THE OCEAN AND SOME OF ITS PHENOMENA.
The Saltness of the Sea—Its Composition—Tons of Silver in the
Ocean—Currents and their Causes—The Great Gulf Stream—Its
Characteristics—A Triumph of Science—The Tides—The Highest Known
Tides and Waves—Whirlpools—The Maelström—A Norwegian
Description—Edgar Allan Poe and his Story—Rescued from the
Vortex—The “Souffleur” at the Mauritius—The Colour of the Sea—Its
Causes—The Phosphorescence of the Ocean—Fields of
Silver—Principally Caused by Animal Life.
Many features and phenomena of the ocean have been incidentally noted in
the foregoing pages; but there are points, hitherto untouched, which
deserve our attention.
Its saltness is due, not merely to the presence of chloride of sodium, or
what we call common salt, but to a large number of other minerals,
including the chlorides of magnesium and potassium, the sulphates of
magnesia and lime, carbonate of lime, sulphuretted hydrogen, bromide of
magnesia, hydrochlorate of ammonia, iodine, iron, copper, and even silver,
varying in proportion according to locality. The copper plates of a ship
examined at Valparaiso showed unmistakable traces of silver deposits.
Calculations have been made showing that the ocean contains 2,000,000 tons
of silver. In 1,000 grains of sea‐water there are thirty‐eight grains of
these ingredients and some little organic matter. The saltness of the sea
is generally greater towards the poles, but to this statement there are
exceptions. In parts of the Irish Channel the water contains salts equal
to the fortieth of its weight, the saline matter rising to one‐sixteenth
of its weight off the coast of Spain. In many places the ocean is less
salt at the surface than at the bottom. Its saltness increases its density
and its buoyancy.
Maury, a recognised authority, finds in the saline properties of the sea
one of the principal forces from which the currents in the ocean proceed.
“The brine of the ocean,” says he, “is the ley of the earth; from it the
sea derives dynamical powers, and the currents their main strength.” Let
us suppose a long tank or, say, swimming‐bath, divided in the middle by a
water‐tight wall, on one side of which should be fresh and on the other
salt water, at equal levels. It is obvious that were the division removed
the waters would not stand side by side as before, for the denser water
would have a tendency not merely to mingle with the lighter, but to form a
current _under_ it. So salt waters of different densities.
[Illustration: CHART OF THE ATLANTIC OCEAN.]
“The ocean,” says Figuier, “is a scene of unceasing agitation; ‘its vast
surface rises and falls,’ to use the image suggested by Schleiden, ‘as if
it were gifted with a gentle power of respiration; its movements, gentle
or powerful, slow or rapid, are all determined by differences of
temperature.’” Heat increases its volume, and therefore lightens it; cold
increases its density, and it will naturally descend. These are, then,
among the obvious reasons of its currents. The duration and force of winds
and the tides are both disturbing influences. Such an oceanic marvel as
the great _Gulf Stream_ could only be explained after a careful study of
all the operating causes of its existence. Dr. Maury has well described
it. He says:—“There is a river in the bosom of the ocean: in the severest
droughts it never fails, and in the mightiest floods it never overflows;
its banks and its bottom are of cold water, while its current is of warm;
it takes its rise in the Gulf of Mexico, and empties itself into the
Arctic seas; this mighty river is the Gulf Stream. In no other part of the
world is there such a majestic flow of water; its current is more rapid
than the Amazon, more impetuous than the Mississippi, and its volume is
more than a thousand times greater.” This great current of water
particularly influences the climates of Northern Europe, and especially
those of Britain and Ireland.
