736 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



the teiTaces, and I have on the map continued the h)w-teiTace color down the 

 canyon side in dots to distinguish it. 



THE TERRACES OF TRIBUTARIES. 



The deep, land-locked basins cut in the lake beds by the tributaries of 

 the Connecticut are among the most remarkable orographic features of the 

 valley. Each stream has first built out the great delta plain and then 

 excavated its basin on the sinking of the main stream. They have this 

 peculiarity in common. Each stream emerges from its gorge in tlie crys- 

 talline rocks, runs across its former delta, and passes through a short rocky 

 gorge just above its mouth, and the stream has thus been fastened at two 

 points like the string of a mvisical instrument, and has vibrated between 

 these two points to form its closed basin. It has eroded with great -sdolence 

 because it has had the rapid fall across the crystalline rocks. 



The Deei-field and Westfield River basins are the most extensive and 

 interesting examples, the one occupied by the most romantic and sleepy 

 old town in the valley, the other by a typical, unattractive, manufacturing 

 town. These rivers have reoccupied their old gorges in the trap ridges, 

 as already explained (p. 512). The others, Green River, Millers River, 

 Mill River in Northampton, and Cushmans Bi'ook at the Golden Gate in 

 Amherst, have by chance struck rock bottom as they cut down through 

 then- deltas, and thus the mouths of their basins are closed below, as are the 

 first two. 



The basins are boimded on all sides by high scarps, and over the low 

 meadow bottoms are many abandoned channels caused by ice obstruction 

 in spring, which in the Deei*field bottom are developed into a most compli- 

 cated network. 



A prominent, flat-topped hill, called Pine Hill or Pine Nook, its surface 

 on a level with the adjacent high terrace, rises in the midst of the Deerfield 

 Meadow and has doubtless been cut off by an old oxbow of the river, and 

 a smaller but similar one, which has been called an Indian mound, but has 

 the structure of the surrounding delta sands, stands in the basin of Mill 

 River alcove Florence. 



