been caused by the earthquake. About twenty minutes after the first
earth-shock the sea was seen to retire, as if about to leave the
shores wholly dry; but presently its waters returned with tremendous
force. A mighty wave, whose length seemed immeasurable, was seen
advancing like a dark wall upon the unfortunate town, a large part of
which was overwhelmed by it. Two ships, the Peruvian corvette America,
and the United States "double-ender" Wateree, were carried nearly half
a mile to the north of Arica beyond the railroad which runs to Tacna,
and there left stranded high and dry. This enormous wave was
considered by the English vice-consul at Arica to have been fully
fifty feet in height.
At Chala three such waves swept in after the first shocks of
earthquake. They overflowed nearly the whole of the town, the sea
passing more than half a mile beyond its usual limits.
At Islay and Iquique similar phenomena were manifested. At the former
town the lava flowed in no less than five times, and each time with
greater force. Afterward the motion gradually diminished, but even an
hour and a half after the commencement of this strange disturbance the
waves still ran forty feet above the ordinary level. At Iquique the
people beheld the inrushing wave while it was still a great way off. A
dark blue mass of water some fifty feet in height was seen sweeping in
upon the town with inconceivable rapidity. An island lying before the
harbor was completely submerged by the great wave, which still came
rushing on black with the mud and slime it had swept from the
sea-bottom. Those who witnessed its progress from the upper balconies
of their houses, and presently saw its black mass rushing close
beneath their feet, looked on their safety as a miracle. Many
buildings were indeed washed away, and in the low-lying parts of the
town there was a terrible loss of life. After passing far inland, the
wave slowly returned sea-ward, and, strangely enough, the sea, which
elsewhere heaved and tossed for hours after the first great wave had
swept over it, here came soon to rest.
At Callao a yet more singular instance was afforded of the effect
which circumstances may have upon the motion of the sea after a great
earthquake has disturbed it. In former earthquakes Callao has suffered
terribly from the effects of the great sea-wave. In fact, on two
occasions the whole town has been destroyed, and nearly all its
inhabitants have been drowned, through the inrush of precisely such
waves as flowed into the ports of Arica and Chala. But upon this
occasion the centre of subterranean disturbance must have been so
situated that either the wave was diverted from Callao, or, more
probably, two waves reached Callao from different sources and at
different times, so that the two undulations partly counteracted each
other. Certain it is that, although the water retreated strangely from
the coast near Callao, insomuch that a wide tract of the sea-bottom
was uncovered, there was no inrushing wave comparable with those
described above. The sea afterward rose and fell in an irregular
manner, a circumstance confirming the supposition that the disturbance
was caused by two distinct oscillations. Six hours after the
occurrence of the earth-shock the double oscillations seemed for a
while to have worked themselves into unison, for at this time three
considerable waves rolled in upon the town. But clearly these waves
must not be compared with those which in other instances had made
their appearance within half an hour of the earth-throes. There is
little reason to doubt that if the separate oscillations had
re-enforced each other earlier, Callao would have been completely
destroyed. As it was, a considerable amount of mischief was effected;
but the motion of the sea presently became irregular again, and so
continued until the morning of August 14th, when it began to ebb with
some regularity. But during the 14th there were occasional renewals of
the irregular motion, and several days elapsed before the regular ebb
and flow of the sea were resumed.
