No. 7. J G. M. DAWSON — SURFACE GEOLOGY. 393 



even hollows holding swamps, is very remarkable, and contrasts 

 strongly with the innumerable lake-basins of British Columbia.* 

 The water indeed seems never to rest from its sources in the 

 mountains till it reaches the sea. This is either due to the pro- 

 longed action of the streams themselves in completely filling 

 rock-basins, if such there have been, and removing all other im- 

 pediments to their flow, or is the result of the original absence of 

 those great masses of material accumulated during a stage of the 

 glacial epoch, which in the north (as I hope elsewhere to show) 

 have in many places been mainly concerned, at a later period, 

 in forming lakes by the blocking of old valleys with detritus. 

 The local colouring of the soil, in its close resemblance to that of 

 the decomposed parts of the underlying rocks, indicating the 

 absence of foreign material, appears also to favour the latter 

 conclusion. 



North of Roseburg the railway passes for some distance, with 

 heavy grades and sharp curves, through a generally hilly country, 

 crossing several branches of the Umpqua, and then reaching 

 the upper part of the great and fertile Willamette Valley, which 

 runs northward to the Columbia, between the Cascade Mountains 

 with their flanking hills, and the lower ranges of the coast. 



Prof. Thomas Condon, of the University of Oregon, has pub- 

 lished some account of the state of this country in the later geo- 

 logical times. This I regret not to have had the advantage of 

 reading ; but, as the paper is entitled " The Willamette Sound," 

 it would seem to imply his belief in the former submergence of 

 this region. Prof. Le Conte indeed states that Prof. Condon 

 has traced an old sea-margin from the coast up the Columbia 

 River to and beyond the Cascade Range. This he compares 

 with the sheet of nearly land-locked water which must have cov- 

 ered Central California at the same period, f 



About two miles south of Creswell station, I noticed what 

 appeared from a distance to be a series of pretty distinct ter- 

 races, on a hill-side, at an estimated elevation of from 100 to 



* This of course applies to the region traversed, west of the Cascade 

 Mountains. East of that range the Klamath and other extensive 

 lakes appear on the map. These differ singularly in their form from 

 the long river-like lakes of British Columbia, and may possibly be 

 due to mountain elevation taking place more rapidly than the drain- 

 ing streams are able to lower their channels. 



f Elements of Geology, 1878, p. 530. 



