1822.] Geology of the hie of Wight, &^c. 331 



its ordinavy appearance. (3.) The red oxide of iron abounds so 

 nauch in some masses of the green sand that, without care, they 

 might be confounded with the ordinary beds of the iron sand. 

 Another distinctive character, founded in the abundance of orga- 

 iiized fossils in the green sand and their entire absence from 

 many parts of the iron sandy might sometimes lead to erroneous 

 conclusions. In the sandy parts of Bedfordshire, one may 

 |;ravel for miles together without seeing even a fragment of a 

 fossil shell ; yet some beds, which are subordinate to the same 

 sand formation in the Isle of Wight, exhibit innumerable traces 

 of beings which once possessed an organized structure. A good 

 account of the fossils of the iron sand is undoubtedly a desidera- 

 tum. Mr. Sowerby's work will, 1 hope, eventually supply this 

 want. I shall consider myself fortunate if this brief notice 

 should induce any one to visit those localities which best illus- 

 trate the zoological history of the formation. 



All the upper beds of the iron sand in the Isle of Wight partake 

 of the high inclination of the central chalk I'ange (Mr. Webster^s 

 Letters, p. 122, &c. &c.). As the bearing of the coast between 

 Freshwater Bay and Brook Point, is considerably incHned to the 

 direction of the strata ; they rise up in succession from the level 

 of the beach, aiid are thus brought out under circumstances most 

 favourable to a minute examination. The natural section between 

 Culver Cliff and the middle of Sandown Bay affords similar faci- 

 lities for observation. Between Brook Point and Sandown the 

 strata are nearly horizontal, and many parts of the coast present 

 perpendicular escarpments. The upper beds would, therefore, 

 be inaccessible, were it not for the deep channels worn in the 

 face of the cliff by the rivulets which descend from the central 

 chalk range. 



As the fossils which characterize the formation are not uni- 

 formly distributed through its mass, it may be proper briefly to 

 enumerate some of the principal changes which are exhibited in 

 the mineral composition of its subordinate beds. 



(1.) Siliceous sand variously coloured by oxide of iron, the 

 colours sometimes very splendid, and beautifully contrasted. 

 With these beds are sometimes associated a kind of coarse sili- 

 ceous grit (carstone) cemented by oxide of iron. 



(2.) Fine white sihceous sand often passing into sandstone. 

 (3.) Beds containing a variable admixture of argillaceous 

 matter. They often contain carbonate of lime, and a considera- 

 ble quantity of green earth. The more siliceous varieties then 

 assume the appearance of green sand. In all these varieties 

 there are fossils, most frequently in the form of casts. 



(4.) Beds of slate clay associated with pyritous wood coal. 

 Some subordinate calcareous beds contain fossil shells, and 

 innumerable bony fragments of a small fish. 



(5.) Beds of impure shell hmestone. They abound in some 

 parts of Sandown Bay, and occur in almost every part of the 



