176 J. D. Dana—The flood from the melting Glacier. 
upper ‘ijten or twenty feet of the formation, and therefore by their 
being the last work of the melting and discharging glacier. 
coarse stony stratum above and fine below is found through 
all the Mill River stony region.* Along the sections made 
through the New Haven plain to the level of the river flats in 
grading the streets, the lower part of the yee section is 
mainly of sand, while the upper is gravel and stones. The 
same has also been found to be true in the excavations for 
sewers in that part of the New Haven region. At one of these 
(at the corner of Orange and _— streets the ae sectiial 
was 12 to 15 feet thick, and below e beds were mostly fine 
sand, the lower stony layer rion on a bed of = quicksand. 
The vicinity of West River presents similar fact 
uch a transition in the drift deposits from the ‘production of 
sand beds with but little fine gravel to that of beds of coarse 
gravel and large stones— cobble stones—proves that 
there was an equivalent change in the flow of the waters. 
These waters were in rapid plunging flow when the lower stra- 
tum was deposited ; for the beds are oo everywhere 
by the flow-and- plunge structure, and a foot is acommon thick- 
ness for the bed made by a single plunge. But, however great 
the previous violence there was an increase afterward to a 
vaster flood. 
The partial decline of the flood is also marked in some portions 
of the deposits by the return to sandy beds in the top portion 
— Z narrowing of the stony region. On the western 
margin of the Mill River stony area, in Grove street above its 
ecean ‘ith Church, the stony beds reach the surface for 
200 feet above Church street; but from that point westward, 
the stony portion thins, and in place of its upper beds there 
are sandy and fine pebbly beds; in 200 feet this upper sandy 
part has bee six feet thick: "indicating thus the narrowing 
of the more violent part of the Mill River flood, as its season 
passed, or bee hein ps of the glacier became completed. 
n the region of the Quinnipiac valley, three to six miles 
north of sew Haven, on both the east and west sides of the 
present lower flats, there are beds of fine clay, from a few feet to 
irty-five or more in thickness. The upper surface is but little, 
if at all, above high tide level. As this Quinnipiac region was 
then (in the Champlain period) a t interior harbor or arm of 
the bay, over fifty feet in depth, still water would have existed 
on one or both sides of the main flow ; hese pd beds, all 
itten I had not recognized 
the distinction between the upper stratan and the beds below. 
