THE GULF STREAM--ITS NATURE--CAUSE--ILLUSTRATION--EFFECT OF SMALL POWERS
UNITED--ADVENTURES OF A PARTICLE OF WATER--EFFECT OF GULF STREAM ON
CLIMATE--ITS COURSE--INFLUENCE ON NAVIGATION--SARGASSO SEA--SCIENTIFIC
EFFORTS OF PRESENT DAY--WIND AND CURRENT CHARTS--EFFECTS ON COMMERCE--
CAUSE OF STORMS--INFLUENCE OF GULF STREAM ON MARINE ANIMALS.
Of the varied motions of the sea, the most important, perhaps, as well
as the most wonderful, is the Gulf Stream. This mighty current has been
likened by Maury to a "river in 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 (hence its name), and empties into
the arctic seas. Its current is more rapid than the Mississippi or the
Amazon, and its volume more than a thousand times greater."
This great current is of the most beautiful indigo-blue colour as far
out as the Carolina coasts; and its waters are so distinctly separated
from those of the sea, that the line of demarcation may be traced by the
eye. Its influences on the currents of the sea, and on the climates and
the navigation of the world, are so great and important, that we think a
somewhat particular account of it cannot fail to interest the reader.
The waters of the Gulf Stream are salter than those of the sea; which
fact accounts for its deeper blue colour, it being well known that salt
has the effect of intensifying the blue of deep water.
The cause of the Gulf Stream has long been a subject of conjecture and
dispute among philosophers. Some have maintained that the Mississippi
river caused it; but this theory is upset by the fact that the stream is
salt--salter even than the sea--while the river is fresh. Besides, the
volume of water emptied into the Gulf of Mexico by that river is not
equal to the _three thousandth part_ of that which issues from it in the
form of the Gulf Stream.
Scientific men are still disagreed on this point. They all, indeed,
seem to hold the opinion that _difference of temperature_ has to do with
the origination of the stream; but while some, such as Captain Maury,
hold that this is the _chief_ cause, others, such as Professor Thompson,
believe the trade-winds to be the most important agent in the matter.
We venture to incline to the opinion that not only the Gulf Stream, but
_all_ the constant currents of the sea are due chiefly to _difference of
temperature and saltness_. These conditions alter the specific gravity
of the waters of the ocean in some places more than in others; hence the
equilibrium is destroyed, and currents commence to flow as a natural
result, seeking to restore that equilibrium. But as the disturbing
agents are always at work, so the currents are of necessity constant.
Other currents there are in the sea, but they are the result of winds
and various local causes; they are therefore temporary and partial,
while the _great_ currents of the ocean are permanent, and are,
comparatively, little affected by the winds. Every one knows that when
a pot is put on the fire to boil, the water contained in it, as soon as
it begins to get heated, commences to circulate. The heated water rises
to the top, the cold descends. When heated more than that which has
ascended, it in turn rises to the surface; and so there is a regular
current established in the pot, which continues to flow as long as the
heating process goes on. This same principle of temperature, then, is
one of the causes of the Gulf Stream. The torrid zone is the furnace
where the waters of the ocean are heated. But in this process of
heating, evaporation goes on to a large extent; hence the waters become
salter than those elsewhere. Here is another agent called into action.
The hot salt waters of the torrid zone at once rush off to distribute
their superabundant caloric and salt to the seas of the frigid zones;
where the ice around the poles has kept the waters cold, and the absence
of great heat, and, to a large extent, of evaporation, has kept them
comparatively fresh. In fact, the waters of the sea require to be
stirred, because numerous agents are at work day and night, from pole to
pole, altering their specific gravity and deranging, so to speak, the
mixture. This stirring is secured by the unalterable laws which the
Creator has fixed for the carrying on of the processes of nature. The
currents of the sea may be said to be the result of this process of
stirring its waters.
