xii INTRODUCTORY CHAPTER. 



sand with specks, here and there coral, and at one or two places, 

 rock. But; in sounding to the westward the surface was found 

 by Captains Cowan and Beville* more irregular ; and apparently 

 resembling the surface of the island, consisting of hollows and 

 ridges- 



Hence it is evident that this island, resting upon a base, which 

 extends at least 25 miles from east to west, is not " a rock rising 

 " abruptly," as had been erroneously supposed ; but is rather the 

 pinnacle of a prominence in the bed of the ocean, gradually 

 ascending, from unfathomable depths, to 2700 feet above water : 

 which is the elevation of Diana's Peak, the highest mountain on 

 the island. 



This deduction seems consonant to the opinions of some theo- 

 rists, who have considered " islands as the tops of lofty mountains ; 

 " the eminences of a great continent, converted into islands by a 

 " tremendous concussion of nature :"t but whether the circum- 

 stances, above stated, may be in any way useful to geologists, or 

 whether they may throw further light upon the origin and for- 

 mation of islands, or lead to new conjectures upon the probable 

 site of the Atlantica Insula, mentioned by Plato, to have been 

 partially destroyed by an earthquake and deluge, I shall not 

 presume to say. 



If, however, any large island ever did exist in the part of the 

 Atlantic under consideration, it might be inferred, according to 

 those theorists, that the islands of St. Helena, Ascension, Sax- 

 cmberg, Tristan d'Acunha, and Gough's Island, may have been 

 its " lofty mountains and eminences ;" and that the whole space 

 within that chain of islands, which is 1800 miles in length, and 

 about 500 in breadth, has been sunk into the sea. 



* Commanders of the Camperdowii cutter, 

 ■f- L'Abb^ Raynal, L'Abbe Pluche, and others. 



