140 ’ EFFECTS of HEAT 
inch *, and drefled its muzzle to a fharp edge. To this barrel: 
was firmly {crewed a collar of iron (aa, fig. 36.) placed at a 
diftance of about three inches from the muzzle, having two 
ftrong bars (64) projecting at right angles to the barrel, and 
dreffed fquare. The barrel, thus prepared, was introduced, 
with its breech downwards, into the vertical muffle (fig. 35.) 5 
its length being fo adjufted, that its breech fhould be placed 
in the ftrongeft heat ; the two projecting bars above defcribed, 
refting on two other bars (cc, fig. 35.) laid upon the furnace 
to receive them ; one upon each fide of the muffle. Into the 
barrel, fo placed, was introduced a cradle, containing carbo- 
nate, with all the arrangements formerly mentioned’; the rod 
connected with it being of fuch length, as_juft to lie within the: 
muzzle of the barrel. The liquid metal was then poured in till 
it filled the barrel, and ftood at the muzzle with a convex fur- 
face; a cylinder of iron, of about ah inch in diameter, and half 
an inch thick, was laid on the muzzle (fig. 35. and 37.), and to: 
it a comprefling weight was inftantly applied. This was firft 
done by the preffure of a bar of iron (de, fig. 35.), three-feet in: 
length, introduced loofely into a hole (¢), made for the purpafe 
in the wall againft which the furnace ftood ; the diftance between. 
this hole and the barrel being one foot. A weight was then fuf- 
pended at the extremity of the bar (e), and thus a compreffing 
force was applied, equal to three times that weight. In the 
courfe of practice, a cylinder of lead. was fubftituted for that 
of iron, and a piece of leather was placed between it and the 
muzzle of the barrel, which laft being drefled to a pretty fharp, 
edge, made an impreflion in the lead: to affift, this: effect, one. 
fmart blow of a hammer was ftruck upon the bar, direly. over 
the barrel, as foon as the weight had been hung on. 
Ir. 
* This was the fize of barrel ufed in all the following experiments, where the. 
fa& is not otherwife expreffed. 
