Old powdery snow, as contrasted with new snow, has a greyer tint when seen from a distance, particularly if not seen in direct sunlight.
Old wet snow, laborious to cross, and deciduous according to its angle, shows a bluish, luminous surface light, especially in its depressions. It is often transected by visible lines of strain or cleavage.
A thawing snow surface, seen from near, is dull and drenched looking, or pitted with small holes.
Surface hard-crusts, or plates, produced alike by wind and sun, which afford pleasant going but possess the avalanche potentiality if the angle is steep and their attachment to the surface below is slight, generally mark themselves off from the surrounding snow slopes by a lower, duller tone; sometimes they are tinged with a yellow shade. The plates vary in thickness, deepening towards the middle, and they can often be recognized by their edges, which run out on the neighbouring snow in darker wavelets, sometimes with eyebrow-markings round their curves.
Old hard snow, of deep attachment and sound progress, lies in alternating wave and hollow of different tones of light and shade, where the sun has been at work on the surface. It is often dust-speckled, or shows bluish finger-prints.
Granulated snow, in strong light, may show bright or prismatic reflections from its facets, similar to, but easily distinguishable from, granular ice prisms.
As confirmation, or correction, of what distant observation may have revealed about the character of ice or snow surfaces, general considerations must also be taken into account: the recency of the snowfall, the subsequent weather, etc. There is also the final test of touch, which is made on the spot, before any snow slope is traversed. The change in the condition of the snow, which may be produced by a day of sun before we can return down the slope, must not be left out of the calculation. Many slopes whose surface may be adjudged and found safe for passage in the early morning cannot be trusted by nightfall.
Angle on Snow.
It is essential to be able to judge of the inclination of a slope; for some harmless conditions may become dangerous if the snow is lying at above a certain angle. New snow, for instance, has been known to slide at as low an angle as twenty degrees. Hard old snow, melted and refrozen, may be supported in small patches, and remain reliable, at as high an angle as sixty degrees.
The power to estimate the angle of a slope by the eye only comes with practice. Most slopes look precipitous in face. But a mountaineer who has trained his eye by first going round to see a number of such slopes in profile, and by then returning to see them in face, has learned what he must deduct from an apparent angle. He is then qualified to make a truer estimate of the real angle of slopes which he may be able to examine in face alone.