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BROOKE'S DEEP-SEA SOUNDING APPARATUS.

Vide page 3 1 3

THE

PHYSICAL GEOGEAPHY

OF

THE SEA,

AND ITS METEOEOLOGY.

BY M. F. MAURY, LL.D.

ixiktnt^ §Vitmx,

BEING THE SIXTH EDITION OF THE AUTHOR'S RECONSTEUCTiON OF
THE WORK. .

WITH NEW AND COMPLETE INDEX.
ILLUSTRATED WITH NUMEROUS CHARTS AND DIAGRAMS.

LONDON:
SAMPSON LOW, MAKSTON, LOW, AND SEARLE,

CROWN BUILDINaS, 188 FLEET STREET.
1874.

\_The right of Tjanslation is reserved.]

^64^'

CEl.VTEl BY WILLIAM CLOWES AND SONS, STAJIFOl'.D STlikE;
AND CHAKING CEOSS.

INTRODUCTION

The Physical Geography of the Sea is a new department of
human knowledge. It has resulted from that beautiful and
admirable system of physical research, in which all the maritime
nations have agreed to unite ; and for the furtherance of which
bureaux have been established, especially in Holland, England,
France, and the United States.

Consequently, research has become very active in this field ;
it is diligent, too ; and in proportion to that activity and that
diligence has been the advancement of our knowledge concerning

the PHYSICAL GEOGRAPHY OF THE SEA AND ITS METEOROLOGY. It

may be doubted whether progress in any department of science
has been more rapid than it has been in this.

The first treatise upon this subject appeared in America six
years ago. Since then such has been the richness of the harvest
of facts gathered, that the work has undergone frequent amend-
ments and improvements ; indeed, within that time it has been
almost entirely re-written thrice. This re-writing was necessary
because it is a main motive with the author to have the work
keep pace with the science itself. The consequence has been,
that each re-cast has really made a new work of it.

The present edition is not only greatly enlarged above its pre-
decessors, but it is believed to be greatly enriched and improved
also. It may even be doubted whether in the variety, extent,
and value of the information now for the first time presented
touching the sea and air, this edition is not so far in advance of
former editions as really to make this a new work. Where error
has been found in previous editions, it has been corrected in this,
— where further research has confirmed opinions that in them
were ventured as such, the confirmation is here given.

The present edition contains a number of chapters entirely new
and not to be found in any of its predecessors. Most, if not all

vi INTRODUCTION.

the chapters contained in them, have also been enlarged, amended,
and improved.

In short, the anthor desires here to state to the friends and
students of this beautiful and elevating science, that it is pra
gressive — that occupying with regard to it somewhat the relation
of a pioneer, his object has been, is, and shall be, truth.

The primary object of the researches connected with " the
Wind and Current Charts," out of which has grown this
Treatise, was to collect the experience of every navigator as to
the winds and currents of the ocean, to discuss his observations
upon them, and then to present the world with the results on
charts for the improvement of commerce and navigation.

By putting down on a chart the tracks of many vessels on the
same voyage, but at different times, in different years, and during
all seasons, and by projecting along each track the winds and
currents daily encountered during the voyage, it was plain that
navigators hereafter, by consulting such a record, would have for
their guide the results of the combined experience of all whose
tracks were thus pointed out.

Perhaps it might be the first voyage of a young navigator to
the given port, when his own personal experience of the winds
to be expected, the currents to be encountered by the way, would
itself be blank. If so, there would be the wind and current
chart for reference. It would spread out before him the tracts of
a thousand vessels that had preceded him on the same voyage,
wherever it might be, and that, too, at the same season of the
year. Such a chart, it was held, would show him not only the
tracks of the vessels, but the experience also of each master as to
the winds and currents by the way, the temperature of the
ocean, and the variation of the needle. All this could be taken
in at a glance, and thus the young mariner, instead of groping
his way along until the lights of experience should come to him
by the slow teachings of the dearest of all schools, would here
find, at once, that he had already the experience of a thousand
navigators to guide him on his voyage. He might, therefore, set
out upon his first voyage with as much confidence in his know-
ledge, as to the winds and currents he might expect to encounter,
as though he himself had already been that way a thousand times
before.

Such a chart could not fail to commend itself to intelligent
ship-masters, and such a chart was constructed for them. They

INTRODUCTION. VU

took it to sea, they tried it, and to their surprise and delight
they found that, with the knowledge it afforded, the remote
corners of the earth were brought closer together, in some
instances, by many days' sail. The passage hence to the equator
alone was shortened ten days. Before the commencement of this
undertaking, the average passage to California was 183 days ;
but with these charts for their guide, navigators have reduced
that average, and brought it down to 135 days.

Between England and Australia, the average time going, with-
out these charts, is ascertained to be 124 days, and coming, about
the same ; making the round voyage one of about 250 days on
the average.

These charts, and the system of research to which they have
given rise, bid fair to bring that colony and the mother country
nearer by many days, reducing in no small measure the average
duration of the round voyage.*

At the meeting of the British Association of 1853, it was stated
by a distinguished member — and the statement was again repeated
at its meeting in 1854 — that in Bombay, whence he came, it was
estimated that this system of research, if extended to the Indian
Ocean, and embodied in a set of charts for that sea, such as I
have been describing, would produce an annual saving to British
commerce, in those waters alone, of one or two mi'^lions of
dollars ;t and in all seas, of ten millions.!

* The outward passage, it has since been ascertained, has been reauced to
97 days on the average, and the homeward passage has been made in 63 under
canvas alone.

t See Inaugural Address of the Earl of Harrowby, President of the Britisli
Association at its 24th meeting. Liverpool, 1854.

X . . . " "N'ow let us make a calculation of the annual saving to the commerce
of the United States effected by those charts and sailing directions. According
to Mr. Maury, the average freight from the "United States to Eio Janeiro is
17*7 cts. per ton per day ; to Australia, 20 cts. ; to California, also, about 20 cts.
The mean of this is a little over 19 cts. per ton per day ; but to be witliin 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 passages to California 30 days,
to Australia 20, to Eio 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

Vni INTRODUCTION.

A system of philosophical research which is so rich with fruits
and abundant with promise could not fail to attract the attention
and commend itself to the consideration of the seafaring com-
munity of the whole civilized world. It was founded on observa-
tion ; it was the result of the experience of many observant men,
now brought together for the first time, and patiently discussed.
The results tended to increase human knowledge with regard to
the laws and phenomena of both sea and air ; and therefore the
system of research could not be wanting in attractions to right-
minded men.

The results of the first chart, however, though meagre and un-
satisfactory, were brought to the notice of navigators ; their
attention was called to the blank spaces, and the importance of
more and better observations than were generally contained in
the old sea-logs was urged upon them.

They were told that if each one would agree to co-operate in a
general plan of observations at sea, and would send regularly, at
the end of every cruise, an abstract log of his voyage to the
National Observatory at Washington, he should, for so doing, be
furnished, free of cost, with a copy of the charts and sailing
directions that might be founded upon those observations.

The quick, practical mind of the enterprising ship-master
seized the proposition at once. To him the field was inviting,
for he saw in it the promise of a rich harvest and of many useful
results.

So, in a little while, there were more than a thousand naviga-
tors engaged day and night, and in all parts of the ocean, in
making and recording observations according to a uniform plan,
and in furthering this attempt to increase our knowledge as to
the winds and currents of the sea, and other phenomena that
I'elate to the safe navigation of its waters, and to its physical
geography.

To enlist the service of such a large corps of observers, and to
have the attention of so many clever and observant men directed

aggregate of $: 2,250,000 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 Stfites, and it will be seen that the annual sum saved will swell to an
enormous amount.'' — Extract Jrum Hunt's Merchant's Magazine, May, 1854.

INTRODUCTION. ' IX

to the same subject, was a great point gained : it was a giant
stride in the advancement of knowledge, and a great step towards
its spread upon the waters.

Important results soon followed, and valuable discoveries were
made. These attracted the Attention of the commercial world,
and did not escape the notice of philosophers generally.

The field was immense, the harvest was plenteous, and there
was both need and room for more labourers. Whatever the
reapers should gather, or the merest gleaner collect, was to
insure to the benefit of commerce and navigation— the increase
of human knowledge — the good of all.

Therefore, all who use the sea were equally interested in the
undertaking. The government of the United States, so consider-
ing the matter, proposed a uniform system of observations at sea,
and invited all the maritime states of Christendom to a conference
upon the subject.

This conference, consisting of representatives from France,
England, and Eussia, from Sweden and Norway, Holland, Den-
mark, Belgium, Portugal, and the United States, met in Brussels,
August 23, 1853, and recommended a plan of observations which
should be followed on board the vessels of all friendly nations,
and especially of those there present in the persons of their re-
presentatives.

Prussia, Spain, Sardinia, Oldenberg and Hanover, the Holy
See, the free city of Hamburg, the republics of Bremen and Chili,
and the empires of Austria and Brazil, have since ofi;"ered their
co-operation also in the same plan.

Thus the sea has been brought regularly within the domains of
jihilosophical research, and crowded with observers.

In peace and in war these observations are to be carried on,
and, in case any of the vessels on board of which they are con-
ducted may be captured, the abstract log — as the journal which
contains these observations is called — is to be held sacred.

The illustrious Humboldt, several 3^ears before his death,
expressed the opinion that the results already obtained from this
system of research had given rise to a new department of science,
which he called the physical geography of the sea.

Earely before has there been such a sublime spectacle presented
to the scientific world : all nations agreeing to unite and co-
operate in carrying out according to the same plan, one system
of philosophical research with regard to the sea. Though they

X INTRODUCTION.

may be enemies in all else, here they are to be friends. Every
ship that navigates the high seas with these charts and blank
abstract logs on board may henceforth be I'egarded as a floating
observatory, a temple of science. The instruments used by
every co-operating vessel are to be compared with standards that
are common to all ; so that an observation that is made anywhere
and in any ship may be referred to and compared with all similar
observations by all other ships in all parts of the world.

But these meteorological observations which this extensive and
admirable system includes will relate only to the sea. This is
not enough. The plan should include the land also, and be
universal. Other great interests of society are to be benefited
by such extension no less than commerce and navigation have
been. A series of systematic observations, directed over large
districts of country, nay, over continents, to the improvement of
agricultural and sanitary meteorology, would, I have no doubt,
tend to the development of many interesting, important, ard
valuable results.

With proper encouragement, this plan of research is capable
of great expansion. With the aid of the magnetic telegraph, and
by establishing a properly devised system of daily weather
reports by telegram, sentinels upon the weather may be so posted
that we may have warning in advance of every storm that
traverses the country. Holland, France, and England, have
recently established such a plan of daily weather reports from
certain stations. And Admiral Fitzroy, at the head of the
Meteorological Department of the Board of Trade in London,
informs me that already, though the plan went into operation
only in the month of September, 1860, yet it is most rich with
the promise of a fine harvest of practical results.

The agricultural societies of many states of America have
addressed memorials to the American Congress, asking for such
extension over that continent.

This plan contemplates the co-operation of all the states of
Christendom, at least so far as the form, method, subjects of
observations, time of making them, and the interchange of
results are concerned. Great good is to come of it — shipwrecks
and disasters are to be prevented by it — the public weal is to be
promoted by it, the convenience of society is to be enhanced by
it, the bounds of human knowledge are to be enlarged by it, and
it is hoped that the friends of meteorology, and all who may find

INTRODUCTION. XI

interest or pleasure in a perusal of these passages, will lend their
assistance to the carrying out of this plan, by advocating it
among their friends. These researches for the land look not only
to the advancement of the great interests of sanitary and agri-
cultural meteorology, but they involve also a study of the laws
which regulate the atmosphei'e, and call for a careful investigation
of all its phenomena.

Another beautiful feature in this system is, that it costs nothing
additional. The instruments that these observations at sea call
for are such as are already in use on board of every well-con-
iitioned ship, and the observations that are required are precisely
those which are necessary for her safe and proper navigation.

As great as is the value attached to what has been accomplished
by these researches in the way of shortening passages and lessen-
ing the dangers of the sea, a good of higher value is, in the
opinion of many seamen, yet to come out of the moral, the
educational influence which they are calculated to exert upon
the seafaring community of the world. A very clever English
ship-master, speaking recently of the advantages of educational
influences among those who' intend to follow the sea, remarks :

" To the cultivated lad there is a new world spread out when
he enters on his first voyage. As his education has fitted, so
will he perceive, year by year, that his profession makes him
acquainted with things new and instructive. His intelligence
will enable him to appreciate the contrasts of each country in its
general aspect, manners, and productions, and in modes of
navigation adapted to the character of coast, climate, and rivers.
He will dwell with interest on the phases of the ocean, the
storm, the calm, and the breeze, and will look for traces of the
laws which regulate them. All this will induce a serious
earnestness in his work, and teach him to view lightly those
irksome and often offensive duties incident to the beginner."*

And that these researches do have such an effect many noble-
hearted mariners have testified. Captain Phinney, of the Ameri-
can ship "Gertrude," writing from Callao, January, 1855, thus
expresses himself :

* " The Log of a Merchant Officer ; viewed with reference to the
Education of young Officers and the Youth of the Merchant Service. By
Robert Methren, Commander in the Peninsular and Oriental Company, and
author of the * Narrative of the Blenheim Hurricane of 1851.' " London :
John Weale, 59 High Holborn ; Smith, Elder & Co., Comhill ; Ackerman A
Co., Strand. 1854.

XI] [NTKODUCTION.

" Having to proceed from this to the Chincha Islands and
remain three months, I avail myself of the present opportunity
to forward to you abstracts of my two passages over your southern ^
routes, although not required to do so until my own return to the
United States next summer ; knowing that you are less amply
supplied with abstracts of voyages over these regions than of
many other parts of the ocean, and, such as it is, I am happy to
contribute my mite towards furnishing you with material to
work out still farther towards perfection your great and glorious
task, not only of pointing out the most speedy routes for ships to
follow over the ocean, but also of teaching us sailors to look
about us, and see by what wonderful manifestations of the
wisdom and goodness of the great God we are continually
surrounded.

" For myself, I am free to confess that for many years I com-
manded a ship ; and, although never insensible to the beauties of
nature upon the sea or land, I yet feel that, until I took up your
work, I had been traversing the ocean blindfolded. I did not
think ; I did not know the amazing and beautiful combination of
all the works of Him whom you so beautifully term ' the Great
First Thought.'

"I feel that, aside from any pecuniary profit to myself from
your labours, you have done me good as a man. You have taught
me to look above, around, and beneath me, and recognize God's
hand in every element by which I am surrounded. I am grateful
for this personal benefit. Your remarks on this subject, so fre-
quently made in your work, cause in me feelings of the greatest
admiration, although my capacity to comprehend your beautiful
theory is very limited.

" The man of such sentiments as you express will not be
displeased with, or, at least, will know how to excuse, so much
of what (in a letter of this kind) might be termed ii-relevant
matter. I have therefore spoken as I feel, and with sentiments
of the greatest respect."

Sentiments like these cannot fail to meet with a hearty re-
sponse fiom all good men, whether ashore or afloat. Admiral
Fitzroy, admitting the value of the practical results already
derived by commerce and navigation from these researches, is of
opinion that their influence in improving and elevating the mind
of the r>ritish seaman also, can scarcely be of less importance.

Never before has such a corps of observers been enlisted ir

INTRODUCTION. XIU

the cause of any department of physical science as is that which
is now about to be engaged in advancing our knowledge of the
Physical Geography of the Sea, and never before have men felt
such an interest with regard to this knowledge.

Under the term " Physical Geography and its Meteorology."
will be included a philosophical account of the winds and currents
of the sea ; of the circulation of the atmosphere and ocean ; of
the temperature and depth of the sea ; of the wonders that lie
hidden in its depths ; and of the phenomena that display them-
selves at its surface. In short, I shall treat of the economy of
the sea and its adaptations— of its salts, its waters, its climates,
and its inhabitants, and of whatever there may be of general
interest in its commercial uses or industrial pursuits ; — for all
such things pertain to this department of science.

The object of this work, moreover, is to show the present
state, and, from time to time, the progress of this new and
beautiful system of research, as well as of the advancement made in
this interesting department of science; and the aim of the author
is to present the gleanings from this new field in a manner that
may be interesting and instructive to all, whether old or young,
ashore or afloat, who desire a closer look into " the wonders of
the great deep," or a better knowledge as to its winds, its
adaptations, or its Physical Geography.*

* There is an old and very rare book wliich treats upon some of the subjects
to which this little work relates. It is by Count L. F. Maksigli, an Italian,
and is called Natural Description of the Seas. The copy to which I refer
was translated into Dutch by Boerhaave in 1786.

The learned count made his observations along the coast of Provence and
Languedoc. The description only relates to that part of the Mediterranean.
The book is divided into four chapters : the first, on the bottom and shape of
the sea ; the second, of sea water ; the third, on the movements of sea water ;
and the fourth, of sea plants.

He divides sea water into surface and deep-sea water ; because, when he
makes salt from surface water (not more than half a foot below the upper
strata), this salt will give a red colour to blue paper ; whereas the salt from
deep-sea water will not alter the colours at all. The blue paper can only
change its colour by the action of an acid. The reason why tliis acid (iodine ?)
is found in surftice and not in deep-sea water is, it is derived from the air ; but
he supposes that the saltpetre that is found in sea water, by the action of the
sun's rays and the motion of the waves, is deprived of its coarse parts, and, by
evaporation, embodied in the air, to be conveyed to beasts or plants for their
existence, or deposited upon the earth's crust, as it occurs on the plains of
Hungary, where the earth absorbs so much of this saltpetre vapour.

Uonati, also, was a valuable labourer in this field. His inquii-ies enabled

XIV INTRODUCTION.

The results that are embodied in Plate I. alone of this edition
would, had the data for it been ccllected by a force specially
employed for the purpose, have demanded constant occupation
from a fleet of ten sail for more than one hundred years. The co-
ordinating of these observations after they were made, and the
bringing of them to the present condensed form, has involved a
vast amount of additional labour. Officers here have been
engaged upon the work for many years. This patient industry
has been rewarded with the discovery of laws and the develop-
ment of truths of great value in navigation and very precious to
science.

It would be presumptuous to claim freedom from error for a
work like this : true progress consists in the discovery of error
as well as of trutli. But I may be pardoned for saying that the
present edition of this work will be found to contain more of
truth and less of error than any of its predecessors, simply
because it is founded on wider research, and based on the results
of more abundant observations than they. Indeed, it could not,
or, rather, it should not be otherwise ; for, as long as we are
making progress in any field of physical research, so long must
the results continue to increase in value ; and just so long must
what at first was conjecture grow and gain as truth, or fade and
fall as error.

The fact seems now to be clearly established that the atmo-
sphere is very unequally divided on opposite sides of the equator,
and that there is a mild climate in the unknown regions of the
antarctic circle. Over the extra-tropical regions of our planet,
the atmosphere on the polar side of 40° N. and 40° S. is so
unequally divided as to produce an average pressure, according
to the parallel, of from 10 to 50 lbs. less upon the square foot of
sea surface in southern than upon the square foot of sea surface
in northern latitudes. These, and many other developments not

Mr. Trembley^ to conclude that there are, "at the bottom of the water,
mountains, plains, valleys, and caverns, just as upon the land."

But by far the most interesting and valuable book touching the physical
geography of the Mediterranean is Admiral Smyth's last work, entitled " The
Mediterranean ; a Memoir, Physical, Historical, and Nal-tioal. By
Rear- Admiral William Henry Smyth, K.S.F., D.C.L.," &c. London ; John
W. Parker and Son. 1854

- Philosophical Transactions.

INTKODUCTION. XV

less interesting, seemed to call for a re-cast of the work. Indeed,
several new chapters have been added to this edition, and many
new subjects have been treated of in it. New views also have
been presented, and the errors of former views corrected wherever
in them farther research has pointed out error. These researches
have grown so wide that they comprehend not only the physics
of the sea, but they relate extensively to its meteorology also ;
hence the present title, The Physical Geogkaphy of the Sea,
AND ITS Meteorology.

i, Albemarle Sfreet, London.

20th Novemher, 1S60.

CONTENTS.

Paos

L The Sea and the Atmosphere 1

II. The Gl-lp Stream 22

III. Ineluence of the GrLF Stream lton Cj.imates and Com-
merce 53

rV. The Atmosphere 75

V. Eatns and Eivers 105

VI. Eed Fogs and Sea Breezes 138

Vn. The Easting op the Trade-Winds, the Crossing at the

Calm Belts, and the Magnetism op the Atmosphere . 153

VIII. Currents of the Sea 179

IX. The Specific Gravity of the Sea, and the Open Water

IN the Arctic Ocean ....... 206

X. The Salts op the Sea 235

XI. The Cloud Eegion, the Equatorial Cloud-Eing, and Sea

Fogs 270

XII. The Geological Agency op the Winds .... 285

XIII. The Depths of the Ocean 303

XrV. The Basin and Bed of the Atlantic . . . . 314

XV. Sea Eoutes, C^^dm Belts, and Variable Winds . . . 334

XVI. Monsoons ,365

XVII The Climates of the Sea . . . . . , , 382

XVIII. Tede-Eips and the Sea-Drift 394

XIX. Storms, Hurricanes, and Typhoons 413

XX. The Winds op the Southern Hemisphere . . . 431

XXI. The Antarctic Eegions and their Climatology . . . 452

XXU. The Actinometry op the Sea 408

EXPLANATION OF THE PLATES.

Plate 1. — This Plate combines in its construction the results of 1,159,353
separate observations on the force and direction of the wind, and a little
upwards of 100,000 observations on the height of the barometer at sea. The
wind observations embrace a period of eight hours each, or three during the
twenty-four hours. Each one of the barometric observations expresses the mean
height of the barometer for the day; therefore each one of the 100,000 may
itself be the mean of many, or it may be only one. Suffice it to say, that 83,334r
of them were obtained by Lieutenant Andrau from the logs of Dutch ships
during their voyages to and fro between the parallels of 50° N. and 36° S. ; that
nearly 6,000 of them were made south of the parallel of 36° S., and obtained
from the log-books at the Observatory in Washington ; that for the others at sea
I am indebted to the observations of Captain Wilkes, of the Exploring Expe-
dition, of Sir James Clark Ross, on board the Erebus and T'error^ in high
southern latitudes, and of Dr. Kane in the Arctic Ocean, Besides these, others
made near the sea have been used, as those at Greenwich, St. Petersburg,
Hobart Tovra, etc., making upwards of 100,000 in all. This profile shows how
unequally the atmosphere is divided by the equator.

The arrows within the circle fly with the wind. They represent its mean
annual direction from each quarter, and by bands 5° of latitude in breadth, and
according to actual observation at sea. They show by their length the annual
duration of the wind in months. They are on a scale of one twentieth of an
inch per month, except the half-bearded arrows, which are on a scale twice as
great, or one tenth of an inch to the month. If will thus be perceived at a
glance that the winds of the longest duration are the S.E. trades, between the
parallels of 5° and 10° south, where the long-feathered arrows represent an
annual average of ten months.

The most prevalent winds in each band are represented by full-feathered
arrows ; the next by half-feathered, except between the parallels of 30° and 35°
N., where the N.E. and S.W. winds, and between the parallels of 35° and 40°,
where the N.W. and S.W. winds contend for the mastery as to average annual
duration.

The rows of arrows on each side of the axis, and nearest to it, are projected
with the utmost care as to direction, and length or duration.

The feathered arrows in the shading around the circle represent the crossing
at the calm belts, and the great equatorial and polar movements by upper and
lower currents of air in its general system of atmospherical circulation.

The small featherless and curved arrows, n g r s, on the shading around the
circle, are intended to suggest how the trade-winds, as they cross parallels of
larger and larger circumference on their way to the equator, act as an undertow,
and draw supplies of pure air down from the counter-current above ; which
supplies are required to satisfy the increasing demands of these winds ; for, as
they near the equator, they not only cross parallels of larger circumference, but,
as actual observations show, they also greatly increase both their duration and

h

XVill EXPLANATION OF THE PLATES.

velocity. In like manner, the counter-trades, as they approach the poles, are
going from latitudes where the parallels are larger to latitudes where the pa-
rallels are smaJler. In other words, they diminish, as they approach the poles,
the area of their vertical section ; consequently there is a crowding out— a slough-
ing oflf from the lower current, and a joining and a turning back with the upper
current. This phenomenon is represented by the small featherless and curved
arrows in the periphery on the polar side of the calm belts of Cancer and Ca-
pricorn.

This dotted or shaded periphery is intended to represent a profile view of the
atmosphere as suggested by the readings of the barometer at sea. This method
of delineating the atmosphere is resorted to in order to show the unequal dis-
tribution of the atmosphere, particularly on the polar side of lat. 40° S. ; also the
piling up over the calm belts, . and the depression— barometrical— over the
equatorial calms and cloud ring.

The engirdling seas of the extra-tropical south suggest at once the cause of
this inequality in the arrangement over them of the airy covering of our planet.
Excepting a small portion of South America, the belt between the parallels of
40° and 65° or 70° south may be considered to consist entirely of sea. This
immense area of water surface keeps the atmosphere continually saturated with
vapour. The specific gravity of common atmospheric air being taken as unity,
that of aqueous vapour is about 0.6 ; consequently the atmosphere is expelled
thence by the steam, if, for the sake of explanation, we may so call the vapour
which is continually rising up from this immense boiler. This vapour displaces
a certain portion of air, occupies its place, and, being one third lighter, also
makes lighter the barometric column. Moreover, being lighter, it mounts up
into the cloud region, where it is condensed into clouds or rain, and the latent
heat that is set free in the process assists still farther to lessen the barometric
column ; for the heat thus liberated warms and expands the upper air, causing it
to swell out above its proper level, and so flow back towards the equator with
the upper current of these regions.

Thus, though the barometer stands so low as to show that there is less
atmosphere o /er high southern latitudes than there is in corresponding latitudes
north, yet, if it were visible and we could see it, we should discover, owing to
the efiect of this vapour and the liberation of its latent heat, and the resulting
intumescence of the lighter air over the austral regions, the actual height of this
invisible covering to be higher there than it is in the boreal regions.

Taking the mean height of the barometer for the northern hemisphere to be
30 inches, and taking the 100,000 barometric observations used as data for the
construction of this diagram to be correct, we have facts for the assertion that
in the austral regions the quantity of air that this vapour permanently expels
thence is from one twelfth to one fifteenth of the whole quantity that belongs to
corresponding latitudes north — a curious, most interesting, and suggestive physical
revelation

Plates II. and III. are drawings of Brooke's Deep-sea Sounding Apparatus for
bringing up specimens of the bottom (§ 573).

Plate IV. (§ 723) is intended to illustrate the extreme movements of the
isotherms 50°, 60°, 70°, etc., in the Atlantic Ocean during the year. The con-
nection between the law of this motion and the climates of the sea is exceedingly
interesting.

Plate V. (§ 781) is a section taken from one of the manuscript charts at the
Observatory. It illustrates the method adopted there for co-ordinating for the
Pilot Charts the winds as reported in the abstract logs. For this purpose the
ocean is divided into convenient sections, usually five degrees of latitude by five
degrees of longitude. These ijarallelograms are then subdivided into a system of
engraved squares, the months of the year being the ordinates, and the points of
the compass being the abscissae. As the wind is reported by a vessel that passes
through any part of the parallelogram, so is it assumed to have been at that time
all over the parallelogram. From such investigations as this the Pilot Charts are
coiiairucfed.

EXPLANATION OF THE PLATES. XIX

Plate VI. illustrates the position of the channel of the Gulf Streati (Chap. II.)
for summer and winter. The diagram A shows a thermometrical profile pre-
sented by cross-sections of the Gulf Stream, according to observations made by
the hydrographical parties of the United States Coast Survey. The elements for
this diagram were kindly furnished me by the superintendent of that work.
They are from a paper on the Gulf Stream, read by him before the American
Association for the Advancement of Science, at its meeting in Washington, 1854.
Imagine a vessel to sail from the Capes of Virginia straight out to sea, crossing
the Gulf Stream at right angles, and taking the temperature of its waters at the
surface and at various depths. The diagram shows the elevation and depression
of the thermometer across this section as they were actually observed by such a

The black lines x^ y, 2;, in the Gulf Stream, show the course which those threads
of warm waters take (§ 130). The lines a, 6, show the computed drift route that
the unfortunate steamer San Francisco would take after her terrible disaster in
December, 1853.

Plate VIT. is intended to show how the winds may become geological agents.
It shows where the winds that, in the general system of atmospherical circulation,
blow over the deserts and thirsty lands in Asia and Africa (where the annual
amount of precipitation is small) are supposed to get their vapours from; where,
as surface winds, they are supposed to condense portions of it ; and whither they
are supposed to transport the residue thereof through the upper regions, retaining
it until they again become surface winds.

Plate VTII. showst he prevailing direction of the wind during the year in all
parts of the ocean. It also shows the principal routes across the seas to various
places. Where the cross-lines representing the yards are oblique to the keel of
the vessel, they indicate that the winds are, for the most part, ahead ; when per-
pendicular or square, that the winds are, for the most part, fair. The figures on
or near the diagrams representing the vessels show the average length of the
passage in days.

The arrows denote the prevailing direction of the wind ; they are supposed to
fly with it ; so that the wind is going as the arrows point. The half-bearded and
half-feathered arrows represent monsoons (§ 630), and the stippled or shaded
belts the calm zones.

In the regions on the polar side of the calms of Capricorn and of Cancer, where
the arrows are flying both from the north-west and the south-west, the idea
intended to be conveyed is, that the prevailng direction of the wind is between
the north-west and the south-west, and that their frequency is from these two
quarters in proportion to th"? number of arrows.

Plate TX, is intended to show the present state of our knowledge with regard
to the drift of the ocean, or, more properly, with regard to the great flow of polar
and equatorial waters, and their channels of circulation as indicated by the ther-
mometer (§ 742). Farther researches will enable us to improve this chart. The
sargasso seas and the most favourite places of resort for the whale— r/^/it in cold,
ftnd sperm in warm weather— are also exhibted on this chart.

Plate X. (p. 208) represents the curves of specific gravity and temperature of
the surface waters of the ocean, as observed by Captain John Rodgers in the
U.S. ship Vincennes, on a voyage from Behring's Strait via California and Cape
Horn to New York.

Plates XI. and XII. speak for themselves. They are orographic for the North
Atlantic Ocean, and exhibit completely the present state of our knowledge with
regard to the elevations and depressions in the bed of that sea as derived from
the deep-sea soundings taken by the American and English navies from the
commencement of the system to Dayman's soundings in the Bay of Biscay, 1859 ;
Plate XII. exhibiting a vertical section of the Atlantic, and showing the contrasts
of its bottom with the sea-level in a line from Mexico across Yucatan, Cuba, Sar
Domingo, and the Cape de Verds, to the coast of Africa, marked A on Plato XL

XX EXPLANATION OF THE PLATES.

Plate XIII.— The data for this Plate are furnished by Maury's Storm and
Kain Charts, including observations for 107,277 days in the North Atlantic, an(i
158,025 in the South; collated by Lieutenant J. J. Guthrie, at the Washington
Observatory, in 1855.

The heavy vertical lines, 5°, 10°, 15^, etc., represent parallels of latitude; the
other vertical lines, months ; and the horizontal lines, per cents., or the number
of days in a hundred.

The continuous curve line stands for phenomena in the North, and the broken
curve line for phenomena in the South Atlantic. Thus the Gales' Curve shows
that in every hundred days, and on the average, in the month of January of
different years, there have been observed, in the northern hemisphere, 36 gales
(36 per cent.) between the parallels of 50° and 55° ; whereas during the same
time and between the same parallels in the southern hemisphere, only 10 gales on
the average (10 per cent.) have been reported.

The fact is here developed that the atmosphere is in a more unstable condi-
tion in the North than in the South Atlantic ; that we have more calms, more
rains, more fogs, more gales, and more thunder in the northern than in the
southern hemisphere, particularly between the equator and the 55th parallel.
Beyond that, the influence of Cape Horn becomes manifest.

Plate XIV. (§ 839) shows the limits of the unexploj-ed area about the south
pole.

Plate XV. shows by curves the prevalence of winds with northing as compared
with winds with southing in them in each of the two hemispheres, north and
south.

Plate XVI. shows the Barometric Curve projected according to actual obser-
vations at sea, from the parallel cf 78° north to the parallel of 56° south, and
carried thence to the poles, by conjecture and in conformity with indications.

THE

PHYSICAL GEOGRAPHY OF THE SEA,
AND ITS METEOROLOGY.

CHAPTER 1.

1-68. — THE SEA. AND THE ATMOSPHERE.

§ 1. Tlie two oceans of air and water. — Our planet is invested with
two great oceans ; one visible, the other invisible ; one is under-
foot, the other overhead; one entirely envelops it, the other
covers about two-thirds of its surface. All the water of the one
weighs about 400 times as much as all the air of the other.

2. TJieir meeting. — It is at the bottom of this lighter ocean
where the forces which we are about to study are brought into
play. This place of meeting is the battle-field of nature, the
dwelling-place of man ; it is the scene of the greatest conflicts
which he is permitted to witness, for here rage in their utmost
fury the powers of sea, earth, and air ; therefore, in treating of
the Physical Geography of the sea, we must necessarily refer
to the phenomena which are displayed at the meeting of these
two oceans. Let us, therefore, before entering either of these
fields for study, proceed first to consider each one in some of its
most striking characteristics. They are both in a state of what
is called unstable equilibrium ; hence the currents of one and
the winds of the other.

3. Their depth. — As to their depth, we know very little more of
the one than of the other ; but the conjecture that the average
depth of the sea does not much exceed four miles is probably as
near the truth as is the cOmmonly received opinion that the height
of the atmosphere does not exceed fifty miles. If the air were,

2 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOllOLOGY.

like water, non-elastic, and not more compressible than this non
elastic fluid, we could sound out the atmospherical ocean with
the barometer, and gauge it by its pressure. The mean height
of the barometer at the level of the sea in the torrid and
temperate zones, is about 30 inches. Now, it has been ascer-
tained that, if we place a barometer 87 feet above the level of
the sea, its average height will be reduced from 30.00 in. to
29.90 in. ; that is, it will be diminished one-tenth of an inch, or
the three hundredth part of the whole ; consequently, by going
up 300 X 87 ( = 26,100) feet, the barometer, were the air non-
elastic, would stand at 0. It would then be at the top of the
atmosphere. The height of 26,100 feet is just five miles lacking
300 feet.

4. Weight of the atmosphere. — But the air is elastic, and very
unlike water. That at the bottom is pressed down by the super-
incumbent air with the force of about 15 pounds to the square
inch, while that at the top is inconceivably light. If, for the
sake of explanation, we imagine the lightest down, in layers of
equal weight and ten feet thick, to be carded into a pit several
miles deep, we can readily perceive how that the bottom layer,
thouo'h it might have been ten feet thick when it first fell, yet
with the weight of the accumulated and superincumbent mass, it
mio-ht now, the pit being full, be compressed into a layer of only
a few inches in thickness, while the top layer of all, being
uncompressed, would be exceedingly light, and still ten feet
thick ; so that a person ascending from the bottom of the pit
would find the layers of equal weight thicker and thicker until
he reached the top. So it is with the barometer and the atmo-
sphere : when it is carried up in the air through several strata
of 87 feet, the observer does not find that it .falls a tenth of an
'\DLch for every successive 87 feet upward through which he may
carry it. To get it to fall a tenth of an inch, he must carry it
hio'her and higher for every successive layer.

5. Three-fourths helow the mountain tops. — More than three-
fourths of the entire atmosphere is below the level of the highest
mountains ; the other fourth is rarefied and expanded in
consequence of the diminished pressure, until the height of many
miles be attained. From the reflection of the sun's rays after he
has set, or before he rises above the horizon, it is calculated that
this upper fourth part must extend at least forty or forty-five
miles higher.

i'HE SEA. AND THE ATMOSPHEEE. 3

6. Its height. — At the height of 26,000 miles from the earth,
the centrifugal force would counteract gravity ; consequently, ail
ponderable matter that the earth carries with it in its diurnal
revolution must be within that distance, and consequently the
.atmosphere cannot extend beyond that. This limit, however,
has been greatly reduced, for Sir John Herschel has shown, by
balloon observations,* that at the height of 80 or 90 miles there
is a vacuum far more complete than any which we can produce
by any air-pump. In 1783 a large meteor, computed to be half
a mile in diameter and fifty miles from the earth, was heard to
explode. As sound cannot travel through vacuum, it was
inferred that the explosion took place within the limits of the
atmosphere. Plerschel concludes that the aerial ocean is at
least 50 miles deep.

7. Data conjectural. — The data from which we deduce our
estimate, both as to the mean height of the atmosj^here and
average depth of the ocean, are, to some extent, conjectural ;
consequently, the estimates themselves must be regarded as
approximations, but sufficiently close, nevertheless, for the
present purposes of this work.

8. Analysis of air. — Chemists who have made the analysis, tell
us that, out of 100 parts of atmospheric air, 99.5 consist of oxygen
and nitrogen, mixed in the proportion of 21 of oxygen to 79 of
nitrogen by volume, and of 23 to 77 by weight. The remaining
half of a part consists of .05 of carbonic acid and .45 of aqueous
vapour.

9. Information respecting the depth of the ocean. — The average
depth of the ocean has been variously computed by astronomers,
from such arguments as the science afi'ords, to be from 26 to 11
miles. About ten years ago I was permitted to organize and set
on foot in the American navy a plan for " sounding out " the
ocean with the plummet.f Other navies, especially the English,
have done not a little in furtherance of tliat object. Suffice it to
say that, within this brief period, though the undertaking has

*"* Those of Mr. Welsh, m his ascent from Kew.

t " And he it further enacted. That the Secretary of the Navy be directed ro
detail three suitable vessels of the navy in testing new routes and perfecting
the discoveries raade by Lieut. Maury in the course of his investigations of tlie
winds and currents of the ocean ; and to cause the vessels of the navy to co-
operate in procuring materials for such investigations, in so far as said co-opera-
tion may not be mcompatible with the public interests." — From Naval Jp-
propriatio^*. Bill, approved March 3, 1849.

B 2

4 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY

been by no means completed — no, not even to the tenth part-
yet more knowledge has been gained concerning the depths and
bottom of the deep sea, than all the world had before acquired in
all previous time.

10. Its p'ohable depth. — The system of deep-sea soundings thus
inaugurated does not thus far authorize the conclusion that the
average depth of ocean water is more than three or four miles
(§ 3), nor have any reliable soundings yet been made in water
over five miles deep.

11. Belation between its depth, and the ivaves of the sea. — In very
shallow pools, where the water is not more than a few inches
deep, the ripples or waves, as all of us, when children, have
observed, are small; their motion, also, is slow. But when the
water is deep, the waves are larger and more rapid in their
progress, thus indicating the existence of a numerical relation
between their breadth, height, and velocity, and the depth of the
water. It may be inferred, therefore, that if we knew the size
and velocity of certain waves, we could compute the depth of the
ocean.

12. Airy's imve tables. — Such a computation has been made, and
we have the authority of Mr. Airy,* the Astronomer Eoyal, that
waves of given breadths will travel in water of certain depths
with the velocities as per table :

Breadth of the Wave in Feet.

the Water
in Feet.

1

10

100

1000

10,000

100,0001,000,000

10,000,000

Corresponding Velocity of Wave per Hour in Miles.

1

1.54

8.81

3.86

3.86

3.86

3.86

3.86

3.86

10

1..54

4.87

11.51

12.21

12.22

12.22

12.22

12.22

100

1..54

4.87

15.18

36.40

38.64

38.66

38.66

38.66

1,000

1.54

4.87

15.18

48.77

115.11

122.18

122.27

122.27

10,000

1.54

4.87

15.18

48.77

154.25

364.92

386.40

386.66

100,000

1.54

4.87

15.18

48.77

154.25

487.79

1150.00

1222.70

13. The earthquake of Simoda. — Accident has afforded us an
opportunity of giving a quasi practical application to Mr. Airy's
formula3. On the 23rd of December, 1854, at 9.45 A.M.,t the

* Encyclop. Metropol.

t Notes of a Eussian Officer, p. 97, No. 2 (Feb. 1856), vol. xxv,

Nauticai

Magazine, London.

THE SEA AND THE ATMOSPHERE. 5

first sliocks of an earthquake were felt on board the Enssian
frisrate " Diana," as she lay at anchor in the harbour of Simoda,
not far from Jeddo, in Japan. In fifteen minutes afterwards
(10 o'clock), a large wave was observed rolling into the harbour,
and the water on the beach to be rapidly rising. The town, as
seen from the frigate, appeared to be sinking. This wave was
followed by another, and when the two receded — which was at
lOh. 15m. — there was not a house, save an unfinished temple,
left standing in the village. These waves continued to come and
go until 2.30 p.m., during which time the frigate was thrown on
her beam ends five times. A piece of her keel 81 feet long was
torn off, holes were knocked in her by striking on the bottom,
and she was reduced to a wreck. In the course of five minutes
the water in the harbour fell, it is said, from 23 to 3 feet, and the
anchors of the ship were laid bare. There was a great loss of
life ; many houses were washed into the sea, and many junks
carried up — one two miles inland — and dashed to pieces on the
shore. The day was beautifully fine, and no warning was given
of the approaching convulsion; the barometer standing at
29.87 in., thermometer 58°; the sea perfectly smooth when its
surface was broken by the first wave. It was calm in the
morning, and the wind continued light all day.

14. The propagation of waves hy it. — In a few hours afterwards,
at San Francisco and San Diego, the tide-gauges showed that
several well-marked and extraordinary waves had arrived off the
coast of California.* The origin of these waves, and those which
(destroyed the town of Simoda, in Japan, and wrecked the
" Diana," was doubtless the same. But where was their birth-
place ? Supposing it to be near the coasts of Japan, we may,
with the tide-gauge observations in California and Mr. Airy's
formulae, calculate the average depth of the sea along the path
of the wave from Simoda both to San Francisco and San Diego.

15. Their breadth and velocity. — Supposing the waves to have
taken up their line of march from some point along the coast of
Japan, the San Francisco wave, having a breadth of 256 miles,
had a velocity of 438 miles an hour ; while the breadth of the
San Diego wave was 221 miles, and its rate of travel 427 miles
an hour.

16. Average depth of the North Pacific. — Admitting these pre-
mises— which are partly assumed — to be correct, then, according

* Ex. Doc. No. 22, Senate, 1st scss. 34th Congress, p. 342.

6 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

to Airy's formulse, the average dex^tli of the North Pacific between
Japan and California is, by the path of the San Francisco wave,
2149 fathoms, by the ^an Diego, 2034 (say 2^ miles).

17. Specific gravity of sea-ivater. — At the temperature of 60°,
the specific gravity of average sea-water is 1.0272,* and the
weight of a cubic foot is 64.003 lbs.

18. Of air. — With the barometer at 30 in. and the thermometer
at 32°, the weight of a cubic foot of dry atmospheric air is 1.291
oz., and its specific gravity .00129. Such is the difference in
weight between the two elements, the phenomena of which give
the physical geography of the sea its charms.

19. Unequal distribution of light, land, and air. — There is in the
northern hemisphere more land, less sea, more fresh water, more
atmospheric air, and a longer annual duration of sunlight, than
there is in the southern. And though the two hemispheres
receive annuall}^ the same amount of heat directly from the sun,
yet the northern, without growing cooler, dispenses the greater
quantity by radiation.

20. Tlie sun longer in northern declination. — In his annual round,
the sun tarries a week (7f days) longer on the north than he
does on the south side of the equator, and consequently the
antarctic night and its winter are longer than the polar winter
and night of the arctic regions. The southern hemisphere is said
also to be cooler, but this is true only as to its torrid and
temperate zones. In the summer of the southern hemisphere the
sun is in perigee, and during the course of a diurnal revolution
there the southern half of our planet receives more heat than the
northern half during the same period of our summer. This
difference, however. Sir John Herschel rightfully maintains is
compensated by the longer duration of the northern summer.
Therefore, admitting the total quantity of heat annually im-
pressed upon the earth by the sun to be equally divided between
the two hemispheres, it does not follow that their temperature
should be the same, for their powers of radiation may be very
different. The northern hemisphere having most land, radiates
the more freely — the land and sea breezes tell us that the land
dispenses heat more freely than the sea by radiation — but the
northern hemisphere is prevented in two ways from gi^owing
cooler than the southern: — 1. by the transfer of heat in the

* Maury's Sailing Directions, vol. i. Sir John Herschel quotes it at 1.0273
for G2^.

THE SEA AND THE ATMOSPHERE. i

latent form with the vapours from the southern seas ; — 2. by the
transfer of heat in the sensible form, by currents such as the
Gulf Stream, et al., from one climate to another in our hemi-
sphere. Hence we infer that the southern hemisphere is in
certain zones cooler than the northern, not by reason of its short
summer or long winter, but it is the cooler chiefly on account of
the latent heat which is brought thence by vapour, and set free
here by condensation.

21. England about the pole of hemisphere luith most land. — Within
the torrid zone the land is nearly equally divided north and
south of the equator, the proportion being as 6 to 4. In the
temperate zones, however, the north with its land is thirteen
times in excess of the south. Indeed, such is the inequality
in the distribution of land over the surface of the globe that the
world may be divided into hemispheres consisting, the one with
almost all the land in it, except Australia and a slip of America
lying south of a line drawn from the desert of Atacama to
Uruguay; England is the centre of this, the dry hemisphere.
The other, or aqueous hemisphere, contains all the great waters
except the Atlantic Ocean; New Zealand is the nearest land
to its centre.

22. Effects of inequality in distribution of land and water. — This
unequal distribution of land, light, air, and Avater is suggestive.
To it we owe, in a measure, the different climates of the earth.
Were it different, they would be different also ; were it not for
the winds, the vapours that rise from the sea would from the
clouds be returned in showers back to the places in the sea
whence they came ; on an earth where no winds blow we should
have neither green pastures, still waters, nor running brooks
to beautify the landscape. Were there no currents in the sea,
nor vertical movements in the air, the seasons might change,
but climates would be a simple affair, depending solely on the
declination of the sun in the sky.

23. Quantity of fresh water in American lakes. — About two-thirds
of all the fresh water on the surface of the earth is contained
in the great American lakes; and though there be in the
northern, as compared vdth the southern hemisphere, so much
less sea surface to yield vapour, so much more land to swallow
up rain, and so many more plants to drink it in, yet the fresh-
water courses are far more numerous and copious on the north
than they are on the south side of the equator.

8 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

24. Southern seas the holler, and northern lands the condenser. — >
These facts have suggested the comparison in which the southern
hemisphere has been likened to the boiler and the northern to
the condenser of the steam-engine. This vast amount of steam
or vapour rising up in the extra-tropical regions of the south,
expels the air thence, causing the barometer to show a much less
weight of atmosphere on the polar side of 40° S., than we find in
corresponding latitudes north.

25. Offices of the atmosphere. — The ofSces of the atmosphere are
many, marvellous, and various. Though many of them are past
finding out, yet, beautiful to contemplate, they aff'ord most
instructive and profitable themes for meditation.

26. Dr. Buist. — When this system of research touching the
physics of the sea first began — when friends were timid and co-
labourers few, the excellent Dr. Buist stood up as its friend and
champion in India ; and by the services he thus rendered, en-
titled himself to the gratitude of all who, with me, take delight
in tlie results which have been obtained. The field which it
was proposed to occupy — the firstlings of which were gathered in
this little book — was described by him in glowing terms, and
with that enthusiasm which never fails to inspire zeal. They are
apropos, and it is a pleasure to repeat the substance of them.

27. Tlie sea and the atmosphere contrasted. — " The weight of the
atmosphere is equal to that of a solid globe of lead sixty miles in
diameter. Its principal elements are oxygen and nitrogen gases,
with a vast quantity of water suspended in them in the shape of
vapour, and commingled with these a quantity of carbon in the
shape of fixed air, equal to restore from its mass many fold,
the coal that now exists in the world. In common with all sub-
stances, the ocean and the air are increased in bulk, and, con-
sequently, diminished in weight, by heat ; like all fluids, they
are mobile, tending to extend themselves equally in all directions,
and to fill up depressions wherever vacant space will admit them ;
hence in these respects the resemblance betwixt their movements.
Water is not compressible or elastic, and it may be solidified into
ice, or vaporized into steam ; the air is elastic ; it may be con-
densed to any extent by pressure, or expanded to an indefinite
degree of tenuity by pressure being removed from it ; it is not
liable to undergo any change in its constitution beyond these, by
any of the ordinary influences by which it is affected.

28. Influence of the sun. — " These facts are few and simple

THE SEA AND THE ATMOSPHERE. 9

enough ; let us see what results arise from them : As the constant
exposure of the equatorial regions of the eai'th to the sun must
necessarily there engender a vast amount of heat, and as his
absence from the polar regions must in like manner promote an
infinite accumulation of cold, to lit the entire earth for a ha-
bitation to similar races of beings, a constant interchange and
communion betwixt the heat of the one, and the cold of the other,
must be carried on. The ease and simplicity with which this is
effected surpass all description. The air, heated near the equator
by the overpowering influences of the sun, is expanded and
lightened ; it ascends into upper space, leaving a partial vacuum
at the surface to be supplied from the regions adjoining. Two
currents from the poles toward the equator are thus established
at the surface, while the sublimated air, diffusing itself by its
mobility, flows in the upper regions of space from the equator
toward the poles. Two vast whirlpools are thus established,
constantly carrying away the heat from the torrid toward the icy
regions, and, there becoming cold by contact with the ice, they
carry back their gelid freight to refresh the torrid zone.

29. Of diurnal rotation. — " Did the earth, as was long believed,
stand still while the sun circled around it, we should have had
directly from north and south two sets of meridional currents
blowing at the surface of the earth toward the equator ; in the
upper regions we should have had them flowing back again to
the place whence they came. On the other hand, were the heat-
ing and cooling influences just referred to to cease, and the earth
to fail in impressing its own motion on the atmosphere, we should
have a furious hurricane rushing round the globe at the rate
of 1000 miles an hour— tornadoes of ten times the speed of the
most violent now known to us, sweeping everything before them.
A combination of the two influences, modified by the friction
of the earth, which tends to draw the air after it, gives us the
trade-winds, which, at the speed of from ten to twenty miles an
hour, sweep round the equatorial region of the globe un-
ceasingly.

30. Carrents. — " Impressed with the motion of the air, constantly
sweeping its- surface in one direction, and obeying the same Jaws
of motion, the great sea itself would be excited into currents
similar to those of the air, were it not walled in by continents
and subjected to other control. As it is, there are constant
currents flowing from the torrid toward the frigid zone to supply

10 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METE0E0L06T.

Xhe vast amouni of vapour there drained off, while other whirl-
pools and enrrents, snch as the gigantic Gulf Stream, come
to perform their part in the same stupendous drama. The waters
of this vast ocean river are, to the north of the tropic, greatly-
warmer than those around; the climate of every country it
approaches is improved by it, and the Laplander is enabled by
its means to live and cultivate his barley in a latitude which,
everywhere else throughout the world, is condemned to per-
petual sterility. There are other laws which the great sea
obeys which peculiarly adapt it as the vehicle of interchange
of heat and cold betwixt those regions where either exists in
excess.

31. Icehm-gs. — " In obedience to these laws water warmer than
ice attacks the basis and saps the foundations of the icebergs —
themselves gigantic glaciers, which have fallen from the moun-
tains into the sea, or which have grown to their present size
in the shelter of bays and estuaries, and by accumulations from
above. Once forced from their anchorage, the first storm that
arises drifts them to sea, where the beautiful law which renders
ice lighter than the warmest water, enables it to float, and drifts
southward a vast magazine of cold to cool the tepid water which
bears it along — the evaporation at the equator causing a deficit,
the melting and accumulation of the ice in the frigid zone giving
rise to an excess of accumulation, which tends, along with the
action of the air and other causes, to institute and maintain the
transporting current. These stupendous masses, which have been
seen at sea in the form of church spires, and gothic towers, and
minarets, rising to the height of from 300 to 600 feet, and ex-
tending over an area of not less than six square miles, the masses
above water being only one-tenth of the whole, are often to be
found within the tropics.

32. Mountain ranges. — "But these, though among the most
regular and magnificent, are but a small number of the con-
trivances by which the vast and beneficent ends of nature are
brought about. Ascent from the surface of the earth produces
the same change, in point of climate, as an approach to the poles ;
even under the tonid zone mountains reach the line of perpetual
congelation at nearly a third less altitude than the extreme
elevation which tliey sometimes attain. At the poles snow is
perpetual on the ground, and at the different intervening lati-
tudes reaches some intermediate point of congelation betwixt one

THE SEA AND THE ATMOSPHEKE, 11

and 20,000 feet. In America, from the line south to the tropics,
as also, as there is now everj reason to believe, in Africa within
similar latitudes, vast ridges of mountains, covered with per-
petual snow, run northward and southward in the line of the
meridian right across the path of the trade-winds. A similar
ridge, though of less magnificent dimensions, traverses the
peninsula of Hindoostan, increasing in altitude as it approaches
the line, attaining an elevation of 8500 feet at Dodabetta, and
about 6000 in Ceylon. The Alps in Europe, and the gigantic
chain of the Himalayas in Asia, both far south in the temperate
zone, stretch from east to west, and intercept the aerial current
from the north. Others of lesser note, in the equatorial or
meridional, or some intermediate direction, cross the paths
of the atmospherical currents in every direction, imparting
to them fresh supplies of cold, as they themselves obtain from
them warmth in exchange : in strictness the two operations are
tlie same.

33. Water. — " Magnificent and stupendous as are the effects
and results of the water and of air acting independently on each
other, in equalizing the temperature of the globe, they are still
more so when combined. One cubic inch of water, when in-
vested with a sufficiency of heat, will form one cubic foot of steam
— the water before its evaporation, and the vapour which it forms
being exactly of the same temperature ; though in reality, in the
process of conversion, 1100 degrees of heat have been absorbed or
carried away from the vicinage, and rendered latent or imper-
ceptible ; this heat is returned in a sensible and perceptible
form the moment the vapour is converted once more into water.
The general fact is the same in the case of vapour carried
off by dry air at any temperature that may be imagined ; for,
down far below the freezing-point, evaporation proceeds unin-
terruptedly.

34. Latent heat. — " The air, heated and dried as it sweeps
over the arid surface cf the soil, drinks up by day myriads of
tons of moisture from the sea — as much, indeed, as would, were
no moisture restored to it, depress its whole surface at the rate
of eight or ten feet annually. The quantitj^ of heat thus con-
verted from a sensible or perceptible to an insensible or latent
state is almost incredible. The action equall}^ goes on, and
with the like results, over the surface of the earth, where there
is moisture to be withdrawn. But nigrht and the seasons of the

12 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

year come round, and the surplus temperature, thus withdrawn
and stored away at the time it might have proved superfluous
or inconvenient, is rendered back so soon as it is required ;
thus the cold of night and the rigour of winter are modified by
the heat given out at the point of condensation by dew, rain,
hail, and snow.

35. Efeds upon the earth. — " The earth is a bad conductor of
heat ; the rays of the sun, which enter its surface and raise the
temperature to 100° or 150°, scarcely penetrate a foot into the
ground ; a few feet down, the warmth of the ground is nearly
the same night and day. The moisture which is there preserved
free from the influence of currents of air is never raised into
vapour; so soon as the upper stratum of earth becomes tho-
roughly dried, capillary action, by means of which all excess of
water was withdrawn, ceases ; so that, even under the heats of
the tropics, the soil two feet down will be found, on the approach
of the rains, sufficiently moist for the nourishment of plants.
The splendid flowers and vigorous foliage which burst forth in
May, when the parched soil would lead us to look for nothing
but sterility, need in no way surprise us ; fountains of water,
boundless in extent and limited in depth only by the thickness
of the soil which contains them, have been set aside and sealed
up for their use, beyond the reach of those thirsty winds or burn-
ing rays which are suffered to carry off only the water which is
superfluous, and would be pernicious. They remove it to other
lands, where its agency is required, or treasure it up, as the ma-
terial of clouds and dew, in the crystal vault of the firmament,
the source, when the flatting season comes round again, of those
deluges of rain which provide for the wants of the year. Such
are some of the examples which may be supplied of general laws
operating over nearly the whole surface of the terraqueous globe.
Among the local provisions ancillary to these are the monsoons
of India, and the land and sea breezes prevalent throughout the
tropical coasts.

36. The tides. — "We have not noticed the tides, which, obe-
dient to the sun and moon, daily convey two vast masses of
water round the globe, and which twice a month, rising to an
unusual height, visit elevations which otherwise are dry. During
one half of the year the highest tides visit us by day, the other
half by night ; and at Bombay, at spring tide, the depths of the
two differ by two or three feet from each other. The tides

THE SEA AND THE ATMOSPHERE. 13

simply rise and fall, in the open ocean, to an elevation of two or
three feet in all ; along our shores, and up gulfs and estuaries,
they sweep with the violence of a torrent, having a general
range of ten or twelve feet — sometimes, as at Fundy, in Ame-
rica, at Brest and Milford Haven, in Europe, to a height of from
forty to sixty feet. The tides sweep our shores from filth, and
purify our rivers and inlets, affording to the residents of our
islands and continents the benefits of a bi-diurnal ablution, and
giving a health, and freshness, and purity wherever they appear.
Obedient to the influence of bodies many millions of miles re-
moved from them, their subjection is not the less complete ; the
vast volume of water, capable of crushing by its weight the most
stupendous barriers that can be opposed to it, and bearing on its
bosom the navies of the world, impetuously rushing against our
shores, gently stops at a given line, and flows back again to its
place when the word goes forth, ' Thus far shalt thou go, and no
farther ;' and that which no human power or contrivance could
have repelled, returns at its appointed time so regularly and
surely that the hour of its approach, and measure of its mass,
may be predicted with unerring certainty centuries beforehand.

37. Hurricanes. — " The hurricanes which whirl with such
fearful violence over the surface, raising the waters of the sea
to enormous elevations, and submerging coasts and islands,
attended as they are by the fearful attributes of thunder and
deluges of rain, seem requisite to deflagrate the noxious gases
which have accumulated, to commingle in one healthful mass
the polluted elements of the air, and restore it fitted for the ends
designed for it. We have hitherto dealt with the sea and air —
the one the medium through which the commerce of all nations
is transported, the other the means by which it is moved along
— as themselves the great vehicles of moisture, heat, and cold
throughout the regions of the world — the means of securing the
interchange of these inestimable commodities, so that excess may
be removed to where deficiency exists, deficiency substituted for
excess, to the unbounded advantage of all. This group of illus-
trations has been selected because they are the most obvious,
the most simple, and the most intelligible and beautiful that
could be chosen.

38. Powers of the air. — "We have already said that the atmo
sphere forms a spherical shell, surrounding the earth to a depth
which is unknown to us, by reason of its growing tenuity, as it

14 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METE0R0L06T.

is released from tlie pressure of its o^vn superincumbent mass.
Its upper surface cannot be nearer to us than fifty, and can
scarcely be more remote than five hundred miles. It surrounds
us on all sides, yet Ave see it not; it presses on us with a load of
fifteen pounds on every square inch of surface of our bodies, or
from seventy to one hundred tons on us in all, yet we do not so
much as feel its weight. Softer than the finest down, more im-
palpable than the finest gossamer, it leaves the cobweb undis-
turbed, and scarcely stirs the lightest flower that feeds gn the
dew it supplies ; yet it bears the fleets of nations on its wings
around the world, and crushes the most refractory substances
with its weight. When in motion, its force is sufficient to level
with the earth the most stately forests and stable buildings, to
raise the waters of the ocean into ridges like mountains, and
dash the strongest ships to pieces like toys. It warms and cools
by turns the earth and the living creatures that inhabit it. It
draws up vapours from the sea and land, retains them dissolved
in itself or suspended in cisterns of clouds, and throws them
down again, as rain or dew, when they are required. It bends
the rays of the sun from their path to give us the aurora of the
morning and twilight of evening ; it disperses and refracts their
various tints to beautify the approach and the retreat of the orb
of dav." But for the atmosphere, sunshine would burst on us in
a moment and fail us in the twinkling of an eye, removing us in
an instant from midnight darkness to the blaze of noon. We
should have no twilight to soften and beautify the landscape, no
clouds to shade us from the scorching heat ; but the bald earth,
as it revolved on its axis, would turn its tanned and weakened
front to the full and unmitigated rays of the lord of day.

39. Its functions.— ''The atmosphere affords the gas which
vivifies and warms our frames ; it receives into itself that which
has been polluted by use, and is thrown off as noxious. It feeds
the flame of life exactly as it does that of the fire. It is in both
cases consumed, in both cases it affords the food of consumption,
and in both cases it becomes combined with charcoal, which
requires it for combustion, and which removes it when com-
bustion is over. It is the girdling encircling air that makes the
whole world kin. The carbonic acid with which to-day our
breathing fills the air, to-morrow seeks its way round the world.
The date-trees that grow round the falls of the Nile will drink it
in by their leaves ; the cedars of Lebanon will take of it to add

THE SEA AND THE ATMOSPHERE . 15

to their stature ; the cocoa-nuts of Tahiti will grow rapidly upon
it; and the palms and bananas of Japan will change it into
flowers. The oxygen we are breathing was distilled for us some
short time ago by the magnolias of the Susquehanna and the
o-reat trees that skirt the Orinoco and the Amazon ; the giant
rhododendrons of the Himalayas contributed to it, and the roses
and myrtles of Cashmere, the cinnamon-tree of Ceylon, and the
forest, older than the flood, that lies buried deep in the heart of
Africa, far behind the Mountains of the Moon, gave it out. The
rain we see descending was thawed for us out of the icebergs
which have watched the Polar Star for ages, or it came from
snows that rested on the summits of the Alps, but which the
lotus lilies have soaked up from the jS'ile, and exhaled as vapour
again into the ever-present air."

40. The operations of ivater. — There are processes no less
interesting going on in other parts of this magnificent field of
research. Water is nature's carrier. With its currents it con-
veys heat away from the torrid zone and ice from the frigid ; or,
bottling the caloric away in the vesicles of its vapour, it first
makes it impalpable, and then conveys it, by unknown paths, to
the most distant parts of the earth. The materials of which the
coral builds the island, and the sea-conch its shell, are gathered
by this restless leveller from mountains, rocks, and valleys in all
latitudes. Some it washes down from the Mountains of the
Moon, or out of the gold-fields of Australia, or from the mines
of Potosi, others from the battle-fields of Europe, or from the
marble quarries of ancient Greece and Eome. These materials,
thus collected and carried over falls ©r down rapids, are trans-
ported from river to sea, and delivered by the obedient waters
to each insect and to every plant in the ocean at the right time
and temperature, in proper form, and in due quantity.

41. Its marvellous powers. — Treating the rocks less gently, it
grinds them into dust, or pounds them into sand, or rolls and
rubs them until they are fashioned into pebbles, rubble, or
bouldeis : the sand and shingle on the sea-shore are monuments
of the abrading, triturating power of water. By water the soil
has been brought down from the hills and spread out into valleys,
plains, and fields for man's use. Saving the rocks on which the
everlasting hills are established, everything on the surface of our
planet seems to have been removed from its original foundation and
lodged in its present place by water Protean in shape, benignant

16 PHTSICA.L GEOGRAPHY OF THE SEA, AND ITS METEOEOLOQY.

in office, water, whether fresh or salt, solid, fluid, or gaseous, is
marvellous in its powers.

42. It caters on land for insects of the sea. — It is one of the chief
agents in the manifold workshops in which and by which the
earth has been made a habitation fit for man. Circulating in
veins below the surface, it pervades the solid crust of the earth
in the fulfilment of its offices ; passing under the mountains it
runs among "the hills and down through the valleys in search of
pabulum for the moving creatures that have life in the sea. In
rivers and in rain it gathers up by ceaseless lixiviation food for
the creatures that wait upon it. It carries off from the land
whatever of solid matter the sea in its economy requires.

43. Leaching. — The waters which dash against the shore, which
the running streams pour into the flood, or with which the tides
and currents scour the bottom of their channel ways, have
soaked from the soil, or leached out of the disintegrated materials
which strew the beach or line the shores, portions of every solu-
ble ingredient known in nature. Thus impregnated, the laugh-
ing, dancing waters come down from the mountains, turning
wheels, driving machinery, and serving the manifold purposes of
man. At last they find their way into the sea, and so make the
lye of the earth brine for the ocean.

44. Solid ingredients. — Iron, lime, silver, sulphur, and copper,
silex, soda, magnesia, potash, chlorine, iodine, bromine, ammonia,
are all found in sea-water ; some of them in quantities too minute
for the nicest appliances of the best chemists to detect, but
which, nevertheless, are elaborated therefrom by physical pro-
cesses the most exquisite.

45. Quantity of silver in the sea. — By examining in Valparaiso
the copper that had been a great while on the bottom of a ship,
the presence of silver, which it obtained from the sea, was
detected in it. It was in such quantities as to form the basis
of a calculation, by which it would appear that there is held in
solution by the sea a quantity of silver sufficient to weigh no less
than two hundred million tons, could it all, by any process, be
precipitated and collected into a separate mass.

46. Its inhabitants — their offices. — The salts of the sea, as its
solid ingredients may be called, can neither be precipitated on the
bottom, nor taken up by the vapours, nor returned again by the
rains to the land ; and, but for the presence in the sea of certain
agents to wliich has been assigned the task of collecting these

THE SEA AND THE ATMOSPHEEE.

17

iiigredients again, in the sea they would have to remain. There,
accunmlating in its waters, they would alter the quality of the
brine, injure the health of its inhabitants, retard evaporation,
change climates, and work endless mischief upon the fauna and
the flora of both sea, earth, and air. But in the oceanic machi-
nery all this is prevented by compensations the most beautiful,
and adjustments the most exquisite. As in the atmosphere the
plants are charged with the office of purifying the air by elabo-
rating into vegetable tissue and fibre the impurities which the
animals are continually casting into it, so also to the mollusks, to
the madrepores, and insects of the sea, has been assigned the
office of taking out of its waters and making solid again all this
lixiviated matter as fast as the dripping streams and searching
rains discharge it into the ocean.

47. Monuments of their industry. — As to the extent and magni-
tude of this endless task some idea may be formed from the
coral islands, the marl beds, the shell banks, the chalk cliffs,
and other marine deposits which deck the sea-shore or strew
the land.

48. Analysis of sea-ivater. — Fresh water is composed of oxygen
and hydrogen gas in the proportion by weight of 1 to 8 ; and the
principal ingredients which chemists, by treating small sampler
of sea-water in the laboratory, have found in a thousand grains,
are —

Water 962.0 grains

Chloride of Sodium
Chloride of Magnesium
Chloride of Potassium
Bromide of Magnesia.
Sulphate of Magnesia
Sulphate of Lime
Carbonate of Lime
Leaving a residuum of

27.1
5.4
0.4
0.1
1.2
0.8
0.1
2.9

= 1000,

consisting of sulphuretted hydrogen gas, hydrochlorate of ammo-
nia, etc., etc., in various quantities and proportions, according to
the locality of the specimen.

49. Proportion of water to the mass of the earth. — If we imagine
the whole mass of the earth to be divided into 1786 equal parts
by weight, then the weight of all the water in the sea would, ac
cording to an estimate by Sir John Herschel, be equivalent to
one of such parts. Such is the quantity, and such some of the
qualities of that delightful fluid to which, in the laboratories and

18 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

workshops of nature, siicli mighty tasks, such, important offices,
such manifold and multitudinous powers have been assigned.

50. Tlie three great oceans. — This volume of water, that out-
weighs the atmosphere (§1) about 400 times, is divided into
three great oceans, the Atlantic, the Pacific, and the Arctic ; for in
the rapid survey which in this chapter we are taking of the field
before us, the Indian and Pacific oceans may be regarded as one.

51. The Atlantic. — The Atlantic Ocean, with its arms, is sup-
posed to extend from the Arctic to the Antarctic — perhaps from
pole to pole ; but, measuring from the icy barrier of the north to
that of the south, it is about 9000 miles in length, with a mean
breadth of 2700 miles. It covers an area of about 25,000,000
square miles. It lies between the Old World and the New:
passing beyond the " stormy capes," there is no longer any bar-
rier, but only an imaginary line to separate its waters from that
great southern waste in which the tides are cradled.

52. Its tides. — The young tidal wave, rising in the circumpolar
seas of the south, rolls thence into the Atlantic, and in 12 hours
after passing the parallel of Cape Horn, it is found pouring its
flood into the Bay of Fundy.

53. Its dejpths. — The Atlantic is a deep ocean, and the middle
its deepest part, therefore the more favourable (§ 13) to the pro-
pagation of this wave.

54. Contrasted loith the Pacific. — The Atlantic Ocean contrasts
very strikingly with the Pacific. The greatest length of one
lies east and west ; of the other, north and south. The cur-
rents of the Pacific are broad and sluggish, those of the Atlantic
swift and contracted. The Mozambique current, as it is called,
has been found by navigators in the South Pacific to be upwards
of 1600 miles wide — nearly as broad as the Gulf Stream is long.
The principal currents in the Atlantic run to and fro between
the equator and the Northern Ocean. In the Pacific they run
between the equator and the southern seas. In the Atlantic the
tides are high, in the Pacific they are low. The Pacific feeds
the clouds with vapours, and the clouds feed the Atlantic with
rain for its rivers. If the volume of rain which is discharged
into the Pacific and on its slopes be represented by 1, that dis-
charged upon the hydrographical basin of the Atlantic into the
Atlantic would be represented by 5. The Atlantic is crossed
daily by steamers, the Pacific rarely. The Atlantic washes the
bhores of the most powerful, intelligent, and Christian nations,-

THE SEA AND THE ATMOSPHERE. 19

but a pagan or a heathen people in the countries to which the
Pacific gives drainage are like the sands upon its shores for
multitude. The Atlantic is the most stormy sea in the world,
the Pacific the most tranquil.

55. The TelegrapMc Plateau. —Among the many valuable dis-
coveries to which these researches touching the physics of the
sea have led, none perhaps is more interesting than the Tele-
graphic Plateau of the Atlantic, and the fact that the bottom of
the deep sea is lined with its own dead, whose microscopic
remains are protected from the abrading action of its currents
and the violence of its waves by cushions of still water.

56. New routes for an Atlantic Telegraph. — The idea of a tele-
graph from England or Ireland along this plateau to America,
seems after the splendid failure of 1858 to have been abandoned,
chiefly however on account of the electrical difficulties which
stand in the way of so long a circuit. Other routes with shorter
circuits are now proposed ; these are engaging the attention of
enlightened governments in Europe, and of enterprising men on
both sides of the Atlantic.

57. The Gree7iland route. — A line via Iceland and Greenland
to Labrador, and thence overland to Canada and the United
States, is attracting attention in England. The Admiralty have
despatched Captain McClintock in the " Fox," of Arctic renown,
to run a line of deep-sea soundings along this route.

58. Hie French route. — Another line from France, via the
Western Islands to St. Pierre Miquelon, a French fishing-station
off Newfoundland, and thence to the United States, is attracting
the attention of the French people. Their emperor has given
his sanction with the most liberal encouragement.

59. TJieir length of circuit. — The longest reach by the Green-
land route may require a circuit not exceeding 400 or 500 miles
in length. The greatest distance between the relay batteries of
the French line will be a little over a thousand. These dis-
tances, with wires properly insulated, are held to be within
effective telegraphic reach.

60. Faulty cables. — One of the chief physical difficulties which
seem now to stand in the way of these lines lies with the
" cables." It so happens that all deep-sea lines have at the
present writing ceased to work. The two Malta lines in the
Mediterranean are out of order ; so also are the Ked Sea lines :
no messages have passed between Kurrachee and Aden for some

c 2

20 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

time, and tlae line to Algiers has been suspended, if not aban
doned, for tbe present.

61. Tlieir ironiorappings. — All tbese lines had cables incased
in a wrapping of iron wire ; — and it is a question whether the
difficulty with them all be not owing to that circumstance. The
wire wrapping of the Atlantic cable has been found in a state
almost of complete disintegration, like the iron fastenings of
coppered ships. This evidence of galvanic action excites suspi-
cions as to the proper insulation of that cable. Iron, sea- water,
and copper, will make a battery of no inconsiderable power ; and
the decayed state of the iron wire in this instance encourages
the belief as to defective insulation.

62. Imperfect insulation. — Such are the facts. But the facts do
not prove that gutta-percha is an imperfect insulator. With
regard to the Atlantic cable, they suggest that the insulation of
that cable, though perfect at first, might have been injured by
the handlings to which the cable was afterwards subjected, and
above all by the heavy strains which were brought upon
it by the "brakes" during the operation of laying it along the
plateau.

63. The Bed Sea and Mediterranean cables. — These facts, how-
ever, do not suggest the same for the Eed Sea and Mediterranean
cables, for these cables had all been down for some time, and had
been working more or less satisfactorily ; nevertheless, we are
reminded by these failures now, and that too from a fresh
quarter, that iron wrappings about a telegraphic wire are of no
use in the deep sea.*

64. A galvanic battery in the sea. — Two metals, as a copper con-
ductor and an iron wrapper, would seem not to be desirable for
the same cord, for in case of leakage a galvanic battery is at once
formed in the sea, and brought into play upon the cable. Not
only so, the cable itself is a long and powerful Leyden jar ; the
iron wrapping assists to make it so. This circumstance may
also assist to excite the two metals still more, and so hasten the
destruction of the cable as an electrical conductor.

65. Two metals should not be used about a submarine cable. — But

* "Therefore it may now be considered a settled principle in submarine
telegraphy, that the true character of a cable for the deep sea is not that of an
iron rope as large as a man's arm, but of a single copper wire, or a fascicle of
wires, coated with gutta-percha, pliant and supple, and not larger than a lady's
finsrer." — ^Letter to Secretary of the Navy, November 8, 1850.

THE SEA AND THE ATMOSPHEEE. 21

independent of these facts and views, tliere is another reason why
iron wrappings and two metals should not be used, at least for
deep-sea cables. Our researches at sea have shown that there is
no running water at the bottom of the deep sea. Hence we infer
that a telegraphic cord once lodged on the bottom of the ocean,
there, as the tree that falls in the forest, it would lie ; for there
is nothing to disturb it more. "Wherefore it has been held,* that
the iron wrapping for deep-sea lines of telegraph, instead of
being advantageous in any aspect, are not only a hindrance,
but an incumbrance also and a waste : the weight of the cord
may be adjusted to sinking by the size of the conducting wire
within as well as by the character of the non-metallic wrapping
without.

66. Bogers's cable "jacket.'' — Whether the insulating material
be gutta-percha, india-rubber, or other matter, it requires to be
protected from chafes and bruises while on board, and when it is
being payed out. And it may be so protected by a covering, not
of wire, but of silk, hemp, flax, or cotton. An ingenious Ame-
rican! has invented a "jacket," which will not only protect the
cable while on board, but afterwards also, and when it is at the
bottom even in shallow and running water. Thus one of the
obstacles which have been interfering with the progress of sub-
marine telegraphy is removed out of the way.

67. Deep-sea temperatures a desideratum. — But notwithstanding
all that has been done with the sea and in the sea for the electro-
magnetic telegraph, and for human progress, there still remain
many agenda. There is both room and need for further research,
more exploration, and many experiments. As bearing upon
the oest insulating material for submarine lines of telegraph, a
good series 'of deep-sea temperatures is much needed. Of all
those who are now engaged in observing and studying with us,
and for us, the phenomena of the sea, are there none who will
make deep-sea temperatures a speciality ? They would no doubt
prove as instructive and as useful too as deep-sea soundings have
been and are.

* Vide Letter to Secretary of tte Navy, Norember 8, 1856. Maury'a
Sailing Directions, chapter SrBMAKiNJ: Telegeaphy; ditto. Physical Geography
of the Sea, chapters XIII. and XXI, Harper Brothers, New York, 1859 ; also
Journal Eoyal Dublin Society, numb ;rs XII. and XIII. Letter to John Locke,
on the Atlantic Telegraph causes of failure and probabilities of ultimate suc-
cess. Eead January, 1859.

t Hemy J. Eogers of Baltimore

22 PHTSICAL GEOGRAPHY OF THE SEA, AIS^D ITS METEOEOLOGY.

68. S;pecimens from the depth of 19,S00 feet. — Lieutenant Brooker,
in the " Hancock," has obtained soundings in the ISorth Pacific
from the depth of 3300 fathoms, with specimens both of the ooze
and the water at the bottom. These have been sent to Professor
Ehrenberg of Berlin, for microscopic examination. He has not
completed his study of these treasures, but he already reports the
discovery in them of more than one hundred new species of
animalculas.

CHAPTER II.

§ 70-147. THE GULF STREAM.

70. Its colour. — There is a river in the ocean : in the severest
droughts it never fails, and in the mightiest floods it never over-
flows; its banks and its bottom are of cold water, while its
current is of warm ; it takes its rise in the Gulf of Mexico, and
empties into Arctic seas ; this mighty river is the Gulf Stream.
There is in the world no other such majestic flow of waters.
Its current is more rapid than the Mississippi or the Amazon, and
its volume more than a thousand times greater. Its waters, as
far out from the gulf as the Carolina coasts, are of indigo blue.
They are so distinctly marked that their line of junction with
the common sea-water may be traced by the eye. Often one-
half of the 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 those
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.

71. How caused.— At the salt-works of France, and along the
shores of the Adriatic, where the " scdines'' are carried on by the
process of solar evaporation, there is a series of vats or pools
through which the water is passed as it comes from the sea, and
is reduced to the briny state. The longer it is exposed to evapo-
ration, the Salter it grows, and the deeper is the hue of its blue,
until crystallization is about to commence, when the now deep
blue water puts on a reddish tint. Now the water of the Gulf
Stream is Salter (§ 102) than the littoral water of the sea through
which it flows, and hence we can account for the deep indigo
blue which all navigators observe in Gulf Stream water off the

THE GULF STREAM. 2H

Carolina coasts. The salt-makers are in the habit of judging of
the richness of sea- water in salt by its colour — the greener the hue,
the fresher the water. We have in this, perhaps, an explanation
of the contrasts which the waters of the Gulf Stream present
with those of the Atlantic, as well as of the light green of the
North Sea and other Polar waters ; also of the dark blue of inter-
tropical seas, and especially of the Indian Ocean, which poets
have described as the " black waters." Seamen who visit the
Falls of Niagara never fail to remark upon the beautiful green of
the water in the river below, and to contrast it with the dark
blue of the sea in the trade- wind regions.

72. Speculations concerning the Gulf Stream. — What is the cause
of the Gulf Stream has always puzzled philosophers. Many are
the theories and numerous the speculations that have been
advanced with regard to it. Modern investigations and examina-
tions are beginning to throw some light upon the subject, though
all is not yet entirely clear. But they seem to encourage the
opinion that this stream, as well as all the constant currents of the
sea, is due mainly to the constant difference produced by tempe-
rature and saltness in the specific gravity of water in certain
parts of the ocean. Such difference of specific gravity is incon-
sistent with aqueous equilibrium, and to maintain this equi-
librium these great currents are set in motion. The agents
which derange equilibrium in the waters of the sea, by altering
specific gravity, reach from the equator to the poles, and in their
operations they are as ceaseless as heat and cold ; consequently
they call for a system of perpetual currents to undo their per
petual work.

73. Agencies concerned. — These agents, however, are not the
sole cause of currents. The winds help to make currents by press-
ing upon the waves and drifting before them the water of the
sea ; so do the rains, by raising its level here and there ; and so
does the atmosphere, by pressing with more or less superincum-
bent force upon different parts of the ocean at the same moment,
and as indicated by the changes of the barometric column. But
M^hen the winds and the rains cease, and the barometer is sta-
tionary, the currents that were the consequence cease. The
currents thus created are therefore ephemeral. But the changes of
temperature and of saltness, and the work of other agents which
affect the specific gravity of sea-water and derange its equili-
brium, are as ceaseless in their operations as the sun in hia

21 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

course, and in their effect they are as endless. Philosophy points
to them as the cTiief cause of the Gulf Stream and of all the con-
stant currents of the sea.

74. Early writers. — Early writers, however, maintained that
the Mississippi River was the father of the Gulf Stream. Its
floods, they said, produce it : for the velocity of this river in the
sea (§ 70) might, it was held, be computed by the rate of the
current of the river on the land.

75. Objection to the fresh-water theory. — Captain Livingston
overturned this hypothesis by showing that the volume of water
which the Mississippi River empties into the Gulf of Mexico is
not equal to the three thousandth part of that which escapes
from it through the Gulf Stream. Moreover, the water of the
Gulf Stream is salt— that of the Mississippi, fresh; and the
advocates of this fresh-water theory (§ 74) forgot that just as
much salt as escapes from the Gulf of Mexico through this
stream, must enter the Gulf through some other channel from
the main ocean ; for, if it did not, the Gulf of Mexico, in process
of time, unless it had a salt bed at the bottom, or was fed with
salt springs from below — neither of which is probable — would
become a fresh- water basin.

76. Livingston's hypothesis. — The above-quoted argument of
Captain Livingston, however, was held to be conclusive ; and
upon the remains of the hypothesis which he had so completely
overturned, he set up another, which, in turn, has also been
upset. In it he ascribed the velocity of the Gulf Stream as
depending " on the motion of the sun in the ecliptic, and the
influence he has on the waters of the Atlantic."

77. Franklins theory. — But the opinion that came to be most
generally received and deep-rooted in the mind of seafaring
people was the one repeated by Dr. Franklin, and which held
that the Gulf Stream is the escaping of the waters that have been
forced into the Caribbean Sea by the trade-winds, and that it is
the pressure of those winds upon the water which drives up into
that sea-head, as it were, for this stream.

78. Objections to it. — -We know of instances in which the waters
have been accumulated on one side of a lake, or in one end of a
canal, at the expense of the other. The pressure of the trade-
winds may assist to give the Gulf Stream its initial velocity, but
are they of themselves sufficient to send such a stream of water all
the way across the ocean, projecting by a single impress a volume

THE GULF STREAM. 25

of water from the shores of America to tlie shores of Europe, that
exceeds in discharge the mighty Mississippi a thousand times ?
Eeason teaches and examination shows that they are not. With
the view of ascertaining the average number of days during the
year that the N.E. trade-winds of the Atlantic operate upon the
currents between 25° N. and the equator, log-books containing
no less than 380,284* observations on the force and direction of
the wind in that ocean were examined. The data thus afforded
were carefully compared and discussed. The results show that
within those latitudes, and on the average, the wind from the
N.E. quadrant is in excess of the winds from the S.W. only
111 days out of the 365. During the rest of the year the
S.W. counteract the effect of the N.E. winds upon the currents.
Now, can the N.E. trades, by blowing for less than one-third
of the time, cause the Gulf Stream to run all the time, and
without varying its velocity either to their force or their pre-
valence ?

79. HerscheVs explanation. — Sir John Herschel maintainsj that
they can ; that the trade- winds are the sole cause'^ of the Gulf
Stream ; not, indeed, by causing " a head of water " in the West
Indian seas, but by rolling particles of water before them some-
what as billiard balls are rolled over the table. He denies to
evaporation, temperature, salts, and sea-shells, any effective
influence whatever upon the circulation of the waters in the
ocean. According to him the winds are the supreme current-
producing power in the sea,§

• 80. Objections to ii.— This theory would require all the currents
of the sea to set with the winds, or when deflected, to be
deflected from the shore, as billiard balls are from the cushions
of the table, making the littoral angles of incidence and reflection
equal. Now, so far from this being the case, not one of the
constant currents of the sea either makes such a rebound or sets
with the winds. The Gulf Stream sets, as it comes out of the
Gulf of Mexico, and for hundreds of miles after it enters the

* Nautical Monographs, Washington Observatory, No. 1.

f Article " Physical Geography," 8th edition Encyclopaedia Britannica.

X " The dynamics of the Gulf Stream have of late, in the work of Lieu-
tenant Maury, already mentioned, been made the subject of much (we cannot
!3ut think misplaced) wonder, as if there could be any possible ground foi
doubting that it owes its origin entirely to the trade-winds." — Art. 57, Phya
Geography, 8th edition Encyc. Brit.

§ Art. 65, Phys. Geography, Eucyc. Brit.

26 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Atlantic, against the trade-winds ; for a part of the way it runs
right in the " wind's eye." The Japan current, " the Gulf
Stream of the Pacific," does the same. The Mozambique current
runs to the south, against the S.E. trade-winds, and it changes
not with the monsoons. The ice-bearing currents of the north
oppose the winds in their course. Humboldt's current has its
genesis in the ex- tropical regions of the south, where the " brave
west winds " blow with almost if not with quite the regularity
of the trades, but with double their force. And this current,
instead of setting to the S.E. before these winds, flows north in
spite of them. These are the main and constant currents of the
sea — the great arteries and jugulars through which its circula-
tion is conducted. In everj^ instance, and regardless of winds,
those currents that are warm flow towards the poles, those that
are cold set towards the equator. And this they do, not by the
force of the winds, but in spite of them, and by the force of those
very agencies that make the winds to blow. They flow thus by
virtue of those efforts which the sea is continually making to
restore that equilibrium to its waters which heat and cold, the
forces of evaporation, and the secretion of its inhabitants are
everlastingly destroying.

81. The supremacy of the winds disputed. — If the winds make
the upper, what makes the under and counter currents? This
question is of itself enough to impeach that supremacy of the
winds upon the currents, which the renowned philosopher, with
whom I am so unfortunate as to diifer, travelled so far out of his
way to vindicate.* The " bottles " also dispute, in their silent
way, the " supremacy of the wdnds " over the currents of the
sea. The bottles that are thrown overboard to try currents are
partly out of the water. The wind has influence upon them,
yet of all those— and they are many— that have been thrown
overboard in the trade-wind region of the North Atlantic, or in
the Caribbean Sea, where the trade-winds blow, none have been
found to drift with the wind : they all drift with the current, and
nearly at right angles to the wind.

* "We have, perhaps, been more diffuse on the subject of oceanic currents
than the nature of this article may seem to justify ; but some such detail
Bcemed necessary to vindicate to the winds their supremacy in the production
of currents, without calling in the feeble and ineffective aid of heated water,
or the still more insignificant influence of insect secretion, which has been
pressed into the service as a cause of buoyancy in the regions occupied by coral
formations."— Art. 65, Pliys. Geography, Encyc. Brit.

THE GULF STEEA3I. 27

82. TJie Bonifaccio current.— Thdit the winds do make currents
in the sea no one will have the hardihood to deny : but currents
that are born of the winds are as unstable as the winds ; un-
certain as to time, place, and direction, they are sporadic and
ephemeral ; they are not the constant currents such as have been
already enumerated. Admiral Smyth, in his valuable memoir on
the Mediterranean (p. 162), mentions that a continuance in the
Sea of Tuscany of " gu^stij gales'" from the south-west has been
known to raise its surface no less than twelve feet above its
ordinary level. This, he says, occasions a strong surface drift
through the Strait of Bonifaccio. But in this we have nothing
like the Gulf Stream; no deep and narrow channel-way to
conduct these waters off like a miniature river even in that sea,
but a mere surface flow, such as usually follows the piling up of
water in any pond or gulf above the ordinary level. The Boni-
faccio current does not flow like a " river in the sea " across the
Mediterranean, but it spreads itself out as soon as it passes the
Straits, and, like a circle on the water, loses itself by broad
spreading as soon as it finds sea-room. As soon as the force that
begets it expends itself, the current is done.

83. The heel of the Gulf Stream an ascending plane. — Supposing
with Franklin, and those of his school, that the pressure of
the waters that are forced into the Caribbean Sea by the trade-
winds is the sole cause of the Gulf Stream, that sea and the
Mexican Gulf should have a much higher level than the
Atlantic. Accordingly, the advocates of this theory require for
its support " a great degree of elevation." Major Rennell likens
the stream to "an immense river descending from a higher level
into a plain." Now we know very nearly the average breadth
and velocity of the Gulf Stream in the Florida Pass. We also
know, with a like degree of approximation, the velocity and
breadth of the same waters off Cape Hatteras. Their breadth
here is about seventy-five miles against thirty-two in the
*' Narrows " of the Straits, and their mean velocity is three knots
off Hatteras against four in the "Narrows." This being the
case, it is easy to show that the depth of the Gulf Stream off
Hatteras is not so great as it is in the " Narrows " of Bemini by
nearly 50 per cent., and that, consequently, instead of descending,
its bed represents the surface of an inclined plane — inclined
downwards from the north towards the south — up which jjlane the
lower depths of the stream must ascend. If we assume its depth

28 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

off Bernini* to be two liundred fatlioms, which are thought to be
within limits, the above rates of breadth and velocity will give
one hundred and fourteen fathoms for its depth off Hatteras.
The waters therefore, which in the Straits are below the level of
the Hatteras depth, so far from descending, are actually forced up
an inclined plane, whose submarine ascent is not less than ten
inches to the mile.

84. TJie Niagara. — The Niagara is an " immense river descend-
ing into a plain." But instead of preserving its character in
Lake Ontario as a distinct and well-defined stream for several
hundred miles, it spreads itself ont, and its waters are imme-
diately lost in those of the lake. Why should not the Gulf
Stream do the same ? It gradually enlarges itself, it is trne ; but,
instead of mingling with the ocean by broad spreading, as the
" immense rivers" descending into the northern lakes do, its
waters, like a stream of oil in the ocean, preserve a distinctive
character for more than three thousand miles.

85. A current counter to the Gulf Stream. — Moreover, while the
Gulf Stream is running to the north from its supposed elevated
level at the south, there is a cold current coming down from the
north ; meeting the warm waters of the Gulf midway the ocean,
it divides itself, and runs by the side of them right back into
those very reservoirs at the south, to which theory gives an
elevation sufficient to send out entirely across the Atlantic a jet
of warm w-ater said (§ 75) to be more than three thousand times
greater in volume than the Mississippi Eiver. This current from
Baffin's Bay has not only no trade-winds to give it a head, but the
prevailing winds are unfavourable to it, and for a great part of
the way it is below the surface, and far beyond the propelling
reach of any wind. And there is every reason to believe that this,
with other polar currents, is quite equal in volume to the Gulf
Stream. Are they not the effects of like causes ? If so, what
have the trade-winds to do with the one more than the other ?

86. Bottle chart. — It is a custom oft^n practised by seafaring
people to throw a bottle overboard, with a paper, stating the
time and place at which it is done. In the absence of other
information as to currents, that afforded by these mute little
navigators is of great value. They leave no tracks behind them,

* Navy officers of the United States Coast Survey have sounded with the
deep-sea lead, and ascertained its depth here to be 370 fathoms (January,

1850).

THE GULF STREAM. 29

it is true, and their routes cannot be ascertained. But knowing
where they were cast, and seeing where they are found, some
idea may be formed as to their course. Straight lines may at
least be drawn, showing the shortest distance from the beginning
to the end of their voyage, with the time elapsed. Captain
Becher, E.N., has prepared a chart representing in this way the
tracks of more than one hundred bottles. From this chart it
aj)pears that the waters from every quarter of the Atlantic tend
toward the Grulf of Mexico and its stream. Bottles cast into the sea
midway between the Old and the New Worlds, near the coasts of
Europe, Africa, and America, at the extreme north or farthest
south, have been found either in the West Indies, on the British
Isles, or within the well-known range of Gulf Stream waters.

