I 



INTRODUCTION. 



27 



From most active volcanoes, smoke issues more or less constantly ; but the eruptions, which 

 are discbarges of stones, ashes, and lava, with columns of flame, violent explosions, and 

 concussions of the earth, happen at irregular, and sometimes at long intervals. There are 

 about 500 volcanoes upon the surface of the eartli. 



A vast volcanic zone surrounds 

 Greece, Italy, Germany and 

 France. Several islands in the 

 Grecian Archipelago, have been 

 raised from the sea by volcanic 

 convulsions. Etna has burnt for 

 3300 3rears, and is surrounded by 

 extinguished volcanoes, which ap- 

 pear still more ancient. The Li- 

 pari islands seem to be formed 

 chiefly of the lava and other sub- 

 stances which have been thrown 

 from their volcanoes. Other parts 

 of Europe exhibit traces of vol- 

 canoes now extinguished. Iceland 

 has several volca-noes, of which 

 Hecla is the most remarkable. 

 The very bottom of the ocean in 

 the neighborhood of this island, 

 is sometimes convulsed, and the 

 waves often heave up whole fields 

 of pumice stones. 



The origin of volcanoes is a 

 Vokanic Island in the Sea. Subject upon which scientific men 



have entertained different opinions ; the most rational of these ascribe them to the burning of 

 oitumen, fossil-wood, pit-coal, &c. set on fire by the spontaneous combustion of pyrites, a 

 metallic substance formed of iron and sulphur. 



The eruption of a volcano is a most frightful and majestic phenomenon. The first signs 

 which announce that the invisible combat of the elements has already commenced, are violent 

 movements, which shake the earth afar off", prolonged bellowings and subterranean thunders, 

 which roll in the sides of the agitated mountain. Soon the smoke ascends in the shape of a 

 black column. This is dispersed by the winds, and formed into trains of clouds. A volume 

 of flame i-ises above the clouds, seeming like a pillar of fire, which rests upon the ground and 

 threatens to set the skies in a blaze. A black smoke environs it, and from time to time mter- 

 oepts the dazzling brightness. Lightnings appear to flash from the midst of the burning mass. 

 On a sudden, the vast pillar of fire seems to fall back into the crater, and its fearful splendor is 

 succeeded by profound darkness. But now ashes, dross, and burning stones are projected in 

 diverging lines, and fall around the mouth of the volcano. Enormous fragments of rocks 

 appear to be heaved against the skies. A torrent of water is often thrown out with impetuosity, 

 and rolls hissing over the inflamed rocks. There is then raised from the bottom of the crater a 

 liquid mass of burning lava, which fills the cavity and reaches to the very top of the opening. 

 This is the prelude to real disasters. The hquid matter overflows, and runs down the sides 

 of the mountain. It advances hke a large and impetuous river, destroys whatever it meets 

 within its course, flows over those obstacles which it cannot overturn, passes along the ram- 

 parts of shaken cities, invades a space of country of several leagues in extent, and transiorms, 

 in a short time, flourishing fields into a burning plain. 



5. Earthquakes. Earthquakes are supposed to be intimately connected with volcanoes, and 

 usually take place in volcanic countries. There have been frequent earthquakes near the 

 borders of the Mediterranean Sea, and around the Gulf of Mexico. These dreadful phenom- 

 ena often change the surface of a country, so that it is difficult to recognise it. During the 

 convulsion, enormous gaps in the earth appear to disclose to the living the empire of the dead ; 

 these fissures emit blue flames and deadly vapors. Vineyards descend from their heights, and 

 settle in the midst of fields of corn ; farms and gardens quit their places and become attached 

 to distant villages ; towns are shaken down, villages are swallowed up, mountains sink mto 



