We dashed on, the water hissing and bubbling and foaming round us, and had almost reached the bottom, when I felt the bow of the canoe strike something.  The next instant I found myself struggling in the seething waters, and instinctively striking out for dear life.  Looking down the stream, I caught a glance of the canoe being rapidly hurried downwards, with Mike clinging to it.  The next moment, he and the canoe had disappeared.