244 PKOCEEDINGS OF THE CALIFORNIA 



notes and specimens, after reference of the fossils obtained to Mr. 

 Gabb and Dr. Newberry. M. Remond has gone to Chili to continue 

 his geological investigations, if his health permits ; and he expects 

 to write out a more detailed account of his Mexican work, when- 

 ever he has an opportunity of doing so. In the mean time, how- 

 ever, it is his desire that this abstract should be drawn up and pub- 

 lished, that at least the more important results may be placed as 

 soon as possible in the hands of those interested in the develop- 

 ment of the geological structure of those countries which border on 

 the Pacific coast. In presenting this paper, Professor Whitney de- 

 sired to express his admiration of the courage and endurance with 

 which M. Remond had prosecuted his investigations in Mexico, 

 where he had to contend with every kind of difficulty and danger, 

 but where, however, he had obtained results of great value, throw- 

 ing the first rays of light on the age of the formations of a very 

 interesting and economically important mining region — a region 

 which has been often visited, but where, previous to M. Re'mond'a 

 examinations, no positive evidence of the geological position of any 

 of the stratified rocks had been obtained, and no clue given to the 

 relations of the metalliferous veins to each other, or to the rocks in 

 which they are inclosed. 



Notice of Geological Explorations in Northern Mexico. 



BY A. REMOND. 



[Compiled from his notes, and prepared for publication, by J. D. Whitney.] 

 I. PRELIMINARY REMARKS. 



The mountainous region comprising the central and western portion of North, 

 ern Mexico, belongs to the four States of Durango, Chihuahua, Sinaloa, and So- 

 nora. Considering how celebrated this portion of Mexico has become for its 

 mines and metalliferous veins, and how much has been written about it, it is 

 surprising how little exact information has hitherto been obtained with regard 

 to either its geography or geology. On comparing the principal published maps* 

 of the region in question, it will be seen at once how much they differ from 

 each other in their delineations of even its main topographical features, while 

 the details are entirely wanting. 



*The best map of Northern Mexico is that of M. de Fleury, published in San Fran- 

 cisco, in 1864; but this makes little pretense to a delineation of the topography; the 

 courses of the principal streams and the position of the larger mining towns are often very 

 far from being correct, as must be expected on a map constructed without a basis of instru- 

 mental surveys. J. D. w. 



