Phenomena in South America. 613 



injury to that of Coquimbo, in lat. 29° 50'*. On the 19th of the same month 

 Valparaiso was almost destroyed. Other instances! might be brought forward 

 to show that most earthquakes, thoug-h appearing sudden, are in truth parts 

 of a prolonged action, as evinced both by the events which precede and those 

 which follow it. 



Although, possibly, we may allow that the eruptions of Aconcagua and 

 Osorno, occurring in the middle of the same night, were connected together, 

 and formed a part of the great subsequent disturbances, — yet what must we 

 conclude respecting their coincidence with Coseguina, so immensely remote? 

 The case is rendered far more extraordinary by two of the three volcanos 

 being generally quiescent. Coseguina, according to Mr. Caldcleugh, burst 

 forth after twenty-six years of repose ; and Aconcagua so seldom manifests 

 any signs of activity, that it had even been doubted whether any part of this 

 gigantic mass, with an altitude of more than 23,000 feet, is of volcanic origin. 

 To illustrate the case: if we suppose Stromboli and Vesuvius to be in violent 

 eruption on the same hour of the night, little would be thought of the coinci- 

 dence; but it would be otherwise if this should happen with Vesuvius and Etna; 

 and our surprise would be greatly increased if we afterwards heard that Hekla, 

 after twenty-six years' repose, had burst forth at the same time with tremendous 

 explosions. Nevertheless, if such a coincidence had occurred in Europe, a 

 country possessing no unity of character, and the two points not being more 

 than 2000 miles apart, it is very doubtful how far the phenomenon would have 

 been worthy of consideration. But the case is different in America, where the 

 volcanic orifices all fall on one great wall or fissure, (for the Andes may be in- 

 differently so called,) and where the immensity of the level area on the eastern 

 side, proves with what wonderful equability the subterranean forces have 

 acted on this portion of the globe. Moreover, when a line of coast more than 

 two thousand geographical miles in length has been elevated (as I hope here- 

 after to prove) within a period so recent, that, as compared to the countless 

 past ages of which we possess records in the works of nature, it may be 



* Journal of Science, Vol. xvii. 



•j- Several distinct cases are known in which springs and wells have been affected, their water 

 rendered turbid, and altered in quantity, previously to bad earthquakes. This was observed at 

 Lisbon in 1755 ; and in New England during two or three days before a shock, " the waters of 

 some wells were rendered muddy and stank intolerably." (Michell, Philosophical Transactions, 

 1760, p. 44.) Humboldt and others have noticed, that the wells in the neighbourhood of Vesuvius 

 are affected previously to its bad eruptions. These facts appear explicable, on the idea of a slight 

 stretching or movement taking place in the crust, before its tension is overcome, a fissure formed, 

 and, as a consequence, an earthquake or eruption caused. Courrejolles, also, has remarked in his 

 memoir on earthquakes (Journal de Phys., Tom. Ixiv. p. 106.), that great earthquakes are almost 

 always preceded by lesser ones. 



4k2 



