Consequences of the Glacial flood. 119 
of the New Haven plain, between Mill Rock on the east and 
Pine Rock on the west, and each is about 1$ths mile long.* 
They are sunk 25 to 85 feet below the level of the plain, and 
are confined for the most part by terrace fronts of this height. 
They have a width mostly of 800 to 1,000 feet, and a botiom 
of peat meadows, though with some encroaching areas of sand 
deposits ; the level of the marshes in the Beaver Pond depres- 
sion is 27 feet above mean tide, and in the Pine Marsh, 83 to 35 
feet. They are much like the West River channel-way be- 
tween its terrace fronts; or, rather, like fragments of it, for 
they are marvelously short for the great breadth and depth. 
The western depression—that of the Beaver Pond Meadows— 
is wholly isolated from any of the rivers of the region both to 
the north and south, but has a lateral connection by a valley 
with Mill River valley. Hach has its stream, one emptying by 
the lateral channel referred to into West River, the other join- 
ing Mill River by its north end. These streams, although not 
two miles long, which is very short for the great valley they 
occupy, are abundant in waters, that of the Beaver Pond de- 
Pression supplying a mill the year around. These copious 
waters are almost wholly sudterranean—whence it is that the 
deeper pools do not freeze over with the thermometer at 0° F. 
_ As shown on the map, the more northern of the two depres- 
sions, Pine Marsh Creek, comes to its southern end abruptly in 
the plain southwest of Mill Rock; while the other, the Beaver 
ond depression, begins almost as abruptly just west of this 
place; the terrace-plain between them is for the most part at its 
ight 
ows, by Mr. Sylvanus Butler, under the direction of the city of 
New Haven, the depth through the peat to firm gravelly bot- 
© borings have been made through the bottom gravel to 
the underlying sandstone, and hence the actual depth of the 
‘rough to solid rock is unknown; we know only, from the fact 
Just stated, that itis more than 25 feet below mean tide. From 
this it appears to be certain that the Beaver Pond channel is 
nly a depression in the plain or the terrace deposits ; 
ae Pond depréssion terminates southward near the junction of Goffe 
Cent streets, and extends northward along the w 
helton Avenue, north of Morse street. 
Powy P The Pine Marsh depression has its southern termination near the extrem- 
a : : s : 
