Report of the Director. 9 



these beds are not persistent. The difficult problem was to find the 

 means of tracing a line or limit between the Chemung and Catskill 

 formations, which could be recognized either by lithological or by 

 palf^ontological characters. 



With a view to a continued and connected series of observations 

 upon these rocks, I engaged the services of Mr. Andrew Sherwood, 

 of Mansfield, Pennsylvania, who had already considerable knowledge 

 of these formations, to trace the outcrop and limits of the Catskill 

 group. 



Mr. Sherwood has devoted the entire season to this work, and to 

 the collecting of fossils, and has made very satisfactory progress 

 towards a solution of some of the difficulties which have heretofore 

 encompassed the subject. It has been more clearly shown that the 

 red rocks, alternating with the higher part of the Chemung group, 

 do assume the character of the Catskill group ; and although the 

 latter is a very distinct and well marked formation, its limits may 

 not always be readily recognized on the borders of the underlying 

 formation. 



In many localities there will likewise be some difficulty in defining 

 the upper limits of the Catskill group, at its junction with the sand- 

 stones of the formation known in the geology of Pennsylvania as the 

 Vespertine formation, or No. X of the geological survey of that 

 State. 



An example of the obstacles to be met with in tracing the limits 

 of these formations may be mentioned in the fact, that soon after 

 beginning the field w^ork, Mr. Sherwood discovered a thin band of 

 gray sandstone, charged with well known Chemung fossils in the 

 midst of the red sandstone, and 150 feet above a line which had been 

 heretofore considered as the established base of the Catskill forma- 

 tion. This band, only a foot in thickness where discovered, is not 

 likely to be continuous with the great mass, and we are elsewhere 

 left without evidence to guide in conclusions upon the limits of the 

 group. 



In another instance a mass of red beds, 100 feet in thickness, were 

 found within the limits of the Chemung group proper. 



These facts prove that the conditions which finally prevailed, 

 giving origin to the great mass of red and gray rocks of the. Catskill 

 formation, began at a much earlier period, but were intermitting in 

 their action and local in their effects for a considerable period. 



I believe we shall soon be able to define, with as much accuracy 



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