Read it through once

Finally we stood in a level, narrow valley (a valley that had been created by the terrific march of some old time irruption) and on either hand towered the two steep peaks of Vesuvius. The one we had to climb --the one that contains the active volcano--seemed about eight hundred or one thousand feet high, and looked almost too straight-up-and-down for any man to climb, and certainly no mule could climb it with a man on his back. Four of these native pirates will carry you to the top in a sedan chair, if you wish it, but suppose they were to slip and let you fall, --is it likely that you would ever stop rolling? Not this side of eternity, perhaps. We left the mules, sharpened our finger-nails, and began the ascent I have been writing about so long, at twenty minutes to six in the morning. The path led straight up a rugged sweep of loose chunks of pumice-stone, and for about every two steps forward we took, we slid back one. It was so excessively steep that we had to stop, every fifty or sixty steps, and rest a moment. To see our comrades, we had to look very nearly straight up at those above us, and very nearly straight down at those below. We stood on the summit at last--it had taken an hour and fifteen minutes to make the trip.