78 



" in its lengfli, into articulate prisms: the lava, in which 

 " the}^ were, descended to the ground, and was incon- 

 " siderable." 



I must observe, that Spalanzani, as well as other ad- 

 vocates for the volcanic origin of basalt, generally uses 

 the terms, lava, and basalt, as synonimous; and that Spa- 

 lanzani talks of the volcanos of Ireland, and of Antrim, 

 Avith as much ease as Mr. St. Fond, or any of them. 



The very critical situation, in which these prisms were 

 found, to wit, the bottom of an unquestioned crater, 

 will, I hope, procure my excuse, for entering into a mi- 

 nute investigation of the circumstances attending them, 

 as related by the Abbe himself; and I will argue from 

 his own facts alone. 



Had this lava been melted in the crater, accompanied 

 by an effervescence, and then a retraife, to which Spa- 

 lanzani ascribes the formation of the pillars; it must have 

 obeyed the laws of other fluids, and assumed an hori- 

 zontal level: but never could have formed a narrow, ver- 

 tical stripe, the lava of which scarcely reached to the bottom 

 of the crater. 



The material, too, of which these prisms were composed, 

 is very important. Their base, Spalanzani says, was petro- 

 silex : that he was well acquainted with such lavas ; in all 

 of which, the ■pctrosilex bore strong marks of fire. On the 

 contrary, the petrosilcx, in these prisms, had not suffered 

 the slightest alteration from the fire, although it is very 

 certain they had been fused. 



Now, 



