79 



Now, this certainti/, that these prisms had been fused, 

 arises solely from the admission of the general position, that 

 all articulated prisms were once fluid lava. Withdraw 

 that admission, and then the total want of any mark of 

 fire, on this petrosilex, is little short of demonstration, that 

 it never had been in fusion. 



For this we have good authority. Mr. Kir wan (Trans. 

 R. I. A. Vol. V. page 7th) tells us, " petrosilex and other 

 " fiftible stones have a quite different aspect, when they 

 " pass through a state of fusion, from that which they 

 " present in their natural state." 



These two circumstances, extracted from Spalanzani's 

 own account of this horrible place (as he calls it), induce 

 me to believe, that these prisms also (though found in so 

 critical a situation, as the crater of an existing volcano), 

 like the others, I have already mentioned, were antece- 

 dent to the first eruption. 



Thus, it appears, that every fact, stated by the advo- 

 cates for the volcanic origin of basalt, when minutely ex- 

 amined, leads to the same conclusion; that the basalts, 

 supposed to be lava, existed, previous to the eruptions, 

 or formation of the volcanos. 



I would be glad to knoif, wliat ideas the advocates 

 for this theory annex, to the terms they are perpetually 

 using; granitic lava, porphjjritic lava, or, as Spalanzani says, 

 petrosilex lava: unless it be, that granite, porpliyry, and 

 petrosilex, were the mother stones, from the fusion of 

 A^ich, these lavas were fonned; and, that the more com- 



L 2 mou 



