divides the foaming waters, one never wearies of the lovely spectacle
their agitation affords; for, whenever a wave makes the ship incline
sidewise, bluish or reddish flames seem to shoot upward from the
keel. Beautiful beyond description is the sight of a troop of
dolphins gamboling in the phosphorescent sea. Every furrow they draw
through the waters is marked by streaks of intense light. In the Gulf
of Cariaco, between Cumana and the peninsula of Maniquarez, this
scene has often delighted me for hours.”
But even in the colder oceanic regions the brilliant phenomenon
appears from time to time in its full glory. During a dark and stormy
September night, on the way from the Sealion Island, Saint George,
to Unalashka, Chamisso admired as beautiful a phosphorescence of
the ocean as he had ever witnessed in the tropical seas. Sparks of
light, remaining attached to the sails that had been wetted by the
spray, continued to glow in another element. Near the south point
of Kamtchatka, at a water temperature hardly above freezing point,
Ermann saw the sea no less luminous than during a seven months’
sojourn in the tropical ocean. This distinguished traveler positively
denies that warmth decidedly favors the luminosity of the sea.
At Cape Colborn, one of the desolate promontories of the desolate
Victoria Land, the phosphoric gleaming of the waves, when darkness
closed in, was so intense that Simpson assures us he had seldom
seen anything more brilliant. The boats seemed to cleave a flood of
molten silver, and the spray, dashed from their bows before the fresh
breeze, fell back in glittering showers into the deep.
Mr. Charles Darwin paints in vivid colors the magnificent spectacle
presented by the sea while sailing in the latitude of Cape Horn on
a very dark night. There was a fresh breeze, and every part of the
surface, which during the day is seen as foam, now glowed with a
pale light. The vessel drove before her bows two billows of liquid
phosphorus, and in her wake she was followed by a milky train. As
far as the eye reached, the crest of every wave was bright, and
the sky above the horizon, from the reflected glare of these livid
flames, was not so utterly obscure as over the rest of the heavens.
While _La Venus_ was at anchor before Simon’s Town, the breaking
of the waves produced so strong a light that the room in which the
naturalists of the expedition were seated was illumined as by sudden
flashes of lightning. Although more than fifty paces from the beach
when the phenomenon took place, they tried to read by this wondrous
oceanic light, but the successive glimpses were of too short duration
to gratify their wishes.
Thus we see the same nocturnal splendor which shines forth in the
tropical seas and gleams along our shores burst forth from the Arctic
waters, and from the waves that bathe the southern promontories of
the Old and the New Worlds.
But what is the cause of the beautiful phenomenon so widely spread
over the face of the ocean? How comes it that at certain times flames
issue from the bosom of an element generally so hostile to their
appearance?
Without troubling the reader with the groundless surmises of ancient
naturalists, or repeating the useless tales of the past, I shall at
once place myself with him on the stage of our actual knowledge of
this interesting and mysterious subject.
It is now no longer a matter of doubt that many of the inferior
marine animals possess the faculty of secreting a luminous matter,
and thus adding their mite to the grand phenomenon. When we
consider their countless multitudes, we shall no longer wonder at
such magnificent effects being produced by creatures individually so
insignificant.
In our seas it is chiefly a minute gelatinous animal, the _Noctiluca
miliaris_, most probably an aberrant member of the infusorial group,
which, as it were, repeats the splendid spectacle of the starry
heavens on the surface of the ocean. In form it is nearly globular,
presenting on one side a groove, from the anterior extremity of which
issues a peculiar curved stalk or appendage marked by transverse
lines, which might seem to be made use of as an organ of locomotion.
Near the base of this tentacle is placed the mouth, which passes into
a dilatable digestive cavity, leading, according to Mr. Huxley, to
a distinct anal orifice. From the rather firm external coat proceed
thread-like prolongations through the softer mass of the body, so as
to divide it into irregular chambers. This little creature, which is
just large enough to be discerned by the naked eye when the water
in which it may be swimming is contained in a glass jar exposed to
the light, seems to feed on diatoms, as this loricæ may frequently
be detected in its interior. It multiplies by spontaneous fission,
and the rapidity of this process may be inferred from the immensity
of its numbers. A single bucket of luminous sea-water will often
contain thousands, while for miles and miles every wave breaking on
the shore expands in a sheet of living flame. It was first described
by Forster in the Pacific Ocean; it occurs on all the shores of the
Atlantic; and the Polar Seas are illumined by its fairy light.
