Apeil 10, 1908] 



SCIENCE 



587 



lakes and reservoirs, in an eiiort to supply 

 data requested by the constructing engineers 

 of reservoirs and irrigation projects, it has 

 been decided to use the Salton Sea, southern 

 California, on account of the intense evapora- 

 tion there prevailing under conditions which 

 are favorable because of the small amount of 

 precipitation and inflow from the rivers in 

 that region. A comparison of several careful 

 studies on evaporation in different parts of 

 the world shows that the formulas result in 

 very different constants, depending apparently 

 upon the local conditions. It seemed proper 

 to attempt to discover the cause of this dis- 

 crepancy in order to plan the Salton Sea work 

 more carefully. We set up a temporary sta- 

 tion at Eeno, Nevada, at the double city 

 reservoir, the two reservoirs being 400 by 800 

 and 300 by 500 feet, approximately, having a 

 large irrigated alfalfa field to the west, in the 

 direction of the Truckee Valley, and a dry 

 field to the east in the direction of Sparks. 

 The meteorological conditions were very fa- 

 vorable, and observations continued from 

 August 1 till September 14, 1907. Five 

 towers, 40 feet high, were erected: No. 1 

 (east) in the dry field. No. 2, No. 3 (center). 

 No. 4, in order, on the bank of the reservoir. 

 No. 6 (west) in the alfalfa field. Twenty- 

 nine pans were set up, five six-foot pans on 

 the ground or in the water, and twenty-four 

 two-foot pans on the stages of the towers, ten 

 feet apart, or on the platforms leading to the 

 pans in the water. The observations were 

 made regularly at the hours, 1 a.m., 5 a.m., 

 8 A.M., 11 A.M., 2 P.M., 5 P.M., 8 P.M., and con- 

 sisted of dry and wet bulb temperatures in 

 the air near the pans, also one half an inch 

 above the water in the pans, the surface water 

 temperature by means of a floating raft, the 

 depth of the water in the pans at each hour, 

 the anemometer at tower No. 2 (east bank), 

 and comparative Piche evaporimeter readings 

 at tower No. 2 on sis stages. The results may 

 be briefly summarized as follows: (1) No dif- 

 ference appeared in the evaporation on ac- 

 count of the size of the pans. (2) The wind 

 effect is given by the formula 



where E^ is the evaporation without wind and 

 w is the velocity in kilometers per hour, E^ 

 being the evaporation in centimeters. (3) 

 The evaporation diminshed from a maximum 

 down the center tower to the water surfaces, 

 something like the amounts indicated by the 

 coefficients following: 



E:, 



:^i(l + Aw) =EA'i- + 0.0175 w) 



The adopted formula is: 



Ji:=Cf{h)ej^{l + Aw), 



where e is the vapor pressure of the air at 

 the dew-point temperature, de/ds the rate of 

 change of the vapor pressure per degree tem- 

 perature centigrade. Cf(h) the variable func- 

 tion. As in the table, the lines for Cf(h) at 

 each pan become asymptotes to the maximum 

 coefficient (the extreme desert station) and 

 they express a complex function of the diffu- 

 sion and mechanical mixture of fresh streams 

 or evaporating vapor. The vapor blanket 

 lying over a lake retards evaporation in this 

 manner, and the location of a pan in the 

 blanket is of prime importance. Note the 

 effect of the alfalfa field on pan (1), tower 

 No. 5 (0.025 which is depressed). We pro- 

 pose to erect towers in the Salton Sea, 

 and shall endeavor to discover the function 

 Cf(h)e, which undoubtedly has a small di- 

 urnal period and probably an annual period. 

 To integrate this function over a lake surface 

 is very difficult, and to pass abruptly from an 

 isolated pan to a lake is not permissible. 



The papers on the Eeno work will appear 

 in the Monthly Weather Review. 



The second paper of the evening was pre- 

 sented by Dr. J. W. Spencer, under the title 

 " Soundings under Niagara Falls and in the 

 Gorge." 



This very interesting paper gave a descrip- 

 tion of the application of sounding methods 



