152 Mr H. Meikle's Refutation of Mr Ivory's New Law of 



In July 1825, Mr Ivory was pretty sure that the value of 



the fraction, which he now calls — , was J, and assigned a most 



absurd reason for it, as noticed in the last Number of this 

 Journal. He also maintained, that it agreed sufficiently with 

 the experiments on sound. In February last, he makes this 

 fraction | ; in March | ; and, by this time, it is hard to say 

 what may have been its fate. But, at all events, he avers and 

 insists, over and over again, that it must be a constant quan- 

 tity ; and he contends, with equal zeal, for the accuracy of the 

 law of Boyle. 



On these two points, viz. the constancy of the ratio of the 

 specific heats and the law of Boyle, Mr Ivory and I are per- 

 fectly agreed. They are the only data required for investigat- 

 ing the true law of temperature in air, and from which it fol- 

 lows as a necessary consequence *. However, when we reflect 

 a little on the unstable nature of Mr Ivory's creed, it would be 

 nothing remarkable, that, ere long, he renounce them both, and, 

 as usual, without wasting time in assigning a reason. 



The fraction of which we were just speaking, is the excess of 

 the specific heat of air under a constant pressure, over its spe- 

 cific heat, reckoned unit, under a constant volume. From the 

 many experiments made with the apparatus formerly described, 

 I have found that fraction always so close on J, that I expect 

 this will ultimately turn out to be the true quantity ; and I 

 think, the circumstance of this value pointing at the existence 

 of a repulsive force, between the particles of air, inversely as^the 

 square of their distance, adds greatly to the probability -f. It 

 scarcely deserves notice, that the value of this fraction, as com- 

 puted by Mr Ivory, from the experiments of Desormes and Cle- 

 ment, was always .3492, till I gave the correct Number .354, 

 which he has now got hold of. 



In the Second Number of this Journal, I instanced the para- 



* This law, it will be recollected, is, that, when the variations of the quan- 

 tity of heat in a mass of air are uniform, those of its volume, under a con- 

 stant pressure, form a geometrical progression ; as do likewise the variations 

 of pressure under a constant volume. 



t See last Number of this Journal, p. 391. 



