A HISTORY OF SCIENCE 



various phenomena which always accompany them, 

 and which continue to exist even after the ice has 

 melted. These phenomena are as follows : 



"i. Moraines. The disposition and composition 

 of moraines enable them to be always recognized, even 

 when they are no longer adjacent to a glacier nor im- 

 mediately surround its lower extremities. I may re- 

 mark that lateral and terminal moraines alone enable 

 us to recognize with certainty the limits of glacial ex- 

 tension, because they can be easily distinguished from 

 the dikes and irregularly distributed stones carried 

 down by the Alpine torrents. The lateral moraines 

 deposited upon the sides of valleys are rarely affected 

 by the larger torrents, but they are, however, often 

 cut by the small streams which fall down the side of 

 a mountain, and which, by interfering with their 

 continuity, make them so much more difficult to rec- 

 ognize. 



"2. The Perched Bowlders. It often happens that 

 glaciers encounter projecting points of rock, the sides 

 of which become rounded, and around which funnel- 

 like cavities are formed with more or less profundity. 

 When glaciers diminish and retire, the blocks which 

 have fallen into these funnels often remain perched 

 upon the top of the projecting rocky point within it, in 

 such a state of equilibrium that any idea of a current of 

 water as the cause of their transportation is complete- 

 ly inadmissible on account of their position. When 

 such points of rock project above the surface of the 

 glacier or appear as a more considerable islet in the 

 midst of its mass (such as i? the case in the Jardin of 

 the Mer de Glace, above Montavert), such projections 



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