The Continent of Australia—Tasmania, or Van Diemen’s Land—Islands—
Continental Islands—Pelasgic Islands—New Zealand—New Guinea—Borneo—
Atolls—Encircling Reefs—Coral Reefs—Barrier Reefs—Volcanic Islands—
Areas of Subsidence and Elevation in the Bed of the Pacific—Active
Volcanos—Earthquakes—Secular Changes in the Level of the Land.
THE continent of New Holland, situate in the Eastern Pacific Ocean, is
so destitute of large navigable rivers that probably no very high land
exists in its interior, which, as far as it has been explored, seems to
be singularly flat and low, but it is still so little known that no idea
can be formed of its mean elevation. It is 2400 miles from east to west,
and 1700 from north to south, and is divided into two unequal parts by
the Tropic of Capricorn; consequently it has both a temperate and a
tropical climate. New Guinea, separated from New Holland by Torres
Straits, and traversed by the same chain of mountains with New Holland
and Van Diemen’s Land, is so perfectly similar in structure, that it
forms but a detached member of the adjacent continent.
The coasts of New Holland are indented by very large bays, and by
harbours that might give shelter to all the navies in Europe. The most
distinguishing feature of the eastern side, which is chiefly occupied by
the British colony of New South Wales, is a long chain of mountains
which never retires far from the coast, and, with the exception of some
short deviations in its southern part, maintains a meridional directing
through 35 degrees of latitude. It is continued at one extremity from
Torres Straits, at the north of the Gulf of Carpentaria, far into the
interior of New Guinea; and at the other it traverses the whole of Van
Diemen’s Land. It is low in the northern parts of New Holland, being in
some places merely a high land; but about the 30th degree of south
latitude it assumes the form of a regular mountain-chain, and, running
in a very tortuous line from N.E. to S.W., terminates its visible course
at Wilson’s Promontory, the southern extremity of the continent. It is
continued, however, by a chain of mountainous islands across Bass’s
Straits to Cape Portland, in Van Diemen’s Land; from thence the range
proceeds in a zigzag line of high and picturesque mountains to South
Cape, where it ends, having, in its course of 1500 miles, separated the
drainage of both countries into eastern and western waters.
The distance of the chain from the sea in New South Wales is from 50 to
100 miles, but at the 32d parallel it recedes to 150, yet soon returns,
and forms the wild group of the Corecudgy Peaks, from whence, under the
names of the Blue Mountains and Australian Alps, its highest part, it
proceeds in a general westerly direction to the land’s end.
The average height of these mountains is only from 2400 to 4700 feet
above the level of the sea, and even Mount Kosciusko, the loftiest of
the Australian Alps, is not more than 6500 feet high; yet its position
is so favourable, that the view from its snowy and craggy top sweeps
over an area of 7000 square miles. The rugged and savage character of
these mountains far exceeds what might be expected from their height: in
some places, it is true, their tops are rounded and covered with
forests; but by far the greater part of the chain, though wooded along
the flanks, is crowned by naked needles, tooth-formed peaks, and flat
crests of granite or porphyry, mingled with patches of snow. The spurs
give a terrific character to these mountains, and in many places render
them altogether inaccessible, both in New South Wales and Van Diemen’s
Land. These shoot right and left from the ridgy axis of the main range,
equal to it in height, and separated from it, and from one another, by
dark and almost subterraneous gullies, like rents in the bosom of the
earth, iron-bound by impracticable precipices, and streams flowing
through them in black silent eddies or foaming torrents. The intricate
character of these ravines, the danger of descending into them, and the
difficulty of getting out again, render this mountain-chain, in New
South Wales at least, almost a complete barrier between the country on
the coast and that in the interior—a circumstance very unfavourable to
the latter.[72]
In New South Wales the country slopes westward from these mountains to a
low, flat, unbroken plain. On the east side, darkly verdant and
round-topped hills and ridges are promiscuously grouped together,
leading to a richly-wooded undulating country, which gradually descends
to the coast, and forms the valuable lands of the British colony.
Discovered by Cook in the year 1770, it was not colonized till 1788. It
has become a prosperous country; and although new settlers in the more
remote parts suffer the privations and difficulties incident to their
position, yet there is educated society in the towns, with the comforts
and luxuries of civilized life.
The coast-belt on the western side of New Holland is generally of
inferior land, with richer tracts interspersed near the rivers, and
bounded on the east by a range of primary mountains from 3000 to 4000
feet high, in which granite occasionally appears. Beyond this the
country is level, and the land better, though nowhere very productive
except in grass.
None of the rivers of New Holland are navigable to any great distance
from their mouths. The want of water is severely felt in the interior,
which, as far as it is known, is a treeless desert of sand, swamps, and
jungle; yet a belief prevails that there is a large sea or fresh-water
lake in its centre; and this opinion is founded partly on the nature of
the soil, and also because all the rivers that flow into the sea on the
northern coast, between the Gulfs of Van Diemen and Carpentaria,
converge towards their sources, as if they served for drains to some
large body of water.
However unpropitious the centre of the continent may be—and the shores
generally have the same barren character—there is abundance of fine
country inland from the coast. On the north all tropical productions
might be raised, and in so large a continent there must be extensive
tracts of arable land, though its peculiar character is pastoral. There
are large forests on the mountains and elsewhere, yet that moisture is
wanting which clothes other countries in the same latitudes with rank
vegetation. In the colonies, the clearing of a great extent of land has
modified in some degree the mean annual temperature, so that the climate
has become hotter and drier, and not thereby improved.
Van Diemen’s Land, of triangular form, has an area of 27,200 square
miles, and is very mountainous. No country has a greater number of deep,
commodious harbours; and as most of the rivers, though not navigable to
any distance, end in arms of the sea, they afford secure anchorage for
ships of any size. The mountain-chain that traverses the colony of New
South Wales and the islands in Bass’s Straits, rises again from Cape
Portland, and, winding through Van Diemen’s Land in the form of the
letter Z, separates it into two nearly equal parts, with a mean height
of 3750 feet, and at an average distance of 40 miles from the sea. It
encloses the basins of Derwent and Heron rivers, and, after sending a
branch between them to Hobart Town, ends at South Cape. The offsets
which shoot in all directions are as savage and full of impassable
chasms as it is itself. There are cultivable plains and valleys along
the numerous rivers and large lakes by which the country is well
watered; so that Van Diemen’s Land is more agricultural and fertile than
the adjacent continent, but its climate is wet and cold. The uncleared
soil of both countries, however, is far inferior to that in the greater
part of North or South America.[73]
Granite constitutes the entire floor of the western portion of New South
Wales, and extends far into the interior of the continent, bearing a
striking resemblance in character to a similar portion of the Altaï
chain described by Baron Humboldt. The central axis of the
mountain-range, in New South Wales and in Van Diemen’s Land, is of
granite, syenite, and quartz rock; but in early times there had been
great invasions of volcanic substances, as many parts of the main chain,
and most of its offsets, are of the older igneous rocks. The
fossiliferous strata of the two colonies are mostly of the Palæozoic
period, but their fossil fauna is poor in species. Some are identical
with, and others are representatives of, the species of other countries,
even of England. It appears from their coal-measures that the flora of
these countries was as distinct in appearance from that of the northern
hemisphere, previous to the carboniferous period, as it is at the
present day.
