Geology of St. Helena. 303 



a portion of an archipelago, which was destroyed by volcanic 

 fires, leaving alone this fragment ? 



" After this passage was written I became acquainted with 

 Mr. Andrew Blaxam, a very ingenious young gentleman, who 

 accompanied the Right Hon. Lord Byron in His Majesty's 

 ship Blonde on a mission to Valparaiso and the Sandwich Is- 

 lands. Warmed by a love of science, and peculiarly devoted 

 to geological studies, at my request Mr. Blaxam drew up a 

 memorandum of the remarks which he was able to make du- 

 ring such a cursory inspection as his short stay permitted. I 

 have much pleasure in reading these remarks to the society, 

 as they are valuable, and may be a foundation for any future 

 geological account of this remarkably formed island. 



" ' The island of St. Helena is peculiarly situated in the 

 South Atlantic; and, like other islands in the same ocean, is 

 entirely volcanic. The external appearance of it presents a 

 forbidding and dreary aspect, on account of the rugged and 

 steep cliffs of lava that surround the island, and form a barrier 

 to the waves. Many of these are regularly stratified by several 

 successive deposits of volcanic matter, and in some places veins 

 of a red sandy appearance are visible. In the interior of the 

 island, the valleys and ridges are composed of basaltic lava in 

 its most compact state, together with cellular and other varieties, 

 and indeed in almost every stage of decomposition. Obsidian 

 or pumice-stone has never, I believe, been found here. 



" 'All the valleys and intermediate ridges appear to concen- 

 trate in one large basin on the south side of the island, which 

 is evidently a part of the volcanic crater from whence this in- 

 sulated mass has been formed. The ridge termed Diana's 

 Peak (the highest spot in the island), forms one edge of this 

 crater : it is entirely composed of lava, but the greater part of 

 it being in a high state of decomposition, possesses great depth 

 of vegetable soil, and is necessarily one of the most fertile 

 spots upon the island : here the indigenous cabbage- tree par- 

 ticularly flourishes; here also are found brambles, with a 

 variety of ferns and other plants, together with shrubs and 

 trees. This ridge, as it approaches the sea, inclines towards it; 

 so that we may suppose the remaining ridge, which is wanting 

 to form the edge of the complete crater, lies buried in the sea. 



" ' The spot known by the name of Sandy Bay, and the 

 fantastical and abrupt pointed rocks in the immediate neigh- 

 bourhood of that place, have, without doubt, suffered much 

 from volcanic agency ; and it is a curious fact, that a calcareous 

 earth, or lime-stone, is found there from which good lime is 

 procured and burnt, sufficient for all purposes of masonry. 



" < The 



