142 



PSYCHROMETRICAL TABLE. 



from 5 to 27. This range falls short of the wants of the extreme climate of Nor 

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

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

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

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

 to be neglected, its application becomes inconvenient. 



USE OF THE TABLE. 



Enter the table with the observed temperatures of the dry and wet bulb thermon 

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

 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, tl 

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

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

 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 



