VICINITY OF OROVILLE AND CHEROKEE FLAT. 



479 



I saw no quartz at all, and almost no volcanic rock of the basaltic or tufaceous types, which are so 

 common on the ridges farther west and south. The prevailing type of rock is coarsely crystalline, 

 and frequently porphyritic, with feldspar or hornblende. The feldspathic crystals, sometimes an 

 inch or more in length, show very plainly as large white spots upon a weathered surface. When 

 freshly broken, the rock ingredients are not so strikingly different in color. Besides these porphy- 

 ritic rocks there are others, which resemble syenite in composition ; hornblende is more abundant 

 than any other mineral. Very few of the boulders are fine-grained. But few of them show many 

 signs of having been worn by water action, and some are decidedly angular. There are also numer- 

 ous large and angular erratics — ten to fifteen feet or more in diameter — scattered over the surface. 

 Along the creek the exposed faces of the banks sometimes show signs of stratification. There are 

 no beds of clay or sand, but the gravel in these banks is finer than elsewhere. In other places the 

 exposed banks more nearly resemble a moraine in structure. The whole deposit is more probably due 

 to glacial than to river action. The upper canon of Jamison Creek, to the southeast of Eureka Peak, 

 is very deep and. steep, and glacial scorings have been reported from the rocks of that and other 

 peaks. The gold that has been found above the " cement " in Jamison Creek probably came from 



the erosion of the Plumas Eureka quartz ledge. 



The gold-bearing gravels at Jackson's Diggings do not throw much light upon the question of 

 the distribution of such deposits in the Feather River basin. The claims are in the N. W. J of 

 Sec. 1, T. 21 N. ; R. 12 E., some seven or eight miles southeasterly from Knott's Ranch; and 

 about one mile from the Wash P. 0., or Mrs. King's ranch. The altitude of the last-named place 

 I made to be 4,450 feet ; that of Jackson's cabin at the mines, 5,025 feet. The claims consist 

 principally of shallow gulch workings upon Wash and other creeks. No mining had been done 

 here prior to the year 1868. The lower portion of this gulch, which has been worked to bed-rock, 

 is now filled with the heavier boulders which could not be carried along by the water. The 

 highest point visited was about 300 feet above the cabin. The most interesting feature of 

 this deposit is the abundance of porphyritic boulders. Mr. Jackson informed me that his ditch 

 crossed a belt, fifty or a hundred feet in width, of the peculiar rock from which the large supply 

 of spotted porphyry boulders might have come. The gold from the gulches between Wash and 



Ohio creeks is very coarse. 



Between Jackson's and Sierraville, to which place I had to go in order to reach Sierra City, I 

 passed over the road in the stage, and did not see much that would add anything to the value of 



this report. 



Section IX. — The Vicinity of Oroville and Cherokee Flat. 



The district to bo described in this section is in the southern part of Butte County, northwest 

 of the junction of the Middle and the North Forks of Feather River. The Official Map of the 

 County of Butte, published in 1877, on the scale of one mile to the inch, will be convenient 

 for reference in the study of this region ; a portion of it, showing the region about to be described, 



i 



is given on Plate Y. The most striking feature in the topography of the region is Table 

 Mountain on or near which the principal deposits of gravel, to which my attention was directed, 

 are found. Leaving out of mind for the present a few localities of less importance, to which 

 reference will be made at the close of the section, I will first take up the description of this 



mountain and its immediate vicinity. 



Table Mountain, so called on account of the flatness of the broad sheet of basalt of which its 

 higher portions consist, maybe said to occupy an area of more than six miles in length from north 

 to south, by nearly three miles in breadth, though the actual area covered by volcanic rock would 

 be considerably less. At several points, particularly on the western side of the mountain, deep 

 ravines, extending nearly across to the opposite side, have been eroded quite through the volcanic 

 rock, and at the southern extremity a small portion of the cap, known as South Table Mountain, 

 has been separated entirely from the main body by Schermer's and Morris ravines. At Cherokee 





