432 NORTHERN CHILE, >June, 1835. 



appears a consequence (and not the determining cause) of 

 the earthquake. I allude to those cases, when rain falls at 

 a period of the year, at which it is a greater prodigy than 

 the earthquake itself: I may instance the rain after the 

 shock of November, 1822, at Valparaiso. A person must 

 be somewhat habituated to these climates, to understand 

 the excessive improbability of rain falling at such seasons, 

 except as a consequence of some law quite unconnected with 

 the ordinary course of the weather. In the case of great 

 volcanic eruptions, as that of Coseguina, where torrents of 

 rain fell at a time of year most unusual for it, and " almost 

 unprecedented in Central America,^^* it is not difficult to 

 understand that the volumes of vapour and clouds of ashes, 

 might have disturbed the atmospheric equiHbrium. Hum- 

 boldtt extends this view to the case of earthquakes ; but 

 for my part, I cannot conceive it possible, that the small 

 quantity of aeriform fluid which at such times escapes from 

 the fissured ground, can produce such remarkable effects. 



Humboldt J has stated that, " on the days when the earth 

 is shaken by violent shocks, the regularity of the horary 

 variations of the barometer is not disturbed under the tropics. 

 I have verified this observation at Cumana, at Lima, and at 

 Riobamba ; and it is so much the more worthy of fixing the 

 attention of natural philosophers, as at St. Domingo, at the 

 town of Cape Francois, it is asserted, that a water barometer§ 

 was observed to sink two inches and a half immediately 



* Caldcleugh. Philosoph. Transact. 1835. 



+ Personal Narrative, vol. ii., p. 219. J Ibid., p. 217. 



§ Courrejolles, in the Journal de Phys., tome liv., p. 106. This de- 

 pression answers only to two lines of mercury. The barometer remained 

 motionless at Pignerol, in April, 1808. —(Ibid., t. Ixvii., p. 292.) [I may 

 add that the earthquake alluded to by Courrejolles at p. 106, was 

 accompanied bv a " trfes-violent coup de vent ;" which explains the fall of 

 his water barometer. More lately, Mr. Williams, in his Narrative of 

 Missionary Enterprise (p. 442), has given an account of a hurricane 

 which devastated the Austral islands (S. W. of the Society Archipelago), 

 and which at the Navigator Islands was accompanied by an earthquake. 

 — C. D.] 



