ON THE PRIMITIVE FORMS OF CRYSTALS. 51 



signed a different nucleus to the same body. In a 

 very extensive examination of the optical constitu- 

 tion of minerals and artificial crystals, I was led to 

 ascertain their number of axes of double refrac- 

 tion ; and I had proceeded only a short way in this 

 inquiry, when it became obvious, that a very un- 

 equivocal connection existed between the form of 

 the primitive nucleus and their number of axes of 

 double refraction. Every new experiment added to 

 the truth and generality of this result ; and when 

 I had examined the greater number of those bodies 

 whose primitive nucleus was known, I had the sa- 

 tisfaction of observing that all the crystals with 

 one axis arranged themselves under a certain series 

 of primitive forms ; and that those with two axes 

 arranged themselves under another series ; while the 

 remaining primitive forms were occupied by those 

 crystals whose doubly refracting forces were in equi- 

 librio by the combined action of three equal and 

 rectangular axes. 



This singular coincidence, to which there is only 

 one or two exceptions, will be readily seen in the 

 following Table. 



Table 