Such were among the phenomena presented in the region where the
earthquake itself was felt. It will be seen at once that within this
region, or rather along that portion of the sea-coast which falls
within the central region of disturbance, the true character of the
sea-wave generated by the earthquake could not be recognized. If a
rock fall from a lofty cliff into a comparatively shallow sea, the
water around the place where the rock has fallen is disturbed in an
irregular manner. The sea seems at one place to leap up and down;
elsewhere one wave seems to beat against another, and the sharpest eye
can detect no law in the motion of the seething waters. But presently,
outside the scene of disturbance, a circular wave is seen to form, and
if the motion of this wave be watched it is seen to present the most
striking contrast with the turmoil and confusion at its centre. It
sweeps onward and outward in a regular undulation. Gradually it loses
its circular figure (unless the sea-bottom happens to be unusually
level), showing that although its motion is everywhere regular, it is
not everywhere equally swift. A wave of this sort, though incomparably
vaster, swept swiftly away on every side from the scene of the great
earthquake near the Peruvian Andes. It has been calculated that the
width of this wave varied from one million to five million feet, or,
roughly, from two hundred to one thousand miles, while, when in
mid-Pacific, the length of the wave, measured along its summit in a
widely-curved path from one side to another of the great ocean,
cannot have been less than eight thousand miles.
[Illustration: OVER A LARGE PORTION OF ITS COURSE ITS PASSAGE WAS
UNNOTED.]
We cannot tell how deep-seated was the centre of subterranean action;
but there can be no doubt it was very deep indeed, because otherwise
the shock felt in towns separated from each other by hundreds of miles
could not have been so nearly contemporaneous. Therefore the portion
of the earth's crust upheaved must have been enormous, for the length
of the region where the direct effects of the earthquake were
perceived is estimated by Professor von Hochsteter at no less than
two hundred and forty miles. The breadth of the region is unknown,
because the slope of the Andes on one side and the ocean on the other
concealed the motion of the earth's crust.
The great ocean-wave swept, as we have said, in all directions around
the scene of the earth-throe. Over a large part of its course its
passage was unnoted, because in the open sea the effects even of so
vast an undulation could not be perceived. A ship would slowly rise as
the crest of the great wave passed under her, and then as slowly sink
again. This may seem strange, at first sight, when it is remembered
that in reality the great sea-wave we are considering swept at the
rate of three or four hundred sea-miles an hour over the larger part
of the Pacific. But when the true character of ocean-waves is
understood, when it is remembered that there is no transference of the
water itself at this enormous rate, but simply a transmission of
motion (precisely as when in a high wind waves sweep rapidly over a
cornfield, while yet each cornstalk remains fixed in the ground), it
will be seen that the effects of the great sea-wave could only be
perceived near the shore. Even there, as we shall presently see, there
was much to convey the impression that the land itself was rising and
falling rather than that the deep was moved. But among the hundreds of
ships which were sailing upon the Pacific when its length and breadth
were traversed by the great sea-wave, there was not one in which any
unusual motion was perceived.
In somewhat less than three hours after the occurrence of the
earthquake the ocean-wave inundated the port of Coquimbo, on the
Chilean seaboard, some eight hundred miles from Arica. An hour or so
later it had reached Constitucion, four hundred and fifty miles
farther south; and here for some three hours the sea rose and fell
with strange violence. Farther south, along the shore of Chile, even
to the island of Chiloe, the shore-wave travelled, though with
continually diminishing force, owing, doubtless, to the resistance
which the irregularities of the shore opposed to its progress.
The northerly shore-wave seems to have been more considerable; and a
moment's study of a chart of the two Americas will show that this
circumstance is highly significant. When we remember that the
principal effects of the land-shock were experienced within that angle
which the Peruvian Andes form with the long north-and-south line of
the Chilean and Bolivian Andes, we see at once that, had the centre of
the subterranean action been near the scene where the most destructive
effects were perceived, no sea-wave, or but a small one, could have
been sent toward the shores of North America. The projecting shores of
northern Peru and Ecuador could not have failed to divert the sea-wave
toward the west; and though a reflected wave might have reached
California, it would only have been after a considerable interval of
time, and with dimensions much less than those of the sea-wave which
travelled southward. When we see that, on the contrary, a wave of even
greater proportions travelled toward the shores of North America, we
seem forced to the conclusion that the centre of the subterranean
action must have been so far to the west that the sea-wave generated
by it had a free course to the shores of California.
