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 down 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 the sea.—The fauna and the flora of the sea are as much the creatures of climate (§ 104), and are as
