Dr. Tyndall on Diamagnetism and Magnecrystallic Action, 179 



will, with his usual frankness, grant the theory the full benefit 

 of the corroboration. 



Faraday has discovered, that if a bismuth crystal be suspended 

 in the magnetic field, it will set itself so that a line perpendicular 

 to the plane of most eminent cleavage will be axial ; this line he 

 calls the magnecrystallic axis of the crystal. In the memoir 

 before alluded to, the position of the magnecrystallic axis is 

 affirmed to be a secondary result, depending on the fact that the 

 mass in the direction of the planes of cleavage is most strongly 

 repelled. 



Here again the torsion-balance furnishes us with the direct 

 proof of this affirmation. Two cubes of bismuth were prepared, 

 in each of which the plane of most eminent cleavage formed two 

 of the opposite sides. Suspended by a fibre of cocoon-silk in 

 the magnetic field, the line perpendicular to the cleavage turned 

 into the axial position, or what amounts to the same as far as 

 the eye is concerned, the cleavage itself receded from the poles 

 and stood equatorial. These cubes were placed one on each end 

 of the torsion-balance ; first, so that the plane of most eminent 

 cleavage was parallel to the axes of the cores, and afterwards 

 perpendicular to these axes. ' The respective repulsions are stated 

 in the following tables. 



Table IX. — Cubes of bismuth, crystal edges 6 millims. Plane 

 of most eminent cleavage parallel to axes of cores. 



Table X. — The same cubes. Plane of most eminent cleavage 

 perpendicular to axes of cores. 



A comparison of these two tables shows us that the repulsion 

 of the cubes, when the plane of most eminent cleavage was parallel 

 to the magnetic axis, is to the repulsion when the said plane was 