87. Their drift. — Of two cast out together in south latitude on
the coast of Africa, one was found on the island of Trinidad ; the
other on Guernsey, in the English Channel. In the absence of
positive information on the subject, the circumstantial evidence
that the latter performed the tour of the Gulf is all but conclu-
sive. And there is reason to suppose that some of the bottles of
the gallant captain's chart have also performed the tour of the Gulf
Stream ; then, without being cast ashore, have returned with the
drift along the coast of Africa into the intertropical region ;
thence through the Caribbean Sea, and so on with the Gulf
Stream again. (Plate VI.) Another bottle, said to be thrown over
off Cape Horn by an American ship-master in 1837, was after-
wards picked up on the coast of Ireland. An inspection of the
chart, and of the drift of the other bottles, seems to force the con-
clusion that this bottle too went even from that remote region to
the so-called higher level of the Gulf Stream reservoir.

88. The Sargasso Sea. — Midway the Atlantic, in the triangular
space between the Azores, Canaries, and the Cape de Yerd Islands,
is the great Sargasso Sea. (Plate VI.) Covering an area equal
in extent to the Mississippi Valley, it is so thickly matted over
with Gulf weed (Fucus natans) that the speed of vessels passing
through it is often much retarded. When the companions of
Columbus saw it, they thought it marked the limits of naviga-
tion, and became alarmed. To the eye, at a little distance, it
seems substantial enough to walk upon. Patches of the weed
are generally to be seen floating along the outer edge of the Gulf
Stream. The sea-weed always " tails to" a steady or a constant
wind, so that it serves the mariner as a sort o"'^ marine anemo-

30 PHYSICAL GEOGEAPECY OF THE SEA, AND ITS METEOEOLOGT.

meter, telling him whether the wind as he finds it has been
blowing for some time, or whether it has but just shifted, and
which way. Columbus first found this weedy sea on his voyage
of discovery ; there it has remained to this day, moving up and
down, and changing its position, like the calms of Cancer,
according to the seasons, the storms, and the winds. Exact
observations as to its limits and their range, extending back for
fifty years, assure us that its mean position has not been altered
since that time. That the water which comes through the
Florida Pass with the Gulf Stream fiows in a circle, going to the
north on the western side, and returning to the south on the east
side of the Atlantic — sloughing off its drift matter always to the
right, is shown not only by the Sargasso and its weeds, but it is
indicated also, by our "bottle papers," by the facts developed in
Plate VI., and by other sources of information. If, therefore,
this be so, why give the endless current a higher level in one
part of its course than another ?

89. A bifurcation. — Nay, more ; at the very season of the year
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 to the south with equal velocity.
Where is the trade-wind that gives the higher level to Baffin's
Bay, or that even presses upon, or assists to put this current
in motion ? The agency of winds in producing currents in the
deep sea must be very partial. These two currents meet off
the Grand Banks, where the latter is divided. One part of it
underruns the Gulf Stream, as is shown by the icebergs which
are carried in a direction tending across its course. The pro-
bability is, that this " fork" flows on towards the south, and
runs into the Caribbean Sea, for the temperature of the water at
a little depth there has been found far below the mean tempera-
ture of the earth's crust, and quite as cold as at a corresponding
depth off the Arctic shores of Spitzbergen.

90. Winds exercise hut little influence upon constant currents. —
More water cannot run from the equator or the pole than to it.
If we make the trade-winds to cause the Gulf Stream, we ought
to have some other wind to produce the Polar flow ; but these
currents, for the most part, and for great distances, are submarine,
and therefore beyond the influence of winds. Hence it should ap-
pear that winds have little to do with the general system of aqueous

THE GULF STEEAM. 31

circulation in the ocean. The other " fork " runs between oui
shores and the Gnlf Stream to the south, as already described.
As far as it has been traced, it warrants the belief that it, too,
runs up to seek the so-called liiglier level of the Mexican Gulf.

91. Effects of diurnal rotation upon the Gulf Stream. — The power
necessary to overcome the resistance opposed to such a body of
water as that of the Gulf Stream, running several thousand miles
without any renewal of impulse from the forces of gravitation or
any other known cause, is truly surprising. It so happens that
we have an argument for determining, with considerable ac-
curacy, the resistance which the waters of this stream meet with
in their motion towards the east. Owing to the diurnal rotation,
they are carried around with the earth on its axis towards the
east, with an hourly velocity of one hundred and fifty-seven*
miles greater when they enter the Atlantic than when they
arrive off the Banks of Newfoundland ; for in consequence of the
difference of latitude between the parallels of these two places,
their rate of motion around the axis of the eai-th is reduced' from
nine hundred and fifteenf to seven hundred and fifty-eight miles
the hour. Hence this immense volume of water would, if we
suppose it to pass from the Bahamas to the Grand Banks in an
hour, meet with an opposing force in the shape of resistance
sufficient, in the aggregate, to retard it two miles and a half the
minute in its eastwardly rate. If the actual resistance be
calculated according to received laws, it will be found equal to
several atmospheres. And by analogy, how inadequate must the
pressure of the gentle trade-winds be to such resistance, and to
the effect assigned them !

92. The Gtdf Stream cannot he accounted for hy a higher level. —
If therefore, in the proposed inquiry, we search for a propelling
power nowhere but in the higher level of the Gulf, or in the
" billiard-ball " rebound from its shores, we must admit, in the
head of water there, the existence of a force capable of putting in
motion, and of driving over a plain at the rate of four miles the
hour, all the waters, as fast as they can be brought down by three

* In this calculation the earth is treated as a perfect sphere, with a diameter
of 7925.56 miles.

t Or, 915.26 to 758.60. On the latter parallel the current has an east set ot
about one and a half mile the hour, making the true velocity to the east, and on
the axis of the earth, about seven hundred and sixty miles au hour at the
Grand Banks.

32 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOEOLOGY,

thousand (§ 75) such streams as the Mississippi Paver — a powei
at least sufficient to OA^ercome the resistance required to reduce
from two miles and a half to a few feet per minute the velocity
of a stream that keeps in perpetual motion one-fourth of all the
waters in the Atlantic Ocean. Not onl}^ so, we must admit the
existence of an engine in the Gulf of Mexico, which, being
plaj'^ed upon by the gentle forces of the trade-winds, is capable of
sending a stream of water from the shores of the New World to
the shores of the Old.

93. Nor hy the trade-wind theory. — The advocates of the trade-
wind theory, whether, with Franklin (§ 77), they make the
propelling power to be derived from a ''■head of loater" in the
Gulf, or, with Herschel (§ 79), from the rebound, a la billiard-
balls, against its shores, require that the impulse then and there
communicated to the waters of the Gulf Stream should be
sufficient to send them entirely across the Ocean ; for in neither
case does their theory provide for any renewal of the propelling
power by the wayside. Can this be? Can water flow on any
more than cannon-balls can continue their flight after the
propelling force has been expended ?

94. Illustration. — When we inject water into a pool, be the
force never so great, the jet is soon overcome, broken up, and
made to disappear. In this illustration the Gulf Stream may be
likened to the jet, and the Atlantic to the pool. We remember
to have observed as children how soon the mill-tail loses its cur-
rent in the pool below ; or we may now see at any time, and on
a larger scale, how soon the Niagara, current and all, is swallowed
up in the lake below.

95. Gulf Stream the effect of some constantly operating power. —
Nothing but a continually-acting power can keep currents in the
sea, any more than cannon-balls in the air or rivers on the land,
in motion. But for the forces of gravitation the waters of the
Mississippi would remain at its fountain, and but for difference
of specific gravity the waters of the Gulf Stream would remain
in the caldron, as the intertropical parts of the Atlantic Ocean
may be called.

96. TJie production of currents without wind. — For the sake of
further illustration, let us suppose a globe of the earth's size,
and with a solid nucleus, to be covered all over with water two
hundred fathoms deep, and that every source of heat and cause
of radiation be removed, so that its fluid temperature becomes

THE GULF STREAM. 3D

constant and imiform tlirongliout. On such a globe, tlio equili-
brium remaining undisturbed, there would be neither wind nor
current. Let us now suppose that all the water within the
tropics, to the depth of one hundred fathoms, suddenly becomes
oil. The aqueous equilibrium of the planet would thereby be
disturbed, and a general system of currents and counter-currents
would be immediately commenced — the oil, in an unbroken
sheet on the surface, running towards the poles, and the M^ater,
in an under-current, towards the equator. The oil is supposed,
as it reaches the polar basin, to be reconverted into water, and
the water to become oil as it crosses Cancer and Capricorn,
rising to the surface in the intertropical regions, and returning
as before. Thus, without wind, we should have a perpetual and
uniform system of tropical and polar currents ; though loithout
wind, Sir John Herschel maintains,* we should have no " con-
siderable currents " whatever in the sea. In consequence of
the diurnal rotation of the planet on its axis, each particle of
oil, were resistance small, would approach the poles on a spiral
turning to the east with a relative velocity greater and greater,
until, finally, it would reach the pole, and whirl about it at the
rate of nearly a thousand miles the hour. Becoming water and
losing its velocity, it would approach the tropics by a similar,
but reversed spiral, turning towards tbe west. Owing to the
principle here alluded to, all currents from the equator to the
poles should have an eastward tendency, and all from the jDoles
towards the equator a westward. Let us now suppose the solid
nucleus of this hypothetical globe to assume the exact form and
shape of the bottom of our seas, and in all respects, as to figure
and size, to represent the shoals and islands of the sea, as well
as the coast lines and continents of the earth. The rmiform
system of currents just described would now be interrupted by
obstructions and local causes of various kinds, such as "unequal
depth of water, contour of shore lines, &c. ; and we should have
at certain places currents greater in volume and velocity than
at others. But still there would be a sj^stem of currents and
counter-currents to and from either pole and the equator. Now,
do not the cold waters of the north, and the warm waiters of the
gulf, made specifically lighter by tropical heat, and which we

* " If there were no atmosphere, tliere would be no Gulf Stream or any
other considerable oceanic current (as distinguished from a mere surface chilt'
whatever.'" — Art. 37, Physical Geography, 8th ed. Eueyclop. Biit,

34 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOCfT,

tsee actually preserving sncli a system of counter-currents, " hold,
at least in some degree, the relation of the supposed water and
oil ?

97. Warm currents flow towards the pole, cold towards the equator,

In obedience to the laws here hinted at, there is a constant

tendency (Plate IX.) of polar waters towards the tropics and o^'
tropical waters towards the poles. Captain Wilkes, of the United
States' Exploring Expedition, crossed one of these hyperborean
under- currents two hundred miles in breadth at the equator.

98. Edges' of the Gulf Stream a strihing feature. — Ko feature of
the Gulf Stream excites remark among seamen more frequently
than the sharpness of its edges, particularly along its inner
borders. There, it is a streak on the water. As high up as the
Carolinas this streak may be seen, like a greenish edging to a
blue border — the bright indigo of the tropical contrasting finely
(§ 70) with the dirty green of the littoral waters. It is this
apparent reluctance of the warm waters of the stream to mix
with the cool of the ocean that excites wonder and calls forth
remark. But have we not, so to speak, a similar reluctance
manifested by all fluids, only upon a smaller scale, or under cir-
cumstances less calculated to attract attention or excite remark ?

99. Illustrations. — The water, hot and cold, as it is let into the
tub for a warm bath, generally arranges itself in layers or
sections, according to temperature ; it requires violent stirring
to break them up, mix, and bring the whole to an even tempe-
rature. The jet of air from the blow-pipe, or of gas from the
burner, presents the phenomenon still more familiarly ; here we
have, as with the Gulf Stream, the dividing line between fluids
in motion aud fluids at rest finely presented. There is a like
reluctance for mixing between streams of clear and muddy water.
This is very marked between the red waters of the Missouri and
the inky waters of the upper Mississippi ; here the waters of each
may be distinguished for the distance of several miles after these
two rivers come together. It requires force to inject, as it were,
the particles of one of these waters among those of the other, for
mere vis inertia tends to maintain in their statu quo fluids that
have already arranged themselves in layers, streaks, or aggre-
nations.

100. Row the water of the Gulf Stream differs from the littoral
ivaters. — In the ocean we have the continual heaving of the ^er^
and agitation of the waves to overcome this vis inertia; and th

THE GULF strea:^!. 35

mai-Tel is, that they in their violence do not, by mingling the
Gulf and littoral waters together (§ 70), sooner break np and
obliterate all marks of a division between them. But the waters
of the Gulf Stream differ from the inshore waters not only in
colour, transparency, and temperature, but in specific gravity,
in saltness (§ 102), and in other properties, I conjecture, also.
Therefore they may have a peculiar viscosity, or molecular
aiTangement of their own, which further tf^nds to prevent
mixture, and so preserve their line of demarkation.

101. Action on copper. — Observations made for the purpose in
the navy show that ships cruising in the AYest Indies suffer in
their copper sheathing more than they do in any other seas.
This would indicate that the waters of the Caribbean Sea and
Gulf of Mexico, from which the Gulf Stream is fed, have some
Deculiar property or other which makes them so destructive
upon the copper of cruisers.

102. Saltness of the Gulf Stream. — The story told by the copper
and the blue colour (§71) indicates a higher point of saturation
with salts than sea-water generally has; and the salometer
confirms it. Dr. Thomassy, a French savant, who has been ex-
tensively engaged in the manufacture of salt by solar evaporation,
informs me that on his passage to the United States he tried the
saltness of the water with a most delicate instrument : he found
It in the Bay of Biscay to contain 3-^ per cent, of salt ; in thc«
trade-wind region 4^^ per cent. ; and in the Gulf Stream, off
Charleston, 4 per cent., notwithstanding the Amazon and the
Mississippi, with all the intermediate rivers, and the clouds of the
West Indies, had lent their fresh water to dilute the saltness of
this basin.

103. Agents concerned. — Now the question may be asked,
What should make the waters of the Mexican Gulf and Caribbean
Sea Salter than the waters in those parts of the ocean through
which the Gulf Stream flows ? There are physical agents that
are known to be at work in different parts of the ocean, tke
tendency of which is to make the waters in one part of the ocean
Salter and heavier, and in another part lighter and less salt than
the average of sea-water. These agents are those employed hy
sea-shells in secreting solid matter for their structures ; they are
also heat* and radiation, evaporation and precipitation. In the

* According to Dr. Marcet, sea-water contracts do^Yn to 28° ; my own to
about 25.6.

D 2

36 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

trade-wind regions at sea (Plate YIII.), evaporation is generally
in excess of precipitation, while in the extra-tropical regions the
reverse is the case ; that is, the clouds let down more water
there than the winds take np again ; and these are the regions
in which the Gulf Stream enters the Atlantic. Along the shores
of India, where observations have been made, the evaporation
from the sea is said to amount to three-fourths of an inch daily.
Suppose it in the trade-wind region of the Atlantic to amount to
only half an inch, that would give an annual evaporation of
fifteen feet. In the process of evaporation from the sea, fresh
water only is taken up; the salts are left behind. Now a layer
of sea-water fifteen feet deep, and as broad as the trade-wind
belts of the Atlantic, and reaching across the ocean, contains an
immense amount of salts. The great equatorial current (Plate
VI.) which often sweeps from the shores of Africa across the
Atlantic into the Caribbean Sea is a surface current ; and may
it not bear into that sea a large portion of those waters that have
satisfied the thirsty trade-winds with saltless vapour ? If so —
and it probably does — have we not detected here the footprints
of an agent that does tend to make the waters of the Caribbean
Sea Salter, and therefore heavier, than the average of sea- water
at a given temperature ?

104. Evaporation and precipitation. — It is immaterial, so far as
the correctness of the principle upon which this reasoning
depends is concerned, whether the annual evaporation from the
trade-wind regions of the Atlantic be fifteen, ten, or five feet.
The layer of water, whatever be its thickness, that is evaporated
from this part of the ocean, is not all poured back by the clouds
upon the same spot whence it came. But they take and pour it
down in showers upon the extra-tropical regions of the earth —
on the land as well as in the sea— and on the land more water is
let down than is taken up into the clouds again. The rest sinks
down through the soil to feed the springs, and returns through
the rivers to the sea. Suppose the excess of precipitation in
these extra-tropical regions of the sea to amount to but twelve
inches, or even to but two — it is twelve inches or two inches, as
the case may be, of fresh Avater added to the sea in those parts,
and which therefore tends to lessen the specific gravity of sea-water
iheie to that extent, and to produce a double dynamical effect, for
tlie simple reason that what is taken from one scale, by being put
into tlie other, doubles the difference.

THS GULF STREAM. 37

105. Current into the Caribbean Sea. — Xow tliat we may form
some idea as to the influence which the salts left by the vapour
that the trade-winds, north-east and south-east, take up from sea-
water, is calculated to exert in creating currents, let us make a
partial calculation to show how much salt this vapour held m
solution before it was taken up, and, of course, while it was yet
in the state of sea- water. The north-east trade-wind regions of
the Atlantic embrace an area of at least three million square
miles, and the yearly evaporation from it is (§ 103), we will
suppose, fifteen feet. The salt that is contained in a mass of sea-
water covering to the depth of fifteen feet an area of three
million square miles in superficial extent, would be su£6cient to
cover the British islands to the depth of fourteen feet. As this
water supplies the trade-winds with vapour, it therefore becomes
Salter, and as it becomes salter, it becomes heavier ; and therefore
we may infer that the forces of aggregation among its particles
are increased.

106. Amoimt of salt left by evaporation. — Whatever be the cause
that enables these trade-wind waters to remain on the surface,
whether it be from the fact just stated, and in consequence of
which the waters of the Gulf Stream are held together in their
channel ; or whether it be from the fact that the expansion from
the heat of the torrid zone is sufficient to compensate for this
increased saltness ; or whether it be from the low temperature
and high saturation of the submarine waters of the intertropical
ocean ; or whether it be owing to all of these influences together
that these waters are kept on the surface, suffice it to say, we do
know that they go into the Caribbean Sea (§103) as a surface
current. On their passage to and through it, they intermingle
with the fresh waters that are emptied into the sea from the
Amazon, the Orinoco, and the Mississippi, and from the clouds,
and the rivers of the coasts round about. An immense volume
of fresh water is supplied from these sources. It tends to make
the sea- water, that the trade-winds have been playing upon and
driving along, less briny, warmer, and lighter : for the waters of
these large intertropical streams are warmer than sea-water.
This admixture of fresh water still leaves the Gulf Stream a
brine stronger than that of the extratropical sea generally, but
not quite so strong (§ 102) as that of the trade-wind regions.

107. Currents created by storms. — The dynamics of the sea con-
fess the power of the winds in those tremendous currents whicli

88 rnrsicAL geography of the sea, and its ?iet30eology.

stoiins are sometimes known to create ; and that even the gentle
trade-winds may have influence and efiect upon the currents of
the sea has not been denied (§ 82). But the effect of moderate
winds, as the trades are, is to cause what may be called the
drift of the sea rather than a current. Drift is confined to sur-
face waters, and the trade-winds of the Atlantic may assist in
creating the Gulf Stream by drifting the waters which have
supplied them with vapour towards the Caribbean Sea. But
admit never so much of the water which the trade-winds have
played upon to be drifted into the Caribbean Sea, what should
make it flow thence with the Gulf Stream to the shores of
Europe ? It is because there is room for it there ; and there is
room for it because of the difference in the specific gravity of
sea-water in an intertropical sea on one side, as compared with
the specific gravity of water in northern seas and frozen oceans
on the other.

108. The dynamical force that calls forth the Gulf Stream to he
found in the difference as to specific gravity of intertropical and polar
vmters. — The dynamical forces which are expressed by the Gulf
Stream may with as much propriety be said to reside in those
northern waters as in the "West India seas ; for on one side we
have the Caribbean Sea, and Gulf of Mexico, with their waters
of brine ; on the other, the Great Polar basin, the Baltic, and the
i^orth Sea, the two latter with waters that are but little more
than brackish.* In one set of these sea-basins the water is
heavy ; in the other it is light. Between them the ocean inter-
venes ; but water is bound to seek its equilibrium as its level :
and here, therefore, we unmask one of the agents concerned in
causing the Gulf Stream. What is the power of this agent — is it
greater than that of other agents, and how much? We cannot
say how much ; we only know it is one of the chief agents con-
cerned. Moreover, speculate as we may as to all the agencies
concerned in collecting these waters, that have supplied the
trade-wdnds with vapour, into the Caribbean Sea, and then in
driving them across the Atlantic — we are forced to conclude that

* Tlie Polar basin has a known water area of 3,000,000 square miles, and on
unexplored area, including land and water, of 1,.500,000 square miles. Whether
tlie water in this basin be more or less salt than that of the intertropical seas,
we know it is quite ditferent in temperature, and difference of temperature wil]
beget currents quite as readily as difference in saltness, for change in specific
gmvity follows either.

THE GULF STREAM. 89

tbe salt which the trade- wind vapour leaves behind in the tropics
has to be conveyed away from the trade-wind region, to be mixed
up again in due proportion with the other water of the sea — the
Baltic Sea and the Arctic Ocean included — and that these are
some of the waters, at least, which we see running off thiough
the Gulf Stream. To convey them away is doubtless one of the
offices which, in the economy of the ocean, has been assigned to
it. But as for the seat of the forces which put and keep the
Gulf Stream in motion, theorists may place them exdusivehj on
one side of the ocean with as much philosophical propriety as on
the other. Its waters find their way into the North Sea and the
Arctic Ocean by virtue of their specific gravity, while water
thence, to take their place, is, by virtue of its specific gravity
and by counter currents, carried back into the Gulf. The
dynamical force which causes the Gulf Stream may therefore be
said to reside both in the polar and in the intertropical waters of
the Atlantic.

109. Winter temperature of the Gulf Stream. — As to the tempe-
rature of the Gulf Stream, there is, in a winter's day, off Hatteras.
and even as high up as the Grand Banks of Newfoundland in
mid-ocean, a difference between its waters and those of the
ocean near by of 20° and even 30°. Water, we know, expands
by heat, and here the difference of temperature may more than
compensate for the difference in saltness, and leave, therefore,
the waters of the Gulf Stream, though Salter, yet lighter by
reason of their warmth.

110. Top of Gulf Stream roof-shaped. — If they be lighter, they
should therefore occupy a higher level than those through which
they flow. Assuming the depth off Hatteras to be one hundred
and fourteen fathoms, and allowing the usual rates of expansion
for sea- water, figures show that the middle or axis of the Gulf
Stream there should be nearly two feet higher than the con-
tiguous waters of the Atlantic. Hence the surface of the stream
should present a double inclined plane, from which the water
would be running down on either side as from the roof of a
house. As this runs off at the top, the same weight of colder
water runs in at the bottom, and so raises up the cold-water bed
of the Gulf Stream, and causes it to become shallower and
shallower as it goes north. That the Gulf Stream is therefore
roof-shaped, causing the waters on its surface to flow off to either
side from the middle, we have not only circumstantial evidence

40 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

to sliow, but observations to prove. Navigators, while drifting
along with the Gnlf Stream, have lowered a boat to try the
surface current. In such cases, the boat would drift either to
the east or to the west, as it happened to be on one side or the
other of the axis of the stream, while the vessel herself would
drift along with the stream in the direction cz its course : thus
showing the existence of a shallow roof-current from the middle
towards either edge, which would carry the boat along, but
which, being superficial, does not extend deep enough to affect
the drift of the vessel.

111. Diift matter sloughed off to tJie right. — That such is the case
(§ 110) is also indicated by the circumstance that the sea- weed
and drift-wood which are found in such large quantities along
the outer edge of the Gulf Stream, are rarely, even with the
prevalence of easterly winds, found along its inner edge — and
for the simple reason that to cross the Gulf Stream, and to pass
over from that side to this, they would have to drift up an
inclined plane, as it were; that is, they would have to stem this
roof-current until they reached the middle of the stream. We
rarely hear of planks, or wrecks, or of any floating substance
which is cast into the sea on the other side of the Gulf Stream
being found along the coast of the United States. Drift-wood,
trees, and seeds from the West India Islands, are often cast up
on the shores of Europe, but rarely on the Atlantic shores of this
country.

112. Why so sloughed off. — We are treating now of the effects
of physical causes. The question to which I ask attention is,
Why does the Gulf Stream slough off and cast upon its outer
edge, sea-weed, drift-wood, and all other solid bodies that are
found floating upon it ? One cause has been shown to be in its
roof-shaped current ; but there is another which tends to produce
the same effect; and because it is a physical agent, it should
not, in a treatise of this kind, be overlooked, be its action never
so slight. I allude now to the effects produced upon the drift
matter of the stream by the diurnal rotation of the earth.

113. Illustration. — Take, for illustration, a railroad that lies
north and south in our hemisphere. It is well known to engi-
neers that when the cars are going north on such a road, their
tendency is to run off on the east side ; but when the train is
going south, their tendency is to run off on the west side of the
track — L e., always on the right-hand side. Whether the road be

THE GULF STREAM. • 41

one mile or one liundred miles in length, the effect of diurnal
rotation is the same ; and, whether the road be long or short, the
tendency to run off, as yoa cross a given parallel at a stated rate
of speed, is the same ; for the tendency to fly off the track is in
proportion to the speed of the train, and not at all in proportion
to the length of the road. Now, vis inertice and velocity being
taken into the account, the tendency to obey the force of this
diurnal rotation, and to trend to the right, is proportionably as
great in the case of a patch of sea-weed as it drifts along the
Gulf Stream, as it is in the case of the train of cars as they speed
to the north along the iron track of the Hudson Eiver, or the
North- Western railway, or any other railway that lies nearly
north and south. The rails restrain the cars and prevent them
from flying oi? ; but there are no rails to restrain the sea-weed,
and nothing to prevent the drift matter of the Gulf Stream from
going off in obedience to this force. The slightest impulse
tending to turn aside bodies moving freely in water is imme-
diately felt and implicitly obeyed.

114:. Drift-wood on the Mississippi. — It is in consequence of this
diurnal rotation that drift-wood coming down the Mississippi is
so very apt to be cast upon the west or right bank. This is the
reverse of what obtains upon the Gulf Stream, for it flows to the
north; it therefore sloughs off (§ 111) to the east.

115. Effect of diurnal rotation upon. — The effect of diurnal rota-
tion upon the winds and upon the currents of the sea is admitted
by all — the trade-winds derive their easting from it — it must,
therefore, extend to all the matter which these currents bear
with them, to the largest iceberg as well as to the smallest spire
of grass that floats upon the waters, or the minutest organism
that the most powerful microscope can detect among the im-
palpable particles of sea-dust. This effect of diurnal rotation
upon drift will be frequently alluded to in the pages of this work.

116. Formation of the Grand Banhs. — In its course to the north,
the Gulf Stream gradually tends more and more to the eastward,
until it arrives off the Banks of Newfoundland, where its course
becomes nearly due east. These banks, it has been thought,
deflect it from its j^roper course, and cause it to take this turn.
Examination will prove, I think, that they are an effect, certainly
not the cause. It is here thafthe frigid current already spoken
of (§ 85), and its icebergs from the north, are met and melted by
the warm waters of the Gulf. Of course the loads of earth,

42 PHYSICAL GEOGSAPHY OF THE SEA, AND ITS METEOROLOGY.

stones, and gravel brought down upon tliese bergs are hero
deposited. Captain Scoresby, far away in the north, counted at
one time five hundred icebergs setting out from the same vicinity
upon this cold current for the south. Many of them, loaded
with earth, have been seen aground on the Banks. This process
of transferring deposits from the north for these shoals, and of
snowing down upon them the infusoria and the corpses of
*' living creatures " that are brought forth so abundantly in the
warm w^aters of the Gulf Stream, and delivered in myriads for
burial where the conflict between it and the great Polar current
(§89) takes place, is everlastingly going on. These agencies,
with time, seem altogether adequate to the formation of extensive
bars or banks.

117. Deep loater near. — The deep-sea soundings that have been
made by vessels of the English and American navies (Plate XI.)
tend to confirm this view as to the formation of these Banks.
The greatest contrast in the bottom of the Atlantic is just to the
south of these Banks. Nowhere in the open sea has the water
been found to deepen so suddenly as here. Coming from the
north, the bottom of the sea is shelving; but suddenly, after
passing these Banks, it dips down by a precipitous descent to
unknown depths — thus indicating that the debris which forms
the Grand Banks comes from the north.

118. The Gulf Stream describes in its course tJie path of a tra-
jectory.— From the Straits of Bemini the course of the Gulf
Stream (Plate YI.) describes (as far as it can be traced over
toward the British Islands which are in the midst of its waters)
the arc of a great circle nearly. Such a course as the Gulf
Stream takes is very nearly the course that a cannon-ball, could
it be shot from these straits to those islands, would follow.

119. Its path from Bemini to Ireland. — If it were possible to see
Ireland from Bemini, and to get a cannon that would reach that
far, the person standing on Bemini and taking aim, intending to
shoot at Ireland as a target, would, if the earth were at rest,
sight direct, and make no allowance for difference of motion
between marksman and target. Its path would lie in the plane
of a great circle. But there is diurnal rotation ; the earth does
revolve on its axis ; and since Bemini is nearer to the equator
than Ireland is, the gun would be moving in diurna] rotation
(§ 91) faster than the target, and therefore the marksman, taking
aim point blank at his target, would miss. He would find, on

THE GULF STREAM. 43

examination, that he had shot south — that is, to the right (§ 103)
of his mark. In other words, that the path actually described
by the ball would be a resultant arising from this difference in
the rate of rotation and the trajectile force. Like a ray of light
from the stars, the ball would be affected by aberration. The
ball so shot presents the case of the passenger in the railroad car
throwing an apple, as the train sweeps by, to a boy standing by
the wayside. If he throw straight at the boy, he will miss, for
the apple, partaking of the motion of the cars, will go ahead of
the boy, and for the very reason that the shot will pass in
advance of the target, for both the marksman and the passenger
are going faster than the object at which they aim.

120. Tendency of alt currents both in the sea and air to move in
great circles a physical laiv. — Hence we may assume it as a law,
that the natural tendency of all currents in the sea, like the
natural tendency of all projectiles through the air, is to describe
each its curve of flight very nearly in the plane of a great circle.
The natural tendency of all matter, when put in motion, is to go
from point to point by the shortest distance, and it requires force
to overcome this tendency. Light, heat, and electricity, ttie
howling wind, running water, and all substances, whether ponde-
rable or imponderable, seek, when in motion, to obey this law.
Electricity may be turned aside from its course, and so may the
cannon-ball or running water; but remove every obstruction,
and leave the current or the shot free to continue on in tho
direction of the first impulse, or to turn aside of its own volition,
so to speak, and straight it will go, and continue to go — if on a
plane, in a straight line ; if about a sphere, in the arc of a great
circle — thus showing that it has no volition except to obey
impulse ; and that impulse comes from the physical requirements
upon it to take the shortest way to its point of destination.

121. This law recognized by the Gulf Stream. — The waters of the
Gulf Stream, as they escape from the Gulf, are bound for the
British Islands, to the North Sea, and Frozen Ocean (Plate IX.).
Accordingly, they take (§ 118), in obedience to this physical law,
the most direct course by which nature will permit them to
reach their destination. And this course, as already remarked,
is nearly that of the great circle, and of the supposed cannon-
ball.

122. Shoals of NantucJcet do not control its course. — Many phil.*'
eophers have expressed the opinion— indeed, the belief (§ 116) is

^i PHYSICAL GEOGRAPHY OF THF. SEA, AND ITS METEOPvOLOGT.

coramon among mariners — that the coasts of the United States
and the Shoals of Nantucket turn the Gulf Stream towards the
east : but if the view I have been endeavouring to make clear be
correct, it would appear that the course of the Gnlf Stream is
fixed and prescribed by exactly the same laws that require the
planets to revolve in orbits, the planes of which shall pass
through the centre of the sun ; and that, were the Nantucket
Shoals not in existence, the course of the Gulf Stream, in the
main, would be exactly as it is and where it is. The Gulf
Stream is bound over to the North Sea and Bay of Biscay partly
for the reason, perhaps, that the waters there are lighter than
those of the Mexican Gulf ; and if the Shoals of Nantucket were
not in existence, it could not pursue a more direct route. The
Grand Banks, however, are encroaching (§ 116), and cold cur-
rents from the north come down upon it : they may, and probably
do, assist now and then to turn it aside.

123. HersclieVs theory not consistent ivitJi Imown facts. — Now if
this explanation as to the course of the Gulf Stream and its east-
ward tendency hold good, a current setting from the north
towards the south should (§ 103) have a westward tendency. It
should also move in a circle of trajection, or such as would be
described by a trajectile moving through the air without resist-
ance and for a great distance. Accordingly, and in obedience to
the propelling powers derived from the rate at which different
parallels are whirled around in diurnal motion (§ 91), we find
the current from the. north, which meets the Gulf Stream on the
Grand Banks (Plate IX.), taking a &0Mt\\-westwardly direction, as
already described (§ 114). It runs down to the tropics by the
side of the Gulf Stream, and stretches as far tO the west as our
own shores will allow. Yet, in the face of these facts, and in
spite of this force, both Major Eennell and M. Arago would
make the coasts of the United States and the Shoals of Nantucket
to turn the Gulf Stream towards the east : and Sir John Herschel
(§79) makes the trade- winds, which blow from the eastward,
drive this stream to the eastward !

124. Tlie Channel of the Gulf Stream shifts ivith the season. — But
there are other forces operating upon the Gulf Stream. The}'-
are derived (§ 80) from the effect of changes in the waters of the
whole ocean, as produced by changes in their temperature and
saltness fiom time to time. As the Gulf Stream leaves the coasts
of the United States, it begins to vary its position according to

THE GULF STREAM. 45

the seasons ; the limit of its nortliern edge, as it passes the
meridian of Cape Eace (Plate YI.), being in winter about lati-
tude 40-41°, and in September, when the sea is hottest, about
latitude 45-46°. The trough of the Gulf Stream, thei-efore, may
be supposed to waver about in the ocean not unlike a pennon in
the breeze. Its head is confined between the shoals of the
Bahamas and the Carolinas ; but that part of it which stretches
over towards the Grand Banks of Newfoundland is, as the tem-
perature of the waters of the ocean changes, first pressed down
towards the south, and then again up towards the north, accord-
ing to the season of the year.

125. The phenomenon thermal in its character. — To appreciate the
extent of the force by which it is so pressed, let us imagine the
Avaters of the Gulf Stream to extend all the wa}^ to the bottom of
the sea, so as completely to separate, by an impenetrable liquid
wall, if you please, the waters of the ocean on the right from the
waters in the ocean on the left of the stream. It is the height of
summer : the waters of the sea on either hand are for the most
part in a liquid state, and the Gulf Stream, let it be supposed,
has assumed a normal condition between the two divisions,
adjusting itself to the pressure on either side so as to balance
them exactly and be in equilibrium. Now, again, it is the dead
of winter, and the temperature of the waters over an area of
millions of square miles in the North Atlantic has been changed
many degrees, and this change of temperature has been followed
likewise by a change in volume of those waters, amounting, no
doubt, in the aggregate, to many hundred millions of tons> over
the whole ocean; for sea-water, unlike fresh (§ lOo), contracts
to freezing, and below. Now is it probable that, in passing from
their summer to their winter temperature, the sea-waters to the
right of the Gulf Stream should change their specific gravity
exactly as much in the aggregate as do the waters in the whole
ocean to the left of it ? If not, the difference must be com-
pensated by some means. Sparks are not more prone to fly
upward, nor water to seek its level, than Nature is sure with her
efforts to restore equilibrium in both sea and air whenever,
wherever, and by whatever it be disturbed. Therefore, thojgh
the waters of the Gulf Stream do not extend to the bottom, and
though they be not impeneti-able to the waters on either hand,
yet, seeing that they have a waste of waters on the right and a
waste of waters on the left, to which (§ 70) they offer a sort of

4:6 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

resisting permeability, we are enabled to compreliend bow the
waters on eitber band, as tbeir specific gravity is increased or
diminisbed, will impart to tbe trongb of this stream a vibratory
motion, pressing it now to tbe right, now to tbe left, according to
the seasons and the consequent changes of temperature in tbe sea.

126. Limits of the Gulf Stream in March and September. — Plato
VI. shows tbe limits of the Gulf Stream for March and Septem-
ber. Tbe reason for this change of position is obvious. The
banks of the Gulf Stream (§ 70) are cold water. In winter tbe
volume of cold water on the American, or left side of tbe stream,
is greatly increased. It must have room, and gains it by press-
ing the warmer waters of the stream farther to the south, or
right. In September, tbe temperature of these cold waters is
modified ; there is not such an extent of them, and then tbe
warmer waters, in turn, press them back, and so the pendulum-
like motion is preserved.

127. Beluctance of layers or patches to mingle. — In the offings of
the Balize, sometimes as far out as a hundred miles or more from
tbe land, puddles or patches of Mississippi water maybe observed
on tbe surface of tbe sea with little or none of its brine mixed
with it. This anti-mixing property in water has already (§ 98)
been remarked upon. It may be observed from the gutters in
tlie street to the rivers in tbe ocean, and everywhere, wherever
two bodies of water that differ in colour are found in juxta-
position. Tbe patches of white, black, green, yellow, and
reddish waters so often met with at sea are striking and familiar
examples. We have seen, . also, that a like proclivity exists
(§ 99) between bodies or streams of water that differ in tempera-
ture or velocity. This peculiarity is often so strikingly developed
in the neighbourhood of the Gulf Stream, that persons have been
led to suppose that the Gulf Stream has forks in tbe sea, and that
these are they.

128. Streaks of warm and cool. — Now, if any vessel will take
up her position a little to tbe northward of Bermuda, and
steering thence for the Capes of Virginia, will try the M^ater-
thermometer all tbe way at short intervals, she will find its
readings to be now higher, now lower; and tbe observe will
discover that be has been crossing streak after streak of wanii
and cool water in regular alternations. He will then cease to
regard them as bifurcations of tbe Gulf Sti-eam, and view them
rather in the light of thermal streaks of water which have, in the

THE GULF STllEATM, I?

plan of oceanic circulation and in the system of unequal lieating
and cooling, been brought together.

129. Waters of the ocean Jcept in motion hy thermo-dynamical means.
— The waters of the Gulf Stream form by no means the only
body of warm water that the thermo-dynamical. forces of the
ocean keep in motion. Nearly all that portion of the Atlantic
which lies between the Gulf Stream and the island of Bermuda
has its surface covered with water which a tropical sun and tropi-
cal winds have played upon — with water, the specific gravity of
which has been altered by their action, and which is now drift-
ing to more northern climes in the endless search after lost equi-
librium. This water, moreover, as well as that of the Gulf
Stream, cools unequally. It would be surprising if it did not :
for by being spread out over such a large area, and then drifting
for so great a distance, and through such a diversity of climates,
it is not probable that all parts of it should have been exposed to
like vicissitudes by the way, or even to the same thermal con-
ditions : therefore all of the water over such a surface cannot be
heated alike ; radiation here, sunshine there ; clouds and rain
one day, and storms the next ; the unequal depths ; the break-
ing up of the fountains below, and the bringing their cooler or
their warmer waters to the surface by the violence of the waves,
may all be expected, and are well calculated, to produce unequal
heating in the torrid and unequal cooling in the temperate zone ;
the natural result of which would be streaks and patches of water
diifering in temperature. Hence it would be surprising if, in
crossing this drift and stream (Plate VI.) with the v/ater-ther-
mometer, the observer should find the water all of one tempera-
ture. By the time it has reached the parallel of Bermuda or
" the Capes " of the Chesapeake, some of this water may have
been ten days, some ten weeks, and some perhaps longer on its
way from the " caldron " at the south. It has consequently
had ample time to arrange itself into those differently-tempered
streaks and layers (§ 127) which are so familiar to navigators,
and which have been mistaken for " forlcs of the Gulf Stream."

130. Fig. A, Plate VI. — Curves showing some of these varia-
tions of temperature have been projected by the Coast Survey
on a chart of engraved squares (Fig. A, Plate VI.). Theso
curves show how these waters have sometimes arranged them-
selves off the Capes of Virginia into a series of thermal eleva-
tions and depressions.

48 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

131. TJie high temperature and drift in the western half of Noi'th
Atlantic and Pacific Oceans. — In studying the Gulf Stream, the
high temperature and drift of the waters to the east of it are
worthy of consideration. The Japan current (§ 80) has a like
drift of warm water to the east of it also (Plates VI. and IX.).
In the western half, reaching up from the equator to the Gulf
Stream, both of the North Atlantic and North Pacific, the water
is warmer, parallel for parallel, than it is in the eastern half.
On the west side, where the water is warm, the flow is to the
north ; on the east side, where the temperature is lower, the
flow is to the south — making good the remark (§ 80) that, when
the waters of the sea meet in currents, the tendency of the warm
is to seek cooler latitudes ; and of the cool, warmer.

132. A Gulf Stream in each. — The Gulf Stream of each ocean
has its genesis on the west side, and in its course it skirts the
coast along ; leaving the coast, it strikes off to the eastward in
each case, losing velocity and spreading out. Between each of
these Gulf Streams and its coasts there is a current of cool water
setting to the south. On the outside, or to the east of each
stream, and coming up from the tropics, is a broad sheet of warm
water ; it covers an area of thousands of square miles, and its
drift is to the north. Between the northern drift on the one
side of the ocean and the southern set on the other, there is in
each ocean a sargasso (§ 88), into which all drift matter, such as
wood and weeds, finds its way. In both oceans the Gulf Streams
sweep across to the eastern shores, and so, bounding these seas,
interpose a barrier between them and the higher parallels of
latitude, which this drift matter cannot pass. Such are the points
of resemblance between the two oceans and in the circulation of
their waters.

1 33. TJieir connection ivith the Arctic Ocean. — A prominent point
for contrast is afforded by the channels or water-ways between
the Arctic and these two oceans. With the Atlantic they are
divers and large ; with the Pacific there is but one, and it is
both narrow and shallow. In comparison with that of the
Atlantic, the Gulf Stream of the Pacific is sluggish, ill-defined,
and irregular. Were ihe water-ways between the Atlantic and
the Arctic Ocean no larger than Beliring's Straits, our Gulf
Stream would fall far below that of the Pacific in majesty and
grandeur.

134. TJie sargassos show the feeble power of the trade-winds ujwn

THL GULF STREAM. 19

currents. — Here I am reminded to turn aside and call attention to
another fact that militates against the vast current-begetting
power that has been given by theory to the gentle trade-winds.
In both oceans these weedy seas lie partly within the trade-wind
]-eo-ion ; but in neither do these winds give rise to any current.
The weeds are partly out of water, and the wind has therefore
more power upon them than it has upon the water itself; they
tail to the wind. And if the supreme power over the currents of
the sea reside in the winds, as Sir John Herschel would have it,
then of all places in the trade-wind region, we should have here
the strongest currents. Had there been currents here, these
weeds would have been borne away long ago ; but so far from it,
we simpl}^ know that they have been in the Sargassc Sea (§ 88)
of the Atlantic since the first voyage of Columbus. But to take
up the broken thread : —

135. The drift matter confined to sargassos hy currents. — The water
that is drifting north, on the outside of the Gulf Stream, turns,
with the Gulf Stream, to the east also. It cannot reach the high
latitudes (§ 80), for it cannot cross the Gulf Stream. Two
streams of water cannot cross each other, unless one dip down
and underrun the other; and if this drift water do dip down, as
it may, it cannot carry with it its floating matter, which, like its
weeds, is too light to sink. They, therefore, are cut ofi" from a
passage into higher latitudes.

136. Theory as to the formation of sargassos. — According to this
view, there ought to be a sargasso sea somewhere in the sort of
middle ground between the grand equatorial flow and reflow
which is performed by the waters of all the great oceans. The
place where the drift matter of each sea would naturally collect
would be in this sort of pool, into which every current, as it goes
from the equator, and again as it returns, would slough ofi' its
drift matter. The forces of diurnal rotation would require this
collection of drift to be, in the northern hemisphere, on the right-
band side of the current, and, in the southern, to be on the left.
(See Chap. XVIII. and Plate IX.)

137. Sargassos of southern seas to the left of the southern, to the
right of the great ^olar and equatorial flow and refloio. — Thus, with
the Gulf Stream of the Atlantic, and the " Black Stream " of the
Pacific, their sargassos are on the right, as they are also on the
right of the returning and cooler currents on the eastern side of
each one of those northern oceans. So, also, with the Mozam-

50 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS MLTEOROLOGT.

bique cmTent, which runs south along the east coast of Africa
from the Indian Ocean, and with the cooler current setting to
the north on the Australian side of the same sea. Between
these there is a sargasso on the left ; for it is in the southern
hemisphere.

138. Tlieir position conforms to the theory. — Again, there is in the
South Pacific a flow of equatorial waters to the Antarctic on the
east of Australia, and of Antarctic waters (Humboldt's current)
to the north, along the western shores of South America; and,
according to this principle, there ought to be another sargasso
somewhere between New Zealand and the coast of Chili. (See
Plate IX.)

139. TJie discovery of a new sargasao. — To test the correctness of
this view, I requested Lieut. Warley to overhaul our sea-journals
for notices of kelp and drift matter on the passage from Australia
to Cape Horn and the Chincha Islands. He did so, and found it
abounding in small patches, with " many birds about," between
the parallels of 40^ and 50° south, the meridians of 140° and
178° west. This sargasso is directly south of the Georgian
Islands, and is, perhaps, less abundantly supplied with drift
matter, less distinct in outline, and less permanent in position
than any one of the others.

140. One in the South Atlantic. — There is no warm current, or if
one, a very feeble one, flowing out of the South Atlantic. Most
of the drift matter borne upon the ice-bearing current into that
sea finds its way to the equator, and then into the veins which
give volume to the Gulf Stream, and supply the sargasso of the
North Atlantic with extra quantities of drift. The sargassos of
the South Atlantic are therefore small. The formations and
physical relations of sargassos will be again alluded to in Chapter
XVIII.

141. The large volume of ivarm water outside of the Gulf Stream. —
Let us return (§ 129) to this great expanse of warm water which,
coming from the torrid zone on the south-western side of the
Atlantic, drifts along to the north on the outside of the Gulf
Stream. Its velocity is slow, not sufficient to give it the name
of current ; it is a drift, or what sailors call a ' ' set." By the
time this water reaches a parallel of 35° or 40° it has parted
with a good deal of its intertropic il heat : consequent upon this
change in temperature is a change in specific gravity also, and
by reason of this change, as well as by the difficulties of crossing

THE GULF STREAM. 51

tlie Gulf Stream, its progress to the north is arrested. It now
turns to the east with the Gulf Stream, and, yielding to the
force of the westerly winds of this latitude, is (§ 107) by them
slowly drifted along : losing temperature by the way, these waters
reach the southwardly flow on the east side with their specific
gravity so altered that, disregarding the gentle forces of the
wind, they heed the voice of the sea, and proceed to unite with
this cool flow, and to set south in obedience to those dynamical
laws that derive their force in the sea from difiering specific
gravity.

142. The resemblance hetween tJie currents in the North Atlantic and
the North Pacific. — The Thermal Charts of the North Atlantic afford
for these views other illustrations which, when compared with
the charts of the North Pacific now in the process of construction,
will make still more striking the resemblance of the two oceans
in the general features of their systems of circulation. We see
how, in accordance with this principle (§ 132), the currents
necessary for the formation of thickly-set sargassos are generally
wanting in southern oceans. How closely these two seas of the
north resemble each other ; and how, on account of the large
openings between the Atlantic and the Frozen Ocean, the flow of
warm waters to the north and of cold waters to the south is so
much more active in the Atlantic than it is in the Pacific.
Ought it not so to be ?

143. A cushion of cool water protects the bottom of the deep sea from
abrasion by its currents. — As a rule, the hottest water of the Gulf
Stream is at or near the surface ; and as the deep-sea thermo-
meter is sent down, it shows that these waters, though still far
warmer than the water on either side at corresponding depths,
gradually become less and less warm until the bottom of the
current is reached. There is reason to believe that the warm
waters of the Gulf Stream are nowhere permitted, in the oceanic
economy, to touch the bottom of the sea. There is everj'-where
a cushion of cool water between them and the solid parts of the
earth's crust. This arrangement is suggestive, and strikingly
beautiful. One' of the benign offices of the Gulf Stream is to
convey heat from the Gulf of Mexico, where otherwise it would
become excessive, and to dispense it in regions beyond the
Atlantic for the amelioration of the climates of the British
Islands and of all Western Europe. Now cold water is one of
the best non-conductors of heat, and if the warm water of tho

E 2

52 PHYSICAL GEOGllAPHY Of THE SEA, AND ITS METEOROLOGY.

Gulf Stream was sent across tlie Atlantic in contact with the
solid crust of the earth— comparatively a good conductor of heat
— instead of being sent across, as it is, in contact with a cold,
non-conducting cushion of cool water to fend it from the bottom,
much of its heat would be lost in the first part of the way, and
the soft climates of both France and England would be, as that
of Labrador, severe in the extreme, ice-bound, and bitterly cold.

144. Why should the Gulf Stream take its rise in the Gulf of
Mexico 9 — That there should be in the North Atlantic Ocean a
constant and copious flow and reflow of water between that ocean
and the Arctic is (§ 107) not so strange, for there are abimdaiit
channel-ways between the two oceans. In one, water is to be
found nearly at blood heat; in the other, as cold as ice. A
familiar experiment shows that if two basins of such water be
brought in connection by opening a water-way between them,
the warm will immediately commence to flow to the cold, and
the cold to seek the place of the warm. But why this warm
flow in the Atlantic Ocean should seem to issue from the Gulf
of Mexico, as if by pressure, is not so clear.

145. The trade-winds as a cause of the Gulf Stream. — To satisfy
ourselves that the trade- winds have little or nothing to do in
causing the Gulf Stream, we may by a process of reasoning,
which ignores all the facts and circumstances already adduced,
show that they cannot create a current to run when or where
they do not blow. The north-east trade-winds of the Atlantic
blow between the parallel of 25° and the equator; the Gulf
Stream flows between the parallel of 25° and the North Pole.

146. Gulf Stream impelled hy a constantly acting force. — A con-
stantly acting power, such as the force of gravitation, is as
necessary (§ 95) to keep fluids as it is to keep solids in motion.
In either case the projectile force is soon overcome by resistance ;
and unless it be renewed, the current in the sea will cease to
flow onward, as surely as a cannon-ball will stop its flight
through the air when its force is spent. When the waters of
Niagara reach Lake Ontario, they are no longer descending an
inclined plane ; there, gravity ceases to act as a propelling force,
^M the stream ceases to flow on, notwithstanding the impulse it
derived from the falls and rapids above. A propelling power,
having its seat only in the Gulf of Mexico, or the trade- wind
region, could (§ 92) no more drive a jet of water across the
aotiin, than any other single impulse could send any other tra-

GULF STREAM, CLIMATES, AND COMMERCE. 53

jectile that distance through either air or water. The power
that conveys the waters of the Gulf Stream across the ocean is
acting upon them (§ 95) every moment, like gravity upon the
current of the Mississippi river ; with this difierence, however,
the Mississippi runs down hill, the Gulf Stream on the dead
level of the sea. But if we appeal (§ 80) to salt and vapour, to
heat and cold, and to the secreting powers of the insects of the
sea, we shall find just such sources of everlasting changes and
just such constantly acting forces as are required (§ 108) to keep
up and sustain, not only the Gulf Stream, but the endless round
of currents in the sea, which run from the equator to the poles,
and from the poles back to the equator ; and these forces are
derived from difference in specific gravity between the flowing
and reflowing water.

147. The true cause of the Gulf Stream, — The waters of the Guli
as they go from their fountain have their specific gravity in a
state of perpetual alteration in consequence of the change of salt-
ness, and in consequence also of the change of temperature. In
these changes, and not in the trade-winds, resides the power
which makes the ojreat currents of the sea.

CHAPTER III.

§ 150-191. — INFLUENCE OF THE GULF STREAM UPON CLIMATES AND

COMMERCE.

150. Soil) the Washington Observatory is warmed. — Modern inge-
nuity has suggested a beautiful mode of warming houses in
winter. It is done by means of hot water. The furnace and
the caldron are sometimes placed at a distance from the apart-
ments to be warmed. It is so at the Washington Observatory.
In this case, pipes are used to conduct the heated water from
the caldron under the superintendent's dwelling over into one oi
the basement rooms of the Observator3% a distance of one
hundred feet. These pipes are then flared out so as to present
a large cooling surface ; after which they are united into one
again, through which the water, being now cooled, returns
of its own accord to the caldron. Thus cool water is returning
all the time and flowing in at the bottom of the caldron, while
hot water is continually flowing out at the top. The ventilation

54 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOLOGY.

of the Observatory is so arranged that the circulation of the
atmosphere through it is led from this basement room, where the
pipes are, to all other parts of the building ; and in the process
of this circulation, the warmth conveyed by the water to the
basement is taken thence by the air and distributed over all the
rooms. NoAv, to compare small things with great, we have, in
the warm waters which are contained in the Gulf of Mexico,
just such a heating apparatus for Great Britain, the North
Atlantic, and Western Europe.

151. An analogy showing how the Gulf Stream raises temperature
in Europe. — The furnace is the torrid zone ; the Mexican Gulf
and Caribbean Sea are the caldrons; the. Gulf Stream is the
conducting pipe. From the Grand Banks of Newfoundland
to the shores of Europe is the basement — the hot-air chamber —
in which this pipe is flared out so as to present a large cooling
surface. Here the circulation of the atmosphere is arranged by
nature ; it is from west to east ; consequently it is such that the
warmth thus conveyed into this warm-air chamber of mid-ocean
is taken up by the genial west winds, and dispensed, in the
most benign manner, throughout Great Britain and the west
of Europe. The mean temperature of the water-heated air-
chamber of the Observatory is about 90°. The maximum
temperature of the Gulf Stream is 86°, or about 9° above the
ocean temperature due the latitude. Increasing its latitude 10°,
it loses but 2° of temperature ; and, after having run three
thousand miles towards the north, it still preserves, even in
winter, the heat of summer. With this temperature it crosses
the 40th degree of north latitude, and there, overflowing its
liquid banks, it spreads itself out for thousands of square leagues
over the cold waters around, covering the ocean with a mantle
of warmth that serves so much to mitigate in Europe the rigours
of winter. Moving now more slowly, but dispensing its genial
influences more freely, it finally meets the British Islands. By
these it is divided (Plate IX.), one part going into the polar
basin of Spitzbergen, the other entering the Bay of Biscay, but
each with a warmth considerably above the ocean temperature.
Such an immense volume of heated water cannot fail to carry
with it beyond the seas a mild and moist atmosphere. And this
it is which so much softens climate thei'e.

152. Depth and temperature.' — We know not, except approxi-
mately in a few places, what the depth of the under temperature

GULF STREAM, CLIMATES, AND COMMERCE. 55

of the Gulf Stream may be ; but assuming the temperature and
velocity at the depth of two hundred fathoms to be those of the
surface, and taking the well-known difference between the
capacity of air and of water for specific heat as the argument, a
simple calculation will show that the quantity of heat discharged
over the Atlantic from the waters of the Gulf Stream in a winter's
day would be sufficient to raise the whole column of atmosphere
that rests upon France and the British Islands from the freezing
point to summer heat.

153. Contrasts of climates in the same latitudes. — Every west
wind that blows crosses this stream on its way to Europe, and
carries with it a portion of this heat to temper there the northern
winds of winter. It is the influence of this stream upon climate
that makes Erin the " Emerald Isle of the Sea," — that clothes
the shores of Albion in evergreen robes; while in the same
latitude, on this side, the coasts of Labrador are fast bound
in fetters of ice. In a valuable paper on curi-ents,* Mr. Eedfield
states, that in 1831 the harbour of St. John's, Newfoundland,
was closed with ice as late as the month of June; yet who
ever heard of the port of Livei^pool, on the other side, though
2° farther north, being closed with ice, even in the dead of
winter ?

] 54. Mildness of an Orhney winter. — The Thermal Chart (Plate
lY.) shows this. The isothermal lines of 60°, 50°, etc., starting
off from the parallel of 40° near the coasts of the United States,
run off in a north-eastwardly direction, showing the same oceanic
temperature on the European side of the Atlantic in latitude 55°
or 60° that we have on the western side in latitude 40°. Scott,
in one of his beautiful novels, tells us that the ponds in the
Orkneys (latitude near 60°) are not frozen in winter. The
people there owe their soft climate to this grand heating appa-
ratus, and to the latent heat of the vapours from it which is
liberated during the precipitation of them upon the regions round
about. Driftwood from the West Indies is occasionally cast
upon the islands of the North Sea and Northern Ocean by the
Gulf Stream.

155. Amount of heat daily escaping through the Gulf Stream. — Nor

do the beneficial influences of this stream upon climate end

here. The West Indian Archipelago is encompassed on one

side by its chain of islands, and on the other by the Cordilleras

* American Journal of Science, vol. xiv., p. 293.

56 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

of the Andes, contracting witli the Isthmus of Darien, and
stretching themselves out over the plains of Central America
and Mexico. Beginning on the summit of this range, we leave
the regions of perpetual snow, and descend first into the tierra
fenqylada, and then into the terra caliente, or burning land. De-
scending still lower, we reach both the level and the surface of
the Mexican seas, where, were it not for this beautiful and benign
system of aqueous circulation, the peculiar features of the
surrounding country assure us we should have the hottest, if not
most pestilential climate in the world. As the waters in these
two caldrons become heated, they are borne off by the Gulf
Stream, and are replaced by cooler currents through the Carib-
bean Sea ; the surface water, as it enters here, being 3° or 4°,
and that in depth even 40° cooler than when it escapes from the
Gulf.* Taking only this difference in surface temperature as an
index of the heat accumulated there, a simple calculation will
show that the quantity of heat daily carried off by the Gulf
Stream from those regions, and discharged over the Atlantic, is
sufficient to raise mountains of iron from zero to the melting-
point, and to keep in flow from them a molten stream of metal
greater in volume than the waters daily discharged from the
Mississippi Eiver.

156. Its benign influences. — Who, therefore, can calculate the
benign influence of this wonderful current upon the climate
of the South ? In the pursuit of this subject, the mind is led
from nature up to the great Architect of nature ; and what mind
will not the study of this subject fill with profitable emotions ?
Unchanged and unchanging alone, of all created things, the
ocean is the great emblem of its everlasting Creator. "He
treadeth upon the waves of the cea," and is seen in the wonders
of the deep. Yea, " He calleth for its waters, and poureth them
out upon the face ot the earth." In obedience to this call, the
aqueous portion of our planet preserves its beautiful system of
circulation. By it heat and warmth are dispensed to the extra-
tropical regions; clouds and rain are sent to refresh the drj'
land ; and by it cooling streams are brought from Polar Seas to
temper the heat of the torrid zone. At the depth of two hundred

* Temperature of the Caribbean Sea (from the journals of Mr. Dunsterville) :
f^urface temperature : 83'^, September; 84^, July; 83^-86^^, Mosquito Coast.
Temperature in depth : 48^,240 fathoms; 43^, 386 fathoms; 42^, 450 fathoms;
iS''-', 500 fathoms.

GULF STREAM, CLIMATES, AND COMMEECE. 57

and fort}- fathoms the temperature of the currents setting into
the Caribbean Sea has been found as low as 48°, while that
of the surface was 85°. Another cast with three hundred and
eighty-six fathoms gave 43° below against 83° at the surface.
The hurricanes of those regions agitate the sea to great depths ;
that of 1780 tore rocks up from the bottom seven fathoms deep,
and cast them ashore. They therefore cannot fail to bring to the
surface portions of the cooler water below.

157. Cold ivater at the bottom of the Gulf Stream. — At the very
bottom of the Gulf Stream, when its surface temperature was 80°,
the deep-sea thermometer of the Coast Survey has recorded a
temperature as low as 35° Fahrenheit. These cold waters
doubtless come down from the north to replace the warm water
sent through the Gulf Stream to moderate the cold of Spitz-
bergen ; for within the Arctic Circle the temperature at corre-
sponding depths off the shores of that island is said to be only
one degree colder than in the Caribbean Sea, while on the shores
of Labrador and in the Polar Seas the temperature of the water
beneath the ice was invariably found by Lieutenant De Haven at
28°, or 4° below the melting-point of fresh-water ice. Captain
Scoresby relates, that on the coast of Greenland, in latitude 72°,
the temperature of the air was 42° ; of the water, 34° ; and 29°
at the depth of one hundred and eighteen fathoms. He there
found a surface current setting to the south, and bearing with it
this extremely cold water, with vast numbers of icebergs, whose
centres, perhaps, were far below zero. It would be curious to
ascertain the routes of these under-currents on their w^ay to the
tropical regions, which they are intended to cool. One has been
found at the equator (§ 97) two hundred miles broad and 23°
colder than the surface water. Unless the land or shoals inter-
vene, it no doubt comes down in a spiral curve (§ 96), approach-
ing in its course the great circle route.

158. Fish and currents. — Perhaps the best indication as to these
cold currents may be derived from the fish of the sea. The
whales, by avoiding its warm waters, pointed out to the fisher-
man the existence of the Gulf Stream. Along our own coasts,
all those delicate animals and marine productions which delight
in warmer waters are wanting; thus indicating, by their absence,
the prevalence of the cold current from the north now known to
exist there. In the genial w^aimth of the sea about the Bermudas
vn one hand, and Africa on the other, we find, in great abundance,

58 .PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGT.

those delicate sliell-fish. and coral formations which are alto-
gether wanting in the same latitudes along the shores of South
Carolina. The same obtains in the west coast of South
America ; for there the immense flow of polar waters known as
Humboldt's Current almost reaches the line before the first sprig
of coral is found to grow. A few years ago, great numbers of
bonita and albercore — tropical fish — following the Gulf Stream,
entered the English Channel, and alarmed the fishermen of
Cornwall and Devonshire by the havoc which ihej created
among the pilchards. It may well be questioned if the Atlantic
cities and towns of America do not owe their excellent fish-
markets, and the watering-places their refreshing sea-bathing in
summer, to this littoral stream of cold water. The temperature
of the Mediterranean is 4° or 5° above the ocean temperature of
the same latitude, and the fish there are, for the most part, Tery
indifferent. On the other hand, the temperature along the
Ameri(;an coast is several degrees below that of the ocean, and
from Maine to Florida, tables are supplied with the most excel-
lent of fish. The sheep's-head of this cold current, so much
esteemed in Virginia and the Carolinas, loses its flavour, and is
held in no esteem, when taken on the warm coral banks of the
Bahamas. The same is the case with other fish : when taken in
the cold water of that coast, they have a delicious flavour, and are
highl}^ esteemed ; but when taken in the warm water on the
other edge of the Gulf Stream, though but a few miles distant,
their flesh is soft and unfit for the table. The temperature of
the water at the Balize reaches 90°. The fish taken there are
not to be compared with those of the same latitude in this cold
stream. New Orleans, therefore, resorts to the cool waters on
the Florida coasts for her choicest fish. The same is the case
in the Pacific. A current of cold water (§ 398) from the south
sweeps the shores of Chili, Peru, and Columbia, and reaches the
Gallipagos Islands under the equator. Throughout this whole
distance, the world does not afibrd a more abundant or excellent
supply of fish. Yet out in the Pacific, at the Society Islands,
where coral abounds, and the water preserves a higher tempera-
ture, the fish, though they vie in gorgeousness of colouring with
the birds, and plants, and insects of the tropics, are held in no
esteem as an article of food. I have known sailors, even after
long voyages, still to prefer their salt beef and pork to a mess of
fish taken there. The few facts which we have bearing upon

GULF STREAM, CLIMATES, AND COMMERCE. 59

this subject seem to suggest it as a point of the inquiry to be
made, whether the habitat of certain fish does not indicate the
temperature of the water ; and whether these cold and warm
currents of the ocean do not constitute the great highways
through which migratory fishes travel from one region to another.
Why should not fish be as much the creatures of climate as
plants, or as birds and other animals of land, sea, and air F
Indeed, we know that some kinds of fish are found only in
certain climates. In other words, they live where the tempera-
ture of the water ranges between certain degrees.

159. A shoal of sea-nettles. — Navigators have often met with
vast numbers of young sea-nettles (medusce) drifting along with
the Gulf Stream. They are known to constitute the principal
food for the whale ; but whither bound by this route has caused
much curious speculation, for it is well known that the habits of
the right whale are averse to the warm waters of this stream.
An intelligent sea-captain informs me that, several years ago, in
the Gulf Stream off the coast of Florida, he fell in with such a
*' school of young sea-nettles as had never before been heard of."
The sea was covered with 'them for many leagues. He likened
them, as they appeared on near inspection in the w^ater, to acorns
floating on a stream ; but they were so thick as completely to
cover the sea, giving it the appearance, in the distance, of a
boundless meadow in the j'-ellow leaf. He was bound to Eng-
land, and was five or six days in sailing through them. In about
sixty days afterwards, on his return, he fell in with the same
school off the Western Islands, and here he was three or four
days in passing them again. He recognized them as the same,
for he had never before seen any like them ; and on both occa-
sions he frequently hauled up buckets full and examined them.

160. Food for luhales. — -Now the Western Islands is the great
place of resort for whales ; and at first there is something curious
to us in the idea that the Gulf of Mexico is the harvest field, and
the Gulf Stream the gleaner which collects the fruitage planted
there, and conveys it thousands of miles oif to the hungry whale
at sea. But how perfectly in unison is it with the kind and pro-
vidential care of that great and good Being that caters for the
sparrow, and feeds the young ravens when they cry !

161. Piazzi Smyth's description. — Piazzi Smyth, the Astronomer
Royal of Edinburgh, when bound to Teneriffe on his celebrated
astronomical expedition of 1 856, fell in with the annual harvest

60 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of these creatures. They were in the form of hollow gelatinous
lobes, arranged in groups of five or nine — each lobe having an
orange vein down the centre. Thus each animal was formed of
an aggregation of lobes, with an orange-coloured vein, or
stomach, in ever}^ lobe. "Examining," saj^s he, "in the micro-
scope a portion of one of the orange veins, apparently the stomach
of the creature, it was found to be extraordinarily ricb in dia-
tomes, and of the most bizarre forms, as stars, Maltese crosses,
embossed circles, semicircles, and spirals. The whole stomach
could hardly have contained less than seven hundred thousand ;
and when we multiply them by the number of lobes, and then
by the number of groups, we shall have some idea of the count-
less millions of diatomes that go to make a feast for the medusae
— some of the softest things in the world thus confounding and
devouring the hardest — the flinty-shelled diatomace^." Each of
these " sea-nettles," as the sailors call them, had in his nine
stomachs not less, according to this computation, than five or six
millions of these mites of flinty shells, the materials of which
their inhabitants had collected from the silicious matter which
the rains washed out from the vallej^s, and which the rivers are
continually rolling down to the sea.

162. Tlie waters of the sea bring forth — oh how abundantly ! — The
medusae have the power of sucking in the sea-water slowly, and
of ejecting it again with more or less force. Thus thej^ derive both
food and the power of locomotion, for, in the passage of the water,
they strain it and collect the little diatomes. Imagine, now,
how many medusa3-mouthfuls of water there must be in the sea,
which, though loaded with diatomes, are never filtered through
the stomachs of these creatures ; imagine how many medusae the
v/hale must gulp down with every mouthful ; imagine how deep
and thickly the bottom of the sea must, during the process of
ages, have become covered with the flinty remains of these little
organisms ; now call to mind the command which was given to
the waters of the sea on the fifth day of creation ; and then the
boasted powers of the imagination are silenced in their very im-
potency, and the emotions of wonder, love, and praise take their
place.

163. Contrasts between the climates of land and sea. — The sea has
its climates as well as the land. They both change with the
latitude ; but one varies with the elevation above, the other
with the depression below the sea level. The climates in each

GULF STEEAM, CLIMATES, AXD COMMERCE. 61

are reo-ulated by circulation ; but the chief regulators are, on the
one hand, winds ; on the other, currents.

164. Order and design. — The inhabitants of the ocean are as
much the creatures of climate as are those of the dry land ; for
the same Almighty hand which decked the lily and cares for the
sparrow, fashioned also the pearl and feeds the great whale ; He
adapted each to the physical conditions by which his providence
has surrounded it. Whether of the land or the sea, the inhabit-
ants are all his creatures, subjects of his laws, and agents in his
economy. The sea, therefore, we may safely infer, has its offices
and duties to perform ; so, may we infer, have its currents, and
so, too, its inhabitants; consequently, he who undertakes to
study its phenomena must cease to regard it as a waste of waters.
He must look upon it as a part of that exquisite machinery by
which the harmonies of nature are preserved, and then he will
begin to perceive the developments of order and the evidences
of design : viewed in this light, it becomes a vast field for study
— a most beautiful and interesting subject for contemplation.

165. Terrestrial adaptations. — To one who has never studied
the mechanism of a watch, its main-spring or the balance-wheel
is a mere piece of metal. He may have looked at the face of
the watch, and, while he admires the motion of its hands, and
the time it keeps, or the tune it plays, he may have wondered in
idle amazement as to the character of the machinery which is
concealed within. Take it to pieces, and show him each part
separately; he will recognize neither design, nor adaptation, nor
relation between them ; but put them together, set them to work,
point out the offices of each spring, wheel, and cog, explain their
movements, and then show him the result; now he perceives
that it is all one design ; that, notwithstanding the number of
parts, their diverse forms and various offices, and the agents con-
cerned, the whole piece is of one thought, the expression of one
idea. He now rightly concludes that when the main-spring was
fashioned and tempered, its relation to all the other parts must
have been considered ; that the cogs on this wheel are cut and
regulated — adapted — to the ratchets on that, &c. ; and his final
conclusion will be, that such a piece of mechanism could not
have been produced by chance ; for the adaptation of the parts
is such as to show it to be according to design, and obedient to
the will of one intelligence. So, too, when one looks out upon
the face of this beautiful world, he may admire its lovely scenery,

62 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

but his admiration can never grow into adoration unless he -will
take the trouble to look behind and study, in some of its details
at least, the exquisite system of machinery by which such beau-
tiful results are brought about. To him who does this, the sea,
with its physical geography, becomes as the main-spring of a
watch ; its waters, and its currents, and its salt, and its inhabit-
ants, with their adaptations, as balance-wheels, cogs, and pinions,
and jewels in the terrestrial mechanism. Thus he perceives that
the}^ too are according to design — parts of the physical machinery
that are the expression of One Thought, — a unity, with har-
monies Avhich One Intelligence, and One Intelligence alone,
could utter. And when he has arrived at this point, then he
feels that the study of the sea, in its physical aspects, is truly
sublime. It elevates the mind and ennobles the man ; for " His
gentleness makes " it great. The Gulf Stream is now no longer,
therefore, to be regarded by such a one merely as an immense
current of warm water running across the ocean, but as a balance-
wheel — a part of that grand machinery by which air and water
are adapted to each other, and by which this earth itself is
adapted to the well-being of its inhabitants — of the flora which
deck, and the fauna which enliven its surface.

166. Metkorology OF the sea : Gulf Stream the weather-breeder
— its storms— the great hurricane of 1780. — Let us now consider the
Influence of the Gulf Stream upon the Meteorology of the Ocean. To
use a sailor's expression, the Gulf Stream is the great " weather-
breeder " of the North Atlantic Ocean. The most furious gales
of wind sweep along with it ; and the fogs of Newfoundland,
which so much endanger navigation in spring and summer,
doubtless owe their existence to the presence, in that cold sea, of
immense volumes of warm water brought by the Gulf Stream.
Sir Philip Brooke found the temperature of the air on each side
of it at the freezing-point, while that of its waters was 80°.
"The heavy, warm, damp air over the current produced great
irregularities in his chronometers." The excess of heat daily
brought into such a region by the waters of the Gulf Stream
would, if suddenly stricken from them, be sufficient to make the
column of superincumbent atmosphere hotter than melted iron.
With such an element of atmospherical disturbance in its bosom,
we might expect storms of the most violent kind to accompany it
in its course. Accordingly, the most terrific that rage on the
ocean have been known to spend their fury within or near its

GULF STREAM, CLIMATES, AND COMMERCE, 63

borders. Of all storms, the hurricanes of the West Indies and
the typhoons of the China seas cause the most ships to founder.
The stoutest men-ot-war go down before them, and seldom, in-
deed, is any one of the crew left to tell the tale. Of this the
Hornet, the Albany, and the Grampus, armed cruisers in the
American navy, all are memorable and melancholy examples.
Our nautical works tell us of a West India hurricane so violent
that it forced the Gulf Stream back to its sources, and piled up
the water in the Gulf to the height of thirty feet. The Ledbury
Snow attempted to ride it out. When it abated, she found her-
self high up on the dry land, and discovered that she had let go
her anchor amoDg the tree-tops on Elliott's Key. The Florida
Keys were inundated many feet, and, it is said, the scene pre-
sented in the Gulf Stream was never surpassed in awful sub-
limity on the ocean. The water thus dammed up rushed out
with frightful velocity against the fury of the gale, producing a
sea that beggared description. The "great hurricane" of 1780
commenced in Barbadoes. In it the bark was blown from the
trees, and the fruits of the earth destroyed ; the very bottom and
depths of the sea were uprooted, and the waves rose to such a
height that forts and castles were washed away, and their great
guns carried about in the air like chaff; houses were razed ;
ships wrecked; and the bodies of men and beasts lifted up in'
the air and dashed to pieces in the storm. At the different
islands, not less than twenty thousand persons lost their lives
on shore, while farther to the north, the " Stirling Castle " and
the " Dover Castle," British men-of-war, went down at sea, and
fifty sail were driven on shore at the Bermudas.

167. Inquiries instituted hy the Admiralty. — Several years ago
the British Admiralty set on foot inquiries as to the cause of the
storms in certain parts of the Atlantic, w^hich so often rage with
disastrous effects to navigation. The result may be summed up
in the conclusion to which the investigation led : that they are
occasioned by the irregularity between the temperature of the
Gulf Stream and of the neighbouring regions, both in the air and
water.

168. The most stormy sea. — The southern points of South
xlmerioa and Africa have won for themselves, among seamen,
the name of " the stormy capes ;" but investigations carried on
in that mine of sea-lore contained in the log-books at the National
Observatory at Washington, have shown that there is not a

64 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

storm-find in the wide ocean can out-top that whicli rages along
the Atlantic coasts of North America. The China seas and the
North Pa.cific may vie in the fury of their gales with this part ol
the Atlantic, but Cape Horn and the Cape of Good Hope cannot
equal them, certainly, in frequency, nor do I believe in fury.

169. Noi'tJiern seas more boisterous than southern. — In the ex-
tropical regions of the south we lack those contrasts which the
mountains, the deserts, the plains, the continents, and the seas
of the north afford for the production of atmospherical disturb-
ances. Neither have we in the southern seas such contrasts of
hot and cold currents. The flow of warm water towards the
pole, and '^f polar water towards the equator, is as great— perhaps
if measured according to volume, is greater in the southern
hemisphere. But in the southern hemisphere the currents are
broad and sluggish ; in the northern, narrow, sharp, and strong.
Then we have in the north other climatic contrasts for which we
may search southern seas in vain. Hence, without further
investigation, we may infer southern seas to be less boisterous
than northern.

170. Storms in the North Atlantic and Pacific. — By a like
reasoning we may judge the North Pacific to be less boisterous
than the North Atlantic; for, though we have continental
climates on either side of each, and a Gulf Stream in both, yet
the Pacific is a very much wider sea, and its Gulf Stream is (§ 54)
not so warm, nor so sharp, nor so rapid; therefore the broad
Pacific does not, on the whole, present the elements of atmo-
spherical disturbance in that compactness which is so striking
in the narrow North Atlantic.

171. Storms along their western shores. — Nevertheless, thougli
the North Pacific generally may not be so stormy as the North
Atlantic, we have reason to believe that meteorological agents of
nearly equal power are clustered along the western shores of
each ocean. Though the Gulf Stream of the Pacific is not so
hot, nor the cool littoral currents so cold, as those of our ocean
are, yet they lave the shores of a broader continent, and hug
them quite as closely as ours do. Moreover, the Japan Current,
with its neighbouring seas, is some 500 miles nearer to the pole
of maximum cold than the Gulf Stream of the Atlantic is. Great
prominence in the brewing of storms is to be given to the latent
heat which is set fi-ee in the air when vapour is condensed into
rain. The North Pacific being broader than the North Atlantic,

GULF STEEAM, CLIMATES, AND COMMEECE. 65

Biipplies its shores (§ 283) more abundantly with vapour than
the Xoi-th Athmtic does. This no doubt assists to make furious
and mo)'e frequent the storms of the North Facific.

172. Position of the poles of maximum cold, and their influence
upon the meteorology of these tivo oceans.— Some philosophers hold
that there are in the northern hemisphere two poles of maximum
cold : the Asiatic, near the intersection of the parallel of 80'^ with
the meridian of 120° E., and the American, near lat. 79° and
long. 100° W. The Asiatic pole is the colder. The distance
between it and the Japan Current is about 1500 miles; the
distance between the other pole and the Gulf Stream is about
2000 miles. The bringing of the heat of summer, as these
two streams do, in such close juxtaposition with the cold of
winter, cannot fail to produce violent commotions in the atmo-
sphere. These commotions, as indicated by the storms, are far
more frequent and violent in winter, when the contrasts between
the warm and cool places aj-e greater, than they are in summer,
w^hen those contrasts are least. Moreover, each of those poles is
to the north-west of its ocean, the quarter whence come the most
terrific gales of winter. Whatever be the exact degree of
influence which future research may show to be exercised by
these cool places, and the heat dispensed so near them by these
mighty streams of tepid water, there is reason to believe that
they do act and react upon each other with no inconsiderable
meteorological power. In winter the Gulf Stream carries the
temperature of summer as far north as the Grand Banks of
Newfoundland.

173. Climates of England and silver fogs of Newfoundland. — The
habitual dampness of the climate of the British Islands, as well
as the occasional dampness of that along the Atlantic coasts of
the United States when easterly winds prevail, is attributable
also to the Gulf Stream. These winds come to us loaded with
vapours gathered from its warm and smoking waters. The Gulf
Stream carries the temperature of summer, even in the dead of
winter, as far north as the Grand Banks of Newfoundland, and
there maintains it in the midst of the severest frosts. It is the
presence of this warm water and a cold atmosphere in juxta-
position there which gives rise to the " silver fogs " of New-
foundland, one of the most beautiful phenomena to be seen
anywhere among the treasures of the frost-king.

174. Influences uygn storms. — The influence which the Gulf

66 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Stream exercises upon the storms of tlie North Atldntic, which
take their rise within the tropics, is felt as far over even as the
coast of Africa : it is also felt upon those which, though not
intertropical in their origin, are known to visit the offings of the
American coasts. These gales, in whatever part of the ocean
east of the Gulf Stream they take their rise, march to the north-
w^est until they join it, when they " recurvate," as the phrase is,
and take up their line of march to the north-east along with it.
Gales of wind have been traced from latitude 10° N. on the other
side of the Atlantic to the Gulf Stream on this, and then with it
back again to the other side, off the shores of Europe. By
examining the log-books of ships, the tracks of storms have been
traced out and followed for a week or ten days. Their path is
marked by wreck and disaster. At a meeting of the American
Association for the Advancement of Science, in 1854, Mr.
Eedfield mentioned one which he had traced out, and in which
no less than seventy odd vessels had been wrecked, dismasted,
or damaged.

175. More observations in and about the Gulf Stream a desideratum. —
Now, what should attract these storms to the Gulf Stream, is a
question which yet remains to be satisfactorily answered. A.
good series of simultaneous barometric observations within and
on either side of the Gulf Stream is a great desideratum in the
meteorology of the Atlantic. At the equator, where the trade-
winds meet and ascend, where the air is loaded with moisture,
and where the vapour from the warm waters below is condensed
into the equatorial cloud-ring above, we have a low barometer.

176. Certain storms make for it and follow it. — How is it with
the Gulf Stream when these storms from right and left burst in
upon it, and, turning about, course along with it? Its waters
are warm ; they give off vapour rapidly ; and, were this vapour
visible to an observer in the moon, he no doubt would, on a
winter's day especially, be able to trace out by the mist in the
air the path of the Gulf Stream through the sea.

177. How aqueous vapour assists in producing winds. — Ijot us
consider the effect of vapour upon winds, and then the import-
ance of the observations proposed (§ 175) wi]l perhaps be better
appreciated. Aqueous vapour assists in at least five, i:»erhaps
six, ways to put air in motion and produce winds. (1.) By
evaporation the air is cooled ; by cooling its specific gravity is
changed, and, consequently, here is one cause of movement in

GULF STREAM, CLIMATES, AND COMMERCE. _^ 67

tlio air, as is manifest in tlie tendency of the cooled aii to Son
off, and of warmer and lighter to take its place. (2.) Excepting
hydrogen and ammonia, there is no gas 'so light as aqueous vapour,
its weight being to common air in the proportion of nearly
5 to 8 ; consequently, as soon as it is formed it commences to
rise; and, as each vesicle of vapour may be likened, in the
movements which it produces in the air, to a balloon as it rises,
it will be readily perceived how these vaporous particles, as
they ascend, become entangled with those of the air, and so,
carrying them along, upward currents are produced : thus the
wind is called on to rush in below, that the supply for the upward
movement may be kept up. (3.) The vapour, being lighter than
air, presses it out, and, as it were, takes its place, causing the
barometer to fall : thus again an in-rush of wind is called fot
below. (4.) Arrived in the cloud-region, this vapour, being
jondensed, liberates the latent heat which it borrowed from the
iir and water below ; which heat, being now set free and made
sensible, raises the temperature of the surrounding air, causing
it to expand and ascend still higher ; and so winds are again
called for. Ever ready, they conie ; thus we have a fourth way.
(5.) Innumerable rain-drops now begin to fall, and in their
descent, as in a heavy shower, they displace and press the air
oat below with great force. To this cause Espy ascribes the
gusis of wind which are often found to blow outward from the
centre, as it were, of sudden and violent thunder-showers.
(6.) Probably, and especially in thunder-storms, electricity may
assist in creating movements in the atmosphere, and so make
claim to be regarded as a wind-producing agent. But the winds
are supposed to depend mainly on the power of agents (2), (3),
and (4) for their violence.

178. A channel of rarefied air in the atmosjphere and over the Ghilj
Stream, — These agents, singly and together, produce rarefaction,
diminish pressure, and call for an inward rush of air from either
side. Mr. Espy asserts, and quotes actual observation to sustain
the assertion, that the storms of the United States, even those
which arise in the Mississippi Valley, travel east, and often
march out to sea, where they join the Gulf Stream in its course.
That those which have their origin at sea, on the other side of
the Gulf Stream, do (§ 174) often make right for it, is a fact well
known to seamen. The Gulf Stream from Bemini to the Grand
Banks is constantly sending up volumes of steam; this, being
lighter than air, produces a channel way of rarefied air through

68 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the atmospliere, as it winds along the course of the stream. The
latent heat of this vapour when it is set free produces a still
greater rarefaction, so that we may imagine there is in the
atmosphere a sort of cast of the Gulf Stream, in which the
barometer often stands low, and into which, as into the equi-
noctial calm belt (§ 175), the wind often blows from both sides.
In this fact is probably to be found an explanation of the phe-
nomena alluded to above, viz. : that certain storms, both in the
Atlantic and in the United States, invariably make for the Gulf
Stream, and, reaching it, turn and follow it in its course some-
times entirely across the ocean. Hence, the interest that is
attached to a proper series of observations on the meteorology of
the Gulf Stream.

179. Storms of — dreaded hy seamen. — Sailors dread its storms
more than they do the storms in any other part of the ocean. It
is not the fury of the storm alone that they dread, but it is the
" ugly sea " which these storms raise. The current of the stream
running in one direction, and the wind bioAving in another,
create a sea that is often frightful.

180. Boutes formerly governed hy tlie Gulf Stream. — TJie influence
of the Stream upon commerce and navigation. — Formerly the Gulf
Stream controlled commerce across the Atlantic by governing
vessels in their routes through this ocean to a greater extent
than it does now, and simply for the reason that ships are faster,
nautical instruments better, and navigators are more skilful now
than formerly they were.

181. Difficulties with early navigators. — Up to the close of the
last century, the navigator guessed as much as he calculated the
place of his ship; vessels from Europe to Boston frequently
made New York, and thought the landfall by no means bad.
Chronometers, now so accurate, were then an experiment. The
Kautical Ephemeris itself was faulty, and gave tables which
involved eiTors of thirty miles in the longitude. The instru-
ments of navigation erred by degrees quite as much as they now
do by minutes; for the rude "cross staff" and "back staff," the
" sea-ring " and " mariner's bow," had not yet given place to
the nicer sextant and circle of reflection of the present day.
Instances are numerous of vessels navigating the Atlantic in
those times being 6°, 8^, and even 10^ of longitude out of their
reckoning in as many days fiom port.

182. Finding longitude hy the Gulf Stream. — Though navigators
had been in the habit of crossing and recros-sing the Gulf Streaii*

GULF STREAM, CLIMATES, AND COMMERCE. 69

almost daily for three centuries, it never occurred to them to
make use of it as a means of giving them their longitude, and of
warning them of their approach to the shores of this continent
Dr. Franklin was the first to suggest this use of it. The contrast
afforded by the temperature of its waters and that of the sea
between the Stream and the shores of America was striking.
The dividing line between the warm and the cool waters was
sharp (§ 70); and this dividing line, especially that on the
western side of the stream, seldom changed its position as much
in longitude as mariners often erred in their reckoning.

183. Folger's Chart. — When he was in London, in 1770, he
happened to be consulted as to a memorial which the Board of
Customs at Boston sent to the Lords of the Treasury, stating that
the Falmouth Packets were generally a fortnight longer to Boston
than common traders were from London to Providence, Ehode
Island. They therefore asked that the Falmouth packets might
be sent to Providence instead of to Boston. This appeared
strange to the doctor, for London was much farther than Fal-
mouth, and from Falmouth the routes were the same, and the
difference should have been the other way. He, however, con
suited Captain Folger, a Nantucket whaler, who chanced to be in
London also; the old fisherman explained to the philosopher
that the difference arose from the circumstance that the Ehode
Island captains were acquainted with the Gulf Stream, while
those of the English packets were not. The latter kept in it,
and were set back sixty or seventy miles a day, while the former
avoided it altogether. He had been made acquainted with it by
the whales which were found on either side of it, but never in
it (§ 168). At the request of the doctor, he there traced on a
chart the course of this stream from the Straits of Florida. The
doctor had it engraved at Tower Hill, and sent copies of it to
the Falmouth captains, who paid no attention to it. The course
of the Gulf Stream as laid down by that fisherman from his
general recollection of it, has been retained and quoted on the
charts for navigation, we may say, until the present day. But the
investigations of which we are treating are beginning to throw
more light upon this subject ; they are giving us more correct
knowledge in every respect with regard to it, and to many other
new and striking features in the physical geography of the sea.

184. Using the Gulf Stream in winter. — No part of the world
aifords a more difficult or dangerous navigation than the ap-
proaches of the North American coast in winter. Before the

70 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

warmtli of the Gulf Stream was known, a voyage at this season
from Europe to jSTew England, New York, and even to the Capes
of the Delaware or Chesapeake, was many times more trying,
difficult, and dangerous than it now is. In making this part of
the coast, vessels are frequently met by snow-storms and gales
which mock the seaman's strength and set at naught his skill.
In a little while his bark becomes a mass of ice ; with her crew
fi'osted and helpless, she remains obedient only to her helm, and
is kept away for the Gulf Stream. After a few hours' run, she
reaches its edge, and almost at the next bound passes from the
midst of winter into a sea at summer heat. Now the ice disap-
pears from her apparel : the sailor bathes his stiffened limbs in
tepid waters ; feeling himself invigorated and refreshed with
the genial warmth about him, he realizes, out theie at sea, the
fable of Antseus 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 some-
times falls to rise no more, for it is terrible. Many ships annually
founder in these gales ; and I might name instances, for they are
not uncommon, in which vessels bound to Norfolk or Baltimore,
with their crews enervated in tropical climates, have encountered,
as far down as the Capes of Virginia, snow-storms that have
driven them back into the Gulf Stream time and again, and have
kept them out for forty, fifty, and even for sixty days, trying to
make an anchorage.

185. Bunning south to spend the winter. — Nevertheless, the
presence of the warm waters of the Gulf Stream, vdth their
sunimer heat in mid -winter, off the shores of New England, is a
great boon to navigation. At this season of the year especially,
the number of wrecks and the loss of life along the Atlantic sea-
front are frightful. The month's average of wrecks has been as
high as three a day. How many escape by seeking refuge from
the cold in the warm waters of the Gulf Stream is matter of
conjecture. Suffice it to sa}^ that before their temperature was
known, vessels thus distressed knew of no place of refuge short
of the West Indies; and the newspapers of that day — Franklin's
Pennsylvania Gazette among them — inform us that it was no
uncommon occurrence for vessels bound for the Capes of the

GULF STREAM, CLIMATES. AND COMMERCE. 71

Delaware in winter to.be blown off and to go the West Indies,
and there wait for the return of spring before they wonld
attempt another approach to this part of the coast.

186. Tliermal navigation. — Accordingly, Dr. Franklin's dis-
covery with regard to the Gulf Stream temperature was looked
upon as one of great importance, not only on account of its
aifording to the frosted mariner in winter a convenient refuge
from the snow-storm, but because of its serving the navigator
with an excellent land-mark or beacon for our coast in all
weathers. And so viewing it, the doctor, through political
considerations, concealed his discovery for a while,. The prize
of 20,000Z., which had been offered, and partly paid, by the
British goveinment, to Harrison, the chronometer maker, for
improving the means of finding longitude at sea, was fresh in
the minds of navigators. And here it was thought a solution of
the grand problem — for longitude at sea was a grand problem —
had been stumbled upon by chance; for, on approaching the
coast, the current of warm water in the Gulf Stream, and of
cold water on this side of it, if tried with the thermometer,
would enable the mariner to judge with great certainty, and in
the worst of weather, as to his position. Jonathan Williams
afterwards, in speaking of the importance which the thermal
use of these waim and cold currents would prove to navigation,
pertinently asked the question, " If these stripes of water had
been distinguished by the colours of red, white, and blue, could
they be more distinctly discovered than they are by the constant
use of the thermometer ?" And he might have added, could
they have marked the position of the ship more clearly ?

187. Commodore Truxton. — 'When his work on Thermometrical
Navigation appeared, Commodore Truxton wrote to him: " Your
publication will be of use to navigation by rendering sea-voyages
secure far beyond what even you yourself will immediatel}'
calculate, for I have proved the utility of the thermometer very
often since we sailed together. It will be found a most valuable
instrument in the hands of mariners, and particularly as to those
who are unacquainted with astronomical observations; * * * «
these particularly stand in need of a simple method of ascertain-
ing their approach to or distance from the coast, especiall}'' in the
winter season ; for it is then that passages are often prolongedj
and ships blown off the coast by hard westerly winds, and
vessels get into the Gulf Stream without its being known ; on
which account they are often hove to by the captains supposing

72 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

themselves near the coast when they are very far off (having
been drifted by the currents). On the other hand, ships are
often cast on the coast by sailing in the eddy of the Stream,
which causes them to outrun their common reckoning. Every
year produces new proofs of these facts, and of the calamities
incident thereto."

