Cn. XIX.] DENUDATION OF THE WEALD. 2S9 



of the flints, it has been thought by some authorities to imply great vio- 

 lence in the removing power, especially in those cases where well-rounded 

 pebbles washed out of Eocene strata are hkewise found broken, sometimes 

 with sharp edges and often with irregular pieces chipped out of them as 

 if by a smart blow. Such fractured pebbles occur not unfiequently in 

 the drift of the valley of the Thames. In explanation, I may remark that, 

 in the Blackheath and other Eocene shingle-beds, hard egg-shaped flint- 

 pebbles may be found in such a state of decomposition as to break in the 

 same manner on the application of a moderate blow, such as stones might 

 encounter in the bed of a swollen river. 



To conclude : It is a fact, not questioned by any geologist, that the 

 area of the Weald once rose from beneath the sea after the origin of 

 the chalk, that rock being a marine product, and now constituting dry 

 land. Few will question, that part of the same area remained under 

 water until after the origin of the Eocene deposits, becav.s6 they also 

 are marine, and reach to the edge of the chalk-downs. Whether, there- 

 fore, we do or do not admit the occurrence of reiterated submersions 

 and emersions of land, the first of them as old as the Upper Cretaceous, 

 the last perhaps of Newer Pliocene or even later date, we are at least 

 compelled to grant that there was a time when, in the region under 

 consideration, the waters of the sea retreated. The presence of land 

 and river-shells, and the bones of terrestrial quadrupeds in some of the 

 gravel, loam, and flint-breccia of the Weald, may indicate a fluviatile 

 origin, but they can never disprove the prior occupation of the area by 

 the sea. Heavy rains, the slow decomposition of rocks in the atmo- 

 sphere, land-floods, and rivers (some of them larger than those now 

 flowing in the same valleys) may have modified the surface and ob- 

 literated all signs of the antecedent presence of the sea. Littoral shells, 

 once strewed over ancient shores, or buried in the sands of the beach, 

 may have decomposed so as to make it impossible for us to assign an 

 exact paleontological date to the older acts of denudation ; but the re- 

 moval of Chalk and Greensand from the central axis of the Weald, the 

 leading inequalities of hill and dale, the long lines of escarpment, the 

 longitudinal and transverse valleys, may still be mainly due to the 

 power of the waves and currents of the sea, co-operating with that up- 

 heaval and subsidence and dislocation of rocks which all admit to have 

 taken place. 



In despair of solving the problem of the present geographical config- 

 uration and geological structure of the Weald by an appeal to ordinary 

 causation, some geologists are fain to invoke the aid of imaginary 

 "rushes of salt water" over the land, during the sudden upthrow of 

 the bed of the sea, when the anticlinal axis of the Weald was formed. 

 Others refer to vast bodies of fresh water breaking forth from subter- 

 ranean reservoirs, when the rocks were riven by earthquake-shocks of in- 

 tense violence. The singleness of the cause and the unity of the result 

 are emphatically insisted upon : the catastrophe was abrupt, tumultuous, 

 transient, and paroxysmal ; fragments of stone were swept along to great 



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