NATURE.
IN this chapter I propose to give a general sketch of the physical
geography of the Aru Islands, and of their relation to the surrounding
countries; and shall thus be able to incorporate the information
obtained from traders, and from the works of other naturalists with
my own observations in these exceedingly interesting and little-known
regions.
The Aru group may be said to consist of one very large central island
with a number of small ones scattered round it. The great island is
called by the natives and traders "Tang-busar" (great or mainland), to
distinguish it as a whole from Dobbo, or any of the detached islands. It
is of an irregular oblong form, about eighty miles from north to south,
and forty or fifty from east to west, in which direction it is traversed
by three narrow channels, dividing it into four portions. These channels
are always called rivers by the traders, which puzzled me much till I
passed through one of them, and saw how exceedingly applicable the
name was. The northern channel, called the river of Watelai, is about
a quarter of a mile wide at its entrance, but soon narrows to abort the
eighth of a mile, which width it retains, with little variation, during
its whole, length of nearly fifty miles, till it again widens at its
eastern mouth. Its course is moderately winding, and the hanks are
generally dry and somewhat elevated. In many places there are low cliffs
of hard coralline limestone, more or less worn by the action of water;
while sometimes level spaces extend from the banks to low ranges of
hills a little inland. A few small streams enter it from right and left,
at the mouths of which are some little rocky islands. The depth is
very regular, being from ten to fifteen fathoms, and it has thus every
feature of a true river, but for the salt water and the absence of a
current. The other two rivers, whose names are Vorkai and Maykor, are
said to be very similar in general character; but they are rather near
together, and have a number of cross channels intersecting the flat
tract between them. On the south side of Maykor the banks are
very rocky, and from thence to the southern extremity of Aru is
an uninterrupted extent of rather elevated and very rocky country,
penetrated by numerous small streams, in the high limestone cliffs
bordering which the edible birds' nests of Aru are chiefly obtained.
All my informants stated that the two southern rivers are larger than
Watelai.
The whole of Aru is low, but by no means so flat as it has been
represented, or as it appears from the sea. Most of it is dry rocky
ground, with a somewhat undulating surface, rising here and there
into abrupt hillocks, or cut into steep and narrow ravines. Except the
patches of swamp which are found at the mouths of most of the small
rivers, there is no absolutely level ground, although the greatest
elevation is probably not more than two hundred feet. The rock which
everywhere appears in the ravines and brooks is a coralline limestone,
in some places soft and pliable, in others so hard and crystalline as to
resemble our mountain limestone.
The small islands which surround the central mass are very numerous;
but most of them are on the east side, where they form a fringe, often
extending ten or fifteen miles from the main islands. On the west there
are very few, Wamma and Palo Pabi being the chief, with Ougia, and
Wassia at the north-west extremity. On the east side the sea is
everywhere shallow, and full of coral; and it is here that the
pearl-shells are found which form one of the chief staples of Aru trade.
All the islands are covered with a dense and very lofty forest.
The physical features here described are of peculiar interest, and, as
far as I am aware, are to some extent unique; for I have been unable
to find any other record of an island of the size of Aru crossed
by channels which exactly resemble true rivers. How these channels
originated were a complete puzzle to me, till, after a long
consideration of the whole of the natural phenomena presented by
these islands, I arrived at a conclusion which I will now endeavour to
explain. There are three ways in which we may conceive islands which
are not volcanic to have been formed, or to have been reduced to their
present condition, by elevation, by subsidence, or by separation from
a continent or larger island. The existence of coral rock, or of raised
beaches far inland, indicates recent elevation; lagoon coral-islands,
and such as have barrier or encircling reefs, have suffered subsidence;
while our own islands, whose productions are entirely those of the
adjacent continent, have been separated from it. Now the Aru Islands are
all coral rock, and the adjacent sea is shallow and full of coral, it is
therefore evident that they have been elevated from beneath the ocean
at a not very distant epoch. But if we suppose that elevation to be the
first and only cause of their present condition, we shall find ourselves
quite unable to explain the curious river-channels which divide them.
Fissures during upheaval would not produce the regular width, the
regular depth, or the winding curves which characterise them; and the
action of tides and currents during their elevation might form straits
of irregular width and depth, but not the river-like channels which
actually exist. If, again, we suppose the last movement to have been
one of subsidence, reducing the size of the islands, these channels
are quite as inexplicable; for subsidence would necessarily lead to
the flooding of all low tracts on the banks of the old rivers, and thus
obliterate their courses; whereas these remain perfect, and of nearly
uniform width from end to end.
Now if these channels have ever been rivers they must have flowed from
some higher regions, and this must have been to the east, because on the
north and west the sea-bottom sinks down at a short distance from the
shore to an unfathomable depth; whereas on the east, a shallow sea,
nowhere exceeding fifty fathoms, extends quite across to New Guinea, a
distance of about a hundred and fifty miles. An elevation of only three
hundred feet would convert the whole of this sea into moderately high
land, and make the Aru Islands a portion of New Guinea; and the rivers
which have their mouths at Utanata and Wamuka, might then have flowed on
across Aru, in the channels which are now occupied by salt water.
