All this time their strange craft, though not floating, was borne slowly but steadily down stream by the force of the current. Every now and then it seemed as though about to capsize; and, had it been empty, it must certainly have done so; but its heavy load, acting like ballast in a boat, kept it upright. It headed in all directions, and at times, when its wheels could revolve on the bottom of the river, it moved steadily and rapidly. It was when it got turned broadside to the current that the two shivering figures, clutching at their uncertain support, became most apprehensive, and expected it to be overturned by the great pressure brought to bear against it.