TABLE 1 7O. 

 PRESSURE OF AQUEOUS VAPOR IN THE ATMOSPHERE. 



This table gives the vapor pressure corresponding to various values of the difference t ^ between the readings of 

 dry and wet bulb thermometers and the temperature i 1 , of the wet bulb thermometer. The differences / / t are 

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

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

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

 top of the columns.* 



* The table was calculated from the formula /=/i 0.00066 (f( t ) (i +0.00115^) (Ferrel, Annual Report 

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



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



SMITHSONIAN TABLES. 



157 



