170 Dr. Tjmdall on Diamagnetis^m and Magnecrystallic Action, 



analogous to the series of attractions in the case of the hall of 

 soft iron. The square roots of thpse attractions give a series of 

 numbers exactly proportional to the currents employed; the 

 question therefore is, — *' Will the square roots of the repulsions 

 give a similar series, or will they not ? ** 



Calling the angle which the needle of the galvanometer, under 

 the influence of the current, makes with the magnetic meridian 

 «, then if the attraction of the iron ball and the repulsion of the 

 bismuth ball follow one ancl the same law, we shall have the 

 equation 



V'T=wtana, 



where T represents thq torsipn necessary \o bring the beam back 

 to zero, and n is a constant depending on the nature of the ex- 

 periment. The following tables will show the fulfilment or non- 

 fulfilment of this equatjpn. 



Table I. — Bismuth spheres, 8 millims. diameter. 

 /i=ll-7. 



A second series was made with a pair of spheres of the bis- 

 muth of commerce with the same result. 



Sulphur is also a diamagnetic substance, but much weaker in 

 this respect than bismuth. The next series of experiments were 

 made with two balls of this substance. 



Table II. —Sulphur spheres, 8 millims. diameter. 

 »=3-3. 



A pair of sulphur balls were nej^t taken of ^early twice the 

 diameter of the preceding. 



