28 SURFACE GEOLOGY. 



valley a series of lakes. The vast amounts of modified drift which accu- 

 mulated in this valley do not appear to have filled ancient lake-basins, but 

 to have been rapidly deposited from the immense floods supplied by the 

 melting of the ice-sheet. These great deposits of modified drift, for which 

 there appears no other adequate cause, should rank with the till, striae, 

 and embossed ledges, as proof of a former continental glacier. 



The Passumpsic river must be considered as occupying the continua- 

 tion of the lower Connecticut valley, but at its mouth it flows through a 

 rocky gorge, which separates its numerous and high terraces from those 

 of the Connecticut. Four or five terraces are shown here on the Monroe 

 side, the highest 190 feet, and the lowest from 15 to 20 feet above the 



~ . The Nine Islands. m 



Fig. 3. — Section in Barnet and Monroe, at Mouth of Pas- 

 sumpsic River. Length, i mile. 



river. The latter forms the Nine Islands, of which only one is above the 

 reach of high water. This is a wooded island close to the Vermont side, 

 and forms a north and south ridge 50 feet above the river, composed in 

 part of kame-like gravel. Delta terraces from 50 to 60 feet above the 

 highest in the main valley have been brought down by Stevens river, 

 which falls 100 feet in Barnet viflage. Gleason's islands, one mile below, 

 like nearly all those found in the river southward, are alluvial interval. 

 Several terraces appear at Mclndoe's falls, on the widest of which the 

 village is situated, 50 feet above the river. The high terraces do not 

 present a broad level top till we come to Monroe village, where we find 

 two, 100 and 150 feet above the river, both of which are continuous a 

 mile and a half, with regular southward slopes of ten and twelve feet. 

 Occasional remnants of the highest of these are found on both sides 

 through Bath and Ryegate ; and the lower is well shown through these 

 towns, agreeing closely in height on opposite sides of the river. On 

 the east side it is continuous for eight miles, from one mile north of 

 Monroe to the Narrows near Woodsville, sloping from 545 to 488 feet 

 above the sea. 



