316 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
the basin. The rim at the gap is composed of till. The lower parts 
of the surface of the gap, between the 260 and 280-foot contours, are | 
strewn with boulders which are evidently a concentration due to the | 
removal of the fine material in which they were enclosed. I recognize { 
here characteristics of wave and current work, rather than those of | 
stream work. I explain this occurrence of boulders, on the hypothesis | 
that when Lake Vermont was lowering, the basin behind the gap 
held an arm of the lake. When the surface of the lake had fallen 
so as to nearly expose the low part of the rim of the basin strong i 
scouring began. The last part of the scouring may have been done | 
by tidal currents, for the position of this boulder-bed falls in line with | 
the upper marine limit. | 
} 
The two small streams next west of this locality flow from narrow 
swampy areas which meet the spurs of the hills abruptly, as if the | 
swamps were formed by the silting up of bay heads. The swamps l 
are at approximately the level of the bouldery slopes above described | 
(270 feet). ‘ 
Four miles north of Vergennes, the cross-road leading west from | 
Shellhouse Mountain crosses a boulder-strewn surface at about the 
270-foot contour. This wave line follows the contour of the hill | 
northward for 2 miles to a projecting point where the signs of wave 
action are strongly developed. North of the point there is a delta- 
filled embayment. 
At a lower level (200 feet), and a mile southwest of the line just | 
described, a gravelly ridge having the proper topographic aspects ' 
of a barrier beach, extends along the road from Vergennes to Ferris- ! 
burg. For 20 feet above this level many of the rock knobs are bare, | 
as if wave washed. \ 
From a well-defined cobble beach 1 mile east of Shelburne Falls, 
a line of wave action may be followed for 4 miles near the 310-foot 
contour. Northward, this shore-line becomes less distinct and appears 
to split up into two lines marked by terraces at elevations of 290 feet 
and 320 feet, east of Shelburne Bay. 
The Winooski Delta. Opposite the north shore of Shelburne Bay, 
about 2 miles from the last locality mentioned, the 290-foot level is 
again represented by a terrace. Terraces with broad flats appear 
below this one, at altitudes of 220 feet and 120 feet. ‘These terraces 
are all sandy. Comparison of them with terraces on the immediate 
shores of Lake Champlain, leaves no doubt that they form parts of 
abandoned shore-lines, the materials of which they are composed 
being the delta deposits of the Winooski River. 
