862 



NEW YORK STATE MUSEUM 



almost to Rosendale from Rondout along Rondout creek, but 

 from Kingston through the Whiteport-Binnewater stations the 

 cement lies on a floor of sandstone (Clinton). 



The cement at Rosendale is also on a base of sandstone, but at 

 this point I have found small Leperditias in large numbers. 

 They seem however to belong to the cement above. 



At High Falls there is a thin shaly layer above the sandstone 

 and distinct from the cement beds above. This shaly layer con- 

 tains an interesting fauna and seems to be equivalent to the 

 Wilbur. 



It is to be noted that, throughout the cement region in Greene 

 and Ulster counties, the cement beds above the Wilbur occur in 

 two layers, between which is found the Cobleskill containing 

 an abundance of corals, mostly Halysites. This limestone in 

 the Whiteport-Rosendale region is about 12 feet thick as a rule. 

 However, in the Newark works at Rondout this layer is only 

 7 inches thick. The fauna! contents of this limestone in Ulster 

 county have not been examined in detail but suggest some very 

 interesting studies. 



The stratigraphy of Becraft mountain. Just east of the city of 

 Hudson in Columbia county, is Becraft mountain, which has 

 long been known as one of the interesting features in the 

 Paleozoic geology of this State. The mountain is the only out- 

 lier east of the Hudson river of the Helderberg series of for- 

 mations, on which lie in proper succession other members of 

 the Devonic series to and into the Onondaga limestone. It has 

 been the subject of much study. Accounts and sections were 

 given of it by Lieutenant Mather in his report on the first dis- 

 trict of New York, and he then indicated the essential tectonic 

 structure, which is that of a low syncline of the higher deposits 

 resting unconformably on the upturned edges of the Hudson 

 river slates. At a later date the structure of the mountain was 

 more fully elaborated by Prof. W. M. Davis; and subsequently 

 the writer specially studied an outcrop of the Oriskany sand- 

 stone thereon of new interest in the composition of its fauna, 

 and published a somewhat extended account of this element in 

 the make-up of the hill [Museum memoir 3], In all these 

 various studies, however, it has been clear to the observers that 

 we had not yet reached a true solution of the structure of the 

 mountain as a whole. Evidence of faulting and displacement 

 at the southeast end was recorded by Mather and reiterated 

 by Davis, but it has not been clear how profound were these 



