of this art, will be therefore noticed. Each 138 CASTING AND FOUNDING. complete set of types consists of five alphabets, A, a, a, A, a, besides many other characters, in all about two hundred, and which are re- quired to be most strictly alike in every respect, except in device and width; the width is the greatest for the W and M, and the least for the i and !. Every required measure of the types, (represented on an enlarged scale in Fig. 89,) is determined by the mould alone, and not by any after correction. Fig. If 94. 1 If the moulds for the rectangular shafts of the types were made as in Figs. 90 or 91, the usual forms of square moulds, they would not admit of alteration in width, as shifting a, Fig. 90, would produce no change, and Fig. 91 would thereby produce the form b. The mould which is used is made in two |_ formed parts, as in Fig. 92, whence it follows that shifting the part a, to the right or left increases or decreases the width of the type without interfering with its thickness, or, as it is technically called, its body, (b, Fig. 89,) the width, w, is adjusted by a piece called the register, fixed at the bottom of the mould. The device is changed by placing across the bottom of the mould one of the two hundred little pieces of copper, Fig. 93, called matrices, into which the face of the latter is impressed by very beautifully formed punches. The length of the letter is determined by a con- traction at the upper part of the mould, as shown at c, Fig. 94, which represents the type as it leaves the mould ; the metal is poured with & jerk, to make a sharp impression of the matrix: the mould, which is held in the left hand, and the ladle in the right, being jerked simul- taneously upwards, at the moment of filling the mould, and without which the face of the type would be rounded and quite imperfect. The breaks c, or the runners of the types, are first broken off, and after a slight correction of the sides, the hollows or channels in the STEREOTYPE FOUNDING. 139 feet are planed out of a whole column of them, fixed between bars of wood, without touching the square shoulders which determine the lengths of the types, and are left as originally cast. In some types with a large face and much detail, such as the illus- trations given on the last page, the motion of the hand is barely sufficient to give the momentum required to throw the metal into the matrix, and produce a clean sharp impression. A machine is then used, which may be compared to a small forcing-pump, by which the mould is filled with the fluid metal ; but from the greater difficulty of allowing the air to escape, such types are in general considerably more unsound in the shaft or body ; so that an equal bulk of them only weigh about three-fourths as much as types cast in the ordinary way by hand, and which for general purposes is preferable and more economical. Some other variations are resorted to in type-founding; sometimes the mould is filled at twice, at other times the faces of the types are dabbed, (the clichee process;) many of the large types and ornaments are stereotyped, and either soldered to metal bodies, or fixed by nails to those of wood. The music type, and ornamental borders and dashes, display much very curious power of combination. The clichee process is rather stamping than casting. The melted alloy is placed in a paper tray, and stirred with a card until it as- sumes the pasty condition. The metal die, or mould, is then "dabbed" upon the soft metal, as in sealing a letter, but with a little more of sluggish force. By the type-founding machine invented by Mr. Bruce, of N. Y., and employed in the extensive foundry of Mr. L. Johnson, of Phila- delphia, 3600 letters may be cast in an hour, much more sound and as perfect as those cast by hand. Plaster of Paris Moulds and Sand Moulds. — Other examples of metallic moulds might be given, but there are far more frequent cases in which one single casting is alone required ; or else the num- ber is so small, or the pieces themselves are so large or peculiar, that the construction of metal moulds would be found almost or quite im- practicable, even without reference to an equally fatal barrier, the expense. In making these single copies in the metals of considerable fusi- bility, plaster of Paris is sometimes employed; thus, after the printer has arranged the loose types into a page, and the requisite correc- tions have been made, a stereotype, or solid type, is taken of the whole as a thin sheet of metal, which serves to be printed from al- most as well as the original letters ; and its small cost enables the printer to retain it for future use, after the types themselves have served perhaps for a hundred similar regenerations, and are ulti- mately worn out. The stereotype founder takes a copy of the entire mass of type in plaster of Paris : this is dried in an oven, and placed face downwards within a cast iron mould, like a covered box, open at the four top- corners. The mould and plaster-cast are heated to the fusing tem- 140 CASTING AND FOUNDING. perature of the type-metal, and gradually lowered into a pan or bath of the same by means of a crane ; the hot fluid metal runs in at the corners of the mould, and raises the inverted plaster, which latter would rise entirely to the surface but for the restraint of the cover of the mould. Type-metal is about eleven times as heavy as water ; and if the mould be immersed four inches below the surface, it is subjected to a pressure equal to that of a column of water forty-four inches high, or of above two pounds upon every square inch. The necessity of this arrangement is shown when a few ounces of type-metal are poured from a ladle on the face of the plaster ; the metal looks like a dump, almost without any mark of the letters, whereas the stereotype-cast is nearly as sharp as the original type. The immersion fulfils the same end as the jerk of the hand-caster, or of the pump occasionally employed ; and the long continuance of the mould in* the fluid metal allows ample time for the air to escape in bubbles to the surface ; after which the mould is raised and cooled in a vessel of water, and the plaster is mostly destroyed in its re- moval. Plaster of Paris, although it may be, and frequently is used for the fusible metals, such as lead, tin, and pewter, cannot be employed alone for iron, copper, brass, and many other metals, the intense melting heats of which would calcine the material, and cause it to crumble ; even the soft metals should not be very hot, or they will make the plaster of Paris blister off in flakes or dust. We must therefore seek a substitute better capable of enduring the heat, and likewise susceptible of receiving definite forms ; for which purpose damp sand, with a small natural or subsequent admixture of clay or loam, is found to be perfectly adapted. The moulding-sand cannot, however, be used without external sup- port, and which is given by shallow iron frames without tops or bot- toms, called flasks, represented in Figs. 95 and 96. The bottom part, 4, 5, is supposed to have been rammed full of sand, and to stand Figs. 95. 96. REMAKES ON FOUNDRY PATTERN'S. 141 upon a flat board, 6. The model of the plain flat bar which is to be cast, is now laid on the surface of the sand, that of the round bar is embedded half way in the same, and the mould is dusted with dry parting sand. The top part of the flask 2, 3, is shown still empty, and in the act of being attached to 4, 5 by its pins, which enter corresponding holes in the latter, easily but without shake : 2, 3 is also rammed full of sand, and covered with a top board, 1, not represented to avoid con- fusion. The mould is now opened, the models are removed, and channels are scooped out from the ends of the cavities left by the models, to the hollows or pouring-holes at the end of the flask; the parts are all replaced in the order 1 to 6, represented in Fig. 95, and the whole are fixed together by screw clamps, so as to assume the condition of Fig. 96. The flask is now placed almost perpendicularly beside the pouring- trough, and the metal is poured into it from the crucible, as shown in Fig. 75, p. 124; but the flask, if small, is put on the surface of the pouring or spill-trough, and propped up with a short bar. This brief sketch of the entire process of moulding and casting in sand moulds, will be now followed by some remarks in greater detail : first, on the patterns of the objects to be cast; secondly, on the con- ditions required in the sand; and thirdly, the process of moulding simple and solid bodies. The section then following will be devoted to moulding cored works, and figures, after which a few lines will be given upon the subject of filling the moulds. Patterns, Moulds, and Moulding Simple Objects.— The per- fection of castings depends much on the skill of the pattern-maker, who should thoroughly understand the practice of the moulder, or he is liable to make the patterns in such a manner that they cannot be used, or at any rate be well used. Straight-grained deal, pine, and mahogany, are the best woods for making patterns, as they stand the best ; screws should be used in preference to nails, as alterations are then more easily made in the models, and glue joints, such as dovetails, tenons, and dowels, are also good as regards the after use of the saw and plane for cor- rections and alterations. Foundry patterns should be always made a little taper in the parts which enter most deeply into the sand, in order to assist their removal from the same, when their purposes will not be materially interfered with by such tapering. The pattern-maker, therefore, works most of the thickness, and the sides or edges, both internal and external, a little out of parallel or square, perhaps as much as about one-sixteenth to one-eighth of an inch in the foot, sometimes much more. When foundry patterns are exactly parallel, the friction of the sand against their sides is so great when they penetrate deeply, that it requires considerable force to extract them; and which violence tears down the sand, unless the patterns are much knocked about in the mould, to enlarge the space around them. This rough usage 142 CASTING AND FOUNDING. frequently injures the patterns, and causes the castings to become irregularly larger than intended, and also defective in point of shape, from the mischief sustained by the moulds; all which evils are less- ened when the patterns are made consistently taper and very smooth. It must be distinctly and constantly borne in mind, that although patterns require all the methods, care, and skill, of good joinery or cabinet-making, they must not, like such works, be made quite square and parallel, for the reasons stated. Sharp, internal angles should in general be also avoided, as they leave a sharp edge or arris in the sand, which is liable to be broken down in the removal of the pattern ; or to be washed down on the entry of the metal into the mould. Either the angle of the model should be filled with wood, wax, or putty, or the sharp edges of the sand should be chamfered off with the knife or trowel. Sharp internal angles are very injudicious in respect also to the strength of castings, as they seem to denote where they will be likely to break; and more resemble carpentry than good metallic construction. Before the patterns reach the founder's hands, all the glue that may have been used in their construction should be carefully scraped off, or it will adhere to and pull down the sand. The best way is to paint or varnish wooden patterns, so as to prevent them from ab- sorbing moisture, as they will then hang to the sand much less, and will retain their forms much better. Whether painted or not, they deliver more freely from the mould when they are well brushed with black lead, like a stove. In patterns made in the lathe, exactly the same conditions are required; the parts which enter deeply into the sand should be neither exactly cylindrical nor plane surfaces, but either a little coned, or rounding, as the case may be; and the internal angles should not be turned exactly to their ultimate form, but rather filled in, or round- ed, to save the breaking down of the sharp edges of the mould. Foundry patterns are also made in metal; these are very excellent, as they are permanent; and when very small are less apt to be blown away by the bellows used for removing the loose sand and dust from the moulds. To preserve iron patterns from rusting, and to make them deliver more easily, they should be allowed to get slight- ly rusty, by lying one night on the damp sand; next, they should be warmed sufficiently to melt bees'-wax, which is then rubbed all over them, and in great part removed, and then polished with a hard brush when cold. Wax is also used by the founder for stopping up any little holes in the wooden patterns ; whitening is likewise employed, as a quicker but less careful expedient; and very rough patterns are seared with a hot iron. The good workman, however, leaves no necessity for these corrections, and the perfection of the pattern is well repaid by the superior character of the castings. Metal patterns frequently require to have holes tapped into them for receiving screwed wires, by way of handles for lifting them out of the sand; and in like manner, large wooden patterns should have screwed metal plates let into them for the same purpose, or the MATERIALS FOR FOUNDRY MOULDS. 143 founder is compelled to drive pointed wires into them, to serve as handles, which is an injurious practice. The flasks or casting-boxes for containing the sand, are made of various sizes; each side is about 2 to 3 inches deep; they are poured at the edge when placed nearly vertical; but for large brass works the practice of the iron-founder is generally followed, who mostly pours his work horizontally, through a hole in the top, as will be ex- plained. The pins of the flask should fit easily but without shake, or the two halves will shift about and cause a disagreement or slip in the casting. The tools used in making the moulds are few and simple, namely, a sieve, shovel, rammer, strike, mallet, a knife, and two or three loosening wires and little trowels, which it is unnecessary to describe. The principal materials for making foundry moulds are very fine sand and loam; they are found mixed in various proportions, so that the respective quantities proper for different uses cannot be well de- fined ; but it is always judicious to employ the least quantity of loam that will suffice. These materials are seldom used in their new or recent states for brass castings, although more so for iron, and the moulds made of fresh sand are always dried, as will be explained. The ordinary moulds are made of the old damp sand, and they are generally poured immediately or whilst they are green ; some- times they are more or less dried upon the face. The old working sand is considerably less adhesive than the new, and of a dark-brown color; this arises from the brick-dust, flour and charcoal dust, used in moulding, becoming mixed with the general stock, which therefore requires occasional additions of new sand or loam, so that when slightly moist and pressed firmly in the hand, it may form a mode- rately hard compact lump. Red brick-dust is generally used to make the partings of the mould, or to prevent the damp sand in the separate parts of the flask from adhering together. The face of the mould which receives the metal is generally dusted with meal-dust, or waste-flour ; but in large works, powdered chalk, and also wood or tan ashes, are used from being cheaper. The moulds for the finest brass castings are faced either with charcoal, loamstone, rottenstone, or a mixture of the same: the moulds are frequently inverted and dried over a dull fire of cork shavings, or when dried they are smoked over pitch or black resin lighted in an iron ladle. The gold and silver casters frequently use a lighted link for facing their sand-moulds, and some of the type-founders' metallic moulds are smoked over a lamp : all these modes deposit a fine layer of soot upon the moulds. The cores or loose internal parts of the moulds for forming holes and recesses, are made of various proportions of new sand, loam and horse-dung, as will be explained in the section on cored works. They all require to be thoroughly dried, and those containing horse-dung must be well burned at a red heat; this consumes the straw and makes them porous and of a brick-red. 144 CASTING AND FOUNDING. In making the various moulds, it becomes necessary to pursue a medium course between the conditions best suited to the formation of the mould, and those best suited to filling them with the red-hot metal, without risk of failure or accident. Thus, within certain limits the more loam and moisture the sand contains, and the more closely it is rammed, the better will be the impression of the model; but at the same time the moist and impervious condition of the mould would then incur the greater risk of accident, both from the moisture and from the non-escape of the air; therefore the policy, on the score of safety, is to use the sand as dry as practicable, so as to avoid the delay of after-drying, and also to keep the mould porous. The founder, therefore, compromises the matter by using a little facing sand containing rather more loam, for the face of the green moulds for general work ; and in those cases where much loam is used, the moulds are thoroughly dried by heat, which is not gene- rally necessary with ordinary sand moulds. The power of conducting heat is considerably less in red-hot iron than in copper and brass, and therefore the moulds for the latter re- quire to be in a drier condition than those which may be used for iron; but in either "case the presence of superfluous moisture is always attended with some danger to the individual as well as to the work. The above is the reason generally assigned for the fact, that the iron-founders may and do use their moulds with safety when sensibly more moist than is admissible for brass and copper castings. It is confirmatory of the fact that the more dense the mould, the drier it must be; as the sand used by iron-founders is also coarser and therefore more porous than that employed by brass-founders. Another point has also been considered ; as castings contract con- siderably in cooling, in moulding large and slight works the face of the mould must not be too strongly rammed, nor too much dried, or its strength may exceed that of the red-hot metal, whilst in the act of shrinking. . The. result would be, that in contracting, the casting would be rent or torn asunder from the restraint of the mould ; whereas it should have the preponderance of strength, so as to pull down the face of. the sand instead of being itself destroyed. But the exact condition both of the mould and of the melted metal, must be determined by the nature of the object to be cast ; matters which can be only referred to with the development of the practice of the foundry, and upon which we shall now commence. The sand having been prepared, and the appropriate flask and boards selected, the moulder first examines every pattern separately to determine the most appropriate way of inserting it in the flask, as explained by Fig. 77, p. 134 ; also to see that patterns, such as/ and 7«, therein shown, are smallest at the parts entering the most deeply into the sand, in order that they may deliver well. It should also be noticed whether they are perfectly smooth, and that there is no glue hang- ing about them, which would cause them to adhere and to pull down the moist sand. The bottom flask, 4, 5, p. 140, is placed on a board not less than INSTRUCTIONS FOR MOULDING ORDINARY WORKS. 145 an inch or two longer and wider than itself, with the face 4, down- wards, and it is filled from the side 5. A small portion of the strong facing-sand is rubbed through a fine sieve ; the remainder is thrown in from the trough with the shovel, and the moulder drives the whole moderately hard into the flask, either with a mallet, the handle of the spade, or other rammer ; or else he jumps up by aid of the rope suspended from the ceiling, and treads the sand in with his feet. The surface is then struck off level with a straight metal bar or scraper, a little loose sand is sprinkled on the surface, upon which another board is placed, and rubbed down close. The two boards and the flask contained between them, are then all three turned over together ; this requires them to be brought to the front of the moulding-trough, so that the individual may rest his chest against them, and his forearms upon the edges of the top board ; he then grasps the three together at the back part with his outstretched hands, and thus retained in contact, the whole are quickly turned over upon the front edge of the moulding-trough, and then slid back upon the transverse bearers or blocks, to the usual position. The top board is afterwards taken off, the clean surface of moist sand then exposed, is well dusted over with red brick-dust, crushed fine and contained in a linen bag; the mouth of the bag is held in the right hand, and the bottom corner in the left, and both hands are shaken up and down together, to scatter the dry powder uniformly over the flask ; a part of the loose powder is removed with the hand-bellows, and the bottom half of the mould is then ready for receiving the patterns. The models are next arranged upon the face of the sand at 4, so as to leave space enough to prevent the parts breaking one into the other, and also for the passages by which the metal is to be intro- duced, and the air allowed to escape. When there are only two or three pieces to be cast, a separate runner is often made to each of them from one of the holes in the end of the flask; when several small patterns are to be moulded, they are arranged on both sides a central runner, or ridge, from which small passages lead into every section of the mould. The whole mass when poured has been compared to a great fern leaf with its leaflets, and is usually called a spray. Those patterns which are cylindrical or thick, are partly sunk in the sand, by scraping out hollow recesses with the bowl of an old copper spoon, and knocking the model into the sand with the mallet; afterwards the general surface is repaired to agreement with the diametrical line of the model, or its largest section, as the case may be, by means of a knife or a little piece of sheet steel, something like the worn-out blade of a dessert-knife bent up a little at the end, or else with very small trowels. After the sand is made good to the edges of the patterns, the brick-dust is again shaken over them, so that the patterns may re- ceive a slight share as well as the general surface of the sand. The upper part of the flask 2, 3, is then fitted to the lower, or 4, 5, by 146 CASTING AND FOUNDING. the pins, and this half likewise is made up ; first a little strong sand is sifted in, it is then filled up from the trough, rammed down, and struck off as before, the dry powder serving to prevent the two halves from sticking together. In order to open the mould for the extraction of the models, a board is placed on the top of flask 2, 3, and struck smartly at differ- ent parts with the mallet, the tool is then laid aside, and the upper part of the flask and its board are lifted up very gently and quite level, after which it is inverted on its board, and now each of the inner faces of the mould is exposed. Should it happen that any con- siderable portion of the mould, say a part as large as a shilling, is broken down in one piece, the cavity is moistened with the end of the knife, the mould is again carefully closed, and lightly struck before the removal of the patterns ; it is probable on the second lifting such piece will be picked up. The breaks are carefully repaired before the extraction of the pat- terns, to effect which they are driven slightly sideways with blows of the mallet, given on a short wire or punch, so as to loosen them by enlarging the space around them ; the patterns are then lifted out very carefully with the finger-nails, or sometimes a pointed wire is driven a little way into the pattern to serve as a handle to lift it by : this process requires some delicacy not to tear away the sand, which accident must be carefully repaired, sometimes by replacing the loose pieces, at other times with a little new sand picked out of any unused part of the mould. A steel wire, pointed and hardened, is convenient as a picker out, and when fixed in the pattern and stuck sideways it serves as a loosen- ing bar likewise. Should the flask only contain one or two objects, the ingate or run- ner is now scooped out of the sand, so as to lead from the object to the pouring hole, and when several objects are contained, a large central channel, and lesser passages sideways, are made as before mentioned. The entrance round about the pouring hole is smoothed and compressed with the thumb that it may not break down when the metal is poured, and all the loose sand is carefully blown out of the mould, both parts of which may be placed edgeways for the more convenient application of the bellows if necessary. The succeeding processes are to dust the faces of both halves of the mould with meal dust or waste flour, as explained with regard to the brick-dust, and to replace the mould and boards: the whole of them are then carried to the spill-trough, upon the edge of which they are rested whilst the one board is placed exactly level with the end of the flask, but the board on the side from which the crucible will be poured, is placed about two inches below, as in Fig. 96, p. 140, and the hand-screws are fixed on as shown. The mould is now held mouth downwards, that any sand loosened in the screwing down may be allowed to fall out, and the flask, according to its size, is sup- ported either on the ground or on the surface of the trough by aid of a little bar resting against the clamp : it is now quite ready to be INSTRUCTIONS FOR MOULDING CORED WORKS. 147 filled, the particulars of which process will be described when the remarks on moulding are concluded. In works that require the first side or 3, 4, to be cut away for em- bedding the models, it is usual when the second part or 2, 3, has been made, to destroy the first or false side, (which is only hastily made,) and to repeat it in a more careful manner by inverting the lower flask upon 2, 3, proceeding in all other respects as before, by which means a much more accurate and sound mould is produced. When many copies of the same patterns are required, an odd side is prepared, that is, a flask is chosen to which there are two bottom sides, 4, 5. One of these latter is very carefully arranged with all the patterns, but which are only embedded barely half way, so that when 2, 3, is filled and both are turned over, the whole of the pat- terns are left in the new side ; a second side, 4, 5, is moulded to serve for receiving the metal, as the mould is destroyed every time the metal is poured in. By this plan the trouble of re-arranging the patterns for every separate mould is saved, as they are merely re- placed in the odd side, and the routine of forming the two working sides is repeated. Moulding Cored Works. — If the objects to be cast require to be so moulded that when they leave the sand they may contain one or several holes, they are said to be cored, and in such cases, a variety of methods are practiced for introducing internal moulds or cores, which shall intercept the flow of the metal, and prevent it from form- ing one solid mass at those respective parts. For example, the pins inserted in the pewterers' moulds, Figs. 83 and 86, pages 136 and 137, for producing the holes in the joints, are essentially cores. Va- rious other methods are pursued, the three most usual of which are represented in Figs. 97, 98, and 99: the upper figures show the ' exact sections of the three models or casting patterns; the lower figure represents the two halves of the mould, which are respectively shaded with perpendicular and horizontal lines, the cores are shaded obliquely; and the white open spaces show the hollows to be occupied by the metal when it is poured in. First. Many works are said to deliver their own cores; of such kind is Fig. 97, in which the cavity extends through the model, and exactly represents that which is required in the casting; the hole is either made quite parallel, or a little larger one side than the other, and gradually taper between the two. In some cases, when the hole is sufficiently taper, it delivers its own core as a continuation of the general mass of sand filling the one side of the flask; but in many or most cases, the space in the model is rammed full of strong sand at first, and it is then moulded as if to produce a plain solid casting. Before the mould is finally closed for pouring, the sand core is pushed carefully out of the pattern, and inserted in the mould; to denote its precise position, one side of the core is scored with one or two deep marks in the first instance, which cause similar ridges or guides in the mould. 148 CASTING AND FOUNDING. Secondly. When the hole extends only part way through, the hole of the pattern, Fig. 98, is fitted with a solid plug, sawn and filed out of soft unburnt brick, principally sand, (or the common Flanders Fi.. n Francis's life-boats. 195 Fig. 191, with rivets, is the common mode of uniting plates of marine boilers, and other works required to be flush externally. Fig. 192 is a similar mode, used of late years for constructing the largest iron steam-ships; the ribs of the vessels are made of y iron, varying from about four to eight inches wide, which is bent to the curve by the employment of very large surface-plates cast full of holes, upon which the wood model of the rib is laid down, and a chalk mark is made around its edge. Dogs or pins are wedged at short intervals in all those holes which intersect the curve ; the rib, heated to redness in a reverberatory furnace, is wedged fast at one end, and bent round the pins by sets and sledge-hammers, and as it grows or yields to the curve, every part is secured by wedges until the whole is completed. The following method of constructing metallic boats, invented by Mr. Francis, of the Novelty Works, New York, is taken from Harper's New Monthly Magazine. In many cases of distress and disaster befalling ships on the coast, it is not necessary to use the car, the state of the sea being such that it is possible to go out in a boat, to furnish the necessary succor. The boats, however, which are destined to this service must be of a peculiar construction, for no ordinary boat can live a moment in the surf which rolls in, in storms, upon shelving or rocky shores. A great many different modes have been adopted for the construction of surf-boats, each liable to its own peculiar objections. The prin- ciple on which Mr. Francis relies in his life and surf-boats, is to give them an extreme lightness and buoyancy, so as to keep them always upon the top of the sea. Formerly it was expected that a boat in such a service, must necessarily take in great quantities of water, and the object of all the contrivances for securing its safety, was to expel the water after it was admitted. In the plan now adopted the design is to exclude the water altogether, by making the structure so light and forming it on such a model that it shall always rise above the wave, and thus glide safely over it. This result is obtained partly by means of the model of the boat, and partly by the light- ness of the material of which it is composed. The reader may per- haps be surprised to hear, after this, that the material is iron. Iron — or copper, which in this respect possesses the same proper- ties as iron — though absolutely heavier than wood, is, in fact, much lighter as a material for the construction of receptacles of all kinds, on account of its great strength and tenacity, which allows of its being used in plates so thin that the quantity of the material em- ployed is diminished much more than the specific gravity is increased by using the metal. There has been, however, hitherto a great prac- tical difficulty in the way of using iron for such a purpose, namely, that of giving to these metal plates a sufficient stiffness. A sheet of tin, for example, though stronger than a board, that is, requiring a greater force to break or rupture it, is still very flexible, while the board is stiff. In other words, in the case of a thin plate of metal, the parts yield readily to any slight force, so far as to bend under 196 WOKKS IN SHEET METAL, MADE BY JOINING. the pressure, but it requires a very great force to separate them entirely; whereas in the case of wood, the slight force is at first re- sisted, but on a moderate increase of it, the structure breaks down altogether. The great thing to be desired therefore, in a material for the construction of boats, is to secure the stiifness of wood in con- junction with the thinness and tenacity of iron. This object is at- tained in the manufacture of Mr. Francis's boats by plaiting or cor- rugating the sheets of metal of which the sides of the boat are to be made. A familiar illustration of the principle on which this stiffen- ing is effected is furnished by the common table waiter, which is made usually, of a thin plate of tinned iron, stiffened by being turned up at the edges all around — the upturned part serving also at the same time the purpose of forming a margin. The platings or corrugations of the metal in these iron boats pass along the sheets, in lines, instead of being, as in the case of the waiter, confined to the margin. The idea of thus corrugating or plaiting the metal was a very simple one ; the main difficulty in the invention came, after getting the idea, in devising the ways and means by which such a corrugation could be made. It is a curious circumstance' in the history of modern inventions that it often requires much more ingenuity and effort to contrive a way to make the article when invented, than it did to invent the article itself. It was, for instance, much easier, doubtless, to invent pins, than to invent the machinery for making pins. The machine for making the corrugations in the sides of these metallic boats consists of a hydraulic press and a set of enormous Fig. 193. Francis's life-boats. 197 dies. These dies are grooved to fit each other, and shut together; and the plate of iron which is to be corrugated being placed between them, is pressed into the requisite form, with all the force of the hydraulic piston — the greatest force, altogether, that is ever em- ployed in the service of man. The machinery referred to will be easily understood by the above engraving. On the left are the pumps, worked, as represented in the engraving, by two men, though four or more are often required. By alternately raising and depressing the break or handle, they work two small but very solid pistons which play within cylinders of corresponding bore, in the manner of any common forcing pump. By means of these pistons the water is driven in small quantities, but with prodigious force, along through the horizontal tube seen passing across, in the middle of the picture, from the forcing-pump to the great cylinders on the right hand. Here the water presses upward upon the under surface of pistons working within the great cylinders, with a force proportional to the ratio of those pistons compared with that of one of the pistons in the pump. Now the piston in the force-pump is about one inch in diameter. Those in the great cylinders are about twelve inches in diameter, and as there are four of the great cylinders the ratio is as 1 to 576. Areas being as the squares of homologous lines, the ratio would be, mathe- matically expressed, l 2 : 4xl2 2 =l: 4x144=1: 576. This is a great multiplication, and it is found that the force which the men can exert upon the piston within the small cylinder, by the aid of the long lever with which they work it, is so great, that when multi- plied by 576, as it is by being expanded over the surface of the large pistons, an upward pressure results of about eight hundred tons. This is a force ten times as great in intensity as that exerted by steam in the most powerful sea-going engines. It would be sufficient to lift a block of granite five or six feet square at the base, and as high as the Bunker Hill Monument. Sup erior, however, as this force is, in one point of view, to that of steam, it is very inferior to it in other respects. It is great, so to speak, in intensity, but it is very small in extent and amount. It is capable indeed of lifting a very great weight, but it can raise it only an exceedingly little way. Were the force of such an engine to be brought into action beneath such a block of granite as we have de- scribed, the enormous burden would rise, but it would ;rise by a motion almost inconceivably slow, and after going up perhaps as high as the thickness of a sheet of paper, the force would be spent, and no further effect would be produced without a new exertion of the motive power. In other words, the whole amount of the force of a hydraulic engine, vastly concentrated as it is, and irresistible, within the narrow limits within which it works, is but the force of four or five men after all; while the power of the engines of a Collins' steamer is equal to that of four or five thousand men. The steam- engine can do an abundance of great work ; while, on the other hand, 198 WORKS IN SHEET METAL, MADE BY JOINING. ■what the hydraulic press can do is very little in amount, and only great in view of its extremely concentrated intensity. Hydraulic presses, before the introduction of D. Dick's anti-fric- tion press, were often used, in such cases and for such purposes as require a great force •within very narrow limits. The indentations made by the type in printing the pages of Harper's magazine, are taken out, and the sheet rendered smooth again, by hydraulic presses ex- erting a force of twelve hundred tons. This would make it neces- sary for us to carry up our imaginary block of granite a hundred feet higher than the Bunker Hill Monument to get a load for them. There are nine of these presses in the printing-rooms of Harper and Brothers, all constantly employed in smoothing sheets of paper after the printing. The sheets of paper to be pressed are placed be- tween sheets of very smooth and thin, but hard pasteboard, until a pile is made several feet high, and containing sometimes two thousand sheets of paper, and then the hydraulic pressure is applied. These presses cost, each, from twelve to fifteen hundred dollars. In Mr. Francis's presses, the dies between which the sheet of iron or copper are pressed, are directly above the four cylinders which we have described, as will be seen by referring once more to the draw- ing. The upper die is fixed — being firmly attached to the top of the frame, and held securely down by the rows of iron pillars on the two sides, and by the massive iron caps, called platens, which may be seen passing across at the top, from pillar to pillar. These caps are held by large iron nuts which are screwed down over the ends of the pillars above. The lower die is movable. It is attached by massive iron work to the ends of the piston-rods, and of course it rises when the pistons are driven upward by the pressure of the water. The plate of metal, when the dies approach each other, is bent and drawn into the intended shape by the force of the pressure, receiving not only the corrugations which are designed to stiffen it, but also the general shaping necessary, in respect to swell and curva- ture, to give it the proper form for the side, or the portion of a side, of a boat. It is obviously necessary that the dies should fit each other in a very accurate manner, so as to compress the iron equally in every part. To make them fit thus exactly, massive as they are in magnitude, and irregular in form, is a work of immense labor. They are first cast as nearly as possible to the form intended, but as such castings always warp more or less in cooling, there is a great deal of fitting afterwards required, to make them come rightly together. This could easily be done by machinery if the surfaces were square or cylindrical, or of any other mathematical form to which the working of machinery could be adapted. But the curved and winding surfaces which form the hull of a boat or vessel, smooth and flowing as they are, and con- trolled, too, by established and well-known laws, bid defiance to all the attempts of mere mechanical motion to follow them. The super- fluous iron, therefore, of these dies, must all be cut away by chisels driven by a hammer held in the hand; and so great is the labor re- Francis's life-boats. 199 quired to fit and smooth and polish them, that a pair of them costs several thousand dollars before they are completed and ready to fulfil their function. The superiority of metallic boats whether of copper or iron, made' in the manner above described, over those of any other construction, is growing every year more and more apparent. They are more light and more easily managed, they require far less repair from year to year, and are very much longer lived. When iron is used for this purpose, a preparation is employed that is called galvanized iron. This manufacture consists of plates of iron of the requisite thickness, coated on each side, first with tin, and then with zinc ; the tin being used simply as a solder, to unite the other metals. The plate presents, therefore, to the water, only a surface of zinc, which resists all action, so that the boats thus made are subject to no species of decay. They can be injured or destroyed only by violence, and even violence acts at a very great disadvantage in attacking them. The stroke of a shot, or a concussion of any kind that would split or shiver a wooden boat so as to damage it past repair, would only indent, or at most perforate, an iron one. And a perforation even, when made, is very easily repaired, even by the navigators them- selves, under circumstances however unfavorable. With a smooth and heavy stone placed upon the outside for an anvil, and another used on the inside as a hammer, the protrusion is easily beaten down, the opening is closed, the continuity of surface is restored, and the damaged boat becomes, excepting, perhaps, in the imagination of the navigator, as good once more as ever. Metallic boats of this character were employed by the party under Lieut. Lynch, in making, some years ago, their celebrated voyage down the river Jordan to the Dead Sea. The navigation of this stream was difficult and perilous in the highest degree. The boats were subject to the severest possible test and trials. They were im- pelled against rocks, they were dragged over shoals, they were swept down cataracts and cascades. There was one wooden boat in the little squadron ; but this was soon so strained and battered that it could no longer be kept afloat, and it was abandoned. The metallic boats, however, lived through the whole, and finally floated in peace on the heavy waters of the Dead Sea, in nearly as good a condition as when they first came from Mr. Francis's dies. The seams of a metallic boat will never open by exposure to the sun and rain, when lying long upon the deck of a ship, or hauled up upon a shore. Nor will such boats burn. If a ship take fire at sea, the boats if of iron, can never be injured by the conflagration. Nor can they be sunk. For they are provided with air chambers in various parts, each separate from the others, so that if 'the boat were bruised and jammed by violent concussions, up to her utmost capaci- ty of receiving injur}'-, the shapeless mass would still float upon the sea, and hold up with unconquerable buoyancy as many as could cling to her. The principle on which these life-boats are made is found equally 200 WORKS IN SHEET METAL, MADE BY RAISING. advantageous in its application to boats intended for other purposes. For a gentleman's pleasure-grounds, for example, how great the convenience of having a boat which is always stanch and tight — which no exposure to the sun can make leaky, which no wet can rot, and no neglect impair. And so in all other cases where boats are required for situations or used where they will be exposed to hard usage of any kind, whether from natural causes or the neglect or inattention of those in charge of them, this material seems far supe- rior to any other. WORKS IN SHEET METAL, MADE BY RAISING. Circular Works Spun in the Lathe. — The former examples have only called into action so small an amount of the malleable or gliding property of the metals, that all the forms referred to could be produced in pasteboard, a material nearly incapable of extension or compression. The raised works now to be considered, call for much of this gliding or malleable action which may be compared with the plastic nature of clay as an opposite extreme. Thus a lump of clay is thrown on the potter's horizontal lathe, a touch of the fingers shapes it into a solid round lump, the potter thrusts his clenched hand into the centre, and it rises in form something like a bason ; by applying the other hand outside to prevent the material from spreading, it will rise as an irregular hollow cylinder, and a gentle pressure from without, and a sustaining pressure from within, will gather up or contract the clay into the narrow mouth suited to a bottle, and which is made somewhat in this manner almost by the fingers alone. A similar and parallel application, due to the malleability of the metals, and one which also requires the turning-lathe, is very ex- tensively practiced : namely, the art of " spinning or burnishing to form" thin circular works in several of the ductile metals and alloys, as for teapots, plated candlesticks, the covers of cups and vessels, the bell mouths of musical instruments, and numerous other objects required in great numbers, and of thin metals. Plated candlesticks are thus formed of several parts soldered together, or retained in po- sition by the fittings of their edges, the whole being strengthened by a central wire, and by filling the entire cavity with a resinous cement. The Figs. 194 and 195, are intended to show the mode of spinning the body of a Britannia metal teapot from one unperforated disk of metal. The wooden mould or chuck a, Fig. 194, is turned to the form of the lower part of the teapot, and a disk of metal b, is pinched tight between the flat surfaces of a and c, by the fixed centre screw d of the lathe, so that a, 5, and c, revolve with the mandrel : and now by means of a burnisher e, which is rested against a pin in the lathe rest, as a fulcrum, and applied near the centre of the metal ; and a wooden stick /, held on the opposite side to support the edge, the metal is rapidly bent or swaged through the successive forms 1, 2, 3, CIRCULAR WORKS. 201 to 4, so as to fit close against the curved face of the block and to extend up its cylindrical edge. The mould a, is next replaced by g, Fig. 195, a plain cylindrical block of the diameter of the intended aperture ; one of various forms of burnishers (h, i, some bent, others T form, and so on, the sur- faces of which are slightly greased,) are used together with the hooked stick or rubbery, first to force the metal inwards as shown at 5, 6, 7, and also to curl up the hollow bead which stiffens the mouth of the finished vessel, 9. Sometimes the moulds are made of the entire form of the inside of the work, but of several pieces, each smaller than the mouth ; so that when the central block is first removed, the others may be successively taken out of the finished vessel, like the parts of a hat-block or of a boot-tree. It is of importance during the whole process, to keep the edge ex- actly concentric and free from the slightest notches, for which pur- pose it is occasionally touched with the turning tool during the pro- cess of spinning. The operation is very pretty and expeditious, and resembles the manipulation of the potter who forms a bottle or vase with a close mouth in a manner completely analogous, although the yielding nature of his material requires the fingers alone, and neither the mould, stick, nor burnisher. The lenses of optical instruments are often fixed in their cells by similar means; a, Fig. 196, shows in excess the form of the metal when turned, and b r the thin edge when curled over the glass by means of a burnisher applied whilst the ring re- volves in the lathe. Much of the cheap Birmingham jewelry is also spun in the lathe, but in a different manner; for instance, to make such an object as the ring represented black in Fig. 197; a steel mandrel is turned upon a lathe to the same form as the ring, but less in diameter. The metal is prepared as a thin tube, it is soldered and cut into short Fig. 196. 202 WORKS IN SHEET METAL, MADE BY RAISING. pieces, each to serve for one ring, and these are spun into shape almost in an instant, between the arbor and the milling tool or roller, as seen in the front view, Fig. 198 ; it is clear that unless the arbor Figs. 197. 198. were smaller than the work, the latter from being undercut could not be released : sometimes only one broad milling tool is employed, at other times two or more narrow ones. This process is most distinctly a modification of two rollers, which travel by surface-contact instead of by toothed wheels, and differs but little from the embossing or matting rollers employed by jewelers and others for long strips instead of rings; extending the same application to the milling-tool upon a solid body, such as milled nut, the interior metal supplies the resistance given by the arbor, in the last figure. Works Raised by the Hammer. — In raising the metals by the hammer, we have to produce similar effects to those in the spinning process ; not however by the gradual and continued pressure of a burnisher, on one circle at a time, but by circles of Mows, applied much in the same order, and as far as possible with the same regu- larity of effect. The art consists, therefore, of two principal points: first, so to proportion the original size and thickness of the metal disk that it shall exactly suffice for the production of the required object ; neither with excess of metal, which would have to be cut off with shears and thrown aside, wasting a part both of the metal and labor, nor with deficiency of metal, which would be nearly a total loss: secondly, that the work shall be produced with the smallest possible number of blows, which sometimes tend to thin, and at other times to thicken, the metal; whereas the finished works should present a uniform thick- ness throughout, and which is, in many cases, just that of the original metal when in the sheet. For instance, a hollow ball six inches diameter is made of two circular pieces of copper, each seven and a half inches diameter : now calling the original circumference of the disk twenty-two and a half inches, this line eventually becomes contracted to eighteen inches, or the circumference of the ball; although at the same time the original diameter of the disk, namely, a line of seven and a, half inches, has become stretched to that of nine inches or the girth of the hemisphere. This double change of dimensions, accomplished by the malleability SOLID AND HOLLOW BLOWS. 203 or gliding of the metal, occurs in a still more striking manner in the illustration of spinning the tea-pot, in which the disk, originally about one foot diameter, becomes contracted to two or three inches only at the mouth. The precise nature of the change is seen on inspecting Figs. 142 and 144, in connection with the radiated pieces, 143 and 145, required for the formation of such polygonal vases, when bent up and soldered at their edges. The same vases wrought to the circular figure from round plates, either by spinning or by the hammer, would not require disks of metal so large as the boundary circles in Figs. 143 and 145; as the pieces between the rays would be entirely in excess, they would cause the vessels to rise beyond their intended sizes, and would require to be pared off. But the original disks for making the vases should be of about the diameters of the inner circles, as then the pieces d, beyond the inner circles, would be nearly equal to the spaces e, within these circles, which Avould leave the vessel of uni- form thickness throughout, and without deficiency or excess of metal, supposing the conversion to be performed with mathematical truth. The first and most important notion to be conveyed in reference to raising works with the hammer, is the difference between those which may be called opposed, or solid blows, that have the effect of stretching or thinning the metal ; and those which may be called unopposed, or hollow blows, that have less effect in thinning than in bending the metal; in fact, it often becomes thickened by hollow blows, as will be shown. Figs. 199. 200. 201. a For example, the hammer in Fig. 199 is directly opposed to the face of the anvil, or meets it face to face, and would be said to give a solid blow ; one which would not jar the hand grasping the plate, were the latter ever so thick or rigid : and this blow would thin the metal by its sudden compression between two hard surfaces, the face of the hammer being represented at /. The hammer in Fig. 200 is not directly opposed to the anvil, or rather to that point of it which sustains the work, consequently this would be called a hollow blow, one which would jar the hand were the plate thick and rigid ; and it would bend the plate partly to th e 204 WORKS IN SHEET METAL, MADE BY RAISING. form of the supporting edge, by a similar exhibition of the forces «, b, c, referred to in the diagrams, Figs. 165 to 168 ; not, however, by the quiet pressure therein employed, but by impact, or by driving blows. The hand situated at a, Fig. 200, would be insufficient to withstand the blows of the hammer at c, but for the great distance of a b, compared with b c, and the thin flexible nature of the ma- terial. From these reasons the coppersmith and others never require tongs for holding the metal, the same as the blacksmith, except at the fire, as in annealing and soldering; in hammering thin works, a constant change of position is required, and which can be in no way so readily accomplished as by the exquisite mechanism given us by nature, the unassisted hand. When, however, the works are too rigid or too small to be thus held, the anvil is made to supply the two points a, c, as in Fig. 201, and the blow of the hammer is directed between them. We will now trace the effects of solid and hollow blows given par- tially on a disk of metal a a, Fig. 202, supposed to be twelve inches diameter: first within a central circle c c, of three inches diameter ; and then around the margin a b 7 to the width of three inches, leaving the other portions untouched in each case : the thickness of the metal is greatly exaggerated to facilitate the expla- nation. The solid blows within the circle c c, would thin and stretch that part of the metal, and make it of greater superficial extent ; but the broad band of metal a c, would prevent it from expanding beyond its original diameter, and therefore the blows would make a central concavity, as in a cymbal, or like Fig. 203. And the more blows that were given, either inside the bulge upon a flat anvil, or outside the bulge upon an anvil or head of a globular form, the more would the metal be raised, from its being thinned and extended ; and thus it might be thrown into the shape of a lofty cone or sugar-loaf. The hollow blows given within the same limited circle would also stretch the metal and drive it into the hollow tools employed, such as Fig. 201; thus producing the same effect as in 203, but by stretch- ing the metal as we should the parchment of a drum, by the pressure of the hand in the centre, or by a blow of the drumstick. The solid blows around the three-inch margin, would thin the metal and cause it to increase externally in diameter ; but the plate would only continue flat, as in Fig. 204, if every part of the ring were stretched proportionally to its increased distance from its first HOLLOWING. 205 position. Were the inner edge towards I, thinned beyond its due amount, its expansion, if resisted by the strength of the outer ring a, would throw part of the work into a curve, and depress the metal, not as in the cymbal, but in the form of a gutter as in Fig. 205 ; it would howevermore probably happen, that the inner edge alone of the marginal ring would be expanded, leaving the outer edge undis- turbed, and, producing the coned figure, 206. The hollow blows given around the edge, as in Fig. 200, would have the effect of curling up or raising the edge, first as a saucer 207, and then into a cylindrical form 208 ; provided that by the skill- ful management of the hammering, the metal could be made to slide upon itself without puckering, so as to contract the original bounda- ry circle of the disk or twelve inches, into six inches, or the measure of the edge of the cylinder resulting from the drawing in of the three- inch margin. In this process the metal would become proportionally thickened at the upper edge, because each little piece of the great circle, Fig. 209, when compressed into a circle of half the diameter, would only occupy half its original length, as it could not be altogether lost; and the metal would therefore increase in thickness in a proportional degree. The remainder of the circle serves for the time as effectu- ally to compress the metal in the direction of the tangent, as if the radii were the sides of an unyielding angular groove dotted in Fig. 209 : this contraction produces in fact the same effect as the jumping or upsetting by endlong blows in smith's-work. Theoretically, the thickness of the upper edge of the cylinder would be doubled, and the lower edge would retain its original thickness, as in 208 ; whereas in extending the margin of the disk by solid blows as in Fig. 204, the thinned edge would be found to taper away, also in a straight line, from the full thickness even to a feather edge if sufficiently continued, but neither of these cases would be admissible, as the general object is to retain a uniform substance. In equalizing the thickness of the cylindrical tube, Fig. 208, the solid blows would thin the metal, but at the same time throw it into a larger circle ; it would then require to be again driven inwards, which would again slightly thicken it. So that in reducing the metal to uniformity, two distinct and opposite actions are going on ; and upon the due alternation, combination, or proportioning of which, will entirely depend the ultimate form: that is, whether the metal be allowed to continue as a cylinder ; to expand or to contract, either as a cone or as a simple curve ; or to serpentine in any arbitrary man- ner, according as the one or other action is allowed to predominate with the gradual development. The treatment of such works with the hammer, is unlike spinning the teapot, at those parts of the work where the metal is folded down in close contact with the solid revolv- ing mould therein employed ; but in completing the upper part on the small block, Fig. 195, the burnisher and the rubber may be con- sidered equivalent to the two antagonist forces, which lead the ham- mered vessel inwards or outwards, at the will of the operator. 206 WORKS IN SHEET METAL, MADE BY RAISING. This subject is too wide to enable anything more to be offered than a few general features, and I shall therefore proceed to trace briefly the practice in some examples. Figs. 210. 211. Fig. 210 represents the first stage of making the half of a cop- per ball ; the metal is first driven with a mallet into a concave bed, generally of wood, in which it is hastily gathered up to a sweep of about the third part of a sphere, as a, a, Fig. 211 ; but this puckers up the edge like a piece of fluted silk, or the serpentine margin of many shells, in the manner represented at ///, Fig. 112, which is of twice the size of 211. The next step is to remove the flutes or puckers by means of blows of the raising hammer, applied externally as indicated by the black lines at h, Fig. 212 ; and in Fig. 213 are represented, on a still more enlarged scale, the relative positions of the hammer, anvil, and work. Thus A represents the globular face of the anvil, B the rounded edge of the raising hammer, which like the pane of an ordinary hammer, stands at right angles to the handle, and a 1, shows the work, a being the edge, and 1 the point of the flute. The blows of the ham- mer are made to fall nearly on the centre o, of the anvil, and at a small angle with the perpendicular, the hand being on the side a. A few blows are given as tangents, or directly across the point of the flute, and when it exceeds the width of the hammer, oblique blows are given to restore the pointed character, to be followed by other blows parallel with the first, as shown at h, Fig. 212. These hollow blows cause the sides of the flutes to slide into one another, almost as when two packs of cards, placed like the ridge of a house, pene- trate into each other and sink down flat : in a manner somewhat re- sembling that by which the original and extreme margin in Fig. 209, becomes, by the successive blows, contracted to the inner circle; but in the present case the plait slides down to the general curve of the spherical dish. Figs. 212. 213. h s f h RAISING HEMISPHERES. 207 If, however, the puckers of a large globe were entirely removed by hollow blows, the central lines of the flutes would become thickened, and therefore solid blows are mingled with them, or rather the one blow partakes of the two natures. Thus from the curvature and ob- lique position of the hammer, Fig. 213, its face is solid at s, to that part immediately below it, but towards A, it rather bends than thins ; the flatter the curves of the two surfaces, the greater the extent of the solid or thinning blows. The plaits are not, however, entirely gathered up, as the dish a, a, Fig. 211, always opens a little, from the metal becoming stretched under the treatment for removing the flutes. Throwing the work into flutes as described is not imperative, for the hemisphere might be entirely raised, as in the succeeding step, by blows on the outer surface upon a convex tool or head, but the flutes quicken the process, and speedily give a concavity which is convenient, as it makes the work hang better on the rounded face of the anvil. The outer curve a a, Fig. 211, p. 206, which represents the cop- per dish when the puckers have been removed, will not be sent into the hemispherical form, or the inner line d d, at one process, but will progressively assume the curvatures b b, e e, and sometimes many others; neither will the work be changed from the curve a a, to that of b b, at one sweep, nor as with the burnisher in spinning even by one consecutive ring or wave. The hammer must necessarily operate by successive blows arrangedin circles, the proximity of which circles will at length include within their range the entire sweep a a, or b 6, each of which is called a course : and before proceeding from one course or sweep to the next, the metal requires to be annealed. Figs. 213 and 214 explain the transition or conversion from the first sweep a, to the second sweep b; the black lines represent the metal after a circles of blows have been given. Figure 214 shows the narrow edge of the raising-hammer, in the act of descending upon the centre of the head or stake, and as a tangent to the circle; it first throws in a little rim at 1, which connects the new and old sweeps by a curve or ogee ; then another little circle 2, will be simi- Figs. 214. 215. m a b n p 208 WORKS IN SHEET METAL, MADE BY RAISING. larly gathered in, then 3, 4, 5, and so on, up to the edge. Now the artifice consists in making the intervals both of the great sweeps, a, b, c, Fig. 211, and of the little waves 1, 2, 3, of Fig. 214, as large as practicable, provided, they do not cause the exterior metal to pucker or become in plaits, as this would endanger its ultimately cracking at those places, where the metal might have become plaited. In thus raising-in the metal, it necessarially becomes thickened from its contraction in diameter, but as in Fig. 213 the hammer at h, gives a hollow blow and bends, whilst the part s, gives a solid blow and thins, the two effects are thus combined ; and when they are duly proportioned, by a hammer more or less round, and blows more or less oblique, the true thickness as well as the desired change of figure are both obtained. It is easier to get the hemisphere by a little excess of thinning, or by a superfluity of blows : so that the less skillful workman will use a piece of copper of seven inches diameter, with additional blows, for a six inch hemisphere ; but the more skillful will take a piece of seven and a half inches diameter, and obtain the work with less labor. Occasionally, when the work is common and thin, from three to six hemispheres or other pieces are hollowed together, the outer piece is cut as a hexagon or octagon, and its angles are bent over to embrace the inner pieces, before the process of hollowing is begun, and which scarcely consumes more time than for one only. This is a general practice in hollowing tin-works, such as the covers of sauce- pans, as the number of thicknesses divide the strength of the blows ; the several pieces are then twisted round at intervals, so as to arrange them in a different order, which mixes the little imperfections, and tends to their mutual correction : the raising process represented in Fig. 214 is also performed upon two or three pieces at a time, when they are sufficiently thin to permit it. One of the most conspicuous and remarkable examples of raised works is the ball and cross of St. Paul's Cathedral, London. The old ball consisted of sixteen pieces riveted together ; the present, also 6 feet diameter and ^ inch thick, was raised in two pieces only, and may therefore be considered to mark the improvement in the coppersmith's art in making large works, such as sugar-pans, stills, &c. The metal was first thinned and partly formed under the tilt-ham- mer at the copper-mills, or sunk in a concave bed ; the raising was effected precisely as explained in Fig. 214, and with hammers but little larger than usual ; the two parts were riveted together in their place, and the joint is concealed by the ornamental band. All the work is modern, and is mostly hammered up, except the cast gun-metal consoles beneath the ball, which formed part of the original metallic edifice ; a name to which it is justly entitled, the height being 29 feet, and the weight of copper 3£ tons. The new ball and cross are strengthened by a most judicious inner framing of copper and wrought-iron bars, stays, bolts, and nuts, extending through the arms and downwards into the building ; thus adding about RAISING VASES, ETC. 209 2 tons of iron to the load of copper, and to the 38 ounces of gold used in its decoration. Having conveyed the full particulars for raising a hemispherical shape, the modifications of treatment required for various other forms will be sufficiently apparent. Thus, below the dotted lines a d, in Fig. 215, the sweeps are exactly the same as in Fig. 211, but the metal rises higher from having been originally larger ; in the courses g h, it is first kept rather thicker on the edge, and towards the conclusion, it is thinned on the edge to the common substance, and curled over by hollow blows from within, although the whole figure might be produced by external blows, but which would be a more tedious method. On the other hand, by the continuance of the raising-in, explained by diagram 214, the metal would be gathered into a smaller diameter through the steps i, j, k, I, in the latter of which the metal would be- come thickened, unless the solid or thinning blows were allowed to predominate. If enough metal had been given in the first instance, when the mouth had been contracted as to the form of a teapot, it might be extended upwards as a cylindrical neck, in the manner ex- plained in Fig. 208, and curled over at the top, as on the opposite side of Fig. 215, at h. To lessen the labor of raising works from a single flat plate, solder- ing is sometimes resorted to ; thus the teapots, Figs. 142 and 144, page 184, might be made in two dished pieces, and soldered at the largest diameter; the lofty vase or coffeepot, Fig. 146, could be made from a cylinder of midway diameter soldered up the side, the bulge being set-out by thinning the metal, and the contraction above being drawn-in by hollow blows. Vases in the shape of an earthen oil jar, or of the line I d n, Fig. 215, could be made from a cone such as o p, with a bottom soldered in ; these preparations would save the work of the hammer, although such forms, and others far more difficult, could be raised entirely by the hammer from a flat piece of metal. Should any of the above vessels require a solid thickened edge or lip, beyond that which would result from the drawing-in of the metal, it would be necessary to select a piece of metal of smaller diameter but thicker, and to retain the margin of the full thickness by direct- ing all the blows within the same; sometimes, on the other hand, works require to be thinned on the edge ; these are then cut out pro- portionally smaller than their intended sizes, as illustrated by the following example, which is considered the most difficult of its kind. The bell of a French horn, together with the first coil of the tube, are made of a flat strip of metal about 4 feet long and 2 inches wide ; for making the bell of the instrument, there is an enlargement at one end of the strip, in the form of the funnel piece 141, and of the width, of 16 to 22 inches, the smaller piece being adopted when the bell is, required to be very thin. The narrower piece of metal, when firsfc bent up, much resembles the butt end of a musket, terminating in ^ small tube; the metal is united and soldered down the edge mtJu u \ 210 WORKS IN SHEET METAL, MADE BY RAISLtti*. cramp or dovetail joint, Fig. 184; it is next thrown into a conical form of about five inches diameter, and expanded from within, first with blows of a wooden mallet upon a wooden block, and then with those of a hammer on iron stakes. When nearly finished, or about one foot diameter, it is hammered very accurately upon a cast-iron mould turned exactly to the form of the bell, which is thus rendered much thinner than the general substance, and remarkably exact; the band containing the wirefor stiffening the edge of the bell is attached by dexterous hammering, and without solder. To bend the tube to the curve without disturb- ing its circular section, it is filled with a cement, principally pitch, which allows the tube to be bent to the scroll of the instrument, without suffering the metal to be puckered or disturbed from its true circular section; and in bending similar tubes to smaller curves, they are filled with lead. These materials serve as flexible and fusible supports, which are easily removed when no longer required. Should any of the raised works have ornamental details, such as concave or convex flutes, or other mouldings, they would be mostly overlooked until the general forms had been given ; and then every little part would be proceeded with upon the same principles of solid and hollow blows. Each of the series of flutes would be first slightly developed all around the object, then more fully, and so on until the completion ; when, however, the details are so large, as to form what may be considered integral parts, it is necessary to prepare for them at an earlier stage. Thus, to take an excellent familiar example, let Fig. 216 repre- sent plans, 217 sections, and 218 elevations of jelly moulds, many of which require the greatest skill of the coppersmith. The general outline is that of a cylinder abed, upon a larger cylinder e f g h, as a base. The twelve large and deeply indented flutes or finials, rise perpendicularly to a great height from the plane surfaces a c and e b, and yet the whole is hammered out of one flat plate. Figs. 216. 217. 218. The first step is to raise the summits of the flutes i or prepara- tory to the general formation of the upper cylinder abed, and then the two are worked up together, leaving for a time the expanded base ef g h, but ultimately the whole receive a general attention in COMPARISON BETWEEN RAISING AND STAMPING. 211 common. If the flutes were polygonal, and terminated in ornaments like spires or finials, as at k, thej would be first treated as if for the more simple or generic form i, and the details would be subsequently produced. The skill called for in such works is greatly enhanced by the at- tention which is required to preserve a nearly uniform thickness in the metal, notwithstanding the apparent torture to which it is sub- mitted ; and this is only endured in consequence of a frequent recur- rence to the process of annealing, which reinstates the malleable property. In cases of extensive repetition, or where large numbers of any specific shape are required, expensive dies of the exact forms are employed; but these are only applicable to objects in small relief, and to those in which the parts are not quite perpendicular. Dies would be entirely inapplicable to objects such as the jelly moulds, Fig. 217, although a common notion exists that they are rapidly made by that^ method, but which is in general utterly impossible when such objects are made in one piece. In all such cases, the metal has to undergo the same bendings and stretchings between the dies as if worked by the hammer, and which unless gradually brought about, are sure to cut and rend the metal ; the production of many such forms with dies is therefore altogether impracticable. Figs. 219. 220. For example, the pattern or moulding, z, Fig. 219, is only in small relief, and yet the flat piece of metal a, would be cut in two or more parts if suddenly compressed between the dies A, B; as the edges i, j, would first abruptly bend and then cut the metal, without giving it the requisite time to draw in, or to ply itself gradually to the die, beginning at the centre as in the process of hammering. In Fig. 220 the successive thicknesses obliterate the effect of the acute edges of the bottom die B ; the face and back of every thick- ness differ, as although parallel they are not alike, but they become gradually less defined, so that in Fig. 220, the top die A, requires nothing more than a flowing line with slight undulations. Therefore, when two or three dozen plates are inserted between the dies, A, B, the transition from a to z is so gradual, that the metal can safely proceed from a to b, from b to c, and so on, and it will be progres- sively drawn in and raised without injury. When one or two pieces alone are required, they are blocked-down to fit the mould, by laying above them a thick piece of lead, which latter is struck with the mal- 212 WORKS IN SHEET METAL, MADE BY RAISING. let or hammer; by the yielding resistance the lead opposes, the thin metal is drawn into the die with much less risk of accident than if it were subjected to the blows without the intervention of the lead. In producing many pieces, however, one piece a, is added at the top, between every blow, and one piece z, is also removed from the bottom ; occasionally two, three or more are thus added and removed at one time, and generally, as the concluding step, every piece is struck singly between the dies, such as Fig. 219, which exactly cor- respond. In general the process of annealing must be also resorted to once or more frequently during the transition from a to z. For the best works the bottom die is mostly of hardened steel, sometimes of cast iron, or hard brass; the top die is also of hardened steel in the best works, but in very numerous cases lead is used, from the readiness with which it adapts itself to the shape required. Stamping is very common for many works in brass, but which would be inapplicable if the pieces had perpendicular and lofty sides, as in Fig. 217, page 210 : such lines, although rounded by the suc- cessive thicknesses of metal, would still present perpendicular sides, and therefore render this mode of treatment with dies impracticable, without r#ference to cost. Thimbles are raised at five or six blows, between as many pairs of conical dies successively higher, but the metal requires to be annealed every time. Peculiarities in the Tools and Methods. — Before concluding the remarks on raised works, it may be desirable to revert to some of the principal and distinguishing features of the tools employed in these arts. As a general rule, it will be observed that all these manifold shapes are the more quickly obtained, the more nearly the various tools assimilate to the works to be wrought. . For instance, the several dies and swage tools quickly and accurately produce mouldings, of the specific forms of the several pairs of dies ; but it is utterly impossible to extend this method to all cases, and the pro- gressive changes required, from the fiat disk, the cylinder or cone, as the case may be, to the finished object; and therefore certain ordinary forms of tools can alone be employed, and they are con- tinually changed as the work proceeds. For hollow works with contracted mouths, the inner tools are required gradually to decrease in bulk and to increase in length, in order to enter the cavities ; but they can be rarely the exact coun- terparts of the transient forms of the works, nor is it always desira- ble they should be so. The tools are often required to be bent at the end, to extend within a shoulder or gorge; the small stake in the tool, Fig. 155, is an example of this ; the dotted line represents the work, such as the perforated cover of a cylinder, or the top of a teakettle: the strong wrought-iron arm or horse, Fig. 155, carries the small steel tools, and which latter may be also fixed by their shanks either in the bench or vice, according to circumstances. There are many curious circumstances respecting the modification of the materials for, as well as the forms of, the hammers and anvils, if the use of these terms may be extended to the various contrivances, PECULIARITIES OF THE TOOLS. 