328 CHARLES DARWIN 



motion of the bottom: moreover, as urged by Mr. Lyell, 

 similar movements of the sea have occurred at island* far 

 distant from the chief line of disturbance, as was the case 

 with Juan Fernandez during this earthquake, and with 

 Madeira during the famous Lisbon shock. I suspect (but the 

 subject is a very obscure one) that a wave, however produced, 

 first draws the water from the shore, on which it is advancing 

 to break: I have observed that this happens with the little 

 waves from the paddles of a steam-boat. It is remarkable 

 that whilst Talcahuano and Callao (near Lima), both situ- 

 ated at the head of large shallow bays, have suffered during 

 every severe earthquake from great waves, Valparaiso, 

 seated close to the edge of profoundly deep water, has never 

 been overwhelmed, though so often shaken by the severest 

 shocks. From the great wave not immediately following the 

 earthquake, but sometimes after the interval of even half an 

 hour, and from distant islands being affected similarly with 

 the coasts near the focus of the disturbance, it appears that 

 the wave first rises in the offing; and as this is of general 

 occurrence, the cause must be general: I suspect we must 

 look to the line, where the less disturbed waters of the deep 

 ocean join the water nearer the coast, which has partaken 

 of the movements of the land, as the place where the great 

 wave is first generated ; it would also appear that the wave 

 is larger or smaller, according to the extent of shoal water 

 which has been agitated together with the bottom on which it 

 rested. 



The most remarkable effect of this earthquake was the per- 

 manent elevation of the land ; it would probably be far more 

 correct to speak of it as the cause. There can be no doubt 

 that the land round the Bay of Concepcion was upraised 

 two or three feet ; but it deserves notice, that owing to the 

 wave having obliterated the old lines of tidal action on the 

 sloping sandy shores, I. could discover no evidence of this 

 fact, except in the united testimony of the inhabitants, that 

 one little rocky shoal, now exposed, was formerly covered 

 with water. At the island of S. Maria (about thirty miles 

 distant) the elevation was greater ; on one part, Captain Fitz 

 Roy founds beds of putrid mussel-shells still adhering to the 



