It must be remembered that on these summits all traces of a path as a rule disappear. What is worse, indications of a path may begin on the other side into the wrong valley and not into the right one.
A second type of this peril is that in which some feature upon the ridge which looks quite unimportant upon the one side turns out to be all-important upon the other. Thus a man coming from A in the map below, where the valleys are hatched and the highest summits are black, would have before him the plain ridge B-C. It is indifferent where he crosses it from that side, but on the far side he finds a confusion of falling valleys, and if he does not pick out the right one he may find himself in a few hours shut in by high walls which constrain him to a journey he never meant to make. He may have intended to follow valley (1), and so to reach food and shelter, he may find himself in valley (2) caught for the night far from men and with walls of 3000 feet between him and them.
Sometimes this confusion takes the form of one’s being led on to an obvious notch in the ridge before one: a notch lower than the general line of the ridge which (one thinks) cannot but be the port. When one has climbed to it, however, one finds that the valley one was seeking lies far to the right or to the left of such a notch, and that the gap which was so noticeable on the one side of the pass corresponded to nothing useful upon the further side.
There is a good example of this under the peak called Negras where an obvious notch which one thinks surely must be the way over to the Gallego, leads to nothing more useful than an enclosed Tarn under the precipices of the mountains.
A sketch of the aspect of this particular ridge will make the difficulty plain.
All the contours upon the Aragonese side invite one to the notch at N, yet the true way lies over the ridge between A and B, and the nearer to B the better is the descent upon the further side. Indeed at A it is perilous, at B it is a very gradual descent of easy grass.