1881.1 ^^« [Ashburner. 



The irregularities which are so characteristic of the Alton group coals ia 

 McKean county* belong not only to the Alton coals, but also to the Cler- 

 mont coal at St. Mary's. Although very little encouragement can be ex- 

 tended the coal operator or land owner as to the value of these beds, it 

 would be presumptuous for the geologist to condemn the territory which by 

 a surface instrumental survey should be found to be high enough to contain 

 these coal seams. The area under which the coal beds might be found is 

 very great. 



On the Monastery lands, on the east side of Silver creek, the Clermont bed 

 has been extensively worked and has produced a good quality of coal. The 

 coal has been explored for on the St. Mary's Coal Company's tract, but has 

 never been found. 



The Alton beds (strata Nos. 17 and 19), have been found on the Monastery 

 lands, on the Keystone and Tannerdale tracts. The interval between the 

 two beds varies from 14 to 23 feet. Each bed is generally composed of two 

 distinct benches of coal, with a stratum of slate or clay between them. 



The Alton group, which represents the same series of strata as the Mercer 

 coal group, sometimes contains three coal beds, as in central McKean, but as 

 a rule it rarely embraces more than two coal beds, as is found to be the case 

 generally throughout Elk. 



Resembling in many of its features the Mercer group of Lawrence and 

 Mercer counties, the Alton group differs essentially from the Mercer in 

 containing no beds to represent the Mercer limestones ; for no calcareous 

 strata have been seen in it, in McKean, Cameron, Elk or Forest counties. 



The shales and clays between the Alton coals frequently contain nodules 

 of iron carbonate ore. The iron is, however, never regularly stratified. 

 These beds represent the Mercer iron shales along the Pennsylvania-Ohio 

 line. 



No. XII. — The Pottsville or Carboniferous conglomerate (Millstone grit 

 of the English geologists), does not consist of one solid bed of conglomer- 

 ate, but is composed of a series of rocks made up of conglomerates, sand- 

 stones, shales, slates, fireclays and coal beds, divided as follows : 



Johnson run and Homewood sandstone 32' 



Alton and Mercer coal groups 24' 



Kinzua creek and Connoquenessing sandstones 45' 



Marshburg Upper and Sharon coal interval 10' 



Olean, Garland and Sharon conglomerates, Second moun- 

 tain sand and Ohio conglomerate 50' 



Total 161' 



The first name given for each subdivision is that which was provisionally 

 adopted in McKean county, the latter names are those which are better 

 known along the Ohio-Pennsylvania State line. 



The individual members of the Pottsville conglomerate have been fully 

 described in the Survey reports to which the reader is referred. 



* Geological Survey, Report R, page 53. 



PROC. AMER. PHILOS. SOC. XIX. 108. 2r. PRINTED MAY 3, 1881. 