188. TJie discovery of the high temperature of the Gulf Stream fol-
lowed hy a decline in Southern commerce. — Though Dr. Franklin's
discovery was made in 1775, yet, for political reasons, it was not
generally made known till 1790. Its immediate effect in navi-
gation was to make the ports of the Northern States as ac-
cessible in winter as in summer. What agency this circumstance
had in the decline of the direct trade of the south, which followed
this discovery, would be, at least to the political economist, a
subject for much curious and interesting speculation. I have
referred to the commercial tables of the time, and have compared
the trade of Charleston with that of the northern cities for
several years, both before and after the discovery of Dr. Franklin
became generally known to navigators. The comparison shows
an immediate decline in the southern trade and a wonderful
increase in that of the north. But whether this discovery in
navigation and this revolution in trade stand in the relation of
cause and effect, or be merely a coincidence, let others judge.

189. Statistics. — In 1769 the commerce of the two Carolinas
equalled that of all the New England States together ; it was
more than double that of New York, and exceeded that of
Pennsylvania by one-third.* In 1702, the exports from New

* From M'Pher son's Annals of Commerce. — Exports and Imports in 17G9,
valued in Sterling Money.

EXPORTS.

To Great Britain.

South of Europe.

West Indiee.

Africa.

Total.

New England
New York ; .
Penniiylvania
North and South
Carolina . .

£ S. d.
142,775 12 9
11.3,382 8 8
28,112 6 9

405,014 13 1

£ s. d.

81,173 16 2

50,885 13 0

203,762 11 U

76,119 12 10

£ s. d.

308,427 9 6

66,324 17 5

178,331 7 8

87,758 19 3

£ s. d.

17,713 0 9

1,313 2 6

560 9 9

691 12 1

£ . s. d.

550,089 19 2
2:i 1,906 1 7
410,756 16 1

569,584 17 3

IMPORTS.

New England
New York . .
Pennsylvania
North and South
Carolina . .

223,695 U 6

75,9.30 19 7

204,979 17 4

327, 0S4 8 6

25,408 17 9
14,927 7 0
14,249 8 4

7,099 5 10

314,749 14 5
897,420 4 0
180,591 12 4

76.26» 17 11

180 0 0
697 10 0

1.37,620 10 9

564,034 3 8
188,976 1 3
399,830 18 0

535.714 2 3

GTULF S1EEAM, CLIMATES, AND COMMERCE.

73

York amounted in value to two millions and a half; from
Pennsylvania, to |f3,820,000; and from Charleston alone, to
^3,834,000. But in 1795 — by which time the Gulf Stream
began to be as well understood by navigators as it now is>
and the average passages from Europe to the north were
shortened nearly one -half, while those to the south remained
about the same — the customs at Philadelphia alone amounted
to |f2,941,000,* or more than one-half of those collected in all
the states together.

190. The shortening of voyages. — Nor did the effect of the
doctor's discovery end here. Before it was made, the Gulf
Stream was altogether insidious in its effects. By it, vessels
were often drifted many miles out of their course without know-
ing it ; and in bad and cloudy weather, when many days would
intervene from one observation to another, the set of the current,
though really felt but for a few hours during the interval, could
only be proportioned out equally among the whole number of
days. Therefore navigators could have only very vague ideas
either as to the strength or the actual limits of the Gulf Stream,
until they were marked out to the Nantucket fishermen by the
whales, or made known by Captain Folger to Dr. Franklin.
The discovery, therefore, of its high temperature assured the
navigator of the presence of a current of surprising velocity, and
which, now turned to certain account, would hasten, as it had
retarded, his voyage in a wonderful degree. Such, at the present
day, is the degree of perfection to which nautical tables and
instruments have been brought, that the navigator may now
detect, and with great certainty, every current that thwarts his

*

Value, of Exports in

Dollars.^

1731.

1792.

1793,

1794,

1795.

1T96.

Massachusetts .
Kew York .
Pennsylvania .
South Carolina .

2,519,651
2,505,465
3,436,000
2,693,000

2,888,104
2,535,790
3,820,000
2,423,000

3,755,347
2,932,370
6,958,000
3,191,000

5,292,441
5,442,000
6,643,000
3,868,000

7,117,907
10,304,000
11,518,000

5,998,009

9,949,345
12,20ri,U27
17,513,866

7,620,0U0

Duties on Imports in Dollars.

Massachusetts .
New York .

Pennsylvania .

South Carolina .

1791

1,006,000

1,334,000

1,466,000

523,000

1793.

723,000j 1,044,000
1,173,000' 1,204,000
1,100,000 1,823,000

359,000 360,000

1794.

1,121,000

1,878,000

1,498,000

661,000

1795.

1,520,000

2,028,000

2,300,000

722.000

1796.

1,460,000

2,187,000

2,050,000

66,000

1833.

3.055,000
10,713,000

2,207,000
389,000

' Doc. No. 330, H. R., 2nd Session, 25th Congress. Some of its statements do not agree witlj
those taken from M'Pherson, and previously quoted.

74 PHYSICAL GEOGRAPHY OF irlE SBA, AND ITS METEOROLOGY'.

way. He makes great use of them. General Sabine, in his
passage, some years ago, from Sierra Leone to New York, was
drifted one thousand six hundred miles of his way b}^ the force
of currents alone ; and, since the application of the thermometer
to the Gulf Stream, the average passage from England has been
reduced from upwards of eight weeks to a little more than four.
Some political economists of America have ascribed the great
decline of southern commerce which followed the adoption of the
Constitution of the United States to the protection given by
federal legislation to northern interests. But I think these
statements and figures show that this decline was in no small
degree owing to the Gulf Stream, the water-thermometer, and
the improvements in navigation ; for they changed the relations
of Charleston — the great southern emporium of the times —
removing it from its position as a half-way house, and placing it
in the category of an outside station.

191. Tlie scope of these researches. — The plan of our work takes
us necessarily into the air, for the sea derives from the winds
some of the most striking features in its physical geography;
and from the air all of its meteorology. Without a knowledge of
the winds, we can neither understand the navigation of the
ocean, nor make ourselves intelligently acquainted with the
great highways across it. As w4th the land, so with the sea ;
some parts of it are as untravelled and as unknown as the great
Amazonian wilderness of Brazil, or the inland basins of Central
Africa. To the south of a line extending from Cape Horn to the
Cape of Good Hope (Plate YIII.) is an immense waste of waters.
None of the commercial thoroughfares of the ocean lead through
it ; only the adventurous whaleman finds his way there now and
then in pursuit of his game ; but for all the purposes of science
and navigation, it is a vast unknown region. Now, were the
prevailing winds of the South Atlantic northerly or southerly
instead of easterly or westerly, this unploughed sea would be an
oft-used thoroughfare. Nay, more, the sea supplies the wind
with food for the rain which these busy messengers convey
away from the ocean to " the springs in the valleys which run
among the hills." To the philosopher, the places which supply
the vapours are as suggestive and as interesting for the instruc-
tion they afford, as the places are upon which the vapours are
showered down. Therefore, as he who studies the physical
geography of the land is expected to make himself acquainted

THE ATMOSPHEKE. «0

with the regions of precipitation, so he who looks into the
physical geography of the sea should search for the regions of
evaporation, and for those springs in the ocean which supply the
reservoirs among the mountains with water to feed the rivers ;
and, in order to condnct this search properly, he must consult
the winds, and make himself acquainted with their circuits.
Hence, in a work on the Physical Geography of the Sea and its
Meteorology, we treat also of the Atmosphere.

CHAPTER IV.

200-268. the" ATMOSPHERE.

200. Likened to a machine. — There is no employment more
ennobling to man and his intellect than to trace the evidences
of design and purpose, which are visible in many parts of the
creation. Hence, to the right-minded mariner, and to him who
studies the physical relations of earth, sea, and air, the atmo-
sphere is something more than a shoreless ocean, at the bottom of
which he creeps along. It is an envelope or covering for the
distribution of light and heat over the surface of the earth ; it is
a sewer into which, with every breath we draw, we cast vast
quantities of dead animal matter ; it is a laboratory for purifi-
cation, in which that matter is recompounded, and wrought
again into wholesome and healthful sliapes ; it is a machine for
pumping up all the rivers from the sea, and for conveying the
water (§ 191) from the ocean to their sources in the mountains ;
it is an inexhaustible magazine, marvellously stored. Upon the
proper working of this machine depends the well-being of every
plant and animal that inhabits the earth. How interesting,
then, ought not the study of it to be ! An examination of the
uses which plants and animals make of the air is sufQcient to
satisfy any reasoning mind in the conviction that when they
were created, the necessity of this adaptation was taken into
account. The connection between any two parts of an artificial
Saachine that work into each other, does not render design in its
/construction more patent than is the fact that the great atmo-
spherical machine of our planet was consti'ucted by an Architect
who designed it for certain purposes ; therefore the management
of it, its movements, and the performance of its offices, cannot be

7G PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

left to chance. Thej^ are, we may re]y upon it, guided by laws
that make all parts, functions, and movements of this machinery
as obedient to order and as harmonious as are the planets in their
orbits.

201. The air and the ocean governed hy stable laws. — Any exami
nation into the economy of the universe v^^ill be sufficient tt
satisfy the well-balanced minds of observant men that the laws
which govern the atmosphere and the laws which govern the
ocean (§ 1 64) ai-e laws which were put in force by the Creator
when the foundations of the earth were laid, and that therefore
they are laws of order ; else, why should the Gulf Stream, for
instance, be alwaj^s where it is, and running from the Gulf of
Mexico, and not somewhere else, and sometimes running into it?
Why should there be a perpetual drought in one part of the
world, and continual showers in another? Or why should the
conscious winds ever heed the voice of rebuke, or the glad waves
ever " clap their hands with joy ?"

202. Importance of observing the works of nature. — To one who
looks abroad to contemplate the agents of nature, as he sees
them at work upon our planet, no expression uttered or act
performed by them is without meaning. By such a one, the
wind and rain, the vapour and the cloud, the tide, the current,
the saltness, and depth, and warmth, and colour of the sea, the
shade of the sky, the temperature of the air, the tint and shape
of the clouds, the height of the tree on the shore, the size of its
leaves, the brilliancy of its flowers — each and all may be re-
garded as the exponent of certain physical combinations, and
therefore as the expression in which Kature chooses to announce
her own doings, or, if we please, as the language in, which she
writes down or elects to make known her own laws. To under-
stand that language and to interpret aright those laws is the
object of the undertaking which we now have in hand. No fact
gathered from such a volume as the one before us can therefore
come amiss to those who tread the walks of inductive philosophy
for, in the handbook of nature, every such fact is a syllable ; and
it is by patiently collecting fact after fact, and by joininic
together syllable after syllable, that we may finally seek t<;
read aright from the great volume which the mariner at sea as
well as the philosopher on the mountain each sees spread out
before him.

203. Materials for this chapter. — There have been examined at

THE ATMOSPHERE. 77

the Observatory more tliaii a million of observations on the force
and direction of the winds at sea.* The discussion of snch a
mass of material has thrown much light upon the circulation of
the atmosphere; for, as in the ocean (§ 201), so in the air, there
is a regular system of circulation.

204. Different belts of ivinds. — Before we proceed to describe
this system, let us point out the principal belts or bands of wind
that actual observation has shown to exist at sea, and which,
with more or less distinctness of outline, extend to the land also,
and thus encircle the earth. If we imagine a ship to take her-
departure from Greenland for the South Shetland Islands, she
will, between the parallels of 60° north and south, cross these
several bands or belts of winds and calms nearly at right angles,
and in the following order: — (1.) At setting out she will find
herself in the region of south-west winds, or counter-trades of
the north — called counter because they blow in the direction
whence come the trade-winds of their hemisphere. (2.) After
crossing 50°, and until reaching the parallel of 35° N., she finds
herself in the belt of westerly winds, a region in which winds
from the south-west and winds from the north-west contend for
the mastery, and with nearly equal persistency. (3.) Between
35° and 30°, she finds herself in a region of variable winds and
calms ; the winds blowing all around the compass, and averaging
about three months from each quarter during the year. Our
fancied ship is now in the " horse-latitudes." Hitherto winds
with ivesting in them have been most prevalent; but, crossing
the calm belt of Cancer, she reaches latitudes where winds with
easting become most prevalent. (4.) Crossing into these, she
enters the region of north-east trades, which now become the
prevailing winds, until she reaches the parallel of 10° N., and
enters the equatorial calm belt, which, like all the other wind-
bands, holds fluctuating limits. (5.) Crossing the parallel of 5°
N., she enters where the south-east trades are the prevailing
winds, and so continue until the parallel of 30° S. is reached.
(6.) Here is the calm belt of Capricorn, where, as in that of
Cancer (3), she again finds herself in a region of shifting winds,
light airs, and calms, and where the winds with westing in them
become the prevailing winds. (7.) Between the parallels of 35°
and 40° S., the north-west and south-west winds contend with

* Nautical Monograpli, No. 1, 1859.

IS PHYSICAL GEOGRAIHY OF THE SEA, AND ITS METEOROLOGY.

equal iDOwer for the mastery. (8.) Crossing 40^, the counter
trades (1), — the north-west winds of the southern hemisphere, — ■
become the prevailing winds, and so remain, as far as our obser-
vations at sea extend towards the south pole.

Such are the most striking movements of the winds at tlie
surface of the sea. But, in order to treat of the general system
of atmospherical circulation, we should consider where those
agents reside which impart to that system its dynamical force.
They evidently reside near the equator on one side, and about
the poles on the other. Therefoie, if, instead of confining our
attention to the winds at the surface, and their relative preva-
lence from each one of the four quarters, we direct our attention
to the upper and lower currents, and to the general movements
hack and forth between the equator and the poles, we shall be
enabled the better to understand the general movements of this
gi-and machine.

205. Tlie trade-ioind hells. — Thus treating the subject, obser-
vations show that from the parallel of about 30° or 35° north
and south to the equator, we have, extending entirely around the
earth, two zones of perpetual winds, viz., the zone of north-east
trades on this side, and of south-east on that. With slight
interruptions, these winds blow perpetually, and are as steady
and as constant as the currents of the Mississippi Eiver, always
moving in the same direction (Plate I.) except when they are
turned aside by a desert or a rainy region here and there to
blow as monsoons, or as land and sea breezes. As these two
main currents of air are constantl}' flowing from the poles toward
the equator, we are safe in assuming that the air which they
keep in motion must return by some channel to the place toward
the poles whence it came in order to supply the trades. If this
were not so, these winds would soon exhaust the jDolar regions
of atmosphere, and pile it up about the equator, and then cease
to blow for the want of air to make more wind of.

206. TJie return current. — This return current, therefore, must
be in the upper i-egions of the atmosphere, at least until it paisses
over those parallels between which the trade-winds are usually
blowing on the surface. The return current must also move in
the direction opposite to that wind the place of which it is
intended to supply. These direct and counter currents are also
made to move in a sort of spiral or loxodronic curve, turning io
the west as they go from the poles to the equator, and in the

THE ATMOSPHERE 79

opposite direction as they move from the equator towards the poles.
This tuiTiing is caused b}^ the rotation of the earth on its axis.

207. Effect of diurnal rotation on the course of the trade-winds. —
The earth, we know, moves from west to east. Now if we
imagine a particle of atmosphere at the north pole, where it is at
rest, to be put in motion in a straight line, towai'ds the equator,
we can easily see how this particle of air, coming from the very
axis of dinrnal rotation, where it did not partake of the diurnal
motion of the earth, would, in consequence of its vis inertice, find,
as it travels sonth, the earth slipping from under it, as it were,
and thus it would appear to be coming from the north-east and
going towards the south-west ; in other words, it would be a
north-east wind. The better to explain, let us take a common
terrestrial globe for the illustration. Bring the island of
Madeira, or any other place about the same parallel, under the
brazen meridian ; put a finger of the left hand on the place ;
then moving the finger down along the meridian to the south, to
represent the particle of air, turn the globe on its axis from west
to east, to represent the diurnal rotation of the earth, and when
the finger reaches the equator, stop. It will now be seen that
the place on the globe under the finger is to the southward and
westward of the place from which the finger stai'ted ; in other
words, the track of the finger over the surface of the globe, like
the track of the particle of air upon the earth, has been from the
northward and eastward. On the other hand, we can perceive
how a like particle of atmosphere that starts from the equator,
to take the place of the other at the pole, would, as it travels
north, and in consequence of its vis inertice, be going towards the
east faster than the earth. It would therefore appear to be
blowing /rom the south-west, and going towards the north-east
and exactly in the opposite direction to the other. Writing
south for north, the same takes place between the south pole and
the equator.

208. Two grand systems of currents. — Such is the process which
is actually going on in nature ; and if we take the motions of
these two particles as the type of the motion of all, we shall have
an illustration of the great currents in the air (§ 204), the
equator being near one of the nodes, and there being at least two
systems of currents, an upper and an under, between it and each
pole. Halley, in his theory of the trade winds, pointed out the
key to the explanation, so far, of the atmospherical circulation;

80 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOROLOG"*.

but, were the explanation to rest here, a north-east trade-wind
extending from the pole to the equator would satisfy it; and
were this so, we shonld have, on the surface, no winds but the
north-east trade-winds on this side, and none but south-east
trade-winds on the other side, of the equator.

209. From the Pole to 30°-35o. — Let us return now to our
northern particle (§ 207), and follow it in a round from the
north pole across the equator to the south pole, and back again.
Setting off from the polar regions, this particle of air, for some
reason which does not appear, hitherto, to have been very satis-
factorily explained by philosophers, instead of travelling (§ 208)
on the surface all the way from the pole to the equator, travels
in the upper regions of the atmosphere until it gets near the belt
between 30o-35°. Here it meets, also in the clouds, the hypo-
thetical particle that is coming from the south, and going north
to take its place.

210. TJie " Jiorse latitudes"— Ahout this belt of 30°-35° north,
then, these two particles press against each other with the whole
amount of their motive power, and produce a calm and an
accumulation of atmosphere : this accumulation is sufficient to
balance the pressure of the two currents from the north and
south. From imder this bank of calms, which seamen call the
" horse latitudes," two surface currents of wind are ejected or
drawn out ; one towards the equator, as the north-east trades,
the other towards the pole, as the south-west " passage-winds,"
or counter-trades. These winds come out at the lower surface
of the calm region, and consequently the place of the air borne
away in this manner must be supplied, we may infer, by down-
ward currents from the superincumbent air of the calm region.
Like the case of a vessel of water which has two streams from
opposite directions running in at the top, and two of equal
capacity discharging in opposite directions at the bottom, the
motion of the water would be downward ; — so is the motion of
the air in this calm zone.

2n. The barometer there. — The barometer, in this calm region,
stands higher than it does either to the north or to the south of
it; and this is another proof as to the accumulation of the
atmosphere here, and pressure from its downward motion. And
because the pressure under this calm belt is greater than it is
on either side of it, the tendency of the air will be to flow
out on either side ; therefore, supposing we were untaught by

THE ATMOSPHEEE. 81

observation as to direction of the wind, reason would teach na
to look for the prevailing winds on each side of this calm belt to
be from it.

212. The equatorial calm belt. — Following onr imaginary particle
of air, however, from the north across this calm belt of Cancer,
we now perceive it moving on the surface of the earth as the
north-east trade-wind ; and as such it continues till it arrives
near the equator, where it meets a like h^'^pothetical particle,
which, starting from the south at the same time the other started
from the north pole, has blown as the south-east trade-wind.
Here, at this equatorial place of meeting, there is another conflict
of winds and another calm region, for a north-east and south-east
wind cannot blow in the same place and at the same time. The
two particles have been put in motion by the same power ; they
meet with equal force ; and, therefore, at their place of meeting,
they are arrested in their course. Here, therefore, there is a
calm belt, as well as at Capricorn and Cancer. Warmed now by
the heat of the sun, and of vapour in the process of condensa-
tion, and pressed on each side by the whole force of the north-
east and south-east trades, these two hypothetical particles,
taken as the type of the whole, cease to move onward and
ascend. This operation is the reverse of that which took
place at the meeting (§ 210) near the belt between the parallels
of 30°-35°.

213. Hie calm belt of Capricorn. — This imaginary particle then,
having ascended to the upper regions of the atmosphere again,
travels there counter to the south-east trades, until it meets,
near the calm belt of Capricorn, another particle from the south
pole ; here there is a descent as before (§ 210) ; it then (§ 211)
flows on towards the south pole as a surface wind from the
north-west.

214. The polar calms and the return current. — Entering the polar
regions obliquely, it is pressed upon by similar particles flowing
in oblique currents across every meridian ; and here again is a
calm place or node ; for, as our imaginary particle approaches
the parallels near the polar calms more and more obliquely, it,
with all the rest, is whirled about the pole in a continued
circular gale ; finally, reaching the vortex of the calm place, it is
carried upward to the regions above, whence it commences again
its flow to the north as an upper current, as far as the calm belt
of Capricorn; here it encounters (§ 213) its fellow from t;^^

G

82 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Dorth (§ 207) ; they stop, descend, and flow out as surface
currents (§ 210j, the one with which the imagination is tra-
velling, to the equatorial calm as the south-east trade-wind;
here (§ 212) it ascends, travelling thence to the calm belt of
Cancer as an upper current counter to the north-east trades.
Here (§ 210 and 209) it ceases to be an upper current, but,
descending (§ 210), travels on with the south-west passage-winds
0 wards the pole.

215. Diagram of the winds. — Now the course we have imagined
an atom of air to take, as illustrated by the " diagram of the
winds " (Plate I.), is this : an ascent in a place of calms about
the north pole, as at V P ; an efflux thence as an upper current,
ABC, until it meets E S (also an upper current) over the calms
of Cancer. Here there is supposed to be a descent, as shown by
the arrows, C D, S T. This current, A B C D, from the pole,
now .becomes the north-east trade-wind, D E, on the surface,
until it meets the south-east trades, 0 Q, in the equatorial
calms, where it ascends as E F, and travels as F G with the
upper current to the calms of Capricorn, thence as H J K,
with the prevailing north-west surface current to the south
pole, thence up with the arrow P', and around with the
hands of a watch, and back, as indicated by the arrows along
LMNOQESTUV.

216. As our knowledge of the laivs of nature has increased, so have
our readings of the Bible imjproved. — The Bible frequently makes
allusion to the laws of nature, their operation and effects. But
such allusions are often so wrapped in the folds of the peculiar
and graceful drapery with which its language is occasionally
clothed, that the meaning, though peeping out from its thin
covering all the while, yet lies in some sense concealed, until
the lights and revelations of science are thrown upon it ; then it
oursts out and strikes us with exquisite force and beauty. As
our knowledge of Nature and her laws has increased, so has our
understanding of many passages in the Bible been improved.
The Psalmist called the earth " the round world ;" yet for ages
it was the most damnable heresy for Christian men to say the
world is round ; and, finally, sailors circumnavigated the globe,
proved the Bible to be right, and saved Christian men of science
from the stake. " Canst thou bind the sweet influences of
Pleiades ?" Astronomers of the present day, if they have not
answered this queistion, have thrown so much light upon it as to

THE A'lMOSPHERE. 83

eliow that, if ever it be answered by man, lie must consult the
science of astronomy. It has been recentlj^ all but proved, that
the earth and sun, with their splendid retinue of comets,
satellites, and planets, are all in motion around some point or
centre of attraction inconceivably remote, and that that point
is in the direction of the star Alcyon, one of the Pleiades !
Who but the astronomer, then, could tell their " sweet influ-
ences ?" And as for the general system of atmospherical circu-
lation which I have been so long endeavouring to describe,
the Bible tells it all in a single sentence: "The wind goeth
towards the south, and turneth about unto the north ; it whirleth
about continually, and the wind returneth again according to his
circuits." — Eccl. i. 6.

217. Sloughing off from the counter trades. — Of course, as the
surface winds, H J K, and T U V, approach the poles, there must
be a sloughing off, — if I may be allowed the expression, — of air
from them, in consequence of their approaching the poles. For
as they near the poles, the parallels become smaller and smaller,
and the surface current must either extend much higher up, and
blow with greater rapidity, or else a part of it must be sloughed
off above, and so turn back before reaching the calms about the
poles. The latter is probably the case.. Such was the conjec-
ture. Subsequent investigations* have established its correct
ness, and in this way : they show that the south-east trade-
winds, as in the Atlantic, blow, on the average, during the year,
124 days between the parallels of 25° and 30° S., and that as you
approach the equator their average annual duration increases
until you reach b° S. Here between 5° and 10° S. they blow on
the average for 329 out of the 365 days.

218. The air which sujpplies the south-east trade-wind in the hand
6° does not cross the band 25°. — "N'ow the question may be asked,
Where do the supplies which furnish air for these winds for 329
days come from ? The " trades " could not convey this fresh
supply of air across the parallel of 25° S. during the time
annually allotted for them to blow in that latitude. They cannot
for these reasons : (1.) Because the trade- winds in lat. 5° are
stronger than they are in lat. 25°, and therefore, in equal times,
they waft larger volumes of air across 5° than they do acro&s
25°. (2.) Because the girdle of the earth near the equator is

* Nautical Monographs, No. 1, Observatory, 'Wasliington, October, 1859.

G 2

84 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

larger than it is farther off, as at 25° ; therefore, admitting equal
heights and velocities for the wind at the two parallels, it would,
in equal times, bear most air across the one of larger circum-
ference. Much less, therefore, can the air which crosses the
parallel of 25° S. annually in the 124 trade-wind days of that
latitude be sufficient to supply the trade-winds with air for their
329 days in lat. 5°. Whence comes the extra supply for them
in 5° ? (3.) Of all parts of the ocean the tr^de- winds obtain
their best development between 5° and 10° S. in the Atlantic
Ocean, for it is there only that they attain the unequalled annual
average duration of 329 days. But referring now to the average
annual duration of the south-east trade-wind in all seas, we may,
for the sake of illustration, liken this belt of winds which en-
circles the earth, say between the parallels of 5° and 25° S., to
the frustum of a hollow cone, with its base towards the equator.
219. Winds with northing and winds with southing in them con-
trasted.— Now, dividing the winds into only two classes, as winds
with northing and winds with southing in them, actual observa-
tions show, taking the world around, that winds having southing
in . them blow into the southern or smaller end of this cone for
209 days annually, and out of the northern and larger end for
286 days.* They appear (§ 221) to come out of the larger end
with greater velocity than they enter the smaller end. But we
assume the velocity at going in and at coming out to be the
same, merely for illustration. During the rest of the year, either
winds with norihing in them are blowing in at the big end, or out
at the little end of the imaginary cone, or no wind is blowing at
all : that is, it is calm. Now, if we suppose, merely for the sake
of assisting farther in the illustration, that these winds with
northing and these winds with southing move equal volumes of air
in equal times, we may subtract the days of the one from the
days of the other, and thus ascertain how much more air comes
out at one end than goes in at the other of our frustum. Winds
with northing in them blow in at the big end for 72 days, and
out at the little end for 146 days annually. Now, if we subtract
the whole number of winds (146) with northing in them that
blow out at the south or small end, from the whole number (209)
with southing in them that blow in, we shall have for the quan-
tity that is to pass through, or go from the parallel of 25° to 6°,

* Nautical Monographs, No. 1, " The Winds of the Sea," Observatory,
Washington, 1859

THE ATMOSPHERE 85

the volume expressed by the transporting power of the south-
, east trade- winds at latitude 25° for 63 days (209-1466-3). In
like manner we obtain, in similar terms, an expression for the
volume which these winds bring out at the large or equatorial
end, and find it to be as much air as the south-east trade-winds
can transport across the parallel of 5° S. in 214 days (28 - 672 =
214). Again :

220. South-east trade-winds stronger near the equatorial limits. —
The south-east trade-winds, as they cross the parallel of 5*' and
come out of this belt, appear to be stronger * than they are when
they enter it. But assuming the velocity at each parallel to be
the same, we have (§ 219) just three limes as much air with
southing in it coming out of this belt on the equatorial side as
with southing in it we find entering (§ 218) on the polar side.
From this it is made plain that if all the air, whether from the
southward and eastward, or from the southward and westward,
which enters the south-east trade-wind belt near its polar borders,
were to come out at its equatorial edge as south-east trade-winds,
there would not be enough air to feed the south-east trade-winds
between these two parallels of 5^ and 10° S : the annual defi-
ciency of air here would be the volume required to supply the
trades for 151 days (214-63 = 151).

221. S;peed of vessels through the trade-winds. — The average speed
which vessels make in sailing through the trade- winds in diff"erent
parts of the world has been laboriously investigated at the
National Observatory. t By this it appears that their average
speed through the south-east trade-winds of the Atlantic is,
between the parallels of 5° and 10°, 6.1 knots an hour, and 5.7
between 25° and 30°.

222. The question, Whence are the soutJi-east trade-winds supplied
with air? answered. — All these facts being weighed, they indi-
cate that the volume of air which investigations show that the
south-east trade-winds of the world annually waft across the
parallels of 10°-5° S. in 285 J days — for that is their average
duration for all oceans taken together — is at least twice as great

* The force of the trade-winds, as determined by the average speed of 2235
vessels saihng through them, is greater between 5^ and 10° S. than it is between
25'° and 30° S. — Maury's Sailing Directions, 1859.

t See " Average Force of the Trade-winds," p. 857, vol. ii., 8th ed., IMaiiry
Sailing Directions, 1859.

+ Nautical Monographs, Plate I., No. 1, " The Winds at Sea."

86 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOLOGY.

as the volume whicli tliey annually sweep across the parallel of
25° in 139 days, which is their like average here. Hence in
answer to the question (§ 218), " Whence comes the excess?"
the reply is, it can only come from above, and in this way, viz. :
the south-east trade- winds, as they rush from 26° S. towards the
equator, act upon the upper air like an under- tow. Crossing, as
they approach the equator, parallels of larger and larger circum-
ference, these winds draw down and turn back from the counter
current above air enough to supply pabulum to larger and larger,
and to stronger and stronger currents of surface-wind.

223. Whither it goes. — The air which the trade- winds pour into
the equatorial calm belt (§ 213) rises up, and has to flow off as an
upper current, to make room for that which the trade-winds are
continually pouring in below. They bring it from towards the
poles — back, therefore, towards the poles the upper currents must
carry it. On their journey they cross parallel after parallel, each
smaller than the other in circumference. There is, therefore, a
constant tendency with the air that these upper currents carry
polarward to be crowded out, so to speak — to slough off and turn
back. Thus the upper current is ever ready to supply the trade-
winds, as they approach the equator, with air exactly at the right
place, and in quantities just sufficient to satisfy the demand.

224. How is it drawn down from ahovef — This upper air, having
supplied the equatorial cloud-ring (§ 514) with vapour for its
clouds, and with moisture for its rains, flows off polarward as
comparatively dry air. The dryest air is the heaviest. This dry
and heavy air is therefore the air most likely to be turned back
with the trade-winds, imparting to them that elasticity, freshness,
and vigour for which they are so famous, and which help to make
them so grateful to man and beast in tropical climates. The curved
arrows, / g and /' g', r s and r' s', are intended to represent, in the
'' diagram of the winds " (Plate I.), this sloughing off and turning
back of air from the upper currents to the trade-winds below.

225. Velocity of south-east shown to he greater than north-east
trade-winds. — According to investigations which are stated at
length in Maury's Sailing Directions, on his Wind and Current
Charts, and in the Monographs of the Washington Observatory,
the average strength and annual duration of the south-east trade-
wiuds of the Atlantic may be thus stated for every band or belt of
5° of latitude in breadth, from 30° to the equator. For the band
between the parallels of —

THE ATMOSPHEEE. 87

Ann. duration. Force. No. of obs.

80^ and 25° S. . . . - . 124 days. 5.6 miles.* 19,81?

25^and203 157 „ 5.7 „ 20,762

20^ and 15^ 244 „ 5.9 „ 17,844

15° and 10^ 295 „ 6.3 „ 14,422 «

lO^and 5^ 329 „ 6*1 „ 13.714

5^ and 0^ 314 „ 6.0 „ 15,463

It thus apioears that the south-east trade-winds of the Atlantic
blow with most regularity between 10° and 5°, and with most
force between 10° and 15°.

226. Tlie air sloughed off from the counter trades, moist air. — On
the polar side of 35°-40°, and in the counter trades (§ 204 [7]), a
different process of sloughing off and turning back is going on.
Here the winds are blowing towards the poles; they are going
from parallels of large to parallels of smaller circumference, while
the upper return current is doing the reverse ; it is widening out
with the increasing circumference of parallels, and creating room
for more air, while the narrowing current below is crowding out
and sloughing off air for its winds.

227. The air sloughed off from the ujpper trade current dry. — In
the other case (§ 224), it was the heavy dry air that was sloughed
off to join the winds below. In this case it is the moist and
lightest air that is crowded out to join the current above.

228. TJie meteorological influences of ascending columns of moist
air. — This is particularly the case in the southern hemisphere,
where, entirely around the globe between the parallels of 40°
and 60° or 65°, all, or nearly all, is water. In this great austral
band the winds are in contact with an evaporating surface all the
time. Aqueous vapour is very much lighter than atmospheric
air : as this vapour rises, it becomes entangled with the particles
of air, some of which it carries up with it, thus producing,
through the horizontal flow of air with the winds, numerous little
ascending columns. As these columns of air and vapour go up,
the superincumbent pressure decreases, the air expands and cools,
causing precipitation or condensation, of the vapour. The heat
that is set free during this process expands the air still further,
thus causing here and there in those regions, and wherever it
may chance to be raining, intumescences, so to speak, from the
wind stratum below; the upper current, sweeping over these
protuberances, bears them off in its course towards the equator

* Distance per hour that vessels average while sailing through it.

88 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

and thus we have another burning back, and a constant mingling.
The curved arrows, h j h and /i' / ^', are intended, on the
"diagram of the winds" (Plate I.), to represent this rising up
from the counter trades and turning back with the upper
current.

229. Sujpposing the air visible, the spectacle that would he presented
between the upper and lower currents. — Let us imagine the air to be
visible, that we could see these different strata of winds, and the
air as it is sloughed off from one stratum to join the other. We
can only liken the spectacle that would be presented between
the upper and the lower stratum of these winds to the combing
of a succession of long waves as they come rolling in from the
sea, and breaking one after another, upon the beach. They curl
over and are caught up, leaving foam from their white caps
behind, but nevertheless stirring up the sea and mixing up its
waters so as to keep them all alike.

230. The importance of atmospherical circulation. — If the ordi-
nances of nature require a constant circulation and continual
mixing up of the water in the sea, that it become not stagnant,
and that it may be kept in a wholesome state for its inhabitants,
and subserve properly the various offices required of it in the
terrestrial economy, how much more imperative must they not. be
with the air ? It is more liable to corruption than water ; stag-
nation is ruinous to it. It is both the sewer and the laboratory
for the whole animal and vegetable kingdoms. Ceaseless motion
has been given to it ; perpetual circulation and intermingling of
its ingTedients are required of it. Personal experience teaches
us this, as is manifest in the recognized necessity of ventilation
in our buildings — the wholesome influences of fresh air, and the
noxious qualities of " an atmosphere that has no circrdation."
Hence, continual mixing up of particles in the atmosphere being
required of the winds in their circuits, is it possible for the
human mind to conceive of the appointment of " circuits " for
them (§ 216) which are so admirably designed and exqui-
sitel}'- adapted to the purpose as are those which this view
suggests ?

231. Its vertical movements — how produced. — As a physical ne-
cessity, the vertical circulation of the air seems to be no less
important than its horizontal movements, which we call wind.
One begets the other. The wind, when it blows across parallels
of latitude — as it always must, except at the equator, for it blows

THE ATMOSPHERE. 89

m arcs of great circles, and not in small ones* — creates a vertical
circulation either by dragging down air from the upper regions
(§ 224), or by sloughing it off and forcing it up from the lower
(§ 228), according as the wind is approaching the pole or equator.

232. Vertical and horizontal movements in the air consequents of,
and dependent upon each other. — Indeed the point may be well
made whether the horizontal circulation of the air be not de-
pendent upon and a consequent of its vertical circulation ; — so
nearly allied are the two motions in their relations as cause and
eifect. Upward and downward movements in fluids are conse-
quent upon each other, and they involve lateral movements.
The sea, with its vapour, is the great engine which gives upward
motion in the air. As soon as aqueous vapour is formed it rises ;
the air resists its ascent ; but it is lighter than the air, therefore
(§ 177) it forces the resisting particles of air up along with it,
and so produces ascending columns in the atmosphere. The
juxta air comes in to occupy the space which that carried up by
the vapour leaves behind it, and so there is a wind produced.
The wind arising from this source alone is so slight generally, as
scarcely to be perceived. But when the ascending vapour is
condensed, and its latent heat liberated and set free in the upper
air, we often have the most terrific storms.

233. Cold belts. — Now suppose the surface from which this
vapour rises, or on which it is condensed, be sufficiently large to
produce a rush of wind from afar ; suppose it, moreover, to be an
oblong lying east and west somewhere, for example, in the tempe-
rate zone of the northern hemisphere. The wind that comes rush-
ing in from the south side will be in the category of the counter
trades of the southern hemisphere (§ 228), viz. : going from
larger to smaller parallels, and giving rise to ascending columns;

* The tendency of all bodies, when put in motion on the surface of the earth,
is, -whether fluid, solid, or gaseous, to go from the point of departure to the point
of destination by the shortest line possible ; and this, when the motion is hori-
zontal, is an are of a great circle. If we imagine a partial vacuum to be formed
at the north pole, we can readily enough perceive that the wind for 5°, 10°, 20^
of polar distance, all around, would tend to rush north, and strive to get there
along the meridians— arcs of great circles. This would be the case whether the
earth be supposed to be with or without diurnal rotation, or motion of any sort.
Now suppose the place of refraction to be anywhere away from the poles, then
draw great circles to a point in the middle of "'t, and the air all around would,
in rushing into the vacuum, seek to reach it by these great circles. Force maj
turn it aside, but such is the tendency (§ 120).

90 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

while that from the northern side, m-oving in the opposite
direction, is, like the trade-winds (§ 223), bringing down air
from above.

234. Tlie upper currents — tlieir numhers and offices. — By the
motion of the clouds upper currents of wind are discerned in
the sky. They are arranged in layers or strata one above the
other. The clouds of each stratum are carried by its winds in a
direction and with a velocity peculiar to their stratum. How
many of these superimposed currents of wind there may be
between the top and bottom of the atmosphere we know not. As
high up as the cloud-region several are often seen at the same
time. They are pinions and ratchets in the atmospherical ma-
chinery. We have seen (§ 230) some of their uses : let us
examine them more in detail. Now, as the tendency of air in
motion is (§ 120) to move in arcs of great circles, and as all great
circles that can be drawn about the earth must cross each other
in two points, it is evident that the particles of the atmosphere
which are borne along as wind must have their paths all in
diverging or converging lines, and that consequently each wind
must either be, like the trade-winds (§ 222), drawing down and
sucking in air from above, or, like the counter trades (§ 226),
crowding out and forcing it off into the upper currents.

235. Tendency of air when put in motion to move in the plane of a
great circle. — This tendency to move in great circles is checked
by the forces of diurnal rotation, or by the pressure of the wind
when it blows towards a common centre, as in a cyclone. In no
case is it entirely overcome in its tendency, bat in all it is
diverted from the great circle path and forced to take up its line
of march either in spirals about a point on the surface of the
earth, or in loxodromics about its axis. In either case the
pushing up or pulling down of the combing, curdling air from
layer to layer is going on.

236. The results upon its circulation of this tendency. — Thus the
laws of motion, the force of gravity, and the figure of the earth
all unite in requiring every wind that blows either to force air
up from the surface into the regions above, or to draw it down
to the earth from the crystal vaults of the upper sky. Add to
these the storm-king : — traversing the air, he thrusts in the
whirlwind or sends forth the cyclone, the tornado, and the hurri-
cane to stir up and agitate, to mix and mingle the whole in one
homogeneous mass. By this perpetual stirring up, this continual

THE ATMOSPHERE. 91

agitation, motion, mixing, and circniation, the airy covering ol
the globe is kept in that state which the well-being of the
organic world requires. Every breath we draw, every fire we
kindle, ever}^ blade of grass that grows or decays, every blaze
that shines and burns adds something that is noxious, or takes
something that is healthful away from the surrounding air.
Diligent, therefore, in their offices must the agents be which
have been appointed to maintain the chemical status of the
atmosphere, to preserve its proportions, to adjust its ingredients,
and to keep them in that state of admixture best calculated to fit
it for its purposes.

237. Experiments hy the French Academy. — Several years ago
the French Academy sent out bottles and caused specimens of air
from various parts of the world to be collected and brought home
to be analyzed. The nicest tests which the most skilful chemists
could apply were incapable of detecting any, the slightest, differ-
ence as to ingredients in the specimens from either side of the
equator ; so thorough in the performance of their office are these
agents. Nevertheless, there are a great many more demands on
the atmosphere by the organic world for pabulum in one hemi-
sphere than in the other ; and consequently a great many more
inequalities for these agents to restore in one than in the other.
Of the two, the land of our hemisphere most teems with life, and
here the atmosphere is most taxed. Here the hearthstone of the
human family has been laid. Here, with our fires in winter and
our crops in summer, with our work-shops, steam-engines, and
fiery furnaces going night and day— with the ceaseless and almost
limitless demands which the animal and vegetable kingdoms are
making upon the air overhead, we cannot detect the slightest
difference between atmospherical ingredients in different hemi-
spheres ; and yet, notwithstanding the compensations and adjust-
ments between the two kingdoms of the organic world, there are
almost in every neighbourhood causes at work which would pro-
duce a difference were it not for these ascending and descending
columns of air ; — were it not for the obedient winds, — for this
benign system of circulation, — these little cogs and ratchets
which have been provided for its perfect working. The study of
its mechanism is good and wholesome in its influences, and the
contemplation of it well calculated to excite in the bosom of
right-minded philosophers the deepest and best of emotions.

238. How supplies of fresh air are brought down from the dipper

92 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

sky. — upon the proper adjustments of the dynamical forces which
keep up these ceaseless movements the life of organic nature
depends. If the air that is breathed were not taken away and
renewed, warm-blooded life would cease ; if carbon, and oxygen,
and hydrogen, and water were not in due quantities dispensed by
the restless air to the flora of the earth, all vegetation would
perish for lack of food. That our planet may be liable to no such
calamity, power has been given to the wayward wind, as it
" bloweth where it listeth," to bring down from the pure blue
sky fresh supplies of life-giving air wherever it is wanted, and to
catch up from the earth wherever it may be found, that which
has become stale — ^to force it up, there to be deflagrated among
the clouds, purified and renovated by processes known only to
Him whose ministers they are. The slightest change in the
purity of the atmosphere, though it may be too slight for recog-
nition by chemical analysis in the laboratory, is sure to be
detected by its effects upon the nicer chemistry of the human
system, for it is known to be productive of disease and death.
Xo chemical tests are sensitive enough to tell us what those
changes are, but experience has taught us the necessity of venti-
lation in our buildings, of circulation through our groves. The
cry in cities for fresh air from the mountains or the sea, reminds
us continually of the life-giving virtues of circulation. Experi-
ence teaches that all air when pent up and deprived of circula-
tion becomes impure and poisonous.

239. Beautiful and benign arrangements. — How minute, then,
pervading, and general, benignant, sure, and perfect must be that
system of circulation which invests the atmosphere and makes
*' the whole world kin ^" In the system of vertical circulation
which I have been endeavouring to describe, we see, as in a
figure, the lither sky filled with crystal vessels full of life-giving
air continually ascending and descending between the bottom
and the top of the atmospherical ocean ; these buckets are let
down by invisible hands from above, and, as they are taken up
again, they carry off from the surface, to be purified in the labo-
ratory of the skies, phials of mephitic vapours and noxious gases,
with the dank and deadly air of marshes, ponds, and rivers.

240. Tlieir influences upon the mind. — Whenever, by study and
research, we succeed in gaining an insight, though never so dim,
into any one of the offices for which any particular part of the
physical machinery of our planet was designed by the GiGG.t

THE ATMOSPHERE, 93

Arcliitect, the mind is enriched with the conviction that it has
comprehended a thought that was entertained at the creation.
For this reason the beautiful compensations which philosophers
have discovered in terrestrial arrangements are sources of never-
failing wonder and delight. How often have we been called on
to admire the benign provision by which fresh water is so con-
stituted that it expands from a certain temperature down to
freezing! We recognize in the formation of ice on the top
instead of at the bottom of freezing water, an arrangement which
subserves, in manifold ways, wise and beneficent purposes. So,
too, when we discern in the upper sky (§ 234) currents of wind
arranged in strata one above the other, and running hither and
thither in different directions, may we not say that we can here
recognize also at least one of the fore-ordained offices of these
upper winds ? That by sending down fresh air and taking up
foul, they assist in maintaining the world in that state in which
it was made and for which it is designed — " a habitation fit for
man?"

241. The effect of downward currents in producing cold. — The
phenomena of cold and warm " spells " are often observed in the
United States, and I suppose in other parts of the world also ;
and here in these downward currents we have the explanation
and the cause of sudden and severe local changes in the weather.
These belts often lie east and west rather than north and south,
and we frequently have much colder or hotter weather in them
than we have even several degrees to the north or to the south
of them. The conditions required for one of these cold " snaps "
in America appear to be a north or north-west wind of consider-
able breadth from west to east. As it goes to the south, its ten-
dency is, if it reach high enough, to bring down cold air from
above in the manner of the trade- winds (§ 238) ; and when the
air thus brought down chances to be, as it often is, dry and cold-,
we have the phenomenon of a cold belt, with warmer weather
both to the north and the south of it. While I write the ther-
mometer is — 4° in Mississippi, lat. 82°, and they are having
colder weather there than we have either in Washington or Cin-
cinnati, 7° farther to the north.

242. The winter northers of Texas. — The winter " northers " of
Texas sometimes bring down the cold air there with terrific
effect. These bitter cold winds are very severe at Nueces, in
the coast countrv or the south-west corner of Texa^ bordering

94 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOROLOGY.

the Gulf of Mexico, lat. 27°.5. They are often felt to the west
in Mexico, but rarely in eastern or northern Texas. The fact
that they are not known in northern Texas goes to show that the
cold thoy bring is not translated by the surface winds from the
north.

243. Tlieir severe cold. — A correspondent in Nueces, lat. 27°
36' N., long. 97° 27' W., has described these winds there during
the winter of 1859-60: They prevail from November to March,
and commence with the thermometer at about 80° or 85°. A
calm ensues on the coast ; black clouds roll up from the north ;
the wind is heard several minutes before it is felt ; the thermo-
meter begins to fall ; the cold norther bursts upon the people,
bringing the temperature down to 28°, and son;ietimes even to
25°, before the inhabitants have time to change clothing and
make fires. So severe is the cold, so dry the air, that men and
cattle have been known to perish in them.* These are the
winds which, entering the Gulf and sucking up heat and mois-
ture therefrom, still retain enough of strength to make them-
Belves terrible to mariners — they are the far-famed northers of
Vera Cruz.

244. " Cold Snaps.'' — The temperature of the atmosphere at
the height of three or four miles is variable — observations and
balloonists tell us so. Air may be brought below the normal
temperature due the height at which it may be, by radiation
and other processes. It may also be raised above that normal
temperature by the setting free there of the latent heat of vapour
or by the action of the solar ray upon the cloud stratum. When
this upper air is brought to the surface in this abnormal con-
dition, the people of the district upon which it descends find
themselves in a " cold snap" or "hot term," as the case may be.

245. Anemometers to determine the inclination oftheivind wanted. —
That our climates, especially the continental, are afi'ected by,
and that many of the changes in the weather are due to, the
vertical circulation of the atmosphere, seems clear. f We have

* "Two men," says Mr. M. A. Taylor, in a letter dated January 11th, 1860
at Nueces, Texas, " were actually frozen to death within a few miles of this
place this winter in a norther. Animals seem to tell by instinct when the
norther is coming, and make their way from the open prairies to timber and
other shelter, starting often on a run when the heat is not oppressive. This is
when the change is to be sudden and violent. Many cattle, horses, and sheep
are frozen to death at such times."

+ Vi'h Cbipter XXI.

THE ATMOSPHEBE. 95

other evidence besides tliat of induction (§ 224) as to upward
and downward movements amongst tlie particles of air. In
violent winds especially are these upward and downward cur-
rents made obvious by the feathers, leaves, thistledown, dust,
and trash that are blown about. It would be well if our wind
gauges and vanes therefore were so constructed as to show the
inclination as well as the azimuth of the wind. With such an
improvement we might ascertain whether certain sudden changes
in the weather be not owing quite as much to the inclination as to
the direction of the wind.

246. TJie hot winds of the Andes. — We may seek in the vertical
circulation of the atmosphere for an explanation in part, not only
of hot and cold terms, but in a measure also of seasons of exces-
sive drought, as well as of other phenomena with which all are
familiar. Travellers in crossing the Andes tell of hot winds
encountered there even on the mountain tops. Streaks of hot air
are also frequently encountered in various parts of America, and
I have no doubt in other countries also.

247. Certain " Hot Spells " exjplained. — To explain one of these
sudden and severe " hot spells," let us suppose the neighbouring
atmosphere to be well loaded with moisture at the temperature
of 80° for example, and with the barometer at 30 in. ; that from
some cause this rain-laden air commences to ascend, and its
vapour to be condensed. In this process the heat which was
latent in the vapour becomes sensible in the air. Now the
height to which this air rises may be such, were it dry air, as to
reduce its temperature 80°, and bring it down to zero ; but it is
moist air, and the liberated heat may be sufficient to raise it to
20°, and so prevent the temperature from going below that read*
ing. Thus this air is at least 20° above* the normal tempera-
ture of the height to which it may have risen. Suppose that
now, in the process of vertical circulation, it be brought down to
the surface again, and submitted to the same barometric pressure
as before : its temperature now. will not be 80°, as before, but it
will be 80° + 20°, or 100°. Thus by going up, precipitating
its moisture ; and coming down, it is made hot.

248. Meservoirs in the sky. — Whenever and wherever air in this
condition descends to the surface, there will be a longer or

* Balloonists often in their voyages pass throngli layers of warm and cool air,
made so doubtless by unequal radiation on one hand, or the liberation of the
iateiit heat of vapour on the ofhei'.

96 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

shorter period of excessively warm weather.* Thus we infer
the existence in the upper air of reservoirs for the heat as well
as of chambers for the cold.

249. The warm winds of the Andes caused hy the trade-winds. — The
streaks of warm air on the Andes (§ 246) derive their warmth in
all probability from the liberated heat of the trade-wind vapours
as they are condensed into snow-storms.

250. Dormant powers of the telegraph in meteorology. — Spells of
wet and dry, as well as " terms " of hot and cold, weather some-
times pass over portions of the country like great waves. They
occupy hours, or days, or weeks in their march. The magnetic
teleo-raph would, were the system of combined research out of
which this work has grown so enlarged as to permit us to use it
as a meteorological implement, "f enable us to give warning of all
such changes in the weather in time for farmers and others, as
well as mariners to profit by the foreknowledge. We could
foretell the coming of storms also.

251. The wind in his circuits. — We now see the general course
of the " wind in his circuits," as we see the general course of
the water in a river. There are many abrading surfaces, irregu-
larities, &c:, which produce a thousand eddies in the main
stream ; yet, nevertheless, the general direction of the whole is
not disturbed nor affected by those counter-currents ; so with
the atmosphere and the variable winds which we find here in

* " Heated Wind Stoem. — A heated wind storm passed over a portion of
Kansas on the 7th instant (July 1860), which proved nearly as destructive to
animal life as the recent tornadoes that visited with such terrible effect portions
of Iowa. The wind arose about half-past ten o'clock a.m., and continued until
three o'clock in the afternoon. At one o'clock the mercury rose to 119J°, and
continued so for about an hour, and then began gradually to decrease. Tlie
effect can scarcely be imagined. The wind blew a brisk gale, carrying with it a
salty, sulphurous smell. Two men, in attempting to cross the country from
lola to Humboldt (distance eight mUes), were overtaken and perished. There
were three others at Humboldt who were caught out with teams, which perished,
the men alone sm-viving, and are now in a fair way to recover. There was
scarcely a chicken left in the country. Hogs and cattle fell in their tracks and
suffocated. Various reasons and conjectures as to its cause are given, but all
unsatisfactoiy.' ' — Newspaper.

t Arrangements for so using it have already been made in Holland, France,
and England, and we hope to see them extended ere long to all other countries,
and wherever lines of telegraph may go. Though the plan only went into
operaticc in England in Sept. 1S60, Admiral Fitzroy informs me, it is already
rich with the promise of practical results the most valuable and impoi-tant.
—London, Nov. 14, 1860.

THE ATMOSPHERE. 97

this latitude. Have I not, therefore, very good grounds for the
opinion (§ 200) that the " wind in his circuits," though ap-
parently to us never so v^^ayward, is as obedient to law and as
subservient to order as were the morning stars v^hen first they
' sang together ?"

252. Forces idMcJi propel the wind. — There are at least two forces
concerned in driving the wind through its circuits. We have
seen (§ 207) whence that force is derived which gives easting to
the winds as they approach the equator, and westing as they
approach the poles ; and allusion, without explanation, has been
made (§ 212) to the source whence they derive their northing
and their southing. Philosophers formerly held that the trade-
winds are drawn towards the equator by the influence of the
direct rays of the sun upon the atmosphere there. They heated
it, expanded it, and produced rarefaction, thereby causing a rush
of the wind both from the north and south ; and as the solar rays
played with greatest effect at the equator, there the ascent of the
air and the meeting of the two winds would naturally be. So it
was held, and such was the doctrine.

253. Effect of the direct heat of the sun upon the trade-winds. —
But the direct rays of the sun, instead of being most powerful
upon the air at the equator, are most powerful where Ihe sun is
vertical ; and if the trade-winds were produced by direct heat
alone from the sun, the place of meeting would follow the sun
in declination much more regularly than it does. But, instead
of so following the sun, the usual place of meeting between the
trade-winds is neither at the equator nor where the sun is
vertical. It is at a mean between the parallels of 5° and 10° or
12'^ N. It is in the northern hemisphere, notwithstanding the
fact that in the southern summer, when the sun is on the other
side of the line, the earth is in perihelion, and the amount of
heat received from the vertical ray in a day there is very much
greater (yij-) than it is when she is in aphelion, as in our mid-
summer. For this reason the southern summer is really hotter
than the northern ; yet, notwithstanding this, the south-east
trade- winds actually blow the air away from under this hot
southern sun, and bring it over into the northern hemisphere.
They cross over into the northern hemisphere annually, and blow
between 0°and 5° N. for 193 days,* whereas the north-east trades'
have rarely the force to reach the south side of the equator at all.

* " The Winds of the SSea," Maury's Nautical Monographs, No. 1.

98 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

254. T/ie two systems of trade-winds unequal both in force, dura-
tion, and stability. — By examining tlie log-books of vessels while
sailing through the north-east and south-east trade- wind beltb,
and comparing their rate of sailing, it has been ascertained that
ships sail faster with the sonth-east than they do with the north-
east trade-winds, and that the south-east blow more days during
the year than do the north-east trades.* The logs of vessels that
spent no less than 166,000 days in sailing through these two
belts of wind show that the average sailing speed through the
south-east trade-wind belt, which lies between the equator and
30° S., is about eight miles an hour, and the average number of
uninterrupted south-east trade-wind days in the year is 227.
For the north-east it is 183 days, with strength enough to give
ships an average speed of only 5.6 miles an hour. Hence it
appears that the two systems of trade-winds are very unequal
both as to force and stability, the south-east surpassing in each
ease.

255. Effects of heat and vapour. — Moreover, the hottest place
within the trade-wind regions is not at the equator : it is where
these two winds meet (§ 253). Lieutenant Warley has collated
from the abstract logs the observations on the temperature of
the air made by 100 vessels, indiscriminately taken, during their
passage across the trade-wind and equatorial calm belts of the
Atlantic. The observations were noted at each edge of the
calm belt, in the middle of it, and 5° from each edge in the trade-
winds, with the following averages : In the north-east trades, 5°
north of the north edge of the equatorial calm belt, say in lati-
tude 14° N., air 78°.69. North edge calm belt, say 9° N., air
80°.90. Middle of calm belt, say 4i° N., air 82°. South edge»
say 0°, air 82°.30 ; and 5° S. (in south-east trades), air 81°.14.
These thermometers had not all been compared with standards,
but their differences are probably correct, notwithstanding the
means themselves may not be so. Hence we infer the south
edge of the calm belt is 1°.4 warmer than the north. The ex-
treme difference between the annual isotherms that lie between
the parallels of 30° N. and 30° S. — between which the trade-
wind belts are included — does not probably exceed 12°. Ac-
coiding to the experiments of Gaj^'-Lussac and Dalton, the dila-
tation of atmospheric air due to a change of 1 2° in temperature is

* See ]Maury's Wind and Current Charts, vol. ii., 8tb edition, Sailin'^ Direc-
tions

THE ATMOSPHERE 99

2 J per cent. ; that is, a column of atmosphere 100 feet high will,
after its temperature has been raised 12°5 be 102 J feet high.
However, only about one-third of the direct heat of the sun is
absorbed in its passage down through the atmosphere. The other
two-thirds are employed in lifting vapour up from the sea, or in
warming the crust of the earth, thence to be radiated off again,
or to raise the temperature of sea and air by conduction. The
air at the surface of the earth receives most heat directly from
the sun ; as you ascend, it receives less and less, and the con-
sequent temperature becomes more and more uniform ; so that
the height within the tropics to which the direct rays of the sun
ascend is not, as reason suggests, and as the snow-lines of Chim-
borazo and other mountains show, very great or very variable..

256. Hurricanes not due to direct heat of the sun. — Moreover,
daily observations show most conclusively that the" strong winds
and the great winds, the hurricanes and tornadoes, do not arise
from the direct heat of the sun, for they do not come in the
hottest weather or in the clearest skies. On the contrary,
winter is the stormy period in the extra-tropical regions of the
north;* and in the south, rains and gales — not gales and
sunshine "f — accompany each other. The land and sea breezes
express more than double the amount of wind force which the
direct heat of the sun is capable of exerting upon the trade-
winds. I say more than double, because in the land and sea
breezes the wind-producing power acts alternately on the land
and on the sea — in opposite scales of the balance ; whereas in
the trade-winds it acts all the time in one scale — in the sea
scale ; and the thermal impression which the solar ray makes
through the land upon the air is much greater than that which
it makes by playing upon the water.

257. The influence of other agents required. — From these facts it
is made obvious that other agents besides the direct and reflected
heat of the sun are concerned in producing the trade- winds. Let
us inquire into the natuie of these agents.

258. Where found. — They are to be found in the unequal dis-
tribution of land and sea, and rains, as between the two hemi-
spheres. They derive their power from heat, it is true, but it is
chiefly from the latent heat of vapour which is set free during
the processes of precipitation. The vapour itself, as it rises from

* Gales of the Atlantic, Observatory, Washington, 1856.
t Storm and Eain Charts.

h2

100 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the sea, is (§ 232) no feeble agent * in the production of wind,
nor is it inconsiderable in its influence upon the trade-winds.

259. Vaj)our as one of the causes of the trade-ioinds. — Let us con-
sider this influence. A cubic foot of water, being converted
into Tapour, occupies the space of 1800 cubic feet. | This
vapour is also lighter than the 1800 cubic feet of air which it
displaces. Thus, if the displaced air weigh 1000 ounces, the
vapour will weigh 623 ; consequently, when air is surcharged
with vapour, the atmosphere is bulged out above, and the
barometric pressure is diminished in proportion to the volume
which flows off above in consequence of this bulging out.
Thus, if we imagine the air over the Atlantic Ocean to be all in
a state of rest, and that suddenly during this calm, columns of
vapour were to commence rising from the middle of this ocean,
we can understand how the wind would commence to flow into
this central space from all around. Now, if we imagine no other
disturbing cause to arise, but suppose the evaporation from this
central area to go on with ceaseless activity, we can see that
there would be a system of winds in the Atlantic as steady, but
perhaps not so strong as the trades, yet owing their existence,
nevertheless, merely to the formation of aqueous vapour. ' But
this is not all.

260. Black's law. — "During the conversion of solids into
liquids, or of liquids into vapours, heat is absorbed, which is
again given out on their recondensation." J In the process of
converting one measure of water into vapour, heat enough is
absorbed — i. e., rendered latent, without raising the temperature
of the vapour in the least — to raise the temperature of 1000
such measures of water 1°; when this vapour is condensed
again into water, wherever the place of recondensation may be
this heat is set free again. If it be still further condensed, ay
into hail or snow, the latent heat rendered sensible during the
process of congelation would be sufficient to raise the tempera-
ture of 140 additional measures of water 1°.

261. The latent heat transported in vapour. — In this heat rendered
latent by the processes of evaporation, and transported hither and

* I am sustained in this view by a recent paper on " the forces that produce
the great currents of tlie air, and of the ocean," recently read before the Eoya]
Society by Thomas Hopkins.

t Black and Watt's Experiments on Heat.

X Blacks law. It is aa important one, and should be remembered.

THE ATMOSPHERE. 101

thither by the winds, resides the chief source of the dynamical
power which gives them motion. In some aspects vapour is to
the winds what fuel is to the steam-engine : they carry it to the
equatorial calm belt; there it rises, entangling the air, ana
carrying it up along with it as it goes. As it ascends it expands,
as it expands it grows cool ; and as it does this its vapour is
condensed, the latent heat of which is thus liberated ; this raises
the temperature of the upper air, causing it to be rarefied and to
ascend still higher. This increased rarefaction calls for in-
creased velocity on the part of the inpouring trade-winds below.

262, The effect of the deserts upon the trade-winds. — Thus the
vapours uniting with the direct solar ray would, were there no
counteracting influences, cause the north-east and south-east
trade-winds to rush in with equal force. But there is on the
polar side of the north-east trade-winds an immense area of arid
plains for the heat of the solar ray to beat down upon, also an
area of immense precipitation. These two sources of heat hold
back the north-east trade-winds, as it were, and, when the two
are united, as they are in India, they are sufScient not only to
hold back the north-east trade-wind, but to reverse it, causing
the south-west monsoon to blow for half the year instead of the
north-east trade.

263. Indications of a crossing at the calm belts. — We have, in this
difference as to strength and stability (§ 254) between the north-
east and south-east trade-winds, another link in the chain of
facts tending to show that there is a crossing of the winds at the
calm belts. The greatest amount of evaporation takes place in
the southern hemisphere, which is known by the simple circum-
stance that there is so much more sea-surface there. The
greatest quantity of rain falls in the northern hemisphere, as
both the rain-gauge and the rivers show. So likewise does the
thermometer ; for the vapour which affords this excess of pre-
cipitation brings the heat — ^the dynamical power — from the
southern hemisphere; this vapour transports the heat in the
upper regions from the equatorial cloud-ring to the calms of
Cancer, on the polar side of which it is liberated as the vapoui
is precipitated, thus assisting to make the northern warmer than
the southern hemisphere. In those northern latitudes where thf*
precipitation of vapour and liberation of heat take place, aerial
rarefaction is produced, and the air in the calm belt of Caiicer,
which is about to blow north-east trade, is turned back and

102 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

called in to supply tlie indrauglit towards the north. Thus the
north-east trade-winds being checked, the south-east are called on
to supply the largest portion of the air that is required to feed
the ascending columns in the equatorial calm belt.

264. TJie counter trades — tliey approach the pole in spirals. — On
the north side of the trade-wind belt in the northern, and on the
south side in the southern hemisphere, the prevailing direction
of the winds is not towards the equator, but exactly in the
opposite direction. In the extra-tropical region of each hemi-
sphere the prevailing winds blow from the equator towards the
poles. These are the counter-trades (§ 204). The precipitation
and congelation that go on about the poles produce in the
amount of heat set free, according to Black's law (§ 260), a
rarefaction in the upper regions, and an ascent of air about the
poles similar to that about the equator, with this difference how-
ever : the place of ascent over the equator is a line, or band, or
belt ; about the poles it is a disc. The air rushing in from all
sides gives rise to a wind, which, being operated upon by the
forces of diurnal rotation as it flows north, for example, will
approach the north pole by a series of spirals from the south-
west.

265. Tliey turn with tlie hands of a watch about the south pole,
against them about the north. — If we draw a circle about this pole
on a common terrestrial globe, and intersect it by spirals to
represent the direction of the wind, we shall see that the wind
enters all parts of this circle from the south-west, and that, con-
sequently, there should be about each pole a disc or circular
space of calms, in which the air ceases to move forward as wind,
and ascends as in a calm ; about the Arctic disc, therefore, there
should be a whirl, in which the ascending column of air revolves
from right to left, or against the hands of a watch. At the south
pole the winds come from the north-west (§ 213), and con-
sequently there they revolve about it with the hands of a watch.
That this should be so will be obvious to any one who will look
at the arrows on the polar sides of the calms of Cancer and
Capricorn (Plate I., § 215). These arrows are intended to
represent the prevailing direction of the wind at the surface of
the earth on the polar side of these calms.

266. TJie arrows in the diagram of the winds. — The arrows that
are drawn about the axis of this diagram are intended to repre-
Eont, by their flight, the mean direction of the wind, and by

THE ATMOSPHERE. 103

their length and their feathers the mean annual duration from
each quadrant. Only the arrows nearest to the axis in each belt
of 5° of latitude are drawn with such nicety. The largest airow
indicates that the wind in that belt blows annually, on the
average, for ten months as the arrow flies. The arrow from the
next most prevalent quarter is half-feathered, provided the
average annual duration of the wind represented is not less than
four months. The unfeathered arrows represent winds having an
average duration of less than three months. The arrows are on
the decimal scale ; the longest arrow — which is that representing
the south-east trade-winds between 5° and 10° S., where their
average duration is ten months— being half an inch. Winds that
blow five months are represented by an arrow half this length,
and so on. The half-bearded arrows are on a scale of two for
one. It appears, at first, as a singular coincidence that the wind
should whirl in these discs about the poles as it does in cyclones,
viz., against the hands of a watch in the northern, with them in
the southern hemisphere.

267. TJie offices of sea and air in the ^physical economy. — To act
and react upon each other, to distribute moisture over the surface
of the earth, and to temper the climate of different latitudes, it
would seem, are two of the many offices assigned by their
Creator to the ocean and the air. When the north-east and
south-east trades meet and produce the equatorial calms (§ 212),
the air, by the time it reaches this calm belt, is heavily laden
with moisture, for in each hemisphere it has travelled obliquely
over a large space of the ocean. It has no room for escape but
in the upward direction (§ 223). It expands as it ascends, and
becomes cooler ; a portion of its vapour is thus condensed, and
comes down in the shape of rain. Therefore it is that, under
these calms, we have a region of constant precipitation. Old
sailors tell us of such dead calms of long continuance here, of
such heavy and constant rains, that they have scooped up fresh
water from the sea to drink. The conditions to which this air is
exposed here under the equator are probably not such as to cause
it to precipitate all the moisture that it has taken up in its long
sweep across the waters. Let us see what becomes of the rest ;
for Nature, in her economy, permits nothing to be taken away
from the earth which is not to be restored to it again in some
form, and at some time or other. Consider the great rivers — the
Amaz<m and the Mississippi, for example. AA'e see them day

104 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLQGT.

after day, and year after year, discharging immense volumes of
water into the ocean. " All the rivers i-un into the sea, yet the
sea is not full." — Eccl. i. 7. Where do the waters so discharged
go, and where do they come from? They come from their
sources, is the ready answer. But whence are their sources
supplied ? for, unless what the fountain sends forth be re-
turned to it again, it will fail and be dry. We see simply, in
the waters that are discharged by these rivers, the amount by
which the precipitation exceeds the evaporation throughout the
whole extent of valley drained by them ; and by precipitation I
mean the total amount of water that falls from, or is deposited
by the atmosphere, whether as dew, rain, hail, or snow. The
springs of these rivers (§ 191) are supplied from the rains of
heaven, and these rains are formed of vapours which are taken
up from the sea, that "it be not full," and carried up to the
mountains through the air. "Note the place whence the rivers
come, thitlier they return again." Behold now the waters of the
Amazon, of the Mississippi, the St. Lawrence, and all the great
rivers of America, Europe, and Asia, lifted up by the atmosphere,
and flowing in invisible streams back through the air to their
sources among the hills (§ 191), and that through channels so
regular, certain, and well-defined, that the quantity thus con-
veyed one year with the other is nearly the same : for that is the
quantity which we see running down to the ocean through these
rivers ; and the quantity discharged annually by each river is,
as far as we can judge, nearly a constant.

268. Powerful machinery. — We now begin to conceive what a
powerful machine the atmosphere must be ; and, though it is
apparently so capricious and wayward in its movements, here is
evidence of order and arrangement which we must admit, and
proof which we cannot deny, that it performs this mighty office
with regularity and certainty, and is therefore as obedient a law
as is the steam-engine to the will of its builder. It, too, is an
engine. The South Seas themselves, in all their vast inter-
tropical extent, are the boiler for it, and the northern hemisphere
is its condenser (§ 24). The mechanical power exerted by the
air and the sun in lifting water from the earth, in transporting it
from one place to another, and in letting it down again, is
inconceivably great. The utilitarian who compares the water-
power that the Falls of Niagara would afford if applied to
machinery, is astonished at the number of figures which are

EAINS AND BIVERS. 105

required to express its equivalent in horse-power. Yet what is
the horse-power of the Niagara, falling a few steps, in comparison
with the horse-power that is required to lift up as high as the
clouds and let down again all the water that is discharged into
the sea, not only by this river, but by all the other rivers and all
the rain in the world? The calculation has been made by
engineers, and, according to it, the force for making and lifting
vapour from each area of one acre that is included on the surface
of the earth is equal to the power of 30 horses.

CHAPTER y.

§ 270-303. RAINS AND RIVERS.

270. Bivers considered as rain-gauges — the ten largest. — Eivers
are the rain-gauges of nature. The volume of water annually
discharged by any river into the sea expresses the total
amount by which the precipitation upon the valley drained by
such river exceeds the evaporation from the same valley during
the year. There are but ten rivers that we shall treat as rain-
gauges ; and there are only ten in the world whose valleys
include an area of more than 500,000 square miles. They
are :

Square miles.

The Amazon, including the Tocantines and Orinoco . . 2,048,000

Mississippi 982,000

La Plata 886,000

Yenisei . . . ... . . . . 785,000

Obi 725,000

Lena 594,000

Amoor 583,000

Yang-tse-kiang 548,000

Hoang-ho 537,000

Nile 520,000

These areas are stated in round numbers, and according to the
best authorities. The basin of the Amazon is usually computed
at 1,512,000 square miles; but such computation excludes the
Tocantines, 204,000 square miles, which joins the Amazon near
its mouth, and the Orinoco, with a hydrographic area of 252,000
square miles, which, by means of the Casiquiare, is connected
also with the Amazon. . We think that these three rivers shouM

i*06 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

all be regarded as belonging to one liydrographic basin, for a
canoe may pass inland from any one to either of the others with-
out portage. Of these hydrographic basins, three, including an
area of 3,916,000 square miles, are American; six, which con-
tain an area of 3,772,000 square miles, belong to Asia, one to
Africa, and none to Europe. The three largest rivers of Asia,
the Yenisei, Obi, and Lena (2,104,000 square miles), discharge
their waters into the Arctic Ocean ; their outlets are beyond the
reach of the commercial world ; consequently they do not pos-
sess the interest which, in the minds of men generally, is at-
tached to the rest. The three others of Asia drain 1,668,000
square miles, and run into the Pacific ; while the whole Ameri-
can system feed with their waters and their commerce the
Atlantic Ocean. These rivers, with their springs, give drink to
man and beast, and nourish with their waters plants and rep-
tiles, with fish and fowl not a few. The capacity of their basins
for production and wealth is without limits. These streams are
the great arteries of inland commerce. Were they to dry up,
political communities would be torn asunder, the harmonies of
the earth would be destroyed, and that beautiful adaptation of
physical forces to terrestrial machinery, by which climates are
regulated, would lose its adjustment, and the seasons would run
wild, like a watch without a balance.

271. Heat required to lift vapour for these rivers. — We see these
majestic streams pouring their waters into the sea, and from the
sea we know those waters must come again, else the sea would
be full. We know, also, that the sunbeam and the sea-breeze
suck them up again ; and it is curious to fancy such volumes of
water as this mighty company of ten great rivers is continually
marching down to the sea, taken up by the winds and the sun,
and borne away again through the invisible channels of the air
to the springs among the hills. This operation is perpetually
going on, yet we perceive it not. It is the work of that in-
visible, imponderable, omnipresent, and wonderful agent called
heat. This is the agent which controls both sea and air in their
movements and in many of their offices. The average amount
of heat daily dispensed to our planet from the source of light in
the heaveus is enough to melt a coating of ice completely en-
casing the earth with a film 1 J in. in thickness.* Heat is the
agent that distils for us fresh water from the sea. It pumps up
♦ Deduced from the expeiiments of Pouillet.

EATNS AND MVERS. 107

out of the ocean all the water for our lakes and rivers, and gives
power to the winds to transport it as vapour thence to the moun-
tains. And though this is but a part of the work which in the
terrestrial economy has been assigned to this mighty agent, we
may acquire much profitable knowledge by examining its opera-
tions here in various aspects. To assist in this undertaking I
have appealed to the ten greatest rivers for terms and measures
in which some definite idea may be conveyed as to the magni-
tude of the work and the immense physico-mechanical power of
this imponderable and invisible agent called heat. Calculations
have been made which show that the great American lakes con-
tain 11,000 cubic miles of water. This, according to the best
computation, is twice as much as is contained in all the other
fresh-water lakes, and rivers, and cisterns of the world. The
Mississippi Eiver does not, during a hundred years, discharge
into the sea so large a volume of water as is at this moment
contained in the great northern lakes of this continent ; and yet
this agent, whose works we are about to study, operating through
the winds, has power annually to lift up from the sea and jDour
down upon the earth in grateful showers fresh water enough to
fill the great American lakes at least twenty times over.

272. Main-fall in tlie 3Iississipjoi Valley. — That we may be
enabled the better to appreciate the power and the majesty of
the thermal forces of the sun, and comprehend in detail the mag-
nitude and grandeur of their operations, let us inquire how
much rain falls annually upon the water-sheds of one of these
streams, as of the Mississippi ; how much is carried oif by the
river ; how much is taken up by evaporation ; and how much
heat is evolved in hoisting up and letting down all this water.
In another chapter we shall inquire for the springs in the sea
that feed the clouds with rain for these rivers. If we had a
pool of water one mile square and six inches deep to be evapo-
rated by artificial heat, and if we wished to find out how much
would be required for the purpose, we should learn from Mr.
Joule's experiments that it would require about as much as is
evolved in the combustion of 30,000 tons of coal. Thus we
obtain (§ 271) our unit of measure to help us in the calculation;
for if the number of square miles contained in the Mississippi
Valley, and the number of inches of rain that fall upon it
annually be given, then it will be easy to tell how many of
such huge measures of heat are set free during the annual ope-

108 i>HYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ration of condensing the rain for our hydrographic basin. And
then, if we could tell how many inches of this rain-water are
again taken np by evaporation, we should have the data for de-
termining the number of these monstrous measures of heat that
are employed for that operation also.

273. Its area, and the latent heat liberated during the processes of
condensation there. — The area of the Mississippi Valley is said by-
physical geographers to embrace 982,000 square miles ; and
upon every square mile there is an annual average rain-fall of
40 inches. Now if we multiply 982,000 by the number of times
6 will go into 40, we shall have the number of our units of heat
that are annually set free among the clouds that give rain to the
Mississippi Valley. Thus the imagination is startled, and the
mind overwhelmed with the announcement that the quantity of
heat evolved from the vapours as they are condensed to supply
the Mississippi Valley with water is as much as would be set
free by the combustion of 30,000 tons of coal multiplied 6,540,000
times. Mr. Joule, of Manchester, is our authority for the heat-
ing power of one pound of coal ; the Army Meteorological Ke-
gister, compiled byLorin Blodget, and published by the Surgeon
General's Office at Washington in 1855, is the authority on which
we base our estimate as to the average annual fall of rain ; and
the annals of the National Observatory show, according to the
observations made by Lieutenant Marr at Memphis in Tennes-
see, the annual fall of rain there to be 49 inches, the annual
evaporation 43, and the quantity of water that annually passes
by in the Mississippi to be 93 cubic miles. The water required
to cover to the depth of 40 inches an area of 982,000 square
miles would, if collected together in one place, make a sea one
mile deep, with a superficial area of 620 square miles.

274. Annual discharge of the Mississippi Biver. — It is estimated
that the tributaries which the Mississippi Eiver receives below
Memphis increase the volume of its waters about one-eighth, so
that its annual average discharge into the sea may be estimated
to be about 107 cubic miles, or about one-sixth of all the rain
that falls upon its water-shed. This would leave 513 cubic
miles of water to be evaporated from this river-basin annually.
All the coal that the present mining force of the country could
raise from its coal measures in a thousand years would not,
during its combustion, give out as much heat as is rendered
latent annually in evaporating this water. Utterly insignificant

RAINS AND EIVERS. 109

are the sources of man's meclianical powers when compared
with those employed by nature in moving machinery which
brings the seasons round and preserves the harmonies of creation !

275. Physical adaptations. — The amount of heat required to
reconvert these 513 cubic miles of rain-water into vapour and
bear it away, had accumulated in the Mississippi Valley faster
than the earth could throw it off by radiation. Its continuance
there would have been inconsistent with the terrestrial economy.
From this stand-point we see how the rain-drop is made to pre-
serve the harmonies of nature, and how water from the sea is
made to carry off by re-evaporation from the plains and valleys
of the earth their surplusage of heat, which could not otherwise
be got rid of without first disturbing the terrestrial arrange-
ments, and producing on the land desolation and a desert. Be-
hold now the offices of clouds and vapour — the adaptations of
heat. Clouds and vapour do something more than brew storms,
fetch rain, and send down thunder-bolts. The benignant vapours
cool our climates in summer by rendering latent the excessive
heat of the noonday sun ; and they temper them in winter by ren-
dering sensible and restoring again to the air, that self-same heat.

276. Whence come the rains for the Mississippi. — Whence came,
and by what channels did the}^ come, these cubic miles of water
which the Mississippi Eivor pours annually into the sea ? The
wisest of men has told us they come from the sea. Let us ex
plore the sea for their place and the air for their channel. The
Gulf of Mexico cannot furnish rain for all the Mississippi V^alley.
The Gulf lies within the region of the north-east trades, and
these winds carry its vapours off to the westward, and deliver
them in rain to the hills, and the valleys, and the rivers of
Mexico and Central America. The winds that bring the rains
for the upper Mississippi Valley come not from the south ; they
come from the direction of the Eocky Mountains, the Sierra
Nevada, and the great chain that skirts the Pacific coast. It is,
therefore, needless to search in the Gulf, for the rain that comes
from it upon that valley is by no means sufficient to feed one
half of its springs. Let us next examine the Atlantic Ocean,
and include its slopes also in the investigation.

277. TJie north-east trades of the Atlantic supply rains only for the
rivers of Central and South America. — The north-east trade-wind
region of this ocean extends (§ 210) from the parallel of 30'^ U\
she equator. These winds carry their vapour before them, and,

110 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS 3IETE0E0L0GY.

meeting the soutli-east trade-wind, the two form clouds which
give rain not only to Central America, bnt they drop down, also,
water in abundance for the Atrato, the Magdalena, the Orinoco,
the Amazon, and all the great rivers of intertropical America ;
also for the Senegal, the Niger, and the Congo of Africa. So.
completely is the rain wrung out of these winds for these
American rivers by the Andes, that they become dry and rainless
after passing this barrier, and as such reach the western shores of
the continent, producing there, as in Peru, a rainless region.
The place in the sea whence our rivers come, and whence Europe
is supplied with rains, is clearly not to be found in this part of
the ocean.

278. The calm belt of Cancer furnishes little or no rain. — Between
the parallels of 30" and 35° N. lies the calm belt of Cancer,
a reo'ion where there is no prevailing wind (see Diagram of the
wdnds, Plate I.). It is a belt of light airs and calms — of airs so
bafflino' that they are often insufficient to carry off the "loom,"
or that stratum of air, which, being charged with vapour, covers
calm seas as with a film, as if to prevent farther evaporation.
This belt of the ocean can scarcely be said to furnish any vapoui
to the land, for a rainless country, both in Africa, and Asia, and
America, lies within it.

279. The North Atlantic insufficient to supply rain for so large a
liortion of the earth as one-sixth of all the land. — All Europe is on
the north side of this calm belt. Let us extend our search, then,
to that part of the Atlantic which lies between the parallels of
35° and 60° N., to see if we have water surface enough there to
supply rains for the 8J millions of square miles that are em
braced by the water-sheds under consideration. The area of
this part of the Atlantic is not quite 5 millions of square miles,
and it does not include more than one-thirtieth of the entire sea
surface of our planet, while the water-sheds under consideration
contain one-sixth part of its entire land surface. The natural
pioportion of land and water surface is nearly as 1 to 3.
According to this ratio, the extent of sea surface required to give
rain for these 8^ millions of square miles would be a little over
25, instead of a little less than 5 millions of square miles.

280. Daily rate of evaporation at sea less than on land — observa-
tions wanted. — The state of our knowledge concerning the actual
amount of evaporation that is daily going on at sea has, notwith-
Btandin"- the activity in the fields of physical research, been bul

RAINS AND EIVERS. Ill

little improved. Eecords as to the amount of water daily
evaporated from a piate or disli on shore afford lis no means jf
judging as to what is going on even in the same latitude at sea.
Sea- water is salt, and does not throw off its vapour as freely as
fresh water. Moreover, the wind that blows over the evaporat-
ing dish on shore is often dry and fresh. It comes from the
mountains, or over the plains where it found little or no water
to drink up ; therefore it reaches the observer's dish as thirsty
wind, and drinks up vapour from it gi^eedily. Now had the
same dish been placed on the sea, the air would come to it over
the water, drinking as it comes, and arriving already quite or
nearly saturated with moisture ; consequently, the observations of
the amount of evaporation on shore give no idea of it at sea.

281. Bivers are gauges for the amount of effective evaporation. —
There is no physical question of the day which is more worthy
of attention than the amount of effective evaporation that is daily
going on in the sea. By effective I mean the amount of water
that, in the shape of vapour, is daily transferred from the sea to
the land. The volume discharged by the rivers into the sea
expresses (§ 270) that quantity ; and it may be ascertained with
considerable accuracy by gauging the other great rivers as I
procured the Mississippi to be gauged at Memphis in 1849.

282. Importance of rain and river gauges. — The monsoons
supply rains to feed the rivers of India, as the north-east and
south-east trade-winds of the Atlantic supply rains to feed the
rivers of Central and South America. Now rain-gauges which
will give us the mean annual rain-fall on these water-sheds, .and
river-gauges which would give us the mean annual discharge of
the principal water-courses, would afford data for an excellent
determination as to the amount of evaporation from some parts of
the ocean at least, especially for the trade-wind belts of the
Atlantic and the monsoon region of the Indian Ocean. All the
rain which the monsoons of India deliver to the land the rivers
of India return to the sea. And if, in measuring this for the
whole of India, our gauges should lead us into a probable error,
amounting in v. ume to half the discharge of the Mississippi
Elver, it would not make a difference in the computed rate of the
effective daily evaporation from the North Indian Ocean exceeding
the one two-thousandth part of an inch (0.002 in.).

283. Hypsometry in the North Atlantic peculiar. — That part of
the oxtra-tropical North Atlantic under consideration is peculiar

112 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

as to its hypsometry. It is traversed by large icebergs, which
are more favourable to the recondensation of its vapours than so
many islets would be. AY arm waters are in the middle of it, and
both the east and the west winds, which waft its vapours to the
land, have, before reaching the shores, to cross currents of cool
water, as the in-shore current counter to the Gulf Stream on the
western side, and the cool drift from the north on the east side.
In illustration of this view, and of the influence of the icebergs
and cold currents of the Atlantic upon the hypsometry of that
ocean, it is only necessary to refer to the North Pacific, where
there are no icebergs nor marked contrasts between the tempera-
ture of its currents. Ireland and the Aleutian Islands are
situated between the same parallels. On the Pacific islands
there is an uninterrupted rain-fall during the entire winter. At
other seasons of the year sailors describe the weather, in their
log-books, there as "raining pretty much all the time." This is
far from being the case even on the western coasts of Ireland,
where there is a rain-fall of only 47* inches — probably not more
than a third of what< Oonalaska receives. And simply for this
reason: the winds reach Ireland after they have been robbed
(partially) of the vapours by the cool temperatures of the ice-
bergs and cold currents which lie in their way ; whereas, such
being absent from the North Pacific, they arrive at the islands
there literally reeking with moisture. Oregon in America, and
France on the Bay of Biscay, are between the same parallels of
latitude ; their situation with regard both to wind and sea is the
same, for each has an ocean to windward. Yet their annual
rain-fall is, for Oregon,! 65 inches, for France, 30. None of the
islands which curtain the shores of Europe are visited as abun-
dantly by rains as are those in the same latitudes which curtain
our north-west coast. The American water-shed receives about
twice as much rain as the European. How shall we account for
this difference, except upon the supposition that the winds from
the Pacific carry (§ 171) more rain than the winds from the
Atlantic ? Why should they do this, except for the icebergs and
cool streaks already alluded to ?J

284. Limited cajpacity of winds to take up and transport, for the
rivers of Europe and America, vapour from the North Atlantic. — It
may well be doubted whether the south-westerly winds — which

• Kuitli Johnston. t Army Meteorological Kep:ister, 1855.

X Keith Jol'iiiitoii, " Physical Atlas."

EAINa AND EIVERS. 113

are the prevailing winds in this part of the Atlantic — carry into
the interior of Europe much more moisture than they bring with
them into the Atlantic. They enter it with a mean annual
temperature not far from 60°, and with an average dew-point of
about 55°. They leave it at a mean temperature varying from
60° to 40°, according to the latitude in which they reach the
shore, and consequently with an average dew-point not higher
than the mean temperature. Classifying the winds of this part
of the ocean according to the halves of the horizon as east and
west, the mean of 44,999 observacions in the log-books of the
Observatory shows that, on the average, the west winds blow
annually 230 and the east winds 122 days.

285. The vapour-strings for all these rivers not in the Atlantic
Ocean. — Taking all these facts and circumstances into considera-
tion, and without pretending to determine how much of the
water which the rivers of ximerica and Europe carry into this
part of the ocean comes from it again, we may with confidence
assume that the winds do not get vapour enough from this part
of the ocean to give rain to Europe, to the Mississippi Valley, to
our Atlantic slopes, and the western half of Asiatic Eussia. We
have authority for this conclusion, just as we have authoiity to
say that the evaporation from the Mediterranean is greater in
amount than the volume of water discharged into it again by the
rivers and the rains ; only in this case the reverse takes place,
for the rivers empty more water into the Atlantic than the winds
carry from it. This fact also is confirmed by the hydrometer,
for it shows that the water of .the North Atlantic is, parallel fur
parallel, lighter than water in the Southern Ocean.

286, The places in the sea whence come the rivers of the north,
discovered — proves the crossing at the calm belts. — The inference,
then, from all this is, that the place in the sea (§ 276) whence
come the waters of the Mississippi and other great rivers of the
northern hemisphere is to be found in these southern oceans, and
the channels by which they come are to be searched out aloft, in
the upper currents of the air. Thus we bring evidence and
facts which seem to call for a crossing of air at the calm belts, as
represented by the diagram of the winds, Plate I. It remains
for those who deny that there is any such crossing — who also
deny that extra-tropical rivers of the northern are fed by rains
condensed from vapours taken up in the southern hemisphere —
to show whence come the hundreds of cubic miles of water which

ill PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

these rivers annually pour into the Atlantic and the Arctic
Oceans. In finding the " place " of all this water, it is incum-
bent upon them to show us the winds which bring it also, and to
point out its channels.

287. Spirit i)i lohich tJie search for truth should he conducted. — "In
the greater number of physical investigations some hypothesis
is requisite, in the first instance, to aid the imperfection of our
senses ; and when the phenomena of nature accord with the as-
sumption, we are justified in believing it to be a general law."*

288. TJie number of known facts that are reconciled hy the theory
of a crossing at the calm helts. — In this spirit this hypothesis has
been made. Without any evidence bearing upon the subject, it
would be as philosophical to maintain that there is no crossing
at the calm belts as it would be to hold that there is ; but nature
suo-o-ests in several instances that there must be a crossinsj.
(1.) In the homogeneousness of the atmosphere (§ 237). The
vegetable kingdom takes from it the impurities with which
respiration and combustion are continually loading it ; and in
the winter, when the vegetable energies of the northern hemi-
sphere are asleep, they are in full play in the southern hemi-
sphere. And is it consistent with the spirit of true philosophy
to deny the existence, because we may not comprehend the
nature, of a contrivance in the machinery of the universe which
guides the impure air that proceeds from our chimneys and the
nostrils of all air-breathing creatures in our winter over into the
other hemisphere for re-elaboration, and which conducts across
the calm places and over into this that which has been re-
plenished from the plains and sylvas of the south ? (2.) Most
rain, notwithstanding there is most water in the southern hemi-
sphere, falls in this. How can vapour thence come to us except
the winds bring it, and how can the winds fetch it except
by crossing the calm places ? (3.) The " sea-dust " of the
southern hemisphere, as Ehrenberg calls the red fogs of the
Atlantic, has its locus on the other side of the equator, but it is
found on the wings of the winds in the North Atlantic Ocean.
If this be so, it must cross one or more of the calm belts. f

* Mrs. Somervillo.

t After this had been written, I received horn my colleague, Lieut. Andrau,
an account of the following little tell-tale upon this subject : —

" I found a confirmation of your theory in a piece of vegetable substance
cftught in a small sack (hoisted up above tlie tops) between 22^-25= lat. N., and
38°-30^° long. W. This piece is of the following dimensions :— 14 milium, long.

EAINS AND RIVERS. 115

(4.) Parallel for parallel, the southern hemisphere from the
equator to 40° or 45° S., is tiie cooler. This fact is consistent
with the supposition that the heat that is rendered latent and
abstracted from that hemisphere by its vapours is set free by
their condensation in this. Upon no other hypothesis than by
these supposed crossings can this fact be reconciled, for the
amount of heat annually received from the sun by the two
hemispheres is, as astronomers have shown, precisely the same.*
(5.) Well-conducted observations made with the hydrometer j
(§ 285) for every parallel of latitude in the Atlantic Ocean from
40° S. to 40° N., show that, parallel for parallel, and notwith-
standing the difference of temperature, the specific gravity of
sea-water is greater in the southern than it is in the northern
hemisphere. This difference as to the average condition of the

1 to IJ mm. large, i mm. thick, and weighing 1 J milligrams. Our famous
microscopist and naturalist, Professor P. Halting, at Utrecht, told me, after au
exact inquiry, ' that this vegetable fragment issued from a leaf of the family
Monocotyledon, probably not from a palm-tree, but from a Padanacese or
Scitaminese' — consequently, irom trees belonging to the tropical regions. Now
I am sure it comes from the tropics. I am greatly surprised to perceive that a
piece of leaf of this dimension could run off a distance of more ihan 1200
geographical miles in the upper regions of the atmosphere; for the nearest
coast-hnes of the two continents, America and Africa, lay at the said distance
from the place where this vegetable fragment was caught, by the carefulness of
Capt. S. Stapert, one of the most zealous co-operators. There can be no doubt
that it comes from South America, because the direction of the trade-winds on
the west coast of Africa is too northerly to bring this fragment to the finding-
place in 25° N. and 38° W." — Letter from Lieut. Andrau, of the Dutch Navv,
dated Utrecht, Jan. 2, 1860.

