from the Lipari Islands. 533 



layers of obsidian, and an earthy substance which appears to be 

 compact pumice. No. 5. is an extremely beautiful example of 

 this. 



No. 6. The ash-grey coloured portion of this specimen is so 

 perfectly vitreous, that doubts may be entertained whether it 

 should properly be considered obsidian or pumice. The cross 

 fracture resembles obsidian, while that parallel to the stratified 

 arrangement exhibits a pumaceous structure. It is intimately 

 blended with alternate layers of black obsidian, and has, on the 

 whole, a very close resemblance to many of the slags from our 

 glass-houses. 



No. 7. is another specimen composed of alternate layers of 

 black and ash-grey obsidian, so closely united as to afford one 

 uniform mass, with a fine flat conchoidal fracture, and smooth 

 vitreous aspect. This is a rare variety, and certainly the most 

 beautiful I met with. 



No. 8. again, is one of the commonest kinds which the island 

 affords; its matrix is a black obsidian like that of No. 3, but so com- 

 pletely interspersed with the white globules, that it sometimes can 

 scarce be recognised as that mineral. These globules are placed so 

 much in parallel lines, as to give the rock the appearance of strati- 

 fication. 



No. 9. is another very beautiful specimen of the same, in 

 which the globules or spheroids are greatly larger, and more ir- 

 regular. Each of them is coated with a soft white silky sub- 

 stance consisting of silex, which appears to have a fibrous struc- 

 ture radiating towards the centre. A nodule of the same mate- 

 rial occupies the middle of the cavity, but is so slightly attached, 

 or rather occurs so often quite loose, that on breaking the rock it 

 disengages itself, and falls out. When a portion of this specimen 

 is held towards the light, the white globules appear quite opake, 

 while the black matrix is as transparent as bottle-glass. 



No. 10. is the same substance in a more compact state, the 



3 v2 



