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THE GEOLOGIST. 



together as to apijear 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 aifixed 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 



* Geol. Trans. Vol. 4, p. 300. 



