MODIFIED by COMPRESSION. 87 



At the 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, or a ftrong folution of 

 muriate of lime ; which laft bears a temperature of 250 of 

 Fahrenheit 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 

 poilible heat *. 



By thefe methods I made a great number of experiments, with 

 refults that were highly interefting in that ftage of the buf> 

 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. 



On the 31ft of March 1801, 1 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 



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 fufible metal, and to fill the reft of the barrel with lead. 



