THE DEEP-SEA SOUNDINGS.
When a landsman, born far away among the mountains, comes down to the
coast, and stands for the first time on the shore of the sea, it excites
in him a feeling of awe and wonder, not unmingled with terror. There it
lies, a level surface, with nothing that lifts up its head like a peak
of his native hills. And yet it is so vast, stretching away to the
horizon, and all over the sides of the round world; with its tides and
currents that sweep from the equator to the pole; with its unknown
depths and its ceaseless motion; that it is to him the highest emblem of
majesty and of power--a not unworthy symbol of God himself.
In proportion to its mystery is the terror which hangs over it. A vague
dread always surrounds the unknown. And what so unknown as the deep,
unfathomable sea? For thousands of years the sails of ships, like winged
birds, have skimmed over it, yet it has remained the one thing in nature
beyond alike man's knowledge and his power:
Man marks the earth with ruin,
His control stops with the shore.
And the little that has been known of the ocean has been chiefly of its
surface, of the winds that blow over it, and the waves that are lifted
up on high. We knew somewhat of its tides and currents as observed in
different parts of the earth. We saw off our coast the great Gulf
Stream--that steady flow of waters, so mighty and mysterious, which,
issuing out of the tropical regions, poured its warm current, sixty
miles broad, right through the cold waters of the North Atlantic; and
sweeping round, sent the airs of a softer climate over all the countries
of Western Europe. Old voyagers told us of the trade-winds that blew
across the Pacific, and of terrible monsoons in China and Indian seas.
But all that did not reveal what was going on a hundred fathoms below
the surface. These old sailors had marvellous tales of Indian
pearl-divers, who, holding their breath, plunged to the depth of a few
hundred feet; but they came up half-dead, with but little to tell except
of the frightful monsters of the deep. The diving-bell was let down over
sunken wrecks, but the divers came up only with tales of riches and
ruin, of gold and gems and dead men's bones that lay mingled together on
the deep sea floor. Was the bottom of the sea all like this? Was it a
vast realm of death, the sepulchre of the world? No man could tell us.
Poets might sing of the caves of ocean, but no eye of science had yet
penetrated those awful depths, which the storms never reach.
It is indeed marvellous how little was known, up to a very recent date,
of the true character of the ocean. Navigators had often tried to find
out how deep it was. When lying becalmed on a tranquil sea, they had
amused themselves by letting down a long line, weighted with a
cannon-ball, to see if they could touch bottom. But the results were
very uncertain. Sometimes the line ran out for miles and miles, but
whether it was all the while descending, or was swayed hither and
thither by mighty under-currents, could not be known.
But this true character of the ocean it was necessary to determine,
before it could be possible to pass the gulf of the Atlantic. What was
there on the bottom of the sea, where the cable was to find its resting
place? Was that ocean-bed a wide level plain, or had it been heaved up
by volcanic forces into a hundred mountain-peaks, with many a gorge and
precipice between? Such was the character of a part of the basin of the
ocean. Here and there, all over the globe, are islands, like the Peak of
Teneriffe, thrown up in some fierce bursting of the crust of our planet,
that shoot up in tremendous cliffs from the sea. Who shall say that the
same cliffs do not shoot down below the waves a thousand fathoms deep?
And might there not be such islands, which did not show their heads
above the surface, lying in the track between Europe and America: or
perchance a succession of mountain ranges, over which the cable would
have to be stretched, and where hanging from the heights it would swing
with the tide, till at last it snapped and fell into the abyss below?
Such at least were possible dangers to be encountered; and it was not
safe to advance a step till the basin of the North Atlantic was
explored.
The progress of invention, so rapid on land, at length found a way of
penetrating the sea, and even of turning up its bottom to the gaze of
men. To measure the depth with something like mathematical accuracy, an
instrument was introduced known among nautical men as Massey's
Indicator, the method of which is very clearly explained in an article
which appeared in one of the New York papers, (The Times,) on the
deep-sea soundings made for the Atlantic Telegraph:
"The old system is with a small line, marked at distances of
one hundred fathoms, and with a weight of thirty or fifty
pounds, the depth being told by the length of line run out.
