106 THE DEVONIAN AND CARBONIFEROUS. - [bull. 80. 



the Pittsburg bed, where it has a thickness of 860 feet, and in Venango 

 County of 650 feet. Its equivalent in Ohio and Kentucky is known as 

 the "Knobstone formation.' 7 



Underlying these rocks is the oil-sand group, having a total thick- 

 ness of 350 feet. The first oil-sand, known as the Gantz rock, was 

 struck at Pittsburg, at 1,435 feet below low-water river level, and has 

 a thickness of 112 feet. The second oil sand is called the Fifty-foot 

 rock, and the third (the Gordon rock) is 260 feet belovV the Gantz rock. 



Concerning the Devonian rocks below the oil-sands little definite 

 knowledge has been attained. 



Frank A. Hill, 1 in 1887, made the following remarks about the cor- 

 relation of the formation of the northern coal fields of Pennsylvania : 



The Northern coal fields are situated chieflyin Luzerne, Lackawanna, Susquehanna, 

 and part of Wayne counties. " The Northern coal field" consists of a single curved, 

 crescent-shaped hasin, with its concave side facing northwest, and "locally divided 

 into the Wyoming and Lackawanna valleys. " The rock series consists, besides the 

 coal beds, of shales, slates, sandstones, and conglomerates. The Pottsville conglom- 

 erate .above the coal seams has an average thickness of 200 feet. The coal beds are so 

 split up that in many parts of the valleys they bear different local names, suggest- 

 ing no relationship whatever. In fact, so little is known concerning the coal beds, 

 that it is at present impossible to make any definite statement concerning their 

 identification and equivalency. 



In 1888 Mr. J. J. Stevenson, as a member of the American commit- 

 tee, prepared a u Report on the Upper Paleozoic (Carbonic)," for the 

 International Congress of Geologists, which contains the following 

 classification of the Upper Carbonic : 2 



UPPER COAL MEASURES. 



Synonyms and local subdhnsions. 



Pennsylvania, XIII in > xyi J Upper Barren group j Wath?nfton P grenp | Permian - 

 part, Mononganeia > xy <^ Upper Productive g roU p; Upper Productive Coal 

 8eries * > [ group. 



Virginia and West Virginia. ) yy > Upper Coal Measures. 



Ohio Upper Coal Measures. 



Merome Sandstone. 



Indiana \ Upper Coal Measures. 



Illinois ) 



Iowa ) Upper Coal Measures. 



ansas. .- > Permo-Carbonic and Coal Measures in part. 



Missouri 5 



Western region Permo-Carbonic and Upper Carbonic in part. 



Nova Scotia Pernio Carbonic. 



New Brunswick Upper Coal Measures. 



1 Hill, Frank A. : Geology and mining in the Northern coal field of Pennsylvania. Am. Inst. Mining 

 Eng., Trans., Vol., 15; 1887 pp. 699-707. 



2 International Congress of Geologists, London session. Reports of the subcommittees appointed by 

 the American committee from its own members, assisted by associates, for the fourth session of the Con- 

 gress to be held in London, September 17, 1888. D. Report of the subcommittee on the Upper Paleo- 

 zoic (Carbonic). J. J. Stevenson, reporter. Pp. D4-D7. 



