﻿2/6 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Julie 25, 



communication is to direct attention to this peculiar deposit, in the 

 hope that further research may bring to light remains of a similar 

 description. 



In a paper on the Brighton Drift, read before the Society on the 

 14th of last May, Sir Roderick Murchison expressed an opinion that 

 the accumulation of the Mammalian chalk- and flint-rubble was sud- 

 den and tumultuous. In this view I quite agree, and also conclude 

 that the same rapid mode of accumulation is to be attributed to the 

 Sangatte Drift*. For, if the action had been slow and gradual, the 

 rolling to which the broken flints would have been subjected, must 

 inevitably have more or less blunted their edges ; and further, any 

 rounded flint-pebbles from the Tertiary strata could only have been 

 more rolled and rounded. But on the contrary, we find in this chalk- 

 rubble broken angular flints with edges as sharp as a knife, and with 

 fractures as clean as though they were just broken with a hammer, 

 whilst the small, hard, round flint-pebbles from the Tertiary strata 

 are often broken into two or more pieces, and these pieces neither 

 rolled nor worn. Some which are entire, and likewise many of the 

 flat broken lumps of iron-sandstone, are also found, as it were, stand- 

 ing on end — their longer axes perpendicular to the lower surface of 

 the deposit. 



Again, with regard to the finer sediment, if the accumulation had 

 been tranquil, this would have tended to have formed separate and 

 distinct layers ; whereas we find an almost impalpable chalk-paste full 

 of small and large angular and rolled fragments of chalk, — and this 

 chalk-paste occasionally replaced by sands apparently of Tertiary ori- 

 gin, almost unmixed, and as though lifted up and transported bodily 

 and without being broken up. The whole mass is roughly stratified 

 into certain divisions ; but in each division the materials are mixed 

 together perfectly independently of their specific gravity. Impal- 

 pable chalk-silt, which the most gentle current, if maintained, would 

 remove, is found enveloping masses of broken chalk-flints, whilst 

 large massive flints, scarcely at all broken or worn, and requiring for 

 their transport considerable power, are found dispersed indiscrimi- 

 nately in the finest sediment and in the coarse shingle. The flint- 

 rubble is also often heaped or piled as it were together, giving rise 

 to a roughly contorted appearance. Further, a deposition under the 

 ordinary conditions of accumulation in water would have led to the 

 probability of traces of the contemporaneous fauna occurring. 



It seems to me probable, that the action which led to the accumu- 

 lation of this Drift was sudden, powerful, tumultuous, not of long 

 continuance, and suddenly arrested. At the same time I do not be- 

 lieve that it was of a nature to break and fracture the great mass of 

 angular flints ; but these having been in greater part broken and 

 shattered by previous disturbances whilst in the body of the Chalk, 

 that they were removed, not so much by rolling at the bottom of 

 the water, as by transportation in mass with the waters. Such a 

 force, while it would uproot and tear away large portions of the Chalk 



* It is also probably of tbe same age. 



