CONTENTS 



terial for a practical filament, p. 230 " Parchmentized thread" 

 filament, p. 233 The tungsten lamp, p. 234 The mercury-vapor 

 light of Peter Cooper Hewitt, p. 236 Advantages and peculiar, 

 ities of this light, p. 240. 



CHAPTER XII 



THE MINERAL DEPTHS 



Early mining methods, p. 242 Prospecting and locating mines, p. 

 243 "Booming," p. 246 Conditions to be considered in mining, 

 p. 248 Dangerous gases in mines, p. 249 Artificial lights and 

 lighting, p. 251 Ventilation and drainage, p. 252 Electric ma- 

 chinery in mining, p. 253 Electric drills, p. 254 Traction in 

 mining, p. 256 Various types of electric motors, p. 257 "Tel- 

 phers," p. 261 Electric mining pumps, p. 263 Some remark- 

 able demonstrations of durability of electric pumps, p. 265 Elec- 

 tricity in coal mining, p. 266 Electric lighting in mines, p. 269. 



CHAPTER XIII 



THE AGE OF STEEL 



Rapid growth of the iron industry in recent years, p. 271 The 

 Lake Superior mines, p. 272 Methods of mining, p. 273 "Open- 

 pit" mining, p. 274 Mining with the steam shovel, p. 276 From 

 mine to furnace, p. 278 Methods of transportation, p. 279 Ves- 

 sels of special construction, p. 281 The conversion of iron ore 

 into iron and steel, p. 283 Blast furnaces, p. 284 Poisonous gases 

 and their effect upon the workmen, p. 286 From pig iron to steel, 

 p. 287 Modern methods of producing pig iron, p. 288 The Besse- 

 mer converter, p. 289 Sir Henry Bessemer, p. 291 The "Besse- 

 mer-Mushet" process, p. 293 Open-hearth method, p. 294 Alloy 

 steels, p. 295. 



CHAPTER XIV 



SOME RECENT TRIUMPHS OF APPLIED SCIENCE 



The province of electro-chemistry, p. 298 Linking the laboratory 

 with the workshop, p. 299 Soda manufactories at Niagara Falls, 

 p. 300 Producing aluminum by the electrolytic process, p. 300 

 Old and new methods compared, p. 301 Nitrogen from the air, 

 P- 33 What this discovery means to the food industries of the 

 world, p. 304 Prof. Birkeland's method, p. 307 Another method 

 of nitrogen fixation, p. 309 Cost of production, p. 312 Elec- 

 trical energy, p. 313 Production of high temperatures with the 

 electric arc, p. 314 The production of artificial diamonds by the 

 explosion of cordite, p. 315 Industrial problems of to-day and 

 to-morrow, p. 316. 



[vi] 



