[ 3^1 ] 



namely, fubterraneous fire and explofion ; and this we muft con- 

 ceive to have operated, in the prefent cafe, with an eruptive 

 force much exceeding whatever has been experienced in the known 

 hiflory of volcanoes*. 



I HAVE chofen to reprefent the feparation of thefe maffes, 

 from the ftratum of which they formed a part., as brought about, 

 rather by their having been heaved up to their prefent fituation 

 from an inferior one, than by their having been left where they 

 r.re, while the reft of the ftratum was funk; but I ftiall not 

 trouble the Academy with the reafons that led me to the one 

 conclufion in preference to the other, as the principal point of 

 enquiry is the nature or quality of the caufe, not its precife 

 mode of operation. Now, whatever may have been the manner 

 in which the effects were produced, the immediate caufe muft, 

 in any cafe, have been one of great violence ; and there are* 

 many reafons, befides fufficiency of force, to conclude it volcanic. 



It is remarkable that, except thefe quarries, nothing of the 

 ftratum to which they belonged is left, not a trace having yet 

 been difcovercd, either at Bolca or in its neighbourhood, to 

 indicate where fuch a ftratum had ever exifted ; all is covered 

 with argillaceous materials, the fuppofed lavas and other ejeflions 

 of ancient fubmarine volcanoes : but this circumftance, until 



Q q 2 it 



* If thefe effefts are fuppofed to have been produced in air, the forces applied 

 luft have been immenfe ; if under water, much lefs would have fufficed. 



