SOILS AND ALKALI. 
17 
the upper surface of this ground water the “ water-table/’ 
and they are familiar with the fact that it lies at very dif¬ 
ferent depths in different soils and places and at different 
seasons of the year. Sometimes the water-table is at the 
very surface of the ground, or at a depth of no more than 
a few inches or a few feet, while in other situations it may 
lie, perhaps, hundreds of feet below the surface of the land. 
Much depends on whether the soil is porous or compact, 
whether or not the upper soil is underlaid by impermeable 
strata, and whether or not there is ready opportunity for 
the water to flow out sidewise and so escape from the soil. 
The height of the ground water, that is to say its dis¬ 
tance from the surface of the earth, varies greatly at dif¬ 
ferent times in any given soil, according to the perme¬ 
ability of the soil and the time which has elapsed since 
heavy rains. When people speak of wells and springs as 
being “ full ” or “ low,” they mean the ground water is up 
or down. The proper height at which ground water 
should stand in order best to conduce to the prosperity of 
the growing plant, is an important question in some local¬ 
ities. The rice, cranberry and ribbon grass flourish with 
their roots actually wet. There are two kinds of move¬ 
ments of water in the soil: First, the movement of per¬ 
colation of the ground water towards the sea, which is, on 
the whole, a downward movement; and secondly, a move¬ 
ment by force of capillarity, which is, or may be, a move¬ 
ment in any direction. A great amount of valuable work 
has been done in this line bv Pettenkofer at Munich, also 
by the lamented W. R. Nichols in his book on “ Water 
Supply.” 
When rain or snow falls upon the earth, it is speedily 
subjected to the influence of capillarity and dragged 
downward. The capillary power of soils has been worked 
out in great detail by Zenger. It takes a heavy shower for 
the rain to penetrate as -such to the depth of an inch. The 
