Magnetic Induction in Spheroids. 155 



molecular temperature seems in general to be accompanied 

 by an increase of the electron temperature. 



As the temperature rises by rubbing, the kinetic energy of 

 the electrons increases also, and the electrons move about 

 with increasing velocity. 



At ordinary temperature the woollen cloth seems to have 

 a lower electron temperature than the glass rod, and the glass 

 shows thus by rubbing with the cloth a positive charge. But 

 the electron temperature of the woollen cloth increases with 

 increasing molecular temperature, and at length the electron 

 temperature of the warm cloth would be higher than the 

 electron temperature of the cold glass rod. If the glass rod now 

 is rubbed with the woollen cloth it will be negatively charged. 



I think these experiments justify the belief that, if two 

 bodies have the same electron temperature, the electrons will 

 be removed in the same proportion from both bodies. But 

 if the electron temperature of two bodies is different, the 

 number of electrons removed from the u electrically warmer" 

 body will be greater than the number of electrons removed 

 from the "electrically colder"' body. The electrically warmer 

 body will thus by rubbing be depleted of electrons and left 

 with an excess of positive ions. It will consequently be 

 positively charged. The electrically colder body will collect 

 the electrons which the electrically warmer body has lost, 

 and it will thus be neoativelv charged. 



The experiments made with two pieces of paraffin, which 

 have the same electron temperature, can be explained on the 

 hypothesis, that the electrons by rubbing remove from the 

 internal mass of the body and are collected on the rubbed 

 surface. Both bodies will thus be negatively charged. 



XLIII. Magnetic Induction in Spheroids. 

 B>j Prof. D. X. Mallik, B.Sc.(Lond.), B.A.(Cantab.) *. 



THE present paper deals with the problem of magnetic 

 induction in a magnetic substance in the form of a 

 prolate spheroid, due to a current circulating in a wire 

 wrapped round it along a part of its length. 



1. The first step is to solve the equation V 2 V = in 

 spheroidal harmonics in the usual way. 

 For this, let 



x = h^/r 2 — 1 sin 6 cos <j> ; 

 y — h^/r 2 — 1 sin 6 sin <£ ; 

 z = hr cos 6. 



* Communicated by the Author. First appeared in the Journal of the 

 Asiatic Society, Bengal. 



