13 
TAB. CCVII. 
SILEX Quartzum. 
Quartz Septarium. 
Div. 2. Imitative. 
Quartz is metamorphosed into so many different shapes, 
that we never can be aware of the varieties; and the ap- 
pearance of the present specimen would by no means indi- 
cate such a substance. From its dull appearance it has ge- 
nerally been taken for Lead, or some other metal, as it 
looks as if easily flexible. The hardness and sharpness of 
the delicately acute edges, however, soon betray it, and the 
fractures, showing its crystallization, pretty readily deter- 
mine it. 
It seems quite natural to most Quartz to have been in 
solution. In this instance, having evidently formed itself 
in the cracks of the Clay, it is the more instructive ; for 
whatever might have held the Quartz in solution, might, 
at the same time, have decomposed the Clay, which, how- 
ever, must have been dry enough to have cracked, and 
formed sharp and neatly distinct fissures, so beautifully 
shown by the Quartz. But if fire had dissolved the Quartz, 
the Clay would have been baked: and that is not the case ; 
as the latter, in its common state, remains in some of the 
fissures. This specimen is the production of Cumberland, 
and I have been favoured by the Rev. Mr. Harriman and 
Mr. Oliver with a piece about a foot in length from which 
the Clay had apparently been washed out, chiefly on one 
