510 Prof. Riicker. On the Magnetic Permeability of 



M= ,-4-~ 

 and N" = 



With the distances actually adopted in one experiment, 

 M = -0-000273, d<10cm., 

 N = 0-000170, r, = 17 -Ocm., D = 103 cm. 



Hence, the term M . d is small, and may be neglected, and, therefore , 



Fd 



p = 



2.N .r,.D 



If I be the intensity of magnetisation of the liquid, 

 A the area of the tube, 



n the number of turns per cm. in the solenoid, 

 C the strength of the current in absolute units, 

 K the susceptibility of the liquid, 



I V.d 



4.7r.ri.C S.w.w.C.N.^.D.A 



where 8 . TT . n . N . rj . D . A is constant for any one position of the ap- 

 paratus, and = N! say ; 



V.d 



therefore K = ^f T^- 



> %<' 



The solenoids were practically identical in construction, and if 

 d^ d 2 be the algebraical difference of the deflections right and left 

 when the tube is introduced into the two solenoids, 



" 2.1^.0 



To determine F the auxiliary solenoid was used. It was placed 

 perpendicular to the axis of the magnet, which bisected it. Its 

 length being 2a, number of turns per cm. n, area A', the distance of 

 its poles from the centre of the magnet u, and the deflections being 

 d\ and d' z to the left and to the right respectively, when the current 

 C' circulated through it, 



8 . a . n' . C' . A! . D 

 u\d\-d' z ) 



1 (rfj-dg) C' n 1 A' a 1 1 

 Jcience, K TT- ' -y-r. -- ^-r * 77- * ' ~r~ ' ~ ' 5 ' xf~ 5 



2ir dd\ C n A i u 6 N 



