CAPILLARY MOVEMENT OF SOIL MOISTURE. 



57 



of soil is farther away from the water and gravity would tend to 

 hold the moisture in the lower layer. Secondly, evaporation from the 

 surface would tend to further reduce the moisture at and near the 

 surface. Thus the laws of physics would indicate a lower percentage 

 of moisture toward the top of the flume than near the bottom. There 

 were, however, several instances where this relationship was inter- 

 changed, and more especially was this noticeable during the winter of 

 1916-17. When this interchanged relationship in the distribution of 

 moisture was observed so frequently during the spring of 1917 as to 

 almost preclude the probability of error from sampling, it seems 

 evident that the unlooked-for distribution of moisture was the result 

 of some natural condition. It soon became apparent that the top part 

 of the flumes showed the greater percentage of moisture during only 

 that time of the year when the air temperature was or recently had 

 been below 30°. In looking back over the results of the preceding 

 winter, this same condition was found. When these facts became 

 evident it was so late in the season that there was no opportunity to 

 prove the matter beyond a question of doubt. For this reason a few 

 of the samples, with percentage of moisture and air temperature, are 

 given in Table 42 for what they may be worth. 



Table 42. — Soil-moisture distribution and air temperature. 



Date. 



Distance. 



Flume. 



Percentage of 

 moisture. 



Temperature for 

 week preceding. 



Top 

 5 inches. 



Bottom 

 5 inches. 



Maxi- 

 mum. 



Mini- 

 mum. 



Mar. 5, 1917... 



Mar. 16, 1917.. 

 Apr. 21, 1917.. 



Inches. 

 21 

 38 

 62 

 92 

 44 

 128 

 201 

 32 

 68 

 104 

 140 

 190 

 32 



56 



90 



Per cent. 

 31.53 

 27.44 

 26.33 

 23.37 

 29.11 

 27.78 

 41.13 

 28.75 

 26.45 

 25.75 

 24.30 

 17.83 

 28.31 

 20.61 

 25.13 



Per cent. 

 29.32 

 36.30 

 25.66 

 23.67 

 26.83 

 26.64 

 28.46 

 30. 44 

 26. 38 

 25.45 

 24.60 

 19.32 

 29.90 

 22.00 

 25.47 



70° 27° 





1 





1 



95 



70° 27° 







92 



77° 25° 













101 



82° j 32° 











At a distance of 82 inches in flume 93 there was taken on March 

 20 a set of samples dividing the boring into four samples, each 

 containing 2^ inches of soil in depth, and the following results ob- 

 tained : 



In the top sample, 28.96 per cent. 

 In the second sample, 27.56 per cent. 

 In the bottom sample, 26.60 per cent. 

 In addition to the samples given above there are several others 

 showing similar results. There are some samples taken at the same 



