88 Dams — Terraces of the Westfield Rivei\ Mass. 



the stratified drift. Till is seldom well carved bj a swinging 

 river ; its texture is significantly firmer than that of stratified 

 sands and clays. A small stream coming ont from the north 

 cuts little trenches in the terrace fronts and spreads its gravel 

 fans on their plains, thus further obscuring their forms. 



The eighth and ninth members of the Pochassic flight are 

 well defined, but instead of conforming to the concave pattern 

 of the higher members of the series, they spring forward to a 

 defended cusp, M, nearly opposite the middle of the reentrant. 

 Here as elsewhere it is perfectly evident that the failure of the 

 river to cut back these lower terraces is not due in the least to 

 any loss of its original strength, but to the increase of resistance 

 offered by the ledges. The river has now swung away from 

 the northward meander that it followed while carving the 

 lowest terrace, jS"', to a correspondingly strong southward 

 meander, T', which is now cutting a low terrace, T, on the 

 south side of the valley. A broad flood plain, N, has thus 

 been opened. It happens curiously enough that the down- 

 valley progress of this southward meander has just now brought 

 it to such a position that it is impinging against a large exposure 

 of the sandstones at M. The normal down-valley advance of 

 the meander, T^ will soon carry it past the ledge, unless the 

 caving bank at T is protected. For the present, the obstruction 

 caused by the ledge in the normal flow of the river seems to 

 have produced a slight bend in the channel a little farther up- 

 stream. When the meander is sufticientl}^ advanced the river 

 will impinge directly on the unprotected bank between M and 

 L, and consume it rapidly, leaving a sharp cusp at M. It is 

 probably in some such way that the sharpening of Brown's 

 spur, referred to above, has been accomplished. There has 

 already been some undercutting of the low terrace east of M, 

 for the main valley road was swept away by the northward 

 swing of the river at L a few years ago. The road has been 

 set back so as to cross Perry's spur, K', north of the railroad, 

 thus causing the desertion of several honses on the low plain, 

 R, in front of the spur. The railroad itself is threatened by 

 the river near L ; the caving bank has been worn back danger- 

 ously near the track, and a quantity of coarse rock blocks has 

 been thrown in there to stop the caving. But for this resist- 

 ance the river would probably continue to swing northward 

 until it encountered a low member of the group of ledges in 

 the southwest base of Perry's spur, K^ 



AVest of Pochassic Street another large reentrant has been 

 swept out on the north side of its valley ; its down-valley side 

 is well defended by ledges in the southwest base of Pochassic 

 hill. 



