As has been already stated, the first of the great snow-storms that replenish the Yosemite fountains seldom sets in before the end of November. Then, warned by the sky, wide-awake mountaineers, together with the deer and most of the birds, make haste to the lowlands or foothills; and burrowing marmots, mountain beavers, wood-rats, and other small mountain people, go into winter quarters, some of them not again to see the light of day until the general awakening and resurrection of the spring in June or July. The fertile clouds, drooping and condensing in brooding silence, seem to be thoughtfully examining the forests and streams with reference to the work that lies before them. At length, all their plans perfected, tufted flakes and single starry crystals come in sight, solemnly swirling and glinting to their blessed appointed places; and soon the busy throng fills the sky and makes darkness like night. The first heavy fall is usually from about two to four feet in depth then with intervals of days or weeks of bright weather storm succeeds storm, heaping snow on snow, until thirty to fifty feet has fallen. But on account of its settling and compacting, and waste from melting and evaporation, the average depth actually found at any time seldom exceeds ten feet in the forest regions, or fifteen feet along the slopes of the summit peaks. After snow-storms come avalanches, varying greatly in form, size, behavior and in the songs they sing; some on the smooth slopes of the mountains are short and broad; others long and river-like in the side cañons of yosemites and in the main cañons, flowing in regular channels and booming like waterfalls, while countless smaller ones fall everywhere from laden trees and rocks and lofty cañon walls. Most delightful it is to stand in the middle of Yosemite on still clear mornings after snow-storms and watch the throng of avalanches as they come down, rejoicing, to their places, whispering, thrilling like birds, or booming and roaring like thunder. The noble yellow pines stand hushed and motionless as if under a spell until the morning sunshine begins to sift through their laden spires; then the dense masses on the ends of the leafy branches begin to shift and fall, those from the upper branches striking the lower ones in succession, enveloping each tree in a hollow conical avalanche of fairy fineness; while the relieved branches spring up and wave with startling effect in the general stillness, as if each tree was moving of its own volition. Hundreds of broad cloud-shaped masses may also be seen, leaping over the brows of the cliffs from great heights, descending at first with regular avalanche speed until, worn into dust by friction, they float in front of the precipices like irised clouds. Those which descend from the brow of El Capitan are particularly fine; but most of the great Yosemite avalanches flow in regular channels like cascades and waterfalls. When the snow first gives way on the upper slopes of their basins, a dull rushing, rumbling sound is heard which rapidly increases and seems to draw nearer with appalling intensity of tone. Presently the white flood comes bounding into sight over bosses and sheer places, leaping from bench to bench, spreading and narrowing and throwing off clouds of whirling dust like the spray of foaming cataracts. Compared with waterfalls and cascades, avalanches are short-lived, few of them lasting more than a minute or two, and the sharp, clashing sounds so common in falling water are mostly wanting; but in their low massy thundertones and purple-tinged whiteness, and in their dress, gait, gestures and general behavior, they are much alike.
Besides these common after-storm avalanches that are to be found not only in the Yosemite but in all the deep, sheer-walled cañon of the Range there are two other important kinds, which may be called annual and century avalanches, which still further enrich the scenery. The only place about the Valley where one may be sure to see the annual kind is on the north slope of Clouds Rest. They are composed of heavy, compacted snow, which has been subjected to frequent alternations of freezing and thawing. They are developed on cañon and mountain-sides at an elevation of from nine to ten thousand feet, where the slopes are inclined at an angle too low to shed off the dry winter snow, and which accumulates until the spring thaws sap their foundations and make them slippery; then away in grand style go the ponderous icy masses without any fine snow-dust. Those of Clouds Rest descend like thunderbolts for more than a mile.
The great century avalanches and the kind that mow wide swaths through the upper forests occur on mountain-sides about ten or twelve thousand feet high, where under ordinary weather conditions the snow accumulated from winter to winter lies at rest for many years, allowing trees, fifty to a hundred feet high, to grow undisturbed on the slopes beneath them. On their way down through the woods they seldom fail to make a perfectly clean sweep, stripping off the soil as well as the trees, clearing paths two or three hundred yards wide from the timber line to the glacier meadows or lakes, and piling their uprooted trees, head downward, in rows along the sides of the gaps like lateral moraines. Scars and broken branches of the trees standing on the sides of the gaps record the depth of the overwhelming flood; and when we come to count the annual wood-rings on the uprooted trees we learn that some of these immense avalanches occur only once in a century or even at still wider intervals.
