22l8 Earthquakes in Sicily. 



tran«missive power of the body moved, and to various local 

 circumstances favourable, or otherwise, to the propagation of 

 motion. After having combated with the obstacles which 

 feppose, roaring under the earth, like the winds of Eolus, to 

 find an outlet from the places in which they were produced, 

 they circulate in various canals, until a cold temperature de- 

 prives them of the heat which gave them such power, and 

 they sink into their former state. Often, however, they 

 drive before them the matter which the heat has liquified ; 

 and urging it towards the ancient mouths of volcanoes, belch 

 it out in flaming rivers in the midst of the terrible phenomena 

 which they themselves produce.* 



Urged by the passion for observation, I have often de- 

 scended into the horrid cavity of the crater, and approached 

 near the blazing brink of the new orifices which have vom- 

 ited forth streams of fire in my own time ; I have seen im- 

 mense torrents of aqueous vapour urged from the vast chim- 

 ney, whose base is lost in the deep furnaces below; I have 

 been bathed in the water, to which the vapour was reduced 

 by the low temperature of the atmosphere into which it en- 

 tered •, often have 1 seen it fall in fine showers all around me. 

 Having penetrated into the recesses of the globe, it is in this 

 manner forced out again by the heat to which it is exposed. 

 I have observed the hydrogen gas; one time, burning with 

 its peculiar colour ; at another, bursting forth with a loud, 

 deep explosion ; the sulphuric and muriatic vapours, whiten- 

 ing the immense clouds of smoke, and filling all the air with 

 their suffocating breath ; or, seizing upon the solid substances 

 around, remaining fixed upon them. Fused substances, forced 

 up by the elastic vapours, are disgorged from the same 

 mouths, spread about in torrents of fire, and consolidated by 

 the contact of the air. Is it not possible that the seat of 



* in my " Description of ^tna," I have proved that the furnaces io 

 this volcano cannot be under the foundation of the mountain, but at va- 

 rious distances from it. The immense vaults, which must have been 

 formed after so many ag'es of conflagration, would, at the first violent 

 shock, have swallowed up the whole mountain ; and the combustible ma- 

 terials would have been exhausted in so small a circumference. The 

 inflamed matter in different situations, from causes established by long' 

 usage, flows towards iEtna, and is ejected by it. Seneca acknowledg'ed 

 this truth ; ignem in ipso iponte non alimentum, sed viam habere;— 

 E-pis. 79, 



