NOME IV. TUFO. 403 



" No. II. Heavy drosses of nearly an oval 

 shape, and weighing from six to eight and nine 

 pounds ; such were projected the distance of 

 four miles from the crater ; superficially they are 

 vitrified, their pores are glossy, and are five or 

 six lines in diameter. The centre of these 

 drosses has rounded and pretty regular pores; 

 it contains crystals of white felspar confusedly 

 dispersed, and some volcanic chrysolites. The 

 crystals of felspar preserve their transparency, 

 and are merely a little glazed, while the chryso- 

 lites have undergone a species of fusion, which 

 has combined their grains, and rendered their 

 surface convex. 



" These drosses are found round the crater, 

 especially from the southern to the eastern side, 

 well as in the valley of Bue. 



No. III. Light whitish drosses, similar to 

 he cavernous pumice-stone of Lipari ; they have 

 he same fibrous texture and prolonged pores ; 

 me little light 'drosses, of a black colour, ad- 

 ere to this pumice, which separately floats on 

 he water, but which when attached to the black 

 rosses, is carried by their gravity to the bottom : 

 his is the first instance known of Etna having 

 >roduced a similar substance. 



" Found on the W. S. W. torrent of lava, near 

 he crater. 



