THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Akt. XIII. — The Terraces of the Westfield River ^ Mass.: by 

 W. M. Dayis. (With Plate IV.) 



1. Tlie several theories of river terraces. — The river terraces 

 that are so abundantly developed in the stratified drift of onr 

 New England valleys, receive scanty explanation in the text- 

 books to which reference is ordinarily made for accounts of 

 such forms, and are, indeed, not exhaustively treated in essays 

 of a more advanced character. Their most significant feature 

 is an arrangement in the form of a flight of steps, of unequal 

 tread and rise, and usually of unlike sequence on the two sides 

 of a valley, but necessarily exhibiting a less cross-valley breadth 

 between the terraces at the bottom of two opposite flights than 

 between those at the top. It is generally agreed that each 

 terrace plain is the remnant of a flood plain, that was formed 

 during the process of valley-carving by the river that now 

 flows on the flood plain or "interval" between the lowest 

 terraces of the series ; and that the terrace fronts or scarps 

 have been carved by the wandering river as it swung laterally 

 on its successive flood plains. The slope of the terrace plains 

 down the valley and the pattern of the terrace scarps in curves 

 concave towards the river, frequently uniting in cusps, give 

 convincing proof of these conclusions. It follows that our 

 terracing rivers habitually had a greater breadth of swinging 

 on the flood plains at high levels, when beginning the work of 

 sweeping the drift from their valleys, than at the low levels on 

 wdiich they are now flowing. The special point that needs to 

 be accounted for is, therefore, the restriction of the belt over 

 which the river swings to a less and less breadth in passing 

 from the initial to the present stage of terrace development. 



There are three theories which offer an explanation for this 

 restriction. The first and most popular postulates a decrease 



Am. Jour. Sci.— Fourth Series, Vol. XIY, No. 80.— August, 1902. 

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