Be this as it may, there can be no doubt that the wave which swept the
shores of Southern California, rising upward of sixty feet above the
ordinary sea-level, was absolutely the most imposing of all the
indirect effects of the great earthquake. When we consider that even
in San Pedro Bay, fully five thousand miles from the centre of
disturbance, a wave twice the height of an ordinary house rolled in
with unspeakable violence only a few hours after the occurrence of the
earth-throe, we are most strikingly impressed with the tremendous
energy of the earth's movement.
Turning to the open ocean, let us track the great wave on its course
past the multitudinous islands which dot the surface of the Pacific.
The inhabitants of the Sandwich Islands, which lie about six thousand
three hundred miles from Arica, might have imagined themselves safe
from any effects which could be produced by an earthquake taking place
so far away from them. But on the night between August 13th and 14th,
the sea around this island group rose in a surprising manner, insomuch
that many thought the islands were sinking, and would shortly subside
altogether beneath the waves. Some of the smaller islands, indeed,
were for a time completely submerged. Before long, however, the sea
fell again, and as it did so the observers "found it impossible to
resist the impression that the islands were rising bodily out of the
water." For no less than three days this strange oscillation of the
sea continued to be experienced, the most remarkable ebbs and floods
being noticed at Honolulu, on the island of Woahoo.
But the sea-wave swept onward far beyond these islands.
At Yokohama, in Japan, more than ten thousand five hundred miles from
Arica, an enormous wave poured in on August 14th, but at what hour we
have no satisfactory record. So far as distance is concerned, this
wave affords most surprising evidence of the stupendous nature of the
disturbance to which the waters of the Pacific Ocean had been
subjected. The whole circumference of the earth is but twenty-five
thousand miles, so that this wave had travelled over a distance
considerably greater than two-fifths of the earth's circumference. A
distance which the swiftest of our ships could not traverse in less
than six or seven weeks had been swept over by this enormous
undulation in the course of a few hours.
More complete details reach us from the Southern Pacific.
Shortly before midnight the Marquesas Isles and the low-lying Tuamotu
group were visited by the great wave, and some of these islands were
completely submerged by it. The lonely Opara Isle, where the steamers
which run between Panama and New Zealand have their coaling station,
was visited at about half-past eleven in the evening by a billow which
swept away a portion of the coal depot. Afterward great waves came
rolling in at intervals of about twenty minutes, and several days
elapsed before the sea resumed its ordinary ebb and flow.
It was not until about half-past two on the morning of August 14th
that the Samoa Isles (sometimes called the Navigator Islands) were
visited by the great wave. The watchmen startled the inhabitants from
their sleep by the cry that the sea was about to overwhelm them; and
already, when the terrified people rushed from their houses, the sea
was found to have risen far above the highest water-mark. But it
presently began to sink again, and then commenced a series of
oscillations, which lasted for several days, and were of a very
remarkable nature. Once in every quarter of an hour the sea rose and
fell, but it was noticed that it rose twice as rapidly as it sank.
This peculiarity is well worth remarking. The eminent physicist Mallet
speaks thus (we follow Lyell's quotation) about the waves which
traverse an open sea: "The great sea-wave, advancing at the rate of
several miles in a minute, consists, in the deep ocean, of a long, low
swell of enormous volume, having an equal slope before and behind, and
that so gentle that it might pass under a ship without being noticed.
But when it reaches the edge of soundings, its front slope becomes
short and steep, while its rear slope is long and gentle." On the
shores visited by such a wave, the sea would appear to rise more
rapidly than it sank. We have seen that this happened on the shores of
the Samoa group, and therefore the way in which the sea rose and fell
on the days following the great earthquake gave significant evidence
of the nature of the sea-bottom in the neighborhood of these islands.
As the change of the great wave's figure could not have been quickly
communicated, we may conclude with certainty that the Samoan Islands
are the summits of lofty mountains, whose sloping sides extend far
toward the east.
This conclusion affords interesting evidence of the necessity of
observing even the seemingly trifling details of important phenomena.
