to notice that the astronomical observations, by which in favourable
weather he estimated the amount of their northerly progress, showed
a want of correspondence with the actual rate at which they were
travelling. At first he could hardly believe that there was not some
mistake; but at length the unpleasant conviction was forced upon him
that the whole ice-field over which he and his companions had been
toiling so painfully was setting steadily southwards before the wind.
Each day the extent of this set became greater and greater, until at
length they were actually carried as fast towards the south as they
could travel northwards.
Parry deemed it useless to continue the struggle. There were certainly
two chances in his favour. It was possible that the north wind might
cease to blow, and it was also possible that the limit of the ice might
soon be reached, and that his boats might travel easily northward upon
the open sea beyond. But he had to consider the exhausted state of his
men, and the great additional danger to which they were subjected by
the movable nature of the ice-fields. If the ice should break up, or if
heavy and long-continued southerly winds should blow, they might have
found it very difficult to regain their port of refuge in Spitzbergen
before winter set in or their stores were exhausted. Besides, there
were no signs of water in the direction they had been taking. The
water-sky of arctic regions can be recognised by the experienced
seamen long before the open sea itself is visible. On every side,
however, there were the signs of widely-extended ice-fields. It seemed,
therefore, hopeless to persevere, and Parry decided on returning with
all possible speed to the haven of refuge prepared for the party
in Spitzbergen. He had succeeded in reaching the highest northern
latitudes ever yet attained by man. (A somewhat higher latitude has
since been reached by Captain Nares’s expedition.)
The most remarkable feature of this expedition, however, is not the
high latitude which the party attained, but the strange circumstance
which led to their discomfiture. What opinion are we to form of an
ocean at once wide and deep enough to float an ice-field which must
have been thirty or forty thousand square miles in extent? Parry had
travelled upwards of three hundred miles across the field, and we
may fairly suppose that he might have travelled forty or fifty miles
farther without reaching open water; also that the field extended fully
fifty miles on each side of Parry’s northerly track. That the whole of
so enormous a field should have floated freely before the arctic winds
is indeed an astonishing circumstance. On every side of this floating
ice-island there must have been seas comparatively free from ice;
and could a stout ship have forced its way through these seas, the
latitudes to which it could have reached would have been far higher
than those to which Parry’s party was able to attain. For a moment’s
consideration will show that the part of the great ice-field where
Parry was compelled to turn back must have been floating in far higher
latitudes when he first set out. He reckoned that he had lost more than
a hundred miles through the southerly motion of the ice-field, and by
this amount, of course, the point he reached had been nearer the Pole.
It is not assuming too much to say that a ship which could have forced
its way round the great floating ice-field would certainly have been
able to get within four degrees of the Pole. It seems to us highly
probable that she would even have been able to sail upon open water to
and beyond the Pole itself.
And when we remember the direction in which Dr. Kane saw an open
sea—namely, towards the very region where Parry’s ice—ship had floated
a quarter of a century before—it seems reasonable to conclude that
there is open water communication between the seas which lie to the
north of Spitzbergen and those which lave the north-western shores of
Greenland. If this be so, we at once obtain an explanation of the tidal
waves which Kane watched day after day in 1855. These had no doubt
swept along the valley of the Atlantic, and thence around the northern
coast of Greenland. It follows that, densely as the ice may be packed
at times in the seas by which Hudson, Scoresby, and other captains have
attempted to reach the North Pole, the frozen masses must in reality
be floating freely, and there must therefore exist channels through
which an adventurous seaman might manage to penetrate the dangerous
barriers surrounding the polar ocean.
