LAKE PASSAIC. 555 
and back of these plains, after it had retreated from the lower 
ground in the same latitude, thus giving rise to the embayment. 
This is shown (a) by the basin-ward slope of the surfaces of 
the foregoing delta plains, showing that they were built from 
the highlands ; (0) by the forward-plunging strata, which, 
where seen, generally dip towards the lake and away from the 
highlands; (¢) by the frequent occurrence at the head of the 
plains, of bowlder-strewn kames, which mark the position of the 
ice edge while the plain was forming; and (d) sometimes by 
the forms of the margins of the deltas. Other possible modes 
of origin were kept in mind as working hypotheses in the field, 
but were finally abandoned, since they did not harmonize with 
the facts. 
The Upper Preakness stage —At a number of places more or 
less well-defined terraces and deltas are present at elevations 
from 65 to 75 feet lower than the maximum water level. These 
lower terraces are sometimes directly in front of the higher, 
which then rise from the upper margin of the lower. In other 
localities the higher are present without the lower, or the lower 
without the higher. The two are seen in close connection 
between Boonton and Montville, at Upper Preakness, and west 
of Haledon. On the assumption that the tops of these lower 
terraces represent the approximate level of the water in which 
they were formed, just as it has been assumed that the surface 
of the subaqueous overwash plain marks the maximum water 
level, these terraces mark a subordinate stage in the lake’s his- 
tory. This stage may be called the Upper Preakness stage, from 
the marked development of the delta plain near Upper Preakness. 
The field relationships are such as to indicate beyond reasonable 
doubt that the lower terraces antedate the upper. The evidence of 
the greater age of the lower is not equally conclusive at all points, 
but nowhere is the relationship. between the two such as to 
necessitate the assumption of the greater age of the upper. 
We must conclude, therefore, that the front of the ice became 
deeply embayed as it retreated from the line of the moraine, and 
that for a time the waters of the lake sank about 70 feet below 
