62 



SCIENCE-GOSSIP. 



is this relationship more clearly shown than in the 

 Isle of Wight. The beds enumerated in the 

 foregoing table strike generally east and west 

 across the island, and the great folding of the rocks 

 of the south-east of England which took place 

 during the Miocene period has thrown them into a 

 series of curves. At the south of the island 

 between Bon church and Blackgang the cretaceous 

 rocks are seen dipping south, whilst in the central 

 hills from Culver Cliff to the Needles the same 

 beds dip to the north. North of the central hills 

 the tertiary area is spread out, lying in a sincline 

 striking approximately from Brading to Yarmouth. 

 A broad valley stretches east and west between the 

 chalk hills from Sandown Bay to Brixton Bay, 

 from which the upper cretaceous rocks have been 

 denuded — a similar condition of things to that seen 

 in the Weald of Kent, Surrey and Sussex. This 

 valley marks the line approximately of the Isle of 

 Wight anticline. The dip of the rocks affected 

 by the folds of the Island is remarkable ; in common 

 with the similar folds on the mainland to the 

 north, the dip on the northern side of the anticline 

 is much in excess of that on the southern side. 

 This is well seen at Alum Bay in the west and at 

 Whitecliff Bay in the east, where the Chalk and 

 Eocene Beds are nearly vertical, the Oligocenes 

 which follow on to the north, although all affected 

 by the folding, very rapidly assume a low dip, that 

 is, they become very nearly horizontal. The dis- 

 tinctive characters of the coast scenery at Culver 

 Cliff, Alum Bay and Freshwater Gate, are entirely 

 due to these conditions, which, it may be mentioned 

 in passing, are continued on the mainland about 

 Ballard Down in Dorsetshire. A striking feature 

 of the scenery on the south side of the island, 

 between Luccomb and Blackgang, is the series of 

 landslips, due to well-recognised geological agents. 

 The rocks along the coast referred to, if free from 

 debris, would show Gault clay followed above by 

 Upper Greensand, both dipping south. Clays are 

 at all times unstable, and liable to collapse when 

 surmounted by hard rocks pervious to water, but 

 in the present instance the insecurity is vastly 

 increased by the dip of the beds towards the sea. 

 The result is seen in the Ventnor and Blackgang 

 Undercliff on a scale probably of unequalled 

 grandeur. The series of landslips which formed 

 the present Undercliff, occurred at the beginning of 

 this century, and although, from the amount of 

 fallen debris, the ground is at present fairly secure, 

 and may remain so for a century or two, neverthe- 

 less, with the existing geological conditions, similar 

 landslips maybe expected to recur from time to time. 

 It is rather startling to the geologist, accordingly, 

 to notice boards near Ventnor and Blackgang, offer- 

 ing land upon building leases for a term of 999 years. 

 The lowest beds which are exposed in the Isle of 

 Wight belong to the Wealden Series. They may 



be examined between Compton Bay and Atherfield 

 in the west, and in Sandown Bay in the east. In 

 both localities the anticlinal dips may be studied in 

 the cliffs. The Wealden is a freshwater formation 

 and consists of clays, with "paper shales," bands of 

 shelly limestone, and beds of sandstone. The series 

 can be most conveniently examined at and near Brook 

 Point in the western outcrop. Here occurs the sc- 

 called "Pine raft," which consists of a number of 

 drifted trunks of coniferous trees lying prostrae in 

 a bed of grey sandstone. It is quite a local occur- 

 rence — the fossil trees cannot bs traced away from 

 Brook Point on this horizon. The Wealden Beds 

 of the island do not yield many fossils to the 

 collector. Cyprids may be obtained in abundance in 

 the " paper shales" at both ends of the outcrop, 

 whilst Cyrena, Paludina and Unio occur in com- 

 pressed masses in the limestone bands. Teeth, 

 scales and pieces of bone of fishes, and reptiles 

 occur on certain horizons. 



Above the Wealden follows the Lower Green- 

 sand, a series of vast importance in the island. 

 The base of this formation is marked by the Perna 

 Bed, which forms the dangerous reef at Atherfield 

 Point, upon which the North German Lloyd S.S. 

 "Eider" was lost a few years ago. The Lower 

 Greensand of the Isle of Wight is divided as 

 follows, in descending order : ■ 



Carstone. — Iron sandy grit. Thickness : 6 feet in 

 Compton Bay, 12 feet at Niton, 34 feet in 

 Monk's Bay, 73 feet at Redcliff. Possibly 

 equivalent to the Ammonites mammilaris zone of 

 the mainland, i.e. the Gault, Lower Greensand 

 junction bed. 



Sand-rock Series. — Slightly coherent white and buff 

 quartz sand. Thickness: 81 feet in Complon 

 Bay, 184 feet to the west of the Undercliff, 113 

 feet at Luccomb, 93 feet at Redcliff. Equiva- 

 lent to the Folkestone Beds of the mainland. 



Ferruginous Sands. — Dark sands, brown and green, 

 with grit, clayey grit, sandy clay and beds cf 

 clay. Thickness : 251 feet in Compton Bay, over 

 500 feet in Chale Bay, not measured between 

 Shanklin and Sandown, 367 feet at Redcliff. 

 Equivalent to the Sandgate and Hythe Beds of 

 the mainland. 



Atherfield Clay. — Pale blue clay with hard argilla- 

 ceous limestone at base, known as the Perna 

 Bed. Thickness: 60 feet in Compton Bay, go feet 

 at Atherfield, obscured by buildings at Sandown, 

 83 feet at Redcliff (the Perna Bed varies from 

 2 to 6 feet in thickness and is included in these 

 figures). Equivalent to the Atherfield clay of 

 the mainland, where, however, the Perna Bed 

 has not been recognised. 



The Lower Greensand is sharply defined from 

 the Wealden below, but the different divisions 

 mentioned above pass upwards into one another ■ 



