ANCIENT WATER LEVELS OF CITA MPLAIN— HUDSON VALLEYS 177 



the Mohawk outlet of the great glacial lakes on the west. As 

 soon as the ice retreated in the valley to a position north of 

 Albany and the drainage of Lake Iroquois came into the Hudson 

 valley Lake Albany properly came into existence. 



The clays, and the deltas marginal to them, extend north of 

 Albany certainly as far as the Moses kill. At this place the 

 Hudson gorge proper widens out and the Albany clays which 

 mantle the rock terrace marginal to the gorge are separable from 

 the clays of the low grounds northward by reason of the partly 

 ice-swept character of the surface apparently indicating that the 

 northern limit of the lake was at one time formed by an ice 

 margin over the Fort Edward district. That Lake Albany with 

 the melting out of the ice from the Champlain valley became 

 confluent with the glacial lake stages of that district is borne 

 out by the extension of clays from one region to the other and 

 by the extension of the water levels of the Lake Champlain area 

 into the upper Hudson valley through the Wood creek pass. 



The shore line of Lake Albany is most clearly shown by the 

 altitude of the deltas of the larger streams which emptied into it. 

 These include the old delta of the Mohawk, that of the Hoosic and 

 the Batten kill and numerous smaller deposits southward in the 

 Hudson valley. I would refer to Lake Albany only those deltas 

 which appear to have been built in open water between the Batten 

 kill and the vicinity of Rhinebeck. South of the last named point 

 the deltalike deposits adjoining the Hudson gorge appear to have 

 been built in front of the retreating ice sheet, and I am led to think 

 that the surface of these proglacial deposits was mainly if not 

 altogether above the level of Lake Albany at the time of its maxi- 

 mum development, the waters escaping from the flooded middle 

 Hudson valley Through the old gorge on the south as waters now 

 escape but perhaps at a still greater depth owing to a higher 

 si and of the land on the south. 



It will be observed that the deltas on the eastern side of the 

 Hudson valley from the Batten kill northward to the Poultney 

 fail to coincide with any one plane. In a report of progress 

 on the held work for 1900 I interpreted the falling off in 

 altitude of the deltas successively northward from that of the 

 Batten kill when compared with the highest shore lines about 



