62 GLACIAL AND SURFACE GEOLOGY OF THE PACIFIC COAST. 



known in regard to the former glaciers of the ranges east of tlie Sierra 

 Nevada, in the same latitude, and also in the Eocky Mountains. 



At the time of the beginning of the California Geological Survey (1860), 

 nothing whatever was known, at least nothing had been published, in regard 

 to the former presence of glaciers anywhere in the Rocky Mountains. Our 

 investigations having made it evident that ice had once covered a consider- 

 able portion of the Sierra Nevada, and having clearly established the most 

 important facts connected with this former glaciation along the Pacific coast 

 as far north as the United States boundary line, it became desirable that 

 something should be ascertained in regard to the occurrence of similar phe- 

 nomena in portions of the Cordilleras lying farther east, namely, the Great 

 Basin Ranges and the Rocky Mountains. Up to the year 1869 nothing had 

 been definitely made out as to the former glaciation of any part of the Cordil- 

 leras outside of the limits of California.* It was, therefore, partly for the pur- 

 pose of obtaining some light on this interesting question that the writer spent 

 a part of the summer in the highest region of the Rocky Mountains, as already 

 mentioned. Previous to this, however, he had personally examined several 

 of the important ranges of the Great Basin, namely, the West Humboldt, the 

 Toyabe, and portions of the Wahsatch Range. Since 1869, the voluminous 

 publications of the Fortieth Parallel and the other United States Surveys 

 have given abundant details in regard to the now well-understood phenom- 

 ena of extinct glaciers in the region in question, and it is now possible to 

 miike out pretty clearly what portions of the I'anges were formerly covered 

 by ice, and how far down their flanks the detrital materials have been carried 

 by glacial agencies. The deficiencies in our knowledge are most marked in 

 the northern portion of the Rocky Mountain ranges within the limits of the 

 United States. Much the larger portion of the detailed work done hy au- 

 thority of the United States has been carried on in the central and southern 

 parts of the region in qnestion, or to the south of the parallel of 42°. The 

 belt of country thus examined, however, includes the higher ranges of the 

 Cordilleras, whose broadest and highest portion lies between the parallels of 

 36° 30' and 42°. 



* From Dr. Hayden's " Report of the Exploration of the Yellowstone and Missouri Rivers" (1859-CO), pub- 

 lished in 1869, it would appear that the fact of the detrital material in the Wind River Mountains having every- 

 where been derived from rocks near at hand had strongly impressed itself on the author's mind. And when it is 

 said (page 84) that, "on the left bank of Wind River, it would seem as though the icebergs had lodged against 

 it and quietly deposited the burden of I'ocks which they had acquired in the more elevated mountains," it is 

 apparent that the intention of the author is to indicate the existence of moraines, and to describe those phenomena 

 which could only have been due to former glaciation. 



