Report of the State Geologist. 157 



shales of the Clinton group rest directly upon the upper 

 arenaceous-shaly beds of the Hudson River group. 



Returning to the neighborhood of Howe's Cave the work on 

 the escarpment was again taken up and continued in a westerly 

 direction. The gradual thinning of the Lower Helderberg mass 

 diminishes the strong feature of the escarpment ; the Oriskany 

 sandstone gradually ceases to be a prominent feature and the 

 gradual thinning and final disappearance of the Cauda-galli grit 

 brings the Upper Helderberg limestone into close proximity and 

 final contact with the lower mass, thus becoming the most 

 prominent feature in the escarpment as we go westward. In the 

 earlier general observations and publications upon the geology 

 of New York this condition was not understood, and the great 

 mass of the Lower Helderberg, so prominent along the Hudson 

 river from Rondout north and thence northwest to Schoharie 

 was regarded as the same limestone terrace which extended to 

 Black Rock on the Niagara river. Even more extreme was the 

 opinion published, identifying the great Helderberg terrace and 

 escarpment with the Niagara Falls escarpment. This generaliza- 

 tion came from the want of a knowledge of the elements com- 

 posing this escarpment at any point, and therefore the bolder 

 features only entered into the result. It should be remembered 

 also that this conclusion was reached without any knowledge of 

 the fossil contents of these strata which at that period were little 

 known and not regarded as a necessary element in geologic 

 generalizations. 



The elements entering into this escarpment in different points 

 in its extension are somewhat variable. In Schoharie and 

 Albany county are at its base, the Hudson River group either in 

 its horizontal or disturbed condition is succeeded by the represen- 

 tatives of the Clinton, Niagara, Waterlime and the Lower Helder- 

 berg mass made up by the Tentaculite limestone, the Pentamerus 

 limestone, Shaly limestone, Upper Pentamerus limestone, or 

 Scutella (Becraft) limestone. 



[The report is incomplete at this point for want of illustrative 

 sections and maji which will appear in next report.} 



However in continuing our investigations to the westward we 

 have proved that the Lower Helderberg limestones in their 

 lower members maintain a greater thickness and are more per- 

 sistent than we have usually believed. It was formerly supposed 



