156 Forty-sixth Report on the State Museum. 



• From the neighborhood of Coeymans to the southward the 

 escarpment of the Lower Helderberg rocks is not so continuous 

 or conspicuous, being interrupted in many places by deep ravines 

 and obscured also by elevations of the Hudson Eiver group, 

 which appear in more or less continuous, or frequently interrupted 

 ridges, and not unfrequently isolated hills, in front of the great 

 escarpment. 



In the neighborhood of Catskill, along the Catskill creek, the 

 Lower Helderberg escarpment of Pentamerus limestone, with its 

 associated beds of Waterlime, forms a strong vertical escarpment, 

 while the bed of the creek presents the Hudson Kiver shales 

 extremely folded and lying in almost vertical position. 



In the neighborhood of Catskill and Kondout so much excel- 

 lent work has been done by Prof. William M. Davis, of 

 Cambridge, that it can be safely adopted for use in laying down 

 the geology of that region upon our map, and, in consequence of 

 this, much time was saved in our investigations. 



To the southward of Pondout, although these limestones hold 

 their place and even present strong continuous escarpments, they 

 are so much broken and disconnected that they can jiot be fol- 

 lowed with the same facility as to the northward and westward 

 from Catskill. 



At Posendale we find the most southern exposure of these 

 high escarpments of the Lower Helderberg limestones underlaid 

 by a great development of the Waterlime which is here 

 extensively manufactured into hydraulic cement. In the bed 

 and banks of the creek at this place the geological formations 

 are exposed from the Hudson river shales upwards to the Lower 

 Helderberg limestones, and there are certain layers of red and 

 greenish marl and sandstone which ^apparently represent the 

 Medina sandstone and Clinton group. This is the first exposure 

 observed after leaving Howe's Cave where we have evidence 

 of the presence of any beds representing the Medina sandstone 

 and Clinton group in the lower part of the great escarpment. 

 At Howe's Cave we have an exposure of about thirty feet of 

 shale below the J^iagara or Coralline limestone which represents 

 the Clmton group in that locality. At this place the pyritiferous 