The Gulf Stream, as it issues from the Florida Channel, has a breadth of
thirty‐four miles, a depth of 2,200 feet, and moves at the rate of four
and a half miles an hour. “Midway in the Atlantic, in the triangular space
between the Azores, Canaries, and Cape de Verd Islands, is the great
Sargassum Sea, covering an area equal to the Mississippi Valley; it is so
thickly matted over with the Gulf weed (_Sargassum bacciferum_) that the
speed of vessels passing through it is actually retarded, and to the
companions of Columbus it seemed to mark the limits of navigation: they
became alarmed. To the eye, at a little distance, it seemed sufficiently
substantial to walk upon.” The difference of temperature between the Gulf
Stream and the waters it traverses constantly gives birth to tempests and
cyclones. In 1780 a terrible storm ravaged the Antilles, in which 20,000
persons perished. The ocean quitted its bed, and inundated whole cities;
the trunks of great trees and large parts of buildings were tossed wildly
in the air. Numerous catastrophes of this kind have earned the Gulf Stream
the title of the “King of the Tempests.” So well had Maury studied the
Gulf Stream and its storms, that he was enabled to point out the exact
position of a vessel overtaken by a terrible gale. “In the month of
December, 1859,” says Figuier, “the American packet _San Francisco_ was
employed as a transport to convey a regiment to California. It was
overtaken by one of these sudden storms, which placed the ship and its
freight in a most dangerous position—a single wave, which swept the deck,
tore out the masts, stopped the engines, and washed overboard 129 persons,
officers, and soldiers. From that moment the unfortunate steamer floated
upon the waters, a waif abandoned to the fury of the wind. The day after
the disaster the _San Francisco_ was seen in this desperate situation by a
ship, which reached New York, although unable to assist her. Another ship
met her some days after, but, like the other, could render no assistance.
When the report reached New York two steamers were despatched to her
assistance; but in what direction were they to go? what part of the ocean
were they to explore? The authorities at the Washington Observatory were
appealed to. Having consulted his charts as to the direction and limits of
the Gulf Stream at that period of the year, Dr. Maury traced on a chart
the spot to which the disabled steamer was likely to be driven by the
current, and the course to be taken by the vessels sent to her
assistance.” The steamers went straight to the exact spot, and found the
wreck; and although by that time the crew and passengers had been taken
off by three passing vessels, it was certainly a triumph of science.
[Illustration: WAVES OFF THE CAPE OF GOOD HOPE.]
The tides are produced by two pairs of great waves which travel round the
earth each day—a greater pair caused by the attraction of the moon, a
lesser pair caused by the sun. The moon, by reason of its nearness to the
earth, produces by far the greater influence, but the tides are also
subject to all kinds of local influences. The eastern coast of Asia and
western side of Europe are exposed to extremely high tides; while in the
South Sea Islands they scarcely reach the height of twenty inches. There
is hardly any tide in the Mediterranean, separated as it is from the ocean
by a narrow strait. “The highest tide which is known occurs in the Bay of
Fundy, which opens up to the south of the isthmus uniting Nova Scotia and
New Brunswick. There the tide reaches forty, fifty, and even sixty feet,
while it only attains the height of seven or eight in the bay to the north
of the same isthmus. It is related that a ship was cast ashore upon a rock
during the night so high, that at daybreak the crew found themselves and
their ship suspended in mid‐air, far above the water.” The winds have an
immense influence on the height of tides, and also on the waves. The
highest known waves are found off the Cape of Good Hope (p. 89) at the
period of high tide, under the influence of a strong north‐west wind which
has traversed the Atlantic, pressing its waters round the Cape. “The
billows there,” says Maury, “lift themselves up in long ridges, with deep
hollows between them. They run high and fast, tossing their white caps
aloft in the air, looking like the green hills of a rolling prairie capped
with snow, and chasing each other in sport. Still, their march is stately
and their roll majestic. Many an Australian‐bound trader, after doubling
the Cape, finds herself followed for weeks at a time by these magnificent
rolling swells, furiously driven and lashed by the ‘brave west winds.’
These billows are said to attain the height of thirty, and even forty
feet; but no very exact measurement of the height of waves is recorded.”
Those off Cape Horn are rather less in height. _Spray_ is dashed over the
Eddystone Light, 130 feet high. After a great storm in Barbadoes in 1780,
some old and heavy cannons were found on the shore, which had been thrown
up from the bottom of the sea. If waves in their reflux meet with
obstacles, whirlpools result, such as those in the Straits of Messina,
between the rocks of Charybdis and Scylla made famous by Homer, Ovid, and
Virgil, and once much dreaded, but now little feared.
