ILocal WfnDs. 103 



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 den- 

 sity has been established. A wonderful exhi- 

 bition 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 or any length of time. For- 

 tunately 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 can- 

 non 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. Ava- 

 lanches 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. 



