16 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 9, 



Medway drainage having been worn down step by step as the Lower- 

 Greensand escarpment rose above the waters, until it presented the 

 condition now exhibited by the trumpet-mouthed gorge cutting 

 through that escarpment at Yalding ; at which time, or even pre- 

 viously, through the opening in the Lower-Greensand hiU to the 

 north of them, the Lower-Tertiary pebbles and angular flints abund- 

 antly present in the gravels near that place, shown in the map, 

 were thus brought from the northward through the Lower-Green- 

 sand escarpment. 



The Lower-Greensand escarpment subsides and disappears near 

 Ashford ; so that where the Kennington, Willesboro', and Smeeth 

 gravels containing the flint and pebble admixture occur, there is no 

 such escarpment at all. The mouth by which the drainage through 

 the Stour vaUey entered the Weald seems therefore not to have much 

 advanced beyond the chalk escarpment ; so that the gravels at these 

 places represent both the gravels above Maidstone, accumulated 

 when the Medway mouth was near the chalk escarpment, and the 

 gravels about Yalding, accumulated either about the same time or 

 else later, when that mouth had become established near the Lower- 

 Greensand escarpment. The highest of the Stour area, viz. those 

 at Kennington, seem to be probably coeval with the gravels above 

 Maidstone ; while those of Willesboro', which are at a lower level, 

 may be synchronous with the gravels about Yalding. 



During the later portion of this change the Hastings-sand country 

 formed, it seems to me, a large island, so that what for convenience' 

 sake I have called sea, was really only an inlet receiving freshwater 

 through these several rivers ; and since the width between this island 

 and the chalk escarpment varies only from eight to eleven miles, and 

 between it and the greensand escarpment from five to six miles only 

 at the narrower parts, there would have been a considerable tidal 

 scour exerted under any circumstances, while the far greater volume 

 of the land-drainage of those postglacial times, compared with what 

 now obtains in the east of England, would tend to push the limit of 

 fresh water further out into estuaries than at present. Great 

 freshets too, carrying with them volumes of river-mud with its 

 associated organisms, would be poured into the Weald ; and through- 

 out it is to be remembered that the fresh water must follow the 

 salt water as the latter recedes by the extension of the shore-line, 

 and occupy its place. In this way it seems to me that there would 

 be nothing repugnant to the events I have traced, if the gravels in 

 question should hereafter be found to yield the remains of land or 

 fresh-water organisms, such as do occur in some of the gravels and 

 brick-earths shown in the map under a different shading, and which 

 are most of them due to the rivers flowing as they do now. 



The views thus sketched assume the Weald, when the sea had retired 

 within the chalk escarpments, to have been the island-studded head of 

 a still longer inlet formed by the British Channel while this channel 

 was closed to the north by an isthmus between Dover and Calais, 

 which had come into existence by means of that elevation of the 

 chalk country which put an end to the Thames gravel and its coeval 



