THE PEAIKIES 199 



made from 7 o'clock A. M. to 7 o'clock P. M. Earlier and later 

 readings were also at first taken but tliev could not be continued 

 as the days grew shorter, and they are not here included. So far 

 as made they did not in any way modify the results obtained. 

 Notwithstanding the care which was exercised in making these 

 readings it is probable that occasional errors were made, the pos- 

 sibility of which will be appreciated by those who have ventured 

 to face the tedium of such work in mid-summer in a rough ter- 

 ritory. The results which were obtained however are so generally 

 consistent, and they agree so well with observations made at other 

 points, notably at Ute by Superintendent D. H. Boot under the 

 writer's direction, and at Omaha and Council Bluffs and in the 

 vicinity of Lake Okoboji. loAva. by the writer himself, that they 

 are here offered with the confident conviction that such errors as 

 may have occurred are rare or insignificant and would not ma- 

 terially affect the general results. 



Rate of Evaporation. 



The several types of evaporimeters did not show the same rela- 

 tive rate of evaporation at the several stations, but this was evi- 

 dently due largely to the difference in position and altitude above 

 the surface. In all cases, however, evaporation was shown to be 

 much greater at the exposed stations 1 and 3 than at the more 

 or less sheltered stations 2 and 4. 



Evaporating Pans. The evaporating pans were filled to the 

 index (a pointed wire) at 7 o'clock A. ^M. Readings were then 

 taken at 2 and 7 o'clock P. M. During the nights of the 13th and 

 14th days of August and the 28th and 29th of August, the pans 

 were also left in the field and readings were taken at 7 o'clock 

 A. ]\r. On the 2Sth of August observations were also made from 

 4 to 7 o'clock P. ^I. and were continued on the following day. 



The total amount of diurnal evaporation increased as the dry 

 season advanced, excepting that on September 5th it was checked, 

 e\Tdently because of the shifting wind and abrupt lowering of 

 temperature late in the day. 



Evaporating pans were located at each of the four stations, 

 and the total amount of evaporation from each for the periods 

 indicated is given in the following table : 



