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 ELEMENTS 2J^^-t 
 
 r 
 
 TECHNOLOGY, 
 
 TAKEN CHIEFLY FROM 
 
 A COURSE OF LECTURES 
 
 DELIVERED 
 
 I 
 
 AT CAMBRIDGE, 
 
 ON THE 
 
 APPLICATION OF THE SCIENCES 
 
 TO THE 
 
 USEFUL ARTS. 
 
 NOW PUBLISHED 
 
 FOR THE USE OF SEMINARIES AND STUDENTS. 
 
 BY JACOB BIGELOW, M. D. 
 
 u 
 Professor of Materia Medica, and late Rumford Professor in Harvard University; Mem- 
 ber of the American Academy of Arts and Sciences ; of the American Philosophical 
 Society ; of the Idnnasan Societies of London and Paris, &c. 
 
 SECOND EDITION, 
 
 WITH ADDITIONS. 
 
 BOSTON; 
 HILLIARD, GRAY, LITTLE AND WILKINS. 
 
 1831. 
 
f4^ 
 
 3t. 
 
 \%'^^ 
 
 DISTRICT OF MASSACHUSETTS.. ..TO WIT : 
 
 District Clerk's Office. 
 Be it remembered, That on the ninth day of July, A. D. 1829 in 
 the fiftyfourth year of the Independence of the United States of America, 
 Jacob Bigelow, of the said District, has deposited in this Office the Title 
 of a Book, the right whereof he claims as Author, in the words following, 
 to wit : 
 
 ' Elements of Technology, taken chiefly from a Course of Lectures de- 
 livered at Cambridge, on the Application of the Sciences to the Useful 
 Arts. Now published for the Use of Seminaries and Students. By Jacob 
 Bigelow, M. D., Professor of Materia Medica, and late Rumford Professor 
 in Harvard University; of the American Academy of Arts and Sciences; 
 of the American Philosophical Society ; of the Linnaean Societies of Lon- 
 don and Paris, &c.' Second Edition, with Additions. 
 
 In conformity to the Act of the Congress of the United States, entitled 
 ' An Act for the encouragement of learning, by securing the copies of Maps, 
 Charts and Books, to the Authors and Proprietors of such copies, during 
 the times therein mentioned ; ' and also to an Act entitled ' An Act sup- 
 plementary to an Act, entitled, an Act for the encouragement of learning, 
 by securing the copies of Maps, Charts and Books, to the Authors and Pro- 
 prietors of such copies during the times therein mentioned ; and extending 
 the benefits thereof to the arts of designing, engraving, and etching his- 
 torical and other prints.' 
 
 JOHN W. DAVIS, Clerk of the District of Massachusetts . ' 
 
 BOSTON PRESS, WATER STREET. 
 
 wov 
 
 5y Tjransfer 
 
 V 3 1916 
 
ADVERTISEMENT 
 TO THE FIRST EDITION 
 
 A COURSE of Lectures on most of the subjects which occupy 
 this volume, has been delivered at Cambridge, during ten years 
 past, in pursuance of the vi^ill of the late Gount Rumford, by 
 whose bequest a professorship is founded in Harvard University, 
 on the Application of the Sciences to the Useful Arts. Parts 
 of the same course have been repeated in Boston, to large au- 
 diences. 
 
 The degree of interest which has been taken in these Lec- 
 tures, has led me to believe that the subject is, in itself, pecu- 
 liarly capable of exciting the attention and curiosity of students. 
 There can be no doubt that the knowledge, which this study is 
 intended to furnish, is of great use in the common affairs of life ; 
 and probably its advancement has contributed, more than that of 
 any other science, to the improved condition of the present age. 
 
 A certain degree of acquaintance with the theory and scien- 
 tific principles of the common arts, is found so generally impor- 
 tant, that most educated men, in the course of an ordinary prac- 
 tical life, are obliged to obtain it from some source, or to suffer 
 inconvenience for the want of it. He who builds a house, or 
 
IV ADVERTISEMENT. 
 
 buys an estate, if he would avoid disappointment and loss, must 
 know something of the arts, which render them appropriate, and 
 tenantable. He who travels abroad to instruct himself, or en- 
 lighten his countrymen, finds in the works of art, the most com- 
 manding objects of his attention and interest. He who remains 
 at home, and limits his ambition to the more humble object of 
 keeping his apartment warm, and himself comfortable, can on- 
 ly succeed through the instrumentality of the arts. 
 
 There has probably never been an age in which the practical 
 applications of science have employed so large a portion of the 
 talent and enterprise of the community, as in the present ; nor 
 one in which their cultivation has yielded such abundant re- 
 wards. And it is not the least of the distinctions of our own 
 country, to have contributed to the advancement of this branch 
 of improvement, by many splendid instances of inventive genius 
 and successful perseverance. 
 
 The importance of the subject, and the prevailing interest, 
 which exists in regard to the arts and their practical influences, 
 appear to me to have created a want, not yet provided for, in 
 our courses of elementary education. Information on these 
 subjects is scattered through the larger works on mechanics, 
 on chemistry, mineralogy, engineering, architecture, domestic 
 economy, the fine arts, Stc, so that it rarely happens that a 
 student in any of our colleges gathers information enough to 
 understand the common technical terms which he meets with in 
 a modern book of travels, or periodical work. It is only by 
 making the elements of the arts themselves, subjects of direct 
 attention, that this deficiency is likely to be supplied. 
 
 To embody, as far as possible, the various topics which be- 
 long to such an undertaking, I have adopted the general name 
 of Technology, a word sufficiently expressive, which is found 
 in some of the older dictionaries, and is beginning to be revived 
 in the literature of practical men at the present day. Under 
 
ADVKRTISEMENT. V 
 
 this title it is attempted to include such an account as the limits 
 of the volume permit, of the principles, processes, and nomen- 
 clatures of the more conspicuous arts, particularly those which 
 involve applications of science, and which may be considered 
 useful, by promoting the benefit of society, together with the 
 emolument of those who pursue them. 
 
 In preparing for the press the lectures on which this work is 
 founded, some variations from the original form have been made, 
 together with such additions as my leisure from professional en- 
 gagements has permitted. In doing this, occasional use has 
 been made of the works of Robison, Young, Tredgold, and sev- 
 eral of the late chemical writers. But as the present elemen- 
 tary volume is composed for the instruction of the uninitiated, 
 rather than for the perfection of adepts, it has been found ne- 
 cessary to condense and to endeavor to render intelligible the 
 subjects of consideration, rather than to dilate them by minute 
 expositions and details. For the use of those students, who 
 may wish to extend their inquiries in reference to any of the 
 particular subjects, a list of some of the more prominent authors, 
 and works of value, that treat upon the several subjects, is sub- 
 joined at the end of each chapter. Among some of these works, 
 the authorities for the facts stated in the preceding chapters, 
 will in most instances be found. 
 
 For the convenience of seminaries which may make use of 
 
 this work, the wood cuts and diagrams which are interspersed 
 
 with the text, are reprinted at the end of the volume. 
 
 J. B, 
 
ADVERTISEMENT 
 TO THE SECOND EDITION 
 
 In the present edition, it has not been thought necessary to 
 make any important deviations from the plan of the first. No 
 material part of the work has been omitted. Such additions as 
 it has been thought proper to make, will be found incorporated 
 with the text under their respective heads. 
 
 Boston, June, 1831. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 Of the Materials used in the Arts. 
 
 Materials from the Mineral Kingdom. Stones and Earths. Marble, page 
 7. Granite. 8. Sienite. 10. Freestone. Slate. Soapstone. 10. Serpentine. 
 Gypsum. 11. Alabaster. Chalk. Fluor Spar. Flint. Porphyry. 12. Buhr- 
 stone. Novaculite. Precious Stones. Emery. 13. Sand. Pumice. 14. 
 Tufa. Peperino. Tripoli. Clay. Asbetus. 15. Cements. Limestone. 16. 
 Puzzolana. 17. Tarras. Other Cements. 18. Maltha. Metals. Iron. Cop- 
 per. 20. Lead. Tin. 21. Mercury. Gold. Silver. Platinum. Zinc. 22. 
 Antimony. Bismuth. Arsenic. Manganese. 23. Combustibles, <^c. Bitu- 
 men. Amber. Coal. Anthracite. 24. Graphite. Peat. Sulphur. 25. 
 Materials from the Vegetable Kingdom. Wood. Bark. Oak. 26. Hicko- 
 ry. Ash. Elm. Locust. 27. Wild Cherry. Chesnut. Beech. Basswood. 
 Tulip Tree. 28. Maple. Birch. Button Wood. 29. Persimmon. Black 
 Walnut. Tupelo. Pine. 30. Spruce. Hemlock. White Cedar. Cypress. 
 Larch, 31. Arbor Vita. Red Cedar. Willow. Mahogany. 32. Boxwood. 
 Lignum Vita. Cork. Hemp. Flax. 33. Cotton. 34. Turpentine. Caout- 
 chouc. 35. Oils. 36. Resins. Starch. Gum. 37. Materials from the 
 Animal Kingdom. Skins. Hair and Fur. auills, and Feathers. 38. 
 Wool. Silk. 39. Bone and Ivory. Horn. Tortoise Shell. Whale Bone. 40. 
 Glue. Oil. 41. Wax. Phosphorus. 42. 
 
 CHAPTER II. 
 
 Of the Form, Condition, and Strength of Materials. 
 
 Modes of Estimation. Stress and Strain. 43. Resistance. Extension. 44. 
 Compression. 45. Lateral Strain. Stifihess. 46. Tubes. Strength. 47. 
 Place of Strain. Incipient Fracture. Resilience. 48. Shape of Timber. Torsion. 
 Limit of Bulk. 49. Practical Remarks. 50. 
 
X CONTENTS. 
 
 * CHAPTER III. 
 
 The Arts of Writing and Printing. 
 
 Letters. Invention of Letters. 54. Arrangement of Letters. Writing Ma- 
 erials. 55. Papyrus. 56. Herculaneum Manuscripts. 57. Parchment. 58. 
 Paper. Instruments. Ink. 59. Cop3'ing Machines. 60. Printing. 61. Types. 
 Case. Sizes. Composing. 62. Imposing. 63. Signatures. Correcting the 
 Press. 64. Press Work. Printing Press. Stereotyping. 67. Machine 
 Printing. 68. History. 69. 
 
 CHAPTER IV. 
 
 Arts of Designing and Painting. 
 
 Divisions. Perspective. 72. Field of Vision. Distance and Foreshortening. 
 73. Definitions. 74. Plate II. 76. Problems. 77. Instrumental Perspec- 
 live. 78. Mechanical Perspective. Perspectographs. 80. Projections. 81. 
 Isometrical Perspective. 82. Chiaro Oscuro. Light and Shade. 83. Asso- 
 ciation. Direction of Light. 84. Reflected Light. Expression of Shape. 85. 
 Eyes of a Portrait. Shadows. Aerial Perspective. 86. Coloring. Colors. 
 87. Shades. Tone. Harmony. 88. Contrast. Remarks. 89. 
 
 CHAPTER V. 
 
 Arts of Engraving and Lithography. 
 
 Engraving. Origin. Materials. 91. Instruments. Styles. Line En- 
 graving. 92. Stippling. Etching. 94. Mezzo Tinto. 96. Aqua Tinta. 97. 
 Copperplate Printing. Colored Engravings. 99. Steel Engraving. Wood 
 Engraving. 100. Lithography. Principles. Origin. 101. Lithographic Stones. 
 102. Preparation. Lithographic Ink and Chalk. Mode of Drawing. 103. 
 Etching the Stone. 104. Printing. Printing Ink. Remarks. 105. 
 
 CHAPTER VI. 
 
 Of Sculpture, Modelling, and Casting. 
 
 Subjects. Modelling. 107. Casting in Plaster. 108. Bronze Casting. 
 Practice of Sculpture. 110. Materials. 111. Objects of Sculpture. Gem 
 Engraving. Cameos. Intaglios. 112. Mosaic. Scagliola. 113. 
 
CONTENTS. Xi 
 
 CHAPTER VII. 
 
 Of Architecture and Building. 
 
 Architecture. Elements. Foundations. 115. Column. 116. Wall. 117. 
 Lintel. Arch. 119. Abutments. 121. Arcade. Vault. Dome. 122. Plate 
 I. 124. Roof. 127. Styles of Building. Definitions. 129. Measures. Draw 
 ings. Restorations. 131. Egyptian Style. 132. The Chinese Style. 133. 
 The Grecian Style. Orders of Architecture. Doric Order. 134. Ionic Order. 
 Corinthian Order. 135. Caryatides. Grecian Temple. 136. Grecian Thea- 
 tre. 139. Remarks. Plate IV. 140. Roman Style. Tuscan Order. Ro- 
 man Doric. Roman Ionic. 141. Composite Order. 143. Roman Structures. 
 Remarks. 144. Plate V. 145. Greco-Gothic Style. 147. Saracenic Style. 
 Gothic Style. 148. Definitions. 149. Plate VI. Plate VII. 151. Applica- 
 tion. 153. 
 
 CHAPTER VIII. 
 
 Arts of Heating and Ventilation. 
 
 Production of Heat. Fuel. Weight of Fuel. 155. Combustible Matter of 
 Fuel. Water in Fuel. 156. Charcoal. 157. Communication of Heat. Radi- 
 ated and Conducted Heat. Fire in the Open Air. 158. Fire Places. 159. 
 Admission of Cold Air. Open Fires. Franklin Stove. 160. Rumford Fire 
 Place. 161. Double Fire Place. 162. Coal Grate. 163. Anthracite Grate. 
 Burns' Grate. Building a Fire. 164. Furnaces. Stoves. 165. Russian Stove. 
 167. Cockle. Cellar Stoves, and Air Flues. 167. Heating by Steam. 169. 
 Retention of Heat. Causes of Loss. 170. Crevices. Chimnies. Entries and 
 Sky Lights. 171. Windows. Ventilation. Objects. Modes. 172. Ventilators. 
 Culverts. Smoky Rooms. 173. Damp Chimnies. Large Fire Places. 174. 
 Close Rooms. Continguous Doors. S'hort Chimnies. Opposite Fire Places. 175. 
 Neighboring Eminences. Turncap, &c. Contiguous Flues. 176. Burning 
 of Smoke. 177. 
 
 CHAPTER IX. 
 
 Arts of Illumination. 
 
 Flame. Support of Flame. 178. Torches and Candles. Lamps. 179. Re- 
 servoirs. Astral Lamp. 180. Hydrostatic Lamps. 181. Automaton Lamp. 
 Mechanical Lamps. Fountain Lamp. 182. Argand Lamp. 183. Reflectors. 
 Hanging of Pictures. 184. Transparency of Flame. Glass Shades. Sinumbral 
 
XU CONTENTS. 
 
 Lamp. Measurement, of Light. 185. Ga« Lights. 186. Coal Gas. 187. Oil 
 Gas. 189. Gasmeter. Portable Gas Lights. Safety Lamp. 190. Lamp with- 
 out Flame. 191. Modes of procuring Light. 192. 
 
 CHAPTER X. 
 
 Arts of Locomotion. 
 
 Motion of Animals. 195. Inertia. Aids to Locomotion. 196. Wheel Car- 
 riages. Wheels. 197. EoUers. Size of Wheels. 198. Line of Traction. 199. 
 Broad Wheels. 200. Form of Wheels. 201. Axletrees. Springs. Attaching 
 of Horses. 202. Highways. Roads. Pavements. 204. McAdam Roads. 205. 
 Bridges. 1. Wooden Bridges. 2. Stone Bridges. 206. 3. Cast Iron Bridges, 
 4. Suspension Bridges. 207. 5. Floating Bridges. Rail Roads. 208. Edge 
 Railway. 209. Tram Road. 210. Single Rail. Passings. 211. Propelling 
 Power. 212. Canals. Embankments. 214. Aqueducts. Tunnels. Gates and 
 Weirs. Locks. 215. Boats. Size of Canals. 217. Sailing. Form of a Ship. 
 218. Keel and Rudder. Effect of the Wind. 220. Stability of a Ship. 222. 
 Steam Boats. 223. Diving Bell. 225. Submarine Navigation. 226. Aeros- 
 tation. Balloon. 228. Parachute. 229. 
 
 CHAPTER XI. 
 
 Elements of Machinery. 
 
 Machines. Motion. 231. Rotary or Circular Motion. Band Wheels. 232. 
 Rag Wheels. Toothed Wheels. 233. Spiral Gear. 234. Bevel Gear. 235. 
 Crown Wheel. Universal Joint. Perpetual Screw. 236. Brush Wheels. 
 Ratchet Wheel. Distant Rotary Motion. 237. Change of Velocity. 238. 
 Fusee. 239. Alternate or Reciprocating Motion. Cams. 240. Crank. 242. 
 Parallel Motion. 243. Sun and Planet Wheel. 244. Inclined Wheel. Epicy- 
 cloidal Wheel. 245. Rack and Segment. 246. Rack and Pinion. Belt and 
 Segment. Scapements. 247. Continued Rectilinear Motion. 248. Band. 
 Rack. Universal Lever. 249. Screw. Change of Direction. Toggle Joint. 
 250. Of Engaging and Disengaging Machinery. 251. Of Equalizing 
 Motion. Governor. 252. Fly Wheel. 254. Friction. 255. Remarks. 256. 
 
 CHAPTER XII. 
 
 Of the Moving Forces used in the Arts. 
 
 Sources of Power. Vehicles of Power. 257. Animal Power. Men. 258. 
 Horses. 260. Water Poicer. Overshot Wheel. 261. Chain Wheel. 264. 
 
CONTENTS. XIU 
 
 Undershot Wheel. 265. Back Water. 267. Besant's Wheel. Lambert's 
 Wheel. 268. Breast Wheel. 269. Horizontal Wheel. Barker's Mill. 270. 
 Wind Power. 271. Vertical Windmill. Adjustment of Sails. 272. Horizon- 
 tal Windmill. Steam Power. Steam. 274. Applications of Steam. 277. By 
 Condensation. 278. By Generation. 279. By Expansion. 280. The Steam 
 Engine. 281, Boiler. 282. Appendages. 283. Engine. Noncondensing 
 Engine. 287. Condensing Engines. 289. Description. 290. Expansion 
 Engines. 293. Valves. 294. Pistons. Parallel Motion. 295. Historical Re- 
 marks. 296. Projected Improvements. Rotative Engines. 298. Use of Steam 
 at High Temperatures. Use of Vapors of Low Temperature. 299. Gas En- 
 gines. 300. Steam Carriages. Steam Gun. 301. Gunpowder. Manufacture. 
 302. Detonation. Force. 303. Properties of a Gun. 305. Blasting. 306. 
 
 CHAPTER XIII. 
 
 Arts of Conveying "Water. 
 
 Of Conducting Water. Aqueducts. 308. Water Pipes. 309. Friction of 
 Pipes. 311. Obstruction of Pipes. 3X2. Syphon. Of Raising Water. ZlA. 
 Scoop Wheel. Persian Wheel. 315. Noria. Rope Pump. Hydreole. 316. 
 Archimedes' Screw. 317. Spiral Pump. 318. Centiifugal Pump. 319. Com- 
 mon Pumps. 320. Forcing Pump. Plunger Pump. 321. Delahire's Pump. 
 322. I-Iydrostatic Press. Lifting Pump. 323. Bag Pump. Double Acting 
 Pump. 324. Rolling Pump. Eccentric Pump. 325. Arrangement of Pipes. 
 Chain Pump. 326. Schemnitz Vessels, or Hungarian Machine. Hero's 
 Fountain. 328. Atmospheric Machines. Hydraulic Ram. 329. Of Project- 
 ing Water. 330. Fountains. 331. Fire Engines. 332. Throwing Wheel, 333. 
 
 CHAPTER XIV. 
 
 Arts of Dividing and Uniting Solid Bodies. 
 
 Cohesion. Modes of Division. Fracture. 334. Cutting. Cutting Machines. 
 335. Penetration. Boring and Drilling. 336. Turning. 337. Attrition. 
 Sawing. Saw Mill. Circular Saw. 338. Crushing. 339. Stamping Mill. 
 Bark Mill. Oil Mill. Sugar MiU. 340. Cider Mill. Grinding. Grist Mill. 
 341. Color Mill. 342. Modes of Union. Insertion. Interposition. 343. Bind- 
 ing. Locking. Cementing. 344. Glueing. 345. Welding. Soldering. 346. 
 Casting, Fluxes. 347. Moulds. 348. 
 
XIV CONTENTS. 
 
 CHAPTER XV. 
 
 Arts of Combining Flexible Fibres. 
 
 Theory of Twisting. 349. Rope Maldng. 350. Cotton Manufacture. 
 Elementary Inventions. 352. Batting. 353. Carding. Drawing. 354. Rov- 
 ing. 355. Spinning. Mule Spinning. 357. Warping. 358. Dressing. 
 Weaving. 359. Twilling. 360. Double Weaving. 361. Cross Weaving. 
 Lace. 362. Carpeting. 363. Tapestry. Velvets. 364. Linens. 365. Wool- 
 lens. Felting. 367. Paper Making. 368. 
 
 CHAPTER XVI. 
 
 Arts of Horology. 
 
 Sun Dial. 371. Clepsydra. 372. Water Clock. Clock Work. 373. Main- 
 taining Power. 374. Regulating Movement. Pendulum. 375. Balance. 376. 
 Scapement. 377. Description of a Clock. 378. Striking Part. 380. Descrip- 
 tion of a Watch. 383, 
 
 CHAPTER XVII. 
 
 Arts of Metallurgy. 
 
 Extraction of Metals. 392. Assaying. Alloys. 394. Gold. Extraction. 
 Cupellation. 396. Parting. 397. Cementation. Alloy, 398. Working. Gold 
 Beating. 399. Gilding on Metals. 400. Gold Wire. Silver. Extraction. 401. 
 Working. 402. Coining. 403. Plating. 404. Copper. Extraction. Working. 
 406. Brass. Manufacture. 407. Buttons. Pins. 408. Bronze. 409. Lead. 
 Extraction. Manufacture. Sheet Lead. 411. Lead Pipes. 412. Leaden Shot. 
 Tin. Block Tin. 413. Tin Plates. 414. Silvering of Mirrors. 415. Iron. 
 Smelting. 416. Crude Iron. Casting. 417. Malleable Iron. 419. Forging. 
 420. Rolling and Slitting. 421. Wire Drawing. 422. JNTail Making. Gun 
 Making. 423. Steel. 424. Alloys of Steel. 425. Case Hardening. Temper- 
 ing. 426. Cutlery. -429. 
 
 CHAPTER XVIII. 
 
 Arts of Communicating and Modifying Color. 
 
 Of Applying Superficial Color. Painting. Colors. 433. Blues. 434. Reds. 
 435. Yellows. Greens. 436. Browns. Blacks. 437. Whites. Preparation. 
 
CONTENTS, XV 
 
 Application. Crayons. 438. Water Colors. Distemper. 439. Fresco. En- 
 caustic Painting. Oil Painting. 440. Varnishing. 441. Japanning. 443. 
 Polishing. Lacquering. 44i. Gilding. 445. Of Changing Intrinsic Color. 
 Bleaching. 446. Dyeing. 447. Mordants. Dyes. 448. Calico Printmg. 452. 
 
 CHAPTER XIX. 
 
 Arts of Vitrification. 
 
 Glass. Materials. 456. Crown Glass. Fritting. Melting. 458. Blowing. 
 Annealing. 459. Broad Glass. FUnt Glass. Bottle Glass. 460. Cylinder 
 Glass. Plate Glass. 461. Moulding. Pressing. 463. Cutting. Stained Glass. 
 464. Enamelling. 466. Artificial Gems. Devitrification. Reaumur's Porce- 
 lain. 467. Crystallo-Ceramie. Glass Thread. 468. Remarks. 469. 
 
 CHAPTER XX. 
 
 Arts of Induration by Heat. 
 
 Bricks. 471. Tiles. Terra Cotta. 473. Crucibles. Pottery. 474. Opera- 
 tions. 475. Stone Ware. White Ware. 476. Throwing. 477. Pressing. 
 Casting. Bui'ning. 478. Printing. Glazing. 479. China Ware. 480. Euro- 
 pean Porcelain. 481. Etruscan Vases. 482. 
 
 CHAPTER XXI. 
 
 On the Preservation of Organic Substances. 
 
 Decomposition. Temperature. 484. Dryness. 485. Wetness. Antiseptics, 
 486. Timber. Felling. 487. Seasoning. 488. Preservation of Timber. 489. 
 Preservationof Animal Textures. Embalming. 493. Tanning. 495. Parch- 
 ment. Catgut. 496. Gold Beater's Skin, Specimens in Natural History. 497- 
 Appert's Process. 499. 
 
INTRODUCTION. 
 
 Whenever we attempt to draw a dividing line between 
 the sciences, usually so called, and the arts, it results in dis- 
 tinctions, which are comparative, rather than absolute. In 
 many branches of human knowledge, the two are so blended 
 together, that it is impossible to make their separation complete. 
 In common language, we apply the name of sciences to those 
 departments of knowledge which are more speculative, or ab- 
 stract, in their nature, and which are conversant with truths 
 or with phenomena, that are in existence at the time we con- 
 template them. The arts, on the contrary, are considered as 
 departments of knowledge, which have their origin in human 
 ingenuity, which depend on the active, or formative processes of 
 the human mind, and which, without these, would not have 
 existed. Our knowledge may be said to have been found out 
 originally by discovery and invention. Discovery is the pro- 
 cess of science ; invention is the work of art. So common, 
 however, is the connexion of the two with each other, that we 
 find both a science and an art involved in the same branch of 
 study. For example, chemistry is a science depending on the 
 immutable relations of matter, which relations must have ex- 
 isted, had there never been minds to study them. Yet these 
 laws of matter would not have become the subjects of science, 
 had not mankmd invented the art of separating their agents, 
 and making them cognizable to the senses. To build a ship, 
 1 
 
A INTRODUCTION. 
 
 to construct a watch, or to paint a picture, are all operations of 
 art ; yet they all have their foundation in a certain acquaint- 
 ance with mathematical rules, and principles of natural philos- 
 ophy. Those artists, who work with a thorough knowledge of 
 principles, we are accustomed to denominate scientific ; while 
 those who experiment at random, or who blindly copy the re- 
 sults of others, we consider empirical. Thus it appears that an 
 intimate connexion and dependence exists between sciences 
 and arts, and it follows that the claim which they offer to our 
 attention is in a great measuie of the same kind. Of the lat- 
 ter, as well as the former, we already require some, as branch- 
 es of a common education ; while of the rest there are few 
 which may not be advantageously studied, either as affording 
 exercise for talents, discipline for taste, or practical advantage 
 in the common concerns of life. 
 
 The connexion of the arts with the sciences is more com- 
 mon and obvious in modern times, than it was in the days of 
 antiquity. During the process of civilization, or the whole 
 period which elapses between barbarism and complete refine- 
 ment, the arts have uniformly taken precedence both of sci- 
 ence and literature. Rude nations commence the improve- 
 ment of their state, by an attention to agriculture, to building, 
 to navigation, and to sculpture. The want of an acquaintance 
 J with the real or scientific principles of these arts, obliges them 
 I to substitute the effects of manual labor and dexterity, for sci- 
 entific method ; and hence the paths in which they excel, have 
 been usually of a different character from those of people 
 whose knowledge and resources are greater. The ancients, 
 who were but recently descended from barbarians, were obhged 
 to make the most of small means, because the stock of pre- 
 vious or common information, from which they could draw, 
 was extremely limited. The moderns have the accumulated 
 learning of ages before them, and have only to select and ap- 
 ply their agents from among a multitude of means already - 
 discovered. The qualities, by which the former arrived 
 at excellence, were more or less concentrated in individuals ; 
 
INTRODUCTION. O 
 
 while with us the means of excellence are recorded in books, 
 and are at the disposal of communities. They possessed 
 the quick eye, the expert hand, acute taste and unwea- 
 ried industry. For these we substitute preparatory sci- 
 ence, economical computation, and mechanical power. Their 
 processes ditfered from ours, as the process of the sav- 
 age who fashions and polishes his war-club, by the truth 
 of his eye, and the patience and dexterity of his hand ; 
 differs from that of the civilized mechanic, who turns the 
 saine kind of thing, in a lathe, which another man has in- 
 vented for him, in a hundredth part of the time. The ancients 
 were prodigal of means, and lavished men and treasures when 
 any great work was to be acconoplished. The moderns save 
 expense, and labor, and time in everything. The economy 
 of the ancients consisted in diminishing their personal wants ; 
 ours, in devising cheap means to gratify them. They pre- 
 pared their soldiers for war by inuring them to hunger and 
 fatigue ; we, by keeping them well fed and clothed. Their 
 stateliest edifices were destitute of chimnies and glass win- 
 dows, yet when left to themselves, they have stood for thou- 
 sands of years. Ours abound in the means of making their 
 present tenants comfortable, but are often built too cheaply to 
 be durable. They conveyed water to their cities in immense 
 horizontal channels supported on arcades of prodigious eleva- 
 tion. We convey it over mountains and under vallies in hy- 
 draulic pipes of the most trivial size. Wherever art could pre- 
 cede philosophy, the ancients have exhibited the grandest 
 productions of genius and strength ; but, in the appUcation of 
 philosophy to the arts, the moderns have achieved what neither 
 genius nor strength, unassisted, could have performed. The 
 imitative arts, and those which required only boldness and 
 beauty of design, or perseverance in execution, were car- 
 ried in antiquity to the most signal perfection. Their sculp- 
 ture has been the admiration of subsequent ages, and their ar- 
 chitecture has furnished models which we now strive to imi- 
 tate, but do not pretend to excel. We might, if this were the 
 
^ INTRODUCTION. 
 
 place, add their poetry, and tTieir oratory, to the list of arts 
 which flourished in perfection during the youthfulness of intel- 
 lectual cultivation. But in modern times there is a maturity, 
 a cautiousness, a habit of induction, which is founded on the 
 advanced state of philosophic knowledge. Our arts have 
 been the arts of science, built up from an acquaintance with 
 principles, and with the relations of cause and effect. With 
 less bodily strength, and probably with not more vigorous in- 
 tellects, we have acquired a dominion over the physical and 
 moral world, which nothing but the aid of philosophy could 
 have enabled us to establish. We convert natural agents into 
 ministers of our pleasure and power, and supply our deficien- 
 cies of personal force by the application of acquired knowledge. 
 Among us, to be secure, it is not necessary that a man should 
 be powerful and alert ; for even where laws fail, the weak 
 take rank with the strong, because the weakest man may arm 
 himself with the most formidable means of defence. The la- 
 bor of a hundred artificers is now performed by the operations 
 of a single machine. We traverse the ocean in security, be- 
 cause the arts have furnished us a more unfailing guide than 
 the stars. We accomplish what the ancients only dreamt of 
 in their fables ; we ascend above the clouds, and penetrate in- 
 to the abysses of the ocean. 
 
 The application of philosophy to the arts is a more fruitful 
 theme, than can well be condensed into a limited work, or 
 course of instruction. While it comprises some of the sources 
 even of ancient refinement, it includes a great part of the 
 grounds of modern superiority. The application of philosophy 
 to the arts may be said to have made the world what it 
 is at the present day. It has not only affected the physical, 
 but has changed the moral and political condition of society. 
 The invention of the printing press, dispersed the darkness of 
 the middle ages, and carried truth and knowledge to every 
 portion of the world. The artificial combination of sulphur, 
 nitre, and charcoal, has revolutionized the customs and the arts 
 of war, and even in military life, has given the mind the ad- 
 
INTRODUCTION. 5 
 
 vantage over the body. The moderns have imparted magnet- 
 ism to a piece of steel, and suspended it on a pivot ; and what 
 has been the consequence ? It has opened to them a path 
 across unknown seas, and lias disclosed a new continent to 
 the inhabitants of the old, a successor to their arts and their 
 power. It has developed the wealth of unknown islands, has 
 brought the remotest countries together, and has made the 
 ocean the resort and support of multitudes. Let any one, who 
 would know what modern arts have accomplished, compare 
 the repeating watch, and the unerring chronometer of the 
 present day, with the rude sun-dial and clepsydra of the an- 
 cients. Let him consider the multiplied advantages which 
 attend the invention of glass, which has enabled us to com- 
 bine light with warmth in our houses ; which has given sight 
 to the aged, w^hich has opened the heavens to the astronomer, 
 and the wonders of microscopic life to the naturalist. Let him 
 attend to the complicated engines and machinery, which are 
 now introduced into almost every manufacturing process, and 
 which render the physical laws of inert matter a substitute for 
 human strength. 
 
 But it is not the contrast with antiquity alone, that enables 
 us to appreciate the benefits which modern arts confer. In 
 the present inventive age, even short periods of time bring with 
 them momentous changes. Every generation takes up the 
 march of improvement where its predecessors had stopped, and 
 every generation leaves to its successors an increased circle of 
 advantages and acquisitions. . Within the memory of many 
 who are now upon the stage, new arts have sprung up, and 
 practical inventions, with dependent sciences ; bringing with 
 them consequences which have diverted the industry, and 
 changed the aspect of civilized countries. The augmented 
 means of public comfort and of individual luxury, the expense 
 abridged and the labor superseded, have been such, that we 
 could not return to the state of knowledge which existed even 
 fifty or sixty years ago, without suffering both intellectual and 
 physical degradation. At that time, philosophy was far distant 
 
b INTRODUCTION. 
 
 from its present mature state, and the arts which minister to 
 national wealth were in comparative infancy. No man then 
 knew the composition of the atmosphere, or of the ocean. 
 The beautiful and intricate machinery, which weaves the fa- 
 bric of our clothing, was not even in existence. When George 
 III. visited the works of Messrs Boulton and Watt, at Birming- 
 ham, and was told that they were manufacturing an article of 
 which kings were fond, and that that article was power ; he 
 was struck with the force and disadvantageousness of the com- 
 parison. Yet the steam engine had not then been launched up- 
 on the ocean, and had developed only half its energies. 
 
 So long as the arts continue to exert the influence, and to 
 yield the rewards, which they have hitherto done, there will 
 be no want of competent minds and hands, to carry forward 
 their advancement. With their increasing consequence, there 
 must also be an increasing attention to their study and dissem- 
 v-ination. Curiosity keeps pace with the interest and magni- 
 / tude of its objects. And unless the character of the present 
 age is greatly mistaken, the time may be anticipated as near, 
 when a knowledge of the elements and language of the arts 
 will be as essentially requisite to a good education, as the exist- 
 ence of the same arts is to the present elevated condition of 
 society. 
 
ELEMENTS OF TECHNOLOGY. 
 
 CHAPTER I. 
 
 OF MATERIALS USED IN THE ARTS. 
 
 The mineral, vegetable, and animal kingdoms, respectively 
 contribute to supply the substances which are necessary in the 
 arts. Of these substances, many have been known and used 
 from the time of the earliest records ; others are of recent in- 
 troduction, and additions are still making to the stock pre- 
 viously known. The value of a substance to the arts, may be 
 estimated from the importance of the object it fulfils, its dura- 
 bihty, the number of purposes to which it may be applied, and 
 the facility with which it is convertible to use. 
 
 MATERIALS FROM THE MINERAL KINGDOM. 
 
 Stones and Earths. — Marble. — The class of stones de- 
 nominated calcareous.! is exceedingly numerous and abundant 
 in nature. Of these, marble is the most important. It is a 
 granular carbonate of lime, varying in color, texture, and 
 hardness. Marble is extensively used for building, statuary, 
 decorations, and inscriptions. In warm countries it is one of 
 the most durable of substances, as is proved by the edifices of 
 Athens, which have retained their polish for more than two 
 thousand years. Severe frost, preceded by moisture, causes it 
 
8 MATERIALS USED IN THE ARTS. 
 
 to crack and scale. Great heat reduces it to quicklime. Mar- 
 ble is wrought by chiseling, and by sawing with smooth plates 
 of iron, with sand and water. It is polished by rubbing with 
 sand and water, and afterwards with putty and soft sub- 
 stances. 
 
 Numerous stones of the calcareous class, more or less ap- 
 proaching to marble in their character, have been converted to 
 use in different countries. The Pyramids of Egypt are built 
 of a greyish white calcareous stone, inclosing shells.* The 
 Parthenon, and other structures of Athens, are of Pentelic 
 marble, distinguished by slight greenish veins. The mosques 
 of Constantinople are of a fine grained limestone from Pappen- 
 heim, the same which is now used in lithography. At Rome, 
 a porous whitish limestone, called tophus by the ancients, and 
 travertino by the moderns, is the material of the Coliseum, of 
 St Peter's church, &c. The ruins of Peestum are of a stone 
 nearly similar. The building called the Tomb of Theodoric, 
 at Ravenna, has a dome consisting of a single stone, which is 
 thirtyfour feet in diameter. It is a grey hmestone from Istria, 
 and is computed to have weighed, when taken from the quar- 
 ry, more than two million pounds. t Paris is built with cal- 
 careous stone, of which there are five kinds. The Portland 
 stone of which St Paul's and other edifices in London are 
 constructed, is a calcareous rock called Oolite by mineralogists. 
 Specimens of marble abound in the United States, and are 
 seen in the City Hall of New York, the United States and 
 Pennsylvania Banks, Philadelphia, the Washington Monu- 
 ment, Baltimore, (fcc. 
 
 In statuary, the Venus de Medicis, and Diana venatrix, are 
 formed of Parian marble. The Apollo de Belvidere, accord- 
 ing to Dolomieu, is made of Luni marble ; and if so, must 
 be posterior to the time of Julius Caesar, before which period 
 that quarry was not opened. 
 
 Gratiite. — Granite is apparently the oldest and the deepest 
 of rocks. It is one of the hardest and most durable which 
 * Brard. t Borgnis. 
 
MATERIALS USED IN THE ARTS. 9 
 
 have been wrought, and is obtained in larger pieces than any- 
 other rock. Granite is a compound stone, varying in color 
 and coarseness. It consists of three constituent parts ; viz. 
 quartz, the material of rock crystal ; feldspar, which gives 
 its colors, and which is the material of porcelain earth ; and 
 lastly mica, a transparent, thin, or foliated substance, which 
 affords a flexible substitute for glass, when obtained in large 
 pieces. Granite is chiefly used for building. It is split from 
 the quarries by rows of iron wedges driven simultaneously in 
 the direction of the intended fissure. This method is thought 
 by Brard to have been known to the ancient Romans and 
 Egyptians. The blocks are afterwards hewn to a plane sur- 
 face by strokes of a sharp-edged hammer. Granite is also 
 chiselled into capitals and decorative objects ; but this operation 
 is difficult, owing to its hardness and brittleness. It is polish- 
 ed by long continued friction, with sand and emery. 
 
 The largest mass of granite, known to have been transport- 
 ed in modern times, is the pedestal of the equestrian statue of 
 Peter the Great, at St Petersburgh. It is computed to weigh 
 three million pounds, and was transported nine leagues by roll- 
 ing it on cannon balls.* Those of cast-iron being crushed, 
 others of bronze were substituted. Sixty granite columns at St 
 Petersburgh consist each of a single stone twenty feet high. 
 The columns in the portico of the Pantheon at Rome, which 
 are thirtysix feet eight inches high, are also of granite.t The 
 shaft of Pom pey's Pillar, so called, t in Egypt, is sixtythree 
 feet in height, and of a single piece. It is said to be of red 
 granite, but is possibly sienite. In the Eastern part of the 
 United States, a beautiful white granite is found in various 
 places, and is now introduced in building. The new Market 
 House in Boston, the United States Bank, &.c. are made of it. 
 
 * Carburi. t Rondelet. 
 
 tThe inscription on this pillar is said by the Earl of Mountnorris, in 
 Brande's Journal, to belong to Dioclesian, and not to Pompey, as was 
 formerly supposed. 
 
 2 
 
10 MATERIALS USED IN THE ARTS. 
 
 Sienite. — This rock is related to granite, and resembles it 
 in its general characters. It consists chiefly of feldspar and 
 hornblende. Sienite is obtained in large pieces, and possesses 
 all the valuable properties of granite ; but being harder, it is 
 somewhat more difficult to chisel. It is found in Egypt, and 
 constitutes the material of many of the obelisks. The Romans 
 imported it from that country. Sienite is found abundantly 
 near Boston, and is introduced into many structures. The 
 Washington Bank and the Bunker Hill Monument consist 
 entirely of this stone. Its extreme hardness renders it one of 
 the best materials for M'Adam roads. A railway is built at 
 Quincy for transporting the stone from the quarry to the sea, 
 and the name of Quincy Stone is now commonly applied to it. 
 
 Freestone. — Freestone consists of sand, or siliceous parti- 
 cles, united by a cement. It is also called sandstone. It va- 
 ries in color, from greyish white to red and dark brown. It is 
 of moderate hardness, in general, and easily wrought by the 
 chisel. Varieties of freestone are used in building in different 
 parts of Europe. In Africa, the temple of Hermopolis is com- 
 posed of enormous masses of this stone. In America, the 
 Capitol at Washington is of the Potomac freestone, likewise 
 the fagade of St Paul's Church in Boston. This stone is used 
 for vrarious other practical purposes, particularly the grinding 
 of steel instruments, and the filtering of water. 
 
 Slate. — Slates are valuable for the property of splitting in 
 one direction, so as to afford large fragments which are perfect- 
 ly flat and thin. The best slates are those which are even, 
 compact, and sonorous ; and which absorb the least water on 
 being immersed. Slates are much used as an incombustible 
 covering for the roofs of houses. Tablets, gravestones, and 
 writing slates, are also formed from them.* 
 
 ♦Various artificial compositions have been employed as substitutes for 
 slate, in forming waterproof coverings for roofs. One of these, which ap- 
 pears to have been successftilly used in the north of Europe, is formed of 
 bolar earth, chalk, glue, pulp of paper, and linseed oil. Franklin Journal, 
 iv. 89. 
 
MATERIALS USED IN THE ARTS. 11 
 
 iSoapstone. — This stone is usually of a greyish color, mode- 
 rately soft, and having an unctuous feel, which is compared to 
 that of soap. It is remarkable for bearing heat, and sudden 
 changes of temperature, without injury. It receives a tolera- 
 ble polish. Soapstone, on account of its softness, is wrought 
 with the same tools as wood. It is sometimes used in build- 
 ing, but is not always durable. It is, however, of great impor- 
 tance in the construction of fireplaces and stoves, and is exten- 
 sively used for this purpose. Slabs of good soapstone, when 
 not exposed to mechanical injury, frequently last eight or ten 
 years, under the influence of a common fire on one side, and 
 of cold air on the other. It grows harder in the fire, but does 
 not readily crack, nor change its dimension sufficiently to af- 
 fect its usefulness. Owing to the facility with which it is 
 wrought, its joints may be made sufficiently tight without de- 
 pendence on cement. Among the best quarries for fire-proof 
 stone, is that of Francestown, New Hampshire. Soapstone is 
 manufactured into various vessels and utensils, and is advan- 
 tageously employed for aqueducts. It is lately found to be one 
 of the best materials for counteracting friction in machinery, 
 for which purpose it is used in powder mixed with oil. 
 
 /Serpentine. — Serpentine is a smooth, compact stone, more 
 or less of a greenish color, composed chiefly of magnesia and si- 
 lex. It is sufficiently soft to be scratched with a knife, and 
 receives a polish like that of marble. It is used in building, in 
 Florence and other parts of Italy, and, in Saxony, is wrought 
 into many small articles of ornament. 
 
 Gypsum. — Gypsum, called in commerce Plaster of Pa- 
 ris, is a sulphate of lime, of which there are many varieties. 
 When dried by heat, ground to fine powder, and mixed with 
 water, it has the property of becoming hard in a few minutes, 
 and of receiving accurately the impression of the most delicate 
 moulds. It is extensively employed for stucco working, and 
 plastering of rooms. It furnishes a delicate, white, and smooth 
 material for casts of statues, architectural models, impressions of 
 seals, &c. In the art of stereotyping, it is indispensable- It is 
 used in agriculture to fertilize certain soils. 
 
12 MATERIALS USED IN THE ARTS. 
 
 Alabaster. — Under this name, two substances are known 
 in commerce. One is a carbonate of lime, deposited by the 
 dripping- of water in stalactitic caves. The other, and the 
 most common, is a compact gypsmn. This is softer than 
 marble, translucent, and susceptible of a fine polish. Many 
 beautiful ornaments, such as vases, statues, shades for lights, 
 (fee, are made from it. As alabaster of the last species is sol- 
 uble in five hundred parts of water, Mr Moore has proposed 
 an easy method of cleansing it, by immersing it for about ten 
 minutes in water, and afterwards rubbing it with a brush dip- 
 ped in dry, powdered plaster. 
 
 C/iaZ/^.— Chalk is a soft carbonate of lime, the properties of 
 which are well known. It is used as the basis of various 
 white pigments, and cementing substances. Common whiting 
 is purified chalk, prepared by reducing the chalk to fine pow- 
 der and agitating it with water. The sand and coarser parti- 
 cles first subside, after which the water is drawn off and the 
 whiting suffered to deposit itself. Chalk by calcination fur- 
 nishes excellent lime. 
 
 Fluor Spar. — This is a fluate of lime. The variety chief- 
 ly used is the Derbyshire spar, which is beautifully vaiiegat- 
 ed with purple and other colors. Ornamental objects and 
 utensils are made from it. Its acid, when disengaged, is 
 sometimes used to corrode glass. 
 
 Flint. — FKnt is found in roundish masses, and is composed 
 almost wholly of silex. Its extreme hardness causes it to 
 strike fire readily with steel, from which property its greatest 
 use is derived. Gun-flints are formed by practised workmen, 
 who break them out with a hammer, a roller, and steel chisel, 
 with small repeated blows. Flints are used also in the man- 
 ufactures of glass, porcelain, and Wedgewood's ware. For 
 this purpose, they are reduced to fine powder by heating red 
 hot and plunging them in water ; afterwards by pounding, 
 sifting, and w^ashing. Flints are broken up to form M'Adam 
 roads. 
 
 Porphyry. — Porphyry is a variegated stone, consisting of 
 
MATERIALS USED IN THE ARTS. 13 
 
 small crystals of feldspar or quartz, imbedded in a basis of a 
 darker color. It receives a beautiful polish, but its extreme 
 hardness renders it difficult to work. The ancients made 
 columns and even statues of this material ; but the moderns 
 confine its use chiefly to smaEer works, such as vases, boxes, 
 mortars, <fcc. 
 
 Buhrstone. — This is a hard, siliceous stone, remarkable for 
 its cellular structure ; containing always a greater or less num- 
 ber of irregular cavities. Hence its surface, however worn and 
 levelled, is always rough. This property renders buhrstone 
 an invaluable material for mill-stones. When it is not found of 
 sufficient size for this use, small pieces of it are fitted together, 
 cemented, and bound with an iron hoop. It is imported fiom 
 France, and is also found in some localities in the United 
 States. 
 
 Novaculite. — This stone is commonly known under the 
 names of hone, Turkey oilstone, &c. It is of a slaty struc- 
 ture, and owes its power of whetting or sharpening steel in- 
 struments, to the fine siliceous particles which it contains. 
 Various other stones are used as whetstones, such as common 
 slate, mica slate, freestone, &c. 
 
 Precious Stones. — These are better known as objects of 
 luxury, than of use ; yet their preparation gives rise to an ex- 
 tensive branch of industry. They are in general distinguish- 
 ed for theii' small size, and great brilliancy, permanency, and 
 hardness. The latter quality renders them useful in the arts. 
 The diamond is generally employed foi" cutting sheets of glass. 
 The diamond, ruby, sapphire, and some others, are used by 
 watchmakers for pivot holes to diminish the friction of theii' 
 verges and axles. These stones are wrought by grinding 
 them with emery and other hard powders. The diamond can 
 only be cut with its own dust. Various hard, siliceous stones 
 of less value, as the carnelian, jasper, agate, (fcc, are used by 
 lapidaries for engraving seals, cameos, and other objects of or- 
 nament. 
 
 Emery. — The best emery is a variety of the corundum 
 
14 MATERIALS USED IN THE ARTS. 
 
 stone, obtained chiefly from the island of Naxos, in the Archi- 
 pelago. Several other substances, however, are sold under this 
 name. Emery is the hardest of all known substances, except 
 the diamond, and its powder is extensively used in grinding 
 and polishing metals, stones, and glass. It is reduced to pow- 
 der by grinding it in a steel mill, and is afterwards assorted 
 into parcels of different fineness, by agitating it with water, 
 and separating the particles which deposit themselves at differ- 
 ent times ; the finest particles being the last which subside. 
 
 Sand. — Sand of the best quaUty, is that which consists of 
 particles of pure quartz, and such only is used in the manu- 
 facture of fine glass. It is found in various localities, but is 
 most commonly procured, in this country, from the banks of 
 the Delaware. Impure sand answers only for bottles and in- 
 ferior glass. For mechanical purposes, such as grinding glass 
 and marble, sharp sand, the particles of which are angular, is 
 best. The sand used for moulds, by brass founders, possesses 
 a somewhat argillaceous character, sufficient to render it mod- 
 erately cohesive when wet, in consequence of which qualitjr it 
 retains its shape. The sand used in mortar should be sharp, 
 and free from all perishable or deliquescent ingredients. 
 
 Pumice. — This is a spongy, porous stone, of a fibrous tex- 
 ture, and so light as often to swim in water. It is considered 
 to be of volcanic origin. It is employed to grind the surface 
 of metals, and other minerals. On account of its lightness, it 
 is sometimes used to construct domes, vaults, and other elevat- 
 ed parts of buildings. The dome of the mosque of St Sophia, 
 at Constantinople, is said to be of this material. 
 
 Tufa. — This name is applied to a number of volcanic pro- 
 ductions, some of which are aggregates of sand, ashes and 
 fragments of scoria and lava united by a cement. The tufa 
 which is found about Rome is of a reddish color, and is suppos- 
 ed to be the lapides ruhri of Yitruvius. Its surface is easily 
 decomposed by the atmosphere, yet some of the ancient Ro- 
 man temples and aqueducts axe built of it, and among others the 
 temple of Fortuna virilis. 
 
MATERIALS USED IN THE ARTS. 15 
 
 Peperino. — The lapis alhanus of the ancients, now called 
 pepeiino, appears to be a kind of tufa, or concretion of volcanic 
 ashes, but somewhat more solid and durable than the other 
 kinds. It is the material of some of the ancient Roman struc- 
 tures, and is found in the forum of INerva and the temple of 
 Antoninus and Faustina. 
 
 Tripoli. — This mineral resembles certain clays, but is 
 rough and friabL^ and does not form a paste with water. It 
 possesses a fine hard grit, and is used to poUsh metals and 
 stones. Common rotten stone and polishing slate are vari- 
 eties of tripoh. 
 
 Clay. — This abundant and useful earth is composed prin- 
 cipally of alumine and silex. It possesses the valuable pro- 
 perty of forming, when wet, a ductile and tenacious paste, 
 which is changed by heat to a stony hardness. Common clay, 
 of which bricks and coarse potter's ware are made', contains 
 oxide of iron, which causes it to turn red in burning. The 
 purer sorts, such as pipe clay, become whiter when exposed to 
 a high heat. The earthy smell, which clays emit when 
 breathed upon, appears also to be owing to oxide of iron. Ab- 
 solutely pure clays emit no smell. Refractory clays are those 
 which endure the greatest heat without melting. The best 
 fire-proof bricks and crucibles are made from slate clay, and 
 contain a good deal of sand. Sometimes they are made of 
 old materials, which have been before exposed to high heat, 
 pounded up and mixed with fresh clay. A mixture of two 
 parts of Stourbridge clay and one part of coke, has been found 
 very refractory. 
 
 Ashestiis. — Asbestus is a mineral of a fibrous structure. One 
 of its varieties, called Amianthus, is composed of very delicate, 
 flexible filaments, resembling fibres of silk. It has been man- 
 ufactured into cloth and paper, which possess the property of 
 being incombustible. It is difficult, however, to find fibres of 
 sufficient length and firmness, to produce objects of any great 
 use. It is sometimes mixed with clay in pottery, to increase 
 its strength. It has also been used for the packing of steam 
 
16 MATERIALS USED IN THE ARTS. 
 
 engines which are of high pressure, or in which steam is used 
 at an elevated temperature. 
 
 Cements. — Limestone. — The substances made use of for 
 the uniting medium between bricks or stones in building, are 
 denominated cements. The calcareous cements, composed of 
 a mixture of Ume, sand, and water ; in consequence of the 
 facility with which they pass from a soft state to a stony 
 hardness, have in common use superseded all others. Lime 
 in the state of quicklime, is obtained by burning in kilns, any 
 of those natural bodies, in which it exists in combination with 
 carbonic acid ; such as limestone, marbles, chalk, and shells. 
 The effect of the burning, or calcination, is to drive off the 
 carbonic acid. If quicklime, thus obtained, be wet with water, 
 it instantly swells and cracks, becomes exceedingly hot, and 
 at length falls into a white, soft, impalpable powder. This 
 process is denominated the slaking of the lime. The com- 
 pound formed is called a hydrate of lime, and consists of about 
 three parts of lime to one of water. When intended for mor- 
 tar, it should immediately be incorporated with sand, and used 
 without delay, before it imbibes carbonic acid anew from the 
 atmosphere. Lime, thus mixed with sand, becomes harder 
 and more cohesive and durable, than if it were used alone. It 
 is found that the sand used in common mortar, undergoes lit- 
 tle or no change ; while the lime, seemingly by crystalization, 
 adheres to its particles, and unites them together.* Cements 
 composed in this manner continue to increase in strength and 
 solidity for an indefinite period, the hydrate of lime being grad- 
 ually converted into a carbonate. The sand most pi'oper to 
 form mortar, is that which is wholly siliceous, and which is 
 sharp, that is, not having its particles rounded by attrition. 
 
 Fresh sand is to be preferred to that taken from the vicinity 
 of the sea shore, the salt of which is liable to deliquesce and 
 weaken the strength of the mortar. The proportions of the 
 lime and sand to each other, are varied in different places ; the 
 amount of sand, however, alwa3's exceeds that of the lime. 
 
 * See Brard and Vicat on this subject. 
 
MATERIALS USED IN THE ARTS. 17 
 
 The more sand can be incorporated with the hme, the better, 
 provided the necessary degree of plasticity is preserved ; for the 
 cement becomes stronger, and it also sets, or consolidates more 
 quickly, when the lime and water are less in quantity and 
 more subdivided. From two to four parts of sand are used to 
 one of lime, according to the quality of the lime and the labor 
 bestowed on it. The more pure is the lime and the more tho- 
 roughly it is beaten or worked over, the more sand it will take 
 up, and the more firm and durable does it become. 
 
 Puzzolaiia. — Water cements, or hydraulic cements, often 
 called, also, Roman cements, are those which have the proper- 
 ty of hardening under water, and of consolidating almost im- 
 mediately on being mixed. Common mortar, although it 
 stands the effect of water very well when perfectly dry, yet oc- 
 cupies a considerable time in becoming so, and dissolves or crum- 
 bles away, if laid.under water, before it has had time to harden. 
 It is found that certain rocks which possess an argillaceous 
 as well as siliceous character, if mixed with lime or mortar, 
 communicate to them the property of hardening in a very few 
 minutes after the mixture has taken place, as well under 
 water as out of it. Substances of this sort have therefore been 
 made the basis of water cements. The ancient Romans, who 
 practised building in the water, and particularly in the sea, to 
 a great extent, first availed themselves of a material of this 
 kind. The Bay of Baise, from the coolness and salubrity of 
 its situation, was a place of fashionable resort for the wealthy 
 of Rome, during the summer months. They erected their 
 villas, not only on the seashore, but on artificial quays and 
 islands constructed in the water. To enable them to erect 
 these marine structures, they fortunately discovered, at the 
 town of Puteoli, a peculiar earth, to which they gave the name 
 of 2^'ilvis piifeola7ius, and which is the same tiow known by 
 the name of Puzzolana. This earth is a light, porous, friable 
 mineral, various in color, and evidently of volcanic origin. 
 When reduced to uniform powder ])y beating and sifting, and 
 thoroughly mixed with lime, either with or without sand, 
 
18 MATERIALS USED IN THE ARTS. 
 
 it forms a mass of great tenacity, which in a short time con- 
 cretes to a stony hardness, not only in the air, but hkewise 
 when wholly immersed in water. 
 
 Tarras. — A substance denominated tarras, terras, or trass, 
 found near Andernach in the vicinity of the Rhine, has been dis- 
 covered to possess the same property with puzzolana, of forming 
 a durable water cement, when combined with lime. It is said 
 to be a kind of decomposed basalt, but resembles puzzolana. 
 It is the material which has been principally employed by the 
 Dutch, whose aquatic structures probably exceed those of any 
 other nation in Europe. Tarras mortar, though very durable 
 in water, is inferior to the more common kinds, when exposed 
 to the open air. 
 
 Other Cements. — It has been found that various other sub- 
 stances, such as baked clay reduced to powder, or the common 
 greenstone calcined and pulverized, afford the basis of very 
 tolerable water cements, wnth lime. Some of the ores of man- 
 ganese are also useful for the same purpose. 
 
 There are some limestones which have the property of form- 
 ing water cements when calcined and mixed with simple sand 
 and water. This is usually in consequence of these stones 
 containing a certain portion of argillaceous earth, united with 
 the lime. A water cement found in New York, was used in 
 constructing the locks of the great canal in that State. Anoth- 
 er hydraulic cement, containing lime, silex, and alumine, has 
 been found and applied to use in the Union Canal of Pennsyl- 
 vania.* 
 
 The cause by which these compounds become hard under 
 water, is not satisfactorily known. It has been supposed, how- 
 
 * M. Berthier states that with one part of common clay and two parts 
 and a half of chalk, a very good hydraulic lime may be made. He con- 
 cludes from many experiments, that a limestone containing six per cent., 
 of clay, affords a mortar perceptibly hydraulic. Lime containing from 
 fifteen to twenty jjer cent., is very hydraulic, and with from twentyfive to 
 thirty per cent., it sets almost instantly. 
 
 According to M. Bruyere, an excellent artificial puzzolana may be form- 
 ed by heating together three parts of clay, and one part of slaked lime, for 
 some hours, to redness. 
 
MATERIALS USED IN THE ARTS. 19 
 
 ever, and not without reason, that the great attraction for mois- 
 ture existing in certain argillaceous earths, causes them to ab- 
 sorb immediately the superabundant moisture from the lime, and 
 thus to expedite its solidification. This explanation is render- 
 ed more probable, by the fact, that burnt clays, which form 
 good hydraulic cements ; cease to do so, if the burning is car- 
 ried so far as to vitrify them.* 
 
 Maltha. — -The name of maltha., or mastich, is given to 
 those cements into which animal and vegetable substances en- 
 ter, such as oil, milk, mucilage, &c. Some of these mixtures 
 have afforded, both to the ancients and moderns, cements of 
 great hardness and permanency, but they are not much used. 
 
 Metals. — Iron. — Of all the metals, iron is the most useful, 
 and one of the most abundantly diffused. Besides its common 
 occurrence in earths and rocks, it is held in solution by mine- 
 ral waters, it enters largely into the composition of meteoric 
 stones, and it circulates in the blood of animals, and the sap of 
 vegetables. Pure iron is of a bluish white color, of great hard- 
 ness, malleable, ductile, and tenacious. For its fusion, it re- 
 quires an intensely high temperature, equal to one hundred 
 
 * M. Vicat, who has experimented extensively upon the subject, has 
 arrived at the conclusion, that the solidification of hydraulic cements form- 
 ed of ordinary mortar, and calcined clays, is the result of a true chemical 
 combination, in which the lime is neutralized by the silica and alumina. 
 But in those formed of hydraulic lime and pure sand, the solidification does 
 not appear to result from chemical combination. 
 
 Clays which by slight calcination become good hydraulic cements, have 
 also the same property, though in a less degree, in their natural state. It 
 has been asserted, by M. Treussart, that the free access of air during the 
 calcination of argillaceous cements, is of great consequence to the tenacity 
 of the mortar and the quickness with which it hardens. To determine 
 whether a stone will furnish hydraulic lime, M. Vicat recommends to cal- 
 cine it by heat, then to slake it in the common way, and make a paste of it, 
 which is to be placed at the bottom of a vessel of pure water. If at the 
 end of eight or ten days it has become hard, and resists the finger, it will 
 furnish hydraulic lime ; but if it remains soft, it has the character of com- 
 mon lime. 
 
 See Brande's Journal, vol. x, p. 407. — vol. xix, 329. — vol. xx, 50. — vol. 
 xxii, 214. Also Franklin Journal, ii, 371 and 287.— iii, 305, 3.55. 
 
20 MATERIALS USED IN THE ARTS. 
 
 and fiftyeight degrees of Wedgewood's pj^rometer. When 
 combined with carbon, it forms steel, and is increased in hard- 
 ness. At a red heat, it becomes soft and more malleable ; and 
 at a white heat, may be joined by welding. It is strong- 
 ly attracted by the magnet, acquires itself the magnetic power, 
 and when in the form of steel, retains it permanently. Cast 
 iron is brittle, and fusible without difficulty, owing to the car- 
 bon which it contains. Wrought iron is flexible, and has the 
 properties of the pure metal. In the arts, iron is applied to in- 
 numerable uses where strength and hardness are required. It 
 is, however, deficient in durability, being readily corroded \^ ith 
 rust, when exposed to the weather, unless protected with a 
 coating of paint. Metallic iron is wrought, while hot, by ham- 
 mering, rolling, stamping, chiseling, punching, &.c. ; and 
 when cold, by the same means, also by filing, turning, drilling, 
 cutting, and drawing. Cast iron is commonly melted, when its 
 form is to be changed ; but it is finished with common tools 
 when cold, and may be cut with a saw when red hot. Cast 
 iron is now the most common material used in the fabrication of 
 machines, and in Europe it is applied to the construction of 
 bridges, and of roofs. Even small ships have been made of iron. 
 
 To the chemical compounds of iron, we are indebted for 
 copperas, writing ink, prussian blue, &c. 
 
 Copper. — Copper is a metal of a light red color, ductile, 
 and malleable, emitting a disagreeable odor when rubbed. It 
 melts at twentyseven degrees of Wedgewood. When exposed 
 to the atmosphere, it loses its lustre, and becomes covered with 
 a green coating, which is carbonate of copper. This coating 
 preserves the remainder from decay, and is the source of some 
 of its most important uses. Copper is employed to cover the 
 bottoms of ships, and tops of houses ; to form various culinary 
 and manufacturers' vessels, also for pumps, and water pipes, 
 for engravers' plates, and for coining. When combined with 
 acids, or oxygen, it becomes more or less poisonous, on which 
 account culinary vessels are coated on the inside with tin. It 
 is this poisonous property, in part, which prevents marine an- 
 
MATERIALS USED IN THE ARTS. 21 
 
 imals from attaching themselves to the bottoms of coppered 
 ships. Copper forms many valuable alloys, among which are 
 brass, which consists of copper and zinc, and bronze, which 
 is made of copper and tin. Its chemical compounds furnish 
 verdigris, blue vitriol, <fcc. It is wrought by the same modes 
 as iron, but is more easily malleable than that metal when cold. 
 
 Lead. — Lead has a light bluish color, Mdth a bright lustre 
 which becomes quickly tarnished on exposure to the air. It is 
 soft, heavy, very malleable, and melts at six hundred degrees 
 of Fahrenheit's thermometer. By exposure to the heat of a 
 furnace, it is converted into a red oxide. Lead is used for the 
 covering of roofs, for aqueducts, for lining cisterns and tight 
 cavities, for weights, bullets, and shot. Some of its alloys are 
 very valuable, such as pewter, type metal, &c. Its oxides and 
 salts afford paints of different colors, and of great use. Lead 
 is deleterious in its influence on health, and requires great 
 caution in those who work it, or use it, in any other than the 
 metallic state. Injury is most frequently received, by inhaling 
 the dust which rises in the manufactories of red and white 
 lead. In leaden aqueducts a carbonate of lead occasionally 
 forms ; but this is insoluble in water, and subsides by its 
 weight. 
 
 Tin. — Tin is a white metal, somewhat harder than lead, 
 and producing a peculiar crackling sound Avhen it is bent. It 
 is very malleable, and is beaten for tinfoil into leaves y oV o- P^'"*' 
 of an inch in thickness. Its ductility and tenacity are not 
 great. Tin is very fusible, melting at about four hundred 
 and fortytwo degrees of Fahrenheit's thermometer. Exposed 
 to the atmosphere, its surface becomes slightly tarnished, but 
 undergoes no further change. On this account it is largely 
 employed for coating other metals, which are more liable to 
 oxidation. Copper vessels are lined with it, as already stated. 
 Tin plates are sheets of iron coated with tin. Tinfoil with 
 mercury forms the silvering of looking glasses. Block tin is 
 used to form vessels not intended for exposure to heat. Some 
 of the salts of tin are very valuable in dyeing. The putty 
 used for polishing glass, stones, and metals, is an oxide of 
 lead and tin. 
 
22 MATERIALS USED IN THE ARTS. 
 
 Mercury.— Mercury, or quicksilver, is fluid at common 
 temperatures, and on this account is used in many philosophi- 
 cal and chemical instruments. Attempts have been made to 
 introduce it in certain forms of the steam engine ; but it is ob- 
 jectionable for this purpose, from its tendency to combine with 
 oxygen, and from the unhealthiness of its use to persons occu- 
 pied about it. Mercury is employed in silvering mirrors, and 
 large quantities are consumed in extracting silver and gold 
 from their ores. Its alloys with other metals are called amal- 
 gams. It amalgamates readily with gold, silver, tin, lead, 
 and zinc ; difficultly with copper and antimony, and scarcely 
 at all with iron and platina. 
 
 Gold. — The value derived from its scarcity, prevents the 
 extensive use of gold in the arts. The power with which it 
 resists tarnishing, and all changes from exposure to air and 
 moisture, rendeis it desirable for many purposes, and has giv- 
 en rise to the art of gilding. The gold leaf used in gilding is 
 often not more than g g 2V00 P^^'^ ^^ ^^ inch, thick, owing to 
 the extreme malleability of the metal. Gold is used in coining, 
 in jewelry, and in coloring porcelain. 
 
 Silver. — Silver possesses the same valuable properties as 
 gold, but is more liable to tarnish, especially when exposed to 
 sulphurous vapors, which convert its surface into a sulphuret. 
 Silver is very ductile, but less so than gold, and the leaves in- 
 to which it is hammered, are usually three times thicker than 
 those of gold. Its uses are well known. 
 
 Platinum. — Platinum is the heaviest substance at present 
 known, its weight being twenty one times and a half, that of 
 water. Like gold, it resists tarnishing from oxidation by the 
 air, and it is furthermore capable of resisting an extremely 
 high temperature without melting. It is very malleable, ap- 
 proaches to iron in hardness, and like that metal, may be weld- 
 ed when hot. It is used for small crucibles, and philosophical 
 instruments. 
 
 Zinc. — Zinc or spelter is a bluish white metal, imperfectly 
 malleable and ductile, but rendered more so by a heat some- 
 what above that of boiling water. It melts below a red heat, 
 
MATERIALS USED IN THE ARTS. 23 
 
 at seven hundred degrees of Fahrenheit. When ignited it 
 burns with a white flame, throwing off an oxide called flow- 
 ers of zinc. Zinc is used as a constituent in brass, and in 
 some other alloys. It is an important material in galvanic 
 combinations. It is easily oxidated, and therefore uirfit for 
 purposes which require durability. 
 
 Antimony. — Antimony is a brittle, whitish metal of a plated 
 or scaly texture. It is tarnished, but not otherwise altered 
 by exposure to the air. In type founderies it is much used to 
 give hardness to lead, in the alloy called type metal. 
 
 Bism^uth. — Bismuth is a metal of a reddish white color 
 and brittle consistence, not readily oxidated by the air. It is 
 very fusible, requiring little more heat than tin to melt it. It 
 enters into various alloys, one of which is the fusible metal, 
 composed of eight parts of bismuth, five of tin, and three of lead, 
 which melts at a heat less than that of boiling w^ater. 
 
 Arsenic. — Arsenic in its metallic state is of a bluish white 
 color, easily tarnishing, brittle^ and volatile at a low heat. In 
 the state of acid, called tohite arsenic, it is well known as a 
 violent poison. Arsenic is used in the manufactures of glass, 
 and of shot, and furnishes the basis of several brilliant pig- 
 ments. 
 
 Manganese. — Manganese is a metal of a dull whitish color, 
 brittle, extremely difficult to melt, and speedily turning to a 
 dark oxide in the air. The native black oxide of this metal 
 is of great use to chemists in furnishing oxygen. In the arts, 
 it is employed in bleaching, pottery, and glass making. 
 
 Combustible substances, &c. — Bitum^en. — This is an 
 inflammable mineral substance, resembling tar or pitch in its 
 properties and uses. Among different bituminous substances, 
 the names naphtha, and petroleum,, have been given to those 
 which are fluid ; onaltha, to that which has the consistence of 
 pitch, and asphaltum,, to that which is solid. 
 
 Am,her. — Amber is a yellowish, translucent, inflammable 
 mineral, hard enough to receive a fine polish, capable of be- 
 ing wrought into various ornamental articles, and forming an 
 ingredient in some varnishes and lacquers. 
 
24 MATERIALS USED IN THE ARTS. 
 
 Coal. — This well known combustible is composed essential- 
 ly of caibon, with a proportion, greater or less, of bitumen, a 
 little sulphur, and a remainder of earthy and incombustible 
 matter. True coal burns with a white flame, a black smoke, 
 and bituminous odor. Some kinds, as the Cannel coal, burn 
 readily, with a large flame, and without softening or concret- 
 ing. Others, as the Newcastle, Liverpool, and Orrel, con- 
 crete, or cake, during combustion, and last longer. The poor- 
 er coals have usually a large admixture of foreign and incom- 
 bustible substances. Coal is of great value as a fuel, both in 
 the arts, and for domestic purposes. As it contains more com- 
 bustible matter in a given volume, than wood, it is capable of 
 evolving and sustaining more heat than that fuel, within the 
 same furnace, or other cavity. When coal is exposed to heat, 
 but prevented from burning, by the exclusion of the air, it 
 loses its moisture and bituminous portion, and is converted in- 
 to coke, a fuel bearing the same relation to coal, as charcoal to 
 wood. Coal has of late years been usefully applied to the pro- 
 duction of inflammable gas^ for the purposes of illumina- 
 tion. 
 
 Anthracite. — This combustible, of which the Lehigh, 
 Schuylkil, and Rhode Island coal are specimens, is harder, 
 heavier, and less black, than the true, or bituminous coals. 
 It burns slowly, without smoke, and with a faint flame. 
 It is more difficult to kindle than most fuels, owing to its great- 
 er conducting power, and the high temperature necessary for 
 its combustion ; but when once on fire it produces an intense 
 and lasting heat. It is more durable than the bituminous 
 coals, but requires to be burnt in masses large enough t,o sus- 
 tain a high temperature. Anthracite has now become a com- 
 mon fuel in many parts of the United States, and is highly 
 valuable both for domestic and manufacturing purposes. It is 
 burnt in various furnaces, forges, stoves, and grates constructed 
 for the purpose. In iron works it is found to occasion less ox- 
 idation and scahng of the metal, than other fuel. But in re- 
 verberating furnaces, where a blaze is required, it does not an- 
 
MATERIALS USED IN THE ARTS. 25 
 
 swer the requisite purpose. Most of the anthracites afford in- 
 flammable gas, not, however, suitable for purposes of illumina- 
 tion.* 
 
 Graphite. — This mineral, otherwise called phiTnbago and 
 black lead, is composed of carbon, with a portion of iron. It 
 is unctuous to the touch and soils the fingers. It is used for 
 pencils and crayons, and, mixed with clay, is formed into cru- 
 cibles. Black lead pencils are made, by inserting the straight 
 edge of a plate of graphite, into a groove made in the wood, 
 and sawing it off, leaving a slender rod of the lead inclosed, 
 which is afterwards covered with wood. 
 
 Peat. — Peat is a substance of vegetable origin, dug from 
 bogs and marshes, and capable of reproducing itself in places 
 from which it has been removed. Peat, when dry, is combus- 
 tible, and is used as such, where better fuel cannot be ob- 
 tained. 
 
 Sulphur. — Sulphur is a simple inflammable body, melting 
 at two hundred and twenty degrees, and taking fire at five 
 hundred, of Fahrenheit. When kept melted for some time, 
 at about three hundred degrees, Fahrenheit, it becomes thick 
 and viscid, and if poured into a basin of water, it becomes duc- 
 tile like wax. In this state it is used for taking impressions of 
 seals. It is also used to form moulds for plaster casts. Sul- 
 phur is an ingredient in gunpowder, and enters into many 
 chemical compounds, which are of great use in the arts. Sul- 
 phur is burnt to produce sulphuric acid. 
 
 MATERIALS FROM THE VEGETABLE KINGDOM. 
 
 Wood. — The woody portion of the trunks of trees, is made 
 up of minute tubes or vessels, running longitudinally, having 
 their parietes strengthened with rigid fibres, and their inter- 
 
 * See a valuable paper on the Anthracites, in Silliman's Journal, vol. x. 
 p. 331, by the editor. 
 
26 MATERIALS USED IN THE ARTS. 
 
 Slices filled with cellular substance. In the common trees of 
 temperate climates, these vessels are arranged in concentric 
 layers or cylinders ; one layer being added for each year of 
 the tree's growth. The outer layers, being those which trans- 
 mit the sap, are more porous, soft and perishable, and are 
 known by the name of alhw^num or sa]3 wood. The inner 
 layers are commonly darker colored, more solid, compact, and 
 durable ; and are known by the name of heart wood. The 
 heart wood is preferred for most purposes in the arts, its ves- 
 sels having become in part obliterated by age, and its density 
 and strength increased. Boards are least liable to warp when 
 they are cut through the centre or pith of the trunk. All 
 wood shrinks in drying, and decays when exposed to the 
 weather ; but different trees vary greatly from each other in 
 this respect. 
 
 Bark. — Bark is the external investment of the trunks and 
 branches of trees, and consists, when yoimg, of three coats or 
 layers, called the cuticle, the cellular integument.^ and the U- 
 ber or inner bark. But during every season, a new hber grows 
 on the inside of the former ones, and pushes them outward, so 
 that old bark is found to consist of numerous cortical layers^ 
 each of which was originally a liber. The outermost of these 
 layers gradually become dead and dry, and merely augment 
 the thickness of the bark, without adding to its usefulness in 
 the arts. 
 
 Oak. — Numerous species of the oak tree are found in the 
 United States. They are generally distinguished for great 
 strength, but are coarse grained, and prone to warp and crack 
 under changes from moisture to dryness. The live oak of the 
 Southern States ( Q,uercus virens) is prized in ship-building, 
 beyond any native timber. The white oak ( Q,uercus alba) is 
 employed for the keels, side timbers, and planks of vessels, al- 
 so for frames of houses, mills and machinery requiring strength ; 
 for wagons, parts of carriages, ploughs, and other agricultural 
 instruments. Large quantities are consumed for the staves 
 and hoops of casks, for which they furnish one of the best ma- 
 
MATERIALS USED IN THE ARTS. 27 
 
 terials. The bark of the black oak ( Quercus tinctoria) fur- 
 nishes the quercitron used by dyers. Most of the species of 
 oak are employed in tanning, and they all furnish a valuable 
 fuel. 
 
 Hickory or Walnut. — The wood of the different species of 
 native walnut or hickory {Juglans, seu Carya) is eminently 
 distinguished for weight, tenacity, and strength. It has, how- 
 ever, important defects. It warps and shrinks greatly, decays 
 rapidly when exposed to the weather, and is very liable to the 
 attacks of worms. On these accounts it is never used for 
 house or ship building, but is chiefly employed for minor pur- 
 poses, where strength is the chief requisite ; as in the teeth of 
 mill wheels, screws of presses, handspikes, capstan bars, bows, 
 hoopS; and handles of tools. As fuel, the hickory stands at 
 the' head of native trees, and commands a higher price than 
 any other wood. 
 
 Ash. — The white ash {Fraxinus Americana) and some 
 other species, are of great utility in the arts. Ash wood is 
 strong, elastic, tough, and light ; and splits with a straight 
 grain. It is also durable, and permanent in its dimensions. 
 It furnishes the common timber used in light carriages, for the 
 shafts, frames, springs, and part of the wheels. Flat hoops, 
 boxes, and the handles of many instruments are made of it. 
 It is almost the only material of oai's, blocks of pullies, cleats, 
 and similar naval implements, in places where it can be ob- 
 tained. 
 
 EItti. — The common American elm ( Ulmiis Americana) 
 is valued for the toughness of its wood, which does not readi- 
 ly split. On this account it is chiefly used for the naves, 
 among us commonly called hubbs, of carriage wheels. 
 
 Locust. — The common locust [Robinia pseudacacia) is one 
 of the hardest, strongest, and most valuable of native trees. 
 The larger pieces of its timber are used in ship-building, and 
 the smaller pieces are in great request to form the treenails * 
 or pins which confine the planks to the timbers. This tree is 
 
 ♦ Commonly pronounced trunnels. 
 
28 MATERIALS USED IN THE ARTS. 
 
 liable, in the Northern States, to be perforated by an insect, so 
 that it is often difficult to procure sound pieces of any consider- 
 able size. Locust wood is exceedingly durable, when exposed 
 to the weather ; and forms excellent fuel. 
 
 Wild Cherrytree. — The wood of this tree (Prii?zzt5 Virgin- 
 iana) is of a deep color, hard, durable, and, when properly sea- 
 soned, very permanent in its shape and dimensions. In the 
 manufacture of cabinet work, it is much used as a cheaper 
 substitute for mahogany. On the Western rivers it is some- 
 times used in ship building. 
 
 Chesrmt. — The American chesnut {Castanea vesca B.) is 
 a large tree of rapid growth. Its wood is coarse and porous, 
 very liable to warp, and seldom introduced into building or 
 furniture. It is chiefly used for fencing stuff, to which use it 
 is fitted by its durability in the atmosphere. Chesnut is an un- 
 safe fuel, in consequence of its tendency to snap, and throw its 
 coals to a distance. 
 
 Beech. — The wood of the red beech {Fagus ferruginea) 
 is liable to decay when exjjosed to alternate moisture and dry- 
 ness. It does not, however, readily warp, and being smooth 
 grained.it is used for some minor purposes, such as the mak- 
 ing of planes, lasts, and card backs. It forms a very good fuel. 
 Basswood. — The American linden or basswood tree ( Tilia 
 Americana) produces a fine grained wood, which is very white, 
 soft, light, and flexible. It is sometimes employed for furni- 
 ture, but its chief use is to form the pannels of coach and chaise 
 bodies, for which its flexibility makes it well suited. 
 
 Tulip tree.- — {Liriodendron tulipifera.) The boards of 
 this tree are sold under the name of white ivood, and errone- 
 ously under that of poplar. Its wood is smooth, fine grained, 
 easily wrought, and not apt to split. It is used for carving 
 and ornamental work, and for some kinds of furniture. In 
 the Western States, where pine is more scarce, the joinery, or 
 inside work of houses, is commonly executed with this materi- 
 al, and sometimes the outer covering. In common with bass- 
 wood, it forms an excellent material for coach and chaise pan- 
 nels. 
 
MATERIALS USED IN THE ARTS. 29 
 
 Maple. — The rock maple, {Acer saccharinum) also several 
 other species, affords wood which is smooth, compact and hard. 
 It is much used for cabinet furniture, and is a common mate- 
 rial for gunstocks. The wood in some of the old trunks, is 
 full of minute irregularities, hke knots. These, if cut in one 
 direction, exhibit a spotted surface, to which the name of bird's 
 eye maple is given ; while if cut in another direction, they pro- 
 duce a wavy or shaded surface, called curled maple. This 
 last effect, however, is more frequently produced by a mere 
 serpentine direction of the fibres. The distinctness of the 
 grain may be increased by rubbing the surface with diluted 
 sulphuric acid. Maple wood forms a good fuel. It is not 
 very lasting when exposed to the weather. The sap of the 
 rock maple and of one or two other species, yields sugar on be- 
 ing boiled. 
 
 Birch. — The white or paper birch [Betula pajpyracea) has 
 properties similar to those of the maple, and is appropriated to 
 the same uses. Its cuticle or outer bark, is made by the In- 
 dians into canoes. The lesser white birch [B. populifolia) is 
 a perishable tree, of little value. The black birch, {B. lenta,) 
 known for its aromatic bark, affords a firm, compact, dark col- 
 ored wood, much valued for furniture, and sometimes used for 
 screws and implements requiring strength. The yellow birch 
 {B. lutea) is applied to the same uses as the last, and makes 
 good fuel. 
 
 Buttomoood. — The button wood or plane tree (Plat amis 
 occidentalis) is in some of the Northern States improperly 
 called sycamore. It is one of the largest inhabitants of the 
 forest, and Michaux states that trees are found in the Western 
 States which measure forty feet in circumference. This ma- 
 jestic tree is chiefly valuable for its shade, as the wood is perish- 
 able, and prone to warp. 
 
 Persimmon. — (Diospyros Virginiana.) The heart wood 
 is dark colored, compact, hard, and elastic ; and is used in the 
 Southern States for screws, shafts of chaises, and various im- 
 plements. 
 
30 MATERIALS USED IN THE ARTS. 
 
 Black Walnut. — {Juglaiis nigra.) This tree is rarely found 
 north of New York. Its heart wood is of a violet color, which, 
 after exposure to the air, assumes a darker shade, and finally 
 becomes nearly black. This wood when deprived of its white 
 part, or sap, remains sound foi" a long time, even if exposed to 
 air and moisture, and is not attacked by worms. It is very 
 strong and tenacious, and when seasoned is not hable to warp, 
 or split. It is used in the Middle and Western States for fur- 
 niture, for gunstocks, for naves of wheels, and to a certain ex- 
 tent, in house and ship building. 
 
 Tupelo. — Different species of the genus Nyssa have re- 
 ceived, in the United States, a great variety of common names^ 
 among which twpelo, pepperidge, and gum tree are the most 
 common. In Massachusetts the name hornheatn is improper- 
 ly applied to one of them. Their wood is smooth grained, 
 and remarkable for the decussation or interweaving of the fibres, 
 which renders it almost impossible to split the logs. This 
 quality causes several of the species to be in demand for naves 
 of wheels, hatters' blocks, and implements requiring lateral te- 
 nacity. 
 
 Pine. — The American pines exceed all other native trees 
 for the value and variety of their uses. The white pine {Fi- 
 nns strohus) has a very tall, straight trunk, the wood of which 
 is light, soft, homogeneous, and easy to work. It is remark- 
 ably exempt from the common fault of timber, that of decay- 
 ing in the open air, and of changing its dimensions with 
 changes of weather. On these accounts it is extensively em- 
 ployed for most of the common purposes of timber. In the 
 Northern States, masts of vessels are commonly made of it. 
 Frames of houses and of bridges are also formed of it ; its de- 
 fect of strength being more than balanced by its steadiness and 
 durability. Its boards form almost the only material used in 
 the Northern States for the joiner's work, or inside finishing 
 of houses ; and for this use it is exported to other countries. 
 Ornamental carving is commonly executed in this material. 
 The southern pitch pine [Pinus palustris L.) covers exten- 
 
MATERIALS USED IN THE ARTS. 31 
 
 sive barrens in the Southern States, and yields vast quantities 
 of tar and turpentine. Its wood is appropriated to the same 
 objects as that of the white pine, but is harder and stronger, and 
 therefore preferred for planks, spars, floors, decks, &c. Many 
 other species of pine exist on this continent, partaking qualities 
 hke those already described, but most of them harder than the 
 white pine. 
 
 Spruce. — The black and white spruce belong to the race 
 of trees commonly called Firs. They are both valuable, but 
 the black spruce {Pinus nigra) unites in a peculiar degree the 
 quahties of strength, elasticity, and lightness, together with 
 the power of resisting exposure to the weather. It is much 
 sought after for the smaller spars of vessels, such as the booms, 
 yards, and topmasts. 
 
 Hemlock. — The hemlock tree [Pinus Canadensis) is in- 
 ferior to the other firs in quality, though it grows to a large 
 size. It is coarse grained, often twisted, and cracks and shiv- 
 ers with age. It furnishes an inferior sort of boards, used in 
 covering houses. Its bark is valuable in tanning. 
 
 White Cedar. — This tree {Cupressus thuyoides) occupies 
 large tracts denominated cedar swamps. The wood is soft, 
 smooth, of an aromatic smell, and internally of a red color. It 
 is permanent in shape, and very durable ; and esteemed as a 
 material for fences. Large quantities of shingles are made of 
 it. It is a favorite material for wooden wares, or the nicer 
 kinds of cooper's work. 
 
 Cypress. — The cypress tree of the Southern States {Cu- 
 pressus disticha) is light, soft, and fine grained ; and at the 
 same time elastic, with a considerable share of strength. It 
 sustains heat and moisture for a long time, without injury. In 
 the Southern States and on the Mississippi, it is much employ- 
 ed for fences, and for the frames, shingles, and inside work of 
 houses. 
 
 Larch. — The American Larch {Pinus microcarpa) is call- 
 ed hackmatack and tamarack, in different parts of the Union. 
 Its wood is strong, elastic, and durable ; and is highly prized, 
 
32 MATERIALS USED IN THE ARTS. 
 
 in places where a suflEicieat quantity can be obtained, for naval 
 and civil architecture. 
 
 Arbor Vitce. — This tree [Thuya occidentalis) is of the 
 middle size, and frequently called while cedar. The wood is 
 reddish, fine grained, very soft, and light. It bears exposure 
 to the weather with very little change, and is esteemed for the 
 posts and rails of fences. 
 
 Red Cedar. — (Juniperus Virginiana.) The name of sa- 
 vin is in some places improperly applied to this tree. Unlike 
 the white cedar, it grows in the driest and most barren soils. 
 The trunk is straight, and knotted by small branches. The 
 heart wood is of a bright red color, smooth and moderately soft. 
 It exceeds most other native trees in durability, and is in par- 
 ticular request for posts of buildings, though it is difficult to ob- 
 tain it of large size. 
 
 Wilhw. — The most common kinds of Salix or wiUow 
 about our seaports, are European species which have become 
 naturalized. Their wood is soft, light, and spongy. Willow 
 charcoal is used in the manufacture of gunpowder. The osier 
 and some other species, with loug slender sh*)ots, are exten- 
 sively cultivated to form wicker work, such as baskets, ham- 
 pers, and the external coverings of heavy glass vessels. 
 
 Mahogany. — In the manufacture of cabinet furniture, ma- 
 hogany [Swietenia mahagoni) has taken precedence of all 
 other kinds of wood. Its value depends not so much on its 
 color, as on its hardness, and the invaluable property of remain- 
 ing constant in its dimensions, without warping or cracking, 
 for an indefinite length of time. The same qualities which 
 render it suitable for furniture, have given rise to its employ- 
 ment for the frames of philosophical instruments, and of dehcate 
 machinery. Mahogany is imported from the West Indies, 
 and different parts of Spanish America. 
 
 Boxwood. — The box tree [Buxus sempervirens) is import- 
 ed from the south of Europe. Its wood is of a well known 
 yellowish color, hard, compact, smooth, tough, and not liable to 
 crack. Musical wind instruments are commonly made of it ; 
 
MATERIALS USED IN THE ARTS. 33 
 
 also mathematical measuring instruments. The handles of 
 many tools, and various articles of turners' work, consist also 
 of this material. Wood engravings are cut upon the end of 
 the grain of boxwood. 
 
 Lignum VitcB. — The wood of the Guiacum officinale is 
 employed in the arts under this name. It is dark colored at 
 the heart, strong, exceedingly hard, and so heavy as to sink 
 in water. It is impregnated with resin, and on this account 
 durable in liquids. Handles of tools, boxes of gudgeons, wheels 
 of pullies, castors, balls, stopcocks, mallets, (fee, are made of it. 
 It is imported from the West Indies and South America. 
 
 Several other tropical woods are imported for use by cabinet 
 makers, such as rose v^ood, ebony, satin wood, (fee. They 
 are generally hard, colored woods, susceptible of a fine polish. 
 Satin wood [Sweiteiiia chloroxyloii) is thought poisonous to 
 the hands of the workmen. 
 
 Cork. — Cork is a fungous substance growing on the bark 
 of a species of oak ( Quercus suber) in the south of Europe. 
 Its lightness and elasticity give it an aptitude for certain pur- 
 poses, in which it would be difficult to find a substitute. 
 
 Hemp. — Hemp is the fibrous portion of the bark of an an- 
 nual plant, ( Canabis sativa) and is of great use in the manu- 
 facture of cordage and canvass. The fibres are separated from 
 the rest of the stalks, by the decomposition of the latter. In 
 the process of dew rotting, the hemp is exposed on the grass for 
 a number of weeks to the weather. In that of water rotting 
 it is immersed for a part of the time in water, and subsequently 
 exposed to the weather. By these processes, the solid parts of 
 the hemp decay ; while the flexible fibres remain strong and 
 but little impaired. The decayed portion is afterwards broken 
 up, by the operations of an instrument called a brake ; and 
 sometimes by a mill or stone roller. The chaff" is separated 
 from the fibres by the strokes of a wooden scotching, or swing- 
 ling knife ; and the fibres still further cleansed by combing 
 them on an instrument called a heckle. 
 
 Flax. — Flax is also the fibrous bark of an annual plant, 
 5 
 
34 MATERIALS USED IN THE ARTS. 
 
 [Linum usitatissimum,) which is smaller and finer than 
 hemp ; and constitutes the material of linen cloth. Flax is 
 rotted, and subsequently dressed, much in the same manner 
 as hemp. When, however, it is intended for finer uses, as 
 for cambric, lace, &c., it is scraped with a blunt knife upon leath- 
 er, and the fibres separated and straightened with a brush. A 
 method has been introduced in England, of dressing flax by 
 machinery, iq its recent state, without rotting. This meth- 
 od is represented as highly economical, affording more flax, 
 and of a stronger texture, than that produced in the common 
 way.* The fibres of flax and hemp are long, straight, and 
 unyielding, so that they cannot be spun by the same machine- 
 ry which is used for cotton and wool. 
 
 Cotton. — Cotton is the product of the Gossypium herha- 
 ceum, an Oriental plant, now cultivated in most parts of the 
 world, which possess a sufficiently warm climate. It grows 
 in pods, forming a light, woolly investment to the seeds ; and 
 seems intended by nature to assist in their dispersion by the 
 winds. The fibres of cotton are extiemely fine, delicate, and 
 flexible. When examined by the microscope, they are found 
 somewhat flat, and two-edged or triangular. Their direction 
 is not straight, but contorted ; so that the locks can be extend- 
 ed or drawn out without doing violence to the fibres. These 
 properties render cotton peculiarly adapted for the operations of 
 machinery, and have given employment to a vast amount of 
 manufacturing skill and industry, both in Great Bjitain and 
 this country. 
 
 Cotton, after being gathered, is cleansed from the seeds by 
 a machine called a gin, of which there are two kinds. The 
 rolle?' gin consists essentially of two small cylinders revolving 
 in contact, or nearly so, with each other. The cotton is drawn 
 between these rollers, while the seeds, being too large to pass, 
 are left behind, and fall out on one side. The saio gin, in- 
 vented by Mr Whitney, is intended for those sorts of cotton, the 
 seeds of which adhere too strongly to be separated by the for- 
 
 ♦ See Brande's quarterly Journal, vol. iv. p. 32!). 
 
MATERIALS USED IN THE ARTS. 39 
 
 mer method. It consists of a receiver, having one side cover- 
 ed with strong parallel wires, placed like those of a cage, and 
 about an eighth of an inch apart. Between these wires enter 
 an equal number of circular saws, revolving on a common 
 axis. The teeth of these saws entangle the cotton and draw it 
 out through the grating of wires, while the seeds are prevented 
 by their size from passing. The cotton thus extricated is 
 swept off from the teeth of the saws by a revolving cylindrical 
 brush ; and the seeds fall out at the bottom of the receiver. 
 
 Tuiyentine. — Turpentine is the juice which exudes from 
 pme trees. The Southern pitch pine furnishes most of that used 
 in commerce. It is procured by making incisions, or cavities, 
 in the ti'unk, and dipping out the turpentine which collects. 
 Tar is an impure turpentine obtained by burning. The resi- 
 nous parts of the wood called lightwood, are collected in pits, 
 and being set on fire at the top, a part of the turpentine is burnt, 
 while the rest is melted and flows out at the bottom. Pitch 
 is tar inspissated by boiling, or burning. If turpentine be dis- 
 tilled, the volatile portion, which passes over, is the oil or spi- 
 rit of turpentine, while the solid part left behind is rosin. 
 
 Caoutchouc. — This substance, called also elastic gum and 
 India rubber, is obtained from different vegetables, but chief- 
 ly fi'om the Jatropha elastica. It exists in the form of juice, 
 and is dried by applying it, in successive coatings, to clay 
 moulds of various shapes. After it is dry, the clay is crushed 
 and shaken out. This substance is wonderfully flexible and 
 elastic, and restores itself instantly, after being extended to 
 many times its original dimensions. It is inflammable and 
 used by the inhabitants of Cayenne for lights. It is insoluble 
 in water, and in alcohol ; but dissolves in either, and in oils. 
 These solutions have been used for varnishes, but have the dis- 
 advantage that they do not readily dry. A mixture of oil of 
 turpentine and alcohol,* is a solvent which has the property of 
 drying more readily and restoring the elastic properties of the 
 
 ♦Chaptal. Chimie appl. aux Arts. 
 
36 MATERIALS USED IN THE ARTS. 
 
 gum. The purified naptha from coal tar has the same proper- 
 ty.* The crude juice may also be imported, and mamifactur- 
 ed into articles here.t Slips of India rubber may be made to 
 cohere by boiling them in contact for a certain time in water, 
 and in this way some articles are made. Caoutchouc is of 
 great use in the formation of many instruments, which re- 
 quire to be elastic, and impenetrable to water. Shoes are now 
 made of it in great numbers, and are found to exclude perfect- 
 ly the wet. The solution of this gum, spread upon leather 
 and cloth, renders them water-proof, and even air-tight. Its 
 adhesiveness and friction are the properties by which it erases 
 black lead from paper. 
 
 Oils. — Oil is an inflammable liquid, which does not unite 
 with water. Volatile oils are those which evaporate, or may 
 be distilled without change, by a moderate heat. Of these, 
 the oil of turpentine is an example. They are used in the arts 
 for solvents, and in varnishes. Fixed oils are those which 
 do not evaporate without decomposition, or chemical change. 
 They produce an unctuous stain, which is not discharged by 
 heat. They do not boil at a temperature much short of that 
 of melting lead. They unite with alkalies, forming soaps. 
 Some of them are called fat oils, which do not lose the unc- 
 tuous character on exposure to the atmosphere, but assume a 
 state like that of tallow ; such for example as Olive oil. Oth- 
 ers are called drying oils, which become solid in the air, after 
 
 * Turner's Chemistry. 
 
 t Mr Faraday states that the Hquid caoutchouc, or juice, as it came from the 
 south of Mexico, was a pale, yellow, thick, creamy looking substance, of a uni- 
 form consistency, with a disagreeable acescent odor. When exposed to the air 
 in films, it is soon dried, leaving caoutchouc of the usual appearance and color. 
 One hundred parts of the sap left nearly fortyfive of solid matter. Heat caused 
 an immediate coagulation of the sap, the caoutchouc separating in a solid form. 
 When the sap is purified hy repeated washings with water, the caoutchouc rises 
 each time to the surface, it is obtained of a white color, and afterwards, when 
 perfectly dry, it becomes transparent, colorless, and elastic, A solution of car 
 outchouc in oil was obtained by mixing the juice with olive oil, and heating the 
 mixture so as to drive off the aqueous parts. This promises to be a useful ele- 
 ment in varnishes. See Brande's Journal, No. xli. page J9, 
 
MATERIALS USED IN THE ARTS. 37 
 
 exposure for a certain time, and remain transparent. This is 
 the case with hnseed oil. Fat oils are used in the arts, to give 
 flexibihty to other materials ; to diminish their friction, and to 
 protect them from water. Drying oils are largely consumed 
 as ingredients in paints, printers' ink, and varnishes. 
 
 Resins. — Various resinous substances are employed in the 
 arts. They are fusible, inflaiTimable, soluble in oil and alcohol; 
 but insoluble in water. For ordinary purposes the rosin of the 
 pine is employed, being the cheapest. For varnishes, copal, 
 mastic, anime, and some others are used. The basis of seal- 
 ing wax is the resin called lac, which is deposited on trees in 
 India by an insect. 
 
 Starch. — Starch or Feciila, is a white substance, obtained 
 from farinaceous grains and roots. It is insoluble in cold wa- 
 ter, but dissolves readily in hot water. In alcohol it does not 
 dissolve. In Europe, starch is commonly made from wheat. 
 In this country it is prepared, for manufacturing purposes, from 
 potatoes. For this object the potatoes are rasped, or ground 
 up, by a machine, to a pulp. This pulp, when washed with 
 cold water, yields a white powder, which, on subsiding, proves 
 to be pure starch. It is heavier and goes further, for practical 
 purposes, than the starch of wheat. Starch is largely consum- 
 ed in cotton factories in the process of dressing, &c. 
 
 Gum. — The true gums are those which dissolve in water, 
 either hot or cold, and form with it a thick, mucilaginous solu- 
 tion. They do not dissolve in alcohol, nor melt by heat. The 
 species principally used are the gum arabic, gum tragacanth, 
 and gum, Senegal. Gum, in the state of mucilage, is employ- 
 ed to give firmness and lustre to linen. Calico printers use 
 it in great quantities, to give their colors such a degree of con- 
 sistency, as will prevent them from running upon the cloth. 
 It is made to form an ingredient in writing ink, and in water 
 colors, for the same reason. 
 
38 MATERIALS USED IN THE ARTS. 
 
 MATERIALS PROM THE ANIMAL KINGDOM. 
 
 Skins. — The cutis, or true skin of animals, from which 
 leather is made, is composed of fibres irregularly situated, and 
 closely interwoven. They are capable of being dissolved by 
 long boiling in water, and are found to consist almost wholly 
 of gelatin, or glue. The skins of a great variety of animals 
 are used in the manufacture of leather. It has been found 
 that those skins which are most flexible, and most easily dis- 
 solved, afford the poorest leather and the weakest glue ; while 
 those which are tough, and difficult of solution, yield leather 
 and glue of the best quality. 
 
 Hair and Fur. — The hairs of animals consist of slender, 
 flexible tubes, having a consistence like that of horn, and 
 possessing the chemical properties of coagulated albumen. 
 The surface of hairs are covered with minute scales or asperi- 
 ties, which give them a rough feel when they are rubbed up- 
 ward ; and which cause them to entangle each other in the 
 processes oi felting and fulling. Pur consists of very fine 
 hair, thickly set, and commonly contorted. It is a very slow 
 conductor of heat, and is provided by nature for the clothing 
 of animals in high latitudes. Hair is a durable and very 
 elastic substance, and is converted to many useful purposes. 
 By means of a linen warp, it is woven into cloth for furniture. 
 It forms the most elastic stuffing for cushions and mattresses. 
 It is combined with mortar in plastering, to increase its cohe- 
 siveness. Furs are converted to important uses, in clothing 
 and in felting. 
 
 Quills and Feathers. — The structure of the quills and 
 feathers of birds is remarkably fitted to combine strength and 
 elasticity with lightness ; the mechanism of the tube, shaft, 
 and feathering, being all adapted to this purpose.* The tube, 
 or barrel of a quill, consists of two laminae or layers, the out- 
 
 * See Chapter II 
 
MATERIALS USED IN THE ARTS. 39 
 
 ermost of which has transverse fibres, and the inner, longitu- 
 dinal. It is the first of these which is scraped off to prepare 
 the quill for splitting. Ctuills are rendered transparent by ex- 
 posing them to heat and moisture. The process recommend- 
 ed by M. Schloz, is to expose the quills to hot steam, by sus- 
 pending them in a covered vessel which contains water in the 
 bottom, and is kept boiling for four hours, the quills being 
 immersed in the vapor only. At the end of this time they 
 are withdrawn, and the next day cut, wiped, and dried with 
 a moderate heat. Feathers.^ as they are obtained from com- 
 mon birds, and down, which is procured from the aquatic 
 birds of northern climates, are among the most elastic substan- 
 ces known, and also the slowest conductors of heat. These 
 properties are the foundation of their usefulness. The chem- 
 ical composition of feathers is nearly similar to that of hair.* 
 
 Wool. — Wool is a fine, soft, long, and contorted hair, deriv- 
 ed chiefly from the sheep. It is said to be the result of culti- 
 vation, and not to be found in the wild sheep, which is cover- 
 ed with short hair. Removal to a tropical climate causes 
 the fleeces of sheep to fall off, and to be succeeded by a cover- 
 ing of short hair. Wool is an invaluable material in the 
 clothing of civihzed nations. The fineness and position of its 
 fibres enable it to be drawn out like cotton, and to be spun 
 by machinery. Their roughness and tendency to curl cause 
 the fibres to be consolidated in the process of felting. 
 
 Silk. — Silk is spun by the larvae or caterpillars belonging to 
 different species of PhalcBna. It forms the ball or cocoon in 
 which the silk worm envelopes himself in passing to the 
 chrysahs state. The fibre, which constitutes this ball, is so 
 small, that a single thread, when unwound, is often twelve 
 hundred yards in length. The original threads are too fine 
 for manufacturing purposes, and therefore in winding or reel- 
 ing them off from the cocoons, the ends or threads of several 
 
 * Feathers are purified by exposing them to heat ; also by immersing them 
 in lime water for several days, and afterwards washing them with pure water, 
 and drying. This process extracts the animal oil. 
 
40 MATERIALS USED IN THE ARTS. 
 
 cocoons are joined together, and reeled out of warm water, 
 which softens their natural g'ummy covering, and causes them 
 to cohere into a single thread. Silk, as it is spun by the ani- 
 mal, is of a color varying from white to reddish yellow. Its 
 texture is very strong and elastic. It communicates to water 
 a mucilaginous character, owing to the solution of its gummy 
 part ; but the silk itself is insoluble in water or alcohol. 
 
 Bone and Ivory. — The bones of animals are composed of a 
 white, hard, lamellar substance, consisting chiefly of phosphate 
 of lime, with a small portion of other earths, and impregnated 
 with oily and gelatinous matter. Exposure to heat causes them 
 to soften and crumble. Bone is used in the arts for the han- 
 dles of cutlery, and various articles of turners' work. It is 
 whitened by exposure to the sun and weather, and sometimes 
 by the use of chlorine gas. It is wrought by sawing, turning, 
 &c., and polished with pumice and tripoli. Ivory is the ma- 
 terial of the elephant's tusks. It agrees with bone in its prin- 
 cipal properties, but is more compact, hard, and white, and re- 
 ceives a finer pohsh. When burnt in close vessels and after- 
 wards reduced to powder, it furnishes the pigment called ivory 
 Mack. The shells of marine animals differ from bone in be- 
 ing composed of carbonate, instead of phosphate of lime. 
 
 Horn. — Horn differs from bone, not only in its texture, which 
 is softer, but also in its composition, being composed chiefly of 
 animal matter resembling coagulated albumen, and contain- 
 ing but httle lime. Horn when heated becomes soft, flexible, 
 and plastic, capable of being cemented and pressed by moulds 
 into a great variety of shapes. 
 
 Tortoise Shell. — This substance exists in the form of plates 
 on the outside of the shell of a species of sea turtle ( Testudo 
 imhricata.) It resembles horn in its general properties, and 
 like that article may be wrought by softening it in boiling wa- 
 ter, and subjecting it, while hot, to pressure in moulds. The 
 edges of different pieces, by pressing them with heated irons, 
 may be joined together and made to cohere firmly. 
 
 Whalebone. — This substance is obtained from the mouth 
 
MATERIALS USED IN THE ARTS. 41 
 
 of several species of whale, where it exists in the form of plates 
 arranged on the outer edge of the upper jaw. These plates 
 terminate in a kind of hair. Whalebone, in its texture and 
 chemical properties, is very similar to horn. It is strong, light, 
 and elastic ; on which accounts it is applied to various mechani- 
 cal uses. Whalebone, when heated by steam, or boihng water, 
 becomes more flexible, and if bent into any shape, retains its 
 form on cooling. Hence it has been manufactured into various 
 woven fabrics.* It may be cemented in the same way as horn 
 or turtle shell. 
 
 Glue. — The skins, tendons, membranes, &c. of animals, are 
 composed principally of a substance known in chemistry by the 
 name of gelatin. This substance is not soluble in cold water, 
 but dissolves freely in boiling water, and on cooling assumes 
 the state of jelly. It has great affinity for tannin^ which ex- 
 ists in astringent barks ; and on this affinity depends the man- 
 ufacture of leather. Common glue is impure gelatin, obtained 
 from hoofs, ears, and refuse portions of hides. These are first 
 cleansed, then boiled to a jelly, which, on cooling, is cut into 
 squares and dried upon nets. Size is a finer kind of glue, 
 made with more care, from select materials. Isinglass is a 
 still more delicate sort, prepared from the swimming bladders 
 of fish. Glue is a cementing material of unequalled strength, 
 for wood and fibrous substances. It is employed in different 
 states of purity, by carpenters, hatters, paper makers, hnen man^ 
 ufacturers, gilders, painters in distemper, and refiners of liquors. 
 In the state of a stiff jelly, it forms, with treacle, the elastic cyl- 
 inders, used to distribute and apply the ink, in printing. 
 
 Oil. — The oil of animals belongs to the class of fixed and 
 fat oils. The oil of those animals which live in a cold medium, 
 as whales, remains fluid at common temperatures ; but that of 
 most land animals becomes solid, when cooled below the heat 
 of the living body. Tallow^ tlie hardest kind, is obtained from 
 ruminating quadrupeds. Animal oils are appropriated to the 
 
 ♦ Repertory of Arts, 1807, page 411. 
 
 6 
 
42 MATERIALS USED IN THE ARTS. 
 
 same purposes as the vegetable ; but their great use is to fur- 
 nish light, by their combustion. 
 
 Wax. — Wax, in its crude state, is obtained by melting the 
 honeycomb of the bee. It is commonly classed with vegetable 
 substances ; but the experiments of Huber have shown, that 
 it is produced by the bees themselves, and not gathered by 
 them directly from plants, as was formerly supposed. Wax 
 melts with a gentle heat, at one hundred and fortytwo degrees 
 of Fahrenheit, is inflammable, dissolves in boiling alcohol, 
 ether, and fixed oils ; but is insoluble in water.^ Beeswax is 
 deprived of its coloring matter by bleaching. To effect this, 
 the melted wax is suffered to run through holes in the bottom 
 of a vessel, upon the surface of a cyhnder which is kept revolv- 
 ing in water, by which means the wax is spread out, and cool- 
 ed in the form of thin laminee or ribbands. It is then exposed 
 to the light and air upon frames, and occasionally wet, till the 
 bleaching is completed. Bayberry or myrtle wax is a harder 
 substance than beeswax, obtained from the berries of the mi/- 
 rica cerifera, by boiling them in water. 
 
 Phosphorus. — Phosphorus is a simple combustible body, 
 usually obtained from animal bones. It is of a soft, waxy con- 
 sistence, and is luminous in the atmosphere at common tem- 
 peratures. At one hundred and fortyeight degrees of Fahren- 
 heit, it takes fire and burns with great brilliancy. On this ac- 
 count it should be kept in water. Phosphorus is the agent, in 
 some kinds of apparatus, for procuring fire. 
 
 References. Among the works, which may be usefully consulted 
 on the subjects of this chapter, are Cleveland's Mineralogy, 2 vols. 
 8vo. 1822 ; — Brard, Miniralogie appliqu6e aux Arts, 3 torn. 8vo. Paris, 
 1821 ;— Eveltn's Sylva, 2 vols. 4to. edit, of 1812 ;— Michaux, North 
 American Sylva, 3 vols. 8vo. 1817 ; — Tredgold's Elementary Princi- 
 ples of Carpentry, 4to. 1820; — Thomson's Chemistry; — Ure's Dic- 
 tionary ; — Vicat, Recherches sur les Chaux, 8>fc. 
 
CHAPTER II. 
 
 OF THE FORM, CONDITION, AND STRENGTH OF MATERIALS. 
 
 When materials are employed for mechanical purposes, the 
 power or strength with which they resist external force, de- 
 pends not merely upon the nature of the material, but upon its 
 shape, its bearings, and upon the manner in which force is ap- 
 plied to it. It is, therefore, important to consider not only the 
 qualities of individual substances, but Ukewise the laws, which 
 are common to different materials, by which they act in resist- 
 ing mechanical change, from forces applied to them. 
 
 Modes of estimation. — Two methods are employed in esti- 
 mating the strength of materials, in different forms and situa- 
 tions ; one by mathematical computation, the other by actual 
 experiment. The fii'st supposes the structure of given bodies 
 to be homogeneous, so that the cohesion of their particles shall 
 be equal throughout. In the second, a single specimen is tak- 
 en as the representative of a class ; or at most the average of a 
 nmnber of specimens, is so taken. Neither method, therefore, 
 is to be looked upon as precisely accurate in its results ; yet 
 these results furnish approximations to truth, which, in many 
 cases, it is useful to understand. 
 
 Stress and strain. — Professor Robison, and some other wri- 
 ters on the strength of materials, have enumerated four modes, 
 commonly called strains, by which any force or stress acting 
 upon a soUd body may operate to overcome the cohesion of its 
 particles. These are, 1. By extension., producing a tendency 
 to rupture ; as in the case of ropes, tie-beams, king-posts, &c. 
 2. By compression, tending to shorten or crush the material ; 
 as in columns, walls, and foundations. 3. By transverse strain, 
 tending to produce flexure or fracture ; as in beams, rails, and 
 oars. 4. By torsion or twisting ; as in screws, rudders, and 
 
44 THE FORM, CONDITION, AND 
 
 axles fixed to wheels. To these Dr Young has added anoth- 
 er, viz ; — detrusion, or pushing aside, as in the case of a pin 
 operated on by the blades of scissors. The changes called 
 flexure, or bending ; fractm^e, or solution of continuity ; and 
 alteration, or permanent change of form without separation ; 
 are to be included in the effects of force exerted on materials. 
 
 Resistance. — To these disturbing influences, bodies oppose 
 certain qualities, which depend, in part, upon the nature of 
 the material, and in part on its form, condition, and connexion. 
 These are their strength, by which they resist all permanent 
 changes resulting from mechanical force, but more particularly 
 fracture. Their hardness, by which they resist impressions, or 
 superficial changes. Their stiffness, by which they resist 
 flexure or bending. Their elasticity, by which they regain 
 their original size and form, after any force producing mechan- 
 ical change in them has ceased to operate. Their tenacity, 
 by which they undergo permanent alteration without fracture. 
 This quality is called ductility, when exposed to extension, 
 and malleability, when exposed to compression. Some au- 
 thors add the term resilience, to express the quality by which 
 a body resists impulse, hke that of a blow, in contradistinction 
 from strength, by which it resists pressure. 
 
 Extension. — When a bar of any material is drawn in the 
 direction of its length, its resistance, or strength, will be pro- 
 portionate to its size at the weakest point ; i. e. to the area of 
 its cross section at that point. The tie-beam of a roof, the 
 posts of a printing press, and the shaft or piston rod of a pump, 
 are exposed to this kind of strain ; and their weakest point is 
 commonly found at the place where they are perforated, or 
 mortised, to connect them with the other parts. Various ex- 
 periments have been made to determine the comparative 
 strength with which different substances resist tension. Al- 
 though they do not fully agree in their results, they neverthe- 
 less, when taken collectively, afford approximations of some 
 use for practical purposes. An idea of the relative strength of 
 the metals, when extended, may be obtained from Mr Rennie's 
 
STRENGTH OP MATERIALS. 45 
 
 experiments detailed in the Philosophical Transactions for 
 1818. His experiments were made with bars six inches long, 
 and a quarter of an inch square. The average number of 
 pounds avoirdupois, which they supported respectively, is, in 
 round numbers, as follows. Steel, about 8000 pounds. Ham- 
 mered ii'on, about 4000. Gun metal and wrought copper, 
 2000. Cast copper and brass, 1000. Tin, 300. Lead, 100. 
 Experiments have been made on the longitudinal strength of 
 the wood of different European trees ; and similar experiments, 
 sufficiently varied, on the trees of this continent, might be a 
 valuable addition to our knowledge. 
 
 Compression. — When a bar or beam is compressed in the 
 direction of its length, it resists more powerfully than in any 
 other way.* If the beam be long, and its strength be over- 
 powered by pressure, it bends, and then breaks ; but if its 
 thickness be as much as a seventh part of its length, it com- 
 monly swells in the middle, splits, and is crushed. When a 
 stone block or pillar is crushed, the parts nearest to the force 
 break away, and slide off diagonally at the sides, leaving a 
 pyramidal base. The lower stories of buildings, the piers and 
 pUes of bridges, the spokes of carriage wheels, and the legs of 
 furniture, are subjects of this force. According to Mr Tred- 
 gold,t a cubic inch of malleable iron will support, without al- 
 teration, a weight of about 17000 pounds ; cast iron, 15000 ; 
 brass, 7000 ; oak and mahogany, nearly 4000 ; tin, 3000 ; 
 lead, 1500. Granite is crushed by 11000 pounds to the square 
 inch : white marble, by 6000 ; Portland stone, by 4000. 
 
 When a force acts on a straight column in the direction of 
 its axis, it can only extend or compress it equally/ through its 
 whole substance. But if the direction of the force is not in the 
 
 * Modulus of elasticity. — This term has been introduced as a measure to 
 express the elastic force of any substance. The Modulus of elasticity of a 
 substance is a column of the same substance, capable of producing a pressure 
 on its base, which is to the weight causing a certain degree of compression, 
 as the length of the substance is to the diminution of its length. 
 
 t Essay on Cast Iron, p. 269, etc. 
 
46 THE FORM, CONDITION, AND 
 
 axis, but parallel to it, the extension or compression will then 
 be partial. In a rectangular column or block, when the com- 
 pressing force is apphed to a point more distant from the axis 
 than one sixth of the depth, the remoter surface will be no 
 longer compressed, but extended. In this case, the distance 
 from the axis of the neutral point, or that which is neither com- 
 pressed nor extended, will be inversely as that of the point to 
 which the force is applied. For example, a £t 
 weight or compressing force being applied on 
 one side of the block or column C D E F, and 
 acting in a direction parallel to its axis, the 
 compression will extend only to the line A B, 
 the parts beyond this being extended. u' ]g E 
 
 Lateral stram. — When a beam is acted on transversely, 
 or by a lateral force, the effect produced is the joint result of 
 extension and compression. For if it be moved or bent by 
 such a force, from its original direction, the part which becomes 
 convex is extended, while the part rendered concave is com- 
 pressed. The properties by which a beam resists lateral pres- 
 sure, are its stiffness and its strength. 
 
 /Stiffness. — The stiffness of any substance is measured by 
 the force required to cause it to bend or recede through a giv- 
 en small space in the direction of the force. It appears to be 
 governed by different laws from those of the strength which 
 resists fracture. When a force is applied to a beam transverse- 
 ly, its stiffness is directly as the breadth, and the cube of the 
 depth of the beam, and inversely as the cube of its length.* 
 Thus if we have a beam which is twice as long as another, we 
 must make it, in order to obtain an equal stiffness, either twice 
 as deep, or eight times as broad. When a beam is supported 
 at both ends, its stiffness is twice as great as that of a beam of 
 half the length inserted in a wall, or otherwise firmly fixed, at 
 
 * Gregory's Mathematics for practical men, 389, also Young's Nat. Philoso- 
 phy, i. 139, and Tredgold's Elements of Carpentry, 31. 
 
STRENGTH OF MATERIALS. 47 
 
 one end. If both ends are firmly fixed, the stiffness is quad- 
 rupled.* 
 
 Tubes. — A tube or hollow beam is much stiffer than the 
 same quantity of matter in a solid form. The stiffiiess is in- 
 deed increased nearly in proportion to the square of the diam- 
 eter ; since the cohesion and repulsion are equally exerted, with 
 a smaller curvature, and act also on a longer lever. We see 
 this principle applied in nature in the stems of reeds, and the 
 bones and quills of animals. 
 
 Strength. — The strength of beams of the same kind, and 
 fixed in the same manner, in resisting a transverse force which 
 tends to break them, is simply as their breadth, as the square 
 of their depth, and inversely as their length. Thus if a beam 
 be twice as broad as another, it will also be twice as strong ; but 
 if it be twice as deep, it will be four times as strong ; for the 
 increase of depth not only doubles the number of the resisting 
 particles, but also gives each of them a double power, by in- 
 creasing the length of the levers on which they act. The in- 
 crease of the length of a beam must obviously weaken it, by 
 giving a mechanical advantage to the power which tends to 
 break it; and some experiments appear to show, that the 
 strength is diminished in a proportion greater than that in 
 which the length is increased. 
 
 The strength of a beam supported at both ends, like its stiff- 
 ness, is twice as great as that of a single beam of half the 
 length, which is fixed at one end ; and the strength of the 
 whole beam is again doubled, if both the ends are firmly 
 fixed. 
 
 * The quantity of timber being the same, a beam will be stronger in propor- 
 tion as the depth is greater ; but there is a certain proportion between the depth 
 and breadth, which, if it be exceeded, the beam will be liable to overturn and 
 break sideways. To avoid this, the breadth should never be less than that 
 given by the following rule, unless the beam be held in its position by some oth- 
 er means. 
 
 Divide the length in feet, by the square root of the depth in inches, and the 
 quotient multipUed by the decimal 0.6 will give the least breadth that should 
 btj given to the beam. — Tredgold's Carpentry, p. 32. 
 
48 THE FORM, CONDITION, AND 
 
 Place of strain. — If a weight or other stress be placed on 
 any given point of a hoiizontal bar which is supported at both 
 ends, the strain on that point will be proportional to the rec- 
 tangle of the two segments into which the point divides the bar. 
 Hence the place where the strain would be greatest is in the 
 middle of the bar, and a given weight would be most likely to 
 break it in that place. 
 
 Incipient fracture. — An incipient or partial fracture, at the 
 place of strain, weakens a beam more, than if the whole side 
 of the beam were cut away to the same depth as the fracture. 
 This is because the sound, or stronger parts of the beam tend 
 to straighten themselves, and thus increase the curvature at the 
 point which is weakened. The same cause occasions the break- 
 ing of glass in the dii'ection of a cut made by a diamond, or of 
 a crack which has commenced. Mr Emerson asserts that a 
 triangular beam, which is so strained that the greatest exten- 
 sion takes place at one of its angles, is rendered stronger, rath- 
 er than weaker, by cutting away this angle to a small depth, 
 so as to convert the beam into a four-sided figure ; thus produ- 
 cing the seeming paradox of a part being stronger tlian the 
 whole. A sharp angle is indefinitely weak, and fracture is 
 more likely to begin in an angle than in a bioad surface. 
 
 Resilience. — The property which resists pressure, is called 
 strength, and that which resists impulse, is termed by Dr 
 Young, resilience.* The lesilience is measured by the pro- 
 duct of the mass, and the square of the velocity of a body ca- 
 pable of breaking it, while the strength is merely measured by 
 the greatest pressure that it can support in a state of rest. 
 
 The resilience of a prismatic beam, resisting a transverse 
 impulse, follows a different law from that which determines its 
 strength ; for it is simply in proportion to the bulk or weight of 
 the beam, whether it be shorter or longer, narrower or wider, 
 shallower or deeper, solid or hollow. Thus a beam ten feet 
 long, will support but half as great a pressure without break- 
 ing, as a beam of the same breadth and depth, which is only 
 * Nat. Philosophy, pp. 143-147. 
 
STRENGTH OP MATERIALS. 49 
 
 five feet in length ; but it will bear the impulse of a double 
 weight, striking against it with a given velocity, and will re- 
 quire that a given body should fall from a double height in or- 
 der to break it.* 
 
 Shape of timber. — It may be inferred from the consideration 
 of the nature of the different kinds of resistance, that if we have 
 a cylindrical tree a foot in diameter, which is to be formed in- 
 to a prismatic beam by flattening its sides, we shall gain the 
 greatest stiffness by making the breadth or thickness six inch- 
 es and the depth ten and a half; the greatest strength by 
 making the breadth seven inches and the depth nine and three 
 quarters, and the greatest i^esilience by making the beam 
 square.t 
 
 Torsion. — The kind of strain called torsion or twisting, con- 
 sists in the lateral displacement or detrusion of the opposite 
 parts of a solid, in opposite directions ; the central particles only 
 remaining in their natural state. The strength, or rather stiff- 
 ness, with which the shaft of a wheel, or crank resists torsion, 
 increases in a rapid ratio to its diameter. Professor Robison 
 has calculated, that the power of resisting torsion is as the cube 
 of the diameter ; and the more recent estimates of M. Duleau 
 make it as the fourth power of the diameter. If the length 
 vary, the resistance to the force of torsion will be inversely as 
 the length, for obvious reasons. It is advantageous in machin- 
 ery to increase the diameter of shafts which are exposed to 
 this strain, the amount of material remaining the same. For 
 this purpose they are sometimes made hollow, and sometimes 
 winged with lateral projections. 
 
 Limit of hulk. — It is important to recollect that when the 
 bulk of a substance employed, becomes very considerable, its 
 own w^eight may bear so great a proportion to its strength, as 
 to add materially to the load to be supported. In most cases, 
 the weight of bodies increases more rapidly than their strength, 
 and thus causes a practical limitation of the magnitude of our 
 machines and edifices. Thus a roof, or a bridge, may be very 
 
 Young's Nat. Philosophy, p. 148. + Ibid. p. 149. 
 
 7 
 
50 THE FORM, CONDITION, AND 
 
 strong, when of small, or moderate size ; but if the size be ex- 
 tended beyond a certain limit, although the materials and pro- 
 portion of parts remain the same, yet the structure will not sup- 
 port its own weight. We see also a similar limit in nature ; 
 for if trees and animals were made many times larger than we 
 now find them, and of the same kinds of substance, they would 
 not sustain their own weight. Small animals endure greater 
 comparative violence, and perform greater feats of strength in 
 proportion to their size, than large ones. It has been observed 
 that whales are larger than any land animals, because their 
 weight is more equally supported by the pressure of the medi- 
 um in which they swim. 
 
 Practical Remarks. — In frames of houses, and for various 
 other purposes, beams are used of a prismatic form, having 
 straight, parallel sides. But such beams, when exposed to a 
 lateral strain, are not of equal, or duly proportioned strength 
 throughout ; and therefore a part of them is superfluous. 
 This consideration is not of much importance in ordinary 
 practical cases. But in cases where economy of the material 
 is important, as in cast iron railroads, also in machinery where 
 it is desirable that the moving parts should be as light as pos- 
 sible, consistently with the requisite strength ; it becomes of 
 consequence to ascertain the best form for resisting a force 
 with the smallest amount of material. Mathematicians have 
 calculated the forms of different beams, which are suited to 
 give them, at all points, a strength proportionate to the pres- 
 sure they sustain, supposing the material to be of uniform 
 texture. But the outline which answers merely to mathemat- 
 ical truth, is in many cases too scanty for actual employment ; 
 so that in order to obtain sufficient length for a secure connex- 
 ion of the beam with its bearings, it is necessary to include 
 the mathematical figure in a somewhat similar one, of larger 
 dimensions. The following rules are, most of them, given in 
 substance by Mr Tiedgold.* 
 
 If a beam be supported at both ends, and the load applied 
 
 * Essay on Cast Iron, Art, 21, et seq. 
 
STRENGTH OF MATERIALS. 
 
 51 
 
 at some one point between the supports, and always acting in 
 the same direction, the best plan appears to be, to make the 
 extended side, or that opposite the load, perfectly straight ; and 
 to make the breadth equal throughout the whole. Then the 
 mathematical form of the compressed side will be that which is 
 formed by drawing two semi-parabolas, A C D and BCD, their 
 vertices being at A and B, and C being the point where the 
 force acts. INow since the curve terminates at A, it is neces- 
 sary, in applying it to use, to add some such parts as are indi- 
 cated by the lines extending to E and F at the extremities, 
 for the sake of better support. 
 
 The same form is proper for abeam supported in the middle, 
 as the beam of a balance. If the beam be strained, sometimes 
 from one side and sometimes from the other, as in the beam of 
 a steam engine, then both sides should be of the same form, 
 and E A and F B should each be equal to half C D. 
 
 It is sometimes desirable to preserve the same depth through- 
 out ; and in this case the section through the length of the 
 beam, made perpendicular to the direction of the straining force, 
 should be a rhombus or trapezium, as in the annexed figure, 
 the force acting perpendicularly at C, and the points of support 
 being at A and B. To give this figure stability, the ends may 
 be formed as shown in the continued outline. 
 
62 
 
 THE FOHM, CONDITION, AND 
 
 If a beam be intended to support a weight uniformly distri- 
 buted throughout its length, or a load rolling over it, as in a rail- 
 way, the line bounding the compressed side should be a semi- 
 ellipse, the other side being straight. In practice the semi-el- 
 lipse may be included in a portion of a circle, to give the re- 
 quisite bearings. 
 
 A, B, ends of the elliptic curve. C, D, ends of the circular 
 curve. 
 
 Where it is necessary that the upper side should be straight, 
 the above form may be inverted, and the ends adapted to the 
 bearings. 
 
 Beams which are fixed at one end only and support weights, 
 should decrease as they recede from the wall, or point of fix- 
 ture. If the weight be at the extremity, the outline, in a beam 
 cut from a vertical plank, should be parabolic ; but if equally 
 distributed throughout, it may be straight. 
 
 If a beam be firmly fixed at both ends, and supports a 
 weight in the middle, it should be largest at the ends and in 
 the middle, the outlines being parabohc. In the annexed fig- 
 ure the shaded part shows the mathematical form, and the 
 outline the form for practical purposes. 
 
STRENGTH OF MATERIALS. 53 
 
 For resisting a cross strain, it is advantageous that 
 the edges of a beam should be made thicker than the 
 rest of its substance, so that a section of the beam 
 would be nearly such as is seen in the adjoining 
 figure.* 
 
 It must be recollected that the foregoing rules prescribe only 
 a general form, the proportions of which must vary with the 
 nature of the material, and the degree of resistance, or load to 
 be supported. 
 
 Works which treat of the strength of materials. — Robison's Mechani- 
 cal Philosophy, 4 vols. 8vo. 1822 ; vol. i. p. 369, &c. ; — Barlow on Tim- 
 ber, 8vo. 1823 ;— Young's Natural Philosophy, 2 vols. 4to. 1807 ; vol. i. 
 p. 335, &c; vol. ii. art. 333, &c. ; — Rennie, in the Philosophical Trans- 
 actions, 1818 ; — DuLEAU, Annales de Chimie, torn. xii. ; — Tredgold's 
 Elementary Principles of Carpentry, 4to. 1820 ; — Tredgold's Essay 
 on Cast Iron, 8vo. 1824; — Emerson's Mechanics; — Gregory's Me- 
 chanics, 3. vols. 8vo. edit. 1826 ; — Gregory's Mathematics for Practical 
 Men, 8vo. 1825. 
 
 * For the form best suited to resist longitudinal pressure, see the article Col- 
 umn in Chap. VII. 
 
CHAPTER III. 
 
 THE ARTS OF WRITING AND PRINTING. 
 
 Letters. — The arts of writing and printing, although com- 
 paratively simple in their processes, are superior to most other 
 arts in the importance of their consequences. Before the in- 
 vention of letters, the growth of knowledge was opposed by 
 insurmountable obstacles. Tradition, which was the earliest 
 mode of transmitting knowledge, depended upon the memory 
 and the will of individuals, and was of course uncertain of 
 continuance. The principal adventitious aids brought to the 
 assistance of traditionary knowledge, were the erecting of mon- 
 u)nents, the celebration of periodical days or years, the use of 
 poetry, a language more captivating and more easily remem- 
 bered than mere narration of facts ; and finally, an approach 
 to written characters in symbolical drawings and hieroglyphic 
 sketches.* All these methods, however, have failed in the object 
 for which they were intended. The ancient founders of ma- 
 ny stupendous structures have not been able to convey to us 
 their names, and the productions of the earliest sages and poets 
 can never be appreciated from acquaintance. History must 
 have remained uncertain and fabulous, and science been left 
 in perpetual infancy, had it not been for the invention of writ- 
 ten characters. 
 
 Invention of Letters. — The credit of the first introduction 
 of letters, was claimed by the Egyptians and Phoenicians, Jews, 
 Chinese, and other nations. Their oiigin is extremely ancient, 
 
 * ,The recent investigations of M. Champollion have led to the discovery 
 that a great part of the hyeroglyphic characters upon the antiquities of Egypt 
 are in reaUty the letters of an alphabet ; and considerable progress has been 
 made in decyphering their import. 
 
THE ARTS OF WRITING AND PRINTING. 55 
 
 and of course preceded all authentic history which was not 
 inspired. If we believe Pliny, sixteen characters of the Gre- 
 cian alphabet were introduced by Cadmus the Phoenician, 1500 
 years before Christ. Four more were added by Palamedes 
 during the Trojan war, and four afterward by Simonides. It 
 is not probable, however, that the Greek w'as the oldest alpha- 
 bet. Mr Astle considers the Phoenicians as having the strong- 
 est claim to be considered the first inventors of letters. 
 
