82 Davis — Terraces of the Westfield River ^ Mass. 



fair indication of the altitude to which the Cretaceous peneplain 

 of this region has been raised, the Triassic sandstones in this 

 part of the Westfield valley (part of the greater Connecticut 

 valley lowland) have been reduced by later Tertiary erosion to 

 a lowland of a second (or n-VV) generation. Yet compared to 

 the silts and gravels of the terraces, the sandstones are very 

 strong ; whenever the river has, in the process of sweeping the 

 drift from its valley, swung against a sandstone ledge, pre- 

 viously buried, further lateral swinging has been peremptorily 

 stopped and the terrace behind the ledge has been preserved. 



It is evidently because of the abundant defending ledges 

 here that the Westlield spur has not been destroyed. The 

 stream has made a most determined effort to destroy the spur by 

 scouring out a hollow, C, at its back, sweeping around in so 

 great a curve that its normal eastward course was locally 

 turned back to the southwest ; but the ledge, C^ on which the 

 stream was caught, could not be removed, and hence the spur 

 still stands there. The river seems to have been withdrawn 

 from the deep recess, C, by taking a short-cut across a more 

 axial part of the valley floor of that time, probably during a 

 flood. When it again swung northward towards the recess, at 

 a somewhat lower level than before, a lower })art, D', of the 

 same ledge was encountered a little farther forward than the 

 point, C^ ; and a small lunate area, C, of the earlier sw^eep was 

 therefore preserved back of the new terrace, D. On the third 

 return of the river into the same locality at a still lower level, 

 it was caught by a small ledge, J)'\ several hundred feet 

 farther forward, and again by larger ledges, Q'\ Q>"' ^ and 

 hence a good stretch of the flood plain between J)' and Y>" 

 was preserved in a terrace. 



The Westfield river is at present making still another effort 

 to remove the spur, and it is noAv for at least the fourth time 

 stopped by a member of this group of ledges, for a strong reef 

 of sandstone is seen in the river bank at E in the. southern 

 corner of the spur. The spur may in the distant future be 

 somewhat sharpened by losing ground on its undefended south- 

 east corner, should the river chance to swing that way ; but 

 such swinging will be for the present strongly resisted by the 

 buttresses of two bridges and by artificial embankment where 

 the Boston and Albany railroad follows the river ; it will cost 

 less to restrain the river than to remove the bridges and the 

 tracks. 



6. No local evidence of decrease of volume in the Westfield 

 river. — Evidently the preservation of the spur of Prospect hill 

 is not due to any incompetence or to any want of effort on the 

 part of the river to remove the sands and gravels. The river 

 has repeatedly and energetically attacked the SjDur ; it has in 



