200 Dr. PiTTON on the Strata below the Chalk. 



1900 — 2000. A bed or group of sand-rock, beneath reddish and variegated marly clay and sand, 

 here occupies the shore for about 100 paces, forming before it rises one of the principal ledges 

 of the coast, which stretches far into the sea, and is called Bull-rock- ledge. This bed in its pro- 

 gress westwards is a remarkable feature in the cliif. It is from 15 to 20 feet thick, and rises 

 gradually to the north-west; attaining its greatest height above the sea near a gap or chasm 

 at Southmore, and then declining very slowly, till it comes down to the shore between 1000 

 and 900 from Brook Chine. It seems therefore to form a curve ; which, however, is only 

 apparent, resulting from the general rise of all the strata from the interior towards the sea, 

 combined with the curvilinear prominence of the coast between Chilton and Brook Chines. 

 The true relation of the beds here is explained in the transverse section, Plate X. b. fig. 4. 



This sand-rock bed, in its progress through the extensive space just mentioned, is of nearly 

 uniform character, the chief difference arising from the frequent concretion of the sand into 

 subcalcareous grit. In several places, the fallen blocks contain cylindrical stems of Siphonia, 

 with shells, occasionally, of the genera Cyclas, Paludina, and Unio ; and the grey sand-rock 

 includes small patches or specks of greenish clay. 



The cliff beneath the apparent curve formed by the sand-rock bed, consists throughout of 

 dark reddish and variegated marl, or sandy clay, which seems to form all the lower portion of 

 the prominence at Southmore ; the greatest height which it attains being about 30 feet above 

 the sea. 



In approaching Brook Chine, from the spot where the sand-rock bed above mentioned sinks 

 below the shore, the cliff is low and partially covered with grass, but seems to consist of red- 

 dish and variegated clays. 



A bed of firm grey sand-rock rises at a small angle from the south-east, about 300 paces 

 from Brook Chine, which it crosses, and forming a very slight but really existing curve, goes 

 down about 320 paces beyond it, on the north-west ; the highest point being near the middle of 

 the Chine. All below this curved sand-rock bed consists of dull red and greenish variegated 

 clays : these are seen especially in the north-west side of the cove, or bay, which leads to Brook 

 Chine ; and the floor beneath high-water mark is composed of them. 



(101.) Strata on the South-West Coast of the Isle of Wight, from the 

 Shore under Afton Down to Brook Chine. 



The line of the coast immediately under Afton Down cuts the strata very obliquely. The Upper 

 green-sand does not offer any important difference from that of the section under Bembridge Down 

 on the east of Sandown Bay. The following measurement commences with the rise of the Gault, 

 which is distinctly marked, this stratum occupying a valley or depression between the upper and 

 lower green-sands. 



— 170 is the width of the obhque section of the Gault. 

 170 — 725. Lower green-sand: — affording nothing so different from the other sections in this 



island already described as to require detail. 

 512. The middle point of Compton Chine. 



725 — 1076. The Weald clay (which appears on the beach below the cliff about 710), first rises 

 distinctly above the beach at 725 ; and thence for a considerable space the shore is occupied 

 by mud and fallen ruins, the remainder of the original cliff being thrown back. Blue clay, 

 however, is visible, apparently in situ, at several points along the shore, and fragments of a thin 

 bed of limestone full of Cyclades, are frequent. 