Though the innumerable islands that are scattered through the ocean and
seas differ much in size, form, and character, they have been grouped by
M. Von Buch into the two distinct classes of Continental and Pelasgic
islands, most of the latter being either of volcanic or coral formation.
Continental islands are long in proportion to their breadth, and follow
each other in succession along the margin of the continents, as if they
had been formed during the elevation of the mainland, or had
subsequently been separated from it by the action of the sea, and still
mark its ancient boundary. These islands, which follow one another in
their elongated dimensions, generally run parallel to the maritime
chains of mountains, and are mostly of the same structure, so that they
suggest the idea of a submarine portion of the maritime range that has
not yet completely emerged from the deep—or, if sinking, has not yet
disappeared below the waves.
America offers numerous examples of this kind of island. On the
north-western coast there is a long chain of them, beginning with the
New Norfolk group, and ending with Vancouver’s Island, all similar and
parallel to the maritime chain. Another range of Continental islands
occurs at the southern extremity of America, extending from Chiloe to
Cape Horn, evidently an exterior range of the Patagonian Andes, and the
southern prolongation of the granitic or coast chain of Chile; in the
Gulf of Mexico, the ancient margin of the mainland is marked by the
curved group of Porto Rico, San Domingo, Jamaica, and Cuba, which nearly
joins the peninsula of Yucatan. The various islands along the American
coast of the Polar Ocean are the shattered fragments of the continent.
The old continent also affords innumerable examples; along the whole
coast of Norway, from North Cape southwards, there is a continuous chain
of rocky islands similar and parallel to the great range of the
Scandinavian Alps; Great Britain itself, with the Hebrides, Orkney, and
Zetland islands, are remarkable instances of Continental islands. It
would be superfluous to mention the various instances which occur in the
Mediterranean, where many of the islands are merely the prolongations of
the mountain-chains of the mainland rising above the sea, as Corsica and
Sardinia, which are a continuation of the Maritime Alps.
The great central chain of Madagascar and its elongated form, parallel
to the Lupata Mountains, show that the island once formed part of the
African continent. Asia, also, abounds in instances, as Sumatra, Java,
and the Moluccas, and another vast chain extends along the western coast
of Asia from Formosa to Kamtchatka.
Pelasgic islands have risen from the bed of the ocean, independently of
the continents, and generally far from land. They are mostly volcanic,
altogether or in part; often very lofty; sometimes single, and
frequently in groups, and each group has, or formerly has had, a centre
of volcanic action in one or more of the islands, round which the others
have been formed. Many have craters of elevation, that is to say, they
have been raised up in great hollow domes by the internal elastic
vapours, and have either remained so, have become rent at the surface
into gigantic fissures, or have collapsed into hollow cups, in which
craters have formed, by the eruption of loose incoherent matter, or of
lava currents, when the pressure from below was removed:[74] a
considerable number have active vents.
The small islands and groups scattered at enormous distances from one
another, within the Antarctic Circle, are all of volcanic formation,
though none are active. In the Atlantic, Tristan da Cunha, St. Helena,
Ascension, and Madeira are volcanic, though not now actively so; whereas
the Cape de Verde, Canaries, and Azores have each volcanic vents: the
peak of Teyda, in Teneriffe, is one of the most magnificent volcanic
cones in the world.
The labyrinth of islands scattered over the Pacific Ocean for more than
30 degrees on each side of the equator, and from the 130th eastern
meridian to Sumatra, which all but unites this enormous archipelago to
the continent of Asia, has the group of New Zealand or Tasmania, and the
continent of Australia, with its appendage, Van Diemen’s Land, on the
south, and altogether forms a region which, from, the unstable nature of
the surface of the earth, is partly the wreck of a continent that has
been engulfed by the ocean, and partly the summits of a new one rising
above the waves. This extensive portion of the globe is in many parts
terra incognita; the Indian Archipelago has been little explored, and,
with the exception of our colonies in New Holland and New Zealand, is
little known.
M. Von Buch conceives that the enormous circuit, beginning with New
Zealand and extending through Norfolk Island, New Caledonia, New
Hebrides, Solomon’s Island, New Britain, New Hanover, New Ireland,
Louisiade, and New Guinea, once formed the western and northern boundary
of the Australian continent.
New Zealand, divided into three islands by rocky and dangerous channels,
is superior to Australia in richness of soil, fertility, and beauty; it
abounds in a variety of vegetable and mineral productions. High
mountains, of volcanic origin, run through the islands, which, in the
most northerly, rise 14,000 feet above the stormy ocean around, buried
two-thirds of their height in permanent snow and glaciers, exhibiting on
the grandest scale all the alpine characters, with the addition of
active volcanos on the eastern and western coasts: that of Tangarara
pours forth deluges of boiling water, which deposit vast quantities of
siliceous sinter like the Geysers in Iceland; and such is the vitality
of the vegetation, that plants grow richly on the banks, and even in
water too hot to be endured.[75] The coast is a frozen country,
overspread with a most luxuriant but dark and gloomy vegetation. There
are undulating tracts and table-lands of great extent without a tree,
over-run by ferns and a low kind of myrtle; but the mountain-ridges are
clothed with dense and gigantic forests. There is much good land and
many lakes, with navigable rivers, the best of harbours, and a mild
climate; so that no country is better suited for a prosperous and
flourishing colony. It may be considered, even at this early period of
its colonial existence, as the Great Britain of the southern hemisphere.
A very different scene from the stormy seas of New Zealand presents
itself to the north of Australia. There, vivified by the glowing sun of
the equator, the islands of the Indian Archipelago are of matchless
beauty, crowned by lofty mountains, loaded with aromatic verdure, that
shelve to the shore, or dip into a transparent glassy sea. Their coasts
are cut by deep inlets, and watered by the purest streams, which descend
in cascades rushing through wild crevices. The whole is so densely
covered with palms and other beautiful forms of tropical vegetation that
they seem to realize a terrestrial paradise.
