Controlling Capilliary Moisture. 
By A. W. Blair, 
Mr. President, Ladies and Gentlemen: 
When rain falls upon fields and groves 
a part of it runs off to the lower places, 
and a part sinks into the soil and per¬ 
meates it. The amount which runs off is 
determined by the condition of the surface 
and the rapidity of the rain. If the sur¬ 
face is hard and compact and also some¬ 
what sloping, much of the water will run 
off. If the surface soil is loose and mel¬ 
low, and contains much organic matter, 
it will absorb much of the water that 
falls on it. When the rains are heavy 
and continue for some time, a part of this 
absorbed water will continue its course 
downward until it reaches the water-ta¬ 
ble or ground-water. 
Another part remains distributed in the 
soil, and it is this part that is thus held 
in the soil against the force of gravity 
that we call capillary water. As the sur¬ 
face of the ground dries out, some of the 
water that has filtered through to the wa¬ 
ter-table may be drawn up into the soil 
again and become capillary water. This 
may be illustrated as follows: Close one 
end of a glass tube by tying over it a 
piece of muslin, then partly fill the tube 
with soil, and pour on water; the entire 
mass of soil becomes saturated and a 
part of the water runs through, provided 
a sufficient quantity has been added. If 
now the soil in the tube is allowed to dry 
for a few days, and then the end over 
which the muslin was tied is dipped into 
a basin of water, the water will slowly 
rise in the tube, being lifted up by cap¬ 
illary attraction against the force of grav¬ 
ity. The water in the basin may be com¬ 
pared to the ground-water in the soil; 
though the cases are not strictly parallel, 
since under natural field conditions the 
soil is constantly in contact with the 
ground-water. The principle however is 
the same. It is from this capillary water, 
for the most part, that trees and plants 
obtain the water necessary for their 
growth. We can readily see then the im¬ 
portance of knowing how best to control 
this source of water supply. The prin¬ 
ciple on which the water, known as capil¬ 
lary water, rises in the soil, is a well- 
known law of physics. When small glass 
tubes of different internal diameters are 
placed in water, the water will rise high¬ 
est in the smallest tube. That is, the 
height to which the water rises is in¬ 
versely proportional to the diameter of 
the tube. A knowledge of this law helps 
us in the study of the movements of soil 
moisture. The small spaces between the 
soil particles or grains, may be likened 
to fine tubes; though in this case the 
tubes are neither straight nor of uniform 
bore. By capillary attraction water is 
drawn up through the pore spaces or fine 
tubes, to take the place of that which is 
lost by surface evaporation or used by 
plants and trees. 
The size of these tube.% will be deter¬ 
mined by the size of the particles or 
grains that make up the soil; that is, if 
the soil is composed largely of coarse 
particles, the capillary tubes will be 
