THE CENTURY'S PROGRESS IN GEOLOGY 



streams of ice called glaciers, " from their far fountains 

 slow rolling on," carrying with them blocks of granite 

 and other debris to form moraine deposits. If these 

 glaciers had once been much more extensive than they 

 no\v are, they might have carried the bowlders and left 

 them where we find them. On the other hand, no other 

 natural agency within the sphere of the chamois-hunt- 



A MOUNTAIN CAKVED FROM HORIZONTAL STRATA 



er's knowledge could have accomplished this, ergo the 

 glaciers must once have been more extensive. Perraudin 

 would probably have said that common-sense drove him 

 to this conclusion ; but be that as it may, he had con- 

 ceived one of the few truly original and novel ideas of 

 which our century can boast. 



133 



