84 EFFECTS of HEA 
medy was found to anfwer completely, and was applied, in 
all the experiments made at this time *. 
I now propofed, in order to keep the carbonate clean, ta 
inclofe it in a fmall veffel ; and to obviate the difficulty of 
removing the refult at the conclufion of the experiment, I 
further propofed to connect that veflel with an iron ramrod, 
longer than the barrel, by which it could be introduced or 
withdrawn at pleafure. 
A smALt tube of glafs +, or of Raumur’s porcelain, about 
a quarter of an inch in diameter, and one or two inches in 
length, (fig. 2. A) was half filled with pounded carbonate of 
lime, rammed as hard as poflible; the other half of the tube | 
being 
* I found it a matter of much difficulty to afcertain the proper quantity of air 
which ought to be thus inclofed. When the quantity was too great, the refult 
was injured by diminution of elafticity,as I {hall have occafion fully to fhew here- 
after. When too {mall, or when, by any accident, the whole of this included air 
was allowed to efcape, the barrel was deftroyed. 
I hoped to afcertain the bulk of air neceffary to give liberty to the ex- 
panfion of the liquid metal, by meafuring the aétual quantity expelled by 
known heats from an open barrel filled with it. But I was furprifed to find, 
that the quantity thus difcharged, exceeded in bulk that of the air which, in 
the fame heats, I had confined along with the carbonate and fufible metal in 
many fuccefsful experiments. As the expanfion of the liquid does not feem ca- 
pable of fenfible diminution by an oppofing force, this fat can only be accounted 
for by a diftention of the barrel. In thefe experiments, then, the expanfiye force 
of the carbonic acid, of the included air, and of the fufible metal, aéted in combi- 
nation againft the barrel, and were yielded to in part by the diftention of the bar- 
rel, and by the condenfation of the included air. My object was to increafe the 
force of this mutual action, by diminifhing the quantity of air, and by other de- 
vices to be mentioned hereafter. Where fo many forces were concerned, the 
laws of whofe variations were unknown, much precifion could not be expected, 
nor is it wonderful, that in attempting to carry the comprefling force to the ut- 
moft, I fhould have deftroyed barrels innumerable. 
+ Lhave fince conftantly ufed tubes of common porcelain, finding glafs much 
too fufible for this purpofe. 
