THE FREE WATER OF THE SOIL. 201 
is held in the wick of a lamp. The adhesion of the water 
to the particles of earth suspends the flow of the liquid, 
and it is no longer subject to the laws of hydrostatics. 
Capillary water is usually designated as moisture, though 
a soil saturated with capillary water would be, in most 
cases, wet. The capillary power of various soils has al- 
ready been noticed, and is for coarse sands 25°|,; for 
loams and clays, 40 to 70°|,; for garden mould and humus, 
much higher, 90 to 300 °|,. (See p. 180.) 
For a certain distance above bottom water, the soil is 
saturated with capillary water, and this distance is the 
greater, the greater the capillary power of the soil, 1. e., 
the finer its pores. 
Capillary water is not visible as a distinct liquid layer 
on or between the particles of soil, but is still recogniza- 
ble by the eye. Even in the driest weather and in the 
driest sand (that is, when not shut off from bottom water 
by too great distance or an intervening gravelly subsoil) it 
may be found one or a few inches below the surface where 
the soil Jooks moist—has a darker shade of color. 
Hygroscopic Water is that which is not perceptible to 
the senses, but is appreciated by loss or gain of weight in 
the body which acquires or is deprived of it. (H.C. G, 
p- 54.) The loss experienced by an air-dry soil when kept 
for some hours at, or slightly above, the boiling point . 
(212° F.,) expresses its content of hygroscopic water. 
This quantity is variable according to the character of the 
soil, and is constantly varying with the temperature ; in- 
creasing during the night when it is collected from the at- 
mosphere, and diminishing during the day when it returns 
in part to the air. (See p. 164.) The amount of hygros- 
copic water ranges from 0.5 to 10 or more per cent. 
Value of these Distinctions.—These distinctions be- 
tween hydrostatic, capillary, and hygroscopic water, are 
nothing absolute, but rather those of degree. Hygroscopic 
water is capillary in all respects, save that its quantity is 