The best known whirlpool, the Maelström, off Lofoden, in Norway, is the
result of opposing currents. One of the most circumstantial accounts of it
is that of a Norwegian, Jonas Ramus, who calls it the Moskoe‐strom
(channel or stream):—“Between Lofoden and Moskoe,” says he, “the depth of
the water is between thirty‐six and forty fathoms; but, on the other side,
towards Ver (Vurrgh), this depth decreases so as not to afford a
convenient passage for a vessel without the risk of splitting on the
rocks, which happens even in the calmest weather. When it is flood the
stream runs up the country between Lofoden and Moskoe with a boisterous
rapidity; but the roar of its impetuous ebb to the sea is scarcely
equalled by the loudest and most dreadful cataracts, the noise being heard
several leagues off; and the vortices or pits are of such an extent and
depth that if a ship comes within its attraction it is inevitably absorbed
and carried down to the bottom, and there beaten to pieces against the
rocks; and when the water relaxes the fragments thereof are thrown up
again. But these intervals of tranquillity are only at the turn of the ebb
and flood and in calm weather, and last but a quarter of an hour, its
violence gradually returning. When the stream is most boisterous, and its
fury heightened by a storm, it is dangerous to come within a Norwegian
mile of it. Boats, yachts, and ships have been carried away by not
guarding against it before they were within its reach. It likewise happens
frequently that whales come too near the stream, and are overpowered by
its violence, and then it is impossible to describe their howlings and
bellowings, in their fruitless struggles to disengage themselves. A bear
once attempting to swim from Lofoden to Moskoe, was caught by the stream
and borne down, while he roared terribly, so as to be heard on shore.
Large stocks of firs and pine‐trees, after being absorbed by the current,
rise again, broken and torn to such a degree as if bristles grew upon
them. This plainly shows the bottom to consist of craggy rocks, among
which they are whirled to and fro. This stream is regulated by the flux
and reflux of the sea, it being constantly high and low water every six
hours. In the year 1645, early in the morning of Sexagesima Sunday, it
raged with such noise and impetuosity that the very stones of the houses
on the coast fell to the ground.” Kuchu and others promulgated the idea
that the maelström is a watery abyss penetrating the globe, and issuing in
some very remote part. This is the view held by most of the Norwegian
peasantry and fishermen to‐day.
Who that has read the works of Edgar Allan Poe will ever forget his
thrilling and detailed story of a descent into the maelström?(30) It bears
the impress of close study, and is founded largely on recorded facts. Two
brothers, the most daring fishermen of their coast, were accustomed to
fish in closer proximity to the maelström than all the rest, because,
although a desperate speculation, they would get more fish in a day than
the others could at the distant fishing grounds in a week. The risk of
life stood for labour, and courage for capital.
In a terrible hurricane they were driven through the surf into the inner
circle of the whirlpool, where (as is likely to be the case in actual
fact) the wind nearly ceased, the surface of the water being lower than
that of the surrounding ocean. “If you have never been at sea in a heavy
gale, you can form no idea of the confusion of mind occasioned by the wind
and spray together. They blind, deafen, and strangle you, and take away
all power of action or reflection.” Now the two fishermen brothers were in
a measure respited, as death‐condemned felons in prison are allowed petty
indulgences forbidden them while their doom is yet uncertain. Round and
round the belt the vessel flew rather than floated, getting nearer and
nearer to the fatal inner vortex, and making wild lurches towards the
abyss. “The boat appeared to be hanging, as if by magic, midway down, upon
the interior surface of a funnel vast in circumference, prodigious in
depth, and whose perfectly smooth sides might have been mistaken for
ebony, but for the bewildering rapidity with which they spun round, and
for the gleaming and ghastly radiance they shot forth as the rays of the
full moon ... streamed in a flood of golden glory along the black walls,
and far away down into the inmost recesses of the abyss.” Round and round
they swept in dizzying swings and jerks. Above and below them were
whirling fragments of vessels, timbers, boxes, barrels, and trunks of
trees. And now a hope arose from the recollection of one circumstance:
that of the great variety of buoyant matter thrown up by the moskoe‐strom
on the coast of Lofoden, some articles were not disfigured or damaged at
all. Further, light and cylindrical articles were the least likely to be
absorbed into any watery vortex: for the last statement there are good
scientific reasons. “I,” says the survivor, “no longer hesitated what to
do. I resolved to lash myself securely to the water‐cask upon which I now
held, to cut it loose from the counter, and to throw myself with it into
the water. I attracted my brother’s attention by signs, pointed to the
floating barrels that came near us, and did everything in my power to make
him understand what I was about to do. I thought at length that he
comprehended my design, but whether this was the case or not, he shook his
head despairingly, and refused to move from his station by the ring‐bolt.
