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two inches indicates a removal of a weight of two millions of tons 
on every square mile of the earth’s surface Now the relief of so 
vast a pressure might readily permit superheated fluid to flash into 
steam (Judd), and produce of volcanic action. The volcano of 
Stromboli, in the Mediterranean, which has been in constant action 
for at least 3,00!) years, not only serves as a flaming beacon to the 
seamen of ‘‘ the Blue Tyrrhenian Sea,” but its intermittent vigour 
is regarded by the native fishermen as an unfailing and trustworthy 
barometer. The popular notion of a volcano is curiously and 
elaborately wrong (Judd). It is generally described as ‘‘ a burning 
mountain, discharging from its summit volumes of fire and cinders.” 
Now, in the first place, voleanoes need not necessarily be moun- 
tains at all, the mountains being only as it were an accidental 
addition built up by the accumulation of the extruded debris of lava, 
scorie, and volcanic products; though certainly some of these 
mountains are of no inconsiderable size, Chimborazo, in the Andes, 
being 21,415 feet above the sea level, and Cotopaxi, nearly 20,000 
feet high ; while Mauna Loa, the far-famed fire fountain of Hawaii, 
is 14,000 feet above the sea, with an area at the base of 18 miles, 
while a section through the cone within 1,800 feet of the summit 
measures no less than 20 miles. Notwithstanding the imposing 
dimensions of these mountains, all that is really necessary to constitute 
a volcano isa mouth or orifice communicating with the molten lava 
below. Then, secondly, the mountain does not burn. Thirdly, there 
are no flames, the fiery appearance, which is often very vivid, being 
the reflection of the glowing lava within the crater from the steam cloud 
aboveit.. I say no flames, but occasionally there is seen some lumin- 
ous hydrogen gas, burning with a faint bluish flame. Fourthly, the 
glowing lava very often comes from the side of the mountain and 
not fromthe top, as was the case in the late eruption of Vesuvius, 
where it poured from a fissure in the side, 12 miles long; and 
fifthly there are no cinders properly so called, the extruded lavas 
bearing no resemblance to carbon, being, in fact, principally com- 
binations of silica, or quartz, as it is popularly called, with the 
various earthy bases, lime, potash, magnesia, &c., or iron. The 
porous appearance of the pumice, which you all know is a volcanic 
product, and with which we are all familiar, 1s caused by the 
passage of gases through its mass while still in a semi-fiuid con- 
dition, just as bread is rendered porous by the bubbles of carbonic 
acid gas generated by the fermenting yeast. Some of the silicious, 
or glassy, lavas are blown out into a substance like spun glass, 
from the forcible passage through it of steam and gas, while still 
in a liquid form in mid-air. 1t abounds in Hawaii, where it is 
called ‘‘ Pele’s Hair,” after Pele, the local goddess of voleanoes; it 
is so soft that birds there use it to make their nests. Another 
