Page:Scribner's Magazine Volume 1.djvu/578

566 storms; except in the path of a hurricane, the wind is unfelt in these shades; they fall as a strong man by a sudden blow. Those who are accustomed to haunt these primeval woods have often observed how, in the months of May or June, when the air is perfectly quiet, oftenest in the dead of night, while the woods are as still as a cavern, there comes through the silent aisles of the forest a roar as of far-off thunder. The din is caused by some old tree, whose trunk, sapped by decay and over-weighted by the burden of its new-made leaves and sap, has fallen into ruin.

The tangle of decayed vegetation which covers the ground beneath the forest is of considerable thickness. On top it consists altogether of the decayed trunks, branches, and leaves, but it shades downward into ordinary dark-colored soil at the depth of a few feet from the surface. This, the decay zone of the forest, lies between the boughs of the air and the branches of the roots. In it go on the most important actions which take place in our forests—actions which affect the history of land and sea. We shall therefore have to consider it in a somewhat painstaking way. The most evident effect of this sheet of decaying wood, and moss which feeds on the decay, is on the rainfall of the region which it mantles. When, after a season of drought, a copious rain falls upon this spongy mass, the water is for a long time absorbed in the interstices, and does not flow to the rivers. Even in times of very heavy rain the water is slowly yielded to the streams; after a dry period of many weeks this sponge retains a good share of water. A like amount of rain falling on tilled fields or prairies slips quickly away to the rivers, and thence to the sea. The first result is, that when the land is destitute of forests it sheds water like house-roofs, breeding floods after every considerable rain, while in the forests the rain is only slowly yielded to the streams.

A second and less evident result of the spongy character of the forest bed is that, by hindering the escape of the rainwater to the rivers, it increases the actual rainfall of the country. To see the nature and importance of this action, we must turn aside for a moment to consider the origin of the rain which falls upon the land. The original source of this water-supply is the sea, which sends into the lands a tolerably regular annual store of moisture. When this falls as rain or snow, either of two things may happen—the water may go away directly to the sea, or it may return to the atmosphere as vapor to be again precipitated