50 GLACIERS 



rock are called " moraines." Those at the sides of a 

 glacier are called " lateral moraines," and the heap at 

 the melting end or "snout" is a "terminal moraine." 

 When two glaciers flow down neighbouring rock valleys 

 which join in a common valley, as the two limbs of the 

 letter Y join on the stem, the glaciers become pressed 

 and fused together where they meet and form one glacier. 

 The left lateral moraine of the right-hand valley (as you 

 descend) joins the right lateral moraine of the left-hand 

 valley, and the two form a " central moraine " on the mid- 

 line of the slowly advancing combined mass of ice. The 

 rock fragments on such a moraine are of all sizes, some 

 as big as a small house, and piled up in some large 

 glaciers to a breadth of a quarter of a mile. They give 

 one a most vivid impression of the tremendous and 

 incessant breaking down of the mountains. Often one may 

 see such huge masses descend with a terrible roar from the 

 heights above on to the glacier or an avalanche of smaller 

 fragments amounting to hundreds of tons in weight, 

 pouring down the precipitous rocks of the higher peaks. 

 Sometimes when one looks from above on to the glacier a 

 thousand or more feet below, the size of the rocky frag- 

 ments of a central moraine is not appreciated. I once 

 heard a newly arrived and inexperienced visitor at the Bel 

 Alp exclaim as he looked down on to the great Aletch 

 glacier, " I suppose they have spread those cinders on the 

 ice to make a path for us to walk on along the glacier." 

 He had no notion that what, at that distance, he took for 

 a cinder-path, consisted of huge pieces of rock mostly of 

 the size of an omnibus ! 



A matter which is now greatly discussed among geolo- 

 gists and upon which different views are held, is as to the 

 " grinding " or " excavating " action of glaciers upon the 

 bed over which they slowly move. It is probable that 

 their excavating activity has been exaggerated. They do 