213 by the action and re-action of which thin metal works are produced ; and the concluding examples are advanced to bring some of these' peculiarities of method into notice. The plated metals have so thin a coating of silver, that they re- quire more expert hammering than similar works in solid silver, otherwise the removal of the bruises left by the hammer, by scraping and polishing, might wear through the silver and show the copper beneath. The bruises are therefore driven to the copper side, by hammering upon the silver or the face, with a very smooth planish- ing hammer, and covering the anvil or bottom tool with cloth. On account of the elasticity thus given, the blows become so far hollow that all the little bruises descend to the copper side, or that which is exposed to the cloth, and the face becomes perfectly smooth. When the inside of a vessel is required to be smooth, it is the hammer that is covered with cloth, stretched over it by an iron ring, and the polished stake or head within the vessel is left uncovered ; and in those cases in which the work is required to be good on both sides, the faces both of the hammer and anvil are each muffled; this gives them some of the elasticity of wooden tools, but with superior definition of figure. Plated works are generally furnished with an additional thickness of silver at the part to be engraved with a crest or cipher, in order that the lines may not penetrate to the copper; should it, however, be requisite to remove the engraved lines for the substitution of others, the following mode is resorted to. The object is laid upon the anvil over a piece of sheet lead and it is struck with a bare hammer upon the engraved lines ; these latter are therefore hollow as regards the face of the hammer; in conse- quence of which, the re-action of the lead causes it to rise in ridges corresponding with the engraved lines, and to drive the thin plated metal before it. The device is thus in great measure obliterated from the silver face and thrown to the copper side, so as to leave much less to he polished out ; this ingenious method is appropriately called reversing. In making vases, such as Figs. 144 and 146, page 184, the metal is first driven into concave wooden blocks with a wooden mallet, as in Fig. 210, in order to gather up the metal into the fluted concave 212, but without making any sensible alteration in its thickness. In the next stage of the work, metal tools are alone employed, whether the object be made by raising-in with hollow blows, or by setting-out with solid blows, as adverted to; and the sizes and curv- atures of the tools require to be accommodated to the changes of the work. Supposing the vases to have either concave or convex flutes, orna- mental details are now sketched with the compasses upon the plain surface of the vase ; and if from the shape of the works swage tools similar to Fig. 164, cannot be employed for raising the projecting parts, they are snarled-up, by the method represented in Fig. 221. Thus at v are the jaws of the tail vice, in which the snarling-iron s, 214 WORKS IN SHEET METAL, MADE BY RAISING. is securely fixed: the extremity b, which is turned up, must be suffi- ciently long to reach any part of the interior of the vessel, but yet small enough to enter its mouth. The work is held firmly in the two hands, with the part to be raised or set out exactly over the end b; and when the snarling-iron is struck with a hammer at 7i, the re- action gives a blow within the vessel, which throws the metal out in the form of the end of the tool, whether angular, cylindrical, or globular: except in small works, two individuals are required, one to hold and the other to strike. Figs. 221. 222. 223. Figure 222 shows the last stage of the work prior to polishing ; thus in finishing the flutes and other ornaments after they are snarled- up, the object is filled with a melted composition of pitch and brick- dust — sometimes the pitch is used alone, or common resin is added — the ornaments are now corrected with punches or chasing tools of the counterpart forms of the several parts ; some portions of the metal are thus driven inwards, whilst those around rise up from the displacement and reaction of the pitch. To avoid injuring the lower surface of the work it is supported upon a sand-bag b, like those used by engravers, and the perpendicular lines p, denote the usual posi- tion of the chasing tool. Works in copper and brass are sometimes filled with lead at the time of their being chased, but the silversmiths and goldsmiths are studious to avoid the use of this metal, as, if it gets into the fire along with their works, it is very destructive to them. Pitch and mixtures of similar kind, are constantly used in the art of chasing in its more common acceptation; from its adhesive and yielding nature it is a most appropriate support, as it leaves both hands at liberty, the left to hold the punch, the right for the small hammer used in striking it. The pitch-block, Fig. 223, is employed to afford the utmost choice of position for works from the smallest size to those of six or eight inches long. The lower part is exactly hemispherical, and it is placed upon a stout metal ring or collar of corresponding shape, covered with leather. The mass of metal makes a firm solid bed to sustain the blows, and the ball and socket contact, allows the work to assume every obliquity, and to be twisted round to place any part towards the artist. Large flat works in high relief are frequently sketched out and commenced from the reverse face, the prominent parts of the sub- FLATTENING THIN PLATES. 215 ject being sunk into the pitch, which after a short time must be melted away to allow the metal to be annealed; and this is frequently required when the works are much raised. In the concluding steps the artist works from the face side. Many of the chased works are cast in sand moulds from metal models, which have been previously chased nearly to the required forms ; the castings are first pickled to remove the sand coat, and in such cases, chisel and gravers are somewhat used in removing the useless and undercut parts. Many ancient specimens of armor, gold and silver plate, vases and ornaments, are excellent examples of raised, chased, inlaid and engraved works, both as regards design and execution. In our own times, the Hungarian silversmith, Szentepeteri, has produced a very remarkable alto-relievo in copper, taken from Le Brun's picture of the battle of Arbela, in which some of the legs of the horses stand out and are entirely in relief from the background. The art of chasing may be considered as the sequel to that of forging, (that is, setting aside the employment of the red-heat,) but the various hammers and swage tools now dwindle into the most diminutive sizes, and are required of as many shapes as may nearly correspond with every minute detail of the most complex works. Some of them are grooved and checkered at the ends, and others are polished as carefully as the planishing hammers, that they may impart their own degree of perfection and finish to the works; in a similar manner that the polish and excellence of coins and medals are entirely due to that of the dies from which they are struck, the chasing process being as it were a minute subdivision of the action of the die itself. The Principles and Practice of Flattening thin Plates of Metal with the Hammer. — I have purposely reserved this sub- ject to be distinct, on account of its great general importance in the arts, and have placed it last, in order that the various applica- tions of the hammer might have been rendered comparatively familiar ; for, although the plane surface may appear to be of more easy attain- ment than many of the complex forms which have been adverted to, such is by no means the case. The methods employed are entirely different from that explained at page 72, in reference to flattening thick rigid plates, which are corrected by enlarging the concave side, with blows of the sharp rectangular edge of the hack-hammer, applied within the concavity. A method which bears some analogy to that employed by the joiner in straightening a board which is curved in its width, namely, the contraction of its convex side by exposure to heat. In thin metal plates neither of these modes is available, as the near proximity of the two sides causes both to be influenced in an almost equal degree by any mode of treatment. Thin plates, are flattened by means of solid and hollow blows, which have been recently explained, but they require to be given with considerable judgment ; and a successful result is onlv to 216 WORKS IN SHEET METAL, MADE BY RAISING. obtained by a nice discrimination and considerable practice. All therefore that can be here attempted is an examination of the princi- ples concerned, and of the general practice pursued ; as the process being confessedly one of a most difficult nature, success is only to be expected or attained by a strict and persevering regard to principle. As respects thin works, no figure is so easily distorted as the true plane, and this arises from the very minute difference which exists between the span or chord of a very flat arch, and its length measured around the curve. For example, imagining the span of an arch to be one inch, and the height of the same to be one-twentieth of an inch, the curve would be only about one 200th of an inch longer than the span : and therefore, if any spot of one inch diameter were stretched until, if unrestrained, it would become one inch and one 200th in diameter, such spot would rise up as a bulge one-twentieth of an inch high. This trivial change of magnitude would be accom- plished with very few blows of the hammer, and much less than this would probably distort the whole plate. In general, however, there would be not one error only, but several, the relationship of which would be more or less altered with nearly every blow of the hammer ; thence arises the difficulty, as the plane surface cannot exist so long as any part of the plate is extended beyond its just and proportional size, and which it is a very critical point to arrive at. There is another test of the unequal condition of flat works besides that of form, namely, their equal or unequal states of elasticity, and which is an important point of observation to the workman. For instance, if we suppose a plate of metal to be exactly uniform in its condition, it will bend with equal facility at every point, so that bend- ing a long spring, or saw, will cause it to assume a true and easy curve ; but supposing one part to be weaker than the remainder, the saw will bend more at the weak part, and the blade will become as it were two curves moving on a hinge. When such objects are held by the one extremity and vibrated, the perfect will feel as a uniform- ly elastic cane ; the imperfect, as a cane having a slight flaw, which renders it weak at one spot ; and in this manner we partly judge of the truth of a hand-saw, as in shaking it violently by the handle, it will, if irregularly elastic, lean towards the character of the injured cane, a distinction easily appreciated. Fig. 224. abed A thin plate of metal can only be perfectly elastic, when it is either a true plane or a true curve, so that every point is under the same circumstances as to strength. Thus a hemisphere, as at a, 224, possesses very great strength and rigidity owing to its convexity, FLATTENING THIN PLATES. 21T but as the figure becomes less convex it decreases gradually in strength, and when it slides down to the plane surface, as at/, the metal assumes its weakest form. A nearly plane surface will necessarily consist of a multitude of convexities or bulges varying in size and strength, connected by intermediate portions, which may be supposed to be plane surfaces ; the whole may be considered as greatly exaggerated in the figure. The bulged parts are stronger than the plane flat parts, it follows that the bending will occur in preference at the plane or weak parts of the plate, precisely as in the injured cane. When the bulges are large but shallow, they flap from side to side with a noise at every bending, as their very existence shows that they cannot rest upon the neutral or straight line ; such parts are said to be buckled, their ready change of position renders them flaccid and yielding under the pressure of the fingers, and they are there- fore called loose parts, but at the same time it is certain that they are too large. On the contrary, those parts which are intermediate between the bulges, feel tight and tense under the fingers, because they are stretched in their positions and rendered comparatively straight, by the strong edges of the bulged or convex parts : the flat portions are the hinges upon which the bulged parts move, and such flat parts are sensibly too small for their respective localities, the others being too large. Now, therefore, in prescribing the rule for the avoidance of these errors, it is simply to treat every part alike, so that none may be stretched beyond its proper size so as to become bulged, and thereby to distort the whole plate. When the mischief has occurred, the remedy is to extend all the too-small parts, or the hinges of the bulges to their true size, so as to put every part of the plate into equal tension, by allowing the bulged or too-large parts room to expand. Uniform blows should be therefore directed upon all the straight or too-small parts of the plate, the force and number of the blows being determined by the respective magnitudes of the errors, and the rigidity of the plate. In flattening plates, the greater part of the work is done with solid blows upon a true and nearly flat anvil; the face of the ham- mer is slightly round, and its weight and the force of the blows are determined by the strength of the plate, the slighter plate requiring more delicate blows, and being more difficult to manage. In the commencement, the rectangular plate is hammered all over with great regularity in parallel lines beginning from one edge ; it is generally turned over and similarly treated on the other side. Cir- cular plates are hammered in circular lines beginning from the centre, that is supposing the plates of metal to be soft, and in about the ordinary condition in which they are left by the laminating rollers; as the equable hammering gives a general rigidity, which serves as a foundation for the correctional treatment finally pursued. With a steel plate hardened in the fire, and which is already far more 218 WORKS IN SHEET METAL, MADE BY RAISING. rigid than the soft plate, it is necessary to begin at once upon the reduction of the errors and distortions, which usually occur in the hardening and tempering. The hammer should be made to fall on one spot with the uni- formity of a tilt-hammer, the work being moved about beneath it. As, however, the regularity of a machine is not to be expected from the hand, it is scarcely to be looked for that the work shall be at once flat. Whilst the errors are tolerably conspicuous or conside- rable, the man accustomed to the work will still keep the hammer in constant motion, and will so shift the work, as to bring the tight parts alone beneath its blows, hammering with little apparent con- cern just around the margins of the loose parts, or at the foot of every rise. As the plate becomes more nearly flat, it is necessary to proceed more cautiously, and to hold the plate occasionally be- tween the eye and the light to learn the exact parts to be enlarged; the straight-edge is also then resorted to. In many works, especially in saws which require very great truth, the elasticity is also examined ; this is frequently done by holding the opposite edges of the plate between the fingers and thumbs, and bending them at various parts. As previously explained, all the portions which are technically called tight, or those lines upon which the loose enlarged parts appear to move as on hinges, are strictly the parts to be extended by gentle hammering. For instance, sup- posing that in the plate, Fig. 225, there were only one central buckle Figs. 225. 226. a, the whole exterior portion would require to be stretched, begin- ning from the base of the bulge: but it must be remembered the extreme edges of the plate will yield with greater facility than the more central parts, and therefore require somewhat fewer blows, as the blows are all given as nearly as possible of the same intensity, and the number of them is the source of variation. If, as it is more to be expected, there are two or more loose parts, such as a, and b c, the more quiescent part between them must be first hammered, as working upon any loose or bulged part only magnifies the evil. Where the intermediate space is narrow, as at d, less blows will be needed, and such tight parts will soon, and sometimes very suddenly, become loose from the two bulges melting into one. It should be rather the general aim to throw the several small errors into a large one, by getting the plate into one regular FLATTENING THIN PLATES. 219 sweep ; dealing the blows principally between the dotted lines, not carelessly so as to increase the general departure from the plane surface, but with an acute discrimination to lead all the defects in the same direction, by making the plate as it were a part of a very great cylinder, as at e or/, Fig. 226, but with as little curvature as possible. When this is accomplished, and that the work is free from loose parts, it is hammered on the rounding side, in lines parallel with the axis of the imaginary cylinder; so that in e, the lines would be parallel with the edge from which the rise commences, and in/, or the plate which is bent diagonally, the lines of blows would be necessarily oblique, although as regards the curvature, the same as in e. The reason why any reduction of curvature should at all result from this treatment, (action and reaction being alike,) is due to the greater roundness of the hammer than the anvil; the rounder hammer effects the change more rapidly, but also the more indents the work. a b ii Fig. 227. b a S In a circular saw, the general aim is first to throw the minor errors into one regular concavity, which may be supposed to extend to b,b, in the imaginary section, Fig. 227, and then the margin a, b, ■would be hammered in a proportional degree, to enlarge it until it just allowed the interior sufficient room to expand to the plane sur- face. It may happen in the course of the hammering that from b to b, becomes loose, whilst the extreme edge a a, is also loose, and that the intermediate part towards b, requires to be stretched. These minor differences cannot be told alone by bending the plate with the fingers, as errors frequently exist which are too minute to yield to their pressure, and then the eye and straight-edge are conjointly employed in the examination. In a saw, the general aim is to leave the edge rather tight or small, as then the small amount of expansion it acquires when at work, from heat and friction, will enlarge the edge just sufficiently to bring the saw into a state of uniform tension. Otherwise, if be- fore the saw is set to work, the edge is fully large enough, when ex- panded by the heat, it is almost sure to become loose on the edge, and to vibrate from side to side, without proper stability; so as to produce a wide irregular cut, and make a flanking whip-like noise, arising from the violent vibration of the buckled parts of the plate, in passing through the saw kerf ; the sides of the wood will then exhibit ridges like the ripple marks on the sandy shore. In hammering all plates, preference should in the like manner be given to keeping the edge rather small or stiff, to serve as a margin or frame to the more loose parts within ; it gives a degree of stability 220 WORKS IN SHEET METAL, MADE BY RAISING. somewhat as if the object had a thickened rim, and when a rim really exists, the process of flattening is comparatively easy. If by undue stretching, the edge is made too loose, the whole piece becomes flaccid and very mobile, and we seem to lose the governing power, or those retaining points by which the changes of the plate are both influenced and rendered apparent; the edge should be there- fore always kept somewhat tight, from being proportionally less ham- mered, especially as the edge more easily admits of expansion than the inner part. As a general rule, it may be said that every part of the plate which is straight and tense, whilst others are curved and flaccid, denotes that every straight part is under restraint; and that its straightness is due to its being, as it were, stretched either lengthways or around its edges, by the other parts which are too loose, and therefore arched and also strong. In such cases, the straight lines require to be ex- tended in length, to allow sufficient room for the curves to expand to their proportional sizes. This refers not only to small local errors towards the inner part of the plate, as explained by diagram, Fig. 225, p. 218; but should the one edge of a plate be tolerably straight, whilst the opposite is loose and flaccid, the rule also applies with equal truth, and the straighter side must be hammered ; in this case the curved side is as it were a great bulge cut in two parts. Should a circular saw have a sudden dent, such as at g, Fig. 227, on the last page, standing the reverse way, and which may result from its having rested upon a small lump of coke whilst in the fire, the first blows will be given on the hollow side, between the lines i i, to lessen the abruptness of the margin by stretching it to the dotted curve, and then it will be driven downwards by violent blows, to form a part of the general sweep or concavity; a little time is gained by these driving blows, over the mode of stretching by the hammer. The foregoing descriptions have all referred to solid blows, upon the face of the hard anvil, but to expedite the process, recurrence is often had to blocking, which is only one application amongst many others of a wooden anvil or block with a narrow flat-faced hammer, such as Fig. 200. In this case the blows are to a certain extent hollow, as the wood immediately beneath the hammer-face yields to the blow, whereas the margin around the same does not. Such blows are therefore unquestionably hollow, and bend with very little stretching. The blocking is considerably employed in saw-making, after the loose parts have been entirely removed, as the hollow blows correct any slight errors of figure, by bending alone, and with little risk of stretching the plates, if the work be delicately performed. Towards the conclusion, however, all the different modes of work are required to be used in combination, as the true condition of the plate is only the exact balancing of all the forces, or of the tension of the several parts ; and it constantly happens that attention to one error causes a partial change and fluctuation throughout the whole. It therefore requires great tact to know when to leave the anvil for "WIRE DRAWING. 221 the block, and when to return to the anvil, and so on alternately ; and also which side of the plate should be upwards for the time, which particular points should be struck, and the required force of the blows. Of course, within certain limits, a thick plate is easier to hammer than a thin one, as the latter is difficult from its excessive mobility ; also a soft plate of iron is more difficult than a hard plate of steel, although the latter requires more blows to produce the same effect ; but when the works are very thick they become laborious, and the difficulty always increases rapidly with the size of the plate. Those who may desire to practice this art should therefore com- mence with a plate some 4, 6, or 8 inches square, and moderately stout, and subsequently proceed to pieces larger and thinner. They will also find some advantage in raising the anvil to within about a foot of the eye, as the alterations can be then more easily seen whilst the work lies on the anvil, and the effect of any predetermined blows can be the better watched. One other observance is essential, namely, patience; as, although the process is thoroughly reducible to system, and no blow should be struck in vain, the beginner will frequently find it necessary to pause, examine, and consider, espe- cially as the errors decrease; whereas the accustomed eye will follow the fluctuations of the plate almost without intermission of the blows, and will also accomplish the task with the fewest possible number of blows, which is the great object. Indeed it may happen from hammering some parts of a plate ex- cessively and improperly, that it is rendered so hard and rigid, as to make its correction very tedious, or indeed nearly impossible without previous annealing, as the plate might burst or crack from the exten- sion being carried beyond the safe limit of malleability. As in raised works, the annealing is mostly done by a gentle red heat ; but in hardened steel plates, a slight increase of temperature barely suffi- cient to discolor the plate, will make a perceptible difference ; and this latter process is always the last step in making a saw, in order to restore, by a gentle heat, the proper elasticity which has been mysteriously lost in the grinding, polishing, and hammering required in its manufacture. PROCESSES DEPENDENT ON DUCTILITY. Drawing Wires, etc. — The ductility of many of the metals and alloys, or the quality which allows them to be drawn into wires, is applied to a variety of curious uses in the manufacturing arts, and the process may be viewed as the sequel to the use of grooved and figured rollers; but the ductile metals submit to this process with various degrees of perfection. In drawing wire, the metal is first prepared to the cylindrical form, either directly by casting, or between rollers with semicircular grooves; and the process is completed by pulling the metal through a series of holes gradually less and less, made in a metallic plate, by 222 PROCESSES DEPENDENT ON DUCTILITY. which the wire becomes gradually reduced in size, and elongated; but, as in rolling, the process of annealing must be resorted to at proper intervals. In general, the draw-plates are made of hardened steel, and they are formed upon the same principle, whether for round, square, or complex sections, either solid as wires, or hollow as tubes; the sub- stance of the metal is partly kept back, as in a wave, by a narrow ridge within the draw-plate, acting as a burnisher. The plates are generally made of hardened steel, or else of alloys of partly similar nature, which allow the holes to be contracted and repaired, by closing them with blows of a pointed hammer or punch around the hole. The holes for round wires are sometimes ground out from both sides upon the same brass cone or grinder, the sides of which vary in obliquity from 10 to 30 degrees, according to the metal to be drawn; for the sake of strength the ridge is mostly nearer to the side on which the metal enters, and the sharp edge is also removed, either by wriggling the plate upon the grinder in order to round the inside, or in any other manner. The end of the wire is pointed, to enable it to be passed through the hole, and it is then caught by a pair of nippers, themselves at the extremity either of a chain, rope, toothed rack, or screw, by which the wire is drawn through by rectilinear motion. The nip- pers or dogs resemble very strong carpenters' pincers or pliers, the handles of which diverge at an angle ; they are sometimes closed by a sliding ring at the end of the strap or chain, which slides down the handles of the nippers; there are some other modifications, all acting upon the same principle, of compressing the nippers the more forcibly upon the wire the greater the draught. It requires a pro- portionally strong support to resist the strain; and to avoid the fracture of the hardened steel draw-plate, it is usually placed against a strong perforated plate of wrought-iron. In manufactories where large quantities of wire are made, the wire is more usually attached to the circumference of a reel, which is made to revolve by steam or other power. It is necessary often to anneal the wire, but no general rule can be stated in respect to its recurrence ; and before resuming the draw- ing process, the wire is invariably immersed in some acid liquor or pickle, to remove the slight coating of oxide, which would otherwise rapidly destroy the plates, (as many of these metallic oxides are used in polishing,) in general some lubricating matter is applied to reduce the friction, as beer-grounds, starch- water or oil ; and for gold and silver, wax is generally used. Most of the wire is drawn upon reels, and is therefore met with in circular coils, and it is necessary, in almost every case, to straighten it before use. The soft annealed wires, such as the copper wire used for bell-hanging, the soft iron binding-wire used in soldering, and others, are stretched and straightened by fixing the one end, STRAIGHTENING WIRE. 223 and pulling the other with a pair of pliers; or short pieces of soft ■wire may be straightened by rolling them between two flat boards. Soft steel wire for making needles is straightened by rolling or rubbing : it is cut up in lengths of 4 or 5 inches; and arranged in cylindrical bundles, within iron hoops of 4 inches diameter; the rub- ber is a bar of cast-iron, about two feet long, narrow enough to lie between the rings. The hard-drawn and unannealed wires, used for making pins, bird- cages, blinds, and numerous other wire-works, are too elastic to yield to the above methods, and Fig. 228 represents the mode employed to take the spring out of them, or in other words, to straighten these hard wires. The coil of wire on the reel/, which revolves on a pin, is drawn through the riddle g, by the pliers. The riddle is a piece of wood or metal with sloping pins, which lean alternately opposite ways, so as to keep the wire close down on the board, and yet to compel it to pursue a slightly zigzag, or rather serpentine course, which is considerably magnified in the figure. In practice, the riddle is made wider than represented, so as to contain about half a dozen rows of pins suitable to as many sizes of wire ; between every set of pins, and fixed close down to the board, is a straight wire about three times the diameter of the one to be straightened : very great importance is attached to this latter or central wire ; being itself straight, it serves as a metallic bed for the small wire to run upon, and it thereby gets worn into furrows cross- ing it obliquely from pin to pin. The board is retained by two staples at the far end, which fit loosely on two studs or nails driven into the work-bench; The pins are equivalent to the three forces a, b, c, of the bending- machine, page 189, several times referred to. Were the first three pins critically placed, they would suffice to bend the wire to the limit of its permanently elastic force, and would leave it perfectly straight ; commonly, however, five pins are used, and sometimes seven or nine. The same riddle will not serve for wires differing in diameter ; and were this simple tool more expensive, so as to render it desirable, a universal riddle might be made by placing the pins b and d, under a simple screw-adjustment ; but in practice, a tap of the hammer is found sufficient to correct their positions. Figs. 228. 229. b 224 PROCESSES DEPENDENT ON DUCTILITY. It is necessary to be very particular in pulling the wire through, not to allow it to lean sensibly against either of the last two pins, or it will assume a curve ; and in this manner, by drawing the wire designedly at different angles, it may be thrown into any required circular arc, instead of the right line. Cylindrical shafts may be viewed as large wires, and when they are turned with ordinary care, in a slide-lathe with a back-stay, it becomes pretty certain that the shafts are circular, and of true diam- eters ; but they are frequently more or less crooked or bent when they leave the lathe. In straightening the axes or shafts intended for the Calculating Machine, which were of steel, about 6 to 10 feet long and £ to 1 inch diameter, three half-round dies, Fig. 229, a, c, fixed to the bed of a fly-press, and b, to the screw of the same, which was so adjusted that b could only bend the portion of the shaft between a, e, to the limit of its elasticity ; and therefore, by keeping the press constantly at work, drawing the rod through, and twisting it round so as to bend it at every point of its length, every shaft was made perfectly straight. The straightening of black wrought-iron shafts previous to turn- ing, is now accomplished by three equidistant rollers, say a foot diameter and twelve feet long, similar to Fig. 168, p. 189. The shaft is heated to redness, and the centre roller is raised at the mo- ment of its introduction, and then a few turns are given to the whole ; this straightens the shaft, and retains it so until partially cooled ; the other end of the shaft, should it exceed the length of the rollers, is then heated, and treated in the same manner. All these modes are highly useful, as they operate upon the ma- terials without partially condensing any point, from which unequal treatment a loss of figure would be almost certain to occur, when any such condensed point is partially removed by the turning-tool or otherwise ; as it appears to be quite impossible to prevent all sorts of perplexities, when, by any mode of operation, the one point of a material receives a different treatment from the re- mainder. The great bulk of wire is cylindrical, but draw-plates are also made of various other forms, as oval, half round, square, and trian- gular, for the wires Figs. 230 ; and also of more complex forms, as for the production of steel of the sections of Figs. 231, known as pinion wire, the whole of the illustrations being printed from the wires themselves. The largest of 231, serves for the pinions of clocks, and the smallest for those of watches ; in these cases the en- tire arbor (which carries one of the toothed wheels) is made of the pinion wire, but the teeth are removed from every part, excepting that which works into the adjoining wheel of the train. The plates for pinion wire are exactly the same as the others in principle, and exhibit a remarkable degree of perfection in their construction, as for every size there must be a series of many holes gradually assum- MULTIFORM WIRES, FOR VARIOUS USES. 225 ing the form of a circular foliated Gothic window, with six, seven eight or more foils. Figs. 230. 231. 232. Some of the printed calicoes and muslins are also curious examples of the wire-drawing process ; the pattern Fig. 232, consists of no less than 205 different pieces of copper wire of various forms, fixed into a wood block ; the surface of the wires, when filed smooth, are printed from after the manner of printers' types; the few detached pieces, Fig. 233, show some of the sections of such wires, and which may be combined in endless variety. In the same manner the specimen of music, Fig. 234, is printed from the surfaces of detached wires and slips of copper fixed in a wooden block ; this is only one amongst the many ingenious processes for printing music by letter-press or surface printing. Figs. 235, 236. 237. 238. Fig. 235 represents the double-plates or swage-lits used for some of the pieces in Figs. 232 and 234 ; the dies are fitted into a small frame or cramp with a side screw, (much the same as dies for cut- ting screws,) so that the metal may be gradually reduced by one pair of swage-bits. This method is very much employed by the silver- smith and goldsmith for mouldings, the tools being much cheaper than rollers : the piece 236 was thus prepared for the edging of silver and gold boxes ; it is bent round to the form of the box or cover, whether square, circular or oval, and the rebate on the straight 226 PROCESSES DEPENDENT ON DUCTILITY. side of the band serves for receiving the flat plate to constitute the cover. The most perfect example of this application of the drawing pro- cess is in the British Mint : two fixed rollers are employed after the manner of a draw-plate, and the long strip of gold or silvery when rolled very nearly to the thickness, is drawn through the stationary rollers, by dogs attached to one of the links of an endless chain, which is in continual motion from the steam-engine. It was found barely possible to make the surfaces of revolving rollers so truly con- centric that the equality of thickness in the metal could be obtained with the rigorous exactness required, so as to dispense entirely with the necessity of scraping every piece individually, a mode still practiced in some of the Continental mints. The metal, when drawn, is tested by punching out one blank at each end ; these are carefully weighed, and if found correct, the whole strip is punched into blanks ; and such is the accuracy of the drawing and punching processes, that without the smallest after- adjustment, any fifty or one hundred blanks weigh alike to the fraction of a grain. The window lead, shown in section in Fig. 237, does not admit of being drawn in the ordinary manner, from the softness of the mate- rial, nor of being rolled, because of its undercut section; the two principles are, therefore, curiously combined in the glazier s vice. It may be conceived that the shade lines of 238, represent parts of two narrow rollers with roughened edges, (equal in thickness to the glass,) which indent the bottom of the groove, and thereby carry the lead between the figured side-pieces s s, one only shown. In some cases cutting is combined with drawing, cutters are then fixed to the draw plate ; this method has been adapted to making rules and similar rods ; and in perfecting the flattened wire for the reeds used in looms, the edges are rounded by reeling the wire beneath a forked cutter, a process intermediate between turning and planing. The process of wire-drawing is seldom practiced by the general mechanician, and still less by the amateur; but when it is necessary to produce a wire either of some unusual section not prepared by the manufacturer, or that the equality of size requires more than usual exactness, the process may be accomplished in the small way, by fixing the draw-plate in the tail-vice and drawing the wire through with the pliers or a hand vice, or by a reel moved by a winch handle. Drawing Metal Tubes. — The perfection of tubes is mainly de- pendent on the drawing process, conducted in a manner similar to that employed for drawing wire. Many of the brass tubes for com- mon purposes, when they have been bent up and soldered edge to edge, as in Fig. 183, page 194, are only drawn through a hole which makes them tolerably round and smooth externally, but leaves the interior of the tubes in the condition in which they left the fire after they were soldered, and nearly as soft as at first. The sliding tubes for telescopes, and many similar works, are " drawn inside and out," and rendered very hard and elastic, by the TUBES DRAWN INSIDE AND OUTSIDE. 227 method represented in Fig. 239, the form of the plate b being ex- aggerated to explain the shape. For example, the tube when sol- dered is forced upon an accurate steel cylinder or triblet, in doing which it is rounded tolerably to the form with a wooden mallet, so as Figs. 239. 240. -\ ; j ;3» ; cm 6 L - to touch the mandrel in places ; the end is set down with the hammer around the shoulder or reduction of the triblet, and on drawing the tube and triblet, by means of the loose key or transverse piece a, through the draw-plate 6, the tube becomes elongated, and con- tracted close upon the triblet at every part, as the metal is squeezed between the mandrel and plate. The fluted tubes for pen- cil-cases, such as c, are drawn in this manner through ornamental plates, the triblets being in general cylindrical. Some of the drawn tube called joint-wire, is much smaller than d, and is used by silver- smiths for hinges and joints. It is drawn upon a piece of steel wire, which being too small to admit the shoulder for holding on the tube, the latter is tapered off with a file, and the tube and wire are grasped together within the dogs, and drawn like a piece of solid wire. A semicircular channel is filed half-way in both the parts to be hinged, and short pieces of the joint-wire are soldered in each alternately. Triangular, square, and rectangular brass tubes are in common use in France for sliding rules and measures; these are made in draw- plates with movable dies, Fig. 240, which admit of adjustment for size ; the dies are rounded on their inner edges, and are contained in a square frame with adjusting screws, and the whole lies against a solid perforated plate. In the general way, tubes of small diameters are completed at two draughts — sometimes three are used — and by this time the tube has received its maxium amount of hardness; therefore the first thickness of the metal and the diameter of the plates require a nice adjustment. The tube, when finished, is drawn off the triblet by putting the key through the opposite extremity of the same, and drawing the triblet through a brass collar, which exactly fits it ; this thrusts off the tube, which will in general be almost perfectly cylindri- cal and straight, except a trifling waste at each end. It requires a very considerable assortment of truly cylindrical triblets to suit all works : and when the tubes are used in pairs, or to slide withinone another, as in telescopes, it calls for a nice cor- 228 PROCESSES DEPENDENT ON DUCTILITY. respondence or strict equality of size, between the aperture of the last draw-plate and the diameter of the triblet for the size next larger; and as these holes are continually wearing, it requires good manage- ment to keep the succession in due order, by making new plates for the last draught and adapting the old ones to the prior stages. Some- times, for an occasional purpose, the triblet is enlarged by leaving a tube upon it and drawing the work thereupon ; but this is not so well as the turned and ground surface of the steel triblet. Tubes from ^ inch internal diameter, and 8 or 10 inches long, up to those of 2 or 3 inches diameter, and 4 or 5 feet long, are drawn vertically by means of a strong chain wound on a barrel by wheels and pinions, as in a crane. In Messrs. Donkin's enormous tube- drawing machine, which is applicable to making tubes, or rather cylinders, for paper-making and other machinery, as large as 26J inches diameter and 6| feet long, a vertical screw is used, the nut of which is turned round by toothed wheels driven by six men at a windlass. . „ , , , All the tubes previously referred to are made ot sneet-metais turned up and soldered edge to edge, but lead and thin pipes for water and other fluids have, for a long period, been cast as thick tubes, some 20 to 30 inches long, and extended to the length of 10, 12 or 15 feet on triblets, which require to be very exactly cylindri- cal, or they cannot be withdrawn from the pipes. The brass tubes for the boilers of locomotive engines are now similarly made by casting and drawing without being soldered, and some of these are drawn taper in their thickness. The ductility of tin is very great; it is from the ordinary tin tube of commerce, (which is cast about 2 feet long, £ inch thick, and drawn out to about 10 feet,) out of which is made the col- lapsable vessels for artists' oils and colors. Pieces 3 inches long were extended to 36 inches by drawing them through ten draw-plates, which are sometimes placed in immediate succession, the one to commence just as the other had finished. The tube seemed to grow under the operation, and it was thus reduced, without annealing, from half an inch thick as cast, to the 170th of an inch thick, and it was stretched fully sixty times in length. This mode of making the tubes of collapsable vessels, has been superseded by another, presenting far greater ingenuity, and described hereafter. Some of the smallest tin tube of commerce, when removed from the ten-foot triblet, is drawn through smaller plates without any triblet being used ; this reduces the diameter with little change of thickness, so that the half-inch tube becomes a nearly solid wire, measuring about \ inch diameter externally, which is known as bead- ing, and used to form the raised ledges around tables and counters covered with pewter. TUBES DEAWN INSIDE AND OUTSIDE. 229 The accompanying sectional view gives the hydraulic press, and an arrangement for manufacturing lead pipe. The principle is claimed by Tetham, Cornell, Burr, and others. C is the hydraulic cylinder, and R the ram rising from it. A cross-head is attached to the hydraulic cylinder, and connected with the upper cross-head IT, by rods D D. On the top of the ram a head-block B is placed. A foot-block F is attached to the bottom of the lead cylin- der L, and the head-block, the foot-block, and the lead cylin- der are secured firmly together by bolts T T. By this ar- rangement the lead "plug" or cylinder L, is moved up- wards by the ram R of the hydraulic press. To the up- per cross-head IT, the hollow piston P is attached by bolts S S. The die Q, placed at the lower end of the piston, hollow throughout, communi- cates with the aperture A, in the upper cross-head. The movable core I, when in use, is firmly fixed to the head- block of the ram and extends upwards through the centre of the lead cylinder, and a little above it, so that it is inserted through the die Q at the end of the hollow piston P. The position of the core is regu- lated by means of the set- screws V V, which move the core and set it centrally to the die. When all the parts are thus arranged the lead cylinder is raised up. to the lower end of the piston, the end of the core passing through the die. The ram is forced upwards, carrying the cylinder X that contains the plug of lead L; this cylinder X passes over the hollow piston P. The pipe is formed at the point of pressure Q, it then passes through the hollow piston and out through the aperture A. 230 SOLDERING. SOLDERING. General Remarks and Tabular View.— Soldering is the pro- cess of uniting the edges or surfaces of similar or dissimilar metals and alloys by partial fusion. In general, alloys or soldersof various and greater degrees of fusibility than the metals to be joined, are placed between them, and the solder when fused unites the three parts into a solid mass; less frequently the surfaces or edges are simply melted together with an additional portion of the same metal. The chemical circumstances to be considered in respect to soldering are, for the most part, set forth in the section on the fusibility of alloys, page 120 to 123, to which the reader is referred. It is there explained that the solders must be necessarily somewhat more fusi- ble than the metals to be united; and that it is of primary importance that the metallic oxides and any foreign matters be carefully re- moved, for which purpose the edges of the metals are made chemi- cally clean, or quite bright, before the application of the solders and heat; and as during this period their affinity for oxygen is violent, they are covered with some flux which defends them from the air, as with a varnish, and tends to reduce any portion of oxide accident- ally existing. The solders are broadly distinguished as hard- solders, and soft- solders ; the former only fuse at the red heat, and are consequently suitable alone to metals and alloys which will endure that temper- ature; the soft-solders melt at very low degrees of heat, and may be used for nearly all the metals. The attachment is in every case the stronger, the more nearly the metals and solders respectively agree in hardness and mallea- bility. Thus, if two pieces of brass or copper, or one of each, are brazed together, or united with spelter-solder, an alloy nearly as tough as the brass, the work may be hammered, bent and rolled al- most as freely as the same metals when not soldered, because of the nearly equal cohesive strength of the three parts. Lead, tin, or pewter, united with soft solder, are also malleable from the near agreement of these substances, whereas when copper, brass and iron are soft-soldered, a blow of the hammer, or any acci- dental violence, is almost certain to break the joint asunder, so long as the joint is weaker than the metal generally; and therefore the joint is only safe when the surrounding metal, from its thinness, is no stronger than the solder, so that the two may yield in com- mon to any disturbing cause. The forms of soldered joints in the thin metals have been figured and explained in pages 192 to 195; and soldered joints in thicker works resemble the several attachments employed in construction generally. When the spaces between the works to be joined are wide and coarse, the fluid solder will probably fall out, simply from the effect of gravity ; but when the crevices are fine and close, the solder will be as it were sucked up by capillary attraction. AH soldered works should be kept under motionless restraint for a period, TABULAR VIEW. 231 as any movement of the parts during the transition of the solder from the fluid to the solid state, disturbs its crystalization and the strict unity of the several parts. In hard-soldering, it is frequently necessary to bind the works together in their respective positions; this is done with soft iron binding-wire, which for delicate jewelry work is exceedingly fine, and for stronger works is the twentieth or thirtieth of an inch in diameter; it is passed around the work in loops, the ends of which are twisted together with the pliers. In soft soldering, the binding wire is scarcely ever used, as from the moderate and local application of the heat, the hands may in general be freely used in retaining most thin works in position during the process. Thick works are handled with pliers or tongs whilst being soft-soldered, and they are often treated much like glue joints, if we conceive the wood to be replaced by metal, and the glue by solder, as the two surfaces are frequently coated or tinned whilst separated, and then rubbed together to distribute and exclude the greater part of the solder. The succeeding " Tabular View of the Processes of Soldering" may be considered as the index, which refers to the ordinary methods of soldering most metals. TABULAR VIEW OP THE PROCESSES OF SOLDERING. Note. — To avoid continual repetition, references are made to the pages of this volume which illustrate the respective sub- jects, and also to the lists on the opposite page, in which some of the solders, fluxes, and modes of applying heat are enumerated. HARD-SOLDERING. 238. Applicable to nearly all metals less fusible than the solders ; the modes of treatment are nearly similar throughout. The hard solders most commonly used are the spelter solders, and silver solders. The general flux is borax, marked A, on page 233; and the modes of heating are the naked fire, the furnace or muffle, and the blowpipe, marked a. b. g. Note. — The examples commence with the solders, (the least fusible first,) followed by the metals for which they are commonly employed. 232 SOLDERING. Fine Gold, laminated and cut into shreds, is used as the solder for joining chemical vessels made of platinum. t Silver is by many considered as much the best solder for German silver. Copper in shreds, is sometimes similarly used for iron. Gold solders laminated, are used for gold alloys. See 96-98 and 239. J Spelter solders granulated whilst hot, are used for iron, copper, brass, gun-metal, German silver &c. 89, 238-40. Silver solders laminated, are employed for all silver works and for common gold work, also for German silver, gilding metal, iron, steel, brass, gun-metal, &c, when greater neatness is required than is obtained with spelter-solder. 105 and 239. White or button solders granulated, are employed for the white alloys called button metals; they were introduced as cheap substi- tutes for silver-solder. 93-94. SOFT-SOLDERING. 240. Applicable to nearly all the metals; the modes of treatment very different. The soft-solder mostly used, is 2 parts tin and 1 part lead; some- times from motives of economy much more lead is employed, and 1\ tin to 1 lead is the most fusible of the group unless bismuth is used. The fluxes B to G, and the modes of heating a to i, are all used with the soft-solders. Note. — The examples commence with the metals to be soldered. Thus in the list Zinc, 8, C. /, implies, that zinc is soldered with No. 8 alloy, by the aid of the muriate or chloride of zinc, and the copper bit. Lead, 4 to 8, F, d, e, implies that lead is soldered with alloys varying from No. 4 to 8, and that it is fluxed with tallow, the heat being applied by pouring on melted solder, and the subsequent use of the heated iron not tinned; but in general one only of the modes of heating is selected, according to circumstances. Iron, cast-iron and steel, 8, B, D, if thick heated by a, b, or - •347. 298 DRILLS. it has the centre and pulley of the ordinary drill, but the opposite end is pierced with a nearly cylindrical hole, just at the inner extremity of which a diametrical notch is filed. The drill is shown separately at a ; its shank is made cylindrical, or exactly to fit the hole, and a short portion is nicked down also to the diametrical line, so as to slide into the gap in the drill-stock, by which the drill is prevented from revolving : the end serves also as an abutment, whereby it may be thrust out with a lever. Sometimes a diametrical transverse mortise, narrower than the hole, is made through the drill-stock, and the drill is nicked in on both sides ; and the designer, Mr. R. Balfe, of Kilkenny, proposes that the cylindrical hole of 346 should be continued to the bottom of the notch, that the end of the drill should be filed off obliquely, and that it should be pre- vented from rotating by a pin inserted through the cylindrical hole parallel with the notch ; the taper end of the drill would then wedge fast beneath the pin. Drills are also frequently used in the drilling -lathe ; this is a miniature lathe-head, the frame of which is fixed in the table vice ; the mandrel is pierced for the drills, and has a pulley for the bow, therein resembling Fig. 347, except that it is used as a fixture. The figure 347, just referred to, represents one variety of another common form of the drill-stock, in which the revolving spindle is fitted in a handle, so that it may be held in any position without the necessity for the breast-plate ; the handle is hollowed out to serve for containing the drills, and is fluted to assist the grasp. Fig. 348 represents the socket of an "universal drill-stock," in- vented by James O'Ryan : it is pierced with a hole as large as the largest of the wires of which the drills are formed, and the hole ter- minates in an acute hollow cone. The end of the drill-stock is tapped with two holes, placed on a diameter ; the one screw, a, is of a very fine thread, and has at the end two shallow diametrical notches ; the other, 5, is of a coarser thread, and quite flat at the extremity. The wire-drill is placed against the bottom of the hole, and allowed to lean against the adjusting-screw a, and if the drill be not central, this screw is moved one or several quarter-turns, until it is adjusted for cen- trality ; after which the tool is strongly fixed by the plain set-screw b. PUMP-DRILL. SMITH'S BRACE. 299 Fig. 349 is a drill-stock, contrived by Mr. Murphy: it consists of a tube, the one end of which has a fixed centre and pulley, much the same as usual ; the opposite end of the tube has a piece of steel fixed into it which is first drilled with a central hole, and then turned as a conical screw, to which is fitted a corresponding screw nut, n ; the socket is then sawn down with two diametrical notches, to make four internal angles, and lastly, the socket is hardened. When the four sections are compressed by the nut, their edges stick into the drill and retain it fast, and, provided the instrument is itself concentric, and the four parts are of equal strength, the centrality of the drill is at once insured. The outside of the nut, and the square hole in the key k, are each taper, for more ready application ; and the drills are of the most simple kind, namely, lengths of wire pointed at each end, as in Fig. 350. The sketch, Fig. 349, is also intended to explain another useful application of this drill-stock, as an upright or pump-drill, well known among the ancient Irish as the breast-drill. Occasionally the pump-drill and the common drill-stock are mounted in frames, by which their paths are more exactly defined; but these con- trivances are far from being generally required, and enough will be said in reference to the use of revolving braces, to lead to such ap- plications, if considered requisite, for reciprocating drills. Holes that are too large to be drilled solely by the breast-drill and drill-bow, are frequently commenced with those useful instruments, and are then enlarged by means of the hand-brace, which is very similar to that used in carpentry, except that it is more commonly made of iron instead of wood, is somewhat larger, and generally made without the spring-catch. Holes may be extended to about half an inch diameter, with the hand-brace ; but it is much more expeditious to employ still larger and stronger braces, and to press them into the work in various ways by weights, levers, and screws, instead of by the muscular effort alone. ' Figure 351 represents the old smith's press-drill, which although cumbrous, and much less used than formerly, is nevertheless simple and effective. It consists of two pairs of wooden standards, between Figs. 351. 352. 300 DRILLS. ■which works the beam a b, the pin near a is placed at any height, but the weight w is not usually changed, as the greater or less pres- sure for large and small drills, is obtained by placing the brace more or less near to the fulcrum a; and this part of the beam is shod with an iron plate, full of small centre holes for the brace. The weight is raised by the second lever c d, the two being united by a chain, and a light chain or rope is also suspended from d, to be with- in reach of the one or two men engaged in moving the brace. It is necessary to relieve the weight when the drill is nearly through the hole, otherwise, it might suddenly break through, and the drill becoming fixed, might be twisted on 0 in the neck. The inconveniences in this machine are, that the upper point of the brace moves in an arc instead of a right line ; the limited path when strong pressures are used, which makes it necessary to shift the fulcrum a ; and also the necessity for re-adjusting the work under the drill for each different hole, which in awkwardly shaped pieces, is often troublesome. A portable contrivance of similar date, is an iron bow frame or clamp, shown in Fig. 352 ; the pressure is applied by a screw, but in almost all cases, whilst the one individual drills the hole, the assistance of another is required to hold the frame ; 352 only ap- plies to comparatively thin parallel works, and does not present the necessary choice of position. Another tool of this kind, used for boring the side holes in cast-iron pipes for water and gas, is doubtless familiarly known ; the cramp or frame divides into two branches about two feet apart, and these terminate like hooks, which loosely em- brace the pipe, so that the tool retains its position Avithout constraint, and it may be used with great facility by one individual. Figure 353 will serve to show the general character of various construc- tions of more modern apparatus, to be used for supplying the pressure in drill- ing holes with hand braces. It con- sists of a cylindrical bar a, upon which the horizontal rectangular rod b, is fit- ted with a socket, so that it may be fixed at any height, or in* any angular position, by the set-screw e. Upon b slides a socket, which is fixed at all distances from a, by its set-screw d ; and lastly, this socket has a long vertical screw e, by which the brace is thrust into the work. The object to be drilled having been placed level, either upon the ground, on trestles, on the work bench, or in the vice, according to circumstances, the screws c and d are Fig. 353. EXPANDING BRACES. LEVER DRILL. 301 loosened, and the brace is put in position for work. The perpendi- cularity of the brace is then examined with a plumb-line, applied in two positions, (the eye being first directed as it were along the north and south line, and then along the east and west,) after which the whole is made fast by the screws c and d. The one hole having been drilled, the socket and screws present great facility in re-adjust- ing the instrument for subsequent holes, without the necessity for shifting the work, which would generally be attended with more trouble, than altering the drill-frame by its screws. Sometimes the rod a is rectangular, and extends from the floor to the ceiling; it then traverses in fixed sockets, the lower of which has a set screw for retaining any required position. In the tool repre- sented, the rod a, terminates in a cast-iron base, by which it may be grasped in the tail- vice, or when required it may be fixed upon the bench; in this case the nut on a is unscrewed, the cast-iron plate, when reversed and placed on the bench, serves as a pedestal, the stem is passed through a hole in the bench, and the nut and washer, when screwed on the stem beneath, secure all very strongly together. Even in establishments where the most complete drilling machines driven by power are at hand, modifications of the press drill are among the indispensable tools: many are contrived with screws and clamps, by which they are attached directly to such works as are sufficiently large and massive to serve as a foundation. Various useful drilling tools for engineering works are fitted with left hand screws, the unwinding of which elongate the tools; so that for these instruments which supply their own pressure, it is only necessary to find a solid support for the centre. They apply very readily in drilling holes within boxes and panels, and the abutment is often similarly provided by projecting parts of the castings ; or otherwise the fixed support is derived from the wall or ceiling, by aid of props arranged in the most convenient manner that presents itself. r Fig. 354 is the common brace, which only differs from that in Fig. 353 in the left hand screw; a right hand screw would be un- wound in the act of drilling a hole when the brace is moved round in the usual direction, which agrees with the path of a left hand screw. The cutting motion produces no change in the length of the instrument, and the screw being held at rest for a moment during the revolution, sets in the cut; but towards the last, the feed is discontinued, as the elasticity of the brace and work, suffice for the reduced pressure required when the drill is nearly through, and sometimes the screw is unwound still more to reduce it. The lever-drill, Fig. 355, differs from the latter figure in many respects; it is much stronger, and applicable to larger holes; the drill socket is sufficiently long to be cut into the left hand screw, and the piece serving as the screwed nut, is a loop terminating in the centre point. The increased length of the lever gives much greater purchase than in the crank formed brace, and in addition the lever-brace may be applied close against a surface where the 302 DRILLS. crank-brace cannot be turned round ; in this case the lever is only moved a half circle at a time, and is then slid through for a new purchase, or sometimes a spanner or wrench is applied directly upon the square drill socket. Figs. 354. ' 357. The same end is more conveniently fulfilled by the ratchet-drill, Fig. 356, apparently derived from the last; it is made by cutting ratchet teeth in the drill shaft, or putting on the ratchet as a separate piece, and fixing a pall or detent to the handle ; the latter may then be moved backward to gather up the teeth, and forward to thrust round the tool, with less delay than the lever in Fig. 355, and with the same power, the two being of equal length. This tool is also peculiarly applicable to reaching into angles and places in which neither the crank-form brace, nor the lever-drill will apply. Fig. 357, the ratchet-lever, in part resembles the ratchet-drill, but the pressure-screw of the latter instrument must be sought in some of the other contrivances referred to, as the ratchet-lever has simply a square aperture to fit on the tang of the drill d, which latter must be pressed forward by some independent means. Fig. 358, which is a simple but necessary addition to the braces and drill tools, is a socket having at the one end a square hole to receive the drills, and at the opposite, a square tang to fit the brace ; by this contrivance the length of the drill can be temporarily extended for reaching deeply seated holes. The sockets are made of various lengths, and sometimes two or three are used together, to extend the length of the brace to suit the position of the prop; but it must be remembered that, with the additional length, the torsion becomes much increased, and the resistance to end-long pressure much dimin- ished, therefore the sockets should have a bulk proportionate to their length. The French brace is also constructed in iron, with a pair of equal bevel pinions, and a left hand centre screw, like the tools Figs. 354, o'kellt's differential screw drill. 303 355, and 356 ; it is then called the corner-drill. Sometimes also, as in Figs. 359 and 360, the bevel wheels are made with a hollow square or axis, as in the ratchet-lever, Fig. 357; the driver then hangs loosely on the square shank of the drill tool, or cutter bar, and when the pinion on the handle is only one-third or fourth of the size of the bevel wheel with the square hole, it is an effective driver for various uses ; the long tail or lever serves to prevent the rotation of the driver, by resting against some part of the work or of the work-bench. All the before-mentioned tools are commonly found in a variety of shapes in the hands of the engineer, but it will be observed they Fig. 359. Fig. 360. are all driven by hand power, and are carried to the work. I shall conclude this section with the description of a more recent drill tool of the same kind, invented by Mr. O'Kelly of Dublin. This instrument is represented of one-eighth size, in the side view, Fig. 361, in the front view, 362, and in the section 363; it is about twice as powerful as Fig. 360, and has the advantage of feeding the cut by a differential motion. The tangent screw moves at the same time the two worm wheels a and b; the former has 15 teeth, and serves to revolve the drill ; the latter has 16 teeth, and by the differ- ence between the two, or the odd tooth, advances the drill slowly and continually, which may be thus explained. The lower wheel a, of 15 teeth, is fixed on the drill shaft, and this is tapped to receive the centre screw c, of four threads per inch. The upper wheel of 16 teeth is at the end of a socket d, (which is represented black in the section Fig. 363,) and is connected with the centre screw c, by a collar and internal key, which last fits a longi- tudinal groove cut up the side of the screw e; now, therefore, the in- ternal and external screws travel constantly round, and nearly at the same rate, the difference of one tooth in the wheels serving con- 304 DRILLS. tinually and slowly to project the screw c, for feeding the cut. To shorten or lengthen the instrument rapidly, the side screw e is loosened ; this sets the collar and key free from the 16 wheel, and the centre screw may for the time be moved independently by a spanner. Figs. 361. 362. The differential screw-drill, having a double thread in the large worm, shown detached at/, requires 1\ turns of the handle to move the drill once round, and the feed is one-64th of an inch for each turn of the drill ; that being the sum of 16 by 4. Drilling and Boring Machines. — The motion of the lathe mandrel is particularly proper for giving action to the various single- cutting drills referred to ; they are then fixed in square or round hole drill-chucks which screw upon the lathe mandrel. The motion of the lathe is more uniform than that of the hand tools, and the popit-head, with its flat boring flange and pressure screw, form a most convenient arrangement, as the works are then carried to the drill exactly at right angles to the face. But in drilling very small holes in the lathe, there is some risk of unconsciously employing a greater pressure with the screw than the slender drills will bear. Sometimes the cylinder is pressed forward by a horizontal lever fixed on a fulcrum ; at other times the cylinder is pressed forward by a spring, by a rack and pinion motion, or by a simple lever, and the best arrangement of this latter kind is that next to be de- In the manufacture of harps there is a vast quantity of small drill- ing, and the pressure of the cylinder popit-head is given by means of a long, straight, double-ended lever, which moves horizontally, (at aboutTone-third from the back extremity,) upon a fixed post or fulcrum erected upon the back-board of the lathe. The front of the lever is connected with the sliding cylinder by a link or connecting rod, and the back of the lever is pulled towards the right extremity of the lathe, by a cord which passes over a pulley at the edge of the back-board, and then supports a weight of about twenty pounds.^ Both the weight and connecting rod may be attached at various distances from the fixed fulcrum between them. When they are fixed at equal distances from the axis of the lever, the weight, if DRILLING AND BORING MACHINES. 305 twenty pounds, presses forward the drill with twenty pounds, less a little friction ; if the weight be two inches from the fulcrum and the connecting rod eight inches, the effect of the weight is reduced to five pounds ; if, on the other hand, the weight be at eight and the connecting rod at two inches, the pressure is fourfold, or eighty pounds. The connecting rod is full of holes, so that the lever may be ad- justed exactly to reach the body of the workman, who, standing with his face to the mandrel, moves the lever with his back, and has there- fore both hands at liberty for managing the work. Sometimes a stop is fixed on the cylinder, for drilling holes to one fixed depth ; gages are attached to the flange, for drilling numbers of similar pieces at any fixed distance from the edge : in fact, this very useful apparatus admits of many little additions to facilitate the use of drills and re- volving cutters. Great numbers of circular objects, such as wheels and pulleys, are chucked to revolve truly upon the lathe mandrel, whilst a stationary drill is thrust forward against them, by which means the concentri- city between the hole and the edge is insured. The drills employed for boring works chucked on the lathe, have mostly long shafts, some parts of which are rectangular or parallel, so that they may be prevented from revolving by a hook wrench, a spanner or a hand-vice, applied as a radius, or by other means. The ends of the drill shafts are pierced with small centre holes, in order that they may be thrust forward by the screw of the popit-head, either by hand or by self-acting motion : namely, a connection be- tween either the mandrel or the prime mover of the lathe, and the screw of the popit-head, by cords and pulleys, by wheels and pinions, or other contrivances. The drills, Figs. 333 and 335, p. 293, are used for boring ordinary holes : but for those requiring greater accuracy, or a more exact repetition of the same diameter, the lathe drills, Figs. 364 to 366 are commonly selected. Fig. 364, which is drawn in three views and to the same scale as the former examples, is called the half-round bit, or the cylinder bit. The extremity is ground a little inclined to the right angle, both horizontally and vertically, to about the extent of three to five degrees. It is necessary to turn out a shallow recess exactly to the diameter of the end of the bit as a commencement ; the circular part of the bit fills the hole, and is thereby retained central, whilst the left angle removes the shaving. This tool should never be sharpened on its diametrical face, or it would soon cease to deserve its appellation of half-round bit : some indeed give it about one-thirtieth more of the circumference. It is generally made very slightly smaller behind, to lessen the friction; and the angle, not in- tended to cut, is a little blunted half-way round the curve, that it may not scratch the hole from the pressure of the cutting edge. It is lubricated with oil for the metals generally, but is used dry for hard woods and ivory, and sometimes for brass. The rose-bit, Fig. 365, is also very much used for light finishing 306 DRILLS. cuts, in brass, iron, and steel; the extremity is cylindrical, or in tie smallest degree less behind, and the end is cut into teeth like a coui- tersink ; the rose-bit, when it has plenty of oil, and but very little to remove, will be found to act beautifully, but this tool is less it for cast-iron than the bit next to be described. The rose-bit may l>e used without oil for the hard woods and ivory, in which it makes a very clean hole ; but as the end of the tool is chamfered, it does n)t leave a flat-bottomed recess the same as the half-round bit, and is therefore only used for thoroughfare holes. Figs. 364. 365. 366. 367. 368. The drill, Fig. 366, is much employed, but especially for cast-inn work ; the end of the blade is made very nearly parallel, the tvo front corners are ground slightly rounding, and are chamfered, the chamfer is continued at a reduced angle along the two sides, to the extent of about two diameters in length : this portion is not strict.y parallel, but is very slightly largest in the middle or barrel-shaped: this drill is used dry for cast-iron. Fig. 366, in common with all drills that cut on the side, may, ly improper direction, cut sideways, making the hole above the intended diameter ; but when the hole has been roughly bored with a common fluted drill, the end of the latter is used as a turning tool, to make an accurate chamfer, the bit 366 is then placed through the stay, as shown in Fig. 367, and is lightly supported between the chamfer upon the work and the centre of the popit-head; the moment any pressure comes on the drill, its opposite edges stick into the inner sides of the loop, (as more clearly explained in Fig. 368,) which thus restrains its position ; much the same as the point and edges of the turning tools for iron dig into the rest, and secure the position of those tools. It is requisite the drill and loop should be exactly central ; Fig. 367 shows the common form of the stay when fitted to the lathe rest, but it is sometimes made as a swing gate, to turn aside, whilst the piece which has been drilled is removed, and the next piece to be operated upon is fixed in the lathe. Sometimes also the drill 366, has blocks of hardwood attached above and below it, to complete the DRILLING AND BORING MACHINES. 307 circle ; this is usual for wrought iron and steel, and oil is then em- ployed. These three varieties are exclusively lathe-drills, and are intended for the exact repetition of a number of holes of the particular sizes of the hits, and which, on that account, should remove only a thin shaving to save the tools from wear. The cylinder bits, however, may be used for enlarging holes below half an inch, to the extent of about one-third their diameter at one cut ; and for holes from half an inch to one inch, about one-fourth their diameter or less, and as the bits increase in size, the proportion of the cut to the diameter should decrease. The cylinder bit is not intended to be used for drilling holes in the solid material, and as the piercing drills are apt to swerve in drilling small and very deep holes, the following rotation in the tools is sometimes resorted to. A drill, Fig. 333, p. 293, say three-six- teenths diameter, is first sent in to the depth of an inch or upwards, and the hole is enlarged by a cylinder bit of one- quarter inch dia- meter. The centre at the end of the hole is then restored to exact truth, by Fig. 337, a re-centering drill, the plug of which exactly fits the hole made by the cylinder bit; the extremity of the re-cen- tering drill then acts as a fixed turning tool, and should the first drill have run out of its position, Fig. 337 corrects the centre at the end of the hole. Another short portion is then drilled with Fig. 333, enlarged with the half-round bit, and the conical extremity is again corrected with the re-centering drill; the three tools are thus used in rotation until the hole is completed, and which may be then cleaned out with one continued cut, made with a half-round bit a little larger than that previously used. Some of the large half-round bits are so made that the one stock will serve for several cutters of different diameters. In the bits used for boring out ordnance, the parallel shaft of the boring bar slides accu- rately in a groove, exactly parallel with the bore of the gun ; the cutting blade is a small piece of steel affixed to the end of the half- round block, which is either entirely of iron, or partly of wood ; and the cut is advanced by a rack and pinion movement, actuated either by the descent of a constant weight, or by a self-acting motion derived from the prime mover. For making the spherical, parabol- ical or other termination to the bore, cutters of corresponding forms are fixed to the bar. The outside of the gun is usually turned, whilst the boring is going on, by hand tools. A plug of copper is screwed into the brass guns to be perforated for the touch-hole, copper being less injured by repeated discharges, than the alloy of nine parts copper and one part tin, used for the general substance of the gun; the curved bit smooths off the end of the plug. There are very many works which from their weight or size, can- not be drilled in the lathe in its ordinary position, as it is scarcely possible to support them steadily against the drill; but these works are readily pierced in the drilling machine, which may be viewed as 308 DRILLS. a lathe with a vertical mandrel, and with the flange of the popit- head, enlarged into a table for the work, which then lies in the ho- rizontal position simply by gravity, or is occasionally fixed on the table by screws and clamps. The structure of these important ma- chines admits of almost endless diversity, and in nearly every man- ufactory some pecularity of construction may be observed. Figs. 369 and 370, exhibit a "Portable Hand-drill," which is introduced as a simple and efficient example, that may serve to Figs. 369. 370. convey the general characters of the drilling machines. The spindle is driven by a pair of bevel pinions, the one is attached to the axis of the vertical fly wheel, the other to the drill shaft, which is de- pressed by a screw moved by a small hand-wheel. Sometimes, as in the lathe, the drilling spindle revolves without endlong motion, and the table is raised by a treadle or by a hand lever; but more generally the drill-shaft is cylindrical and revolves in, and also slides through fixed cylindrical bearings. The drill spindle is then depressed in a variety of ways; sometimes by a sim- ple lever, at other times by a treadle, which either lowers the shaft only one single sweep, or by a ratchet that brings it down by several small successive steps, through a greater distance ; and mostly a counterpoise weight restores the parts to their first position when the hand or foot is removed. Friction clutches, trains of differential wheels, and other modes are also used in depressing the drill spindle, or in elevating the table by self-acting motion. Frequently also the platform admits of an adjustment independent of that of the spindle, for the sake of admitting larger pieces; the horizontal posi- tion of the platform is then retained by a slide, to which a rack and pinion movement, or an elevating screw is added. Drilling machines of these kinds are generally used with the ordi- nary piercing drills, and occasionally with pin drills ; the latter in- strument appears to be the type of another class of boring tools, namely, cutter bars, which are used for works requiring holes of greater dimensions, or of superior accuracy, than can be attained by the ordinary pointed drills. DRILLING AND BORING MACHINES. 309 The small application of this principle, or of cutter bars, is shown on the same scale as the former drills, in Fig. 371 ; the cutter c, is placed in a diametrical mortise in a cylindrical boring bar, and is fixed by a wedge ; the cutter c extends equally on both sides, as the two projections or ears embrace the sides of the bar, which is slightly flattened near the mortises. Cutter bars of the same kind are occasionally employed with cutters of a variety of forms, for making grooves, recesses, mould- ings, and even screws, upon parts of heavy works, and those which cannot be conveniently fixed in the ordinary lathe. Fig. 372 repre- sents one of these, but its application to screws will be found in the chapter on the tools for screw cutting. Figs. 371. 