148 R E M A R K S o n t h e
D IM I N U T
I O N OF
T H E S E A .
habitations o f the natives. It appears therefore evidently, either
that the water had receded, or that thefe objects-had- been, raifed
above water; but what might be the caufe o f either, I will not
pretend to decide. It might be owing to the receflion. o f the fea,
and its gradual, yearly diminution. ■ But an earthquake,., and a.
fubterranegus fire, are moll likdly to have raifed thefe lithophytes,,
and parts o f the neighbouring ifle above water.-
S E C T I O N IV..'
T h e T H E O R Y o f the F O R M A T IO N o f ISLES.
F O R M A T
I O N OF
I S L E S .
T J A V I N G thus offered a few remarks on the various: changes off
thofe parts o f the globe, which we vifited during our circumnavigation,
I might here leave the fubjeCt, were it not. in fome
meafure neceffary, to add a few obfervations, which may ferve to.
eftablilh a theory for the formation'of the tropical ifles in the
South-Sea,
When we'firft came within the tropics in 1 7 7 3 , I applied particularly
to ftudy the conflitution and nature o f the tropical ifles.
When we vifited them-again in 1774, I added- many more obfervations
; and, after all, I found the nature o f thefe ifles to be .juft
fuch as I reprefented them in ths feCtion, where I deferibed the-
lands we had fallen in with.
W e found low ifles, connected by reefs o f coral rocks; we met
with iflands more elevated, lome without a reef, and others fur-
rounded by a reef o f lithophytes..
A ll the low ifles feem to me to be a production of the fea, or rather
its inhabitants, the polype-like animals forming the litho-
phy.tes. Thefe animalcules raife their habitation gradually from a
fmall bafe, always fpreading more and more, in proportion as the.
ftruCture grows higher. Th e materials are a kind o f lime mixed
with Tome animal fiibftance. ’ I. have feen thefe large fixuCtures in
all ftages, and.of various, extent. Near Turtle-Iiland, we found, at
a few miles' diftance, and to leeward of it, a confiderable large circular
reef, , over which the fea broke every where,. and no part of it
was above water ■ it included a large,, deep lagoon. T o the Eaft and
North-Eafl of the- Society-Ifles,. are a great many ifles,: which, in.
fome parts, are above water ; in others, the elevated parts are connected
by reefs, fome of whichare dry at low-water,, and others.are
conftantly under water.. Th e elevated parts, confift o f a foil formed
by afand o f fhells and coral rocks, mixed, with a light black-mould,
produced from putrefied vegetables,, and the dung of fea-fowls ; and.
are commonly covered by coco-put trees and other fhrubs,. and a
few antifcorbutic plants'. Th e lower parts have only a few fhrubs,
and the above plants; others ftill lower, are walked by the fea at
high-water. A ll thefe ifles are' connected, and include a lagoon in
F O R M A T
IO N OF
I S L E S . .