362 Analysis of' Scientific Books and Memoirs. 



of nature do not vary, but that similar results always are, have been, 

 and will be produced, by similar preceding circumstances. 



An appendix is added to the work, containing a list of known volcanos 

 in recent or habitual activity; and an examination of the anomalous 

 phenomena described by M. de Humboldt, as having accompanied the 

 eruption of Jorullo in Mexico.* The work is illustrated by engravings, 

 lithographs, and numerous wood-cuts. 



II. An Account of the Earthquake* u-hich occurred in Sicily, in March 1823. 

 By Sig. Abate Ferrara, Professor of Natural Philosophy in the Uni- 

 versity of Catania. 



( Concluded from last Number, p. \6l.) 



When the people about Jitna perceived their houses beginning 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 phenomena of nature, for the sake 

 of reducing to the same class those of an analogous origin, and thence to 

 deduce them from the same cause, observes the link which connects earth- 

 quakes 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 iEtna in 1811 was inter- 

 esting from the grandeur of the spectacle which it presented, and no less 

 so, from the instruction which it conveyed to the naturalist. A new 

 opening 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 incessantly thrown up- 

 wards, aud whose approach was announced by horrid roarings and ex- 

 plosions, which filled the air to a great distance. Each explosion was 

 accompanied by shocks : and as the interval between them was of but 

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

 continued undulation. For many days at Catania, eighteen miles distant, 

 we were rocked as though we had been upon the sea. Some of the shocks 

 were very violent. The door of my chamber, which I left purposely ajar, 

 kept a continued beating against its side posts. The shocks lasted as long 

 as the volcano was in operation, that is, for more than nine months ; and 

 when the external phenomena disappeared, the internal fire not being yet 

 extinguished, deep subterranean rumblings and explosions were heard, 

 and shocks felt at each report. 



When the fire invests substances, it rarefies their masses to a great de- 

 gree ; the acquisition of new volume produces a proportionate expansion ; 

 and under the action of an enormous accumulation of inflamed matter, a 

 passage is made for it with sudden and fearful energy. The expansion of 



* See our Last Number, p. 50. 



