NOME II. VESICULAR LAVA. 335 



thrown up, notwithstanding the resistance of 

 gravity, from the bottom to so great a height as 

 the highest crater of Etna. It is evident, there- 

 fore, that the effervescence in the eruptions of 

 the months of July and October 1787, was ex- 

 tremely violent. The torrent of the month of 

 October is every where covered with scorise, 

 which resemble those ejected in the month of 

 July in their black colour, but differ from them 

 in the great adhesion they have to the lava, in 

 their exterior vitreous appearance, their greater 

 weight, and their hardness, which is so great 

 that they give sparks with steel almost as plen* 

 tifully as flints. These differences, however, 

 are to be attributed only to accidental combina- 

 tions of the same substance ; the constituent 

 principles of the scoriae of this lava not being 

 different from those of the detached scorise 

 mentioned above. Both likewise contain the 

 same felspar lamellae. 



" This new current was however very dim*- Difficulties of 

 cult, and even dangerous, in the passage. In 

 some places the scoriae projected in prominent 

 angles and points, and in others sunk in hollows, 

 or steep declivities ; in some, from their fragility 

 and smoothness, they resembled thin plates of 

 ice, and in others they presented vertical and 

 sharp projections. In addition to these diffi* 



ascent. 



