OF CORNWALL. i 2 J 
mel, (ib. page 166.) THe zig-zag angular fillets of Fig. vn. are 
found in Cheltenham falts, (page 154, ib.) In the fait of anti- 
mony we find the conick fpires of Fig. xxviu. and in- general it 
may be affirmed, that there is fcarce a figure among the cryftals but 
may be traced among the falts analyzed ; here therefore I would 
obferve, that all the influence which metals have upon the fhape of 
cryftals, is probably owing to the falts of thofe metals ; for it is 
obfervable in the falts procured from tin (as exhibited by Mr. Baker, 
ib. Plate IV. page 128) that they are exadly of the fame polygonal 
fhape as the real fiony cryftals, including this metal which in Corn- 
wall we call Tin-grains \ Again : Let it not pafs unnoted, that 
cryftals in feveral fpecimens have all the indications neceffary to 
fhew that they were protruded, fometimes from one common inter- 
mediate line, as Fig. v. vi. fometimes from a point, like rays from 
a center, as Fig 5 , xxm. xxv. xxix. and xxxm. herein alfo 
imitating the agility of cryftallizing falts, which fhoot and extend 
their rays vifibly in like manner ; and forafmuch as here are proofs 
of the fame procedure of figured bodies from an unfigured mafs, and 
of the fame figures produced by that procefs, it feems but reafona- # 
ble to conclude, notwithftanding the objections of fome moderns, 
that the figures oi cryftals are owing to the adventitious falts which 
prevail in the cryftalline matter. 
As cryftals, efpecially thofe of the hexagonal kind, are frequently sect. xi. 
found in clufters with one end fixed in a bed of coarfer cryftal than The pointing 
the ffioots, and that bed broke off from a larger mafs of ftill coarfer ^Comiftt ^ 
materials, I went not many years fince into a mine* on purpofe to c 7 ftals in the 
obforve thefe cryftal productions in their natural fite. 
The cavity to which we were introduced, was not much larger than 
a common baker’s oven, and much of that figure, about five feet high 
from the floor. The roof was the moft furprizing piece of fret- 
work imaginable, confifting of hexagonal cryftals pointing forth in 
every direction very plentifully x of feveral fizes, fometimes project- 
ing in groupes and clufters from large protuberances in the deling, 
fometimes tingle, now crofting each other, now ftanding by each 
other with parallel fides ; the fineft were thofe which had innume- 
rable little diamonds or fparks of the cleareft water befprinkled upon 
their fides : I obferved that their pointing was ufually according and 
nearly perpendicular to the planes from which they proceeded ; from 
which I conclude, that as the plane, the fhape, and turn of the 
* See Plate XX. of the figured-tins. 
w Pillion-erth, in the parifh of St. Juft. 
x In Norway hexagonal cryftals, “ are called 
Mountain Drops, and known from experience 
(fays Biftiop Pontoppidan, page Eng. 170) to be 
generated in a chalky porous ftone, in fhape like 
a drop-ftone but if this was their original, 
fuch bodies could only point to the center of the 
earth, as all ftalaftites muft by gravitation of 
their parts ; but the reverie is true. 
