There was no bridge across the Mississippi then, either at St. Louis or elsewhere. Great four-horse transfer coaches from the several hotels were waiting for passengers beside the train where it stopped, and these were borne to the opposite bank by a steam ferry-boat with a peculiar name and of peculiar construction. The _Cahokia_ looked like a regular river steamer, except that she had no visible paddle-wheels, not even one behind, like a wheelbarrow, as some of the very shoal-draught boats had. For some time Glen could not discover what made her go, though go she certainly did, moving swiftly and easily across the broad expanse of tawny waters towards the smoky city on its farther bank. He would not ask Mr. Hobart, for he loved to puzzle things out for himself if he possibly could. At length he discovered that the boat was double-hulled, and that its single paddle-wheel was located between the two hulls. Glen was obliged to ask the object of this; but when he was told that it was to protect the wheel from the great ice-cakes that floated down the river in winter, he wondered that he had not thought of that himself.