58 



STRATA OF TILGATE FOREST. 



assigns to both the same relative situation ; yet the latter are well known 

 to he immediately beneath the iron sand formation, while the strata in 

 question, are almost in contact with the weald clay, appearing on the 

 surface, as represented in the annexed diaffram. 



a. Chalk of the South Do^vns. b. Blue chalk marl. c. Green sand. 

 d. Weald clay. e. Sand. / Tilgate beds. g. Iron sand. 



It is obvious from this section, that the only hypothesis by which the 

 connexion of the Tilgate and Purbeck beds can be rationally explained, 

 is that of supposing them to form a protrusion through the iron sand ; 

 the relative position of the respective substances being such, that a de- 

 nudation, or removal of the upper beds, could not have occasioned their 

 present appearance. And as the thickness of the iron sand is estimated 

 at 500 feet, the Tilgate strata, according to this supposition, must be 

 situated on the summit of a hillock, or peak, 500 feet above the level of 

 the uppermost beds of the Purbeck hmestone. 



a. a. Iron sand. b. Tilgate beds. c. Purbeck hmestone. 



and plates of one or more species of turtle ; and the bones and teeth of an animal of the lizard 

 tribe allied to the crocodile. The circumstances under which these strata appear, difer greatly. 

 They are distinctly seen in the Isle of Purbeck, and form a considerable district m Yorkshire, 

 called the Vale of Pickering. The same strata appear in Kent, rising together with others, from 

 beneath the chalk ; where from the coarseness of the limestone, it has been called the Kentish Rag. 

 (Phillips' Outlines of Geology.) 



