318 



ENVIRONMENTAL CONDITIONS. 



Table 17. — Summary of data of precipitation (P) and evaporation (E) for three 5-week 

 periods for the summer of 190S {data from table 16), together with averages and precipi- 

 tation-evaporation ratios (P/E) for the 15-week period May 26 to September 7. 



To obtain a single number to represent each station for this 15-week 

 period (May 26 to September 7), the three 5-week means have been 

 averaged, to give a mean intensity of atmospheric evaporating power 

 for approximately the three summer months. The three 5-week aver- 

 ages and the resulting 15-week means are shown in table 17, together 



