INTRODUCTORY NOTE, 



Under the title of " Lithological Studies," a work is here preseuted to the public 

 which is, in point of fact, a continuation of the publications of the Geological Survey of 

 California, begun under my direction, in 1860. Had that Survey been completed, the 

 investigation of the rocks of the State would naturally have l}eeu one of tlie matters to 

 which our attention would, at the proper time, have been turned ; and, after the stoppage 

 of the Survey, in planning for the elaboration of the materials in my hands, I, in 1877, 

 determined that the lithological collections which 1 had accumulated, and which repre- 

 sented a wide area, should be described and classified. For this purpose Dr. Wadsworih 

 was selected ; aiul, a portion ot his results being now ready, it is thought best that it sliould 

 lie published, without waiting for the completion of the entire work. It will undoubt- 

 edly seem to the reader that what is here furnished does not exactly correspond with 

 or carry out the idea suggested on the title-page, namely, tliat this is a description and 

 classification of the rocks of the Cordilleras. The reason is this : Dr. Wadsworth having 

 been led by his investigations to place his work on a considerably different basis from 

 that built upon by otlier lithologists, has found it desirable, and indeed necessary, to 

 incorporate in it results obtained from the study of material not iurnished by the Cor- 

 dilleran collections. In the portion of the work herewith offered to the public, rocks more 

 basic tlian the basalts are brought under consideration ; and in doing this, it has been 

 found that it was not pnssibk' to arrive at tlie end souglit to be gaineil witliout using the 

 materials furnished by other regions and by other lithologists. Should this investigation 

 be continued and completed — as it is hoped will be the case, a large amount of work 

 having been already done with tliat end in view — the Cordilleran collections will yield 

 the chief portion of the material drawn upon for the remaining portion of the volume, so 

 that it will be fouud that the work is essentially based on the collections made on llie 

 western side of the North American continent, the study of wliicii gave rise to tlie ideas 



presented in this first part. 



J. D, WHITNEY, 



CAMBRIDGE, M.\ss., October 18. 1884. 



