TH E 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. I. — On the Energy of the Cathode Hays / by W. G. 



Cady. 



[An investigation carried out at the Physical Institute of the University at Berlin.] 



It has long been known that the cathode rays possess a con- 

 siderable amount of energy ; yet the relation between this and 

 the other discharge phenomena has hitherto received but little 

 attention. Ebert and Wiedemann,* E. Wiedemann, f and 

 Ewers;}; measured the energy of cathode rays by means of 

 calorimeters. For exact work, however, the thermo- element is 

 to be greatly preferred. Among the recent investigations 

 based upon the emission hypothesis, this method has been em- 

 ployed by J. J. Thomson § ; 0. Berg has also used a thermo- 

 element in his work with the cathode rays.f 



According to the emission hypothesis there exists the follow- 

 ing relation between the energy of the cathode rays, potential 

 of discharge, and amount of electricity transported by the 

 rays. Suppose that we have a bundle of rays given off from 

 a cathode of potential V, and striking a metallic conductor 

 which is led to earth through a galvanometer; let the con- 

 ductor be struck by JV particles per second. We will at first 

 assume that the entire charge of the particles, as well as all 

 their energy in the form of heat, is given up to the conductor. 

 Then if v [cm. sec -1 ] be the velocity of the particles, and m 



* H. Ebert and E. Wiedemann, Sitzungsb. der phys. med. Soc. zu Erlangen, 

 Dec. 14, 1891. 



f E. Wiedemann, Wied. Ann., lxvi, p. 61, 1898. 



X P. Ewers, Wied. Ann., lxix, p. 167, 1899. 



§ J. J. Thomson, Phil. Mag., xliv, p. 293, 1897. 



|| 0. Berg. Ber. d. naturforsch. Gesellsch, zu Freiburg i. Br. XI, vol. ii, p. 73, 

 July, 1899. 



An. Jour. Sci. — Fourth Series, Vol. X, No. 55.— Jult, 1900. 



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