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- VOLCANOES.

tree. Tremendous explosions, like thefiringofartillery, commence after the increase of smoke,and are succeeded by red-coloured flames andshowers of stones : at length the lava flows outfrom the top of the crater, or breaks throughthe sides of the mountain and covers the neigh-bouring plains with melted matter, whichbecoming consolidated, forms a stony massoften not less than some hundred square milesin extent, and several yards in thickness. Theeruption has been known to continue severalmonths. The quantity of volcanic powdercalled ashes thrown out, is inconceivably great.During one eruption offlEtna, a space of 150miles in circuit was covered with a stratumof sand twelve feet thick. When the lava flowsfreely, the earthquakes and explosions becomeless violent; which proves that they were oc-casioned by the confinement of the eruptedmatter both gaseous and solid. The smokeand vapour of volcanoes are highly electrical.

The long period of repose which sometimestakes place between two eruptions of the samevolcano is particularly remarkable. Fromthe building of Rome to the 79th year of the. . Christian