 Arrangement of Letters. — The mode of arranging letters 
 has been subject to considerable variation, some nations haAdng 
 written in perpendicular lines, others from right to left, and 
 others in Unes alternately reversed, as in the j8s?T^a4);j<5av of the 
 ancient Greeks.* The mode of writing from left to right, now 
 generally pursued, is the most natural ; because the hand, as it 
 advances in this direction, leaves constantly uncovered that 
 portion of the page upon which writing has been made. 
 
 Writing Materials. — The most ancient materials employ- 
 ed for writing, appear to have been the surfaces of stones and 
 bricks. The ten commandments were written upon stone, 
 and the arrow-headed alphabet, as it is called, belonging to an 
 extinct language, is only known to us by the pages of inscrip- 
 tions w^hich remain on the Babylonian bricks. After these, 
 plates of metal, of various kinds, were emplo^'^ed. The Ro- 
 mans wTote upon tables of brass thinly coated with Avax, using 
 an iron pencil wdth a sharp point denominated /Stylus. Lead 
 was also used by them, and at the seige of Modena a corres- 
 pondence was carried on by Decimus Brutus, and the consul 
 Hirtius, upon plates of lead. Pausanius mentions books of 
 Hesiod, and Phny speaks of public records, inscribed on the 
 
 * The bustrophedon was disused by the Greeks about 450 years before the 
 christian era ; but a similar method appears to have been in use among the Irish 
 at a much later period. The following example of the Greek bustrophedon is 
 from an inscription on a marble in the national museum at Paris. 
 NEKH0E NEM 20AAT 
 - APISTOKTAES N0H2:EN 
 em decaip sullyH 
 Aristocydes designed me. 
 
56 THE ARTS OP WRITING AND PRINTING. 
 
 same material. A less durable, but more cheap receptacle 
 for written characters, was found in the leaves of trees and 
 their inner bark, denominated liher by the Latins. These 
 were used for the more temporary or perishable writings.* 
 
 Papyrus. — As the literature of antiquity advanced, it be- 
 came necessary to find a material adapted for works of magni- 
 tude, which, besides permanency and enlarged size, should have 
 a fineness of texture sufficient to permit a large surface to be 
 folded into a compact form. A species of reed, growing in 
 Egypt, was found capable of being manufactured into a sub- 
 stance of this sort. Sheets and rolls were prepared from it of 
 the finest texture, and of any dimensions, and it became the 
 receptacle on which a great part of the ancient manuscripts 
 were written. This was the celebrated Egyptian papyrus. 
 The discovery of its manufacture, though it afforded a substance 
 far inferior to modern paper, was nevertheless a great auxiliary 
 to ancient learning, and became the means of a much more 
 extensive multiplication of manuscripts than could have taken 
 place had it remained unknown. The papyrus was an aqua- 
 tic reed growing on the banks of the Nile.t The manufacture 
 of paper was performed by divesting this reed of its outer cover- 
 ing and then carefully separating the internal membranes or 
 laminae by the point of a needle or knife. X These laminae 
 were spread parallel to each other on a table, having their edges 
 
 * Pliny says that tables of wood were in use for writing before the time of 
 Homer. In the Slonian library at Oxford, there are some specimens of ancient 
 Arabic writing on boards about two feet long and six inches wide. 
 
 The edicts of the Roman Senate were written on tablets of ivory, thence de- 
 nominated lihri elephantini. 
 
 According to Pliny, the most ancient mode of writing, was upon the leaves 
 of Palm trees, afterward upon the inner bark of trees. This method is still 
 common in Tanjore, and some other parts of the East Indies where the Palmyra 
 leaf is used. 
 
 The old Egyptians frequently wrote on linen, and specimens of this land are 
 sometimes found enclosed in the garments or swathing clothes of mummies. 
 
 + Cyperus papyrus. L. 
 
 t The delicate substance now imported from India under the name of rtce paper, 
 is a cellular membrane of the Artocarpus incisifolia, or Bread-fruit-tree. Brews- 
 ter'e Journal, ill. 136. 
 
THE ARTS OF WRITING AND PRINTING. 57 
 
 in contact, in sufficient numbers to form a sheet. A second 
 stratmn was then laid, with the strips crossing those of the 
 first at right angles. The whole was moistened with water, 
 and subjected to pressure between two polished surfaces. Up- 
 on drying, the mass was found agglutinated into a smooth 
 and unifoim sheet. The adhesion of the strips of papyrus to 
 each other was doubtless owang to the glutinous juice of the 
 reed, though the Romans, who were ignorant of the Egyptian 
 mode of manufacturing it, attributed this effect to a peculiar 
 quality in the waters of the Nile. The most delicate paper, 
 which was made from the inner membranes or tunics of the 
 reed, was rendered extremely white, and pohshed by rubbing 
 it with a shell, or tooth of an animal. 
 
 Herculaneum Manuscripts. — The papyrus continued in 
 use as late as the tenth or twelfth century, when it was super- 
 seded by parchment and cotton paper. A few ancient man- 
 uscripts written on it are preserved as curiosities in different 
 libraries of Europe, though they are less numerous than those 
 of parchment and vellum. The most interesting collection of 
 papyri is undoubtedly that found at Herculaneum, and was 
 probably buried with that city in an eruption of Vesuvius, 
 which happened during the reign of Titus. In the excava 
 tions which the moderns have made into the earth which cov 
 ers that city, these rolls of papyri, nearly 1700 in number 
 were found in a house, the roof and floors of which had been 
 crushed in by the substances ejected from the volcano. The 
 rolls were found in a state so near to decomposition that the 
 least violence causes them to break and crumble ; their color is 
 so nearly black that the characters are distinguishable from 
 the paper only by a slight shade of difference ; and the whole 
 roll is cemented together, so as not to be separable into layers 
 without great difficulty. This state has been supposed to be 
 produced by the carbonization, or converting into coal, of the 
 papyri, by the heat of the ashes and lava, in which they were 
 buried. Sir Humphrey Davy, however, has given a different 
 opinion of the state of these manuscripts. He supposes that 
 8 
 
58 THE ARTS OF WRITING AND PRINTING. 
 
 their present condition is not the result of carbonization or of 
 heat apphecl to them, but is tlie consequence of their remain- 
 ing for so many ages under ground, until the vegetable mat- 
 ter of which they are composed, has undergone a spontaneous 
 change, and become converted into a substance analogous to 
 peat, or Bovey coal. This conclusion is the result of chemi- 
 cal examination, and is likewise inferred from the fact that some 
 specimens of gilding, and of vermilion, which remained on 
 the walls of the apartment, were not changed in color, which 
 could not have been the case, had tlie heat been sufficient to 
 convert vegetable matter into charcoal. 
 
 About ninety of these manuscripts have been unrolled by a 
 very tedious process, which consists in glueing pieces of gold 
 beaters' skin to the outside of the rolls, and suffering them to 
 dry on. They are then gradually raised by means of screws, 
 lifting with them a layer of the papyrus, which is copied and 
 the process renewed. Several days, in this way, are requisite 
 for a single page. Sir Humphrey Davy thinks a more expedi- 
 tious way might be adopted, by subjecting the rolls to the action 
 of a chemical solvent, capable of destroying the adhesion of 
 the folds to each other. He supposes that of the manuscripts 
 which remain, not more than from eighty to one hundred and 
 twenty are in a state to be unrolled, the rest being too much 
 defaced, by crushing or otherwise, to render it probable they will 
 ever be decyphered. 
 
 Parchment. — Next to the papyrus, the skins of animals, 
 in the form of parchment and vellum, were extensively used 
 for writing, by the ancients, from a remote period. When 
 Eumenes, or Attains, attempted to found a library at Pergamus, 
 200 years B. C, which should rival the famous Alexandrian 
 library, one of the Ptolemies, then king of Egypt, jealous of 
 his success, made a decree prohibiting the exportation of pa- 
 pyrus. The inhabitants of Pergamus set about manufacturing 
 parchment as a substitute, and formed their library principally 
 of manuscripts on this material ; whence it was known among 
 
THE ARTS OF WRITING AND PRINTING. 59 
 
 the Latins by the name of Pergamena. The term rnem- 
 brana was also apphed by them to parchment. 
 
 Paper. — Paper like that used at the present day, composed 
 of flexible fibres reduced to a pulp by minute division, and 
 cemented into sheets by means of size or glue, began to be 
 known in the East in the beginning of the tenth century. 
 It was first composed of cotton or silk, and called bombycina, 
 and was not made from linen rags until the fourteenth century. 
 Coarse brown paper was first manufactured in England in 
 1588 ; writing and printing paper in that country not till 1690, 
 previously to which, it was imported from the continent. 
 
 Instruments. — While writing was practised upon hard sub- 
 stances, as stone and metal, a hard metallic point was the in- 
 strument with which letters were formed. The stylus, which 
 the Romans employed for writing on brass tablets covered 
 with wax, was acute at one end for writing, and flattened or 
 blunt at the other, for erasing what was written. For writing 
 in colored fluids, or ink, the calamus was used, a reed sharp- 
 ened at the point, and split like our pens, duills were not 
 introduced till the fourth or sixth century.* 
 
 Some of the eastern nations still write with reeds, canes, 
 and bamboos, instead of quills. The Chinese write with small 
 brushes hke camel's hair pencils. 
 
 I?iks. — The ink of the ancients consisted of a carbonace- 
 ous substance, such as lampblack, soot, or pulverized coal, united 
 with a viscid or gummy liquid. The black liquor of the cut- 
 tle fish {Sepia) was sometimes employed. Colored inks of 
 vermilion, red lead, and purple, were also used. The eastern 
 emperors signed their edicts with red ink, the use of which was 
 prohibited to others, under pain of death. 
 
 * The earliest notice of the use of quills, is by an anonymous author of the 
 life of Constantius, who says that Theodoric, the Ostrogothic king of Rome, was 
 so illiterate, and so dull of intellect, that, during the ten years of his reign, he 
 could not learn four letters to sign at the bottom of his edicts ; so that they were 
 cut for him in a plate of gold, through which he traced the letters with a quill. 
 One of the oldest certain mentions of the use of quills, is by Isidore, who died 
 in 636. 
 
60 THE ARTS OP WRITING AND PRINTING. 
 
 Modern ink is essentially a tanno-gallate of iron suspended 
 by mucilage. It may be made from salts of iron, and infu- 
 sions of various astringent vegetables. But as many products 
 of this kind are apt to fade by time, it is not safe to trust to 
 any which have not had the testimony of long experience in 
 their favor. The best materials are the nutgall and sulphate 
 of iron, with gum arable. Other ingredients are sometimes 
 added, such as logwood, sulphate of copper, and sugar. When 
 ink fades, it is commonly from the fugitive nature of the gallic 
 acid and tannin ; and it may be revived by moistening the 
 page with a fresh infusion of galls. When ink grows thin 
 from freezing, or dihition, so that its particles subside, they 
 may again be suspended, by agitating it with sugar, or gum. 
 If writing with common ink has been obliterated by chlorine, 
 it may be again rendered legible, by the vapor, or solution, of 
 sulphuret of ammonia. Indelible ink is produced by writing 
 with dissolved nitrate of silver on a surface impregnated with 
 carbonate of soda. 
 
 Copying Machines. — Various modes have been devised, 
 for making extemporaneous copies of written pages. Dr Frank- 
 lin's method consisted in covering the writing, while yet moist, 
 with fine powdered emery ; and afterwards passing the sheet 
 through a press, in contact with a plate of pewter, or copper ; 
 which thus became marked with the letters, so as to yield im- 
 pressions, as in the common mode of copperplate printing. 
 Mr Watt's copying machine consists of a press, in which a 
 thin, bibulous paper, previously moistened, is forced into close 
 contact with the page, while newly written. A part of the 
 ink, sufficient to produce legible characters, is thus transferred 
 to the thin paper. The writing is of course reversed, but the 
 thinness of the paper permits it to be read on the opposite side, 
 which restores the order of the letters. Mr Hawkins' poly- 
 graph is a machine carrying two or more pens in different pla- 
 ces, which are so connected as to pursue a similar path with 
 each other, and execute two or more copies at once. Lithog- 
 raphy likewise offers a ready method of multiplying copies. 
 
THE ARTS OF WRITING AND PRINTING, 61 
 
 PRINTING. 
 
 The art of printing, as it is now practised, by the composition 
 of moveable types, is so simple and obvious in its principles, 
 that it is truly wonderful the process was not earlier known. 
 The ancients many times made near approaches to the discov- 
 ery, but by some singular fatality, they were kept from its pro- 
 fitable use. Arts far more curious, and sciences far more diffi- 
 cult, were known, and carried to perfection, by the patient in- 
 dustry of the ingenious and enterprising in former times. But 
 this art, which was to give permanency to all the rest, and 
 which now seems to be at the root of all human knowledge, 
 was never in useful operation in Europe until three or four 
 centuries ago. 
 
 Types. — Printing at the present day is executed with move- 
 able types, which are oblong square pieces of metal, each bear- 
 ing a letter in relief at one extremity. The metal of which 
 they are made, is an alloy, which consists essentially of lead 
 and antimony. The lead is selected in preference to other 
 metals, because it is fusible at a low temperature, and retains 
 accurately the shape it receives from the mould. But as lead 
 alone is too soft to sustain the friction and pressure to which it 
 is liable in use, about a fifth part of antimony is added. This 
 gives it a superior hardness when cast ; and as this alloy has 
 the property of shrinking less than most other metals as it 
 cools, the type receives all the sharpness and finish, which it can 
 acquire, by filling every part of the mould. In making types, 
 the letter is first cut by an artist upon the end of a steel punch, 
 answering to the shape of the intended type. This punch is 
 driven into a piece of copper, which forms the matrix or bottom 
 of the mould intended to produce the letter. As many vari- 
 eties of punches must be made of steel, as there are sizes and 
 species of characters required. In casting, the types are form- 
 ed with great rapidity, owing to the quickness with which the 
 metal cools. An expert operator will make 2000 or 3000 
 
62 THE ARTS OF WRITING AND PRINTING. 
 
 types in a day. Some machines have been introduced, for 
 casting types, which operate with much greater rapidity. The 
 characters upon types are of course reversed, so that in ar- 
 ranging them for the press, the compositoj; or printer who 
 sets the types, begins at the right hand of each hne. 
 
 Case. — Before the types are applied to use, they are arrang- 
 ed in the cells or compartments of a long wooden receptacle, 
 called a case ; each species of letter, character, or space, by it- 
 self. In arranging the compartments, the collections of letters 
 do not succeed each other in alphabetical order, nor are they 
 all of equal size. T'hose letters which occur most frequently 
 in printing, are required in greater numbers. They are there- 
 fore made to occupy the largest compartments, and are placed 
 nearest to the compositor. Thus the letter e, which is of fre- 
 quent occurrence, fills a large compartment, and is nearest the 
 compositor, while the letter x, which occurs much less frequent- 
 ly, is provided in small numbers, and placed at the extremity 
 of the case. In a bill or collection of types of the size called 
 pica, weighing in all 800 pounds, the number of the letter e is 
 12000 ; of t, 9000 ; of a, 8500 ; of i, n, o, and s, 8000 each ; 
 of c, there are 3000 ; of b, 1600 ; k, 800 ; x, 400 ; z, 200. This 
 is for the English language. In other languages, the compar- 
 ative frequency must be different. 
 
 Sizes. — Different names are given to the various sizes of 
 types, of which the following are most employed in common 
 book printing. 
 
 Pica. — a bcdefghij klmnopqrstu 
 
 Small Pica. — a bcdefghijklmnopqrstuvw 
 Long Primer. — a bcdefghijklmnopqrstuvw 
 Bourgeois. — a bcdefghijklmnopqrstuvwxyz 
 Brevier. — a bcdefghijklmnopqrstuvwxyz 
 Minion. — a bcdefghijklmnopqrstuvwxyz 
 Nonpareil. — a bcdefghijklmnopqrstuvwxyz 
 
 Composing. — The compositor is first provided with an in- 
 strument called the coinposing stick. This is a plate, com- 
 monly of iron or brass, surrounded with ledges, one of which 
 
THE ARTS OF WRITING AND PRINTING. 63 
 
 is moveable, so that the length of the lines may be adjusted to 
 the width of the page. The compositor selects from their pla- 
 ces the letters successively, to constitute the first word, which 
 are arranged in an inverted order from that in which they are 
 to appear on the printed page, beginning at the right. At the 
 end of the word a quadrat is inserted to produce a space be- 
 tween this word and the next following. The quadrats, of 
 which there are various kinds, diiferently named from their 
 width, are blunt types, bearing no letter on their extremities. 
 In printing, they do, not come up to the surface, and of course 
 yield no impression. As the beauty of the page depends upon 
 the evenness of the margin produced by the equality of the 
 Mnes, these quadrats are used to swell out the shorter lines and 
 bring them to an equality with the rest. When one line is 
 finished, the printer shifts the rule from below it to the top, and 
 commences setting the types for a second line. The rule is a 
 thin brass plate used to make the types slide easily, and not 
 catch upon the line below them. 
 
 The quickness with which an expert compositor advances 
 in his work, is greater than would appear possible from a first 
 consideration of the subject. The familiarity with the situa- 
 tions of the letters and their arrangement, produced by long 
 habit, is such, that to select the types and place them, does not 
 require a thought to be bestowed on the process. It is only 
 necessary to perceive the meaning of each word, and the put- 
 ting it together follows as mechanically as writing. It is even 
 possible for a printer to compose in the dark, for the exact sit- 
 uation of each letter in the case before him being known, and 
 the upper side of each being known by notches in the type, 
 they can be selected and arranged by the sense of feehng 
 alone. 
 
 Jniposiyig. — When a sufiicient number of lines, as six or 
 eight, are formed in the composing stick, they are einptied into 
 another instrument called the galley, which is a flat board or 
 plate, partly or wholly surrounded by a rim. In this galley, 
 the types are accumulated, generally in the form of long col- 
 
64 THE ARTS OP WRITING AND PRINTING. 
 
 umns, which are afterwards divided into pages, each page be- 
 ing tied together with a string to prevent the types from falling 
 asunder. When a sufficient number of pages are complet- 
 ed to constitute what is called a/orme, or in other words, to 
 fill one side of a sheet, they are arranged upon an imposing 
 stone^ and strongly locked up, or wedged together, in an iron 
 frame, denominated a chase, to prepare them for the press. 
 
 Signatures. — A sheet intended for a folio, has two pages 
 on a side, and will form two leaves. A quarto has four ; an 
 octavo, eight; a duodecimo, twelve, <fec. , These pages are so 
 arranged in the forme, that in the impression they will assume 
 their true order, after the sheet is folded. The sheets are 
 marked at the bottom of certain pages with successive num- 
 bers, or capital letters ; the object of which is to afford the nec- 
 essary instructions for the order of folding and gathering them. 
 These are called signatures. 
 
 Correcting the Press. — The first impression taken from 
 the types is called a proof. This is carefully read over, and 
 the errors and inaccuracies marked. To correct them, the 
 wedges or quoins, are knocked out, so as to loosen the types ; 
 the erroneous letters are drawn out, and the proper ones sub- 
 stituted, and the whole is again wedged into the frame. 
 
 Many of the errors of the press, which remain uncorrected 
 in books, arise from a want of understanding between the au- 
 thor, or corrector, and the printer, in the characters used in 
 correction. It is not enough that the author should detect 
 these errors and note them in the margin. He must express, 
 by intelligible marks, how these defects are to be altered, and 
 unless he uses such marks as are employed by printers them- 
 selves, his attempts at correctness will be defeated. Every 
 person who has occasion to appear in print, should first know 
 how to correct the press.* 
 
 * If the error is confined to a letter or word, it is easily corrected. But if it 
 involves the addition or erasure of a sentence or a number of lines, the correc- 
 tion is more difficult. The whole forme must be deranged, and as the adding 
 or expungmg of lines affects the length of the page, it must be adjusted at the 
 
THE ARTS OF WRITING AND PRINTING. 65 
 
 The following signs for correcting the press, are era- 
 ployed by printers themselves. 
 
 When a wrong letter is discovered, a line is drawn 
 through it, and the true letter written in the margin, thus ; 
 
 To be, or not to be, that iifi the question. 5 
 
 If a letter is found to be omitted, a caret is placed 
 under its place, and the letter written in the margin, thus ; 
 
 To be, or not to be, tht is the question. a 
 
 A 
 
 If a superfluous letter is detected, it is crossed out, 
 and a character which stands for dele^ introduced in 
 the margin. 
 
 To be, or not to<j> be, that is the question. ^ 
 
 If two words are improperly joined together, a char- 
 acter indicating a space, or quadrat, is used. 
 
 To be, or not tobe, that is the question. d£ 
 
 If syllables of the same word are improperly separated, 
 they are joined by a horizontal parenthesis. 
 
 To be, or not to be, that is the ques tion. '^ 
 
 When words are found to be transposed, they are 
 connected by a curved line, and the letters tr. written 
 in the margin. 
 
 To be, or not to be, (Isyt jiat) the question. tr. 
 
 expense of the next following page ; so that all the subsequent pages may be dis- 
 turbed, before the necessary correctness is obtained. An author who corrects 
 the press for his own works, will very much abridge the labor of the printer, if, 
 in all cases of an erased word, he will substitute another of nearly the same 
 length in its neighborhood, or, if a new word is added, by striking out one in the 
 paragraph which can be better spared. 
 
 9 
 
G6 THE ARTS OP WRITING AND PRINTING. 
 
 When a letter is inverted, it is expressed by a char- 
 acter of this sort in the margin. 
 
 Marks of punctuation, if of small size, are inclosed in 
 circles, thus ; 
 
 A comma is placed after a short stroke, an apostrophe 
 before it. 
 
 9 
 
 
 Words intended to be printed in Italics, are marked beneath 
 with a single line ; if in small capitals, with two lines ; and if 
 in large capitals, with three. Thus a line marked in this 
 manner. 
 
 Oh thou, in Hellas deemed of heavenly birth. 
 
 would be printed thus ; — 
 
 Oh thou, in HELLAS deemed of heavenly birth. 
 
 In correcting with these marks, the abbreviations Ital. Rom. 
 Caps. &c. should also be written in the margin. 
 
 Corrections themselves sometimes require to be corrected. 
 Thus if a word has been improperly altered, and it is after- 
 wards thought best to retain it, dots are placed beneath and 
 the word stet written in the margin. 
 
 When lines are crooked, or letters have been disturbed from 
 their places, or blemishes appear, it is sufficient to call the at- 
 tention of the printer, by a dash of the pen, at the place. 
 
 Press work. — After the sheet is corrected and revised, it is 
 then ready for the press, to which it is accordingly transferred. 
 The ink is first applied over the whole surface of the types ; 
 the paper, previously moistened, is then laid down upon them, 
 the whole is passed under the press, and the paper being brought 
 into forcible contact with the types, receives from their sur- 
 face the ink necessary for a distinct impression. Printers' ink 
 is composed chiefly of lampblack and oil inspissated by boiling 
 and burning. Oil is necessary, that the ink may not dry 
 during the operation, and it is reduced by boiling, to prevent 
 
THE ARTS OF WRITING AND PRINTING. 67 
 
 it from spreading on the paper. It is applied to the types by- 
 large elastic balls made of leather and stuffed with wool, or by 
 elastic rollers, hke those used in printing machines. 
 
 Printing Press. — The common or old printing press, de- 
 rives its power from a screw, which is turned by a lever, and acts 
 perpendicularly on the platten, or level part, which transmits 
 the pressure. Various improvements have been made in the 
 printing press, by Lord Stanhope, and other inventors, in most 
 of which a cast-iron frame is substituted for a wooden one, be- 
 ing more inflexible ; and a combination of levers is used, so ar- 
 ranged as to cause the platten to descend with decreasing ra- 
 pidity, and consequently with increasing force, till it exerts the 
 greatest power at the moment of contact of the paper with the 
 types. 
 
 Stereotyping. — In stereotype printing, instead of moveable 
 types, blocks or plates are used, each containing all the char- 
 acters requisite to form a page. The process of stereotyping is 
 simple. A page of any work proposed to be stereotyped, is 
 set up in the usual manner with moveable types. From this 
 page, when corrected, a mould in plaster, is taken off, and 
 from this mould a plate of type-metal is cast, having all the 
 characters in relief, and being a fac-simile of the original page. 
 From this plate the printing is executed, and there must be, of 
 course, as many plates cast, as there are pages in the book to 
 be printed. It will thus be seen, from the accounts already 
 given, that the stereotyped letter press constitutes the sixth 
 time that the character has been formed, viz. 1, in the steel 
 punch ; 2, in the matrix ; 3, in the moveable type ; 4, in the 
 plaster cast ; -5, in the stereotyped character, and 6, in the print- 
 ed page. 
 
 The plaster used for forming the moulds is pulverized gyp- 
 sum, dried by heat, and mixed with water ; to which is ad- 
 ded a little whiting to diminish the tendency of the plaster to 
 shrink and crack. After the forme of types has been slightly 
 oiled, and surrounded with a brass frame, fluid plaster is ap- 
 plied over the surface with a brush or roller, so as to fill every 
 
68 THE ARTS OP WRITING AND PRINTING. 
 
 cavity of the letters. A quantity of plaster mixed with water 
 to the consistence of cream, is then poured on the type, and 
 the superfluous part scraped off. When the plaster has become 
 hard, it is lifted off by the frame, and detached from it. It is 
 then baked to dryness in an oven, and when quite hot, it is 
 placed in aa iron box or casting pot, which has also been heat- 
 ed in an oven. The box is now plunged into a large pot of 
 melted type-metal, and kept about ten minutes under the sur- 
 face, in order that the weight of the metal may force it into all 
 the finer parts of the letters. The whole is then cooled, the 
 mould broken and washed off, and the back of the plate turn- 
 ed smooth in a lathe, or planed by a machine. The earlier 
 stereotype founders, as Didot and others, formed their moulds 
 with a soft metal, or a metal at the point of congelation, in- 
 stead of plaster. 
 
 Stereotype printing is chiefly useful for standard and classi- 
 cal works, for which there is a regular demand, and of which 
 the successive editions require no alteration. It is now execut- 
 ed with such increased economy, as to be applicable to works 
 even of less durability. 
 
 Machine 'printing. — Printing by machinery, is one of the 
 latest achievements of art, having had its origin within the 
 present century. It has produced a very great inaproveraent 
 in the expedition with which work is executed, and is now ex- 
 tensively apphed to the printing of newspapers and even of 
 books. Various machines are already introduced into use, 
 most of which perform the processes of inking the types, con- 
 veying the paper, and giving the impression. For distributing 
 the ink on the types, elastic cylinders are employed, called 
 inking rollers, made of a composition of glue and treacle, which 
 combines the properties of smoothness, elasticity, and sufficient 
 durability. These transmit the ink to the types by rolling 
 over their surface. The impression is performed in most of 
 the English machines, by large cylinders which revolve upon 
 the types, having the sheet of paper confined to their surface 
 by bands of tape. The types are arranged in some machines 
 
THE ARTS OP WRITING AND PRINTING. 69 
 
 in the common flat form ; in others, the characters are placed in a 
 convex form upon the surface of cyhnders. To produce the 
 latter effect, Mr Nicholson proposed to cast the body of the types 
 with a tapering or wedge form, like the stones of an arch, but 
 Mr Cowper has produced the same object more expeditiously, 
 by curving stereotype plates into the required shape. Messrs 
 Donkin and Bacon placed their types on the four sides of a re- 
 volving prism, while the ink was applied by a roller which rose 
 and fell with the irregularities of the prism, and the sheet was 
 wrapped on another prism so formed as to meet the suifaces 
 of the first. A common printing press gives about 2.50 im- 
 pressions per hour, whereas of the Times, a London newspa- 
 per, printed by Applegath and Cowper's machine, it is stated 
 that 4000 per hour are printed on one side. The first work- 
 ing machine which printed by steam, was erected by Mr 
 Koenig, in 1814. 
 
 In this countr}'^, Treadwell's power press is the mac^hine most 
 employed. In this invention, the types aie inked by elastic 
 rollers, and the distribution of the ink rendered equal, by a re- 
 volving table which passes in contact with the rollers. The 
 impressions are made by a flat surface or platten, instead of a 
 cylinder, so that cleaner and better impressions are supposed 
 to be obtained from it than from any other machine. 
 
 History. — The art of printing was first carried into success- 
 ful operation, a little before the middle of the fifteenth century. 
 The honor of having given birth to the invention, is claimed 
 by the cities of Haerlem, Mentz, and Strasburgh, in each of 
 which the art was successfully practised at an early period. 
 The best authors, however, agree in considering that the orig- 
 inal inventor of printing, was Laurentius, otherwise called 
 Coster, of Haerlem, who made his first attempt in 1430, with 
 separate wooden types. He died ten years after, having printed 
 the ' Horarium,' the ' Speculum Belgicum,' and two different 
 editions of Donatus, which were the first books. After his 
 death, printing was carried on at Mentz, by John Gensfleisch, 
 who had possessed himself of some of Laurentius' types, and 
 
70 THE ARTS OF WRITING AND PRINTING. 
 
 who, like his master, printed in wood. This man, with the 
 assistance of his brothe r who is usually called Guttenberg, af- 
 terward invented cut metal types, with which was printed the 
 earliest edition of the bible. This edition appeared in 1450, 
 having taken seven or eight years for its completion. 
 
 Guttenberg used none but wooden or cut metal types. The 
 art received its consummation soon after, from Peter Schoeffer, 
 who invented the mode of casting types in matrices. The cel- 
 ebrated Faustus, who has often been considered as the inventor 
 of printing, was in partnership with the persons already men- 
 tioned, and furnished funds to defray the expenses of the en- 
 terprise, the processes being kept secret. The well known tale 
 of the practice of necromancy, by Faustiis, was owing to his 
 carrying a parcel of his bibles to Paris, and offering them for 
 sale as manuscripts. The French, finding so great a number 
 of books resembling each other exactly, and more so than it 
 was possible for any chirographer to have made them, conclud- 
 ed there was witchcraft in the case, and by inditing Faustus 
 as a conjuror, compelled him to disclose the secret in his own 
 defence. 
 
 After the invention of printing with fusible types, it spread 
 rapidly into many of the cities of Europe, and was practised 
 at an early period at Tours, Rome, and Venice. It was first 
 carried on in England by Caxton and Corsellis, about 1470, 
 and the earliest press was established at Oxford. 
 
 It is remarkable that this important art, after becoming 
 once established, underwent no essential improvement for a 
 period of more than 300 years. Having remained stationary 
 for three centuries, it has received a fresh impulse within the 
 last few years, by the invention of stereotyping, and of print- 
 ing by machinery. 
 
 Although printing with moveable types is exclusively a 
 modern art, yet there are some steps in the discovery, which 
 have claim to greater antiquity. The Chinese have printed 
 with their characters for more than 900 years ; but as the na- 
 ture of this character requires that much should be expressed 
 
THE ARTS OF WRITING AND PRINTING. 71 
 
 by a single figure, they are obliged to cut each character with 
 all its complications in a block of wood, so that their method 
 resembles a limited kind of stereotype printing. 
 
 Among the relics of ancient Rome, there have been found let- 
 ters, cut in brass and raised above the surface, exactly like our 
 printing types. Some of these contain the names of individu- 
 als, and, from their shape and appendages, were evidently used 
 for the purpose of signature, the letters being small, smooth, 
 and even, while the ground beneath them is unequal, and 
 rough, so that they must have been employed, not for impres- 
 sions into soft substances, but for printing with colored liquids, 
 on a surface like parchment or paper. Had the individuals, 
 whose names were thus printed, been visited with the thought 
 that by separating the letters, they might print the name of 
 another, it is probable that the art would have been at once 
 discovered, and that the dark ages might never have happened. 
 
 Works of Reference. — Astle, on the Origin and Progress of 
 writing, 4to. London, 1803 ; — Fry's Pantographia, 4to. London, 1799 ; 
 — Townlet's Illustrations of Biblical Literature, 1821; — Stower's 
 Printers' Grammar, 8vo. London, 1808 ; — Thomas' History of Print- 
 ing, 8vo. Worcester, U. S. 1810 ; — Meerman, Origines Typographicce 
 HagcB, 1765 ; — Cowper, in Brand's Journal of Science, 1828 ; — Han- 
 sard's Typographia, large 8vo. 1825. 
 
CHAPTER IV. 
 
 ARTS OF DESIGNING AND PAINTING. 
 
 Designing is the art of delineating or drawing the appear- 
 ance of natural objects, by lines on a plane surface.* Paint- 
 ing may be considered as the same art, so extended as to in- 
 clude coloring, and whatever else is necessary to produce com- 
 plete or finished resemblances. It is obvious, that if the art of 
 painting was carried to perfection, these resemblances could 
 not be told, at sight, from their originals ; since we are supposed 
 to discern objects by the medium of their pictures painted on 
 the retina of the eye, and since a polished mirror gives us ev- 
 ery appearance of reahty, in the forms reflected from it, though 
 they all proceed from the same plane. 
 
 Divisions. — To produce perfect representations of nature, 
 three things must receive attention, and the study of these 
 may be considered as constituting distinct departments in the 
 art of painting. These are, i. '^Vhe perspective, by which the 
 outhnes of figures are placed on the picture in situations de- 
 pending on their position in regard to the eye. 2. The chiaro 
 oscuro, or Hght and shade, by which the prominence and de- 
 pression of different parts of the piece are made to appear. 
 3. The coloring, by which the hues and tints of the painting 
 are made conformable to those of the original. 
 
 Perspective. — Perspective is the art of delineating the out- 
 lines of objects on any given surface, as they would appear to 
 the eye, if that surface were transparent, and the objects them- 
 selves were seen through it from a fixed position. It is the 
 foundation of correctness in painting, and a strict attention to 
 
 * Rees' Cyclopedia. 
 
ARTS OF DESIGNING AND PAINTING. 73 
 
 its rules, is indispensable to perfection in the art. The first 
 attempts at drawing, have, in all countries, consisted of dia- 
 grams, and sketches, representing merely the plans, or profiles 
 of objects, without regard to their perspective relations. But a 
 continued attention to their actual appearance or images, com- 
 bined with the application of a few geometrical and optical prin- 
 ciples, has furnished the means of fixing the outlines of objects, 
 in their true situation on a perspective plane. 
 
 If we look through a window at a mass of buildings, or 
 any external objects, and observe that part of the glass to 
 which each object, line, or point, appears opposite, we find that 
 their apparent situation is very different from their real. We 
 find that horizontal lines sometimes appear obhque, or even 
 perpendicular, that circles, in certain situations, look like ellip- 
 ses, and squares like trapezoids or parallelograms. High ob- 
 jects are seen beneath low ones, and large bodies are exceeded, 
 in apparent magnitude, by small ones. The foundation of all 
 these appearances exists in the rectilinear motion of the rays 
 of light passing from the object to the eye. 
 
 Field of Vision. — When the eye is fixed, the rays entering 
 it from the whole field of vision, constitute a cone having its 
 apex in the eye. The field presented to the eye, and occupy- 
 ing the base of the cone, cannot well subtend an angle of more 
 than 90 degrees, and we cannot have a convenient and agreea- 
 ble view of a field occupying more than 60 degrees. Even 
 the most satisfactory views of objects are obtained at such dis- 
 tances as cause them to subtend an angle of 30 or 40 degrees. 
 Panoramic views subtend a larger angle than those which 
 have been specified, and of course cannot be taken in by the 
 eye at a single view. It becomes, therefore, necessary to 
 take successive views with the eye, in different directions. 
 
 Distance and Foreshortening. — Of objects situated with- 
 in the field of vision, those necessarily appear largest, cmteris 
 paribus, which are nearest to us, because they subtend a larger 
 angle at the eye. Objects or surfaces situat,ed obhquely in 
 regard to the axis of the eye, are altered in apparent shape by 
 10 
 
74 ARTS OF DESIGNING AND PAINTING. 
 
 the shortening of their oblique diameters. This is what is 
 technically called foreshortening. If several objects, for ex- 
 ample, of equal si^e, be placed at different distances, and in 
 different positions [See Plate III. Fig. 5.] the one nearest the 
 eye, as X, will subtend the largest angle, and its comparative 
 length in the picture will be represented by the line A B. The 
 object Y, bein T further off, subtends a smaller angle, and will 
 be represented by the line A C. The object Z, being still fur- 
 ther removed, and also foreshortened by its obhque position, 
 will produce an image no longer than from A to D. 
 
 A simple instrument m ly be formed by any person, to rep- 
 resent the effect of distance and of foreshortening in perspective. 
 Let four straight, stiff wires [PL III. Fig. 6.] be connected at one 
 end, at A. by a string or socket, which will allow them to diverge. 
 Let a thin, square board, or tin plate, be attached at the other 
 end, at C, by loops at its four corners, through which the wires 
 pass. Let a string of elastic gum be placed around the wires 
 at B, about half way between A and C. The elastic string 
 will represent the picture, the board the object, and the wires 
 the rays passing from the object to the eye at A. If now the 
 board be moved upon the wires toward the eye, the elastic 
 string will be extended, or the picture enlarged. The reverse 
 will happen, if the board be carried away from the place of the 
 eye. The board may also be turned into various oblique po- 
 sitions, and the elastic string will represent the figure produced 
 by the foreshortening. 
 
 Definitions. — There are used in perspective a certain num- 
 ber of terms peculiar to the art, definitions of which are neces- 
 sary to an intelligent use of them. 
 
 The original object is that which is made the subject of 
 the picture. 
 
 Original planes or liyies are the surfaces or lines of orig- 
 inal objects. 
 
 The point of view is the situation of the eye. 
 
 The point of sight is the point in the perspective plane 
 which is nearest to the eye. As far as the picture is concern- 
 
ARTS OF DESIGNING AND PAINTING. 75 
 
 ed, these two points coincide, so that some authors have used 
 them indiscriminately one for the otlier. The point of sight 
 is also called the centre of the picture. 
 
 A visual ray is a line from the object to the eye. If the 
 object is a point, there is but one visual ray ; if it is a line, the 
 visual rays form a triangle ; if it is a square, diey form a pyra- 
 mid ; if a circle, a cone, &c. The j^^^'^ncipal visual ray is 
 that from the nearest point in the picture, or point of sight. 
 
 The jiersj^ective plane is the surface on which ihe picture 
 is delineated ; or, it is the transparent surface through which 
 we suppose objects to be viewed. 
 
 The directing plane is a plane supposed to pass through the 
 eye of the spectator, parallel to the perspective plane. 
 
 The ground plane is the earth, or the plane surfe.ce on 
 which the spectator and objects are situated. 
 
 The horizon, or horizontal plane^ is one parallel to the 
 ground plane, and at the height of the spectator's eye. 
 
 The horizontal line is the intersection of the picture or per- 
 spective plane with the horizontal plane. 
 
 The ground line is the intersection of the perspective plane 
 with the ground plane ; or, it is the hne on which the picture 
 is supposed to stand. 
 
 The 'perpendicular is a line on the perspective plane, drawn 
 though the point of sight, perpendicular to the ground line and 
 horizontal line. 
 
 The points of distance are points on the perspective plane, 
 set off from the point of sight, sometimes on the horizontal 
 line, and sometimes on the perpendicular, at the same distance 
 from the point of sight, that the eye is supposed to be at, from 
 the perspective plane. 
 
 To render the foregoing definitions more obvious, a diagram 
 [PL II. Fig. 2.] is introduced, in which the several planes are 
 supposed to be visible, and themselves, or a part of each of 
 them, seen in perspective. X is the eye of a spectator, or 
 point of \'iew. S T, the original object. X T, and X S, visual 
 rays. X Y, the principal visual ray. A B O P, the picture, or 
 
76 ARTS OF DESIGNING AND PAINTING. 
 
 part of the perspective plane. V W, the image of the original 
 object in the picture, or perspective plane. D, the point of 
 sight, or centre of the picture. H N R Q,, the ground plane. 
 I K L M, the horizon or horizontal plane. A B, the ground 
 line, or bottom of the picture. F G, the horizontal line. C E, 
 the perpendicular. E, a point of distance. Other points of 
 distance would be at F and G, if equally distant from D with 
 X or E. In Fig. 1, corresponding letters are used. 
 
 The vanishing 'point of the image of a right line is the point 
 in which a line parallel to it, passing through the eye, cuts the 
 perspective plane. Lines which in the original are parallel, in 
 the picture converge to the same vanishing point. Thus the 
 parallel railings of a bridge, or the parallel rows of windows in 
 a building, all appear to converge to the same point. In PI. III. 
 Fig. 8. c, is the vanishing point of the lines y x.fk, and of all 
 lines parallel to them. All lines which are perpendicular to the 
 perspective plane, have for their vanishing point the centre of 
 the picture. Thus D, in PI. II. Fig. 1, is the vanishing point 
 of all such lines. 
 
 Plate II. — A general idea of the nature of perspective may 
 be derived from the inspection of PI. II. Fig. 1. In adjusting 
 this plate for use, the folded or thick part must be raised per- 
 pendicularly, the rest being kept level. The part thus raised 
 will represent the perspective plane, while the rest of the plate 
 is the ground plane. The spectator is supposed to stand upon 
 Z, with his eye at a height equal to that of D, above the ground 
 plane. If now the perpendicular part be supposed to be trans- 
 parent, so that the lines or objects beyond, can be seen through 
 it, the appearance which they present on this perpendicular 
 plane, will be their true perspective representation. This may 
 be rendered obvious, by placing upon Z, a chess man, or any 
 other object, the height of which is equal to C D, representing 
 the height of the spectator's eye from the ground plane. If 
 then straight wires or threads, representing rays, were carried 
 from^he top of this object to any of the large letters upon the 
 black lines of the ground plane, they would pass through the 
 
ARTS OF DESIGNING AND PAINTING. 77 
 
 perspective plane in the points indicated by the corresponding 
 small letters. The lines also which connect these letters, will 
 assume the situations represented in the diagram. 
 
 Problems. — Since the figures of all objects are contained within defi- 
 nite lines, it is evident that the whole art of perspective consists in a 
 method of finding the situation of all lines upon the perspective plane, 
 and of cutting those lines in any given proportion, according to the 
 length required. The same diagram [PL II. Fig. 1.] will serve to illus- 
 trate several of the most obvious problems. 
 
 I. Suppose, for instance, that it is required to find the perspective 
 situation of straight lines, such as H I and O P, situated on the ground 
 plane, and parallel to the ground line. It is first obvious, that if they 
 are parallel to the ground line, they are also parallel to one another, 
 and to the picture. We then know that the line H I is to be drawn 
 parallel to A B, and we only require to know at what distance it must 
 be drawn from it.* To ascertain this, we measure the perpendicular 
 distance C M, of the given line fi-om the perspective plane, and set off 
 this distance from C to q. We then draw the line G q, cutting the 
 line C D in m, and the line h i, drawn through m, parallel to the ground 
 line A B, is the perspective situation of the line H I, required. 
 
 The reason of this will appear evident, from considering that G be- 
 ing situated at the height of the eye from the ground line A B, andG 
 D being equal to the distance of the eye from the perspective plane ; 
 the line D C may be imagined to be the perspective plane seen edge- 
 ways ; and then any point q, situated at a givpn distance beyond it, 
 must appear at m, in a straight line drawn from the eye at G, toit. 
 Therefore m, is the proper distance from C, at which that point in the 
 line required must be drawn. In like manner, the situation of the point 
 k, determining the perspective distance of the line o p, may be found. 
 
 II. If it is required to find the perspective place of a line on the 
 ground plane that is perpendicular to the ground line, we measure its 
 distance from the perpendicular C E, and setting it off from C upon the 
 ground line, we draw a line from the point, thus set off, to the point of 
 sight D, which will give the situation required. Thus, for example, if 
 we wish to find the perspective appearance of a line Q, D, which is 
 perpendicular to the ground line A B, and parallel to C D, we take the 
 distance Q, C, and set it off from C to q, and then D g is the line re- 
 quired. For the same reason, D r represents the line D R ; also D s 
 
 * Such lines are considered parallel by writers on perspective, because a 
 line parallel to them, passing through the eye, can never cut the perspective 
 plane. Therefore they can have no vanishing point on the perspective plane. 
 
78 ARTS OF DESIGNING AND PAINTING. 
 
 represents D S, and D t represents D T. Since all lines perpendicu- 
 lar to the ground line, when infinitely produced, seem to meet on the 
 perspective plane, in the point of sight D, it is the vanishing point of 
 those lines. 
 
 III. If it is required to find the perspective situation of a line which 
 is vertical, i. e. perpendicular to the ground plane, having first ascer- 
 tained the point upon which it stands in the ground plane, we draw 
 from the corresponding point in the perspective plane, a line perpen- 
 dicular to the ground line. Thus if we have ascertained that the place 
 at which a vertical line stands on the ground plane, is at W, we find 
 the corresponding point w in the perspective plane, and from it raise a 
 line w X, perpendicular to A B, and somewhere in that line continued, 
 will the required line terminate. The reason of this will appear, when 
 we recollect that vertical lines are parallel to the picture, and perpen- 
 dicular to the ground line. 
 
 IV. If circles or curved lines are to be put in perspective, this may 
 be done by describing squares about them, and putting these in per- 
 spective. This will assist the judgment in completing the curved 
 lines. Or we may find the perspective situations of a number of points 
 in the curve, and join these with a steady hand. 
 
 A great number of problems, founded on the principles of perspec- 
 tive, are to be found in works on that science, and constitute an in- 
 teresting study. But in practice, artists find it convenient to resort to 
 some more direct and compendious method of obtaining the perspec- 
 tive situation of objects, without the trouble of mensuration. 
 
 Instrumental Perspective. — The rules usually laid down 
 for drawing in perspective, suppose a previous knowledge of 
 the real distances, magnitudes, and relative positions of all the 
 objects that are introduced into the picture. But, in many 
 cases, a person may be so situated, that this knowledge cannot 
 be obtained ; and in many cases, likewise, the labor, which this 
 method requires, is troublesome and discouraging. Dr Priest- 
 ley has described a method of drawing objects in true perspective, 
 without moving from the place in which they are viewed. It 
 consists simply in taking observations of the various points of 
 an object, so as to determine their elevation above the horizon, 
 and their declination from a perpendicular. 
 
 To supply the pi ace of actual mensuration, an azimuth quadrant or a 
 theodolite, is used, or any instrument by which the elevation of an ob- 
 
ARTS OF DESIGNING AND PAINTING. 79 
 
 ject can be found, and likewise its angle of declination from the per- 
 pendicular which goes through the point of sight. 
 
 The artist having this instrument, and placing himself at what dis- 
 tance he thinks most convenient, from any objects that he proposes to 
 draw, lays down upon the paper of his drawing-board, two lines, cross- 
 ing each other at right angles ; one of them F G, [PI. III. Fig. 8.] to rep- 
 resent the horizon, and the other C E, the perpendicular, passing through 
 the point of sight D. He must also choose any distance he may think 
 proper to work at, and set it off from D to E. 
 
 Having thus prepared for the operation, he pitches upon any point 
 in the object in sight, as, for instance, that which corresponds to x; and, 
 by the help of the instrument, first of all, finds its declination from the 
 perpendicular to the right or left hand. Supposing it to be 10 degrees 
 to the right, he sets off the angle D E a, equal to ten degrees, and con- 
 cludes, that the point he Avants to fix must be somewhere in the per- 
 pendicular a e. To find in what part of this line the point is, he must 
 take its elevation above the horizon, and, supposing it to be 20 degrees, 
 he makes a b equal to a E, and the angle ab x, equal to twent}' degrees ; 
 which finds x the point required. 
 
 In this method may the situation of any other point be found, and 
 these points, being joined bylines, the whole object will be delineated. 
 
 But if the objects to be represented, contain many right lines, that 
 are parallel to each other, such as occur in buildings, machines, &c. 
 there will be no occasion to take many points ; because the situations 
 of the lines may be determined by vanishing points, found by the help 
 of a few of them. Thus having found y, in the same manner as we 
 found X, and knowing that the line xy is parallel to the horizon, we 
 produce it till it touches the horizontal line in c, which is, therefore, the 
 vanishing point for that line, and all that are parallel to it, several of 
 which are represented in the figure. The distance at which these par- 
 allels are drawn, may either be guessed by the eye, or be determined 
 with more accuracy by finding a point at one of their extremities, in 
 the manner just described. 
 
 Also, if we know the angle that any line, as y z, makes with another 
 line, as x y, the situation of which is known, there is no occasion to 
 take any point, in order to determine the direction of it. In this figure, 
 xyz represents a right angle, Avhich is that which most frequently oc- 
 curs in buildings, machines, &c. To determine, therefore, the situa- 
 tion of the line y z, we consider that c, the vanishing point of 3/ x, makes 
 the angle D E c, equal to 20 degrees, the complement of which, from 
 90, is 70. We therefore make the angle D E H equal to 70 degrees, and 
 a line E H, produced till it meets the horizontal line in a place without 
 the bounds of this figure, gives the vanishing point of 3/ 2, and of every 
 
80 ARTS OF DESIGNING AND PAINTING. 
 
 other line parallel to it which is at right angles with the line xy. To 
 this point, therefore, we draw the line y z, and all the others in that 
 plane that are parallel to it. 
 
 The point x, is to the right hand of the perpendicular, and it has an 
 elevation above the horizon ; but it can require no additional instruc- 
 tion, to be able from this, to fix any point to the left hand of the per- 
 pendicular, and one that has a depression below the horizon. 
 
 If we would introduce measures into a drawing made in this manner, 
 or find a scale for the picture, we measure some one line in the original, 
 as kf. In order to this, from c, the vanishing point of the line kf, we 
 take c d, equal to c E, which gives d the measuring point of the line, 
 and from this point, we draw two lines, one from each extremity of the 
 line kf, to i h, in the line that bounds the picture, or any other line drawn 
 parallel to the horizontal line. Then we divide the line i h, in the same 
 proportion as kf; and by this means get a scale, by which we can 
 measure any other line in the picture, or insert in it other objects of 
 any given magnitudes. 
 
 Mechanical Perspective. — To avoid wholly the delay and 
 trouble of computation, artists frequently make use, in practice, 
 of some mechanical method of perspective drawing, by which 
 the outlines of objects can be obtained with expedition, and 
 sufficient correctness. Thus the camera, ohscura and camera 
 lucida, cast upon paper a perspective image, which can be im- 
 mediately traced. A method of drawing by squares is like- 
 wise easily practised. For this purpose, the paper, or surface 
 which is to receive the picture, is divided by pencil lines into a 
 certain number of squares. A small frame, of corresponding 
 size, is divided into a like number of squares by threads, or by 
 lines drawn upon glass. This frame is placed perpendicularly 
 between the eye and the object, and kept at a stationary dis- 
 • tance from the eye, which is also fixed. The outlines and 
 parts of objects which appear in particular squares of the frame, 
 are transferred to corresponding ones on the paper, and in this 
 way the principal points of the perspective view may be obtained. 
 
 Perspectographs. — Various instruments have been invent- 
 ed under the name of perspectographs, to be used in obtain- 
 ing the points and outlines of original objects. They common- 
 ly consist of a fixed part, perforated with a small hole in the 
 
ARTS OF DESIGNING AND PAINTING. 81 
 
 point of view, and a moveable part situated in the perspective 
 plane, and capable of traversing any part of it. This movea- 
 ble part may consist of any minute substance, or, which is 
 better, a moveable point may be obtained by the intersection 
 of two threads. Any points in the perspective plane may thus 
 be found, and transferred to the pictme, by bringing the part 
 of the instrument which contains them, into contact with the 
 paper. 
 
 A simple and very useful perspectograph may be made by 
 erecting a pane of glass upon one end of a board, or short ta- 
 ble, and a moveable piece with an aperture for the eye at the 
 other end.* The moveable piece is to be fixed at any conve- 
 nient distance, and the object is to be viewed from it, through 
 the pane of glass. The outlines, as they appear, are traced 
 upon the glass with a stick of wax sharpened hke a crayon, 
 and they may be afterwards rendered very plain, and transfera- 
 ble, by sprinkling them with any black powder. 
 
 The geometrical and mechanical methods which have been 
 described, will enable a person not previously conversant with 
 the art, to obtain correct perspective representations of any ob- 
 ject. But by long practice, in drawing from nature, a certain 
 tact is acquired by painters, which enables them, by the accura- 
 cy of the eye and judgment alone, to make correct views of 
 objects, without the aid of any computation or mechanical pro- 
 cess. Thus miniature painters produce the nicest resemblance 
 of the human countenance, in any position, with no other guide, 
 than the faculty obtained by experience, of estimating the ex- 
 act shape and proportion, which each part of the original should 
 bear upon the picture. 
 
 Projections. — The projections of a body, are the different 
 modes by which it may be delineated on a plane surface. 
 That which has already been described, is called the sceno- 
 grajphic projection, and represents objects as they actually ap- 
 pear to the eye, at limited distances. The orthographic pro- 
 
 * No method fixes the eye so effectually, as to rest the teeth upon a sdid or 
 fixed body. 
 
 11 
 
82 ARTS OF DESIGNING AND PAINTING. 
 
 jection represents objects as they would appear to the eye at an 
 infinite distance, the rays which proceed from them being 
 parallel, instead of converging. The shadow, which a body 
 casts in the rays of the sun, may be considered as an ortho- 
 graphic projection. In this projection, lines which are parallel 
 in the original, are parallel in the picture, and do not converge 
 to any vanishing point. Their comparative length, also, is not 
 affected by difference of apparent distance. The orthographic 
 projection is much used in delineating buildings, machinery, 
 (fee, because those parts of the drawing which are not fore- 
 shortened, maintain their true relative size, so that measures 
 can be taken from them. In PI. III. Fig. 7, No. 1 is the scen- 
 ographic, and No. 2, the orthographic projection of a cube. 
 In addition to these,^ the term ichnographic projection is 
 sometimes used to express the horizontal delineation, or ground 
 plan of an object. A bird's eye view is a scenographic or orl ho- 
 graphic projection, taken from an elevated point in the air, 
 from which the eye is supposed to look down upon the objects. 
 Isometrical Perspective. — This name has been introduced 
 by Professor Farrish, to express a kind of drawing peculiarly 
 convenient in delineations of machinery, and bodies of regular 
 figure. It is a species of orthographic projection, in which 
 three planes, at right angles with each other, appear simi- 
 lar. and equal. An idea of it may be formed, by supposing a 
 cube to be so placed, that one of its angles will appear in the 
 centre, while its outline will be a true hexagon. In this pro- 
 jection, the sides of the cube appear equal, and all sections of 
 the cube parallel to either side, will also be equal. All right 
 angles are represented by angles of 60 degrees, or the supple- 
 ment of 60 degrees. All circles parallel to either of the three 
 planes, will be represented by similar ellipses. Figures not 
 parallel to either of the planes, may be calculated by easy rules. 
 It is therefore the easiest and most expressive kind of drawing 
 for the wheelwork, axles, and regular frames of machinery ; for 
 philosophical instruments, and for many architectural designs.* 
 
 * For the principles of isometrical drawing, see the Cambridge Philosophical 
 Transactions ; or Gregory's Mathematics for Practical Men, p. 179. 
 
ARTS OF DESIGNING AND PAINTING. 83 
 
 In PL III. fig. 9, is an isometvical view of a cube, with circles 
 inscribed on its sides, and the axes of those circles projecting a 
 short way. 
 
 CHIARO OSCURO. 
 
 Next to correct perspective, the most important circumstance 
 in painting, is the correct distribution of light and shade. To 
 the skilful management of these, we are indebted for the 
 strength and liveliness of pictures, and what is technically call- 
 ed their relief, or the elevation which certain parts appear to 
 assume above the plane upon which the picture is made. 
 
 Light and Shade. — -Light and shade, as they appear to us 
 upon natural objects, are the consequences of the rectilinear 
 motion of the rays cast upon them by luminous bodies. If an 
 object be exposed to the rays of the sun, or of a single lamp or 
 candle, those parts or surfaces which are presented directly to 
 these rays, become strongly illuminated, and acquire a lighter 
 cast, approaching to white. Those surfaces, which stand ob- 
 liquely to the light, receive less of the rays, and of course have 
 a deeper tinge. Those lastly, which are averted from the light, 
 and receive no rays but such as are reflected to them from oth- 
 er objects, acquire a very dark shade, approaching, when con- 
 trasted with the others, towards black. 
 
 The distribution of hght and shade upon any object, is al- 
 ways proportionate and correspondent to its shape. An even 
 or plane surface, exposed to the sun's rays, will be equally il- 
 luminated throughout, since whatever be its position, its parts 
 will all make a similar angle with the rays. But uneven or 
 irregular surfaces will be unequally illuminated, the prominent 
 parts receiving most hght, and the depressed portions most 
 shade, an effect which will be increased, if the hght falls ob- 
 Uquely or sideways. If the irregularities of surface be sharp 
 and strong, the changes from light to shade will be sudden, 
 and the contrast great. On the other hand, if they are smooth 
 and rounded, the transition will be soft and gradual. 
 
84 ARTS OP DESIGNING AND PAINTING. 
 
 Association. — As bodies are never seen, except when they 
 are illuminated, the manner in which light and shade are dis- 
 tributed upon them, forms by association a part of our ideas of 
 their shape. Painters have learned to imitate this arrange- 
 ment of light and shade, by varying the quantity and intensi- 
 ty of their coloring substances, so as to produce in the mind 
 the same associations of shape from a plane svirface, as would 
 arise from the falling of light on the original object itself. 
 This art constitutes what is technically called the chiaro os- 
 curo, from the Italian words signifying clear and obscure. 
 Next to perspective it is the most important part of painting, 
 and there are many cases in which perspective alone would 
 wholly fail to convey to us a correct idea of the form of objects, 
 were it not assisted by appropriate insertion of lights and shades. 
 Thus a circle, a sphere, and a cone, viewed vertically, may all 
 have the same perspective outline ; but their difference of figure 
 becomes apparent, as soon as we consider their distribution of 
 light and shade. 
 
 Directio?i of Light. — The most distinct perceptions of 
 shape are produced when the light falls in one direction, e. g. 
 when it is received immediately from the sun, or from a sin- 
 gle window or candle. The distinctness of an object is always 
 impaired, when it is situated between cross lights, or when it 
 is illuminated by a variety of windows or candles on different 
 sides of the room. An object may even be so surrounded with 
 lights, that it shall be impossible to discover its exact shape. 
 Its outline indeed will be discernible, but the equal illumina- 
 tion on all sides, will exclude the existence of shadow, and of 
 course we shall lose the power of appreciating the comparative 
 distance of its parts from the eye. In most paintings, we find 
 that the principal mass of light falls in one direction. An ob- 
 lique or a sideway direction, is most common, though a front, 
 and even a back light, is managed to produce very striking ef- 
 fects. Painters also exercise their skill with the introduction 
 of cross lights, from different windows, or lamps ; but the suc- 
 cessful execution of a piece of this sort is more difficult, than 
 with a single light. 
 
ARTS OF DESIGNING AND PAINTING. OO 
 
 Reflected Light. — Owing to the reflection which takes 
 place from all terrestrial bodies, we find that objects, in most 
 situations, have not only a principal or direct light, but also a 
 secondary or reflected one. Hence the darkest part of globu- 
 lar and cylindrical bodies, is not that w^hich is most remote 
 from the original hght. This part receives from the reflection 
 of objects beyond it, a faint illumination, so that the darkest 
 part wiU be found between it and the part on which the light 
 directly falls. See the sphere represented, PI. III. Fig. 4. 
 
 Sharp lights, or such as are intense and sudden, indicate 
 polished surfaces, and are employed to represent them. Where 
 they are accompanied by very deep shades, they express great 
 elevation above the common surface. Faint lights, on the 
 contrary, imply a dull surface, obscure illumination, or small 
 elevation. 
 
 Exjpression of Shape. — Light and shade are not adequate, 
 in all cases, to give us certain indications of the forms of bodies. 
 Surfaces which appear concave in one direction of the hght, 
 may appear convex, if the light is introduced from the oppo- 
 site side. In contemplating an undulating object, like a cur- 
 tain, or its picture upon paper hangings, we are often at a loss 
 to distinguish the elevated, from the depressed portions ; and 
 by a little effort of the imagination, we can persuade ourselves 
 that a particular part is at one time elevated, and at another, 
 depressed. Cameos and intaglios may be mistaken for each 
 other, and any of the figures [PI. III. fig. 4.] may appear 
 prominent or depressed, in the same part, by reversing the di- 
 rection in which the light is supposed to strike upon them. 
 
 In cases of this sort, our final ideas of shape are derived, not 
 only from the object itself, but from its relations with contigu- 
 ous objects. 
 
 Eyes of a Portrait. — The influence which the association 
 of contiguous objects has upon our ideas, is strikingly exempli- 
 fied in the eyes of a portrait. We estimate the direction of 
 the eyes, not only from the position of the ball in regard to the 
 eyelids, but also from the relative position of the remaining 
 
86 ARTS OF DESIGNING AND PAINTING. 
 
 features of the face. Dr WoUaston has shown, that the same 
 eyes in a picture, which looks at us, may be made to appear 
 averted from us, if we apply new features to the lower half of 
 the face. [PI. IIT. Fig. 3.] The reason, why the eyes of a 
 portrait appear to follow us, in all parts of the room, is simply, 
 that the relative position of the features cannot change, so that 
 if the picture appears to look at us once, it must appear to look 
 at us always, If we move to one side of a portrait, the change, 
 which happens, is unlike that which would take place in a bust, 
 or living face. The picture is merely foreshortened, so that we 
 see a narrower image of a face, but it is still that of a face look- 
 ing at us. And if the canvass be transparent, the same effect 
 takes place from the back of the picture. 
 
 Shadows. — Shadows are cast in the direction opposite to 
 that by which we suppose the light to enter, and their intro- 
 duction in pictures, always heightens the effect. A painted 
 object, is relieved, or raised from the surface, by the expression 
 of light and shade on itself But the relief is greatly increas- 
 ed, if the shadow which it makes on the ground, or other sur- 
 face, be also introduced. Shadows are commonly softened 
 off at the edges, or terminate gradually. When, however, the 
 light is strong, or the shadow very near to the object, its ter- 
 mination is more abrupt. 
 
 Aerial Perspective. — This name is given by painters, to 
 the mode of producing the effect of distance, by a diminution 
 in the distinctness and brightness of objects, according to their 
 remoteness from the eye, and the condition of the medium 
 through which they are seen. It is well know^n, that distant 
 objects appear indistinct, and of a greyish or blueish tinge, from 
 the effect produced by the intervening atmosphere. Their in- 
 distinctness is increased, if the atmosphere is hazy. Their ap- 
 pearance is also modified by the degree of their illumination, and 
 by the character of the light which falls on them. The paint- 
 er, therefore, finds it necessary to consider the depth of atmos- 
 phere which is interposed between him and his object, the 
 condition of this atmosphere, and the quantity and color of the 
 
ARTS OF DESIGNING AND PAINTING. 87 
 
 light which falls on it, and on the objects. A want of atten- 
 tion to these circumstances, gives rise to the defect called hard- 
 ness in painting. 
 
 COLORING. 
 
 By the aid of perspective, and the chiaro oscuro alone, very 
 good representations of objects may be obtained. All our com- 
 mon engravings, wood cuts, drawings in Indian ink, in black 
 crayons, &c., derive their expressiveness from these only. But 
 a stUl nearer approach to the appearance of nature, is made, by 
 the employment of colors analogous to those which are found 
 to exist in the objects represented. 
 
 Colors. — From the science of optics, we learn that the solar 
 beam is divisible into seven primary colors, white being the 
 mixture, and black the privation of all of them. These colors, 
 are violet, indigo, blue, green, yellow, orange, red.* Three of 
 these are capable of producing all the rest, by their intermix- 
 ture and degree, viz. blue, red, and yellow. 
 
 The color belonging to different natural objects, was sup- 
 posed, by Newton, to be occasioned by a power which their 
 surfaces possess, to reflect certain rays, while they absorb all 
 the rest. This power is so infinitely diversified in nature, that 
 we find not only every kind of primary ray reflected, but like- 
 wise every possible tint, and intermediate grade, which can be 
 produced by the admixture of two or more original colors. 
 To represent these various hues, it is necessary that the painter 
 should possess coloring substances analogous to them all, or 
 capable of producing them all by mixture, and that he should 
 apply them in such a manner, that the true color may remain 
 distinct, independently of the lights and shades necessary to 
 place the objects in relief. 
 
 * Dr Wollaston found the spectrum formed in looking through a prism at a 
 narrow line of light, to consist of four colors, red, green, blue, and violet, with 
 a narrow stripe of yellow. The three simple colors, red, green, and violet, 
 may produce yellow, by the admixture of red and green ; crimson, by red and 
 violet ; blue, by green and violet, and white by the combination of all three. 
 
88 ARTS OF DESIGNING AND PAINTING. 
 
 Shades. — In a colored painting of an object which has any 
 rotundity of form, there are usually, at least, three tints, or de- 
 grees of color. These are the light, the middle tint, and the 
 shade. Of these, the middle tint is the one which represents 
 the true color of the object, and occupies an intermediate situ- 
 ation between the light and shade. Thus in the painting of 
 a red fruit, for instance the cherry, the middle tint is vermilion, 
 or some similar color, being that which the surface of the fruit 
 would have, if it were perfectly flat. The part of the fruit 
 nearest the light, has a very bright color, partaking of white 
 while the remote parts are shaded with lake or some darker 
 red. In like manner, a yellow fruit, like the lemon, has not 
 only the true color of the rind, but is lightened at the top with 
 straw color or white, and shaded with brown toward the edges. 
 It is necessary that the colors used for dark shading, should 
 be in some degree correspondent with the middle tint, and not 
 diametrically opposite to it. Thus, in single objects, yellow 
 cannot be shaded with blue, nor red with green. 
 
 Tone. — Pictures differ from each other in the respective 
 depth of color, which pervades the whole piece. The word 
 tone, borrowed from the art of music, signifies, in painting, the 
 peculiar cast, or governing hue, which a picture, or a color, 
 possesses. Thus if dark masses of color, with feeble lights, 
 predominate, the piece has a deep or low tone, while if the re- 
 verse exists, a bright or light tone is produced. It is essential 
 to harmony that a picture should have the same tone through- 
 out, or that its lights and shades should correspond in their 
 intensity to the tone which governs the whole. 
 
 Harmojiy. — When different objects are grouped together in 
 the same view, each one possesses two kinds of color, the o?^ig- 
 inal color, and the adventitious. The original color, often 
 called among painters the local color, is that which belongs to 
 the object itself, independent of situation. The adventitious 
 color, is that which is reflected upon it from neighbouring objects, 
 and which of course depends upon situation. For example, 
 the color of the human face is that which we call flesh color, 
 
ARTS OP DESIGNING AND PAINTING, 89 
 
 and, if painted alone, may be represented by the shades of that 
 color. If, however, it is surrounded by a purple drapery, it re- 
 ceives a purplish tinge, and requires to be so represented. In 
 like manner, a yellow dress communicates to it a yellowish cast, 
 &c. An attention to this adventitious coloring, combined with 
 a uniformity of tone, constitutes the basis of what is technical- 
 ly called harmony in painting. Harmony requires that strong 
 and glaring colors should never be forcibly contrasted with each 
 other, but that each object should partake at its edges of a cer- 
 tain portion of the color which predominates in objects near to 
 it. This rule not only produces effects most grateful to the 
 eye, but an observance of it gives, in fact, the only true repre- 
 sentation of nature. 
 
 Contrast. — Colors are divided, by painters, into the warm 
 and the cold. Warm colors are those in which red and yel- 
 low predominat-e. Cold colors are blue, grey, and others allied 
 to them. Neutral colors are iatermediate tints, or mixtures. 
 Of the various pigments or coloring substances, which painters 
 employ, none have the genuine brilliancy of the prismatic 
 rays ; and all fall short of the hues produced by nature in liv- 
 ing objects. The petal of a flower, the feather of a bird, and 
 the Aving of an insect, are tinged with a richness and splendor, 
 which no factitious colors can equal. Painters can only ap- 
 proach, when necessary, towards the brightness of natural col- 
 ors, by availing themselves of the effect of contrast, and by 
 heightening one color by the introduction of others, which pre- 
 pare the eye for its more perfect and favorable reception. 
 
 Remarks. — The power of giving true representations of ob- 
 jects, is derived, originally, from an attentive study of the colors 
 and appearance which they actually exhibit in nature ; after- 
 wards from a comparison of the success of different artists, and 
 an attention to the means they have employed. What belongs 
 to the philosophical part of painting, can hardly be said to ex- 
 tend ]7eyond the correct imitation of nature. But the inven- 
 tive part, the design and composition of great pieces, such as 
 have not necessarily any originals in nature, requires not only 
 12 
 
90 ARTS OF DESIGNING AND PAINTING. 
 
 philosophic accuracy, and practical skill, but also demands 
 original genius, strength and fertility of imagination, and a 
 strong perception of sublimity and beauty, whether natural 
 or moral. To paint a portrait or landscape from nature, requires 
 no more than a faculty of correct imitation. But to express on 
 the canvass a scene of history or of fiction, to create forms of 
 ideal beauty exceeding the realities of life, and to express, by 
 attitudes and lineaments, passions, which tell the events they 
 accompany, — this excellence is attained by few ; it is not to 
 be taught by any rules of art, but, like poetry, and eloquence, 
 it is within the reach of those only, whom a strong and exclusive 
 interest in the pursuit has qualified to feel deeply, and to ex- 
 press powerfully. 
 
 Note. — For the modes of painting in water, oil, fresco, &/C.j 
 also for coloring substances, see Chapter XVIII. 
 
 Malton's Treatise on Perspective, fol. 1779 'y — Priestley's Intro- 
 duction to Perspective, 8vo. 1770; — Wood's Lectures on Perspective, 
 with an Apparatus, 1809 ; — Blunt's Essay on Mechanical Drawing, 
 4to. 1811 ; — Lucas' Progressive Drawing Book, Baltimore, 1827; — 
 Burnet, on Light and Shade, 4to. 1827 ; — Burnet, on Coloring, 4to. 
 1827 ; — Vallee, TraiU de la Science du Dessin, 4to. Paris, 1821 ; — Mil- 
 LiN, Dictionnaire de Beaux Arts,Stom.8vo. 1806 ; — Elmes' Dictionary 
 of Fine Arts, 8vo. 1826 ; — Works of Sir J. Reynolds, — Opie, — ^Puseli> 
 — Barry, — ^West, — De Piles, «&c. &c. 
 
CHAPTER V. 
 
 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 The arts of engraving and lithography, bear tlie same rela- 
 tion to drawing, that the art of printing does to that of writing ; 
 the first being intended for the expression of original designs, 
 the latter for the multiplication of copies of the design, when 
 made. * 
 
 ENGRAVING. 
 
 Origin. — The origin of copperplate engraving appears to 
 have been in the fifteenth century, previously to which time it 
 was probably unknown. The first inventors of engraving, 
 were the goldsmiths, who, from the habit of marking ciphers 
 and little devices on their wares, acquired a dexterity and des- 
 patch in the use of the graving tool, and at the same time, a 
 power of producing subjects of such neatness and delicacy, that 
 a desire was naturally excited in them, to preserve and increase 
 the products of the art, by transferring them to paper. This 
 object was etfected by the use of a suitable pigment, and the 
 aid of the rolling press. 
 
 Materials. — -Common engraving differs from printing, in 
 having its subjects or devices cut into, or below, the surface of 
 a metallic plate, instead of being elevated or raised above it, as 
 in types, and wood cuts. For the purpose of engraving, a va- 
 riety of metals have been employed, and various combinations 
 or alloys. Copper has, however, been selected by common 
 consent, as uniting the greatest number of desirable qualities ; 
 having sufficient softness to permit it to be cut when cold, and 
 sufficient hardness and tenacity, to resist the action of the press, 
 
92 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 and the wearing of continued friction. A plate of the best 
 copper is selected, about one fourth of an inch thick, having 
 one side finely polished, and its edges rounded, to prevent it 
 from cutting the paper. The engraver woiks opposite to a 
 window, having a screen interposed to soften the light, and 
 the plate placed on an oblique table in the most convenient 
 position for seeing. 
 
 Instruments. — The instruments employed in the practice 
 of the art, are the following. 1. The graver. This is a 
 small steel bar, of a prismatic form, having one end attached 
 to an oblique handle, and the other ground off obliquely, so as 
 to produce a sharp point at one angle. In working, this instru- 
 ment is held in the palm of the ha*l^d, and pushed forward, so 
 as to cut out a portion of the copper. 2. The dry point. 
 This is a strong bluntish needle, fixed in a handle, and intend- 
 ed for drawing the finer lines. It is held in the fingers, in the 
 same way as a pen or pencil. 3. The scraper, a triangular 
 instrument, with concave sides, and sharp edges, intended for 
 removing or scraping off portions, which are accidentally raised 
 above the surface. 4. The burnisher. This is merely a 
 blunt smooth tool, for rubbing out blemishes, and smoothing 
 the surface of the copper. Various kinds of varnish, rosin, 
 wax, charcoal, and mineral acids, are also employed in differ- 
 ent parts of the operation, according to the subject and the style 
 of engraving which is adopted. 
 
 Styles. — The principal varieties, or styles, of engraving on 
 copper, are the following. 1. Line engraving. 2. Stippling. 
 3. Etching. 4. Mezzo tinto. 5. Aqua tinta. Lithography, 
 and some other modes of multiplying designs, are imitations 
 and substitutes, rather than species of engraving.* 
 
 Line Engraving: — Line engraving, called by the French, 
 Gravure en. taille do7ice, is one of the most common species 
 of engraving ; and though less elaborate than the second mode, 
 
 * Musical characters are sometimes executed in a mode different from all 
 these, by making impressions with a punch upon pewter, or some other soft 
 metal. 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 93 
 
 has produced most of the finest and boldest specimens of the 
 art. In this species, the surfaces and figures, the hghts and 
 shades, are produced by the multiphcation of minute Hnes, cut 
 in by the graver and dry point, approaching each other so 
 nearly, that the inequality produced by the admixture of black 
 and white does not offend the eye, nor interrupt the harmony 
 of the piece. T he effect and beauty of line engravings, depends 
 much upon the smoothness of the lines, their gradual swell 
 and decrease, and their evenness or parallel situation. 
 
 For engraving in this manner, the artist transfers the out- 
 lines of his original drawing, by tracing them with black lead, 
 on an oiled paper,* and afterwards passing this paper through 
 the press in contact with the copperplate, which is previously 
 covered with a thin coating of wax. A sufficient quantity of 
 the lead adheres to the copper, to enable him to engrave the 
 outlines with great accuracy. The graver is then held in the 
 palm of the hand, and pushed forward with a strong but 
 steady and regular motion until a hne is completed. The gra- 
 ver, by its operation, removes a thread of copper from the line, 
 and at the same time raises the surface on each side of it, form- 
 ing what is called a hurr. This burr is subsequently removed 
 by the process of scraping and burnishing. After the outlines 
 are finished, the dark surfaces are introduced by means of close 
 parallel lines cut in, in the same manner as before. Grada- 
 tions of light and shade are produced by the gradual and si- 
 multaneous tapering of all the lines which constitute the dark 
 portions, and the softness and regularity with which this is 
 accomplished, greatly affects the beauty of the piece. Very 
 dark shades are produced by lines crossing each other, either 
 in squares or lozenges, which are varied according to the na- 
 
 * Paper rendered transparent with spermaceti, is useful in tracing figures 
 with a lead pencil. If paper be varnished with a mixture of Canada balsam, 
 and oil of turpentine, very distinct lines may be traced on it with the dry point 
 only, and these may be again transferred, by varnishing the copper, and tracing 
 them upon it, through the paper. This method is now much employed by en- 
 gravers. 
 
94 THE ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 tuie of the subject. Very light shades, on the contrary, are left 
 untouched, or covered with broken lines. Lines which swell 
 or taper, are first cut of a uniform size, and afterwards deep- 
 ened by a second or third stroke of the graver. Mistakes or 
 blemishes, are erased from the plate, either by burnishing, 
 with the proper instrument, or by rubbing with charcoal. 
 
 Stippling. — The second mode of engraving, is that called 
 stippling, or engraving in dots. This resembles the last men- 
 tioned method in its processes, except that instead of lines, it is 
 finished by minute points or excavations in the copper. These 
 punctures, when made with the dry point, are circular, when 
 made with the graver, they are rhomboidal or triangular. The 
 variations and progressive magnitude of these dots, give the 
 whole effect to stippled engraving. This style of work, is al- 
 ways more slow, laborious, and of course more expensive, than 
 engraving in lines. It has, however, some advantages in the 
 softness and delicacy of its lights and shades, and approaches 
 nearer to the effect of painting, than the preceding method. A 
 more expeditious way of multiplying the dots, has been con- 
 trived in the instrument called a roulette, a toothed wheel, fix- 
 ed to a handle, which by being rolled forcibly along the cop- 
 per produces a row of indentations. This method, however, 
 is less manageable than the other, and generally produces a 
 stiff effect. 
 
 Etching. — Etching is the third mode of engraving, and is 
 performed by chemical corrosion. It is apparently the easiest 
 mode of engraving, requiring least practice in the operator. In 
 fact, any person who can draw, may etch coarse designs tole- 
 rably well, after having acquainted himself with the theory 
 only. Hence we find that engineers, naturalists, surgeons, &c. 
 sometimes etch their own plates, especially of light subjects. 
 
 A plate for etching, is prepared in the same manner as for 
 common engraving. It is then covered throughout its whole 
 surface, with a very thin coating of varnish made of wax, mas- 
 tic, and asphaltum ; sometimes of rosin, and animal oil, or of 
 linseed oil inspissated by boiling. This varnish is blackened 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 95 
 
 by the smoke of a lamp, in order that the operator may see 
 the progress and state of his woik. The instrument used in 
 etching, is a needle, resembling the dry point, but of different 
 sizes, according to the nature of the work. The plate being 
 prepared, the operator, supporting his hand on a ruler, begins 
 to make his drawing with the needle in the coat of varnish, 
 taking care to penetrate always to the copper. In the use of 
 the needle, those lines which require to be deepest, must have 
 the greatest force bestowed on them, but it is not possible to 
 produce so perfect an effect in this way, as by incisions of the 
 graver. After the design is completed, the operator proceeds 
 to the second part of the process, the corrosion, or as it is techni- 
 cally called, biting in. For this purpose, the plate is surround- 
 ed with a wall of soft wax, to prevent the escape of fluid from 
 its surface. A quantity of diluted nitric acid, is then poured 
 upon it, and suffered to remain for some time. A chemical 
 action immediately takes place in all the lines or points where 
 the copper is denuded by the strokes of the needle, while the rest 
 of the surface is defended by the varnish. In the mean time, 
 the operator brushes the surface frequently, with a feather, to 
 clear away the bubbles and saturated portions of the metal. Af- 
 ter the first biting is continued for a sufficient length of time 
 in the judgment of the operator, the acid is poured off, and the 
 plate examined. The light shades, if found sufficiently deep, 
 are then covered with varnish, to protect them from further 
 action of the acid, or as it is technicall}^ called, stopped out. 
 The biting is then continued for the second shades, which are 
 next stopped out, and these processes are alternately repeated 
 till the piece is finished. The plate is then freed from varnish, 
 by melting and wiping it off, and cleansed by washing with oil 
 of turpentine. It must, in this state, be carefully examined 
 or proved, and any deficiencies in the lines owing to the acci- 
 dental presence of varnish, must be finished with the graver. 
 The plate is then ready for the press. 
 
 The productions of the etching needle, can never have the 
 smoothness and beauty of mechanical engravings. Notwith- 
 
96 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 standing all the care which may be taken, the lines will have 
 an irregularity and roughness, owing to the unequal action of 
 the acid. There are, nevertheless, subjects, to which this very 
 irregularity renders etched work peculiarly suited. Those 
 objects which in nature are rough, and coarse, are well repre- 
 sented by this species of engraving. The trunks of trees, 
 broken ground, rocks, walls, cottages, (fcc, especially when 
 executed on a large scale, receive a more natural aspect from 
 the rough effect of etching than they could do without great 
 labor from the softer touches of the graver. In landscape en- 
 graving we commonly find a mixture of methods, the coarser 
 parts being etched, while objects of more delicacy are cut with 
 the graver. Letters and written characters, are mostly cut, and 
 but seldom etched. 
 
 Mezzo Tinto. — Engraving in mezzo ti?ito, or mezzotint, 
 is the fourth species. This method is the reverse of all those 
 hitherto mentioned, and consists in bringing up lights from a 
 dark ground. The mezzo tinto was invented by Prince Ru- 
 pert, in 1649. Since his time, it has been greatly improved, 
 and though not calculated for general use, it has been applied 
 to various subjects with great success. For engraving in mez- 
 zo tinto, the whole surface of the copperplate is first roughen- 
 ed or covered with minute prominences and excavations, too 
 small to be obvious to the naked eye ; so that if an impression 
 be taken from it in this state, it has an uniform velvety black 
 appearance. This roughness is produced mechanically, by the 
 operations of a small toothed instrument denominated a cradle. 
 This instrument, by continual turns and impressions, which oc- 
 cupy a great length of time, gradually breaks up and produces 
 an uniform roughness on the whole surface of the plate. That 
 the ground, as it is called, may be of the requisite fineness, the 
 operation must be repeated a considerable number of times, 
 the position of the plate in regard to the instrument, being va- 
 ried each time. This is the most tedious part of the labor. 
 When the plate is prepared, the rest of the process, to a skilful 
 engraver, is easy, when compared with cutting or stippling. 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 97 
 
 It consists in pressing down or rubbing out the roughness of the 
 plate, by means of the burnisher and scraper, to the extent of 
 the intended figure, obhterating the ground for hghts, and leav- 
 ing it for shades. Where a strong light is required, the whole 
 ground is erased. For a medium hght it is moderately burn- 
 ished, or partially erased. For the deepest shades, the ground is 
 left entire. Care is taken to preserve the insensible gradations 
 of light and shade upon which the effect and harmony of the 
 piece essentially depend. 
 
 Engraving in mezzo tinto, approaches more nearly to the ef- 
 fect of oil paintings than any other species. It is well calculat- 
 ed for the representation of obscure pieces, such as night scenes, 
 &c. Some individuals have applied it with good success to the 
 engraving of portraits. The principal objection to the method 
 is, that the plates wear out speedily under the press, and of 
 course yield a comparatively small number of impressions. 
 
 Aqua Tinta. — Engraving in aqua tinta, is the only re- 
 maining mode, "^rhis is done by a process partly chemical, 
 and partly mechanical. It consists in producing chemically, a 
 rough ground covering the surface of the figure to be engraved, 
 and afterwards introducing the lights and shades by mechan- 
 ical means. It may, however, be executed by a process wholly 
 chemical. For engraving in aquatint, the surface of the cop- 
 per, after having the outhne engraved or etched in the usual 
 way, is covered throughout with minute particles of resin, in- 
 visible to the naked eye, detached from each other and adher- 
 ing to the surface of the metal. This process, caUed laying 
 the ground, is effected in different ways. One method, is to 
 inclose a quantity of finely powdered rosin or mastic, in a flan- 
 nel or linen bag. This is held at a certain height above the 
 plate, and beat with a stick. A fine cloud of dust issues from 
 the bag, and settles upon the surface of the plate, with the 
 same uniformity as the dust of the atmosphere settles upon 
 furniture in dry weather. This dust is fixed to the surface, 
 by heating the plate till the resin melts. The ground is thus 
 laid. A second mode, is to cover the plate with a coat of very 
 13 
 
98 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 thin spirit varnish prepared for the purpose. This varnish is 
 so fluid, or contains so little resin, that when it dries by the eva- 
 poration of the spirit, the whole surface breaks up, or cracks 
 into an infinite number of particles, all adhering to the plate. 
 After the ground is completed, the vacant parts of the plate, or 
 those not intended to be occupied by the figure, are stopped 
 out ; i. e. covered by a thick varnish, impenetrable to acid. 
 The plate is now surrounded by a wall of wax, as for etching, 
 and diluted nitric acid is poured on. A chemical action im- 
 mediately commences in all the interstices between the resin- 
 ous particles ; and the face of the plate, for the desired extent, 
 is converted into a porous surface, made up of little prominen- 
 ces and excavations. The lighter shades are stopped out at 
 an early stage of the process, and the corrosion continued for 
 the dark ones. After the plate is judged to be sufficiently bit- 
 ten in, it is cleaned and proved by an impression. If the 
 ground is good, i. e. not too faint, too coarse, or too uneven, 
 the work is then finished by burnishing the shadings to give 
 them greater softness, and if necessary, by cutting deep lines 
 or dots in the darkest parts. 
 
 Engraving in aqua tinta has the greatest resemblance to 
 paintings in water colors, or in Indian ink. When well exe- 
 cuted, the white points which diversify the surface, are nearly 
 invisible to the naked eye, so that a uniform surface is present- 
 ed. The art was first invented by a Frenchman, by the name 
 of Leprince, who for some time kept his art a secret, and sold 
 his impressions for original drawings. It is a mode of engra- 
 ving well adapted to light subjects, sketches, landscapes, &c., 
 and for subjects of which only a few copies or impressions are 
 wanted. Owing to the fineness of the ground, the plates 
 wear out rapidly, and seldom yield, when of the ordinary 
 strength, more than 600 impressions. 
 
 Aqua tinta is the most precarious kind of engraving, and re- 
 quires much experience and attention on the part of the artist, 
 to siicceed well. If the ground is laid too thick, or too thin, 
 the result is imperfect. If the corrosion by the acid is not 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 99 
 
 continued long enough, the giound is too faint; if continued 
 too long, the acid acts laterally, and destroys the whole surface. 
 It is often necessary to repeat the whole process, and to go 
 through the operations of laying the ground, stopping out, and 
 biting, a number of successive times, before a ground is obtain- 
 ed of sufficient strength and regularity to answer for the press. 
 Copperplate Printing. — Copperplate printing is performed 
 by means of a rolling press, in which the plate and paper are 
 strongly compressed together between a c3''linder of wood and 
 a sliding platform. The ink employed for copperplates, is 
 made of a carbonaceous substance called Frankfort black, and 
 linseed oil, inspissated by boiling. Oil must be used, instead 
 of water, that the ink may not dry during the process ; it is 
 boiled till it becomes thick and viscid, that it may not spread 
 upon the paper. Previously to the operation, the paper is wet, 
 as for printing with types. The printer, having warmed his 
 plate over a bed of coals, proceeds to cover its surface with ink 
 by an instrument resembling a printer's roller. When the 
 cavities of tlie engraving are thoroughly charged with ink, the 
 smooth surface of the plate is wiped as clean from ink as pos- 
 sible. The latter part of the wiping is always performed by 
 the pahn of the hand, aided by a little dry powder, commonly 
 whiting. The ink remains only in the crevices of the engra- 
 ving, into which the hand does not penetrate in wiping the 
 surface. The plate is next laid on the sliding plank, with its 
 face upward, and the paper laid upon it. An elastic substance, 
 commonly folds of woollen cloth, is placed above and below. 
 A turn of the cylinder carries the plate under a very strong 
 pressure, by which portions of the paper are forced down into 
 all the cavities of the engraving. The ink, or a part of it, 
 leaves the copper and adheres to the paper, giving an exact 
 representation of the whole engraving. 
 
 Colored Engravings. — Colored engravings are variously 
 executed. The most common are printed in black outhne, 
 and afterward painted separately in water colors. Sometimes 
 a surface is produced by aqua tinta, or stippling, and different 
 
100 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 colors applied in printing to different parts, care being taken 
 to wipe off the colors in opposite directions, that they may not 
 interfere with each other. But the most perfect as well as 
 elaborate productions, are those which are first printed in colors 
 and afterwards painted by hand. 
 
 Steel Engraving. — The process of steel engraving-, intro- 
 duced by Mr Perkins, depends on the property, which steel has, 
 of being softened, by losing a part of its carbon ; and afterwards 
 of being hardened, by regaining it. If a steel plate, prepared 
 for engraving, be inclosed in a box with iron filings, and ex- 
 posed to a white heat for some hours, the surface loses a por- 
 tion of carbon and becomes sufficiently softened to be cut with 
 the graver. If then the plate, after being engraved, is re-expos- 
 ed to heat in a box with animal charcoal, the surface becomes 
 again carbonated, and an engraved steel plate is thus obtained. 
 
 The great advantage of steel plates consists in their hardness, 
 by which they last for an indefinite time, and yield an almost 
 unlimited number of impressions ; whereas a copperplate wears 
 out after two or three thousand impressions, and even much 
 sooner, if the engraving be fine. An engraving on a steel plate, 
 may be transferred in relief to a softened steel cylinder, by 
 pressure ; and this cylinder, after being hardened, may again 
 transfer the design, by rolling it upon a fresh steel plate ; and 
 thus the design may be multiplied at pleasure. 
 
 Steel engraving is of use, where a great number of impres- 
 sions are called for ; as it saves the expense of engraving the 
 plate anew, and furnishes copies more exactly resembling each 
 other, than can be obtained by any other mode. Of course, it 
 affords the greatest security against counterfeiting. 
 
 Etching on steel plates, is practised with various chemical 
 agents, one of which consists of a mixture of six parts of acetic 
 acid, with one of nitric acid. Another menstruum is made by 
 dissolving an ounce of corrosive sublimate, and a quarter of 
 an ounce of alum, in half a pint of water. 
 
 Wood Engraving. — Engravings in wood are differently 
 executed from those already described, the subjects being cut 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 101 
 
 in relief ; so that they require to be printed in the same man- 
 ner as common types, and not with the rolHng press. The 
 material used is boxwood, which unites the properties of hard- 
 ness, fineness, and density. It is cut across the grain into 
 pieces of the height of common types, in order that the engrav- 
 ing may be made upon the end of the grain, for the strength 
 and durabihty. The surface being planed very smooth, the 
 design is drawn upon it with a black lead pencil. The lines 
 of this design are left untouched, but the whole of the inter- 
 mediate spaces between the lines are cut away with a common 
 graver, or chisel. Wood engravings have the advantage that 
 the blocks m:iy be inserted in a page wnth common types, and 
 printed without separate expense. They are exceedingly du- 
 rable, and may, if desired, be multiplied by the process of stereo- 
 typing. 
 
 LITHOGRAPHY. 
 
 Lithography is the art of taking impressions from draw- 
 ings or writings made on stone, without engraving. 
 
 Principles. — This art is founded on the property which 
 stone possesses, of imbibing fluids by capillary attraction, and 
 on the chemical repulsion which oil and water have for each 
 other. A drawing is first made on stone with an ink, or cray- 
 on, of an oily composition, and the surface is washed over 
 with water, which sinks into all the parts of the stone, not 
 defended by the drawing. A cylindrical roller, charged with 
 printing ink, is then passed over the surface of the stone. 
 The drawing receives the ink, W'hich is oily, while the other 
 parts of the stone repel it, being defended by the water. The 
 process, therefore, depends entirely on chemical principles, and 
 is thus distinct from letter-press or copperplate printing, which 
 are mechanical. On this account, it has, in Germany, been 
 called chemical printing. 
 
 Origin. — The invention of lithography is generally ascrib- 
 ed to Alois Senefelder, the son of a performer at the Theatre 
 
102 ARTS OP ENGRAVING AND LITHOGRAPHY. 
 
 of Munich, wlio received his education at the University of In- 
 goldstadt. Having become an author, and being too poor to 
 pubhsh his works, he tried many plans with copperplates, and 
 compositions, and accidentally with stone, as substitutes for let- 
 ter-press, in order to be his own printer. His first essays to 
 print for publication, were some pieces of music, executed in 
 1796, after which he attempted various drawings and writings. 
 The first productions of the art were rude and of little promise. 
 Its progress, however, has been so rapid, that it now gives em- 
 ployment to a vast number of ajtists, and works are produced 
 which rival the finest engravings, and even surpass them in 
 the expression of certain subjects. 
 
 Lithographic Stones. — As calcareous stones will all im- 
 bibe oil and water, and receive the action of acids, they are all 
 capable of being used for lithography. Those, however, are 
 best adapted to the purpose, which are compact, of a fine and 
 equal grain, and free from veins, oi- imbedded fossils or crystals. 
 A conchoidal fracture is considered a good characteristic. 
 
 The quarries of Solenhofen, near Pappenheim, in Bavaria, 
 furnished the first plates, and none have as yet been found to 
 equal them in quality. They are of a uniform, pale yellowish 
 or bluish white color, and the fracture is perfectly conchoidal. 
 Generally, the hardest are considered best, provided they are 
 uniform in texture. Such are necessary for fine chalk draw- 
 ings, while softer ones answer for ink, or for coarser drawings 
 in chalk. 
 
 In France, stones have been found near Chateauroux, of a 
 similar color to those of Solenhofen, and even harder, and of a 
 finer grain, but they are full of spots of a softer nature, so that 
 it is difficult to procure pieces of the necessary size. In Eng- 
 land, a stone has been used for lithography, which is found at 
 Corston, near Bath. It is one of the white lias beds, but not 
 so fine in grain, nor so close in texture as the German stone, 
 and therefore inferior. In the extensive limestone tracts of the- 
 United States, there is little doubt that future observation will 
 bring to light stones of a suitable character for lithography. 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 103 
 
 To bear the pressure used in taking impressions, a stone 
 twelve inches square, should be an inch or two thick ; and the 
 thickness must increase with the size of the stone. 
 
 Pi'eparation. — The stones are first ground to a level sur- 
 face, by rubbing two of them face to face with sand and water. 
 To prepare them for ink drawings^ they are next polished 
 with pumice-stone. But when they are intended for chalk 
 drawings, they are merely ground with fine sand, which has 
 been passed through a sieve, and which produces a smooth and 
 uniform surface, which is grained and not polished, this sur- 
 face being best adapted for holding the chalk. 
 
 Lithographic Ink and Chalk. — For these materials, the 
 union of several qualities is required, to obtain which, it is ne- 
 cessary to combine several substances together. 
 
 For lithographic ink, a great many different receipts have 
 been given, one of the most approved of which is a composi- 
 tion made of equal parts of tallow, wax, shell lac, and com- 
 mon soap, with about one twentieth part of the whole, of lamp- 
 black. These materials are mixed in an iron vessel. The 
 wax and tallow are first put in, and heated till they take fire, 
 after which, the other ingredients are successively added. The 
 burning is allowed to continue until the composition is reduced 
 about one third. 
 
 Lithographic chalk should have the qualities of a good draw- 
 ing crayon ; it should be even in texture, and carry a good 
 point. The following proportions are among the best. Soap, 
 1^ oz. ; tallow, 2 oz. ; wax, IJ oz. ; shell lac, 1 oz. ; lamp- 
 black, ^ oz. The manipulation is similar to that for the ink. 
 
 Mode of Drawing. — With these materials, the artist pro- 
 ceeds to work on the prepared stone, after wiping it with a dry 
 cloth. The ink being rubbed with warm water, like Indian 
 ink, is used on the polished stone, and a gradation of tints 
 can be obtained, only by varying the thickness of the lines, 
 and the distance at which they are placed apart. It is neces- 
 sary to mix the ink to such a consistency, that, while it Avorks 
 freely, it shall yet be strong enough to stand perfect, through 
 
104 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 the process of printing. A consistency, a little greater than 
 that of writing ink, is suiiicient for this purpose. The instru- 
 ments used for drawing with ink, are steel pens, and fine 
 camel's hair pencils. 
 
 The chalk will not hold upon the polished stone. But the 
 grained stone prepared for chalk, may be drawn upon with the 
 chalk crayon, as easily as paper. The subject may be traced 
 on the stone, with lead pencil or red chalk, but it should be 
 done so lightly, as not to fill up any of the grain of the stone. 
 In drawing, the degree of pressure of the hand will vary the 
 strength of the tint, and it is desirable to give the requisite 
 strength at once, as the surface of the stone is a little altered, 
 by receiving the chalk, and hence it does not take any additional 
 lines with the same equality. Practice is necessary to give 
 a command of the material, as it does not work quite like the 
 common crayon, there being great difficulty in keeping a good 
 point. There is also difficulty in obtaining the finer tints per- 
 fect in the impression ; and for the light tints, the chalk must 
 be used in a reed, as the metal port-crayon is too heavy to draw 
 them, even without any pressure from the hand. A scraper is 
 used to correct errors, and also to produce lights. 
 
 It is necessary to observe that the grain with which the 
 stone is prepared, should vary with the fineness of the drawing. 
 Several pieces of chalk should be prepared to use in succession, 
 as the warmth of the hand softens it. It is useful to cut the 
 chalk to the form of a wedge, rather than a point, as it is less 
 likely to bend in that form. Small portions of the point will 
 break off during the drawing ; these must be carefully removed 
 with a small brush. 
 
 Etching the Stotie. — After the drawing is finished on the 
 stone, as before described, it is sent to the lithographic printer, 
 who proceeds to etch the drawing, as it is called. The stone 
 is placed obliquely on one edge over a trough, and very dilute 
 nitric or sulphuric acid is poured over it. The degree of strength, 
 which is little more than one per cent, of cicid, should be such 
 as to produce a very slight effervescence. The object of this 
 
ARTS OF ENGRAVING AND LITHOGRAPHY. 105 
 
 slight etching appears to be to produce a chemical, rather than 
 a mechanical change of surface, and it is by some considered 
 superfluous, except to discharge the alkali of the soap. 
 
 The stone is now carefully washed, by pouring clean rain 
 water over it, and afterwards gum water ; and when not too 
 wet, the roller, charged with printing ink, is rolled over it in 
 both directions, till the drawing takes the ink. It is then well 
 covered with a solution of gum-arabic in water, of about the 
 consistency of oil. This is allowed to dry, and preserves the 
 drawing from any alteration, as the lines cannot spread, in 
 consequence of the pores of the stone being filled with gum. 
 
 Printing. — When the stone is ready for the press, the 
 printing ink is applied to it, by means of an elastic roller, cov- 
 ered with leather. In the lithographic press, the paper is first 
 brought in contact with the stone, and protected by a tight 
 cover of strong leather. The whole is then passed under the 
 edge of a blunt wooden scraper, which is powerfully pressed 
 down by a double lever, and thus every part of the paper is 
 successively brought into forcible contact with the stone, and an 
 accurate impression received of the drawing. The ink is then 
 reapplied to the stone, and the process repeated for each im- 
 pression. 
 
 Printing Ink. — This is composed, as other printing inks 
 are, of oil-varnish, and fine lampblack. To prepare the var- 
 nish, a vessel is about half filled with pure hnseed oil, and 
 heated till it takes fire from the flame of a piece of burning 
 paper. It should then be allowed to burn, till it is reduced to 
 the degree of density required. 
 
 Remarks. — The great distinction of hthography from engra- 
 ving is, that it gives a fac-simile of the original drawing, which 
 retains the freedom and touch of the artist's own hand, while, 
 on the contrary, an engraving must be a copy. This charac- 
 ter in a lithographic print, arises from the facility with which 
 the drawing is produced, as the process is exactly that which 
 the artist would follow, in making a common drawing. A 
 further advantage, derived from the same cause, is, that the 
 14 
 
106 ARTS OF ENGRAVING AND LITHOGRAPHY. 
 
 drawing- being made at once on the stone, the whole expense 
 of engraving is saved. 
 
 The more finished drawings in ink, however, have not the 
 same advantages ; for the gradations can only be obtained by 
 the variations in the breadth and the distance of the lines, which 
 is the same principle as that on which the engraver works ; 
 and hence the labor is more nearly equal in the two methods. 
 
 The number of impressions, which can be taken from a li- 
 thographic chalk drawing, will vary according to the fineness 
 of the tints. A fine drawing, will give 400, or 500 ; a strong 
 one, 1000, or 1500. Ink drawings, and writings, give consid- 
 erably more than copperplates. The finest will yield 6000, or 
 8000 ; and strong lines, and writings, many more. Upwards 
 of 80,000 impressions have been taken at Munich, from one 
 writing, of a form for regimental returns. 
 
 A method has been introduced, by which copies of valuable 
 engravings may be multiplied indefinitely. An inipression on 
 paper, is taken, in the usual manner, from the copperplate, and 
 immediately laid with its surface upon water. When sufficient- 
 ly wet, it is carefully applied to the surface of a stone, pre- 
 pared in the usual manner, and pressed down upon it by the 
 application of a roller, till the ink leaves the paper, and adheres 
 to the stone. It is then printed in the common way. Auto- 
 graphic writiugs may be transferred from paper to stone, and 
 printed in a manner nearly similar. 
 
 Landseer's Lectures on Engraving, 8vo. London, 1807 ; — Meadows' 
 Lectures on Engraving, London, 1811 ; — Partington's Mechanic's 
 Gallery, 8vo. 1825; — Rees' Cyclopaedia, under the various heads; — 
 Hulmandel's Treatise on Lithography, 8vo, 1817 ; — Senefelder's 
 Complete Course of Lithography, 4to. ; — London Journal of Arts, pas- 
 sim ; — De Lasteyrie, Journal de Connaisances usuelles, translated, 
 Franklin Journal, vol. iv. 
 
CHAPTER VI. 
 
 OF SCULPTURE, MODELLING, AND CASTING. 
 
 Subjects. — Sculpture in its most general sense, is the art of 
 producing resemblances of visible forms, out of solid materials. 
 The required shapes are produced by carving, when the ma- 
 terial is solid and brittle ; and to this sense the terra sculpture 
 is sometimes limited. They are also formed by modelling, 
 when the material is soft ; and by casting, when it is liquid 
 or fusible. The productions of this art are known under va- 
 rious denominations, according to their character and subject. 
 Of thesej the most important are statues, which are entire re- 
 semblances of living objects. Busts consist of the upper por- 
 tions of statues. Bas-reliefs, in the common acceptation of 
 the term, are partial sculptures, or lateral views of figures, raised 
 upon a plane surface. Their different degrees of prominence 
 are distinguished by the Itahans, under different names. These 
 are, alto relievo, or high relief, when the figures are nearly 
 complete, or appear to issue from the back ground ; 'mezzo 
 relievo, or middle relief, in which they are half raised from 
 the surface ; and basso relievo, low relief, or bas-relief proper- 
 ly so called, when the figures have not the prominence which 
 their outline requires, but appear as if compressed. The prin- 
 cipal remaining objects of sculpture, are vases, armatures, or 
 trophies, and the decorative parts of architecture. 
 
 ModelliTig. — Before any object is executed in stone, it is the 
 practice of sculptors to complete a representation of their de- 
 sign, by modelhng it in clay, or some other soft materiaL The 
 genius of the artist is displayed altogether in the model ; for the 
 process of afterwards copying the model in stone, is chiefly 
 mechanical, and may often be executed by another person, as 
 
108 OF SCULPTURE, MODELLING, AND CASTING. 
 
 well as by the sculptor himself. When a clay model is under- 
 taken, if the proposed figure be large, a frame of wood or iron 
 is erected to give support to the Hmbs and different parts of the 
 figure. Upon this frame, a proper quantity of wet clay is dis- 
 tributed, and wrought into the form of the intended statue. 
 The moulding of the clay is performed with the hands, and 
 with various instruments of wood and ivory. When the mod- 
 el is completed, copies may be taken from it, either by casting 
 them in plaster, or in metal ; or by chiseling them in marble. 
 
 Casting in Plaster. — Copies are most frequently taken, 
 both from new models, and from old statues, by casting them 
 in plaster. For this purpose, a mould in plaster is first made 
 from the surface of the statue, or figure, itself ; and this mould 
 is afterwards used to reproduce the figure by casting. Plaster 
 is prepared for use by pulverizing common gypsum, and ex- 
 posing it to the heat of a fire until its moisture is wholly ex- 
 pelled.* While in this dry state, if it be mixed with water to 
 the consistence of cream or paste, it has the property of hard- 
 ening in a few minutes, and takes a very sharp impression. 
 The hardness afterwards increases by keeping, till it approach- 
 es the character of stone. 
 
 Moulds are formed in the following manner. The statue 
 or figure to be copied, is first oiled, to prevent it from cohering 
 with the gypsum. A quantity of liquid plaster sufficient for 
 the mould, is then poured on, immediately after being mixed, 
 and is suffered to harden. If the subject be a bas-relief, or any 
 figure which can be withdrawn without injury, the mould may 
 be considered as finished, requiring only to be surrounded with 
 an edging. But if it be a statue, it cannot be withdrawn, with- 
 out breaking the mould; and on this account it becomes neces- 
 sary to divide the mould into such a number of pieces, as will 
 sepai'ate perfectly from the original. These are taken off from 
 the statue, and when afterwards replaced, or put together, 
 
 ♦ The heat requisite for this purpose must be greater than that of boiling wa- 
 ter. Care must be taken not to raise the heat too high, as in that case the suU 
 phate of lime would be decomposed. 
 
OF SCULPTURE, MODELLING, AND CASTING. 109 
 
 without the statue, they constitute a perfect mould. This 
 mould, its parts having been oiled to prevent adhesion, is 
 made to receive a quantity of plaster, by pouring it in at a 
 small orifice. The mould is then turned in every direction, 
 in order that the plaster may fill every part of the surface ; 
 and when a sufficient quantity is poured in to produce the 
 strength required in the cast, the remainder is often left hollow, 
 for the sake of hghtness, and economy of the material. When 
 the cast is dry, it is extricated by separating the pieces of the 
 mould, and finished by removing the seams and blemishes 
 with the proper tools.* If the form or position require it, the 
 limbs are cast separately, and afterwards cemented on. 
 
 Moulds and busts are obtained in a similar manner from 
 living faces, by covering them with new plaster, and removing 
 it in pieces as soon as it becomes hard. It is necessary that 
 the skin of the face should be oiled, and, during the operation, 
 the eyes are closed, and the person breathes through tubes in- 
 serted in the nostrils. 
 
 Elastic moulds have been formed by pouring upon the fig- 
 ure to be copied, a strong solution of glue. This hardens up- 
 on cooling, and takes a fine impression. It is then cut into 
 suitable pieces and removed. The advantage of the elastic 
 mould is that it separates more easily from irregular surfaces, 
 or those with uneven projections and under cuttings, from 
 which a common mould could not be removed without vio- 
 lence.! 
 
 * Plaster casts are varnished by a mixture of soap and white wax in boiling 
 water. A quarter of an ounce of soap is dissolved in a pint of water, and an 
 equal quantity of wax afterwards incorporated. The cast is dipped in this li- 
 quid, and after drying a week, is polished by rubbing with soft linen. The sur- 
 face produced in this manner approaches to the polish of marble. 
 
 When plaster casts are to be exposed to the weather, their durability is great- 
 ly increased by saturating them with linseed oil, with which wax or rosin may 
 be combined. When intended to resemble bronze, a soap is used, made of lin- 
 seed oil and soda, colored by the sulphates of copper and iron. Walls and ceil- 
 ings are rendered water proof in the same way. See an abstract of a memoir 
 of D'Arcet and Thenard, in Brande's Journal, vol. xxii. 184, and Franklin 
 Journal, ii. 276. 
 
 t See a paper by Mr Fox, republished in the Franklin Journal, vol. iii. 
 
110 OF SCULPTURE, MODELLING, AND CASTING. 
 
 Architectural models and other complex pieces of work- 
 manship, are made by casting the constituent parts separately, 
 and afterwards cementing them together. If the form of the 
 parts is complicated, a mould is required which can be taken 
 to pieces to extract the cast. The cementing of the parts is 
 performed by a thin mixture of plaster and water, recently 
 made, and it is necessary that the surfaces to be joined should 
 be thoroughly wet, before the cement is applied to them. 
 
 For small and delicate impressions, which are merely in re- 
 lief, melted sulphur is sometimes used, also a strong solution 
 of isinglass in proof spirit. The latter material has the ad- 
 vantage that it is not brittle when dry, but possesses a consist- 
 ence like that of horn. Both substances yield very accurate 
 and sharp impressions. 
 
 Bronze Casting. — Statues intended to occupy situations 
 in which they may be exposed to violence, are commonly made 
 of bronze. This material resists both mechanical injuries, and 
 decay from the influence of the atmosphere. The moulds in 
 which bronze statues are cast, are made on the pattern, out of 
 plaster and brick dust ; the latter material being added to resist 
 the heat of the melted metal. The parts of this mould are 
 covered on their inside with a coating of clay, as thick as the 
 bronze is intended to be. The mould is then closed, and fill- 
 ed on its inside with a nucleus or core of plaster and brick 
 dust, mixed with water. When this is done, the mould is 
 opened, and the clay carefully removed. The mould with its 
 core, are then thoroughly dried, and the core secured in its cen- 
 tral position by short bars of bronze which pass into it through 
 the external part of the mould. The whole is then bound 
 with iron hoops, and when placed in a proper situation for cast- 
 ing, the melted bronze is poured in through an aperture left 
 for the purpose. Of course, the bronze fills the same cavity 
 which was previously occupied by the clay, and forms a me- 
 tallic covering to the core. This is afterwards made smooth 
 by mechanical means. 
 
 Practice of Sculpture. — To execute a statue in marble. 
 
OF SCULPTURE, MODELLING, AND CASTING. Ill 
 
 which shall exactly correspond to a pattern or model, is a work 
 of mechanical, rather than of inventive skill. It is performed 
 b}?^ finding, in the block of marble, the exact situation of nu- 
 merous points corresponding to the chief elevations and cavi- 
 ties in the figure to be imitated, and joining these by the pro- 
 per curves and surfaces, at the judgment of the eye. These 
 points are found, by measuring the height, depth, and lateral 
 deviation of the corresponding points in the model; after which, 
 those in the block are found by similar measurements. Some- 
 times the points are ascertained, by placing the model horizon- 
 tally under a frame, and suspending a plumb-line successively 
 from different parts of the frame, till it reaches the parts of the 
 figure beneath it. Sometimes an instrument is used consist- 
 ing of a moveable point, attached by various joints to an up- 
 right post, so that it ma}?^ be carried to any part of the statue, 
 and indicate the relative position of that part in regard to the 
 post. Machines have also been contrived for cutting any re- 
 quired figure from a block, the cutting instrument being direct- 
 ed by a giiage which rests upon the model in another part of 
 the machine. 
 
 Marble is wrought to the rough outUne of the statue, by the 
 chisel and hammer, aided by the occasional use of drills and oth- 
 er perforating tools. It is then smootlied with rasps and files, 
 and when required, is polished with pumice stone and putty. 
 The hair of statues is always finished with the chisel ; and for 
 this object, very sharp instruments with different points and 
 edges are necessary. The ancient sculptors appear to have re- 
 lied almost wholly upon the chisel, and to have used that in- 
 strument with great boldness and freedom, such as could have 
 been justified only by consummate skill in the art. The mod- 
 erns, on the contrary, approach the surface of the statue with 
 great caution, and employ safer means for giving the last fin- 
 ish. Some of the most celebrated antique statues, such as the 
 Laocoon, the Apollo Belvidere, and Yen us de Medicis, are 
 thought to have been finished with the chisel alone. 
 
 Materials. — Although marble has been the common mate- 
 
112 OF SCULPTURE, MODELLING, AND CASTING. 
 
 rial of sculpture, both in ancient and modern times, yet other 
 substances have been occasionally made subjects of the chisel. 
 Statues of porphyry, granite, serpentine, and alabaster, are found 
 among the remains of antiquity. Other materials of a less du- 
 rable kind, were also employed. Some of the principal wOrks 
 of Phidias were made of ivory and gold, particularly his co- 
 lossal statues of Jupiter Olympius, and Minerva, at Athens. 
 
 Objects of Sculpture. — In sculpture, as in the other imita- 
 tive arts, two ends propose themselves to the skill of the artist. 
 One consists in the imitation of a particular object, in which 
 case the art of the sculptor can be expected only to equal, but 
 not to surpass, his original. The other consists in new combi- 
 nations of excellence, and in the invention of forms and ex- 
 pressions, which are not known to exist together in nature, 
 but are embodied in the imagination of the artist. Beauty in 
 objects thus conceived, constitutes the beau ideal in art, to 
 attain which, has ever been the ambition of cultivators of the 
 fine arts. In statuary, the specimens which have descended 
 to us from the ancient Greeks, are by universal consent admit- 
 ted to be the most perfect designs of beauty, and furnish the 
 common models for study and imitation, at the present, as in 
 all former ages. 
 
 Gein Engraving. — Tiie art of cutting precious stones, is 
 more properly a species of sculpture, than of engraving. The 
 hardness of these stones renders it impossible to operate on them 
 by the strongest steel instruments. They are therefore wrought 
 in a slow manner, by grinding them away upon the surface 
 of a wheel, commonly made of metal, and covered with the 
 grit, or fine powder of some hard substance. The diamond 
 can only be ground, or cut, with its own dust. Rubies, agates, 
 emeralds, &c., are cut and polished with emery or tripoli, in 
 fine powder. Lapidaries make use of small wheels, balls, 
 and drills, of various forms, made of iron, or copper, which 
 revolve with great rapidity, and act upon the stone through 
 the medium of the pulverized material on their surface. They 
 also use wires covered with emery, for the purpose )f sawing 
 plates. 
 
OF SCULPTURE, MODELLING, AND CASTING. 113 
 
 The imitative designs, which are cut upon hard stones, are 
 chiefly of two kinds. The first of these are cameos, which 
 are little bas-reliefs or figures, raised above the surface. They 
 are commonly made from stones, the strata of which are of 
 different colors, so that the raised figure is of a different color 
 from the ground to which it is attached. Varieties of agate, 
 carnelian, onyx, &c., are made use of for this purpose. Some- 
 times several successive strata of different colors, are so wrought 
 as to produce the appearance of painting. A cheaper kind of 
 cameos are made from marine shells. These having lime for 
 their basis, may be scratched with steel, or corroded with acids. 
 Intaglios are the second kind of engraved gems. They 
 differ from cameos in having the figure cut into, or below, the 
 surface, so that they serve as seals to produce impressions in 
 relief upon soft substances. 
 
 Mosaic. — ^Mosaics are imitations of paintings made by com- 
 bining together an infinite number of minute stones of different 
 colors, and cementing them on a plane surface. In the most 
 costly mosaics, precious stones have been cut, and arranged to 
 produce this effect. But in common works of this art, enamels 
 of different colors, manufactured for the purpose, are the ma- 
 terial employed. The enamel is first formed into sticks, from 
 the ends of which, pieces of the requisite size are cut or broken 
 off. These are confined in their proper places upon a plate 
 of metal or stone, by a cement made of quicklime, pulverized 
 lime-stone, and linseed oil. After the whole has adhered, it is 
 allowed to dry two months, and is then polished with a flat stone 
 and emery.* Inlaid loorks of agate, and other costly stones, 
 are executed on the same principle as mosaic ; except that the 
 stones are larger, and cut to the shape of different parts of the 
 object to be represented ; whereas in mosaic, the pieces are of 
 the same size and shape. The opus reticulatum of the an- 
 
 ♦ One of the largest mosaics which has been executed, is a copy of Leonardo 
 da Vinci's celebrated picture of the last supper. It measures 24 feet by 13, 
 and employed eight or ten artists for eight years. It was executed under the 
 direction of Raffaelli, at Milan, by order of the French government. Cadell. 
 
 15 
 
114 OF SCULPTURE, MODELLING, AND CASTING. 
 
 cients, with which columns and walls were sometimes incrust- 
 edj is found to consist of small stones, of a pyramidal form, the 
 apex of which is imbedded in mortar, while the base, which is 
 polished, forms the outer surface. 
 
 iScagliola. — This name is given at Rome, to a sort of artifi- 
 cial inlaid work, composed of plaster, but resembling stone. 
 For works of this kind, gypsum, dried and powdered, is mixed 
 with a solution of glue, and spread on a tablet for the ground 
 of the picture. Cavities of the form intended in the design, are 
 then made in it with an engraving tool. These are successive- 
 ly filled up with portions of plaster of different colors, so man- 
 aged as to produce the effect of painting. In this way build- 
 ings, and various natural objects are represented. The sur- 
 ace is finely polished, by rubbing it with different powders, 
 and. where the ground is white, with rushes. 
 
 WiNCKELMANN, Histoirc dc V AH chez les Anciens, 3 vols. 4to. tr. 1802 ; 
 — MiLLiN, Didionnaire des Beaux Arts, 3 vols. 8vo. 1806; — Fjlaxman's 
 Lectures on Scuplture, large 8vo. 1829; — Rees' Cyclopaedia; — Works 
 
 of VaSARI; QUATREMERE DE QuiNCY CiCOGNARA ViSCONTI, &C. ; 
 
 — Travels, and Works of Clarke — Eustace — Cadell— Dodwell — 
 Stuart — Elgin, &c. &c. 
 
CHAPTER VII. 
 
 OF ARCHITECTURE AND BUILDING. 
 
 Architecture. — Architecture, in its most general sense, is 
 the art of erecting buildings, of any kind. In modern use, 
 this name is sometimes restricted to the external forms, or 
 styles, of building, in which sense, architecture is one of the 
 fine arts. It appears to have been among the earhest inven- 
 tions, and its works have been commonly regulated by some 
 principle of hereditary imitation. Whatever rude structure 
 the climate and materials of any country have obliged its 
 early inhalaitants to adopt for their temporary shelter, the same 
 structure, with all its prominent features, has been afterwards 
 kept up by their refined and opulent posterity. Thus, the 
 Eg3^ptian style of building has its origin in the cavern and 
 mound ;* the Chinese architectme is modelled from the tent ; 
 the Grecian, is derived from the wooden cabin, and the Go- 
 thic, from the hoiver of trees. 
 
 Elements. — The essential elementary parts of a building, 
 are those which contribute to its support, inclosure, and cover- 
 ing. Of these, the most important are the foundation, the col- 
 umn, the wall, the lintel, the arch, the vault, the dome, and 
 the roof. 
 
 Foundations. — In laying the foundation of any building, it 
 is necessary to dig to a certain depth in the earth, to secure a 
 sohd basis, below the reach of frost and common accidents. 
 The most sohd basis is rock, or gravel which has not been 
 moved. Next to these, are clay and sand, provided no other 
 excavations have been made in the immediate neighbourhood. 
 
 * Wilkins' Vitruvius, p. xviL 
 
116 OF ARCHITECTURE AND BUILDING. 
 
 From this basis, a stone wall is carried up to the surface of the 
 ground, and constitutes the foundation. Where it is intended 
 that the superstructure shiill press unequally, as at its piers, 
 chimnies, or columns, it is sometimes of use to occupy the 
 space between the points of pressure, by an inverted arch. 
 This distributes the pressure equally, and prevents the foun- 
 dation from springing between the different points. In loose 
 or muddy situations, it is always unsafe to build, unless we 
 can reach the solid bottom below. In salt marshes and flats, 
 this is done by depositing timbers, or driving wooden piles, in- 
 to the earth, and raising walls upon them. The preservative 
 quality of the salt, will keep these timbers unimpaired for a 
 great length of time, and makes the foundation equally secure 
 with one of brick or stone. 
 
 Column.— The simplest member in any building, though 
 by no means an essential one to all, is the column, or pillar. 
 This is a perpendicular part, commonly of equal breadth and 
 thickness, not intended for the purpose of inclosure, but simply 
 for the support of some part of the superstructure. The prin- 
 cipal force which a column has to resist, is that of perpendicu- 
 lar pressure. In its shape, the shaft of a column should not 
 be exactly cylindrical ; but since the lower part must support 
 the weight of the superior part, in addition to the weight which 
 presses equally on the whole column, the thickness should 
 gradually decrease from bottom to top. The outline of col- 
 umns, should be a little curved, so as to represent a portion of 
 a very long spheroid, or paraboloid, rather than of a cone. 
 This figure is the joint result of two calculations, independent 
 of beauty of appearance. One of these is, that the form best 
 adapted for stability of base, is that of a cone. The other is, 
 that the figure which would be of equal strength throughout 
 for supporting a superincumbent weight, would be generated 
 by the revolution of two parabolas round the axis of the col- 
 umn, the vertices of the curves being at its extremities.* 
 
 * See Tredgold's Principles of Carpentry, p. 50, 
 
OF ARCHITECTURE AND BUILDING. 
 
 317 
 
 In the accompanying wood cut, No. 1 is the figure having 
 the greatest stability of base ; 2, the figure which is of equal 
 strength throughout for resisting vertical pressure; and 3, the 
 intermediate, or common form of the column, a little more 
 curved than is usual in practice, and having its top truncated, 
 to give stability to the entablature. 
 
 The swell of the shafts of columns, was called the entasis, 
 by the ancients. It has been lately found,* that the columns 
 of the Parthenon, at Athens, which have been commonly 
 supposed straight, deviate about an inch from a straight line, 
 and that their greatest swell is at about one third of their 
 height. 
 
 Columns in the antique orders are usually made to diminish 
 one sixth, or one seventh, of their diameter, and sometimes even 
 one fourth. The Gothic pillar is commonly of equal thickness 
 throughout. 
 
 Wall. — The wall, another elementary part of a building, 
 may be considered as the lateral continuation of a column, an- 
 swering the purpose both of inclosure and support. A wall 
 must diminish as it rises, for the same reasons, and in the 
 same proportion, as the column. It must diminish still more 
 rapidly if it extends through several stories, supporting weights 
 at different heights. A wall, to possess the greatest strength, 
 must also consist of pieces, the upper and lower surfaces of 
 which are horizontal and regular, not rounded nor oblique. 
 The walls of most of the ancient structures, which have stood 
 to the present time, are constructed in this manner, and fre- 
 
 ♦ By Messrs Allason and Cockerel. See Brande's Journal, vol. x. p. 204. 
 
118 OF ARCHITECTURE AND BUILDING. 
 
 qiientl)^ have their sto)3es bound together with bolts and cramps 
 of iron. The same method is adopted in such modern struc- 
 tures as are intended to possess great strength and durability ; 
 and in some cases the stones are even dovetailed together, as 
 in the hght houses at Eddystone, and Bell Rock. But many 
 of our modern stone walls, for the sake of cheapness, have on- 
 ly one face of the stones squared, the inner half of the wall be- 
 ing completed with brick ; so that they can in reality be con- 
 sidered only as brick walls faced with stone. Such walls are 
 said to be liable to become convex outwardly, from the differ- 
 ence in the shrinking of the cement. 
 
 Rubble walls are made of rough, irregular stones laid in 
 mortar. The stones should be broken, if possible, so as to pro- 
 duce horizontal surfaces. The coffer walls of the ancient Ro- 
 mans were made by inclosing successive portions of the intend- 
 ed wall in a box, and filling it with stones, sand, and mortar, 
 promiscuously. This kind of structure must have been ex- 
 tremely insecure. The Pantheon, and various other Roman 
 buildings, are surrounded with a double brick waU, having its 
 vacancy filled up with loose bricks and cement. The whole 
 has gradually consolidated into a mass of great firmness. The 
 reticulated walls of the Romans, having bricks with oblique 
 surfaces, w^ould at the present day be thought highly unphilo- 
 sophical. Indeed they could not long have stood, had it not 
 been for the great strength of their cement. 
 
 Modern brick walls are laid with great precision, and depend 
 for firmness more upon their position than upon the strength 
 of their cement. The bricks being laid in horizontal courses, 
 and continually overlaying each other, or breaking joints, 
 the whole mass is strongly interwoven, and bound together. 
 Wooden walls, composed of timbers covered with boards, are 
 a common, but more perishable kind. They requiie to be 
 constantly covered with a coating of a foreign substance, as 
 paint or plaster, to preserve them from spontaneous decompo- 
 sition. 
 
 In some parts of France, and elsewhere, a kind of wall is 
 
OF ARCHITECTURE AND BUILDING. 119 
 
 made of earth, rendered compact by ramming it in moulds or 
 cases. This method is called building in Pise, and is much 
 more durable than the nature of the material would lead us to 
 suppose. 
 
 Walls of all kinds are greatly strengthened by angles and 
 curves, also by projections, such as pilasters, chimnies, and but- 
 tresses. These projections serve to increase the breadth of the 
 foundation, and are always to be made use of in large build- 
 ings, and in walls of considerable length. 
 
 Lintel. — The lintel, or beam, extends in a right line over a 
 vacant space, from one column or wall to another. The 
 strength of the lintel will be greater in proportion as its trans- 
 verse vertical diameter exceeds the horizontal, the strength be- 
 ing always as the square of the depth. [See page 47.] The 
 Jloor is the lateral continuation or connexion of beams by 
 means of a covering of boards. 
 
 Arch. — The arch is a transverse member of a building an- 
 swering the same purpose as the lintel, but vastly exceeding it 
 in strength. The arch, unlike the lintel, may consist of any 
 number of constituent pieces, without impairing its strength. 
 It is, however, necessary that all the pieces should possess a 
 uniform shape, the shape of a portion of a wedge ; and that 
 the joints, formed by the contact of their surfaces, should point to- 
 wards a common centre. In this case, no one portion of the arch 
 can be displaced or forced inwaid ; and the arch cannot be bro- 
 ken by any force which is not sufficient to crush the materials 
 of which it is made. In arches made of common bricks, the 
 sides of which are parallel, any one of the bricks might 
 be forced inward, were it not for the adhesion of the cement. 
 Any two of the bricks, however, constitute a Avedge, by the 
 disposition of their mortar, and cannot collectively be forced 
 inward. An arch of the proper form, when complete, is ren- 
 dered stronger, instead of weaker, by the pressure of a consid- 
 erable weight, provided this pressure be uniform. [PI. I. Fig. A'.] 
 While building, however, it requires to be supported by a cen- 
 tring of the shape of its internal surface, until it is complete. 
 
120 OF ARCHITECTURE AND BUILDING. 
 
 The upper stone of an arch is called the key-stone^ but is 
 not more essential than any other. 
 
 In regard to the shape of the arch, its most simple form is that 
 of the semi-circle. [PI. 1. Fig. /r.] It is, however, very fre- 
 quently a smaller arc of a circle, and still more frequently a 
 portion of an ellipse. The simplest theory of an arch support- 
 ing itself only, is that of Dr Hooke. The arch, when it has 
 only its own weight to bear, may be considered as the inver- 
 sion of a chain, suspended at each end. The chain hangs 
 in such a form, that the weight of each link or portion is held 
 in equilibrum by the result of two forces acting at its extrem- 
 ities ; and these foices, or tensions, are produced, the one by 
 the weight of the portion of the chain below the link, the other 
 by the same weight increased by that of the link itself, both of 
 them acting originally in a vertical direction. Now, supposing 
 the chain inverted, so as to constitute an arch of the same 
 form and weight, the relative situations of the forces will be 
 the same, only they will act in contrary directions, so that 
 they are compounded in a similar manner, and balance each 
 other on the same conditions. The arch thus formed, is de- 
 nominated a catenary arch. [PI. I. Fig. Z.] In common 
 cases it differs but little from a circular arch of the extent of 
 about one third of a whole circle, and rising from the abut- 
 ments with an obliquity of about 30 degrees from a perpen- 
 dicular. 
 
 But though the catenary arch is the best form for supporting 
 its own weight, and also all additional weight which presses 
 in a vertical direction, it is not the best form to resist lateral 
 pressure, or pressure like that of fluids, acting equally in all 
 directions. Thus the arches of bridges and similar structures, 
 when covered with loose stones and earth, are pressed side- 
 ways, as well as vertically, in the same manner as if they sup- 
 ported a weight of fluid. In this case, it is necessary that the 
 arch should arise more perpendicularly from the abutment, and 
 that its general figure should be that of the longitudinal seg- 
 ment of an ellipse. [PI. I. Fig. m.] In small arches in com- 
 
OF ARCHITECTURE AND BUILDING. 121 
 
 mon buildings, where the disturbing force is not great, it is of 
 little consequence what is the shape of the curve. The out- 
 hnes may even be perfectly straight, as in the tier of bricks 
 which we frequently see over a window. This is, strictly 
 speaking, a real arch, provided the surfaces of the bricks tend 
 towards a common centre. [PI. 1. Fig. s.] It is the weak- 
 est kind of arch, and a part of it is necessarily superfluous, 
 since no greater portion can act in supporting a weight above 
 it, than can be inchided between two curved o)" arched lines. 
 
 Besides the arches already mentioned, various others are in 
 use. The acute or lancet arch, [PL I. Fig. o] much used in 
 Gothic architecture, is described usually from two centres out- 
 side the arch. It is a strong arch for supporting vertical pres- 
 sure. The 7'a?npant arch [Fig. w] is one, in which the two 
 ends spring from unequal heights. The horse shoe or Moor- 
 ish arch [Fig. p and q] is described from one or more centres 
 placed above the base line. In this arch, the lower parts are 
 in danger of being forced inward. The ogee arch [Fig. r] is 
 concavo-convex, and therefore fit only for ornament. 
 
 In describing arches, the upper surface is called the extra- 
 dos, and the inner, the intrados. The springmg lines are 
 those where the intrados meets the abutments, or supporting 
 walls. The span is the distance from one spiinging line to 
 the other. The wedge-shaped stones which form an arch, 
 are sometimes called voussoirs, the uppermost being the key- 
 stone. [PI. I. Fig. /:.] The part of a pier from which an 
 arch springs, is called the impost, and the curve formed by the 
 upper side of the voussoirs, the archivolt. 
 
