10-4 Prot. H. A. Rowland on a new Theory 



or the field is uniform. If the electric potential of the sphere 

 on the electrostatic system is V, we may write 



3 n ' 



which is independent of the dimensions of the sphere. 



In this uniform field in the interior of the sphere, let a 

 smaller sphere of radius a! be situated ; the potential of its 

 induced magnetization will be 



/jl + 2 r 4 



Hence the expression for the potential for the space between 

 the two spheres will be 



U= 5 -Vi — rcos0+ — — ,a' 3 — r; 

 3 n I fju + 2 r- } 



and outside the electrified sphere it will be 



n \ /JL + 2J r 2 



Let us now take the most favourable case for the production 

 of magnetism that we can conceive, making a' ' = a and fi = qo ; 

 we then have 



n r* 



which is the potential of an elementary magnet of magnetic 

 moment 



n 



But Gauss* has estimated the magnetic moment of the earth to 

 be 



3-3092 a 3 



on the millimetre mg. second system. Hence we have 

 V=3-3092- 



W 



for the potential in electrostatic units on the mm. mg. second 

 system. In electromagnetic units it is thus 



Vx = 3-3092-; 



w 



and hence in volts it is this quantity divided by 10 n . 

 * Taylor's Scient. Mem. vol. ii. p. 225. 



