NOME VII. VOLCANIC INTfclTE. 



few days, it neither injures the olive nor the 

 pear-tree, which, in the midst of the general de- 

 struction, constantly retain their verdure and 

 strength. This is a fact confirmed by all farm- 

 ers, and which I have many times verified my- 

 self. 



" On examining this mephitic gas by the or- Gas. 

 dinary means, I found it to be composed of car- 

 bonic acid gas, azotic gas, and a portion of sul- 

 phuric acid, as is shewn by the precipitation of 

 barytes, by the solution of muriate of barytes. 

 The bad effect, therefore, of this gas on plants, 

 is little matter for wonder, the deleterious nature 

 of carbonic acid to the vegetable reign being 

 known. 



The colour of the lava of 1794 is a darkish Lava of 1794. 

 grey, its hardness such as to yield sparks with 

 steel, its grain coarse and earthy, its fracture ir- 

 regular, its porousness various, for in some parts 

 is so compact as to resemble petrosilex in its 

 rain ; on moistening it, even by breathing, or 

 u being wetted, it exhales an earthy smell: 

 nally, it powerfully answers the magnet. Sel- 

 om is mica found in this lava in laminae, but 

 /,|ften in groups and small united masses; on 

 it pese occasions it presents the same phenomena 

 in the lava of Granatello. The lava is rich in 

 gite, which is frequently seen crystallised in 

 VOL. IT. 2 K 



