Declimb

It has saddled us with an insoluble puzzle: How to declimb from heights that make us dizzy and that we cannot endure forever without slipping into an incalculable slide that we can [not] arrest with all existing brakes[…]

I had been told that, if the principal really didn't like you, he would assign you five classrooms, one for each period and each on different floors, so that you might find yourself climbing and declimbing four flights of stairs, plus descending to the half basement, whose windows were half-covered with snow during the winter and tall grass the rest of the time.