the Arseniates of Copper, and of Iron . 
179 
Variety 1. Capillary , of a determinate form. 
In this variety, the crystals are extremely slender, yet pre- 
serve their form, which is that of a very lengthened octaedron. 
The small slender crystals often form themselves into a con- 
fused group ; sometimes, however, they form small mamillce, 
by the divergence of a number of them from a common centre. 
Their colour is either a fine grass green, or a yellowish green, 
or a golden yellow ; and they have generally a beautiful trans- 
parency. 
Variety 2. Capillary , of an indeterminate form. 
In this variety, the very thin needle-like crystals are not ter- 
minated by the diedral apex of 112 0 , representing two planes 
of the octaedron, but gradually become smaller, and termi- 
nate in a very sharp pyramid. This variety has the same 
colours as the preceding ; and its very slender crystals are 
grouped in the same manner as in that. 
Substances in a crystallized state, in passing from a determi- 
nate form to an indeterminate or fibrous one, frequently assume 
an intermediate form, in which the crystal insensibly terminates 
in a very acute pyramid. 
Variety 3. In crystals perfectly regular for a part of their length , 
and fhrous at their extremity. 
In this variety, the crystals are perfect during a part of their 
length ; but their substance insensibly divides as it approaches 
the extremity, which very often is in fact nothing but a cluster 
of extremely delicate fibres, the colour of which always appears 
lighter than that of the solid part of the crystal. 
A a 2 
