418 NATURAL HISTORY. 



First Period. A short time before the catastrophe 

 or outbreak commences, a dull, rumbling noise is heard, 

 as occurring far down in the earth ; tremblings more or 

 less violent are sure to succeed ; these shakings continue 

 for a shorter or longer time, at irregular intervals. These 

 movements of the earth are of different kinds; sometimes in 

 horizontal oscillations, at others in successive rising and 

 falling of the soil, often jerking and twisting as if tortured 

 by some internal agony, and are not less dangerous than 

 open eruption. If in the neighborhood of the sea, the 

 waters, violently agitated, sometimes advance far inward, 

 making fearful irruptions on the coasts, at others retreat- 

 ing so far outward as to leave their foundations exposed. 

 At such times the air is hot, dry, and oppressive. 



Second Period. Whilst the subterranean rumblings 

 continue, and the tremblings of the earth seems to threaten 

 a removal from its firm foundations, the melted lava is, 

 like boiling fluid in a caldron, rising to the top of the 

 crater, -whence or else by fissures in the side of the 

 mountain it pours forth in streams of liquid fire. Col- 

 umnar volumes of fire rise like gigantic pillars above the 

 crater, amid which are seen jets of large red hot stones, 

 ashes, and sand, hurled with Titanic force from two to 

 three thousand feet in the air. The stream of lava is 

 enveloped in a dark cloud of smoke : at the same time 

 immense volumes of steam, or aqueous vapor, are evolved. 

 Clouds of fiery volcanic dust, sand, and ashes, or pumice, 

 fall everywhere, even to a great distance, like rain, whilst 

 loud grumblings, like thunder, and fearful subterranean 

 explosions issuing from the mountain, shake the earth to 

 its very center. After the overflowing of the melted 

 lava, these commotions gradually cease, the volume and 

 force of the fiery stream gradually diminish, after hav- 



