148 Effects of Heat modified ly Compression. 



In this manner, a pressure upwards was applied to the barrel 

 equal to the weight of 10 cwt. 



In the former method, in which the barrel stood with its 

 muzzle upwards, the weight wa9 applied while the metal 

 was liquid. In this case it was necessary to let it previously 

 congeal, otherwise the contents would have run out in 

 placing the barrel in the muffle, and to allow the liquefac- 

 tion essential to these trials to be produced by the propaga- 

 tion of heat from the muffle downwards. This method re- 

 quired, therefore, in every case the use of an air-tube; for, 

 without it, the heat acting upon the breech, while the metal 

 at the muzzle was still cold, would infallibly have destroyed 

 the barrel. A great number of these experiments failed, 

 with verv considerable waste of the fusible metal, which on 

 these occasions was nearly all lost. But a few of them suc- 

 ceeded, and afforded very satisfactory results, which I shall 

 now mention. 



In November 1803, some good experiments were made 

 in this way, all with a bore of 0*73, and a pressure of 

 10 cwt. 



No. 3. — On the 19th a good limestone was obtained in 

 an experiment made in a temperature of 21°, with a loss 

 of only VI per cent. 



No. 4. On the 22d, in a similar experiment, there was 

 little exudation by the muzzle. The pyrometer gave 31°. 

 The carbonate was in a porous and almost frothy state. 



No. 5. — In a second experiment, made the same day, the 

 heat rose to 37° or 41°. The substance bore strong marks 

 of fusion, the upper part having spread on the little tube :. 

 the whole was very much shrunk, and run against one side. 

 The mass sparkling and white, and in a very good state. 



No. 6. — On the 23th an experiment was made with chalk 

 and some fragments of snail shell, with about half a grain 

 of water. Tin heat had risen to near 31° or 10\ The 

 barrel had been held right by the beam, but was rent and a 

 little swelled at the breech. The rent was wide, and such 

 as has alwkys appeared in the strongest barrels when they 

 failed. The caibonate was quite calcined; it had boiled over 

 the little tube, and was entirely in a frothy state, with large 



and 



