52 ON THE PRIMITIVE FORMS OF CRYSTALS. 



Table shewing the Connection between the Pri- 

 mitive Forms of Crystals, as determined by 

 Hatty*, and the Number of their Aoces of 

 Double Refraction, 



1ST CLASS OF PRIMITIVE FORMS. 



CRYSTALS WITH ONE AXIS. 



1. Rhomboid with Obtuse Summit, 

 Carbonate of lime. 

 Carbonate of lime and magnesia. 

 Carbonate of lime and iron. 

 Tourmaline. 

 Rubellite. 

 % Ruby Silver f . 



%, Rhomboid with Acute Summit, 

 Corundum. Bournon, Phil, Trans, 

 Sapphire. 

 Ruby. 



Cinnabar, Annal, de Chimie, torn. viii. p. 60, 



D 2 



* Traite de Minerahgie, torn. i. p. 273. ; and the Edinburgh 

 Encyclopaedia, art. Crystallography, vol. vii, p. 474. 



t In the crystals printed in Italics, the number of their axes 

 has been deduced from an examination of the tints, and not 

 from the direct exhibition of the system of coloured rings ; so 

 that it is possible that they may have a different number of axes 

 from what is here assigned to them. 



