Snowmelt

“ It is the air entangled among the snow crystals, then, which makes the snow blanket, as we often call it, so sure a protection from cold. The ground may have frozen to a considerable depth before the snow comes, but if it stays throughout the winter there is no frost in the earth beneath it when the spring melts it away. No sooner is the ground protected from further freezing from above than the greater warmth below begins to melt the frost and change it to life-giving moisture. ”

“ In summer these layers of snow, from a partial melting and subsequent freezing, become changed to ice on their surfaces, so that we have three kinds of deposits—beds of snow, sheets of dust, and layers of ice. As the whole is pushed down into the valley, these layers tend to assume a vertical position from the bottom of the mass, moving faster than the top; and, the snow in summer melting from the surface as far as the snow-line, the edges of the layers are found passing transversely across the glacier. ”

“ The use of clouds in the formation of rain, is too obvious to need pointing out more particularly. Snow is frozen vapour aggregated by a confused action of crystalline laws, and ice is water, solidified while in its fluid state, by the same crystalline forces. These are bad conductors of cold, and when the ground is covered with snow, or the surface of the soil, or if the water is frozen, the roots or bulbs of plants beneath are protected by the congealed water from the influence of the atmosphere, the temperature of which in northern winters, is usually very much below the freezing point ”

“ The frosts are severe at night, and the meadow grass turns dry and wan. The last lilac crocuses die upon the fields. Icicles, hanging from watercourse or mill-wheel, glitter in the noonday sunlight. The wind blows keenly from the north, and now the snow begins to fall and thaw and freeze, and fall and thaw again. The seasons are confused; wonderful days of flawless purity are intermingled with storm and gloom. At last the time comes when a great snowfall has to be expected. There is hard frost in the early morning, and at nine o'clock the thermometer stands at 2°. ”

“ Water runs over them only in the spring, in the rare cases when they have been pressed down smoothly and compactly by the weight of the snow—a state in which they remain only until they are dry, when shrinkage and the action of the wind soon roughen the surface so as effectually to stop, by absorption, all flow of water. I have observed that when a sudden frost succeeds a thaw at the close of the winter, after the snow has principally disappeared, the water in and between the layers of leaves sometimes freezes into a solid crust, which allows the flow of water over it. ”

“ Frost pricked the taste to each breath. Endless reaches of frost were all that met the sight. Frost-crackling the only sound. Frost in one's throat like a drink of water, and the tingle of the frost in the blood with a leap that was fulness of life.
Up drifts with the help of our muskets! Down hills with a rush of snow-shoes that set the powdery snow flying! Skimming the levels with the silent speed of wings! Past the snow mushrooms topping underbrush and the snow cones of the evergreens and the snow billows of under rocks and the snow-wreathed antlers of the naked forest in a world of snow! ”

“ Other things, such as stones, are melted only by terrific heat.
When the little particles of water that make up the clouds become very cold, they freeze as they gather and so make snowflakes. When the little particles of water in the air, that usually make dew, freeze while they are gathering on a blade of grass, we call it frost. When [pg 98] raindrops are carried up into colder, higher air while they are forming, they freeze and turn to hail. When snow or frost or hail or ice is heated, it melts and turns back to water. ”

“ The gale had hardly been blowing for ten or fifteen minutes, when the snow began to whirl down. It came in the tiniest possible flakes, consisting this time of short needles that looked like miniature spindles, strung with the smallest imaginable globules of ice—no six-armed crystals that I could find so far. Many a snowstorm begins that way with us. And there was even here, in the chasm of the road, a swing and dance to the flakes that bespoke the force of the wind above. ”

“ Or suppose a fresh layer of light porous snow to have accumulated above one the surface of which has already been slightly glazed with frost; rain or dew, falling upon the upper one, will easily penetrate it; but when it reaches the lower one, it will be stopped by the film of ice already formed, and under a sufficiently low temperature, it will be frozen between the two. This result may be frequently noticed in winter, on the plains, where sudden changes of temperature take place. ”

“ Suddenly it tears up a few hundred thousand cubic feet of this snow, and whirls it up high into the air, leaving it to the mercy of the upper current, to fall to the ground again in the form of the thickest snow-storm, or to be dispersed at will like glittering ice-crystals. At times the wind sweeps up large tracts of the dry ice-dust, and pours them down upon a deep-lying valley amid the mountains, or on to the summit of the passes, obliterating in a few seconds the laboriously excavated mountain road, at which a whole company of rutners have toiled for days. ”

“ The fresh fall of snow, which had come over night, was exceedingly slight. It had come down softly, floatingly, with all the winds of the prairies hushed, every flake consisting of one or two large, flat crystals only, which, on account of the nearly saturated air, had gone on growing by condensation till they touched the ground. Such a condition of the atmosphere never holds out in a prolonged snowfall, may it come down ever so soft-footedly; the first half hour exhausts the moisture content of the air. ”

“ Nothing, indeed, can be more fascinating than the new world revealed by frost. In shaded places of the valley you may walk through larches and leafless alder thickets by silent farms, all silvered over with hoar spangles—fairy forests, where the flowers and foliage are rime. The streams are flowing half-frozen over rocks sheeted with opaque green ice. Here it is strange to watch the swirl of water freeing itself from these frost-shackles, and to see it eddying beneath the overhanging eaves of frailest crystal-frosted snow. ”

“ The hard snow-crust, which in the early spring is a source of such keen enjoyment to the children and youth of the North—and to many older persons in whom the love of nature has kept awake a relish for the simple pleasures of rural life—is doubtless due to the congelation of the vapor condensed by the snow rather than to the thawing and freezing of the superficial stratum; for when the surface is melted by the sun, the water is taken up by the absorbent mass beneath before the temperature falls low enough to freeze it. ”

