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GEOLOGICAL SOCIETY OF PENNSYLVANIA. 217 



I cannot close tliis article without adverting to the 

 remarkable variations or differences in the strata, at 

 different localities within this district. The sections of 

 these ravines are dissimilar, in the number, position and 

 thickness of the mineral beds, and the nature of the 

 accompanying rocks. In some situations the silicious 

 rocks prevail ; in others, the argillaceous. Sometimes 

 six or eight coal veins exist in one locality, and two or 

 three only appear in another. The quality of the coal, 

 too, is different at different points. These discrepances 

 can only be explained by more extensive and detailed 

 investigations. 



ESTIMATION OF THE QUANTITY OF COAL WITHIN THE 

 BLOSSBURG OR TIOGA COAL BASIN. 



The area of land beneath which we have evidence of 

 the existence of coal, within the limits of what I have 

 denominated for the present the mineral basin of Tioga, 

 comprises thirty-five square miles, or upwards of twenty- 

 two thousand seven hundred acres. Should it hereafter 

 prove that the mineral beds are continuous farther to 

 the west and unite with the great western bituminous 

 coal field, which I do not expect, the following estimates 

 will, of course, be materially increased. 



It has been stated, that in the numerous ravines by 

 which this coal basin is intersected, there are traces of 

 from four to nine veins of coal. So little has been ef- 

 fected in determining the real thickness of these, ex- 

 cept at two or three points, that I am unwilling to risk 

 a calculation of their maximum value. We know, how- 

 ever, that in nearly every valley, one vein at least has 

 been proved of the thickness of 3 to 3^ feet, and in one 

 instance of 6 feet. I think it will be perfectly safe to 

 found an estimate on the presence of a single vein of 

 about 3 feet, which will yield about five thousand tons 

 to each acre. 

 I.— 2 c 