This is, of course, the most natural apparatus that suggests
itself, and has been in use from the earliest ages. Experience
has given directions for its use, avoiding some of the grosser
causes of error from driftage and other causes. Yet its success
in immense ocean depths is problematical, and a problem decided
in the negative by many of the first scientific authorities at
home and abroad. In the mechanical improvements of the last
half-century substitutes for this simple but rather uncertain
method began to be devised. It was proposed to ascertain the
depth by the amount of pressure, or by explosions under water,
with other equally impracticable plans. At last was noticed the
perfect regularity of the movements of a spirally-shaped wheel,
on being drawn through the water. Experiments proved that this
regularity, when unaffected by other causes, could be relied on
with perfect accuracy, and that an arrangement of cog-wheels
would register its revolutions with mathematical precision.
Very soon it came in use as a ship's log. So perfect was their
precision, that they were even introduced in scientific
surveys. Base lines, where the nicest accuracy is required,
were run with them, and we have the highest authority of the
Royal Navy for believing that they never failed. At this point
it was proposed to apply them in a perpendicular as well as in
a horizontal motion through the water. Massey's apparatus
promising to solve those problems of submarine geography left
unsolved by the old method of obtaining depth with a simple
line and sinker, and this more especially as some causes of
error, considerable on the surface, disappear in the still
water below."
To make our knowledge of the sea complete, one thing more was wanting--a
method not only of reaching the bottom, but of laying hold of it, and
bringing it up to the light of day. This was now to be supplied.
[Illustration: BROOKE'S DEEP SEA SOUNDING APPARATUS.
A shows the instrument ready for sounding. It is very simple, consisting
only of a cannon-ball, pierced with an iron rod, and held in its place
by slings. As the ball goes down swiftly, it drives the rod into the
bottom like the point of a spear, when an opening at the end catches the
ooze in its iron lips. The same instant (see B) the slings loosen, the
ball drops off, and the naked rod, C, with its "bite" is drawn up to the
surface.]
It is to the inventive genius of a lieutenant of the United States navy,
Mr. J. M. Brooke, that the world owes the means of finding out what is
at the bottom of the sea. This is by a very simple contrivance, by which
the heavy weight, used to sink the measuring line, _is detached as soon
as it strikes bottom_, leaving the line free so that it can be drawn up
lightly and quickly to the surface without danger of breaking. Below the
weight, and driven by it into the ooze, is a rod, in which is an open
valve, that now closes with a spring, by which it catches a cupful of
the soil, which is thus brought up to the surface, to be placed under
the microscope, and be subjected to the sharp eye of science. With this
simple instrument the skilful seaman explores the bottom of the ocean by
literally feeling over it. With a long line he dives to the very lowest
depths, while the clasp at the end of it is like the tip of the
elephant's trunk, serving as a delicate finger with which he picks up
sand and shells that lie strewn on the floor of the deep. What important
conclusions are derived from this inspection of the bottom of the sea,
is well stated by Lieutenant Maury in the letter already quoted.
In happy concurrence with this, as an additional preparation, a partial
survey of the Atlantic had been made the very year before this
enterprise was begun, in 1853. Lieutenant Berryman was the first who
applied this new method of taking deep-sea soundings to that part of the
Atlantic lying between Newfoundland and Ireland, with results most
surprising and satisfactory. But to remove all doubt it seemed desirable
to have a fresh survey. To obtain this, Mr. Field went to Washington and
applied to the Government in behalf of the Company for a second
expedition.
The request was granted, and the Arctic, under command of the same
gallant Lieutenant Berryman, was assigned to this service. He sailed
from New York on the eighteenth of July, 1856, and the very next day Mr.
Field left on the Baltic for England, to organize the Atlantic Telegraph
Company. The Arctic proceeded to St. John's, and thence with a clear eye
and a steady hand, this true sailor went "sounding on his dim and
perilous way" across the deep. In about three weeks he made the coast of
Ireland, having carried his survey along the great circle arc, which the
telegraph was to follow as the nearest path from the old world to the
new. The result fully confirmed his belief of the existence of a great
plateau underneath the ocean, extending all the way from one hemisphere
to the other.