It is curious and interesting to note the apparently insignificant
instruments which God has seen fit to use in the carrying out of his
plans. The smallest coral insect that builds its little cell in the
southern seas exercises an influence in the production of the Gulf
Stream. It has been said, with some degree of truth, that one such
insect is capable of setting in motion the entire ocean! The coral
insect has, in common with many other marine creatures, been gifted with
the power of extracting from sea water the lime which it contains, in
order to build its cell. The lime thus extracted leaves a minute
particle of water necessarily destitute of that substance. Before that
particle can be restored to its original condition of equality, every
other particle of water in the ocean must part with a share of its
superabundant lime! The thing _must_ be done. That bereaved particle
cannot rest without its lime. It forthwith commences to travel for the
purpose of laying its brother-particles under contribution; and it
travels far and wide--round and round the world. Myriads upon myriads
of coral insects are perpetually engaged in thus robbing the sea water
of its lime; shells are formed in a similar manner: so that our particle
soon finds itself in company with innumerable other particles of water
in a like destitute condition. It rises to the surface. Here the sun,
as if to compensate it for the loss of its lime, bestows upon it an
unusual amount of heat; and the surrounding particles, not to be
outdone, make it almost unlimited presents of salt. Full to overflow
with the gifts of its new companions, it hastens to bestow of its
superabundance on less favoured particles; joins the great army of the
ocean's currents; enters, perchance, the Gulf of Mexico, where it is
turned back, and hastens along with the Gulf Stream, with all its
natural warmth of character, to ameliorate the climate of Great Britain
and the western shores of Europe. Having accomplished this benevolent
work, it passes on, with some of its heat and vigour still remaining, to
the arctic seas--where it is finally robbed of all its heat and nearly
all its salt, and frozen into an icicle--there for many a long day to
exert a chilling influence on the waters and the atmosphere around it.
Being melted at last by the hot sun of the short arctic summer, it
hurries back with the cold currents of the north to the genial regions
of the equator, in search of its lost caloric and salt, taking in a full
cargo of lime, etcetera, as it passes the mouths of rivers. Arrived at
its old starting-point, our wanderer receives once more heat and salt to
the full, parts with its lime, and at once hastens off on a new voyage
of usefulness--to give out of its superabundance in exchange for the
superabundance of others: thus quietly teaching man the lesson that the
true principles of commerce were carried out in the depths of the sea
ages before he discovered them and carried them into practice on its
surface.
Perchance another fate awaits this adventurous particle of water.
Mayhap, before it reaches the cold regions of the north, it is
evaporated into the clouds, and descends upon the earth in fresh and
refreshing rain or dew. Having fertilised the fields, it flows back to
its parent ocean, laden with a superabundant cargo of earthy substances,
which it soon parts with in exchange for salt. And thus on it goes,
round and round the world; down in the ocean's depths, up in the cloudy
sky, deep in the springs of earth; ever moving, ever active, never lost,
and always fulfilling the end for which it was created.
All ocean currents are composed of water in one or other of the
conditions just described;--the hot and salt waters of the equator,
flowing north to be cooled and freshened; the cold and fresh waters of
the north, flowing south to be heated and salted. The Gulf Stream is
simply the stream of equatorial hot water that flows towards the pole
through the Atlantic. Its fountain-head is the region of the equator,
_not_ the Gulf of Mexico; but it is carried, by the conformation of the
land, into that gulf and deflected by it, and from it out into the ocean
in the direction of Europe. This stream in the Atlantic is well
defined, owing to the comparative narrowness of that sea.
The Gulf Stream, then, is like a river of oil in the ocean,--it
preserves its distinctive character for more than three thousand miles.
It flows towards the polar regions, and the waters of those regions flow
in counter-currents towards the equator, because of the fixed law that
water must seek its equilibrium as well as its level, thus keeping up a
continuous circulation of the hot waters towards the north and the cold
towards the south. There are similar currents in the Pacific, but they
are neither so large nor so regular as those of the Atlantic, owing to
the wide formation of the basin of the former sea.
The effect of the Gulf Stream on climate is very great. The dreary
fur-trading establishment of York Factory, on the shores of Hudson's
Bay, is surrounded by a climate of the most rigorous character--the
thermometer seldom rising up so high as zero during many months, and
often ranging down so low as 50 degrees below zero, sometimes even
lower, while the winter is seven or eight months long: the lakes and
rivers are covered with ice upwards of six feet thick, and the salt sea
itself is frozen. Yet this region lies in the same latitude with
Scotland, York Factory being on the parallel of 57 degrees north, which
passes close to Aberdeen! The difference in temperature between the two
places is owing very much, if not entirely, to the influence of the Gulf
Stream.
