Davis — Terraces of the Westfield River ^ Mass. 93 



volume or for repeated movements of uplift in the terrace 

 problem of the Westfield river. 



15. Southern terraces at Westfield. — l^earer Westfield 

 the complication of the southern terraces increases somewhat, 

 and there is one member of the series at a higher level than 

 elsewhere on the south side of the valley in this district. It 

 may be therefore inferred that the river belt has hereabouts 

 been shifting northward, and this would be confirmed by the 

 high terrace of the opjDOsite northern reentrant. Yet no 

 ledges are found on the south side of the valley as a cause of 

 this shifting. The only explanation that I have thought of 

 for it is that Little river once entered the Westfield from the 

 south near the present site of Westfield village, and thus 

 slowly, pushed the Westfield river northward from the course 

 it had previously followed. Interference of one river with 

 another in this way has been suspected in the eastern basin, 

 beyond Westfield, and in several other localities in the Connec- 

 ticut valley. 



16. Conclusions.— 'The most manifest conclusion to be 

 drawm from this study is the one already announced ; namely, that 

 Millers theory of defending ledges gives a better explanation 

 than any other for the terraces of our Xew England valleys. 

 It is not desired to imply by this that all our terraces are de- 

 fended, but that most of them are ; and especially that all the 

 many-stepped flights of terraces owe their preservation to 

 defending ledges. Decrease of river volume and intermittent 

 uplifts do not seem to have had any significant part to play in 

 the restriction of the swinging rivers to narrower and nar- 

 rower belts. Another conclusion is that the normal action of 

 a meandering and swinging river snfiices to account for prac- 

 tically all the details of terrace form ; and hence that terraces, 

 like other land forms, are susceptible of explanation, even 

 down to their most minute elements. Following this there is a 

 third conclusion, of interest to those who concern themselves 

 especially with the study of land forms ; namely, that in this 

 division of the subject as well as elsewhere, observation is 

 greatly aided by the discovery of a successful theory ; for 

 the essential facts are then quickly acquired by well directed 

 search. It is also apparent that here as elsewhere description 

 is greatly facilitated by explanation, for explanation enables the 

 student to bring the local example into proper relation to the 

 generalized type. There may seldom be necessity of giving 

 minute description of forms so small and so ephemeral as 

 drift terraces ; but when that necessity arises it will be met 

 better by characterizing terraces in terms explanatory of their 

 origin than by an attempt at absolute or empirical descrijDtion ; 



Am. Jour. Sci.— Fourth Series, Yol. XLY, No. 80— August, 1902. 



7 



