Island Life; Or, The Phenomena and Causes of Insular Faunas and FlorasWallace, Alfred Russel
Science
Island Life; Or, The Phenomena and Causes of Insular Faunas and Floras
Wallace, Alfred Russel
Biogeography; Glacial epoch; Island ecology
_The Red Clay of Bermuda._--Besides the calcareous rocks there is found in
many parts of the islands a layer of red earth or clay, containing about
thirty per cent. of oxide of iron. This very closely resembles, both in
colour and chemical composition, the red clay of the ocean floor, found
widely spread in the Atlantic at depths of from 2,300 to 3,150 fathoms, and
occurring abundantly all round Bermuda. It appears, therefore, at first
sight, as if the ocean bed itself has been here raised to the surface, and
a portion of its covering of red clay preserved; and this is the view
adopted by Mr. Jones in his paper on the "Botany of Bermuda." He says,
after giving the analysis: "This analysis tends to convince us that the
deep chocolate-coloured red clay of the islands found in the lower levels,
and from high-water mark some distance into the sea, originally came from
the ocean floor, and that when by volcanic agency the Bermuda column was
raised from the depths of the sea, its summit, most probably broken in
outline, appeared above the surface covered with this red mud, which in the
course of ages has but slightly changed its composition, and yet possesses
sufficient evidence to prove its identity with that now lying contiguous to
the base of the Bermuda column." But in his _Guide to Bermuda_ Mr. Jones
tells us that this same red earth has been found, two feet thick, under
coral rock at a depth of forty-two feet below low-water mark, and that it
"rested on a bed of compact calcareous sandstone." Now it is quite certain
that this "calcareous sandstone" was never formed at the bottom of the deep
ocean 700 miles from land; and the occurrence of the red earth at different
levels upon coralline sand rock is therefore more probably due to some
process of decomposition of the rock itself, {266} or of the minute
organisms which abound in the blown sand.[55]
_Zoology of Bermuda._--As might be expected from their extreme isolation,
these islands possess no indigenous terrestrial mammalia, frogs, or
snakes.[56] There is however one lizard, which Professor Cope considers to
be distinct from any American species, and which he has named _Plestiodon
(Eumeces) longirostris_. It is said to be most nearly allied to _Eumeces
quinquelineatus_ of the south-eastern States, from which it differs in
having nearly ten more rows of scales, the tail thicker, and the muzzle
longer. In colour it is ashy brown above, greenish blue beneath, with a
white line black-margined on the sides, and it seems to be tolerably
abundant in the islands. This lizard is especially interesting as being the
only vertebrate animal which exhibits any peculiarity.
Public-domain text, read in full here on John Shaqi.
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