Bocks of the North of Scotland. 87 



boundaries. Thus the main physical features of the High- 

 lands are connected with the foliation of the gneiss and schists; 

 but the granites and porphyries which have broken through 

 those rocks, and disturbed the regularity of the foliation, have 

 also greatly modified the surface of the country. 



The contortions of gneiss and schists being unaccompanied 

 by fracture, must, the author considers, have been produced 

 when the matter of those rocks was semifluid ; in this state 

 the mineral ingredients appear to have separated and re-ar- 

 ranged themselves in layers according to their affinities, while 

 the whole was subjected to pressure acting along certain axes 

 of elevation, which raised those layers into arches. 



On the Structure of the Iguanodon, and on the Fauna and 

 Flora of the IVealden Formation. By G. A. MANTELL, 

 Esq. LL.D., F.RS.* 



The geological phenomena of the south-east of England, compris- 

 ing the lithological characters and organic remains of the Diluvial, 

 Tertiary, Cretaceous, Wealden, and Oolitic deposits, were described 

 in two Lectures delivered to the Members of the Royal Institution by 

 Dr Mantell in 1836 and 1849. In those discourses the fauna and 

 flora of the Wealden were cursorily noticed, and the Iguanodon and 

 other gigantic terrestrial reptiles, whose fossil remains have invested 

 the strata of Tilgate Forest with a high degree of interest, were briefly 

 alluded to. The present lecture was restricted to a consideration 

 of the fauna and flora of the countries whence the deposits consti- 

 tuting the Wealden districts were derived ; and the osteological 

 characters of the most remarkable fossil Saurians peculiar to this 

 geological epoch were especially illustrated. 



After a concise exposition of the characters of the various forma- 

 tions which have succeeded, and now overlie, or, in other words, are 

 of more recent origin than the Wealden — namely, the Drifts or 

 Diluvium, containing bones of large mammalia, as the mammoth, 

 mastodon, rhinoceros, horse, deer, &c. ; — the Eocene, or ancient 

 tertiary strata of the London basin, abounding in marine exuviae of 

 special and for the most part extinct types ; — and the Cretaceous or 

 chalk-formation, comprising the white chalk of the North and South 

 Downs, and the chalk-marl, gait, and greensand of Surrey, Kent, 

 and Sussex, the whole characterised by innumerable marine shells, 

 zoophytes, fishes, reptiles, &c. of extinct species and genera; — Dr 



* Read in the Royal Institution on March 5, 1852. 