I cannot take leave of the name of this gallant officer, who rendered
such services to science and to his country, without a word of tribute
to his memory. Lieutenant Berryman is in his grave. He died in the navy
of his country, worn out by his devotion to her service. When the great
civil war broke out, he was placed in a position most painful to a man
of large heart, who loved at once his country and the state in which he
was born. He was a Southerner, a native of Winchester, Va., and was
assigned to duty in the South. At the first attack on Southern forts and
arsenals, he was in command of the Wyandotte, in the harbor of
Pensacola, in Florida. His officers, who were nearly all Southerners,
were in secret sympathy with the rebellion. All the influences around
him, both on ship and on shore, were such as might have seduced a weaker
man from his loyalty. But, to his honor, he never hesitated for a
moment. He stood firm and loyal to his flag. Not knowing whom to trust,
he had to keep watch day and night against surprise and treachery. It
was the testimony of Lieutenant Slemmer, then in command of Fort
Pickens, that but for the ceaseless exertions of Lieutenant Berryman not
only the ship but the fort would have been lost. But this service to his
country cost him his life. His constant exertions brought on a brain
fever, of which he died. His wife, also a native of Winchester, when the
war came near her early home, removed to Baltimore, saying that "she
would not live under any other flag than that under which her husband
had lived and died."
It was to the honor of the American navy, to have led the way in these
deep-sea soundings. But after this second voyage of exploration, Mr.
Field applied to the British Admiralty, "to make what further soundings
might be necessary between Ireland and Newfoundland, and to verify those
made by Lieutenant Berryman." It was in response to this application
that the Government sent out the following year a vessel to make still
another survey of the same ocean-path. This was the steamer Cyclops,
which was placed under Lieutenant Commander Joseph Dayman, of the
British navy, an officer who had been with Captain Sir James Ross when
he made his deep-sea soundings in the South Atlantic in 1840, where he
attained a depth of twenty-six hundred and sixty-seven fathoms; and who
by his intelligence and zeal, was admirably fitted for the work. To
speak now of this _third_ survey, is anticipating in time. But it will
serve the purpose of unity and clearness in the narrative, to include
all these deep-sea soundings in one chapter. He was directed to proceed
to the harbor of Valentia in Ireland, and thence to follow, as nearly as
possible, along the arc of a great circle to Newfoundland. "The
soundings for the first few miles from the coast should be frequent,
decreasing as you draw off shore."
These orders were thoroughly executed. Every pains was taken to make the
information obtained precise and exact. Whenever a sounding was to be
taken, the ship was hove to, and the bow kept as nearly as possible in
the same spot, so that the line might descend perpendicularly. This was
repeated every few miles until they had got far out into the Atlantic,
where the general equality of the depths rendered it necessary to cast
the line only every twenty or thirty miles. Thus the survey was made
complete, and the results obtained were of the greatest value in
determining the physical geography of the sea.
The conclusions of Commander Dayman confirmed in general those of
Lieutenant Berryman, though in comparing the charts prepared by the two,
we observe some differences which ought to be noticed. Both agree as to
the general character of the bottom of the ocean along this
latitude--that it is a vast plain, like the steppes of Siberia. Yet on
the chart of Dayman the floor of the sea seems _not such a dead level_
as on that of Berryman. (This may be partly owing to a difference of
route, as Dayman passed a little to the north of the track of Berryman.)
There are more unequal depths, which in the small space of a chart,
appear like hills and valleys. Yet when we consider the wide distances
passed over, these inequalities seem not greater than the undulations on
our Western prairies. "This space," says Dayman, "has been named by
Maury the telegraphic plateau, and although by multiplying the soundings
upon it, we have depths ranging from fourteen hundred and fifty to
twenty-four hundred fathoms, these are comparatively small inequalities
in its surface, and present no new difficulty to the project of laying
the cable across the ocean. Their importance vanishes when the extent of
the space over which they are distributed (thirty degrees of longitude)
is considered."
