ee 
_ 
REVIEW AND GENERAL DISCUSSION. 499 
just cutting across the tops of the modern spurs, but afterwards entering the ridge which it then 
seems to follow as far as Flora’s mine, whence it evidently passed out over the modern river-caiion 
and has been washed away. All these channels have not simply a perceptible, but a considerable 
gerade, falling in the directions of their flow as indicated above, and all point to the same general 
conclusion respecting the ancient topography of the country, namely, that the great spur of the Sierra, 
which for so many miles above Georgetown now forms the divide between the South and Middle 
Forks of the American River, existed in the gravel period as well as now, with its relative prominence 
above the adjacent country, perhaps, even greater then than now, owing to the subsequent filling of 
the basin of the Middle Fork with volcanic matter, etc. ; and that then, as now, it formed the divide 
between the South and Middle Forks of -the American River. It may indeed be possible, for aught 
I know yet to the contrary, that during the whole or a part of the gravel period the South Fork of 
the American may have been an independent stream, not joining the North Fork, but reaching the 
valley separately somewhere southeast of Folsom. But I know of no proof of this, and the topog- 
raphy of the country below Shingle Springs leads me to think it improbable. There is much more 
plausibility in the idea that at one time before the modern canon of the South Fork was excavated 
to any considerable depth that stream may have flowed across the present ridge at Centreville 
(that is, Pilot Hill), and joined the North Fork somewhere in the vicinity of Lacey’s or Rattlesnake 
Bar. There is a depression here across the ridge which might have permitted of such a course, 
and the presence of the granite pebbles in the gravel at Pilot Hill may seem to speak in favor of 
it; but the evidence that I saw is not very strong, after all, though some of the miners are con- 
tident that it was so. 
To return to Georgetown. A line drawn from the junction of Long Cation and the South Fork 
of the Middle Fork of the American, southeasterly along the crest of the Tunnel Hill ridge, and 
curving westerly a mile or two south of Work’s ranch by Tipton Hill, and thence to George- 
town, then following the Spanish Dry Diggings road and the crest of the ridge to the Middle Fork 
of the American at a point between Spanish Dry Diggings and the mouth of Cation Creek, would 
include between it and the river all the voleanic matter and all the unquestionably ante-volcanic 
gravel that exists, so far as I know, between the South and Middle Forks to the west of Tunnel Hill. 
To the south from Georgetown the country slopes gradually towards the cation of the South Fork 
of the American, and here, as well as to the west and southwest of the ridge between Spanish Dry 
Diggings and the branches of Caion Creek, it consists entirely of the bed-rock, slates, etc., covered 
only by the varying quantities of scil and comparatively recent gravel which have accumulated 
over it. The ridge last referred to stretches southeasterly from the river west of Cation Creek for 
several miles, to within a mile or two of Georgetown, where it connects with the main watershed 
between the South and Middle Forks of the American. This ridge, though not high enough to be 
conspicuous, is yet an easily distinguishable feature in the topography, and overlooks the country 
for several miles to the eastward from it. As already stated, it is bed-rock to the crest, neither gravel 
nor volcanic matter being found upon it ; and it seems to have formed a barrier to the southwestern 
course of some of the smaller ancient as well as modern streams, and to have turned them northerly 
towards the Middle Fork. The entire absence of volcanic matter to the westward from it is cer- 
tainly an argument in favor of this idea. It thus appears that not only the great general skeleton, 
but even some of the minor features of the ancient topography may be found, which remain to-day 
almost as they were then. In connection with this idea of similarity between the bed-rock 
topography of then and now, another locality, which may be worthy of a passing notice, is the vicinity 
of Wilcox’s claim (otherwise known recently as the China claim), on the North Fork of Long 
Caiion.* Here a channel of considerable magnitude appears to come through the ridge in a south- 
east direction and cross the present North Fork of Long Cajon ; after which, in all probability, it 
curves southwesterly. The gravel in this channel is mainly of metamorphic rocks, and yet all the 
bed-rock here is granite ; and it is several miles from here, either northwesterly or northerly, to the 
nearest point at which I have any information of any considerable quantity of metamorphic rocks 
* See ante, p. 97. 
