VII. 



AGASSIZ'S great service to geology 

 proper (apart from palaeontology or 

 the study of fossils) is that thanks to 

 him and his coworkers ice has been 

 introduced as a great geologic agent, 

 almost as important as fire and water. 

 "The peasant had told his strange story 

 of boulders carried on the back of the 

 ice, of the alternate retreat and advance 

 of glaciers, now shrinking to narrower 

 limits, now plunging forward into ad- 

 joining fields by some unexplained 

 power. " The Alpine herdsman and the. 

 guide knew the moraines and dikes, the 

 polished or furrowed rocks of their own 

 valley 5 but educated men were not 

 familiar with these things, and did not 

 recognise them when the ice was not 

 there to draw attention to its own doings. 

 The idea that such phenomena were not 

 restricted to regions where glaciers now 

 are found, but that traces of glacial 



