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Page:Popular Science Monthly Volume 19.djvu/190

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THE POPULAR SCIENCE MONTHLY.

be given out again to a drier atmosphere and to surrounding objects. It is well known, also, that the leaves of the trees, as they fall from year to year and decay, form a spongy soil, which absorbs the rains that fall upon it, and retains them, when otherwise, where there is any declivity, the water would run off almost immediately. The roots of the trees, likewise, penetrating deeply into the ground, conduct a considerable portion of the moisture falling from the clouds far below the spongy surface-soil. Shaded by the leaves and branches of the trees, the moisture thus stored up is not soon evaporated, as it would be from the open ground, but passes off slowly into the surrounding air, and imparts its benefits in the largest measure to the adjacent lands.

While thus sending out their moisture upon the cultivated fields around them, and thereby favoring the growing crops, the forests aid the work of husbandry in another way. By their very mass they serve as a mechanical barrier against the winds, which are often so injurious to crops. Every one who has visited the forest with any frequency knows that he is obliged to go but a short distance within its borders to escape the influence of even a violent wind. So it is also well known that the woodmen engaged in felling trees in the forest, which they usually do in the winter, find no inconvenience from cold winds, as these penetrate the wood but a short distance, even when the trees are stripped of their leaves. And as the woods shelter those within them from the winds, so do they protect the adjacent fields from the blasts which would otherwise sweep over them, and, by their cold, their mechanical force, and their desiccating influence, prove very injurious to crops. The presence of a forest is often, on this account, in its effect upon adjacent lands, equivalent to a change of latitude of several degrees. This is sufficient to make the cultivation of certain crops successful which otherwise could not be undertaken. There are districts of France and Italy where the olive and the orange once flourished, but where now, on account of the change of climate resulting from the extensive removal of the forests which formerly abounded, they can no longer be grown with success. It is not going too far to say that, if one fourth of the land now under cultivation were converted into forests and groves so disposed as to form barriers against the coldest and strongest or most prevalent winds, the remaining three fourths would have more value for agricultural purposes than the whole has at present. This would result from the greater variety of crops which could be raised, their earlier maturity, the greater certainty of growth, and the larger aggregate yield, while there would be, in addition, the large product of the forest itself, to be used, as occasion might demand, for fuel and lumber.

The effect of trees in preventing or diminishing the evaporation from the ground caused by the passage of drying winds is far from being properly appreciated. We often speak of the effect of wind in