APPEARANCES OF GLACIERS AND SNOW-FIELDS. 16? 



ing its channel, eroding valleys, often covering vast areas, 

 an agent of great destructive power. 



' The motion of a glacier being largely due to expansion 

 from the consequences of its melting, is slower at night 

 than during the day, and in winter than in summer; the 

 movement is greater in the middle, than on the sides, 

 where it is held in check by friction, and also more slug- 

 gish at the bottom than at the top. A glacier will accom- 

 modate itself to the sinuosities and unevenness of its bed, 

 expanding or contracting like the waters of a river, and 

 will precipitate itself over a ledge, making a cascade of 

 ice : these I have seen in almost every glacier in Norway. 

 The ice is often broken transversely, the moraines are 

 engulphed in the crevasses and lost. The main glacial 

 stream starts with a moraine on each side ; long dark bands 

 raised above the ice are formed by the stones and earth 

 which have fallen down the side of the mountain, in the 

 same manner as the heaps of stones and debris we find at 

 the base of mountains, and in many ravines and valleys. 

 These lateral or marginal moraines vary in height accord- 

 ing to the amount of the deposits massed together, and to 

 the time of their formation ; they range from a few feet to 

 twenty feet in height, but are never much more, for there 

 is 110 time for accumulation ; the material is collected as 

 the ice moves downward, and the motion of the Norwegian 

 glacier may be a few hundred feet a year. These moraines 

 stand in regular ridges, and are slowly and surely carried 

 to the end of the glacier ; their origin, by the materials, 

 ,can often be traced back for great distances. As the 

 frozen river moves onward, it is joined by others, all uniting 

 in one solid mass ; the moraines meet side by side, and 

 remain distinct on the journey down. The number of 

 these moraines indicates how many branch streams have 

 united with the main trunk. Sometimes a glacier is com- 

 pelled to make its way through a narrow defile; then the 

 mass of ice contracts, and becomes deeper, and a grinding 

 process takes place on the sides and at the base with im- 

 mense force ; many valleys with perpendicular walls have 



