MODIFIED ly COMPRESSION. 87 
' Arthe conclufion of the experiment, the metal was generally 
removed by placing the barrel in the tranfverfe muffle, with 
its muzzle pointing a little downwards, and fo that the heat 
was applied firft)to the muzzle, and then to the reft of the 
barrel in fucceflion. (This operation is fhewn in fig. 8). In 
fome of the firft of thefe experiments, I loofened the cradle, by 
plunging the barrel into heated brine, ora {trong folution of 
muriate of lime ; which laft bears a temperature of 250° of 
Faurenueir before it boils. For this purpofe, I ufed a pan 
three inches in diameter, and three feet deep, having’ a flat bafon 
at top to receive the liquid when it boiled over. The method 
anfwered, but was troublefome, and I laid it afide. I have had 
occafion, lately, however, to refume it in fome experiments in 
which it was of confequence to open the barrel with the leaft 
poflible heat *. 
By thefe methods I made a great number of experiments, with 
refults that were highly interefting in that ftage of the bufi- 
nefs, though their importance is fo: much diminifhed by the 
fubfequent progrefs of the inveftigation, that I think it proper 
to mention but very few of them. . 
Ow the 31ft of March r8or, I rammed forty grains of pound- 
ed chalk into a tube of green bottle-glafs, and placed it in the 
cradle as above defcribed.. A pyrometer in the muffle along 
with the barrel indicated 33°. The barrel was expofed to heat 
during feventeen or eighteen minutes. On withdrawing the 
cradle, the carbonate was found in one folid mafs, which had 
vifibly fhrunk in bulk, the fpace thus left within the tube being 
pata be ye accurately 
* In many of the following experiments, lead was ufed in place of the fufible 
metal, and often with fuccefs ; but I loft many good refults in this way: for the 
heat required to liquefy the lead, approaches fo near to rednefs, that it is difficult 
to difengage the cradle without applying a temperature by which the carbonate 
is injured. I have found it anfwer well, to furround the cradle and a few inches 
of the rod, with fufjble metal, and to fill the reft of the barrel with lead. 
