THE WEALDEN. 
183 
of septaria of argillaceous ironstone, forms the sub- 
soil of the Wealds of Sussex and Kent, and sepa- 
rates the Shanklin sand from the central mass of 
the Hastings beds. It constitutes a low tract, from 
five to seven miles in breadth, which forms a zone 
round the Hastings sands, and extends from the 
Sussex coast, near Pevensey, to Petworth and 
Harting Combe in the west of the county, and 
from thence passes to near Tunbridge and the Isle 
of Oxney in Kent. At its western angle at Hart- 
ing Combe, it forms a narrow gorge for several 
miles, which is flanked on the north by the lofty 
hills of Blackdown, and on the south by the cor- 
responding ridge, which extends from Holder and 
Bexley hills to near Petworth ; the valley then 
suddenly exj)ands to three times its former breadth, 
by the retirement at a right angle of the sand 
escarpment of Blackdown and Haslemere.* 
Presenting; no remarkable characters on the sur- 
face, except that the soil it produces is favourable to 
the growth of the oak, its range and extent scarcely 
require further observation. Its outcrop forms a 
valley between the hills of the Shanklin sand on 
the one hand, and the Forest Ridge on the other, 
throughout the northern and north-western divi- 
sion of the “ southern denudation of the chalk;” 
but in the south-eastern part of Sussex, where the 
Shanklin sand is scarcelv seen on the surface, it 
constitutes a valley at the foot of the northern 
escarpment of the Downs, its beds of limestone and 
sandstone forming longitudinal ridges. 
The Sussex marble, so strikingly characteristic 
* Mr. Murcliison’s Memoir. Geol. Trans, vol.ii. p. 104. 
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