It was impossible to reach him; the emergency admitted of no delay; and
so, with a bitter struggle, I resigned him to his fate, fastened myself to
the cask by means of the lashings which secured it to the counter, and
precipitated myself with it into the sea without another moment’s
hesitation.” The smack soon after made a few gyrations in rapid
succession, then sank to the bottom for ever, bearing with it the
unfortunate brother. “The barrel to which I was attached had sunk very
little farther than half the distance between the bottom of the gulf and
the spot at which I leaped overboard before a great change took place in
the character of the whirlpool. The slope of the sides of the vast funnel
became momentarily less and less steep. The gyrations of the whirl grew
gradually less and less violent.” By degrees the waters rose, and he found
himself in full view of the shores of Lofoden, and above the spot where
the pool of the moskoe‐strom _had been_. He was picked up by a boat; those
on board were old mates and daily companions, but they knew him no more
than they would have known a traveller from the spirit‐land. His hair,
which had been raven black the day before, was now as white as snow.
Thus far Poe. It shows how the vivid imagination of a great poet, dealing
with facts, can put those facts before the reader in artistically life‐
like and graphic form.
[Illustration: WHIRLPOOL OF CORRIEVRECKAN, OFF THE HEBRIDES.]
Another remarkable whirlpool is that of Corrievreckan, off the Hebrides,
in the south of Scotland, shown in an illustration on page 93.
A phenomenon of another character is exhibited on the south side of the
Mauritius, at a point called “The Souffleur,” or “The Blower.” “A large
mass of rock,” says Lieutenant Taylor, of the United States navy, “runs
out into the sea from the mainland, to which it is joined by a neck of
rock not two feet broad. The constant beating of the tremendous swell
which rolls in has undermined it in every direction, till it has exactly
the appearance of a Gothic building with a number of arches. In the centre
of the rock, which is about thirty‐five or forty feet above the sea, the
water has forced two passages vertically upward, which are worn as smooth
and cylindrical as if cut by a chisel. When a heavy sea rolls in, it of
course fills in an instant the hollow caverns underneath; and finding no
other egress, and being borne in with tremendous violence, rushes up these
chimneys, and flies, roaring furiously, to a height of full sixty feet.
The moment the wave recedes, the vacuum beneath causes the wind to rush
into the two apertures with a loud humming noise, which is heard at a
considerable distance.
“My companion and I arrived there before high water; and, having climbed
across the neck of rock, we seated ourselves close to the chimneys, where
I proposed making a sketch, and had just begun, when in came a thundering
sea, which broke right over the rock itself, and drove us back much
alarmed.
“Our negro guide now informed us that we must make haste to re‐cross our
narrow bridge, as the sea would get up as the tide rose. We lost no time,
and got back dry enough; and I was obliged to make my sketches from the
mainland.
“In about three‐quarters of an hour the sight was truly magnificent. I do
not exaggerate in the least when I say the waves rolled in, long and
unbroken, full twenty‐five feet high, till, meeting the headland, they
broke clear over it, sending the spray flying over to the mainland; while,
from the centre of this mass of foam, the Souffleur shot up with a noise
which we afterwards heard distinctly between two and three miles. Standing
on the main cliff, more than a hundred feet above the sea, we were quite
wet.”