The wave which visited the New Zealand Isles was altogether different
in character, affording a noteworthy illustration of another remark of
Mallet's. He says that where the sea-bottom slopes in such a way that
there is water of some depth close inshore, the great wave may roll in
and do little damage; and we have seen that so it happened in the case
of the Samoan Islands. But he adds that, "where the shore is shelving
there will be first a retreat of the water, and then the wave will
break upon the beach and roll far in upon the land." This is precisely
what happened when the great wave reached the eastern shores of New
Zealand, which are known to shelve down to very shallow water,
continuing far away to sea toward the east.
At about half-past three on the morning of August 14th the water began
to retreat in a singular manner from the port of Littleton, on the
eastern shores of the southernmost of the New Zealand Islands. At
length the whole port was left entirely dry, and so remained for about
twenty minutes. Then the water was seen returning like a wall of foam
ten or twelve feet in height, which rushed with a tremendous noise
upon the port and town. Toward five o'clock the water again retired,
very slowly as before, not reaching its lowest ebb until six. An hour
later a second huge wave inundated the port. Four times the sea
retired and returned with great power at intervals of about two hours.
Afterward the oscillation of the water was less considerable, but it
had not wholly ceased until August 17th, and only on the 18th did the
regular ebb and flow of the tide recommence.
Around the Samoa group the water rose and fell once in every fifteen
minutes, while on the shores of New Zealand each oscillation lasted no
less than two hours. Doubtless the different depths of water, the
irregular conformation of the island groups, and other like
circumstances, were principally concerned in producing these singular
variations. Yet they do not seem fully sufficient to account for so
wide a range of difference. Possibly a cause yet unnoticed may have
had something to do with the peculiarity. In waves of such enormous
extent it would be quite impossible to determine whether the course of
the wave motion was directed full upon a line of shore or more or less
obliquely. It is clear that in the former case the waves would seem to
follow each other more swiftly than in the latter, even though there
were no difference in their velocity.
Far on beyond the shores of New Zealand the great wave coursed,
reaching at length the coast of Australia. At dawn of August 14th
Moreton Bay was visited by five well-marked waves. At Newcastle, on
the Hunter River, the sea rose and fell several times in a remarkable
manner, the oscillatory motion commencing at half-past six in the
morning. But the most significant evidence of the extent to which the
sea-wave travelled in this direction was afforded at Port Fairy,
Belfast, South Victoria. Here the oscillation of the water was
distinctly perceived at midday on August 14th; and yet, to reach this
point, the sea-wave must not only have travelled on a circuitous
course nearly equal in length to half the circumference of the earth,
but must have passed through Bass's Straits, between Australia and Van
Diemen's Land, and so have lost a considerable portion of its force
and dimensions. When we remember that had not the effects of the
earth-shock on the water been limited by the shores of South America,
a wave of disturbance equal in extent to that which travelled westward
would have swept toward the east, we see that the force of the shock
was sufficient to have disturbed the waters of an ocean covering the
whole surface of the earth. For the sea-waves which reached Yokohama
in one direction and Port Fairy in another had each traversed a
distance nearly equal to half the earth's circumference; so that if
the surface of the earth were all sea, waves setting out in opposite
directions from the centre of disturbance would have met each other at
the antipodes of their starting-point.
