l6o NEW YORK STATE MUSEUM 



which appears at Rondout, and whether it is not also one with 

 the similar horizontal overthrust described by Davis at Aus- 

 tin's millroad near Catskill [Folded Helderberg Limestones. 

 Mns. Comp. Zool. Bui. v. 7, No. 10, fig. 3 and p. 324], with 

 like puzzling features (not yet worked out) in the Kalkberg 

 at Alsen and Cementon, and finally with the great fault 

 near Schodack Landing and southward along the Appalachian 

 front into Georgia. The influence of such a plane, nearly hori- 

 zontal but rising and falling in great gentle undulations, would 

 affect a wide area (compare the Rome folio, in Georgia) and 

 produce seemingly very irregular, disconnected and puzzling 

 results, especially where it hades, as in this case and so often, 

 considerably beyond the horizontal. 



If not one and the same plane, these instances must at least 

 appertain to the same set of movements, the same " rift," ex- 

 tending along the entire eastern edge of the folded Appalachians 

 as a constant and normal feature. The recognition of this for 

 our miniature Appalachian hills of the Hudson valley will as- 

 sist the field worker materially and will rapidly multiply the 

 known occurrences of this structure. 



The writer owes the opportunity for these observations to 

 the Rev. Thomas Cole, Episcopal rector at Saugerties and an 

 acute observer of local geology, in company of whom and of 

 Prof. J. W. Eggleston of Harvard the reconnaissance was made. 