[Illustration: “THE SOUFFLEUR,” ISLAND OF MAURITIUS.]
To the combined influences of tides and waves may also be attributed the
monsoon hurricanes which so often visit the Indian Ocean. The air may have
been just previously without a breath, when immense waves, accompanied by
whirlwinds, come rolling in. “At the period of the changing monsoons, the
winds, breaking loose from their controlling forces, seem to rage with a
fury capable of breaking up the very foundations of the deep,” and ships
are often literally whirled round, or bodily lifted up, their crews being
utterly impotent.
Turning to another subject, partially discussed before—the colour of the
sea—it may be remarked that by itself as sea water it is really
colourless. Its varying colours are caused by reflection, by the varied
bottoms it covers, or by the presence of actual animal, vegetable, and
mineral bodies. The ocean,
“When winds breathe soft along the silent deep,”
is azure blue or ultramarine, becoming greener in‐shore. There are some
days when it is generally green, others sombre and grey. A bottom of white
sand will give a greyish or apple‐coloured green; of chalk, a pure clear
green; if the bottom is brownish‐yellow sand, the green is naturally
duller in character. In the Bay of Loango the waters appear of a deep red,
from the red bottom. The Red Sea owes its colour to actual floating
microscopic algæ and to red coral bottoms. Sea water, concentrated in the
salt marshes of the south of France by the heat of the sun, is also red:
this is due to the presence of a red‐shelled animal of microscopic size.
These minute creatures do not appear till the salt water has attained a
certain concentration, while they die when it has reached a further
density. Navigators often traverse patches of green, red, white, or
yellow‐coloured water, their coloration being due to the presence of
microscopic crustaceans, medusæ, zoophytes, and marine plants.
[Illustration: A SHIP SAILING IN PHOSPHORESCENT SEA.]
The pleasing phenomenon known as the phosphorescence of the sea is
generally, though by no means entirely, due to myriads of minute globular
creatures, called _Noctiluca_. Captain Kingman reported having traversed a
zone twenty‐three miles in length, and so filled with phosphorescent
matter that during the night it presented the appearance of a vast field
of snow. “There was scarcely a cloud in the heavens,” he tells us; “yet
the sky for about 10° above the horizon appeared as black as if a storm
were raging; stars of the first magnitude shone with a feeble light, and
the ‘milky way’ of the heavens was almost entirely eclipsed by that
through which we were sailing.” Several varieties of molluscs and
acalephes shine by their own light, while phosphorescence is often due to
the decomposition of animal matter.
[Illustration: PHOSPHORESCENCE ON THE SURFACE OF THE SEA.]
A French author thus describes the effect produced by the molluscs known
to scientists as _Pyrosoma_, on a voyage to the Isle of France. He
says:—“The wind was blowing with great violence, the night was dark, and
the vessel was making rapid way, when what appeared to be a vast sheet of
phosphorus presented itself, floating on the waves, and occupying a great
space ahead of the ship. The vessel having passed through this fiery mass,
it was discovered that the light was occasioned by organised bodies
swimming about in the sea at various depths around the ship. Those which
were deepest in the water looked like red‐hot balls, while those on the
surface resembled cylinders of red‐hot iron. Some of the latter were
caught; they were found to vary in size from three to seven inches. All
the exterior of the creatures bristled with long thick tubercles, shining
like so many diamonds, and these seemed to be the principal seats of their
luminosity. Inside also there appeared to be a multitude of oblong narrow
glands, exhibiting a high degree of phosphoric power. The colour of these
animals when in repose is an opal yellow, mixed with green; but on the
slightest movement the animal exhibits a spontaneous contractile power,
and assumes a luminous brilliancy, passing through various shades of deep‐
red, orange‐green, and azure‐blue.” A ship plunging through these
phosphorescent fields seems to advance through a sheet of white flame, a
field of luminous silver, scattering a spray of sparks in all directions.