REVIEW AND GENERAL DISCUSSION. 



49i» 





just cutting across the tops of the modern spurs, hut 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-canon 

 and has been washed away. All these channels have not simply a perceptible, but a considerable 

 grade, falling in the directions of their How 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 lowed 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- 

 fident that it was so. 



To return to Georgetown. A line drawn from the junction of Long Canon 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 Canon Creek, would 

 include between it and the river all the volcanic 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 Mill. 

 To the south from Georgetown the country slopes gradually towards the canon 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 Canon Creek, it consists entirely of the bed-rock, slates, etc., covered 

 only by the varying quantities of soil and comparatively recent gravel which have accumulated 

 over it. The ridge last referred to stretches southeasterly from the river west of Canon 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 south western 

 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 thru. 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 

 Canon.* Hero a channel of considerable magnitude appears to come through the ridge in a south- 

 east direction and cross the present North Fork of Long Canon ; 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. 



