42 BULLETIN 721, U. S. DEPARTMENT OF AGRICULTURE. 
within the soil, such as size and grading of soil particles, presence of 
organic matter, mineral salts, colloids, etc. Some of these properties 
produce opposite effects. The following table shows the height to 
which capillary water rises in certain soils in one day. 
Table 11. — Height to which capillary water rises. 
Inches. 
Light sandy soil 1-4 
Gravelly soil 16 
Decomposed granite (loam) 21 
Heavy granite loam _ . _ 16 
Heavy clay loam _ 11 
Heavy lava ash 16 
Pure sand . 9 
In one day the capillary water moves upward about one-half its 
apparent final limit. In three days it moves about two-thirds its 
apparent final limit. In some soils the movement upward in the 
first two hours is as high as one-third of its movement for 30 days. 
In pure sand it rises in one-half hour approximately one-half as 
high as in one day and in one day about TO per cent as high as in 
12 days. The movement is more rapid at the start in light soils, and 
slows down rapidly. After three days the movement is exceedingly 
slow in pure sand. In heavy soils the movement is uniformly slower 
and more sustained. In light soils the per cent of water in the soil 
decreases rapidly with the height above the source, while in some 
heavy soils the moisture content is strikingly uniform at different 
depths. Horizontal capillarity occurs with much faster water move- 
ment and greater uniformity of moisture content. The speed and 
distance varies with different soils and ranges from 7 to 33 feet in 
the first 21 hours. 1 
The action of capillarity indicates that if water is to stand or flow 
"along a road embankment for even a few hours, regard must be given 
to the height of the subgrade above the water line, and the lateral 
distance of the water course from the road crust or foundation. 
Assuming that the supply of free water will not endure more than 
one day at a time, it is apparent that a height in the subgrade of 18 
inches above the water line will insure that the moisture content of 
the surface is not increased. TThere the free water is present at a 
considerable distance to one side this height may be safely reduced. 
Shallow ditches a short distance from the center line tend, by hori- 
zontal capillarity, to increase the water content of the subgrade at a 
higher level than deep ditches similarly located. If the grade be 
through standing water or against a continuous source of free water 
so that the soil remains moist continuously, capillarity will lift the 
1 Capillary movement of soil moisture. Unpublished report of Riverside Exp.. 101."- 
1917. W. W. McLaughlin. 
