SCIENTIFIC MEMOIRS. 



VOL. v.— PART XIX. 



Article VIII. 



On the Repulsion of the Optic Axes of Crystals by the Poles of 

 a Magnet*. By M. Plucker, Professor of Natural Philo- 

 sophy in the University of Bonn. 



[From PoggendorfF's Annalen, Vol. Ixxii., No. 10, October 1847.] 



1. The object of the present memoir is to make known a 

 series of new observations, which form a sequel to the last dis- 

 coveries of Faraday, from which the idea of making them origi- 

 nated. The results of these observations, when arranged in the 

 form of a general expression, lead to the following empirical 

 laws : — 



When any crystal having a single optic axis is placed between 

 the two poles of a magnet, this axis is repelled by each of the 

 two poles. If the crystal has two optic axes, each of these two 

 axes is repelled by each of the two poles with the same force. 



The force which produces this repulsion is independent of the 

 magnetic or diamagnetic condition of the mass of the crystal; it 

 diminishes less, as the distance from the poles of the magnet in- 

 creases, than the magnetic or diamagnetic forces emanating from 

 these poles, and acting upon the crystal. 



2. To facilitate as much as possible the survey and criti- 

 cal investigation of my observations, and the conclusions de- 

 duced from them, the best method appears to me to be that of 

 detailing them in exactly the same course as that by which I 

 was conducted to the above results. It will however be indis- 

 pensable previously to relate briefly the method and means used 

 in my experiments. 



First, with the view of repeating Faraday's experiments upon 



• Translated by Dr. J. W, Griffith. 

 VOL. V. PART XIX. 2 B 



