LAKE PASSAIC. 557 
outlet, once established during the retreat of the ice, could again 
be closed during the further retreat of the ice, when its motion was 
probably diminishing in vigor, and when its rate of melting was 
very likely increasing, and when it was becoming thinner. Nev- 
ertheless, the stopping of the outlet, even under these adverse 
conditions, seems to be indicated. 
The final draining of Lake Passaic.—After the Montville stage 
had endured for a time sufficient for the formation of the glacial 
deltas which mark that stage, the ice was melted back so as to 
permit the escape of the lake drainage through the Little Falls 
and Paterson gaps. The intra-morainic part of the lake was 
soon drained to the level of the barrier at Little Falls, 175 to 190 
teet. Below this level in the area of the Great Piece and Troy 
meadows, and perhaps in Black meadows and Hatfield swamp, 
shallow bodies of water may have lingered until the outlet was 
brought down to this level. Such bodies of water must have 
existed for a time, if relative levels were the same as now. As 
deformation of the basin has taken place since the ice disappeared, 
it may be that these swampy areas were not then lower than the 
Little Falls outlet. After the Little Falls outlet was established, 
a small post-glacial lake remained in the extra-morainic basin 
over the low land between Second mountain and Long Hill, in 
the valleys of the Passaic and Dead rivers. It was held at 230 
feet by the drift barrier at Stanley, through which the river has 
since cut a passage. 
Judging by the meager developments of the shore features of 
Lake Passaic save in those cases where the supply of material 
from the glacier was abundant, their indefinite form in many 
instances, and their entire absence in localities where they might 
rationally be expected to exist, we cannot but conclude that the 
entire life of the lake, was, geologically speaking, brief. During 
its maximum extension, just before its final draining, Lake 
Passaic must have been about 30 miles long and 10 miles wide at 
its widest part. It must have had a maximum depth of about 
225 feet in the intra-morainic part, and of about 140 feet in the 
extra-morainic. 