Starting from its caldron in the Gulf of Mexico, it carries a freight of
caloric towards the North Atlantic. Owing partly to the diurnal motion
of the Earth on its axis, its flow trends towards the east; hence its
warm waters embrace our favoured coasts, and ameliorate our climate,
while the eastern sea-board of North America is left, in winter, to the
rigour of unmitigated frost.
But besides the powerful influence of this current on climate, it exerts
a very considerable influence on navigation. In former times, when men
regarded the ocean as a great watery waste--utterly ignorant of the
exquisite order and harmonious action of all the varied substances and
conditions which prevail in the sea, just as much as on the land--they
committed themselves to the deep as to a blind chance, and took the
storms and calms they encountered as their inevitable fate, which they
had no means of evading. Ascertaining, as well as they could from the
imperfect charts of those days, the position of their desired haven,
they steered straight for it through fair weather and foul, regarding
interruptions and delays as mere unavoidable matters of course.
But when men began to study the causes and effects of the operation of
those elements in the midst of which they dwelt, they soon perceived
that order reigned where before they had imagined that confusion
revelled; and that, by adapting their operations to the ascertained laws
of Providence, they could, even upon the seemingly unstable sea, avoid
dangers and delays of many kinds, and oftentimes place themselves in
highly favourable circumstances. Navigators no longer dash recklessly
into the Gulf Stream, and try to stem its tide, as they did of yore;
but, as circumstances require, they either take advantage of the
counter-currents which skirt along it, or avail themselves of the warm
climate which it creates even in the midst of winter. There is a
certain spot in the Atlantic known by the name of the Sargasso Sea,
which is neither more nor less than a huge ocean-eddy, in which immense
quantities of sea-weed collect. The weed floats so thickly on the
surface as to give to the sea the appearance of solid land; and ships
find extreme difficulty in getting through this region, which is
rendered still further unnavigable by the prevalence of long-continued
calms. This Sargasso Sea is of considerable extent, and lies off the
west coast of Africa, a little to the north of the Cape Verd Islands.
In former years, ships used to get entangled in this weedy region for
weeks together, unable to proceed on their voyage. The great Columbus
fell in with it on his voyage to America, and his followers, thinking
they had reached the end of the world, were filled with consternation.
This Sargasso Sea lies in the same spot at the present day, but men now
know its extent and position. Instead of steering straight for port,
they proceed a considerable distance out of their way, and, by avoiding
this calm region, accomplish their voyages with much greater speed.
The ocean currents have been, by repeated and long-continued
investigation, ascertained and mapped out; so also have the currents of
the atmosphere, so that, now-a-days, by taking advantage of some of
these currents and avoiding others, voyages are performed, not only in
much shorter time, but with much greater precision and certainty. As it
was with ocean currents long ago, so was it with atmospheric.
Navigators merely put to sea, steered as near as possible on their
direct course, and took advantage of such winds as chanced to blow. Now
they know whither to steer in order to meet with such winds and currents
as will convey them in the shortest space of time to the end of their
voyage. The knowledge necessary to this has not been gained by the
gigantic effort of one mind, nor by the accidental collocation of the
results of the investigations of many ordinary minds. But a few
master-minds have succeeded in gathering within their own grasp the
myriad facts collected by thousands of naval men, of all countries, in
their various voyages; and, by a careful comparison and philosophical
investigation of these facts, they have ascertained and systematised
truths which were before unknown, and have constructed wind and current
charts, by the use of which voyages are wonderfully shortened,
commercial enterprises greatly facilitated, and the general good and
comfort of nations materially advanced.
The truth of this has of late been proved by incontestable facts. For
instance, one year particular note was taken of the arrival of all the
vessels at the port of San Francisco, in California; and it was found
that of 124 vessels from the Atlantic coast of the United States, 70
were possessed of Maury's wind and current charts. The average passage
of these 70 vessels, on that long voyage round Cape Horn, was 135 days;
while the average of those that sailed _without_ the charts (that is,
trusted to their own unaided wisdom and experience) was 146 days.
Between England and Australia the average length of the voyage out used,
very recently, to be 124 days. With the aid of these charts it has now
been reduced to 97 days on the average.
The saving to commerce thus achieved is much greater than one would
suppose. At the risk of becoming tedious to uninquiring readers, we
will make a brief extract from Hunt's "Merchants' Magazine" of 1854, as
given in a foot-note in Maury's "Physical Geography of the Sea."
"Now, let us make a calculation of the annual saving to the commerce of
the United States effected by these charts and sailing directions.
