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













Table 



III.— 



Ring No. III. 









Temperature = — 17°. 



Temperature =15°. 



Temperature = 



100°. 



,"» 



("1+2 



23 



^ 



/"l + 2 



S 



i"i 



/"l+S 



2? 



58- 



63-3 



92-4 



69 





83-2 



117- 



127- 



143- 



181- 



69 





106- 



378- 



80 





135- 



438- 



139- 



212- 



677- 



78 





165- 



970- 



95 





193- 



1120- 



152- 



248- 



1390- 



87 





201' 



2070- 



105 





217- 



2290- 



139- 



259- 



2280- 



91 





192- 



2820- 



104 





200- 



3040- 



130- 



219- 



3270- 



87 





166- 



3580- 



103 





206- 



2860- 



113- 



186- 



3750- 



73 





129- 



4320- 



100 





178- 



3580- 



90- 



139- 



4380- 



60 





100- 



4670' 



80 





130- 



4320- 



70- 



105- 



4750- 



37 





58-2 



5280- 



67 





106- 



4640- 



42- 



59-4 



5160- 















42- 



62-1 



5220- 















Temperature=210°. 



Temperature= 300°. 



/"i 



/"l+2 



23 



/"i 



,"1 + 2 



£ 



191 





191- 



139- 



268- 



271- 







193- 



187 





227- 



339- 



245- 



349- 







557- 



197 





266- 



727- 



245- 



388- 







1040- 



190 





295- 



1890- 



218- 



337- 







1820- 



175 





286- 



2300- 



169- 



274- 







2140- 



161 





246- 



2800- 



158- 



226- 







2380- 



111 





157* 



3740- 



83- 



113- 







2780- 



100 





139- 



3890- 













54 





68-3 



3800- 



..... 



.... 







.... 



EiDg III was re-wound between the third and fourth experi- 

 ments, and owing no doubt to a contact in the primary coil, 

 the later values of jut were too small. In the fourth and fifth 

 series, as given in the table, fi is multiplied by 1^. On this 

 account these experiments are of less value, but the error does 

 not affect the determination of the maximum value of 33 as 

 given later. 



The last series in table I was taken at varying temperatures 

 above the previous. To secure this the ring, properly insu- 

 lated, was placed on a plate of copper in a brass vessel and 

 sand piled upon it. The whole was then heated slowly, and 

 at intervals very rapid observations were made of the mag- 

 netic condition of the ring, and this was continued till the 

 metal was nearly non-magnetic. The points thus found are 

 indicated on the diagram. At the end the bottom of the vessel 

 seemed slightly red. 



An examination of the curves shows — 



I. A rise nearly in a straight line at first and more rapid as 

 the temperature is higher. 



II. A sharp curvature, the sharper as the temperature is 

 higher. 



III. A descent which also is more abrupt as the temperature 

 rises. 



There was a limit to the extent to which the current could 



