“But if we land above the town, how do we know the man owning the land on which we tie up won’t charge us just as much?” asked Irv Strong, who had never seen a large city and wanted to get as good a glimpse as he could of this one. “Because the Mississippi River and its tributaries are not ‘navigable’ waters, but _are_ ‘public highways for purposes of commerce,’” responded Ed. “If they weren’t that last, we couldn’t run this boat down them at all.” “Not navigable?” queried Will Moreraud. “Well, looking at that big steamboat out there, which has just come from Cincinnati, that statement seems a trifle absurd.” “Let me explain,” said Ed. “The English common law, from which we get ours, calls no stream ‘navigable’ unless the tide ebbs and flows in it. And as the tide does not ebb and flow in the Mississippi much above New Orleans, neither that great river nor any of its splendid tributaries are recognized by the law as navigable.” “Then the law is an idiot,” said Irv Strong. “One of Dickens’s characters said something like that,” responded Ed, “when he was told that the law supposes a married woman always acts under direction of her husband. But both he and you are wrong, particularly you, as you’ll see when I explain. It is absolutely necessary for the law to determine just how far a man’s ownership of land lying along a stream extends. You see that?” “Of course,” was the general response. “Yes,” continued Ed, “otherwise very perplexing questions would arise as to what a man might or might not do along shore. Now in England, where our law on the subject comes from, it is a fact that the tide ebbs and flows in all the navigable parts of the rivers and nowhere else. So the law made the tide the test, or rather recognized it as a test already established by nature. “Now in order that commerce might be carried on, the law decreed that the owner of land lying on a navigable stream should own only to the edge of the bank--or to the ‘natural break of the bank,’ as the law writers express it. This was to prevent owners of the shores from levying tribute on ships that might need to land or anchor in front of their property. “But on streams that were not navigable, no such need existed. On the contrary, it was very desirable, for many reasons, that the owners of the banks should be free to deal as they saw fit with the streams in front--to straighten or deepen them, and all that sort of thing. So the law decreed that on streams not navigable the owner of the bank should own to ‘the middle thread of the water,’ wherever that might happen to be.