OF HERTFORDSHIRE. 
143 
to them. The occurrence of these deposits at the time when the 
drainage changed from its former west to east direction to its 
present one is very significant, and, when viewed together with 
the former southerly fluviatile connection with the Weald, strongly 
suggests the extreme probability that one cause for the facts 
observed is to be found in a modification or accentuation of the 
synclinal basin of the Lower Thames Yalley. 
The Gravels oh the Dip-slope of the Chalk, etc., connected 
WITH THE PRESENT RlVER-SYSTEM. 
The lower part of the “ Drift Series ” at Goring Gap forms three 
terraces, and can be traced along the sides of the present Thames 
through South Bucks, North Surrey, Middlesex, Southern Essex, 
and Northern Kent. They differ from the higher gravels not only 
in general direction and level, but also in containing the remains 
of Pleistocene Mammalia, Palaeolithic implements, and fresh-water 
shells. The Colne and the Lea, by cutting back their valleys, 
have captured between them the drainage of Hertfordshire. The 
remains of extinct Mammalia, Palaeolithic implements, etc., found in 
this part of Hertfordshire, come from these gravels.* A palseolith 
was obtained recently by the author from the gravel-pit on the 
left of the road from the station leading to Welwyn, and is now 
in the County Museum at St. Albans, f 
The contents of these gravels depend upon the materials found 
in their drainage areas, and much has been derived from the older 
gravels already described. Sections may be seen near Croxley 
Green east of Rickmans worth, where there are two large pits, at 
King’s Langley, Watford, The Noke, Burston, Sutton Colney, 
Wheathampstead, Welwyn, Digswell, two miles from Wattonon the 
Walkern Road (left), Hertingfordbury,J Amwell, Ware, Hoddes- 
don, Rye House, Broxbourne, and Theobalds, near Old Temple 
Bar; at Latton and Netteswell just over the Herts border in 
Essex, Castle Anstey south of Barkway, Rye Street, Bishop’s 
Stortford, and north of Much Hadham. Jurassic material occurs in 
them when the area drained by them contains the drift-clays, etc., 
described in section 4. These are mainly found in the eastern part 
of the county. In the western part Jurassic debris, basalt, granite, 
etc., do not occur, so far as I have been able to ascertain. 
The fluviatile connection with the Midlands by means of the 
Stevenage Gap ceased owing to the cutting back of the Chalk 
escarpment by denudation, assisted probably by the earth-movements 
referred to in the last section. 
* Cf. 1 Man the Primaeval Savage,’ by Worthington G. Smith, and the 
following by the same author:— 44 Primaeval Man in the Yalley of the Lea,” 
* Essex Nat.,’ vol. i, pp. 36, 83, 125 ; 4 Nature,’ vol. xxiii, p. 604; vol. lii, 
p. 222; vol. lix, p. 506; vol. lx, p. 390 ; also 4 A Guide to the Antiquities of 
the Stone Age in the British Museum, Bloomsbury.’ 
t The Rev. H. Kendall, formerly of Hatfield Hyde, informs me that he also 
has obtained two, which he has sent to the British Museum (Bloomsbury). 
+ A. E. Salter, 44 Excursion to Hertingfordbury, Bayford, and Brickendon 
Green,” 4 Proc. Geol. Assoc., 5 vol. xvi, p. 447. 
