These currents are as regular at certain seasons of the year as the land and sea breeze. Of course, they may be obliterated for the time being, by the presence of a stronger wind due to some other cause, such as during the prevalence of a storm. In some of the regions of California hottest during the day time, the nights are made endurable, and even delightful, by the cool breezes that sweep down from the tops of the mountains. It often happens that on the shady side of a high and steep mountain where the sun's rays strike it so obliquely, if at all, that the earth will be but little heated, there will be a vast mass of cold air stored up. After the valley has become intensely heated by the sun there is an ascending current of air which in turn causes a down rush of the cold body of air from the mountain side. These local winds are frequently very severe, only lasting, however, for a short time, until an equilibrium of temperature and density has been established. A wonderful exhibition of this sort of wind is said to occur at certain times of the year on the coast at Tierra del Fuego, where a blast which they call the "Williwaus," comes down from the mountain side, without warning, with such tremendous force that no ship could stand the strain if it should continue for any length of time. Fortunately the shock does not last more than eight or ten seconds, when it is followed by a perfect calm. It is as though a great volume of air had been fired from some enormous cannon from the top of the mountain to the sea. The water is pulverized into a spray that is driven in every direction. Sometimes these violent blasts occur in the Alps, but from a very different cause. Avalanches of great extent often take place on the sides of the mountains, when a vast amount of material, equal to three or four hundred million cubic feet of earth, will fall several thousand feet. Often an avalanche of this kind will produce a wind, which is confined, of course, to a restricted area, that is said to be so violent as to tear one's clothes into shreds. This is not caused by any difference of temperature, but by a violent compression. There is a peculiar wind that occurs in Switzerland, often, between the months of November and March. These winds last from two to three days and are of great violence--especially near the mountains. They are warm and dry and are caused by an area of low barometer and an ascending current of air occurring at some point north of the Alps, which causes the air from Italy to flow over the Alpine range, causing a tremendous precipitation of snow and rain, which not only takes the moisture from the air, but sets free in the form of heat the energy that was stored in the process of evaporation, and this, together with the compression of the air as it flows down the slope of the mountains, makes it hot and dry. This wind is called the "Fohn."