272 DESCRIPTION OF THE MUSEUM. 



The last class is that of rocks incontestably 

 volcanic ; in which we see, not only vitreous 

 and scorified substances, which clothe the upper 

 and lower surfaces of the current of lava, but 

 also the materials which constitute the internal 

 masses of these currents ; substances which, in 

 coagulating more slowly than those of the sur- 

 face, produce aggregates of a stony aspect, and 

 so similar to crystallized rocks of ancient forma- 

 tion, that unless apprised of the fact, we should 

 be in danger of considering them as such. 



We will terminate the examination of this 

 room by noticing the works of art, which are 

 for the present placed in the five cases to the left 

 on entering. 



On the first shelf, the uppermost, we see four 

 large vases of the Vesuvian lava, a large and 

 beautiful cup of limpid rock crystal, a large slab 

 of greenish serpentine, and a mirror of black 

 obsidian similar to those used by the Peruvians 

 before their conquest by the Spaniards. 



On the second shelf are several cups of agate, 

 chalcedony, and jasper of different colours, an- 

 other of rock crystal, and one of violet-coloured 

 fluate of lime, two of greenish jade, a vase of the 

 same matter, and a small one of lapis-lazuli. 



On the third shelf we find a numerous suite of 

 small slabs of jasper, agate and chalcedony, a row 