“The nature of its luminosity,” says Dr. Carpenter, “is found by
microscopic examination to be very peculiar; for what appears to the
eye to be a uniform glow is resolvable under a sufficient power into
a multitude of evanescent scintillations, and these are given forth
with increased intensity whenever the body of the animal receives any
mechanical shock.”
The power of emitting a phosphorescent light is widely diffused,
both among the free-swimming and the sessile _Cœlenterata_. Many
of the _Physophoridæ_ are remarkable for its manifestation, and a
great number of the jelly-fishes are luminous. Our own _Thaumantias
lucifera_, a small and by no means rare medusid, displays the
phenomenon in a very beautiful manner, for, when irritated by
contact of fresh water, it marks its position by a vivid circlet of
tiny stars, each shining from the base of a tentacle. A remarkable
greenish light, like that of burning silver, may also be seen to glow
from many of our Sertularians, becoming much brighter under various
modes of excitation.
Among the _Ctenophora_ the large _Cestum Veneris_ of the
Mediterranean is specially distinguished for its luminosity, and
while moving beneath the surface of the water gleams at night like a
brilliant band of flame.
The Sea-pens are eminently phosphorescent, shining at night with a
golden-green light of a most wonderful softness. When touched, every
branchlet above the shock emits a phosphoric glow, while all the
polyps beneath remain in darkness. When thrown into fresh water
or alcohol, they scatter sparks about in all directions, a most
beautiful sight; dying, as it were, in a halo of glory.
But of all the marine animals the Pyrosomas, doing full justice to
their name (fire bodies), seem to emit the most vivid coruscations.
Bibra relates in his _Travels to Chili_ that he once caught half a
dozen of these remarkable light-bearers, by whose phosphorescence
he could distinctly read their own description in a naturalist’s
vade-mecum. Although completely dark when at rest, the slightest
touch sufficed to elicit their clear blue-green light. During a
voyage to India, Mr. Bennett had occasion to admire the magnificent
spectacle afforded by whole shoals of Pyrosomas. The ship, proceeding
at a rapid rate, continued during an entire night to pass through
distinct but extensive fields of these mollusks, floating and
glowing as they floated on all sides of her course. Enveloped in a
flame of bright phosphorescent light, and gleaming with a greenish
lustre, the Pyrosomas, in vast sheets, upward of a mile in breadth,
and stretching out till lost in the distance, presented a sight the
glory of which may be easily imagined. The vessel, as it chased
the gleaming mass, threw up strong flashes of light, as if plowing
through liquid fire, which illuminated the hull, the sails, and the
ropes with a strange, unearthly radiance.
In his memoir on the Pyrosoma, M. Péron describes with lively
colors the circumstances under which he first made its discovery,
during a dark and stormy night, in the tropical Atlantic. “The
sky,” says this distinguished naturalist, “was on all sides loaded
with heavy clouds; all around the obscurity was profound; the wind
blew violently; and the ship cut her way with rapidity. Suddenly we
discovered at some distance a great phosphorescent band stretched
across the waves, and occupying an immense tract in advance of the
ship. Heightened by the surrounding circumstances, the effect of this
spectacle was romantic, imposing, sublime, riveting the attention of
all on board. Soon we reached the illuminated tract, and perceived
that the prodigious brightness was certainly and only attributable to
the presence of an innumerable multitude of largish animals floating
with the waves. From their swimming at different depths they took
apparently different forms--those at the greatest depths were very
indefinite, presenting much the appearance of great masses of fire,
or rather enormous, red-hot cannon-balls; while those more distinctly
seen near the surface perfectly resembled incandescent cylinders of
iron.
