210 



was thrown into the ah", when the sea reth'ed so far that a number of 

 old anchors and brass guns became visible ; but it soon returned with 

 great violence, carrying off all the houses of the convicts. A volcano 

 also burst forth at the point where the sea was first agitated. The 

 brig Glanmalin was in the latitude of Talcahuano, and about 100 miles 

 to the westward of it, at the time of the earthquake, when the crew 

 felt a shock as if the vessel had struck upon a rock. 



Mr. Alison also mentions the existence near Valparaiso of the re- 

 cent marine shells 1400 feet above the level of the sea, and of recent 

 marine shells being dug near Conuco for the purpose of making lime. 

 In the bay of Valparaiso, he says, a rock which in 1 81 7 could be passed 

 over in a boat^ is now dry, except at spring tides. 



" Geological notes made during a survey of the East and West 

 Coasts of South America, in the years 1832, 1833, 1834, and 1835, 

 with an account of a transverse section of the Cordilleras of the Andes 

 between Valparaiso and Mendoza ; " by F. Darwin, Esq., of St. John's 

 College, Cambridge ; communicated by Prof Sedgwick^ were after- 

 wards read. 



Prof Sedgwick began by observing that the notes were extracted 

 from a series of letters (addresssd to Professor Henslow), containing 

 a very great mass of information connected with almost every branch 

 of natural history; and that he had selected for the occasion those re- 

 marks only which he thought more especially interesting to the Geo- 

 logical Society. 



Mr. Darwin's first letter contained some account of St. Jago (one 

 of the Cape Verde Islands), which he visited early in 1832 5 and he 

 considered that he had good evidence of its recent elevation, as he 

 found on its surface beds of recent shells and corals considerably above 

 the actual level of the sea. 



In various portions of the notes he shortly described the vast extent 

 of primary rocks along the shores of Patagonia, the existence of highly 

 crystalline schists in the Falkland Islands, alternating v.'ith micaceous 

 .slaty sandstone, exhibiting the casts of bivalves (Terebratulae), and 

 encrinital stems, and a rock near Cape Famine containing some sort of 

 Ammonites. On the line of the western coast of South America, from 

 Chiloe toTres Montes,he found a widely extended formation of mica- 

 slate, traversed and burst through by a grand transverse chain of gra- 

 nite, and penetrated by innumerable dykes of great complexity of 

 mineral structure. 



From the position of the tertiary deposits, which exist on both sides 

 of the Southern Andes, he concludes that the primary chain must have 

 had a great elevation anterior to the tertiary period : and he thinks 

 that a rough approximation may be made to the date of the com- 

 mencement of the volcanic period, by observing the first associa- 

 tion of streams of lava, with certain tertiary groups on the Patagonian 

 side. 



A considerable portion of the extracts was devoted to a descrip- 

 tion of the great tertiary groups on both sides of the chain of the Andes. 

 Some of the details respecting the eastern side were derived from 