373. > -1 s e ~ L — - 2 e=r t=i iimwtwt^^ 3- 372. The larger application of this principle is shown in Fig. 372, in which a cast-iron cutter-block is keyed fast upon a cylindrical bar ; the block has four, six, or more grooves in its periphery. Sometimes, the work is done with only one cutter, and should the bar vibrate, the remainder of the grooves are filled with pieces of hard wood, so as to complete the bearing at so many points of the circle ; occa- sionally cutters are placed in all the grooves, and carefully adjusted to act in succession, that is, the first stands a little nearer to the axis than the second, and so on throughout, in order that each may do its share of the work ; but the last of the series takes only a light finishing cut, that its keen edge may be the longer preserved. In all these cutters, the one face is radial, the other differs only four or five degrees from the right angle, and the corners of the tools are slightly rounded. These cutter bars, like the rest of the drilling and boring ma- chinery, are employed in a great variety of ways, but which resolve themselves into three principal modes : — First, the cutter bar revolves without endlong motion, in fixed centres or bearings, in fact, as a spindle in the lathe ; the work is traversed, or made to pass the revolving cutter in a right line, for which end the work is often fixed to a traversing, slide rest. This mode requires the bar to measure between the supports, twice the length of the work to be bored, and the cutter to be in the middle of the bar ; it is therefore unfit for long objects. Secondly, the cutter bar revolves, and also slides with endlong 310 DRILLS. motion, the work being at rest ; the bearings of the bar are then frequently attached in some temporary manner to the work to be bored, and are often of wood. Cylinders of forty inches diameter for steam engines, have been thus bored, by attaching a cast-iron cross to each end of the cylinder ; the crosses are bored exactly to fit the boring bar, one of them carries the driving gear, and the bar is thrust endlong by means of a screw, moved by a ratchet or star wheel. In another common arrangement, the boring bar is mounted in headstocks, much the same as a traversing mandrel, the work is fixed to the bearers carrying the headstocks, and the cutter bar is advanced by a screw. The screw is then moved either by the hand of the workman ; by a star- wheel, or a ratchet wheel, one tooth only in each revolution ; or else by a system of differential wheels, in which the external screw has a wheel say of 50 teeth, the internal screw a wheel of 51 teeth, and a pair of equal wheels or pinions drives these two screws continually, so that the advance of the one- fiftieth of a turn of the screw, or their difference, is equally divided over each revolution of the cutter bar, much the same as in the differental motion of the screw drill, Fig. 361. This second method only requires the interval between the fixed bearings of the cutter bar, to be as much longer than the work as the length of the cutter block; but the bar itself must have more than twice the length of the work, and requires to slide through the supports. Cutter bars of this kind are likewise used in the lathe ; in the act of boring, the end of the bar then slides like a piston into the man- drel. Such bars are commonly applied to the vertical boring ma- chines of the larger kinds, which are usually fitted with a differential apparatus, for determining the progress of the cut ; the bar then slides through a collar fixed in the bed of the machine. In some of the large boring machines either one or two horizontal slides are added, and by their aid, series of holes may be bored in any required arrangement. For instance, the several holes in the beams, or side levers, and cranks of steam engines, are bored exactly perpendicular, in a line, and at any precise distances, by shifting the work beneath the revolving spindle upon the guide or railway; in pieces of other kinds, the work is moved laterally during the re- volution of the cutters, for the formation of elongated countersinks and grooves. Thirdly. In the largest applications of this principle, the boring bar revolves upon fixed bearings without traversing ; and it is only needful that the boring bar should exceed the length of the work, by the thickness of the cutter block, of which it has commonly several of different diameters. The cutter block, now sometimes ten feet diameter, traverses as a slide down a huge boring bar, whose diame- ter is about thirty inches. There is a groove and key to couple them together, and the traverse of the cutter block down the bar, is caused by a side screw, upon the end of which is a large wheel, that en- BROACHES FOR MAKING TAPER HOLES. 311 gages in a small pinion, fixed to the Fi s- 374 - stationary centre or pedestal of the machine. With every revolution of the cutter bar, the great wheel is carried around the fixed pinion, and supposing these be as ten to one, the great wheel is moved one-tenth of a turn, and therefore moves the screw one-tenth of a turn also, and slowly traverses the cutter block. The contrivance may be viewed as a huge, self-acting, and revolv- ing sliding-rest, and the diagram 374 shows that the cutter bars are equally applicable to portions of circles, such as the D valves of steam engines, as well as to the enormous interior of the cylinder itself. All the preceding boring tools cut almost exclusively upon the end alone. They are passed entirely through the objects, and leave each part of their own particular diameter, and therefore cylindrical ; but I now proceed to describe other boring tools, that cut only on their sides, go but partly through the work, and leave its section a coun- terpart of the instrument. These tools are generally conical, and serve for the enlargement of holes to sizes intermediate between the gradations of the drills, and also for the formation of conical holes, as for valves, stopcocks, and other works. The common pointed drill, or its multiplication in the rose countersink, is the type of the series ; but in general the broaches have sides which are much more nearly parallel. Broaches for making Taper Holes.— The tools for making taper holes are much less varied than the drills and boring tools for cylindrical holes. Figs. 375. 376. 377. 378. 379. 380. 381. 382. The broaches for metal are made solid, and of various sections ; as half-round, like Fig. 375 ; the edges are then rectangular, but more commonly the broaches are polygonal, as in Fig. 376, except that they have 3, 4, 5, 6, and 8 sides, and their edges measure re- spectively 60, 90, 108, 120, and 135 degrees. The four, five, and six-sided broaches are the most general, and the watchmakers em- ploy a round broach in which no angle exists, and the tool is there- 312 BROACHES. fore only a burnisher, which compresses the metal and rounds the hole. Ordinary broaches are very acute, and Fig. 382 may be consi- dered to represent the general angle at which their sides meet, namely, less than one or two degrees; the end is usually chamfered off with as many facets as there are sides, to make a penetrating point, and the opposite extremity ends in a square tang, or shank, by which the instrument is worked. Square broaches, after having been filed up, are sometimes twisted whilst red hot; Fig. 381 shows one of these; the rectangular sec- tion is but little disturbed, although the faces become slightly con- cave. _ The advantage of the tool appears to exist in its screw form : when it is turned in the direction of the spiral, it cuts with avidity and requires but little pressure, as it is almost disposed to dig too forcibly into the metal : when turned the reverse way, as in unscrew- ing, it requires as much or more pressure than similar broaches not twisted. This instrument, if bent in the direction of its length, either in the act of twisting or hardening, does not admit of cor- rection by grinding, like those broaches having plane faces. It is not much used, and is almost restricted to wrought iron and steel. . Large countersinks that do not terminate in a point, are some- times made as solid cones ; a groove is then formed up one side, and deepest towards the base of the cone, for the insertion of a cutter ; see Fig. 377. As the blade is narrowed by sharpening, it is set a little forward in the direction of its length, to cause its edge to con- tinue slightly in advance of the general surface, like the iron of a plane for cutting metal. Figure 383 represents the broach, invented by James Kinselaugh, of Wicklow, Ireland, in which four detached blades are introduced, for the sake of retaining the cone or angle of the broach with Fig. 383. greater facility. The bar or stack has four shallow longitudinal grooves, which are nearly radial on the cutting face, and slightly undercut on the other. The grooves are also rather deeper behind, and the blades are a little wedge-form both in section and in length' to constitute the cone, and the cutting edges. In restoring °the edges of the blades, they are removed from the stock, and°their angles are then more easily tested : when replaced, they are set nearer to the point, to compensate for their loss of thickness. Broaches are also used for perfecting cylindrical holes, as well as for making those which are taper. The broaches are then made almost parallel, or a very little the highest in the middle ; they are filed, with two or three planes at angles of 90 degrees, as in Figs. 378 or 379. The circular part not being able to cut, serves as a DRILLS AND BROACHES COMPARED. 313 more certain base or foundation, than when the tool is a complete polygon ; and the stems are commonly made small enough to pass entirely through the holes, which then agree very exactly as to size. Such tools are therefore rather entitled to the name of finishing drills, than broaches. The size of the parallel broaches is often slightly increased, by placing a piece or two of paper at the convex part; leather and thin metal are also used for the same purpose. Gun-barrels are broached with square broaches, the cutting parts of which are about eight to ten inches long; they are packed on the four sides with slips or spills of wood, to complete the circle, as in Fig. 380, in which the tool is supposed to be at work. The size of the bit is progress- ively enlarged by introducing slips of thin paper, piece by piece, between two of the spills of wood and the broach; the paper throws the one angle more towards the centre of the hole, and causes a corresponding advance in the opposite or the cutting angle. Some- times, however, only one spill of wood is employed. A broach used by the philosophical instrument makers in finishing the barrels of air pumps, consisted of a thin plate of steel inserted diametrically between two blocks of wood, the whole constituting a cylinder with a scraping edge slightly in advance of the wood; slips of paper were also added. According to the size of the broaches, they are fixed in handles like brad-awls; they are used in the brace, or the tap wrench, namely, a double-ended lever with square central holes. Sometimes also broaches are used in the lathe just like drills, and for large works, broaching machines are employed ; these are little more than driv- ing gear terminating in a simple kind of universal joint, to lead the power of the steam-engine to the tool, which is generally left under the guidance of its own edges, according to the common principle of the instrument. In drills and broaches, the penetrating angles are commonly more obtuse than in turning tools; thus in drills of limited dimensions, the hook-form of the turning tool for iron is inapplicable, and in the larger examples, the permanence of the tool is of more consequence than the increased friction. But on account of the additional friction excited by the nearly rectangular edges, it is commonly necessary to employ a smaller velocity in boring than in turning corresponding diameters, in order to avoid softening the tool by the heat generated*; and in the ductile fibrous metals, as wrought iron, steel, copper and others, lubrication with oil, water, &c, becomes more necessary than in turning. The drills and broaches form together a complete series. First, the cylinder bit, the pin drills, and others with blunt sides, produce cylindrical holes by means of cutters at right angles to the axis; then the cutter becomes inclined at about 45 degrees, as in the common piercing drill and cone countersink; the angle becomes much less in the common taper broaches; and finally disappears in the parallel 314 SCREW-CUTTING TOOLS. broaches, by which we again produce the cylindrical hole, but with cutters parallel with the axis of the hole. Still considering the drills and broaches as one group, the drills have comparatively thin edges, always less than 90 degrees, yet they require to be urged forward by a screw or otherwise, the resist- ance being sustained in the line of their axes. The broaches have much more obtuse edges, never less than 90, and sometimes extend- ing to 135 degrees; and yet the greater force required to cause the penetration of their obtuse edges into the material, is supplied with- out any screw, because the pressure in all these varied tools is at right angles to the cutting edge. Thus supposing the sides of the broach extended until they meet in a point, as in Fig. 382, we shall find the length will very many times exceed the diameter, and by that number will the force em- ployed to thrust forward the tool be multiplied, the same as in the wedge, whether employed in splitting timber or otherwise ; and the broach being confined in a hole, it cannot make its escape, but acts with lateral pressure, directed radially from each cutting edge; and the broach under proper management leaves the holes very smooth and of true figure. SCREW-CUTTING TOOLS. An elementary idea of the form of the screw, or helix, is obtained by considering it as a continuous circular wedge ; and it is readily modeled by wrapping a wedge-formed piece of paper around a cylin- der ; the edge of the paper then represents the line of the screw, and which preserves one constant angle to the axis of the contained cy- linder, namely, that of the wedge. The ordinary wedge, or the diagonal, may be produced by the composition of two uniform rectilinear motions, which, if equal, pro- duce the angle of 45°, or if unequal, various angles more or less acute ; and in an analogous manner, the circular wedge or the screw, may be produced of every angle or coarseness, by the composition of an uniform circular motion, with an uniform rectilinear motion. And as either the rectilinear or the circular motion, may be given to the work or to the tool indifferently, there are four distinct modes of producing screws, and which are all variously modified in practice. The screw admits of great diversity; it may possess any diameter; it may also have any angle, that is, the interval between the threads may be either coarse or fine, according to the angle of the wedge, or the ratio of the two motions ; and the wedge may be wound upon the cylinder to the right hand or to the left, so as to produce either right or left hand screws. The idea of double, triple, or quadruple screws, will be conveyed by considering two, three, or four black lines drawn on the uncovered edge of the wedge-formed paper, or likewise by two, three, or four strings or wires placed in contact, and coiled as a flat band around the cylinder, the angle remains unaltered, it is only a multiplication INTRODUCTORY REMARKS. 315 of the furrows or threads ; and lastly, the screw may have any sec- tion, that is, the section of the worm or thread may be angular, square, round, or of any arbitrary form. Thus far as to the variety in screws. The importance of this mechanical element, the screw, in all works in the constructive arts, is almost immeasurable. For instance, great numbers of screws are employed merely for connecting together the different parts of which various objects are composed ; no other at- tachment is so compact, powerful, or generally available ; these bind- ing or attachment screws require, by comparison, the least degree of excellence. Other screws are used as regulating screws, for the guidance of the slides and the moving parts of machinery, for the screws of presses and the like ; these kinds should possess a much greater degree of excellence than the last. But the most exact screws that can be produced, are quite essential to the good performance of the engines employed in the graduation of right lines and circles, and of astronomical and mathematical instruments ; in these delicate micro-metrical screws, our wants ever appear to outstrip the most re- fined methods of execution. The attempt to collect and describe all the ingenious contrivances which have been devised for the construction of screws, would be in itself a work of no ordinary labor or extent : I must, therefore, prin- cipally restrict myself to those varied processes now commonly used in the workshops, for producing with comparative facility, screws abundantly exact for the great majority of purposes. It has been found rather difficult to arrange these extremely different processes in tolerable order, but that which seems to be the natural order has been adopted, thus : — There appears to be no doubt, but that in the earliest production of the apparatus for cutting screws, the external screw was the first piece made ; this plain circular metal screw was serrated and thus converted into the tap, or cutting tool, by which internal screws of corresponding size and form were next produced ; and one of these hollow screws or dies became in its turn the means of regenerating, with increased truth and much greater facility, any number of copies of the original external screw. In these several stages there is a progressive advance towards perfection, as will be hereafter ad- verted to. These hand processes are mostly used for screws, which are at least as long, if not longer, than their diameters. The rotatory and rectilinear guides, and the one or several series of cutting points, are then usually combined within the tool. This first group will be con- sidered in the succeeding order : — On originating screws. On cutting internal screws, with screw taps. On cutting external screws, with screw dies. Subsequent improvements have led to the employment of the lathe in producing from the above, and in a variety of ways, still more accurate screws. These methods are sometimes used for screws 316 SCREW-CUTTING TOOLS. ■which possess only a portion of a turn, at other times for screws twenty or thirty feet long and upwards. The rotatory guide is al- ways given by the mandrel, the rectilinear guide is variously ob- tained, and the detached screw tool or cutter, may have one single point, or one series of points -which touch the circle at only one place at a time. This second group will be arranged thus: — On cutting screws, in the common lathe by hand. On cutting screws, in lathes with traversing mandrels. On cutting screws, in lathes with traversing tools. It may be further observed that the modes described under these heads are in general applied to very different purposes, and are only to a limited extent capable of substitution one for the other; it is to be also remarked that it has been considered convenient, in a great measure to abandon, or rather to modify, the usual distinction be- tween the tools respectively used for wood and for metal. The eighth and concluding section of this subject describes some refine- ments in the production of screws which are not commonly practised, and it is in some measure a sequel to the second section. On Originating Screws. — It appears more than probable, that in the earliest attempts at making a screw, a sloping piece of paper was cemented around the iron cylinder; this oblique line was cut through with a stout knife or a thin edged file, and was then gradu- ally enlarged by hand until it gave a rude form of screw. Doubtless as soon as the application of the lathe was generally known, the work was mounted between centres, so that the progress of filing up the groove could be more easily accomplished, or a pointed turning tool could be employed to assist. Such, in fact, is one of the modes recommended by Plumier, for cutting the screw upon a lathe mandrel for receiving the chucks, even in preference to the use of the die- stocks, which, he urged, were liable to bend the mandrel in the act of cutting the screw. Nearly similar modes have been repeatedly used for the production of original screws ; one account differing in several respects from the above, is described as having been very successfully resorted to above fifty years back, at the Soho works, Birmingham, by a workman of the name of Joe Baggs, before the introduction of the screw-cutting lathe. This is an English account of an English supposed invention. The screw was seven feet long, six inches diameter, and of a square triple thread ; after the screw was accurately turned as a cy- linder, the paper was cut parallel exactly to meet around the same, and was removed and marked in ink with parallel oblique lines, re- presenting the margins of the threads ; and having been replaced on the cylinder, the lines were pricked through with a centre punch. The paper was again removed, the dots were connected by fine lines cut in with a file, the spaces were then cut out with a chisel and hammer and smoothed with a file, to a sufficient extent to serve as a lead or guide. The partly formed screw was next temporarily suspended in the centre of a cast-iron tube or box strongly fixed against a horizontal MODES FORMERLY EMPLOYED FOR ORIGINATING SCREWS. 317 beam, and melted lead mixed with tin, was poured into the box to convert it into a guide nut; it then only remained to complete the thread by means of cutters fixed against the box or nut, but with the power of adjustment, in fact in a kind of slide-rest, the screw being handed round by levers. ^ Another very simple way of originating screws, and which is suffi- ciently accurate for some purposes, is to coil a small wire, around a larger straight wire as a nucleus ; this last is frequently the same wire the one end of which is to be cut into the screw. The covering wire, whose diameter is equal to the space required between the threads of the screw, is wound on close and tight, and made fast at each end. The coiled screw, being enclosed between two pieces of hard wood, indents a hollow or counterpart thread, sufficient to guide the helical traverse, and a fixed cutter completes this simple apparatus. t Common screws, for some household purposes, have been made of tinned iron wire ; two covering wires are rolled on together, the one being removed leaves a space such as the ordinary hollow of the thread, and when these screws are dipped in a little melted tin, the two wires become soldered together. Other modes have been resorted to for making original screws, by indenting a smooth cylinder with a sharp-edged cutter placed across the same at the required angle ; and trusting to the surface or rolling contact, to produce the rotation and traverse of the cylinder, with the development of the screw. In the most simple application of this method, a deep groove is made along a piece of board, in which a straight wire is buried a little beneath the surface ; a second groove is made, nearly at right angles across the first, exactly to fit the cutter, which is just like a table knife, and is placed at the angle required in the screw. The cutter when slid over the wire, indents it, carries it round, and traverses it endways in the path of a screw; a helical linens thus obtained, which, by cautious management, may be perfected into a screw sufficiently good for many purposes. t M r - Walsh, of Dublin, employed a cutter upon cylinders of wood, tin, brass, iron, and other materials, mounted to revolve between centres in a triangular bar lathe ; the knife was hollowed to fit the cylinder, and fixed at the required angle on a block adapted to slide upon the bar ; the oblique incision carried the knife along the revolv- ing cylinder. Some hundreds of screws were thus made, and their agreement with one another was in many instances quite remarkable ; on the whole he gave the preference to this mode of originating screws. The apparatus for originating screws for astronomical and other purposes is represented in plan in Fig. 384, in side elevation in Fig. 385, and 386 is the front elevation of the cutter frame alone. This method is also due to Mr. Walsh. The piece intended for the screw, namely, a a, Fig. 384, is turned cylindrical, and with two equal and cylindrical necks ; it is supported in a metal frame with two semi- circular bearings, b b, which are fixed on a slide moved by an adjust- ing screw c. 318 SCREW-CUTTING TOOLS. r The instrument generates original screws perfectly true, of any number of threads, and right or left handed. In this case, the stock and cutter are made as in Figs. 384, 385, and 386 ; the back of the stock is made into the segment of a circle, s ; and the top of the cutter is continued into an index, t. The cutter is a single thread, and moves on its edge, v, as a centre. This must fit true, and the stock fit close to the cutter, to keep it perfectly steady : u, u, two screws, to adjust and fasten the cutter to any required angle. The cutter should be rather elliptical, for it is best to fit well to the cylinder at the greatest angle it will be ever used. When one turn has been given to the cylinder, Fig. 384, a tooth, w, is put into the Figs. 384. Figs. 387. 388. 389. 390. cut, and screwed fast ; this tooth secures the lead, and causes every following thread to be a repetition of the first ; and though it might do without, yet this is a satisfactory security. In cutting ordinary screws, the dies shown separately in Figs. 387 to 390, the consideration of which is for the present deferred, take, the place of the oblique cutter in the former figures. The screw is also originated, by traversing the tool in a right line alongside a plain revolving cylinder. Sometimes the tool has many points, and is guided by the hand alone; at other times the tool has but one single point, and is guided mechanically so as to proceed, say one inch or one foot in a right line, whilst the cylinder makes a definite number of revolutions. The tool is then traversed either by SCREW TAPS. 319 * ."'*'. ' ;;' • a wedge placed transversely to the axis, by a chain or metallic band placed longitudinally, or by another screw connected in various ways with the screw to be produced, by wheel-work and other contrivances. On Cutting Internal Screws, with Screw Taps.— The screw is converted into the tap by the removal of parts of its circumference, in order to give to the exposed edges a cutting action ; whilst the circular parts which remain, serve for the guidance of the instrument within the helical groove, or hollow thread, it is required to form. In the most simple and primitive method, four planes were filed upon the screw, as in Fig. 391, but this exposes very obtuse edges which can hardly be said to cut, as they form the thread partly by indenting, and partly by raising or burring up the metal; and as such they scarcely produce any effect in cast iron or other crystaline materials. Conceiving, as in Fig. 391, only a very small portion of the circle to remain, the working edges of squared taps, form angles of (90 + 45 or) 135 degrees with the circumference, and the angle is the greater, the more of the circle that remains. It is better to file only three planes, as in Fig. 392, but the angle is then as great as 120 degrees even under the most favorable circumstances. In taps of the smallest size it is imperative to submit to these conditions, and to employ the above sections. Sometimes small in- termediate facets or planes are tipped off a little obliquely with the file, to relieve the surface friction; this gives the instrument partly the character of a six or eight sided broach, and improves the cutting action. ° There appears to be no doubt that, for general purposes, the most favorable angle for the edges of the screw taps and dies is the radial line, or an angle of 90 degrees. This condition manifestly exists in the half-round tap, Fig. 393. I propose that this should be made half-round, as it will be found that a tap formed in this way will cut a full clear thread, (even if it may be of a sharp pitch ) without making up any part of it by the burr, as is almost universally the case when blunt-edged or grooved taps are used. It has sometimes been objected to me by persons who had not seen half-round taps in use, that from their containing less substance than the common forms do, they must be very liable to be broken by the strain required to turn them in the work. It is proved how- ever, by experience, that the strain in their case is so much smaller than usual, that there is even less chance of breaking them than the stouter ones. Workmen are aware that a half-round opening bit makes a better hole and cuts faster than a five sided one, and yet that it requires less force to use it. 320 SCREW-CUTTING TOOLS. Fig. 394, in which two-thirds of the circle are allowed to remain, has been also employed for taps ; this, although somewhat less pen- etrative than the last, is also less liable to displacement with the tap wrench. It is much more usual to employ three radial cutting edges instead of one only ; and as in the best forms of taps, they are only required to cut in the one direction, or when they are screwed into the nut, the other edges are then chamfered to make room for the shavings; thereby giving the tap a section somewhat like that of a ratchet wheel, with either three, four, or five teeth, as in Figs. 395 and 403. It is more common, however, either to file up the side of the tap, or to cut by machinery, three concave or elliptical flutes, as in 396 ; this form sufficiently approximates to the desideratum of the radial cutting edges, it allows plenty of room for the shavings, and is easily wiped out. What is of equal or greater importance, it pre- sents a symmetrical figure, little liable to accident in the hardening, either of distortion from unequal section, as in Figs. 393 and 394, or of cracking from internal angles, as in 394 and 395. Still, considering alone the transverse section of the tap, it will be conceived that before any of the substance can be removed from the hole that is being tapped, the circular part of the instrument must become embedded into the metal a quantity equal to the thick- ness of the shaving ; and in this respect Figs. 391 and 392, in w T hich the circular parts are each only the tenth or twelfth of the circumference, appear to have the advantage over the modern taps 395 and 396, in which each arc is twice as long. Such, however, is not the case, as the first two act more in the manner of the broach, if we conceive that instrument to have serrated edges ; but Figs. 395 and 396 act nearly as turning tools, as in general the outer or the circular surface is slightly relieved with a file, so as to leave the cutting edges a, somewhat in advance of the general periphery ; which is equivalent to chamfering the lower plane of the turning tool some three degrees to produce that relief which has been appro- priately named the angle of separation. But in the tap Fig. 397, invented by F. O'Neill, this is still more effectually accomplished. The instrument, instead of being turned of the ordinary circular section in the lathe, (or as the outer dotted line,) is turned with three slight undulations, by means of an alter- nating radial motion given to the tool. From this it results that, when the summits of these hills are converted into the cutting edges, that not only are the extreme edges or points of the teeth made prominent, but the entire serrated surface becomes inclined at about the three degrees to the external circle, or the line of work, so as exactly to assimilate to the turning tool; and therefore there is little doubt but that, under equal circumstances, O'Neill's tap would work with less friction than any other. The principle of chamfering, or relieving the taps, must not, how- ever, be carried to excess, or it will lead to mischief. For example, the tap, if sloped behind the teeth as in Fig. 398, would be much TRANSVERSE SECTIONS OF TAPS. 321 exposed to fracture ; and the instrument being entirely under its own guidance, the three series of keen points would be apt to stick Figs. 397. 398. 399. 400. irregularly into the metal, and would not produce the smooth, circu- lar, or helical hole, obtained when the tool, Fig. 399, is used. The relief should be slight, and the surfaces of the teeth then assimilate to the condition of the graver for copper-plates, and thereby direct the tap in a very superior manner. The teeth sloped in front, as in Fig. 400, would certainly cut more keenly than those of 399, but they would be much more ex- posed to accident, as the least backward motion or violence would be liable to snip off the keen points of the teeth; and therefore, on the score of general economy and usefulness, the radial and slightly relieved teeth of Fig. 399, or rather of 396, are proper for working taps. It appears further to be quite impolitic, entirely to expunge the surface-bearing, or squeeze, from the taps and dies, when these are applied to the ductile metals; as not only does it, when slight, greatly assist in the more perfect guidance of the instrument, but it also serves somewhat to condense or compress the metal. Unless the taps cut very freely, it is the general aim to avoid the necessity for tapping cast-iron, which is a granular and crystaline substance, apt to crumble away in the tapping, or in the after use. The general remedy is the employment of bolts and nuts made of wrought-iron, or fixing screwed wrought-iron pins in the work, by means of transverse keys and other contrivances, and sometimes by the insertion of plugs of gun-metal, to be afterwards tapped with the screw-threads. In general also, the small screws for cast-iron are coarse and shallow in the thread compared with those for wrought- iron, steel, and brass. The transverse sections hitherto referred to, are always used for those taps employed in screwing the inner surfaces of the nuts, and holes required in general mechanism. The longitudinal section of the working tap is taper and somewhat like a broach, the one end being small enough in external diameter to enter the blank hole to be screwed, and the other end being as large as the screw for which the nut is intended. 21 322 SCREW-CUTTING TOOLS. In many cases a series of two, three, or four taps must be used instead of only one single conical tap, and the modifications in their construction are explained by the above diagrams; namely, Fig. 401, the tap formerly used for nuts and thoroughfare holes, and Fig. 402, the modern tap for the same purposes : the dotted lines in each represent the bottoms of the threads. Fig. 401. t sab a f g In the former kind, the thread was frequently finished of a taper figure, with the screw tool in the lathe ; after which either the four or three plane surfaces were filed upon it, as shown by the section at 8 ; the neck from / to g was as small as the bottom of the thread, and the tang from g to h was either square or rectangular for the tap wrench. The tang, if square, was also taper, the tap wrench then wedged fast upon the tap ; the sides of the tang, if parallel, were rectangular, and measured as about one to two, and there were shoulders on two sides to sustain the wrench. In the modern thoroughfare taps for nuts, drawn to the same scale in Fig. 402, the thread is left cylindrical, from the screw tool or the dies ; then from a to b, or about one diameter in length, is turned down cylindrical until the thread is nearly obliterated ; from d to /, also nearly one diameter in length at the other end, is left of the full size of the bolt, and the intermediate part, b to d, equal to three or four diameters, is turned to a cone, after which the tap is fluted as seen at s. The neck/#, as before, is as small as the bottom of the thread, and the square g h, measures diagonally the same as the turned neck. In using the modern instrument, Fig. 402, the hole to be tapped is bored out exactly to fit the cylindrical plug a 5, which therefore guides the tap very perfectly in the commencement; the tool is simply passed once through the nut without any rGtro^r&dc motion whatever, and the cylindrical part df, takes up the guidance when the larger end of the cone enters the hole; at the completion, the tap drops through, the head being smaller than the bottom of the thread. The old four square taps could not be thus used, for as they rather squeezed than cut, they had much more friction; it was necessary to move them backwards and forwards, and to make the MODES OF WORKING OR USING TAPS. 323 square for the wrench larger, to avoid the risk of twisting off the head of the tap. In taps of modern construction of less than half an inch diameter, it- is also needful to make the squares larger than the proportion employed in Fig. 402. In tapping shallow holes, as only a small portion of the end of the tap can be used, the screwed part seldom exceeds two diameters in length, and as they will not take hold when made too conical, a succession of three or four taps is generally required. The screwed part of the first may be considered to extend from a to b of Fig. 401, of the second, from c to d, of the third from e to /; so that the prior tap may, in each case, prepare for the reception of the following one. The taps are generally made in sets of three ; the first, which is also called the entering or taper tap, is in most cases regularly taper throughout its length ; the second, or the middle tap, is sometimes taper, but more generally cylindrical, with just two or three threads at the end tapered off; the third tap, which is also called the plug or finishing tap, is always cylindrical, except at the two or three first threads, which are slightly reduced. Taps are used in various w r ays, according to the degree of strength required to move them. The smallest taps should have considerable length, and should be fixed exactly in the axis of straight handles ; the length serves as an index by which the true position of the instru- ment can be verified in the course of work ; with the same view as to observation, and as an expeditious mode, taps of a somewhat larger size are driven round by a hand brace, whilst the work is fixed in the vice. Still larger taps require tap wrenches, or levers with central holes to fit the square ends of the taps ; for screw taps from one to two inches diameter, the wrenches have assumed the lengths of from four to eight feet, although the recent improvements in the taps have reduced the lengths of the wrenches to one-half. Notwithstanding that the hole to be tapped may have been drilled straight, the tap may by improper direction proceed obliquely, the progress of the operation should be therefore watched ; and unless the eye serve readily for detecting any falseness of position, a square should be laid upon the work, and its edge compared with the axis of the tap in two positions. In tapping deeply seated holes, the taps are temporarily length- ened by sockets, frequently the same as those used in drilling, which are represented in Fig. 358, page 302; the tap wrench can then sur- mount those parts of the work which would otherwise prevent its application. Sometimes for tapping two distant holes exactly in one line, the ordinary taper tap, Fig. 402, is made with the small cylindrical part a b exceedingly long, so as to reach from the one hole to the other and serve as a guide or director. This is only an extension of the short plug a b, Fig. 402, which it is desirable to leave on most taps used for thoroughfare holes. Some works are tapped whilst they are chucked on the lathe man- drel ; in this case the shank of the tap, if in false position, will swing 324 SCREW-CUTTING TOOLS. round in a circle whilst the mandrel revolves, instead of continuing quietly in the axis of the lathe. Sometimes the centre point of the popit-head is placed in the centre hole in the head of the tap ; in those which are fixed in handles it is better the handle of the tap should be drilled up to receive the cylinder of the popit-head, as in the lathe taps for making chucks ; this retains the guidance more easily. Taps of large size, as well as the generality of cutting instruments, have been constructed with detached cutters. For those exceeding about If inch diameter, two steel plugs a a, may be inserted within taper holes in the body of the tap, as represented in Fig. 403, and in the two sections b and c; the whole is then screwed and hardened. Fig. 403. b c The advance of the cutters slightly beyond the general line of the thread, is caused by placing a piece of paper within the mortises a b, and to relieve the surface friction, each alternate tooth in the middle part of the length of the tap is filed away. Sometimes the cutters are parallel and inserted only partway through, and are then pro- jected by set-screws placed also on the diameter,'as in the section c. The cutter bar, Fig. 372, p. 309, may also be viewed as a tap with detached cutters. The cylindrical bar is supported in temporary fixed bearings, one of which embraces the thread, (sometimes by having melted lead poured around the same,) the bar moves therefore in the path of a screw. In cutting the external thread, the cutter represented is shifted inwards with the progress of the work ; or a straight cutter shifted outwards, serves for making an internal screw: pointed instead of serrated cutters may be also used ; they are fre- quently adjusted by a set screw instead of the hammer, and are worked by a wrench. This screw cutter bar, independently of its use for large awkward works, is also employed for cutting, in their respective situations, screws required to be exactly in a line with holes or fixed bearings, as the nuts of slides, presses, and similar works. Some taps or cutters are made cylindrical, and are used for cut- ting narrow pieces and edges, such as screw-cutting dies, screw tools, and worm wheels ; therefore it is necessary to leave much more of the circle standing, and to make the notches narrower than the width of the smallest pieces to be cut. But the grooves should still possess radial sides, and when these are connected by a curved line, as in Fig. 404, there is less risk of accident in the hardening. The number of the notches increases with the diameter, but the annexed figure SCREW-TOOL CUTTERS. 325 would be better proportioned if it had one or two less notches, as inadvertently the teeth have been drawn too weak. When the tool, Figs. 404 and 405, is used for cutting the dies of die-stocks it is called an original tap, of which further particulars Figs. 404. 405. will be given in the succeeding section ; the tool is then fixed in the vice, and the die-stock is handed round, as in cutting an ordinary screw. When Fig. 405 is used for cutting up screw tools, or the chasing-tools for the use of the turning lathe, the cutter is then called a hob, or a screw-tool cutter, and its diameter is usually greater ; it is now mounted to revolve in the lathe, and the screw tool to be cut, is laid on the rest as in the process of turning, and is pressed forcibly against the cutter. Another method is proposed ; the inside screw tool is laid in a lateral groove in a cylindrical piece of iron, and the tool and cylinder are cut up with the die-stocks as a common screw ; by which mode the inside screw tool obviously be- comes the exact counterpart of the hollow thread of that particular diameter. Fig. 405 is also used as a worm-wheel cutter, that is, for cutting or for finishing the hollow screw-form teeth, of those wheek which are moved by a tangent screw ; as in the dividing-engine for circular lines, and many other cases in ordinary mechanism. The worm wheel cutter is frequently set to revolve in the lathe, and the wheel is mounted on a temporary axis so as to admit of its being carried round horizontally by the' cutter ; sometimes the wheel and cutter are connected by gear. The contact of the ordinary tangent screw with the worm-wheel, resembles that of the tangent to the circle, whence the name ; but Hindley, of York, made the screw of his dividing engine to touch 15 threads of the wheel perfectly, by giving the screw a curved section derived from the edge of the wheel, and smallest in the middle. In cutting the metal screw, or the bolt, the tools are required to be the converse of the tap, as they must have internal instead of external threads, but the radial notches are essential alike in each. For small works, the internal threads are made of fixed sizes and in thin plates of steel; such are called screw plates; for larger works, the internal threads are cut upon the edges of two or three detached pieces of steel, called dies; these are fitted into grooves within die- stocks, and various other contrivances which admit of the approach of the screwed dies, so that they may be applied to the decreasing diameter of the screw, from its commencement to the completion, 326 SCREW-CUTTING TOOLS. The thickness of the screw plate is in general from about two-thirds to the full diameter of the screw, and mostly several holes are made in the same plate ; from two to six holes are intended for one thread, and are accordingly distinguished into separate groups by little marks, as in Fig. 406. The serrating of the edges is sometimes done by making two or three small holes and connecting them by the lateral cuts of a thin saw, as in Fig. 407. The notches alone are sometimes made, and when the holes are arranged as in Fig. 408, should the screw be broken short off by accident, it may be cut in two with a thin saw, and thus removed from the plate. In making small screws, the w r ire is fixed in the hand-vice, tapered off with a file, and generally filed to an obtuse point; then, after being moistened with oil, it is screwed into the one or several holes in the screw plate, which is held in the left hand. At other times, the work fixed in the lathe is turned or filed into form, and the plate is held in the right hand ; but the force then applied is less easily appreciated. The harp-makers and some others, attach a screw plate with a single hole to the sliding cylinder of the popit- head. Figs. 406. 407. 408. The screw plate is sometimes used for common screws as large as from half to three-quarters of an inch diameter ; such screws are fixed in the tail vice, and the screw plate is made from about 15 to 30 inches long, and with two handles; the holes are then made of different diameters, by means of a taper tap, so as to form the thread by two, three, or more successive cuts, and the screw should be entered from the large side of the taper hole. It is, however, very advisable to use the diestocks, in preference to the screw plates, for all screws exceeding about one-sixteenth of an inch diameter, although the unvarying diameter of the screw plate has the advan- tage of regulating the equal size of a number of screws, and as such, is occasionally used to follow the diestocks, by way of a gage for size. The diestock, in common with other general tools, has received a great many modifications that it would be useless to trace in greater detail, than so far as repects the varieties in common use, or those which introduce any peculiarity of action in the cutting edges. A notion of the early contrivances for cutting metal screws will be gathered from the figures 409 to 412, which are copied half-size from "Leupold's Theatrum Machinarum Generale, 1724." For in- EARLY FORMS OF DIESTOCKS. 327 stance, Fig. 409 is the screw plate in two, and jointed together like a common rule ; the inner edges are cut with threads, the larger of which is judiciously placed near the joint, that it may be more forci- bly compressed ; there is a guide a, a, to prevent the lateral displace- ment of the edges, which would be fatal to the action. Similar instruments are still used, but more generally for screws made in the turning lathe. Figs. 409. 4 10. 412. In one of these tools, the frame or stock is made exactly like a pair of flat pliers, but with loose dies cut for either one or two sizes of threads. Plier diestocks are also made in the form of common nut- crackers, or in fact, much like Fig. 409, if we consider it to have handles proceeding from a a, to extend the tool to about two or three times its length ; the guide a a is retained, and removable dies are added, instead of the threads being cut in the sides of the in- strument. In general, however, the two dies are closed together in a straight line, instead of the arc of a circle : one primitive method, Fig. 412, ex- tracted from the work referred to, has been thus remodeled; the dies are inserted in rectangular taper holes, in the ends of two long levers, which latter are connected by two cylindrical pins, carefully fitted into holes made through the levers, and the ends of the pins are screwed and provided with nuts, which serve more effectually to compress the dies than the square rings represented in Fig. 412. The diestock in its most general form has a central rectangular aperture, within which the dies are fitted, so as to admit of compres- sion by one central screw; the kinds most in use being distinguished as the double chamfered diestocks, Figs. 413 and 414; and the single chamfered diestock, Figs. 41b' and 417, the handles of which are partly shown by dotted lines. In the former, the aperture is about as long as three of the dies ; about one-third of the length of the chamfer is filed away at the end, for the removal of the dies laterally, and one at a time. In the single chamfered diestock 417, which is preferable for large threads, the aperture but little exceeds the length of two dies, and these are removed by first taking off the side plate b a, which is either attached by its chamfered edges as a 328 SCREW-CUTTING TOOLS. slide, or else by four screws ; these, when loosened, allow the plate to be slid endways, and it will be then disengaged, as the screws will leave the grooves at a, and the screw heads 'will pass through the holes at b. t Figs. 413. 414. 415. 417. b a Sometimes dies of the section of Fig. 415 are applied after the manner of 414, and occasionally the rectangular aperture of Fig. 417 is made parallel on its inner edges, and without the side plate b a; the dies are then retained by steel plates either riveted or screwed to the diestock, as represented in Fig. 418, or else by two steel pins buried half-way in the sides of the stock, and the remain- ing half in the die, as shown in Fig. 419. These variations are of little moment, as are also those concerning the general form of the stock ; for instance, whether or not the handles proceed in the directions shown, (the one handle s, being occasionally a continuation of the pressure screw,) or whether the handles are placed as in the dotted position t. In small diestocks, a short stud or handle is occasionally attached at right angles to the extremity, that the die- stock may be moved like a winch handle ; and sometimes graduations are made upon the pressure screw, to denote the extent to which the dies are closed. These and other differences are matters compara- tively unimportant, as the accurate fitting of the dies, and their exact forms, should receive the principal attention. In general only two dies are used, the inner surface of each of which includes from the third to nearly the half of a circle, and a notch is made at the central part of each die, so that the pair of dies present four arcs, and eight series of cutting points or edges ; four of which operate when the dies are moved in the one direction, and the other four when the motion is reversed ; that is when the curves of the die and screw are alike. PROPORTIONS OF MASTER TAPS. 329 The formation of these parts has given rise to much investigation and experiment, as the two principal points aimed at, require directly opposite circumstances. For instance, the narrower the edges of the dies, or the less of the circle they contain, the more easily they penetrate, the more quickly they cut, and the less they compress the screw by surface friction or squeezing, which last tends to elongate the screw beyond its assigned length. But, on the other hand, the broader the edges of the dies, or the more of the circle they contain, the more exactly do they retain the true helical form, and the gene- ral truth of the screw. The action of screw-cutting dies is rendered still more difficult, because in general, one pair of dies, the curvatures and angles of which admit of no change, are employed in the production of a screw, the dimensions of which, during its gradual transit from the smooth cylinder to the finished screw, continually change. For instance, the thread of a screw necessarily possesses two magnitudes, namely, the top and bottom of the groove, and also two angles at these respective diameters, as represented by the dotted lines in the diagrams, Figs. 420, 422, and 424, (which are drawn with straight instead of curved lines.) The angles are nearly in the inverse proportion of the diameters ; or if the bottom were half the diameter of the top of the thread, the angle at the bottom would be nearly twice that at the top. The figures show the original taps, master taps, or cutters, from which the dies, Figs. 421, 423, and 425, are respectively made ; and in each of the three diagrams, the dies a are supposed to be in the act of commencing, and the dies b in finishing, a screw of the same diameter throughout, as that in Fig. 420. Figs, 420. 422. 424. Small Master Tap. Medium Master Tap. Large Master Tap. Same diameter as Screw. One depth larger than Screw. Two depths larger than Screw. 421. 423. 425. Of course the circumstances become the more perplexing the greater the depth of the thread, whereas in shallow threads the interference may be safely overlooked. As the dies cannot have 330 SCREW-CUTTINa TOOLS. both diameters of the screw, it becomes needful to adopt that curva- ture which is least open to objection. If, as in Fig. 421, the curved edges of the dies a and b have the same radii as the finished screw, in the commencement, or at a, the die will only touch at the corners, and the curved edges being almost or quite out of contact, there will be scarcely any guidance from which to get the lead, or first direction of the helix, and the dies will be likely to cut false screws, or else parallel grooves or rings. In addition to this, the curved edges present, at the commencement, a greater angle than that proper for the top of the screw, but at the completion of the screw, or at 5, the die and screw will be exact counterparts, and. will be therefore perfectly suitable to each other. If, as in Fig. 425, the inner curvature of the dies a and b be the same as in the blank cylinder, a will exactly agree both in diameter and angle at the commencement of the screw, but at the conclusion, or as at b, each will be too great, and the die and screw will be far from counterparts, and therefore ill adapted to each other. The most proper way of solving the difficulty in dies made in two parts, is by having two pairs of dies, such as 425 and 421, and which is occasionally done in very deep threads, see Figs. 389 and 390. But it is more usual to pursue a medium course, and to make the original tap or cutter, Fig. 422, used in cutting the dies, not of the same diameter as the bolt, as in Figs. 420 and 421, not to exceed the diameter of the bolt by twice the depth of the thread, as in Figs. 424 and 425, but with only one depth beyond the exact size, or half-way between the extremes, as in Figs. 422 and 423, in which latter it is seen the contact although not quite perfect either at a or 5, is suffi- ciently near at each for general practice. The obvious effect of different diameters between the die and screw, must be a falsity of contact between the surfaces and angles of the dies ; thus, in 421, the whole of the cutting falls upon e, the external angles, until the completion of the screw in b, when the action is rather compressing than cutting. In Fig. 425, the first act is that of compressing, and all the work is soon thrown on i, the internal angles of the die, which become gradually more penetrative, but eventually too much so, being in all respects the reverse of the former. In the medium and most common example, Fig. 423, the cut falls at first upon the external angles e, it gradually dies away, and it is dur- ing the brief transition of the cut from the external to the internal angles, i, that is when the screw is exactly half formed, that the com- pression principally occurs. The compression or squeezing, is apt to enlarge the diameter of the screw, (literally by swaging up the metal,) and also to elongate it beyond its assigned length, and that unequally at different parts. Sometimes the compression of the dies makes the screw so much coarser than its intended pitch, that the screw refuses to pass through a deep hole cut with the appropriate tap ; not only may the total in- crease in length be occasionally detected by a common rule, but the CORRECTIONAL MODIFICATIONS IN DIES. 331 differences between twenty or thirty threads, measured at various parts with fine pointed compasses, are often plainly visible. Other and vastly superior modes for the formation of long screws, or those requiring any very exact number of threads in each inch or foot of their length, will be shortly explained. Yet notwithstand- ing the interferences which deprive the diestocks of the refined per- fection of these other methods, they are a most invaluable and pro- per instrument for their intended use ; and the disagreement of curvature and angle is more or less remedied in practice, by reducing the circular part of the dies in various ways ; and also in some in- stances, by the partial separation of the guiding from the cutting action. The most usual form of dies is shown in Fig. 426, but if every measure be taken at the mean, as in Fig. 427, the tool possesses a fair, average, serviceable quality ; that is, the dies should be cut over an original tap of medium dimensions, namely, one depth larger than the screw, such as Fig. 422 ; the curved surface should be halved, making the spaces and curves as nearly equal as may be ; and the edges should be radial. Fig. 428, nearly transcribed from Leupold's figure, 410, has been also used, but it appears as if too much of the curve were then removed. Sometimes the one die is only used for guiding, and the other only for cutting : thus a, Fig. 429, is cut over two different diameters of master taps, which gives it an elliptical form. A large master tap, Fig. 424, is first used for cutting the pair of dies ; this leaves the large parts of the curve in a; the dies are subsequently cut over a small master tap, 420. Figs. 426. 427. 428. 429. 430. ? o 6 a IS b In beginning the screw, the die a, serves as a bed with guiding edges ; these indent without cutting, and also agree at the first start, with the full diameter of the bolt ; with the gradual reduction of the bolt, it sinks down to the bottom of a, which continually presents an angular ridge, nearly agreeing in diameter, and therefore in angle with the nascent screw. The inconveniences of the dies, Fig. 429, are, that they require a large and a small master tap for the forma- tion of every different sized pair of dies, and which latter are rather troublesome to repair. The dies also present more friction than most others, apparently from the screw becoming wedged within the angular sides of the die a. In Fig. 430, the dies are first cut over a small master tap, Fig. 332 SCREW-CUTTING TOOLS. 421, the threads are then partially filed or turned out of b, to fit the blank cylinder; which therefore rests at the commencement upon blunt, triangular, curved surfaces, instead of upon keen edges ; and as the screw is cut up, its thread gradually descends into the por- tions of the thread in 5, which are not obliterated. About one-third of the thread is turned out from each side of the cutting die a, leav- ing only two or three threads in the centre, as shown in the last view ; and the surface of this die is left flat, that it may be ground up afresh when blunted, and which is also done with other dies hav- ing plane surfaces. Mr. William Ryan and Mr. Patrick Mullen have each proposed to assist the action of dies for large screws, by means of cutters ; their plans will be sufficiently explained by the diagrams, Figs. 431 and 432. This mode to large screws of square threads was applied for gun carriages ; the dies were cut very shallow, say one-third of the full depth, and they were serrated on their inner faces to act like saws or files. The dies were used to cut up the commencement of the thread, but when it filled the shallow dies, their future office was not to cut, but only to guide the ascent and descent of the stocks, by the smooth surfaces of the dies rubbing upon the top of the square thread. The remaining portion of the screw was afterwards ploughed out by a cutter like a turning tool, the cutter being inserted in a hole in the one die, and advanced by a set screw,, somewhat after the manner represented in the figures 431 and 432. Figs. 431. 433. 435. 432 434. Mullen employed a similar method for angular thread screws, and the cutter was placed within a small frame fixed to the one die. The screw bolt was commenced with the pair of dies which were closed by the set screw a, 431, the cutter being then out of action. When the cutter was set to work by its adjusting screw b, it was ad- vanced a little beyond the face of the die, and not afterwards moved ; but the advance of a closed the dies upon the decreasing diameter of the screw, the cutter always continuing prominent and doing the principal share of the work. Figure 433 is the plan, and 434 the side elevation, of an old SCREW STOCKS. 333 although imperfect expedient, for producing a left-handed screw from a right-handed tap. It will be remembered the right and left hand screws only differ in the direction of the angle, the thread of the one coils to the right, of the other to the left hand ; and on com- paring a corresponding tap and die, the inclinations of the external curve of the one, and the internal curve of the other, necessarily differ in like manner as to direction. The mode employed, therefore, is to carry a right-hand tap around the screw to be cut ; the tem- porary screw-cutter possesses the same interval or thread as before, but the cutting angles of the tap, having the reverse direction of those of the die, the screw becomes left-handed. The one die in 433 and 434 is merely a blank piece of brass or iron without any grooves, the other is a brass die in which the tap is fixed ; as may be expected, the thread produced is not very perfect, but in the absence of better means, this mode is available as the germ for the production of a set of left-hand taps- and dies. Figs. 435 and 436 represent a different mode of originating a left-handed screw, proposed by Mr. Walsh ; the tool is to be a small piece of a right-handed screw, which is hardened and mounted in a frame like an ordinary milling or nurling tool, and intended to act by pressure alone; the diameter of the tool and cylinder should be like. The screw stock represented in Fig. 437 : three narrow dies were Figs. 437. 438. 439. fitted in three equidistant radial grooves in the stock, the ends of the dies came in contact with an exterior ring, having on its inner edge three spiral curves, (equivalent to three inclined planes,) and on its outer surface a series of teeth into which worked a tangent screw, so that on turning the ring by the screw, the three dies were simul- taneously and equally advanced towards the centre. These screw stocks were found to cut very rapidly, as every cir- cumstance was favorable to that action. For instance, on the principle of the triangular bearing, all the three dies were constantly at work ; the original tap being slightly taper, every thread in the length of the die was performing its part of the work, the same as 334 SCREW- CUTTING TOOLS. in a taper tap, every thread of which removes its shaving or share of the material; and the dies were narrow, with radial edges, which admitted of being easily sharpened. The diestock has been abandoned in favor of the screw stock, which is represented in Fig. 438. The one die embraces about one- third of the circle, the two others much less ; the latter are fitted into grooves which are not radial, but lead into a point situated near the circumference of the screw-bolt; the edges of the dies are slightly hooked or ground respectively within the radius, and they are simultaneously advanced by the double wedge and nut: the dies are cut over a large original, such as Fig. 424, that is, two depths larger than the screw. The large die serves to line out or commence the screw, and the two others act alternately ; the one whilst the stock descends down the bolt, the other during its ascent. We will notice but one more screw stock. It is seen that the one die embraces about one-third the screw, the other is very narrow ; the peculiarity of this construction is that a circular recess is first turned out of the screw stock, and a parallel groove is made into the same, the one handle of the stock, (which is shaded,) nearly fills this recess, and receives the small die. If the handle fitted mathe- matically true, it is clear it would be immovable, but the straight part of the handle is narrower than the width of the groove; when the stock is turned round, say in the direction from 2 to 1, the first process is to rotate the handle in the circle, and to bring it in hard contact with the side 1, this slightly rotates the die also, and the one corner becomes somewhat more prominent than the other. When the motion of the stock is reversed, the handle leaves the side 1, of the groove, and strikes against the other side 2, and then the opposite angle of the die becomes the more prominent; and that without any thought or adjustment on the part of the workman, as the play of the handle in the groove 1, 2, is exactly proportioned to cause the required angular change in the die. The cutting edges of the die act exactly like turning tools, and therefore they may very safely be beveled or hooked as such ; as when they are not cutting, they are removed a little way out of con- tact, and therefore out of danger of being snipped off, or of being blunted by hard friction. The opposite die affords during the time an efficient guidance for the screw, and the broad die is advanced in the usual manner, by the pressure screw made in continuation of the second handle of the diestock ; the dies are kept in their places by a side plate, which is fitted in a chamfered groove in the ordinary manner. There is less variety of method in cutting external screws with the diestocks, than internal screws with taps, but it is desirable in both cases, to remove the rough surface the work acquires in the foundry or forge, in order to economize the tools ; and the best works are either bored or turned cylindrically to the true diameters corresponding with the screwing tools. The bolt to be screwed is mostly fixed in the tail vice vertically, BOLT-SCREWING MACHINES. 335 but sometimes horizontally, the dies are made to apply fairly, and a little oil is applied prior to starting. As a more expeditious method suitable to small screws, the work is caused to revolve in the lathe, whilst the diestock is held in the hand; and larger screws are sometimes marked or lined out whilst fixed in the vice, the principal part of the material is then removed with a chasing tool or hand- screw tool, and the screw is concluded in the die-stocks. In cutting up large screw bolts, two individuals are required to work the screw stocks, and they walk round the standing vice or screwing clamp, which is fixed to a pedestal in the middle of the workshop. For screwing large numbers of bolts, the engineer employs the bolt-screwing machine, which is a combination of the ordinary taps and dies, with a mandrel, driven by steam power. In the machine the mandrel revolves, traverses, and carries the bolt, whilst the dies are fixed opposite to the mandrel ; or else the mandrel carries the tap, and the nut to be screwed is grasped opposite to it. In another machine, the mandrel does not traverse, it carries the bolt, and the dies are mounted on a slide; or else the mandrel carries the nut, and the tap is fixed on the slide. The tap or die gives the traverse in every case, and the engine and strap supply the muscle ; of course the means for changing the direction of motion and closing the dies, as in the hand process, are also essential. The screwing table is a useful modification of the bolt machine, intended to be used for small bolts, and to be worked by hand. The mandrel is replaced by a long spindle running loosely in two bear- ings; the one end of the spindle terminates in a small wheel with a winch-handle, the other in a pair of jaws closed by a screw. The jaws embrace the head of the bolt, which is presented opposite to dies that are fixed in a vertical frame or stock, and closed by a loaded lever to one fixed distance. In tapping the nut, it is fixed in the place before occupied by the dies, and the spindle then used, is bored up to receive the shank of the tap, which is fixed by a side screw. This machine insures the rectangular position of the several parts, and the power is applied by the direct rotation of a hand wheel. It will be gathered from the foregoing remarks, that the diestock Figs. 440. 441. 336 SCREW-CUTTING TOOLS. is an instrument of most extensive use, and it would indeed almost appear as if every available construction had been tried, with a general tendency to foster the cutting, and to expunge the surface friction or rubbing action ; by the excess of which latter, the labor of work is greatly increased, and risk is incurred of stretching the thread. Figures 440 and 441 show a shaping machine, built at the Lowell Machine Shop, Lowell, Mass. Many of the machines built at the Lowell Machine Shop, were much improved by W. B. Bement. This shaping and planing instrument will plane either flat or curved sur- faces. SCREWS CUT IN THE COMMON LATHE. 337 The tool bar is moved by a variable crank adjustable to any length of motion not exceeding eight inches. It has a self-acting horizontal and circular feed motion, with a hand feed motion for internal curves. Figs. 442, 443 show a geer cutting machine manufactured at the Lowell Machine Shop, Lowell, Massachusetts. The dividing plate is forty-eight inches in diameter. This machine will cut every number of teeth up to 133, and every even number to 268, also 272, 276, and 360 teeth. The cutter stock is so arranged as to move either horizontally or vertically, or at any angle, so as to cut bevel, spur, and spiral wheels and geering. Screws Cut by Hand in the Common Lathe. — Great numbers of screws are required in works of wood, ivory and metal, that cannot be cut with the taps and dies, or . the other apparatus hitherto con- sidered. This arises from the nature of the materials, the weakness of the forms of the objects, and the accidental proportions of the screws, many of which are comparatively of very large diameter and incon- siderable length. These, and other circumstances, conspire to prevent the use of the diestocks for objects such as the screws of telescopes and other slender tubes, those on the edges of disks, rings, boxes, and very many similar works. Screws of this latter class are frequently cut in the lathe with the ordinary screw tool, and by dexterity of hand alone ; there is little to be said in explanation of the apparatus and tools, which then consist solely of the lathe with an ordinary mandrel incapable of traversing endways, and the screw tools or the chasing tools, with the addition of the arm rest. The screw tool held at rest would make a series of rings, because at the end of the first revolution of the object, the points A B C of the tool would fall exactly into the scratches ABC commenced re- spectively by them. But if in its first revolution, the tool is shifted exactly the space between two of its teeth, at the end of the revolu- tion, the point B of the tool, drops into the groove made by the point A, and so with all the others, and a true screw is formed, or a continuous helical line, which appears in steady lateral motion during the revolution of the screw in the lathe. It is likely the tool will fail exactly to drop into the groove, but if the difference be inconsiderable, a tolerably good screw is never- theless formed; as the tool being moved forward as equally as the hand will allow, corrects most of the error. But if the difference be great, the tool finds its way into the groove with an abrupt break in the curve ; and during the revolution of the screw, as it progresses it also appears to roll about sideways, instead of being quiescent, and is said by workmen to be "drunk:" this error is frequently beyond correction. It sometimes happens that the tool is moved too rapidly, and that the point C drops into the groove commenced by A ; in this case the coarseness of the groove is the same as that of the tool, but the 22 338 SCREW-CUTTING TOOLS. inclination is double that intended, and the screw has a double thread, or two distinct helices instead of one ; the tool may pass over three or four intervals and make a treble or quadruple thread, but these are the results of design and skill, rather than of accident. On the other hand, from being moved too slowly, the point B of the tool may fail to proceed so far as the groove made by A, but fall midway between A and B ; in this case the screw has half the rise or inclination intended, and the grooves are as fine again as the tool ; other accidental results may also occur which it is unnecessary to notice. On Cutting Screws in Lathes with Traversing Mandrels.-— One of the oldest, most simple, and general apparatus for cutting short screws in the lathe, by means of a mechanical guidance, is the screw-mandrel or traversing-m&ndrel, which appears to have been known almost as soon as the iron mandrel itself was introduced. Figure 444 is copied from an old French mandrel mounted in a wooden frame, and with tin collars cast in two parts ; the upper halves of the collars are removed to show the cylindrical necks of the mandrel, upon the shaft of which are cut several short screws. In ordinary turning, the retaining key Jc, which is shown detached in the view Jc', prevents the mandrel from traversing, as its angular and circular ridge enters the groove in the mandrel ; but although not represented, each thread on the mandrel is provided with a simi- Fig. 444. lar key, except that their circular arcs are screw-form instead of angular. In screw cutting, Jc is depressed to leave the mandrel at liberty ; the mandrel is advanced slightly forward, and one of the screw-keys is elevated by its wedge until it becomes engaged with its corresponding guide-screw, and now as the mandrel revolves, it also advances or retires in the exact path of the screw selected. The modern screw-mandrel lathe has a cast-iron frame, and hard- ened steel collars which are not divided ; the guide screws are fitted as rings to the extreme end of the hardened steel mandrel, and they work in a plate of brass, which has six scollops, or semicircular APPLICATION OP THE SCREW-MANDREL. 339 screws upon its edge. When this mandrel is used for plain turning, its traverse is prevented by a cap which extends over the portion of the mandrel protruding through the collars. In cutting screws with either the old or modern screw-mandrel, the work is chucked, and the tool is applied, exactly in the manner of turning a plain object ; but the mandrel requires an alternating motion backwards and forwards, somewhat short of the length of the guide screw ; this is effected by giving a swinging motion or par- tial revolution to the foot wheel. The tool should retain its place with great steadiness, and it is therefore often fixed in the sliding rest, by which also it is then advanced to the axis of the work with the progress of the external screw ; or by which it is also removed from the centre in cutting an internal screw. To cut a screw exceeding the length of traverse of the mandrel, the screw tool is first applied at the end of the work, and when as much has been cut as the traverse will admit, the tool is shifted the space of a few threads to the left, and a further portion is cut ; and this change of the tool is repeated until the screw attains the full length required. When the tool is applied by hand, it readily assumes its true position in the threads ; when it is fixed in the slide rest, its adjustment requires much care. In screwing an object which is too long to be detached to the mandrel by the chuck alone, its opposite extremity is sometimes supported by the front centre or popit head ; but the centre point must then be pressed up by a spring, that it may yield to the ad- vance of the mandrel : this method will only serve for very slight works, as the pressure of the screw-tool is apt to thrust the work out of the centre. It is a much stronger and more usual plan, to make the extremity or some more convenient part of the work cylin- drical, and to support that part within a stationary cylindrical bear- ing, or collar plate, which retains the position of the work notwith- standing its helical motion, and supplies the needful resistance against the tool. The amateur who experiences difficulty in cutting screws flying, or with the common mandrel and hand-tool unassistedly, will find the screw-mandrel an apparatus by far the most generally convenient for those works, in wood, ivory, and metal turning, to which the screw box, and the taps and dies are inapplicable ; for the screw- mandrel requires but a very small change of apparatus, and what- ever may be the diameter of the work, it insures perfect copies of the guide screws, the half dozen varieties of which will be found to present abundant choice as to coarseness, in respect to the ordinary purposes of turning. On Cutting Screws in Lathes with Traversing Tools. — A great number of the engines for cutting screws, and also of the other shaping and cutting engines now commonly used, are clearly to be traced to a remote date, so far as their principles are concerned. For instance, the germs of many of these cutting machines, in which the principles are well developed, will be found in the primi- 340 SCREW-CUTTING TOOLS. tive rose engine machinery with coarse wooden frames, and arms, shaper plate, cords, pulleys, and weights, described in the earliest works on the lathe, whilst many are as distinctly but more care- fully modeled in metal, in the tools used in clock and watch making, many of which have also been published. The principles of these machines being generally few and simple, admit of but little change; but the structures, which are most diver- sified, nay, almost endless, have followed the degrees of excellence of the constructive arts at the periods at which they have been severally made, combined with the inventive talent of their project- ors. In most of the screw-cutting machines a previously-formed screw is_ employed to give the traverse; such are copying machines, and will form the subject of the present section; and a few other engines serve to originate screws, by the direct employment of an inclined plane, or the composition of a rectilinear and a circular motion. The earliest screw-lathe known to the author, bears the date of 1569, and this curious machine, which is represented in Fig. 445, is thus described by its inventor, Besson; "Espece de Tour en nulle part encore veiie et qui n'est sans subtilite, pour engraver petit d petit la Vis d Ventour de toute Figure ronde et solide, voire mesmes ovale." Fig. 445. The tool is traversed alongside the work by means of a guide- screw, which is moved simultaneously with the work to be operated upon, by an arrangement of pulleys and cords too obvious to require explanation. It is however worthy of remark, that bad and im- perfect as the constructive arrangement is, this early machine is capable of cutting screws of any pitch, by the use of pulleys of dif- grandjean's screw-cutting lathe. 