38 NEW YORK STATE MUSEUM 



several inches to a foot or more occur interbedded with the thinner 

 layers. 



The direction of flow is with the dip so that in general the wear 

 of the rocks at the front of the precipice is on the faces of their 

 bedding planes. Because of this the process of wear goes on 

 slowly. But at the summit of the falls the water flows over the 

 edges of the rocks and the destructive process is more rapid. The 

 erosive agents lodge in the depressions resulting from unequal 

 wear of alternating soft and hard strata and deepen them into pot- 

 holes. There are very many of these in the bed of the river imme- 

 diately above the falls. Due to the more rapid wear of the strata 

 on their upper ends than on their faces, the angle of slope of the 

 falls is greater than that of the dip of the strata. 



At the base of the falls where the impetus of the falling water 

 is greatest somewhat rapid wear takes place, forming pools, and 

 the eddies in these pools, through undermining, may contribute 

 somewhat to the recession of the falls. 



The Hoosic gorge. A postglacial gorge of interesting physi- 

 ographic and scenic features is that of the Hoosic river west of 

 Schaghticoke. The river has here sunk its bed through the mass 

 of delta deposits and into the underlying bedrock. Where the 

 stream enters the gorge at Schaghticoke its course turns abruptly 

 northward, evidently in conformity to the strike of the rocks. 

 After emerging from the first gorge the river turns westward and 

 its slopes consist of the delta materials. It then enters the second 

 rock gorge and its further course describes the shape of the letter 

 U, the direction of the arms of the U corresponding to the dip of 

 the strata. There is a fall of 120 feet from the head of the upper 

 gorge to the foot of the lower rock gorge, furnishing abundant 

 power. This has long been utilized for manufacturing industries 

 and, in recent years, for the generating of electric energy. 



East of Schaghticoke the general valley of the Hoosic has the 

 appearance of a preglacial valley although the shallow rock gorge 

 at Valley Falls may mark a diversion of the river from its old bed. 

 The course of the preglacial Hoosic from near Schaghticoke to 

 the Hudson is unknown. 



In that portion of the course of Tomhannock creek which crosses 

 the delta formation, the stream has in places sunk its bed into the 

 underlying rock forming gorges and cascades. One of these occurs 

 a short distance northwest of Schaghticoke hill and another of pic- 

 turesque scenic features about one and one-half miles farther on. 