Then the intervening land sunk down, we must suppose the land that
now constitutes Aru to have remained nearly stationary, a not very
improbable supposition, when we consider the great extent of the
shallow sea, and the very small amount of depression the land need have
undergone to produce it.
But the fact of the Aru Islands having once been connected with New
Guinea does not rest on this evidence alone. There is such a striking
resemblance between the productions of the two countries as only exists
between portions of a common territory. I collected one hundred species
of land-birds in the Aru Islands, and about eighty of them, have been
found on the mainland of New Guinea. Among these are the great wingless
cassowary, two species of heavy brush turkeys, and two of short winged
thrushes; which could certainly not have passed over the 150 miles of
open sea to the coast of New Guinea. This barrier is equally effectual
in the case of many other birds which live only in the depths of the
forest, as the kinghunters (Dacelo gaudichaudi), the fly-catching wrens
(Todopsis), the great crown pigeon (Goura coronata), and the small wood
doves (Ptilonopus perlatus, P. aurantiifrons, and P. coronulatus).
Now, to show the real effect of such barrier, let us take the island of
Ceram, which is exactly the same distance from New Guinea, but separated
from it by a deep sea. Cut of about seventy land-birds inhabiting Ceram,
only fifteen are found in New Guinea, and none of these are terrestrial
or forest-haunting species. The cassowary is distinct; the kingfishers,
parrots, pigeons, flycatchers, honeysuckers, thrushes, and cuckoos, are
almost always quite distinct species. More than this, at least twenty
genera, which are common to New Guinea and Aru, do not extend into
Ceram, indicating with a force which every naturalist will appreciate,
that the two latter countries have received their faunas in a radically
different manner. Again, a true kangaroo is found in Aru, and the same
species occurs in Mysol, which is equally Papuan in its productions,
while either the same, or one closely allied to it, inhabits New Guinea;
but no such animal is found in Ceram, which is only sixty miles from
Mysol. Another small marsupial animal (Perameles doreyanus) is common
to Aru and New Guinea. The insects show exactly the same results. The
butterflies of Aru are all either New Guinea species, or very slightly
modified forms; whereas those of Ceram are more distinct than are the
birds of the two countries.
It is now generally admitted that we may safely reason on such facts
as those, which supply a link in the defective geological record. The
upward and downward movements which any country has undergone, and the
succession of such movements, can be determined with much accuracy;
but geology alone can tell us nothing of lands which have entirely
disappeared beneath the ocean. Here physical geography and the
distribution of animals and plants are of the greatest service. By
ascertaining the depth of the seas separating one country from another,
we can form some judgment of the changes which are taking place. If
there are other evidences of subsidence, a shallow sea implies a former
connexion of the adjacent lands; but if this evidence is wanting, or if
there is reason to suspect a rising of the land, then the shallow
sea may be the result of that rising, and may indicate that the two
countries will be joined at some future time, but not that they have
previously been so. The nature of the animals and plants inhabiting
these countries will, however, almost always enable us to determine this
question. Mr. Darwin has shown us how we may determine in almost every
case, whether an island has ever been connected with a continent or
larger land, by the presence or absence of terrestrial Mammalia and
reptiles. What he terms "oceanic islands" possess neither of these
groups of animals, though they may have a luxuriant vegetation, and a
fair number of birds, insects, and landshells; and we therefore conclude
that they have originated in mid-ocean, and have never been connected
with the nearest masses of land. St. Helena, Madeira, and New Zealand
are examples of oceanic islands. They possess all other classes of life,
because these have means of dispersion over wide spaces of sea, which
terrestrial mammals and birds have not, as is fully explained in Sir
Charles Lyell's "Principles of Geology," and Mr. Darwin's "Origin of
Species." On the other hand, an island may never have been actually
connected with the adjacent continents or islands, and yet may possess
representatives of all classes of animals, because many terrestrial
mammals and some reptiles have the means of passing over short distances
of sea. But in these cases the number of species that have thus migrated
will be very small, and there will be great deficiencies even in birds
and flying insects, which we should imagine could easily cross over.
The island of Timor (as I have already shown in Chapter XIII) bears this
relation to Australia; for while it contains several birds and insects
of Australian forms, no Australian mammal or reptile is found in it,
and a great number of the most abundant and characteristic forms of
Australian birds and insects are entirely absent. Contrast this with the
British Islands, in, which a large proportion of the plants, insects,
reptiles, and Mammalia of the adjacent parts of the continent are fully
represented, while there are no remarkable deficiencies of extensive
groups, such as always occur when there is reason to believe there has
been no such connexion. The case of Sumatra, Borneo, and Java, and the
Asiatic continent is equally clear; many large Mammalia, terrestrial
birds, and reptiles being common to all, while a large number more
are of closely allied forms. Now, geology has taught us that this
representation by allied forms in the same locality implies lapse of
time, and we therefore infer that in Great Britain, where almost
every species is absolutely identical with those on the Continent, the
separation has been very recent; while in Sumatra and Java, where a
considerable number of the continental species are represented by allied
forms, the separation was more remote.
