Mr, Darwin on certain Volcanic Phenomena, 585 



Caldcleugh*; likewise communications received by him from Mr. 

 Douglas, a resident on the island of Chiloe. 



A few days after the earthquake, several volcanos within the Cor- 

 dilleras, to the north of Concepcion, though previously quiescent, 

 were in great activity. It is doubtful, however, if the volcano of 

 Antujo, in nearly the latitude of Concepcion, was affected, while the 

 island of Juan Fernandez, 360 miles to the north-east of the city, 

 was apparently more violently shaken than the opposite shore of the 

 main land. Near Bacalao Head, a submarine volcano burst forth 

 in sixty-nine fathoms water, and continued in action during the day 

 as well as part of the following night. That island was also affected 

 in a remarkable manner, by the earthquake which overthrew Con- 

 cepcion in 1751. 



In Concepcion, the undulations of the surface appeared, to the in- 

 habitants, to proceed from the south-west; and this direction was 

 likewise inferred, from the effects observed in the buildings; for 

 those walls, which had their extremities towards the point of dis- 

 turbance, remained erect, though much fractured ; whilst those (and 

 the streets cross each other at right angles) which extended parallel 

 to the line of the vibration, were hurled to the ground. This was 

 strikingly exemplified in the cathedral, where the great buttresses of 

 solid brick-work were cut off, as if by a chisel, and thrown down ; 

 while the wall, for the support of which they had been built, though 

 much shattered, remained standing. 



In Chiloe, south of Concepcion, the shocks were very severe, but 

 they entirely ceased in about eight minutes. The motion, as de- 

 scribed by Mr. Douglas, was horizontal, and similar to that of a ship 

 going before a high, regular swell ; from three to five shocks being 

 felt in a minute ; and the direction being from N.E. to S.W. Forest- 

 trees nearly touched the soil in these directions ; and a pocket com- 

 pass placed level on the ground vibrated, during the violent shocks, 

 two points to westward, but only half a point to eastward ; and during 

 the minor shocks the needle pointed north. At Calbuco, a village 

 on the mainland opposite the northern extremity of Chiloe, as well 

 as at Valdivia, between Chiloe and Concepcion, the earthquake was 

 much less severely felt ; and near MellipuUi, in the Cordilleras (not far 

 from Calbuco), not at all. The volcano of Villareca, near Valdivia, 

 which is said to be more frequently in irruption than almost any other 

 in the chain, was not the least affected ; though the volcanos of central 

 Chili are stated by Mr. Caldcleugh to have been seen, some days af- 

 terwards, in great activity. Several of the culminating points of the 

 Cordillera in front of the island of Chiloe, exhibited increased energy 

 during the earthquake, and immediately after it. During the shocks, 

 Osomo, which had been in activity for at least forty- eight hours 

 previously, threw up a thick column of dark blue smoke ; and di- 

 rectly it had passed away, a large crater was seen forming in the 

 S.S.E. side of the mountain; Minchinmadiva also, which had been 

 in its usual state of moderate activity, commenced a fresh period of 



• Phil. Trans., 1836; Part I. p. 21. [An abstract of Mr. Caldcleugh 's' 

 paper appeared in, Load, and Edinb. Phil. Mag. vol. viii. p. 148.] 



