18 On Volcanos and Earthquakes. 
ing; minerals, sand, and stones are melting, vitrifying, and 
running at the bottom of the cavern in the s shape of lava, of 
which it forms a permanent lake in fusion, j at as melted iron 
is collected at the bottom of a casting furnace. These things 
being in this situation, if asudden vacuum is icles what 
will ? But I may be stopped here, and be as 
how can a pects vacuum be produced? [see many cau- 
why it may, but the most simple and natural, and conse- 
quently the leas objectionable one, is, that after a certain 
time, a num ears that cannot be foreseen, for it is not 
periodical, a See of the coal being burnt, reduced to ashes, 
the mineral to lava, the ground above, no 2. longer aperits 
with a-  surtac on 
crumbles down, ‘ she ia a 
cold ground. is put in in contact. w 
vapours, and a sudden — is produced ; a 
vacuum follows: it is sudden, that it communicates a 
r to the daiettind ground, which is felt as the first 
shock of an earthqua xe. This vacuum produces in its turn 
furnace. Then, a reverse effect is aati mage ; water oe 
or wave ; ‘niet part may be thrown off through the gap- 
ing ground, and even may issue mixed i with the flames of the 
mountains. _ In the meanwhile, new shocks are felt, until the 
weakest point has yielded to ‘the combined powers of the 
steam and ae actuated by the heat and a pressure of eight 
bonnes, atmospheres. Generally, the former crater, filled 
in part with ~ stones, lava, and ashes of the preceding 
eruption, is the: est point; all is thrown up; a column 
3 by the: burning hydrogen, is raised to the 
clouds; ashes, the result perhaps of twenty years’ combustion, 
antity to fee: vil 
in sufficient lages and. cities, and stones 
all sizes, loosened, are- cted to an immense distance ; 
and, finally, the lava, swept away by the steam, gases, and 
air, 1s raised up to the summit of the crater, or runs 
ea ee ean CR ea Bee Ie Vs RN eee mt 