[Illustration: BED OF THE ATLANTIC, NORTH AND SOUTH, THROUGH THE CAPE DE
VERDS, AZORES, AND TELEGRAPH PLATEAU.]
According to Berryman and Dayman both, the ocean in its deepest part on
this plateau, measured but two thousand and three or four hundred
fathoms, or about fourteen thousand feet--a depth of but little over
two and a half miles. This is not great, compared with the enormous
depths in other parts of the Atlantic;[A] yet that it is _something_ may
be realized from the fact that if the Peak of Teneriffe were here "cast
into the sea," it would sink out of sight, island, mountain and all,
while even the lofty head of Mont Blanc would be lifted but a few
hundred feet above the waves.
The only exception to this uniform depth, lies about two hundred miles
off the coast of Ireland, where within a space of about a dozen miles,
the depth sinks from five hundred and fifty to seventeen hundred and
fifty fathoms! "In 14 deg. 48' west," says Dayman, "we have five hundred
and fifty fathoms rock, and in 15 deg. 6' west we have seventeen hundred
and fifty fathoms ooze. This is the greatest dip in the whole ocean."
"In little more than ten miles of distance a change of depth occurs,
amounting to seventy-two hundred feet." This is indeed a tremendous
plunge from the hard rock into the slime of the sea.
The same sharp declivity was noticed by Berryman, and has been observed
in the several attempts to lay the cable. Thus in the second expedition
of 1858, as the Agamemnon was approaching the coast of Ireland, we read
in the report of her voyage: "About five o'clock in the evening, the
steep submarine mountain which divides the telegraphic plateau from the
Irish coast, was reached; and the sudden shallowing of the water had a
very marked effect on the cable, causing the strain on, and the speed of
it, to lessen every minute. A great deal of slack was paid out to allow
for inequalities which might exist, though undiscovered by the
sounding-line."
This submarine mountain was then regarded as the chief point of danger
in the whole bed of the Atlantic, and as the principal source of anxiety
in laying a cable across the ocean. Yet, after all, the ascent or
descent of less than a mile and a half in ten miles, is not an
impassable grade. More recent soundings reduce this still farther.
Captain Hoskins, of the Royal Navy, afterwards made a more careful
survey of this precipitous sea bottom, and with results much more
favorable. The side of the mountain, it is now said, is not very much
steeper than Holborn Hill in London, or Murray Hill in New York.[B] But
the best answer to fears on this point, is the fact that in 1857, 1858,
and 1865, the cable passed over it without difficulty. In 1857 the
Niagara was a hundred miles farther to sea, when the cable broke. In
1865 the strain was not increased more than a hundred pounds. In the
final expedition, that of 1866, this declivity was passed over without
difficulty or danger.
Next to the depth of the ocean, it was important to ascertain the nature
of its bottom. What was it--a vast bed of rock, the iron-bound crust of
the globe, hardened by internal fires, and which, bending as a vault
over the still glowing centre of the earth, bore up on its mighty arches
the weight of all the oceans? or was it mere sand like the sea-shore? or
ooze as soft as that of a mill-pond? The pressure of a column of water
two miles high would be equal to that of four hundred atmospheres. Would
not this weight alone be enough to crush any substance that could reach
that tremendous depth? These were questions which remained to be
answered, but on which depended the possibility of laying a cable at the
bottom of the Atlantic.
By the ingenious contrivance of Lieutenant Brooke, the problem was
solved, for we got hold of fragments of the under-coating of the sea;
and to our amazement, instead of finding the ocean bound round with
thick ribs of granite, its inner lining was found to be soft as a silken
vest. The soil brought up from the bottom was not even of the hardness
of sand or gravel. It was mere ooze, like that of our rivers, and was as
soft as the moss that clings to old, damp stones on the river's brink.
At first it was thought by Lieutenant Berryman to be common clay, but
being carefully preserved, and subjected to a powerful microscope, it
was found to be composed of shells, too small to be discovered by the
naked eye!
