Belaying means making fast on a projection of rock a loop of the rope which is wound round one’s waist, and so disposing the weight of the body that, if the climber above or below happens to slip and fall, the belay will hold and the whole party will not go down together. Alpine rope has a breaking point of a third its own length. Only one member of the climbing team is moving at any given time, the others are belayed. Sometimes on a precipice it is necessary to move up fifty or sixty feet before finding a secure belay as a point from which to start the next upward movement, so that if the leader falls and is unable to put on a brake in any way he must fall more than twice that length before being pulled up. On the same day I was taken on a spectacular though not unusually difficult climb on Crib Goch. At one point we traversed round a knife-edge buttress. From this knife-edge a pillar-like bit of rock, technically known as a monolith, had split away. We scrambled up the monolith, which overhung the valley with a clear five hundred feet drop, and each in turn stood on the top and balanced. The next thing was to make a long, careful stride from the top of the monolith to the rock face; here there was a ledge just wide enough to take the toe of a boot, and a handhold at convenient height to give an easy pull-up to the next ledge. I remember George shouting down from above: ‘Be careful of that foothold, Robert. Don’t chip the edge off or the climb will be impossible for anyone who wants to do it again. It’s got to last another five hundred years at least.’ I was only in danger once. I was climbing with Porter on an out-of-the-way part of the mountain. The climb, known as the Ribbon Track and Girdle Traverse, had not been attempted for about ten years. About half-way up we came to a chimney. A chimney is a vertical fissure in the rock wide enough to admit the body; a crack is only wide enough to admit the boot. One works up a chimney sideways with back and knees, but up a crack with one’s face to the rock. Porter was leading and fifty feet above me in the chimney. In making a spring to a handhold slightly out of reach he dislodged a pile of stones that had been wedged in the chimney. They rattled down and one rather bigger than a cricket ball struck me on the head and knocked me out. Fortunately I was well belayed and Porter was already in safety. The rope held me up; I recovered my senses a few seconds later and was able to continue.