Papua or New Guinea, the largest island in the Pacific after New
Holland, is 1100 miles long and 400 in width, with mountains rising
above mountains, till in the west they attain the height of 16,000 feet,
capped with snow, and two volcanos burn on its northern shores. From its
position so near the equator it is probable that New Guinea has the same
vegetation with the Spice Islands to the east, and, from the little that
is known of it, must be one of the finest countries in existence.
Borneo, next in size to New Guinea, is a noble island, divided into two
nearly equal parts by the equator, and traversed through its whole
length by magnificent chains of mountains, which end in three branches
at the Java Sea. Beautiful rivers flow from them to the plains, and
several of these spring from a spacious lake on the table-land in the
interior, among the peaks of Keni-Balu, the highest point of the island.
Diamonds, gold, and antimony are among its minerals; gums, gutta percha,
precious woods, and all kinds of spices and tropical fruits are among
its vegetable productions.
Situate in the centre of a vast archipelago, and in the direct line of
an extensive and valuable commerce, it will in the course of time become
the seat of a great nation, whose civilization and prosperity will hand
down to posterity the name of the enterprising, philanthropic Sir James
Brooke, Rajah of Sarawak, with the highest honour to which man can
aspire. The climate is healthy, tempered by sea-breezes, and in some
parts even European; and its appendage, the small island of Labuan, rich
in coal, is happily situate in the route of steam-vessels between India
and China.
A volume might be written on the beauty and riches of the Indian
Archipelago. Many of the islands are hardly known; the interior of the
greater number has never been explored, so that they offer a wide field
of discovery to the enterprising traveller, and they are now of easier
access since the seas have been cleared of pirates by the exertions of
the Honourable Captain Keppel, and other officers of Her Majesty’s Navy.
They have become of much importance since our relations with China have
been extended, on which account surveys of their coasts have been
already made, and are going on, under the able direction of the
Hydrographer of the Navy, Sir F. Beaufort. The great intertropical
islands of the Pacific, likewise other large islands, as Ceylon and
Madagascar, in the Indian Seas, which by the way do not differ in
character from the preceding, are really continents in miniature, with
their mountains and plains, their lakes and rivers; and in climate they
vary, like the main land, with the latitude, only that continental
climates are more extreme both as to heat and cold.
It is a singular circumstance, arising from the instability of the crust
of the earth, that all the smaller tropical pelasgic islands in the
Pacific and Indian Oceans are either volcanic or coralline, except New
Caledonia and the Seychelles; and it is a startling fact, that in most
cases where there are volcanos the land is rising by slow and almost
imperceptible degrees above the ocean, whereas there is every reason to
believe that those vast spaces, studded with coral islands or atolls,
are actually sinking below it, and have been for ages.[76]
There are four different kinds of coral formations in the Pacific and
Indian Oceans, all entirely produced by the growth of organic beings,
and their detritus, namely, lagoon islands or atolls, encircling reefs,
barrier reefs, and coral fringes. They are all nearly confined to the
tropical regions; the atolls to the Pacific and Indian Oceans alone.
An atoll or lagoon island consists of a chaplet or ring of coral,
enclosing a lagoon or portion of the ocean in its centre. The average
breadth of the part of the ring above the surface of the sea is about a
quarter of a mile, oftener less, and it seldom rises higher than from 6
to 10 or 12 feet above the waves. Hence, the lagoon islands are not
discernible, even at a very small distance, unless when they are covered
with the cocoa-nut, palm, or the pandanus, which is frequently the case.
On the outer side this ring or circlet shelves down to the distance of
100 or 200 yards from its edge, so that the sea gradually deepens to 25
fathoms, beyond which the sides plunge at once into the unfathomable
depths of the ocean, with a more rapid descent than the cone of any
volcano. Even at the small distance of some hundred yards, no bottom has
been found with a sounding-line a mile and a half long. All the coral at
a moderate depth below water is alive—all above is dead, being the
detritus of the living part, washed up by the surf, which is so
tremendous on the windward side of the tropical islands of the Pacific
and Indian Oceans, that it is often heard miles off, and is frequently
the first warning to seamen of their approach to an atoll.
On the lagoon side, where the water is calm, the bounding ring or reef
shelves into it by a succession of ledges, also of living coral, though
not of the same species with those which build the exterior wall and the
foundations of the whole ring. The perpetual change of water brought
into contact with the external coral by the breakers probably supplies
them with more food than they could obtain in a quieter sea, which may
account for their more luxuriant growth. At the same time, they deprive
the whole of the coral in the interior of the most nourishing part of
their food, because the still water in the lagoon, being supplied from
the exterior by openings in the ring, ceases to produce the hardier
corals; and species of more delicate forms, and of much slower growth,
take their place.[77] The depth of the lagoon varies, in different
atolls, from 20 to 50 fathoms, the bottom being partly detritus and
partly live coral. By the growth of the coral, some few of the lagoons
have been filled up; but the process is very slow from the causes
assigned, and also because there are marine animals that feed on the
living coral, and prevent its indefinite growth. In all departments of
nature, the exuberant increase of any one class is checked and limited
by others. The coral is of the most varied and delicate structure, and
of the most beautiful tints: dark brown, vivid green, rich purple, pink,
deep blue, peach-colour, yellow, with dazzling white, contrasted with
deep shadows, shine through the limpid water; while fish of the most
gorgeous hues swim among the branching coral, which are of many
different kinds, though all combine in the structure of these singular
islands. Lagoon islands are sometimes circular, but more frequently oval
or irregular in their form. Sometimes they are solitary or in groups,
but they occur most frequently in elongated archipelagos, with the
atolls elongated in the same direction. The grouping of atolls bear a
perfect analogy to the grouping of the archipelagos of ordinary islands.
The size of these fairy rings of the ocean varies from 2 to 90 miles in
diameter, and islets are frequently formed on the coral rings by the
washing up of the detritus, for they are so low that the waves break
over them in high tides or storms. They have openings or channels in
their circuit, generally on the leeward side, where the tide enters, and
by these ships may sail into the lagoons, which are excellent harbours,
and even on the surface of the circlet or reef itself there are
occasionally boat-channels between the islets.
Dangerous Archipelago, lying east of the Society Islands, is one of the
most remarkable assemblages of atolls in the Pacific Ocean. There are 80
of them, generally in a circular form, surrounding very deep lagoons,
and separated from each other by profound depths. The reefs or rings are
about half a mile wide, and seldom rise more than 10 feet above the edge
of the surf, which beats upon them with such violence that it may be
heard at the distance of 8 miles; and yet on that side the coral insects
build more vigorously, and vegetation thrives better, than on the other.
