92 GLACIAL AKD SUEFACE GEOLOGY OF THE PACIFIC COAST. 



must have found its way out by the Valley of the Fraser. Here, again, the 

 evidences of such passage of a great glacier 300 miles long are singularly 

 defective. The few isolated boulders observed resting on the surface of the 

 local detritus, by Dr. Hector and others, are but a poor representation of 

 the former passage of a mass of ice larger than any now existing in the 

 world, unless in Greenland or at the South Pole. That these and other 

 similar difficulties did not fail to impress themselves on the mind of Mr. 

 Dawson, and that he was inclined to look with suspicion on his own " highly 

 probable " theory, is shown by the following extract from his report on the 

 region in question, which follows immediately after the suggestion of the 

 great confluent glacier, which he supposed to have covered so large a part of 

 the interior of British Columbia. He says: "It is well to remember, how- 

 ever, that the hypothesis of an Arctic current bearing heavy polar ice 

 through the Peace River gaps at the north, and thence southward down the 

 region of the plateau, would serve almost equalhj ivell to accouiit for its glaciationr 

 And he adds : " Any theory of the cause of these traces of the earlier gla- 

 ciation shall at present be held tentatively, and subject to the result of further 

 exploration." 



In the preceding pages will be found, it is believed, all that it is necessary 

 to set forth in regard to the former glaciation of the western side of the 

 North American continent. With the facts which have been given, the 

 reader will be prepared to enter into the discussion of the probable relation 

 of the phenomena of past glaciation, as manifested on the Pacific Coast and 

 in the Rocky Mountains, to similar occurrences in other parts of the world. 

 Before advancing another step in the present inquiry, however, it will be 

 desirable to add to what has already been said about glacial phenomena 

 proper something in regard to one or two points of surface geology more 

 or less directly connected with the former occurrence of ice in the regions 

 which have been passed over in review in the preceding pages. And it will 

 also be proper to inquire whether there are any points in regard to the dis- 

 tribution of the superficial detrital material, in the non-glaciated portion of 

 region in question, which require special elucidation, as preparatory to the 

 discussion which it is proposed to enter upon in the succeeding chaptei's. 



One of the first questions suggesting itself to the student of dynamical 

 geology, in connection with the phenomena of past glaciation which have been 

 described in the preceding pages, is this : Are there any marked, character- 

 istic features in the topography of the glaciated regions which distinguish 



