The spike was covered, but the covering was shallow, for the current flowed from it in a rose-shaped spray.

If a man could get to that spike and could get a foot on it without being swept down, it might be possible--just possible--to do something with the wall of the chasm above the cave.

Of course I knew nothing about the nature of that wall.

It might be as smooth as a polished pillar.
The result of these cogitations was that I decided to prospect the right wall of the cave close to the waterfall.

But first I went rummaging in the back part to see if I could find anything to assist me.