Milford chronicle., 1889-05-31
FORMATION OF ISLANDS.
THEIR CREATION DUE TO VOLCANIC
ERUPTloNs AND OTHER CAUSES.

Observation-Disclosures which Have Been
Blown Up from the Oceans Bottom.
Detached Pieces Of Land.
Your ordinary text hook Of geography,
s'as she Is written" talks bqrely and badly
about the size Of countries, their boundaries,
their rivers and lakes, capes and head lands,
their populations, their religions and their.
chief products These are all facts, no
doubt; but they are facts which resemble
pearls destitute Of any string whereby they
NAV be converted into a necklace and thus
made useful and ornamental both. My be
lief. therefore, leads to the assertion that we
should become more scientido-but not there
by less popular-in our geographical teach
ing in schools; and this very subject Of Islands
shows the way Of reform Science, in this
sense, dives below the bare facts OF the text
books, and seeks 70 give reasons for these
facts It places itself In the position of an
expositor and expounder Of the manner In
which our world and its affairs have come to
assume their existing order.
DUE TO VOLCANIC ACTION.
Geographically, all islands are regarded as
Of much the same constitution They are de-
tached masses Of land, surrounded by sea,
and differing, to the mind Of the sehoelboy
or schoolgirl, chiefly In size. Australia is
big island; Madagascar is not so big, and
from Ceylon onward to Mauritius or the
Azores there are found all degrees and grada-
lions Of magnitude. This, with few details
about the quarters Of the world in which
Hands exist, and with some ideas about pro
ducts and peoples, complete the geographical
knowledge Of the average man and woman.
Science takes up the matter where common
place geography ends its story. It asks, first
Of ALL what Islands really are, and how one
island differs from another. AS a result Of its
Investigations, science soon discovers that
Islands may be divided by their nature into
two distinct sets or Glasses. or these two
divisions, the first includes islands which can
lay claim to that title from the first day of
their existence, in that they have never
formed part and parcel of any larger mass of
land. Thus we first distinguish the so called
''volcanic" islands, which, like the Azores,
have been thrust up from the sea depths by
volcanic action, to form detached masses OF
land existing, 1t may be, many miles from
continent or mainland.
Then comes a second class Of Islands which
are called continental" because, whatever
their size, form or situation, we can prove
them to be geologicslly part and parcel Of a
bigger tract Of land. They are separated and
disjoined fragments, so to speak, Of a larger
land mass Under this head are to be included
many islands we know. The British islands
are simply detached parts Of the European
continent; Just as Trinidad Is fragment Of
South America; or Us the Malay archipelago
represents the broken up land which, once
upon 3 time in its hale and solid state con-
.,.,&,I Aefo o,,d Australia Eryau Navry Tnn-
land and Madagascar are continental islands
In their way, although the exact dates Of
their separation may be very hard to trace in
the mists Of geological time
THE DIFFERENCE SCIENTIFICALLY EXPLAINED
Having thus succeeded In Distinguishing
between islands which, like st. Helena, the
Azores, the Galapagos and so forth, represent
the eruptions into the earth's outside mass Of
volcanic matter, and those which, like Brit
ain, Trinidad and the West Indies, are really
the detached pieces Of large land tracts, it be-
hooves US to inquire further into the history
Of each group They are separated from
their mainlands, It may be, by abysses of
ocean On the other hand the continental
Islands have, relatively, shallow seas separat-
ing them from their nearest continents.
Witness, to prove this statement, tho Ger
man ocean, the English channel, the sea be-
tween Trinidad and America or the general
depth Of the seas around the Malayan Isl
Ands. We find test not only Of the nature
Of an island In the depth Of the seas around it
apart from its rock structure-but in the
case Of the continental islands we can assure
ourselves Of the length of time they have
been separated from their mainlands by hav-
ing regard to the same matter Of ocean deep
mesa
The Azores, as volcanic Islands, are thus
separated from Portugal by sea varying
FROM 1000 to Z, 800 fathoms Within short
distance from tho islands themselves the sea
Is about 1000 fathoms deep; within 800 miles
II e 1, 800 fathoms and soon deepens to 2, 800.
With the Bermudas the case Is similar; some
$50 miles of we reach the sea bottom at
S,S25 and 8, sT5 fathoms st. Helena has sea
OF 2, 500 fathoms deep between 1t and Africa,
some LOO miles Of Contrariwise, the sea
around our own shores Is comparatively shall
low; but, as / have remarked, whenever a
continental island shows, like Madagascar, q
deep channel between it and Its main land;
the story such depth tells US is one Of long de-
tlchmept from the mother country.
PLANT AND ANIMAL LIFE
So far, islands have shown US that geologic.
ally their history Is interesting in respect Of
Not less interesting Is the additional evidence
about islands which their animals and plants
have to tell. Whence, let us ask, have de-
tAched Islands, like the Azores, obtained their
animals and plantsi Upraised from the sea
bsd, IS have been these islands, their living
population must have been derived from
other and previously peopled lands. This sup
position is confirmed by our finding that on
ths AsOres we discover no animals or plants
excluding those Of mans Introduction
which are not found on the Portuguese coast.
The rabbits, Weasels, mice and single kind
Of lizard found In the Azores are importa-
tonR
The birds which, Of course, can fly over the
intervening sea, are those Of Europe; such
aleo are the insects, and such, again, are the
plants. In a word, there Is nothing about
The animals and plants Of the Azores which
No cannot explain by reference to their Eu-
ropean origin. Then also, on such detached
Islands, we cannot expect to find native
quadrupeds or frogs; for these animals viii
not face and brave long swim in the sea.
In a word It Is precisely those animals and
plants which have ways and means Of con
veyance over tracts Of sea which people
these distant islands and come to live and
flourish thereon.
Very different Is the case with our CONT
mental islands Here the animals and plants
are those OF the adjacent mainland, altered
and modified only IN 50 far as the length of
the separation OF the islands indicates and
allows Our British animals and plants are
those Of the continent, and the life Of Trim
dad Is that Of South America, because there
has been no tune, practically, for change.
But In Madagascar, Australia and New zea-
land, as islands long separated, each from Its
mainland, We find living things utterly I'M
Ike the great land mass from which each
island was derived Thus it Is that together
geology and biology teach US much about
islands Of which geography takes no heed =
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