Semi-Centennial Volume. 129 



November, 191G, would not have shown an excess if the whole month had 

 been recorded. The record was terminated by severe freezing weather 

 on November 13, a few days after a heavy rainfall. 



If we divide the evaporation for any month by the rainfall for that 

 month, the quotient gives a number which is known as the monthly 

 evaporation-rainfall ratio. The evaporation-rainfall ratio for the months 

 so far recorded, including the parts of months in August and November, 



1916, are shown in table 1. 



'^■•^"'''■' ^- Kvai):)rafioii- 



Ycar. Month. Evaporation. Rainfall, rainfall Ratio. 



19U). August (25 days) 8.245 .99 8.33 



September 7.761 3.21 2.42 



October 5.128 3.82 1.34 



November (12 days) 2.012 3.03 .66 



Total, 1916 23.146 11.05 2.09 



1917. Marrh 5.953 1.55 3.84 



April 5.681 3.39 1.68 



Mav 5.701 3.97 1.44 



June 8.385 2.11 3.97 



Julv 11.061 .50 22.12 



August 6.956 4.69 1.48 



September 5 . 445 5.70 .95 



Ortober 4.114 1.37 3.00 



November 3.079 .02 153.95 



Total, 1917 56.378 23.30 2.42 



The mean daily evaporation for each month is shown in plate XV. The 

 annual curve of evaporation intensity indicated by these means are much 

 more closely related to temperature and humidity than to wind velocity, 

 for surface wind velocity is highest in spring and fall, when the vegeta- 

 tion offers least resistance to air flow, while the lowest average wind 

 velocities occur in midsummer or later, when vegetation is at its maximum 

 development. In March the surface velocity was about four times as 

 great as in August and September, and in November it was about twice 

 as great as in September. 



Comparison of the evaporation in western Kansas with that in eastern 

 Kansas can be made as yet only in a fragmentary way, owtng to the in- 

 completeness of the records from the Tribune station. Only four com- 

 plete monthly records have been made at Tribune, and the comparative 

 data for these months at Lawrence and Tribune are shown in table 2. 



T.ABLE 2. 



Yenr. Month. Tribune. I.,awrenoe. Difference. 



1916. September 9.347 7.761 1.586 



1917. April 6.880 5.681 1.199 



May 7.689 5.701 1.988 



September 8 . 494 5 . 445 3 . 049 



From this table it is seen that the evaporation is from one to three 

 inches per month greater in the western part of the state than in the 

 eastern part. During a season this would amount to perhaps eighteen 

 inches. It seems fair to conclude that the evaporation intensity of the 

 atmosphere is on the average about 25 per cent greater at Tribune than 

 at Lawrence. At the same time the precipitation is 4.5 per cent less at 

 Tribune than at Lawrence, based upon the average annual precipitation 

 for the eastern and western divisions of the .state. 



9 — .\rad. Sci. — 2199 



