﻿MURCHISON FLINT DRIFT OF S.E. ENGLAND. 389 



found its way into a broad torrential river or estuary between the 

 Surrey and Hertfordshire hills, in which fluviatile action afterwards 

 prevailed, so as to wear off the angles of the fragments which had 

 been hurled into it. My own opinion is, however, that nearly all 

 this rounded flint-gravel was derived from the breaking-up of the 

 old tertiary pebble-beds (as explained p. 374), which were infinitely 

 more developed in the London tertiary basin than in that of South 

 Sussex and Hants ; in other words, that the rounding of the flints 

 in the gravel was an operation of the early Tertiary Period. At all 

 events, from the slopes of the South Downs to the sea where very 

 few rounded tertiary pebbles have ever existed in situ, we clearly see 

 that after the first rush of waters, whether down the talus of the 

 chalk or through lateral openings, the fractured flints must have been 

 left as originally piled up, and, being desiccated, have never more 

 been subjected to the action of water and have remained in their an- 

 gular state. 



Let me here remind the reader, that if shocks of earthquakes in 

 this and the other hemisphere of which we have historical records 

 have occasioned the rise and fall of great waves, so such dismember- 

 ments as those in question will much more readily enable us to form 

 an idea of the transporting influence of ancient volumes of subter- 

 ranean water resulting from convulsions that opened out chasms in 

 the crust of the earth infinitely exceeding anything known in the 

 historical era. 



In reverting, then, to the chief point in this memoir, I would re- 

 peat, that the principal and upper masses of debris which are spread 

 out on the external slope of the South and North Downs, or within 

 the "Wealden denudation, must have been suddenly translated, and as 

 suddenly accumulated, in the rude piles or infillings of cavities they 

 now occupy ; since no analogy of tidal or fluviatile action can explain 

 either the condition or position of the debris and the unrolled flints 

 and bones. On the contrary, by referring their distribution to those 

 great oscillations and ruptures by which the earth's surface has been 

 so powerfully affected in former times, we may well imagine how the 

 large area under consideration was suddenly broken up and submerged. 

 This hypothesis seems to me to be an appeal to a vera causa com- 

 mensurate with the results. As respects the South-east of England, 

 the operation must have been modern in a geological sense ; for our 

 present line of sea-coast had then been formed, our lands, including 

 great longitudinal valleys in the Weald, were tenanted by herds of great 

 quadrupeds : whilst even anterior to the catastrophe by which such 

 land-animals were destroyed, sea-beaches of rolled pebbles, containing 

 species of molluscs still living, had previously been accumulated on 

 our southern shores, together with some remains of extinct quadru- 

 peds which had been derived from the adjacent lands ! In short, 

 the cliffs of Brighton afford distinct proofs, that a period of perfect 

 quiescence and ordinary shore-action, very modern in geological par- 

 lance, but very ancient as respects history, was followed by oscilla- 

 tions and violent fractures of the crust, producing the tumultuous 

 accumulations to which attention has been drawn. 