In such an expedition, chance unfortunately plays a large part. Whalers
tell us that there is great uncertainty as to the winds which may
blow during an arctic summer. The icebergs may be crowded by easterly
winds upon the shores of Greenland, or by westerly winds upon the
shores of Spitzbergen, or, lastly, the central passage may be the most
encumbered, through the effects of winds blowing now from the east and
now from the west. Thus the arctic voyager has not merely to take his
chance as to the route along which he shall adventure northwards, but
often, after forcing his way successfully for a considerable distance,
he finds the ice-fields suddenly closing in upon him on every side,
and threatening to crush his ship into fragments. The irresistible
power with which, under such circumstances, the masses of ice bear
down upon the stoutest ship, has been evidenced again and again;
though, fortunately, it not unfrequently happens that some irregularity
along one side or the other of the closing channel serves as a sort
of natural dock, within which the vessel may remain in comparative
safety until a change of wind sets her free. Instances have been known
in which a ship has had so narrow an escape in this way, and has
been subjected to such an enormous pressure, that when the channel
was opened out again, the impress of the ship’s side has been seen
distinctly marked upon the massive blocks of ice which have pressed
against her.
(From the _St. Paul’s Magazine_, June 1869.)
FOOTNOTES:
[5] So far back as 1789, John Williams, in his _Natural History of
the Mineral Kingdom_, discussed the question of the ‘Limited Quantity
of Coal in Great Britain.’ The following extracts are taken from an
excellent paper on the exhaustion of our coal in the _Popular Science
Review_ for July 1866, by Mr. Lemoran, Colliery Viewer. ‘I have no
doubt,’ says Williams, ‘that the generality of the inhabitants of
Great Britain believe that our coal mines are inexhaustible; and the
general conduct of the nation, so far as relates to this subject,
seems to imply that this is held as an established fact. If it was
not a generally received opinion, would the rage for exporting coals
be allowed to go on without limitation or remorse? But it is full
time that the public were undeceived in a matter which so nearly
concerns the welfare of this flourishing island.... When our coal
mines are exhausted, the prosperity and glory of this flourishing and
fortunate island are at an end. Our cities and great towns must then
become ruinous heaps for want of fuel, and our mines and manufactories
must fail from the same cause, and then, consequently, our commerce
must vanish. In short, the commerce, wealth, importance, glory, and
happiness of Great Britain will decay and gradually dwindle away to
nothing, in proportion as our coal and other mines fail.’ Mr. Williams
also solves in a very summary manner the problem of England’s fate
after her coal stores shall be exhausted. ‘The future inhabitants
of this island must live,’ says he, ‘like its first inhabitants, by
fishing and hunting.’
[6] In 1854, the yield was 64,661,401 tons; in 1864, the yield was
92,787,873: the average increase per annum was, therefore, no less than
2,812,647 tons.
[7] I have obtained a somewhat different result from a computation
I have just gone through. I make the consumption 291 millions in
1900, and 1,446 millions in 1950. Mr. Lemoran seems to have taken
the percentage at 3½ instead of 3¼. It is worth noticing how
seriously a small change in the percentage affects the result; the
consumption in 1950 becoming 1,760 millions of tons, instead of 1,446
millions.
[8] The year 1863 was the last whose statistics were available for Mr.
Jevons’s purpose; and estimating from either 1860 or 1862 would give a
result smaller than either of the above. Indeed, the consumption was
less in 1862 than in 1861.
_IS THE GULF STREAM A MYTH?_
The Gulf Stream has recently attracted a large share of the attention
of our men of science. The strange weather which we experienced
last winter (see date of essay) has had something to do with this.
The influence of the Gulf Stream upon our climate, and the special
influence which it is assumed to exercise in mitigating the severity
of our winters, have been so long recognised that meteorologists began
to inquire what changes could be supposed to have taken place in the
great current to account for so remarkable a winter as the last. But
it happened also that at a meeting of the Royal Geographical Society
early in the present year the very existence of the Gulf Stream was
called in question, just when meteorologists were disposed to assign to
it effects of unusual importance. And in the course of the discussion
whether there is in truth a Gulf Stream—or rather whether our shores
are visited by a current which merits such a name—a variety of
interesting facts were adduced, which were either before unknown or had
attracted little attention. As at a recent meeting of the same society
these doubts have been renewed, I propose to examine briefly, in the
first place, a few of the considerations which have been urged against
the existence of a current from the Gulf of Mexico to the neighbourhood
of our shores; and then, having rehabilitated the reputation of
this celebrated ocean river—as I believe I shall be able to do—I
shall proceed to give a brief sketch of the processes by which the
current-system of the North Atlantic is set and maintained in motion.
