1 66 TRAVELS THROUGH 



and there is no doubt of their having been origi- 

 nally lavas arid afties of the ancient volcano, pene- 

 trated by the ho: fleams of fulphureous acid, and 

 by them changed into an argillaceous nature. Mr. 

 Beaume, a very fkilfu! and learned chemift at Pa- 

 ris, has deduced *, from a great many afiays, and 

 from a great many experiments, that clays are 

 produced by a clofe conned ion of fulphureous 

 acid, with vitrefcent or vitreous earth. . The afhes 

 and lavas of the ancient Soltatara volcano have 

 been undoubtedly, as every other volcanic lavas or 

 afhes, of a vitreous or virrefcent nature, and thefe 

 appear at prefent changed and argillaceous. Some 

 fragments of this lava are but half or at one fide 

 changed into clay, which either is vifcid or duc- 

 tile, or hard and ftony, and refembling a white 

 limeftone. In fome appear ftill the forms of the 

 old inclofed white garnet- fherls, which are fo com- 

 mon in the Italian lavas ; and are likewiie in this 

 Solfatara clay changed and argillaceous f. Gene- 



* In His Treatife on clays. 



j- I have noticed already that thefe fherl-cryftalHzations 

 appear very often in the moil ancient lavas opaque, milky, 

 and friable into a white powder, which is argillaceous, and 

 owing to the acid of the air. \ cannot Kelp obfervitig here, 

 that the white or coloured potters and china clays and boles, 

 in the Vicentine volcanic countries, may be volcanic mate- 

 rials, changed into clay by iubterraneous fulphur acid. 



rail/ 



