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fhows that this rock was once fluid from 

 the adlion of the fire ; fince otherwife thefe 

 innumerable vacuities would not have been 

 produced ; and, fecondly, that it has been 

 in motion, in confequence of which the 

 bubbles, naturally of a round figure, have 

 taken a form more or lefs oblong. The 

 truth of this deduction is confirmed by 

 what has been obferved in many of the 

 lavas of Lipari. Some of thefe cavities are 

 filled with cryflallized carbonate cf lime. 



This lava is likewife remarkable for the 

 large fize of the fhoerls it contains ; feveral 

 of Vvdiich are ten lines in length, and fome 

 even an inch. They are of a black colour, 

 have a fcaly fracture, and facets of fo lively 

 a luftre, that they may compare with the 

 moft beautiful cryf^als of fpecular iron. 

 Both when detached, and v;hen incorpo- 

 rated with the lava, they melt, in the fur- 

 nace, into a black, compadl enamel, giving 

 fparks copioufly with fteel, and of a luftre 

 little inferior to that of the fnoerls them- 

 felves. Fufion fucceeds equally in the other 



lavas 



