ill 



THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENC 



[SIXTH SERIES.] 



JUNE 1909. 



LXXY. The Motion of Electrons in Solids. Part I. — *&ectric« 

 Conductivity, Kirchhojfs Law and Radiation of fHgftf 

 Wave-length. By J. H. Jeans, M.A., F.R.S., Professor 

 of Applied Mathematics in Princeton University *. 



1. rriHE Electron-theory of metals has been developed 

 A by Drude, Thomson, Lorentz, and others. The 

 work of all these writers postulates a motion consisting of 

 free paths and collisions. These and other conceptions im- 

 ported from the Kinetic Theory of Gases have led very 

 successfully to a general interpretation of many of the 

 phenomena of solids, but cannot be expected to lead to 

 accurate quantitative results. I have therefore thought it 

 would be of value to try to develop a theory which shall be 

 free from all suppositions for which there is not direct 

 numerical justification. Such a theory, if it can be con- 

 structed, ought to lead not only to predictions of the nature 

 of the phenomena with which it is concerned, but also to 

 an exact evaluation of the quantities involved in these 

 phenomena. 



Electrl' Conductivity, 



2. In a conductor whi< h is under the influence of no 

 externally-impressed elecl :ic force, we suppose that there 

 are N electrons per unit \ olume, moving with the velocities 



* Cominuiicated by the Author. 

 Phil. Mag. S. 6. Yol. 17. No. 102. June 1909. 3 G 



