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two inches indicates a removal of a weight of two minions 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 3,00h 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, volcanoes 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, 

 scoriae, 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 reallynecessary to constitute 

 a volcano is a mouth or orifice communicating with the molten lava 

 below. Then, secondly, the mountain does nothurn. Thirdly, there 

 are no flames, the fiery appearance, which is often very vivid, being 

 the reflection ofthe glowing lava within the crater from the steam cloud 

 above it. 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 from the 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, is caused by the 

 passage of gases through its mass while still in a semi-fluid 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. It abouads in Hawaii, where it is 

 called " Pele's Hair," after Pele, the local goddess of volcanoes; it 

 is so soft that birds there use it to make their nests. Another 



