40 STRATA OF TILGATE FOREST. 



appear to be of chemical origin, and not derived from the ruin of other 

 strata. The intermediate layers are a pure bluish grey, or greenish Hme- 

 stone, in texture and appearance very much resembhng the finer beds of 

 the Swindon stone*. 



The inferior layers are very analogous to the Purbeck limestone, and 

 where in contact with the clay, contain remains of the same kinds of tes- 

 tacege. 



The bed is traversed by thin veins of calcareous spar of a light amber 

 colour; and this substance generally occupies the fissures in the wood, 

 bones, and other organic remains, forming groups of tabular, and lenti- 

 cular crystals in the cavities of the limestone. It also contains small no- 

 dular masses of carbon, and charred wood. Every kind of fossil that has 

 been discovered in the strata of Tilgate forest, occurs in this bed, viz. 

 bones and teeth of the gigantic monitor or crocodile ; bones and plates of 

 turtles; teeth of fishes; leaves and stems of euphorbiae ; casts of univalves 

 and bivalves, &c. 



The sand and sandstone, (No. 3,) vary from a Hght fawn colour to a 

 deep brown, and in some parts are highly ferruginous. The sandstone 

 is soft and friable, and alternates with thin layers of calcareous slate. The 

 latter is compact, but readily separates into thin flakes, and these are di- 

 vided by the workmen into slabs, from one, to a foot and a half square, 

 which are used for roofing in that part of the country. The surface of this 

 slate presents a most extraordinary appearance, being every where marked 

 with undulating furrows, so strikingly resembling the impressions made on 

 the sand of the sea shore, by the action of the waves, that I cannot but 

 regard them as the result of a similar operation. 



The sandstone contains the teeth, vertebrse, and bones of the croco- 

 dile, and large portions of the stems of vegetables allied to the euphorbiae 

 and dicksoniffi ; besides others, v.^hich are in too imperfect a state to admit 

 of their characters being determined. The slate abounds with the car- 



* Swindon, near Marlborough, Wilts; the stone quarried in its vicinity is a member of the 

 Portland limestone. 



