CONTENTS 



by means of compressed gas, p. 138 The "Otto cycle," p. 139 

 Adaptation of gas engines to automobiles, p. 140 Rapid increase 

 in the use of gas engines, p. 141 Defects of the older hot-air 

 engines, p. 145 Recent improvements and possibilities in the use 

 of hot-air engines, p. 146. 



CHAPTER VIII 



THE SMALLEST WORKERS 



The relative size of atoms and electrons, p. 148 What is electricity? 

 p. 149 Franklin's one-fluid theory, p. 150 Modern views, p. 153 

 Cathode rays and the X-ray, p. 156 How electricity is developed, 

 p. 159 The work of the dynamical current, p. 162 Theories of 

 electrical action, p. 165 Practical uses of electricity, p. 168. 



CHAPTER IX 

 MAN'S NEWEST CO-LABORER: THE DYNAMO 



The mechanism of the dynamo, p. 173 The origin of the dynamo, 

 p. 176 The work of Ampere, Henry, and Faraday, p. 177 Per- 

 fecting the dynamo, p. 178 A mysterious mechanism, p. 180 

 Curious relation between magnetism and electricity as exemplified 

 in the dynamo, p. 182. 



CHAPTER X 



NIAGARA IN HARNESS 



The volume of water at the falls, p. 184 The point at which the 

 falls are "harnessed," p. 185 Within the power-house, p. 186 

 Penstocks and turbines, p. 188 A miraculous transformation of 

 energy, p. 189 Subterranean tail-races, p. 191 The effect on the 

 falls, p. 192 The transmission of power, p. 194 "Step-up" and 

 "step-down" transformers, p. 198. 



CHAPTER XI 



THE BANISHMENT OF NIGHT 



Primitive torch and open lamp, p. 202 Tallow candle and per- 

 fected lamp, p. 205 Gas lighting, p. 207 The incandescent gas 

 mantle, p. 208 Early gas mantles, p. 209 How the incandescent 

 gas mantle is made, p. 211 The introduction of acetylene gas, p. 

 212 Chemistry of acetylene gas, p. 214 Practical gas-making, 

 p. 215 The triumph of electricity, p. 218 Davy and the first 

 electric light, p. 220 Helpful discoveries in electricity, p. 222 

 The Jablochkoff candle, p. 223 Defects of the Jablochkoff candle, 

 p. 225 The improved arc light, p. 226 Edison and the incandescent 

 lamp, p. 228 Difficulties encountered in finding the proper ma- 



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