‘ 
MODIFIED ty COMPRESSION. 83 
the carbonate by calcination, though ating upon it in free- 
dom ; and then, that the fubje&t of chpeviment might, as be> 
fore, ‘and taken out of the barrel. 
. Tuts {cheme, with various modifications and additions, 
“which: practice has fuggefted, forms the bafis of moft of the 
following methods. 
In the firft trial, a ftriking phenomenon occurred, which 
gave rife to the moft important of thefe modifications. Ha- 
’ ying filled a gun-barrel with the fufible metal, without any 
carbonate ; and having placed the breech in a muffle, I was 
furprifed to fee, as the heat approached to rednefs, the liquid 
metal exuding through the iron in innumerable minute drops, 
difperfed all round the barrel. As the heat advanced, this 
exudation increafed, till at laft the metal flowed out in 
continued ftreams, and the barrel was quite deftroyed. On 
feveral occafions of the fame kind, the fufible metal, being 
forced through fome very minute aperture in the barrel, 
fpouted from it to the diftance of feveral yards, depofiting 
upon any fubftance,oppofed to the ftream, a beautiful af- 
femblage of fine wire, exactly in the form of wool.’ I imme- 
diately underftood, that the phenomenon was produced by the 
fuperior expanfion of the liquid over the folid metal, in con- 
fequence, of which, the fufible metal was driven through the 
iron as water was driven through filver * by mechanical per- 
cuffion in the Florentine experiment. It occurred to me, that 
this might be prevented by confining along with the fufible 
metal a fmall quantity of air, which, by yielding a little to 
the sag of the liquid, would fave the barrel. This re- 
L2 medy 
* Effays of Natural Experiments made in the Academie del Cimento, tranfla- 
ted by WaxteR, London, 1684, page 117. The fame in MusscHENBROEK’s La-- 
tin tranflation, Lugd. Bat. 1731, p. 63. 
