RE AAO TR 
Earthquakes in Sicily. 227 
santly belched out towards heaven, and whose ppueeoct 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 of but 4 
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 [ 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 sioattie and when the external phenomena disappear- 
ed, the internal fire not being yet extinguished, deep subter- 
ranean J aroma and explosions were heard, and shocks felt 
at each report. 
When the fire invests substances, it rarefies their masses to 
a great degree ; the acquisition of new volume produces a 
proportionate expansion; and under the action of an enc 
mous accumulation of inflamed matter, a passage is made for 
it with sudden and fearful energy. ‘The expansion of water, 
for example, under a medium pressure of the Phage 15 
1728 times its first volume, and it increases in the ratio of 
the heat. At 110° of Rea. the pressure is equal to four at- 
ye She only. The explosion of a single barrel of powder, 
ocks and overthrows the whole vicinity. If, then, a sub- 
tensed stream of water happens upon places where vol- 
canic fires are burning, it is at once converted into steam, 
vee given any external meatlis of its existence. It seems 
that the return of the terrible phenomenon is owing to the 
flow of water into places on fire—of water, the streams of 
which are determined only by accidental causes. 
The vast furnace in the interior of the earth being inflamed, 
the fire attacks every thing exposed to its influence, some 
are liquified, while others are converted to vapour; these, 
developing their volumes, form a system of force movi 
with immeasurable power. ‘The subterranean cavities, little 
able to contain them, are violently convulsed in all their di- 
mensions ; and this effect is transmitted by the solid earth, 
to distances proportioned to the quantity of force, to the 