341 ferent diameters; and right and left-hand screws at pleasure, by crossing or uncrossing the cord ; and also that in this first machine the inventor was aware that a screw- cutting-lathe might be used upon elliptical, conical, and other solids. The next illustration, Fig. 446, represents a machine described as "A Lathe in which without the common art all sorts of screws and other curved lines can be made ;" this was invented by M. G-randjean prior to 1729. The constructive details of this machine, which are also sufficiently apparent, are in some respects superior to those in Besson's ; but the two are alike open to the imperfection due to the transmissions of motion by cords ; and Grandjean's is addition- ally imperfect, as the scheme represented will fail to produce an equable traverse of the mandrel compared with its revolution, owing to the continual change in the angular relations between the arms of the bent lever, and the mandrel and cord respectively. Some- times the spiral board or templet s, is attached to the bent lever to act upon the end of the mandrel ; this also is insufficient to produce a true screw in the manner proposed. Several of the engines for cutting screws, appear to be derived from those used for cutting fusees, or the short screws of hyperbo- lical section, upon which the chains of clocks and watches are wound, in order to counteract the unequal strength of the different coils of the spiral springs. The fusee engines, which are very numerous, have in general a guide-screw from which the traverse of the tool is derived, and the illustration Fig. 447, selected from an old work published in 1741, is not only one of the earliest, but also of the most exact of this kind ; and it exhibits likewise the primitive appli- cation of change wheels, for producing screws of varied coarseness from one original. This instrument is nearly thus described by Thiout: "A lathe which carries at its extremity two toothed wheels ; the upper is s Fig. 446. 342 SCREW-CUTTING TOOLS. attached to the arbor, the clamp at the end of which holds the axis of the fusee to be cut, the opposite extremity is retained by the centre; the fusee and arbor constitute one piece, and are turned by the winch handle. The lower wheel is put in movement by the upper, and turns the screw which is fixed in its centre ; the nut can traverse the entire length of the screw, and to the nut is strongly hinged the lever that holds the graver or cutter, and which is pressed up by the hand of the workman. Several pairs of wheels are re- quired, and the smaller the size of that upon the mandrel, the less is the interval between the threads of the fusee." Fig. 447. In the general construction of the fusee engine, the guide-screw and the fusee are connected together on one axis, and are moved by the same winch handle; the degree of fineness of the thread on the fusee is then determined by the intervention of a lever generally of the first order; a great variety of constructions have been made on this principle. Three are described in Thiout's Treatise: namely, in plates 25, 26, and 27, the first by Regnaud de Chaalon. The mode of action will be more clearly seen in the next figure, wherein precisely the same movements are applied to the lathe for the pur- pose of cutting ordinary screws. The apparatus now referred to is that invented by Mr. Healey of Dublin, an amateur ; it is universal, or capable within certain limits of cutting all kinds of screws, either right or left-handed, and is represented in plan in Fig. 448, in which C is the chuck which carries the work to be screwed, and t is the tool which lies upon r r' the lathe-rest, that is placed at right angles to the bearer, and i8 always free to move in its socket s, as on a centre, because the bind- ing screw is either loosened or remove^ On the outside of the chuck C is cut a coarse guide screw, which we will suppose to be right-handed. The nut n n, which fits the crew of the chuck, is extended into a long arm, and the latter com- municates with the lathe-rest by the connecting rod c c. As the SCREW-CUTTING APPARATUSES. 343 Fig. 448. lathe revolves backwards and forwards the arm n, (which is retained horizontally by a guide pin g,) traverses to and fro as regards the chuck and work, and causes the lathe- rest r r', to oscillate in its socket s. The distance s t being half s r', a right-hand screw of half the coarseness of the guide will be cut ; or the tool being nearer to, and on the other side of, the centre s, as in the dotted position t', a finer and left- hand screw will be cut. The rod e c may be attached indiffer- ently to any part of n n, but the smallest change of the relation of s t to s r', would mar the correspondence of screws cut at different periods, and therefore t and r should be united by a swivel joint capable of being fixed at any part of the lathe-rest r r f . The apparatus represented in plan in Figs. 449 and 450, although it does not present the universality of the last, is quite correct in its action ; it is evidently a combination of the fixed mandrel, and the old screw mandrel, Fig. 444. Four different threads are cut on the tube which surrounds the mandrel, and the connection between the guide screw and the work, is by the long bar b b, which carries at the one end a piece g filed to correspond with the thread, and at the other, a socket in which is fixed a screw tool t, correspond- ing with the guide at the time employed. Figs. 449. . 450. The lathe revolves with continuous motion ; and the long bar or rod being held by the two hands in the position shown, the guide g, and the tool t, are traversed simultaneously to the left by the screw guide ; and when the tool meets the shoulder of the work, both hands are suddenly withdrawn, and the bar is shifted to the right for a re- petition of the cut, and so on until the completion of the screw. The guide g, is supported upon the horizontal plate p, which is parallel with the mandrel, and the tool £, lies upon the lathe rest r. Beneath the tool is a screw which rubs against the lathe rest r, 344 SCREW-CUTTING TOOLS. and serves as a stop ; this makes the screw cylindrical or conical, ac- cording as the rest is placed parallel or oblique. For the internal screw, the tool is placed parallel with the bar, as in Fig. 450 ; and the check screw is applied on the side towards the centre, against a short bar, parallel with the axis of the lathe. None of the machines which have been hitherto described, are proper for cutting the accurate screws, of considerable length or of great diameter, required in the ordinary works of the engineer ; but these are admirably produced by the screw-cutting lathes, in which the traverse of the tool is effected by a long guide-screw, connected with the mandrel that carries the work, by a system of change wheels, after the manner employed a century back, as in Fig. 447. The accu- racy of the result now depends almost entirely upon the perfection of the guide-screw, and which we will suppose to possess very exactly 2, 4, 5, 6, or some whole number of threads in every inch, although we shall for the present pass by the methods employed in producing the original guide-screw, which thus serves for the reproduction of those made through its agency. The smaller and most simple application of the system of change wheels for producing screws, is shown in Fig. 451. The work is at- Fig. 451. tached to the mandrel of the lathe by means of a chuck to which is also affixed a toothed wheel marked M, therefore the mandrel, the wheel, and the work partake of one motion in common ; the tool is carried by the slide-rest, the principal slide of which is placed parallel with the axis of the lathe as in turning a cylinder, and upon the end of the screw near the mandrel, is attached a tooth wheel S, which is made to engage in M, the wheel carried by the mandrel. As the wheels are supposed to contain the same number of teeth, they will revolve in equal times, or make continually turn for turn ; and therefore in each revolution of the mandrel and work, the tool will be shifted in a right line, a quantity equal to one thread of the guide-screw, and so with every coil throughout its extent of motion. Consequently, the motion of the two axes being always equal and FIXED SLIDE-REST AND CHANGE WHEELS. 345 continuous, the screw upon the work will become an exact copy of the guide-screw contained in the slide-rest, that is, as regards the interval between its several threads, its total length, and its general perfection. But the arrows in M and S, denote that adjoining wheels always travel in opposite directions; when, therefore, the mandrel and slide- rest are connected by only one pair of wheels, as in Fig. 451, the direction of the copy screw is the reverse of that of the guide. The right-hand screw being far more generally required in mechanism, when the combination is limited to its most simple form, of two wheels only, it is requisite to make the slide-rest screw left-handed, in order that the one pair of wheels may produce right-hand threads. But a right-hand slide-rest screw may be employed to produce at pleasure both right and left-hand copies, by the introduction of either one or two wheels, between the exterior wheels M and S, Fig. 451. Thus, one intermediate axis, to be called I, would produce a right- hand thread ; two intermediate axes, I I, would produce a left-hand thread, and so on alternately ; and this mode, in addition, allows the wheels M and S to be placed at any distance asunder that circum- stances may require. In making double thread screws the one thread is first cut, the wheels are then removed out of contact, and the mandrel is moved exactly half a turn before their replacement, the second thread is then made. In treble threads the mandrel is twice disengaged, and moved one-third of a turn each time, and so on. Figs. 452. 453. 454. When the intermediate wheels are employed, it becomes necessary to build up from the bearers some description of pedestal, or from the lathe-head some kind of bracket, which may serve to carry the axes or sockets upon which the intermediate wheels revolve. These parts have received a great variety of modifications, three of which are introduced in the diagrams Figs. 452 to 454 ; the wheels sup- posed to be upon the mandrel, are situated on the dotted line M M, and those upon the slide-rest on the line S S. The rectangular bracket in Fig. 452, has two straight mortises ; by the one it is bolted to the bearers of the lathe, and by the other 346 SCREW-CUTTING TOOLS. it carries a pair of wheels, whose pivots are in a short piece, which may be fixed at any height or angle in the mortise, so that one or both wheels, I I, may be used according to circumstances. In Fig. 453, the intermediate wheel, or wheels, are carried by a radial arm, which circulates around the mandrel, and is fixed to the lathe head by a bolt passed through the circular mortise. In Fig. 453, a simi- lar radial arm is adjustable around the axis of the slide-rest screw, in the fixed bracket. Sometimes the wheel supposed to be attached to the slide-rest, is carried by the pedestal or arm, fixed to the bed or headstock of the lathe ; in order that a shaft or spindle may proceed from the wheel S, and be coupled to the end of the slide-rest screw, by a hollow square or other form of socket, so as to enable the rest to be placed at any part of the length of the bearer, and permit a screw to be cut upon the end of a long rod. The shaft sometimes terminates at each end in universal joints, in order to accommodate any trifling want of parallelism in the parts; if, however, the shaft be placed only a few degrees oblique, the mo- tion transmitted ceases to be uniform, or it is accelerated and re- tarded in every revolution, which is fatal in screw cutting. This change in the position of the slide-rest, is also needful in cutting a screw which exceeds the length the rest can traverse, as such long screws may then be made at two or more distinct opera- tions ; before commencing the second trip the tool is adjusted to drop very accurately into the termination of that portion of the screw cut in the first trip, which requires very great care, in order that no falsity of measurement may be discernible at the parts where the separate courses of the tool have met. This method of proceeding has, however, from necessity been followed in producing some of the earliest of the long regulating screws, which have served for the production of others by a method much less liable to acci- dent, namely, when the cut is made uninterruptedly throughout the extent of the work. In the larger application of the system of change wheels, the entire bed of the lathe is converted into a long slide-rest, the tool carriage with its subsidiary slides for adjusting the position of the tool, then traverses directly upon the bed ; this mode has given rise to the name " traversing or slide-lathe," a machine which has re- ceived, and continues to receive, a variety of forms in the hands of different engineers. It would be tedious and unnecessary to attempt the notice of their different constructions, which necessarily much resemble each other ; more especially as the principles and motives, which induce the several constructions and practices, rather than the precise details of apparatus, are here under consideration. The arrangement for the change wheels of a screw-cutting lathe given in Fig. 455, resembles the mode frequently adopted. The guide-screw extends through the middle of the bed, and projects at the end ; there is a clasp nut, so that when required, the slide-rest COMPARISON OF THE SLIDE-REST AND SLIDE-LATHE. 347 may be detached from the screw and moved independently of the same. The train of wheels is placed at the left extremity of the lathe ; there is a radial arm which circulates Fig 455 around the end of the main screw, the arm has one or two straight mortises, in which are fixed the axes of the intermediate wheels, and there are two circular mortises, by which the arm may be secured to the lathe bed, in any required position, by its two binding screws. On comparing the relative facilities for cutting screws, either with the slide-rest furnished with a train of wheels, or with the traversing or screw-cutting lathe, the advan- tage will be found greatly in favor of the latter; for instance: — With the slide-rest arrangement, Fig. 451, the work must be always fixed in a chuck to which the first of the change wheels can be also attached ; the wheels frequently prevent the most favorable position of the slides from being adopted ; and in cutting hollow screws the change wheels entirely prevent the tool carriage of the slide-rest from being placed opposite to the centre, and therefore awkward tools, bent to the rectangular form, must be then used. The slide-rest also requires frequent attention to its parallelism with the axis of the lathe, or the screws cut will be conical instead of cylindrical. With the traversing lathe, from the wheels being at the back of the mandrel, no interference can possibly arise from them, and con- sequently the work may be chucked indiscriminately on any of the chucks of the lathe ; every position may be given to the slide car- rying the tool, and therefore the most favorable, or that nearest to the work, may be always selected, and the tools need not be crooked. As the tool carriage traverses at once on the bearers of the lathe, the adjustment for parallelism is always true, and the length of traverse is greatly extended. The system of screw-cutting just explained is very general and practical : for instance, one long and perfect guide-screw, (which we will call the guide,) containing 2, 4, 6, 8, 10, or any precise number of threads per inch having been obtained, it becomes very easy to make from it subsequent screw, (or copies,) which shall be respect- ively-coarser and finer in any determined degree. The principle is, that whilst the copy makes one revolution, the guide must make so much of one revolution, or so many, as shall traverse the tool the space required between each thread of the copy ; and this is accom- plished by selecting change wheels in the proportions of these quan- tities of motion, or, in other words, in the proportion required to exist between the guide-screw and the copy. In explanation, we will suppose the guide to have 6 threads per inch, and that copies of 18, 14, 12 J, 8, 3, 2, 1, threads per inch 348 SCREW-CUTTING TOOLS. are required ; the two wheels must be respectively in the proportions of the fractions T %, T 6 ? , T 6 S i, §, §, §, |, the guide being constantly the numerator. The numerator also represents the wheel on the man- drel, and the denominator that on the guide-screw ; any multiples of these fractions may be selected for the change wheels to be em- ployed. For example, any multiples of T 6 5 , as |§, $f, § f, &c, will pro- duce a screw of 18 threads per inch, the first and finest of the group ; and any multiples of £ , as, f § , ^ 2 G °, &c, will produce a screw of 1 thread per inch, which is the last and coarsest of those given. Screws 2, 4, or 6 times as fine, will result from the interposing a second pair of wheels, respectively multiples of |, J, ^, and placed upon one axis. For instance, the pair of wheels f |, used for producing a screw of 18 threads per inch, would, by the combination A, produce a copy three times as fine, or a screw of 54 threads per ineh. Fig. 453 represents the wheels referred to in combination A, and Fig. 454 those in combination B. Combination A. M Interm. S 24 60 20 72 Combination B. M Interm. S 120 24 72 20 Combination C. M Interm. S 27 53 39 107 And the wheels used for the screw of one thread per inch, would by the combination B, produce a copy three times as coarse, or of three inches rise. Whatsoever the value of the intermediate wheels, whether multiples of f , g, f , &c, they produce screws re- pectively of f, g, f , the pitches of those screws, which would be otherwise obtained by the two exterior wheels alone ; and in this manner a great variety of screws, extending over a wide range of pitch, may be obtained from a limited number of wheels. For instance, the apparatus Holtzapffel and Co. have recently added to the slide-rest, after the manner of Figs. 451 and 453, has a series of about fifteen wheels, of from 15 to 144 teeth, employed with a screw of 10 threads per inch: several hundred varieties of screws may be produced by this apparatus, the finest of which has 320 threads per inch, the coarsest measures 7^ inches in each coil or rise: and the screws may be made right or left handed, double, triple, quadruple, or of any number of threads. The finest combina- tions are only useful for self-acting turning; those of medium coarse- ness serve for all the ordinary purposes of screws ; whilst the very coarse pitches are much employed in ornamental works, and in cutting these coarse screws, the motion is given to the slide-rest screw, and by it communicated to the mandrel. The value of any combination of wheels may be calculated as vulgar fractions, by multiplying together all the driving wheels as numerators, and all the driven wheels as denominators, adding also the fractional value, or pitch, of the guide-screw ; thus in the first example A : — MODES OF COMPUTING THE TRAINS OF WHEELS. 349 24 x 20 x 1 = 480 1 — — or reduced to its lowest terms — . 60 x 72 x 6 = 25920 54 The fraction denotes that ^ th of an inch is the pitch of the screw, or the interval from thread to thread ; also that it has 54 threads in each inch, and which is called the rate of the screw. And in 0, the numbers in Avhich example were selected at random, the screw would be found to possess rather more than 35 threads per inch. The fractions should be reduced to their lowest terms before cal- culation, to avoid the necessity for multiplying such high numbers. Thus the first example would become reduced to | X ^ X | = g 1 ^, and would be multiplied by inspection alone, as the numerators and denominators may be taken crossways if more convenient ; thus f I is equal to J, and § % is also equal to fractions which are smaller than § and. T 5 5 , the lowest terms respectively of §^ and §§ ; the second case could not be thus treated, and the whole numbers must there be multiplied, as they will not admit of reduction. Other details will be advanced, and tables of the combinations of the change-wheels will be also given, in treating of the practice of cutting screws. 27 x 39 x 1 1114 1 — — - or reduced to its lowest terms . 53 x 107 X 6 39026 ^Ah In imitation of the method of change-wheels, the slide-rest screw is sometimes moved by an arrangement of catgut bands, resembling that represented in Besson's screw-lathe, page 340. One band proceeds from the pulley on the mandrel to a spindle overhead having two pulleys, and a second cord descends from this spindle to a pulley on the slide rest. This apparatus has been ap- plied to cutting the expanding horn snakes. See Manuel du Tour- neur, first edit., 1796, vol. ii., plate 21; and second edit., 1816, vol. ii., plate 16. The method offers facility in cutting screws of various pitches, by changing the pulleys, and also either right or left-hand screws, by crossing or uncrossing one of the bands. The plan is unexceptionable, when applied for traversing the tool slowly for the purpose of turning smooth cylinders, or surfaces ; (which is virtually cutting a screw or spiral of about 100 coils in the inch ;) and in the absence of better means, pulleys and bands are sometimes used in matching screws of unknown or irregular pitches, by the tedious method of repeated trials ; as on slightly reducing, with the turning tool, the diameter of either of the driv- ing pulleys, the screw or the work becomes gradually finer ; and reducing either of the driven pulleys makes it coarser ; but the mode is scarcely trustworthy, and is decidedly far inferior to its descendant, or the method of change wheels. The screw tools, or chasing tools, employed in the traversing 350 SCREW-CUTTING TOOLS. lathes for cutting external and internal screws, resemble the fixed tools generally, except as regards their cutting edges ; the following figures, 456 to 458, refer to angular threads, and 459 and 460 to square threads. Angular screws are sometimes cut with the single point, Fig. 456, a form which is easily and correctly made ; the general angle of the point is about 55° to 60°, and when it is only allowed to cut on one of its sides or bevels, it may be used fearlessly, as the shavings easily curl out of the way and escape. But when both sides of the single point tool are allowed to cut, it requires very much more cautious management ; as in the latter case, the duplex shavings being disposed to curl over opposite ways, they pucker up as an* angular film, and in fine threads they are liable to break the point of the tool, or to cause it to dig into, and tear the work. Some- times, also, a fragment of the shaving is wedged so forcibly into the screw by the end of the tool, that it can only be extricated by a sharp chisel and hammer. In cutting angular screws, it is very much more usual and expe- ditious to employ screw tools with many points, which are made in the lathe by means of a revolving cutter or hob, Figs. 404 and 405, page 325. Screw tools with many points, are always required for those angular threads which are rounded at the top and bottom, and which are thence called rounded or round threads. To the screw tool for rounded threads is given the profile of Fig. 457, which construction allows the tool to be inverted, so that the edges may be alternately used for the purpose of equalizing the section of the thread. In making the tool 457, the hob, (which is dotted,) is put between centres in the traversing lathe, and those wheels are applied which would serve to cut a screw of the same pitch as the hob ; the bar of steel is then fixed in the slide-rest, so that the dotted line or the axis of the tool intersects the centre of the hob. The tool is afterwards hollowed on both sides with the file, to facilitate the sharpening, and it is then hardened. In using the tool, it is depressed until either edge comes down to the radius, pro- ceeding from the (black) circle, which is supposed to represent the screw to be cut ; the depression gives the required penetration to the upper angle, and removes the lower out of contact. In the chasing tool represented in Fig. 458, the cutter, c, is made as a ring of steel which is screwed internally to the diameter of the bolt, and turned externally with an undercut groove, for the small screw and nut by which it is held in an iron stock, s, formed of. a corresponding sweep ; for distinctness the cutter and screw are also shown detached. The centre of curvature of the tool is placed a little below the centre of the lathe, to give the angle of separation or penetration; and after the tool has been ground away in the act of being sharpened, it is raised up, until its points touch a straight- edge applied on the line a a of the stock ; this denotes the proper height of centre, and also the angle to which the tool is intended to SCREW TOOLS FOR SQUARE THREADS. 351 be hooked, namely, 10 degrees : each ring makes four or five cutters, and one stock may be used for several diameters of thread. Angular thread screws are fitted to their corresponding nuts simply by reduction in diameter; but square thread screws require attention both as to diameter and width of groove, and are conse- quently more troublesome. Square thread screws are in general of twice the pitch, or double the obliquity, of angular screws of the same diameters; and, consequently, the interference of angle before explained as concerning the die-stocks, refers with a two-fold effect to square threads, which are in all respects much better produced in the screw-cutting lathe. The ordinary tool for square thread screws is represented in three views in Fig. 459: the shaft is shouldered down so as to terminate in a rectangular part which is exactly equal to the width of the groove ; in general the end alone of the tool is required to cut, and Screw Took for Angular Threads. Screw Tools for Square Threads. Figs. 456. 459. a 458. the sides are beveled according to the angle of the screw, to avoid rubbing against the sides of the thread. Tools which cut upon the side alone, are also occasionally used for adjusting the width of the groove. In either case it requires considerable care to maintain the exact width and height of the tool ; the inclination of which should also differ for every change of diameter. To obviate these several inconveniences, the author several years back contrived a tool-holder, Fig. 460, for carrying small blades made exactly rectangular. In height, as at h, the blades are alike, in width, w, they are exactly half the pitch of the threads, and they 352 SCREW- CUTTING TOOLS. are ground upon the ends alone. The parallel blades are clamped in the rectangular aperture of the tool socket by the four screws c c ; and when the screws s s, which pass through the circular mortises in the sockets, are loosened, the swivel joint and graduations allow the blades to be placed at the particular angle of the thread, which is readily obtained by calculation, and is estimated for the medium depth of the thread, or midway between the extreme angles at the top and bottom. One blade, therefore, serves perfectly for all screws of the same pitch, both right and left-handed, and of all diameters ; as the tool exactly fills the groove, it works steadily, and the width of the groove and the height of the centre of the tool, are also strictly maintained with the least possible trouble. The depth of the groove, which is generally one-sixth more than its width, is read off with great facility by means of the adjusting screw of the slide-rest ; especially if, as usual, the screw and its miscrometer agree with the decimal division of the inch. The holder, Fig. 460, has been much and satisfactorily used for screws from about 20 to 2 threads per inch ; but when the screw is coarse and oblique, compared with its diameter, the blade is ground away to the dotted line in A, and is sometimes beveled on the sides almost to the upper edge, to suit the obliquity of the thread, but without altering the extreme width of the tool. The tools for external screws of very coarse pitch, are necessarily formed in the lathe by aid of the corresponding wheels, and a re- volving cutter bar resembling Fig. 372, p. 309. The soft tool is fixed in the slide-rest, and is thereby carried against the revolving cutter bar, 372, which has a straight tool, either pointed or square as the case may be. The end of the screw tool is thus shaped as part of an eternal screw, the counterpart of that to be cut ; the face of the screw tool is filed at right angles to the obliquity of the thread, and the end and sides are slightly beveled for penetration, previously to its being hardened. Internal square threads of small size, are usually cut with taps which resemble Fig. 402, p. 322, except in the form of the teeth. When internal square threads are cut in the lathe, the tool assumes the ordinary form, of a straight bar of steel with a rectangular point standing off at right angles, in most respects like the common pointed tool for inside work. For very deep holes, and for threads of very considerable obliquity, cutter bars, such as Fig. 372, p. 309, are used. The work and the temporary bearings of the bar, are all immovably fixed for the time, and the bar advances through the bearings in virtue of its screw thread ; or otherwise a plain bar, having a cutter only, and not being screwed, may be mounted between centres in the screw lathe, and the work, fixed to the slide-rest, may traverse parallel with the bar by aid of the change wheels. The cutter bar in some cases requires a ring to fill out the space between itself and the hole, to prevent vibration ; and it is necessary to increase the radial distance of the VARIOUS SCREW-TOOLS OR CUTTERS. 353 cutter between each trip, by a set screw, or by slight blows of a hammer. Very oblique inside cutters are turned to their respective forms with a fixed tool, in a manner the converse of that explained above ; and some peculiarities of management are required in using them, in order to obtain the under-cut form of the internal thread. In cutting screws in the turning lathe, the tool only cuts as it traverses in the one direction ; therefore whilst the cutter is moved backwards, or in the reverse direction, for the succeeding cut, it must be withdrawn from the work. Sometimes the tool is traversed back- wards by reversing the motion of the lathe ; and in lathes driven by power, the back motion is frequently more rapid than the cutting motion, to expedite the process ; at other times the lathe is brought to rest, the nut is opened as a hinge, so as to become disengaged from the screw, and the slide-rest is traversed backwards by hand, or by a pinion movement, and the nut is again closed on the screw, prior to the succeeding cut. This mode answers perfectly for screws of the same thread as the guide, and for those of 2, 4, 6, 8 times as coarse or as fine ; hut for those of 2|, 4|, or any fractional times the value of the guide screw, the clasp nut cannot in general be em- ployed advantageously. The progressive advance of the tool between each cut, is com- monly regulated by a circle of divisions or a micrometer on the slide- rest screw, which should always correspond with the decimal divi- sion of the inch. The substance of the shaving may be pretty con- siderable after the first entry is made, butit should dwindle away to a very small quantity, towards the conclusion of the screw. To avoid the necessity for taxing the memory with the graduation at which the tool stood when it was withdrawn for the back stroke, the author has been in the habit of employing a micrometer exactly like that on the screw, which is set to the same graduation, and serves as a remembrancer; another method is to employ an arm or stop, which fits on the axis of the screw or handle with stiff friction, but never- theless allows the tool to be shifted the two or three divisions required for each cut. In the screw lathe used by Mr. Roberts, the nut of the slide screw instead of being a fixture, is made with two tails as a fork, which embraces an eccentric spindle ; by the half rotation of which spindle, the nut together with the adjusting screw, the slide, and the tool,' are shifted, as one mass, a fixed distance to and from the centre, between each cut; so as first to withdraw and then to replace the tool. Whilst the tool is running back, the screw is moved by its adjusting screw and divisions, the minute quantity to set in the tool for the succeeding cut, and the continual wear upon the adjusting screw, as well as the uncertainty of its being correctly moved to and fro by the individual, are each avoided. Sometimes, with the view of saving the time lost in running back, two tools are used, so that the one may cut as the tool slide traverses 23 354 SCREW-CUTTING TOOLS. towards the mandrel, the other in the contrary direction. An ar- rangement for this purpose, as applied to the screwing of bolts in the lathe, is shown in Fig. 461; /represents the front, and b the back tool, which are mounted on the one slide s s, and all three are^ moved as one piece by the handle h, which does not require any micrometer. Fig. 461. In the first adjustment, the wedge w, is thrust to the bottom of the corresponding angular notch in the slide s, and the two tools are placed in contact with the cylinder to be screwed. For the first cut the wedge is slightly withdrawn to allow the tool /, to be ad- vanced towards the work ; and for the return stroke, the wedge is again shifted under the observation of its divisions, and the slide s a, is brought forwards, towards the workman, up to the wedge; this relieves the tool/, and projects b, which is then in adjustment for the second cut; and so on alternately. The command of the two topis is accurately given by the wedge, which is moved a small quantity by its screw and micrometer, between every alternation 'of the pair of tools, by the screw h. . In cutting very long screws, the same as in turning long cylin- drical shafts, the object becomes so slender, that the contrivance called a backstay, is always required for supporting the work in the immediate neighborhood of the tool. The backstay is fixed to the slide plate, or the saddle of the lathe which carries the tool, and is brought as near to the tool as possible ; sometimes the dies or bear- ings are circular, and fit around the screw; at other times they touch the same at two, three, or four parts of the circle only. Some of the numerous forms of this indispensable guide or backstay, will hereafter be shown. In using the screw-lathe with a backstay for long screws, it is a valuable and important method, just at the conclusion, to employ a MODES OF ORIGINATING AND IMPROVING SCREWS 355 pair of dies in the place usually occupied by the tool ; as they are a satisfactory test for exact diameter, and they remove triflingVrrors attributable to veins and irregularities of the material, which the Th 6 e tool & Z t'f / ailS en t elj t0 reduCe t0 the genial surface! ±ne tool and backstay may be each considered to be built on the tops of pedestals more or less lofty, and therefore, more susceptible of separation by elasticity, than the pair of dies fixed in S square frame. It has been judiciously proposed, in effect, toTink he backstay and, turning tool together, b/ the employment of a small frame carrying a semicircular die of lignum-viL, and a fixed turmng tool, adjusted by a pressure screw; the frame to be appli d either m the hand alone or in the slide rest, and to be inverted so that the shavings may fall away without clogging the cutter . Vamous Modes of Originating and Improving ScREws.-The improvement of the screw has given rise to many valuable schemes and modes of practice, which have not been noticed in the E - ing sections notwithstanding their collective length. These prac- tices, indeed, could not consistently have been placed in the former pages of this subject because some of them must be viewed as re- finements upon the general methods, the earlier notice of which would have been premature ; and others exhibit various combinations of methods pursued by different eminent individuals with one com mon object and are therefore too important to be passed in siW notwithstanding their miscellaneous nature. ' To render this section sufficiently complete, it appears needful to take a slight retrospective glance of the early and the modern mod s of originating screws and screw apparatus^ some account of the Wh^Sry e / 0Und m Writin * 8 ° f ^ Hved * ^ ♦W the ^° Yk ! 0f Pa PP us Alexandrinus, a Greek mathematician of screws! "* t0 b ° f0Und praCti ° al directions for mak 4 The process is simply to make a templet of thin brass of the form of a right-angled triangle, the angles of which are made in accorT ance with the inclination of the proposed screw. ms trlZe is then to be wrapped round the cylinder which is to be the dfsired screw, and a spiral line traced along its edge. The screw is sub sequently to be excavated along this line, fiinute practTcIl direc ions are given not only for every step of this process, but also for he division setting out, and shaping the teeth of a worm-wheel of The progressive stages which may be supposed to have been for- eTum J era n te P d:- y ^ ^ ^ ma^ be thus i™r T aI firS ? f r 7-l a P ma ? be supposed to have been made b y the inclined templet, the file, and screw tool; it was imperfect in aU re- spects and not truly helical, but full of small irregularities? * Ihe dies formed by the above were considerably nearer to 356 SCREW-CUTTING TOOLS. perfection, as the multitude of pointed edges of 1, being passed through every groove of the die, the threads of the latter became more nearly equal in their rake or angle, and also in their distances and form. 3. The screw cut with such dies would much more resemble a true helix than 1 ; but from the irregularities in the first tap, the grooves in the die 2, would necessarily be wide, and their sides, instead of meeting as a simple angle, would be more or less filled with ridges, and 3 would become the exact counterpart of 2. 4. A pointed tool appliednn the lathe, would correct the form of the thread or groove in 3, without detracting from its improved cylindrical and helical character ; especially if the turning tool were gradually altered, from the slightly rounded to the acute form, in accordance with the progressive change of the screw. The latter is occasionally changed end for end, either in the die-stocks or in the lathe, to reverse the direction in which the tools meet the work, and which reversal tends to equalize the general form of the thread. 5. The corrected screw 4, when converted into a master-tap, would make dies greatly superior to 2 ; it would also serve for cut- ting -up screw tools ; and lastly, 6. The dies 5 would be employed for making the ordinary screws and working taps ; and this completes the one series of screwing apparatus. , One original tap having been obtained, it is often made subser- vient to the production of others ; for example, a screw tool with several points cut over the corrected original 4, would serve for striking, in the lathe, other master-taps of the _ same thread but different diameters. The process is so much facilitated by the per- fection of the screw tool, that a clever workman would thus, with- out additional correction, strike master-taps sufficiently accurate for cutting up other dies larger or smaller than 4. Sometimes also the dies 5 are used for marking out original taps a little larger or smaller than 4. As a temporary expedient, the screw tool may be somewhat spread at the forge fire to make a tool a little coarser, or it may be upset for one a little finer, and afterwards corrected with a file ; or screw tools may be made entirely with the file, and then employed for producing, in the lathe, master-taps of corresponding degrees of coarseness and of all diameters. These are in truth some of the progressive modes by which, under very careful management, great numbers of good useful screwing apparatus have been produced, and which answer perfectly well for all the ordinary requirements of " binding' or " attachment" screws ; or as the cement by which the parts of mechanism and structures generally, are firmly united together, but with the power of separa- tion and reunion at pleasure. In this comparatively inferior class of screws, considerable latitude of proportion may be allowed, and whether or not their pitches or rates have any exact relationship to the inch, is a matter of indiffer- FUSEE ENGINE WITH INCLINED PLANE. 357 ence as regards their individual usefulness ; but in superior screws, or those which maybe denominated "regulating" and " micrometri- cal" screws, it does not alone suffice that the screw shall be good in general character, and as nearly as possible a true helix ; but it must also bear some defined proportion to the standard foot or inch, or other measure. The attainment of this condition has been attempted in various ways, to some of which a brief allusion was made, and a few descriptive particulars will now be offered. Fig. 462. The apparatus for cutting original screws by means of a wedge or inclined plane, appears to be derived from the old fusee engine, a drawing of which is given in Fig. 462 ; in principle it is perfect, and it is also universal within the narrow limitation of its structure. The drawing is the half size of Fig. 1, Plate xvii., of Ferdinand Berthoud's JEssai sur L'llorlogerie, Paris, 1763. M. Berthoud says, " The instrument is the most perfect with which I am ac- quainted ; it is the invention of M. Le Lievre, and it has been re- constructed and improved by M. Gideon Duval." The templet or shaper plate determines the hyperbolical section of the fusee. The modification, with an inclined plane, is due to Hindley, of York. The handle k, gives rotation to the work ; and at the same time, by means of the rack r r, and the pinion fixed on its axis, the handle traverses a slide which carries on its upper surface a bar i; the lat- ter moves on a centre, and may be set at any inclination by the ad- justing screw and divisions ; it is then fixed by its clamping screws. 358 SCREW-CUTTING TOOLS. The slide s, carries the tool, and the end of this slide rests against the inclined plane t, through the intervention of a saddle or swing piece; the slide and tool are drawn to the left hand by the chain which is coiled round the barrel b, by means of a spiral spring con- tained within it. Supposing the bar i i, to stand square or at zero, no motion would be impressed on the tool during its traverse, which we will suppose to require 10 revolutions of the pinion. But if the bar were inclined to its utmost extent, so that we may suppose the one end to project exactly one inch beyond the other, in reference to the zero line or the path of the slide, then during the 10 revolutions of the screw, the tool would traverse one inch, or the difference between the ends of the inclined bar i; and it would thereby cut a screw of the length of one inch, or the total inclination of the bar, and containing ten coils or threads. _ But the inclination of the bar is arbitrary, and may be any quan- tity less than one inch, and may lean either to the right or left ; consequently the instrument may be employed in cutting all right or left-hand screws, not exceeding 10 turns in length, nor measuring in their total extent above one inch, or the maximum inclination of the bar. The principle of this machine may be considered faultless ; but in action it will depend upon several niceties of construction, particu- larly the straightness of the slide and inclined bar, the equality of the rack and pinion, and the exact contact between the tool slide and the inclined plane. These difficulties augment very rapidly with the increase of dimensions ; and probably the machine made by Mr. Adam Reid exclusively for cutting screws, is as large as can be safely adopted: the inclined plane is 44 inches long, but the work cannot exceed l^ths inch diameter, inches long, or ten threads in total length. The application of the inclined plane to cutting screws is therefore too contracted for the ordinary wants of the engineer, which are now admirably supplied by the screw-cutting lathes with guide screws and change wheels. The accuracy of screws has always been closely associated with the successful performance of engines for graduating circles and right lines, and the next _ examples will be extracted from the published accounts of the dividing engines made by Mr. Ramsden. This eminent individual received a reward from the Board of Longitude, upon the condition that he would furnish, for the benefit of the public, a full account of the methods of constructing and using his dividing machines, and which duly appeared in the following tracts: "Description of an Engine for Dividing Mathematical In- struments, by Ramsden, 4to., 1777." Also, "Description of an Engine for Dividing Straight Lines, by Ramsden, 4to., 1779, from which the following particulars are extracted : — The circular dividing engine consisted of a large wheel moved by a tangent screw ; the wheel was 45 inches diameter, and had 2160 teeth, so that six turns of the tangent screw moved the circle one ramsden's screw-cutting engines. 359 degree ; the screw had a micrometer, and also a ratchet wheel of 60 teeth, therefore one tooth equalled one-tenth of a minute of a degree. The screw could be moved a quantity equal to one single tooth, or several turns and parts, by means of a cord and treadle, so that the circular works attached to the dividing wheel could be readily graduated into the required numbers, by setting the tangent screw to move the appropriate quantities ; the dividing knife or diamond point always moved on one fixed radial line, by means of a swing frame. "In ratching or cutting the wheel," says Mr. Ramsden, " the circle was divided with the greatest exactness I was capable of, first into 5 parts, and each of these into 3 ; these parts were then bisected 4 times;" this divided the wheel into 240 divisions, each intended to contain 9 teeth. The ratching was commenced at each of the 240 divisions, by setting the screw each time to zero by its micrometer, and the cutter frame to one of the great divisions by the index; the cutter was then pressed into the wheel by a screw, and the cutting process was interrupted at the ninth revolution of the screw. It was resumed at the next 240th division, (or nine degrees off,) as at first, and so on. This process was repeated three times round the circle, after which the ratching was continued uninterruptedly around the wheel about 300 times ; this completed the teeth with satisfactory accu- racy. The tangent screw was subsequently made, as explained in the text. The first application of the tangent screw and ratchet to the pur- poses of graduation, appears to have been in the machine for cutting clock and watch wheels, by Pierre Fardoil; see plate 23 of Thiout's TraitS d' Horlogerie, &c. Paris, 1741. At page 55 is given a table of ratchets and settings for wheels with from 102 to 800 teeth- In Mr. Ramsden's description of his dividing engines for circles, he says: "Having measured the circumference of the dividing wheel, I found it would require a screw about one thread in a hun- dred coarser than the guide screw." He goes on to explain that the guide-screw moved a tool fixed in a slide carefully fitted on a triangular bar, an arrangement equivalent to a slide-rest and fixed tool : the screw to be cut was placed parallel with the slide, and the guide-screw and copy were connected by two change wheels of 198 and 200 teeth, (numbers in the proportion required between the guide and copy,) with an intermediate wheel to make the threads on the two screws in the same direction. As no account is given of the mode in which the guide-screw was itself formed, it is to be presumed it was the most correct screw that could be obtained, and was produced by some of the means described in the beginning of the present sections. Mr. Ramsden employed a more complex apparatus in originating the screw of his dividing engine for straight lines, which it was essential should contain exactly 20 threads in the inch ; a condition uncalled for in the circular engine, in which the equality of the teeth of the wheel required the principal degree of attention. This second 360 SCREW-CUTTING TOOLS. screw-cutting apparatus, which maybe viewed as an offspring of the circular dividing engine, is represented in plan, in Fig. 463, and may be thus briefly explained. Fig. 463. The guide-screw G is turned round by the winch, and in each revolution moves the larger tangent wheel one tooth ; the tangent wheel has a small central boss or pulley p, to which is attached the one end of an elastic slip of steel, like a watch-spring ; the other end of the slip is connected with the slide 8, that carries the tool t, in a rightline besides the screw C, which latter is the piece to be cut ; and 0 is connected with the guide-screw Gr, by a bevel pinion and wheel, g and c, as 1 to 6. To proportion the traverse of the tool to the interval or pitch of the screw, two dots were made on the slide s, exactly five inches asunder ; and in that space the screw should contain 100 coils, to be brought about by 600 turns of the handle. The guide-screw was moved that number of revolutions, and the diameter of p was reduced by trial, until the 600 turns traversed the slide exactly from dot to dot ; these points were observed at the time through a lens placed in a fixed tube, and having a fine silver wire stretched dia- metrically across the same as an index. See "Description of an Engine for Dividing Straight Lines." In the construction of his dividing engine for straight lines, Ramsden very closely followed his prior machine for circular lines, if we conceive the wheel spread out as a rectangular slide. On the one edge of the main slide which carried the work, was cut a screw- form rack, with twenty teeth per inch,' which was moved by a short fixed screw of the same pitch, by means of ratchets of 50, 48, or 32 teeth respectively ; the screw could be moved a quantity equal to one single tooth, or to several turns and parts, by means of a treadle. To obtain divisions which were incompatible with the sub- division of the inch into 1000, 960 or 640 parts, the respective METHODS OF ORIGINATING SCREWS. 361 values of one tooth, the scale was laid on the slide at an angle to the direction of motion ; when the swing frame was placed to tra- verse the knife at right angles to the path of the slide, the gradua- tions were lengthened ; when the knife was traversed at right angles to the oblique position of the scale being divided, they were short- ened. This was to a small degree equivalent to having a screw of variable length. In cutting the screw-form teeth of the rectilinear dividing engine, the entire length, namely, 25.6 inches, was first divided very carefully by continual bisection into spaces of eight- tenths of an inch, by hand as usual, and the screw cutter was placed at zero at each of these divisions, pressed into the edge of the slide, and revolved sixteen times ; after three repetitions at each of the principal spaces, the entire length was ratched continuously until the teeth were completed. With the view of producing screws of exact values, engineers have employed numerous modifications of the chain or band of steel, the inclined knife, the inclined plane, and indeed each of the known methods, which however were remodeled as additions to the ordinary turning-lathe with a triangular bar. Some give a preference to the inclined knife, applied against a cylinder revolving in the lathe, by means of a slide running upon the bar of the lathe ; which, besides being very rapid, reduced the mechanism to its utmost simplicity. This made the process to de- pend almost alone on the homogeneity of the materials, and on the relation between the diameter of the cylinder and the inclination of the knife ; whereas in a complex machine, every part concerned in the transmission of motion, such as each axis, wheel and slide, en- tails its risk of individual error, and may depreciate the accuracy of the result ; and to these sources of disturbance, must be added those due to change of temperature, whether arising from the at- mosphere or from friction, especially when different metals are concerned. A rod of wood, generally of alder and about two feet long, was put between the centres, and reduced to a cylinder by a rounder or witchet, attached to a slide running on the bar ; the slide with the inclined knife was then applied, and the angle of the knife was gradually varied by adjusting screws, until several screws made in succession, were found to agree with some fixed measure. _ The experiment was then repeated with the same angle, upon cylinders of the same diameter, of tin, brass, and other comparatively soft metals, and hundreds, or it might almost be said, thousands of screws were thus made. ( , From amongst these screws were selected those which, on trial m the lathe, were found to be most nearly true in their angle, or to have a quiescent gliding motion ; and which would also best endure a strict examination as to their pitch or intervals, both with the rule and compasses, and also when two were placed side by side, and their respective threads were compared, as the divisions on two equal scales. 362 SCREW-CUTTING TOOLS. The most favorable screw having been selected, it was employed as a guide-screw, in a simple apparatus which consisted of two tri- angular bars fixed level, parallel, and about one foot asunder, in appropriate standards with two apertures; the one bar carried the mandrel and popit heads as in the ordinary bar lathe. The slide rest embraced both bars, and was traversed thereupon by the guide-screw placed about midway between the bars ; the guide screw and mandrel were generally connected by three wheels, or else by two or four, when the guide and copy were required to have the reverse direction. The mandrel was not usually driven by a pulley and cord ; but on the extremity of the mandrel was fixed a light wheel, with one arm serving as a winch handle for rapid motion in running back ; and six or eight radial arms, (after the manner of the steering wheels of large vessels,) by which the man- drel and the screw were slowly handed round during the cut. In a subsequent and stronger machine the bar carrying the man- drel stood lower than the other, to admit of larger change wheels upon it, and the same driving gear was retained. And in another structure of the screw-cutting lathe, the triangular bar was placed for the lathe heads in the centre, whilst a large and wide slide-plate, moving between chamfer bars attached to the framing, carried the sliding rest for the tool ; in this last machine, the mandrel was driven by steam power, and the retrograde motion had about double the velocity of that used in cutting the screw. _ The relations between the guide-screw and the copy were varied in all possible ways : the guide was changed end for end, or different parts of it were successively used ; sometimes, also, two guide-screws were yoked together with three equal wheels, their nuts being con- nected by a bar jointed to each, and the centre of this link, (whose motion thus became the mean of that of the guides,) was made to traverse the tool. Steel screws were also cut, and converted into original taps, from which dies were made, to be themselves used in correcting the minor errors, and render the screws in all respects as equable as possible. In fact, every scheme that he could devise, which appeared likely to benefit the result, was carefully tried, in order to perfect to the utmost, the helical character and equality of subdivision of the screw. The change of the thousandth part of the total length, was there- fore given to the tool as a supplementary motion, which might be added to, or subtracted from, the total traverse of the tool, in the mode explained by the diagram, Fig. 464, in which all details of construction are purposely omitted. The copy C, and the guide- screw G, are supposed to be connected by equal wheels in the usual manner ; the guide-screw carries the axis of the bent lever, whose arms are as 10 to 1, and which moves in a horizontal plane ; the short arm carries the tool, the long arm is jointed to a saddle which slides upon a triangular bar i i. In point of fact, the tool was mounted upon the upper of two METHODS OF ORIGINATING SCREWS. 363 longitudinal and parallel slides, which were collectively traversed by the guide-screw G. In the lower slide was fixed the axis or fulcrum of the bent lever, the short arm of which was connected by a link with the upper slide, so that the compensating motion was given to the upper slide relatively to the lower. Fig. 464. I Ijpfl 1 The triangular bar % i, when placed exactly parallel with the path of the tool, would produce no movement on the same, and C, and G, would be exactly alike ; but if i i were placed out of the paral- lelism one inch in the whole length, the tool, during its traverse to the left by the guide-screw G, would be moved to the right by the shifting of the bent lever, one-tenth of the displacement of the bar, or one-tenth of an inch. Therefore, whilst the guide-screw G, from being coarser than required, moved the principal slide the one-thousandth part of the total length in excess ; the bent lever and inclined straight bar i pulled back the upper or compensating slide, the one-thousandth part, or the quantity in excess; making the absolute traverse of the tool exactly seven feet, or the length required for the new screw C, instead of seven feet and one-sixteenth of an inch, the length of G. To have lengthened the traverse of the tool, the bar i i must have been inclined the reverse way ; in other words, the path of the tool is in the diagram the difference of the two motions ; in the reverse inclination,, its path would be the sum of the two motions, and i i being a straight line, the correction would be evenly distributed at every part of the length. Other experimentalists preferred, however, the method of the chain, or flexible band, for traversing the tool the exact quantity; because the reduction of a diameter of the pulley or drum, afforded a very ready means of adjustment for total length; and all the wheels of the mechanism being individually as perfect as they could be made, a near approach to general perfection was naturally anti- cipated on the first trial. This mode, however, is subject to the error introduced by the elasticity or elongation of the chain or band, and which is at the maximum when the greatest length of chain is uncoiled from the barrel. About the year 1820, Mr. Clement put in practice a peculiar mode for originating the guide-screw of his screw-lathe, the steps of which plan will be now described. 1. He procured from Scotland some hand-screw tools cut over a hob with concentric grooves ; and to prevent the ridges or points of 364 SCREW-CUTTING TOOLS. the _ screw tools from being cut square across the end, the rest was inclined to compensate for the want of angle in the hob or cutter. 2. A brass screw was struck by hand, or chased with the tool 1. 3. The screw 2, was fixed at the back of a traversing mandrel, and clipped between two pieces of wood or dies to serve as a guide, whilst 4. A more perfect guide-screw was cut with a fixed tool, and substituted on the mandrel for 3 ; as Mr. Clement considered the movement derived from the opposite sides of the one screw, became the mean of the two sides, and corrected any irregularities of angle, or of drunkenness. 5. A large and a small master-tap m, Fig. 465, were cut on the traversing mandrel with a fixed tool, the threads were about an inch long and situated in the middle of a shaft eight or ten inches long ; the small master-tap was of the same diameter as the finished screw, the large master-tap measured at the bottom of the thread the same as the Wank cylinder to be screwed. The master-taps m, were used in cutting up the rectangular dies required in the apparatus shown in Fig. 465, and now to be described. 6. On the parallel bed of a lathe, were fitted two standards or collar-heads h h', intended to receive the pivots of the screw to be cut, on the extremity of which was placed a winch handle, or some- times an intermediate socket was interposed between the screw and Fig. 465. the winch, to carry the latter to the end of the bed. The bed had also an accurate slide plate s s', running freely upon it, the slide plate had two tails which passed beside the head 7i',and at the other end, a projection through which was made a transverse rectangular mortise for the dies, the one end of the mortise is shown by the removal of the front die d, and the back die d' is seen in its proper situation; one extremity of each die was cut from the large master tap m, and the other from the small. The clamp or shackle c c', was used to close the two dies upon the screw simultaneously ; it is shown out of its true position in order that the dies and mortise may be seen, but when in use the shackel would be shifted to the right, so as to embrace the dies d d'. The plain extremity c' rested against the back die, whilst the screw o bore against the front die, METHODS OF ORIGINATING SCREWS. 365 through the intervention of the washer loosely attached to the clamp to save the teeth from injury ; the pressure screw c had a graduated head and an index, to denote how much the dies were closed. 7 A cylinder ahout two feet long, prepared for the screw, was placed between the heads h h>, and the large dies whose inner edges were of the same diameter as the cylinder, were closed upon it mode- rately tight, and the screw was turned round with the winch, to trace a thread from end to end; this was repeated a few times, the dies being slightly closed between each trip. . . ... 8 A screw-tool was next fixed on the slide s m a chamfer slide t t' with appropriate adjusting screws, so as to follow the dies and remove a shaving, much the same as in turning ; the dies having arrived at one end of the screw, the same screw tool or a second tool was placed on the opposite side of the side-plate, so as to cut during the return movement. With the progress of the screw, the screw-too was applied at a variety of distances from the pair of dies, as well as on opposite sides of the screw, so that the metal was cut out by the tool, and the dies were used almost alone to guide the traverse. Of course the dies were closed between each trip, and when the screw was about half cut up, the small dies were substituted for the large ones used at the commencement of the process. 9 The screw thus made, which was intended for a slide-rest, was found to be very uniform in its thread, and it was used for some time for the ordinary purposes of turning. When, however, it was required to be used for cutting other screws, it was found objectionable that its rate was nearly nine, whereas it was required to have eight threads per inch; it was then used in cutting anew guide-screw by means of a pair of change wheels of 50 and 56 teeth, which upon calculation were found to effect the conversion with sufficient precision. Fig. 466. 10 From 9, the screw of 24 inches in length, one of 8 feet in length was obtained; the thread was cut one-third of its depth, with the wheels, successive portions being operated upon and the tool being carefully adjusted to the termination of the part previously 366 SCREW-CUTTING TOOLS. cut. The general troth of the entire length was given bv a repeti- tion of the tedious mode of correction represented in the figure with L»%tofrhesc°r 0 ew PPlled ^ * *** ««edh| the Ml *£$, S&ffiJ* 3 krSe built at Fig. 467. tureo at Lowell. This instrument is geered with t rest for holdim? drills and reamers moved by a toothed rack, backhead stock adjust 8 steel ^ mt - ,r0n C0M *"> bearings, and S- Figs. 468. 469. METHODS OF ORIGINATING SCREWS. 367 Although the processes 7 and 8 will produce a most uniforin screw, Mr. Clement attaches little importance to the use of the dies and guide-frame alone, when several screws are wanted strictly of the same length. Of some few thus made, as nearly as possible under equal circumstances, two screws were found very nearly to agree, and a third was above a tenth of an inch longer in ten inches. This difference he thinks to have arisen in marking out the threads, from a little variation in the friction of the slide, or a difference in the first penetration of the dies. The friction of the slide, when sufficient to cause any retardation, he considers to produce a constant and accumulative effect ; first as it were, reducing the screw of 15 threads per inch, say to the fine- ness of 151, then acting upon that of 15|, reducing it to 15J, and so on; and that to such an extent, as occasionally to place the screw entirely beyond the correctional process. This cannot be the case when the thread is first marked out with the change wheels, instead of the dies. Fig. 470 is an engine lathe, manufactured at the Lowell Machine Shop, Lowell, Massachusetts. Its swing is 50 inches over the sills, and 32 over the rest. The bed of this lathe is cast in one piece, the feed motion is carried by a screw, the tool rest held down by gibs under the slides, and moved on a toothed rack and pinion by hand. Fig. 470. One very important application of the screw, is to the graduation of mathematical scales, the screw is then employed to move a plat- form, which slides very freely, and carries the scale to be graduated ; and the swing frame for the knife or diamond point is attached to some fixed part of the framing of the. machine. Supposing the screw to be absolutely perfect, and to have fifty threads per inch, successive movements of fifty revolutions would move the platform and graduate the scale exactly into true inches ; but on close exami- nation, some of the graduations will be found to exceed, and others to fall short of the true inch. 368 SCREW-CUTTING MACHINE. The scales assume, of course, the relative degree of accuracy of the screwemployed. No test is more severe; and when these scales are examined by means of two microscopes under a magnifying power of ten or twenty times, the most minute errors become abundantly obvious, from the divisions of the scales failing to in- tersect the cross wires of the instrument ; the result clearly indi- cates corresponding irregularities in the coarseness of the screw at the respective parts of its length. An accustomed eye can thus detect, with the microscope, differences not exceeding the one thirty- thousandth part of an inch, the twenty-five-thousandth part being comparatively of easy observation. Screw Threads Considered in Respect to their Proportions Porms, and General Characters.— The proportions given to screws employed for attaching together the different parts of works, are in nearly every case arbitrary, or in other words, they are de- termined almost by experience alone rather than by rule, and with little or no aid from calculation, as will be shown. In addition to the ordinary binding screws, which although arbi- trary, assume proportions not far distant from a general average, many screws, either much coarser or finer than usual, are continu- ally required for specific purposes ; as are likewise other screws of some definite numbers of turns per inch, as 2, 10, 12, 20, &c, in order to effect some adjustment or movement having an immediate reference to ordinary lineal measure. But all these must be con- sidered as still more distant, than common binding screws, from any fixed proportions, and not to be amenable to any rules beyond those of general expediency. Neither the pitch, diameter, nor depth of thread, can be adopted as the basis from which to calculate the two other measures, on account of the different modes in which the three influence the effectiveness of the screw ; nor can the proportions suitable to the ordinary f inch binding screw, be doubled for the 1J inch screw, or halved for that of f inch ; as every diameter requires its individual scale to be determined in great measure by experiment, in order to produce something like a mean proportion between the dissimilar conditions, which will be separately explained in various points of view. The reasons for the uncertainty of measure in the various fixing screws required in the constructive arts, are sufficiently manifest*; as first, the force or strain to which a screw is exposed, either in the act of fixing, or in the office it has afterwards to perform, can rarely be told by calculation ; and secondly, a knowledge of the strain the screw itself will safely endure without breaking in two, or without drawing out of the nut, is equally difficult of attainment; nor thirdly, can the deduction for friction be truly made from that force the screw should otherwise possess, from its angle or pitch, when viewed as a mechanical power, or as a continuous circular wedge. RELATIVE STRENGTH OF SCREWS. 369 The force required in the fixing of screws takes a very wide range, and is faintly indicative of the strain exerted on each. The watch- maker, in fixing his binding screws, employs with great delicacy a screw-driver the handle of which is smaller than an ordinary drawing pencil ; while for screws, say of five inches diameter, a lever of six or seven feet long must be employed by the engineer, with the united exertions of as many men. But in neither case do we arrive at any available conclusion, as to the precise force exerted upon, or by each screw ; nor of the greatest strain that each will safely endure. The absolute measures of the strength of any individual screw being therefore nearly or quite unattainable, all that can be done to assist the judgment, is to explain the relative or comparative mea- sures of strength in different screws, as determined by the three conditions which occur in every screw ; whether it be right or left- handed, of single or of multiplex thread, or of any section what- ever ; and which three conditions follow different laws, and con- jointly, yet oppositely, determine the fitness of the screw for its particular purpose, and therefore tend to perplex the choice. The three relative or comparative measures of strength in differ- ent screws are : first, the mechanical power of the thread, which is derived from its pitch ; secondly, the cohesive strength of the bolt, which is derived from its transverse section ; thirdly, the cohesive strength of the hold, which is derived from the interplacement of the threads of the screw and nut. These conditions will be first considered, principally as regards ordinary binding screws, and screw bolts and nuts, of angular threads, and which indeed constitute by far the largest number of all the screws employed ; screws of angular and square threads will be then compared, The comparative sections, Figs. 471 to 474, represent screws of the same diameters, and in all of which the depth of the thread is equal to the width of the groove ; Figs. 472 and 474 show the or- dinary proportions of f inch angular and square thread screws ; 471 and 473 are respectively as fine and as coarse again as 472. Figs. 471. 472. 473. • 474. Various measures of the screws which require little further expla- nation are subjoined in a tabular form ; and the relative degrees of strength possessed by each screw under three different points of view, are added. 24 370 SCREW-CUTTING TOOLS. Fig. Fig. Fig. Fig. MEASURES AND RELATIVE STRENGTHS OF THE SCREWS. 471 472 473 474 External diameters in hundredths of an inch . . . .75 .75 .75 .75 Internal diameters in hundredths of an inch . . . .65 .55 .35 .55 Number of threads per inch, or rates of the screws 20. 10. 5. 5. Depths and widths of the threads in hundredths . . .05 .10 .20 .10 Angles of the threads on the external diameters* . . 1° 16' 2° 33' 5° 5' 5° 5' Angles of the threads on the internal diameters* . . 1°28 / 3° 28' 10° 47' 6° 55' Relative mechanical powers of the threads . . . . 20 10 5 5 Relative cohesive strengths of the bolts 4 3 1 3 Relative cohesive strengths of hold of the screws . . 65 55 35 27£ Relative cohesive strengths of hold of the nuts . . . 75 75 75 m Square thread screws, have about twice the pitch of angular threads of similar diameters, and Fig. 474 estimated in the same manner as the angular, will stand by comparison as follows. The square thread, Fig. 474, will be found to be equal in power to Fig. 473, the pitch being alike in each. In strength of bolt to be equal to Fig. 472, their transverse areas being alike. And in strength of hold, to possess the half of that of Fig. 472, because the square thread will from necessity break through the bottom of the threads, or an interrupted line exactly like the dotted line in Fig. 473, that denotes just half the area or extent of base, of the thread of Fig. 472 ; which latter covers the entire surface of the contained cylin- der, and not the half only. The mechanical power of the thread, is derived from its pitch. The power, or the force of compression, is directly as the number of threads per inch, or as the rate; so that neglecting the friction in both cases, Fig. 471 grasps with four times the power of Fig. 473, because its wedge or angle is four times as acute. When, however, the angle is very great, as in the screws of fly- presses, which sometimes exceed the obliquity of 45 degrees, the screw will not retain its grasp at all ; neither will a wedge of 45 degrees stick fast in a cleft. Such coarse screws act by impact ; they give a violent blow on the die from the momentum of the fly (namely, the loaded lever, or the wheel fixed on the press-screw) being suddenly arrested ; they do not wedge fast, but on the' con- * The angles of the threads of screws are calculated trigonometrically, the circumfer- ence of the bolt being considered as the base of a right-angled triangle, and the pitch as the height of the same. The author has adopted the following mode, which will be found to require the fewest figures; namely, to divide the pitch by the circumference, and to seek the product in the table of tangents; decimal numbers are to be used, and it is sufficiently near to con- sider the circumference as exactly three times the diameter. For the external angle of Fig. 473 say .20 -i- 2.25=.0888, and this quotient by Hut- toirs Tables gives 5 deg. 5 min. For the internal angle of Fig. 471 say .05-7-1. 95=0.2564, and by Hutton's Tables, 1 deg. 28 min. In this method the pitch is considered as the tangent to the angle, and the division effects the change of the two sides of the given right-angled triangle, for two others, the larger of which is 1 or unity, for the convenience of using the tables. IMPORTANCE OF AGREEMENT IN PITCH. 371 trary, the reaction upwards unwinds and raises the screw for the succeeding stroke of the fly-press. Binding screws which are disproportionately coarse, from leaning towards this condition, and also from presenting less surface-friction, are liable to become loosened if exposed to a jarring action. But when, on the contrary, the pitch is very fine, or the wedge is very acute, the surface friction against the thread of the screw is such, as occasionally to prevent their separation when the screw-bolt has remained long in the hole or nut, from the adhesion caused by the thickening of the oil, or by a slight formation of rust. The cohesive strength of the bolt is derived from its transverse section. The screw may be thus compared with a cylindrical rod of the same diameter as the bottom of the thread, and employed in sustaining a load; that is, neglecting torsion, which if in excess may twist the screw in two. The relative strengths are represented by the squares of the smaller diameters: in the screws of 20, 10, and 5 angular threads, the smaller diameters are 65, 55, and 35; the squares of these numbers are 4225, 3025, and 1225, which may be expressed in round numbers as 4, 3, 1; and, therefore, the coarsest screw, Fig. 473, has transversely only one-fourth the area, and consequently one-fourth the strength of the finest, represented in the three diagrams. The cohesive strength of the hold is derived from the helical ridge of the external screw, being situated within the helical groove of the internal screw. The two helices become locked together with a degree of firmness, approaching to that by means of which the differ- ent particles of solid bodies are united into a mass ; as one or both of the ridges must be in a great measure torn off in the removal of the screw, unless it be unwound or twisted out. A slight difference in the diameter or the section of a screw and nut, is less objectionable than any variation in the coarseness or pitch ; as the latter difference, even when very minute, will pre- vent the screw from entering the hole, unless the screw is made considerably smaller than it ought to be, and even then it will bear very imperfectly, or only on a few places of the nut. To attempt to alter a screwed hole by the use of a tap of a dif- ferent pitch, is equally fatal, as will be seen by the annexed diagram, Fig. 475. 