Many of the islets are inhabited.
The Caroline Archipelago, the largest of all, lies north of the equator,
and extends its atolls in 60 groups over 1000 miles. Many are of great
size, and all are beat by a tempestuous sea and occasional hurricanes.
The atolls in the Pacific Ocean and China Sea are beyond enumeration.
Though less frequent in the Indian Ocean, none are more interesting, or
afford more perfect specimens of this peculiar formation, than the
Maldive and Laccadive archipelagos, both nearly parallel to the coast of
Malabar, and elongated in that direction. The former is 470 miles long
and about 50 miles broad, with atolls arranged in a double row,
separated by an unfathomable sea, into which their sides descend with
more than ordinary rapidity. The largest atoll is 88 miles long and
somewhat less than 20 broad; Suadiva, the next in size, is 44 miles by
23, with a large lagoon in its centre, to which, there is access by 42
openings. There are inhabited islets on most of the chaplets or rings
not higher than 20 feet, while the reefs themselves are nowhere more
than 6 feet above the surge.
The Laccadives run to the north of this archipelago in a double line of
nearly circular atolls, on which are low inhabited islets.
Encircling reefs differ in no respect from atoll-reefs, except that they
have one or more islands in their lagoon. They commonly form a ring
round mountainous islands, at a distance of two or three miles from the
shore, rising on the outside from a very deep ocean, and separated from
the land by a lagoon or channel 200 or 300 feet deep. These reefs
surround the submarine base of the island, and, rising by a steep ascent
to the surface, they encircle the island itself. The Caroline
Archipelago exhibits good examples of this structure in the encircled
islands of Hogoleu and Siniavin; the narrow ring or encircling reef of
the former is 135 miles in its very irregular circuit, on which are a
vast number of islets: six or eight islands rise to a considerable
height from its lagoon, which is so deep, and the opening to it so
large, that a frigate might sail into it. The encircling reef of
Siniavin is narrow and irregular, and its lagoon is so nearly filled by
a lofty island, that it leaves only a strip of water round it from 2 to
5 miles wide and 30 fathoms deep.
Otaheite [Tahiti], the largest of the Society group, is another instance
of an encircled island of the most beautiful kind; it rises in mountains
7000 feet high, with only a narrow plain along the shore, and, except
where cleared for cultivation, it is covered with forests of cocoa-nut,
palms, bananas, bread-fruit, and other productions of a tropical
climate. The lagoon, which encompasses it like an enormous moat, is 30
fathoms deep, and is hemmed in from the ocean by a coral band of the
usual kind, at a distance varying from half a mile to three miles.
Barrier-reefs are of precisely the same structure as the two preceding
classes, from which they only differ in their position with regard to
the land. A barrier reef off the north-east coast of the continent of
Australia is the grandest coral formation existing. Rising at once from
an unfathomable ocean, it extends 1000 miles along the coast, with a
breadth varying from 200 yards to a mile, and at an average distance of
from 20 to 30 miles from the shore, increasing in some places to 60 and
even 70 miles. The great arm of the sea included between it and the land
is nowhere less than 10, occasionally 60 fathoms deep, and is safely
navigable throughout its whole length, with a few transverse openings by
which ships can enter. The reef is really 1200 miles long, because it
stretches nearly across Torres Straits. It is interrupted off the
southern coast of New Guinea by muddy water, which destroys the coral
animals, probably from some great river on that island. There are also
extensive barrier-reefs on the islands of Louisiade and New Caledonia,
which are exactly opposite to the great Australian reef; and as atolls
stud that part of the Pacific which lies between them, it is called the
Coralline Sea. The rolling of the billows along the great Australian
reef has been admirably described. “The long ocean-swell, being suddenly
impeded by this barrier, lifted itself in one great continuous ridge of
deep blue water, which, curling over, fell on the edge of the reef in an
unbroken cataract of dazzling white foam. Each line of breaker ran often
one or two miles in length with not a perceptible gap in its continuity.
There was a simple grandeur and display of power and beauty in this
scene that rose even to sublimity. The unbroken roar of the surf, with
its regular pulsation of thunder, as each succeeding swell fell first on
the outer edge of the reef, was almost deafening, yet so deep-toned as
not to interfere with the slightest nearer and sharper sound.... Both
the sound and sight were such as to impress the spectator with the
consciousness of standing in the presence of an overwhelming majesty and
power.”[78]
Coral-reefs are distinct from all the foregoing; they are merely fringes
of coral along the margin of a shore, and, as they line the shore
itself, they have no lagoons. A vast extent of coast, both on the
continents and islands, is fringed by these reefs, and, as they
frequently surround these shoals, they are very dangerous.
Lagoon islands are the work of various species of coral animals; but
those particular polypi which build the external wall, the foundation
and support of the whole ring or reef, are most vigorous when most
exposed to the breakers; they cannot exist at a greater depth than 25 or
30 fathoms at most, and die immediately when left dry: yet the coral
wall descends precipitously to unfathomable depths; and although the
whole of it is not the work of these animals, yet the perpendicular
thickness of the coral is known to be very great, extending hundreds of
feet below the depth at which these polypi cease to live. From an
extensive survey of the Coralline Seas of the tropics, Mr. Darwin has
found an explanation of these singular phenomena in the instability of
the crust of the earth.
Since there are certain proofs that large areas of the dry land are
gradually rising, and others sinking down, so the bottom of the ocean is
not exempt from the general change that is slowly bringing about a new
state of things; and as there is evidence, on multitudes of the volcanic
islands in the Pacific, of a rise in certain parts of the basis of the
ocean, so the lagoon islands indicate a subsidence in others—changes
arising from the expansion and contraction of the strata under the bed
of the ocean.
