80 GLACIAL AND SUEFACE GEOLOGY OF THE PACIFIC COAST. 



are any proofs that the valleys of the region in question are filled with de- 

 trital materials of other than local origin, or Avhether there is anything in 

 the character of the surface geology radically difierent from what has been 

 observed in the ranges and valleys to the east and south. As far as can be 

 made out from published documents, there is no reason whatever to suppose 

 the previous existence of any other than small local glaciers (if any at all) 

 in the region at the head of the Fraser and Columbia ; neither is there any 

 evidence that the drift is not of local origin. The form of the cross-sections 

 of the valleys, as revealed in photographs and drawings taken at various 

 times, shows clearly that there is almost invariably a steep slope of the 

 detrital material downward from the enclosing moimtain ranges towards the 

 rivers, and this is abundant evidence that these materials came from the ad- 

 joining elevations, and that they in fact are exactly similar to the ordinary 

 slopes of detritus, or " washes," with which we have already become familiar 

 as occurring; on such a larije scale in California and the Great Basin. It 

 is true that Mr. G. M. Dawson, in entire contradiction to all the flicts, as the 

 writer thinks, believes it possible that glaciers may once have filled these 

 valleys.* The observations and theories of this observer will be referred to 

 and discussed further on. He seems, however, not wholly to reject the view 

 maintained above in regard to the real character of these terraces, for he 

 says: "In some cases they [the terraces] may show merely stages in the 

 descent of the rivers to their present levels through the wide-spread de- 

 posits of the Glacial period." 



The statements made by the writer in the quotation given above from the 

 California Academy's Proceedings, seem to be entirely borne out by an over- 

 whelmino- weio-ht of evidence, for the whole area embraced within the Cor- 

 dilleras, with the exception of the portion which remains yet to be inquired 

 into, namely, the ranges bordering the coast in British Columbia from Van- 

 couver Island northward. To this region the attention of the reader may 

 now, therefore, be called. At the time the article in question was written, 

 or fourteen years ago, almost nothing was definitely known of the character 

 of the coast north of Oregon. The investigations of the writer and Mr. Gabb 

 on Vancouver Island and up the Fraser Ri^•er were necessarily of the nature 

 of hasty reconnaissances.t Mr. Ashburner, formerly of the Geological Survey 



* Mr. Dawson admits, however, tliat the lienches in question " look like shore-lines, caused by tlie accunuilatiou 

 aud horizontal arrangement below the water-line of debris from tlie mountain slopes." 



t The prineipal object of Mr. Gabb's visit to Vancouver Island was to fi.K the age of the coal of that region : 

 that of the wiiter was to learn something of the surface geology of the northwestern portion of our territory. 



