MODIFIED ly 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 refifted it, and afforded fome re- 
fults 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 limeftene 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, 
diffolved 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 ftained black throughout, to the 
diftance of two-thirds of the length of the barrel from its 
breech. This circumftance is of importance, by fhewing, 
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 toa flat plate, and the furnace was blown to pieces. Dr 
Kenneby, 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 affift the force of compreffion. I have fince made great ufe 
of this valuable fuggeftion: but he 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 rifk in any other experiment with: iron barrels; matters 
being fo arranged, that the ftrain againft 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. 
Vo. VI.—P. I. L 