There are strong reasons for believing that a continent once occupied a
great part of the tropical Pacific, some part of which subsided by slow
and imperceptible degrees. As portions of it gradually sank down below
the surface of the deep, the tops of mountains and table-lands would
remain as islands of different magnitude and elevation, and would form
archipelagos elongated in the direction of the mountain-chains. Now, the
coral-animal, which constructs the outward wall and mass of the reefs,
never builds laterally, and cannot exist at a greater depth than 25 or
30 fathoms. Hence, if it began to lay the foundation of its reef on the
submerged flanks of an island, it would be obliged to build its wall
upwards in proportion as the island sank down, so that at length a
lagoon would be formed between it and the land. As the subsidence
continued, the lagoon would increase, the island would diminish, and the
base of the coral-reef would sink deeper and deeper, while the animal
would always keep its top just below the surface of the ocean, till at
length the island would entirely disappear, and a perfect atoll would be
left. If the island were mountainous, each peak would form a separate
island in the lagoon, and the encircled islands would have different
forms, which the reefs would follow continuously. This theory perfectly
explains the appearances of the lagoon islands and barrier-reefs, the
continuity of the reef, the islands in the middle of the lagoons, the
different distances of the reefs from them, and the forms of the
archipelago, so exactly similar to the archipelagos of ordinary islands,
all of which are but the tops of submerged mountain-chains, and
generally partake of their elongated forms.[79]
Every intermediate form between an atoll and an encircling reef exists:
New Caledonia is a link between them. A reef runs along the
north-western coast of that island 400 miles, and for many leagues never
approaches within 8 miles of its shore, and the distance increases to 16
miles near the southern extremity. At the other end the reefs are
continued on each side 150 miles beyond the sub-marine prolongation of
the land, marking the former extent of the island. In the lagoon of
Keeling Atoll, situate in the Indian Ocean, 600 miles south of Sumatra,
many fallen trees and a ruined store-house show that it has subsided:
these movements take place during the earthquakes at Sumatra, which are
also felt in this atoll. Violent earthquakes have lately been felt at
Vanikora (celebrated for the wreck of La Pérouse), a lofty island of the
Queen Charlotte group, with an encircling reef in the western part of
the South Pacific, and on which there are marks of recent subsidence.
Other proofs are not wanting of this great movement in the beds of the
Pacific and Indian Oceans.
The extent of the atoll formations, including under this name the
encircling reefs, is enormous. In the Pacific, from the southern end of
Low Archipelago to the northern extremity of Marshall or Radick
Archipelago, a distance of 4500 miles, and many degrees of latitude in
breadth, atolls alone rise above the ocean. The same may be said of the
space in the Indian Ocean between Saya de Matha and the end of the
Laccadives, which includes 25 degrees of latitude—such are the enormous
areas that have been, and probably still are, slowly subsiding. Other
spaces of great extent may also be mentioned, as the large archipelago
of the Carolinas, that in the Coralline Sea of the north-west coast of
Australia, and an extensive one in the China Sea.
Though the volcanic islands in the Pacific are so numerous, there is not
one within the areas mentioned, and there is not an active volcano
within several hundred miles of an archipelago, or even group of atolls.
This is the more interesting, as recent shells and fringes of dead
coral, found at various heights on their surfaces, show that the
volcanic islands have been rising more and more above the surface of the
ocean for a very long time.
The volcanic islands also occupy particular zones in the Pacific, and it
is found from extensive observation that all the points of eruption fall
on the areas of elevation.[80]
One of the most terribly active of these zones begins with the Banda
group of islands, and extends through the Sunda group of Timor, Sumbawa,
Bali, Java, and Sumatra, separated only by narrow channels, and
altogether forming a gently curved line 2000 miles long; but as the
volcanic zone is continued through Barren Island and Narcondam in the
Bay of Bengal, northward through the islands along the coast of Aracan,
the entire length of this volcanic range is a great deal more. During
the last hundred years all the islands and rocks for 100 miles along the
coast of Aracan have been gradually rising. The greatest elevation of 22
feet has taken place about the centre of the line of upheaval, in the
north-west end of the island of Cheduba, containing two mud volcanos,
and is continued through Foul Island and the Terribles.[81]
The little island of Gonung-Api, belonging to the Banda group, contains
a volcano of great activity; and such is the elevating pressure of the
submarine fire in that part of the ocean, that a mass of black basalt
rose up, of such magnitude as to fill a bay 60 fathoms deep, so quietly
that the inhabitants were not aware of what was going on till it was
nearly done. Timor and the other adjacent islands also bear marks of
recent elevation.
There is not a spot of its size on the face of the earth that contains
so many volcanos as the island of Java.[82] A range of volcanic
mountains, from 5000 to 13,000 feet high, forms the central crest of the
island, and ends to the east in a series of 38 separate volcanos with
broad bases, rising gradually into cones. They all stand on a plain but
little elevated above the sea, and each individual mountain seems to
have been formed independently of the rest. Most of them are of great
antiquity, and are covered with thick vegetation. Some are extinct, or
only emit smoke; from others sulphureous vapours issue with prodigious
violence; one has a large crater filled with boiling water; and a few
have had fierce eruptions of late years. The island is covered with
volcanic spurs from the main ridge, united by cross chains, together
with other chains of less magnitude, but no less fury.
In 1772 the greater part of one of the largest volcanic mountains was
swallowed up after a short but severe combustion; a luminous cloud
enveloped the mountain on the 11th of August, and soon after the huge
mass actually disappeared under the earth with tremendous noise,
carrying with it about 90 square miles of the surrounding country, 40
villages, and 2957 of their inhabitants.
The northern coast of Java is flat and swampy, but the southern
provinces are beautiful and romantic; yet in the lovely peaceful valleys
the stillness of night is disturbed by the deep roaring of the volcanos,
many of which are perpetually burning with slow but terrific action.
Separated by narrow channels of the sea, Bali and Sumbawa are but a
continuation of Java, the same in nature and structure, but on a smaller
scale, their mountains being little more than 8000 feet high.
The intensity of the volcanic force under this part of the Pacific may
be imagined from the eruption of Tomboro in Sumbawa in 1815, which
continued from the 5th of April till July. The explosions were heard at
the distance of 970 miles; and in Java, at the distance of 300 miles,
the darkness during the day was like that of deep midnight, from the
quantity of ashes that filled the air: they were carried to Bencoolen, a
distance of 1100 miles, which, with regard to distance, is as if the
ashes of Vesuvius had fallen at Birmingham. The country round was
ruined, and the town of Tomboro was submerged by heavy rollers from the
ocean.
In Sumatra the extensive granitic formations of Eastern Asia join the
volcanic series which occupies so large a portion of the Pacific. This
most beautiful of islands presents the boldest aspect; it is indented by
arms of the most transparent sea, and watered by innumerable streams; it
displays in its vegetation all the bright colouring of the tropics. Here
the submarine fire finds vent in three volcanos on the southern, and one
on the northern side of the island. A few atolls, many hundreds of miles
to the south, show that this volcanic zone alternates with an area of
subsidence.
More to the north, and nearly parallel to the preceding zone, another
line of volcanic islands begins to the north of New Guinea, and passes
through New Britain, New Ireland, Solomon Islands, and the New Hebrides,
containing many open vents. This range or area of elevation separates
the Coralline Sea from the great chain of atolls on the north between
Ellice’s group and the Caroline Islands, so that it lies between two
areas of subsidence.
