78 Davis — Terraces of the Westfield River, Mass. 



in river volume during and after the uplift of the region by 

 which the erosion of the valley was prompted. The river is 

 by this theory supposed to have been so large when terracing 

 began that it needed a broad space on which to swing ; now 

 that the river has diminished in volume it is relatively enfeebled 

 and is contented to swing over a narrower belt than formerly ; 

 so the later formed terraces do not undercut and destroy those 

 of earlier date. 



The second theory postulates successive uplifts of the region. 

 The river, revived by each uplift, wears its channel beneath its 

 previous flood plain and, on reaching grade, begins to swing 

 laterally. It is then further postulated, sometimes tacitly, that 

 the later uplifts have succeeded each other at shorter and shorter 

 intervals, allowing less and less time for lateral swinging as the 

 valley was worn deeper and deeper. 



2. Miller'' s theory of river terraces. — The third theory, sug- 

 gested in explanation of terraces in Scotland by Hugh Miller, 

 the younger, in 1882,^ recognizes slow regional uplift as the 

 cause of valley erosion and then calls attention to the increase 

 in the number of resistant obstacles — rock ledges, boulders, 

 till — that the degrading river will encounter as it swings later- 

 ally while eroding the valley floor to lower and lower levels, 

 and ascribes the decrease of interscarp breadth to this simple, 

 effectual and observable cause. 



As Miller's theory has not, to my knowledge, been quoted in 

 this country, except in a brief note of my own,f a brief exposi- 

 tion of its merits may be made. I have found it very generally 

 applicable to the terraced valleys of ^N^ew England, and nowhere 

 more so than in the valley of the Westfield river, between the 

 eastern base of the Berkshire hills and the village of Westfield, 

 Mass., a distance of about five miles, where I have repeatedly 

 examined it. This district was the scene of an intercollegiate 

 excursion in the autumn of 1901, in which Yale, Amherst, 

 Williams, Wesley an. Institute of Technology, and Harvard, 

 together with six secondary schools, were represented by 

 teachers and students to the number of forty-six ; and it is not 

 too much to say that at the end of the day's walk along the 

 north side of the valley no doubt remained as to the competence 

 of Miller's theory to explain the occurrence and the pattern of 

 the terraces there seen. Decrease of volume and intermittent 

 uplift seemed to be of altogether secondary importance, if 

 indeed they had produced any recognizable effect. 



The Westfield terraces. — The following pages give a brief 

 account of the Westfield terraces, beginning with those on tlie 



* Eiver terracing, its methods and their results, Proc. Eoy. Phys. Soc. 

 Edinb., 1883, 263-305. 



f Bull. Geol. Soc. Amer., xii, 1900, 483-484. 