 Abutments. — It is necessary that the walls, abutments, and 
 piers, on which arches are supported, should be so firm as to 
 resist the lateral thrust, as well as vertical pressure, of the arch. 
 It will at once be seen that the lateral or sideway pressure of 
 an arch is very considerable, when we recollect that every stone, 
 or portion of the arch, is a wedge, a part of whose force acts 
 to separate the abutments. For want of attention to this cir- 
 cumstance, important mistakes have been committed, the 
 16 
 
122 OP ARCHITECTURE AND BUILDING. 
 
 strength of buildings materially impaired, and their ruin accel- 
 erated. In some cases, the want of lateral firmness in the 
 walls, is compensated by a bar of iron stretched across the span 
 of the arch and connecting the abutments, like the tie beam of 
 a roof. This is the case in the cathedral of Milan, and some 
 other Gothic buildings.* 
 
 Arcade. — In an arcade, or continuation of arches, it is only 
 necessary that the outer supports of the terminal arches should 
 be strong enough to resist horizontal pressure. In the inter- 
 mediate arches, the lateral foj'ce of each arch is counteracted 
 by the opposing lateral force of the one contiguous to it. In 
 bridges, however, where individual arches are liable to be de- 
 stroyed by accident, it is desirable, that each of the piers should 
 possess sufficient horizontal strength, to resist the lateral pres- 
 sure of the adjoining arches. 
 
 Vault.— ^\\s, vault is the lateral continuation of an arch, 
 serving to cover an area, or passage, and bearing the same re- 
 lation to the arch, that the wall does to the column. A simple 
 vault is constructed on the principles of the arch, and distrib- 
 utes its pressure equally along the walls, or abutments. A 
 complex or groined vault is made by two vaults intersecting 
 each other ; in which case, the pressure is thown upon spring- 
 ing points, and is greatly increased at those points. The 
 groined vault is common in Gothic architecture. [PI. VI. 
 Fig.6.] 
 
 Dome. — The dome, sometimes called cupola, is a concave 
 covering to a building, or part of it, and may be either a seg- 
 ment of a sphere, of a spheroid, or of any similar figure. 
 When built of stone, it is a very strong kind of structure, even 
 more so than the arch, since the tendency of each part to fall, 
 is counteracted, not only by those above and below it, but also 
 by those on each side. It is only necessary that the constitu- 
 ent pieces should have a common form, and that this form 
 should be somewhat like the frustrum of a pyramid, so that 
 
 " Cadell's Journey through Carniola and Italy, vol. ii. p. 77. 
 
OF ARCHITECTURE AND BUILDING. 123 
 
 when placed in its situation, its four angles may point toward 
 the centre, or axis, of the dome. During the erection of a 
 dome, it is not necessary that it should be supported by a cen- 
 tring, until complete, as is done in the arch. Each circle of 
 stones, when laid, is capable of supporting itself, without aid 
 from those above it. It follows, that the dome may be left 
 open at top, without a key-stone, and 3^et be perfectly secure, 
 in this respect, being the reverse of the arch. The dome of 
 the Pantheon, at Rome, has been always open at top, and yet 
 has stood unimpaired for nearly 2000 j^ears. The upper cir- 
 cle of stones, though apparently the weakest, is nevertheless 
 often made to support the additional weight of a lantern or 
 tower above it. In several of the largest cathedrals^ there are 
 two domes, one within the other, which contribute their joint 
 support to the lantern which rests upon the top. In these 
 buildings, the dome rests upon a circular wall, which is sup- 
 ported in its turn by arches upon massive pillars or piers. This 
 construction is called building upon 'pendentives, and gives 
 open space and room for passage, beneath the dome. 
 
 The remarks which have been made in regard to the abut- 
 ments of the arch, apply equally to the walls immediately sup- 
 porting a dome. They must be of sufficient thickness and 
 solidity to resist the lateral pressure of the dome, which is ve- 
 ry great. The walls of the Roman Pantheon are of great 
 depth and soUdity, In order that a dome in itself should be 
 perfectly secure, its lower parts must not be too nearly vertical, 
 since in this case, they partake of the nature of perpendicular 
 walls, and are acted upon by the spreading force of the parts 
 above them. The dome of St Paul's church, in London, and 
 some others of similar construction, are bound with chains or 
 hoops of iron, to prevent them from spreading at bottom. 
 Domes which are made of wood, depend in part for their 
 strength, on their internal carpentry. The Halle du Bled, in 
 Paris, had, originally, a wooden dome more than 200 feet in 
 diameter, and only one foot in thickness. This has since been 
 replaced by a dome of iron. 
 
124 OF ARCHITECTURE AND BUILDING. 
 
 Plate I. — In the first plate is given a comparative view in 
 outline of some of the most remarkable domes in a,ncient and 
 modern buildings^ together with the edifices to which they 
 belong, likewise various other structures reduced to the same 
 scale. 
 
 The highest dome, [No. 3] is that of St Peter's church, at 
 Rome, generally considered the most splendid building in the 
 world, and one of the largest in size. This edifice was a cen- 
 tury in building, from about 1510 to 1610. It was begun by 
 Bramante, and finished by Michael Angelo and Yignola. The 
 dome is of an ellipsoidal form, solid at bottom, but divided into 
 two thin, concentric domes at top, between which is the stair 
 leading to the lantern. The whole height from the ground 
 to the cross at top, is about 470 feet. The base of the dome 
 rests upon arches, supported by massive stone piers. Within 
 the last century, some fissures of dangerous appearance were 
 discovered in this dome ; to remedy which, it was surrounded 
 with iron chains by the artist Zabaglia. 
 
 The next dome in height, [No. 4] is that of the church of St 
 Maria del Fiore, at Florence. Its vertical section is an elon- 
 gated ellipsoid, its horizontal section octagonal. This church 
 is about 380 feet high, and was built between 1298 and 1472. 
 The dome was erected by Bruneleschi, one of the earliest re- 
 vivers of antique architecture. 
 
 St Paul's cathedral, London, [No. 5] was erected by Sir 
 Christopher Wren, between 1685 and 1710. It has two 
 domes at different heights, the inner being made of brick, and 
 the outer of wood. Between the two, is a hollow, truncated 
 cone of brick work, which furnishes the support of the lantern 
 at top. The outline of the dome is somewhat more than a 
 semicircle, and is prevented from spreading at bottom, by a 
 strong iron hoop. 
 
 The church of St Genevieve, in Paris, [No. 6] which, dur- 
 ing the absence of the Bourbon family, was called the Panthe- 
 on, was begun by SouflSot, in 1757. Tiiis edifice has been 
 threatened with ruin, in consequence of the piers, which sup- 
 
OF ARCHITECTURE AND BUILDING. 125 
 
 port the dome, being made too small for the nature of the ma- 
 terial, and the superincumbent weight. It became necessary 
 to replace a part of the stones which were crushed, and to in- 
 crease the amount of support, to obtain present security. 
 
 The Mosque of St Sophia, at Constantinople, [No. 7] pre- 
 sents a specimen of the kind of dome used by the ancients, 
 which was more flat than any of the preceding examples, and 
 was usually a small segment of a sphere. This edifice was 
 erected during the reign of Justinian, in the sixth century. 
 Owing to the want of suflicient solidity in the supporting wall, 
 the dome fell down at two successive times, and the architect 
 was under the necessity of filling up the subjacent arcades, 
 and of building large buttresses on the outside of the wall, to 
 resist the pressure, and give to the dome eventual stability. 
 The span of this dome is 112 feet. 
 
 The Pantheon, at Rome, [No. 8] is probably the oldest 
 dome now standing, and is one of the best constructed. Its 
 outer and inner suifaces are of different curvatures, so that the 
 thickness increases downward, the inner surface being a hemis- 
 phere. The walls of this edifice are of great solidity, and to 
 this circumstance the security of the superstructure is in part 
 owing. This dome is open at the top. It was built by 
 Agrippa, in the reign of Augustus Ceesar. A more perfect 
 view of the Pantheon is given in Plate V. 
 
 The outline of St Mark's church, at Venice, which has sev- 
 eral domes ; that of the front of the Parthenon, at Athens, 
 which shows the lownessof the Grecian pediment; that of 
 the restored temple of Vesta, at Tivoli, and lastly that of the 
 small Ionic temple which stood upon the Ilissus, are added 
 merely to give an idea of their comparative size. The column 
 erected to the memory of the emperor Trajan, also one of the 
 obelisks brought from Egypt by the ancient Romans, are in- 
 troduced upon the same scale. 
 
 No. 1, in the same plate, represents the outline of the lar- 
 gest of the Egyptian Pyramids, respecting the dimensions of 
 which, travellers vary greatly in their accounts. One of the 
 
126 OF ARCHITECTURE AND BUILDING. 
 
 more moderate of their estimates is here taken, which makes 
 the height a Httle less than 500 feet. 
 
 No. 2, shows the length and height of the Coliseum, at 
 Rome, a vast elliptical amphitheatre, which 15,000 men were 
 occupied ten years in completing. It was built in the reign of 
 Vespasian and Titus, and its walls are standing at the present 
 day. 
 
 No. 15, represents the celebrated leaning tower of Pisa. 
 The several stories of this structure are supported by arcades 
 upon columns, in the Greco-gothic style. The height of the 
 w^hole is 180 feet. This tower leans over about 14 feet from 
 a perpendicular. The view here taken of it, does not repre- 
 sent its greatest inclination. Whether the obliquity was the 
 effect of design, or of the settling of the foundation on one 
 side, is a point upon which writers are not agreed. It was 
 built in the twelfth century. 
 
 No. 16, is the steeple of the Gothic Cathedral, at Strasburg. 
 It is among the highest steeples in Europe, and is introduced 
 to show its comparative elevation. No. 17, is the centre stee- 
 ple of the Duomo or Cathedral of Milan, about 350 feet high. 
 This edifice is of white marble. Its general character is Goth- 
 ic, intermixed with details in the later Roman style. 
 
 The proportions of most of the foregoing buildings are taken 
 from Durand, who has reduced them to a scale. The same 
 scale applies to the other architectural plates in this volume, 
 with the exception of perspective representations, in which 
 more than one side is seen. 
 
 The outlines of several American edifices, reduced to the 
 same scale, are added in this plate, for the convenience of com- 
 parison. No. 18, is that of the Capitol, at Washington, built 
 of freestone, the length of which is 350 feet, the height of the 
 front 70 feet, and the height of the centre dome 148 feet. No. 
 19, is the City Hall, at New York, built chiefly of marble ; its 
 length 220 feet, and the height of the statue at top, 120 feet. 
 No. 20, is the State House, in Boston, 173 feet in length, built 
 of brick, and painted. No. 21, is the Bank of the United 
 
OF ARCHITECTURE AND BUILDING. 127 
 
 States, at Philadelphia, a marble building, having its front 86 
 feet wide, copied in most respects from the Parthenon at Athens. 
 No. 22, the monument erected at Baltimore, in commemora- 
 tion of the battle and victory at that place. Height about 55 
 feet. 
 
 Roof. — The roof is the most common and cheap method of 
 covering buildings, to protect them from rain and other effects 
 of the weather. It is sometimes flat, but more frequently ob- 
 hque in its shape. The flat or platform roof is the least ad- 
 vantageous for shedding rain, and is seldom used in northern 
 countries. The 'pent roof, consisting of two oblique sides 
 meeting at top, is the most common form [PL I. Fig. w.\ 
 These roofs are made steepest in cold climates, where they are 
 liable to be loaded with snow. Where the four sides of the 
 roof are all oblique, it is denominated a hipped roof, [Fig. x\ 
 and where there are two portions to the roof, of different obli- 
 quity, it is a curb, or onansard roof. [Fig. y.] In modern 
 times, roofs are made almost exclusively of wood, though fre- 
 quently covered with incombustible materials. The internal 
 structure or carpentry of roofs, is a subject of considerable me- 
 chanical "contrivance. The roof is supported by rafters, which 
 abut on the walls on each side, Uke the extremities of an arch. 
 If no other timbers existed, except the rafters, they would ex- 
 ert a strong lateral pressure on the walls, tending to separate 
 and overthrow them.* To counteract this lateral force, a tie 
 beam, as it is called, extends across, receiving the ends of the 
 rafters, and protecting the wall from their horizontal thrust. 
 To prevent the tie beam from sagging, or bending down- 
 ward with its own weight, a king post is erected from this 
 
 * The largest roof that has hitherto been built, is supposed to have been that 
 of the riding house, at Moscow. Its span was 235 feet, and the slope of the 
 . roof, about 19 degrees. The principal support of this immense truss, consist- 
 ed in an arch of timber in three thicknesses, indented together, and strapped 
 and bolted with iron. The prhicipal rafters and tie beams, were supported by 
 several vertical pieces, notched to this arch, and the whole stiffened by diagonal 
 braces. Tredgold's Carpentry, p. 87. 
 
128 OF ARCHITECTURE AND BUILDING. 
 
 beam, to the upper angle of the rafters, serving to connect the 
 whole, and to suspend the weight of the beam. This is called 
 trussing. Queen posts are sometimes added, parallel to the 
 king post, in large roofs, also various other connecting timbers. 
 In Gothic buildings, where the vaults do not admit of the use 
 of a tie beam, the rafters are prevented from spreading, as in 
 an arch, by the strength of the buttresses. 
 
 In comparing the lateral pressure of a high roof, with that 
 of a low one, the length of the tie beam being the same, it will 
 be seen that a high roof, from its containing most materials, 
 may produce the greatest pressure, as far as weight is concern- 
 ed. On the other hand, if the weight of both be equal, then 
 the low roof will exert the greater pressure, and this will in- 
 crease in proportion to the distance of the point at which per- 
 pendiculars drawn from the end of each rafter, would meet. 
 
 In roofs, as well as in wooden domes, and bridges, the ma- 
 terials are subjected to an internal strain, to resist which, the co- 
 hesive strength of the material is relied on. On th's account, 
 beams should, when possible, be of one piece. Where this 
 cannot be effected, two or more beams are connected together 
 by splicing. Spliced beams are never so strong as whole ones, 
 yet they may be made to approach the same strength, by affix- 
 ing lateral pieces, or by making the ends overlay each other, 
 and connecting them with bolts and straps of iron. The ten- 
 dency to separate is also resisted, by letting the two pieces into 
 each other, by the process called scarfing. Mortises, intended 
 to t7'uss or suspend one piece by another, should be formed 
 upon similar principles. 
 
 Roofs in this country, after being boarded, receive a second- 
 ary covering of shingles. When intended to be incombustible, 
 they are covered with slates or earthen tiles, or with sheets of 
 lead, copper, or tinned iron. Slates are preferable to tiles, be- 
 ing lighter, and absorbing less moisture. Metallic sheets are 
 chiefly used for flat roofs, wooden domes, and curved and an- 
 gular surfaces, which require a flexible material to cover them, 
 or have not a sufficient pitch to shed the rain from slates or 
 
OF ARCHITECTURE AND BUILDING- 129 
 
 shingles. Yarious artificial compositions are occasionally used 
 to cover roofs, the most common of which are mixtures of tar 
 with lime, and sometimes with sand and gravel. 
 
 Styles of Building. — The architectuie of different countries^ 
 has been characterized by peculiarities in external form, and 
 in modes of construction. These peculiarities, among ancient 
 nations, were so distinct, that their structures may be identi- 
 fied even in the state of ruins ; and the origin and era of each 
 may be conjectured with tolerable accuracy. Before we pro- 
 ceed to describe architectural objects, it is necessary to explain 
 certain terms, which are used to denote their different constitu- 
 ent portions. The architectural 07'c?er5 will be spoken of un- 
 der the head of the Grecian and Roman styles, but their com- 
 ponent parts ought previously to be understood. 
 
 Definitions. — -The front or /ap«c?e of a building, made after 
 the ancient models, or any portion of it, may present three parts, 
 occupying different heights. 
 
 The -pedestal is the lower part, usually supporting a column. 
 The single pedestal is wanting in most antique structures, and 
 its place supplied by a stylohate. The stylobate is either a 
 platform with steps, or a continuous pedestal, supporting a row 
 of columns. The lower part of a finished pedestal is called the 
 plinth* the middle part is the die^ and the upper part the 
 cornice of the pedestal, or surhase. 
 
 The colutnti, is the middle part, situated upon the pedestal 
 or stylobate. It is commonly detached from the wall, but is 
 sometimes buried in it for half its diameter, and is then said 
 to be engaged. Pilasters are square or flat columns, attach- 
 ed to walls. The lower part of a column, when distinct, is 
 called the base ; the middle, or longest part, is the shaft, and 
 the upper, or ornamented part, is the capital. The height of 
 columns is measured in diameters of the column itself, taken 
 always at the base. 
 
 • The name plinth, in its general sense, is applied to any square projecting 
 basis, such as those at the bottom of walls, and under the base of columns. 
 
 17 
 
130 
 
 OF ARCHITECTURE AND BUILDING. 
 
 The entablature^ is the horizontal, continuous portion, 
 which rests upon the top cf a row of columns. The lower part 
 of the entablature is called the architrave^ or epistyllum. 
 The middle part is the frieze, which, from its usually con- 
 taining sculpture, was called zophorus by the ancients. The 
 upper, or projecting part, is the cornice. 
 
 Entablature ^ 
 
 Column < 
 
 Sttlobate or 
 Pedestal 
 
 Cornice. 
 
 Frieze. 
 Architrave. 
 
 Capital. 
 
 Plinth. 
 
 A pediment, is the triangular face, produced by the extrem- 
 ity of a roof. The middle, or flat portion, inclosed by the cor- 
 nice of the pediment, is called the tympanum. Pedestals for 
 statues, erected on the summit and extremities of a pediment, 
 are called acroteria [PI. V. Fig. 2.] An attic, is an upper 
 part of a building, terminated at top by a horizontal line, in- 
 stead of a pediment. 
 
OF ARCHITECTURE AND BUILDING. 131 
 
 The different mouldings in architecture are described from 
 their sections, or from the profile which they present,, when 
 cut across. Of these the ton/.s is a convex moulding, the sec- 
 tion of which is a semicircle or nearly so [PI. I. Fig. a.] The 
 astragal, is like the torus, but smaller [Fig. 6.] The ovolo is 
 convex, but its outline is only the quarter of a circle [Fig. c] 
 The echinus resembles the ovolo, but its outline is spiral, not 
 circular [Fig. c?.] The scotia is a deep, concave moulding 
 [Fig. e.] The cavetto is also concave, and occupying but a 
 quarter of a circle [Fig. /.] The cymatium is an undulated 
 moulding, of which the upper part is concave, and the lower 
 convex [Fig. g.'] The ogee or talon, is an inverted cymatium 
 [Fig. h.'\ TheJiUet is a small square or flat moulding [Fig. i.] * 
 
 Measures. — In architectural measurement, a diameter 
 means the width of a column at the base. A Tnjdide is half a 
 diameter. A minute is a sixtieth part of a diameter. 
 
 Drawings. — In representing edifices by drawings, archi- 
 tects make use of ihe.plan, elevation, section, and perspective. 
 The plan is a map, or design, of a horizontal surface, show- 
 ing the ichnographic projection, or ground work, with the re- 
 lative position of walls, columns, doors, (feet "^rhe elevation 
 is the orthographic projection of a front, or vertical surface ; 
 this being represented, not as it is actually seen in perspective, 
 but as it would appear if seen from an infinite distance. The 
 section shows the interior of a building, supposing the part in 
 front of an intersecting plane, to be removed. The perspec- 
 tive shows the building as it actually appears to the eye, sub- 
 ject to the laws of scenographic perspective. The three former 
 are used by architects; for purposes of admeasurement, the lat- 
 ter is used also by painters, and is capable of bringing more 
 than one side into the same view, as the eye actually perceives 
 them. 
 
 * By a singular mixture of derivations, the Greek, Latin, Italian, French, and 
 English languages are laid under contribution for the technical terms of Ar- 
 chitecture. 
 
 t See various plans of temples on pages 137, 138. 
 
132 OF ARCHITECTURE AND BUILDING. 
 
 Restorations. — As the most approved features in modern 
 architecture are derived from buildings whicli are more or less 
 ancient, and as many of these buildings are now in too dilapi- 
 dated a state to be easily copied, recourse is had to such imita- 
 tive restorations in drawings and models, as can be made out 
 from the fragments and ruins which remain. In consequence 
 of the known simplicity and regularity of most antique edifices, 
 the task of restoration is less difficult than might be supposed. 
 The ground work, which is commonly extant, shows the 
 length and breadth of the building, with the position of its walls, 
 doors, and columns. A single column, whether standing or fall- 
 ing, and a fragment of the entablature, furnish data from which 
 the remainder of the colonnade, and the height of the main 
 body, can be made out. A single stone from the cornice of 
 the pediment, is often sufficient to give the angle of inclination, 
 and consequently the height of the roof. In this way, beauti- 
 ful restorations are obtained of structures, when in so ruinous 
 a state, as scarcely to have left one stone upon another. 
 
 EGYPTIAN STYLE. 
 
 In ancient Egypt, a style of building prevailed, more mas- 
 sive and substantial than any which has succeeded it. The 
 elementary features of Egyptian architecture, were chiefly as 
 follows. 1. Their walls were of great thickness, and sloping 
 on the outside. This feature is supposed to have been derived 
 from the mud walls, mounds, and caverns of their ancestors. 
 2. The roofs and covered ways were flat, or without pedi- 
 ments, and composed of blocks of stone, reaching from one 
 wall or column to another. The principle of the arch, although 
 known to them, was seldom, if ever, employed by them. 3. 
 Their columns were numerous, close, short, and very large, 
 being sometimes 10 or 12 feet in diameter. They were gen- 
 erally without bases, and had a gi'eat variety of capitals, from a 
 simple square block, ornamented with hieroglyphics, or faces, 
 to an elaborate composition of palm leaves not unlike the Co- 
 
OP ARCHITECTURE AND BUILDING. 133 
 
 rinthian capital. 4. They used a sort of concave entablature, 
 or cornice, composed of vertical flutings, or leaves, and a wing- 
 ed globe in the centre. 5. Pyramids, well known for their 
 prodigious size, and obelisks composed of a single stone, often 
 exceeding 70 feet in height, are structures peculiarly Egyptian. 
 6. Statues of enormous size, sphinxes carved in stone, and 
 sculptures in outline of fabulous deities and animals, with innu- 
 merable hieroglyphics, are the decorative objects which belong 
 to this style of architecture. 
 
 For Egyptian specimens, see PI. I. Fig. 1. ; PI. YI. Fig. 
 1, and PI. VII. Fig. 1, 2, and 3. 
 
 The architecture of the ancient Hindoos, appears to have 
 been derived from the same original ideas as the Egyptian. 
 The most remarkable relics of this people, are their subterra- 
 neous temples, of vast size and elaborate workmanship, carved 
 out of the solid rock, at Elephanta, EUora, and Salsette. One 
 of their columns is shown in Plate VII. Fig. 4. 
 
 THE CHINESE STYLE. 
 
 The ancient Tartars, and wandering shepherds of Asia, ap- 
 pear to have lived from time immemorial in tents, a kind of 
 habitation adapted to their erratic life. The Chinese have 
 made the tent the elementary feature of their architecture, 
 and of their style any one may form an idea, by inspecting 
 the figures which are depicted upon common china ware. 
 Chinese roofs are concave on the upper side, as if made of can- 
 vass instead of wood. A Chinese portico, is not unlike the 
 awnings spread over our shop windows in summer time. The 
 verandah, sometimes copied in dwelling houses here, is a struc- 
 ture of this sort. The Chinese towers and pagodas, have con- 
 cave roofs, like awnings, projecting over their several stories. 
 The lightness of the style used by the Chinese, leads them to 
 build with wood, sometimes with brick, and seldom with stone 
 [PI. VI. Fig. 2, and VII. Fig. 18.] 
 
134 
 
 or ARCHITECTURK AND BUILIDINO. 
 
 THE GRECIAN STYLE. 
 
 Grecian arcbitectiire, from which have been derived the 
 most splendid structures of later ages, has its origin in the 
 wooden hut or cabin, formed of posts set in the earth, and 
 covered with transverse poles and rafters. Its beginnings were 
 very simple, being little more than imitations, in stone, of the 
 original posts and beams. By degrees these were modified 
 and decorated, so as to give rise to the distinction of what are 
 now called the orders of architecture. 
 
 Orders of Architecture. — By the architectural orders, are 
 understood certain modes of proportioning and decorating the 
 column and its entablature. They were in use during the 
 best days of Greece and Rome, for a period of six or seven 
 centuries. They were lost sight of in the dark ages, and again 
 revived by the Italians at the time of the restoration of letters. 
 The Greeks had three orders, called the Doric, Ionic, and Co- 
 i^inthian. These were adopted and modified by the Romans, 
 who also added two others, called the Tuscan and Composite. 
 
 Doric OrcZer.-— The Doric is the earliest and most massive 
 order of the Greeks. It is known by its large columns with 
 plain capitals; its triglyphs resembling the ends of beams, 
 and its niutides corresponding to those of rafters. The column, 
 in the examples at Athens, is about six diameters in height. 
 In the older examples, as those at Peestum, it is but four or five. 
 The shaft had no base, but stood directly on the stylobate. It 
 had 20 fluting.?, which were superficial, and separated by angu- 
 lar edges. The perpendicular outline was nearly straight. 
 The Doric capital was plain, being formed of a few annulets 
 or rings, a large echitius, and a flat stone at top called the 
 abacus. The architrave was plain ; the frieze was intersect- 
 ed by oblong projections called triglyphs, divided into three 
 parts by vertical furrows, and ornamented beneath, by guttcB 
 or drops. The spaces between the triglyphs were called me- 
 topes, and commonly contained sculptures. The sculptures 
 
OP ARCHITECTURE AND BUILDING. 135 
 
 representing Centaurs and Lapithee, carried by Lord Elgin to 
 London, were metopes of the Parthenon, or temple of Minerva, 
 at Athens. The cornice of the Doric order consisted of a few 
 large mouldings, having on their under side a series of square, 
 sloping projections, resembling the ends of rafters, and called 
 mntules. These were placed over both triglyphs and metopes, 
 and were ornamented, on their underside, with circular ^M^/te. 
 The best specimens of the Doric order, are found in the Par- 
 thenon, the Propylsea, and the Temple of Theseus, at Athens 
 [PI. VI. Fig. 7. PI. IV. Fig. 1, 2, 3, 4, 5, and 6.] 
 
 Ionic Order. — The Ionic is a lighter order than the Doric, 
 its column being eight or nine diameters in height. It had a 
 base often composed of a torus, a scotia, and a second torus, 
 with intervening fillets. This is called the Attic base [PI. 
 VII. Fig. 9.] Others were used in different parts of Greece. 
 The shaft had 24, or more, flutings, which were narrow, as 
 deep as a semicircle, and separated by a fillet or square edge. 
 The capital of this order consisted of two parallel double scrolls, 
 called volutes., occupying opposite sides, and supporting an ab- 
 acus, which was nearly square, but moulded at its edges. 
 These volutes have been considered as copied from ringlets of 
 hair, or perhaps from the horns of Jupiter Amnion. When 
 a column made the angle of an edifice, its volutes were placed, 
 not upon opposite, but on contiguous sides ; each fronting out- 
 ward. In this case the volutes interfered with each other at 
 the corner, and were obliged to assume a diagonal direction. 
 The Ionic entablature consisted of an architrave and frieze, 
 which were continuous or unbroken, and a cornice of various 
 successive mouldings, at the lower part of which was often a 
 row of dcniels or square teeth. The examples at Athens, of 
 the Ionic order, are the temple of Erectheus, and the temple 
 on the Ilissus, which was standing in Stuart's time 70 years 
 since, but is now extinct [PI. VII. Fig. 9. PL IV. Fig. 8, 9, 
 10, and U.] 
 
 Corinthian Order. — The Corinthian was the lightest and 
 most decorated of the Grecian orders. Its base resembled that 
 
136 OF ARCHITECTURE AND BUILDING. 
 
 of the Ionic, but was more complicated. The shaft was often 
 ten diameters in height, and was fluted like the Ionic. The 
 capital was shaped like an inverted bell, and covered on the 
 outside with two rows of leaves of the plant acanthus,* above 
 which were eight pairs of small volutes. Its abacus was 
 moulded and concave on its sides, and truncated at the corners, 
 with a flower on the centre of each side. The entablature of 
 the Corinthian order, resembled that of the Ionic, but was more 
 complicated and ornamented, and had, under the cornice, a 
 row of large oblong projections, bearing a leaf or scroll on their 
 under side, and called modillions. No vestiges of this order 
 are now found in the remains of Corinth, and the most legiti- 
 mate example at Athens, is in the choragic monument of 
 Lysicrates. The Corinthian order was much employed in the 
 subsequent structures of Rome, and its colonies [PI. VII. Fig. 
 10. PL V. Fig. 1, 2, 3, &c.] 
 
 Caryatides. — The Greeks sometimes departed so far from 
 the strict use of the orders, as to introduce statues, in the place 
 of columns, to support the entablature. Statues of slaves, he- 
 roes, and gods, appear to have been employed occasionally for 
 this purpose. The principal specimen of this kind of archi- 
 tecture, which remains, is in a portico, called Pandroseum, at- 
 tached to the temple of Erectheus, at Athens, in which statues 
 of Carian females, called Caryatides, are substituted for col- 
 umns [PI. IV. Fig. 9.] One of these statues has been carried 
 to London. 
 
 Grecian Temple. — The most remarkable pubhc edifices of 
 the Greeks, were their temples. These being intended as 
 places of resort for the priests, rather than for the convening of 
 assemblies within, were in general obscurely lighted. Their 
 form was commonly that of an oblong square, having a colon- 
 nade without, and a walled cell within. The cell, was usually 
 
 * The origin of the Corinthian capital has been ascribed to the sculptor Cal- 
 limachus, who is said to have copied it from a basket accidentally enveloped in 
 leaves of acanthus. A more probable supposition traces its origin to some of th« 
 Egyptian capitals, which it certainly resembles. 
 
OF ARCHITECTURE AND BUILDING. 
 
 137 
 
 without windows, receiving its light only from a door at the 
 end, and sometimes from an opening in the roof. The part 
 of the colonnade which formed the front portico, was called the 
 pronaos, and that which formed the back part, the 'posticus. 
 The colonnade was subject to great variety in the number and 
 disposition of its columns, from which Vitruvius has described 
 seven different species of temples. These were, 1. The tem- 
 ple with antce. In this the front was composed of pilasters, 
 called antse, on the sides, and two columns in the middle. 
 
 2. The Prostyle. This had a row of columns at one end 
 only. 
 
 3. The Amphiprostyle, having a row of columns at each 
 
 O 
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 4. The Peripteral temple. This was surrounded by a 
 single row of columns, having six in front, and in rear, and 
 eleven, counting the angular columns, on each side. 
 
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138 OF ARCHITECTURE AND BUILDING. 
 
 5. The Di'ptei'al, with a double row of cokwnns all round 
 the cell, the front consisting" of eight. 
 
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 6. The Pseudo-dipteral differs from the dipteral, in hav- 
 ing a single row of columns on the sides, at the same distance 
 from the cell, as if the temple had been dipteral. 
 
 ooooooooooooooo 
 
 o o 
 
 o o 
 
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 7. The Hypmthral temple had the centre of its roof open 
 to the sky. It was colonnaded without, like the dipteral, but 
 had ten columns in front. It had also an internal colonnade, 
 called peristyle, on both sides of the open space, and compos- 
 ed of two stories or colonnades, one above the other. 
 
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 Temples, especially small ones, were sometimes made of a 
 circular form. When these were wholly open, or without a 
 «ell, they were called Monopteral temples. When there was 
 
OP ARCHITECTURE AND BUILDING. 139 
 
 a circular cell within the colonnade, they were called Perip- 
 teral* 
 
 Grecian Theatre. — The theatre of the Greeks, which was 
 afterwards co|Died by the Romans, was built in the form of a 
 horse shoe, being semicircular on one side, and square on the 
 other. The semicircular part, which contained the audience, 
 was filled with concentric seats, ascending from the centre, to 
 the outside. In the middle, or bottom, was a semicircular floor 
 called the orchestra. The opposite, or square part, contained 
 the actors. Within this was erected, in front of the audience, 
 a wall ornamented with columns and sculpture, called the 
 scena. The stage, or floor, between this part and the orches- 
 tra, was called the proscenium. Upon this floor was often 
 erected a moveable wooden stage, called, by the Romans j pul- 
 pitum. The ancient theatre was open to the sky, but a tem- 
 porary awning was erected to shelter the audience from the 
 sun and rain. 
 
 Remarks. — Grecian architecture is considered to have been 
 in its greatest perfection in the age of Pericles and Phidias. 
 The sculpture of this period, is admitted to have been superior 
 to that of any other age ; and although architecture is a more 
 arbitrary art, than sculpture, yet it is natural to conclude, that 
 the state of things which gave birth to excellence in the one, 
 must have produced a corresponding power of conceiving sub- 
 limity and beauty in the other. Grecian architecture was, in 
 general, distinguished by simphcity of structure, fewness of 
 parts, absence of arches, lowness of pediments and roofs, and 
 by decorative curves, the outline of which was a spiral line, or 
 conic section, and not a circular arc, as afterwards adopted by 
 the Romans. 
 
 * The intercolumniation, or distance between the columns, according to Vi- 
 truvius, was differently arranged under the following names. In the pycnostyle, 
 the columns were a diameter and a half apart. In the sy style they were two di- 
 ameters apart. In the diastyle, three. In the arceostyle, more than three. In 
 the eustyle, two and a quarter. 
 
140 OF ARCHITECTURE AND BUILDING. 
 
 Plate IV. — This plate is intended to give a view, upon the 
 same scale as PL 1, of various examples of Grecian architec- 
 ture, the remains of which are extant at the present day. 
 The limits of the plate permit only the front elevation to be 
 given, which, in the oblong Grecian temples, was the end of 
 the building. 
 
 No. 1, represents the principal temple at Psestum, in Italy. 
 At this place are now standing, the walls and colonnades of 
 three temples, built in the ancient Doric style, and undoubted- 
 ly erected by a Grecian colony in that country. The charac- 
 ters of this early Doric, are short and heavy columns, much 
 diminished upwards, large capitals, and a massive entablature, 
 nearly half as high as the columns. The outline of the col- 
 umns in this building is straight, or without entasis. The 
 temple appears to have been hypeetiiral, though the number 
 of columns is less than in the rule prescribed b}^ Vitruvius. 
 
 No. 2, is the Temple of Concord, commonly so called, at 
 Agrigentum, now Girgenti, in Sicily. It is erected in the mas- 
 sive style of the older Doric, on a stylobate of four steps, and, 
 with the exception of the roof, is in a state of good preservation 
 at the present day. Other Doric ruins are found in the same 
 place, also at Segesta, Selinus, and other parts of Scicily. Views 
 of these structures are given in Wilkins' Magna Gi^cecia. 
 
 No. 3, is the Temple of Theseus, at Athens, situated in the 
 lower part of that city, some way from the Acropolis. It is the 
 most perfectly preserved of any of the Athenian edifices, its col- 
 umns and walls having suffered scarce any dilapidation. At 
 the top of its stone platform, or stylobate, it measures 104 feet 
 in length, by 45 in breadth, and has six columns on each front, 
 with thirteen on each side, counting those at the angles. The 
 temple of Theseus was erected by Cimon, the son of Miltiades, 
 about 450 years before Christ. The sculptures upon the frieze 
 of this building, are supposed by Stuart, and others, to refer to 
 the exploits of Theseus, but according to Mr Wilkins,* they 
 represent the labors of Hercules. 
 
 * Topography and buildings of Athens, 8vo. 1816. 
 
OP ARCHITECTURE AND BUILniNG. 141 
 
 No. 4, is the Propylaea, at Athens, a structure of much 
 beauty, which commanded the entrance to the AcropoUs, or 
 citadel. Besides a portico of six Doric columns on each front, 
 it had an Ionic colonnade within, and a separate quadrangular 
 building- attached to each side. Before the entrance, are two 
 large pedestals, supposed to have supported equestrian statues. 
 The Propylsea were ascended by steps at different stages, and 
 had also an inclined plane for carriages. This building was 
 erected in the time of Pericles, and is now in a ruinous state, 
 a great portion of what remains being hidden by the walls of 
 the Turks. No. 5, is a transverse section of the Propylsea, 
 made at right angles with the former view, and showing the 
 different ascents. 
 
 No. 6, is the fagade of the Parthenon, or temple of Miner- 
 va, situated on the summit of the Acropohs, at Athens. This 
 building is now considered the best model for the Doric order, 
 and no edifice, ancient or modern, commands such general ap- 
 plause at the present day. It was built by the architect Ictinus, 
 during the administration of Pericles, about 440 years before 
 Christ. Its decorative sculptures are supposed to have been 
 executed under the direction of Phidias. The Platform or 
 stylobate, consists of three steps, the uppermost of which is 
 227 feet in length, and 101 in breadth. The number of col- 
 umns is eight in the portico of each front, and seventeen on 
 each flank, besides which there is an inner row of six columns 
 at each end of the cell. The proportional height of the col- 
 umns is five diameters and 33 minutes, and they diminish 
 thirteen minutes in diameter, from bottom to top. The sculp- 
 tures on the frieze represent the combats of the Centaurs and 
 Lapithee. Those on the eastern pediment, represented the 
 fabulous birth of Minerva ; and those on the western, the con- 
 tests between that goddess and Neptune, for the right of pre- 
 siding over the city. When Athens was visited by Wheler, 
 in 1676, the Parthenon remained entire, with the exception of 
 its roof. But during the siege of the city by the Venetians, iu 
 1687, a shell which exploded in the midst of the cell, destroy- 
 
142 OF ARCHITECTURE AND BUILDING. 
 
 ed the whole central part of the wall, together with nineteen 
 of the columns. Most of the sculpture of both pediments has 
 also disappeared. 
 
 No. 7, is the choragic monument of Thrasyllus, situated 
 without the Acropolis, and constituting the front of a grotto. 
 It is not, strictly speaking, of any architectural order, but de- 
 parts from the Doric, in having a row of circular wreaths, in- 
 stead of triglyphs, and a continuous row of guttee at the bottom 
 of the frieze. 
 
 No. 8, is the small Ionic amphiprostyle temple on the 
 banks of the Ilissus, which was standing in Stuart's time, but 
 has now wholly disappeared. The delineations obtained from 
 this building by Stuart, have since furnished tlie most popular 
 models of the Ionic order. 
 
 No. 9, is the Erectheum, anionic building, much admired, 
 in the Acropolis, at Athens. It comprises two temples, one 
 dedicated to Minerva Polias, the other to the nymph Pandrosus. 
 The smaller portico of the Pandroseum, is remarkable for a 
 row of Caryatides, or female statues, which perform the office 
 of columns in supporting the entablature.* No. 10, is an 
 Ionic capital from the temple on the Ilissus. Those of the 
 temple of Minerva Polias were similar in the general form of 
 the volutes, but had also an ornamented neck above the 
 flutings. 
 
 No. 11, represents the facade of the Temple of Apollo Did- 
 ymeeus, near Miletus. It was among the most celebrated 
 Grecian structures. It was termed by Strabo, the greatest of. 
 all temples, and was ranked by Vitruvius, with that of Diana, 
 at Ephesus. Although few of its columns are now standing, 
 the ruins give evidence of its original size and magnificence. 
 It appears to have been a dipteral temple, surrounded with a 
 double row of columns, triple in front, and in all 112. Views 
 
 * One of these statues was carried off by Lord Elgin, and is placed with 
 other Athenian marbles in the British Museum. Stuail makes this building 
 to consist of three temples, viz. those of Erectheus, Minerva Polias, and Pan- 
 drosus. Mr Wilkins divides it into two. 
 
OP ARCHITECTURE AND BUILDING. 143 
 
 of this building are given in the Ionian Antiquities, and in the 
 Voyage Pittoresque of Choiseul Gouffier. 
 
 No. 12, is the choiagic monument of Lysicrates, at Athens, 
 sometimes improperly called the Lantern of Demosthenes, 
 This elegant little structure has a circular ornamented roof of 
 one stone, and six Coiinthian columns engaged in a ciixular 
 wall, the whole supported on a square basis. It is now half 
 inclosed in a modern convent. 
 
 No. 13, is the octagon tower, at Athens, commonly called 
 the Tower of the ivinds, from the emblematic sculptures on its 
 sides. Its sides are marked with lines for indicating the hour 
 of the day by the shadows of gnomons. 
 
 ROMAN STYLE. 
 
 Roman architecture had its origin in copies of the Greek 
 models. All the Grecian orders were introduced into Rome, 
 and variously modified. Their number was augmented by the 
 addition of two new orders, the Tuscan and the Composite. 
 
 Tuscan Order. — This order, derived from the ancient 
 Etruscans, is not unlike the Doric deprived of its triglyphs and 
 mutules. It had a simple base containing one torus. Its^' col- 
 umn was seven diameters in height, with an astragal below 
 the capital. Its entablature, somewhat like the Ionic, consisted 
 of plain, running surfaces. There is no vestige of this order 
 among ancient ruins, and the modern examples of it are taken 
 from the descriptions of Yitruvius [PL VII. Fig. 6]. 
 
 Roman Doric. — The Romans modified the Doric order by 
 increasing the height of its column to eight diameters. In- 
 stead of the echinus which formed the Grecian capital, they 
 employed the ovolo, with an astragal and neck below it. 
 They placed triglyphs over the centre of columns, not at the 
 corners, and used horizontal mutules, or introduced foreign or- 
 naments in their stead. The Theatre of Marcellus has exam- 
 ples of the Roman Doric [PI. VII. Fig. 8]. 
 
 Roman Ionic. — The Romans diminished the size of the vo- 
 
144 OF ARCHITECTURE AND BUILDING. 
 
 lutes ill the Ionic order. They also introduced a kind of Ionic 
 capital in which there were four pairs of diagonal volutes, in- 
 stead of two pairs of parallel ones. This they usually added 
 to parts of some other capital, but at the present day it is often 
 used alone, under the name of modern Ionic. 
 
 Composite Order. — This fifth order was made by the Ro- 
 mans out of the Corinthian, simply by combining its capital 
 with that of the diagonal, or modern Ionic [PL VII. Fig. 11.] 
 Its best example is found in the arch of Titus. The favorite 
 order, however, in Rome and its colonies, was the Corinthian, 
 and it is this order which prevails among the ruins, not only 
 of Rome, but of Nismes, Pola, Palmyra, and Balbec. 
 
 Rom,an Structures. — The temples of the Romans, some- 
 times resembled those of the Greeks, but often differed from 
 them. The Pantheon, which is the most perfectly preserved 
 temple of the Augustan age, is a circular building, lighted only 
 from an aperture in the dome, and having a Corinthian por- 
 tico in front. The am,phitheatre differed from the theatre, 
 in being a complete circular, or rather elliptical building, filled 
 on all sides with ascending seats for spectators, and leaving 
 only the central space, called the arena, for the combatants 
 and public shows. The Coliseum is a stupendous structure of 
 this kind. The aqueducts were stone canals, supported on 
 massive arcades, and conveying large streams of water, for the 
 supply of cities. The triumphal arches were commonly solid 
 oblong structures, ornamented with sculptures, and open with 
 lofty arches for passengers below [PI. VI. Fig. 8.] The Bcb- 
 silica of the Romans, was a Hall of Justice, used also as an 
 exchange, or place of meeting for merchants. It was lined on 
 the inside with colonnades of two stories, or with two tiers of 
 columns one over the other. The earliest christian churches 
 at Rome, were sometimes called basilicse, from their possessing 
 an internal colonnade. The monumental pillars, were tow- 
 ers in the shape of a column on a pedestal, bearing a statue on 
 the summit, which was approached by a spiral staircase within. 
 Sometimes, however, the column was solid. The Thermm^ 
 
OF ARCHITECTURE AND BUILDING. 145 
 
 or baths, were vast structures, in which multitudes of people 
 could bathe at once. They were supplied with warm and cold 
 water, fitted up with numerous rooms for purposes of exercise 
 and recreation. 
 
 Remarks. — In several particulars, the Roman copies differed 
 from the Greek models, on which they were founded. The 
 stylobate or substructure, among the Greeks, was usually a 
 plain succession of platforms, constituting an equal access of 
 steps, to all sides of the building. Among the Romans, it be- 
 came an elevated structure, like a continued pedestal, accessible 
 by steps only at one end. The spiral curve of the Greeks, 
 was exchanged for the geometrical circular arc, as exemplified 
 in the substitution of the ovolo for the echinus in the Doric 
 capital. The changes in the orders, have been already men- 
 tioned. After the period of Hadrian, Roman architecture is 
 considered to have been on the decline. Among the marks of a 
 deteriorated style introduced in the later periods, were columns 
 with pedestals, columns supporting arches, convex friezes, en- 
 tablatures squared so as to represent the continuation of the 
 columns, pedestals for statues projecting from the sides of col- 
 umns, niches covered with little pediments, &c. See Plates 
 VI. and VII. 
 
 Plate V. — In this plate is represented a series of buildings 
 in the Roman style, reduced to a scale, after Durand. They 
 are all of the Corinthian order. No. 1, is the Pantheon, al- 
 ready mentioned, of which the portico is of stone, while the 
 body, or circular part covered by the dome, is of brick. The 
 occurrence in this building, of two pediments, one above the 
 other, is considered a defect, and probably indicates that the 
 parts of the edifice were erected at different times. The en- 
 tablature consists only of a cornice. In most other respects, 
 the symmetry of this building is much admired. 
 
 No. 2, is the tsn pie of Antoninus and Faustina, at Rome. 
 The walls and columns are raised upon an elevated stylobate, 
 and are approached by steps in front only, differing in this re- 
 19 
 
146 OF ARCHITECTURE AND BUILDING. 
 
 spect from the Grecian temples, which were accessible on all 
 sides. 
 
 No. 3, is the Maison carree at Nismes, in France. It is 
 pseudo-peripteral, having its columns engaged in the wall, with 
 the exception of ten, which form the portico in front. It has 
 been lately discovered that this building, which remains in ex- 
 cellent preservation, was erected to the memory of Caius and 
 Lucius Csesar, sons of Agrippa, and grandsons of Augustus.* 
 
 No. 4, is the circular, peripteral temple of Vesta, at Rome. 
 The temple of Vesta, at Tivoli, outlined in Plate I, differs from 
 this, in having a raised stylobate. The dome, in both these 
 buildings, is an imaginary restoration, made after the rules of 
 Vitruvius. Messrs Taylor and Cresy have given to the tem- 
 ple at Tivoli, a conical roof, like that of the monument of Ly- 
 sicrates. 
 
 No. 5, is a temple at Pola, in Istria, dedicated to Rome and 
 Augustus. At this place are many interesting antiquities, 
 among which are an amphitheatre and triumphal arch. 
 
 No. 6, is the structure commonly called the Arch of Theseus, 
 at Athens. It was erected probably by the Roman emperor 
 Hadrian, to divide the new city from the old, and bears an in- 
 scription on each side, indicating that on one side is seen the 
 city of Theseus, and on the other the city of Hadrian. 
 
 No. 7, is a sepulchre at Mylassa, in Asia Minor, apparently 
 of Roman origin, and described in the Ionian antiquities. Its 
 angular pillars are square, but the intermediate columns have 
 a form very unusual in ancient or modern architecture, being 
 compressed, so that a section of the shaft represents an ellipse. 
 They are fluted for half their length. 
 
 No. 8, is the triumphal arch of Constantine, at Rome, which, 
 with the exception of a part of its sculptures, is entire at the 
 present day. This arch was built after the arts had begun to 
 
 * The origin and date of this beautiful temple were unknown, until an artist, 
 named Seguier, made out the inscription on the frieze, by connecting together 
 the holes in which the nails were driven, that formerly confined bronze letters 
 upon the wall. 
 
OP ARCHITECTURE AND BUILDING. 147 
 
 decline, and is constructed chiefly of materials taken from the 
 arch of Trajan, erected two centuries before. Its columns 
 stand upon separate, projecting pedestals, and have a part of 
 the entablature squared upon the top of each. 
 
 No. 9, is the external portico of the Temple of the Sun, at 
 Pahnyra. The ruins of this city exceed in extent and magnifi- 
 cence anything else which remains of antiquity in Europe, or 
 Asia, It is built in the Corinthian order, and in the later style 
 of Roman architecture, characterized by niches in the walls at 
 different heights containing statues, by numerous small pedi- 
 ments and entablatures, also in some cases by statues support- 
 ed on brackets, or pedestals projecting from the sides of columns. 
 In this portico, an example occurs of double columns, a fea- 
 ture rarely met with, in antique architecture, but sometimes 
 used by the moderns, upon an extensive scale.* 
 
 No. 10, is the circular temple at Balbec, a place distinguish- 
 ed by the magnificence and colossal size of its ruins. This 
 temple is singular in the form of its outline, which is circular, 
 with large concave recesses between all the columns, as shown 
 more distinctly in the ground plan. No. 11, of the same build- 
 ing. In other respects it partakes of the later Roman style. 
 
 No. 12, is the octagonal temple of Jupiter, forming part of 
 the palace erected by the Roman emperor Diocletian, at Salo- 
 na, now Spalatro, in Dalmatia, where its extensive ruins are 
 still extant. 
 
 GRECO-GOTHIC STYLE. 
 
 After the dismemberment of the Roman empire, the arts 
 degenerated so far, that a custom became prevalent of erecting 
 new buildings with the fragments of old ones, which were di- 
 lapidated and torn down for the purpose. This gave rise to an 
 irregular style of building, which continued to be imitated, es- 
 
 * To the regular duplicatuie of columns introduced in the colonnade of the 
 Louvre, in Paris, Perraulthas given the name of arceo-sy style. See note p. 139. 
 
148 OF ARCHITECTURE AND BUILDING. 
 
 p3cially in Italy, during the dark ages. It consisted of Grecian 
 and Roman details, combined under new forms, and piled up 
 into structures wholly unlike the antique originals. Hence the 
 names Greco-gothic and Romanesque architecture have been 
 given to it. It frequently contained arches upon columns, form- 
 ing successive arcades, which were accumulated above each 
 other to a great height. The effect was sometimes imposing. 
 The Cathedral and Leaning Tower, at Pisa, and the Church 
 of St Mark, at Venice, are cited as the best specimens of this 
 style [Pi. I. Fig. 15. and PI. VII. Fig. 13.] The Saxon 
 architecture, used anciently in England, has some things in 
 common with this style [PI. VII. Fig. 14.] 
 
 SARACENIC STYLE. 
 
 The edifices erected by the Moors and Saracens in Spain, 
 Egypt, and Turkey, are distinguished, among other things, 
 by a peculiar form of the arch. This is a curve, constituting 
 more than half of a circle, or ellipse. This construction of this 
 arch, is unphilosophical, and comparatively insecure. A simi- 
 lar peculiarity exists in the domes of the oriental Mosques, 
 which are sometimes large segments of a sphere, appearing as 
 if inflated ; and at other times concavo-convex in their outline, 
 as in the mosque of Achmet. The minaret is a taU, slender 
 tower, peculiar to Turkish architecture. A peculiar flowery 
 decoration, called arabesque, is common in the Moorish build- 
 ings of Europe, and Africa [PI. VI. Fig. 3.— PI. VII. Fig. 16. 
 PI. I. Fig. p and ^.] 
 
 GOTHIC STYLE. 
 
 The Goths, who plundered Rome, had nothing to do with 
 the invention of Gothic architecture. The name was intro- 
 duced by Sir Christopher Wren, and others, as a term of re- 
 proach, to stigmatize the edifices of the middle ages, which 
 departed from the purity of the antique models. The term 
 
OF ARCHITECTURE AND BUILDING. 149 
 
 was, at first, very extensive in its application, but it is now 
 confined chiefly, to what may be called the modern Gothic, — 
 the style of building' cathedrals, churches, abbeys, &c. which 
 was introduced in England six or eight centuries ago, and 
 adopted, nearly at the same time, in Prance, Germany, and 
 other parts of Europe. The Gothic style is pecuUar and 
 strongly marked. Its principle seems to have originated in the 
 imitation of groves, and bowers, under which the Druids per- 
 formed their sacred rites. Its characteristics, at sight, are, its 
 pointed arches, its pinnacles and spires, its large buttresses, clus- 
 tered pillars, vaulted roofs, profusion of ornaments, and the 
 general predominance of the perpendicular over the horizon- 
 tal. 
 
 Although the Gothic style of building was originated at a 
 period, when the arts were less successfully cultivated than 
 they were in the time of the Greeks ; it has nevertheless given 
 rise to some of the most lofty, the most highly decorated, and 
 the most imposing structures now in existence. 
 
 Definitions. — As the common place for the display of Go- 
 thic architecture, has been in ecclesiastical edifices, it is neces- 
 sary to understand the usual plan and construction of these 
 buildings. A church or cathedral is commonly built in the 
 form of a cross, having a tower, lantern, or spire, erected at the 
 place of intersection. The part of the cross, situated toward 
 the west, is called the nave. The opposite or eastern part is 
 called the choir, and within this is the chancel. The trans- 
 verse portion, forming the arms of the cross, is called the tran- 
 sept. 
 
 
 
 
 Nave. 
 
 a. 
 c 
 
 Choir. 
 
 
 
 
150 OF ARCHITECTURE AND BUILDING. 
 
 Any high building erected above the roof, is called a steeple ; 
 if square topped, it is a tower ; if long and acute, a spire, and 
 if short and light, a lantern. Towers of great height, in pro- 
 portion to their diameter, are called turrets. The walls of 
 Gothic churches, are supported on the outside, by lateral pro- 
 jections, extending from top to bottom, at the corners, and be- 
 tween the windows. These are called buttresses, and they 
 are rendered necessary to prevent the walls from spreading 
 under the enormous weight of the roofs [PL YI. Figs. 4, and 
 5.] On the tops of the buttresses, and elsewhere, are slender 
 pyramidal structures, or spires, called pinnacles. These are 
 ornamented on their sides, with rows of projections, appearing 
 like leaves or buds, which are named crockets. The summit, 
 or upper edge of a wall, if straight, is called a parapet ; if in- 
 dented, a battlement. Gothic windows were commonly crown- 
 ed with an acute arch. They were long and narrow, or if 
 wide, were divided into perpendicular lights by mullions. 
 The lateral spaces on the upper and outer side of the arch, are 
 called spandrells ; and the ornaments in the top, collectively 
 taken, are the tracery. An oriel, or bay vnndow, is a project- 
 ing window. A wheels or rose window, is large and circular. 
 A corbel, is a bracket or short projection from a wall, serving 
 to sustain a statue, or the springing of an arch. 
 
 Gothic pilkirs or columns, are usually clustered, appearing 
 as if a number were bound together. The single shafts thus 
 connected, are called boltels. They are confined chiefly to 
 the inside of buildings, and never support anything like an 
 entablature. Their use is to aid in sustaining the vaults under 
 the roof, which rest upon them at springing points [PI. YI. 
 Fig. 6.] Gothic vaults intersect each other, forming angles 
 called groins. The parts which are thrown out of the per- 
 pendicular, to assist in forming them, are the pendentives. 
 The ornamented edge of the groined vault, extending diagonal- 
 ly, like an arch, from one support to another, is called the 
 ogyve. The gothic term gable, indicates the erect end of a 
 roof, and answers to the Grecian pediment, but is more acute. 
 
OF ARCHITECTURE AND BUILDING. 151 
 
 The Gothic style of building is move unposing, and more 
 difficult to execute, than the Grecian. This is because the 
 weight of its vaults and roofs is upheld at a great height, by 
 supporters acting at single points, and apparently but barely 
 sufficient to effect their object. Great mechanical skill is ne- 
 cessary, in balancing and sustaining the pressures ; and archi- 
 tects at the present day, find it difficult to accomplish what 
 was achieved by the builders of the middle ages, 
 
 Plate VI. — No. 1, is the front of an ancient Egyptian 
 temple, at Essenay. It has the sloping walls, concave entabla- 
 ture, crowded columns, and hieroglyphic sculptures, peculiar 
 to the edifices of that country. The roof is flat, and support- 
 ed on twentyfour columns inside. — ^No. 2, represents an octa- 
 gonal pagoda, at Sinkicien, in China, It gives an example 
 of the curved Chinese roof, formed in imitation of the tent, — 
 No. 3, the Mosque of Achmet, at Constantinople, built in 1610, 
 It has a central dome, surrounded by four half domes, which 
 cover vast recesses resembling niches. Its court is surrounded 
 by a sort of cloister, covered by numerous small cupolas, and 
 having tall minarets at the angles and sides, — No. 4, is a per- 
 spective view of York Cathedral, one of the most admired 
 specimens of Gothic architecture. It is built in the form of a 
 cross, and has three towers, of which the two front ones are 
 surmounted by pinnacles, and the central one by battlements. 
 It was built between the years 1171 and 1426. — No. 5, is a 
 Gothic exterior, from the wall of Westminster Abbey, showing 
 the buttresses, which support the walls, also the short pinnacles 
 and battlements. The slanting braces at top are called flying 
 buttresses. — No. 6, is a Gothic interior, from the nave of 
 York Cathedral. It shows the clustered pillars, pointed arches, 
 groined vaulting, and tracery, which belong to the Gothic style. 
 
 Plate VII. — ^In this plate is presented a series of columns, 
 with some of their entablatures, arches, (fee, illustrative of the 
 styles of building which have prevailed in different epochs, and 
 
152 OF ARCHITECTURE AND BUILDING. 
 
 countries. The three first figures are those of Egyptian col- 
 umns, all serving to show the massiveness of structure which 
 prevailed in the buildings of that nation. A great variety of 
 these columns exist at the present day in Upper Egypt, par- 
 ticularly at Karnac and Luxor, the remains of ancient Thebes. 
 No. 1, is from a tomb of Silsilis, and has an outline which is 
 common among the Egyptian ruins. — No. 2, likewise a com- 
 mon form, has a capital composed of faces.^No. 3, is a column 
 from Komonbu. The idea of the Corinthian capital; seems to 
 have been borrowed from Egyptian specimens of this kind. 
 The column No. 4, is from the great cave at Elephanta, near 
 Bombay, one of the wonderful subterranean structures exca- 
 vated by the ancient inhabitants of Hindostan out of solid rock. 
 No. 5, is a column from the ruins of Persepolis. At this place, 
 which contains the most remarkable relics of the ancient arts 
 of Persia, the style of architecture partakes of the Egyptian 
 and Hindoo characteristics, the columns, however, being more 
 slender. — No. 6, represents the Tuscan order, used by the an- 
 cient inhabitants of Etruria. — No. 7, is the Grecian Doric, of 
 the age of Pericles, at which time it is considered to have been 
 in greatest perfection.^ — No. 8, is the Roman Doric, represent- 
 ed with a base, after the restorations of the moderns. — No. 9, 
 is the Grecian Ionic. The base represented in this figuie, and 
 the next, is called the Attic base. — No. 10, the Corinthian or- 
 der. — No. 11, the Composite order, in which the volutes are 
 larger than in the Corinthian. The modern Ionic is taken 
 from the upper part of this capital. The frieze is represented 
 as convex, a feature which is considered pecuhar to the later 
 or declining period of Roman architecture. — No. 12, is a com- 
 bination of the column with a pedestal, and a squared portion 
 of the entablature, usually attached to the main edifice, by one 
 side. This peculiarity was introduced after the arts had begun 
 to dechne, and appears in many of the later Roman edifices. 
 It has been absurdly imitated in more modern times, by mak- 
 ing a squared entablature to constitute a portion of the column, 
 and placing another entablature above it. — No. 13, shows a 
 
OP ARCHITECTURE AND BUILDING. 153 
 
 mode of building with arches between the columns and the 
 entablature. It is taken from the remains of Diocletian's pal- 
 ace at Spalatro, and seems to have given rise to the Greco-gothic 
 style. — No. 14, which also exhibits arches upon columns, is a 
 specimen of Saxon architecture from the Cathedral at Ely. 
 — No. 15, is a twisted column from a cloister belonging to St 
 Paul's church, without the walls, at Rome, rebuilt about the 
 year 800. Columns of this sort occur in various Italian struc- 
 tures, but it is difficult to conceive of a form more at variance 
 with architectural fitness or security. — No. 16, Moorish double 
 columns, arches, and arabesques, from the Alhambra, at Gre- 
 nada. In the same building, the true Saracenic or horse-shoe 
 arch, also occurs. — No. 17, a Gothic pillar from Salisbury Ca- 
 thedral. Other Gothic forms are seen in Plate VI. Fig. 6. — No. 
 18, a Chinese column from the viceroy's palace, at Canton. 
 — No. 19, section of a reeded Egyptian column. — No. 20, sec- 
 tion of a fluted Doric column. — No. 21, section of a fluted Ionic 
 column. — No's 22, 23, and 24, sections of different Gothic 
 columns. 
 
 Application. — In edifices erected at the present day, the 
 Grecian and Gothic outUnes are commonly employed, to the 
 exclusion of the rest. In choosing between them, the fancy of 
 the builder, more than any positive rule of fitness, must direct 
 the decision. Modern dwelling houses have necessarily a style 
 of their own, as far as stories and apartments, and windows and 
 chimnies, can give them one. No more of the styles of for- 
 mer ages can be applied to them, than what may be called the 
 unessential and decorative parts. In general, the Grecian style, 
 from its right angles and straight entablatures, is more conveni- 
 ent and fits better with the distribution of our common edifices, 
 than the pointed and irregular Gothic. The expense also is 
 generally less, especially if anything like thorough and genu- 
 ine Gothic is attempted ; a thing, however, rarely undertaken 
 as yet, in this country. But the occasional introduction of the 
 Gothic outline, and the partial employment of its ornaments, 
 has undoubtedly an agreeable effect, both in public and private 
 20 
 
154 OF ARCHITECTURE AND BUILDING. 
 
 edifxes ; and we are indebted to it, among other thing?, f )r the 
 spire, a structure exclusively Gothic, which, thcugh often mis- 
 placed, has become an object of gene:al approbation, and a 
 pleasing landmark to our cities and villages. 
 
 WiLKiNs' Translation of Vitruvius, 4to. 1817; — Elmes' Lectures 
 on Architecture, 8vo. 1823 ; — Stuart's Antiquities of Athens, 4 vols, 
 fol. 1763, &c. ; — Antiquities of Ionia, by the Dilettanti Society, 2 
 vols. fol. 1817-21 ; — Antiquities of Attica, by the same, fol. 1817 ; — 
 WiLKiNs' Magna Grsecia, fol. 1807 ; — Desgodetz's Buildings of Rome, 
 2 vols. fol. tra. 1771 ; — Taylor and Cresys' Antiquities of Rome, 2 
 vols. fol. 1821-2; — DuRAND, Recueil des Edifices, oblong fol. 1801 ; — 
 PuGiNs' Specimens of Gothic Architecture, 2 vols. 4to. 182.3; — Brit- 
 tons' Architectural Antiquities of Ore at Britain, 4 vols. 4to. 1815, &.c.,- 
 — Tredgold's Elements of Carpentry, 4to, 1821 ; — Nicholsons' Arch- 
 itectural Dictionary, 3 vols. 4to. 1821. 
 
CHAPTER VIU. 
 
 ARTS OF HEATING AND VENTILATION. 
 
 In cold and temperate climates, a \m-ge portion of human 
 labor is devoted to procure and sustain such a degree of heat, 
 as is necessary to a comfortable existence. The means of ef- 
 fecting this object, as far as the economy of fires and dwelling 
 houses is concerned, will be considered in the present chapter. 
 To procure heat, to distribute it, to retain it, and to obviate its 
 inconveniences by ventilation, are the principal objects that 
 present themselves in a survey of the subject, 
 
 PRODUCTION OF HEAT. 
 
 Fhiel. — Heat is artificially obtained for common purposes, by 
 the combustion of fuel. Fuel may be usefully considered with 
 regard to its compactness or weight, its quantity of combustible 
 matter, and its quantity of water. 
 
 Weig-ht of Fuel. — In regard to the first consideration, if 
 other things be equal, the more compact and heavy any fuel is, 
 the more difiiicult it is to kindle, but the more permanent will it 
 be found when once on fire. Coal, for example, is a compact 
 fuel, when compared with light dry wood. Coal cannot so 
 well be kindled by a small blaze, nor by a very small quantity 
 of other combustible matter on fire, because its density renders 
 it a rapid conductor, and it carries off the heat of the kindling 
 substance, so as to extinguish it, before it is itself raised to the 
 temperature necessary for its combustion. But if the heat of 
 other fuel be applied to it in sufficient quantity, and long 
 enough, to ignite it, it then produces a powerful fire, and a much 
 more durable one than lighter fuel. Light fuel, on the other 
 
156 ARTS OP HEATING AND VENTILATION. 
 
 hand, being a slow conductor of heat, kindles easily ; and, 
 from the admixture of atmospheric air in its pores and crevices, 
 burns out rapidly, pioducing a comparatively temporary though 
 often a strong heat. 
 
 Combustible matter of Fuel. — The quantity of combusti- 
 ble matter of fuel, if the weight and other circumstances be 
 equal, may be learnt from the ashes, or residuum, left after the 
 combustion. For example, good Newcastle coal contains a 
 greater portion of combustible matter than Nova Scotia coal, 
 and leaves behind a smaller amount of earthy and incombus- 
 tible substance. The heating power, and consequent value, 
 of different kinds of fuel, is affected by this circumstance, 
 though by no means dependent on it. The fitness of fuel for 
 various purposes, is furthermore affected by the facility, with 
 which it gives off a part of its combustible matter in the form 
 of vapor, or gas ; which, being burnt in that state, produces 
 fiawje* For example, the bituminous coals abound in vola- 
 tile matter, which, when ignited, supports a powerful blaze. 
 On the other hand, the Lehigh and Rhode Island coals are des- 
 titute of bitumen, and yield but little flame. It is from similar 
 causes, that dry pine wood pioduces a powerful blaze, while 
 its charcoal yields comparatively little. A blaze is of great 
 service, where heat is required to be applied to an extensive 
 surface, as in reverberating furnaces, ovens, glass houses, (fee. 
 But when an equable, condensed, or lasting fire is wanted, the 
 more solid fuels, which blaze less, are to be preferred. 
 
 Water in Fuel. — The quantity of watery fluid contained 
 in fuel, greatly affects the amount of heat it produces, much 
 more, indeed, than is commonly admitted in practice. It is a 
 well known law of chemistry, that the evaporation of liquids, 
 or their conversion into steam, consumes, and renders latent, a 
 great amount of caloric. When green wood, or wet coal, are 
 added to the fire, they abstract from it by degrees, a sufficient 
 part of its heat, to convert their own sap or moisture into steam, 
 
 * See Chapter IX. Art. Flame. 
 
ARTS OF HEATING AND VENTILATION. 157 
 
 before they are capable of being burnt. And as long as any 
 considerable part of this fluid remains unevaporated, the com- 
 bustion goes on slowly, the fire is dull, and the heat feeble. 
 Green wood commonly contains a third, or more, of its weight 
 of watery fluid, the quantity varying according to the greater 
 or less porosity of different trees. Nothing is further from true 
 economy than to burn green wood, or wet coal, on the suppo- 
 sition that because they are more durable, they will in the end 
 prove more cheap. It is true, their consumption is less rapid ; 
 but to produce a given amount of heat, a far greater amount of 
 fuel must be consumed. Wood that is dried under cover is bet- 
 ter than wood dried in the open air, being more free from de- 
 composition. 
 
 Not only the pioduction of steam, but hkewise the forma- 
 tion of different gases, which are evolved during combustion, 
 affect the usefulness of fuel, according to their quantity and 
 capacity for heat. It is difficult, however, to estimate with 
 accuracy the amount of their practical effect. 
 
 Charcoal. — Charcoal is prepared from wood, and coke in a 
 similar manner from pitcoal ; by raising those substances to a 
 high temperature, sufficient to deprive them of their moisture 
 and volatile matter. When intended for chemical uses, char- 
 coal is made by exposing wood to heat in iron cylinders, or 
 other close vessels. But for the common purposes of fuel, it 
 is made by a sort of smothered combustion, in which masses of 
 wood, when set on fire, are covered with earth, so as nearly 
 to exclude the atmospheric air. This exclusion of air prevents 
 the wood from being consumed, while the red heat, which is 
 kept up for some time, dissipates the moisture from its pores. 
 Charcoal is generated in a small way, every night, in fires 
 which are raked up ; the brands and half burnt coals, are kept 
 from consuming, by the partial exclusion of the air, while the 
 light ashes, being a slow conductor of caloric, prevent them 
 from cooling below a red heat. Charcoal, when newly made 
 fi'om the heavier kinds of wood, such as oak and walnut, is a 
 powerful, and for some purposes, an economical kind of fuel. 
 
158 ARTS OF HEATING AND VENTILATION. 
 
 Coke, a kind of fuel used for certain purposes in England, is 
 charred pitcoal. It produces a strong and steady heat, but 
 does not blaze. Large quantities of coke are formed in the 
 manufactories of coal gas. 
 
 COMMUNICATION OF HEAT. 
 
 Radiated and conducted Heat. — Caloric, or heat, is com- 
 municated to apartments, by fires kept in thein, in two ways. 
 A part of it is radiated, the rest is conducted. The first por- 
 tion passes through the air wit'i great velocity, in diverging 
 rays. The second, penetrates slowly through the densest bo- 
 dies, whether transparent, or opaque. In a fire place or open 
 stove, the heat which is felt by holding the hand before the 
 fire, is radiated caloric. That which is felt by placing the hand 
 on the iron or bricks, is conducted caloric. To enjoy the full 
 eflfect of radiated caloric, we must be in presence or sight of 
 the radiating object. To receive conducted heat, we must be 
 in contact with the substance which imparts it. Since, how- 
 ever, we cannot remain in contact with the fire itself, we de- 
 rive our conducted heat from the air, a fluid, which constantly 
 touches, and envelopes our persons ; and which, when heated 
 in itself, becomes a source of warmth to us. The object of the 
 various contrivances, known under the names of stoves and 
 fire places, is to enable us to use fire with safely, and to obtain 
 from it a due supply of radiated caloric, and heated air. 
 
 In common cases, radiant heat is more agreeable, than con- 
 ducted heat, when we wish to obtain a sudden warmth ; since 
 its degree may be increased at pleasure, by altering our proxi- 
 mity to the fire ; the effect of the radiation being inversely 
 proportionate to the square of the distance. But as only one 
 half of the recipient bod}^ can be warmed at a time by radia- 
 tion, no person surrounded by a cold atmosphere, can be 
 made uniformly warm, by the radiated heat of a fire. It is 
 only when the surrounding atmospheric air has become warm, 
 that we obtain all the advantage which fire is capable of af- 
 fording. 
 
ARTS OF HEATING AND VENTILATION. 159 
 
 Fire in the open Air. — The simplest, and least effectual 
 mode, by wliicli heat can be obtained, is from a five in the open 
 ail-. The hunter, or backwoodsman, when he encamps for 
 the night, builds a fire of logs, and lays down to sleep, with 
 his feet extended towards it. In this situation he can enjoy 
 only a small portion of the radiated heat of the fire, this heat 
 being thrown off equally in all other directions. Of the con- 
 ducted heat he obtains none ; for the air which surrounds the 
 fire having nothing to confine it, ascends by its diminished 
 specific gravity, as fast as it is warmed, and its place is imme- 
 diately supplied by strata of colder air from beneath. Hence 
 a current of cold air will take place from the atmosphere on all 
 sides, towards the fire, so that the person who derives warmth 
 from the fire on one side, will on the other be exposed to addi- 
 tional cold. The first step towards remedying this inconve- 
 nience, is to build up a barrier, or imperfect wall, on the out- 
 side of the place occupied by the tenant. This will intercept 
 the current of cold air, and oblige it to approach the fire by 
 other directions, at the same time that it will gradually become 
 heated itself, and radiate back a portion of its warmth. The 
 next improvement consists in extending the wall, so as com- 
 pletely to surround the fire, thus obliging the air to approach 
 it from above, or from doors and avenues purposely left for its 
 entrance. This is, in fact, the commencement of a dwelling 
 house. A roof with an aperture for the escape of the smoke, 
 is a further improvement on the plan, and lastly the introduc- 
 tion of a chimney, at once renders the mansion convenient and 
 tenant able.* 
 
 Fire places. — Chimnies from their usual situation in regard 
 to rooms, and also for the sake of a more perfect draught, have 
 an opening on one side of their base, to which we give the name 
 of fire place. The fire place in former times was an oblong 
 or cubical cavity, having its sides nearly at right angles with 
 the back. In a cavity of this description, the greater part of 
 
 ♦ See Sylvester's account of the Derbyshire Infirmary. 
 
160 ARTS OF HEATING AND VENTILATION. 
 
 the heat generated by the fire, was totally lost to the apart- 
 ment, nearly all the conducted heat being carried, with the 
 air, up the chimney ; while of the radiated heat, but a small 
 part could directly enter the room, viz. the part radiated from 
 the front of the fire ; the heat of the other sides being chiefly 
 thrown into the hearth, back, and sides, or up the chimney. 
 In the old fire places, the inconvenience was still further aug- 
 mented by increasing their dimensions to an enormous size, so 
 that seats or benches could be placed on each side, on the in- 
 side of the jambs. The consequence was, that a prodigious 
 current of air was constantly carried up the chimney, and the 
 seats, on the inside of the fire place, became the only comfort- 
 able ones in the room. 
 
 Admission of cold Air. — It is obvious, that in apartments 
 with open fire places, the air must be continually shifting, and 
 that cold air must enter at the crevices of the doors and win- 
 dows, to supply the place of that which maintains the combus- 
 tion, or escapes up the chimney. In moderate weather this 
 change of air is an advantage, since it freshens and ventilates 
 the room, the air of which would otherwise become close and 
 impure. In moderate weather also, the radiant heat is ade- 
 quate to warm the walls of the room, which in their turn be- 
 come sources of radiant heat, and likewise contribute to warm 
 the air by their contact. But in very cold weather, it is 
 nearly or quite impossible to render a large apartment warm 
 by means of a common open fire place ; for, in proportion to 
 the briskness of the fire itself, will be the rapidity with 
 which the cold air presses into the room, and a person near 
 the hearth feels perhaps as much cold on one side of his body, 
 as heat on the other. 
 
 Open Fires. — The cheerful sight of an open fire, to which 
 habit and association have attached us, has created a strong 
 and almost general preference to the open fire place over the 
 close stove, and a desire, by remedying its defects, to make it 
 more effectual and useful. Of various philosophers who have 
 exercised their ingenuity on this subject, the two who appear 
 
ARTS OF HEATING AND VENTILATION. 161 
 
 to have labored with most success, are oui' countrymen, Dr 
 Franklin, and Count Rumford. 
 
 Franklin Stove. — Dr Franklin, whose writings on the econ- 
 omy of fire contain the basis of many of the improvements 
 which have since been introduced, invented an apparatus of 
 cast-iron, to which he gave the name of the Pennsylvania 
 Fire Place, but which is now often known by the name of 
 Franklin Stove. This fire place, when executed agreeably 
 to the author's instructions, is one of the most effective and 
 economical modes in which an open fire can be managed. By 
 means of a narrow and circuitous smoke flue, which is sur- 
 rounded and intersected with air passages, a great part of the 
 heat of the fire is retained in the room, and at the same time 
 a current of fresh air, warmed by the fire place, is introduced 
 into the apartment. In Plate YIII. Fig. 1. is seen a section 
 of the Pennsylvania fire place. A, is the place of the fuel and 
 fire ; B C D, the smoke flue, passing first upward, then down- 
 ward to the floor, and escaping by the chimney D, next the 
 wall, K. E H, is the air chamber into which the air is admit- 
 ted from without the house through the passage I. After be- 
 ing heated, it is discharged into the apartment by lateral open- 
 ings at the top G.* 
 
 Fire places which stand out into the room, also fire places 
 with hollow backs or pipes for hot air, are to be viewed, in most 
 instances, as simplifications only, of Franklin's plan. 
 
 Rwinford Fire Place. — Count Rumford's fire place forms a 
 pleasant and effectual mode of economizing the heat of an 
 open fire, besides which, its cheapness and simplicity give it 
 the advantage over more comphcated plans, and have occasion- 
 
 * Most of the articles now sold as Franklin stoves, are very different from 
 the original Pennsylvania fire place. If any defect existed in the plan of the 
 inventor, it wras in the small quantity of air admitted through a circuitous and 
 obstructed channel, and in the bad character of the material, cast-iron being lia- 
 ble to warp and crack, if exposed to great heat and cold on opposite sides. 
 
 The first person who suggested the introduction of heated air, through hollow 
 passages, appears to have been M. Gauger, in a work entitled La Mechanique 
 de Feu, published in 1709. 
 
 21 
 
162 ARTS OF HEATING AND VENTILATION. 
 
 ed its very general introduction. The peculiarities of this fire 
 place consist, 1st, ia an advanced back, which brings the fire 
 nearer into the room, and at the same time by narrowing the 
 throat of the chimney diminishes the current of air which es- 
 capes through it ; 2dly, in the oblique sides or covings of the 
 fire place, which are enabled, when heated, to radiate their 
 warmth into the room. Count Rumford recommends that the 
 angle, made by the sides with the back, should be one of 135 
 degrees. He also advises that the color of the covings should 
 be white, this color being best adapted for radiation. 
 
 Double Fire Place. — For parlors, and common apart- 
 ments, no contrivance appears so pleasant and effectual, as the 
 double fire place, which has of late years been extensively in- 
 troduced in this city and vichiity. It is a modification of 
 Franklin's plan, and is made from any common fire place, by 
 inserting within it another fire place made of soapstone, leaving 
 an empty space, of about an inch in depth, between the two, 
 so that when finished, the back and sides may be hollow. 
 This hollow space does not communicate with the fire, but 
 has two openings, one at bottom, communicating with the ex- 
 ternal atmosphere by a perforation in the wall, or by a tin pipe 
 laid in the floor ; the other, opening into the apartment, at a 
 point higher than the fire place, and commonly at the side of 
 the chimney. In this fire place, an open fire, of wood or coal, 
 may be used with the full advantage, ever obtained, of its ra- 
 diant heat. A large part of the conducted heat is also saved, 
 since the air which enters from without, becomes heated in the 
 hollow space, and ascends by it, in consequence of its dimin- 
 ished specific gravity, entering the room in a strong warm 
 current. This air serves the purpose of ventilation ; it super- 
 sedes the entrance of cold air through the crevices and key- 
 holes, and is also a preventive against smoking. The circum- 
 stances to be attended to in the construction, are as follows, 
 1. The openings for the air should be large, in common cases 
 from four to seven inches in diameter, since it is better to in- 
 troduce a large quantity of air moderately warmed, than a 
 
ARTS OF HEATING AND VENTILATION. 163 
 
 small quantity made very hot. More heat will in this case be 
 conducted from the stone, and the unpleasant effects of burnt 
 air will be avoided. 2. The openings into the room should 
 be made, when practicable, at least a foot higher than the top 
 of ths f-re place, for when they are on a level with it, or lower, 
 the warm air is liable to be drawn up the chimney, and the 
 main object defeated. But if the opening is above the fire 
 place, then the warm air will ascend and be diffused through 
 the upper parts of the room, till the whole is gradually warmed. 
 3. The cold air should be taken from without the house, and 
 not from an entrjr or cellar, because changing the air of those 
 places in winter, is apt to reduce them to a freezing tempera- 
 ture. The external opening should be guarded with a wire 
 net, to exclude leaves and light substances ; and the internal, 
 should be commanded by a shutter, to regulate the heat. For 
 safety, it is best, though not always necessary, that the hot air 
 passage should not be in contact with the wood work of the 
 house, 4. Good soapstone is the best material for these fire 
 places, and with careful use will last many years. See Soap- 
 stone. For wood fires, the stone should be an inch and a half 
 thick, and for coal fires, two or three inches. 
 
 In Plate VIII. Fig. 2, is a section of a double fire place. A, 
 is the place of the fire ; H, the soapstone back ; B, the throat ; C, 
 the chimney ; E, the external opening ; D G G, the hollow, or 
 passage for heated air ; M, a pipe for conveying the hot air to 
 N, a lateral opening into the room ; P, the mantel piece. A 
 soapstone fire place may be rendered very effectual, by causing 
 it to project a little into the room, and by adding an air box to 
 the top, as seen in PL YIII. Figs. 3 and 4. In the section, 
 Fig. 3, A, is the fire ; B B, the smoke passage ; C c c, the air 
 passage ; D, a box for heated air covering the fire place, and 
 communicating with the hollow back c c, by a side passage at 
 the dotted lines ; E, a side opening for discharging the hot air 
 into the room ; G, the mantle piece. In fire places of cheap 
 construction, a simple hollow back, made by one slab of soap- 
 stone, with openings as have been described, will contribute 
 much to increase the warmth of the room. 
 
164 ARTS OP HEATING AND VENTILATION. 
 
 Coal Grate. — When coals are used for fuel, it is necessary, 
 on account of their small size, to confine them together with a 
 grate. As they contain more combustible matter, in the same 
 space, than wood, and produce a greater degree of heat, a 
 much smaller fire place answers for them. A very small throat 
 also in the chimney, is sufficient to carry off the smoke from a 
 common coal grate. With this exception, it has the same 
 characteristics as a common fire place. 
 
 Anthracite Grate. — Grates for burning anthracite, require 
 more perpendicular height than others, and should be of such 
 a proportionate depth as will keep the coal together, and not 
 offer too great a surface to the atmosphere. In extremely cold 
 weather, it is observed that the front surface of anthracite grows 
 black and burns feebly in an open grate, while it does not in a 
 furnace or stove. In this case, the cold air conducts ofi" the 
 heat of the surface faster than the combustion renews it ; and 
 if the amount of surface be too great in proportion for that of 
 the solid contents, the fire will go out. Anthracite grates are 
 usually provided with a very narrow throat, to carry off the 
 gases which result from the combustion ; there being no visible 
 smoke. The throat, however, should always be large enough 
 to transmit the smoke of any other fuel ; for otherwise, a part 
 of the carbonic acid which is formed, will escape into the room, 
 and contaminate the atmosphere, in the same way as burning 
 charcoal. See Chap. I. art. Anthracite. 
 
 Burn&^ Grate. — Mr Burns, of Glasgow, has made an al- 
 teration in the coal grate, by intioducing the external air through 
 an opening immediately under the grate. This air supplies 
 the fuel with oxygen, and furnishes most of the current which 
 passes up the chimney. The air of the room of course re- 
 mains comparatively stationary, and is sooner heated. This 
 plan, when combined with the double fire place, already men- 
 tioned, [PI. VIII. Figs. 3 and 4J is a pov/erful mode of obtain- 
 ing heat. A moveable stone screen should be placed in front 
 of the ash pit, to prevent the ashes from being blown into the 
 room. The external opening whicli admits the air, should 
 
ARTS OF HEATING AND VENTILATION. 165 
 
 not be near any wood work, as sometimes the current is re- 
 versed by winds, and sparks and smoke are driven out at the 
 opening. 
 
 Building a Fire. — In building and maintaining an open 
 fire, whether of wood oi" coal, certain circumstances deserve at- 
 tention, in the common fire places. It is advantageous to make 
 the perpendicular height of the fuel as great as is consistent 
 with safety. A stratum of coals, or ^nited wood, will radiate 
 more heat into the lower part of the room, if placed vertically, 
 than if laid horizontally. Fuel, for economy, should be so sub- 
 divided, as to be easy of ignition, and so placed as to give free 
 access for the air to its different surfaces. In this way the 
 smoke is more likely to be burnt. To secure the greatest ef- 
 fect of radiation, the combustion should be kept, as much as 
 possible, to the front surface. In kindling a fire, the live coals 
 should be kept together, and placed near the bottom. A blow- 
 er, added to a common grate, converts it, for the time being, 
 into a wind furnace. 
 
 Furnaces. — The object of the furnaces used by artists and 
 manufacturers, is the reverse of that intended to be produced 
 by stoves and fire places ; furnaces being required to produce 
 an intense heat, and to confine it to a limited space. Hence 
 furnaces and their chimneys are surrounded with nonconduct- 
 ors, that they may expend as little of their heat as possible, on 
 the air and surrounding objects. They are commonly made 
 of fire-proof bricks, and when small, are inclosed in iron. 
 Their most simple form is that of an upright, hollow cylinder, 
 with a grate at bottom. Air or wind furnaces have their 
 combustion supported by a draught of air, which ascends ra- 
 pidly because it is strongly heated and rarified. Blast furna- 
 ces have the air driven through their fuel with bellows. Re- 
 verberating furnaces are provided with a concave covering, 
 which reverberates, or throws back the flame, upon the sub- 
 stances to be heated or melted. There are some cases in 
 Avhich furnaces are used for warming dwelling houses, partic- 
 ularly when fuel is used which requires strong ignition, such 
 as the Anthracites. 
 
166 ARTS OF HEATING AND VENTILATION. 
 
 Stoves. — Stoves differ from fire places by inclosing the fire 
 so as to exclude it from sight, the heat being given out through 
 the material of which the stove is composed. The common 
 Holland stove, of which we have an almost infinite variety of 
 modifications, is an iron box of an oblong square form, intend- 
 ed to stand in the middle of a room. The air is admitted to 
 the fire through a small opening in the door, and the smoke 
 passes off through a narrow funnel. The advantages of this 
 stove are — 1. That being insulated and detached from the 
 walls of the room, a greater part of the heat produced by the 
 combustion is saved. The radiated heat being thrown into 
 the walls of the stove, they become hot, and in their turn ra- 
 diate heat on all sides to the room. The conducted heat is also 
 received by successive portions of the air of the room which 
 pass in contact with the stove. 2. The air being made, as 
 in furnaces, to pass through the fuel, a very s ma 1 supply is 
 sufficient to keep up the combustion, so that little need be ta- 
 ken out of the room. 3. The smoke being confined by the 
 cavity of the stove, cannot easily escape into the room, and 
 may be made to pass off by a small funnel, which, if sufficient- 
 ly thin and circuitous, may cause the smoke to part with a 
 great portion of its heat, before it leaves the apartment. These 
 circumstances render the Holland stove one of the most powerful 
 means we can employ for keeping up a regular and effectual 
 heat, wi,th a small expense of fuel. 
 
 The disadvantages of these stoves are, that houses contain- 
 ing them are never well ventilated, but that the same air re- 
 mains stagnant in a room for a great length of time. Hence 
 it necessarily becomes impure by the breath of persons who 
 remain in it, and by the burning of dust and other substances 
 which settle on the heated iron of the stove. A dryness of the 
 air is also produced, which is oppressive to most persons, so 
 that it often becomes necessary to place an open vessel of wa- 
 ter on the stove, the evaporation of which, may supply mois- 
 ture to the atmosphere. Where rooms are kept very warm by 
 stoves, it is found advantageous even to cause the v/ater to boil, 
 
ARTS OF HEATING AND VENTILATION. 167 
 
 in order to insure a sufficient supply of vapor. Stoves are 
 very useful in large rooms, which are frequented occasionally, 
 but not inhabited constantly ; as halls, churches, &c. But for 
 common rooms, which are occupied at all times, they are ob- 
 jectionable, for the reasons which have been stated. 
 
 Russiaji Stove. — In cold countries, where it is desirable to 
 obtain a comfortable warmth, even at the sacrifice of other con- 
 veniences, various modifications of the common stoves have 
 been introduced, to render them more powerful, and their heat 
 more effectual. The Swedish and Russian stoves are small fur- 
 naces, with a very circuitous smoke flue. In principle, they 
 resemble a common stove, with a funnel bent round and round, 
 until it has performed a great number of turns or revolutions 
 before it enters the chimney. It differs, however, in being 
 wholly enclosed in a large box of stone or brick work, which 
 is intersected wuth air pipes. In operation, it communicates 
 heat more slov;ly, being longer in becoming hot, and also slow- 
 er in becoming cold, than the common stove. Russian stoves 
 are usually provided with a damper, or valve, at top, which is 
 used to close the funnel or passage, when the smoke has ceas- 
 ed to ascend. Its operation, however, is highly pernicious, 
 since burning coals when they have ceased to smoke, always 
 give out carbonic acid in large quantities, which, if it does not 
 escape up chimney, must deteriorate the air of the apartment, 
 and render it unsafe. 
 
 Cockle. — The name of cockle is given to an upper part of 
 a stove or furnace, resembling an inverted vessel. A large 
 cockle saves much heat, since its extensive surface conveys the 
 heat from the flame and smoke, and coinmunicates it to the at- 
 mosphere. In some stoves, the cockle is filled with a chequer 
 work of bricks, among which the smoke and flame circulate. 
 After becoming once heated, these bricks are slow in cooling, 
 and continue to yield warmth to the apartment, like the Rus^ 
 sian stoves, for some time after the fire is extinguished. 
 
 Cellar Stoves and Air Flues. — Such is the tendency of 
 heated or rarified air to ascend, that buildings may be effectu- 
 
168 ARTS OP HEATING AND VENTILATION. 
 
 ally warmed by air flues communicating with stoves in the 
 cellar, or any part of the building below that to be warmed. 
 A large suite of apartments may be sufficiently heated in this 
 way by a single stove. The stove for this purpose should be 
 large and of a kind best adapted to communicate heat. It 
 should be entirely enclosed in a detached brick chamber, the 
 wall of which should be double, that it may be a better non- 
 conducter of heat. The space between the brick chamber and 
 stove should not exceed an inch. In the apparatus of the 
 Derbyshire and Wakefield Infirmaries, which has been imita- 
 ted in this country, the whole of the air is repeatedly conduct- 
 ed by numerous pipes within half an inch of the stove and its 
 cockle. For the supply of fuel, the same door which opens 
 into the chamber, should open also into the stove, that there 
 may never be any communication with the air of the cellar. 
 A current of external air should be brought down by a sepa- 
 rate passage, and delivered under the stove. A part of this 
 air is admitted to supply the combustion ; the rest passes up- 
 ward in the cavity between the hot stove and the wall of the brick 
 chamber, and afteV becoming thoroughly heated, is conducted 
 through passages in which its levity causes it to ascend, and 
 be delivered into any apartment of the house. Different branch- 
 es being established from the main pipe, and commanded 
 by valves or shutters, the hot air can be distributed at pleasure, 
 to any one or more rooms at a time. This plan is very useful 
 in large buildings, such as manufactories, hospitals, &c. on 
 account of the facility with which the same stove may be made 
 to warm the whole, or any part of them. The advantage of 
 a long vertical draught enables us to establish a more forcible 
 current of warm air. See page 175. The rooms, while they 
 are heated, are also ventilated ; for the air which is continually 
 brought in by the warm pipes, displaces that which was pre- 
 viously in the room, and the air blows out at the crevices and 
 key-holes, instead of blowing in, as it does in rooms with com- 
 mon fire places. 
 
ARTS OF HEATING AND VENTILATION. 169 
 
 Heating hy Steatn. — Steam is found to be a useful medium 
 for communicating heat to large buildings. It has the advan- 
 tage that it conveys heat in any direction, horizontally, upward, 
 or downward, and to the most remote apartments of the larg- 
 est buildings. In green-houses it has been made to yield a 
 sufficient supply of heat, at the distance of 800 feet from the 
 boiler in which it is produced.* When steam of low pressure is 
 employed, the heat never exceeds 212 degrees of Fahrenheit, 
 so that the air in contact with the apparatus, is never contami- 
 nated by the burning of dust. 
 
 In constructions for heating by steam, a strong boiler is 
 made use of, provided with a safet}^ valve, and the other ap- 
 pendages common to the boilers of steam engines. From this 
 boiler a steam pipe is cariied in any required direction, and dis- 
 tributes branches to the different apartments which are to be 
 warmed. Whenever the water in the boiler is heated to the 
 point of ebullition, steam yjasses into the pipes, and drives out 
 the atmospheric air through valves provided for the purpose. 
 As long as the surface of the pipes remains of a less heat than 
 212 degrees, a part of the steam continually condenses, and is 
 immediately succeeded by fresh steam from the boiler. In the 
 act of condensing, it gives out its latent heat to the material of 
 which the pipe is made, and this material, in turn, imparts it 
 to the air of the room. In this manner the steam will continue 
 to be condensed, and to give out heat, as long as the air of the 
 room is at any point below 212 degrees. By the condensa- 
 tion, a quantity of water is constantly formed, which, for econ- 
 omy of heat, is returned by a separate pipe, while it is yet 
 warm, to the boiler. Inverted syphons containing water, are 
 used to prevent the air and steam from communicating. If the 
 steam pipes are made of thin or weak materials, it is necessary 
 to provide them with safety valves opening inward ; otherwise 
 they would ba crushed by the pressure of the atmosphere, when 
 the fire is extinguished. 
 
 • At Messrs Loddiges, at Hackney. Tredgold, on Warming, &c. p. 19. 
 22 
 
170 ARTS OF HEATING AND VENTILATION. 
 
 In calculating the effect of this method, it has been ascer- 
 tained that under favorable circumstances, one cubic foot of 
 boiler will heat about 2000 cubic feet of space in a cotton mill, 
 where the required temperature is from 70 to 80 degrees of 
 Fahrenheit.* And if we allow 25 cubic feet of a boiler for 
 one horse's power, in a steam engine supphed by it, it will fol- 
 low, that such a boiler is adequate to warm .50,000 cubic feet 
 of space for every horse's power. It is said also that every 
 square foot of surface in a steam pipe, will warm 200 cubic 
 feet of space. These calculations, however, do not apply to 
 buildings unfavorably arranged, nor to very cold weather. The 
 pipes, employed to distribute the steam, should be made of 
 materials which cool most rapidly. Iron, of which the surface 
 is tarnished with rust, is found to exceed tinned iron, in the 
 rapidity of cooling, in the proportion of about 18 to lO.t 
 Room must be allowed for the expansion of the pipes, which 
 in cast-iron may be taken at a tenth of an inch for every ten 
 feet in length. In cotton and calico manufactories, steam is 
 found very advantageous in drying cloths quickly and well. 
 
 In comparing the effect of steam heat, with that of smoke 
 flues, different representations have been made by writers on 
 the subject. Mr Tredgold observes that ' he must be a novice 
 in the science of heat, who cannot produce nearly the same 
 effect by the one as by the other, all other circumstances being 
 the same.' The steam apparatus, however, requires more 
 careful management, and does not admit of neglect. Although 
 easily kept in order by a skilful attendant, yet it cannot, in 
 common cases, be entrusted to ordinary or careless persons. 
 
 RETENTION OP HEAT. 
 
 Causes of Loss. — However advantageously heat may be 
 produced and distributed, it will fail in producing its desired 
 effect, unless suitable provision is made for retaining it, where 
 
 ♦ Buchanan on Heat and Fuel, p. 160. + Tredgold, p. 58. 
 
ARTS OF HEATING AND VENTILATION. 171 
 
 it is wanted. Heat constantly tends to an equilibrium, and, 
 unless this tendency be retarded, dwelling houses and their 
 apartments will cool, as fast as they are warmed. The chief 
 causes which operate to cool apartments, are — 1. The escape 
 of the warm air upward, through crevices, apertures, and 
 chiranies. 2. The power of conducting and of radiating heat, 
 which all substances possess in a greater or less degree, and 
 by which the internal heat of houses is gradually conveyed to 
 the external atmosphere. To obviate the first of these causes, 
 apartments should be made as tight as possible ; and to pre- 
 vent the second, at least in part, their walls should be made 
 thick, and of materials which are slow conductors of heat 
 
 Crevices. — As crevices in rooms commonly occur from the 
 shrinking of their materials, care should be taken to employ, in 
 building, wood which is thoroughly seasoned, and which is 
 known to be permanent in its dimensions. Of the kinds of 
 wood employed for doors and windows, mahogan)- is the most 
 permanent, and next to this is pine. Oak, and some other 
 hard woods, are very liable to shrink and crack. 
 
 Chimnies. — Cliimnies occasion less expenditure of warm air 
 from rooms, than their size would lead us to expect, because 
 they open at the bottom, or near the floor. If, therefore, the 
 room be tight, and the chimney cold, the warm air, while at 
 rest, will be retained in the upper portion of the room, or that 
 which is above the fire place, as effectu-ally as in a gasometer. 
 But if a chimney is heated, and a current thus established 
 through it, it may then drain off the air of the apartment ; and 
 hence the foundation for the common belief that a room be- 
 comes colder in the night, for having had a fire in the day. 
 The warm air may be retained, if the throat of the fire place 
 be closed with a damper. 
 
 Entries and Skylights. — Entries, as they are commonly 
 constructed, extending from the bottom of a house to the top, 
 hkve a bad influence on the retention of heat. The evil is in- 
 creased, when they are surmounted with a skylight, the panes 
 of which are arranged like tiles, and not air tight. Such en- 
 tries are difficult to warm, and serve to drain oflf the warm air 
 
172 ARTS OP HEATING AND VENTILATION. 
 
 of apartments, whenever the communicating doors are left 
 open ; and to transmit it to the roof.* To prevent this effect, 
 entries should be commanded with doors in different stories ; 
 and skylights should be made sufficiently erect, to have their 
 sashes complete, or else a tight horizontal window should be 
 added underneath the skylight. 
 
 Windows. — The heat conducted off by the external atmos- 
 phere, passes, most readily, through the windows , since, the 
 walls of houses, especially when thick, are slow in conducting 
 caloric, while a pane of glass interposes but a slight barrier 
 against its escape. On this account, the unnecessary multipli- 
 cation of windows should be avoided. In cold climates, a great 
 advantage is obtained from using double windows in winter, 
 which, by confining between them a stratum of air, interpose a 
 powerful nonconductor between the room and the atmosphere. 
 To secure the full benefit of tlie double window, it should be 
 made as tight as possible, so that the included stratum of air 
 may not easily change ; otherwise the expected benefit will not 
 be obtained. 
 
 VENTILATION. 
 
 Objects. — If the only object of human habitations were to 
 procure heat, it would be best obtained by keeping the. air in a 
 state of stagnation, and employing those means to create 
 warmth, which are attended with the least circulation, or 
 change. But since the air of inhabited rooms would become 
 in time unfit for respiration, it is necessary that it should be 
 removed, as fast as deteriorated, and be replaced by fresh air 
 from abroad. 
 
 Rooms which are heated with stoves are never well ventila- 
 ted. Those heated by common fire places, are ventilated, at 
 
 ♦ The opposite currents in an open door, by which cold air enters at bottom, 
 and warm air escapes at top, may be made obvious, in the familiar experiment 
 of holding a lighted candle at the bottom and top of the door. In one case the 
 flame will point into the room, and in the other out of it. 
 
ARTS OF HEATING AND VENTILATION. 173 
 
 the expense of losing much of their warmth by the admission 
 of cold air. Those heated by the double fire place [p. 162,] 
 are sufficiently ventilated, with air at an agreeable temperature. 
 Rooms heated by steam are not at all ventilated, unless it be by 
 additional arrangements. Those warmed by hot air flues are 
 apparently well ventilated, yet in hospitals and crowded build- 
 ings, it is sometimes necessary to add fire places, or other 
 openings, for discharging the air. 
 
 Ventilators. — The principal gases, which it is the object of 
 ventilation to remove, are carbonic acid and nitrogen ; these be- 
 ing produced in excess by the process of respiration, by the com- 
 bustion of lamps, and by fires with an imperfect draught. The 
 specific gravity of carbonic acid is greater than that of common 
 air. That of nitrogen is somewhat less. These gases when 
 evolved, are at an higher temperature than the surrounding air, 
 and are mixed with steam ; therefore, while rarefied by heat, they 
 ascend to the top of the apartment. On this account the venti- 
 lators intended to discharge them, are made to consist of open- 
 ings, commanded by shutters, at the upper part of the room. 
 In rooms which are liable to be crowded with people, these 
 ventilators have a good effect, especially in warm weather, and 
 the larger they are, the greater is the ati vantage derived from 
 them. In cold weather, however, they have the disadvantage 
 that they discharge tlie pure heated air, in common with the 
 noxious vapors, and thus defeat our efforts to obtain warmth. 
 In common dwelling houses, no more ventilation is necessary, 
 than can be obtained from doors, open fire places, and win- 
 dows which open at top as well as at bottom. 
 
 Culverts. — In the Derbyshire Infirmary an ingenious mode 
 of ventilation is adopted, by means of an empty culvert, or sub- 
 terranean passage ; one end of which opens into the building, 
 while the other end is provided with a turncap, presenting its 
 open mouth to the wind. The air, in passing this culvert, 
 partakes of the temperature of the earth, and is thus warmed 
 in winter, and cooled in summer. The effect, however, is ob- 
 viously of a limited kind, since the continual transmission of 
 
174 ARTS OF HEATING AND VENTILATION. 
 
 air must bring the surface of the culvert to a temperature ap- 
 proaching that of the surface of the ground. 
 
 Smoky Rooms. — Under the head of ventilation may be 
 placed the art of remedying smoky apartments. Smoke is a 
 heterogeneous vapor, composed of the gases which result from 
 combustion, together with a quantity of opaque matter, which 
 escapes from the fuel without being burnt. Smoke is specifi- 
 cally heavier than the atmosphere, and always descends after 
 it is cooled, as may be seen by observing the current of smoke 
 from a chimney in a cold morning. At the time however of 
 its disengagement from the fire, it is rarefied by heat, and will 
 always ascend through a chimney properly constructed, if it 
 is not prevented by some opposing influence. The causes 
 which produce smoky apartments are principally the following. 
 
 Dmnp Chim,nies. — When a fire is first made in a chim- 
 ney which has not been used for many months, it is apt to 
 smoke. This is because the chimney is cold, and the column 
 of air which it contains is not lighter than the surrounding at- 
 mosphere. The difficulty of remedying this evil is greater, if 
 the bricks have absorbed much moisture, or the chimney be 
 new ; as in this case the chimney will not be well heated, till 
 the moisture is evaporated. To expedite the drying and heat- 
 ing of the chimney, a window should be kept open on the 
 side against which the wind blows, and the communication 
 with the rest of the house, at the same time, closed. This 
 will mechanically assist the smoke and hot air in ascending 
 the chimney. 
 
 Large Fire Places. — If a fire place be made too high, it wUl 
 be liable to smoke ; for, since the throat of the chimney takes 
 in air from all directions, if the fire be too remote from this 
 point, its smoke will be less likely to find its proper way. On 
 the other hand, the lower the mantel piece is brought, the 
 nearer will the fire place approach to the character of a wind 
 furnace. In like manner, if the throat of the fire place be too 
 large, the air of the room, as well as that of the fire, will pass free- 
 ly up the chimney, and thus the whole included air being cold- 
 er, its current wiU be more sluggish. The advanced back of 
 
ARTS OF HEATING AND VENTILATION. 175 
 
 the Rumford fire place, by contracting the throat, remedies this 
 difficulty ; and 3.1 the same time presents a mechanical obstacle 
 against sudden counter currents. 
 
 Close Rooms. — Closeness of a room is a cause of its being 
 smoky. If the walls, doors, and windows, are air tight, or 
 nearly so, the outer air cannot enter to take the place of that 
 which passes up the chimney. The current of heated air and 
 smoke will therefore be interrupted, and expand into the room. 
 In most rooms it happens that the crevices occasioned by the 
 shrinking of the wood, or by the want of exactness in finish- 
 ing, admit air enough, and more than enough, to supply the 
 chimney. In new apartments, however, where all the join- 
 ings have been made with great accuracy, it has been found 
 necessary to make perforations in the walls, to admit air suffi- 
 cient to keep up a current. These should always be made 
 behind the back of the fire place, when possible, for reasons 
 already explained. 
 
 Contiguous Doors. — The doors of a room, if placed very 
 near a fire place, or on the same side of the room with it, are 
 apt to occasion a smoke, as often as they are opened. The 
 gust of air which enters at an open door so situated, blows 
 across the chimney. A part of it ascends the flue, while the 
 rest extends into the room, carrying with it a part of the smoke. 
 
 Short Chimnies. — The longer a chimney is, the more per- 
 fect is its draught, since the upward tendency is proportionate 
 to the difference of weight between the column of air included 
 in the chimney, and a similar column of external air. Short 
 chimnies or flues are liable to smoke from the heated passage 
 not being long enough to establish a strong current. The 
 fire places in upper stories are more apt to smoke than those 
 in the lower apartments. In low houses, outhouses, &c., the 
 chimney should always be carried to the greatest practicable 
 height. Two flues in the same chimney or stack should not 
 communicate at any point short of the top. 
 
 O'pposite Fire Places. — When two chimnies exist in dif- 
 ferent parts of the same room, or in rooms which communicate 
 by doors, it is difficult to kindle a fire in one, while the other 
 
176 ARTS OF HEATING AND VENTILATION. 
 
 is burning, especially if the room be tight ; because in this case 
 the fire which is first estabUshed, feeds itself by a current 
 brought down the vacant chimney. After both fires are kin- 
 dled, it is necessary to keep up a certain equilibrium between 
 them, otherwise the stronger will overpower the latter, and 
 draw down its smoke into the room. If doors or windows be 
 opened, the evil is obviated. If the fires are in different rooms, 
 the communicating doors between them should be shut. 
 
 Neighbourmg Eminences. — ^The vicinity of elevated ob- 
 jects, such as hills, precipices, or very high buildings, is produc- 
 tive of smoky rooms to houses in their neighbourhood. Whenthe 
 wind blows in a direction from the elevated object to the house, 
 it falls down in an oblique direction upon the roof; a part of it 
 enters the chimney, and beats down the smoke, by overpow- 
 ering ils current. On the other hand, when the wind sets to- 
 wards the hill or elevated object, its passage becomes obstruct- 
 ed, and it presses in every direction to escape ; and while its 
 upper portions pass off by the top of the opposing body, the 
 lower portions press downward through any passages which 
 may afford them an escape. Chimnies in houses thus situated 
 should be carried up to a great height, so a?, if possible, to 
 overtop the eminence, their sides being secured by iron braces. 
 
 Turnca'p, ^°c. — In many instances, a turncap, which is a 
 curved tube regulated by a weathercock, so as always to turn 
 its mouth in a direction from the wind, will prevent smoking, 
 in the case last stated. The turncap offers, also, a security 
 against the influence of strong winds, wliich in common cases 
 and in houses most favorably situated, often invert the course 
 of the smoke by the strong pressure they exert on the tops of 
 chimnies, and by impinging against their inner side. In like 
 manner, the ^o;f5, which are frusta of cones or pyramids, placed 
 on the tops of chimnies, assist the escape of smoke, by causing 
 the wind to glance upward from their sides. 
 
 Contiguous Flues. — When two chimnies are contiguous 
 to each othei', or in the same stack, one is frequently liable to 
 smoke, when the other contains a fire, from a variety of cir- 
 cumstance*. Not only the effect of high winds, but also any 
 
ARTS OF HEATING AND VENTILATING. 177 
 
 circumstance, which tends to produce an inverted current, may 
 bring down the smoke from one chimney into the apartment 
 which contains the other. To prevent this evil, the fire places 
 should be furnished with dampers which can be closed when 
 the flue is not in use. 
 
 Burning- of iSmoke. — This subject has excited great atten- 
 tion, owing to the nuisance produced by smoke in large cities 
 and manufacturing towns, chiefly where coal is burnt. In an 
 economical view it deserves attention, since it renders the same 
 fuel more effective. Several methods of getting rid of smoke 
 have been proposed and executed with some success. The 
 first mode is to cause the smoke to pass through a portion of 
 fuel which is perfectly ignited and does not smoke, and which, 
 if accurately managed, burns it up. This has been effected 
 by an inverted draught, in a syphon chimney, and also by a 
 revolving grate, which places the ignited fuel between the fresh 
 fuel and the chimney. Another mode is to mix a current of 
 fresh air with the smoke, which causes it to burn upon passing 
 in contact with a clear fire. A third method which has been 
 adopted for disposing of smoke, consists in building chimnies 
 of an extraordinary height, so that most of the smoke may be 
 deposited in soot upon their sides. It has also been proposed 
 to build circuitous chimnies, in one part of which the smoke 
 should pursue a descending course, and that in this part a 
 shower of water should be kept up, to precipitate the denser 
 particles of the smoke. The expense of this method will prob- 
 ably prevent its use, unless in some cases to get rid of danger- 
 ous metalMc fumes in manufactories. 
 
 FRANKiirf's Works ; — Rumford's Works; — Tredgold, on Warm- 
 ing and Ventilating Buildings, 8vo. 1824 ; — Buchanan, on the Econo- 
 my of Fuol and Management of Heat, 8vo. 1810; — Sylvester's Phi- 
 losophy of Domestic Economy, and account of the Derbyshire Infirma- 
 ry, 4to. ; — Account of the Wakefield Asylum, fol. ; — Brande's Quar- 
 terly Journal, No's 22, 24, 27, 37, &c. 
 23 
 
CHAPTER IX. 
 
 ARTS OF ILLUMINATION. 
 
 Flame. — Artificial light is obtained for common purposes, 
 by the combustion of substances, which afford a permanent 
 and luminous flame. All flames are not equally luminous. 
 Those substances which, during- combustion, produce chiefly 
 gaseous or volatile matter, emit from their flame a very feeble 
 light, as is seen in burning hydrogen, or sulphur. Those, on 
 the other hand, which produce particles of solid matter during 
 their combustion, yield a whiter flame, and a greater illumina- 
 tion. Sir Humphrey Davy is of opinion that the brilliancy of 
 the flames, used for illumination, is owing to the decomposi- 
 tion of the gaseous matter towards the interior of the flame, by 
 which solid charcoal is produced, and strongly ignited, bsfore 
 it is burnt. In a conical flame, like that of a candle, the com- 
 bustion takes place most rapidly toward the surface, where the 
 inflammable gas mixes with the atmospheric air. At the cen- 
 tre of the base, there is a darker portion, which consists of the 
 matter, which is volatilized, but not yet fully on fire. In the 
 interior, or most luminous part, the solid particles are brought 
 to a white heat, just before they are burnt. The degree of 
 their ignition is very powerful, since it is found that the flame 
 of a common candle is hot enough to melt a small filament of 
 platinum. 
 
 Support of Flmne. — That a flame may burn steadily, and 
 produce a uniform light, it is necessary that the supply of com- 
 bustible matter should be constant and uniform. For this pur- 
 pose the combustible must be in a liquid, or gaseous state, 
 when it approaches the flame, so that it may flow in an unin- 
 terrupted current. This current is commonly sustained either 
 
ARTS OF ILLUMINATION. 179 
 
 by capillary attraction, or by mechanical pressure, operating 
 on the reservoir which contains the combustible. 
 
 Torches and Candles. — The rudest materia] us xl for af- 
 fording light, is the torch, composed of the resinous part of 
 wood of the pine or fir. In such torches, the turpentine, or 
 melted resin, oozes out through the pores of the wood, and is 
 gradually burnt, the wood interposing a vehicle, which regu- 
 lates the supply, and prevents it from being consumed at once ; 
 thus sustaining a dull and irregular light, with much smoke, 
 for some time. A common candle is an improvement upon 
 this natural mechanism. It consists, as is well known, of a 
 fusible sohd, as tallow, w^ax, or spermaceti, formed into a cylin- 
 der, having a wick of cotton, or some other porous substance, 
 for its axis. As the tallow melts by the radiated heat of the 
 flame, it is carried upward by the capillary attraction of the 
 wick, and is converted into vapor as fast as it reaches the sur- 
 face. The end of the wick, although it is blackened by the 
 heat, is prevented from consuming, merely because it is sur- 
 rounded by inflammable vapor, so that the oxygen of the at- 
 mosphere has no access to it. If the wick be turned to one 
 side, so as to project from the blaze into the atmospheric air, it 
 is immediately burnt off". Tallow being more fusible than 
 wax, requires to be burnt with a larger wick. The reason 
 why this wick requires continual snuffing is, that if it is suffered 
 to became long, it divides the blaze, and intercepts a part of the 
 light ; it also cools the flame by its radiation, obstructs the com- 
 bustion, and thus causes the escape of smoke and the deposi- 
 tion of charcoal. Wax and spermaceti, being less fusible, 
 may be burnt with a smaller wick, which, if made sufficient- 
 ly slender, bends out of the flame and burns off, so as not to 
 requirer snuffing. 
 
 Lamps.—When the combustible used is fluid at common 
 temperatures, a vessel is necessary to contain this fluid and 
 supply it to the flame. In this country, and in England, whale 
 oil is the principal fluid which is burnt in lamps.* In France 
 
 • The oil which is extracted in cold weather, and called winter strained oil, 
 remains fluid at low temperatures. The summer strained oil is Uable to con- 
 
180 ARTS OP ILLUMINATION. 
 
 and the south of Europe, the oil of poppies, of nuts, rape seed, 
 and the inferior kinds of olive oil, are used for this purpose. 
 The volatile oils are but seldom burnt, since they exhale a 
 strong odor, and throw off soot during their combustion. They 
 are also liable to take fire over their whole surface, unless 
 guarded with great care. Naptha, however, as it is found na- 
 tive, or as it is distilled from pitcoal, is used for supplying street 
 lamps in some of the cities of Europe. 
 
 Reservoirs. — As the flame of a lamp is intended to consume 
 no more oil than is attracted upward by the capillary action of 
 the wick, it is necessary that a sufficient body of oil should be 
 so placed, as to keep its surface permanently at a small distance 
 below the level of the flame. The Greeks and Romans em- 
 ployed lamps of various forms, having the wick projecting from 
 a sort of beak at the side, nearly on a level with the surface of 
 the oil. A similar plan is now practised in our street lamps. 
 At the present day, portable lamps of small size, are made with 
 a central wick, having the reservoir of oil immediately below 
 the flame. These reservoirs, if small, require frequent filling, 
 and if large, cast an inconvenient shadow. All closed lamps 
 require a minute hole for the admission of air, otherwise the 
 pressure of the atmosphere will prevent the oil from ascending 
 the wick. If this hole be obstructed, the oil will also some- 
 times overflow, from the expansion of the confined air, when 
 heated. 
 
 Astral Lamp. — With a view to get rid of the effect of 
 shadow, various contrivances have been introduced, in which 
 the reservoir is placed at a distance from the flame. In the 
 Astral and Sinumbral lamps, the principle of which was in- 
 vented by Count Rumford, the oil is contained in a large hor- 
 izontal ring, having a burner at the centre, communicating 
 with the ring by two or more tubes placed like rays. The 
 ring is placed a little below the level of the flame, and from its 
 
 geal in winter. To obviate this inconvenience, lamps have been contrived for 
 melting the summer oil by the heat of the blaze . This is clone either by placing 
 the reservoir of oil immediately over the blaze, or by conducting the hcnt by a me- 
 tallic bar, which extendg from the flame into the reservoir, 
 
A.RTS OF ILLUMINATION. 
 
 181 
 
 large surface affords a supply of oil for mauy hours. A small 
 aperture is left for the admission or escape of air, in the upper 
 part of the ring. When these lamps overflow, it is usually be- 
 cause the ring is not kept perfectly horizontal, or else because 
 the air hole is obstructed, a circumstance which may even 
 happen from filling the lamp too high with oil. 
 
 Hydrostatic Lamps. — ^In several cases, the laws of hydros- 
 tatics have been applied to raise oil to the flame from a reser- 
 voir placed so far below the wick as to be out of the reach of 
 its effective capillary attraction. One of these hydrostatic 
 lamps is constructed on the principle of Hero's fountain. It is 
 composed of three vessels or cavities, occupying 
 different heights, and comminiicating by tubes 
 or syphons. One portion of oil, by descending 
 gradually from the middle vessel A, to the 
 lower vessel B, causes another portion of oil to 
 ascend from the upper vessel C, to the flame 
 at D, the hydrostatic equilibrium being kept 
 up by the intervention of the column of air 
 BC. 
 
 The lamps of Girard de Marselle, and of King, are on this 
 principle, though the form of their apparatus is that of a cylin- 
 der, with internal tubes opening into different cavities. 
 
 Other hydrostatic lamps are constructed, so as to contain, in 
 one part, a column of some fluid, the specific gravity of which 
 is considerably greater than that of oil; such, for example, as 
 water saturated with salt. This fluid acts in such a manner 
 as to raise the oil, by its greater weight. Thus if 
 an inverted syphon contain oil in one part, and 
 salt water in another, the surfaces of the two fluids 
 will stand at different heights, inversely propor- 
 tionate to their specific gravities. In the diagram, 
 A represents the surface of the heavier fluid, and 
 B, that of the oil. The bulbs serve as reservoirs to prolong the 
 action. Mr Kiers' lamp is constructed on this principle. 
 Those of Barton and Edelkrantz depend on the same princi- 
 
182 
 
 ARTS OF ILLUMINATION. 
 
 pie ; but in their construction, an open tube of oil is made to 
 float in an upright vessel containing a heavier fluid, which in 
 some cases is salt water, in others mercury. As the oil con- 
 sumes, the tube, with the wick arid light, descend in the sup- 
 porting fluid, and follow the surface of the oil, as it lowers. 
 
 Automaton Lamp. — The automaton lamp of Porter, is a 
 simple and effectual contrivance for keeping the smface of the 
 oil near the level of the blaze. It consists of an oblong tin 
 box, having the wick tubes at one end, this end being thus 
 rendered heavier than the other. The box is suspended on 
 pivots, placed a little out of the centre, and toward the tubes, 
 so -that when the lamp is full of oil, the box will hang level. 
 As the oil burns out, however, the end containing the tubes 
 will preponderate, so as to keep the flame always near the sur- 
 face of the oil. The annexed figures show the position of the 
 lamp w^hen full, and when half exhausted. This lamp is of 
 cheap construction, and is said to be extensively used in cotton 
 mills and other manufactories in the north of England. 
 
 ■mr 
 
 \ 
 
 
 = 
 
 ^ 
 
 ■ 
 
 
 ^ 
 
 Mechanical Lamps. — Some lamps are manufactured in 
 France, in which the oil is raised from a large reservoir below, 
 to a small one near the flame, by means of a pump. This in 
 some instances is worked by hand, and in others is carried by 
 clock work, the motion being derived from a spring, which is 
 wound up as often as necessary. 
 
 Fountain Lamp. — The most common mode of disposing 
 of the oil in large lamps, is to place the reservoir above the 
 level of the flame, so that the burner, or part containing the 
 wick, may be supplied in small quantities, as fast as its oil is 
 
ARTS OF ILLUMINATION. 183 
 
 consumed. These reservoirs are constructed on the principle 
 of the bird fountain. They are open at bottom, but the oil 
 is kept from running out at once, by the pressure of the at- 
 mosphere. The reservoir commonly terminates in a neck at 
 bottom, with an opening on one side. This neck is immersed 
 beyond the opening, in a small cavity, which contains oil near- 
 ly on a level with the burners, and communicates with them 
 by tubes. So long as the whole of the opening is immersed, 
 no oil can descend fiom the reservoir, because no air can enter 
 to take its place. But whenever the oil in the lower cavity is 
 consumed so far as to sink below the upper edge of the open- 
 ing, a bubble of air will enter the neck and ascend into the 
 reservoir ; at the same time displacing an equal bulk of oil, 
 which descends to feed the lamp. For convenience, the open- 
 ing is commanded by a sliding valve, and when the reservoir 
 is to be filled, it is unscrewed from the lamp, inverted, and the 
 oil poured in at the neck. When these lamps overflow, it is 
 commonly owing to an increase in the heat of the room, which 
 causes the air in the upper pait of the reservoir to expand, 
 and drive out a portion of oil. As it is not easy to prevent 
 this occurrence, lamps are usually provided wdth receptacles at 
 bottom, to receive the waste oil which runs over at the wick. 
 
 Argand Lamp. — This name is applied, after one of the 
 inventors, to all lamps with hollow or circular wicks ; and of 
 course, most of the lamps already described, may be also Ar- 
 gand lamps, if furnished with a circular burner. The inten- 
 tion of the Argand burner, is to furnish a more rapid supply 
 of air to the flame, and to afford this air to the centre, as well 
 as the outside of the flame. It is constructed by forming a 
 hollow cyhndrical cavity, which receives oil from the main 
 body of the lamp, and at the same time transmits air through 
 its axis, or central hollow. In this cavity is placed a circular 
 wick, attached at bottom to a moveable ring. This ring is 
 capable of being elevated or depressed, by means of a rack and 
 pinion, or more commonly by a screw ; so that the height of 
 the wick may be varied to regulate the size of the flame. On 
 
184 ARTS OF ILLUMINATION. 
 
 the outside is placed a glass chimney, which is capable of trans- 
 mitting a current of air, on the same principles as a common 
 smoke flue. When this lamp is lighted, the combustion is 
 vivid, and the light intense, owing to the free and rapid supply 
 of air. The flame does not waver, and the smoke is wholly 
 consumed. The brilliancy of the light is still further increas- 
 ed, if the air be made to impinge laterally against the flame. 
 This is done either by contracting the glass chimney near the 
 blaze, so as to direct the air inwards, or by placing a metallic 
 button over the blaze, so as to spread the internal current out- 
 ward. 
 
 Reflectors. — For obvious reasons, a lamp yields most availa- 
 ble light, when it is placed in the centre of a room or space to 
 be illuminated. In this situation, if a reflecting surface be 
 brought near to it, this surface by its reflection will increase 
 the amount of light in one direction, at the expense of inter- 
 cepting it in another, so that the total advantage is not increas- 
 ed by the reflector. But when a lamp is placed near a wall, 
 so that a part of its rays are wasted by falling immediately 
 upon the wall, in this case if a polished surface be placed be- 
 hind the flame, it reflects back most of the rays, which would 
 otherwise be lost upon the nonreflecting wall ; and thus it in- 
 creases the effect of the light. The familiar fact that rooms 
 with light colored walls are most easily lighted, is owing to the 
 greater reflective power which such walls possess, when com- 
 pared with darker surfaces. 
 
 Hanging of Pictures. — As the surface of varnished paint- 
 ings has a considerable reflecting power, it happens that when 
 the spectator stands in the way of the reflected light, his eye 
 is dazzled, and rendered incapable of distinctly perceiving the 
 picture. Paintings, therefore, should not be hung opposite to 
 lights, nor in any situation in which a line drawn from the 
 place intended for spectators will make the same angle with 
 the surface of the picture, as a line drawn from a window or 
 other illuminating point ; the angle of reflection being always 
 equal to the angle of incidence. As a general rule, a picture 
 
ARTS OF ILLUMINATION. 185 
 
 will be in a bad light with regard to a spectator, whenever the 
 image of a window could be seen by him in a looking glass 
 occupying the same place as the picture. 
 
 Transparency of Flame. — If two lamps be placed by the 
 side of each other, the flame of the one, when clear of smoke, 
 does not interce|)t the light of the other, and casts httle or no 
 shadow. Count Rumford found that the brilliancy of flame 
 is, in some high ratio, proportionate to its elevation of tempera- 
 ture. If several concentric circular wicks, or several parallel flat 
 wicks, be burnt near together, they produce more light, in con- 
 sequence of the accumulation of heat, than they would do if 
 burnt separately. 
 
 Glass Shades. — To relieve the eye from the glare of light, 
 produced by bright lamps, shades of roughened glass are fre- 
 quently used. A rough surface upon glass n)ay be produced 
 by grinding it with sand or emery, by corroding it with fluo- 
 ric acid, or by covering it with powdered glass and exposing it to 
 heat till the particles adhere. Glass shades have the effect to 
 disperse the rays of light, by the numerous reflections and re- 
 fractions whxh they occasion ; till at length the light issues 
 f.jin all parts of their surface, and it appears as if the glass it- 
 self were the luminous body. 
 
 Siniinibral Lamp. — The reservoir of the sinumbral lamp 
 is constructed on the same general principles with that of the 
 astral. The ring, however, which holds the oil, is so formed 
 as to oppose the smallest diameter of its section to the rays of 
 light. A large shade of ground glass is used, which nearly in- 
 closes the light, and by tlie different refractions and reflections 
 given to the rays by the ground glass, they escape in all direc- 
 tions, so that there is no perceptible shadow at a small dis- 
 tance from the ring. Reflectors are sometimes added, when it 
 is desired to throw the principal mass of light in one direction. 
 
 Measurem,ent of Light. — The following method of measur- 
 ing the comparative illuminating power of different lights, is 
 founded on the law, that the amount of rays thrown on a given 
 surface, is inversely as the square of the distance of the illumi- 
 24 
 
186 ARTS OF ILLUMINATION. 
 
 nating body. Place two lights, which are to be compared with 
 each other, at the distance of a few feet, or yards, from a screen 
 of white paper, or a white wall. On holding a small card 
 near the wall, two shadows will be projected on it, the darker 
 one by the interception of the brighter hght, and the fainter 
 shadow by the interception of the duller light. Bring the faint- 
 er light nearer to the card, or remove the brighter light farther 
 from it, till both shadows acquire the same intensity, which the 
 eye can judge of with great precision, particularly from the 
 conterminous shadows at the angles. Measure now the distan- 
 ces of the two lights from the wall or screen, and the squares 
 of these distances will give the ratio of illumination. Thus if 
 an argand flame and a candle stand at the distances of ten 
 feet and four feet respectively, when their shadows are equally 
 deep we have the square of ten and the square of four, or 100 
 and 16, as their relative quantities of light. In this experiment 
 the spectator should be equidistant from each shadow. 
 
 Gas Lights. — In the flame of a common lamp or candle, 
 the combustible matter is not burnt until it has first been con- 
 verted into vapor, or inflammable gas. This gaseous matter is 
 burnt as fast as it is generated, in consequence of being brought 
 immediately in contact with the atmospheric air, and set on 
 fire by the same heat which produces it. It is found^ however, 
 if certain combustibles be exposed to heat, and if the inflam- 
 mable gas, which they yield, be kept separate from the atmos- 
 pheric air, that this gas may be conveyed in pipes to any dis- 
 tance, and burnt for light in any place where a stream of it is 
 discharged into the atmosphere. In this way various combus- 
 tibles may be used which are not capable of being burnt in 
 lamps, and a brilliant and economical light obtained from them. 
 The materials chiefly employed for this purpose, are pitcoal, 
 and animal oil. Yaiious other substances are capable of sup- 
 porting gas lights, such as bitumen, rosin, oleaginous vegetable 
 seeds,* other oily or resinous bodies, and even wood, and turf. 
 
 * Professor Olmstead has found that cotton seed produces gas of a superior 
 kind for purposes of illumination. See his account of this article in Silliman'» 
 Journal, ■vol. viii. p. 294, and x. 363. 
 
ARTS OF ILLUMINATION. 187 
 
 The inflammable gas, which is procured from all these substan- 
 ces is chiefly carburetted hydrogen. Of this, two kinds are 
 known, the first sometimes called olefiant gas, and the other 
 subcarbu retted hydrogen. Mr Brande, however, considers the 
 last species as merely a mixture of the first with hydrogen, 
 l^he fitness of a mixed gas for purposes of illumination, is de- 
 pendent on the quantity of carburetted hydrogen which it con- 
 tains, other things being equal. 
 
 Coal Gas. — The use of coal gas for puposes of illumina- 
 tion, appears to have been first introduced by Mr Murdoch, in 
 1792, although its power of affording a luminous flame was 
 known much earlier. It is found that the bituminous coals, 
 and particularly cannel coal, afford the most and the best illu- 
 minating gas. Some of the Anthracites, according to Profes- 
 sor SiUiman, afford as much gas as Liverpool coal, but it burns 
 with a feeble flame, and is unfit for the purposes of illumina- 
 tion. 
 
 In the manufacture of coal gas, the coal is placed in iron 
 retorts, which are subjected to a strong heat in a furnace. The 
 gas is thus driven off, mixed with the vapor of tar, oil, and am- 
 moniacal water, and in this state is conducted by pipes first in- 
 to a horizontal trunk of cast-iron, called the hydraulic main, 
 and from thence into a condensing apparatus, surrounded 
 with cold water, where the vapors of the tar, oil, and water, 
 are condensed and fall down, while the gaseous product is con- 
 veyed along, containing several impure gases, such as sulphur- 
 etted hydrogen, and carbonic acid. 
 
 In order to separate the caiburetted hydrogen from these 
 impurities, various contrivances have been adopted. The 
 usual method of purifying coal gas, is to make it pass through 
 a mixture of lime and water, called Cream of Lime, which 
 absorbs or combines with the contaminating gases. For this 
 purpose, a considerable number of purifiers are erected, and the 
 lime and water are kept in a state of constant agitation, either 
 by a steam engine, or by one or two men, till the gas is ren- 
 dered sufiiciently pure. Sometimes the purification is effected 
 
188 ARTS OF ILLUMINATION. 
 
 by causing the gas to pass in contact with solid lime, newly- 
 slaked ; and sometimes by passing it through letoits contain- 
 ing clippings of iron made red hot. When thus purified, the 
 gas is conveyed by a pipe to the gasometer. 
 
 The Gasometer, is a large inverted vessel, made of mallea- 
 ble iron, or copper, either of a cyhndrical or rectangular form, 
 and suspeaded over a reservoir of water of a little larger size, 
 by means of counter- weights. The gas is introduced by pipes 
 ascending from the bottom of the reservoir, and rising a little 
 above the surface of the water. While the gasometer is filling 
 with gas, it gradually rises out of the water, until it is filled, 
 after which no more gas is admitted, and its contents are ready 
 to be distributed through the pipes by which it is to be convey- 
 ed to the place intended to be illuminated by burning it. As 
 the gas is forced out by the weight of the gasometer, and is 
 burned, the gasometer descends gradually in the water, till the 
 whole of its contents are expelled, when it is again filled by the 
 same process as before. 
 
