668 DYNAMICAL GEOLOGY. 



frozen mist of regions above the limits of perpetual frost. They 

 stretch on 5000 to 7500 feet below the snow-line (limit of perpetual 

 snow), because they are so thick masses of ice that the heat of the 

 summer season is not sufficient to melt them. Some of them reach 

 down between green hills and blooming banks into open culti- 

 vated valleys. The extremities of the glaciers of the Grindelwald 

 and Chamouni Valleys lie within a few hundred feet of the gardens 

 and houses of the inhabitants. Each glacier is the source of a 

 stream, made from the melting ice. The stream begins, high in the 

 mountains, from the waters that descend through the crevasses to 

 the ground beneath, and often makes a tunnel in the ice above its 

 course ; finally it gushes forth from its cavernous crystal recesses a 

 full torrent, and hurries along over its stony bed down the valley. 



2. Glacier regions. — The best known of glacier regions if that of 

 the Alps. The chain west of the head-waters of the Ehone is 

 divided into two nearly parallel ranges, a southern and a northern. 

 The latter includes, besides minor areas, two large glacier districts, 

 — the Mt. Blanc and the Mt. Rosa or Zermatt district ; and the 

 former, one of equal extent, though its peaks are less elevated, — 

 that of the Bernese Oberland. There is another district of glaciers 

 at the head-waters of the Rhone, and others farther eastward. 



Glaciers occur also in the Pyrenees, the mountains of Norway, 

 Spitzbergen, Iceland, the Caucasus, the Himalayas, the southern 

 extremity of the Andes, in Greenland, and on Antarctic lands. 

 One of the Spitzbergen glaciers stretches eleven miles along the 

 coast, and projects in icy cliffs 100 to 400 feet high. The great 

 Humboldt glacier of Greenland, north of 79° 20 / , has a breadth at 

 foot, where it enters the sea, of forty-five miles ; and this is but one 

 among many about that icy land. 



3. Many Glaciers from one Glacier district. — The following map (fig. 

 948) represents the Mt. Blanc glacier region, excepting a small part 

 at its southwestern extremity. The vale of Chamouni along the 

 river Arve bounds it on the northwest, and the valley of the river 

 Doire on the southeast. This mountainous area, though one vast 

 field of snow, gives origin to numerous glaciers on its different sides, 

 — each principal valley having its ice-stream. The series of dotted 

 curves show the courses of the several glaciers. B is Mt. Blanc ; 

 bs, the Glacier des Bois, or Bois Glacier (so named from a village 

 near the foot of the glacier) ; m, the Mer de Glace, an upper portion 

 of this glacier. The river Arveiron issues from the extremity of 

 the glacier, and, after a short course, joins the Arve near the village 

 of Chamouni. The Geant (g), Talefre {to), and Lechaud {I) glaciers 

 are the three largest of the upper glaciers which combine to form 