* The amount of solar heat annually impressed upon the two hemispheres is
identically the same ; yet within certain latitudes the southern hemisphere is,
paralled for parallel, the cooler. How does it become so ? If it be the cooler
by radiation, then it must be made so by radiating more heat than it receives ;
such a process would be cumulative in its effects, and were it so, the southern
hemisphere would be gradually growing cooler. There is no evidence that it ia
so gro\\ing, and the inference that it is seems inadmissible. In fact, the
southern hemisphere radiates less heat than the northern, though it receives
as much from the sun. And it radiates more, for this reason : there is more
land in the northern — land is a better radiator than water — therefore the
northern radiates more heat than tlie southern hemisphere ; the southern has
more water and more clouds — clouds prevent radiation — therefore the southern
hemisphere radiates less heat than the northern ; still it is the cooler. How is
this paradox to be reconciled but upon the supposition that tlie southern sur-
plusage is stowed away in vapours, tmnsported thence across the calm belts by
the winds, and liberated by precipitation on our side of the equator ?

t Rodgers, in the Vincennes. Mamy's Sailing Du-ections,8tlied.. vol. i.,p. 235

i2

116 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

sea on different sides of the line is reconciled by the hypothesis
which requires a crossing at the calm belts. The vapour which
conveys fresh water and caloric from the southern hemisphere to
the northern will in part account for this difference both of spe-
cific gravity and temperature, and no other hypothesis wilL
This hydrometric difference indicates the amount of fresh water
which, as vapour in the air, as streams on the land, and as
currents in the sea,* is constantly in transitu between the two
hemispheres. All these facts are inconsistent with the supposi-
tion that there is no crossing at the calm belts, and consistent
with the hypothesis that there is. It is no argument £^'ainst the
hypothesis that assumes a crossing, to urge our ignorance of any
agent with power to conduct the air across the calm belts. It
would be as reasonable to deny the red to the rose or the blush
to the peach, because we do not comprehend the processes by
which the colouring matter is collected and given to the fruit or
flower, instead of the wood or leaves of the plant. To assume
that the direction of the air is, after it enters the calm belts, left
to chance, would be inconsistent with our notions of the attri^
butes 0-^ the great Architect. The planets have their orbits, the
stars their course, and the wind " his circuits." And in the con-
struction of our hypotheses, it is pleasant to build them up on
the premiss that He can and has contrived all the machinery
necessary for guiding every atom of air in the atmosphere
through its channels and according to its circuits, as truly and
as surely as He has contrived it for holding comets to their
courses and binding the stars in their places. These circum-
stances and others favouring this hypothesis as to these air-
crossings, are presented in further detail in Chaps. VII., IX.,
XL, and XII., also §349.

289. Tlie atmosphere to he studied like any other machinery, by its
operations. — In observing the workings and studying the offices of
the various parts of the physical machinery which keeps the
world in order, we should ever remember that it is all made
for its purposes, that it was planned according to design, and
arranged so as to make the world as we behold it : — a place for
the habitation of man. Upon no other hypothesis can tlie
student expect to gain profitable knowledge concerning the
physics of sea, earth, or air. Regarding these elements of the

* The water which the rivers empty into the North A.tlantic has to find its
way south with the ciuTcnts of the sea.

KAINS AND ItrVERS. 117

old pMlosopliers as parts only of the same piece of macliineiy, we
are struck with the fact, and disposed to inquire why is it that
the proportion of land and water in the northern hemisphere is
very different from the proportion that obtains between them in
the southern ? In the northern hemisphere, the land and water
are nearly equally divided. In the southern, there is several
times more water than land. Is there no connection between the
machinery of the two hemispheres ? Are they not adapted to
each other? Or, in studying the physical geography of our
planet, shall we regard the two hemispheres as separated from
each other by an impassable barrier ? Eather let us regard them
as made for each other, as adapted to each other, the one as an
essential to the other, and both as parts of the same machine.
So regarding them, we observe ^at all the great rivers in the
world are in the northern hemisphere, where there is less ocean
to supply them. Whence, then, are their resources replenished ?
Those of the Amazon are, as we have seen (§ 277), supplied
with rain from the equatorial calms and trade- winds of the
Atlantic. That river runs east, its branches come from the
north and south ; it is always the rainy season on one side or
the other of it ; consequently, it is a river without periodic
stages of a very marked character. It is always near its high-
water mark. For one half of the year its northern tributaries
are flooded, and its southern for the other half. It discharges
under the line, and as its tributaries come from both hemispheres,
it cannot be said to belong exclusively to either. It is supplied
with water made of vapour that is taken up from the Atlantic
Ocean. Taking the Amazon, therefore, out of the count, the Rio
de la Plata is the only great river of the southern hemisphere.
There is no large river in New Holland. The South Sea Islands
give rise to none, nor is there one in South Africa entitled to be
called great that we know of.

290. Arguments furnished hy the rivers. — The great rivers of
North America and North Africa, and all the rivers of Europe
and Asia, lie wholly within the northern hemisphere. How is
it, then, considering that the evaporating surface lies mainly in
the southern hemisphere — how is it, I say, that we should have
the evaporation to take place in one hemisphere and the conden-
sation in the other ? The total amount of rain which falls in
the northern hemisphere is much greater, meteorologists tell us,
than that which falls in the southern. The annual amount of

118 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOPvOLOGT.

rain in the north temperate zone is half as much again as that of
the south temperate. How is it, then, that this Taponr gets, as
stated, from the southern into the northern hemisphere, and
comes with such regularity that our rivers never go dry and our
springs fail not ? It is because of these air-crossings — these
beautiful operations, and the exquisite compensation of this grand
machine, the atmosphere. It is exquisitely and wonderfully
counterpoised. Late in the autumn of the north, throughout its
winter, and in early spring, the sun is pouring his rays with the
greatest intensit}^ down upon the seas of the southern hemisphere,
and this wonderful engine which we are contemplating is pump-
ing up the water there (§ 268) with the greatest activity, and
sending it over here for our rivers. The heat which this heavy
evaporation absorbs becomes latent, and, with the moisture, is
carried through the upper regions of the atmosphere until it
reaches our climates. Here the vapour is formed into clouds,
condensed, and precipitated. The heat which held this water in
the state of vapour is set free, it becomes sensible heat, and it is
that [ (4), § 288] which contributes so much to temper our
winter climate. It clouds up in winter, turns warm, and we
say we are going to have fallen weather. That is because the
process of condensation has already commenced, though no rain
or snow may have fallen : thus we feel this southern heat, that
has been collected from the rays of the sun by the sea, been
bottled away by the winds in the clouds of a southern summer,
and set free in the process of condensation in our northern
winter. If Plate I. fairly represent the course of the winds, the
south-east trade-winds would enter the northern hemisphere,
and, as an upper current, bear into it all their moisture, except
that which is precipitated in the region of equatorial calms, and
in the crossing of high mountain ranges, such as the Cordilleras
of South America.

291. More rain in the noriJiern than in the southern hemisphere. —
The South Seas, then (§ 290), should supply mainly the water
for this engine, while the northern hemisphere condenses it ; we
should, therefore, have more rain in the northern hemisphere.
The rivers tell us that we have — the rain-gauge also. The
yearl}^ average of rain in the north temperate zone is, according
to Johnston, thirty-seven inches. He gives but twenty-six in the
sr)uth temperate. The observations of mariners are also cor-
roborative of the same. Log-books, containing altogether the

EAINS AND RIVERS. 11?>

records for upwards of 260,000 days in tlie Atlantic Ocean north
and south (Plate XIII.), have been carefully examined for the
purpose of ascertaining, for comparison, the number of calms,
rains, and gales therein recorded for each hemisphere. Pro-
portionally the number of each as given is decidedly greater
for the north than it is for the south. The result of this ex-
amination is very instructive, for it shoves the status of the atmo-
sphere to be much more unstable in the northern hemisphere,
with its excess of land, than in the southern, witli its excess
of land. Eains, and fogs, and thunder, and calms, and storms,
all occur much more frequently, and are more irregular also as" to
the time and place of their occurrence on the north side, than
they are on the other side of the equator. Moisture is never ex-
tracted from the air by subjecting it from a low to a higher
temperature, but the reverse. Thus all the air which comes
loaded with moisture from the other hemisphere, and is borne
into this with the south-east trade-winds, travels in the upper
regions of the atmosphere (§ 213) until it reaches the calms
of Cancer ; here it becomes the surface wind that prevails from
the southward and westward. As it goes north it grows cooler,
and the process of condensation commences. We may now liken
it to the wet sponge, and the decrease of temperature to the
hand that squeezes that sponge. Finally reaching the cold
latitudes, all the moisture that a dew-point of zero, and even
far below, can extract, is wrung from it ; and this air then com-
mences " to return according to his circuits" as dry atmosphere.
And here we can quote Scripture again : " The north wind
driveth away rain." This is a meterological fact of high au-
thority, and one of great significance toa

292. The trade-winds the evajporatvay wtnas. — By, reasoning in
this manner and from such facts, we are forced to the conclusion
that our rivers are supplied with their waters principally from
the trade-wind regions — the extra-tropical northern rivers from
the southern tirades, and the extra-tropical southern rivers from
the northern trade-winds, for the trade-winds are the evaporating
winds.

293. The saltest jpart of the sea. — Taking for our guide such
faint glimmerings of light as w^e can catch from these facts,
and supposing these views to be correct, then the saltest portion
of the sea should be in the trade-wind regions, where the water
for all the rivers is evaporated; and there the saltest portions

120 PHYSICAL GEOGEAPHY OF THE SEA, AIsD ITS METEOEOLOGY.

are found. There, too, the rains fall less frequently (Plate XIII.).
Dr. Euschenberger, of the Kavj^ on his last voyage to India, was
kind enough to conduct a series of observations on the specific
gravity of sea-water. In about the parallel of 17° north and
south — midmay of the trade-wind regions — he found, the heaviest
water. Though so warm, the water there was heavier than the
cold water to the south of the Cape of Good Hope. Lieutenant
D. D. Porter, in the steam-ship Golden Age, found the heaviest
water about the parallels of 20° north and 17° south. Captain
Eodgers, in the United States ship Vincennes, found the heaviest
water in 1 7° north, and between 20° and 25° south.

294. Seeing that the southern hemisjphere affords the largest eva-
porating surface, how, unless there he a crossing, could we have most
rain and the great rivers in the northern ? — In summing up the
evidence in favour of this view of the general system of atmo-
fc>pherical circulation, it remains to be shown how it is, if the
vie^ be correct, there should be smaller rivers and less rain
in the southjern hemisphere. The winds that are to blow as
polar the north-east trade-winds, returning from the regions,
where the moisture (§ 292) has been compressed out of them,
remain, as we have seen, dry winds until they cross the calm
zone of Cancer, and are felt on the surface as the north-east
trades. About two-thii'ds of them only can then blow over the
ocean ; the revst blow over the land, over Asia, Africa, and North
America, where there is comparatively but a small portion of
evaporating surface exposed to their action. The zone of the
north-east trades extends, on an average, from about 29° north to
7° north. Now, if we examine the globe, to see how much
of this zone is land and how much water, we shall find, com-
mencing with China and coming over Asia, the broad part of
Africa, and so on, across the continent of America to the Pacific,
land enough to fill up, as nearly as may be, just one-third
of it. This land, if thrown into one body between these pa-
rallels, would make a belt equal to 120° of longitude by 22°
of latitude, and comprise an area of about twelve and a half
millions of square miles, thus leaving an evaporating surface
of about twenty-five millions of square miles in the northern
against about seventy-five millions in the southern hemisphere.
According to the hypothesis, illustrated by Plate I., as to the
circulation of the atmosphere, it is these north-east trade-winds
that take up and carry over, after they rise up in the belt

RAINS AND EIVERS. 121

of equatorial calms, the vapours whicli make the lains that feed
the rivers in the extra-tropical regions of the southern hemi-
sphere. Upon this supposition, then, two-thirds only of the
northern trade-winds are full}^ charged with moisture, and only
two-thirds of the amount of rain that falls in the northern hemi-
sphere should fall in the southern ; and this is just about the
proportion (§ 292) that observation gives. In like manner, the
south-east trade-winds take up the vapours which make our
rivers, and as they prevail to a much greater extent at sea, and
have exposed to their action about twice as much ocean as the
north-east trade-winds have, we might expect, according to this
hypothesis, more rains in the northern — and, consequently, more
and larger rivers — than in the southern hemisphere. A glance
at Plate VIII. will show how very much larger that part of
the ocean over which the south-east trades prevail is than that
where the north-east trade-winds blow. This estimate as to
the quantity of rain in the two hemispheres is one which is not
capable of verification by any more than the rudest approxi-
mations ; for the greater extent of south-east trades on one side,
and of high mountains on the other, must each of necessity, and
independent of other agents, have their effects. Nevertheless,
this estimate gives as close an approximation as we can make out
from our data.

295. The Bainy Seasons, hoio caused. — The calm and trade-wind
regions or belts move up and down the earth, annually, in latitude
nearly a thousand miles. In July and August, the zone of equa-
torial calms is found between 7° north and 12° north ; sometimes
higher ; in March and April, between latitude 5° south and 2°
north.* With this fact and these points of view before us,
it is easy to perceive why it is that we have a rainy season
in Oregon, a rainy and dry season in California, another at
Panama, two at Bogota, none in Peru, and one in Chili. In
Oregon it rains every month, but about five times more in the
wdnter than in the summer months. The winter there is the
summer of the southern hemisphere, when this steam-engine
(§ 24) is working with the greatest pressure. The vapour that
is taken up by the south-east trades is borne along over the
region of north-east trades to latitude 35° or 40° north, where
it descends and appears on the surface with the south-west winds^
of those latitudes. Driving upon the highlands of the continent,
* See the Trade- wind Chart,

122 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOPvOLOGY.

this vapour is condensed and precipitated, during this part of tlie
year, almost in constant showers, and to the depth of about
thii'ty inches in three months.

29 G. Tlie rainy seasons of California and Panama. — In the winter
the cahn belt of Cancer approaches the equator. This whole
system of zones, viz., of trades, calms, and westerly winds,
follows the sun; and they of our hemisphere are nearer the
equator in the winter and spring months than at any othei
season. The south-west winds commence at this season to
prevail as far down as the lower part of California. In winter
and spring the land in California is cooler than the sea air, and is
quite cold enough to extract moisture from it. But in summer
and autumn the land is the warmer, and cannot condense the
vapours of water held by the air. So the same cause which
made it rain in Oregon now makes it rain in California. As the
sun returns to the north, he brings the calm belt of Cancer and
the north-east trades along with him ; and now, at places where,
six months before, the south-west winds were the prevailing
winds, the north-east trades are found to blow. This is the case
in the latitude of California. The prevailing winds, then, in-
stead of going from a w^armer to a cooler climate, as before,
are going the opposite way. Consequently, if, under these
circumstances, they have the moisture in them to make rains of,
they cannot precipitate it. Proof, if proof were wanting that
the prevailing winds in the latitude of California are from the
westward, is obvious to all who cross the Rocky Mountains
or ascend the Sierra Madre. In the pass south of the Great
Salt Lake basin those west winds have worn away the hills and
polished the rock by their ceaseless abrasion and the scouring
eftects of the driving sand. Those w^ho have crossed this pass
.are astonished at the force of the wind and the marks there
exhibited of its geological agencies. Panama is in the region of
equatorial calms. This belt of calms travels during the year,
back and forth, over about 17° of latitude, coming farther north
in the summer, where it tarries for several months, and then
returning so as to reach its extreme southern latitude some time
in March or Apiil. AYhere these calms are it is always raining,
and the chart* shows that they hang over the latitude of Panama
from June to November ; consequently, from June to November
is the rainy season at Panama. The rest of the year that place id
* Vide Trade- wind Cliart '^Maury's Wind and Current;.

BAINS AND EIVERS. 123

in the region of the north-east trades, which before they arrive
there have to cross the mountains of the isthmus, on the cool
tops of which they deposit their moistnre, and leave Panama
rainless and pleasant nntil the sun returns north with the belt of
equatorial calms after him. They then push the belt of north-
east trades farther to the north, occupy a part of the winter zone,
and refresh that part of the earth with summer rains. This belt
of calms moves over more than double of its breadth, and nearly
the entire motion from south to north is accomplished generally
in two months, May and June. Take the parallel of 4° north as
an illustration : during these two months the entire belt of calms
crosses this parallel, and then leaves it in the region of the south-
east trades. During these two months it was pouring down rain
on that parallel. After the calm belt passes it the rains cease,
and the people in that latitude have no more wet weather till the
fall, when the belt of calms recrosses this parallel on its way
to the south. By examining the " Trade-wind Chart," it may be
seen what the latitudes are that have two rainy seasons, and that
Bogota is within the bi-rainj^ latitudes.

297. The Bainless Begions. — The coast of Peru is within the
region of perpetual south-east trade-winds. Though the Peru-
vian shores are on the verge of the great South Sea boiler, yet it
never rains there. The reason is plain. The south-east trade-
winds in the Atlantic Ocean first strike the water on the coast of
Africa. TraA^elling to the north-west, they blow obliquely across
the ocean till they reach the coast of Brazil. By this time they
are heavily laden with vapour, which they continue to bear
along across the continent, depositing it as they go, and supply-
ing with it the sources of the Eio de la Plata and the southern
tributaries of the Amazon. Finally they reach the snow-capped
Andes, and here is wrung from them the last particle of moisture
that that very low temperature can extract. Peaching the sum-
mit of that range, they now tumble down as cool and dry winds
on the Pacific slopes beyond. Meeting with no evajDorating
surface, and with no temperature colder than that to which they
were subjected on the mountain-tops, they reach the ocean
before they again become charged with fresh vapour, and be-
fore, therefore, they have any which the Peruvian climate can
extract. The last they had to spare was deposited as snow on
the tops of the Cordilleras, to feed mountain streams under the
heat of the sun, and irrigate the valleys on the western slopes.

124: PHYSICAL GEOGRAl'HY OF THE SEA, AND ITS M3TE0R0L0GT.

Thus we see how the top of the Andes becomes the reservoir
from which are supplied the rivers of Chili and Peru. The
other rainless or almost rainless regions are the western coast of
Mexico, the deserts of Africa, Asia, North America, and Australia.
Now study the geographical features of the country surrounding
those regions ; see how the mountain ranges run ; then turn to
Plate VIII. to see how the winds blow, and where the sources
are (§ 276) which supply them with vapours. This Plate shows
the prevailing direction of the wind only at sea ; but,, knowing
it there, we may infer what it is on the land. Supposing it to
prevail on the land as it generally does in corresponding latitudes
at sea, then the Plate will suggest readily enough how the winds
that blow over these deserts came to be robbed of their moisture,
or, rather, to have so much of it taken from them as to reduce
their dew-point below the Desert temperature ; for ilie air can
never deposit its moisture when its temperature is higher than its dew-
point. We have a rainless region about the Eed Sea, because
the Red Sea, for the most part, lies within the north-east trade-
wind region ; and these winds, when they reach that region, are
dry winds, for they have as yet, in their course, crossed no wide
sheets of water from which they could take up a supply of
vapour. Most of New Holland lies within the south-east trade-
wind region ; so does most of intertropical South America. But
intertropical South America is the land of showers. The largest
rivers and most copiously watered country in the world are to
be found there, whereas almost exactly the reverse is the case in
Australia. Whence this difference ? Examine the direction of
the winds with regard to the shore-line of these two regions,
and the explanation will at once be suggested. In Australia —
east coast — the shore-line is stretched out in the direction of tho
trades; in South America — east coast — it is perpendicular to
their direction. In Australia they fringe this shore only with
their vapour ; thus that thirsty land is so stinted with showers
that the trees cannot afford to spread their leaves out to the sun,
for it evaporates all the moisture from them ; their vegetable
instincts teach them to turn their edges to his rays. In inter-
tropical South America the trade-winds blow perpendicularly
upon the shore, penetrating the very heart of the country with
their moisture. Here the leaves, measuring many feet square —
as the plantain, &c. — turn their broad sides up to the sun, and
court his rays.

BAINS AND mVEBS. 125

298. TJie rainy side of mountains. — WJiy there is more rain on
one side of a mountain than on the other. — We may now, from what
has been said, see why the Andes and all other mountains which
lie athwart the course of the winds have a dry and a rainy side,
and how the prevailing winds of the latitude determine which
is the rainy and which the dry side. Thus, let us take the
southern coast of Chili for illustration. In our summer-time,
when the sun comes north, and drags after him the belts of per-
petual winds and calms, that coast is left within the regions of
the north-west winds — the winds that are counter to the south-
east trades — which, cooled by the winter temperature of the
highlands of Chili, deposit their moisture copiously. During
the rest of the year, 'the most of Chili is in the region of the
south-east trades, and the same causes which operate in Cali-
fornia to prevent rain there, operate in Chili ; only the dry
season in one place is the rainy season of the other. Hence we
see that the weather side of all such mountains as the Andes is
the wet side, and the lee side the dry. The same phenomenon,
from a like cause, is repeated in intertropical India, only in that
country each side of the mountain is made alternately the wet
and the dry side by a change in the prevailing direction of the
wind. Plate YIII. shows India to be in one of the monsoon
regions : it is the most famous of them all. From October to
April the north-east trades prevail. They evaporate from the
Bay of Bengal water enough to feed with rains, during this
season, the western shores of this bay and the Ghauts range of
mountains. This range holds the relation to these winds that
the Andes of Peru (§ 297) hold to the south-east trades ; it first
cools and then relieves them of their moisture, and they tumble
down on the western slopes of the Ghauts, Peruvian-like, cool,
rainless, and dry ; wherefore that narrow strip of country be-
tween the Ghauts and the Arabian Sea would, like that in Peru
between the Andes and the Pacific, remain without rain for
ever, were it not for other agents which are at work about India
and not about Peru. The work of the agents to which I allude
is felt in the monsoons, and these prevail in India and not in
Peru. After the north-east trades have blown out their season,
which in India ends in April, the^ great arid plains of Central
Asia, of Tartary, Thibet, and Mongolia become heated up ; they
rarefy the air of the north-east trades, and cause it to ascend.
This rarefaction and ascent, by their demand for an indraught^

126 PHYSICAL GEOGKAPHT OF THE SEA, AND ITS METEOROLOGY.

are felt by the air wliicli the south-east trade-winds bring to the
equatorial Doldrums of the Indian Ocean : it rushes over into
the northern hemisphere to supply the upward draught from the
heated plains as the south-west monsoons. The forces of diurnal
rotation assist (§ 113) to give these winds their westing. Thus
the south-east trades, in certain parts of the Indian Ocean, are
converted, during the summer and early autumn, into south-
west monsoons. These, then, come from the Indian Ocean and
Sea of Arabia loaded with moisture, and, striking with it per-
pendicularly upon the Ghauts, precipitate upon that narrow
strip of land between this range and the iirabian Sea an amount
of water that is truly astonishing. Here, then, are not only the
conditions for causing more rain, now on the west, now on the
east side of this mountain range, but the conditions also for the
most copious precipitation. Accordingly, when we come to
consult rain gauges, and to ask meteorological observers in
India about the fall of rain, they tell us that on the western
slopes of the Ghauts it sometimes reaches the enormous depth of
twelve or fifteen inches in one day.* Were the Andes stretched
along the eastern instead of the western coast of America, we
should have an amount of precipitation on their eastern slopes
that would be truly astonishing ; for the water which the Ama-
zon and the other majestic streams of South America return to
the ocean would still be precipitated between the sea-shore and
the crest of these mountains. These winds of India then con-
tinue their course to the Himalaya range as high winds. In
crossing this range, they are subjected to a lower temperature
than that to which they were exposed in crossing the Ghauts.
Here they drop more of their moisture in the shape of snow and
rain, and then pass over into the thirsty lands beyond with
scarcely enough vapour in them to make even a cloud. Thence
they ascend into the upper air, there to become counter-currents
in the general system of atmospherical circulation. By studying
Plate YIII., where the rainless regions and inland basins, as
well as the course of the prevailing winds, are shown, these
facts will become obvious.

299. The regions of greatest p-ecipitation — Cherraponjie and

Patagonia. — We shall now be enabled to determine, if the

views which I have been endeavouring to presant be coiTect,

what pai-ts of the earth are subject to the greatest fal]

* Keith JolinBtou.

BAINS AxN'D EIVEliS. 12?

of rain. They should be on the slopes of those motintainp
which the trade-winds or monsoons first strike after hav-
ing blown across an extensive tract of ocean. The more
abrupt the elevation, and the shorter the distance between the
mountain top and the ocean ('§ 298), the greater the amount of
precipitation. If, therefore, we commence at the parallel of
about 30° north in tne Pacific, where the north-east trade-winds
first strike that ocean, and trace them through their circuits till
they first meet high land, we ought to find such a place of heavy
rains. Commencing at this parallel of 30°, therefore, in the
North Pacific, and tracing thence the course of the north-east
trade-winds, we shall find that they blow thence, and reach the
region of equatorial calms near the Caroline Islands. Here they
rise up ; but, instead of pursuing the same course in the upper
stratum of winds through the southern hemisphere, they, in
consequence of the rotation of the earth (§ 207), are made to
take a south-east course. They keep in this upper stratum
until they reach the calms of Capricorn, between the parallels of
30° and 40°, after which they become the prevailing north-west
winds of the southern hemisphere, which correspond to the
south-west of the northern. Continuing on to the south-east,
they a]"e now the surface winds ; they are going from warmer to
cooler latitudes; they become as the wet sponge (§ 292), and are
abruptlj^ intercepted by the Andes of Patagonia, whose cold
summit compresses them, and with its low dew-point squeezes
the water out of them. Captain King found the astonishing fall
of water here of nearly thirteen feet (one hundred and fifty-one
inches) in forty-one days; and Mr. Darwin reports that the
surface water of the sea along this part of the South American
coast is sometimes quite fresh, from the vast quantity of rain
that falls. A similar rain-fall occurs on the sides of Cherra-
ponjie, a mountain in India. Colonel Sykes reports a fall there
during the south-west monsoons of 60 5 i inches. This is at the
rate of 86/ee^ during the year; but King's Patagonia rain-fall is
at the rate of 114 feet during the same period. Cherraponjie is
not so near the coast as the Patagonia range, and the monsoons
lose moisture before they reach it. We ought to expect a corre-
sponding rainy region to be found to the north of Oregon ; but
there the mountains are not so high, the obstruction to the
south-west winds is not so abrupt, the highlands are farther
from the coast, and the air which these winds carry in their

128 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

circulation to that part of the coast, though it be as heavily
charged with moisture as at Patagonia, has a greater extent of
country over which to deposit its rain, and, consequently, the
fall to the square inch will not be as great. In like manner, we
should be enabled to say in what part of the world the most
equable climates are to be found. They are to be found in the
equatorial calms, where the north-east and south-east trades
meet fresh from the ocean, and keep the temperature uniform
under a canopy of perpetual clouds.

300. Amount of evaporation greatest from the Indian Ocean. —
The mean annual fall of rain on the entire surface of
the earth is estimated at about live feet. To evaporate water
enough annually from the ocean to cover the earth, on
the average, five feet deep with rain ; to transport it from one
zone to another; and to precipitate it in the right places,
at suitable times, and in the proportions due, is one of
the offices of the grand atmospherical machine. All this evapo-
ration, however, does not take place from the sea, for the water
that falls on the land is re-evaporated from the land again and
again. But in the first instance it is evaporated principally
from the torrid zone. Supposing it all to be evaporated thence,
we shall have, encircling the earth, a belt of ocean three
thousand miles in breadth, from which this atmosphere hoists up
a layer of water annually sixteen feet in depth. And to hoist
up as high as the clouds, and lower down again all the water in
a lake sixteen feet deep, and three thousand miles broad, and
twenty-four thousand long, is the yearly business of this in-
visible machinery. What a powerful engine is the atmosphere 1
and how nicely adjusted must be all the cogs, and wheels, and
springs, and comjpensaiions of this exquisite piece of machinery'-,
that it never wears out nor breaks down, nor fails to do its work
at the right time and in the right way ! The abstract logs at the
Observatory in Washington show that the water of the Indian
Ocean is warmer than that of any other sea ; therefore it may be
inferred that the evaporation from it is also greater. The North
Indian Ocean contains about 4,500,000 square miles, while its
Asiatic water-shed contains an area of 2,500,000. Supposing all
the rivers of this water-shed to discharge annually into the sea four
times as much water as the Mississippi (§ 274) discharges into the
Gulf, we shall have annually on the average an effective evaporation
(§ 282) from the North Indian Ocean of G.O inches, or 0.0165 per day.

BAINS AND RIVERS.

129

301. Tlie rivers of India, and the measure of the effective evaiiora-
tionfrom that ocean. — The rivers of India are fed by the monsoons,
which have to do their work of distributing their moisture in
about three months. Thus we obtain 0.065 inch as the average
daily rate of effective (§ 282) evaporation from the warm waters
of this ocean. If it were all rained down upon India, it would
give it a drainage which would require rivers having sixteen
times the capacity of the Mississippi to discharge. Neverthe-
less, the evaporation from the Korth Indian Ocean required for
such a flood is only one-sixteenth of an inch daily throughout
the year.* Availing myself of the best lights — dim at best — as
to the total amount of evaporation that annually takes place in
the trade-wind region generally at sea, I estimate that it does not
exceed four feet.

302. Physical adjustments. — We see the light breaking in upon
us, for we now begin to perceive why it is that the proportions
between the land and water were made as we find them in
nature. If there had been more water and less land, we should
have had more rain, and vice versa ; and then climates would
have been different from what they are noAv, and the inhabitants,
neither animal nor vegetable, would not have been as they are.
And as the}^ are, that wise Being who, in his kind providence,
so watches over and regards the things of this world that he
takes note of the sparrow's fall, and numbers the very hairs of
our head, doubtless designed them to be. The mind is delighted,
and the imagination charmed, by contemplating the physical
arrangements of the earth from such points of view as this is
which we now have before us ; from it the sea, and the air, and
the land, appear each as a part of that grand machinery upon
which the well-being of all the inhabitants of earth, sea, and

* In his annual report of the Society (Transactions of the Bomhaij Geogra-
phical Society from May, 1849, to August, 1850, vol. ix.;, the late Dr. Buist,
the secretary, stated, on the authority of Mr. Laidly, the evaporation at Cal-
cutta to be "about fifteen feet annually ; that between the Cape and Calcutta
it averages, in October and November, nearly three-fourtlis of an incli daily ;
between 10° and 20^ in the Bay of Bengal, it was found to exceed an inch
daily. Supposing this to be double the average throughout the year, we
should," continues the doctor, " have eighteen feet of evaporation annually.'
All the heat received by the intertropical seas from the sun annually would
not be sufficient to convert into vapour a layer of water from them sixteen
feet deep. It is these observations as to the rate of evaporation on shore that
liavfe led C§ 280; to such extravagant estimates as to the rate at sea.

K

130 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLeCY.

air depends ; and which, in the beautiful adaptations that we
are endeavouring to point out, affords new and striking evidence
that they all have their origin in one omniscient idea, just
as the different parts of a watch may be considered to have been
constructed and arranged according to one human design. In
some parts of the earth the precipitation is greater than the
evaporation : thus the amount of water borae down by every
liver that runs into the sea (§ 270) toub.j be considered as the
excess of the precipitation over the evaporation that takes place
in the valley drained by that river. In other parts of the earth
the evaporation and precipitation are exactly equal, as in those
inland basins such as that in which the city of Mexico, Lake
Titicaca, the Caspian Sea, etc., etc., are situated, which basins
have no ocean drainage. If more rain fell in the valley of the
Caspian Sea than is evaporated from it, that sea would finally
get full and overflow the M'hole of that great basin. If less fell
than is evaporated from it again, then that sea, in the course of
time, would dry up, and plants and animals there would all
perish for the want of water. In the sheets of water which we
find distributed over that and every other inhabitable inland
basin, we see reservoirs or evaporating surfaces just sufficient
for the supply of that degree of moisture which is best adapted
to the well-being of the plants and animals that people such
basins. In other parts of the earth still, we find places, as the
Desert of Sahara, in which neither evaporation nor precipitation
takes place, and in which we find neither plant nor animal to fit
the land for man's use.

303. Adaptations — their beauties and siiblimity. — In contem-
plating the system of terrestrial adaptations, these researches
teach one to regard the mountain ranges and the great
deserts of the earth as the astronomer does the counterpoises
to > his telescope — though they be mere dead weights, they
are, nevertheless, necessary to make the balance complete, the
adjustment of his machine perfect. These counterpoises give
ease to the motions, stability to the performance, and accuracy
to the workings of the instrument. They are " compensations.'*
Whenever I turn to contemplate the works of nature, I am
struck with the admirable system of compensation, with the
beauty aud nicety with which every department is adjusted,
adapted, and regulated according to the others : things and
))rinciples are meted out in directions apparently the most

BAINS AND EIVEKS. 131

opposite, but in proportions so exactly balanced that results the
most harmonious are produced. It is by the action of opposite
and compensating forces that the earth is kept in its orbit, and
the stars are held suspended in the azure vault of heaven; and
these forces are so exquisitely adjusted, that, at the end of a
thousand years, the earth, the sun, and moon, and every star in
the firmament, is found to come and twinkle in its proper place
at the proper moment. Nay, philosophy teaches us that when
the little snowdrop — w^hich in our garden walks we see raising
its head at " the singing of birds," to remind us that "' the winter
is passed and gone" — was created, the whole mass of the earth,
from pole to pole, and from circumference to centre, must have
been taken into account and weighed, in order that the proper
degree of strength might be given to its tiny fibres. Botanists
tell us that the constitution of this plant is such as to require
that, at a certain stage of its growth, the stalk should bend, and
the flower should bow its head, that an operation may take place
which is necessary in order that the herb should produce seed
after its kind : and that, after this fecundation, its vegetable
health requires that it should lift its head again and stand erect.
Now, if the mass of the earth had been greater or less, the force
of gravity would have been different ; in that case, the strength
of fibre in the snowdrop, as it is, would have been too much or
too little ; the plant could not bow or raise its head at the right
time, fecundation could not take place, and its family would
have become extinct with the first individual that was planted,
because its " seed" would not have been " in itself," and there
fore could not have reproduced itself, and its creation would
have been a failure. Now, if we see such a perfect adaptation,
such exquisite adjustment in the case of one of the smallest
flowers of the field, how much more may we not expect "com
pensation " in the atmosphere and the ocean, upon the right
adjustment and due peiformance of which depends not only the
life of that plant, but the well-being of every individual that is
found in the entire vegetable and animal kingdoms of the w^orld '?
When the east winds blow along the Atlantic coast for a little
while, they bring us air saturated with moisture from the Guli
Stream, and we complain of the sultry, oppressive, heavy atmo-
sphere; the invalid grows worse, and the well man feels ill,
because, when he takes this atmosphere into his lungs, it is
already so charged with moisture that it cannot take up "and

K 2

132 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOEOLGGY,

carry off that which encumbers his lungs, and which nature hati
caused his blood to bring and leave there, that respiration may
take up and carry off. At other times the air is dry and hot ; he
feels that it is conveying off matter from the lungs too fast ; he
realizes the idea that it is consuming him, and he calls the
sensation burning. Therefore, in considering the general laws
which govern the physical agents of the universe, and which
regulate them in the due performance of their offices, I have felt
myself constrained to set out with the assumption that, if the
atmosphere had had a greater or less capacity for moisture, or if
the proportion of land and water had been different — if the
earth, air, and water had not been in exact OQunterpoise — the
whole arrangement of the animal and vegetable kingdoms would
have varied from their present state. But God, for reasons
which man may never know, chose to make those kingdoms
w^hat they are ; for this purpose it was necessary, in his judg-
ment, to establish the proportions between the land and water,
and the desert, just as they are, and to make the capacity of the
air to circulate heat and moisture just what it is, and to haA^e it
^0 do all its work in obedience to law and in subservience to
order. If it were not so, why was power given to the winds to
lift up and transport moisture, and to feed the plants with
nourishment? or why was the property given to the sea by
which its waters may become first vapour, and then fruitful
showers or gentle dews? If the proportions and properties
of land, sea, and air were not adjusted according to the reci-
procal capacities of all to perform the functions required of each,
why should we be told that He " measured the waters in the
hollow of his hand, and comprehended the dust in a measure,
and weighed the mountains in scales, and the hills in a balance ?"
Why did he span the heavens but that he might mete out the
atmosphere in exact proportion to all the rest, and impart to it
those properties and powers which it M^as necessar}^ for it to
have, in order that it might perform all those offices and duties
for which he designed it ? Harmonious in their action, the air
and sea are obedient to law and subject to order in all their
movements ; when we consult them in the performance of their
manifold and marvellous offices, they teach us lessons concern-
ing the wonders of the deep, the mysteries of the sky, the great-
ness, and the wisdom, and goodness of the Creator, which make
1^6 wiser and better men. The investigations into the broad-

RED FOGS AND SEA BREEZES. 133

spreading circle of phenomena connected with the winds of
heaven and the waves of the sea are second to none for the
good which they do and for the lessons which they teach. The
astronomer is said to see the hand of God in the sky ; but
does not the right-minded mariner, who looks aloft as he ponders
over these things, hear his voice in every wave of the sea that
" claps its hands," and feel his presence in every breeze that
blows ?

CHAPTEE YI.

§ 311-382. RED FOGS AND SEA BREEZES.

811. The alternations of land and sea hreezes. — The inhabitants of
the sea-shore in tropical countries wait every morning with
impatience the coming of the sea breeze. It usually sets in
about ten o'clock. Then the sultry heat of the oppressive morn-
ing is dissipated, and there is a delightful freshness in the air
which seems to give new life to all for their daily labours.
About sunset there is again anothe-r calm. The sea breeze is
now done, and in a short time the land breeze sets in. This
alternation of the land and sea breeze — a wind from the sea by
day and from the land by night — is so regular in intertropical
countries, that they are looked for by the people with as much
confidence as the rising and setting of the sun.

312. The sea breeze at Valparaiso. — In extra-tropical countries,
especially those on the polar side of the trade-winds, this pheno-
menon is presented only in summer and fall, when the heat of
the sun is sufficiently intense to produce the requisite degree of
atmospherical rarefaction over the land. This depends in a
measure, also, upon the character of the land upon which the sea
breeze blows ; for when the surface is arid and the soil barren,
the heating power of the sun is ^xerted with most effect. In
such cases the sea breeze amounts to a gale of wind. In the
summer of the southern hemisphere the sea breeze is more power-
fully developed at Valparaiso than at any other place to which
my services afloat have led. me. Here regularly in the after-
noon, at this season, the sea breeze blows furiously ; pebbles
are torn up from the w^alks and whirled about the streets ;
people seek shelter ; the Almendral is deserted, business inter-
rupted, and all communication from the shipping to the shore is

134 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

cut off. Suddenly the winds and the sea, as if they had again
heard the voice of rebuke, are hushed, and there is a great
calm.

313. The contrast. — The lull that follows is delightful. The
sk}^ is without a cloud ; the atmosphere is transparency itself ;
the Andes seem to draw near ; the climate, always mild and soft,
becomes now doubly sweet by the contrast. The evening in-
vites abroad, and the population sally forth — the ladies in ball
costume, for now there is not wind enough to disarrange the
lightest curl. In the southern summer this change takes place
day after day with the utmost regularity, and j^et the calm-
always seems to surprise, and to come before one has time to
realize that the furious sea wind could so soon be hushed. Pre-
sently the stars begin to peep out, timidly at first, as if to see
Avhether the elements here below had ceased their strife, and if
the scene on earth be such as they, from their bright spheres
aloft, may shed their sweet influences upon. Sirius^ or that
blazing world ?; Argus, may be the first watcher to send down a
feeble ray ; then follow another and another, all smiling meekly ;
but presently, in the short twilight of the latitude, the bright
leaders of the starry host blaze forth in all their glory,- and the
sky is decked and spangled with superb brilliants. In the
twinkling of an eye, and faster than the admiring gazer can tell,
the stars seem to leap out from their hiding-places. By invisible
hands, and in quick succession, the constellations are hung out ;
but first of all, and with dazzling glory, in the azure depths of
space appears the Great Southern Cross. That shining symbol
lends a holy grandeur to the scene, making it still more impres-
sive. Alone in the night-watch, after the sea breeze has sunk to
rest, I have stood on the deck under those beautiful skies gazing,
admiring, lapt. I have seen there, above the horizon at once,
and shining with a splendour unknown to these latitudes, every
star of the first magnitude — save only six — that is contained in
the catalogue of the 100 principal fixed stars of astronomers.
There lies the city on the sea-shore wrapped in sleep. The sky
looks solid, like a vault of steel set with diamonds. The stillness
])elow is in haraiony with the silence above, and one almost fears
to speak, lest the harsh sound of the human voice, reverbeiating
through those vaulted " chambers of the south," should wake up
echo, and drown the music that fills the soul. On looking aloft,
the first emotion gives birth to a homeward thought : bright and

BED FOGS AND SEA BEEEZES. 135

lovely as tlie}^ are, those, to northern sons, are not the stars nor
the skies of fatherland. Alpha Lyr^e, with his pure white light,
has o'one from the zenith, and only appears for one short hour
above the top of the northern hills. Polaris and the Great Bear
have ceased to watch from their posts ; they are away down
below the horizon. But, glancing the eye above and around,
you are dazzled with the splendours of the firmament. The
moon and the planets stand out from it; they do not seem to
touch the blue vault in which the stars are set. The Southern
Cross is just about to culminate. Climbing up in the east are
the Centaurs, Spica, Bootes, and Antares, with his lovely little
companion, which only the best telescopes have power to unveil.
These are all bright particular stars, differing from one another
in colour as they do in glory. At the same time, the western
sky is glorious with its brilliants too. Orion is there, just about
to march down into the sea ; but Canopus and Sirius, with
Castor and his twin-brother, and Proc^^on, rj Argus, and Eegulus
— these are high up in their course ; they look down with great
splendour, smiling peacefully as they precede the Southern Cross
on its western way. And yonder, farther still, away to the
south, float the Magellanic clouds, and the " Coal Sacks " — those
mysterious, dark spots in the sky, which seem as though it had
been rent, and these were holes in the " azure robe of night,"
looking out in the starless, empty, black abyss beyond. One
who has never watched the southern sky in the stillness of the
night, after the sea breeze with its turmoil is done, can have no
idea of its grandeur, beauty, and loveliness.

314. Land and sea breezes along the shores of intertropical coun-
tries.— Within the tropics, however, the land and sea breezes are
more gentle, and, though the night scenes there are not so sug-
gestive as those just described, yet they are exceedingly delight-
ful and altogether lovely. I'he oppressive heat of the sun and
the climate of the sea-shore is mitigated and made both refresh-
ing and healthful by the alternation of those winds which in-
variably come from the coolest place — the sea, which is the
cooler by day, and the land, which is the cooler by night.
About ten in the morning the heat of the sun has played upon
the land with sufficient intensity to raise its temperature above
that of the water. A portion of this heat, being imparted to the
superincumbent air, causes it to rise, when the air, first from
the beach, then from the sea, to the distance of several miles,

186 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

begins to flow in with a most delightful and invigorating fresh-
ness.

315. Cause of land and sea breezes. — When a fire is kindled on
the hearth, we may, if we will observe the moats floating in the
room, see that those nearest to the chimney are the first to feel
the draught and to obey it — they are drawn into the blaze. The
circle of inflowing air is gradually enlarged, until it is scarcely
perceived in the remote parts of the room. Xow the land is the
hearth, the rays of the sun the fire, and the sea, with its cool and
calm air, the room ; and thus we have at our firesides the sea
breeze in miniature. When the sun goes down the fire ceases ;
then the dry land commences to give off its surplus heat by radi-
ation, so that by dew-fall it and the air above it are cooled below
the sea temperature. The atmosphere on the land thus becomes
heavier than on the sea, and, consequently, there is a wind sea-
ward which we call the land breeze.

316. Lieut. Jansen on the land and sea hreezes in the Indian Archi-
pelago.— " A long residence in the Indian Archipelago, and, con-
sequently, in that part of the world where the investigations of
the Observatory at Washington have not extended, has given
me," says Jansen,* in his Appendix to the Physical Geography
of the Sea, " the opportunity of studying the phenomena which
there occur in the atmosphere, and to these phenomena my at-
tention was, in the first place, directed. I was involuntarily led
from one research to another, and it is the result of these investi-
gations to which I would modestly give a place at the conclusion
of Maury's Physical Geography of the Sea, with the hope that
these first-fruits of the log-books of the Netherlands may be
speedily followed by more and better. Upon the northern coast
of Java, the phenomenon of daily land and sea breezes is finely

* I have been assisted in my investigations into these phenomena of the sea
by many thinking minds ; among those whose debtor I am stands first and
foremost the clear head and warm heart of a foreign officer, Lieutenant Marin
.Jansen, of the Dutch Navy, whom I am proud to call my friend. He has
served many years in the East Indies, and has enriched my humble contribu-
tions to the " Physical Geography of the Sea " with contributions from the
store-house of liis knowledge, set off and presented in many fine pictures, and
lias appended them to a translation of the first edition of this work in the
Dutch language. He has added a chapter on the lantl and sea breezes ;
another on the changing of the monsoons in the East Indian Archipelago : he
has also extended his remarks to the north-west monsoon, to hurricanes, the
b(juth-east trades of the South Atlantic, and to winds and currents gpuerally.

RED FOGS AND SEA BREEZES. 137

developed. There, as the gorgeous ' eye of day ' rises almost
perpendicularly from the sea with fiery ardour, in a cloudless
sky, it is greeted by the volcanoes Avith a column of white smoke,
which, ascending from the conical summits high in the firina-
ment above, forms a crown, or assumes the shape of an immense
bouquet,*" that they seem to offer to the dawn ; then the joyful
land breeze plays over the flood, which, in the torrid zone, fur-
nishes, with its fresh breath, so much enjoyment to the inhabit-
ants of that sultry belt of the earth, for, by means of it, every-
thing is refreshed and beautified. Then, under the influence of
the glorious accompaniments of the break of day, the silence of
the night is awakened, and we hear commencing everywhere the
morning hymn of mute nature, whose gesticulation is so expres-
sive and sublime. All that lives feels the necessity of pouring
forth, each in its way, and in various tones and accents, from the
depths of inspiration, a song of praise. The air, still filled with
the freshness of the evening dew, bears aloft the enraptured
song, as, mingled with the jubilee tones which the contemplation
of nature everywhere forces from the soul, it gushes forth in
deep earnestness to convey the daily thank-offering over the sea,
over hill and dale.j As the sun ascends the sky, the azure vault
is bathed in dazzling light ; now the land breeze, wearied with
play, goes to rest. Here and there it still plays over the water,
as if it could not sleep ; but finally becoming exhausted, it sinks
to repose in the stillness of the calm. But not so with the atmo-
sphere : it sparkles, and glitters, and twinkles, becoming clear
under the increasing heat, while the gentle swelling of the now
polished waves reflects, like a thousand mirrors, the rays of light
which dance and leap to the tremulous but vertical movements
of the atmosphere. Like pleasant visions of the night, that pass
before the mind in sleep, so do sweet phantoms hover about the
land breeze as it slumbers, upon the sea. The shore seems to
approach and to display all its charms to the mariner in the
of&ng. All objects become distinct and more clearly delineated, J

* Upon the coast of Java I saw daily, during tlie east monsoon, such a column
of smoke ascending at sunrise from Bromo, Lamongan, and Smiro. Probably
there is no wind above. — Jansen.

t In the very fine mist of the morning, a noise — for example, the firing of
cannon — at a short distance is scarcely heard, while at midday, with the sea-
breeze, it penetrates for miles with great distinctness. — Jansen.

X The transparency of the atmosphere is so great that we can somethnea
discover Venus in the sky in the middle of the day. — Jansen,

13(S PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

vvliile, upon the sea, small fisliing-boats loom up like large ves
sels.* The seaman, drifting along the coast, and misled by the
increiising clearness and mirage, believes that he has been driven
oy a current towards the land; he casts the lead, and looks
anxiously out for the sea breeze, in order to escape from what he
believes to be threatening danger. The planks burn under his
feet ; in vain he spreads the awning to shelter himself from the
broiling sun. Its rays are oppressive; repose does not refresh;
motion is not agreeable. The inhabitants of the deep, awakened
by the clear light of day, prepare themselves for labour. Corals,
and thousands of Crustacea, await, perhaps impatiently, the coming
of the sea breeze, which shall cause evaporation to take place
more rapidly, and thus provide them with a bountiful store of
building material for their picturesque and artfully constructed
dwellings : these they know how to paint and to polish in the
depths of the sea more beautifully than can be accomplished by
any human art. Like them, also, the plants of the sea are de-
pendent upon the winds, upon the clouds, and upon the sun-
shine : for upon these depend the vapour and the rains which
feed the streams that bring nourishment for them into the sea.f
When the sun reaches the zenith, and his stern eye, with burn-
ing glare, is turned more and more upon the Java Sea, the air
seems to fall into a magnetic sleep ; yet even as the magnetizer
exercises his will upon his subject, and the latter, with uncertain
and changeable gestures, gradually puts himself in motion, and
sleeping obeys that will, so also we see the slow efforts of the
sea breeze to repress the vertical movements of the air, and to
obey the will which calls it to the land. This vertical move-
ment appears to be not easily overcome by the horizontal which
we call wind. Yonder, far out upon the sea, arises and disap-
pears alternately a darker tint upon the otherwise shining sea-
carpet ; finally that tint remains and approaches ; that is the
long-wished-for sea breeze: and yet it is sometimes one, yes,
even two hours before the darker tint is permanent, before the

* Especially in the rainy season the land looms very gxeatly ,■ then we see
mountains which are from 5000 to 6000 feet high at a distance of 80 or 100
English miles.

t The archipelago of coral islands on the north side of the Straits of Sunda
is remarkable. Before the salt water flowed from the Straits it was deprived of
the solid matter of which the Thousand Islands are constructed. A similar
group of islands is found between the Straits of Macassar and Balie— Janseit.

RED FOGS AND SEA BREEZES. 139

s.ea breeze lias regularly set in. Now small white clourls begin
to rise above the horizon ; to the experienced seaman they are a
prelude to a fresh sea breeze. We welcome the jB.rst breath from
the sea; it is cooling, but it soon ceases ; presently it is suc-
ceeded by other grateful puffs of air, which continue longer;
presently they settle down into the regular sea breeze, with its
cooling and refreshing breath. The sun declines, and the sea
wind — that is, the common trade-wind or monsoon which is
drawn towards the land — is awakened. It blows right earnestly,
as if it would perform its daily task with the greatest possible
ado. The air, itself refreshed upon the deep, becomes gray from
the vapour which envelops the promontories in mist, and cur-
tains the inland with dark clouds. The land is discernible only
by the darker tint which it gives to the mist ; but the distance
cannot be estimated. The sailor thinks himself farther fiom
shore than he really is, and steers on his course carelessly, while
the capricious wind lashes the waters, and makes a short and
broken sea, from the white caps of which light curls are torn,
with sportive hand, to float away like parti-coloured streamers
in the sunbeam. In the meanwhile clouds appear now and them
high in the air, yet it is too misty to see far. The sun ap-
proaches the horizon. Far over the land the clouds continue to
heap up ; already the thunder is heard among the distant hills ;
the thunder-bolts reverberate from hill-side to hill-side, while
through the mist the sheets of lightning are seen.* Finally, the
' king of day ' sinks to rest ; now the mist gradually disappears ;
and as soon as the wind has laid down the lash, the sea, which,
chaiing and fretting, had with curled mane resisted its violence,
begins to go down also. Presently both wind and waves are
hushed, and all again is still. Above the sea, the air is clearer or
slightly clouded; above the land, it is thick, dark, and swollen.
To the feelings, this stillness is pleasant. The sea breeze, the
driving brine, that has made a salt-pan of the face, the short,
restless sea, the dampness — all have grown wearisome, and wel-
come is the calm. There is, however, a somewhat of dimness in
the air, an uncertain but threatening appearance. Presently,
from the dark mass of clouds, which hastens the change of day
into night, the thunder-storm peals forth. The rain falls in tor-

* At Buitenzorg, near Batavia, 40 EBglisb miles from the sliore, five hun-
dred feet above the sea, with high hills around, these thunder-storms occujf
between 4 p.m. and 8 p.m.

140 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

rents in the monntains, and the clouds gradually overspread the
whole sky. But for the wind, which again springs up, it would
be alarming to the sailor, who is helpless in a calm. What
change will take place in the air? The experienced seaman,
who has to work against the trade-wind or against the monsoon,
is off the coast, in order to take advantage of the land breeze (the
destroyer of the trade) so soon as it shall come. He rejoices
when the air is released from the land and the breeze comes, at
first feebly, but afterward growing stronger, as usual during the
whole night. If the land breeze meets with a squall, then it is
brief, and becomes feeble and uncertain. We sometimes find
then the permanent sea breeze close to the coast, which otherwise
remains twenty or more English miles from it. One is not
always certain to get the land breeze at the fixed time. It some-
times suffers itself to be waited for ; sometimes it tarries the
whole night long. During the greatest part of the rainy season,
the land breeze in the Java Sea cannot be depended upon. This
is readily explained according to the theory which ascribes the
origin of the sea and land breezes to the heating of the soil by
day, and the cooling by means of radiation by night ; for, during
the rainy season, the clouds extend over land and sea, interrupt-
ing the sun's TSbjs by day and the radiation of heat by night,
thus preventing the variations of temperature ; and from these
variations, according to this theory, the land and sea breezes
arise. Yet there are other tropical regions where the land and
sea breezes, even in the rainy season, regularly succeed each
other."

317. Sanitary influences of land and sea breezes. — One of the causes
which make the west coast of Africa so very unhealthy when
compared with places in corresponding latitudes on the opposite
side of the Atlantic, as in Brazil, is no doubt owing to the differ-
ence in the land and sea breezes on the two sides. On the coast
of Africa the land breeze is " universally scorching hot."*
There the land breeze is the trade-wind. It has traversed the
continent, sucking up by the way disease and pestilence from
the dank places of the interior. Seeking with miasm, it reaches
the coast. Peru is also within the trade-wind region, and the
winds reach the west coast of South America, as they do the west
coast of Africa, by an overland path ; but, in the former case,
instead of sweeping over dank places, they come cool and fresh

* Jansen,

EED FOGS AND SEA BREEZES. 141

from the pure snows of the Andes. Between this range and the
coast, instead of marshes and a jungle, there is a desert — a rain-
less country, upon which the rays of the sun play with sufficient
force not only to counteract the trade-wind power and j)roduce a
calm, but to turn the scale, and draw the air back from the sea,
and so cause the sea breeze to blow regularly.

318. Influences which regulate their strength. — On the coast of
Africa, on the contrary, a rank -vegetable growth screens the soil
from the scorching rays of the sun, and the rarefaction is not
every day sufficient to do more than counteract the trade- wind
force and produce a calm. The same intensity of ray, however,
playing upon the intertropical vegetation of a lee-shore, is so
much force added to the sea breeze ; and hence, in Brazil, the
sea breeze is fresh, and strong, and healthful ; the land breeze
feeble, and therefore not so sickly. Thus we perceive that
the strength as well as regularity of the land and sea breezes
not only depend upon the to^oography of a place, but also upon
its situation with regard to the prevailing winds ; and also that
a given difference of temperature between land and water, though
it may be sufficient to produce the phenomena of land and sea
breezes at one place, will not be adequate to the same efiect at
another ; and the reason is perfectly philosophical.

319. Land breezes from the ivest coast of Africa scorching hot. — It
is easier to obstruct and turn back the current in a sluggish than
in a rapid stream. So, also, in turning a current of air first
upon the land, then upon the sea — very slight alternations of
temperature would suffice for this on those coasts where calms
would prevail were it not for the land and sea breezes, as, for
instance, in and about the region of equatorial calms ; there the
air is in a state of rest, and will obey the slightest call in any
direction ; not so in regions where the trades blow over the land,
and are strong. It requires, under such circumstances, a con-
siderable degree of rarefaction to check them and produce a
calm, and a still farther rarefaction to turn them back, and convert
them into a regular sea breeze. Hence the scorching land breeze
(§ 317) on the west coast of Africa : the heat there may not have
been intense enough to produce the degree of rarefaction required
to check and turn back the south-east trades. In that part of the
world, their natural course is from the land to the sea, and there-
fore, if this view be correct, the sea breeze should be more feeble
than the land breeze, neither should it last so long.

I.4i; PKfc.CAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGT.

320. Land hreeze in Brazil and Cuba. — But on tlie opposite side
—on the coast of Brazil, as at Pernambuco, for instance — where
the trade-wind comes from the sea, we should have this condition
of things reversed, and the sea breeze will prevail for most of
the time — then it is the land breeze M^hioh is feeble and of short
duration : it is rarely felt. Again, the land and sea breezes in
Cuba, and along the Gulf shores of the United States, will be
more regular in their alternations than they are along the shores
of Brazil or South Africa, and for the simple reason that the
Gulf shores lie nearly parallel with the prevailing direction of
the winds. In Eio de Janeiro, the sea breeze is the regular
trade-wind made fresher by the daily action of the sun on the
land. It is worthy of remark, also, that, for the reason stated
by Jansen, the land and sea breezes in the winter time are
almost unknown in countries of severe cold, though in the
summer the alternation of wind from land to sea, and sea to land,
may be well marked.

321. NigTit scenes ivlien sailing with the land hreeze. — " Happy
he," remarks Jansen, " who, in the Java Sea at evening, seeking
the land breeze off the coast, finds it there, after the salt-bearing,
roaring sea wind, and can, in the magnificent nights of the
tropics, breathe the refreshing land breeze, ofttimes laden with
delicious odours.* The veil of clouds, either after a squall, with
or without rain, or after the coming of the land breeze, is
speedily withdrawn, and leaves the sky clearer during the night,
only now and then flecked with dark clouds floating over from
the land. Without these floating clouds the land breeze is
feeble. When the clouds float away from the sea, the land
breeze does not go far out from the coast, or is wholl}^ replaced
by the sea breeze, or, rather, by the trade-wind. If the land
breeze continues, then the stars loom forth, as if to free them-
selves from the dark vault of the heavens, but their light does
not wholly vanquish its deep blue, which causes the Coal-sacks
to come out more distinctly near the Southern Cross, as it smiles
consolingly upon us, while Scorpio, the emblem of the tropical
climate, stands like a warning in the heavens. The starlight,
which is reflected by the mirrored waters, causes the nights to
vie in clearness with the early twilight in high latitudes.
Numerous shooting stars weary the eye, although they break the
monotony of the sparkling firmament. Their unceasing motion

* lu the Roads of Batavia, however, they are not very agreeable. — Jansen.

RED FOGS AND SExi BREEZES. 143

in the nnfathomaLle ocean affords a great contrast to the seeming
quiet of the gently-flowing, aerial current of the land breeze.
But at times, when, 30° or 40° above the horizon, a fire-ball
arises which suddenly illumines the whole horizon, appearing to
the eye the size of the fist, and fading away as suddenly as it ap-
peared, falling into fiery nodules, then we perceiYe that, in the
apparent calm of nature, various forces are constantly active, in
order to cause, even in the invisible air, such combinations and
combustions, the appearance of which amazes the crews of ships.
When the slender keel glides quickly over the mirrored waters
upon the wings of the wind, it cuts for itself a sparkling way,
and disturbs in their sleep the monsters of the deep, which whirl
and dart quicker than an eight-knot ship ; sweeping and turning
around their disturber, they suddenly clothe the dark surface of
the water in brilliancy. Again, when we go beyond the limits
of the land breeze, and come into the continuous trade-wind, we
occasionally see from the low-moving, round black clouds (unless
it thunders), light blue sparks collected upon the extreme points
of the iron belaying-pins, etc. ;* then the crew appear to fear a
new danger, against which courage is unavailing, and which the
mind can find no power to endure. The fervent, fiery nature
inspires the traveller with deep awe. They who, under the
beating of the storm and terrible violence of the ocean, look
danger courageously in the face, feel, in the presence of these
phenomena, insignificant, feeble, anxious. Then they perceive
the mighty power of the Creator over the works of his creation.
And how can the uncertain, the undetermined sensations arise
which are produced by the clear yet sad light of the moon ? she
who has always great tears in her eyes, while the stars look
sweetly at her, as if they loved to trust her and to share her af-
fliction.j In the latter part of the night the land breeze sinks to
sleep, for it seldom continues to blow with strength, but is
always fickle and capricious. With the break of day it again
awakes, to sport a while, and then giadually dies away as the

* I have seen this in a remarkable degree upon the south coast of Java ;
these sparks were then seen six feet above the deck, upon the frames of timber
(houssen der hlokken), in the implements, etc. — Jansen.

t Some one has ventured the remark that at full moon, near the equator,
more dew falls than at new moon, and to this are ascribed the moonheads
{maan hoofden), which I have seen, however, but once dui'ing all the ycnra
r/hich I have spent between the tropics. — Jansen.

144 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOEOLOGY.

sun rises. The time at wliicli it becomes calm after the land and
sea breezes is indefinite, and the calms are of unequal duration.
Generally, those which precede the sea breeze are rather longer
than those which precede the land breeze. The temperature of
the land, the direction of the coast-line with respect to the pre-
vailing direction of the trade-wind in which the land is situated,
the clearness of the atmosphere, the position of the sun, perhaps
also that of the moon, the surface over which the sea breeze
blows, possibly also the degree of moisture and the electrical
state of the air, the heights of the mountains, their extent, and
their distance from the coast, all have influence thereon. Local
observations in regard to these can afford much light, as well as
determine the distance at which the land breeze blows from the
coast, and beyond which the regular trade-wind or monsoon con-
tinues uninterruptedly to blow. The direction of land and sea
winds must also be determined b}^ local observations, for the
idea is incorrect that they should always blow perpendicularly to
the coast-line. Scarcely has one left the Java Sea — which is, as
it were, an inland sea between Sumatra, Borneo, Java, and the
archipelago of small islands between both of the last named —
than, in the blue waters of the easterly part of the East Indian
Archipelago, nature assumes a bolder aspect, more in harmony
with the great depth of the ocean. The beauty of the Java Sea,
and the delightful phenomena which air and ocean displa}'-, have
here ceased. The scene becomes more earnest. The coasts of
the eastern islands rise boldly out of the water, far in whose
depths they have planted their feet. The south-east wind,
which blows upon the southern coasts of the chain of islands, is
sometimes violent, always strong through the straits which sepa-
rate them from each other, and this appears to be more and more
the case as we go eastward. Here, also, upon the northern coast,
we find land breezes, yet the trade-wind often blows so violently
that they have not sufficient power to force it beyond the coast.
Owing to the obstruction which the chain of islands presents to
the south-east trade-wind, it happens that it blows with violence
away over the mountains, apparently as the land breeze does
upon the north coast;* yet this wind, which onl}^ rises when it
blows hard from the south-east upon the south coast, is easily
distinguished from the gentle land breeze. The regularity of

* Such is the case, among otliers, in the Strait of Madura, upon tlie Leighb:
of Bezockie.

EED FOGS AND SEA BKEEZES. 145

tlie laud and sea breezes in the Java Sea and upon the coasts of
the northern range of islands, Banca, Borneo, Celebes, etc.,
during the east monsoon, must in part be ascribed to the
hindrances which the south-east trade-wind meets in the islands
which lie directly in its way — in part to the inclination towards
the east monsoon which the trade-wind undergoes after it has
come within the archipelago — and, finally, to its abatement as it
approaches the equator. The causes which produce the land
breezes thus appear collectively not sufficiently powerful to be
able to turn back a strong trade-wind in the ocean."

322. Bed fogs in the Mediterranean. — Seamen tell us of " red
fogs " which they sometimes encounter, especially in the vicinity
of the Cape de Verd Islands. In other parts of the sea, also, they
meet showers of dust. What these showers precipitate in the
Mediterranean is called " sirocco dust," and in other parts
"African dust,"* because the winds which accompany them are
supposed to come from the Sirocco desert, or some other j)arched
land of the continent of Africa. It is of a brick-red or cinnamon
colour, and it sometimes comes down in such quantities as to
obscure the sun, darken the horizon, and cover the sails and
rigging with a thick coating of dust, though the vessel may be
hundreds of miles from the land.

323. Bed fogs near the equator. — Dr. Clymer, Fleet-surgeon of
the African squadron, reports a red fog which was encountered
in February, 1856, by the U. S. ship Jamestown. " We were,"
says he, " immersed in the dust-fog six days, entering it abruptly
on the night of the 9th of February, in lat. 7° 30' N., and long.
15° W., and emerging from it (and at the same time from the
zone of the equatorial calms into the north-east trades) on the
15th instant, in lat. 9° N., and long. 19° W. With these winds,
we beat to Porto Praya (in lat. 14" 54' N. and long. 23'^ 30' W.),
crossing a south-west current of nearly a mile an hour, arriving
at Porto Praya on the 22nd of February. The red dust settled
thickly on the sails, rigging, spars, and decks, from which it was
easily collected. It was an impalpable ]Dowder, of a brick-dust
or cinnamon colour. The atmosphere was so dusky that we
could not have seen a ship at mid-day beyond a quarter of a
mile."t

324. Putting tallies on the wind. — Now the patient reader, who

* Prof. Ehrenberg calls it " Sea-dust."

+ See Sailing Directions, 8th ed., vol. ii., p. 877.

L

146 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

has had the heart to follow me in a preceding chapter (IV.)
aroimd T\dth "the wind in his circuits," will perceive that
evidence in detail is yet wanting to establish it as a fact that the
north-east and south-east trades, after meeting and rising up in
the ecjuatorial calms, do cross over and take the paths repre-
sented by E S and F G, Plate I. Statements, and reasons, and
arguments enough have already been made and adduced (§ 288)
to make it highly probable, according to human reasoning, that
such is the case ; and though the theoretical deductions showing
such to be the case be never so plausible, positive proof that
they are true cannot fail to be received with delight and
satisfaction. Were it possible to take a portion of this air,
which should represent, as it travels along with the south-east
trades, the general course of atmospherical circulation, and to
put a tally on it by which we could follow it in its circuits and
always recognize it, then we might hope actually to prove, by
evidence the most positive, the channels through which the air
of the trade-winds, after ascending at the equator, returns
whence it came. But the air is invisible ; and it is not easily
perceived how either marks or tallies may be put on it, that it
may be traced in its paths through the clouds. The sceptic,
therefore, who finds it hard to believe that the general circu-
lation is such as Plate I. represents it to be, might consider him-
self safe in his unbelief, were he to declare his willingness to
give it up the moment any one should put tallies on the wings
of the wind, which would enable him to recognize that air and
those tallies again, when found at other parts of the earth's
surface. As difScult as this seems to be, it has actually been
done. Ehrenberg, with his microscope, has established, almost
beyond a doubt, that the air which the south-east trade-winds
bring to the equator does rise up there and pass over into
tne northern hemisphere. The Sirocco or African dust, which
he has been observing so closely, has turned out to be tallies put
upon the wind in the other hemisphere; and this beautiful
instrument of his enables us to detect the marks on these little
tallies as plainly as though those marks had been written upon
labels of wood and tied to the wings of the wind.

325. Tliey tell of a crossing at the calm belts. — This dust, when
subjected to microscopic examination, is found to consist of
infusoria and organisms whose habitat is not Africa, but South
Ajnorica, and in the south-east trade-wind region of Soutli

RED FOGS AND SEA BREEZES. 147

America. Professor Ehrenberg has examined specimens of sea-
dust from the Cape de Verds and the regions thereabout — from
Malta, Genoa, Lyons, and the Tyrol — and he has found a simi-
larity among them as striking as it would have been, had these
specimens been all taken from the same spot. South American
forms he recognizes in all of them ; indeed, they are the pre-
vailing forms in every specimen he has examined. It may, I
think, be now regarded as an established fact that there is a
perpetual upper current of air from South America to North
Africa ; and that the volume of air which flows to the northward
in these upper currents is nearly equal to the volume which
flows to the southward with the north-east trade-winds, there
can be no doubt. The "rain dust" has been observed most
frequently to fall in spring and autumn; that is, the fall has
occurred after the equinoxes, but at intervals from them varying
from thirty to sixty days, more or less. To account for this sort
of periodical occurrence of the falls of this dust, Ehrenberg
thinks it " necessary to suppose a dust-cloud to he constantly swim-
ming in the atmosphere hy continuous currents of air, and lying in the
region of the trade-winds, hut suffering partial and periodical devia-
tions.'' It has already been shown (§ 295) that the rain or calm
belt between the trades travels up and down the earth from
north to south and back again, making the rainy season wher-
ever it goes. The reason of this will be explained in another
place. This dust is probably taken up in the dry, and not in the
wet season; instead, therefore, of its being "held in clouds
suffering partial and periodical deviations," as Ehrenberg sug-
gests, it more probably comes from one place about the vernal,
and from another about the autumnal equinox ; for places which
have their rainy season at one equinox have their dry season at
the other. At the time of the vernal equinox, the valley of the
Lower Orinoco is then in its dry season — everything is parched
up with the drought; the pools are dry, and the marshes and
plains become arid wastes. All vegetation has ceased ; the great
serpents and reptiles have buried themselves for hibernation;*
the hum of insect life is hushed, and the stillness of death reigns
through the valley. Under these circumstances, the light breeze,
raising dust from the bed of lakes that are dried up, and lifting
motes from the brown savannas, will bear them away like clouds
in the air. This is the period of the year when the surface oi
* HuniboldL

L 2

148 fHTSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGT.

the earth in this region, strewed with impalpable and feather-
light remains of animal and vegetable organisms, is swept over
by whirlwinds, gales, and tornadoes of terrific force : this is the
period for the general atmospheric disturbances which have
made characteristic the equinoxes. Do not these conditions
appear sufficient to afford the " rain dust " for the spring showers "
At the period of the autumnal equinox, another portion of the
Amazonian basin is parched with drought, and liable to winds
that fill the air with dust, and with the remains of dead animal
and vegetable matter : these impalpable organisms, which each
rainy season calls into being, to perish the succeeding season of
drought, are perhaps distended and made even lighter by the
gases of decomposition which has beeD going on in the period of
drought. May not, therefore, the whirlwinds which accompany
the vernal equinox, and sweep over the lifeless plains of the
Lower Orinoco, take up the " rain dust" which descends in the
northern hemisphere in April and May ? and may it not be the
atmospherical disturbances which accompany the autumnal
equinox that take up the microscopic organisms from the Upper
Orinoco and the great Amazonian basin for the showers of
October ?

326. Huwholdfs description of the dust-wMrlwinds of the Orinoco. —
The Baron von Humboldt, in his Aspects of Nature, thus contrasts
the wet and the dry seasons there : " When, under the vertical
rays of the never-clouded sun, the carbonized turfy covering
falls into dust, the indurated soil cracks asunder as if from the
shock of an earthquake. If at such times two opposing currents
of air, whose conflict produces a rotary motion, come in contact
with the soil, the plain assumes a strange and singular aspect.
Like conical- shaped clouds, the points of which descend to the
earth, the sand rises through the rarefied air on the electrically-
charged centre of the whirling current, resembling the loud
water-spout, dreaded by the experienced mariner. The lowering
sky sheds a dim, almost straw-coloured light on the desolate
plain. The horizon draws suddenly nearer, the steppe seems to
contract, and with it the heart of the wanderer. The hot, dusty
particles which fill the air increase its suffocating heat, and the
east wind, blowing over the long-heated soil, brings with it no
refreshment, but rather a still more burning glow. The pools
which the yellow, fading branches of the fan-palm had protected
from evaporation, now gradually disappear. As in the icy north

KED FOGS AND SEA BREEZES. 149

tlie animals become torpid with cold, so here, nnder the influence
of the parching drought, the crocodile and the boa become
motionless and fall asleep, deepl}^ buried in the dry mud. . . .
The distant palm-bush, apparently raised by the influence of the
contact of unequally heated and therefore unequally dense strata
of air, hovers above the ground, from which it is separated by a
narrow intervening margin. Half-concealed by the dense clouds
of dust, restless with the pain of thirst and hunger, the horses
and cattle roam around, the cattle lowing dismally, and the
horses stretching out their long necks and snnffing the wind, if
haply a moist current may betray the neighbourhood of a not
wholly dried-up pool. ... At length, after the long drought,
the welcome season of the rain arrives ; and then how suddenly
is the scene changed ! . . . Hardly has the surface of the earth
received the refreshing moisture, when the previously barren
steppe begins to exhale sweet odours, and to clothe itself with
killingias, and a variety of grasses. The herbaceous mimosas,
with renewed sensibility to the influence of light, unfold their
drooping, slumbering* leaves to greet the rising sun ; and the
early song of birds and the opening blossoms of the water-plants
join to salute the morning."

327. Are the great deserts centres of circulation ? — The arid plains
and deserts, as well as high mountain ranges, have, it may well
be supposed, an influence upon the movements of the great
aerial ocean, ' as shoals and other obstructions have upon the
channels of circulation in the sea. The deserts of Asia, for
instance, produce (§ 299) a disturbance upon the grand system
of atmospherical circulation, which, in summer and autumn, is
felt in Europe, in Liberia, and away out upon the Indian Ocean,
as far as the parallel of the 10th degree. of south latitude. There
is an indraught from all these regions towards these deserts.
These indraughts are known as monsoons at sea; on the land, as
the prevailing winds of the season. Imagine the area within
which this indraught is felt, and let us ask a question or two,
hoping for answers. The air which the indraught brings into
the desert places, and which, being heated, lises up there,
whither does it go ? It rises up in a column a few miles high
and many in circumference, we know, and we can imagine that
it is like a shaft many times thicker than it is tall ; but how ib
it crowned ? Is it crowned like the stem of a mushroom, with
an efflorescence or ebullition of heated air flaring over and

150 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

spreading out in all directions, and then gradually thinning out
as an upper current, extending even unto the verge of the area
whence the indraught is drawn ? If so, does it then descend and
return to the desert plains as an indraught again ? Then these
desert p'laces would constitute centres of circulation for the
monsoon period ; and if they were such centres, whence would
these winds get the vapour for their rains in Europe and Asia?
Or, instead of the mushroom shape, and the flare at the top in
all directions from centre to circumference, does the uprising
column, like one of those submarine fountains which are said to
be in the Gulf Stream off the coast of Florida, bubble up and
join in with the flow of the upper current ? The right answers
and explanations to these questions would add greatly to our
knowledge concerning the general circulation of the atmosphere.
It may be in the power of observation and the microscope, or of
the magnetic telegraph, to give light here. Let us hope.

328. The colour of '^sea-dust." — The colour of the " rain- dust,"
when collected in parcels and sent to Ehrenberg, is " brick-red,"
or " yellow ochre ;" when seen by Humboldt in the air, it was
less deeply shaded, and is described hy Mm as imparting a
"straw colour" to the atmosphere. In the search of spider-
lines for the diaphragm of my telescopes, 1 procured the finest
and best threads from a cocoon of a dirty-red colour ; but the
threads of this cocoon, as seen singly in the diaphragm, were of a
golden colour: there would seem, therefore, no difficulty in
reconciling the difference between the colours of the rain-dust
when viewed in little piles by the microscopist, and when seen
attenuated and floating in the wind by the great traveller.

329. A clew leading into the chamhers of the south. — It stppears,
therefore, that we here have placed in our hands a clew, which,
attenuated and gossamer-like though it at first appears, is never-
theless palpable and strong enough to guide us along through the
" circuits of the wind " even unto "the chambers of the south."
The frequency of the fall of "rain dust " between the parallels
of 17° and 25° north, and in the vicinity of the Cape Verd
Islands, is remarked upon with emphasis by the microscopist.
It is worthy of remark, because, in connection with the investi-
gations at the Observatory, it is significant. The latitudinal
limits of the northeiii edge of the north-east trade-winds are
variable. In the spring they are nearest to the equator, extend-
ing sometimes at this season not farther from the equator thou

RED FOGS AND SEA BREEZES. 151

the parallel of 15° north. The breadth of the calms of Cancer is
also variable ; so also are their limits. The extreme vibration of
this zone is between the parallels of 17° and 38° north, according
to the season of the year.

330. Bed fogs do not alwmjs occur at the same place, hut tliey occur
on a north-east and south-west range. — According to the hypothesis
(§ 210) suggested by my researches, this is the region in which
the Tipper currents of atmosphere that ascended in the equatorial
calms, and flowed off to the northward and eastward, are sup-
posed to descend. This, therefore, is the region in which the
atmosphere that bears the "rain dust," or "African sand," de-
scends to the surface ; and this, therefore, is the region, it might
be supposed, which would be the most liable to showers of this
" dust." This is the region in which the Cape Verd Islands are
situated; they are in the direction which theory gives to the
upper current of air from the Oiinoco and Amazon with its "rain
dust," and they are in the region of the most frequent showers of
" rain dust :" all of which, though they do not absolutely prove,
are nevertheless strikingly in conformity with this theory as to
the circulation of the atmosphere.

331. Condition requisite to the production of a sea fog. — It is true
that, in the present state of our information, we cannot tell why
this " rain dust " should not be gradually precipitated from this
upper current, and descend into the stratum of trade-winds, as it
passes from the equator to higher northern latitudes; neither
can we tell why the vapour which the same winds carry along
should not, in like manner, be precipitated on the way ; nor why
we should have a thunder-storm, a gale of wind, or the display of
^ny other atmospherical phenomenon to-morrow, and not to-day :
all that we can say is, that the conditions of to-day are not such
as the phenomenon requires for its own development. There-
fore, though we cannot tell why the "sea-dust" should not
always fall in the same place, we may nevertheless suppose that
it is not always in the atmosphere, for the storms that take it up
occur only occasionally, and that when up, and in passing the
same parallels, it does not, any more than the vapour from a
given part of the sea, always meet with the conditions — electrical
and others — favourable to its descent, and that these conditions,
as with the vapour, may occur now in this place, now in that.
But that the fall does occur always in the same atmospherical
vein or general direction, my investigations would suggest, and
Ehrenberg's researches prove. Judging bv the fall of sea or rain

152 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

dust, we may suppose that tlie currents in the upper regions of
the atmosphere are remarkable for their general regularity, as
well as for their general direction and sharpness of limits, so to
speak. We may imagine that certain electrical conditions are
necessary to a shower of " sea-dust " as well as to a thunder-
storm ; and that the interval between the time of the equinoctial
disturbances in the atmosphere and the occurrence of these
showers, though it does not enable us to determine the true rate
of motion in the general system of atmospherical circulation, yet
assures us that it is not less on the average than a certain rate.
We cannot pretend to prescribe the conditions requisite for
brino-ino- the dust-cloud down to the earth. The radiation from
the smoke-dust — as the particles of visible smoke may be called
— has the effect of loading each little atom of smoke with dew,
causing it to descend in the black fogs of London. Any circum-
stances, therefore, which may cause the dust that ascends as a
straw-coloured cloud from the Orinoco, to radiate its caloric and
collect moisture in the sky, may cause it to descend as a red fog
in the Atlantic or Mediterranean.

332. WJiat is the agent that guides the air across the calm belts ? —
I do not offer these remarks as an explanation with which we
ought to rest satisfied, provided other proof can be obtained ; I
rather offer them in the true philosophical spirit of the distin-
guished microscopist himself, simply as affording, as far as they
are entitled to be called an explanation, that explanation which
is most in conformity with the facts before us, and which is
suggested by the results of a novel and beautiful system of
philosophical research. It is not, however, my province, or that
of any other philosopher, to dictate belief. Any one may found
hypotheses if he will state his facts and the reasoning by which
he derives the conclusions which constitute the hypothesis.
Having done this, he should patiently wait for time, farther
research, and the judgment of his peers, to expand, confirm, or
reject the doctrine which he may have conceived it his duty to
proclaim. Thus, though we have tallied the air, and put labels
on the wind, to "tell whence it cometh and whither it goeth,"
yet there evidently is an agent concerned in the circulation of
the atmosphere whose functions are manifest, but whose presence
has never yet been clearly recognized. When the air which the
north-east trade-winds bring down, meets in the equatorial
calms that which the south-east trade-winds convey, and the two
streams rise up together, what is it that makes them cross ?

EASTING OF THE TRADE-WINDS, ETC.

153

where is the power that guides that from the north over to the
south, and that from the south up to the north? The conjectures
in the next chapter as to " the relation between magnetism and
the circulation of the atmosphere " may perhaps throw some
light upon the answer to this question.

CHAPTER VII.

§ 341-368.— THE EASTING OF THE TRADE-WINDS, THE CROSSING AT
THE CALM BELTS, AND THE MAGNETISM OF THE ATMOSPHERE.

341. Halley's theory not fully confirmed hy observations. — Halley's
theory of the trade-winds, especially so much of it as ascribes
their easterly direction to the effect of the diurnal rotation of the
earth, seems to have been generally received as entirely correct.
But it is only now, since all the maritime nations of the world
have united in a common sj^stem of research concerning the
physics of the sea, and occupied it with observers, that we have
been enabled to apply the experimentum crucis to this part of the
famous theory. The abstract logs, as the observing-books are
called, have placed within my reach no less than 632,460 obser-
vations— each one itself being the mean of many separate ones —
upon the force and direction of the trade-winds. It appears
from these that diurnal rotation being regarded as the sole cause,
does not entirely account for the easting of these winds.

342. Observed course of the trade-winds. — From these observa-
tions the following table has been compiled. It shows the mean
annual direction of the trade-winds in each of the six belts,
north and south, between the parallels of 30° and the equator,
together with the number of observations from which the mean
for the belt is derived ; —

30° aud 25°
25° and 20°
20° and 15°
15° and 10°
10° and 5°
5° and 0°

iMean . . .

N.E. Trades.

Course.

N. 51° E.
51° 30'
53° 30'
52° 30'
53° 30'
54° 30'

N. 52° 45' E.

No. of Obs.

68,777
44,527
33,103
30,339
36,841
67,829

S.E. Trades.

Course.

S. 46° E.
49° 20'
52°

49° 40'
51° 40'
48° 40'

S. 49° 33' E.

No. of Obs.

66,635
66,395
46,604
43,817
54,648
72,945

154 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Between tlie equator and 5'^ north, tlie annual average duration
of the trades is 67 days for the north-east, and 199 for the south-
east, with a mean direction for the latter — which are the prevail-
ing winds between those parallels — of S. 47° 30' E. According
to the Halleyan theory these should be south-west winds.

34.3. Velocities of the trade-winds. — In the Atlantic the average
velocity of the south-east is greater than the average velocity Oi
the north-east trades.* I estimate one to be from 14 to 18, the
other from about 25 to 30 miles an hour. Assuming their velo-
city to be 14 and 25 respectively, the following departures show
the miles of easting which the trade-winds average per hour

through each of the above-named belts :

HouKLY Rate of Depaetuee of the Trade-winds aukoss the

Belts.

Between

N.E. Trades.

S.E. Trades.

Easting per hour.

Easting per Hour.

SO^- and 25°

10.9 miles

18. miles

25° and 20°

11.

19. „

20° and 15°

11.2 „

19.7 „

15° and 10°

11.

19.1 „

10° and 5°

11.2 „

19.6 „

5° and 0°

11.4 „

18.8 „

344. Difference between observation and theory. — That diurnal
rotation does impart easting to these winds there is no doubt ;
but the path suggested by the table does not conform to that
which, according to any reasonable hypothesis, the trade-winds
would follow if left to obey the forces of diurnal rotation alone,
as they would do were diurnal rotation the sole cause of their
easting. As these winds approach the equator, the effect of
diurnal rotation becomes more and more feeble. But the table
shows no such diminution of effect. They have as much easting
between 5° and 0° as they have between 30° and 25°. Nay, the
south-east trades between the equator and 5° N. — where, by the
Halleyan theory, they should have westing — have as much easting
(§ 342) as they have between 30^ and 25° south. We cannot tell
how much the air is checked in its easterly tendency by resisting
agents, by friction, etc., but we know that that tendency is about
ten times stronger 'between 30° and 25° than it is between 5° and
0°, and yet actual observations show no difference in their
course. This table reminds us that diurnal rotation should not,

* "Average Force of the Trade-winds," p. 857, vol. ii., Maury's Sailing
Directions, 1859.

EASTING OF THE TKADE-WINDS, ETC. 155

imtil more mimerous and accurate observations shall better
satisfy the theory than those half a million and more now do, be
regarded as the sole cause of the easterly direction of the trade-
winds. It suggests either that other agents are concerned in
giving the trade-winds their easting, or that the effect of the
upper and counter current, when drawn down and turned back
(§ 232), is such as to counteract their unequal turning in obe-
dience to the varying forces of diurnal rotation. No apology is
needed for applying the tests of actual observatie»n to this part of
the Halleyan theory, notwithstanding the general concurrence of
opinion as to its sufficiency. With equal favour that feature of
it also was received which ascribes the rising up in the belt
of equatorial calms to the direct influence of the solar ray. But
the advancement which has been made in our knowledge of
physical laws since Halley expounded his trade-wind theory
suggested a review of that feature, and it was found that, though
the direct heat of the sun is one of the agents which assists the
air to rise there, it is not the sole agent ; the latent heat which is
set free by condensing vapour for the equatorial cloud-ring and
its rains is now also (§ 252) recognized as an agent of no feeble
power in this calm belt.

345. Faraday's discovery of magnetism in the air. — Where shall
those who are disposed to search, look for this other agent that
is supposed to be concerned with the trade-winds in their east-
ing ? I cannot say where it is to be found, but considering the
recent discoveries in terrestrial magnetism — considering the
close relations between many of its phenomena and those both of
heat and electricity — the question may be asked whether some
power capable of guiding " the wind in his circuits " may not
lurk there ? Oxygen comprises more than one-fifth part (two-
ninths) of the atmosphere, and Faraday has discovered that
oxygen is para-magnetic. If a bar of iron be suspended between
the poles of a magnet, it will arrange itself axially, and point
towards them ; but if, instead of iron, a bar of bismuth be used,
it will arrange itself equatorial ly, and point in a direction
perpendicular to that in which the iron pointed. To distinguish
these two kinds of forces, Dr. Faraday has said iron is para-
magnetic, bismuth dia-magnetic. Oxygen and iron belong to
the same class, and all substances in nature belong to one or
the other of the two classes of which iron and bismuth are the
types.

156 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

346. Lines of magnetic force. — This eminent philosopher has
also shown that if you place a magnetized bar of iron on a smooth
surface, and sift fine iron filings down upon it, these filings will
arrange themselves in curved lines as in Fig. 1 ; or, if the bar be
broken, they will arrange themselves as in Fig. 2. The earth it-
self, or the atmospheric envelope by which it is surrounded, is a
most powerful magnet, and the lines of force which proceed
whether from its interior, its solid shell, or vaporous covering.

Fig. 1.

Fig. 2.

^g^^^^^^

^^^iS'

are held to be just such lines as those are which surround arti-
ficial magnets ; proceed whence they may, they are supposed to
extend through the atmosphere, and to reach even to the plane-
tary spaces. Many eminent men and profound thinkers, Sir
David Brewster among them, suspect that the atmosphere itself
is the seat of terrestrial magnetism. All admit that many of
those agents, both thermal and electrical, which play highly
important parts in the meteorology of our planet, exercise a
marked influence upon the magnetic condition of the atmosphere
also.

347. Tlie magnetic influences of the oxygen of the air and of the
spots on the sun. — Now, when, referring to Dr. Faraday's dis-
covery (§ 345), and the magnetic lines offeree as shown by the
iron filings (§ 346), we compare the particles of oxygen gas to

EASTING OF THE TRADE-WINDS, ETC. 157

these minute bits of ferruginous dust that arrange themselves in
lines and curves about magnets ; when we reflect that this great
magnet, the earth, is surrounded by a para-magnetic gas, to the
molecules of which the finest atom from the file is in comparison
gross and ponderous matter ; — that the entire mass of this air is
equivalent to a sea of mercury covering the earth around and
over to the depth of 30 inches, and that this very subtile mass is
in a state of unstable equilibrium, and in perpetual commotion
by reason of various and incessant disturbing causes ; — when we
reflect farther upon the recent discoveries of Schwabe and of
Sabine concerning the spots on the sun and the magnetic ele-
ments of the earth, which show that if the sun or its spots be
not the great fountain of magnetism, there is at least reason to
suspect a close alliance between solar and terrestrial magnetism
— that certain well-known meteorological phenomena, as the
aurora, come also within the category of magnetic phenomena.;
— that the magnetic poles of the earth and the poles of maximum
cold are at or near the same spot ; — that the thermal equator is
not parallel to or coincident with either the terrestiial or with
that which the direct solar ray would indicate, but that it follows,
and in its double curvatures conforms to the magnetic equator ;
— moreover, when we reflect upon Barlow's theory and Fox's
observations, which go to show that the direction of metallic
veins of the northern hemisphere, which g enerally lie north-east
and south-westwardly, must have been influenced by the direc-
tion of the magnetic meridians of the earth or air ; — finally, I
say, when we reflect upon magnetism in all its aspects, we may
well inquire whether such a mass of highly magnetic gas as that
which surrounds our planet does not intervene, by reason of its
magTietism, in influencing the circulation of the atmosphere and
the course of the winds.

348. The needle in its diurnal variations, the barometer in its
readings, and the atmosphere in its electrical tension, all have the same
hours for their maxima and minima. — This magnetic sea, as the
atmosphere may be called, is continually agitated ; it is dis-
turbed in its movements by various influences which prevent it
irom adjusting itself to any permanent magnetic or other dy-
namical status ; and its para-magnetic properties are known to
vary with every change of pressure or of temperature. The
experiments of Faraday show that the magnetic force of the ah-
changes with temperature ; that it is least near the equator, and

158 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

greatest at the poles of maximum cold ; that it varies with the
seasons, and changes night and day ; nay, the atmosphere has
regular variations in its electrical conditions expressed daily at
stated hours of maximum and minimum tension. Coincident
with this, and in all parts of the world, hut especially in sub-
tropical latitudes, the barometer also has its maxima and minima
readings for the day. So also, and at the same hours, the needle
attains the maxima and minima of its diurnal variations. With-
out other time-piece, the hour of the day may be told by these
maxima and minima, each group of which occurs twice a-day
and at six-hour intervals. These invisible ebbings and Sowings
— the diurnal change in the electrical tension — the diurnal
variation of the needle, — and the diurnal rising and falling of
the barometer, — follow each other as closely and as surely, if
not quite as regularly, as night the day. Any cause which
produces changes in atmospheric pressure invariably puts it
in motion, giving rise to gentle airs or furious gales, according
to degree ; and here, at least, we have a relation betw^een the
movements in the air and the movements of the needle so close
that it is difficult to say which is cause, which effect, or whether
the two be not the effects of a common cause.

