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 equilibrium. Hum- 

 boldtt extends this view to the case of earthquakes 5 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. 



Humboldtf 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. 



I Personal Narrative, vol. ii., p. 219. f 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 " tres-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.] 



