Did the reader ever see a medical or anatomical chart of the human body, showing the arteries and veins that carry the blood from our hearts to every main and every minute part of our bodies? How like a tree it looks, with its main stem or trunk, with its great branches, with its delicate boughs and switches and twigs. Well, a Croton-water chart of the system by which a river is brought to our bedrooms, instead of our having to go to the river with our buckets, would be just such another complicated, marvellous, treelike object, only I really think it would be more astonishing in one sense, because it is so wholly the hard brain-work of man instead of the mysterious divine creation of the Almighty, whose works are so profound that their wonders do not surprise us so much as when man produces something a tenth part or a thousandth part as extraordinary. If we could cut away all the earth of the island, leaving the water-mains bare, and if we could tear down all the buildings of the city so as to allow the water-pipes to stand up, bare and naked, just as they now stand up in their covers of brick and plaster, I suppose the sight of that wonderful forest of big and little pipes would be as surprising as anything that any human being ever saw. Just try to fancy Manhattan Island all under a tangle of towering pipes and crisscrossed tubes, and then, while we are about it, just fancy a lot of savages landing here and tampering with those pipes until one of them should touch some cock and turn on the water. What a rain there would be, in big streams and middling streams and tiny little streams, out of millions of fixtures! No shower bath that was ever conceived or heard of would compare with it. And yet--see how small and weak man is, after all--it would not begin to equal an ordinary rain-storm. Of water mains--or big pipes sunk in the streets to distribute the Croton water from the reservoirs--there are no less than 715 miles, but when the reader thinks how at every twenty-five feet smaller pipes branch out of the mains to carry the water to every floor of every building and sometimes to every office or room, he will see that of smaller pipes there must be tens of thousands of miles, making up that grand tree which is as much the "tree of life" of a great city as the arterial system is the tree of life of each of our bodies. To carry off the water that courses through all these thousands of miles of pipes we have 456 miles of sewers--or much bigger pipes; some of which men can walk through or even paddle a boat in. [Illustration: AQUEDUCT TUNNEL UNDER THE HARLEM.]