372 SCREW-CUTTING TOOLS. Fig.475. For instance, the upper line a, contains exactly 4 threads per inch, and the middle line or b, has 4J threads ; they only agree at distant intervals. The lowest line c, shows that which would result from forcing a tap of 4 threads such as a, into a hole which had been previously tapped with the 4J thread screw 6, the threads would be said to cross, and would nearly destroy each other ; the same result would of course occur from employing 4 or 5 thread dies on a screw of 4J threads per inch. Therefore, unless the screw tackle exactly agree in pitch with the previous thread, it is needful to remove every vestige of the former thread from the screw or hole; otherwise the result drawn at c, must ensue in a degree proportionate to the difference of the threads, and a large portion of the bearing surface, and consequently, of the strength and the durability of the contact, would each be lost. Some idea may thence be formed of the real and irremediable draw- back frequently experienced from the dissimilarity of screwing ap- paratus ; nearly to agree will not suffice, as the pitch should be identical. The nut of a f-inch screw bolt is usually f inch thick, as it is considered that when the threads are in good contact, and collec- tively equal to the diameter of the bolt, that the mutual hold of the threads exceeds the strength either of the bolt or nut ; and therefore that the bolt is more likely to break in two, or the nut to burst open, rather than allow the bolt to draw out of the hole, from the thread stripping off. When screws fit into holes tapped directly into the castings or other parts of mechanism, it is usual to allow still more threads to be in contact, even to the extent of two or more times the diame- ter of the screw, so as to leave the preponderance of strength greatly in favor of the hold ; that the screw, which is the part more easily renewed, may be nearly certain to break in two, rather than damage the casting by tearing out the thread from the tapped hole. Should the internal and external screws be made in the same material, that is both of wood, brass or iron, the nut or internal screw is somewhat the stronger of the two. For example, in the screw Fig. 472, the base of the thread is a continuous angular ridge, which occupies the whole of the cylindrical surface represented by the dotted line. Therefore the force required to strip off the thread from the bolt, is nearly that required to punch a cylindrical hole of the same diameter and length as the bottom of the thread ; for in either case the whole of the cylindrical surface has to be stripped or thrust off laterally, in a manner resembling the slow quiet action of the punching or shearing engine. But the base of the thread in the nut, is equal to the cylindrical surface measured at the top of the bolt, and consequently, the mate- rials being the same, and the length the same, considering the strength of the nut for Fig. 472 to be 75, the strength of the bolt would be only 55, or they would be respectively as the diameters of the top and bottom of the thread ; although when the bolt pro- RELATIVE STRENGTH OF SCREWS AND NUTS. 373 trades through the nut, the thread of the bolt derives a slight addi- tional strength, from the threads situated beyond the nut, and which serve as an abutment. It is however probable that the angular thread will not strip off at the base of the threads, either in the screw or nut, but will break through a line somewhere between the top and bottom : but these results will occur alike in all, and will not therefore materially alter the relation of strength above assumed. Comparing Figs. 471, 472, and 473, upon the supposition that the bolts and nuts exactly fit or correspond, the strengths of the three nuts are alike, or as 75, and those of the bolts are as 65, 55, and 35, and therefore the advantage of hold lies with the bolt of finest thread ; as the finer the thread, the more nearly do the bolt and nut approach to equality of diameter and strength. Supposing however, for the purpose of explanation, that instead of the screws and nuts being carefully fitted, the screws are each one-tenth of an inch smaller than the diameters of the respective taps employed in cutting the three nuts; Fig. 471 would draw entirely out without holding at all ; the penetration and hold of Fig. 472 would be reduced to half its proper quantity ; and that of Fig. 473 to three-fourths; and the last two screws would strip at a line more or less elevated above the base of the thread, and therefore the more easily than if the diameters exactly agreed. The supposed error, although monstrous and excessive, shows that the finer the tread, the greater also should be the accuracy of contact of such screws; and it also shows the impolicy of employ- ing fine threads in those situations where they will be subjected to frequent screwing and unscrewing, and also to much strain. As although when they fit equally well, fine threads are somewhat more powerful than coarse, in hold as well as in mechanical power; the fine are also more subject to wear, and they receive from such wear, a greater and more rapid depreciation of strength, than threads of the ordinary degrees of coarseness. In a screw of the same diameter and pitch, the ultimate strength is diminished in a twofold manner by the increase of the depth of the thread ; first it diminishes the traverse area of the bolt, which is therefore more disposed to break in two ; and secondly, it dimin- ishes the individual strength of each thread, which becomes a more lofty triangle erected on the same base, and is therefore more ex- posed to fracture or to be stripped off. But the durability of machinery is in nearly every case increased by the enlargement of the bearing surfaces, and therefore as the thread of increased depth presents more surface-bearing, the deep screw has constantly greater durability against the friction or wear, arising from the act of screwing and unscrewing. The durability of the screw becomes, in truth a fourth condition, to be borne in mind collectively with those before named. It frequently happens that the diameters of screwed works are so considerable, that they can neither break nor burst after the 374 SCREW-CUTTING TOOLS. manner of bolts and nuts; and if such large works yield to the pressures applied, the threads must be the part sacrificed. If the materials are crystaline, the thread crumbles away, but in those which are malleable and ductile, the thread, instead of stripping off as a wire, sometimes bends until the resisting side presents a perpen- dicular face, then overhangs, and ultimately curls over: this dispo- sition is also shown in the abrasive wear of the screw before it yields. Comparing the square with the angular thread in regard to fric- tion, the square has less friction, because the angular edges of the screw and nut, mutually thrust themselves into the opposite angular grooves in the manner of the wedge. The square thread has also the advantage of presenting a more direct thrust than the angular, because in each case the resistance is at right angles to the side of the thread, and therefore in the square thread the resistance is very nearly in the line of its axis, whereas in the angular it is much more oblique. From these reasons, the square thread is commonly selected for presses, and for regulating screws, especially those in which rapidity of pitch, combined with strength, is essential; but as regards the ordinary attachments in machinery, the grasp of the angular thread is more powerful, from its pitch being generally about as fine again, and, as before explained, angular screws and nuts are somewhat more easily fitted together. The force exerted in bursting open a nut, depends on the angle formed by the sides of the thread, when the latter is considered as part of a cone, or as a wedge employed in splitting timber. For instance, in the square thread screw, the thread forms a line at right angles to the axis, and which is dotted in the figure 476 ; it is not therefore a cone, but simply compresses the nut, or attempts to force the metal before it. In the deep thread, Fig. 497, the wedge is obtuse, and exerts much less bursting effort than the acute cone Figs. 476. 477. 478. represented in the shallow thread screw, Fig. 478; therefore, the shallower the angular thread, the more acute the cone, and the greater the strain it throws upon the nut. The transverse measure of nuts, whether they are square or hexagonal, is usually about twice the diameter of the bolt, as represented in the figures, and this in general suffices to withstand the bursting effort of the bolt. In the table of dimensions of nuts, in " Byrne's Engineer's Pocket NUTS CAPABLE OF BEING ADJUSTED. 375 Companion," the traverse measures decrease in the larger nuts; the breadth of the nut for a £ inch bolt is stated as 1 inch, that for a 2i inch bolt as 4 inches. . Those nuts, however, which are not used for grasping, but tor the regulating screws of slides and general machinery, are made much thicker, so as to occupy as much of the length of the screw as two, three, or more times its diameter ; this greatly increases their sur- face-contact, and durability. Should it be required to be able to compensate the nut, or to re- adapt it to the lessened size of the screw when both have been worn, the nut is made in two parts and compressed by screws, or it is made elastic so as to press upon the screw. The nuts for angular threads are divided diametrically, and re-united by two or more screws as in Fig 479, in fact, like the semi-circular bearings of ordinary shafts ; as then by filing a little of the metal away from between the two halves of the nut, they may be closed upon the angular ridges ot the thread. . , The nuts of square threads, by a similar treatment, would, on being closed, fit accurately upon the outer or cylindrical surface ot the square thread screw; but the lateral contact would not be restored; these nuts are, therefore, divided transversely, as shown in Fig. 480, or they are made as two detached nuts placed in con- tact. When, therefore, a small quantity is removed from between them with the file, or that they are separated by one or more thick- nesses of paper, the one-half of the nut bears on the right hand side of the square worm, the other on the left. 481. Fms. 479. 480. 482. E E — I~l — t-, , ! lb !l 1 1 . — i j— — j ! -4K =^ — Either of these methods removes the " end play" or the " loss of time" by which expression is meant that partial revolution, to and fro, which may be given to a worn screw without producing any movement or traverse in the slide upon which the screw acts. It is usual, before cutting the nuts in the lathe or with screw traps, to divide the nuts, and to re-unite them with soft solder, or it is better to hold them together with the permanent screws whilst cutting the thread. . , But the screws of slides are very apt to become most worn m the 376 SCREW-CUTTING TOOLS. middle of their length, or at the one end, leaving the other parts nearly of their original size : it is then best to replace them by new screws, as the former method of adjusting the nuts cannot be used ; although recourse may occasionally be had to some of the various methods of springing, or the elastic contrivances commonly em- ployed in delicate mathematical and astronomical instruments. Although these should be perfectly free from shake or uncertainty of motion, they do not in general require the firm, massive, unyielding structure of engineering works and machinery. Two kinds of the elastic nuts alone are shown ; in Fig. 481 the saw-cut extends throughout the length of the nut, but sometimes a portion in the middle is left uncut ; the nut is usually a little set-in, or bent inwards with the hammer, so as to press upon the screw. In Fig. 482, the two pieces a and b, bear against opposite sides of the threads, and b only is fixed to the slide, as in Fig. 480 ; the correc- tion is now accomplished by interposing loosely around the screw, and between the halves of the nut, a spiral spring sufficiently strong to overcome the friction of the slide upon the fittings; the same contrivance is variously modified, sometimes two or four spiral springs are placed in cavities parallel with the screw. The slide resists firmly any pressure from a to b, as the fixed half of the nut lies firmly against the side of the thread presented in that direction, but the pressure from b to a is sustained alone by the spiral spring ; when, therefore, the pressure exceeds the strength of the spring, the slide nevertheless moves endways to the extent of the misfit in the piece b, and which, but for the spring, would allow the slide to shake endways. In absolute effect the contrivance is equiva- lent to a single nut such as b alone, which although possessing end play, if pulled towards b by a string and weight, would always keep in contact with the one side of the worm, unless the resistance were sufficient to raise the weight. The method is therefore only suited to works requiring delicacy rather than strength, and the spring if excessively strong, would constantly wear the two halves of the nut with injudicious friction and haste. t The several threads represented in Figs. 483 to 495, may be con- sidered to be departures from the angular thread Fig. 483, and the square thread Fig. 492, which are by far the most common. The choice of section is collectively governed : First, by the facility of construction, in which the plain angular thread excels. Secondly, by the best resistance to strain, which is obtained in the square thread. Thirdly, by the near equality of strength in the internal and external screw. For similar materials the space and thread should be symmetrical, as in the square thread, and in Figs. 483 to 487, which screws are proper for metal works generally ; whereas in dissimilar materials, the harder of the two should have the slighter thread, as in the iron screws, Figs. 488 to 491, intended to be screwed into wood ; the substance of the screw is supposed to be below the line, and the head to the right hand. Fourthly, by the resistance to accidental violence, either to the screws, or to the screwing tools, DIFFERENT SECTIONS OF SCREW THREADS. 377 Figs. Sections derived from die ANGULAR THREAD. «83. MVWWVW which is best obtained by the rejection of sharp angles or edges, as in the several rounded threads. This fourfold choice of section, like every other feature of the screw, is also mainly determined by expe- rience alone. Fig. 483, in which the angle is about 60 degrees, is used for most of the screws made in wood, whether in the screw-box or the turning- lathe ; and also for a very large proportion of the screw bolts of ordinary mechanism. Some- times the points of the screw tool measure nearly 90 degrees, as in the shallow thread, Fig. 484, used for the thin tubes of telescopes ; or at other times they only measure 45 degrees, as in the very deep thread, Fig. 485, used for some mathemati- cal and other instruments ; the angles represented may be con- sidered as nearly the extremes. In originating accurate screws, the angular thread is always selected, because the figure of the thread is still maintained, whether the tool cut on one or on both sides of the thread, in the course of the correctional 484. 485. 486. AAMAAAAAA7 487. A/VWWVVW 488. JUUUUUUUU\j^ 489. .AAAAAAAAAAy 490. / VVVVV1/M 491. AJLAAJIAJIAAJIA Sections derived from the SQ.UARE THREAD. process. Fig. 486 is the angular thread in which the ridges are more or less truncated, to increase the strength of the bolt ; it may be viewed as a compound of the square and angular thread. Fig. 487 is the angular thread in which the tops and bottoms are rounded ; it is much used in engineering works, and is fre- quently called a round thread. In Fig. 488 the thread is more acute, and truncated only at the bottom of the screw ; this is used for joinery-work, and greatly increases the hold upon the wood ; Fig. 489 is obviously derived from Fig. 488, and is used for the same purpose. In Fig. 490, which is also a screw for wood, the face that sustains the hold is rectangular, as in the square thread, the other is beveled. Fig. 491 is the form of the patent wood screw, sometimes called the 492. 493. 494. 495. "u~u~u~i_n_r 378 SCREW-CUTTING TOOLS. German screw ; it is hollowed, to throw the advantage of bulk in favor of the softer material, or the wood, the head of which is sup- posed to be on the right hand. In the last four figures, the substance of the screw is imagined to be situated below the line, and that of the wood above. The screws which are inserted into wood are generally made* taper, and not cylindrical, in order that they may cut their own nut or in- ternal thread ; some of them are pointed, so as to penetrate without any previous hole being made : they merely thrust the fibres of wood on one side. Screws hold the most strongly in wood, when inserted horizontally as compared with the position in which the tree grew, and least strongly in the vertical position. Fig. 492 represents the ordinary square thread screw ; the space and thread are mostly of equal width, and the depth is either equal to the width, or a trifle more, say one-sixth. Fig. 493 is a departure from Fig. 492, and has been made for presses ; and Fig. 494 has obviously grown out of the last from the obliteration of the angles ; various proportions intermediate between Figs. 494 and 487 are used for round threads. In some cases where the screw is required to be rapid, one single shallow groove is made of angular, square, or circular section leaving much of the original cylinder standing, as in Fig. 495. For very slight purposes, a pin only is fitted to the groove, to serve as the nut ; should the resistance be greater, many pins, or a comb may be em- ployed, and this was the earliest form of nut ; otherwise a screwed nut may be used with a single thread. But when the greatest resist- ance is required, the surface bearing of the nut is extended, by making the thread double, triple, &c, by cutting one or more intermediate grooves and a counterpart nut. The nuts or boxes of very coarse screws for presses are now mostly cut in the lathe, although, when the screwing tools were less per- fectly understood, the nuts were frequently cast. Sometimes lead, or alloys of similar fusibility, were poured in betwixt the screw and the framework of the machinery ; but for nuts of brass and gun-metal, sand moulds were formed. The screw was always warmed to avoid chilling the metal ; and for brass, it was sometimes heated to redness and allowed to cool, so as slightly to oxidize the surface, and lessen the disposition to a union or natural soldering of the screw and nut. It was commonly necessary to stretch the brass by an external hammering, to counteract the shrinkage of the metal in the act of cooling, and to assist in releasing from the screw, the nut cast upon it in this manner. The mode is by no means desirable, as the screw is exposed to being bent from the rough treatment, and to being ground by particles of sand adhering to the brass. The tangent screws used for screw wheels, have mostly angular or truncated angular threads, Fig. 486, as screws absolutely square can- not be fitted with good contact and freedom from shake between the thread and teeth ; and probably the same rules by which the teeth of ordinary wheels and racks are reciprocally set out, should be also TANGENT SCREWS, PIEDMONT SCREW WHEELS. 379 applied to the delineation of the teeth of worm wheels, and the threads or teeth of their appropriate screws. Tangent screws are occasionally double, triple, or quadruple, in order that 2, 3, or 4 teeth of the wheel may be moved during each revolution of the screw. In the Piedmont silk-mills, this principle is carried to the extreme, as the screw and wheel become alike, and revolve turn for turn ; the teeth, supposing them to be 20, are then identical with those of a 20 thread screw, the angular coils of which cross the axis at the angle of 45°, that is, when the shafts lie at right angles to each other; other proportions and angles maybe adopted. In reality they fulfil the office of bevel wheels, or rather of skew- bevel wheels, in which latter also, the axes, from being in different planes, may cross each other ; so that the skew-bevel wheels may be in the centre of long shafts, but Avhich cannot be the case in ordinary bevel wheels, the teeth of which lie in the same plane as the axis of the wheel. The Piedmont wheels act with a very reduced extent of bearing or contact surface, and a considerable amount of the sliding action of screws, which is disadvantageous in the teeth of wheels, although inseparable from all those with inclined teeth, and which are indeed more or less distant modifications of the screw. When the obliquity of the teeth of worm wheels is small, it gives a very smooth action, but at the expense of friction ; but in ordinary toothed wheels, the teeth are exactly square across or in the plane of the axis, and the aim is to employ rolling contact, with the greatest possible exclusion of sliding, from amongst the teeth. Having treated somewhat in detail the different forms of screws, and the circumstances which adapt them to their several purposes, I have now to consider some of the inconveniences which have unavoid- ably arisen from the indefinite choice of proportions in ordinary screws, and also some of the means that have been proposed for their correction. The slight discussion of the more important of these topics will permit the introduction of various additional points of in- formation on this almost inexhaustible subject, the screw. No inconvenience is felt from the dissimilarities of screws, so long as the same screwing tools are always employed in effecting repairs in, or additions to, the same works. But when it is considered, how small a difference in either of the measures will mar the correspond- ence of the screw and nut ; and further, the very arbitrary and acci- dental manner, in which the proportions of screwing apparatus have been determined by a variety of individuals, to suit their particular wants, and without any attempt at uniformity of practice, (sometimes on the contrary, with an express desire to be peculiar,) it is perhaps some matter of surprise when the screws made in different establish- ments properly agree. Indeed their agreement can be hardly ex- pected, unless they are derived from the same source, and that some considerable pains are taken not to depart from the respective pro- portions first adopted. In a few isolated cases this inconvenience has been partially reme- died by common consent and adoption, as in the so-called air-pump 380 SCREW-CUTTING TOOLS. thread, which is pretty generally used by the makers of pneumatic apparatus ; and to a certain degree also in some of the screws used in gas-fittings and in gun-work. But the non-existence of any com- mon standard or scale, enhances both the delay and expense of re- pairs in general mechanism, and leads to the occasional necessity for making additional sizes of tools to match particular works, however extensive the supply of screw apparatus. The perplexity is felt in a degree especially severe and costly, as regards marine and locomotive engines, which from necessity, have to be repaired in localities far distant from those in which they were made ; and therefore require that the packet station, or railway depot, should contain sets of screwing tackle, corresponding with those used by every different manufacturer whose works have to be dealt with ; otherwise, both the delay and expense are from necessity aggravated. Some engineers suggested that for steam machinery and for the purpose of engineering in general, " an uniform system of screw threads" should be adopted. The following table may be considered as a mean between the different kinds of threads used by the leading engineers : — Table for Angular Thread Screws. Diameters in inches .... ] s l 6 lb 2 8 7 IB I h 8 i 7 8 l" 1* if H if '2 2" Nos. of threads to the inch . . 20 16 1-1 12 11 10 9 8 7 7 6 6 5 5 H 22 3" 34 H 3| 4" 4| 5" H H H ti" Nos. of threads to the inch . . 4 4 34 H 3* H 3 2£ 2| H H ■4 2* H 2| In selecting this scale, the following very judicious course was adopted : An extensive collection was made of screw-bolts from the principal workshops, and the average thread was carefully ob- served for different diameters. The J inch, | inch, 1 and inch, were particularly selected, and taken as the fixed points of a scale by which the intermediate sizes were regulated, avoiding small frac- tional parts in the number of threads to the inch. The scale was afterwards extended to 6 inches. The pitches thus obtained for angular threads were as above : — Above the diameter of 1 inch the same pitch is used for two sizes, to avoid small fractional parts. The proportion between the pitch and the diameter varies throughout the entire scale. Thus the pitch of the \ inch screw is £th of the diameter ; that of the -| inch ^th, of the 1 inch £th, of the 4 inches ^oth, and of the 6 inches T J s th. The depth of the thread in the various specimens is then alluded to. In this respect the variation was greater than in the pitch. The angle made by the sides of the thread being taken as an expression for the depth, the mean of the angle in 1 inch screws was found to be about 55°, which was also nearly the mean in screws of different diameters. Hence it was adopted throughout the scale, and a constant TABLES FOR SCREW THREADS. 381 proportion was thus established between the depth and the pitch of the thread. In calculating the former, a deduction must be made for the quantity rounded off, amounting to ^d of the whole depth, i. e., ^th from the top, and ^th from the bottom of the thread. Making this deduction, the angle of 55° gives for the actual depth rather more than f ths, and less than fds of the pitch. As regards the smaller mechanism, made principally in brass and steel, such as mathematical instruments and many others, the screws in the above scale below half an inch diameter are admitted to be too coarse ; and the acute angular threads which are not rounded, are decidedly to be preferred from their greater delicacy and dura- bility, that is when their strengths are proportioned to the resistances to which they are exposed. In these respects the following table may be considered preferable : — Table for Small Screws of Fine Angular Threads. Diameters in vulgar fractions of the inch i *f 7 re 1 3 3 8 i ] 3 2 ft i 4 7 3F i Diameters in hundredths of the inch nearly .50 .4 7 .44 .41 .37 .34 31 .25 .22 .20 Number of threads to the inch .... 16 IS 18 20 20 ■24 24 28 28 32 36 Diameters in hundredths of the inch . . .18 .16 .14 .12 .10 .09 .08 .07 .06 .05 .04 Numbers of threads to the inch .... 3G 40 40 48 4S 50 56 64 72 81 100 The tables above given, and which have been selected and not cal- culated, will serve to explain the inapplicability of the mode of cal- culation proposed in various popular works; namely, for angular thread screws, to divide the diameter by 8 for the pitch, when, it is said, such screws will all possess the angle of 3 J degrees nearly ; and for square threads to divide by 4, thus giving an angle of 7 de- grees nearly ; therefore Angular thread screws of 8642 l^i inches diameter would have pitches of 1 | | } | T ' f 3 'j inches rise or rates of 1 1§ 2 4 8 16 32 threads per inch, which differ greatly from 2£ 3 A\ 8 12 20 Whitworth's observational numbers. By the use of the constant divisor 8, the one-inch screw agrees with Whitworth's table, the extremes are respectively too coarse and too fine; as instead of 8 being employed, the actual divisors vary from about 5 to 16, and therefore a theoretical mode would probably require a logarithmic scheme. But were this followed out with care, the adjustment of the fractional threads so obtained, for those of whole numbers, would completely invalidate the precision of the rule ; and the result would not be in any respect better than when adjusted experimentally, as at present. There is little doubt that if we could entirely recommence the labors of the mechanist, or if we could sweep away all the screw- ing tools now in use, and also all the existing engines, machines, tools, instruments, and other works, which have been in part made through their agency, these proposed scales, or others not greatly differing from them, (as the choice is in great measure arbitrary,) would be found of great general advantage ; the former for the 382 SCREW-CUTTING TOOLS. larger, the latter for the smaller works. But until all these myriads of objects are laid on one side, or that repairs are no longer wanted in them, the old tools must from absolute necessity be retained, in addition to those proposed in these or any other schemes. It would be of course highly judicious in new manufacturing establishments to adopt such conventional scales, as they would, to that extent, promote this desirable but almost impracticable end, namely, that of unity of system ; but which, although highly fascinating and appa- rently tenable, is surrounded by so many interferences, that it may perhaps be considered both as needless and hopeless to attempt to carry it out to the full, or to make the system absolutely universal ; and some of the circumstances which affect the proposition will be now briefly given. First, agreement with standard measure, although convenient, is not indispensable. It may be truly observed, that as regards the general usefulness of a screw such as Fig. 473, which was supposed to measure § inch diameter, and to have 10 threads per inch, it is nearly immaterial whether the diameter be three or four hundredths of an inch larger or smaller than f of an inch ; or whether it have 9, OJgth, 9f, 10J, or 11, threads per inch, or any fractional num- ber between these ; or whether the thread be a trifle more or less acute, or that it be slightly truncated or rounded; so long as the threads in the screw and nut are but truly helical and alike, in order that the threads mutually bear upon each other at every part ; that is, as regards the simple purpose of the binding screw or bolt, namely, the holding of separate parts in firm contact. And as the same may be said of every screw, namely, that a small variation in diameter or pitch is commonly immaterial, it follows, that the good office of a screw does not depend on its having any assigned rela- tion to the standard measure of this or any other country. Secondly, The change of system would cause an inconvenient in- crease in the number of screwing tools used. — Great numbers of ex- cellent and useful screws, of accidental measures, have been made by various mechanicians ; and the author hopes to be excused for citing the example with which he is most familiar. Between the years 1794 — 1800, the author's father made a few varieties of taps, dies, hobs, and screw tools, after the modes ex- plained at pages 355 and 356 ; these varieties of pitch were ulti- mately extended to twelve kinds, of each of which was formed a deep and shallow hob, or screw tool-cutter. These, when measured many years afterwards, were found nearly to possess in each inch of their length, the threads and decimal parts that are expressed in the following table. Approximate Values of I. I. EoltzapffeV s Original Screw threads. Number . . . 1 2 3 4 5 6 1 7 8 9 10 ii 12 Threads in 1 inch 6.58 8.25 9.45 13.09 16.5 19.89 22.12 25.71 28.88 36.10 39.83 55.11 The angle of the deep threads is about 50 degrees: of the shallow 60 degrees. SCREWS OF STANDARD MEASURES. 383 This irregularity of pitch would not have occured had the screw- lathe with change-wheels been then in use ; but such was not the case. For a long series of years 1. 1. HoltzapfFel, (in conjunction with his partner, I. Gr. Deyerlein, from 1804 to 1827,) made, as occasion required, a large or small screw, a coarse or fine, a shallow or deep thread, and so forth. By which accumulative mode, their series of working taps and dies, together with screw tools, gauges, chucks, carriers, and a variety of subordinate apparatus, became extended to not less than one hundred varieties of all kinds. About one-third of these sizes have been constantly used, up to the present time, both by H. & Co., and by other persons to whom copies of these screw tackles have been supplied, and consequently many thousands of screws of these kinds have been made: this im- plies the continual necessity for repairs and alterations in old works, which can only be accomplished by retaining the original sizes. Since the period at which H. & Co. made their screw lathe, they have employed the aliquot threads for all screws above half an inch ; indeed, most of these have also been cut in the screw lathe. To have introduced the same method in small binding screws which are not made in the screw lathe, but with the diestocks and chasing tools, would have doubled the number of their working-screw tackle, and the attendant apparatus; with the risk of confusion from the increased number, but without commensurate advantage as regards the purposes to which they are applied. Doubtless the same reasons have operated in numerous other factories, as the long existence of good useful tools has often lessened, if not annulled, the advantage to be derived from a change which refers more immediately to engineering works ; and in which a par- tial remedy is supplied, as steam-engines, &c. are frequently accom- panied with spare bolts and nuts, and also with corresponding screw apparatus, to be employed in repairs ; the additional cost of such parts being insignificant, compared with the value of the machinery itself. Thirdly : Unless the standard sizes of screws become inconveni- ently numerous, many useful kinds must be omitted, or treated as exceptions. For instance, in ordinary binding screws, more particu- larly in the smaller sizes, two if not three degrees of coarseness should exist for every diameter, and which might be denominated the coarse, medium, and fine series ; and again, particular circum- stances require that threads should be of shallow or of deep angular sections, or that the threads should be rounded, square, or of some other kinds ; in this way alone, a fitness for all conditions would in- conveniently augment the number of the standards. In many cases besides, screws of several diameters are made of the one pitch. In order, for example, that the hole when worn may be tapped afresh, and fitted with screws of the same pitch or thread but a trifle larger ; or that a partially worn screw may be corrected with the dies or in the lathe, and fitted with a smaller nut of the same pitch. A succession of taps of the same pitch also readily 384 SCREW-CUTTING TOOLS. permits a larger screw to be employed, when that of smaller diameter has been found to break, either from an error of judgment in the first construction of the machine, or from its being accidentally sub- mitted to a strain greater than it was intended ever to bear. It is also in some cases requisite to have right and left-hand screws of the same pitch, that, amongst other purposes, they may effect simultaneous yet opposite adjustments in machinery, as in some uni- versal chucks: and also some few screws, the threads of which are double, triple, quadruple, and so forth, for giving to screws of small diameters considerable rapidity of pitch or traverse, or a fixed ratio to other screws associated with them, in the same piece of mechanism. Under ordinary and proper management, the production of a number of similar pieces may be obtained with sufficient exactitude, by giving to the tool some constant condition. For example, a hun- dred nuts tapped with the same tap, will be very nearly alike in their thread; and a hundred screws passed through the hole of a screw- plate, will similarly agree in size, because of the nearly constant dimensions of the tools, for a moderate period. In practice, the same relative constancy is given to the dies of die-stocks and bolt screwing engines, and partly so to the tools of the screw-cutting lathe. Sometimes the pressure or adjusting screw has graduations or a micrometer ; and numerous contrivances of eccentrics, cams, and stops, are employed to effect the purpose of bringing the die or turning-tool to one constant position, for each succeeding screw ; these matters are too varied and general to re- quire more minute notice. Part of such modes may serve sufficient- ly well for ten, or even a hundred screws, provided that no accident occur to the tool ; but if it were attempted to extend this mode to a thousand, or a hundred thousand pieces, the same tool could not, even without accident, endure the trial; it would have become not only unfit for cutting, but also so far worn away as to leave the last of the works materially larger than the first. In respect to screws, the instrument, the size of which claims the most importance, is perhaps the plug-tap, or that which removes the last portion of the material, and therefore determines the diameter of the internal thread ; but as the tap is continually, although slowly, wearing smaller, the first and the last nut made with it unavoidably differ a little in size. It is on account of the wearing of the tap, amongst other circumstances, that when screws and nuts are made in large numbers, and are required to be capable of being interchanged, it becomes needful to make a small allowance for error, or to make the screws a trifle smaller than the nuts. In order to retain the size of the taps used by Holtzapffel & Co. they some years ago made a set of original taps exactly of the size of the proposed screws, and to be called A ; these, when two or three times used to rub off the burrs, were employed for cutting regulating dies B, of the form of Fig. 496, with two shoulders, so that the dies could be absolutely closed, and yet leave a space for the shaving or SCREWS OF STANDARD MEASURES. 385 cuttings. In making all their plug-taps, they are first prepared with the ordinary shop tools, until the taps are so nearly completed, that, grasped between the Fig- 496. regulating dies B, the latter close within the ^ ^ fortieth or fiftieth of an inch, therefore leaving the dies B next to nothing to perform in the way of cutting, but only the office of regulating the diameter of the working plug-taps. Should the dies B meet with any accident, the taps A, which have to this stage been only used for one pair of re- gulating dies, exist for making repetitions of B. This method has been found to fulfil its intended purpose very effectually for several years, but at the same time it is not proposed to apply this or any other system universally. In conclusion, it may be said that by far the most important argu- ment in favor of the adoption of screws of aliquot pitches applies to steam machinery and similar large works, and that, principally, because it brings all such screws within the province of the screw- lathe with change-wheels, which has become, in engineering estab- lishments and some others, a very general tool. This valuable tool alone renders each engineer in a great measure independent of his neighbor, as screws of 2, 2J, 2|, 3, 10, or 20 threads in the inch, are readily measured with the common rule, and copied with the screw-wheels, and a single-pointed tool, or an ordinary comb or chas- ing tool with many points. And therefore, with the modern facility of work, were engineers severally to make their screw tackle from only the written measures of any conventional table, they would be at once abundantly within reach of the adjustment of the tools, and that without any standard gauges ; the strict introduction of which would almost demand that all the tools made in uniformity with them should emanate from one centre, or be submitted to some office for inspection and sanction — and this would be indeed to buy the occasional advantage at too dear a rate. It must, however, be unhesitatingly granted, that the argument applies but little, if at all, to a variety of screws which from their smaller size are not made in the screw lathe, but with die-stocks and the hand-chasing tools only ; and which are employed in branches of art that maybe considered as almost isolated from one another, and therefore not to require uniformity. For instance, the makers of astronomical, mathematical, and philo- sophical instruments, of clocks and watches, of guns, of locks and ironmongery, of lamps and gas apparatus, and a multitude of other works, possess, in each case, an amount of skill which applies speci- fically to these several occupations : so that unless the works made by each are returned to the absolute makers for reparation, they are at any rate sent to an individual engaged in the same line of business. 25 386 SCREW- CUTTING TOOLS. Under these circumstances, it is obvious that the gun-makers, watchmakers, and others, would derive little or no advantage from one system of threads prevailing throughout all their trades ; in many of which, as before noticed, partial systems respectively adapted to them already exist. The means employed by the generality of artisans in matching strange threads, are, in addition, entirely in- dependent of the screw lathe, and apply equally well to all threads, whether of aliquot measures or not ; as it is usual to convert one of the given screws, if it be of steel, into a tap, or otherwise to file a screw tool to the same pitch by hand, wherewith to strike the thread of the screw or tap ; and when several screws are wanted, a pair of dies is expressly made. But at the same time that, from manifold considerations, it ap- pears to be quite unnecessary to interfere with so many existing arrangements and interests, it must be freely admitted that advan- tage would ultimately accrue from making all new screws of aliquot measures ; and which, by gradually superseding the old irregular threads, would tend eventually, although slowly, to introduce a more defined and systematic arrangement in screw tackle, and also to improve their general character. Mr. Oliver Byrne, the editor of this work, has given in his Dic- tionary of Machines, Mechanics, Engine work and Engineering, published in New York, many useful and practical details respect- ing the working of metals, under the heads of Iron, Brass, Grold, Metallurgy, §c. ELECTRO-METALLURGY. DESCRIPTION OF GALVANIC BATTERIES, AND THEIR RESPECTIVE PECULIARITIES. Nomenclature. — The terms that are employed to denote the vari- ous parts of a galvanic battery, and of other electrotype arrange- ments, frequently puzzle the student, and lead him into difficulties. Before we proceed to describe the various forms of the battery, we shall, for this reason, give a preliminary account of the nomencla- ture of galvanism. The two extremities of a battery have long been called Poles ; one of them the Positive, and the other the Negative, Pole. But objections have been taken to the use of the terms negative, positive, and pole, on the ground that such terms do not convey a correct idea of the circumstances or of the effects produced. Before connecting the two metals or extremities of a battery, no electricity is evolved, and when the connection is formed the electricity simply makes a cir- cuit, but it is stated, or rather supposed, that no particular portion of that circuit can be said to be either negative or positive to another portion. Proposed Terms. — Various terms have been suggested as sub- stitutes for negative and positive, and also for pole. Dr. Michael Faraday has proposed the following : for pole, he substitutes elect- rode, which signifies a way ; for the negative pole, cathode, signify- ing downwards ; and for the positive pole, anode, or upwards. To understand these terms properly, we must suppose a battery lying upon the ground with its copper (positive) end to the east, and the wire connecting the ends of the battery bent into an arch similar to the course of the sun ; the electric current will thus flow up from the east end of the battery, and descend into it at the west end. The fluid that is decomposed by a current passing through it is termed by Faraday an electrolyte; the elements liberated by this decompo- sition, he terms ions, distinguishing those liberated at the cathode as cations, which in sulphate of copper would be the metal, and those liberated at the anode as anions, which would be the acid por- tion of the sulphate of copper. The late Professor Daniell, disapproving of the terms cathode and anode, substituted platinode for the negative, and zincode for 388 BATTERIES. the positive, pole. "We think these terms are better adapted for electro-metallurgy, than cathode and anode, which have no direct reference to ordinary conditions ; while zincode distinctly expresses the substance dissolved, and platinode the element not acted upon. Professor Graham adopts the terms zineous and chlorous poles, as synonymous with zincode and platinode, or positive and negative. Although the terms positive, negative, and pole, may not be the best, still, under all the conditions of electro-metallurgy, we deem them as appropriate as any of the proposed substitutes, some of which are based on supposed conditions which have not been proved, and may be found incorrect. When we shall have occasion to use the two terms pole and elec- trode, these will be used synonymously : positive and negative elec- trode are synonymous with positive and negative pole. Electrolyte will be applied to a solution when undergoing decom- position by the electric current passing through it. The 'positive electrode, or pole, is that metal in the electrolyte which is being dissolved, or, if not capable of being dissolved, at which the acid or solvent of the electrolyte, is being liberated, as when sulphate of copper forms the electrolyte, the sulphuric acid is liberated. The negative electrode, or pole, is that metal or substance in the electrolyte upon which the metal is being deposited by the influence of the electric current. Graham is a native of Scotland, Faraday and Daniell are Irishmen. BATTERIES. Single Pair of Plates. — If a piece of ordinary metallic zinc be put into dilute sulphuric acid, it is speedily acted upon by the acid, and hydrogen gas is at the same time evolved from its surface, hav- ing a disagreeable smell arising from impurities. If the zinc be taken out, and a little mercury be rubbed over its surface, an amal- gamation takes place between the two metals. If the zinc thus amalgamated be again put into the dilute acidj there is no action, for the mercury retains the zinc with sufficient force to protect it from the acid. If a piece of copper be immersed along with the zinc, and the two metals be made to touch each other, a particular influence is induced among the three elements, zinc, copper, and acid; the acid again acts upon the zinc as if no mercury was upon it, but the hydrogen is now seen to escape from the surface of the copper : this action will go on as long as the two metals are kept in contact. Or if, instead of causing the two metals to touch, a wire be attached to each, and their opposite ends are placed in a little dilute acid in another vessel, the same action will take place between the zinc and copper as when they were in contact ; but in this instance, the ends of the two wires which dip into the vessel containing acid will undergo a change : the one attached to the zinc will give off a quantity of hydrogen gas, while the one attached to the copper, supposing it to be also copper, will rapidly dissolve. The copper and zinc, with AMALGAMATION OF ZINC PLATES. 389 the acid in the first vessel, constitutes a battery of one pair. The second vessel with acid, in which the wires are placed, is termed the decomposition cell. Fig. 497. When zinc and copper, placed in dilute suphuric acid, are brought into contact, gas may be seen escaping from the copper. Fig. 498. Zinc and copper, placed in dilute acid, may be con- nected by a wire, when the same effects are produced as in the first case. Figs. 497. 498. 499. Fig. 499. Or they may be connected by putting the wires into a liquid, such as acid and water, &c. Best kind of Zinc. — The zinc used for the battery should be milled or rolled zinc, not thinner than ^th of an inch, otherwise the waste will be very great ; for amalgamated zinc, when it becomes thin, is so tender and brittle, that the utmost care cannot preserve it whole. The best thickness for the zincs, when their size is up- wards of four inches square, is |th of an inch ; but if under this size, |th to T 3 5 ths of an inch is the proper thickness. Cast plates of zinc should not be used, as they are negative to rolled zinc, and give less electrical power: they are so porous that no amalgamation will protect them from the action of the acid — "local action,'' as it is termed — which is not only a waste of zinc and acid, but prevents to a great extent the production of the quantity of electrical force which the surface of* the zinc in use is calculated to give. Amalgamation of the Zinc Plates. — The amalgamation of zinc is a process exceedingly simple ; nevertheless, if care be not taken, a very great loss in mercury and zinc is soon effected. A stone-ware pan is best to use, and should be sufficiently capacious to allow the zinc plate to lie flat within it : a mixture of eight parts water, and one part sulphuric acid, should he put into the pan, sufficient in quantity to cover the zinc plate, which should lie in it till the surface is perfectly bright. The pan is now raised on the one side, and a little mercury put into the lower part, care being taken that the zinc does not touch the mercury, to prevent which is the object of raising the pan on one side. A little coarse tow, tied to the end of a piece of wood, is dipped into the mercury, and then rubbed with considerable pressure upon both sides of the zinc plate, over which the mercury flows easily : the plate is then washed by dipping it 390 BATTERIES. into clean water, and is next made to stand upon its edge in another pan, with two small pieces of wood under it, so as to allow the mercury to drain from it. Instead of tow, the old scratch brush is generally used in plating factories ; this is a brush made of fine brass wire, tied upon a piece of wood; but we prefer tow, when carefully employed, as the brass wire amalgamates with the mercury, and causes a loss of that metal. After the zincs have drained for a few hours, the process should be repeated, only it is not necessary to allow the metal to lie in the acid in the second process previous to rubbing in the mercury: after draining a few hours the second time, amalgamation is completed. In the first process a plate, of a foot square, amalgamated on both sides, will retain three ounces of mer- cury; but for the second process, or any time after, the same size of plate will only retain ounces of mercury. The zinc should never be allowed to lie in the acid when the battery is not in use, but should be taken out, and the surface care- fully brushed with a hard hair brush in water, and then laid by in a safe place. The matter thus brushed off, being an amalgam of zinc, is to be carefully collected and kept in dilute sulphuric acid, or in the waste acid from the batteries: most of the zinc will dis- solve out, so that the mercury may be recovered from it by filtration, A great portion of the mercury used to amalgamate the zincs may thus be recovered. Economy in Amalgamation. — If the battery is to be used seldom, and only for a short period at a time, another method of amalgama- tion may be adopted. The zinc plate, after lying in the dilute acid till the surface is bright, may be rubbed over with a solution of nitrate of mercury, which gives a very thin amalgamation ; but this method is unsuitable if the battery is to be in use for several hours together. When a battery is being worked daily, it will be advisable to repeat the amalgamation from time to time, otherwise local action will begin, and the working power of the battery be weakened, while the loss in zinc will be increased. The following is the proportional rate which we have found on the large scale under the most favorable circumstances. A new zinc plate, amalgamated as described, working continuously 24 hours, zinc lost 12| ounces — Copper deposited 12 ounces ; 48 hours, zinc lost 20J ounces — Copper deposited 17 ounces; 60 hours, zinc lost 34 ounces — Copper deposited 24J ounces. The most economical way of using zincs is this : after being in the battery twenty-four hours, they are to be taken out, brushed, and laid aside ; after other twenty-four hours, they are to be again brushed, and immediately reamalgamated : if these directions are attended to, J ounce of mercury will be sufficient for one foot square of zinc, both sides. We have only to add here, in consequence of an oft-expressed fear of the danger of working with quicksilver, that no apprehen- sion need be felt: the skin does not absorb it, and there being no DIFFERENT ELEMENTS OF BATTERIES. 391 heat required in the operation that could convert the mercury into vapor, the only state in which it is dangerous, no salivation can take place. Distance between the Battery Plates. — To return again to the battery-cells — the zinc and copper in acid: it will be found that if the two metals be put very close to each other, the action will be much more rapid than when they are far apart. It will also be found that, allowing the zinc and copper to be kept at one distance, but the wires in the decomposition-cell to be put at different dis- tances, similar results will take place. When the wires are close the action in the battery-cell will be more powerful than when the two wires are put further apart : these properties are applicable to all batteries and decomposition-cells of every kind. The following results will give an idea of the relations of these several condi- tions : — 1st. One pair of copper and zinc plates, measuring superficially 6 square inches, were immersed in a solution consisting of 1 acid to 35 water : plates of copper of equal size to those of zinc and copper were laid in the decomposition-cell, which was then filled with a liquid of equal strength to that in the battery-cell: the plates in the battery-cell and the decomposition-cell were then placed one inch apart : in four hours The zinc in the battery-cell lost by dissolving 10 J grains ; The copper dissolved in decomposition-cell 10 grains. 2d. The battery plates were put 12 inches apart, and the plates in decomposition 1 inch apart : in four hours There were dissolved in the battery-cell, zinc 7 grains ; In decomposition-cell, copper 6 grains. 3d. The battery plates were placed 1 inch apart, and the plates in decomposition-cell 12 inches apart: in four hours The zinc in battery-cell lost 4 \ grains ; The copper in decomposition-cell lost Z\ grains. These results show the importance of attending to the conditions of the respective agents, and also, that distance in the decomposi- tion cell offers greater resistance than distance in the battery-cell. Different Elements of Batteries. — Although our observations have been made on zinc, copper, and dilute sulphuric acid in the battery cell, still these are not the only essential elements in a battery, as almost any two metals with a liquid similarly arranged will produce an electric current ; but the current will vary accord- ing to the nature of the metals employed, and the effects produced upon them by the solution in which they are placed. If the excit- ing solution has the power of acting upon both metals, as when zinc and copper are immersed in dilute nitric acid, the current of elec- tricity produced by the action of the acid upon the zinc will be neutralized to an extent corresponding to the relative action of the acid upon the copper. To have any effective electrical power, it is necessary that one of the metals employed be capable of combining easily with one of the elements of the solution in which they are 392 BATTERIES. placed, while the other does not; and the power obtained under proper circumstances has an intimate relation with these two pro- perties in contrast. The metal which undergoes solution is termed the positive metal, tne other the negative metal. Metals are not considered to possess any intrinsic, negative, or positive principle ; their relations in this respect are governed solely by the circum- stances in which they may be placed. For instance, if we connect a piece of copper and a piece of iron, and immerse them in acidu- lated water, the iron is dissolved, and is positive in relation to the copper; but if the same metals are immersed in a solution of yellow hydro-sulphuret of potassium, the copper is dissolved, and is posi- tive relatively to the iron. Hence, to obtain a galvanic battery, the conditions are simply to provide two metals, and immerse them in a solution capable of acting upon the one, and not upon the other. The following table shows the order in which the common metals stand to each other, in respect of their relative, negative, and posi- tive properties, when immersed in water acidulated with sulphuric or muriatic acid — the most intensely negative metal standing highest, and the metal which acts most positively standing lowest: — Platinum Copper Gold Lead Antimony Iron Silver Tin Nickel Cadmium Bismuth Zinc. According to this arrangement, each metal is positive with respect to all that stand before it, and the electrical conditions of any pair become the more contrasted the further apart they stand in the scale. Thus, a battery composed of zinc and platinum is much more powerful than one composed of zinc and copper; and again, copper and iron make a very weak battery. A battery may also be formed by having one metal and two kinds of solutions, separated by a porous diaphragm. For example, we may have strong nitric acid in one division, and dilute sulphuric or muriatic acid in the other ; and by putting into each a piece of clean iron, a powerful current is obtained. These, and several other ar- rangements of solutions and metals, are expensive, and troublesome to keep in order, and are, therefore, never used for practical purposes in the art of electro-metallurgy. Properties of Metals fit for Batteries. — In looking to the above table, it may be asked, " Since lead stands next to copper, and is so much cheaper, why should it not be used instead ? The reason is, that there are other properties which a metal, especially that used as the negative element, ought to possess, to fit it for use in a voltaic arrangement ; such as the power of freely conducting an electric current, of keeping a bright surface, and not becoming oxidized; none of which properties belong to lead. Could that metal be kept from oxidizing, a very powerful current of electricity PROPERTIES OE METALS FIT FOR BATTERIES. 393 might be obtained by using it with zinc ; but its surface soon gets coated with an oxide possessing none of the properties of the metal, and hence the arrangement becomes zinc and oxide of lead, which produces but a weak current of electricity. These remarks refer to any metal that is subject to oxidation — an incident which is ever a source of annoyance to the electrotypist when using copper plates. Lead slightly amalgamated, and used as the negative metal with zinc, produces a very constant current for a time. Lead is also a very bad conductor of the electric current, which renders it unsuitable for an element in the battery, the negative metal being considered as only acting the part of a conductor; this property materially affects the available power of an arrangement. The following table shows the relative conducting power of the respective metals : — Silver 120 Copper . 120 Gold 80 Zinc 40 Platinum 24 Iron 24 Tin 20 Lead 12 In fitting up a voltaic arrangement with a negative metal that is not a good conductor, such as platinum, the closer it is placed to the exciting liquid, in connection with another metal that is a good con- ductor, the better ; because the current obtained will be the more effectual. Figs. 500. 501. 3 7 When working it was found that the energy of the battery did not depend, as was supposed, upon the extent of surface of the zinc and copper which were in contact, but upon the extent of surface of these metals in contact with the liquid with which the battery was excited ; and that it was sufficient if the zinc and copper touched each other in a single point ; provided that the plates were plunged into the liquid, and that the copper plate should be exactly opposite to a zinc plate in the same cell, a space being between them. Hence, instead 394 BATTERIES. of soldering the zinc and copper together, it was enough to effect a communication by turning over a portion of the copper plate at the top, and soldering it to the upper extremity of the zinc. Thus — c, the copper, is bent over to touch and be soldered to the zinc plate, z. Fig. 502. For this arrangement the wooden trough was divided, by plates of glass or varnished wood, into as many cells as there were pairs of zinc and copper. The cells being filled with the acid, or exciting solution, the metals were then placed into them in such a manner that each pair of zinc and copper plates had a partition between. By this arrangement the zinc of one pair faced the copper of the next pair in the cell, as shown in Figs. 501 and 502. The former represents the plates immersed in the solution ; the latter, the plates suspended on a rack over the solution. Although we have spoken of the great value of amalgamated zinc for batteries, still at the period when the arrangement just described was introduced, amalgamation was not known ; and the zinc plates Fig. 503. were, therefore, always liable to be destroyed by the acid. It was, consequently, of importance that no zinc should be exposed to the action of the acid that was not calculated to give electricity, as the energy of each pair of plates depends upon the extent of surface of the two metals exactly opposite to each other. It will be evident that in the above arrangement only one side of the zinc was effective COPPER AND ZINC PLATES. 395 in giving electricity, while both sides were exposed to the action of the acid. To obviate this defect required but little ingenuity, the copper plate is made to surround the zinc, by which the whole sur- face of the zinc exposed to the acid was made effective in producing electricity. Fig. 503 shows this construction. This little change in the construction is called an English discovery. In the arrangement represented above, when amalgamated zincs are used, small quantities of amalgam fall from the zinc plates upon the copper, which not only occasion local action, but the mercury amalgamates with the copper, spreads over it, and to a great extent lessens its efficiency ; and as the copper must be made red hot to expel the mercury, much loss of copper is the result. To obviate this defect, the copper is connected above the zinc and left open at bottom ; as, for example, a thin sheet of copper, of dimensions ac- cording with the size of the cells in the battery, is cut thus : — Fig. 504. b IIIIIHlllli-'iS a c a This copper is bent in the middle at h, the ends a a dip into the cells, while c is bent over to connect with the zinc plate of the neigh- boring cells, thus — Figs. 505. 506. The zinc plates are placed between the bent copper a a. # The fol- lowing diagram of a battery of several pairs of plates will illustrate these observations : — • Fig. 507. 396 BATTERIES. _ Fig. 507, zzzz, The zinc plates, cccc, Copper plates, ppp, Par- titions of trough, which are generally made of thin wood, ww, Wires from battery. The zinc and copper are connected together by a binding screw. In operating with any arrangement composed of similar elements, such as zinc, sulphuric or muriatic acid, and copper, silver or plati- num, it will be found that the current of electricity obtained dimin- ishes in quantity and strength in proportion to the time of action. This is the result of various causes : 1st. The hydrogen which is evolved at the surface of the negative metal in the battery, which we shall say is copper, adheres with considerable force to the surface of the metal, and consequently obstructs its superfical influence, so that the quantity of electricity which the surfaces of the two metals are calculated to give is much lessened. 2d. After the battery is in action a short time, a portion of the sulphate or chloride of zinc, formed in the battery by the solution of the zinc, becomes reduced upon the surface of the copper. It generally begins at the lower edge of the copper plate, and spreads upwards. This weakens the electric current, both by inducing a galvanic action between the zinc and the copper, upon which it is deposited, and by its tendency to send a current of electricity in an opposite direction to the main current, thereby neutralizing to a great extent the original power of the circle. 3d. When copper is used it becomes gradually covered over with a thin, black, slimy coating of oxide and other impurities, which ma- terially affects the regularity and strength of the current : this is a source of considerable annoyance in working, and necessitates a regu- lar cleaning of the coppers, which should be done immediately on being taken out of the battery, by brushing with a hard hair brush in water ; but when the battery has been long in action, this mode of cleaning is insufficient ; the plates will then require to be rubbed over with a little dilute nitric acid, and then washed. If the black coating be allowed to dry upon the coppers, they must then be dipped into strong nitric acid till their surfaces are acted upon ; or they may be moistened with a little urine, then brought to a dull red in the fire, and immediately plunged into water; but in both cases there is a loss of copper. A small quantity of the black matter, upon being tested, gave oxide of copper, with a trace of iron, antimony, and lead, which are the general impurities of sheet copper. Another source of weakness to the electric current, and which affects more or less all batteries of whatever construction, arises from the action of the acid upon the zinc. The more freely this action is allowed to proceed, the more constant and powerful is the battery. The acid in combining with the zinc forms a salt, which, if it adhered to the surface of the plate, would soon stop further action ; but this salt being soluble in water, is dissolved from the surface of the plate as soon as formed, allowing a new surface to be exposed. But water can only dissolve a certain quantity of the salt, and its power of dissolving decreases as it approaches to the limit of saturation : DEPOSITION OF ZINC. 39T hence there is a constant tendency to a decrease of power in the bat- tery, and if means be not taken to withdraw the salt of zinc formed, the battery will continue to decrease in power, till at length it ceases to act. But long before the battery ceases to act, the presence of sulphate of zinc manifests itself in several ways, neutralizing the efficacy of the battery. The zinc salt, as it dissolves from the plate, being heavier than the acid solution, falls to the bottom; hence in a very short time the solution is formed of strata of differ- ent densities, and this induces a galvanic action between the lower and upper portions of the plates, both copper and zinc, and ac- counts for the deposition of zinc on the bottom part of the plates, as above referred to. This local galvanic action between the bot- tom and top part of the zinc plate is sometimes so great when the battery has been long in action, as to double the thickness of the zinc plate at bottom, while the part near the surface of the solution is nearly penetrated by the acid ; and when a battery is formed of a number of pairs, the terminal zincs are those most affected, the one forming the negative terminal or pole more so than the other. We have found a deposition of 6 J ounces of zinc upon the two lower inches of a plate terminal, which measured, in the solution, six inches by five, the battery having been in operation but eighteen hours. When this occurs, the quantity of electricity circulating through the battery is very small. Although this evil may not proceed to the extent of having quantities of zinc deposited upon the bottom part of the plates, still the tendency to deposition which every one who em- ploys a battery must have observed, as also the more rapid action of the acid on the upper parts of the plates, shows that the action of the acid over the surface of the plate is very irregular, and con- sequently the quantity of electricity must be irregular in the same degree. Various means have been devised for removing the sulphate of zinc, and adding corresponding quantities of new acid water ; the most simple and effective of which, according to our experience, is to make the battery trough much deeper than is required for the plates, which may be supported either by grooves in the sides of the trough, cut to the proper depth, or by a fillet of wood, or perforated false bot- tom ; so that the zinc salt when formed may fall under the plates, and thus a much longer time elapse before its presence produces any decidedly bad effect. There can be no doubt, we think, that some easy means will yet be devised of carrying off the dense solution of sulphate of zinc, before it rises to the plates, and replacing it by acid water from above, thus giving to the battery a uniformity and steadiness of action it does not at present possess. Some of the disadvantages now detailed were to a great extent overcome by the separation of the zinc from the copper by a porous diaphragm, such as bladder, unglazed porcelain, &c, and the use of two distinct fluids. The construction of a single pair is as follows: — A cell of this battery consists of a cylinder of copper 3| inches in 398 BATTERIES. diameter, which experience has proved to afford the most advantages between the generating and conducting surfaces, but which may vary in height according to the power which it is wished to obtain. A membranous tube, formed of the gullet of an ox, is hung in the centre by a collar, and a circular copper plate, resting upon a rim, is placed near the top of the cylinder, and in this is suspended, by a wooden cross-bar, a cylindrical rod of amalgamated zinc, half an inch in diameter ; the cell is charged with eight parts water, and one of oil of vitriol, which has been saturated with sulphate of copper, and Figs. 508. * 509. portions of the solid salt are placed upon the upper copper plate, which is perforated like a colander, for the purpose of keeping the solution always in the state of saturation. The internal tube is filled with the same acid mixture without the copper. A tube of porous earthenware may be substituted for the membrane with great convenience, but probably with some little loss of power. A number of such cells may be connected very readily, by attach- ing the zinc of the one to the copper of the other, and (as shown in Fig. 509) thus forming an intensity arrangement of great power and constancy. Another battery, constructed upon the same prin- Fig. 510. ciple, but differing in the arrangement of the me- tals, and the substances used to excite them. In this arrangement, platinum is used instead of cop- per, and strong nitric acid instead of the sulphate of copper. One pair may be fitted up conveniently in a tumbler or jelly pot. A cylinder of zinc is placed inside the tumbler; within this cylinder is placed a porous vessel, in which is a slip of platinum, either in sheet or foil ; the porous vessel is filled with strong nitric acid, and the tumbler with dilute sulphuric acid ; a wire is next attached to each metal and the battery is complete. The zinc is placed in the cell of the trough, and the porous vessel, which should be flat, is placed within the zinc, so that the platinum in it may be connected with the zinc of the neighboring pair, as re- presented in Fig. 511. Fig. 511. zzz, are the zinc plates of the form of Figure 510. aaa. Porous cells filled with nitric acid. BATTERY OF EIGHT CELLS. 399 ccc, Plates of platinum united to the zinc at top by binding screws. pp, are partitions. The divisions of the battery trough need not be water tight, but merely such as will prevent the zincs from touch- ing one another. Figs. 511. 512. It will be seen that by this means any number of pairs may be easily arranged. Care, however, must be taken, when fitting up such an arrangement, that the platinum be kept closely connected with the zinc by a large surface, otherwise the platinum will be fused at the connections. A flat piece of wood, with a groove to fit the zinc, is often made the means of keeping the two metals together; but we prefer flat binding screws of brass, for if kept clean they assist the connection, being good conductors. The fusion of the platinum connections, a pratical and often expensive annoyance, may, however, be completely prevented by coating about half an inch of the end of the platinum, either with copper or silver, which is easily effected by the electro-process : the coated part is then connected with the zinc by any convenient means without the risk of fusing. Fig. 512 represents a battery of eight cells complete. Its parts are as follows — a, b, binding screws connected with the terminal poles of the battery ; c, binding screw to be used when only half the cells are required : d, band connecting the zinc plates to the screw b ; e, band connecting the platinum plates to the screw a; g, porous cell ; h y platinum plate ; i, zinc plate; k, binding screw to connect the zinc to the platinum. The ordinary defects in the common battery of zinc and copper were much lessened by a simple contrivance. It was observed that if the copper plate of the battery be roughened, either by corrosive acids or by rubbing the surface with sand-paper, its action was made much more efficient, the rough surface evolving the hydrogen much more freely. Taking advantage, therefore, of this principle, the platinum foil was covered with a finely divided black powder of pla- tinum, deposited by electricity from a solution of that metal, and this was used in place of the copper in the ordinary battery. Instead of platinum foil, silver was soon after adopted, which is much less expensive. The method of preparing these plates is given as fol- lows : The silver to be prepared for this should be of a thickness sufficient to carry the current of electricity, and should be roughened 400 BATTERIES. by brushing it over with a little strong nitric acid, so that a frosted appearance is obtained. It is then washed and placed in a vessel with dilute sulphuric acid, to which a few drops of nitro-muriate of platinum has been added. A porous tube is then placed into this vessel with a few drops of dilute sulphuric acid ; into this tube a piece of zinc is put, contact being made between the zinc and silver ; the platinum will in a few seconds be thrown down upon the silver as a black metallic powder. The operation is now completed, and the platinized silver ready for use. A simple method which obviates the use of a battery is thus described : lay the silver between two pieces of sand-paper, and press it with a common smoothing iron, then pull the silver out while under the pressure. The platinum solution is made very hot, and the silver dipped in it for some time, which effects the coating. The nitro-muriate of platinum is easily prepared : take one part of nitric acid, and two parts of hydrochloric acid (muriatic acid) ; mix together and add a little platinum, either as metal or sponge ; keep the whole at or near a boiling heat ; the metal is then dissolved, form- ing the solution required. Several alterations have been tried, with a view to substitute a cheaper metal than silver to deposit the platinum upon, but not with much success. Cheap metals have also been coated with silver by the electro-process, and then used. The most successful is a compo- sition metal made of tin, lead, and a little antimony, rolled into sheet and plated by silver ; this was found very convenient, because it could be easily bent into any required shape, and it keeps its place without the necessity of fixing in frames as required by thin silver ; nevertheless, for constant work these plates are found not to present any permanent advantage. Figs. 513. 514. Figure 513 represents a single cell of this form of battery. A, is the jar containing the solution. Z, Z, the two amalgamated zinc plates. S, the platinized silver plate. The whole are suspended by a cross-bar of wood ; and as it is essential to the proper working of .the battery that the plates be always parallel to one another, the BATTERY WITH SIX CELLS. 401 wooden frame is generally extended round the edge of the thin silver plate, though it is not so represented in the figure. One of the clamps at the top of the wooden bar is connected with the platinized silver plate, and the other with the pair of zinc plates. When intensity of electricity is required, it is necessary to use a number of such cells, which may be arranged in a wooden frame, in the manner shown by Fig. 514, where a b represent the two poles of the battery, and o c, the wires by which the cells are connected with one another. A superior form of this battery is given in the next figure. In this apparatus, the plates are all connected to a frame that can be elevated or depressed by means of an iron rod and ratchet Avheel, so that the plates may be either partially or entirely immersed in the Fig. 515. solution, or raised at pleasure out of it. The connections are so contrived, that by a slight alteration the battery is adapted to afford either quantity or intensity of electric power. It is usually made to contain six cells, any number of which can be used at once that a given process may require. The exciting fluid is contained in an incorrodible stoneware trough, placed in a mahogany box. A bat- tery of this description, each silver plate of which measures 20 square inches, has sufficient power, when decomposing water, to disengage one cubic inch of mixed gases in 50 seconds, and will heat to red- ness 4 inches of platinum wire. Letter b in Fig. 515 represents an apparatus for showing the de- composition of water into oxygen and hydrogen gas by the voltaic battery. It will be observed that there are two surfaces of zinc, in every pair exposed to the acid, which do not give off any electricity, but when long in use are much acted upon, forming a consideration of some value to a manufacturer. The silver used is very thin, and liable to crack when taken from 26 402 ELECTROTYPE PROCESSES. its frame, and therefore cannot be made into different constructions of battery in the same manner as we can do with copper. It is also liable to have zinc deposited upon its surface when long in action. ELECTROTYPE PROCESSES. Single-cell Operations. — We shall now proceed to detail the process of electrotjping, the materials for which are of the most simple nature. Let us suppose that the object of the student is to copy a copper medal — for example, the side of a cent. Dissolve a quantity of the crystals of sulphate of copper in any convenient vessel ; if distilled water can be had, the better. This is conveni- ently done by suspending the crystals in a coarse cloth on the sur- face of the water, or the crystals may be put into the water, and well stirred till dissolved : crushing the crystals facilitates their solu- tion. The water should be kept cold and be fully saturated with the salt, and the solution allowed to stand untouched for several hours. This last precaution is not always essential, but only neces- sary when the copper solution is not perfectly clear and transparent. The sulphate of copper of commerce has often a large quantity of iron in it, a portion of which becomes per-oxidized, and will pre- cipitate or fall to the bottom of the solution on standing ; indeed, when it is known that the salt contains much iron, it is best to crush the salt very fine, and expose it to the air for some time ; when dis- solved, after this exposure, a great quantity of iron will settle at the bottom of the solution, which should be carefully decanted and the last portion filtered. The clear solution should now have about one-fourth of its quantity of water added to it, as a completely saturated solution is not the best. A newly-formed solution does not deposit so freely as one that has been in use for some time. The addition of a few drops of sulphuric acid, or, what we have found better, a little sulphate of zinc — about one ounce to the pound of sulphate of copper — improves the condition of a new solution. Next, put the solution of sulphate of copper into the vessel in- tended for use, say it is a large jelly-pot, in which let a vessel of unglazed porcelain (porous vessel) be placed, filled to within half an inch of the mouth with a mixture of 24 parts water and 1 sulphuric acid, taking care that the copper solution is of the same depth as the solution in the porous cell. Preparation of the Coin. — A fine copper wire must now be put round the edge of the coin and fastened by twisting. Then cover the back part, upon which the deposit is not required, with bees'- wax or tallow, or what is better, imbed the back of the coin with gutta percha. Have the fore part or face well cleaned, and the surface moistened with sweet oil, by a camel's-hair pencil, and then cleaned off by a silk cloth, till the surface appears dry : or, instead of oil, the surface may be brushed over with black lead, which will impart to it a bronze appearance. The use of the oil or black lead is to prevent the deposit adhering to the face of the coin. TORMS OF APPARATUS. 