182 



THE AUBIFEBOUS GRAVELS OF THE SIERRA NEVADA. 



The other branch of the lava flow, mentioned above as dividing near Ban- 

 ner Mountain, runs for nearly ten miles almost due west, passing a little to 

 the north of Grass Valley, and terminating just before reaching Rough and 

 Ready. There are numerous hydraulic mining claims at various points along 

 the edge of this branch ; but they are not now, neither have they ever been, 

 of very considerable importance. 



The group of gravel mines near Nevada City, which is only three miles 

 northwest of Grass Valley, is connected with another flow than that just 

 indicated as having come down from the direction of Mount Oro. This flow, 

 one point of which, just north of Nevada City, is quite a conspicuous eleva- 

 tion, and, as usual, known by the name of the " Sugar Loaf," seems to have 

 come down on what is now the divide between the South Yuba and Deer 

 Creek, having headed, however, not far from the great volcanic centre near 

 Mount Stanford, or very near where the other flow originated, which has 

 made its way along to the north of the North Fork of the American, and 

 which appears to be connected with the occurrence of the Dutch Flat and 

 Gold Run gravels. In fact the whole appearance of these volcanic masses 

 which occupy so much of the space between the North Fork of the American 

 and the South Yuba rivers, is that of a connected series of flows, originating 

 nearly at the same central focus, spreading fixn-Iike in their descent, and 

 terminating at the various points already indicated, which are from four to 

 five thousand feet lower than the starting-place. 



There are a large number of gravel deposits connected with these lava 

 flows, the position of which can, however, be better made out from a consul- 

 tation of the map than from a written description. Some of these were ex- 

 amined at various times, both by the writer and by Messrs. Pettee and Bow- 

 man, and such particulars as are on record in regard to them will here be 

 given, beginning with the localities near Grass Valley and following chiefly 

 the notes of Professor Pettee. 



i 



On Alta Hill, just northwest of the town of Grass Valley, there is a capping of lava overlying 

 travel into which several shafts have been sunk, the sill of the shaft-house at " Alta No. 2 " being 

 2,758 feet above the sea-level, those of " Alta No. 1 " ten and a half lower, and those of the Hope 

 Company ten higher. In regard to these mines, which were not very extensive and which were ex- 

 amined by Mr. Bowman, the writer has no information of importance. In the Grass Valley Eavine 

 there is a locality known as the Grass Valley slide, the opposite side of the ravine being called the 

 Kureka slide. The elevation of the bed-rock here is 2,490 feet. It seems clear, according to Pro- 

 fessor Pettee, that this is really a " slide/' and not a part of any main channel. This conclusion 

 seems justified, partly because the measurements show the bed-rock to be so much below the bot- 

 tom of the shafts on Alta Hill, and partly because the ravine seems to be filled with alternations 



