472 



University of California. 



[Vol. 3. 



Scott River, below Scott Valley, crosses the axis. Lawson has 

 called my attention to the fact that the broad-floored Scott Val- 

 ley presents strong evidences of being an aggraded valley. It 

 appears that the arching across the lower Scott River has been 

 so pronounced that the stream has been unable to cut a canon 

 through it down to an average grade, and a filling of Scott 

 Valley has resulted. The Upper Trinity Valley, lying east of 

 the axis, also shows evidence of aggrading, but to a less extent 

 than Scott Valley. For fifteen miles the Upper Trinity River, 

 instead of flowing in a small canon, has a Modern flood-plain 

 that averages a quarter of a mile wide. 



The maximum elevation seems to have been at a point near 

 the head of the South Pork of Salmon River, where the moun- 

 tains are now highest and the glacial phenomena of the last 

 stage most intense. West of the axis the tilting seems to have 

 been toward the west-southwest. The lower terrace seems to be 

 higher where the streams are flowing in that direction than 

 where they are flowing northwest. This is only a suggestion, 

 as very little accurate information on the subject is available. 



Last year I discussed* the terrace system as it is developed 

 near Summerville, in the valley of the South Fork of Salmon 

 River. The highest terrace (that over Channel A) of the Sum- 

 merville Basin corresponds to the 850-foot terrace of the Orleans 

 Basin. Associated with the former there are apparent very old 

 glacial deposits, representing the first glacial stage. The 120- 

 foot terrace of the Orleans Basin has its counterpart in the 

 terrace over Channel C of the Summerville Basin. The latter 

 has a similar height and the characteristic coarse torrent fans. 

 I traced it into direct connection with deposits of the Interme- 

 diate glacial stage. I want to emphasize the fact that in two 

 distinct areas, thirty-five miles apart, I have found glacial 

 deposits closely related to a terrace which has unique characters. 

 Being mutually corroborative, they greatly strengthen the 

 hypotheses of a short period of excessive rainfall immediately 

 following the maximum extension of the glaciers in the Inter- 

 mediate stage. 



The lowest terrace of the Orleans Basin is the correlative 

 ^Journal of Geology, Vol. XI, No. 5, July-August, 1903, pp. 431-458. 



