OF CRYSTALS BY THE POLES OF A MAGNET. 373 



its centre of gravity was in the horizontal middle line between 

 the two surfaces of the poles, arranged itself eqtiaiorially as long as 

 the centre of gravity was within the two planes of the lateral sur- 

 faces of the keeper. As soon as it passed beyond one of these 

 two planes, two stable positions of equilibrium were apparent, 

 one in the direction of the middle line (axial), the other perpen- 

 dicular to it (equatoi'ial) ; when the centre of gravity was moved 

 further away, the second only of these two stable positions of 

 equilibrium remained. All these phaenomena are perfectly ex- 

 plicable on the assumption of a non-polar repulsion of the mass 

 of bismuth by the poles of the electro-magnet. 



45. These phasnomena, as also the position which a magnetic 

 mass between the surfaces of the poles assumes, must be borne 

 in mind when we allow a crystal to oscillate between the sur- 

 faces of the poles, and we wish to determine a priori the phaeno- 

 mena about to result. The prism of tourmaline mentioned in 

 paragraph 8, when suspended in the same manner as the cylinder 

 of bismuth, became placed in the centre axially, in the planes of 

 the lateral surfaces of the keeper equatorially, and further away 

 again axially. The large plate of calcareous spar (paragraph 20), 

 in all positions of suspension, arranged itself with its axis towards 

 the middle line, overcoming the diamagnetism of the mass within 

 the two planes of the lateral surfaces of the keeper, but beyond 

 them supported by the diamagnetism. 



46. There could hardly be any necessity for confirming the 

 fact, that the electi'o-magnet acts in the above experiments 

 exactly in the same manner as a permanent magnet ; but it was 

 of interest to determine whether the latter possessed power 

 enough to render the repulsive force of the axes visible. 



At my request, M. vom Koike, who with great talent and pa- 

 tience acted the part of my assistant during all the experimental 

 investigations, repeated the experiments described in paragraphs 

 4 to 6, first with the magnet of Ettinghausen's magneto-electric 

 rotation apparatus, and subsequently with a small horse-shoe 

 magnet, which sustained barely a kilogramme at each pole. To 

 approximate the poles, he placed at each end of the magnet, 

 lying horizontally, a thick iron rod, the extremities of which 

 were situated at a proper distance, so as to allow the plate of tour- 

 maline to oscillate between them in the aii*. The result was 

 perfectly decisive. 



47. Tlic experiments detailed in the present memoir are, in 



