March, 1834. 



GEOLOGY. 



253 



The geological structure of these islands is in most respects 

 simple. The lower country consists of clay-slate and sand- 

 stone associated together, and the hills of white granular 

 quartz rock. The strata of the latter are frequently arched 

 with perfect symmetry, and the appearance of some of the 

 masses is in consequence most singular. Pernety* has de- 

 voted several pages to the description of a hill of ruins, the 

 successive strata of which he has justly compared to the 

 seats of an amphitheatre. The quartz rock must have been 

 quite pasty when it underwent such remarkable flexure 

 without being shattered into fragments. As a passage be- 

 tween the quartz and the sandstone can be traced, it seems 

 probable that the former owes its origin to the sandstone 

 having been heated to such an excess, that it became viscid^ 

 and upon cooling crystallized. While in the soft state it 

 must have been pushed up through the overlying beds. 



The sandstone and clay-slate contain numerous casts of 

 organic remains. These chiefly consist of shells allied to 

 terebratula, of encrinites, of a branching coral divided into 

 alternate compartments, and lastly, of an obscure impression 

 of the lobes of a trilobite. These fossils possess great in- 

 terest, because none hitherto have been brought to Europe 

 from a latitude nearly so far south. Mr. Murchison, who 

 had the kindness to look at my specimens, says that they 

 have a close general resemblance to those belonging to 

 the lower division of his Silurian system; and Mr. James 

 Sowerby is of opinion that some of the species are identical. 

 This would be a most remarkable circumstance in the an- 

 cient natural history of the world ; for shells now living in 

 latitude 50° on opposite sides of the equator, are totally 

 distinct. From the similarity of the Falkland fossils with 

 those in England which are associated with remains that 

 indicate a climate of a tropical character, we may I pre- 

 sume infer that, during this same epoch, nearly the whole 

 world was thus circumstanced. 



* Pernety, Voyage aux Isles Malouines, p. 526. 



