OF CORNWALL. 125 
point ; that Fig. xxvn is of the cleared cryftal inclofing fomething 
of the mofs kind, which could never happen but when the cryftal 
was in a fluid ftate. Fig. xxxi is a groupe of hexagonal cryftals 
pointed at each end, and immerfed in the fubftance ol one another, 
in Inch a manner as could not have happened but when fome or 
all of them were in a ftate of fluidity, the hardeft making their way 
into the fofteft, and the fofteft clofely cohering to the hardeft, fo as 
that they both confolidated into one lump. All thefe fads are plain 
from the infpedion of the bodies before us, and there is not the 
leaft occafton to have recourfe (as fome moderns have done) to any 
operofe chemical analysis to prove, that cryftal has been fluid, and 
therefore may be fo again. Another confequence is alfo plain, viz. 
that, during this ftate of fluidity, they received the feveral figures 
in which we now find them ; but to what caufe this variety of 
figures is owing, muft be the next enquiry, and is very .difficult to 
be fatisfied. That ftone, quatenus ftone, has not the faculty of 
producing thefe configurations, is a truth fufficiently confirmed, one 
would think, from the vaft Jlrata of quarries, cliffs, and fiflures 
of ftone in which there is no regular redilinear form : the fhootings 
of ftone into figure are fmall in comparifon, few, and rare, owing 
to accident and mixture, not the eflential produds of the Jlrata. 
All fmall quantities of lapideous matter would probably form them- 
felves by the mutual attradion of fimilar parts, and the equal pref- 
fure of furrounding fluids into globular mafles, as water, oil, quick- 
filver, and liquid bodies do, were it not for fomething which inter- 
mixes with the ftony matter, and prevents this Ample figure from 
taking- place. The cryftal which appears in the ftaladical form, 
has nothing in it which tends to configuration, more than any com- 
mon fhapelefs marble, fpar, or killas, and may convince us that 
meer cryftal covets no particular figure. Cryftal in this ftate wants 
that adive principle which throws the fame ftone at other times into 
a great variety of fhapes ; what that principle is, the learned do 
not agree ; but clear it is, that it is fomething adventitious and 
different from cryftal. It has been imagined, that the angularly- 
figured cryftals owe their fhape to the different metals which they 
encounter during their fluidity ; but this is feldom the cafe % for 
cryftals, which are of four, five, or, what is ftill more common fix 
angles, are oftentimes extreamly clear, and have no appearance of 
any metal in them, neither do they yield any metal upon trial by 
fire that ever I could learn. “ Pure cryftal, and without mixture of 
other matter, fays Dr. Woodward r , concretes ever into an hexagonal 
figure, pyramidal or columnar, terminating in an apex : but we 
K k 
r Cat. vol. I. page 220. 
* See page 127. 
have 
