364 Prof. E. Wilson. [May 23, 



and this reduces to 



greater than unity ; 



8B 2 /W7r2j-7r 2 / . /(1-» 2 )\1 



— tttt^ ^ ?; tan _i A / 7- ^ when m is less 



10 16 /) \ 2?i n N /(l - ?7 4 ) V V (1 + ?i 2 )/ J 



than unity. 



The average watts per cubic centimetre of the cylinder as given by 

 the above formulae are 



152/272 "R2/'2/2 



7-16 t£t- = 1-79 ££4- when n = 1. 

 19-7 32? = 4-9 S 7 ^ 2 when n = 200. 



10 lb /) 10 1D /D 



When n = ^ the yalue of ^ ~ — tjt l\ ( tan_1 A /rri ) is 



very small indeed. 



By modifying the expression for the resistance of the rectangular 



path, Mr. Dale shows that the watts per cubic centimetre = 4*69 ., / , 

 r r 10 lb /j 



when w = 1, and 12 '6 — — when n is much greater than unity. 



(2.) There is the distribution assumed in connection with the ex- 

 periments, that is, the induced currents distribute themselves on the 

 surfaces of cylinders similar to and concentric with the cylinder experi- 

 mented upon. Mr. Dale has dealt with this case theoretically for a 

 uniform magnetic field, and shows that the watts per cubic centimetre 



J^2/2^2 JJ2/2/2 



of the cylinder = 3 '95 ., , when n = 1, and 7*9 -r— rr- when n is 



much greater than unity. The former coefficient is in very good agree- 

 ment with the graphical result, which is 3 '93. 



(3.) There is the case in which the current density in any path is 

 constant throughout the whole length of the path. Mr. Dale has also 

 dealt with this case theoretically and shows that the watts per cubic 



J>2/2^2 ]g2/272 



centimetre = 4*09 —~- when n = 1, and 11-1 ■ ' , when n is much 



10 lb /3 10 1O /3 



greater than unity. 