The third and greatest of all the zones of volcanic islands includes
Gilolo, one of the Molucca group, which is bristled with volcanic cones;
and from thence it may be traced northwards through the Philippine
Islands and Formosa: bending thence to the north-east, it passes through
Loo-Choo, the Japan Archipelago, and is continued by the Kurile Islands
to the peninsula of Kamtchatka, where there are several volcanos of
great elevation.
The Philippine Islands and Formosa form the volcanic separation between
the atoll region in the China Sea, and that of the Caroline and Pellew
groups.
There are six islands east of Jephoon in the Japan Archipelago which are
subject to eruptions, and the internal fire breaks through the Kurile
Islands in 18 vents, besides having raised two new islands in the
beginning of this century, one 4 miles round, and the other 3000 feet
high, though the sea there is so deep that the bottom has not been
reached with a line 200 fathoms long.
Thus, some long rent in the earth had extended from the tropics to the
gelid seas of Okhotsk, probably connected with the peninsula of
Kamtchatka: a new one begins to the east of the latter in the Aleutian
Islands, which are of the most barren and desolate aspect, perpetually
beaten by the surge of a restless ocean, and bristled by the cones of 24
volcanos; they sweep in a half-moon round Behring’s Sea till they join
the volcanic peninsula of Russian America.
The line of volcanic agency has been followed far beyond the limits of
the coral-working animals, which extend but a short way on each side of
the tropics; but it has been shown that in the equatorial regions
immense areas of elevation alternate with as great areas of subsidence:
north of New Holland they are so mixed that it indicates a point of
convergence.[83]
On the other side of the Pacific the whole chain of the Andes, and the
adjacent islands of Juan Fernandez and the Galapagos, form a vast
volcanic area, which is actually now rising; and though there are few
volcanic islands north of the zone of atolls, yet those that be indicate
great internal activity, especially in the Sandwich Islands, where the
volcanos of Owhyhee [Hawaii] are inferior to none in awful sublimity.
That of Kirawah is on the flanks of Mowna Roa, which is itself a
volcano. It was seen in high activity by Mr. Douglas in 1834; he
describes it as a deep sunken pit, occupying five square miles, covered
with masses of lava which had been in a state of recent fusion. In the
midst of these were two lakes of liquid lava: in both there was a vast
caldron in furious ebullition, occasionally spouting to the height of
from 20 to 70 feet, whence streams of lava, hurrying along in fiery
waves, were finally precipitated down an ignited arch, where the force
of the lava was partly arrested by the escape of gasses, which threw
back huge blocks, and literally spun them into threads of glass, which
were carried by the wind like the refuse of a flax-mill. He says the
noise could hardly be described—that of all the steam-engines in the
world would be a whisper to it; and the heat was so overpowering, and
the dryness of the air so intense, that the very eyelids felt scorched
and dried up.[84]
It may be observed that, where there are coral fringes, the land is
either rising or stationary; for, were it subsiding, lagoons would be
formed. On the contrary, there are many fringing reefs on the shores of
volcanic islands along the coasts of the Red Sea, the Persian Gulf, and
the West Indian islands, all of which are rising. Indeed, this
occurrence, in numberless instances, coincides with the existence of
upraised organic remains on the land.
As the only coral formations in the Atlantic are fringing reefs, and as
there is not one in its central expanse, except in Bermuda, it may be
concluded that the bed of the ocean is not sinking; and with the
exception of the Leeward Islands, the Canaries, the Azores, and the Cape
de Verde groups, there are no active volcanos on the islands or on the
coasts of that ocean.
At present the great continent has few centres of volcanic action in
comparison with what it once had. The Mediterranean is still undermined
by fire, which occasionally finds vent in Vesuvius and the stately cone
of Etna. Though Stromboli constantly pours forth inexhaustible showers
of incandescent matter, and a temporary island now and then starts up
from the sea, the volcanic action is diminished, and Italy has become
comparatively more tranquil.
The table-land of Western Asia, especially Azerbijan, had once been the
seat of intense commotion, now spent, as the Seiban Dagh and Ararat, or
only smoking from the snowy cone of Demavend. The table-land of Eastern
Asia furnishes the solitary instance of igneous explosion at a distance
of 1500 miles from the sea, in the volcanic chain of the Thean-Tchan.
Besides the two active volcanos of the Pe-shan and Ho-tcheou in the
chain itself, at the distance of 670 miles from each other, with a
solfatara between them, it is the centre of a most extensive volcanic
district, extending northward to the Altaï Mountains, in which there are
many points of connection between the interior of the earth and the
atmosphere, not by volcanos, but by solfataras, hot springs, and
vapours. In the range of Targatabai, in the country of the Kirghiz,
there is a mount said to emit smoke and even flame, which produces
sulphur and sal-ammoniac in abundance. It is not ascertained that there
are any mountains in China that eject lava, but there are many
fire-hills and fire-springs; the latter are real Artesian wells five or
six inches wide, and from 1500 to 3000 feet deep: from some of these
water rises containing a great quantity of common salt; from others
gases issue; and when a flame is applied, fire rushes out with great
violence, rising 20 or 30 feet high, with a noise like thunder. The gas,
conducted in tubes of bamboo cane, is used in the evaporation of salt
water from the neighbouring springs.
There are altogether about 270 active volcanos, of which 190 are on the
shores and islands of the Pacific. They are generally disposed in lines
or groups. The chain of the Andes furnishes a magnificent example of
linear volcanos. The peak of Teneriffe, encompassed by the volcanic
islands of Palma and Lancerote, is an equally good specimen of a central
group. Eruptions are much more frequent in low than in high volcanos:
that in the island of Stromboli is in perpetual activity; whereas
Cotopaxi, 18,775 feet high, and Tungaragua in the Andes, have only been
active once in a hundred years. On account of the force requisite to
raise lava to such great elevations, it rarely flows from very elevated
cones. Antisana is the only instance to the contrary among all the lofty
volcanos in Quito. In Etna also the pressure is so great that the lava
forces its way through the sides of the mountain or at the base of the
cone.
An explosion begins by a dense volume of smoke issuing from the crater,
mixed with aqueous vapour and gases; then masses of rock and molten
matter in a half-fluid state are ejected with tremendous explosion and
violence; after which lava begins to flow, and the whole terminates by a
shower of ashes from the crater—often the most formidable part of the
phenomenon, as was experienced at the destruction of Pompeii. There are
several volcanos which eject only streams of boiling water, as the
Volcano de Agua in Guatemala; others pour forth boiling mud, as in the
islands of Trinidad, Java, and Cheduba in the Bay of Bengal. A more
feeble effort of the volcanic force appears in the numerous solfataras.
