24 PROCEEDINGS OF THE CALIFORNIA 



the State, with the view of acquiring a knowledge of its general geological 

 structure, the age of the various formations which occur in it, and as com- 

 plete a geueral idea as possible of their range and extent, so that a foundation 

 might be laid for the detailed work which would follow the preliminary exam- 

 ination ; the second idea was, at the same time that the general examination 

 was going on, to work up in detail certain more important districts, so that the 

 public might have light on questions of economical interest, and at the same 

 time be able to form an idea of what the work might be if ever carried to com- 

 pletion. Besides this, the natural history part of the survey was to be carried 

 on, in connection with the geological work, as rapidly as possible, progress in all 

 departments being necessarily proportioned to the varying amounts of the an- 

 nual appropriations. 



California is covered by a vast net-work of mountain ranges, separated by 

 comparatively narrow valleys, with the exception of those of the Sacramento 

 and San Joaquin, which do not, together, cover more than one-fifteenth of the 

 area of the State. The remaining fourteen-fifteeuths may be called mountain- 

 ous, as the valleys include but a small portion of its surface. Into this mount- 

 ainous region no accurate surveys have ever been carried ; even the General 

 Land Office work stops at the base of the mountains. A few ranch lines have 

 been run among the moderately elevated portions of the Coast Ranges ; but, as 

 a general thing, the genuine Mexican grants were limited to the plains. 



Without considerable topographical work in connection with the geological 

 survey we should, then, be entirely unable to carry on our geological work with 

 any pretense to accuracy, as we could neither locate our observations nor make 

 our descriptions of the country intelligible. The authority for doing something 

 for the increase of the geographical knowledge of the State is found in the clause 

 of the act authorizing the survey, which requires " proper maps " to accompany 

 the reports. 



What has been done, up to the present time, in this department may be 

 briefly recapitulated as follows : 



A series of maps, forty-nine in number, has been compiled by Mr. Hoffmann 

 from the original documents at the United States Surveyor-General's Office ; 

 the scale of these is half an inch to the mile. They contain a compilation of 

 nearly all that is known at that office in regard to the geography of the State. 

 The maps, as thus blocked out, have been used by us in the field, by filling in 

 the topography wherever our route has laid. 



The maps which have been or are now being prepared for publication are : 



1st. A map of the vicinity of the Bay of San Francisco, on a scale of half 

 an inch to the mile, four feet by three ; it extends from near Santa Cruz on the 

 south to Napa on the north, and from the Pacific to Corral Hollow, east and 

 west. The area of land which it covers is 4,248 square miles, which is just 

 twice that of the State of Delaware, and only lacks two hundred square miles 

 of equaling that of Connecticut. As near as can be ascertained, it contains 

 one-third of the population of the State, and has about thirty inhabitants to 

 the square mile — the average density of the population of California being 

 but little over two to the square mile. This map, on which all the details 



