42 SURFACE GEOLOGY. 
which they appear to have been carried up by the prevailing north-west. 
winds. Southward they are found in many places on the east side of this 
valley, but none were seen in Vermont. 
Deltas. A large amount of modified drift occurs on Blow-me-down 
brook. Three miles from its highest source, where the road crosses 
23 = ny Se See 
Brie PRers 2s . 
a y BS 
is Ey] e 
Sy | Hees 
so NR Earl 
Mice os ae i 
ere fee LES 
oS Serene ae! 
SS 8 ° 
Fig. 11.—SAND DUNE, NEAR THE SOUTH LINE OF LEBANON. 
Croydon mountain, it has formed the plain of Cornish Flat, 855 feet above 
the sea, and six miles lower that of Plainfield village, 520 feet above the 
sea, with an older deposit 30 feet higher, at the north end of the village. 
Two miles farther down, where this stream opens into the broad valley, it 
has formed a delta of irregular slope from 512 to 420 feet. These trib- 
utary deposits often throw light on the history of the modified drift of the 
main river. We have seen that the deltas north of the continuous kame, 
as of Wait’s river at Bradford, and Jacob’s brook at Orford, were deposited 
before the completion of the original flood-plain of the Connecticut; but 
the deltas of Quechee river and Lull’s brook appear to have been brought 
down at about the same time with this upper terrace, which is notably 
increased in height by them for a considerable distance; while the long 
sloping delta of Blow-me-down brook, covering a square mile and descend- 
ing to nearly 100 feet below the normal highest plain, seems to be of 
a date subsequent to its formation and partial removal by the river. A 
conspicuous dune at the east side of this delta, derived from it and from 
the original high plain, is 610 feet above the sea, or 100 feet higher than 
the deposits from which it was blown. 
