6 



California ; this exploration we expect to continue as soon as it is in our 

 power to take the field again in the Sierra. 



In the meantime, Mr. Gabb has left for the southern part of the State, 

 to make a thorough examination of portions of the Coast Eanges, where 

 the occurrence of bituminous matter in large quantity has, especially 

 during the last twelve months, been exciting much attention. 



The above is all the geological fieldwork which it has been in our 

 power to undertake, with the extremely limited appropriation made by 

 the last Legislature, a portion of which had necessarily to be used in the 

 preparation of the "Geological, Botanical, and Zoological History of the 

 State/' provided for in the Act under which we are now at work. What 

 progress has been made in the preparation of our results for publication, 

 in conformity with the Act, will now be stated under the appropriate 

 heads. 



I. TOPOGRAPHY. 



In addition to the maps previously described as forming a portion of 

 the results of our topographical work, we have commenced a new one, 

 which embraces the most valuable and important part of the State, and 

 covers the area on which, as near as can be ascertained, somewhat over 

 nine tenths of the population are now residing. This map extends from 

 the parallel of thirty-six degrees and thirty minutes to that of forty 

 degrees and thirty minutes, and from the one hundred and eighteenth 

 to the one hundred and twenty-third meridian, thus including the whole 

 Sierra from Owen's Lake north, to Lassen's Peak, the Coast Ranges from 

 Point Sur and New Idria on the south, to Clear Lake on the north. It 

 also includes the western portion of Nevada. The scale of this map is 

 six miles to the inch, and its size four and a half feet square, so that i't 

 can be engraved to four sheets. On this all the topographical work of 

 the survey has been compiled, together with such materials of an authen 

 tic character as could be obtained from other sources, especially from the 

 offices of the United States Surveyor-General, and the United States 

 Coast Survey. The work of Mr. Wackenrcudcr in the high Sierra, 

 which was continued for a short time during the summer of eighteen 

 hundred and sixty-four, forms an important portion of the new material 

 incorporated in our map of Central California. The drawing of this 

 map is considerably advanced, and has been executed by Mr. Hoffman, 

 the topographer of the survey, in the most creditable manner; if ever 

 completed, it will not only form a highly important contribution to the 

 geography of the State, but will be of great practical value. A consid 

 erable amount of fieldwork, however, remains to be done in the region 

 which it covers. The extreme northwestern portion, including the region 

 north of Clear Lake, has never been even approximately mapped, and 

 portions of the Sierra, especially the region between the Mono and the 

 Silver Mountain Passes, and that north of the Henness Pass, have never 

 been instru mentally surveyed. 



The "map of the region adjacent to the Bay of San Francisco," and 

 that of the vicinity of Mont Diablo, are ready to be placed in the engrav 

 er's hands, and the last named one will be photolithographed as soon as 

 an establishment for doing this kind of work by the " Osborne process" 

 is set in operation in this country, Mr. Osborne being at present in Boston 

 for this purpose. Some difficulty has been met with in finding an artist 

 who could be trusted to do justice to the bay map; but the close of the 

 war and the contraction of the currency will, it is to be presumed, 

 relieve our engravers on copper and steel from a large portion of the 



