52 ROCHESTER ACADEMY OF SCIENCE. [Jan. II, 



thousand six hundred and forty feet or half a mile below their rela- 

 tive situation near Lake Ontario." (') The red Medina of the (iene- 

 see Falls was correlated with " the old red sandstone of European 

 geologists." While it was further stated: "On this sandstone rests 

 a series of slates, limestones, shales,and siliceous strata, which corre- 

 sponds perfectly to the mountain limestone of Europe." ('") 



For a continuation of the history of the correlation of these 

 terranes, bringing the classification into harmony with that of the 

 present, the reader is referred to the excellent presentation of the sub- 

 ject in the correlation paper of Professor H. S. Williams on the 

 Devonian and Carboniferous. (') 



Correlation of the Upper Devonian and Lower Carboniferous. 



The first well record to be considered is that of one situated 

 between Richburgh and Clarksville, Allegany Co.; but before giving 

 this record it is necessary to hastily review the geological position of 

 the Olean conglomerate and underlying rocks. The opinions of the 

 geologists who have recently studied this series of rocks most 

 thoroughly — Ashburner, Carll and H. S. Williams — are hot in com- 

 plete harmony as to their geological age, therefore it is necessary 

 to state briefly the different correlations and to indicate which is 

 followed in this paper. 



Ashburner in 1880 published the following section of the rocks 

 of McKean County, Penn.: (^) 



Base of the 



Pottsville conglomerate, No. XII — Olean conglomerate 



Mauch Chunk, No. XI — Cannel slate 10' (') 



Upper — Shales and sandstones. . 60'^ 

 Pocono, No. X, \ Middle — Sub-Olean conglomerate 40' [- 250' {'') 

 Lower— Shales and sandstones 150) 



(i.) Am. Jour. Science, ist ser., vol. .xxxiii, p. 121. 



(2.) Ibid., p. 122. 



(3.) Bull. U. S. Geol. Surv., No. 80, in particular Chapters I and II. 



(4.) Report R, 2d Geol. Surv. Penn. The Geology of McKean Co. Seethe " vertical section " 

 on p. 43 and the detailed account of the following part of the section from p. 56 to p. 76. Also, a paper 

 by the same author on "The Bradford oil district of Pennsylvania," in Trans. Am. Inst. Min. Eng., 

 vol. vii, p. 316-328, and especially pp. 320, 321. 



(5.) /bid., p. 64. "Generally throughout central and northern McKean the Mauch Chunk 

 formation is represented by 5 to 10 feet of ferruginous argillaceous shale or black slate, sometimes 

 containing cannelly layers or a thin slaty coal, {Marshburg lowfr coai.y 



(6.) Ibid., p. 65. " The thickness of the entire group varies ; at Bradford it is 247 feet." 



