On the Agricultural Geology of the IVealil. ■ 253 
Rag, as it is called, or stone, is usually found. These wells re- 
ceive the water from the different drains which empty into them, 
and as the Kentish Rag is of great extent and thickness, and 
very porous, the wells are capable of receiving any quantity of 
water which may issue from the drains. Part of Knole Park 
has been drained upon the same principle, and could have been 
drained in no other way without a very great expense, as from 
the formation of the surface much difficulty would have been 
found in obtaining a fall. The wells are arched over at top, or 
filled up with stones, so that a stranger walking over the farm 
would not be aware that any draining had been accomplished."* 
This power of taking away water is possessed by all porous 
rocks, especially limestones, that are not themselves saturated ; 
and is frequently made use of in a similar manner to that just 
described. Water on clayey land over chalk may always be 
readily discharged, at any point, by such means. In Hertford- 
shire chalk is got by sinking shallow pits through the clay in 
various parts of the field, and these pits are afterwards used as 
outlets for drains. 
From near the borders of Surrey, westwards, an important 
change occurs in the composition of the Hythe Beds. The 
Kentish Rag is gradually lost, and the division assumes the 
sandy character which distinguishes it in West Surrey. Be- 
tween Limpsfield and Dorking its outcrop is narrowed ; the 
ground is of moderate elevation, only a few places attaining to 
500 feet, and the highest being under 600 feet. 
Immediately on the west of Dorking the character of the 
country changes. The Lower Greensand escarpment shoots 
suddenly out for three miles beyond its general line east of that 
place, and forms the lofty range of hills, of which Leith Hill 
is the summit (967 feet).t This district is highly picturesque, 
and is deeply furrowed by narrow valleys which, commencing 
near the crest of the escarpment, run northward, and reach 
down to the Atherfield and Weald Clay : hence they are plen- 
tifully supplied with water. The northern half of the area is 
cultivated, but the higher land, near the escarpment, is mostly 
either in open common or woodland. The ground* sinks towards 
the valley through which the southern branch of the River Wey 
escapes, but rises again rapidly to the high land of Hascombe 
and Hambledon. This valley forms the line of communication 
* "Account of Hall Farm, near Sevenoaks, Kent." 'Journal of the Eoyal 
Agricultural Society,' -vol. viii., p. 34. 
t This and some other heights given in this paper do not agree with those 
generally taken for the points mentioned. They are, however, more correct, 
being the result of recent observations by the Ordnance Survey. All are calculated 
from mean sea level. 
