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XLII. — On the Connexion of certain Volcanic Phenomena in South 

 America ; and on the Formation of Mountain Chains and Volcanos, 

 as the Effect of the same Power by which Continents are elevated. 



By CHARLES DARWIN, Esq., Sec, G.S., F.R.S. 



[Read March 7th, 1838.] 



Plate XLIX. 



CONTENTS. 



Introddction, p. GOl. 



Observations on the earthquake in Chile of 

 Feb. 20th, 1835, p. 601. 



On the identity of the force which elevates 

 Continents, with that which causes volcanic 

 outbursts, p. 606. 



On periods of increased volcanic action affect- 

 ing large areas, p. 610. 



Nature of the earthquakes on the coasts of 

 South America, p. 615. 



On different kinds of earthquakes ; and conclu- 

 sions regarding those which accompany ele- 

 vatory movements, p. 622. 



Theoretical considerations on the slow eleva- 

 tion of mountain chains, p. 625. 



Concluding remarks, p. 629. 



Introduction. 



A HE object of the present memoir is to describe the principal phenomena 

 generally accompanying the earthquakes on the west coast of South America ; 

 and more especially those which attended the shock that overthrew the city 

 of Concepcion on the morning of the 20th of February, 1835. These phe- 

 nomena evince, in a remarkable manner, the intimate connexion between the 

 volcanic and elevatory forces ; and it will be attempted to deduce from this 

 connexion, certain inferences regarding the slow formation of mountain 

 chains. 



Observations on the Earthquake in Chile of Feb. 20th, 1835. 



This earthquake has been the subject of several published memoirs : the 



sixth volume of the Geographical Journal* contains an admirable account of it 



by Capt. Fitz Roy, R.N., in which many interesting facts are detailed, and the 



elevation of a large extent of coast is incontestably proved. The Philosophical 



* " Sketch of the Surveying Voyage of His Majesty's ships Adventure and Beagle." Vol. vi. 

 Part II. p. 311. 



