CHAP. XIV.] 
ST. HELENA. 
283 
northern rim forms the highest and central ridge of the island. 
Many other hills and peaks, however, are more than two thousand 
feet high, and a considerable portion of the surface consists of a 
rugged plateau, having an elevation of about fifteen hundred to 
two thousand feet. Everything indicates that St. Helena is an 
isolated volcanic mass built up from the depths of the ocean. 
Mr. Wollaston remarks : “ There are the strongest reasons for 
believing that the area of St. Helena was never very much larger 
than it is at present — the comparatively shallow sea-soundings 
within about a mile and a half from the shore revealing: an 
abruptly defined ledge, beyond which no bottom is reached at a 
depth of 250 fathoms ; so that the original basaltic mass, which 
was gradually piled up by means of successive eruptions from 
beneath the ocean, would appear to have its limit definitely 
marked out by this suddenly-terminating submarine cliff — the 
space between it and the existing coast-line being reasonably 
referred to that slow process of disintegration by which the 
island has been reduced, through the eroding action of the 
elements, to its present dimensions.” If we add to this that 
between the island and the coast of Africa, in a south-easterly 
direction, is a profound oceanic gulf known to reach a depth of 
2,860 fathoms, or 17,160 feet, while an equally deep, or perhaps 
deeper, ocean, extends to the west and south-west, we shall be 
satisfied that St. Helena is a true oceanic island, and that it 
owes none of its peculiarities to a former union with any 
continent or other distant land. 
Change effected by European occupation. — When first dis- 
covered, 378 years ago, St. Helena was densely covered with a 
luxuriant forest vegetation, the trees overhanging the seaward 
precipices and covering every part of the surface with an ever- 
green mantle. This indigenous vegetation has been almost 
wholly destroyed ; and although an immense number of foreign 
plants have been introduced, and have more or less completely 
established themselves, yet the general aspect of the island is 
now so barren and forbidding that some persons find it difficult 
to believe that it was once all green and fertile. The cause of 
the change is, however, very easily explained. The rich soil 
formed by decomposed volcanic rock and vegetable deposits 
