THE EARTH. 79 



ness to burst out into flames. Marcasites and 

 pyrites, in particular, by being humified with 

 water, or air, contract this heat, and often en- 

 deavour to expand with irresistible explosion. 

 These, therefore, being lodged in the depths of 

 the earth, or in the bosom of mountains, and 

 being either washed by the accidental influx of 

 waters below, or fanned by air, insinuating it- 

 self through perpendicular fissures from above, 

 take fire at first by only heaving in earthquakes, 

 but, at length, by bursting through every ob- 

 stacle, and making their dreadful discharge in a 

 volcano. 



These volcanoes are found in all parts of the 

 earth : in Europe there are three that are very 

 remarkable ; ^Etna in Sicily, Vesuvius in Italy, 

 and Hecla in Iceland. ^Etna has been a volca- 

 no for ages immemorial. Its eruptions are very 

 violent, and its discharge has been known to 

 cover the earth sixty-eight feet deep. In the 

 year 1537, an eruption of this mountain pro- 

 duced an earthquake through the whole island, 

 for twelve days, overturned many houses, and 

 at last formed a new aperture, which overwhelm- 

 ed all within five leagues round. The cinders 

 thrown up were driven even into Italy, and its 

 burnings were seen at Malta at the distance of 

 sixty leagues. There is nothing more awful, 

 says Kircher, than the eruptions of this mountain, 

 nor nothing more dangerous than attempting to 

 examine its appearances, even long after the erup- 

 tion has ceased. As we attempt to clamber up its 

 steepy sides, every, step we take upward, the feet 



