344 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



the southern part of Springfield thei-e are several ledges and some ex- 

 posures of bouldery till, by which the opening of the valley to the east 

 has been restrained, and a little further south, by the mouth of Pecowsic 

 brook, a strong ledge deflects the river to the southwest. 



No ledges are found in the terrace scarps on the western side of the 

 valley hereabouts, although several rather well-formed cusps project 

 forward towards the river : one at the grounds of the Country club ; 

 another at the old Meeting-house north of West Springfield and a third 

 between West Springfield and the Agawam. The Westfield river 

 enters the main valley in the re-entrant between the second and third 

 cusps, while south of the third cusp the Connecticut has repeatedly 

 scoured out re-entrants from which it has been withdrawn by short-cuts 

 or cut-offs. I am inclined to think that the Connecticut has been 

 pushed eastward by the action of the Westfield ; that it has therefore 

 repeatedly swung westward from the Pecowsic ledges, and that the 

 Agawam re-entrants are thus to be explained. If so, they fall into the 

 same class with those of the Westfield in the re-entrant next west of 

 the trap-ridge notch (page 330). The southernmost of the three free 

 cusps on the west side of the Connecticut valley, below the entrance of 

 the Westfield, would thus correspond with the free cusp on the south 

 side of the Westfield, below the entrance of Little river. The other free 

 cusps of the Connecticut may perhaps come to find an explanation in a 

 process similar to that suggested for the free cusps between Bellows 

 Falls and Westminster (page 341). 



There is nothing in this stretch of the river to suggest a significant 

 diminution of volume since terracing began. The frequent occurrence of 

 high single scarps would on the other hand suggest that the river is 

 to-day demanding a breadth of swinging as great as or greater than it 

 ever did before. 



The Merrimac between Concord and Manchester, N. H. The 

 Merrimac, near Concord, has opened a broad flood plain, on which a 

 number of former meanders are now represented by ox-bow lakes. On 

 the east the plain is commonly bounded by a single high scarp, which 

 the river is actively under-cutting at one point. On the west there is a 

 single high scarp bordering part of the plain north of the city ; but a 

 few ledges appear, and the scarp is divided into several terraces as the 

 city is entered. Passing down the valley (southward) ledges appear more 

 frequently, the breadth of the flood plain gradually decreases, and ter- 

 races appear in increasing numbers. The valley about Concord is one 

 of the best examples for illustration of the capacity of an unconstrained 