349. The question raised hy modern researches. — Indeed, such is
the nature of this imponderable called magnetism, and such the
suggestions made by Faraday's discoveries, that the question has
been raised in the minds of the most profound philosophers of
the age whether the various forces of light, heat, and gravitation,
of chemical affinity, electricity, and magnetism, may not yet be
all traced to one common source. Surely, then, it cannot be
considered as unphilosophical to inquire of magnetism for some
of the anomalous movements that are observed in the atmosphere.
These anomalies are many ; they are not confined to the easting
of the trade-winds ; they are to be found in the counter-trades
and the calm belts also. There is reason to believe, as has
already been stated (§ 288), that there is a crossing of the winds
at the calm belts (§ 212), and it was promised to go more into
detail concerning the circumstances which seem to favour this
belief. Our researches have enabled us, for instance, to trace
from the belt of calms, near the tropic of Cancer, which extends
entirely across the seas, an efflux of air both to the north and to
the south. From the south side of this belt the air flows in a
steady breeze, tailed the north- cast trade-winds, towards the

EASTING OF THE TEADE-WINDS, ETC. 159

equator (Plate I.) ; on the nortL. side of it, the prevailing winds
come from it also, but they go towards the north-east. They are
the well-known westerly winds which prevail along the route
from this country to England in the ratio of two to one. But
why should we suppose a crossing to take place here ? We
suppose so from these facts : because throughout Europe, — the
land upon which these westerly winds blow, — precipitation is
in excess of evaporation, and because at sea they are going from
a warmer to a colder climate ; and therefore it may be inferied
that Nature exacts from them what we know she exacts from the
air under similar circumstances, but- on a smaller scale, before
our eyes, viz., more precipitation than evaporation. In other
words, they probably leave in the Atlantic as much vapour as
they take up from the Atlantic. Then where, it may be asked,
does the vapour which these winds carry along, for the re-
plenishing of the whole extra-tropical regions of the north, come
from ? They did not get it as they came along in the upper
regions, as a counter-current to the north-east trades, unless they
evaporated the trade-wind clouds, and so robbed those winds of
their vapour. They certainly did not get it from the surface of
the sea in the calm belt of Cancer, for they did not tarry long
enough there to become saturated with moisture. Thus circum
stances again pointed to the south-east trade-wind regions as the
place of supply. This question has been fully discussed in
Chapter V., where it has been shown they did not get it from
the Atlantic. Moreover, these researches afforded groxmds for
the supposition that the air of which the north-east trade- winds
are composed, and which comes out of the same zone of calms
as do these south-westerly winds, so far from being saturated
with vapour at its exodus, is dry ; for near their polar edge, the
nortn-east trade- winds are, for the most part, dry winds.

350. Wet and dry air of the calm belts. — Facts seem to confirm
this, and the calm belts of Cancer and Capricorn both throw a
flood of light upon the subject. These are two bands of light
airs, calms, and baffling winds, which extend entirely around
the earth. The air flows out north and south from these belts.
That which comes out on the equatorial side goes to feed the
trades, and makes a dry wind; that which flows out on the
polar side goes to feed the counter- trades (§ 349), and is a rain
wind. How is it that we can have from the same trough or
receiver, as these calm belts may be called, an efiiux of dry air

160 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

on one side and of moist on the other ? Answer : upon the
supposition that the air without rain comes from one quarter,
that wdth rain from another — that, coming from opposite direc-
tions to this place of meeting, where there is a crossing, they
pass each other in their circuits. They both meet here as upper
currents, and how could there be a crossing, without an agent or
influence to guide them ? and why in the search should we not
look to magnetism for this agent as well as to any other of the
hidden influences which are concerned in giving to the winds
their force and direction ?

351. Principles according to which the physical machinery of our
planet should he studied. — He that established the earth " created
it not in vain ; He formed it to be inhabited." And it is pre-
sumptuous, arrogant, and impious to attempt the study of its
machinery upon any other theory : it was made to he inhahited.
How could it be inhabitable but for the sending of the early and
the latter rain ? How can the rain be sent except by the winds ?
and how can the fickle winds do their errands unless they have
a guide ? Suppose a new piece of human mechanism were
shown to one of us, and we were told the object of it was to
measure time ; now, if we should seek to examine it with the
view to understand its construction, would we not set out upon
the principle — the theory — that it was made to measure time ?
By proceeding on any other supposition or theory we should be
infallibly led into error. And so it is with the physical
machinery of the world. The theory upon which this work is
conducted is that the earth ims made for man ; and I submit that
no part of the machinery by which it is maintained in a con-
dition fit f(jr him is left to chance, any more than the bit of
mechanism by which man measures time is left to go by chance.

352. Division into wind hands. — That I might study to better
advantage the workings of the atmospherical machinery in
certain aspects, I divided the sea into bands or belts 5° of
latitude in breadth, and stretching east and west entirely around
the earth, but skipping over the land. There are twelve of
those bands on each side of the equator that are traversed more
or less frequently by our fleet of observers ; they extend to the
parallel of 00° in each hemisphere. To determine the force and
direction of the wind for each one of these bands, the abstract
logs were examined until all the data afforded by 1,159,533
observations were obtained ; and the mean direction of the wind

EASTING OF THE TRADE- WINDS, ETC. 161

for each of the four quarters in every band was ascertained.
Considering difference of temperature between these various
bands to be one of the chief causes of movement in the atmo-
sphere,— that the extremes on one hand are near the equator,
and on the other about the poles; — considering that the tendency
of every wind (§ 234) is to blow along the arc of a great circle,
and that consequently every wind that was observed in any one
of these bands must have moved in a path crossing these bands
more or less obliquely, and that therefore the general movements
in the atmosphere might be classed accordingly, as winds either
with northing or with southing in them; — we have so classed
them ; and we have so classed them that we might study to more
advantage the general movements of the great atmospherical
machinery. See Plate XV.

353. The medial hands. — Thus, when, after so classing them,
we come to examine those movements in the band between 5°
and 10° south, and to contrast them with the movements in the
band between 55° and 60° south, for example, we find the general
movements to be exactly in opposite directions. Observations
show that during the year the winds in the former blow towards
the equator 283, and /rom it 73 days ; and in the latter they blow
toward the pole for 224, and from it 132 days. These facts show
that there must be a place of rarefaction — of low barometer, an
indraught towards the poles as well as the equator ; — and that
consequently, also, there must be a medial line or band some-
where between the parallels of lO"" and 55° south, on one side of
which the prevailing direction of the wind is towards the equator,
on the other towards the pole. So, in the northern hemisphere,
the same series of observations point this medial band out to us.
They show that one is near the calm belt of Capricorn, the other
near the calm belt of Cancer, and that they both probably lie
between the parallels of 35° and 40°, where the winds north and
south are equal, as per t^ble, page 162.

The wind curves (Plate XV. and the table) afford a very
striking view of these medial bands, as the parallels in either
hemisphere between which the wdnds with northing and the
winds with southing are on the yearly average exactly equal.
In the northern hemisphere the debatable ground appears by the
table to extend pretty nearly from 25° to 50° N. By the plate
the two w^inds first become equal between 25° and 30° ; the two
curves then recede and approach very closely again, but witho'dt

i'62 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Winds loith Northing and Winds with Southi

tq in each

Hemisphere, expressed

% Average Number of Days for which they blow annually.

Bands.

Northern Hemisphere.

Southern Hemisphere.

Northing.

Southing.

No. of Obs.

Northing.
Davs.

Southing.

No. of Obs.

Between

DavR.

Days.

Days.

0^ and 5^

78

268

67,829

84

269

72,945

53 and 10^

158

182

36,841

73

283

54,648

j lO^andlS^

278

73

27,339

82

275

43,817

15^ and 20^

272

81

33,103

91

266

46,604

20^ and 25^

246

101

44,527

128

227

66,395

253 and 30^

185

162

68,777

146

208

66,635

80^ and 352

155

195

62,514

150

2(i4

76,254

1 S5^ and 40°

173

178

41,233

178

177

107,231

! 40^ and 45°

163

186

33,252

202

155

63,669

453 and 50^

164

188

29,461

209

148

29,132

50^ and oo^

147

204

41,570 ;

208.

151

14,286

55^ and GO^

141

213

17,874 i

224

132

13,617
655,233

Total i

504,320

Observations, 1,159,553

crossing, between 35° and 40°. In the southern hemispliere, the
conflict between the polar and equatorial indraught, as expressed
by winds with southing and winds with northing, is more de-
cided. There the two curves march, one up, the other down,
and cross between the parallels of 35° and 40° S., thus confirming
what from other data we had already learned, viz., that the con-
dition of the atmosphere is more unstable in the northern than
it is in the southern hemisphere.

354. Hie rainless regions and ilie cahnbelts. — Such, for the winds
at sea, is their distribution between the two halves of the horizon
in the several bands and in each hemisphere. Supposing a like
distribution to obtain on shore, we shall find it suggestive to
trace the calm belts of the tropics across the continents (Plate
VIII.), and to examine, in connection with them, the rainless
regions of the earth, and those districts of country which, though
not rainless, are nevertheless considered as " dry countries," by
reason of the small amount of precipitation upon them. So,
tracing the calm belt of Cancer, which at sea lies between the
parallels of 28° and 37° (Plate VIII.), but which, according to
Sir John Ilerscliel,* reaches higher latitudes on shore, it will be
perceived that the wands that flow out on the north side blow
* § 273, p. 614, vol. xvil (Phys. Geog.), Encjclupffidia Britannica,

EASTING OF THE TRADE-WINDS, ETC. 163

over countries abounding in rivers, which, countries are therefore
abundantly supplied with rains. Hence we infer (§ 360) that
those winds are rain winds. On the other hand, the winds that
flow out on the equatorial side blow either over deserts, rainless
regions, or dry countries. Hence we infer that these winds
are dry winds. These " dry" winds traverse a country abound-
ing in springs and rivers in India, but it is the monsoons there
which bring the water for them. The winds which come out of
this calm belt on its equatorial side give out no moisture, except
as dew, until they reach the sea, and are replenished with vapour
thence in sufficient quantities to make rain of; whereas the
winds which come out on the polar side leave moisture enough
as they come for such rivers as the Obi, the Yenisei, the Lena,
and the Amoor, in Asia ; the Missouri, the Sascatchawan, the
Red Eiver of the North, and others, in America. Between this
calm belt and the head waters of these rivers tbere are no seas or
other evaporating surfaces, neither are they so situated -v^vith
regard to the sea-coast that they maybe, as the shores of Eastern
China and the Atlantic slopes of the United States are, supplied
with vapour by the winds from the sea-board. When we con-
sider the table (§ 353), the situation of the rainless regions and
dry countries with regard to the calm belt of Cancer, we are
compelled to admit that, come whence it may and by what
channels it may, there are flowing out of this calm belt two kinds
of air, one well charged with moisture, the other dry and thirsty
to a degi'ee.

355. The theory of the crossings re-stated, and the facts reconciled
})y it^ — The supposition that the dry air came from the north and
the moist from the south, and both as an upper current, is the
only hypothesis that is consistent with all the known facts of
the case. The dry air gave up all its moisture when, as a surface
wind, it played upon the frozen summits of the northern hills ;
the wet obtained its moisture when, as the south-east trade-
winds, it swept across the bosom of intertropical seas of the
soutliern hemisphere. Eising up at the equator, it did not leave
all its moisture with the cloud-ring, but, retaining a part, con-
veyed it through the cloud region, above the north-east trades,
to this calm belt, where there was a descent and a crossing.
The fact that these dry places are all within or on the equatorial
side of this calm belt, while countries abounding with rains and
well watered with running streams are to be found all along its

M 2

154 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

polar side, is clearly indicative of a crossing. Upon no other
supposition can we account for the barrenness on one side, the
fertility on the other. The following are also links in the chain
of facts and circumstances which give strength to the supposition
that the rains for the Lena and the Missouri are brought across
the calm belt of Cancer by those currents of air which flow thence
towards the pole as the prevailing counter-trades or south-
westerly winds of the extra-tropical north. "We have already
seen (§ 353) that, on the north side of this calm zone of Cancer,
the prevailing winds on the surface are from this zone towards
the pole, and (Plate I., § 215) that these winds return as A B C
through the upper regions from the pole ; that, arriving at the
calms of Cancer, this upper current, ABC, meets another upper
cuiTcnt, S E, from the equator, where they neutralize each other,
produce a calm, descend, and come out as surface winds, D E, or
the trade-winds ; and as T IT, or the counter-trades. Now ob-
servations have shown that the winds represented by T U are
rain winds ; those represented by D E, dry winds ; and it is
evident that ABC could not bring any vapours to these calms
to serve for T U to make rains of; for the winds represented by
ABC have already performed the circuit of surface winds as far
as the pole, during which journey they parted with all their
moisture, and, returning through the upper regions of the air to
the calm belt of Cancer, they arrived there as dry winds. The
winds represented by D E are dry winds ; therefore it was sup-
posed that these are, for the most part, but a continuation of the
winds ABC. On the other hand, if the winds ABC, after
descending, do turn about and become the surface winds T U,
they would first have to remain a long time in contact with the
sea, in order to be supplied with vapour enough to feed the gTcat
rivers, and supply the rains for the whole earth between us and
the north pole. In this case, we should have an evaporating
region at sea and a rainless region ashore on the north as well as
on the south side of this zone of Cancer ; but investigation shows
no such region. Hence it was inferred that B C and E S do
come out on the surface as represented by Plate I. But what is
the agent that should lead them out by such opposite paths ?
According to this mode of reasoning, the vapours which supply the
rains for T U would be taken up in the south-east trade- wind
region by 0 Q, and conveyed thence along the route Q E S to T.
Ana if this mode of reasoning bo admitted as plausible — if it be

EASTING OF THE TRADE-WINDS, ETC. 165

true that E S carry the vapour which., by condensation, is to water
with showers the extra-tropical regions of the northern hemi-
sphere, Nature, we may be sure, has provided a guide for con-
ducting S T across this belt of calms, and for sending it on in the
right w^ay. Here it was, then, at this crossing of the winds, that
I thought I first saw the footprints of an agent whose character I
could not comprehend. Can it be the magnetism that resides in
the oxygen of the air ? Heat and cold, the early and the latter
rain, clouds and sunshine, are not, we may rely upon it, distributed
over the earth, by chance ; they are distributed in obedience to
laws that are as certain and as sure in their operations as the
seasons in their rounds. If it depended upon chance whether the
dry air should come out on this side or on that of this calm belt, or
whether the moist air should return or not whence it came — if such
were the case in nature, we perceive that, so far from any regularity
as to seasons, we should have, or might have, years of drought the
most excessive, and then again seasons of rains the most destruc-
tive ; but, so far from this, we find for each place a mean annual
proportion of both, and that so regulated withal, that year after
year the quantity is preserved with remarkable regularity.
Having thus shown that there is no reason for supposing that
the upper currents of air, when they meet over the calms of
Cancer and Capricorn, are turned back to the equator, but
having shown that there is reason for supposing that the air of
each current, after descending, continues on in the direction
towards which it was travelling before it descended, we may go
farther, and, by a similar train of circumstantial evidence,
afi'orded by these researches and other sources of information,
show that the air, kept in motion on the surface by the two
systems of trade-winds, when it arrives at the belt of equatorial
calms and ascends, continues on thence, each curreat towards
the pole which it was approaching w^hile on the surface. In a
problem like this, demonstration in the positive way is difficult,
if not impossible. We must rely for our proof upon philo-
sc phical deduction, guided by the lights of reason ; and in all
cases in which positive proof cannot be adduced, it is permitted
to bring in circumstantial evidence ; and the circumstantial
evidence afforded by my investigations goes to show that the
winds represented by 0 Q, § 215, do become those represented
by R S T U V A, and A B C D E F respectively. In the first
place, 0 Q represents the south-east trade-winds — i. e., all the

166 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

winds of the soutliern hemisphere as they approach the equator ;
and is there any reason for supposing that the atmosphere does
not pass freely from one hemisphere to another? On the con-
trary, many reasons present themselves for supposing that it
does. If it did not, the proportion of land and water, and
consequently of plants and warm-blooded animals, being so
different in the two hemispheres, we might imagine that the con-
stituents of the atmosphere in them would, in the course of ages,
probably become different also, and that consequently, in such
a case, man could not safely pass from one hemisphere to the
other. Consider the manifold beauties in the whole system of
terrestrial adaptations ; remember what a perfect and wonderful
machine (§ 268) is this atmosphere ; how exquisitely balanced
and beautifully compensated it is in all its parts. We know
that it is perfect ; that in the performance of its various offices
it is never left to the guidance of chance — no, not for a moment.
Wherefore I was led to ask myself why the air of the south-east
tirades, when arrived at the zone of equatorial calms, should not,
after ascending, rather return to the south than go on to the
north ? Where and what is the agenc}^ by which its course is
decided ? Here I found circumstances which again induced me
to suppose it probable that it neither turned back to the south
nor mingled with the air which came from the regions of the
north-east trades, ascended, and then flowed indiscriminately to
the north or the south. But I saw reasons for supposing that
what came to the equatorial calms as the south-east trade-winds
continued to the north as an upper current, and that what had
come to the same zone as north-east trade-winds ascended and
continued over into the southern hemisphere as an upper current,
bound for the calm zone of Capricorn. And these are the prin-
cipal reasons and conjectures upon which these suppositions
were based : At the seasons of the year when the area covered
by the south-east trade-winds is large, and when they are
evaporating most rapidly in the southern hemisphere, even up
to the equator, the most rain is falling in the northern. There-
fore it is fair to suppose that much of the vapour which is taken
up on that side of the equator is precipitated on this. The
evaporating surface in the southern hemisphere is greater, much
greater, than it is in the northern ; still, all the great rivers are
in the northern hemisphere, the Amazon being regarded as
common to both ; and this fact, as far as it goes, tends to corrc

EASTING OF THE TRADE -WINDS, ETC. 167

borate the suggestion as to the crossinsi; of the trade-winds at the
equatorial calms. Taking the laws and rates of evaporation into
consideration, I could find (Chapter V.) do part of the ocean of
the northern hemisphere from which the sources of the Mississippi
the St. Lawrence, and the other great rivers of onr hemisphere
could be supplied. A regular series of meteorological obser-
vations has been carried on at the military posts of the United
States since 1819. Eain maps of the whole country* have been
prepared from these observations by Mr. Lorin Blodget at the
Surgeon-General's office, and under the direction of Dr. Cool-
edge, U.S.A. These maps, as far as they go, sustain these views
in a remarkable manner, for they bring out facts in a most
striking way to show that the dry season ui California and
Oregon is the wet season in the Mississippi Valley. The winds
coming from the south-west, and striking upon the coast of
California and Oregon in winter, precipitate there copiously.
They then pass over the mountains robbed in part of their
moisture. Of course, after watering the Pacific shores, they
have not as much vapour to make rains of, specially for the
upper Mississippi Valley, as they had in the summer-time, when
they dispensed their moisture, in the shape of rains, most
sparingly upon the Pacific coasts. According to these views,
the dry season on the Pacific slopes should be the wet, especially
in the upper Mississippi Valley, and vice versa. Blodget's maps
show that such is actually the case. Meteorological observations
in the "Eed River country" and other parts of British America
would throw farther light and give farther confirmation, I doubt
not, both to these views and to this interesting question. These
army observations, as expressed in Blodget's maps, reveal other
interesting features, also, touching the physical geography of
the country. I allude to the two isothermal lines 45° and 65°
(Plate VIII.), which include between them all places that have
a mean annual temperature between 45° and 65°. I have drawn,
for the sake of comparison, similar lines on the authority of
Dove and Johnston (A. K., of Edinburgh), across Europe and
Asia. The isotherm of 65° skirts the northern limits of the
sugar-cane, and separates the intertropical from the extra-tropical
plants and productions. I have drawn these two lines across
America in order to give a practical exemplification of the nature
of the advantages which the industrial pursuits and the politica)
* See Army ]Meteorological ObserTations, published 1855.

168 pinrsiCAL geogkapht of the sea, and its meteorology.

economy of the country would derive by the systematic extension
of onr meteorological observations from the sea to the land.
These lines show how much we err when we reckon climates
according to parallels of latitude. The space that these two
isotherms of 45° and 65° comprehend between the Mississippi
and the Eocky Mountains, owing to the singular effect of those
mountains upon the climate, is larger than the space they
comprehend between the Mississippi and the Atlantic. Hyeto-
graphically it is also different, being dryer, and possessing a
purer atmosphere. In this grand range of climate between the
meridians of 100° and 110° W., the amount of precipitation is
just about one-half of what it is between those two isotherms
east of the Mississippi. In this new country west of it, winter
is the dry, and spring the rainy season. It includes the climates
of the Caspian Sea, which Humboldt regards as the most salu-
brious in the world, and where he found the most delicious
fruits that he saw during his travels. Such w^as the purity of
the air there, that polished steel would not tarnish even by night
exposure. These two isotherms, with the remarkable loop
which they make to the north-west, beyond the Mississippi,
embrace the most choice climates for the olive, the vine, and
the poppy ; for the melon, the peach, and almond. The finest
of wool may be grown there; and the potato, with hemp,
tobacco, maize, and all the cereals, may be cultivated there in
great perfection. No climate of the temperate zone will be
found to surpass in salubrity that of this Piedmont trans-Mis-
sissippi country. The calm zone of Capricorn is the duplicate
of that of Cancer, and the winds flow from it as they do from
that, both north and south, but with this difference : that on
the polar side of the Capricorn belt they prevail from the north-
west instead of the south-west, and on the equatorial side from
the south-east instead of the north-east. Now if it be true that
the vapour of the north-east trade-winds is condensed in the
extra-tropical regions of the southern hemisphere, the following
path, on account of the effect of diurnal rotation of the earth
upon the course of the winds, would represent the mean circuit
of a portion of the atmosphere moving according to the general
system of its circulation over the Pacific Ocean, viz. : coming
down from the north as an upper current, and appearing on the
surface of the earth in about longitude 120° west, and near the
tropic of Cancer, it would here commence to blow the north-east

EASTING OF THE TRADE-^VINDS, ETC. 169

hrado-winds of that region. To make this clear, see Plate VII.,
on which I have marked the course of such vapour-bearing
ivinds ; A being a breadth or swath of vs^inds in the north-east
trades ; B, the same v^ind as the upper and counter-current to
the south-east trades ; and C, the same wind after it has de-
scended in the calm belt of Capricorn, and come out on tlie
polar tide thereof, as the rain winds and prevailing north-west
winds of the extra-tropical regions of the southern hemisphere.
This, as the north-east trades, is the evaporating wind. As the
north-east trade-wind, it sweeps over a great waste of waters
lying between the tropic of Cancer and the equator. Meeting no
land in this long oblique track over the tepid waters of a tropical
sea, it would, if such were its route, arrive somewhere about the
meridian of 140° or 150° west, at the belt of equatorial calms,
which always divides the north-east from the south-east trade-
winds. Here, depositing a portion of its vapour as it ascends,
it would, with the residuum, take, on account of diurnal rotation,
a course in the upper region of the atmosphere to the south-east,
as far as the calms of Capricorn. Here it descends and continues
on towards the coast of South America, in the same direction,
appearing now as the prevailing north-west wind of the extra-
tropical regions of the southern hemisphere. Travelling on
the surface from warmer to colder regions, it must, in this part
of its circuit, precipitate more than it evaporates. Now it is a
coincidence, at least, that this is the route by which, on account
of the land in the northern hemisphere, the north-east trade-
winds have the fairest sweep over that ocean. This is the route
by which they are longest in contact with an evaporating
surface ; the route by which all circumstances are most favour-
able to complete saturation ; and this is the route by which they
can pass over into the southern hemisphere most heavily laden
with vapours for the extra- tropical regions of that half of the
globe; and this is the supposed route which the north-east
trade-winds of the Pacific take to reach the equator and to pass
from it. Accordingly, if this process of reasoning be good, that
portion of South America between the calms of Capricorn and
Cape Horn, upon the mountain langes of which this part of the
atmosphere, whose circuit I am considering as type, first im-
pinges, ought to be a region of copious precipitation. Now let
us turn to the works on Physical Geography, and see what we
can find upon this subject. In Berghaus and Johnston — depart-

170 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ment Hyetograpliy — it is stated, on the aiithority of Captain
King, E.jS., that upwards of twelve feet (one hundred and fifty-
three inches) of rain fell in forty- one days on that part of the
coast of Patagonia which lies within the sweep of the winds just
described. So much rain falls there, navigators say, that they
sometimes find the water on the top of the sea fresh and sweet.
After impinging upon the cold hill-tops of the Patagonian coast,
and passing the snow-clad summits of the Andes, this same
wind tumbles down upon the eastern slopes of the ranges as a
dry wind ; as such, it traverses the almost rainless and barren
regions of cis-Andean Patagonia and South Buenos Ayres, Plate
VIII. These conditions, the direction of the prevailing winds,
and the amount of precipitation, may be regarded as evidence
afforded by nature, if Qot in favour of, certainly not against, the
conjecture that such may have been the voyage of this vapour
through the air. At any rate, here is proof of the immense
quantity of vapour which these winds of the extra-tropical
regions carry along with them towards the poles ; and I can
imagine no other place than that suggested, whence these winds
could get so much vapour.

356. The question, How can two currents of air cross ? answered. —
Notwithstanding the amount of circumstantial evidence that has
already been brought to show that the air which the north-east
and the south-east trade-winds discharge into the belts of equa-
torial calms, does, in ascending, cross — that from the southern
passing over into the northern, and that from the northern pass-
ing over into the southern hemisphere (see 0 Q E S, and
D E F G, § 215) — 3^et some have implied doubt by asking the
question, " How are two such currents of air to pass each
other ?" And, for the Avant of light upon this point, the cor-
rectness of my reasoning, facts, inferences, and deductions has
been questioned. In the first place, it may be said in reply, the
belt of equatorial calms is often several hundred miles across,
seldom less than sixty ; whereas the depth of the volume of air
that the trade-winds pour into it is only about three miles, for
that is supposed to be about the height to which the trade-winds
extend. Thus we have the air passing into these calms by an
ox^ening on the north side for the north-east trades, and another
on the south for the south-east trades, having a cross section of
three miles vertically to each opening. It then escapes by an
opening upward, the cross section of which is sixty or one hun-

EASTING OF THE TRADE-WINDS, ETC. 171

dred, or even three hundred miles. A very slow motion upward
there will carry off the air in that direction as fast as the two
sj^stems of trade-winds, with their motion of twenty miles an
hour, can pour it in ; and that curds or JiaJces of air can readily
cross each other and pass in different directions without inter-
fering the one with the other, or at least without interfering to
that degree which prevents, we all know. The brown fields in
summer afford evidence in a striking manner of the fact that, in
nature, flakes, or streamlets, or curdles of air do really move
among each other without obstruction. That tremulous motion
which we so often observe above stubble-fields, barren wastes, or
above any heated surface, is caused by the ascent and descent, at
one and the same time, of flakes of air at different temperatures,
the cool coming down, the warm going up. They do not readily
commingle, for the astronomer long after nightfall, when he
turns his telescope upon the heavens, perceives and laments the
unsteadiness they produce in the sky. If the air brought to the
calm belt by the north-east trade-winds differ in temperature
(and why not?) from that brought by the south-east trades, we
have the authorit}^ of nature for saying that the two currents
would not readily commingle (§ 98). Proof is daily afforded
that the}^ would not, and there is reason to believe that the air
of each current, in streaks, or patches, or flakes, does thread its
way through the air of the other without difficulty. Therefore
we may assume it as a postulate which nature concedes, that there
is no physical difficulty as to the two currents of air, which come
into those calm belts from different directions, crossing over,
each in its proper direction, without mingling.

357. The rain winds in the Mississippi Valley. — The same pro-
cess of reasoning which conducted us (§ 355) into the trade-wind
region of the northern hemisphere for the sources of the Pata-
gonian rains, now invites us into the trade-wind regions of the
South Pacific Ocean to look for the vapour springs of the Missis-
sippi. If the rain winds of the Mississippi Valley come from
the east, then we should have reason to suppose that their
vapours were taken up from the Atlantic Ocean and Gulf
Stream ; if the rain winds come from the south, then the vapour
springs might, perhaps, be in the Gulf of Mexico ; if the rail,
winds come from the north, then the great lakes might be sup-
posed to feed the air with moisture for the fountains of that
river ; but if the rains come from the west, where, short of the

172 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY

great Pacific Ocean, should we look for the place of evaporation ?
Wondering where, I addressed a circular letter to farmers and
planters of the Mississippi Valley, requesting to be informed as
to the direction of their rain winds. I received replies from
Virginia, Mississippi, Tennessee, Missouri, Indiana, and Ohio ;
and subsequently^ from Colonel W. A. Bird, Buffalo, New York,
who says, " The south-west winds are our fair-weather winds ;
we seldom have rain from the south-west." Buffalo may get
much of its rain from the Gulf Stream with easterly winds.
But I speak of the Mississippi Valley ; all the respondents there,
with the exception of one in Missouri, said, " The south-west
winds bring us our rains." These winds certainly cannot get
their vapours from the Eocky Mountains, nor from the Salt Lake,
for they rain quite as much upon that basin as they evaporate
from it again ; if they did not, they would in the process of time
have evaporated all the water there, and the lake would now be
dry. These winds, that feed the sources of the Mississippi with.
rain, like those between the same parallels upon the ocean, are
going from a higher to a lower temperature ; and the winds in
the Mississippi Valley, not being in contact with the ocean, or
with any other evaporating surface to supply them with moisture,
must bring with them from some sea or another that which they
deposit. Therefore, though it may be urged, inasmuch as tha
winds which brought the rains to Patagonia (§ 355) came direct
from the sea, that they therefore took up their vapours as they
came along, yet it cannot be so urged in this case ; and if theso
winds could pass with their vapours from the equatorial calms
through the upper regions of the atmosphere to the calms of Can-
cer, and then as surface winds into the Mississippi Valley, it was
not perceived why the Patagonian rain winds should not bring their
moisture by a similar route. These last are from the north-west,
from warmer to colder latitudes ; therefore, being once charged
with vapours, they must precipitate as they go, and take up less
moisture than they deposit. The circumstance that the rainy
season in the Mississippi Valley (§ 355) alternates with the dry
season on the coast of California and Oregon, indicates that the
two regions derive vapour for their rains from the same fountains.
358. Ehrenherg and his microscope. — During the discussion on
this subject, my friend Baron von Gerolt, the Prussian minister,
had the kindness to ])lace in my hand Ehrenberg's work,
" Passat- Staub und Blut-Regen." Here T found another clew

EASTING OF THE TRADE-WINDS, ETC. 173

leading across the calm places. That celebrated microscopist
reports that he found South American infusoria in the blood-
rains and sea-dust of the Cape Yerd Islands, Lyons, Genoa, and
other places (§ 325); thus confirming, as far as such evidence
can, the indications of our observations, and increasing the pro-
bability that the general course of atmospherical circulation is
in conformity with the suggestions of the facts gathered from the
sea as I had interpreted them, viz., that the trade- winds of the
southern hemisphere, after arriving at the belt of equatorial
calms, ascend and continue in their course towards the calms of
Cancer as an upper current from the south-west, and that aftei
passing this zone of calms, they are felt on the surface as the
prevailing south-west winds of the extra-tropical parts of our
hemisphere; and that for the most part, they bring their
moisture with them from the trade-wind regions of the opposite
hemisphere. I have marked on Plate YII. the supposed track
of the " Passat-Staub," showing where it was taken up in South
America, as at P P, and where it was found, as at S S ; the part
of the line in dots denoting where it was in the upper current,
and the unbroken line where it was wafted by a surface current ;
also on the same plate is designated the part of the South Pacific
in which the vapour-springs for the Mississippi rains are sup-
posed to be. The hands (s^) point out the direction of the
wind. Where the shading is light the vapour is supposed to be
earned by an upper current. Such is the character of the cir-
cumstantial evidence which induced me to suspect that some
agent, whose office in the grand system of atmospherical circula-
tion is neither understood nor recognized, was at work in these
calm belts and other places. It may be electrical, or it may be
magnetic, or both conjoined.

359. Quetelefs observations. — The more we study the workings
of the atmospherical machinery of our planet, the more are we
impressed with the conviction that we as yet know very little
concerning its secret springs, and the little "governors" here
and there which regulate its movements. My excellent friend
M. Quetelet, the astronomer royal at Brussels, has instituted a
most excellent series of observations upon atmospherical elec-
tricity. He has shown that there is in the upper regions of the
air a great reservoir of positive electricity, which increases as
the temperature diminishes. So, too, with the magnetism of the
oxygen in the upper regions.

174 PHYSICAL GEOGSAPHT OF THE SEA, AND ITS METEOROLOGY.

360. At sea in the southern hemisphere ice have tlie rule, on land in
the northern the exceptions, as to the general circulation of the atmo-
sphere.— In the southern hemisphere, we may, by reason of its
great aqueous area, suppose the general law of atmospherical
movements to be better developed than it is in the northern
hemisphere. We accordingly see by the table (§ 353) that the
movements north and south between 45° and 50° correspond
with the movements south and north between 25° and 30° ; that
as you go from the latter band towards the equator the winds with
southing in them increase, while the winds with northing in
them increase as you go from the former towards the pole.

361. TJie magnetic poles, the poles of the wind and of cold coinci-
dent.— This is the law in both hemispheres : thus indicating that
there must be in the polar regions, as in the equatorial, a calm
place, where these polar-bound winds cease to go forward, rise
up, and commence their return (§ 214) as an upper current. So
we have theoretically a calm disc, a polygon — not a belt — about
each pole. The magnetic poles and the poles of maximum cold
(§ 347) are coincident. Do not those calm discs, or " poles ot
the wind," and the magnetic poles, cover the same spot, the two
standing in the relation of cause and effect ? This question was
first asked several years ago,* and I was then moved to pro-
pound it by the inductions of theoretical reasoning. Observers,
perhaps, may never reach those inhospitable regions with their
instruments to shed more light upon this subject; but Parry and
Barrow have found reasons to believe in the existence of a per-
petual calm about the north pole, and later, Bellot has reported
the existence of a calm region within the frigid zone. Professoi-
J. H. Coffin, in an elaborate and valuable paper t on the " Winds
OF THii Northern Hemisphere," arrives by deduction at a like
conclusion. In that paper he has discussed the records at no
less than five hundred and seventy-nine meteorological stations,
embracing a totality of observations for two thousand eight hun-
dred and twenty -nine years. He places his " meteorological
pole " — pole of the winds — near latitude 84° north, longitude 105°
west. The pole of maximum cold, by another school of philo-
sophers, Sir David Brewster among them, has been placed in
latitude 80° north, longitude 100° west; and the magnetic pole,
by still another school, J in latitude 7o° 35' north, longitude

* l\Iaury's Sailinj^ Directions.

t Smitlibouian Contributions to Knowledge, vol. vi., 1854. t Gauss.

EASTING OF THE TRADE-WINDS, ETC. 175

95° 39' west. Neither of these poles i« a point susceptible of
definite and exact position. The polar calms are no more a point
than the equatorial calms are a line ; and, considering that these
poles are areas or discs, not points, it is a little curious that phi-
losophers in different parts of the world, using different data,
and following up investigation each through a separate and in-
dependent system of research, and each aiming at the solution of
different problems, should nevertheless agree in assigning very
nearly the same position to them all. Are these three poles
grouped together by chance or by some ph^^sical cause ? By the
latter, undoubtedly. Here, then, we have another of those gos-
samer-like clews, that sometimes seem almost palpable enough
for the mind, in its happiest mood, to lay hold of, and follow up
to the very portals of knowledge, where we pause and linger,
fondly hoping that the chambers of hidden things may be thrown
open, and that we may be permitted to behold and contemplate
the mysteries of the winds, the frost, and the trembling needle.
In the polar calms there is (§ 215) an ascent of air; if an ascent,
a diminution of pressure and an expansion; and if expansion, a
decrease of temperature. Therefore we have palpably enough a
connecting link here between the polar calms and the polar place
of maximum cold. Thus we establish a relation between the
pole of the winds and the pole of cold, with evident indications
that there is also a physical connection between these and the
magnetic pole. Here the out-croppings of a relation between
magnetism and the circulation of the atmosphere again appear.

362. Tlie barometer in the wind hands. — Thousands of observa-
tions, made by mariners and recorded in their abstract logs, have
enabled us to determine approximately the mean height of the
barometer for the various bands (§ 352) at sea. Between the
parallels of 36° S. and 50° N., Lieut. Andrau, of the Dutch Navy,
has collected from the abstract logs at the Meteorological Insti-
tute of Utrecht no less than 83,334 observations on the height of
the barometer in the following bands. (See table, page 176.)

863. More atmosphere in the northern than in the southern hemi-
sphere.—Tho diagram of the winds (Plate I.) has been c-on-
structed so as to show by its shaded border this unequal
distribution of the atmosphere between the two hemispheres.
Have we not here proof that the southern hemisphere (§ 261) is
indeed the boiler to this mighty atmospherical engine ? The
aqueous vapour rising from its waste of waters drives the nir

176 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOROLOGY,

Number of Observations and Mean Height of the Barometer between the Faralldn

of 780 37' jv. and 74° S*

North.

Barometer.

No.

Soutlj.

Barometer.

No.

0^ and 50 0)

29.915

5114

00 and 5^

29.940

3692

5^ and 10^

29.922

5343

53 and 100

29.981

3924

10^ and \rP

29.964

4496

10° and 15°

30.028

4166

150 and 203

30.018

3592

15° and 20°

30.060

4248

20^ and 2.5 ^

30.081

3816

20° and 253

30.102

4536

253 and 30^

30.149

4392

25^ and 30 ^

30.095

4780

30^ and 35^

30.210

4989

30° and 36° (i)

30.052

6970

353 and 40^

30.124

5103

42° 53'

29.90 {")

40^ and 453

30.077

5898

450 0'

29.66 (6)

453 and 50^

30.060

8282

49° 08'

29.47

5P 29'

29.99 (2)

51° 33'

29.50

59'^ 51'

29.88 (3)

540 26'

29.35

78^ 37'

29.759 (4j

55° 52'
60° 0'
66° 0'
74° 0'

29.36
29.11

29.08
28.93

(1) From 50° N. to 36° S. the observations are the mean of 83,334 taken from " Maandelijksche
ZeilaanwijziDgen van Java naar het Kanaal Koninklijk Nederlandsch Meteorologisch Instituut
1859."

(2) Greenwich ; mean of 4 years' observations.

(3) St. Petersburg; mean of 10 years' observations.

(*) Dr. Kane"; 12,000 observations (mean of 17 months' observations).
(5) Hobart Town ; mean of 10 yeai's' observations.
(«) Sir J. C. Eoss ; " Erebus and Terror."

away from tlie austral regions, just as the vapour that is fonned
in the real steam-boiler expels the air from it. This difference
of atmosphere over the two halves of the globe, as indicated by
the barometer, is very suggestive.

364. A standard of comparison for the barometer at sea. — Admiral
Fitzroy has also reduced from the abstract logs in the Meteoro-
logical Department of the Board of Trade in London a great
number of barometrical observations. He has discovered that
near the parallel of 5° N. in the Atlantic Ocean the pressure of
the atmosphere is so uniform as to afford navigators a natural
standard by which, out there at sea, they may, as they pass to
and fro, compare their barometers. This pressure is said to be
so uniform, that after allowing for the six-hourly fluctuations,
the mariner may detect any error in his barometer amounting to
the two or three thousandth part of an inch.

365. South-east trade-winds having no moisture traced over into

* Below the parallels of 50"^ N. and 36° S. the observations are iceduced to
the te-icp. of 32"^ Fahr

E\STING OF THE TEADE-WINDS, ETC. lit

rainless regions of the northern hemisphei'e. — According to the views
presented in § 358 and Plate YII., the south-east trade-winds,
which reach the shores of Brazil near the parallel of Eio,
and which blow thence for the most part over the land, should
be the winds which, in the general course of circulation, would
be carried, after crossing the Andes and rising up in the belt of
equatorial calms, towards Northern Africa, Spain, and the South
of Europe. They might carry with them the infusoria of Ehren-
berg (§ 358), but according to this theory, they would be wanting
in moisture. Now, are not those portions of the Old World, for
the most part dry countries, receiving but a small amount of pre-
cipitation ? Hence the general rule : those countries to the
north of the calms of Cancer, which have large bodies of land
situated to the southward and westward of them, in the south-
east trade- wind region of the earth, should have a scanty supply
of rain, and vice versa. Let us try this rule : The extra-tropical
part of New Holland comprises a portion of land thus situated in
the southern hemisphere. Tropical India is to the northward
and westward of it ; and tropical India is in the north-east trade-
wind region, and should give extra-tropical New Holland a
slender supply of rain. But what modifications the monsoons of
the Indian Ocean may make to this rule, or what effect they may
have upon the rains in New Holland, my investigations in that
part of the ocean have not been carried far enough for final
decision ; though New Holland is a dry country.

oQQ. Each hemisphere receives from the sun the same amount of
heat. — The earth is nearer to the sun in the summer of the
southern hemisphere than it is in the summer of the northern ;
consequently, it has been held that one hemisphere annually
receives more heat than the other. But the northern summer is
7*7 days longer than the southern; and Sir John Herschel has
shown, and any one who will take the trouble may demonstrate,
that the total amount of direct solar heat received annually
by each hemisphere is identically the same, and therefore the
northern hemisphere in its longer summer makes up with heat
for the greater intensity but shorter duration of the southern
sinnmer. But though the amount of heat annually impressed by
the sun upon each hemisphere be identically the same, it by no
means follows that the amount radiated off into space by each
hemisphere again is also identically the same. There is no
reason to believe that the earth is growing warmer or cooler, and

178 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOPvOLOGY.

therefore we infer that the total amount of heat received annu
ally by the whole earth is again annually radiated from the whole
earth. Nevertheless, the two hemispheres may radiate very
unequally.

367. Tlie northern radiates most. — Direct observations concernino*
the amount of radiation from different parts of the surface of our
planet are meagre, and the results as to quantity by no means
conclusive ; but we have in the land and sea breezes a natural
index to the actinometry of sea and land, which shows that the
radiating forces of the two are very different. Notwithstanding
the temperature of the land is raised so much above that of the
waters during the day, its powers of radiation are so much
greater than those of water that its temperature falls during the
night below that of the sea, and so low as to produce the land
breeze. From this fact it may be inferred that the hemisphere
that has most land dispensed most heat by radiation.

368. Another proof of the crossings at the calm helts. — The
question now may be well put : Since the two hemispheres
receive annually the same amount of heat from the sun, and
since the northern hemisphere, with its greater area of land,
radiates most, whence does it derive the surplus ? The theory of
the crossing at the calm belts indicates both the way and the
means, and suggests the answer ; for it points to the latent heat
of vapour that is taken up in the southern hemisphere, trans-
ported by the winds across the calm belts, and liberated, as the
clouds drop down their fatness upon northern fields. It is
not only the difference of radiating power between land and
water that makes the northern continents the chimneys of the
earth, but the diffe^rence of cloud in a continental and an oceanic
sky must also greatly quicken the radiating powers of the
northern hemisphere. Radiation goes on from the upper surface
of the clouds and from the atmosphere itself, but we know that
clouds in a great measure obstruct radiation from the surface of
the earth ; and as the surface of the earth receives more of the
direct heat of the sun than the atmosphere, the point under dis-
cussion relates to the mode in which the surface of the earth gets
rid of that heat. It gets rid of it chiefly in three ways : some is
carried off by convection in the air ; some by evaporation ; and
some by radiation ; and such is the interference of clouds with
this last-named process, that we are told that during the rainy
season in intertropical countries, as on the coast of Africa, ther^

CURRENTS OF THE SEA. 179

IS often not radiation enough to produce the phenomena of land
and sea breezes. The absence of dew in cloudy nights is a
familiar instance of the anti-radiatiiig influence of clouds. The
southern hemisphere, being so much more aqueous, is no doubt
much more enveloped with clouds where its oceans lie, than is
the northern where its continents repose, and therefore it is that
one hemisphere radiates more than the other.

369. Facts and pearls. — Thus, by obserying and discussing, by
resorting to the force of reason and to the processes of induction,
we have gathered for the theory that favours the air-crossings at
the calm belts fact upon fact, which, like pearls for the necklace,
seemed only to require a string to hang them together.

CHAPTEE VIII.

§ 370-409. — CURRENTS OF THE SEA.

370. Ohedient to order. — We here set out with the postulate that the
sea, as well as the air, has its system of circulation, and that this
system whatever it be, and wherever its channels lie, whether in
the waters at or below the surface, is in obedience to law. The
sea, by the circulation of its waters, doubtless has its offices to
perform in the terrestrial economy ; and when we see the
currents in the ocean running hither and thither, we feel that
they were not put in motion without a cause. On the contrary,
we know they move in obedience to some law of Nature, be it
recorded down in the depths below, never so far beyond the
reach of human ken ; and being a law of Nature, we know who
gave it, and that neither chance nor accident had anything to do
with its enactment. Nature grants us all that this postulate
demands, repeating it to us in many forms of expression : she
utters it in the blade of green grass which she causes to grow in
climates and soils made kind and genial by warmth and moisture
that some current of the sea or air has conveyed far away from
under a tropical sun. She murmurs it out in the cooling current
of the north ; the whales of the sea tell of it (§ 1 58) ; and all its
inhabitants proclaim it.

371. TJie fauna and flora of the sea. — The fauna and the flora of
the sea are as much the creatures of climate (§ 164), and are aa

N 2

180 PHTBICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

dependent for their well-being upon temperature, as are the
fauna and the flora of the dry land. Were it not so we should
find the fish and the algae, the marine insect and the coral, dis-
tributed equally and alike in all parts of the ocean. The arctic
whale would delight in the torrid zone, and the habitat of the
pearl oyster would be also under the iceberg, or in the frigid
waters of polar seas

372. Those of scuthern unlike tliose of nortliern seas. — Never-
theless, though the constituents of sea water be the same in kind,
we must not infer that they are the same in degree throughout
all parts of the ocean, for there is a peculiarity, perhaps of
temperature, perhaps of transparency, which marks the inhabit-
ants of trans-equatorial seas. MM. Peron and Le Sueur, who
have turned their attention to the subjectj assert that out of
many thousand examples they did not find a single one in which
the inhabitants of trans-equatorial were not distinguishable from
those of their species in cis-equatorial seas.

373. Tlie capacity of icaier to convey heat. — Water, while its
capacities for heat are scarcely exceeded by those of any other
substance, is one of the most complete of non-conductors. Heat
does not permeate water as it does iron, for instance, or other
good conductors. Heat the top of an iron plate, and the bottom
becomes warm ; but heat the top of a sheet of water, as in a pool
or basin, and that at the bottom remains cool. The heat passes
through iron by conduction, but to get through water it requires
to be conveyed by a motion, which in fluids we cali currents.
Therefore the study of the climates of the sea involves a know-
ledge of its currents, both cold and warm. They are the channels
through which the waters circulate, and by means of which the
harmonies of old ocean are preserved.

374. Currents of the sea to he considered in pairs. — Hence, in
studying the system of oceanic circulation, we set out with the
very simple assumption, viz., that from whatever part of the
ocean a current is found to run, to the same part a current of
equal volume is bound to return ; for upon this principle is based
the whole system of currents and counter- currents of the air as
well as of the water. Hence, the advantage of considering them
as the anatomist does the nerves of the human system — in pairs.
Currents of water, like currents of air, meeting from various
directions, create gyrations, which in some parts of the sea, as on
the coast of Norway, assume the appearance of whirlpools, as

CURRENTS OF THE SEA. 181

tbongli the water were drawn into a cliasm below. The cele-
brated Maelstrom is caused by such a conflict of tidal or other
streams. The late Admiral Beechey, E.N.,* gave diagrams
illustrative of many " rotatory streams in the English Channel, a
number of which occur between the outer extremities of the
channel tide and the stream of the oceanic or parent wave."
" They are clearly to be accounted for," says he, " by the streams
acting obliquely upon each other."

375. Marine currents do not, like those on land, run of necessity
from higher to lower levels. — It is not necessary to associate with
oceanic currents the idea that they must, of necessity, as or^
land, run from a higher to a lower level. So far from this
being the case, some currents of the sea actually run up hill,
while others run on a level. The Gulf Stream is of the first
class (§ 83).

376. The Bed Sea current. — The currents which run from the
Atlantic into the Mediterranean, and from the Indian Ocean into
the Eed Sea, are the reverse of this. Here the bottom of the
current is probably a water-level, and the top an inclined plane,
running down hill. Take the Eed Sea current as an illustration.
That sea lies, for the most part, within a rainless and riverless
district. It may be compared to a long and narrow trough.
Being in a rainless district, the evaporation of it is immense ;
none of the water thus taken up is returned to it either by rivers
or rains. It is about one thousand miles long ; it lies nearly
north and south, and extends from latitude 13° to the parallel of
30° north. From May to October, the water in the upper part
of this sea i« said to be two feet lower than it is near the mouth. f
This change or difference of level is ascribed to the effect of the
wind, which, prevailing from the north at that season, is supposed
to blow the water out. But from May to October is also the hot
season ; it is the season when evaporation is going on most
rapidly : and when we consider how dry and how hot the winds
are which blow upon this sea at this season of the year ; that it is
a narrow sea ; that they blow across it and are not saturated, we
may suppose the daily evaporation to be immense. The evapo-
ration from this sea and the Persian Gulf is probably greater
than it is from any other arms of the ocean. We know that the

* See an interesting paper by him on Tidal Streams of the North Sea and
English Channel, p. 703 ; Phil. Transactiens, Part ii., 1851.
t Johnston's Physical Atlaa.

182 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

waste from canals by evaporation, in the summer-time, is an
element which the engineer, when taking the capacity of his
feeders into calculation, has to consider. With him it is an
important element : how much more so must the waste by
evaporation from this sea be when we consider the physical
conditions under which it is placed ! Its feeder, the Arabian
Sea, is a thousand miles from its head ; its shores are burning
sands ; the evaporation is ceaseless ; it is a natural evaporating
dish (§ 525) on a grand scale; none of the vapours which the
scorching winds that blow over it carry away are returned to it
again in the shape of rains. The Eed Sea vapours are carried off
and precipitated elsewhere. The depression in the level of its
head waters in the summer-time, therefore, it appears, is owing
to the effect of evaporation, as well as to that of the wind blowing
the waters back. The evaporation in certain parts of the Indian
Ocean is supposed to be (§ 103) from three fourths of an inch to
an inch daily. Whatever it be, it is doubtless greater in the
Eed Sea. Let us assume it, then, in the summer-time to average
only half an inch a day. Now, if we suppose the velocity of the
current which runs into that sea to average, from mouth to head,
twenty miles a day, it would take the water fifty days to reach
the head of it. If it lose half an inch from its surface by evapo-
ration daily, it would, by the time it reaches the Isthmus of
Suez, have lost twenty-five inches from its surface. Thus the
waters of the Eed Sea ought to be lower at the Isthmus of Suez
than they are at the Straits of Babelmandeb. Independently of
the forcing out by the wind, the waters there ought to be lower
■from two other causes, viz., evaporation and temperature ; for the
temperature of that sea is necessarily lower at Suez, in latitude
30'^, than it is at Babelmandeb, in latitude 13°. To make it
quite clear tha-t the surface of the Eed Sea is not a sea level, but
is an inclined plane, suppose the channel of the Eed Sea to have a
perfectly smooth and level floor, with no water in it, and a wave
ten feet high to enter the Straits of Babelmandeb, and to flow up
the channel, like the present surface current, at the rate of twenty
miles a day for fifty days, losing daily, by evaporation, half an
inch ; it is easy to perceive that, at the end of the fiftieth day,
this wave would not be so high by two feet (twenty-five inches)
as it was the first day it commenced to flow. The top of that sea,
therefore, may be regarded as an inclined plane, made so by
evaporation.

CURRENTS OF THE SEA. 183

377. JTpper and under currents through straits explained. — But tlie
salt water, wliicli has lost so much of its freshness by evapo-
ration, becomes salter, and therefore heavier. The lighter water
at the Straits cannot balance the heavier water at the Isthmus,
and the colder and salter, and therefore heavier water, must
either run out as an under current, or it must deposit its surplus
salt in the shape of crystals, and thus gradually make the bottom
of the Eed Sea a salt-bed, or it must abstract all the salt from the
ocean to make the Eed Sea brine — and we know that neither the
one process nor the other is going on. Hence we infer that
there is from the Eed Sea an under and outer current, as there is
from the Mediterranean through the Straits of Gibraltar, and
that the surface waters near Suez are salter than those near the
mouth of the Eed Sea. And, to show why there should be an
outer and under current from each of these two seas, let us
suppose the case of a vat of oil, and a vat of wine connected by
means of a narrow trough — the trough being taken to represent
the straits connecting seas the w^aters of which differ as to
specific gravity. Suppose the trough to have a flood-gate, which
is closed until we are ready for the experiment. Now let the
two vats be filled, one with wine the other with oil, up to the
same level. The oil is introduced to represent the lighter water
as it enters either of these seas from the ocean, and the wine the
same water after it has lost some of its freshness by evaporation,
and therefore has become salter and heavier. Now suppose the
flood-gate to be raised, what would take place? Why, the oil
would run in as an upper current, overflowing the wine, and the
wine would run out as an under current.

378. The Mediterranean current. — The rivers which discharge
their waters into the Mediterranean are not sufficient to supply
the waste of evaporation, and it is by a process similar to this
that the salt which is carried in from the ocean is returned to
the ocean again : were it not so, the bed of that sea would be a
mass of solid salt. The unstable equilibrium of the seas is a
physical necessity. Were it to be lost, the consequences would
be as disastrous as would be any derangement in the forces of
gravitation. Without doubt, the equilibrium of the sea is pre-
served by a system of compensation as exquisitely adjusted as
are those by which the " music of the spheres " is maintained.
It is difficult to form an adequate conception of the immense

184 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

quantities of solid matter whicli the current from the Atlantic,
holding in solution, carries into the Mediterranean. In his
abstract log for March 8th, 1855, Lieutenant William Grenville
Temple, of the United States ship Levant, homeward bound,
has described the indraught there : " Weather fine ; made 11 pt.
lee-way. At noon, stood in to Almiria Bay, and anchored off the
village of Eoguetas. Found a great number of vessels waiting
for a chance to get to the westward, and learned from them that
at least a thousand sail are weather-bound between this and
Gibraltar. Some of them have been so for six weeks, and have
even got as far as Malaga, only to be swept back by the current.
Indeed, no vessel had been able to get out into the Atlantic for
three months past." Now suppose this current, which baffled
and beat back this fleet for so many days, ran no faster than two
knots the hour. Assuming its depth to be 400 feet only, and its
width seven miles, and that it carried in with it the average pro-
portion of solid matter — say one thirtieth — contained in sea
water; and admitting these postulates into calculation as the
basis of the computation, it appears that salts eilough to make no
less than 88 cubic miles of solid matter, of the density of water,
were carried into the Mediterranean during these 90 days.
Now, unless there were some escape for all this solid matter, which
has been running into that sea, not for 90 days merely, but for
ages, it is very clear that the Mediterranean would, ere this, have
been a vat of very strong brine, or a bed of cubic crystals.

379. Tlie Suez Canal. — 'We have in this fact, viz., the difiSculty
of egress from the Mediterranean, and the tedious character of
the navigation, under canvas, within it, the true secret of the
indifference which, in commercial circles in England and the
Atlantic states of Europe, is manifested towards the projected
Suez Canal. But to France and Spain on the Mediterranean, to
the Italian States, to Greece, and Austria, it would be the
greatest commercial boon of the age. The Mediterranean is a
great gulf running from west to east, penetrating the old world
almost to its very centre, and separating its most civilized from
its most savage communities. Its southern shores are inhabited,
for the most part by an anti-commercial and thriftless people.
On the northern shores the climates of each nation are nearly
duplicates of the climates of her neighbours to the east and the
west; consequently, these nations all cultivate the same staples,

CUEEENTS OF THE SEA. 185

and have wants that are similar : for a commerce among them-
selves, therefore, they lack the main elements, viz., difference of
production, and the diversity of wants which are the consequence
of variety of climates. To reach these, the Mediterranean people
have had to encounter the tedious navigation and the sometimes
difficult egress — just described — from their sea. Clearing the
Straits of Gibraltar, their vessels do not even then find them-
selves in a position so favourable for reaching the markets of
the world as they would be were they in Liverpool or off the
Lizard. Such is the obstruction which the winds and the current
• from the Atlantic offer to the navigation there, that vessels
bound to India from the United States, England, or Holland,
may often double the Cape of Good Hope before one sailing
with a like destination from a Mediterranean port would find
herself clear of the Straits of Gibraltar. It is therefore not
surprising that none of the great commercial marts of the pre-
sent day are found on the shores of this classic sea. The people
who inhabit the hydrographic basin of the Mediterranean —
which includes the finest parts of Europe — have, ever since the
discovery of the passage around the Cape of Good Hope, been com-
mercially pent up. A ship-canal across the Isthmus of Suez will
let them out into the commercial world, and place them within a
few days of all the climates, wants, supplies, and productions of
India. It will add largely to their wealth and prosperity. As
these are increased, trading intercourse is enhanced, and so by
virtue of this canal they will become better customers for
England and Holland, and all other trading nations whose ports
are havens of the Atlantic. Occupying this stand-point in their
system of commercial economy, the people of the United States
await with a lively interest the completion of the Suez Canal.

380. Hydrometrical observations at sea wanted. — Of all parts of
the ocean, the warmest water, the saltest and the heaviest too,
is said to be found in the seas of the Indian Ocean. A good
series of observations there with the hydrometer, at the different
seasons of the year, is a desideratum. Taking, however, such as
we have upon the density of the water in the Eed Sea and the
Mediterranean, and upon the under currents that run out from
these seas, let us examine results.

381. Specific gravity of Med Sea water. — Several years ago, Mr.
Morris, chief engineer of the Oriental Company's steam-ship
Ajdaha, collected specimens of Ked Sea water all the way from

186 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOKOLOGY.

Suez to the Straits of Babelmandeb, wliicli were afterwards ex
amined by Dr. Giraud, who reported the following results : *

No.

Latitude,
Degrees.

Longitude:
Degrees.

Spec. Grav.

Saline Co
1000 par

1.

Sea of Suez . .

.

1027

41.0

2.

Gulf of Suez

. 27.49

33.44

1026

40.0

3.

Eed Sea . . .

24.29

36.

1024

39.2

4.

Ditto . . .

. 20.55

38.18

1026

40.5

5.

Ditto . . .

. 20.43

40.03

1024

39.8

6.

Ditto . . •.

. 14.35

42.43

1024

39.9

7.

Ditto . . .

12.39

44.45

1023

39.2

These observations agree with the theoretical deductions just
announced, and show that the surface waters at the head are
heavier and Salter than the surface waters at the mouth of the
Eed Sea.

382. Evaporation from. — ^In the same paper, the temperature of
the air between Suez and Aden often rises, it is said, to 90'^,
" and probably averages little less than 75° day and night all
the year round. The surface of this sea varies in heat from 65°
to 85°, and the difference between the wet and dry bulb ther-
mometers often amounts to 25° — in the kamsin, or desert winds
to from 30° to 40° ; the average evaporation at Aden is about
eight feet for the year." " Kow assuming," says Dr. Buist,
'' the evaporation of the Eed Sea to be no greater than that ol
Aden, a sheet of water eight feet thick, equal in area to the
whole expanse of that sea, will be carried off annually in vapour ;
or, assuming the Eed Sea to be eight hundred feet in depth at
an average — and this, most assuredly, is more than double the
fact — the whole of it would be dried up, were no water to enter
from the ocean, in one hundred years. The waters of the Eed
Sea, throughout, contain some four per cent, of salt by weight —
or, as salt is a half heavier than water, some 2.7 per cent, in
bulk — or, in round numbers, say three per cent. In the course
of three thousand years, on the assumptions just made, the Eed
Sea ought to have been one mass of solid salt, if there were no
current running out." Now we know the Eed Sea is more than
three thousand years old, and that it is not filled with salt ; and
the reason is, that as fast as the upper currents bring the salt in
at the top, the under currents carry it out at the bottom.

383. Thk MKDiTiaaiANEAX Cuiirents. — With regard to aji
*• Tranijfict. of the Bombay Gcograph. See. vol. ix., May, 1849, to August, ISoO.

CUREENTS OF THE SEA. 187

nnder current from the Mediterranean, we may begin by re-
marking that we know that there is a current always setting
in at the surface from the Atlantic, and that this is a salt-water
current, which carries an immense amount of salt into that sea.
We know, moreover, that that sea is not salting up ; and there-
fore, independently of the postulate (§ 374) and of observations,
we might infer the existence of an under current, through which
this salt finds its way out into the broad ocean again.*

384. Tlie drift of the Phoenix. — With regard to this outer and
under current, we have observations telling of its existence as
long ago as 1712. " In the year 1712," says Dr. Hudson, in a
^japer communicated to the Philosophical Society in 1724,
" Monsieur du L'Aigle, that fortunate and generous commander
of the privateer called the Phoenix, of Marseilles, giving chase
near Ceuta Point to a Dutch ship bound to Holland, came up
with her in the middle of the Gut between Tariffa and Tangier,
and there gave her one broadside, which directly sunk her, all
her men being saved by Monsieur du L'Aigle ; and a few days
after, the Dutch ship, with her cargo of brandy and oil, arose on
the shore near Tangier, which is at least four leagues to the
westward of the place where she sunk, and directly against the
strength of the current, which has persuaded many men that
there is a recurrency in the deep water in the middle of the Gut

* Dr. Smith appears to have been the first to conjecture this explanation,
which he did in 1673 {vide Philosophical Transactions). This continual in-
draught into the Mediterranean appears to have been a vexed question among
the navigators and philosophers even of those times. Dr. Smith alludes to
several hypotheses which had been invented to solve these phenomena, such as
subterraneous vents, cavities, exhalation by the sun's beams, etc., and then offers
his conjecture, wliich, in his own words, is, "that there is an under current, by
which as great a quantity of water is carried out as comes flowing in. To con-
firm which, besides what I have said above about the difference of tides in the
offing and at the shore in the Downs, which necessarily supposes an under
current, I shall present you with an instance of the like nature in the Baltic
Sound, as I received it from an able seaman who was at the making of the
trial. He told me that, being there in one of the king's frigates, they went
with their pinnace into the mid stream, and were carried violently by the cm--
rent; that, soon after this, they sunk a bucket with a heavy cannon ball to a
certain depth of water, which gave a check to the boat's motion ; and, sinking
it stiU. lower and lower, the boat was driven ahead to the windward against the
upper current : the current aloft, as he added, not being over four or five
fathoms deep, and that the lower the bucket was let fall, they found the uiidei
current the stronger."

188 PHYSICAL GECGEAPHY OP THE SEA, AND ITS 31ETE0E0L0QT.

that sets outward to the grand ocean, which this accident very
much demonstrates ; and, possibly, a great part of the water
which runs into the Straits returns that way, and along the two
coasts before mentioned; otherwise this ship must, of course,
have been driven towards Ceuta, and so upwards. The water in
the Gut must be very deep ; several of the commanders of our
ships of war having attempted to sound it with the longest lines
they could contrive, but could never find any bottom."

385. Saltness of the Mediterranean. — In 1828, Dr. Wollaston, in
a paper before the Philosophical Society, stated that he found
the specific gravity of a specimen of sea water, from a depth of
six hundred and seventy fathoms, fifty miles within the Straits
to have a " density exceeding that of distilled water by more
than four times the usual excess, and accordingly leaves, upon
evaporation, more than four times the usual quantit}^ of saline
residuum. Hence it is clear that an under current outward of
such denser water, if of equal breadth and depth with the
current inward near the surface, would carry out as much salt
below as is brought in above, although it moved with less than
one fourth part of the velocity, and would thus prevent a per-
petual increase of saltness in the Mediterranean Sea beyond that
existing in the Atlantic." The doctor obtained this specimen of
sea water from Captain, now Admiral Smyth, of the English
Navy, who had collected it for Dr. Marcet. Dr. Marcet died
before receiving it, and it had remained in the admiral's hands
some time before it came into those of Wollaston. It may,
therefore, have lost something by evaporation ; for it is difficult
to conceive that all the river water, and three fourths of the sea
water which runs into the Mediterranean, is evaporated from it,
leaving a brine for the under current having four times as much
salt as the water at the surface of the sea usually contains. Very
recently, M. Coupvent des Bois is said to have shown, by actual
observation, the existence of an outer and under current from
the Mediterranean.

386. The escape of salt and heavy water hy under currents. — How-
ever that may be, these facts, and the statements of the Secre-
tary of the Geographical Society of Bombay (§ 382), seem to
leave no room to doubt as to the existence of an under current
both from the Ked Sea and Mediterranean, and as to the cause of
the surface current which flows into them. I think it a matter
of demonstration. It is accounted for (§ 377) by the salts of tha

CURRENTB OF THE SEA. 189

sea. Writers whose opinions are entitled to great respect differ
with me as to the conclusiveness of this demonstration. Among
those writers are Admiral Smyth, of the British Kavy, and Sir
Charles Lyell, who also differ with each other. In 1820, Dr.
Marcet being then engaged in studying the chemical composition
of sea water, the admiral, with his nsnal alacrity for doing "a
kind tiim," undertook to collect for the doctor specimens of
Mediterranean water from various depths, especially in and
about the Straits of Gibraltar. Among these was the one (§ 385)
taken fifty miles withia the Straits from the depth of six hundred
and seventy fathoms (four thousand and twenty feet), which,
being four times Salter than common sea water, left, as we have
just seen, no doubt in the mind of Dr. Wollaston as to the
existence of this under current of brine. But the indefatigable
admiral, in the course of his celebrated survey of the Mediterra-
nean, discovered that, v>^hile inside of the Straits the depth was
upwards of nine hundred fathoms, yet in the Straits themselves
the depth across the shoalest section is not more than one
hundred and sixty* fathoms. " Such being the case, we can
now prove," exclaims Sir Charles Lyell, " that the vast amount
of salt brought into the Mediterranean does not pass out again by
the Straits ; for it appears by Captain Smyth's soundings, which
Dr. Wollaston had not seen, that between the Capes of Trafalgar
and Spartel, which are twenty-two miles apart, and where the
Straits are shallowest, the deepest part, which is on the side of
Cape Spartel, is only two hundred and twenty fathoms. | It is
therefore evident, that if water sinks in certain parts of the
Mediterranean, in consequence of the increase of its specific
gravity, to greater depths than two hundred and twenty fathoms,
it can never flow out again into the Atlantic, since it must
be stopped by the submarine barrier which crosses the shallowest
part of the Straits of Gibraltar. J"

387. Vertical circulation in the sea a pliysical necessity. — Accord-
ing to this reasoning, all the cavities, the hollows, and the
valleys at the bottom of the sea, especially in the trade-wind
region, where evaporation is so constant and great, ought to be
salting up or filling up with brine. Is it probable that such a
process is actually going on ? No. According to this reasoning,

* " The Mediterranean."

t One hundred and sixty, Smyth.
J I^y ell's Principles of Geology, p, 334-5, ninth edition. London, 1858.

190 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

the water at the bottom of the great American lakes ought (o
remain there for ever, for the bottom of Erie is far below the
barrier which separates this lake from the Falls of Niagara, and
so is the bottom of every one of the lakes below the shallows in
the straits or rivers that connect them as a chain. We may
presume that the water at the bottom of every extensive and
quiet sheet of water, whether salt or fresh, is at the bottom
by reason of specific gravity ; but that it does not remain there
for ever we have abundant proof. If so the Niagara River
would be fed by Lake Erie only from that layer of water which
is above the level of the top of the rock at the Falls. Con-
sequently, wherever the breadth of that river is no greater
than it is at the Falls, we should have a current as rapid as
it is at the moment of passing the top of the rock to make
the leap. To see that such is not the way of Nature, we
have but to look at any common mill-pond when the water
is running over the dam. The current in the pond that feeds
the overflow is scarcely perceptible, for " still water runs
(Jeep." Moreover, we know it is not such a skimming current
as the geologist would make, which runs from one lake to
another ; for wherever above the Niagara Falls the water is
deep, there we are sure to find the current sluggish, in com-
parison with the rate it assumes as it approaches the Falls ; and
it is sluggish in deep places, rapid in shallow ones, because it is
fed from below. The common " wastes " in our canals teach us
this fact.

388 Tlie bars at the mouths of the Mississip]?i an illustration. — Th^
reasoning of this celebrated geologist appears to be founded
upon the assumption that when water, in consequence of its
specific gravity, once sinks below the bottom of a current where
it is shallowest, there is no force of traction, so to speak, in fluids,
nor any other power, which can draw this heavy water up again.
If such were the case, we could not have deep water immediately
inside of the bars which obstruct the passage of the great rivers
into the sea : the bar at the mouth of the Mississippi, with only
fifteen feet of water on it, is estimated to travel out to sea at
rates varying from twenty to one hundred yards a year. In the
place where that bar was when it was one thousand yards nearer
to New Orleans than it now is, whether it were fifteen years ago
or a century ago, with only fifteen or sixteen feet of water on it,
we have now four or five times that depth. As new bars were

CUERENTS OF THE SEA. 191

successively formed seaward from the old, wliat dug up the
sediment which formed the old, and lifted it up from where
specific gravity had placed it, and carried it out to sea over a
barrier not more than a few feet from the surface ? Indeed, Sir
Charles himself makes this majestic stream to tear up its own
bottom to depths far below the top of the bar at its mouth. He
describes the Mississippi as a river having nearly a uniform
breadth to the distance of two thousand miles from the sea.* He
makes it cut a bed for itself out of the soil, which is heavier than
Admiral Smyth's deep sea water, to the depth of more than two
hundred feetf below the top of the bar which obstructs its en-
trance into the sea. Could not the same power which scoops out
this solid matter for the Mississippi draw the brine up from the
pool in the Mediterranean, and pass it out across the barrier in
the Straits ? The currents which run over the bars and shoals
in our rivers are fed from the pools above with water which we
know comes from depths far below the top of such bars. The
breadth of the river where the bar is may be the same as its
breadth where the deep pool is, yet the current in the pool may
be so sluggish as scarcely to be perceptible, while it may dash
over the bar or down the rapids with mill-tail velocity. Were
the brine not drawn out again from the hollow places in the sea,
it would be easy to prove that this indraught into the Mediter-
ranean has taken, even during the period assigned by Sir Charles
to the formation of the Delta of the Mississippi — one of the
newest formations — salt enough to fill up the whole basin of the
Mediterranean with solid matter. Admiral Smyth brought up
bottom with his briny sample of dee^ sea water (six hundred
and seventy fathoms), but no salt crystals.

389. VieiDS of Admiral Smyth and Sir C. Lyell. — The gallant
admiral — appearing to withhold his assent both from Dr. Wol-
laston in his conclusions as to this under current, and from the
geologist in his inferences as to the effect of the barrier in the
Straits — suggests the probability that, in sounding for the heavy
specimen of sea water, he struck a brine spring. But the

* " From near its mouth at the BeHze, a steam-boat may ascend for two thou-
&md miles with scarcely any perceptible difference in the width of the river." —
LyeU, p, 263.

t " The Mississippi is continually shifting its course in the great alluvial plain,
cutting frequently to the depth of one himdred, and even sometimes to the depth
of two hundred and fifty feet."— LyeU,, p. 273.

192 PKYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOEOLOGT.

specimen, according to analysis, was of sea water, and it is not
necessary to call in the supposition of a brine spring to account
for this heavy specimen. If we admit the principle assumed by
Sir Charles Lyeil, that water from the great pools and basins of
the sea can never ascend to cross the ridges which form these
pools and basins, then the harmonies of the sea are gone, and we
are- forced to conclude they never existed. Every particle of
water that sinks below a submarine ridge is ijpso facto, by his
reasoning, stricken from the channels of circulation, to become
thenceforward for ever motionless matter. The consequence
would be " cold obstruction " in the depths of the sea, and a
system of circulation between different seas of the waters only
that float above the shoalest reefs and barriers of each. If the
water in the depths of the sea were to be confined there — doomed
to everlasting repose, — then why was it made fluid, or why was
the sea made any deeper than just to give room for its surface
currents to skim along? If water once below the reefs and
shallows must remain below them, — why were the depths of the
ocean filled with fluid instead of solid matter ? Doubtless, when
the seas were measured and the mountains stood in the balance,
the solid and fluid matters of the earth were adjusted in exact
proportions to insure perfection in the terrestrial machiner}^ I
do not believe in the existence of any such imperfect mechanism,
or in any such failure of design as the imparting of useless pro-
perties to matter, such as fluidity to that which is doomed to be
stationary, would imply. To my mind, the proofs — the theoreti-
cal proofs, — the proofs derived exclusively from reason and
analogy — are as clear in favour of this under current from the
Mediterranean as they were in favour of the existence of
Leverrier's planet before it was seen through the telescope at
Berlin. Now suppose, as Sir Charles Lyell maintains, that none
of these vast quantities of salt which this surface current takes
into the Mediterranean find their way out again. It would not
be difiicult to show, even to the satisfaction of that eminent
geologist, that this indraught conveys salt away from the Atlantic
faster than all the /res/i-water streams empty fi-esh supplies of
salt into the ocean. Now, besides this drain, vast quantities of
salts are extracted from sea water for coral reefs, shell banks,
and marl beds ; and by such reasoning as this, which is perfectly
sound and good, we establish the existence of this under current,
or else we are forced to the very unphilosophical conclusion that

CURRENTS OF THE SEA. 198

tlie sea must be losing its salts, and becoming less and less
briny.

390. Tlie currents of tlie Indian Ocean. — By carefully examining
the physical features of this sea (Plates VIII. and IX.) and
studying its conditions, we are led to look for warm currents that
have their genesis in this ocean, and that carry from it volumes
of overheated water, probably exceeding in quantity many times
that which is discharged by the Gulf Stream from its fountains
(Plate TI.). The Atlantic Ocean is open at the north, but tropical
countries bound the Indian Ocean in that direction. The waters
of this ocean are hotter than those of the Caribbean Sea, and the
evaporating force there (§ 300) is much greater. That it is
greater we might, without observation, infei- from the fact of a
higher temperature and a greater amount of precipitation on the
neighbouring shores (§ 298). These two facts, taken together,
tend, it would seem, to show that large currents of warm water
have their genesis in the Indian Ocean. One of them is the
well-known Mozambique current, called at the Cape of Good Hope
the Lagulhas current. Another of these warm currents from the
Indian Ocean makes its escape through the Straits of Malacca,
and, being joined by other warm streams from the Java and
China Seas, flows out into the Pacific, like another Gulf Stream,
between the Philippines and the shores of Asia. Thence it at-
tempts the great circle route for the Aleutian Islands, tempering
climates, and losing itself in the sea as its waters grow cool on
its route towards the north-west coast of America.

391. Tlie Black Stream of the Pacific contrasted loitJi the Gidf
Stream of the Atlantic. — Between the physical features of this, the
"Black Stream" of the Pacific, and the Gulf Stream of the
Atlantic there are several points of resemblance. Sumatra and
Malacca correspond to Florida and Cuba ; Borneo to the Bahamas,
with the Old Providence Channel to the south, and the Florida
Pass to the west. The coasts of China answer to those of the
United States, the Philippines to the Bermudas, the Japan
Islands to Newfoundland. As with the Gulf Stream, so also
here with this China current, there is a counter current of cold
water between it and the shore. The climates of the Asiatic
coast correspond with those of America along the Atlantic, and
those of Columbia, Washington, and Vancouver resemble those
of Western Europe and the British Islands ; the climate of Cali-
fornia (State) resembles that of Spain ; the sandy plains and

194: PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

rainless regions of Lower California reminding me of Africa,
with its deserts between the same parallels, etc. Moreover, the
North Pacific, like the North Atlantic, is enveloped, where these
warm waters go, with mists and fogs, and streaked with lightning.
The Aleutian Islands are almost as renowned for fogs and mists
as are the Grand Banks of Newfoundland. A surface current
flows north from Behring's Strait into the Arctic Sea : but in the
Atlantic the current is fro7n, not into the Arctic Sea : it flows
south on the surface, north below ; Behring's Strait being too
shallow to admit of mighty under currents, or to permit the in-
troduction from the polar basin of any large icebergs into the
Pacific. Behring's Strait, in geographical position, answers to
Davis' Strait in the Atlantic ; and Alaska, with its Aleutian
chain of islands, to Greenland. But instead of there being to the
east of Alaska, as there is to the east of Greenland, an escape into
the polar basin for these warm waters of the Pacific, a shore-line
intervenes : being cooled here, and having their specific gravity
changed, they are turned down through a sort of North Sea along
the western coast of the continent toward Mexico. They appear
here as a cold current. The effect of this body of cold water
upon the littoral climate of California is very marked. Being
cool, it gives freshness and strength to the sea breeze of that
coast in summer-time, when the "cooling sea breeze" is most
grateful. These contrasts show the principal points of resem
blance and of contrast between the currents and aqueous circula-
tion in the two oceans. The ice-bearing currents of the North
Atlantic are not repeated as to volume in the North Pacific, for
there is no nursery for icebergs like the frozen ocean and its
Atlantean arms. The seas of. Okotsk and Kamtschatka alone, and
not the frozen seas of the Arctic, cradle the icebergs for the
North Pacific.

392. TJie LagulJias Current and the storms of the (7<xpe.— The
Lagulhas current, as the Mozambique is sometimes called, skirts
the coast of Natal as our Gulf Stream does the coast of Georgia,
where it gives rise to the most grand and terrible displays
of thunder and lightning that are anywhere else to be
witnessed. Missionaries thence report to me the occurrence
there of thunder-storms in which for hours consecutively they
have seen an uninterrupted blaze of lightning, and heard a
continuous peal of thunder. Pteaching the Lagulhas banks, the
current spreads itself out there in the midst of cooler waters,

CURRENTS OF THE SEA. 195

and becomes the centre of one of the most remarkable storm-
regions in the world. My friend and fellow-labonrer, Lieut.
Andran of the Dutch Navy, has made the storms upon these
banks a specialty for study. He has pointed out from, the
abstract logs at Utrecht the existence there of some curious and
interesting atmospherical phenomena to which this body of warm
water gives rise. The storms that it calls up come rushing
from the westward ; — sweeping along parallel with the coast of
Africa, they curve along it. Though so near the land, they
seldom reach it. They march into these warm waters with
furious speed ; reaching them with a low barometer, they pause
and die out. That officer has conferred a boon upon the Indiamen
of all flags, for he has taught them how to avoid these dreadful
winter storms of the Cape.

393. The currents and drift of the Indian Ocean. — There is some-
times, if not always, another exit of warm water from the Indian
Ocean. It seems to be an overflow of the great intertropical
caldron of India ; — seeking to escape thence, it works its way pole-
ward more as a drift than as a current. It is to the Mozambique
current what the northern flow of warm waters in the Atlantic
(§ 141) is to the Gulf Stream. This Indian overflow is very
large. The best indication of it is afforded by the sperm whale
curve (Plate IX.). This ovei^flow finds its way south midway
between Africa and Australia, and appears to lose itself in
passing round a sort of Sargasso Sea, thinly strewed with patches
of weed. Nor need we be surprised at such a vast flow of warm
water as these three currents indicate from the Indian Ocean,
when we recollect that this ocean (§ 392) is land-locked on the
north, and that the temperature of its waters is frequently as
high as 90° Fahr. There must, therefore, be immense volumes
of water flowing into the Indian Ocean to supply the waste
created by these warm currents.

394. The ice-hearing currents from the Antarctic regions. — On either
side of this warm current that escapes from the intertropical
parts of the Indian Ocean, but especially on the Australian side,
ail ice-bearing current (Plate IX.) is found wending its way
from the Antarctic regions with supplies of cold water to modify
climates and restore the aqueous equilibrium in that part of the
world. There is a general drift up into the South Atlantic of
ice-bearing waters from Antarctic seas. The icebergs brought
thence, being often very laige and high, are set to the eastward

o 2

196 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

b}^ the " brave west winds " of those regions. Hence the icebergs
that are so often seen to tlie south of the Cape of Good Hope.
They set off for the Atlantic, but are driven to the eastward by
the west winds of these latitudes. The Gulf Stream seldom
permits icebergs from Arctic waters to reach the parallel of 40°
in the North Atlantic ; but I have known the ice-bearing current
which passes east of Cape Horn into the South Atlantic to convey
its bergs as far as the parallel of 37° south latitude. This is the
nearest approach of icebergs to the equator. These currents
which run out from the intertropical basin of that immense sea —
Indian Ocean — convey along immense volumes of water contain-
ing vast quantities of salt, and we know that sea water enough to
convey back equal quantities of salt, and salt to keep up supplies
for the outgoing currents, must flow into the intertropical regions
of the same sea ; therefore, if observations were silent upon the
subject, reason would teach us to look for currents here that
keep in motion immense volumes of water.

395. Tlie currents of the Facific— drift-wood. — The contrast has
been drawn (§391) between the Japan or "Black Stream " of
the North Pacific, and the Gulf Stream of the North Atlantic.
The course of the former has never been satisfactorily traced out.
There is (Plate IX.), along the coast of California and Mexico, a
southwardlj^ movement of waters, as there is along the west
coast of Africa towards the Cape de Yerd Islands. In the open
space west of this southwardly set along the African coast there
is the famous Sargasso Sea (Plate IX.), which is the general
receptacle of the drift-wood and sea-weed of the Atlantic. So,
in like manner, to the west from California of this other south-
wardly set, lies the pool into which the drift-wood and sea-weed
of the North Pacific are generally gathered, but in small quanti-
ties. The shores of Johnston's Islands (17° N., 169° 30' W.),
which are near the edge of this pool, are lined with drift-wood
from the Columbia, and the red cedar of California. The
immense trees that have been cast up on these guano islands
were probably drifted down with the cool California current into
the north-east trades, and by them wafted along to the west, thus
showing that the currents of the North Pacific flow in a sort of
circle, on tlie outer edge of which lie the Japanese and Aleutian
Islands, and the north-west coast of America.

395. TJie Black Current of the Pacific, like the Gulf Stream, Salter
than the adjacnt waters. — The natives of the Aleutian Inlands,

CURRENTS OF THE SEA. 197

where no trees grow, depend upon the drift-wood cast ashore
there for all the timber used in the constrnction of their boats,
fishing-tackle, and household gear. Among this timber, the
camphor-tree, and other woods of China and Japan, are said to
be often recognised. In this fact we have additional evidence
touching this China Stream, as to which (§ 395) but little, at
best, is known. " The Japanese," says Lieutenant Bent,* in a
paper read before the American Geographical Society, January,
1856, "are well aware of its existence, and have given it the
name of ' Kuro-Siwo,' or Black Stream, which is undoubtedly
derived from the deep blue colour of its water, when compared
with that of the adjacent ocean." From this we may infer (§71)
that the blue waters of this China Stream also contain more salt
than the neighbouring waters of the sea.

397. Tlie cold current of Okotsh. — Inshore of, but counter to
the " Black Stream," along the eastern shores of Asia, is found
(§ 391) a streak or layer, or current of cold water answering to
that between the Gulf Stream and the American coast. This
current, like its fellow in the Atlantic, is not strong enough at
all times sensibly to affect the course of navigation ; but, like
that in the Atlantic, it is the nursery (§ 158) of most valuable
fisheries. The fisheries of Japan are nearly as extensive as
those of Newfoundland, and the people of each country are
indebted for their valuable supplies of excellent fish to the cold
waters which the currents of the sea bring down to their shores.

398. Humholdfs Current. — The currents of the Pacific are but
little understood. Among those about which most is thought to
be known is the Humboldt Current of Peru, which the great and
good man whose name it bears was the first to discover. It has
been traced on Plate IX. according to the best information —
defective at best — upon the subject. This current is felt as far
as the equator, mitigating the rainless climate of Peru as it goes,
and making it delightful. The Andes, with their snowcaps, on
one side of the narrow Pacific slopes of this intertropical republic,
and the current from the Antarctic regions on the other, make its
climate one of the most remarkable in the world ; for, though
torrid as to latitude, it is such as to temperature that clothes
are seldom felt as oppressive during any time of the year,
especially after nightfall.

* Lieutenant Bent was in the Japan Expedition with Commodore Perry, and
Ucsed the opportunities thus afforded to study the phenomena of this stream.

198 PHYSICAL GEOGRAPHY OF THE SEA, AND IT^ liiilTEOKOLOGY.

399. TJie '^desolate" region. — Between Humboldt's Current and
tlie great equatorial flow, there is an area marked as the " desolate
region," Plate IX. It was observed that this part of the ocean
was rarely visited by the whale, either sperm or right ; why, it
lid not appear ; but observations asserted the fact. Formerly,
this part of the ocean was seldom whitened by the sails of a ship,
or enlivened by the presence of man. Neither the industrial
pursuits of the sea nor the highways of commerce called him
into it. Now and then a roving cruiser or an enterprising
whale-man passed that way; but to all else it was an un-
frequented part of the ocean, and so remained until the gold-
fields of Australia and the guano islands of Peru made it a
thoroughfare. All vessels bound from Australia to South America
now pass through it, and in the journals of some of them it is
described as a region almost void of the signs of life in both sea
and air. In the South Pacific Ocean especially, where there is
such a wide expanse of water, sea-birds often exhibit a com-
panionship with a vessel, and will follow and keep company with
it through storm and calm for weeks together. Even those
^inds, as the albatross and Cape pigeon, that delight in the
stormy regions of Cape Horn and the inhospitable climates of
the Antarctic regions, not unfrequently accompany vessels into
the perpetual summer of the tropics. The sea-birds that join
the ship as she clears Australia will, it is said, follow her to this
region, and then disappear. Even the chirp of the stormy-petrel
ceases to be heard here, and the sea itself is said to be singularly
barren of life.

400. Polynesian drift. — In the intertropical regions of the
Pacific, and among the heated waters of Polynesia, a warm
current or drift of immense volume has its genesis. It rather
drifts than floats to the south, laving as it goes, the eastern shore
of Australia and both shores of New Zealand. These are the
waters in which the little corallines delight to build their atolls
and their reefs. The intertropical seas of the Pacific aiford an
immense surface for evaporation. No rivers empty there ; the
annual fall of rain there, except in the " Equatorial Doldrums," is
small, and the evaporation is all that both the north-east and
the south-east trade-winds can take up and carry off. I have
marked on Plate IX. the direction of the supposed warm-water
current which conducts these over-heated and briny waters from
the tropics in mid-ocean to the ex tra- tropical regions where

CUEKENTS OF THE SEA. 199

precipitation is in excess. Here, being cooled, and agitated,
and mixed up with waters that are less salt, these over-heated
and over-salted waters from the tropics are replenished and
restored to their rounds in the wonderful system of oceanic
navigation.

401. Equatorial currents. — There are also about the equator iii
this ocean some curious currents, which I have called the
" Doldrum Currents " of the Pacific, but w^hich I do not under-
stand, and as to which observations are not sufficient yet to
aiiord the proper explanation or description. There are many
of them, some of which at times run with great force. On a
voyage from the Society to the Sandwich Islands I encountered
one running at the rate of ninety-six miles a day. These currents
are generally found setting to the west. They are often, but
not always, encountered in the equatorial Doldrums on the
voyage between the Society and the Sandwich Islands. In Cap-
tain Pichon's abstract log of the French corvette "L'Eurydice,"
from Honolulu to Tahiti, in August, 1857, a " doldrum " current
is recorded at 79 miles a day west by north. He encountered it
between 1° N. and 4° S., where it was 300 miles broad. On the
voyage to Honolulu in July of the same year, he experienced no
such current ; but in 6° N. he encountered one of 36 miles,
setting south-east, or nearly in the opposite direction. This
current does not appear to have been more than 60 miles broad.
What else should we expect in this ocean but a system of currents
and counter-currents apparently the most uncertain and compli-
cated ? The Pacific Ocean and the Indian Ocean may, in the
view we are about to take, be considered as one sheet of watei.
This sheet of water covers an area quite equal in extent to one-
half of that embraced by the whole surface of the earth ; and,
according to Professor Alexander Keith Johnston, who so states
it in the new edition of his splendid Physical Atlas, the total
annual fall of rain on the earth's surface is one hundred and
eighty-six thousand two hundred and forty cubic imperial miles.
Not less than three-fourths of the vapour which makes this rain
comes from this waste of waters ; but supposing that ojilj half of
this quantity, i.e., ninety-three thousand one hundred and twenty
cubic miles of rain falls upon this sea, and that that much, at
least, is taken up from it again as vapour, this would give two
hundred and fifty-five cubic miles as the quantity of water which
is daily lifted up and poured back again into this expanse. It is

200 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

taken up at one place and rained down at another, and in this
process, therefore, we have agencies for multitudes of partial and
conflicting currents — all in their set and strength, apparently as
uncertain as the winds.

402. The influence of rains and evaporation upon currents. — The
better to appreciate the operation of such agencies in producing
currents in the sea, now here, now there, first this way, and then
that, let us, by way of. illustration, imagine a district of two
hundred and fifty-five square miles in extent to be set apart, in
the midst of the Pacific Ocean, as the scene of operations for one
day. We must now conceive a machine capable of pumping up,
in the twenty-four hours, all the water to the depth of one mile
in this district. The machine must not only pump up and bear
off this immense quantity of water, but it must discharge it again
into the sea on the same day, but at some other place. Now
here is a force for creating currents that is equivalent in its
results to the effect that would be produced by baling up, in
twenty-four hours, two hundred and fifty-five cubic miles of
water from one part of the Pacific Ocean, and emptying it out
again upon another part. The currents that would be created
by such an operation would overwhelm navigation and desolate
the sea ; and, happily for the human race, the great atmo-
spherical machine which actually does perform every day, on the
average, all this lifting up, transporting and letting down of
water upon the face of the grand ocean, does not confine itself to
an area of two hundred and fifty-five square miles, but to an
area three hundred thousand times as great; yet, nevertheless,
the same quantity of water is kept in motion, and the currents, in
the aggregate, transport as much water to restore the equilibrium
as they would have to do were all the disturbance to take place
upon our hypothetical area of one mile deep over the space of
two hundred and fifty-five square miles. Now when we come to
recollect that evaporation is lifting up, that the winds are trans-
porting, and that the clouds are letting down every dsij actually
such a body of water, we are reminded that it is done by little
and little at a place, and b}^ hairs' breadths at a time, not by
parallelopipedons one mile thick, and that the evaporation is
most rapid and the rains most copious, not always at the same
place, but now here, now there. We thus see actually existing
in nature a force perhaps quite sufficient to give rise to just such
a system of currents as that which mariners find in the Pacific

CTJRRifilCTS OF THE SEA. 201

(§ 401) — currents which, appear to rise in mid ocean, run at
unequal rates, sometimes east, sometimes west, but which always
lose themselves where they rise, viz., in mid ocean.

