482 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 
The heaviest bed of pipe-clay rests upon the purple gravel. Where exposed to view on the face 
of the bank it is nearly one hundred feet thick, and is probably thicker than that a little way 
back from the face. The altitude of the highest point of the big bank I made to be 1,460 feet ; 
that of the base of the Sugar Loaf, 1,550 feet ; and that of its summit, 1,647. The gravel in Saw 
Mill Ravine, when mining was begun, had no pipe-clay upon it, and the beds now visible on the 
western bank do not appear to have any connection with those under the Sugar Loaf. The distri- 
bution of the pipe-clay on the northwestern side of the upper mine deserves a detailed notice on 
account of the bearing it has upon the question of the antiquity of the stone mortars and other 
implements which have been found in the gravel. In some cases this clay appears to take the 
place of the white gravel almost entirely ; in others, it rests upon the rotten boulders ; and, at one 
point, it has been seen to rest upon the blue gravel. It thins out rapidly towards the high bank 
of purple gravel on the opposite side of the mine, The lamination of this clay is not horizontal, 
but is highly inclined, in conformity with the general sloping surface of the gravel on which it rests. 
These circumstances, taken in connection with the great differences of altitude, show that these 
masses of clay have had no direct stratigraphical connection with those previously referred to. A 
cross section of the upper mine, from S. E. to N. W., through the Sugar Loaf, shows these differ- 
ences of arrangement in a very striking manner. See section on Plate V, Fig. 7. Attention is 
called to the position of the clay (vit), between two layers of gravel, and their inclined position. 
I have little doubt that the northwestern portions of the deposit have been subjected to some 
rearrangement since the deposition of the main mass of the gravel. 
The relations of these facts to the finding of the stone implements will appear from the follow- 
ing considerations.* In a conversation with Mr. Eaholtz in regard to the mortar found in 1858, 
I learned that he was then working where the bank was about forty feet in height, the lower ten 
or fifteen feet being gravel, the remainder pipe-clay and sand. In working the bank, the top 
stratum was allowed to fall as a “cave.” Mr. Eaholtz was confident that the mortar came from 
the gravel, but he could not remember positively whether the gravel was blue or white. The 
place of working was about 300 yards above the junction of Saw Mill Ravine and Campbell’s 
Ravine, that is to say, in the neighborhood where the strata of gravel and clay show signs of re- 
arrangement. The result of my inquiries and my examination of the locality inclines me to the 
opinion that this particular discovery cannot be depended on as proving beyond question that the 
mortars were in use among men during the period of the deposition of the gravel, and prior to 
the time of the volcanic overflow. Of the other mortars which have been found here, but few are 
supposed to have come from any remarkable depth below the surface, and, as they were mostly 
found below the point between the two ravines, where an Indian “rancherie” used to stand, as I 
was told by Mr. Pulliam, they need not be of very great antiquity. Doubtless they are pre- 
historic ; the Indians of the present day, at any rate, deny all knowledge of them, and refuse to 
use them. I made many inquiries in the hope of hearing of the discovery of the works of man in 
the gravels of the higher banks, but without suecess. The universal testimony is, that nothing of 
the kind has been found since the era of deep mining began. 
The thickness of the basaltic cap at the Sugar Loaf has been already alluded to. There can 
be no doubt that the gravel beds extend underneath the basalt at this point. At no other points 
have the hydraulic banks been washed back so near to the base of the lava bluff; but there is 
every reason to believe that the beds are continuous to the west and southwest beyond the face 
of the bluff. The practical questions are, How far does the gravel extend? and How far does 
it carry gold in paying quantities? To these questions only probable answers can yet be given. 
It is evident that the difficulties of working by the hydraulic process will increase from year to 
year, and that finally drifting will have to be resorted to. I understand that it is the intention 
of the new company to commence drifting at once on the lower part of its property. 
The gold at Cherokee Flat is very fine and scaly, excepting near the bed-rock, where grains 
* See ante, p. 278. 
