PREFACE. 



The facts stated and questions discussed in this work 

 have occupied some portion of the attention of the author 

 since 1855, and he has from time to time published his 

 results in the Canadian Naturalist and Geologist, and 

 elsewhere. In 1872 the subject up to that time was 

 summed up in a pamphlet of about 100 pages, entitled 

 " Notes on the Post-pliocene of Canada," now out of 

 print ; but since that date no general work on the subject 

 has appeared, though many separate memoirs and papers 

 have been issued by the author and other Canadian 

 geologists. 



These papers include a large mass of information bear- 

 ing on the history of the northern half of the continent 

 of North America in that Ice-age which was in some 

 sense peculiarly its own ; and as this material is difficult 

 of access both to geologists and to the general public, no 

 excuse seems necessary for attempting to collect it in a 

 convenient form. 



The author has studied the widespread and complex 

 glacial formations of Canada too long to be content to 

 explain them all by one dominant cause, in the rough 

 and ready method employed by so many of his juniors. 

 He has long been convinced that we must take into 



