226 C. A. Perkins — Magnetic Permeability of Nickel. 



The value of the second term of the series never reaches 

 -g-^-jj- in the rings used and hence is entirely imperceptible. 



Q oc2AH =C sin 5' 



Q' oc2tt'A'23 oc 4m *>' A ' =C sin 5 

 R 



• H \ * 



i=-~r tan o 



sin 5 _ 2nn'fx A' H' tan tf 

 sm~S' "" "R - A H ~G~~ 



l R A H G sin 5 



km' A' H' tan d sin <&' 

 HA sin S- 



and 23 = 



n'A' sin 3-' 



All measurements given in this paper are in C. Gr. S. units. 

 The values of some of the quantities used in the experiment 

 are as follows : 



H = -1873 



H' = -1883 



The values of n are 



Ring I 205 

 Ring II 183 



Ring III 



292 

 169 



To vary n', several sets of coils were wound about each ring 

 containing from eight to ninety-five turns, according to the 

 currents used and the cross section of the ring. The different 

 coils in the same ring were of the same resistance, but any 

 slight changes in the adjustment would be eliminated by the 

 earth inductor. 



In one case the ring was cooled to —17° by means of ice 

 and calcium chloride, but the change produced by this was so 

 small that it was not considered worth doing in the other 

 cases. 



The results obtained for the three rings were as follows : 

 (//j is the permeability for temporary magnetism and z^+g for 

 total.) 



