It is a curious fact that these gales are often confined to the crests of the mountains, so that the wind may be raging among the peaks while a few hundred feet lower down there is comparative calm.
The chief of the prevailing winds in the Alps is the Föhn. This is a hot blast from the south which probably comes from the African deserts. On its approach the air becomes close and stifling, the sky, at first of unusual clearness, gradually thickens to a muddy and murky hue, animals become restless and disquieted by the unnatural dryness of the hot blast which now comes sweeping over the hills. In some villages, it is said, all the fires are extinguished when this wind begins to blow, for fear lest some chance spark should fall on the dry wooden roofs and set the whole place in a blaze. Still the Föhn is not altogether an "ill wind that blows nobody any good," for under its warm touch the winter snows melt away with marvellous rapidity. In the valley of Grindelwald it causes a snow-bed two feet thick to disappear in about a couple of hours, and produces in twenty-four hours a greater effect than the sun does in fifteen days. There is a Swiss proverb which rather profanely says: "If the Föhn does not blow, the golden sun and the good God can do nothing with the snow."
In summer-time, however, the south wind is never welcome, for the vapour which it brings from the Italian plains is condensed by the snows of the Alps, and streams down in torrents of rain.
A thunder-storm is always a grand spectacle. Among mountains such storms are more frequent than on the plains, and also, as might be expected, far more magnificent, especially at night. Flashes, or rather sheets, of unutterable brilliancy light up the sky; distant chains of mountains are revealed for a moment, only to be instantly eclipsed by the pall of night. Says Professor Bonney,—
"No words can adequately express the awful grandeur of these tempests when they burst among the mountains. I have often been out in them,—in fact, far more frequently than was pleasant; but perhaps the grandest of all was one that welcomed me for the first time to Chamouni. As we entered the valley, and caught sight of the white pinnacles of the glacier des Bossons, a dark cloud came rolling up rapidly from the west. Beneath it, just where two tall peaks towered up, the sky glowed like a sheet of red-hot copper, and a lurid mist spread over the neighbouring hills, wrapping them, as it seemed, in a robe of flame. Onward rolled the cloud; the lightning began to play; down the valley rushed a squall of wind, driving the dust high in air before it, and followed by a torrent of rain. Flash succeeded flash almost incessantly,—now darting from cloud to cloud; now dividing itself into a number of separate streaks of fire, and dancing all over the sky; now streaming down upon the crags, and at times even leaping up from some lofty peak into the air. The colours were often most beautiful, and bright beyond description."
A STORM ON THE LAKE OF THUN. After Turner.
The mountain traveller, when caught in a thunder-storm, undergoes a strange experience, not unattended with danger. One observer[12] thus describes his sensations:—