408 



SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 



The granite rock near Bowman's is distinctly scored with glacial markings. This is the only 

 point on this ridge where I saw unmistakable signs of ice action. A careful examination of these 

 higher regions would doubtless develop much of interest in relation to glacial phenomena, but time 

 did not allow of my pushing inquiries any farther in that direction. 



From several sources I heard of the existence of so-called " high gravel " on Fall Creek and 

 Grouse Ridge. This is a district which is most easily reached from the Emigrant Gap station on 

 the Central Pacific Railroad. It is hardly settled at all, and would be a difficult country to explore 

 without animals or a camp outfit. I had the good fortune to meet, at Washington, a miner from 

 the ridge who gave me such information about the deposits of gravel that I was satisfied I should 

 not neglect anything of importance if I failed to go there. He spoke of shallow gravel banks, 

 perhaps from ten to twenty feet in thickness, associated with granite boulders, and so situated that 

 they might very well be of comparatively recent origin. 



Section IV. — The Washington Ridge, south of the South Yuba River. 



The careful exploration of any part of the gravel region lying to the south of the South Yuba River 

 was not contemplated in the plan of my summer's work. A hasty trip to Omega and its neighborhood 

 was all that I expected to have time to accomplish. By way of Relief Hill I reached the town 

 of Washington, which lies low in the canon on the left bank of the South Yuba, and has no very 

 close relations with the high gravel deposits, on the evening of the day I left Malakoff. During 

 the next six days I visited Alpha, Omega, and Diamond Creek, and returned to Malakoff by way 

 of Sailor Flat and Blue Tent. The gravel deposits known as Phelps's Hill, Phelps's Point, Jeffer- 

 son Hill, Gold Hill, and Cotton (or Colton, as it is called in Raymond's Report) Hill, which follow 

 in order downwards from Alpha on successive spurs of the ridge, and which can be seen to good 

 advantage from almost any prominent point on the ridge above Relief Hill, and from some of the 

 high points near Omega, I was obliged to leave un visited. The ravines are deep and steep, 

 opposing very effectual barriers to easy communication between places which are in full view of ' 

 each other, as, for example, Alpha and Omega, on opposite sides of Scotchman's Creek. 



There can be no doubt of the former connection of the gravel between Omega and Cotton (or 

 Colton X) Hill, and probably Relief Hill, prior to the erosion of the lateral valleys. Seen from any 

 high point commanding a view of all the gravel, the deposits appear to be arranged in a regular 

 series, nearly parallel with the present stream and having an easy grade downward towards Relief 

 Hill. The series bears a very striking resemblance to that on the divide next north between Snow 

 Point and Woolsey Flat. The deposits between Omega and Relief Hill are not capped with lava, 

 the lower line of the lava at the present day being at a considerably higher altitude than the top 

 of the gravel banks, excepting at Omega, where the difference of altitude is not so great. Indeed, 

 if we were to regard alone the present appearance of these gravel beds, as they lie upon the high 

 benches, there would be no difficulty in supposing them to have been deposited since the deposi- 

 tion of the lava, at the time when the present South Yuba followed a channel twelve or fourteen 

 hundred feet above its present bed. The objections to such an hypothesis, however, are too many 

 and too important to be overlooked. The principal of these objections are, the total absence of 

 tufaceous material in the gravel, the probable extension of the gravel under the lava in place at 

 Relief Hill, and the certainty of the extension of gravel, similar in character and presumably 

 formed at the same time and under the same conditions, under the lava of Malakoff and Woolsey 

 Flat. 



My observations for altitude at Washington, Alpha, and Omega have not given very satisfactory 

 results. The difference of bed-rock level at the two places last mentioned is certainly much less 

 than my computations make it to be. Either Alpha is made too low or Omega too high ; prob- 

 ably the former. The greatest element of uncertainty is in the determination of the altitude of 

 Washington, to which station alone the altitude of Alpha was referred. The total fall from Omega 





