116 THE FOKMS OF WATER IN 



surface lises, the part on which the sand lies thickest 

 rising highest. Little peaks and eminences jut forth, 

 and when the distribution of the sand is favourable, 

 and the action sufficiently prolonged, you have little 

 mountains formed, sometimes singly, and sometimes 

 grouped so as to mimic the Alps themselves. The Sand 

 Cones of the Mer de Glace are not striking; but on 

 the Gorner, the Aletsch, the Morteratsch, and other 

 glaciers, they form singly and in groups, reaching 

 sometimes a height of ten or twenty feet. 



§ 44. The Glacier Mills or Moulins. 



293. You and I have learned by long experience the 

 character of the Mer de Glace. We have marched over 

 it daily, with a definite object in view, but we have 

 not closed our eyes to other objects. It is from side 

 glimpses of things which are not at the moment occu- 

 pying our attention that fresh subjects of enquiry arise 

 in scientific investigation. 



294. Thus in marching over the ice near Trelaporte 

 we were often struck by a sound resembling low rumbling 

 thunder. We subsequently sought out the origin of 

 this sound, and found it. 



295. A large area of this portion of the glacier is 

 unbroken. Driblets of water have room to form rills; 

 rills to unite and form streams ; streams to combine to 

 lorm rushing brooks, which sometimes cut deep chan 

 nels in the ice. Sooner or later these streams reach a 



