332 ^^^f' Sedgwick on the [May, 



<5lifF between Brook Point and Freshwater Bay. Along with 

 them are several of those concretions described in the fifth 

 volume of the Geological Transactions under the name of Curl* 

 Only such beds have been described as are found in the Isle of 

 Wight, and may serve in some measure as guides to those who 

 are examining its fossil history. It would be quite foreign to 

 the objects of this paper to describe the beds of fuller's earth, 

 plastic clay, yellow ochre, &c. which are found in other parts of 

 England subordinate to this formation. 



II. Fossils of the Iron Sand. 



1. Obscure impressions of reeds and other vegetable bodies 

 mixed with carbonaceous matter, and sometimes disposed in 

 regular layers. They abound in the argillaceous beds, and are 

 contaminated with the presence of much iron pyrites. 



Carbonized wood is found in all parts of the formation. It 

 sometimes makes an approach to the appearance of jet. More 

 commonly the particles adhere so imperfectly that the specimens 

 crumble between the fingers. Near Brook Poinl the masses of 

 minerahzed wood are seen at the time of low water scattered 

 about the strand like the great beams of a timber yard. Mr. 

 Webster f has given an accurate and graphical description of 

 this portion of the coast. The changes undergone by these 

 bodies are various and interesting. Traces of the original bark 

 are by no means uncommon ; and in one instance we found it 

 marked with deep lozenge-formed indentations. Carbon and 

 pyrites abound in almost all the specimens ; and the several 



Earts are often held firmly together by carbonate of lime which 

 as insinuated itself into every portion of the mass, and partially 

 displaced the woody fibre. When the lime is taken up by acids, 

 there remains behind a friable skeleton of carbon. In other 

 examples, the process of replacement is so complete, that the 

 specimens may be regarded as true petrifactions. I thought this 

 the more remarkable as all the specimens of similar origin which 

 I have seen in the iron sand of Norfolk and other parts of 

 England, are siHcified. The existence of this vast quantity of 

 fossil wood is the more interesting, as it points out an analogy 

 between the iron sand and the quader-sandstein of Werner. J Our 



♦ These concretions are found occasionally in the greywacke formations ; they 

 abound in many of our coal districts, and are by no means rare in certain portions o£ 

 the Lias clay, the Oxford clay, and the Kimmeridge clay. Perhaps there is not one of 

 our great argillaceous deposits in which traces of them may not be found. They most 

 frequently appear in the form of distinct hemispheroidal concretions adhering either to 

 the upper or lower surface of beds of ironstone, or impure argillaceous limestone, which 

 traverse the masses of slate clay. Sometimes also they exhibit a conformable arrange- 

 ment between two indurated beds, and seem intimately associated with layers of impure 

 carbonate of lime which have a fibrous structure transverse to the strata. All these varie* 

 ties are found in the Isle of Wight. 



f Letters to Sir H. Knglcfield, p. 1 53. 



% Sk D'Aubuisson Traite de Geognotie, vol. ii. p. 228, &c 



