( 21 ) 



or three lines in length to twelve or four- 

 teen, and of proportional thicknefs. They 

 appeared to Iiave appertained to branches of 

 trees or fhrubs 5 they are buried in the tuf^ 

 at various depths, and are found, though 

 thinly fcattered, through its whole extent. 



This fad:, never before, to my knowledge, 

 obferved by others in volcanic tufas, might 

 induce us to imagine that the two methods, 

 the humid and the dry, had here been com- 

 bined ; and that the watery Hime, when it 

 flowed down the mountain, had been pene-^ 

 trated by the fire in fuch a manner that it 

 had inflamed, and converted into coal, the 

 vegetables it met with in its way. This ex-- 

 planation is certainly not free from diffi- 

 culties, as the reader, no doubt, already 

 perceives ; it thereiore may appear more 

 probable that the earthy inundation had 

 involved, and carried with itfelf, thefe car- 

 bonaceous fubftances, which exifled pre- 

 vious to its eruption, and which derived 

 their origin from a fhower of ignited matter 

 leaving burned, but not entirely confumed, 

 C 3 thQ 



