VOLCANIC ERUPTIONS. 245 



ground, increase, and the whole neighborhood gives evidence of 

 the immense pressure which is being exerted; presently the mol- 

 ten lava, is by the immense force raised into the crater, and fill- 

 ing- it up, or melting its passage through the side, flows in a red 

 hot stream down the flanks of the mountain in a river, or rather 

 a torrent of fire. The eruption is sometimes attended with enor- 

 mous currents of water, mud, and noxious gasses. A period of 

 rest succeed?, generally of short duration; again the same phe- 

 nomena are repeated, and thus the action continues fo? a varia- 

 ble length of time, until finally, the crisis is past and the volca- 

 no resumes its original quiet. 



The substance:? principally ejected by volcanoes are smoke, 

 ashes, sand, scoriae, volcanic glass and bombs, and masses of 

 rock. The ashes thrown out in volcanic eruptions appear to be 

 the substance of the lava very finely divided. These ashes are 

 raised so high that they are carried by the winds to almost incred- 

 ible distances. Ashes from the eruption of a volcano in St. Vin- 

 cent in 1812, were carried twenty leagues, and fell in Barbadoes, 

 and from the eruption of Hecla in 1766, they fell in Glaumba, a 

 distance of fifty leagues; and it is said that ashes from Vesuvius 

 have fallen in Constantinople, a distance of four hundred and 

 fifty leagues. The volcanic saud, is composed of particles some- 

 what larger, but of the same character as the ashes, being commi- 

 nuted particles of lava, and forming a principal part of the eject- 

 ed matter pf volcanic eruptions. Scoria}, and pumice stone, are 

 caused by the gasses, which bursting through the melted lava, 

 carry up with them certain portions into the atmosphere, which 

 becoming consolidated, present the appearance so well known 

 under the name of slag and cinders. Volcanic glass or obsidian, 

 is often ejected in small melted masses ; sometimes, the winds 

 catching this, spin it into the finest threads. We have seen many 

 specimens of this kind irom the eruptions of Kirauea, in the 

 Sandwich Islands. Among the extinct volcanoes of France, 

 drops, tears, and elongated spheroids, being drops of lava thrown 

 out, and consolidated in the air, are continually found, they are 

 called vdlcanic bombs. Masses of rock are always ejected in 

 severe eruptions; in many cases these are undoubtedly torn off 



