GLACIERS, EIVEES, AND LAKES. 



13 



melted away ou the highest summits of the Stubay. Ou the other hand, a few- 

 small glaciers have recently formed in the Eastern Tauern. 



The Vernagt glacier, in the Oetzthal, is one of those which exhibit the greatest 

 regularity in their alternate advance and retreat. Five times since 1599 has it 

 crept down the valley and melted away again. Its advance is usually more 

 rapid than its decay, and in 1845 its terminal face advanced 150 feet in a single 

 day. The Yernagt is, however, more dangerous when it retreats, for then the 

 water pent up in its tributary valleys is freed, and carries destruction to the lower 

 valleys. 



Owing to the friable nature of the rocks, disasters such as this, as well as 



Fig. 5. — The Vernagt and other Glaciers of the Oetzthal. 



Scale 1 : 120,000. 



iio°45' E of Gr 



'lO-AS 



2 Miles. 



landslips and floods, are frequent in the Austrian Alps. The Salzach, which rises 

 in the Tauern and flows past Salzburg to the Daijube, has frequently been dammed 

 up by the masses of detritus brought down by its tributary torrents. In 1798 an 

 avalanche of mud and stones blocked up the gorge of Oefen, above Hallein, and 

 two villages, with their fields, were buried beneath 50,000,000 cubic yards of 

 débris. In the valley of the Adige sloping mounds of detritus constitute a 

 marked feature, and they sometimes block up the river. The huge accumulation 

 of stones, mud, and clay, interesting on account of its stone-capped earth pillars, 

 known as the Salvini di San Marco, is probably the result of a landslip which 

 occurred in 833, and for a time reduced the Lower Adige to a simple rivulet. Five 



