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Many of the most terrible accidents in the Alps have been due to avalanches, and perhaps, as avalanches take place from different causes and have various characteristics, according to whether they are of ice, snow, or débris, some account of them may not be out of place.

We may briefly classify them as follows:—

 1. Ice avalanches, only met with on or near glaciers.

 2. Dust avalanches, composed of very light, powdery snow.

 3. Compact avalanches (Grund or ground avalanches, as the Germans call them), consisting of snow, earth, stones, trees, and anything which the avalanche finds in its path. These take place only in winter and spring, while the two other kinds happen on the mountains at any season.

An ice avalanche is easily understood when it is borne in mind that a glacier is always moving. When this river of ice comes to the edge of a precipice, or tries to crawl down a very steep cliff, it splits across and forms tottering crags of ice, which lean over more and more till they lose their balance and go crashing down the slope. Some of the ice is crushed to powder by its fall, yet many blocks generally survive, and are occasionally heaped up in such huge masses below that they form another glacier on a small scale. If a party of mountaineers passes under a place overhung by threatening ice, they are in great danger, though at early morning, before the sun has loosened the frozen masses, the peril is less. Sometimes, too, if the distance to be traversed is very short and the going quite easy, it is safe enough to dash quickly across.

A Tunnel 300 feet long through an Avalanche.

Tree trunks, etc., can be seen embedded in it.

An Avalanche near Bouveret, Lake of Geneva.

Dust avalanches occur when a heavy fall of light, powdery snow takes place on frozen hillsides or ice-slopes, and so long as there is no wind or disturbance, all remains quiet, and inexperienced people would think there was no danger. But in reality dust avalanches are the most to be feared of any, for they fall irregularly in unexpected places, and their power is tremendous. While all seems calm and peaceful, suddenly a puff of wind or the passage of an animal disturbs the delicately-balanced masses, and then woe betide whoever is within reach of this frightful engine of destruction. First, the snow begins to slide gently down, then it gathers pace and volume, and even miles away the thunder of its fall can be heard as it leaps from ledge to ledge. Covered with a cloud of smoking, powdery dust, it is a veritable Niagara of giant height, and as it descends towards the forests, it carries with it whatever it finds in its path. Trees are mown down with as much ease as the tender grass of spring. Houses are lifted from the ground and tossed far away.

An avalanche is preceded by a blast even more destructive than the masses of snow which it hurls along. As it advances with ever-increasing rapidity the air in front is more and more compressed as the avalanche rushes on with lightning-like speed behind it. The wind sweeps everything before it, and many are the tales related by those who have survived or witnessed a display of its power. On one occasion more than a hundred houses were overwhelmed by a huge avalanche at Saas (Prättigau, near Davos), and during the search afterwards the rescue party found amidst the ruins a child lying asleep and uninjured in his cradle, which had been blown to some distance from his home, while close by stood a basket containing six eggs, none of which were broken. I have myself seen a row of telegraph posts in an Alpine valley in winter thrown flat on the ground by the air preceding an enormous avalanche, which itself did not come within 300 yards of them. It is a very wonderful thing that persons buried beneath an avalanche can sometimes hear every word spoken by a search party, and yet not a sound that they utter reaches the ears of those outside. A great deal of air is imprisoned between the particles of snow, and so it is possible for those overwhelmed by an avalanche to live inside it for hours. Cases have been known where a man, buried not far below the surface, has been able to melt a hole to the outer air with his breath, and eventually free himself from his icy prison. On 18th January, 1885, enormous avalanches fell in some of the mountainous districts of northern Italy, houses, cattle, crops, and granaries being carried away, and many victims buried beneath the ruins. Some touching episodes of wonderful escapes were related. "For instance, at Riva, in the valley of Susa, a whole family, consisting of an old woman of seventy, her two daughters, her four nieces, and a child four months old, were buried with their house in the snow, exposed apparently to certain death from cold and hunger. But the soldiers of the Compagnie Alpine, hearing of the sad case, worked with all their might and main to save them, and at last they were found and brought out alive, the brave old grandmother insisting that the children should be saved first, and then her daughters, saying that their lives were more precious than her own." The soldiers, who worked with a will above all praise, were obliged in several cases to construct long galleries in the snow in order to reach the villages, which were sometimes buried beneath 40 feet of snow.

Compact avalanches, though very terrible on account of their frequently great size, can be more easily guarded against than dust avalanches, because they always fall in well-defined channels. A compact avalanche consists of snow, earth, stones, and trees, and comes down in times of thaw. Many fall in early spring in Alpine valleys, and though it is not unusual for them to come right across high roads, the fatal accidents are comparatively few. The inhabitants know that wherever, high up on the hills, there is a hollow which may serve as a reservoir or collecting-basin for the snow, and below this a funnel or shoot, there an avalanche may be expected. Often they take means to prevent one starting, for an avalanche, whose power is irresistible when once it has begun to move quickly, is very easily kept from mischief if it is not allowed a running start. The best of all ways for preventing avalanches is to plant the gullies with trees, but where this cannot be done, rows of stakes driven into the ground will serve to hold up the snow, and where the hillside is extremely steep, and much damage would be caused if an avalanche fell, stone walls are built one above another to keep the soil and the snow together, very much as we see on precipitous banks overlooking English railways.

The driving roads over Alpine passes are in places exposed to avalanches in winter. At the worst spots galleries of stone are built, through which the sleighs can pass in perfect safety, and if an avalanche fell while they were inside it would pass harmlessly over their heads. On the Albula Pass, in Switzerland, as soon as the avalanches come down, tunnels are cut in the snow through them, and are in constant use till early summer.

Occasionally houses or churches are built in the very path of an avalanche. A V-shaped wall, called an avalanche-breaker, is put behind, and this cuts the snowy stream in two parts, which passes on harmlessly on either side of the building. Sometimes avalanche-breakers of snow, hardened into ice by throwing water over them, are constructed behind barns which have been put in exposed places.

In order that an avalanche may get up speed enough to commence its swift career, the slope the snow rests on where it starts must be at an angle of from 30° to 35° at least.