THE ACTINOMETRY OF THE SEA. 473 



Is it not to them that has been assigned the task of bringino- 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, im- 

 portant 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 ade- 

 quate supplies of caloric ; the consequence would be less precipi- 

 tation 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 j)lanet would be different from what they are. 



893. Tlie radiating poivers of earth, air, and ivater compared.— \Yg 

 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 pro- 

 vided, 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 



