282 'THEORY of the EARTH. 



true ; but naturalifts, imagining that there are no other marks 

 of fubterraneous fire and fufion, except in the production of a 

 lava, attribute to a volcano, as a caufe, thefe effects, which only 

 indicate the exertion of that power which might have been the 

 caufe of a volcano. 



IF the theory now given be juft, a rock of marble is no lefs 

 a mark of fubterraneous fire and fufion, than that of the ba- 

 faltes ; and the flowing of bafaltic flreams among ftrata broken 

 and difplaced, affords the mofl fatisfatflory evidence of thofe 

 operations by which the body of our land had been elevated 

 above the furface of the fea ; but it gives no proof that the 

 eruptive force of mineral vapours had been difcharged in a 

 burning mountain. Now, this difcharge is eJTential in the pro- 

 per idea of a volcano. 



BESIDES this internal mark of an unerupted lava in the fub- 

 ftance of the ftone or body of the flowing mafs, there are 

 others which belong to it in common with all other mineral 

 ftrata, consolidated by fubterraneous fire, and changed from, 

 the place of their original formation ; this is, the being broken 

 and diflocated, and having veins of foreign matter formed in 

 their feparations and contractions. 



IF thefe are mineral operations, proper to the lower regions 

 of the earth, and exerted upon bodies under immenfe compref- 

 fion, fuch things will be fometimes found in the unerupted 

 lavas, as well as in the contiguous bodies with which they are 

 aflbciated. If, on the contrary, thefe are operations proper to 

 the furface of the earth, where the diflblving power of water 

 and air take place, and where certain ftala&ical and ferruginous 

 concretions are produced by thefe means ; then, in erupted lavas, 

 we mould find mineral concretions, which concretions fhould 

 be denied to bodies which had been confolidated at the bottom 

 of the fea ; that is to fay, where, without the operation of fub- 

 terraneous fire, no changes of that kind could have taken 

 place, as has already been obferved. But in the unerupted fpe- 



cies 