Hot springs show that the volcanic fire is not extinguished, though not
otherwise apparent. To these may be added acidulous springs, those of
naphtha, petroleum, and various kinds of gas, as carbonic acid gas, the
food of plants—and, when breathed, the destruction of animals, as is
fearfully seen in the Guero Upas, or “Valley of Death,” in Java: it is
half a mile in circumference, and about 35 feet deep, with a few large
stones, and not a vestige of vegetation on the bottom, which is covered
with the skeletons of human beings and the bones of animals and birds
blanched white as ivory. On approaching the edge of the valley, which is
situate on the top of a hill, a nauseous sickening sensation is felt;
and nothing that has life can enter its precincts without being
immediately suffocated.[85]
The seat of activity has been perpetually changing, but there always has
been volcanic action, possibly more intense in former times, but even at
present it extends from pole to pole.
Notwithstanding the numerous volcanic vents in the globe, many places
are subject to violent earthquakes, which ruin the works of man, and
often change the configuration of the country. The most extensive
district of earthquakes comprises the Mediterranean and the adjacent
countries, Asia Minor, the Caspian Sea, Caucasus, and the Persian
mountains. It joins a vast volcanic district in Central Asia, whose
chief focus seems to be the Thean-Tchan, which includes Lake Baikal and
the neighbouring regions. A great part of the continent of Asia is more
or less subject to shocks: but, with the exception of the shores of the
Red Sea and the northern parts of Barbary, Africa is entirely free from
these tremendous scourges; and it is singular that, notwithstanding the
terrible earthquakes which shake the countries west of the Andes, the
Andean chain itself, and all the countries round the Gulf of Mexico and
the Caribbean Sea, they are extremely rare in the great eastern plains
of South America. For the most part the shocks are transmitted in the
line of the primary mountain-chains, and seem often to be limited by
them in the other direction.
There must be some singular volcanic action underneath part of Great
Britain, which has occasioned 255 slight shocks of earthquake, of which
139 took place in Scotland: the most violent of them have been felt at
Comre, in Stratherne; of the rest 14 took place on the borders of
Yorkshire and Derbyshire, 30 in Wales, and 31 on the south coast of
England: they were preceded by singular phenomena, as a sudden fall of
the barometer, fogs, and unusual sultriness; the two latter are said to
indicate these convulsions about Siena, and in the Maremma of Tuscany,
where they have of late years been attended with very disastrous
effects.
Earthquakes are probably produced by fractures and sudden heavings and
subsidences in the elastic crust of the globe, from the pressure of the
liquid fire, vapour, and gases in its interior, which there find vent,
relieve the tension which the strata acquire during their slow
refrigeration, and restore equilibrium. But whether the initial impulse
be eruptive, or a sudden pressure upwards, the shock originating in that
point is propagated through the elastic surface of the earth in a series
of circular or oval undulations, similar to those produced by dropping a
stone into a pool, and like them they become broader and lower as the
distance increases, till they gradually subside; in this manner the
shock travels through the land, becoming weaker and weaker till it
terminates. When the impulse begins in the interior of a continent, the
elastic wave is propagated through the solid crust of the earth, as well
as in sound through the air, and is transmitted from the former to the
ocean, where it is finally spent and lost, or, if very powerful, is
continued in the opposite land. Almost all the great earthquakes,
however, have their origin in the bed of the ocean, far from land,
whence the shocks travel in undulations to the surrounding shores.
No doubt many of small intensity are imperceptible: it is only the
violent efforts of the internal forces that can overcome the pressure of
the ocean’s bed, and that of the superincumbent water. The internal
pressure is supposed to find relief most readily in a belt of great
breadth that surrounds the land at a considerable distance from the
coast, and being formed of the débris, the internal temperature is in a
perpetual state of fluctuation, which would seem to give rise to sudden
flexures and submarine eruptions.
When the original impulse is a fracture or eruption of lava in the bed
of the deep ocean, two kinds of waves or undulations are produced and
propagated simultaneously—one through the bed of the ocean, which is the
true earthquake shock, and coincident with this a wave is formed and
propagated on the surface of the ocean, which rolls to the shore, and
reaches it in time to complete the destruction long after the shock or
wave through the solid ocean-bed has arrived and spent itself on the
land. The sea rose 50 feet at Lisbon and 60 at Cadiz after the great
earthquake; it rose and fell 18 times at Tangier on the coast of Africa,
and 15 times at Funchal in Madeira. At Kinsale in Ireland a body of
water rushed into the harbour, and the water in Loch Lomond in Scotland
rose two feet four inches—so extensive was the oceanic wave.[86] The
height to which the surface of the ground is elevated, or the vertical
height of the shock-wave, varies from one inch to two or three feet.
This earth-wave, on passing under deep water, is imperceptible, but when
it comes to soundings it carries with it to the land a long, flat,
aqueous wave; on arriving at the beach, the water drops in arrear from
the superior velocity of the shock, so that at that moment the sea seems
to recede before the great ocean-wave arrives.
It is the small forced wave that gives the shock to ships, and not the
great wave; but when ships are struck in very deep water, the centre of
disturbance is either immediately under, or very nearly under, the
vessel.
Three other series of undulations are formed simultaneously with the
preceding, by which the sound of the explosion is conveyed through the
earth, the ocean, and the air, with different velocities. That through
the earth travels at the rate of from 7000 to 10,000 feet in a second in
hard rock, and somewhat less in looser materials, and arrives at the
coast a short time before, or at the same moment with, the shock, and
produces the hollow sounds that are the harbingers of ruin; then follows
a continuous succession of sounds, like the rolling of distant thunder,
formed, first, by the wave that is propagated through the water of the
sea, which travels at the rate of 4700 feet in a second, and, lastly, by
that passing through the air, which only takes place when the origin of
the earthquake is a submarine explosion, and travels with a velocity of
1123 feet in a second. The rolling sounds precede the arrival of the
great wave on the coasts, and are continued after the terrific
catastrophe when the eruption is extensive.
When there is a succession of shocks all the phenomena are repeated.
Sounds sometimes occur when there is no earthquake: they were heard on
the plains of the Rio Apure, in Caraccas, at the moment the volcano in
St. Vincent’s, 700 miles off, discharged a stream of lava. The
bellowings of Guanaxuato afford a singular instance: these subterraneous
noises have been heard for a month uninterruptedly when there was no
earthquake felt on the table-land of Mexico, nor in the rich
silver-mines 1600 feet below its surface.
