612 C. Darwin, Esq., on Volcanic 



Aconcagua. It may be asked, were these three eruptions, which burst through 

 the same chain of mountains, in any respect connected, or was the coinci- 

 dence accidental ? We cannot be too cautious in guarding against the as- 

 sumption that phenomena are connected, because they happen at periods 

 bearing some determined relation to each other. If we wished to show that the 

 subterranean forces acted after periods of a century, as has sometimes been 

 believed, we might adduce the case of Lima, violently shaken by an earth- 

 quake on the 17th of June, 1578, and again on the very same day in 1678 ; 

 or the eruptions of Coseguina in the years 1709 and 1809, which are the only 

 two on record previous to that of 1835. Again, we might urge, on such 

 o-rounds, that the Guatimala convulsions follow, at the interval of one year, 

 those near Pasto; for a district in the neighbourhood of the latter place was 

 overthrown by a violent shock precisely one year before the explosion of 

 Coseguina ; both having occurred on the 20th of January. Cosme Bueno 

 imagined that this relation actually did exist between the subterranean move- 

 ments in Guatimala and Peru, and this case makes one more to the list which 

 I have subjoined* as extracted from Humboldt. With respect to the simul- 

 taneous eruptions of Aconcagua and Osorno, there is little difficulty in ad- 

 mitting that they may have been connected, because in this same region, 

 and only a month subsequently, volcanos further apart were affected by the 

 same impulse. There is nevertheless this remarkable difference in the two 

 cases ; — the last, or that of February the 20th, was a period of commotion 

 throughout the kingdom of Chile, while the simultaneous eruption of Acon- 

 cagua and Osorno appears to have been unaccompanied by any general 

 movement in the subterranean regions. This eruption, probably, was the 

 first indication of those great volcanic disturbances which ensued exactly one 

 month afterwards; for it seems to be a very general occurrence in earth- 

 quakes, that weak spasms precede the worst convulsions. Thus, in 1822, on 

 the 4th of November, Copiapo (lat. 27° 10') was visited by a severe shock, 

 which damaged many houses ; and was followed the next day by a much more 

 violent earthquake, which nearly destroyed the town, and did considerable 



* Mexico. Peru. Difference of time. 



(Lat. 13° 32' North. (Lat. 12° 2' South.) 



30th of November, 1577. 17th of June, 1578. Six and a half months subsequent. 



4th of March, 1679. 17th of June, 1678. Eight months in advance. 



12th of February, 1689. 10th of October, 1688. Four months in advance. 



27th of September, 1717. 8th of February, 1716. Seven and a half months in advance. 



Humboldt's Personal Narrative, Vol. ii. p. 227. These facts perhaps tend to show that periods 

 of increased volcanic energy are common to remote parts of the continent ; but as the order of 

 priority is not constant, I cannot believe any other law is indicated. 



