Page:Popular Science Monthly Volume 78.djvu/184

180 40 per cent, of the total fall, the gross discharge through surface drainage per year from the entire area of Britain is equal only to about one fifth the annual discharge of the Mississippi River system. All of the streams in Britain have the major part of their courses where the land is well under an altitude of 1,000, an elevation less than that of most of the Mississippi drainage basin. In the streams of the latter system the available water power has been estimated to be as high as 25,000,000 horse power. Calculated on the same basis, and in terms of their total discharge, the maximum power capacity of the British streams would not exceed 5,000,000 horse power, which, even if increased by 50 per cent., to give a generous estimate because of the shorter and more rapid descent of some of the British streams, falls far short of meeting the present British needs for mechanical energy. Hence, the dependence of Britain on her streams for power would mean not merely the inability to take care of an increasing population, but also an actual lessening of her ability to support, as at present, the numbers already existing.

This amount of power from streams, however, might be materially supplemented by the utilization of energy in the rise and fall of the ocean waters in the tides, the feasibility of which, under favorable conditions, has already been demonstrated at different places along the coast of this country. Here once more the position of Britain, its size and configuration, are decidedly favorable for the development and general use of such wave and tidal power; practically every locality in the kingdom being so situated as to be able to benefit from its use under the present condition of transmission of power over wires in the form of electricity. Estimates of the extent to which energy of the tides can be utilized for commercial purposes are still largely conjecture, since the need for turning to that source of power has not yet risen, but it seems not unlikely that the future of Britain is to depend, perhaps more closely than ever, on those same physical factors which have been so significant in practically every chapter in the past—her insular position, compactness and configuration of the coast.

Germany, on the other hand, confronted by the same problem of coal exhaustion, has a less hopeful outlook because of her different surroundings. Germany with a large and rapidly increasing population, already grown well beyond the food capacity of the national area, recognizes the necessity for providing for her increasing numbers by increasing commercial and industrial activity—all dependent on mechanical energy. In this respect Germany is less favored than Britain, not only as regards coal, but also as regards water power to replace coal. Calculated on the basis of an average rainfall of 30 inches and a run-off of 40 per cent., both of which figures are high, the total