From these examples we may see how important a supplement to geological
evidence is the study of the geographical distribution of animals and
plants, in determining the former condition of the earth's surface; and
how impossible it is to understand the former without taking the latter
into account. The productions of the Aru Islands offer the strangest
evidence, that at no very distant epoch they formed a part of New
Guinea; and the peculiar physical features which I have described,
indicate that they must have stood at very nearly the same level then as
they do now, having been separated by the subsidence of the great plain
which formerly connected them with it.
Persons who have formed the usual ideas of the vegetation of the tropics
who picture to themselves the abundance and brilliancy of the flowers,
and the magnificent appearance of hundreds of forest trees covered with
masses of coloured blossoms, will be surprised to hear, that though
vegetation in Aru is highly luxuriant and varied, and would afford
abundance of fine and curious plants to adorn our hothouses, yet bright
and showy flowers are, as a general rule, altogether absent, or so very
scarce as to produce no effect whatever on the general scenery. To give
particulars: I have visited five distinct localities in the islands, I
have wandered daily in the forests, and have passed along upwards of a
hundred miles of coast and river during a period of six months, much of
it very fine weather, and till just as I was about to leave, I never saw
a single plant of striking brilliancy or beauty, hardly a shrub equal to
a hawthorn, or a climber equal to a honeysuckle! It cannot be said that
the flowering season had not arrived, for I saw many herbs, shrubs,
and forest trees in flower, but all had blossoms of a green or
greenish-white tint, not superior to our lime-trees. Here and there on
the river banks and coasts are a few Convolvulaceae, not equal to our
garden Ipomaeas, and in the deepest shades of the forest some fine
scarlet and purple Zingiberaceae, but so few and scattered as to be
nothing amid the mass of green and flowerless vegetation. Yet the noble
Cycadaceae and screw-pines, thirty or forty feet high, the elegant tree
ferns, the lofty palms, and the variety of beautiful and curious plants
which everywhere meet the eye, attest the warmth and moisture of the
tropics, and the fertility of the soil.
It is true that Aru seemed to me exceptionally poor in flowers, but
this is only an exaggeration of a general tropical feature; for my
whole experience in the equatorial regions of the west and the east has
convinced me, that in the most luxuriant parts of the tropics, flowers
are less abundant, on the average less showy, and are far less effective
in adding colour to the landscape than in temperate climates. I have
never seen in the tropics such brilliant masses of colour as even
England can show in her furze-clad commons, her heathery mountain-sides,
her glades of wild hyacinths, her fields of poppies, her meadows of
buttercups and orchises--carpets of yellow, purple, azure-blue, and
fiery crimson, which the tropics can rarely exhibit. We, have smaller
masses of colour in our hawthorn and crab trees, our holly and
mountain-ash, our boom; foxgloves, primroses, and purple vetches, which
clothe with gay colours the whole length and breadth of our land, These
beauties are all common. They are characteristic of the country and the
climate; they have not to be sought for, but they gladden the eye at
every step. In the regions of the equator, on the other hand, whether it
be forest or savannah, a sombre green clothes universal nature. You may
journey for hours, and even for days, and meet with nothing to break the
monotony. Flowers are everywhere rare, and anything at all striking is
only to be met with at very distant intervals.
The idea that nature exhibits gay colours in the tropics, and that the
general aspect of nature is there more bright and varied in hue than
with us, has even been made the foundation of theories of art, and we
have been forbidden to use bright colours in our garments, and in the
decorations of our dwellings, because it was supposed that we should be
thereby acting in opposition to the teachings of nature. The argument
itself is a very poor one, since it might with equal justice be
maintained, that as we possess faculties for the appreciation of
colours, we should make up for the deficiencies of nature and use the
gayest tints in those regions where the landscape is most monotonous.
But the assumption on which the argument is founded is totally false,
so that even if the reasoning were valid, we need not be afraid of
outraging nature, by decorating our houses and our persons with
all those gay hues which are so lavishly spread over our fields and
mountains, our hedges, woods, and meadows.
It is very easy to see what has led to this erroneous view of the nature
of tropical vegetation. In our hothouses and at our flower-shows we
gather together the finest flowering plants from the most distant
regions of the earth, and exhibit them in a proximity to each other
which never occurs in nature. A hundred distinct plants, all with
bright, or strange, or gorgeous flowers, make a wonderful show when
brought together; but perhaps no two of these plants could ever be seen
together in a state of nature, each inhabiting a distant region or a
different station. Again, all moderately warm extra-European countries
are mixed up with the tropics in general estimation, and a vague idea
is formed that whatever is preeminently beautiful must come from
the hottest parts of the earth. But the fact is quite the contrary.
Rhododendrons and azaleas are plants of temperate regions, the grandest
lilies are from temperate Japan, and a large proportion of our most
showy flowering plants are natives of the Himalayas, of the Cape, of the
United States, of Chili, or of China and Japan, all temperate regions.
True, there are a great number of grand and gorgeous flowers in the
tropics, but the proportion they bear to the mass of the vegetation is
exceedingly small; so that what appears an anomaly is nevertheless a
fact, and the effect of flowers on the general aspect of nature is far
less in the equatorial than in the temperate regions of the earth.