22 



Sierra Club Bulletin. 



made each year by Professor H. F. Reid, of Baltimore, 

 and published in the Journal of Geology. I present the 

 subject here in the hope that the members of the Sierra 

 Club will make use of the opportunities afforded by their 

 excursions to secure for science a record of the changes of 

 Sierra glaciers. It is true that the Sierra glaciers are 

 small, and their changes from year to year are probably 

 much less than in the case of the relatively large glaciers 

 to which such studies have usually been restricted. But 

 this fact does not interfere in the least with the value 

 and interest of comparative observations, if they shall 

 be made. It is desirable that the studies of glacier varia- 

 tion be not limited to a single district, and the greater 

 the variety of general physical conditions under which 

 the observed variations occur the better the prospect 

 of reaching a theory of causation which shall be entirely 

 general. 



In 1885 I. C. Russell published, in the Fifth Annual 

 Report of the United States Geological Survey, an ac- 

 count of the existing glaciers of the United States, and 

 his paper not only summarized what was then known of 

 the glaciers of the Sierra Nevada, but gave references to 

 the earlier literature. The most important contributors 

 to that early literature were John Muir, Galen Clarke, 

 and Joseph Le Conte. Russell himself made an important 

 addition, and all later contributions, so far as I know 

 them, have been pubHshed by the Sierra Club. 



Russell's paper gives several illustrations of the Dana 

 Glacier, from photographs made in August, 1883, and the 

 original negatives are still accessible in the files of the 

 United States Geological Survey, so that it will be pos- 

 sible, by means of new photographs, to determine how far 



