AQUEOUS VAPOR IN THE ATMOSPHERE 
343 
prepared for /« where T ranges from — 50° C. to + 50° C., and 
B from 800 mm. to 20 mm. 
Grams of Aqueous Vapor in One Kilogram of Saturated Air. 
(743) ¡i = 0.6221 +0.235 ~ 
e 0 is the saturated vapor pressure for temperatures ranging 
from — 50° C. to -f- 50° C. 
When the air is not saturated the following formula serves: 
e 0 = the saturated vapor pressure, t = the dry-bulb temperature, 
t x = the wet-bulb temperature. 
Vapor Pressure in Millimeters when the Air is not Saturated 
(744) e = e Q - 0.00066 B (t - h) (l + . 
Tables applicable to practical work may be found in Bulletin 
No. 2, Oficina Meteorologica Argentina, 1912. 
In the free air the aqueous vapor is distributed approximately 
by Hann’s formula, 
h 
(745) e = e 0 10 6517 , 
where h is the height in meters. 
The Laws of the Evaporation of Water from Lakes, Pans, and 
Soils with Plants 
The subject of the evaporation of water has been very ex 
tensively studied, and there is a large literature on the results. 
These, however, are unsatisfactory as concerns the terms and 
the coefficients of the proposed formulas. Another research 
was undertaken by the writer in 1907 for the U. S. Weather 
Bureau, at Reno, Nevada, where the proper type of formula was 
determined; it was continued in 1908 at Indio and Mecca, So. 
California, and at the Salton Sea, 1909, 1910, in co-operation 
with numerous stations in various parts of the United States, 
during which the coefficients were approximately computed; the