CATSKILL FORMATION. G 5 . 71 



tion of the thicknesses of the subdivisions, (1530') can only 

 be approximately correct for any given part of the district, 

 because the upper subdivisions have been measured in 

 southeastern Susquehanna and middle Wayne, while the 

 lower subdivisions have been measured in middle and north- 

 ern Susquehanna county. 



What the thickness of the lower subdivisions maybe un- 

 derneath Wayne, only bore-holes can determine, and we can- 

 not now find out in any way what the original thickness of 

 its upper subdivisions was in northern Susquehanna, for 

 they have been all removed. 



It is plain enough that the whole formation was thicker 

 towards the south and southeast, and thinner towards the 

 north and northwest.* Therefore, while 1500' may be a 

 large total for the formation as it originally existed on the 

 Bradford county line and along the New York State line, 

 it is probably much too small a total for the whole forma- 

 tion under southern Wayne. This the future survey of 

 Pike and Lackawanna counties will reveal. 



At Mauch Chunk and Pottsville the nearly vertical out- 

 crops of the Catskill mass may be easily measured, and its 

 thickness was reported by the First Geological Survey at 

 about 5000'. 



In the Hudson river face of the Catskill mountain Mr. 

 Sherwood's detailed section (Report R, p. 219) sums up 2400'. 



2. The areas colored as Chemung on the geological map 

 accompanying Report G along the eastern border of Brad- 

 ford, and naturally extending over into Susquehanna 

 county, should, in my opinion, have been colored as Cats- 

 Jcill ; because, in nearly every place where I have seen the 

 surface of these areas I have found it occupied by what I 

 have classified as the lower groups of the Catskill forma- 

 tion, and have thus colored them on the geological map ac- 

 companying this report ; the only genuine Chemung area 

 being in the northwestern corner of the county. Elsewhere 

 along the western border the New Milford lower sandstone 

 and rocks overlying it occupy the ground. I suspect that 



*The individual strata grow coarser and thicker in that direction, gravel re- 

 placing sand, and sand replacing mud in their constitution. 



