136 EFFECTS of HEAT 
the fharp end of the periwinkle, retained its original fhape in 
a great meafure, fo as to be quite difcernible ; but the whole 
was glazed over with a truly vitreous luftre. This glaze co- 
vered, at one place, a fragment of the fhell which had been ori- 
ginally loofe, and had welded the two together. All the angles 
are rounded by this vitrifaction; the {pace between the en-~ 
tire fhell and the fragment being filled, and the angles 
of their meeting rounded, with this fhining fubftance. The 
colour is a pale blue, contrafted, in the fame little glafs, 
with a natural piece of periwinkle, which is of a reddifh-yel- 
low... One of the fragments had adhered to the lid, and had 
been converted into a complete drop, of the fize of a muftard- 
feed. It is fixed on the wax (at 4), along with the other {pe- 
cimens of the experiment (fig. 32.). This refult fhews, as yet, 
no fign of decay, notwithftanding fo great a lofs of weight. 
Tne laft experiment was repeated on the fame day, and pre- 
pared in the fame manner, with large fragments of hell, and the 
point of the periwinkle ftanding up in the cup. A heat of 34° 
was applied; a lofs took place of 13° per cent. All the original 
form had difappeared, the carbonate lying in the cup as a com- 
plete liquid, with a concave furface, which did not fhine, but 
was ftudded all over with the white {phericles or tufts, like 
thofe feen in the former refults, without any fpace between 
them. When detached from the cup, the furface moulded on 
the platina, was white and pearly, with a flight glofs. The 
mafs was quite folid ; no veftige whatever appearing, of the 
original form of the fragments, (fig. 33.).. A fmall piece, bro- 
ken off near the apex of the cone, fhewed the internal ftruc- 
ture to be quite faline. In the act of arranging the {fpecimen on 
its ftand, another piece came off in a new direction, which pre- 
fented to view the moft perfect cryftalline arrangement : the 
fhining plane extended acrofs the whole fpecimen, and was 
more than the tenth of an inch in all directions. This fraaure, 
likewife, 
