LAKE PASSAIC. 553 
could not have come into existence until the first of these gaps 
was closed by the ice and drift. 
THE HISTORY OF LAKE PASSAIC. 
Something can be inferred as to the preglacial drainage of 
the lake basin from the gaps in its rim. Through the lowest 
gap, that at Short Hills and Millburn, the larger part of the pre- 
glacial drainage of the Passaic basin doubtless escaped. It is 
probable that another stream of less size, draining the north- 
eastern part of the Passaic basin, flowed through the gaps at 
Little Falls and Paterson. The drainage areas of these two 
basins could have been separated by no more than a low divide, 
as shown by the present topography. 
The advance of the ice-—When the ice sheet closed the 
gap at Little Falls, the drainage must have accumulated in front 
' of the ice in the northern basin referred to above. Any lake 
which may have been formed at this time must have been small 
and shallow, for it must soon have overflowed the low divide 
which separated the drainage basin having its outlet at Little 
Falls, from that which had its outlet through the Short Hills 
gap. As the ice advanced, it encroached upon this hypothetical 
lake, displacing its water and diminishing its area and finally 
destroying it altogether. 
No lake could have been formed in the drainage area of the 
river which flowed through the Short Hills gap, until after the 
ice reached that gap and filled it. Then, and not until then, 
could a lake have existed in the basin south of Morristown. So 
soon as this gap was closed, water from the melting ice began to 
accumulate in that part of the basin which the ice did not fill. 
This was the beginning of Lake Passaic. The water rose until 
it reached the level of the Moggy Hollow outlet, through which 
it drained. As already stated, the bottom of the notch in the 
rim of the lake basin at this point, is 331 feet above tide. Dur- 
ing the period when this notch served as the outlet, erosion is 
believed to have lowered it not more than 25 feet. 
The Madison stage-—When the ice had blocked the Short 
