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fulphureous fumes; and when lavas are 

 fituated around or within there, they will 

 be more or lefs afFeded by them. But in 

 the fame tradis of ground there are more 

 places than one impenetrable to thefe fumes, 

 and there, in confequence, the lavas fuffer 

 no other alterations than thofe produced by 

 time. Thefe interrupted exhalations of ful- 

 phureous vapours I have obferved at Vefu-» 

 vine, Etna, and Stromboli, and have noticed 

 them before in my accounts of thefe vol- 

 canos. It is only to be remarked that, at 

 the Stoves of Lipari, the quantity of decom- 

 pofed lavas being very great, and extending 

 for the moft part to a great depth, the ful- 

 phureous-acid vapours muft have there if» 

 fued in extraordinary abundance, and at the 

 fame time have been of long duration. The 

 intenfity of them, and their confequently 

 greater efficacy, might, indeed, have fup- 

 plied the place of long continuance ; for I 

 have obferved, that when the lava of Vefu* 

 vius flowed before my eyes, and feveral 

 of its lateral branches had ceafed to move, 

 two of thefe, which had been penetrated 

 E a by 



