[ 143 ] 



XXTIT. Account of a Series of Experiments, showing the 

 Effects of Compression in modifying the Action of Heai, 

 By Sir James Hall, Bart. F.R.S. Lond. and Edin. 



[Continued from p. 26.] 



§ VII. 



JJeasttrement of the Force required to constrain the Carbonic 

 Acid. — Apparatus with the Muzzle of the Barrel upwards, 

 and the Weight acting by a long Lever. — Apparatus ivith 

 the Muzzle downwards. — Apparatus with Weight acting 

 directly on the Barrel. — Comparison of various Results. 



An order to determine, within certain limits at least, what 

 force had been exerted in the foregoing experiments, and 

 what was necessary to ensure their success, \ made a num- 

 ber of experiments in a mode nearly allied to that followed 

 by Count Rumford in measuring the explosive force of gun- 

 powder. 



I began to use the following simple apparatus in June 

 1 803 : — I took one of the barrels, made as above described, 

 for the purpose of compression, having a bore of 0*75 of an 

 jnch*, and dressed its muzzle to a sharp edge. To this 

 barrel was firmly screwed a collar of iron (aa, fig. 36) placed 

 at a distance of about three inches from the muzzle, having 

 two strong bars (b b) projecting at right angles to the barrel, 

 and dressed square. The barrel, thus prepared, was intro- 

 duced, with its breech downwards, into the vertical muffle 

 (fio-. 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 (cc, 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 wa3 then poured in till it filled the barrel, and stood 



* This was the size of barrel unol in all the following experiments, where 

 the fact is not otherwise expressed. 



at 



