the Heat extricated from Air by Cojidensation. 151 



his reasons for such a change. Our author, as we shall hereaf- 

 ter see, is blamable in this respect. 



After some introductory remarks which had been repeatedly 

 given in his former papers, the pretended investigation of the 

 new law proceeds thus : — " We must next inquire according to 

 what law the latent heat accumulates when air expands. When 

 a mass of air, under a constant pressure, varies by the applica- 

 tion of heat, I assume it as an acknowledged principle, that equal 

 quantities of absolute heat produce equal increments of volume." 

 Now, on this I need only observe, that assumed principles and 

 acJcnowledged principles are too often erroneous principles ; and 

 it is the business of science to challenge the legitimacy of all such 

 random and gratuitous assumptions. 



In assuming this acknowledged principle, Mr Ivory has been 

 forced to transgress the much more sound and safe principle of 

 Newton, — That no more principles are to be admitted than are 

 necessary to solve the problem. Now, Mr Ivory knows very 

 well, that I have repeatedly shewn that the problem can be 

 solved in a most satisfactory manner, without this assumed and 

 acknowledged principle. Nay more, I have shewn that it is a 

 false and unfounded principle, as will farther appear by the 

 perusal of this essay, which I hope will have the salutary effect 

 of finally settling the true scale of the air-thermometer. 



Having thus noticed the loose hypothetical foundation of Mr 

 Ivory^s investigation, I shall now advert to its remarkable inconsist- 

 ency with his previously avowed doctrines. Thus, his laws or 

 formulae given in Phil. Mag., July 1824, page 9.5 set no limit 

 to the heat extricated from air by compression ; but, as we shall 

 shortly see, he has now confined that rise of temperature with- 

 in a very narrow compass, and without assigning a sufficient 

 reason for effecting such an extraordinary revolution in the un- 

 alterable laws of nature ! In 1825, the greatest cold produced 

 by the dilatation of air, could never descend below — 448° Fahr. ; 

 but, under the new law, it is bottomless and unfathomable.* 



* By looking into page 338, No. II. of this Journal, it will be found, that 

 though I had anticipated the scanty production of heat by the new law of con- 

 densation, yet I did not then foresee, but doubted, its enormous frigorific 

 powers. 