403. Under currents — Parkers deejp-sea sounding. — Lieutenant
J. C. Walsh, in the U. S. schooner " Taney," and Lieutenant
S. P. Lee, in the U. S. brig "Dolphin," both, while they were
carrying on a system of observations in connection with the Wind
AND Current Charts, had their attention directed to the subject
of submarine currents. They made some interesting experiments
upon the subject. A block of wood was loaded to sinking, and,
by means of a fishing-line or a bit of twine, let down to the depth
of one hundred or five hundred fathoms, at the will of the experi-
menter. A small barrel as a float, just sufficient to keep the block
from sinking farther, was then tied to the line, and the whole let
go from the boat. To use their own expressions, " It was wonder-
ful, indeed, to see this harrega move oif, against wind, and sea,
and surface cuiTent, at the rate of over one knot an hour, ae was
generally the case, and on one occasion as much as 1|- knots.
The men in the boat could not repress exclamations of surprise,
for it really appeared as if some monster of the deep had hold of
the weight below, aiid was walking off with it."* Both officers
and men were amazed at the sight. The experiments in deep-
sea soundings, have also thrown much light upon the subject of
under currents. There is reason to believe that they exist in all, or
almost all parts of the deep sea, for never in any instance yet has
the deep-sea line ceased to run out, even after the plummet had
reached the bottom. If the line be held fast in the boat, it in-
variably parts, showing, when two or three miles of it are out,
that the under currents are sweeping against the bight of it with
what seamen call a swigging force, that no sounding twine has yet
proved strong enough to withstand. Lieutenant J. P. Parker, of
the United States frigate " Congress," attempted, in 1852, a deep-
sea sounding off the coast of South America. He was engaged
with the experiment eight or nine hours, during which time a
line nearly ten miles long was payed out. Night coming on, he
had to part the line (which he did simply by attempting to haul
it in) and return on board. Examination proved that the ocean
there, instead of being over ten miles in depth, was not over
three, and that the line was swept out by the force of one oi

* Lieutenant "Walsh.

202 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

more -ander currents. But in what direction these currents were
running is not known.

404. Tlie compressibility of water — effect of in the oceanic circula-
lion. — Vertical circulation is as important in the sea as it is in
the air (§ 231). in striviDg to understand the physical machinery
of our planet and to comprehend its workings, we mast, if we
would learn, proceed upon the principle (§ 351) that at creation
the waters were measured, the hills weighed, and the atmosphere
meted out, and that each was endowed with its peculiar pro-
perties so proportioned and so adjusted as exactly to answer its
purposes in the grand design. And, consequently, we are en-
titled to infer that fluidity instead of solidity was imparted to a
certain quantity of matter which we call water, to enable it to
perform the offices to be required of fluid matter, and which, in
the terrestrial economy, solid matter was not adapted to perform.
By this mode of reasoning we are taught to regard the fluidity of
all the water in the sea as a physical necessity — and by this
mode of reasoning we are required to reject as insufficient, any
hypothesis touching the system of aqueous circulation on our
planet which ignores, even in the profoundest depths of the ocean,
an interchange of its particles between the bottom and the top
Were such interchange not to take place— were the water in tht
sea which once sinks below the level of its horizontal circulation
doomed to remain there for ever, it would not be difficult to
show that the sea would lose its balance and its counterpoises ;
that, not being able to preserve its status, the water at the bottom
would have grown heavier and heavier, while that at the top
would have become lighter and lighter, until the one became
saturated with salt, the other entirely fresh. To prevent this
state of things, we recognize the influences of the winds and tides,
as well as the necessity of vertical movements in the sea.
Whence, therefore, let us inquire, when a given quantity A
water once finds its way to the bottom of the sea, whence — since
it goes there by virtue of its own specific gravity, whence is
power to be derived for bringing it up again? for sooner or later,
according to this view, up it must come. We thus arrive pre-
cisely at one of those points (§ 287) at which hypothesis becomes
absolutely necessary if we would make further progress. Here,
therefore, let us pause to search among the physics of the sea
for such a power and the foundation for hypothesis. Leslie has
pointed out exactly such a power for the atmospheric ocean,— a

CURRENTS OF THE SEA. 203

power wliich, after the heaviest air has settled at the bottom of
its subtile sea — after the lightest has come to rest at the top, and
the whole arranged itself according to specific gravity— can
haul that which is below to the top, and send that which is on
the top down into the recesses and cavities below. Suppose the
entire atmosphere to be, from the bottom to the top, nearly of the
same temperature, and in a perfect state of the quiescent equi-
librium, and that from some cause a certain volume of air above
has its specific gravity so changed that it commences to descend.
As it descends the pressure upon it increases — and air, being
compressed, contracts and gives out heat. A like volume ascends
to take its place, and in ascending it expands and grows cool.
Thus the total mass, and the total pressure, and the total amount
of caloric remain the same ; but there is a transfer of heat from
the top to the bottom, by which the equilibrium of the mass is
destroyed, and a force established at the bottom of the atmo-
spherical ocean which, with the assistance of an agent at the top
to alter specific gravity, is capable of sending up the heavy air
from the bottom, of drawing down the light from the top, and of
turning, in course of time, the whole atmosphere upside down.
All philosophers acknowledge the power of this omnipresent
agent in the air, and that, by alternately assuming the latent and
the sensible form, it, to say the least, assists to give to the atmo-
sphere the dynamical force required for its system of vertical
circulation as well as its horizontal. So with water and the salt
sea where we do have an agent that is continually altering specific
gravity at the surface. Notwithstanding the Florentine experi-
ment upon water in the gold ball, it has since been abundantly
proved that water is compressible — so much so, that at the depth
of ninety-three miles its density would be doubled. Conse-
quently, a given quantity of water — such, for instance, as a cubic
foot measured at the surface— would not, if sunk to the depth of
four miles, measure a cubic foot by seventy-two cubic inches.
As a rule, the compressibility of water in the depths of the sea is
one per cent, for every 1000 fathoms. Here, then, in the latent
heat which is liberated in the processes of descent, have we not a
power which is capable of sending up to the top water from the
uttermost depths of the sea ? Suppose that this cubic measure of
water, by supplying vapour to the winds at the surface, to have
its saltness so increased as to alter its specific gravity to sinking :
Like the air, it is compressed, and contracts in its descent, giving

204 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

out lieat, raising the temperature, and changing the specific
gravity of like quantities in the various thermal strata through
which it has to pass. Thus heat is conveyed from the top to the
bottom of the sea, there to be liberated and impart to its waters
dynamical force for their upv/ard movement. This is the power
we paused to search for : whatever be its amount it is in the
nature of a vera causa, and we must therefore recognize it, if not
as the sole agent, nevertheless as one of the principal agents
which Kature employs in the system of vertical circulation that
has been ordained for the waters of the sea.

405. Assisted hy its salts. — Now, but for the salts of the sea
this process could not go on so long as the laws of thermal
dilatation remain as they are for sea water. Unlike fresh water,
which expands as it is cooled below 89°. 5, sea water contracts
until it has passed its freezing-point and attained the temperature
of 2 5°. 6.* Were it not for its salts, sea water once near the
surface within the tropics would, by reason of its warmth and
thermal dilatation, remain near the surface. Vertical circulation
would be confined to polar seas, and many of the living creatures
that inhabit its waters would perish for the lack of currents to
convey them their food.

406. The origin of currents. — If we except the tides, and the
partial currents of the sea, such as those that may be created by
the wind, we may lay it down as a rule (§ 103) that all the
currents of the ocean owe their origin to difference of specific
gravity between sea water at one place and sea water at
another; for wherever there is such a difference, whether it be
owing to difference of temperature or to difference of saltness,
etc., it is a difference that disturbs equilibrium, and currents are
the consequences. The heavier water goes towards the lighter,
and the lighter whence the heavier comes ; for two fluids differ-
ing in specific gravity (§ 106), and standing at the same level,
can no more balance each other than unequal weights in opposite
scales of a true balance. It is immaterial, as before stated,
whether this difference of specific gravity be caused by tempera-
ture, by the matter held in solution, or by any other thing ; the
effect is the same, namely, a current. That the sea, in all parts,
holds in solution the same kind of solid matter ; that its waters
in this place, where it never rains, are not Salter than the
strongest brine ; and that in another place, where the rain is

* See Prof. Hubbard's experiments, vol. 1., Sailing Directions,

OURKENTS OF THE SEA. 205

incessant, they are not entirely without salt, may be taken as
evidence in proof of a system of currents or of circulation in the
sea, by which its waters are shaken up and kept mixed together
as though they were in a phial.

407. Currents of the Atlantic. — The principal currents of the
Atlantic have been described in the chapter on the Gulf Stream.
Besides this, its eddies and its offsets are the equatorial current
(Plate YI.), and the St. Eoque or Brazil Current. Their fountain-
head is the same : it is in the warm waters about the equator,
between Africa and America. The former, receiving the Amazon
and the Orinoco as tributaries by the way, flows into the
Caribbean Sea, and becomes, with the waters (§ 103) in which
the vapours of the trade-winds leave their salts, the feeder of the
Gulf Stream. The Brazil current, coming from the same fountain,
is supposed to be divided by Cape St. Roque, one branch going
to the south under this name (Plate IX.), the other to the west-
ward. This last has been a great bugbear to navigators, princi-
pally on account of the difficulties which a few dull vessels
falling to leeward of St. Roque have found in beating up against
it. It was said to have caused the loss of some English transports
in the last century, which fell to leeward of the Cape on a
voj^age to the other hemisphere ; and navigators, accordingly,
were advised to shun it as a danger.

408. TJie St. Boque current. — This current has been an object of
special investigation during my researches connected with the
"Wind and Current Charts, and the result has satisfied me that as
a rule it is neither a dangerous nor a constant current, notwith-
standing older writers. Horsburgh, in his East India Directory,
cautions navigators against it ; and Keith Johnston, in his great
Physical Atlas, published in 1848, thus speaks of it: "This
current greatly impedes the progress of those vessels which cross
the equator west of 23° west longitude, impelling them beyond
Cape St. Eoque, when they are drawn towards the northern
coast of Brazil, and cannot regain their course till after weeks or
months of delay and exertion." So far from this being the case,
my researches abundantly prove that vessels which cross the
equator five hundred miles to the west of longitude 23° have no
difficulty on account of this current in clearing that cape. I
receive almost daily the abstract logs of vessels that cross the
equator west of long. oO°, and in three days from that crossing
they are generally clear of that cape. A few of them report the

20fi PHYSICAL GKOGBAPHY OF THE SEA, AND ITS METEOROLOGY.

current in their favour ; most of them experience no current at
all ; but, now and then, some do find a current setting to the
northward and westward, and operating against them at the rate
of 20 and occasionally of 50 miles a day. The intertropical
regions of the Atlantic, like those of the other oceans (§ 401),
abound with conflicting currents, which no researches yet have
enabled the mariner to unravel so that he may at all times know
where they are and tell how they run, in order that he may be
certain of their help when favourable, or sure of avoiding them
if adverse.

409. Tlie Greenland current. — There are other currents, such as
the Greenland Current, the cold current from Davis' Strait, the
ice-bearing current from the antarctic regions, all setting into the
Atlantic and the Gulf Stream, one branch of which finds its way
into the Arctic Sea; the other (§89) finds its way back to the
south partly as Eennell's current, all of which have been fully
treated of in Chap. II., or are delineated on Plates YI. and IX.
Judging by these, there would seem to be a larger flow of polar
waters into the Atlantic than of other waters from it; and I
cannot account for the preservation of the equilibrium of this
ocean by any other hypothesis than that which calls in the aid
of under currents. They, I have no doubt, like the water-ways,
the mineral veins, the passages in the bowels of the earth, bear
in their secret ways, an important part in the grand system of
the terrestrial economy.

CHAPTER IX.

§ 420-460. — THE SPECIFIC GRAVITY OF THE SEA, AND THE OPEN
WATER IN THE ARCTIC OCEAN.

420. Interesting physical inquiries. — The crust of the planet
Tipon which we live, with the forces that have been and are at
work upon it, is the most interesting subject of physical inquiry
and study that can claim the attention of diligent students.
Precisely as the progr-ess of man has been upward and onward,
precisely has he looked more earnestly and with deeper longings
towards the mysteries that encircle this crust. It is but a shell,
and at most we can reach only a little way either above or below
its very surface, and yet upou the tablets of this thin shell are

THE SPECIFIC GRAVITY OF THE SEA, ETC. 207

the recorda of all that he may ever know concerning this hia
cosmical hearthstone.

42 1 . Voyages of discovery to tlie North Pole. — Eesearches have
been carried on from the bottom of the deepest pit to the top of
the highest mountain, but these have not satisfied. Voyages of
discovery, with their fascinations and their charms, have led
many a noble champion of human progress both into the torrid
and frigid zones ; and notwithstanding the hardships, sufferings,
and disasters to which many northern parties have found them-
selves exposed, seafaring men, as science has advanced, have
looked with deeper and deeper longings towards the mystic
circles of the polar regions: there icebergs are framed and
glaciers launched : there the tides have their cradle, the whales
their nursery : there the winds complete their circuits, and the
currents of the sea their round in the wonderful system of oceanic
circulation: there the Aurora Borealis is lighted up and the
trembling needle brought to rest ; and there too, in the mazes of
that mystic circle, terrestrial forces of occult power and of vast
influence upon the well-being of man are continually at play.
Within the arctic circle is the pole of the winds and the poles of
the cold ; the pole of the earth and of the magnet. It is a circle of
mysteries; and the desire to enter it, to explore its untrodden
wastes and secret chambers, and to study its physical aspects, has
grown into a longing. Noble daring has made arctic ice and
snow-clad seas classic ground. It is no feverish excitement nor
vain ambition that leads man there. It is a higher feeling, a
holier motive— a desire to look into the works of creation, to
comprehend the economy of our planet, and to grow wiser and
better by the knowledge. Soon after the discovery of America,
John Cabot and his sons, with five ships, sailed upon the first
arctic expedition. Between that year and the present no less
than 155 vessels, besides boat and land parties, have at various
periods, and with divers objects in view, been sent from Europe
and America, up into those inhospitable regions. Whatever maj
have been the immediate object of these various expeditions,
whether to enlarge the fields of commerce, to carry the Bible, to
spread civilization, to push conquests, or to bring back contribu-
tions to science, they have never lost sight of the promise made
by Columbus of a western route to India.

422. Tlie first suggestions of an open sea in the Arctic Ocean. — Like
the air, like the body, the ocean must have a system of circulation

208 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

for its waters. No other hypothesis will explain the fact which
observations reveal concerning the saltness of the sea, the con-
stituents of sea-water, and many other phenomena. An attentive
stiidv of the currents of the sea, and a close examination of the
laws which govern the movements o'f the waters in their channels
of circulation through the ocean, will lead any one irresistibly
to the conclusion that always, in summer and winter, there must
be, somewhere within the arctic circle, a large body of open
water. This o^^en water must impress a curious feature upon
the physical aspects of those regions. The whales had taught us
to suspect the existence of open water in the arctic basin, and in
their mute way told of a passage there, at least sometimes. It is
the custom among whalers to have their harpoons marked with
date and the name of the ship ; and Dr. Scoresby, in his work on
arctic voyages, mentions several instances of whales that have
been taken near the Behring's Strait side with harpoons in them
bearing the stamp of ships that were known to cruise on the
Baffin's Bay side of the American continent ; and as, in one or
two instances, a very short time had elapsed between the date of
capture in the Pacific and the date when the fish must have been
struck on the Atlantic side, it was argued therefore that there
was a north-west passage by which the whales passed from one
side to the other, since the stricken animal could not have had
the harpoon in him long enough to admit of a passage — even if
that were possible — around either Cape Horn or the Cape of Good
Hope.

423. Harpoons — habits of the whales. — The whale-fishing is,
among the industrial pursuits of the sea, one of no little import-
ance ; and when the system of investigation out of which the
" Wind and Current Charts " have grown was commenced, the
haunts of this animal did not escape attentive examination. The
log-books of whalers were collected in great numbers, and
patiently examined, co-ordinated, and discussed, in order to find
out what parts of the ocean are frequented by this kind of whale,
what parts by that, and what parts by neither. (See Plate IX.)
Log-books containing the records by difierent ships for hundreds
of thousands of days were examined, and the observations in
them co-ordinated for this chart. And this investigation, as
Plate IX. shows, led to the discovery that the tropical regions of
the ocean are to the right whale as a sea of fii«, through which
he cannot pass, and into which he ne^er enters. The fact was

THE SPECIFIC GliA-VITY OF THE SEA, ETC. 209

also brought out that the same kind of whale that is found ofi
the shores of Greenland, in Baffin's Bay, &c., is found also in tho
North Pacific, and about Behring's Strait, and that the right
whale of the northern hemisphere is a different animal from that
of the southern. Thus the fact was established that the harpooned
whales did not pass around Cape Horn or the Cape of Good
Hope, for they were of the class that could not cross the equator.
In this way we were furnished wdth circumstantial evidence
affording the most irrefragable proof that there is, at times at
least, open-water communication through the Arctic Sea from one
side of the continent to the other, for it is known that the whales
cannot travel under the ice for such a great distance as is that
from one side of this continent to the other. But this did not
prove the existence of an open sea there ; it only established the
existence — the occasional existence, if you please — of a channel
through which w^hales had passed. Therefore we felt bound to
introduce other evidence before, we could expect the reader to
admit our proof, and to believe with us in the existence of an
open sea in the Arctic Ocean.

424. The under current into the Arctic Ocean — its influences. —
There is an under current setting from the Atlantic through Daids'
Strait into the Arctic Ocean, and there is a surface current
setting out. Observations have pointed out the existence of this
under current there, for navigators tell of immense icebergs
which they have seen drifting rapidly to the north, and against a
strong surface current. These icebergs w^ere high above the
water, and their depth below, supposing them to be parallele-
pipeds, was at least seven times greater than their height above.
No doubt they were drifted by a powerful under current. Now
this under current comes from the south, where it is warm, and
the temperature of its waters is perhaps not below 30° ; at any rate,
they are comparatively warm. There must be a place somewhere
in the arctic seas where this under current ceases to flow north,
and begins to flow south as a surface current ; for the surface
current, though its waters are mixed with the fresh waters of the
rivers and of precipitation in the polar basin, nevertheless bears
out vast Quantities of salt, which is furnished neither hy the
rivers nor the rains. These salts are supplied by the under
current ; for as much salt as one current brings in, other currents
must take out, else the polar basin would become a basin of
salt ; and where the under current transfers its waters to the

210 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

surface, there is, it is supposed, a basin in whicli the waters, as
they rise to the surface, are at 30°, or whatever be the tempera-
ture of the under current, which we know must be above the
freezing-point, for the current is of water in a fluid, not in a solid
state. An arrangement in nature, by which a basin of consider-
able area in the frozen ocean could be supplied by water coming
in at the bottom and rising up at the top, with a temperature
not below 30°, or even 27°.2 — the freezing-point of sea water —
would go far to mitigate the climate in the regions round, about.

425. Indications of a milder climate. — And that there is a
warmer climate somewhere in that inhospitable sea, the observa-
tions of many of the explorers who have visited it indicate. Its
existence may be inferred also from the well-known fact that the
birds and animals are found at certain seasons migrating to the
noi th, evidently in search of milder climates. The instincts of
these dumb creatures are unerring, and we can imagine no miti-
gation of the climate in that direction, unless it arise from the
proximity, or the presence there of a large body of open water.
It is another furnace (§ 151) in the beautiful economy of Nature
for tempering climates there.

426. How the littoral waters, hy being diluted from the rivers and the
rains, serve as a mantle for the salter and warmer sea water heloio. —
The hydrographic basin of the Arctic Ocean is large, and it
delivers into that sea annually a very copious drainage. Such an
immense volume of fresh water discharged into so small a sea as
the Arctic Ocean is, must go far towards diluting its brine.
Fig. 2, Plate X. (§ 433), shows the extent to which the brine of
our littoral seas is diluted by the drainage from the Atlantic
slopes of the United States. It will be observed by that figure
that suddenly after crossing the parallel of 34° N. the water
begins to grow cooler and lighter. The observations for the two
curves are a part of the celebrated series made by Captain Rodgers
in the U. S. ship " Vincennes " all the way from Behring's
Straits by the way of Cape Horn to New York. He cleared the
inner edge of the Gulf Stream in 34°, where the waters began to
grow cooler and lighter, and so continued to do as he approached
the shore. The remarkable and sudden approach of the thermal
and specific gravity curves after crossing 34° N. can be explained
by no other hypothesis than this, viz. : the surface water of the
sea was so diluted with the fresh water from the Chesapeake, the
Delaware, and New York Bays, that, notwithstanding the tern

THE SrECIFIO GRAVITY OF THE SEA, ETO. 211

perature decreased as Eodgers approached the shore, jet the
specific gravity decreased also, because the saltness decreased by
reason of the increasing proportion of river water as he neared
the shore. And thus we have in our own waters an illustration
and an example of how water that is cool and light — because not

so salt may be made to cover and protect as with a mantle, a

sheet of warmer, but Salter and heavier water below.

427. An under current of warm hat salt and heavy water. — The
mean specific gravity of the Arctic Ocean water as observed by
Eodgers, and reduced to the freezing-point (27".2) of sea water,
was 1.02G3. The specific gravity of the Gulf Stream water, as
observed by him, and reduced to the same temperature (27°.2),
was 1.0303. If these be taken as fair specimens of the water of
the torrid and frigid zones, it would appear that the waters of
intertropical seas have 15 per cent, more salt in them than the
surface water of the Arctic Ocean has. It is to be regretted that
the hydrometer has not been more frequently used in the Arctic
Ocean, for a careful series of observations upon the specific
gravity of the water there at the surface and at various depths
would indicate to us not only the extent to which the water
there is diluted by the rivers and the rains, but it would yield
other highly interesting results. Now this salt and heavy
water, whose specific gravity at 27°.2 would have been 1.0303, is
the very water which Eodgers observed in the Gulf Stream on its
way to the arctic regions. This is the water which, after passing
the Grand Banks and meeting the diluted water as an ice-bearing
current from the north, dips down, but continues its course as an
under current. It is protected from farther loss of heat, after the
manner of our own littoral waters, by the colder but lighter and
upper current from the north, until it enters the Arctic Ocean,
there to rise up like a boiling spring in the centre of an open
sea.

428. De Haven's water shy. — Eelying upon a process of reasoning
like this, and the deductions flowing therefrom. Lieutenant De
Haven, when he went in command of the American expedition in
search of Sir John Franklin and his companions, was told in his
letter of instructions, to look, when he should get well up into
Wellington Channel, for an open sea to the northward and west-
ward. He looked, and saw in that direction a " water sky."
Captain Penny afterwards went there, found open water, and
sailed upon it. The open sea in the Arctic Ocean is probably not

p 2

212 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

always in the same place, as the Gulf Stream (§ 126) is Pot
always in one place. It probably is always where the waters of
the under currents are brought to the suiface ; and this, we may
imagine, would depend upon the freedom of ingress and egiess
for the currents. Their course may perhaps be modified more cjt
less by the ice on the surface, by changes, from whatever cause,
in the course or velocity of the surface current, for obviously the
under current could not bring more water into the frozen ocean
than the surface current would carry out again, either as ice or
water. Exploring parties may have been near this open sea
without perceiving the warmth of its climate, for every winter,
an example of how very close warm water in the sea and a very
severe climate on the land or the ice may be to each other is
afforded to us in the case of the Gulf Stream and the Labrador-
like climate of New England, Nova Scotia, and Newfoundland.
In these countries, in winter, the thermometer frequently sinks
far below zero, notwithstanding that the tepid waters of the
Gulf Stream may be found with their summer temperature within
one day's sail of these very, very cold places.

429. Dr. Kane. — Dr. Kane reports an open sea north of the
parallel of 82°. To reach it, his party crossed a barrier of ice 80
or 100 miles broad. Before gaining this open water, he found
the thermometer to show the extreme temperature of — 60°.
Passing this ice-bound region by travelling north, he stood on
the shores of an iceless sea, extending in an unbroken sheet of
water as far as the eye could reach towards the pole. Its waves
were dashing on the beach with the swell of a boundless ocean.
The tides ebbed and flowed in it, and I apprehend that the tidal
wave from the Atlantic can no more pass under this icy barrier
to be propagated in the seas beyond, than the vibrations of a
musical string can pass with its notes a fret upon which the
musician has placed his finger. The swell of the sea cannot pass
wide fields or extensive barriers of ice ; for De Haven, during
his long imprisonment and drift (§ 475), found the ice so firm
that he observed regularly from an artificial horizon placed upon
it, and found the mercury always ''perfectl}^ steady." These
tides, therefore must have been born in that cold sea, having
their cradle about the North Pole. If these statements and de-
ductions be correct, then we infer that most, if not all the unex-
plored regions about the pole are covered with deep water ; for,
were this unexplored area mostly land or shallow water, it could

THE SPECIFIC GRAVITY OF THE SEA, ETC. 213

not ""ive birtli to regular tides. Indeed, the existence of these
tides, with the immense flow and drift which annually take place
from the polar seas into the Atlantic, suggests many conjectures
concerning the condition of these unexplored regions. Whale-
men have always been puzzled as to the place of breeding for the
right whale. It is a cold-water animal, and, following up this
iraiji of thought, the question is prompted. Is not the nursery for
lhe great whale in this polar sea, which has been so set about
and hemmed in with a hedge of ice that man may not trespass
there ? This providential economy is still farther suggestive,
prompting us to ask, Whence comes the food for the young whales
there ? " Do the teeming waters of the Gulf Stream (§ 1 60)
convey it there also, and in channels so far down in the depths of
the sea that no enemy may wajday and spoil it on the long
journey ? Seals were sporting and water-fowl feeding in this
open sea of Dr. Kane's. Its waves came rolling in at his feet,
and dashing with measured tread, like the majestic billows of
old ocean, against the shore. Solitude, the cold and boundless
expanse, and the mysterious heavings of its green waters, lend
their charm to the scene. They suggested fancied myths, and
kindled the ai'dent imagination of the daring mariner's many
longings. The temperature of its waters was only 36°! Such
warm water could get there from the south only as a current far
down in the depths below. The bottom of the ice of this eighty
miles of barrier was no doubt many — perhaps hundreds of — feet
below the surface level. Under this ice there was also doubtless
water above the freezing-point.

430. Under currents change temperature slowly. — Nor need the
presence of warm water within the arctic circle excite surprise,
when we recollect that the cold waters of the frigid zone are
transferred to the torrid without changing their temperature
perhaps more than 7° or 8° by the way. This transfer of cold
waters for a part of the way may take place on the surface, and
until the polar flow (§ 89) dips down and becomes submarine.
At any rate, officers on the Coast Survey have found water at the
bottom of the Gulf Stream, in latitude 25° 30' N., as low in tem-
perature as 35°. Now, if water flowing out of the polar basin at
the temperature of 28° may, by passing along the secret paths of
the sea, reach the Gulf of Mexico in summer at a temperature of
only 3° above the freezing-point of fresh water, why may not
water leaving the torrid zone at a temperature of 82°, and travel-

214 PHYSICAL GEOGKAPHT OF THE SEA, AND ITS METEOROLOGY.

liug by the f-'ame hidden ways, reacli the frigid zone without
losing more than the cold currents gained in temperature, viz., 7° ?
In 1840, Sir James C. Eoss, being in the antarctic regions with
tlie surface water at 32°, found the temperature in depth to be
38°.8 at 400 fathoms, and 39°.8 at 600. At a greater depth thert>
is a greater pressure ; and there ought to be (§ 404) a certain
temperature, that after passing a certain depth in the deep sea
grows higher and higher as the depth increases. The thermal
laws of " deep-sea" temperatures for fresh and for salt water are
very different. In September, when the surface water of Loch
Lomond and Loch Katrine — Scottish lakes — which are between
500 and 600 feet deep, is 58°, that at the bottom is uniformly
41°, which is very near the point of maximum density for fresh
water. Saussure has shown the same for the Italian lakes : onlj-,
at the depth of 1000 feet in the Lake of Geneva, it was a little
warmer, probably on account of pressure (§ 404), than it was at
less depth in Lakes Lucerne and Thun. In these it was 41°, or
1° colder than the bottom of Geneva, their surface water being
about 60°. In Lago Sabatino, near Eome, with the surface
water at 77°, Barlocci reports 44° at the depth of 490 feet. The
winter in Eome is not severe enough to cool such a mass of water
below 44°. But with the exception of the Lake of Geneva,
which is deep enough to have the temperature of its water some-
what influenced by pressure (§ 404), the law is uniform : as you
descend in fresh-water lakes, the temperature decreases to that of
maximum density. Saussure extended his experiments to the
Gulfs of Kice and Genoa— salt-water bays in the neighbourhood
of his fresh- water lakes. Here, with the surface temperature of
69°, he found even at the depth of 1720 feet, the water no cooler
than 55°.8. This salt water might have been cooled 30° lower
before it would have reached the maximum density (25°. 6) of
average sea water. We see that the severest winters are not
sufficient to bridge our deep fresh-water lakes over with ice,
though their waters being cooled below 39°.6, grow light, and
remain on the surface to be frozen. On the contrary, sea water
contracts, grows heavy, and sinks, until the whole basin, from
the bottom to the top, be reduced to 27°. 2. Yet many confess
no surprise at the open water in fresh-water lakes that are com-
paratively shallow, while they can conceive of no such thing in
the Arctic Ocean, though it be very much deeper than the
deepest fresh-water lakes !

THE SPECIFIC GRAVITY OF THE SEA, ETC. 215

431. Solid matter annually drifted out of the polar hasin. — At the
very time that the doctor was gazing with longing eyes npon
these strange green waters (§ 429), there is known to have been
a powerful drift setting out from another part of this Polar Sea,
and carrying with it from her moorings the English exploring
ship "Eesolute," which her officers and men had abandoned fast
bound in the ice several winters before. This drift carried a
field of ice that covered an area not less than 300,000 square
miles, through a distance of a thousand miles to the south. The
drift of this ship was a repetition of De Haven's celebrated drift
(§ 474) ; for in each case the ice in which the vessel was fastened
floated out and carried the vessel along with it; by which I
mean to be understood as wishing to convey the idea that the
vessel was not drifted through a line or an opening in the ice, but,
remaining fast in the ice, she was carried along with the whole
icy field or waste. This at least was the case with De Haven,
A field of ice covering to the depth of seven feet an area of
300,000 square miles, would weigh not less than 18,000,000,000
tons. This, then, is the quantity of solid matter that is drifted
out of the polar seas through one opening — Davis' Straits — alone,
and during a part of the year only. The quantity of water which
was required to float and drive this solid matter out was probablj^
many times greater than this. A quantity of water equal in
weight to these two masses had to go in. The basin to receive
these inflowing waters, i. e., the unexplored basin about the
North Pole, includes an area of a million and a half square miles ;
and as tbe outflowing ice and water are at the surface, the return
current must be submarine. A part of the water that it bears
probably flows in beneath Dr. Kane's barrier of ice (§ 429).

432. Volume of water kept in motion hy the arctic flow and reflow. —
These two currents therefore, it may be perceived, keep in
motion between the temperate and polar regions of the earth a
volume of water, in comparison with which the mighty
Mississippi, in its greatest floods, sinks down to a mere rill. On
the borders of this ice-bound sea Dr. Kane found subsistence for
his party — another proof of the high temperature and comparative
mildness of its climate.

433. The hydrometer at sea. — The Brussels Conference recom-
mended the systematic use of the hydrometer at sea. Captain
Eodgers, Lieutenant Porter, and Dr. Kuschenberger, all of the
United States Navy, with Dr. Eaymond, in the American steamei

216 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY^

" Golden Age," and Captain Toynbee, of the English East India-
man the " Gloriana," have each returned to me valuable observa-
tions with this instrument. Eodgers, however, has afforded the
most extended series. It embraces 128° of latitude, extending from
71° in one hemisphere to 57° in the other. And here I beg to
remark that those navigators who use the hydrometer systemati-
cally and carefully at sea are quietly enlarging for us the
bounds of knowledge; and they are gleaning in our field of
research. These observations have already led to the discovery
of new and beneficent relations in the workshops of the sea. In
the physical machinery of the universe there is no compensation
to be found that is more exquisite or beautiful than that which,
by means of this little instrument, has been discovered in the sea
between its salts, the air, and the sun. The observations made
with it by Captain Eodgers, on board the U. S. ship " Vincennes,"
have shown that the specific gravity of sea water varies but little
in the trade-wind regions, notwithstanding the change of tempe-
rature. The temperature was a little greater in the south-east
trade-wind region of the ]'acific; less in the Atlantic. But,
though the sea at the equatorial borders of the trade-wind belt is
some 20° or 26° warmer than it is on the polar edge, yet the
specific gravity of its waters at the two places in the Atlantic
differs but little. Though the temperature of the water was
noted, his observations on its specific gravity have not been
corrected for temperature. The object which the Brussels Con-
ference had in view when the specific gravity column was intro-
duced into the sea-journal was, that h3^drographers might find in
it data for computing the dynamical force which the sea derives
for its currents from the difference in the specific gravity of its
waters in different climes. The Conference held, and rightly
held, that a given difference as to specific gravity between the
w^ater in one part of the sea and the water in another would give
rise to certain currents, and that the set and strength of these
currents would be the same, whether such difference of specific
gravity arose from difference of temjoerature or difference of salt-
ness, or both.

434. Sjieciftc gravity of average seaimter. — According to Eodgers'
observations, the average specific gravity of sea water, as it is
taken from the sea on the parallels of 34° north and south, at a
mean temperature of 64", is just what, according to saline and
thermal laws, it ought to be ; but its specific gravity when taken

THE SPECIFIC GEAVITY OF THE SEA, ETC. 217

from tlie equator, at a mean temperature of 81°, is mucli greater
than, according to the same laws, it ought to be. The observed
difference of its specific gravity at 64° and 81° is .0015; whereas
it ouo-ht to be .0025. Now as we approach the equator, the water
is warmer, and it should therefore, were it of equal saltness, be
proportionably lighter; but instead of the specific gravity of
equatorial w^ater being .0025 lighter— as by thermal law^s it
ouo-ht to be — than sea water at the temperature of 61° in latitude
84°, it is only .0015. What makes the equatorial water of the
sea so much heavier than according to thermal laws it ought to
be ? Let us inquire :

435. An anomaly. — ^The anomaly is in the trade-wind region,
and is best developed (Plate X., Fig. 2) in the North Atlantic,
between the parallel of 40° and the equator. Though it is suffi-
ciently apparent both in the North and South Pacific {Fig. 1) — it
is masked by the Gulf Stream in the North Atlantic — commencing
at the polar borders of these winds, the anomaly is developed as
you approach the equator. The water grows warmer, but not
proportionably lighter : this is in the trade-wind region. These
winds evaporate as they go ; but can it be possible that they are
so regulated and adjusted, counterpoised and balanced, that the
salt which they, by evaporation, leave behind, is just sufficient to
counterbalance the dilatation due to the increasing warmth of the
sea?

436. Influence of the trade-ivinds u^pon the speciflc gravity of sea
y^ater.—li is the trade-winds, then, which prevent the thermal
and specific gravity curves from conforming with each other in
intertropical seas. I'he water they suck up is fresh water, and
the salt it contained, being left behind, is just sufficient to counter-
balance, by its weight, the eifect of thermal dilatation upon the
specific gravity of sea water between the parallels of 34° north
and south. As we go from 34° to the equator, the water grows
warm and expands. It would become lighter, but the trade-
winds, by taking up vapour without salt, make the water Salter,
and therefore heavier. The conclusion is, the proportion of salt
in sea water, its expansibility between 62° and 82° (for its
thermal dilatability varies with its temperature), and the thirst of
the trade-winds for vapour are, where they blow, so balanced as
to produce perfect compensation ; and a more beautiful compen-
sation cannot, it appears to me, be found in the mechanism of the
universe than that which we have here stumbled upon. It is a
triple adjustment : the power of the sim to expand, the power of

218 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the winds to evaporate, and the quantity of salts in the sea —
these are so proportioned and adjusted that when both the wind
and the sun have each played with its forces upon the inter-
tropical waters of the ocean, the residuum of heat and of salt
should be just such as to balance each other in their effects, and
so the aqueous equilibrium of the torrid zone is preserved.

437. Compensating influences. — Nor are these the only adjust-
ments effected by this exquisite combination of compensations.
If all the intertropical heat of the sun were to pass into the seas
upon which it falls, simply raising the temperature of their
waters, it would create a thermo-dynamical force in the ocean
capable of transporting water scalding hot from the torrid zone,
and spreading it, while still in the tepid state, around the poles.
The annual evaporation from the trade-wind region of the ocean
has been computed, according to the most reliable observation,
to be as much as 15 feet, which is at the rate of half an inch per
day. The heat required for this evaporation would raise from the
normal temperature of intertropical seas to the boiling-point a
layer of water covering the entire ocean to the depth of more
than 100 feet. Such increase of temperature, by the consequent
change which it would produce upon the specific gravity of the
sea, would still further augment its dynamical power, until, even
in the Atlantic, there would be force enough to put in motion
and feed with boiling-hot water many Gulf Streams. But the
trade-winds and the seas are so adjusted that this heat, instead ol
penetrating into the depths of the ocean to raise inordinately the
temperature of its waters, is sent off by radiation or taken iip by the
vapour, or borne away by under currents, or carried off by the
winds, and dispensed by the clouds in the upper air of distant
lands. Xor does this exquisite system of checks and balances,
compensations and adjustments, end here. In equatorial seas
the waters are dark blue, in extra-tropical they are green. This
difference of colour bears upon their heat-absorbing properties,*
and it comes in as a make- weight in the system of oceanic clima-
tology, circulation, and stability. Now, suppose there were no
trade-winds to evaporate and to counteract the dynamical force of
the sun ; this hot and light "water, by becoming hotter and lighter,
would flow off" in currents with almost mill-tail velocity, towards
the poles, covering the intervening sea with a mantle of warmth
as with a garment. The cool and heavy water of the polar basin,
coming out as under currents, would flow equatorially with equal
* See chap. XXII. on the Actinometky of the Sea.

TIIE SPECIFIC GEAVITT OF THE SEA, ETC. 219

velocity. How mucli, if to any extent, the former warm climates
of the British Islands and Northern Asia may be due to such
a warm covering of the sea, may perhaps, at some future time, be
considered worthy of special inquiry. We have already seen
(§ 434) that there is something else besides temperature that is
at work in effecting changes in the specific gi'avity of sea water.
Whatever increases or diminishes its saltness, increases or
diminishes its specific gravity ; and the agents that are at work in
the sea doing this are sea shells, the rivers, and the rains, as
well as the winds. Between 35° or 40° and the equator evapora-
tion is in excess of precipitation ; at any rate, there is but little
precipitation except under the equatorial cloud-ring (see Storm
and Eain Chart, Plate XIII.) ; and though, as we approach the
e(iuator on either side from these parallels, the solar ray warms
and expands the surface water of the sea, the winds, by the
vapour they carry off and the salt they leave behind, prevent it
from making that water lighter.

438. Nicely adjusted. — Thus two antagonistic forces are un-
masked, and, being unmasked, we discover in them a most ex-
quisite adjustment — a compensation — by which the dynamical
forces that reside in the sunbeam and the trade- wind are made to
counterbalance each other; by which the climates of inter-
tropical seas are regulated; and by which the set, force, and
volume of oceanic currents are measured. This compensation is
most beautiful ; it explains the paradox (§ 434), gives volume to
the harmonies of the sea, and makes them louder in their song of
Almighty praise than the noise of many waters. Philosophers
have admired the relations between the size of the earth, the
force of gravity, and the strength of fibre in the flower-stalks of
plants (§ 303), but how much more exquisite is the system of
counterpoises and adjustments here presented between the sea
and its salts, the winds and the heat of the sun ! The capacity
of the sun to warm, of the sea water to expand, the quantity of
salts these contain, and the power of the wind to suck up vapour,
are all in such nice adjustment the one with the other, that there
is the most perfect compensation. By it they make music in the
sea, and the harmony that comes pealing thence, though not of so
lofty a strain, is nevertheless, like the songs of the stars, divine.

439. A thermal tide. — Suppose there were no winds to suck up
fresh water from the brine of the ocean ; that its average depth
were 3000 fathoms ; that the solar ray were endowed with power
to penetrate with its heat from the top to the bottom ; and that,

220 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

from bottom to top, the seas of each hemisphere, in thermal alter-
nation with the seasons, were raised to snmmer heat and lowered
to winter temperature : the change of sea level from summer to
winter, and from winter to summer, in one hemisphere, would,
from this cause alone, be upwards of 125 feet ; and in its rise and
fall we should have, from pole to pole, the ebb and flow of a
great thermal tide that would turn with the sun in the ecliptic,
and tell the equinoxes by the march n the tide staff of its rising
and falling waters. But difference of level would not be all that
would give strength and volume to this tide ; difference of specific
gravity would lend its weight as so much dynamical force, which"
difierence would create an upper and under annual tide from one
hemisphere to the other. This double disturbance of equilibrium
would not give rise to a tidal wave — not mere motion without
translation — but to a tidal flow and reflow of water from one
hemisphere to the other in volumes of vast magnitude, power,
and majesty. This is an exaggerated view of the dynamical
force of the sunbeam ; but it is presented to show the origin of the
thermal tide shown on Plate lY. The difference betv/een the
actual and the supposed thermal tides is one of degree merely ;
for the sea water that is liable to any considerable change of
temperature, instead of reaching from the bottom to the top, is
scarcely more than a " pellicle " to the ocean, Nevertheless,
there is a regular periodical flow and reflow between the poles
and the equator. It is the annual ebb of this tide which fills the
upper half of the North Atlantic with icebergs every spring and
summer. The heated portion forms a stratum or layer which is
thickest at the equator, and which comes to the surface near the
polar edge of the temperate zones ; it then dips again as it recedes
towards the region of perpetual winter.

4-40. The isothermal floor of the ocean. — The observations of
Kotzebue, Admiral Beechey, and Sir James C. Pioss first sug-
gested the existence in the ocean of this isothermal floor. Its
temperature, according to Kotzebue, is 36°. The depth of this
bed of water of invariable and uniform temperature is 1200
fathoms at the equator. It gradually rises thence to the parallel
of about 56' N. and S., when it crops out, and there the tempe-
rature of the sea, from top to bottom, is conjectured to be perma-
nently at 36°. The place of this outcrop, no doubt, shifts with
the seasons, vibrating up and down, Le., north and south, after
the manner of the calm belts. Proceeding, in our description,
onwardtothefngid zones, this aqueous stratum of an unchanging

THE SPECnnC GRAVITY OF THE SEA, ETC.

221

temperature dips again, and continues to incline till it reaches the
poles at the depth of 750 fathoms. So that on the equatorial side
of the outcrop the water above this floor is the warmer, but on
the polar side the supernatant water is the colder. By this floor,
with its waters of one uniform and permanent temperature, " the
ocean," says Sir John Herschel, "is divided into three great
reo-ions — two polar basins in which the surface temperature is
below, and one medial zone in which it is above 39°.5,* being 80°
at the equator ; and at the poles, of course, the freezing-point of
sea water. It will be very readily understood that in this state-
ment there is nothing repugnant to hydrostatical laws, the com-
pressibility of water insuring an increase of density in de-
scending within much wider limits of temperature than here
contemplated."

441. Tliermal dilatation of the imter. — The temperature of 3 9°. 5
was assigned to this floor probably under the supposition that sea
water follows fresh in its laws of thermal dilatation. IS^ot so;
while fresh water attains its maximum density at 39^.5, average
sea water does not arrive at its degree of maximum density until
it passes its freezing-point (27°. 2) and reaches the temperature of
25°.6. In the winter of 1858 a very elaborate series of observa-
tions was conducted at the National Observatory, by Professor
Hubbard, upon the thermal dilatation of sea water, and with the
following results, 60° being the standard temperature :
Thermal Dilatation of Sea Water. -f

Temp.

Dilatation.

Temp.

Dilatation.

Temp.

Dilatation.

Temp.

Dilatation.

O

o

o

o

22

0.99807

32

0.991?i5

50

0.99895

110

0950

23

801

33

Idl

55

943

120

1218

24

798

34

800

60

1.00000

LSO

1506

25

795

35

803

65

067

140

1804

26

793

36

806

70

142

150

2118

27

792

37

810

75

221

160

2460

28

791

38

814

80

309

170

2S2r.

29

791

1 39

819

85

402

180

3192

30

792

1 40

.99823

90

503

i 190

3588

31

793

45

0.99856

100

0716

1 200

1.03993

* This remark was made by Sir Jolm on the supposition, probably, that the
maximum density of sea water was at the same temperature as that of fresh, but
it is the same 12^ or 14° lower.

t This agrees more nearly with Despretz (p. 245) than with Dr. Marcet.
The latter states that sea water decreases in weight to tlie freezing point until
actually congealed. In four experimf nts Dr. Maxcet cooled sea water down tc

22? PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

442. Experiments on the freezing-point. — The dilatation of the
glass tube is included in this table. To determine the freezing-
point of average sea water I filled a glass jar 18 inches high,
and 3 inches in diameter, with specimens of average sea water
obtained in mid-ocean and near the equator. On the 12th of
February, 1858, the thermometer in the shade being 23°, I ex-
posed this jar of water, with a standard thermometer immersed,
to the out-door temperature. When the thermometer in the jar
reached 27°, small crystals of ice, like macles of snow, were ob-
served to form near the bottom, to rise, and to increase as they
rose. In truth, the phenomenon presented most beautifully in
miniature a snow-storm reversed, for the flakes appeared literally
to " fall upward ;" and while it was " snowing up " in the jar,
covering the top with ice, the water in it rose in temperature
from 27°. 2 to 28°, thus showing the maximum density of the
water to be not above 27°.2. As soon, and invariably as soon, as
the first crystals of ice began to appear, the water immediately
rose to 28°, and there remained as long as the process of congela-
tion was going on. In some instances the water was brought
down, as in a confined vessel, to 18° before freezing; but as soon
as freezing commenced, the thermometer would mount up to 28°.
The same water was used for the following series of observations
upon the thermal changes of the specific gravity of sea water,
fresh water being the unit :

Temperature 27°-l Spec. grav. 1.0290 Temperature 38^.0 Spec. grav. 1.0287

28^.3 „ 89

28^.8 „ 91

29°0 „ 885

290.5 „ 906

30O.0 „ 885

32O.0 „ 88

340.0 „ 88

340.4 „ 89

350.2 „ 89

430.5

7>

86

540.7

j»

775

55^.5

77

620.5

jj

69

630.5

)»

675

640.5

665

8OO.5

)»

43

880.3

)>

30

'930.3

1.0221

between 18° and 19° Fahr., and found that it decreased in bulk till it reached
220, after which it expanded a little, and continued to do so till the fluid was
reduced to between I90 and I80, when it suddenly expanded, and became ice
with a temperature of 280. It should always be recollected that a saturated
solution of common salt does not become solid, or converted into ice, at a less
temperature than 40 Fahr. ; and, therefore, if the sea should be, as is sometimes
supposed, more saline at great depths, and as it appears to be in the Mediterra-
nean from the experiments of Dr. WoUaston, ice could not be formed there at
the same temperature as it could nearer the surface. — ( Vide M. de la Becho.
Manual Geology, p. 22.)

* Specific gravity at 200 0 = 0-Q!}QSi

THE SPECIFIC GRAVITY OF THE SEA, ETC. 22rl

443. Sea water at summer more expansible than sea imter at winter
temperature. — All these experiments unite in showing that sea
water at equatorial temperatures is many times more expansible
than sea water at polar temperatures ; that is, sea water, ac-
cording to its rate of dilatation (§ 441), will expand about seven-
teen times as much for 5°, when its temperature is raised from
85°, as it will when raised from 28° ; and yet, according to Plate
X., the curves of temperature and specific gravity are symmetrical
in polar, non-symmetrical in equatorial seas. These experiments,
and the compressibility of sea water (§ 404), show that we have
not yet data sufficient to establish the depth, or even the ex-
istence of such an isothermal floor all the way from pole to pole.

444. Data for Plate X. — " The physical consequences of this
great law, should it be found completely verified by farther re-
search, are in the last degree important." The observations
which furnished the data for Fig. 1 were made in the North
Pacific between the months of August, 1855, and April, 1856, and
in the South Pacific during April and May ; whereas for Fig. 2
the southern observations were made in May and June, the
northern in June and July.

445. A thermal tide : it ebbs and flows once a year.— It is well to
bear this difference as to season north and south in mind, and to
compare these curves with those of the thermal charts ; for the
two together indicate the existence in the ocean of the thermal
tide, which, as before stated, ebbs and flows but once a year.
By this figure the South Atlantic appears to be cooler and
heavier than the northern. The season of observation, however,
is southern fall and winter vice northern summer. In January,
February, and March, the waters of the southern ocean are de-
cidedly warmer, as at the opposite six months they are decidedly
cooler, parallel for parallel, than those of the northern oceans.
Thus periodically diff'ering in temperature, the surface waters of
the two hemispheres vary also in specific gravity, and give rise to
an annual ebb and flow — an upper and an under tide — not from
one hemisphere to the other, but between each pole and equator.
In contemplating the existence and studying the laws of this
thermal tide we are struck with the compensations and adjust-
ments that are allotted to it in the mechanism of the sea ; for
these feeble forces in the water remind one of the quantities of
small value — residuals of compensation — with which the astro-
nomer has to deal when he is working out the geometry of the

224 PHYSICAL GEOGHAPHY OF THE SEA, AND ITS METEOEOLOGY.

heavens. He finds tliat it is these small quantities which make
the music of the spheres ; and so, too, it is the gentle forces like
this in the waters which preserve the harmony of the seas.
Equatorial and polar seas may be of an invariable temperature,
but in middle latitudes the sunbeam has power to wrinkle and
crumple the surface of the sea by alternate expansion and con-
traction of its waters. In these middle latitudes is the cradle of
the tiny thermal tide here brought to light; feeble, indeed, and
easily masked are its forces, but they surely exist. It may be
that the thermometer and hydrometer are the only instruments
which are nice enough to enable us to detect it. Its footprints,
nevertheless, are well marked in our tables showing the thermal
dilatation of sea water. The movements of the isothermal lines,
marching up and down the ocean, show by signs not to be mis-
taken its rate and velocity. These movements are well repre-
sented on the thermal charts. The tiny ripplings of this feeble
tide have, we may be sure, their office to perform in the general
system of aqueous circulation in the sea. Their influence may
be feeble, like small perturbations in the orbits of planets ; but
the physicist is no more at liberty to despise these than the
astronomer is to neglect those.

446. Sea ivater of the southern cooler and heavier, parallel for
parallel, than sea water of the northern hemisphere. — The problem
that we now have in hand, and which is represented by the
diagrams of Plate X., is to put the seas in scales, the ocean in a
balance, and to weigh in the specific-gravity bottle, the waters of
the northern with the waters of the southern hemisphere. By
Fig. 2 it would appear that both the water and the air of the south
Atlantic are decidedly both cooler and heavier, parallel for parallel,
than the waters of the north Atlantic ; but this difference may be
more apparent than real ; for the observations were made in the
northern summer on this side, and in the southern fall and winter
on the other side of the equator. Had we a series of observations
the converse of this, viz., winter in the north Atlantic, summer in
the south, perhaps the latter would then appear to be specifically
the lighter ; at any rate, the mean summer temperature of each
Atlantic, north and south, is higher than its mean winter tempera-
ture, and consequently the specific gravity of the waters of each
must change witli the seasons. A diagram — had we the data for
such a one — to show these changes, would be very instructive ; it
would show beautifully, by its marks, the ebb and flow of this new-

THE SPECIFIC GRAVITY OF THE SEA, ETC. 2'25

oorn tide of the ocean. BjFig. 1 the south Pacific also outweighs
the north in specific gravity ; but here again the true difi'erence,
v^hatever it be, is somewhat masked by the time of year when the
observations were made. Those north were made during the fall,
winter, and spring ; those south, during the fall and first v^intei
months of that hemisphere. Nevertheless, the w^eight of the
observations presented on Plate X. does, as far as they go, indicate
that the seaa of the southern do outweigh in specific gravity the
seas of the northern hemisphere in the proportion of 1.0272 to
1.0262 of specific gravity.* Daubeny, Dove, et al., have pointed
out an excess of salt contained in sea water south of the equator,
as compared with that contained in sea water north.

447. Testimony of the hydrometer in favour of the air crossings at
the calm belts. — These indications, as far as they go, and this view
of the subject, whatever future investigations may show to be its
true worth, seem to lean in support of the idea advanced and
maintained by facts and arguments in Chapter IV., viz., that the
southern seas are the boiler and the northern hemisphere the con-
denser for the grand atmospherical engine, which sucks up vapour
from the south to feed the northern hemisphere with rains. If it
be true, — and Dove also thinks it is — that the clouds which sup
ply our fountains with rain for the great American lakes, and
with rains for the majestic wr.ter-courses of Europe and Asia,
Korthern Africa and America, are replenished from seas beyoftd
the equator, then the waters of the ocean south should be a little
Salter, and therefore specifically a little heavier, parallel for
parallel, and temperature for temperature, than the waters of cis-
equatorial seas. We begin to filnd that the hydrometer is bearing
testimony in support of the evidence adduced in Chapters IV. and
VII., to show that when the trade-winds meet and rise up in the
equatorial calm belt, the atmosphere which came there as south-
east trade-winds passes with its vapour over into the northern
hemisphere. We had not anticipated that this little instrument
could throw any light upoR this subject ; but if, as it indicates, the
sea water of the other hemisphere be Salter and heavier than the
sea water of this, what makes it so but evaporation, and what pre-
vents currents from restoring its equilibrium but the winds, w4iich
are continually sucking up from the brine of trans- equatorial seas
and pouring it down as fresh water upon cis-equatorial seas and

* AcccTcling to Dr. INIarcet, the southern ocean contains more sidt than the
northern in the proportion of 1.02919 to 1.02757.

Q

226 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

land ? It is taking out of one scale of the balance and putting
into the other ; and the difference of specific gravity between the
sea water of the opposite hemisphere may give us a measure for
determining the amount of fresh water that is always in transitu.
Certainly, if evaporation and rains were to cease, if the rivers were
to dry up, and the sea-shells to perish, the waters of the ocean
would, in the course of time, become all of the same saltness, and
the only difference of specific gravity in the sea would be due to
thermal agencies. After having thus ceased, if evaporation were
then to commence only in the other hemisphere, and condensation
take place only in this, half the difference, as to saltness of the sea
water in opposite hemispheres, would express the ratio in volumes
of fresh water, whether as vapour or liquid, that would then be
kept in transitu between the two hemispheres. But it evaporates
on both sides and precipitates on both ; nevertheless, more on one
side than on the other, and the difference of saltness will still in-
dicate the proportion in transitu. If we follow the thermal and
specific gravity curves from the parallels of 30° — 34° to the equa-
tor {Figs. 1 and 2, Plate X.), we see, as I have said, that sea water
in this part of the ocean does not grow lighter in proportion as it
grows warmer. This is accounted for on the supposition that the
effects of the thermal dilatation on the specific gravity is counter
acted by evaporation. Xow, if we knew the thickness of the
stratum which supplies the fresh water for this evaporation, we
should not only have a measure for the amount of water which as
vapour is sucked up and carried off from the trade- wind regions of
the sea, to be deposited in showers on other parts of the earth, but
we should be enabled to determine also the quantity which is eva-
porated in one hemisphere and transported by the clouds and the
winds to be precipitated in the other. These are questions which
are raised for contemplation merely; they cannot be answered
■now ; they grow out of some of the many grand and imposing
thoughts suggested by the study of the revelations which the
hydrometer is already beginning to make concerning the wonders
of the sea. Eeturning from this excursion towards the fields of
speculation, it will be perceived that these observations upon the
temperature and density of sea water have for their object to weigh
the seas, and to measure in the opposite scales of a balance the
specific gravity of the waters of one hemisphere with the specific
gravity of the waters of the other. This problem is quite within
the compass of this exquisite system of research to solve. But, in

THE SPECIFIC GRAVITY OF THE SEA, ETC. 227

order to weigh the seas in this manner, it is necessary that the little
hydrometric balance by which it is to be done should be well and
truly adjusted.

448. Amount of salt in, and mean sjpecijic gravity of sea wateic, —
From these premises it would not be difficult to show that the
saltness of the sea is a physical necessity. In some of the aspects
presented, the salts of the sea hold the relation in the terrestrial
mechanism that the balance-wheel does to the machinery of a
watch. Without them the climates of the earth could not harmo-
nize as they do ; neither could the winds, by sucking up -vapour,
hold in check the expansive power of tropical heat upon the sea ;
nor counteract, by leaving the salts behind, the thermal influence
of the sun in imparting dynamical force to marine currents ; nor
prevent the solar ray from unduly disturbing the aqueous equi-
librium of our planet. As evaporation goes on from a sea of fresh
water, the level onl}^ and not the specific gravity, of the remain-
ing water is changed. The waters of fresh intertropical seas
would, instead of growing heavy by reason of evaporation between
the tropics, become lighter and lighter by reason of the heat ;
while the water of fresh polar seas would grow heavier and
heavier by reason of the cold — a condition which, by reason ol
evaporation and precipitation, is almost the very reverse of that
which nature has ordained for the salt sea, and which, therefore,
is the wisest and the best. The average amount of salts in sea
water is not accurately known. From such data as I have, 1
estimate it to be about 4 per cent. (.039), and the mean specific
gravity of sea water at 60" to be about 1.0272. Supposing these
conditions to be accurate — and they are based on data which
entitle them to be considered as not very wide of the mark —
the hydrometer and thermometer, with the aid of the table (§ 441),
will give us a direct measure for the amount of salt in any specimen
of sea water into which the navigator will take the trouble to dip
these two instruments.

449. Light cast hy Plate X. on the open sea in the Arctic Ocean. — ■
These specific gravity and thermal curves, as they are presented
on this Plate (X.), throw light also on the question of an open sea
in the Arctic Ocean. That open sea is like a boiling spring
(§ 427) in the midst of winter, which the severest cold can never
seal up ; only it is on a larger scale than any spring, or pool, or
lake, and it is fed by the under currents with warm water from

Q 2

228 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOllOLOCT.

the south, which, b}^ virtue of its saltness (see Fig. 2), is heaviet
than the cool and upper current which runs out of the polar basin,
and which is known as an ice-bearing current. It is the same
which is felt by mariners as far down as the Grand Banks of
Newfoundland, and recognized by philosophers off the coast of
Florida. This upper current, though colder than its fellow below,
is lighter, because it is not so salt. Figure 2 reveals to us a
portion of sea between the parallels of 34° and 40° north, exactly
in such a physical category as that in which this theory presents
the Arctic Ocean. Here, along our own shores, the thermal curve
loses 12°. of heat; and what does the specific gravity curve gain
in the same interval ? Instead of increasing up to 1'.027, accord-
ing to the thermal law, it decreases to 1.023 for the want of salt
to sustain it. Now recollect that the great American chain of
fresh- water lakes never freezes over. Why? Because of their
depth and their vertical circulation. The depths below are con-
tinually sending water above 32° to the surface, which, before it
can be cooled down to the freezing-point, sinks again. Now
compare the shallow soundings in these lakes with the great depths
of the Arctic Ocean ; compute the vast extent of the hydrographic
basin which holds this polar sea ; gauge the rivers that discharge
themselves into it ; measure the rain, and hail, and snow that the
clouds pour down upon it ; and then contrast its area, and the fresh-
water drainage into it, with the like of Long Island Sound,
Delaware Bay, and the Chesapeake ; consider also the volume of
diluted sea water between our shore-line and the Gulf Stream ;
strike the balance, and then see if the arctic supply of fresh water
be not enough to reduce its salts as much as our own fresh-water
streams are diluting the brine of the sea under our ovm eyes.
The very Gulf Stream water, which the observing vessel left as
she crossed 34° and entered into those light littoral waters, was
bound northward. Suppose it to have flowed on as a surface
current until it, with its salts, was reduced to. the temperature of
4r»°. Its specific gravity at that temperature would have been
1 .030, or specifically 30 per cent, heavier than the sea water of our
own coasts. Could two such currents of water meet anywhere
at sea, except as upper and under currents ? If water that freezes
at 32°, that grows light and remains on the surface as you cool it
below 39°, is prevented from freezing in our great fresh-water
lakes by vertical circulation, how much more would both verticaJ
and horizontal circulation prevent congelation in the open polai

THE SPECTFIC GRAVITY OF THE SEA, ETC. 229

sea. that is many times deeper and larger than the lakes, and the
water of which contracts all the way down to its freezing-point
of 27°.2' !

450. Tlie heaviest water. — The heaviest w^ater in the sea, un-
corrected for the temperature, as shown by the observations before
us, is 1.028. This water was found (Figs. 1 and 2) off Cape Horn.
Let us examine a little more closely into the circumstances con-
nected with the heaviest water on our side of the equator. It was
a specimen of water from the Sea of Okotsk, which is a sea in a
riverless region, and one where evaporation is probably in excess
of precipitation — thus fulfilling the physical conditions for heavy
w^ater. The Eed Sea is in a riverless and rainless region. Its
waters ought to be heavier than those of any other mere arm of
the ocean, and the dynamical force arising from the increase of
specific gravity acquired by its waters after they enter it at Babel-
mandeb is sufficient to keep up a powerful inner and outer current
through those straits. At the ordinary meeting of the Bombay
Geographical Society for November, 1857, the learned secretary
stated that recent observations then in his possession, and which
were made by Mr. Eitchie and Dr. Giraud (§ 381), go to show
that the saltest water in the Red Sea is where theory (§ 377) makes
it, viz., in the Gulf of Suez ; and that its waters become less and
less salt thence to its mouth, and even beyond, till you approach
the meridian of Socotra ; after which the saltness again increaseh-
as you approach Bombay.

451. Chapman's experiments. — Its waters, from the mouth of the
straits for 300 or 400 miles up, have been found as high in
temperature as 95° Fahrenheit — a sea at blood heat ! The ex-
periments of Professor Chapman, of Canada, which indicated as
law — the Salter the water the slower the evaporation, seem to
suggest an explanation of this, at least in part. Evaporation
ought to assist in keeping the surface of intertropical seas cool in
the same way that it helps to cool other wet surfaces. And if the
waters of the Red Sea become so salt that they cannot make vapour
enough to carry off the excessive heat of the solar ray, we may
be sure that nature has provided means for carrying it off. But
for the escape which these highly heated waters are, by means of
their saltness, enabled to make from that sea, its climate, as well
as the heat of its waters, would be more burning and blasting
than the sands of Sahara. Even as it is, the waters of this sea are
hotter than the air of the desert.

230 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

452. TJie hydrometer indicates the rainy latitudes at sea. — There is
another indication which this little instrument has afforded con-
cerning the status of the sea, and which deserves notice. We
are at first puzzled with the remarkably light water between 9°
and 16° S., Fig. 1, and in Fig. 2 between 7° and 9° N., as well as
in 19° N. But after a little examination, we are charmed with
the discovery that the hydrometer points out the rainy regions
at sea. Eodgers' observations on his homeward passage from
San Francisco to Cape Horn furnish the data for the curves
{Fig. 1) between 37° N. and 57° S. Now Plate VIII. shows that
the equatorial calm belt lies south of the line where it is inter-
sected by the homeward route from California. It also shows
that when he crossed the " Doldrums " in the Atlantic, that belt
was in north latitude about 7°-10°, and that when he was in
18°-20° N. (Fig. 2) he was then passing through the offings of
what are called the " Leeward Islands " of the AVest Indies, and
that these are rainy latitudes at sea — the first two being under
the cloud ring, the last being near the land in the trade-wind
region, and confirming the remark so often made concerning the
influence of islands at sea upon vapour, clouds, and precipitation.

453. Astronomical view. — The most comprehensive view that
we are permitted to take of cosmical or terrestrial arrangements
and adaptations is at best naiTow and contracted. Nevertheless,
in studying the mechanism which Wisdom planned and the Great
Architect of nature designed for the world, we sometimes fancy
that we can discover a relation between the diff'erent parts of the
wonderful machinery, and perceive some of the reasons and
almost comprehend the design which Omnipotent Intelligence
had in view when those relations were established. Such fancies,
rightly indulged, are always refreshing, and the developments of
the hydrometer which we have been studying point us to one of
them. This fancied discovery is, that a sea of fresh water instead
of salt would not afi'ord the compensations that are required in
the terrestrial economy, and we also fancy that we have almost dis-
covered a relation between the orbit of the earth and the arrange-
ment of land and water on its surface and their bearing upon
climate. Our planet passes its perihelion during the southern
summer, when it is nearer the centre and source of light and heat
by more than three millions of miles than it is at its winter
solstice, so that, on the 1st of January, the total amount of heal
received by the earth is about y^g- more than it receives during a

THE SPECIFIC GRAVITY OF THE SEA, ETC. 231

day in July, wlien it is in aphelion.* January is tlie midsLimmer
month of the southern hemisphere, consequently that half of the
globe receives more heat in a day of its summer than the other
half receives in a day of the northern summer. But the northern
summer is a week the longer, by the reason of the ellipticity of
the earth's orbit. What becomes of this diurnal excess of southern
summer heat, be it in its aggregate never so small, and why does
it not accumulate in trans-equatorial climes ? So far from it the
southern hemisphere is the cooler.

454. Tlie latent heat of vapour. — In the southern hemisphere
there is more sea and less land than in the northern. But the
hydrometer indicates that the water in the seas of the former are
Salter and heavier than the waters of seas cis-equatorial ; and
man's reasoning faculties suggest, in explanation of this, that this
diiference of saltness or specific gravity is owing to the excess
of evaporation in the southern half, excess of precipitation in the
northern half of our planet. " When water passes, at 212° Fah-
renheit, into steam it absorbs 1000° of heat, which becomes in-
sensible to the thermometer, or latent ; and conversely, when
steam is condensed into water, it gives out 1000° of latent heat,
which thus becomes free, and aifects both the thermometer and
the senses. Hence steam of 212° Fahrenheit will, in condensing,
heat five and a half times its own weight of water from the
freezing to the boiling point." — M'CuUocli. Now there is in the
southern a very much larger water surface exposed to the sun
than there is in the northern hemisphere, and this excess of heat
is employed in lifting up vapour from that broad surface, in
transporting it across the torrid zone and conveying it to extra-
tropical northern latitudes, where the vapour is condensed to
i-eplenish our fountains, and where this southern heat is set free
to mitigate the severity of northern climates.

455. Its influence upon climates. — In order to trace a little
farther, in our blind way, the evidences of wisdom and design,
vrhich we imagine we can detect in the terrestrial arrangement
of land and water, let us fancy the southern hemisphere to have
the land of the northern, and the northern to have the water of
the southern, the earth's orbit remainiug the same. Is it not
obvious to our reason that by this change the whole sj^stem of
climatology in both hemispheres would be changed ? The climates
of our planet are as obedient to law as the hosts of heaven.

* Sir Johu Herschel.

232 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

They are as they were designed to be ; and all those agents
which are concerned in regulating, controlling, and sustaining
them are " ministers of His." Johnston, in the chapter to
Plate XVni. of his great Physical Atlas, thus alkides to the
seas, land, and climates of the two hemispheres : " The mild
winter of the southern hemisphere, plus the contemporaneous
hot summer of the northern hemisphere, necessarily gives a
higher sum of temperature than the cool summer of the southern,
plus the cold winter of the northern hemisphere. The above-
described relations appear to furnish the motive power in the
machinery of the general atmosphere of the earth in the periodical
conversion of the aqueous vapours into liquid form. In this
manner the circuit of the fluid element, the essential support of
all vegetable and animal life, no longer appears to depend on
mere local coolings, or on the intermixture of atmospheric cur-
rents of different temperatures ; but the unequal distribution of
land and sea in the northern and southern hemispheres supplies
an effectual provision, from whence it necessarily follows that
the aqueous vapour, which from the autumnal to the vernal equi-
nox is developed to an immense extent over the southern hemi •
sphere, returns to the earth, in the other half of the year, in tha
form of rain or snow. And thus the wonderful march of the
most powerful steam-engine with which we are acquainted, the
atmosphere, appears to be permanently regulated. The irregular
distribution of physical qualities over the earth's surface is here
seen to be a preserving principle for terrestrial life. Professor
Dove considers the northern hemisphere as the condenser in this
great steam-engine, and the southern hemisphere as its water
reservoir ; that the quantity of rain which falls in the northern
hemisphere is, therefore, considerably greater than that which
falls in the southern hemisphere ; and that one reason of the
high temperature of the northern hemisphere is that the larger
quantity of heat which becomes latent in the southern hemi-
sphere in the formation of aqueous vapour is set free in the north
in great falls of rain and snow."

456. The results of the marine hydrometer. — In this view of what
our little hydrometer has developed or suggested, we trace the
principles of compensation and adjustment, the marks of design,
the evidence of adaptation between the orbit of the earth and
the time from the vernal to the autumnal, and from the autumnal
to the vernal equinox ; between the arrangement of the land in

THE SPECIFIC GRAVITY OP THE SEA, ETC. 233

one liemisphere and the arrangement of the water in the other ;
between the rains of the northern and the winds of the southern
hemisphere ; between the vapour in the air and the salts of the
sea ; and between climates on opposite sides of the equator. And
all this is suggested by merely floating a glass bubble in sea
water during a voyage to the Pacific ! Thus even the little
hydrometer, in its mute way, points the Christian philosopher to
the evidences of design in creation. That the arrangements
suggested above are adapted to each other, this instrument affords
us evidence as clear as that which the telescope and the micro-
scope bear in proof that the eye, in its structure, was adapted to
the light of heaven. The universe is the expression of one
thought, and that it is so every new fact developed in the pro-
gress of our researches is glorious proof.

457. Barometer indications of an open sea. — In the course of our
investigations into the physics of the sea, 100,000 observations
of the barometer, and more than a million on the direction of the
winds have been discussed. They indicate an open water in the
Arctic Ocean. They show that about the poles there is a high
degree of aerial rarefaction — higher, indeed, than there is about
the equator; for the barometer not only stands lower in this
place of polar calms than it does in the equatorial calm belt, but
the inrushing air comes from a greater distance to the cold than
to the warm calms.*

458. Polar rarefaction. — The question may be asked, Whence
comes the heat that expands and rarefies the atmosphere in these
polar places ? The answer is, it comes from the condensation 'of
vapour. The south pole is surrounded by water, the north pole
by land. But the unexplored regions within the arctic basin are
(§ 429) for the most part probably sea, within the antarctic, land.
The rarefaction produced in the latter by the latent heat of
vapoiir is such that the mean height of the barometer there is
about 28 inches, while that in the arctic calm place is such as to
reduce the barometer there to a mean not far from 29.5 inches.
In the equatorial calm its mean height is about 29.9 inches. The
hypothesis of an open sea in the Arctic Ocean becomes necessary
to supply a source for this vapour ; for the winds, entering the
Arctic Ocean as they do after passing over land and mountain
heights of America, Europe, and Asia, must be robbed of much
of their moisture ere they reach that ocean ; it will require an

* Plate IV., Nautical Monograph Na 1,

234: PHYSICAL GEOGRAPHY OF THE SEA, ANt ITS METEOEOLOGT.

abundant supply of vapour to create there by precipitation and
the liberation of latent heat a degree of rarefaction sufficient to
cause a general movement of the air polarward for the distance
of 40° of latitude all round. That there is an immense volume
of comparatively warm water going into the Arctic Ocean is
abundantly shown by observation, and the rising up there of this
water to the surface would afford heat and vapour enough for a
vast degree of rarefaction.

459. Tlie middle ice. — The records of arctic explorations,
together with the whalemen's accounts of " middle ice " in
Baffin's Bay and Davis' Straits, go to confirm this view, which
is further elaborated in the next chapter (§ 475). The facts
there stated, and this " middle ice," go to show that every winter
a drift takes place which brings out of the Frozen Ocean a
tongue of ice a thousand miles or more in length : it is the com-
pact and cold " middle ice." In our fresh-water streams it is the
middle ice that first breaks up ; that which is out of the way of
the curent remains longest. Not so in this bay and strait ; there
the littoral ice first gives way, leaving an open channel on either
side in spring and early summer, while the "middle ice"
remains firm and impassable. The explanation is simple enough :
the middle ice was formed in the severe cold of more northern
latitudes, from which it has drifted down, while that on the sides
was formed in the less severe climates of the bay and straits.
This winter tongue of ice, which we know by actual observation
is in motion from December till May, must, during that time, be
detached from the main mass of ice in the Arctic Ocean, conse-
quently there must be water between the ice that is in motion
and the ice that is at rest. Not only so. In early summer the
whalemen will run up to the north in the open water at the side
of the " middle ice " in Davis' Strait and Baffin's Bay, even as
far sometimes as Cape Alexander in 78°, to look for a crossing-
place. Here, though so far north, they will find the " middle
ice " gone, or so brollen up that they can cross over to the west
side. They trace it up thus far, because at the south, and in
spite of a higher thermometer, they find the " middle ice " com-
pact and fiiTQ, so much so as to be impassable. In this fact we
recognize another circumstance favouring the theory of an open
8ea at the noi'th, and giving plausibility to the conjecture that
this " middle ice " drifts out from the southern edge of the open
Bea as fast as it is formed during the winter. According to this

THE SALTS OF THE SEA. 235

conjecture, the thickest part of the " middle ice " should be that
which has been exposed to the longest and severest cold, and
this is probably that which began to be formed on the edge oi
the open sea in January. As it drifted to the south it continued,
to form and grow thick, and perhaps would be the last to melt .
while that which began to be formed at the edge of the open sea
in March or April would drift out, and not attain much thick-
ness before it would cease to freeze and commence to thaw. It
is this spring-made " middle ice " then, which, as it drifts to the
south, would, being thin, be the first to break up ; and experience
has taught the whalemen to look north, not south, for the first
breaking up and the earliest passage through the "middle ice."

460. Position of the open sea. — The open sea, therefore, is, it
may be inferred, at no gr&at distance from the several straits,
which, leading in a northwardly direction, connect Baffin's Bay
with the Arctic Ocean. It is through these straits that the
winter drift takes place. The ice in which the Fox, the Eesolute,
the Advance, and the Rescue each drifted a thousand miles or more,
came down through these straits. The fact of this annual winter
drift from the Arctic Ocean is a most important one for future
explorers. Had Captain Franklin known of it, he might have
put his vessels in the line of it, and so escaped the rigours of
that second winter. It would have brought him safely to the
parallel of 65° or 60°, and set him free, as it did four other
vessels, in the glad waters of the Atlantic Ocean.

CHAPTEE X.

§ 461-499. — THE SALTS OF THE SEA.

461. The hrine of the ocean. — The brine of the ocean is the ley
of the earth (§ 43). From it the sea derives dynamical power,
and its currents their main strength. Hence, to understand the
dynamics of the ocean, it is necessary to study the efi'ects of
their saltness upon the equilibrium of its waters ; wherefore this
chapter is added to assist in the elucidation of what has already
been said concerning the currents and other phenomena of the
sea. Why was the sea made salt ? It is the salts of the sea that

part to its waters those curious anomalies in the laws of
freezing and of thermal dilatation which have been described in a

236 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOOT.

previous chapter (IX.). It is the salts of the sea that assist the
rays of heat to penetrate its bosom ;* but for these, the solar ray,
instead of heating large masses of water like the Gulf Stream,
would play only at or near the surface, raising the temperature
of the waters there, like the sand in desert places, to an inordi-
nate degree. The salts of the sea invest it with adaptations
which it could not possess were its waters fresh. Were they
fresh, they would attain their maximum density at 3 9°. 5 instead
of 25°. 6, and the sea then would not have dynamical force enough
to put the Gulf Stream in motion, nor could it regulate those
climates we call marine.

462. Were the sea of fresh water. — Were the sea fresh and not
salt, Ireland would never have presented those ever-green shores
which have won for her the name of the "Emerald Isle;" and
the climate of England would have vied with Labrador for
inhospitality. Had not the sea been salt, the torrid zone would
have been hotter and the frigid colder for lack of aqueous
circulation ; had the sea not been salt, intertropical seas would
have been at a constant temperature higher than blood heat, and
the polar oceans would have been sealed up in everlasting fetters
of ice, while certain parts of the earth would have been deluged
with rain. Had the seas been of fresh water, the amount of
evaporation, the quantity of rain, the volume and size of our
rivers, would all have been different from what they are ; the
quantity of electricity in the air would have been permanently
changed from what it is, and its tension in the sky would have
been exceedingly feeble. In the evaporation of fresh water at
nonnal temperatures, but little of that fluid is evolved ; while
vapour from salt water carries off vitreous, and leaves behind
resinous electricity in abundance. Hence, with seas of fresh
water, our thunder-storms would be feeble contrivances, flashing
only with such sparks as the vegetable kingdom might, when
the juices of its plants were converted into vapour, lend to the
clouds. It might seem strange, this idea that the thunderbolt of
the sky, the sheet-lightning of the clouds, and the forked flashes
of the storm, all have their genesis chiefly in the salts of the sea,
and so it would be held were it not that Faraday has shown that
a single grain of water and a little zinc can evolve electricity
enough for a thunder-clap ; therefore, were there no salts in the

* Melloui has shown that tlie power of salt water to transmit heat is very
much greater thap that of i'resh.

THE SALTS OF THE SEA. 237

uaters of the ocean, the sound of thunder would scarce "be heard
ill the sky* — there would be no Gulf Stream, and no open sea in
the Arctic Ocean.

463. Uniform character of sea ivater. — As a general rule, the
constituents of sea water are as constant in their proportions as
are the components of the atmosphere. It is true that we some-
times come across arms of the sea, or places in the ocean, wheie
we find the water more salt or less salt than sea water is
generally ; but this circumstance is due to local causes of easy
explanation. For instance : when we come to an arm of the sea,
as the Red Sea (§ 376), upon which it never rains, and from
which the atmosphere is continually abstracting, by evaporation,
fresh water from the salt, we may naturally expect to find a
greater proportion of salt in the sea water that remains than we
do near the Inouth of some great river, as the Amazon, or in the
regions of constant precipitation, or in other parts, as on the polar
side of 40° in the North Atlantic, where it rains more than it
evaporates. Yet in the case of the Eed Sea, and all such natural
salt-pans, as that and other rainless portions of the sea may be
called, there is, on account of currents which are continually
bearing away the water that has given off its vapours and bringing
forward that which is less concentrated as to brine, a moderate
degree of saltness which its waters cannot exceed. We moreover
find that, though the constituents of sea water, like those of the
atmosphere, are not for every place invariably the same as to
their proportions, yet they are the same, or nearly the same, as
to their character. When, therefore, we take into consideration the
fact that, as a general rule, sea water is, with the exception above
stated, everywhere and always the same, and that it can only be
made so by being well shaken together^ we find grounds on
which to base the conjecture that the ocean has its sj'stem of cir-
culation, which is well calculated to excite our admiration, for it
is as wonderful as the circulation of the blood.

* The great American lakes afford, it may be supposed, a considerable por-
tion of the vapour which goes to make rain for the hydrographic basin in which
they are. Visiting the Lake country in 1858, 1 was struck with the fact that
so few trees bore the marks of lightning. The rule appeared to be, the nearer
the lakes, the more rare was it for one of these ornaments of the forest to have
been defaced by h'ghtning ; and, on inquiry from the Lake Board of Under-
writers, I was informed that among the records of lake disasters there was not
a single instance of a vessel having been struck by lightning on the North
A.merioan lakes !

238 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

464. Hypotheses. — In order to investigate the effect of the salts
of the sea upon its currents, and to catch a glimpse of the laws
by which the circulation of its waters is governed, hypothesis, in
the present meagre state of absolute knowledge with regard to
the subject, seems to be as necessary to progress as is a corner-
stone to a building. To make progress with such investigations
we want something to build upon. In the absence of facts, we
are sometimes permitted to suppose them ; only, in supposing
them, we should take not only the possible, but the probable ;
aud in making the selection of the various hypotheses which ai-e
suggested, we are bound to prefer that one by which the greatest
number of phenomena can be reconciled. When we have found,
tried, and offered such a one, we are entitled to claim for it a
respectful consideration at least, until we discover it leading us
into some palpable absurdity, or until some other hj^pothesis be
suggested which will account equally as well, but for a greater
number of phenomena. Then, as honest searchers after truth,
we should be ready to give up the former, adopt the latter, and
hold it until some other better than either of the two be offered.
With this understanding, I venture to offer an hypothesis with
i3gard to the agency of the salts or solid matter of the sea in
imparting dynamical force to the waters of the ocean, and to
suggest that one of the purposes which, in the grand design, it
was probably intended to accomplish by having the sea salt, and
not fresh, was to impart to its waters the forces and powers
necessary to make their circulation complete. In the first place,
we rely mainly upon hypothesis or conjecture for the assertion
that there is a set of currents in the sea by which its waters are
conveyed from place to place with regularity, certainty, and
order. But this conjecture appears to be founded on reason, and
we believe it to be true ; for if we take a sample of water which
shall fairly represent, in the proportion of its constituents, the
average water of the Pacific Ocean, and analyze it, and if we do
the same by a similar sample from the Atlantic, we shall find the
analysis of the one to resemble that of the other as closely as
though the two samples had been taken from the same bottle
after having been well shaken. How, then, shall we account for
this, unless upon the supposition that sea water from one part of
the world is, in the process of time, brought in contact and mixed
up with sea water from all other parts of the world ? Agents,
therefore, it would seem, are at work, which shake up the waters

THE SALTS OF THE SEA. 239

of the sea as thougli they were in a bottle, and which, in the
course of time, mingle those that are in one paii; of the ocean
with those that are in another as thoroughly and completely as it
is possible for a man to do in a vessel of his own construction.
This fact as to uniformity of components appears to call for the
hypothesis that sea water which to-day is in one part of the ocean,
will, in the process of time, be found in another part the most
remote. It must, therefore, be carried about by currents ; and
as these currents have their offices to perform in the terrestrial
economy, they probably do not flow by chance, but in obedience
to physical laws ; they no doubt, therefore, assist to maintain
the order and preserve the harmony which characterize every
department of God's handywork, and as such we treat them.

465. Arguments afforded by corallines in favour of. — This hypo-
thesis about currents is based upon our faith in the physical
adaptations with which the sea is invested. Take, for example,
the coral islands, reefs, beds, and atolls with which the Pacific
Ocean is studded and garnished. They were built up of materials
which a certain kind of insect quarried from the sea water. The
currents of the sea ministered to this little insect — they were its
hod carriers. When fresh supplies of solid matter were wanted
for the coral rock upon which the foundations of the Polynesian
Islands were laid, these hod-carriers brought them in unfailing
streams of sea water, loaded with food and building materials for
the coralline. The obedient currents, therefore, must thread the
widest and the deepest seas, for they never fail to come at the right
time, nor refuse to give place and go after they have ministered
to the hungry creature. Unless the currents of the sea were
employed to carry off from this insect the waters that have been
emptied by it of their lime, and to bring to it others charged
with more, it is evident the little creature would have perished
for want of food long before its task was half completed. But
for currents, it would have been impaled in a nook of the very
drop of water in which it was brought forth ; for it would have
soon secreted the lime contained in this drop, and then, without
the ministering aid of currents to bring it more, it would have
perished for the want of food for itself and materials for its
edifice ; and thus, but for the benign currents which took this
exhausted water away, there we perceive this emptied drop
would have remained, not only as the grave of the little architect,
but as a monument in attestation of the shocking monstrosity that

240 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

there had been a failure in the isubliine system of terrestrial
adaptations — that the sea had not been adapted by its Creator to
the well-being of all its inhabitants. Now we do know that its
adaptations are suited to all the wants of every one of its inha-
bitants— to the wants of the coral insect as well as to those of
the whale. Thus our simple hypothesis acquires the majesty of
truth, for we are now prepared boldly to assert we know that the
sea has its system of circulation, because it' transports materials
for the coral insect and its rock from one part of the world to
another ; because its currents receive them from the rivers, and
hand them over to the little mason for the structure of the most
stupendous works of solid masonry that man has ever see^i — the
coral islands of the sea. Thus, and moreover, by a process of
reasoning which is perfectly philosophical, we are irresistibly
led to conjecture that there are regular and certain, if not
appointed channels through which the water travels from one
part of the ocean to another, and that those channels belong to
an arrangement which may make, and which, for ought we know
to the contrary, does make the system of oceanic circulation as
complete, as perfect, and as harmonious as is that of the atmo-
sphere or the blood. Every drop of water in the sea is as
obedient to law and order as are the members of the heavenly
host in the remotest regions of space; for when the morning
stars sang together in the almighty anthem, we are told " the
waves also lifted up their voice " in chorus ; and doubtless,
therefore, the harmony in the depths of the ocean is in tune with
that which comes from the spheres above. "We cannot doubt it ;
for, were it not so, were there no channels of circulation from
one ocean to another, and if, accordingl}', the waters of the
Atlantic were confined to the Atlantic, or if the waters of the
arms and seas of the Atlantic were confined to those arms and
seas, and had no channels of circulation by which they could pass
out into the ocean, and traverse different latitudes and climates
— if this were so, then the machinery of the ocean would be as
incomplete as that of a watch without a balance-wheel.

466. Ditto by the Bed Sea. — For instance, take the Eed Sea and
the Mediterranean by way of illustration. Upon the Red Sea
there is no precipitation ; it is a rainless region ; not a river runs
aown to it, not a brook empties into it ; therefore there is no
process by which the salts and washings of the earth, which are
taken up and held in solution by rain or river water, can be

THE SALTS OF THE SEA. 241

broHO'lit down into the Red Sea. Its salts come from the ocean,
and the air takes up from it, in the process of evaporation, fresh
water, leaving behind, for the currents to carry away, the solid
matter which, as sea water, it held in solution. On the other
hand, numerous rivers discharge themselves into the Mediter-
ranean, some of which are filtered through soils and among
minerals which yield one kind of salts or soluble matter, another
river runs through a limestone or volcanic region of country, and
brino's down in solution solid matter — it may be common salt,
sulphate or carbonate of line, magnesia, soda, potash, or iron —
either or all may be in its waters. Still, the constituents of sea
water from the Mediterranean and of sea water from the Red Sea
are quite the same. But the waters of the Dead Sea have no
connection with those of the ocean ; they are cut off from its
channels of circulation, and are therefore quite different, as to
their components, from any arm, frith, or gulf of the broad ocean
Its inhabitants are also different from those of the high seas.
" The water which evaporates from the sea is nearly pure,
containing but very minute traces of salts. Falling as rain upon
the land, it washes the soil, percolates through the rocky layers^
and becomes charged with saline substances, which are borne
seaward by the returning currents. The ocean, therefore, is the
great depository of everything that water can dissolve and carry
down from the surface of the continents ; and, as there is no
channel for their escape, they of course consequently accumu-
late."* They would constantly accumulate, as this very shrewd
author remarks, were it not for the shells and insects of the sea
and other agents mentioned.

467. A general system of circulation required for tlie ocean. — How,
therefore, shall we account for this sameness of compound, this
structure of coral (§ 465), this stability as to animal life in the sea,
but upon the supposition of a general system of circulation in the
ocean, by which, in process of time, water from one part is
conveyed to another part the most remote, and by which a
general interchange and commingling of the waters take place ?
In like manner, the constituents of the atmosphere, whether it
be analyzed at the equator or the poles, are the same. By o.utting
ofi" and shutting up from the general channels of circulation any
portion of sea water, as in the Dead Sea, or of atmospheric air, as
vn mines or wells, we can easily charge either with gases or
* YoTunan'^ Chemistry.

242 rnYSicAL geography of tuk sea, and its meteosoloqt.

other matter that shall very much affect its character, or alter
the proportion of its ingredients, and affect the health of its
inhabitants ; but in the open sea or open air we can do no such
thing.

468. Dynamical agents. — The principal agents that are supposed
to be concerned in giving circulation to the atmosphere, and in
preserving the ratio among its components, are light, heat, elec-
tricity, and perhaps magnetism. But v^ith regard to the sea, il
is not known what office, if any, is performed by electricity, in
giving dynamical force to its system of circulation. The chief
motive power from which marine currents derive their velocity
has been ascribed to heat ; but a close study of the agents
concerned has suggested that an important — nay, a powerful and
active agency in the system of oceanic circulation is derived from
the salts of the sea w^ater, through the instrumentality of the
winds, of marine plants, and animals. These give the ocean
great dynamical force. Let us, for the sake of illustrating and
e^cplaining the nature of this force, suppose the sea in all its
pai'ts — in its depths and at the surface, at the equator and about
the poles — to be of one uniform temperature, and to be all of
fresh water ; and, moreover, that there be neither wind to disturb
its surface, nor tides nor rains to raise the level in this part, or to
depress it in that. In this case there would be nothing of heat to
disturb its equilibrium, and there would be no motive power
(§ 461) to beget currents, or to set the water in motion by reason
of the difference of level or of specific gravity due to water at
different densities and temperatures. Now let us suppose the
winds, for the first time since the creation, to commence to blow
upon this quiescent sea, and to ruffle its surface ; they, by their
force, would create partial surface currents, and thus agitating the
waters, as they do, but only for a little way below the surface, would
give rise to a feeble circulation in the supposed sea of fresh
water. The surface drift thus created — currents they would hardly
}3e, — would set with the wind, giving rise to counter movements
in the shape of under-tows and eddies. This, then, is one of the
sources whence power is given to the system of oceanic circula-
tion ; but, though a feeble one, it is one which exists in reality,
and, therefore, need nor be regarded as hypothetical. Some (§79)
think it the " sole cause r Let us next call in evaporation and
precipitation, with heat and cold — more powerful agents still.
Suppose the evaporation to commence from this imaginary fresh-

THE SALTS OF THE SEA. 243

water ocean, and to go on as it does from the seas as they are.
In those regions, as in the trade- wind regions, where evaporation
is in excess of precipitation (§ 545), the general level of this
supposed sea would be altered, and immediately as much water
as is carried off by evaporation would commence to flow in from
north and south towards the trade- wind or evaporating region to
restore the level. On the other hand, the winds would have
taken this vapour, borne it off to the extra-tropical regions, and
precipitated it, we will suppose, where precipitation is in excess
of evaporation. Here is another alteration of sea level by
elevation instead of by depression ; and hence we have the motive
power for a surface current from each pole towards the equator,
the object of which is only to supply the demand for evaporation
in the trade-wind regions — demand for evaporation being taken
here to mean the difference between evaporation and precipitation
for any part of the sea. Now imagine this sea of uniform tem-
jDcrature to be suddenly stricken with the invisible wand of heat
and cold, biinging its waters to the various temperatures at which
they at this instant are standing. This change of temperature
would make a change of specific gravity in the watefs, which
would destroy the equilibrium of the whole ocean ; upon this a
set of currents would immediately commence to flow, namely, a
current of cold and heavy water to the place of the warm, and a
current of warm and lighter to the place of the cold. The motive
power of the currents thus created would be difference of specific
gravity arising from difference of temperature in fresh water.
We have now traced the effect of two agents, which, in a sea of
fresh water, would tend to create currents, and to beget a system
of aqueous circulation ; but a set of currents, and a system of
circulation which, it is readily perceived, would be quite feeble
in comparison with those which we find in the salt sea. One of
these agents would be employed in restoring, by means of one or
more polar currents, the water that is taken from one part of the
ocean by evaporation, and deposited in another by precipitation.
The other agent would be emploj-ed in restoring, by the forces
due to difference of specific gravity, the equilibrium, which has
been disturbed by heating, and of course expanding, the waters
of the torrid zone on one hand, and by cooling, and consequently
contracting, those of the frigid zone on the other. This agency,
would, if it were not modified by others, find expression in a
system of currents and counter currents, or rather in a set of

B 2

244 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOEOLOGY.

surface currents of warm and lighter water, from the equatoi
towards the poles, and in another set of under currents of cooler,
dense, and heav}^ water from the poles towards the equator.

