The Theory of Glacier motion. y^ 



motion have overlooked, namely, that this granular structure 

 of glacier ice separates it in a very important respect from 

 other ice. 



A glacier, then, consists of a solid mass of frozen water, 

 the upper part of loose snow, the middle of semi-consoli- 

 dated ice, and the lower of ice, properly so-called, which 

 mass is either embowelled in a single mountain valley, or 

 formed of several converging portions, filling several radia- 

 ting subsidiary valleys, and uniting in one mass in the main 

 depression. 



The fact that a glacier is not stationary, but moves in 

 its bed, must have been known at a very early date to the 

 mountaineers of Switzerland. They were witnesses of the 

 gradual progression of its lower part, called the ice foot, which 

 in many cases has overwhelmed meadows and fields and 

 even houses. They must also have noticed the gradual 

 movement of the great masses of stone on the glacier's back, 

 which could be seen year after year to alter their position 

 relatively to the sides. This homely evidence must have 

 made it plain in very early times to the Swiss shepherds 

 and hunters, that glaciers are not reservoirs of stationary 

 ice, but are rather frozen streams in motion. Facts of a 

 more dramatic kind must also have occurred similar to 

 those named by more recent travellers. Thus : — 



Toussaint de Charpentier tells us how he was assured by 

 Jacques Balmat, a native of Chamounix, when he was 

 travelling there in 1818, that once in the summer months the 

 Savoyard peasants went with their sheep to graze on a kind 

 of oasis on the Mer de Glace known as "le Jardin," when 

 one of these animals fell into a crevasse and was killed. Some 

 years afterwards the animal came to the surface some 

 distance down the valley^ and the flesh had been preserved 

 quite fresh {Naturwissenschaftlicher Anzeiger der AIL 

 Schweiz. Gesell. filr die Ges.Naturwiss. for 1821, page yZy 



In 1832 Forbes discovered, near the Moulins, portions of 



