Table 1 50. 

 PRESSURE OF AQUEOUS VAPOR IN THE ATMOSPHERE. 



157 



rhis table gives the vapor pressure corresponding to various values of the difference i — ii between the readings of 

 dry and wet bulb thermometers and the temperature ^, of the wet bulb thermometer. The differences t — tj are 

 given by two-degree steps in the top line, and /, by degrees in the first column. Temperatures in Centigrade 

 degrees and Regnault's vapor pressures in millimeters of mercury are used throughout the table. The table was 

 calculated for barometric pressure B equal to 76 centimeters, and a correction is given for each centimeter at the 

 top of the columns.* Ventilating velocity of wet thermometer about 3 meters per second. 



,T !^ T,*?* J^^'^ "'^^ calculated from the formula /=/i —0.00066 .5(/—/i) (i -fo.ooiis^) (Ferrel, Annual Renort 

 U. S. Chief Signal Officer, 1886, App. 24). 



t When B is less than 76 the correction is to be added, and when B is greater than 76 it is to be subtracted. 

 Smitiisonian Tables. 