469. Currents without wind. — Such, keeping out of view the
influence of the winds, which we may suppose would be the
same whether the sea were salt or fresh, would be the system of
oceanic circulation were the sea all of fresh water. But fresh
water, in cooling, begins to expand near the temperature of 40°,*
and expands more and more till it reaches the freezing-point, and
ceases to be fluid. This law of expansion by cooling would im-
part a peculiar feature to the system of oceanic circulation were
the waters all fresh, which is not necessary here to notice farther
than to say it cannot exist in seas of salt water, for salt water
(§ 405) contracts as its temperature is lowered, and until it passes
its freezing-point. Hence, in consequence of its salts, changes of
temperature derive increased power to disturb the equilibrium of
the ocean. If this train of reasoning be good, we may infer that,
in a system of oceanic circulation, the dynamical force to be derived
from difference of temperature, where the waters are all fresh,
would be quite feeble ; and that were the sea not salt, we should
(§ 462) probably have no such current in it as the Gulf Stream.
So far we have been reasoning hypothetically, to show what would
be the chief agents, exclusive of the winds, in disturbing the equi-
librium of the ocean were its waters fresh and not salt. And
whatever disturbs equilibrium there may be regarded as the
p'imum mobile in any system of marine currents.

470. Influence of salts and evaporation. — Let us now proceed
another step in the process of explaining and illustrating the
effect of the salts of the sea in the system of oceanic circulation.
To this end, let us suppose the imaginary ocean of fresh water
suddenly to become that which we have, namely, an ocean of salt
water which contracts as its temperature is lowered (§ 441) till it
reaches 25°.6. Let evaporation now commence in the trade- wind
region, as it was supposed to do (§ 468) in the case of the fresh-
water seas, and as it actually goes on in nature — and what
lakes place ? Why, a lowering of the sea level, as before. But as
the vapour of salt water is fresh, or nearly so, fresh water only is
taken up from the ocean ; that which remains behind is therefore
more salt. Thus, while the level is lowered in the salt sea, the
equilibrium is destrojed because of the saltness of the water ; foi

TEE SALTS OF THE SEA. 245

the water that remains after the evaporation takes place is, en
account of the solid matter held in solution, specifically heavier
than it was before any portion of it was converted into vapour.
The vapour is taken from the surface water ; the surface water
thereby becomes more salt (§ 463), and, under certain conditions,
heavier ; when it becomes heavier, it sinks ; and hence we have,
due to the salts of the sea, a vertical circulation, namely, a descent
of heavier — because Salter and cooler — water from the surface,
and an ascent of water that is lighter — because it is not so salt,
or, being as salt, is not so cool (§ 404)— from the depths below.
This vapour, then, which is taken up from the evaporating regions
(§ 293), is carried by the winds through their channels of circula-
tion, and poured back into the ocean where the regions of pre-
cipitation are ; and by the regions of precipitation I mean those
parts of the ocean, as in the polar basins, where the ocean receives
more fresh water in the shape of rain, snow, etc., than it returns
to the atmosphere in the shape of vapour. In the precipitating
regions, therefore, the level is destroyed, as before explained, by
elevation ; and in the evaporating regions, by depression ; which,
as already stated (§ 468), gives rise to a system of surface currents,
moving on an inclined plane, from the poles towards the equator.
But we are now considering the effects of evaporation and pre-
cipitation in giving impulse to the circulation of the ocean where
its waters are salt. The fresh water that has been taken from the
evaporating regions is deposited upon those of precipitation,
which, for illustration merely, we will locate in the north polar
basin. Among the sources of supply of fresh water for this
basin, we must include not only the precipitation which takes
place over the basin itself, but also the amount of fresh water
discharged into it by the rivers of the great hydrographical
basins of Arctic Europe, Asia, and America. This fresh water,
being emptied into the Polar Sea and agitated by the winds,
becomes mixed with the salt ; but as the agitation of the sea by
the winds is supposed to extend to no great depth (§ 468), it is
only the upper layer of salt water, and that to a moderate depth,
which becomes mixed with the fresh. The specific gravity of
this upper layer, therefore, is diminished just as much as the
specific gravity of the sea water in the evaporating regions was
increased. And thus we have a surface current of saltish water
from the poles towards the equator, and an under current of water
Salter and heavier from the equator to the poles. This under

246 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

current of brine supplies, in a great measure, the salt which the
upper current, freighted with fresh water from the clouds and
rivers, carries back.

471. The under currents oiving entirely to the salts of sea loater. —
Thus it is to the salts of the sea that we owe that feature in the
system of oceanic circulation which causes an under current to
flow from the Mediterranean into the Atlantic (§ 385), and
another (§ 377) from the Eed Sea into the Indian Ocean. And
it is evident, since neither of these seas is salting up, that just as
much, or nearly just as much salt as the under current brings out,
just so much the upper currents carry in. We now begin to per-
ceive what a powerful impulse is derived from the salts of the
sea in giving effective and active circulation to its waters.
Hence we infer (§ 461) that the currents of the sea, by reason
of its saltness, attain their maxim of volume and velocity.
Hence, too, we infer that the transportation of warm water from
the equator towards the frozen regions of the poles, and of cold
water from the frigid towards the torrid zone, is facilitated ; and
consequently here, in the dynamical power which the sea derives
from its salts, have we not an agent by which climates are
mitigated — by which they are softened and rendered much
more salubrious than it would be possible for them to be were
the waters of the ocean deprived of their property of saltness ?

472. A proj>erty peculiar to seas of salt water. — This property of
saltness imparts to the waters of the ocean another peculiarity,
by which the sea is still better adapted for the regulation of
climates, and it is this : by evaporating fresh water from the salt
in the tropics, the surface water becomes heavier than the average
of sea water (§ 427). This heavy water is also warm water ; it
sinks, and being a good retainer, but a bad conductor of heat,
this Avarm water is employed in transporting through under
currents, heat for the mitigation of climates in far-distant regions.
Now this also is a property which a sea of fresh water could not
have (§ 430). Let the winds take up their vapour from a sheet
of fresh water, and that at the bottom if not disturbed, for there
is no change in the specific gravity of that at the surface by
which that at the bottom may be brought to the top ; but let
evaporation go on, though never so gently, from salt water, and
the specific gravity of that at the top will soon be so changed aa
(§ 404) to bring that from the -N-ery lowest depths of the s^a to
tho top.

THE SALTS OF THE SEA. 247

473. Quantity of salt in the sea. — If all tlie salts of the sea were
precipitated and spread out equally over the northern half of
this continent, it would, it has been computed, cover the ground
one mile deep. What force could move such a mass of matter on
the dry land ? Yet the machinery of the ocean, of which it forms
a part, is so wisely, marvellously, and wonderfull}^ compensated,
that the most gentle breeze that plays on its bosom, the tiniest in-
sect that secretes solid matter for its sea-shell, is capable of put-
ting it instantly in motion. Still, when solidified and placed in a
heap, all the mechanical contrivances of man, aided by the tre-
mendous forces of all the steam and water power of the world,
could not, in centuries of time, move even so much as an inch
this matter which the sunbeam, the zephyr, and the infusorial
insect keep in perpetual motion and activity.

474. Deductions. — If these inferences as to the influence of the
salts upon the currents of the sea be correct, the same cause
which produces an under current from the Mediterranean (§ 471),
and an under current from the Eed Sea into the ocean, should
produce an under current from the ocean into the north polar ba-
sin ; for it may be laid down as a law, that whenever two oceans,
or two arms of the sea, or two sheets of water, differing as to salt-
ness, are connected with each other, there are currents between
them, viz., a surface current from, and an under current into the
sea of lightest water. In every case, the hypothesis with regard
to the part performed by the salt, in giving vigour to the system
of oceanic circulation, requires that, counter to the surface current
of water with less salt, there should be an under current of water
with more salt in it. That such is the case with regard both to
the Mediterranean and the Eed Sea has been amply shown in
other parts of this work (§ 471), and abundantly proved by other
observers. That, in obedience to. this law, there is a constant
current setting out of the Arctic Ocean through Davis' and other
straits thereabout, which connect it with the Atlantic Ocean, is
generally admitted. Lieutenant De Haven, United States Navy,
when in command of the American expedition in search of Sir
John Franklin, was frozen up with his vessels — the Advance and
the Eescue — in mid-channel near Wellington Straits ; and during
the nine months that he was so frozen, his vessels, like H.B.M.
ship Eesolute and the Fox (§ 431), each holding its place in the
ice, were drifted with it bodily for more than a thousand miles
towards the south.

248 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

475. Drift of the Besolute. — The drift of these vessels is suf-
ficient, were there no other evidence, to establish the existence
of an open sea in the Arctic Ocean ; for this drift cannot be ac-
counted for upon any other hj^pothesis, as a slight examination
of the arctic regions on a terrestrial globe, and a careful study of
the facts (§ 459), and other phenomena Avill show.

476. De Haven's drift. — About the middle of September, 1850,
being in latitude 74° 40', and in the fair way of Wellington
Channel, De Haven found himself, with the Advance, frozen in
her tracks, as M'Clintock did the Fox,* in August, 1857, who
tried to reach the shore, but he was fast bound, and drifting to
the west. De Haven, after having been carried as far as 75° 25',
and M'Clintock as far as 75° 30', say within nine hundred miles
of the pole, found their northerly course was arrested ; then com-
menced with each that celebrated drift of a thousand miles to
the south, and which from December lasted, the one till June,
the other till April 25th. These vessels were not drifted through
the ice, but with the ice ; for in lat. 65° 30', when De Haven was
liberated on the 9th of June, he had the same "hummocks," the
same snowdrifts, and the same icy landscape which set out with
him on December 2nd, when he commenced his drift from the
parallel of 75° 25'.t

477. An anti-^olynian view. — Now, upon the theory of no open
water, and upon the supposition of an ice-covered sea that seals
up in winter all the unexplored regions of the north, let us, in
imagination, take a survey of that sea just as the anti-polynians,
according to their theorj^ would have it. Let the time of the
survey be at the beginning of winter, when De Haven commenced
his southwardly drift. From the Advance to the pole — a dis-
tance of 900 miles — no water is to be seen : the frost has bridged
it all over. From the pole to the distance of 900 miles beyond,
and all around, it is one field of thick-ribbed ice. The flat, and
tame, and dreary landscape may be relieved here and there,
perhaps, by islands, capes, and promontories dotting the surface,
but nevertheless it is now at least as cold— being winter — from

* A screw yacht of 177 toiis.

t De Haven was frozen in lat. 74^ 40', long. 92^ 55'; was carried up ta
75^ 25' N., and thence down to 66^ 15' K, 58^ 35' W., when he was liberated.
The Fox was frozen in 75° 80' N., 64'^ W. ; was carried west to 69^ in the same
latitude, and thence down to 63^ 50' N., and 57° W., when she was liberated,
Thii Eesolute was abandoned in lat. 74^ 40', long. 101° 20', and was picked up
afloat, off Cape Mercy in 65^ N.

THE SALTS OF THE SEA. 249

the pole all around to the parallel of 75°, as it was in early fall
when De Haven being near that parallel in Wellington Channel,
found his vessel fast bound with the fetters of the frost-king.
Wherefore we may suppose that these theorists would admit the
whole to be frozen by December. So that, according to the
anti-polynian view, we have, measuring from the pole as a centre,
a disc of ice more than five thousand miles in circumference, and
extending quite down to the shores of arctic America and Asia.
Such is the aspect presented by the polar sea without an open
water in winter; now, on the 2nd of December — the moment
before this remarkable drift commenced — was the entire sheet of
ice with which we have supposed the Arctic Ocean to be covered,
put in motion, or was that only put in motion which drifted out ?
By the hypothesis there is no open water in all the circumference
of this sea into which the ice might drift. We therefore may
well ask the anti-polynians again. How did this drift commence ?
for commence it did ; its movement was out of that sea, and from
the pole towards the equator, and so it continued to move for six
months at the average rate of 5i miles a day. But whence — on
what parallel — did it commence ? Was the whole disc in motion
from the shores of Siberia over across hy way of the north pole
towards Wellington Channel ? If one part of this disc be put in
motion, either the whole must be, or there must be somewhere,
a split or a rent in it, with open water between. If, during the
winter and spring — the coldest period — the edge of this ice-disc
nearest Wellington Channel be carried by the currents a thousand
miles towards the south, the edge along the Russian shores on
the opposite side must have been drifted towards the north a
thousand miles also, and so leave an open water behind. Now
we simply know there was no such drifting up from the Siberian
shores, and the case is put simply to show that in an}^ case the
northerly edge of the drifting ice must have come from open water ;
for if we deny the existence of an open water in that direction,
then we must go back and admit that at the beginning of the
drift there was ice all the way from Wellington Channel to the
iSorth Pole, and thence all the way from the North Pole to the
nearest land beyond, which is supposed to be the Siberian shores
of the Old World. But, on the other hand, we must also admit
the fact — for the Advance, the Rescue, the Fox, and the Resolute
are witnesses of it — that a tongue of this ice 1000 miles long was
in each of these winters thrust out of the polar basin down
Lhiough Baffin's Bay into Davis' Straits. These ships came

250 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

down upon it. It would be difficult for those who oppose the
existence of an open water here in the Arctic Ocean to discover
a force there which, during the extreme cold months of the
northern night, when the ice is making all the time, could tear
from its fastenings and move 5i miles a day all through the
winter and spring a disc of ice seven feet thick* and 1800 geo-
graphical miles in diameter. Yet such seem to be the conditions
which the absence of open water would require ; for, when the
Advance was thawed out, there was a thousand miles of ice to
the northward of her, and between her and Wellington Channel.
This 1000 miles of ice had drifted out of the polar basin during
her journey to the south ; for when she was liberated there was
doubtless a continuous sheet of ice between her in lat. 65°, and
Wellington Channel in lat. 75°. This tongue of ice is what the
whalemen call the "middle ice" of Baffin's Bay. When the
Advance was at Wellington Channel, this thousand miles of ice
must, according to the anti-polynians, have been to the north of
her ; oi^, according to the other school, it must, as it drifted
towards the south, have been forming towards the north at the
edge of an open sea (§ 459). And towards the north De Haven
saw a water-sky, and towards the north Penny afterwards found
an open sea and sailed upon it.

478. The drift explained. — Upon the supposition that the ice
which drifts out of the Arctic Ocean in the dead of winter is
formed on the edge of an open water not far from the channel
through which it drifts, we can account for all the known facts
Avhich attended the celebrated drifts of De Haven M'Clintock,!
and the Eesolute. Upon no other theory can these well-known
and well-authenticated facts be reconciled. If there be no open
water during this winter drift, which there is reason to believe
takes place annually, both the Advance, Fox, and the Eesolute
indicate that the whole icy covering— the frost-shell of the polar
sea in winter — must have drifted bodily far enough, on these
three several occasions at least, to set each vessel a thousand
miles on her way towards the south. And thus, without bringing
in again the long chain of evidence from Chapter IX., the physical
necessity of an open sea in the Arctic Ocean is proved. \

* De Haven found the ice upon which his vessel was brought out 7 feet
2 inches thick.

t In the Fox, 1857-1858.

J " The Fox accomplished another of those remarkable drifts which can be
explained upon no other hypotliesis but that of an open water in the Arctic

THE SALTS OF THE SL\ 251

479. Tliickness of a ivinter's ice. — On the first of April De
Haven measured the ice, and found it seven feet two inches
thick. It was formed probably mostly of rain and river water,
which, like our own littoral waters (§ 426), protect the Salter and

Ocean, and that, too, not far from the entrance into it of some of the channels
which connect it with BaflSn's Bay on the polar side of 75°. The Fox was
attempting to pass from Melville Bay over to Lancaster Sound, in August, 1857,
when, on the 18th day of that month she fell in with ice, in which she was
finally frozen up, and remained so for 242 days, during which time she was
drifted to the southward 1194 miles, which gives an average rate of five miles a
day.

" This drift, the drift of the Eesolute, of the Advance, and Rescue, each up-
wards of a thousand miles — appears to indicate that a similar drift takes place
every year. They show the existence of a polynia, and indicate that the open
sea is to be sought for at no greater distance from Kennedy's Channel on the
one hand, and Maury's on the other. This conclusion is reached by a process
of reasoning of this sort :

" When each one of these vessels was released from her cold fetters, there was
doubtless behind her, and between her place of release and her place of original
imprisonment, an uninterrupted reach of a thousand miles covered with ice ;
which ice, during the fall, the winter, and early spring, drifted out of the Arctic
Ocean. Now we have the choice of two suppositions, and of only two, in expla-
nation of this phenomenon, and they are : Either that the great body of all
the winter-formed ice of the Arctic Ocean must have drifted in an unbroken
mass over towards Baffin's Bay ; for these vessels were brought out upon a
tongue of ice thrust through that bay down into Davis' Straits ; or that this
tongue must have been separated from the main mass, leaving behind that from
which it had been severed.

" By the latter supposition aU the known facts of the case may be reconciled ;
by the former not one.

" If we suppose this drifting field of ice to be formed upon the very verge of
an open sea, and to drift to the south as fast as it is formed, then the whole phe-
nomenon becomes one of easy solution. At any rate, we are now possessed of a
physical fact which probably would have returned Captain Crozier and his
companions to us all safe and sound had they been aware of its existence ; and
that fact is in this oft-occurring, if not regular and annual, southward drift of ice
from the Arctic Ocean down through Bafiin's Bay into Davis' Strait. Captain
Franklin, being ignorant of it, placed his vessels out of its reach on the south,
where he was frozen in and died, and where Captain Crozier, his successor,
remained imprisoned for eighteen months and then abandoned his ships : their
drift in the mean time, and for obvious reasons, being almost, if not quite in-
<jensible, except as influenced by the summer thaw and 'winter wedgings.'
Now if those vessels, with their scurvy-riddled, frost-worn and disabled crews,
could have been placed farther to the north, as in Barrow's Strait, or in the fair
way of any of those channels connecting with it from the northward and west-
ward, or with Baffin's Bay, the probabilities are that this regularly occurring

252 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

lieavier waters below from the cold, fur De Haven invariably
found the temperature of the water under the ice 28°, which is
the temperature that average sea water invariably assumes
during the process of congelation (§ 442). Moreover, the specific
gravity of the surface water which Rodgers measured in the
Arctic Ocean was (§ 427) less than that of average sea water — a
fact in confirmation of this conjecture as to the office of rain and
river water in the polar seas. The freezing-point of strong brine
is 4° ; consequently the freezing-point of water in the sea may
vary according to the proportion of salts in it, from 4° all the
wa}^ up to just below 32°. Thus the salts of the sea impart to its
waters an elasticity, as it were, giving a law, — a sort of sliding-
scale — both for the thermal dilatation and of congelation, which
varies between that of fresh water and the saltest sea water
according to the degree of its saltness,

480. Layers ofivater of different temperature in the Arctic Ocean. —
Eodgers tried with his hydrometer and thermometer the waters
of the Arctic Ocean at the surface, below, and at the bottom, and
as often as he tried he found this arrangement : warm and light
water on the top, cool in the middle, " hot and heav}^ " at the
bottom. His experiments were made near Behring's Straits in
August, 1855, between the parallels of 71°-2°, and are as per
example following :

])ate.

Aug. 13
Arg. 15

Depth.

Temp.

Sp. Grav.

surface

43.8

.0264

20 fath.

33.5

.0266

40 fath.i

40.5

.0266

surface

42.5

.0258

12 fath.

39.8

.0264

25 fath.i

40.2

.0264

Place.

Lat. 72^ 2' Long. 174° 37' W
,',' 7l"21' ',' 175° 22'

1 Near bottom.

Assuming the surface water which Rodgers used for these experi-
ments to be a fair average of arctic surface waters generally, this

winter drift would have brought them down safely into milder climates, and
into the glad waters of the Atlantic Ocean, as it did those four other vessels.

" The frequent, if not the regular annual occurrence of this drift down
through Baltin's Bay is a fact which will be considered by all future arctic
explorers as one of great importance, for it affords the means of escaping from
the Arctic Ocean in the .severest winter." — Transactions of the Amprlcan Geo.
Society, 1860.

THE SALTS OF THE SEA. 253

table affords data that show the proportion of rain and river
water that the Arctic Ocean receives annually. The quantity
may be inferred from ihe fact that average sea water has ten per
cent, more salt than attained by Eodgers in the Arctic.

481. The ice-hearing drift from the Arctic liJce tlie ordinary drift
from the Baltic. — Eeturning now to the drift of the ice, and the
drift of the Advance and her followers, we see that, so far as
currents are concerned, we have in the Arctic Ocean a repetition
merely of the more familiar phenomenon that is seen in the
Baltic, where (§ 383, note) an under current of salt water runs in,
and an upper current of brackish water runs out. Then, since
there is salt always flowing out of the north polar basin, we
infer that there must be salt always flowing into it, else it would
either become fresh, or the whole Atlantic Ocean would become
more and more briny, and be finally silted up with salt. It
might be supposed, were there no evidence to the contrary, that
this salt was supplied to the polar seas from the Atlantic around
North Cape, and from the Pacific through Behring's Straits, and
through no other Channels. But, fortunately, arctic voyagers
who have cruised in the direction of Davis' Straits, have con-
firmed by their observations a law of nature (§ 474), and afforded
us proof positive as to the fact of this other source for supplying
the polar seas with salt. They tell us of an under currenfc setting
from the Atlantic towards the polar basin. They describe huge
icebergs, with tops high up in the air, and of course the bases of
which extend far down into the depths of the ocean, ripping and
tearing their way with terrific force and awful violence through
the surface ice or against a surface current, on their way into the
polar basin.

482. Icebergs drifting north. — Passed Midshipman S. P. Griffin,
who commanded the brig Eescue in the American searching ex-
pedition after Sir John Franklin, informs me that, on one occa-
sion, the two vessels were endeavouring, when in Baffin's Bay, to
warp up to the northward against a strong surface current, which
of course was setting to the south ; and that, while so engaged,
an iceberg, with its top many feet above the water, came '• drift-
ing up " from the south, and passed by them " like a shot."
Although they were stemming a surface current against both the
berg and themselves, such was the force and velocity of the under
current that it carried the berg to the northward faster than the
crew could warp the vessel against a surface but courier current

254 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

They hooked on to it, and were towed to the north by it. Captain
Duncan, master of the English whale-ship Dundee, says, at page
7G of his interesting little narrative:* ''December ISth (1826).
It was awful to behold the immense icebergs working their way
to the north-east from us, and not one drop of water to be seen ;
they were working themselves right through the middle of the
ice." And again, at page 92, etc. : '' February 23rd. Latitude
68° 37' north, longitude about 63° west. The dreadful appre-
hensions that assailed us yesterday by the near approach of the
iceberg were this day most awfully verified. About three p.m.
the iceberg came in contact with our fioe, and in less than one
minute it broke the ice ; we were frozen in quite close to the
shore ; the floe was shivered to pieces for several miles, causing
an explosion like an earthquake, or one hundred pieces of heavy
ordnance fired at the same moment. The iceberg, with awful
but majestic grandeur (in height and dimensions resembling a
vast mountain), came almost up to our stern, and every one

expected it would have run over the ship The iceberg,

as before observed, came up very near to the stern of the ship ;
the intermediate space between the berg and the vessel was
filled with heavy masses of ice, which, though they had been
previously broken by the immense weight of the berg, were
again formed into a compact body by its pressure. The berg
was drifting at the rate of about four knots, and by its force on
the mass of ice was pushing the ship before it, as it appeared, to
inevitable destruction. Feb. 24tJi. The iceberg still in sight, but
drifting away fast to the north-east. Feb. 2bth. The iceberg that
so lately threatened our destruction had driven completely out of
sight to the north-east from us."

483. Temperature of the under current. — Now, then, whence,
unless from the difference of specific gravity due to sea water of
different degrees of saltness and temperature, can we derive a
motive power in the depths of the sea, with force sufficient to
give such tremendous masses of ice such a velocity ? AVhat is
the temperature of this under current? Eodgers's observations
<'§ 480) would seem to indicate that at the depth of 150 feet it is
not below 40"^. Assuming the water of the surface current which
runs out with the ice to be all at 28°, as De Haven found it
(§ 479), we observe that it is not unreasonable to suppose that

* Arctic Kegions ; Voyage to Davis' Stmit, by Dorea Duncan, Master of the
ship Dundee, 1826, 1827.

THE SALTS OF THE SEA. 255

the water of the under current, inasmuch as it comes from the
south, and therefore from warmer latitudes, is not so cold ; and
if it be not so cold, its temperature, before it comes out again,
must be reduced to 28°, or whatever be the average temperature
of the outer but surface current. Dr. Kane found the temperature
of the oj)en sea in the Arctic Ocean (§ 429) as high as 36°. Can
water in the depths below flow from the mild climate of the
temperate zones to the severer climates of the frigid zone without
falling below 86° ? To what, in the depths of the sea, can a
warm current of large volume impart its heat ? The temperature
of sea water from the tropics in which ice is forming is invariably
(§ 442) 28°. Does not the circumstance of De Haven's invariably
finding this to be the temperature below the ice on which he
drifted tend to confirm the conjecture (§ 479) about the ice and
the river water ?

484. It comes to the surface. — This under polar current water,
then, as it rises to the top, and is brought to the surface by the
agitation of the sea in the arctic regions, gives out its surplus
heat to warm the atmosphere there till the temperature of this
warm under current water is lowered to the requisite degree for
going out on the surface. Hence the water-sky of those regions.
And the heat that it loses in falling from its normal temperature,
be that what it may, till it reaches the temperature of 28°, is so
much caloric set free in the polar regions, to temper the air and
mitigate the climate there. Now is not this one of those modifi-
cations of climate which may be fairly traced back to the effect of
the saltness of the sea in giving energy to its circulation ? More-
over, if there be a deep sea in the polar basin, which serves as a
receptacle for the waters brought into it by this under current,
which, because it comes from towards the equatorial regions,
comes from a milder climate, and is therefore warmer, we can
easily imagine why there might be an open sea in the polar
regions — why Lieutenant De Haven, in his instructions (§ 428),
was directed to look for it ; and why both he and Captain Penny,
of one of the English searching vessels, and afterwards Dr. Kane,
found it there. And in accounting for this polynia, we see that
its existence is not only consistent with the hypothesis with
which we set out, touching a perfect system of oceanic circulation,
but that it may be ascribed, in a great degree at least, if not
wholly, to the effect produced by the salts of the sea upon the
mobility and circulation of its waters. Here, then, is an office

256 PHYSICAL GEOGRAPHY OF THE SlilA, AM) ITS METEOROLOGY,

wliicli the sea performs in tlie economy of the universe by virtue
of its saltness, and which it could not perform were its waters
altogether fresh. And thus philosophers have a clew placed in
their hands which will probably guide them to one of the many
hidden treasures that are embraced in the true answer to the
question, " Vv^hy is the sea salt ?"

485. Sea shells — theh' influence upon currents. — We find in sea
water other matter (§ 48) besides common salt. Lime is dis-
solved by the rains and the rivers, and emptied in vast quantities
into the ocean. Out of it, coral islands and coral reefs of great
extent — marl-beds, shell-banks, and infusorial deposits of enormous
magnitude, have been constructed by the inhabitants of the deep.
These creatures are endowed with the power of secreting, ap-
parently for their own purposes onl}^, solid matter, which the
waters of the sea hold in solution. But this power was
given to them that they also might fulfil the part assigned
them in the economy of the universe. For to them, probably,
has been allotted the important office of assisting to give
circulation to the ocean, of helping to regulate the climates
of the earth, and of preserving the purity of the sea. The better
to comprehend how such creatures may influence currents and
climates, let us again suppose the ocean to be perfectly at rest —
that throughout, it is in a state of complete equilibrium — that,
with the exception of those tenants of the deep which have the
power of extracting from it the solid matter held in solution,
there is no agent in nature capable of disturbing that equilibrium
— and that all these fish, etc., have suspended their secretions, in
order that this state of a perfect aqueous equilibrium and repose
throughout the sea might be attained. In this state of things —
the waters of the sea being in perfect equilibrium — a single
mollusk or coralline, we will suppose, commences his secretions,
and abstracts from the sea water (§ 465) solid matter for his
cell. In that act this animal has destroyed the equilibrium of
the whole ocean, for the specific gravity of that portion of water
from which this solid matter has been abstracted is altered.
Having lost a portion of its solid contents, it has become spe-
cifically lighter than it was before ; it must, therefore, give
place to the pressure which the heavier water exerts to push it
aside and to occupy its place, and it must consequently travel
about and mingle with the waters of the other parts of the ocean
until its p;oportion of solid matter is returned to it, and until it

THE SALTS OF THE SEA. 257

attains the exact degree of specific gravity due to sea water
generally.

486. Solid matter secreted hy tJiem. — How mncli solid matter
does the whole host of marine plants and animals abstract from
sea water daily ? Is it a thousand pounds, or a thousand millions
of tons ? No one can say. But, whatever be its weight, it is so
much of the power of gravity applied to tbe dynamical forces of
the ocean. And this power is derived from the salts of the sea,
through the agency of sea-shells and other marine animals, that of
themselves scarcely possess the power of locomotion. Yet they
have power to put the v^^hole sea in motion, from the^equator to
the poles, and from top to bottom. But we have yet to inquire
how far may currents be due to the derangement of equilibrium
arising from the change of specific gravity caused by the secretions
of the myriads of marine animals that are continually at work in
various parts of the ocean. These little creatures abstract from
sea water solid matter enough to build continents of. And, also,
we have to remember as to the extent to v/hich equilibrium in the
sea is disturbed by the salts which evaporation leaves behind.
Thus, w^hen we consider the salts of Ihe sea in one point of view,
we see the winds and the marine animals operating upon the
waters, and, in certain parts of the ocean, developing by their
action upon the solid contents of the same those very principles
of antagonistic forces which hold the earth in its orbit, and pre-
serve the harmonies of the universe.

487. Dynamical force derived from. — From another point of
view, we see the sea-breeze and the sea-shell, in performing
their appointed offices, so acting as to give rise to a reciprocating
motion in the waters ; and thus they impart to the ocean d}^-
namical forces also for its circulation. The sea-breeze plays
upon the surface ; it converts only fresh water into vapour, and
leaves the solid matter behind. The surface water thus becomes
specifically heavier, and sinks. On the other hand, the little
marine architect below, as he works upon his coral edifice at the
bottom, abstracts from the water there a portion of its solid con-
tents ; it therefore becomes specifically lighter, and up it goes,
ascending to the top with increased velocity, to take the place of
the descending column, which, by the action of the winds, has
been sent dow^n loaded with fresh food and materials for the busy
little mason in the depths below. Seeing, then, that the inhabit-
ants of the sea, with their powers of secretion, are competent to

s

258 PHYSICAL GEOGRAPnT OF THE SEA, AND ITS METEOEOLOGY.

exercise at least some degree of influence in disturbing equilibrium,
are not these creatures entitled to be regarded as agents which
have their offices to perform in the system of oceanic circulation,
and do they not belong to its physical geography ? Their in-
fluences upon the economy of the sea are like those outstanding
quantities which the astronomer finds in the periods of heavenly
bodies. He calls them perturbations ; for short, or even duriog
considerable intervals, their effects maybe inappreciable; for they
are pendultims that require ages for a single vibration; but
unless there was a balance provided somewhere, they would,
during th# progress of time, accumulate their small perturbations
so as to produce disorder, and finally cause the destruction of
worlds. So, too, with the salts of the sea, and those little micro-
scopic inhabitants of its waters. They take care of its outstand-
ing quantities of solid matter, and by their influence preserve
harmony in the ocean. It is immaterial how great or how small
that influence may be supposed to be ; foy, be it great or small,
it is cumulative ; and we therefore may rest assured it is not a
chance influence, but it is an influence exercised by design, and
according to the commandment of Him whose " voice the winds
and the sea obey." Thus God speaks through sea-shells to the
ocean.

488. Their physical relations. — It may therefore be supposed
that the arrangements in the economy of nature are such as to
require that the various kinds of marine animals, whose secretions
are calculated to alter the specific gravity of sea water, to destroy
its equilibrium, to beget currents in the ocean, and to control its
circulation, should be distributed according to order. Upon this
supposition — the like of which Nature warrants throughout her
whole domain — we may conceive how the marine animals of
which we have been speaking may impress other features upon
the physical relations of the sea by assisting also to regulate cli-
mates, and to adjust the temperature of certain latitudes. For
instance, let us suppose the waters in a certain part of the torrid
zone to be 90*^, but, by reason of the fresh water which has beer
taken from them in a state of vapour, and consequently by reason
of the proportionate increase of salts, these waters are heavier
than waters that may be cooler, but not so salt (§ 105). This
being the case, the tendency would be for this warm, but salt and
heavy water to flow off as an under current towards the polar or
some other regions of lighter water; but these creatures take

THE SALTS OF THE SEA. 259

from it a portion of these salts for their own purposes, and so
make it light enough to flow oif on the surface instead of the
bottom — it then goes polar- ward, dispensing warmth and moisture
as it goes ; and so climate may be influenced. Moreover, if the
sea were not salt, there would be no coral islands to beautify its
landscapes and give variety to its features ; sea-shells and marine
insects could not operate upon the specific gravity of its waters,
nor assist in giving diversity to its climates ; neither could
evaporation give dynamical force to its circulation; its waters,
ceasing to contract as their temperature falls below 39°, would
give but little impulse to its currents, and impart no motion
(§ 404) to its waters in the depths below : thus its circulation
would be torpid, and its bosom lack animation. In some other
parts of the ocean, instead of there being organic life capable of
changing, by animal or vegetable secretions, the specific gravity
of the suj)posed salt and heavy and hot water at 90°, there may
be none such, as in a " Desolate Eegion." This water then may
go ofi" as an under-current freighted with heat to temper some
hyperborean region or to soften some extra-tropical climate, for
we know that such is among the eff'ects of marine currents. At
starting, it might have been, if you please, so loaded with solid
matter that, though its temperature were 90°, yet, by reason of
the quantity of such matter held in solution, its specific gravity
might have been greater even than that of extra-tropical sea
water generally at 28°. jS'otwithstanding this, after travelling
below to certain latitudes, it ma}^ be brought into contact by the
way, with those kinds and quantities of marine organisms that
shall abstract solid matter enough to reduce its specific gravity,
and, instead of leaving it greater than common sea water at
28°, make it less than common sea water at 40°; consequently, in
such a case, this warm sea water, when it comes to the cold lati-
tudes, would be brought to the surface throagh the insti:Timentality
of shell-fish, and various othor tribes that dwell far down in the
depths of the ocean. Thus we perceive that these creatures,
though they are regarded as beings so low in the scale of creation,
may nevertheless be regarded as agents of much importance in
the terrestrial economy ; for we now comprehend how they are
capable of spreading over certain parts of the ocean those benign
mantles of warmth which temper the winds, and modify, more or
less, all the marine climates of the earth.

489. The regulators of the sea.-. — The makers of nice astronomica]

2 GO PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

instruments, when they have put the different parts of theii
machinery together, and set it to work, find, as in the chrono-
meter, for instance, that it is subject in its performance to many
irregularities and imperfections ; that in one state of things there
is expansion, and in another state contraction among cogs, springs,
and wheels, with an increase or diminution of rate. This defect
the makers have sought to overcome ; and with a beautiful dis-
play of ingenuity, they have attached to the works of the instru-
ment a contrivance which has had the effect of correcting these
irregularities by counteracting the tendency of the instrument to
change its performance with the changing influences of tempera-
ture This contrivance is called a compensation ; and a chrono-
meter or clock that is well regulated and properly compensated
will perform its office with certainty, and preserve its rate under
all the vicissitudes of heat and cold to which it may be exposed.
In the clock-work of the ocean and the machinery of the universe,
order and regularity are maintained by a system of compensa-
tions. A celestial body, as it revolves around its sun, flies off
under the influence of centrifugal force; but immediately the
forces of compensation begin to act, the planet is brought back
to its elliptical path, and held in the orbit for which its mass, its
motions, and its distances were adjusted. Its compensation is
perfect. So, too, with the salts and shells of the sea in the
machinery of the ocean ; from them are derived principles of
compensation the most perfect ; through their agency the undue
effects of heat and cold, of storm and rain, in disturbing the
equilibrium and producing thereby currents in the sea, are com-
pensated, regulated, and controlled. The dews, the rains, and the
rivers are continually dissolving certain minerals of the earth,
and carrying them off to the sea. This is an accumulative pro-
cess ; and if it were not compensated, the sea would finally become,
as the Dead Sea is, saturated with salt, and therefore unsuitable
for the habitation of many fish of the sea. The sea-shells and
marine insects afford the required compensation. They are the
conservators of the ocean. As the salts are emptied into the sea,
these creatures secrete them again and pile them up in solid
masses, to serve as the bases of islands and continents, to be in
the process of ages upheaved into dry land, and then again dis-
solved by the dews and rains, and washed by the rivers away
into the sea again.

490. WJience does the sea derive its salts ?— The question as ta

THE SALTS OF THE SEA. 261

whence the salts of the sea were originally derived, of course has
not escaped the attention of philosophers. I once thought with
Darwin and those other philosophers who hold that the sea
derived its salts originally from the washings of the rains and
rivers. I now question that opinion ; for, in the course of the
researches connected with the "Wind and Current Charts," I
have found evidence, from the sea and in the Bible, which seems
to cast doubt upon it. The account given in the first chapter of
Genesis, and that contained in the hieroglyphics which are traced
by the hand of Nature on the geological column as to the order
of creation, are marvellously accordant. The Christian man of
science regards them both as true ; and he never overlooks the
fact that, while they differ in the mode and manner as well as in
the things they teach, yet they never conflict ; and they contain
no evidence going to show that the sea was ever fresh; on the
contrary, they both afford circumstantial evidence sufficient for
the belief that the sea was salt as far back as the morning of
creation, or at least as the evening and tho morning of the day
when the dry land appeared. That the rains and the rivers do
dissolve salts of various kinds from the rocks and soil, and empty
them into the sea, there is no doubt. These salts cannot be
evaporated, we know ; and we also know that many of the lakes,
as the Dead Sea, which receive rivers and have no outlet, are
salt. Hence the inference by some philosophers that these
inland water-basins received their salts wholly from the washings
of the soil ; and consequently the conjecture arose that the great
sea derived its salts from the same source and by the same pro-
cess. But, and per contra, though these solid ingredients cannot
be taken out of the sea by evaporation, they can be extracted by
other processes. We know that the insects of the sea do take
out a portion of them, and that the salt ponds and arms which,
from time to time in the geological calendar, have been separated
from the sea, afford an escape by which the quantity of chloride
of sodium in its waters — the most abundant of its solid ingredients
— is regulated. The insects of the sea cannot build their struc-
tures of this salt, for it would dissolve again, and as fast as they
could separate it. But here the ever-ready atmosphere comes
into play, and assists the insects in regulating the salts. It can-
hot take them up from the sea, it is true, but it can take the sea
away from them ; for it pumps up the water from these pools
that have been barred off, transfers it to the clouds, and they

262 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

deliver it back to the sea as fresh water; leaving the salts it
contained in a solid state behind. These are operations that
cave been going on for ages ; proof that they are still going on
is continually before onr eyes; for the "hard water" of onr
fountains, the marl- banks of the vallej^s, the salt-beds of the
plains, Albion's chalky cliffs, and the coral islands of the sea,
are monuments in attestation. These masses of solid matter have
been secreted from the sea waters ; they express the ability of
these creatures to prevent the accumulation of salts in the sea.

491. Their antiquity. — There is no proof, nor is there any
reason for the belief, that the sea is growing Salter or fresher.
Hence we infer that the operations of addition and extraction are
reciprocal and equal ; that the effect of rains and rivers in wash-
ing do^m is compensated by the processes of evaporation and
secretion in taking out. If the sea derived its salts originally
from the rivers, the geological records of the past would show
that river beds were scored out in the crust of our planet before
the sea had deposited any of its fossil shells and infusorial re-
mains upon it. If, therefore, we admit the Darwin theory, we
must also admit that there was a period when the sea was without
salt, and consequently without shells or animals either of the
silicious or calcareous kind. If ever there was such a time, it
must have been when the rivers were collecting and pouring in
the salts which now make the brine of the ocean. But while
the palseontological records of the earth, on one hand, afford no
evidence of any such fresh-water period, the Mosaic account is
far from being negative with its testimony on the other. Ac-
cording to it, we infer that the sea was salt as early, at least, as
the fifth day, for it was on that day of creation that the waters
were commanded to "bring forth abundantly the moving creature
that hath life." It is in obedience to that command that the sea
now teems with organisms ; and it is marvellous how abundantly
the obedient waters do bring forth, and how wonderful for
variety as well as multitude their progeny is. All who pause
to look are astonished to see how the prolific ocean teems and
swarms with life. The moving creatures in the sea constitute in
their myriads of multitudes one of the " wonders of the deep."

492. Insects of the sea — their abundance. — It is the custom of
Captain Foster, of the American ship Garrick, who is one of
my most patient of observers, to amuse himself by making
drawings in his abstract log of the curious animalculee which,

TEE SALTS OF THE SEA. 263

with tlie microscoj^e, he finds in the surface water alongside;
and though he has been following the sea for many years, he
never fails to exjDress his wonder and amazement at the immense
numbers of living creatures that the microscope reveals to him in
sea water. Hitherto his examinations related only to the surface
waters, but in the log now before me he went into the depths,
and he was more amazed than ever to see how abundantly
the waters even there bring forth. "-January 28th, 1855. — In
examining animalculee in sea water, I have," sa^^s he, " heretofore
used surface water. This afternoon, after pumping for some
time from the stern pump seven feet below the surface, I ex
amined the water, and was surprised to find that the fluid was
literally alive with animated matter, embracing beautiful varieties."
Of some he says, " Numerous heads, purple, red, and variegated."
There is wonderful meaning in that word abundantly, as it
stands recorded in that Book, and as it is even at this day
repeated by the great waters, a striking instance of which has
been furnished by Piazzi Smyth, the Astronomer Eoyal of
Edinburgh, during his voyage in 1856, on. an astronomical
expedition to Tenerifie. On that occasion he fell in with the
annual harvest of medusae (§ 160) that are sent by the Gulf
Stream to feed the whales. His description of them (§ 161) has
already been quoted. According to the computation made by
him, it appears that each one of these sea-nettles, as they are
sometimes called, had in his stomachs not less than five or sis
millions of flinty shells, the materials for which their builders
had collected from the silicious matter which the rains washed
out from the mountains, and which the rivers bring down to the
sea. The medusee have the power of sucking in the sea water
slowly, drop by drop, at one end, and of ejecting it at the other.
From this they derive both food and locomotion; for in the
passage of the water, they strain it, and collect the little
diatomes. Imagine, then, how many drops of water in the
sea, which, though loaded with diatomes, never pass through
the stomach of the medusee. Imagine how many the whale must
gulp down with every mouthful of medusee. Imagine how deep
and thickly the bottom of the sea must, during the process of
ages, have become covered with the flinty shells of these little
creatures. And then recollect the command which was given to
the waters of the sea on the fifth day, and we may form some
idea of how literally they have obeyed this order, bringing forth

264 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

most abundantly even now the moving creature tliat hath life,
and doing it in obedience to that command.

493. Ditto, calcareous in the Pacific, silicious in the Atlantic. — In
the waters of the Pacific Ocean, the calcareous matter seems to
be in excess, for the microscopic shells there, as well as the conch
and the coral, are built mostly of lime. In contemplating this
round of compensations, the question may be asked, Where is the
agent that regulates the supply of solid materials for the insects
of the sea to build their edifices of ? Answer : The rivers.
They bring down, and pour into the sea continually, the pabu-
lum which those organisms require. This amount again depends
upon the quantity and power of the rains to wash out from the
solid rock ; and the rains depend upon the amount of vapour that
the sea delivers to the winds, which, as Chapman's observations
show, depends directly upon the salts of the sea.

494. Tlie records of the sea and of revelation agree. — So far the
two records agree, and the evidence is clear that the sea was salt
when it received its command. Do they afford any testimony as
to its condition previously ? Let us examine : — On the second
day of creation the waters were gathered together unto one place,
and the dry land appeared. Before that period, therefore, there
were no rivers, and consequently no washings of brine by mists,
nor dew, nor rains for the valleys among the hills. The water
covered the earth. This is the account of revelation; and the
account which Nature has written, in her own peculiar charac-
ters, on the mountain and in the plain, on the rock and in the sea,
as to the early condition of our planet, indicates the same. The
inscriptions on the geological column tell that there was a period
when the solid parts of the earth's crust which now stand high
in the air were covered by water. The geological evidence that it
was so, with perhaps the exception of a solitary mountain peak
here and there, is conclusive ; and when we come to examine the
fossil remains that are buried on the mountains and scattered over
the plains, we have as much reason to say that the sea was salt
v/hen it covered or nearly covered the earth, as the naturalist, when
he sees a skull or bone whitening on the wayside, has to say that
it was once covered with flesh. Therefore we have reason for the
conjecture that the sea was salt " in the beginning," when " the
waters under heaven were gathered together under one place,"
and the dry land first appeared ; for, go back as far as we may in
the dim records which young Nature has left inscribed upon the

THE SALTS OP THE SEA. 265

geological column of her early processes, and there we find the
fossil shell and the remains of marine organisms to inform ns
that when the foundations of our mountains were laid with
granite, and immediately succeeding that remote period when
the primary formations were completed, the sea was, as it is now,
salt ; for had it not been salt, whence could those creeping things
which fashioned the sea-shells that cover the tops of the Andes, or
those madrepores that strew the earth with solid matter that has
been secreted from briny waters, or those infusorial deposits which
astound the geologist with their magnitude and extent, or those
fossil remains of the sea which have astonished, puzzled, and be-
wildered man in all ages — whence, had not the sea been salt
when its metes and bounds were set, could these creatures have
obtained solid matter for their edifices and structures? Much
of that part of the earth's crust which man stirs up in cultivation,
and which yields him bread, has been made fruitful by these
" salts," which all manner of marine insects, aqueous organisms,
and sea-shells have secreted from the ocean. Much of this
portion of our planet has been filtered through the sea, and its
insects and creeping things are doing now precisel}^ what they
were set about when the dry land appeared, namely, preserving
the purity of the ocean, and regulating it in the due performance
of its great of&ces. As fast as the rains dissolve the salts of the
earth, and send them dovni through the rivers to the sea, these
faithful and everlasting agents of the Creator elaborate them into
pearls, shells, corals, and precious things; and so, while they
are preserving the sea, they are also embellishing the land by
imparting new adaptations to its soil, fresh beauty and variety
to its landscapes. Whence came the salts of the sea originally
is a question which perhaps never will be settled satisfactorily
to every philosophic mind, but it is sufScient for the Christian
philosopher to recollect that the salts of the sea, like its waters
and the granite of the hills, are composed of substances which,
when reduced to their simple state, are found for the most part
to be mere gaseous or volatile matter of some kind or other.
Thus we say that granite is generally composed of feldspar,
mica, and quartz, yet these three minerals are made of substances
more or less volatile in combination with oxygen gas. Iron, of
which there is merely a trace, is the only ingredient which, in its
uncombined and simple state, is not gaseous or volatile. Now,
was the feldspar of the granite originally formed in one heap,

266 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

tlie mica in another, and the quartz in a third, and then the
three brought together by some mighty power, and welded into
the granite rock for the everlasting hills to stand upon? or were
they, as they were formed of the chaotic matter, made into rock?
Sea water is composed of oxygen and hydrogen, and its salts,
like the granite, also consist of gases and volatile metals. But
whether the constituents of sea water, like those of the primitive
rocks, were brought together in the original process of formation,
and united in combination as we now find them in the ocean, or
whether the sea was fresh " in the beginning," and became salt
by some subsequent process, is not material to our present pur-
pose. Some geologists suppose that in the Chalk period, when
the ammonites, with their huge chambered shells, lived in the
sea, the carbonaceous material required by these creatures for
their habitations must have been more abundant in its waters
than it now is ; but, though the constituents of sea water may
have varied as to proportions, they probably were never, at least
*' since its waters commenced to bring forth," widely different
from what they now are. It is true, the strange cuttle-fish, with
its shell twelve feet in circumference, is no longer found alive in
the sea : it died out with the Chalk period ; but then its com-
panion, the tiny nautilus, remains to tell us that even in that
remote period the proportion of salt in sea water was not un-
suited to its health, for it and the coral insect have lived through
all the changes that our planet has undergone since the sea was
inhabited, and they tell us that its waters were salt as far back,
at least, as their records extend, for they now build their edifices
and make their habitations of the same materials, collected in
the same way that they did then, and, had the sea been fresh in
the interim, they too would have perished, and their family
would have become extinct, like that of the great ammonite,
which perhaps ceased to find the climates of the sea, not the
proportion of its salts, suited to its well-being.

495. Cvbic miles of sea salt. — Did any one who maintains that
the salts of the sea were originally washed down into it by the
rivers and the rains overtake the trouble to compute the quantity
of solid matter that the sea holds in solution as salts ? Taking
the average depth of the ocean at three miles, and its average salt-
ness at 3i per cent., it appears that there is salt enough in the
sea to cover to the thickness of one mile an area of several millions
Oi square miles. These millions of cubic miles of crystal salt

THE SALTS OF THE SEA. 267

have not made the sea any fuller. All this solid matter has been
received into the interstices of sea water without swelling the
mass ; for chemists tell us that water is not increased in volume
bv the salt it dissolves. Here we have therefore displayed before
us an economy of space calculated to surprise even the learned
author himself of the "Plurality of Worlds."

496. Tlie saltness of ivater retards evaporation. — There has been
another question raised which bears upon what has already been
said concerning the offices which, in the sublime system, of terres-
trial arrangements, have been assigned to the salts of the sea. On
the 20th of January, 1855, Professor Chapman, of the University
College, Toronto, communicated to the Canadian Institute a paper
on the " Object of the salt condition of the sea," which, he main-
tains, is " mainly intended to regulate evaporation."" To establish
this hypothesis, he shows by a simple but carefully conducted set
of experiments that, the Salter the water, the slower the evapora-
tion from it ; and that the evaporation which takes place in 24
hours from water about as salt as the average of sea water is 0.54
per cent, less in quantity than from fresh water. " This sugges-
tion and these experiments give additional interest to our
investigations into the manifold and marvellous offices which, in
the economy of our planet, have been assigned by the Creator to
the salts of the sea. It is difficult to say what, in the Divine
arrangement, was the main object of making the sea salt and not
fresh. Whether it was to assist in the regulation of climates, or
in the circulation of the ocean, or in re-adapting the earth for new
conditions by transferring solid portions of its crust from one
part to another, and giving employment to the corallines and
insects of ih^ sea in collecting this solid matter into new forms,
and presenting it under different climates and conditions, or
whether the main object was, as the distinguished professor
suggests, to regulate evaporation, it is not necessary now or here
to discuss. I think we may regard all the objects of the salts of
the sea as niain objects. But we see in the professor's experiments
the dawn of more new beauties, and the appearance of other
exquisite compensations, which, in studying the ' wonders of the
deep,' we have so often paused to contemplate and admire : — As
the trade- wind region feeds the air with the vapour of fresh water,
the process of evaporation from the sea is checked, for the water
which remains, being Salter, parts with its vapour less readily ;
and thus, by the salts of the sea, floods may be prevented. But

268 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

again, if the evaporating surface were to grow sailer and Salter,
whence would the winds derive vapour duly to replenish the
earth with showers ? for the Salter the surface, the more scanty
the evaporation. Here is compensation, again, the most exquisite ;
and we perceive how, by reason of the salts of the sea, drought
and fiood, if not prevented, may be, and probably are, regulated
and controlled ; for that compensation which assists to regulate
the amount of evaporation is surely concenied in adjusting also
the quantity of rain. Were the salts of the sea lighter instead of
heavier than the water, they would, as they feed the winds with
moisture for the cloud and the rain, remain at its surface, and be-
come more niggardly in their supplies, and finally the winds would
liowl over the salt-covered sea in very emptiness, and, instead of
cool and refreshing sea-breezes to fan the invalid and nourish the
plants, we should have the gentle trade- winds coming from the
sea in fitful blasts of parched, and thirsty, and blighting air.
But sea salts, with their manifold and marvellous adaptations,
come in here as a counterpoise, and, as the waters attain a certain
degree of saltness, they become too heavy to remain longer in
contact with the thirsty trade-winds, and are carried down,
because of their weight, into the depths of the ocean ; and thus
the winds are dieted with vapour in due and wholesome quantities."
— Maury's Sailing Directions, 7th ed., p. 862.

497. Tlie harmonies of the ocean. — Since the offices which, in the
operations of the physical machinery of the earth, have been
assigned to the salts of the sea, are obviously so important and
manifold, it is fair for us to presume that, as for the firmament
above, so with that below, the principles of conservation were in
the beginning provided for each alike, for the world in the sky
and the drop in the sea ; that when the Creator gathered the
waters together into one place, and pronounced his handiwork
" GOOD," some check or regulator had already been provided for
the one as well as the other — checks which should keep the sea
up to its office, preventing it from growing, in the process of ages,
either larger or smaller, fresher or Salter. As we go down into
the depths of the sea, we find that we are just beginning to
penetrate the chambers of its hidden things, and to comprehend
its wonders. The heart of man was never rightly attuned to the
music of the spheres until he was permitted to stand with his eye
at the telescope, and then, for the first time, the song of the
morning stars burst upon him in all its glory. And so it is with

THE SALTS OF THE SEA. 269

the harmonies of old Ocean when contemplated through the
microscope ; then every drop of water in the sea is discovered to
be in tune with the hosts of heaven, for each stands forth a peopled
world.

498. The microscope and the telescope. — Catching, as we contem-
plate the hosts of heaven through the telescope and the moving
creatures of the sea through the microscope, the spirit of Chalmers,
and borrowing his fine imagery, let us draw a contrast between
the glories of the heavens and the wonders of the insect world of
earth and sea, as to the mind of a devout jDhilosopher they are
presented through these instruments : " One leads him to see a
world in every atom, the other a system for every star. One
shows him that this vast globe, with its mighty nations and mul-
titudinous inhabitants, is but a grain of sand in the immensity of
space ; the other, that every particle of clay that lies buried in the
depths of the sea has been a living habitation, containing within
it the workshops of a busy population. One tells him of the
insignificance of the world we inhabit ; the other redeems it from
that insignificance by showing in the leaves of the forest, in the
flowers of the field, and in every drop of water in the sea, worlds
as numberless as the sands on its shores, all teeming with life,
and as radiant with glories as the firmament of heaven. One
suggests that, beyond and above all that is visible to man, there
are fields of creation which sweep immeasurably along, and carry
to the remotest regions of space the imjDress of the Almighty hand ;
the other reminds us that, within and beneath all that minuteness
which the eye of man has been able to explore, there may be a
region of invisibles, and that, could we draw aside the veil that
hides it from our senses, we should behold a theatre of as many
worlds as astronomy has unfolded — a universe within tho compass
of a point so small as to elude the highest power of the microscope,
but where the wonder-working finger of the Almighty finds room
for the exercise of his attributes — where He can raise another
mechanism of worlds, filling and animating them all with the
evidences of his glory." When we lay down the microscope, and
study the organisms of the sea by the light of reason, we find
grounds for the belief that the sea was made salt in the beginning,
for the marine fossils that are found nearest the foundation of the
geological column remind us that in their day the sea was salt ;
and then, when we take up the microscope again to study the
foraminiferae, the diatomes, and corallines, and examine the struc-

270 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ture of the most ancient inliabitants of tlie deep, comparing their
physiology with that of their kindred in the fossil state, we ara
left to conjecture no longer, but are furnished with evidence and
proof the most convincing and complete that the sea is salt from a
physical necessity.

499. Sea-shells and animalculce in a new light. — Thus beholding
sea shells and animalculae, may we not now cease to regard them
as beings which have little or nothing to do in maintaining the
hannonies of creation ? On the contrary, do we not see in them
the principles of the most admirable compensation in the system
of oceanic circulation ? We may even regard them as regulators,
to some extent, of climates in parts of the earth far removed from
their presence. There is something suggestive, both of the grand
and the beautiful, in the idea that, while the insects of the sea are
building up their coral islands in the perpetual summer of the
tropics, they are also engaged in dispensing warmth to distant
parts of the earth, and in mitigating the severe cold of the polar
winter. Surely an hypothesis v/hich, being followed out, suggests
so much design, such perfect order and arrangement, and so many
beauties for contemplation and admiration as does this, which, for
want of a better, I have ventured to offer with regard to the solid
matter of the sea water, its salts and its shells— surely, I say, such
an hypothesis, though it be not based entirely on 'the results of
actual observation, cannot be regarded as wholly vain or as alto-
gether profitless.

CHAPTER XL

§ 501-526. THE CLOUD REGION, THE EQUATORIAL CLOUD

RING, AND SEA FOGS.

501. Cloud region — highest in the calm belts. — To simplify the
discussion of these phenomena, let us consider fogs at sea to be
in character like clouds in the sky. So treating them, and con-
fining our attention to them as they appear to the mariner, we
discover that the cloud region in the main is highest in the
trade-wind and calm belts, lowest in extra-tropical regions.

502. Fogless regions. — At sea, beyond " the offings," fogs are
not often seen between the parallels of 30° N. and S. Sea fogs,
therefore, may be considered a rare phenomenon over one-half of

THE CLOUD EEGION, ETC. 271

the surface of the globe. These fogless regions, though certain
parts of them are not unfrequently visited by tempests, tornadoes,
and hurricanes, are nevertheless much less frequented by gales of
•wind, as all furious winds are called, than are the regions on the
polar side of these two parallels.

503. The most stormy latitudes. — Taking the Atlantic Ocean,
north and south, as an index of what takes place on other waters,
ihe abstract logs of the Observatory show, according to the
records of 265,304 observing days contained therein, that for
every gale of wind that seamen encounter on the equatorial side
of these two parallels of 30° N. and S., they encounter 10.4 on
the jpolar side ; and that for every fog on the equatorial they en-
counter 83 on the polar side. As a rule, fogs and gales increase
both in numbers and frequency as you recede from the equator.
The frequency of these phenomena between the parallels of 5° N.
and 5° S., compared with their frequency between the parallels of
45° and 50° N. and S., is as 1 to 103 for gales, and as 1 to 102 for
fogs. The observations do not extend beyond the parallels of
60°. It appears from these, however, that both the most stormy
and foggy latitudes in the North Atlantic are between the
parallels of 45° and 50° ; that in the South Atlantic the most
stormy latitudes are between the parallels of 55° and 60°, the
most foggy between 50° and 55°.

504. Influences of the Gulf Stream and the ice-hearing currents of
ihe south,. — How suggestively do these two groups of phenomena
remind us, on the one hand, of the Gulf Stream and the ice-
bearing currents of the north, and, on the other, of Cape Horn
and the Antarctic icebergs which cluster off the Falkland
Islands ! *

505. Sea fogs rare loithin 20° of the equator — red foqs. — Though
sea fogs within 20° on either side of the equator are so rarely
seen, yet within this distance, on the north side, red fogs of " sea-
dust" (§ 322) are not unfrequently encountered by navigators.
These can scarcely be considered as coming within the category

* Captaia Chadwick reports, by letter of 30th April, 1860, an iceberg, seen
first by him lith September, 1859, in S. lat. 52° 25', long. 51° 8' W. : next, on
October 10th, in 47° 15' S., 59° 30' W., by the Wild Pigeon Five days
later he fell in with it in lat. 45° 40', long. 58° 40'. It was last seen 7th
November, in lat. 43° 44' S., long. 57° 14' W., by the British ship "City of
Candy." Whether this were the same " berg " or not, it shows that icebergs
are not unknown to the north of the Falkland Islands, as, indeed, the aqueous
isotherm of 60°, Plate IV., indicates by its sharp curve about those islands.

272 PHYSICAL GEOGBAPHY OF THE SEA, AND ITS METEOROLOGY.

of sea fogs. The falling of this dust in the form of fog is no
doubt owing to those influences (§ 331), the effects of which are
BO often observable morning and evening in the settling smoko
from neighbouring chimneys. The fogs which at early dawn
are discovered hovering over our cities or skirting the base of the
hills near by are of the ssame sort. The " black fogs " of London
may be taken as the type of them. These particles of dust, like
the atoms of smoke, are brought into conditions favourable for
radiation on occasions when the air in which they are floating
happens to have a high dew-point. Thus each one of these in-
numerable little atoms of smoke and microscopic particles of sea-
dust become loaded with dew, and, being made visible, have the
appearance of fog. Eed fogs, therefore, do not properly come
under our classification of sea fogs.

o06. Cloudless regions and height of clouds at sea. — On the
polar side of 40° at sea the weather is for the most part cloudy.
On the equatorial side, and especially within the trade-wind
region, it is for the most part clear until we approach the
cloud-ring, where clouds again indicate the normal state of the
sky at sea. What is the height of the cloud region at sea ? for
vapour j^kwe it can scarce be called. As yet our sailor observers
have not turned their attention either to the height or the
velocity of clouds. It is to be hoped that they will. Observa-
tions here are to be made rather under the direction of the com-
mander of a fleet or squadron than of a single ship, and it is
hoped that some of the distinguished admirals and brave old
commodores who cruise about the world, with willing hearts and
ready hands for the cause we advocate, may signalize their flag
by contributing, for the advancement of human knowledge
touching the physics of the sea and the machinery of the air, a
series of well-conducted observations upon the force of the trade-
winds,* upon the height and velocity of the clouds, the height
and velocity of the waves, etc., in different parts of the ocean.

507. Height and velocity of waves— ;plan for determining. —
Commodore Wullerstorf, of the Austrian frigate Novara, made an
interesting series of observations upon the height and velocity of
the waves during his cruise in that vessel upon his last scientific
mission. These, no doubt, will be published with the other im-
portant results of that admirably conducted expedition. The

* See Maury's SaiUng Directions, vol. ii., "Average Force of the Trade-
winds."

THE CLOUD REGION, ETC. 27B

most simple plan for determining the velocity of waves — and it
may be hourly practised on board of every vessel — is the plan
which is followed by Captain Ginn, of the American ship John
Knox, one of our co-operators. When he heaves the log with the
seas following, instead of hauling in the line immediately, he
leaves the chip to tow, watching till he observes it on the crest
of a wave; he then turns the glass, or notes his watch, and
marks the time it takes the wave to reach the ship. The usual
velocity of the waves in the Atlantic is 22-3 miles an hour, off
Cape Horn 26-8.*

508. Determining the height of clouds at sea. — It would aiford a
pleasant and agreeable diversion for a squadron of men-of-war,
as they pursue their voyage at sea, to amuse themselves and
instruct their friends at home with observations upon all such
phenomena. Those who are willing to undertake the clouds
will have no difficulty in devising a plan both for the upper and
the lower strata.

509. Cloud region at sea in the shape of a double inclined plane. —
Over the land the cloud region is thought to vary from three
to five miles in height ; there the height of clouds is known to be
ver}^ variable. At sea it is no doubt less so. Here the cloud
region is somewhat in the form of a double inclined plane,
stretching north and south from the equatorial cloud-ring as a
sort of ridge-pole. In the balloon ascents which have taken

* From Captain Ginn's Abstract Log : —

" Saturday, September 1 1th, 1858, doubling Cape Horn. The long regular
swell during this part of the day afforded me another oppoi'tunity of trying the
velocity of the waves. This I did by paying out the log-line enough to be
equal to 13 knots with the ll-second glass; then by watching the chip — to
which I had fixed a piece of white rag to render it more distinguishable — as it
appeared on the crest of a well-defined wave, and turning the glass at the same
time, and then noting where the crest of a wave is at the moment the glass is
♦ out.'

" I have several times before tried the experiment in this way with the same
length of line out astern, and have always found about the same rate for the
velocity, namely, 22 to 23 miles an hour ; but to-day I found it to be consider-
ably more, namely, 26 to 28 miles an horn-. Thus the crest of a wave would
pass, while the 14-second glass ran out, from the place where the log-chip was
towing astern (13 knots) to just ahead of the ship. The length of the ship is
equal to about 6^ knots : the ship's speed at the time was 8 knots ; thus,
13+6i+8 = 27i. A few days ago I tried the same experiment, and found the
velocity to be 22 to 23. What has accelerated the velocity of these waves?
Have the soundings anything to do with it ?"

T

274 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

place from the Kew Obsei-vatory in England, it lias been ascer-
tained that there the cloud region is from 2000 to 6500 feet high,
with a thickness var^dng from 2000 to 3000 feet, and that its
temperature at the top is not lower than it is at the bottom of the
cloud, notwithstanding its thickness. We are also indebted to
Piazzi Smyth for interesting observations on the cloud region in
the belt of north-east trades and of the upper counter current
there. They were made from the Peak of Teneriife, at the height
of 12,200 feet, during the months of August and September, 1856.*
The cloud region of the trades was between 3000 and 5000 feet
high ; of the upper or south-west current, it was above the
mountain. Islands only a few hundred feet high are generally
cloud-capped in the trade-wind regions at sea ; another indication
that, with a given amount of moisture in the wind, the cloud
region is higher --it sea than it is over the land. For most of the
time during his sojourn on the Peak, the sea was concealed from
view by the cloud stratum below, though the sky was clear over-
head. Farther to the north, in the Atlantic, however, as in the
fos: rescion about the meeting of the cool and warm currents near
the Grand Banks, the look-out at the mast-head often finds himself
above the fog or cloud in which the lower parts of the ship are
enveloped. Going still farther towards the north and reaching
Mie ice, the cloud region would again, for obvious reasons, mount
up until you reached the open sea there, when again it would
touch the earth with its smoke.

510. Fogs in the harbour of Callao. — In the harbour of Callao,
in Peru, which is filled with the cool waters of Humboldt's
current, I have seen the bay covered with a fog only a few
inches high. I have seen fogs there so dense, and with outlines
so sharp, as to conceal from view the row-boats approaching the
ship's side. These fogs, especially early in the morning, will
conceal from view not only the boat, but the persons of the crew
up to the neck, so as to leave nothing visible but two rows of
trunkless heads nodding catenaries at the oars, apparently skim-
ming through the air and dancing on the fog in a manner at once
both magical and fantastic. At other times the cloud stratum is
thicker and higher. Then may be seen three masts coming into
port with topgallant-sails and royals set, but no ship. These sails,
nicely trimmed and swelling to the breeze in the sky, swim along
over the clouds, and seem like things in a ftiiry scene. However,
" Tencriffe. An Astronomer's Experiment. London, 1858.

TITS CLOUD REGION, ETC. 275

there are influences exerted in the formation of clouds and fogs
over and near the land which appear not to be felt at sea.

511. The cloudy latitudes. — In the extra-tropical north, the cloud
region is high over the land, low over the water ; and, as a rule,
the farther inland, the dryer the air and the higher the cloud
region. In the circum-Antarctic regions, where all is sea, the
rising vapours form themselves into clouds low down, and keep
the face of the sky almost uninterruptedly obscured. The
southern eaves of the cloud plane (§ 509), like the cajp belts,
vary their latitude as the sun does its declination, though their
place is generally found between the parallels of 50° and 70° S. —
farther or nearer according to the season ; but under this edge,
wherever it be, the mariner's heart is seldom made glad by the
cheering influences of a clear sky. If not wrapped in mist, or
covered with snow, or pelted with hail, or drenched with rain, as
he sails through these latitudes, he is dispirited under the in-
fluences of the gloomy and murk}^ weather which pervades those
regions. His hope in the " brave west winds " and trust in the
prowess of a noble ship are then his consolation and his comfort.

512. Why there should he less atmosphere in the southern than in
the northern hemisphere. — Such are the quantities of vapour rising
up from the engirdling ocean about those austral regions, that it
keeps permanently expelled thence a large portion of the atmo-
sphere. The specific gravity of dry air being 1, that of aqueous
vapour is 0.6 (§ 252). According to the table (§ 362), the mean
height of the barometer at sea, between the equator and 78° 37
north, is 30.01 ; whilst its mean height in lat. 70° S. is 29.0. To
explain the great and grand phenomena of nature by illustrations
drawn from the puny contrivances of human device is often a
feeble resort, but nevertheless we may, in order to explain this
expulsion of air from the watery south, where all is sea, be
pardoned for the homely reference. We all know, as the steam
or vapour begins to form in the tea-kettle, it expels air thence,
and itself occupies the space which the air occupied. If still
more heat be applied, as to the boiler of a steam-engine, the air
will be entirely expelled, and we have nothing but steam above
the water in the boiler. Xow at the south, over this great
waste of circumfluent waters, we do not have as much heat for
evaporation as in the boiler or the tea-kettle ; but, as far as it
goes, it forms vapour which has proportionally piecisely the same
tendency that the vapour in the tea-kettle has to drive off the

T 2

276 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLGGT.

air above and occup}^ tlie space it held. Nor is tliis all. Tliis
austral vapour, rising up, is cooled and condensed. Thus a vast
amount of heat is liberated in the upper regions, which goes to
heat the air there, expand it, and thus, by altering the level,
causing it to flow off. This unequal distribution of atmosphere
between the two halves of the globe is imperfectly represented in
larometric profile on Plate I. (§ 215) — the shading around the
periphery of the circle being intended to represent the relative
height, and the scales standing up in it, the barometric column.

513. Influence of Antarctic icebergs in expelling the air from
austral regions. — This part of the southern ocean where the
barometer shows diminished pressure is frequented by icebergs,
many of them very large and high, and some of them sending up
towers, minarets, and steeples, which give them the appearance
in the distance of beautiful cities afloat. Each one of them is a
centre of condensation. Could an eye from aloft look down upon
the scene, the upper side of the cloud stratum would present
somewhat the appearance of an immense caldron, boiling, and
bubbling, and intumescing in the upper air. These huge bergs
condense the vapour, and the liberated heat causes the air above
them to swell out, and to stand like so many curiously-shaped
fungi above the general cloud level. And thus, where the
icebergs are thick, the clouds are formed low down. Icebergs,
like islands, facilitate the formation of clouds and promote
precipitation.

514. The hoi'se latitudes — the doldrums. — Turn we now to the
equatorial cloud-ring. Seafaring people have, as if by common
consent, divided the ocean off into regions, and characterized
them according to the winds ; e.g., there are the " trade-wind
regions," the " variables," the "horse latitudes," the "doldrums,"
etc. The " horse latitudes" are the belts of calms and light airs
(§ 210) which border the polar edge of the north-east trades.
They were so called from the circumstance that vessels formerly
bound from New England to the West Indies, with a deck-load of
horses, were often so delayed in this calm belt of Cancer, that for
the want of water for their animals, they were compelled to
throw a portion of them overboard. The " equatorial doldrums "
is another of these calm places (§ 212). Besides being a region
of calms and baffling winds, it is a region noted for its rains and
clouds, which make it one of the most oppressive and disagreeable
places at sea. The emigrant ships from Europe for Australia

THE CLOUD REGIO:?^, ETC. 277

have to cross it. Tliey are often baffled in it for two or three
weeks ; then the children and the passengers who are of delicate
health suffer most. It is a frightful graveyard on the wayside to
that golden land. A vessel bound into the southern hemisphere
from Europe or America, after clearing the region of variable
winds and crossing the " horse latitudes," enters the north-east
trades. Here the mariner finds the sky sometimes mottled with
clouds, but for the most part clear. Here, too, he finds his
barometer rising and falling under the ebb and flow of a regular
atmospherical tide, which gives a high and low barometer every
day with such regularity that the hour within a few minutes
may be told by it. The rise and fall of this tide, measured by
the barometer, amounts to about one-tenth (0.1) of an inch, audit
occurs daily and everywhere between the tropics ; the maximum
about 10 h. 30 m. a.m., the minimum between 4 h. and 5 h. p.m.,
with a second maximum and minimum about 10 p.m. and 5 a.m.*
The diurnal variation of the needle (§ 344) changes also with the
turning of these invisible tides. Continuing his course towards
the equinoctial line, and entering the region of equatorial calms
and rains, the navigator feels the weather to become singularly
close and oppressive ; he discovers here that the elasticity of
feeling which he breathed from the trade-wind air has forsaken
him; he has entered the doldrums, and is under the "cloud-
ring."

515. A frigate under the cloud-ring. — I find in the journal of the
late Commodore Arthur Sinclair, kept on board the United
States frigate Congress during a cruise to South America in
1817-18, a picture of the weather under this cloud-ring that is
singularly graphic and striking. He encountered it in the
month of January, 1818, between the parallel of 4'^ north and
the equator, and between the meridians of 19° and 23° west. He
says of it, " This is certainly one of the most unpleasant regions
in our globe. A dense, close atmosphere, except for a few hours
after a thunderstorm, during which time torrents of rain fall,
when the air becomes a little refreshed ; but a hot, glowing sun
soon heats it again, and but for j^our awnings, and the little air
put in circulation by the continual flapping of the ship's sails, it
would be almost insufferable. No person who has not crossed
this region can form an adequate idea of its unpleasant effects.

* See paper on Meteorological Observations in India, by Colonel Sykes,
Pliilosopliical Transactions for 1850, part ii., page 297.

278 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

You feel a degree of lassitude unconquerable, which not even
the sea-bathing, which everywhere else proves so salutary and
renovating, can dispel. Except when in actual danger of ship-
wreck, I never speot twelve more disagreeable days in the pro-
fessional part of my life than in these calm latitudes. I crossed
the line on the 17th of January, at eight a.m., in longitude 21° 20',
and soon found I had surmounted all the difficulties consequent
to that event ; that the breeze continued to freshen and draw
round to the south-south-east, bringing with it a clear sk}- and
most heavenly temperature, renovating and refreshing beyond
description. Nothing was now to be seen but cheerful counte-
nances, exchanged as by enchantment from that sleepy sluggish-
ness which had borne us all down for the last two weeks."

516. Subjects which at sea present themselves for contemplation. —
One need not go to sea to perceive the grand work which the
clouds perfonn in collecting moisture from the crystal vaults of
the sky, in sprinkling it upon the fields, and making the hills
glad with showers of rain. Winter and summer, " the clouds
drop fatness upon the earth." This part of their office is obvious
to all, a,nd I do not propose to consider it now. But the sailor
at sea observes phenomena and witnesses operations in the
terrestrial economy which tell him that, in the beautiful and
exquisite adjustments of the grand machinery of the atmosphere,
the clouds have other important offices to perform besides those
merely of dispensing showers, of producing the rains, and of
weaving mantles of snow for the protection of our fields in
winter. As important as are these offices, the philosophical
mariner, as he changes his sky, is reminded that the clouds
have commandments to fulfil, which, though less obvious, are
not therefore the less benign in their influences, or the less
worthy of his notice. He beholds them at work in moderating
the extremes of heat and cold, and in mitigating climates. At
one time they spread themselves out ; they cover the earth as
with a mantle ; they prevent radiation from its crust, and keep
it warm. At another time they interpose between it and the
sun ; they screen it from his scorching rays, and protect the tender
plants from his heat, the land from the drought ; or, like a gar-
ment, they overshadow the sea, defending its waters from the
intense forces of evaporation. Having performed these offices
for one place, they are evaporated and given up to the sunbeam
and the winds again, to be borne on their wings away to other

THE CLOUD EEGION. ETC. 279

places wliicii gland in need of like offices. Familiar witli clouds
and sunshine, tlie storm and the calm, and all the phenomena
which find expression in the physical geography of the sea, the
right-minded mariner, as he contemplates "the cloud without
rain," ceases to regard it as an empty thing ; he perceives that
it performs many important offices ; he regards it as a great
moderator of heat and cold — as a " compensation" in the atmo-
spherical mechanism which makes the performance perfect.
Marvellous are the offices and wonderful is the constitution
of the atmosphere. Indeed, I know of no subject more fit for
profitable thought on the part of the truth-loving, knowledge-
seeking student, be he seaman or landsman, than that aiforded
by the atmosphere and its offices. Of all parts of the physical
machinery, of all the contrivances in the mechanism of the
universe, the atmosphere, wdth its offices and its adaptations,
appears to me to be the most wonderful, sublime, and beautiful.
In its construction, the grandeur of knowledge is disjjlayed.
The perfect man of Uz, in a moment of inspiration, thus bursts
forth in laudation of this part of God's handiwork, demanding
of his comforters, " But where shall wisdom be found, and where
is the place of understanding? The depth saith. It is not in me;
and the sea saith, It is not with me. It cannot be gotten for
gold, neither shall silver be weighed for the price thereof. No
mention shall be made of coral or of pearls, for the price of
wisdom is above rubies. Whenee, then, cometh wisdom, and
where is the place of understanding? Destruction and Death
say, we have heard the fame thereof with our ears. God under-
standeth the way thereof, and he knoweth the place thereof; for
he looketh to the ends of the earth, and seeth under the whole
heaven ; to make the weight for the winds ; and he weigheth the
waters by measure. When he made a decree for the rain, and a
way for the lightning of the thunder, then did he see it and
declare it ; he prepared it, yea, and searched it out."* When
the pump-maker came to ask Galileo to explain how it was that
his pump would not lift water higher than thirty-two feet, the
philosopher thought, but was afraid to say, it was owing to " the
weight of the winds ;" and though the fact that the air has
weight is here so distinctly announced, philosophers never re-
cognized the fact until within comparatively a recent period, and
then it was proclaimed by them as a great discovery. Never-
* Job, chap, sxviii.

280 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGy,

theless, the fact was set forth as distinctly in the Book of Xature
as it is in the Book of Eevelatiou ; for the infant, in availing
itself of atmospherical pressure to draw milk from its mother's
breast, unconsciously proclaimed it.

517. The harometer under the cloud-ring. — The barometer* stands
lower under this cloud-ring than on either side of it (§ 362).
After having crossed it, the attentive navigator may perceive
how this belt of clouds, by screening the parallels over which he
may have found it to hang from the sun's rays, not only promotes
the precipitation which takes place within these parallels at
certain periods, but how, also, the rains are made to change the
places upon which they are to fall ; and how, by travelling with
the calm belt of the equator up and down the earth, this cloud-
ring shifts the surface from which the heating rays of the sun
are to be excluded ; and how, by this operation, tone is given to
the atmospherical circulation of the world, and vigour to its
vegetation.

518. Its motions. — Having travelled with the calm belt to the
north or south, the cloud-ring leaves a clear sky- about the
equator; the rays of the torrid sun then pour down upon the
solid crust of the earth there, and raise its temperature to a
scorching heat. The atmosphere dances (§ 356), and the air is
seen trembling in ascending and descending columns, with busy
eagerness to conduct the heat off and deliver it to the regions
aloft, where it is required to give dynamical force to the air in
its general channels of circalation. < The dry season continues;
the sun is vertical ; and finally the earth becomes parched and
dr}^ ; the heat accumulates faster than the air can carry it away ;
the plants begin to wither, and the animals to perish. Then
comes the mitigating cloud-ring. The burning rays of the sun
are intercepted by it : the place for the absorption and reflection,
and the delivery to the atmosphere of the solar heat, is changed ;
it is transferred from the upper surface of the earth to the upper
surface of the clouds.

519. Meteorological processes. — Eadiation from land and sea
below the cloud-belt is thus interrupted, and the excess of heat
in the earth is delivered to the air, and by absorption carried up
to the clouds, and there transferred to their vapours to prevent

* Observations now show that the thermometer stands highest under th*>
cloud-ring. Indeed, the indications are that it coincides with the thermal
etjuator.

THE CLOUD REGIO>', KTO- 281

excess of precipitation. In the mean time, the trade-winds north
and south are pouring into this cloud-covered receiver, as the
calm and rain belt of the equator may be called, fresh supplies in
the shape of ceaseless volumes of heated air, which, loaded to
saturation with vapour, has to rise above and get clear of ihe
clouds before it can commence the process of cooling by radia-
tion. In the mean time, also, the vapours which the trade-
winds bring from the north and the south, expanding and
growing cooler as they ascend, are being condensed on the lower
side of the cloud stratum, and their latent heat is set free, to
check precipitation and prevent a flood. While this process and
these operations are going on upon the nether side of the cloud-
ring, one not less important is, we may imagine, going on upon
the upper side. There, from sunrise to sunset, the rays of the
sun are pouring down without intermission. Every day, and all
day long, they play with ceaseless activity upon the upper
surface of the cloud stratum. When they become too powerful,
and convey more heat to the cloud vapours than the cloud
vapours can reflect and give ofi" to the air above them, then, with
a beautiful elasticity of character, the clouds absorb the surplus
heat. They melt away, become invisible, and retain, in a latent
and harmless state, until it is wanted at some other place and on
some other occasion, the heat thus imparted. We thus have an
insight into the operations which are going on in the equatorial
belt of precipitation, and this insight is sufficient to enable us to
perceive that exquisite indeed are the arrangements which
Kature has provided for supplying this calm belt with heat,
and of pushing the snow-line there high up above the clouds, in
order that the atmosphere may have room to expand, to rise up,
overflow, and course back into its channels of healthful circT:^a-
tion. As the vapour is condensed and formed into drops of rain,
a two-fold object is accomplished ; coming from the cooler
regions of the clouds, the rain-drops are cooler than the air
and earth below ; they descend, and by absorption take up the
heat which has been accumulating in the earth's crust during the
dry season, and which cannot now escape by radiation.

520. Snow-line mounts up as it crosses the equatorial calm belt. —
In the process of condensation, these rain-drops, on the other
hand, have set free a vast quantity of latent heat, which has been
gathered up with the vapour from the sea b}^ the trade-winds and
brought hither. The caloric thus liberated is taken by the ait

382 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

and carried up aloft still farther, to keep, at the proper distance
from the earth, the line of perpetual congelation. Were it pos-
sible to trace a thermal curve in the upper regions of the air to
represent this line, we should no doubt find it mounting some-
times at the equator, sometimes on this side, and sometimes on
that, but always so mounting as to overleap this cloud-ring. This
thermal line would not ascend always over the same parallels : it
would ascend over those between which this ring happens to be ;
and the distance of this ring from the equator, north or south, is
regulated according to the seasons. If we imagine the atmo-
spherical equator to be always where the calm belt is which
separates the north-east from the south-east trade- winds, then the
loop in the thermal curve, which should represent the line of per-
petual congelation in the air, would be always found to stride
this equator ; and it may be supposed that a thermometer, kept
sliding on the surface of the earth, so as always to be in the
middle of this rain-belt, would show very nearly the same tempe-
rature all the year round ; and so, too, would a barometer the
same pressure, though the height of the atmosphere over this
calm belt would, in consequence of so much heat and expansion,
be very much greater than it is over the trade-winds or tropical
calms.

521. Offices of the cloud-ring. — Returning and taking up the
train of contemplation as to the office which this belt of clouds,
as it encircles the earth, performs in the system of oceanic adapta-
tions, we may see how the cloud-ring and calm zone which it
overshadows perform the office both of ventricle and auricle in
the immense atmospherical heart, where the heat and the forces
which give vitality and power to the system are brought into
play — where dynamical strength is gathered, and an impulse
given to the air sufficient to send it thence through its long and
tortuous channels of circulation.

522. It acts as a regulator. — Thus this ring, or band, or belt of
clouds is stretched around our planet to regulate the quantity of
precipitation in the rain-belt beneath it; to preserve the due
quantum of heat on the face of the earth ; to adjust the winds ;
and send out for distribution to the four corners vapours in
proper quantities to make up to each river-basin, climate, and
season its quota of sunshine, cloud, and moisture. Like the
balance-wheel of an artificial machine, this cloud-ring affords the
grand atmospherical machine the most exquisitely-arranged self-

THE CLOUD REGION, ETC. 283

compensation. If the sim fail in his supply of heat to this region
more of its vapours are condensed, and heat is discharged from its
latent store-houses in quantities just sufficient to keep the machine
in the most perfect compensation. If, on the other hand, too
much heat be found to accompany the rays of the sun as they
impinge upon the upper circumference of this belt, then again
on that side the means of self- compensation are ready at hand :
so much of the cloud-service as may be requisite is then resolved
into invisible vapour — for of invisible vapour are made the
vessels wherein the surplus heat of the sun is stored away and
held in the latent state until it is called for, when it is instantly
set free, and becomes a palpable and an active agent in the grand
design.

523. Hie latent heat liberated in the ^processes of condensation from
and under the cloud-ring, true cause of the trade-winds. — Evaporation
under this cloud-ring is suspended almost entirely. We know that
the trade-winds encircle the earth ; that they blow perpetually ;
that they come from the north and the south, and meet each
other near the equator ; therefore we infer that this line of meet-
ing extends around the world. By the rainy seasons of the torrid
zone, except where it may be broken by the continents, we can
trace the declination of this cloud-ring, stretched like a girdle
about our planet, up and down the earth ; it travels after the sun
up and down the ocean, as from north to south and back. It is
broader than the belt of calms out of which it rises. As the air,
with its vapours, rises up in this calm belt and: ascends, these
vapours are condensed into clouds, and this condensation is fol-
lowed by a turgid intumescence, which causes the clouds to
overflow the calm belt, as it were, both to the north and
the south. The air flowing off in the same direction assumes
the character of winds that form the upper currents that
are counter (Plate I.) to the trade-winds. These currents
carry the clouds still farther to the north and south, and thus
make the cloud-ring broader. At least we infer such to be the
case, for the rains are found to extend out into the trade-winds,
and often to a considerable distance both to the north and the
south of the calm belt.

524. Imagined appearance of the cloud-ring to a distant observer. —
Were this cloud-ring luminous, and could it be seen by an ob-
server from one of the planets, it would present to him an appear-
ance not unlike the rings of Saturn do to us. Such an obsei-ver

284 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOEOLOGT.

would remark that this cloud-ring of the earth has a motion con-
trary to that of the axis of our planet itself — that while the earth
was revolving rapidly from west to east, he would observe the
cloud-ring to go slowly, but only relatively, from east to west.
As the winds which bring this cloud-vapour to this region of
calms ritse up with it, the earth is slipping from under them ; and
thus the cloud-ring, though really moving from west to east with
the earth, goes relatively slower than the earth, and would there-
fore appear to require a longer time to complete a revolution.
But, unlike the rings of Saturn through the telescope, the outer
surface, or the upper side to us, of this cloud -ring, would appear
exceedingly jagged, rough, and uneven.

525. Thunder. — The rays of the sun, playing upon this peak
and then upon that of the upper cloud-surface, melt away one set
of elevations and create another set of depressions. The whole
stratum is, it may be imagined, in the most turgid state ; it is in
continued throes when viewed from above ; the heat which is
liberated from below in the process of condensation, the currents
of warm air ascending from the earth, and of cool descending
from the sky— all, we may well conceive, tend to keep the upper
cloud-surface in a perpetual state of agitation, upheaval, and
depression. Imagine in such a cloud-stratum an electrical dis-
charge to take place ; the report, being caught up by the cloud-
ridges above, is passed from peak to peak, and repeated from
valley to valley, until the last echo dies away in the mutterings
of the distant thunder. How often do we hear the voice of the
loud thunder rumbling and rolling away above the cloud-surface,
like the echo of artillery discharged among the hills ! Hence
we perceive or infer that the clouds intercept the progress of
sound, as well as of light and heat, and that this ujDper surface is
often like Alpine regions, which echo back and roll along with
rumbling noise the mutterings of the distant thunder.

526, Exceeding interest attached to jphijsical research at sea. —
It is by trains of reasoning like this that we are continually re-
minded of the interest which attaches to the observations which
the mariner is called on to make. There is no expression uttered
by nature which is unworthy of our most attentive consideration
— for no physical fact is too bald for study — and mariners, by
registering in their logs the kind of lightning, whether sheet,
forked, or streaked, and the kind of thunder, whether rolling,
muttering, or sharp, may be furnishing facts which will throw

THE GEOLOGICAL AGENCY OF THE WINDS. 285

much lio-lit on tlie features and character of the clouds in different
latitudes and seasons. Physical facts are the language of Nature,
and every expression uttered by her is worthy of our most atten-
tive consideration, for it is the voice of Wisdom.

CHAPTER XII.

§ 531-555. THE GEOLOGICAL AGENCY OF THE WINDS.

531. Tlie sea and air regarded as parts of the same machine. —
Properly to appreciate the various offices which the winds and
the waves perform, we must regard nature as a whole, for all the
departments thereof are intimately connected. If we attempt to
study in one of them, we often find ourselves tracing clews which
insensibly lead us off into others, and before we are aware, we
discover ourselves exploring the chambers of some other depart-
ment. The study of drifts takes the geologist out to sea, and
reminds him that a knowledge of waves, winds, and currents, of
navigation and hydrography, are closely and intimately connected
with his speciality. The astronomer directs his telescope to the
most remote star or to the nearest planet in the sky, and makes
an observation upon it. He cannot reduce this observation, nor
make any use of it, until he has availed himself of certain prin-
ciples of optics — until he has consulted the thermometer, gauged
the atmosphere, and considered the effect of heat in changing its
powers of refraction. In order to adjust the pendulum of his
clock to the right length, he has to measure the water of the sea
and weigh the earth. He, too, must therefore go into the study
of the tides ; he must examine the earth's crust, and consider the
matter of which it is composed, from pole to pole, circumference
to centre ; and in doing this, he finds himself, in his researches,
alongside of the navigator, the geologist, and the meteorologist,
with a host of other good fellows, each one holding on by the
same thread, and following it up into the same labyrinth— all,
it may be, with different objects in view, but nevertheless, each
one feeling sure that he is to be led into chambers where there
are stores of knowledge and instruction especially for him. And
thus, in undertaking to explore the physical geography of the
sea, I have found myself standing side by side with the geologist
on the land, and with him, far away from the sea-shore, engaged

286 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

in considering marine fossils, changes of climates, the effects of
deserts upon the winds, or the influence of mountains upon rains,
or some of the many phenomena which the inland basins of the
earth — those immense indentations on its surface that have no
sea-drainage— present for contemplation and study.

532. Tlie level of the Bead /S^ea.-^Among the most interesting of
these last is that of the Dead Sea. Lieutenant Lynch, of the
United States Navy, has run a level from that sea to the Mediter-
ranean, and finds the former to be about one thousand three
hundred feet below the general sea-level of the earth. In seeking
to account for this great diflerence of water-level, the geologist
examines the neighbouring region, and calls to his aid the forces
of elevation and depression which are supposed to have resided
in the neighbourhood; he then points to them as the agents
which did the w-ork. Truly they are mighty agents, and they
have diversified the surface of the earth with the most towering
monuments of their power. But is it necessary to suppose that
they resided in the vicinity of this region ? May they not have
come from the sea, and been, if not in this case, at least in the
case of other inland basins, as far removed as the other hemi-
sphere ? This is a question which I do not pretend to answer
definitely. But the inquiry as to the geological agency of the
winds in such cases is a question w^hich my investigations have
suggested. It has its seat in the sea, and therefore I propound it
as one which, in accountiug for the formation of this or that
inland basin, is worthy, at least, of consideration.

533. An ancient river from it. — Is there any evidence that the
annual amount of precipitation upon the water-shed of the Dead
Sea, at some former period, was greater than the annual amount
of evaporation from it now is ? If yea, from what part of the
sea did the vapour that supplied the excess of that precipitation
come, and what has cut off that supply ? The mere elevation of
the rim and depression of the lake basin would not cut it off'. If
we establish the fact that the Dead Sea at a former period did
send a river to the ocean, we carry along with this fact the
admission that when that sea overflowed into that river, then the
water that fell from the clouds over the Dead Sea basin was more
than the winds could convert into vapo7ir and carry away again ;
the river carried off the excess to the ocean whence it camo
(§ 207).

