in the Approaches to New York Bay. 477 
“sandy clay strata” of the New Jersey geological survey which 
underlies nearly the whole of the peninsula of lower New 
Jersey. 
The disappearance of the submerged valley at a less depth 
than 19 fathoms must be attributed to the obstructive action of 
Sandy Hook bar. By taking this depth as the greatest ever 
reached by the channel over the bar near Sandy Hook, we can 
form an estimate of the geological age of this bar. 
Professor Cook, in a statement made before the Riparian Com- 
mission of New Jersey, November 17, 1883, estimates the pres- 
ent rate of subsidence of the coast of New Jersey at about two 
feet in a hundred years. At this rate, the decrease of depth 
from 19 fathoms to 4 fathoms which is about the present mean 
depth of the New York bar, would cover a period of four thou- 
sand five hundred years. 
The transfer, per saltum, of a bar at the depth of 41 fathoms 
and at a distance of 75 miles from the Hook to one of 19 fathoms 
depth and in the immediate vicinity, however, cannot well be 
explained upon the theory of such a gradual and moderate sub- 
sidence as is believed to be going on at the present time. 
The State Geologist, Professor Cook, assuming a mean ee 
of twenty-five feet to the mile for the marl beds, has indicate 
lines of strike upon his geological map, showing the depth 
below sea level of the red sand bed (a subordinate stratum of 
the Cretaceous marl formation) and the lines A and B on the 
map (see Plate) are such lines for the depths respectively of 250 
feet and 1040 feet. These lines produced to the submerged 
channel strike the top of the clay bank at points the respective 
depths of which are 108 and 162 feet below the ocean level. 
This great difference in dip (790 feet against 54 feet) may be 
accounted for by supposing that the top of the clay bank does 
not coincide with the line of stratification (its slope being about 
two feet to the. mile), or there may be a flattening out of dip 
toward the sea. And, again, the sandy clay bed may not rest 
conformably on the formations which crop out on the dry land. 
In the geological surveys of Pennsylvania and New Jersey, 
the terminal moraine was accurately traced through these two 
States, and the sketch shows its course from the valley of the 
Alleghany in western New York, eastward and southward to 
New York Bay. ‘The line as there shown was taken from a 
map by Professor Lewis in this Journal, 1884; and from the 
geological map of New Jersey, 1882. It will be = a 
glance that this line and the submerged valley of the Hu cn 
orm a continuous line, and this coincidence suggests that t 2 
valley stands as a mark of the limit of the glacial drift an 
as one of the “great waste-weirs of the melting cape id 
use an expression which Professor Lewis applies to the Lehig 
