Mr, Ivory's Observations 07i Mr. Meikle's Beply, S^-c. 105 



given condensation, is absorbed by an equal dilatation, the short 

 proposition enunciated, without any formula, contains the 

 whole of my doctrine. 



In this Journal for November 1828, I have deduced the 

 same conclusion immediately from the usual theory of the 

 thermometer ; that is, on the supposition that the absolute 

 heat, or, which is the same thing, the sum of the heat of tem- 

 perature and the latent heat, is proportional to the indication 

 of the thermometer, or to the change of volume when air 

 varies under a constant pressure. This is expressed, p. 323, 

 by the equation 



i = {k-l)j = f T, 



T being the change of temperature, and i the variation of la- 

 tent heat. 



My opinion on this subject was suggested by the very in- 

 genious and important experiment of MM. Clement and 

 Desormes. It appears to me that we learn nothing directly 

 from that experiment, respecting the relation between the heat 

 evolved when air is condensed, and the magnitude of the con- 

 densation : what it does bring us acquainted with, is the pro- 

 portion between the heat evolved and the change of tempera- 

 ture, supposing the air to vary under a constant pressure. It 

 is proved by repeating the experiment under different pres- 

 sures and temperatures, that the proportion mentioned is con- 

 stant within certain limits; which agrees with the conclusion 

 deduced from the theory of the thermometer. It might there- 

 fore have been inferred a priori, that the proportion is con- 

 stant, but its numerical value can only be found by experi- 

 ment. 



The observations I have made are not intended to defend my 

 opinion, but to rescue it from misrepresentation. Mr. Meikle 

 makes a great handle of the algebraic formulas, and, by a sort 

 of legerdemain of which he is a master, extracts from them 

 many absurdities. He regards not the principles of the ex- 

 planation I have given ; he is content to play tricks with the 

 algebraic expressions. All the absurdities he finds, are of his 

 own making. In this Journal for November 1828, p. 324, I 

 have obtainctl these expressions, 



|{i + ««)(^,--t> 



'■= -s-(l+'.»)(-f -1): 



here V is the volume, q' the densitj^, and fl the lcm|)oraturc, of 



the given mass of air ; and i is the variation t)f latent heat when 



tlie volume changes from V to V, and the density iVom g' to q. 



New Series. Vol. 5. No, 26. Feb. 1829. V Now 