It is impossible to contemplate the effects which followed the great
earthquake--the passage of a sea-wave of enormous volume over fully
one third of the earth's surface, and the force with which, on the
farthermost limits of its range, the wave rolled in upon shores more
than ten thousand miles from its starting-place--without feeling that
those geologists are right who deny that the subterranean forces of
the earth are diminishing in intensity. It may be difficult, perhaps,
to look on the effects which are ascribed to ancient earth-throes
without imagining for a while that the power of modern earthquakes is
altogether less. But when we consider fairly the share which time had
in those ancient processes of change, when we see that while mountain
ranges were being upheaved or valleys depressed to their present
position, race after race, and type after type appeared on the earth,
and lived out the long lives which belong to races and to types, we
are recalled to the remembrance of the great work which the earth's
subterranean forces are still engaged upon. Even now continents are
being slowly depressed or upheaved; even now mountain ranges are being
raised to a new level, tablelands are in process of formation, and
great valleys are being gradually scooped out. It may need an
occasional outburst, such as the earthquake of August, 1868, to remind
us that great forces are at work beneath the earth's surface. But, in
reality, the signs of change have long been noted. Old shore-lines
shift their place, old soundings vary; the sea advances in one place
and retires in another; on every side Nature's plastic hand is at work
modelling and remodelling the earth, in order that it may always be a
fit abode for those who are to dwell upon it.
[Illustration]
THE PHOSPHORESCENT SEA
(FROM STUDIES OF ANIMATED NATURE.)
BY W.S. DALLAS.
[Illustration]
It is not merely on land that this phenomenon of phosphorescence is to
be seen in living forms. Among marine animals, indeed, it is a
phenomenon much more general, much more splendid, and, we may add,
much more familiar to those who live on our coasts. There must be many
in the British Isles who have never had the opportunity of seeing the
light of the glow-worm, but there can be few of those who have
frequented in summer any part of our coasts, who have never seen that
beautiful greenish light which is then so often visible, especially on
our southern shores, when the water is disturbed by the blade of an
oar or the prow of a boat or ship. In some cases, even on our own
shores, the phenomenon is much more brilliant, every rippling wave
being crested with a line of the same peculiar light, and in warmer
seas exhibitions of this kind are much more common. It is now known
that this light is due to a minute living form, to which we will
afterward return.
But before going on to speak in some detail of the organisms to which
the phosphorescence of the sea is due, it will be as well to mention
that the kind of phosphorescence just spoken of is only one mode in
which the phenomenon is exhibited on the ocean. Though sometimes the
light is shown in continuous lines whenever the surface is disturbed,
at other times, and, according to M. de Quatrefages, more commonly,
the light appears only in minute sparks, which, however numerous,
never coalesce. "In the little channel known as the Sund de Chausez,"
he writes, "I have seen on a dark night each stroke of the oar kindle,
as it were, myriads of stars, and the wake of the craft appeared in a
manner besprinkled with diamonds." When such is the case the
phosphorescence is due to various minute animals, especially
crustaceans; that is, creatures which, microscopically small as they
are, are yet constructed more or less on the type of the lobster or
cray-fish.
At other times, again, the phosphorescence is still more partial.
"Great domes of pale gold with long streamers," to use the eloquent
words of Professor Martin Duncan, "move slowly along in endless
succession; small silvery disks swim, now enlarging and now
contracting, and here and there a green or bluish gleam marks the
course of a tiny, but rapidly rising and sinking globe. Hour after
hour the procession passes by, and the fishermen hauling in their nets
from the midst drag out liquid light, and the soft sea jellies,
crushed and torn piecemeal, shine in every clinging particle. The
night grows dark, the wind rises and is cold, and the tide changes; so
does the luminosity of the sea. The pale spectres below the surface
sink deeper, and are lost to sight, but the increasing waves are
tinged here and there with green and white, and often along a line,
where the fresh water is mixing with the salt in an estuary, there is
a brightness so intense that boats and shores are visible.... But if
such sights are to be seen on the surface, what must not be the
phosphorescence of the depths! Every sea-pen is glorious in its light,
in fact, nearly every eight-armed Alcyonarian is thus resplendent, and
the social Pyrosoma, bulky and a free swimmer, glows like a bar of hot
metal with a white and green radiance."
Such accounts are enough to indicate how varied and how general a
phenomenon is the phosphorescence of the sea. To take notice of one
tithe of the points of interest summed up in the paragraph just quoted
would occupy many pages, and we must therefore confine the attention
to a few of the most interesting facts relating to marine
phosphorescence.