

80 



AUBIFEROUS GRAVELS OF THE SIERRA. NEVADA. 



they extend high up towards the crest of the Sierra. He also explored the 

 region about the South Fork of the American, and examined all the im- 

 portant points in El Dorado County, especially the neighborhood of Placer- 

 ville, as well as a considerable portion of El Dorado and Amador counties, as 

 far south as the Mokelumne River. Nearly or quite all the hydraulic mining 

 districts where any work was doing between that river and the North Fork 

 of the American were examined by Mr. Goodyear during the course of the 

 summer. The region north of the North Fork of the American, as far as the 

 Middle Yuba, was assigned to Mr. A. Bowman, who took the field early in 

 the spring of 1870. Professor W. II. Pettee joined him in July, and they 

 together spent nearly all the remainder of the year in working out the 

 geology, and mapping the detailed topography over the area indicated. 

 From their surveys, aided by such information as could be obtained from the 

 various gravel mining and ditch companies in the region, the map, which is 

 appended to this volume, was compiled by Messrs. Hoffmann and Craven. 

 This map, which is on a scale of one mile to the inch, extends over the area 

 between the Middle Fork of the American and the Middle Yuba, embracing 

 the most important hydraulic mining region of the State. The work of 

 Messrs. Bowman and Pettee was supplemented on the north by surveys made 

 for private companies by Mr. Hoffmann, so long chief topographer of the 

 Geological Survey; the work thus introduced was especially important as 

 including perhaps the most important of all the gravel deposits in the State, 

 those between the South and Middle Yuba. A considerable number of ditch 

 lines in the region surveyed are also laid down from information furnished 

 by the various companies; also all the quartz and gravel mining claims 

 which had, up to 1873, been patented or officially surveyed for the purpose 

 of securing a patent under the United States laws are indicated upon this 



map 



* 



In regard to the extension of the gravel ranges north of the Middle Yuba, 

 our data are far from complete. The region was traversed at different times 

 by various members of the Survey, but never systematically explored. This 

 is especially true for the interesting district between the Middle Yuba and 

 Slate Creek. Plumas County was explored by the writer in 1866 ; but here 

 the gravels have by no me*ans the importance which they possess farther south. 



* As the location of these claims is not a matter of scientific interest, it has not been considered neces- 

 sary to have the map brought up to date in respect to the additional patents which have been issued 

 since 1873. 



