560 COSMOS. 



over, by differences of heat, in exciting atmospheric and 

 oceanic currents; the latter of which have continued for 

 thousands of years (though in an inconsiderable degree) to 

 accumulate or wash away alluvial strata, and thus change 

 the surface of the inundated land; it operates in the gene- 

 ration and maintenance of the electro-magnetic activity of 

 the Earth's crust, and that of the oxygen contained in the 

 atmosphere ; at one time calling forth calm and gentle forces 

 of chemical attraction, and variously determining organic life 

 in the endosmose of cell-walls and in the tissue of muscular 

 and nervous fibres; at another time evoking light-processes 

 in the atmosphere, such as the coloured coruscations of the 

 polar light, thunder and lightning, hurricanes, and water- 

 spouts. 



Our object in endeavouring to compress in one picture the 

 influences of solar action, in as far as they are independent 

 of the orbit and the position of the axis of our globe, has 

 been clearly to demonstrate, by an exposition of the connec- 

 tion existing between great, and at first-sight heterogeneous, 

 phenomena, how physical nature may be depicted in the 

 History of the Cosmos as a Whole, moved and animated by 

 internal and frequently self-adjusting forces. But the waves 

 of light not only exert a decomposing and re-combining 

 action on the corporeal world ; they not only call forth the 

 tender germs of plants from the earth, generate the green 

 colouring matter (chlorophyll) within the leaf, and give 

 colour to the fragrant blossom they not only produce myriads 

 of reflected images of the Sun in the graceful play of the 

 waves, as in the moving grass of the field but the rays of 

 celestial light, in the varied gradations of their intensity and 

 duration, are also mysteriously connected with the inner life 

 of man, his intellectual susceptibilities, and the melancholy 

 or cheerful tone of his feelings. " Cceh tristitiam discutit 

 Sol et humani nubila animi serenat" (Plin. Hist. Nat. ii. 6.) 



