256 MOLECULAR ARRANGEMENT. 



in solution, water being diamagnetic, it loses its 

 property. The yellow prussiate of potash dissolved 

 in water is a diamagrietic body ; but the red 

 prussiate, which contains an atom less of potassium, 

 is magnetic: but in the solid state they are both 

 diamagnetic.* 



From this it would appear that the chemical compo- 

 sition of a body regulated its relation to magnetism. 

 The following facts will show, however, that the mole- 

 cular structure is more particularly concerned in de- 

 termining the molecular condition of substances. 



M. Pliicker, being desirous of finding the extent to 

 which the direction of the fibres in organic bodies might 

 influence their magnetic or diamagnetic properties, was 

 led to inquire whether in crystals the direction of the 

 optic axes, which itself depends upon the arrangement 

 of the particles, might not also exercise some influence. 

 The first submitted to the action of the electro-magnet 

 a thin plate of tourmaline, such as is employed in experi- 

 ments upon polarization, having its optic axis parallel to 

 its longest length. It was very quickly perceived that 

 the plate was magnetic, by the effect of the iron that it 

 contains; but it was suspended successively in three 

 ways, first, so that its longest side was vertical, then as 

 that the shortest side was vertical, and finally so that 

 the plate itself was horizontal. In the first case it is 

 directed between the two points of the conical curvatures 

 of the poles like a magnetic body ; but, in the other 

 two cases, on the contrary, it took the direction assumed 

 by diamagnetic bodies that is to say, a direction such 

 that its longest length was perpendicular to the line 

 joining the poles. This direction indicated that the 

 optical axis was repelled by the two poles, and that this 



* On Diamagnetism ; by Professor Pliicker, of Bonn. Philo 

 sopbical Magazine, July, 1848. 



