madam how and lady why(豪夫人和怀女士)-第33节
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compared with theirs。 One single reef； for instance； which is entirely
made by them； stretches along the north…east coast of Australia for nearly a
thousand miles。 Of this you must read some day in Mr。 Jukes's Voyage
of H。M。S。 〃Fly。〃 Every island throughout a great part of the Pacific is
fringed round each with its coral…reef； and there are hundreds of islands of
strange shapes； and of Atolls； as they are called； or ring…islands； which are
composed entirely of coral； and of nothing else。
A ring…island？ How can an island be made in the shape of a ring？
Ah！ it was a long time before men found out that riddle。 Mr。 Darwin
was the first to guess the answer； as he has guessed many an answer beside。
These islands are each a ring； or nearly a ring of coral； with smooth
shallow water inside： but their outsides run down； like a mountain wall；
sheer into seas hundreds of fathoms deep。 People used to believe； and
reasonably enough； that the coral polypes began to build up the islands
from the very bottom of the deep sea。
But that would not account for the top of them being of the shape of a
ring； and in time it was found out that the corals would not build except in
shallow water； twenty or thirty fathoms deep at most； and men were at
their wits' ends to find out the riddle。 Then said Mr。 Darwin； 〃Suppose one
of those beautiful South Sea Islands； like Tahiti； the Queen of Isles； with
its ring of coral… reef all round its shore； began sinking slowly under the
sea。 The land； as it sunk； would be gone for good and all： but the coral…
reef round it would not； because the coral polypes would build up and up
continually upon the skeletons of their dead parents； to get to the surface
of the water； and would keep close to the top outside； however much the
land sunk inside； and when the island had sunk completely beneath the sea；
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what would be left？ What must be left but a ring of coral reef； around
the spot where the last mountain peak of the island sank beneath the sea？〃
And so Mr。 Darwin explained the shapes of hundreds of coral islands in
the Pacific； and proved； too； some strange things besides （he proved； and
other men； like Mr。 Wallace； whose excellent book on the East Indian
islands you must read some day； have proved in other ways） that there was
once a great continent； joined perhaps to Australia and to New Guinea； in
the Pacific Ocean； where is now nothing but deep sea； and coral…reefs
which mark the mountain ranges of that sunken world。
But how does the coral ever rise above the surface of the water and
turn into hard stone？
Of course the coral polypes cannot build above the high…tide mark； but
the surf which beats upon them piles up their broken fragments just as a
sea…beach is piled up； and hammers them together with that water hammer
which is heavier and stronger than any you have ever seen in a smith's
forge。 And then； as is the fashion of lime； the whole mass sets and
becomes hard； as you may see mortar set； and so you have a low island a
few feet above the sea。 Then sea…birds come to it； and rest and build； and
seeds are floated thither from far lands； and among them almost always
the cocoa… nut； which loves to grow by the sea…shore； and groves of cocoa
palms grow up upon the lonely isle。 Then； perhaps； trees and bushes are
drifted thither before the trade…wind； and entangled in their roots are seeds
of other plants； and eggs or cocoons of insects； and so a few flowers and a
few butterflies and beetles set up for themselves upon the new land。 And
then a bird or two； caught in a storm and blown away to sea finds shelter
in the cocoa…grove； and so a little new world is set up； in which （you must
remember always） there are no four…footed beasts； nor snakes； nor lizards；
nor frogs； nor any animals that cannot cross the sea。 And on some of those
islands they may live （indeed there is reason to believe they have lived）； so
long； that some of them have changed their forms； according to the laws of
Madam How； who sooner or later fits each thing exactly for the place in
which it is meant to live； till upon some of them you may find such strange
and unique creatures as the famous cocoa…nut crab； which learned men call
Birgus latro。 A great crab he is； who walks upon the tips of his toes a
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foot high above the ground。 And because he has often nothing to eat but
cocoa…nuts； or at least they are the best things he can find； cocoa…nuts he
has learned to eat； and after a fashion which it would puzzle you to imitate。
Some say that he climbs up the stems of the cocoa…nut trees； and pulls the
fruit down for himself； but that； it seems； he does not usually do。 What he
does is this： when he finds a fallen cocoa…nut； he begins tearing away the
thick husk and fibre with his strong claws； and he knows perfectly well
which end to tear it from； namely； from the end where the three eye…holes
are； which you call the monkey's face； out of one of which you know； the
young cocoa…nut tree would burst forth。 And when he has got to the eye…
holes； he hammers through one of them with the point of his heavy claw。
So far； so good： but how is he to get the meat out？ He cannot put his
claw in。 He has no proboscis like a butterfly to insert and suck with。 He
is as far off from his dinner as the fox was when the stork offered him a
feast in a long…necked jar。 What then do you think he does？ He turns
himself round； puts in a pair of his hind pincers； which are very slender；
and with them scoops the meat out of the cocoa…nut； and so puts his dinner
into his mouth with his hind feet。 And even the cocoa…nut husk he does
not waste； for he lives in deep burrows which he makes like a rabbit； and
being a luxurious crab； and liking to sleep soft in spite of his hard shell； he
lines them with a quantity of cocoa…nut fibre； picked out clean and fine；
just as if he was going to make cocoa…nut matting of it。 And being also a
clean crab； as I hope you are a clean little boy； he goes down to the sea
every night to have his bath and moisten his gills； and so lives happy all
his days； and gets so fat in his old age that he carries about his body nearly
a quart of pure oil。
That is the history of the cocoa…nut crab。 And if any one tells me that
that crab acts only on what is called 〃instinct〃； and does not think and
reason； just as you and I think and reason； though of course not in words
as you and I do： then I shall be inclined to say that that person does not
think nor reason either。
Then were there many coral…reefs in Britain in old times？
Yes； many and many； again and again； some whole ages older than this；
a bit of which you see； and some again whole ages newer。 But look： then
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judge for yourself。 Look at this geological map。 Wherever you see a bit
of blue； which is the mark for limestone； you may say； 〃There is a bit of
old coral…reef rising up to the surface。〃 But because I will not puzzle
your little head with too many things at once； you shall look at one set of
coral…reefs which are far newer than this bit of Dudley limestone； and
which are the largest； I suppose； that ever were in this country； or； at least；
there is more of them left than of any others。
Look first at Ireland。 You see that almost all the middle of Ireland is
coloured blue。 It is one great sheet of old coral…reef and coral…mud；
which is now called the carboniferous limestone。 You see red and purple
patches rising out of it； like islandsand islands I suppose they were； of
hard and ancient rock； standing up in the middle of the coral sea。
But look again； and you will see that along the west coast of Ireland；
except in a very few places； like Galway Bay； the blue limestone does not
come down to the sea； the shore is coloured purple and brown； and those
colours mark the ancient rocks and high mountains of Mayo and Galway
and Kerry； which stan
