BY COMPRESSION. 341 



ct)litatning tlie carbonate, Thefe articles generally occupied 

 ihe whole cradle; when any fpace remained, it was filled up 

 by a piece of chalk dreffed for the purpofe. (Fig. 4, repre- 

 fents the cradle filled, as juft defcribed). 



Things being thus prepared, the gun-barrel, placed ere(5t ^^tliod of ufing 

 with its muzzle upwards, was half filled with the liquid fufible ' 



rnelal. The cratlle was then introduced into the barrel, a«d 

 plunged to the bottom of the liquid, fo that the carbonate was 

 placed very near the breech, (as reprefented in fig. 5, the fu- 

 fible metal ftanding at o). , The air-tube (B) being placed fo 

 as to enter the liquid with its muzzle downwards, retained 

 great part of the air it originally contained, though fome of it 

 might be driven off by the heal, fo as to efcape through the 

 Jfquid. The metal being now allowed to cool, and to fix round 

 (he cradle and ramrod, the air remaining in the air-tube was 

 effeflually confined, and all was held faft. The barrel being 

 then filled to the brim with fufible metal, the apparatus was 

 ready for the application of heat to the breech, (as fliewn in 

 %. 6.) Plate X. 



. In the experiments made at this time, I ufed a fquare brick the furnace and 

 r 11- /Yi X !- • 1 muffle arrange- 



Jurnace, (figs. 7 and 8, havmg a muffle (r s) traverfing it ho- ment, &c. 



rizontally and open at both ends. This muffle being fupported 



i-n the middle by a very flender prop, was expofed to fire from 



below, as well as all round. The barrel was placed in the 



Riuffle, with its breech in the hotteft part, and the end next 



the muzzle proje6ling beyond the furnace, and Turrounded 



with cloths which were drenched with water from time to time, 



(This arrangement is fliewn in fig. 7.) In this fituation, the 



IJafible metal furrounding the cradle being melted, the air 



contained in the air^tube would of courfe feek the highefl po- 



iition, and its firft place in the air-tube would be occupied 



by fufible metal. (In fig. 6, the new pofition of the air is 



Ihewn at;) q)* 



At the conclufion of the experiment, the metal was generally Method of dlC- 



removed by placing the barrel in the tranfverfe muffle, vvith^"^j^g^^'"^^3Pjgj. 



its muzzle pointing a little downwards, and fo that the heat expsriment. 



was applied firfl: to the muzzle, and then to the reft of the 



barrel in fuccenfion. (This operation is fliewn in fig. 8.) In 



place at the 28th degree; but I am convinced that his obfervations 

 muft have been made with fome fct different from that which was 

 afterwards fold. 



Vol. XIII. — April, 180S. Bb fome 