“Taken from the water, these animals entirely resembled each other
in form, color, substance, and the property of phosphorescence,
differing only in their sizes, which varied from three to seven
inches. The large, longish tubercles with which the exterior
of the Pyrosomas was bristled were of a firmer substance, and
more transparent than the rest of the body, and were brilliant
and polished like diamonds. These were the principal scene of
phosphorescence. Between these large tubercles, smaller ones,
shorter and more obtuse, could be distinguished; these also were
phosphorescent. Lastly, in the interior of the substance of the
animal, could be seen, by the aid of the transparency, a number of
little, elongated, narrow bodies (viscera), which also participated
in a high degree in the possession of phosphoric light.”
In the Pholades or Lithodomes, that bore their dwellings in hard
stone, as other shell-fish do in the loose sands, the whole mass of
the body is permeated with light. Pliny gives us a short but animated
description of the phenomenon in the edible date-shell of the
Mediterranean (_Pholas dactylus_):
“It is in the nature of the pholades to shine in the darkness with
their own light, which is the more intense as the animal is more
juicy. While eating them, they shine in the mouth and on the hands,
nay, even the drops falling from them upon the ground continue to
emit light, a sure proof that the luminosity we admire in them is
associated with their juice.”
Milne-Edwards found this observation perfectly correct, for, wishing
to place some living pholades in alcohol, he saw a luminous matter
exude from their bodies, which, on account of its weight, sank in
the liquid, covering the bottom of the vessel, and there forming a
deposit as shining as when it was in contact with the air.
Several kinds of fishes likewise possess the luminous faculty. The
sunfish, that strange deformity emits a phosphoric gleam; and a
species of Gunard (_Trigla lucerna_) is said to sparkle in the night,
so as to form fiery streams through the water.
With regard to the luminosity of the larger marine animals, Ermann,
however, remarks that he so often saw small luminous crustacea in
the abdominal cavity of the transparent _Salpa pinnata_ that it may
well be asked whether the phosphorescence of the larger creatures is
not in reality owing to that of their smaller companions.
According to Mr. Bennett--_Whaling Voyage Round the Globe_--a
species of shark first discovered by himself is distinguished by
an uncommonly strong emission of light. When the specimen, taken
at night, was removed into a dark apartment, it afforded a very
interesting spectacle. The entire inferior surface of the body and
head emitted a vivid and greenish phosphorescent gleam, imparting
to the creature by its own light a truly ghastly and terrific
appearance. The luminous effect was constant, and not perceptibly
increased by agitation or friction. When the shark expired (which
was not until it had been out of the water more than three hours),
the luminous appearance faded entirely from the abdomen, and more
gradually from other parts, lingering longest around the jaws and on
the fins.
The only part of the under surface of the animal which was free from
luminosity was the black collar round the throat; and while the
inferior surface of the pectoral, anal, and caudal fins shone with
splendor, their superior surface (including the upper lobe of the
tail fin) was in darkness, as were also the dorsal fins and the back
and summit of the head.
Mr. Bennett is inclined to believe that the luminous power of this
shark resides in a peculiar secretion from the skin. It was his
first impression that the fish had accidentally contracted some
phosphorescent matter from the sea, or from the net in which it
was captured; but the most rigid investigation did not confirm
this suspicion, while the uniformity with which the luminous gleam
occupied certain portions of the body and fins, its permanence during
life, and decline and cessation upon the approach and occurrence
of death, did not leave a doubt in his mind but that it was a
vital principle essential to the economy of the animal. The small
size of the fins would seem to denote that this fish is not active
in swimming; and, since it is highly predaceous and evidently of
nocturnal habits, we may perhaps indulge in the hypothesis that the
phosphorescent power it possesses is of use to attract its prey, upon
the same principle as the Polynesian islanders and others employ
torches in night-fishing.
Some of the lower sea-plants also appear to be luminous. Thus, over
a space of more than 600 miles (between lat. 8° N. and 2° S.), Meyen
saw the ocean covered with phosphorescent _Oscillatoria_, grouped
together into small balls or globules, from the size of a poppy-seed
to that of a lentil.
But if the luminosity of the ocean generally proceeds from living
creatures, it sometimes also arises from putrefying organic fibres
and membranes, resulting from the decomposition of these living light
bearers. “Sometimes,” says Humboldt, “even a high magnifying power is
unable to discover any animals in the phosphorescent water, and yet
light gleams forth wherever a wave strikes against a hard body and
dissolves in foam. The cause of this phenomenon lies then most likely
in the putrefying fibres of dead mollusks, which are mixed with the
waters in countless numbers.”
