THE AURIFEROUS GRAVELS 



OF THE SIERRA NEVADA OF CALIFORNIA. 



CHAPTER I. 



GENERAL DISCUSSION OF THE TOPOGRAPHICAL FEATURES AND GEOLOGICAL 



STRUCTURE OF THE STATE OF CALIFORNIA. 



Section I. — Topographical Sketch. 



It seems a necessary preliminary to a detailed account of the Auriferous 

 Gravels of the Sierra Nevada, that the general features of the geography 

 and geology of the State of California should be sketched. Without such an 

 introduction the reader of this volume will hardly be able to have a clear 

 idea of the nature of the frame into which the special results here set forth 

 ftre to be fitted. The sketch must necessarily be brief, and may the more 

 properly be made so ? because it is the expectation of the writer that, in a 

 future volume, the topics rapidly passed over in this chapter will be much 

 *nore fully discussed. Reference may be made by the student of Californian 

 eology to the already published volume of the Survey, as also to the maps 

 which have been issued during the progress of that work. # 



The principal topographical features of California are so striking in their 

 general aspect, that they could not fail of early recognition; they were first 

 clearly indicated on Fremont's map, accompanying his Geographical Memoir, 

 published in 1848. Well known as these features are in their outline to most 



5 



"" r " Geology of California, Vol. I. A Report of Progress and Synopsis of the Field-work, from 1860 to 



i-864. This volume will be quoted in the present work as " Geol. I." The principal maps issued are : 



General Map of California and Nevada, on a scale of eighteen miles to one inch ; A Map of the Region 



wjacent to the Bay of San Francisco, scale two miles to an inch ; Map of Central California, on a scale of 



x niiles to an inch, in four sheets, the whole covering an area, of about 60,000 square miles of the most 

 important and thickly settled region of the State, and about 1 8,000 square miles of Nevada. Of this latter 



a P on h r two sheets have been finished and published ; these embrace a strip of about 150 miles in width, 

 extending across the State from east to west, having Visalia on its southern border, and Santa Rosa on 

 1 s northern. The other two sheets of this map were nearly completed when the Survey was stopped. 



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