198 FE. D. Chester—Distribution of Delaware Gravels. 
for the great thickness of gravel which washes their bases, but 
also for the enormous rounded bowlders of trap which cover 
their faces. The height of Iron Hill as stated in the previous. 
te and confirmed by a late measurement is 227 feet, or 275 
eet above tide. This hill must have then been totally submerged. 
To those who still think that the trap bowlders are of dike ori- 
gin, it will be best to present the following arguments: 
1. At the northern foot of Iron Hill, there was found an 
immense pile of rounded and sub-angular bowlders piled on 
top of each other, like stone dumped froma cart. These were 
not rolled bowlders, for their size of many tons would preclude 
all idea of their being thus piled up. With these were asso- 
ciated large quartzose bowlders of undoubted iceberg origin. 
2. Bowlders similar to those covering the hills are found to 
the northeast, and in fact as far off as Christiana and Stanton. 
8. Bowlders are found lying upon the ground above the iron 
ore pits, while no signs of a similar rock are found in the cut- 
tings either fresh or decomposed. 
4. The trap bowlders of supposed dike origin are found 
associated with other rocks of which we have: one bowlder of 
red orthoclase granite, one bowlder of black micaceous gneiss, 
one bowlder of limestone, numerous bowlders of decomp 
ferruginous quartz, and bowlders of a coarse ferruginous sand- 
eston which have been found scattered quite widely over the area — 
to the northeast. These latter rocks were found in such large 
quantities upon the hill that they were utilized as trimmings 
for the Presbyterian church of Newark. — 
With the main facts of the case thus briefly stated, it seems 
that there can be left no room for doubt as to the iceberg origi 
of the trap-bow]lders even in such isolated positions 
Morainic Phenomena.—We have already referred to the m0- 
rainic character of the whole region of which we have beet — | 
treating. These hummocky elevations are cut through by 
every road, whereby their internal nature is revealed. Some 
times they rise to a height of fifty feet, but have a general ele 
vation of from ten to twenty. y are absent from no part 
€ ee 
the region, and with the enclosed bowl-like depressions which . 
separate them, the whole country assumes a rolling characte 
This is generally due merely to a swelling of both’the clay and = 
underlying gravel, but as the clay has but slight thicknes® 
compared with the height of the moraines, and as this thickness 2 
is usually uniform, the swelling becomes mainly confined to t 
underlying gravel. This gravel deposited in the troubled w& 
ters of the glacial and post-glacial estuary, with its strong CUr 
rents, eddies, and waves, was therefore deposited unevenly over e 
the estuary floor. Taking into further consideration the a co 
which the gravel must have suffered during the deposiion 
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