 The gas being thus ready for use, must be carried off by 
 pipes, the diameter of which is proportional to the degree of 
 Ught required. It has besn found that a pipe one inch ia di- 
 ameter, will, under a pressure of a column of water from five 
 eighths to three fourths of an inch, supply gas equal to 100 can- 
 dles; and if there was no friction, or mechanical impediment, 
 the number of candles would be found for other diameters of 
 pipe, by multiplying the square of the diameter of the pipe in 
 inches by 100. The friction, however, or obstruction, dimin- 
 ishes so rapidly with the diameter of the pipe, that the num- 
 ber of candles is always greater than this rule gives. Thus a 
 pipe three inches in diameter will supply light equal to 1000 
 candles — a pipe four inches, 2000^ — a pipe six inches, 5000- — 
 and a pipe ten inches, about 14,000.* 
 
 When the gas is to be burned in rooms, shops, or streets, it 
 is allowed to escape through small circular apertures of from 
 one fortieth to one sixtieth of an inch in diameter, which may 
 
 * Brewster's edition of Ferguson's Mechanics, vol. ii. p. 273, 
 
ARTS OF ILLUMINATION. 189 
 
 be arranged in various ornamental ways, or disposed in a cir- 
 cle, like an argand burner, with a current of air running be- 
 tween them. The lights thus produced are equal, steady, and 
 of the most brilliant kind. When the supply of gas is cut off, 
 they are instantly extinguished. When it is restored, the in- 
 visible current flows out, and may be instantly lighted again 
 by the contact of flame. 
 
 Oil Gas. — It has been long known to chemists, that wax, 
 oil, tallow, &.C., when passed through ignited tubes, are resolv- 
 ed into combustible gaseous matter, wliich burns with a bright 
 light. Of late years this gas has been mry:h used for purpo- 
 ses of illumination. Oil gas is considered in many respects 
 superior to coal gas, and free from its inconveniences. The 
 material from which it is produced containing no sulphur or 
 other matter by wliich coal gas is contaminated, it never produ- 
 ces a suffocating smell in rooms ; so that the costly operation 
 of purifying the gas by lime, and other means, is avoided. 
 Nothing is contained in oil gas which can injure the metal of 
 which the conveyance pipes are made. 
 
 The oil gas has a further advantage over coal gas, in con- 
 taining a greater proportion of carburetted hydrogen, so that 
 one cubic foot of oil gas is said to go as far as two or three of 
 coal gas. This circumstance is of importance, as it reduces in 
 the same proportion, the size of the gasometers, which are ne- 
 cessary to contain it. Oil gas contains about 7.5 per cent, of 
 carburetted hydrogen, while purified coal gas but seldom con- 
 tains more than 40 per cent. 
 
 In procuring this gas, a quantity of oil is placed in an air- 
 tight vessel, in such a manner, that it may pass slowly into 
 retorts or iron tubes, which are kept at a moderate red heat. 
 Fragments of coke or brick, are usually enclosed in ihs tubes. 
 The oil, in its passage through the retorts, is principally de- 
 composed, and converted into gas proper for illumination, car- 
 rying with it, however, some oil in the state of vapor. To 
 purify the gas from this oil, which is suspended in it, and 
 which occasions an empyreumatic smell, it is conveyed into 
 
190 ARTS OF ILLUMINATION. 
 
 wash vessels, where, by bubbling^ through water, or through 
 fresh oil, it is cooled and rendered fit for use. It then passes 
 by a proper pipe into a gasometer, from which it is suffered to 
 pass off in pipes, in the usual manner, to its places of destination. 
 
 The poorest kinds of oil, which are unfit for burning in 
 lamps, produce excellent gas. This is, indeed, the chief source 
 of economy in the process. 
 
 According to Mr Brande, a light equal to ten wax candles 
 for one hour, rec{uires for its production, 2600 cubic inches of 
 pure carburetted hydrogen, or olefiant gas, 4875 cubic inches 
 of oil gas, or 131^0 cubic inches of coal gas. 
 
 Gasmeter. — In dispensing gas for the illumination of par- 
 ticulai' rooms, it was found necessary to possess some method 
 of measuring the quantity expended in each place. An in- 
 genious instrument, called the gasmeter, has been introduced 
 for this purpose. It consists of a horizontal cylinder partly 
 filled with water, within which another cylinder revolves on 
 an axis, having its interior surface divided into several compart- 
 ments. These compartments, being successively filled with 
 the gas, as it passes through, rise out of water like inverted 
 buckets of an overshot wheel, and cause the inner cylinder to 
 revolve. The number of revolutions is registered by machine- 
 ry, and thus the quantity of gas which escapes in a given time 
 is estimated. 
 
 Portable Gas Lights. — The magnitude and expense of 
 gas works, prevents the use of them, except in cases where a 
 large number of lights are wanted, within a convenient^distance 
 from the gasometer. The gas, however, may be conveyed to 
 any distance, by condensing it in strong vessels of iron or cop- 
 per, made of a small or portable size. The gas is forced into 
 these vessels by a condensing pump, and when afterwards suffer- 
 ed to escape through a small orifice, is capable of supporting a 
 flame for many hours. The economy, however, of this pro- 
 cess has with reason been doubted. 
 
 Safety Lamp. — In coal mines an inflammable gas is gen- 
 erated, called ^re damp by the miners, and composed chiefly 
 
A.RTS OF ILLUMINATION. 191 
 
 of carburetted hydrogen. This gas, when mixed with atmos- 
 pheric air is hable to take fire from the flame of a lamp or 
 candle, and to explode with great violence. Terrible accidents 
 have happened, and many lives have been destroyed, from 
 these explosions. To prevent such accidents, several trouble- 
 some and circuitous modes of obtaining light were resorted to 
 by the miners ; such as striking sparks from a wheel, and in- 
 closing a lamp within a tight lantern, which was supplied with 
 air from a bellows. All these are now superseded by the safe- 
 ty lamp of Sir Humphrey Davy. This important invention 
 consists simply of a lamp, the flame of which is wholly enclo- 
 sed in a cylinder of fine wire gauze. Its operation depends 
 on the principle discovered by Sir H. Davy, that explosive 
 mixtures cannot be inflamed through minute apertures in me- 
 tallic surfaces, or tissues. The wire gauze, being a powerful 
 conductor and radiater of heat, cools a flame which is in con- 
 tact with it, so as to deprive it of the power of producing an 
 explosion on the other side. If this lamp be immersed in an 
 explosive mixture, the gas will be inflamed, and burn on the 
 inside of the gauze cylinder, but not on the outside. In these 
 cases the flame of the lamp first enlarges, and is then extin- 
 guished, the whole of the cage being filled with a lambent 
 blue light. If the supply of gas be withdrawn, this appearance 
 gradually ceases, and the wick becomes rekindled. 
 
 Lamp ivithoLit Flame. — This curious instrument may be 
 made by winding upon the wick of a lamp containing alcohol, 
 a fine wire of platinum, not more than a hundredth part of an 
 inch in thickness. There should be about sixteen spiral turns, 
 one half of which should surround the wick, and the other 
 half rise above it. Having lighted the lamp for an instant, on 
 blowing it out, the wire will become brightly ignited, and will 
 continue to glow as long as any alcohol remains, without the 
 blaze being any more renewed. The principle depends upon 
 the slow combustion which is found to take place in inflam- 
 mable or explosive mixtures, at a lower temperature than is 
 necessary to produce inflammation. This combustion is not 
 
192 ARTS OF ILLUMINATION. 
 
 visible, but the heat is nevertheless sufficient to ignite minute 
 solids exposed to its influence. In the lamp which has been 
 described, the explosive niixtuie is the vapor of alcohol and at- 
 mospheric air. But the experiinent may be varied, by using 
 ether, camphor, &c., and by substituting platinum leaf for 
 wire. 
 
 Modes of 'procuring Light. — To obtain light and fire, 
 when wanted, in an expeditious manner, various instruments 
 have been introduced, constructed on optical, mechanical, and 
 chemical principles. The methods by which they operate are 
 chiefly the following. 1. By concentration of the solar rays, 
 as in the focus of a common lens, or burning glass. 2. By 
 friction. Dry wood takes fire, if rubbed violently in the man- 
 ner practised by savages, or if it be held against the surface of 
 a wheel which revolves rapidly.. Phosphorus takes fire by 
 very slight friction, and on this account is used in the phos- 
 phoric Jire bottles, the matches of which, after being charged 
 w^ith a minute quantity of phosphorus, take fire by rubbing 
 them on the cork. 3. By percussion. When hard bodies, 
 such as flint and steel, are brought into collision, small parti- 
 cles of ignited matter are struck o(f in the form of sparks, which 
 are sufflciently hot to set fire to linder, gvmpowder, &.c. Com- 
 mon firelocks, tinder-boxes, &c., operate on this principle. 4. 
 By compression. If a piece of tinder is confined in a small 
 cavity at the end of a condensing syringe, it will take fire, if 
 the piston of the syringe be driven down with a stroke, so as 
 suddenly to condense the air. The tinder commonly used for 
 this purpose, is what is called German tinder, made of a fun- 
 gus that grows on trees, (Boletus igniarius) boiled in a solu- 
 tion of nitre and dried. 5. By chemical action. In the oxy- 
 muriatic fire hexes, the matches are charged with chlorate of 
 potash mixed with sulphur or some other combustible. When 
 these are brought into contact with sulphuric acid, a violent 
 chemical action takes place, and the match takes fire. Hom- 
 herg's pyrophoriis takes fire on exposure to the air. It may be 
 made by calcining alum with less than an equal quantity of 
 
ARTS OP ILLUMINATION. 193 
 
 flour or sug^ar, until the smoke and flame disappear. It is then 
 kept in close stopped bottles ; and if a little of it be shaken out 
 upon any light combustible, as cotton or tow, it causes it to in- 
 flame. The platinum lights depend on a remarkable prop- 
 erty discovered by Dobereinei', in platinum, by which a sponge 
 made of that metal, becomes ignited when exposed to a stream 
 of hydrogen gas. 
 
 AccuM, on Gas-light, 8vo. 1816; — Peckston, on Gas-lighting; — 
 Rcmford's Works ; — Nicholson's Philosophical Journal, vol. i. 4to. 
 vol. xiv. 8vo., &.C. — Rees' Cyclopedia ; — Ure's Chemical Dictionary. 
 
 25 
 
CHAPTER X. 
 
 ARTS OF Lo:;OMOTION. 
 
 Animals of the more perfect kinds, possess the power of 
 shifting their place at will, which power they exercise both in 
 transporting their own bodies and in conveying other n)asse3 
 of matter. The chief obstacles which oppose locomotion, or 
 change of place, are gravity and friction, the last of which is 
 in most cases a consequence of the first. Gravity confines all 
 terrestrial bodies against the surface of the earth, with a force 
 proportionate to the quantity of matter which composes them. 
 Before they can be removed from one spot of this surface to 
 another of equal height, they must either be lifted from the 
 ground against the foice of gravity, or carried hoiizontally 
 along the surface, resisting with a degree of friction, which 
 increases with their weight. Most kinds of mechanism, both 
 natural and artificial, which assist locomotion, are arrangements 
 for obviating the effects of gravity and friction. 
 
 Motion of Animals. — Animals that walk, obviate friction 
 by substituting paints of their bodies instead of large surfaces; 
 and upon these points they turn, as upon centres, for the length 
 of each step, raising themselves wholly or partly from the 
 ground in successive arcs, instead of drawing themselves along 
 the surface. The line of arcs which the centre of gravity de- 
 scribes, is converted into an easy or undulating line, by the com- 
 pound action of the different joints. As the feet move in sepa- 
 rate lines, the body has also a lateral, vibratory motion. A m-an, 
 in walking, puts down one foot before the other is raised, but 
 not in running. Quadrupeds in walking have three feet upon 
 the ground for most of the time ; in trotting, only two. An- 
 imals which walk against gravity, as the common fly, the tree 
 
ARTS OF LOCOMOTION. 195 
 
 toad, &c., support themselves by suctioiij using cavities en the 
 under side of their feet, which ihey enlarge at pleasure, till the 
 pressure of the atmosphere causes them to adhere. In other 
 respects, thsir Io2jni3tioa u ejected like that of other walking 
 animals. Birds perform the motion of flying by striking the 
 air with the broad SLiiface of their wings in a downward and 
 backward direction, thus propelling the body upward and for- 
 ward. After each stroke the wings are contracted, or slightly 
 turned, to lessen their reiistanceto the atmosphere, then raised 
 and spread anew. The downward stroke also, being more 
 sudden than the upward, is more resisted by the atmosphere. 
 The tail of birds serves as a rudder to direct the course upward 
 or downward. When a bird sails in the air without moving 
 the wings, it is done in some cases by the velocity previously 
 acquired, and an oblique direction of the wings upwaro ; — in 
 others, by a gradual descent, with the wings slightly tm-ned 
 in an oblique direction downward. Fishes, in swimming for- 
 ward, are propelled chiefly by strokes of the tail, the extremity 
 of which being bent into an oblique position, propels the body 
 forward and laterally at the same time. The lateral motion is 
 conected by the next stroke, in the opposite direction, while 
 the forward course continues. The fins serve partly to assist 
 in swimming, but chiefly to balance the body, or keep it up- 
 right ; for the centre of gravity being neare;t the back, a fish 
 turns over, when it is dead, or disabled.* Some other aquatic 
 animals, as leeches, swim with a sinuous or undulating motion 
 of the body, in which several parts at once are made to act ob- 
 liquely against the water. Serpents in like manner advance 
 by means of the winding or serpentine direction which they 
 give to their bodies, and by which a succession of oblique for- 
 ces are brought to act against the groimd. Sir Everard Home 
 is of opinion that serpents use their ribs in the manner of legs, 
 
 * The swimming bladder, which exists in most fishes, though not in all, is 
 supposed to have an agency in a !apting the specific gravity of the fish to the 
 particular depth in which it resides. The power of the animal to rise or sink, 
 by altering the dimensions of this organ, has been, with some reason, disputed. 
 
196 ARTS OF LOCOMOTION. 
 
 and propel the body forwards by bringing the plates on the un- 
 der surface of the body to act successively hke feet against the 
 ground.* Some worms and larvae of slow motion, extend a 
 part of their body forwards, and draw up the rest to overtake it ; 
 some performing this motion in a direct line, others in cin^ves. 
 
 When land animals swim in water, they are supported, be- 
 cause their whole weight, with the lungs expanded with air, is 
 less than that of an equal bulk of water. The head, however, 
 or a part of it, must be kept above water, to enable the animal to 
 breathe ; and to effect this, and also to make progress in the 
 water, the limbs are exerted in successive impulses against the 
 fluid. Q,uadrupeds and birds swim with less effort than man, 
 besause the weight of the head, which is carried above water, 
 is, in them, a smaller proportional part of the whole, than it is 
 in man. 
 
 Inertia. — In consequence of the action of gravity upon bod- 
 ies, tlieir inertia becomes a greater obstacle to locomotion than 
 it would otherwise be. Every body tends by its inertia to pre- 
 serve a state of rest, if it is still, and of uniform rectilinear mo- 
 tion, if it is not still. Changes, therefore, not only from rest 
 to motion, but also changes of direction and changes of speed, 
 are resisted by the force of inertia. Bodies moving upon the 
 earth's surface are obliged by their gravity to accommodate their 
 motions to the irregularities of this surface, and consequently 
 to change often both their direction and velocity. The inertia 
 thus becomes a continual source of expenditure of power, al- 
 though it would not be so, if bodies moved at a uniform rate 
 and in a straight course. 
 
 Aids to Locomotio7i. — All animals are provided by nature 
 with organs of locomotion best adapted to their structure and 
 situation ; and it is probable that no animal, man not being ex- 
 
 * Lectures on comparative Anatomy, vol. i. p. 116, &c. Sir E. Home deduces 
 this fact from the anatomy of the animal, and from the movements which he 
 perceived, in suffering a large coluber to crawl over his hand. The ribs appear- 
 ed to be raised, spread, carried forward, depressed and pushed backward, succes- 
 sively. 
 
ARTS OF LOCOMOTION. 197 
 
 cepted, can exeit his strength more advantageously by any oth- 
 er than the natural mode, in moving himself over the common 
 surface of the ground* TJms walking cars, velocipedes, 6cc., 
 although they may enable a man to increase his velocity in 
 favorable situations for a short time, yet they actually require 
 an increased expenditure of power, for the purpose of transport- 
 ing the machine made use of, in addition to the w^eight of the 
 body. When, however, a great additional load is to be trans- 
 ported with the body, a man, or animal, may derive much 
 assistance from mechanical arrangements. 
 
 Wheel Carriages. — For moving weights over the common 
 ground with its ordinary asperities and inequalities of substance 
 and structure, no piece of ineit mechanism is so favorably 
 adapted as the wheel carriage. It was introduced into use in 
 very early ages, as affording a facility for the carrying of hea- 
 vy loads, and tinally for transporting man himself; r ot by his 
 own powers, but by the strength of other animals which he 
 had subjugated to his use. . Chariots we;e used in war, and 
 wagons in agriculture, at a very remote period. 
 
 Wheels. — The mechanical action of wheels applied to loco- 
 motive carriages is twofold. They diminish friction, and also 
 surmount obstacles or inequalities of the road, with more ad- 
 vantage than bodies of any other form, in their place, could 
 do. The friction is diminished by transferring it from the sur- 
 face of the ground to the centre of the wheel, or rather to the 
 place of contact between the axletree and the box of the wheel. 
 So that it is lessened by the mechanical advantage of the le- 
 ver, in the proportion which the diameter of the axletree bears 
 to the diameter of the wheel. The rubbing surfaces also, be- 
 ing kept poUshed and smeared with some unctuous substance, 
 are in the best possible condition to resist friction. 
 
 In like manner, the common obstacles that present them- 
 selves in the public roads, are suimounted by a wheel with 
 peculiar faciliiy. As soon as the wheel strikes against a stone 
 
 * This remark of course does not apply to situations in which friction is ob- 
 viated, as upon water, ice, rail roads, &c. 
 
198 ARTS OF LOCOMOTION". 
 
 or similar hard body, it is converted into a lever for lifting the 
 load over the resisting- object. If an obstacle eight or ten inch- 
 es in height were presented to the body of a carriage unprovid- 
 ed with wheels, it would stop its progress, or subject it to such 
 violence as would endanger its safety. But by the action of a 
 wheel, the load is lifted, and its centre of gravity passes over 
 in the direction of an easy arc, the obstacle furnishing the ful- 
 crum on which the lever acts. 
 
 Rollers. — Rollers placed under a heavy body diminish the 
 friction in a greater degree than wheels, provided they are true 
 spheres or cylinders, without any axis on which they are con- 
 strained to move. If the rollers be perfectly elastic and also 
 the plane upon which they move, theie will be no sliding fric- 
 tion whatever ; whereas the wheel always rubs at its axis. 
 But an offset for this advantage is found in the circumstance, 
 that the wheel maintains its relative place in regard to the load, 
 while the roller constantly falls behind, and is obliged to be 
 taken up and replaced, at an expense of power. A cylindrical 
 roller likewise occasions friction, whenever its path deviates in 
 the least from a straight line. 
 
 Size of Wheels. — The mechanical advantages of a wheel 
 are proportionate toils size ; and the larger it is, the moie effec- 
 tually does it diminish the ordinary resistances. A large wheel 
 will surmount stones and similar obstacles better than a small 
 one, since the arm of ilie lever on which the force acts is lon- 
 ger, and the curve described by the centre of the load is the 
 arc of a larger circle, and of couise the ascent is more gradual 
 and easy.* 
 
 A further advantage is derived from the circumstance, that 
 in passing over holes, ruts, or excavations, a large wheel sinks 
 less than a small one, and consequently occasions less jolting 
 and expenditure of power. The wear also of small wheels 
 
 * If the plane on which a carriage moves, and the line of draught be both 
 horizontal, the advantage for surmounting an immoveable obstacle of a given 
 beicrht, is as the square root of the radius of the wheel. — See Playfair^s Out- 
 lines of Natural Philosophy, vol. i. p. 103. 
 
ARTS OF LOCOMOTION. 199 
 
 exceeds that of larger ones ; for if we suppose a wheel to be 
 three feet in diameter, it will turn round twice, while a wheel 
 six feet in diameter turns round once. Of course, its tire will 
 come twice as often in contact with the ground, and its spokes 
 will twice as often have to support the weight of the load- So 
 that by calculation, it should last but half the length of time. 
 On these accounts it would be advantageous to augment the 
 diameter of wheels to a great extent, were it not for certain 
 practical limits which it is not found useful to exceed. One of 
 these is found in the nature of the materials which we are 
 obliged to use, and which, if employed to make wheels of great 
 size, at the same time preserving the requisite strength, v»xuld 
 render them cumbersome and too heavy for use.* Another 
 reason for regulating the size of wheels by a limited standard 
 arises from the relative size of the animals commonly employed 
 for draught. A wheel should seldom be of such dimensions 
 that its centre would exceed in height the breast of the horse, 
 or other animal, by which it is drawn ; because if this were 
 the case, the horse would draw obliquely downward, as well 
 as forward, and expend a part of his strength in acting against 
 the ground. 
 
 Line of Traction. — In practice it is even found necessary 
 to place the point of draught or centre of the wheels lower than 
 the middle of the horse's breast, for various reasons. 1. The 
 shape of the animal's shoulders require this direction. 2. The 
 horse exerts a greater force in proportion as the line of draught 
 passes near the fulcrum, which is in his hind feet. 3. If a 
 horse draws obliquely upward, a part of his force is employed 
 in lessening the pressure en the ground, and to answer this 
 purpose most efrectuall}^, it has been remaiked that the inclina- 
 tion of the traces, or shafts, ought to be the same with that of 
 a road, upon which the carriage would just descend by its own 
 weight. t According to Dr Giegorv, a power which moves a 
 eliding body along a horizontal plane, acts with the greatest 
 
 • Sec the article Limit of Bulk, p. 48. 
 
 t Young's Natural Philosophy, vol. i. p. 216. 
 
200 ARTS OF LOCOMOTION. 
 
 advantage as far as friction is concerned, when the hne of di- 
 rection makes sin angle of about 18^ degrees with the plane,* 
 M. Deparcieux states from experiments with carriages, that the 
 angle made by the trace with a horizontal line, should be one 
 of 14 or 15 degrees. 4. Another reason for inchning the line 
 of draught, is, that a horse depresses his body in proportion to 
 the force he is obhged to exert, in order that he may bring his 
 own weight to act more advantageously upon the load. M. 
 Deparcieux has demonstrated that animals draw through the 
 medium of their weight, in all our common vehicles ; and this 
 fact becomes obvious when we consider, that if a horse had no 
 weight, he would be unable to draw, but would simply be 
 raised on his hind feet, by any exertion to advance while in 
 his harness. 
 
 In the foregoing considerations, it is necessary to recollect 
 that the conditions which enable a horse to exert his greatest 
 force, are not those which promote his greatest velocity, and 
 that the means of increasing his speed, are obtained, as in other 
 cases, by the sacrifice of power. 
 
 When there are four wheels, the line of draught ought to 
 be directed to a point between the two axletrees, or rather to a 
 point directly under the centre of gravity of the load, and such 
 a line should always pass above the axle of the fore wheels. 
 
 Broad Wheels. — Much controversy has existed in regard 
 to the comparative utility of wheels having a broad, or a nar- 
 row circumference. The disadvantages of broad wheels are, 
 that they are heavier than narrow ones, that they are more 
 expensive, and that they include in their path a greater num- 
 ber of stones or projecting obstacles. Their advantages are, 
 that they pass more easily over ruts and holes, and that in soft 
 and sandy roads they sink to a smaller depth, t But the great 
 
 * Treatise on Mechanics, vol. ii. p. 18. 
 
 t The latter advantage, however, is of a more equivocal kind than appears 
 at first view ; for although they sink less deeply, they displace more earth in 
 sinking to the same depth. Still, however, the advantage, upon calculation, 
 remains on the side of the broad wheel. 
 
ARTS OF LOCOMOTION. 201 
 
 benefit which results from broad wheels is of an indirect kind, 
 and arises from the improvement of the roads which takes 
 place under their use. They tend to prevent deep and narrow 
 ruts, and act as rollers in levelling the surface. 
 
 Form of Wheels. — If roads were in all cases level and 
 smooth, wheels should be made exactly cylindrical, or with all 
 their spokes parallel to the same plane. But since the unequal 
 surface of most roads exposes carriages to frequent and sudden 
 changes of position, it is found advantageous to make the 
 wheels a little conical, or, as it is commonly termed, dishing, 
 so that the spokes may all diverge with their extremities from 
 the carriage. In this case, whenever the carriage is thrown 
 into an inclined position, and the centre of gravity shifted to- 
 wards one wheel, the spokes on the under side of that wheel 
 become more nearly vertical, and are in a more advantageous 
 position to sustain the pressure. This will be seen in Fig. 1, 
 at the bottom of the page. In muddy roads there is a conve- 
 nience attending the dished wheel, in having its circumference 
 further from the body of the carriage, than that of a straight 
 wheel upon the same hubb * would be. Some disadvantages 
 at the same time attend upon this form of the wheel, the prin- 
 cipal of which is, the increase of friction which it occasions. 
 A conical wheel, if left to itself, tends to travel in a circle 
 round a point where the apex of the cone would be situated. 
 If it is obliged to advance in a straight line, it has a degree of 
 lateral motion and friction, which increases in proportion as it 
 deviates from the cylindrical form. In common cases, a slight 
 degree of the dishing form is best, but it should never be car- 
 ried to such an extent as to create much friction, or endanger 
 the bending of the spokes. F'i'g- 1- 
 
 In the opposite figure, A represents the 
 cylindrical, and B the dished form of the 
 wheel. 
 
 * This word, instead of nave, is so generally used in this country, that it 
 
 26 
 
203 ARTS OF LOCOMOTION. 
 
 Axletrees. — When wheels are perfectly upright, the ends of 
 the axles should be cylindrical ; but in dished wheels they are 
 made conical and inclined downward, so as to make their under 
 surface horizontal. In this case, the wheels spread most at top, 
 and the lower spokes are most nearly vertical. The ends of 
 the axletree are often inchned a little forward, which arrange- 
 ment causes the wheels to run inward, and prevents them from 
 pressing on the linch-pin. The friction, however, is increased. 
 In some locomotive carriages, the axle is fixed to both wheels, 
 and turns with them. This mode of connexion causes great 
 strain and friction, whenever the path is in any other than a 
 straight line, from the necessity, which is produced, that the 
 wheels should keep pace with each other in their revolu- 
 tions. 
 
 Springs. — The eifect of suspending a carriage on springs, 
 is to equalize the motion, by causing every change to be more 
 gradually communicated to it, and to obviate shocks by con- 
 verting percussion into pressure. Springs are not only useful 
 for the convenience of passengers, but they also diminish the 
 labor of draught ; for whenever a wheel strikes a stone, it rises 
 againsl the pressure of the spring, in many cases without ma- 
 terially disturbing the load ; whereas, without the spring, the 
 load, or a part of it, must rise with every jolt of the wheel, and 
 will resist this change of place with a degree of inertia piopoi- 
 tionate to the weight and the suddenness of the percussion. 
 Hence springs are highly useful in baggage waggons and other 
 vehicles used for heavy transportation.* 
 
 Attacliing of Horses. — Horses draw most advantageously 
 when they are either single, or harnessed abreast of each other. 
 When two horses draw side by side, they are equally near to 
 the load, and have the same line of traction. If their traces 
 are attached, as is frequently done, to hooks on the ends of a 
 crossbar, whicli in its turn is connected to the carriage by a 
 staple projecting behind, a compensation will be thus made 
 
 would be a useless refinement to avoid it. The same is true of the word factory 
 for manufactory, and also of many mechanical terms. 
 
 ♦ See a paper by Mr Gilbert, in Brande's Journal, vol. 19, 
 
ARTS OF LOCOMOTION. 
 
 203 
 
 for any difference in the strength or activity of the animals. 
 In Fig. 2, the centre E upon which the bar moves is consider- 
 ably behind the points of attachment, A and B. Hence, when 
 one end falls back, so that the arm A B assumes the position 
 C D, the foremost horse will have Fig. 2. 
 
 the disadvantage of acting by a 
 lever equal only to E F, while the 
 other horse acts by a lever equal _^t 
 to E C. In the na.rrow streets of ^' je f 
 
 cities, a custom has arisen of harnessing draught horses before 
 each other, in a single line, probably for the sake of room and 
 the convenience of the driver. But in this situation, only the 
 shaft horse has an advantageous hne of draught. The re- 
 maining horses draw nearly in a hori^.ontal line, and of course 
 at a disadvantage. Besides this, the foremost horses being at- 
 tached to the ends of the shafts, do not act directly upon the 
 load, but expend a part of their force in vertical pressure upon the 
 back of the shaft horse, which is increased in drays, sleds, and 
 all low carriages. This will be seen by inspecting Fig. 3, where 
 
 Fis. 3. 
 
 it is obvious that the line of draught of the first horse cannot 
 become direct, without crippling down the shaft horse. The 
 best mode of remedying this difficulty, would apparently be, to 
 attach the traces of the forward horse to a strong hook project- 
 ing downward horn the end of each shaft, so as to bring the 
 traces into the proper line of traction, by directing them more 
 nearly towards the centre of the wheels. It is true that the 
 shaft horse derives a certain degree of mechanical advantage 
 from vertical pressure, hke that which would result from an 
 increase of his weight. Yet this, although useful in short ex- 
 ertions, is not so when continued through a day's fatigue. 
 
204 ARTS OF LOCOMOTION. 
 
 HIGHWAYS. 
 
 Roads. — Roads intended for the passage of wheel carriages 
 are made more level and of harder materials, than the rest of 
 the ground. In roads, the travel on which does not authorize 
 great expense, natural materials alone are employed, of which, 
 the best are hard gravel and very small stones. The surface 
 of roads should be nearly flat, with gutters at the sides to facili- 
 tate the running off of water. If the surface is made too con- 
 vex, it throws the weight of the load unequally upon one 
 wheel, and also that of the horses on one side, whenever the 
 carriage takes the side of the road. Hence drivers prefer to 
 take the middle or top of the road, and by pursuing the same 
 track occasion deep ruts. The prevention of ruts is best effect- 
 ed by flat and solid roads, and by the use of broad wheels. It 
 would also be further effected if a greater variety could be in- 
 troduced in the width of carriages. Embankments at the 
 sides to keep the earth from shding down, are best made by 
 piling sods upon each other, like bricks, with the grassy sur- 
 face at right angles with the surface of the bank. But stone 
 walls are preferable for this purpose, when the material can 
 be readily obtained. 
 
 Pavements. — Pavements are stone coverings of the ground, 
 chiefly employed in populous cities and the most frequented 
 roads. Among us they are made of pebbles of a roundish 
 form, gathered from the sea beach. They should consist of 
 the hardest kinds of stone, such as granite, sienite, (fcc. If flat 
 stones are used, they require to be artificially roughened, to 
 give secure foothold to horses. In Milan, and some other pla- 
 ces, tracks for wheels are made of smooth stones, while the 
 rest of the way is paved with small or rough stones.* 
 
 The advantage of a good pavement consists not only in its 
 durability, but in the facility with which transportation on it is 
 
 * The streets of many of the ancient cities were paved, as those of Rome, 
 Pompeii, &c. But the streets of London were not paved in the eleventh centu- 
 ry, nor those of Paris in the twelfth. 
 
ARTS OF LOCOMOTION. 205 
 
 effected. Horses draw more easily on a pavement, than on a 
 connnon road, because no part of their power is lost in chang- 
 ing the form of the surface. The disadvantages of pavements 
 consist in their noise, and in the wear which they occasion of 
 the shoes of horses, and tires of wheels. They should never be 
 made of pebbles so large as to produce much jolting- by the 
 breadth of the interstices.* 
 
 McAdam Roads. — The system of road-making which takes 
 its name from Mr McAdara, combines the advantages of the 
 pavement and gravel road. The McAdam roads are made en- 
 tirely of hard stones, such as granite, flint, (fee, broken up with 
 hammers into small pieces not exceeding an inch in diameter. 
 These fragments are spread upon the ground to the depth of 
 from six to ten inches. At first, the roads thus made are heavy 
 and laborious to pass ; but in time, the stones become consolidat- 
 ed, and form a mass of great hardness, smoothness, and perma- 
 nency. The stones become partly pulverized by the action of 
 carriage wheels, and partly imbedded in the earth beneath them. 
 The consolidation seems to be owing to the angular shape of 
 the fragments, which prevents them from rolling in their beds, 
 after the insterstices between them are filled. Mr McAdam 
 advises that no other material should be added to the broken 
 stones, appai'ently with a view to prevent the use of clay and 
 chalk, which abound in England. It appears, however, that a 
 little clean gravel spread upon the stones, causes them to con- 
 solidate more quickly, and has the good effect of excluding the 
 light street dirt, which otherwise never fails to become incorpo- 
 rated in large quantities among the stones. 
 
 * Mr Telford has constructed in England, a kind of paved road, in which 
 the foundation consists of a pavement of rough stones and fragments, having 
 their points upward. These are covered with very small stone fragments and 
 gravel, for the depth of four inches, the whole of which, when rammed down and 
 consolidated, forms a hard, smooth, and durable road. 
 
206 • ARTS OF LOCOMOTION. 
 
 BRIDGES. 
 
 The construction of small bridges is a simple process, while 
 that of large ones, is, under certain circumstances, extremely 
 difficult, owing to the fact that the strength of materials does 
 not increase in proportion to their weight, and that there are 
 limits beyond which no structure of the kind could be carried, 
 and withstand its own gravity. Bridges differ in their construc- 
 tion, and in the materials of which they are composed. The 
 principal varieties are the following. 
 
 1. Wooden Bridges. — These, when built over shallow and 
 sluggish streams, are usually supported upon piles driven into 
 the mud, at short distances, or upon frames of timber. But in 
 deep and powerful currents it is necessary to support them on 
 strong stone piers and abutments, built at as great a distance as 
 practicable from each other. The bridge between these piers 
 consists of a stiff frame of carpentry, so constructed with refer- 
 ence to its material, that it may act as one piece, and may not 
 bend, or break, with its own weight and any additional load 
 to which it maybe exposed. When this frame is straight, the 
 upper part is co7npressed by the weight of the whole, while the 
 lower part is extended like the tie-beam of a roof. But the 
 strongest wooden bridges are made with curved ribs, which rise 
 above the abutments in the manner of an arch, and are not sub- 
 jected to a longitudinal strain by extension. These ribs are 
 commonly connected and strengthened with diagonal braces, 
 keys, bolts, and straps of iron. The flooring of the bridge may 
 be either laid above them, or suspended by trussing underneath 
 them. Wooden bridges are common in this countr}^, and 
 some of them are of large size. One of the most remarkable 
 is the upper Schuylkill bridge at Philadelphia, which consists 
 of a single arch, the span of which is 340 feet. 
 
 2. Stone Bridges. — These, for the most part, consist of 
 regular arches built upon stone piers constructed in the water, 
 or upon abutments at the banks. Above the arches is made a 
 
ARTS OP LOCOMOTION. 207 
 
 level or sloping road. From the nature of the material, these 
 are the most durable kind of bridges, and many are now stand- 
 ing which were built by the ancient Romans. Several of the 
 stone bridges across the Tliames, at London, are distinguished 
 for elegance and strength. The stone piers on which bridges 
 are supported, require to be of great solidity, especially when 
 exposed toiapid currents, or to floating ice. Piers are usually 
 built with their greatest length in the direction of the stream, 
 and with their extremities pointed or curved, so as to divide 
 the water, and allow it to glide easily past them. In building 
 piers, it is often necessary to exclude the water by means of a 
 coffer dam. This is a temporary inclosure, formed by a double 
 wall of piles and planks, having their interval filled with clay. 
 The interior space is made dry by pumping, and kept so till 
 the structure is finished. 
 
 3. Cast-iron Bridges. — These have been constructed in 
 England out of l^locks or frames of cast-iron, so shaped as to fit 
 into each other, and collectively to form ribs and arches. 
 These bridges possess great strength, but are liable to be dis- 
 turbed by the expansion and contraction of the metal Avith 
 heat and cold. 
 
 4. Suspension Bridges. — In these the flooring, or main 
 body of the bridge, is supported on strong iron chains, or rods, 
 hanging in the form of an inverted arch from one point of 
 support to another. The points of support are the tops of 
 strong pillars, or small towers, erected for the purpose. Over 
 these pillars the chain passes, and is attached at each extremity 
 of the bridge to rocks or massive frames of iron firmly secured 
 under ground. The great advantage of suspension bridges 
 consists in their stability of equilibrium, in consequence of which 
 a smaller amount of mateiials is necessary for their construc- 
 tion, than for that of any other bridge. If a suspension bridge 
 be shaken, or thrown out of equilibrium, it returns by its weight 
 to its proper place, whereas the reverse happens in bridges 
 which are built above the level of their supporters. One of 
 the most remarkable suspension bridges, is that over theMenai 
 
208 ARTS OP LOCOMOTION. 
 
 Strait, on the coast of Wales, the span of which, or rather the 
 water way, is 500 feet, and the distance between the points of 
 support, or centre of the piers, 560 feet. It is suspended by- 
 four wrought-iroQ cables, which pass over rollers on the tops of 
 the pillars, and are fixed to iron frames under ground which 
 are kept down by masonry. 
 
 5. Floating Bridges. — Upon deep and sluggish water, sta- 
 tionary rafts of timber are sometimes employed, extending 
 from one shore to another, and covered with planks, so as to 
 form a passable bridge. In military operations, temporary 
 bridges are often formed by planks laid upon boats, pontoons, 
 and other buoyant supporters. 
 
 RAIL ROADS. 
 
 In the best constructed public roads, a great amount of pow- 
 er is expended in overcoming the disadvantages which are in- 
 separable from their construction, and the nature of their mate- 
 rials. The chief loss of power depends on the continual change 
 of form which carriages occasion in roads, by the crushing of 
 stones, cutting of ruts, and other displacements of the material 
 of which the road is made ; which processes serve to consume 
 power, without forwarding the progress of the carriage. 
 
 The object of a rail road is to furnish a hard, smooth, and 
 unchanging surface for wheels to run upon. These surfaces, 
 in most cases, consist of parallel rails of iron, raised a little 
 above the general level of the ground, and liaving a gravelled 
 road between the rails, so that the rail road combines the ad- 
 vantages of good foothold for horses, and of smooth, hard sur- 
 faces for the wheels to roll upon. The wheels are made smooth 
 and true, and guides, to prevent them from slipping off, are 
 affixed either to the wheels or to the rails. 
 
 Rail roads are a modern invention, and their greatest im- 
 provements have been made within the present century. In 
 comparing the effect of a rail road with that of a common turn- 
 
ARTS OF LOCOMOTION. 
 
 209 
 
 pike road, a saving is made, according to Mr Tredgold,* of 
 seven eighths of the power, one horse on a rail road producing 
 as much effect as eight horses on a turnpike road. In the ef- 
 fect produced by a given power, tlie rail road is about a mean 
 between the turnpike road and a canal, when the rate is about 
 three miles per hour; but when greater speed is desirable, the 
 rail road may equal the canal in effect, and even greatly sur- 
 pass it. In the winter season, w^hen canals are liable to be 
 frozen, rail roads, if kept clear from snow and ice, may be al- 
 ways passable. 
 
 The earhest rail roads appear to have been constructed of 
 wood only. But at the present day iron is employed in all 
 rails from which durability is expected. In some cities tracks 
 of hewn stone are laid for wheels in the streets, but these are 
 seldom executed with sufficient accuracy to deserve the name 
 of railways. Of the iron rail road, there are three principal 
 varieties. 1. The Edge rail. 2. The Tram road. 3, The 
 Single rail. 
 
 Edge Railway. — In this species, which is now preferred to 
 all others, the rails are laid with the edge upward, and the 
 carriage is retained upon them by a. flange, or projecting edge, 
 attached to the wheels, instead of the rail. These rails, when 
 made of cast-iron, are commonly about three feet long, and 
 four or five inches deep in the middle, the outline being curv- 
 ed on the under side, to produce equality of strength. Fig. 
 4 represents a side view of a common cast-iron railway. The 
 ends of the rails are received in a piece of cast-iron, called a 
 
 Fig. 4. 
 
 chair, and these chairs are affixed to large blocks of stone, with 
 
 ♦ Treatise on Rail Roads and Carriages, p. 3. 
 
 27 
 
210 
 
 ARTS OF LOCOMOTION. 
 
 a broad base, called sleep- 
 ers, which are previously 
 placed in the ground upon 
 a proper level. Fig. 5 is a 
 section, or end view of the 
 rail road, together with the 
 wheels of a carriage, and 
 the flange which serves to 
 guide them. 
 
 Fig. 5. 
 
 Rails are now frequently made of wrought-iron with a form 
 nearly similar to that which has I een represented. As this 
 material is costly when employed alone, it is sometimes used 
 in thin bars as a covering to wooden rails, paiticularly in this 
 country where timber is plenty, and iron expensive.* Another 
 and a better method has been adopted of laying straight bars 
 of wrought-iron upon tracks of liammered granite. Wrought- 
 iron rails have the advantage of reducing the number of joints, 
 a circumstance which greatly increases the strength as well as 
 smoothness of the road. The comparative durability of 
 wrought, and of cast iron rails, is as yet not fully settled. 
 
 In the Liverpool and Manchester rail road, which is thirty 
 three miles in length, the rails are made of wrought-iron, their 
 shape being given them in a loUing-mill, by the method in- 
 troduced by Mr Birkinshaw. The shape of these rails is some- 
 what different from the common form, the upper edge being 
 considerably broader than the loM'er. 
 
 Tram Road. — Tram roads are flat rails, made usually of 
 cast-iron, with an elevated edge or flange, on one side, to guide 
 the wheels of carriages in their path. Tram rails are weaker 
 than edge rails, when made of the same amount of material, 
 and it is sometimes necessary to strengthen them with ribs un- 
 derneath. They are capable of being used for ordinary wheel 
 
 • The durability of this combination of wood and iron, remains to be settled 
 by longer experience. It must be greatly inferior to that of iron and stone. 
 
ARTS OF LOCOMOTION. 2il 
 
 carriages, but the introduction of wheels which are not perfect- 
 ly smooth, is always injurious to the road. Tram roads are 
 more liable to be covered with dirt than rails of other kinds. 
 
 Single Rail. — -Carriages may be made to run upon a sin- 
 gle rail, by elevating the rail from the ground, and suspending 
 the load beneath it. In Mr Palmer's railway, the rail is about 
 three feet above the surface of the ground, and is supported by 
 pillars placed at distances of about nine feet from each other. 
 The carriage consists of two receptacles, or boxes, suspended 
 one on each side of the rail by an iron frame, and having two 
 wheels placed one before the other. The rims of the wheels 
 are concave, and fit the convex surface of the rail ; and the cen- 
 tre of gravity of the carriage, whether loaded or empty, is so 
 far below the upper edge of the rail, that the receptacles hang 
 in equilibrium, and will bear a considerable inequality of load 
 without inconvenience, owing to the change of fulcrum allowed 
 by the breadth of the rail, which is about four inches. The 
 alleged advantages of the single rail are, that it is more fiee 
 from lateral friction than the other kinds of railway, and that 
 being higher from the ground, it is less liable to be covered 
 with dust and gravel ; and lastly, that it is more economical, 
 the construction of one rail being less expensive than of two.* 
 
 Passings. — When the amount of travel on a rail road is 
 very great, it becomes necessary that the road should be double, 
 one set of tracks being provided for carriages moving in each 
 direction. Where there is less travel, a single road is sufficient, 
 if it be provided with double places, called sidelings, for car- 
 riages to pass each other at convenient distances. But in both 
 cases the travelling is liable to be retarded by the difficulty 
 which exists, during a great part of the way, for carriages to 
 pass each other when moving in the same direction, those of 
 slow motion obstructing the progress of those which are in- 
 tended for greater speed. In order to obviate this difficulty, 
 and also to diminish the number of passing places, Mr Tread- 
 
 * A railway of this kind was invented, more than twenty years ago, by 
 Henry Sargent, Esq. of Boston. 
 
212 ARTS OF LOCOMOTION. 
 
 well proposes * to regulate the times of starting in both direc- 
 tions, and also the velocity of the faster and the slower car- 
 riages, by a uniform arrangement, so that they shall always move 
 in concert, and meet at the passing places at stated times, and 
 at no other times or places. By an easy calculation, the more 
 rapid vehicles may be so regulated as to overtake the slower 
 ones exactly at the passing places, and a coach moving at the 
 rate of nine miles an hour, may experience no hindrance from 
 a multitude of waggons moving with a third part of the ve- 
 locity. 
 
 When forks in a rail road occur, at the passing places, or 
 elsewhere, a part of the rails is rendered moveable, so as to di- 
 rect the wheels upon either track. When the railway crosses 
 a public road, it is made to pass at a lower level than the com- 
 mon surface, and is protected from carriage wheels by an ele- 
 vated edging of wood or stone ; but when the single rail crosses 
 a road, a part of it must be made to swing open Uke a turnpike 
 gate. Railways require to be kept as free as possible from dirt, 
 which greatly increases the resistance. Mr Palmer found upon 
 a tram road, that it required 19 per ceiit. more power to draw 
 the same carriages when the rails were slightly covered with 
 dust, than when they were swept clean. 
 
 Propelling Poiver. — Horses are extensively employed for 
 drawing loads upon railways, a horse being supposed capable 
 of drawing eight times as much as upon a common road. 
 hocomotive steam engines are now much employed upon 
 railways, particularly in England. They were at first made 
 to propel carriages by means of a toothed wheel, which acted 
 upon a rack attached to one of the rails ; but at the present 
 day, they are made to act by the friction only of the carriage 
 wheels upon the plain rail. These engines are alwa3rs made 
 of high pressure, since those of low pressure are rendered too 
 heavy by the weight of the water necessary for condensation. 
 Great improvements have lately been made in the construction 
 of locomotive eiigines, particularly by Messrs Brathwaite and 
 " Franklin Journal, vol. iv. p. 278. 
 
ARTS OF LOCOMOTION. 213 
 
 Ericsson, in consequence of which they have been enabled to 
 attain the extraordinary speed of thirty miles per hour. (See 
 Steam Engine.) 
 
 It has been proposed to place stationary engines at short dis- 
 tances, which should draw carriages forward from one to the 
 other by endless chains, thus saving the transportation of the 
 engines. Where the declivity of the road is great, loaded car- 
 riages sometimes descend by their own gravity, and at the 
 same time draw up the empty ones by means of pullies. To 
 prevent carriages from acquiring too great a velocity in descend- 
 ing, a crooked lever, called a brake or convoy, is applied to the 
 surface of the wheels, so as to retard them by itsfriction.* When 
 loaded carriages are transferred from one part of the road to 
 another of greater elevation, they are either drawn up an in- 
 clined plane with ropes, by horses, or stationary engines ; or 
 ihey ma)^ be hfted perpendicularly, by pullies. 
 
 CANALS. 
 
 Canals are artificial channels for water, cut for the purpose 
 of admitting inland navigation. The great utihty of canals 
 in facilitating transportation, has caused them to be constructed 
 in all ages. The canals of the ancients were chiefly made on 
 one level, so as to form merely artificial rivers, or creeks. Those 
 of the moderns, by means of locks, are carried indiscriminately 
 over ground which is depressed or elevated. In level tracks of 
 country, if the earth is of suitable character, canals are easily 
 made. But in loose and crumbling soils, in undulating, rocky, 
 and mountainous tracts, and in those which are intersected by 
 large streams, their construction becomes expensive and diffi- 
 cult. To surmount these difficulties, loose soils are defended 
 
 * A retarding friction is produced, when necessary, in mountainous countries, 
 upon common roads, by chaining one of the wheels, when the carriage goes 
 down hill, so as to prevent its turning. The same effect is produced in a safer 
 manner, by placing a wooden shoe like a runner, under one of the wheels. 
 
214 ARTS OF LOCOMOTION. 
 
 with firmer materials, vallies are passed by embankments, hills 
 are penetrated by deep cuttings or tunnels, rivers are crossed 
 with aqueducts, and declivities are ascended and descended by 
 locks. In order that water may not be wanting in any part of 
 the canal, a supply is insured at the highest level, and this 
 gradually passes off through the locks, to the lowest. The 
 streams which furnish the water at this, and other points, are 
 called feeders. 
 
 Eonhankments. — Canals are dug with sloping sides, to pre- 
 vent the banks from caving in. The boats being in almost 
 all cases drawn by horses, a firm, uninterrupted towing path is 
 fjrmed on one of the banks. The banks are liable, in time, to 
 become indented and washed away, by the constant agitation 
 of the water, occasioned by the passage of boats. To prevent 
 this, they are sometimes secured by driving close rows of stakes 
 against the banks ; but the onl}^ effectual protection is found 
 in walling the banks with stone. When the canal crosses a 
 section of country, the surface of which is lower than the in- 
 tended surface of the water, the canal is raised to the proper 
 level by means of etJibankments. These aje artificial banks, 
 or dykes, made of such materials as will not be liable to leak, 
 and of such form and strength that they will not be broken by 
 the pressure of the water. The surface of these banks is of a 
 sloping form, and is secured by sodding, and, in some instances, 
 by piles, or stone walls. Where the nature of the earth renders 
 leakage probable, it is common to cover the bottom and sides 
 of the canal with a lining of puddle, which is formed from 
 loam, or clay and grave!, worked up with water. For addi- 
 tional security, a trench is dug in each bank to a greater depth 
 than the bottom of the canal, and filled with puddle. 
 
 It sometimes happens that the embankments act as a dam, 
 to pi event the land on one side of the canal from being prop- 
 erly diained. In this case, culverts, or subterranean passages 
 are constructed underneath the canal, but not communicating 
 with it ; to effect the necessary draining. Culverts are made 
 of brick or stone, and require to be strong and tight. 
 
ARTS OF LOCOMOTION. 215 
 
 Aqueducts. — When a canal crosses a river, or a deep ravine, 
 it is supported at the proper level by an aqueduct. This 
 structure resembles a stone bridge, formed of strong piers and 
 arches, of regular n)asonry, rendered as tight as possible with 
 hydraulic cement. Upon the top, a level channel for the wa- 
 ter is formed. This is secured with strong and tight walls on 
 the sides, and hned within by a coating of clay. Room for 
 the towing path must be preserved, on one of the sides. In 
 England, aqueducts have sometimes been made of cast-iron. 
 
 Tunnels. — Tunnels are subterranean passages, most fre- 
 quently cut through the base of hills, to afford a level water 
 course for canals. Tunnels are also made for the passage of 
 railways, and, in some cases, of highway roads. Wi en they 
 are obliged to be cut through solid rock, which is done chiefly 
 by blasting, their formation is difficult, but they require no ar- 
 tificial security for their subsequent protection. But tunnels 
 which are made in soft earth, require to be arched over for 
 their whole length with stone or brick ; and in loose, springy 
 ground, the bottom likewise must be defended with an inverted 
 arch. That tunnels may be properly ventilated, especially 
 while digging, shafts or vertical passages are sunk at proper 
 distances, in which fires are kept burning to create a current 
 for discharging the foul air. One of the most remarkable tun- 
 nels is that at Worsley, on the Duke of Bridgewater's canal, 
 which with all its branches is estimated at eighteen miles in 
 length. 
 
 Gates and Weirs. — As all canals are hable to have their 
 banks broken through during violent rains and freshets, it is 
 important to lessen the injury which results from such acci- 
 dents, by retaining as much of the water in the canal as pos- 
 sible. To effect this object, safety gates and stop gaies are 
 placed at suitable distances from each other, on the canal, so 
 that by closing them at any time, in case of accident, the es- 
 cape of that part of the water which is beyond them, may be 
 prevented. These gates are sometimes attached to the sides, 
 and sometimes lie upon the bottom. 
 
216 ARTS OP LOCOMOTION. . 
 
 Certain parts of the banks called weirs, are made lower 
 than the rest, to discharge the superfluous water, and keep the 
 surface at a proper level. To prevent them from being gullied 
 or worn away by the attrition of the water, they are commonly 
 made of stone, or sometimes of wood. 
 
 Locks. — When a canal changes from one level lo another 
 of different elevation, the place where the change of level takes 
 place, is commanded by a lock. Locks are tight oblong in- 
 closures in the bed of the canal, furnished with gates at each 
 end, which separate the higher from the lower parts of the 
 canal. When a boat passes up the canal, the lower gates are 
 opened, and the boat glides into the lock, after which the lower 
 gates are shut. A sluice communicating with the upper part 
 of the canal is then opened, and the lock rapidly fills with wa- 
 ter, elevating the boat on its surface. When the lock is filled 
 to the highest water level, the upper gates are opened, and the 
 boat, being now on the level of the upper part of the canal, 
 passes on its way. The reverse of this process is performed 
 when the boat is descending the canal. 
 
 Locks are made of stone or brick, sometimes of wood. The 
 walls are sometimes erected upon an inverted arch, and also 
 upon piles, if the soil is alluvial, or loose. They are laid with 
 hydraulic cement, and rendered impervious to water. The 
 gates are commonly double, resembling folding doors, turning 
 upon coin posts which are next the walls. They meet each 
 other in most instances, at an obtuse angle, and the pressure 
 of the water serves to keep their contact more firm. The hy- 
 drostatic pressure in these cases, being in full force in a direc- 
 tion perpendicular to the surface of the gates, has a different 
 action from that of the pressure of gravity applied to a roof, or 
 similar structure, and gives to long gates a greater compara- 
 tive disadvantage than to short ones. Cast-iron gates are 
 sometimes used in England, curved in the form of a horizon- 
 tal arch, with their convex side opposed to the water. Valves 
 are small sliding shutters, which admit a stream of water for 
 the purpose of gradually filling or emptying the lock, to pre- 
 vent the shock of suddenly opening the gates. 
 
ARTS OF LOCOMOTION. 217 
 
 In situations where there is a scarcity of water, the waste 
 occasioned by frequently opening the gates for the passage of 
 boats, is too great for the amount supphed to the canal. In 
 these cases, to economize the water, reservoirs are provided at 
 different heights on each side of the lock. The water in the 
 upper parts of the lock is discharged into these reservoirs, and 
 only that in the lower parts is suffered to escape into the lower 
 canal. Afterwards, the water in these reservoirs is used to fill 
 again the lower parts of the lock, and thus the same water is 
 made use of a second time. 
 
 In China, where inland navigation is much practised, it is 
 said there are no locks, but boats are transferred from one level 
 to another, by means of inclined planes. This method is 
 sometimes practised in Europe, and it had a zealous advocate 
 in the late Mr Fulton. To effect this transfer most advanta- 
 geously, two boats passing in opposite directions, are connected 
 together by a chain passing over a puUy. One boat in de- 
 scending the plane assists by its weight to draw the other up- 
 ward. Sometimes, instead of inclined planes, perpendicular 
 lifts have been proposed, by which the boats are hoisted direct- 
 ly by puUies from one level to another, or lowered in the op- 
 posite direction by the same means. The objection to all these 
 modes exists in the strain to which the boats are exposed, un- 
 supported by the pressure of the water. Various expedients 
 have been proposed for altering the level of the water, and trans- 
 ferring boats, by means of large phmgers, diving chests, &c. ; but 
 none of them, as yet, appear to have been approved in practice.* 
 
 Boats. — Canal boats are made narrow, for passing each 
 other, and draw water proportioned to the depth of the canal. 
 Their length is limited only by that of the locks. They are 
 drawn by horses on the tow path, Fig. 6. 
 
 being kept by the rudder from 
 coming in contact with the bank. 
 No species of oars, poles, or pad- 
 
 * Repertory of Arts, vol. i. ii. and xxiii. 
 28 
 
218 ARTS OF LOCOMOTION. 
 
 die wheels are allowed, on account of the injury done to the 
 bottoms and banks, by their use. It is said, however, that the 
 steam engine has in some cases been used without injury to 
 the canal, by causing the paddle wheels to work in a water 
 passage, or cusing. which passes through the boat above its 
 bottom. 
 
 Size of Canals. — Canals differ greatly from each other, not 
 only in their length, but tlieir size, and the draught of water 
 which they admit. One of the largest canals, as far as the 
 volume of water is concerned, is the Great Dutch canal which 
 connects the city of Amsterdam with the Helder, on the north 
 coast of Holland. This canal is 50 miles in length, 124 feet 
 in width, at the surface of the water, 36 feet wide at bottom, 
 and about 21 feet deep. It is large enough to permit one frig- 
 ate to pass another. The Caledonian canal extends from the 
 Murray Frith, on the eastern coast of Scotland, to Lonh Eil, 
 on the western, and admits of the passage of large ships. It 
 is 120 feet wide at the water surface, and .50 wide at bottom. 
 The deptli of water is 20 feet. The distance from sea to sea 
 is about 59 miles, of which 37^ is lake navigation, and 21^ is 
 cut.* The canal of Languedoc, in France, is 64 leagues in 
 length, and connects the Atlantic ocean with the Mediterranean 
 sea. It is 64 feet wide at the surface, and navigable for vessels 
 of 100 tons. The great New York, or Erie Canal, is 360 
 miles long, and extends from the Hudson River, at Albany, to 
 Lake Erie, at Buffalo. It is 40 feet wide at the surface, 2S 
 feet wide at bottom, and has four feet depth of water. 
 
 SAILING, 
 
 Form of a Ship. — The movement of bodies through water, 
 if performed within certain limits of velocity, is attended with 
 less resistance than that which takes place in most other modes 
 of transportation. A body, however, of given size will encoun- 
 ter a greater or less resistance from the water, according to its 
 
 * Supplement to the Encyclopedia Britanaica, and Edinburgh Encyclopedia. 
 
ARTS OF LOCOMOTION. 
 
 219 
 
 proportions, and the sort of surface which it opposes to the 
 fluid. In calculating the proper form for a ship, it is necessa- 
 ry to consider the kinds of pressure to which bodies moving in 
 fluids are subject. If we suppose an oblong square box, or 
 parallelopiped, as A B C D, Fig. 7. 
 
 in Fig. 7, to move through ^.. - ^- -B 
 
 the water in the direction of q. .„...-—-"" 
 its length, the pressure will be ""••-,.. 
 
 ■ 'JM 
 
 increased before, and dimin- ^ J^ 
 
 ished behind it, the surface of the water being elevated at the 
 anterior extremity, and depressed at, the posterior ; an effect 
 which increases in a high ratio as the velocity becomes great- 
 er. The principal part of the water which is before the mov- 
 ing body, divides and passes off by the sides ; but a certain 
 quantity of what is called dead icate?', is pushed along in ad- 
 vance of the moving body, nearly in the same manner as if it 
 were a part of the body itself. The shape of this dead water 
 at the surface, is found to be that of an irregular triangle, and 
 hence it becomes advantageous to add to the moving body aa 
 extremity, or how, having nearly the same.shape as the dead 
 water, and occupying its place, as in the dotted line BED. 
 On the other hand, there occurs behind the moving body a 
 depression of surface, and a partially empty space, which is also 
 of a triangular or wedge form, consisting of the room which 
 the moving body has just left, and into which the water upon 
 each side has not yet flowed. The cavity which is thus form- 
 ed, resists the progress of the body by its negative pressure^ 
 Its effect is readily understood, when we consider that if the 
 water before the moving body be raised one foot, while the 
 water behind it is depressed one foot, the difference of pressure 
 upon the two extremities will be equal to that resulting from 
 two feet. On this account it is advantageous to add to the 
 moving body a tapering or wedge-shaped extremity behind, 
 capable of occupying this cavity, and nearly answering to it in 
 shape, as represented by the dotted line AGO. The con- 
 sequence will be, that the water, which is advancing from botla 
 
220 
 
 ARTS OF LOCOMOTION. 
 
 sides to fill up the vacuity, will meet the tapering sides of the 
 vessel soon enough to obviate or greatly diminish the negative 
 pressure. The form produced by this general outhne, varied 
 by a proper curvature of the sides and bottom, corresponds near- 
 ly to that which is adopted in the construction of ships, and 
 also to that pursued by nature in the structure of fishes. If a 
 vessel be intended for a fast sailer, its proportionate length and 
 its sharpness before and behind, must be increased, since both 
 the positive and negative pressure, and the extent of the dead 
 water and vacant space, will increase with the velocity. 
 
 Keel and Rudder. — -The use of the keel, which is a project- 
 ing timber, extending the whole length of the ship's bottom, is 
 to assist in confining the motion of the ship to its proper direc- 
 tion, and by its lateral resistance, to diminish the disposition to 
 roll or vibrate from side to side. The rudder, which is a per- 
 pendicular part attached by braces resembling hinges, to the 
 stern post of the vessel, serves to govern the ship's course, by 
 altering the relative resistance of its two sides. Thus, while 
 the ship is under way, if the rudder is turned to one side, it re- 
 ceives an impulse from the water on that side, causing the 
 stern to turn towards the opposite side, where no such resistance 
 exists, thus altering the direction of the keel, and the general 
 course of the vessel. 
 
 Effect of the Wind. — When a ship sails in the same direc- 
 tion as the wind, she is said to be scudding., or sailing before 
 the wind, and if she had but one sail, it would act with the 
 greatest advantage, when perpendicular, or nearly so, to the 
 wind. 
 
 When a ship advances against the wind, and endeavors to 
 proceed in the nearest direction possible to the point of com- 
 pass from which the wind blows, she is said to be close hauled. 
 A large ship will sail against the wind with her keel at an an- 
 gle of six points, with the direction of the wind, and sloops and 
 smaller vessels may sail much nearer. When a ship is nei- 
 ther sailing before the wind, nor close hauled, she is said to be 
 sailing large. In this case, her sails are set in an oblique 
 
ARTS OF LOCOMOTION. 221 
 
 position, between tlie direction of the wind and that of the 
 intended course ; as represented in the various plans of vessels 
 in Fig. 8, where the direction of the wind is represented by the 
 
 Fig. 8. 
 
 arrow, and the position of the yards and sails, which is neces- 
 sary for proceeding on the various points of compass, is shown 
 by the transverse lines on each plan. The relation of the wind 
 to the course of the vessel is determined by the number of 
 points of the compass between the comse she is steering, and 
 the course which she would be steering, if close hauled. In 
 Fig. 8, the ships a and h are close hauled, and the ships c 
 and d, the former steering east by north, and the latter west 
 by north, have the wind one point large. The ships e and/, 
 one steering east, and the other west, have the wind two points 
 large. In this case, the wind is at right angles with the keel, 
 apd is said to be upon the beam. The ships g and A, steer- 
 
222 ARTS OF LOCOMOTION. 
 
 ing southeast, and southwest, have the wind six points large, 
 or, as it is commonly termed, upon the quarter, and this is 
 considered as a very favorable manner of sailing, because all the 
 sails cooperate to increase the ship's velocity, whereas when the 
 wind is directly aft, as in the vessel m, it is partl}^ intercepted 
 by the after sails, and prevented from striking with its full force 
 on those which are forward. The force of a wind which strikes 
 obliquely upon the sails, supposing them flat surfaces, is resolv- 
 able into two forces, one of which tends to push the vessel 
 ahead, and the other to push her sideways. If the form of the 
 vessel, instead of being oblong, were circular, like a tub, she 
 would move in the direction of the diagonal of a rectangle, 
 representing these two forces, and her course would be at right 
 angles with the position of the sail, or in the direction of the 
 line A B, in Fig. 9. But, owing to the oblong shape of the 
 vessel, and the influence of her keel, it requires about twelve 
 times as much force to push her sideways, as to push her head 
 foremost.* The oblique impulse, therefore, will carry her a 
 great distance forward, in the time that she is drifting a short 
 distance to the leeward, and it is this relative difference of pro- 
 gress which enables a vessel to advance even against the wind. 
 The angular deviation of a ship's real course from her apparent 
 course upon which her head is directed, is called the leeway. 
 In the vessel. Fig. 9, with the wind 
 blowing in the direction of the arrows, 
 and the sails set as represented, if the 
 vessel were moving in a railway, or un- 
 changeable channel, her course would 
 be B D ; but in the water she drifts so 
 much to the leeward, that her real 
 course is B C, and the angle C B D represents the amount of 
 leeway. 
 
 Stability of a Ship. — The masts of a ship, when acted 
 upon by the pressure of the wind against the sails, are so many 
 
 * Robinson's Mechanical Philosophy, vol. iv. p. 620. 
 
ARTS OF LOCOMOTION. 223 
 
 levers, the tendency of which, is, to overset her. To coun- 
 teract this tendency, a sufficient weight of ballast, or cargo, is 
 stowed in the bottom of the hold, to carry the centre of gravity 
 into the lower part of the hull, so that this part will always 
 preponderate, while the relative buoyancy of the upper part 
 causes the vessel to right, as often as her position is disturbed. 
 If the ballast is too light, or is stowed too high in the hold, 
 the vessel is said to be too cranky and rolls more, and cannot 
 carry so much sail without danger of oversetting. On the 
 other hand, if the ballast is too heavy, and placed too low, the 
 vessel is said to be too stiff, and not only draws so nmch wa- 
 ter as to impede her velocity, but is liable to have her masts 
 endangered by the shocks which result from the suddenness 
 of her motions. In regard to shape, an increase of the width 
 of a ship increases her stabihty, but at the same time detracts 
 from her power as a fast sailer. 
 
 Steam Boats. — Experiments on the propulsion of vessels 
 by steam, were made in Europe, and this countiy, at different 
 times during the last century ; but the first successful introduc- 
 tion of steam navigation on a large scale, was made in America 
 by the late Mr Fulton, about the year 1807. The application 
 of the steam engine to navigation, has given to vessels the ad- 
 vantage of greater speed and regularity in the performance of 
 their passages, without interruption from the changeable, and 
 often adverse, operation of the elements. In the action of the 
 steam engine, as in that of rowing, a vessel is propelled by a 
 succession of impulses, which act against the inertia of the 
 water. 
 
 A power acting within a boat, whether of men, of horses, or 
 of steam, may be applied to the water in various ways. Some 
 of the piincipal of these, are the following. 1. A system of 
 oars or paddles have been made to act with alteinating strokes, 
 rising out of water at the end of each stroke. 2. An alter- 
 nating paddle has been contrived, which is continually immers- 
 ed, and which folds up like the foot of a water-fowl, during the 
 backward stroke. 3. It has been proposed to drive a current 
 
224 
 
 ARTS OF LOCOMOTION. 
 
 of air, or a current of water, out at the stern of the vessel. 4. 
 Spiral wheels and water screws, or wheels with oblique vanes, 
 like those of a windmill, have been made to turn under water, 
 with their axes parallel to the keel of the vessel. 5. Oblique 
 planes acting with an alternate, instead of a revolving stroke, 
 were recommended by Bernoulli. 6. Paddle wheels. These, 
 from their simplicity and advantageous mode of action, have in 
 common use superseded all the rest. They consist of paddles 
 or float-boards attached to the arms, or spokes, of a wheel, the 
 axis of which is at right angles with the keel. Their common 
 place is on the sides of the boat, as in the annexed figure. 
 Fig. 10. 
 
 The outline of the float-boards, or paddles, is commonly rec- 
 tangular, though Mr Tredgold recommends that their outer 
 extremity should be pai abolic. The best position for the pad- 
 dles is in a plane passing thiough the axis of the wheels, but 
 with this position they strike the water obUquely in entering, 
 and lift a considerable quantity on quitting it ; both of which 
 motions occasion loss of power. Attempts have been made to 
 correct this disadvantage by various mechanical arrangements, 
 in which the paddles are made to enter and leave the water 
 perpendicularly ; but want of simplicity, and objections of vari- 
 ous other kinds, have prevented them from coming into use. 
 It has been proposed to fix a series of paddles upon longitudi- 
 nal chains, passing round wheels, and parallel to each side of 
 the vessel. By this mode a number of perpendicular paddles 
 would act upon the water at once ; but it will be seen, that as 
 no more of these paddles can operate usefully, than are suffi- 
 
ARTS OF LOCOMOTION. 225 
 
 cient to put the water between them into motion, a part of the 
 series will be less useful than if it acted upon water at rest. In 
 wheels of the common form, it is advantageous to have a dou- 
 ble row of paddles, one outside the other, and so placed that the 
 paddles of one series shall be opposite the intervals of the other, 
 and thus enter the water successively, and in different places.* 
 In Perkins' propelling wheel the paddles are placed oblique- 
 ly in regard to the axis of the wheel, and the wheel itself is 
 placed obliquely in regard to the keel of the boat. This 
 arrangement is such that the paddles enter and leave the 
 water obliquely, but at the time of their greatest immersion 
 they are at right angles with the keel, and in the most favor- 
 able position for propelling the boat. 
 
 Steam-boats are best adapted to the navigation of rivers and 
 straits, or sounds, where the water is comparatively smooth. 
 They are also used in the open sea ; but the violence of the 
 waves renders the action of the paddle wheels irregular, and it 
 is found difficult for them to carry fuel sufficient to supply the 
 engine during long voyages. These obstacles, however, have 
 been in part surmounted, and steam-boats now ply along the 
 coasts both of America and Europe. The steam-ship Savan- 
 nah crossed the Atlantic, in 1819, and was 21 days from land 
 to land, during IS of which she was able to use her engine. 
 
 DIVING BELL. 
 
 The diving bell is an inverted vessel, containing air, and 
 used for the purpose of enabhng persons to descend with safe- 
 ty to great depths imder water. It is made tight at the top 
 and sides, but is entirely open at bottom. Its principle is the 
 same with that of a gasometer, and may be famiharly illustra- 
 
 * For examinations of the different propelling powers, see the Edinburgh 
 Encyclopedia, article ' Navigation Inland,' ascribed to Mr Telford; also 
 Tredgold on the Steam Engine, p. 309. 
 
 29 
 
226 ARTS OF LOCOMOTION. 
 
 ted by immersing an inverted tumbler in a vessel of water. 
 The air cannot escape from the inside of tlie vessel, being 
 necessitated, by the order of specific gravities, to occupy the up- 
 per part of the cavity. 
 
 Diving bells appear to have been first introduced in the be- 
 ginning of the sixteenth century. They were first known as 
 objects of curiosity only, but have been since applied to the re- 
 covery of valuable articles from wrecks, the blasting and min- 
 ing of rocks at the bottom of the sea, and the practice of sub- 
 marine architecture. They may be made of almost any shape, 
 but the common form has been that of a bell, or hollow cone, 
 made of wooden staves, and strongly bound with hoops, having 
 seats for the occupants on the inside. It is suspended with 
 ropes from a vessel above, and is ballasted with heavy weights 
 at bottom, which serve to sink it, and to prevent it from turning 
 over. More recently diving bells have been made of cast iron. 
 The kind of bell used at Howth, near Dublin,* is an oblong 
 iron chest, six feet long, four broad, and five high, thicker at 
 bottom than at top, and weighing four tons. It has a seat at 
 each end, .and is capable of holding four persons. The upper 
 part is pierced with eight or ten holes, in which are fixed the 
 same number of strong convex glasses, which transmit the light. 
 As the air in the bell becomes contaminated by breathing, it is 
 renewed by letting down barrels, or small bells, of fresh air, 
 which is transferred to the large bell ; or else by keeping up 
 a constant supply through a pipe, by means of a forcing pump, 
 which is worked by men at the surface. 
 
 Persons who descend in diving bells, often experience a pain 
 in the ears, and a sense of pressure, occasioned by the con- 
 densation of the air within the cavity of the bell. These symp- 
 toms gradually pass off, or habit renders the body indifferent 
 to them, so that workmen remain under water, at the depth of 
 twenty feet or more, for seven or eight hours in a day, without 
 detriment to the health. 
 
 Submarine Navigation. — A machine was invented during 
 
 * Edinburgh Philosophical Journal, vol. v. p. 8. 
 
ARTS OP LOCOMOTION. 227 
 
 the American revolution, by Mr Bushnell, of Connecticut, which 
 was capable of containing a person in safety under water, and 
 of being governed and steered in any direction at pleasure. It 
 is described * as being a hollow vessel of a spheroidal form, 
 composed of curved pieces of oak, fitted together and bound 
 with iron hoops, the seams being caulked and covered with tar 
 to render them tight. A top or head, was closely fitted to the 
 vessel, and served the purpose of a door. In this were insert- 
 ed several strong pieces of glass, to admit the light. The ma- 
 chine contained air enough to render it buoyant, and to support 
 respiration. A quantity of lead was attached to the bottom for 
 ballast. The vessel was made to sink by admitting water, and 
 to rise, by detaching a part of the leaden ballast, or by expel- 
 ling water with a forcing pump. It was propelled horizontally 
 by means of revolving oars placed obliquely like the sails of a 
 windmill, on an axis which entered the boat through a tight 
 collar, or water-joint, and was turned with a crank within. A 
 rudder was also employed for steering the vessel. When fresh 
 air was required, the vessel rose to the surface, and took in air 
 through apertures at the top. The intention of this machine 
 was to convey a magazine of powder under ships of war for the 
 purpose of blowing them up. Several experiments were made 
 with it, which, though unsuccessful in their object, nevertheless 
 proved the practicability of this species of locomotion. 
 
 The late Mr Fulton made various experiments on subma- 
 rine navigation, in a boat large enough to contain several per- 
 sons, furnished with masts and sails, so as to be capable of pro- 
 ceeding at the surface of the water, and also of plunging, when 
 required, below the surface.t While under water, its motions 
 were governed by two machines, one of which caused it to ad- 
 vance horizontally, while the other regulated its ascent and 
 descent, its depth below the surface being known by the pres- 
 sure on a barometer. A supply of fresh air was carried down 
 in the boat, condensed into a strong copper globe, by which 
 
 ♦ Silliman's Journal, vol. ii. p. 94. 
 
 t See Colden's Life of Fulton, 8vo. New York, 1810. 
 
228 
 
 ARTS OF LOCOMOTION. 
 
 the air of the boat was replaced when it became unfit for res- 
 piration. Mr Fulton's object was the destruction of ships of 
 war, by bringing underneath them an explosive engine, called a 
 torpedo. 
 
 AEROSTATION. 
 
 Balloon. — A Balloon is a sphere, or bag, formed of some 
 light material, such as silk, and rendered impervious to the 
 air, hy covering it with elastic varnish. It is filled with a gas- 
 eous fluid, lighter than the surrounding atmospheric air, and 
 has a car suspended at the bottom. If the specific gravity of 
 the whole mass is less than that of an equal bulk of the atmos- 
 pheric air which surrounds it, the balloon will ascend into the 
 atmosphere, and remain suspended, until, by the escape of its 
 gas, or other means, it becomes heavier than the surrounding 
 air, when it will again descend. Balloons were invented in 
 France, by the Montgolfiers, about 1782. Those which were 
 first employed by them were filled with common air rarefied by 
 heat ; but these required that a fire should be constantly kept 
 burning beneath them, to keep them afloat. Hydrogen gas 
 was afterwards employed ; and this fluid, being permanently 
 about fourteen times less dense than common air, is undoubted- 
 ly the best material for aerostation. Carburetted hydrogen, 
 though heavier than hydrogen, has also been employed of late, 
 on account of its cheapness, being furnished in large quantities 
 at the manufactories of illuminating gas. 
 
 Balloons are made by sewing together pieces of silk, the 
 shape of which corresponds to that of the part included by two 
 meridians of the artificial globe. They have also been made 
 of linen and of paper. They are varnished with a solution of 
 elastic gum, to render them tight. A net-work is thrown over 
 the top of the balloon, to which is attached, by strings, a car of 
 wicker-work, underneath the balloon. The whole is kept 
 down by a sufficient quantity of ballast, and ascends into the 
 
ARTS OF LOCOMOTION. 229 
 
 atmosphere, when a part of the ballast is thrown over. It is 
 made to descend again by suffering a part of the gas to escape 
 through a valve provided for the purpose. 
 
 The regtdation of the ascent and descent of balloons, is the 
 extent of control, which has been hitherto obtained over them. 
 All attempts to guide or propel them, by means of wings, sails, 
 oars, &c., have hitherto failed, and the machine can only pro- 
 ceed at the mercy of the winds. The small degree of buoy- 
 ancy which balloons possess, does not permit them to carry suf- 
 ficient weight of material, to furnish the medium of an adequate 
 propeUing force. By taking advantage, however, of favorable 
 winds, voyages have been made in them to the distance of 300 
 miles ; and persons have ascended to the height of 20,000 feet 
 and upwards. The velocity of balloons varies with that of 
 the wind, but has in some instances amounted to the rate of 
 70 miles an hour.* 
 
 Parachute. — The danger which attends falHng from great 
 heights, is in consequence of the continual acceleration of ve- 
 locity which falling bodies experience. When, however, the 
 resistance of the atmosphere becomes equal to the force of grav- 
 ity, the motion is no longer accelerated, but becomes uniform. 
 A parachute is an appendage to a balloon, formed somewhat 
 like an umbrella, and is designed to break the force of a fall, by 
 means of the large surface which it opposes, in its progress, to 
 the atmosphere. It is made of silk, or canvass, and is placed 
 underneath the balloon, having the car suspended from it by 
 cords. When the balloon is at any height in the air, the par- 
 achute may be detached from it, and will immediately fall with 
 the car to the ground. But the resistance of so large a surface 
 to the atmosphere, causes the fall to be gradual and easy, so 
 that a person may descend with a parachute in safety from the 
 greatest heights. The size of the parachute employed by M. 
 
 * M. Gay-Lussac, on the 6th of September, 1804, ascended 23,100 feet 
 above Paris. M. Garnerin, September 21st, 1827, passed, in seven hours and 
 a half, from Paris to Mount Tonnere, a distance of 300 miles. This voyage 
 was performed in the night, and during a storm. 
 
230 ARTS OF LOCOMOTION. 
 
 Garnerin, and with which he descended from a height of 2000 
 feet, at Paris, in 1797, was 25 feet in diameter. The par- 
 achute was folded up at the beginning of the fall, but soon ex- 
 panded itself by the resistance of the atmosphere. The only 
 inconvenience which was experienced, arose from a violent os- 
 cillating motion. 
 
 Brewster's Edition of Ferguson's Lectures on Mechanics, &c. 2 
 vols. 8vo. 1823 ; — Anstice on Wheel Carriages ; — Edgeworth on 
 Roads and Carriages, 8vo. ; — Deparcieux sur le tirage des chevaux, in 
 the Mem. de VAcad. Paris, 1760 ; — Young's Lectures on Natural Phi- 
 losophy ; — McAdam, on roads, 8vo. 1823 ; — Tredgold, on Rail Roads, 
 8vo. 1825 ; — Wood, on Rail Roads, 8vo. 1825 ; — Strickland's Re- 
 ports on Canals, Rail Roads, &c., oblong fol. Philad. 1820 ; — Article Ca- 
 nal, in Rees' Cyclopedia, written by Mr J. Farey; — Articles Naviga- 
 tion Inland, Railway, Bridges, Aeronautics, &c., in the Edinburgh En- 
 cyclopedia ; — Chapman on Canal Navigation, 4to. 1797 ; — Fulton on 
 Canal Navigation, 4to. 1796 ; — Smeaton's Reports, 3 vols. 8vo. 1812 ; 
 — Pront, Architecture Hydraulique, 2 torn. 4to. 1790 ; — Belidor, Archi- 
 tecture Hydraulique, 4 torn. 4to. 1750; — De Cessart, Travaux Hy- 
 drauliques, 2 torn. 4to. 1808 ; — Reports to the House of Commons on 
 Roads, Steam-Boats, &c., 1822, &c. ; — Article Seamanship, in the En- 
 cyclopedia Britannica, by Prof. Robinson ; — Dupin, Voyage dans la 
 Grand Bretange, 6 vols. 8vo. with plates, fol. 1825. 
 
CHAPTER XL 
 
 ELEMENTS OF MACHINERY. 
 
 Machines. — By a machine, may be understood a combina- 
 tion of mechanical powers, adapted to vary the direction, appH- 
 cation, and intensity, of a moving force, so as to produce a 
 given result. The advantage which machines possess over 
 common manual labor, is generally that of increasing or im- 
 proving the product of an operation. This end they accom- 
 plish, by enabling us to apply a common force more advanta- 
 geously, or to employ the most powerful force derived from 
 natural agents, with precision and efficacy. By the aid of 
 machinery any number of instruments, or operative parts, may 
 be made to move in concert, in every possible direction, with 
 any degree of velocity ; and to reciprocate with each other in 
 perfect harmony, so that complex operations are performed by 
 them, with a precision which often exceeds the skill of the 
 most expert artist. 
 
 Motion. — The motion which takes place in machines is for 
 the most part, either rotary or reciprocating. A rotary motion 
 is that in which the moving parts revolve round an axis, as in 
 a wheel, a crank, or a fly. A reciprocating or alternate motion 
 is that in which a body retraces its own path, or moves alter- 
 nately backward and forward in the same track, which may 
 be curved, as in the beam of a steam engine, or rectilinear, as 
 in the piston. Most compound machines possess both these 
 kinds of motion, or varieties deiived from them ; and the dif- 
 ferent ways of producing and communicating them, in the re- 
 quisite times and places, constitute a principal subject of atten- 
 tion with machinists. 
 
232 
 
 ELEMENTS OF MACHINERY. 
 
 ROTARY, OR CIRCULAR MOTION. 
 
 When it is intended that one wheel or axle shall propel 
 another, various contrivances are adopted to connect the pro- 
 pelling part with that which is to be moved. The mode of 
 connexion is varied according to the distance, the relative ve- 
 locity required, and the direction in which motion is to be 
 communicated. 
 
 Band Wheels. — If two wheels be connected by a belt, or 
 band, passing round their circumferences, they will move 
 simultaneously, provided the friction of the band is sufficient 
 to prevent it from slipping. When a round cord is used, any 
 degree of friction may be produced by receiving the cord in a 
 sharp groove, at the edge of the wheel. But the stiffness of 
 cords forms, in many cases, an objection to their use. When 
 a strap, or flat band, is used, its friction may be in- Fig. 1. 
 creased by increasing its width. The surface at 
 the circumference of a wheel, or drum, which car- 
 ries a flat band, should not be exactly cylindrical, but 
 a little convex ; in which case, if the band inchnes 
 to slip off at either side, it returns again by the 
 tightening of its inner edge, as may be seen in a 
 turner's lathe. When wheels are connected in the 
 shortest manner by a band, as in Fig. 1, they 
 move in the same direction. If the band be cross- 
 ed, as in Fig. 2, they will move in opposite direc- 
 tions. Wheels, whose axes are situated in different 
 planes, may turn each other, if the band be suffi- 
 ciently long. If no slipping were to take place in 
 the band, wheels of equal size would move with 
 equal velocity, and those of different sizes, with ve- 
 locities inversely proportionate to their respective 
 circumferences. But since the band is liable to 
 yield or shde somewhat during the revolution, the 
 velocity of the driven wheel is commonly a little less in propor- 
 tion, than that of the wheel which drives it. 
 
 Fig. 2. 
 
ELEMENTS OP MACHINERY. 233 
 
 Rag Wheels. — Where it is necessary that the velocities 
 should be exactly proportionate, also where great resistance is 
 to be overcome, chains of various kinds are substituted, by 
 passing them round wheels, in the place of belts and ropes. 
 These chains lay hold upon pins, or enter into notches on the 
 circumference of the wheels, Fig. 3. 
 
 so as to cause them to turn si- 
 multaneously. Such wheels 
 are denominated rag wheels, 
 and have a^uniform relative 
 velocity. Fig. 3. They are 
 used in locomotive steam engines, chain water wheels, &c. 
 
 Toothed Wheels. — Toothed wheels afford a more regular 
 and effectual mode of communicating rotary motion than any 
 other kind of connecting mechanism. They move of necessity 
 in opposite directions, and their relative velocity is inversely 
 proportionate to their number of teeth. Thus if a wheel hav- 
 ing forty teeth drives another of ten teeth, the second will 
 make four revolutions while the first makes one. The con- 
 nexion of one toothed wheel with another, is called gear or 
 gearing, and when both wheels with their teeth are in the 
 direction of the same plane, it is called spur gearing. It is 
 desirable in toothed wheels, as far as possible, to diminish fric- 
 tion, and to produce uniformity of force and motion. A uni- 
 form motion may be produced, if the form of the acting face 
 of the teeth be a curve of the epicycloidal kind ; the outline of 
 the teeth of one wheel being the curve which would be de- 
 scribed by the revolution of a curve upon a given circle, while 
 the outline of the teeth of the other wheel is described by the 
 same curve rolhng within the circle. It may also be produ- 
 ced, if the teeth of one wheel be straight, circular, or of any 
 regular figure whatever ; provided the teeth of the other wheel 
 be of a figure compounded of that figure and of an epicycloid.* 
 
 * For investigations relating to the teeth of wheels, see Camus on the Teeth 
 of Wheels, translated, London, 8vo. 180ti ;— Buchanan on Mill Work, chap. i. 
 
 30 
 
234 
 
 ELEMENTS OF MACHINERY. 
 
 Of two wheels which are unequal in size, the larger is called 
 the wheel, and the smaller the opinion. The acting portions of 
 the wheel are called teeth ; and of the pinion, more commonly, 
 leaves. The name of lanterns is given to pinions with two 
 heads connected by cylindrical teeth, or trtmdles. In Fig. 4^ 
 the line joining the centres Fig. 4. 
 
 B and F of the wheel and pin- 
 ion, is called the line of centres, 
 and when this line is divided 
 into two parts, F A and B A, 
 which are to each other as the 
 number of leaves in the pinion 
 is to the number of teeth in the 
 wheel ; B A is called the prim- 
 itive radius * of the wheel, and 
 F A, the primitive radius of the 
 pinion ; while the lines or dis- 
 tances F f and B b are called the 
 true radii. The circle X A X 
 and R A R are called the prim- 
 tive circumferences, and by woi'kmen, the pitch lines. 
 
 Friction, to a certain extent, cannot be avoided, in teeth of 
 the common kind, whose acting faces are at right angles with 
 the plane of the wheels to which they belong. It may, howev- 
 er, be much diminished, by making the teeth as small and as 
 numerous as is consistent with their strength ; for the quantity 
 of friction necessarily increases with the distance of the point 
 of contact from the line of centres. 
 
 /Spiral Gear. — In common cases, the teeth of wheels are 
 cut across the circumference, in a direction parallel to the axis. 
 -In the spiral gear, now much used in cotton mills, in this coun- 
 try, the teeth are cut obliquely, so that if continued they would 
 pass round the axis like the threads of a screw. In conse- 
 
 &c. ; — Brewster's Ferguson's Lectures, vol. ii. p. 119; — Gregory's Mechanics, 
 vol. ii. p. 451 ; — also a Treatise by Mr Blake, in Silliman's Journal, vol. vii. 
 p. 86. 
 
 * Called the proporiional radius by Buchanan. 
 
ELEMENTS OF MACHINERY. 
 
 235 
 
 quenee of this disposition, the teeth come in contact only in the 
 line of centres, and thus operate without friction. Fig. 5. 
 
 Fisf. 5, The action of these wheels, it is true, is 
 compounded of tw^o forces, one of which acts in 
 the direction of the plane of the wheel, and the 
 other in the direction of its axis. The latter 
 force occasions a degree of friction, which being 
 expended at the end of the axle, may be regard- 
 ed as inconsiderable. The remaining force 
 goes to produce rotary motion. 
 
 The spiral gearing has been applied to clockwork, and has 
 the peculiarity that it admits of a smaller pinion than any other 
 gearing. Thus, if a very small cylinder have a spiral groove 
 so cut in it as to extend once round its circumference, it will 
 perform one revolution for every tooth of the wheel which 
 drives it. The groove may be cut indefinitely near to the 
 centre of the pinion or cylinder, without weakening it so much 
 as would happen in other forms of the pinion.* 
 
 Bevel Gear. — When wheels are not situated in the same 
 plane, but form an angle with each other, the spur gearing al- 
 ready described, is changed for teeth of a different description. 
 In this case, the hevel gearing is commonly employed, consist- 
 ing of wheels w4iich are frusta of cones, having their teeth cut 
 obliquely, and converging toward the point where the apex of 
 the cone would be situated. According as the relative magni- 
 tude of the wheels varies the angle of the Fig. 6. 
 bevel must be different, so that the velocities 
 of the wheels may be in the same proportion 
 at both ends of their oblique sides or faces. 
 For this purpose, the faces of all the teeth 
 must be directed to the point where the axes 
 of the two wheels would meet. The bevel 
 gearing is shown in Fig. 6, and Fig. 12. 
 
 * The spiral gear has been used at Waltham, Mass. and elsewhere, for about 
 fifteen years, and is commonly considered here as the invention of Mr White. 
 Something analogous to it, under the name of Inclined Plane Wheels, was 
 published in London, by Mr T. Sheldrake, in 1811. 
 
236 
 
 ELEMENTS OP MACHINERY. 
 
 Crown Wheels. — Circular motion is also communicated 
 at right angles, by means of teeth or cogs, situated parallel to 
 the axis of the wheel. Wheels thus formed Fig. 7. 
 are denominated croton or contrate wheels. 
 They act either upon a common pinion, or 
 upon a lantern. The crown wheel is repre- 
 sented in Fig. 7. It is less in use than the 
 bevel gear before described, having more 
 friction. 
 
 Universal Joint. — The contrivance called Hooke's univer- 
 sal joint, is sometimes used instead of wheels, to communicate 
 circular motion in an oblique direction. It consists of two 
 shafts, or axes, each terminating in a semicircle, and connected 
 together by means of a cross, upon which each semicircle is 
 hinged. Fig. 8. It is obvious that Fig. 8. 
 
 when one shaft is turned, the other 
 must revolve likewise ; and this will 
 be the case whenever the angle by 
 which one shaft deviates from the 
 direction of the othei", does not ex- 
 ceed 40 degrees. By means of a 
 double universal joint, circular mo- 
 tion may be communicated at an 
 angle of from 50 to 90 degrees. 
 
 Perpetual Screw. — The perpetual or endless screw, some- 
 times called wor?n by mechanics, is made use of to convey 
 circular motion from an axle to a toothed wheel, situated in 
 the direction of the same plane wiJi the axle. The relative 
 velocity of a wheel driven by a screw is Fig. 9. 
 
 very slow ; for if the screw have only a 
 single thread, the wheel will advance the 
 breadth of one tooth only for each revolu- 
 tion of the screw. This mechanism is 
 of great use in producing an equable slow 
 motion in machinery, and also in increas- 
 ing mechanical power. Fig. 9. The 
 
 
ELEMENTS OF MACHINERY. 
 
 23r 
 
 motion may be reversed, or conveyed from the wheel to the 
 screw, if the obhquity of the threads be sufficiently increased. 
 A spiral wheel and a toothed wheel may be made Fig. 10. 
 to turn with equal velocity, or any desired pro- 
 portion of velocity, by the construction repre- 
 sented in Fig. 10. A is a wheel seen edgeways, 
 its axis being B C. Its circumference is fur- b 
 nished with spiral ridges, which, as the wheel 
 turns, cause the pinion D to revolve in the plane 
 of the axis B C. 
 
 Brush Wheels. — In light machinery, wheels sometimes turn 
 each other by means of bristles or brushes fixed to their cir- 
 cumference. They may also communicate circular motion by 
 friction only. In this case the surface brought in contact is 
 formed of the end grain of wood, or it is covered with leather 
 or some other elastic substance, and the two wheels are pressed 
 together to increase the friction. 
 
 Ratchet Wheel. — The ratchet or detent wheel is intended 
 to prevent motion in one direction, while it permits it in another. 
 For this purpose the teeth are cut with their faces inclining in 
 one direction, and a small lever or catch, is so Fig- 11. 
 placed as to enter the indentations and stop the 
 wheel if it turns backward, but slides over the 
 teeth without obstructing them, if it moves for- 
 ward. Fig. 11. Ratchet wheels are general- 
 ly employed to prevent a weight raised by a 
 machine from descending, and to obviate other retrograde 
 movements. 
 
 Distant Rotary Motion. — When it is required to transmit 
 circular motion to a distance, for example from one extremity 
 or story of a building to an- Fig. 12. 
 
 other, various methods are em- 
 ployed. The most common is 
 by band wheels, or drums con- 
 nected by leather belts of the 
 requisite length. This mode 
 
238 
 
 ELEMENTS OP MACHINERY. 
 
 is considered most economical. When a precise velocity is 
 required, a rolling shaft, geared at both ends, as in Fig. 12, is 
 to be preferred, A double crank having its two parts at right 
 angles with each other, and Fig. 13. 
 
 connected with a similar 
 crank by stiff rods or bars, 
 answers the same purpose. 
 Fig. 13. If triple cranks are 
 used, cords will serve instead 
 of bars for connexion, because in this case, some part of the 
 first crank will always be in a situation to draw the second, 
 and a rigid medium will not be necessary. 
 
 Change of Velocity. — It is sometimes necessary that a ma- 
 chine should be propelled with a velocity which is not equable, 
 but which continually changes in a given ratio. This happens 
 in cotton mills, where it is necessary that the speed of certain 
 parts of the machinery should continually decrease from the 
 beginning to the end of an operation. To effect this object, 
 two cones, or conical drums, are used, hailing their larger diam- 
 eters in opposite directions. They are connected by a belt, 
 which is so governed by proper mechanism,'' Fig. 14. 
 that it is gradually moved from one extremity 
 of the cones to the other, thus acting upon 
 circles of different diameter, causing a con- 
 tinual change of velocity in the driven cone, 
 with relation to that which drives it. Fig. 14. D" 
 
 A change of speed is also effected by a decreasing series of 
 toothed wheels placed in the order of their size upon a com- 
 mon axis, and fixed. A corresponding series in an inverted 
 order are placed upon another axis, and not fixed, but capable 
 of revolving about the axis, hke loose puUies. The axis of 
 this second series is made hollow, and contains a moveable 
 rod, which has a tooth projecting through a longitudinal slit in 
 one side of the axis. This tooth serve to lock any one of the 
 wheels, by entering a notch cut for its reception. Only one 
 
ELEMENTS OF MACHINERY. 
 
 239 
 
 Fig. 16. 
 
 wheel, however, can be locked at a time, the Fig. 15. 
 others remaining loose, so that the axis will 
 revolve with a velocity which is due to the rela- 
 tive size of the particular wheel which is lock- 
 ed, and of the wheel which drives it. By 
 successively locking the different wheels, !"an 
 increase or decrease of speed is obtained.* 
 Fig. 15. 
 
 Another mode of changing speed is prodnced by a large 
 and small wheel placed at right angles with 
 each other, and acting by friction only. . The 
 edge of the smaller wheel is kept in close 
 contact with the disc or flat surface of the 
 larger wheel, so that the smaller wheel will 
 revolve faster or slower, according to the dis- 
 tance at which it is kept from the centre of 
 the larger wheel. The distance may be varied 
 at pleasure. Fig. 16. 
 
 It is sometimes requisite that a wheel or axis should move 
 with different velocity in different parts of a single revolution, 
 as in orreries, &c. This may be Fig. 17. 
 
 effected by an eccentric crown 
 wheel acting on a long pinion, as 
 in Fig. 17. It may also be accom- 
 phshed in a different way by a cone 
 furnished with a spiral line of teeth 
 acting on another cone, the position of which is reversed. 
 
 Fusee. — In the preceding arrangements for changing veloci- 
 ty, there is a corresponding change of force, which is in an in- 
 verse ratio to the change of velocity. They may therefore be 
 employed for varying force, as well as speed. The fusee of a 
 common watch is a contrivance adapted to this purpose. When 
 a watch is recently wound up, the spring which propels it is 
 
 * A mechanism of this kind is used in the Cotton Factory at Newton, Mass. 
 and there is one nearly similar in Bramah's planing macliine. 
 
240 
 
 ELEMENTS OP MACHINERY. 
 
 in the state of greatest tension. As this spring relaxes or un- 
 coils itself, its power decreases, and in order to correct this 
 inequality, the chain through which it acts, is wound upon a 
 spiral fusee. The fusee B is an axis surrounded by a spiral 
 groove, the distance of the groove from the axis being made 
 to increase gradually from the top to the bottom, so that in 
 proportion as the force of the spring is diminished, it may act 
 on a longer lever. The general outline of the fusee must be 
 nearly such, that its thickness at any part may diminish in the 
 same proportion as it becomes more distant from the point at 
 which the force would 
 cease altogether, the 
 general curve being 
 that of a hyperbola ; 
 but the workmen have, 
 in general, no other rule than 
 Fig. 18. 
 
 that of habitual estimation. 
 
 ALTERNATE OR RECIPROCATING MOTION. 
 
 This name is applied to movements which take place con- 
 tinually backwards and forwards in the same path. An alter- 
 nate motion may take place about a centre, in which case the 
 moving parts will describe arcs of circles, as in a tilt hammer, 
 or the beam of a steam engine ; or it may be confined by guides 
 so as to pursue a rectihnear path, as in the saw of a sawmill. 
 In most complex machines, both rotary and reciprocating mo- 
 tions occur, and these motions are converted into each other by 
 any of the following contrivances. 
 
 Cams. — If the axis of a wheel be situated in any other 
 point than its centre, the wheel thus rendered eccentric may 
 produce by its revolution an alternate motion in any part ex- 
 posed to its action. Circles, hearts, ellipses, parts of circles, and 
 projecting parts of various forms, are made to produce alternate 
 motion, by contmually altering the distance of some moveable 
 
ELEMENTS OF MACHINERY. 
 
 241 
 
 part of the machine, from the axis about which (hey revolve^ 
 Such projecting parts are called cams* In the various forms 
 which are shown in the figures, the part removed by the cam 
 is supposed to return by its own gravity, or by some other pow- 
 er, so as to keep up the alternate nx)tion. In the circular ec- 
 centric cam, or wheel. Fig. 19, the sliding or reciprocating part, 
 A B, will ascend and descend with an easy motion, being never 
 at rest unless at the instant of changing its direction. Ec- 
 centric wheels, if surrounded by a hoop, as at H, in PL IX, 
 perform the same office as cranks. In the semicircular cam. 
 Fig. 20, the reciprocating part will remain at rest on the peri- 
 phery of the cam during half the revolution, but in the remain- 
 ing half it will approach the axis and return. In the quad- 
 rant cam. Fig. 21, the reciprocating part will remain at rest 
 on the periphery during the first quarter of the revolution ; 
 during the second it will descend to the axis ; during the 
 third it will be at rest upon the axis, and during the fourth it 
 will return to its original situation. The narrow cam, Fig. 
 22, causes the reciprocating part to rise and fall in one half 
 the revolution, and to remain at rest on the axis during the 
 other half In these figures, the angles of the earns are made 
 sharp, for the sake of demonstration, but in practice they are 
 generally rounded, to produce more gradual changes of mo- 
 tion. The elliptical cam, Fig. 23, causes two alternate move- 
 
 Pig. 19. Fig. 20. Fig, 21. Fig. 22. Fig. 23. 
 A A A A A 
 
 O 
 
 S 
 
 C3 
 
 H 
 
 O ^ 
 
 Cii 
 
 s 
 
 V 
 
 This word is spelt cam, camm, and camb, by different writer*. In French 
 came. Borgnis. 
 
 31 
 
U2 
 
 ELEMENTS OF MACHINERY. 
 
 merits for each revolution ; and the triple cam in Fig. 24, ap- 
 plied to a tilt, or trip hammer, causes 
 three strokes for one revolution. In 
 this case, the cams are called loipers, 
 and it is common to accelerate the re- 
 ciprocal motion, by adding to the ac- 
 tion of gravitation, the elastic force of 
 a spring, or by the recoil of the handle 
 from a fixed obstacle. A cam in the form of a heart, called a 
 heart wheel, is much used in cotton mills, to cause a regular 
 ascent and descent of the rail on which the spindles are situa- 
 ted.* 
 
 When an easy motion is desired, as in most large machine- 
 ry, the acting outline of the cam should be curved ; but to pro- 
 duce a sudden stroke it should be straight. The number of 
 cams may be indefinitely multiplied, if a rapid, or vibrating 
 movement is required. This is in effect done, when the 
 teeth of a wheel act upon a spring or weight, as in a watch- 
 man's rattle, or in the feeder of a grist-mill. 
 
 Crank. — The common crank affords one of the simplest 
 and most useful methods for changing circular into alternate 
 motion, and vice versa. The single crank, Fig. 25, can only 
 be used upon the end of an axis. The bell crank. Fig. 26, may 
 be used in any part of an axis. The double crank. Fig. 27, 
 Fig-. 25. Fig. 26. Fig. 27. 
 
 fo^ 
 
 \M 
 
 ♦ For an investigation of the curves proper for different cams and wipers, see 
 Brewster's edition of Ferguson's Mechanics, vol. ii. p. 126, &c. For produc- 
 ing an easy and uniform motion, spiral, epicycloidal, and other curves are re- 
 quisite ; but for abrupt, forcible motions, such as occur in tilt hammers, curves 
 of equal action are to be avoided. 
 
ELEMENTS OP MACHINEHY. 
 
 243 
 
 produces two alternate motions, reciprocating with eacti other. 
 The alternating parts in all these cases, are attached to the 
 crank by connecting rods, or by some of the kinds of mechan- 
 ism hereafter described. The motion prodaced by cranks is 
 easy and gradual, being most rapid in the middle of the stioke, 
 and gradually retarded toward the extremes ; so that shocks 
 and jolts in the moving machinery are diminished, or wholly 
 prevented by their use. 
 
 Parallel Motion. — The name of parallel motions is given 
 to those arrangements which convert circular motion, whether 
 continued or alternate, into alternate rectilinear motion, and 
 vice versa. Thus the beam of a steam engine moves in cir- 
 cular arcs, while the piston moves in right lines. They can- 
 not, therefore, be rigidly connected together, without doing vi- 
 olence to the machine, and it becomes necessary to convert 
 one movement into the other by the intervention of proper me- 
 chanism. A moveable parallelogram is principally used for 
 this purpose, and will be described under the head of Steam 
 Engine. A similar contrivance of a more simple form is 
 shown in Fig. 28. C D is a rod moving back and forwards in a 
 right line. Every point of junction is a hinge or joint. G 
 E is a rod moveable about E as a centre ; and F H a rod of 
 the same length, moveable about 
 F as a centre ; these centres be- 
 ing equally distant from the path 
 of C D. G H is a bar connect- 
 ing these two rods, and having 
 the rod C D attached by a joint 
 to its centre. When the whole 
 is set in motion, the joint G will 
 describe the circular arc I K, and 
 the joint H will describe the cir- 
 cular arc G H, while the joint C 
 will pursue an intermediate or 
 rectilinear comse. 
 
 Yarious other methods are practised to insure a rectilinear 
 
244 
 
 ELEMENTS OP MACHINERY. 
 
 motion, though most of them are attended with greater friction 
 than that last described. Thus the alternating part is often con- 
 fined to a rectiHnear path, by sUding in grooves, guides, or holes, 
 or between friction wheels ; a 
 connecting rod uniting the 
 straight and circular motions, 
 as in the last instance. In 
 Oartwright's steam engine, the 
 straight movement of the pis- 
 ton is secured by connecting it 
 with two cranks acting in op- 
 position to each other, and hav- 
 ing their axles geared together 
 by wheels, as represented in 
 Fig. 29. 
 
 The connecting rod may be dispensed with, 
 if a transverse groove, or slit, be cut in the al- 
 ternating part, of a length equal to the diameter 
 of the crank's revolution; as in Fig. 30. The 
 end of the crank, seen at a, in its revolution ^ 
 traverses the whole length of this groove which 
 is cut in the crossbar A B, while the main bar 
 C D has an alternate motion in the straight 
 path to which it is confined. As the space of 
 ascent or descent of the bar C D is always equal 
 to the versed sine of the arc described by the 
 crank, the motion of the bar will be accelerated towards the 
 middle of its oscillations, and retarded towards the extremes, 
 A more equal motion can be produced, if desired, by substitut- 
 ing for the straight groove, a curvilinear groove somewhat like 
 the figure co ; but this method is attended with much friction 
 and little use. 
 
 Sun and Planet Wheel. — The mechanism which bears 
 this name, was invented by Mr Watt, to convert reciprocating 
 into circular motion in the Steam Engine ; the use of the crank 
 for this purpose being at one time secured by patent to another 
 
ELEMENTS OF MACHINERY. 
 
 245 
 
 ir dividual. In Fig. 31, a view is given 
 of the sun and planet wheel. A is the 
 end of a beam having a reciprocating mo- 
 tion. B is the fly wheel of the engine, 
 to which a rotary motion is to be com- 
 municated. Upon the axis of this fly 
 wheel a small toothed wheel is firmly fix- 
 ed. A second toothed wheel is connect- 
 ed to the first, by a loose crank, so as to ' 
 be capable of revolving freely about it. 
 This second wheel is firmly fixed upon 
 the end of a connecting rod, which is at- 
 tached by a joint to the beam of the engine. The two wheels 
 being in gear, it is obvious that as the beam A rises and falls, 
 the second wheel, with the assistance of the fly, will revolve 
 quite round the first ; and if the number of teeth be equal, the 
 first, or sun wheel, must perform two rotations on its axis, 
 while the second, or planet wheel, revolves once round it. 
 
 The necessity of this wi llbe more obvious, when we consider, 
 that if one tooth of the planet wheel were connected by a joint 
 to one tooth of the sun wheel, it would act as a simple crank, 
 and cause one revolution. But an additional revolution is also 
 necessary, because, during the circuit, all the teeth of the plan- 
 et wheel must act upon tho^ of the sun wheel, thus turning 
 it round, as in common wheel work. 
 
 Inclined Wheel. — In Fig. 32, A B is a 
 wheel placed obliquely on its axis C D. 
 The edge, or periphery, of this wheel is receiv- 
 ed in a notch at B, of a sliding bar E F. As 
 the wheel revolves, the bar E F will move 
 up and down, once during each revolution. 
 This reciprocal motion may be indefinitely 
 varied by bending the edge of the wheel into 
 different curves and angles. 
 
 Epicycloidal Wheel. — A very beauti- 
 
 Fig. 32. 
 c E 
 
M6 
 
 ELEMENTS OF MACHINERY, 
 
 ful method of converting circular into alter- Fig. 33, 
 nate motion, or alternate into cir- 
 cular, is shown in Fig. 33. A 
 B is a fixed ring, or wheel, tooth- 
 ed on its inner side. C is a tooth- 
 ed wheel of half the diameter of ^ 
 the ring, revolving about the 
 centre of the ring. While this 
 revolution of the wheel C is tak- 
 ing place, any point whatever on 
 its circumference will describe a straight line, or will pass 
 and repass through a diameter of the circle once during each 
 revolution. This is an elegant application of the law that i^ 
 a circle rolls on the inside of another of twice its diameter, the 
 epicycloid described is a straight hne. In practice, a piston rod, 
 or other reciprocating part, may be attached to any point on the 
 circumference of the wheel C. 
 
 Rack and /Segment. — If an alternating motion is required, 
 the velocity of which shall be alv/ays equal, a rack is bes^ 
 adapted to produce this ef- Fig. 34. 
 
 feet. In Fig. 34, A B is a 
 parallelogram having a rack 
 on two opposite sides. C is 
 a half wheel toothed on its 
 curved side, and having its 
 ^centre equally distant from S 
 the two racks. It is obvioUs from inspection, that as this half 
 wheel revolves, its teeth will act successively upon the two 
 racks, and cause the parallelogram to move back and forwards 
 with a uniform motion. The change, however, from one di- 
 rection to the other will be nearly instantaneous, so that this 
 plan will only answer in machinery which is very hght, or of 
 slow motion. The teeth of the half wheel must cover some- 
 what less than half a circle, that they may not become en- 
 gaged ift one rack, before they are disengaged from the other. 
 
ELEMENTS OF MACHINERY, 
 
 24.7 
 
 
 U^ 
 
 ^ 
 
 "^y^ 
 
 
 '>< 
 
 Back and Pinion. — Another contrivance which renders 
 the change more gradual, is Pis'- 35. 
 
 represented in Fig. 35. A B 
 is a double rack, with circu- 
 lar ends fixed to a beam, ca- 
 ble of moving in the direction 
 of its length. The rack is 
 driven by a pinion P, which 
 is capable of moving up and down in a groove m n, cut in the 
 cross-piece. When the pinion has moved the rack and 1 earn 
 until it comes to the end B, the projecting piece a meets the 
 spring s, and the rack is pressed against the pinion. The 
 pinion, then woiking in the circular end of the rack, will be 
 forced down the groove /a n until it works in the lower side 
 of the rack, and moves the beam back in the opposite direc- 
 tion ; and in this way the motion is continued. The motion 
 of the pinion in the groove will be diminished, if instead of a 
 double rack, we use a single row of pins which are parallel to 
 the axis of the pinion, as in some of the machines, called 
 maiiglcs. 
 
 Belt and Segment. — An alternate circular 
 motion is converted into an alternate rectilinear 
 motion, in fire engines, dressing machines, &c. 
 by a belt or chain fastened to each end of a seg- 
 ment, or other portion of a wheel. The two 
 belts pass by each other, and are attached to the 
 opposite ends of an alternating part. When the 
 segment turns in either direction, it draws after it 
 the alternating part in a straight line. Fig. 36. 
 
 iScapetnents. — In clocks and watches an alternating motion 
 is produced in the pendulum and balance wheel, by means of 
 the mechanism called a scapement. In the more simple 
 scapements two teeth, called pallets, are made to vibrate on a 
 common axis. They are connected with a toothed wheel in 
 such a manner, that one pallet enters between the teeth of the 
 wheel whenever the other is thrown out of their reach. As 
 
248 
 
 ELEMENTS OP MACHINERY^ 
 
 the whe^l revolves, its t^eth successively impinge against one 
 or the other of these pallets, and by causing ihem successively 
 to escape, communicate to their axis a vibrating, or alternate 
 motion. The crutch scapement, Fig. 37, is an arch situated 
 in the same plane with the scape wheel, and parallel to the 
 plane in which the pendulum vibrates. Its pallets successively 
 enter and escape from the teeth of the wheel and receive 
 from it a vibrating motion. In the old or common watch 
 scapement, Fig. 38, a contrate, or crown wheel is used as the 
 scape wheel, and the pallets a and h are placed upon the axis 
 of the balance wheel, so as to meet the teeth successively on 
 opposite sides of the circumference of the scape wheel. A va- 
 riety of other more complicated forms of the scapement are also 
 in use. 
 
 Fig. 37. , Fig. 38. 
 
 _^/>t.'f\J^A yiyi^ -, 
 
 CONTINUED RECTILINEAR MOTION. 
 
 A long continued rectilinear motion is not to be produced in 
 the parts of a machine, except so far as it partakes of the na- 
 
ELEMENTS OP MACHINERY. 24^ 
 
 ture of a rotary or a reciprocating" motion. Thus a band pass- 
 ing round puUies is a modification of rotary motion, and a 
 rack, which is obUged to return at intervals, has a reciproca-^ 
 ting motion. But to a certain extent, the motions of both 
 may be regarded as continuously rectihnear. 
 
 Band. — If it is required to produce motion in a right line, 
 which shall be always in one direction, as for example in the 
 feeding parts of machines, a band passing round pullies or 
 drums, is the method most commonly practised, as in Fig. 1, 
 If a precise velocity is required, the band may be perforated 
 with holes, and received upon short pins at the circumference 
 of the wheels ; or the rag wheel and chain, represented in Fig. 
 3, may be substituted. 
 
 Rack. — If a slow rectilinear motion is required only for lim- 
 ited times, such a mechanism may be used as will permit the 
 moving part to retrace its own path at intervals, and regain its 
 original situation. Fig. 39. Fig. 39. 
 
 A rack, which is a straight 
 
 bar having teeth on one ^""^njuwu^ 
 side, will move in this man- 
 ner if it be acted on by a 
 toothed wheel, or by a per- 
 petual screw. If the thread 
 of a perpetual screw be formed of different obliquity in different 
 parts of its circumference, the progressive velocity of the rack 
 will be unequal, instead of being uniform. And if a part of the 
 thread be in a plane at right angles with the axis of the screw, 
 the rack will be at rest while that part of the screw revolves in 
 contact with it. 
 
 Universal Lever.— K rack is also propelled by means of a 
 catch, or dog, connected with some part of the machine which 
 has an alternating motion. The catch causes the rack to ad- 
 32 
 
250 
 
 ELEMENTS OF MACHINERY, 
 
 vance the length of one tooth, at each stroke Fig. 40. 
 
 of the alternating part. The universal le- 
 ver, sometimes called the lever of La Ga- 
 rousse, consists of a bar moving upon a cen- 
 tre, and having a moveable catch or hook at- 
 tached to each side, and acting upon the 
 obhque teeth of a double rack, or of a ratchet 
 wheel, so that the alternating motion of the 
 bar causes a progressive motion of the rack 
 or wheel. Fig. 40. 
 
 Screv). — A common screw is often made use of to produce- 
 rectilinear movements, when the motion is intended to be very- 
 slow, or when great power is required. 
 
 Change of Direction. — A change from one path or direc- 
 tion to another, forming an angle with it, may be produced 
 by several of the mechanical powers. Thus a cord passing 
 over a pulley, may change a perpendicular to a horizontal 
 motion, as at P, PI. VIII, or to one at any other angle requir- 
 ed. A bent lever like that represented by ^Z ^ in PL IX, pro- 
 duces the same effect, provided the moving parts are confined, 
 by guides, to their respective paths. An inchned plane also, if 
 it moves through th© length of one side of a parallelogram, will 
 eause another body to move through the length of the contig- 
 uous side at right angles. This method, however, is attended 
 with much friction. 
 
 Toggle Joint. — The knee joints commonly called in this 
 country, toggle jom^, affords a very useful mode of convert- 
 ing velocity into power, the motion produced being nearly at 
 right angles with the direction of the force. Its operation is 
 seen in the iron joints which are used to uphold the tops of 
 
ELEMENTS OF MACHINERT. "251 
 
 fchaises. It is also introduced into various i^ig- 41. 
 
 Diodifications of the printing press, in order to ^ 
 
 obtain the greatest power at the moment of the Lr\A 
 
 impression. It consists of two rods or bars V\ 
 
 connected by a joint, and increases rapidly in \ \ 
 
 power as the two rods approach to the direc- - i^ 
 
 tioa of a straight line.* In Fig. 41, a moving / / 
 
 •force applied in the direction C D, acts with _A/ 
 
 great and constantly increasing power to sep- [ [ 
 
 arate the parts A and B. P 
 
 OF ENGAGING AND DISENGAGING MACHINERY. 
 
 'In many cases, particularly where numerous machines are 
 propelled by a common power, it is important to possess the 
 means of stopping any one of them at pleasure, and of restor- 
 ing its motion, without interfering with the rest. To produce 
 this effect, a great variety of combinations have been invented 
 under the name of couplings. These, in most instances, are 
 sliding boxes, which move longitudinally upon shafts or axles, 
 and serve to engage or lock a shaft which is at rest, with one 
 which is in motion ; so as practically to convert the two into 
 one, until they are again unlocked. Couplings are sometimes 
 provided with clutches, or glcaids, which are projecting teeth, 
 intended to catch on otlier teeth or levers, and thus lock the 
 shafts together. Sometimes they have bayonets., or pins 
 adapted to enter holes. Sometimes the connexion is produced 
 by friction alone, by pressing together surfaces, which are 
 either^a^ or conical. Sometimes, also, wheels are thrown in- 
 to, and out of gear, which is done by causing wheels to slide 
 in the direction of their axles, or in some cases by elevating 
 and depressing the axle itself. These methods, however,, are 
 difficult and unsafe. The live and dead fvlley afford .per- 
 
 "An investigation of the power of this combination, is given by the late Pro- 
 fessor Fisher, in SilUman's .Tournal, vol, iii. p. 320. 
 
^5^ 
 
 ELEMElJfTS OF MACHINERT-. 
 
 haps the simplest mode of engagement. They consist of two 
 parallel band-wheels on the same axle, one of which is fast, 
 and the other loose, or capable of turning without the axle. 
 The band which communicates the power, is placed upon the 
 loose pulley, when it is desired to stop the machine, and upon 
 the fast pulley, when it is intended to set the machine in motion. 
 A common band may also be made to admit of motion or rest, 
 according as it is rendered tense or loose, hy a tightening 
 wheel pressed against its side by a lever. 
 
 OF EaUALIZING MOTION. 
 
 In most machines, both the moving force and the resistance 
 to be overcome are liable to fluctuations of intensity at differ- 
 ent times. As such variations influence both tlie safety and 
 efficiency of machines, it is necessary to provide against them, 
 by some appendage, which shall equalize either the supply, or 
 the distribution, of the power. 
 
 Governor. — The name of governor has been given to an 
 ingenious piece of mechanism, which has been introduced to 
 regulate the supply of steam in steam engines, and of water in 
 water mills, so as to render the power equable, and proportion- 
 ate to the resistance to be surmounted. It is represented in 
 Fig. 42. A B and A C are two levers or 
 arms, loaded with lieavy balls at their ex- 
 tremities B and C, and suspended by a 
 joint at A upon the upper extremity of a 
 revolving shaft A D. At a, is a collar, or 
 sliding box, connected to the levers by the 
 rods a b, and a c, with joints at their ex-^ 
 tremities. It follows that when the weights 
 B and C diverge, the collar a will move 
 upward on the shaft A D, and vice versa. 
 The governor thus constructed, is attach- 
 ed to some revolving part of the machine. ]n this state, if it 
 
ELEMENTS OF MACHINERY. 253 
 
 turns too ra':)idly, the balls B and C move outwards by their 
 centrifugal force, and draw upward the collar a. If, on the 
 other hand, the s|:eed diminishes, the balls are allowed to sub- 
 side, and the collar moves down upon the shaft. In the steam 
 engine the collar has a circular groove, which receives the end 
 of a forked lever. As the collar rises and falls, this lever turns 
 upon its fulcrum, and acts lemotely to open or close a throttle 
 valve which is placed in the main steam pipe.* Whenever, 
 therefore, the machine moves too rapidly, the balls recede from 
 the centre, the collar rises, the lever moves the valve, and by 
 partially closing the pipe, diminishes the quantity of steam 
 admitted from the boiler. If the machine moves too slowly, 
 the reverse takes place, and a larger amount of steam is ad- 
 mitted. 
 
 In water wheels, where a greater power is necessary to con- 
 trol the supply of water, the governor is usually connected to 
 the sluice gate by the intei-vention of wheel work. This may 
 be done in several ways, one of which is as follows. The 
 lower part of the shaft A D, carries a wheel at D, acting upon 
 two others beneath it, M and N. While the machinery moves 
 with its proper speed, the wheels M and N are both unlocked 
 and turn loosely round their axles, and the gate is stationary. 
 But when the velocity increases or diminishes, the collar a rises 
 or falls, and by means of a cam, acts upon a lever above it, or 
 upon another below it, so as to lock one of the wheels M or N, 
 by moving a clutch situated at d. These wheels being upon 
 a common axle, are capable of turning this axle different ways. 
 When, therefore, one wheel is locked to the axle, it acts by 
 turning a perpetual screw, to open the sluice gate. When the 
 other is locked, the axle and the screw turn in the opposite di- 
 rection, and partially close the gate. 
 
 The foregoing are some out of various modes in which the 
 governor is applied. In windmills it is so adapted as to increase 
 the feeding, or supply of corn, when the mill goes too fast, and 
 
 • For a further account of the governor, see the article Steam Engine. 
 
254 ELEMENTS OF MACHINERY, 
 
 also to vary the distance of the millstones from each other, if 
 necessary. It has also been applied to dothe and unclothe 
 the sails in proportion to the strength of the wind. 
 
 Fly Wheel. — It is an objectof great importance, in machines, 
 to have the means of accumulating power when the moving 
 force is in excess, and of expending it when the moving force 
 operates more feebly, or the resistance increases. This equal- 
 ization of motion is obtained by w^hat is called a^y, which is 
 generally made in the form of a heavy wheel, though some- 
 times in the form of arms or crossbars, with weights at their 
 extremities, A fly being made to revolve about its axis, keeps 
 up the force by its own inertia, and distributes it in all parts of 
 its revolution. If the moving power slackens, it impels the 
 machine forward ; and if the power tends to move the machine 
 too fast, it keeps it back. 
 
 Fly wheels are capable of accumulating power to a great 
 extent. A small force continually applied to the surface of a 
 heavy revolving wheel will accelerate its velocity till it shall be 
 equal to that of a musket-ball, and its momentum almost irre- 
 sistible. Fl}'" wheels, to act with the greatest efficacy, should 
 be made with the least possible surface, that their motion may 
 not be impeded by the resistance of the air. They should be 
 made of iron, and if they cannot be cast in one piece, they 
 should be firmly hooped or bolted together, that the parts may 
 not separate by their centrifugal force. Fatal accidents have 
 •occurred from the bursting of large stones used as flies, or as 
 grindstones in cutlery w^orks, their velocity and centrifugal 
 force being so great as to overcome their cohesive attraction, 
 ■and 'to project 'the parts to a distance with great violence. 
 
 Beside the modes already described, other methods are em- 
 ployed to retard and equalize the velocity of machinery. A 
 kind of fly is used in music boxes, and in the striking part of 
 clocks, in which the broad surface of vanes, upon the circum- 
 ference of a wheel, is made to act against the air, until the re- 
 sistance becomes equal to the propelUng force, so that the velo- 
 city can increase no further, but becomes uniform. Pendu- 
 
ELEMENTS OF M-ACHINERY. 255 
 
 liims and balances, acted on through the different kinds of 
 scapements, are also means of equalizing motion. 
 
 FRICTION. 
 
 A part of the force by which machines are moverl^ is ex- 
 pended in overcoming their friction. Hence it is desirable to 
 obviate as far as possible this kind of resistance. Friction is 
 supposed to arise chiefly from the roughness and inequaUty of 
 the surfaces of bodies. No polish can be given to a surface 
 mechanically, so fine as to render it perfectly smooth. When 
 surfaces move over each other, a certain force is necessary to 
 disengage the minute asperities of one surface from those of 
 the other, either by causing them to rise over each other, or by 
 bending or breaking them down. 
 
 Friction is increased by the roughness of bodies, and also 
 by the force with which they are pressed together. But it is 
 very little affected by the extent of the surfaces in contact. It 
 is greatest at the moment when motion begins : it does not, 
 however, change afterwards as the velocity changes, but con- 
 tinues to retard with a uniform force, whether the motion per- 
 formed be slow or rapid. There are several points in regard 
 to friction upon which writers are not agreed. 
 
 Friction in machinery is to be diminished by making the 
 surfaces which rub upon each other as smooth as possible, and 
 by covering them with some unctuous substance. Black lead 
 in fine powder is sometimes interposed between surfaces to 
 diminish friction, and soapslone applied in the same manner is 
 still more useful. It is supposed, by some, that different me- 
 tals moving upon each other, occasion less friction than sur- 
 faces of the same metal. But the most important mode of 
 diminishing friction, is to employ a rolling, or turning motion, 
 instead of a sliding motion, in all cases where it is practicable ; 
 and by simplicity of construction to avoid all unnecessary con- 
 tact of moving surfaces. 
 
256 ELEMENTS OE' MACHINERY. 
 
 Remarks. — ^In the construction of machines, no subject is 
 more deserving of attention than simphcity of parts and struc- 
 ture. The more complex machines are, the more expensive 
 they are to erect, the more hable to get out of order, and the 
 more difficult to repair. An increased expenditure of power 
 is also occasioned by their friction. A complex machine may 
 evince great ingenuity on the part of the inventor, and may 
 have cost much labor and science to complete it. Yet it is suie 
 to be superseded, the moment that a more simple, cheap, or 
 expeditious way of attaining the same object is discovered. 
 The improvement of the mechanist or engineer more frequent- 
 ly consists in the simplification of his means, than it does in the 
 construction of complex and difficult pieces of workmanship. 
 
 Buchanan on Mill Work and other Machinery, 2 vols. 8vo. 1823'; — 
 Robison's Mechanical Philosophy, vol. ii. p. 18J ; — Nicholson's 
 Operative Mechanic, 8vo. 1825; — Gregory's Mechanics, 1826; — 
 Brewster's edition of Ferguson's Mechanics, 1823; — Borgnis, JTf - 
 chanique Applijuee aux t.^rts , 4io. Paris, 1818, Tom. 3, Composition des 
 Mad.iats ; — Lanz et Bettancourt, sur la Composition des Machines, 
 Paris, 4to. 1819; — Hachette, Traite Elementaire des Machines; — 
 Leupold, Theatrum, Machinarum Universale, 7 vols, folio, Leipsic, 
 1724, to 1774. 
 
CHAPTER XII. 
 
 OF THE MOVING FORCES USED IN THE ARTS- 
 
 Sources of PoiDer. — It is the office of machines to receive 
 and distribute motion derived from an external agent, since no 
 machine is capable of generating motion, or moving power, 
 within itself. The sources from which the moving power ap- 
 plied to machinery is obtained, are various, according to the 
 nature of the object, and the amount of force which is required. 
 Men and animals, water, wind, steam, and gunpowder are the 
 principal agents employed as first movers in the arts. Their 
 power may be ultimately resolved into those of muscular ener- 
 gy, gravity, heat, and chemical affinity. But although these 
 are the sources of all the important force which is artificially 
 employed in moving large masses of matter, yet certain other 
 agents are also capable of producing motion upon a more 
 limited scale, such as magnetism, electricity, capillary attrac-^ 
 tion, (fee. 
 
 Vehicles of Powers — Besides the original forces which have' 
 been mentioned, there are certain intermediate agents which 
 serve to accumulate and transmit power, after the first mover 
 has ceased to operate. These agents commonly act either by 
 their elasticit}^, their gravit}^, or their inertia. Springs and 
 compressed air are examples of vehicles acting by their elasti- 
 city, and their usefulness continues only till they have recover- 
 ed the situation from which they were disturbed by another 
 force. In like manner, a weight acting by its gravity on an 
 axle or wheel, prolongs for a season the influence of the power 
 by which it was wound up. Fly wheels are also vehicles which 
 serve by their inertia to continue the action of a force while it 
 intermits. Vehicles of power are highly useful in equalizing 
 33 
 
258 OF THE MOVING FORCES USED IN THE ARTS. 
 
 the irregularities which are incident to prime movers, in pro- 
 longing their action through convenient periods of time, and 
 in multiplying the modes of their application. 
 
 A fundamental distinction among mechanical agents, both 
 original and secondary, consists in this ; that in some the inten- 
 sity of their action, or the acceleration they produce in a given 
 time, is the same, whether the body acted upon be at rest or 
 in motion ; in others it is greatest when the body acted on is at 
 rest, and becomes less as its velocity increases. Gravity is the 
 only force which is certainly known to act with equal intensity 
 on bodies in motion, and at rest ; though magnetism probably 
 possesses the same property. Every other important power 
 acts more forcibly on a body at rest, than on one which has 
 ali"eady acquired motion in the direction in which it acts.*- 
 This happens with the strength of animals, the impulse of 
 fluids, and the elasticity of springs. 
 
 ANIMAL POWER. 
 
 Muscular energy is exerted through the contraction of ther 
 fibres which constitute animal muscles. The bones act as 
 levers to facilitate and direct the application of this force, the 
 muscles operating on them through the medium of tendons, 
 or otherwise. Muscular power is much greater in some ani- 
 mals, than it is in man, owing to their size, or more active 
 mode of life. It is greatest in beasts of prey. 
 
 Men. — The }X)wer of a man to produce motion in weights 
 or obstacles, varies according to the mode in which he applies 
 his force, and the number of muscles which are brought into 
 action. In the operation of turning a crank, a man*s power 
 changes in every part of the circle which the handle de- 
 scribes. It is greatest when he pulls the handle upward from 
 the height of his knees, next greatest when he pushes it down 
 on the opposite side, though here the power cannot exceed the 
 
 * See Playfair's Outlines of Natural Philosophy, vol. i. p. 107. 
 
 "^ 
 
OF THE MOVING FORCES USED IN THE ARTS. 259 
 
 weight of his body, and is therefore less than can be exerted in 
 pulhng upward. Tlie weakest points are at the top and 
 bottom of the circle, where the handle is pushed or drawn 
 horizontally. 
 
 If a windlass be provided with two cranks placed at right an- 
 gles with each other, two men will perform much more work 
 than they could if the cranks were disconnected, because at the 
 moment one puts forth his strength to the least advantage, the 
 other is exerting his with the greatest effect. 
 
 The mode in which a man can exert the greatest active 
 strength, is in pulling upward from his feet, because the strong 
 muscles of the back as well as those of the upper and lower 
 extremities, are then brought advantageously into actioiijandthe 
 bones are favorably situated by the fulcra of the levers being 
 near to the resistance. Hence the action of rowing is one of 
 the most advantageous modes of muscular exertion ; and no 
 method which has been devised for propelling boats by the la- 
 bor of men, has hitherto susperseded it. 
 
 According to Mr Buchanan, the comparative effect produced 
 by different modes of applying the force of a man, is nearly as 
 follows. In the action of turning a crank, his force may be 
 represented by the number 17. In working at a pump, by 29. 
 In pulling downward, as in the action of ringing a bell, by 39, 
 And in pulling upward from the feet, as in rowing, by 41.* 
 
 In estimating the different applications of animal force, we 
 must take into consideration not only the resistance they can 
 overcome, but the velocity with which they move, and the 
 length of time for which they can be continued. Violent ef- 
 forts are not true specimens of a man's labor, since they can 
 be exerted for a short time only. A moderate computation of 
 an ordinary man's uniform strength, is that he can raise a 
 iDeight q/'lO pounds to the height of 1^ feet once in a sec- 
 ond, and continue this labor for 10 hours in the day.\ 
 
 ♦ See Brewster's edition of Ferguson's Mechanics, vol. ii. p. 9. Thewhole 
 numbers are 1742, 2856, 3883, and 4095. 
 
 t Young's Lectures on Natural Philosophy, vol. i. p. 131. 
 
260 OP THE MOVING FORCES USED IN THE ARTS. 
 
 This is supposing him to use his force under common mechan-r 
 ical advantages, and without any deduction for friction. 
 
