My knowledge came into play at this time.

I took my felt hat and put it over my mouth, and then tied it around my neck so that the felt rim came over my cheeks and throat.

Thus I secured a plentiful supply of air, and the felt acted as a kind of ventilator to prevent the access to my lungs of too much of the sulphurous vapor.

Of course such a contrivance would not be good for more than five minutes; but then, you know, five minutes were all that I wanted.
"So up I rushed, and, as the slope was only about a hundred feet, I soon reached the top.

Here I could see nothing whatever.