NOTES. l xv ii 



et cum iuturaescit assurgens alternoque motu residet, innoxium et cum 

 concurrentia tecta contrario ictu arietant ; quoniam alter motus alteri renititur. 

 Undantis inclinatio et fluctus more qwedam volutio infesta est, aut cum in 

 unam partem totus se motus impellit (Plin. ii. 82). 



( 184 ) p. 193. The absence of any connection between earthquakes, and the 

 state of the weather or appearance of the sky immediately preceding their 

 occurrence, begins to be recognised even in Italy. The numerical data 

 obtained by Friedrich Hofimann on this subject agree perfectly with the 

 experience of the Abbate Scina of Palermo. See F. Hoffmann's " hinterlassens 

 Werke," Bd. ii. S. 366375. I have indeed myself observed more than 

 once the appearance of reddish clouds a short time before earthquake shocks ; 

 and on the 4th November, 1799, I experienced two strong shocks simul- 

 taneously with a violent clap of thunder (Relation historique, Liv. iv. chap. 10) ; 

 and a physicist of Turin, Vasalli Eandi, observed great disturbance in Volta's 

 electrometer during the long-continued earthquakes at Pignerol, which lasted 

 from April 2 to May 17, 1808 (Journal de Phys. T. lxvii. p. 291). But we 

 have no reason for regarding any of these phenomena, such as haze or clouds, 

 disturbances in the electric state of the atmosphere, or calms, as having any 

 general and necessary connection with earthquakes ; for in Quito, Peru, and 

 Chili, as well as in Canada and Italy, shocks have been felt when the sky 

 was most serene and free from clouds or haze, and when the freshest land or 

 sea breezes were blowing. But although we have no reason to believe that 

 earthquakes are preceded or accompanied by any particular meteorologies 

 indications, yet we ought not peremptorily to reject altogether the popular 

 belief of the influence of particular seasons, the vernal and autumnal equinoxes, 

 the settmg-in of tropical rains after long-continued drought, and the change 

 of the monsoons, solely because we do not at present understand the causal 

 connection which may exist between meteorological and subterranean pheno- 

 mena. Numerical data, collected with great care by M. de Hoff, Peter Merian, 

 and Friedrich Hoffmann, for the purpose of elucidating the comparative 

 frequency of earthquakes at the different seasons of the year, indicate a 

 maximum about the times of the equinoxes. It deserves notice, that Pliny, at 

 the end of his fanciful theory of earthquakes, terms these awful phenomena 

 "subterranean storms," not so much on account of the noise resembling 

 thunder, which often accompanies them, as from a notion that the elastic 

 forces which by their increasing tension thus agitate the ground, accumulate 

 beneath the sin-face of the earth when they are wanting in the atmosphere : 



