As the moon climbed higher in the sky, I began to see that the slopes of the valley were not quite so perpendicular as I had imagined. Ledges and outcroppings of rock afforded fairly easy footholds for a descent, whilst after a drop of a few hundred feet, the declivity became very gradual. Urged on by an impulse which I cannot definitely analyse, I scrambled with difficulty down the rocks and stood on the gentler slope beneath, gazing into the Stygian deeps where no light had yet penetrated.