Intelligence and Miscellaneous Articles. 317 



vanometer-needle was also in equilibrium. The micrometer-reading 

 and the resistance of the shunt were then set down as the results of 

 the experiment. 



The mean of twelve satisfactory experiments, at distances varying 

 from "25 to *5 inch, gave for the ratio of the electromagnetic to the 

 electrostatic unit of electricity — 



v=27'79 Ohms, or B. A. units. 

 = 2/7,900,000 metres per second. 

 = 174,800 statute miles per second. 



This value is considerably lower than that found by MM. Weber 

 and Kohlrausch by a different method, which was 310,740,000 metres 

 per second. Its correctness depends on that of the B. A. unit of 

 resistance, which, however, cannot be very far from the truth, as it 

 agrees so well with Dr. Joule's thermal experiments. 



It is also decidedly less than any estimate of the velocity of light, 

 of which the lowest, that of M. Foucault, is 298,000,000 metres per 

 second. 



In a note to this paper the author gave his reasons, in as simple a 

 form as he could, for believing that the ratio of the electrical units 

 and the velocity of light, are one and the same physical quantity, 

 pointing out the difference between his theory and those of MM. 

 Riemann and Lorenz, which appear to lead to the same conclusion. 



XLI. Intelligence and Miscellaneous Articles. 



SECOND NOTE ON THE LAWS OF INDUCTION. 

 BY MM. JAMIN AND ROGER. 



T N a previous communication we announced that the heat developed 

 ■*■ in the external circuit of a magneto-electrical machine, working 

 with a constant velocity, was governed by the same law as in the case 

 of an ordinary battery. Our machine consisted of six rotating plates, 

 each provided with sixteen coils mounted in tension. The plates 

 themselves were united in quantity ; that is, the similar poles of each 

 of them terminated in two common points, with which were connected 

 the external circuit. Since then the machine has been arranged 

 afresh, so as to combine the various plates in all possible manners. 

 We will now give the results obtained by associating 1,2,. . . 6, . . n 

 plates in quantity. 



By joining in the same manner n piles, each having the electro- 

 motive force A and the resistance r, we have a single electromotor 



of the force A and resistance -; the intensity i of the current with 



a 



an external resistance r will be 



n 



