324 GEOLOGY. 



No volcano, strictly so called, is known with cer- 

 tainty to exist in Africa ; but in what are called the 

 African Isles, there are several. 



Not one volcano is to be found in the interior of 

 any continent, or, indeed, any where remote from the 

 sea. 



The Island of Owhyhee. 



Owhyhee, covering a space of 4000 square miles, 

 is one complete mass of lava in different stages of de- 

 composition, perforated with innumerable apertures 

 in the shape of craters ; in fact this island is an enor- 

 mous hollow cone, 18,000 feet high, over a vast fur- 

 nace, situated in the heart of this gigantic marine 

 mountain. 



Subterranean Communication of Volcanoes. 



During the eruptions of the great volcano of Tom- 

 boro, on the island of Sumbhawa, in the East Indies, 

 on the llth of April, 1816, the noise was so loud in 

 the neighbourhood of Mocomoco, although the dis- 

 tance exceeded 1400 miles, and so much resembled 

 discharges of artillery, that the chiefs of the interior, 

 supposing Fort Anne, at Mocomoco, was attacked 

 from the sea, armed their followers and marched 

 down in a body to assist the garrison. 



Mud Volcanoes. 



On the plains of Grobogang, in the island of Java, 

 are some remarkable mud volcanoes, having, at a dis- 

 tance, the appearance of the surf breaking over rocks. 

 On approaching them, (in 1815,) an elevated plain of 

 mud is perceived about two miles in circumference, 

 in the centre of which immense bodies of salt mud 

 are thrown up, to the height of ten or fifteen feet, in 

 the shape of large globes or bubbles, which are con- 

 tinually throwing up and bursting seven or eight 



