Cryjlallizatiom obferved on Glafs * 533 
hexagonal fedlion is divided by thefe pairs, are filled up 
partly by final ler plates affixed to the Tides of the princi- 
pal plates, and of each other, at an angle of 6o°, and 
partly by a fubftance fomewhat lefs opaque and darker- 
coloured than that of the plates. The fize of the conti- 
guous and ol the neighbouring cryftals does not vary 
much, although that of cryftals, found at different depths 
of the Time pot, were obferved to differ confiderably. 
The greateft diameter of the cryftals, from which the 
figures 1. 2. 3. and 4. were copied, was about ~th part 
of an inch, fo that thefe figures reprefent the cryftals 
confiderably magnified. All the cryftals are not by any 
means formed with the fame exadfnefs as thofe defcribed ; 
fome having the hexagonal form lefs diftincftly marked ; 
but the regularity of moft of them is fo obvious, that no 
doubt can remain of the perfection of the cryftallization. 
Another kind of vitreous cryftallization appears on the 
piece of glafs marked N° 2. which was taken from thb 
bottom of a pot, that had been pulled out of the furnace, 
while the glafs was red-hot. The cryftals are of two 
kinds; thofe reprefented by fig. 5. are of the columnar 
form ; their altitude is about one-eighth of an inch, and 
the diameter of their bafes about one-fifth part of their 
altitude; their fides feem to be irregularly fluted, or cut 
in grooves. The other kinds of cryftals, which are re- 
prefented by fig. 6. 7. and 8. have bafes of nearly the 
fame diameter as the columnar ones ; but their altitude is 
much lefs, being only about one-fixth part of their dia- 
meter. Their bafes are bounded by lines, feemingly' 
4 A ‘2 ragged 
