264 The Mathematical Electricians of the 



current consists in a transport of one kind of electricity with a 

 definite velocity relative to the wire, it might be expected that 

 a coil rotated rapidly about its own axis would generate a 

 magnetic field different from that produced by the same coil 

 at rest. Experiments to determine the matter were performed 

 by A. Foppl* and by E. L. Nichols and W. S. Franklin,f but 

 with negative results. The latter investigators found that the 

 velocity of electricity must be such that the quantity conveyed 

 past a specified point in a unit of time, when the direction of 

 the current was that in which the coil was travelling, did not 

 differ from that transferred when the current and coil were 

 moving in opposite directions by as much as one part in ten 

 million, even when the velocity of the wire was 9096 cm./sec. 

 They considered that they would have been able to detect 

 a change of deflexion due to the motion of the coil, even though 

 the velocity of the current had been considerably greater than 

 a thousand million metres per second. 



During the decades in the middle of the century consider- 

 able progress was made in the science of thermo-electricity, 

 whose beginnings we have already described. J In Faraday's 

 laboratory note-book, under the date July 28th, 1836, we 

 read : " Surely the converse of thermo-electricity ought to be 

 obtained experimentally. Pass current through a circuit of 

 antimony and bismuth." 



Unknown to Faraday, the experiment here indicated had 

 already been made, although its author had arrived at it by a 

 different train of ideas. In 1834 Jean Charles Peltier|| (b. 1785, 

 d. 1845) attempted the task, which was afterwards performed 

 with success by Joule,1J of measuring the heat evolved by the 

 passage of an electric current through a conductor. He found 

 that a current produces in a homogeneous conductor an elevation 



* Ann. d. Phys. xxvii (1886), p. 410. 



t Amer. Jour. Sci., xxxvii (1889), p. 103. 



J Cf. pp. 92, 93. Bence Jones's Life of Faraday, ii, p. 76. 



II Annales de Ciiimie, Ivi (1834), p. 371. If Cf. p. 239. 



