Fad 
eg pie eyeing Rye ty Sai as 
Pie oe arte: 
£., D. Chester—Distribution of Delaware Gravels. 199 
the clay, with the comparatively slight erosion from surface 
washings and weathering, since the region became land, we can 
easily account for all the physical features of the surface. 
But besides these mere swellings of the surface formations, 
there are occasionally found coarse gravel hills, which probably 
were shoal deposits. They rest upon the Philadelphia clay, 
with their bases ground into it. They are later in age than the 
latter deposit, belonging to the time when by the final eleva- 
tion of the land, the waters of the estuary became more shal- 
low and thus more efficient in piling up such shoal deposits. 
Between Newark and Elkton, a gravel hill rises to a height of 
50 feet above the railroad. It is made up of coarse, clean, 
yellow sand, with pearly white quartzose pebbles. No stratifi- 
cation is visible and the gravel extends downward for the 
whole 50 feet before the true estuary deposit is reached. 
odern alluvium.—Following the river, from the northern 
to the southern limits of the region one notices a belt of marsh 
land upon the Delaware side, beyond which are the gentle 
swellings of the gravels. This marsh land has been made in 
very recent times, and consists of black mud, blue clays and 
mver sand of great thickness. A boring made upon the Fort 
Delaware Island has penetrated through alluvium for a dis- 
tance of 100 feet. 
This alluvial formation has no particular geological interest, 
xcept that it indicates a greater width, but not necessarily a 
greater height of the river than at present. 
Resumé.—In conclusion, the following are, in brief, the main 
events of the Delaware flood history as revealed by the ob- 
Served facts. Toward the close of the Glacial period, the land 
of the peninsula became depressed to a distance of at least 350 
feet. Into the Delaware estuary thus formed the river of the 
Same name, fed by the melting glacier, poured its swollen rush- 
ng Hood. such a tremendous head, . 
Pushed its way across the States of Delaware and Maryland, to — 
=~ head of the Chesapeake. By means of this current and the 
ee distributing action of the waves, the red gravel was 
vOSIted, , 
+ater on, the extreme violence of the flood subsided, the 
land began to rise, and the glacier of the far north to break 
Until the water became shallow, when the shoal gravels were 
Piled up by the waves and tides, and the elevation still contin- 
“hae the river began more and more to assume its presen 
channel, and the waters of the Delaware and Chesapeake — 
ed f 
_ “Slaware College, Jan. ist, 1884. 
