588 HISTORY OF THERMOTICS. 



answer all obvious objections, we may consider it as 

 upon its trial, to be confirmed or modified by future 

 discoveries, and especially by an enlarged know- 

 ledge of the laws of the polarization of heat (VA). 



Atmological Theories. Hypotheses of the rela- 

 tions of heat and air almost necessarily involve a 

 reference to the forces by which the composition of 

 bodies is produced, and thus cannot properly be 

 treated of till we have surveyed the condition of 

 chemical knowledge. But we may say a few words 

 on one such hypothesis; I mean the hypothesis on 

 the subject of the atmological laws of heat, pro- 

 posed by Laplace, in the twelfth Book of the Me- 

 canique Celeste, and published in 1823. It will be 

 recollected that the main laws of phenomena for 

 which we have to account, by means of such an 

 hypothesis, are the following : 



(1). The Law of Boyle and Mariotte, that the 

 elasticity of an air varies as its density. See p. 556 

 of this volume. 



(2). The Law of Gay-Lussac and Dalton, that all 

 airs expand equally by heat. See p. 550. 



(3). The production of heat by sudden com- 

 pression. See p. 553. 



(4). Dalton's principle of the mechanical mix- 

 ture of airs. See p. 568. 



(5). The Law of expansion of solids and fluids 

 by heat. See p. 551 and note (QA). 



(6). Changes of consistence by heat, and the 

 doctrine of latent heat. See p. 554. 



