336 RATIO OF EVAPORATION TO HUMIDITY* 



of 15° [65*75° F.]. I repeated the same experiments with 

 air at the temperature of 20° [77° F.] and 5° [4325° F.], 

 and I found, that it required in the first case about 16-75 

 grs., and in the second 4'5. These three quantities are 

 nearly in the same ratio as the evaporations under these de- 

 grees of heat given in the table inserted in this Journal*; 

 and it is obvious, that it could not be otherwise. 

 Humidity of From this principle we have the proportion 17*1 : 4*4 : : 

 muratedairat 1Q grg . 2<6 grg ^ the weight of the quant ity of water con- 

 tained by a cubic foot of air at the temperature of melting 

 ice, when completely saturated. The weight of a cubic 

 inch of water being 373*5 grs, this is the weight of 12 cub. 

 lines of water; which, divided by the bulk of the air, will 



12 

 give for the humidity of the air at the temperature 



of melting ice, when completely saturated with water. 

 Rute for finding By the same reasoning may be found the humidity of a 

 the point of sa- cubicfoot of air at the temperature X, and at the point of 

 turation at- ■ i ' 



other tempera- saturation ; by meaus of the proportion 

 tares. X 



(2*718) U ' 05 (4*4) : (2.718) ll /° 5 (4.4) : :^ily : 



11-05 



•12(2718) ^ 



(144) 3 

 This 4th terra expresses the humidity to which the evapora- 

 tion in air perfectly dry, at the temperature X, is propor- 

 tional. 



If we call Z the number of cubic lines of water sus- 

 pended in a cubic foot of air, the temperature of which is 

 equally X, the humidity of this air will be expressed by 



, and the evaporation in this air, agreeably to 



what has been said, will be proportionate to 

 X 



12(2*781) n ' 05 Z 



(144) 3 (144) 3 



* Journ. dePhys., vol. LXV, p. 451 ; or our Journ. vol. XXVII, 

 p. 22. 



Conscq'iently 