Few Yosemite visitors ever see snow avalanches and fewer still know the exhilaration of riding on them. In all my mountaineering I have enjoyed only one avalanche ride, and the start was so sudden and the end came so soon I had but little time to think of the danger that attends this sort of travel, though at such times one thinks fast. One fine Yosemite morning after a heavy snowfall, being eager to see as many avalanches as possible and wide views of the forest and summit peaks in their new white robes before the sunshine had time to change them, I set out early to climb by a side cañon to the top of a commanding ridge a little over three thousand feet above the Valley. On account of the looseness of the snow that blocked the cañon I knew the climb would require a long time, some three or four hours as I estimated; but it proved far more difficult than I had anticipated. Most of the way I sank waist deep, almost out of sight in some places. After spending the whole day to within half an hour or so of sundown, I was still several hundred feet below the summit. Then my hopes were reduced to getting up in time to see the sunset. But I was not to get summit views of any sort that day, for deep trampling near the cañon head, where the snow was strained, started an avalanche, and I was swished down to the foot of the cañon as if by enchantment. The wallowing ascent had taken nearly all day, the descent only about a minute. When the avalanche started I threw myself on my back and spread my arms to try to keep from sinking. Fortunately, though the grade of the cañon is very steep, it is not interrupted by precipices large enough to cause outbounding or free plunging. On no part of the rush was I buried. I was only moderately imbedded on the surface or at times a little below it, and covered with a veil of back-streaming dust particles; and as the whole mass beneath and about me joined in the flight there was no friction, though I was tossed here and there and lurched from side to side. When the avalanche swedged and came to rest I found myself on top of the crumpled pile without bruise or scar. This was a fine experience. Hawthorne says somewhere that steam has spiritualized travel; though unspiritual smells, smoke, etc., still attend steam travel. This flight in what might be called a milky way of snow-stars was the most spiritual and exhilarating of all the modes of motion I have ever experienced. Elijah's flight in a chariot of fire could hardly have been more gloriously exciting.
In the spring, after all the avalanches are down and the snow is melting fast, then all the Yosemite streams, from their fountains to their falls, sing their grandest songs. Countless rills make haste to the rivers, running and singing soon after sunrise, louder and louder with increasing volume until sundown; then they gradually fail through the frosty hours of the night. In this way the volume of the upper branches of the river is nearly doubled during the day, rising and falling as regularly as the tides of the sea. Then the Merced overflows its banks, flooding the meadows, sometimes almost from wall to wall in some places, beginning to rise towards sundown just when the streams on the fountains are beginning to diminish, the difference in time of the daily rise and fall being caused by the distance the upper flood streams have to travel before reaching the Valley. In the warmest weather they seem fairly to shout for joy and clash their upleaping waters together like clapping of hands; racing down the cañons with white manes flying in glorious exuberance of strength, compelling huge, sleeping boulders to wake up and join in their dance and song, to swell their exulting chorus.
In early summer, after the flood season, the Yosemite streams are in their prime, running crystal clear, deep and full but not overflowing their banks -- about as deep through the night as the day, the difference in volume so marked in spring being now too slight to be noticed. Nearly all the weather is cloudless and everything is at its brightest -- lake, river, garden and forest with all their life. Most of the plants are in full flower. The blessed ouzels have built their mossy huts and are now singing their best songs with the streams.
In tranquil, mellow autumn, when the year's work is about done and the fruits are ripe, birds and seeds out of their nests, and all the landscape is glowing like a benevolent countenance, then the streams are at their lowest ebb, with scarce a memory left of their wild spring floods. The small tributaries that do not reach back to the lasting snow fountains of the summit peaks shrink to whispering, tinkling currents. After the snow is gone from the basins, excepting occasional thundershowers, they are now fed only by small springs whose waters are mostly evaporated in passing over miles of warm pavements, and in feeling their way slowly from pool to pool through the midst of boulders and sand. Even the main rivers are so low they may easily be forded, and their grand falls and cascades, now gentle and approachable, have waned to sheets of embroidery.