532 Natural Histmy of the N.E. Extremity 



the south and east. It is to the same circumstance we trace 

 the preservation of the Lycoming coal basin, and of one or 

 two small detached coal fields in Bradford county to the 

 east, which have been similarly protected, while a great inter- 

 mediate space to the west remains barren of mineral strata. 

 These undulations, though not very apparent to the eye of 

 the casual observer, amidst so much vegetation and broken 

 ground, are easily proved by the requisite observation, and 

 are quite adequate to produce all the modifications which we 

 have indicated. 



These remarks are made with a view to explain, on geolo- 

 gical grounds, why so large a portion of the lands in this 

 section of the great Alleghany coal range, even where the 

 mountains attain their greatest altitude, are still without that 

 useful mineral. In such situations the lowest members only 

 of the coal formation are found in situ. We perceive the 

 platform upon which the coal measures usually repose ; but the 

 soft strata containing the coal itself are absent, or can only be 

 traced by their detritus; and sometimes the old red sand- 

 stone rises to the summit without any covering of secondary 

 rocks. 



With respect to the scale of these curvatures, it will con- 

 vey an adequate view of the configuration, derived from cor- 

 rect data, to state that the Lycoming coal field in its shortest 

 transverse diameter, from south to north, represents an arc 

 whose chord is three miles, and whose versed sine is only 

 110 ft. The Tioga coal field, which lies seven miles north of 

 this, is a vast arc, having a chord of seven miles in length, 

 the versed sine of which is only 200 ft. 



In this portion of the Alleghany range the coal veins are 

 commonly five in number, comprised within a thickness of 

 from 100 ft. to 150 ft. About three of these are of sufficient 

 size to be worked, averaging about 3 ft thick. 



From the analysis which Mr. Clemson was good enough to 

 make, the Tioga coal yielded the following proportions, in 

 different veins : — 



Splint coal. Pitch coal. 



Carbon - 69*3 - 54*26 



Volatile matter 14*6 - 18-50 



Ashes or cinder 16*1 - 27*24 



ioo ;oo 



100 ioo 



Interstratified with these veins of coal, are several beds of 

 argillaceous carbonate of iron. That of the Lycoming coal, on 

 analysis by a professor at the West Point establishment, pre- 

 sents results of the following nature : — ■ 



