xxi Proceedings. 
summit of this hill are the remains of an ancient (? Roman) 
camp, but the entrenchments have been much encroached on 
and destroyed by the excavations which have been subsequently 
made on the sides of the hill. This is especially the case on the 
east side, where the wall of the camp has been entirely destroyed 
by a very large excavation, now disused and converted into a 
recreation ground for Woolwich. The numerous large excava- 
tions, now mostly disused, which exist along the ridge of hill 
overlooking the Thames, were made in former times, chiefly for 
the purpose of digging sand and gravel as ballast for ships 
returning to the Tyne and other northern ports after having 
brought cargoes of coal to London. The digging of sand and 
gravel for this purpose has now been superseded by the use of 
water ballast. Mr. Gilbert’s pit is worked chiefly for the pur- 
pose of obtaining moulding sand for foundry use. It exhibits 
a fine section of the strata from the Oldhaven Pebble beds 
to the Upper Chalk inclusive. The Upper Chalk is seen in 
the bottom of the pit, and a few specimens of Inoceramus and the 
commoner sea-urchins were obtained from it. At the junction 
of the chalk with the superjacent Thanet Sand is a béd of green- 
coated unworn flints. This bed ranges in thickness from 6 to 
18 in. or more, being thicker where it fills up hollows in the 
surface of the chalk beneath. Above this is the Thanet Sand, 
for which the pit is worked. This bed is some 30 to 40 ft. thick. 
The lowermost portion, 7 ft. thick, and locally called ‘ blackfoot,’ 
is of a somewhat loamy nature, and is valuable for moulds for 
brass castings. The next twelve feet above this consist of 
larger-grained and less cohesive sand, better adapted for mould 
for iron castings. The upper part of the Thanet Sand is a 
sharp white sand. In the lower part of the pit a pocket was 
observed in the sand containing a current-bedded infilling with 
clayey partings. Above the Thanet Sand, and separated from it 
by a pebble layer, come the Woolwich Beds, some 20 ft. in thick- 
ness ; these consist of an alternating series of sands with ferru- 
ginous concretions, shelly clays, and pebble beds. These beds 
dip and thin out to the west on the slope of the hill on that side, 
this being due to their having slid down the hill and become 
thereby drawn out. At the top of the pit the Oldhaven pebble 
beds are seen. 
“The shelly clays of the Woolwich Series, and the Oldhaven 
pebble beds, are, however, better seen on the steep face at the 
east side of the hill, where they abound in fossil shells. These 
are mostly in fragments, but by careful search good specimens 
may be found. The most plentiful fossils in the Woolwich Beds 
are two species of Cyrena (C. cordata and C. cuneiformis), and the 
turreted gasteropod, Melania inquinata ; another similar shell, 
Cerithium funatum ; and a large species of oyster (O. bellovacina) 
