of the red oxyd of Copper and arseniated Iron, 37 



SIXTH MODIFICATION. 



This modification is the result of a decrease, by which each solid 

 angle is replaced by eight triangular planes, two on each face of the 

 primitive crystal, and inclining on the axis that passes through the 

 angles. Fig. 106 ; I have not seen this modification as thus de- 

 scribed, but only, as in the following figures, in combination with 

 other modifications. The crystal represented by fig. 108 contains 

 all the modifications of the primitive crystal of this substance, which, 

 I believe, have hitherto been noticed. 



