NOME VI. OBSIDIAN. 455 



ence. As a proof of this conjecture the furnace 

 produced a complete homogeneity of parts in the 

 enamel containing these extraneous globules. 



" 6. When treating of the rocks of the castle 

 of Lipari, I said they were formed of a cinereous 

 lava of a felspar base, which in many places has 

 passed into glass. I likewise remarked that the 

 lava, as well as the large pieces of glass, was 

 filled with globules apparently not dissimilar to 

 the base. At the beginning of the Monte della 

 Castagna, not far from a cottage, the habitation 

 of one of the labourers who dig pumice, there is 

 a current of similar glass that falls into the sea in 

 several branches, and which I shall here con- 

 sider as the sixth species. This glass, however, 

 has a more fine and shining grain, and its frac- 

 ture is exactly such as we observe in glass, yet 

 in beauty it is little inferior to the fifth kind; 

 and if whiteness, or more properly the want 

 of colour, is particularly valuable in volcanic 

 glasses (since those which have this quality are 

 extremely rare), this certainly has considerable 

 claim to our attention : not that it is entirely 

 colourless, as it contains a kind of obscure cloud, 

 which gives it, when viewed in the mass, a 

 blackish hue, but at the edges it appears white. 

 The round cinereous bodies with which it is 

 filled form the most pleasing and conspicuous 



