KEY AND INDEX 



example, in copper-plating, silver-plating, etc.) in solution; or 

 (2) the agency of high temperatures, as developed in the elec- 

 tric furnace, whereby substances are decomposed and purified 

 or allowed to reunite in new compounds. See "Humphry Davy 

 and Electro-chemistry," Vol. IV, p. 46. The use of electro- 

 chemistry is the development of the first telegraphs. See 

 "Galvanism Gives a New Stimulus to Inventors," Vol. VIII, 

 p. ii. In connection with the reproduction of illustrations, see 

 "The Introduction of Process Work," Vol. VIII, p. 202. 



Electrolysis. The dissociation or decompounding of sub- 

 stances in solution through the passage of electric currents. In 

 a solution of silver salts, for example, the silver (being 

 "electro-positive") passes to the negative pole (cathode) and is 

 there deposited. This is the action in the practical process of 

 electro-plating. Similarly, solutions of copper compounds are 

 used to plate surfaces with copper, as in making the plates from 

 which books, half-tone pictures, etc., are printed. See "The 

 Introduction of Process Work," Vol. VIII, p. 202. Cavendish's 

 decomposition of the water atom by the use of electricity, Vol. 

 IV, p. 14. See also "Electro-chemistry" of this index. 



Electro-magnetism. A manifestation of energy due to the 

 curious relations that exist between magnetism and electricity, 

 whereby, under certain circumstances, one may be induced by 

 the other. See "Faraday and Electro-magnetic Induction," Vol. 

 Ill, p. 240. See also in the present index, "Dynamo," "Elec- 

 tricity," "Electron," "Hertzian Waves." 



Electron. The hypothetical unit structure of electricity, the 

 theory of which has been chiefly developed by Prof. J. J. Thom- 

 son. The negative electron is believed to have about one one- 

 thousandth the mass of the hydrogen atom. It may be the 

 basis of all matter. Professor Thomson made tentative an- 

 nouncement of the probable discovery of the positive electron 

 in 1910. See "Professor J. J. Thomson and the Nature of Elec- 

 tricity," Vol. V, p. 92. 



Electro-plating. See Electrolysis. 



Element. The final chemical analysis, so far as at present 

 achieved, resolves all known forms of matter into seventy-odd 

 so-called elements, each having an atomic structure, which re- 

 sists further dissociation, and which presents definite and charac- 

 teristic properties of size and chemical valency. Their names 

 and atomic weights are: 



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