DHIFT-STAGES OP THE DARKNT VALLEF. 120 



relation that these drifts bear to the river-drifts of the Thames Valley. 

 This section passes through the summit-level of the Swanscombe 

 Hills, which are there capped by Tertiary strata and an outlier of the 

 older drift. Though the height of this hill does not much exceed 

 300 feet, it corresponds with the level that the gradient of the 

 plateau at West Yoke and Ash should have, if extended thus far. 

 North of this hill, at Milton Street, near the village of Swanscombc, 

 and at a level here 200 feet lower than the plateau-drift, the high- 

 level river-drift of the Thames Valley is met with. It contains tlint 

 implements of a distinct and more advanced type than those of Ash 

 and AVest Yoke, while at a lower level still are brick-earths and 

 gravel with Mammalian remains and implements of a yet later 

 period. This is, I conceive, conclusive of the great antiquity of the 

 Chalk-Plateau drift and implements, and if we are to assume, as 

 there is every reason to suppose, that the great denudation of the 

 valleys has been the work of Glacial times, then these implements 

 may probably be assigned, as I have before suggested, to a pre- 

 Glacial or early Glacial period. 



The plateau which constitutes the table-land west of the lower 

 Darent Valley presents features precisely similar to those at Ash, 

 Bower Lane, and other places on the plateau east of the Darent 

 Valley. There is the same spread of Red Clay-with-flints 

 over all the Chalk Plateau, and the same slight sprinkling in 

 places of a drift of much worn brown-stained flints, with a 

 few subangular fragments of chert and ragstoue from the Lower 

 Greensand *. I have found this drift on the hills just above 

 Shoreham. Ch«rt and ragstoue arc particularly abundant in the 

 field over the railway tunnel opposite Colegates Farm. They 

 occur less abundantly around Halstead, and have been found by 

 Mr. Harrison on the very summit of the escarpment, at a height 

 of 700 feet, on Morant's Court Hill (see PI. VI., fig. 3). Farther 

 west, Mr. De B. Crawshay has found the brown-stained worn flints 

 on Betsom Hill (790 feet) above Westerham, and on Titsey Hill 

 (864 feet) above Limpsfield, both being on the crest, and forming 

 the highest summit-levels of the Chalk escarpment. The inter- 

 mediate ground between Morant's Court Hill and Betsom Hill has 

 at present yielded no specimens, though the Bed Clay-with-flints 

 is continuous throughout. On the hill above Stonehouse, north 

 of Halstead, I have found a considerable proportion of the brown- 

 stained flints with numerous Tertiary flint-pebbles, some Tertiary 

 sandstones, and a little Lower-CJreensand debris. 



At the time my Ightham paper was read, the only Palaeolithic 

 fliut-implement known on this western plateau was the one at 

 Currie Farm, south of Halstead t, found 20 years ago and described 

 by Dr. John Evans. Its surroundings and position were such as to 

 lead me to group it with the Ash specimens as of early Glacial or 

 pre-Glacial age. My friend Dr. Evans, however, considered thut 



* I include any Lower-Greensand debris, such as grit and ironstone. 

 t The Rev. R. Ashington BuUen, the Vicar of Shoreliam, has recently found 

 a very similar specimen in the same field. 



