Effects of Heat modified ly Compression. 11 



ting it into a vessel full of water till the temperature had 

 sunk to the proper pitch, which I knew to be the case 

 when the hissing noise, produced in the water by the heated 

 barrel, ceased ; the cradle, during the last stage of this ope- 

 ration, being held close to the muzzle of the barrel, and 

 ready to be thrust into it. 



On the ed of May I made my first experiment in this 

 way, using - the same air-tube as in the last experiment, 

 which was equal in capacity to one- thirtieth of a cubic inch. 

 Half a grain of water was introduced in the manner just de- 

 scribed. The barrel, after an hour of red heat, was let down 

 by a rope and pulley, which I took care to use in all experi- 

 ments in which there was any appearance of danger. All 

 was sound. The metals rushed out smartly, and a flash of 

 flame accompanied the discharge. The upper pyrometer 

 gave 24°, and the lower one 14°. The contents of the inner 

 tube had lost less than ] per cent., strictly 0*84. The car- 

 bonate was in a stale of good limestone; but the heat had 

 been too feeble : the lower part of the chalk in the little tube 

 was not agglutinated : the chalk round the fragment of pipe- 

 stalk (used to introduce the water), which had been more 

 heated than the pyrometer, and the small rod, which had 

 moulded itself in the boll of the stalk, were in a state of 

 marble. 



On the 4th of May I made an experiment like the last, 

 but with the addition of 1*Q5 grains water. After appli- 

 cation of heat, tile tire was allowed to burn out till the barrel 

 was black. The metal w&s discharged irregularly. Towards 

 the end, the inflammable air produced, burnt at the muzzle, 

 with a lambent flame, during some time, arising doubtless 

 from hydrogen gas, more or less pure, produced bv the de- 

 composition of the water. The upper pyrometer indicated 

 3fi°, and the lower one \{>". The chalk which lay in the 

 outer part of the larrc tube was in- a state of marble. Th-? 

 inner tuhe was united to the outer one by a star of fused 

 matter, black at the edges, and spreading all round, sur- 

 rounding one of the fragments of porcelain which had fallen 

 by accident in between the tubes. The inner tube, with the 

 tarry matter adhering to it, but without ihc coated fragJ 



llll'l.t, 



