,32 Outlines of Geology, 



of fragmented and decomposing masses ; it is immediately suc- 

 ceeded by horizontal seams, containing chert, flints, and some 

 fine specimens of petrified wood ; below it is the useful Portland 

 stone. In this island, the beds dip to the south, and alternate 

 with strata of bituminous shale. The limestones belonging to the 

 oolite formation, are of various degrees of granular fineness, and 

 when made up of an agglutination of small rounded concretions, 

 they are particularly called roestone. 



In contact with the lower beds of the oolite, we find more com- 

 pact limestone or lias, which may be considered as the lowest 

 member of this formation ; its different layers present various 

 shades of white, gray, and blue, and it is generally speaking 

 so argillaceous, as to exhale a strong earthy odour when breathed 

 upon. To this ingredient, and to a portion of oxide of iron, the 

 peculiarities of lime from this lias are referrible. It accompanies 

 the great oolite formation, and is . seen extending from Ilchester 

 in Somersetshire, by Bath and Gloster across the centre of the 

 kingdom, terminating near Lincoln. A little to the north of 

 Gloster, it forms eminences of more than 1000 feet high. These 

 strata enclose a great variety of sea-shells, ammonites ; and at 

 Lyme, on the Dorset coast, they contain the skeletons and de- 

 tached bones of a large animal, which has generally been re- 

 garded as the crocodile, but which Sir Everard Home has shown 

 not to be that animal, but a peculiar extinct species, which from 

 an analogy that exists between its spine and that of the Proteus, 

 he has called Proteorachius. As these strata contain such re- 

 mains of amphibious animals, they make it probable, in the opi- 

 nions of certain geologists, that fresh water and dry land existed 

 previous to the formation or deposition of the oolitic strata, and 

 consequently, of course, anterior to the chalk hills and their vari- 

 ous superincumbent substances. 



V. 



We have now cleared our way to the great red sandstone for- 

 mation, or to the red marie of modern geologists,— a substance 



