Position and Physical Features of St. Helena--Change Effected by
European Occupation--The Insects of St.
Helena--Coleoptera--Peculiarities and Origin of the Coleoptera of St.
Helena--Land-shells of St. Helena--Absence of Fresh-water
Organisms--Native Vegetation of St. Helena--The Relations of the St.
Helena Compositae--Concluding Remarks on St. Helena.

In order to illustrate as completely as possible the peculiar phenomena of
oceanic islands, we will next examine the organic productions of St. Helena
and of the Sandwich Islands, since these combine in a higher degree than
any other spots upon the globe, extreme isolation from all more extensive
lands, with a tolerably rich fauna and flora whose peculiarities are of
surpassing interest. Both, too, have received considerable attention from
naturalists; and though much still remains to be done in the latter group,
our knowledge is sufficient to enable us to arrive at many interesting
results.

{293} [Illustration: MAP OF THE SOUTH ATLANTIC OCEAN SHOWING THE POSITION
OF ST. HELENA.]

The light tint shows depths of less than 1,000 fathoms.
The figures show depths of the sea in fathoms.

_Position and Physical Features of St. Helena._--This island is situated
nearly in the middle of the South Atlantic Ocean, being more than 1,100
miles from the coast of Africa, and 1,800 from South America. It is about
ten miles long by eight wide, and is wholly volcanic, consisting of ancient
basalts, lavas, and other volcanic products. It is very mountainous and
rugged, bounded for {294} the most part by enormous precipices, and rising
to a height of 2,700 feet above the sea-level. An ancient crater, about
four miles across, is open on the south side, and its 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 fa