On Water and Air . 
[May, 
324 
height upon a glacier and see these moraines perhaps like 
tracks or roads, in point of fadt, coming down along the 
banks of the glaciers ; but when you come to examine them 
you will find that they are very different from what they 
appear to be. These moraines rise sometimes to a height of 
50 or 60 feet above the level of the glacier. Looking at 
them you would imagine them to be heaps of stone and clay 
and dirt that have been brought together — a ridge of this 
debris heaped upon the glacier; but when you come to 
examine them more closely you find that there is simply a 
superficial covering of debris with a ridge of ice underneath. 
What is the reason of this ? You will understand me im- 
mediately. Conceive the glacier covered with this debris . 
It is thereby protected from the melting adtion of the sun. 
Fig. 33 
The sun is free to play upon the ice right and left of the 
moraine, which it melts, and the consequence is that the 
protedted part — that part on which the debris rests — is not 
melted, but remains as a great ridge of ice. In the same 
way are formed the glacier tables, as they are called. You 
sometimes find upon the glaciers rocks lifted up as if they 
had grown, as it were, out of the heart of the glacier : these 
are due entirely to an adtion of the same kind. There 
(Fig. 33) is the glacier table upon a surrounding of ice. 
That rock was thrown from the adjacent mountains upon 
the glacier, and has protedted the ice beneath. The ice all 
round this protedted ice melted, and by-and-bye this rock 
