“All the rivers” meant to him a great many streams, large and small, in southern Asia, and in southern Europe, with some in northern Africa. “All the rivers” of the world now—— Let us see what it means.
The chief work of a river is to drain the land; to bear superfluous waters into the great deep. Water lying stagnant on land becomes harmful. Immense supplies are perpetually needed; but it must be fresh water, clear water, running water, water newly fallen from the skies, or newly received from ever fresh because ever renewed springs. Never stagnant water.
So Earth’s rivers—we are talking of land-rivers now—gathering to themselves the multitude of lesser streams and tributaries, which in their turn have been earlier fed by an infinite number of burns and runnels in country and town, hurry downward to the Ocean, with rich presents from the Land. But all the while, Land expects “to receive as much again.”
When we stand beside a broad river, watching the steady flow, hearing the little murmurs of sound and the soft suck and “swish” against the banks, we do not often realise the greatness of the task which that river may have in hand.
Suppose we are on the banks of the Seine, the mother-stream of gay Paris. Many a century has Paris lived; but the Seine existed countless centuries before Paris was ever heard of. Year by year the Seine drains away surplus water from some twenty-three thousand square miles of French territory. Year by year the Seine carries down to the Ocean a gift of more than five cubic miles of water. Five hundred cubic miles in the course of a century!
Or suppose we turn to the Rhine, that river of castles and legends, which starts with the meltings of over one hundred and fifty glaciers, and is said to be fed in its course by something like twelve thousand lesser streams. The Rhine drains, at the very least, between thirty and forty thousand square miles of country; and it pays to the Ocean an annual tribute of more than ten cubic miles of water. More than a thousand cubic miles each hundred years.
Let us take a look at the Yangtsekiang—a Chinese river of special interest for British trade. It drains over six hundred and fifty thousand square miles of land; and each year it hands over to the Ocean more than one hundred and twenty-five cubic miles of water.
See the Mississippi. More than a million square miles of American territory are drained by it; and its annual gift to the Ocean amounts, like that of the great Chinese river, to over one hundred and twenty-five cubic miles of water.
Or once more—take the Amazon. By that mighty stream more than two million square miles of land are drained; and more than five hundred cubic miles of water are poured annually into the sea. So the Amazon presents to the Ocean in the course of a year what the Seine presents in the course of a century.
It has been reckoned that “all the rivers” of Earth combined pour every year into the sea a mass of water equal to about six thousand five hundred cubic miles. This would suffice to fill a vast tank, one mile broad, one mile deep, reaching the whole way from the north of Scotland to the south of Africa.