According to Mr Maury, the average freight from the United States to
Rio Janeiro is 17.7 cents per ton per day; to Australia, 20 cents; to
California, also about 20 cents. The mean of this is a little over 19
cents per ton per day; but, to be within the mark, we will take it at
15, and include all the ports of South America, China, and the East
Indies.
"The sailing directions have shortened the passage to California 30
days; to Australia, 20; to Rio Janeiro, 10. The mean of this is 20; but
we will take it at 15, and also include the above-named ports of South
America, China, and the East Indies.
"We estimate the tonnage of the United States engaged in trade with
these places at 1,000,000 tons per annum.
"With these data, we see that there has been effected a saving for each
one of these tons, of 15 cents per day for a period of 15 days, which
will give an aggregate of 2,250,000 dollars (468,750 pounds) saved per
annum. This is on the outward voyage alone, and the tonnage trading
with all other parts of the world is also left out of the calculation.
Take these into consideration, and also the fact that there is a vast
amount of foreign tonnage trading between these places and the United
States, and it will be seen that the annual sum saved will swell to an
enormous amount."
Before the existence of the Gulf Stream was ascertained, vessels were
frequently drifted far out of their course in cloudy or foggy weather,
without the fact being known, until the clearing away of the mists
enabled the navigators to ascertain their position by solar observation.
Now, not only the existence, but the exact limits and action of this
stream are known and mapped; so that the current, which was formerly a
hindrance to navigation, is now made to be a help to it. The line of
demarcation between the warm waters of the Gulf Stream and the cold
waters of the sea is so sharp and distinct, that by the use of the
thermometer the precise minute of a ship's leaving or entering it can be
ascertained. And by the simple application of the thermometer to the
Gulf Stream the average passage from England to America has been reduced
from upwards of eight weeks to little more than four!
But this wonderful current is useful to navigators in more ways than
one. Its waters, being warm, carry a mild climate along with them
through the ocean even in the depth of winter, and thus afford a region
of shelter to vessels when attempting to make the Atlantic coast of
North America, which, at that season is swept by furious storms and
chilled by bitter frosts. The Atlantic coasts of the United States are
considered to be the most stormy in the world during winter, and the
difficulty of making them used to be much greater in former days than
now. The number of wrecks that take place off the shores of New England
in mid-Winter is frightful. All down that coast flows one of the great
cold currents from the north. The combined influence of the cold
atmosphere above it, and the warm atmosphere over the Gulf Stream, far
out at sea, produces terrific gales. The month's average of wrecks off
that coast has been as high as three a day. In making the coast,
vessels are met frequently by snow-storms, which clothe the rigging with
ice, rendering it unmanageable, and chill the seaman's frame, so that he
cannot manage his ship or face the howling blast. Formerly, when unable
to make the coast, owing to the fury of these bitter westerly gales, he
knew of no place of refuge short of the West Indies, whither he was
often compelled to run, and there await the coming of genial spring ere
he again attempted to complete his voyage. Now, however, the region of
the Gulf Stream is sought as a refuge. When the stiffened ropes refuse
to work, and the ship can no longer make head against the storm, she is
put about and steered for the Gulf Stream. In a few hours she reaches
its edge, and almost in a moment afterwards she passes from the midst of
winter into a sea of sunnier heat! "Now," as Maury beautifully
expresses it, "the ice disappears from her apparel; the sailor bathes
his limbs in tepid waters. Feeling himself invigorated and refreshed
with the genial warmth about him, he realises out there at sea the fable
of Antaeus and his mother Earth. He rises up and attempts to make his
port again, and is again, perhaps, as rudely met and beat back from the
north-west; but each time that he is driven off from the contest, he
comes forth from this stream, like the ancient son of Neptune, stronger
and stronger, until, after many days, his freshened strength prevails,
and he at last triumphs, and enters his haven in safety--though in this
contest he sometimes falls to rise no more, for it is terrible."
The power of ocean currents in drifting vessels out of their course, and
in sweeping away great bodies of ice, is very great; although, from the
fact that there is no land to enable the eye to mark the flow, such
drifts are not perceptible. One of the most celebrated drifts of modern
times, and the most astonishing on account of its extent, was that of
the _Fox_ in Baffin's Bay in the year 1857, a somewhat detailed account
of which will be found in a succeeding chapter.