 Horses.— Horses are often employed as movers of machine- 
 ry by their draught. A horse draws with greatest advantage 
 when the Hne of draught is not horizontal, but inclines upward, 
 making a small angle with the horizontal plane, as already 
 stated, page 197. The force of a horse diminishes as his speed 
 increases. The following proportions are given by Professor 
 Leslie, for the force of the horse employed under different ve- 
 locities. If his force when moving at the rate of two miles 
 per hour, is represented by the number 100, his force at three 
 miles per hour will be 81, — -at four miles per hour 64, — at 
 five miles 49,— and at six miles 36. These results are con- 
 firmed very nearly by the observations of Mr Wood.* In this 
 way the force of a horse continues to diminish, till he attains 
 his greatest speed, when he can barely carry his own weight. 
 
 Various estimates have been made of a horse's power, by Dcr 
 saguhers, Smeaton, and others ; but the estimate now generally 
 adopted as a standard for measuring the power of steam en- 
 gines, is that of Mr Watt, whose computation is about the av- 
 erage of those given by the other writers. The measure of a 
 horse's power, according to Mr Watt, is, that he can raise a 
 weight of 33000 pounds to the height of one foot in a min- 
 ute. 
 
 In comparing the strength of horses with that of men, Desa- 
 guliers and Smeaton consider the force of one horse to be 
 equal to that of five men ; but writers differ on this subject. 
 
 When a horse draws in a mill or engine of any kind, he is 
 commonly made to move in a circle, drawing after him the 
 end of a lever which projects like a radius from a vertical shaft. 
 Care should be taken that the horse-walk, or circle, in which 
 he moves, be large enough in diameter ; for since the horse is 
 continually obliged to move in an obhque direction, and to adT 
 vance sideways as well as forward, his labor becomes more fa^ 
 tiguing, in proportion as the circle in which he moves becomes 
 smaller. 
 
 * Treatise on Rail Roads, p. 239. 
 
OF THE MOVING FORCES USED IN THE ARTS, 261 
 
 In some ferry boats and machines, horses are placed on a 
 reyolving platform, which passes backward under the feet 
 whenever the horse exerts his strength in drawing against a 
 fixed resistance, so that the horse propels the machinery with- 
 out moving from his place. A horse may act within still 
 narrower limits, if he is made to stand on the circumference of 
 a large vertical wheel, or upon a bridge supported by endless 
 chains which pass round two drums, and are otherwise support- 
 ed by friction wheels. Various other methods have been prac- 
 tised for applying the force of animals, but most of them are 
 attended with great loss of power, either from friction, or from 
 the unfavorable position of the animal. 
 
 WATER POWER, 
 
 Water and wind, considered as prime movers, are applica- 
 tions of the force of gravity, since without gravity there 
 would be neither wind, nor currents of water. The force 
 of water is generally applied to the cirdftmference of 
 wheels, which it causes to revolve, either by its weight, by 
 its lateral impulse, or by both conjointly. Water wheels are 
 generally used in one of three forms. These are the overshot 
 wheel, in which the water descends from the top of the wheel 
 to the bottom ; the breast wheel, in which it is received at 
 about half the height of the wheel, and the undershot wheel, 
 where it acts by the impulse of a current flowing under the 
 wheel. The overshot wheel is the most powerful kind, and is 
 always to be employed where a sufficient fall of water can be 
 obtained. 
 
 Overshot Wheel. — This is a wheel, or drum, the circumferr 
 ence of which is occupied by a series Fig. 1. 
 
 of cavities, commonly called buckets, in- 
 to which the water is delivered from one 
 or more spouts at the top of the wheel. 
 By inspecting Fig. 1, it will be seen that 
 the buckets on one side of the wheel are 
 erect, and will consequently become load- 
 ed with water ; while those on the other 
 
 a's 
 
262 OF THE MOVING FORCES USED IN THE ARTS. 
 
 side are inverted, and of course empty. It follows that the 
 loaded side will always preponderate, and by descending will 
 cause the wheel to revolve. 
 
 If it were possible, says Dr Robison,* to construct the buckets 
 in such a manner, as to remain completely filled with water 
 till they came to the botton of the wheel, the pressure with 
 which the water urges the wheel round its axis, would be the 
 same as if the extremity of the horizontal radius were continu- 
 ally loaded with a cjuantity of water sufficient to fill a square 
 pipe, whose section is equal to that of the bucket, and whose 
 length is the diameter of the wheel. But such a state of things 
 is impossible ; and if a bucket be full while at top, it will begin 
 to lose water as soon as it turns into an oblique position, and 
 must continue to do so, till it reaches the bottom. 
 
 The attention of engineers has been directed to giving the 
 buckets such a form as will enable them to retain the water 
 for the longest time on the circumference of the Fig. 2. 
 wheel. The form represented in Fig. 2, answers \\ 
 this purpose*olerably well, and from its simplicity 
 is the one most commonly used, but it may be im- 
 proved still farther by giving an additional inclination 
 inward to the outer edge of the bucket, as seen in 
 Fig. 3. As the best economy of the water power 
 requires that the buckets should not be completely 
 filled, the form here represented will retain the water 
 until it has descended low on the wheel. To pro- 
 mote this object still further, Mr Burns has divided 
 the bucket by a partition which is parallel to the rim of the 
 wheel, constituting one bucket within another. In this mode 
 of construction, the water does not enter with the same facility, 
 but is longer in escaping.t 
 
 In order to prevent the inertia of the water, when it is first 
 
 * Mechanical Philosophy, vol. ii. p. 592. 
 
 t We are informed by Dr Brewster, that Burns' improvement has not been 
 introduced by him into practice, owing to the difficulty of filling the inner buck- 
 ets. Mechanics, vol. it p. 49. 
 
OF THE MOVING FORCES USED IN THE ARTS. 263 
 
 laid upon the buckets, from impeding the motion of the wheel, 
 it is desirable that the water when it enters, should have a velo- 
 cit}^ corresponding as nearly as possible to that with which the 
 wheel is revolving. And as we cannot give to the water the 
 direction of a tangent to tlie wheel, the velocity with which it 
 is delivered on the wheel must be so much greater than the 
 intended velocity of the rim, that it shall be equal to it when it 
 is estimated in the direction of a tangent. To facilitate as 
 much as possible the entrance of the water, it is common to 
 deliver the water through an aperture, which is divided by thin 
 plates of board or metal, placed in an oblique position so as ta 
 direct the stream of water into the buckets in the most perfect 
 manner, as represented in Fig. 6. In order to detain the 
 water as long as possible, the lower part of the wheel is often 
 made to revolve in a concave cavity just large enough to receive 
 it, and called in this country, the apron, as seen in Fig. 9. 
 
 A difficulty often occurs in the entrance of water into the 
 buckets, by the resistance of the air already in the bucket, 
 which causes the water to regurgitate and spill. This evil may 
 be entirely prevented by making tlie spout considerably narrow- 
 er than the wheel, so as to leave room for the escape of the air 
 at the two ends of the bucket. 
 
 The pressure of the atmosphere occasions sometimes a seri- 
 ous obstruction to the motion of overshot wheels, by causing a 
 quantity of back water to be lifted, or sucked up, by the as- 
 cending inverted bucket, when it first leaves the water. This 
 difficulty is remedied by making a few small holes near the 
 base of the bucket, and communicating with the next bucket. 
 Through these the air will enter, and prevent the suction. It 
 is true that, when on the descending side, these holes vdll allow 
 the escape of some water ; but as this water only flows from 
 one bucket to the next, its effect is inconsiderable when com- 
 pared with the advantage gained. Air, as Professor Robison 
 observes, will escape through a hole about 30 times faster than 
 water, under the same pressure. 
 
 With respect to variations in the fall, the same writer remarks 
 
264 OP THK MOVING FORCES USED IN THE ARTS. 
 
 tiiat since the active pressure is measured by the pillar of water 
 reaching from the horizontal plane, where it is delivered on the 
 wheel, to the horizontal plane, where it is spilled by the wheel, 
 it is evident that it must be proportionate to this pillar, and 
 therefore we must deliver it as high and retain it as long as 
 possible. This maxim obliges us to use a wheel whose diam- 
 eter is equal to the whole fall. We shall not gain anything by 
 employing a larger wheel ; for although we should gain by 
 using only that part of the circumference, where the weight 
 will act more perpendicularly to the radius, we shall lose more 
 by the necessity of discharging the water at a greater height 
 from the bottom.* 
 
 Chain Wheel. — -When there is a very small suppty of water 
 falling from a very great head, the double overshot wheel, with 
 a chain of buckets, is a valuable machine. This wheel is re- 
 presented in Fig. 4, where too rag wheels Fig. 4. 
 are placed, one at top, and the other at 
 bottom, and a series of buckets are fixed to 
 an endless chain, the links of which fall into 
 notches in the circumference of the rag 
 wheels. The water issuing from the mill 
 course is introduced into the buckets on one 
 side at top. The descent of the loaded 
 buckets on this side puts the rag wheels in 
 motion, and the power is conveyed from 
 the shaft of the upper wheel, to turn any 
 kind of machinery. When the buckets 
 reach the bottom they allow the water to escape ; and ascend- 
 ing empty on the opposite side, they again return to the spout, 
 to be filled as before. In this machine, the buckets have in 
 
 * Mechanical Philosophy, vol. ii. p. 600. 
 
 On this subject Dr Brewster remarks, that if we employ a wheel the diam- 
 eter of which is higher than the fall, we may take advantage of any casual rise 
 of the water above its usual level, and by a particular form of the delivering 
 sluice, introduce the water higher upon the wheel, and thus actually increase 
 the height of the fall. 
 
OF THE MOVING FORCES USED IN THE ARTS. 265 
 
 every part of their path the same mechanical effect to turn the 
 wheels, and they do not allow the water to escape till they 
 have reached almost the lowest part of the fall. 
 
 This species of wheel possesses another advantage, namely, 
 that by raising the lower wheel and taking out two or three of 
 the buckets it may be made to work when there is such a 
 quantity of back water as would otherwise prevent it from 
 moving. 
 
 Dr Robison has described a machine of this kind, in which 
 plugs, or horizontal float-boards, are fixed to a chain. On the 
 descending side, these plugs pass through a tube, a little great- 
 er in diameter than that of the floats ; and the water acting 
 upon these floats as it does in the case of a breast wheel, gives 
 motion to the two rag wheels. 
 
 In regard to the most advantageous velocity to be produced 
 with a given quantity of water in an overshot wheel, various 
 mathematicians have concluded, that the slower a wheel moves, 
 the greater is its power of performance. But the experiments 
 of Mr Smeaton lead to the conclusion, that in practice there is 
 a limit of velocity, and that overshot wheels do most work 
 when their circumference moves at the rate of about three feet 
 in a second. 
 
 Undershot Wheel. — An undershot Fig 5. 
 
 water wheel, is a wheel furnished with 
 a series of plane surfaces, called floats 
 or float-boards, projecting from its cir- 
 cumference for the purpose of receiving 
 the impulse of the water, which is de- 
 Uvered b}'^ a proper canal, with great ve- 
 locity, upon the under part of the wheel. 
 A wheel of this kind is represented in 
 Fig. 5. 
 
 When an undershot wheel is put in motion by a stream of 
 water striking against one of its float-boards, in a diiection at 
 right angles with the radius, the action of the water will dimin- 
 ish, as the velocity of the wheel increases, till at last the mo- 
 34 
 
266 OF THE MOVING FORCES USED IN THE ARTS. 
 
 mentum of the water, or of the accelerating force, is just equal 
 to the momentum of the resistance, or of the retarding force. 
 The motion of the wheel will then become uniform. 
 
 By calculation it appears that a machine thus driven by the 
 impulse of a stream produces the greatest eflect, or does most 
 work in a given time, when the wheel moves with one third of 
 the velocity with which the water moves.* But in practice 
 this rule is liable to some variation ; for the water does not es- 
 cape as soon as it has given its impulse, but is confined by the 
 channel for some time, and acts with a variety of influences. 
 In Mr Smeaton's experiments, which are cited as authorities 
 by most writers since his time, it was found that an undershot 
 wheel when working to the greatest advantage, had a velocity 
 which varied from one third to one half the velocity of the 
 stream ; and that in great machines it was nearer to the latter 
 of these hmits, than the foimer. 
 
 It is advantageous that the size of undershot wheels should 
 be as great as circumstances will permit, and it ought never, 
 says Dr Brewster, to be less than seven times the natural depth 
 of the stream at the bottom of the course.t In regard to the 
 best number of float-boards a difference of opinion has prevailed, 
 but it is now generally admitted that the more float-boards a 
 wheel has, the greater and more uniform will be its effect, t 
 According to the experiments of Bossut, it appeared that a 
 wheel with 48 float-boards produced a greater effect than one 
 with 24, and the latter a greater effect than one with 12. 
 Smeaton's experiments justify the same conclusion, though he 
 found that on adapting to the wheel a circular sweep of such 
 length, that one float-board entered into the curve, before an- 
 other left it, the effect came so near to the former, as not to 
 give any hopes of advancing it by increasing the number of 
 floats beyond 24 in the wheel experimented on. § 
 
 * Playfair's Outlines of Natural Philosophy, vol. i. p. 214 — and Robison, 
 623. 
 
 t Ferguson's Mechanics, vol. ii. p. 17. 
 t Gregory's Mechanics, vol. i. p. 462. 
 § Ibid. p. 476. 
 
OF THE MOVING FORCES USED IN THE ARTS. 267 
 
 In regard to the position of the float-boards, they should not 
 be in the direction of the radius, but indined from it sHghtly 
 backwards. From the experiments of Deparcieux and Bossut, 
 it appears that there is a very sensible advantage gained by 
 inclining the float-boards to the radius of the wheel about 20 de- 
 grees, so that the lowest float-board shall not be perpendicular, 
 but have its point turned up the stream about 20 degrees. 
 This inclination causes the water to heap up along the float- 
 board, and act by its weight.* The floats should for this pur- 
 pose be made much broader in the direction of the radius than 
 the vein of water which they intersect, is deep. Another ad- 
 vantage attending tiiis obliquity of the floats is, that they are 
 less resisted, when they rise out of the water. 
 
 The best way of delivering the water on an undershot wheel 
 in a close mill course, according to Dr Robison, is to let it 
 slide down a very smooth channel without touching the wheel, 
 till it arrives near the bottom, at which place the wheel should 
 be exactly fitted to the course. The floats should be broader 
 than the depth of the water, so as never to be wholly immersed, 
 but allowing the intercepted water to heap up against them. 
 If the bottom of the course be an arc of a circle having a great- 
 er radius than that of the wheel, the water which slides down 
 will be gradually intercepted by the floats, or strike upon more 
 than one at a time. In this country it is often the practice to 
 admit the water directly from the bottom of a pond, or reser- 
 voir, instead of causing it to glide down a separate channel 
 from near the top ; and this method is found very effec- 
 tual. 
 
 Back Water. — The back water, or tail water, is that por- 
 tion which has past by the wheel. This portion is not only 
 useless, but in most cases injurious, since by its inertia and 
 weight, it resists the escape of the floats and empty buckets in 
 their passage upward. Its effect is increased in times of floods 
 or freshets, so that it is often necessary to place wheels higher 
 
 * Robison's Mechanical Philosophy, vol. ii. p. 625. 
 
268 
 
 OP THE MOVING FORCES USED IN THE ARTS, 
 
 than they otherwise would be, to provide against it. A method 
 of getting rid of back water in times of flood, has been invented 
 by Mr Perkins in this country, and Mr Burns in Scotland. It 
 consists in a separate passage by which a current of water is 
 taken from the mill-lead, or flume, as at A in Fig. 6, and Tpnss- 
 
 Pig. 6. 
 
 es with great rapidity under the wheel, and thence under the 
 flooring at B. This rapid current has the effect to take off 
 and carry away the back water from beneath the wheel, while 
 it is prevented from returning by the force of the same current, 
 and the barrier at C. The water which is expended to main- 
 tain this current is no more than would run over the waste gate , 
 m a time of freshet. 
 
 Besanfs Wheel. — To diminish the retardation occasioned 
 by back water, Mr Besant has invented a wheel in which the 
 floats are placed obliquely in a double row, Fig. 7. 
 
 as in Fig. 7, where the wheel is represent- 
 ed as seen edgeways. Each pair of floats 
 forms an acute angle, open at its vertex. 
 By this construction the floats escape more e^ 
 gradually and with less resistance from the 
 back water, and likewise the resistance of 
 the atmosphere is prevented, by the admis- 
 sion of air at the open angle of the floats. 
 
 Lamherfs Wheel. — As water acts most advantageously 
 upon undershot wheels, when the floats are perpendicular to 
 the surfaces of the st]eam, it has been attempted in diflferent 
 
OF THE MOVING FORCES USED IN THE ARTS. 
 
 269 
 
 ways to keep them always in a vertical position. In the meth- 
 od proposed by Mr Lambert, the floats are hung upon hinges or 
 pivots at the extremities of the spokes, and are kept in a ver- 
 tical position by a large iron ring, which is suspended from the 
 lower extremities of the whole, and is allowed to pass during 
 the revolution through a slit in the middle of each float. In Fig. 
 8, is a view of one side of the wheel Fig. 8. 
 
 with the ring attached. A is the 
 centre of the wheel, B B are spokes 
 or arms of the water wheel C D, 
 C D are the float-boards which are 
 here seen edgeways. E E is a /ji 
 large iron ring connected by joints/^ 
 to the lower extremity of all the o 
 float-boards, and serving by its I n 
 weight to keep them in a vertical \ j 
 position. This wheel is probably 
 too complicated for common use. 
 The iron ring is kept from mov- 
 ing sideways by guides, or friction wheels, placed at each side. 
 Breast WJieel. — The breast wheel is intermediate between 
 the overshot and undershot wheels, having the water delivered 
 upon it at about half its height, or at Fig, 9. 
 
 the level of its axis. In breast wheels 
 in England, buckets are not common- 
 ly employed, but the float-boards are 
 fitted accurately, with as little play as 
 possible, to the mill course, so that 
 the water, after acting upon the float- 
 boards by its impulse, is detained be- 
 tween them in the mill course, and acts by its weight till it 
 reaches the lowest part of the wheel. A breast wheel is repre- 
 sented in Fig. 9, as it is often constructed in this country 
 with buckets, instead of floats, and with a part of its circum 
 ference fitted to the mill course, or apron. 
 
 
270 
 
 OF THE MOVING FORCES USED IN THE ARTS. 
 
 Horizontal Wheel. — A horizontal wheel with oblique 
 floats, sometimes called in this country a tub wheel^ is turned 
 by a current of water discharged against the floats in the man- 
 ner represented in Fig. 10. 
 This method is said to be 
 in common use on the 
 continent of Europe, and 
 but seldom employed in 
 England. It is a disad- 
 vantageous mode of ap- 
 plying power, and is only 
 recommended in corn-mills 
 by its simplicity, the mill- 
 stones being turned directly by the axis of the water wheel, 
 without the intervention of other wheels, or gearing. In the 
 same manner, another kind of tub ivheel, which is a sort of in- 
 verted cone furnished with spiral floats on its inside, is made 
 ta'revolve horizontally, by discharging into it a current of wa- 
 ter from above. 
 
 Barker's Mill. — This machine, which is also sometimes 
 called Parents mill, is driven by an application of the force of 
 water different from any of those which have been already 
 described. This application con- 
 sists, not in the direct use of the 
 weight or impulse of water, but in that 
 of its reaction, or counter pressure- 
 The principle of this simple machine 
 may be seen by inspecting Fig. 11, 
 where C D is a revolving vertical 
 tube, carrying a mill-stone m on the 
 upper part of its axis. At the hot" 
 tom of this tube is a horizontal tube 
 A B, at the extremities of which are 
 two apertures A and B, opening in 
 opposite directions. A stream of water is introduced from the 
 
OF THE MOVING FORCES USED IN THE ARTS. 271 
 
 mill course above, and flows out at the apertures at A and B^ 
 and in this way keeps up a continued horizontal rotary motion 
 around the axis D m. 
 
 In order to understand how this rotary motion is produced, 
 we may suppose the apertures to be shut, and the tube C D 
 filled with water. The area of the apertures A and B will 
 then be pressed outward by a force equal to a column of water 
 whose height is C D, and whose base is equal to the area of 
 the apertures. Every part of the tube A B sustains a similar 
 pressure ; but as these pressures are balanced by equal and 
 opposite pressures, the machine remains at rest. But when the 
 aperture at B is opened, the pressure at that place is removed, 
 and therefore the arm will be carried round in a direction op- 
 posite to that of the aperture, by a pressure which is due to the 
 height of the column and area of the aperture. The same 
 thing happens with the other arm, and the two pressures carry 
 round the vertical axis in the same direction. 
 
 An improvement has been made in Barker's mill by dispen- 
 sing with the tube C D, retaining only its axis ; and introduc- 
 ing the water on the under side of the transverse tube at D. 
 For this purpose the water is brought down from the reservoir 
 at E, by a separate passage, and introduced at D through a 
 water joint, which suffers the arms of the tube to revolve with- 
 out much loss of water. Such a passage is represented by the 
 shaded part E F D. The upward pressure of the water may 
 be made to support a great part of the weight of the machine. 
 
 WIND POWER. 
 
 Currents of water, being limited in magnitude, can be con- 
 fined in their action to one side of a wheel. But it is not easy 
 to do the same with currents of wind, on account of their in- 
 definite magnitude, and the difficulty of screening one half of 
 the wheel advantageously from their action. It is therefore 
 common to employ vertical windmills, having a number of sails 
 
272 OF THE MOVING FORCES USED IN THE ARTS. 
 
 placed obliquely to the wind, and turning on a horizontal axis 
 which is parallel to the wnnd, or nearly so. The action of the 
 wind in this case is resolved into two forces ; and since the sails 
 cannot obey the first by moving in the direction of the wind, 
 they obey the second, and move at right angles with it. 
 
 Vertical Windmill. — The common windmill has usually 
 four sails, and sometimes six or eight. The power of these 
 sails to turn their axis depends, w^hen other things are equal, 
 upon their degree of obliquity in regard to the wind. The an- 
 gle which is most effectual for giving motion to the sails from 
 a state of rest, is an angle of 35^ degrees with the weather, or 
 with the plane in which the sails revolve.* But the angle 
 which produces the greatest action upon a sail at rest, is not 
 the most effectual when a sail is in motion. As the motion 
 increases, the action of the wind diminishes, and in order to 
 preserve this action, the sails require to be brought nearer to the 
 wind. And since each part of the sail, in revolving, has a 
 different velocity, those parts which are nearest the circumfer- 
 ence, being swiftest, are not acted upon so powerfully b}'' the 
 wind as those which are nearer the centre ; on which account 
 it is useful to give the sails a slight spiral curvature, so as to 
 make the angle with the weather at the extremity of the sail 
 less than it is at the centre. When, however, the sails are per- 
 fectly plane, it is advantageous, according to Mr Smeaton, that 
 the angle of the sails with the weather, should be 18 degrees, 
 or less ; in other words, that their angle with the axis should 
 be 72 degrees, or more. The velocity of the sails in this case, 
 at their outer extremity, is often found to be more than twice 
 that of the wind. 
 
 Adjustment of >Sails. — On account of the inconstant na- 
 ture of the motion of the wind, it is necessary to have some 
 provision for accommodating the resistance of the sails, to the de- 
 gree of violence with which the wind blows. This is com- 
 monly done by clothing and unclothing the saUs ; that is, by 
 covering with canvass or thin boards, a greater or smaller por- 
 
 * Determined by Parent — see Brewster's Ferguson's Mechanics, vol. ii. p. 69. 
 
OF THE MOVING FORCES USED IN THE ARTS. 273 
 
 tion of the frame of the sails, according to the force of the wind 
 at different times. A method has been devised for producing 
 the same effect, by altering the obliquity of the sails ; and 
 windmills have been so made, as to regulate their own adjust- 
 ment, by the force of the wind. If we suppose a windmill, or 
 windwheel, to consist of four arms, and that the sails were con- 
 nected to these arms at one edge, by means of springs ; the 
 yielding of these springs would allow the sails to turn back, 
 when the wind should blow wnth violence ; and their elastici- 
 ty would bring them up to the wind, whenever its force abated. 
 This effect has been produced by a weight acting on the sails 
 through a series of levers. A loose iron rod, passing through 
 the centre of the axle of the windwheel, receives the action of 
 the weight at one end, and communicates it to the sails at the 
 other. 
 
 Sometimes a governor hke that described on page 249, is 
 used to regulate the velocity of windmills which are built for 
 grinding, by increasing the supply of corn to be ground, or of 
 work to be done, whenever the force of the wind increases. 
 The governor is also applied in a very ingenious manner to 
 furl or unfurl a portion of the sails, thus accommodating them 
 to variations of the wind. 
 
 As it is necessary that a windmill should face the wind from 
 whatever point it blows, the whole machine, or a part of it, 
 must be capable of turning horizontally. Sometimes the whole 
 mill is made to turn upon a strong vertical post, and is there- 
 fore called a -post mill ; but more commonly the roof, or head 
 only, revolves, carr5dng with it the windwheel and its shaft, the 
 weight being supported on friction rollers. In order that the 
 v/ind itself may regulate the position of the mUl, a large vane, 
 or weathercock, is placed on the side which is opposite the 
 sails, thus turning them always to the wind. But in large 
 mills the motion is regulated by a small supplementary wind- 
 wheel, or pair of sails, occupying the place of the vane, and 
 situated at jight angles with the principal windwheel. When 
 3.5 
 
274 OP THE MOVING FORCES USED IN THE ARTS. 
 
 the windmill is in its proper position, with its shaft parallel to 
 the wind, the supplementary sails do not turn. But when the 
 wind changes, they are immediately brought into action, and 
 by turning a series of wheelwork, they graduallybri ng round 
 the head to its proper position. 
 
 As the resistance occasioned by the side of the building 
 makes a difference in the force of the wind upon the upper 
 and under sails, it is common to incline the sails, and their ax- 
 is, in such a manner that the lower sails shall be farther from 
 the building, than they would be if in a vertical position. 
 
 Horizontal Windmill. — This name is given to those wnnd- 
 mills which turn on a vertical axis. Various methods are em- 
 ployed in their construction, in most of which the wind acts by 
 its direct impulse, as in an undershot water wheel. In the 
 most common forms, the sails, like float-boards, present their 
 broadside to the wind on the acting side of the wheel, but are 
 folded up, or turned edgewise on the returning side. These 
 wheels, however, are found to be greatly inferior to the verti- 
 cal windmill, in the amount of work which they are capable 
 of performing, and at the present day they are little used. 
 
 As wind is the most uncertain of all the moving agents^ and 
 fails totally in times of calm, it is not common to depend upon 
 this power in large works, provided other moving forces can 
 be obtained. The steam engine has in many cases super- 
 seded it, but it is still used in ceitain places for grinding corn, 
 pumping water, and driving inferior machinery. Upon the 
 ocean it is a locomotive agent of incalculable importance. 
 
 STEAM POWER. 
 
 Steam. — The power of steam depends on the tendency 
 which water possesses to expand into vapor, when heated to a 
 certain temperature. Many other substances, and perhaps all, 
 have the same tendency, and those which are volatile at low 
 
OF THE MOVING FORCES USED IN THE ARTS. 275 
 
 temperatures might doubtless be made the sources of moving 
 power in the arts. But since water, which is the most cheap 
 and abundant of these substances^ fortunately possesses also 
 the greatest number of requisites for an expansive agent, it is 
 not hkely to be superseded by any other material. 
 
 When water is converted into steam, it expands to about 
 1700 times its original volume,* so that a cubic inch of water 
 furnishes about a cubic foot of steam, at 212 degrees of Fah- 
 renheit, under the common pressure of the atmosphere. Water 
 cannot, however, be converted immediately into steam by the 
 application of a boihng temperature, but requires a certain pe- 
 riod to effect its volatihzation. This period is about six times 
 as great as that which is necessary to raise it from the freezing 
 to the boiling point, supposing the supply of heat to be uniform. 
 The amount of heat which is absorbed, or rendered latent, by 
 the conversion of water into steam, is about 950 degrees.t 
 
 The power of steam to produce motion in other bodies, de- 
 pends upon the increase of its ovv^n volume ; and whatever body 
 resists this increase, will be acted upon by a force proportionate 
 to the elastic poAver of the steam, and the circumstances un- 
 der which the resistance is made. In a vessel boiling in the 
 open air we are not sensible of the magnitude of this force, be- 
 cause the steam, and the resisting medium against which it 
 acts, are both invisible. But when we consider that the steam, 
 when first generated, has to lift off from the water, before it 
 can assume its elastic form, the weight of the superincumbent 
 atmosphere, and that this weight in the atmospheric column 
 which presses on a vessel only two feet in diameter, is equal to 
 several tons, we may easily conceive of the force which attends 
 this expansion. 
 
 Furthermore, since steam has the propeity of immediately 
 
 ^ * 1633 times, according to Gay-Lussac. See Ure's Dictionary, article Calo- 
 ric. — 1711 times, according to Tredgold. 
 
 t 950, according to Watt.— 967, Ure. 
 
276 OF THE MOVING FORCES USED IN THE ARTS. 
 
 condensing into water, as soon as its temperature is reduced 
 below 212 degrees, it follows that the atmospheric weight 
 which has been lifted by the formation of the steam, will im- 
 mediately fall, when the steam condenses ; and with a force 
 equal to that by which it was raised. This furnishes an indi- 
 rect or secondary application of the power of steam. 
 
 But the powers of steam are not limited by the effects which 
 it produces at the common boiling temperature. If steam be 
 separated from the contact of water, and exposed to a farther 
 increase of temperature, it will continue to expand by the law 
 which governs the increase of all gaseous bodies, and will 
 double its volume once for every 480 degrees of Fahrenheit's 
 thermometer.* And furthermore, if water itself be inclosed 
 in strong vessels and thus heated, its expansive force will be 
 prodigiously greater than that of steam alone, since every par- 
 ticle of the water tends to generate steam of high temperature, 
 and to occupy the space which is due to such steam. In a 
 common boiler containing water and steam, each addition of 
 caloric causes a fresh portion of steam to rise, and to add its 
 elastic force to that of the steam previously existing, so that an 
 excessive pressure is soon exerted against the inside of the 
 vessel, if the augmentation of heat has been considerable. At 
 212 degrees Fahrenheit, steam has an elastic force equal to the 
 pressure of the atmosphere. If it be farther heated in contact 
 with water, it will have a force equal to that of two atmos- 
 pheres at about 250 degrees, of four atmospheres at 293 de- 
 grees, and of eight atmospheres at 344 degrees. These are 
 the results in round numbers of Mr Southern's experiments, 
 and they are nearly confirmed by those of Drs Robison and 
 Ure.t 
 
 * Ure's Dictionary of Chemistry, Art. Caloric and Gas. 
 
 t The recent and elaborate experiments of Messrs Arago and Dulong have 
 corrected these results, and carried the scale as high as fifty atmospheres. 
 Thus an elastic force, equal to the pressure of 20 atmospheres, is produced by a 
 heat of about 418 degrees Fahrenheit, and one of 50 atmospheres by 510 degre^. 
 
OF THE MOVING FORCES USED IN THE ARTS. 277 
 
 At temperatures below 212 degrees, steam has still a certain 
 elastic force, which discovers itself whenever the pressure of 
 the atmosphere is taken off. Thus its elastic force at 180 de- 
 grees is equal to about half an atmosphere ; and it has some 
 force at all temperatures above the freezing point. 
 
 Steam expands in all directions ahke, and is useful as a mov- 
 ing agent, only by its pressure. It cannot, like water and 
 wind, be made to act advantageously by its impulse in the 
 open air ; for the momentum of so hght a fluid, unless generated 
 in vast quantities, would be inconsiderable. Some of the ear- 
 hest attempts, however, at forming a steam engine, consisted 
 in directing the current of steam from the mouth of an eoHpile, 
 against the vanes or floats of a revolving wheel.* In order 
 that the pressure of steam may be rendered available in ma- 
 chinery, the steam must be confined within a cavity which is 
 air-tight, and so constructed that its dimensions, or capacity, 
 may be altered without altering its tightness. When the steam 
 enters such a vessel, it enlarges the actual cavity, by causing 
 some moveable part to recede before it, and from this moveable 
 part, motion is communicated to machinery. A hollow cyl- 
 inder having a moveable piston accurately fitted to its bore, 
 constitutes a vessel of this kind. It was used more than a 
 century ago by Newcomen, and as it is found to combine more 
 advantages than any other kind of arrangement for motion, its 
 use has never been superseded. The piston thus employed 
 has a reciprocating motion, which is converted, when neces- 
 sary, into a rotary one, by the appropriate mechanism. 
 
 Applications of Steam. The pressure of steam is capable 
 of being applied to use in three different ways, and these modes 
 have given rise to some of the most important varieties of the 
 steam engine. The three methods which are used for obtain- 
 ing power from steam are, 1. By condensation, as in the at- 
 mospheric engine. 2. By generation, as in the simple high 
 
 * Such was the engine of Branca, in the beginning of the 17th century^ 
 
278 
 
 OF THE MOVING FORCES USED IN THE ARTS. 
 
 pressure engines, 3. By expansion, as Fi^, 12. 
 
 in Woolfs engine, Watt's expansion en- 
 gine, and some others. These methods 
 have been illustrated by Mr Tredgold 
 by a figure like that in the margin. Sup- 
 pose a cylindric vessel A B C D to be 
 placed in a vertical position, with a giv- 
 en depth of water in the bottom, and 
 an air-tight piston above the watei" bal- 
 anced by a weight D equal to its own 
 weight and friction. In this state let 
 heat f)e applied to the base A C ; then 
 as the water becomes converted into 
 steam of slightly greater force than the 
 atmospheric pressure, the piston will rise 
 till the whole water is in a state of steam. 
 It must be observed, however, that the 
 generation of this steam, which is of at- 
 TTiospheric elastic force, affords no available power, but is sim- 
 ply sufficient to balance the column of atmospheric air, and ex- 
 clude it from a given height of the cylinder. 
 
 By Condensation. — In the state of things just described, if 
 the steam be suddenly condensed into water by the application 
 of cold, it is obvious that the piston will be driven downward 
 with a force equal to the weight of the atmosphere which pres- 
 ses on the piston, and through a distance equal to that which 
 the piston had been raised by the generation of steam. It fol- 
 lows that the power of steam which is of atmospheric elastic 
 force, is, when speedily condensed, directly proportionate to the 
 space which it occupies. If the temperature of this steam be 
 raised above 212 degrees, it will occupy a larger space, the in- 
 crease being equal to the expansion of steam by the given 
 change of temperature. But a quantity of heat nearly equiv- 
 alent to the increase of volume will be absorbed ; and hence, 
 
OF THE MOVING FORCES USED IN THE ARTS. 279 
 
 says Mr Tredgold, the effect of a given quantity of fuel would 
 not be increased by the expedient.* 
 
 By Generation. — Suppose the same C3^hnder and appara- 
 tus to have heat applied to its base, with only the difference of 
 the piston being loaded with a given pressure per inch of its 
 area. The generation of the steam will raise the loaded pis- 
 ton, but the height through which it will be raised will be less 
 than if it were not loaded. The steam having to act in oppo- 
 sition both to the pressure of the atmosphere and the load on 
 the piston, the space it will occupy will be in the inverse ratio 
 of the pressures which oppose it, supposing the steam of atmos- 
 pheric elastic force to have been of the same temperature. 
 Thus, if the load on the piston be equal to twice the atmos- 
 pheric pressure, the piston will be raised only one third of the 
 height ; but on rapid condensation it descends with three times 
 the pressure ; and, therefore, whether the steam be generated of 
 atmospheric elastic force, or of a greater force, the power it af- 
 fords by generation and condensation is the same at the same 
 temperature, and this power is directly as the elastic force of 
 the steam, multiplied by the space it occupies, supposing that 
 the motion of the piston is rectilinear. 
 
 But if, as in the last case, a loaded piston be raised, and then 
 a valve be opened which allows the steam to escape, the whole 
 power gained will be equal only to the weightraised, descend- 
 ing from the height to which it was raised ; and the power 
 which would have resulted from condensation will be lost, and 
 the loss is equal to the pressure of the atmosphere acting through 
 the height to which the piston was raised by steam. This 
 is the nature of the common high pressure steam engine. It 
 is obvious, that the greater the elastic force of the steam, the 
 less is the proportionate loss by neglecting to condense it under 
 these cii^cumstances ; but, it may be remarked, that unless the 
 valve aperture be equal to the diameter of the cylinder, the 
 steam cannot escape at the necessary rate without part of the 
 load acting to expel it ; and so much more of the effective 
 
 * Tredgold on the Steam Engine, p. 157 — 159. 
 
280 OP THE MOVING FORCES USED IN THE ARTS. 
 
 force will of course be lost. The effective power is as the 
 space the steam occupies, multiplied by the excess of elastic 
 force above the atmospheric pressure. 
 
 By Exj)cmsio7i. — Retaining the same loaded piston, let it 
 be raised by the conversion of a given quantity of water into 
 steam, to the height which corresponds to the load and tempera- 
 ture. Then if the load on the piston be wholly removed at 
 that height, the steam will raise the piston by expanding till it 
 becomes nearly of the same elastic force as the atmosphere, 
 and its condensation will produce the same effect as if the steam 
 had been generated of atmospheric elastic force at first. Con- 
 sequently, the effect in raising the load on the piston is wholly 
 additional, and the joint effect of a high pressure and condens- 
 ing engine is produced by the same steam. Hence by this 
 combination of effect, the power of steam of high elastic force 
 will be nearly doubled. 
 
 This is not, however, the mode by which steam can be ap- 
 plied with the greatest advantage ; for, instead of removing 
 the load on the piston wholly at the height to which it was 
 raised by the generation of the high pressure steam, a part of 
 it may be removed, and then the steam would expand to a 
 height depending on the portion of the load removed ; at that 
 height remove a second portion, and so on, successively, till 
 the steam becomes of atmospheric elastic force. In this case, 
 as far as the load was raised in parts by the expansion of the 
 steam, the effect is greater than in the preceding combination. 
 This illustrates the principle of the high pressure expansion 
 engines of Evans, Woolf, and some others. 
 
 Again : let the piston be raised unloaded, as in the first case, 
 by the conversion of a certain quantity of water into steam of 
 atmospheric elastic force. When the piston is at that height, 
 add a weight equal to half the atmospheric pressure to the line 
 passing over the pulley. Then the elastic force of the steam 
 being unbalanced, the piston would rise till that elastic force 
 would be half the atmospheric pressure, or till the piston would 
 be at double its former height. Now, suppose the steam to be 
 
OP THE MOVING FORCES USED IN THE ARTS. 281 
 
 condensed, and the weight removed from the pulley at the 
 same instant. Then the power of the descent, after deducting 
 the power added to produce the ascent, will be one half more 
 than it would have been by simply condensing steam of atmos- 
 phere elastic force. This illustrates the principle of the ex- 
 pansion engines of Hornblower and Watt ; and it differs from 
 tlie principle of Woolf in using steam only of low pressure. 
 The weight added to the line passing over the pulley is intro- 
 duced here merely to exemplify the mode of applying a portion 
 of the excess of power which is accumulated in the fly wheel, 
 in one part of the operation, to assist the machine through the 
 rest. 
 
 It has been assumed that steam at least of atmospheric elas- 
 tic force was generated, but this is not a necessary condition, 
 for it frequently occurs that engines work with steam of less 
 elastic force. The same inode of illustration will show whence 
 this happens. Let half the pressure of the atmosphere on the 
 piston be balanced by a weight over a pulley. Then on the 
 application of heat, steam of half the atmospheric elastic force 
 would be generated, and raise the piston to double the height 
 that it would be raised, in common cases, by steam capable of 
 supporting the atmospheric pressure. Consequently on its 
 being condensed, the descending force will be half the atmos- 
 pheric pressure acting through double the height ; and the 
 steam produces the same effect as before. 
 
 The foregoing methods of the application of steam will be 
 found apparent in the different forms of the steam engine, in 
 which they have been called into use. 
 
 The Steam Engine.— -The steam engine is a machine by 
 which the power derived from steam is converted to practical 
 use. It has occupied the attention of philosophers and artists 
 for more than a century, and is now brought to so great a de- 
 gree of perfection as, in the opinion of many scientific men, to 
 leave little probability of its further improvement. Whether 
 viewed with reference to the great skill which has been era- 
 ployed in perfecting it, or the importance and extent of its ap- 
 36 
 
282 OF THE MOVING FORCES USED IN THE ARTS, 
 
 plication, it may justly be viewed as the noblest production of 
 the arts in modern times. For acquiring a clear conception of 
 the steam engine as it is now^commonly constructed, it will be 
 useful to consider, first, the boiler in which the power is gene- 
 rated, and secondly the engine in which it is directed and ap- 
 plied to use. 
 
 Boiler. -^On account of the gradual rate at which water 
 boils away, it is necessary in most engines to keep a large quan- 
 tity constantly heated, to aflTord steam with sufficient rapidity 
 for its consumption by the engine. This water is enclosed in a 
 strong tight vessel, called the boiler, which is made of iron or 
 copper, and rests in contact with a furnace. It is requisite^ 
 that a boiler should be of sufficient strength to resist the great- 
 est pressure which is ever liable to occur from the expansion of 
 the steam. It must also offer a sufficient extent of surface to 
 the fire, to insure the requisite amount of vaporization. In 
 common low pressure boilers, it requires about eight feet of 
 surface of the boiler to be exposed to the action of the fire and 
 flame, to boil off a cubic foot of water in an hour ; and a cubic 
 foot of water thus converted into steam is equal to a one-horse 
 power. * 
 
 The strongest form for a boiler, and one of the earliest which 
 was used, is that of a sphere ; but this form is the one which of- 
 fers least surface to the fire. The figure of a cylinder is on 
 many accounts the best, and it is now extensively used, espe- 
 cially for engines of high pressure. It has the advantage of 
 being easily constructed from sheets of metal, and the form is 
 of equal strength except at the ends. In such a boiler, the 
 ends should be made thicker than the other parts. The fur- 
 nace is so constructed that the flame and hot smoke may pass 
 under the whole length of the boiler, and afterwards around 
 both its sides, before escaping to the chimney. 
 
 In what are cailed_^?«e boilers j a cylindrical furnace is placed 
 within a cylindrical boiler, so that the fuel is surrounded by 
 
 * See Tredgold on the Steam Engine, with the following correctionj p. 124, 
 line 2 from the bottom. For steam read icater. 
 
OP THE MOVING FORCES USED IN THE ARTS. 283 
 
 water on all sides, and communicates to it nearly all its heat, 
 except the portion which passes np the chimnej''. 
 
 In large engines, which are of low pressure, the form of the 
 boiler, which was used by Mr Watt, still continues to be em- 
 ployed, particularly in England. In this boiler the upper half 
 is a semicyhnder, while the lower half is nearly rectangular, 
 with the under side concave, so that a cross section would 
 nearly resemble a horse-shoe. This boOer is less strong than 
 those of a cylindrical form, but it offers a larger surface to the 
 fire, without occupying much more space. A boiler of this 
 kind, as it is fitted up in large engines, with appendages for 
 regulating its own fire, water, and steam, is represented in PL 
 VIII. Fig. 5. A part of the furnace is supposed to be taken 
 away, to bring the boiler into view, and also a portion of the 
 boiler is removed to show its inside. 
 
 Appendages. — In the figure above referred to, B B B B is 
 the boiler, made of thick sheets or plates of rolled iron strongly 
 rivetted together, a part of v^diich are removed to show the 
 interior. It is supposed to be half full of water at the boiling 
 temperature. C is the steam gauge, the object of which is to 
 determine the degree of pressure acting within the boiler. It 
 is a bent iron tube, or inverted syphon, one end of which com- 
 municates with the boiler, and the other end with the atmos- 
 phere. The tube is partly filled with mercury, and as the 
 pressure of the steam increases, the mercury will be driven 
 outward and will rise in the external leg of the syphon. As 
 the height of the column of mercury cannot be seen, the tube 
 being opaque, a small wooden stem is made to float in the tube, 
 with its end projecting by the side of a graduated scale. Every 
 inch in height which the stem rises, shows a difference of two 
 inches in the two surfaces of the mercury in the tube, and in- 
 dicates a pressure of about a pound upon every square inch of 
 the inner surface of the boiler. And as low pressure engines 
 are seldom worked with more than three or four pounds to the 
 square inch, the mercury seldom rises higher than three or four 
 inches in such engines. In high pressure engines, the mercu- 
 
284 OF THE MOVING FORCES USED IN THE ARTS. 
 
 rial gauge is not so easily applied ; for these engines are fre- 
 quently worked at a pressure of several atmospheres, and each 
 additional atmosphere requires an addition of nearly 15 inches 
 to the column of mercury. 
 
 W is a large opening called the man hole, of sufficient size 
 to permit a man to enter the boiler to clean or examine it. It 
 is closed by a strong iron plate. D is the steam pipe which 
 conveys the steam to the engine. It is provided with a throt- 
 tle valve, which is a circular disc, or partition, turning on an 
 axis, and connected with the governor, described on page 252. 
 Its use is to regulate the supply of steam by closing the pipe, 
 if the engine goes too fast, or by opening it, if it is too slow. 
 F F are the gauge cocks, which indicate the height of wa- 
 ter in the boiler. Their extremities stand at different depths 
 in the boiler, one being below the surface of the water, and the 
 other above it. When the water is at the proper height, one 
 of these will emit steam, on being opened, and the other will 
 emit water. They are frequently placed on the end instead 
 of the top of the boiler. 
 
 For keeping up a regular supply of water to the boiler, a 
 vertical tube G, called ih& feed pipe, is used. Upon its top is a 
 small cistern H H H H, which is kept full of water by a pump 
 worked by the engine. At the bottom of this cistern is a valve 
 E, connected to one end of the lever a h. At the other end of 
 this lever is a wire a c, which passes through a steam-tight 
 opening at d, and supports a stone float c upon the surface of 
 the water, the stone being counterbalanced by a weight at the 
 valve e. When the water lowers in the boiler, the stone float 
 descends, and by acting upon the lever a h, opens the valve e. 
 Water immediatel}^ flows in from the cistern, and continues to 
 do so, till the float rises and shuts the valve. It will be ob- 
 served that the column of water in the feed pipe must be suffi- 
 ciently high to counterbalance the pressure of steam in the 
 boiler. On this account it cannot be applied in high pressure 
 engines, without making it of a very inconvenient height. In 
 these engines, therefore, water is supplied to the boiler by a 
 
OF THE MOVING FORCES USED IN THE ARTS. 285 
 
 small forcing pump, worked by one of the reciprocating parts 
 of the engine ; and it is frequently heated before being pump- 
 ed in, that it may not check the production of steam. 
 
 For the purpose of regulating the fire, the feed pipe is fur- 
 nished with an iron bucket O, hung by a chain which passes 
 over two pullies P P, and is attached by its other extremity to 
 an iron damper A, which commands the chimney. When the 
 steam in the boiler is urged to too great an extent, it forces the 
 water upward in the feed pipe, and causes the iron bucket to 
 ascend. This lowers the damper into the smoke flue, and by 
 thus intercepting the current of air, checks the force of the fire. 
 In some boilers the passage, which brings air to the fire, is in- 
 tercepted, instead of the smoke flue. 
 
 To prevent the boiler from bursting, if by accident the pres- 
 sure of the steam should become too great for the strength of 
 the boiler, a safety valve is provided at S, opening outward. 
 It is kept down by a weight, so that it cannot be raised except 
 by a greater force than that which is required to work the en- 
 gine. It is highly important, however, that it should not be 
 liable to any other weight or incumbrance than that which 
 the engine requires ; and to prevent this danger, it is inclosed 
 in a case which is kept locked. When the engine stops work- 
 ing, or the steam is generated too rapidly for its expenditure, 
 the safety valve rises, and the superfluous steam rushes out 
 with a hissing noise. 
 
 Another safety valve is also provided, which differs from the 
 preceding, in opening inwards. It is kept up by a counter 
 weight on a lever, and its use is to prevent the weight of the 
 atmosphere from crushing in the sides of the boiler, when the 
 engine stops working, and the steam cools. 
 
 As boilers are usually proved before being submitted to use, 
 the accident of bursting does not happen from a general want 
 of strength, unless the safety valve be overloaded. It is most 
 likely to happen either from neglect, in suffering the water to 
 get too low, in some part of the boiler, so that the metal is ex- 
 cessivelyheatedj or else from the coiTosion of the metal in places, 
 
286 OF THE MOVING FORCES USED IN THE ARTS. 
 
 by oxidation, after long exposure to the fire. If a sediment ig 
 suffered to accumulate to a considerable depth on the bottom 
 of the boiler, it has the effect to exclude the water from con- 
 tact with the metal, so that the metal becomes hotter, and is 
 more rapidly oxidated, and even softened, by the heat. 
 
 The violent explosions which have sometimes occurred, 
 projecting the contents and fragments of the boiler to a great 
 distance, have been rationally accounted for, by supposing that 
 certain parts of the metal, through neglect, become heated to 
 a high temperature, and that portions of water being sudden- 
 ly brought into contiguity with them, produce steam, of which 
 the initial elastic force is extremely great. In this case, the 
 boiler may burst before the inertia of the water, or safety valves, 
 is overcome ; and the stronger is the boiler, the greater may be 
 the explosion. 
 
 As a great number of lives has been lost by the explosion of 
 boilers, particularly on board of steam-boats, much attention 
 has been bestowed on the means of preventing such accidents. 
 The principal attempts have consisted in a more accurate reg- 
 ulation of the safety valves, and in the introduction of plugs 
 of fusible metal which melt when the temperature is raised a 
 little above the boiling point of water, and thus suffer the steam 
 to escape. But absolute security has only been found in plac- 
 ing the boiler in such a situation that if it should burst, it would 
 occasion no injury to the passengers in the boat. This is ef- 
 fected by placing the engine in a boat by itself, or by interpos- 
 ing a strong barrier between the boilers and the persons on 
 board the boat. Mr Treadwell has proposed to use the steam 
 at a pressure not greater than that of the atmosphere, and to 
 compensate the loss of force by an increase in the size of the 
 cylinder and piston.* 
 
 Besides the forms of the boiler already mentioned, various 
 others have been employed, such as combinations of tubes, and 
 other figures, intended to multiply surface, for the purpose of 
 
 * See Appendix. 
 
OP THE MOVING FORCES USED IN THE ARTS. 28T 
 
 raising more steam from the same amount of water, in a given 
 time. They have been apphed in some high pressure engines, 
 but in most cases, the simpler forms are preferred.* In Brath- 
 waite and Ericsson's engine, which has been apphed with par- 
 ticular success to propelling carriages on rail roads, the hot air 
 of the furnace is forcibly drawn in a circuitous flue, through 
 the boiler, by means of a revolving, fan-like apparatus ; thus com- 
 municating to the boiler a greater quantity of heat in a given 
 time, than could be obtained from the common atmospheric 
 draught. 
 
 Engine. — The steam being generated in sufficient quanti- 
 ties in the boiler, it is next applied to use in the working or 
 moving part, which we have called the engine. Of this en- 
 gine a great variety of forms and modifications have been pro- 
 posed and adopted, &t different times. A few of those which 
 are effectual in their principle, and most extensively employed, 
 will now be considered. 
 
 Noncondensitig Engine. — The simplest form of the steam 
 engine, is that of the noncondensing, commmonly called the 
 high pressure engine. In this engine, the apparatus for con- 
 densation is dispensed with, and the steam is worked at a high 
 temperature, and afterwards discharged into the open air. Of 
 course, a part of the force of the steam is expended in overcom- 
 ing the pressure of the atmosphere, and the surplus only can 
 be applied to drive machinery. That this surplus may be suf- 
 ficient to produce the requisite power, a pressure of 30 or 40 
 pounds on a circular inch, above the atmospheric pressure, is 
 commonly kept up in these engines, t 
 
 The manner in which the engine is made to operate, is 
 briefly as follows. The steam in escaping from the boiler to 
 the open air, is obliged to pass through the cylinder, the cav- 
 
 ♦ In Perkins' engine, a strong vessel called a generator, is kept full of water 
 heated to a high temperature. Portions of the water are successively forced out ; 
 and reliance is placed on the heat already in this water, to produce from it the 
 requisite amount of steam. 
 
 t See Tredgold on the steam engine, p. 181. 
 
288 OP THE MOVING FORCES USED IN THE ARTS. 
 
 ity of which is closed, except where it communicates with the 
 valves. By the opening and shutting of these valves, the 
 steam is made to enter the cylinder alternately at each end, 
 and escape by the opposite end. But in doing this, its passage 
 is always intercepted by the piston, so that before it can escape, 
 it must move the piston from one end to the other of the cy- 
 linder. The repetition of this movement gives motion to a 
 beam, or other alternating part, from which it is communica- 
 ted by a connecting rod and crank, to a fly wheel, in the same 
 manner as is seen in the condensing engine, PI. IX. hereafter 
 to be described. The figure there represented may be consid- 
 ered as a noncondensing engine, if we remove from it the con- 
 denser and its appendages, occupying the lower part of the 
 plate. B represents the boiler, C the pipe which conveys the 
 steam, D the cylinder, E the piston, F the beam, h the crank, 
 G the fly wheel. 
 
 The different apparatus of valves, by which the entrance 
 and escape of steam is regulated, also the other appendages of 
 the engine, wiU be considered in another place. In arranging 
 the time of their opening and shutting, it is usual to allow not 
 quite all the steam to escape at the end of the stroke. A small 
 portion is retained to receive the shock of the piston, and by 
 its elasticity to destroy its momentum, and cause it to recoil 
 back without loss of force. 
 
 Noncondensing engines sometimes work by the generative 
 force of steam, and sometimes by the generative and expansive 
 force. They are used in cases where simplicity and lightness 
 is required, as in locomotive engines ; also in situations where 
 a sufficient supply of water for condensation cannot easily be 
 obtained. They are inferior in safety to condensing engines ; 
 yet as they cost much less at the outset for the expense of 
 building, they are often preferred for small, or temporary 
 works. In proportion to the high temperature at which the 
 steam is worked, great caution is necessary in regard to the 
 strength and management of the boiler in these engines. 
 
OP THE MOVING FORCES USED IN THE ARTS. 289 
 
 Condensing Engines. — Engines of this class are fitted up 
 with an apparatus for condensing the steam into water, so that 
 a vacuum, nearly complete, is formed in one part of the cylin- 
 der, just before the stroke of the piston into that part takes 
 place. By this construction the resistance of the atmosphere 
 is avoided, and thus the power of the engine to perform work, 
 is much increased. The steam also is sufficiently powerful 
 for use, at comparatively low temperatures, and hence arises the 
 increase of safety which is found in loio pressure etigines, a 
 name given to those condensing engines, which are worked 
 with steam of moderate elastic force. 
 
 In the atmospheric engine, invented by Newcomen, the 
 piston was raised by the steam, aided by a counter weight, till 
 it arrived at the top of the cylinder, which was left perfectly 
 open. A jet of water was then admitted into the bottom of 
 the cylinder, which suddenly condensed the steam, so that, a 
 vacuum being formed, the piston was driven down by a force 
 equal to the weight of the column of superincumbent air. The 
 water was now excluded by a stop cock, and the steam re- 
 admitted. The piston was thus again raised, and the process 
 repeated as before. 
 
 A great inconvenience attended this method, arising from the 
 cii"cumstance, that the cylinder itself required to be heated and 
 cooled at each stroke of the piston, thus occasioning great de- 
 lay, and an unnecessary expense both of fuel and of cold 
 water. To remedy this evil, Mr Watt invented the separate 
 condenser, which is a strong vessel situated at a distance from 
 the cylinder, but communicating with it by a pipe, so as to 
 form with it a common cavity, without reducing materially its 
 temperature. Into this vessel the jet of cold water is thrown, 
 and as all the communicating pipes are governed by valves, or 
 cocks, the cyhnder below the piston is alternately filled with 
 steam from the boiler, and emptied of steam by the condenser. 
 In the double acting efigirie, invented by Mr Watt, the top 
 of the cylinder was closed, and rendered air-tight, the rod of the 
 piston only passing through it. Thus the cyhnder is divided 
 37 
 
290 OF THE MOVING FORCES USED IN THE ARTS. 
 
 by the piston into two cavities, both communicating with the 
 boiler, and both with the condenser. By the aid of valves, an 
 alternate communication is kept up, so that the steam being al- 
 ternately admitted at both ends, impels the piston successively 
 in both directions, while the condenser, at the same time, de- 
 stroys the resistance. In this engine, compared with the sin- 
 gle engine of Mr Watt, which was previously in use, a double 
 quantity of steam is used, and a double power exerted in the 
 same space and time. 
 
 Description. — In PL IX is a view of a double acting steam 
 engine, nearly as constructed by Murray, and upon the same 
 general principles as those of Mr Watt, varying, however, in 
 the valves, and some other particulars. 
 
 A represents the furnace, which is here shown in section, as 
 is also the boiler above it, and all the principal cavities of the 
 engine. The flame and hot smoke, after passing underneath 
 the boiler for its whole length, return through the side passages 
 d d, before they are discharged into the chimney. 
 
 B is the boiler, which, in this example, is of a cylindrical 
 foim, a shape better adapted for strength than that represented 
 in PI. VIII. The appendages represented in PI. VIII. are not 
 here repeated. Some of them, indeed, are not used in steam 
 boats, and in small engines. The boiler is commonly made of 
 sheets of iron, strongly rivetted together and tightened by ham- 
 mering. If intended to contain salt water, the boiler is made 
 of copper, to prevent corrosion. 
 
 C C C is the steam pipe, Avhich carries the steam from the 
 boiler to the cylinder through the valve I. It is made of cast- 
 iron, and its joints screwed together by flanges. 
 
 D is the cylinder, communicating by passages at the top and 
 bottom with the valve I. The cylinder is made of cast-ii'on, 
 and accurately bored, to make its inner surface smooth and 
 true. 
 
 E the piston, which, by its rod e, gives an alternating motion 
 to the beam//, about its centre F, the other end of which, by 
 another connecting rod g, gives motion to the heavy fly wheel 
 
OF THE MOVING FORCES USED IN THE ARTS. 291 
 
 G G, by means of a crank h. Thus, after the engine has be- 
 gun to work, its power is accumulated in the fly wheel, and a 
 circular motion may be communicated from it to any ma- 
 chinery. 
 
 H is an eccentric circle on the axle of the fly wheel G. It 
 gives motion through the medium of its levers w x and y z, 
 and the connecting rods Ji w a: y and 2; I, in a manner easily 
 understood, by inspection, to the valve I. 
 
 I is a coffer valve, capable of sliding up and down, and hav- 
 ing a cavity on the side next the cylinder. By moving up and 
 down, it opens and shuts the passages, and admits the steam 
 alternately to each end of the cyUnder ; and at the same time 
 forms a communication between the opposite end and the con- 
 denser. 
 
 W is the governor, which regulates the speed of the engine. 
 It resembles the governor described in Chap. XI, but has its 
 moveable collar on the top at s. It may be turned by a band 
 from the axle of the fly wheel, or placed directly over the axle, 
 and geared to it by bevel Avheels. When the fly wheel moves 
 too fast, the balls of the governor recede from their centre, and 
 by acting on the lever r s, cause it to turn upon its fulcrum t, 
 and partially to close the steam pipe by a throttle valve at K. 
 When the velocity abates, the balls subside, and the valve 
 opens so as to admit more steam. 
 
 L is the air pump, the use of which is to discharge the air 
 and water which coUect in the condenser, M. 
 
 M is the condenser, which is an empty cylindrical vessel 
 immersed in a cistern of cold water, S S, and communicating 
 with the cylinder by the pipe O. It has a valve or cock com- 
 municating with the cistern, and moved by the rod g g; through 
 which a jet of cold water enters it for the purpose of condensing 
 the steam. 
 
 N a small cistern, filled with w^ater. Into this cistern enters 
 a pipe from the condenser M, the top of which pipe is covered 
 by a valve, which is called the blow-valve, or sometimes the 
 snifting-valve. Through this valve, the air contained in the 
 
292 OP THE MOVING FORCES USED IN THE ARTS. 
 
 cylinder D, and passages from it, is discharged, on the engine 
 being first set in motion. 
 
 O the eduction-pipe, which conducts the steam from the 
 valve I. to the condenser M. 
 
 P the pump which supplies with water the cistern, or cold 
 well S S, in which the condenser and discharging pump 
 stand. 
 
 Q, Q, iron columns which support the beam. Of these the 
 engine has four, although only two are shown. They gtand 
 upon one entire plate, seen edgewise, on which the principal 
 parts of the engine are fixed. 
 
 R R the recess below the floor, for containing the cistern of 
 the discharging pump, condenser, &.c. 
 
 The condenser M, and the air pump L, communicate by 
 means of a horizontal pipe containing a valve m, opening to- 
 wards the pump ; the piston n of this pump also contains two 
 valves, and the cistern T, at the top of the pump cylinder, con- 
 tains other two valves, which, like those of the piston n, open 
 upwards. When the piston E of the cylinder is depressed, the 
 piston n of the discharging pump, it will be obvious to inspec- 
 tion, will be depressed likewise, and its valves open, while the 
 valve m closes ; hence the water of the condensed steam, as 
 well as the injection water, and any vapor of air which may 
 be present, having passed through the valve m, passes through 
 the piston ?i ; and when that piston is drawn up, its valves close 
 and prevent their return, as in common pump work. The 
 water and air that have thus got above the piston, as the latter 
 rises, open the valves at the bottom of the cistern T, in which 
 the water remains till it is full, but the air passes into the at- 
 mosphere. As the water in the cistern T is in a hot state, a 
 part of it, for the purpose of economizing fuel, is pumped up 
 and returned to the boiler, the pump rod being attached to the 
 great beam. 
 
 The steam constantly rushing into the condenser M,. has a 
 perpetual tendency to heat that vessel, as well as the water of 
 the cistern S S, in which it stands ; the whole of the steam, 
 
OF THE MOVING FORCES USED IN THE ARTS. 293 
 
 if this were unchecked, would not be condensed, or the con- 
 densation would not be sufficiently rapid, because the injection 
 water itself flows out of this cistern. A part of the water 
 is therefore allowed to flow from this cistern by a waste pipe, 
 and an equal quantity of cold water is constantly supplied by 
 the pump P. 
 
 The cylinder D is in many cases surrounded by a case, to 
 keep it from being cooled too much by contact with the exter- 
 nal atmosphere. 
 
 Expansion Engines. — The steam which impels an engine 
 is always diminished in volume, by the resistance which it has 
 to overcome, and tends naturally to occupy a larger space than 
 that to which it is confined while the engine is at work. If it 
 be dismissed into the air, or into the condenser, while under 
 its greatest working pressure, it will not have produced all the 
 useful effect which it is capable of affording. If, on the con- 
 trary, it be separated and placed under circumstances where it 
 can still expand further, before it is dismissed, this expansion 
 will be so much additional gain to the power of the engine. 
 Its general principles have already been discussed. 
 
 The expansive power of steam may be converted to use in 
 various ways, and most of the common forms of the steam en- 
 gine may be made to act expansively by a proper arrangement 
 of their valves. In Watt's engine, this effect is produced by 
 cutting off" the steam from the cylinder before the stroke of the 
 piston is completed, leaving it to the steam already in the 
 cylinder to assist by its expansion in completing the stroke. 
 The steam in the boiler being thus intercepted, acts only at 
 intervals. Nevertheless, its whole disposable force is accumulat- 
 ed in the fly wheel, while, at the same time, the force arising 
 from the expansion of steam in the cylinder serves to increase 
 the total amount. A great augmentation is thus produced in 
 the useful effect of an engine, with the same amount of fuel 
 and water. 
 
 Mr Hornblower, who was one of the first inventors of the 
 application of expansive steam, employed two cylinders hav- 
 
294 OP THE MOVING FORCES USED IN THE ARTS. 
 
 ing their pistons connected to the same beam. In the smaller 
 of these, the steam was used at full pressure, after which it was 
 discharged into the larger cylinder, where it again acted by its 
 expansive force. This method affords a more equable mode 
 of applying the expansive force of steam than that used by 
 Mr Watt, but the engine is more complex and expansive. 
 
 Mr Woolf afterwards adopted the plan of two cylinders with 
 the addition of using his steam at a high pressure, together 
 with a condenser. He appears to have exaggerated the ex- 
 pansive force of steam, at high temperatures, as various other 
 projectors have done. His engines, however, continue to be 
 used and approved, in some parts of England and Wales. 
 
 Valves. — The valves of steam engines are shutters, which 
 guard the avenues to the boiler and condenser, so that by open- 
 ing and shutting them, at the required time, the steam may 
 be made to enter, or escape, at either end of the cylinder. 
 Valves of a great variety of forms, have been used in different 
 engines, some of which have a reciprocating, others a rotary 
 motion. The puppet valve is a cone, or frustum of a cone, 
 which is fitted, like a cover, to a conical aperture, which it 
 opens by rising, and closes by falling. A valve of this kind 
 is seen at Y. in PI. IX. Sliding valves are those which do not 
 rise, but slide on and off of their apertures. Some of these 
 have a cavity on their under side, capable of connecting two 
 apertures together, or of forming a communication between 
 them, while a third aperture is shut. This is the case with 
 the valve I, in PI. IX. Rotary valves are usually constructed 
 like common stopcocks, excepting that they command more 
 passages than one at the same time. If the handle be placed 
 in one position, it opens one passage while it closes another ; if 
 in a different position, it closes the first, and opens the second. 
 A throttle valve is a partition turning on an axis, and placed 
 across the interior of a pipe. If turned edgewise, it permits 
 the steam to pass ; but if turned transversely, it obstructs its 
 passage. This valve is commonly placed in the main steam 
 pipe, and connected with the'governor to regulate the quantity 
 oi steam supplied by the boiler. See K, in PI. IX. 
 
OF THE MOVING FORCES USED IN THE ARTS. 295^ 
 
 On account of the heat which is kept up in steam engines, 
 the principal valves require to be of metal, and are fitted by 
 grinding closely to their seats. Yalves made with leather, like 
 the common clack valve of a pump, can only be used about 
 the condenser, where the temperature is low, as the valve m 
 Pi. IX. 
 
 Pistons. — As the piston is liable to continual wear by its 
 friction against the inside of the cylinder, it can only be kept 
 sufficiently tight by rendering its circumference elastic. This 
 is commonly done by winding it with hemp loosely twisted. 
 The hemp packing, however, gets out of order in time, and 
 requires to be renewed. To remedy this, evil, various plans 
 have been introduced, for making elastic pistons of metal only. 
 The pistons invented by Cartwright and Barton, consist of 
 several parallel circular plates in close contact with each other. 
 These are cut into segments, and the segments pressed out- 
 ward by steel springs, care being taken that the fissures in the 
 different plates do not coincide. In the piston of Jessop, a spi- 
 ral coil of steel is wound on the circumference of the piston, 
 which expands by its own elasticity, so as to keep in tight con- 
 tact with the cyUnder. To increase the tightness and elas- 
 ticity of the piston, a hempen packing is placed within the 
 coil. 
 
 Parallel Motion. — A simple form of a parallel motion, for 
 converting the rectilinear motion of the piston into the curvili- 
 near one of the beam, has already been described on page 243. 
 Another form is shown in PL IX, where the rod a b turns up- 
 on the joint a as a fixed centre, while the rod c b turns upon 
 & as a centre. While the point c would describe a curve about 
 its centre b, the point b describes an opposite curve about its 
 centre a. These two curvatures compensate each other, so 
 that the point c, to w^hich the piston is attached, describes near- 
 ly a straight line. 
 
 The parallel motion was introduced by Mr Watt, and is 
 probably attended with less friction than any other arrangement 
 for effecting the same object. It requires, however, to be con- 
 
296 OP THE MOVING FORCES USED IN THE ARTS. 
 
 structed with great accaiacy. Various other methods have 
 been apphed to convert the rectihnear into a curvihnear move- 
 ment. Sometimes the piston is confined to its path by guides, 
 or friction wheels, and connected to the beam by a double 
 joint. In Newcomen's engine, where the principal force was 
 in the downward stroke, the piston was connected by a chain 
 to an arched head at the end of the beam. In Cartwright's 
 engine, the piston was attached to two opposite cranks which 
 were geared together, as shown on page 244. In some of 
 Murray's engines, the epicycloidal movement was employed. 
 See page 246.* In Maiidslay's engine, and some others, in- 
 stead of a beam, a crosss head is used, the whole of which 
 moves up and down in guides, instead of turning on a centre. 
 In the vibrating engines of Lester and others, the cylinder is 
 hung upon a moveable axis, and in Morey's engine, the cylin- 
 der revolves like a fly wheel, the piston being made to act on 
 a fixed crank. 
 
 Historical Remarks. — The following are some of the most 
 interesting facts in the history of the Steam Engine. 
 
 The ancient Greeks and Romans appear to have been ac- 
 quainted with the power of steam to produce motion, and in- 
 vented the eolipile, which was a close vessel containing water, 
 and which gave out a forcible current of steam whenever the 
 water was heated. The force of this current was used by 
 Hero to produce a revolving motion. 
 
 The power of confined steam, acting by its pressure, was 
 discovered by the Marquis of Worcester, and an account of its 
 effect published by him in 1663. He produced a steam pow- 
 er sufficient to burst a cannon, and constructed a machine ca- 
 pable of raising water to the height of forty feet. He has not, 
 however, left any drawings or particular description of his ma- 
 chine. 
 
 In 1698, a patent was granted to Thomas Savery, for a 
 method of raising water by steam. This apparatus consisted 
 
 * For an account and figure of an engine of this kind, see Farey on the Steam 
 Engine, p. 686, and PI. XVII. 
 
OF THE MOVING FORCES USED IN THE ARTS. 297 
 
 of a boiler, a separate steam vessel, and pipes commanded l^y 
 valves. The steam from the boiler was first admitted so as to 
 fill the steam vessel. It was then condensed, and the steam 
 vessel filled with water which rose by the atmospheric pressure 
 from the well or mine. The steam was then readmitted, and 
 the water in the vessel was driven upward to the top of tlie 
 pipes, and discharged. 
 
 About the year 1705, Thomas Newcomen, constructed a 
 working steam engine, which has since been called the atmos- 
 j)herlc engine. It contained a cylinder and piston, and an al- 
 ternating beam, which was applied to raise water by working 
 a pump. The water was condensed in the cylinder itself, and 
 the valves were moved by hand, until an attendant contrived 
 to make the machine move its own valves, by attaching strings 
 to the working beam. 
 
 After this the steam engine continued without any impor- 
 tant alteration, for more than half a century, when, about 1769, 
 the discoveries and inventions of James Watt gave a new 
 spring to the energies of this machine, and have more than 
 doubled the power which it formerly possessed. Mr Watt's im- 
 provements were numerous and important, but those of great- 
 est value were the following. 1. He introduced the separate 
 condenser. 2. He applied the double action of steam by 
 closing the top of the cylinder, and admitting the steam alter- 
 nately at each end. 3. He converted to use the expansive 
 power of steam, by cutting off the current before the end of 
 the stroke. Mr Watt also invented the principle of the par- 
 allel motion, and appHed the governor, to regulate the supply of 
 steam. 
 
 In 1802, the first high pressure or noncondensing engines 
 were constructed by OUver Evans, in Philadelphia, and in the 
 same year by Trevithick and Vivian, in England. The idea 
 of such an engine had before occurred to Leupold, Watt, and 
 others. The first steam carriage was put in motion on a rail- 
 way, by Trevithick and Yivian, in 1805. 
 
 Steam ?iavigaiion was suggested in England by Jonathan 
 
298 OF THE MOVING FORCES USED IN THE ARTS. 
 
 Hulls, in 1736. It was first tried in practice by the Marquis 
 de Jouffroy in France, in 1782, and nearly at the same time in 
 America, by James Rumsey of Virginia, and John Fitch of 
 Philadelphia. It was first made practically successful by Rob- 
 ert Fulton, at New York, in 1807. The first steam vessel 
 w^iich crossed the Atlantic, was the American ship Savannah, 
 in 1819. 
 
 Projected Improve^nents. — Besides the improvements which 
 have been actually effected in the construction and application 
 of the steam engine, a variety of projects for increasing the 
 power and usefulness of this agent, have from time to time 
 occupied the attention of ingenious men. Of the improve- 
 ments which have been attempted, some are opposed by ob- 
 stacles which have not yet been satisfactorily surmounted, and 
 others by difficulties in themselves insurmountable. The fol- 
 lowing have been among the most prominent subjects of spec- 
 ulation. 
 
 1. Rotative Engines. — These are engines in which the 
 steam is so applied as to produce a direct rotary motion with- 
 out the intervention of a rectilinear movement. Engines on 
 this principle have been constructed in many different ways. An 
 idea of one of the most obvious forms may be obtained from 
 the eccentric pumps described in the following Chapter, which 
 have been converted into steam engines, by reversing the mo- 
 tions, and changing the resistance for the power. Some rota- 
 tive engines have been constructed on the principle of Barker's 
 mill ; others have been made by immersing an overshot wheel 
 in a cistern of heated fluid, either water, oil, or melted metal, 
 and delivering the steam under the ascending or inverted buck- 
 ets, so that w^hen these were filled with steam, the full buckets 
 on the opposite side might preponderate and cause the wheel 
 to revolve. But in general the rotary engines hitherto con- 
 structed, have either been feeble in power, or encumbered with 
 excessive friction, on account of the extensive packing which 
 is necessary to keep them tight ; so that none of them have 
 found their way into use. It is probable that no method of 
 
OF THE MOVING FORCES USED IN THE ARTS. 299 
 
 constructing a variable cavity for steam, which is in other re- 
 spects suitable, affords so advantageous a mode of applying 
 the power, as the cylinder and piston producing rectilinear 
 motion. 
 
 Use of Steam at high Temperatures. — In noncondensing 
 or high pressure engines, the power which is convertible to use, 
 consists of the surplus, which remains, after overcoming the 
 pressure of the atmosphere. Of course, the higher is the tem- 
 perature at which the steam is worked, the greater is the total 
 gain, supposing the absorption of heat and the production of 
 power to continue to take place in equal proportions. This 
 consideration, with other expected advantages, has given rise 
 to many attempts to improve the steam engine, by devising 
 modes of applying steam at much higher temperatures than 
 those which it has been ordinarily found practicable to employ. 
 Attempts of this kind have also frequently been founded upon 
 an undue estimate of the elastic force of steam at high tem- 
 peratures, and of the absorption of heat during its production. 
 In practice, it is found difficult to obtain a material capable of 
 confining water and steam in safety, when raised to such a 
 temperature as to produce a pressure of ten or more atmos- 
 pheres ; since, independently of the strain upon the joinings, 
 the cohesive strength of metals is diminished, and their oxi- 
 dation promoted, by exposure to great heat. 
 
 Use of Vapors ofloio Temperature. — Certain liquids, such 
 as alcohol, ether, sulphuret of carbon, and a liquid obtained by 
 condensing oil gas, have been proposed as substitutes for wa- 
 ter, in producing steam, on account of the low temperature at 
 which they are converted into vapor. Thus alcohol boils at 
 about 173 degrees of Fahrenheit, sulphuric ether at 9S degrees, 
 muriatic ether at 51 degrees,* sulphuret of carbon at 116 de- 
 grees, and oil gas liquid at 1S6 ; all of which are lower than 
 the boiling point of water. Some of these, when raised to the 
 boiling point of water, have a much greater elastic force than 
 that fluid. Thus the sulphuret of carbon at 212 degrees, has 
 
 * Ure's Dictionary. 
 
300 OF THE MOVING FORCES USED IN THE ARTS. 
 
 an elastic force equal to about four atmospheres,* and sulphuric 
 ether of nearly six atmospheres. Bat these advantages 
 are nearly counterbalanced by the small spaces through 
 which these vapors act, their volume at their boiling point be- 
 ing only from about an eighth to a third part of that of steam, 
 at the boiling point of water. To this disadvantage may be 
 added the expensive character of these substances, and the 
 difKculty of condensing them without loss, in any working en- 
 gine. Some of them likewise, as the ethers, act chemically 
 upon metals, and could not on this account be employed in 
 engines made of the common materials. 
 
 Oas Engines. — It has been attempted to obtain power for 
 propelling machinery, from the combustion, or explosion, of 
 inflammable elastic fluids, such as coal gas, and the vapor of 
 combustible liquids, mixed with atmospheric air. In com- 
 bustions of this kind, rarefaction and subsequent condensa- 
 tion take place, which, if conducted within suitable cavities, 
 may be made to aflford a moving power, applicable to machin- 
 ery. The principal engines which have been constructed for 
 using this power, are those of Messrs Morey, in this country, 
 and Brown, in England. If a power of this kind could be 
 made to afford an adequate propelling force for locomotive en- 
 gines upon public roads, it would possess an advantage in the 
 lightness of the machinery, compared with the weight of steam 
 engines with their water and fuel. But it remains for experi- 
 ence to determine, whether the space through which the force 
 will act, taken in connexion with the cost of the materials, can 
 render this an economical source of power. 
 
 In addition to the foregoing method of procuring power by 
 the combustion of gases, Sir H, Davy has proposed the em- 
 ployn^ont of certain fluids which are volatile at common tem- 
 per; , res, but which have been condensed into liquids under 
 great pressure, such as carbonic acid, ammonia, &c. His 
 views are founded upon the immense difference which exists 
 
 * See Tredgold's tables, Steam Engine, p. 78—81. 1 
 
OF THE MOVING FORCES USED IN THE ARTS. 301 
 
 between the increase of elastic force in gases under high and 
 low temperatures, by similar increments of temperature. But 
 doubts have been raised upon this subject, with regard to the 
 space through which the force of these gases will act, and also 
 in regard to the quantity of h«at required to produce the change 
 of temperature required.* 
 
 Steam Carriages. — It has long been a favorite object with 
 projectors to construct a form of the steam engine in connexion 
 with a carriage, which should be capable of propeUing itself 
 upon the public roads. Locomotive engines are capable of 
 moving themselves upon rail roads, and of drawing with them 
 additional loaded carriages ; because in this case the motion is 
 uniform, and very little of the power is expended in surmount- 
 ing obstacles, or changing the form of the road. But upon a 
 public highway it requires, by a common estimate, about eight 
 times as much power to propel a carriage, as it does upon a 
 rail road. Of course, the weight and inertia of an engine ca- 
 pable of producing this power, must increase somewhat in the 
 same proportion, and a great part of the power will become 
 necessary to transport the machine itself. The inertia, also, 
 will be continually brought into unfavorable action by the jolts 
 and concussions inseparable from highway travelling, and thus 
 endanger the destruction of a machine requiring such nice 
 adaptation of parts as the steam engine. It appears that steam 
 carriages have been made to run upon good roads, during 
 short experiments, while the engine was new. But we have 
 no account, as yet, of any one having long performed this kind 
 of service. 
 
 Steam Gun. — Mr J. Perkins,t whose experiments on the 
 steam engine are well known, has attempted the employment 
 of the expansive force of steam, as a substitute for gunpof^der, 
 in thro wmg projectiles. The steam gun invented by hi; ' -is 
 somewhat similar in its construction to the air gun, but the 
 
 * Philosophical Transactions, 1826, Tredgold on the Steam Engine, p. 84. 
 t The public are indebted to Mr Perkins for the art of steel engraving, the 
 nail machine, and many other useful inventions. 
 
302 OP THE MOVING FORCES USED IN THE ARTS. 
 
 power is derived from a magazine of water heated to a very 
 high temperature, so that when portions of it are discharged 
 from the vessel containing it, they produce steam enough to 
 project a cannon ball with great force. The balls are admit- 
 ted into the gun, in succession, from a hopper, and can be dis- 
 charged at the rate of 24 in a minute. It appears from some 
 experiments made with these guns in France,, that the projec- 
 tile force of steam is greatly inferior to that of gunpowder, a 
 consequence, no doubt, of the vast difference which is known 
 to exist in the initial force of the two agents ; nevertheless, the 
 rapidity with which the discharges may be made, seems capa- 
 ble of advantageous employment in some situations. 
 
 GUNPOWDER. 
 
 Manufacture. — Gunpowder is a solid explosive mixture 
 composed of nitre, sulphur, and charcoal, reduced to powder, 
 and mixed intimately with each other. The proportion of the 
 mgredients varies very considerably ; but good gunpowder may 
 be composed of the following proportions ; — 76 parts of nitre, 
 15 charcoal, and 9 sulphur, equal to 100. These ingredients 
 are first reduced to a fine powder separately, then mixed inti- 
 mately, and formed into a thick paste. This is done by 
 pounding them for a long time in wooden mortars, at the same 
 time moistening them with water, to prevent the danger of ex- 
 plosion. The more intimate is the mixture, the better is the 
 powder ; for since nitre does not detonate, except when in con- 
 tact with inflammable matter, the Avhole detonation will be 
 more speedy, the more numerous the surfaces in contact. Af- 
 ter the paste has dried a little, it is placed upon a kind of sieve 
 full of small holes, through which it is forced. By that pro- 
 cess it is divided into grains, the size of which depends upon 
 the size of the holes through which they have passed. 
 
 The powder when dry, is put into barrels, which are made 
 to turn round on their axis. By this motion the grains of gun- 
 
OP THE MOVING FORCES USED IN THE ARTS. 303 
 
 powder rub against each other, their asperities are worn off, and 
 their surfaces are made smooth ; the powder is then said to be 
 glazed. The granulation and glazing of the powder causes it 
 to explode more quickly, perhaps by facilitating the passage of 
 the flame among the particles. 
 
 Detonation. — When gunpowder comes in contact with any 
 ignited substance, it explodes, as is well known, with great vi- 
 olence. This effect may take place even in a vacuum. A 
 vast quantity of gas or elastic fluid is emitted, the sudden pro- 
 duction of which, at a high temperature, is the cause of the vi- 
 olent effects which this substance produces. The combustion 
 is evidently owing to the decomposition of the nitre by the 
 charcoal and sulphur. The products are caibonic oxide, car- 
 bonic acid, nitrogen, sulphurous acid, and probably sulphuret- 
 ed hydrogen. Mr Cruikshanks has ascertained that no per- 
 ceptible quantity of water is formed. What remains after the 
 combustion, is potash combined wdth a small portion of carbon- 
 ic acid, sulphate of potash, a very small proportion of sulphur- 
 et of potash, and unconsumed charcoal. 
 
 Force. — The elastic fluid which is genei'ated, when gun- 
 powder is fired, being very dense, and much heated, begins io 
 expand with a force at least lOUO times greater than that of air 
 under the ordinary pressure of the atmosphere. And allowing 
 the pressure of the atmosphere to be 14f pounds upon every 
 square inch, the initial force, or pressure, of fired gunpowder 
 will be equal to at least 14,750 pounds upon every square inch 
 of the surface wdiich confines it. But this estimate, which is 
 that of Mr Robins, is one of the smallest which has been 
 made. According to Bernoulli, the initial elasticity with 
 which a cannon ball is impelled, is at least equal to 10,000 
 times the pressure of the atmosphere, and from Count Rum- 
 ford's experiments it appears more than three times greater 
 than this. 
 
 Gunpowder, on account of its expensiveness, and the sud- 
 denness and violence of its action, is not employed as a regu- 
 lar moving force for machinery. It is chiefly applied to 
 
304 OF THE MOVING FORCES USED IN THE ARTS. 
 
 the throwing of shot and other projectiles, and the blasting of 
 rocks. 
 
 When a ball is thrown from a gun, the greatest force is ap- 
 plied to it by each particle at the moment of its explosion. 
 But since the ball cannot at once acquire the same velocity 
 Avith which the elastic fluid if at liberty would expand, it con- 
 tinues to be acted upon by the fluid, and its motion is accele- 
 rated in common cases, until it has escaped from the mouth of 
 the piece. The accelerating force, however, is not uniform, 
 and hence the following circumstances deserve attention. 1. 
 The elasticity is inversely as the space which the fluid occu- 
 pies, and, therefore, as it forces the ball out of the gun, it con- 
 tinually diminishes. 2. The elasticity would diminish in this 
 ratio, even if the temperature remained the same ; but it must 
 diminish in a much greater ratio, because a reduction of tem- 
 perature takes place, both from the dispersion of the heat, and 
 the absorption of it by the fluid itself, during its rarefaction. 
 3. The fluid propels the ball by following it, and acts with a 
 force that is, cetmrus 'paribus^ proportionate to the excess of 
 its velocity above the velocity of the ball. The greater the 
 velocity that the ball has acquired, the less, therefore, is its 
 momentary acceleration. 4. From this change of relative ve- 
 locity, there mvist be a period, when the velocity of the ball 
 will exceed that of the elastic fluid, and therefore the proper 
 length for a gun must be that, in which the ball would leave 
 the mouth, at the time when the velocities are equal ; and all 
 addititional length of the piece beyond this, can only serve 
 to retard the ball, both by friction and atmospheric pressure. 
 
 The force of fired gunpowder is found to be very nearly 
 proportionate to the quantity employed ; so that if we neglect 
 to consider the resistance of the atmosphere, then the height 
 to which the ball will rise, and its greatest horizontal range, 
 must be directly as the quantity of powder, and inversely as 
 the weight of the ball. Count Rumford, however, found that 
 the same quantity of powder exerted somewhat more force 
 upon a large ball than on a smaller one. 
 
OF THE MOVIjNTG FORCES USED IN THE ARTS. 305 
 
 Properties of a Gun. — The essential properties of a gun, 
 are to confine the elastic fluid as completely as possible, and 
 to direct the course of the ball to a rectilinear path ; and 
 hence arises the necessity of an accurate bore. The ivindage^ 
 or space produced by the difference of diameter between flie 
 ball and the bore, greatly diminishes the effect of the powder, 
 by allowing a part of the elastic fluid to escape before the ball. 
 The advantage of a rifle barrel is chiefly derived from the more 
 accurate contact of the ball with its cavity. When the bore is 
 twisted, it is also supposed to produce a rotation of the ball 
 round an axis, in the direction of its motion, w^hich renders it 
 less liable to deviate from its path on account of irregularities 
 in the resistance of the air. The usual charge of powder is 
 one fifth, or one sixth of the weight of the ball ; and for batter- 
 ing, one third. When a twenty four pounder is fired with 
 two thirds of its weight of powder, it may be thrown about four 
 miles, the distance being reduced by the resistance of the air, 
 to about one fifth of that which it would describe if thrown in 
 a vacuum.* 
 
 It is certain that the grains of gunpowder do not inflame at 
 once, but that the inflammation occupies time in being commu- 
 nicated from one particle to another, so that they act succes- 
 sively, rather than simultaneously, in impelling the ball. This 
 circumstance contributes greatly to the safety of fire-arms, for 
 if the whole charge of powder exploded at once, the piece 
 would be in danger of bursting before the inertia of the ball 
 would be overcome. It is on account of the suddenness of their 
 detonation, that the various fulminating powders are inapplica- 
 ble to use in fire-arms. The bursting of a gun may be occa- 
 sioned by the defective condition of the metal, the dispropor- 
 tionate amount of the charge, the adhesion and inertia of the 
 shot, or the inertia of some other body opposing the escape 
 of the charge. It is from this last circumstance that a gun is 
 liable to burst, if fired with its muzzle under water. 
 
 * Young's Natural Philosophy, vol. i. p. 350. 
 
 39 
 
306 OP THE MOVING FORCES USED IN THE ARTS. 
 
 To enable gunpowder to exert its full effect, the proportions 
 of the cavity of the piece, to the charge, should be such, as to 
 allow all the grains to explode before they leave the cavity ; 
 and also to permit the elastic fluid to expend as much of its 
 pressure as is capable of accelerating the ball. The superiori- 
 ty of a musket over a pistol, arises from its prolonging the ac- 
 tion of the powder in this way. But for reasons already stat- 
 ed, there are hmits to the length of the barrel, which cannot 
 be usefully exceeded, and these have been nearly settled by 
 common practice. 
 
 Blasting. — The splitting of rocks by gunpowder is perform- 
 ed by drilling holes to a certain depth, and inserting a charge 
 of powder at the bottom. The hole is then filled up by ram- 
 ming in fragments of stone, bricks, or other hard substances, 
 keeping in a steel wire, which is afterwards withdrawn to fur- 
 nish a passage for the priming by which fire is communicated 
 to the charge. To prevent the danger of a spark, copper wire 
 is often used instead of steel. And to prevent the small frag- 
 ments from flying about, it is found useful to cover the rocks 
 with brush wood, or some other elastic substance. 
 
 Rocks may be blasted at a considerable depth under water, 
 by means of the diving bell, which enables workmen to drill 
 and charge them in safety. In the method practised at Howth, 
 in Ireland, after the charge is inserted, a tin tube is carried up 
 from the rock to the surface of the water. It is kept empty 
 and made water tight by screwing the joints to each other as 
 the bell ascends. The povi'der is ignited by dropping pieces 
 of red hot iron through the tube, from a boat at the surface. 
 When the depth exceeds twelve feet, no danger or inconve- 
 nience is experienced by the boats, beyond a violent eruptive 
 ebullition of the water. 
 
OF THE MOVING FORCES USED IN THE ARTS. 307 
 
 Smeaton'5 Miscellaneous papers, 4to. 1814; — Robison's Mechani- 
 cal Philosophy, vol. ii. and iii. ; — (Jregory's Mechanics ; — Brewster's 
 Ferguson's Mechanics ; — Nicholson's Operative Mechanic, 8vo. ; — 
 Farey's Treatise on the Steam Engine, 4to. 1827 ; this is the most ex- 
 tensive work on its subject ; — Tredgold on the Steam Engine, 4to. 
 1828 ; this is the most philosophic work on the subject ; — Stuart on the 
 Steam Engine, 8vo. 1824 ; — Partingdon on the Steam Engine, 8vo. 
 1825; — Kenwick on the Steam Engine, 8vo. New York, 1830; — Bos- 
 SUT Traite Theoretique et Experimentnl (T Hydrodynamique, 1771 ; — 
 Du BuAT TraiU d' Hydraulique, &c. 1786, &c.; — Playfair's Outlines 
 of Natural Philosophy, 8vo. 1819; — Ure's Dictionary of Chemistry; — 
 Works of Coulomb, Desaguliers, De La Hire, Deparcieux, Hut- 
 ton, Robins, Rumford, &c. 
 
CHAPTER XIIL 
 
 ARTS OF CONVEYING WATER. 
 
 The employment of water as an agent for producing mo- 
 tion, has already been considered. It remains to attend to the 
 various modes by which this liuid may be conveyed from one 
 place to anothei-, either for use in the arts, or for application to 
 the necessary purposes of life. The principal circumstances 
 which require attention under this head are the following. 1. 
 The conducting of water from one place to another having 
 the same, or a lower, level. 2. The raising of water to a 
 higher level. 3. The projection of water through the atmos- 
 phere. 
 
 OF CONDUCTING WATER. 
 
 Aqueducts. — When water flows in a current or stream, as 
 in rivers or canals, it does so in obedience to gravitation, and 
 in consequence of the surface being lower at the end towards 
 which it is flowing, than in that from which it proceeds. Its 
 motions are governed by laws somewhat different from those of 
 solid bodies descending upon inclined planes, and this differ- 
 ence is owing to the want of cohesion among the particles. 
 Instead of moving simultaneously, the particles continually 
 change their relative position, so that while one portion of the 
 fluid may be moving rapidly, another may be stationary, or 
 even moving by an eddy in a contrary direction. The mo- 
 tion, however, will continue both in open channels, and in 
 properly constructed pipes, until an equilibrium is produced, by 
 the surface at both ends of the channel, arriving at the same 
 
ARTS OF CONVEYING WATER. 309 
 
 level. Aqueducts are artificial channels or conduits for the 
 conveyance of water in a horizontal or descending direction. 
 The aqueducts constructed by the ancient Romans, were 
 among the most costly monuments of their arts. Several of 
 these were from thirty to a hundred miles in length, and con- 
 sisted of vast covered canals built of stone. They were car- 
 ried over valleys and level tracts of country upon arcades, 
 which were sometimes of stupendous height and solidity. A 
 similar metliod has been practised in some modern cities of 
 warm or temperate climates. 
 
 In colder latitudes, if the course of the aqueduct is above 
 the ground, the water is liable to be interrupted by freezing in 
 winter. It has therefore become common to resort to subter- 
 ranean passages for water, which are placed so deep as to be 
 below the reach of frost, and are, also, favorably situated both 
 for convenience and economy. Culverts and drains which are 
 intended merely to remove and expend water, are usually made 
 of brick oi* stone ; but for conveying water with the smallest 
 expenditure by loss, water j^ipes are most frequently resorted 
 to. 
 
 Water Pipes. — The pipes by which water is conveyed be- 
 neath the ground, are generall}^ of small or moderate size, and 
 are intended to be water tight. In consequence of a well 
 known law of fluids, a water pipe may possess any degree of 
 flexure, and any number of cui'vatui'es below the level of the 
 fountain head ; yet if it be not obstructed by air, or any other 
 internal obstacle, it will rise at the discharging end, and may 
 be delivej-ed at the height of the original level.* Pipes for 
 transmitting water have been made from a great variet}^ of 
 materials. It is desirable that they should possess strength, 
 tightness, and durability, and that the material of which they 
 are composed should not be capable of contaminating the wa- 
 ter. Wooden pipes are commonly hollow logs, perforated by 
 
 * It appears that the use of water pipes was not unknown to the ancients. 
 Some rules respecting the use of leaden and earthen pipes are given by Vitruvius, 
 de Architectura, Lib. viii. 
 
310 ARTS OF CONVEYING WATER. 
 
 boring through their axis, and connected together by making 
 the end of one log conical, and insertirig it into a conical cavi- 
 ty in the next. When large trunks are required, they are 
 composed of thick staves, and hoops, like a cask. The)'^ should, 
 where practicable, be imbedded in clay, and buried at a great- 
 er depth than the frost is ever known to penetrate. Wooden 
 pipes are in common use in this country, but are liable to de- 
 cay, especially at the joints, where their thickness is smallest, 
 In salt marshes they are more durable, though still liable to de- 
 cay from the attrition and decomposing effect of the water with- 
 in them. 
 
 Iron "pipes are, at the present day, considered preferable to 
 those of wood, being stronger, and in most situations more du- 
 rable. They are made of cast-iron, with a socket, or enlarged 
 cavity at one end, into which the end of the next pipe is re- 
 ceived. The joints thus formed are rendered tight, either by 
 filling the interstices with lead, or by driving in a small quan- 
 tity of hemp, and filling the remainder of the socket with iron 
 cement, made of sulphur, muriate of ammonia, and chippings 
 of iron. Copper pipes are extremely durable, and are made 
 of sheet copper, with the edge turned up and soldered. They 
 require to be tinned inside, on account of the poisonous char- 
 acter of some of the compounds, which are liable to be formed 
 in them. Lead pipes are much employed for small aqueducts, 
 owing to the facility with which they can be soldered and 
 bent in any direction. They are commonly cast in short 
 pieces, and afterwards elongated by drawing them through 
 holes, in the same manner as wire. Leaden pipes, in general, 
 are supposed not to contaminate the water contained in them, 
 because the carbonate of lead, which is sometimes formed in 
 them, is insoluble in water. They are not safe, however, for 
 pumps and pipes intended to convey acid liquors. Stone pipes 
 preserve the water contained by them in a very pure state. 
 They are, however, expensive, on account of the labor of work- 
 ing them, with the exception of soap stone, which, being easi- 
 ly shaped and bored, may be usefull}'^ applied to the purpose of 
 conveying water, in those places where it is easily procured, 
 
ARTS OP CONVEYING WATER. 311 
 
 Earthen pipes, made of comrnon pottery wate and glazed on 
 the inside, are sometimes used, but are more liable to be brok- 
 en than most of the other kinds. 
 
 Friction of Pipes. — In a river, or open channel, it is observ- 
 able that the water flows most rapidly in the middle of the 
 upper surface, while it is most retarded at the edges and at the 
 bottom. In like manner in a cylindrical pipe, the fluid has the 
 greatest velocity at the centre, or axis, and the smallest velocity 
 at the surface, or where it is in contact with the pipe. The 
 force by which this retardation is occasioned, is commonly called 
 friction. It differs in many respects from the friction of solids, 
 and more resistance is occasioned by the internal action of the 
 fluid particles upon each other, than by the contact of the solid 
 surface in which they are contained. The investigation of 
 the laws which govern the movements of fluids is intricate, 
 and the results of experiment have not agreed with the previ- 
 ous conclusions of theory. Various writers on the science of 
 hydraulics have treated this subject with an extensiveness of 
 research, which can only be understood from their own works. 
 Among the more simple practical facts, to whicli it is useful 
 to attend, the following may be briefly stated. 1. The velocity 
 of water is greater in a large pipe than in a small one having 
 the same position, and hence a large pipe will discharge more 
 water in a given time, than a number of small ones having 
 jointly the same capacit}^ A pipe of two inches diameter will 
 give more water than five pipes of one inch diameter ; it being 
 ascertained that the squares of the discharges are very nearly 
 as the fifth powers of the diameters.* 2. Irregularities and 
 inequalities in the diameter of the pipe, diminish the amount 
 of water which they transmit, by altering the direction of the 
 particles, and by changing their velocity, so as to renew the 
 resistance of inertia, 3. In like manner all curves and angles, 
 which occur in the pipe, have a similar retarding effect, by 
 creating new motions or counter currents. 4. The form of 
 the end of the pipe which communicates with the fountain 
 
 * Robison's Mechanical Philosophy, vol. ii. p. 578. 
 
312 ARTS OF CONVEYINa WATER. 
 
 head, or reservoir, greatly affects the quantity of water re- 
 ceived by it. If it be gradually enlarged like a trumpet mouth, 
 a larger quantity of water will be received than by any of the 
 modes which follow, because the direction given to the particles 
 by this form, is most favorable to their adaiission. If the en- 
 trance to the pipe be abrupt, in consequence of the cavity be- 
 ing wholly cylindrical, the particles will have a tendency to 
 cross each other, and less water will enter the pipe in a given 
 time. And if the end of the pipe projects into the reservoii', a 
 variety of opposing forces will be produced among the particles 
 moving toward the entrance, so that a smaller quantity \vill 
 be received b}^ the pipe, than in either of the preceding cases. 
 
 The form of the discharging orifice also influences the quan- 
 tity of water delivered by a pipe in a given time. If the end 
 of the pipe be enlarged, by adding to it a frustrum of a hollow 
 cone, the amount of water dis''harged in some cases, may be 
 prodigiously increased.* This fact, described by Venturi, ap- 
 pears to be the result of the pressure of the atmosphere, aided 
 by the inertia and cohesiveness of the water. 
 
 Obstruction of Pipes. — Water pipes are liable to be ob- 
 structed, chiefly by the following circumstances. 1. By the 
 freezing of the water in winter, if the pipe has not been laid 
 sufficiently deep. 2. By the deposition of sand and mud in 
 the lower parts of the pipe. To obviate this, the water should 
 pass through a strainer before it enters the pipe. And if plugs 
 are placed at the lower parts of the bendings, then, whenever 
 these are opened, the water rushes out with sufficient rapidity, 
 and carries the deposition with it. 3. By the penetration of 
 roots, or the growth of aquatic vegetables, in the cavity of the 
 pipe. This principally happens in wooden pipes, after they 
 begin to decay. 4. By the collection of air in the upper parts 
 of the bendings. This is a serious evil, and may take place 
 in all pipes which have an undulating course, or more vertical 
 curvatures than one. When air is thus confined in the pipes, 
 the water will not rise to the same height at the discharging 
 
 * See Edinburgh Encyclopedia, Art. Hydrodynamics, pp. 494, 495. 
 
ABTS OF CONVEYING WATEK. 
 
 313 
 
 end, as at the fountain head. The air being the lighter fluid, 
 tends to occupy the highest part of the bendings. Any pres- 
 sure apphed at the fountain head tends to push this air a httle 
 beyond the highest part, so as to make it occupy a portion of 
 the descending side of the curve. Of course the sum of the 
 weights in the descending sides, will be less than the sum of 
 the weights in the ascending sides, and the fluids will not be 
 in equilibrium, except when the water at the fountain head is 
 higher than that at the discharging end. The conditions 
 upon which this equilibrium is produced are the same as those 
 which sustain the fluid at different levels in Hero's fountain, 
 the spiral pump, and the hydrostatic lamp. 
 
 The prevention of this evil consists in avoiding vertical 
 curves, and in laying the pipe, if possible, with an uninterrupt- 
 ed slope or at least with only one slope in each direction. 
 When this is done, the air will escape, at one, or both, ends 
 of the pipe. But when vertical curves are unavoidable, an 
 open tube, the height of which is equal to that of the foun- 
 tain head, should be attached to the highest part of the curve. 
 By this arrangement the air will readily escape. In like 
 manner, if a tight air-box be fastened upon the upper part of 
 the curve, and filled with water, the air will escape into this 
 box and displace the water, without interrupting the current 
 in the pipe. The aii-box may be made to regulate itself, and 
 to discharge the air when it is full, by means of a valve in the 
 top connected with a floating, hollow copper ball. As the air 
 increases, the copper ball will subside with the water, till it 
 opens the valve for the air to escape. In Fig. 1, A B repre- 
 
 Fig. 1. C A 
 
314 ARTS OP CONVEYING WATER. 
 
 sents an undulating pipe, of which A is the fountain head and 
 B the discharging end. The water and air will arrange 
 themselves as represented hy the darker and hghter paris 
 of the tube, and being in equilibrium, no water will be dis- 
 charged. If an upright tube, C, be attached to either of the 
 upper flexures, it will discharge the air from that flexure. Or 
 if a tight box, or vessel, D, be substituted, with a copper float 
 and valve, it will have a similar effect. Simple punctures 
 made in the upper part of the pipe also answer a temporary 
 purpose. 
 
 Syphon. — The syphon may be regarded as an instrument 
 for the lateral conveyance, rather than the rising of water, 
 since the fluid must always be delivered at a lower level than 
 that at which it is received. The syphon is a bent tube, of 
 which one extremity, or leg, is longer than the other. If the 
 shorter leg be inserted in a fluid, and the air be exhausted 
 from the longer leg, by suction or otherwise, till the syphon is 
 full of water, then the column of fluid in the longer leg will 
 preponderate, and the current will take place. This will con- 
 tinue either till the water in the feeding vessel sinks below the 
 end of the syphon, or that in the receiving vessel rises to the 
 same height with the other. As the movement depends upon 
 the pressure of the atmosphere, water cannot be raised in a 
 syphon to a greater height than 34 feet. 
 
 For practical use the longer leg of the syphon is often clbs- 
 ed with a stop cock, and the air exhausted fiom it by a small 
 pump, till the leg is full. The stop cock is then opened, and 
 the fluid immediately flows through the syphon. 
 
 OF RAISING WATER. 
 
 The lateral conveyance of water is eflfected in the modes 
 already described, by the aid of its own gravity. The raising 
 of water is effected against gravity, by the employment of some 
 moving force. Hydraulic machines for raising water, may be 
 
ARTS OF CONVEYING WATER. 315 
 
 impelled by a current, or fall, of the water itself, or by any 
 other moving agent. Among a great variety of machines 
 which have been constructed for this use, the following are 
 some of the most noticeable. 
 
 Scoop Wheel. — If a water wheel is provided with a hol- 
 low axle, and if in the place of spokes, or radii, it is fur- 
 nished with crooked tubes, or cavities, of a suitable curva- 
 ture, it will raise water to the height of its own axis, when- 
 ever it revolves in the direction of the mouths of the tubes. 
 Each spoke, or curved tube, as it dips its extremity in the 
 water, lifts a certain portion of the fluid, and as the revolu- 
 tion continues, this water will flow Fig. 2. 
 through the tube approaching near- 
 er to the axis, until it is discharg- 
 ed into the central hollow. To pre- 
 vent the water from regurgitating, 
 the inner ends of the tubes must be 
 guarded by valves, or else made to 
 project for a short distance into the 
 central cavity, as seen at A in Fig. 2. 
 In the latter case it is necessary that 
 they should enteral different distances from the end of the axle. 
 The axle may also be divided into as many longitudinal com- 
 partments, as there are tubes in the wheel. This was done 
 in the ancient tympanum, a machine described by Virtruvius, 
 which was somewhat similar in its principle to the scoop 
 wheel. 
 
 Persian Wheel. — The Persian wheel, in certain respects, 
 resembles the scoop wheel, and is sometimes combined with it 
 in the same machine. It differs from it in its efl^ect, by raising 
 the water through the whole diameter of the wheel. Its form 
 is easily understood, by supposing a number of buckets to be 
 hung round the circumference of a water wheel, upon pivots, 
 at equal distances. As the wheel turns, the buckets are suc- 
 cessively immersed in the water at the bottom, and filled. 
 
$16 ARTS OF CONVEYING WATER. 
 
 They then pass upwards till they arrive at the top of the wheel, 
 where the}' strike a fixed obstacle aiid are overset, discharging 
 their water into a trough placed at the top to receive it. This 
 machine is said to be in common use in several of the Oriental 
 countries. 
 
 Noria. — The machine used in Spain under the name of 
 noria, consists of revolving buckets like the Persian wheel. 
 But instead of a single wheel, two drums, or trundles, are em- 
 ployed, and the buckets are attached to ropes or chains passing 
 round them. In Spain, earthen pitchers are said to be used, 
 but in other countries wooden buckets are employed, like those 
 of an overshot wheel. A sufficient idea of the form of the 
 noria may be obtained by inspecting the figure of the chain 
 wheel, on page 264, and supposing the motion reversed. 
 
 Rope Pump. — Instead of a series of buckets connected by 
 ropes or chains, a similar effect is sometimes produced by a 
 simple rope, or a bundle of ropes, passing over a wheel above, 
 and a pulley below, moving with a velocity of about 8 or 10 
 feet in a second, and drawing up a certain quantity of water by 
 its friction. It is probable that the water commonly ascends 
 with about half the velocity of the rope. While the water is 
 principally supported by the friction of the rope, its own cohe- 
 sion is sufficient to prevent it from wholly falling, or being 
 scattered, by any accidental inequality of the motion. The 
 portion raised is collected in a trough at the top. 
 
 Hydreole. — This name is given by M. Mannoury Dectot, 
 to an invention for raising water by the admixture of atmos- 
 pheric air. If a column of wafer be intimately mixed with 
 air in small bubbles, the air will occupy some time in ascending 
 to the surface, and the mean while the collective specific grav- 
 ity of the whole column will be much less than if it consisted 
 of water alone. If a vertical tube be placed in a reservoir of 
 water, and if a quantity of air be injected into the bottom of 
 the tube, by a bellows, or forcing pump, the water in the tube 
 will immediately rise to a higher level, arid remain until the 
 
ARTS OF CONVEYING WATER. 
 
 317 
 
 air has escaped at the top. And if the tube be of proper height, 
 the wafer will overflow in the same manner as it does during 
 the ebullition of Wiing liquids. This appears, however, not 
 to be a very economical mode of applying forc*^.. 
 
 Archimedes' Srreio. — This name is given to a machine 
 formed by one or more pipes wound spirally round a cylinder 
 which revolves on an axis in an oblique situation. It is used 
 in some places imder the name of water snail. Its mode of 
 operation may be easily conceived, by supposing a tube, form- 
 ed into a hoop, to be rolled up an incUned plane, in which 
 case the fluid would be forced, by the elevation of the tube be- 
 hind it, to run as it were up hill. The Fig. 3. 
 screw is usually turned by a water 
 wheel. During each revolution the 
 lower end of each spiral tube is immers- 
 ed in the water, and dips up a certain 
 quantity. This water, by its gravity, 
 keeps to the lower side of the screw, as 
 seen in Fig. 3, but at the same time, in ^^H 
 consequence of the revolutions of the 
 screw, it passes continually upward until it is delivered at the 
 highest end. 
 
 This instrument -is sometimes made by fixing a spiral par- 
 tition round a cyUnder, and covering it with an external coat- 
 ing, either of wood or of metal. It should be so placed with 
 Tespect to the surface of the water, as to fill in each turn one 
 half of a convolution ; for when the orifice remains always im- 
 mersed, its etfect is much diminished. It is generally inclined 
 to the horizon in an angle of between 45 and 60 degrees ; 
 hence it is obvious that its utility is limited to those cases in 
 which the water is only to be raised to a moderate height. 
 The spiral is seldom single, but usually consists of three or 
 four separate coils, forming a screw which rises more rapidly 
 round the cylinder. 
 
 A water screw, which operates in a similar manner, may be 
 
318 ARTS OF CONVEYING WATER. 
 
 made by a spiral partition wound upon a central axis, and re- 
 volving by itself within a smooth hollow cyhnder, to the cavi- 
 ■ty of which it is nearly fitted. In this form, however, there is 
 some loss by the leakage between the screw and the cylinder 
 which contains it. 
 
 Spiral Pmnp. — This machine is formed by a spiral pipe 
 consisting of many convolutions, arranged either in a single 
 plane, as in Fig. 4, or in a cylindrical or 
 conical surface, and revolving round a 
 horizontal axis. The pipe is connected 
 at one end by a central water tight joint, 
 to an ascending pipe, while the other end 
 receives, during each revolution, nearly 
 equal quantities of air and water. It was 
 invented about 1746, by Andrew Wirtz, ^S 
 a pewterer at Zurich, whence it is often called the Zurich 
 machine. It is said to have been used with great success at 
 Florence, and in Russia. Dr Young states that he has made 
 use of it for raising water to a height of forty feet. The end of 
 the pipe is furnished v/ith a spoon, containing as much water 
 .as will fill half of one of its coils. The water enters the pipe 
 'a little before the spoon has arrived at its highest situation, 
 the other half remaining full of air. The air communicates 
 ■ the pressure of the column of water to the preceding portion, 
 .and in this manner the effect of nearly all the water in the 
 wheel is united, and becomes capable of supporting the column 
 of water, or of water mixed with air, in the ascending pipe. 
 'The air nearest the joint is compressed into a space much 
 •smaller than that which it occupied at its entrance, so that 
 •where the height is considerable, it becomes advisable to admit 
 .a larger portion of air than would naturally fill half the coil. 
 This lessens the quantity of water raised, but it lessens also 
 the force required to turn the machine. The joint should be 
 conical, in order that it may be tightened when it becomes loose, 
 and the pressure ought to be. removed from it as much as pos- 
 
ARTS OF CONVEYING WATJER. 
 
 319 
 
 sible. The loss of power, supposing the machine well con- 
 structed, arises only from the friction of the water on the pipes, 
 and the friction of the wheel on its axis ; and where a large 
 quantity of water is to be raised to a moderate height, both of 
 these resistances may be rendered inconsiderable. But when 
 the height is very great, the length of the spiral must be much 
 increased, so that the weight of the pipe becomes extremely 
 cumbersome, and causes a great friction on the axis,^ as well as 
 a strain on the machinery. 
 
 Centrifugal Pump. — The centrifugal force has sometimes 
 been employed, in conjunction with the pressure of the atmos- 
 phere, as an immediate agent in raising water, by means of a 
 rotary pump. The machine called centrifugal pump^ consists 
 of a vertical pipe, capable of revolving round its axis, and con- 
 nected above with a horizontal pipe, which is open at one, or at 
 both ends, the whole being furnished with proper valves to 
 prevent the escape of the water, when the machine is at rest. 
 As soon as the rotation becomes sutiiciently rapid, the centrifu- 
 gal force of the water in the horizontal pipe causes it t ) be 
 discharged at tlie ends, its place being supplied by means of 
 the pressure of the atmosphere on the reservoir below, which 
 forces the water to ascend through the vertical pipe. This 
 machine may be so arranged, that, according to theory, very 
 little of the force applied is lost ; but it 
 has failed of producing in practice a 
 
 very advantageous efi'ect. In Fig. 5, 
 
 a centrifugal pump is represented, ^p 
 The machine is first filled with water 
 through the funnel A, while the valve 
 at D prevents the water from descend- 
 ing. The whole is then made to turn 
 rapidly, and the water is discharged 
 from the ends of the horizontal part, 
 into a circular trough, a section of 
 which is seen at B and C. 
 
320 
 
 ARTS OP CONVEYING WATER. 
 
 Common Pumips. — A pump is a machine so well known, 
 and so generally used, that the denomination has sometimes 
 been extended to hydraulic m&chines of all kinds. The teim, 
 however, in its strictest sense^ is to be understood of those ma- 
 chines, in which the water is raised by the motion of one sohd 
 within another, and this motion is usually alternate, but some- 
 times continued, so as to constitute a rotation. In the pumps 
 most commonly used, a cavity is enlarged and contracted by 
 turns, the water being admitted into it through one valye, and 
 discharged through another. 
 
 The common household pump has otherwise been called 
 the sucking pump, from the circumstance that the water is 
 raised in it, by the pressure of the atmosphere. In tliis coun- 
 try, pumps are made for common use, both in wells, and in 
 ships, by boring logs so as to produce a large hollow, and in- 
 serting two hollow wooden plugs called boxes, at diflerent 
 heights, both of which are furnished with valves, or clap- 
 pers, opening upwards. The lower box is made Fig. 6. 
 stationary, and serves merely to prevent the water 
 which is raised, from running back. The upper 
 box is a hollow moveable piston, attached by its .— -^ 11 
 rod to the handle or brake of the pump. When 
 the pump is full of water, every stroke of the han- 
 dle raises this box, together with the column of 
 water above it. When the handle is lifted, the 
 box is pushed further down into the water, while 
 its valve opens to allow the water to pass through. 
 In Fig. 6, this pump is represented with the box 
 just beginning to descend. The valve then shuts, 
 and the second stroke of the pump raises another 
 column of water to the spout. As the action of this pump de- 
 pends upon the pressure of the atmosphere, water cannot be 
 raised by it from a depth of more than 34 feet below the up- 
 per valve, and in practice a much shorter limit is commonly 
 assigned. 
 
ARTiS OF CONVEYING WATER. 
 
 321 
 
 Forcing Pump. — The forcing pump differs Fig' 7. b. 
 from the common sucking pump just described, 
 in having a solid piston without a valve, and the 
 spout, or discharging orifice, placed below the 
 piston. When the piston is raised, the lower 
 valve of the pump rises and admits the water 
 from below, as in the common pump. But 
 when the piston is depressed, the water is thrown 
 out through a spout in the side, which has a 
 valve opening outward, at a, in Fig. 7. In a 
 forcing pump the water cannot be brought from 
 a depth of more than 34 feet below the piston, 
 but it can afterwards be sent up to any height 
 desired, in a pipe a b, because the pressure communicated by 
 the downward stroke of the piston, is not dependeat on the 
 pressure of the atmosphere, but upon the direct force applied 
 to the piston. 
 
 Plunger Pump. — A very effectual pump for raising a 
 large quantity of water to a small height, is shown in Fig. 8. 
 
 Fig. 8. 
 
 D C 
 
 It is made by fitting two uptight beams or plungers, A and B, 
 of equal thickness throughout, into cavities nearly of the same 
 size, allowing tliem only room to move without friction, and 
 connecting the plungers together by a horizontal beam mov- 
 ing on a pivot. The water being admitted, during the ascent 
 41 
 
322 
 
 ARTa OP CONVEYING WATEBI. 
 
 of each plunger, by a large valve in the bottom of the cavityv 
 at C and D ; it is forced, when the plunger descends, to es- 
 cape through a second valve at E or F, in the side of the cav- 
 ity, and to asceiid by a wide pipe to the top of the nyachinev 
 The plungers ought not to be in any degree tapered ^ because 
 in this case a great force would be unnecessarily consumedy 
 when they descend, in throwing out the water with great ve- 
 locity, from the interstice formed by their elevation^ This- 
 ^amp may be worked by a laborer walking backwards and 
 forwards, either on the beam, or on a board suspended below 
 it. By means of an apparatus of this kind, described by Pro- 
 fessor Robison, an active man, loaded with a weight of 30 
 pounds, has been able to raise 580 pounds of water every 
 minute, to a height of 11 4 feet, for ten hours a day, without 
 fatigue. This, says Dr Young,^ is the greatest effect produced 
 by a laborer that has ever beer^ correctly stated by any author ^ 
 it is equivalent to somewhat more than 11 pounds raised 
 through 10 feet in a second, instead of 10 pounds, which is a 
 fair estimate of the usual force of a man, without any deduce 
 tion for friction, 
 
 Delakire's Pump. — A pump, partaking of the natrare of a 
 foi'cing and a sucking pump, is sometimes called a mixed pmBpc. 
 In Delahke's pump, which is of this kind, and Fig. 9. 
 shown in Fig. 9, the same piston is made to- 
 serve a double purpose, the rod working in a 
 collar of leathers, and the water being admitted 
 and expelled in a similar manner, above and 
 below the piston, by means of a double appa- 
 ratus of valves and pipesr When the piston is 
 depressed, the water enters the barrel at the 
 vdve A, and goes out at B, When the pis- 
 ton is elevated, it enters at C, and escapes at 
 D. 
 
 For forcing pumps of all kinds, the common piston, with a 
 collar of loose and elastic leather, is preferable to those of a 
 
ARTS OF CONVEYING WATER. 
 
 323 
 
 snore complicated structure. The pressure of the water on the 
 inside of the leather makes it sufficiently tight, and the fric- 
 tion is inconsiderable. In some pumps the leather is omitted, 
 for the sake of simplicity, the loss of water being compensated 
 by the greater durability of the pumps ; and this loss will be 
 the smaller in proportion as the motion of the piston is more 
 ffapid- 
 
 Hydrostatic Press. — -This powerful machine is essentially 
 a forcing pump, aided in its action by the well known proper- 
 ties of hydrostatic pressure. It appears to have ]>een invented 
 by Pascal, previously to 1664, and recommended by him as a 
 new mechanical power. It was, however, practically lost sight 
 of, till it was reinvented by Mr Bramah, more than a century 
 afterwards- In this press the water is forced, by a small pump, 
 into a strong iron cylinder, in which it acts on a much larger 
 piston ; consequently this piston is urged by a force as much 
 
 Fig. 10. 
 
 greater than that which acts on the 
 first pump rod, as its surface is greater 
 than that of the small one. In Fig. 
 10, the water is forced by the pump 
 A through the pipe B, into the cylin- 
 der C, in which it acts very powerful- 
 ly upon the large piston D, and raises 
 the bottom of the press E. The up- 
 ward force, by which the material 
 above E is compressed, exceeds the 
 force which is applied to the pump, as much as the surface 
 of the piston D exceeds that of the piston of the pump. In 
 practice, the cylinder C requires to be made much thicker than 
 here represented. 
 
 Lifting PuTnp. — Where the height through which the 
 water is to be raised is considerable, some inconvenience might 
 arise from the length of the barrel through which the piston 
 rod of a sucking pump would have to descend, in order that 
 the piston might remain within the limits of atmospheric 
 
324 
 
 ARTS OF CONVEYING WATER. 
 
 pressure. This may be avoided by placing the moveable 
 valve below the fixed valve, and introducing the piston at the 
 bottom of the barrel. It is then worked by means of a frame 
 on the outside. Such a machine is called a lifting pump. 
 In common with other forcing pumps, it has the disadvantage of 
 thrusting the piston before the rod, and thus tending to bend 
 the rod, and produce an unequal friction on the piston, while, in 
 the sucking pump, the principal force always tends to straight- 
 en the rod. 
 
 Bag Pump.— A bag of leather has sometimes 
 been employed for connecting the piston of a 
 pump with the barrel, and in this manner nearly 
 all friction is avoided. It is probable, however, 
 that the want of durability would be a great ob- 
 jection to such a machine. In Fig. 11, A rep- 
 resents a leathern bag attached to a number of 
 hoops. This bag is alternately extended and 
 contracted, like a bellows, by every stroke of the 
 piston, and raises the water without friction 
 again^ the pump. 
 
 Double acting Pump. — The rod of a sucking pump may 
 also be made to work in a collar of leather at the top, as at A 
 in Fig. 12, and the water may be forced through Fig. 12. 
 a valve into an ascending pipe B. By applying 
 an air vessel to this, or to any other forcing pump, 
 as is done in fire engines, its motion may be equal- 
 ized, and its performance improved ; for if the ori- 
 fice be large enough, the water may be forced into 
 the air vessel, during the stroke of the pump, with 
 any vdocity that may be required, and with little 
 resistance from friction ; whereas the loss of force, 
 from the frequent accelerations and retardations of 
 the whole body of water, in a long pipe, must always be con- 
 siderable. The condensed air, reacting on the water, expels it 
 more gradually, and in a continual stream, so that the air ves- 
 sel has an effect analogous to that of a fly wheel in mechanics. 
 
ARTS OF CONVETING WATER. 
 
 325 
 
 Rolling Pump. — A pump of this 
 kind is formed by a barrel, or hollow 
 cylinder, shown in section in Fig. 13, 
 having two partitions. One of these, 
 A B, is fixed, and the other, C D, is 
 composed of two wings, or valves, 
 capable of an alternate motion about 
 the axis of the cylinder. When the partition C D turns in 
 one direction, the water in the cavity C is driven out at the 
 orifice a, and will rise in a pipe attached to that orifice. At 
 the same time the water in the cavity D is forced out at the 
 orifice d. While this is taking place, fresh portions of water 
 enter the remaining cavities at w and z. When the partition 
 C D has moved as far as possible, it then returns in the op- 
 posite direction, and drives out the water through y and ^, and 
 receives fresh water through b and c. The orifices which re- 
 ceive the water have valves opening inward, and those which 
 discharge it have valves opening outward. The machine is 
 worked by arms attached to the axis of the cylinder, which for 
 this purpose projects through a collar in the ends of the vessel. 
 
 For the sake of simplicity, a sector of a cylinder, is some- 
 times used, in which case a single partition, or valve, like a 
 door on hinges, traverses the whole cavity, and only half the 
 number of orifices are necessary, to admit and discharge the 
 water. Fire engines, for projecting water, have been con- 
 structed in both these methods by different inventors. 
 
 Eccentric Pump. — The eccentric pump, 
 a section of which is shown at Fig. 14, con- 
 sists of a hollow cylinder a c?, in the interior 
 of which a solid cyhnder 6, of the same length, 
 but of about half the diameter, is made to re- 
 volve, by its axle passing through water tight ^ 
 collars in the ends of the extenor cylinder. 
 The internal cylinder is so placed, that its 
 surface comes in contact with some part of 
 the internal surface of the larger cylinder. 
 The surface of the small cyhnder, is also fur- 
 
326 ARTS OF CONVEYING WATER. 
 
 nished with four large valves, or flaps, tnrning on hinges, and 
 partaking of its own curvature, so that when they are shut 
 down, they form no projections, but appear as parts of the 
 same cylinder. These valves are made to open by springs or 
 otherwise, so that when one of them is brought by the revolu- 
 tion of the internal cylinder into the narrowest part of the in- 
 ternal space, it is pressed down and shut ; but as the inner cyl- 
 inder moves on, the valve being gradually carried forward, will 
 continue to open until it arrives at the widest part of the cavity. 
 It is then pressed down again by a continuation of the revolu- 
 tion. In this way the water behind the valve is drawn up 
 from the feeding pipe by the atmospheric pressure, while that 
 before the valve is forced upward into the delivering pipe. As 
 each of the valves performs the same operation in its turn, this 
 pump affords a constant supply of water. 
 
 Rotative steam engines have been constructed by different 
 projectors, on the principle of this pump, as well as the follow- 
 ing. 
 
 Another form of an eccentric pump, is seen F\g- 15. 
 in Fig. 15, The roller, or sohd cylinder, A. 
 revolving within the reservoir, or hollow cy- 
 linder, B F, carries with it the shder, D E, 
 
 which is made to sweep the internal surface 
 of this cylinder by revolving in the direction 
 from C to F, so that the water is drawn up 
 by the pipe C, and discharged by the pipe F. 
 
 An objection to all pumps of this sort, is, that if they are 
 made tight enough to hold water, they occasion a great degree 
 of friction on account of the extensive contact of the moving 
 surfaces. The continual change, also, which takes place, both 
 in the direction and velocity of the water, is productive of 
 great resistance from inertia. The stream at the delivering 
 orifice, although never wholly intermitted, is by no means uni- 
 form in its velocity. 
 
 Arrangement of Pipes. — The pipes, through which wa- 
 ter is raised, by pumps of any kind, ought to be as short 
 
ARTS OF COKViiYlNG WATEK, 327 
 
 and as straight as possible. Thus, if we have to raise water to 
 a height of 20 feet, and to carry it to a horizontal distance of 
 100, by means of a forcing pump, it will be more advanta- 
 geous to raise it first vertically into a cistern 20 feet above the 
 reservoir, and then to let it run along horizontally, or find its 
 level in a bent pipe, than to connect the pump immediately 
 with a single pipe, carried to the place of its destination. And 
 for the same reason a sucking pump should be placed as nearly 
 over the well as possible, in order to avoid a loss of force in 
 working it. If very small pipes are used, they will much in- 
 crease the resistance, by the friction which they occasion. 
 
 Chain pump. — Water has sometimes been raised by stuffed 
 cushions, or by oval blocks of wood, connected with an endless 
 rope, or chain, and caused, by means of two wheels, or drums, 
 to rise in succession in the same ban-el, carrying the water in a 
 continual stream before them. The magnitude, however, of 
 the friction, appears to be an objection to this method. From 
 the resemblance of the apparatus to a string of beads, it has 
 been called a head pump^ or paternoster work. When flat 
 boards are united by chains, and employed instead of these 
 cushions, the machine has been denominated a cellular pump ; 
 and in this case the barrel is usually square, and placed in an 
 inchned position. There is, however, a considerable loss from 
 the facility with which the water runs back. The chain 
 pump, used in the navy, is a pump of this kind, with an up- 
 right barrel, through which leathers, strung on a chain, are 
 drawn in constant succession. These pumps are only employ- 
 ed when a large quantity of water is to be raised, and they 
 must be worked with considerable velocity in order to produce 
 any effect at all. 
 
 The Chinese work their cellular pumps, or bead pumps, by 
 walking on bars which project from the axis of the wheel, or 
 drum that drives them ; and whatever objection may be made 
 to the choice of the machine, the mode of communicating mo- 
 tion to it must be allowed to be advantageous. 
 
328 
 
 ARTS OF CONVEYING WATER. 
 
 Schemnitz Vessels, or Hungarian Machine. — The me- 
 diation of a portion of air, is employed for raising water^ not 
 only in the spiral pump, but also in the air vessels of SchemnitZy 
 in the manner sliown in Fig, 16. A column of 
 water, descending^ through a pipe C, into a 
 closed reservoir B, containing air, obliges the air 
 to act, by means of a pipe D, leading from the 
 upper part of the reservoir or air vessel, on the 
 water in a second reservoir A, at any distance 
 either below or above it, and forces this water to 
 ascend through a third pipe E, to any height less ' 
 than that of the J&rst column. The air vessel is 
 then emptied, the second resei'voir filled, and 
 the whole operation repeated. The air must, 
 however, acquire a density, equivalent to the 
 pressure, before it can begin to act ; so that if the height of the 
 columns were 34 feet, it must be reduced to half its dimensions 
 before any water would be raised ; and thus half of the force 
 would be lost. But where the height is small, the force lost in 
 this manner is not greater than that which is usually spent in 
 overcoming friction, and other imperfections of the machinery 
 employed ) for the quantity of water, actually raised by any 
 machine, is not often greater than half the power which is con- 
 sumed. The force of the tide, or of a river rising and falling 
 with the tide, might easily be applied by a machine of this kindy 
 to the purpose of raising water. Thus, if at low tide the ves- 
 sel A was filled with air,, then at high tide the water flowing 
 down the tube E, would cause the water in the vessel B to 
 ascend in the pipe C. 
 
 Hero's Fountain.— Th.^ fountain of Hero, precisely resem- 
 bles, in its operation, the hydraulic vessels of Schemnitz, which 
 were probably suggested to their inventor by the construction 
 of this fountain. It may be used simply to raise water, or to 
 
ARTS OF CONVEYING WATER. 
 
 329 
 
 project it upwards in the form of a jet, as in Fig. 
 17. The first reservoir C of the fountain is 
 lower than the orifice of the jet. A pipe de- 
 scends from it to the air vessel, B, which is at 
 some distance below, and the pressure of the 
 air is communicated, by an ascending tube, D, 
 to a third cavity, A, containing the water which 
 supplies the jet. In this form of the machine, 
 the water will continue to spout from the pipe 
 E, until all the water in the reservoir C has 
 descended into the vessel B. The principle of 
 Hero's fountain has been applied to raise oil in lamps, and one 
 of its most simple forms has already been described under the 
 head of hydrostatic lamp, page 181. 
 
 Atmospheric Machines. — The spontaneous vicissitudes of 
 the pressure of the ak, occasioned by changes in the weight 
 and temperature of the atmosphere, have been applied by 
 means of a series of reservoirs, furnished with proper valves, to 
 the purpose of raising water by degrees to a moderate height. 
 But it seldom happens that such changes are capable of pro- 
 ducing an elevation in the water of each reservoir of more than 
 a few inches, or at most a foot or two, in a day ; and the whole 
 quantity raised must therefore be inconsiderable. 
 
 Hydraulic Ram. — The momentum of a stream of water, 
 flowing through a long pipe, has also been employed for raising 
 a small quantity of water to a considerable height. The pas- 
 sage of the pipe being stopped by a valve, which is raised by 
 the stream, as soon as its motion becomes sufiiciently rapid, 
 the whole column of fluid must necessarily concentrate its ac- 
 tion almost instantaneously on the A^alve. In this manner 
 it loses the characteristic property of hydraulic pressure, and 
 acts as if it were a single solid ; so that, supposing the pipe to 
 be perfectly elastic, and inextensible, the impulse may overcome 
 any pressure, however great, that might be opposed to it. If 
 the valve opens into a pipe leading to an air vessel, a certain 
 quantity of the water will be forced in, so as to condense the 
 42 
 
330 
 
 ARTS OF CONVEYING WATER. 
 
 air, more or less rapidly, to the degree that may be required 
 for raising a portion of the water contained in it, to a given 
 height. Mr Whitehurst appears to have been the first that 
 employed this method ; it was afterwards improved by Mr 
 Boulton ; and the same machine has attracted much attention 
 in France under the denomination of the hydrauhc ram of M. 
 Montgolfier. 
 