403 A very common and excellent method to prevent the copper de- posit adhering to the copper mould is this : Take a gill of rectified spirits of turpentine, and add to it about the size of an ordinary- pea of bees'-wax. When this is dissolved, wet over the surface of the mould with it, and then allow it to dry: the mould is then ready to put into the solution. Medals taken from moulds so prepared retain their beautifully bright color for a long time. But when fine line engravings are to be coated, the little wax dissolved in the tur- pentine may be objectionable ; so also is black lead, for both have a tendency to fill up the fine lines. In this case, let the wash be wiped off by a silk handkerchief instead of drying it : but for ordi- nary medals this objection will scarcely apply. This being done, the opposite end of the copper wire round the penny piece is to be connected with a piece of amalgamated zinc, either by means of a binding screw or a hole in the zinc. Then place the zinc in the acid within the porous cell, and put the penny piece into the copper solution : bring the face of the metal or coin parallel to the zinc, at the distance of about half an inch or one inch from the porous vessel. Deposition immediately begins, and the metal thickens according to the length of time the action is kept up. In about twenty-four hours, the deposit will be of the thickness of a com- mon card, and it may then be taken off. The zinc is to be brushed and washed, before it is put aside. The wire round the coin is now to be untwisted, and by a slight turn will come off easily. The de- posit is also easily separated from the mould, which will be a perfect counterpart of the face of the penny piece. This mould is next to be treated exactly as described for obtain- ing it from the penny piece, and the deposit from it will be a, fac- simile of the penny piece. With care, any number of duplicates may be taken from this mould. It need hardly be remarked, that as copper is deposited the solu- tion becomes proportionally exhausted, and in a short time the cur- rent of electricity passing will be too much for the strength of the solution, which will then give a deposit of a sandy consistence, with- out tenacity: it is therefore necessary, while the deposition is going on, to suspend some crystals of sulphate of copper at the top of the solution, which, being dissolved, will maintain its strength. Forms op Apparatus. — It will be observed that no particular form of apparatus is required for electrotyping, but certain modifi- Figs. 516. 517. 518. 404 ELECTROTYPE PROCESSES. cations maybe adopted for convenience and economy. As every por- tion of the zinc in the acid is capable of giving off electricity, by placing the cell that contains the zinc in the centre of the copper solution, moulds may be suspended on each side of that cell. We have also observed that the zinc plate should not be allowed to touch the cell, as the copper will be reduced upon it and the cell destroyed. To avoid this, the zinc may be suspended by a small wooden peg, put through it and made to rest upon the edges of the cell: see Fig. 508. Figs. 516, 517, and 518 represent several convenient forms of apparatus for electrotyping. Instead of porous vessels made of earthenware, a bladder may be used, in which the acid and zinc are placed. We have also seen a vessel divided by a porous partition, being either a plate of biscuit porcelain, or of plaster of Paris, or very thin sycamore wood or dressed skin. The porcelain, as before mentioned, is the best ; plaster is too porous, and the solution soon destroys it : wood is too close, and the deposit is consequently very slow ; skin does very well for a short time, but it is soon destroyed. When porous cells were not convenient, we have made electrotypes by wrapping the zinc plates in two or three folds of stout cartridge paper, moistened with a solu- tion of salt, and placing this in the copper solution with the mould. Of course, this is only to be adopted when a porous vessel cannot be obtained. The paper lasts but a short time, and has therefore, to be frequently renewed; besides which, there is always a deposit of copper upon the paper, thus occasioning a loss. Common coarse garden-pots answer excellently for porous vessels, closing the aperture at bottom by a cork. Comparative Value of Exciting Solutions. — We have recom- mended the porous cell being filled by dilute sulphuric acid, which we consider best ; but other saline solutions will serve the same pur- pose : solutions of common salt, sal ammonia, and sulphate of zinc, have been recommended, and each has been calledbest in its turn. The following results of experiments with these solutions in the porous cell will show their relative qualities, and enable the student to judge for himself. The size of the zinc plate in the cell measured 6 inches by 6 inches ; the copper plates upon which the deposits were formed were the same size; the solution of copper was kept at the same strength ; the time that each was in solution was 16 hours. COMPARATIVE VALUE OF EXCITING SOLUTIONS. 405 Solution in Porous Cell. Sal ammonia. Saturated solution . . 1 part saturated solution 1 part water .... 1 part saturated solution 3 parts water .... :} Common Salt. Saturated solution . . 1 part saturated solution 1 part water .... 1 part saturated solution 3 parts water .... Sulphate of Zinc. Saturated solution . . 1 part saturated solution 1 part water .... 1 part saturated solution 3 parts water .... : Sulphuric Acid. 1 part to 8 of water 1 part to 16 of water . 1 part to 24 of water . Zinc dissolved. dwt. 5 0 12 16 18 0 14 5 13 3 9 3 18 0 14 1 11 7 16 Copper deposited. dwt. 2 3 10 14 17 12 10 17 12 0 19 16 19 19 0 18 0 14 1 4 2 1 2 5 G How often Solutions should be Changed and Zinc Amalga- mated. — Students have often put this question to us: "How often should the solution in the cell be renewed, and the zinc plate be amal- gamated?" The following is the result of many trials made to answer this inquiry: the zinc plates used were nearly one foot square, and the copper plate upon which the deposit was made was of the same size as the zinc plates. In the first series the zinc plates were not taken out either to brush or reamalgamate, neither were the solutions renewed during the time specified. 2 lbs. common salt in one gal- lon of water 24 hours 48 hours 60 hours 2 lbs. sulphate of zinc in one f ^ t° urS i, c < 48 hours gallon ot water | nr , , ° (50 hours 1 lb. sulphuric acid to 24 of j 24: hours water. \ 48 hours Copper Zinc deposited. dissolved. oz. dwt. oz. dwt. 12 9 12 17 17 13 20 17 24 15 34 3 9 13 9 18 16 4 17 10 23 10 24 8 15 17 17 15 27 16 32 3 406 ELECTROTYPE PROCESSES. From these results it is evident that the best and most economical manner of treating the solution and the zinc would be to renew the solution every 24 hours, as the second 24 hours does not give half the deposit of the first 24 hours without renewal. The next series of experiments was with the same zinc and the same kind of solutions, but the zinc was taken out every 24 hours, and brushed, but not reamalgamated, and put back again with new solution in the porous cell. Copper Zinc deposited. dissolved, oz. dwt. oz. dwt. Salt and water, . 4 days of 24 hours . 49 16 51 8 Sulphate of zinc . 4 days of 24 hours . 47 14 48 9 Acid and water . 3 days of 24 hours . 48 13 53 7 ] These results give the most ample reply to the question so often put, and will guide the student in his operations, whether time or material be of the greatest consequence to him in his operations. We may remark that the sulphate of zinc solution does not re- quire renewal, but simply to half empty the cell and refill it with water. The sulphate of zinc poured out being nearly saturated, may be crystalized, and will serve other electro-metallurgical ope- rations. Making of Moulds. — The directions given for obtaining a mould from a penny piece, by deposition, are applicable to taking moulds from any metallic medal, engraving, or figure, that is not undercut ; and for depositing within the moulds so produced. On the first discovery of this art, the electrotypist was confined to metallic moulds, as the deposition would not take place except upon metallic surfaces; but the discovery that polished plumbago, or black lead, had a conducting power similar to that of metal, and that the de- posit would take place upon its surface with nearly the same facility as upon metal, freed the art at once from many of its trammels, and enabled the operator to deposit upon any substance — wood, plaster of Paris, wax, &c. — by brushing over the surface with black lead. It obliged the electro-metallurgist, however, to render himself ex- pert in the art of moulding, since no good electrotype can be obtained without a perfect mould. We shall, for this reason, endeavor now to give such instructions as will enable the student to make good moulds after a very short practice ; but we need hardly add, that in this as well as in every operation, however plain may be the instruc- tions and easy the manipulations, practice is necessary to insure suc- cess ; so that the student ought not to lose patience should his first attempt not succeed to his wishes. The substances used for taking moulds from objects to be copied by electrotype are bees'-wax, stearine, plaster of Paris, and fusible metal ; recently, gutta percha has been very successfully used. The articles to be copied are gene- rally composed either of plaster of Paris or metal. Suppose, in the first place, the article to be copied is of metal, and a mould is to be WAX AND PLASTER MOULDS. 407 taken from it in wax or stearine. The latter we have not found to answer well, alone : when used it should be mixed with wax, about half and half. Preparation of Wax. — Whether the bees'-wax have stearine in it or not, it is best to prepare it in the following manner : Put some common virgin wax into an earthenware pot or pipkin, and place it over a slow fire ; and when it is all melted, stir into it a little white lead (flake white) — say about one ounce of white lead to the pound of wax ; this mixture tends to prevent the mould from cracking in the cooling, and from floating in the solution: the mixture should be re-melted two or three times before using it for the first time. To take Moulds in Wax. — The medal to be copied must be brushed over with a little sweet-oil ; a soft brush, called a painter's sash tool, suits this purpose well : care must be taken to brush the oil well into all the parts of the medal, after which the superfluous oil must be wiped off with a piece of cotton or cotton wool. If the medal has a bright polished surface, very little oil is required, but if the surface be matted or dead, it requires more care with the oil. A slip of card-board or tin is now bound round the edge of the medal, the edge of which slip should rise about one-fourth of an inch higher than the highest part on the face of the medal : this done, hold the medal with its rim a little sloping, then pour the wax in the lowest portion, and gently bring it level, so that the melted wax may gradu- ally flow over ; this will prevent the formation of air-bubbles. Care must be taken not to pour the wax on too hot, as that is one great cause of failure in getting good moulds ; it should be poured on just as it is beginning to set in the dish. As soon as the composition poured on the medal is set (becomes solid), undo the rim, for if it were allowed to remain on till the wax became perfectly cool, the wax would adhere to it, and, being thus prevented from shrinking, which it always does a little, would be liable to crack. Put the medal and wax in a cool place, and in about an hour the two will separate easily. When they adhere, the cause is either that too little oil has been used, or that the wax was poured on too hot. Rosin with Wax. — Rosin has been recommended as a mixture with wax ; mixtures of which, in various proportions, we have used with success : but when often used, decomposition, or some change takes place, which makes the mixture granular and flexible, render- ing it less useful for taking moulds. When rosin is used, the mixture, when first melted, should be boiled, or nearly so, and kept at that heat until effervescence ceases; it is then to be poured out upon a flat plate to cool, after which it may be used as described. Moulds in Plaster. — If a plaster of Paris mould is to be taken from the metallic medal, the preparation of the medal is the same as described above ; and when so prepared with the rim of card-board or tin, get a basin with as much water in it as will be sufficient to make a proper-sized mould (a very little experience will enable the operator to know this), then take the finest plaster of Paris and sprinkle it into the water, stirring it till the mixture becomes of the consist- 408 ELECTROTYPE PROCESSES. ence of thick cream ; then pour a small portion upon the face of the medal, and, with a brush similar to that used for oiling it, gently brush the plaster into every part of the surface, which will prevent the formation of air-bubbles; then pour on the remainder of the plaster till it rises to the edge of the rim : if the plaster is good, it will be ready for taking off in an hour. The mould is then to be placed before a fire, or in an oven, until quite dry, after which it is to be placed back downwards in a shallow vessel containing melted wax, not of sufficient depth to flow over the face of the mould, allow- ing the whole to remain over a slow fire until the wax has penetrated the plaster, and appears upon the face. Having removed it to a cool place to harden, it will soon be ready for clectrotyping. If the mould is large and the plaster thick, the wax may be put upon the surface, and only as much as will penetrate a small way into the plaster. In both these instances the wax used is generally lost, and there is always liability of the copper solution passing through, and causing what is termed surface deposit, making the face of the medal rough. We may remark that, although occasionally there may be a very good electrotype obtained from a plaster mould, still they are in general very inferior; as the saturating of the plaster has a tendency to blunt the impression, and the wax used for the purpose of satura- tion becomes expensive. It may be partially recovered by boiling the plaster in water ; the wax melts out, and is obtained when the water cools. Plaster should not be used for moulds where wax can be em- ployed, being neither so good nor so economical ; but there are cases in which, the moulds being very large, the use of plaster is unavoidable. Moulds in Fusible Alloy.— The next means of taking moulds is by fusible metal : this name is given to alloys of two or more metals which melt at very low temperatures ; it suits the purpose of taking moulds of small objects very well. The following are exam- ples of such compositions: — Tin. Lead. Bismuth. Zinc. 112 0 12 3 0 10 11 These all melt at a temperature below that of boiling water; the ingredients are melted together in an iron ladle, poured out upon a flat stone, broken up, and re-melted in the same way two or three times, in order that they be thoroughly mixed. The medal from which the mould is to be taken is prepared in the same manner as described for wax. The fusible alloy is melted and poured into a saucer, or, what does better, a small wooden tray : the operator now watches till it cools down into a semi-fluid state, or to the point of setting, when he brings the medal suddenly upon it, face downwards, and holds it DEPOSITION ON LARGE OBJECTS. 409 there until the alloy has fairly set ; he then allows it to cool, and undoes the slip around the medal, from which the mould will easily separate. The height of the slip of paper above the surface of the medal determines, of course, the thickness of the mould. The beginner very seldom succeeds with his first attempts at making moulds in fusible alloy ; but as a little experience teaches more than the reading of an essay upon the subject, he will soon find both his patience and labor rewarded with gratifying success. Some of the finest moulds are taken by this process, but, from the constant loss of the materials by oxidation, &c, it is expensive ; so that its use amongst electro-metallurgists is very limited. Moulds in Gutta Percha. — Gutta percha, as a material for moulding, serves the purpose most admirably. , We have seen moulds of this substance equal, if not superior, to any that we ever saw taken in wax; and of a depth of cutting which it would have been very dif- ficult to have taken in wax. The method adopted for taking moulds is to heat the gutta percha in boiling water, or in a chamber heated to the temperature of boiling water, which makes it soft and pliable. The medal is fitted with a metallic rim, or placed in the bottom of a metal saucer with a cylindrical rim a little larger than the medal; the medal being placed back down, a quantity of gutta percha is pressed into the saucer, and having as much as will cause it to stand above the edge of the rim : it is now placed in a common copying press, and kept under pressure until it is quite cold and hard. The impressions taken in this way are generally very fine ; when the medal is not deep cut, a less pressure may suffice, but when the pressure is too little the impression will be blunt. Deposition on Large Objects. — When busts or figures, whether of wax or plaster of Paris, are to be coated with copper, with no other conducting surface than black lead, it is attended with considerable difficulty to the inexperienced electrotypist. The deposit grows over all the prominent parts, leaving hollow places, such as arm- pits, neck, &c, without any deposit ; and when once missed, it re- quires considerable management to get these parts coated, as the coated parts give a sufficient passage for the current of electricity. It is recommended by some electrotypists to take out the bust, and coat the parts deposited upon with wax, to prevent any further deposit on them ; but this practice is not good, especially with plaster of Paris, for an electrotype ought never to be taken out till finished. Sometimes the resistance of the hollow parts is occa- sioned by the solution becoming exhausted from its position in regard to the positive pole. In this case, a change of position effects a remedy. It may be remarked, that when a bust or any large sur- face having hollow parts upon it, is to be electrotyped, as many copper connections as possible ought to be made between these parts and the zinc of the battery. Let the connections with the hollow parts be made with the finest wire which can be had, and let the zinc plate in the cell have a large surface compared to the surface of the figure, and the battery be of considerable intensity : if atten- 410 ELECTROTYPE PROCESSES. tion is paid to these conditions, the most intricate figures and busts may be covered over in a few hours. Care has to be observed in taking off the connections from the deposit, or the operator may tear off a portion of the deposit: if the wires used are fine, they should be cut off close to the deposited surface. To make Busts and Figures. — Busts and figures, and other com- plicated works of art, which cannot be perfectly coated with black lead, may' be covered by a film of silver or gold, which serves as a conducting medium to the copper. This is effected by a solution of phosphorus in sulphuret of carbon. The operation being patented, we will take advantage of the description given of it in the specifi- cation. " The solution of phosphorus is prepared by adding to each pound of that substance fifteen pounds of the bisulphuret or other sulphuret of carbon, and then thoroughly agitating the mixture ; this solution is applicable to various uses, and amongst others, to obtaining deposits of metal upon non-metallic substances, either by combining it with the substances on which it is to be deposited, as in the case of wax, or by coating the surface thereof. Any of the known preparations of wax may be treated in this way, but the one preferred is composed of from six to eight ounces of the solution — five pounds of wax, and five pounds of deer's fat, melted together at a low heat, on account of the inflammable nature of the phosphorus. The article formed by this composition is acted upon by a solution of silver or gold in the manner hereinafter described with respect to articles which have been coated with the solution." Coating of Flowers, &c. — " If the solution is to be applied to the surface of the article, an addition is made to it of one pound of wax or tallow, one pint of spirits of turpentine, and two ounces of India rubber, dissolved with one pound of asphalte, in bisulphuret of carbon, for every pound of phosphorus contained in the solution. The wax and tallow being first melted, the solution of India rubber and asphalte is stirred in; then the turpentine, and after that the solution of phosphorus is added. The solution prepared in this manner is applied to the surfaces of non-metallic substances, such as wood, flowers, &c, by immersion or brushing; the article is then immersed in a dilute solution of nitrate of silver, or chloride of gold; in a few minutes the surface is covered with a fine film of metal, sufficient to insure a deposit of any required thickness on the article, being connected with any of the electrical appa- ratus at present employed for coating articles with metal. The solution intended to be used is prepared by dissolving four ounces of silver in nitric acid, and afterwards diluting the same with twelve gallons of water; the gold solution is formed by dissolving one ounce of gold in nitro-muriatic acid, and then diluting it with ten gallons of water." We have frequently repeated the operations described by this patentee with entire satisfaction, and were enabled to cover every variety of surface with great facility. The solutions of silver and gold, prepared as above, will last for ELECTROTYPES AND DAGUERREOTYPES. 411 a long time, and do a great many articles. When it is convenient it is best to use both solutions. The connecting wire should first be attached to the article to be coated, before being dipped into the phosphorus solution, but connected at such parts as will not hurt the appearance of the object by leaving a mark when it is taken off*. Care should be taken not to touch the article with the hands after it is dipped into the solution. The object supported by the connec- tions is immersed in the phosphorus solution, where it remains for two or three minutes. When taken out, it is dipped into the silver solution, and as soon as the surface becomes black, having the appearance of a piece of black china, it is to be dipped several times in distilled water, and then immersed in the solution of pro- tochloride of gold for about three minutes: the surface takes a bronze tinge by the reduction of the gold. It is next washed in distilled water by merely dipping, not by throwing water upon it. The wire connection is now attached to the zinc of the battery, and then the article put into the copper solution, and in a few minutes the article is coated over with a deposit of copper. A thin copper surface may thus be given to small busts or figures without sensibly distorting the features by want of proportion. Figures from Elastic Moulds. — When taking a wax cast from the elastic mould, we prefer the phosphorized mixture. After taking out the mould it is only necessary to make the connections, and pass it through the gold and silver solutions, as described, and then to connect it with the battery. We may also mention that the principal object of making copper moulds by this process, in the manufactory, is not to make fac- similes in copper, but to make articles of solid silver or gold. Copies of highly wrought work, either chased or engraved, or of articles, duplicates of which cannot be obtained or of which the workmanship is costly, may by this means be made in solid silver or gold, at little more expense than the cost of the metal. Having obtained the copper mould, silver is deposited in it to any thickness, and the copper dissolved off. However, an extensive trade is now being carried on in figures and other works of art deposited in copper and then bronzed, which gives them an appearance often not much inferior to that of antique works of the highest art. Electrotypes from Daguerreotypes. — What may be justly termed the perfection of electrotyping, is the production of electro- types from daguerreotypes. The daguerreotype picture being taken, a small portion of the back is cleaned with sand-paper, taking care not to allow anything to touch the face ; a little fine solder is placed on this part; a piece of flattened wire, also cleansed, is placed upon the solder, the whole moistened with dilute muriatic acid, or chloride of zinc. The wire is now held over the gas or a lamp about half an inch from the plate ; the heat is transmitted through the wire to the solder, which melts, and the wire is soldered to the type ; the back is then protected by wax, and the daguerreotype is now put into the copper solution in the same manner as a medal; the deposit 412 ELECTROTYPE PROCESSES. proceeds rapidly, and when sufficiently thick the two easily separate, and an impression of the picture is obtained from the daguerreo- type, with an expression softer and finer than the original : several electrotypes may, with care, be taken from one picture. The elec- trotype may now be passed through a weak solution of cyanide of gold and potassium, with the smallest quantity of electricity con- nected, and thus a beautiful golden tint be given to the picture, which serves to protect it from the action of the atmosphere; but they should also be protected by a glass, which may be fixed on in the manner pointed out in another section. Depositing by Separate Battery. — Having described, so far as we know them, the best and most simple means of obtaining moulds, and their preparation for receiving the deposit of the metal, we return again to the management of solutions and batteries, and the application to other metals besides copper. Though in our account of the porous, or single cell system, we have recommended it as the best and most economical for electro- typing, still many eminent electro-metallurgists prefer using the battery system; and, indeed, there are solutions of copper and of other metals to which the porous cell system cannot be applied, from the nature of the solution and the necessity of intensity to decompose them. While depositing upon a mould by the single cell, let the wire which connects them be cut in the middle, and a mould be attached to the end of the portion remaining upon the zinc plate, and a small plate of copper to the end of the wire remaining upon the mould in the copper solution, and let these two be put into a second vessel containing a solution of sulphate of copper. The action between the zinc and metal in the double or first cell will go on as before — namely, the electricity passing through the porous cell and the solution to the medal; but on returning to the zinc it must pass through the copper solution, which is in the second vessel, between the mould and copper plate, where it produces the same effects as in the first cell. The sulphuric acid is liberated at the copper plate and dissolves it, and the copper is deposited upon the mould, so that the solution in this cell is maintained at one strength: hence there is no necessity for hanging crystals of sulphate of copper in this solution. Fig. 519. COMPOUND CELL PROCESS. 413 It will be observed that the electricity, having to pass through a second solution, is made to perform double duty, and must conse- quently be much more economical. We found the results to be these : A single cell, with a mould, was placed two inches from the porous cell, and of the same size as the zinc plate, and another, similarly arranged, but connected with a metal mould and copper plate of similar size to the zinc and copper, was placed one inch apart in the copper solution of second cell. The mould in the single cell had gained 100 grains, and the zinc plate lost 108 grains. The mould in the battery cell of the other arrangement had only depo- sited upon it 30 grains, the zinc plate had lost 35 grains ; but the mould in the second or decomposition cell had also deposited upon Fig. 520. it 30 grains, making in all 60 grains deposited, for 35 zinc dissolved, but losing nearly double the time. • Figs. 519 and 520 represent troughs adapted to operations of this kind. In the first of these figures a battery is represented in connection. The latter figure represents a trough adapted for seve- ral metals at one operation. Compound Cell Process.— Another method of economizing power was proposed in what is termed the compound cell system, by which it was said that the electricity passing through a series of cells would be able to produce the same quantity of work in every cell with no more cost. This plan may be stated thus :— Fig. 521. 414 ELECTROTYPE PROCESSES. A is a battery; the wire z is conducting the electricity to the com- pound trough, which is composed of a series of water-tight cells, as a a, and is connected with a piece of copper c, forming a positive electrode; in the same cell, and facing this electrode, is a medal, connected by a copper wire to a piece of copper placed in the second cell, opposite which is another medal connected in the same manner with another piece of copper, and so on through the series, which terminates with a medal attached to the wire of the battery. The electricity from the battery passes through all these cells, and re- duces its equivalent in each cell. Thus the reduction of 32 grains of zinc in the battery would deposit 32 grains of copper multiplied by 6 times, or as many times as there are cells. This is correct in principle, and at first sight seems to be exceed- ingly economical; but it is not so, for every cell adds so much to the resistance of the current, that intensity batteries must be used: — So that, supposing we have a compound cell of 6 divisions, in which are placed 6 separate medals, it would require a battery of 6 pairs of plates to give intensity sufficient to overcome the resistance, and the same number of medals could be made of the same weight by 6 separate zincs, and in less than half the time they could be made by this arrangement, and with a less destruction of zinc. For large operations, where the article receiving the deposit and the electrode are necessarily a good way apart, the process is altogether imprac- ticable in a commercial point of view. This is one of the remarka- ble instances where theoretical possibility and commercial economy are at variance. Mode of Suspending Objects for Coating. — In beginning to operate in the art of electrotyping, the student often pauses, and asks the question, What is the best position Fig- 522. [ n which a medal should be hung in the solu- tion ? Convenience has brought into general practice the suspending of it perpendicularly in the solution, having the positive electrode or pole facing it in a parallel direction ; but to this method there are some objections. If, for instance, the porous diaphragm, or single- cell system be used, for obtaining the medals, it is found that upon the lower portion of the medal the deposition is much thicker than upon the upper portion. Indeed, when even ordinary attention is not paid, the lower part becomes not only thicker, but studded over with round nodules of copper, or with lines composed of these nodules, while the upper part remains thin, and is covered over with what is termed the sandy deposit copper, in dark brown grains, capable of being rubbed off with the slightest friction. No doubt this is in a great measure prevented by agitating the solu- tion ; but it is inconvenient, and requires constant attention. If a separate battery is used, and the deposition of the medal i8 effected in a separate vessel, by having a copper positive electrode, the same inconvenience takes place to a greater or less extent accord- NON-TRANSFER OF ELEMENTS. 415 ing to the distance at which the two poles are placed. These incon- veniences are known to all electrotypists, and the cause is ascribed to the different densities of the solution. The reason why the solution becomes of different densities is easily understood in the single-cell process : there being no copper pole to maintain the strength of the solution, as it becomes exhausted of copper by the deposition, the lighter portion floats on the top, and the heavier portion remains below ; and although crystals of sulphate of copper be suspended in the solution, as they dissolve they sink by their gravity, and cause a flow upon the lower portion of the medal, and consequently a much more powerful deposit. But why the same should take place with a separate battery, where there is a positive electrode of copper being dissolved, just in proportion to the copper extracted from the solu- tion by the medals, has but recently been discovered. Non-Transfer of Elements. — It has been shown that during the deposition of metal, say copper, in electrotyping, the acid when ex- hausted of the copper at the surface of the medal, is transferred to the positive pole, and dissolves a portion of copper ; but this portion is not transferred by the electric current to the medal: hence it will be observed, that the solution next the medal will become exhausted of copper, and will consequently rise to the surface from its greater lightness. There is no doubt a flow of stronger solution in a hori- zontal direction from the positive pole to the medal, caused by the lighter portion ascending ; but this does not mend the evil : the light portion is increasing on the surface, and the whole solution soon be- comes of different densities from the surface to the bottom of the medal ; and this constant current of the solution flowing up the sur- face upon which the electrotypist is depositing, causes the lines that are observed in deposits under certain circumstances, and which are sometimes very annoying. If a small hollow be in the mould, or even if a small portion of Fig- 523. a plain surface resist, the metal will accumu- late round the edge of the resisting portion, giving the deposit an appearance as if made in a flowing stream, like a stone standing up in a current of water. The black point in the centre represents the resisting spot, around which the deposit will thicken, causing a ridge of metal to radiate to a point immediately above the resisting portion. These disappoint- ments are much more annoying in solutions of gold and silver than in sulphate of copper, as will be noticed when we come to treat of plating and gilding. A point of grease or dirt, or small hole not cleaned out, hardly visible to the naked eye, will give a very promi- nent effect upon the plain polished surface of a piece of metal. From these observations, the reader will now be able to answer the question — What is the best position to place a medal in the so- lution ? To make it still more apparent, take a glass jar, filled with a solution of sulphate of copper ; place a piece of copper upon the 416 APPLICATIONS OF COATING WITH COPPER. bottom of the jar, and suspend the medal at the top, having their two faces parallel ; connect them with a battery ; in a short time the solution round the medal becomes exhausted, and even colorless, the medal covered with a dirty-brown powder, and no further deposit will take place. But reverse the case : place the medal at the bot- tom, and the copper positive electrode at the top ; the deposition goes on constant and smooth ; the solution is maintained in the same condition as it was at the first, there being a constant transfer ; the acid is transferred by the current from the medal to the copper pole ; the sulphate of copper formed, descends by its gravity to the medal. There are, no doubt, a few slight objections to placing the medal under the positive electrode — such as the impurities in the copper getting disintegrated, and falling upon the surface, but a piece of cloth wrapped round the pole prevents this. However, when a fine surface is wanted, care ought always to be taken to have clean solu- tions filtered, and kept covered from dust ; and when the single cell is used, the crystals of sulphate of copper should be suspended in a fine linen bag, or the shelf holding them be lined with linen. Effects of Difference in the Density of Solution. — Although this is the best method, we believe that very few practice it, because of the trouble attending the arrangement of the electrodes in this position. When the medals are small the annoyances from unequal density are not so material, but if the surface of the article which is being deposited be large — say eight inches or upwards — the dif- ference in the thickness of the lower and upper portion of the medal is very great. If it is not convenient to place them horizontally, they should be shifted several times, making the upper portion the lower, besides occasionally stirring the solution, or shaking the article. Indeed, when convenient, the article receiving the deposit, if suspended perpendicularly, should be kept as much in motion as possible, as it regulates the deposit, making it smoother and less brittle. Crystals of Copper on Electrodes. — It will be found, when working with a battery, that the sulphate of copper solution will become stronger round the positive electrode, which is gradually dis- solved by the transferred acid. A frequent effect is, that the elec- trode often gets coated over with crystals of sulphate of copper, which adhere with great tenacity, and stop the electric action. Under such circumstances, it is only necessary to clean the elec- trode from the crystals, and to add a little water to the solution, which will prevent a recurrence of the crystals for a time. But the stirring of the solution occasionally will do much to prevent this crystalization. OTHER APPLICATIONS OF COATING WITH COPPER. Besides the applications and processes which we have described under the general term of electrotyping, there are many other appli- cations of the process of depositing metals upon various substances, calico-printers' rollers. 417 ■which have been, and may be still more, usefully applied. We may, at a trifling cost, impart a coating of copper to cornices for decorat- ing buildings, to terra cotta, carvings in wood, &c. &c. Cloth may also be easily covered, and made to assume the appearance of a sheet of copper, having the lightness and pliability of cloth. Lace has been covered with copper, and used for battery plates, and has also been gilt and made into beautiful ornaments. Table-covers with metallic ornaments richly gilt, and book-covers, have all been tried with less or more success, although they have not yet been profitably produced. Coppered Cloth. — Ordinary cloth, covered with copper, was pre- pared a few years ago in considerable quantity for the covering of roofs, wagons, &c. ; but the necessary price precluded its use when competing with the ordinary materials for these purposes, although it possesses many eminent qualities for some of these uses — such as forming fire-proof covers to shelter wagons from the sparks of fire discharged by a locomotive. The choice of the kind of cloth was another difficulty: linen was too expensive, and required a good coat- ing of copper to make it water-tight ; the best substance was a felted cotton with India-rubber, but after a few months' exposure the India- rubber in the cloth decomposed. The operations of coating cloth with copper were the same as described for the wax medals : the cloth was brushed over with a polish of black-lead, and then stretched upon a frame of wood having a copper band round it, in which were placed small hooks or pins, and the cloth attached to these. A vat, four feet deep and twelve yards long, was made of brick and cement ; this was divided lengthwise by a wooden frame with panes the same as a window, which were filled in with unglazed earthenware plates, cemented by marine glue, and the whole made water-tight. Into one division of the vat was placed the dilute acid and sheets of zinc, in the other, the solution of copper, in which was placed the cloth upon the frame. The arrangement was so perfect that we have often seen pieces of cloth twelve yards long by one yard wide completely covered with copper in one hour. The result of many trials was, that one pound weight of copper gave a perfect solid covering to twenty superficial square feet of cloth. A similar thickness is quite sufficient for other surfaces not affected by the atmosphere, such as wood, &c. &c. Besides these applications, a host of others have been suggested and tried with variable success. Some have probably been aban- doned too soon, others have had both capital and talent applied, and success is yet to come. We shall only name a few of these ap- plications. Calico-Printers' Rollers. — So early as 1841 active means were tried to apply the electro-deposition of copper to the preparation of rollers for printing calicos, both by depositing the copper upon wax or other moulds, to make an entire roller of copper, or to deposit a surface of copper on other metals, such as iron or brass ; but none of them have yet succeeded. To make an entire roller is much more 27 418 APPLICATIONS OF COATING WITH COPPER. expensive, without an equivalent advantage over the ordinary method of casting, rolling, and boring. To deposit a layer of copper on iron is attended with many practical difficulties, both in protecting the iron from the acid solution for so long a time as is required to deposit the proper thickness, and in securing the adhesion of the two metals during the subsequent operations. It requires a deposit of about a quarter of an inch in thickness to allow for turning before engraving. There is then the annealing to soften the copper, &c, which inter- feres with the adhesion of the two metals, probably from their differ- ent rates of expansion, and other causes. Similar objections may be made to the coating of brass rollers with copper. Numerous and varied have been the experiments made, but all without success. Etching of Rollers. — The last application of the process to printers' rollers was to plate the surface of the roller with silver for the purpose of etching. The engraving is then made through the silver coating ; the roller is next passed through nitric acid, which acts upon the exposed copper, the silver taking the place of varnish in ordinary etching : but practical difficulties have caused the aban- donment of this method also ; so that, so far as we are aware, no really practical and useful application of the electrotype process has yet been made to printers' rollers. Printing. — The electro-metallurgical process has been applied to many operations in ordinary printing. It has also been applied to plates for printing music, and for embossing soft materials, such as leather. By depositing a sheet of copper upon a skin of morocco leather, it may be used for imparting an impression to other skins of leather. Copying of Copper-plate Engravings. — Copper-plate engravings of all sizes, and of every degree of excellence, have been copied by electrotype. The process is exactly the same as that of making a copy of a penny piece, as described at page 402 ; namely, an electrotype mould is first made in copper, on which of course, the engraving appears in relief ; upon which mould any number of electrotype copies of the copper-plate engraving may be deposited successively. The duplicates thus made are accurate copies of the original engraving ; but they are rapidly worn away by the friction they undergo in the ordinary process of copper-plate printing. The process has there- fore not displaced the use of engravings on steel. Coating of Glass and Porcelain. — This is done by putting a fine coating of copal varnish over the glass, then black-leading it, and depositing the copper. Another method has been proposed, namely, to make a varnish of two parts asphaltum and one part mastic, by fusing these together, and, when cool, dissolving the mix- ture in spirits of turpentine to a syrupy consistence. To prevent the deposit coming off the glass, the vessel is first corroded by the fumes of hydrofluoric acid. A solution of gutta percha or benzole has also been proposed as a varnish for fixing on the black lead and deposit. Retorts, basins, and other chemical vessels, are sometimes covered with copper for their protection during boiling and evaporation. China saucepans have also been made and covered with copper to GALVANIC SOLDERING. 419 take the place of tinned copper vessels, but the adhesion of the metal upon these substances, even when we attempt to secure it by the means above referred to, is never so perfect but that after a short use the deposit of copper loosens from the vessels. There is then great liability for liquids to get between the coating and the vessel, and when heat is afterwards applied these liquids, saturated with verdigris, boil out. Consequently, such coverings are not well adapted, either for culinary purposes or delicate chemical operations. They have, notwithstanding, been highly recommended, and the prac- tice of covering the bulbs of large plain retorts, &c, maybe useful in a few large manufacturing operations, but our experience is cer- tainly not favorable to their general use. On Galvanic Soldering. — Under the name of galvanic soldering a process is known by means of which two pieces of metal may be united by means of another metal, which is precipitated thereon through the agency of a galvanic current. This mode of soldering by the wet method has been often recommended in various periodi- cals relating to the industrial arts; but it has been objected that, practically speaking, the union between two pieces of metal could not be effected by means of a metal precipitated by galvanic agency. In order, however, to arrive at a definite conclusion upon this question, M. Eisner, a Frenchman, undertook the following experiments, the results of which are in favor of the practical use of the operation of soldering by galvanic agency. Upon the end of the copper wire, which formed the negative electrode, a strong ring of sheet-copper was placed. This ring was cut asunder at one point, and the distance left between the several parts was about the sixtieth of an inch. At the end of a few days (during which time the exciting liquors were several times renewed) the space in the severed portion of the ring was completely filled up with copper regulus, which had been preci- pitated ; and on partially cutting with a file through the part thus filled up, and examining it with a lens, it was observed to be very equally filled with solid and coherent copper. Another copper ring was then cut into two parts, and the two semi-annular segments thus obtained were placed with the faces of the sections opposite each other, and submitted to the action of a galvanic current. At the end of a few days, the segments were united by the copper precipitated, thus forming again a complete ring. It was also found in this case, on removing with a file a por- tion of the thickness of the ring at the points of contact, that the spaces had been completely filled up by copper galvanically preci- pitated, which had united the whole. On observing these points carefully with a lens, the regular deposition of the copper could be readily traced between the formerly separated portions of the ring. A third experiment was made in the following manner: Two strong rings of sheet-copper were laid with their freshly-cut faces one upon another, so that the two rings constituted a cylinder. These rings were surrounded by a band of sheet-tin, which was coated with a solution of wax, so that the two rings were equally sur- 420 APPLICATIONS OF COATING WITH COPPER. rounded by a conducting material. Thus disposed, these rings were attached to the negative wire of the battery, and immersed in the bath of sulphate of copper. At the end of a few days, the interior sur- face of the ringswas covered with precipitated copper, and between the contact surfaces of the two rings copper was also precipitated. These rings had only been submitted to the galvanic current to such an ex- tent as to cover their interior surface with a thin coating of preci- pitated copper, and yet they were already completely re-united, and formed a cylinder consisting of a single piece. The exterior conduct- ing covering, consisting of a sheet of tin, was of course removed be- fore testing the cohesion or persistence of the galvanic precipitate. It may be remarked, that these rings, after being for a certain time in contact (during the galvanic action), together with the plate of copper upon which they rested, became so incrusted with precipitated metallic copper that some force was found necessary to effect their detachment from the copper wire. There would appear to be no doubt, then, according to the results obtained in the preceding experiments, that two pieces of metal may be firmly united by means of galvanically-precipitated copper ; in a word, that soldering by galvanic agency is perfectly practicable. It will, therefore, be possible to firmly unite the different parts of a large piece of metal, and to make a perfect figure of them by gal- vanic precipitation of a metal (copper, in ordinary cases). If solu- tions of salts of gold or silver were employed in as concentrated a form as those of copper above mentioned, there is reason to believe that galvanic soldering would also result. In fact, M. de Hackewitz states, that in some experiments on a larger scale which he undertook to obtain hollow figures by galvano-plastic means, he had remarked that galvanic union often took place between the pieces operated upon. M. Eisner states, that while conducting the experiments above mentioned, he remarked that, by employing too powerful a current, the negative electrodes of copper, and even the plate of copper, and ring of the same metal resting thereon, became covered with a deep brown substance, in the same manner as this occurs under similar circumstances in galvanic gilding, as is well known. After several unsuccessful attempts to prevent the formation of this brown coating, M. Eisner, of Paris, found that it was possible to remove it entirely on immersing the articles covered therewith, during a few seconds, in a mixture of sulphuric and nitric acids. By this means the pre- cipitated copper was made to assume its natural red color. The possibility of practically effecting the operation of soldering by gal- vanic agency may be explained in a few words, in a theoretical point of view. The article is, in fact, in an electro-negative state of ex- citation, whilst the zinc operates positively ; the result is, that the faces which are placed opposite each other, when the ring has been cut, are negative ; that is to say, in an electric condition of the same denomination. During the progress of the electrolytic decomposition of the metallic salt in solution (sulphate of copper in the above case), the electro-positive molecules of copper which are detached simul- BROWN BRONZES. 421 taneously arranged themselves upon the two opposite faces, and in the direction of the break. Now, from the moment that these mole- cules are deposited they constitute, with the piece, a homogeneous mass ; and from that time act negatively upon the copper which is contained in the' solution, and again precipitate copper in the form of regulus. This method of operation continues until the space which existed between the two separate pieces of metal is filled up with m etallic copper ; in fact, the layers of copper which become deposited in an equal manner upon the contiguous faces of the metal, gradually diminish the distance which separated the latter, until at length the metallic layers which cross in the opposite direction meet each other ; the result being that the whole of the break which originally existed between the faces will have disappeared, and become filled up with copper. With respect to the solidity (the degree of cohesion) of the gal- vanic soldering, it is the same as that of copper or other metal pre- cipitated by galvanic agency. It will, moreover, be well understood, that too energetic galvanic excitation must have an injurious influ- ence upon the cohesion of the metal precipitated; and in this case precisely the same phenomena will be observed as those which have long manifested themselves in ordinary galvano-plastic operations. BRONZING. We have already mentioned that when a medal has been made from a metal mould, protected by a little wax dissolved in turpentine, it retains its bright copper lustre for a long time, even when exposed to the air, but generally the copper medals and other objects are very liable to tarnish ; for which reason it is usual to give them a coating of bronze, that they may acquire a permanently agreeable appearance. Brown Bronzes. — Bronzing is effected by several very simple methods, the most common of which is the following: — Take a wine-glass of water, and add to it four or five drops of nitric acid ; with this solution wet the medal (which ought to have been previously well cleaned from oil or grease) and then allow it to dry; when dry impart to it a gradual and equable heat, by which the surface will be darkened in proportion to the heat applied. Another Method. — Make a thin paste of crocus and water ; lay this paste on the face of the medal, which must then be put into an oven, or laid on an iron plate over a slow fire: when the paste is perfectly reduced to powder, brush it off and lay on another coating; at the same time quicken the fire, taking care that the additional heat is uniform ; as soon as the second application of paste is thoroughly dried, brush it off. The medal being now effectually secured from grease, which often occasions failures in bronzing, coat it a third time, but add to the strength of the fire, and sustain the heat for a considerable time : a little experience will soon enable the amateur to decide when the medal may be withdrawn : the third 422 BRONZING. coating being removed, the surface will present a beautiful brown bronze. If the bronze is deemed too light the process can be re- peated. Another very simple method is this: after the medal is well cleaned from wax or grease, by washing it in a little caustic alkali, brush some black lead over the face of it, and then heat it in the same way as described for crocus, or, a thin paste of black lead may be used, and the processes already referred to be repeated until the desired brown tint is obtained. In this kind of bronze a little he- matitic iron ore, which has an unctuous feel, may be brushed over the face of the bronze, by which a beautiful lustre is imparted to it, and a considerable variety in the shade may be obtained. In the brown bronzes the copper is slightly oxidized on the surface. Black Bronzes. — A very dark-colored bronze may be obtained by using a little sulphureted alkali (sulphuret of ammonia is best). The face of the medal is washed over with the solution, which should be dilute, and the medal is to be dried at a gentle heat. It should afterwards be polished by a hard hair brush. Sulphureted hydro- gen gas is sometimes employed to give this black bronze, but the effect of it is not so good, and the gas is very deleterious when breathed. In these bronzes the surface of the copper is converted into a sulphuret. Many metallic solutions, such as weak acid solutions of platinum, gold, palladium, antimony, &c, will impart a dark color to the sur- face of medals when they are dipped into them. The medal after being dipped into the metallic solution is to be well washed and brushed. In such bronzes the metals contained in the solution are precipitated upon the face of the copper medal, which effect is accompanied by a partial solution of the copper. Green Bronzes. — Green bronzes require a little more time than those already described. They depend upon the formation of an acetate, carbonate, or other green salt of copper upon the surface of the medal. Steeping for some days in a strong solution of com- mon salt will give a partial bronzing which is very beautiful, and if washed in water and allowed to dry slowly, is very permanent. Sal ammoniac may be substituted for common salt. Even a strong solu- tion of sugar alone, or with a little acetic or oxalic acid, will pro- duce a green bronze : so also will exposure to the fumes of dilute acetic acid, to weak fumes of hydrochloric acid, and to several other vapors. A dilute solution of ammonia allowed to dry upon the copper surface will leave a green tint, but not very permanent. Electrotypes may also be bronzed green, having the appearance of ancient bronze, by a very- simple process: take a small portion of bleached powder, place it in the bottom of a dry vessel, and suspend the medal over it, and cover the vessel ; in a short time the medal will take on a green coating, the depth of which may be re- gulated by the quantity of bleaching powder used, or the time that the medal is suspended in its fumes: of course any sort of vessel, or any means by which the electrotype may be exposed to the fumes DEPOSITION OP METALS UPON ONE ANOTHER. 423 of the powder, will answer the purpose : a few grains of the powder is all that is required. According as the medal is clean or tarnished, dry or wet, when suspended, different tints with different degrees of adhesion will be obtained. The green bronzes are generally applied to figures and busts. DEPOSITION OP METALS UPON ONE ANOTHER. Coating of Iron with Copper. — Besides making articles of solid copper, we may at a small cost give a coating of copper to another metal, such as iron, which if kept in a dry place will retain the appearance of copper for any length of time. But in covering iron with copper, or any one metal with another, great care must be taken that a proper kind of solution be used. It is a familiar fact, that if a piece of iron, such as the blade of a knife, be dipped into a solution of sulphate of copper, it receives a coating of that metal. This is often described as the result of galvanic action, but there is no more galvanic action in this than in any ordinary chemical combination ; it is simply a case of che- mical substitution : the acid that is in union with the copper haying a stronger attraction for iron, leaves the copper, and combines with the iron: the copper is left on the surface of the iron, but the two metals not having sufficient polar attraction to cause them to adhere so firmly as to exclude the action of the acid, the copper is undermined, and falls to the bottom of the solution as a powder. After some copper has fallen upon the surface of the iron, local galvanic action is induced between it and the iron ; but this second- ary action is altogether distinct from that which first takes place. Any solution that has the power to give a metallic coating to a metal when dipped into it, should not be used to coat that metal by electricity. The attraction of the common mineral acids for the ordinary metals is as follows: Zinc, iron, copper, nickel, silver, gold, pla- tinum. If the metal to be deposited be copper held in solution by an acid, say sulphuric acid, then iron or zinc cannot be coated with copper from this solution ; the acid having a greater attraction for these metals, will leave the copper and combine with them as described above ; but if the metal to be coated be any of those under copper, in the above table, then no chemical action will take place, and no deposit will be made, except as the effect of the elec- tric current introduced by the battery. This we believe is the cause why Mr. Muggins, and others, failed, at an early stage of the art, in their experiments in plating and gilding, as they employed acid solutions, which are quite impracticable when used for depositing upon inferior metals. Under these circumstances, other solvents for the metals must be used, which have a different relative attrac- tion for the metals than the acids have. The substance first applied 424 COATING OF IRON WITH COPPER. for this purpose is, after ten years' experience, still found to be the best — namely, cyanide of potassium. Cyanide of Potassium. — This substance may be prepared by ex- posing ferrocyanide of potassium (yellow prussiate of potash) to a read heat in an iron crucible ; then pounding the mass, and boiling it in alcohol of about spec. grav. 0.900 : cyanide of potassium crys- talizes on cooling the resulting solution. It is now, however, almost universally prepared for electro-metallurgical purposes. Ferrocyanide of potassium, pounded fine, is dried over a slow fire (we have found an iron plate, or clean shovel, to serve the purpose very well) ; it must be constantly stirred to prevent its forming a cake upon the hot iron ; when perfectly free from moisture, eight parts must be thoroughly well mixed with three parts of carbonate of potash, also well dried : put a cast-iron crucible into the fire, and when it is red hot, nearly fill it with the mixture, and keep up the heat by occasional augmentations of fuel : the crucible should be kept covered as much as possible. In a short time the whole fuses into a beautiful liquid with the evolution of gas. It should be kept in this state for ten or fifteen minutes, being occasionally stirred with an iron rod: the portion adhering to the rod should be examined from time to time, and when the liquid on it cools white, it is an indication that it is ready to be removed from the fire; but the first time a cast-iron crucible is used, this test will not be so accurate, the salt having then a light gray color. When the crucible is removed from the fire, it should be placed upon a stove ; the mass stirred, and then allowed to settle for a short time, after which the clear, or liquid part, is to be poured off into a clean iron vessel. The sedi- ment should be scraped clean out of the crucible while it is hot, as the crucible will do to use again several times ; but if the mass at bottom be allowed to cool, it will be difficult to remove it from the crucible. The clear liquid poured off is cyanide of potassium, having from twenty-five to thirty per cent, of cyanate of potash and other impurities generally contained in commercial yellow prussiate of potash : eighty per cent, of cyanide of potassium is the greatest pro- portion that this process can give. We have occasionally obtained it at seventy-eight per cent, from commercial materials, but more generally at seventy and seventy-two per cent. ; and we have found cyanide of potassium in the market containing as little as forty-nine per cent, of pure cyanide. The results of the manufacture of this salt on a large scale, from the ordinary materials of commerce, show that 55 lbs. of yellow prussiate, dried as directed above, yield 48 lbs. ; and 19 lbs. of car- bonate of potash give 18 lbs. of dry salts; in all, 66 lbs. of the proper mixture. The crucible used was of this shape, capable of holding from two to three pints : in general two of them were used up in making the above quantity of cyanide, even when great care was taken. One great cause of the crucible giving way is the depth of the fire, and openness of the bars of the grate. The bottom of the crucible, between each pair of bars, fuses from the CYANIDE OF COPPER. 425 great heat concentrated near the opening. To remedy this evil, a square tile of fire-clay should be laid upon the bars, upon which the crucible is to rest. The tile must not cover all the bars, else the draught will be stopped — an equal space must be left at each side of the tile, which will preserve a regular heat around the crucible. The quantity of clean cyanide of potassium obtained from the above quantity of materials was about 38 lbs.; the sediment scraped out of the crucible, being put into water, yielded about 6 lbs. more in solution, but of inferior quality; good enough, however, for precipita- tions, the cleaning of silver, and other general purposes in the factory. It may be mentioned that in those operations the crucible is never allowed to cool, but as soon as the sediment is scraped out, it is again put into the furnace. If the iron sediment is not well cleared out, it imbibes oxygen rapidly, and the charge next taken from the crucible will have an excess of cyanate of potash, besides lessening the capacity of the crucible. Generally speaking, however, even when the utmost care is taken, the last charge has more cyanate of potash than the first. Cyanide of Copper. — To prepare copper solutions by means of cyanide of potassium, for covering iron and other positive metals, there are several methods. First Method. — To a solution of sulphate of copper, add by de- grees a solution of cyanide of potassium, which will give a yellowish green precipitate, with slight effervescence. There will be evolved a gas, having a most pungent odor, to prevent the inhalation of which the most watchful carefulness has to be exercised, as it is very deleterious. It will be found that the copper is not all precipitated by the cyanide of potassium, for according to this mode, when a precipitate ceases to be formed, the solution remains greenish blue, probably owing to the decomposition of the cyanate of potash, and the formation of ammonia, which holds copper in solution, and forms also some complicated compounds with the cyanides of copper. If cyanide of potassium is added until the blue solution disappears, still copper is held in the solution, and may be detected by taking out a little, and adding to it a few drops of sulphuric acid, which will give a white precipitate of subcyanide of copper. The loss of copper sustained is the only objection to this mode of preparing a. copper solution. The cyanide of potassium is added until a precipi- tate is no longer formed; it is then allowed to settle, the clear liquid is poured off, and the vessel is to be filled with water; when the precipitate has again settled, the liquor is poured off, and this washing is repeated four or five times, in order to wash out the sulphate of potash which is formed during the precipitation. After being thus washed, a solution of cyanide of potassium is added to the precipitate until it dissolves. The coppering solution is now complete: it is of a light yellow color, and is well adapted for ordinary purposes. The loss of copper is, however, considerable, being about one-fifth of the whole. Second Method. — A coppering solution may also be prepared by 426 COATING OF IRON WITH COPPER. adding cyanide of potassium to oxide of copper, or to carbonate of copper, until it is dissolved. But these solutions are objectionable, the latter especially so, as it contains a great quantity of carbonate of potash, formed from the mutual decomposition of the carbonate of copper and cyanide of potassium, and the carbonate of potash deteriorates the solution; the former leaves potash in the solution, but this is not so bad as the carbonate of potash. Third Method. — The method we have adopted in manufacturing purposes is as follows : To a solution of sulphate of copper, we add a solution of ferrocyanide of potassium, so long as a precipitate continues to be formed : this is allowed to settle, and the clear liquor being decanted, the vessel is filled with water, and when the precipi- tate settles, the liquor is again decanted, and we continue to repeat these washings until the sulphate of potash is washed quite out. This is known by adding a little chloride of barium to a small quantity of the washings, and when there is no white precipitate formed by this test, the precipitate is sufficiently washed. A solu- tion of cyanide of potassium is now added to this precipitate until it is dissolved, during which process the solution becomes warm by the chemical reaction that takes place. The solution is filtered, and allowed to repose all night. If the solution of cyanide of potas- sium that is used is strong, the greater portion of the ferrocyanide of potassium crystalizes in the solution, and may be collected and preserved for use again. If the solution of cyanide of potassium used to dissolve the precipitate is dilute, it will be necessary to con- dense the liquor by evaporation, to obtain the yellow prussiate in crystals: the remaining solution is the coppering solution. Should it not be convenient to separate the yellow prussiate by crystaliza- tion, the presence of that salt in the solution does not deteriorate it, nor interfere with its power of depositing copper. Peculiarities in working Cyanide of Copper Solution. — The true composition of the salts thus formed by copper and cyanide of potassium has not yet been determined, but their relations to the battery and electrolyzation are peculiar. The solution must be worked at a heat of not less than from 150° to 200° Fahrenheit. All other solutions we have tried follow the laws, that if the elec- tricity is so strong as to cause gas to be evolved at the electrode, the metal will be deposited in a sandy or powdered state ; but the solution of cyanide of copper and potassium is an exception to these laws, as there is no reguline deposit obtained unless gas is freely evolved from the surface of the article upon which the deposit is taking place. As this solution is used hot, a considerable evaporation takes place, which requires that additions be made to the solution from time to time. If water alone is used for this purpose, it will pre- cipitate a great quantity of the copper as a white powder, but this is prevented by dissolving a little cyanide of potassium in the water at the rate of about four ounces to the gallon. The vessels used in factories for this solution are generally of copper, which are heated CONDUCTING POWER IN SOLUTIONS AND METALS. 42T over a flue, or in a sand-bath — the vessel itself serving as the posi- tive electrode of the battery : but any vessel will suit if a copper electrode is employed, when the vessel is not of copper. Preparation of Iron for coating with Copper. — When it is required to cover an iron article with copper, it is first steeped in hot caustic potash or soda, to remove any grease or oil. Being washed from that, it is placed for a short time in dilute sulphuric acid, consisting of about one part of acid to sixteen parts of water, which removes any oxide that may exist. It is then washed in water, and scoured with sand till the surface is perfectly clean, and finally attached to the battery, and immersed in the cyanide solu- tion. All this must be done with dispatch, so as to prevent the iron from combining with oxygen. An immersion of five minutes' duration in the cyanide solution is sufficient to deposit upon the iron a film of copper. But it is necessary to the complete protection of the iron, that it should have a considerably thick coating; and, as the cyanide process is expensive, it is preferable, when the iron has received a film of copper by the cyanide solution, to take it out, wash it in water, and attach it to a single cell or weak battery, and put it into a solution of sulphate of copper. If there is any part not sufficiently covered with copper by the cyanide solution, the sul- phate will make these parts of a dark color, which a touch of the finger will remove. When such is the case, the article must be taken out, scoured, and put again into the cyanide solution till per- fectly covered. A little practice will render this very easy. The sulphate solution for covering iron should be prepared by adding to it by degrees a little caustic potash, so long as the precipitate formed is redissolved. This neutralizes a great portion of the sulphuric acid, and thus the iron is not so readily acted upon. Effects of Conducting Power in Solutions and Metals. — In covering iron, platinum, or such comparatively bad-conducting me- tals, with other metals that are good conductors, or the solutions of which are good conductors, the property of conduction in relation to the solution is beautifully illustrated. If we take a copper wire, say 8 or 10 feet long, one end of which is attached to the zinc of a bat- tery, and laid parallel with the positive electrode into a solution for the purpose of receiving a deposit, it will be found that the greatest amount of deposit has taken place at the end furthest from the bat- tery : but if an iron or platinum wire be substituted for the copper one, the contrary result will take place ; for the end furthest from the battery will be the last to receive the coating, and will have the least quantity of metal deposited upon it. If the copper wire were 30 feet long, little alteration would be seen in the deposit: but upon an iron or platinum wire of that length the deposit proceeds only a certain distance, and no deposit will take place on the end furthest from the battery until the current has passed a considerable time, after which the deposit is observed to advance gradually. The cop- per as it becomes deposited on the iron acts as a conductor, trans- mitting the deposit further onwards to its final point, as well as 428 COATING OF IRON WITH COPPER. adding to the deposition already effected upon the iron. The length of deposit that would be formed on the first immersion of the wire depends upon the conducting power of the solution ; for, as already stated, solutions vary in this property as well as metals. We have found that a few feet of iron wire offer a greater resistance to the passage of the current than the solution between the iron wire and the positive electrode, which is only about 2 or 3 inches ; but their exact relations to each other we have not yet had an opportunity of investigating. Under these circumstances, it may be asked, why not increase the intensity of the battery, and so force it along the wire ? But this, as will be apparent, can only be done within certain limits; for by increasing the intensity of the battery, it may be rendered too strong for the solution near the battery, and thus a sandy deposit will be given at the one end and none at the other. The electro-metal- lurgist, when coating long rods of iron wire with any metal, has to make connections with the battery every few feet. The wire is generally coiled up in the form of a cork-screw, and suspended by copper wires. We have found it very convenient to coil it upon a reel, having its armatures tipped with copper, and connected with the battery. This plan insures a regular coating, but the position of the wire requires to be changed during the operation, otherwise the parts which press upon the arms of the reel will be left without deposit. Illustration op Conduction.— As an illustration of the pro- perty of conduction, we mention the following circumstance. Hav- ing a large iron shaft, or rod, about twelve feet long and three inches average diameter, to cover with copper, we had it properly cleaned, placed in a hot solution of cyanide of copper and potas- sium, and surrounded by sheets of copper as a positive electrode. Two batteries of seven pair intensity were attached, one at each end of the shaft ; but by an oversight one of the batteries was not pro- perly connected, the copper terminal of the battery having been attached to the shaft. Had the shaft been of copper, the one bat- tery would have neutralized the other, so that there would not have been any deposit ; or had the one battery been stronger than the other, there would have been a current and deposit equal to the excess of power of the one over the other. But, under the stated circumstances, a different result was obtained. After the batteries had been in action two hours, we found that a beautiful copper coat- ing was imparted to that half of the shaft which extended from the point properly connected, while the other half was quite bare — no deposit having taken place upon it; but a deposit had been made upon the copper electrode opposite this non-affected half. The bat- teries did not (as we could perceive) affect one another, except that the one improperly connected prevented the deposit effected by the other proceeding further than the half length of the shaft ; but it made the deposit obtained more perfect than would have been the case had there been only one battery at one end. COATING OF IKON WITH ZINC. 429 In this instance, the distance of the shaft from the electrode was six inches, so that the resistance of six feet of the iron was more than six inches of the solution ; hence the influence of the contra-acting battery could not reach further : or if any power passed further it was neutralized by the other battery — which we are inclined to think did not take place — as the amount or thickness of deposit upon the one-half was fully more than we would have anticipated upon the whole had the batteries been properly connected. Non-adherence of Deposit. — Objections have been made to co- vering iron with copper for its protection, from an impression that the copper will not adhere to the iron ; but if the operation is care- fully performed the copper will adhere : when it does not, it will generally be found that it is the copper deposited from the sulphate which loosens from the copper deposited from the cyanide; occa- sioned, no doubt, by the article not having been sufficiently washed from the cyanide solution, and thus having a thin film of cyanide of copper precipitated upon the surface, which prevents the adhesion of the after deposit. Or, as it happens sometimes, on putting the article into water, the cyanide of copper is precipitated upon the surface. If a little cyanide of potassium is dissolved in .the first water used for washing out the depositing solution, this will be prevented. We have repeatedly deposited copper upon iron wire, and after- wards had it drawn out to twice its original length without the copper stripping off ; but as the copper becomes hard and brittle, it is liable to break if the wire is much bent. And if it be made red hot, to anneal or soften it, the copper will oxidize, and if the coating is thin, the iron will be left bare in some places. We have seen iron bolts, covered with copper, driven through seventeen inch wood, and nails of all sizes subjected to rough work, without the de- posit being injured. These remarks are also applicable to iron covered with zinc. COATING OF IRON WITH ZINC. In covering iron with zinc, the precautions necessary for copper are not required ; zinc being the positive metal, acids have a stronger affinity for it than for iron, and therefore an acid solution may be used. The one generally used is the sulphate. Sulphate of Zinc. — Zinc dissolves easily in sulphuric acid, and the solution by evaporation yields crystals of sulphate of zinc ; but as the salt is very cheap and abundant in the market, it is more con- venient and economical to buy than to make it. The solution for depositing is made by dissolving two pounds of the crystalized salt in one gallon of water. The single cell process cannot be used ad- vantageously with this solution. A separate battery is necessary, and a zinc positive electrode. Zinc may be deposited upon black-leaded surfaces in the same manner as copper; but unless more than ordinary precautions are observed, an article formed in this manner is so brittle that it can 430 INFLUENCE OF GALVANISM IN PROTECTING hardly be handled "without breaking, from its crystaline character. When the deposition upon black lead is attempted, the best method is to have the solution saturated with the salt, employing a battery of six or seven pairs of plates, and keeping the article on which the deposit is taking place constantly in motion. Use of Zinc Coating. — The principal application of zinc is upon iron, to protect it from corrosion, which it does, not only as a coat- ing, but, from its more electro-positive character, it protects it from galvanic influence. The voltaic influence of zinc for protecting iron is a subject that has occupied the attention of practical men for a long time : it is one of high importance ; nevertheless there seems yet a great deficiency in our knowledge of the extent of this influence, and how and when it is effective. ' INFLUENCE OF GALVANISM IN PROTECTING METALS FROM DESTRUCTION BY OXIDATION AND SOLUTION. The galvanic influence of one metal in protecting another is in relation to their negative and positive qualities together with their conducting powers. Their relations in sea-water are — silver, copper, bismuth, tin, lead, cobalt, nickel, iron, cadmium, zinc ; the first the most negative, the last the most positive in the series. So that according to this scale, the further apart the metals may be which are selected for experiment, the more decided will be the power of the positive to protect the negative. Copper and zinc operate more strongly together than iron and zinc. A metal that is insoluble when placed singly in a fluid, may be made soluble by connection with a relatively negative metal placed in the same fluid. For example, pure zinc put into muriatic acid is unaffected, but when connected with copper in the same fluid it is rapidly operated upon. Or a metal may be soluble in a fluid alone, but may be rendered insoluble by connection with a relatively posi- tive metal, which undergoes decomposition instead. Thus: copper is dissolved in sea-water when alone, but when a piece of zinc is connected with it, the copper is unaffected. This last effect is the substance of a method of protection, in applying the principle of which it is necessary to take into consideration — 1st. The amount and power of electricity generated by the connected metals in the same fluid ; and 2d. The conducting power of the metal which is being pro- tected. 