Natural History of Volcanos and Eai^thquakes. 51 



confined to any particular season of the year, although it is cer- 

 tainly remarkablcj that of fifty-seven earthquakes, which were 

 felt at PalerTno during a period of forty years^ abnost a fourth 

 part happened in the month of March.* Perhaps the best means 

 of ascertaining whether any connection exists between earth- 

 quakes and meteorological phenomena, is the observation of the 

 barometer. But Hoffman was unable to discover anything pe- 

 culiar or extraordinary, either in the relative height of the barom- 

 eter^ in the direction of its motion, or in the extent of the oscilla- 

 tion, during the fifty-seven earthquakes above alluded to. The 

 oscillations never went beyond their ordinary limits; indeed, in 

 most cases they were very inconsiderable.! Von Humboldt also 

 says that between the Tropics, on days when the earth is agitated 

 by violent earthquakes, the regularity of the hourly variations of 

 the barometer is not disturbed. J 



If aqueous vapors and compressed gases are the cause of earth- 

 quakes, there can be no doubt that hot springs and exhalations of 



Sloane's Letter with several accounts of the earthquake in Peru, October 20th, 

 IfoTy at Jamaica, 10th February, 1688, 7th June, 16025 ibid, y. 1604, p. 78} Hist. 



assac 



p. 223. 



* Hoffman, loco cit. p. 52. It is also well known that in other countries, es- 

 pecially in Chili and the Moluccas, the periods of the equinox, for reasons of which 

 we are ignorant, are considered as those most favorable to earthquakes. During 

 the above named period of forty years, this law does not seem to have been appli- 

 cable to the autumnal equinox in that part of Europe. 



f During the earthquakes the barometer stood decidedly oflener above the me; 

 than under it. However, Hoffman remarks, p. 56, that during the only shock of 

 importance wliich occurred in this period at Palermo, viz., in March, 1823, the bar- 

 ometer remained the whole month constantly below the monthly mean. 



t Reise, t. i, p 487; also Relat. hist. t. iv, 19. Likewise Boussingault in Ann. 

 de Chira. et de Phys. t. lili, p. 82. Other observations have also proved that the 

 hei'^ht of the barometer is totally unconnected with the cause of earthquakes, as 

 for instance those of Don Felixe Castillo Albo, during the earthquake in Chili in 

 the year of 1822. See also Meyen in his " Reise urn die Erde,*' t.'i, p. 210. 

 Those also made in the county of Pignerol in Savoy, by the committee of the 

 academy of Turin, during the earthquakes in the year 1808. The slate of the 

 barometer was also invariable, whilst the shocks -aX Lisbon, the 9th December, 

 1755 were very strongly felt at Turin Philos. Trans, t. xHx. The observations 

 made on the island of Meleda. near the coast of Dabnatia, from the 15th November, 

 1824, to the 28th February, 1826, which likewise prove, that no connection exists 

 between earthquakes and the pressure of the atmosphere, are very important, the 

 shocks felt on this island having been the only ones of their kind as regards length 

 of duration.— Die Detonations-Plianomene auf der Insel Meleda von P, Partsch, 



Wien, 1826, p. 204. 



