10 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE. 
The smaller quantities of water penetrated practically as deep as 
the larger amounts that stood for a much longer time. In five min- 
utes the water in hole No. 17 penetrated to a depth as great as was. 
reached by that in some of the others in several days. 
There is an apparent lack of consistency in the time required for 
some of the larger quantities of water to disappear. This is due to 
the fact that in some cases the amount of water added was sufficient 
to raise the water level to a point that allowed it to escape laterally 
through the cracked soil. This is shown also by the lack of differ- 
ence in the depth of penetration of the different quantities. The 
best measure of time and depth of penetration is found in hole No. 
24, in which a supply of water was maintained by the addition of 
2 gallons at three separate times. Ten days were required for the 
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WATER ADDED  /QZ 
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t - i i I 
WHE TO DISAPPEAR 572 PR euR SIR F9HR SEHR FPHR 10 DAIS 
Fig. 4—Diagram showing the time taken for various quantities of water to disappear 
and the depth of penetration in each case from the bottoms of a series of holes 8 
inches in diameter and 18 inches deep. The heavy lines indicate the lowest points 
reached by the water from the different holes. 
disappearance of the entire quantity, but the total depth of pene- 
tration during this time was only a little over an inch more than it 
was from those holes in which water stood for a much less time. 
These experiments indicate that while the water movement is com- 
paratively rapid in the dry soil it is very slow in the wet soil. 
Since there is no evidence of a layer of soil actually impervious to 
water, it appears that the exceedingly slow movement of water is due 
to the fact that the soil in contact with the water quickly becomes so 
swollen and compact that further movement of water within it is 
very difficuit. Penetration into the dry soil almost stops, not because 
of the resistance offered by the dry soil itself, but on account of 
the extremely slow movement of the water through the layer of wet 
soil that is between the source of water supply and the dry soil. 
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