200 



NEW YORK STATE MUSEUM 



Glenmont the 100 foot contour line embraces the continuation 

 of this old terrace till it blends with the flats in the vicinity of 

 Wemple. The terrace thus marked out near the 120 foot level is 

 probably a congeries of terraces. It is noticeable that the system 

 falls about 10 feet in a distance of 1 miles from north to south. 



Dissection of the Hoosic delta [see pis. 10 and 24]. The delta ot 

 the Hoosic river constructed on the borders of Lake Albany at a 

 level now as high as '6i>0 feet above existing sea level has oeen 

 dissected by tne stream in its adjustment to the local tiudson 

 drainage base. In this dissection, the Hoosic river has 

 meandered in a most complicated fashion in the clays and sands 

 of the delta terrace, leaving a rather confusing tangle of terraces 

 within the gorge. The adjoining plate 21 shows the position of 

 the more prominent of these terraces, which are grouped on the 

 hypothesis that the uppermost are the oldest and the lowest the 

 most recent, that those at approximately the same level are 

 approximately of the same age. It will be observed that the 

 highest terrace developed at o00 feet is traceable in the middle 

 of the gorge; that below this is a series of fragmentary terraces 

 from 28Q feet near the rock falls to 200, 210, 220, and possibly 

 indicated by one of the 200 foot benches near or at the mouth of 

 the gorge. This last group was probably not made at one move- 

 ment of the stream but represents several ancient grades in the 

 sinking of the stream from 300 feet to 200 feet in the soft clays 

 and sands below the rock at the falls. 



The 200 foot terrace level is widely developed in the middle 

 and lower part of the gorge and seems to indicate waters running 

 at about this level in the Hudson gorge for a considerable length 

 of time. Then follows a brief stage at 150 feet; followed by well 

 incised meanders at 120 feet, and a brief stage at 100 feet. From 

 this 100 foot level there appears to have been a drop rather 

 quickly accomplished to the present channel which enters the 

 Hudson at about 80 feet above sea level. 



Scant as are the evidences here adduced there are other simi- 

 lar facts yet to be studied in this field, pointing to the filling of 

 the gorge of the upper Hudson with drift deposits and with the 

 overlying Albany clays, and to their subsequent removal on the 

 withdrawal of the waters of Lake Albany and the entrenchment 

 of the new Hudson river in the old gorge. 



