I always liked the little boy's definition of a river system. "Rivers that empty into other rivers that empty into other rivers that empty into the sea." What is still more interesting, the sea at the same time is emptying into the rivers; for the waters of all the lands and the waters of all the seas, are one, and what the rivers give to the sea the sea returns in the rain clouds that are blown landward by the winds. The Earth's waters are thus always in circulation like the blood in our bodies. In making this endless circuit they do an immense amount of useful and beautiful work, and have many strange and curious ways of doing it. It's a great family affair of the Waters people. Everybody has a hand in it, from the baby rill that toddles across the country road, the brook it meets in the meadow, the creek that runs through the wood, and the river into which it flows, to the greater river which carries forward these mingled waters to the sea. [Illustration: THE MISSISSIPPI RIVER SYSTEM] I. What I Brought Back from the Creek I met a rain-drop once that had followed the thing through, starting where a little creek began, and got such a load of information I could hardly carry it, about the wonderful part the rivers take and have taken in the making and remaking of the world. We see the April rains carve fairy canyons in the soft clay of the roadside or the creek, but it is hard to realize, as we stand on some pinnacle of the Alps and look out over the deep and wide valleys, the gorges, the cliffs, and mountains cut in two, that all are but the handiwork of the rain-drops banded together as flowing waters. For a long time this was questioned by scientific men, because the idea so upset the old theory that great changes in this world of ours came about all of a sudden and from causes not at work in these days. Now, however, nobody doubts that the big things are done by the little people, working together over long periods of time; little snowflakes, little rain-drops, little cells in plants. As a result, the Alps, so far as the expression of their faces is concerned, are as little like the Alps of the past as the face of the old farm of to-day is like the farm of those ancient yesterdays, when the brontosaurus browsed where old Dobbin is nipping the meadow grass and the mammoth ate the leaves of trees that stood where White Face is thoughtfully chewing her cud in the shade. [Illustration: HOW THEY STUDY GEOGRAPHY IN BOSTON This is what, in the Boston schools, they call an "umbrella party." "Umbrella party" sounds much more attractive than "geography lesson," but as a matter of fact it is a geography lesson and a fine one. As soon as they get off that brick pavement the boys and girls will see those rain-drops cutting out little Mississippi River systems, filling little Great Lakes, plunging over Niagaras two inches high! ]