Page:The Ancient Stone Implements (1897).djvu/687

Rh important springs would be those along the sea-shore; while irrespective of this, the greater rainfall would keep the soil so saturated, that floods would be as readily produced by heavy storms of rain as if the soil were the most unabsorbent of rocks. If after some lapse of time the rainfall diminished, and the valleys were deepened, so that the outlets for the springs were at a considerably lower level than that of the principal area of the country, the case would be altered, and the tendency to floods would be immediately reduced.

At the commencement of the state of things supposed in our hypothesis, these outlets, with the exception of those on the sea-shore, would be but little lower than the general surface of the country, which, however, would not be perfectly plane. For it seems probable that the waters of the retreating sea would, during the elevation of the tract of land, form shallow channels, cutting down some little distance into the clay or chalk; and thus, as it were, mark out a course along which streams or rivers would flow, after the land was completely free from the sea. In some places, perhaps, shallow lakes might be left, but these also would have channels draining off their waters when they rose above a certain elevation.

With a bare surface, such as a newly-elevated tract would expose, there can be no doubt that the eroding power of heavy rains would be highly effective; as may be seen at the present day in the far greater effects of heavy showers on bare soil than on that which is protected by turf and vegetation. At the same time, with a rigorous climate, such as that supposed, the winter accumulation of snow and ice would be great, and its thawing during the summer months would add enormously and rapidly to the streams draining the area, which would in consequence have great power to deepen and widen their channels. The outflows from the lakes, if any such existed, would also be enlarged, while their upper portions would be filled with material brought down by the streams, and eventually they would be drained, with the exception of some channels in their beds through which the streams would pass.

We may therefore readily suppose that in the course of no very great interval of time, geologically speaking, a river-system for carrying off the waters falling from the heavens, analogous in character to those of the present day, but with shallower valleys, would be formed on the surface of the elevated tract. Let us