142 



PSYCHROMETRICAL TABLE. 



from 5° to 27°. This range falls short of the wants of the extreme climate of North 

 America, where temperatures above 90° and far below 10° are of usual occurrence 

 over a great portion of the continent. The same may be said of the range of the 

 differences between the two thermometers in the first part of the table. The double 

 interpolation for the fractions of degrees of both thermometers being rather too large 

 to be neglected, its application becomes inconvenient. 



Use of the Table. 



Enter the table with the observed temperatures of the dry and wet bulb thermom- 

 eters. On the same line as the last, and in their appropriate columns, the results 

 deduced from these data will be found. 



Example. 

 The observation has given. 



Temperature of the air by the dry thermometer = 62° F. 



Temperature of evaporation by the wet-bulb thermometer = 53° F. 



Page 129, find in the first column, headed Reading of the Dry Thermometer, the 

 temperature of 62°, and in the second, that of the wet, 53°. On the line beginning 

 with 53° are found, in their respective columns, the results deduced from these 

 data, viz. : — 



The temperature of the Dew-point = 46°. 7 F. 



The force of vapor in the air = 0.333 inch. 



The weight of vapor in a cubic foot of air = 3.72 grains. 



The amount of vapor required for saturation = 2.53 grains. 



The relative humidity in thousandths =^ 0.595 



B 106 



