402 Wood — On the East Essex Gravels. 



Sea, or rather that part of it which intervenes between Essex and 

 Belgium, not having, according to the evidence afforded by the val- 

 leys of the Crouch and Blackwater, and by the mouth of the Thames, 

 yet come into existence. Now if we apply to such a state of con- 

 figuration the result which takes place where the tide, passing up 

 a long furuiel-shaped opening has no outlet, we shall get a tidal 

 erosive action of which our present coasts offer no parallel'; for the 

 funnel, whose head terminated in th-e Weald valley, would have its 

 base far down towards the South- West of England. The Bay of 

 Fundy, it is well known, acts in this way, the tide having no outlet, 

 and were the isthmus between Dover and Calais restored, I can see 

 no reason why the same should not recur in the British Channel. 

 At the present day, however, the branch tidal wave, which, parting 

 from the great ocean tidal wave beyond the Land's End, flows up the 

 British Channel, is met near Beachy Head by another, and more 

 rapidly travelling branch wave, that passes round Scotland, flows uj) 

 the North Sea, and the erosive power, or excessive rise and fall of 

 tide, which would be produced by each, if arrested by an isthmus 

 between Dover and Calais, is thus neutralized. It seems to me that 

 in such a power ^ we have an agent equal to the formation of the 

 scarp-line of the Downs ; and when we know that this line is dis- 

 tinctly carried round the Bas Boulonnais, and only broken through 

 by the Straits of Dover, it seems rational to adopt it in explana- 

 tion of the case presented. Let us, then, sujDpose a series of further 

 upcasts over the Weald, accompanied with those disturbances which 

 we have seen evidence to consider took place at a very late period, 

 and produced the rectilinear mouths of the Thames and Crouch, gave 

 rise to the re-excavation of the valleys of the Crouch and Blackwater 

 Estuary, and brought into existence the North Sea between Essex 

 and Belgium, with eventually a reversal of the drainage of the 

 Medway and contiguous rivers. We should, in the state of things 

 supposed, have the North Sea much as it is, and the British Channel 

 only differing from its present form between Kent and Sussex, and 

 the French coast by an extension of it up that portion of the Weald 

 Valley, which is occupied by the Weald clay bottom, and both seas 

 exerting their tidal scour until by the giving way of the isthmus, by 

 fracture, or erosion, the present neutralizing effect of the tidal meeting 

 ended that state of things, and allowed the rise of the land to proceed 

 without the counterbalancing effect of this erosion. 



In this review of hypothetical causes, I have supposed the North 

 Sea as exerting, though in a less marked degree, the same erosive 

 tidal power near its head by Essex, and we should look for some 

 evidences there of its action. I think that these may be found in the 

 lofty inland cliffs of London clay, bounding the marshes of the 



1 Probably aided by the passage of shore-ice, as suggested by Mr. Brodie in re- 

 ference to the Somme Valley (Vol. III., p. 278, of this Mag.). Iu that view of 

 Mr. Brodie, so far as it goes, I concur, as I regard the Somme Valley as contempo- 

 raneous with that of the Weald, but without the previous formation of an isthmus to 

 cut oif the North Sea tide, I cannot see how any more tidal rush could arise in the 

 old trough of the Somme than now exists iu the equally funnel-shaped mouth of the 

 Thames Eiver. 



