BIBLIOGRAPHY. 



In the hihliography to follow 1 have endeavored to include all papers which 

 contain information about the Paleozoic, and especially the Carboniferous, rocks of 

 Colorado. It would be hard to overestimate the service which the general bibli- 

 ographic Avorks on American geologj' compiled by N. H. Darton and Ijy F. B. Weeks 

 ha\'e rendered in this effort. Without them it would have been practically impossible 

 to attain the completeness now reached with comparative ease. 



The bibliography as it now stands includes nearly 140 entries, all of which have 

 been examined with greater or less care, as occasion seemed to demand. Only a 

 comparatively few of these, however, were found to contain mattei' which it is 

 necessary to bring into discussion. On the other hand, the works included in the 

 bibliography form but a small portion of those more hastilv examined in the search 

 for matter relating to the subject in hand. Selection was frequently not easy and 

 may not always have been made with discernment and uniformity. Many, works, of 

 which the very e&vly accounts of travel form one class and the briefer papers of an 

 economic nature another, touch so lightly upon the stratigrajihic and historical sides 

 of the geologic question that it really seems to matter little whether they are 

 included or not. They seldom contribute much, still less often anything different or 

 new, to the subject. I endeavored to select from this material in a uniform manner. 

 If failure has arisen it has been not through an}' wish, but through an inability, 

 to select impartially. 



The earliest publications seen by me in which rocks of Carboniferous age are 

 reported in Colorado are two geologic maps of the United States, one by 

 Hitchcock, the other by Marcou. Both appeared in 1853. Marcou colors in a small 

 area of Mountain limestone in the northern part of the State. Hitchcock represents 

 three areas of Coal Measure rocks, one having somewhat the position of that drawn 

 by Marcou, another apparently occupying somewhat the j^osition of the San Juan 

 Mountains, while a third appears to be situated about where lies the Sangre de Cristo 

 Range. As has long been known, Marcou's Mountain limestone in the West is for 

 the most part really Upper Carbonifei-ous, so that for the State of Colorado 

 Hitchcock's map is rather more accurate than Marcou's, but geologic knowledge of 

 the West at that early daj was so imperfect and fragmentary that neither map has 

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