No. 4.] DAWSON — POST-PLIOCENE. 411 



verted, first, by the fact that clays full of stones and boulders 

 contain marine shells, and in Canada at least, the boulders im- 

 beded in such hard chiys of the nature of till, often have Bryozoa 

 and Acorn-shells attached to them ; and, secondly, by the fact 

 that the clays holding numerous boulders sometimes are stratified. 

 Holding, however, his peculiar views about the Boulder-clay, 

 Mr. Geikie must account for it by land glaciers, and the facts, 

 according to him, shew that these could not have been merely a 

 number of small local glaciers, but a general mer de glace. To 

 reconcile this with the occurrence of the marine beds, he is 

 obliged to have recourse to a series of cold and warm periods, 

 and of emergences and submergences, some of them of sufficient 

 duration to enable the country to be occupied with forests and with 

 terrestrial mammalia. Thus it becomes necessary to exaggerate 

 the duration of the glacial period, and indeed to invoke the aid, 

 not of one glacial period, but of many, separated from each other 

 by long periods of ameliorated climate. All this would be 

 avoided by at once admitting the existence of marine Boulder-clays, 

 and endeavouring to separate these either by their fossils or by 

 their chemical and mechanical character from the glacial moraines, 

 which I have no doubt will be found in Scotland as in North 

 America to belong merely to local glaciers flowing in the existing 

 valleys. The kames or eskers, which used both in Scotland and 

 this country to be confounded with moraine ridges, Mr. Geikie 

 now, with all other good geologists, regards as marine, though he 

 attributes some of them to an older date than that held by 

 Home and others. 



My general conclusion on this subject is therefore precisely 

 what it was many years ago, and that on which I have proceeded 

 throughout this paper ; namely, that we have in Canada evid- 

 ence of a glacial period in which all the hilly ranges above water, 

 were covered with snow and had glaciers in their valleys ; these 

 glaciers terminating and giving off" icebergs at the mouths of the 

 valleys, where these opened on the plain of the St. Lawrence, then 

 under water. In the earlier part of the period the elevated land 

 of the Pliocene epoch gradually sunk under the waters, and the 

 remainder of it became refrigerated and covered with snow and 

 ice. At the period of greatest subsidence, nearly all the hills 

 were submerged, and heavy ice from the north ground over 

 their summits ; while the upper part of the Boulder-clay and 

 the lower beds of the Leda clay were deposited in the valleys. 



