BEACHES, ETC., OP THE SOUTH OP EXGLAND. 309 



It is also possible that the dry valley which descends from near 

 Bredhurst, and passing by Luton joins the Medway Valley at 

 Chatham, may have contributed to the low-level drift around 

 Strood and Rochester. Those near Prindsbury are rich in mam- 

 malian remains. In the Luton Valley the brick-earth ascends 

 farther from its river-base, owing possibly to the check received 

 by the flood-waters at its junction with the Med way Valley. 



(4) The Cray and other Valleys. — Amongst others of these 

 dry valleys in the Chalk hills is the long narrow vale of Longfield 

 which, commencing in the hills above "Wrotham, winds its course of 

 10 miles by Eidley to its junction with the Darent Valley a short 

 distance above Dartford. A long narrow trail of flint-gravel from 3 

 to 5 feet deep lies along its whole length, but although it is worked 

 in many places I cannot learn that any organic remains have been 

 found in it. 



The thin trail of flint-gravel in the upper dry valley of the Cray is 

 also probably connected with this drift. At Green Street Green, 

 where a tributary valley joins the Cray Valley, the gravel swells to a 

 thickness of from 20 to 30 feet, and is confusedly heaped together 

 without a trace of stratification. The gravel consists of a mass of 

 broken and sharply angular chalk-flints, of flint-pebbles derived from 

 Tertiary beds on the adjacent hills, and of large, much rolled and 

 worn flints, derived probably from an older gravel, of which an out- 

 lier caps Well Hill. It rests upon a very uneven and broken surface 

 of Chalk, and a good deal of chalk-rubble is mixed up with the lower 

 portion of the gravel, or forms irregular beds or masses in a manner 

 much resembling the deposit of rubble in the cliff at Birling Gap. 

 Eemains of the Mammoth, Rhinoceros, Horse, and Ox are occa- 

 sionally met with, and with these has been found part of the skull 

 of the Musk Ox. In a smaller adjacent pit I found a few specimens 

 of Pupa marginata in a thin intercalated seam of loam. A very 

 few rolled and much-worn Palaeolithic flint-implements have also 

 been found there by Mr. de B. Crawshay, and one was got in a 

 small shallow pit near the Orpington pumping station, lower down 

 the valley, by Mr. I. Allen. The drift in the upper dry valley of 

 the Ravensbourne is of similar origin. 



In speaking of these dry valleys with their trail of angular flints 

 as belonging to this drift, I do not mean to imply that streams have 

 had nothing to do with their denudation at a former period. Their 

 early erosion was probably due to that agency, but the deposits 

 formed by the streams have been destroyed and lost in the intrusion 

 of the later rubble-drift. 



(5) Folkestone. — On the scarped or steep face of the Downs the 

 accumulation of this drift is less. We have before noticed the 

 Folkestone rubble-bed at the Battery, and to this we may perhaps add 

 the brick-earth (with similar mammalian remains and land-shells) 

 north of the town as a different manifestation of the same drift. 

 At Charing it consists of a great mass of chalk-rubble at the base of 

 the Chalk Escarpment, and at Maidstone of a chalky rubble with a 

 capping of brick-earth and flints, extending down the slope of the 



