133 



it is only a series of radiating, or partly radiating crystals, 

 which crowd together wedge-like, as happens with cal- 

 careous Spar, terminating with octaedrons so crowded as 

 to show in general only as much as resembles the sides of 

 a cube placed obliquely with the edge upwards : see the 

 left hand figure. The other outlines show how it accords 

 with the modification of the preceding figures. 



There is a tendency to a concave formation of the faces 

 which belongs to this cctaedron, and often may be seen in 

 cubes of Arseniate of Iron, tab. 87 : it in some measure 

 aids the deception. The Arseniate of Iron is generally of 

 a yellow-green. 



The Arseniate of Copper in these three tables rests upon 

 Quartz in part crystallized, but chiefly in broken fragments 

 mixed with Oxide of Iron. 



VOL. II. M 



