"The sum-total of heat transferred by this agency is too great for comprehension. Look at the Amazon rolling to the ocean a flood broad as an arm of the sea. That great river is brought from the Atlantic Ocean on the shoulders of the trade-wind. As the vapor is slowly lifted by the rise of the land from the sea level to the summits of the Andes, it is condensed, and falls as rain. Well is it for South America that the Andes were thrown up on the western coast, for the winds west of the mountains are dry as a pressed sponge, and the most of that narrow slope is barren and desolate. South America would be a desert if the Andes ran along the eastern coast. Look at the Mississippi, and the great rivers of Europe, and the matchless rivers of Southern Asia. All the rivers of the world represent only the _wastage_ of the rain which falls upon the land after supplying the wants of the vegetable kingdom and keeping the lands moist. All this water is lifted into the air by heat, and every movement of vapor is a movement of heat. Every particle of vapor goes freighted with heat. Every cloud driven across the sky represents the transfer of heat, and every transfer is in the direction of equalization. Everywhere the tendency is to equilibrium. Nature has no processes for transferring heat from colder to warmer regions. "We may form a conception of the amount of heat transferred by the agency of vapor by estimating the amount of heat-force required to evaporate the water which forms our rain-clouds and lift them into the upper regions. According to a calculation of Mr. Allen, late of Providence, to evaporate one-eighth of an inch of water daily from that belt of the surface of the earth lying within the tropics, and raise it five thousand feet high, requires 4,700,000,000 horse-power, or one hundred and thirty times the effective force of the whole human race, reckoning it at 250,000,000 able-bodied men. But the actual evaporation from the sea within the tropics is believed to be about half an inch daily--four times as great as Mr. Allen's supposition. "I see, however, that our time is nearly exhausted, and I wish before closing to revert to that more important theme upon which I spoke this forenoon. I do not know how the truths preached interested or affected you, nor do I now wish to have you tell me. I wish only to say that, as the sermon was preached at your request, I hope it proved applicable to you, and that you will give the truths presented earnest attention. Consider them well, and make your conclusions known this evening." The conclusion which the evening made known, you, reader, have already learned. CHAPTER XIII. OCEAN CURRENTS AND ICEBERGS.