NOTE. 



The following reports will constitute the series of the Geological 



EXPLOEATION OF THE FOETIETH PaEALLEL : 



Volume I. Systematic Geology. 



Volume II. Descriptive Geology. 



Volume III. Mining Industry. 



Volume IV. Zoology and Paleontology. 



Volume V. Botany. 



The present, or Volume III, has been first prepared and published, 

 because its subject, Mining Industry, is most directly applicable to the mate- 

 rial development of that great extent of mountain territory opened up by the 

 Pacific Railroad. 



The other volumes will be pressed to completion with all possible rapid- 

 ity. The Atlas of Topographical and Geological maps, necessarily the latest 

 of the publication, will be issued in 1871. 



CLARENCE KING, 



U. S. Geologist in charge. 



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