326 
THE GEOLOGIST. 
together as to appear almost to have been artificially imbedded, so as 
to expose their general character. Many of these shells I have obtained 
in a perfect state, but a large proportion of them are broken and 
scattered throughout the deposit. One of my specimens consists of a 
mass of about six oyster shells attached to a large oval flint-pebble, which 
evidently have grown on their original site without injury from the 
neighbouring pebbles. Dr. Buckland had in his collection a specimen 
in which five oyster shells were affixed to the opposite sides of a large 
kidney-shaped pebble, from which he inferred the existence of a state 
of sufficient tranquillity for the shells to live and die undisturbed in the 
midst of these pebbles.* All these pebbles — the shingle that formed 
the native bed of the shells — are of a black colour, are well worn and 
rounded, and exist in countless thousands in this pit, and are scattered 
throughout the neighbouring land for many miles ; they illustrate very 
forcibly the immense scale in which the aqueous destruction of the 
superficies of the chalk was carried on, and, as geologists correctly 
assume, the long period of time which intervened between the deposition 
of the chalk and that of the plastic clay. 
The pit in which this deposit can be well seen and studied is situated 
to the south of a hill, into which the excavation runs in a northernly 
direction, and varies in depth from 40 to 60 feet. The strata of sand 
and shells are seen to advantage on the left of the entrance, and dip 
towards the north-east ; the upper layers, however, occupying the north 
half of the pit, dip at an angle of twenty-five degrees, whilst those at 
the south half, which are lower down in position, dip at an angle of 
twelve degrees. The lowest stratum consists of a light gray or drab 
sand, uniform in colour, free from pebbles or shells, and averaging 
twelve feet in thickness ; upon this is a conformable layer of light brown 
sand, twelve inches thick, filled with myriads of the fragments of small 
shells. Next succeeds a lighter sand with small rolled flint pebbles, 
and of small, very friable shells of the genus Cyrena and Cerithium, 
sixteen inches thick. Variegated brown sands with very few pebbles 
next succeed, from three to four feet thick, over which is a bed of brown 
sand and pebbles, free from shells, in layers thinning out, but in the 
middle fourteen inches in thickness. Light brown and variegated sand, 
with a few pebbles and a few shells, also thinning out, succeeds to the 
last, the thickness not exceeding two or three inches. Then follows 
* Gcol. Trans. Vol. 4, p. 300, 
