26^ Mr MantelPs Remarks on the Strata 



^ d<etail on this interesting subject, I refer the reader to the 

 learned dissertations of Linnasus, the Station es et Coloniae Plan- 

 tarum, to the Tentamen Historiae Geographicse Vegetabihum of 

 Professor Strohmeyer, and particularly to the Memoirs of Mes- 

 sieurs de Humboldt and Hamond *. 



Remarks on the Geological Position 0/ the Strata of Tilgate Fo- 

 rest in Sussex. By Gideon Mantell, Esq. F. R. S., &c. 

 In a Letter to Professor Jameson. 



A HERE appeared in the Edinburgh Philosophical Journal for 

 April, " Observations on the Position of the Fossil Megalosau- 

 i?ttSy^^d Didelphis or^Opossiim at Stonesfield,'" in which the 

 writer alludes to the strata of Tilgate Forest ; and remarking on 

 the extraordina4'y nature of their organic remains, very summa- 

 rily conffludes, that doubts may be raised regarding the geolo- 

 gical position, both of the limestone schist of Stonesfield, and the 

 sandstone of Tilgate Forest. I shall leave to the abler pen of 

 Dr Buckland, the defence of the assumed situation of the Stones- 

 field slate, and confine my observations to the consideration of 

 the writer'*s conjecture, that the Tilgate strata should be ranked 

 as tertiary, and not as secondary, deposits ; — a conjecture no one 

 could, for a moment, entertain, who had examined the strata of 

 the south-eastern part of England with any degree of attention. 

 The only argument brought forward in support of an opi- 

 nion so entirely oppdsed to that held by persons who have de- 

 voted considerable time and labour to the subject, is, that " the 

 strata which contains the organic bodies do not appear clearly 

 ccwered by those of the formations which are said to be more re- 

 cent." If such an argument be considered valid, the progress 

 of geology must be slow indeed. In other branches of natural 

 history induction and analogy are frequently admitted to supply 

 the place of actual observation ; and I cannot understand why 

 the same privilege should not be extended to geology. In the 

 present instance, however, it is unnecessary; and I am willing 

 the question shall be decided by demonstration only. That the 

 strata of Tilgate Forest are not actually covered by the newer 



• Poiret's Lecons De Flore, Paris 1825. 