The velocity of the great oceanic wave varies as the square root of the
depth; it consequently has a rapid progress through deep water, and less
when it comes to soundings. That raised during the earthquake at Lisbon
travelled to Barbadoes at the rate of 7·8 miles in a minute, and to
Portsmouth at the rate of a little more than two miles in a minute. The
velocity of the shock varies with the elasticity of the strata it passes
through. The undulations of the earth are subject to the same laws as
those of light and sound; hence, when the shock or earth-wave passes
through strata of different elasticity, it will partly be reflected, and
a wave will be sent back, producing a shock in a contrary direction, and
partly refracted, or its course changed, so that shocks will occur both
upwards and downwards, to the right or to the left of the original line
of transit. Hence, most damage is done at the junction of deep alluvial
plains with the hard strata of the mountains, as in the great earthquake
in Calabria in the year 1783.
When the height of the undulations is small, the earthquake will be a
horizontal motion, which is the least destructive; when the height is
great, the central and horizontal motions are combined, and the effect
is terrible. The concussion was upwards in the earthquake which took
place at Riobamba in 1797. Baron Humboldt mentions that some of the
inhabitants were thrown across a river, several hundred feet in height,
on a neighbouring mountain. The worst of all is a vorticose or twisting
motion, which nothing can resist; it is occasioned by the crossing of
two waves of horizontal vibration, which unite at their point of
intersection and form a rotatory movement. This, and the interferences
of shocks arriving at the same point from different origins or routes of
different lengths, account for the repose in some places, and those
extraordinary phenomena that took place during the earthquake of 1783 in
Calabria, where the shock diverged on all sides from a centre through a
highly elastic base covered with alluvial soil, which was tossed about
in every direction. The dynamics of earthquakes are ably discussed by
Mr. Mallet in a very interesting paper in the “Transactions of the Royal
Irish Academy.”
There are few places where the earth is long at rest, for, independently
of those secular elevations and subsidences that are in progress over
such extensive tracts of country, small earthquake-shocks must be much
more frequent than we imagine, though imperceptible to our senses, and
only to be detected by means of instruments. The shock of an earthquake
at Lyons in February, 1822, was not generally perceptible at Paris, yet
the wave reached and passed under that city, and was detected by the
swinging of the large declination needle at the Observatory, which had
previously been at rest.
The undulations of some of the great earthquakes have spread to an
enormous extent. The earthquake that happened in 1842 in Guadaloupe was
felt over an extent of 3000 miles in length; and that which destroyed
Lisbon had its origin in the bed of the Atlantic, from whence the shock
extended over an area of about 700,000 square miles, or a twelfth part
of the circumference of the globe; the West Indian islands, and the
lakes in Scotland, Norway, and Sweden were agitated by it. In linear
distance the effects of that earthquake extended through 300 miles, the
shocks were felt through a line of 2700 miles, and the vibrations or
tremors were perceptible in water through 4000 miles. It began without
warning, and in five minutes the city was a heap of ruins.
The earthquake of 1783, in Calabria, which completely changed the face
of the country, only lasted two minutes; but it was not very extensive,
yet all the towns and villages for 22 miles round the small town of
Oppido were utterly ruined. The destruction is generally accomplished in
a fearfully short time; the earthquake at Caraccas, in March 1812,
consisted of three shocks, which lasted three or four seconds, separated
by such short intervals that in 50 seconds 10,000 people perished. Baron
Humboldt’s works are full of interesting details on this subject,
especially with regard to the tremendous convulsions in South America.
Sometimes a shock has been perceived under-ground which was not felt at
the surface, as in the year 1802, in the silver-mine of Marienberg, in
the Hartz. In some instances miners have been insensible to shocks felt
on the surface above, which happened at Fahlun, in Sweden, in 1823—
circumstances in both instances depending on the elasticity of the
strata, the depth of the impulses, or obstacles that may have changed
the course of the terrestrial undulation. During earthquakes
dislocations of strata take place, the course of rivers is changed, and
in some instances they have been permanently dried up, rocks are hurled
down, masses raised up, and the configuration of the country altered;
but if there be no fracture at the point of original impulse, there will
be no noise.
The power of the earthquake in raising and depressing the land has long
been well known, but the gradual and almost imperceptible change of
level through immense tracts of the globe is altogether a recent
discovery; it has been ascribed to the expansion of rocks by heat, and
subsequent contraction by the retreat of the melted matter from below
them. It is not at all improbable that there may be motions, like tides,
ebbing and flowing in the internal lava, for the changes are by no means
confined to those enormous elevations and subsidences that appear to be
in progress in the basin of the Pacific and its coasts, nor to the Andes
and the great plains east of them—countries for the most part subject to
earthquakes; they take place, to a vast extent, in regions where these
convulsions are unknown. There seems to be an extraordinary flexibility
in the crust of the globe from the 54th or 55th parallel of north
latitude to the Arctic Ocean. There is a line crossing Sweden from east
to west in the parallel of 56° 3ʹ N. lat., along which the ground is
perfectly stable, and has been so for centuries. To the north of it for
1000 miles, between Gottenburg and North Cape, the ground is rising, the
maximum elevation, which takes place at North Cape, being at the rate of
five feet in a century, from whence it gradually diminishes to three
inches in a century at Stockholm. South of the line of stability, on the
contrary, the land is sinking through part of Christianstad and Malmo,
for the village of Stassten in Scania is now 380 feet nearer to the
Baltic than it was in the time of Linnæus, by whom it was measured 87
years ago. The coast of Denmark on the sound, the island of Saltholm,
opposite to Copenhagen, and that of Bornholm are rising, the latter at
the rate of a foot in a century. The coast of Memel on the Baltic has
actually risen a foot and four inches within the last 30 years, while
the coast of Pillau has sunk down an inch and a half in the same period.
The west coast of Denmark, part of the Feroe Islands, and the west coast
of Greenland are all being depressed below their former level. In
Greenland, the encroachment of the sea, in consequence of the change of
level, has submerged ancient buildings on the low rocky islands, and on
the main land. The Greenlander never builds near the sea on that
account, and the Moravian settlers have had to move inland the poles to
which they moor their boats. It has been in progress for four centuries,
and extends through 600 miles from Igalito Firth to Disco Bay.[87] Mr.
Robert Chambers has shown that in our own country the land has been for
ages on the rise, and that the parallel roads in Glen Roy, which have so
long afforded matter of discussion, are merely margins left by the
retreat of the water, as the land alternately rose and remained
stationary. In the present day the elevation is going on in many places,
especially on the Murray Firth and in the Channel islands. The notice of
this curious subject of the gradual changes of level on the land has
been chiefly revived by Sir Charles Lyell, in whose admirable works on
geology all the details will be found.[88]