2P2 ACTION OF HEAT M015IF1ED 



would admit. In order to exclude as much of the fufible me- 

 tal as poffible; for the expanfion of the liquid metal being in 

 proportion to the quantity heated, the more that quantity 

 could be reduced, the lefs rifk there was of deftroying the 

 barrels. 

 Simple mnde of In the courfe of pra6lice, a fimple mode occurred of remov- 



wUhdravvlng the J the metal and withdrawing the cradle: it confifted in 



contents iiom = => 



the tube. placing the barrel with its muzzle downwards, fo as to keep 



the breech above the furnace and cold, while its muzzle was 

 expofed to ftrong heat in the muffle. In this manner, the 

 metal was difcharged from the muzzle, and the pofition of 

 the barrel being lowered by degrees, the whole metal was 

 removed in fiicceffion, till at laft the cradle and its contents 

 became entirely loofe. As the metal was delivered, it was 

 received in a crucible, filled with water, (landing on a plate 

 of iron placed over the pit, which had been ufed, during 

 the firft Hage of the experiment, to contain the water-velTel. 

 ' It was found to be of fervice, efpecially where lead was ufed, 

 to give much more heat to the muzzle than fimply what was 

 required to liquefy the metal it contained ; for when this was 

 not done, the muzzle growing cold as the breech was heating, 

 fome of the metal delivered from the breech was congealed 

 at the muzzle, fo as to flop the paflage. 



According to this method, many experiments were made 

 in gun-barrel*', by which fome very material fieps were gain- 

 ed in the invefligation. 

 Experiment In On the 2-Uh of February, I made an experiment with fpar 

 the new method, and chalk ; the fpar being placed nearefl to the breech of the 

 barrel, and expofed to the greateft heat, fome baked clay in- 

 tervening between the carbonates. On opening the barrel, a 

 long-continued hiding noife was heard. The fpar was in a 

 ftate of entire calcination ; the chalk, though crumbling at 

 the outfide, was uncommonly hard and lirm in the heart. The 

 temperatur.e had rifen to 32®, 

 Internal calcl- In this experiment, we have the firft clear example, in iron 

 "h '^'''"'b'^^^'^^ barrels, of what I call Internal Calcination ; that is to fay, where 

 acid did not the carbonic acid feparated from the earthy bafis, has been 

 cfcapeoutof accumulated in cavities within the barrel. For, fubfequently 

 '^ ^PP ' to the a6lion of ftrong heat, the barrel had been completely 

 cooled ; the air therefore introduced by means of the air- 

 tube, muft have refumed its original bulk, and by itfelf could 



have 



