i 4 © EFFECT'S of HEAT 



inch *, and drefled its muzzle to a iharp edge. To this barrel 

 was firmly fcrewed a collar of iron {a a, fig. 36.) placed at a 

 diflance of about three inches from the muzzle, having twa 

 flrong bars (b b) projecting at right angles to the barrel, and 

 drefTed fquare. The barrel, thus prepared, was introduced, 

 with its breech downwards, into the vertical muffle (fig. 35.) ; 

 its length being fo adjufled, that its breech mould be placed 

 in the flrongeft heat j the two projecting bars above defcribed, 

 retting on two other bars (c c, 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, asjuil to lie within the 

 muzzle of the barrel. The liquid metal was then poured in .till' 

 it filled the barrel, and flood 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 compreffing weight was inflantly applied. This was firfl 

 done by the prefTure of a bar of iron {de> r]g. 35.), three feet in 

 length, introduced loofely into a hole (/I)', made for the purpofe 

 in the wall againfl which the furnace flood ; the diflance 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 

 cpurfe 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 lad being drefTed to a pretty fharp 

 edge, made an impreflion in the lead : to aflift. this effect, one 

 fmart blow of a hammer was flruck upon the bar, directly over 

 the barrel, as foon as the weight had been hung on. 



It- 



* This was the lize of barrel ufed in all the following experiments, where the. 

 fad is not otberwife exprefTed. 



