INTRODUCTION 

 Of Thermotics and Atmoloyy. 



I EMPLOY the term Thermotics, to include nil the doctrines re- 

 specting Heat, which 'have hitherto been established on proper 

 scientific grounds. Our survey of the history of this branch of 

 science must be more rapid and less detailed than it has been in those 

 subjects of which we have hitherto treated : for our knowledge is, in 

 this case, more vague and uncertain than in the others, and has made 

 less progress towards a general and certain theory. Still, the narrative 

 is too important and too instructive to be passed over. 



The distinction of Formal Thermotics and Physical Thermotics, 

 of the discovery of the mere Laws of Phenomena, and the discovery 

 of their causes, is applicable here, as in other departments of our 

 knowledge. But we cannot exhibit, in any prominent manner, the 

 latter division of the science now before us ; since no general theory 

 of heat has yet been propounded, which affords the means of calcu- 

 lating the circumstances of the phenomena of conduction, radiation, 

 expansion, and change of solid, liquid, and gaseous form. Still, on 

 each of these subjects there have been proposed, and extensively 

 assented to, certain general views, each of which explains its appro- 

 priate class of phenomena ; and, in some cases, these principles have 

 been clothed in precise and mathematical conditions, and thus made 

 bases of calculation. 



These principles, thus possessing a generality of a limited kind, con- 

 necting several observed laws of phenomena, but yet not connecting 

 all the observed classes of facts which relate to heat, will require our 

 separate attention. They may be described as the Doctrine of Con- 

 duction, the Doctrine of Radiation, the Doctrine of Specific Heat, and 

 the Doctrine of Latent Heat ; and these, and similar doctrines 

 respecting heat, make up the science which we may call Thermotics 

 proper. 



But besides these collections of principles Avhich regard heat by 

 itself, the relations of heat and moisture give rise to another extensive 

 and important collection of laws and principles, which I shall treat of 

 in connexion with Thermotics, and shall term Atmology, borrowing 