In reality the Gulf Stream is only a part of a system of oceanic
circulation; but in dealing with the arguments which have been urged
against its very existence, we may confine our attention to the fact
that, according to the views which had been accepted for more than a
century, there is a stream of water which, running out of the Gulf
Stream through the Narrows of Bemini, flows along the shores of the
United States to Newfoundland, and thence right across the Atlantic to
the shores of Great Britain. It is this last fact which is now called
in question. The existence of a current as far as the neighbourhood of
Newfoundland is conceded, but the fact that the stream flows onward to
our shores is denied.
The point on which most stress is placed is the shallowness of the
passage called the ‘Bemini Narrows,’ through which it is assumed that
the whole of the Gulf current must pass. This passage has a width of
about forty miles, and a depth of little more than six hundred yards.
The current which flows through it is perhaps little more than thirty
miles in width, and a quarter of a mile in depth. It is asked with
some appearance of reason, how this narrow current can be looked upon
as the parent of that wide stream which is supposed to traverse the
Atlantic with a mean width of some five or six hundred miles. Indeed,
a much greater width has been assigned to it, though on mistaken
grounds; for it has been remarked that since waifs and strays from the
tropics are found upon the shores of Portugal, as well as upon those of
Greenland, we must ascribe to the current a span equal to the enormous
space separating these places. But the circumstance here dwelt upon can
clearly be explained in another way. We know that of two pieces of wood
thrown into the Thames at Richmond, one might be picked up at Putney,
and the other at Gravesend. Yet we do not conclude that the width of
the Thames is equal to the distance separating Putney from Gravesend.
And doubtless the tropical waifs which have been picked up on the
shores of Greenland and of Portugal have found their way thither by
circuitous courses, and not by direct transmission along opposite edges
of the great Gulf current.
But certainly the difficulty associated with the narrowness of the
Bemini current is one deserving of careful attention. Are we free to
identify a current six hundred miles in width with one which is but
thirty miles wide, and not very deep? An increase of width certainly
not less than thirtyfold would appear to correspond to a proportionate
diminution of depth. And remembering that it is only near the middle of
the Narrows that the Gulf Stream has a depth of four hundred yards, we
could scarcely assign to the wide current in the mid-Atlantic a greater
depth than ten or twelve yards. This depth seems altogether out of
proportion to the enormous lateral extension of the current.
But besides that even this consideration would not suffice to
disprove the existence of a current in the mid-Atlantic, an important
circumstance remains to be mentioned. The current in the Narrows flows
with great velocity,—certainly not less than four or five miles an
hour. As the current grows wider it flows more sedately; and opposite
Cape Hatteras its velocity is already reduced to little more than
three miles an hour. In the mid-Atlantic the current may be assumed to
flow at a rate little exceeding a mile per hour, at the outside. Here,
then, we have a circumstance which suffices to remove a large part of
the difficulty arising from the narrowness of the Bemini current, and
we can at once increase our estimate of the depth of the mid-Atlantic
current fivefold.
But this is not all. It has long been understood that the current
which passes out through the Narrows of Bemini corresponds to the
portion of the great equatorial current which passes into the Gulf
of Mexico between the West Indian Islands. We cannot doubt that the
barrier formed by those islands serves to divert a large portion of
the equatorial current. The portion thus diverted finds its way, we
may assume, along the outside of the West Indian Archipelago, and thus
joins the other portion—which has in the meantime made the circuit of
the Gulf—as it issues from the Bemini Straits. All the maps in which
the Atlantic currents are depicted present precisely such an outside
current as I have here spoken of, and most of them assign to it a width
exceeding that of the Bemini current. Indeed, were it not for the
doubts which the recent discussions have thrown upon all the currents
charted by seamen, I should have been content to point to this outside
current as shown in the maps. As it is, I have thought is necessary
to show that such a current must necessarily have an existence, since
we cannot lose sight of the influence of the West Indian Isles in
partially damming up the passage along which the equatorial current
would otherwise find its way into the Gulf of Mexico. Whatever portion
of the great current is thus diverted must find a passage elsewhere,
and no passage exists for it save along the outside of the West Indian
Isles.
