NATURAL SCIENCES OF PHILADELPHIA. 363 



ON THE OCCURRENCE OF URANIUM, SILVER, IRON, ETC., IN THE 

 TERTIARY FORMATION OF COLORADO TERRITORY. 



BY E. L. BERTHOUD. 



November 24th, 1874, 1 was called upon to measure and examine 

 a coal mine called the Lyden Coal Mine, six miles north of Golden, 

 Colorado Territory. The measurement and the examination were 

 required to ascertain precisely what the explorations to that 

 date had done towards striking and opening up one of the largest 

 beds of tertiary coal that lie in the upturned stratification of the 

 Northern Colorado Coal Field, which the exhaustive examinations 

 and reports of Professors Hay den, Lesquereux, Cope, Gardner, 

 and Mauris on the coal fields of the eastern slope of the Rocky 

 Mountains have so largely elucidated ; but where close proximity 

 to the cretaceous, and the "delusion" of a local inversion, have 

 given some cause for doubts on the part of eminent geologists 

 as to the real position of the beds. But conceiving that this point 

 is now settled, it appears that the "raison d'etre" of the dispute 

 lies in offending cretaceous mollusca, that in Wyoming are found 

 regularly above beds of lignite coal, whose position is inferentially 

 identified with that of other formations lying above them that are 

 confessedl}' acknowledged to be tertiary ; until the general "homo- 

 logies" or succession of beds in Wyoming Territory are more 

 definitely settled, and compared rigorously with our Colorado 

 lignite deposits of like age, we must admit them by force of evi- 

 dence as cretaceous. 



But in the Colorado coal formation east of the mountains the 

 cretaceous fossils we find at the base of the Rocky Mountains are 

 invariably west of the outcrop of coal, and in the descending series ; 

 thus we are compelled to believe that this is no longer a question 

 for argument, and we shall speak of this coal field as, without 

 doubt, a tertiary deposit. The Lyden coal mine of Jefferson Co , 

 Colorado Terr., lies in Section Twenty-eight (28), Township 2 S., 

 Range 70 west, C. T., about 1^ miles east of the metamorphic and 

 eruptive rocks of the five ranges of the Rocky Mountains. The 

 trend of the outcrop of cretaceous and tertiary strata that here 

 are locally known as "Hogbacks" is N. 17 to N. 19 west, which 

 is also that of the coal beds intercalated in the tertiary shales, 

 clays, and sandstones. The coal and its accompanying walls are 



