MODIFIED by COMPRESSION. 83 



the carbonate by calcination, though acting upon it in free- 

 dom ; and then, that the fubject of experiment might, as be* 

 fore, be taken out of the barrel. 



This fcheme, with various modifications and additions, 

 which practice has fuggefted, forms the bafis of moft of the 

 following methods. 



In the firft trial, a flriking phenomenon occurred, which 

 gave rife to the moft important of thefe modifications. Ha- 

 ving 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 understood, 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 expanfion of the liquid, would fave the barrel. This re- 



L 2 medy 



* EJfays of Natural Experiments made in the Academie del Cimento, transla- 

 ted by Waller, London, 1684, page 117. The fame in Musschenbroek's La-<- 

 tin tranflation, Lugd. Bat. 1731, p. 63. 



