156 NEW YORK STATE MUSEUM 



regarded as " Catskill " certain areas obviously of Carbonic age 

 and now designated as such on our geological charts. The 

 formal subtraction of these elements has left certain restricted 

 areas which express, how truly we do not yet know, the presence 

 of Devonic Catskill sedimentation in that region. Study of the 

 so-called " Bonaventure formation " in the northeastern Appa- 

 lachians, of like composition, color and attitude to the Catskill, has 

 fairly indicated continuous sedimentation through the last term of 

 the Devonic time into the early terms of Carbonic time, and in- 

 creases the probability that this type of " Old Red " sedimentation 

 in the middle Appalachians also overpassed the Devono-Carbonic 

 boundary line. 



To students of geology and topography the attitude of the Cat- 

 skills in New York has presented an unanswered question. While 

 one may be impressed with the rapid degradation of the 

 Catskill mountains massive and the deep downcutting of the drain- 

 age belonging to its successive peneplains, still the most conspicuous 

 and most striking feature of this topography is the abrupt eastern 

 face which fronts the Hudson river. Exposed as this face is 

 throughout its entire length to the great thoroughfare of traffic 

 up and down the Hudson valley, its origin excites constant 

 inquiry and its explanation has never been satisfactorily set 

 forth. While these eastern walls of the Catskills are sheer and 

 their almost horizontal strata stand out bare and conspicuous to the 

 observer, they are nevertheless somewhat rounded off by wear and 

 the approaches to the heart of the mountains from the east not so 

 abrupt as they may seem, yet to everyone who attacks them from 

 this side their abruptness is their most impressive feature. 



The question that promptly arises in the thoughtful mind, look- 

 ing upon this high pile made up of the edges of horizontal strata, 

 is this : What has become of the east and northeast continuation 

 of these horizontal beds which, if continued at the angle at which 

 the beds now lie, would have stretched as a mantle far over the 

 Hudson valley and the western hills of New England ? 



I am not aware that the geological conditions surrounding those 

 mountains themselves present an immediate solution to this problem. 

 and yet I think the answer is to be found by turning to sonic other 

 part of this sedimentation chapter where the mode of such mountain 

 building is more lucidly set forth. The Catskills of New York in 

 their eastern portion have been deposited on an area of old rocks 

 which were folded and distorted before this later sedimentation 

 began. Part of the pavement area on which the Catskill sedimenta- 



