42 



salt upon it, thinks it necessary to account for a Tact so 

 hostile to his favourite theory. He says, " the basalts were 

 " all carried off from Vesuvius, to viake Ro?nan roads." 



I will not presume to comment on the conjecture of so 

 zealous a naturalist; and, as he establishes for me the total 

 want of basalt, on this theatre of his repeated observa- 

 tions, I will, in my turn, admit, that he accounts satis- 

 factorily for its disappearance from this volcano. 



But the same conjecture will not account for the Avant 

 of basalt, at the volcanos of Madeira, TenerifT, or the Isle 

 of Amsterdam, which Dr. Gillan examined carefully, with- 

 out noticing a particle of basalt. 



The late Mr, Forster accompanied Captain Cook in his 

 second voj^age, undertaken soon after the publication of 

 Mr. Desmarest's Memoir, and avows his adoption of the 

 volcanic theory ; yet, though Mr. Forster paid the greatest 

 attention, both to basalt, and volcanic productions, he 

 appears never to have found them together in the same 

 place. His testimony bears directly against the confident 

 position of the Academy; for he found undeniable marks, 

 that proved the existence of former volcanos, at St. Jago, 

 at Huaheine, at Bolabola, at Ulietea, at Easter-island, 

 at the Marquesas, at St. Helena, and at Ascension-island. 

 He also found volcanos, actually burning, at Tanna, and 

 at Ambrymm; but at not one of these places does he 

 take notice of any basalt. Yet his observations at Otaheite 

 and New Zealand, shew, that he was well acquainted with 

 it; and, from his having, for a time, mistaken trees for 



basalt 



