For several thousand feet down, as far as the 10,000-foot level, in fact, does the snow retain this granular consistency. One reason for the slowness with which it compacts is found in the low temperatures that prevail at high altitudes and preclude any considerable melting. The air itself seldom rises above the freezing point, even in the middle of the day, and as a consequence the snow never becomes soft and mushy, as it does at lower levels.
When snow assumes the mushy, "wet-sugar" state, it is melting internally as well as at its outer surface, owing both to the water that soaks into it and to the warming of the air inclosed within its innumerable tiny pores (which tiny air spaces, by the way, give the snow its brilliant whiteness). Snow in this condition has, paradoxical though it may sound, a temperature a few tenths of a degree higher than the melting point—a fact recently established by delicate temperature measurements made on European glaciers. It is this singular fact, no doubt, that explains how so many minute organisms are able to flourish and propagate in summer on the lower portions of many glaciers. It may be of interest to digress here briefly in order to speak of these little known though common forms of life.
Several species of insects are among the regular inhabitants of glaciers. Most of them belong to a very low order—the Springtails, or Thysanura—and are so minute that in spite of their dark color they escape the attention of most passers-by. If one looks closely, however, they may readily be observed hopping about like miniature fleas or wriggling deftly into the cavities of the snow. It seems to incommode them but little if in their acrobatic jumps they occasionally alight in a puddle or in a rill, for they are thickly clad with furry scales that prevent them from getting wet—just as a duck is kept dry by its greasy feathers.
Especially plentiful on the lower parts of the Rainier glaciers, and more readily recognized, are slender dark-brown worms of the genus Mesenchytraeus, about 1 inch in length. Millions and millions of them may be seen on favorable days in July and August writhing on the surface of the ice, evidently breeding there and feeding on organic matter blown upon the glacier in the form of dust. So essential to their existence is the chill of the ice that they enter several inches, and sometimes many feet below the surface on days when the sun is particularly hot, reappearing late in the afternoon.
Mention also deserves to be made of that microscopic plant Protococcus nivalis, which is responsible for the mysterious pink or light, rose-colored patches so often met with on glaciers—the "red snow" of a former superstition. Each patch represents a colony or culture comprising billions of individuals. It is probable that they represent but a small fraction of the total microflora thriving on the snow, the other species remaining invisible for lack of a conspicuous color.
To return to the frigid upper névés, it is not to be supposed that they suffer no loss whatever by melting. The heat radiated directly to them by the sun is alone capable of doing considerable damage, even while the air remains below the freezing point. At these high altitudes the sun heat is astonishingly intense, as more than one uninitiated mountain climber has learned to his sorrow by neglecting to take the customary precaution of blacking his face before making the ascent. In a few hours the skin is literally scorched and begins to blister painfully.
At the foot of the mountain the sun heat is relatively feeble, for much of it is absorbed by the dust and vapor in the lower layers of the atmosphere, but on the summit, which projects 2 miles higher, the air is thin and pure, and lets the rays pass through but little diminished in strength.
The manner in which the sun affects the snow is peculiar and distinctive. Instead of reducing the surface evenly, it melts out many close-set cups and hollows, a foot or more in diameter and separated by sharp spires and crests. No water is visible anywhere, either in rills or in pools, evaporation keeping pace with the reduction. If the sun's action is permitted to continue uninterrupted for many days, as may happen in a hot, dry summer, these snow cups deepen by degrees, until at length they assume the aspect of gigantic bee cells, several feet in depth. Snow fields thus honeycombed may be met with on the slopes above Gibraltar Rock. They are wearisome to traverse, for the ridges and spines are fairly resistant, so that one must laboriously clamber over them. Most exasperating, however, is the going after a snowstorm has filled the honeycombs. Then the traveler, waist deep in mealy snow, is left to flounder haphazard through a hidden labyrinth.
Of interest in this connection is the great snow cliff immediately west of Gibraltar Rock. Viewed from the foot of that promontory, the sky line of the snow castle fairly bristles with honeycomb spines; while below, in the face of the snow cliff, dark, wavy lines, roughly parallel to the upper surface, repeat its pattern in subdued form. They represent the honeycombs of previous seasons, now buried under many feet of snow, but still traceable by the dust that was imprisoned with them.
The snow cliff west of Gibraltar Rock is of interest also for other reasons. It is the end of a great snow cascade that descends from the rim of the old crater. Several such cascades may be seen on the south side of the mountain, separated by craggy remnants of the crater rim. Above them the summit névés stretch in continuous fields, but from the rim on down, the volcano's slopes are too precipitous to permit a gradual descent, and the névés break into wild cascades and falls. Fully two to three thousand feet they tumble, assembling again in compact, sluggish ice fields on the gentler slopes below.