[ S02 ] 

 Of the Ufes of the foregoing Tahle. 



The ufe of this tabic is to difcover, when different obfervations 

 are made at diiFerent times or places and at different degrees of 

 heat, what the real quantity of moifture is, as pointed out by the 

 hygrometer ; for as this inftrument equally de/cends to drynefr 

 when the heat increafes, or the quantity of vapours in the air de- 

 creafes, and equally afcends to moifiure when the heat decreafes, or 

 the quantity of vapours in the air increafes; it is neceffary to find 

 .ioh which of thefe caufes, and to what degree, this variation de- 

 pends. Now thefe problems may eafily be refolved by this table* 

 I fhall begin by the circumftances of an increafe of heat. 



If the h^t increafes after the firft obfervation, and the hygro- 

 Itieter defcends, three cafes may have happened, i ^, There may 

 have been no variation of vapour ; or, 2do, There may have been 

 an increafe of vapour but difproportionate to the heat j or, 3tio, 

 There may have been alfo a decrafe of vapour as well as an in- 

 '■treafe of heat. — We may alfo imagine a fourth cafe, in which there 

 may be ^n increafe of vapour proportionate to the increafe of heat, 

 but in that cafe the hygrometer would not defcend. 



The firfl flep to be taken in this inveftigation is to obferve what 

 effeil the increafed degrees of heat fhould have on the hygrometer, 



abiirading 