1st. The amount and power of the electricity evolved is in pro- portion to the difference of the relative negative and positive con- ditions of the metals employed. The more negative the coated metal is, the less it requires protection, although its powers of pro- tection are the greatest. And the more positive the coated metal, the more liable it is to be destroyed, and the greater the amount of electricity required to protect it; but, unfortunately, it is less able METALS FROM DESTRUCTION. 431 to generate this electricity when in contact with another metal. Thus these two conditions are opposed to the application of galvanic influence for protecting iron. Suppose, for example, that 4 square inches of zinc, in connection with 4 square feet of copper, give out sufficient electricity to pro- tect the copper from sea-water, it will be found that to obtain the same amount of electricity by iron and zinc, 2 square feet of the latter to 4 square feet of the former are required. These proportions, given in round numbers, are nearly accurate; but they vary accord- ing to the kind of iron, the state of the water, the distance of the metals, &c, &c. Besides which, the same quantity of electricity that protects copper will not protect iron; nor will any quantity of zinc protect iron from corrosion in sea- water — even a bar of iron placed in a zinc vessel filled with sea-water is not completely protected. 2d. The conducting power of the negative or protected metal subjected to submarine immersion is a subject of very great import- ance. Suppose a piece of copper and a piece of zinc be connected under a solution — say a copper bar (c) 4 feet long, with a piece of Fig. 525. zinc (z) 4 inches in length, erected on one end, as in the annexed sketch. The conducting power of the copper is so much superior to that of the solution that the whole length of the bar will become in- stantly negative, and the current of electricity will pass to and from all parts of the bar at the same time in the lines b, b, b; but the current will be more active towards the point of contact than towards the distant extremity — the resistance of the solution being less in proportion to the proximity of the metals. But if a bar of iron, and a piece of zinc as a protector, be placed in the same cir- cumstances, the phenomena assume quite a different aspect; the conducting power of iron being much less than that of copper, the distant extremity will not be affected by the electric current, which will find a more easy passage, as indicated by the dotted lines e, e, e, beyond which the electric effort ceases ; and even in that portion of the bar which is under the influence of the current, the part nearest the zinc is better defended than those parts which are farther distant. This partial protection, while it induces a negative state at the near end, renders the other end more positive. Such a diversity of condition gives rise to voltaic action between the two extremities of the bar, and the result is the destruction of the far end. In all cases of voltaic protection the more equal the influence over 432 ELECTRO-PLATING. the whole surface protected the more perfect is the protection. An inequality of. protection, such as we have described, is productive of numerous evils. It is, we believe, the source of many of the injuries occurring in our day to copper sheathing. One part of a sheet becoming, by some local cause, negative, the other parts are thus rendered positive; the result is, that upon the borders of an individual sheet either overlapping or underlying its neighboring sheet, an electric current is excited, passing through the stratum of moisture which may intervene, and the ultimate effect is that the positive edge is dissolved as effectually as if cut by a knife. The evil arising in one place may be so contagious as to affect a whole neighborhood — sometimes the whole side of a ship's bottom. In fresh water iron cannot be protected any length of time, for the zinc coating speedily passes into a blackish substance, which peels off and exposes the iron to rust. When iron is simply exposed to the air, a good coating of zinc is a sure protection. We have seen iron of various qualities coated by the electro-process and ex- posed to the atmosphere, in all weathers, for several years, without being more affected than a piece of zinc would be. In spots where abrasion has taken place by accident, the protecting power of the zinc is lost, and the iron rusts as if there were no zinc present. No other result, however, could be anticipated, as there can be no elec- tric excitation without a liquid to connect the two metals. The iron to be coated by zinc is to be cleaned and prepared in the same manner as we have described for the purpose of covering it with copper. ELECTRO-PLATING. The next applications of the electro-deposition we have to notice are those relating to silver and gold, embracing the arts of plating and gilding — arts which are gradually revolutionizing some extensive branches of manufacture. To Make Silver Solution.— The solution of silver used for plating consists of cyanide of silver dissolved in cyanide of potas- sium, which may be prepared in various ways. We shall first de- scribe some of the preparations most in use, and also point out practical objections, which, in special cases, have occurred under our own observation, not omitting to specify and recommend those me- thods which have approved themselves to us as being most simple and effective. The method generally adopted is as follows : Metallic silver is dissolved in four parts of nitric acid, diluted with one part of water : the diluted acid is heated in a vessel, and the silver is added by de- grees. The operator must avoid breathing the fumes which ascend, as they are highly deleterious. The metal being dissolved, the so- lution is transferred to a large vessel, and diluted with water. To this is added a solution of cyanide of potassium as long as a white precipitate is formed. This precipitate is cyanide of silver, and the action which ensues may be thus represented : — CYANIDE OF SILVER SOLUTION. 433 Substances used : Substances produced : Nitrate of silver = AgO,N0 5 Cyanide of potassium == KCy Nitrate of potash = KO,N0 5 Cyanide of silver = AgCy AgO,N0 5 + KCy = KO,N0 5 + AgCy. The propriety of diluting the nitrate of silver before precipitating by the cyanide of potassium arises from the fact that the salts of potash and soda (such as the nitrates, chlorides, and sulphates), when in strong solution, dissolve small quantities of the silver salt, and thus cause a loss, 'which is prevented by previous dilution with water. When the precipitate of cyanide of silver has settled, the clear solution is carefully decanted, and the vessel filled up with water, which is again decanted as soon as the precipitate has settled. This process is to be repeated three or four times, so as effectually to wash out the soluble salts. When properly washed, a solution of cyanide of potassium is added to the precipitate until it is all dis- solved. The resulting solution constitutes the cyanide of potassium and silver, and forms the plating solution. It ought to be filtered previous to using, as there is always formed a black sediment, com- posed of iron, silver, and cyanogen, which, if left in the solution, would fall upon the surface of the article receiving the deposit, and make it rough. The sediment, however, must not be thrown away. The cyanide of potassium, used to dissolve the cyanide of silver, may be so diluted that the plating solution, when formed, shall con- tain one ounce of silver in the gallon : of course, the proportion of silver may be larger or smaller, but that given is what we consider best for plating. In dissolving 100 ounces of silver, the following proportions of each ingredient are those which we have found in practice to be the best. Take 7 pounds of the best nitric acid, (the nitric acid must be free from hydrochloric (muriatic) acid: to a small quantity of the acid add a few drops of a solution of nitrate of silver : if it gives a milky white precipitate, it contains muriatic acid, and should be rejected,) and 61 ounces of cyanide of potassium, of the average quality described at page 424: this quantity will precipitate the 100 ounces of silver dissolved in the acid solution. After this is washed, take 62 ounces more of cyanide of potassium, the solution of which will dissolve the precipitate : this being done, the plating solution is then formed. Of course, these proportions will vary according to the difference in the quality of the materials; but they will serve to give an idea of the cost of the silver solution prepared in this manner. Cyanide of Silver dissolved in Yellow Prussiate of Potash. — We have occasionally dissolved the cyanide of silver by yellow prussiate of potash; three pounds of which are required to dissolve one ounce of silver. This forms an excellent plating solution, and yields a beautiful surface of silver. It must have weak battery power, and, consequently, the silver is very soft. The positive electrode 28 434 ELECTRO-PLATING. does not dissolve in this solution: there is formed upon its surface a white scaly crust, which drops off and falls to the bottom : and the solution soon becomes exhausted of silver. Solution made with Oxide of Silver. — It has been recom- mended to dissolve the oxide of silver in cyanide of potassium, which forms a solution of cyanide of potassium and silver : but this prepa- ration is less economical, because the materials used in converting the silver into an oxide are lost: it requires the same amount of cyanide of potassium as the process just described, and brings, moreover, an equivalent of potash into the solution, which is a disadvantage. The following diagram shows the reactions that occur : — Substances used: Substances produced: Oxide of Silver = AgO Cyanide of Potassium = KCy Cyanide of Potassium = KCy Potash = KO Cyanide of Silver ) rrr . A „ and Potassium } = KC J> A Z C J AgO + 2 KCy=KO + KC,AgCy. Solution made with Chloride of Silver.— The nitrate of silver may also be precipitated by adding a solution of common salt to it, and treating it in the same way as described for precipitation by cyanide of potassium : this would form chloride of silver, which may be dissolved in cyanide of potassium, thus forming the silver solution. But the objection urged against the use of oxide of silver is equally applicable in the case of chloride; and much greater care is required in participating large quantities and strong solutions of silver by common salt, than by cyanide of potassium, the chloride of silver being more soluble in the salts of the alkalies — as the nitrates, chlo- rides, and sulphates — than cyanide of silver is; and there is, there- fore, great liability to loss by this process, in which we have not the redeeming quality of a saving of materials, as the following diagram will show : — Substances used : Substances produced : Chloride of Silver = AgCl Cyanide of Potassium = KCy Cyanide of Potassium = KCy Chloride of Potassium = KC1 Cyanide of Silver \, Kc . p and Potassium f\- ^7t A S^J AgCl+2 KCy = KCl + KCy,AgCy. Thus, we observe that the action taking place is not mere solution but decomposition, which upon one hundred ounces of silver in this preparation produces an impurity of seventy ounces of chloride of potassium, which, although not very injurious to the solution, would be much better away. The Best Method of Making Silver Solution.— The best and cheapest method of making up the silver solution is by the battery, which saves all expense of acids and the labor of precipitations. This is effected by taking advantage of the principle of non-transfer of metal in electrolytes. To prepare a silver solution which is in- tended to have an ounce of silver to the gallon, observe the following HYPOSULPHITE OF SILVER SOLUTION. 435 directions: Dissolve 123 ounces of cyanide of potassium in 100 gallons of water; get one or two flat porous vessels, and place them in this solution to within half an inch of the mouth, and fill them to the same height with the solution : in these porous vessels place small plates or sheets of iron or copper, and connect them with the zinc terminal of a battery : in the large solution place a sheet or sheets of silver connected with the copper terminal of the battery. This arrangement being made at night, and the power employed being two batteries, of five pairs of plates, the zincs 7 inches square, it will be found in the morning that there will be dissolved from 60 to 80 ounces of silver from the sheets. The solution is now ready for use: and by observing that the articles to be plated have less surface than the silver plate forming the positive electrode, for the first two days, the solution will then have the proper quantity of silver in it. We have occasionally found a little silver in the porous cells ; it is, therefore, not advisable to throw away the solu- tion in them without first testing it for silver, which is done by adding a little muriatic acid to it. The amateur electrotypist may, from this description, make up a small quantity of solution for silvering his medals or figures; for example, a half-ounce of silver to the gallon of solution will do very well : a small quantity may be prepared in little more than an hour. Hyposulphite op Silver Solution. — The simplest method known to us for forming the hyposulphite of silver solution is this : Take one pound of pure carbonate of soda well dried as described at p. 424; mix it intimately with five ounces of flour of sulphur; place the mixture over a slow fire without flame, in a porcelain or stoneware basin, which must be supported by an iron trellis, or any convenient support: keep the mixture constantly stirring, and main- tain the heat till the sulphur melts, and the mass inclines to get pasty and rough : while in this state, keep stirring for about fifteen minutes, in order to bring every part in contact with the air. Set the mixture to cool, after which dissolve it in water: boil the solu- tion for some time, adding sulphur ; then filter it, and allow it to evaporate at a slow heat : the crystals formed are hyposulphite of soda. To prepare the silver solution, the silver is first dissolved in nitric acid, and then precipitated by a solution of common salt, and wash- ed, with the precautions stated at page 433. When the precipitated chloride of silver is well washed, some of the crystals of hyposul- phite of soda are dissolved, and the solution is added to. the chloride of silver, which it dissolves, forming the plating solution. It is not necessary to crystalize the hyposulphite of soda, if used as soon as made. The hyposulphite of silver solution is very easily decomposed by the electric current, so that a weak battery will suffice to plate by it : but its great objection is its liability to decompose in the light, and to deposit the silver as sulphuret: unless great care is exercised, 436 ELECTRO-PLATING. Fig. 526. the silver deposited from it will be in a granular condition, which is a great objection in plating. Sulphite of Silver Plating Solution. — The sulphite of silver solution is prepared in the following manner, as described by the patentee of the process : — " The solution which I use is made in the following manner : I take of the best pearlash of commerce 28 lbs. (avoirdupois) and add to it 30 lbs. (avoirdupois) of water, and boil them in an iron vessel until the pearlash is dissolved ; the solution should then be poured into an earthenware or other suitable vessel, and suffered to stand until the liquor becomes cold. It should then be filtered, and 14 lbs. (avoirdupois) of distilled water added thereto ; sulphurous acid gas (obtained by any of the known processes) should then be passed into the filtered liquor until it is saturated, taking care not to add sul- phurous acid gas in excess. The liquor should be again filtered, and the liquor so filtered is what I term the solvent, or sulphite of potash. " To make the Silvering Liquor which I use in coating with silver the surface of articles formed of metal or metallic alloys, I dissolve 12 oz. (avoirdupois) of crystalized nitrate of silver in 3 lbs. of distilled water (in a clean earthenware vessel), and add to the solution, by a little at a time, the before-mentioned solvent, so long as a whitish colored precipi- tate is produced (care being taken not to add more of the solvent than is necessary). After the precipitate has subsided, I pour off the supernatant liquor, and wash the precipitate with distilled water. To the precipitate I add as much of the before-mentioned solvent as will dissolve it, and after- wards add about ^th part more of the solvent, so that the solvent may be in excess ; I then stir them well together, and let them remain about 24 hours, and then filter the solution, when it will be ready for use. This is what I designate Silvering Liquor. Sulphurous acid gas for making the above liquor may be prepared by heating sulphuric acid, undiluted, in a flask or any convenient vessel, to which should be added small pieces of copper or charcoal: the gas escaping is made to pass into the solution to be saturated with it. Fig. 526 is a very convenient apparatus for the preparation of this gas for saturating solutions. This solution is also very easily decomposed by the electric cur- rent, and serves the purposes of plating very well; but it is also liable to decomposition by light, and is not so good in practice as PREPARATION OF ARTICLES FOR PLATING. 43T the solution of cyanide of potassium and silver. The latter solution is, however, liable to a kind of decomposition not yet fully investi- gated, but it is wholly confined to its impurities, and it never deposits its silver ; whereas the decomposition that takes place in the sulphite or hyposulphite affects the silver compound, and pre- cipitates the silver from solution. To Recover Silver from Solution. — When a silver solution gets out of order, and cannot be recovered so as to be fit for use again, instead of throwing down the silver by muriatic acid it is better to evaporate the solution to dryness, and to fuse the product. When the solution has contained yellow prussiate of potash, it is found that during this fusion portions of the metal sometimes form a nodule which floats about the crucible, and all the heat that can be applied will not fuse it. This refractory piece, when cooled, has generally a rough scoriaceous surface, and is exceedingly hard. When filed it has more the color of German silver than of real sil- ver ; it has considerable malleability, and retains its bright appear- ance for a long time without tarnish. An analysis of this alloy gave — If we suppose the carbonaceous matter to be an accidental impu- rity, this alloy will nearly agree with the formula Ag 3 CuFe. . Preparation of Articles for Plating. — Articles that are to be plated are first boiled in an alkaline ley, to free them from grease, then washed from the ley, and dipped into dilute nitric acid, which removes any oxide that may be formed upon the surface ; they are afterwards brushed over with a hard brush and sand. The alkaline ley should be in a caustic state, which is easily effected by boiling the carbonated alkali with slaked lime, until, on the addition of a little acid to a small drop of the solution, no effervescence occurs. The lime is then allowed to settle, and the clear liquor is fit for use. The ley should have about half a pound of soda ash, or pearlash, to the gallon of water. The nitric acid, into which the article is dipped, may be diluted to such an extent that it will merely act upon the metal. Any old acid will do for this purpose. In large factories the acid used for dipping before plating is generally after- wards employed for the above purpose of cleaning. The article being thoroughly cleaned and dried, has a copper wire attached to it, either by twisting it round the article or putting it through any open part of it, to maintain it in suspension. It is then dipped into nitric acid as quickly as possible, and washed through w r ater, and then immersed in the silver solution, suspending it by the wire which crosses the mouth of the vessel from the zinc Silver . . . . , Copper . . . . , Iron Carbonaceous matter 82.15 9.12 7.50 .46 99.23 438 ELECTRO-PLATING. of the battery. The nitric acid used for dipping is of specific gra- vity 1.518, and contains 10 per cent, sulphuric acid. The article is instantaneously coated with silver, and ought to be taken out after a few seconds and well brushed. On a large scale, brushes of brass wire attached to a lath are used for this purpose; but a hard hair brush, with a little fine sand, will do for small work. This brush- ing is used in case any particle of foreign matter may be still on the surface. It is then replaced in the solution, and in the course of a few hours a coating of the thickness of tissue-paper is deposited on it, having the beautiful matted appearance of dead silver. If it is desired to preserve the surface in this condition, the object must be taken out, care being taken not to touch it by the hand, and im- mersed in boiling distilled water for a few minutes. On being with- drawn, sufficient heat has been imparted to the metal to dry it instantly. If it is a medal, it ought to be put in an air-tight frame immediately, or if a figure, it may be at once placed under a glass shade, as a very few days' exposure to the air tarnishes it, by the formation of a sulphuret of silver, and that more especially in a room where there is fire or gas. If the article is not wanted to have a dead surface, it is brushed with a wire brush and old ale or beer, but the amateur may use a hard brush and whiting. It may be afterwards burnished according to the usual method of burnish- ing, by rubbing the surface with considerable pressure with polished steel or the mineral termed bloodstone. We may remark, that in depositing silver from the solution, a weak battery may be used ; though when the battery is weak the silver deposited is soft, but if used as strong as the solution will allow, say 8 or 9 pairs, the silver will be equal in hardness to rolled or hammered silver. If the bat- tery is stronger than the solution will stand, or the article very small compared to the size of the plate of silver forming the positive electrode, the silver will be deposited as a powder. The average cost of depositing silver in this way is 2d. per ounce. Gas should never be seen escaping from either pole : the surface of the article should always correspond as nearly as possible with the surface of the positive electrode, otherwise the deposit runs the risk of not being good ; it requires more care, and the solution is apt to be altered in strength. In plating large articles (such as those plated in factories) it is not always sufficient to dip them in nitric acid, wash and immerse them in the solution, in order to effect a perfect adhesion of the two metals. To secure this, a small portion of quicksilver is dissolved in nitric acid, and a little of this solution is added to water in suffi- cient quantity to enable it to give a white silvery tint to a piece of copper when dipped into it: the article then, whether made of cop- per, brass, or German silver, is, after being dipped in the nitric acid and washed, dipped into the nitrate of mercury solution till the sur- face is white: it is then well washed by plunging it into two separate vessels containing clean water, and finally put into the plating solu- tion. This secures perfect adhesion of the metals. One ounce of PRACTICAL INSTRUCTION IN PLATING. 439 quicksilver thus dissolved will do for a long time, though the liquor is used every day. When the mercury in this solution is exhausted, it is liable to turn the article black upon being dipped into it. This must be avoided, as in that case it also causes the deposited metal to strip off. Practical Instruction in Plating. — We need hardly add that it is necessary the battery should be so arranged that the quantity of eleclricity generated should correspond with the surface of the articles to be coated, and that the intensity should bear reference to the state of the solutions ; that is to say, that the quantity should be sufficient to give the required coating of metal in a given time, and the intensity such as to cause the electricity to pass through the solution to the articles. It is also essential, for regular work- ing, that the plates of metal forming the positive pole in the solution should be of corresponding surface to the articles to be coated, and face them on both sides. The following is the arrangement adopted in some of the large plating manufactories : The vat, or plating vessel, measures about feet in length, by 33 inches in breadth and 33 inches in depth, and generally contains from 200 to 250 gallons of solution ; the silver plates serving as electrodes, which formerly were nailed upon frames of wood, are now generally fixed upon light iron frames, because these are not affected by the solution. Two battery troughs are arranged, as seen in Fig. 527, consisting of 6 batteries of 3 pair intensity. The zinc plates immersed in the acid measure 6 inches by 7 inches, the exposed surfaces of which measure fc'4 square inches ; these, multiplied by 6, give 504 square inches, from which electri- city is disengaged. The surface of the silver electrodes exposed to Fig. 527. 440 ELECTRO-PLATING. the articles receiving the deposit vary from 3000 to 4000 square inches of surface. Fig. 527, with explanation, will illustrate these observations. A, Vat or vessel containing the solution ; B, Battery with zinc pole Z, connected with rods RR; and copper pole C, connected with the metallic sheets PP, in the solution, by means of the copper slip F ; DD, are articles suspended in the solution by wires from the rods RR ; S, the solution. So soon as the articles, which are con- nected with the negative pole of the battery, and the metallic sheets, connected with the positive pole, are both immersed in the solution, the galvanic circuit is completed. In some plating establishments, the batteries are placed outside the house, and the connecting rods are brought from them into the vats, so as to preserve the workmen from the injury arising from inhaling the hydrogen gas which is given oif by the zincs, as it often contains arsenic, and hence is highly injurious to health; but where- ever the batteries are placed, they should not be exposed to cold, as their operation is much affected by the temperature. To ascertain the amount of metal deposited, it is only necessary to weigh the articles carefully before and after plating. But between the first weighing and the immersion of the articles in the plating solution there is the dipping into nitric acid to be accounted for. This, on an average, will cause a loss of about one penny- weight upon an article of the size of a foot square ; thus, if a waiter of a foot square, made of copper or German silver, show, when coated, a difference in weight of 19 pennyweights, the silver laid on must be estimated at an ounce, or 20 pennyweights. When the article is a "replate," i. e., an old plated article that has become bare of silver in parts, the allowance or reduction for the dipping in the acid is only to include the portions left bare, for the silvered parts are not acted upon by it. One of the practical difficulties which the inexperienced will occasionally meet with when a "replate" is dipped in the nitric acid, is, that a galvanic action is produced between the silver and the copper portions, which causes a black line round the edge of the silver ; this ought immediately to be rubbed off, but even with rapid and careful rubbing there is great danger that the .coating will loosen and blister at those parts ; and, besides this, it happens that the parts of the "replate" which are sound, the silver not being acted upon by the acid, but rather protected by the galvanic action, are not in a fit state to receive and maintain a perfect adhesion of the deposit, and, therefore, the risk is great that the new coating will separate from the old, or, in technical language, that the part will strip. Under these circumstances, experience has taught that the best way to proceed is to take all the old silver off the article, and deposit an entirely new coating. There are two methods of taking off the silvers — Taking Silver from Copper, &c— First, stripping or dissolving it off: this is done by putting into a stoneware or copper pan some strong sulphuric acid, (vitriol,) to which a little nitrate of potash is added ; CYANIDE OF SILVER AND POTASSIUM. 441 the article is laid into this solution, which will dissolve the silver, without materially affecting the copper: saltpetre is added by degrees as occasion requires; and if the action is slow a little heat is applied to the vessel. The silver being removed, the article is washed well and then passed through the potash solution, and finished for plating. When the sulphuric acid becomes saturated with silver it is diluted, and the silver is precipitated by a solution of common salt : the chloride of silver formed is collected and fused in a crucible with carbonate of potash, when the silver is obtained in a metallic state. The article thus stripped by acid often shows a little roughness, not from the effects of the acid, but because the copper under the silver had not been polished: it is therefore a common practice in the plating factories to polish the articles before plating. This is done by means of a circular brush, more or less hard, as required, fixed upon a lathe, and a thin paste made of oil and pumice-stone ground as fine as flour. By this process the surface of any article can be smoothened and polished ; but a little experience is required to insure success, and enable the operator to polish the surface equally without leaving brush marks. We need scarcely say that, after this process the article must be cleaned before it is plated. Second Method. — Instead of stripping off the silver by means of acid, it is a more common and preferable mode to brush off the silver by the operation just described. In this case the brushings must be collected, dried, and burned, and the remainder fused with carbon- ate of soda and potash, when the silver is obtained, in combination with a little copper. Cyanide of Silver and Potassium, its Decomposition during the Plating Process. — The silver salt in the plating solution is a true double salt, being, as already described, a compound of one equivalent of cyanide of silver, and one of cyanide of potassium — two distinct salts. In the decomposition of the silver solution by the electric current, the former, cyanide of silver, is alone affected; the silver is deposited, and the cyanogen passes to the positive plate or electrode. The cyanide of potassium is therefore set at liberty upon the surface of the article receiving the silver deposition, and its solution being specifically lighter than the general mass of the plating solution, rises to the top ; this causes a current to take place along the face of the article being plated. If the article has a flat surface, supposed that of a waiter or tray, upon which a prominence exists, as a mounting round the edge, such as a gad- roon, see Fig. 528, it will cause lines and ridges from the bottom to the top, as al- ready decribed. Newly-formed solutions are most subject to produce this annoyance. Fig. 528. 442 ELECTRO-PLATING. e Other Effects produced in Working.— As the cyanogen com- bines with the silver plate forming the positive electrode, it is dis- solved by the free cyanide of potassium, which the solution must have ; and being specifically heavier sinks to the bottom, by which a current downwards is excited : this is of no greater annoyance than that it renders the solution of unequal density, which in its turn yields an unequal deposit, more being laid upon the lower parts of the article than on the upper: the silver plate also is destroyed more rapidly at the bottom than at the top, except at the surface of the solution, if the silver be above it, where the plate gets cut through. In a new solution which contained 1J ounces of silver to the gallon, we have found, just before taking out the articles, that the top part of the solution contained 200 grains of silver less, and the bottom part 200 grains more, per gallon, than when the articles were put into it. These difficulties and annoyances may, however, be nearly surmounted by keeping the articles in motion : agitating or stirring the solution would also obviate these annoyances; but this is not advisable, for if the sediment (which always forms) were stirred up it would settle upon the face of the articles and make them rough. Where there is engine power, it is an easy matter to Figs. 529. 530. EFFECTS PRODUCED IN WORKING. 443 keep the articles in motion ; but where this power is not available, a very simple apparatus, invented by Mr. Mitchell, may be fitted up at a trifling cost, to give the necessary motion by clock-work. (Figs. 529 and 530 exhibit this apparatus). Machine for Moving Goods while subjected to the Electro- plating Process. — Fig. 530, side elevation, with front frame off ; Fig. 529, end elevation of that part of front frame where the fly is held ; Figs. 531 and 532, the plating vat, with frame moving on inclined plane. Figs. 531. The large wheel A, Fig. 530, is propelled by a weight suspended from the roof by a cord which winds round its barrel, the same as common clock-work. The circumference is studded with small pins which catch the arm B, moving it in a downward direction, and con- sequently moving the arm C in a forward direction. The latter being attached to the frame by a small rod R, Figs. 530 and 532, moves it up the inclined plane B, Fig. 532, until the pin fixed in the wheel A passes the end of the arm B. The frame then moving down the incline E, brings B in gear with the next pin, and the same mo- tion again takes place, and so on successively. The speed is regu- lated by the train moving in an endless screw fitted on the last wheel of the arbor of a fan. The four holes in Fig. 530 are for bolts or pillars for screwing the two frames together. The frame has four pulleys and inclines, the latter adjustable to a greater or less degree by the screw and groove at E. Deposit Dissolving off in Solution. — In depositing any metal, but more particularly such as require solutions having an excess of the solvent, such as of cyanide of potassium in the depositing of gold 444 ELECTRO-PLATING. and silver, care should be taken that nothing stops the current of electricity suddenly, while the article being deposited upon remains in the solution, otherwise the metal deposited will speedily dissolve off. This we have often experienced, and many others have no doubt done the same. Indeed, we have seen a beautiful deposit going on, and left the operation with great hope of excellent results, but on returning shortly after have found the whole dissolved off. And often, when the process was apparently going on well, and the arti- cles had been in the solution the usual time to receive a fair coating of metal, upon taking them out and weighing them, there was hardly any perceptible difference from the original weight ; in short, there had been no material deposit. These phenomena will be found to occur with the greatest frequency when the solutions and the bat- teries are in the best condition for working, and when the article upon which the deposit is going on, and the pole, or plate, of metal forming the positive electrode, are at a considerable distance from each other. But, before explaining what we consider to be the cause of these annoyances, we will refer to another phenomenon connected with them. Opposite Currents op Electricity from Vats. — If, under the circumstances referred to, and when the deposit has gone on for some time, the wires connecting the battery with the electrodes in the depositing solution be disconnected from the battery, and their two ends be joined together, a current of electricity nearly as strong as that from the battery will pass through the wires, but in the opposite direction from that which was obtained by the battery ; and if two pieces of metal were attached to these wires and put into a solution of copper, or any metal, a deposition would occur, the original elec- trodes now constituting a battery in relation to this second decom- position cell: the current, however, would gradually weaken until it ceased. The cause of all these actions and reactions is this: the article being plated with silver in connection with the battery, ex- hausts the solution of silver around it, leaving free cyanide of potas- sium in solution, while around the sheet of silver which is serving as the positive electrode the solution is on the contrary becoming saturated with silver, so that we have all the conditions necessary to constitute a battery, having silver in two kinds of solution ; the one capable of dissolving silver, the other not. In these conditions lie the source of the annoyances described above. From the moment the deposition of metal begins, there also arises an opposite current of electricity, tending to neutralize the effects of the battery, which current goes on increasing in quantity until the two currents neutral- ize each other, or it may be until the current from the trough over- powers that from the battery. In the latter case, as we have said, there may, at the termination of the ordinary period, be little or no silver deposited on the articles intended to be plated. Motion in the silver or depositing solution will prevent all these annoyances; and this being now generally adopted, these phenomena are not now observed, but the effects take place less or more in every solution. TESTS OF FREE CYANIDE OF POTASSIUM IN SOLUTIONS. 445 Test for the Quantity of Free Cyanide of Potassium in So- lutions. — It has been already mentioned, that the cyanide of silver, as it forms upon the surface of the silver plate, is dissolved by the cyanide of potassium : this renders it necessary to have always in the solution free cyanide of potassium. Were we to use the pure crystaline salt of cyanide of potassium and silver, dissolved in water, without any free cyanide of potassium, we should not obtain a deposit beyond a momentary blush; as the silver plate or electrode would get an instantaneous coating of cyanide of silver, and this not being dissolved the current would stop. The quantity of free cyanide of potassium required in the solution varies according to the amount of silver that is present, and the rapidity of the deposition. If there be too little of it, the deposit will go on slowly ; if there be too much, the silver plate will be dissolved in greater proportion than the quan- tity deposited, and the solution will consequently get stronger. The proportion we have found best is about half by weight of free cyanide of potassium to the quantity of silver in solution ; thus, if the solu- tion contains two ounces of silver to the gallon, it should have one ounce of free cyanide of potassium per gallon. This is known by taking some nitrate of silver, dis- Fi s- 533 - solving it in distilled water, and placing it in a com- mon alkalimeter, graduated into one hundred parts, Fig. 533. The proportion of the nitrate of silver ^§A in the solution is, that every two graduations of the solution should contain one grain. A given quantity of the plating solution is now taken — say one ounce by measure, and the test solution of nitrate of silver is added to it by degrees, as long as the precipitate formed is re-dissolved : when this ceases, the number of graduations is then noted, and the following equation gives the quan- tity of free cyanide. Every 175 nitrate of silver is equal to 130 cyanide of potassium in solution. Suppose 20 graduations were taken, equal to 10 grains nitrate of silver, then 175 : 130 : : 10 : 7.4 grains free cyanide of potassium. This, multiplied by 160, the num- ber of fluidounces per gallon, will make about 2| ounces. We have taken 2 graduations to one grain of nitrate of silver, that the solu- tion may be considerably dilute and less liable to error. The fol- lowing table is calculated at a half grain nitrate of silver, to the graduation, and will be a guide to the student or workman: the quan- tity of solution tested is one ounce by measure : — 446 ELECTRO-PLATING. Number of Free cyanide per gallon, graduations used. oz. dwt. gr. 1 0 2 13 2 0 5 3 3 0 7 16 4 0 10 6 5 0 12 19 6 0 15 9 7 0 17 22 8 1 0 13 9 1 3 1 10 1 5 12 11 1 8 5 12 1 10 19 13 1 13 8 14 1 15 22 15 1 18 11 16 2 1 2 17 2 3 14 18 2 6 2 19 2 8 11 20 2 11 0 Rate of Depositing Silver. — When articles are taken out of the solution they are swilled in water, and then put into boiling water ; they are afterwards put into hot sawdust, which dries them perfectly. Their color is chalk-white. They are generally weighed before being scratch-brushed; that is, brushed with the fine wire- brushes and stale beer, as already described. Although this opera- tion does not displace any of the silver, still, in taking off the chalky appearance, there is a slight loss of weight; the appearance after scratching is that of bright metallic silver. Any thickness of silver may be given to a plate by continuing the operation a proper length of time. One ounce and a quarter to one ounce and a half of silver, to the square foot of surface, will give an excellent plate about the thickness of ordinary writing paper. Bright Deposit. — A little sulphuret of carbon added to the plat- ing solution prevents the chalky appearance, and gives the deposit the appearance of metallic silver: the reaction which takes place in this mixture is not yet understood. The best method of applying the sulphuret of carbon is to put one or two ounces into a large bot- tle, then fill it with strong silver solution, and let it repose for several days, shaking it occasionally. A little of this silver solution is added, as required, to the plating solution, which will give the articles plated the same appearance as if scratched. Different Metals for Plating. — Silver may be deposited upon any metal, but not upon all with equal facility. Copper, brass, and German silver, are the best metals to plate ; iron, zinc, tin, and THE OLD METHOD OF PLATING. 447 pewter, are much more difficult ; lead is easier, but it is not a good metal, because of the rapidity with which it tarnishes, and from its softness easily yields to the pressure of the burnisher ; nevertheless all these metals and alloys may be, and are, plated, but cannot give the satisfaction which brass, copper, or German silver afford. Electricity given off from Sandy Deposits. — We may men- tion that when depositing silver upon a large surface, and the solu- tion or battery being in the condition to give the sandy deposit, or rather when the deposit has gone on for a long time and the solution not been agitated, so that it has become very much exhausted of silver round the article, the deposit towards the end of the time has been almost impalpable to the touch, like flour : sometimes the grains were a little coarser. The practice, in such cases, is to lift the articles from the solution, and to place them in boiling water, and after steep- ing there some time, to take them out, when the heat of the metal soon causes it to dry. Under these circumstances, when the deposit was of the sort stated, we have seen, on a large waiter or tray, when the hand was rapidly drawn over the surface, after it was dried in the manner described, the same effect produced as when the hand is drawn over an electrified handerchief, or sheet of paper, accompanied with a crackling noise and pricking sensation. We have repeatedly observed these phenomena, but never having chanced to be in the dark, no light was visible from the surface rubbed. Although these are the conditions under which the observations were made, the phenomena were not produced every time these conditions were found. It is probably caused by the fact that this kind of deposit, which is of the chalky appearance, is a bad conductor of electricity, and as the boiling water was often very impure, holding salts in solution, the rapid evaporation of the water from the surface of this sort of deposit might leave it excited for a short time, and, the hand being drawn across at the time of excitation, the electricity was liberated. The Old Method of Plating. — Many objections have been urged against the application of electro-deposition to the purposes of plating, as a branch of manufacture, either as a competitor or sub- stitute for the old method. To enable our readers to form a proper estimate of the objections urged, by enabling them to judge of the relative importance and value of the two processes, we shall add a brief description of the old method. An ingot of copper being cast, was filed square and smooth, and a piece of silver was placed upon it, the two surfaces being perfectly clean : a little borax having been introduced between the two metals they were bound together with iron wire, and then heated in a fur- nace nearly to the melting point; the small quantity of borax in- creased the fusibility of the two metals at their surface, and thus they were fused together. When fusion was effected the metals were subjected to the dilating process of heavy rollers, the dimensions in length and width being regulated according to the articles to be made. This sheet formed the base or foundation of every article, 448 ELECTRO-PLATING. of whatever shape or form, and however it was to be ornamented when finished. To produce ornaments, leaf silver was stamped in iron dies repre- senting the ornaments required, which, when removed from the dies, were filled with an alloy of lead and tin. These were then soldered upon the flat or shaped plain surface with soft solder, which melts at a very low temperature: thus were produced the silver edges, or mounts. The quality of the ornament depended entirely upon the price of the article ; but whatever the quality, all ornaments in the old mode of plating were thus made, the only difference being the thickness of the silver leaf used: Ornamental feet, handles, knobs, &c, were made in the same manner, being struck up in two parts, filled with lead and tin, soldered together with soft solder, and afterwards sol- dered to the main body. Articles (such as table candlesticks) which would be too heavy if filled with lead, were filled with rosin, pitch, or any other similar substance, for the purpose of preventing the article being flattened by pressure. Hence it is evident that no solid article could be made by the old mode of plating, the only way of producing articles being to work them up by the hammer, or to strike them in dies from a flat surface:* and being restricted to the use of soft solder, on account of the plated metal and the shells of silver, forming the edges, not supporting the required heat to melt silver solder, it is equally evident that the joinings so constructed would be easily removed either by force or heat. The nearest approach to solid articles made by the old method of plating, were forks and spoons: these were generally made of iron, thin silver being soldered upon the surface, which w r as afterwards dressed smooth, and polished. The heat used in this operation was merely that of an ordinary soldering iron; because, were a greater heat applied, the silver would form an alloy with the tin and lead of the solder, and melt : the same heat that cemented the metals in the first instance would be sufficient to disunite them ; and thus, when these forks were exposed in hot gravy, the solder was liable to become soft, and the silver covering, yielding readily to the knife, to peel up or become abraded, in consequence of the soft intervening metal. Advantages of Electro-plating. — The advantages offered to the plater by the electro-process are many, arising from the fact of the articles being plated after, instead of before, being manufactured. This at once entirely removed all those restrictions on taste and design, under which the plater was forced, by the nature of his pro- cess, to labor. The following may be considered some of the principal differ- ences existing in the two processes of plating, the old method and the electro-process : — 1. The electro-plater is not limited in the use of the metal upon which he plates. There is generally used, as the basis of all electro- plated goods, a hard white metal, which possesses the sound, and OBJECTIONS TO ELECTRO-PLATING. 449 approaches very nearly to the color, of silver. Inferior goods are sometimes made in brass. 2. The electro-plater Is not restricted to the use of soft solder, which melts at a very low temperature, and forms a very insufficient joint, besides preventing any sound or ring in the article so soldered. Where cheap goods are required, this may be used in this process as well as in the old, but is always open to the same objection. All goods of superior quality, made for the electro-process, are soldered with what is termed in the trade hard silver solder, composed of 2 parts of silver and 1 part of brass melted together, which is not af- fected by any ordinary degree of heat, and presents a joint as strong as the metal itself. The common solder of braziers may also be used with advantage: it is very hard and durable, and requires a strong heat to melt it. 3. The electro-plater, in producing ornamental articles, is not obliged to incur the expense of cutting iron dies for every minute portion ; being under no restriction, he models his pattern, and by casting and chasing in solid metal, produces an exact copy, which is afterwards plated or gilt. Thus, any pattern which can be executed in silver may be readily made in plate by this method. 4. The junction of the plating with the metal below, by the electro-process, is perfect, without the presence of any intervening substance: the forks and spoons thus made are not open to the ob- jection of the old process, and are found to answer all the purposes of silver, in sound, appearance, and wear: they are generally tested, previously to polishing, by exposure in a furnace to a red heat. 5. From the facility with which old goods may now be restored, these goods bear an intrinsic value ; whereas, before the introduction of the electro-process, a plated article worn through in any part was valueless. Objections to Electro-plating. — Several objections to the elec- tro-process have been keenly urged ; but they may all be reduced to the following : — 1st objection: Deposited metal is crystaline, and, therefore, though it may impart in appearance a silver coating, it must necessarily be full of minute interstices between the crystals: hence when a metal, such as copper, is plated, it is liable to be acted upon by the atmo- sphere, or injured by whatever is brought into contact with it. This objection was not without foundation, as all deposited metals are crystaline in texture, but they do not necessarily leave interstices: the objection, however, is almost entirely removed by keeping the articles in motion during the deposition: by motion and proper arrangement of battery we have deposited silver of as high specific gravity as hammered silver, which could not be the case if it were porous. 2d objection: As only pure silver is deposited, it must necessarily be soft, and consequently liable to abrasion, and more rapid wear. This objection is also partly true. Only pure silver can be depo- 29 450 ELECTRO-PLATING. sited; but it is not necessarily soft: the quality of the deposit, in this respect, depends (as already noticed) a great deal upon the nature of the solution and the battery power. Intensity of battery gives hardness to the metal deposited. There is no complaint more common amongst the burnishers of electro-plated articles, than that the metal is hard; and it is far from being an uncommon occurrence, that some goods have to be heated so that they may be more easily- burnished or polished. That the silver is pure we think an advan- tage — hence the superior color which electro-plated goods possess; besides which, purchasers are not subject to the risk of having a plate much alloyed. 3d objection: The mounts or prominences of articles, which must have the greatest wear, have the least and thinnest deposit. This objection is entirely without foundation, as the prominences have always the greatest portion of deposit, and the hollow parts the least. Solid Silver Articles made by the Battery. — Silver may be deposited from its cyanide solution upon wax moulds polished with black-lead, almost as easily as copper ; but for this purpose it is better to have the solution much stronger in silver than for plating. We have found that eight ounces of silver to the gallon of solution make a very good strength. Nevertheless, no articles are made in silver by depositing upon wax in this manner. Strong solutions of cyanide of potassium and silver act upon wax, and would soon de- stroy a mould. The method of making articles in solid silver by the electro-process has been already explained, namely, a copper mould is made by the electrotype, and the silver is deposited within this mould to the proper thickness; after which it is kept in a hot solution of crocus and muriatic acid, or boiled in dilute hydro-chloric acid, which dissolves the copper without injuring the silver. The method which we esteem as best is this: an iron solution is first made by dissolving a quantity of copperas in water, placing it on a fire till it begins to boil : a little nitric acid is then added — nitrates of potash and soda will do just as well — the iron, which is thus per-oxidized, may be precipitated either by ammonia, or car- bonate of soda : the precipitate being washed, muriatic acid is added till the oxide of iron is dissolved. This forms the solution for dis- solving the copper. When the solution becomes almost colorless, and has ceased to act on the copper, the addition of a little ammo- nia will precipitate the iron again; after a little exposure, the copper remains in solution, which is decanted off and preserved for recover- ing the copper; this is done by neutralizing the ammonia by an acid, and putting in pieces of iron, which deposit the copper in the me- tallic state. The precipitate of iron is again dissolved in muriatic acid, and employed in dissolving the copper. Thus the iron may be used over and over again with little trouble, and the persalt of iron will be found to dissolve the copper more rapidly than an acid: per- sulphate of iron must not be used, as it dissolves the silver along with the copper. The silver article is then cleaned in the usual way, DEAD SILVERING FOR MEDALS. 451 and heated to redness over a clear charcoal fire, which gives it the appearance of dead silver, in which state it may be kept, or, if de- sired, it may be scratched and burnished. Copper moulds intended for receiving a deposit must be protected on the back, but if the solution is very strong, there is every danger that it will decompose the protecting substance, thus rendering the solution very dirty, and causing a sediment. For the purpose of protecting the mould, various suggestions and experiments have been made; amongst other substances, pitch has been tried: it is easily affected alone, but on boiling it in potash, a Ireavy and dirty sedi- ment is left, destitute of any adhesive property; on putting a quan- tity of this sediment into a pot nearly filled with melted pitch, a violent effervescence will take place, setting free a volume of white fumes having a creosotic smell. After all effervescence has ceased, which will not be before a considerable time, and when all the mass seems to have been acted upon, the process of making an excellent protecting coating is completed — a coating which will not yield in the solution, and which is at once both good and cheap, its only fault being its brittleness. In the manufacture of solid silver articles, the electro-process has not yet been of extensive application; and in making duplicates of rare objects of art, and costly chased or engraved articles in silver, one prevailing and as yet insurmountable objection has been felt, namely, they have no "ring," and seem, when laid suddenly upon a table, to be cracked or unsound, or like so much lead; this disad- vantage is no doubt partly owing to the crystaline character of the deposit, and partly to the pure character of the silver, in which state it has not a sound like standard or alloyed silver. That this latter cause is the principal one, appears from the fact that a piece of silver thus deposited is not much improved in sound by being heated and hammered, which would destroy all crystalization. We may mention that the same objections are applicable to arti- cles made in gold by the electro-deposit ; nevertheless, for figures and ornaments these objections are of little weight. Dead Silvering for Medals. — The perfect smoothness which a medal generally possesses on the surface, renders it very difficult to obtain a coating of dead silver upon it, having the beautiful silky lustre which characterizes that kind of work, except by giving it a very thick coating of silver, which takes away the sharpness of the impression. This dead appearance can be easily obtained by put- ting the medal, previous to silvering, into a solution of copper, and depositing upon it, by means of a weak current, a mere blush of copper, which gives the face of the medal that beautiful crystaline richness that copper is known to give. The medal is then to be washed from the copper solution, and immediately to be put into the silver solution. A very slight coating of silver will suffice to give the dead frosty lustre so much admired, and in general so diffi- cult to obtain. Protection of Silver Surface. — All silver or plated articles 452 ELECTRO-GILDING. are subject to tarnish by exposure to the air, and where coals con- taining so much sulphur are used ; the tarnish being generally a sulphuret of silver. Deposited silver is more easily tarnished than standard silver. Medals, or figures silvered for the sake of their appearance, ought to be protected from the air, or they very soon lose their silver color; a medal may be put into a frame air-tight, and a figure should be covered with a glass shade ; if the silver has been left dead, any attempt to clean it destroys its appearance. Varnishes have been tried to protect the 'silver from the atmosphere; but all varnishes, however colorless, detract from the silver lustre, and are not good. For ordinary purposes, medals may be very conveniently protected by laying a piece of common glass over the surface, cut to the exact size, and held close by a strip of paper pasted round the edges of both, and then a stout piece on the back. We have had silver medals, preserved by this means, for more than six years. Little round medals may be conveniently covered by watch-glasses, fastened on in the same manner. Cleaning of Silver. — A weak solution of cyanide of potassium, used as a wash over tarnished silver, will brighten it. This solu- tion was sold in small bottles for this purpose, but it is not good, as it dissolves the silver rapidly, and is such a deadly poison that it must be used with great caution on articles that may be required for domestic purposes. ELECTRO-GILDING. The operation of gilding, or covering other metals with a coating of gold, is performed in the same manner as the operation of plating, with the exception of a few practical modifications, which we shall now notice in detail : — Preparation op Solution of Gold. — The gold solution for gild- ing is prepared by dissolving gold in three parts of muriatic acid and one of nitric acid, which forms the chloride of gold. This is digested with calcined magnesia, and the gold is precipitated as an oxide; the oxide is boiled in strong nitric acid, which dissolves any magnesia in union with it : the oxide, being well washed, is dissolved in cyanide of potassium, which gives cyanide of gold and potassium ; thus: — Substances used: Substances produced : Oxide of Gold = AuO Cyanide of Gold \ _ F p , A n 2. Cyanide of Potassium = 2KCy and Potassium / -^y + AuOy Potash =KO AuO + 2KCy = KO -}- (KCy + AuCy) By this method, a proportion of potash is formed in the solution as an impurity ; it is not, however, very detrimental to the process. In preparing the oxide of gold, there is always a little of the gold PROCESS OP GILDING. 453 lost, to recover which the washings should be kept, evaporated to dryness, and fused. Another and very simple method is this : Add a solution of cyanide of potassium to the chloride of gold, until all the precipitate is re- dissolved ; but this gives chloride of potassium in the solution, which is not good. In the preparation of the solution by this means there are some interesting reactions. As the chloride of gold has always an excess of acid, the addition of cyanide of potassium causes violent effervescence, and no precipitate of gold takes place until all the free acid is neutralized, which causes a considerable loss of the cyanide of potassium. There is always formed in this decomposition a quantity of ammonia and carbonic acid, from the decomposition of the cyanate of potash; and if the chloride of gold be recently prepared and hot, there is often formed some aurate of ammonia (fulminate of gold), which precipitates with the cyanide of gold. Were this precipitate to be collected and dried, it would explode when slightly heated. On previously diluting the chloride of gold, or using it cold, this compound is not formed. After the free acid is neutralized by the potash, further addition of the cyanide of potassium precipitates the gold as cyanide of gold, having a light yellow color ; but as this is slightly soluble in am- monia and some of the alkaline salts, it is not advisable to wash the precipitate, lest there be a loss of gold: cyanide of potassium is generally added until the precipitate is redissolved ; consequently much impurity is formed in the solution, namely, nitrate and carbon- ate of potash with chloride of potassium and ammonia. Notwith- standing, this solution w 7 orks very well for a short time, and it is very' good for operations on a small scale. Battery Process of Preparing Gold Solution. — The best method of preparing the gold solution is that described for silver; having a solution of cyanide of potassium, with a gold positive electrode, and the negative electrode, which may be iron or copper, in a porous vessel also charged with cyanide of potassium. But for this process, and for all the operations of gilding by the cyanide solution, it must be heated to at least 130° Fah. The articles to be gilt are cleaned in the way described for silver, but are not dipped into nitric acid previously to being put into the gold solution. Three or four minutes is sufficient time to gild any small article. After the articles are cleaned and dried, they are weighed; and, when gilt, they are weighed: again: thus the quantity of gold deposited is ascertained. Any convenient means may be adopted for heating the solution. The one generally adopted is, to put a stoneware pan containing the solution into a vessel of water, which is kept at the boiling point. The hotter the solution, the less battery power is required : generally three or four pairs of plates are used for gild- ing, and the solution is kept at 130° to 150° Fah. ; but one pair will answer if the solution is heated to 200°. Process of Gilding. — As the process of gilding is generally performed upon silver articles, the previous immersion in nitric acid 454 ELECTRO-GILDING. is unnecessary. The method of proceeding is as follows: When the articles are cleaned, as described in our chapter on plating, they are weighed and well scratched with wire brushes, which cleans away any tarnish from the surface and prevents the formation of air-bubbles; they are then kept in clean water until it is convenient to immerse them in the gold solution. One immersion is then given, which merely imparts a blush of gold ; they are taken out and again brushed; they are then put back into the solution, and kept there for three or four minutes, which will be sufficient if the solution and battery are in good condition ; but the length of time necessarily depends on these two conditions. Iron, tin, and lead are very difficult to gild direct : they there- fore generally have a thin coating of copper deposited upon them by the cyanide of copper solution, after which they must be imme- diately put into the gilding solution. Conditions required in Gilding. — The gilding solution gene- rally contains from one-half to an ounce of gold in the gallon, but for covering small articles, such as medals for tinging, daguerreo- types, gilding rings, thimbles, &c, a weaker solution will do. The solution should be sufficient in quantity to gild the articles at once, so that it should not have to be done bit by bit; for when there is a part in the solution and a part out, there will generally be a line mark at the point touching the surface of the solution. The rapidity with which metals are acted upon at the surface line of the solution is remarkable. If the positive electrode is not wholly im- mersed in the solution, it will, in a short time, be cut through, at the edge of the water, as if cut by a knife. This is also the case in silver, copper, and other solutions, as before referred to. Maintaining the Gold Solution. — As the gold solution evapo- rates by being hot, distilled water must from time to time be added : the water should always be added when the operation of gilding is over, not when it is about to be commenced, or the solution will not give so satisfactory a result. When the gilding operation is con- tinued successively for several days, the water should be added at night. The means of testing the free cyanide of potassium, as described for silver, is not applicable to the gold solution. To obtain a deposit of a good color, much depends upon the state of the solution and battery ; it is, therefore, necessary that strict attention be paid to these, and more so as the gold solution is very liable to change if the relative size of the article receiving the deposit is not according to that of the positive plate. The result of a series of observations and experiments, continued daily throughout a period of nine months, showed that in five in- stances only the deposit was exactly equal to the quantity dissolved from the positive plate. In many cases the difference did not ex- ceed 3 per cent., though occasionally it rose to 50 per cent. The average difference, however, was 25 per cent. In some cases, double the quantity dissolved was deposited, in others the reverse TO DISSOLVE GOLD FROM GILT ARTICLES. 455 occurred — both resulting from alterations made in the respective processes ; for in these experiments we varied, as far as practicable, the state of the solution and the relative sizes of the negative and positive electrodes. The most simple method of keeping a constant register of the state of the solution is to weigh the gold electrode before putting it into the solution ; and, when, taking it out, to compare the loss with the amount deposited ; a little allowance must be made for small portions of metal dissolved in the solution, from the articles that are gilt, which is considerable in a year. A constant control can thus be exercised over the solution, to which must be added, from time to time, a little cyanide of potassium, a simple test of require- ment being that the gold pole should always come out clean; for if it has a film or crust, it is a certain indication that the solution is deficient of cyanide of potassium. To Regulate the Color of the Gilding. — The gold upon the gilt article, on coming out of the solution, should be of a dark yellow color, approaching to brown ; but this, when scratched, will yield a beautifully rich deep gold. If the color is blackish it ought not to be finished, for it will never either brush or burnish a good color. If the battery is too strong, and gas is given off from the article, the color will be black ; if the solution is too cold, or the battery rather weak, the gold will be light-colored ; so that every variety of shade may be imparted. A very rich dead gild may be made by adding ammoniuret of gold to the solution just as the arti- cles are being put in. Coloring of Gilding. — A defective colored gilding may be im- proved by the same method as that adopted in the old process to color gilding or gold, namely, by the help of the following mixture: — 3 parts Nitrate of Potash Alum 1^ Sulphate of Zinc 1J Common Salt. These ingredients are put into a small quantity of water, to form a sort of paste, which is put upon the articles to be colored : they are then placed upon an iron plate over a clear fire, so that they will attain nearly to a black heat, when they are suddenly plunged into cold water : this gives them a beautiful high color. Different hues may be had by a variation in the mixture. To Dissolve Gold from Gilt Articles. — Before regilding arti- cles which are partly covered with gold, or when the gilding is im- perfect, and the articles require regilding, the gold should be removed from them by putting them into strong nitric acid ; and when the arti- cles have been placed in the acid, by adding some common salt, not in solution, but in crystals. By this method, gold may be dissolved from any metal, even from iron, without injuring it in the least v After coming out of the acid, the articles must be polished. The 456 ELECTRO-GILDING. best method, however, is to brush off the gold as described for silver. Objections to. Electro-gilding. — Objections have also been made to the application of electro-gilding to the arts, of the same kind as those urged against electro-plating ; but the now almost uni- versal adoption of this process by gilders, because of the perfection to which the articles are brought, forms the best answer we can give to such objections. However, let us take a hasty glance at the old process and its consequences, that we may be enabled to judge of the comparative merits of both methods. Before the introduction of electro-deposition, the only method of gilding was by forming an amalgam of gold and mercury, which, at the consistence of a thin paste, was brushed upon the articles over a strong heat : the mercury being gradually dissipated, the gold re- mained fixed upon the articles. This process is most pernicious, and destructive to human life : the mercury, volatilized by the heat, in- sinuates itself into the bodies of the workmen, notwithstanding the greatest care : and those who are so fortunate as to escape for a time absolute disease, are constantly liable to salivation from its effects. Paralysis is common among them, and the average of their lives is very short : it has been estimated as not exceeding 35 years. It is difficult to believe that men could be found to engage in such a business, reckless of the consequences so fearfully exhibited before them ; and it would naturally be thought they would hail with plea- sure the introduction of any process which would put a stop to such a dreadful sacrifice of human life. But it is very difficult to over- come interest and prejudice, even when the object to be gained is of such vast importance. Effects of Cyanogen upon Health. — The effects produced upon the health of those who work constantly over cyanide solutions are not yet fully tested, by which we could form a comparison with the old process ; for every new trade, or operation, gives rise to a new disease, or new forms of some old disease. Having ourselves in- haled much of the fumes of that "ominous" gas given off from the cyanide of potassium solution, we are not prepared to stand its ad- vocate, but would rather warn all employed at the business, or who may in any degree have to do with these solutions, to be very care- ful not to use too much freedom. The hands of those engaged in gilding or plating are subjected to ulceration, particularly if they have been immersed in the solution. The ulcers are not only annoy- ing, but painful ; and on their first appearance, if care is not properly taken to wash them in strong cyanide of potassium, and then in acid water, the operator will, in a short time, have to take a few. days' rest. We have repeatedly seen, by the aid of a magifying glass, gold and silver reduced in these ulcerations. We have also known of eruptions breaking out over the bodies of workmen after inhaling those deleterious fumes, when they were very bad, as when solutions were precipitated by acids, or being evaporated to dryness in a close apartment for the recovery of the metal. Repeatedly PRACTICAL SUGGESTIONS IN GILDING. 457 have we seen the legs of workmen thus afflicted, and always after they have been exposed to extra fumes. The following statement of the general effects of electro-plating and gilding on the health of those engaged in them, as experienced by ourselves and others, may not be uninteresting to our readers: but it is necessary to premise that the apartments in which we were employed were improperly ventilated. The gas has a heavy sickening smell, and gives to the mouth a saline taste, and scarcity of saliva; the saliva secreted is frothy. The nose becomes dry and itchy, and small pimples are found within the nostrils, which are very painful (we have felt these effects in the nose from the hydrogen of the batteries, where there were no cyanide solutions). Then follows a general languor of body; disinclination to take food, and a want of relish. After being in this state for some time, there follows a benumbing sensation in the head, with pains, not acute, shooting along the brow; the head feels as a heavy mass without any individuality in its operations. Then there is bleeding at the nose in the mornings when newly out of bed; after that comes giddiness; objects are seen flitting before the eyes, and momentary feelings as of the earth lifting up, and then leaving the feet, so as to cause a stagger. This is accompanied with feelings of terror, gloomy apprehension, and irritability of temper. Then fol- lows a rushing of blood to the head ; the rush is felt behind the ears with a kind of hissing noise, causing severe pain and blindness: this passes off in a few seconds, leaving a giddiness which lasts for several minutes. In our own case the rushing of blood was without pain, but attended with instant blindness, and then followed with giddiness. For months afterwards a dimness remained as if a mist intervened between us and the objects looked at; it was always worse towards evening, when we grew very languid and inclined to sleep. Then we rose comparatively well in the morning; yet we were rest- less, our stomach was acid, visage pale, features sharp, eyes sunk in the head, and circles round them dark in color: these effects were slowly developed. Our experience was nearly three years. We have been thus particular in detailing these effects, as a warn- ing to all employed in the process; but we have no doubt that in lofty rooms, airy and well ventilated, these effects would not be felt. Employers would do well to look to this matter; and amateurs, who only use a small solution in a tumbler, should not, as the custom sometimes is, keep it in their bed-rooms: the practice is decidedly dangerous. Practical Suggestions in Gilding. — According to the amount of gold deposited, so will be its durability: a few grains will serve to give a gold color to a very large surface, but it will not last: this proves, however, that the process may be used for the most inferior quality of gilding. Gold thinly laid upon silver will be of a light color, because of the property of gold to transmit light. The solu- tion for gilding silver should be made very hot, but for copper it should be at its minimum heat. A mere blush may be sufficient for 458 EXPERIMENTS IN METAL COATING. articles not subjected to wear; but on watch-cases, pencil-cases, chains, and the like, a good coating should be given. An ordinary sized watch-case should have from 20 grains to a pennyweight; a mere coloring will be sufficient f-»r the inside, but the outside should have as much as possible. A watch-case, thus gilt, for ordinary wear, will last five or six years without becoming bare. We have known some to be in use full six years without losing their covering. Small silver chains, such as those sold at eight shillings, should have 12 grains ; pencil-cases of ordinary size should have from 3 to 5 grains ; a thimble from 1 to 2 grains : these suggestions will serve as a guide to amateur gilders, many of whom, having imparted only a color to their pencil-cases, feel chagrin and disappointment upon seeing them speedily become bare: hence arises much of the obloquy thrown upon the process. RESULTS OF EXPERIMENTS ON THE DEPOSITION OF OTHER METALS AS COATINGS. Coating: with Platinum.