VI CONTENTS. 



The Climatic Conditions of the United States — continued. page. 



III. Moisture conditions — continued. 



3. Removal of water from plant — continued. 



B. Atmospheric evaporating power in United States — continued. 



(2) Russell's data of evaporation in United States — continued. 



Evaporation intensities for the period of the average 



frostless season (table 11, plate 53, and fig. 14) . . . 292 

 Annual evaporation intensities (table 15, plate 54) . . 296 

 Evaporation intensities for the three summer months 



(table 15, plate 55) 298 



Table 15. — Precipitation and evaporation data 



for the year and for the three summer months . . 298 

 (3) Evaporation studies in 1908. 



Presentation of data 304 



Table 16. — Weekly precipitation (P) and weekly 

 rates of evaporation (E), the latter from cylin- 

 drical porous-cup atmometers, summer of 1908. 306 

 Summer march of evaporation at selected stations. . 311 

 Mean evaporation values for 5-week periods and 



for 15-week season (table 17, plate 56) 316 



Table 17. — Summary of precipitation and evapo- 

 ration for summer of 1908, with averages and 

 precipitation-evaporation ratios (P/E) for the 



15 weeks, May 26 to Sept. 7 318 



Comparison between plates 55 and 56 320 



Summer evaporation, 1908, as shown by geographic 



profiles (fig. 13) 322 



• (4) Conclusionsfromstudy of evaporation conditions(fig. 14) 323 

 C. Ratios of precipitation to evaporation . 



(1) Preliminary considerations 326 



(2) Ratios of total precipitation, for the period of the average 



frostless season, to total evaporation for the same 

 period, July 1887 to June 1888 {P/E) (table 11, 

 plate 57, and fig. 16) 326 



(3) Ratios of total precipitation to total evaporation, for 



the period of the average frostless season, July 1887 



to June 1888 (P/E) (table 18 plate 58) 328 



Table 18. — Data of precipitation and evaporation 

 for the period of the average frostless season, 

 for the year July 1887 to June 1888, and corre- 

 sponding ratios of precipitation to evaporation, 

 together with similar ratios derived by employ- 

 ing normal data of precipitation instead of those 

 for this single year 329 



(4) Ratios of normal total precipitation, for the period of 



the average frostless season plus 30 days, to total 

 evaporation for the same period, Juty 1887 to June 

 1888 (tt/E) (table 11, plate 59) 333 



(5) Ratios of normal total annual precipitation to total 



annual evaporation, July 1887 to June 1888 

 (Pa/Ea) (table 15, plate 60) 333 



(6) Ratios of normal total precipitation for the three sum - 



mer months, June to August, to total evaporation for 

 July and August 1887 and June 1888 (Ps/Es) 

 (table 15, plate 61) 338 



(7) Ratios of total precipitation for 15 weeks, summer of 



1908, to total evaporation for the same period and 



year (P, ma/Es im) (table 17, plate 62) 339 



(8) Conclusions from study of precipitation-evaporation 



ratios (fig. 16) 342 



