468 MES. Ws VEE Te SOM 
sravel is abrupt, Ate Keithsm Sprne | (bien si G)\ 200mmcer 
above sea, is a little hill of the laminated clays at the foot of 
the bluff, with its strata running squarely into the sand of the 
bluff across the intervening air. No other agency than the dif- 
ferent rates of atmospheric wear on clay and sand is apparent 
to account for the notch between the clay hillock and the 
bluff. A similar hillock of laminated clays occurs half a mile 
further north. These three occurrences and the varying upper 
limit of the clays observed point to erosion of the clays before 
the sands were laid down. Yet in several of the sections the 
true surface may be masked by sand that has fallen down from 
above. 
The present course of the Connecticut around the plain is of 
course postglacial and much of it is gorge cut in the rocks. 
Such rock-cutting is indicated on the map by heavy lines on the 
river margin. Though superposed on the rock structure under- 
lying the plain this part of the river has now a certain adjust- 
ment to the structure as may be seen by the stratigraphic marks 
on Fig. 1 which indicate well-established facts. 
Preglacially the channel was probably straight down from 
the northeast corner of the map by Millers Falls, and Lake 
Pleasant and thence westward to the present channel some- 
where between J and /, points where ledges are now exposed. 
Between the occupation of the ancient and modern channels 
there are indications of some persistence of the drainage across 
the plain by a west channel and an east channel. Indications 
of water passing through the west channel are: 
(1) the gentle depression between G and D (Fig. 1), and 
(2) the frayed and waterworn state of a rock ledge at the 220- 
foot level (Y), a hundred feet above the present river. 
The east channel is better marked, being indicated today by 
deep sags in the plain at Millers Falls; kettles to the south, two 
of them occupied by the Lake Pleasant ponds; and the long 
deep valley to the south by which the lake\drainage escapes 
tor the mver ine higher cround \between ithe wkettlesmismyer 
below the surface of the plain. This is shown in Fig. 7, taken 
