196 Prof. J. V. Jones. Calculation of the Coefficient of 



' 2 

 d* = , g\ and 



;, K 3 , K 4 , &c., by successive applications of (-4), 



and finally M@ = (A + a)c 2 2 (_i)K w . 



6. An example may be useful in showing the magnitudes of the 

 various quantities concerned. 



If 2A = 21-02673 inches, 



2a = 13'01997 inches, 

 2x 5*02480 inches, 

 = 201 ar, 



then c = 0-9719540, 



c = 0-2351708, 



F = 2-8598352, 



E = T0655716, 



K = 0-9387751, 



J *' g z = 0-02178146, 



K! = 0-0561543, 



d z = 0-4156218, 



e 3 = 0-0206400, 



K 2 = 0-0076057, 



K 3 = 0-0014623, 



K 4 = 0-0003387, 



K 5 = 0-0000876, 



Ke = 0*0000244, . 



K 7 = 0-0000071, 



2( l)"*K m = 0-8890325, 



3k[0 = 9028-182 inches = 22931*166 cm. 



If the circle is in the mean plane of a helix of axial length 2x, the 

 coefficient of mutual induction will be 2M , or in case of the above 

 dimensions, 



M = 2M = 18056-364 inches = 45862'332 cm. 

 The value of M@ given above was obtained in 1896 by 



