88 EFFECTS of HEA 
accurately filled with metal, which plated the carbonate. all 
over without penetrating it in the leaft, fo that the metal was 
eafily removed. The weight was reduced from forty to thirty- 
fix grains. The fubftance was very hard, and refifted the knife 
better than any refult of the kind previoufly obtained ; its frac- 
ture was cryftalline, bearing a refemblance to white faline 
marble; and its thin edges had a decided femitranfparency, 
a circumftance firft obferved in this refult. 
On the 3d of March of the fame year, I made a fimilar 
experiment, in which a pyrometer-piece was placed with- 
in the barrel, and another in the muffle ; they agreed in indi- 
cating 23°. The inner tube, which was of Reaumur’s porce- 
lain, contained eighty grains of pounded chalk. The carbo- 
nate was found, after the experiment, to have loft 34 grains. 
A thin rim, lefs than the 2oth of an inch in thicknefs, of 
whitifh matter, appeared on the outfide of the mafs. In other 
refpects, the carbonate was in a very perfect flate ; it was of a 
yellowith colour, and had a decided femitranfparency and 
faline fracture. But what renders this refult of the greateft 
yalue, is, that on breaking the mafs, a {pace of more than the 
tenth of an inch fquare, was found to be completely cryftal- 
lized, having acquired the rhomboidal fraéture of calcareous 
{par. It was white and opaque, and prefented to the view 
three fets of parallel plates which are feen under three different 
angles. This fubftance, owing te partial calcination and fub- 
fequent abforption of moifture, had loft all appearance of its 
remarkable properties in fome weeks after its production ; but 
this appearance has fince been reftored, by a frefh fracture, 
and the fpecimen is now well preferved by being hermetically 
inclofed. 
iil. 
