168 Prof. Ferrara's Account of the Earthquakes 



In conclusion, it may not perhaps be improper to assign 

 the reason why the analysis of Laplace coincides exactly with 

 the particular law of probability. It arises from the approxi- 

 mation employed by the French geometer; according to which 

 the squares only of the errors are retained in the expressions of 

 the probabilities, the higher powers being dismissed. There is 

 thus the most perfect agreement between the results obtained 

 both ways ; a convincing proof, in point of fact, that the two 

 methods are fundamentally tlie same, and are different only 

 in the mode of investigation. 



March 2, 1825. James Ivory. 



XXVI. An Account of the Earthquakes "which occurred in Sicily 

 in March 1823. By Sig. Abate Ferrara, Prcfessor of 

 Natural Philosophy in the University of Catania, Sfc. Sj-c. 



[Concluded from p. 100.] 



Physical Ohservatioiis. 



"IT/'HEN the people about ^tna perceived their houses be- 

 '* ginning to shake, they turned their eyes towards the 

 volcano, and waited in expectation of an immediate eruption. 

 And while they looked, fearful apprehensions filled their minds, 

 and they prayed that the event, be it what it would, might 

 take place at once. 



The philosopher, who observes the phaenomena of nature 

 for the sake of reducing to the same class those of an analo- 

 gous origin, and thence to deduce them from the same cause, 

 observes the link which connects earthquakes with volcanic 

 operations, and sees with the ignorant vulgar those mighty 

 forces preparing in the subterranean furnace, which are able 

 to put in motion immense masses of the solid globe, and to 

 agitate them as water is agitated by a violent wind. The 

 eruption of -^itna in 1811 was interesting from the grandeur of 

 the spectacle which it presented, and no less so from the in- 

 struction which it conveyed to the naturalist. A new open- 

 inor was made on the surface of the mountain. Explosions of 

 tremendous force preceded the emission of immense columns 

 of smoke and inflamed masses of matter, which were inces- 

 santly belched out towards heaven, and whose approach was 

 announced by horrid roarings and explosions which filled the 

 air to a great distance. Each explosion was accompanied by 

 shocks ; and as the interval between them was but of a few 

 minutes duration, the city and country to a vast extent were 

 in a continued undulation. For many days at Catania, eigh- 

 teen 



