( z^z ) 



JriAVING finifhed the defcriptlon of the 

 products I obferved in my excurfion to the 

 Euganean mountahis, I might confider my 

 Volcanic travels as concluded ; br.t agree- 

 ably to the plan I propofed to myfelf in the 

 Introdudion to this work, it ftill remains 

 for me to difcufs fome particulars which 

 have a relation to volcanos in general, and 

 are too intimately conneded with the fub- 

 jeds hitherto treated of to be omitted, 

 without juftly incurring the blame of the 

 reader. In various parts of this work men- 

 tion has been made of the gafes of volcanos. 

 It has been fhown that, by their elafticity, 

 ftony fubftances fufed in the fire are rare- 

 fied, inflated, and become cellular ; as is 

 proved by a great number of lavas, glaiTes 

 and enam.els. We have feen that, by the 

 violence of thefe gafes, the liquefied matters 

 are haftily raifed from the bottom of the 

 craters to the top, filling their whole in- 

 ternal capacity, and flowing over their 

 fides ; fmce, by the adion of the fame 

 gafes, we frequently obferve fimilar pheno- 

 Y 2 mena 



