For one instant I paused to think whether I ought to venture.

Then I made up my mind, and dashed into it.
For you see, Peterkin, although I take some time to tell this, it happened in the space of a few seconds, so that I knew I had wind enough in me to serve to bring me out o' the hole and up to the surface again.
Well, I was just on the point of turning,--for I began to feel a little uncomfortable in such a place,--when it seemed to me as if there was a faint light right above me.

I darted upwards, and found my head out of water.

This relieved me greatly, for I now felt that I could take in air enough to enable me to return the way I came.

Then it all at once occurred to me that I might not be able to find the way out again; but, on glancing downwards, my mind was put quite at rest by seeing the green light below me streaming into the cave, just like the light that we had seen streaming out of it, only what I now saw was much brighter.
"At first I could scarcely see anything as I gazed around me, it was so dark; but gradually my eyes became accustomed to it, and I found that I was in a huge cave, part of the walls of which I observed on each side of me.