 Fig. 18 represents this machine. When the water in the 
 Fig. 18. 
 
 pipe A B has acquired sufficient velocity, it raises the valve B, 
 which immediately stops its further passage. The momentum 
 which the water has acquired will then force a portion of it 
 through the valve C into the air vessel D. The condensed 
 air at D causes the water to rise into the pipe E, as long as 
 the effect of the horizontal column continues. When the water 
 becomes quiescent, the valve B will open again by its own 
 weight, and the current will be renewed, until it acquires force 
 enough to shut the valve, and repeat the operation. 
 
 OF PROJECTING WATER. 
 
 If a degree of force, or pressure, be applied to water suffi- 
 cient to raise it through a tube to a given height, the same 
 force would also cause it to spout through an orifice, in a con- 
 tinued stream, or jet, to nearly the same height, in common 
 cases. The height, however, can never be fully as great, for 
 various reasons. One of these is found in the friction of the 
 ajutage, or discharging orifice, which acts as a retarding force. 
 
ARTS OF CONVEYING WATER. 331 
 
 Another obstacle is the resistance of the atmosphere, which 
 increases in a rapid ratio, as the velocity of the water becomes 
 greater, and which is also greatly augmented as the water di- 
 vides, and spreads out a greater surface to the resistance of 
 the air. A third obstacle consists in the resistance which the 
 water offers to itself. The parts first projected, being constant- 
 ly retarded in their ascent by gravity and atmosplieric resist- 
 ance, oppose the progress of the parts which are last projected, 
 and which have the greatest velocity. And as fluids move in 
 all directions, this impulse of different parts of the water against 
 each other, tends to widen, and consequently to shorten the 
 column. In a vertical jet, moreover, the weight of the falling 
 water opposes the ascending column, and hence a fluid will 
 spout higher, if the jet be turned a little to one side, than if it 
 be perpendicular. 
 
 Fountains. — Artificial fountains which throw a perpetual 
 jet of water, usually act by the pressure of a reservoir of water, 
 situated at a greater height than that of the jet produced. The 
 water is conveyed from the reservoir to the place of the foun- 
 tain, in pipes, and if the orifice from which it issues be directed 
 upward, it Vvdll spout to a height approaching that of the res- 
 ervoir. It will always, however, fall short of this height, 
 for the reasons already stated ; and the difference will be 
 greater in jets of great height, than it is in lower ones ; since 
 it is found by experiment, that the diflferences between the 
 heights of the jets and of the reservoirs, are as the squares of 
 *be heights of the jets themselves.* Fountains are chiefly 
 used .or purposes of ornament, and when of large size require 
 to be fed from the elevated parts of rivers, or bodies of water 
 having a high level. At Peterhoff", in Russia, there are two 
 fountains which spout a column of water 9 inches in dianae- 
 ter, to the height of sixty feet, and the fall of the returning 
 water produces a concussion sufficient to shake the ground. 
 
 * Ascertained by Mariotte. Eossut, Tom. ii, § 615. 
 
332 ARTS OP CONVEYING WATER. 
 
 Fire Engines. — The engines used for extinguishing fires 
 in buildings, are in effect a species of forcing pumps, in which 
 the water is subjected to pressure sufficiently strong to raise it, 
 by a jet or otherwise, to the required height. But if the forc- 
 ing pump were used alone, the water would issue only in in- 
 termitting jets, in consequence of the reciprocating motion of 
 the pump, and thus a great part of it would become ineffectu- 
 al. In order to make the discharge uniform, and thus keep 
 up a continual stream, a strong vessel filled with air, is attached 
 to the engine. Into this vessel the water is forced by the 
 pumps, and as the air cannot escape, it is condensed in propor- 
 tion as the water accumulates, until it reacts upon the surface 
 of the water with great power. If the air be condensed into 
 half the space which it originally occupied, it will act upon 
 the water with a pressure equal to that of two atmospheres, 
 and will be adequate to raise water through a tube to the height 
 of 33 feet, or to project it through the atmosphere to nearly the 
 same height. When the air is condensed to one third of its for- 
 mer volume, in consequence of the air vessel being two thirds 
 filled with Vv^ater, its elasticity will be three times greater than 
 that of the atmosphere. It will therefore raise water in a tube 
 to the height of 66 feet, and would throw it to nearly the same 
 height v/ere it not for the resistances, which have already been 
 explained. 
 
 The foregoing principle of the fire engine has been various- 
 ly modified, by adapting different kinds of pumps to the air 
 vessel, and by altering various details. In the engines of 
 Newsham and others, two cylinders, constructed like forcing 
 pumps, are worked by the reciprocating motions of transverse 
 levers, to which the handles are attached. In this way the 
 water is forced into the air vessel, from which it afterwards 
 spouts through a moveable pipe. In some other engines a 
 single cylinder is used, the piston rod passing through a tight 
 collar, as it does in Watt's steam engine, thus alternately re- 
 ceiving and expelling the water at each end of the cylinder. 
 In Rowntree's engine, and some others, a mechanism is used 
 
ARTS OP CONVEYING WATER. 333 
 
 like that of the rolHiig pump, a part of the inside of a cyhnder 
 being traversed by a partition hke a door hinged upon the ax- 
 is of the cyhnder, which drives the water successively from 
 each side of the cylinder, into the air vessel. 
 
 A long, flexible tube, made of leather, and known among 
 firemen by the naiTie of hose, is of great use in carrying the 
 spouting orifice near to the flames, and thus preventing the 
 water from being scattered too soon. It also serves an impor- 
 tant purpose in bringing water from distant reservoirs, by suc- 
 tion created in the pumps of the engine. 
 
 Throwing Wheel. — A throwing wheel, otherwise called a 
 flash wheel, or fen wheel, is used for raising water, both by 
 lifting and projecting it. Its structure resembles that of an un- 
 dershot water wheel, or more properly of a breast wheel. Its 
 under surface is received in a trough or channel, which curves 
 upward. When the wheel is made to revolve, it drives the 
 water before it, and throws it out from the trough at a consid- 
 erable elevation. These wheels are used for draining ponds, 
 marshes, &c., and are turned by wind-mills, or any other pow- 
 er. If their movement is slow, they simply lift the water, and 
 cause it to overflow at the end of the trough. But if they re- 
 volve with much velocity, they are capable of throwing the 
 water to a still higher level. 
 
 Robison's Mechanical Philosophy, Articles Theory of Rivers, Wa- 
 ter Works, &c. ; — Gregory's Mechanics, vol. i. ; — Young's Natural 
 Philosophy, vol. i. ; — Bossut TraiU Theoretique et Experimental d^ Hy- 
 drodynamique, 1771, &c. ; — Du Buat TraiU d' Hydraulique, et Pyrody- 
 namique, 1786, &c. ; — Venturi, R6cherches Experimentales sur les Flu- 
 ides, 1797 ; — Rees' Cyclopedia, article Water ; — Edinburgh Encyclope- 
 dia, article Hydrodynamics ; — And the Hydraulic Works of Mariotte, 
 Guglielmini, Michelotti, D. and J. Bernoulli, D'Alembert, Fon- 
 TANA, M. Young, Prony, Vince, Juan, Eytelwein, &c. 
 
CHAPTER XIV. 
 
 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 Cohesion.' — The attraction of cohesion, which retains to- 
 gether the particles of sohd bodies, is the foundation of their 
 strength. It exists in all solids, though in different degrees ; 
 and requires, before it can be overcome, the application of force 
 or of art, adapted to the strength and character of the particu- 
 lar body. In some substances, cohesion, when once overcome, 
 cannot be reproduced in its original state. In others it may 
 be restored by the intervention of fluidity, and in all, its effects 
 may be imitated by mechanical arrangements. The various 
 modes by which bodies may be divided, or united, have an im- 
 portant agency in mechanical constructions, and other processes 
 of art. 
 
 MODES OF DIVISION. 
 
 Fracture. — The simplest and least artificial mode by which 
 mechanical division is effected, is by breaking. The circum- 
 stances which influence the production of fracture by extension, 
 compression, lateral strain, and torsion, have been considered 
 in the second chapter of this work. In general, a force act- 
 ing suddenly is more liable to occasion fracture, than one which 
 acts more gradually ; for in this case the parts which are first 
 strained may give way, before the stress is proportionally dis- 
 tributed among the remaining parts. A mass of plastic clay, 
 or of warm sealing wax, will bear to be gradually bent, but 
 will break if the motion is sudden. In like manner, percussion 
 occasions fracture more readily than pressure. A crack, or 
 partial fracture, in a body, greatly promotes the separation of 
 
ARTS OF DIVIDING AND UNITING SOLID BODIES. 335 
 
 the remainder, whenever a lateral force is applied ; because 
 the strength of the small parts tends to throw the strain more 
 immediately upon the w^eakened points, as explained on page 
 48. 
 
 Cutti7ig:-—CvLUing instruments act, in dividing bodies, up- 
 on the same principle as the wedge. The blade of the instru- 
 ment is in general a thin wedge, but the edge itself is usually 
 much more obtuse. Mr Nicholson has estimated the angle 
 which is formed ultimately by.the finest cutting edge, at about 
 56 degrees. If the edge of an instrument W'Cre not angular, 
 but rounded or square, it would still act as a wedge, by push- 
 ing before it a wedge-shaped portion of the opposing particles, 
 as is done by obtuse bodies moving in fluids. In general an 
 obhque motion is more favorable to cutting than a direct, 
 and this is because the edges of steel instruments are rough 
 with minute asperities, like saw teeth. This circumstance, 
 however, is of less importance when the material operated up- 
 on is very firm and the cutting is deep ; for in this case the 
 friction and compression consume more force, than the actual 
 division. This takes place with axes and chisels, which are 
 necessarily made thick, to secure the requisite strength. 
 
 The quality in tools which is called temper, is opposed to 
 brittleness on the one hand and to flexibility on the other. In- 
 dependently of the quality of the metal, it appears to be some- 
 what influenced by temperature, since axes and other tools are 
 hable to break, or gap, in frosty weather, and razors cut best 
 after being immersed in hot water. 
 
 The kind of cutting which is performed by scissors, depends 
 upon the process called detrusion, in which the coherent par- 
 ticles are pushed by each other in opposite directions. In this 
 case, the cutting edges require to be angular, but the angle not 
 very acute. The shearing of woollen cloths, the shtting and 
 punching of metals, the cutting of nails, and various other me- 
 chanical processes, are performed on this principle. 
 
 Cutting' Machines. — A variety of fibrous and woody sub- 
 stances, used by druggists and dyers, require to be reduced to 
 
336 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 a coarse powder like saw dust, to facilitate the extraction of 
 their soluble matter. This is not easily done in any of the 
 common mills, owing to the toughness of the material. It is 
 sometimes effected by machinery with circular rasps or saws, 
 but a more economical application of a dividing force in these 
 cases, is obtained by the rapid revolutions of a sharp cutting 
 instrument. In a machine for cutting straw, a number of 
 blades revolve upon an axis, with a fly. In Bramah's sur- 
 face planing machinery ^ and in Blanchard's ingenious en- 
 gine for cutting definite forms by a pattern, sharp instruments 
 of different forms, are made to revolve upon axles, or slide in 
 grooves, while the material operated on is put in motion, so as 
 to place itself in the proper position to receive the cut. 
 
 Penetration. — Bodies are penetrated either by pushing 
 aside a portion of their substance, as in driving a nail ; or by 
 removing a portion, as in boring and drilling. In addition to 
 the force of cohesion, the resistance opposed by a solid, or 
 even by a soft substance, to the motion of a body tending to 
 penetrate it, appears to resemble, in some measure, the force of 
 friction, which is nearly uniform, whether the motion be slow 
 or rapid, destroying a certain quantity of momentum in a cer- 
 tain time, whatever the whole velocity may be, or whatever 
 may be the space described. Hence arises an advantage in 
 giving a great velocity to a body which is to penetrate another, 
 since the distance to which a body penetrates will be nearly as 
 the square of its velocity.* The same remark applies equally 
 to the action of cutting instruments. The effect of a hammer 
 in driving a nail, depends partly on the influence of velocity 
 in modifying friction, and partly upon the momentum accu- 
 mulated in the hammer, the effect of which resembles that of 
 a fly wheel. 
 
 Boring and Drilling. — The processes of boring and drilling, 
 performed by gimlets, augers, centrebits, drills, &c., is a spe- 
 cies of circular cutting, in which a cylindrical portion of the sub- 
 
 * See Young's Natural Philosophy, vol. i. p. 225, and Playfair's, vol. i. p. 97. 
 
ARTS OF DIVIDING AND UNITING SOLID BODIES. 337 
 
 stance is gradually removed. Drills are made to turn rapidly, 
 either in one direction by means of a lathe wheel and pulley, 
 or alternately in opposite directions, by a spiral cord which 
 coils and uncoils itself successively upon the drill, and is aided 
 by a weight or fly. In boring cannon, the tool is at rest, while 
 the cannon revolves, and by this arrangement the bore of the 
 cannon is formed with more accuracy than according to the 
 old method of putting the borer in motion, perhaps because 
 the inertia of so large a mass of matter assists in defining the 
 axis of the revolution with more accuracy. The borer is kept 
 pressed against the cannon by a regular force. Cylinders of 
 steam engines are cast hollow, and afterwards bored ; but in 
 this case the borer revolves, and the cylinder remains at rest. 
 In either case, it is important that the axis of the borer, and 
 that of the cylindrical material, should coincide ; for when it 
 is otherwise, if the borer revolves, it will perforate obliquely, 
 and if the material revolves, the perforation will be conical. 
 
 Turiiing. — Turning is an elegant operation, used to pro- 
 duce regular figm^es, the section of which is circular. Like 
 boring, it is a species of circular cutting, and is performed in 
 a well known machine called a lathe, in which the material 
 to be cut revolves about its axis, while the tool is kept station- 
 ary and supported by a rest. Besides circular forms, it may also 
 be used to produce regular curvilinear figures, which may be 
 multiphed indefinitely. The effect of most lathes of comph- 
 cated construction, depends on a certain degree of motion, of 
 which the axis is capable. If this motion be governed by a 
 frame producing an elliptic curve, any number of ovals having 
 the same centre may be described at once ; and if a moveable 
 point connected with the work, be pressed by a strong spring 
 against a pattern of any kind, placed at one end of the axis, a 
 copy of the same form may be made at the other end of the 
 axis. Geometrical lathes, governed by eccentric wheels, and 
 capable of describing an indefinite variety of complex figures, 
 upon a metallic plate, are used for bank notes and orna- 
 mental designs. 
 
 43 
 
338 ARTS OP DIVIDING AND UNITING SOLID BODIES. 
 
 Attrition. — The action of files, rasps, grindstones, and 
 hones, consists in successively cutting or breaking av^ray mi- 
 nute particles from the surface of bodies. They are used 
 chiefly for wearing off portions of hard substances, particularly 
 metals. The surface of grindstones and whetstones, is kept 
 moist with water or oil, the use of which is not so much to 
 obviate the production of heat by friction, as to prevent the 
 adhesion of foreign particles from filling up the interstices of 
 the grit. In the finer kinds of grinding and polishing, cer- 
 tain hard substances are used in the form of powder, such as 
 emery, tripoli, sand, putty, oxide of iron, <fec. 
 
 Sawing. — Saw Mill. — A saw, in many respects, resembles 
 a rasp, and acts by cutting or breaking away large particles 
 in the direction of its own plane. The thinner the saw is, the 
 easier is the operation, since a smaller amount of substance 
 is removed by the teeth. For the sake of this advantage, and 
 for economy of the material, the blades of saws are made thin, 
 and often stretched upon frames, to compensate the want of 
 rigidity. Saw mills erected for cutting logs into boards, con- 
 sist usually of saws attached to fratoes, which have a recipro- 
 cating motion communicated to them by a crank connected 
 with a water wheel or steam engine. A ratchet wheel is 
 connected with the saw by means of a bar and click ; so that 
 at every stroke of the saw, the wheel is turned the length of 
 one tooth. The ratchet wheel acts by means of a rack, upon 
 a carriage, which supports the log, causing it slowly to ad- 
 vance, until the whole length of the log has passed the saw. 
 
 Circular Saw. — Circular saws, revolving upon an axis^ 
 have the advantage that they act continually in the same di- 
 rection, and no force is lost by a backward stroke. They also 
 are susceptible of much greater velocity than the reciprocating 
 saws, an advantage which enables them to cut more smooth- 
 ly. The size of circular saws, however, is limited ; for, if 
 made too large, and of the usual thinness, they are liable to 
 waver, and bend out of their proper plane ; and, on the other 
 hand, if made thick enough to secure an adequate degree of 
 
ARTS OF DIVIDING AND UNITING SOLID BODIES. 339 
 
 strength, they waste both the power and the material, by cut- 
 ting away too much. Hence, they are not commonly apphed 
 to the sHtting of large timber, but are nevertheless very useful 
 in smaller works, for cutting off bodies which can be included 
 within a certain distance of the axis, and thus allow the saw 
 to be of small size. Circular saws, however, of large size, are 
 used in cutting thin layers of mahogany for veneering ; for 
 in this case the saw can be strengthened by thickening it on 
 one side towards the centre, the flexibility of the layer of wood al- 
 lowing it to turn aside, as fast as it is sawn off. Circular saws 
 may be rendered more steady by giving them a greater veloci- 
 ty, so that the centrifugal force shall assist ia confining the 
 saw to its proper plane. 
 
 An ingenious machine has been mvented in Maine, for 
 sawing off sheets of wood of an indefinite length, for veneer- 
 ing, by cutting a spiial layer from the surface of a cyhndri- 
 cal log, the layer being turned off like a ribbon when unwound 
 from a roUer. The sheets of rice jjaper, mentioned on page 56, 
 note, are said to be cut in the same spiral manner. 
 
 The sawing of marble is performed by saws made of soft 
 iron, and without teeth. A quantity of sand and water is kept 
 interposed between them, and the sand, becoming partly im- 
 bedded in the iron, serves to grind away the marble. These 
 saws are worked horizontally for the convenience of retaining 
 the sand, and are moved either by hand, or hj reciprocating 
 machinery. The cylindrical blocks which form the tambours, 
 or frusta, of columns, are sometimes cut out of marble, by per- 
 forating the block at the centre, and inserting an iron axis, to 
 the ends of which are attached frames, upon which a narrow 
 or a concave saw is stretched parallel to the axis. An alter- 
 nating motion is then given to the frame, until the saw has 
 cut its way round the axis. 
 
 Crushing. — When materials require to be broken into 
 minute parts, or when the texture of vascular substances is to 
 be destroyed, that they may yield their fluid contents, the op- 
 eration of crushing is resorted to. It is performed either by 
 
340 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 percussion, with hammers, stampers, and pestles, or by simple 
 pressure, with weights, rollers, and runner stones. 
 
 Stamping Mill. — For reducing the ores of metals to pow- 
 der, a number of heavy vertical bars, called stampers, are al- 
 ternately raised, and suffered to fall, by the action of cams, or 
 wipers, projecting from the arbor of the mill wheel. The ore 
 is placed in a trough or mortar beneath, where it is acted upon 
 by the stampers until it is sufficiently comminuted. A stream 
 of water continually runs through the stamping trough, carry- 
 ing with it the particles, which have become fine enough to 
 pass through a screen provided for the purpose. 
 
 Bark Mill. — The bark used by tanners is reduced to a 
 coarse powder in various ways. One of the most common 
 methods, is to crush the bark by the revolutions of a circular 
 stone, called a runner stone, which rese^iibles the wheel of a 
 carriage, travelling round in a continued circuit. The axis of 
 the stone is connected with a vertical shaft, so that the stone 
 has two motions, one round its own axis, which is horizontal, 
 and the other round the vertical shaft. The bark is raked up 
 into a ridge before the stone, and is crushed or ground up, by 
 the edge of the stone rolling over it. In some more complicated 
 mills, the bark is successively cut with knives, beaten with 
 hammers, and ground with stones, or cylinders. 
 
 Oil Mill. — The oleaginous seeds from which oil is ex- 
 pressed, require to have their substance previously broken up 
 by the operations of a mill. In one of the best forms of the 
 oil mill, the seeds are first bruised to the consistence of paste, 
 by the action of runner stones. The paste is received in 
 troughs perforated with holes, through which a portion of the 
 oil drips, and this part is considered the most pure. The paste 
 is then put into strong bags, and subjected to pressure as long 
 as it yields oil. The remaining paste, or oil cake, is next taken 
 out of the bags, broken to pieces, and put into mortars. It is 
 here beaten by the action of heavy stampers, until reduced 
 to a very minute state of subdivision. The oil which is next 
 pressed out from it, is inferior in quaUty to the first, in conse- 
 
ARTS OP DIVIDING AND UNITING SOLID BODIES. 341 
 
 quenceof its containing more mucilage and farinaceous particles. 
 The seeds are nevertheless subjected to another pressure, after 
 having been exposed to heat, which enables them to yield a 
 quantity more of oil, but of a still poorer quality. 
 
 Sugar Mill. — The machine by which sugar canes are 
 crushed, usually consists of three vertical rollers, the middle 
 one of which is turned by a horse, or other power, and turns 
 the remaining two by friction, or by toothed wheels ; the lat- 
 ter method being most advantageous. The canes are supplied 
 by attendants, and are drawn in and crushed betv/een the first 
 and second rollers, after which they return and pass between 
 the second and third. The juice which is pressed out by the 
 same operation, flows into a trough beneath. 
 
 Cider Mill. — When the substances to be crushed are so 
 large that they cannot readily be drawn in between smooth 
 cylinders, it is necessary that the rollers should be indented at 
 their circumference. The common cider mill is formed with 
 two indented cylinders, the teeth of one of which enter the in- 
 dentations of the other. By this arrangement, the fruit to be 
 ground is caught by the projecting parts of the rollers, and reg- 
 ularly carried forward and crushed. Formerly it was the 
 custom to grind apples by runner stones, similar to those used 
 in bark mills. And at the present day cylindrical rasps are 
 sometimes employed, being supposed capable of destroying 
 the texture of the fruit more effectually. 
 
 Grinding. — Grinding, in its most Umited sense, may be con- 
 sidered as a species of crushing, or breaking, in which the force 
 acts partly in a lateral direction, so as to lacerate, rather than 
 compress the material acted upon. It is frequently produced 
 in small mills, by a cylinder or cone, turning within another, 
 which is hollow, the surfaces of both being cut obliquely into 
 teeth. In larger mills, it is commonly performed by one stone 
 moving upon another. 
 
 Grist Mill. — The common mill for grinding grain, is con- 
 structed with two circular stones placed horizontally. Buhr- 
 stone is the best material of which mill stones are made, but 
 
342 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 sienite and granite are frequently used, for Indian corn and rye. 
 The lower stone is fixed, while the upper one revolves with 
 considerable velocity, and is supported by an axis passing 
 through the lower stone, the distance between the two being 
 capable of adjustment, according to the fineness which it is in- 
 tended to pi'oduce in the meal, or flour. When the diameter 
 is five feet, the stone may make about 90 revolutions in a min- 
 ute, without the flour becoming too much heated. The corn 
 or grain is shaken out of a hopper by means of projections 
 from the revolving axis, which give to its lower part or feeder, 
 a vibrating motion. The lower stone is slightly convex, and 
 the upper one somewhat more concave, so that the corn which 
 enters at the middle of the stone, passes outward for a short 
 distance, -before it begins to be ground. After being reduced 
 to powder, it is discharged at the circumference, its escape be- 
 ing favored by the centrifugal force, and by the convexity of 
 the lower stone. The surface of the stones is cut into grooves, 
 in order to make them act more readily and effectually on the 
 corn ; and these grooves are cut obliquely, that they may assist 
 the escape of the meal, by throwing it outward. The opera- 
 tion of bolting, by which the flour is separated from the bran, 
 or coarser particles, is performed by a cylindrical sieve placed 
 in an inclined position, and turned by' machinery. The fine- 
 ness of flour is said to be greatest when the bran has not been 
 too much subdivided, so that it may be more readily separated 
 by bolting. This takes place when the grinding has been per- 
 formed more by the action of the particles upon each other, 
 than by the grit of the stone. For this sort of grinding, the 
 buhrstone is peculiarly suited. 
 
 Color Mill. — The various coloring substances used by paint- 
 ers, when they are not soluble in oil or water, require to be 
 reduced to an impalpable powder by grinding. This is com- 
 monly performed upon a smooth stone slab, by trituration with 
 another stone, called a muller. When the grinding is perform- 
 ed by machinery, a large muller of the shape of a pear, having 
 a groove cut in it for the admission of the paint, is made to revolve 
 
ARTS OF DIVIDING AND UNITING SOLID BODIES. 343 
 
 in a mortarj the bottom of which is of a corresponding shape. 
 In some color mills a horizontal stone cylinder revolves in 
 contact with another stone, which is concave, and covers a part 
 of its convex surface. In most cases, the substance to be g^round 
 is mixed with oil or water. As some of the substances used for 
 pigments are of a poisonous character, they should be ground 
 in close cavities, or under water. 
 
 MODES OF UNION. 
 
 Insertio?i. — The mechanical modes of attaching bodies to 
 each other, usually consist in the insertion of their parts 
 among each other, or in the application of other substances 
 specially adapted for the purpose of connexion. Insertion is 
 performed by various modes, the principal of which are, 1. 
 Mortising, in which the projecting extremity of one timber is 
 received into a perforation in another, 2. Scarfing and inter- 
 locking, in which the ends of pieces overlay each other, and 
 are indented together, so as to resist longitudinal strain by ex- 
 tension, as in tie beams, and ends of hoops. 3. Tongueing 
 and rabating, in which the edges of boards are wholly, or 
 partly, received by channels in each other. 4, Dovetailing, 
 when the parts are connected by wedge-shaped indentations, 
 which permit them to be separated only in one direction. 5. 
 Linking, where the ends of flexible rods are bent over each 
 other. 6, Folding, when the edges of flexible plates are con- 
 nected in a similar manner. 7. To these may be added the 
 combinations of flexible fibres, by tying, twisting, weaving, 
 <fcc., in which the permanency of the union depends upon 
 friction. 
 
 Interposition. — When two substances are mechanically 
 united by the intervention of a third, the latter, from its smaller 
 size, should be made of the strongest material. Nails are a 
 common connecting medium in wooden structures. The sta- 
 bility of a nail depends upon its friction, or adhesion, and is 
 
344 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 increased by its roughness, the smaUness of the angle made by 
 its sides, and the elasticity of the material into which it is 
 driven. 
 
 When the force tending to produce separation is great, nails 
 do not afford an adequate security. In such cases, it is com- 
 mon to employ screws, which are inserted by the force of tor- 
 sion and cannot be withdrawn by that of extension, while the 
 material is sound. Where great strength is required, holts of 
 metal are used, which pass through the substances to be con- 
 nected, and are secured at their smaller extremity by a nut and 
 screw, or by a transverse key. Rivets are short bolts, the 
 two ends of which are headed, or spread by hammering, after 
 they are inserted. 
 
 Binding. — In some cases the materials to be connected are 
 not perforated, but surrounded by the connecting substance. 
 Hoops and bands of metal, wood, and flexible fibres, are used 
 for this purpose. In cases where it is applicable, binding or- 
 dinarily affords the strongest mode of connexion, but is attend- 
 ed with the greatest expenditure of the connecting material. 
 
 JLocking. — For the temporary connexion of parts, which 
 require to be often repeated, latches, bolts, hooks, buttons, and 
 locks are employed. Of these, the lock is the only one whose 
 structure is at all complicated. The principle upon which locks . 
 depend, is the application of a lever to an interior bolt, by 
 means of a communication from without. The lever is the 
 key, and the bolt receives from it a progressive motion in either 
 direction. The security of a lock depends upon the number 
 of obstacles which can be interposed between the movement of 
 the bolt, and the action of any instrument, except the proper 
 key. The wards of locks are impediments of this kind, and 
 to enable the key to pass them, certain portions of its substance 
 are cut away. Various complicated and difficult locks have 
 been constructed by Messrs Bramah, Taylor, Spears, and 
 others. In a very ingenious lock invented by Mr Perkins, 
 twentysix small blocks of metal, of different sizes, are introduced, 
 corresponding to the letters of the alphabet. Out of these 
 
ARTS OP DIVIDING AND UNITING SOI.ID BODIES. 34o 
 
 an indefinite number of combinations may be made. The 
 person locking the door, selects and places the blocks neces- 
 sary to spell a particular word known only to himself, and no 
 other person, even if in possession of the key, can open the 
 door, without a knowledge of the same word. 
 
 Cementing. — Cements are, for the most part, soft or semi- 
 fluid substances, which have the propert}^ of becoming hard in 
 time, and cohering with other bodies to which they have been 
 applied. A variety of these substances are used for uniting 
 different materials. The compounds of lime and sand, which 
 constitute the ordinary building cements, have been considered 
 in Chapter First. For uniting pieces of marble, plaster of Par- 
 is, dried by heat, and mixed with water, or with rosin and wax, 
 is employed. A cement for iron is made by mixing sulphur 
 and muriate of ammonia with a large quantity of iron chip- 
 pings. This is used for the joints of iron pipes, and the flanges of 
 steam' engines. Turners, and some other mechanics, confine 
 the material on which they are working, by a cement compo- 
 sed of brick-dust and rosin, or pitch. The cement used by 
 glaziers, under the name oiputty^ is a mixture of linseed oil 
 and powdered chalk. China ware is cemented by common 
 paint, made of white lead and oil, or by resinous substances, 
 such as mastic and shell lac, or by isinglass dissolved in proof 
 spirit or water. Bookbinders, and paper hangers, eiw^Xoyp aste,' 
 made by boiling flour, and a similar but more elegant article 
 under the name of rice glue, is prepared by boiling ground' 
 rice in soft water to the consistence of a thin jelly, Wafei^s 
 are made of flour, isinglass, yeast, and white of eggs, dried in 
 thin strata upon tin plates, and cut by a circular instrument. 
 The color is given by red lead, and other pigments. Stealing 
 wax is composed of shell lac and rosin, and is commonly col- 
 ored with Vermillion. 
 
 Glueing. — For uniting wood and similar porous substances,' 
 
 common glue takes precedence of all other cements. Jt is dis- ' 
 
 solved by heating it with water, and is applied with a brush to' 
 
 both the surfaces to be united. Glue does not adhere so readi-"' 
 
 44 
 
346 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 ly, if the surfaces be in the least oily, or if a coating of old glue 
 is previously upon them, or, indeed, if the pores are filled with 
 any foreign substance. The cementing power of glue depends 
 upon the strength which it possesses when dry, and the hold 
 which it obtains upon the wood, by penetrating its pores. It 
 does not furnish a sufficient bond of union for surfaces which 
 are not porous, as those of metals ; and it is not durable when 
 exposed to the action of water. 
 
 Weldi7ig. — Certain metals, such as iron and platinum, 
 which are exceedingly difficult of fusion, are capable of being 
 united by the process of welding. This consists in hammer- 
 ing them together while they are at a very high temperature. 
 Bar iron cannot be welded without raising it to a heat of near- 
 ly 60 degrees of Wedgewood's pyrometer. Cast steel would 
 be melted at this temperature, and therefore in welding iron to 
 steel, the steel is raised only to a common white heat. Care 
 is taken to prevent the surfaces which are to be welded from 
 being oxidized too much, or else to detach the scales when 
 the metal is brought to a welding heat. The union of welded 
 pieces probably depends on an incipient fusion of their surfaces. 
 When properly conducted, the metal is supposed to be as strong 
 in the welded part as in any other. 
 
 Soldering. — The process of soldering consists in uniting to- 
 gether parts of the same, or of different metals, by the inter- 
 vention of a metallic substance employed in a state of fusion. 
 It is necessary that the uniting substance should melt sooner 
 than the substance to be soldered, that it should adhere firmly 
 to its surface, and, as far as practicable, approach to the]metal sol- 
 dered, in hardness and color. Iron is usually soldered with 
 brass, and hence the process is commonly called brazing. 
 An alloy of tin and iron is sometimes used instead of brass for 
 the same purpose. Copper may be united either by a hard 
 solder made of brass and zinc, or a soft solder composed of zinc 
 and lead. Tin is soldered with pewter made of tin and lead, 
 with sometimes a portion of bismuth. Gold and silver are 
 united with solders made of gold or silver, alloyed with copper 
 
ARTS OF DIVIDING AND UNITING SOLID BODIES. 347 
 
 or brass. Platinum is soldered with gold. The adhesion of 
 solders depends upon an alloy being formed between the sur- 
 faces in contact. 
 
 As the oxidation of the surface of metals tends to prevent 
 the adhesion of the solder, it is common to unite with the sol- 
 der some additional substance, which may obviate this diffi- 
 culty. In soldering copper, brass, iron, &c., it is common to 
 employ borax, a salt which fuses at the time when the metals 
 would be most liable to oxidate, and by enveloping the metal- 
 lic surface, prevents the farther action of the oxygen of the at- 
 mosphere. Potash, soda, tartar, and various salts are used for 
 the same purpose. Muriate of ammonia has a remarkable 
 effect in freeing the surfaces of metals from oxygen, which it 
 does, apparently, by combining with the metallic oxide, and 
 carrying it off as it sublimes. In soldering the more fusible 
 metals, as tin and lead, a carbonaceous substance is employed, 
 such as rosin, or oil, which tends to cover the surface, and also 
 to reduce the oxide to its metallic state, as fast as it is foimed. 
 
 Casting. — The process of fusion, or melting, affords in 
 many substances, the most effectual method both of destroying 
 the cohesion of their particles, and of afterwards restoring it 
 under new arrangements. Many substances, both simple and 
 compound, such as metals, glass, wax, (fcc, may become liquid 
 and again solid, without essentially changing their physical 
 qualities. On the other hand, many natural bodies, crystal- 
 hzed minerals, and organic combinations, cannot be fused with- 
 out changing their characteristic properties. Some substances 
 are with difficulty fusible when alone, but become more fusible 
 when combined with another substance, as is the case of sand 
 with an alkali, or iron with carbon. Others again have their 
 fusibility lessened by combination, as happens in metals when 
 they become oxidized. 
 
 Fluxes. — The name otjluxes has been given to certain sub- 
 stances which assist fusion, either by expediting the process, or 
 by protecting the substance melted from alteration. In sepa- 
 rating metals from their ores, fluxes are employed to render the 
 
348 ARTS OF DIVIDING AND UNITING SOLID BODIES. 
 
 substances with which the metal is combined, capable of fu- 
 sion. Thus if the ore abound with sihceous earth or stone, 
 an alkaUne flux, such as potash, soda, or tartar, has the effect 
 of combining with the sihceous substances, and forming with 
 them a vitreous compound, which floats upon the top of the melt- 
 ed metal. Tartar also contains a portion of vegetable matter, 
 the carbon and hydrogen of which serve to deoxidize, the met- 
 al. Borax, common salt, and many other saline bodies, when 
 melted, prevent the oxidation of metals, by protecting their sur- 
 face from the atmosphere. Muriate of ammonia, rosin, fatty sub- 
 stances, powdered charcoal, (fcc, prevent or remove oxidation, 
 by combining either with the oxygen, or with the oxide when 
 formed. 
 
 Moulds. — The moulds used for casting melted bodies must 
 be suited to the temperature at which the body melts. For 
 metals which melt at a high heat, as copper, brass, cast-iron, 
 &c., the moulds are made of some refractory substance, such 
 as loam, sand, pounded brick with plaster, or clay, &c. Glass 
 is cast in moulds made of copper, but these require to be fre- 
 quently cooled. Those bodies which melt at temperatures be- 
 3ow that of ignition, as tin, lead, wax, &c., may be cast in 
 moulds of any convenient metal, or of wood, and other inflam- 
 mable materials. 
 
 The forms of some bodies may be changed, and their sepa- 
 ration or union effected, without the agency of fusion, in vari- 
 ous ways. It may be done by mixture with water, as in clay 
 and plaster ; by solution in water, as in glue, rice, and gum ; 
 and by sublimation, as in camphor, and muriate of ammo- 
 nia. 
 
 Young's Lectures on Natural Philosophy ; — Gregory's Mechanics; — 
 Nicholson's Operative Mechanic, 8vo.; — Grat's Operative Chemist, 
 Svo. 1828 ; — Rees' Cyclopedia, and Brewster's Edinburgh Encyclo- 
 pedia, under various heads. 
 
CHAPTER XV. 
 
 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 Theory of Twisting.— ^he strength of cordage, which is 
 employed in uniting bodies, and the utihty of flexible textures, 
 which serve for furniture or for clothing, depend principally 
 upon the friction or lateral adhesion, produced by the twisting 
 and intermixture of their constituent fibres. 
 
 A twisted cord is not so strong as the fibres which compose 
 it, supposing the fibres and cord to be of the same length. The 
 object of twisting is to connect successive numbers of short 
 fibres in such a manner, that, besides the mutual pressure 
 which their own elasticity causes them to exert, any addition- 
 al force applied in the direction of the length of the aggregate, 
 may tend to bring their parts into closer contact, and augment 
 their adhesion to each other. The simple art of tying a knot, 
 and the more complicated processes of spinning, rope making, 
 weaving, and felting, derive most of their utility from this prin- 
 ciple. 
 
 By considering the effect of a force which is counteracted 
 by other forces acting obliquely, it will be seen that the opera- 
 tion of twisting has a useful effect in binding the parts of a 
 rope or thread together, and also that it has an inconvenience 
 in causing the strength of the fibres to act with a mechanical 
 disadvantage. The greater is the obliquity of the fibres, the 
 greater will be their adhesion to each other, but the greater al- 
 so will be their immediate strain or tension, when a force acts 
 upon them in the direction of the whole cord. From this it 
 follows that after employing as much obliquity and as much 
 tension as is sufficient to connect the fibres firmly together, all 
 that is superfluously added tends to weaken the cord, by over- 
 
350 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 powering- the primitive cohesion of the fibres in the direction of 
 their length. 
 
 The mechanism of simple spinnhig is easily understood. 
 Care is taken, where the hand is emplo3'^ed, to intermix the 
 fibres sufficiently, and to engage their extremities as much as 
 possible in the centre ; for it is obvious, that if any fibre were 
 wholly external to the rest, it could not be retained in the yarn. 
 In general, however, the materials are "previously in such a 
 state of intermixture, as to render this precaution unneces- 
 sary. 
 
 Rope Making. — A single thread of yarn, consisting of fi- 
 bres twisted together, has a tendency to untwist itself, the ex- 
 ternal parts being strained by extension, and the internal parts 
 by compression ; so that the elasticity of all the parts resists, and 
 tends to restore the thread to its natural state. But if two such 
 threads similarly twisted, are retained in contact at a given 
 point of the circumference of each, this point is rendered sta- 
 tionary by the opposition of the equal forces acting in contrary 
 directions, and becomes the, centre, round which both threads 
 are carried by the forces which remain ; so that they continue 
 to twist round each other, till the new combination causes a 
 tension, capable of counterbalancing the remaining tension of 
 the original threads. Three, four, or more threads, may be uni- 
 ted nearly in the same manner. A strand, as it is called by 
 rope-makers, consist of a considerable number of yarns thus 
 twisted together, generally from sixteen to twent3^five ; a hal- 
 ser consists of three strands, shroud of four, and a cable of 
 three halsers or shrouds. Shroud laid cordage has the disad- 
 vantage of being hollow in the centre, or else of requiring a 
 great change of form in the strands to fill up the vacuity ; so 
 that in undergoing this change, the cordage stretches, and is 
 unequally strained. The relative position and the compara- 
 tive tension of all the fibres in these complicated combinations 
 are not very easily determined by calculation ; but it is found 
 by experience to be most advantageous for the strength of ropes, 
 to twist the strands, when they are to be compounded, in such 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 351 
 
 a direction as to untwist the yarns of which they are formed j 
 that is, to increase the twist of the strands themselves ; and 
 probably the greatest strength is obtained when the ultimate 
 obliquity of the constituent fibres is least, and the most equa- 
 ble.* 
 
 A very strong rope may also be made by twisting five or six 
 strands round a seventh, as an axis. In this case, the central 
 strand, or heart, is found after much use to be chafed to oakum. 
 Such ropes are, however, considered unfit for rigging, or for 
 any use in which they are liable to be frequently bent. 
 
 Ropes are most commonly made of hemp, but various other 
 vegetables are occasionally employed. The Chinese even use 
 woody fibres ; and the barks of trees furnish cordage to other 
 nations. In spinning the yarn, in the process of rope makings 
 the hemp is fastened round the waist of the workman ; one 
 end of it is attached to a wheel turned by an assistant, and the 
 spinner, walking backwards, draws out the fibres with his 
 hands. When one length of the walk has been spun, it is 
 immediately reeled to prevent its untwisting. The machines 
 employed in continuing the process of rope making, are mostly 
 of simple construction, but both skill and attention are required 
 in applying them so as to produce an equable texture in every 
 part of the rope. The tendency of two strands to twist, in con- 
 sequence of the tension arising from the original twist of the 
 yarns, is not sufficient to produce an equilibrium, because of the 
 friction and rigidity to be overcome. Hence it is necessary to 
 employ force to assist this tendency, and the strands or ropes 
 will afterwards retain spontaneously the form which has thus 
 been given them. The largest ropes even require external 
 force in order to make them twist at all. 
 
 The constituent ropes of a common cable, when separate, 
 are stronger than the cable, in the proportion of about four to 
 three ; and a rope worked up from yarns 180 yards in length, 
 to 135 yards, has been found to be stronger than when reduced 
 
 * Young's Natural Philosophy, vol. i. Lect. xvi. 
 
352 ARTS OP COMBINING FLEXIBLE FIBRES. 
 
 to 120 yards, in the ratio of six to five. The differences is 
 owing partly to the obhquity of the fibres, and partly to the 
 unequal tension produced by twisting.* 
 
 COTTON MANUFACTURE. 
 
 When the fibres of cotton, wool, or flax, are intended to be 
 woven, they are reduced to fine threads of uniform size, by 
 the well known process of sjnnyiing. Previously to the mid- 
 dle of the last century, this process was performed by hand, 
 with the aid of the common spinning wheel. Locks of cotton 
 or wool, previously carded, were attached to a rapidly revolv- 
 ing spindle driven by a large wheel, and were stretched or 
 drawn out by the hand, at the same time that they were tv/ist- 
 ed by the spindle, upon which they w^ere afterwards Wound. 
 Flax, the fibres of which are longer and more parallel, was 
 loosely wound upon a distaff, from which the fibres were se- 
 lected and drawn out by the thuiub and finger, and at the 
 same time were twisted by flyers and wound upon a bobbin, 
 which revolved with a velocity somewhat less than that of the 
 flyers. 
 
 The manufacture of flexible stuffs by means of machinery, 
 operating on a large scale, is an invention of the last century. 
 Although of recent date, it has given birth to some of the most 
 elaborate and wonderful combinations of mechanism, and al- 
 ready constitutes, especially in England and in this countiy, 
 an important source of national wealth and prosperity. 
 
 Elementary Inventions. — ^The character of the machinery 
 which has been applied to the manufacture of cotton at differ- 
 ent times, has been various. There are, how^ever, several 
 leading inventions, upon v/hich most of the essential processes 
 are founded, and which have given to their authors a greater 
 shareof celebrity than the rest. These are, 1. ^h& spinning 
 
 * Young's Natural Philosophyj voi. i. Lect. xvi. 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 353 
 
 jenny. This machine was invented by Richard Hargreaves,* 
 in 1767, and in its simplest form resembled a number of spin- 
 dles turned by a common wheel, or cylinder, which was work- 
 ed by hand. It stretched out the threads as in common spin- 
 ning of carded cotton. 2. The water sjnnning frame, in- 
 vented by Richard Arkwright, in 1769. The essential and 
 most important feature in this invention, consists in the 
 drawing out, or elongating of the cotton, by causing it to pass 
 between successive pairs of rollers, which revolve with differ- 
 ent velocities, and Avhich act as substitutes for the finger and 
 thumb, as applied in common spinning. These rollers are 
 combined with the spindle and flyers of the common flax 
 wheel. 3. The mule. This was invented by Samuel Cromp- 
 ton, in 1779. It combines the principles of the two preceding 
 inventions, and produces finer yarn than that which is spun 
 in either of the other machines. It has now nearly superseded 
 the jenny. 4. The poiver loom for weaving by water or 
 steam power, which was introduced about the end of the eigh- 
 teenth century, and has received various modifications. 
 
 The foregoing fundamental machines are used in the same 
 or different establishments, and for different purposes. But 
 besides these, various auxiliary machines are necessary to per- 
 form intermediate operations, and to prepare the material as 
 it passes from one stage of the manufacture to another. The 
 number of these machines, and the changes and improvements 
 which have been made in their construction, from time to time, 
 render it impossible to convey, in a work Uke the present, any 
 accurate idea of their formation in detail. A brief view, how- 
 ever, of the offices which they severally perform, may be tak- 
 en by following the raw material through the principal changes 
 which it undergoes in a modern cotton factory, founded and 
 improved upon the general principles of Arkwright. 
 
 Batting. — The cotton, after having been cleared from its 
 
 Mr Guest, in a late work, attributes the invention, both of the jenny and wa- 
 ter spinning frame, to Thomas Highs, of Leigh, England. 
 
 45 
 
354 ARTS OP COMBINING FLEXIBLE FIBRES. 
 
 seeds, at the plantation, by the operation of ginning, described 
 on page 34, is compressed into bags for exportation, and ar- 
 rives at the factory in a dense and matted mass. The first 
 operation to Vv'hich it is submitted has for its object to disentan- 
 gle the fibres, and restore the cotton to a light, open, and uni- 
 form state. For this purpose, after being weighed out, it is 
 submitted to the operation of a machine called a picker, or of 
 another denominated a batter. In some of these machines it 
 is subjected to the action of a series of pins, in others to a sort 
 of blunt knives, revolving with great rapidity ; the effect of 
 which is to beat up and separate the fibres, to disengage their 
 unequal adhesions, and to reduce the whole to a very light, 
 uniform, flocculent mass. 
 
 Carding. — The cotton next passes to the carding machines, 
 of which, when there are two, the first is called the breaker, 
 and the second the finisher. In this operation the cotton is 
 carried over the surface of a revolving cylinder which is cov- 
 ered with card teeth of wire, and which passes in contact with 
 an arch, or part of a concave cylinder, similarly covered with 
 teeth. From this cylinder it is taken off by another, called the 
 dojing cylinder, which revolves in an opposite direction ; and 
 from this it is again removed by the rapid vibrating movement 
 of a transverse comb, otherwise called the doffing plate, moved 
 by cranks. It then exists in the state of a flat, uniform fleece, 
 or lap, which, after passing the breaker, undergoes the process 
 of plying, or doubling, by causing it to perform a certain 
 number of revolutions upon a cylinder, or a perpetual cloth. 
 It is then carded a second time, by the finisher, and the fleece, 
 after being taken off from this machine, is drawn by rollers 
 through a hollow cone, or trumpet mouth, which contracts it 
 to a narrow band or sliver, and leaves it coiled up in a tin can, 
 ready for the next operation. The process of carding serves 
 to equalize the substance of the cotton, and to lay its fibres 
 somewhat in a more parallel direction. 
 
 Drawing. — The slivers of cotton are next elongated by the 
 process of drawing. This operation is the ground work or 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 355 
 
 principle of Arkwright's invention, and is used in the roving 
 and spinning as well as in the drawing frame. It is an 
 imitation of what is done by the finger and thumb in spinning 
 by hand, and is performed by means of two pairs of rollers. 
 The upper roller of the first pair is covered with leather, which, 
 being an elastic substance, is pressed by means of a spring or 
 weight. The lower roller, made of metal, is fluted in order to 
 keep a firm hold of the fibres of cotton. Another similar pair 
 of rollers are placed near those which have been described. 
 The second pair, moving with a greater velocity, pull out the 
 fibres of cotton from the first pair of rollers. If the surface 
 of the last pair move at twice or thrice the velocity of the first 
 pair, the cotton will be drawn twice or thrice finer than it was 
 before. This relative velocity is called the draught of the ma- 
 chine. This mechanism being understood, it will be easy to 
 conceive the nature of the operation of the drawing frame. 
 Several of the narrow ribbands or slivers from the cards, 
 (sometimes termed card ends) by being passed through a sys- 
 tem of rollers, are thereby reduced in size. By means of a 
 detached single pair of rollers, the several reduced ribbands 
 are 'plied or united into one sliver. 
 
 The operations of drawing and plying serve to equalize still 
 farther the body of cotton, and to bring its fibres more into a 
 longitudinal direction. These slivers are again combined and 
 drawn out, so that one sliver of the finished drawing contains 
 many plies of card ends. Hitherto the cotton has acquired no 
 twist, but is received into moveable tin cans or canisters, sim- 
 ilar to those used for receiving the cotton from the cards. 
 
 Roving. — The operation of roving communicates the first 
 twist to the cotton. It is performed by a machine called the 
 roving frame, or double speeder. The tin cans containing 
 the slivers of cotton, are placed upon this machine, and are 
 made to revolve slowly about their axes so as to produce a shght 
 degree of twisting. The slivers then pass again through seve- 
 ral pairs of rollers moving with different speeds, and are thus 
 still further attenuated by drawing. They are then slightly 
 
356 ARTS OP COMBINING FLEXIBLE FIBRES. 
 
 spun by the revolution of flyers, and are wound upon the bob- 
 bhis of the spindles, in the form of a loose, soft, imperfect thread, 
 denominated the rovino-. 
 
 The mechanism of the double speeder is complicated and 
 interesting, and great ingenuity has been displayed in overcom- 
 ing the difficulties of its construction. In order that the yarn, 
 or roving, may be wound upon the bobbins in even cylindrical 
 layers, it is necessary that the spindle rail, or horizontal bar 
 which supports the spindles, should continually rise and fall 
 with a slow, alternate motion. This is effected by heart wheels, 
 or cams, in the interior of the machine. Again, since the col- 
 lective size of the bobbin is augmented by the addition of each 
 layer of roving, it is obvious that if the axis of the bobbin re- 
 volved always with the same velocity, the thread of roving 
 would be broken in consequence of being wound up too fast. 
 To prevent this accident, the velocity of the spindles, and like- 
 wise the motion of the spindle rail, is obliged gradually to di- 
 minish from the beginning to the end of an operation. This 
 diminution of speed is effected by transmitting the motion both 
 to the spindle rail, and to the bobbins, through two opposite 
 cones, one of which drives the other with a band, the band 
 being made to pass slowly from one end to the other of the 
 cones, and thus continually to alter their relative speed, and 
 cause a uniform retardation of the velocity of the moving parts.* 
 As the roving is not strong enough to bear any violence, the 
 spindles which support the bobbins are geared to each other, 
 so as to prevent any deviation from the proper velocity. 
 
 A more simple form of the roving frame has been invented,! 
 in which the gearing is dispensed with, as well as the pair of 
 cones which regulates the motion of the bobbins. In this ma- 
 chine the bobbins are not turned by the rotation of their axis, 
 but by friction applied to their surface by small wooden cylin- 
 ders which revolve in contact with them. In this way the ve- 
 
 * Instead of band cones, an ingenious mode of using geared cones, now in- 
 troduced ia several American factories, has already been described, page 239. 
 + By Mr Danforth, of Massachusetts. 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 357 
 
 locity of the surface of the bobbin will always be the same, 
 whatever may be its growth from the accnraulation of roving-, 
 so that the v/inding goes on at an equable rate. To prevent 
 the roving from being stretched, or broken, in its passage 
 from the drawing rollers to the bobbins, it is made to pass 
 through a tube which has a rapid rotation, and which twists 
 it in the middle into a cord of some firmness. It is again un- 
 twisted, as fast as it escapes from the tube, and is wound upon 
 the bobbins in the form of a dense even cord, but without any 
 twist. 
 
 tSjntmmg'. — The bobbins which contain the cotton in a state 
 of roving, are next transferred to the spinning frame. It is here 
 once more drawn out by rollers and twisted by flyers, so that 
 the spinning is little more than a repetition of the process gone 
 through in making the roving, except that the cotton is now 
 twisted into a strong thread, and cannot any longer be extend- 
 ed by drawing. The flj^ers of the spinning frame are driven 
 by bands, which receive their motion in some cases from a 
 horizontal fly wheel, and in others from a longitudinal cylin- 
 der.* As the thread is sufficiently strong not to break with a 
 slight force, the resistance of the bobbins by friction is relied on 
 to wind it up, instead of having the spindles geared together 
 and turned with an exact velocity, as they are in the common 
 double speeder. In the spinning frame the heart motion is re- 
 tained to regulate the rise and fall of the rail, and in those 
 frames which spin the woof, or filling, it is applied by a pro- 
 gressive sort of cone, the section of which is heart-shaped, and 
 which acts remotely to distribute the thread in conical layers 
 upon the bobbins, that it may unwind the more easily when 
 placed afterwards in the shuttle. 
 
 Mtde jSpinni?ig. — The processes of water spinning already 
 described, are adequate to produce yarns of sufficient fineness 
 for ordinary fabrics. But for producing threads of the finest 
 kind, another process is necessary, which is called stretching, 
 
 * The latter method which had gone into disuse, is beginning to be revived 
 and to be considered most advantageous. 
 
358 ARTS OF COMBINING FLEXIBLE FIBRES, 
 
 and which is analogous to that which is performed with carded 
 cotton upon a common spinning wheel. In this operation, por- 
 tions of yarn, several yards long, are forcibly stretched in the 
 direction of their length. It differs, therefore, from the opera- 
 tion of drawing, in which a few inches only are extended at a 
 time. The stretching is performed with a view to elongate 
 and reduce those places in the yarn, which have a greater di- 
 ameter and are less twisted than the other parts, so that the 
 size and twist of the thread may become uniform throughout. 
 To effect the process of stretching, the spindles are mounted 
 upon a carriage, which is moved back and forwards across the 
 floor, receding when the threads are to be stretched, and re- 
 turning when they are to be wound up. The yarn produced 
 by mule spinning is more perfect than any other, and is em- 
 ployed in the fabrication of the finest articles. The sewing 
 thread spun by mules is a combination of two, four, or six con- 
 stituent threads, or plies. Threads have been produced of such 
 fineness, that a pound of cotton has been calculated to reach 
 167 miles. 
 
 Warping. — The first step preparatory to weaving is to form 
 a warj), which consists of parallel threads continued through 
 the whole length of the intended piece, and sufficient in number 
 to constitute its breadth. It was formerly the practice to attach 
 the threads to as many pins, and to draw^ them out to the re- 
 quired length. But as this method required too much room, a 
 warping machine was subsequently used, in which the mass of 
 threads intended to constitute a warp, was wound in a spiral 
 course upon a large revolving frame, which rose and fell so as 
 to produce the spiral distribution. 
 
 These methods are now superseded in this country by 
 Moody's warping machine,* an ingenious piece of mechanism, 
 in which a number of bobbins, equal to one eighth part of the 
 
 * Mr Paul Moody, formerly of Waltham, and now of Lowell, is the inventor 
 of this machine; likewise of the spinning frame, which winds the woof in con- 
 ical layers ; and of great improvements in the roving frame, the dressing frame, 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 359 
 
 number of threads in the intended warp, are arranged upon 
 the surface of a concave frame. The threads pass through a 
 reed which separates the alternate threads as they are to be 
 kept in the loom ; after which they are wound upon a beam, 
 with rods interposed at the end to preserve the separation. 
 But the most interesting part of the mechanism is a contrivance 
 for stopping the machine if a single thread of the warp breaks, 
 to effect this object, a small steel weight, or flattened wire, is 
 suspended by a hook from each thread, so that it falls if the 
 thread is broken. Beneath the row of weights, a cylinder re- 
 volves, furnished with several projecting ledges extending its 
 whole length parallel to the axis. When one of the weights 
 falls by the breaking of its thread, it intercepts one of the ledges, 
 and causes the cylinder to exert its force upon an elbow, or 
 toggle joint, which disengages a clutch, and stops the machine. 
 After the thread is tied, and the weight raised, the machine 
 proceeds. 
 
 Dressing. — As the threads which constitute the warp are 
 liable to much friction in the process of weaving, they are sub- 
 jected to an operation called dressing, the object of which is to 
 increase their strength and smoothness, by agglutinating their 
 fibres together. To this end they are pressed between rollers 
 impregnated with mucilage made of starch, or some gelatinous 
 material, and immediately afterwards brought in contact with 
 brushes, which pass repeatedly over them so as to lay down the 
 fibres in one direction, and remove the superfluous mucilage 
 from them. They are then dried by a series of revolving fans, 
 or by steam cylinders, and are ready for the loom. 
 
 Weaving. — Woven textures derive their stiength from the 
 same force of lateral adhesion which retains the twisted fibres 
 of each thread in their situations. The manner in which these 
 textures are formed, is readily understood. On inspecting a 
 piece of plain cloth, it is found to consist of two distinct sets 
 of threads running perpendicularly to each other. Of these, 
 the longitudinal threads constitute the v)arp, while the trans- 
 verse threads are called the woof, weft, or filling, and consist 
 
360 
 
 ARTS OP COMBINING FLEXIBLE FIBRES. 
 
 of a single thread passing backwards and forwards. In weav- 
 ing with the common loom, the warp is wound upon a cylin- 
 drical beam, or roller, Fiom this, the threads pass through a 
 harness, composed of moveable parts called the heddles, of 
 which there are two or more, consisting of a series of vertical 
 strings connected to frames, and having loops through which 
 the warp passes. Y/hen the heddles consist of more than one 
 set of strings, the sets are called leaves. Each of these hed- 
 dles receives its portion of the alternate threads of the warp ; 
 so that when they are moved reciprocally vip and down, the 
 relative position of the alternate threads of the warp is reversed. 
 Each time that the warp is opened by the separating of its al- 
 ternate threads, a shuttle containing the woof, is thrown across 
 it, and the thread of woof is immediately driven into its place 
 by a frame called a lay, furnished with thin reeds, or wires, 
 placed among the warp like the teeth of a comb. The woven 
 piece, as fast as it is completed, is wound up on a second beam 
 opposite to the first. 
 
 Power looms, driven by water or steam, although a late in- 
 vention, are now universally introduced into manufactories of 
 cotton and woollens. As the motions of the loom are chiefly 
 of a reciprocating kind, they are produced in some looms by 
 the agency of cranks, and in others by cams or wipers, acting 
 upon weights or springs. 
 
 Twilling. — In the mode of plain weaving last described, it 
 will be observed that every thread of the warp crosses at every 
 thread of the woof, and vice versa. In articles which are 
 tvnlled or tiveeled, this is not the case ; for in this manufacture 
 only the third, fourth, fifth, sixth, &-c. threads cross each other 
 to form the texture. In the coarsest kinds every third thread 
 is crossed, but in finer fabrics the intervals are less frequent, 
 and in some very fine twilled silks, the crossing does not take 
 place tiU the sixteenth interval. In Fig. 1 is shown a magnified 
 
 Fig. 1. 
 
ARTS OF COMBINING FLEXIBLE FIBRES, 361 
 
 section of a piece of plain cloth, in which the woof passes al- 
 ternately over and under every thread of the warp. In Fig. 2 
 
 Fio-. 2. 
 
 is a piece of twilled cloth, in which the thread of the woof 
 passes alternately over four, and under one, of the threads of 
 the warp, and performs the reverse in its return. To produce 
 this effect, a number of leaves of heddles are required, equal 
 to the number of threads contained in the interval between 
 each intersection, inclusive. By the separate movements of 
 these, the warp is placed in the requisite position before each 
 stroke of the shuttle. A loom invented in this country, by Mr 
 Batchelder, of Lowell, has been applied to the weaving of twilled 
 goods by water power. 
 
 Twilled fabrics are thicker than plain ones, when of the 
 same fineness, and more flexible when of the same thickness. 
 They are also more susceptible of ornamental variations, 
 Jeans, dimoties, serges, (fee, are specimens of this kind of 
 textm'e. 
 
 Double Weaving-. — ^In this species of weaving, the fabric 
 is composed of two webs, each of which consists of a separate 
 warp and a separate woof. The two, however, are interwoven 
 at intervals, so as to produce various figures. The junction of 
 the two webs is formed by passing them at intervals through 
 each other, so that each particular part of both is sometimes 
 above, and sometimes below. It follows, that when different 
 colors are employed, as in carpeting, the figure is the same on 
 both sides, but the color is reversed. A section of double cloth 
 is shown in Fig, 3. 
 
 Flo-. 3. V 
 
 The weaving of double cloths is commonly performed by a 
 46 
 
3'62 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 Gomplicated machine, called a draw loom, in which the weaver, 
 aided by an assistant, or by machinery, has the command of 
 each particular thread by its number. He works by a pattern, 
 in which the figure before him is traced in squares, agreeably 
 to which the threads to be moved are selected and raised, be- 
 fore each insertion of the woof. Kidderminster carpets, and 
 Marseilles quilts, are specimens of this mode of weaving-. 
 
 Cross Weaving. — This method is used to produce the 
 lightest fabrics, such as gauze, netting, catgut, &c. In the 
 kinds of weaving which have been previously described, the 
 threads of the warp always remain parallel to each other, or 
 without crossing. But in gauze weaving, the two threads of 
 warp which pass between the same splits of the reed, are cross- 
 ed over each other, and partially twisted like a cord, at every 
 stroke of the loom. They are, however, twisted to the right 
 and left, alternately, and each shot, or insertion of the woof, 
 preserves the twist which the warp has received. A great va- 
 riety of fanciful textures are produced by variations of the 
 same general plan. Fig. 4 represents the cross weaving used 
 in common gauze. 
 
 Fig. 4. 
 
 Lace. — Lace is a complicated, ornamental fabric, formed of 
 fine threads of linen, cotton, or silk. It consists of a net work of 
 small meshes, the most common form of which is hexagonal. 
 In perfect thread lace, four sides of the hexagon consist of 
 threads which are twisted, while in the remaining two, they are 
 simply crossed. Lace has been commonly made upon a cush- 
 ion or pillow, by the slow labor of artists. A piece of stiff 
 parchment is stretched upon the cushion, having holes pricked 
 through it, in which pins are inserted. The threads previously 
 wound upon small bobbins, are woven round the pins and 
 twisted in various ways, by the hands, so as to form the required 
 pattern. The expensiveness of the different kinds of lace is 
 proportionate to the tediousness of the operation. Some of 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 363 
 
 the mo>re simple fabrics are executed with rapidity, while oth- 
 ers, in which the sides of the meshes are plaited, as in the 
 Brussels lace, and that made at Valenciennes, are difficult, and 
 bear a much greater price. 
 
 The cheaper kinds of laoe have long been made by ma- 
 chinery ; and recently the invention of Mr Heathcoat's lace 
 machine has effected the fabrication of the more difficult or 
 twisted lace, with precision and despatch. This machine is 
 exceedingly complicated and ingenious, and is now in operation 
 in this country and in France, as well as in England. 
 
 Carpeting. — Carpets are thick textures composed wholly 
 or partly of wool, and wrought by several dissimilar methods. 
 The simplest mode is that used in weaving the Venetian car- 
 pets, which is a plain texture, composed of a striped woollen 
 warp, on a thick woof of linen thread. Kiddermifister' car- 
 peting is composed by two woollen webs, which intersect each 
 other in such a manner as to produce definite figures. Brus- 
 sels carpeting has a basis composed of a warp and woof of 
 strong linen thread. But to every two threads of linen in the 
 warp, there is added a parcel of about ten threads of woollen 
 of different colors. The linen thread never appears on the up- 
 per surface, but parts of the woollen threads are from time to 
 time drawn up in loops, so as to constitute ornamental figures, 
 the proper color being each time selected from the parcel to which 
 it belongs. A sufficient number of these loops is raised to pro- 
 duce a uniform surface, as seen in Fig. 5, and to render them 
 
 Fig. 5. 
 
 equal, each row passes over a wire, which is subsequently with- 
 drawn. In some cases, the loops are cut through with the end 
 of the wire, which is sharpened for the purpose, so as to cut off 
 the threads as it passes out. In forming the figure, the weav- 
 er is guided by a pattern, which is drawn in squares upon a 
 paper. Turkey carpets appear to be fabricated upon the same 
 
364 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 genera] principles as the Brussels, except that the texture is all 
 woollen, and the loops larger and always cut. 
 
 Tapestry. — The name of tapestry is given to certain deli- 
 cate and complicated fabrics, in which the forms \ m\ cv lors of 
 natural objects are produced with such accuracy, as to resem- 
 ble fine paintings. The mode of texture used to produce this ef- 
 fect, is in many respects analogous to that by which the finer 
 carpetings are made. The minuteness, however, of the con- 
 stituent parts, causes the sight of the texture to be lost in the 
 general effect of the piece. The fabrication of tapestry is slow, 
 intricate, and very expensive. The most celebrated manufac- 
 tory is that established by the family of Gobelins, and kept up 
 by their successors, at Paris. 
 
 Velvets. — The fine, soft knap, by which velvet is covered, 
 is produced by a method not unlike that which is used in car- 
 peting and tapestry. It is formed of a part of the threads of 
 the warp, which the workman puts in loops on a long chan- 
 nelled wire. Before the wire is withdrawn, the row of loops 
 is cut open by a sharp steel instrument, which is drawn along 
 the channel of the wire. Various other fabrics of silk, cotton, 
 and wool, such as thicksets, plushes, corduroys, velveteens, (fee, 
 are cut in a similar manner. 
 
 Cotton counterpanes are woven with two shuttles, one con- 
 taining a much coarser woof than the other. The coarser of 
 the threads is picked up at intervals, with an iron pin, which 
 is hooked at the point, thus forming knobs which are made to 
 constitute regular figures. 
 
 In cotton fabrics, the web, when taken from the loom, is cov- 
 ered with an irregular knap, or down, formed by the project- 
 ing ends of the fibres. This is removed in the finest articles, 
 by burning it off, the heat being so managed as not to injure 
 the texture of the cloth. The operation is performed by draw- 
 ing the web very rapidly over an iron cylinder, which is kept 
 constantly red hot, by a fire within it. The velocity of the 
 cloth prevents it from burning, while the loose filaments, which 
 
ARTS OP COMBINING FLEXIBLE FIBRES. 365 
 
 constitute the knap, aie singed off. The flame of coal gas has 
 of late been applied to the same purpose. 
 
 Linens. — This name belongs to fabrics which are manufac- 
 tured from flax, but those made of hemp are similar in tiieir 
 properties, except in fineness. The length and comparat ve 
 rigidity of the fibres of flax, present difficulties in the way of 
 spinning it by the machiner)^ which is used for cotton and wool. 
 It cannot be prepared by carding, as these other substances 
 are, and the rollers are capable of drawing it but very imper- 
 fectly. The subject of spinning flax by machinery, has attract- 
 ed much attention, and the emperor Napoleon at one time of- 
 fered a reward of a million of francs to the inventor of the best 
 machine for this purpose. Various individuals, both in this 
 country and in Europe, have succeeded in constructing ma- 
 chines which spin coarse threads of linen very well, and with 
 great rapidity. But the manufacture of fine threads, such as 
 those used for cambrics and lace, continues to be performed by 
 hand upon the ancient spinning wheel. 
 
 WOOLLENS. 
 
 The fibres of wool, being contorted and elastic, are drawn 
 out and spun by machinery in some respects similar to that 
 used for cotton, but differing in various particulars. Indepen- 
 dently of the quality of fineness, there are two sorts of wool 
 which afford the basis of different fabrics, the long wool and 
 the short. Long wool is that in which the fibres are rendered 
 parallel by the process of combing. It is also known by the 
 name of worsted, and is the material of which camlets, bom- 
 bazines, &c. are made. Short wool is prepared by carding, 
 like cotton, and is used, in different degrees of fineness, for 
 broadcloths, flannels, and a mifltitude of other fabrics. This 
 wool, when carded, is formed into small cylindrical rolls, which 
 are joined together, and stretched and spun, by a sluhhing or 
 roving machine, and a jenny or mule, in both of which the 
 
366 ARTS OP COMBINING FLEXIBLE FIBRES. 
 
 spindles are mcunted on a carriage, which passes backwards 
 and forwards, so as to stretch the material, at the same time 
 that it is twisted. On account of the roughness of the fibres, 
 it is necessary to cover them with oil or grease, to enable them 
 to move freely upon each other during the spinning and weav- 
 ing. After the cloth is woven, the oily matter is removed by 
 scouring, in order to restore the roughness to the fibres prepa- 
 ratory to the subsequent operation of fulling. 
 
 In articles which are made of long wool, the texture is com- 
 plete when the stuff issues from the loom. The pieces are 
 subsequently dyed, and a gloss is communicated to them by 
 pressing them between heated metallic surfaces. But in cloths 
 made of short wool, the weaving cannot be said to have com- 
 pleted the texture. When the web is taken from the loom, it 
 is too loose and open, and consequently requires to be submitted 
 to another operation, called fulling. This is performed by a 
 fulhng mill, in which the cloth is immersed in water, and sub- 
 jected to repeated compressions by the action of large beaters, 
 formed of wood, which repeatedly change the position of the 
 cloth, and cause the fibres to felt and combine more closely 
 together. By this process the cloth is reduced in its dimen- 
 sions, and the beauty and stability of the texture are greatly 
 improved. The tendency to become thickened by fulling, is 
 peculiar to wool and hair, and does not exist in the fibres of 
 cotton or flax. It depends on a certain roughness of these an- 
 imal fibres, which permits motion in one direction, while it re- 
 tards it in another. It thus promotes entanglements of the fi- 
 JDres, which serve to shorten and thicken the woven fabric. 
 Before the cloth -is sent to the fulling mill, it is necessary to 
 cleanse it from all the unctuous matter, which was applied to 
 prepare the fibres for spinning. 
 
 The knap, or downy surface of broadcloths, is raised by a 
 process, which, while it improves the beauty, tends somewhat 
 to diminish the strength of the texture. It is produced by 
 -carding the cloth with a species of burrs, the fruit of the com- 
 mon teazle, (Dipsacus fullo7ium) wliich is cultivated for the 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 367 
 
 purpose. This operation extricates a part of the fibres, and 
 lays them in a parallel direction. The knap, composed of these 
 fibres, is then cut off to an even surface, by the process of shear- 
 ing. This is performed in various ways, but in one of the 
 most common methods a large spiral blade revolves rapidly in 
 contact with another blade, while the cloth is stretched over a 
 bed, or support, just near enough for the projecting filaments to 
 be cut off at a uniform length, while the main texture remains 
 uninjured. 
 
 FELTING. 
 
 The texture of modern hats, which are made of fur and 
 wool, depends upon the process oi felting, which is similar to- 
 that of fulling already described. The fibres of these sub- 
 stances are rough in one direction only, a circumstance which 
 may be perceived by passing a hair through the fingers in op- 
 posite dii'ections. This roughness allows the fibres to glide 
 among each other, so that when the mass is agitated, the ante- 
 rior extremities slide forward in advance of the body or poste- 
 rior half of the hair, and serve to entangle and contract the 
 whole mass together. The materials commonly used for hat 
 making, are the furs of the beaver, seal, rabbit, and other ani- 
 mals, and the wool of sheep. The furs of most animals are 
 mixed with a longer kind of thin hair, which is obliged to be 
 first pulled out, after which the fur is cut off with a knife. 
 The materials to be felted are intimately mixed together by the 
 operation of bowing, which depends on the vibrations of an 
 elastic string ; the rapid alternations of its motion being pecu- 
 liarly well adapted to remove all irregular knots and adhesions 
 among the fibres, and to dispose them in a very light and uni- 
 form arrangement. This texture, when pressed under cloths 
 and leather, readily unites into a mass of some firmness. This 
 mass is dipped into a liquor containing a little sulphuric acid, 
 and when intended to form a hat, it is first moulded into a large 
 
368 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 conical figure, and this is afterwards reduced in its dimensions 
 by working it for several hours with the hands. It is then 
 formed into a fiat surface, with several concentric folds, which 
 are still further compacted, in order to make the brim, and the 
 circular part of the crown, and forced on a block, which serves 
 as a mould for the cylindrical part. The knap, or outer por- 
 tion of the fur, is raised with a fine wire brush, and the hat is 
 subsequently dyed, and stiffened on the inside with glue. 
 
 An attempt has been made, and at one time excited consid- 
 erable expectation in England, to form woollen cloths by the 
 process of felting, without spinning or weaving. Perfect imita- 
 tions of various cloths were produced, but they were found defi- 
 cient in the firmness and durability which belongs to woven 
 fabrics. 
 
 PAPER MAKING- 
 
 The combination of flexible fibres by which paper is pro- 
 duced, depends on the minute subdivision of the fibres, and 
 their subsequent cohesion. Linen and cotton rags, are the 
 common material of which paper is made, but hemp and some 
 other fibrous substances are used for the coarser kinds. These 
 materials, after being washed, are subjected to the action of a 
 revolving cylinder, the surface of which is furnished with a 
 number of sharp teeth, or cutters, which are so placed as to 
 act against other cutters fixed underneath the cylinder. The 
 rags are kept immersed in water, and continually exposed to 
 the action of the cutters for a number of hours, till they are 
 minutely divided, and reduced to a thin pulp. During this 
 process a quantity of chloride of lime is mixed with the rags, 
 the effect of which is to bleach them, by discharging the color- 
 ing matter, with which any part of them may be dyed, or oth- 
 erwise impregnated. Before the discovery of this mode of 
 bleaching, it was necessary to assort the rags, and select only 
 those which were white, to constitute white paper. If, howev- 
 
ARTS OF COMBINING FLEXIBLE FIBRES. 369 
 
 er, the bleaching process be carried too far, it injures the tex- 
 ture of the paper by corroding and weakening the fibres. 
 
 The pulp composed of the fibrous particles mixed with wa- 
 ter is transferred to a large vat, and is ready to be made into 
 paper. The workman is provided with a mould, which is a 
 square frame with a fine wire bottom, resembling a sieve, of 
 the size of the intended sheet. With this mould he dips up a 
 portion of the thin pulp, and holds it in a horizontal direction. 
 The water runs out through the interstices of the wires, and 
 leaves a coating of fibrous particles, in the form of a sheet, 
 upon the bottom of the mould. The sheets thus formed are 
 subjected to pressure, first between felts or woollen cloths, and 
 afterwards alone. They are then sized, by dipping them in a 
 thin solution of gelatin, or glue, obtained from the shreds and 
 parings of animal skins. The use of the size is to increase 
 the strength of the paper, and by filling its interstices, to pre- 
 vent the ink from spreading among the fibres, by capillary at- 
 traction. In blotting paper the usual sizing is omitted. 
 
 The paper, after being dried, is pressed, examined, selected 
 and made into quires and reams. Hot pressed paper is ren- 
 dered glossy by pressing it between hot plates of polished metal. 
 
 Paper is also manufactured by machinery, and one of the 
 most ingenious methods is that invented by the Messrs Four- 
 drinier. In this arrangement, instead of moulds, the pulp is 
 received in a continual stream, upon the surface of an endless 
 web of brass wire, which extends round two revolving cylin- 
 ders, and is kept in continual motion forwards, at the same 
 time that it has a tremulous or vibrating motion. The pulp is 
 thus made to form a long, continual sheet, which is wiped off 
 from the wire web, by a revolving cylinder covered with flan- 
 nel, and after being compressed between other cylinders is final- 
 ly wound into a coil, upon a reel prepared for the purpose. 
 
 Another machine for making paper consists of a horizontal 
 revolving cylinder of wire web, which is immersed in the vat 
 to the depth of more than half its diameter. The water pene- 
 trates into this cyhnder, being strained through the wire web, 
 47 
 
870 ARTS OF COMBINING FLEXIBLE FIBRES. 
 
 at the same time depositing a coat of fibrous particles on the 
 outside of the cyhnder, which constitute paper. The strained 
 water flows off through the hollow axis of the cylinder, and the 
 paper is wound off from the part of the cylinder which is above 
 water, in the form of a continued sheet. 
 
 Gray's Treatise on Spinning Machinery, 8vo. 1819 ; — Duncan's Es- 
 say on the Art of Weaving, Bvo. 1808 ; — Guest's History of the Cot- 
 ton Manufacture, 4to. 1823 ; — Borgnis' Mechanique Appliquee aux Arts 
 1818 ; torn. 7, Machines a Confedionner les Etoffes ; — Rees' Cyclope- 
 dia, articles Cotton Manufacture, Woollen Manufacture, &c. ; — Edin- 
 burgh Encyclopedia, articles Cotton Spinning, Cloth Manufacture, &c. 
 Much of the machinery invented in this country, is not described in 
 European works. 
 
CHAPTER XVI. 
 
 ARTS OF HOROLOGY. 
 
 Horology, or the art of measuring time, has received the 
 attention, and exercised the ingenuity of mankind from the 
 earUest periods. The lapse of thought and the routine of or- 
 dinary occupation, afford but imperfect indications of the real 
 passage of time ; and the only exact standard by which periods 
 of duration can be estimated, is that of governed and regular 
 motion. 
 
 Su7i Dial. — The diurnal movement of the earth with rela- 
 tion to the heavenly bodies, is the most perfect standard of ad- 
 measurement for large periods of time. It is the only one by 
 which the brute creation and the uncivilized part of mankind 
 govern their habits of life. This motion has been converted 
 to practical use, for measuring small periods, by the employ- 
 ment of the sun dial, an invention apparently of great antiqui- 
 ty, in which the falling of a shadow on a surface opposite to 
 the sun, indicates the hour of the day. The sun dial was 
 known to the ancient Egyptians, Chinese, and Bramins, and 
 was used by the latter for astronomical purposes. It appeare 
 also to have been known to the Jews in the time of Ahaz, 
 about 740 years before Christ. The first sun dial at Rome 
 was set up by Papirius Cursor, about 300 "years before Christ, 
 previously to which time, Pliny tells us, there is no mention 
 of any account of time, but by the sun's rising and setting. 
 
 At Athens, there is now standing an octagonal building 
 erected by Andronicus Cyrrhestes, and commonly called the 
 Tower of the winds. It is shown in PI. lY. Fig. 13. Upon 
 each of the eight sides of this building, is a flying figure, carv- 
 ed in reUef, representing the particular wind which blew 
 
372 ARTS OF HOROLOGY. 
 
 against that side. Upon each side was also placed a vertical 
 sun dial ; the gnomon or index, which cast the shadow, pro- 
 jecting from the side, while the lines indicating the hour, were 
 cut upon the wall. On the top, according to Vitruvius, was 
 the figure of a Triton, which turned with the wind in the 
 same manner as a modern weathercock. The lines of the 
 dial upon the wall are distinctly extant at the present day ; and 
 although the gnomons have disappeared, the places where 
 they were inserted are still visible. 
 
 Clepsydra. — Since the sun dial could be used only in the 
 day time, and in clear weather, a different instrument was in- 
 vented by the ancients, to be used within doors, at all times ; 
 and to this was given the name of clepsydra. The clepsydra 
 was formed by a vessel of water, having a minute perforation 
 in the bottom, through which the water issued drop by drop. 
 It fell into another vessel, in which a light body floated, hav- 
 ing attached to it an index or graduated scale. As the water 
 increased in the receiving vessel, the floating body rose, and 
 by its regularly increasing height furnished an approximation 
 to the correct indication of time.* 
 
 The original clepsydra was but a rude instrument, and 
 must have given imperfect indications of the true divisions of 
 time. When the vessel was first filled, the drops must have 
 fallen faster, owing to the greater height and pressure of the 
 fluid ; and in proportion as it became empty, the dropping 
 would be slower, in consequence of the diminution of this 
 pressure. The disadvantage, however, was remedied in vari- 
 ous ways by the employment of two vessels, one of which was 
 kept constantly full by a supply from the other, and thus the 
 water being always at the same height, furnished its drops 
 under an equable pressure. 
 
 * This instrument was invented in Egypt, but was brought into Rome from 
 Athens. Pompey, while consul, introduced it into the Roman Senate House, 
 and the orators were obliged to limit the length of their speeches by its divis- 
 ions of time, so that Pompey is designated by one of the historians, as the first 
 Roman who put bridles upon eloquence. 
 
ARTS OF HOROLOGY. 373 
 
 Wafer Clock. — An instrament called a water clock, was in 
 use at a much later date, and was a subject of extensive man- 
 ufacture in some parts of Europe, a few centuries ago. Sev- 
 eral modes of constructing this instrument were devised, but 
 the following is one of the most ingenious. A tight hollow 
 cylinder, PI. X. Fig. 4, is suspended by cords wound round its 
 axis, which will unwind as it runs down. It has its interior 
 divided into several compartments, situated like the buckets of 
 a water wheel. These compartments communicate with each 
 other by a minute aperture, through which water can pass slow- 
 ly from one compartment to another. Before the machine is 
 put in motion, a small quantity of water is introduced into the 
 lower compartments. As the cylinder descends by the unwind- 
 ing of the cords, it is obliged to revolve on its axis, until the 
 lower compartments which contain the water, have risen so far 
 on the ascending side as to produce an equilibrium. It can 
 then unwind no faster than the water escapes from one com- 
 partment to another, through the minute apertures. As this 
 requires a considerable time, the cylinder may occupy a day, 
 if required, in descending from the top to the bottom of the 
 frame to which it is attached. And if the sides of the frame 
 be marked with the hours of the day, the axis of the cylinder, 
 as it passes by them, wiU indicate the time of the day with as 
 much accuracy as so imperfect a machine permits. 
 
 Clock Work. — In modern days, all other methods of meas- 
 uring time have given place to the equable motion produced 
 by the action of machinery on the pendulum and balance. 
 Timekeepers constructed on this principle, began to be known 
 in Europe about the 14th century, but were formed in a rude 
 and imperfect manner, until the middle of the 17th. Since 
 that period, the learning of philosophers and the ingenuity of 
 artists have been extensively applied to their improvement, and 
 few subjects connected with the mechanic aits, have called 
 forth more inventive acuteness, elaborate experiment, and exact 
 calculation. 
 
 Before proceeding to a description of the entire mechanism 
 
374 
 
 ARTS OP HOROLOGY. 
 
 of a clock or watch, it will be useful to attend to some of the 
 general principles and essential parts of a timekeeper. These 
 will be most easily made intelligible by directing the attention 
 to the following subjects. 1. The maintaining power. 2. 
 The regulating movement. 3. The method of connexion. 
 
 Maintaining Power. — The force which is employed to sus- 
 tain the motions of timekeepers, does not require to be of a 
 powerful kind. It must, however, be steady and uniform in 
 its action. Gravity and elasticity, applied through the medi- 
 um of weights and springs, are the only means now employed 
 to communicate motion to these machines. In clocks, the 
 maintaining force is usually derived from a weight. A weight 
 acts with perfect uniformity from the beginning to the end of 
 its descent, proviiied the line which suspends it is of equal size 
 throughout, and that this line is wound upon a true and perfect 
 cylinder. In portable timekeepers, the weight, for obvious 
 reasons, cannot be employed, and the springy although a less 
 perfect and equable power, is obliged to be substituted. From 
 the oldest clocks which remain, it appears that the spring was 
 in use before the weight, and one of the first ever made is still 
 preserved at Brussels, in which the spring is an old sword 
 blade, from which a piece of catgut is wound upon the cylinder 
 of the first wheel. The principal difficulty in the use of the 
 spring, is, that its action is unequal, and that the more it is 
 bent, the greater force it exerts to return to its natural situation. 
 The spring of a watch, as it is now used, is a long plate of 
 steel coiled up into a spiral form. From the outside of this ' 
 proceeds a chain, which is attached, not to a cylinder, as is 
 done with the weight, but to a spiral roller called a fusee, which, 
 by its conical form, gives to the spring an increased mechanical 
 advantage, in proportion as its power diminishes. The fusee 
 has already been described, page 240. 
 
 In some of the watches which are now made, the fusee and 
 the chain are dispensed with. The barrel which incloses the 
 spring, has a toothed circle on its outside, which turns round as 
 the spring unwinds, and gives motion to the machinery. But 
 
ARTS OF HOROLOGY. 375 
 
 in this case, the spring is made larger than common, and only 
 the middle part of its action is used, it being never wound up 
 so far as to call forth its greatest strength, nor suffered to run 
 down so far as to be materially weakened. 
 
 Regulating Movement. — In the mechanism of clocks and 
 watches, it is necessary so far to retard the movement of the 
 maintaining force, i. e. of the weight or spring, that it may be 
 hours and days in expending itself, and that the timekeeper 
 may require to be wound up only at distant and convenient 
 periods. This is in part effected by the successive combination 
 of wheels and pinions, the last of which turns round many 
 hundred times, while the first turns round once. But if a time- 
 keeper possessed only wheels and pinions, it would run down 
 with a rapidly accelerated motion in the course of a few sec- 
 onds. Tt becomes, therefore, necessary to connect with it an- 
 other motion, which cannot be accelerated beyond a certain 
 degree, by any given force. This motion is obtained in clocks 
 from the 'pendulum, and in watches from the balance ; and it 
 is the one which it was proposed to consider as the second head, 
 under the name of the regulating movement. 
 
 Pendulum. — A pendulum is a weight capable of vibrating 
 about a point from which it is suspended. If the curve in 
 which the penduhim moves be a circular arc, it is necessary 
 that the length of the vibrations should be exactly equal ; other- 
 wise the pendulum will not keep true time. But if the curve 
 be a cycloidal one, the pendulum will move back and forward 
 in equal times, whatever be the length of its vibrations. In 
 practice, it is found difficult to make a pendulum move in a 
 cycloidal path without too much friction. It is therefore cus- 
 tomary in clocks to use pendulums moving in circular arcs, 
 these arcs being made to approximate to cycloids, by being as 
 short as possible. 
 
 Pendulums, when set in motion, would continue to vibrate 
 forever, were it not for the retarding effect of friction and the 
 resistance of the atmosphere. The former of these is partly 
 obviated by hanging the pendulum upon a thin spring, and thet 
 
376 ARTS OP HOROLOGY. 
 
 latter by forming it with a sharp edge. Still a considerable 
 force is requisite to sustain the motion, and this force in clocks 
 is derived from the weight. 
 
 That pendulums may vibrate in equal periods, and thus 
 furnish a correct measure [of time, it is necessary that they 
 should always be of uniform length ; for pendulums of different 
 lengths differ in their vibrations as the square roots of their 
 lengths. Now such is the effect of heat in expanding all known 
 substances, particularly metals, that the same pendulum is al- 
 ways longer in summer than it is in winter, and sufficiently 
 so, to affect the correctness of the timepiece to which it is at- 
 tached. To remedy this difficulty, various ingenious contri- 
 vances have been resorted to, the most common of which are 
 combinations of metals, so connected as to expand in opposite 
 directions, counterbalancing each other, so as to keep the cen- 
 tre of oscillation in one place. This is sometimes effected in 
 the gridiron pendulum, by combining bars, or rods, of steel 
 and brass ; and in the mercurial pendulum, by inclosing a 
 quantity of quicksilver in a tube, near the bottom of the pen- 
 dulum. 
 
 Balance. — As the pendulum depends upon the force of 
 gi'avity for its motions, it obviously cannot be employed for 
 watches, or portable timekeepers, which are liable to change 
 their position. A substitute is found in the balance, which is 
 commonly a wheel moving on an axis, and which, when thrown 
 backward and forward, by opposite applications of the moving 
 force, performs its vibrations in equal times. The balance is 
 liable to the same irregularities from expansion and contraction, 
 as the pendulum, and is corrected in a similar manner ; and 
 watches go best, when they are kept in the uniform heat of 
 the body. 
 
 The quantity of matter accumulated in the balance wheel 
 of a common watch, is so extremely small, that it seems im- 
 possible that it should exert a perfect regulating power. The 
 want of weight; however, is in some measure made up by 
 causing it to perform large vibrations, and to move with great 
 
ARTS OP HOROLOGY. 
 
 37^ 
 
 velocity. The rim of the balance wheel in a good watch, fre- 
 quently moves through ten inches in every second. This ve- 
 locity is produced by the hair spring, which throws the balance 
 back to the point of equilibrium, as fast as it is thrown out in 
 either direction by the moving force, thus performing for the 
 balance what gravity does for the pendulum. If the hair 
 spring be taken away, a watch will lose more than 12 hours in 
 24, and go much more irregularly. The operation of the 
 common regulator of a watch, is to tighten or relax this hair 
 spring by making its effective part longer or shorter, thus ac- 
 celerating or retarding the speed of the balance. 
 
 ^cape7nent. — It remains to consider the third part or scape- 
 ment, by which the rotary motion of the wheels is converted 
 into the reciprocating one of the pendulum and balance. In 
 the scapement, a certain part connected with the pendulum or 
 balance, is put in the way of the last or most rapid wheel, so 
 that only one tooth of this wheel can escape by it during each 
 vibration. Thus the pendulum or balance, while it receives 
 its motion from this wheel, becomes in its turn the regulator of 
 its velocity. 
 
 The crutch or anchor scapement, used in clocks, and the 
 common pallet scapement with a contrate wheel, which is the 
 kind most extensively used in watches, have been already ex- 
 plained under the head of machinery, page 245. The hori- 
 zo7ital scapement. Fig. 
 1, consists of a wheel A, 
 with elevated teeth, the 
 outer surface of which is 
 curved obliquely. These 
 teeth act upon the edges 
 of a hollow half cyhnder, 
 C, the axis of which is parallel to that of the wheel, and car- 
 ries the balance upon one of its extremities. When a tooth of 
 the scape wheel strikes the first edge of the cylinder, it causes it 
 to recede, moving the balance in one direction. The tooth then 
 enters the hollow part of the cylinder, and strikes upon the op- 
 48 
 
378 ARTS OP HOROLOGY. 
 
 posite side. Before it can escape, the cylinder is obliged to 
 turn in the opposite direction, and thus a vibrating movement 
 is kept up in the cylinder and balance. 
 
 A multitude of other scapements, have also been introduced 
 by different artists, varying from each other in the compUcation 
 of their structure, and accuracy of their movements. But 
 these must necessarily be omitted. The operation of the sim- 
 pler forms already described, will be more intelligible taken in 
 connexion with the wheel work next to be noticed. 
 
 Description of a Clock. — InPl.X, several views are given of 
 the mechanism of a clock, consisting of the going part, which 
 moves constantly and carries the hands ; and the striking 
 part, which announces the hour. Fig. 1, PL X, is an eleva- 
 tion of the clock with the wheels seen edgewise, showing the 
 going part ; the striking movements being omitted in this figure, 
 to avoid confusion. Fig. 2 is a front view of the wheel work of 
 both going and striking parts ; and Fig. 3 is the dial work or 
 mechanism immediately under the dial, or face of the clock, 
 and is that part which puts the striking train in motion every 
 hour. A clock of this kind contains two independent trains of 
 wheel work, each with its separate first mover. One is con- 
 stantly going, to indicate time by the hands on the dial plate ; 
 the other is put in motion once in an hour, and strikes a bell to 
 tell the hour at a distance. The part marked a, in Figures 1 
 and 2, is the barrel of the going part ; it has a catgut band, b, 
 wound round it, suspending the weight which keeps the clock 
 in motion. The part marked 96, is a wheel, called the first or 
 great wheel, of ninetysix teeth upon the end of a barrel, turning 
 a pinion 8, of eight leaves, on an arbor,* which carries the 
 minute hand ; also 64 is a wheel of 64 teeth, on the same 
 arbor, called the centre wheel, turning the wheel 60 by a pin- 
 
 * The terms arhor, shaft, axle, and axis, are synonymously used by mechan- 
 ics, to express the bar, or rod, which passes through the centre of a wheel. The 
 terminations of a horizontal arbor are called gudgeons, and of an upright one, 
 frequently, pivots. The term axis in a more exact sense may mean merely 
 t^e longest central diameter, or a diameter about which motion takes place. 
 
ARTS OP HOROLOGY. 379 
 
 ion of eight leaves on its arbor. This last wheel gives motion 
 to the pinion of eight, on the arbor of the swing wheel 30, 
 which has 30 teetli. The parts d h, are the pallets of the 
 scapement fixed on an arbor e, Fig. 1st, going through the back 
 plate of the clock's frame, and carrying a long lever/. This 
 lever has a small pin projecting from its lower end, going into 
 an oblong hole made in the rod B of the pendulum. 
 
 The pendulum consists of an inflexible metallic rod, sus- 
 pended by a very slender piece of steel spring D, from a brass 
 bar E, screwed to the frame of the clock, having a weight at its 
 lower end not seen in the figure ; in the present case 39 J inches 
 from the suspension D. When this pendulum is moved from 
 the perpendicular line, in either direction, and suffered to fall 
 back again, it swings nearly as much beyond the perpendicular 
 on the contrary side, and then returns. This it will continue 
 to do for some time, and each of these vibrations will be per- 
 formed in one second of time, when the pendulum is of the 
 above length. This is the measurer of the time ; and the office 
 of the clock is only to indicate the number of vibrations it has 
 made, and to give it a small impulse each time to keep it go- 
 ing, as the resistance of the air and elasticity of the spring D, 
 w^ould otherwise in a short time cause it to stop. By the ac- 
 tion of the weight applied to the cord &, which is called the 
 maintaining power, the wheels are aU turned round ; and if 
 the pallets d and h were removed, the swing wheel 30 would 
 revolve with great velocity in the direction from 30 to c?, untU 
 the weight reached the ground. The teeth of these pallets are 
 so placed, that one of them always engages the wheel and pre- 
 vents it from turning more than half a tooth at a time. In the 
 figure, the pallet d has the nearest tooth of the wheel resting 
 on it, and the pendulum is on the side h of the perpendicular. 
 When it retmiis, it moves the pallet d, so as to aUow the tooth 
 of the wheel to sHp off ; but in the mean time the pallet h has 
 interposed its point in the way of the tooth next it, and stops 
 the wheel till the next vibration or second. The distance be- 
 tween the two pallets d and It is so adjusted, that only half a 
 
380 auts of horology. 
 
 tooth of the wheel escapes at each vibration ; and as the wheel 
 has 30 teeth, it will revolve once in 60 vibrations, of one second 
 each, or in one minute ; consequently, a hand on the arbor of 
 this wheel, will indicate seconds on the dial plate F, which is 
 a circle divided into 60. The pinion of eight on its arbor is 
 turned by a wheel of 60, which consequently will turn once in 
 seven turns and a half of the other, or in seven minutes 30 
 seconds, or in one eighth of an hour. Its pinion of eight is 
 moved by a wheel of 64, or eight times itself, which will turn 
 in one eighth part of the time. This will be an hour, and there- 
 fore the arbor of this wheel carries the minute hand of the clock. 
 The great wheel of 96, being 12 times the number of the pinion 
 eight, will turn once in 12 hours, and the barrel a with it. The 
 cord of catgut goes round 16 times, so that the clock will go 
 eight days. 
 
 The hour hand of the clock is turned by the wheel work, 
 shown in Figs. 1 and 3. On the end of the arbor of the cen- 
 tre wheel 64, a tube is fitted so as to go round with it by friction. 
 This carries the minute hand, and if the clock should require 
 correction, the hand may be slipped round v/ithout moving the 
 wheels. This tube has a pinion of 40 teeth on its lower end, 
 indicated by a dotted circle. This turns another wheel 40, of 
 40 teeth, which has a pinion of six teeth on its arbor, turning 
 a wheel 72, of 72 teeth. The two wheels 40 will both turn 
 in an hour ; and 72 in 12 hours. The arbor of this wheel 
 has the hour hand, and is a tube going over the arbor of the 
 minute hand, so that the two hands are concentric. The bar- 
 rel a, is fitted to an arbor coming through the plate of the clock, 
 and filed square to put on a key to wind up the weight. The 
 great wheel 96 is not fixed fast to the arbor, but has a click 
 on it, which takes the teeth of a ratchet wheel cut on the bar- 
 rel ; so that the barrel may be turned in one direction to wind 
 up the weight, without the wheel ; but by the descent of the 
 weight, the wheels will be turned with the barrel by the 
 click. 
 
 Striking Part. — Having now considered the going part of 
 
ARTS OF HOROLOGY. 381 
 
 the clock, it remains to describe the mechanism by which the 
 hour is struck. In Fig. 2, 78 is a great wheel of 78 teeth, 
 pro^^.ded with a barrel and click as in 96 ; it turns a pinion of 
 eight. On the same arbor is a wheel 64, turning a pinion of 
 eight, on the arbor of the wheel o, of 48. This turns another 
 pinion of eight, and wheel p, of 48, which turns a pinion of 
 six, on the same arbor with a thin vane of metal, seen edge- 
 wise, which is called the Jly, and which, by the resistance of 
 the air to its motion, regulates the velocity of the wheels. 
 
 The wheel 64 has eight pins projecting from it, which raise 
 the tail n of the hammer, as they revolve. The hammer is re- 
 turned violently when the pins leave its tail, by a spring m, 
 pressing on the end of a pin put through its arlDor ; and strikes 
 the bell. The hammer and bell are behind the plate, and 
 therefore unseen. There is a short epring I, which the other 
 end of the pin through the arbor touches, just before the ham- 
 mer strikes the bell. Its use is to lift the hammer off the bell, 
 the instant it has struck, that it may not stop the sound. The 
 pins in the wheel 64, must pass by the hammer tail 78 times 
 in striking the twelve hours, l+2+3+4+5+6+7-|-8+9+10 
 11+12=78, and as its pinion has eight leaves, each leaf of the 
 pinion answers to a pin in the wheel 64. Now, as the great 
 wheel has 78 teeth, it will turn once in 12 hours, the same as 
 the other great wheel 96. In the wheel 64, eight of its teeth 
 correspond to one of the pins of the hammer, and as the pin- 
 ion of the wheel o has eight teeth, it (wheel o) will turn once 
 for each stroke of the hammer. By the remaining wheels, 
 one, 0, multiplying six times, and the other, jy, eight times, 
 the fly will turn 6x8=48 times for one turn of o, which an- 
 swers to one stroke of the hammer. 
 
 Fig. 3 is also mechanism relating to the striking part. Be- 
 hind r there is a small pinion of one tooth, called the gather- 
 ing 'pallet^ on the arbor of the wheel o, which consequently 
 turns once for each stroke of the hammer. The part marked 
 S r a; is a portion of a large wheel, and is called the rack. 
 The part t is an arm attached to the rack, whose end rests 
 
382 ARTS OF HOROLOGY. 
 
 against a spiral plate, V, called the snail^ which is fixed on 
 the tubular arbor before described, of the hour hand and wheel 
 72, and turns round with it once in 12 hours. The snail is 
 divided into 12 equal angles, of 30 degrees each, and as it 
 turns, each of these answers to an hour. The circular arcs, 
 forming the circumference of the snail, are struck from the 
 centre of the arbor between each division, with a different ra- 
 dius, decreasing a certain quantity each time in the order of 
 the hours. The circular part of the rack, 14, is cut into teeth, 
 each of which is of such a length, that every step upon the 
 snail shall answer to one of them. At id is a spring pressing 
 against the tail of the rack, and acting to throw the arm of 
 the rack against the snail. The part ^ is a click called the 
 hawk's bill, taking into the teeth of the rack, and holding it 
 up in opposition to the spring w. The part i /: is a three- 
 armed detent, called the ivar?iing piece. The arm k is bent 
 at its end, and passes through a hole in the front plate of the 
 clock, so as to catch a pin placed in one of the arms of the 
 wheel p. Fig. 2, and which describes the dotted circle in Fig. 
 3. The other arm i stands so as to fall in the way of a pin 
 in the wheel 40. In the present position of the figure, the 
 wheels of the striking train are in motion, and would continue 
 turning until the gathering pallet at r, which turns once at 
 each stroke of the hammer, by its tooth lifts the rack s, in op- 
 position to the spring w, one tooth each turn ; and the hawk's 
 bill g retains the rack, until a pin in the end of the rack is 
 brought in the way of the lever of the gathering pallet r, and 
 stops the wheels from turning any farther. It is in this posi- 
 tion with the rack wound up, till its pin arrests the tail r, that 
 we shall begin to describe the operation of the strikmg of the 
 clock. 
 
 The wheel 40, as has been said before, turns once in an 
 hour, and consequently, at the expiration of every hour, the 
 pin in it takes the end ?', and moves it towards the spring near 
 it. This depresses the end k, until it falls in the circle of the 
 motion of the pin in the wheel p, Fig. 2. A.t the same time 
 
ARTS OP HOROLOGY. 383 
 
 the short tail depresses one end of the hawk's bill, and raises 
 the other g^ so as to clear the teeth of the rack s. Immedi- 
 ately the spring w throws the rack back, until the end of its 
 tail ^, touches that part of the snail which is nearest it. When 
 the rack falls back, the pin in it is moved clear of the gather- 
 ing pallet r, and the wheels set at hberty. The maintaining 
 power puts them in motion ; but in a very short time before 
 the hammer has struck, the pin in the wheel p falls against 
 the end of k, and stops the whole. This operation happens a 
 few minutes before the clock strikes, and this noise of the 
 wheels turning, is called the warning. When the hoiu' is ex- 
 pii'ed, the wheel 40 has turned so far, as to allow the end of i 
 to slip over its pin, as in the figure. The small spring pressing 
 against it raises the end k, so as to be within the circle of the 
 pin in the wheel p, Fig. 2. Every obstacle is now" removed, 
 and the wheels run on the pinion ; the wheel 64 raises the 
 hammer r, and it strikes on the bell; the gathering pallet r 
 takes up the rack, one tooth at each turn, the hawk's bill g 
 retaining it, until the pin x in the rack comes under the gath- 
 ering pallet r, and stops the motion of the whole machine, till 
 the pin in the wheel 40 at the next hour takes the warning 
 piece i k, and repeats the operation we have now described. 
 As the gathering pallet turns once for each blow of the ham- 
 mer, and its tooth gathers up one tooth of the rack at each turn, 
 it is evident, that the number of teeth which the rack is al- 
 lowed to fall back, limits the number of strokes the hammer 
 will make. This is done by the rack's tail t resting on the 
 snail. Each step of the snaU answers to one tooth of the rack, 
 and one stroke of the hammer. At each hour, a fresh step of 
 the snail is turned to the tail of the rack, and by this means the 
 number of strokes is made to increase one at each time from 
 1 to 12. 
 
 Description of a Watch. — In PI. XL several views are 
 given of the construction of a common portable watch. Fig. 1 
 represents the wheel work immediately beneath the dial plate, 
 and also its hands, the circles of hours and minutes being mark- 
 
384 ARTS OP H0R0L0C4Y. 
 
 ed, though the dial on which these are engraved is removed. 
 Fig. 2 is a plan of the wheel work all exhibited at one view, 
 for which purpose the upper plate of the watch is removed. 
 Fig. 3 is a plan of the balance, and the work situated upon 
 the upper plate. Fig. 4 shows the great wheel and the pot- 
 tance wheel detached. Fig. 5 the spring barrel, chain, 
 and fusee detached ; and Fig. 6 is an elevation of all the 
 movements together, the works being supposed to be opened 
 out into a straight line, to exhibit them all at once. Fig. 7 
 is a detached view of the balance, together with the scapement, 
 in action. 
 
 The principal frame for supporting the acting parts of the 
 watch, consist of two circular plates, marked C and D in the 
 figures. Of these the former is called the upper plate, and the 
 latter the pillar plate, from the circumstance that the four pil- 
 lars, E E, which unite the two plates and keep them a proper 
 distance asunder, are fastened firmly into the lower plate ; 
 while the other ends pass through hol'es in the upper plate, C, 
 and have small pins put through the ends of the pillars, to keep 
 the whole together. By drawing out these pins, the watch 
 may be taken to pieces. The pivots of the several wheels be- 
 ing received in small holes made in these plates, they of course 
 fall to pieces as soon as the plates are separated. 
 
 The maintaining power is a spiral steel spring, which is coil- 
 ed up close by a tool used for the purpose, and put into a brass 
 box called the ftarreZ. It is marked A in all the figures, and 
 is shown separate in Fig. 5, with the spring in it. The spring 
 has a hook at the outer end of its spiral, which is put through 
 a hole, a. Fig. 5, in the side of the barrel, and rivetted fast to 
 it. The inner end of the spiral has an oblong opening cut 
 through it, to receive a hook upon the barrel arbor, B, Fig. 5. 
 The pivots of this arbor pass through the top and bottom of the 
 barrel, and one of them is filled square to hold a ratchet wheel, 
 6^ Figs. 1 and 6, which has a click, and keeps the arbor from 
 turning round, except in one direction. The two pivots of the 
 arbor are received in pivot holes in the plates C D of the watch, 
 
ARTS OP HOROLOGY. 385 
 
 and the pivot which has the ratchet wheel upon it, passes 
 through the plate. The wheel marked h, Figs. 1 and 6, with 
 its click, is therefore on the outside of the pillar plate D of the 
 watch. The top of the barrel has a cover or lid fitted into it, 
 through which the upper pivot of the arbor projects ; thus the 
 arbor of the barrel is to be considered as a fixture, the click of 
 the ratchet wheel preventing it from turning round, while the 
 interior end of the spii'al spring being hooked, assists in ren~ 
 dering it stationary. The barrel thus mounted has a small 
 steel chain, d, Figs. 2 and 6, coiled round its circumference, 
 and attached to it by a small hook of the chain which enters 
 a little hole, made in the circumference of the barrel at its up- 
 per end. The other extremity of this chain is hooked to 
 the lower part of the fusee, marked F, Figs. 2, 5, and 6, and 
 the chain is disposed either upon the circumference of the bar- 
 rel, or in the spiral groove cut round the fkisee for its reception, 
 the arbor of which has pivots at the ends, v/hich are received 
 into pivot holes made in the plates of the watch. One pivot 
 is formed square, and projects through the plate, to fit the key 
 by which the watch is wound up. 
 
 It is evident that v/hen tlie fusee is turned by the watch-key, 
 it will wind the chain off the circumference of the barrel on it- 
 self ; and as the outer end of the spring is fastened to the bar- 
 rel, and the other is liooked to the barrel arbor, which as be- 
 fore mentioned, is prevented from turning by the click of the 
 ratchet wheel, ah ; the spring will be coiled up into a smaller 
 compass than before. Its reaction, therefore, when the key is 
 taken off, will turn the barrel, and b)^ the chain, turn the fu- 
 see and give motion to the wheels of the watch. The fusee 
 has a spiral groove cut round it, in which the chain lies ; this 
 groove is cut by an engine, in such a form that the chain shall 
 pull from the smallest part, or radius, of the fusee, when the 
 spring is quite wound up, and therefore acts with its greatest 
 force on the chain. From this point the groove gradually in- 
 creases in diameter, so that as the spring unwinds and acts with 
 less power, the chain operates on a larger radius of the fusee : 
 49 
 
386 ARTS OF HOROLOGY. 
 
 and the effect upon the arbor of the fusee, or the toothed wheel 
 attached to it, will always be equal, and cause the watch to go 
 with regularity. 
 
 To prevent too much chain being wound upon the fusee, 
 and by that means breaking the chain or overstraining the 
 spring, a contrivance called a guard-gut is added. It is a small 
 lever, e, Fig. 2, moving on a stud fixed to the upper plate C 
 of the watch, and pressed downwards by a small spring, /. As 
 the chain is wound up upon the fusee, it rises in the spiral groove, 
 and lifts up the lever until it touches the upper plate. It is 
 then in a position to intercept the edge or tooth, g, of the spi- 
 ral piece of metal seen on the top of the fusee, and thus stops 
 it from being wound up any further. 
 
 The power of the spring is transmitted to the balance by 
 means of several toothed wheels, w^hich multiply the number 
 of revolutions which the chain makes on the fusee, to such a 
 number, that though the last or balance wheel turns 9J times 
 every minute, the fusee will at the same time turn so slowly, 
 that the chain will not be drawn off from it in less than 28 or 
 30 hours, and it will make only one turn in four hours. This 
 assemblage of wheels is called the train of the watch. The 
 first toothed wheel, G, is attached to the fusee, and is called 
 the great wheel. It is shown separated from the fusee, in Fig. 
 4, having a hole through the centre to receive the arbor of the 
 fusee, and a projecting ring upon its surface. The under sur- 
 face of the base of the fusee is shown in Fig. 5, at F, having 
 a circular cavity cut in it to receive the corresponding ring up- 
 on the great wheel G, Fig. 4. A ratchet wheel, i, is fixed 
 fast upon the fusee arbor, and sunk within the cavity excava- 
 ted in the lower surface of the fusee. When the wheel 
 and fusee are put together, a small click, h, Fig. 4, takes into 
 the teeth of the ratchet i. As the fusee is turned by the watch- 
 key to wind up the watch, this click slips over the sloping 
 slides of the teeth without turning the great wheel ; but when 
 the fusee is turned the other way by drawing the chain from 
 
ARTS OP HOROLOGY. 3S7 
 
 the spring barrel, the dick catches the teeth of the ratchet 
 wheel, and causes the toothed wheel to turn with the fusee. 
 
 The great wheel^ G, has 48 teeth on its circumference, 
 which take into and turn a pinion of 12 teeth, fixed on the 
 same arbor with the 
 
 Centre wheel, H, so called from its situation in the centre of 
 the watch ; it has 54 teeth to turn a pinion of six leaves, on 
 the arbor of the 
 
 Third ivheel, I, which has 48 teeth. It is sunk in a cavi- 
 ty formed in the pillar plate, and turns a pinion of six, on the 
 arbor of the 
 
 Contrate loheel, K, which has 48 teeth cut parallel with its 
 axis, by which it turns a pinion of six leaves, fixed to 
 
 The balance loheel, L. One of the pivots of the arbor of 
 this wheel turns in a frame, M, called the 'pottance or fotence, 
 fixed to the upper plate, and shown separately in Fig. 4. The 
 other pivot runs in a small piece fixed to the upper part, called 
 the counter pottance, not shown in any of the figures ; so that 
 when the two plates are put together, the balance wheel pinion 
 may work into the teeth of the contrate wheel, as shown in 
 Fig. 6. The balance wheel, L, has 15 teeth, by which it im- 
 pels the balance o p. The arbor of the balance, which is call- 
 ed the verge, has two small leaves or pallets projecting from 
 it, nearly at right angles to each other. These are acted up- 
 on by the teeth of the balance wheel, L, in such a manner, 
 that at every vibration the balance receives a slight impulse to 
 continue its motion, and every vibration so made, suffers a 
 tooth of the wheel to escape or pass by, whence this part is call- 
 ed the scapement of the watch, and constitutes its most essen- 
 tial part. The wheel L is sometimes called the scajoe wheel, 
 or crown wheel. Its action is explained by Fig. 7, which 
 shows the wheel and balance detached. Suppose in this 
 view, the pinion h, on the arbor of the balance wheel or crown 
 wheel, i k, to be actuated by the main spring which forms the 
 maintaining power, by means of the train of wheel-work, in 
 the direction of the arrow, while the pallets m and n, attached 
 
388 ARTS OF HOROLOGY. 
 
 to the axis of the balance, and standing at right angles to each 
 other, or very nearly so, are long enougli to fall in the way of the 
 ends of the sloped teeth of the wheel when turned round at an 
 angle of 45 degrees, so as to point to opposite directions, as in 
 the figure. Then a tooth in the wheel below, for instance, 
 meets with the pallet ?z, supposed to be at rest, and drives it 
 before it a certain space, till the end of the tooth escapes. In 
 the mean time the balance, o s p r, attached to the axis of the 
 pallets, continues to move in the direction r o s p, and winds 
 up the small spiral, or hair spring; q, one end of which is fast 
 to the axis, and the other to a stud on the upper plate of the 
 frame. In this operation, the spring opposes the momentum 
 given to the balance by this push of the tooth upon the pallet, 
 and prevents the balance going quite round ; but the instant 
 the tooth escapes, the upper pallet, m, meets with another tooth 
 at the opposite side of the wheel's diameter, moving in an op- 
 posite direction to that below. Here this pallet receives a push 
 which carries the balance back again, its momentum as yet 
 being small in the direction os p r, and aids the spring, which 
 now unbends itself till it comes to its quiescent position, then 
 swings beyond that point, partly by the impulse from the main- 
 taining power on the pallet m, and partly by the acquired mo- 
 mentum of the moving balance, particularly when this pallet 
 ni has escaped. At length the pallet n again meets with the 
 succeeding tooth, and is carried backward by it in the direction 
 in which the balance is now moving, till the maintaining pow- 
 er and force of the unwound spring together overcome the mo- 
 mentum of the balance, during which time the recoil of the 
 balance wheel is apparent, and also of the seconds hand, if the 
 watch has one, its place being on the arbor of the contrate 
 wheel. Then the wheel brings the pallet n back again till it 
 escapes, and the same process takes place with the pallet m as 
 has been desciibed with respect to pallet n. Thus two contra- 
 ry excursions or oscillations of the balance take place before 
 one tooth has completely escaped ; and for this reason there 
 must always be an odd number of teeth in this wheel, that a 
 
ARTS OF HOROLOGY. 
 
 389 
 
 space on one side of the wheel may always be opposite to a 
 tooth on the other, in order that one pallet may be oat of ac- 
 tion while the other is in action. 
 
 The upper pivot of the verge is supported in a cover screwed 
 to the upper plate, as shown at N, in Fig. 6, which extends 
 over the balance, and protects it from violence. The lower pivot 
 works in the bottom of the pottance, M, at t^ Fig. 4. The 
 socket for the pivot of the balance wheel, is made in a small 
 piece of brass, v, which slides in a groove made in the pottance, 
 as shown Fig. 4, so that by drawing the slide in or out, the 
 teeth of the balance wheel shall just clear one pallet before it 
 takes the other; and upon the perfection of this adjustment, 
 which is called the scaping of the watch, the performance of 
 it very greatly depends. 
 
 It now remains to show the communication of this motion 
 to the hands of the watch, which indicate the time on the dial 
 plate. The hands are moved by the central arbor, which 
 comes through the pillar plate and projects a considerable 
 length. It has a pinion of 12 leaves, called 
 
 The common pinion, to, Fig. 6, fitted upon it, the axis of 
 which is a tube formed square at the end, to fix on the minute 
 hand W. It fits tight upon the projecting arbor of the centre 
 wheel, and therefore turns with it, but will slip round to set the 
 hands when the watch is wrong and requires to be rectified. 
 The common pinion is situated close to the pillar plate, and 
 its leaves engage the teeth of 
 
 The minute wheel, X, Figs. 1 and 6, of 48 teeth, which is 
 fitted on a pin fixed in the plate, and its pinion, x, of 16 leaves, 
 which is fixed to it, turns 
 
 The hour wheel, Y, of 48 teeth. The arbor of this is a 
 tube, which is put over the tube of the cannon pinion carrying 
 the minute hand, and has the hour hand, Z, fixed on it, to in- 
 dicate the time upon the dial plate. Thus, by the cannon 
 pinion, w, which is to the minute wheel, X, as one is to four, 
 and the pinion x of this, which is to the hour wheel, Y, as one 
 is to three, the hour wheel Y, and its hand z, though concentric 
 
390 ARTS OF HOROLOGJY. 
 
 with the cannon pinion and minute hand, make but one revo- 
 lution during 12 revokitions of the other ; therefore one turns 
 round in an hour, and the other turns round once in 12 hours, 
 as the figures on the dial show. 
 
 It is necessary to have some regulation by which the rate 
 of the watch's movement may be adjusted, for hitherto we have 
 only spoken of making the watch keep always to a uniform or 
 certain rate of motion, but it is necessary to make it keep true 
 time. This can be done by two means, either by increasing 
 or diminishing the force of the main spring, which increases 
 or diminishes the arc which the balance describes ; or it may be 
 done by strengthening or weakening the hair spring, which 
 will cause the balance to move quicker or slower. 
 
 The hair spring, otherwise called the the pendulum spring, 
 q, Fig. 3, is fixed to a stud, upon the plate c, by one end, and 
 is attached to the verge of the balance by the other. 
 
 The regulation is effected by means of what is called the 
 curb. This is a small lever, z, Fig. 3, projecting from a circu- 
 lar ring, r r, which may be considered as its centre of motion, 
 but perforated with a hole through the centre, large enough to 
 contain the hair spring within it. A circular groove is turned 
 out in the upper plate, nearly concentric with the balance, and 
 the ring, r r, fits into this. Both are turned rather largest at 
 the bottom, in the manner of a dove-tail ; but the ring being 
 divided at the side opposite to the lever, z, can be sprung up and 
 rendered so much smaller as to get it into the groove, and, being 
 once in, the elasticity of the ring expands it, so as to fill the groove 
 completely. In this state it may be considered as a lever which 
 describes a circuit round the verge as a centre, and the end of 
 it points to a divided arc engraved on the upper plate, one end 
 of which is marked F, and the other S, denoting that the index 
 or lever, z, is to be moved towards one or the other, to make the 
 watch move faster or slower as its regulation requires. 
 
 The manner of its operation is thus ; the end of the lever, 
 or index, z, continues within the circle a small distance towards 
 its centre, and passing beneath the outer turn of the spiral 
 
ARTS OF HOROLOGY. 391 
 
 spring g, has two very small pins rising up from it, which in- 
 clude the spring between them. The actual length of the hair 
 spring is therefore to be estimated from these pins to the place 
 of its connexion with the verge. Now, by altering the position 
 of the index, this acting length can be regulated at pleasure, to 
 produce such vibration of the balance as will make the watch 
 keep true time. By shortening the length, the spring becomes 
 more po\verful, and returns the balance quicker, so that it will 
 vibrate in less time. This is effected by moving the index to- 
 wards F. On the other hand, turning the index toward S, 
 lengthens the spring by which it becomes more delicate, and 
 less powerful, returning the balance slower than before. 
 
 Many watches, instead of the arc and index, have a circular 
 curb, or regulator, which is turned by a central arbor, to which 
 the watch-key is applied, when it is necessary to move it. 
 
 Delicate watches have jewelled pivot holes for the top and 
 bottom of the verge,' to diminish the friction. These jewels 
 are diamonds, rubies, and other stones, which unile great hard- 
 ness with durabihty. Each consists of two pieces, one of which 
 has a cylindrical hole drilled through it to receive the pivot, the 
 other is a flat piece, making the rest or stop which forms the 
 bottom of the hole. Both stones are ground circular on the 
 edge, and are fitted and burnished into small brass rings, which 
 are fastened into the bearings above and below by two smaD 
 screws applied to each. The addition of jewels to a watch is 
 a great advantage, as they do not tend to thicken the oil, which 
 brass is apt to do, in consequence of the oxidation of the metaL 
 
 Cumming's Elements of Clock and Watch Work, 4to. 1766 ; — Ber- 
 THouD Histoire de la Mesure du Temps par Its Horloges, 2 torn. 4to, 
 1802; — Harrison on Clock Work and Music, 8vo. 1775 ; — Robison's 
 Mechanical Philosophy, article Watch Work, vol. iv. ; — Martin's 
 Circle of Mechanical Arts, 4to. 1818;— and the Encyclopedias of 
 Brewster, Rees, and Nicholson, under various heads. 
 
CHAPTER XVII. 
 
 ARTS OP METALLURGY. 
 
 The term metallurgy, in its most comprehensive sense, sig- 
 nifies the art of working metals in every different way. In a 
 more precise and limited sense, it is confined to the separating 
 of metals from their ores, and assaying them to ascertain their 
 value. In the present chapter, it is proposed to make use of 
 the term in its more general meaning, so far, at least, as to 
 comprehend certain processes in the management and manu- 
 feicture of metals, which are sufficiently interesting to merit 
 the attention of the general student. 
 
 Extraction of Metals. — Metals are found in nature in vari- 
 ous states. When uncombined, or when combined only with 
 each other, they are said to be in a native state. When com- 
 bined with other substances, so that the metallic properties are 
 in some measure disguised, thej^^ are said to be mineralized, or 
 in the state of ore. The substance with which the metal is 
 combined, is termed its miner alizer. The most common states 
 of combination in which the metallic ores are found, are ox- 
 ides, combinations of oxides with carbonic, sulphuric, muriatic, 
 and phosphoric acids ; and sulphurets. These ores occur under 
 various forms, sometimes crystallized, and often destitute of 
 any regular figure. They are met with, generally, in veins, 
 penetrating the strata ; and in this case, are usually blended or 
 intermixed with various earthy fossils, as calcareous spar, fluor 
 spar, quartz, (fcc. The accompanying fossil is termed the 
 gangue or matrix of the metal. Some metallic ores occur in 
 beds, or in large insulated masses. 
 
 To separate the metal, after it is dug from the mine, the 
 mass is broken up and subjected to the operations of sorting, 
 
ARTS OF METALLURGY. 393 
 
 stamping, washing, roasting, smelting, and refining. Sorting 
 consists merely in the separation of the different pieces of ore 
 into lots, according to the products they are expected to afford, 
 and the treatment they are likely to require. After the ore is 
 sorted, it is carried to the stamper, or stamping mill, which has 
 been described in a former chapter. The process of stamping, 
 breaks and pounds up the ore, together with its gangue, into 
 a coarse powder. From the stamping mill, the pounded ore 
 is conveyed to the washing, a process in which advantage is 
 taken of the difference of specific gravity. The operation of 
 washing is sometimes performed b}'' hand, in wooden vessels, 
 or in troughs which cross a current of water ; and sometimes, 
 if the ore is rich and valuable, upon inclined tables covered 
 with cloth. In this process the heavier parts, consisting of the 
 metaUic ore, sink first to the bottom, while the stony matter, 
 which is lighter than the ore, being longer in sinking, is 
 carried farther down the current, and thus separated from the 
 rest. 
 
 The next operation, which is that of roasting, is employed 
 to drive off the sulphur, arsenic, and other volatile parts which 
 the mineral may contain. It is performed in a variety of ways, 
 and by different processes, according to the nature of the ore, 
 and the degree of heat required. The roasting is sometimes 
 performed in the air, and sometimes in furnaces, among the 
 fuel. Smelting consists, in general, in fusing the roasted ore, 
 with a viev/ to extract the metal, though the term is sometimes 
 applied to the melting of metal in any state, especially iron. 
 The immediate object of this process is to reduce the metal, or 
 to separate the oxygen with which the metal has either been 
 naturally combined, or has united during the operation of roast- 
 ing. This is done, by placing in a furnace alternate layers of 
 charcoal, or coke, and of the metallic matter ; a strong heat is 
 then excited by bellows ; the carbonaceous matter attracts the 
 oxygen, while the metal is reduced, melted, and run out at the 
 bottom of the furnace. The volatile metals are obtained by 
 sublimation or distillation. Even after these operations, the 
 50 
 
394 ARTS OF METALLURGY. 
 
 metal is seldom pure, but is combined with some other metal, 
 or metals, which have been present in the ore. If these are 
 in small quantity, and do not injure the metal, they are in gen- 
 eral disregarded. If it is necessary, however, to separate them, 
 or if, from their value, the separation is an object of importance, 
 different processes are followed, adapted to each particular 
 metal. All the operations subsequent to smelting, are compre- 
 hended under the general name of refining^ because their ef- 
 fect is always to obtain a pui"er metal. The different metals 
 are refined by different processes. 
 
 Assaying. — The art of assaying metallic ores, is that of an- 
 alyzing them in small quantities, so as to discover their compo- 
 nent parts. It requires a knowledge of the relations of the 
 metals to the other chemical agents, and is varied in its differ- 
 ent stages as applied to each. The general process consists in 
 selecting proper specimens of the oie, which is done by taking 
 equal portions of that which appears to be the richest, the 
 poorest, and of medium value, and reducing these to coarse 
 powder, which is washed to carry off any earthy or stony mat- 
 ter. It is then roasted in a shallow earthen vessel under a 
 muffle, to expel the volatile principles. It is lastly reduced, 
 by mixing it with fluxes, and applying a more or less intense 
 heat, as the metal is more or less refractory. The metallic 
 matter existing in the ore is thus obtained. This, it is obvious, 
 may consist of various metals, and if there is reason to believe 
 this, and it be of impoiLance to ascertain it, it is submitted to 
 operations adapted to the metals which may be supposed pre- 
 sent. Sometimes, an accurate analysis is made at once of the 
 metallic ore in the humid way ; the metal being dissolved by 
 the different acids, and precipitated by the alkalis, earths, and 
 other re-agents. The assaying of the precious metals is usual- 
 ly confined to ascertaining the quantity of gold or silver in any 
 alloy or compound, without regard to the other constituents. 
 
 Alloys. — The metals are capable of combining with each 
 other by fusion, and to these combinations, the name of alloy 
 is given. They aU retain the general metallic properties, — 
 
A.RTS OP METALLURGY. 395 
 
 lustre, opacity, and density ; and even, in the greater number 
 of cases, the properties of the constituent inetals remain in the 
 combination, only somewhat modified. In general, alloys are 
 more hard and brittle than the individual metals of which they 
 consist, though this, as well as the other changes of properties, 
 is considerably influenced by the proportions in which the in- 
 gredients are combined. They have also in general a greater 
 fusibility than the mean fusibility of the respective metals. 
 The alloys of quicksilver, called amalgams, are usually soft, 
 or liquid, according to the proportions. The metals combined 
 in alloys are generally more susceptible of oxidizement than in 
 their separate state, owing probably to the diminution in the 
 power of cohesion, by the combination, or perhaps to an elec- 
 trical action. From their peculiar properties, seme of the alloys 
 are extensively used, as brass, which is an alloy of copper and 
 zinc ; and pewter, which is an alloy of tin and zinc, or lead. 
 
 A degree of condensation usually attends these combinations, 
 so that the specific gravity of the alloy is greater than the 
 mean specific gravity of its constituent metals. In brass, for 
 example, it is one tenth greater, and in some cases, the con- 
 densation is such, that the density is even greater than that of 
 the heavier metals combined, as in the alloy of silver and 
 quicksilver. Sometimes, however, the particles assume such 
 an arrangement, that the density is less than the mean, as in 
 the examples of the alloy of copper with silver, and of gold 
 with tin, and gold with iron. 
 
 In these combinations, there exists a certain order of attrac- 
 tions, by which one metal is more disposed to unite with anoth- 
 er, than a third is. The difference, however, is not very con- 
 siderable ; hence, three, four, or more metals can be combined 
 together. Some, however, are difficult to unite, as iron and 
 lead, and iron and quicksilver. The combination seems to be 
 in some measure regulated by the relations of fusibility and 
 specific gravity ; so that the afilnities being equal, the metals 
 are less disposed to combine, as they diifer more in their fusi- 
 bility and specific gravity ; and where the affinity is weak, a 
 
396 ARTS OP METALLURGY. 
 
 considerable difference of this kind may prevent any combina- 
 tion whatever. 
 
 GOLD. 
 
 Gold exists in various minerals, but the greatest part of the 
 gold in the possession of mankind, has been found in the form 
 of grains and small masses, among the alluvial sands which 
 constitute certain plains, and margins of rivers. In this state 
 it is usually alloyed with small portions of other metals, partic- 
 ularly silver and copper. 
 
 Extraction. — When native gold is found in a state of mix- 
 ture with foreign matters, its extraction is commonly perform- 
 ed by amalgamation with quicksilver. After having been 
 freed, by pounding and washing, from most of the stony mat- 
 ter mixed with it, it is triturated with ten times its weight of 
 quicksilver, until an amalgam is formed. This is separated 
 from any superfluous earthy matter, and subjected to pressure, 
 inclosed in leather, by which the more fluid part is separated 
 and forced through the leather, while the more consistent 
 amalgam, containing the greater part of the gold, remains. 
 It is then subjected to distillation in retorts of earthen ware, to 
 separate the quicksilver, and the remaining gold is afterwards 
 fused. When the gold is contained in other ores, the ore is 
 roasted, to drive off the more volatile principles, and to oxidize 
 the other metals. The gold is then extracted by amalgama- 
 tion, by liquefaction with lead, by the action of nitric acid, or 
 other methods adapted to each ore, according to its constituent 
 parts. 
 
 Cupellation. — Gold obtained in any of these ways, is al- 
 ways more or less alloyed, particularly with silver or copper. 
 The first step in its purification, is the process of cupellation. 
 To explain the nature of this, it is necessary to observe, that 
 lead is a metal very fusible, and extremely easy of oxidize- 
 ment, forming an oxide which easily vitrifies, and which fa- 
 
ARTS OP aiETALLURGY. 3-97 
 
 vors the oxidizement and vitrification of other metals, A por- 
 tion of lead, therefore, is added to the impure gold, more or 
 less, according to the quantity of alloy which it contains, of 
 which the workman judges by the color, hardness, elasticity^ 
 and specific gravity of the gold. They are melted together^ 
 and exposed to heat on a cupel, which is a vessel made of bone 
 ashes, or sometimes of wood ashes, under a muffle, or, in the 
 large way, on the hearth of a refining furnace. The lead 
 passes to the state of oxide, is vitrified, and at the same time 
 promotes the oxidizement and vitrification of the foreign me- 
 tals. The vitrified oxide is absorbed by the porous cupel, or, 
 in the large way, the greater part is driven off by the blast of 
 bellows, and removed. When the greater part of the foreign 
 metals is abstracted, the remaining fused metal exhibits vari- 
 ous prismatic colors, which succeed each other quickly. It at 
 length suddenly brightens, and its surface becomes highly lu- 
 minous. This is regarded as the completion of the process. 
 The metal is allowed to become solid^ and while yet hot, is 
 detached. 
 
