GO GLACIAL AND SUEFACE GEOLOGY OF THE PACIFIC COAST. 



and traces of former glaciation of the region were carefully sought for by 

 liun. He reports as follows in reference to this point : — 



" On the divide between the South and Middle Yubas I saw distinct mark- 

 ings and polishings of the granite rocks near the Bowman reservoir, at an 

 altitude of about 5,500 feet. No time, however, was taken for any detailed 

 examination of this region. The markings seen were all near the reservoir 

 in the canon ; no note was made of their direction. On the divide between 

 the Middle and North Yubas, I saw glacial markings on granite near the 

 head-waters of the North Yuba, at a point about six miles above Sierra City, 

 and at an altitude of about 5,800 feet. The locality is near the Blue Gravel 

 location, on Milton Creek, one of the head-Avaters of the North Yuba. The 

 amount of bed-rock uncovered was not large, but the parallel strife were 

 exceedingly distinct. Their course was northwest and southeast, bearing 

 directly for the highest visible point of the Sierra Buttes, about six or eight 

 miles distant. To the north of the North Yuba I frequently reached alti- 

 tudes sufficiently great for glacial markings ; but I saw no exposed bed-rodk 

 which showed signs of being scored and polished. Erratic boulders, difficult 

 to account for except on the theory of glacial transportation, were seen near 

 La Porte and Howland Flat. And similarly, near Forest City, south of 

 Downieville, on the other divide, there were peculiar boulders quite differ- 

 ent from those which made up the mass of the surface debris. The altitude 

 at which these last were found was a little less than 5,000 feet ; of the for- 

 mer, about 5,200. At Jami.son City, the altitude of which is about 5,000 

 feet, to the northeast of Eureka Peak and the Plumas Eureka quartz-mine, 

 there is a remarkable deposit of heavy gravel and boulders, none of Avhich 

 are very much rounded, while some are quite angular. The deposit is a 

 portion of an extensive range of similar materials, which is said to be trace- 

 able for several miles along the upper course of the Feather River, towards 

 Mohawk and Sierra Valleys. Upon the surftice of the gravel there are nu- 

 merous erratic boulders, as much as ten or fifteen feet in diameter, different 

 in character from the main mass of the gravel. When exposed to view, a 

 section of the gravel frequently showed a morainic structure. I was inclined 

 to the view that the glaciers had considerable to do with the formation of 

 this deposit, but I could find no further corroborative evidence. The day 

 after I left Jamison City a heavy snow-storm set in, which prevented my 

 pushing inquiries any further in that direction. The region to the north 

 and northwest of the Sierra Buttes — forming the divide between the 