Summing up the foregoing in a few words, it is thus an indisputable
fact that the phosphorescence of the sea is by no means an electrical
or magnetic property of the water, but exclusively bound to organic
matter, living or dead. But although thus much has been ascertained,
we have as yet only advanced one step toward the unraveling of
the mystery, and its prominent cause remains an open question.
Unfortunately, science is still unable to give a positive answer, and
we are obliged to be content with a more or less plausible hypothesis.
We know as little of what utility marine phosphorescence may be. Why
do the countless myriads of Mammariæ gleam and sparkle along our
coasts? Is it to signify their presence to other animals, and direct
them to the spot where they may find abundance of food? So much is
certain, that so grand and widespread a phenomenon must necessarily
serve some end equally grand and important.
As the phosphorescence of the sea is owing to living creatures, it
must naturally show itself in its greatest brilliancy when the ocean
is at rest; for during the daytime we find the surface of the waters
most peopled with various animals when only a slight zephyr glides
over the sea. In stormy weather, the fragile or gelatinous world of
the lower marine creatures generally seek a greater depth, until the
elementary strife has ceased, when it again loves to sport in the
warmer or more cheerful superficial waters.
In the tropical zone, Humboldt saw the sea most brilliantly luminous
before a storm, when the air was sultry and the sky covered with
clouds. In the North Sea we observe the phenomenon most commonly
during fine, tranquil autumnal nights; but it may be seen at
every season of the year, even when the cold is most intense. Its
appearance is, however, extremely capricious; for, under seemingly
unaltered circumstances, the sea may one night be very luminous
and the next quite dark. Often months, even years, pass by without
witnessing it in full perfection. Does this result from a peculiar
state of the atmosphere, or do the little animals love to migrate
from one part of the coast to another?
It is remarkable that the ancients should have taken so little
notice of oceanic phosphorescence. The _Periplus_ of Hanno contains,
perhaps, the only passage in which the phenomenon is described.
To the south of Cerne the Carthaginian navigator saw the sea burn, as
it were, with streams of fire. Pliny, in whom the miracle (miraculum,
as he calls it) of the date-shell excited so lively an admiration,
and who must often have seen the sea gleam with phosphoric light,
as the passage proves where he mentions in a few dry words the
luminous gurnard (_lucerna_) stretching out a fiery tongue, has
no exclamation of delight for one of the most beautiful sights of
nature. Homer also, who has given us so many charming descriptions of
the sea in its ever-changing aspects, and who so often leads us with
long-suffering Ulysses through the nocturnal floods, never once makes
them blaze or sparkle in his immortal hexameters. Even modern poets
mention the phenomenon but rarely. Camoens himself, whom Humboldt,
on account of his beautiful oceanic descriptions, calls, above all
others, the “poet of the sea,” forgets to sing it in his _Lusiad_.
Byron in his _Corsair_ has a few lines on the subject:
“Flash’d the dipt oars, and, sparkling with the stroke,
Around the waves phosphoric brightness broke;”
but contents himself, as we see, with coldly mentioning a phenomenon
so worthy of all a poet’s enthusiasm. In Coleridge’s wondrous ballad
of _The Ancient Mariner_ we find a warmer description:
“Beyond the shadow of the ship
I watch’d the water-snakes:
They moved in tracks of shining white,
And, when they rear’d, the elfin light
Fell off in hoary flakes.
“Within the shadow of the ship
I watch’d their rich attire--
Blue, glossy green, and velvet black:
They coiled and swam, and every track
Was a flash of golden fire.”
These, indeed, are lines whose brilliancy emulates the splendor of
the phenomenon they depict, but, even they are hardly more beautiful
than Crabbe’s admirable description:
“And now your view upon the ocean turn,
And there the splendor of the waves discern;
Cast but a stone, or strike them with an oar,
And you shall flames within the deep explore;
Or scoop the stream phosphoric as you stand,
And the cold flames shall flash along your hand;
When, lost in wonder, you shall walk and gaze
On weeds that sparkle, and on waves that blaze.”
