558 THE JOURNAL OF GEOLOGY. 
The sequence of events outlined above is based upon the 
assumption that all the drift in the Short Hills gap is late ghacial, 
and that, until the ice reached the line of the moraine, drainage 
escaped through this gap at the level of the rock bottom. The 
presence of the thick deposits of (lacustrine ?) clay in the region 
of the Great Swamp, which by their relationship to overlying 
deposits, are clearly shown to antedate the moraine and accom- 
panying overwash plain, indicate that a lake may have existed in 
the Great Swamp area for a considerable period before the ice of 
the last epoch formed the moraine. 
Three hypotheses concerning a pre-morainic lake in the Lake 
Passaic region may be considered. (1) Some part, perhaps a 
large part of the drift filling of the Short Hills gap, may belong 
to an earlierice sheet which deposited the extra-morainic drift 
found more or less abundantly about the lake basin and above 
the lake level. In this case, the inter-glacial drainage may have 
been through the Little Falls outlet and Lake Passaic may have 
come into existence, so soon as the ice of the last epoch closed 
the Little Falls gap. Under this hypothesis, the Great Swamp 
clays would be referred to this early stage of the lake’s history. 
In this event we must suppose that the ice advanced very slowly, 
so slowly that a great thickness of clay accumulated before the 
deposition of the overlying loam, sand, and gravel, which are 
contemporaneous with the moraine or which but slightly antedate 
it. The clays north of the moraine, which are similar to lacustrine 
clays, arealso in general at low levels, and so far as elevation 
goes, may have been formed in such a lake. 
(2) We may conceive that the earlier ice invasion wrought 
such changes in the preglacial topography, that, after its retreat, 
a low-level lake occupied the area of the Great Swamp, and 
perhaps also the lowlands northeast of the moraine. In this 
inter-glacial lake much of the lacustrine clay may have been 
formed. We may suppose further that the lake was drained 
during inter-glacial time by the clearing out of the Short Hills 
gap. In this case we should expect to find the clays overlain by 
an old soil developed after the lake was drained. Above this old 
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