ACADEMY OP NATURAL SCIENCES. 25 



of the topography are given, as minutely as the scale allows, is nearly completed, 

 and will be soon ready for the engraver. 



2d. A detailed map, on a scale of two inches to the mile, of the vicinity of 

 Mount Diablo ; this is about two and one-half by three feet in dimensions, and 

 includes the most important coal mining district yet known to exist in the State. 

 The map can be made ready for the engraver in a few days. 



3d. A map of the Coast Eanges, from the Bay of Monterey south to Santa 

 Barbara. It is about three feet by two and one-half in dimensions, is on a scale 

 of six miles to the inch, and embraces about 16,000 square miles of territory. 

 To complete it will require about another year's work in the field with two sub- 

 parties. 



4th. Map of the "Washoe silver-mining region — three and one-half by two and 

 one-half feet in dimensions, on a scale of two inches to the mile — and extending 

 over all the important mining ground of the district. This map is from an 

 accurate trigonometrical survey by V. Wackenreuder ; it is nearly completed. 



5th. Map of the Comstock Lode, on a scale of four hundred feet to the inch, 

 completed. 



6th. Map of the central portion of the Sierra Nevada ; scale not yet deter- 

 mined on. Extensive surveys have been made by Mr. Wackenreuder for this part 

 of the work, and these will be continued during the present season. 



Of the above mentioned maps, Nos. 1 and 2 will accompany the first volume 

 of the Report. Nos. 4, 5, and probably 6, the second volume. 



It is intended, if the survey is carried to completion, to construct a final map 

 of the State on a scale of six miles to the inch, in nine sheets, each about three 

 feet square. 



In addition to the regular topographical work, an extensive series of baro- 

 metrical observation has been made, for the determination of altitudes, some two 

 hundred and fifty important points having been ascended and measured. The 

 most interesting operation in this department was the determination of the 

 height of Mount Shasta, which, by an elaborate series of observations, we found 

 to be 14,440 feet above the sea level. This is the first of the lofty volcanic 

 peaks of the Sierra Nevada which has been accurately measured. 



In the department of geology proper, our explorations have extended over 

 portions of forty of the forty-six counties into which the State is divided ; and 

 when it is remembered that the average size of a county is equal to half that of 

 the State of Massachusetts, (California having just twenty-four times the area 

 of that State,) some idea of the magnitude of our work may be obtained. The 

 chain of the Sierra Nevada may be parallelized with that of the Alps for extent 

 and average elevation ; while the Coast Ranges are nearly as extensive as the 

 Appalachian chain of mountains. 



We have obtained a pretty clear idea of the general structure of the Coast 

 Ranges from Los Angeles t6 Clear Lake ; the vicinity of the Bay of San 

 Francisco has been worked out in considerable detail, including all of San 

 Francisco, San Mateo, Santa Clara, Alameda, Contra Costa, and Marin Coun- 

 ties, with portions of Santa Cruz, Solano, Napa, and Sonoma. Considerable 

 field-work has been done in the Sierra Nevada, chiefly in the lower portion of 



