KEY AND INDEX 



indispensable to the carpenter, is really a sharp-edged wedge, 

 and operates on the principle of the inclined plane. It has been 

 used, practically unmodified, from a very early period. 



Chloroform. A compound prepared by cautiously distilling 

 together a mixture of alcohol, water, and chloride of lime. 

 Chemical symbol C H Cl s - The use of chloroform as an anaesthetic 

 was introduced by the Scottish surgeon, Sir J. Y. Simpson; not, 

 however, until the anaesthetic power of ether had been clearly 

 demonstrated by Morton in America. See "Painless Surgery," 

 Vol. IV, p. 208. 



Choke-damp. A colloquial name for carbonic acid gas (C O 2 ) 

 when found in mines. The name is used (in contradistinction to 

 the explosive "fire-damps") because this gas is non-explosive, 

 but may cause death by asphyxiation literally choking the 

 miner to death. See "Conditions to be Considered in Mining," 

 Vol. VI, p. 247. 



Chromosomes. Minute, usually thread-like structures within 

 the organic cell nucleus, which have peculiar interest because 

 their number varies in different animals, but is always the same 

 for each cell of any given species. The chromosomes are 

 bisected when the cell divides. See pp. 131-134 of Vol. V for 

 recent researches in this field. 



Chronometer. Generically, any time-measurer; but specifically 

 a name for the nautical watch or clock carried in duplicate or 

 triplicate by navigators and explorers, which records the time 

 at a given meridian (usually that of Greenwich), thus supplying 

 information with the aid of which the navigator may compute 

 his longitude from sidereal observations. See "Perfecting the 

 Chronometer," Vol. VII, p. 23. 



Chrono-photography. Generic name applied to the method of 

 taking series of photographs at brief intervals, to the end that 

 "moving pictures" may be produced. The apparatuses with which 

 these pictures are reproduced are familiar under the trade names 

 of kinetoscope, biograph, vitascope, etc. Names of Muybridge, 

 Marey, Anschiitz, and Edison are associated with the invention. 

 See "Chrono-photography Moving Pictures," Vol. VIII, p. 248. 



Circuit. The medium or mediums connecting the poles of a 

 battery or other generator of electricity. The ground, or a body 

 of water, may serve as the medium of the so-called "return 

 circuit"; but some conducting medium must give unbroken com- 

 munication (however circuitous the route) or the current will 



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