“ If cold it cools the air and the earth somewhat while passing through or over them, but produces no permanent effect on temperature, because a few hours of sunshine restore to the air or the surface-soil all the heat they had lost. But if snow falls for a long time, the effect, as we all know, is very different, because it has no mobility. It remains where it fell and becomes compacted into a mass, and it then keeps the earth below it and the air above, at or near the freezing-point till it is all melted. ”

“ The Usefulness of Snow.—Snow, as it is well known, is a great impediment to the inroads of frost into anything enveloped by it. A covering of snow on an ice field is a great impediment to the escape of heat from the water, as well as protecting the ice from the direct action of the cold air, and greatly retards the growth of the ice. It is essential to remove this snow as early as practicable, as the ice harvester has always in view a possible thaw or rain, and endeavors to secure his crop at the earliest practicable moment. ”

“ The conditions favorable to glaciation are, therefore, heavy precipitation and low annual temperature. If the precipitation is scanty, the small snowfall is soon melted; and if the temperature be too high, the moisture is precipitated not in the form of snow but as rain. It is important here to keep in mind that snow is a poor heat conductor and itself protects its deeper layers from melting. ”

“ With southerly winds, near the borders of the ice, or in situations where humid air, blowing from the sea, assimilates with a gelid breeze from the ice, the heaviest falls of snow occur. In this case, a depth of two or three inches is sometimes deposited in an hour. The thickest precipitations also frequently precede sudden storms. The form of the particles of snow presents an endless variety. When the temperature of the air is within a degree or two of the freezing point, much snow falls, frequently consisting of large irregular flakes, such as are common in Britain. ”

“ Ice formed in the atmosphere, and descending to the ground in the form of hail, often causes great destruction to vegetation and not infrequently to animal life. Where the frozen moisture reaches the earth as snow, it serves to protect rock, soil and vegetation from the effects of frost; but on sloping ground it is apt to give rise to destructive avalanches or landslips, while indirectly, by its rapid melting, it may cause serious floods in rivers. ”

“ It blows under at all seasons of the year, but most readily and strongly from a surface of snow whose electricity is always positive. Hence it blows most strongly and continuously when snow has fallen at the north, and prevails during winter very much in proportion to the extent and continuance of the covering of snow which invests the earth in that direction. It follows after storms, and particularly warm rains, during the autumn, winter, and spring months, which have a lateral southern extension. ”

“ The former contribute much to the seeker after the picturesque in Nature, and the latter are a source of joy to the true alpine enthusiast. Both effects are from the same cause, viz.: the large amount of precipitation deposited in the form of snow, accumulating from year's end to year's end until the entire cap of the range appears in perspective as an endless succession of snow-fields, with precipitous black faces of rock rising at intervals from their midst, where the sheer is too steep for snow to lie. ”

“ When the ground is cleared and brought under cultivation, the leaves are ploughed into the soil and decomposed, and the snow, especially upon knolls and eminences, is blown off, or perhaps half thawed, several times during the winter. The water from the melting snow runs into the depressions, and when, after a day or two of warm sunshine or tepid rain, the cold returns, it is consolidated to ice, and the bared ridges and swells of earth are deeply frozen. ”

“ No doubt a certain proportion of the snow is given off to the atmosphere by direct evaporation, but in the woods, the protection against the sun by even leafless trees prevents much loss in this way, and besides, the snow receives much moisture from the air by absorption and condensation. Very little water runs off in the winter by superficial water-courses, except in rare cases of sudden thaw, and there can be no question that much the greater part of the snow deposited in the forest is slowly melted and absorbed by the earth. ”

“ The snow which falls in great volume upon mountains is a dry powdery mass, and cannot be consolidated until some liquefaction has taken place. This quickly occurs. Through the clear air of great altitudes the sun's rays fall with intense power upon objects, even while the temperature is at freezing in the shade. Portions of the surface snows are thus melted, the under portions are moistened by the percolating waters, and regelation begins. ”

“ These layers of ice become numerous and are parallel to each other, like the layers of ice formed from slosh. Such crusts of ice I have myself observed again and again upon the glacier. This stratified snowy ice is now the bottom on which the first autumnal snow-falls accumulate. These sheets of ice may be formed not only annually before the winter snows set in, but may recur at intervals whenever water accumulating upon an extensive snow-surface, either in consequence of melting or of rain, is frozen under a sharp frost before another deposit of snow takes place. ”

“ The temperature rises daily in the interval; the winter fall of snow, which has so long shrouded the gaunt hills and lain upon the valleys, rolls up before the rays of the rising sun; and the melted snow pours in noisy torrents and flashing cascades through the rugged ravines and over the dark sides of the lofty cliffs: everywhere the air resounds with the din of falling waters. ”

“ It frequently happens that a powerful thaw sets in after a long period of frost, and the snow which had been months in accumulating is dissolved and carried off in a few hours. When the snow is deep, it, to use a popular expression, "takes the frost out of the ground" in the woods, and, if it lies long enough, in the fields also. But the heaviest snows usually fall after midwinter, and are succeeded by warm rains or sunshine, which dissolve the snow on the cleared land before it has had time to act upon the frost-bound soil beneath it. ”

“ In lesser quantities, it may be started by wind or by an incautious passage. On ice or rock it is never stable, until it has been cleared away or melted and refrozen.
New snow, as a wet powder on rocks, is desperately chilly for the hands, and has the disagreeable quality of transforming itself into an ice glaze under the pressure of the boots or the glove. If we are caught out by a fall of new wet snow on rock, ice-claws will protect our foothold, but nothing will save the hands. ”