( 273 ) 



cannot pronounce with certainty relative to 

 its origin. It is poffible that this glals may 

 be the produdi .n of thofe very ancient vol- 

 canos, fince Sir John Strange, at number 61 

 of his Catalogue before cited, mentions 

 fome pieces of fofTil glafs, but winch are fo- 

 iitary and accidental, found in fome parts of 

 the Euganean mountains. It is not, how- 

 ever, dbfolutely impoffible but that it may 

 be glafs from the furnace ; at leafl: the 

 acci.lent of the glafs of Murano ought to 

 teach us to be cautious, and fufpend our 

 judgnnent relative to the queftion, whether 

 a mountain may have been volcanic or not, 

 when we have no other proof than finding 

 a loofe piece of glafs, fcoria, or other fab- 

 ftance deriving its origin frc^m fire, while 

 we are uncertain whether that fire was, or 

 was not, volcanic. For, even though the 

 pieces found (hould be really volcanic, they 

 cannot afford a certain proof of the volcani- 

 zation of the place wh.re they are found 

 detached. Of this 1 can produce an inftance 

 which happened to myfelf in a curfory vifit 

 that 1 made to Capo Colonne, a promontory 

 VOL. fii. T of 