Or the graphic numbers of Sir Walter Scott:
“Awak’d before the rushing prow,
The mimic fires of ocean glow,
Those lightnings of the wave;
Wild sparkles crest the broken tides,
And dashing round, the vessel’s sides
With elfish lustre lave;
While, far behind, their vivid light
To the dark billows of the night
A blooming splendor gave.”
THE SEASHORE
--P. MARTIN DUNCAN
The seashore is the debatable ground where the sea is constantly
striving to wear away the land. It is the present limit to the ocean
and sea, and a little beyond, for it reaches inland further than the
wildest waves and the highest tides can attain.
Where the seashore begins and ends is a matter of opinion; but all
of it is influenced in some way or other by the sea. In some places,
high cliffs or rocks keep the sea from driving in upon the land;
they are lofty, and may reach for miles along the coast. The high
tide comes up their steep faces for many yards, and when it retires
a rocky strip is seen at their feet, and thence a breadth of rock,
shingle, or sand leads down with a greater or less slope to the
water’s edge. Here there can be no doubt how far the shore reaches
inland, for the cliffs limit it. In other parts of our own and other
maritime countries, there may be no high land on the coast; but
marshes and low lands, with, or without sand-hills, form barriers to
the incursion of the sea. The highest tides have their limit in those
places, but the wash of the sea and the spray, together with the
drainage of the sea into the land, make the water saltish for some
distance inland, and the earth close by is sodden with salt. Then,
long stretches of mud or of sand form the slope, over which the sea
rolls up to the land, and which is exposed and remains more or less
wet at low tide.
In these low-lying parts of the coast the shore is not very
distinctly separated from the land, and often miles of swamp, marsh,
and sand-banks are invaded by the sea during storms and very high
tides. The ditches near the sea contain salt or brackish water, and
the whole of this kind of coast-line has a peculiar and desolate
appearance. If these two kinds of coast are taken as the extremes,
all the varieties of seashores will fit in between them; but still it
will appear that while in some the limit between the land and the sea
is very decided, in others it is not so.
Seaward the shore is very variable in its extent. In some places
it may barely exist, or may only be a ledge of rock, between the
cliff, the high land, and the water; and in others, miles of sand,
shingle, and mud may be between the furthest reach of the waves and
the limit of the low tide. The commonest examples of shores are
those which are between these extremes. Some seashores slope very
gradually to the sea and their extent is then usually great; and
others, which are limited in their breadth, are more precipitous.
Perhaps it is best to say that a seashore is the part of a coast
which, at some time or other, is covered or uncovered by the sea;
and that it has an extension inland, where the spray and wind are
felt and act on the land, and also seaward, where some shore is only
uncovered during excessively low tides. According to this view, it
is possible to portion out a seashore into a greater or less number
of breadths, which may be placed, side by side, from the land to the
sea. First, a breadth will pass along the coast, and will contain
the marshy, swampy land, or the hard rock down to the edge of the
highest tide-mark. It may be miles across, or only a few feet in
extent. Secondly, a breadth will be found between this last and the
sea, where it is highest during common tides and storms. Thirdly, a
breadth will exist four times in the twenty-four hours as dry land,
and for the rest of the time it will be beneath the waves, and this
is situated between ordinary high and low-tide marks. Finally, a
breadth will be between this last and the everlasting sea; it is
narrow, and is only uncovered for a few hours, in the months of the
year when there are what are called “low spring tides.” These four
breadths are termed zones, or belts; and in common language the first
is the beach and coast-line, the second is the shore, the third is
the tide-shore, and the fourth is “low spring shore.”
Differing in their extent, and in the nature of their surface,
in every few miles of the coast of a maritime country like Great
Britain, the zones have their peculiar animals and plants, and
waifs and strays--the wreckage of the sea, of its floor, and of the
coast-line. When the whole of the shore slopes very rapidly to the
sea, the third and fourth zones are small in extent, but when the
slope is gradual, they are large. And when the tide rises much and
falls correspondingly, the third zone is usually uncovered but for
a short time. The tide usually moves along the shore, and does not
simply come in on to the land and recede; for one tide moves in one
direction and the next in the opposite. Thus floating substances are
carried along the coast for miles by the rising tide, and come back
again, more or less, with the falling tide.