74 



THE WATER-SUPPLYING POWER OF THE SOIL 



It is to be noted, however, that the initially high rate is much more 

 pronounced here than in the water tests presented in table 2. 



The soil sample containing 25 per cent of water (on dry volume basis) 

 exhibits here, again, a prolonged fall in water-supplying power, though 

 the average hourly absorption rates more nearly approach uniformity 

 in the present than in the former case. The two 20 per cent samples 

 here agree very well in supplying power, but give a final mean markedly 

 higher than that obtained in either case with osmometer A. This is 

 probably mainly due to uncontrolled packing. The 15 per cent mix- 

 ture exhibits a well-maintained water-supplying power after the first 

 hour, the value of the final mean being somewhat but not markedly 

 higher than in the case of instrument A. 



TABLE 10. Average hourly absorption rates for osmometer B, operating against water and 



various soil mixtures. 



* After hour 1. 



tBut there appears to be here, as with osmometer A (table 9) , a general fall in rate through- 

 out the experiment. 



Considering the facts that the packing of our soil samples was inade- 

 quately controlled and that constant temperature was not maintained, 

 the results of these tests appear to be in very satisfactory agreement 

 with those already presented. 



OSMOMETER C. 



WATER AND SOIL TESTS WITH OSMOMETER C. 



This instrument had an effective absorbing area of 13.3 sq. cm. and 

 a calibration coefficient of 0.754. Below will be presented the results 

 of two water tests with this instrument, together with those obtained 

 by operating it against 5 per cent soil in the usual manner. Also, 

 this instrument was employed for studying the effect of placing a dry 

 soil layer between the absorbing surface and the supplying soil, and 



