458 The Theory of Aether and Electrons in the 



Most of the later writers on metallic conduction have pre- 

 ferred to take the hypothesis of Arrhenius* rather than that of 

 Grothuss as a pattern ; and have therefore supposed the 

 interstices between the molecules of the metal to be at all 

 times swarming with electric charges in rapid motion. In 

 1898 E. Eieckef effected an important advance by examining 

 the consequences of the assumption that the average velocity of 

 this random motion of the charges is nearly proportional to the 

 square root of the absolute temperature T. P. DrudeJ in 1900 

 replaced this by the more definite assumption that the kinetic 

 energy of each moving charge is equal to the average kinetic 

 energy of a molecule of a perfect gas at the same temperature , 

 and may therefore be expressed in the form qT, where q denotes 

 a universal constant. 



In the same year J. J. Thomson remarked that it would 

 accord with the conclusions drawn from the study of ionization 

 in gases to suppose that the vitreous and resinous charges play 

 different parts in the process of conduction : the resinous 

 charges may be conceived of as carried by simple negative 

 corpuscles or electrons, such as constitute the cathode rays : 

 they may be supposed to move about freely in the interstices 

 between the atoms of the metal. The vitreous charges, on the 

 other hand, may be regarded as more or less fixed in attachment 

 to the metallic atoms. According to this view the transport of 

 electricity is due almost entirely to the motion of the negative 

 charges. 



An experiment which was performed at this time by Eiecke|| 

 lent some support to Thomson's hypothesis. A cylinder of 

 aluminium was inserted between two cylinders of copper in 

 a circuit, and a current was passed for such a time that the 

 amount of copper deposited in an electrolytic arrangement 



* Cf. p. 384. 



t G-ott. Nach., 1898, pp. 48, 137. Ann. d. Phys. Ixvi (1898), pp. 353, 545, 

 1199; ii. (1900), p. 835. 



I Ann. d. Phys. (4) i (1900), p. 566 ; iii (1900), p. 369 ; vii (1902), p. 687. 

 Rapports pres. au Congres de Physique, Paris, 1900, iii, p. 138. 

 || Phys. Zeitsch. iii (1901), p. 639.' 



