A familiar instance of the use of such inspection would be almost any great Welsh cliff or Irish sea cliff. Seen from below, it appears to be continuous steep slabs, with only vertical cracks for the climber; seen from above, it looks a jumble of vague cross-terraces of grass, snow or rock, hardly offering a chance of good articulated climbs. Both estimates would be false. Only by collating the two points of view can a fair judgment of the character of the climbing be formed. A number of delightful climbs, of late discovery, have owed their neglect to the fact that they were only easily visible from a single aspect, and that this produced an abiding false estimate of their quality. The importance of securing corrective views, from different angles, be it only of a section of a proposed route, or of a passage of similar character more conveniently situated, attaches also to our inspection of the half-seen on big ridges. With points to remember in such inspection I have already dealt.
It does, in fact, belong not a little to the reasoning from the seen to the unseen; to which more metaphysical division of reconnoitring it leads over.
The Unseen
The investigation of the unseen is a chief concern of mountaineers in new regions. But it can also be of service to the expert, in examining even a peak he knows well, to ascertain for him the condition of its invisible side on a particular day.
As I have said before, it is possible only to indicate where signs may be sought, and what relative differences the expert eye may discover and convert into information.
The mountaineer, after inspection of the near side of a ridge or summit in a big range, wishes to supplement this knowledge by the discovery of the character or general formation of the unseen side. He wishes to know whether it will give him snow of easier progress, or a subordinate ridge for better assault or descent; also whether he can look for clear rock on the far side, to assist his ascent of a ridge unfavourable in its visible aspects, or whether he must be prepared for ice slopes.
The first conditions for the inspection are experience, good glasses, clear sunlight and no recent snowfall. Also, if he wishes to confirm or increase the detail of his observations, he must be prepared to spend a whole day of good light, with the sun aiding him from different points in the sky.
As he looks over and across his high ridges from some distant view-point, in good sunlight, the mountaineer is able to distinguish several different kinds of sky, according to the different character of the unseen surfaces from which the sunlight is being reflected upward on to clear atmosphere or on to low clouds.
The Snow Sky.—This he will find has a distinguishable tint, identifiable by the practised eye, as different on a given day from the normal coloration of the sky above as is the light reflected from different qualities of steel, or from silver as compared with electroplate.
If the sky seen over his ridge is purely a snow sky, of uniform appearance, it is just to assume that the unseen side of the ridge consists of large snow slopes, and rises at a comparatively gentle angle, since we know already that upon broad surfaces, at a steep angle, snow can only rest while it remains new and adhesive.