The possibility that the wide current which has been assumed to
traverse the mid-Atlantic may be associated with the waters which
flow from the Gulf of Mexico, either through the Narrows or round
the outside of the barrier formed by the West Indies, has thus been
satisfactorily established. But we now have to consider difficulties
which have been supposed to encounter our current on its passage from
the Gulf to the mid-Atlantic.
Northwards, along the shores of the United States, the current has been
traced by the singular blueness of its waters until it has reached the
neighbourhood of Newfoundland. Over a part of this course, indeed,
the waters of the current are of indigo blue, and so clearly marked
that their line of junction with the ordinary sea-water can be traced
by the eye. ‘Often,’ says Captain Maury, ‘one half of a vessel may
be perceived floating in Gulf Stream water, while the other half is
in common water of the sea—so sharp is the line, and such the want
of affinity between the waters, and such, too, the reluctance, so to
speak, on the part of those of the Gulf Stream, to mingle with the
littoral waters of the sea.’
But it is now denied that there is any current beyond the neighbourhood
of Newfoundland—or that the warm temperature, which has characterised
the waters of the current up to this point, can be detected farther out.
It is first noticed that, as the Gulf current must reach the
neighbourhood of Newfoundland with a north-easterly motion, and, if
it ever reached the shores of the British Isles, would have to travel
thither with an almost due easterly motion, there is a change of
direction to be accounted for. This, however, is an old, and I had
supposed exploded, fallacy. The course of the Gulf Stream from the
Bemini Straits to the British Isles corresponds exactly with that which
is due to the combined effects of the motion of the water and that of
the earth upon its axis. Florida being much nearer than Ireland to
the equator, has a much more rapid easterly motion. Therefore, as the
current gets farther and farther north, the effect of the easterly
motion thus imparted to it begins to show itself more and more, until
the current is gradually changed from a north-easterly to an almost
easterly stream. The process is the exact converse of that by which the
air-currents from the north gradually change into the north-westerly
trade-winds as they get farther south.
But it is further remarked that as the current passes out beyond the
shelter of Newfoundland, it is impinged upon by those cold currents
from the arctic seas which are known to be continually flowing out
of Baffin’s Bay and down the eastern shores of Greenland; and it is
contended that these currents suffice, not merely to break up the
Gulf current, but so to cool its waters that these could produce no
effect upon the climate of Great Britain if they ever reached its
neighbourhood.
Here, again, I must remark that we are dealing with no new discovery.
Captain Maury has already remarked upon this peculiarity. ‘At the very
season of the year,’ he says, ‘when the Gulf Stream is rushing in
greatest volume through the Straits of Florida, and hastening to the
north with the greatest rapidity, there is a cold stream from Baffin’s
Bay, Labrador, and the coasts of the north, running south with equal
velocity.... One part of it underruns the Gulf Stream, as is shown
by the icebergs, which are carried in a direction tending across its
course.’ There can be no doubt, in fact, that this last circumstance
indicates the manner in which the main contest between the two currents
is settled. A portion of the arctic current finds its way between the
Gulf Stream and the continent of America; and this portion, though
narrow, has a very remarkable effect in increasing the coldness of
the American winters. But the main part, (heavier, by reason of its
coldness, than the surrounding water,) sinks beneath the surface. And
the well-known fact mentioned by Maury, that icebergs have been seen
stemming the Gulf Stream, suffices to show how comparatively shallow
that current is at this distance from its source, and thus aids to
remove a difficulty which we have already had occasion to deal with.