— This metal has never yet been suc- cessfully deposited as a protecting coating to other metals. A solu- tion may be made by dissolving it in a mixture of nitrate and muriatic acids, the same as is employed in dissolving gold; but heat must be applied. The solution is then evaporated to dryness, and to the remaining mass is added a solution of cyanide of potassium ; next, it must^ be slightly heated for a short time, and then filtered. This solution, evaporated, yields beautiful crystals of cyanide of platinum and potassium ; but it is unnecessary to crystalize the salt. A very weak battery power is required to deposit the metal : the solution should be heated to 100°. Great care must be taken to obtain a fine metallic deposit : indeed, the operator may not succeed once in twenty times in getting more than a mere coloring of metal over the surface, and that not very adhesive. The causes of the difficulty are probably these: the platinum used as an electrode is not acted upon; the quantity of salt in solution is very little; it requires a particular battery strength to give a good deposit, and the slightest strength beyond this gives a black deposit; so that, were the proper relations obtained, whenever there is any deposit, the relations of battery and solution are changed, and the black pulverulent deposit follows. We have occasionally succeeded in obtaining a bright metallic deposit of platinum, possessing the qualities of adhesion and dura- bility: some of the articles thus covered presented no signs of change at the end of seven years : but we have never been so fortunate as to get a platinum deposit that could protect any metal from the action of acids, or other fluids by which the metal could be affected. We have covered iron, such as the end of a glass-blower's blow-pipe, so that it could be made red hot without the iron rusting, but rather taking the characteristic appearance of platinum; but even that did not protect the iron from rusting when it was put a short time into water, or kept exposed to moist air. COATING WITH PALLADIUM, NICKEL, ETC. 459 Coating with Palladium. — Palladium is a metal very easily de- posited. The solution is prepared by dissolving the metal in nitro- muriatic acid, and evaporating the solution nearly to dryness ; then adding cyanide of potassium till the whole is dissolved: the solution is then filtered and ready for use. The cyanide of potassium holds a large quantity of this metal in solution, and the electrode is acted upon while the deposit is proceeding. Articles covered with this metal assume the appearance of the metal ; but, so far as we are aware, it has not yet been applied to any practical purpose. It re- quires rather a thick deposit to protect metals from the action of acids, which is, probably, the only use it can be applied to. Coating with Nickel. — Nickel is very easily deposited; and may be prepared for this purpose by dissolving it in nitric acid, then adding cyanide of potassium to precipitate the metal ; after which the precipitate is washed and dissolved by the addition of _ more cyanide of potassium. Or the nitrate solution may be precipitated by carbonate of potash: this should be well washed, and then dis- solved in cyanide of potassium: a proportion of carbonate of potash will be in the solution, which we have not found to be detrimental. This latter method of preparing the nickel plating solution is simple, and, therefore, has our recommendation. The metal is very easily deposited; it yields a color approaching to silver, which is not liable to tarnish on exposure to the air. A coating of this metal would be very useful for covering common work, such as gasaliers, and other gas-fittings, and even common plate. The great difficulty experienced is to obtain a positive electrode: the metal is so very difficult to fuse, and so brittle, that we have never been able to obtain either a plate or sheet of it. Could this difficulty be easily overcome, the applica- tion of nickel to the coating of other metals would be expensive, and the property of not being liable to tarnish would make it eminently useful for all general purposes. We coated articles with nickel seven years since, and, though they have been exposed to the air from that period to the present, they still retain their brilliancy, and continue untarnished. Antimony, Arsenic, Tin, Iron, Lead, Bismuth, and Cadmium. — We have deposited these metals from their solutions in cyanide of potassium ; but not for any useful application. Iron. — Iron may be very easily deposited from its sulphate : dis- solve a little crystaline sulphate of iron in water, and add a few drops of sulphuric acid to the solution. The metal in this pure state has a very bright and beautiful silver color. Lead. — Lead maybe deposited from an acid solution, such as the acetate, but requires some management of strength of battery : it may also be deposited from its solution in potash or soda. Tin. — Tin is easily deposited from a solution of protochloride of tin. If the two poles or electrodes be kept about two inches apart, a most beautiful phenomenon may be observed: the decomposition of the solution is so rapid that it shoots out from the negative elec- trode like tentacula, or feelers, towards the positive, which it reaches 460 EXPERIMENTS IN METAL COATING. in a few seconds: the space between the poles seems like a mass of crystalized threads, and the electric current passes through them without effecting further decomposition. So tender are these me- tallic threads, that when lifted out of the solution they fall upon the plate like cobweb. Seen through a glass, they exhibit a beautiful crystaline structure. If a circular electrode of tin is used, and a small wire put in the centre of the chloride solution, the thread-like crystals will shoot out all around, and give quite a metallic con- fervae. Tin may also be deposited from its solution in caustic potash or soda. Deposition op Alloys.— Many attempts have been made to deposit alloys of metals from their solutions. That two or more metals can be deposited from a solution, we have seen sufficient evi- dence ; but the means to regulate the proportions of each, and to make such a process practical, have yet to be discovered. It is hardly possible to get a mixed solution of any two metals that are exactly equally decomposable ; or, in other words, that the metals under the circumstances in which they are placed are exactly of equal conducting power : hence the electric current will always travel through the one that offers the least resistance, and there will be none of the other metallic solution decomposed, or metal depo- sited, until the quantity of electricity is greater than the best con] ducting metal in the solution will allow to pass; then the other metal will be deposited in proportion to the extra electrical power that passes. As, for example, take a mixture of cyanide of gold, silver, and copper, in cyanide of potassium. The silver in this state is so much superior in its conducting power to the other salts, that all the silver may be deposited from the solution by a weak battery without any of the other metals : if the solution be afterwards heated, and the battery power kept so that no gas is allowed to escape from the articles, the gold may be deposited without any cop- per ; but if the gas is allowed to flow from the article receiving the deposit, the copper will be deposited, and often more abundantly than the gold, as the escape of gas is not consistent with a reguline deposit of gold. We h ave thus deposited an alloy of gold and cop- per; we have also deposited gold and silver, but the alloy was very inferior and irregular. Alloys can be obtained from silver and pal- ladium, from cyanide solutions, from zinc and copper, from a solu- tion of their sulphates ; but in no instance have we found good alloys, or alloys that could pass as such in name or appearance. We have seen articles, such as iron, covered with copper and zinc in this man- ner, or in alternate layers, and the articles having the coating heated in charcoal, by which means a brass of fair appearance was obtained, but the process is attended with practical difficulty, and the product cannot be called deposited brass. Deposition op Bronze.— The following solution of different metals is given as being capable of giving a deposit of bronze : — THEORETICAL OBSERVATIONS. 461 50 parts Carbonate of Potash. 2 " Chloride of Copper. 4 " Sulphate of Zinc. 25 " Nitrate of Ammonia. A bronze plate is used as the positive electrode. The deposit given by this solution bears comparison with any ordinary bronze in appearance. A solution of the above materials in water strikes the ear as somewhat hypothetical : that a mixed solution of copper and zinc will give, under certain conditions, a compound deposit, we know, and also that, with a quantity of other salts present, will give pecu- liar tints of color, a circumstance which may be obtained without a compound deposit. But the difficulty to be overcome is to propor- tion the deposit of different metals, so that we may make up a solu- tion and battery that will deposit yellow metal, gun metal, or common brass, at pleasure; and that we may be able to produce compounds that are constant and unvarying: so that, for example, we could deposit silver or gold of the standard quality, all which, notwith- standing the many statements that have been made in print, have yet to be discovered. THEORETICAL OBSERVATIONS. We have described at considerable length the practical details con- nected with the art of electro-metallurgy, without pausing to inquire into the philosophy of the action of the electric currents by which the effects are produced. It will be unnecessary to enter into a long discussion of the numerous theories that have been advanced from time to time to explain the action that takes place in a battery or decomposing cell, while the current is passing through the solution ; a brief reference to the more commonly received opinions being suffi- cient for the present purpose. Action of Sulphate of Copper on Iron. — In order to convey our ideas accurately, let us suppose that the solution undergoing decomposition is sulphate of copper. This salt, is composed of sul- phuric acid and copper, which maybe represented as S0 4 -fCu: these are held together according to the law of chemical affinity ; but if iron is put into the solution, the combination of the acid and copper will be dissolved by the attraction of the acid to the iron, for which it has a stronger affinity than for the copper. Hence iron, put into sulphate of copper, decomposes it thus : — Cu, S0 4 +Fe = Fe, S0 4 +Cu. "Were we to put a piece of copper into a solution of sulphate of cop- per there would be no action, the forces being equal ; but if by any means we were to communicate to this piece of copper a higher at- tractive force for the SO 4 than that of the copper which is already in union with it, we should cause the acid to leave the copper it was originally combined with, and to combine with the new piece of cop- 462 THEORETICAL OBSERVATIONS. per. Bearing these general principles in view, we shall proceed to state the different opinions of authors on this subject. Faraday's Theory of Electrolysis. — Professor Faraday says — " Passing to the consideration of electro-chemical decomposition, it appears to me that the effect is produced by an internal corpuscular action, excited according to the direction of the electric current, and that it is due to a force either superadded to, or giving direction to, the ordinary chemical affinity of the bodies present. The body under decomposition" (say sulphate of copper) " may be considered as a mass of acting particles, all those which are included in the course of the electric current contributing to the final effect ; and it is be- cause the ordinary chemical affinity is relieved, weakened, or partly neutralized by the influence of the electric current in one direction parallel to the course of the latter, and strengthened or added to in the opposite direction, that the combining particles have a tendency to pass in opposite courses. " In this view the effect is considered as essentially dependent upon the mutual chemical affinity of the particles of opposite kinds. Par- ticles aa could not be transferred or Fig. 534. travel from one pole N, towards the other No & a b p pole P, unless they found particles of the O • O 9 O O opposite kind bb, ready to pass in the contrary direction, for it is by virtue of their increased affinity for those particles, combined with their diminished affinity for such as are behind them in their course, that they are urged forward. " I conceive the effects to arise from forces which are internal, relative to the matter under decomposition, and not external, as they might be considered, if directly dependent upon the poles. I sup- pose that the effects are due to a modification by the electric current of the chemical affinity of the particles, through or by which that current is passing, giving them the power of acting more forcibly in one direction than in another, and consequently making them travel by a series of successive decompositions, in opposite directions, and finally causing their expulsion or exclusion at the boundaries of the body under decomposition, in the direction of the current, and that in larger or smaller quantities, according as the current is more or less powerful." In the above figure, the particles aa may be termed copper Cu, and the particles bb, sulphuric acid SO 4 , which will enable us to fol- low the comparissn of the different views. Graham's Theory of Electrolysis. — Professor Graham sup- poses that the compound particles, such as sulphate Fig. 535. of copper, possess polarity, so that the particles in so 1 cu so* cu the battery or decomposition cell will stand in re- O O O O lation to each other in a polar chain, as in Fig. 535. He then represents electrotyping by the porous cell system, as follows : — THEORETICAL OBSERVATIONS. 463 " The liquids on either side of the porous division may also be dif- ferent, provided they have both a polar molecule. Thus, in Fig. 536, the polar chain is composed of molecules of hydrochloric acid, extending from the zinc to the porous divisions at a, and of mole- cules of chloride of copper from a, to the copper plate. When the CI of molecule 1 unites with zinc, the H of that molecule unites with the CI of molecule 2 (as indicated by the connecting bracket below); the H of molecule 2 with the CI of molecule 3; the Cu of molecule 3 with the CI of molecule 4; and the Cu of this molecule being the Fig. 536. t ^ a Cl H Cl H 1 CI Cu Cl Cu oo oo OO OO 1 ~ 2 -h 3 - ~ 4 last in the chain, is deposited upon the copper plate ; dilute sulphuric acid in contact with an amalgamated zinc plate, and the same acid fluid saturated with sulphate of copper in contact with the copper plate, are a combination of fluids of most frequent application." According to this theory, all the particles between the zinc and cop- per during the action of the batteries will be performing a whirling motion; for, when the Cl of molecule 1 is liberated, the H of 1 will combine with the Cl of 2, which compound molecule must whirl round to be in its proper polar position, which will necessitate that inter- change distinctly referred to by Professor Faraday — a mutual trans- fer of the elements : the Cl will pass towards the zinc plate, and the H and Cu towards the copper plate. Daniell's and Miller's Views. — Theories varying little from these were held by the late Professor Daniell, till by a series of in- teresting experiments, in company with Professor Miller, he found that there is no mutual transfer of the elements; that the negative element, or that represented above as Cl or So 4 , is transferred from the copper to the zinc, or in a decomposition cell from the negative electrode to the positive electrode : but the positive element — that represented by H or Cu — is not transferred ; therefore the theories of Professors Faraday and Graham are opposed to a fundamental truth experimentally proved. Professors Daniell and Miller con- clude their paper, read before the Royal Society, by the following observations : — " These facts are, we believe, irreconcilable with any of the mole- cular hypotheses which have been hitherto imagined to account for the phenomena of electrolysis, nor have we any more satisfactory at present to substitute for them : we shall therefore prefer leaving them to the elucidation of further investigations to adding one more to the already too numerous list of hasty generalizations." In this paper, the authors state that they found certain positive elements transferred in small proportions: thus, potassium from sul- phate of potash, in J of an equivalent : barium, from nitrate of barytes, 464 THEORETICAL OBSERVATIONS. | equivalent : and magnesium, from sulphate of magnesia, equi- valent. In all cases where two liquids are separated by a porous diaphragm, there is a mutual transfer of the liquids in distinct ratios, according to time, either by what is called endosmosis, or by diffusion ; and the rate of transfer is materially affected by a galvanic current passing through them. From observations and operations made on a large scale, and from experiments on various kinds of solutions, we are inclined to think that the fractional transfers of Professors Daniell and Miller are the results of endosmosis or diffusion rather than of electrolytic transfer : we are therefore of opinion that no transfer of any base or positive element takes place by electrolysis. Proposed Theory. — Having carefully considered the various phe- nomena attending electrolysis, in the decomposition of metallic salts, we think that the electricity is conducted through the eolution by the base, or positive element, in the electrolyte, which it does as if it was a solid chain of particles — or wire. We have already said, that if to a solution of sulphate of copper we put a piece of iron, the acid in union with the copper will leave it and combine with the iron. If a piece of copper be put into the same solution, no change will take place ; but if we by any means give to this copper an increased tendency to unite with the acid, it will attract the acid from the copper in solution by virtue of this increased attraction. Suppose two wires coming from a battery are placed in a solution of sulphate of copper, thus (Fig. 537) : the double row representing the compound Fig. 537. N P cO O c cO Oc CO 5 4 3 2 1 Q C co O O O O O oc SO 4 SO 4 SO 4 SO 4 SO 4 v -' u CO 5 4 3 2 1 0 C o o o o o c c c c c atoms of sulphate of copper forming the electrolyte : C C the copper or positive element, and SO 4 the sulphuric acid or negative element of the solution. The two single rows, C C, &c, at each end of the double row, represent the wire, or solid conductors of the electricity, from the battery to the decomposition cell : the last particle of the single rows nearest the double row may be viewed as the electrodes. The sulphuric acid, SO 4 , and the copper, C, in solution, are held together by their affinity for each other. The celebrated American chemist, Dr. Medcalf, in his Treatise on Caloric, published by William Pickering, of London, establishes one of the soundest theories of both heat and electricity. Byrne's Great Calculator!! INDEX TO THE PRACTICAL MODE CALCULATOR, FOR THE Engineer, Machinist, Mechanic, Manufacturer of Engine Work, Naval Architect, Miner, and Millwright. BY OLIVEE BYKNE, CIVIL, MILITARY, AND MECHANICAL ENGINEER, EDITOR AND COMPILER OP THE DICTIONARY OF MECHANICS, ENGINE WORK, AND ENGINEERING. How publishing in TWELVE PARTS, at Twenty-Five Cents each ; forming, when completed, One large Volume, Octavo, of nearly Six Hundred Pages. Hgi 11 * The greatest Booh of Calculations for Engineers and Me- chanics ever published. As evidence of the extent of its range, the Index is referred to with entire confidence. PHILADELPHIA: PUBLISHED BY HENRY CAREY BAIRD, (SUCCESSOR TO E. L. CAREY,) PUBLISHER OF PRACTICAL BOOKS. For sale in New York by Dewitt & Davenport ; Boston, by Hotchkiss & Co ; Cincinnati, Post & Co. ; St. Louis, Post & Co. ; and Booksellers and News Agents generally throughout the United States. INDEX. Abbreviation of the reduction of decimals,17. Abrasion, limits of, 301. Absolute resistances, 288. Absolute strength of cylindrical columns, 274. Accelerated motion, 386. Accelerated motion of wheel and axle, 419. Acceleration, 415. Acceleration and mass, 422. Actual and nominal horse power, 240. Addition of decimals, 22. Addition of fractions, 20. Adhesion, 297. Air, expansion of, by heat, 173. Air that passes through the lire for each horse power of the engine, 210. Air, water, and mercury, 355. Air-pump, 254. Air-pump, diameter of, eye of air-pump cross head, 145. Air-pump machinery, dimensions of several parts of, 144. Air-pump strap at and below cutter, 147. Air-pump studs, 144. Ale and beer measure, 8. Algebra and arithmetic, characters used in, 12. Algebraic quantities, 134. Alloys, strength of, 287. Ambiguous cases in spherical trigonometry, 381. Amount of effective power produced by steam, 266. Anchor rings, 90. Angle iron, 91, 408, 409, 410. Angles of windmill sails, 445. Angles, measurement of, by compasses only, 382. Angular magnitudes, 359. Angular magnitudes, how measured, 373. Angular velocity, 412. Apothecaries' weight, 6. Apparent motion of the stars, 353. Application of logarithms, 334. Approximating rule to find the area of a seg- ment of a circle, 67. Approximations for facilitating calculations, 55. Arc of a circle, to find, 49. Arc of one minute, to find the length of, 361. Arc, the length of which is equal to the ra- dius, 357. Architecture, naval, 453. Arcs, circular, to find the lengths of, 68. Area of segment and sector of a circle, 51. Area of steam passages, 220. Areas of circles, 57. Areas of segments and zones of circles, 64, 65, 66, 67. Arithmetic, 10. Arithmetical progression, to find the square root of numbers in, 126. Arithmetical solution of plane triangles, 366. 2x2 Arithmetical proportion and progression, 35 to 38. Ascent of smoke and heated air in chimneys, 208. Atmospheres, elastic force of steam in, 195, 196. Atmospheric air, weight of, 356. Average specific gravity of timber, 396. Avoirdupois weight, 6. Axle and wheel, 417. Axle of locomotive engine, 168, 169. Axle-ends or gudgeons, 301. Axles, friction of, 298, 300. Balls of cast iron, 407. Bands, ropes, Longitudinal distance of the centre of gravity of displacement, 470, 500. Loss of force by the decrease of temperature in the steam pipes, 221. Low pressure engines, 243. Lunes, 54. Machinery, elements of, 425. Machinery worked by hydraulic pressure, 330. INDEX. 573 Major and minor diameters of cross-head, 253. Main beam at centre, 249. Malleable iron, 396. Marble, 283. Marine boilers, 217. Mass, 267. Mass, gravity, and weight, 386. Mass of a body, to find, when the weight is given, 389. Materials employed in the construction of machines, 267. Materials, their properties, torsion, deflexion, &c, 267. Maximum accelerating force, 421. Maximum velocity and power of water wheels, 443. Measures and weights, 5. Measurement of angular magnitudes, 374. Measurement of angles by compasses only, 382. Mechanical effect, 417. Mechanical powers, 422. Mechanical power of steam, 261. Mensuration of solids, 79. Mensuration of timber, 93. Mensuration of superficies, 45. Mercury, density of, 350. Mercury, to calculate the force of steam in inches of, 201. Method to calculate the logarithm of any given number, 340. Metacentre, 453, 466, 483. Metre, 5. Midship, or greatest transverse section, 460, 488. Millboard, 405. Millstones, 445. Millstones, strength of, 451. Modulus of elasticity, 278. Modulus of logarithms, 343. Modulus of torsion and of rupture, 279. Moment of inertia, 412. Motion of elastic fluids, 205. Motion of steam in an engine, 206. Multiplication of decimals, 23. Multiplication of fractions, 21. Multiplication by logarithms, 335. Musical proportion, 40. Natural sines, cosines, tangents, cotangents, secants, and cosecants, to every degree of the quadrant, 411. Naval architecture, 453. New method of multiplication, 342. Nitrogen, weight of, 356. Nominal horse power, tables of, for high and low pressure engines, 243, 244. Notation and numeration, 10. Notation, trigonometrical, 359. Number corresponding to a given logarithm, 351. Number of teeth, or the pitch of small wheels, 435. Numbers, fourth and fifth powers of, 129. Numbers, logarithms of, 540, 756. Numbers, reciprocals of, 73 to 78. Numbers, squares, cubes, &c, of, 100 to 116. Numeral solution of the several cases of trigonometry, 361. Nuts and bolts, 406. Oak, Dantzic, 280. Obelisk, to find the height of, 371. Oblique triangles, 368. Observatory at Paris <7 = 9-80896 metres,346.- O'Byrne's turbine tables, 331. Octagon, 48. Octaedron, 89. O'Neill's experiments, 447. O'Neill's rules employed in the art of ship- building, 454. Opium, specific gravity of, 394. Orders of lever, 426. Ordinates employed in the art of ship-build- ing, 455, 456, 458, 500. Orifices and tubes, discharge of water by, 312. Orifices, rectangular, 314. Oscillation, centre of, 187, 391. Outside bearings of crank axle, 168. Outside discharging turbines, 331. Overshot wheels, 329. Overshot wheels, maximum velocity of, 443. Ox-hide, 299. Oxygen, 214, 356. PADDLE-shaft journal, 137, 251. Paraboloid, 88. Parabolic conoid, 88. Parallel angle iron, 409. Parallel motion, 242 to 246. Parallelogram of forces, 422. Parallelopipedon, 80. Partnership, 41. Partial contraction of the fluid vein, 316. Passages, area of steam, 220. Peclet's expression for the velocity of smoke in chimneys, 213. Pendulums, 183, 391. Pendulum, conical, 184. Pendulums, vibrating seconds at the level of the sea in various latitudes, 393. Percussion, centre of, 391. Periodic time, 179. Permanent weight supported by beams, 2S4. Permutations and combinations, 44. Pillars, strength of, 293. Pinions and wheels in continuous circular motion, 432. Pipes, discharge and drainage of water through, 321, 322, 325. Pipes of cast iron, 395. Pipes for marine engines, 149. Piston, 251. Piston of steam engine, 414. Piston rod, 140, 171, 253. Piston rod of air-pump, 146. Pitch circle, 436. Pitch of teeth, 441. Pitch of wheels, 435, 439. Plane triangles, solution of, 364, 365. Plane trigonometry, 359. Planks, deals, 94. Polygons, 47, 48. Polygons, irregular, 54. Port, upper and lower, 229. Position, double, 44. Position, single, 43. Pound, 5. Power, actual and nominal, 241. Power and properties of steam, 261. Power that a cast-iron wheel is capable of transmitting, 442. 574 INDEX. Power of shafts, 294. Practical application of the mechanical powers, 425. Practical limit to expansion, 261. Practical observations on steam engines, 260. Principle of virtual velocities, 423. Prism,, 80. Prismoid, 85. Properties of bodies, 401. Proportional dimensions of nuts and holts, 406. Proportion, 14. Proportion, musical, 40. Proportion and progression, arithmetical, 35 to 38. Proportion and progression, geometrical, 38 to 40. Proportion, or the rule of three by loga- rithms, 338. Proportion of wheels for screw-cutting, 433. Proportions of boilers, grates, &c, 213. Proportions of the lengths of circular arcs, 68. Proportions of undershot wheels, 328. Pulleys, 422, 427. Pump and pumping engines, 446. Pumping engines, 422. Pyramid, 82. Pyrometer, 63. Quadrant, 359. Quadrant, log. sines, cosines, &c, for every minute in, 540, 576. Quadrant, natural sines and cosines for every degree of, 411. Quadrant, to take angles with, 370. Quantities, known and unknown, 134. Quantity of water that flows through a cir- cular orifice, 313, 319. Quiescence, friction of, 299. Radius bar, 242. Radius bar, length of, corrected, 248. Radius of the earth at Philadelphia, 356. Radius of gyration, 412. Radius, length of, in degrees, 357. Rails, temporary, 411. Railway carriage, 268. Railway iron, 410. Raising of powers by logarithms, 33S. Reciprocals of numbers, 73 to 78. Recoil, 449. Rectangle, rhombus, rhomboides, to find the areas of, 45, 46. Reduction of fractions, 16, 17, to 19, 20. Regnault's experiments on oxygen, &c, 356. Regular bodies, 90. Relative capacities of the two bodies under the same displacement, 456, 470. Relative strength of materials to resist tor- sion, 294. Revolving shaft, 250. Riga fir, 290. Right-angled spherical triangles, 374. Ring, circular, to find the area of, 53. Ring, cylindrical, 90. Roads, traction of carriages on, 307. Rolled iron, 395. Roman notation, 11. Rope, strength of, 282. Ropes, bands, &c, 267. Ropes, blocks, pulleys, 428. Ropes, stiffness of, resistance of, to bendin 302. Ropes, tarred and dry, 304, 306. Rotative engines, 260. Rotation, moment of, 414. Rotation of a body about a fixed axis, 416. Rotations of millstones, 452. Round and rectangular bars, strength of, 281. Round bar-iron, 403. Round steel and brass, 408. Rules for pumping engines, 448. Rule of three, 13. Rule of three by logarithms, 338. Rule of three in fractions, 21. Rupture, 272. Safety valves, 149, 150, 224. Sails of windmills, 332. Sash iron, 410. Scales of chords, how to construct, 360. Scale of displacement, 465. Scantling, 95. Screw cutting by lathe, 433. Screw, power of, 430. Screw, to cut, 434. Sectional area measured, 456. Segments of circles, 64 to 67. Sheives, cords, blocks, 428. Ship-building and naval architecture, 453. Sidereal day, 9. Side lever, to find the depth across the centre of, 144. Side rod, 246, 254. Side rod of air-pump, 146. Sines, cosines, &c, 411. Sines, tangents and secants, 359. Singular phenomena, 237. Sleigh, 268. Slide valve, 225. Slide valve, a cursory examination of, 232. Slopes It to 1, 2 to 1, and 1 to 1, 97. Sluice board, 316. Smoke and heated air in chimneys, 202. Solid inches in a solid foot, 96. Solids, mensuration of, 79. Space described by a body during a free de- scent in vacuo, 388. Specific gravity, 3S6, 391. Sphere, 85. Spheres, 397 to 400. Spheroid, 86, 87, 88. Spherical trigonometry, 373. Spheroidal condition of water in boilers, 236. Spindle and screw wheels, 434. Square, to find the area of, 45. Square and sheet iron, 402. Squares and square roots of numbers, 100 to 116. Square root, 30. Square root of fractions and mixed numbers, 31. Square measure, 6. Stability, 459, 499. Stars, apparent motion of, 353. Statical moment, 417. Steam engine, 135. Steam dome, 171. Steam passages, 220. Steam pipes, loss of force in, 222. Steam port, 147, 148. Steam room, 259. INDEX. 575 Steam, elastic force of, 188 to 202. Steam, temperature of, pressure of, 172. Steam, volume of, 202 to 206. Steam, weight of, 204. Steel, 408. Stiffness of a vessel under canvas, 485. Stiffness of ropes, 302, 306. Stowage, 503. Stowing the hold of a vessel, 453, 456. Strap at cutter, 141. Strap, mean thickness of, at and before cut- ter, 143. Strength of bodies, 282. Strength of boilers, 218. Strength of materials, 173, 271. Strength of rods when the strain is wholly tensile, 250. Strength of the teeth of cast iron wheels, 437. Studs of lever, 143. t ud-wheel and pinion, 434. Subtraction of decimals, 23. Subtraction of fractions, 21. Table by which to determine the number of teeth or pitch of small wheels, 435. Table containing the circumferences, squares, cubes, and areas of circles, from 1 to 100, advancing by a tenth, 57, 58, 59, 60 to 63. Table containing the weight of columns of water, each one foot in length, in pounds avoirdupois, 401. Table containing the weight of square bar iron, 402. Table containing the surface and solidity of spheres, together with the edge of equal cubes, the length of equal cylinders, and weight of water in avoirdupois pounds, 397. Table containing the weight of flat bar iron, 400. Table containing the specific gravities and other properties of bodies; water the stand- ard of comparison, 401. Table containing the weight of round bar iron, 403. Table containing the weights of cast iron pipes, 404. Table containing the weight of solid cylin- ders of cast iron, 404. Table containing the weight of a square foot of copper and lead, 405. Table for finding the weight of malleable iron, copper, and lead, 405. Table for finding the radius of a wheel when the pitch is given, or the pitch when the ra- dius is given, for any number of teeth, 439. Table for the general construction of tooth wheels, 442. Table for breast wheels, 329. Table of polygons, 48. Table of decimal approximations for facili- tating calculations, 55. Tabic of decimal equivalents, 56. Table of the areas of the segments and zones of a circle of which the diameter is unity, 64, 65, 66, 67. Table of the proportions of the lengths of semi-elliptic arcs, 69, 70, 72. Table of flat or board measure, 93. Table of solid timber measure, 94. Table of reciprocals of numbers, or of the decimal fractions corresponding to com- mon fractions, 71 to 77, 78. Table of weights and values in decimal parts, 79. Table of regular bodies, 90. Table of the cohesive power of bodies, 175. Table of hyperbolic logarithms, 130 to 133. Table of the pressure of steam, in inches of mercury at different temperatures, 172. Table of the temperature of steam at differ- ent pressures, in atmospheres, 172. Table of the expansion of air by heat, 173. Table of the strength of iron, 173. Table of the superficial and solid content of spheres, 96. Table of solid inches in a solid foot, 96. Table of squares, cubes, square and cube roots, of numbers, 100, 101, 116, 125. Table of cover on the exhausting side of the valve in parts of the stroke and distance of piston from the end of its stroke, 231. Table of the proportions of the lengths of circular arcs, 68. Table of the fourth and fifth power of num- bers, 129. Table of the properties of different boil- ers, 215. Table of the economical effects of expan- sion, 216. Table of the comparative evaporative power of different kinds of coal, 218. Table of the cohesive strength of iron boiler plate at different temperatures, 219. Table of diminution of strength of copper boilers, 219. Table of expanded steam, 239. Table of the proportionate length of bearings, ' or journals for shafts of various diameters, 287. Table of tenacities, resistances to compres- sion and other properties of materials, 288. Table of the strength of ropes and chains, 288. Table of the strength of alloys, 289. Table of data of timber, 289. Table of the properties of steam, 261. Table of the mechanical properties of steam, 263. Table of the cohesive strength of bodies, 281. Table of the strength of common bodies, 283. Table of torsion and twisting of common ma- terials, 286. Table of the length of circular arcs, radius being unity, 63. Table of experiments on iron boiler plate at high temperature, 220. Table of the absolute weight of cylindrical columns, 274. Table of flanges of girders, 276. Table of mean pressure of steam at different densities and rates of expansion, 239. Table of nominal horse power of high pres- sure engines, 244. Table of nominal horse power of low pres- sure engines, 243. Table of dimensions of cylindrical columns of cast iron to sustain a given load with safety, 293. Table of strength of columns, 294. 576 INDEX. Table of comparative torsion, 294. Table of the depths of square beams to sup- port from 1 cwt. to 14 tons, 295, 296. Table of the results of experiments on fric- tions, with unguents interposed, 299, 300. Table of the results of experiments on the gudgeons or axle-ends in motion upon their bearings, 301. Table of friction, continued to abrasion, 301. Table of friction of steam engines of differ- ent modifications, 302. Table of tarred ropes, 303. Table of white ropes, 305. Table of dry and tarred ropes, 306. Table of the pressure and traction of car- riages, 308. Table of traction of wheels, 309. Table of the ratio of traction to the load, 310. Table of the coefficients of the efflux through rectangular orifices in a thin vertical plate, 315. Table of the coefficients of efflux, 315. Table of comparison of the theoretical with the real discharges from an orifice, 317. Table of discharge of tubes of different en- largements, 322. Table of the comparison of discharge by pipes of different lengths, 323. Table of the comparison of discbarge by ad- ditional tubes, 323. Table of the friction of fluids, 325. Table of discharges of a 6-inch pipe at seve- ral inclinations, 326. Table of the velocity of windmill sails, 333. Table of outside discharging turbine, 331. Table of inward discharging turbines, 332. Table of peculiar logarithms, 340. Table of useful logarithms, 345. Table of the specific gravity of various sub- stances, 394. Table of the weight of a foot in length of flat and rolled iron, 395. Table of the weight of cast iron pipes, 395. Table of the weight of one foot in length of malleable iron, 396. Table of comparison, 396. Table of the weight of a square foot of sheet iron, 402. Table of the weight of a square foot of boiler plate from £ of an inch to 1 inch thick, 403. Table of the weights of cast iron plates, 403. Table of the weight of mill-board, 405. Table of the weight of wrought iron bars, 406. Table of the proportional dimensions of nuts and bolts, 406. Table of the specific gravity of water at dif- ferent temperatures, 406. Table of the weight of cast iron balls, 407. Table of the weight of flat bar iron, 407. Table of the weight of square and round brass, 408. Table of taper T iron, 410. Table of sash iron, 410. Table of rails of equal top and bottom, 410. Table of temporary rails, 411. Table of natural sines, cosines, tangents, co- tangents, secants, and cosecants, to every degree of the quadrant, 411. Table of inclined planes, showing the ascent or descent the yard, 430. Table of the weight of round steel, 408. Table of parallel angle iron of equal sides, 408. Table of parallel angle iron of unequal sides, 409. Table of taper angle iron of equal sides, 409. Table of parallel T iron of unequal width and d#pth, 409. Table of change wheels for screw-cutting, 435. Table of the diameters of wheels at their pitch circle, to contain a required number of teeth, 436. Table of the angle of windmill sails, 445. Table of the logarithms of the natural num- bers, from 1 to 100000, by the help of dif- ferences, 502 to 540. Table of log. sines, cosines, tangents, cotan- gents, secants and cosecants, for every de- gree and minute in the quadrant, 540 to 576. Table of the strength of the teeth of cast iron wheels at a given velocity, 437. Table of approved proportions for wheels with flat arms, 441. Table showing the cover required on the steam side of the valve to cut the steam off at any part of the stroke; 228. Table showing the cover required, 227. Table showing the resistance opposed to the motion of carriages on different incli- nations of ascending or descending planes, 429. Table showing the number of linear feet of scantling of various dimensions which are equal to a cubic foot, 95. Table showing the weight or pressure a beam of cast iron will sustain without destroying its elastic force, 292. Table showing the circumference of rope equal-to a chain, 282. Table to correct parallel motion links, 248. Table of parallel T iron of equal depth and width, 410. Tables of cuttings and embankments, slopes, 1 to 1 ; 1J to 1 ; and 2 to 1, 97. Tables of the heights corresponding to differ- ent velocities, 389. Tables of the mechanical properties of the materials most commonly employed in the construction of machines and framings, 280. Tangents, 360. Tangents and secants, to compute, 362. Taper angle iron, 410. Teeth of wheels in continuous circular motion, 432. Teeth of wheels, 422, 436. Temperature of steam, 172. Temperature and elastic force of steam, 188. Tension of chain-bridge, 414. Tetraedron, 89. Threshing machines, 445. Throttling the steam, 234. Timber measure, 93. Timber, to measure round, 95. Time, 7. Tonnage of ships, 461. Torsion, 279. Torsion and twisting, 286. Traction of carriages, 307. Transverse strength of bodies, 282. INDEX. 57T Transverse strain, 278. Transverse strain, time weight, 273. Trapezium, 47. Trapezoid, 47. Triangle, to find the area of, 46, 47. Trigonometry, 359. Trigonometry, spherical, 373. Troy weight, 7. Trussed beams, 291. Tubes, discharge of water through, 312. Tubular boilers, 257. Turbine water-wheels, 330. Ultimate pressure of expanded steam, 236. Undecagon, 47. Undershot wheels, 327, 443. Unguents, 299. Ungulas, cylindrical, 81. Ungulas, conical, 83, 84. Unit of length, 5. Unit of weight, 5. Unit of dry capacity, 5. Units of liquids, 5. Units of work, 269, 297, 414, 4lD. Universal pitch table, 442. Upper steam port, 229. Useful formula, 271. Use of the table of squares, cubes, &c, 127. Vacuum, perfect one, 235. Vacuum below the piston, 251. Vacuo, bodies falling freely in, 388. Valves, different arrangements of, 233. Valve, length of stroke of, in inches, 228. Valve shaft, 147. Valve, safety, 224. Valve, slide, 225. Valve spindle, 171. Vapour in the cylinder, 229. Vein, contraction of fluid, 330. Velocity, force, and work done, 267. Velocity of steam rushing into a vacuum, 207. Velocity of smoke in chimneys, 209, 213. Velocity of piston of steam engine, 266. Velocity of threshing machines, millstones, boring, Ac, 445. Velocity of wheels on ordinary roads, 307. Venturi, experiments of, on the discharge of fluids, 421. Versed sine, tabular, 52. Versed sine of parallel motion, 244. Versed sine, 359. Vertical sectional areas, 454. Virtual velocities, 424. Vis viva, principle of, calculations on, 276, 388. Volume of a ship immersed, 456. Volume of steam in a cubic foot of water, 202, 205. Water, modulus of elasticity of, 190. Water level, 214. Water, feed and condensing, 223. Water, spheroidal condition of, in boilers,236. Water in boiler, and water level, 358. Water, discharge of, through different orifi- ces, 312, 318. Water wheels, 327. Water wheels, maximum velocity of, 443. Web of crank at paddle shaft centre, 136. Web of cross-head at middle, 139. Web of crank at pin centre, 142. Web at paddle centre, 252. Web of cross-head at journal, 140. Web of air-pump cross-head, 145. Wedge, 85. Wedge and screw, 430. Weights and measures, 5. Weights, values of, in decimal parts, 79. Weight, mass, gravity, 386. Weirs, and rectangular apertures, 314, 323. Wheel and axle, 417. Wheel and pinion, 427. Wheels, drums, pulleys, 438. Windmills, 332. Wine measure, 8. Woods, 280. Woods, specific gravity, 394. Work done, weight, 267. Wrought iron bars, 406. Yard, 5. Yacht, admeasurement of, 469 470. Yarns of ropes, 303. Yellow brass, 281. Yew, 280. Zinc, 280. Zinc, sheet, 288. Zone, spherical, 86. Zone, to find the area of a circular, 53. Zones of circles, to find the areas of, 64, 65, 66. 11 PUBLICATIONS OF HENRY CAREY BAIRD, SUCCESSOR TO E. L. CAREY, South-east comer of Market and Fifth Streets, Philadelphia. SCIENTIFIC AND PRACTICAL. THE PRACTICAL MODEL CALCULATOR, For the Engineer, Machinist, Manufacturer of Engine Work, Naval Architect, Miner, and Millwright. By Oliver Byrne, Compiler and Editor of the Dictionary of Machines, Mechanics, Engine Work and Engineering, and Author of various Mathematical and Mechanical Works. Illustrated by numerous Engravings. To be published in Twelve Parts, at Twenty-five Cents each, forming, when completed, One large Volume, Octavo, of nearly six hundred pages. It will contain such calculations as are met with and required in the Mechanical Arts, and establish models or standards to guide practical men. The Tables that are introduced, many of which are new, will greatly economize labour, and render the every-day calculations of the practical man comprehensive and easy. From every single calculation given in this work numerous other calculations are readily modelled, so that each may be considered the head of a numerous family of practical results. The examples selected will be found appropriate, and in all cases taken from the actual practice of the present time. Every rule has been tested by the unerring results of mathematical research, and confirmed by experiment, when such was necessary. The Practical Model Calculator will be found to fill a vacancy in the library of the practical working-man long considered a requirement. It will be found to excel all other works of a similar nature, from the great extent of its range, the exemplary nature of its well-selected examples, and from the easy, simple, and sys- tematic manner in which the model calculations are established. NORRIS'S HAND-BOOK FOR LOCOMOTIVE ENGINEERS AND MACHINISTS: Comprising the Calculations for Constructing Locomotives, Manner of setting Valves, &c. &c. By Septimus Norris, Civil and Mechanical Engineer. In One Volume, 12mo, with illustrations $1.50 A TREATISE ON THE AMERICAN STEAM ENGINE. Illustrated by numerous "Wood Cuts and other Engravings. By Oliver Byrne. In One Volume, royal 8vo. (In press.) 2 PUBLICATIONS OF HENRY CAREY BAIRD. THE PRACTICAL COTTON-SPINNER AND MANUFACTURER ; OR, THE MANAGER'S AND OVERLOOKER'S COMPANION. This work contains a Comprehensive System of Calculations for Mill Gearing and Machinery, from the first moving power through the different processes of Carding, Drawing, Slabbing, Eoving, Spinning, and Weaving, adapted to American Machinery, Practice, and Usages. Compendious Tables of Yarns and Reeds are added. Illustrated by large Working-Drawings of the most approved American Cotton Machinery. Complete in One Volume, octavo $3.50 This edition of Scott's Cotton-Spinner, by Oliver Byrne, is designed for the American Operative. It will be found intensely practical, and will be of the greatest possible value to the Manager, Overseer, and Workman. THE PRACTICAL METAL-WORKER'S ASSISTANT ; For Tin-Plate Workers, Brasiers, Coppersmiths, Zinc-Plate Ornamenters and Workers, Wire Workers, Whitesmiths, Blacksmiths, Bell Hangers, Jewellers, Silver and Gold Smiths, Electrotypers, and all other Workers in Alloys and Metals. By Charles Holtzappfel. Edited, with important additions, by Oliver Byrne. Complete in One Volume, octavo $4.00 It will treat of Casting, Founding, and Forging; of Tongs and other Tools; Degrees of Heat and Manage- ment of Fires; Welding; of Heading and Swage Tools; of Punches and Anvils; of Hardening and Tem- pering; of Malleable Iron Castings, Case Hardening, Wrought and Cast Iron. The management and manipulation of Metals and Alloys, Melting and Mixing. The management of Furnaces, Casting and Founding with Metallic Moulds, Joining and Working Sheet Metal. Peculiarities of the different Tools employed. Processes dependent on the ductility of Metals. Wire Drawing, Drawing Metal Tubes, Solder- ing. The use of the Blowpipe, and every other known Metal-Worker's Tool. To the works of Holtzappfel, Oliver Byrne has added all that is useful and peculiar to the American Metal-Worker. A COMPLETE TREATISE ON TANNING, CURRYING, AND EVERY BRANCH OF LEATHER-DRESSING. From the French and from original sources. By Campbell Morfit, one of the Editors of the "Encyclopedia of Chemistry," Author of "Chemistry Applied to the Manufacture of Soap and Candles," and other Scien- tific Treatises. Illustrated with several hundred Engravings. Complete in One Volume, royal 8vo. (In press.) This important treatise will be issued from the press at as early a day as the duties of the editor will per- mit, and it is believed that in no other branch of applied science could more signal service be rendered to American Manufacturers. The publisher is not aware that in any other work heretofore issued in this country, more space has been devoted to this subject than a single chapter; and in offering this volume to so large and intelligent a class as American Tanners and Leather Dressers, he feels confident of their substantial support and encourage- ment. THE MANUFACTURE OF IRON IN ALL ITS VARIOUS BRANCHES: To which is added an Essay on the Manufacture of Steel, by Frederick Overman, Mining Engineer, with one hundred and fifty Wood Engra- vings. A new edition. In One Volume, octavo, five hundred pages $5.00 We have now to announce the appearance of another valuable work on the subject which, in our humble opinion, supplies any deficiency which late improvements and discoveries may have caused, from the lapse of time since the date of "Mushet" and "Schrivenor." It is the production of one of our transatlantic brethren, Mr. Frederick Overman, Mining Engineer: and we do not hesitate to set it down as a work of great importance to all connected with the iron interest; one which, while it is sufficiently technological fully to explain chemical analysis, and the various phenomena of iron under different circumstances, to the satisfaction of the most fastidious, is written in that clear and comprehensive style as to be available to the capacity of the humblest mind, and consequently will be of much advantage to those works where the pro- prietors may see the desirability of placing it in the hands of their operatives. — London Morning Journal. PUBLICATIONS OF HENRY CAREY BAIRD. 3 PRACTICAL SERIES. The volumes in this Series are published in duodecimo form, and the design is to furnish to Artisans, for a moderate sum, Hand-books of the different Arts and Manufactures, in order that they may be enabled to keep pace with the improvements of the age. There have already appeared — THE AMERICAN MILLER AND MILLWRIGHT'S ASSISTANT. $1. THE TURNER'S COMPANION. 75 cts. THE PAINTER, GILDER, AND VARNISHER'S COMPANION. 75 cts. THE DYER AND COLOUR-MAKER'S COMPANION. 75 cts. THE BUILDER'S COMPANION. $1. THE CABINET-MAKER'S COMPANION. 75 cts. The following, among others, are in preparation : — A TREATISE ON A BOX OF INSTRUMENTS. By Thomas Kentish. THE PAPER-HANGER'S COMPANION. By J. Arrowsmith. THE AMERICAN MILLER AND MILLWRIGHT'S ASSISTANT: By William Carter Hughes, Editor of " The American Miller," (newspaper), Buffalo, N. Y. Illustrated by Drawings of the most approved Machinery. In One Volume, 12mo $1 The author offers it as a substantial reference, instead of speculative theories, which belong only to those not immediately attached to the business. Special notice is also given of most of the essential improvements which have of late been introduced for the benefit of the Miller. — Savannah Republican. The whole business of making flour is most thoroughly treated by him. — Bulletin. A very comprehensive view of the Millwright's business. — Southern Literary Messenger. THE TURNER'S COMPANION: Containing Instructions in Concentric, Elliptic, and Eccentric Turning. Also, various Plates of Chucks, Tools, and Instruments, and Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and Circular Rest ; with Patterns and Instructions for working them. Illustrated by numerous Engrav- ings. In One Volume, 12mo 75 cts. The object of the Turner's Companion is to explain in a clear, concise, and intelligible manner, the rudi- ments of this beautiful art. — Savannah Republican. There is no description of turning or lathe-work that this elegant little treatise does not describe and illustrate. — Western Lit. Messenger. THE PAPER-HANGER'S COMPANION : In which the Practical Operations of the Trade are system- atically laid down ; with copious Directions Preparatory to Papering ; Preventions against the effect of Damp in Walls ; the various Cements and Pastes adapted to the several purposes of the Trade ; Observations and Directions for the Panelling and Ornamenting of Rooms, &c, &c. By James Akrowsmith. In One Volume, 12mo. 4 PUBLICATIONS OF HENRY CAREY BAIRD. THE PAINTER, GILDER, AND VARNISHER'S COMPANION: Containing Rules and Regulations for every thing relating to the arts of Painting, Gilding, Varnishing, and Glass Staining ; numerous useful and valuable Receipts ; Tests for the detection of adulterations in Oils, Colours, &c, and a Statement of the Diseases and Accidents to which Painters, Gilders, and Varnishers are particularly liable ; with the simplest methods of Prevention and Remedy. Second Edition. In One Volume, 12mo, cloth 75 cts. Rejecting all that appeared foreign to the subject, the compiler has omitted nothing of real practical worth. — Hunt's Merchants' Magazine. An excellent practical work, and one which the practical man cannot afford to be without. — Farmer and Mechanic. It contains every thing that is of interest to persons engaged in this trade. — Bulletin. This book will prove valuable to all whose business is in any way connected with painting. — Scott's Weekly. Cannot fail to be useful.— iV. T. Commercial. THE DYER AND COLOUR-MAKER'S COMPANION: Containing upwards of two hundred Receipts for making Colours, on the most approved principles, for all the various styles and fabrics now in existence ; with the Scouring Process, and plain Directions for Preparing, Washing-off, and Finishing the Goods. Second Edition. In One Volume, 12mo, cloth 75 cts. This is another of that most excellent class of practical books, which the publisher is giving to the public. Indeed, we believe there is not, for manufacturers, a more valuable work, having been prepared for, and expressly adapted to their business. — Farmer and Mechanic. It is a valuable book. — Otsego Republican. We have shown it to some practical men, who all pronounced it the completest thing of the kind they had seen. — N. T. Nation. THE BUILDER'S POCKET COMPANION: Containing the Elements of Building, Surveying, and Archi- tecture ; with Practical Rules and Instructions connected with the subject. By A. C. Smeaton, Civil Engineer, &c. Second Edition. In One Volume, 12mo $1 Contents. — The Builder, Carpenter, Joiner, Mason, Plasterer, Plumber, Painter, Smith, Practical Geometry, Surveyor, Cohesive Strength of Bodies, Architect. It gives, in a small space, the most thorough directions to the builder, from the laying of a brick, or the felling of a tree, up to the most elaborate production of ornamental architecture. It is scientific, without being obscure and unintelligible, and every house-carpenter, master, journeyman, or apprentice, should have a copy at hand always. — Evening Bulletin. Complete on the subjects of which it treats. A most useful practical work. — Baltimore American. It must be of great practical utility. — Savannah Republican. To whatever branch of the art of building the reader may belong, he will find in this something valuable and calculated to assist his progress. — Farmer and Mechanic. This is a valuable little volume, designed to assist the student in the acquisition of elementary knowledge, and will be found highly advantageous to every young man who has devoted himself to the interesting pursuits of which it treats. — Virginia Herald. A TREATISE ON A BOX OF INSTRUMENTS, And the Slide Rule, with the Theory of Trigonometry and Logarithms, including Practical Geometry, Surveying, Measuring of Timber, Cask and Malt Gauging, Heights and Distances. By Thomas Kentish. In One Volume, 12mo. PUBLICATIONS OF HENRY CAREY BAIRD. 5 THE CABINET-MAKER AND UPHOLSTERER'S COMPANION: Comprising the Rudiments and Principles of Cabinet-making and Upholstery, -with familiar Instructions, illustrated by Examples, for attaining a proficiency in the Art of Drawing, as applicable to Cabinet- Work ; the processes of Veneering, Inlaying, and Buhl Work ; the art of Dyeing and Staining Wood, Bone, Tortoise-shell, &c. Directions for Lackering, Japanning, and Varnishing ; to make French Polish ; to prepare the best Glues, Cements, and Compositions, and a number of Receipts particularly useful for Workmen generally, with Ex- planatory and Illustrative Engravings. By J. Stokes. In One Volume, 12mo, with Illustrations 75 cts. A large amount of practical information, of great service to all concerned in those branches of business. — Ohio State Journal. PROPELLERS AND STEAM NAVIGATION: With Biographical Sketches of Early Inventors. By Robert Macfarlane, C. E., Editor of the " Scientific American." In One Volume, 12mo. Blustrated by over Eighty Wood Engravings 75 cts. The object of this " History of Propellers and Steam Navigation" is twofold. One is the arrangement and description of many devices which have been invented to propel vessels, in order to prevent many in- genious men from wasting their time, talents, and money on such projects. The immense amount of time, study, and money thrown away on such contrivances is beyond calculation. In this respect, it is hoped that it will be the means of doing some good. — Preface. TABLES OF LOGARITHMS FOR ENGINEERS AND MACHINISTS : Containing the Logarithms of the Natural Numbers, from 1 to 100000, by the help of Proportional Differences. And Logarithmic Sines, Co- sines, Tangents, Co-tangents, Secants, and Co-secants, for every Degree and Mi- nute in the Quadrant. To which are added, Differences for every 100 Seconds. By Oliver Bykne, Civil, Military, and Mechanical Engineer. In One Vol. 8vo. cl.... $1 THE FRUIT, FLOWER, AND KITCHEN GARDEN. By Patrick Neill, L. L. D., F. R. S. E., Secretary to the Royal Caledonian Horticultural Society. Adapted to the United States, from the Fourth Edition, revised and improved by the Author. Illustrated by fifty Wood Engravings of Hothouses, &c. &c. In One Volume, 12mo $1.25 This volume supplies a desideratum much felt, and gives within a moderate compass all the horticultural information necessary for practical use. — Newark Mercury. A valuable addition to the horticulturist's library. — Baltimore Patriot. This work is the production of a most celebrated British horticulturist, Dr. Neill, of Scotland, for up- wards of thirty years the Secretary of the Caledonian Horticultural Society, and in every way qualified to make a standard book upon the subject it discusses. The careful adaptation of the work to the peculiar circumstances and necessities of our own people, is a subject of congratulation, since good books upon hor- ticulture cannot be too much multiplied. We are pleased with the comprehensiveness of Dr. Neill's treatise. — Southern Literary Gazette, ELEMENTARY PRINCIPLES OF CARPENTRY. By Thomas Tredgold. In One Volume, quarto, with nume- rous Illustrations $2.50 6 PUBLICATIONS OF HENRY CAREY BAIRD. THE ENCYCLOPEDIA OF CHEMISTRY, PRACTICAL AND THEORETICAL : Embracing its Application to the Arts, Metallurgy, Mineralogy, Geology, Medicine, and Pharmacy. By James C. Booth, Melter and Refiner in the United States Mint, Professor of Applied Chemistry in the Franklin Institute, &c. ; assisted by Campbell Morfit, Author of "Chemical Manipulations," &c. Complete in One Volume, royal octavo, 978 pages, with numerous Woodcuts and other Illustrations. Second Edition. Full bound $5 It covers the whole field of Chemistry as applied to Arts and Sciences. * * * As no library is complete without a common dictionary, it is also our opinion that none can be without this Encyclopedia of Chemis- try. — Scientific American. A work of time and labour, and a treasury of chemical information.— North American. By far the best manual of the kind which has been presented to the American public. — Boston Courier. An invaluable work for the dissemination of sound practical knowledge. — Ledger. A treasury of chemical information, including all the latest and most important discoveries. — Baltimore American. At the first glance at this massive volume, one is amazed at the amount of reading furnished in its compact double pages, about one thousand in number. A further examination shows that every page is richly stored with information, and that while the labours of the authors have covered a wide field, they have neglected or slighted nothing. Every chemical term, substance, and process is elaborately, but in- telligibly, described. The whole science of Chemistry is placed before the reader as fully as is practicable with a science continually progressing. * * * Unlike most American works of this class, the authors have not depended upon any one European work for their materials. They have gathered theirs from works on Chemistry in all languages, and in all parts of Europe and America; their own experience, as practical chemists, being ever ready to settle doubts or reconcile conflicting authorities. The fruit of so much toil is a work that must ever be an honour to American science. — Evening Bulletin., SYLLABUS OF A COMPLETE COURSE OF LECTURES ON CHEMISTRY: Including its Application to the Arts, Agriculture, and Mining, prepared for the use of the Gentlemen Cadets at the Hon. E. I. Co.'s Military Seminary, Addiscombe. By Professor E. Solly, Lecturer on Chemistry in the Hon. E. I. Co.'s Military Seminary. Revised by the Author of " Chemical Manipu- lations." In One Volume, octavo, cloth $1.25 The present work is designed to occupy a vacant place in the libraries of Chemical text-books. It is admirably adapted to the wants of both teacher and pupil ; and will be found especially convenient to the latter, either as a companion in the class-room, or as a remembrancer in the study. It gives, at a glance, under appropriate headings, a classified view of the whole science, which is at the same time compendious and minutely accurate; and its wide margins afford sufficient blank space for such manuscript notes as the student may wish to add during lectures or recitations. The almost indispensable advantages of such an impressive aid to memory are evident to every student who has used one in other branches of study. Therefore, as there is now no Chemical Syllabus, we have been induced by the excellences of this work to recommend its republication in this country; confident that an examination of the contents will produce full conviction of its intrinsic worth and usefulness. — Editor's Preface. AN ELEMENTARY COURSE OF INSTRUCTION ON ORDNANCE AND GUNNERY. Prepared for the use of the Midshipmen at the Naval School. By James H. Ward, U. S. N. In One Volume, octavo $1.50 STEAM FOR THE MILLION. Vn Elementary Outline Treatise on the Nature and Manage- ment of Steam, and the Principles and Arrangement of the Engine. Adapted for Popular Instruction, for Apprentices, and for the use of the Navigator. With an Appendix containing Notes on Expansive Steam, &c. In One Volume, 8vo...37£ cts. PUBLICATIONS OF HENRY CAREY BAIRD. 7 HOUSEHOLD SURGERY ; OR, HINTS ON EMERGENCIES. By J. F. South, one t)f the Surgeons of St. Thomas's Hospi- tal. In One Volume, 12mo. Illustrated by nearly fifty Engravings $1.25 contents : The Doctor's Shop. — Poultices, Fomentations, Lotions, Liniments, Ointments, Plasters. Surgery. — Blood-letting, Blistering, Vaccination, Tooth-drawing, How to put on a Roller, Lancing the Gums, Swollen Veins, Bruises, Wounds, Torn or Cut Achilles Ten- don, What is to he done in cases of sudden Bleeding from various causes, Scalds and Burns, Frost-bite, Chilblains, Sprains, Broken Bones, Bent Bones, Dislocations, Rup- tures, Piles, Protruding Bowels, Wetting the Bed, Whitlow, Boils, Black-heads, In- growing Nails, Bunions, Corns, Sty in the Eye, Blight in the Eye, Tumours in the Eyelids, Inflammation on the Surface of the Eye, Pustules on the Eye, Milk Abscesses, Sore Nipples, Irritable Breast, Breathing, Stifling, Choking, Things in the Eye, On Dress, Exercise and Diet of Children, Bathing, Infections, Observations on Ventilation. HOUSEHOLD MEDICINE. By D. Francis Condie, M. D. In One Volume, 12mo. Uni- form with, and a companion to, the above. (In immediate preparation.) ELWOOD'S GRAIN TABLES: Showing the value of Bushels and Pounds of different kinds of Grain, calculated in Federal Money, so arranged as to exhibit upon a single page the value at a given price from ten cents to two dollars per bushel, of any quantity from one pound to ten thousand bushels. By J. L. Elwood. A new Edition. In One Volume, 12mo $1 To Millers and Produce Dealers this work is pronounced by all who have it in use, to be superior in ar- rangement to any work of the kind published — and unerring accuracy in every calculation may be relied upon in every instance. Oj" A reward of Twenty-five Dollars is offered for an error of one cent found in the work. PERFUMERY; ITS MANUFACTURE AND USE: With Instructions in every branch of the Art, and Eeceipts for all the Fashionable Preparations ; the whole forming a valuable aid to the Perfumer, Druggist, and Soap Manufacturer. Illustrated by numerous Woodcuts. From the French of Celnart, and other late authorities. With Additions and Im- provements, by Campbell Morfit, one of the Editors of the "Encyclopedia of Chemistry." In One Volume, 12mo, cloth , $1 ELECTROTYPE MANIPULATION : Being the Theory and Plain Instructions in the Art of Work- ing in Metals, by Precipitating them from their Solutions, through the agency of Galvanic or Voltaic Electricity. By Charles V. Walker, Hon. Secretary to the London Electrical Society, &c. Illustrated by Woodcuts. From the Thirteenth London Edition. In One Volume, 24mo, cloth 62 cts. 8 PUBLICATIONS OF HENRY CAREY BAIRD. PHOTOGENIC MANIPULATION: Containing the Theory and Plain Instructions in the Art of Photography, or the Production of Pictures through the Agency of Light ; in- cluding Calotype, Chrysotype, Cyanotype, Chromatype, Energiatype, Anthotype, Amphitype, Daguerreotype, Thermography, Electrical and Galvanic Impressions. By George Thomas Fisher, Jr., Assistant in the Laboratory of the London In- stitution. Illustrated by Wood-cuts. In One Volume, 24mo, cloth 62 cts. MATHEMATICS FOR PRACTICAL MEN: Being a Common-Place Book of Principles, Theorems, Eules, and Tables, in various Departments of Pure and Mixed Mathematics, 'with their . Applications, especially to the pursuits of Surveyors, Architects, Mechanics, and ' Civil Engineers. With numerous Engravings. By Olinthtjs Gregory, L. L. D., F. R. A. S '.. $1.50 Only let men awake, and fix their eye, one while on the nature of things, another while on the application of them to the use and service of mankind. — Lord Bacon. SHEEP HUSBANDRY IN THE SOUTH: Comprising a Treatise on the Acclimation of Sheep in the Southern States, and an Account of the different Breeds. Also, a Complete Ma- nual of Breeding, Summer and Winter Management, and of the Treatment of Diseases. With Portraits and other Illustrations. By Henry S. Randall. In One Volume, octavo $1.25 MISS LESLIE'S COMPLETE COOKERY. Directions for Cookery, in its Various Branches. By Miss Leslie. Forty-first Edition. Thoroughly Revised, with the Addition of New Receipts. In One Volume, 12mo, half bound, or in sheep $1 In preparing a new and carefully revised edition of this my first work on cookery, I have introduced improvements, corrected errors, and added new receipts, that I trust will on trial be found satisfactory. The success of the book (proved by its immense and increasing circulation) affords conclusive evidence that it has obtained the approbation of a large number of my countrywomen ; many of whom have informed me that it has made practical housewives of young ladies who have entered into married life with no other ac- quirements than a few showy accomplishments. Gentlemen, also, have told me of great improvements in the family table, after presenting their wives with this manual of domestic cookery, and that, after a morn- ing devoted to the fatigues of business, they no longer find themselves subjected to the annoyance of an ill-dressed dinner. — Preface. MISS LESLIE'S TWO HUNDRED RECEIPTS IN FRENCH COOKERY. A new Edition, in cloth 25 cts. TWO HUNDRED DESIGNS FOR COTTAGES AND VILLAS, &c. &c, Original and Selected. By Thomas U. Walter, Architect of Girard College, and John Jay Smith, Librarian of the Philadelphia Library. In Four Parts, quarto $10 PUBLICATIONS OF HENRY CAREY BAIED. STANDARD ILLUSTRATED POETRY. THE TALES AND POEMS OF, LORD BYRON: Illustrated by Henry Warren. In One Volume, royal 8vo, with 10 Plates, scarlet cloth, gilt edges $ 5 Morocco extra $^ It is illustrated by several elegant engravings, from original designs by Warren, and is a most splendid work for the parlour or study.— Boston Evening Gazette. CHILDE HAROLD; A ROMAUNT BY LORD BYRON: Illustrated by 12 Splendid Plates, by Warren and others. In One Volume, royal 8vo, cloth extra, gilt edges. Morocco extra Printed in elegant style, with splendid pictures, far superior to any thing of the sort usually found in books of this kind.— N. Y. Courier. SPECIMENS OF THE BRITISH POETS. From the time of Chaucer to the end of the Eighteenth Cen- tury. By Thomas Campbell. In One Volume, royal 8vo. (In press.) THE FEMALE POETS OF AMERICA. By Rufus W. Griswold. A new Edition. In One Volume, royal 8vo. Cloth, gilt $2.50 Cloth extra, gilt edges $ 3 Morocco super extra $4.50 The best production which has yet come from the pen of Dr. Griswold, and the most valuable contribu- tion which he has ever made to the literary celebrity of the country. — N. Y. Tribune. THE LADY OF THE LAKE : By Sir Walter Scott. Illustrated with 10 Plates, by Cor- bould and Meadows. In One Volume, royal 8vo. Bound in cloth extra, gilt edges $ 5 Turkey morocco super extra $7 This is one of the most truly beautiful books which has ever issued from the American press. LALLA ROOKH; A ROMANCE BY THOMAS MOORE: Illustrated by 13 Plates, from Designs by Corbould, Meadows, and Stephanoff. In One Volume, royal 8vo. Bound in cloth extra, gilt edges... $5 Turkey morocco super extra $7 This is published in a style uniform with the " Lady of the Lake." 10 PUBLICATIONS OF HENRY CAREY BAIRD. THE POETICAL WORKS OF THOMAS GRAY: With Illustrations by C. W. Radcliffe. Edited with a Me- moir, by Henkt Reed, Professor of English Literature in the University of Penn- sylvania. In One Volume, 8vo. Bound in cloth extra, gilt edges $3.50 Turkey morocco super extra $5.50 It is many a day since we have seen issued from the press of our country a volume so complete and truly elegant in every respect. The typography is faultless, the illustrations superior, and the binding superb.— Troy Whig. 6 r We have not seen a specimen of typographical luxury from the American press which can surpass this volume in choice elegance. — Boston Courier. It is eminently calculated to consecrate among American readers (if they have not been consecrated already in their hearts) the pure, the elegant, the refined, and, in many respects, the sublime imaginings of Thomas Gray. — Richmond Whig. THE POETICAL WORKS OF HENRY WADSWORTH LONGFELLOW: Illustrated by 10 Plates, after Designs by D. Huntingdon, with a Portrait. Ninth Edition. In One Volume, royal 8vo. Bound in cloth extra, gilt edges $5 Morocco super extra $7 This is the very luxury of literature— Longfellow's charming poems presented in a form of unsurpassed beauty. — NeaVs Gazette. POETS AND POETRY OF ENGLAND IN THE NINETEENTH CENTURY: By Rufus W. Griswold. Illustrated. In One Volume, royal 8vo. Bound in cloth $3 Cloth extra, gilt edges $3.50 Morocco super extra $5 Such is the critical acumen discovered in these selections, that scarcely a page is to be found but is redo- lent with beauties, and the volume itself may be regarded as a galaxy of literary pearls— Democratic Review. THE POETS AND POETRY OF THE ANCIENTS : By William Peter, A. M. Comprising Translations and Spe- cimens of the Poets of Greece and Rome, with an elegant engraved View of the Coliseum at Rome. Bound in cloth $3 Cloth extra, gilt edges $3.50 Turkey morocco super extra $5 THE FEMALE POETS OF GREAT BRITAIN. With Copious Selections and Critical Remarks. By Frederic Rowton. With Additions by an American Editor, and finely engraved Illustra- tions by celebrated Artists. In One Volume, royal 8vo. Bound in cloth extra, gilt edges $5 Turkey morocco $7 Mr. Rowton has presented us with admirably selected specimens of nearly one hundred of the most celebrated female poets of Great Britain, from the time of Lady Juliana Bernes, the first of whom there is any record, to the Mitfords, the Hewitts, the Cooks, the Barretts, and others of the present day.— Hunt's Merchants' Magazine. PUBLICATIONS OF HENRY CAREY BAIRD. 11 THE TASK, AND OTHER POEMS. By William Cowper. Illustrated by 10 Steel Engravings. In One Volume, 12mo. Cloth extra, gilt edges $ 2 Morocco extra THE POETICAL WORKS OF NATHANIEL P. WILLIS. Illustrated by 16 Plates, after Designs by E. Leutze. In One Volume, royal 8vo. A new Edition. Bound in cloth extra, gilt edges $5 Turkey morocco super extra $7 This is one of the most beautiful works ever published in this country.— Courier and Inquirer. MISCELLANEOUS. ADVENTURES OF CAPTAIN SIMON SUGGS; And other Sketches. By Johnson J. Hooper. With Illus- 12mo, paper 50 cts trations. Cloth.... 62 cts. AUNT PATTY'S SCRAP-BAG. Bv Mrs. Caroline Lee Hentz, Author of " Linda." 12mo. Paper Cloth Paper covers £0 cts ' 62 cts. BIG BEAR OF ARKANSAS ; And other Western Sketches. Edited by W. T. Porter. In One Volume, 12mo, paper 50 cts. Cloth... 62 cts - COMIC BLACKSTONE. By Gilbert Abbot a' Becket. Illustrated. Complete in One Volume. Cloth 75 cts. GHOST STORIES. Illustrated by Designs by Darley. In One Volume, 12mo, paper covers 50 cts. MODERN CHIVALRY; OR, THE ADVENTURES OF CAPTAIN FARRAGO AND TEAGUE O'REGAN. By H. H. Brackenridge. Second Edition since the Author's death. "With a Biographical Notice, a Critical Disquisition on the Work, and Ex- planatory Notes. With Illustrations, from Original Designs, by Daklet. Two Volumes, paper covers Ii'ok Cloth or sheep $1.25 12 PUBLICATIONS OF HENRY CAREY BAIRD. THE COMPLETE WORKS OF LORD BOLINGBROKE : With a Life, prepared expressly for this Edition, containing Additional Information relative to his Personal and Public Character, selected from the best authorities. In Four Volumes, 8vo. Bound in cloth $6.00 In sheep $7.50 FAMILY ENCYCLOPEDIA Of Useful Knowledge and General Literature; containing about Four Thousand Articles upon Scientific and Popular Subjects. With Plates. By John L. Blake, D. D. In One Volume, 8vo, full bound $5 CHRONICLES OF PINEVILLE. By the Author of " Major Jones's Courtship." Illustrated by Darley. 12mo, paper 50 cts. Cloth 62 cts. GILBERT GURNEY. By Theodore Hook. With Illustrations. In One Volume, 8vo, paper 50 cts. MEMOIRS OF THE GENERALS, COMMODORES, AND OTHER COMMANDERS, "Who distinguished themselves in the American Army and Navy, during the War of the Revolution, the War with France, that with Tripoli, and the War of 1812, and who were presented with Medals, by Congress, for their gallant services. By Thomas Wyatt, A. M., Author of "History of the Kings of France." Illustrated with Eighty-two Engravings from the Medals. 8vo, cloth gilt $2.00 Half morocco $2.50 VISITS TO REMARKABLE PLACES : Old Halls, Battle Fields, and Scenes Illustrative of striking passages in English History and Poetry. By William Howitt. In Two Volumes, 8vo, cloth $3.50 THE MISCELLANEOUS WORKS OF WILLIAM HAZLITT ; Including Table-talk ; Opinions of Books, Men and Things ; Lectures on Dramatic Literature of the Age of Elizabeth ; Lectures on the Eng- lish Comic Writers ; The Spirit of the Age, or Contemporary Portraits. Five Volumes, 12mo, cloth $5.00 Half calf $6.25 FLORAL OFFERING : A Token of Friendship. Edited by Frances S. Osgood. Il- lustrated by 10 beautiful Bouquets of Flowers. In One Volume, 4to, muslin, gilt edges $3.50 Turkey morocco super extra $5.50 THE HISTORICAL ESSAYS, Published under the title of " Dix Ans D' Etude Historique," and Narratives of the Merovingian Era ; or, Scenes in the Sixth Century. With an Autobiographical Preface. By Augustus Thierry, Author of the "History of the Conquest of England by the Normans." 8vo, paper 75 cts. Cloth $1.00 PUBLICATIONS OF HENRY CAREY BAIRD. 13 BOOK OF THE SEASONS ; Or, The Calendar of Nature. By William Howttt. One Volume, 12mo. Cloth * $1 Calf extra $2 NOTES OF A TRAVELLER On the Social and Political State of France, Prussia, Switzer- land, Italy, and other parts of Europe, during the present Century. By Samuel Laing. In One Volume, 8vo, cloth $1 HISTORY OF THE CAPTIVITY OF NAPOLEON AT ST. HELENA. By General Count Montholon, the Emperor's Companion in Exile and Testamentary Executor. One Volume, 8vo, cloth $2.50 Half morocco , $3.00 MY SHOOTING BOX. By Frank Forrester, (Henry Wm. Herbert, Esq.,) Author of " Warwick Woodlands," &c. With Illustrations, by Darley. One Volume, 12mo, cloth 62 cts. Paper covers 50 cts. MYSTERIES OF THE BACKWOODS : Or, Sketches of the South-west — including Character, Scenery, and Rural Sports. By T. B. Thorpe, Author of " Tom Owen, the Bee-Hunter," &c. Illustrated by Dakley. 12mo, cloth 62 cts. Paper , 50 cts. NARRATIVE OF THE LATE EXPEDITION TO THE DEAD SEA. From a Diary by one of the Party. Edited by Edward P. Montague. 12mo, cloth $1 MY DREAMS: A Collection of Poems. By Mrs. Louisa S. McCord. 12mo, boards 75 cts. RAMBLES IN YUCATAN : Or, Notes of Travel through the Peninsula : including a Visit to the Remarkable Ruins of Chi-chen, Kabah, Zayi, and Uxmal. With numerous Illustrations. By B. M. Norman. Seventh Edition. In One Volume, octavo, cloth $2 PICKINGS FROM THE " PORTFOLIO OF THE REPORTER OF THE NEW ORLEANS PICAYUNE ;" Comprising Sketches of the Eastern Yankee, the Western Hoosier, and such others as make up Society in the great Metropolis of the South. With Designs by Darley. 18mo, paper 50 cts. Cloth 62 cts. THE AMERICAN IN PARIS. By John Sanderson. A New Edition. In Two Volumes, 12mo, cloth $1 This is the most animated, graceful, and intelligent sketch of French manners, or any other, that we have had for these twenty years. — London Monthly Magazine. B 14 PUBLICATIONS OF HENRY CAREY BAIRD. AMERICAN COMEDIES. By James K. Paulding and Wi. Irving Paulding. One Volume, 16mo, boards 50 cts. ROBINSON CRUSOE. A Complete Edition, with Six Illustrations. One Volume, 8vo, paper covers $1.00 Cloth, gilt edges $1.25 SCENES IN THE ROCKY MOUNTAINS, And in Oregon, California, New Mexico, Texas, and the Grand Prairies ; or, Notes by the Way. By Rufus B. Sage. Second Edition. One Volume, 12mo, paper covers 50 cts. With a Map, bound in cloth 75 cts. THE PUBLIC MEN OF THE REVOLUTION : Including Events from the Peace of 1783 to the Peace of 1815. In a Series of Letters. By the late Hon. Wm. Sullivan, LL. D. With a Bio- graphical Sketch of the Author, by his son, John T. S. Sullivan. With a Por- trait. In One Volume, 8vo, cloth.. $2 ACHIEVEMENTS OF THE KNIGHTS OF MALTA. By Alexander Sutherland. In One Volume, 16mo, cloth $1.00 Paper 75 cts. ATALANTIS. A Poem. By William Gilmore Simms. 12mo, boards 37 cts. NARRATIVE OF THE ARCTIC LAND EXPEDITION. By Captain Back, R. N. In One Volume, 8vo, boards • $1.50 LIVES OF MEN OF LETTERS AND SCIENCE. By Henry Lord Brougham. Two Volumes, 12mo, cloth $1.50 Paper $1.00 THE LIFE, LETTERS, AND JOURNALS OF LORD BYRON. By Thomas Moore. Two Volumes, 12mo, cloth $2 THE BOWL OF PUNCH. Illustrated by Numerous Plates. 12mo, paper 50 cts. CHILDREN IN THE WOOD. Illustrated by Harvey. 12mo, cloth, gilt 50 cts. Paper 25 cts. CHARCOAL SKETCHES. By Joseph C. Neal. With Illustrations. 12mo, paper 25 cts. THE POEMS OF C. P. CRANCH. In One Volume, 12mo, boards 37 cts. GEMS OF THE BRITISH POETS. By S. C. Hall. In One Volume, 12mo, cloth $1.00 Cloth, gilt $1.25 PUBLICATIONS OF HENRY CAREY BAIRD. 15 A SYSTEMATIC ARRANGEMENT OF LORD COKE'S FIRST INSTITUTES OF THE LAWS OF ENGLAND. By J. H. Thomas. Three Volumes, 8vo, law sheep $12 . THE WORKS OF BENJ. DISRAELI. Two Volumes, 8vo, cloth $2 Paper covers $1 NATURE DISPLAYED IN HER MODE OF TEACHING FRENCH. By N. G. Dufief. Two Volumes, 8vo, boards $5 NATURE DISPLAYED IN HER MODE OF TEACHING SPANISH. By N. G. Dufief. Li Two Volumes, 8vo, boards $7 FRENCH AND ENGLISH DICTIONARY. By N. G. Dufief. In One Volume, 8vo, sheep $5 FROISSART BALLADS AND OTHER POEMS. By Philip Pendleton Cooke. In One Volume, 12mo, boards 50 cts. AN ACCOUNT OF SOME OF THE MOST IMPORTANT DISEASES OF WOMEN. By Robert Gooch, M. D. In One Volume, 8vo, sheep $1.50 THE LIFE OF RICHARD THE THIRD. By Miss Halsted. In One Volume, 8vo, cloth $1.50 THE LIFE OF NAPOLEON BONAPARTE. By William Hazlitt. In Three Volumes, 12mo, cloth $3 Half calf. $4 TRAVELS IN GERMANY, BY W. HOWITT. EYRE'S NARRATIVE. BURNE'S CABOOL. In One Volume, 8vo, cloth $1.25 STUDENT LIFE IN GERMANY. By William Howitt. In One Volume, 8vo, cloth $2 IMAGE OF HIS FATHER. By Mathew. Complete in One Volume, 8vo, paper 25 cts. TRAVELS IN AUSTRIA, RUSSIA, SCOTLAND, ENGLAND AND WALES. By J. G. Kohl. One Volume, 8vo, cloth $1.25 A TOUR TO THE RIVER SAGUENAY, IN LOWER CANADA. By Charles Lanman. In One Volume, 16mo, cloth 62 cts. Paper 50 cts. SPECIMENS OF THE BRITISH CRITICS. By Christopher North (Professor Wilson). 12mo, cloth 75 cts. THE LIFE OF OLIVER GOLDSMITH. By James Prior. In One Volume, 8vo, boards $2 MRS. CAUDLE'S CURTAIN LECTURES : 12J cts / 16 PUBLICATIONS OF HENRY CAREY BAIRD. OUR ARMY AT MONTEREY. By T. B. Thorpe. 16mo, cloth 62 cts Paper covers ......"'.i'.ilisQ cts! OUR ARMY ON THE RIO GRANDE. By T. B. Thorpe. 16mo, cloth * 62 cts Paper covers ......"L'.'.'.'.vSO cts. THE LIFE OF LORENZO DE MEDICI. By William Roscoe. In Two Volumes, 8vo, cloth $3 THE MISCELLANEOUS ESSAYS OF SIR WALTER SCOTT. In Three Volumes, 12mo, cloth $3.50 Half morocco $4.25 SERMON ON THE MOUNT. Illuminated. Boards |j 50 SZZllZZZZ\ZZ'.lZ$£w " Morocco super $3.00 THE MISCELLANEOUS ESSAYS OF THE REV. SYDNEY SMITH. In Three Volumes, 12mo, cloth $3 50 Half morocco ZZZZZZZ 25 SERMONS BY THE REV. SYDNEY SMITH. One Volume, 12mo, cloth 75 cts THE MISCELLANEOUS ESSAYS OF SIR JAMES STEPHEN. One Volume, 12mo, cloth $j 25 THREE HOURS ; OR THE VIGIL OF LOVE. A Volume of Poems. By Mrs. Hale. 18mo, boards 75 c t 3 TORLOGH O'BRIEN : A Tale of the Wars of King James. 8vo, paper covers 12* cts Illustrated ZZZZtf] cts, AN AUTHOR'S MIND. Edited by M. F. Tupper. One Volume, 16mo, cloth 6? cts Paper covers ZZZZZ'.^tB, HISTORY OF THE ANGLO-SAXONS. By Sharon Turner. Two Volumes, 8vo, cloth $4.50 THE PROSE WORKS OF N. PARKER WILLIS. In One Volume, 8vo, 800 pp., cloth, gilt $3 qo Cloth extra, gilt edges $3 50 Library sheep ....... ZZZZZZZZZ'.ZZZZ'. ZZ'MM Turkey morocco backs $3 -.5 extra ....v.v.y.i" 11; ".*//.*". *. r.'.ls'so THE MISCELLANEOUS ESSAYS OF PROFESSOR WILSON. Three Volumes, 12mo, cloth $3 50 WORD TO WOMAN. By Caroline Fry. 12mo, cloth 60 cts. WYATT'S HISTORY OF THE KINGS OF FRANCE. Illustrated by 72 Portraits. One Volume, 16mo, cloth $1 00 Cloth, extra gilt $1 25