138 THERMOTICS. ATMOLOGY. 



the term from the Greek Avord (CCT/JWS,) which signifies vapor. The 

 Atmosphere was so named by the Greeks, as being a sphere of vapor ; 

 and, undoubtedly, the most general and important of the phenomena 

 Avhich take place in the air, by which, the earth is surrounded, are 

 those in which water, of one consistence or other (ice, water, or steam,) 

 is concerned. The knowledge which relates to what takes place in 

 the atmosphere has been called Meteorology, in its collective form : 

 but such knowledge is, in fact, composed of parts of many different 

 sciences. And it is useful for our purpose to consider separately those 

 portions of Meteorology which have reference to the laws of aqueous 

 vapor, and these Ave may include under the term Atmology. 



The instruments which have been invented for the purpose of mea- 

 suring the moisture of the air, that is, the quantity of vapor which 

 exists in it, have been termed Hygrometers ; and the doctrines on 

 which these instruments depend, and to which they lead, have been 

 called Hygrometry ; but this term has not been used in quite so exten- 

 sive a sense as that which we intend to affix to Atmology. 



In treating of Thermotics, we shall first describe the earlier progress 

 of men's views concerning Conduction, Radiation, and the like, and 

 shall then speak of the more recent corrections and extension?, by 

 which they have been brought nearer to theoretical generality. 



