Page:Physical Geography of the Sea and its Meteorology.djvu/499

Rh Is it not to them that has been assigned the task of bringing up by their agitation of the surface the layers of warm water that are spread out below; and are they not concerned also, as they draw up the genial waters, in regulating the supply of heat for the winds by night, as well as in cold or cloudy days, for the purposes of evaporation? Thus even the waves of the sea are made by this beautiful study to present themselves as parts, important parts, in the terrestrial machinery. We now view them as it were, like balance-wheels in the complicated system of mechanism by which the climates of the earth are governed. If the waves did not stir up the heated waters from below (§ 881), the winds would evaporate slowly by night, for the want of adequate supplies of caloric; the consequence would be less precipitation and a more scanty supply of latent heat for liberation in the cloud region. As a consequence of this, the winds would have less motive power, and the whole climatic arrangements of our planet would be different from what they are.

893. The radiating powers of earth, air, and water compared.—may note also another peculiarity as to the difference in the direct heat-absorbing and radiating properties of sea, land, and air: it is one which presents the atmosphere in the light of a regulator between the land on one hand, and the heating powers of the sun on the other. It is suggestive also of other benign compensations and lovely offices in the physical machinery of our planet: both land and water receive more heat from the sun than they radiate again; but the atmosphere receives less heat direct from the sun than it radiates off again into space: as the heat comes from the sun, part of it is absorbed by the atmosphere; but the largest portion of it is impressed upon the land and water from them a portion passes off into the atmosphere by conduction, while another portion is radiated directly off into the realms of space. What becomes of the remainder? Let us inquire, for there is a remainder, and unless means for its escape were provided, the land and water, especially the latter, would continue to grow warmer and warmer, and so produce confusion in the terrestrial economy. The remainder of this heat, being that which is neither radiated by sea and land directly off into space, nor imparted to the air by conduction from them, is absorbed in the processes of evaporation; it is then delivered to the atmosphere latent in the vesicles of vapour, to be set free in the cloud region, rendered sensible and imparted to the upper air, whence it is sent