646 MR. J. V. ELSDEN ON THE SUPERFICIAL GEOLOGY OF 



resting upon Weald-clay. In some cases faint signs of stratification 

 are visible, and there are intercalated seams of clay. Many of 

 the larger stones have their axes horizontal, and, as at Inholmes 

 Farm, the gravel penetrates eroded hollows in the "Weald-clay 

 beneath. The angular flints continue to occur in jmtches wherever 

 the ground rises above the 200 feet contour, and thick coatings 

 may be seen covering the fields near Middleton Common Farm, 

 and again in parts of Blackbrook Wood ; but the drift suddenly 

 disappears on descending to the lower levels north of Plumpton 

 Green. 



Thus we see that the line of watershed from near the chalk 

 escarpment at Ditchling to the very edge of the central dome of 

 Hastings beds still retains, on its highest levels, isolated patches of 

 angular gravel, in every respect resembling the watershed gravels 

 previously described near Sullington and Heath Common; while 

 along the margins of the Adur and its tributaries there occur, in 

 several localities, true river-gravels at various heights above the 

 present level of the water. 



The Ouse Basin. — Descending from the watershed at Ditchling 

 Common, a small belt of river-gravel may be traced along the 

 course of the stream which flows from Blackbrook Farm past 

 Plumpton Railway Station. This stream joins the Ouse at Bar- 

 combe Mill, near which gravels occur in several localities. One 

 patch occupies the 50 feet contour at Crink Hill, and ascends at Bar- 

 combe Cross to an altitude of 100 feet above sea-level, or nearly 70 

 feet above the present level of the Ouse. This gravel contains flints, 

 Wealden-sandstone and Lower-Greensand debris, and rests upon 

 Weald-clay. It is separated by a small valley from another similar 

 patch at Barcombe village, where it occurs at a height of 120 feet, 

 near the windmill, while a third patch is seen at Banks Farm, on 

 the north of the stream which runs from Plumpton. About a mile 

 north of Cooksbridge the ground rises considerably, and near Folly 

 Farm the 200 feet contour is reached. Here angular flints again 

 become numerous ; but it does not seem probable that these have 

 any connexion with the present drainage-channels, since they 

 occur at some distance from any existing stream, and are consider- 

 ably higher than the gravels at Barcombe. In level they agree 

 with the watershed gravels at Ditchling previously described, and 

 they may possibly be the last remnants of a plateau-drift. 



Continuing along the margin of the Ouse, gravel with many angu- 

 lar flints occurs again at North End, near Hamsey, where it attains 

 an elevation of about 60 feet above the sea-level, and near Welling- 

 ham, on the opposite side of the river, other small patches occur at 

 nearly the same altitude. These are about 50 feet above the level 

 of the river, and are evidently old river-gravels of the Ouse. At 

 about the same level we find gravel at Mailing House, near Lewes, 

 and again on the opposite bank of the river in a well-defined 

 terrace between the 50 and 100 feet contours. A good section of 

 this gravel is seen in the railway-cutting near St. John's Farm. 

 The flints are very angular, but there are some Tertiary pebbles. 



