130 EFFECTS of HEAT 
tween the filex and the carbonate. The fhell, fufed in the ex- 
periment, diflolved entirely im the acid, with violent effervef- 
cence. 
In the three laft experiments, and in feveral others made at 
the fame time, the carbonate had not been weighed; but no 
water being introduced to aflift the compreflion, it is probable 
there was much lofs by internal calcination ; and owing doubt- 
lefs to this, the carbonates have crumbled almoft entirely co 
duft, while the compounds which they had formed with filex 
remain entire. 
On the 13th of March, I made a fimilar experiment, in which, 
befides fome pounded oyfter-fhell, I introduced a mixture of 
chalk, with 10 per cent. of filex mtermixed, and ground to- 
gether in a mortar with water, in a ftate of cream, and then 
well dried. The contents of the tube when opened, were 
difcharged with fuch- violence, that the tube was broken to 
pieces ; but I found a lump of chalk, then in a ftate of 
white marble, welded to the compound; which laft, in its 
fraGure, fhewed that irregular black colour, interfperfed 
roughly through a cryftalline mafs, that belongs to the al- 
pine marbles, particularly to the kind called at Rome Cipol- 
line. It was very hard and firm; I think unufually fo. It effer- 
veiced conftantly to the laft atom, in diluted nitric acid, but 
much more fluggifhly than the marble made of pure chalk. A 
cloudinefs appeared pervading all the liquid. When the 
effervefcence was. over, a feries of bubbles continued during 
the whole day in the acid, without any difpofition to burtt, 
or rife to the furface. After ftanding all next day and night, 
they maintained their ftation; and the folution being ftirred, 
was found to be entirely agglutinated into a tranfparent jelly, 
breaking with fharp angles. This experiment affords a direct 
and pofitive proof of a chemical union having taken place be- 
tween the carbonate and filex. 
VI. 
