MODIFIED by COMPRESSION. 81 



out danger from an explofion *. I likewife, about this time, 

 clofed the muzzle of the barrel, by means of a plug, fixed by 

 folder only ', which method had this peculiar advantage, that 

 I could fhut and open the barrel, without having recourfe 

 to a workman. In thefe trials, though many barrels yielded 

 to the expanfive force, others refitted it, and afforded fome re- 

 mits that were in the higheft degree encouraging, and even 

 fatisfactory, could they have been obtained with certainty on 

 repetition of the procefs. In many of them, chalk, or com- 

 mon limeftone previoufly pulverifed, was agglutinated into a 

 ftony mafs, which required a fmart blow of a hammer to 

 break it, and felt under the knife like a common limeftone > 

 at the fame time, the fubftance, when thrown into nitric acid, 

 dhTolved entirely with violent effervefcence. 



In one of thefe experiments, owing to the action of heat on 

 the cartridge of paper, the baked clay, which had been 

 ufed to fill the barrel, was flamed black throughout, to the 

 diflance of two-thirds of the length of the barrel from its 

 breech. This circumftance is of importance, by mewing, 

 that though all is tight at the muzzle, a protrufion may 

 take place along the barrel, greatly to the detriment of com- 

 plete 



* On one occafion, the importance of this precaution was ftrongly felt. Having 

 inadvertently introduced a confiderable quantity of moifture into a welded barrel, 

 an explofion took place, before the heat had rifen to rednefs, by which, part of the 

 barrel was fpread out to a flat plate, and the furnace was blown to pieces. Dr 

 Kennedy, who happened to be prefent on this occafion, obferved, that notwith- 

 ftanding this accident, the time might come when we fhould employ water in 

 thefe experiments to auift the force of compreffion. I have fince made great ufe 

 of this valuable fuggeftion : but lie fcarcely lived, alas ! to fee its application ; 



fer my firft fuccefs in this way, took place during his laft illnefs. I have 



been expofed to no rifle in any other experiment with iron barrels ; matters 

 being fo arranged, that the ftrain againfl; them has only commenced in a red 

 heat, in which the metal has been fo far foftened, as to yield by laceration like a 

 piece of leather. 



Vol. VI.— P.I. L 



