CURRENTS OF THE SEA. 179 



is often not radiation enough to produce the phenomena of land 

 and sea breezes. The absence of dew in cloudy nights is a 

 familiar instance of the anti-radiating influence of clouds. The 

 southern hemisphere, being so much more aqueous, is no doubt 

 much more enveloped with clouds where its oceans lie, than is 

 the northern where its continents repose, and therefore it is that 

 one hemisphere radiates more than the other. 



369. Facts and pearls. — Thus, by observing and discussing, by 

 resorting to the force of reason and to the processes of induction, 

 we have gathered for the theory that favours the air-crossings at 

 the calm belts fact upon fact, which, like pearls for the necklace, 

 seemed only to require a string to hang them together. 



CHAPTER VIII. 



§ 370-409. — CURRENTS OF THE SEA. 



370. Obedient to order. — We here set out with the postulate that the 

 sea, as well as the air, has its system of circulation, and that this 

 system whatever it be, and wherever its channels lie, whether in 

 the waters at or below the surface, is in obedience to law. The 

 sea, by the circulation of its waters, doubtless has its offices to 

 perform in the terrestrial economy ; and when we see the 

 currents in the ocean running hither and thither, we feel that 

 they were not put in motion without a cause. On the contrary, 

 we know they move in obedience to some law of Nature, be it 

 recorded do\\^l in the depths below, never so far beyond the 

 reach of human ken ; and being a law of Nature, we know who 

 gave it, and that neither chance nor accident had anything to do 

 with its enactment. Nature grants us all that this postulate 

 demands, repeating it to us in many forms of expression : she 

 utters it in the blade of green grass which she causes to grow in 

 climates and soils made kind and genial by warmth and moisture 

 that some current of the sea or air has conveyed far away from 

 under a tropical sun. She murmurs it out in the cooling current 

 of the north ; the whales of the sea tell of it (§ 158) ; and all its 

 inhabitants proclaim it. 



371. The fauna and flora of tlie sea. — The fauna and the flora of 

 the sea are as much the creatures of climate (§ 104), and are as 



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