1815.] Sir Benjamin Thompson, Knt. Count Ruviford. 219 



chiefly converted into carbonic acid gas, which does not alter the 

 bulk of the oxygen. VVe do not know the heat generated by the 

 combustion ; but it cannot be less than 1000°. Such a temperature 

 would just triple the elasticity of the generated gas, and therefore 

 render it equal to 91*0 atmospheres ; so that, according to this sup- 

 position, the calculation of Robins is exact. But probably the heat 

 may considerably exceed 1000°; and there is reason to conclude 

 from Count Ruaiford's experiments that the sulphuret of potash 

 which remains after the explosion of the gunpowder is at first in a 

 gaseous state. All these causes must render the elasticity consider- 

 ably greater than 1000 atmospheres. Probably Daniel Bernoulli's 

 supposition is not very far from the truth. 



The diminution of elasticity which took place when the elastic 

 fluid generated from powder was prevented from escaping, and the- 

 formation of the hard stony substance, which astonished Count. 

 Rumford so much, is easily explained. The dissipation of the heat 

 would speedily reduce the elasticity to one-third. Potash is capable 

 of absorbing nine-tenths of its weight of carbonic acid. Therefore 

 a considerable portion of the carbonic acid (the principal gas gene- 

 rated) would be absorbed, which would diminish the elasticity still 

 farther. The stony body was a mixture of bicarbonate of potash 

 and sulphuret of potash, the last of which would speedily absorb 

 moisture from the atmosphere, and generate sulphureted hydrogen. 

 — Count Run)ford's notion that the elasticity of the elastic fluid from 

 gunpowder is partly owing to steam is certainly erroneous. Mitre 

 contains no water of crystallization. The charcoal that answers 

 best for gunpowder is that which absorbs the least moisture. The 

 drier the gunpowder is made, the stronger it is found to be. Hence 

 it follows that moisture, instead of increasing, very much dimi- 

 nishes, the strength of gunpowder. 



9. An Inquiry concerning the Source of the Heat which is 

 excited by Friction. Phil. Trans. 1798. P. 80. — This is also a 

 very curious paper. He found that by the friction of a steel borer 

 against gun metal, pressing against it with a force of 10,000 lbs., 

 while the gun metal turned round 32 times in a minute, ISf lbs. 

 avoirdupois of water were made to boil in two hours and a half. 

 'I'he heat produced was as great as would have been given out by 

 nine large wax candles burning with a clear flame all the time. He 

 showed that this heat was not owing to any change in the specific 

 lieat of the metal, nor was it derived from the air. As no source 

 could be pointed out, he draws as a conclusion, that heat is not a 

 subntance, but mere motion. But such a conclusion is going rather 

 funher th;in the experiments warrant. There is nothing absurd iu 

 supposing tliat friction has the property of drawing heat continually 

 from the surrounding bodies, just as it does ciectricity, though it is 

 not in our pfuver lo explain how it produces this effect. 



10. On the Chomital Properties that have been attributed to 

 Light. Phil.'lVans. 1798. P. 419.-^11^1 certain subitantes are 



