[Sidenote: Capillary attraction causes an upward movement of the
water.]
Through capillary attraction an ascending movement of the water is
caused in direct opposition to the laws of gravity, and the height to
which water will thus ascend depends mainly on the smallness of the
pores; large pores do not assist in this movement. As the same,
however, extends over the whole pore-volume the quantity of water thus
raised may exceed the water-retentive power of soil.
[Sidenote: Capillary attraction also causes lateral and downward
movements.]
In addition to the upward movement brought about by capillary
attraction, this power is also continually at work in a lateral and
downward direction; but for the present purposes only the upward
movement will be noticed.
[Sidenote: Time occupied by upward movement. Height reached by upward
movement.]
In observing the upward movement, it is interesting to notice the time
occupied by it and the total height reached. As to the time occupied,
it has been established that the upward movement in gravel and coarse
sand is much quicker than in fine and loamy sand, but the heights
attained are reversed. For whereas the height in a material consisting
of coarse or large pores amounts to from 2 inches to 4 inches; a
height of about 4 feet after thirty to thirty-five days has been
recorded in fine or loamy sand; in peaty soil one observer states that
the upward movement of the water may reach a height of 20 feet.