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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



of the whole body of water, such as that of a stream-current. I have 

 elsewhere suggested that the cross-lamination, which certain marine 

 deposits exhibit over wide areas, may be referable to the more rapid 

 and effective tidal action of enclosed and moderately deep seas. If, 

 in the instance of the Guildford Valley gravels, this form of arrange- 

 ment was due to currents of water produced by streams, which flowed 

 into that area from the central Wealden region, and which discharged 

 outwards through the gorge in the chalk-range, the direction of such 

 currents being constant, that of the laminae would be so also, or 

 northerly ; whereas we constantly find them dipping southerly, as if 

 the prevailing set of the water when in movement had been from the 

 north. The gravel-beds, here described, pass through the gorge at 

 Guildford, and are continuous and identical with those which cover 

 the whole of the London-area-basin ; we have, therefore, a definite 

 water-level, or, in other words, the Guildford Valley was a land-locked 

 bay of that great northern ocean, of which the " drift-gravel" beds 

 are the sub-littoral accumulations. Under these conditions the pro- 

 cess of accumulation would have been identical with what now takes 

 place in all deep bays or estuaries along sea-boards ; whilst under the 

 other supposition, the mechanical power of a perfectly enclosed area 

 of water of the dimensions of that here described (Map, fig. 1) could 

 never have conveyed and arranged the beds of gravel as we here find 

 them. But definite geological epochs are very indefinite periods of 

 past time ; and no one representation of ancient physical conditions 

 can hold good for more than one portion of a geological period : in 

 this case we have the distinct features of the old bay, the gorge com- 

 municating with the external area of water, its latest level, and me- 

 chanical arrangements ; but it by no means follows that the materials 

 so disposed were for the first time placed there. There are good 

 grounds for the supposition that there was here an anterior and very 

 different configuration. 



It will be seen by the tabulated order of succession (p. 281) that 

 there is a progressive change from coarse gravels up to fine clay, a 

 change which indicates a diminution of moving power ; but this re- 

 sult may be brought about, whether the displacement of a portion of 

 the volume of water happen from elevation on the land side, or by 

 the simple process of filling up, the water-level remaining the same 

 throughout. 



It will be also seen from the Map, that the gravel-beds, here 

 noticed, extend some way up several valleys which branch off from 

 the main one ; of these, that of the Tillingbourne stream, which ex- 

 tends some miles in an easterly direction, offers some points of in- 

 terest. The general slope of the ground, covered by gravel, is to the 

 north, and this slope is occasionally considerable, as in the section 

 from above Locknor Farm to the stream at Collyers Hanger (fig. 2) . 

 The Locknor cutting, on the Reading and Reigate Railway, is 3 1 feet 

 deep, of which the greater portion was through layers of gravel 

 with beds of diagonal drift -sand. This cutting is perhaps at the 

 highest point at which these beds have been noticed, being rather 

 more than 1 30 feet above the great collection of flint-gravel at the 