This was a revelation of the myriad forms of animated existence which
fill the sea: a plenitude of life that is more wonderful by contrast. As
Maury well puts it: "The ocean teems with life, we know. Of the four
elements of the old philosophers--fire, earth, air, and water--perhaps
the sea most of all abounds with living creatures. The space occupied on
the surface of our planet by the different families of animals and their
remains are inversely as the size of the individual. The smaller the
animal, the greater the space occupied by his remains. Take the elephant
and his remains, or a microscopic animal and his, and compare them. The
contrast, as to space occupied, is as striking as that of the coral reef
or island with the dimensions of the whale. The graveyard that would
hold the corallines is larger than the graveyard that would hold the
elephants."[C]
These little creatures, whose remains were thus found at the bottom of
the ocean, probably did not live there, for there all is dark, and
shells, like flowers, need the light and warmth of the all-reviving sun.
It was their sepulchre, but not their dwelling-place. Probably they
lived near the surface of the ocean, and after their short life, sunk to
the tranquil waters below. What a work of life and death had been going
on for ages in the depths of the sea! Myriads upon myriads, ever since
the morning of creation, had been falling like snow-flakes, till their
remains literally covered the bottom of the deep.
Equally significant was the fact that these shells were _unbroken_. Not
only were they there, but preserved in a perfect form. Organisms the
most minute and delicate, fragile as drooping flowers, had yet sunk and
slept uninjured. The same power which watches over the fall of a sparrow
had kept these frail and tender things, and after their brief existence,
had laid them gently on the bosom of the mighty mother for their eternal
rest.
The bearing of this discovery on the problem of a submarine telegraph
was obvious. For it too was to lie on the ocean-bed, beside and among
these relics that had so long been drifting down upon the watery plain.
And if these tiny shells slept there unharmed, surely an iron chord
might rest there in safety. There were no swift currents down there; no
rushing waves agitated that sunless sea. There the waters moved not; and
there might rest the great nerve that was to pass from continent to
continent. And so far as injury from the surrounding elements was
concerned, there it might remain, whispering the thoughts of successive
generations of men, till the sea should give up its dead.
FOOTNOTES:
[A] "The ocean bed of the North Atlantic is a curious study; in some
parts furrowed by currents, in others presenting banks, the
accumulations perhaps of the debris of these ocean rivers during
countless ages. To the west, the Gulf Stream pours along in a bed from
one mile to a mile and a half in depth. To the east of this, and south
of the Great Banks, is a basin, eight or ten degrees square, where the
bottom attains a greater depression than perhaps the highest peaks of
the Andes or Himalayas--six miles of line have failed to reach the
bottom! Taking a profile of the Atlantic basin in our own latitude, we
find a far greater depression than any mountain elevation on our own
continent. Four or five Alleghanies would have to be piled on each
other, and on them added Fremont's Peak, before their point would show
itself above the surface. Between the Azores and the mouth of the Tagus
this decreases to about three miles."
[B] The results obtained are thus summed up in the London Times:
"The dangerous part of this course has hitherto been supposed to be the
sudden dip or bank which occurs off the west coast of Ireland, where the
water was supposed to deepen in the course of a few miles from about
three hundred fathoms to nearly two thousand. Such a rapid descent has
naturally been regarded with alarm by telegraphic engineers, and this
alarm has led to a most careful sounding survey of the whole supposed
bank by Captain Dayman, acting under the instructions of the Admiralty.
The result of this shows that the supposed precipitous bank, or
submarine cliff, is a gradual slope of nearly sixty miles. Over this
long slope the difference between its greatest height and greatest depth
is only eighty-seven hundred and sixty feet; so that the average incline
is, in round numbers, about one hundred and forty-five feet per mile. A
good gradient on a railway is now generally considered to be one in one
hundred feet, or about fifty-three in a mile; so that the incline on
this supposed bank is only about three times that of an ordinary
railway. In fact, as far as soundings can demonstrate any thing, there
are few slopes in the bed of the Atlantic as steep as that of Holborn
Hill. In no part is the bottom rocky, and with the exception of a few
miles, which are shingly, only ooze, mud, or sand is to be found."
[C] Physical Geography of the Sea.