 Painting. — The gold, even after having been submitted to 
 this process, may still be alloyed with silver, which being near- 
 ly as difiicult of oxidizement, is not removed by the action of 
 the lead. It is therefore lastly subjected to the operation of 
 parting. The metalis rolled out thin, and cut into small 
 pieces. These are digested with a moderate heat in diluted 
 nitric acid, which dissolves the silver, leaving the gold undis- 
 solved in a porous mass. It has been found, however, that 
 when the proportion of silver is small to that of gold, the latter 
 protects the former from the action of the acid. The previous 
 step of quartation, as it is named, is therefore employed, which 
 consists in fusing three parts of silver with one of the gold, and 
 then subjecting this alloyed metal, rolled out, to the operation 
 of the acid. These are the operations employed in commerce. 
 To obtain gold perfectly pure, still another process is perhaps 
 necessary, — dissolving it in nitro-muriatic acid, and adding to 
 
398 ARTS OP METALLURGY. 
 
 the solution a solution of sulphate of iron, which, attracting the 
 oxygen, precipitates the gold in the metallic state. 
 
 Cementation.' — The process oi cementation is performed hy 
 beating the alloy into thin plates, and placing these in alternate 
 layers, with a cement containing nitrate of potass, and sulphate 
 of iron. The whole is then exposed to heat, until a great part 
 of the alloying metals are removed by the action of the nitric 
 acid, which is liberated by the nitre. Cementation is some- 
 times employed by goldsmiths to refine the surface of articles 
 in which gold is alloyed with baser metals. 
 
 Alloy. — There is a peculiar language established in com- 
 merce, and often referred to by writers, to denote the purity of 
 gold, or the degree of its alloy with other metals. The mass 
 is supposed to consist of 24 equal parts, these imaginary parts 
 being termed carats. If perfectly pure or unalloyed, it is said 
 to be gold 24 carats fine ; if alloyed with one part of any other 
 metal, or mixture of metals, it is said to be 23 carats fine. In 
 this way the proportion of alloy is expressed. The standard 
 gold coin of the United States and Great Britain, is 22 carats 
 fine, or contains one twelfth part of alloy. 
 
 Gold, when perfectly pure, is not so fit for coin, on account 
 of its softness, in consequence of which the impression is soon 
 obliterated, and it sustains loss from friction. Hence it is al- 
 ways alloyed, to give it hardness. The metals that have been 
 used for this purpose, are silver or copper. Gold made stand- 
 ard by an alloy consisting of equal parts of silver and copper, 
 has a color approaching more to that of pure gold than any 
 other alloy. This color also remains uniform, while that with 
 copper, after a certain degree of wear, becomes unequal.* 
 
 * Mr Hatchet with Mr Cavendish, subjected the different alloys that have 
 been used as coin to friction, as similar as possible to that to which they 
 must be subjected in the course of circulation. The loss was by no means 
 considerable, and it appeared as the general result, that the present stand- 
 ard of gold, or an alloy of one part in 12, is, all circumstances considered, 
 the best, or at least, as good as any that could be chosen. If the copper be 
 in larger proportions, more loss is sustained from friction. The same alloy 
 is employed in the fabrication of plate, and of trinkets, and lace, and, by 
 
ARTS OP METALLURGY. 399 
 
 Working. — Common goldsmiths' work is performed by 
 casting in moulds, beating with hammers, and rolling between 
 polished steel rollers. Works that have raised or embossed 
 figures, are commonly cast in moulds and afterwards polished ; 
 or, they are struck in dies, cut for the purpose. Yessels, both 
 of gold and silver, are beat out from flat plates. When the 
 form is difiicult, they are made of several plates and soldered 
 together. The solder used for this purpose is an alloy of gold 
 with silver, copper, or brass. Small ornamental works are 
 commonly executed by encha,sing. This process is performed 
 upon thin plates of gold, with a block and hammer. It consists 
 in driving in portions of the metal on one side in such a man- 
 ner that they stand in relief, forming the figures required on 
 the opposite side. Many small articles are also made from 
 gold wire, variously wrought and ornamented. 
 
 Gold Beating. — The great utility of gilding in the arts, in 
 furnishing an incorruptible covering to various substances, has 
 given rise to an extensive consumption of gold leaf, which is 
 formed, by beating the metal to a state of extreme tenuity. 
 The gold is first forged into plates on an anvil, and then re- 
 duced, by passing it between polished steel roUers, till it be- 
 comes a ribband as thin as paper. This ribband is divided 
 into small pieces, which are again beat upon an anvil tiU they 
 are about an inch square, after which they are thoroughly an- 
 nealed.* Two ounces of gold make 150 of these squares. 
 All these squares are interlaid with leaves, first of vellum, and 
 afterwards of gold beater's skin, a thin membranous substance, 
 obtained from the intestines of animals. The whole is then 
 beaten with a heavy hammer till the gold is extended to the 
 same size as the pieces of skin. The gold leaves are then 
 
 other additions, various shades of color are obtained. Its alloy with a fifth 
 of silver, forms the green gold of the jewellers, and the addition of iron 
 gives a blue tint. 
 
 * The process o^ annealing is applied to metals and some other substan- 
 ces to diminish their brittleness, or increase their flexibility and ductility. 
 It is performed by heating the substance, and suffering it to cool in a very 
 gradual manner. 
 
40'0 ARTS OP METALLURGY. 
 
 taken out, and eachcut into four part ; sand the 600 pieces 
 tliiis produced, are again interlaid in the same manner with 
 skins, and the beating repeated witli a hghter hammer. They 
 are afterwards redivided as before, and formed into parcels 
 which are separately beat, at one or more operations, until the 
 leaf has attained the requisite thinness. The use of the mem- 
 branes which are interposed between the leaves, is to prevent 
 them from cohering together, at the same time that they are 
 permitted to expand ; and also to soften the blows of the ham- 
 mer. Notwithstanding the vast extent to which gold is beaten 
 between these skins, and the great tenuity of the skins them- 
 selves, yet they are said to sustain continual repetitions of the 
 process for a long time without receiving injury. The kind 
 of leaf called party gold, is formed by laying a thin leaf of 
 gold upon a thicker one of silver. They are then heated and 
 pressed together till they unite and cohere, after which they 
 are beaten into leaves as before. 
 
 Gilding on Metals. — Gilding on copper is commonly per- 
 formed with an amalgam of gold and mercury. The surface 
 of the copper, being freed from oxide, is covered with the amal- 
 gam, and afterwards exposed to heat till the mercury is driven 
 off, leaving a thin coat of gold. It is also performed by dipping 
 a linen rag in a saturated solution of gold, and burning it to 
 tinder. The black powder thus obtained is rubbed on the 
 metal to be gilded, with a cork dipped in salt water, till the 
 gilding appears. Iron or steel is gilded by applying gold leaf 
 to the metal, after the surface has been well cleaned, and heated 
 until it has acquired the blue color, which at a certain temper- 
 ature it assumes. The surface is previously burnished, and 
 the process is repeated when the gilding is required to be more 
 durable. It is also performed by diluting the solution of gold 
 in nitro-muriatic acid, with alcohol, and applying it to the clean 
 surface.* 
 
 * This last process has been improved by Mr Stoddart, A saturated solution 
 of gold in nitro-muriatic acid, being mixed with three times its weight of sul- 
 phuric ether, dissolves the muriate of gold, and the solution is separated 
 
ARTS OP METALLURGY. 401 
 
 Gold Wire. — The common, gold or gilt wire, is in reality 
 silver wire covered with gold. In making it, a silver rod is 
 enclosed in thick leaves of gold. It is then drawn successive- 
 ly through conical holes of different sizes, made in plates of 
 steel, in a manner similar to that pursued in making iron Vv ire. 
 The wire may thus be reduced to an extreme degree of fine- 
 ness, the gold being drawn out with the silver, and constituting 
 a perfect coating to the wire. When it is intended to be used 
 in forming gold thread, the wire is flattened by passing it be- 
 tween rollers of polished steel. The coating of gold remains 
 unbroken, though so far reduced by these processes as not to 
 occupy the millionth part of an inch in thickness. The gold 
 thread commonly used in embroidery, consists of threads of 
 yellow silk, covered by flattened gilt wire, closely wound upon 
 them by machinery. 
 
 SILVER. 
 
 Extraction. — Silver is in general extracted without much 
 difficulty. When native, it is separated from the earthy matter 
 by washing, and amalgamation with mercury ; the latter being 
 separated again by distillation. When alloyed with antimony, 
 or arsenic, or when mineralized, the ore is roasted to expel these 
 metals, with the sulphur, or other volatile principles ; and the 
 residual matter is fused with lead, and refined by cupeliation, 
 in a manner similar to that described under the head of gold ; 
 the alloy of lead and silver being exposed to heat on the hearth 
 of the refining furnace, the lead being oxidized along with the 
 foreign metals, the oxidizeraent and vitrification of which it 
 promotes, and the vitrified oxide being in part absorbed, and 
 in part driven off by the blast of the bellows. The appearance 
 
 from the acid beneath. To gild the steel, it is merely necessary to dip it, the 
 surface being previously well polished and cleaned, in the etherial solution, 
 for an instant ; and on withdrawing it, to wash it instantly by agitation in wa- 
 ter. By this method steel instruments are very commonly gilt. 
 
 51 
 
402 ARTS OF METALLURGY. 
 
 of a vivid incandescence, or brightening, denotes when the 
 silver has become sufficiently pure. It retains a httle gold in 
 combination, but this does not alter its qualities, and the 
 quantity is seldom such, as to render its separation, by the op- 
 eration of parting, an object of importance. 
 
 If the ore which is wrought contain only a small portion of 
 silver, the previous operation of eliquation is sometimes per- 
 formed on it. This consists in adding a certain portion of lead 
 to the metallic matter which remains after roasting and fusing 
 the ore. This alloy is then exposed to a degree of heat just 
 sufficient to melt the lead, which runs out, and from its affinity 
 to the silver, carries it along with it, leaving the copper, or 
 other metals with which the silver had been combined. The 
 alloy of silver and lead is then subjected to the usual refining 
 process. 
 
 Working. — Silver is cast into bars, or ingots, and afterwards 
 wrought by hammering and rolling. The bars are beaten up- 
 on anvils, being heated from time to time to render them more 
 ductile. The hammering is conducted while the heat is below 
 redness. They are then passed between polished steel rollers, 
 until they are reduced to plates of a suitable thickness. To 
 form utensils of different kinds, these plates are hammered in 
 moulds till they acquire the proper shape. Vessels are often 
 made in pieces, which are afterwards united by soldering. The 
 solder used for silver, consists of an alloy of silver with more 
 than an equal part of copper or brass. Figures which are 
 raised upon the silver, are produced by hammering the metal 
 upon steel dies, in which the figure is cut, or by passing it 
 through engraved rollers. Silver is polished by burnishing 
 it with steel instruments, or with hard polished stones ; and 
 by rubbing it with the oxide of iron called colcothar, in fine 
 powder. 
 
 Silver, in the arts, is usually alloyed with a little copper, 
 which increases its hardness, and renders it more sonorous with- 
 out debasing its color. The standard silver of the British 
 coins contains 18 pennyweights of copper in a pound Troy of 
 
ARTS OP METALLURGY. 403 
 
 silver ; and in the United States 1664 grains of silver contain 
 179 grains of copper. 
 
 Coining. — The coining of silver, and other metals, was 
 originally performed by the hammer, in matrices, or dies, en- 
 graved for the purpose. At the present day, coins of every 
 description are more commonly milled. In coining by the 
 mill, the bars, or ingots, of gold or silver, after having been cast, 
 are taken out of the moulds and their surfaces cleaned. They 
 are then flattened by rollers, and reduced to the proper thick- 
 ness to suit the species of money about to be coined. To ren- 
 der the plates more uniform, they are sometimes wire drawn, 
 by passing them through narrow holes in a steel plate. The 
 plates, whether of gold, silver, or copper, when reduced to their 
 proper thickness, are next cut out into round pieces called 
 blanks or planchets. This cutting is performed by a circular 
 steel punch of the size of the coin, which is driven downward 
 by a powerful screw, and passes through a corresponding cir- 
 cular hole, carrying before it the piece of metal which is 
 punched out. The pieces which are thus cut, are brought to 
 the standard weight, if necessary, by filing or rasping ; and 
 the deficient pieces, together with the corners and pieces of the 
 plates left by the circles, are returned to the melter. 
 
 The milling, by which the inscription, or other impression, 
 is given to the edge of the coin, is performed by rolling the coin 
 edgewise, between two plates of steel, in the form of rulers, 
 each of which contains half of the engraved edging. One of 
 these plates is fixed, and the other is moveable by a rack and 
 pinion. The coin, being placed between them, is carried along 
 by the motion of the rack, till it has made half a revolution and 
 received the whole impression on its edge. The most impor- 
 tant part of the coining still remains to be done, and consists 
 in stamping both sides with the appropriate device, or figure 
 in relief. For this purpose, the circular piece is placed between 
 two steel dies upon which the figures to be impressed are sunk, 
 or engraved in the manner of an intaglio. The two dies are 
 then forcibly pressed together, by the action of a powerful screw, 
 
404 AP.TS OF METALLURGY. 
 
 to which is attached a heavy transverse beam, which serves 
 the purpose of a fly, and concentrates the force at the moment 
 of the impression. The coin is now finished, and is thrown 
 out when the screw rises. 
 
 In the coining machinery erected by Boulton and Watt, and 
 introduced at the mint in England, the process is performed by 
 steam power, and both the edges and faces of the money are 
 coined at the same time.* By means of this machinery, eight 
 presses attended by boys, can strike 19,000 pieces of money in 
 an hour, and an exact register is kept by the machine of the 
 number of pieces struck. 
 
 For the coining of medals the process is nearly the same as 
 for that of money. The principal difference consists in this, 
 that money having but a small relief, receives its impressions 
 at a single stroke of the engine ; whereas in medals, the high 
 relief makes several strokes necessary ; for which purpose the 
 piece is taken out from between the dies, heated, and returned 
 again. This process for medallions is sometimes repeated as 
 many as a dozen or more times before the full impression is 
 given them. Some medallions, in a very high relievo, are 
 obliged to be cast in sand, and afterwards perfected by being 
 sent to the press. 
 
 Plating. — The great value of silver, and the useful proper- 
 ty which it possesses of resisting oxidation, has given rise to the 
 art of plating^ in which vessels and utensils of other metals, 
 but chiefly of copper, are covered with a thin coating of silver, 
 so as to protect them from the influence of the atmosphere. 
 Plating is sometimes executed by heating the articles which 
 are to be coated, and rubbing on them portions of leaf silver, 
 with a steel burnisher, till it adheres. But it is performed in a 
 better manner, by plating solid ingots of copper, and afterwards 
 working these into any shape desii-ed. The ductility of the 
 coating of silver causes it to be extended, and drawn out with 
 
 * A particular account of this machinery is given in the London Mechanic's 
 Magazine, vol.iii. 
 
ARTS OF METALLURGY. 405 
 
 the copper, so that the latter metal never appears at the surface. 
 The copper used in plating, is alloyed with a little brass. Great 
 care is taken in casting-, to form the ingots sound, and free 
 from pores or flaws. The surface of the ingot is cleaned with 
 a file, and a thin plate of silver is applied to one, or to both 
 sides, according to the article to be manufactured. A saturated 
 solution of borax is then insinuated between the edges, the 
 object of which is to protect the copper from oxidation, which 
 would otherwise prevent the silver from adhering. The in- 
 got is then carried to the farnace, and exposed to heat until 
 the metals adhere to each other. Their adhesion is owing to 
 the formation of an alloy between the silver and copper, 
 which being fusible at a lower temperature than either of the 
 metals, acts as a solder to unite thein together. The ingot 
 is then rolled into sheets, by passing it repeatedly between iron 
 rollers, aimealing it from time to time, as it becomes hard and 
 brittle. 
 
 The plated sheets which are thus obtained, are formed into 
 articles of different kinds, by hammering them in moulds cor- 
 responding to the intended shape. When vessels are to be 
 made, they are formed in pieces of a convenient shape, and 
 these are soldered together with a^ alio}'" of silver, copper, and 
 brass. Mouldings, and other ornamental parts, are made by 
 hammering the metal in steel dies, or rolling it between steel 
 rollers, upon which the pattern is cut. As the edges of plated 
 ware are most liable to be injured by wear, they are commonly 
 protected by what are called silver edges. These are formed 
 of a shell of silver, rolled out, or hammered in dies, and having 
 its inside filled up with a mixture of tin and lead. When fin- 
 ished, these edges are soldered to the vessel. The handles, 
 feet, and solid parts of vessels, are often made in the same 
 way. Plated baskets and other light articles are made from 
 copper cylinders covered with silver, and afterwards drawn in- 
 to wire. 
 
 Plating on iron, as it is used for the buckles of harnesses and 
 other ornaments, is executed by first covering the iron with a 
 
403 ARTS OP METALLURGY. 
 
 coating of tin, and then applying closely to the surfoce a thin 
 plate of silver. The union i;9 effected by a moderate heat, suf- 
 ficient to melt the tin, and form an alloy ; and it is aided by 
 the use of a resinous flux. 
 
 COPPER. 
 
 Extraction. — The various sulphurets of copper are the most 
 abundant of its ores, and of these the most so is copper pyrites. 
 The malachite, red copper ore, and others, are generally asso- 
 ciated with these in small quantities. Copper mines are 
 wrought in many countries, but those of Sweden are said to 
 furnish the purest copper of commerce. The sulphurets are the 
 ores from which copper is usually extracted. The ore is roast- 
 ed by a low heat, in a furnace with which flues are connected, 
 in which the sulphur, that is volatilized, is collected. The re- 
 maining ore is then smelted in contact with the fuel. The iron 
 present in the ore, not being so easily reduced, or fused, as the 
 copper, remains in the scoria, while the copper is run out. It 
 often requires repeated fusions, and even after these, it may be 
 still alloyed with portions oi metals, which are not volatile, 
 and are of easy fusion. Hence the copper of commerce is never 
 altogether pure, but generally contains a little lead, and a small- 
 er portion of antimony. 
 
 The carbonates of copper reduced by fusion, in contact with 
 the fuel, afford a purer copper, as does also the solution of sul- 
 phate of copper which is met with in some mines, the copper 
 being precipitated in its metallic state, by immersing iron in 
 the solution. The precipitate which is thus formed, is after- 
 wards fused. 
 
 Working-. — Copper, being ductile and easily wrought, is ap- 
 plied to many useful purposes. It is formed into thin sheets 
 by being heated in a furnace, and subjected to pressure between 
 iron rollers. These sheets being both ductile and durable, are 
 applied to a variety of uses, such as the sheathing of the hot- 
 
ARTS OP METALLURGY. 40T 
 
 toms of ships, the coverings of roofs and domes, the construct- 
 ing of boilers and stills of a large size, &c. Copper is also fab- 
 ricated into a variety of household utensils, the use of which, 
 however, for preparing or preserving articles of food, is by no 
 means free from danger, on account of the oxidizement, to 
 which copper is liable. It has been attempted to obviate this 
 danger, by tmning- the copper, or applying to its surface a 
 thin covering of tin. This method answers the purpose as 
 long as the coating of tin remains entire. 
 
 Copper may be forged into any shape, but will not bear 
 more than a red heat, and of course requires to be heated 
 often. The bottoms of large boilers are frequently forged with 
 a large hammer worked by machinery. The bolts of copper 
 used for ships, and other purposes, are either made by the 
 hammer, or cast into shapes and rolled. The copper cylinders 
 used in calico printing, are either cast solid upon an iron axis, 
 or are cast hollow and fitted upon the axis. The whole is af- 
 terwards turned to render the surface true. 
 
 Brass. — Brass is an alloy of copper and zinc. The pro- 
 portions of these two metals differ in almost every place in 
 which brass is manufactured, and the proportion of zinc is 
 found in different specimens to vary from 12 to 25 parts in a 
 hundred. The alloy is commonly made from the ores of zinc 
 mixed with copper, and with a sufficient quantity of charcoal 
 to reduce them to a metallic state. The volatility of the zinc 
 gives it a tendency to escape in vapor, on which account the 
 combination is effected at a lower heat than that v/hich would 
 be necessary to melt the copper. Several other alloys of the 
 same metals, are also known in the arts, differing in the pro- 
 portions of the ingredients ; such as pinchbeck, prince's metal, 
 toinbac, Bath metal, &c. 
 
 Manufacture. — The value of brass in the arts, consists in 
 its bright color, in its being more fusible than copper, and in its 
 being more easily wrought with common tools. In the work- 
 ing of brass, the larger articles, as well as those of complicated 
 forms, are cast in moulds. When it is intended, for economy 
 
ARTS OP METALLURGY. 
 
 of the metal, that the article shall be hollow, as in the case of 
 andirons, &c., it is cast in halves, or pieces, which are after- 
 wards soldered together, and turned in a lathe, or otherwise 
 polished. Brass is also rolled into thin sheets, and drawn into 
 wire. A variety of figured and ornamental articles are made 
 by stamping it in dies or moulds. Brass knobs and similar 
 implements, if large, are made in pieces, and soldered. The 
 wheel work of time-pieces, and of other machinery which is 
 not subjected to great strain or wear, is usually made of brass. 
 The comparative softness of this all 03^, permits it to be cut with 
 thin saws, and to be turned in a lathe, with much greater ease 
 than iron. 
 
 Buttons are either struck out of sheets of brass with a cir- 
 cular punch, driven by a fly press, or they are cast in large 
 numbers at once in a mould, or flask of sand. The eye, or 
 shank, of the button is made separately by a machine, and 
 soldered on, if the button has been cut out by the punch. 
 If the button is cast, the eye is previously placed in the mould, 
 so that its extremity is immersed in the centre of the melted 
 metal. If the button is to be plain, its surface is planished by 
 the stroke of a smooth die ; and if figured, it is stamped with 
 an engraved die. The edges are afterwards turned off in a 
 lathe. The gilding of brass buttons is performed by covering 
 them with amalgam of gold and mercury, from which the 
 mercury escapes when heated, and leaves the gold. White 
 metal buttons are made of an alloy of brass and tin, and sub- 
 sequently coated with tin. The brass eyes of pearl buttons 
 are inserted by drilling a conical hole, which is largest on the 
 inside, in the mother of pearl, or shell, of which the button is 
 made. The eye, having an extremity like a hollow cone, is 
 then driven in, till it spreads and fills the cavity. 
 
 Pins are made of brass wire cut into proper lengths. The 
 pieces are pointed by turning them with the fingers, upon 
 stones, or steel mills. The heads are cut from a spiral coil of 
 wire, in pieces of a suitable length ; and after being placed 
 upon the pins, are shaped and fastened by the stroke of an in- 
 
ARTS OP METALLURGY. 409 
 
 slrument like a hammer. Several machines have been invent- 
 ed for this manufacture, one of which makes a solid head 
 from the body of the pin itself Pins are whitened by immers- 
 ing them in a vessel containing tin and lees of wine, and are 
 polished by agitating them with bran in a revolving cask. 
 
 Bronze.— A series of alloys is formed from the combination 
 of copper with tin. The combination appears to have a ten- 
 dency to form in certain proportions, regulated in some meas- 
 ure by the specific gravities and fusibilities of the metals ; for 
 when kept in fusion, and allowed to cool without agitation, 
 two allo3^s are formed, the under part of the mass being one of 
 copper with a small portion of tin, and the upper part tin with 
 a small proportion of copper, while between these there is 
 probably a gradation. By agitation, this separation is counter- 
 acted. In general, tin lesseris the ductility of copper, while it 
 renders it more hard, rigid, and sonorous ; these qualities be- 
 ing possessed in various degrees by the different alloys, accord- 
 ing to their proportions, the hardness and brittleness being 
 greater as the tin predominates. The density of the compound 
 is also always greater than the mean density ; the contraction 
 from the combination being about one eighth. The principal 
 of these alloys, are bronze, gun metal, from which pieces, of 
 artillery are cast, hell metal, and speculum m.eial which. has 
 been used for the mirrors of reflecting telescopes. Bronze is 
 one of those in which the proportion of tin is least, not exceed- 
 ing 10 or 12 parts in 100. It is of a greyish yellow color, harder 
 than copper, less liable to rust, and more fusible, so as to be 
 easily cast in moulds. Hence it is employed in the casting of 
 statues. The metal from which pieces of artillery are cast, is 
 of a similar composition, containing rather less tin. It appears 
 that an alloy very similar to bronze, was much m use among 
 the ancients ; and swords, darts, and other warlike instruments 
 were formed of it, as were also various utensils.* 
 
 * According to Dr Pearson's experiments made on various instruments of 
 this kind, the alloy appears to have consisted of about eight or nine parts of 
 copper, with one of tin, and, as he justly remarks, this alloy still affords the 
 
 52 
 
410 ARTS OF METALLURGY. 
 
 When the proportion of tin is inci'easedj the alloy is render- 
 ed more brittle and elastic, and at the same time highly sono- 
 rous. Bell metal is an alloy of this Idndj in which the pro- 
 portion of tin varies from one third to one fifth of the weight 
 of the copper, according to the size of the bell, and the sound 
 required. 
 
 When the proportion of tin is still greater, an alloy is form- ' 
 ed, called speculum 7netal, which is of a white color, and 
 which, from the closeness of its texture, and its susceptibility of 
 a fine polish, exceeds most metals in the property of reflecting 
 light. Hence it is used in forming the speculum of reflecting 
 telescopes. It has also the advantage of not being liable to 
 tarnish on exposure to the air. The proportion in which these 
 qualities were best attained, appeared, from the experiments of 
 Mr Mudge, to be a little less than one part of tin, with two 
 parts of copper.* The Chinese pakfong, or white copper, 
 which is sometimes imported from that country, is an alloy, 
 according to Dr Fyfe, of copper, zinc, nickel, and iron. 
 
 oest substitute for iron or steel. Wliile the art, therefore, of manufacturing 
 malleable iron was imperfectly known, and difficult to be practised, it must 
 have been much used. The hardness of this alloy observed in ancient arms, 
 had even given rise to an opinion, that the ancients were acquainted with 
 a method of hardening copper, which had been lost. Of this alloy, medals 
 and coins were also often formed, as appears from the experiments of Dize, 
 on several Greek, Roman, and Gallic coins, which consisted of copper and 
 tin alone. 
 
 * Mr Edwards, by an extensive series of experiments on the proportions 
 of these metals, and the effects of different additions, succeeded in forming 
 alloys much superior in brightness to those that had been before used. 
 That which he preferred, was composed of 33 ounces of copper, 15 or 16 
 oz. tin, according to the purity of the copper, to which were added brass, 
 arsenic, and silver, of each one ounce; the copper and the tin being melt- 
 ed in separate crucibles, when in fusion, the one being added to the other, 
 and the composition, when well stirred, being poured into cold water. The 
 other metals are added in a second fusion. The arsenic appears to give a 
 greater degree of density and compactness to the alloy, the brass more 
 tenacity, and the silver adds to the whiteness. According to the more re- 
 cent experiments of Mr Little, the best composition, is 32 parts of bar cop- 
 per, four parts of brass, sixteen and a half parts of tin, and one and three 
 quarters of arsenic. 
 
ARTS OP METALLURGY. 411 
 
 LEAD. 
 
 Extraction. — ^Lead mineralized by sulphur, forms by far 
 the most abundant ore of the metal, and has been long known 
 to mineralogists by the name of galena. This is the ore 
 which is generally wrought, and from which nearly all the 
 lead of commerce is procured. The ore, after being pounded, 
 and freed from the admixture of any stony matter by washing, 
 is fused in a furnace, with the addition of lime, which com- 
 bines with the sulphur of the sulphuret ; the lead is melted, 
 and run out by an aperture towards the bottom of the furnace. 
 When the native salts of lead are found with the galena, so as 
 to render it of importance to work them, they are selected un- 
 til a sufficient quantity be obtained. They are then roasted to 
 expel the volatile matter, and are afterwards fused in contact 
 wnth the fuel, with an addition of lime. The lead obtained 
 from galena, sometimes contains so much silver as to be sub- 
 jected to an additional process to separate the silver. In this 
 case, the lead is oxidized in a furnace, a current of air being 
 directed on its surface when in fusion, by bellows. Towards 
 the end of the operation, the silver remains with a small por- 
 tion of lead, from which it is freed by cupellation ; and the 
 oxide of lead is either applied to the purposes for which it is 
 used, or is reduced to the metaUic state. 
 
 Manufacture. — Lead, being fusible at alow^ temperature, re- 
 quires only to be cast in smooth moulds, to form weights, bul- 
 lets, and other articles of small size. The linings of cisterns, 
 and the coverings of roofs, gutters, (fcc. are made of sheet lead ; 
 pumps, and aqueducts, of leaden pipes. 
 
 Sheet Lead, of the thicker kinds, is cast upon large tables 
 covered wdth sand, and having an elevated rim. The melted 
 lead is poured upon the surface out of a box which moves up- 
 on rollers across the table, and is spread out with a uniform 
 thickness, by passing over it a straight piece of wood, called a 
 strike. The sheets thus cast are afterwards rendered thinner, 
 
412 ARTS OP METALLURGY. 
 
 by reducing tliem between rollers. The sheet lead with which 
 tea chests are lined, is an alloy of lead and tin, and is made 
 by the Chinese, by suddenly compressing the melted metal 
 between flat, polished stones. 
 
 Lead pipes, for conveying water, may be made in various 
 ways. They were at first formed of sheet lead bent round a 
 cylindrical bar, or mandrel, and soldered ; but these pipes are 
 liable to crack and leak, especially when bent. A second 
 method is to cast a short tube of lead in a cylindrical mould 
 with a core. This tube, when cold, is drawn nearly out of 
 the mould, and a fresh portion of melted lead poured in at 
 apertures in the sides of the mould. The melted lead unites 
 with the tube previously formed, so as to increase its length; 
 and by repeating the process, any length of pipe may be pro- 
 duced. But pipes cast in this manner are found to have im- 
 perfections arising from flaws and air bubbles. A third method, 
 which is now most commonly practised, is to cast a short, thick 
 tube of lead, upon one end of a long, polished iron cylinder, or 
 mandrel, of the size of the bore of the intended pipe. The lead 
 is then reduced in size, and drawn out in length, either by 
 drawing it on the mandrel, through circular holes, of different 
 sizes, in a steel plate ; or by rolling it between contiguous rol- 
 lers, which have a semi-circular groove cut round the circum- 
 ference of each. A fourth mode, invented by Mr Bramah, 
 consisted in forcing melted lead, by means of a pump, into 
 one end of a mould ; while it was discharged in the form of a 
 pipe at the opposite end. Care was taken so to regulate the 
 temperature, that the lead should chill, just before it left the 
 mould. 
 
 Leaden shot consist of drops of metal which are discharg- 
 ed in a melted state from small orifices, and cool in falling. 
 The best shot are cast in high towers built for the purpose. 
 The lead is previously alloyed with a portion of arsenic, v\ hich 
 increases ii.e cohesiveness of its particles, and causes it to as- 
 sume more readily the globular form. It is melted at the top 
 of the tower, and poured into a vessel, which is perforated 
 
ARTS OF METALLURGY. 413 
 
 at bottom with numerous small holes. The lead, after run- 
 ning through these perforations, immediately separates into 
 drops, which cool in falling through the height of the tower, 
 and are received in a reservoir of water at bottom, to break the 
 force of the fall. The shot are then proved by rolling them 
 down an inclined board. Those, which are irregular in shape, 
 roll off at the sides, or stop, while the spherical ones continue to 
 the end. They are then assorted by passing them through 
 wire sieves of different fineness. The glazing is given by agi^ 
 tating them with small quantities of black lead. 
 
 Shot is sometimes made mechanically, by cutting sheets of 
 lead into cubes, and agitating these for a long time in a cylin- 
 drical vessel turned upon an axis. The attrition thus pro- 
 duced, communicates a globular form to the cubes. 
 
 TIN. 
 
 Native oxide of tin, or tinstone, as it is commonly named, 
 is the only ore that is wrought to obtain this metal. Being 
 freed by washing, from the intermixture of any stony matter, 
 it is roasted, and then fused in contact with the fuel, by a mod- 
 erate heat. The tin of Cornwall is supposed to be purer than 
 the German tin, though it is still inferior to the tin from India. 
 
 Block tin, consisting of the metal in its solid state, is used 
 for vessels which are not exposed to a temperature much ex- 
 ceeding that of boiling water. Vessels of this kind, being not 
 readily tarnished, form a cheaper substitute for silver and plated 
 ware. A kind of ware denominated Biddery ware, consists 
 of tin vessels alloyed vdth a little copper, and having their sur- 
 face made black by the application of substances containing 
 nitre, common salt, with sal ammoniac. Tinfoil is made by 
 rolling, in the same way as the plates for tinned iron hereafter 
 described. It is also sometimes hammered. The most exten- 
 sive use, however, to which metallic tin is applied, is to form 
 a coating for other metals, which are stronger than itself, but 
 
414 ARTS OF METALLURGY. 
 
 at the same time more liable to oxidation by exposure to the 
 air. 
 
 Tin plates^ which constitute the material of the common tin 
 ware, so extensively used, are thin sheets of iron coated with 
 tin. The mode of rolling these sheets will be described under 
 the head of Iron. To prepare them for tinning, they are 
 steeped in water acidulated with muriatic acid, and then lieat- 
 ed, scaled, and rolled, to remove all oxide, and enable the tin 
 to adhere to the iron. The tin is kept melted in oblong, rec- 
 tangular vessels, and to preserve its surface from oxidation, a 
 quantity of melted fat and oil is kept floating upon it. The 
 iron plates are taken up with pincers, and immersed in the tin 
 for some time. When withdrawn they are found to have ac- 
 quired a bright coating of the tin, which adheres closely, ow- 
 ing to the formation of an intermediate alloy. The dipping is 
 repeated twice, or more times, according to the thickness of 
 the coat intended to be given, and also to produce a smooth 
 surface, and between these processes the tin is equalized with 
 a brush.* 
 
 Various other articles of iron, such as spoons, nails, bridle 
 bits, small chains, &c. are coated w4th tin, by immersing them 
 in that metal while in a state of fusion. From the affinity be- 
 tween tin and copper, a thin layer of the former metal can be 
 easily applied to the surface of the latter ; and this practice of 
 tinning, as it is named, is often employed to pi-event the erosion 
 or rusting of copper vessels, and the noxious impregnation 
 which they would otherwise communicate to liquors kept in 
 them. The surface of the copper is polished so as to be quite 
 bright ; sal ammoniac is appUed to it, when hot, by which the 
 oxidation appears to be prevented ; or pitch is sometimes used 
 for the same purpose. The melted tin, or sometimes an alloy 
 of tin and lead, is then applied to the surface of the copper, to 
 which it readily adheres. 
 
 * For a full account of the present mode of manufacturing tin plate, see 
 Parkes' Chemical Essays, vol. ii. 
 
ARTS OF METALLURGY. 415 
 
 iSilveiHng of Mirrors. — The siufaces best adapted for re- 
 flecting light, are those of pohshed metals. To constitute a 
 good reflector, it is necessary that a metal should be susceptible 
 of an equal, unbroken, and exquisite polish, and that it should 
 retain this polish, without being tarnished by the atmosphere. 
 Speculum metal is chiefly employed for reflecting surfaces in 
 telescopes ; but for common purposes an amalgam of tin and 
 mercury is used in a state of adhesion to glass. The use of 
 the glass is, in the first place, to produce a smooth surface in 
 the amalgam ; and afterwards to protect it from oxidation by 
 the atmosphere. 
 
 In the _silvering of plain looking-glasses, a flat, horizontal 
 slab of stone is used as a table. This is smoothly covered 
 with paper, and a sheet of tin foil, equal to the size of the glass, 
 is extended over it. A quantity of mercury is then laid upon 
 the tin foil, and immediately spread over it with a roll of cloth, 
 or a hare's foot. Afterwards, as much mercury as the surface 
 will hold, is poured on. While this mercury is yet in a fluid 
 state, the plate of glass is shd on at the edge of the table, so as 
 to pass over the tin foil, driving the superfluous mercur}?" before 
 it. In this way any bubbles of air and particles of dust are 
 prevented from getting between the glass and the metal, and 
 an uninterrupted coating is formed. In order to force out the 
 remaining liquid mercury, the glass is placed in a sloping po- 
 sition, to allow the mercury to drain off, after which heavy 
 weights are placed upon the glass, and suffered to remain for 
 some time. The portion which is left, amalgamates with the 
 tin, and forms a permanent reflecting surface, the smoothness 
 and perfection of which, depends upon the degree of regularity 
 and polish which the glass possesses. 
 
 In silvering concave and convex mirrors, instead of a stone 
 table, the tinfoil is spread upon a plaster mould, previously 
 cast on the surface of the glass itself. The inside of glass 
 globes is si] veered by pouring into them a fusible alloy of tin, 
 lead, bismuth, and mercury, the heat of which, when liquid, 
 is not sufficient to break the glass. By turning the globe 
 
416 ARTS OF METALLURGY* 
 
 about, a thin metallic coating is deposited on the whole interi- 
 or surface* 
 
 IRON. 
 
 The properties which iron possesses in its various forms, 
 i'ender it the most useful of all the metals. The toughness of 
 malleable iron adapts it to purposes where great strength is re- 
 quired ; while its combination of difficult fusibility with the 
 property of sofiening by heat, so as to admit of forging and 
 welding, renders it capable of being easily worked, and of 
 withstanding an intense heat. Cast-iron, from its cheapness, 
 and the facility with which its form is changed by fusion, is 
 made the material of numerous structures and machines. 
 Steel, which is the most important compound of iron, exceeds 
 all other metals in the combination of hardness and tenacity ; 
 and hence it is particularly adapted to the fabrication of cutting 
 instruments. It is equally superior in elasticity, a quality by 
 which it is suited to be the spring of motion in various ma- 
 chines. 
 
 Smelting. — The principal ores which are wrought for the 
 extraction of iron, are the different species of the native oxides. 
 The process is somewhat different, as carried on in different 
 countries, and as adapted to different ores ; but the following 
 is the general outhne of it, as it is conducted on the haematite, 
 bog ores, and other oxides of iron. 
 
 The ore is first roasted with a strong heat, to expel the car- 
 bonic acid, and any portion of sulphur or other volatile matter 
 that may be present. The remaining ore is put into a furnace 
 of a conical form with charcoal, or with coke, and exposed to 
 a heat rendered sufficiently intense by a blast of air urged 
 through the furnace. A quantity of lime is at the same time 
 added to the ore, and fuel ; the advantage of which appears to 
 be, that in combination with the argillaceous and sihceous 
 substances generally contained in the iron ores, it acts as a flux. 
 
ARTS OF METALLURGY-. 417 
 
 to vitrify the foreign matter, and thus facihtate the separation 
 of the melted metal. The proportions of these are extremely 
 various, according to the nature of the ore. When the furnace 
 is once charged, the charge is renewed at the upper part as 
 fast as the materials sink, and the process is carried on for a 
 long time without interruption. During this process, the oxy- 
 gen of the oxide of iron unites with one portion of the carbon, 
 and the metal with another, producing carbonic acid, and car- 
 buret of iron ; while the earthy substances, together wath a 
 little oxide of iron, enter into combination, forming a vitreous 
 substance called slag or scoria, and which being lighter than 
 the metal, rises upon its surface. The slag is drawn off by 
 an opening, and the melted metal is collected in a cavity at 
 bottom, from which, as it accumulates, it is conveyed off at in- 
 tervals into moulds. 
 
 Crude Iron. — The metal thus obtained, is named pig iron 
 and crude, or cast-iron. It is far from being pure, containing 
 always more or less oxygen and carbon ; and often several 
 other heterogeneous ingredients, such as manganese, and the 
 metallic bases of lime, clay, and silex, with portions of unre- 
 duced ore and charcoal. The oxygen is partly a portion of 
 what was originally combined with the metal in the ore, and 
 partly, perhaps, derived from the blast of air, which is driven 
 through the furnace, and necessarily presented to the metal 
 in a state of fusion. Hence the quahties of cast-iron are very 
 various, according as one or other of the principles predomi- 
 nate. 
 
 Iron in this state is readily capable of being fused, and cast 
 into moulds. It is, however, much more brittle than when 
 pure, and cannot be wTought, or flattened under the hammer. 
 Hence it is altogether unfit for many purposes, to which 
 pure, or malleable iron is, from its tenacity, and softness, well 
 adapted. 
 
 Casting. — Iron, as well as brass, and other metals which melt 
 at temperatures above ignition, is cast in moulds made of sand. 
 The kind of sand most employed is loam, which possesses^ 
 53 
 
418 ARTS OP METALLURGY. 
 
 sufficient portion of argillaceous matter, to render it moderate- 
 ly cohesive, when damp. The mould is formed by burying 
 in the sand a wooden pattern, having exactly the shape of the 
 article to be cast. The sand is most commonly inclosed in 
 flasks, which are square frames resembling wooden boxes open 
 at top and bottom. If the pattern be of such form that it can 
 be lifted out of the sand, without deranging the form of the 
 mould, it is only necessary to make an impression of the pat- 
 tern in one flask ; and articles of this kind are sometimes cast 
 in the open sand upon the floor of the foundry. But when 
 the shape is such that the pattern could not be extracted with- 
 out breaking the mould, two flasks are necessary, having half 
 the mould formed in each. The first flask is filled with sand, 
 by ramming it close, and is smoothed off at the top. The pat- 
 tern is separated into halves, one half being imbedded in this 
 flask. A quantity of white sand, or burnt sand, is sprinkled 
 over the surface to prevent the two flasks from cohering. The 
 second flask is then placed upon the top of the first, having 
 pins to guide it. The other half of the pattern is put in its 
 place, and the flask is filled with sand, which of course receives 
 the impression of the remaining half of the pattern on its un- 
 der side. After one or more holes are made in the top, to per- 
 mit the metal to be poured in, and the steam and air to escape, 
 the flasks are separated and the pattern withdrawn. When the 
 flasks are again united, a perfect cavity, or mould, is formed, 
 into which the melted metal is poured. 
 
 The arrangement of the mould is of course varied for dif- 
 ferent articles. When the form of the article is complex and 
 difficult, as in some hollow vessels, crooked pipes, &c., the 
 pattern is made in three or more pieces, which are put togeth- 
 er to form the mould, and afterwards taken apart to extract 
 them. In some other irregular articles, as andirons, one part 
 is cast first, and afterwards inserted in the flask which is to 
 form the other part. 
 
 The metal for small articles is usually dipped up with iron 
 ladles, coated with clay, and poured into the moulds. In large 
 
ARTS OF METALLURGY. 419 
 
 articles, such as cannon, the mould is formed in a pit dug in 
 the earth near the furnace, and the melted metal is conveyed 
 to it in a continued stream, through a channel communicating 
 with the bottom of the furnace. 
 
 Cannon balls are sometimes cast in moulds made of iron ; 
 and to prevent the melted metal from adhering, the inside of 
 the mould is covered with powder of black lead. Rollers for 
 flattening iron are also cast in iron cases. This method is call- 
 ed chill castings and has for its object the hardening of the 
 surface of the metal, by the sudden reduction of temperature, 
 which takes place in consequence of the superior conducting 
 power of the iron mould. These rollers are afterwards turned 
 smooth in a powerful lathe, which has a slow motion, that the 
 cutting tool may not become heated by the friction. 
 
 Malleable Iron. — To obtain pure iron, that is, to free crude 
 iron from the oxygen, carbon, and other foreign substances 
 contained in it, it is subjected to two operations, — melting, and 
 forging. The fusion is performed in different furnaces. The 
 melted metal is in some cases run out, to free it from the scoria 
 which has separated ; and this process is repeated until the 
 iron attains a degree of consistence sufficient to be submitted 
 to the action of the forge hammer. But more commonly the 
 metal is kept in fusion in a reverberatory furnace, called a 
 iniddling furnace, where it is raised to a very high tempera- 
 ture. The liquid is stirred frequently, to faciUtate the combi- 
 nation of the carbon and oxygen. At length, a lambent blue 
 flame appears on its surface, probably from the formation and 
 disengagementof carbonic oxide ; and after some time the fluid- 
 ity of the metal diminishes, until it at length assumes the con- 
 sistence of a stiff paste. It is then subjected to the action of a 
 very large hammer, or to the more equable pressure of rollers, 
 by which a portion of oxide of iron, carbon, and other hetero- 
 geneous substances not consumed during the fusion, are forced 
 out. The iron in this state, is no longer granular in its texture, 
 but is soft, ductile, and malleable, and much less fusible. It 
 is then named wro?*^/i^ iron., forged, or bar iron, as it is gen- 
 
420 ARTS OF METALLURGY. 
 
 erally formed into long bars. A considerable loss of weight 
 attends the process from the dissipation of the foreign substan- 
 ces contained in the crude iron, and from the oxidation of the 
 surface of the metal. The operation is generally performed on 
 the varieties called white, or grey crude iron. 
 
 Forging. — Forging consists in changing the form of iron 
 and other malleable metals, by percussion applied to them, 
 while they are softened by heat. Iron when exposed to the 
 action of great heat, becomes highly malleable and ductile. It 
 is also capable of welding, at a sufficiently high temperature. 
 Most other metals have their malleability improved by a cer- 
 tain degree of heat, but become brittle if the heat is carried 
 near to their fusing point. The strength and quality of iron, 
 on the contrary, are improved by forging at a strong white 
 heat, sirice the parts become consolidated, and the flaws oblit- 
 erated, by hammering at a welding temperature. 
 
 The joint action of the heat and current of air, used in 
 forges, tends to oxidate rapidly the surface of iron. The oxide 
 which is formed has some tendency to vitrification when com- 
 bined with siliceous matter. Hence it is a common practice 
 among workmen, to immerse the iron in sand, when it is near 
 to a welding heat. A vitreous coating is by this means form- 
 ed, which protects the surface of the iron from further oxida- 
 tion. This coating would prevent the different pieces from 
 uniting by welding, were it not that its fluidity causes it to es- 
 cape, while under the action of the hammer. .. 
 
 The forging at the furnaces, of large masses of iron, called 
 bloo?ns, is performed by the aid of tilt hammers, as is also 
 that of anchors and various other massive implements and 
 parts of machines. Bars of iion are commonly rolled, and 
 when heavier articles, such as anchors, are to be made, a suffi- 
 cient number of bars for the purpose are welded together. 
 
 A tilt hammer of the kind used in iron works, is shown in 
 PI. IX. Fig. 2. A B is the hammer, which turns upon the 
 fulcrum C. At D is a Avheel or cylinder furnished with wi- 
 pers, a b c, (fcc. each of which, as it passes, strikes the end A 
 
ARTS OF METALLURGY. 421 
 
 of the helve, and causes the hammer end B to rise. The 
 hammer then descends with its own weight, and is accelerated 
 by the recoil of the end A, from the fixed obstacle E. The 
 wipers may be indefinitely varied in number and position, and 
 are sometimes applied on the other side of the fulcrum. The 
 recoil likewise, is sometimes produced by a spring placed 
 over the end B of the hammer. The motions of these en- 
 gines is extremely rapid, and is commonly regulated by a fly 
 w4ieel. 
 
 Rolling and Slitting. — Malleable iron is commonly wrought 
 into those shapes which have flat, parallel surfaces, by submit- 
 ing it to compression between rollers. Bars, plates, and sheets 
 of iron are formed in this way. A pair of heavy cylindrical 
 rollers, made of iron, chill cast, and turned smooth, are con- 
 nected together by strong iron bearings, a space being left be- 
 tween them equal to the intended thickness of the metal which 
 is to be rolled. This distance is varied by adjusting it with 
 powerful screws. The iron which is to be rolled, is prepared 
 by heating it red hot, and in this state it is presented to the 
 rollers. As soon as any part has entered so as to fill the space 
 between the rollers, the friction, or adhesion, becomes sufficient 
 to draw in the remainder, in opposition to the force with which 
 the metal resists compression. The iron, in passing through, is 
 compressed into a uniform plate of equal thickness, and is at 
 the same time extended in length, but is very little increased 
 in breadth. As the rollers usually move with considerable ve- 
 locity, the heated iron may be passed several times between 
 different pairs of rollers, before it cools. To prevent the rollers 
 from becoming heated, a continual stream of water is let fall 
 upon their surface. 
 
 As the principal extension, which plates receive, is in a 
 longitudinal direction, it is necessary to vaiy their position 
 when it is desired to increase their width. This is sometimes 
 done by passing them in an oblique direction, but in making 
 sheet iron and wide plates, it is necessary to pass the pieces 
 through the rollers in the direction of their breadth, as well as 
 
422 ARTS OF METALLURGY. 
 
 length, that they may be extended in both directions. Very 
 thin plates, hke those used for tinned iron, are repeatedly 
 doubled, and passed between the rollers, so that in the thinnest 
 plates 16 thicknesses are rolled together, care being taken to 
 change their relative positions, and to interpose oil to prevent 
 them from cohering. The last rollings are performed while 
 the metal is cold. Bars which are square, round, and of vari- 
 ous other shapes, are formed between rollers which have 
 grooves cut upon their circumferences, corresponding in shape 
 to half the bar to be made. Even rails of malleable iron, 
 for rail roads, have lately been made between rollers formed 
 for the purpose. And at some furnaces where malleable iron. 
 is made, the forge hammer is dispensed with, and reliance is 
 placed on the rollers alone to consolidate and equalize the 
 masses of metal. 
 
 Slitting rollers, or those intended for dividing plates of iron 
 into narrow rods, are formed with elevated rings upon their 
 circumferences, which reciprocally enter between each other, 
 their edges being angular and passing in close contact with 
 each other, so as to cut like shears. These rings are separate- 
 ly made, so that they can be removed from the rollers for the 
 purpose of sharpening them, when necessary. 
 
 Wire Drawing. — The manufacture of wire consists in 
 drawing a piece of metal through a conical hole, in a steel plate, 
 which forms it into a regular cylindrical filament. The size 
 of this filament may be reduced, and the length extended, in- 
 definitely, by passing it through successive holes, which grad- 
 ually diminish in diameter. 
 
 To prepare the iron for drawing, it is first subjected to the 
 action of the hammer, till it is reduced to a size that will ad- 
 mit of its being drawn through the plate. Sonaetimes the iron 
 is prepared by rolling, but the best wire is produced when the 
 metal has been thoroughly hammered. 
 
 The rod of iron which has been prepared in this manner is 
 next drawn through one of the larger holes in the steel plate. 
 Various machines are employed to overcome the resistance 
 
ARTS OF METALLURGY. 423 
 
 which the plate opposes to the compression and passage of the 
 wire. In general, the end of the wire is held by pincers, and 
 as fast as the wire is drawni tlirough the plate, it is wound upon 
 a roller by the action of a Avheel and axle, or other power. 
 Sometimes a rack and pinion is eraplo3^ed for this purpose, and 
 sometimes a lever which acts at intervals, and takes fresh hold 
 of the w^ire each time that the force is applied. 
 
 The finer kinds of wire are made from the larger by repeat- 
 ed drawings, each of wdiich is performed through a smaller 
 hole than the preceding. As the metal becomes stiff and hard 
 b)?^ the repetition of this process, it is necessary to anneal it from 
 time to time, to restore its ductility. It is also occasionally 
 immersed in an acid liquid, to loosen the superficial oxide 
 which is formed in the process of annealing. 
 
 Nail Making. — Nails are made both by hand, and by ma- 
 chinery. Wrought nails are made singly at the forge and 
 anvil, by workmen who acquire from practice great despatch 
 in the operation. Machines have been made for making these 
 nails perfectly, and with rapidity ; yet they have not come into 
 general use, owdng to the cheapness of the product by manual 
 labor. Cut nails are made almost wholly by machinery, in- 
 vented in this country. The iron, after having been rolled 
 and slit into rods, is flattened into plates of the thickness intend- 
 ed for the nails, by a second roUing. TJie end of this plate is 
 then presented to the nail machine, by a workman, who turns 
 the plate over once for every nail. The machine has a rapid 
 reciprocating motion, and cuts off at every stroke a wedge- 
 shaped piece of iion, constituting a nail without a head. This 
 is immediately caught near its largest end, and compressed be- 
 tween gripes. At the same time a strong force is applied to a 
 die at the extremity, which spreads the iron sufficiently to form 
 a head to the nail. Some nails are made of cast-iron, but 
 these are always brittle, unless afterw-ards converted into mal- 
 leable iron by the requisite process. 
 
 Gun Making. — Cannon, carronades, &c., whether of iron 
 or brass, are cast in sand, and afterwards bored. Muskets and 
 
424 
 
 ARTS OF METALLURGY. 
 
 fowling-pieces are forged from bars of malleable iron. The 
 bar is first flaltened by hammeiing, till it attains the requisite 
 width. It is then made into a tube by turning it over a man- 
 drel, or cylindrical rod, of a size which is smaller than that of 
 the intended bore. The edges are made to overlap each oth- 
 er about half an inch, and are firmly welded together. The 
 whole is then consolidated and strengthened, by hammering it 
 for some time in semicircular grooves on a swage, or anvil, 
 which is furrowed for the purpose. To render the barrel 
 smooth on the inside, and perfectly true, it is afterwards bored 
 out with an instrument somewhat larger than the mandrel; 
 and several such instruments of diflferent sizes are employed in 
 succession. The breech of the barrel is closed by a strong 
 plug which is firmly screwed in at the extremity. The pro- 
 jecting parts of the barrel, such as the sight, and the loops 
 which confine it to the stocks, are soldered on. The construc- 
 tion of the lock, and other appendages, is readily understood 
 from inspection. 
 
 Steel. — When malleable iron is recombined with carbon in 
 a much smaller proportion, it forms steel. Different methods 
 are followed to form this combination. The product varies 
 according to the method pursued, and is also affected by the 
 introduction of other substances into the combination. The 
 best steel is made from Swedish and Russian iron. 
 
 The general method of forming steel, is by the process of 
 cementation. A furnace is constructed of a conical form, in 
 which are two large cases, or troughs, of fire brick, capable of 
 holding some tons of iron. Beneath these is a long grate, on 
 which the fuel is placed. On the bottom of the case is placed 
 a layer of charcoal dust ; over this a layer of bars of malleable 
 iron ; over this, again, a layer of charcoal powder ; and the 
 series of alternate layers of charcoal and iron, is thus raised 
 to a considerable height. The whole is covered with clay to 
 exclude the air ; and flues are carried through the pile from the 
 furnace, so as to communicate the heat more completely and 
 equally. The fire is kept up for eight or ten days. The pro- 
 
ARTS OP METALLURGY. 425 
 
 gvess of the cementation is discovered by withdrawing a bar, 
 called the test har^ froman aperture in the side. When 
 the conversion of iron into steel, appears to be complete, the 
 fire is extinguished, the whole is left to cool for six or eight 
 days longer, and is then removed. 
 
 The iron prepared in this manner, is named blistered steely 
 from the blisters which appear on its surface. To render it 
 more perfect, it is subjected to the action of the hammer, in 
 nearly the same manner which is practised with forged iron : 
 it is beat very thin, and is thus rendered more firm in its tex- 
 ture, and more convenient in its form. In this state it is often 
 called tilted steel. When the bars are exposed to heat in a 
 furnace sufficient to soften them, and afterwards doubled, 
 drawn out, and welded, the product is called shear steel. Cast 
 steel is made by fusing bars of common blistered steel with a 
 flux of carbonaceous and vitreous substances, in a large cruci- 
 ble, placed in a wind furnace. When the fusion is complete, it 
 is cast into smaU bars or ingots. Cast steel is harder and 
 more elastic, has a closer texture, and receives a higher polish, 
 than common steel. It is capable of still farther improvement 
 by being subjected to the action of the hammer.* 
 
 Steel is generally prepared from malleable iron. It can also 
 be formed from crude cast-iron, as in Mr Lucas' method here- 
 after described. Several varieties of cast-iron have been used 
 for this purpose. The crude iron from certain ores, as the 
 sparry ii'on ore, is capable of this conversion. The steel thus 
 obtained, is named natural steel, but is inferior to that obtained 
 by cementation. 
 
 Alloys of Steel. — Messrs Stodart and Faraday have suc- 
 ceeded in making some useful alloys of steel with other metals, t 
 
 * Writers differ in regard to the proportion of carbon contained in cast steel. 
 Mr Buttery, in Ure's Dictionary, states that the amount is less than in common 
 steel, and that no charcoal is added in making it. He also states that it does 
 not melt at a welding temperature, but falls to pieces like sand, under the ham- 
 mer, and the parts refuse to become again united. 
 
 t Philosophical Transactions, for 1823. 
 
 54 
 
426 ARTS OF METALLURGY. 
 
 Their experiments induced them to beheve that the celebrated 
 Indian steel called ivootz, is an alloy of steel with small quanti- 
 ties of sihcium and aluminum ; and they succeeded in prepar- 
 ing a similar compound, possessed of all the properties of wootz. 
 They ascertained that silver combines with steel, forming an 
 alloy, ^vhich, although it contains only 1 -500th of its weight of 
 silver, is superior to wootz, or to the best cast steel in hardness. 
 The alloy of steel vAth. 100th part of platininn, though less 
 hard than that with silver, possesses a greater degree of tough- 
 ness, and is therefore highly valuable when tenacity as well as 
 hardness is required. The alloy of steel with rhodium even 
 exceeds the two former in hardness. The compound of steel 
 with palladium, and of steel with iridium and osmium, is like- 
 wise exceedingly hard ; but these alloys cannot be applied to 
 useful purposes, owing to the rarity of the metals of which they 
 are composed. M. Berthier has also produced a useful alloy 
 b}^ combining with the steel a small portion of chromium. 
 
 Case Hardening: — The process of case hardening consists 
 in converting the sujface of iron into steel, and is used for giv- 
 ing a superficial hardness to various instruments. It is effect- 
 ed by inclosing the article which is to be case hardened, in a 
 box with some carbonaceous substance, usually animal charcoal, 
 and exposing it to heat, until the surface is converted into steel. 
 The sanie term is sometimes im properly "appKed to the method 
 of chill casting, which has been already mentioned. 
 
 Tempering. — The most remarkable, as well as the most 
 useful of the properties of steel, is the power which it has of 
 changing permanently its degree of hardness, by undergoing 
 certain changes of temperature. No other metal, says Thenard, 
 is known to possess this property, and iron itself acquires it 
 only when it is combined with a minute portion of carbon. 
 If steel is heated to redness, and suddenly plunged in cold wa- 
 ter, it is found to become extremely hard, but at the same time, 
 it is too brittle for use. On the other hand, if it be suffered to 
 cool very gradually, it becomes more soft and ductile, but is 
 deficient in strength. The process of tempering is intended 
 
ARTS OP METALLURGY. 427 
 
 to give to steel instruments a quality intermediate between 
 britileness and ductility, which shall insure them the proper 
 degree of strength under the uses to which they are exposed. 
 For this pui'pose, after the steel has been sufficiently hardened^ 
 it is partially softened, or let down to the proper temper, by 
 heating it again in a less degree, or to a particular temperature, 
 suited to the degree of hardness required ; after which it is 
 again plunged in cold water. 
 
 DifTerent methods have been pursued, for determining the 
 temperature proper for giving the requisite temper to different 
 instruments. One method is to observe the shades of color 
 which appear on the surface of the steel, and succeed each other 
 as the temperature increases. Thus at 430 degrees of Fah- 
 renheit, the color is pale, and but slightly inclining to yellow. 
 This is the temperature at which lancets are tempered. At 
 450 degrees, a pale straw color appears, which is found suita- 
 ble for the best razors and surgical instruments. At 470 de- 
 grees a full yellow is produced, suitable for penknives, common 
 razors, (fee. At 490 degrees, a brown color appears, which is 
 used to temper shears, scissors, garden hoes, and chisels intend- 
 ed for cutting cold iron. At 510 degrees, the brown becomes 
 dappled with purple spots, which show the proper lieat for 
 tempering axes, common chisels, plane irons, (fee. At 530 
 degrees, a purple color is established, and at this degree the 
 temper is given to table knives and large shears. At 550 de- 
 grees, a bright blue appears, used for swords and watch 
 springs. At 560 degrees, the color is a full blue, and is used 
 for fine saws, augers, &c. At 600 degrees, a dark blue, ap- 
 proaching to black, has become settled, and is attended with 
 the softest of all the grades of temper, used only for the larger 
 kinds of saws. 
 
 Another method of giving the requisite temper has been 
 practised upon various articles. The pieces of steel are cover- 
 ed with oil or tallow, or put into a vessel containing eithei- of 
 these ingredients, &nd heated over a modeiate fire. The ap- 
 pearance of the smoke from the oil or tallow, indicates the de- 
 
428 2\.RTS OF METALLURGY. 
 
 gree of heat. If the smoke just appear, the temper corresponds 
 with that indicated by the straw color when the metal is heat- 
 ed alone. If so much heat is applied that a black smoke arises, 
 this points out a different degree of hardness ; and so on, till 
 the vapor catches flame. By this method, a number of pieces 
 may be done at once, with comparatively little trouble, and the 
 heat is also more equally aj)plied. 
 
 A still more accurate method of producing any desired de- 
 gree of temper, is to immerse the steel in some fluid medium, 
 the temperature of which is kept regulated by the thermome- 
 ter. Thus oil, which boils at about 600 degrees, may be used 
 for this purpose at any degree of heat which is below that 
 number of degrees. Mr Parkes has recommended the em- 
 ployment of metallic baths, chiefly composed of lead and tin, 
 in different proportions, which pass into fusion at definite tem- 
 peratures, and which can be used for tempering steel, as soon 
 as they arrive at their melting points.* t 
 
 * The following table of metallic baths is given in Parkes' Chemical Es- 
 says, Appendix to vol. ii. 
 
 No. Edge Tools to be tempered in the various 
 
 Baths. 
 
 1 Lancets, in a Bath composed of 
 
 2 Other surgical instruments 
 
 3 Razors, &c. 
 
 4 Penknives and some implements of 
 
 surgery 
 
 5 Larger penknives, scalpels, &c. 
 
 6 Scissors, shears, garden hoes, cold 
 
 chisels, &c. 
 
 7 Axes, firmer chisels, plane irons, 
 
 pocket knives, ifcc. 
 
 8 Table knives, large shears, &c. 
 
 9 Swords, watch springs, &c. 
 
 10 Large springs, daggers, augers, small 
 
 fine saws, &c. 
 
 11 Pit saws, hand saws, and some par- 
 
 ticular springs 
 
 12 Articles which require to be still 
 
 somewhat softer 
 t Formerly, no man in Great Britain knew how to temper a sword in 
 
 Composition 
 
 Temper. 
 
 of the Bath. 
 
 Fahren. 
 
 7 lead 4 tin 
 
 420° 
 
 7^ lead 4 tin 
 
 430 
 
 8 lead 4 tin 
 
 442 
 
 8^ lead 4 tin 
 
 450 
 
 10 lead 4 tin 
 
 470 
 
 14 lead 4 tin 
 
 490 
 
 19 lead 4 tin 
 
 509 
 
 30 lead 4 tin 
 
 530 
 
 48 lead 4 tin 
 
 550 
 
 50 lead 2 tin 
 
 558 
 
 Boiling linseed oil 
 
 600 
 
 Melting lead 
 
 612 
 
ARTS OF METALLURGY. 429 
 
 Cutlery. — Under the head of cutlery, are comprehended 
 numerous instruments, designed for cutting or penetration, and 
 which are made of steel, mostly by the processes of forging, 
 tempering, grinding, and polishing. The inferior kinds of 
 cutlery are made of blistered steel welded to iron. Tools of 
 a better quality are manufactured from shear steel, while the 
 sharpest and most delicate instruments, are formed of cast 
 steel. 
 
 The first part of the process consists in forging, and is varied 
 according to the kind of article to be formed. Common table 
 knives, have the blade forged of steel, and welded to a piece 
 of iron, out of which the shoulder, and part which enters the 
 handle, are made, the sliape being given to them by hammer- 
 ing in a die antl swage. They are afterwards tempered and 
 ground. Forks are made by forging the shank, and flatten- 
 ing the other end to the length intended for the prongs. The 
 prongs are made by stamping the metal at a white heat, be- 
 tween two dies, the uppermost of which is attached to a heavy 
 weight, and falls from a height. The shape is thus given to 
 the fork, leaving, however, a flat thin piece of metal between 
 
 such a way that it would bend for the point to touch the heel and spring 
 back again uninjured, except one Andrew Ferrara, who resided in the 
 Highlands of Scotland. The demand which this man had for his swords 
 was so great, that he employed workmen to forge them, and spent all his 
 own time in tempering them ; and found it necessary, even in the day time, 
 to work in a dark cellar, that he might be better able to observe the pro- 
 gress of the heat, and that the darkness of his workshop might favor him 
 in the nicety of the operation. 
 
 The swords which were formerly in the highest repute, were made at 
 Damascus in Syria. The method by which these were made, has long been 
 lost, or perhaps it was never thoroughly known to Europeans ; but from their 
 striated appearance, it has been supposed that they were formed by alternate 
 layers of extremely thin plates of iron and steel, bound together with iron 
 wire, and then firmly cemented together by welding. These weapons never 
 broke, even in the hardest conflict, and retained so powerful an edge, as to 
 be capable of cutting through armor. Various other explanations have 
 been given in regard to the character and structure of the Damascus, or 
 damasked, steel. 
 
430 ARTS OP METALLURGY. 
 
 the prongs, which is aftenvards cut out with a fly press. They 
 are subsequently filed, bent, hardened, and pohshed. 
 
 Blades of penknives are forged from the end of a rod of 
 steel, and cut off, togeiher with metal enough to form the joint. 
 The small recess in which the nail is inserted to open the 
 knife, is made with a curved chisel, while the steel is hot. 
 Razoi's are forged from cast steel, much in the same manner 
 as knives. The anvil is commonly a little rounded at the 
 sides, for the purpose of making the sides of the razor a little 
 concave, and the edge thinner. In forging scissors, the shape 
 is given to the different parts, by hammering them upon differ- 
 ent indented surfaces, called bosses. The bows, which receive 
 the finger and thumb, are made by punching a hole in the metal, 
 and enlarging it by hammering it round a tool, called a beak 
 iron. The halves are finished by fiUng and grinding, and 
 afterwards united by a joint. iSaws are made from steel plates 
 rolled. for the purpose, and have their teeth cut, and finished 
 by filing, and set by a suitable instrument. Axes, adzes, and 
 other large tools, are forged from iron, and have a steel piece 
 welded on, of the proper size to form the edge. 
 
 To enable the steel to be wrought, it is brought to its softest 
 state, but after the shape is given to the instrument, the steel 
 is hardened and tempered by the methods already described. 
 The remaining part of the manufacture consists in grinding, 
 polishing, and setting the instrument, to produce a smooth sur- 
 face and a sharp edge. The grinding is performed upon stones 
 of various kinds, among which freestone is perhaps the most 
 common. These stones are made to revolve by machinery, 
 and move with prodigious velocity, so that ihe surface, in some 
 cases, passes over six or seven hundred feet in a second, and 
 stones have been burst by their own centrifugal force. For 
 grinding flat surfaces, like those of saws, the largest stones are 
 used ; while for concave surfaces, like the sides of razors, smaller 
 stones are used on account of their greater convexity. The 
 internal surfaces of scissors, forks, &c. which cannot be applied 
 
ARTS OF METALLURGY. 431 
 
 to the stone, are ground with sand and emerj^, applied with in- 
 struments of wood, leather, and other elastic substances. The 
 last polish is given by the impure oxide of iron, called colcothar 
 crocus, and by the Fj'ench Rouge (T Angleterre. The edges 
 are lastly set with Irones and whetstones, according to the de- 
 gree of keenness required. The test used by cutlers for de- 
 termining the goodness of the edge and point of a lancet, is, 
 that it shall pass through a piece of soft leather without sensible 
 resistance. Needles are polished by tying them in large bun- 
 dles with emery and oil, and rolling them under a heavy plank 
 till they become smooth by mutual attrition. The shape is 
 previously given, and the eye made with a steel punch. 
 
 A process has been invented by Mr Lucas, for converting 
 edge tools, nails, &c., made of cast-iron, into good steel. It 
 consists in stratifying the cast articles, in cylindrical metallic 
 vessels, with native oxide of iron, and then submitting the 
 whole to a regular heat in a furnace built for the purpose. It 
 is not, however, necessary that the oxide employed should be 
 a native oxide, any artificial oxide being equally effectual. 
 
 The cast-iron, of which this cutlery is made, is brittle in the 
 first instance, Uke other cast-iron, in consequence of the carbon 
 contained in it ; but the great heat which it undergoes, aided 
 by the pulverized oxide, separates a part of the carbon. This 
 uniting with the oxygen of the ground oxide of iron, is dissipated 
 in the state either of carbonic oxide, or carbonic acid gas, and 
 the articles are then converted into a state nearly similar to that 
 of good cast steel cutlery. They do not, however, receive so 
 fine an edge, and do not bear hardening and tempering in the 
 common manner. 
 
432 ARTS OF METALLURGY. 
 
 Murray's System of Chemistry, 4 vols. 8vo. 3806; — Parkes' 
 Chemical Essays, 2 vols. 8vo. 1823; — Gray's Operative Chemist, 8vo. 
 1828 ; — Dumas, TraiU de Chimie Appliquee aux Arts, &fc. 4 tom. 8vo. 
 1828-9; — FouRCROY, Systeme des Connaissances Chimiques, 31 tom. 
 1801 ; — Aiken's Dictionary of Chemistry and Mineralogy, 2 vols. 4to. 
 1807; — Martin's Circle of Mechanic Arts, 4to. 1818 ; — Emporium of 
 Arts and Sciences, Philadelphia, 1812-14; — Franklin Journal, Phila- 
 delphia, 1826, and after; — Rees' Cyclopedia, various heads ; — Ure's 
 Dictionary of Chemistry ; — Thenard, Traite de Chimie, 5 tom. 8vo. 
 1824 ; — Works of Bergman, Klaproth, Lewis, &lq,. 
 
CHAPTER XVm. 
 
 ARTS OF COMMUNICATING AND MODIFYING COLOR. 
 
 An extensive branch of industry has for its object the effect- 
 ing of changes in the natural colors of bodies. The artificial 
 modifications, produced in color, may be either mechanical and 
 superficial, or chemical and intrinsic. In painting, gilding, and 
 similar processes, the original color of a substance is not alter- 
 ed, but it is mechanically concealed by another substance which 
 covers it from view. On the other hand, in bleaching and 
 dyeing, the color of the v\^hole substance is intrinsically chang- 
 ed, by a chemical action. This difference of character has 
 given rise to distinct arts in coloring, the processes of which are 
 for the most part dissimilar. 
 
 OF APPLYING SUPERFICIAL COLOR. 
 
 Painting. — Common painting, when disconnected with de- 
 sign, has for its object to produce a uniform and permanent 
 coating upon surfaces, by applying to them a compound, which 
 is more or less opaque. In many cases painting is applied 
 only for ornament, but it is more frequently employed to pro- 
 tect perishable substances from the changes to which they wcs 
 liable when exposed to the atmosphere, and other decomposing 
 agents. The effect and durability of different coverings em- 
 ployed in this way, depends upon the kind of pigment used, 
 and still more upon the vehicle, or uniting mediunj, by the in- 
 tervention of which it is applied. 
 
 Colors. — The coloring substances, employed by painters, 
 comprise a great variety of articles derived from the mineral, 
 55 
 
434 ARTS OP COMMUNICATING 
 
 yegetable, and animal kingdoms. They are employed in a 
 fstate of minute subdivision, and commonly mixed with a fluid 
 "which is more or less viscid and tenacious. When appUed 
 upon the surface of canvass, wood, or other bodies, they com- 
 imunicate their color, by covering and concealing the original 
 color of the surface, while they substitute their own in stead. 
 Those which are perfectly opaque, are called body colors, such 
 as white lead, and vermilion ; while those which are partially 
 pellucid, are called transparent colors, as prussian blue, terra 
 di sienna, and lake. Transparent colors do not wholly conceal 
 the colors beneath them, but produce the combined effect of 
 the two. The process called by painters glazing, consists in 
 laying a transparent color over one of a different tint. Trans- 
 parent colors are sometimes mixed with a white earth, to give 
 them a body, where it is necessary to cover entirely the pre- 
 vious surface. Common whiting is usually employed for this 
 purpose. 
 
 The following list comprises the principal coloring substan- 
 ces, used as paints, exclusive of those which belong only to 
 the art of dyeing. 
 
 Blues. — TJltramarine is the richest and most durable of all the blues. 
 It is not altered by time, and bears exposure to a red heat without 
 changing its color. It is made only from the lapis lazuli, a stone 
 brought from several parts of Asia, which bears an extremely high 
 price. 
 
 Prussian Hue is a strong and durable color. In the present language 
 of chemistry, it is a ferrocyanate of the peroxide of iron. It is made 
 iom blood, and other animal matters, dried and heated to redness with 
 ai equal weight of pearl-ash. The residue, which consists chiefly of 
 'Cyanuiet of potassium, and carbonate of potass, is dissolved in water, 
 and after being filtered, is mixed with a solution of alum and proto- 
 sulphate of iron. A greenish precipitate ensues, which, by exposure 
 to the atmosphere, passes through different shades, till it arrives at a 
 fine blue color. 
 
 Blue verditer is a nitrate of copper combined with hydrate of lime. 
 It is made by adding quicklime to a solution of copper in nitric acid, 
 and mixing the precipitate with a small portion more of lime. It is a 
 full blue, much used in paper staining, but is liable to grow dull. 
 
AND MODIFYING COLOR. 435 
 
 Smalt is a powdered glass, which derives its blue color from the 
 oxide of cobalt. It is chiefly used by strewing it on a ground of some 
 other color. 
 
 Bice consists of smalt finely levigated. It is rather lighter, and 
 very durable, but not extensively used. 
 
 Lidigo is the deepest of all the blues in common use. It is very 
 durable, but more u^ed in dyeing (which see) than in painting. Stone 
 blue, Fig blue, Qween'^ blue, &c., consist of indigo reduced by starch. 
 
 Reds. — Vermilion is a bisulphuret of mercury, formed by fusing 
 sulphur with about six times its weight of mercury, and subliming in 
 close vessels. The product is called Cinnabar, and, when powdered, 
 vermilion. It is of a bright scarlet color, and stands tolerably well. 
 
 Red lead, otherwise called minium, is a deutoxide of lead, formed by 
 exposing lead, or litharge, to heat in a furnace, in open vessels, with a 
 current of air passing over it. The metal is gradually converted into 
 an oxide of a bright orange red. Red lead is extensively consumed 
 in the manufacture of flint glass. As a pigment, it is brilliant at first, 
 but liable in time to turn black. 
 
 Chrome red is a fine scarlet, formed by boiling carbonate of lead 
 with an excess of chromate of potass. By Dulong's method, 67 parts 
 of white lead are boiled with 82~parts of chrome yellow, in water. 
 
 Colcothar, also called crocus martis, and rouge d' angleteiire, is an un- 
 pure brown red oxide of iron which remains after the distillation of 
 the acid firom sulphate of iron. It forms a dm'able color, but is most 
 used by artists in polishing glass and metals. 
 
 Ochres. — The ochres are various earths containing iron in a greater 
 or less degree of oxidation. Venetian red is a coarse ochre of a dark 
 red color. Indian red is an ochre brought from the East Indies, and 
 has a shade inclining to purple. Red ochre is formed from yellow ochre 
 by exposing it to heat. Burnt sienna is made from the raw terra 
 di sienna by exposure to heat, by which process its color is changed 
 from yellow to red. Bole is a fine clay, colored by oxide of iron, of 
 which there are many varieties, from yellowish red to brown. 
 
 Carmine, the most beautiful of aU the reds, is an animal substance 
 made from the cocliineal insect, or coccus cacti. It is deposited fi.-om 
 a decoction of powdered cochineal in water, to which alum, carbonate 
 of soda, or oxide of tin is added ; but the preparation of tlie finest va- 
 rieties is kept secret by the manufacturers, and probably depends much 
 upon the delicacy of the manipulations. A fine color is said to be 
 made by adding acetic acid to a solution of carmine in ammonia. 
 
 Lakes of various shades are formed fi-om cochineal precipitated by 
 salts of tin, and other agents. Beautiful lakes are also prepared fi-om 
 madder, by a process of Sir H. Englefield, in which the coloring sub- 
 
4ot) ARTS OF COMMUNICATING 
 
 stance is precipitated from an infusion of madder, by adding solutions 
 of alum, and carbonate of potass. The lake called rose pink, is an 
 extract of Brazil wood, mixed with whiting and alum. 
 
 Rouge is made from the flowers of the Carthamus tinctorius, or 
 Dyer's saffron, also called safflower ; by dissolving an alkali in the in- 
 fusion, and precipitating the coloring matter by lemon juice. It is 
 very fugacious. Under the same name other pigments are also used. 
 
 Yellows. — Gamboge is the concrete juice of a tree growing in the 
 East Indies, (Stalagmitis cambogioides.) It is externally of a dull 
 orange color, but becomes of a bright yellow, when wet, or thinly 
 spread upon a white surface. It is partially soluble in water and alco- 
 hol, and is chiefly used in water colors. 
 
 Orpiment is a sulphuret (sesquisulphuret) of arsenic. The paint 
 called king^s yelloiv, is made from this substance, or from its constitu- 
 ents. It is a brilliant, but not very durable color, and its use is in 
 some cases dangerous to the health. 
 
 JVaples yelloiv is prepared by exposing lead and antimony with pot- 
 ass, to the heat of a reverberatory furnace. It stands tolerably well 
 but turns black upon the contact of iron. A native pigment of this 
 kind is also obtained from a species of lava. 
 
 Yellow ochre is a native earth, the finer particles of which, are sepa- 
 rated by washing, as in similar substances. Although not very bright, 
 its cheapness and durability have caused it to be extensively used. 
 
 Terra di sienna is also an ochre, of a deeper and brighter yellow 
 than most of the others. 
 
 Massicot, or masticot, is the protoxide of lead, prepared by collecting 
 the gray film which floats upon the surface of melted lead, and ex- 
 posing it to heat and air until it assumes a yellow color. 
 
 Chrome yellow is a chromate of lead. It is precipitated by adding 
 chromate of potass in solution, to a solution of nitrate, or acetate, of 
 lead. It forms one of the most brilliant yellows, and is extensively 
 manufactured in this country, from the chromate of iron found near 
 Baltimore. 
 
 Turpeth mineral is a subsulphate of mercury, or rather a sub-bisul- 
 phate. It is a pale yellow, and moderately durable. 
 
 Patent mineral yelloiv is a fused muriate of lead, made by decompos- 
 ing common salt by means of litharge, triturating the product with 
 water, washing away the soda, and drying and fusing the muriate. 
 
 Dutch pink is a cheap color used by paper stainers, composed of 
 [whiting colored by a decoction of dyers' wood, quercitron, or French 
 berries, with alum. 
 
 Greens. — Verdigris is an acetate of copper, or strictly, an impure 
 jicetate of the peroxide of copper. It is manufactured in the south of 
 
AND MODIFYING COLOR. 437 
 
 France by covering plates of copper with the refuse of the grapes, 
 after making wine. It may also be formed by exposing copper to the 
 vapor of vinegar. 
 
 Terra verte is a native blue-green ochre. It is semitransparent and 
 durable, but not very bright. 
 
 B)-unsivick gi-een, called also mineral green, is an ammoniaco-muriate 
 of copper, much used for paper hangings, and occasionally in oil paint- 
 ing. 
 
 Sap green IS \\\e inspissated juice of the berries of the buckthorn, 
 {Rhamnus catharticus.) It is semitransparent, and chiefly used in wa- 
 ter colors. 
 
 Many of the greens in common use are compound colors, made by 
 the admixture of blue with yellow. 
 
 Browis's. — Umber is a light brown ochre. Burnt umber is the same 
 substance, having, its color darkened by exposui-e to heat. It is dura- 
 ble in both states. 
 
 Spanish brown is a coarse durable ochre, its color inclining to red. 
 
 Bistre is prepared from common soot of wood, by pulverizing and 
 washing. The soot of the beech is said to afford the best. 
 
 Asplialtum is prepared from the bituminous substance of that name. 
 When dissolved in oil of turpentine, it is semitransparent, and is used 
 as a glaze. 
 
 Ox gall consists of the biliary concretions found in the gall bladder 
 of cattle. It is not soluble in water or alcohol, but dissolves readily in 
 a solution of potass. It is of a yellowish brown, and is much valued 
 for the brightness and permanence of its tint. The liquid ox gall is 
 used by painters to facilitate the laying on of colors. 
 
 Blacks. — Lamp black is a light carbonaceous substance, thrown off 
 during the combustion of resinous and oily substances. The chips of 
 fir and pine trees are burnt under tents, to the inside of which the 
 lamp black adheres. 
 
 Frankfort black. This is a charcoal made from the lees of wine. It 
 is used in the ink of copper plate printers. 
 
 Ivory black, called also Cologne black, is made from the shavings and 
 dust of ivory, heated in covering iron pots. Various other carbonace- 
 ous colors are made from cork, vine twigs, peach stones, &c., converted 
 into charcoal. 
 
 Indian ink is said to be made from different sorts of lamp black, mix- 
 ed with water and glue. The black is obtained from the smoke of oil, 
 of fir wood, or of horse chesnuts. A solution of lac with borax, in wa- 
 ter, is said to be the vehicle of the lamp black in some kinds. 
 
 (Sepia is the black liquid obtained from the cuttle fish. It is of a viscid 
 consistence, and is presei-ved by drying it upon saucers or shells. 
 
4d0 ARTS OF COMMUNICATING 
 
 Whites. — White lead, formerly ceruse, is a carbonate of lead, pre- 
 pared by exposing- coils of sheet lead, in earthen pots, to the vapor of 
 vinegar for several weeks. It is sometimes also formed by precipita- 
 tion with carbonic acid from a solution of acetate of lead in water. 
 
 Flake white consists of the densest and thickest scales, which are 
 separated in making the foregoing article from sheet lead. It is very 
 pure, whereas the white lead of commerce is adulterated with chalk. 
 
 Pearl ivhite is the subnitrate of bismuth, formerly called magistery 
 of bismuth, precipitated by water from its solution in nitric acid. It 
 has been used as a cosmetic, but grows yellow by age and light. 
 
 Whiting. — Common chalk separated in the form of an impalpable 
 powder by washing-. Blanc de Troyes is similar to whiting. 
 
 Zinc white is the oxide of zinc. It does not work easily, but is 
 thought very durable. Various marls and clays from Bougival, Rouen, 
 Moudon, &c., are used for white pigments. 
 
 Preparation. — Coloring substances, before being used in 
 painting, require to be reduced to a state of extreme fineness. 
 For this purpose they are ground in a color mill, and levigated 
 with a stone and mailer. In many cases, colors ^?llicll are 
 insoluble in water, are separated by washing, the water being 
 first made turbid with the coloring substance, and left to stand 
 a short time, till the coarser particles have subsided. The up- 
 per part of the fluid with the finer particles in suspension is 
 then poured off, and the second deposit which takes place from 
 this is sufficiently fine for mixing. When a greater degree of 
 tenuity is required, the washing is repeated. 
 
 Ap'plication. — As colors are first prepared for use by simply 
 reducing them to powder, it is necessary tliat some tenacious 
 fluid should be introduced to make their particles adhere to the 
 surface on which they are spread. To effect this end, various 
 fluids ai'e employed, and the difference of the material used, 
 with the method of employing it, has given rise to the modes 
 of painting in water, in oil, in fresco, in distemper, &c. 
 
 Crayons. — The most simple mode of applying colors is by 
 the use of crayons. Crayons are cylindeis, or sticks of dry 
 colors, cemented into a friable mass like chalk, by the assist- 
 ance of gum or size, and sometimes of clay. They are used 
 
AND MOCIFYING COLOR. 439 
 
 by simply rubbing them upon papei-, and afterwards blending 
 and softening the shades by means of a sticmp^ or small roll of 
 leather, or paper. But drawings in crayons and chalks, have 
 always the disadvantage that they do not adhere to the paper, 
 but are rubbed off, and defaced, with the slightest attrition. In 
 this state they can be safely kept and examined only in frames 
 under glass. Various modes have been practised for fixing 
 crayon drawings upon paper, so as not to be liable to deface- 
 ment. Among other means, this end may be eflfected by 
 brushing the back of the paper with a strong solution of isiu- 
 glass, or by passing the drawing through a powerful press, in 
 contact with amoist paper. 
 
 Watej' Colors. — The most common mode of painting on 
 paper, is by the use of water colors. These are formed into 
 hard cakes or lozenges with a larger quantity of gum, than is 
 employed for crayons. When used, they are rubbed down 
 with water upon glass, or a glazed surface, and applied while 
 wet with a camels' hair pencil. The gum with which they 
 are mixed causes them to adhere so closely to the paper that 
 they cannot be rubbed off. 
 
 Distemper. — Painting in distemper is used for works to be 
 executed upon a larger scale, such as stage scenery, the walls 
 of apartments, &-c. The c<^ors are used in the form of pow- 
 der, and are mixed with water rendered glutinous by size, or 
 other solutions of animal glue. The mixture requires, in many 
 cases, to be used warm, as the solution becomes stiff upon cool- 
 ing. Skimmed milk also serves as a vehicle for painting in dis- 
 temper, and its tenacity is increased by adding small portions 
 of liuie, and of linseed or poppy oil. The mixture dries speedily, 
 the oil being converted into a soap by the lime.* Distemper 
 in hadigeon is employed by the French to restore the original 
 color to stone walls which have become brown by time ; and 
 consists in washing them with powder of the same kind of 
 stone, properly mixed. Chipolin is a varnished distemper. 
 
 * This method is highly recommended Ly Tingry, who gives the following 
 recipe. Skimmed milk 4 pounds ; lime newly slaked 6 ounces ; linseed, nut or 
 poppy oil 4 ounces ; Spanish white (wlaite clay) 3 pounds. 
 
440 ARTS OP COMMUNICATING 
 
 Fresco. — Paintings in fresco are executed upon walls re- 
 cently plastered, before they have become dry. The coloring 
 substance mixed with water being applied while the wall is 
 wet, sinks in and incorporates itself with the grain of the mor- 
 tar, so as to become very duiable. When a wall is to be done 
 in fresco, it is covered with a coating of stucco or fine mortar, 
 which is applied in successive portions, no more being put on 
 at once than can be painted before it is dry. This mode of 
 finishing by piecemeal, renders it necessary that the artist 
 should have his whole design either drawn upon paper, or thor- 
 oughly digested in his mind before he begins. The drawings 
 which are executed upon large paper to serve as patterns for 
 fresco paintings, are called cartoons. They are transferred to 
 the walls by puncturing through the outlines with a sharp 
 point.* Many of the greatest works of the most eminent Italian 
 masters are executed in fresco, upon the walls and ceilings of 
 the different churches and cathedrals. 
 
 Encaustic Painting. — The ancients made use of a mode 
 denominated encaiistic painting, the knowledge of which at 
 the present day is lost. From the writings of Pliny it appears 
 that the material with which the colors were incorporated, was 
 wax, and that this was applied by the assistance of heat. It 
 is represented as having been very brilliant and durable, though 
 no specimens of it remain at this day. The principal paint- 
 ings which have been discovered upon the walls at Herculane- 
 um and Pompeii, appear to have been done in fresco. 
 
 Oil Painting. — Painting, in oil, which on many accounts 
 has a great superiority over other methods, was first applied to 
 the execution of designs about the year 1410, by John Van 
 Eyck, in Flanders. The oils used for painting must be of the 
 class denominated drying oils. Of these, linseed oil is the 
 kind most commonly employed, and its tendency to dry is in- 
 creased by its being boiled. Its color renders it sometimes in- 
 jurious to light tints j so that in delicate pieces it is better to em- 
 
 * Cartoons are also used as patterns in tapestry and mosaic. 
 
AND MODIFYING COLOR. 441 
 
 ploy nut oil, or poppy oil, which are nearly transparent, and do 
 not turn dark in drying. The drying of paint is owing, not 
 so much to evaporation, as to a chemical combination of the oil 
 with the pigment, especially when the latter is a metallic ox- 
 ide, or other substance, having a direct affinity for the oil. The 
 oxygen of the atmosphere appears also to enter into this com- 
 bination. The drying will be frastrated if a small quantity of 
 any fat oil be present. Hence in painting old surfaces, which 
 have been exposed to contract any greasiness, it is necessary 
 first carefully to cleanse them, or to wash them "^vith lime in 
 water, or vnth some alkalme solution, which combines with 
 the oil. The latter method is practised by house painters. 
 
 Oil paintings of designs are executed either on canvas, on 
 wood, or on copper. When the colors used are chiefly of the 
 kind denominated body colors, each successive layer conceals 
 those beneath it, so that the work may be heightened, amended, 
 or altered, at pleasure during any stage of the process. Paint- 
 ings in oil are very durable, and acquire a mellowness firom 
 age which unproves rather than injures theii* effect, provided 
 permanent colors have been used. 
 
 Painting in the large way, with uniform colors mixed in oil, is 
 employed not so much for ornament, as for the protection of 
 perishable substances from decay. Thus wood may be pre- 
 seiTed from decomposition, and metals from oxidation, for an 
 indefinite time, by keeping them covered with a thick coating 
 of paint, which is impervious to air and moisture. 
 
 Varnishing. — The name of varnishes is given to certain 
 compounds, chiefly solutions of resinous substances, which, after 
 being spread over surfaces, and dried, possess the qualities of 
 hardness, brilliancy, and transparency. They are employed 
 to give lustre and smoothness to painted surfaces, and to de- 
 fend them from the action of the air. 
 
 The principal substances which form the basis of varnishes, 
 
 are copal, mastic, anime, sandarac, lac, benzoin, amber, and 
 
 asphaltum. Of these, copal is a hard, shining, transparent 
 
 resin, of a Ught citron color, originally brought from Spanish 
 
 56 
 
442 ARTS OF COMMUNICATING 
 
 America, and erroneously considered as the product of the Rhus 
 copallmum* True copal is soluble in oil, but is difficult of 
 solution in alcohol. It is commonly made into varnish by dis- 
 solving it in hot linseed oil, rendered drying by quicklime, and 
 diluting the solution with oil of turpentine. By mixture with 
 camphor, it becomes soluble in alcohol, or in oil of turpentine. 
 Mastic is a resinous substance, in the form of tears, of a pale 
 yellow color, brittle and semitransparent. It comes from the 
 Levant, and is produced by the Pistacia lentiscus. A greater 
 part of it is soluble in alcohol and in oil of turpentine. Animi 
 is brought from Spanish America, and is said to be obtained 
 from the Hymencea courharil. It resembles copal very much 
 in its appearance, but is easily soluble in alcohol, while copal 
 is not. It is often sold under the name of copal. Sandarac 
 is the resin of the Thuya articulata, which grows in Bar- 
 bary. It resembles mastic, but is rather more transparent 
 and brittle. When chewed, it crumbles to powder, whereas 
 mastic softens in the mouth. It is soluble in alcohol and oil. 
 Lac is deposited on certain ti'ees in the East Indies, by an in- 
 sect called Coccus lacca. The substance in its natural state 
 incrusting the twigs, is called stick lac ; when broken off and 
 boiled in water, till it loses its red color, it is termed seed lac, 
 and when melted and reduced to a thin crust, it is called shell 
 lac. Stick lac has a deep red color, and yields to water a red 
 substance which is used as a dye. Lac is soluble in alcohol. 
 Benzoin is the product of the iStyrax benzoe, a tree growing 
 in Sumatra. It is a solid, brittle substance, in yellowish white 
 tears, joined together by a brown substance, and is sometimes 
 wholly brown. It is a balsam, and affords benzoic acid. Am- 
 ber and asphaltum are mineral substances, already mentioned 
 in the first chapter. 
 
 * The Rhus copalUnum is a common shrub in the United States, and is not 
 known to produce any substance resembUng copal. According to Hernandez 
 the copal of Spanish America is obtained from various trees. I am informed 
 that the copal used in this country comes almost wholly from the East Indies, 
 It is probably the produce of the Elccocarpus copalifera. 
 
AND MODIFYING COLOR. 443 
 
 Varnishes are divided into three kinds, according to the men- 
 struum in which the resinous substance is dissolved. These 
 are spirit varnishes, in which the solvent is alcohol ; essential 
 varnishes, in which a volatile oil, commonly oil of turpentine, is 
 used ; and oil varnishes, which consist of a resin dissolved in a 
 drying oil. Some vegetable juices may be applied in their 
 liquid state. Thus the viscid juice of the Rhus vernix affords 
 the celebrated black varnish used in Japan. The same shrub, 
 which grows in this country, affords a whitish juice, which, 
 upon boiling, yields a strong, glossy black varnish.* 
 
 An elastic varnish may be made by dissolving caoutchouc 
 in Unseed oil and oil of turpentine ; but this preparation dries 
 slowly. Besides the solvents mentioned in the first chapter of 
 this work, it is found that the naptha of coal tar dissolves 
 caoutchouc readily, and on drying leaves its properties un- 
 altered, t 
 
 Japanning. — Japanning is the art of varnishing in colors, 
 and is therefore a species of painting. It is most easily exe- 
 cuted upon wood and metal, or such other substances as retain 
 a determinate form, and are capable of sustaining the operation 
 of diying the varnish. Paper and leather, when wrought 
 into forms in which they remain stretched, stiff, or inflexible, 
 are common subjects for japanning. 
 
 The article to be japanned is first brushed over with two or 
 three coats of seed lac varnish, to form the priming. It is 
 then covered with varnish previously mixed with a pigment of 
 the tint desired. This is called the ground color ; and if the 
 subject is to exhibit a design, the objects are painted upon it, 
 in colors mixed with varnish, and used in the same manner 
 as for oil painting. The whole is then covered with additional 
 coats of transparent varnish, and all that remains to be done, 
 is to dry and polish it. 
 
 Japanning requires to be executed in warm apartments, and 
 
 * See American Medical Botany, vol. i. p. 101. The shrub is poisonous to 
 many persons, 
 t Annals of Philosophy, vol, xii. 
 
444 ARTS OF COMMUNICATING 
 
 the articles are warmed before the varnish is applied to them. 
 One coat of varnish, also, must be dry before another is laid 
 on. Ovens are employed to hasten the drying of the work. 
 
 The same pigments which are employed in oil or water, 
 answer also in varnish. For painting figures, shell lac varnish 
 is considered best, and easiest to work ; it is therefore employ- 
 ed in most cases where its color permits. For the lightest 
 colors, mastic varnish is employed, unless the fineness of the 
 work admits the use of copal dissolved in alcohol. 
 
 Polishing. — Pictures, and other subjects, to which only a 
 thin coat or two of varnish is given, are generally left to the 
 polish which the varnish naturally possesses, or are brightened 
 only by rubbing them with a woollen cloth when dry. But 
 whenever several coats of varnish or japan are laid on, a more 
 glossy surface can be produced, by means similar to those 
 which are used to polish metals ; the surface having first been 
 suffered to become completely dry and hard. Where the coat 
 of varnish is very thick, the surface is first rubbed with pum- 
 ice stone and oil, till it becomes uniformly smooth ; the pum- 
 ice having been previously reduced to a smooth flat face, by 
 rubbing it on freestone. The japanned or varnished surface 
 may afterwards be rubbed with pumice reduced to an impal- 
 pable powder, the workman using oil and leather to lay on 
 the powder. The finishing may be given by oil and a piece 
 of woollen only. 
 
 Where the varnish is thinner, and of a more delicate nature, 
 it may be rubbed with tripoli, or rotten stone, in fine powder, 
 finishing with oil as before. Where the ground is white, putty, 
 or Spanish white, finely washed, may be used instead of rotten 
 stone, of which the color might have some tendency to injure 
 the ground. 
 
 Lacquering. — ^Lacquering consists in the application of 
 transparent varnishes to metals, to prevent their tarnishing, or to 
 give them a more agreeable color. When the color of the me- 
 tal to be lacquered is to be changed, the varnish is tinged 
 with some coloring matter ; but where preservation from rust, 
 
AND MODIFYING COLOR. 445 
 
 or tarnish, is the sole object, any of the transparent varnishes 
 will answer, the best and hardest being used where the great- 
 est durability is required. Shell lac is the most common basis 
 of the varnishes used in lacquering. An imitation of gilding 
 is effected by covering the surface of tin or lead with a clear 
 varnish tinged with annotto, turmeric, or gamboge. The 
 Chinese gilt paper appears to be made in this manner. 
 
 Gilding. — The process of gilding on metals, described in a 
 former chapter, depends on a chemical union, or alloy, between 
 the gold and the metal to which it is applied. But gilding, as 
 it is commonly performed upon wood, leather, &c., is a me- 
 chanical process, and consists in cementing gold leaf upon 
 surfaces, for which it has no affinity. In common oil gilding, 
 the surface to be gilt is covered with an adhesive coating of 
 paint or gold size, composed of yellow ochre ground in oil. 
 When this is partially dried, so as to feel adhesive, the gold 
 leaf is laid upon it and pressed down with cotton wool. When 
 the whole surface is covered, it is left to dry, and the superflu- 
 ous gold leaf brushed off. In burnish gilding , the surface to 
 be gilt is first covered with a mixture of whiting and size, pre- 
 pared by boiling shreds of parchment or skins, in water. This 
 is rubbed smooth, and covered with a gilding size containing 
 a little ochre or Armenian bole. This is suffered to dry, and 
 is rubbed smooth with a linen rag. The gilding is then per- 
 formed by moistening successively the parts of the sized sur- 
 face with water, and applying the gold leaf before it becomes 
 dry. When the work has become firm, it is burnished by 
 rubbing it with a hard polished substance, such as agate, dog's 
 tooth, or steel. 
 
 Gilding on leather and on paper may be performed by ap- 
 plying gold leaf with gum arabic or size. The edges of paper 
 and of books are gilded with a size composed of whites of eggs, 
 beaten with three or four times their quantity of water, and 
 mixed with a httle Armenian bole. Bookbinders gild the 
 leather of books by coating it two or three times with whites of 
 eggs, and suffering it to dry. A minute quantity of tallow is 
 
446 ARTS OP COMMUNICATING 
 
 then rubbed on, and the gold leaf laid loosely upon the surface. 
 The stamps and letters are cut in brass ; or printing types are 
 used. These are moderately heated, as much as the leather 
 will bear, and are then pressed upon the gold leaf, by which a 
 portion of gold corresponding to the letters is made to adhere ; 
 after which the superfluous gold leaf is brushed off. 
 
 Shell gold is prepared by grinding up gold leaf with honey 
 until it is completely subdivided ; the honey is then washed 
 away with water, and the gold powder mixed with gum water 
 or some other adhesive fluid. It is usually kept for use on 
 shells, and is applied with a pencil or brush in the manner of 
 common painting. 
 
 OP CHANGING INTRINSIC COLOR. 
 
 The processes considered in the previous part of this chap- 
 ter, are used to produce an external modification of color, and 
 consist in mechanically covering the surfaces upon which they 
 are applied. The remaining division includes those arts which 
 depend more exclusively upon chemical processes, and which, 
 by operating on the internal texture of bodies, produce a total 
 and intrinsic change of color. Of this kind are the arts of 
 bleaching, dyeing, and calico printing. The operations, how- 
 ever, which belong to these arts, are too extensive to be con- 
 sidered in all their details in this place. 
 
 Bleaching. — Bleaching is the process by which fibrous tex- 
 tures, such as linen, cotton, silk, &c. are deprived of their col- 
 or, and rendered white. The coloring matter, which is inhe- 
 rent in vegetable fibres, appears to be of a resinous character, and 
 the effect of the operation of bleaching is to dissolve, or dis- 
 charge it. In manufactories of linen and cotton goods, the 
 yarn or cloth passes through a number of successive processes, 
 the principal of which are the steeping, in which the goods are 
 fermented in an acescent liquid at a temperature of about 100 
 degrees, Fahrenheit — the bucking and boiling, in which a 
 
AND MODIFYING COLOR. 447 
 
 hot alkaline ley is made to percolate through ihem for some 
 time — the souring, performed with dilated sulphuric acid — the 
 bleaching with chlorine, in which the stuff is exposed to the 
 action of some compound of that substance, usuaUy chloride 
 of lime called bleaching salt. Various mechanical operations, 
 washings, and repetitions of the processes, are commonly prac- 
 tised to complete the discharge of the color. Formerly the 
 process of bleaching was very tedious, and was effected by al- 
 kaline leys and by exposure to the sun and air, with frequent 
 irrigations, for many weeks. The discovery of the bleaching 
 power of chlorine has greatly abridged and simplified the pro- 
 cess. 
 
 Chemists explain the effect of chlorine in bleaching,* by 
 supposing that it unites with the hydrogen of the coloring 
 matter, and forms muriatic acid, which again acts upon the 
 color in its altered state. The acid may be detected in the 
 altered coloring matter. In bleaching, which is performed by 
 exposure to the air and moisture, it is supposed that oxygen 
 combines with the coloring matter, and renders a portion of 
 it more easy of solution, during the other parts of the pro- 
 cess. 
 
 The fibres of wool and silk are not bleached by chlorine, 
 but after being deprived of the saponaceous or gummy matter, 
 which adheres to them, are exposed to the fumes of burning 
 sulphur to discharge their color. 
 
 Dyeing. — The art of dyeing consists in impregnating cloths 
 and other flexible fabrics, with coloring substances, in such a 
 manner, that the acquired color may remain permanent under 
 the common exposures to which the stuffs may be hable. It 
 is effected by producing a chemical union between the material 
 to be dyed and the coloring matter. It is found that different 
 materials not only possess different attractions for dye stuffs, 
 but that they absorb the coloring matter in different proportions. 
 Wool appears in this respect to have the greatest attraction for 
 
 * Gay Lussac, Cours de Chimie, Lee, 30, p. 21.— Ure's Notes to Berthol- 
 let, ii. 344. 
 
448 ARTS OF COMMUNICATING 
 
 coloring' substances ; silk comes next to it, then cotton, and 
 lastly hemp and flax. 
 
 Mordants. — The coloring substances used in dyeing have 
 been divided by Dr Bancroft into substantive and adjective 
 colors. Substantive colors are those which communicate their 
 tint immediately to the material to be dyed, without the aid of 
 any third substance. Adjective colors require the intervention 
 of a third substance, which possesses a joint attraction for the 
 coloring matter and the stuff to be dyed. The substance ca- 
 pable of thus fixing the color, is called a mordarit, and by Mr 
 Henry, a basis. 
 
 The agents which are capable of acting in some way as 
 mordants, are very numerous, including many oxides and salts. 
 But those which are principally employed in practice, are the 
 acetate of alumina, the sidphate or acetate of iron, and the 
 muriate of tin. The substance, to be dyed is first impregna- 
 ted with the mordant, and then passed through a solution of 
 the coloring matter. The mordant fixes the color, and, in 
 many cases, alters or improves and heightens its tint. 
 
 Dyes. — The coloring substances capable of being used as 
 dyes, are very numerous, but a few of the most important have 
 in practice taken precedence of the rest. Indigo, madder, 
 quercitron, and some of the woods are consumed in vast quan- 
 tities by dyers, and are capable of producing an indefinite va- 
 riety of tints, under the action of different mordants. They 
 are somewhat differently treated, according as the substance to 
 be dyed is of wool, silk, or cotton. 
 
 Blue Dyes. — Indigo is the chief substance employed for giving the 
 blue dye. The best indigo is obtained from a plant cultivated in warm 
 climates, the indigo/era tinctoria. The plant is cut a short time before 
 its flowering, and put into large vats covered with water, when fer- 
 mentation spontaneously ensues, during which the indigo subsides in 
 the form of a pulverulent, pulpy matter. Its color is at first green, but 
 by exposure to the air, it absorbs oxygen and becomes blue. 
 
 Indigo is a light brittle substance, of a deep blue color, and without 
 either taste or odor. At 550 degrees Fahrenheit it sublimes, forming 
 
AND MODIFYING COLOR. 449 
 
 & violet vapor with a tint of red, and condensing into long flat acicular 
 crystals, which appear red by reflected, and blue by transmitted light. 
 The process of subliming indigo is one of considerable delicacy, owing 
 to the circumstance that the temperature at which it sublimes, is very 
 near that at which it is decomposed. Indigo, in its dry state, may be 
 preserved without change ; but when kept under water it is gradually 
 decomposed. It is quite insoluble in water and alcohol, and is attack- 
 ed by the alkalies in a partial manner. Its only proper solvent is con- 
 centrated sulphuric acid. When indigo is put into this acid, a yellow 
 solution is at first formed, which, after a few hours, acquires a deep 
 blue color. If the indigo is pure, sulphurous acid is not generated, nor 
 is the acid decomposed ; but the indigo undergoes a change, for it is 
 rendered soluble in water. To the indigo thus modified, Mr Crum has 
 applied the name cerulin, and he regards it as a compound of one atom 
 of indigo and four atoms of water. This solution properly diluted with 
 water, is employed by dyers for forming what is called the Saxon blue. 
 Mr Crum has also described another compound of indigo and water, 
 under the name of PAcenecm, because it acquires a purple color on the 
 addition of a salt. It appears to consist of one atom of indigo and two 
 atoms of water. 
 
 When indigo, suspended in water, is brought into contact with cer- 
 tain deoxidizing agents, it is deprived of oxygen, becomes green, and 
 is rendered soluble in water, and still more in the alkalies. This effect 
 is produced, for example, by sulphuretted hydrogen, by the hydrosul- 
 phuret of ammonia, by the protoxide of iron, precipitated by lime or 
 potass, or by a solution of the sulphuret of arsenic in potass. On dip- 
 ping cloth into a solution of deoxidized indigo, it receives a green tint, 
 which becomes blue by exposure to the air. This is the usual method 
 of dyeing blue by means of indigo, a color -which adheres permanently 
 to cloth without the intervention of a basis. 
 
 Woadis prepared from the leaves of the Isatis tindoria, a plant cul- 
 tivated in Europe. Gay Lussac, and others, consider it chemically as 
 a species of indigo. It is prepared by grinding, and several processes 
 of fermentation. Gloth dyed in woad liquor is at first green, but turns 
 blue on exposure to the air, in the same manner which takes place with 
 indigo. 
 
 Ited Dyes. — The chief substances which are employed for giving a 
 red dye, are madder, cochineal, archil, Brazil wood, logwood, and saf- 
 flower, all of which are adjective colors. 
 
 Madder, which is one of the most valuable drugs in the art of dyeing, 
 is the root of the Ruhia linctoruvi, a plant extensively cultivated in 
 Europe, and particularly in Holland. It is properly classed with red 
 
 57 
 
450 ARTS OF COMMUNICATING 
 
 dyes, but by the use of different mordants, it is made to produce every 
 shade of red, purple, and even black. In calico printing, apiece may 
 be stamped with several mordants, which are bases of different colors ; 
 and upon immersing it in a madder bath, as many colors will appear as 
 there are mordants used. The quality of madder is said to be improv- 
 ed by age, provided it is kept packed in casks which exclude the air. 
 Its quality is also affected by the mode of cultivating and curing it, and 
 the judgment which is used in separating the samples. 
 
 Cochineal is obtained from an insect already mentioned, which feeds 
 upon the leaves of several species of the cactus, and which is supposed 
 to derive this coloring matter from its food. It is very soluble in wa- 
 ter, and is fixed on cloth by means of alumina or the oxide of tin. Its 
 natural color is crimson, but when the bitartrate of potass is added to 
 the solution, it yields a rich scarlet dye. Cochineal, according to Pel- 
 letier and Caventou, is composed of, 1. Carminium, which is the name 
 given to the coloring matter. 2. A peculiar animal matter. 3, A fatty 
 substance. 4. Salts of lime and potass. 
 
 Archil. — The dye called archil, is obtained from a kind of lichen, 
 {lichen roccella) which grows chiefly in the Canary Islands, and is em- 
 ployed by the Dutch in forming the blue pigment called litmus or 
 iurnsol. The coloring ingredient of litmus is a compound of the red 
 coloring matter of the lichen and an alkali ; and hence, on the addition 
 of an acid, the coloring matter is set free, and the red tint of the plant 
 is restored. Litmus is not only used as a dye, but is employed by 
 chemists for detecting the presence of a free acid. 
 
 Logwood is a dense, heavy wood, derived from the Hcematoocylum 
 Campechianum, which grows in the tropical parts of America. A de- 
 coction made from this wood, is of a fine red, inclining a little to violet 
 or purple. This, if left to itself, becomes in time yellowish, and at 
 length black. The violet color of logwood is fixed by alum, and a blue 
 is obtained from it by verdigris. But the great consumption of log- 
 wood is for blacks, to which it gives a peculiar depth, and velvety lus- 
 tre. The coloring principle of logwood has been procured in a sepa- 
 rate state by M. Chevreul, who has applied to it the name of hematin. 
 It is obtained in crystals, by digesting the aqueous extract of logwood 
 in alcohol, and allowing the alcoholic solution to evaporate spontane- 
 ously. 
 
 Brazil wood is the heart, or central part of the Ccesalpinia echinata, 
 a large tree of Brazil. It produces very lively and beautiful red tints, 
 with solutions of alumina and tin, but they are deficient in permanency. 
 Sappan wood, brought from the East Indies, and JSPicaragua wood, or 
 Peackwood, from Central America, are also said to be species of Cse- 
 salpinia, and resemble BrazU wood in their properties, but yield a 
 
AND MODIFYING COLOR. 451 
 
 smaller amount of coloring matter. Brazildto and Camwood are among 
 the poorest. of the red dyes. 
 
 Safflower is the diied flowers of the Carthamus imdorius, and affords 
 a bright but fugitive red. See Rouge. 
 
 Ydloiv Dyes. — The chief yellow dyes are the quercitron bark, tur- 
 meric, hickory, weld, fustic, and safiron. They are all adjective colors. 
 
 Quercitron bark, which is one of the most important of the yellow 
 dyes, is an extract made from the bark of the Queixus tindoria, or com- 
 mon black oak of the United States, and was introduced into notice by 
 Dr Bancroft. With a basis of alumina, the decoction of this bark gives 
 a bright yellow dye. With the oxide of tin it communicates a variety 
 of tints, which may be made to vary from a pale lemon color to deep 
 orange. With the oxide of iron it gives a drab color. 
 
 Hickory. — Several species of American v/alnut or hickory, particu- 
 larly the Juglans, or Carya alba, yield a yellow dye from their bark, 
 leaves, and rinds, resembling quercitron, but less abundant in quantity. 
 
 Weld is derived from a European plant. Reseda luteola. When fixed 
 with a basis of alum, it gives a lively and permanent yellow. 
 
 Fustic is the wood of the Morus tinctoria, a tree of the West Indies. 
 It affords, with an aluminous basis, a less brilliant, but more durable 
 yellow, than the preceding articles. It is also employed to produce 
 certain greens and drab colors. 
 
 Jinnotto, otherwise called Rocou, is a soft substance prepared from 
 the seeds of the Bixa orellana, a shrub of tropical America. The col- 
 oring matter is combined with a resin which renders it difficult of solu- 
 tion in water. An alkali facilitates the solution and improves the 
 color. 
 
 Turmeric is the root of the Curcuma lonsra, a native of the East In- 
 dies. Paper, stained with a decoction of this substance, constitutes 
 the turmeric or curcuma paper employed by chemists as a test of free 
 alkali ; by the action of which it receives a brown stain. 
 
 Saffron. — The coloring ingredient of saffron ( Crocus sativus) is solu- 
 ble in water and alcohol, has a bright yellow color, is rendered blue 
 and then lilac by sulphuric acid, and receives a green tint on the addi- 
 tion of nitric acid. From the great diversity of colors which it is ca- 
 pable of assuming under different circumstances, M. M. Bouillon, 
 Lagrange, and Vogel, have proposed for it the name of Folychroite. 
 
 French Berries. — The unripe berries of the Rhamnus infedorius 
 afford a lively but fugitive yellow. 
 
 Black Dyes. — The black dye is made of the same ingredients as 
 writing ink, and therefore contains usually a compound of the oxide of 
 iron with gallic acid and tannin. From the addition of logwood and 
 acetate of copper, the black receives a shade of blue. 
 
452 
 
 ARTS OF COMMUNICATING 
 
 Galls. — The common nutgall is an excrescence produced upon an 
 Asiatic species of oak, {Quercus infedoria) by the puncture of an 
 insect, a species of cynips. It contains tannin, gallic acid, and accord- 
 ing to Dr Bancroft, a coloring matter distinct from these. Galls pro- 
 duce a black color with salts of iron, well known as the basis of wri- 
 ting ink. 
 
 Maple. — The common red maple of this country (Acer rubrum) when 
 applied with the sulphate or acetate of iron, produces, according to 
 Dr Bancroft, a more intense and perfect black than any of the common 
 vegetable dyes. With the aluminous basis, it produces a lasting 
 cinnamon color, both on wool and cotton. Both the bark and leaves 
 may be used. 
 
 Butternut. — The bark of the butternut (Juglans cathartica) affords 
 a durable brown upon cotton Avith an aluminous basis, and upon wool 
 without any mordant. 
 
 By the dexterous combination of the four leading colors, blue, 
 red, yellow, and black, all other shades of color may be procur- 
 ed. Thus green is communicated by forming a blue ground 
 with indigo, and then adding a yellow by means of quercitron 
 bark. 
 
 One of the latest improvements in the art of dyeing, consists 
 in the employment of colois derived from the mineral king- 
 dom. Prussian blue, orpiment, cliromate of lead, and other 
 mineral compounds, have by appropriate processes been made 
 to conununicate their colors to different stuffs. An abstract of 
 the processes is given in Ure's notes to BerthoUet on dyeing. 
 
 Calico Printing. — (Calico printing is a combination of the 
 arts of engraving and dyeing, and is used to produce upon wo- 
 ven fabrics, chiefly of cotton, a variety of ornamental combina- 
 tions, both of figure and color. In this process the whole fab- 
 ric is immersed in the dyeing liquid, but it is previously pre- 
 pared in such a manner, that the dye adheres only to the parts 
 intended for the figure, while it leaves the remaining parts un- 
 altered. In calico printing, adjective colors are most frequent- 
 ly employed. The cloth is prepared by bleaching and 
 other processes, which dispose it to receive the color. It is 
 then printed with the mordant, in a manner similar to that of 
 
AND MODIFYING COLOR. 453 
 
 copperplate printing-, except that the figure is engraved upon a 
 cylinder, instead of a plate. The cyhnder, in one part of its 
 revolution, becomes charged with the mordant mixed to a 
 proper consistence with starch. The superfluous part of the 
 mordant is then scraped ojff by a straight steel edge, in contact 
 Avith which the cylinder revolves, leaving only that part which 
 remains in the lines of the figure. The cloth then passes in 
 forcible contact with the other side of the cylinder, and receives 
 from it a complete impression of the figure in the pale color of 
 the mordant. The cloth is then passed through the coloring 
 bath, in which the parts previously printed become dyed with 
 the intended color. When it is afterwards exposed, and wash- 
 ed, the color disappears from those parts which are not im- 
 pregnated with the mordant, but remains permanently fixed to 
 the rest. When additional colors are required, they are printed 
 over the rest with ditTerent mordants, suited to the color in- 
 tended to be produced. This secondary printing is in most 
 instances performed with blocks, engraved in the manner of 
 wood cuts, and applied by hand to the successive parts of the 
 piece. 
 
 In some articles, white spots upon a dark ground are pro- 
 duced by covering the parts with wax, tallow, pipe clay, or 
 other materials, which prevent the contact of the color. Some- 
 times the color is discharged in places by the application of 
 chlorine. A preparation of one of the salts of copper, applied 
 in spots, or figures, has the effect to oxygenate indigo, so as to 
 render it insoluble, and consequently incapable of dyeing these 
 spots, when the stuff is immersed. To these and similar pro- 
 cesses, the name of resist toork has been given. 
 
 Fast Colors. — The following are the dye stuifs used by the calico 
 printers for producing fast colors.* The mordants are thickened with 
 gum, or calcined starch, and applied with the block, cylinder, plates, 
 or otherwise. 
 
 *Ure's Dictionary. 
 
454 ARTS OP COMMUNICATING 
 
 1. Black. The cloth is impregnated with acetate of iron (iron 
 liquor) and dyed in a bath of madder and logwood. 
 
 2. Purple. The preceding mordant of iron, diluted ; with the same 
 dyeing bath. 
 
 3. Crimson. The mordant for purple, united with a portion of 
 acetate of alumina, or red mordant, and the above bath. 
 
 4. Red. Acetate of alumina is the mordant, and madder is the dye 
 stuff. 
 
 5. Pale red of different shades. The preceding mordant diluted 
 with water, and a weak madder bath. 
 
 6. Brown or Pompadour. A mixed mordant, containing a somewhat 
 larger proportion of the red than of the black ; and the dye of madder. 
 
 7. Orange. The red mordant; and a bath first of madder, and then 
 of quercitron. 
 
 8. Yelloiv. A strong red mordant ; and the quercitron bath, whose 
 temperature should be considerably under the boiling point of water. 
 
 9. Blue. Indigo, rendered soluble and greenish yellow colored, by 
 potash and orpiment. It recovers its blue color, by exposure to air, 
 and thereby also fixes firmly on the cloth. An indigo vat is also made, 
 with that blue substance, diffused in water with quicklime and copperas. 
 These substances are supposed to deoxidize indigo, and at the same 
 time to render it soluble. 
 
 Golden-dye. The cloth is immersed alternately in a solution of 
 copperas and lime water. The protoxide of iron precipitated on the 
 fibre, soon passes, by absorption of atmospherical oxygen, into the 
 golden-colored deutoxide. 
 
 Buff. The preceding substances, in a more dilute state. 
 
 Blue vat, in which white spots are left on a blue ground of cloth, 
 is made, by applying to these points a paste composed of a solution of 
 sulphate of copper and pipe clay ; and after they are dried, immersing 
 it stretched on frames for a definite number of minutes, in the yellow- 
 ish-green vat, of one part of indigo, two of copperas, and two of lime, 
 with water. 
 
 Green. Cloth dyed blue, and well washed, is imbued with the alum- 
 inous acetate, dried, and subjected to the quercitron bath. 
 
 In the above cases, the cloth, after receiving the mordant paste, is 
 dried, and, after some preparation, put into the dyeing vat of copper. 
 
 Fugitive Colors. — 'All these colors are given, by making decoctions 
 of the different coloring woods; and receive the slight degree of fixity 
 they possess, as well as great brilliancy, in consequence of their com- 
 bination or admixture with the nitro-muriate of tin. ' 
 
 1. Red is frequently made from Brazil and Peachwood. 
 
AND MODIFYING COLOR. 455 
 
 2. Black. A strong extract of galls, and deuto-nitrate of iron. 
 
 3. Purple. Extract of logwood and the deuto-nitrate. 
 
 4. Yelloiv. Extract of quercitron bark, or French berries, and the 
 tin solution. 
 
 5. Blue. Prussian blue and solution of tin. 
 
 Fugitive colors are thickened with gum tragacanth, which leaves 
 the cloth in a softer state than gum Senegal ; the goods being some- 
 times sent to market without being' washed. 
 
 Tingrt's Painter and Varnisher's Guide, 8vo. translated 1816 ; — 
 Elmes' Dictionary of Fine Arts, Svo. 1826; — James' Panorama of 
 Science and Art, 2 vols. 8vo. 1816; — Bancroft on permanent Colors, 
 2 vols. Svo. 1814 ; — Berthollet, Elements of the Art of Dyeing, 
 translated by Ure, 2 vols. Svo. 1824 ; — Gay Lussac, Cours de Chimie, 
 2 vols. Svo. 1828 ; — Brande's Chemistry, 1820 ; — Turner's Chemis- 
 try, 1828 ; — Parkes' Chemical Essays, 1823 ; — Ure's Dictionary ;— » 
 ViTALis, Cours elimentaire de teinture, 1823. 
 
CHAPTER XIX. 
 
 ARTS OF VITRIFICATION. 
 
 A GREAT number of earths, and other mineral bodies, after 
 being fused, do not resume their original character upon cool- 
 ing, but pass into a dense, hard, shining, and brittle state, hav- 
 ing the character of glass ; and are thus said to be vitrified. 
 Most of these substances do not immediately become hard, upon 
 the reduction of their temperature, but go through an interme- 
 diate or ductile state, in which a combination of softness with 
 tenacity, enables them to be wrought into articles of use and 
 ornament. Of these, common glass is the most important, 
 while enamels, artificial gems, &c. belong to the same species 
 of manufacture. 
 
 Glass. — Glass is a compound substance artificially produced 
 by the combination of siliceous earth with alkalies, and in 
 some cases with other metallic oxides. These substances being 
 melted together at a high temperature, unite, lose their opacity, 
 and are fused into a homogeneous mass, which, on coohng, has 
 the properties of hardness, transparency, and brittleness. 
 
 Materials.* — The most important ingredient, and in fact 
 the basis of transparent glass, is siUca, or oxide of silicium. 
 This earth, nearly in a state of purity, is found in the sand of 
 certain situations, and also in common flint, and quartz peb- 
 bles. Sand has the advantage of being already in a state of 
 
 * The term metals, which appears to be a corruption of materials, is in com- 
 mon use among glass manufacturers, to express the ingredients or substan- 
 ces upon which their operations are performed. The same term is em- 
 ployed in a similar sense by other manufacturers and artists, and by some 
 writers on road making. The term metal, in the singular, is applied to 
 glass in a state effusion. 
 
ARTS OF VITRIFICATION. 457 
 
 minute division, not requiring to be pulverized. Pure silice- 
 ous sand, proper for the glass furnace, is found in many local- 
 ities. A great portion of that used in the United States, is ta- 
 ken from the banks of the Delaware. Yv^hen flints or quartz 
 are employed, they must be first reduced to powder, which is 
 done by heating them red hot and plunging them in cold wa- 
 ter. This causes them to whiten and fall to pieces^ after 
 which they are ground and sifted, before they are ready for the 
 furnace. 
 
 An alkahne substance, either potash or soda, is the second 
 ingredient in glass. For the finer kinds of glass, pure pearl 
 ash is used, or soda procured by decomposing sea salt ; but for 
 the inferior sorts, impure alkalies and even wood ashes are 
 made to answer the purpose. Lime is often employed in small 
 quantities, also borax, a salt which facilitates the fusion of the 
 silica. 
 
 Instead of the common alkalies, the sulphate of soda may 
 be employed in glass making. But in this case it is necessary 
 to liberate the alkali, by decomposing the sulphuric acid of the 
 salt. This may be done by charcoal, or in flint glass by me- 
 tallic lead. Lime is also used with this salt. 
 
 Of the metallic oxides which are added in different cases, 
 the deutoxide of lead (red lead) is the most common. This 
 substance renders flint glass more fusible, heavy, and tough, 
 and more easy to be ground and cut. At the same time it 
 imparts to it a greater brilliancy, and refractiv^e power. Black 
 oxide of manganese in small quantities, has the effect of 
 cleansing the glass, or of rendering it more colorless and trans- 
 parent. This effect it seems to produce by imparting oxygen 
 to the carbonaceous impurities, thus forming with them car- 
 bonic acid, which subsequently escapes. Common nitre pro- 
 duces a similar effect. If too much manganese be added, it 
 commmiicates a purple tinge to the glass, which, however, may 
 be destroyed by a little charcoal, or wood. Arsenious acid 
 (white arsenic), in small quantities, promotes the clearness of 
 glass, but if too much be used, it communicates a milky white- 
 58 
 
458 ARTS OF VITRIFICATION. 
 
 ness. Its use in drinking' vessels, is not free from danger, 
 when the glass contains so nauch alkah as to render any part 
 of it soluble in acids. 
 
 Crown Glass. — Glass is of various kinds, which are named 
 not only from the character of their ingredients, but from the 
 mode in which they are wrought. The name of crown glass 
 is given to the best kind of window glass, that which is hardest 
 and most free from color. It is made almost entirely of sand 
 and alkali, and a Httle lime, without lead or any other metalUc 
 oxide, except a minute quantity of manganese, and sometimes 
 of cobalt, which are added to counteract the effect of any im- 
 purities in giving color to the glass. Crown glass requires a 
 greater heat to melt its ingredients than those kinds which 
 contain a larger quantity of metallic oxide, especially of lead. 
 
 Fritting. — After the materials have been intimately mixed, 
 they are subjected to the operation called fritting. This con- 
 sists in exposing them to a dull red heat, which is not sufficient 
 to producs their fusion. The use of this process is to drive 
 off the carbonic acid, and other gaseous and volatile matters, 
 which would otherwise prove troublesome by causing the ma- 
 terials to swell up in the glass pots. The heat is gradually in- 
 creased, and the materials constantly stirred for some hours, 
 until they unite into a soft, adhesive mass, the alkali having 
 gradually combined with the siliceous earth. The reason why 
 the fritting is conducted at a low heat, is, that if a high tem- 
 perature were apphed at once, the alkali would be driven off, 
 before it had time to combine with the silica. 
 
 Melting. — The homogeneous mass, ox frit, is next transfer- 
 red to the glass pots of the melting furnace. These are cru- 
 cibles made of the most refractory clays and sand. A quantity 
 of old glass is commonly placed upon the top of the frit, and 
 the heat of the furnace is raised to its greatest height, at which 
 state it is continued for 30 or 40 hours. During this time the 
 materials become perfectly united, and form a transparent, 
 uniform mass, free from specks and bubbles. The whole is 
 then suffered to cool a little, by slackening the heat of the fur- 
 nace, until it acquires sufficient tenacity to be wrought. 
 
ARTS OF VITRIFICATION. 459 
 
 Blowing. — The formation of window glass is effected by 
 blowing the melted matter, or metal, as it is called, into hollow 
 spheres, which are afterwards made to expand into circular 
 sheets. The workman is provided with a long iron tube, one 
 end of which he thrusts into the melted glass, turning it round 
 until a certain quantity sufficient for the purpose, is gathered^ or 
 adheres to the extremity. The tube is then withdrawn from 
 the furnace, the lump of glass, which adheres, is rolled upon a 
 smooth iron table, and the workman blows strongly with his 
 mouth through the tube. The glass, in consecjuence of its 
 ductility, is gradually inflated, like a bladder, and is prevented 
 from falling off by a rotary motion constantly communicated to 
 the tube. The inflation is assisted by the heat, which causes 
 the air and moisture of the breath to expand with great power. 
 Whenever the glass becomes so stiff from cooling, as to render 
 the inflation difficult, it is again held over the fire to softer! it, 
 and the blowing is repeated until the globe is expanded to the 
 requisite thinness. It is then received by another workman, 
 upon an iron rod,* while the blowing iron is detached. It is 
 now opened at its extremity, and by means of the centrifugal 
 force acquired from its rapid whirling, it spreads into a smooth 
 uniform sheet, of equal thickness throughout, excepting a pro- 
 minence at the centre, where the iron rod was attached. 
 
 Annealing. — After the glass has received the shape which 
 it is to retain, it is transferred to a hot chamber, or annealing 
 furnace, in which its temperature is gradually reduced until it 
 becomes cold. This process is indispensable to the durability 
 of glass, for if it is cooled too suddenly, it becomes extremely 
 brittle, and flies to pieces upon the slightest touch of any hard 
 substance. This effect is shown in the substances called Ru- 
 •perts drops, which are made by suddenly cooling drops of 
 green glass, by letting them fall into cold water. . These drops 
 fly to pieces with an explosion, whenever their smaller extrem- 
 ity is broken off. The Bologna phials, and some other ves- 
 
 * Called a funt, or punting iron. 
 
460 APT3 OP VITRIFICATiaN. 
 
 sels of unannealed glass, break into a thousanrl pieces, if a flint, or 
 other hard and ang^ular substance, is dropped into them. This 
 phenomenon seems to depend upon some permanent and strong 
 ineqiiaiiiy of pressure ; for when these drops are heated so red 
 as to be soft, and left to cool gradually, the property of burst- 
 ing is lost, and the specific gravity of the drop is increased. 
 
 Broad Glass. — This is a coarser kind of window glass, and 
 is made from sand with kelp and soap boilers' waste. It is 
 blown into hollow cones, about a foot in diameter, and these, 
 while hot, are touched on one side with a cold iron dipped in 
 water. This produces a crack which runs through the length 
 of the cone, nearly in a right line. The glass then expands 
 into a sheet, in its form, resembling somewhat the shape of a 
 fan. This appears to have been one of the oldest methods of 
 manufacturing glass. 
 
 Flint Glass. — Flint glass, so called from its having been 
 
 originally made of pulverized flints, differs from window glass, 
 
 in containing a large quantity of the red oxide of lead. The 
 
 proportions of its materials differ ; but in round numbers, it 
 
 consists of about three parts of fine sand, two of red lead, and 
 
 one of pearl ash, with small quantities of nitre, arseiiic, and 
 
 manganese. It fuses at a lower temperature than crown glass, 
 
 has a beautiful transparency, a great refractive power, and a 
 
 comparative softness, which enables it to be cut and polished 
 
 with ease. On this account it is much used for glass vessels 
 
 of every description, and especially those which are intended 
 
 to be ornamented by cutting. It is also employed for lenses, 
 
 and other optical glasses. Flint glass is worked by blowing, 
 
 moulding, pressing, and grinding. Articles of complex form, 
 
 such as lamps and wine glasses, are formed in pieces, which 
 
 are afterwards joined by simple contact, while the glass is hot. 
 
 It appears that the red lead used in the manufacture of flint 
 
 glass, gives up a part of its oxygen, and passes to the state of 
 
 a protoxide. 
 
