The
experiments were all conducted upon a soil bare of vegetation.
Prof. Sanborn concludes from his experiments thus far that the surface
gains moisture from soil beneath it by capillary action, but gathers
nothing from the air. This is made strongly probable, if not shown;
first, because the soil is warmer by night than the air. (He relies upon
other facts than his own for this assertion.) 2nd. Because he found more
moisture in the soil when covered over night than when left bare. 3d.
Because when hoed, thereby disturbing capillary action, he found less
moisture than when unhoed, in surface soil. Finally, he concludes the
position proven, for, when he shut off the upward flow of water to the
surface of the soil, he found not only less moisture above the cut off
or in the surface soil than where no disturbance of capillary action
had been made, but actually less moisture in the surface soil than the
night before. Strongly corroborating this conclusion is the fact that
all of the tests conspire to show that the gain of moisture in the
surface of the soil by night is traceable to one source, and only one
source.
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