220 



Mr. E. Wilson. The Growth of Magnetism in 



tions could be noted. The speed of rotation was varied, from one 

 revolution in ten to one revolution in two and a half minutes. 



The electromotive force curves have been integrated, and therefrom 

 the maximum average induction per sq. cm. of the area considered has 

 been obtained. The data are set forth in the appended table. Since 

 similar magnetic and electric events will happen in different sized 

 cylinders at times varying inversely as the square of their linear 

 dimensions, it is easy to infer what will happen in a cylinder 1 mm. 



diameter. Similar events will happen in this wire at 150 periods per 

 second, as have been observed in the 12-inch core with a periodic 

 time of ten minutes. A useful way of illustrating the results obtained 

 is to express in the form of curves the relation between the maxi- 

 mum average B over Area No. 4, that is, near the surface of the core, 

 and the percentage amounts by which this maximum has to be reduced 

 to give (1) the maximum average over Area No. 1, and (2) the maxi- 

 mum average over the whole core as given by coil No. 5. This is 

 done in figs. 3 and 4, in which the number on each curve refers to the 



