332 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
northern side there are four groups of defended terrace cusps, forming 
what may be called the Pochassic (just to the left of Figure 39), Perry’s, 
Kk, Brown’s, F, and Prospect spurs, A, while curved re-entrants have been 
excavated between the spurs where ledges are rare or wanting. The 
re-entrants show that the river has everywhere attempted to widen its 
valley, while the terraces on the defended spurs show that the widening 
has been locally prevented by the outcropping ledges. Wherever free 
cusps occur they exhibit the patterns deduced as of common occurrence 
on page 308. None of the combinations there deduced as rare are 
found. ‘The cusps are usually more closely trimmed on the up-valley 
than on the down-valley side. It would be difficult to imagine a more 
complete confirmation of Miller’s theory than is here presented. 
Special mention may be made of a few features. Just east of Po- 
chassic Street a series of at least nine terraces, H to M, may be counted. 
They range in height from eight to fifteen feet, and thus suggest a 
rough measure for the amount of valley deepening during a swing of the 
river southward across the valley and back again. This maximum num- 
ber is evidently dependent on the numerous ledges here discovered at all 
levels from highest to lowest. Although no other part of the valley 
shows so many terraces, it must be concluded that flood plains, con- 
tinuous with the remnants here preserved, were made far up and down 
the valley ; and hence that the river was essentially at grade during the 
whole process of valley degradation. ‘Two terraces at the top of this 
flight, in the re-entrant east of Pochassic Street, exhibit minor re-en- 
trants of small radius and large are near H and H’, comparable to the 
curves of the present river, thus indicating that no significant change of 
volume has occurred since the work of terracing began. A broad 
terrace plain stretches back of Perry’s spur, K, and four low terraces 
rise above it to higher levels, showing that four broad northward swings 
were here executed. he fifth terrace (counting from the top of the 
series) runs forward to Perry’s spur, because the highest ledge of that 
spur was discovered when the river was making its fifth northward 
swing. It is worth noting that several defending ledges in this spur 
would be unseen but for road and railroad cuts. ‘The fourth terrace 
swings forward in a long sweeping curve to the apex of Brown’s spur, 
because the summit ledge was there found by the fourth northward 
swing. Only two distinct terraces occur on the high plain back of 
Prospect spur, because the ledges in that spur rise still higher than in 
Brown’s spur. In a word the river has always shown a capacity for 
broad swinging until it became hampered in its movements by coming 
