UY COMPRESSION:. 121 



fhg at right angles to the barrel, and dressed square. The 

 barrel, thus prepared, was introduced, with its breech down- 

 wards, into the vertical muffle (fig. 35.) ; its length being so 

 adjusted, that its breech should be placed in the strongest 

 heat; the two projecting bars above described, resting on 

 two other bars (c c, fig. 35.) laid upon the furnace to receive 

 them ; one upon each side of the muffle. Into the barrel, so 

 placed, was introduced a cradle, containing carbonate, with 

 all the arrangements formerly mentioned ; the rod connected 

 with it being of such length, as just to lie within the muzzle of 

 the barrel. The liquid metal was then poured in till it filled 

 the barrel, and stood at the muzzle with a convex surface; a 

 cylinder of iron, of about an inch in diameter, and half art 

 inch thick, was laid on the muzzle (fig. 35. and 37.), and to 

 it a compressing weight was instantly applied. This was first 

 done by the pressure of a bar of iron (d e, fig. 35.), three feet 

 in length, introduced loosely into a hole (dj, made for the 

 purpose in the wall against which the furnace stood ; the 

 distance between this hole jjind the barrel being one foot. A 

 weight was then suspended at the extremity of the bar Ce^, and 

 thus a compressing force was applied, equal to three times 

 that weight. In the course of practice, a cylinder of lead was 

 substituted for that of iron, and a piece of leather was placed 

 between it and the muzzle of the barrel, which last being dress- 

 ed to a pretty sharp edge, made an impression in the lead : 

 to assist this effect, one smart blow of a hammer was struck 

 upon the bar, directly over the barrel, as soon as the weight 

 had been hung on. 



It was essential, in this mode of operation, that the whole -*-the fusible 

 of the metal should continue in a liquid state during the action JJfid^alTthe*^* 

 of heat ; but when I was satisfied as to its intensity and dura- time, 

 tion, I congealed the metal, either by extinguishing the 

 furnace entirely, or by pouring water on the barrel. As soon 

 as the heat began to act, drops of metal were seen to force 

 themselves between the barrel and the leather, following each 

 other with more or less rapidity, according to circumstances,^ 

 In some experiments, there was little exudation ; but few o£ 

 them were entirely free from it. To save the metal thus ex- 

 truded, I placed a black-lead crucible, having its bottom 

 perforated, round the barrel, and luted close to it, (fig. 37-) ; 



Vol. XIV. — June, IS06. R some 



