TECHNICAL INDEX AND GLOSSARY 



Electric Light. The light engendered by rendering a badly- 

 conducting material incandescent by passing a current of elec- 

 tricity through it. The possibility of producing light in this way 

 was discovered by Davy early in the nineteenth century; but 

 no commercial use was made of the discovery till the middle of 

 the century; and the first important commercial light (the 

 Jablochkoff "candle") was not invented till 1876. Brush's arc 

 light followed; and Edison's incandescent light is still more 

 recent. See "The Banishment of Night," Vol. VI, p. 218. 



Electricity. A familiar but inscrutable manifestation of 

 energy, having for its unit structure, according to the most 

 recent theory (J. J. Thomson), an infinitesimal corpuscle, or 

 electron. Frictional electricity (e.g., due to rubbing amber) 

 was known to the ancients; galvanic electricity was discovered 

 by Galvani and Volta; dynamic electricity has been placed at 

 the service of man in our own generation. For the earliest ex- 

 periments in electricity, see "William Gilbert and the Study of 

 Magnetism," Vol. II, p. in; also, "Progress in Electricity from 

 Gilbert and Von Guericke to Franklin," Vol. II, p. 259; "The 

 Modern Development of Electricity and Magnetism," Vol. Ill, 

 p. 229; "Prof. J. J. Thomson and the Nature of Electricity," 

 Vol. V, p. 92. For such subjects as "The Electric Telegraph," 

 "Electric Railways," "Electric Lighting," the reader is referred 

 to chapters under these headings in this index and the general 

 index. 



Electric Railways. Electricity as a traction power owes its 

 popularity simply to the fact that it can be transmitted con- 

 veniently to a distance over a wire (trolley) or third rail, or 

 (less importantly) in a so-called storage battery. The initial ex- 

 periments in this line were made as early as 1835 (Thomas 

 Davenport); a little later (1847-1857), Thomas Hall, Dr. Colton, 

 and Prof. C. C. Page continued the work, followed by a 

 host of others. Galvanic cells and storage batteries were first 

 used with some success, but the dynamo presently superseded 

 other generators, although the storage battery, as perfected by 

 Edison, again entered the field prominently in 1910. See "The 

 Development of Electric Railways," Vol. VII, p. 175. 



Electro-chemistry. An important branch of practical chemis- 

 try, that finds application in a multitude of commercial indus- 

 tries. The activities involved are chiefly either (i) the prin- 

 ciple of electrolysis, whereby chemicals are dissociated (as, for 



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