132 



TAB. CLXIX. 



In describing the crystals on this specimen I may use the 

 words of Count Bournon, who, after speaking of the 

 elongated octaedron of the former table, says, " The angles 

 of 96° are replaced by a plane which is equally inclined on 

 the adjacent sides, and is frequently very broad. Then 

 the tetraedral prism is changed into a flat hexaedral prism 

 having two angles of 84°, and the others of 138°." The 

 Count never saw the angles of 84° replaced. il The average 

 specific gravity of this Arseniate of Copper taken on five 

 pure pieces was 4* 280." 



TAB. CLXX. 



Mr. rashleigh, with his usual ardour for the promotion 

 of science, sent me the present specimen of Arseniate of 

 Copper. It has the appearance of cubic crystals of Arseniate 

 of Iron on the apex or ends of the radii of Wood Copper. 

 However, a good crystallographer may find out the real con- 

 formation ; and as it is truly curious and instructive, we 

 were pleased to have such a specimen come under our in- 

 spection, that it may be understood hereafter. The two 

 preceding Tables show the nature of this modification, and 



