858 Prof. Bischof on the Natural Historic of 



forty years, almost a fourth part happened in the month of 

 March.* Perhaps the best means of ascertaining whether any 

 connexion exists between earthquakes and meteorological phe- 

 nomena, is the observation of the barometer. But Hoifman 

 was unable to discover anything peculiar or extraordinary, 

 either in the relative height of the barometer, in the direc- 

 tion of its motion, or in the extent of the oscillations, during 

 the fifty-seven earthquakes above alluded to. The oscillations 

 never went beyond their ordinary limits ; indeed, in most cases 

 they were very inconsiderable. t Von Humboldt also says that 

 between the Tropics, on days when the earth is agitated by vio- 

 lent earthquakes, the regularity of the hourly variations of the 

 barometer is not disturbed.]: 



If aqueous vapours and compressed gases are the cause of 

 earthquakes, there can be no doubt that hot springs and ex- 



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

 especially in Chili and the Moluccas, the periods of the equinox, for reasons 

 of which we are ignorant, are considered as those most favourable to earth- 

 quakes. During the above-named period of forty years, this law does not 

 seem to have been applicable to the autumnal equinox in that part of Eu- 

 rope. 



t During the earthquakes the barometer stood decidedly oftener above 

 the mean than under it. However, Hoffman remarks, p. 56, that during 

 the only shock of importance which occurred in this period at Palermo, viz. 

 in March 1823, the barometer remained the whole month constantly below 

 the monthly mean. 



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

 in Ann. de Chim. et de Phys. t. liii. p. 82. Other observations have also 

 proved that the height of the barometer is totally unconnected with the 

 cause of earthquakes, as for instance those of Don Felixe Castillo Albo, du- 

 ring the earthquake in Chili in the year of 1822. See also Meyen in his " Reise 

 um die Erde," t. i. p. 210. Those also made in the county of Pignerol in Sa- 

 roy by the committee of the academy of Turin, during the earthquakes in 

 the year 1808. The state of the barometer was also invariable, whilst the 

 shocks at Lisbon, the 9th December 1755, were very strongly felt at Turin. 

 Philos. Trans, t. xlix. The observations made on the island of Meleda, near 

 the coast of Dalmatia, 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 du- 

 ration. — Die Detonations-Phanomene auf der Insel Meleda von P. Partsch, 

 Wien, 1826, p. 204. 



