142 PROF. PRESTWICII OX THE AGE, FORMATION, AND 



of Ragstone, but there the Lower-Greens and hills are prolonged above 

 the pit. Between Sundridge Place and Dryhill, nearly a mile farther 

 down the valley, is another well-marked outlier forming a small 

 knoll a little above the 400-ft. contour-line. This gravel, which is 

 verj' sandy, is not worked, and we can therefore judge of its com- 

 position only from surface exposures. These show it to consist of : — 



1. Angular and white, and other slightly subangular flints. 



2. Tertiary flint-pebbles of all sizes. 



0. Subangular pieces of Chert, Eagstone, and Ironstone, much worn. 

 4. Numerous very subangular brown-stained flints, 



I could not determine their relative proportions, but the large 

 proportion of Lower-Greeusand debris, and of the stained flintSy 

 mostly of small size, is very noticeable. Many of the flints show 

 the ragged sponge-structure so common with some of the layers of 

 flint near the summit of the Chalk escarpment. I noticed also a 

 large piece of much- worn Sarsen stone*. 



From Parley Hill to the Sundridge outlier (410 feet) is a distance 

 of a little over three miles, and the difl'erence of level amounts to 68 

 feet, giving a gradient of 22| feet to the mile, or taking the whole 

 distance from Limpsfield, of 24 feet to the mile. 



In descending the valley from Sundridge, the next important 

 outlier is on the opposite side of the Darent, and, like the outlier at 

 Farley, it rises considerably above the surrounding plain. This 

 gravel, which caps Broughton Hill f, near Dunton. Green (PL YI., 

 fig. 1), is more stratified than the Limpsfield bed, and contains 

 a less proportion of Tertiar^^ flint-pebbles, and a larger pro- 

 portion of Lower-Greensand debris ; but this arises from its being 

 farther from the source of the Tertiary pebbles, and from the in- 

 creased number of afiluents from the Lower-Greensand hills. It 

 more nearly resembles the Sundridge-Knoll gravel, consisting, in 

 the order of relative abundance, of : — 



1. Subangular Chalk flints of all sizes, with some angular ones. 



2. Numerous Tertiary flint-pebbles. 



3. A good many subangular Chert and Kagstone fragments. 



4. Much worn and stained brown and ochreous flints. 



Embedded in a light brown or reddish clay, Avith some seams of sand. 



This hill is 357 feet high, and 2| miles distant from the Sundridge 

 outlier, which, taken at 410 feet, gives a difl'erence of level of 53 

 feet, or a gradient of 21 1 feet per mile, but the line here drawn is a 

 little devious. 



A short distance beyond, the two branches of the vaUey meet, 

 and pass through the Chalk escarpment. The few high-level gravels 

 in the eastern branch of the valley are still more fragmentary and 

 imperfect than those in the western branch. I have before mentioned 



* Mr. Topley also mentions a patch of gravel in Montreal Park, a little above 

 the 300-ft. contour-line. I have not seen it, and cannot say whether it be- 

 longs to tliis or to the next stage, as may also the traces of gravel on the top of 

 the railway-cutting through the hill adjacent to Riverhead. 



t ' Geology of the Weald,' p. 189. Mr. Topley saw the railway-cutting 

 when freshly made. 