Doubtless the cooling influence of the arctic currents is appreciable;
but it would be a mistake to suppose that this influence can suffice
to deprive the Gulf current of its distinctive warmth. If all the
effect of the cold current were operative on the Gulf Stream alone we
might suppose that, despite the enormous quantity of comparatively
warm water which is continually being carried northwards, the current
would be reduced to the temperature of the surrounding water. But
this is not so. The arctic current not only cools the Gulf current,
but the surrounding water also—possibly to a greater extent, for it
is commonly supposed that a bed of ordinary sea-water separates the
two main currents from each other. Thus the characteristic difference
of temperature remains unaffected. But in reality we may assume that
the cooling effect actually exercised by the arctic current upon the
neighbouring sea is altogether disproportionate to the immense amount
of heat continually being carried northwards by the Gulf Stream.
It is astonishing how unreadily two sea-currents exchange their
temperatures—to use a somewhat inexact mode of expression. The very
fact that the littoral current of the United States is so cold—a fact
thoroughly established—shows how little warmth this current has drawn
from the neighbouring seas. Another fact, mentioned by Captain Maury,
bears in a very interesting manner upon this peculiarity. He says:
‘If any vessel will take up her position a little to the northward of
Bermuda, and steering thence for the capes of Virginia, will try the
water-thermometer all the way at short intervals, she will find its
reading to be now higher, now lower; and the observer will discover
that he has been crossing streak after streak of warm and cool water in
regular alternations.’ Each portion maintains its own temperature, even
in the case of such warm streaks as these, all belonging to one current.
Similar considerations dispose of the arguments which have been founded
on the temperature of the sea-bottom. It has been proved that the
living creatures which people the lower depths of the sea exist under
circumstances which evidence a perfect uniformity of temperature; and
arguments on the subject of the Gulf Stream have been derived from the
evidence of what is termed a minimum thermometer—that is, a thermometer
which will indicate the lowest temperature it has been exposed to—let
down into the depths of the sea. All such arguments, whether adduced
against or in favour of the Gulf Stream theory, must be held, to be
futile, since the thermometer in its descent may pass through several
submarine currents of different temperature.
Lastly, an argument has been urged against the warming effects of the
Gulf Stream upon our climate which requires to be considered with
some attention. It is urged that the warmth derived from so shallow
a current as the Gulf Stream must be, by the time it has reached our
shores, could not provide an amount of heat sufficient to affect our
climate to any appreciable extent. The mere neighbourhood of this water
at a temperature slightly higher than that due to the latitude could
not, it is urged, affect the temperature of the inland counties at all.
This argument is founded on a misapprehension of the beautiful
arrangement by which Nature carries heat from one region to distribute
it over another. Over the surface of the whole current the process of
evaporation is going on at a greater rate than over the neighbouring
seas, because the waters of the current are warmer than those which
surround them. The vapour thus rising above the Gulf Stream is
presently wafted by the south-westerly winds to our shores and over
our whole land. But as it thus reaches a region of comparative cold,
the vapour is condensed—that is, turned into fog, or mist, or cloud,
according to circumstances. It is during this change that it gives out
the heat it has brought with it from the Gulf Stream. For precisely as
the evaporation of water is a process requiring heat, the change of
vapour into water—whether in the form of fog, mist, cloud, or rain—is a
process in which heat is given out. Thus it is that the south-westerly
wind, the commonest wind we have, brings clouds and fogs and rain to us
from the Gulf Stream, and with them brings the Gulf Stream warmth.
Why the south-westerly winds should be so common, and how it is that
over the Gulf Stream there is a sort of air-channel along which winds
come to us as if by their natural pathway, are matters inquired into
farther on (see p. 164). The subject is full of interest, but need not
here detain us.
It would seem that a mechanism involving the motion of such enormous
masses of water as the current-system of the Atlantic should depend
on the operation of very evident laws. Yet a variety of contradictory
hypotheses have been put forward from time to time respecting this
system of circulation, and even now the scientific world is divided
between two opposing theories.