80 Davis — Terraces of the Westfield River ^ Mass. 



close to their present grade by the trap sheet which their 

 united current has come upon in the notch in the trap ridge 

 about two miles east of Westfield. 



4. Terrace diagrams. — The single high terrace scarp, here 

 so well developed and typified in figure 1, is of more general 

 occurrence in the terraced valleys of Kew England than is 

 generally supposed to be the case. It may indeed be taken as 

 typical of many terraced valleys where no ledges have been 

 discovered to prevent the free swinging of the rivers. A few 

 lower terraces may still be unconsumed here and there, as in 

 figure 2 ; this arrangement of terraces also being of common 

 occurrence where ledges are wanting. The ordinary diagram of 

 a terraced valley, such as is here reproduced in figure 3, is there- 

 fore misleading in implying that the stepping terraces have 

 been carved in drift alone, witliout relation to the rock beneath. 

 These many-stepped flights of terraces need for their preserva- 

 tion a number of ledges, as in figure 4 ; but this figure is very 

 faulty in implying that ledges occur all along the base of the 

 terrace scarps. As a matter of fact, the ledges do not occupy 

 more than a small percentage of the terrace lengths, and far 

 from all lying on the line of a single cross section, as figure -i 

 implies, they are frequently distributed somewhat irregularly 

 up and down the valley sides. The true relation of ledges 

 and terraces is better shown in a block diagram, such as figure 

 6 ; and even here the area of the ledge? exposed in the terrace 

 cusps is exaggerated over that commonly observed. 



5. The 'Westfield spur (Prospect hill). — If the terrace by 

 Westfield station is now crossed to the west, it is soon found 

 to be a spur of a high, but not of the highest plain, extending 

 forward (southward on the north side of the valley) from the 

 broad plain in the background. It is known as Prospect hill. 

 The apex of the spur, E, figure 6, reaches the river; its 

 breadth, east and west, is about a quarter of a mile. From its 

 western side the valley floor again widens, making a recess or 

 re-entrant in the high plain on the north; but here four sub- 

 ordinate terraces are found beneath a stronger scarp that rises 

 to the highest level ; they combine in a charming landscape, 

 when seen from the western scarp of Prospect hill. As the 

 river is thus found to have been competent to widen its valley 

 both east and west of the terrace spur, some reason for the pre- 

 servation of the spur should be looked for ; and it is discovered 

 clearly enough on descending the western scarp, which is found 

 to be defended at various points along its bank by sandstone 

 ledges, C^ C, C^'. The sandstones are, to be sure, relatively 

 friable ; they are weak compared to the schists and gneisses of 

 the Berkshire hills to the west ; so weak, indeed, that while 

 the Berkshires retain in the equable height of their uplands a 



