THE WEST BlIOOK DELTA. 635 



tliin layers of a coarser sand included within it are so t\visted into the mass 

 that they can be followed for only a short distance. 



A mile south, in the Northampton quadrangle, in the delta at the road 

 south from Mill River village, where Bloody Brook joins Mill River, I 

 found in the same position a layer identical with this in all respects, and 

 it may be continuous between the two places, and repre.sent a time when 

 the river was clogged with ice, so that its current was stopped and an 

 unwonted thickness of the very fine sands deposited and thrown into confu- 

 sion by the stranded ice. The layer resembles so exactly the thicker one 

 described from the Wajjping cutting (PI. XVIII, p. 6!I4) that one diagram 

 would serve for both. 



Farther out, ^ear the outer edge of the bar, the coarse sand and 

 gravel layers thicken downward and pitch sharply southeast in broad, 

 cross-laminated layers, and the finer sands have disappeared or gone below 

 the level of the cutting. It is plain that these latter, which lie below and 

 continue everywhere below the level of the railroad certainly for many 

 feet, represent the front of the delta as it was pushed out into deep water 

 Their varying dip corresponds to the varying slope of the face of the delta, 

 and I am inclined to believe that the thick layers of fine sand (1 to 2 feet) 

 represent the product of a single flood, upon whose rippled surface rests in 

 each case the finer deposit of the succeeding winter. 



The front of the delta narrows southward and is continuous, at the 

 same level, with the delta, also very large, of Mill Ri^'er, upon which is the 

 village of the same name. This is more complete, though Mill River 

 escapes through it in a broad, low plain of ei'osion, and skirts the hill for a 

 long distance south. Then, for a still longer distance south, across the line 

 into Whately, the bench is wholly wanting. At present the broad lake- 

 bottom plain stretching across from South Deei-field abuts against the steep 

 cliffs with no change of level. 



THE ■WEST BROOK DELTA. 



From Roaring Brook down through Wliatel}' the hills have aii easier 

 slope and were covered with much drift material, out of which the waters 

 have formed an irregular bench, which is only in part built up to true level. 

 This continues almost to the south line of Whately, where, near West 

 Brook, the bench (1 s h) is again well developed and is very complicated and 



