in a Magnetic Field at Different Temperat 



ures. 



689 



The change in resistance of the wire in the magnetic field 

 was then found from the relation 



or = ~ x 



146 , 1 

 9T X * = Id X 



146 

 95 



X0; 



where 9 is the mean deflexion on reversal due to the field in 

 any case. In this way the following results were obtained. 



c. 



H. 



Deflexion on 

 reversal. 



ffrXlO*. 



i r xio*, 



r 



H'-xlO -7 . 



1-8 



8450 



14-6 



225 



1-22 



744 



25 



9300 



171 



263 



1-42 



8-65 



3-4 



10200 



191 



294 



1-59 



10 4 



4-4 



11000 



22 1 



340 



1-85 



121 



5-6 



11 800 



27-6 



42 5 



231 



13-9 



7-5 



12600 



297 



457 



248 



159 



100 



13300 



322 



496 



270 



17-7 



The strengths of the field for each current used were 

 measured by snatching a coil from between the pole-pieces 

 and observing the throw of the galvanometer (the same 

 instrument as for other measurements). To reduce damping, 

 the coil and galvanometer were connected through a standard 

 resistance varying from 800 to 1000 ohms. 



Interposed in this circuit was also the secondary of a 

 standardizing apparatus. 



The latter consisted of a primary coil — a long solenoid — 

 through which a known current could be passed, and a short 

 secondary placed at its centre having 322 turns of fine silk- 

 covered wire in a single layer. 



The throws of the galvanometer were standardized by 

 reversing the currents in the primary. 



If, then, 0i be the throws of the exploring coil and 2 those 

 of the standardizing coil, while C x and C 2 are the correspond- 

 ing currents,, we have 



2^_ 2 N 2 477-rV 0, 



M ~ ^ 2 'nV 10 Y 2 ; 



where N x and N 2 are the number of turns in the exploring 

 and standardizing secondary coils respectively, d x and d 2 

 their respective diameters, while n represents the number of 

 turns per unit length of the primary of the standardizing 

 solenoid. 



In these experiments Nj = 8 : N 2 = 322 : n = 31'7 : 

 di ='838 cm. : d 2 = 3' 90 cm. 

 Phil. Mag. S. 6. Vol. 19. No. 113. May 1910. 2 Y 