The Gulf Stream is the cause of many of the most furious storms. The
fiercest gales sweep along with it, and it is supposed that the spring
and summer fogs of Newfoundland are caused by the immense volumes of
warm water poured by it into the cold seas of that region. We are told
that Sir Philip Brooke found the temperature of the sea on each side of
this stream to be at the freezing-point, while that of its waters was 80
degrees. From this it may be easily seen how great are the disturbing
influences around and above it; for, as the warm and moist atmosphere
over it ascends in virtue of its lightness, the cold air outside rushes
in violently to supply its place, thus creating storms.
The warm waters of this stream do not, it is believed, anywhere extend
to the bottom of the sea. It has been ascertained, by means of the
deep-sea thermometer, that they rest upon, or rather flow over, the cold
waters which are hastening from the north in search of those elements
which, in their wanderings, they have lost. As cold water is one of the
best non-conductors of heat, the Gulf Stream is thus prevented from
losing its caloric on its way across the Atlantic to ameliorate the
climates of the western coasts of Europe, and moderate the bitterness of
the northern seas. Were it otherwise, and this great stream flowed over
the crust of the Earth, so much of its heat would be extracted, that the
climates of France and our own islands would probably resemble that of
Canada. Our fields would be covered, for two, three, or four months,
with deep snow; our rivers would be frozen nearly to the bottom; our
land traffic would perhaps be carried on by means of sledges and
carioles; our houses would require to be fitted with double
window-frames and heated with iron stoves and our garments would have to
be made of the thickest woollens and the warmest furs.
The presence and the unchanging regularity of these great hot and cold
currents in the ocean is indicated very clearly by the living
inhabitants of the deep. These, as certainly as the creatures of the
land, are under the influence of climate; so much so, that many of them
never quit their native region in the sea. All the beautiful and
delicate marine creatures and productions which dwell in the warm waters
of the south are utterly absent from those shores which are laved by the
cold currents that descend from the north; while, owing to the influence
of the Gulf Stream, we find many of those lovely and singular creatures
upon our comparatively northern shores. Of late years, as every one
knows, we have all over the land been gathering these marine gems, and
studying their peculiar habits with deep interest in that miniature
ocean the aquarium. In the same parallel on the other side of the
Atlantic none of these little lovers of heat are to be found.
On the other hand, the whale, delighting as it does to lave its huge
warm-blooded body in iced water, is never found to enter the Gulf
Stream. Thus these fish, to some extent, define its position. Other
fish there are which seem to resemble man in their ability to change
their climate at will but, like him also, they are apt in so doing to
lose their health, or, at least, to get somewhat out of condition. Some
kinds of fish, when caught in the waters off Virginia and the Carolinas,
are excellent for the table; but the same species, when taken off the
warm coral banks of the Bahamas, are scarcely worth eating. In fact, we
see no reason for doubting that when these fish find their health giving
way in the warm regions of the south, they seek to reinvigorate
themselves by change of water; and, quitting for a time the beauteous
coral groves, spend a few of the sunnier months of each year in
gambolling in the cool regions of the north, or, what is much the same
thing, in those cool currents that flow from the north in clearly
defined channels.
Besides its other useful and manifold purposes, the Gulf Stream would
seem to be one of the great purveyors of food to the whales.
Sea-nettles, or medusae, are well known to constitute the principal food
of that species of whale which is termed the right whale. Navigators
have frequently observed large quantities of these medusae floating
along with the Gulf Stream; and one sea captain in particular fell in
with an extraordinarily large quantity of them, of a very peculiar
species, off the coast of Florida. As we have said, no whales ever
enter the warm waters of the Gulf Stream; therefore, at that time at
least, the leviathan could not avail himself of this rich provision.
The captain referred to was bound for England. On his return voyage he
fell in with the same mass of medusae off the Western Islands, and was
three or four days in sailing through them. Now, the Western Islands is
a great place of resort for the whale, and thither had the Gulf Stream
been commissioned to convey immense quantities of its peculiar food.
We might enlarge endlessly on this great ocean current, but enough, we
think, has been said to show that the sea, instead of being an ocean of
unchanging drops, driven about at random by the power of stormy winds,
is a mighty flood flowing in an appointed course--steady, regular, and
systematic in its motions, varied and wonderful in its actions, benign
and sweet in its influences, as it sweeps mound and round the world,
fulfilling the will of its great Creator.