TECHNICAL INDEX AND GLOSSARY 



pinging on the glass receptacles, they generate X-rays. See 

 "Professor J. J. Thomson and the Nature of Electricity," Vol. V, 

 p. 92, for the investigations of Crookes, Leonard, Roentgen, 

 Becquerel, Thompson, and others. 



Cell, (i) The unit structure of living tissues. See Vol. IV, 

 p. 115, for the investigations of Brown, Schleiden, Schwann, 

 Von Mohl, and Virchow; also "The Mechanism oi the Cell," 

 Vol. V, p. 225. (2) The unit structure of a galvanic battery as 

 devised originally by Galvani and Volta. See "Electricity," of 

 the present index. 



Centrosome. A minute structure (discovered by Van Beneden) 

 within the organic cell, the precise function of which is in doubt. 



Chemical Affinity. A term designating the attractive and 

 selective influence that operates between chemical substances. 

 The preference of the various chemical atoms are perfectly 

 definite and unvarying, under given conditions, and the entire 

 science of chemistry is built upon the knowledge of such inter- 

 relations between the different elementary atoms; but this knowl- 

 edge is, in each case, matter of experimental observation. See 

 "Chemical Affinity," Vol. IV, p. 57. 



Chemistry. The science that deals with the interrelations of 

 the different kinds of matter, as regards their elementary or 

 atomic structure. The border-line between chemistry and 

 physics is not always quite sharply defined (as, for example, in 

 the matter of radio-activity, which encroaches upon both do- 

 mains), but in general chemistry deals with atoms themselves; 

 physics with the aggregations of atoms which we call molecules. 

 Thus it was the province of the chemist to determine that water 

 is a compound of hydrogen and oxygen, and that air is a mixture 

 of nitrogen, oxygen, and other gases; while the study of such 

 things as hydrostatic pressure, the expansion of gases, etc., be- 

 longs to the physicist. See "The Beginnings of Modern Chemis- 

 try," Vol. IV, p. II, and "Chemistry Since the Time of Dalton," 

 Vol. IV, p. 38. 



Chimney. This seemingly essential architectural element of 

 the dwelling-house was not known in antiquity, but was de- 

 veloped in the Middle Ages, or at the beginning of the modern 

 period. See Vol. IX, p. 150. 



China. A name applied to various kinds of glazed pottery, the 

 exact implications of the word not being very closely defined. 

 See "The Products of Clay and Fire," Vol. IX, p. 227. 



Chisel. This familiar implement for gouging and cutting wood, 



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