 Bottle Glass. — Common green glass, of which bottles are 
 made, is the cheapest kind, and formed of the most ordinary 
 
ARTS OF VITRIFICATIOJC. _ 461 
 
 materials. It is composed of sand with lime, and sometimes 
 clay, and alkaline ashes of any kind, such as kelp, barilla, or 
 even wood ashes. The green color is owing to the impurities 
 in the ashes, but chiefly to oxide of iron. This glass is hard, 
 strong, and well vitrified. It is less subject to corrosion by 
 strong acids than flint glass, and is superior to any cheap mate- 
 rial for the purposes to which it is ordinarily applied. 
 
 Cylinder Glass. — The plates of crown glass which are ob- 
 tained in the common manner by blowing them in circular 
 plates, afford the common material for window glass, being cut 
 into squares by first marking the surface deeply with a diamond, 
 and then breaking the glass in the same directions, the crack 
 always following the exact course of the incision made by the 
 diamond. But there is alwa)'^s a loss or waste in cutting 
 squares from a circular plate ; besides which, thej^ can never be 
 very large, owing to the protuberance, or hdVs eye, which 
 fills the centre of the plate, so that a square can never be larger 
 than can be described within less than half the circle. To 
 remedy this disadvantage, plates for looking glasses, and others 
 of large size, are executed in a different way, either by blowing 
 them in cylinders, or by casting them in plates at first. 
 
 Cylinder glass is blown at first in spheres like window glass. 
 These are elongated into spheroids by a swinging motion which 
 the workman gives to his rod. The ends of this spheroid are 
 successively perforated, thus converting it into an irregular 
 cylinder. One side of this cylinder is cut through with shears, 
 and the glass is laid upon a flat surface, where it expands into 
 a uniform plate, without any protuberance. It is then anneal- 
 ed by diminishing the heat in the common way. When the 
 plates are intended for looking glasses, the finest materials are 
 used, and the heat kept at its greatest height for a long time, 
 to dissipate all impurities and remove any specks or bubbles. 
 
 Plate Glass. — Looking glass plates may be blown in cyl- 
 inders when they do not exceed about four feet in length. But 
 they cannot well be blown of a larger size than this, from such 
 a quantity of glass as the rod will take up, without becoming 
 
462 ARTS OF VITRIFICATION. 
 
 too thin to bear polishing. Plates, however, may be made of 
 more than double this size, by another process which is called 
 casting, and which is the only mode by which very large 
 plates are produced. 
 
 When glass is to be cast, it is melted in great quantities in 
 large pots, or reservoirs, until it is in a state of perfect fusion, 
 in which state it is kept for a long time. It is then drawn out 
 by means of iron cisterns of considerable size, which are low- 
 ered into the furnace, filled, and raised out by machinery. 
 The glass is poured out from these cisterns, upon tables of 
 polished copper of a large size, having a rim elevated as high 
 as the intended thickness of the plate. In order to spread it 
 perfectly, and to make the two surfaces parallel, a heavy roller 
 of polished copper, weighing 500 pounds, or more, is rolled 
 over the plate, resting upon the rim at the edges. The glass, 
 which is beginning to grow stiff, is pressed down and spread 
 equally, the excess being driven before the roller till it falls off 
 at the extremity of the table. The plate is then ready to be 
 annealed. 
 
 As the plates which are cast for looking glasses are always 
 uneven and dull at their surface, it is necessary to grind and 
 polish them, before they are fit for use. The process employ- 
 ed for producing a perfectly even and smooth surface, is very 
 similar to that employed in polishing marble, except that the 
 glass being the harder substance, requires more labor and 
 nicety in the operation. The plate to be polished is first ce- 
 mented to a table of wood, or stone, with plaster of Paris. A 
 quantity of wet sand or emery is spread upon it, and another 
 glass plate similarly cemented to another wooden surface, is 
 brought in contact with it. The two plates are then rubbed 
 together until the surfaces have become mutually smooth and 
 plane. The emery which is first used is succeeded by emery 
 of a finer grain, and the last polish is given by colcothar, or 
 putty. When one surface has become perfectly polished, the 
 cement is removed, the plate turned, and the opposite side pol- 
 ished in the same manner. 
 
ARTS OF VITRIFICATION. 463 
 
 As the grinding of glass causes an expenditure of a consid- 
 erable portion of its substance, a great waste of glass takes 
 place when foreign materials are employed in the manner 
 which has been described. To prevent this loss, a more 
 economical mode has been introduced, in which the glass is 
 ground with purejlint reduced to powder. The mixture of 
 glass and flint, which is left after the operation, is valuable 
 for forming fresh glass. 
 
 Moulding. — A variety of ornanriental forms are produced 
 upon the surface of glass vessels, by impressions given to them 
 with a metallic mould, while the glass is in a hot state. Flint 
 glass is tlie kind, which is used for articles intended to possess 
 much brilliancy ; but coarser kinds, even of colored glass, are 
 also subjected to the same process. The simplest manner in 
 which the operation is conducted, consists in blowing the glass 
 into the mould, till it receives the impression on its outside. 
 For this purpose, a quantity of glass, sufficient to form the in- 
 tended vessel, is taken up on the end of a pipe, and inserted at 
 the top of the mould. The workman then blows with his 
 mouth till a hollow portion of glass is driven into the mould, 
 and expands so as to fill every part, and receive an impression 
 on its outside. The mould is usually made of copper, with 
 the figure cut on its inside, and opens with hinges to permit 
 the glass to be inserted, and taken out. As the mould is of 
 necessity much colder than the glass, the latter substance is 
 chilled at its surface, as soon as it comes in contact with the 
 copper ; hence its ductility is impaired, and the impression 
 given is never so sharp as that which is obtained with sub- 
 stances, which are nearly at the same temperatures. Moulded 
 bottles, phials, decanters, &.c. are made in this way. 
 
 Pressmg". — An improvement has been made in the process 
 of moulding glass, by subjecting the material to pressure, on 
 the inside and outside at the same time, by different parts of a 
 mould, which are brought suddenly together b)'^ mechanical 
 power. This process has been carried to great perfection in 
 
464 ARTS OP VITRIFICATION. 
 
 several of the manufactories in this country,* and produces 
 specimens which compare with cut glass in the accuracy and 
 beauty of the workmanship. It is applied only to solid articles, 
 and to vessels which are not contracted at top. The hot glass 
 being dropped into the mould, a part called the follower, an- 
 swering to the inside or top of the vessel, or other article, is 
 immediately pressed down upon it by a lever, and the glass is 
 thus stamped with a very distinct impression of the figure on 
 both sides at once. The glass vessel is sometimes transferred 
 from the mould to another receptacle called the receiver, in 
 order to preserve its shape till it is cool enough to stand. 
 
 Cutting. — The name of cut glass, is given in commerce to 
 glass which is ground and polished in figures with smooth sur- 
 faces, appearing as if cut by incisions of a sharp instrument. 
 This operation is chiefly confined to flint glass, which, being 
 more tough, soft, and brilliant than the other kinds, is more 
 easily wrought, and produces specimens of greater lustre. 
 An establishment for cutting glass contains a great number of 
 small wheels of stone, metal, and w^ood, which are made to 
 revolve rapidly by a steam engine, or other power. The cut- 
 ting of the glass consists entirely in grinding aw^ay successive 
 portions, by holding them upon the surface of these wheels. 
 The first, or rough cutting, is sometimes given by wheels of 
 stone, resembling grindstones. Afterwards wheels of iron are 
 used, having their edges covered with sharp sand, or with 
 emery in different states of fineness. The last polish is given 
 by brush wheels covered with putty, which is an oxide of tin 
 and lead. To prevent the friction from exciting so much 
 heat as to endanger the glass, a small stream of water contin- 
 ually drops upon the surface of the wheel, 
 
 Stained Glass. — The name of staining has been applied 
 to the process by which painting with vitrifiable colors, is ex- 
 ecuted upon the surface of glass. The pigments used are 
 chiefly metallic oxides, which do not exhibit their full color, 
 
 • Particularly at Lechmere's Point, and Sandwich. 
 
ARTS OF VITRIFICATION. 465 
 
 until they have been exposed to the heat of the furnace. This 
 art has been repeatedly described as being no longer known ; 
 but this is not the fact, except in respect to some particular 
 colors which are found in the windows of the ancient cathe- 
 drals. 
 
 The metallic oxides used in staining glass are difficult of 
 fusion, on which account it is necessary to mix them with a 
 flux, composed of glass, with lead or borax. This renders the 
 oxide fusible at a temperature which does not injure its color ; 
 also by enveloping the particles, it causes them to adhere to the 
 glass, and afterwards protects them from the atmosphere. 
 
 A very beautiful violet, but liable to turn blue, is made from 
 a flux composed of borax and flint glass colored with one sixth 
 part of the purple of Cassius, precipitated from muriate of gold 
 by protomuriate of tin. 
 
 A fine red is made from red oxide of iron, prepared by nitric 
 acid and heat, mixed with a flux of borax and a small propor- 
 tion of red lead. 
 
 A yellow, equal in beauty to that produced by the ancients, 
 may be made from muriate of silver, oxide of zinc, white clay, 
 and the yellow oxide of iron, mixed together without any flux. 
 A powder remains on the surface after the glass has been bak- 
 ed, but this is easily cleaned off. 
 
 Blue is produced by oxide of cobalt, with a flux composed 
 of fine sand, purified pearl ash, and red lead. 
 
 Black is produced by mixing the composition for blue, with 
 the oxides of manganese and iron. 
 
 To stain glass green, it may be painted blue on one side, 
 and yellow on the other. 
 
 The colors ground with water being laid upon the glass, 
 must be exposed to heat under a muffle, so as to be heated 
 equally until the color is melted upon the surface. To prevent 
 the panes of glass from bending, they are placed upon a bed 
 of bone ashes, of quicklime, or of unglazed porcelain. A bed 
 of gypsum has been recommended, but the sulphuric acid ex- 
 haling from it is apt to injure the glass. 
 59 
 
466 
 
 ARTS OF VITRIFICATION. 
 
 Among ancient specimens of painted glass, some pieces have 
 been found in which the colors are found to penetrate through 
 the glass, so that the figure appears in any section made par- 
 allel to the surface. It is supposed that such pieces can only 
 have been made in the manner of mosaic, by accumulating 
 transverse filaments of glass of different colors, and uniting 
 them by heat, the process being one of great labor. They are 
 described by Winckelmann, and Caylus, from some specimens 
 brought from Rome. 
 
 Enamelling. — Enamels are compositions of various sub- 
 stances, which, when vitrified upon the surface of opacjue bodies, 
 communicate their colors, and produce the effect of painting. 
 Enamels differ from stained glass, as a common picture differs 
 from a transparency, the former producing its effect when 
 viewedby reflected, and the latter by transmitted light. En- 
 amels are executed upon the surface of copper and other me- 
 tals, by a method similar to painting. One coat, or color, often 
 requires to be vitrified before another is laid upon it, and thus 
 the plate to be enamelled is obliged to be exposed to heat sev- 
 eral successive times. 
 
 Transparent enamels are usually rendered opaque, by add- 
 ing putty, or the white oxide of tin, to them. The basis of all 
 enamels is therefore a transparent and fusible glass. The ox- 
 ide of tin renders this of a beautiful white, the perfection of which 
 is greater when a small quantity of manganese is hkewise 
 added. If the oxide of tin be not sufficient to destroy the trans- 
 parency of the mixture, it produces a semiopaque glass, resem- 
 bling the opal. 
 
 The metals employed as coloring materials are; — 1. Gold. 
 The purple of Cassius imparts a fine ruby tint. 2. Silver. 
 Oxide or phosphate of silver gives a yellow color. 3. Iron. 
 The oxides of iron produce green, yellow, and brown, depend- 
 ing upon the state of oxidizement and quantity. 4. Copper. 
 The oxides of copper give a rich green ; they also produce a 
 red, when mixed with a small proportion of tartar, which tends 
 partially to reduce the oxide. 5. Antimony imparts a rich 
 
ARTS OP VITRIFICATION. 467 
 
 yellow. 6. Manganese. The black oxide of this metal, in 
 large quantities, forms a black glass ; in smaller quantities, 
 various shades of purple. 7. Cobalt,' in the state of oxide, 
 gives beautiful blues of various shades ; and with the yellow 
 of antimony, or lead, it produces green. 8. Chrome produces 
 fine greens and reds, depending upon its state of oxidizement. 
 
 Artificial Gems. — The great value of the precious stones 
 has led to artificial imitations of their color and lustre, by com- 
 positions in glass. In order to approximate as near as possible 
 to the brilliancy and refractive power of native gems, a basis, 
 called a paste, is made from the finest flint glass, composed of 
 selected materials, combined in different proportions, according 
 to the preference of the manufacturer. This is mixed with 
 metallic oxides capable of producing the desired coloi". A great 
 number of complex recipes are in use among manufacturers of 
 these jEiirticles. 
 
 Devitrification. — It is found that if certain kinds of glass be 
 exposed to heat sufficient to keep them in a soft state for some 
 hours, and are suffered to cool gradually, they lose their trans- 
 parency, and pass into the state of an opaque substance, of a 
 greyish white color. M. Dartrigues,* who has examined the 
 cause of this change, asserts that it is owing to a real crystalli- 
 zation of the vitreous silicate. Common bottle glass is most 
 easily changed in this manner, while those varieties which 
 contain neither lime nor alumina, are the most difficult to de- 
 vitrify. In aU cases, glass which has undergone this change 
 requires a stronger heat to melt it than before. 
 
 Reaumilfs Porcelain. — It has been frequently observed, 
 that during the annealing of green glass, some parts of it become 
 white and opaque. M. Reaumur made experiments on this 
 apparent devitrification of glass, and found it was owing to 
 the alkali flying off by the too long continuance, or too great 
 degree of the heat, and that the opaque changed glass had ac- 
 quii'ed the quality of bearing sudden transitions of heat and 
 cold as well as the best porcelain. 
 
 * Journal de Physique^ 1804. — Thenar d, Chimie, ii. 473. 
 
468 ARTS OF VITRIFICATION. 
 
 For he purpose of making vessels of this kind, common 
 bottle glass is chosen, and blown into the proper form. The 
 vessel is then to be filled to the top with a mixture of white 
 sand and gypsum, and is set in a large crucible upon a quantity 
 of the same mixture, with which the glass vessels must also 
 be surrounded, and covered over, and the whole pressed down 
 rather hard. The crucible is then to be covered with a lid, 
 the junctures well luted, and put into a potter's kiln, where it 
 remains during the whole time that the pottery is baking, after 
 which the glass will be found changed into a milk white 
 porcelain. 
 
 An imitation of porcelain which is lately introduced into our 
 shops, and which combines whiteness with a beautiful semi- 
 transparency, is made of flint glass, containing a portion of 
 white arsenic, on which its opacity depends. 
 
 Crystallo-Ceramie. — This name is given to an elegant, 
 but diflScult, species of manufacture, in which medallions, por- 
 traits, and other subjects executed in an opaque material, are 
 inclosed or incrusted, with glass. This art was first attempted 
 by inclosing in glass small figures made of a peculiar kind of 
 clay ; but these experiments were but in few instances sucess- 
 ful, owing' to the unequal expansion and contraction of the two 
 substances, and their consequent fracture. More recently a 
 composition has been employed for the opaque figure, which is 
 less liable to these accidents. It is necessary that the substance 
 employed in these devices, should be less fusible than glass, 
 incapable of generating air, and at the same time susceptible 
 of expansion and contraction, as the glass becomes hot or cold. 
 The ornamental figures are introduced into the glass while 
 hot, and thus become incorporated with it. 
 
 Glass Thread. — The great ductility of glass is one of its 
 most remarkable properties. When heated to a sufficient de- 
 gree, it may not only be moulded into any possible form with the 
 utmost facility, but it can be drawn out into the finest fibres. The 
 method of spinning glass is very simple. The operator holds a 
 piece of glass over the flame of a lamp with one hand ; he then 
 
ARTS OF VITRIFICATION. 46'9 
 
 fixes a hook to the melted mass, and by withdrawing it, obtains 
 a thread of glass attached to the hook. The hook is then fixed 
 in the circumference of a cylindrical drum, which can be turned 
 round by the hand ; and a rapid rotary motion being given to 
 the drum, the glass is drawn in the finest threads from the 
 fluid mass, and coiled round the cylindrical circumference. 
 M. Reaumur supposed, with great reason, that the flexibihty 
 of glass increased with the fineness of the threads, and he 
 therefore conjectured, that if they were drawn to a sufficient 
 degree of fineness, they might be used in the fabrication of 
 stuffs. He succeeded in making them as fine as a spider's web, 
 but he was never able to obtain them of a sufficient length, 
 when their diameter was so much reduced. The circumference 
 of these threads is generally a flat oval, about three or four 
 times as broad as it is thick. By using opaque and transparent 
 glass, of different colors, artists have been able to produce many 
 beautiful ornaments. 
 
 Remarks. — Pure glass possesses the remarkable property of 
 suffering no change by the application of an intense heat. 
 The effect of great heats is only to melt the glass, or to dissi- 
 pate it in vapor ; but as long as any of the glass remains, it 
 still preserves its transparency, and other distinguishing pro- 
 perties. 
 
 Of all the solid substances whose expansibility has been ac- 
 curately examined, glass possesses the property of being least 
 affected by heat or cold. Its expansion, according to General 
 Roy, with an increase of heat equal to 180 degrees of Fahren- 
 heit's thermometer, is only 0.000776, while that of platina is 
 0.000856, and that of hammered zinc, 0.003011. On account 
 of this property, glass is pecuharly fitted for containing fluids 
 whose expansions are under examination, as its own change of 
 form may in ordinary cases be neglected. For the same rea- 
 son it is better than any other substance for the simple pendu- 
 lum of a clock. 
 
 The invention of glass seems to have been extremely an- 
 cient, and imperfect specimens are found in the sarcophagi of 
 
470 ARTS OF VITRIFICATION. 
 
 Egyptian mummies. Glass windows appear not to have been 
 in use among the Romans of the Augustan age ; though vessels 
 and plates of glass are found at Herculaneum and Pompeii. 
 Most of the important improvements in the manufacture of this 
 substance have been made by the moderns. 
 
 Parkes' Chemical Essays, 8vo. vol. ii. ; — Loysel, Essai sur VArt 
 de Ja Verrerie, 8vo. 1800 ; — Brogniart, Art de VEmailleur, Amiales 
 de ChimU, torn. ix. and other works ; — Franklin Journal, v. 80 ; — Arti- 
 cle Glass in Rees' Cyclopedia, and in the Edinburgh Encyclopedia ; — 
 Chaptal, Chimii Appliquie aux Aiis, 4 vols. 8vo. 1806 ; — Gray's 
 Operative Chemist, 8vo, 1828; — Thenard, Traits de Chimid, vol. ii. ; — 
 Brande's Chemistry ; — Beckman's History of Inventions, 4 vols. 8vo. 
 translated 1797; — ^Works of Neri, Blancourt, Kunckel, Reaumur, 
 
CHAPTER XX. 
 
 ARTS OF INDURATION BY HEAT, 
 
 Common clay, with its varieties, consisting essentially of 
 alumina and silica ; also the artificial imitations of clay, into 
 which these earths enter, possess properties adapted to render 
 them highly useful in the arts. When mixed with water, they 
 form a ductile and tenacious paste, capable of being moulded 
 into various forms, and of acquiring, when exposed to the heat 
 of a furnace, a durable and stony hardness. These com- 
 pounds are used in different states, to form the materials both 
 for the largest structures, and the most delicate ornaments ; 
 and they are surpassed by few substances in the power of 
 resisting the effects of exposure and time. Bricks, tiles, terra, 
 cotta, pottery, and porcelain, are the most noticeable products 
 of the branch of industry, in the operations of which indurated 
 clay is the material. 
 
 Bricks. — The use of bricks in building, may be traced to 
 the earliest ages, and they are found among the ruins of almost 
 every ancient nation. The walls of Babylon, some of the an- 
 cient structures of Egypt and Persia, the walls of Athens, the 
 Rotunda of the Pantheon, the temple of Peace, and the Ther- 
 mae, at Rome, were all of brick. The earliest bricks were 
 dried in the sun, and were never exposed to great heat, as ap- 
 pears from the fact that they contain reeds and straws, upon 
 which no mark of burning is visible. These bricks owe their 
 preservation to the extreme dryness of the (Jlimate in which 
 they have remained, since the earth, of which they are made, 
 often crumbles to pieces when immersed in water, after hav- 
 ing kept its shape for more than two thousand years. This 
 is the case with some of the Babylonian bricks, with inscrip- 
 
472 ARTS OP INDURATION BT HEAT. 
 
 ions in the arrow-headed character, which have been brought 
 to this country. The ancients, however, at a later period, burnt 
 their bricks, and it is these chiefly which remain at the present 
 day. The antique bricks were larger than those employed 
 by the moderns, and were almost universally of a square form. 
 Besides bricks made of clay, the ancients also employed a kind 
 of factitious stone, composed of a calcareous mortar.* 
 
 Modern bricks receive their hardness from exposure to heat 
 in the process of burning. The common clay of which they 
 are made, consists of a mixture of argillaceous earth and sand. 
 Most of our common clays contain also oxide of iron, which 
 causes the bricks to turn red in burning. Pure clays become 
 white in the furnace, such as that of which pipes are made, 
 and common crockery ware. Clay, after it is taken from the 
 earth, requires to be thoroughly mixed, incorporated, and mel- 
 lowed, before it is fit for the manufacture of bricks. For this 
 purpose, it is to be dug in the summer, or fall, and exposed to 
 the influence of the frost through the winter. It should be 
 worked over repeatedly with the spade, and not made into 
 bricks till the ensuing spring, previously to which, it is well 
 tempered, either by treading it with oxen, or by a horse mill, 
 till it is reduced to a tough, homogeneous paste. In propor- 
 tion to the labor bestowed on this process, the bricks become 
 sohd, hard, and strong. The clay, after being thus prepared, 
 is forced into moulds to receive the shape of bricks, and after- 
 wards dried in the sun. 
 
 Pressed bricks, which are used to form the facing of walls 
 in the better kinds of structures, are finished in a machine. 
 The roughness and change of form to which common bricks 
 are liable, is owing in part to the evaporation of a portion of 
 the water which the clay contains. To remedy the difficulty 
 arising from this cause, the bricks, after being moulded in the 
 common manner, are exposed to the sun till they are nearly 
 dried, retaining, however, sufficient plasticity to be still capable 
 
 * Some travellers have even advanced an opinion that the Pyramids of Egypt 
 are constructed vyith an artificial stone. 
 
ARTS OF INDURATION BY HEAT. 473 
 
 of a slight change of form. In this state they are placed in 
 an iron mould and subjected to a strong pressure, by which 
 they become regular in shape, and very smooth. A machine 
 usually contains a number of moulds arranged in a circle, or 
 otherwise, so that the power is applied to them in succession, 
 and the bricks pressed with rapidity. 
 
 The burning of bricks is commonly performed in this coun- 
 try, by forming them into large square piles, denominated 
 clamps, or with us, kibis, having flues or cavities at the bottom 
 for the insertion of the fuel, and interstices between the bricks 
 for the fire and hot air to penetrate. A fire is kindled in these 
 cavities, and gradually increased for the first twelve hours, af- 
 ter which it is kept up at a uniform height for several days 
 and nights, till the bricks are sufficiently burned. Much care 
 and experience are necessary in regulating the fire, since too 
 much heat vitrifies them, and too httle leaves them soft and 
 friable. In some places the burning of bricks is conducted in 
 permanent kilns erected for the purpose. 
 
 Tiles. — Tiles are plates of burnt clay, resembling bricks in 
 their composition, and manufacture, and used for the covering 
 of roofs. They are necessarily made thicker than slates or 
 shingles, and thus impose a greater weight upon the roofs. 
 Their tendency to absorb water, promotes the decay of the 
 wood work beneath them. Tiles are usually shaped in such 
 a manner that the edge of one tile receives the edge of that 
 next to it, so that water cannot percolate between them.* Tiles, 
 both of burnt clay and marble, w^ere used by the ancients, and 
 the former continue to be employed in various parts of Eu- 
 rope. Floors made of flat tiles are used in many countries, par- 
 ticularly in Italy. 
 
 Terra Cotta. — The Italian name terra cotta, in French 
 terra cuite, in its most general sense, implies clay indurated 
 by heat. In the arts, however, its use seems to be restricted to 
 the finer clays, in which ornamental designs have been exe- 
 
 * For different forms of tiles used at Florencej Trieste, &c. see Cadell's 
 Journey in Italy and Carniola, Plate X. 
 
 60 
 
474 ARTS OF INDURATION BT HEAT. 
 
 cuted, both by the ancients and moderns. Not only vases, but 
 imitations of sculpture, and architectural decorations, are suc- 
 cessfully made from this material. Among other things, a 
 complete restoration of the Choragic monument of Lysicrates, 
 at Athens, has been made from terra cotta in the court of the 
 Louvre, at Paris. From the facility with which it is moulded 
 into any form, this substance would be of great use in archi- 
 tecture, were it not for the unequal shrinking of the clay from 
 heat, and the difficulty of preserving accurately the original 
 proportions. 
 
 Crucibles. — Crucibles, melting pots, and other vessels in- 
 tended for use in the furnace, require to be made of substances 
 which sustain a high temperature without fusion. When they 
 are made of about one part of pure clay, mixed with three of 
 sand, and slowly dried and annealed, they are found to bear a 
 great heat, and will retain most of the metals which are melted 
 for use in the arts. Such crucibles, however, are liable to be 
 acted upon, and destroyed at high temperatures, if the metals 
 are suffered to become oxidized, or if saline fluxes are used. 
 To prevent this accident, some crucibles are made entirely of 
 clay, which is burnt, coarsely powdered, and mixed with fresh 
 clay. These are found very refractory in the furnace. Cruci- 
 bles are also made of plain Stourbridge clay, of Wedgewood's 
 ware, of graphite, and of platina. 
 
 Pottery. — In manufactures of vessels from argillaceous com- 
 pounds, the different degrees of beauty and costliness depend 
 upon the quality of the raw material used, and upon the labor 
 and skill expended in the operation. The cheapest products 
 of the art are those made of common clay, similar to that of 
 which bricks are formed, and which, from the iron it contains, 
 usually turns red in burning. Next to this is the common 
 crockery ware, formed of the purer and whiter clays in which 
 iron exists only in minute quantities. Porcelain, which is the 
 most beautiful and expensive of all, is formed only from argil- 
 laceous minerals of extreme delicacy, united with siliceous 
 earths capable of communicating- to them a semitransparency, 
 by means of its vitrification. 
 
ARTS OP INDURATION BY HEAT. 475 
 
 Clay, although it is a compound body, and possesses more 
 silica than alumina, ueveitheless derives characters from the 
 latter, which abundantly distinguish it from minerals which are 
 more purely siliceous. The processes of its manufacture are 
 in most respects the reverse of those applied to glass, that sub- 
 stance being softened by heat, and wrought at a high tem- 
 perature, whereas the clay is wrought while cold, and after- 
 ■wards hardened by heat. 
 
 Operations. — Though the various kinds of pottery and 
 porcelain differ from each other in the details of their manu- 
 facture, yet there are certain general principles and processes 
 which are common to them all. The first belongs to the pre- 
 paration of the clay, and consists in dividing and washing it, 
 till it acquires the requisite fineness. The quality of the clay 
 requires the intermixture of a certain proportion of siliceous 
 earth, the effect of which is to increase its firmness, and render 
 it less liable to shrink and crack, on exposure to heat. In 
 common clay, a sufficient quantity of sand exists in a state 
 of natural mixture, to answer this purpose. But in the finer 
 kinds, an artificial adraixt.ure of silica is necessary. The paste 
 which is thus formed, is thoroughly beaten and kneaded to 
 render it ductile, and to drive out the air. It is then ready to 
 receive its form. The form of the vessel intended to be made, 
 is given to the clay either by turning it on a wheel, or by cast- 
 ing it in a mould. When dry, it is transferred to the oven or 
 furnace, and there burnt till it acquires a sufficient degree of 
 hardness for use. Since, however, the clay is still porous, and 
 of course penetrable to water, it is necessary to glaze it. This 
 is done by covering the surface with some vitrifiable substance, 
 and exposing it a second time to heat, until this substance is con- 
 verted into a coating of glass. 
 
 In the coarse earthen ware, which is made of common clay, 
 the clay, after being mixed and kneaded until it has acquired 
 the proper ductility, is transferred to a sort of revolving table, 
 called the wheel. A piece of clay of sufficient size, being placed 
 in the centre of this table, a rotary motion is communicated to 
 
476 ARTS OP INDURATION BY HEAT, 
 
 it by the feet. The potter then begins to shape it with his 
 hands, which are previously wet to prevent its adhering to the 
 finsfers. The rotary motion gives it a circular form, and it is 
 gradually wrought up to the intended shape, a tool being oc- 
 casionally used to assist the finishing. The vessels are now 
 set aside to dry, after which they are baked in the oven, or kiln. 
 The glazing of this kind of pottery is given by metallic oxides, 
 which vitrify at a low heat. A yellow glazing is communicated 
 by the oxide of lead, black by the oxide of manganese, and white 
 by the oxide of tin. Unglazed ware is porous and permeable 
 to water, as is seen in common flower-pots and coolers. 
 
 Sto7ie Ware. — The kinds of pottery denominated stone 
 ware, may be formed of the clays which are used for other ves- 
 sels, by applying to them a much greater degree of heat, the 
 effect of which is to increase very much their strength and 
 solidity. These vessels do not require to be glazed with any 
 metallic oxides, but afford the material of their own glazing by 
 a vitrification of their surface. When the furnace in which 
 they are burnt has arrived at its greatest heat, a quantity of 
 muriate of soda, or common salt, is thrown into the body of 
 the kiln. The salt rises in vapor and envelopes the hot ware, 
 and by the combination of its alkali with the siliceous particles 
 on the surface of the ware, a perfect vitrification is produced. 
 This glazing, consisting of an earthy glass, is insoluble in most 
 chemical agents, and is free from the objections to which ves- 
 sels glazed with lead are liable, that of communicating an un- 
 wholesome quality to liquids contained in them, by the solution 
 of the lead in common acids, which they frequently contain. 
 
 White Ware. — The better sorts of earthen ware are made 
 of white clay, or of clay containing so little oxide of iron that 
 it does not turn red in burning, but on the contrary, improves 
 its whiteness in the furnace. This kind, commonly called 
 'pipe clay, is found very pure in Devonshire and Dorsetshire, 
 in England. In the manufactory of Mr Weclgewood, to whose 
 industry and ingenuity the public are indebted for some of the 
 finest specimens of the art, the clay is prepared by first bring- 
 
ARTS OF INDURATION BY HEAT- 477 
 
 ing it to a state of minute division, by the aid of machinery. 
 This machinery consists of a seiies of iron blades or knives 
 fixed to an upright axis, and made to revolve in a cylinder, 
 and intersecting or passing between another set of blades which 
 are fixed to the cylinder. The clay, by the continual inter- 
 section of these blades, is minutely divided, and when suffi- 
 ciently fine, is transferred to a vat. It is here agitated with 
 water until it assumes the consistence of a pulp, so thin, that 
 the coarser or stony particles can subside to the bottom after 
 a little rest, while the finer clay remains in suspension. This 
 last is poured off and suffered to subside, after which it is pass- 
 ed through sieves of difierent fineness, and becomes sufficiently 
 attenuated for use. 
 
 To this clay is added a certain quantity of flint reduced to 
 powder by heating it red hot, and throwing it into cold water 
 to diminish the cohesion of its parts. Afterwards it is pounded 
 by machinery, ground in a mill, sifted and washed precisely 
 as the clay is treated, and made into a similai" pulp. In this state 
 the two ingredients are intimately mixed together, in such 
 quantities that the clay bears to the flint the proportion of about 
 five to one. 
 
 The object of adding flint to the clay, is twofold. It lessens 
 the shrinking of the clay in the fire, and thus renders it less 
 liable to warp and crack in the burning. At the same time, 
 by its partial fusion, it communicates to the ware that beauti- 
 ful translucency which is so much admired in porcelain, and 
 of which the simple clay wares are destitute. 
 
 The fine pulp of flint and clay being intimately mixed, is 
 then exposed to evaporation by a gentle heat, until the super- 
 fluous water is dissipated, and the mass reduced to a proper 
 consistency to work. To produce a uniformity in the thick- 
 ness of the material, it is taken out in successive pieces, which 
 are repeatedly divided, struck, and pressed together, till every 
 part becomes blended with the rest. 
 
 Throioing. — The formation of circular vessels is done by 
 the process called throwing, performed on the potter's wheel, 
 
47S ARTS OP INDURATION BY HEAT, 
 
 in the manner already described, except that in large manu- 
 factories the wheel is not turned by the operator himself, but 
 by an assistant, or a steam engine. The handles and similar 
 appendages are made by forcing the clay witli a piston, through 
 an aperture of the size and shape which it is desired to pro- 
 duce. When formed, the handles are cemented to the ware 
 by a thin mixture of the clay with water, which the workmen 
 call slip. The vessels, when complete, are dried with a grad- 
 ual heat, in a room heated to 80 or 90 degrees, and after be- 
 ing smoothed from any irregularities of surface, they are con- 
 veyed to the kiln. 
 
 Pressing. — The only vessels which can be made in the 
 wheel or lathe, are those of a circular form. When the form 
 is different, the vessel must be made either by press work or 
 casting. The press work is executed in moulds made of 
 plaster of Paris, one half the figure being on one side of the 
 mould and the other half on the other side. These fit accu- 
 rately together. The clay is first made into two flat pieces, of 
 the thickness of the articles ; one of these is pressed into one 
 side of the mould, and the other into the other side. The 
 superfluous clay being cat away, the two sides of the mould 
 are brought together to unite the two halves of the vessel. 
 The mould is now separated from the clay, and the article is 
 finished as to form. When dry, it is completed by the addi- 
 tion of handles, or other parts belonging to it. All vessels of 
 an oval form, or which have flat sides, may be made in this 
 way. 
 
 Casting. — In the third method called casting, the clay is 
 used in the state of pulp, sufficiently thin to flow. It is poured 
 into moulds made of plaster, by which the superfluous water 
 being rapidly absorbed, the clay is deposited, and acquires 
 sufficient solidity to preserve the shape communicated by the 
 mould. It is then taken out and dried, and transferred to the 
 kiln. 
 
 Burning. — All vessels, when formed, are in a very tender 
 and frangible state, before they are submitted to the action of 
 
ARTS OF INDURATION BY HEAT. 479 
 
 fire. The burning, or hardening, is performed in kilns ; and 
 to preserve the ware from injury, it is inclosed in cases, or 
 boxes, of burnt clay, called saggars, in which it is heated red 
 hot, by the flame circulating among the cases. The fire is 
 kept up from 24 to 48 hours, and the saggars suffered to cool 
 before they are removed. The ware is then found to have 
 acquired great hardness, and is converted into a dry, sonorous, 
 and extremely bibulous solid. In this state it is called the 
 biscuit. It adheres strongly to the tongue, and absorbs water 
 in such quantities, that vessels in this state are used as coolers, 
 being kept saturated with water, which, as it passes constantly 
 to the outer surface, generates cold by its evaporation. 
 
 Printing. — When colors, or designs, are to be impressed 
 upon the vessels, it is necessary in most cases, that it should 
 be done before the ware is glazed. In China, the drawings 
 on the suiface of porcelain, and other wares, are executed by 
 hand, with the pencil ; and the same method is pursued in 
 Europe, in elaborate pieces of workmanship. But in the 
 common figured v/hite ware, the designs are first engraved up- 
 on copper, and an impression taken on thin paper, in the com- 
 mon mode of copperplate printing, except that the color is a me- 
 tallic oxide. The paper is then moistened, applied closely to 
 the biscuit, and rubbed on ; by which process the coloring 
 matter is absorbed, in consequence of the porosity of the earth- 
 en material. The paper is then washed off", leaving the print- 
 ed figure transferred to the sides of the vessel. Blue and white 
 ware is printed with oxide of cobalt,* and a black color is im- 
 parted by an admixture with the oxides of manganese and 
 iron. 
 
 Glazing. — To prevent the penetration of fluids, it is neces- 
 sary that vessels should be glazed, or covered, with a vitreous 
 coating. The materials of common glass would afford the 
 most perfect glazing to crockery ware, were it not that the ra- 
 
 * Mr Parkes informs us that such improvements are made in the manufac- 
 ture of this article, that the Chinese potters are now supplied from England, 
 with all the cohalt they consume. 
 
480 ARTS OF INDURATION BY HEAT. 
 
 tic of its expansion and contraction is not the same with that 
 of the clay, so that a glazing of this sort is liable to cracks 
 and fissures, when exposed to changes of temperature. A mix- 
 ture of equal parts of oxide of lead and ground flints is found 
 to be a durable glaze for the common cream colored ware, and 
 is generally used for that purpose. These materials are first 
 ground to an extremely fine powder, and mixed with water to 
 form a thin liquid. The ware is dipped into this fluid and 
 drawn out. The moisture is soon absorbed by the clay, leav- 
 ing the glazing particles upon the surface. These are after- 
 wards melted by the heat of the kiln, and constitute a uniform 
 and durable vitreous coating. 
 
 The English and French manufacturers find it necessary to 
 harden their vessels by heat, or bring them to the state of bis- 
 cuit, before they are glazed ; but the composition used by the 
 Chinese, resists water, after it has been once dried in the air, 
 so as to bear dipping in the glazing liquid, without injury. 
 This gives them a great advantage in the economy of fuel. 
 
 China Ware. — The Chinese porcelain excels other kinds 
 of ware, in the delicacy of its texture, and the partial trans- 
 parency which it exhibits when held against the light. It has 
 been long known and manufactured by the Chinese, but has 
 never been successfully imitated in Europe, until within the 
 last century. In China, porcelain is made by the union of 
 two earths, to which they give the name oipetimtze and kaolin^ 
 the former of which is fusible in the furnace, the latter not. 
 Both these earths are varieties of feldspar, the kaolin being 
 feldspar in a state of decomposition, and which is rendered in- 
 fusible by having lost the small quantity of potass which origi- 
 nally entered into its composition. The petuntze is feldspar 
 undecomposed. These earths are reduced to an impalpable 
 powder, by processes similar to those already described, and in- 
 timately blended together. When exposed to a strong heat, 
 the petuntze partially melts, and enveloping the infusible kao- 
 lin, communicates to it a fine semitransparency. The glazing 
 
ARTS OF INDURATION BY HEAT. 481 
 
 is produced by the petimtze alone, applied in minute powder 
 to the ware, after it is dry. 
 
 European Porcelain. — Since the nature of the Chinese 
 earths has been understood, materials nearly of the same kind, 
 have been found in different parts of Europe, and the manu- 
 facture of porcelain has been carried on in several countries, 
 but particularly at Sevres, in France, with great success. The 
 European porcelains, in the elegance and variety of their forms 
 and the beauty of the designs which are executed upon them, 
 excel the manufactures of the Chinese. But the Oriental 
 porcelain has not yet been equalled in hardness, strength, du- 
 ]"ability, and the permanency of its glaze. Several of the pro- 
 cesses which are successfully practised by the Chinese, remain 
 still to be learnt by Europeans. The manufacturers in Saxony, 
 are said to have approached most nearly in their products, to 
 the character of the Asiatic porcelain. 
 
 The porcelain earths are found in vaiious parts of the United 
 States, and will doubtless hereafter constitute the material of 
 important manufactures. 
 
 The finer and more costly kinds of porcelain derive their 
 value, not so much from the quality of their material, as from 
 the labor bestowed on their external decoration. When the 
 pieces are separately painted by hand, with devices of different 
 subjects, their value, as specimens of art, depends upon the 
 size of the piece, the number and brilliancy of the colors em- 
 ployed, and more especially upon the skill and finish, exhibited 
 by the artist in the design. The manual part of the operation 
 consists in mixing the coloring oxide with a fluid medium, 
 commonly an essential oil, and applying it with camels' hair 
 pencils. The colors used are the same as those employed in 
 other kinds of enamelling. When one color requires to be 
 laid over another, this is performed by a second operation ; and 
 it often happens that a piece of porcelain has to go into the en- 
 amel kiln four or five times, when a great variety of colors is 
 contained in the painting. 
 61 
 
482 ARTS OP INDURATION BY HEAT. 
 
 Gilding upon porcelain is performed by applying the gold 
 after its solution in nitro-muriatic acid, ground up with oil of 
 turpentine, and mixed with a flux. When exposed to heat, 
 the oxygen, if any is present, escapes, and a coating of metallic 
 gold remains fixed to the porcelain. This has at first the 
 appearance of dead gold, but is subsequently burnished with 
 an instrument of polished steel, or with an agate, or blood 
 stone. 
 
 The articles called lustre umre, are of two kinds. The first 
 of these, called gold lustre, is made of red clay, and is brush- 
 ed over with a thin coating of gold obtained from its solution 
 in nitro-muriatic acid, the acid being driven off by heat. The 
 other kind is called silver lustre, and is made of the cream- 
 colored ware, covered in the same manner with a film of pla- 
 tinum. 
 
 Etruscan Vases. — This name is given to a kind of painted 
 antique vases, of great beauty, lightness, and delicacy, which 
 are dug up in the graves of lower Italy. Many of them are 
 supposed to be of Grecian, and not of Etruscan origin. Some 
 of these vases are entirely black, and in this case there is no 
 separate glazing, but the interior of the mass has the same ap- 
 pearance with the outside. Other vases are furnished with a 
 simple black coating,' but unhke the modern glazing. It ap- 
 pears from analysis, that this black color is produced by a car- 
 bonaceous substance, perhaps bitumen ; but the art of applying 
 it is unknown to the moderns. 
 
 The celebrated Portland vase, discovered in the tomb of 
 Alexander Severus, and for which the Dutchess of Portland 
 paid a thousand guineas, is said to be made, not of porcelain, 
 but of glass. The body of the urn consists of a deep blue glass, 
 over which is applied a coating of white semitransparent glass. 
 The white covering appears to have been cut away by the 
 lapidary, in the same way as the subjects of antique cameos on 
 colored grounds. Mr Wedgewood, at a great expense, pro- 
 duced imitations of this vase in porcelain. 
 
ARTS OF INDURATION BY HEAT. 483 
 
 Among the curiosities of this ait, may be mentioned the 
 magic porcelain of the Chinese. The figures upon the sur- 
 face of this ware are executed in such a manner, that they are 
 said to be invisible when the vessels are empty,* but become 
 apparent when the vessels are filled with water. 
 
 * See the article Porcelain, in the Edinburgh Encyclopedia, ascribed to M. 
 Brogniart. 
 
 Parkes' Chemical Essays, vol. ii. ; — Rees' Cyclopedia and Edin- 
 burgh Encyclopedia, articles Pottery, Porcelain, &c. ; — Chaptal, Chi- 
 mU Appliquie aux Arts, torn. iii. ; — Gray's Operative Chemist, 8vo. 
 1828. 
 
CHAPTER XXL 
 
 ON THE PRESERVATION OF ORGANIC SUBSTANCE. 
 
 Decomposition. — The compounds which are spontaneously 
 formed by organic bodies, both vegetable and animal, are of a 
 different nature from those which exist in unorganized matter. 
 They are the peculiar results of vital processes, and neither 
 their structure nor composition can be imitated by art. Dur- 
 ing life, the elements of organic bodies are held together by 
 vital affinities, under the influence of which they were originally 
 combined. But no sooner does life cease, than these elements 
 become subject to the laws of inert matter. The original af- 
 finities, which had been modified, or suspended, during life, 
 are brought into operation ; the elementary atoms react upon 
 each other, new combinations are formed, and the organized 
 structure passes sooner or later into decay. 
 
 The rapidity with which decomposition takes place in or- 
 gainc bodies, depends upon the nature of the particular sub- 
 stance, and upon the circumstances under which it is placed. 
 Temperature, moisture, and the presence of decomposing 
 agents, greatly affect both the period, and extent of this pro- 
 cess. By regulating, or preventing, the operation of these 
 causes, the duration of most substances may be prolonged, and 
 many materials are rendered useful, which, if left to themselves, 
 would be perishable and worthless. The preservation of tim- 
 ber, of fibrous substances, of leather, of food, and of various 
 objects of art, are subjects of the highest importance, and have 
 received, at various times, much attention from scientific ex- 
 perimentalists. 
 
 Temperatwe. — The influence of temperature, in accelerat- 
 ing or retarding the decay of organized substances, is gene- 
 
ON THE PRESERVATION OF ORGANIC SUBSTANCES. 485 
 
 rally known. Cold tends to check the progress of destructive 
 fermentation, and when it extends so far as to produce conge- 
 lation, its preservative power is complete. Bodies of men and 
 animals have been found fi'ozen, in situations where they had 
 remained for years, and even ages ; and the recent discovery 
 of an elephant in the ice of Siberia, shows that the period of 
 this preservation is unlimited. On the other hand, in warm 
 seasons and in hot climates, everything tends to corruption and 
 decay. Both animal and vegetable substances, pass rapidly 
 into the putrefactive fermentation ; alimentary substances are 
 difficult to preserve, and when moisture is combined with heat, 
 ships, houses, and other structures of wood, as well as cordage, 
 canvass, and clothing, have the period of their duration greatly 
 abridged. 
 
 Dryness. — Although certain degrees of heat, especially 
 "when combined with moisture, tend greatly to promote decom- 
 position, yet if the degree of heat, and the circumstances under 
 which it acts, are such as to produce a perfect dissipation of 
 moisture, the further progress of decay is arrested. The exer- 
 tion of chemical affinities usually requires that one of the 
 agents at least should be in a fluid state. And while a body 
 is in a state of perfect dryness, no internal chemical change is 
 likely to befall it. The beams and furniture of houses, often 
 remain entire for centuries. In the arid cai^erns of Egypt, the 
 wood of sarcophagi appears to have undergone no alteration in 
 the lapse of two or three thousand years, the fibres of linen 
 textures are found distinct and perfect, though weakened in 
 strength, and the dried flesh of the mummies themselves dis- 
 cover no marks of decomposition. In cabinets of Natural His- 
 tory, the specimens, so long as they are kept perfectly dry, un- 
 dergo no alteration from spontaneous decay. They are, how- 
 ever, extremely liable to the depredations of insects, from which 
 they require to be protected, either by impregnating them 
 with poisonous substances, or by inclosing them in cases which 
 are hermetically tight. 
 
486 ON THE PRESERVATION 
 
 Wetness. — Some materials, especially wood, are capable of 
 lasting for a long time, if kept continually immersed in water, 
 especially at low temperatures. Thus the lower part of a 
 pump log is much more durable than the upper, if kept always 
 under water. The effect of pure water is to dissolve and car- 
 ry off the soluble parts, leaving the fibrous structure in a state 
 less liable to fermentation than before. Some animal substan- 
 ces, likewise, such as leather, bear immersion in water for a 
 considerable time. It must be observed, however, that the 
 effect of wetness upon most organized bodies, is to soften their 
 texture, and render them less able to support mechanical vio- 
 lence, than when dry. Wood, after having been long immers- 
 ed, if taken out and dried, is found to be more brittle than it 
 was before. 
 
 But the state which most rapidly promotes decay, is that of 
 alternate moisture and dryness, attended with exposure to the 
 atmospheric air. It appears in regard to wood, that in each 
 wetting, a sensible portion of substance is dissolved, and that 
 in each drying, a new portion of soluble matter is formed. In 
 a ship, under common circumstances, the parts which first de- 
 cay, are those which are situated between wind and water, or 
 are subjected to alternate dryness and moisture. So also in a 
 post standing in the earth, the part which first decays, is usu- 
 ally that which is nearest the surface of the ground. Exposure 
 to the vicissitudes of weather, is also one of the most common 
 and active causes of decomposition. 
 
 Antiseptics. — A certain class of substances has received the 
 name of antiseptics, from their power, when present, of resist- 
 ing putrefaction in organic bodies, as well as in their products. 
 Such are charcoal, tannin, resins, camphor, bitumen, sugar, 
 chlorine, alcohol, oils, acids, and salts of various kinds. The 
 manner in which they exert their preservative agency is not 
 fully understood. It appears, however, that in some cases 
 they combine with the substance to be preserved, forming a 
 less perishable compound, as in the instance of leather ; and 
 probably in other instances they unite with and qualify the 
 decomposing agents which are present. 
 
OF ORGANIC SUBSTANCES. 487 
 
 Timber. — A vast expense is every year created by the pre- 
 mature decay of wood, employed in ships and other structures, 
 which are exposed to vicissitudes of weather, and especially if 
 they are subjected to the influence of warmth combined with 
 moisture. Trees of different species, vary greatly in the du- 
 rability of their wood, j^et none of the species commonly em- 
 ployed, are capable of withstanding', for many years, the effect 
 of unfavorable exposures and situations. The decay of tim- 
 ber is sometimes superficial, and sometimes internal. In the 
 former case, the outside of the wood first perishes and crum- 
 bles away, and successive strata are decomposed, before the 
 internal parts become unsound. In the other species, which 
 is distinguished by the name of the diy rot, the disease begins 
 in the interior substance of the wood, particularly of that which 
 has not been well seasoned, and spreads outwardly, causing 
 the whole mass to swell, crack, and exhale a musty odor. 
 Different fungous vegetables sprout out of its substance, the 
 wood loses its strength, and crumbles finally into a mass of 
 dust. This disease prevails most in a warm, moist, and con- 
 fined atmosphere, such as frequently exists in the interior of 
 ships, and in the cellars and foundations of houses. Its de- 
 structive effects in ships of war, have given rise of late to nu- 
 merous publications. Some writers consider that the dry rot 
 is not essentially different from the more common kinds of de- 
 cay, but there seems to be sufficient reason for the distinction 
 which has usually b ;en drawn. The prevention of the evil 
 has been attempted in various ways, and with some degree of 
 success. 
 
 Felling. — It is agreed by most writers that the sap of vege- 
 tables is the great cause of their fermentation and decay. 
 Hence it appears desirable, if there is any season, in which 
 the trunk of a tree is less charged with sap than at others, that 
 this time should be selected for felling it. The middle of sum- 
 mer and the middle of winter, are undoubtedly the periods when 
 the wood contains least sap. In the months of spring and fall, 
 in which the roots prepare sap, but no leaves exist to expend 
 
488 ON THE PRESERVATION 
 
 itj the trunk is overcharged with sap ; and in many trees, as 
 the maple and birch, sap will flow out at these seasons, if the 
 trunk is wounded. In summer, on the contrary, when the 
 leaves are out, the sap is rapidly expended, and in winter, 
 when the roots are dormant, it is sparingly produced ; so that 
 no surplus of this fluid apparently exists. From reasoning a 
 priori, it would seem that no treatment would be so effectual 
 in getting rid of the greatest quantity of sap, as to girdle the 
 tree, by cutting away a ring of alburnum, in the early part of 
 summer, thus putting a stop to the further ascent of the sap, 
 and then to suffer it to stand until the leaves should have ex- 
 pended, by their growth, or transpiration, all the fluid which 
 could be extracted by them previously to the death of the tree.* 
 The wood would thus probably be found in the driest state to 
 which any treatment could reduce it in the living state. 
 Buffon has recommended stripping the trees of their bark in 
 spring, and felling them in the subsequent fall. This method 
 is said to harden the alburnum, but the cause is not very 
 apparent, nor is the success at all certain. 
 
 /■Seasojiing. — At whatever period timber is felled, it requires 
 to be thoroughly seasoned, before it is fit for the purposes of 
 carpentry. The object of seasoning is partly to evaporate as 
 much of the sap as possible, and thus to prevent its influence 
 in causing decomposition ; and partly to reduce the dimensions 
 of the wood, so that it may be used without inconvenience 
 from its further shrinking. Timber seasons best, when placed 
 in dry situations, where the air has a free circulation round it. 
 Gradual drying is considered a better preservative of wood, than 
 a sudden exposure to warmth, even of the sun ; for waimth 
 abruptly applied, causes cracks and flaws from the sudden and 
 unequal expansion produced in different parts. Two or three 
 years' seasoning is requisite to produce tightness and durability 
 in the wood work of buildings. It must be observed that 
 seasoning in the common way, only removes a portion of the 
 
 * See Mc,William on the Dry Rot, pages 151, and 158. 
 
OF ORGANIC SUBSTANCES. 489 
 
 aqueous and volatile matter from the wood. The extractive 
 and other soluble portions still remain, and are liable to 
 ferment, though in a less degree^ whenever the wood reabsorbs 
 moisture. Such, indeed^ is the force of capillary attraction, 
 that wood, exposed to the atmosphere in our climate, never 
 gives up all its moisture. 
 
 Preservation of Timber.— ^When wood is to be kept in a 
 dry situation, as in the interior of houses, no other preparation 
 is necessary than that of thoi'ough seasoning. But when it is 
 to be exposed to the vicissitudes of weather, and still more 
 when it is to remain in a warm and moist atmosphere, its pre- 
 servation often becomes extremely difficult. Numerous ex- 
 periments have been made, and many volumes written, upon 
 the preservation of timber, and the prevention of the dry rot ; 
 but the subject is not yet brought to a satisfactory conclusion. 
 The methods which have hitherto been found most successful, 
 consist in extracting the sap, in excluding moisture, and in im- 
 pregnating the vessels of the wood with antiseptic substances. 
 
 For extracting the sap, the process of ivater seasoning is 
 reconnnended. It consists in immersing the green timber in 
 clear water for about two weeks, after which it is taken out 
 and seasoned in the usual manner. A great part of the sap, 
 together with the soluble and fermentable matter, is said to be 
 dissolved or removed, by this process. Running water is more 
 effectual than that which is stagnant. It is necessary that the 
 timber should be sunk, so as to be completely under water, 
 since nothing is more destructive to wood, than partial immer- 
 sion. Mr Langton* has proposed to extract the sap by means 
 of an air pump, the timber being inclosed in tight cases, with a 
 temperature souiewbat elevated, and the sap being discharged 
 in vapor by the operation of the pump. 
 
 It appears extremely probable, that if trees were felled in 
 summer, and the buts immediately placed in water without re- 
 movirjg the branches, a great part of their sap would be ex- 
 
 * Rspertory of Arts, 1826. Franklin Journal, ii. and vi. 
 
 62 
 
490 ON THE PRESERVATIOIsr 
 
 pended by the vegetative process alone, and replaced by water. 
 It is well known that branches of plants, if inserted in water, 
 continue for some days, to grow, to transpire, and to perform 
 their other functions. This they probably do at the expense 
 of the sap, or assimilated fluid, which was previously m them, 
 while they replace it by the water they consume. This state 
 of things continues until the juices are too far diluted to be 
 capable of any longer sustaining life. 
 
 The charring of timber by scorching, or burning its outside, 
 is commonly supposed to increase its durability, but on this 
 subject the results of experiment do not agree. Charcoal is 
 one of the most durable of vegetable substances, but the con- 
 version of the surface of wood into charcoal, does not neces- 
 sarily alter the character of the interior part. As far, how- 
 ever, as it may operate in excluding worms, and arresting the 
 spreading of an infectious decay, like the dry rot, it is useful. 
 Probably also, the pyrohgneous acid which is generated when 
 wood is burnt, may exert a preservative influence. 
 
 The exclusion of moisture by covering the surface with a 
 coating of paint, varnish, tar, &c., is a well known perserva- 
 tive of wood which is exposed to the weather. If care is taken 
 to renew the coat of paint, as often as it decays, wood on the 
 outside of ^buildings, is sometimes made to last for centuries. 
 But painting is no preservative against the internal or dry rot. 
 On the contrary, when this disease is begun, the effect of paint, 
 by choking the pores of the wood, and preventing the exhala- 
 tion of vapors and gases which are formed, tends rather to ex- 
 pedite, than prevent the progress of decay. Paint itself is 
 rendered more durable, by covering it with a coating of fine 
 sand. Wood should never be painted, which is not thoroughly 
 seasoned. 
 
 The impregnation of wood with tar, bitumen, and. other re- 
 sinous substances, undoubtedly promotes its preservation. It 
 is the opinion of some writers,* that ' woods abounding in re- 
 
 * Tredgold's Elementary Principles of Carpentry, page 166. 
 
OF ORGANIC SUBSTANCES. 491 
 
 sinous matter, cannot be more durable than others,' but the 
 reverse of this is proved every year in the pine forests of this 
 country, where the lighhoood, as it is called, consisting of the 
 knots and other resinous parts of pine trees, remains entire, 
 and is collected for the purpose of affording tar, long after the 
 remaining wood of the tree has decayed. A coating of tar or 
 turpentine, externally applied to seasoned timber, answers the 
 same purpose as paint in protecting the wood, if it is renewed 
 with sufficient frequency. Wood impregnated with drying oils, 
 such as hnseed oil, becomes harder, and more capable of re- 
 sisting moisture. It is frequently the custom, in this country, 
 to bore a perpendicular hole in the top of a mast, and fill it 
 w4th oil. This fluid is gradually absorbed by the vessels of 
 the wood, and penetrates the mast to a great distance. Ani- 
 mal oils, in general, are less proper for this purpose, being 
 more liable to decomposition. 
 
 The preservative quality of common salt (muriate of soda), 
 is well known. An example of its effect is seen in the hay of 
 salt marshes, which is frequently housed before it is dry, and 
 which often becomes damp afterwards from the deliquescence 
 of its salt, yet remains unchanged for an indefinite length of 
 time. In the salt mines of Poland and Hungary, the galleries 
 are supported by wooden pillars, which are found to last 
 unimpaired for ages, in consequence of being impregnated 
 with the salt, while pillars of brick and stone, used for the 
 same purpose, crumble away in a short time by the decay of 
 their mortar. Wooden piles driven into the mud of salt flats 
 and marshes, last for an unlimited time, and are used for the 
 foundations of brick and stone edifices. In canals which 
 have been made in the salt marshes about Boston and other 
 places, trunks of oak trees are frequently found with the heart 
 wood entire and fresh, at a depth of five or six feet below the 
 surface. At Medford, Mass. the stumps of trees are found 
 standing in the gravelly bottom of the salt marsh where the 
 tide rises in the canals four or five feet above them. This 
 bottom must originally have constituted the surface of the 
 
492 ON THE PRESERVATION 
 
 ground, and must have settled long enough ago for the marsh 
 mud to have accumulated, as it has done for miles round, 
 apparently since that period. 
 
 The application of salt in minute quantities, is said rather 
 to hasten than prevent the decay of vegetable and animal 
 bodies. Yet the practice of docking timber, by immersing it 
 for some time in sea water, after it has been seasoned, is 
 generally admitted to promote its durability. There are some 
 experiments which appear to show, that after the dry rot has 
 commenced, immersion in salt water effectually checks its 
 progress, and preserves the remainder of the timber.* In 
 some of the public ships built in the United States, the inter- 
 stices between the timbers in various parts of the hull, are 
 filled with dry salt. When this salt dehquesces, it fills the 
 pores of the wood with a strong saline impregnation, but it has 
 been said, in some cases, to render the inside of the vessel 
 uncomfortably damp. If timber is immersed in a brine made 
 of pure muriate of soda, without the bitter delicjuescent salts 
 which sea water contains, the evil of dampness is avoided. 
 
 A variety of other substances besides common sail, act as 
 antiseptics in preventing the dry rot, and the growth of the 
 fungus w^hich attends it. Nitre and alum have been recom- 
 mended for this purpose, and some of the metallic salts are 
 considered still more effectual. Of these, the sulphates of iron, 
 copper, and zinc, have the effect to harden and preserve the 
 timber. Wood boiled in a solution of the former of these, 
 and afterwards kept some days in a warm place to dry, is said 
 to become impervious to moisture. Corrosive subhraate, which 
 is recommended by Sir H. DviVj, is a powerful preservative 
 of organized substances from decay, and proves destructive to 
 
 * The British frigate Resistaiacc, which went down in Malta harbor, and 
 the Eden, which was sunk in Plymouth Sound, were both affected with dry 
 rot. These ships, after remaining many months under water, were raised, and 
 it was found that the disease was wholly arrested. Every vestige of fungus 
 had disappeared, and the ships remained in service afterwards, perfectly sound 
 from any further decay. Supplement to the Encyclopedia Britannica, iii, 083. 
 
OF ORGANIC SUBSTANCES. 493 
 
 parasitic vegetables and animals ; but its safety, in regard to 
 the health of crews if used in large quantities about the wood 
 of a ship, may be considered as doubtful. 
 
 An opinion has been supported in this country, that the 
 decay of timber in ships, by dry rot, is owing to the impure 
 atmospliere generated by bilge water, and that it is to be rem- 
 edied by constructing ships with a view to their free and effec- 
 tual ventilation.* 
 
 Preservation of Aninial Textures. — The solid and fibrous 
 portions of organic bodies, such as wood, bone, shell, horn, hair, 
 cotton, &c., are most easy of preservation. But the soft and 
 succulent parts, such as the pulp of vegetables, and the flesh 
 of animals, are extremely perishable, owing to the decompo- 
 sing influence of their fluid contents ; and require the assist- 
 ance of art to communicate to them any degree of durability. 
 These substances, when the}'^ cannot be dried, are usually 
 preserved by enveloping or impregnating them with antisep- 
 tics. For alimentary substances the antiseptics used are sugar, 
 alcohol, salt, and the acetous and pyroligneous acids ; while, 
 for scientific specimens and preparations, alcohol, oil of turpen- 
 tine, resinous and bituminous varnishes, alum, and corrosive 
 sublimate are found most effectual. 
 
 Embalming. — As the art of embalming can hardly be 
 ranked among the useful arts, any further than it can be made 
 subservient to the promotion of anatomy, or natural history, it 
 is not much cultivated at the present day. The ancient Egyp- 
 tians converted the dead bodies of their friends into mummies, 
 by removing the viscera from the large cavities, and replacing 
 them with aromatic, saline, aud bituminous substances, particu- 
 larly asphaltum ; and also enveloping the outside of the body 
 in cloths impregnated with similar materials. These impreg- 
 nations prevented decomposition, and excluded insects, until 
 perfect dryness took place. In times comparatively modern, 
 embalming has been practised with great success, particularly 
 
 * See a pamphlet on Dry Rot, by Commodore Barron, Norfolk, 1828. 
 
494 ON THE PRESERVATION 
 
 where bodies have remained at a low and uniform temperature, 
 and have been protected from the access of the air. The body 
 of king Edward the First, of England, appears upon record to 
 have been embalmed. He died in July, 1307, and was buried 
 in Westminister Abbey. In 1770, his tomb was opened, and 
 the contents examined, and after this lapse of 463 years, the 
 body of the monarch remained entire. The flesh upon the 
 face was a little wasted, but not putrid. The body of Canute, 
 king of Denmark, who invaded England in 1017, was found 
 very fresh in 1776, by the workmen employed in repairing 
 Winchester Cathedi-al. The bodies of WiUiam the Conqueror, 
 and of Matilda his wife, both buried at Caen, were found entire 
 in the sixteenth century. In like manner, the remains of va- 
 rious other princes, and persons of note, have been discovered 
 to be undecayed some centuries after their decease. In cer- 
 tain cases, bodies not embalmed have been preserved, merely 
 by the exclusion of air, and a uniform low temperature. 
 
 But the most perfect of all the modes of preserving the an- 
 imal body, without continued immersion, appears to be a thor- 
 ough impregnation with corrosive sublimate. This may be 
 performed, by saturating the soft solids with a strong solution, 
 consisting of about four ounces of bichloride of mercury to a 
 pint of alcohol. This is injected into the blood vessels, and 
 after the viscera are removed, the whole body is immersed for 
 three months in the same solution. At the end of this period 
 it easily dries, and is afterwards nearly imperishable.* 
 
 In what are called by anatomists ivet preparations, the ob- 
 jects are kept immersed in alcohol, and last for an indefinite 
 time. Oil of turpentine answers the same purpose, and in the 
 Museum of Natural History, in Paris, there is a head prepared 
 in yiiis way, more than a hundred years ago, by the celebrated 
 Ruytch, which preserves all the vivacity of its colors. In cold 
 weather the liquid becomes opaque, but is again rendered 
 transparent in the spring. 
 
 * See a paper by Dr J. C. Warren, on Embalming, in the Boston Journal 
 of Arts, vol. i. p. 269. 
 
OF ORGANIC SUBSTANCES. 495 
 
 Tanning. — The skins of animals, when prepared by merely 
 drying them, are stiff, incapable of resisting- water, and liable 
 to decay. If, however, they are impregnated with the tannin 
 w^hich is found in astringent vegetables, that substance com- 
 bines with the gelatin of the skin, and forms a durable com- 
 pound, which is no longer soluble in water. Common tan- 
 ned leather is prepared in this way. The skins are previously 
 prepared by soaking them in lime water, which facilitates the 
 separation of the cuticle and hair. A shght degree of putres- 
 cenc}^ assists the same object. They are then immersed in the 
 tan pits, in a strong infusion of some astringent vegetable. 
 Oak bark, from its cheapness, and the quantity of tannin it 
 contains, is commonly employed in the preparation of leather, 
 both in this country, and in Europe. The bark of the hem- 
 lock spruce, and of the chesnut, the leaves of the different spe- 
 cies of sumach, and various other astringent vegetables, are 
 used in sections of country where oak is scarce. The strength 
 of the astringent infusion is increased from time to time, untii 
 the skin is saturated Avith tannin. A portion of extractive 
 matter likewise combines with the hide, and to this the brown 
 color, which is common in leather, is owing. The presence 
 of this extractive is supposed to render leather more tough and 
 pliable. 
 
 When strong or saturated solutions of tannin are used, the 
 leather is formed in a much shorter time, but it is observed 
 that leather tanned in this way is more rigid and more liable to 
 crack, than that made in the common mannerj with weaker 
 infusions, gradually increased in strength. But sole leather, 
 the most important requisites of which are firmness and resist- 
 ance to water, is immersed in an infusion kept nearly saturated 
 by alternate strata of bark. The full impregnation requires 
 from 10 to 18 months. 
 
 The currying of leather is performed by covering the skin 
 or leather, while yet moist, with common oil, which, as the 
 moisture eyaporates, penetrates into the pores of the skin, giv- 
 ing it a peculiar suppleness, and rendering it, to a certain ex- 
 
496 ON THE PRESERVATION 
 
 tent, water proof. During the process, it is pared, Avashed, 
 and rubbed, to increase its flexibility. .The black color is also 
 imparted by the currier, by rubbing the outside with a solution 
 of copperas, or any solution of iron, which immediately turns 
 it black, by combining with the tannin in the leather. 
 
 Taioing is the method by which skins are dressed of a 
 white color, and it is performed without the use of bark. The 
 skins are first prepared by steeping them in lime water, and 
 subjecting them to various processes of scraping and fulling. 
 They are then fermented with wheat bran, and afterwards 
 impregnated with a solution of alum and common salt. Be- 
 fore being dried, they are fulled with wheat bran and yolks of 
 eggs, and are thoroughly trodden, steeped, and washed. In 
 this process, the place of tannin appears to be supplied by 
 some principle extracted from the alum. 
 
 As examples of the foregoing processes, common sole leather 
 is simply tanned^ the upper leather of boots and shoes, is tan- 
 ned and curried^ the white leather for gloves is tawed, and 
 fine morocco leather is tawed, and afterwards slightly tanned 
 with sumach, and dyed. Chamois, and other kinds of wash 
 leather, are steeped in hme pits, and afterwards fulled with oil. 
 Before the dressing is finished, the superfluous oil is scoured 
 out with an alkaline liquor. 
 
 Parchment. — Parchment used for writing, is prepared from 
 the skins of sheep and goats. These, after being steeped in 
 pits impregnated with lime, are stretched upon frames and re- 
 duced by scraping and paring, with sharp instruments. Pul- 
 verized chalk is rubbed on with a pumice stone resembling a 
 muUer, which smooths and softens the skin, and improves its 
 color. After it is reduced to something less than half its orig- 
 inal thickness, it is smoothed and dried for use. Vellum is a 
 similar substance to parchment, made from the skins of very 
 young calves. 
 
 Catgut. — The strings of certain musical instruments, the 
 cords of clock weights, and those of some other machines and 
 implements, are made of a dense strong, animal substance. 
 
OF ORGANIC SUBSTANCES. 497 
 
 among us usually denominated catgut. It is derived from the 
 intestines of different quadrupeds, particularly those of cattle 
 and sheep. The manufacture is chiefly carried on in Italy and 
 France. The texture from which it is made, is that which 
 anatomists call the Tnuscular coat, which is carefully separated 
 from the peritoneal and mucous membranes. After a tedious 
 and troublesome process of steeping, scouring, fermenting, in- 
 flating, (fcc, the material is twisted, rubbed with horsehair 
 cords, fumigated with burning sulphur, to improve its color, 
 and dried. Cords of different size, and strength, and delicacy, 
 are obtained from different domestic animals. The intestine 
 is sometimes cut into uniform strips with an instrument made 
 for the purpose. To prevent offensive effluvia during the pro- 
 cess, and to get rid of the oily matter, the French make use 
 of an alkaline hquid called eau de Javelle. 
 
 Gold Beatefs Skin. — This delicate membrane is also 
 manufactured from the intestines of animals. The workman 
 strips off that part of the peritoneal membrane which surrounds 
 the caecum. He then takes about two feet of it in length, 
 turns it inside out, and leaves it to dry. It is afterwards 
 steeped in a weak solution of potash, cleansed by scraping, 
 and cut open. It is then stretched to dry upon wooden frames, 
 and notwithstanding the tenuity of the membrane when dry, 
 every piece of it is double, or consists of two membranes glued 
 together. It is finished by washing it with a solution of alum, 
 and coating it with isinglass and whites of eggs, together with 
 some aromatics to repel insects.* 
 
 Sjiecimens in Natural History. — Preparations of animals 
 intended to show their external form and characters, are 
 made by detaching their skins, and stuffing or mounting 
 these so as to represent the natural figure and attitudes of the 
 animal. Quadrupeds and birds are preserved by extracting 
 the body through an opening on the under side, at the same 
 
 * See Franklin Journal, iii. 223, and London Mechanics Magazine, vi. 63 ; 
 also the Prize Essay of Labarraque, 1822. 
 
 63 
 
498 ON THE PRESERVATION 
 
 time inverting the skin. The fleshy parts of the limbs are 
 extracted through the same opening, also the neck, brain, and 
 eyes, leaving the skull, if the animal be small. Care is taken 
 not to injure the hair, or plumage. When the fleshy parts 
 are removed, the inside of the skin is rubbed with some 
 poisonous substance, usually arsenic,* to prevent insects. The 
 skin is then returned to its natural situation, and filled with 
 cotton or tow, or, what is still better, an artificial body, shaped 
 out of wood, cork, or dried clay, may be introduced within 
 the skin. The opening is sew^ed up, and wires are passed 
 longitudinally through the legs and neck. These are after- 
 wards bent into the proper position to give the attitude 
 desired. Glass eyes are inserted, and the hair and feathers 
 rendered as smooth as possible, and retained^ while drying, in 
 paper bandages. 
 
 Reptiles, and fishes without scales^ are extracted by carefully 
 separating the bones of the neck through an opening in the 
 throat, or gills, and inverting the skin. In serpents, the 
 whole body is easily extracted through the mouth. Fishes 
 with scales cannot be turned without injury. It is therefore 
 necessary to detach the skin carefully, without doubling it. 
 Insects may be killed, without hurting their texture, by the 
 fumes of burning sulphur, or prussic acid, or, in many cases, 
 by pinching the breast. They are then secured by pins, and 
 placed to dry with the wings and legs in the natural attitudes. 
 Arsenic, or corrosive sublimate, is generally necessary to secure 
 them from the depredations of other insects. 
 
 An Herbarium, or collection of dried plants, is usually 
 formed by subjecting the plants, while fresh, to a sufiicient 
 pressure between folds of paper, to preserve their natural 
 smoothness and regularity, until they become dry. The 
 plants should be gathered at a time when their characters are 
 most perfectly developed. A specimen in flower should be 
 
 * The following is the arsenical soap of Becoeur, much used in France : 
 Camphor 5 ounces, powdered arsenic 2 pounds, white soap 2 pounds, salt of 
 tartar 12 ounces, lime 4 ounces, melted and triturated together. 
 
OF ORGANIC SUBSTANCES. 499 
 
 preserved, and, if possible, one also in fruit. The plant must 
 be carefully spread out on smooth, bibulous paper, so that the 
 leaves, petals, &c.. may be displayed as perfectly as possible. 
 In this situation it is retained, and another sheet of paper 
 turned gradually over it, commencing at one side, till the 
 whole is covered. Several sheets of paper are then to be 
 added to each side, and the whole placed to dry under a strong, 
 equal pressure. In this way many plants may be preserved 
 without further trouble, especially if the weather be warm and 
 dry. The process, however, may be expedited by shifting the 
 papers, or by passing over them occasionally a warm iron. 
 These precautions are more necessary for succulent plants, or 
 for others in cold and damp weather. 
 
 Apperfs Process. — A method brought into notice by M. 
 Appeit, for preserving articles of food unchanged for several 
 years, deserves to be noticed among the practical improvements 
 of the present centmy. This method was partially known at 
 a much earlier period, but its most successful modes of appli- 
 cation were undoubtedly discovered by M. Appert. It con- 
 sists in a very simple process. The articles to be preserved 
 are inclosed in bottles, which are filled to the top with any li- 
 quid ; for example, with the water in which the article, if solid, 
 has been boiled. The bottles are closely corked, and cement- 
 ed, to render them hermetically tight. They are then placed 
 in kettles filled with cold water, and subjected to heat till the 
 water boils. After the boiling temperature has been kept up 
 for a considerable time, in some cases an hour, but varying 
 with the character of the article to be preserved, the bottles 
 are suffered to cool gradually. In this state, meats, vegetables, 
 fruits, milk, and other substances, are preserved perfect^ fresh, 
 without any condiments, for long periods, of from one to six 
 years. Instead of bottles, tin canisters are sometimes used, 
 and rendered tight by soldering. 
 
 The remarkable effect of this process has been explained, by 
 attributing the preservation of the articles to the total exclusion 
 of atmospheric air. But as air, in common cases, is always 
 
500 ON THE PRESERVATION OF ORGANIC SUBSTANCES. 
 
 present in sufficient quantities to excite fermentation, it is sup- 
 posed that the apphcation of heat serves to fix the small portion 
 of atmospheric oxygen which is present, by combining it with 
 some principle in the other substances ; so that it is no longer 
 capable of producing the fermentative action, which in paral- 
 lel cases leads to decomposition. 
 
 Chapman's Treatise on the Preservation of Timber, 8vo. 3817; — 
 Tredgold's Elementary Principles of Carpentry, 4to. 1820; — Mc- 
 WiLLiAM, on the Dry Rot, 4to. 1818 ; — Article Dry Rot, in the sup- 
 plement to the Encyclopedia Britannica; — Aiken's Chemical Dic- 
 tionary, article Leather ; — Labarraque, VArt du Boyaudeur ; Bulletin, 
 de la Soci6t6 de F Encouragement pour VIndustrie, 1822 ; — Lettsom's 
 Naturalist's Companion, 8vo. ; — Taxidermy, or the Art of Collecting, 
 Preparing, and Mounting Specimens in Natural History, London, 
 1823 ; — Appert, Art of Preserving Animal and Vegetable Substan- 
 ces, London, translated, 1812 ; — Edinburgh Review, vol. 23, p. 104. 
 
APPENDIX. 
 
 Safety of Steam Engine Boilers. The accidents which 
 have happened to the boilers of steam engines may properly 
 be divided into two classes ; those of simple rupture, and those 
 of explosion. These two casualties apparently occur under 
 different states of things. The simple rupture of boilers has 
 usually taken place at a temperature not greatly exceeding that 
 at which engines are commonly worked, and has in many in- 
 stances been the consequence of some weakness or defective 
 condition of the metal. In such cases, the elastic force of the 
 steam not being very great, the strain has been gradual, the 
 accident has in some cases been preceded by a swelling out, 
 or gradual yielding of the weakened part ; and when the rup- 
 ture has taken place, the consequences have not usually been 
 of a very alarming nature. Against this accident a sufficient 
 remedy is found in attending to the proper preservation of 
 the metal, and regulation of the safety valves. 
 
 The explosions of boilers, in which the contents and frag- 
 ments are projected to a distance with great force, are in many 
 cases apparently the result of an extraordinary initial force in 
 the steam, and are probably caused by a portion of the metal 
 which is not in contact with the water, becoming excessively 
 heated ; so that when water is brought suddenly into contigu- 
 
502 APPENDIX. 
 
 ity with it, steam of great elastic force is suddenly generated. 
 In this case, as in fire-arras, the bursting takes place before the 
 inertia of surrounding moveable objects can be overcome, so 
 that the water and safety valve, which would yield easily un- 
 der gradual pressure, become insurmountable obstacles under 
 sudden pressure. 
 
 Unfortunately, no remedy for this evil can well be applied 
 to engines as they are now fitted up for use. In steam boats 
 particularly, the sudden rolHng and pitching of the vessel in 
 rough weather, may cause heated portions of the boiler which 
 were raised above the surface of the water at one minute, to be 
 depressed below it at another. When this motion is regular, 
 it serves to correct its own effects ; but when it suddenly takes 
 place in a greater degree than before, it is not free from danger. 
 In still water the same thing may happen by the changing of 
 the passengers or freight from one side of the boat to another. 
 Even stationary boilers on land, may, in case of violent ebulli- 
 tion, be caused to explode, if the water is suffered to get too 
 low, so that the metal becomes over-heated, and therefore ca- 
 pable of forming steam of great elastic force, when a sudden 
 effervescence brings the water near to the heated parts. 
 
 The method which promises most effectually to obviate the 
 danger, is that proposed by Mr Treadwell, and originally pub- 
 lished in the Boston Daily Advertiser of May 17, 1830. This 
 is a proposed plan for working steam at a pressure not exceed- 
 ing that of the atmosphere. The importance of this paper 
 will justify the insertion of the principal part of it at length, in 
 the author's own words. 
 
 After speaking of the frequency and causes of these acci- 
 dents, and the utter impossibility of guarding against the care- 
 lessness of attendants and subordinate agents employed about 
 the engines, Mr Treadwell goes on to remark : — 
 
 ' These considerations naturally suggest the question ; 
 whether it be possible to obtain a power, from steam, particu- 
 larly for steam boats, without any pressure over that of the 
 atmosphere ? for this, and this alone, would put an end to all 
 
APPENDIX. 503 
 
 possibility of accident. Before attempting to show that there 
 is no obstacle whatever in the way of this, it may be well to 
 state briefly the mode ia which engines are made to operate. 
 I speak here altogether of the low pressure, or, more properly, 
 the condensing engine ; this, as I have before stated, being 
 the most safe, although by no means free from danger. In 
 working an engine, of this sort, it is usual to raise the steam 
 in the boiler to exert a pressure of about 12 pounds, above the 
 'pressure of the atmosphere^ upon every square inch of the 
 surface which surrounds it. A portion of this steam is then 
 suffered to pass into one end, suppose the top, of the cylinder, 
 where it exerts, essentially, the same pressure which it pos- 
 sessed in the boiler. By this the piston is made to move through 
 the cylinder to the bottom. When the piston has thus arrived 
 at the bottom of the cylinder, the steam, with which the cyl- 
 inder is now filled, is, by the operation of a peculiar apparatus, 
 which it is not necessary to describe, condensed ; at the same 
 time, more steam, from the boiler, is let in to the bottom of the 
 cylinder, and the piston is driven to the top, when this steam 
 is condensed, and the piston is, by a further supply of steam, 
 at the top of the cyhnder, driven again to the bottom ; and 
 these operations are continually repeated. 
 
 ' Let us now examine the force with which the piston is 
 moved through the cylinder, under the conditions here nam- 
 ed. If we take the steam to possess an elastic force of 12 
 pounds upon every inch of the area of the piston, above the 
 pressure of the atmosphere, its whole elastic force must be 27 
 pounds, the force of the atmosphere never varying much fi'om 
 15 pounds. Suppose the piston to be 50 inches in diameter, 
 it will then contain an area of 1950 square inches nearly. 
 We have then a force of 52,650 pounds pressure upon the end. 
 of the piston exposed to the steam. Now, on the opposite end 
 of the piston, the steam having been condensed as much as 
 possible, there is a vacuum. It is perfectly practicable to car- 
 ry the condensation as low as 3 pounds to the inch ; which, 
 multiplied by 1950 inches, as before, gives 5850 pounds ; and 
 
504 APPENDIX. 
 
 this small force only is opposed to the 52,650 pounds, which I 
 have shown to be the pressure of the steam upon the piston. 
 The piston will then move with a force of 52,650, less 5850 
 or 46,800 pounds. Let us now suppose that instead of using 
 steam of an elastic force of 12 pounds above the pressure of 
 the atmosphere, we use it at precisely the atmospheric pressure. 
 It is evident that the force on the piston will then be 1950, the 
 number of square inches, multiplied by 15, the. pressure on 
 each inch, or 29,250 pounds. The resistance on the opposite 
 end will be as before, 5850 pounds, leaving the effective force 
 23,400 pounds. The same piston then will, if wrought with 
 steam which exerts no pressure whatever, on the boiler, above 
 the force of the atmosphere, give half as much force as when 
 wrought with steam of 12 pounds to the inch.— To obtain an 
 equal force, then, we have only to double the area of the piston, 
 or to make its diameter 70,7 inches instead of 50. A boiler 
 for such steam may be made of any material whatever, that 
 will hold water. It may be made of sheet iron, of tin, of sheet 
 lead ; I might almost say of paper, for it is possible to boil 
 water in a paper vessel. The boiler may be closed with a 
 common pot-lid, and can no more burst than a tea-kettle. 
 
 ' The facts before stated are so famihar to all engineers, that 
 I ought not, perhaps, to have detailed them. They may not, 
 however, have been known to all persons who yet travel 
 in peril of life and limb. It is not to be expected that any 
 change of this kind will be made in engines, unless they can 
 be constructed and wrought without a greater cost than is re- 
 quired in the present mode. It is perfectly easy to show that 
 this will be the case ; for, first, no greater cost would be required 
 in any part, except in the cylinder, piston, steam-pipes and 
 valves, which must be made of double size, in this to the com- 
 mon engine, to furnish an equal force. The piston rod, lever 
 beam, or cross head, connecting rods, shafts, cranks, indeed 
 all the other moveable parts would be required of like size, for 
 engines of like force, in either form of construction. The in- 
 crease of size required in the cylinder and piston would be 
 
APPENDIX. 5U5 
 
 much more than compensated, by a diminution in the cost of 
 the boiler. There would in fact be a very great saving of ex- 
 pense by adopting this mode of construction. The cost of 
 working an engine consists principally in the maintenance of 
 the fire ; it is therefore directly as the quantity of fuel consum- 
 ed or the quantity of heat required for the production of the 
 steam. Now it may be said that for an engine of this con- 
 struction, as the cylinder must be of twice the size of that or- 
 dinarily used, to produce an equal force, therefore a double 
 quantity of steam must be used, and, consequently, a double 
 quantity of fuel will be required for its production. This will, 
 on examination, be found altogether fallacious. It is true that 
 a double volume of steam will be required, but its density will 
 be but little more than half as great as that of steam of double 
 elastic force. — Now the heat contained in steam, from the boil- 
 er of an engine, is known to be, very nearly, in the direct ra- 
 tio of its density. Two volumes therefore, the density of which 
 shall be represented by 1, and one volume of a density repre- 
 sented by 2, will contain very nearly equal quantities of heat ; 
 and as the same quantity of heat may, in both cases, be ob- 
 tained from the same fuel, we have the same power obtained 
 at about the same cost, whether we use steam at the usual 
 elastic force, or, merely sufficient to sustain the weight of the 
 atmosphere. 
 
 ' In the preceding statement I have constantly supposed 
 the engines to be wrought in the ordinary mode, that is, at 
 full pressure. If the steam were used expansively, there would 
 be a difference in favor of that having the greater elastic force. 
 But this is a hypothetical case, for the engines of steam boats 
 are seldom used expansively, and, in the few instances where 
 they are so used, it is not carried to an extent which would af- 
 fect in any great degree the results above stated. 
 
 ' There are many advantages incidental to the use of at- 
 mospheric steam, which are important besides those before 
 enumerated. Amongst these are the saving of weight, in the 
 64 
 
506 APPENDIX. 
 
 boiler, the diminution of friction, in the piston, and the saving 
 of a portion of the heat now lost by radiation. 
 
 ' The mode of construction and use, here recommended, can 
 hardly be called a new mode. The engine, as constructed by 
 Newcomen, depended entirely upon the vacuum for its force ; 
 and the improvements by which that engine has been super- 
 seded, consisted, not in increasing the elastic force of the steam, 
 but, in a different organization of the machine. In engines 
 now used at the manufactories, in England, the steam is rare- 
 ly raised to an elastic force greater than 4 pounds to the inch 
 above the atmospheric pressure. Such engines are compara- 
 tively safe, and we seldom hear of accidents occasioned by 
 them. Perfect safety, however, is only to be obtained by the 
 use of steam of an elastic force not exceeding the weight of 
 the atmosphere.' 
 
 FINIS. 
 
INDEX. 
 
 Abutments, 121 
 
 Acanthus, 136 
 
 Achmet, Mosque of, 151 
 
 Acroteria, 130 
 
 Aerial Perspective, 85 
 
 Aerostation, 228 
 
 Agate, 13 
 
 Agrigentum, 140 
 
 Air Flues, 167 
 
 Alabaster, 12 
 
 Aihambra, 153 
 
 Alloys, 394 
 
 Alloy of Gold, 398 
 
 Alternate Motion, 240 
 
 Amalgam, 22 
 
 Amalgamation, 394 
 
 Amber, 23 
 
 Amianthus, 15 
 
 Amphiprostyle Temple, 137 
 
 Amphitheatre, 144 
 
 Annealing, 399, 459 
 
 Animals, Motion of, 194 
 
 Animal Power, 258 
 
 Anime, 442 
 
 Annotto, 451 
 
 Anthracite, 24 
 
 Anthracite Grate, 164 
 
 Antimony, 23 
 
 Antiseptics, 486 
 
 AntaB, Temple with, 137 
 
 Antoninus and Faustina, 145 
 
 Apollo de Belvidere, 8 
 
 Apollo Didymeus, Temple of, 142 
 
 Appert's Process, 499 
 Apron, 263 
 Aqua Tinta, 97 
 •Aqueducts, 215 
 
 , 308 
 
 Arabesque, 148 
 ArsBOstyle, 139 
 Arseo Systyle, 147 
 Arbor, note, 378 
 Arbor VitsB, 32 
 Arcade, 122 
 Arch, 119 
 Archil, 450 
 
 Archimedes' Screw, 317 
 Architecture, 115 
 Architrave, 130 
 Archivolt, 121 
 Arena, 144 
 Argand Lamp, 183 
 Arkwriglit, Richard, 353 
 Arsenic, 23 
 Asbestus, 15 
 Ash, 27 
 Asphaltum, 23 
 
 ,437 
 
 Assaying, 394 
 Astragal, 113 
 Astral Lamp, 180 
 Atmospheric Engine, 289 
 Attic, 130.— Base, 135 
 Attrition, 338 
 Automaton Lamp, 182 
 Axis, note, 378 
 
508 
 
 INDEX. 
 
 Axle, note, 378 
 Axletrees, 202 
 Azure. -See Ultramarine. 
 
 Back Water, 267 
 
 Badigeon, 439 
 
 Balance, 376 
 
 Balbec, Temple at, 147 
 
 Ballast, 223 
 
 Balloon, 228 
 
 Baltimore Monument, 127 
 
 Band, 249 
 
 Band Wheels, 232 
 
 Bark, 26 
 
 Bark Mills, 340 
 
 Barker's Mill, 270 
 
 Base of Columns, 129 
 
 Basilica, 144 
 
 Basis, in Dyeing, 448 
 
 Bass Wood, 28 
 
 Batting, 353 
 
 Battlement, 150 
 
 Bay Window, 150 
 
 Bayonets, 251 
 
 Beams, Shape of, 50 
 
 Beech, 28 
 
 Bell Metal, 409 
 
 Belt and Segment, 247 
 
 Benzoin, 442 
 
 Besant's Wheel, 268 
 
 Bevel Gear, 235 
 
 Bice, 435 
 
 Biddery Ware, 413 
 
 Birch, 29 
 
 Birds, Flying of, 195 
 
 Biscuit, 479 
 
 Bismuth, 23 
 
 Bistre, 437 
 
 Bitumen, 23 
 
 Black Lead, 25 
 
 Black Walnut, 29 
 
 Blasting with Powder, 306 
 
 Bleaching, 446 
 
 Blowing Glass, 459 
 
 Blue Verditer, 434 
 
 Body Colors, 434 
 
 Boiler, 282 
 
 Bole, 435 
 
 Bologna Phials, 459 
 
 Boltels, 150 
 
 Bone, 40 
 
 Boring, 336 
 
 Boston State House, 126 
 
 Bottle Glass, 460 
 
 Boustrophedon, 53 
 
 Boxwood, 32 
 
 Brake, 213 
 
 Brass, 21 
 
 , 407 
 
 Brazil Wood, 450 
 Breast Wheel, 269 
 Bricks, 471 
 Bridges, 206 
 
 Bridgewater's Canal, 215 
 Broad Glass, 460 
 
 Wheels, 200 
 
 Bronze, 21 
 
 , 409 
 
 Casting, 110 
 
 Brunswick Green, 437 
 Brush Wheel, 237 
 Buckets, 264 
 Buhrstone, 13 
 Bulk, Limit of, 48 
 Bunker Hill Monument, 10 
 Burning Pottery, 478 
 Burning of Smoke, 177 
 Burns' Grate, 164 
 Bushnell's Machine, 227 
 Butternut Dye, 452 
 Buttons, 408 
 Buttonwood, 29 
 Buttress, 150 
 , Flying, 150 
 
 Calamus, 58 
 Calcareous Stones, 7 
 Caledonian Canal, 218 
 Calico Printing, 452 
 Cameos, 113 
 Cams, 240 
 Canals, 213 
 
INDEX. 
 
 509 
 
 Canals, size of, 218 
 Canal Boats, 217 
 Candles, 179 
 Caoutchouc, 35 
 Capitals of Columns, 129 
 Capitol at Washington, 10 
 
 ,126 
 
 Carats, 398 
 
 Card Ends, 355 
 
 CardiYig, 354 
 
 Carmine, 435 
 
 Carpets, 363 
 
 Carthamus Tinctorius, 436 
 
 Cartoons, 440 
 
 Cartwright's Steam Engine, 244 
 
 Caryatides, 136 
 
 Case, 62 
 
 Case Hardening, 426 
 
 Casting, 347 
 
 Cast Iron, 417 
 
 Casting in Plaster, 108 
 
 Pottery, 478 
 
 Catenary Arch, 120 
 Catgut, 496 
 Cathedral, 148, 151 
 
 , Milan, 126 
 
 , Strasburg, 126 
 
 , York, 151 
 
 Cavetto, 131 
 
 Cedar, 31, 32 
 
 Cell, 136 
 
 Cementation of Gold, 398 
 
 Cementing, 345 
 
 Cements, 16 
 
 Cerulin, 449 
 
 Chain Pump, 327 
 
 Wheel, 264 
 
 Chalk, 12 
 
 Chamois Leather, 496 
 Chancel, 149 
 Charcoal, 157 
 Charring of Timber, 490 
 Cherry Tree, 28 
 Chesnut, 28 
 Chiaro Oscuro, 83 
 Chill Casting, 419 
 
 Chimnies, 171, 174 
 
 China Ware, 480 
 
 Chinese Style, 133 
 
 Chipolin, 439 
 
 Choir, 149 
 
 Choragic Monument, 143 
 
 Chrome Red, 435 
 
 Chrome Yellow, 436 
 
 Church, 149 
 
 Cider Mills, 341 
 
 Circular Saw, 338 
 
 Clay, 15 
 
 Clepsydra, 372 
 
 Clock, Description of^ 378 
 
 Clock Work, 373 
 
 Close Hauled, 220 
 
 Close Rooms, 175 
 
 Clutches, 251 
 
 Coal, 24 
 
 Gas, 187 
 
 Grate, 164 
 
 Cochineal, 435, 450 
 Cockle, 167 
 Coffer Dam, 207 
 
 Walls, 118 
 
 Cohesion, 334 
 
 Coin, 398 
 
 Coining, 403 
 
 Coin Posts, 216 
 
 Coke, 23 
 
 Coliseum at Rome, 126 
 
 Colcothar, 435 
 
 Colors, 87 
 
 Coloring, 87 
 
 Colored Engravings, 99 
 
 Color Mills, 342 
 
 Coloring Substances, 433 
 
 Column, 129, 116 
 
 Composing, 62 
 
 Composite Order, 144 
 
 Compression, 45 
 
 Concord, Temple of, 140 
 
 Condensation of Steam, 278 
 
 Condensing Engine, 289 
 
 Cones, Double, 238 
 
 , Geared, 238 
 
510 
 
 INDEX. 
 
 Constantinej Arch of, 146 
 
 Contrast, 89 
 
 Contrate Wheel, 236 
 
 Convoy, 213 
 
 Copal, 37, 441 
 
 Copper, 20 
 
 Copper, Extraction of, 406 
 
 , Working of, 406 
 
 Plates, 91 
 
 Copperplate Printing, 99 
 Copying Machines, 60 
 Corbel, 150 
 Cordage, 349 
 Corinthian Order, 135 
 Cork, 33 
 Cornelian, 13 
 Cornice, 129 
 Correcting the Press, 64 
 Corundum, 13 
 Cotton, 34 
 
 Gin, 34 
 
 Spinning, 352 
 
 Counterpanes, 364 
 Couplings, 251 
 Covering of Roofs, 128 
 Cranks, 238, 242 
 Crayons, 438 
 Crevices, 171 
 Crockets, 150 
 Crocus Martis, 435 
 Crown Glass, 458 
 
 Wheel, 236 
 
 Cross Weaving, 362 
 Crucibles, 474 
 Crushing, 339 
 Crystallo Ceramic, 468 
 Culverts, 173, 214 
 Cupellation, 396 
 Cupola, 122 
 Curb, 390 
 
 Roof, 127 
 
 Currying, 495 
 Cutlery, 429 
 Cutting, 335 
 
 , Glass, 464 
 
 Machines, 335 
 
 Cuttle Fish Liquor, 437 
 Cylinder Glass, 461 
 Cymatium, 131 
 Cypress, 31 
 
 Danforth's Speeder, 356 
 
 Davy's Safety Lamp, 190 
 
 Dead Water, 219 
 
 Decomposition, 484 
 
 Dentels, 135 
 
 Derbyshire Spar, 12 
 
 Designing, 72 
 
 Devitrification, 467 
 
 Dial, 371 
 
 Diameter of a Column, 131 
 
 Diamond, 13 
 
 Diastyle, 139 
 
 Die, 129 
 
 Diocletian's Palace, 153 
 
 Dipteral Temple, 138 
 
 Direction of Light, 84 
 
 Disengaging Machinery, 251 
 
 Dishing Wheels, 201 
 
 Distemper, 439 
 
 Dividing of Bodies, 335 
 
 Diving Bell, 225 
 
 Docking of Timber, 492 
 
 Dome, 122 
 
 Doric Order, 134 
 
 Double Fire Place, 162 
 
 Double Speeder, 355 
 
 Double Weaving, 361 
 
 Dovetailing, 343 
 
 Draviring, 72, 131 
 
 Drawing of Cotton, 354 
 
 Dressing, 359 
 
 Drilling, 330 
 
 Drying Oils, 36 
 
 Dry Point, 92 
 
 Ductility, 44 
 
 Dutch Pink, 436 
 
 Dyeing, 447 
 
 Dyes, 448 
 
 Ebony, 33 
 Echinus, 134, 131 
 
INDEX. 
 
 611 
 
 Edge Railway, 209 
 Egyptian Style, 132 
 Elastic Gum, 35 
 Elasticity, 44 
 Elastic Moulds, 109 
 Elephanta, 133 
 Elevation, 131 
 Eliquation, 402 
 Elm, 27 
 
 Embalming, 493 
 Embankments, 214 
 Emery, 1 3 
 Enamelling, 466 
 Encaustic Painting, 440 
 Enchasing, 399 
 Engaging Machinery, 251 
 Engines, Fire, 332 
 Engine, Steam, 287, 281 
 Engraving, 91 
 Engraving of Gems, 112 
 Entries, 171 
 Entablature, 130 
 Entasis, 117 
 
 Epicycloidal Wheel, 245 
 Epistylium, 130 
 Equalizing Motion, 252 
 Erectheum, 142 
 Erie Canal, 218 
 Essenay, Temple at, 151 
 Etching, 94 
 Etruscan Vases, 482 
 Eustyle, 139 
 Expansion Engines, 293 
 Expansion of Steam, 280 
 Extension, 44 
 Extrados, 121 
 Eyes of a Portrait, 85 
 
 Faqade, 129 
 Fast Colors, 453 
 Fat Oil, 35 
 Feathers, 38 
 Fecula, 36 
 Feeders, 214 
 Feedpipe, 284 
 Feldspar, 9 
 
 Felling of Timber, 487 
 
 Felting, 367 
 
 Fibres, Combination of Flexible, 349 
 
 Field of Vision, 73 
 
 Fig Blue, 435 
 
 Fillet, 131 
 
 Filtering Stone. See Freestone. 
 
 Fire Engines, 332 
 
 in the open Air, 159 
 
 Modes of Procuring, 192 
 
 Fireplaces, 159, 174 
 
 Firs, 30 
 
 Fishes, Swimming of, 195 
 
 Flake White, 438 
 
 Flame, 178 
 
 Tlafige, 209 
 
 Flash Wheel, 333 
 
 Flat Boards, 266 
 
 Flax, 33 
 
 Flint, 12 
 
 Flint Glass, 460 
 
 Flue Boilers, 282 
 
 Fluor Spar, 12 
 
 Fluxes, 347 
 
 Fly, 381 
 
 Flying Buttress, 151 
 
 Fly Wheel, 254 
 
 Forces, Moving, 257 
 
 Forcing Pump, 321 
 
 Foreshortening, 73 
 
 Forging, 420 
 
 Forks, 429 
 
 Form of Materials, 43, 5i 
 
 Foundations, 115 
 
 Fountain Lamp, 182 
 
 Fountains, 331 
 
 Frankfort Black, 437 
 
 Franklin Stove, 161 
 
 Freestone, 10 
 
 French Berries, 451 
 
 Fresco Painting, 440 
 
 Friction, 255 
 
 Friction of Pipes, 311 
 
 Frieze, or Frize, 130 
 
 Fritting, 458 
 
 Fuel, 155 
 
512 
 
 INDEX. 
 
 Fugitive Colors, 454 
 Fulling, 366 
 Fur, 38 
 Furnaces, 165 
 Fusee, 239 
 Fusible Metal, 22 
 Fustic, 451 
 
 Gable, 150 
 Galena, 411 
 Galls, 452 
 Gamboge, 436 
 Gangue, 392 
 Gas Engines, 300 
 Gas Lights, 186 
 Gasmeter, 190 
 Gasometer, 188 
 Gates, 215 
 Gauze, 362 
 Gear, Bevel, 235 
 
 , Spiral, 234 
 
 Gearing, 233 
 Gelatin. See Glue. 
 Gem Engraving, 112 
 Gems, Artificial, 467 
 Generation of Steam, 279 
 Generator, 287 
 Gilding, 445 
 
 on Metals, 400 
 
 on Porcelain, 482 
 
 Gin, Cotton, 33 
 Glass, 456 
 
 Blowing, 459 
 
 , Broad, 460 
 
 , Crown, 458 
 
 Cutting, 464 
 
 Cylinder, 461 
 
 , Flint, 460 
 
 , Plate, 461 
 
 Shades, 185 
 
 , Stained, 464 
 
 Thread, 468 
 
 Glazing, 434 
 
 . Porcelain, 479 
 
 Glue, 41, 345 
 Gold, 22, 396 
 
 Gold Beater's Skin, 497 
 
 Beating, 399 
 
 Leaf; 399 
 
 Goldsmiths' Work, 399 
 Gold Thread, 401 
 Gold Wire, 401 
 Gothic Style, 148 
 Governor, 252 
 Granite, 8 
 Graphite, 25 
 Grate, Anthracite, 164 
 Graver, 92 
 Grecian Style, 134 
 
 Temple, 136 
 
 Greco Gothic Style, 147 
 
 Grinding, 341 
 
 Grindstone. See Freestone. 
 
 Gristmill, 341 
 
 Groins, 150 
 
 Gudgeons, note, 378 
 
 Gum, 37 
 
 Tree, 29 
 
 Gun Making, 423 
 
 Metal, 409 
 
 Gunpowder, 302 
 Gun, Properties of, 305 
 Guttte, 134 
 Gypsum, 11 
 
 Hackmatack, 31 
 Hair, 38 
 
 Spring, 377, 388 
 
 Halle du Bled, 123 
 Hardness, 43 
 Hargreaves, Richard, 353 
 Harmony, 88 
 
 Harnessing of Horses, 202 
 Hanging of Pictures, 184 
 Hat Making, 367 
 Heart Wheel, 242 
 Heating, 155 
 
 by Steam, 169 
 
 Heddles, 360 
 Hematine, 450 
 Hemlock, 31 
 Hemp, 33 
 
INDEX. 
 
 513 
 
 Herbarium, 493 
 Herculaneum Manuscripts, 57 
 Hermopolis, Temple of, 10 
 Hero's Fountain, 328 
 Hickory, 27 
 
 Dye, 451 
 
 High Steam, 297 
 
 Pressure Engine, 287 
 
 Highways, 204 
 
 Hindoo Architecture, 133 
 
 Hipped Roof, 127 
 
 History of Printing, 69 
 
 Hollow Backs of Fire Places, 161 
 
 Hose, 13 
 
 Horizontal Wheel, 270 
 
 — . Wind Mill, 274 
 
 Horn, 40 
 
 Hornbeam, 29 
 
 Hornblower's Engine, 293 
 
 Horology, 371 
 
 Horses, Attaching of, 203 
 
 , Power of, 260 
 
 Hubb, 201 
 
 Hungarian Machine, 328 
 
 Hydraulic Cement, 16 
 
 Ram, 329 
 
 Hydreole, 316 
 Hydrostatic Lamp, 181 
 
 Press, 323 
 
 Hypaethral Temple, 138 
 
 Ichnographic Projection, 80 
 
 Ilissus, Temple on the, 142 
 
 Illumination, 178 
 
 Imposing, 63 
 
 Impost, 121 
 
 Incipient Fracture, 48 
 
 Inclined Wheel, 245 
 
 Indelible Ink, 59 
 
 India Ink, 437 
 
 Indian Red, 435 
 
 India Rubber, 35 
 
 Indigo, 448 
 
 Induration by Heat, 471 
 
 Inertia, 196 
 
 Ink, 59 
 
 65 
 
 Ink, Printers', 66 
 
 Inlaid Work, 113 
 
 Insertion, 343 
 
 Instrumental Perspective, 78 
 
 Intaglios, 113 
 
 Intercolumniation, 139 
 
 Interposition, 343 
 
 Intrados, 121 
 
 Intrinsic Color, Changing of, 446 
 
 Invention of Letters, 54 
 
 Ionic Order, 135 
 
 Iron, 416 
 
 ,19 
 
 Isinglass, 41 
 
 Isometrical Perspective, 82 
 
 Jupiter, Temple of, 147 
 
 Ivory, 40 
 
 Ivory Black, 437 
 
 Japanning, 443 
 Jasper, 13 
 
 Jenny, Spinning, 352 
 Jewelling Watches, 391 
 
 Kaolin, 472 
 Karnac, 152 
 Keel, 220 
 Key Stone, 120 
 King Posts, 127 
 King's Yellow, 436 
 Knee Joint, 250 
 Knives, 429 
 
 Lac, 37, 442 
 
 Lace, 362 
 
 Lacquering, 444 
 
 Lagarousse's Lever, 249 
 
 Lakes, 435 
 
 Lambert's Wheel, 268 
 
 Lamp Black, 437 
 
 Lamps, 17 1> 
 
 Lamp without Flame, 191 
 
 Lancet Arch, 121 
 
 Languedoc Canal, _218 
 
 Lanterns, 150, 234 
 
 Lantern of Demosthenes, 143 
 
514 
 
 INDEX. 
 
 Lapis Lazuli, 434 
 Larch, 32 
 Lateral Strain, 46 
 Lathe, 337 
 Lead, 21 
 
 , Extraction of, 411 
 
 Pipes 412 
 
 Leaning Tower at Pisa, 126 
 
 Leather, 495 
 
 Leaves of Pinions, 234 
 
 Lehigh Coal, 23 
 
 Letters, 54. 
 
 Lignum Vitse, 33. 
 
 Light and Shade, 83 
 
 , Measurement of, 185 
 
 , Modes of Procuring, 192 
 
 Lightwood, 491 
 
 Limestone, 16 
 
 Limit of Bulk, 49 
 
 Line Engraving, 92 
 
 Line of Traction, 199 
 
 Linens, 365 
 
 Lintel, 119 
 
 Lithography, 101 
 
 Litmus, 450 
 
 Locks, 344 
 
 Locks of Canals, 216 
 
 Locomotion, 194 
 
 Locomotive Steam Engine, 212 
 
 Locust, 27 
 
 Logwood, 450 
 
 Loom, 359 
 
 Luni Marble, 8 
 
 Lustre Ware, 482 
 
 Luxor, 152 
 
 Lysicrates, Monument of, 143 
 
 Machinery, 231 
 Machine Printing, 68 
 Madder, 449 
 Magic Porcelain, 483 
 Mahogany, 32 
 Maison Carrce, 146 
 Malleability, 43 
 Maltha, 19, 24 
 Manganese, 23 
 
 Man Hole, 284 
 Maple, 29 
 
 Dye, 452 
 
 Marble, 7 
 
 Marie del Fiore, St, 124 
 
 Marseilles Quilts, 362 
 
 Massicot, 436 
 
 Mastic, 37, 442 
 
 Materials, Estimation of, 43 
 
 Materials for Writing, 55 
 
 Matrix, 392 
 
 McAdam Roads, 205 
 
 Measurement of Light, 185 
 
 Measures, Architectural, 131 
 
 Mechanical Lamp, 182 
 
 Perspective, 80 
 
 Medals, 404 
 
 Melting Glass, 458 
 
 Menai Bridge, 207 
 
 Men, Power of, 258 
 
 Mercury, 22 
 
 Metallurgy, 392 
 
 Metals, Extraction of, 392 
 
 Metopes, 134 
 
 Mezzo Tinto, 96 
 
 Mica, 9 
 
 Milan Cathedral, 126 
 
 Mill, Bark, 340 
 
 , Barker's, 270 
 
 , Cider, 341 
 
 , Color, 342 
 
 , Grist, 341 
 
 , Stamping, 340 
 
 , Sugar, 341 
 
 , Oil, 340 
 
 , Parent's, 270 
 
 , Stone. See Buhrstone. 
 
 Millingof Coins, 403 
 Minaret, 148 
 Mineral Green, 437 
 Mineralizer, 392 
 Minerva, Temple of, 141 
 
 — Polias, Temple of, 142 
 
 Minute Architectural, 131 
 Modelling, 107 
 Modillions, 136 
 
INDEX. 
 
 515 
 
 Module, 131 
 
 Monopteral Temple, 138 
 
 Moody's Machines, 358 
 
 Moorish Arch, 121 
 
 Mordants, 448 
 
 Mortar, 15 
 
 Motion of Animals, 194 
 
 Morey's Engine, 296 
 
 Mortise, 128 
 
 Mortising, 343 
 
 Mosaic, 113 
 
 Moscow, Riding House at, 127 
 
 Mosque of Achmet, 151 
 
 of St Sophia, 125 
 
 Moulding Glass, 463 
 Mouldings, 131 
 Moulds, 348 
 
 for Casting, 108 
 
 Moving Forces, 257 
 
 Mule Spinning, 357 
 
 MuUions, 150 
 
 Mutules, 134 
 
 Mylassa, Sepulchre at, 146 
 
 Nailing, 343 
 
 Nail Making, 423 
 
 Naples Yellow, 436 
 
 Naptha, 24 
 
 Natural History, Specimens in, 497 
 
 Nave, 149, 199 
 
 Needles, 431 
 
 Newcomen's Engine, 297 
 
 New York Canal, 218 
 
 City Hall, 126 
 
 Nicaragua Wood, 450 
 Nismes, Temple at, 146 
 Noncondensing Engine, 287 
 Noria, 316 
 Noyaculite, 13 
 
 Oak, 26 
 Obelisk, 125 
 Obelisks, 10 
 
 Obstruction of Pipes, 312 
 Ochres, 435 
 Ogee, 131 
 
 Ogee Arch, 121 
 
 Ogyve, 150 
 
 Oil Gas, 189 
 
 Oils, 36, 41 
 
 Oil Mill, 340 
 
 — Painting, 440 
 
 Opus Reticulatum, 113 
 
 Orchestra, 139 
 
 Orders of Architecture, 134 
 
 Ores, 392 
 
 Oriel, 150 
 
 Orpiment, 436 
 
 Orthographic Projection, 81 
 
 Overshot Wheel, 261 
 
 Ovolo, 131 
 
 Oxgall, 437 
 
 Paddle Wheels, 224 
 Passtum, 140 
 Pagodas, 133 
 Painting, 72, 433 
 
 in Distemper, 43& 
 
 ■ in Fresco, 440 
 
 in Oil, 440 
 
 Paints, 433 
 Pak Fong, 410 
 Pallets, 247, 387 
 Palmer's Rail Way, 211 
 Palmyra, Temple at, 147 
 Pandroseum, 142 
 Panoramic Views, 73 
 Pantheon at Rome, 125, 145 
 Paper, 59 
 Papermaking, 368 
 Pappenheim Limestone, 8 
 Papyrus, 56 
 Parachute, 229 
 Parallel Motion, 243, 295 
 Parapet, 150 
 Parent's Mill, 270 
 Parchment, 58, 496 
 Parthenon at Athens, 141 
 Parting of Metals, 397 
 Party Gold, 400 
 Passings, 211 
 Patent Mineral Yellow, 436 
 
516 
 
 INDEX. 
 
 Pavements, 204 
 
 Peachwood, 450 
 
 Pearl, White, 438 
 
 Peat, 25 
 
 Pedestal, 129 
 
 Pediment, 130 
 
 Penetration, 336 
 
 Pencils, Black Lead, 25 
 
 Pendentives, 122, 150 
 
 Pendulum, 375 
 
 Pendulum Spring, 377, 390 
 
 Pentelic Marble, 8 
 
 Pent Roof; 127 
 
 Peperino, 15 
 
 Pepperidge, 28 
 
 Peripteral Temple, 137 
 
 Perkins' Generator, 287 
 
 Perkins' Lock, 344 
 
 Perpetual Screw, 236 
 
 Persian Wheel, 315 
 
 Persepolis, 152 
 
 Persimmon, 29 
 
 Perspective, 72, 131 
 
 Perspectographs, 79 
 
 Petersburgh, Columns at, 9 
 
 Peter the Great, Statue of, 9 
 
 Petroleum, 23 
 
 Petuntze, 472 
 
 Pewter, 20 
 
 Philadelphia U. S. Bank, 126 
 
 Phoenicin, 441 
 
 Phosphorus, 42 
 
 Picker, 354 
 
 Pictures, Hanging of, 184 
 
 Pilaster, 129 
 
 Pillar, 150 
 
 Pine, 30 
 
 Pinchbeck, 407 
 
 Pinion, 234 
 
 Pin making, 408 
 
 Pinnacles, 150 
 
 Pipes for Water, 309 
 
 Pisa, Leaning Tower at, 126 
 
 Pise, Building in, 118, 119 
 
 Piston, 290, 295 
 
 Pitch, 35 
 
 Pitch Lines, 234 
 Pivots, note, 378 
 Place of Strain, 46 
 Plan, 131 
 Plate Glass, 461 
 Plaster, Casting in, 108 
 Plaster of Paris, 11 
 Platinum, 22 
 Plating, 404 
 Plinth, 129 
 Plumbago, 25 
 Plying, 354 
 Pola, Temple at, 146 
 Polishing, 444 
 
 Glass, 462 
 
 Slate, 15 
 
 Steel, 431 
 
 Pompey's Pillar, 9 
 Porcelain, 481 
 
 , Magic, 483 
 
 Porphyry, 12 
 
 Portable Gas Light, 190 
 
 Portland Stone, 8 
 
 Portland Vase, 482 
 
 Portrait, Eyes of, 85 
 
 Posticus, 137 
 
 Pottery, 474 
 
 Power, Maintaining, 374 
 
 Powers, Moving, 257 
 
 Precious Stones, 13 
 
 Preservation of Food, 499 
 
 of Organic Substances, 484 
 
 Press, Correction of, 64 
 
 , Hydrostatic, 323 
 
 , Printing, 67 
 
 Pressing Glass, 478 
 Printing, 61,67 
 Porcelain, 479 
 
 — Press, 67 
 
 Projections, 81 
 Projection of Water, 330 
 Pronaos, 137 
 Propyloea at Athens, 141 
 Proscenium, 139 
 Prostyle Temple, 137 
 Prussian Blue, 434 
 
INDEX. 
 
 517 
 
 Pseudo Dipteral Temple , 138 
 Puddle, 214 
 Fuddling Furnace, 419 
 Pulley, Live and Dead, 251 
 Pulpit, 139 
 Pumice, 14 
 Pump Bag, 324 
 
 , Centrifugal, 319 
 
 , Chain, 327 
 
 , Common, 320 
 
 , Delahire's, 322 
 
 . , Double Acting, 324 
 
 , Eccentric, 325 
 
 , Forcing, 321 
 
 , Lifting, 323 
 
 , Plunger, 321 
 
 , Rolling, 325 
 
 Rope, 316 
 
 , Spiral, 318 
 
 , Sucking, 320 
 
 Puppet Valve, 294 
 Puteolanus Pulvis, 16 
 Putty, 21, 345 
 Puzzolana, 17 
 Pycnostyle, note, 139 
 Pyramid of Eygpt, 125 
 Pyramids, 8 
 
 Quadrupeds, Motion of, 194 
 Quartation, 397 
 Quartz, 9 
 Queen Posts, 128 
 Quercitron, 451 
 Quicklime, 15 
 Quills, 38 
 duincy Stone, 10 
 
 Rabating, 313 
 Rack, 249 
 
 and Pinion, 247 
 
 and Segment, 216 
 
 Radius, 234 
 Rafters, 127 
 Rag Wheels, 233 
 Rail Roads, 208 
 Rampart Arch, 121 
 
 Ratchet Wheel, 237 
 Reaumur's Porcelain, 467 
 Reciprocating Motion, 240 
 Rectilenear Motion, 248 
 Red Cedar, 31 
 Red Lead, 435 
 Reduction of Metals, 393 
 Reeded Column, 153 
 Reflected Light, 84 
 Reflectors, 184 
 Refractory Clay, 14 
 Reservoirs, 180 
 Resilience, 44, 48 
 Resins, 37 
 Resistance, 44 
 Restorations, 132 
 Retention of Heat, 170 
 Reticulated Walls, 118 
 Rhode Island Coal, 23 
 Rhus Copallinum, 442 
 
 Vernix, 443 
 
 Rice Paper, note, 55 
 
 Rivets, 344 
 
 Roads, 204 
 
 Roasting Ores, 393 
 
 Rocou, 451 
 
 Rollers, 198 
 
 Rolling Iron, 420 
 
 Roman Cement, 16 
 
 Roman, Doric, and Ionic, 143 
 
 Romanesque Architecture, 148 
 
 Roof, 127 
 
 Rope Making, 350 
 
 Rope Pump, 316 
 
 Rose Wood, 33 
 
 Rosin, 35 
 
 Rotary Motion, 231 
 
 Rotten Stone, 15 
 
 Rouge, 436 
 
 Rouge d' Angleterre, 435 
 
 Roving, 355 
 
 Rubble Walls, 118 
 
 Ruby, 13 
 
 Rudder, 220 
 
 Ruraford Fireplace, 161 
 
 Rupert's Drops, 459 
 
518 
 
 INDEX. 
 
 Safety Gates, 215 
 
 Lamp, 190 
 
 Valve, 285 
 
 Saffron, 451 
 
 Safflower, 451 
 
 Saggars, 479 
 
 Sand, 14 
 
 Sandarac, 442 
 
 Sand Stone, 10 
 
 Salona, Temple at, 147 
 
 Sap Green, 437 
 
 Sappan Wood, 450 
 
 Sapphire, 13 
 
 Saracenic Style, 148 
 
 Satin Wood, 33 
 
 Sawing, 338 
 
 Saw Mill, 338 
 
 Saws, 430 
 
 Savannah Steam Ship, 225 
 
 Saxon Architecture, 148 
 
 Scagliola, 114 
 
 Scapements, 247. 377 
 
 Scarfing, 128, 343 
 
 Scena, 139 
 
 Scenographic Projection, 80 
 
 Scheranitz Vessels, 328 
 
 Schuylkill Bridge, 206 
 
 Scissors, 430 
 
 Scoop Wheel, 315 
 
 Scotia, 131 
 
 Scraper, 92 
 
 Screwing, 344 
 
 Screw, Archimedes, 317 
 
 , Perpetual, 236 
 
 Sculpture. 107, 110 
 Sealing Wax, 345 
 Seasoning of Timber, 488 
 Section, 131 
 Sepia, 59, 437 
 Serpentine, 11 
 Serpents, Motion of, 195 
 Shades, 88 
 Shades, Glass, 185 
 Shadows, 86 
 Shaft, note, 378 
 of Columns, 129 
 
 Shafts, 215 
 Shape of Timber, 49 
 Shearing, 367 
 Sheet Lead, 411 
 Shell Lac. See Lac. 
 
 Gold, 346 
 
 Shot, Leaden, 412 
 Sidelings,211 
 Sienna, Burnt, 435 
 
 , Terra di, 436 
 
 Sienite, 10 
 Signatures, 64 
 Silk, 39 
 Silver, 22 
 
 , Extraction of, 401 
 
 Silvering of Mirrors, 415 
 Silver Edges, 405 
 Silversmiths' Work, 402 
 Singeing, 364 
 Sinkicien, Pagoda at, 151 
 Single Rail, 211 
 Sinumbral Lamp, 185 
 Size, 40 
 
 Size of Wheels, 198 
 Skins, 38 
 Skylights, 171 
 Slaking of Lime, 15 
 Slate, 10 
 Slitting, 422 
 Smalt, 435 
 Smelting, 393 
 
 , 416 
 
 Smoke, Burning of, 177 
 Smoky Rooms, 174 
 Snail, 382 
 Soap Stone, 11 
 Soldering, 346 
 Sources of Power, 257 
 Spalatro, Temple at, 147 
 Spandrells, 150 
 Span of an Arch, 121 
 Speculum Metal, 409 
 Spelter, 22 
 Spinning, 352, 3.57 
 Spiral Gear, 234 
 Spiral Pump, 318 
 
INDEX. 
 
 519 
 
 Splicing, 128 
 Spire, 150 
 Springs, 202 
 Spruce, 31 
 
 Stability of a Ship, 222 
 Stamping Mill, 340 
 Stained Glass, 464 
 Starch, 37 
 Steam, 274 
 
 Boats, 223 
 
 Steam Carriages, 301 
 
 Engine, 281, 287 
 
 Engine, History of, 296 
 
 Gauge, 283 
 
 Gun, 301 
 
 , Heating by, 169 
 
 Navigation, 297 
 
 Power, 274 
 
 Steel, 20 
 
 ,424 
 
 Engraving, 100 
 
 Steeple, 130 
 
 Stereotyping, 67 
 
 Stiffness, 46 
 
 St Genevieve's Church, Paris, 124 
 
 Stippling, 94 
 
 St Marie del Fiore, 124 
 
 St Mark's Church, Venice, 125 
 
 Stone Blue, 427 
 
 Stones, Lithographic, 102 
 
 Stone Ware, 476 
 
 Stoves, 166 
 
 St Paul's, London, 124 
 
 St Peter's, Rome, 124 
 
 Strasburgh Cathedral, 126 
 
 Strain, 43 
 
 Strength, 44, 47 
 
 • of Materials, 42 
 
 Stress, 42 
 
 Striking Part of a Clock, 380 
 
 St Sophia, Mosque of, 125 
 
 Stucco, 11 
 
 Stylobate, 12.9 
 
 Stylus, 55, 59 
 
 Styles of Building, 129 
 
 Sublimation, 348 
 
 Submarine Navigation, 226 
 Sugar Mill, 341 
 Sulphur, 25 
 Sun Dial, 371 
 
 Sun and Planet Wheel, 244 
 Surbase, 129 
 Suspension Bridges, 207 
 Swell of Columns, 117 
 Swimming, 195 
 
 Bladder of Fish, 195 
 
 Sycamore, 28 
 Syphon, 314 
 Systyle, 139 
 
 Talon, 131 
 
 Tamarack, 31 
 
 Tanning, 495 
 
 Tapestry, 364 
 
 Tar, 35 
 
 Tarras, 18 
 
 Taunton Spindle. See Danforth. 
 
 Tawing, 496 
 
 Teazle, 366 
 
 Teeth of Wheels, 234 
 
 Telford's Road, 205 
 
 Tempering, 426 
 
 Temple of Vesta, at Tivoli, 125 
 
 Tenacity, 43 
 
 Tents, Origin of, Chinese Style, 133 
 
 Terra Cotta, 473 
 
 Verte, 437 
 
 Theatre, Grecian, 139 
 Thebes, Ruins of, 152 
 Theodoric, Tomb of, 8 
 Thermae, 144 
 Theseus, Arch of, 146 
 
 • '■ , Temple of, 140 
 
 Thrasyllus, Monument of, 142 
 
 Throttle Valve, 294 
 
 Throwing, 477 
 
 Throwing Wheel, 333 
 
 Tie Beam, 127 
 
 Tiles, 473 
 
 Timber, 487 
 
 Tin, 21 , 413 — 
 
 Tinfoil, 413 
 
520 
 
 INDEX. 
 
 Tin Plates, 414 
 
 Toggle Joint, 250 
 
 Tombac, 407 
 
 Tone, 88 
 
 Tongueing, 343 
 
 Toothed Wheels, 233 
 
 Tophus, 8 
 
 Torches, 179 
 
 Torpedo, 228 
 
 Torsion, 49 
 
 Tortoise Shell, 40 
 
 Torus, 131 
 
 Tower, 150 
 
 Tower of the Winds, 143, 371 
 
 Tracery, 150 
 
 Tracing Paper, 92 
 
 Traction, Line of, 199 
 
 Trajan's Column, 125 
 
 Tram Road, 210 
 
 Transept, 149 
 
 Transparent Colors, 434 
 
 Transparency of Flame, 185 
 
 Travertino, 8 
 
 Treadwell on Rail Roads, 211 
 
 Tredgold on Rail Roads, 209 
 
 Triglyphs, 134 
 
 Tripoli, 15 
 
 Triumphal Arches, 144 
 
 Trundle, 234 
 
 Trussing, 128 ' 
 
 Tubes, 47 
 
 Tufa, 14 
 
 Tulip Tree, 28 
 
 Tunnels, 215 
 
 Tupelo, 30 
 
 Turmeric, 451 
 
 Tumcap, 176 
 
 Turning, 337 
 
 Turnsol, 450 
 
 Turpeth Mineral, 436 
 
 Turpentine, 35 
 
 Turret, 150 
 
 Tuscan Order, 143 
 
 Twilling, 360 
 
 Twisted Column, 153 
 
 Twisting, Theory of, 349 
 
 Tympanum, 130 
 Types, 61, 62 
 
 Ultramarine, 434 
 Umber, 437 
 Undershot Wheel, 265 
 Union, Modes of, 343 
 Universal Joint, 236 
 Lever, 249 
 
 Valves of Canals, 216 
 
 Valves of Steam Engines, 294 
 
 Vanishing Point, 76 
 
 Vapors of Low Temperature, 299 
 
 Varnishing, 441 
 
 Vases, Etruscan, 474 
 
 Vaults, 122, 150 
 
 Vehicles of Power, 257 
 
 Vellum, 496 
 
 Velocity, Change of, 238 
 
 Velvets, 364 
 
 Venetian Red, 435 
 
 Ventilation, 172 
 
 Ventilators, 173 
 
 Venus de Medici, 8 
 
 Verandah, 133 
 
 Verdigris, 436 
 
 Vermillion, 435 
 
 Vesta, Temple of, 146 
 
 , Temple of, at Tivoli, 125 
 
 Vitrification, 456 
 Volutes, 135 
 Voussoirs, 121 
 
 Wall, 117 
 Walnut, 27, 30 
 Wafers, 345 
 Warping, 358 
 Washing Ores, 393 
 Washington, Capitol at, 126 
 Watch, Description of, 383 
 Water Cements, 16 
 
 Clock, 373 
 
 Colors, 439 
 
 , Conveying of, 308 
 
 in Fuel, 156 
 
IN»EX. 
 
 52! 
 
 Water Pipes, 309 
 
 Power, 261 
 
 , Raising of, 314 
 
 Snail, 317 
 
 Watt's Steam Engine, 289 
 Wax, 42 
 
 , Sealing, 345 
 
 Weaving, 359 
 Wedgewood^s Ware, 476 
 Weight of Fuel, 155 ' 
 Weirs, 215 
 Weld, 451 
 Welding, 340 
 Westminster Abbey, 15i 
 Whalebone, 40 
 Wheels, 197 
 Wheel, Besant's, 266 
 
 , Breast, 269 
 
 , Brush, 237 
 
 Carriag«s, 197 
 
 , Chain, 264 
 
 , Contrate, 236 
 
 , Crown, 236 
 
 , Epicycloidal, ^5 
 
 , Flash, 333 
 
 , Horizontal, 270 
 
 , Inclined, 245 
 
 , Lambert's, 26b 
 
 , Overshot, 261 
 
 , Ratchet, 237 
 
 , Throwing, 333 
 
 , Undershot, 265 
 
 , Window, 150 
 
 Wheels, Form of, 20J 
 
 Whetstone. See Novaculite 
 White Cedar, 30, 31 
 
 Lead, 438 
 
 Pigments, 43b 
 
 Ware, 476 
 
 White Wood, 27 
 Whiting, 438 
 
 . See Chalk 
 
 Willow, 32 
 
 Windage, 305 
 
 Wind, Effect of, on Sails, 220 
 
 Windmills, 272 
 
 Windows, 172 
 
 Wind Power, 271 
 
 Wipers, 242 
 
 Wire Drawing, 422 
 
 Woad, 449 
 
 Wood, 25 
 
 Wooden Bridges, 206 
 
 Wood Engravings, 100 
 
 Wool, 39 
 
 Woolf's Engine, 294 
 
 Woollens, 365 
 
 Worm, 236 
 
 Worsted, 365 
 
 Writing Materials, 55 
 
 Yellow Ochre, 436 
 
 Zintj, 22 
 
 , White, 43b 
 
 Zophorus, 130 
 Zurich Machine, 31b 
 

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 Fig. 1. 
 
 Pl^TE XII. 
 
 ^B 
 
 
 Fig. 2. 
 
 
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ARCHITECTURE. ILLUMINATION. 
 
 Fig. 1. 
 
LOCOMOTION. 
 
 MACHINERY. 
 Fig. 10. 
 
 Plate XIV. 
 
 Fig. 9. 
 
 Fig. 5. 
 
 Fig. 6. 
 
 Fig. I. Fig. 2. 
 
 Fig. 4. 
 
LOCOMOTION. 
 
 Fig. 3. 
 
 Pl^TE XV. 
 
 Fig. 4. 
 
 Fi2. 5. 
 
 n 
 
 Fig. 6. 
 
 Fis. 1. 
 
 A -8 
 
 a •-::: 
 
 >^ 
 
 Fig. 8. 
 
 C B 
 
MACHINERY. Plate XVI. 
 
 Fig. 10. Fig. 11. Fig. 12. 
 
 o 
 
 U 
 
 Fig. 13. 
 
 Fig. 16. 
 
 Fig. 14. Fig. 15. 
 
 Fig, 18. 
 
 Fig. 19. Fig. 20 
 
 A A 
 
 cp 
 
 Fig. 23. 
 
 A 
 
 C3 O 
 
 B^B .-SL B _H 
 
 
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MACHINERY. 
 
 Plate XVII. 
 
 Fig. 24 
 
 Fig. 25. Fig. 26. Fig. 27. 
 
MACHINERY. 
 
 Fig. 32. 
 C E 
 
 MOVING FORCES. Plate XVIII. 
 
 Fig. 37. Fig. 38. 
 
MOVING FORCES. 
 Fig. 6. 
 
 Plate XIX. 
 
 Fig. 8. 
 
 Fis. 11. 
 
CONVEYING WATER. 
 Fig. 1. c 
 
 Plate XX. 
 
 A 
 
 Fig. 2. 
 
 Fig. 3. 
 
 Fig. 5. 
 
 Fig. 6. 
 
 Fig. 7. 
 
 Fig. 11, 
 
CONVEYING WATER. 
 
 Fig. 8. 
 
 Plate XXI. 
 
WATER. FLEXIBLE FIBRES. HOROLOGY. Plate XXIL 
 
 Fig. 18. 
 
 Fig. 2. 
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 F\s. 3. 
 
 Fi2. 4. 
 
 Fiff. 5. 
 
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Deacidified using the Bookkeeper process. 
 Neutralizing agent; Magnesium Oxide 
 Treatment Date; Aug. 2003 
 
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