INGHEILH CA LIONS. 363 
lated on the ice, partially as dust, and left on the surface of the till 
when the melting occurred. The fact that superglacial material, 
especially on stagnant ice-sheets, is subjected to many changes of posi- 
tion and experiences many falls, and is thus broken,-and that it is also 
disintegrated on account of changes of temperature, might, it seems to 
the present writer, be cited in connection with the hypotheses suggested 
in reference to superglacial origin of the loam. 
Lake Passatc.—The conclusion that a large glacial lake formerly 
existed in the drainage basin of Passaic River, in north-central New 
Jersey, was advanced by Professor George H. Cook, the late state geol- 
ogist, in his annual report for 1880. The strength of the evidence on 
which this conclusion was based has since been questioned, and several 
geologists who have visited the region have doubted if Lake Passaic, 
as the old lake was named, ever had an existence. This subject has 
been restudied by Salisbury and Ktimmel, and so much consistent 
evidence advanced that the former presence of the water-body referred 
to must not only be accepted, but given a prominent place among exam- 
ples of ice-dammed lakes of the nature of Merjelen Lake, Switzerland, 
the first existing example of the type to be studied. 
The trap ridges of central New Jersey, rising above low-lying areas 
of Newark sandstone and shale, have such a form that an ice-sheet 
advancing from the north would occupy the depressions through which 
the drainage escapes, and thus shut off a considerable basin from free 
discharge to the sea. This in general was the history of the origin of 
Lake Passaic. The evidence furnished by lacustral deposits, terraces 
and other shore features, as well as by the position of the great ter- 
minal moraine, although indefinite at times and seldom pronounced, 
is, on the whole, sufficient to prove the former presence of Lake Passaic 
and to admit of the mapping of its shores. Like most lakes held by 
ice dams, the glacial lake of New Jersey had a varied history, several 
chapters of which have been deciphered. During its maximum it was 
about thirty miles long from north to south and ten miles broad at its 
widest part, and over 225 feet deep. 
Since the lake was drained, the region it occupied has undergone 
changes in elevation and the old shore lines are no longer horizontal. 
An increase in elevation from south to north of sixty-seven feet in 
thirty miles, or at the rate of 2144 feet per mile, has been shown to exist. 
These changes are supposed to be due to a re-adjustment of isostatic 
conditions after the disturbances produced by the weight of the Pleis- 
tocene ice -sheets. 
