Page:Physical Geography of the Sea and its Meteorology.djvu/130

104 after day, and year after year, discharging immense volumes of water into the ocean. All the rivers run into the sea, yet the sea is not full."—Eccl. i. 7. Where do the waters so discharged go, and where do they come from? They come from their sources, is the ready answer. But whence are their sources supplied? for, unless what the fountain sends forth be returned to it again, it will fail and be dry. We see simply, in the waters that are discharged by these rivers, the amount by which the precipitation exceeds the evaporation throughout the whole extent of valley drained by them; and by precipitation I mean the total amount of water that falls from, or is deposited by the atmosphere, whether as dew, rain, hail, or snow. The springs of these rivers (§ 191) are supplied from the rains of heaven, and these rains are formed of vapours which are taken up from the sea, that "it be not full," and carried up to the mountains through the air. "Note the place whence the rivers come, thither they return again." Behold now the waters of the Amazon, of the Mississippi, the St. Lawrence, and all the great rivers of America, Europe, and Asia, lifted up by the atmosphere, and flowing in invisible streams back through the air to their sources among the hills (§ 191), and that through channels so regular, certain, and well-defined, that the quantity thus conveyed one year with the other is nearly the same: for that is the quantity which we see running down to the ocean through these rivers; and the quantity discharged annually by each river is, as far as we can judge, nearly a constant.

268. Powerful machinery.—We now begin to conceive what a powerful machine the atmosphere must be; and, though it is apparently so capricious and wayward in its movements, here is evidence of order and arrangement which we must admit, and proof which we cannot deny, that it performs this mighty office with regularity and certainty, and is therefore as obedient a law as is the steam-engine to the will of its builder. It, too, is an engine. The South Seas themselves, in all their vast intertropical extent, are the boiler for it, and the northern hemisphere is its condenser (§ 24). The mechanical power exerted by the air and the sun in lifting water from the earth, in transporting it from one place to another, and in letting it down again, is inconceivably great. The utilitarian who compares the waters power that the Falls of Niagara would afford if applied to machinery, is astonished at the number of figures which are