IJJO TRAVELS THROUGH 



aflies have gone further, even to Africa, Syria, 



and Egypt. 



: This I think may be fufficient of the fnerl- 



cryftallizations inclofed in the lavas ; and will be 



probably confirmed by my nearer examination of 



the ancient volcanos, near Rome, J/ilerbo, and 



Bolfena. 



Befides them, the black comparer lava con- 

 tains fmall pebbles, of a black, cryfolite-green, 

 emerald-green, dark-green, hyacinth, and topaz- 

 yellov/ colour. They are in nothing differing 

 from the lava fherls, but in their greater hardnefs 

 and a want of a regular form. They are true 

 flints (/ilices), or natural hard vitrifications or 

 frittasj exactly agreeing .with the hyacinths, cry- 

 folites, and pietre obfidiane, in the Vicentine 

 lavas j and, in fome refpecl, deferving the deno- 

 mination of gems, though their hue be fcarce 

 comparable to the colours of the true precious 

 ftones; which, being produced by an avueous cryf- 

 tallization, are on no account above the fherls, 

 but on account of their greater hardnefs and 

 refractor inefs (fcbwerfiijfigkeil) to the fire a 

 circumftance, which cauied Mr. Cronftedt (Mine- 

 ralcg. 63,) to feparate the garnets and fherls- 

 from the quartz and horn-ilones (filices), and 

 plainly (hews, that the denomination fine and pre- 

 cious ftones, is rather a hint of their conventional. 

 7 orna- 