534. Frecijpitation and evajjoration in the Dead Sea valley. — In the

THE GEOLOGICAL AGENCY OF THE WINDS. 287

basin of the Dead Sea, in the basin of the Caspian, of the Sea of
Aral, and in the other inland basins of Asia, we are entitled to
infer that the precipitation and evaporation are at this time
exactly equal. Were it not so, the level of these seas would
be rising or sinking. If the precipitation were in excess, these
seas would be gradually becoming fuller ; and if the evaporation
were in excess, they would be gradually drying up ; but observa
tion does not show, nor history tell us, that either is the case.
As far as we know, the level of these seas is as permanent as
that of the ocean, and it is difficult to realize the existence of
subterranean channels between them and the great ocean. Were
there sach a channel, the Dead Sea being the lower, it would be
the recipient of ocean waters ; and we cannot conceive how it
should be such a recipient without ultimately rising to the level
of its feeder.

535. Wlience cmie its rains f — It may be that the question
suggested by my researches has no bearing upon the Dead Sea ;
that local elevations and subsidences alone were concerned in
placing the level of its waters where it is. But is it probable
that throughout all the geological periods, during all the changes
that have taken place in the distribution of land and water
surface over the earth, the winds, which in the general channels
of circulation pass over the Dead Sea, have alone been un-
changed ? Throughout all ages, periods, and formations, is it
probable that the winds have brought us just as much moisture
to that sea as they now bring, and have just taken up as much
water from it as they now carry off? Obviously and clearly not.
The salt-beds, the water-marks, the geological formations, and
other facts traced by Nature's own hand upon the tablets of the
rock, all indicate plainly enough that not only the Dead Sea, but
the Caspian also, had upon them, in fonner periods, more abundant
rains than they now have. Where did the vapour for those rains
come from ? and what has stopped the supply ? Surely not the
elevation or depression of the Dead Sea basin. My researches
with regard to the winds have suggested the probability (§ 290)
that the vapour which is condensed into rains for the lake valley,
and which the St. Lawrence carries off to the Atlantic Ocean, is
taken up by the south-east trade winds of the Pacific Ocean.
Suppose this to be the case, and that the winds which bring this
vapour arrive with it in the lake country at a mean dew-point of
50^. Let us also admit the south-west winds to be the rain

28S PHYSICAL GEOGEAPHY OF THE SEA, AND ITS BIETEOROLOGY.

winds for the lakes generall}-, as well as for the Mississippi
Yalley ; they are also, speaking generally, the rain winds of
Europe, and, I have no doubt, of extra-tropical Asia also.

536. The injiuence of mountain ranges. — ISow suppose a certain
mountain range, hundreds of miles to the south-west of the lakes,
but across the path of these winds, with their dew-point at 50°,
were to be suddenly elevated, and its crest pushed into the
regions of snow, having a mean temperature at its summit of 30°
Fahrenheit. The winds, in passing that range, would be sub-
jected to a mean dew-point of 30°; and, not meeting (§ 297)
with any more evaporating surface between such range and the
lakes, they would have no longer any moisture to deposit at the
supposed lake temperature of 50° ; for they could not yield their
moisture to anything above 30°. Consequently, the amount of
precipitation in the lake country would fall off ; the winds which
feed the lakes would cease to bring as much water as the lakes
now give to the St. Lawrence. In such a case, that river and
the Niagara would drain them to the level of their own beds ;
evaporation would "be increased by reason of the dryness of the
atmosphere and the want of rain, and the lakes would sink to
that level at which, as in the case of the Caspian Sea, the pre-
cipitation and evaporation would finally become equal.

537. How the level of Caspians is reduced. — There is a self-
regulating principle that would bring about this equality ; for as
the water in the lakes becomes lower, the area of its surface
would be diminished, and the amount of vapour taken from
it would consequently become less and less as the surface was
lowered, until the amount of water evaporated would become
equal to the amount rained down again, precisely in the same
way that the amount of water evaporated from the sea is exactly
equal to the whole amount poured back into it by the rains, the
fogs, and the dews.* Thus the great lakes of this continent
would remain inland seas at a permanent level ; the salt brought
from the soil by the washings of the rivers and rains would cease
to be taken off to the ocean as it now is ; and finally, too, the
great American lakes, in the j^rocess of ages, would become first
brackish, and then briny. Kow suppose the water basins which
hold the lakes to be over a thousand fathoms (six thousand feet)
deep. We know they are not more than four hundred and

* The quantity of dew in England is about five inches duiing a year. —
Glaiehe^:

THE GEOLOGICAL AGENCY OF THE WINDS. 289

twenty feet deep ; but suppose tliem to be six thousand feet deep.
The process of evaporation, after the St. Lawrence has gone dry,
might go on until one or two thousand feet or more were lost
from the surface, and we should then have another instance of
the level of an island water-basin being far below the sea-level,
as in the case of the Dead Sea ; or it would become a rainless
district, when the lakes themselves would go dry. Or let us
take another case for illustration. Corallines are at v/ork about
the Gulf Stream ; they have built up the Florida Eeefs on one
side, and the Bahama Banks on the other. Suppose they should
build up a dam across the Florida Pass, and obstruct the Gulf
Stream ; and that, in like manner, they were to connect Cuba
with Yucatan by damming up the Yucatan Pass, so that the
waters of the Atlantic should cease to flow into the Gulf of
Mexico. What should we have ? The depth of the marine basin
which holds the waters of that Gulf is, in the deepest part, about
a mile. We should therefore have, by stopping up the channels
between the Gulf and the Atlantic, not a sea-level in the Gulf,
but we should have a mean level between evaporation and
precipitation. If the former were in excess, the level of the
Gulf waters would sink down until the surface exposed to the air
would be just sufficient to return to the atmosphere, as vapour,
the amount of water discharged by the rivers — the Missis-
sippi and others — into the Gulf. As the waters were lowered,
the extent of evaporating surface would grow less and less, until
Nature should establish the proper ratio between the ability of
the air to take up and the capacity of the clouds to let down.
Thus we might have a sea whose level would be much farther
below the water-level of the ocean than is the Dead Sea.

538. Tlie formation of inland hasins — a third process. — There id
still another process, besides the one already alluded to, by which
the drainage of these inland basins may, through the agency of
the winds, have been cut off by the great salt seas, and that is
by the elevation of continents from the bottom of the sea in
distant regions of the earth, and the substitution caused thereby
of dry land instead of water for the winds to blow upon. Kow
Suppose that a continent should rise up in that part of the ocean,
wherever it may be, that supplies the clouds with the vapour
that makes the rain for the hydrographic basin of the great
American lakes. W^hat would be the result? Why, surely,
fewer clouds and less rain, which would involve a change of

290 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

climate in the lake country ; an increase of evaporation from it,
because a decrease of precipitation upon it ; and, consequently, a
diminution of cloudy screens to protect the waters of the lakes
from being sucked up by the rays of the sun ; and consequently,
too, there would follow a low stage for water-courses, and a
lowering of the lake-level would ensue.

•539. Examples. — So far, I have instanced these cases only
hypothetically ; but, both in regard to the hydrographical basins
of the Mexican Gulf and American lakes, I have confined myself
strictly to analogies. Mountain ranges have been upheaved
across the course of the winds, and continents have been raised
from the bottom of the sea ; and, no doubt, the influence of such
upheavals has been felt in remote regions by means of the winds,
and the effects which a greater or less amount^of moisture brought
by them would produce. In the case of the Salt Lake of Utah, we
have an example of drainage that has been cut off, and an illus-
tration of the process by which Nature equalizes the evaporation
and precipitation. To do this, in this instance, she is salting up
the basin which received the drainage of this inland water-shed.
Here we have the appearance, I am told, of an old channel by
which the water used to flow from this basin to the sea. Sup-
posing there was such a time and such a water-course, the watei
returned through it to the ocean was the amount by which the
precipitation used to exceed the evaporation over the whole
extent of country drained through this now dry bed of a river.
The winds have had something to do with this ; they are the
accents which used to brino; more moisture from the sea to this
water-shed than they carried away ; and they are the agents
which now carry off from that valley more moisture than is
brought to it, and which, therefore, are making a salt-bed of
places that used to be covered by water. In like manner, there
is evidence that the great American lakes formerly had a drainage
with the Gulf of Mexico ; for boats or canoes have been actually
known, in former years, and in times of freshets, to pass from the
Mississippi Eiver over into the lakes. At low water, the bed of
a dry river can be traced between them. Now the Salt Lake of
Utah is to the southward and westward of our northern lake
basin ; that is the quarter (§ 357) whence the rain-winds have
been supposed to come. May not the same cause which lessened
the precipitation or increased the evaporation in the Salt Lake
water-shed, have done the same fer the water-shed of the great

THE GEOLOGICAL AGENCY OF THE WINDS. 291

American system of lakes? If the mountains to the west— the
Sierra Nevada, for instance — stand higher now than they formerly
did, and if the winds which, feed the Salt Lake valley with pre-
cipitation formerly had, as I suppose they now have, to pass the
summits of these mountains, it is easy to perceive why the winds
should not convey as much vapour across them now as they did
when the summit of the range was lower and not so cool. The
Andes, in the trade-wind region of South America, stand up so
high, that the wind, in order to cross them, has to part with all
its moisture (§ 297), and consequently there is, on the west side,
a rainless region. Now suppose a range of such mountains as
these to be elevated across the track of the winds which supply
the lake country with rains ; it is easy to perceive how the whole
country to the leeward of such range, a.nd now watered by the
vapour which such winds bring, would be converted into a rain-
less region. I have used these hypothetical cases to illustrate a
position which any philosopher, who considers the geological
agency of the winds, may with propriety consult, when he is
told of an inland basin the water-level of which, it is evident, was
once higher than it now is ; and that position is that, though the
evidences of a higher water-level be unmistakable and conclusive,
it does not follow therefore that there has been a subsidence of
the lake basin itself, or an upheaval of the water-shed drained by
it. The cause which has produced this change in the water-
level, instead of being local and near, may be remote ; it may
have its seat in the obstructions to " the wind in his circuits,"
which have been interposed in some other quarter of the world,
which obstructions may prevent the winds from taking up or
from bearing ofl' their wonted supplies of moisture for the region
whose water-level has been lowered.

540. Tlie influence of tlie South American continent upon the climate
of the Dead Sea. — Having therefore, I hope, made clear the
meaning of the question proposed, b^ showing the manner in
which winds may become important geological agents, and
having explained how the upheaving of a mountain range in one
part of the world may, through the winds, bear upon the physical
geography of the sea, affect climates, and produce geological
phenomena in another, I return to the Dead Sea and the great
inland basins of Asia, and ask, How far is it possible for the eleva-
tion of the South American continent, and the ui^heaval of its
mountains, to have had any effect upon the water-level of these

u2

292 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

seas? There are indications (§ 535) that they all once had a
higher water-level than they now have, and that formerly the
amonnt of precipitation was greater than it now is ; then what
has become of the sources of vapour ? What has diminished its
supply? Its supply would he diminished (§ 538) either by the
substitution of dry land for water-surface in those parts of the
ocean which used to supply that vapour; or the quantity of
vapour deposited in the hydrographical basins cf those seas
would have been lessened if a snow-capped range of mountains
(§ 536) had been elevated across the path of these winds, between
the places where they were supplied with vapour and these
basins. A chain of evidence which it would be difficult to set
aside is contained in the chapters IV., YI., and VII., going to
fchow that the vapour which supplies the extra-tropical regions of
the north with rains comes, in all probability, from the trade- wind
regions of the southern hemisphere.

5-il. The path of the S.E. trade-ioinds over into the northern hemi-
sphere.— Now if it be true that the trade-winds from that part of
the world take up there water which is to be rained in the
extra-tropical north, the path ascribed to the south-east trades of
Africa and America, after they descend and become the pre-
variling south-west winds of the northern hemisphere, should
pass over a region of less precipitation generally than they would
do if, while performing the office of south-east trades, they had
blowTi over water instead of land. The south-east trade-winds,
with their load of vapour, whether great or small, take, after
ascending in the equatorial calms, a north-easterly direction ;
they continue to flow in the upper regions of the air in that
direction until they cross the tropic of Cancer. The places of
least rain, then, between this tropic and the pole, should be
precisely those places which depend for their rains upon the
vapour which the winds that blow over south-east trade-wind
Africa and America convey. Now, if we could trace the path of
the winds through the extra-tropical regions of the northern
hemisphere, we should be able to identify the track of these
Andean winds by the droppings of the clouds ; for the path of
the winds which depend for their moisture upon such sources of
supply as the dry land of Central South America and Africa
cannot overshadow a country that is watered well. It is a re-
Qiarkable fact that the countries in the extra-tropical regions of
the north that are situated to the north-east of the south-east

THE GEOLOGICAL AGENCY OF THE WINDS. 293

trade-winds of South Africa and America — that these countries,
over which theory makes these winds to blow, include all the
great deserts of Asia, and the districts of least precipitation in
Europe. A line from the Galapagos Islands through Florence in
Italy, another from the mouth of the Amazon through Aleppo in
Holy Land (Plate VII.), would, after passing the tropic of Cancer,
mark upon the surface of the earth the route of these winds ;
this is that "lee country" (§ 298) which, if such be the system
of atmospherical circulation, ought to be scantily supplied with
raijis. Kow the hyetographic map of Europe, in Johnston's
beautiful Physical Atlas, places the region of least precipitation
between these two lines (Plate VII.).

542. Belays for supplying them ivith vapour hy the way. — It would
seem that Nature, as if to reclaim this " lee " land from the
desert, had stationed by the wayside of these winds a succession
of inland seas to serve them as relays for supplying them with
moisture. There is the Mediterranean, with its arms, the Caspian
Sea and the Sea of Aral, all of which are situated exactly in this
direction, as though these sheets of water were desig-ned, in the
grand system of aqueous arrangements, to supply with fresh
vapour winds that had abeady left rain enough behind them to
make an Amazon and an Orinoco of. Now that there has been
such an elevation of land out of the water, we infer from the fact
that the Andes were once covered by the sea, for their tops are
now crowned with the remains of marine animals. When they
and their continent were submerged — admitting that Europe in
general outline was then as it now is — it cannot be supposed, if
the circulation of vapour were then such as it is supposed now to
be, that the climates of that part of the Old World which is under
the lee of those mountains were then as scantily supplied with
moisture as they now are. When the sea covered South America,
nearly all the vapour which is now precipitated upon the
Amazonian water-shed was conveyed thence by the winds, and
distributed, it may be supposed, among the countries situated
along the route (Plate VII.) ascribed to them.

543. Adjustments in this hygrometry of Caspians. — If ever the
Caspian Sea exposed a larger surface for evaporation than it
now does — and no doubt it did; if the precipitation in that
valley ever exceeded the evaporation from it, as it does in all
valleys drained into the open sea, then there must have been
a change of hygrometrical conditions there. And admitting thg

294: PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

vapour-springs for that valley to be situated in the direction
supposed, the rising up of a continent from the bottom of the sea,
or the upheaval of a range of mountains in certain parts of
America, Africa, or Spain, across the route of the winds which
brought the rain for the Caspian water-shed, might have been
sufficient to I'ob them of the moisture which they were wont to
carry away and precipitate upon this great inland basin. See
how the Andes have made Atacama a desert, and of Western
Peru a rainless country : these regions have been made rainless
simply by the rising up of a mountain range between them and
the vapour-springs in the ocean which feed with moisture the
winds that blow over those now rainless regions.

544. Countries in the temperate zone of this hemisphere that are
under the lee of land in the trade-wind regions of the other are dry
countries. — That part of Asia, then, which is under the lee of
southern trade-wind Africa, lies to the north of the tropic of
Cancer, and between two lines, the one passing through Cape
Palmas and Medina, the other through Aden and Delhi. Being
extended to the equator, they will include that part of it which
is crossed by the continental south-east trade-winds of Africa
after they have traversed the greatest extent of land surface
(Plate VII.). The range which lies between the two lines
which represent the course of the American winds with their
vapours, and the two lines which represent the course of the
African winds with their vapours, is the range which is under
the lee of winds that have, for the most part, traversed water
surface or the ocean in their circuit as south-east trade-winds.
But a bare inspection of Plate VII. will show that the south-east
trade-winds which cross the equator between longitude 15°
and 50° west, and which are supposed to blow over into this
Hemisphere between these two ranges, have traversed land
as well as water; and the Trade-wind Chart* shows that it
is precisely those winds which, in the summer and fall, are
convei-ted into south-west monsoons for supplying the whole
extent of Guinea with rains to make rivers of. Those winds,
therefore, it would seem, leave much of their moisture behind
them, and pass along to their channels in the grand system
of circulation, for the most part, as dry winds. Moreover, it
is not to be supposed that the channels through which the winds
blow that cross the equator at the several places named are
* Series of Maury's Wind and Current Charts,

THE GEOLOGICAL AGENCY OF THE WINDS. 295

as sliai-ply defined in nature as the lines suggested, or as Plate
VII. would represent them to he.

545. TliGir situation, and tile range of dry ivinds. — The whole
region of the extra-tropical Old World that is included within
the ranges marked is the region which has most land to windward
of it in the southern hemisphere. Now it is a curious coincidence,
at least, that all the great extra-tropical deserts of the earth, with
those regions in Europe and Asia which have the least amount
of precipitation upon them, should lie within this range. That
they are situated under the lee of the southern continents,
and have but little rain, may be a coincidence, I admit ; but
that these deserts of the Old World are placed where they are
is no coincidence — no accident : they are placed where they are,
and as they are, by design; and in being so placed, it was
intended that they should subserve some grand purpose in the
terrestrial economy. Let us see, therefore, if we can discover
any other marks of that design — any of the purposes to be sub-
served by such an arrangement — and trace any connection
between that arrangement and the supposition which I maintain
as to the place where the winds that blow over these regions
derive their vapours. It will be remarked at once that all the
inland seas of Asia, and all those of Europe except the semi-
fresh-water gulfs of the north, are within this range. The
Persian Gulf and the Eed Sea, the Mediterranean, the Black,
and the Caspian, all fall within it. And why are they planted
there ? Why are they arranged to the north-east and south-west
under this lee, and in the very direction in which theory makes
this breadth of thirsty winds to prevail ? Clearly and obviously,
one of the purposes in the divine economy was, that they might
replenish with vapour the winds that are almost vapourless
when they arrive at these regions in the general system of
circulation. And why should these winds be almost vapourless ?
They are almost vapourless because their route, in the general
system of circulation, is such, that they are not brought into
contact with a water-surface from which the needful supplies of
vapour are to be had; or, being obtained, the supplies have
since been taken away by the cool tops of mountain ranges over
which these winds have had to pass.

546. The Mediterranean within it. — In the Mediterranean, the
evaporation is greater than the precipitation. Upon the Red
Sea there never falls a drop of rain ; it is all evaporation. Are

296 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

we not, therefore, entitled to regard the Eed Sea as a make-
weight, thrown in to regulate the proportion of cloud and sun-
shine, and to dispense rain to certain parts of the earth in due
season and in proper quantities ? Have we not, in these two facts,
evidence conclusive that the winds which blow over these two
seas come, for the most part, from a dry country — from regions
which contain few or no pools to furnish supplies of vapour ?

547. Heavy evaporation. — Indeed, so scantily supplied with
vapour are the winds which pass in the general channels of
circulation over the water-shed and sea-basin of the Mediter-
ranean, that they take up there more water as vapour than they
deposit as rain. But, throwing out of the question what is
taken up from the surface of the Mediterranean itself, these
winds deposit more water upon the water-shed whose drainage
leads into the sea than they take up from it again. The excess
is to be found in the rivers which discharge themselves into the
Mediterranean ; but so thirsty are the winds which blow across
the bosom of that sea, that the}' not only take up again all the
water that those rivers pour into it, but they are supposed
by philosophers to create a demand for an immense current
from the Atlantic to supply the waste. It is estimated that
three* times as much water as the Mediterranean receives from
its rivers is evaporated from its surface. This may be an over-
estimate, but the fact that evaporation from it is in excess of the
precipitation, is made obvious by the current which the Atlantic
sends into it through the Straits of Gibraltar; and the difference,
we may rest assured, whether it be much or little, is carried off
to modify climate elsewhere — to refresh with showers and make
fruitful some other parts of the earth.

548. The winds that give rains to Siberian rivers have to cross the
stepi^es of Asia. — The great inland basin of Asia, which contains
the Sea of Aral and the Caspian, is situated on the route which
this hypothesis requires these thirsty winds from south-east
trade-wind Africa and America to take ; and so scant of vapour
are these winds when they arrive in this basin, that they have
no moisture to leave behind ; just as much as they pour down
they take up again and carry off. We know (§ 267) that the
volume of water returned by the rivers, the rains, and the dews,
into the whole ocean, is exactly equal to the volume which
the whole ocean gives back to the atmosphere ; as far as our

* Vide article " Physical Ge.itcrapliy," Encyclopaedia Britannica.

THE GEOLOGICAL AGENCY OF THE WINDS. 297

knowledge extends, the level of each of these two seas is as
permanent as that of the great ocean itself. Therefore, the
volume of water discharged by rivers, the rains, and the dews,
into these two seas, is exactly equal to the volume which these
two seas give back as vapour to the atmosphere. These winds,
therefore, do not begin pennanently to lay down their load of
moisture, be it great or small, until they cross the Oural
Mountains. On the steppes of Issam, after they have supplied
the Amazon and the other great equatorial rivers of the south,
we find them first beginning to lay down more moisture than
they take up again. In the Obi, the Yenesi, and the Lena is to
be found the volume that indicates the load of water which these
winds have brought from the southern hemisphere, from the
Mediterranean, and the Eed Sea; for in these almost hyper-
borean river-basins do we find the first instance in which,
throughout the entire range assigned these winds, they have,
after supplying the Amazon, etc., left more water behind them.
than they have taken up again and carried off. The low
temperatures of Siberian Asia are quite sufficient to extract from
these winds the remnants of vapour which the cool mountain-tops
and mighty rivers of the southern hemisphere have left in them.
549. How climates in one hemisj)here de2)end upon the arrangement
of land in the other, and upon the course of the idnds. — Here I may
be jDermitted to pause, that I may call attention to another
remarkable coincidence, and admire the marks of design, the
beautiful and exquisite adjustments that we here see provided,
to insure the perfect workings of the great aqueous and atmo-
spherical machine. This coincidence — may I not call it cause
and effect ? — is between the hygrometrical conditions of all the
countries within, and the hygrometrical conditions of all the
countries without, the range included within the lines which I
have drawn (Plate VII.) to represent the route in the northern
hemisphere of the south-east trade-winds after they have blown
their course over the land in South Africa and America. Both
to the right and left of this range are countries included between
the same parallels in which it is, yet these countries all receive
more water from the atmosphere than they give back to it
again ; they all have rivers running into the sea. On the one
hand, there is in Europe the Ehine, the Elbe, and all the great
livers that empty into the Atlantic ; on the other hand, there
are in Asia the Ganges, and all the great Chinese rivers; and in

298 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOT.OGT.

Nortli America, in the latitude of the Caspian Sea, is our great
system of fresh-water lakes; all of these receive from the
atmosphere immense volumes of water, and pour it back into
the sea in streams the most majestic. It is remarkable that none
of these copiously-supplied water-sheds have to the south-west
of them, in the trade-wind regions of the southern hemisphere,
any considerable body of land ; they are, all of them, under the
lee of evaporating surfaces in the trade-wind regions of the
south. Only those countries in the extra-tropical north which
I have described as lying under the lee of trade-wind South
America and Africa are scantily supplied with rains. Pray
examine Plate VII. in this connection. It tends to confirm the
views taken in Chapter VII. The surface of the Caspian Sea is
about equal to that of our lakes ; in it, evaporation is just equal
to the precipitation. Our lakes are between the same parallels,
and about the same distance from the western coast of America
that the Caspian Sea is from the western coast of Europe ; and
yet the waters discharged by the St. Lawrence give us an idea of
how greatly the precipitation upon its hydrographic basin is in
excess of the evaporation. To windward of the lakes, and in the
trade-wind regions of the southern hemisphere, is no land ; but
to windward of the Caspian Sea, and in the trade- wind region of
the southern hemisphere, there is land. Therefore, supposing
the course of the vapour-distributing winds to be such as I
maintain it to be, ought they not to carry more water from
the ocean to the American lakes than it is possible for them
to carry from the land — from the interior of South Africa and
America — to the valley of the Caspian Sea ? In like manner
(§ 365), extra-tropical New Holland and South Africa have each
land — not water — to the windward of them in the trade- wind
regions of the northern hemisphere, where, according to this
hypothesis, the vapour for their rains ought to be taken up :
they are both countries of little rain ; but extra-tropical South
America has, in the trade-wind region to windward of it in the
northern hemisphere, a great extent of ocean, and the amount
of precipitation (§ 299) in extra-tropical South America is
wonderful. The coincidence, therefore, is remarkable, that the
countries in the extra-tropical regions of this hemisphere, which
lie to the north-east of large districts of land in the trade-wind
regions of the other hemisphere, should be scantily supplied with
rains ; and likewise that those so situated in the extra-tropical

THE GEOLOGICAL AGENCY OF THE WINDS. 299

south, with regard to land in the trade-wind region of the north,
should also be scantily supplied with rains.

550, Tei-restrial adaptations. — Having thus remarked upon these
dry coincidences, let us contemplate the beautiful harmony
displayed in the arrangement of the land and water, as we find
them along this conjectural "wind-road." (Plate VII.) Those
who admit design in terrestrial adaptations, or who have studied
the economy of cosmical arrangements, will not be loth to grant
that by design the atmosphere keeps in circulation a certain
amount of moisture ; that the water of which this moisture is
made is supplied by the aqueous surface of the earth, and that it
is to be returned to the seas again through rivers and the process
of precipitation ; for were it not so, there would be a permanent
increase or decrease of the quantity of water thus put and kept in
circulation by the winds, which would be followed by a cor-
responding change of hygrometrical conditions, which, in turn,
would draw after it permanent changes of climate ; and per-
manent changes of climate would involve the ultimate well-being
of myriads of organisms, both in the vegetable and animal king-
doms. The quantity of moisture that the atmosphere keeps in
circulation is, no doubt, just that quantity which is best suited
to the well-being, and most adapted to the proper development of
the vegetable and animal kingdoms; and that quantity is de-
pendent upon the arrangement and the proportions that we see
in nature between the land and the water — between mountain
and desert, river and sea. If the seas and evaporating surfaces
were changed, and removed from the places they occupy to other
places, the principal places of precipitation probably would also
be changed : whole families of plants would wither and die for
want of cloud and sunshine, dry and wet, in proper proportions
and in due season : and, with the blight of plants, whole tribes
of -animals would also perish. Under such a chance arrange'
ment, man would no longer be able to rely upon the early and
the latter rain, or to count with certainty upon the rains being
sent in due season for seed-time and harvest. And that the rain
will be sent in due season we are assured from on high ; and
when we recollect who it is that " sendeth " it, we feel the
conviction strong within us, that He who sendeth the rain has the
winds for his messengers ; and that they may do his bidding, the
land and the sea were arranged, both as to position and relative
proportions where they are, and as they are.

300 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

551. 'Tlie Red Sea and its vajpours. — It should be borne in mini
that, by this hypothesis, the south-east trade-winds, after they
rise up at the equator (Plate I.), have to overleap the north-east
trade-winds. Consequently, they do not touch the earth until
near the tropic of Cancer (see the bearded arrows, Plate VIL),
more frequently to the north than to the south of it ; but for a
part of every year, the place where these vaulting south-east
trades first strike the earth, after leaving the other hemisphere,
is Very near this tropic. On the equatorial side of it, be it
remembered, the north-east trade- winds blow ; on the polar side,
what were the south-east trades, and what are now the prevailing
south-westerly winds of our hemisphere, prevail. Now examine
Plate VII., and it will be seen that the upper half of the Eed Sea
is north of the tropic of Cancer ; the lower half is to the south of
it ; that the latter is within the north-east trade-wind region ;
the former, in the region where the south-west passage winds are
the prevailing winds. The Eiver Tigris is probably evaporated
from the upper half of this sea by these winds ; while the north-
east trade-winds take up from the lower half those vapours which
feed the Nile with rain, and which the clouds deliver to the cold
demands of the Mountains of the Moon. Thus there are two
" wind-roads" crossing this sea: to the windward of it, each
road runs through a rainless region ; to the leeward there is, in
each case, a river rained down. The Persian Gulf lies, for the
most part, in the track of the south-west winds ; to the windward
of the Persian Gulf is a desert ; to the leeward, the Eiver Indus.
This is the route by which theory would require the vapour from
the Eed Sea and Persian Gulf to be convej^ed, and this is the
direction in which we find indications that it is conveyed. For
to leeward do we find, in each case, a river, telling to us, by
signs not to be mistaken, that it receives more water from the
clouds than it gives back to the winds.

552. Certain seas and deserts considered as counterpoises in the
terrestrial macMnery. — Is it not a curious circumstance, that the
winds which travel the road suggested from the southern hemi-
sphere should, when they touch the earth on the polar side of
the tropic of Cancer, be so thirst}^ more thirsty, much more, than
those which travel on either side of their path, and which are
supposed to have come from soiathern seas, not fi'om southern
lands? The Mediterranean has to give those winds three times
as much vapour as it receives from them (§ 547) ; the Eed Sea

THE GEOLOGICAL AGENCY OF THE WINDS. 301

gives them as much as they can take, and receives nothing back
in return but a little dew (§ 376) ; the Persian Gulf also gives
more than it receives. What becomes of the rest ? Doubtless it
is given to the winds, that they may bear it off to distant regions,
and make lands fruitful, that but for these sources of supply
would be almost rainless, if not entirely arid, waste, and barren.
These seas and arms of the ocean now present themselves to the
mind as countei'poises in the great hygrometrical machinery of
our planet. — As sheets of water placed where they are to balance
the land in the trade-wind region of South America and South
Africa, they now present themselves. When the foundations of
the earth were laid, the Great Architect " measured the waters
in the hollow of his hand, and meted out the heavens with a span,
and comprehended the dust of the earth in a measure, and
weighed the mountains in scales, and the hills in a balance ;"
and hence we know that they are arranged both according to
proportion and to place. Here, then, we see harmony in the
winds, design in the mountains, order in the sea, arrangement for
the dust, and form for the desert. Here are signs of beauty and
works of grandeur ; and we may now fancy that, in this exquisite
system of adaptations and compensations, we can almost behold,
in the Eed and Mediterranean Seas, the very waters that were
held in the hollow of the Almighty hand when He weighed the
Andes and balanced the hills of Africa in the comprehensive
scales. In that great inland basin of Asia which holds the
Caspian Sea, and embraces an area of one million and a half of
geographical square miles, we see the water-surface so exquisitely
adjusted, that it is just sufficient, and no more, to return to the
atmosphere as vapour exactly as much moisture as the atmosphere
lends in rain to the rivers of that basin — a beautiful illustration of
the fact that the span of the heavens was meted out according to
the measure of the waters. Thus we are entitled to regard
(§ 542) the Mediterranean, the Eed Sea, and Persian Gulf as
relays, distributed along the route of these thirsty winds from
the continents of the other hemisphere, to supply them with
vapours, or to restore to them that which they have left behind
to feed the sources of the Amazon, the jSIiger, and the Congo.

553. Hypothesis supported hy facts. — The hypothesis that the
winds from South Africa and America do take the course through
Europe and Asia which I have marked out for them (Plate VII.),
is supported by so many coincidences, to say the least, that wo

302 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

are entitled to regard it as probably correct, until a train of
coincidences at least as striking can be adduced to show that such
is not the case. Eeturning once more to a consideration of the
geological agency of the winds in accounting for the depression
of the Dead Sea, we now see the fact palpably brought out before
us, that if the Straits of Gibraltar were to be barred up, so that
no water could pass through them, we should have a great
depression of water-level in the Mediterranean. Three times as
much water (§ 547) is evaporated from that sea as is returned to
it through the rivers. A portion of water evaporated from it is
probably rained down and returned to it through the rivers ; but,
supposing it to be barred up : as the demand upon it for vapour
Avould exceed the supply by rains and rivers, it would commence
to dry up ; as it sinks down, the area exposed for evaporation
would decrease, and the supplies to the rivers would diminish,
until finally there would be established between the evaporation
and precipitation an equilibrium, as in the Dead and Caspian
Seas. But, for aught we know, the water-level of the Mediter-
ranean might, before this equilibrium were attained, have to
reach a stage far below that of the Dead Sea level. The Lake
Tadjura is now in the act of attaining such an equilibrium.
There are connected with it the remains of a channel by which
the water ran into the sea ; but the surface of the lake is now
five hundred feet below the sea-level, and it is salting up. If
not in the Dead Sea, do we not, in the valley of this lake, find
outcropping some reason for the question, What have the winds
had to do with the phenomena before us ?

554. How, hy the winds, the age of certain geological phenomena in
one hemisphere may he compared with the age of those in the other, —
The winds, in this sense, are geological agents of great power.
It is not impossible but that they may afford us the means of
comparing, directly, geological events which have taken place in
one hemisphere, with geological events in another : e.g., the tops
of the Andes were once at the bottom of the sea. — Which is the
oldest formation, that of the Dead Sea or the Andes ? If the
former be the older, then the climate of the Dead Sea must
have been hygrometrically very different from what it now is.
In regarding the winds as geological agents, we can no longer
consider them as the type of instability. We should i-ather treat
them in the light of ancient and faithful chroniclers, which, upon
being rightly consulted, will reveal to us truths that Nature has

THE DEPTHS OF THE OCEAN. 303

written upon their wings in characters as legible and enduring as
any with which she has ever engraved the history of geological
events upon the tablet of the rock.

555. The Andes older ilian the Dead Sea as an inland water. — The
waters of Lake Titicaca, which receives the drainage of the great
inland basin of the Andes, are only brackish, not salt. Hence
we ma}'" infer that this lake has not been standing long enough
to become briny, like the waters of the Dead Sea ; consequently,
it belongs to a more recent period. On the other hand, it will
also be interesting to hear that my friend Captain Lynch informs
me that, in his exploration of the Dead Sea, he saw what he took
to be the dry bed of a river that once flowed from it. And thus
we have two more links, stout and strong, to add to the chain of
circumstantial evidence going to sustain the testimony of this
strange and fickle witness which I have called up from the sea to
testify in this presence concerning the works of Nature, and to
tell us which be the older — the Andes, watching the stars with
their hoary heads, or the Dead Sea, sleeping upon its ancient beds
of crystal salt.

CHAPTER XIIL

§ 560-575. THE DEPTHS OF THE OCEAN.

560. Submarine scenery. — "We dive," says Schleiden,* "into the
liquid crystal of the Indian Ocean, and it opens to us the most
wondrous enchantments, reminding us of fairy tales in child-
hood's dreams. The strangely branching thickets bear living
flowers. Dense masses of meandrinas and astreeas contrast witli
the leafy, cup-shaped expansions of the explanaries, the variously-
ramified Madrepores, which are now spread out like fingers, now
rise in trunk-like branches, and now display the most elegant
array of interlacing branches. The colouring surpasses every-
thing ; vivid green alternates with brown or yellow ; rich tints
of purple, from pale red-brown to the deepest blue. Brilliant
rosy, yellow, or peach-coloured jSTullipores overgrow the decaying
masses, and are themselves interwoven with the pearl-coloured
plates of the Eetipores, resembling the most delicate ivory
carvings. Close by wave the yellow and lilac fans, perforated
* " The Flaut."

304 PHYSICAL GEOGRAPHY OP IHE SEA, AN! ITS METEOROLOGY.

like trellis- work, of the Gorgonias. The clear sand of the bottom
is covered with the Ihousand strange forms and tints of the sea-
urchins and star-fishes. The leaf-like flustras and escharas
adhere like mosses and lichens to the branches of the corals ; the
yellow, green, and purple-striped limpets cling like monstrous
cochineal insects upon their trunks. Like gigantic cactus-
blossoms, sparkling in the most ardent colours, the sea-anemones
expand their crowns of tentacles upon the broken rocks, or more
modestly embellish the flat bottom, looking like beds of variegated
ranunculuses. Around the blossoms of the coral shrubs play the
humming-birds of the ocean, little fish sparkling with red or blue
metallic glitter, or gleaming in golden green, or in the brightest
silvery lustre. Softly, like spirits of the deep, the delicate milk-
white or bluish bells of the jelly-fishes float through this charmed
world. Here the gleaming violet and gold-green Isabelle, and
the flaming yellow, black, and vermilion-striped coquette, chase
their prey ; there the band-fish shoots, snake-like, through
the thicket, like a long silver ribbon, glittering with rosy and
azure hues. Then come the fabulous cuttle-fishes, decked in all
the colours of the rainbow, but marked by no definite outline,
appearing and disappearing, intercrossing, joining company and
parting again, in most fantastic ways ; and all this in the most
rapid change, and amid the most wonderful play of light and
shade, altered by every breath of wind, and every slight curling
of the surface of the ocean. When day declines, and the shades
of night lay hold upon the deep, this fantastic garden is lighted
ap in new splendour. Millions of glowing sparks, little micro-
scopic medusas and crustaceans, dance like glovv-worais through
the gloom. The sea-feather, which by daylight is vermilion-
coloured, waves in a greenish, phosphorescent light. Every
corner of it is lustrous. Parts which by day were perhaps dull
and brown, and retreated from the sight amid the universal
brilliancy of colour, are now radiant in the most wonderful play
of green, yellow, and red light; and, to complete the wonders of
the enchanted night, the silver disk, six feet across, of the moon
fish,* moves, slightly luminous, among the cloud of little spark-
ling stars. The most luxuriant vegetation of a tropical landscape
cannot unfold as great wealth of form, while in the variety and
splendour of colour it would stand far behind this garden land-
scape, which is strangely composed exclusively of animals, and
* Orthaoforiscus mola.

THE DEPTHS OF THE OCEAN. 305

not of plants ; for, characteristic as the luxuriant development of
vegetation of the temperate zones is of the sea bottom, the full-
ness and multiplicity of the marine Fauna is just as prominent in
the regions of the tropics. Whatever is beautiful, wondrous, or
uncommon in the great classes of fish and Echinoderms, jelly-
fishes and Polypes, and the Mollusks of all kinds, is crowded
into the warm and crystal waters of the tropical ocean — rests in
the white sands, clothes the rough cliffs, clings, where the room
is already occupied, like a parasite, upon the first comers, or
swims through the shallows and depths of the elements — while
the mass of the vegetation is of a far inferior magnitude. It is
peculiar in relation to this that the law valid on land, according
to which the animal kingdom, being better adapted to accommo-
date itself to outward circumstances, has a greater diffusion than
the vegetable kingdom — for the polar seas swarm with whales,
seals, sea-birds, fishes, and countless numbers of the lower
animals, even where every trace of vegetation has long vanished
in the eternally frozen ice, and the cooled sea fosters no sea-
weed— that this law, I say, holds good also for the sea, in the
direction of its depth; for when we descend, vegetable life
vanishes much sooner than the animal, and, even from the depths
to which no ra}^ of light is capable of penetrating, the sounding-
lead brings np news at least of living infusoria." — Schleiden's
Lectures, p. 403—406.

561. Ignorance concerning the deptJi of ^'■blue ivater." — Until the
commencement of the plan of deep-sea soundings, as they have
been conducted in the American and English navies, the bottom
of what the sailors call " blue water" was as unknown to ns as
is the interior of any of the planets of our system. Koss and
Dupetit Thenars, with other officers of the English, French, and
Dutch navies, had attempted to fathom the deep sea, some with
silk threads, some with spun-yarn (coarse hemp threads twisted
together), and some with the common lead and line of navigation.
All of these attempts were made upon the supposition that when
the lead reached the bottom, either a shock would be felt, or the
line, becoming slack, wonld cease to run out.

562. Early attempts at deep-sea soundings — unwortliy of reliance. —
The series of systematic experiments recently made upon this
subject show that there is no reliance to be placed on such a sup-
position, for the shock cansed by striking bottom cannot be com-
municated through very great depths. Furthermore, the lights

306 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of experience show that, as a general rule, the under currents of
the deep sea have force enough to take the line out long after the
plummet has ceased to do so. Consequently, there is but little
reliance to be placed upon deep-sea soundings of former methods,
when the depths reported exceeded eight or ten thousand feet.

563. Various methods tried or proposed, — Attempts to fathom the
ocean, both by sound and pressure, had been made, but out in
" blue water " every trial was only a failure repeated. The most
ingenious and beautiful contrivances for deep-sea soundings were
resorted to. By exploding petards, or ringing bells in the deep
sea, when the winds were hushed, and all was still, the echo or
reverberation from the bottom might, it was held, be heard, and
the depth determined from the rate at which sound travels
through water. .But, though the concussion took place many
feet below the surface, echo was silent, and no answer was re-
ceived from the bottom. Ericsson and others constructed deep-
sea leads having a column of air in them, which, by compression,
would show the aqueous pressure to which they might be sub-
jected. This was found to answer well for ordinary purposes,
but in the depths of the sea, where the pressure would be equal
to several hundred atmospheres, the trial was more than this
instrument could stand. Mr. Baur, an ingenious mechanician of
Xew York, constructed, according to a plan which I furnished
him, a deep-sea sounding apparatus. To the lead was attached,
upon the principle of the screw propeller, a small piece of clock-
work for registering the number of revolutions made by the little
screw during the descent, and it having been ascertained by
experiment in shoal water that the apparatus, in descending,
wo aid cause the propeller to make one revolution for every
tathom of perpendicular descent, hands provided with the power
of self-registration were attached to a dial, and the instrument
was complete. It worked beautifully in moderate depths, but
failed in blue water, from the difficulty of hauling it up if the
line used were small, and from the difficulty of getting it down if
the line used were large enough to give the requisite strength for
hauling it up. An old sea-captain proposed a torpedo, such as is
sometimes used in the whale fishery for blowing up the monsters
of the deep, only this one was intended to explode on touching
the bottom. It was proposed first to ascertain by actual experi-
ment the rate at which the torpedo would sink, and the rate at
which the sound or the gass would ascend, and so, by timing the

THE DEPTHS OF THE OCEAX. 307

interval, to determine the depth. This plan would afford no
specimens of the bottom, and its adoption was opposed bj^ other
obstacles. One gentleman proposed to use the magnetic teio,
graph. The wire properly coated, was to be laid np in ttui
sounding-line, and to the plummet was attached machinery, so
contrived that on the increase of every 100 fathoms, and by moarxs
of the additional pressure the circuit would be restored, some-
what after the manner of Dr. Locke's electro-chronograph, and a
message would come up to tell how many hundred iathoms up
and down the plummet had sunk. As beautiful as this idea was,
it was not simple enough in practical application to answo,r our
purposes.

564. Physical problems more difficult than that of measuring the
depth of the sea have been accomplished. — Greater difiicalties than
any presented by the problem of deep-sea soundings had been
overcome in other departments of physical research. These plans
and attempts served to encourage, nor were thoy fruitless, though
they proved barren of practical results. Astronomers had mea-
sured the volumes and weighed the masses of the most distant
planets, and increased thereby the stock of human knowledge.
Was it creditable to the age that the depths of the sea should
remain in the category of an unsolved problem ? Its " ooze and
bottom " was a sealed volume, rich with ancient and eloquent
legends, and suggestive of many an instructive lesson that might
be useful and profitable to man. The seal which covered it was
of rolling waves many thousand feet in thickness. Could it not
be broken ? Curiosity had always been great, yet neither the
enterprise nor the ingenuity of man had as yet proved itself equal
to the task. No one had succeeded in penetrating and bringing
up from beyond the depth of two or three hundred fathoms below
the aqueous covering of the earth any solid specimens of solid
matter for the study of philosophers.

565. The deep-sea sounding apparatus of Peter the Great. — The
honour of the first attempt to recover specimens of the bottom
from great depths belongs to Peter the Great of Russia. That
remarkable man and illustrious monarch constructed a deep-sea
sounding apparatus especially for the Caspian Sea. It was some-
what in the shape of a pair of ice-hooks, and such as are seen in
the hands of the " ice-man," as, in his daily rounds, he lifts the
blocks of ice from his cart in the street for delivery at the door.
It was so contrived that when it touched the bottom the plum-

X 2

308 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

met would become detached, and the hook would bring up the
specimen.

56 G. A plan of deep-sea sounding devised for the American navy.
— The sea, with its mj^ths, has suggested attractive themes to all
people in all ages. Like the heavens, it affords an almost endless
variety of subjects for pleasing and profitable contemplation, and
there has remained in the human mind a longing to learn more
of its wonders and to understand its mysteries. The Bible often
alludes to them. Are they past finding out ? How deep is it ?
and what is at the bottom of it ? Could not the ingenuity and
appliances of the age throw some light upon these questions ?
The government was liberal and enlightened ; times seemed pro-
pitious ; but when or how to begin, after all these failures, with
this interesting problem, was one of the difficulties first to be
overcome. It was a common opinion, derived chiefly from a
supposed physical relation, that the depths of the sea are about
equal to the heights of the mountains. But this conjecture was,
at best, only a speculation. Though plausible, it did not satisfy.
There were, in the depths of the sea, untold wonders and in-
explicable mysteries. Therefore the contemplative mariner, as
in mid- ocean he looked down upon its gentle bosom, continued
to experience sentiments akin to those which fill the mind of the
devout astronomer when, in the stillness of the night, he looks
out upon the stars, and wonders. Nevertheless, the depths of the
sea still remained as fathomless and as mysterious as the firma-
ment above. Indeed, telescopes of huge proportions and of vast
space-penetrating powers had been erected here and there by the
munificence of individuals, and attempts made with them to
gauge the heavens and sound out the regions of space. Could it
be more difficult to sound out the sea than to gauge the blue
ether and fathom the vaults of the sky ? The result of the astro-
nomical undertakings* lies in the discovery that what, through
other instruments of less power, appeared as clusters of stars,
were, by these of larger powers, separated into groups, and what
had been reported as nebulaa, could now be resolved into clusters ;
that in certain directions, the abyss beyond these faint objects is
decked with other nebulas, which these great instruments may
bring to light but cannot resolve ; and that there are still regions
and realms beyond which the rays of the brightest sun in the sky
have neither the intensity nor the force to reach, much less to
* See the works of Herscliel and Kosse, and their telescopes.

THE DEPTHS OF THE OCEAN. 309

penetrate. And what is more, these monster instruments have
revealed to us, in those distant regions, forms or aggregations of
matter which suggest to some the idea of the existence of physical
forces there that we do not understand, and which raise the ques-
tion in speculative minds, Is gravitation a universal thing, and
do its forces penetrate every abyss of space? Could we not
gauge the sea as well as the sky, and devise an instrument for
penetrating the depths of the ocean as well as the depths of
space ? Mariners were curious concerning the bottom of the sea.
Though .nothing thence had been brought to light, exploration
had invested the subject with additional interest, and increased
the desire to know more. In this state of the case, the idea of a
common twine thread for a sounding-line, and a cannon ball for
a sinker, was suggested. It was a beautiful conception; for,
besides its simplicity, it had in its favour the greatest of recom-
mendations, it could be readily put into practice.

567. The great depths and failures of the first attempts. — Well-
directed attempts to fathom the ocean began now to be made
with such a line and plummet, and the public mind was astonished
at the vast depths that were at first reported. Lieutenant Walsh,
of the United States schooner " Taney," reported a cast with the
deep-sea lead at thirty-four thousand feet without bottom. His
sounding-line was an iron wire more than eleven miles in length.
Lieutenant Berryman, of the United States brig " Dolphin," re-
ported another unsuccessful attempt to fathom mid-ocean with a
line thirty-nine thousand feet in length. Captain Denham, of
Her Britannic Majesty's ship " Herald," reported bottom in the
South Atlantic at the depth of forty-six thousand feet; and Lieu-
tenant J. P.Parker, of the United States frigate "Congress,"
afterwards, in attempting to sound near the same region, let go
his plummet, and saw it run out a line fifty thousand feet long as
though the bottom had not been reached. There are no such
depths as these. The three last-named attempts were made with
the sounding-twine of the American navy, which has been intr*-
duced in conformity with a very simple plan for sounding out the
depths of the ocean. It involved for each cast only the expen-
diture of a cannon ball, and twine enough to reach the bottom.
This plan was introduced as a part of the researches conducted
at the National Observatory, and which have proved so fruitful
and beneficial, concerning the winds and currents and other phe-
nomena of the ocean. These researches had already received the

310 PHYSICAL GEOGRAPHy OF THE SEA, AND ITS METEOROLOGY.

approbation of the Congress of the United States ; for that body,
in a spirit worthy of the representatives of a free and enlightened
people, had authorized the Secretary of the Navy to employ three
public vessels to assist in perfecting the discoveries, and in con-
ducting the investigations connected therewith.

568. Tlie jplan finally adopted. — The plan of deep-sea soundings
finally adopted, and now in practice, is this : Every vessel of the
navy, when she puts to sea, is, if she desires it, furnished with
a sufficient quantity of sounding-twine, carefully marked at every
length of one hundred fathoms — six hundred feet — and wound
on reels of ten thousand fathoms each. It is made the duty of
the commander to avail himself of every favourable opportunity
to try the depth of the ocean, whenever he may find himself out
upon " blue water." For this purpose he is to use a cannon-ball
of 32 or 68 pounds as a plummet. Having one end of the twine
attached to it, the cannon-ball is to be thrown overboard from a
boat or a steamer, and suffered to take the twine from the reel
as fast as it will. The reel is made to turn easily. A silk thread,
or the common wrapping-twine of the shops, would, it was
thought, be strong enough for this purpose, for it was supposed
there would be no strain upon the line except the very slight one
required to drag it down, and the twine having nearly the specific
gravit}^ of sea water, this strain would, it was imagined, be very
slight. Moreover, when the shot reached the bottom, the line, it
was thought (§ 561), would cease to run out; then breaking it
off, and seeing how much remained upon the reel, the depth of
the sea could be ascertained at any place and time simply at the
expense of one cannon-ball and a few pounds of common
twine.

569. Discovery of currents in the depths of the sea. — But practical
difficulties that were not expected at all were lurking in the
way, and afterwards showed themselves at every attempt to
sound; and it was before these practical difficulties had been
fairly overcome that the great soundings (§ 567) were reported.
In the first place, it was discovered that the line, once started
and dragged down into the depths of the ocean, never would
cease to run out (§ 562), and, consequently, that there was no
means of knowing when, if ever, the shot had reached the
bottom. And, in the next place, it was ascertained that the
ordinary twine (§ 566) would not do; that the sounding-line,
in going down, was really subjected to quite a heavy strain,

THE DEPTHS OF THE OCEAN. 311

and that, consequently, the twine to be nsed must be strong ;
it was therefore subjected to a test which required it to bear
a weight of at least sixty pounds freely suspended in the air.
So we had to go to work anew, and make several hundred
thousand fathoms of sounding- twine especially for the purpose.
It was small, and stood the test required, a pound of it measur-
ing about six hundred feet in length. The officers intrusted
with the duty soon found that the soundings could not be made
from sailing vessels with any certainty as to the depth. It was
necessary that a boat should be lowered, and the trial be made
from it ; the men with their oars keeping the boat from drifting,
and maintaining it in such a position that the line should be "up
and down " the while. That the line would continue to run out
after the cannon-ball had reached bottom, was explained by the
conjecture that there is in the ocean, as in the air, a system of
currents and counter currents one above the other, and that it
was one or more of these submarine currents, operating uj)on the
bight of the line, which caused it to continue to run out after the
shot had reached the bottom. In corroboration of this con-
jecture, it was urged, with a truth-like force of argument, that it
was these under currents, operating with a " swigging " force
upon the bights of the line — for there might be several currents
running in different directions, and operating upon it at the same
time — which caused it to part whenever the reel was stopped
and the line held fast in the boat.

570. Evidence in favour of a regular system of oceanic circulation.
— A powerful train of circumstantial evidence was this (and
it was derived from a source wholly unexpected), going to
prove the existence of that system of oceanic circulation which
the climates, and the offices, and the adaptations of the sea
require, and which its inhabitants (§ 465) in their mute way
tell us of. This system of circulation commenced on the third
day of creation, with the "gathering together of the waters,"
which were "called seas ;" it will probably continue as long
as sea water shall possess the properties of saltness and
fluidity.

571. Method of making a deep-sea sounding, — In making these
deep-sea soundings, the practice is to time the hundred fathom
marks (*§ 568) as they successively go out ; and by always using
aline of the same size and "make," and a sinker of the same
tihape and weight, we at last established the law of descent.

312 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

Thus the mean of our experiments gave ns, for the sinker and
twine used,

2 111. 21 s. as the average time of descent from 400 to 500 fathoms.

„ 1000 to 1100 „ „ 1000 to 1100

4 m. 29 s. „ „ „ 1800 to 1900

572. The law of the plummet's descent — Now, by aid of the
law here indicated, w^e could tell very nearly when the ball
ceased to carry the line out, and when, of course, it began to
go out in obedience to the current and drift alone ; for currents
would sweep the line out at a uniform rate, while the cannon-
ball would drag it out at a decreasing rate. The development
of this law was certainly an achievement, for it enabled us to
show that the depth of the sea at the places named (§ 567) was
not as great as reports made it. These researches were interest-
ing : the problem in hand was important, and it deserved every
effort that ingenuity could suggest for reducing it to a satis-
factory solution.

573. Brooke's sounding cqoj^aratus. — As yet no specimens of the
bottom had been brought up. The line was too small, the shot
was too heavy, and it could not be weighed ; and if we could
reach the bottom, why should we not know its character ? In
this state of the case. Passed Midshipman J. M. Brooke, United
States Navy, who at the time was associated with me on duty at
the Observatory, proposed a contrivance by which the shot,
on striking the bottom, would detach itself from the line, and
send up a specimen of the bottom. This beautiful contrivance,
called Brooke's Deep-sea Sounding Apparatus, is represented
on p. 313. A is a cannon-ball, having a hole through it for the
rod B. Figure 1 represents the rod B, and the slings D D, with
the shot slung, ready for sounding. Figure 2 represents the
apparatus in the act of striking the bottom ; it shows how the
shot is detached, and how specimens of the bottom are brought
up, by adhering to a little soap or tallow,* called "arming,"
in the cup C, at the lower end of the rod B. With this con-
trivance specimens of the bottom have been brought up from the
depth of nearly four miles.

* The barrel of a common quill attached to the rod has been found to
answer better.

THE DEPTHS OF THE OCEAN.

313

574. TJie deepest part of the Atlantic Ocean. — The greatest
depths at which the bottom of the sea has been reached with
the phammet are in the North Atlantic Ocean, and the places
where it has been fathomed do not show it to be deeper than
twenty-five thousand feet. The deepest place in this ocean
(Plate XI.) is probably between the parallels of 35° and 40°
north latitude, and immediately to the southward of the Grand
Banks of Xewfoundland. The first specimens have been
received from the coral sea of the Indian Archipelago and from
the North Pacific. They were collected by the surveying
expedition employed in those seas. A few soundings have been
made in the South Atlantic, but not enough to justify deduction
as to its depths or the precise shape of its floor.

575. Deep-sea soundings hy the English navy. — The friends of
physical research at sea are under obligations to the officers

314 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of the English navy for much valuable information touching this
interesting subject. Certain officers in that service have taken
up the problem of deep-sea soundings with the most praise-
worthy zeal, energy, and intelligence. Dayman in the Atlantic,
Captains Spratt and ]\iansell in the Mediterranean, with Captain
Pullen in the Eed Sea, have all made valuable contributions
to the stock of human knowledge concerning the depths and
bottom of the sea. To Mansell and Spratt we are indebted
for all we know about deep-sea soundings in the Mediterranean,
as we are to Pullen for those in the Eed Sea. By their lines
of soundings, their maps and profiles, they have enabled physical
geographers to form, with some approach towards correctness, an
idea as to the orography of the basins which hold the water
for these two seas. We are also indebted to the French for
deep-sea soundings in the Mediterranean. That sea appears
to be about two miles deep in the deepest parts, which are
in the isleless spaces to the west of Sardinia and to the east of
Malta.

CHAPTEPt XIV.

§ 580-619. THE BASIN AXD BED OF THE ATLANTIC.

580. Hie ivonders of the sea. — The wonders of the sea are as
marvellous as the glories of the heavens ; and they proclaim, in
songs divine, that they too are the work of holy fingers. Among
the revelations which scientific research has lately made con-
cerning the crust of our planet, none are more interesting to
the student of nature, or more suggestive to the Christian
philosopher, than those which relate to the bed and bottom of the
ocean.

581. Its hottom and Chimhorazo. — The basin of the Atlantic,
according to the deep-sea soundings made by the American and
English navies, is shown on Plate XI. This plate refers chiefl}^
to that part of the Atlantic which is included within our
hemisphere. In its entire length, the basin of this sea is a
long trough separating tlie Old World from the New, and
extending probably from pole to pole. As to breadth, it
contrasts strongly with the Pacific Ocean. From the top of
Chimborazo to the bottom of the Atlantic, at the deepest place

THE BASIN AND BED OF THE ATLANTIC. 315

yet reached by the plummet in that ocean, the distance, in a
vertical line, is nine miles.

582. An orographic vieiv. — Could the waters of the Atlantic be
drawn off so as to expose to view this great sea-gash which
separates continents, and extends from the Arctic to the Antarctic,
it would present a scene the most rugged, grand, and imposing.
The very ribs of the solid earth, with the foundations of the sea,
would be brought to light, and we should have presented to us
in one view, in the empty cradle of the ocean, "a thousand
fearful wrecks," with that array of " dead men's skulls, great
anchors, heaps of pearl and inestimable stones," which, in the
poet's 63^6, lie scattered on the bottom of the sea, making it
hideous with sights of ugly death. To measure the elevation of
the mountain-top above the sea, and to lay down upon our maps
the elevated ranges of the earth, is regarded in geography as an
important thing, and rightly so. Equally important is it, in
bringing the physical geography of the sea regularly within the
domains of science, to present its orology, by map23ing out the
bottom of the ocean so as to show the depressions of the solid
parts of the earth's crust there, below the sea-level.

583. Plate XI. — Plate XI. presents the latest attempt at such a
map. It relates exclusively to the bottom of that part of the
Atlantic Ocean which lies north of 10° south. It is stippled with
four shades : the darkest (that which is nearest the shore-line)
shows where the water is less than six thousand feet deep ; the
next, where it is less than twelve thousand feet deep ; the third,
where it is less than eighteen thousand ; and the fourtli, or
lightest, where it is not over twenty-four thousand feet deep.
The blank space south of Nova Scotia and the Grand Banks in-
cludes a district within which casts showing very deep water
have been reported, but which subsequent investigation and dis-
cussion do not appear to confirm. The deepest part of the North
Atlantic is probably somewhere between the Bermudas and the
Grand Banks, but how deep it maybe jet remains for the cannon-
ball and sounding-twine to determine. The waters of the Gulf
of Mexico are held in a basin about a mile deep in the deepest
part. The bottom of the Atlantic, or its depressions below
the sea-level, are given, perhaps, on this plate with as much ac-
curacy as the best geographers have been enabled to show, on a
map, the elevations above the sea-level of the interior either of
Africa or Australia.

316 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

584. " Wliafs tlie use'' of deej)-sea soundings? — " What is to be
tlie use of these deep-sea soundings ?" is a question that often
occurs ; and it is as difficult to be answered in categorical terms as
Franklin's question, " What is the use of a new-born babe ?"'
Every physical fact, every expression of nature, every feature of
the earth, the work of any and all of those agents which make
the face of the world what it is, and as we see it, is interesting
and instructive. Until we get hold of a group of physical
facts, we do not know what practical bearings they may have,
though right-minded men know that they contain many precious
jewels, which the experts of philosophy will not fail to bring-
out, polished and bright, and beautifully adapted, sooner or later,
to man's pui-poses. Already we are obtaining practical answers
to this question as to the use of deep-sea soundings ; for, as soon
as Ihey were announced to the public, they forthwith assumed a
practical bearing in the minds of men with regard to the question
of a submarine telegraph across the Atlantic.

585. The telegraphic jplateau. — There is, at the bottom of this sea,
between Cape Kace, in Newfoundland, and Cape Clear, in Ireland,
a remarkable steppe, which is already known as the telegraphic
plateau, and has already been made famous by the attempts to
run a telegraphic cable across the ocean upon it. In August,
1858, a cable was laid upon it from Valencia in Ireland to Trinity
Bay in Newfoundland, and but a few messages were passed
through it, when it ceased to work. Whether messages can ever
be success/idly sent, in a commercial sense, through such a length
of continuous submarine wire, is by no means certain ; but
that the wires of 1858 so soon ceased to pass any current at
all was no doubt owing to the fact that the cable was constructed
upon erroneous principles. Its projectors, in planning its con-
struction, did not, unfortunately, avail themselves of the light
which our deep-sea soundings had cast upon the bed of the
ocean.

586. The first s])ecimens of deejp-sea soundings. — It was upon this
plateau that Brooke's sounding apparatus brought up its first
trophies from the bottom of the sea. These specimens the
officers of the Dolphin judged to be clay; but they took the
precaution to label them, carefully to preserve them, and, on
their return to the United States, to send them to the proper
bureau. They were divided ; a part was sent for examination to
Professor Ehrenberg, of Berlin, and a part to the late Professor

THE BASIN AND BED OF THE ATLANTIC. 317

Bailey, of West Point — eminent microscopists both. The latter
thus responded : —

587. Bailey's letter. — ■" I am greatly obliged to you for the
deep soundings you sent me last week, and I have looked at them
with great interest. They are exactly what I have wanted to get
hold of. The bottom of the ocean at the depth of more than two
miles I hardly hoped ever to have a chance of examining; yet,
thanks to Brooke's contrivance, we have it clean and free from
grease, so that it can at once be put under the microscope. I was
greatly delighted to find that all these deep soundings are filled
with microscopic shells ; not a particle of sand or gravel exists
in them. They are chiefly made up of perfect little calcareous
shells (Foraminiferd), and contain, also, a number of silicious
shells (Diatomaceee). It is not probable that these animals lived
at the depths where these shells are found, but I rather think that
they inhabit the waters near the surface ; and when they die,
their shells settle to the bottom. With reference to this point, I
shall be very glad to examine bottles of water from various
depths which were brought home by the Dolphin, and any similar
materials, either ' bottom,' or water from other localities. I shall
study them carefully. . . . The results already obtained are of
very great interest, and have many important bearings on
geology and zoology. ... I hope you will induce as many as
possible to collect soundings with Brooke's lead, in all parts of
the world, so that we can map out the animalcula^ as you have
the whales. Get your whalers also to collect mud from pancake
ice, etc., in the polar regions ; this is always full of interesting
microscopic forms."

588. Specimens from the coral sea.- — Lieutenant Brooke, of the
North Pacific Exploring Expedition, procured specimens of the
bottom from the depth of 2150 fathoms in the coral sea, lat. 13° S.,
long. 162° E. With regard to these, the admirable and lamented
Bailey wrote in 1855, " Vou may be sure 1 was not backwards
in taking a look at the specimens you sent me, which, from their
locality, promised to be so interesting. The sounding from 2150
fathoms, although very small in quantity, is not so bad in quality,
yielding representatives of most of the great groups of micro-
scopic organisms usually found in marine sediments. The pre-
dominant forms are silicious spicules of sponges. Various forms
of these occur : some long and spindle-shaped, or acicular ; others
pin-headed ; some three-spined, etc., etc. The Diatomes (silicious

318 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

infusoria of Ehrenberg) are very few in number, and mostly frag
mentary. I found, however, some perfect valves of a coscino'
discus. The Foraminifera (Polythalamia of Ehrenberg) are very
rare, only one perfect shell being seen, with a few fragments of
others. The polycistineae are present, and some species of ha-
liomma were quite perfect. Fragments of other forms of this
group indicate that various interesting species might be obtained
if we had more of the material. You will see by the above that
this deep sounding differs considerably from those obtained in
the Atlantic. The Atlantic soundings were almost wholly com-
posed of calcareous shells of the Foraziinifera ; these, on the con-
trary, contain very few Foraminifera, and are of a silicious rather
than a calcareous nature. This only makes the condition of
things in the Northern iVtlantic the more interesting."

589. They helong to the animal, not to the vegetable or mineral Mng-
dom. — The first noticeable thing the microscope gives of these
specimens is, that nearly all of them are of the animal, few of the
mineral or vegetable kingdom. 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 seems to be
inversely as the size of the individual. The smaller the animal,
the greater the space occupied by its remains. Though not in-
variably the case, yet this rule, to a certain extent, is true, and
will, therefore, answer our present purposes, which are simply
those of illustration. 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 the difference between
great and small. The graveyard that would hold the remains of
the coral insect is larger than the graveyard that would hold
those of the elephant.

590. Quiet reigns in the depth of the sea. — We notice another
practical bearing in this group of physical facts that Brooke's
apparatus has fished up from the bottom of the deep sea. Bailey,
with his microscope (§ 587), could detect scarcely a single
particle of sand or gravel among these little mites of shells.
They were from the great telegraphic plateau (§ 585), and the
inference is that there, if anywhere, the waters of the sea are at
rest. There was not motion enough to abrade these very delicate
organisms, nor current enough tx) sweep them about and mix up

THE BASIN AND BED OF THE ATLANTIC, 319

with them a grain of the finest sand, nor the smallest particle of
gravel torn from the loose beds of debris that here and there
strew the bottom of the sea. This plateau is not too deep for the
wire to sink down and rest upon, yet it is not so shallow that
currents, or icebergs, or any abrading force can derange the wire
after it is once lodged there.

591. Is there life in them ? — As Professor Bailey remarks (§ 587),
the animalculge, whose remains Brooke's lead has brought up
from the bottom of the deep sea, probably did not live or die
there. They would have had no light there, and, had they lived
there, their frail little texture would have been subjected, in its
growth, to the pressure of a column of water twelve thousand feet
high, equal to the weight of four hundred atmospheres. They
probably lived and died near the surface, wnere tliey could feei
the genial influence of both light and neat, and were buried in tho
lichen caves below after death.

592. The ocean in a new light. — Jt5rooke's lead ana trie micro-
scope, therefore, it would seem, are about to teacn us to regard
the ocean in a new light. Its bosom, which so teems with ani-
mal life — its face, upon which time writes no wrinkles, makes no
impression, are, it would now seem, as obedient to the great law
of change as is any department whatever either of the animal or
the vegetable kingdom. It is now suggested that henceforward
we should view the surface of the sea as a nursery teeming with
nascent organisms, its depths as the cemetery for families of
living creatures that out-number the sands on the sea shore for
multitude. Where there is a nursery, hard by there will be found
also a graveyard ; such is the condition of the animal world.
But it never occurred to us before to consider the surface of the
sea as one wide nursery, its every ripple a cradle, and its bottom
one vast burial-place.

593. Levelling agencies. — On those parts of the solid portions of
the earth's crust which are at the bottom of the atmosphere,
various agents are at work, levelling both upwards and down-
wards. Heat and cold, rain and sunshine, the winds and the
streams, all, assisted by the forces of gravitation, are unceasingly
wasting away the high places on the land, and as perpetually
filling up the low. But in contemplating the levelling agencies
that are at work upon the solid portions of the crust of our planet
which are at the bottom of the sea, one is led, at first thought,
almost to the conclusion that these levelling agents are powerless

320 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

there. In tlie deep sea there are no abrading processes at work ;
neither frosts nor rains are felt there, and the force of gravitation
is so paralyzed there that it cannot nse half its power, as on dry-
land, in tearing the overhanging rock from the precipice and
casting it down into the valley below.

594. Tlie offices of animalculce. — Hitherto we have, in imagina-
tion, been disposed to regard the waters of tne sea as a great
cushion, placed between the air and the bottom of the ocean,
to protect and defend it from these abrading agencies of the atmo-
sphere. The geological clock may, we thought, strike new
periods ; its hands may point to era after era ; but, so long as the
ocean remains in its basin, so long as its bottom is covered with
blue water, so long must the deep furrows and strong contrasts
in the solid crust below stand out boldly, rugged, ragged, and
grandly. Nothing can fill up the hollows there ; no agent now
at work, that we know of, can descend into its depths, and level
off the floors of the sea. But it now seems that we forgot the
myriads of animalculge that make the surface of the sea sparkle
and glow with life : they are secreting from its surface solid
matter for the very purpose of filling up those cavities below.
These little marine insects build their habitations at the surface,
and when they die, their remains, in vast multitudes, sink down
and settle upon the bottom. They are the atoms of which
mountains are formed — plains spread out. Our marl- beds, the
clay in our river-bottoms, large portions of many of the great
basins of the earth, even flinty rocks are composed of the remains
of just such little creatures as these, which the ingenuity of
Brooke has enabled us to fish up from the depth of neaiiy four
miles (two thousand feet) below the sea-level.* These Fora-
minifera, therefore, when living, may have been preparing tho
ingredients for the fruitful soil of a land that some earthquake or
upheaval, in ages far away in the future, may be sent to cast up
from the bottom of the sea for man's use.

595. The study of them projitahle. — The study of these "sunless
treasures," recovered with so much ingenuity from the rich
bottom of the sea, suggests new views concerning the physical
economy of the ocean. It not only leads us into the workshops
of the inhabitants of the sea— showing us through their nurseries
and cemeteiies, and enabling us to study their economy, — but it

* The greatest depth, from which specimens of bottom have been obtained,
is 19,800 feet (3300 tathoms; in the North Pacific.

THE BASIN AND BED OF THE ATLANTIC. 321

conducts US into tlie very chambers of the deep. Our investiga-
tions go to show that the roaring waves and the mightiest billows
of the ocean lepose, not upon hard or troubled beds, but upon
cushions of still water ; that everywhere at the bottom of the
deep sea the solid ribs of the earth are protected, as with a
garment, from the abrading action of its currents, and that the
cradle of its restless waves is lined by a stratum of water at rest,
or so nearly at rest that it can neither wear nor move the lightest
bit of drift that once lodges there.

596. The abrasion of currents. — The tooth of running water is
ver}' sharp. See how the Hudson has gnawed through the
Highlands, and the Niagara cut its way through layer after layer
of the solid rock. But what are the Hudson and the Niagara,
with all the fresh water-courses of the world, by the side of the
Gulf Stream and other great '• rivers in the ocean ?" And what
is the pressure of fresh water upon river-beds in comparison
with the pressure of ocean water upon the bottom of the deep
sea ? It is not so great by contrast as tne gutters in the streets
are to the cataract. Then why have not the currents of the sea
worn its bottom away ? Simply because they are not permitted
to get down to it. Su^ppose the currents which we see at and
near the surface of the ocean were permitted to extend all the
way to the bottom in deep as well as shallow water, let us see
what the pressure and scouring force would be where the sea is
only 3000 fathoms deep — for in many places the depth is even
greater than that. It is equal there, in round numbers, to the
pressure of six hundred atmospheres. Six hundred atmospheres,
piled up one above the other, would press upon every square
foot of solid matter beneath the pile with the weight of l,2i)6,000
pounds, or 648 tons.

597. Their pressure on the bottom. — The better to comprehend
the amount of such a pressure, let us imagine a column of water
just one foot square, where the sea is 3000 fathoms deep, to be
frozen from the top to the bottom, and that we could then, with
the aid of some mighty magician, haul this shaft of ice up, and
stand it on one end for inspection and examination. It would be
18,000 feet high ; the pressure on its pedestal would be more
than a million and a quarter of pounds ; and if placed on a ship o^
648 tons burden, it would be heavy enough to sink her. There
are currents in the sea where it is 3000 fathoms deep, and some
of them — as the Gulf Stream — run with a velocity of four miles

322 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOROLOGY.

an hour and even more. Every square foot of the earth's crust
at the bottom of a four-knot current 3000 fathoms deep would
have no less than 506,880 — in round numbers, half a million — of
such columns of water daily dragging, and rubbing, and scouring,
and chafing over it, under a continuous pressure of 648 tons.
\Yhat would the bottom of the sea have to be made of to with-
stand such erosion ? Water running with such a velocity, and
with the friction upon the bottom which such a pressure would
create, would in time wear away the thickest bed, though made
of the hardest adamant. Why, then, has not the bottom of the
sea been worn away ? Why have not its currents cut through
the solid crust in which its billows are rocked, and ripped
out from the bowels of the earth the masses of incandescent,
molten matter which geologists tell us lie pent up and boiling
there ?

598. Why they cannot chafe it. — If the currents of the sea, with
this four-mile velocity at the surface, and this hundreds of tons
pressure on the bottom, were permitted to chafe against its bed,
the Atlantic, instead of being two miles deep and 3000 miles
broad, would, we may imagine, have been long ago cut down into
a narrow channel that might have been as the same ocean turned
up on edge, and measuring two miles broad and 3000 deep. But
had it been so cut, the proportion of land and water surface
would have been destroyed, and the winds, for lack of area to
play upon, could not have sucked up from the sea vapours for
the rains, and the face of the earth would have become as a
desert withoiit water. Kow there is a reason why such changes
should not take place, why the currents should not uproot nor
score the deep bed of the ocean, why they should not throw out
of adjustment any physical arrangement whatever : because, in
the presence of everlasting wisdom, a compass was set upon the face
of the deep ; because its waters were measured in the hollow of the
Almighty hand ; because hars and doors were set to stay its proud
waves ; and because, when He gave to the sea His decree that its
waters should not pjass His command, He laid the foundations of the
world so fast that they should not he removed for ever.

599. WJiat it consists of — By bringing up specimens from the
depth of the ocean, and studying them through the microscope,
it has been ascertained that the bed of the ocean is lined with
the microscopic remains of its own dead, with marine feculences
which lie on the bottom as lightly as gossamer. How frail yet

THE BASIN AND BED OF THE ATLANTIC. 323

how stroiig, how light yet how firm are the foundations of the
sea ! Its waves cannot fret them, its currents cannot wear them,
for the Led of the deep sea is protected from abrasion by a
cushion of still and heavy water. There it lies — that beautiful
arrangement — spread out over the bottom of the deep, and
covering its foundations as with a garment, so that they may not
be worn. If the currents chafe upon it now here, now there, as
in shallow seas they sometimes do, this protecting cushion is
self-adjusting ; and the moment the unwonted pressure is removed
the liquid cushion is restored, and there is again compensation.

600. The causes that produce currents in the sea reside near its
surface. — The discovery of this arrangement in the oceanic
machinery suggests that the streams of running water in the sea
play rather about its surface than in its depths ; that the causes
which produce currents reside at and near the surface ; that
these causes are changing heat and alternating cold with their
powers of contraction and expansion — winds and sea-shells with
evaporation and precipitation ; and it is certain that none of
these agents appear capable of reaching with their influences
very far down into the depths of the great and wide sea. They
go not much, if any, farther down than the light can reach. On
the other hand, the most powerful agents in the atmosphere
reside at and near its bottom; so that, where these two great
oceans meet — the aqueous and the aerial — there we probably
have the greatest conflict and the most powerful display of the
forces that set and keep them in motion, making them to rage
and roar.

601. Tlieir depth. — The greatest depth at which running water
is to be found in the seU is probably in the narrowest part of the
Gulf Stream, as, coming from its mighty fountain, it issues
through the Florida Pass. The deep-sea thermometer shews
that even here there is a layer of cold water in the depths
beneath, so that this "river in the sea" may chafe not against
the solid bottom. What revelations of the telescope, what
wonders of the microscope, what fact relating to the physical
economy of this terrestrial globe, is more beautiful or suggestive
than some of the secrets which have been fished up from the
caverns of the deep, and brought to light from the hidden paths
of the sea ?

602. Tlie cushion of still water — its thichiess. — In my researches
I have as yet found no marks of running water impressed upon

y2

324 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the foundations of the sea beyond tlie depth of two or three
thousand feet. Should future deep-sea soundings establish this
as a fact in other seas also, it will prove of the greatest value to
submarine telegraphy. What may be the thickness of this
cushion of still water that covers the bottom of the deep sea is a
question of high interest, but we must leave it for future inves-
tigation.

603. Tlie conservators of the sea. — In Chapter X. (The Salts of the
Sea), I have endeavoured to show how sea-shells and marine
insects, may, by reason of the offices which they perform, be
regarded as compensations in that exquisite system of physical
machinery by which the harmonies of nature are preserved.
But the treasures of the lead and revelations of the microscope
present the insects of the sea in a new and still more striking
light. We behold them now, serving not only as compensations
by which the motions of the water in its channels of circulation
are regulated and climates softened, but acting also as checks
and balances by which the equipoise between the solid and the
fluid matter of the earth is preserved. Should it be established
that these microscopic creatures live at the surface, and are only
buried at the bottom of the sea, we may then view them as
conservators of the ocean ; for, in the offices which they perform,
they assist to preserve its status by maintaining the purity of its
waters.

604. The anti-biotic view the most natural. — Does any portion of
the shells which Brooke's sounding-rod brings up from the bottom
of the deep sea live there ; or are they all the remains of those
that lived near the surface in the light and heat of sun, and were
buried at the bottom of the deep after de'ath ? Philosophers are
divided in opinion upon this subject. The facts, as far as they go,
seem at first to favour the one conjecture nearly as well as the
other. Under these circumstances, I incline to the anti-biotic
hypothesis, and chiefly because it would seem to conform better
with the Mosaic account of creation. The sun and moon were
set in the firmament before the waters were commanded to bring
forth the living creature ; and hence we infer that light and heat
are necessary to the creation and preservation of marine life ;
and since the light and heat of the sun cannot reach to the
bottom of the deep sea, my own conclusion, in the absence of
positive evidence upon the subject, has been, that the habitat of
these mites of things hauled up from the bottom of the great

THE BASIN AND BED OF THE ATLANTIC. 325

deep is at and near the sniface. On the contrary, others main-
tain, and perhaps with equal reason, the biotic side of thf^
question. Professor Ehrenberg, of Berlin, is of this latter class.

605. The question stated. — This is an interesting question. It is
a new one ; and it belongs to that class of questions which mere
discussion helps to settle. It is therefore desirable to state both
sides — present all the known facts; and then, provided with
such lights as they afford, we may draw conclusions.

606. TJie arguments of the hiotics, — As soon as the deep-sea
specimens were mounted on the slides of the microscope, the two
great masters of that instrument in Europe and America — ^Bailey
of West Point, and Ehrenberg of Berlin — discovered the greater
part of the small calcareous carapaces to be filled with a soft
pulp, which both admitted to be fleshy matter. From this fact
the German argued that there is life at the bottom of the deep
sea ; the American (§ 587), that there is only death and repose
there.

607. Ehrenherg's statement of them. — " The other argument,"
says Ehrenberg, " for life in the deep which I have established
is the surprising quantity of new forms which are wanting in
other parts of the sea. If the bottom were nothing but the
sediment of the troubled sea, like the fall of snow in the air, and
if the biolithic curves of the bottom were nothing else than the
product of the currents of the sea which heap up the flakes,
similarly to the glaciers, there would necessarily be much less of
unknown and peculiar forms in the depths. The surface and the
borders of the sea are much more productive and much more
extended than the depths ; hence the forms peculiar to the depths
should not be perceived. The great quantity of peculiar forms
and of soft bodies existing in the innumerable carapaces, accom-
panied by the observation of the number of unknowns, increasing
with the depths — these are the arguments which seem to me to
hold firmly to the opinion of stationary life at the bottom of the
deep sea." *

608. TJie anti-hiotic view. — The anti-biotics, on the other hand,
quoted the observations of Professor Forbes, who has shown that,
the deeper you go in the littoral waters of the Mediterranean,
the fewer are the living forms.

609. Their arguments based on the tides. — As for the number of
unknowns increasing with the depth (§ 607), they contend that
the tides, the currents, and the agitation of the waves all reach to

826 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

the bottom in shallow water ; that they sweep and scour from it
the feculences of the sea, as these insect remains may be called,
and bear them off into deep water. After reaching a certain
depth, then this sediment passes into the stratum of quiet waters
that underlie the roaring waves and tossing currents of the
surface, and through this stratum these organic remains slowly
find their way to the final place of repose as ooze at the bottom
of the deep sea. Through such agencies the ooze of the deep sea
ought, said the anti-biotics, to be richer than that of shallow
water with infusorial remains ; mud and all the light sedimentary
matter of river waters are deposited in the deep pools, and not in
the shoals and rapids of our fresh-water streams ; so we ought,
reasoned they of this school, to have the most abundant deposits
at the bottom of the deep sea.

610. On the antiseptic properties of sea water. — The anti-biotics
referred to the antiseptic properties of sea water, and told how it
is customary with mariners, especially with the masters of the
sailing packets between Europe and America, to " com " fresh
meat by sinking it to great depths overboard. If they sink it too
deep, or let it stay down too long, it becomes too salt. According
to them, this process is so quick and thorough, because of the
pressure and the affinity which not only forces the water among
the fibres of the meat, but which also induces the salt to leave the
water and sitrike into the meat ; and that the fleshy part of these
microscopic organisms have been exposed to powerful antiseptic
agents is proved by the fact that they are brought up in the
middle of the ocean, and remain on board the vessel exposed to
the air for months before they reach the hands of the microsco-
pist ; some of them have remained so exposed for more than a
year, and then been found full of fleshy matter : a sure proof that
it had been preserved from putrefaction and decay by processes
which it had undergone in the sea, and before it was brought up
into the air.

611. On pressure. — Thus the anti-biotics held that these little
creatures were preserved for a while after death, and until they
reached a certain depth, by salt, and afterwards by pressure.
They held that certain conditions are requisite in order that the
decay of organic matter may take place ; that the animal tissues
of these shells during the process of decay are for the most part
converted into gases; that these gases, in separating from the
animal compound, are capable of exerting only a certain mechan-

THE BASIN AND BED OF THE ATLANTIC. 327

ical force, and no more ; that this force is not very great ; and,
unless it were sufficient to overcome the pressure of deep-sea
water, their separation could not go on, and that, consequently,
there is a certain depth in the sea beyond which animal decom-
position or vegetable decay cannot take place. In support of
this view, they referred to the well-known effects of pressure in
arresting or modifying the energies displayed by certain chemical
affinities ; and in proof of the position that great compression in
the sea prevents putrefaction, they referred to the fact well-
known to the fishermen of Nantucket and New Bradford, viz.,
that when a whale that they have killed sinks in shallow water,
he, as the process of decay commences, is seen to swell and rise ;
but when he sinks in deep water, the pressure is such as to
prevent the formation of the distending gases, and he never does
rise. Some of these specimens have come from depths where the
pressure is equal to that of 400 or 500 atmospheres. Specimens
have been obtained by Lieutenant Brooke, in the Pacific, with
" fleshy parts " among them, at the depth of 3300 falhoms, and
where the pressure is nearly 700 atmospheres. We have brought
up fleshy matter from the deep sea as deep down as we have
gone ; and we may infer that if we were to go to 4000 fathoms,
we should still find pulpy matter among the dead organisms
there. At that depth, or a little over, common air, according to
" Mariotte's law,'' would be heavier than water, and an air-bubble
down there, if any one may imagine such a thing, would be
heavy enough to sink. Under such conditions, and with the
antiseptic agencies of the sea, the fleshy matter of these infusoria
might be preserved at the bottom of the deep sea for a great
length of time.

612. Arguments from the Bible. — Moreover (§ 604), the anti-
biotics pointed to the first chapter of Genesis to show that light
and heat were ordained before the waters were commanded
to bring forth. Hence they maintained that light and heat are
necessary to marine life. In the depth of the sea there is
neither light nor heat, wherefore they brought in circumstantial
evidence from the Bible to sustain them in their view.

613. A plan for solving the question. — This was an exceedingly
interesting question, and we could suggest but one way of
deciding it, which was this: Many of these little organisms
of the sea are in the shape of plano-convex discs; all such,
when alive, live with the convex side up, the flat side down ;

S2S PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

but when placed dead in the water and allowed freely to sink,
the force of gravity always, and for obvious reasons, causes all
such forms to sink with the convex side down. Brooke's lead
will bring up these shells exactly as they lie on the bottom, and
so he proposed to observe with regard to their manner of lying.
Of course, if they lived at the bottom, they would die as they
lived, and lie as they died, for (§ 590) there is nothing to turn
them over after death at the bottom of the deep sea, conse-
quently their skeletons would be brought up in the quills of the
sounding machine flat side down, convex side up ; but if ihey
lived near the surface, and reached the bottom after death, they
would be found flat side up.

614. An unexpected solution afforded. — But, before there was
an opportunity of trying this plan, Ehrenberg himself afforded
the solution in a most unexpected way : — in examining sound-
ings from a great depth in the Mediterranean, he found many
fresh-water shells with their fleshy parts still in them, though
the specimens were taken from the middle of that sea. That
savant, with his practised eye, detected among them Swiss
forms, which must have come down the Danube, and so out into
the Mediterranean hundreds of miles, and on journeys which
would require months, if not years, for these slowly-drifting
creatures to accomplish. And so the anti-biotics maintain
(§ 603) that their doctrine is established.*

* In a paper upon the organic life-forms from miexpected great depths of tlie
Mediterranean, obtained by Captain Spratt from deep-sea soundings between
Malta and Crete, in 1857, and read before the Berlin Academy, November 27,
1857, Ehrenberg said, " Especially striking among all the forms of the deep are
the Phytolitharia, of which fifty-two in number are found. It would not be
strange if these fifty-two forms were spongoliths, since we expect to find sponge
in the sea. But a large number, not less than twenty kinds of Phytolitharia,
are fresh-water and land forms. Hence the question arises, How came these
forms into those depths in the middle of the sea ?

" Naturally one looks at first to the Nile and the coasts ; but the sea current
carries the turbid Nile water eastward; for the current, according to Captain
Smyth, especially in the middle of the sea, not only in the Levant, but also in
the southern edge, is clearly a constant eastwardly one. Besides, there are
among the forms some northern ones— e. g., Eunotia triodon, Campylodiscus
dyjjeus, and many gallionella. This peculiarity may, perliaps, indicate a lower
retui-n current, hithei-to observed only at Gibraltar, which probably brings into
this basin the forms from the Northern European rocks. Thus, for instance,
the Danube may bring the Swiss forms in that ciiculation. But, on the otLei-
hand, a highly striking agreement witli the forms of the ' trade-wind dust ja
not to be overlooked.

THE BASIN AND BED OF THE ATLANTIC. 329

615. A discovery suggested by it. — Having thus discovered that
the most frail and delicate organisms of the sea can remain in
its depths for an indefinite length of time without showing a
single trace of decay, we find ourselves possessed of a fact which

" In reference to the question of permanent life in these most recent deep-sea
materials, it may be observed, that the forms which we find are astonishingly
well preserved, and in very large proportion, sometimes forming the principal
mass of the earthy bottom.

" The striking fact, moreover, that every one who has the opportunity to
compare accurately the microscopic forms of the whole land and sea under great
variety of circumstance does, out of even the smallest specimens of the bottom,
deduce so much that is new and peculiar to him, is no light testimony to show
that the depth is not merely a collection of rubbish of the dead surface-like,
however much there must be of fragments which naturally and undoubtedly
deposit themselves there. I have considered this final remark necessary, be-
cause the distinguished Sea-knower in Washington, often so kindly supplying
and instructing me with material, has recently, in a report on Sub-oceanic Geo-
graphy, New York, January 8, 1857, page 5, and yet more in detail m a late
private letter, expressed a view opposite to that here laid down by me, in which
however, I cannot coincide, for the reasons given above."

As these sheets are passing through the press (Nov. 22, 1860), a copy of
Dr. Wallach's " Notes on the Presence of Animal Life in Vast Depths of the
Sea," dated " Off Kockall, Nov. 8, 1860," has been placed in my hands. From
this interesting monograph it appears that Captain Sir Leopold M'Clintock,
during his recent survey, in H. M. steamer the " Bulldog," of the telegraphic
route via Greenland, brought up living star-fish, adhering to the deep-sea line.

"In sounding," says the doctor, p. 22, "not quite midway between Cape
Farewell and Eockall, in 126 fathoms, whilst the sounding apparatus brought
up an ample specimen of coarse gritty-looking matter, consisting of about 95
per cent, of clean Glohigerina-shells,, a number of star-fishes, belonging to the
genus OpMocoma, came up, adherent to the lowest 50 fathoms of the deep-sea
line employed."

These star-fishes were alive. They continued to move about for upwards of a
quarter of an hour. The " red and light-pink colom-ed tints " being as clear
and brilliant, says the doctor, as seen in their congeners inhabiting its shallow
waters ivhere the sun's rays jyenetrate freely.

One of the animals was dissected, which was found to differ in no respect
(p. 23), as regards internal anatomy, from the species inhabiting shallow water.
He found in the ahmentary cavity numerous Glohigerina-shells, more or less
completely freed of their soft contents.

These contents, and the briuging up of these hving specimens, is held by the
" biotics " to be proof conclusive as to the existence of animal life in the depths
of the sea.

So far from settling the question, these star-fishes leave it, I submit, exactly
as it was before. They were not brought up by the arming of the lead. They
were adhering to the line by their own volition. They might have taken hold
of the line near the surface as well as near the bottom. It is cUlficult, it is true.

suggests many beautiful fancies, some touching thoughts, and a
few useful ideas ; and among these last are found reasons for the
conjecture that the gutta perch a or other insulating material in
which the conducting wires of the sub-Atlantic telegraph and
other deep-sea lines are incased, becomes, M4ien lodged beyond a
certain depth, impervious to the powers of decay ; that, with the
weight of the sea upon them, the destructive agents which are
so busy upon organic matter in the air and near the surface
cannot find room for play. Curious that destruction and decay
should be imprisoned and rendered inoperative at the bottom of
the great deep I

616. Specimens of the three oceans all tell the same story. — Speci-
mens of the " ooze and bottom of the sea " have also been
obtained by the ingenuity of Brooke from the depth of 2700
fathoms in the North Pacific, and examined by Professor
Bailey.* We have now had specimens from the bottom of
" blue water " in the narrow Coral Sea, the broad Pacific, and
the long Atlantic, and they all tell the same story, namely, that
the bed of the ocean is a vast cemetery. The ocean's bed has
been found everywhere, wherever Brooke's sounding-rod has
touched, to be soft, consisting almost entirely of the remains
of infusoria. The Gulf Stream has literally strewed the bottom
of the Atlantic with these microscopic shells ; for the Coast
Survey has caught up the same infusoria in the Gulf of Mexico
and at the bottom of the Gulf Stream off the shores of the

to account for their being afloat so far out at sea ; but how often are frogs and
fishes found under circumstances and in conditions which cannot be accounted
for ! Their coming out of the sea adherent to the line proves nothing.

But the creature had GloUgerina-sheWs in its stomach ; therefore, say the
biotics, these shells must also have lived at the depth of 1260 fathoms. Not so :
wherever the star-fish lived, he must have food, and he could collect these
mites of things as well near the top as the bottom of the sea.

Its anatomical structure, and the brilliancy of its colour — red and pink —
seem to prove the anti-Uotic view quite as much as the other circumstances of
the case prove the hiotic.

Life in the depths of the sea is an interesting question, and the plan which
eeems most capable of settling it has been already suggested, vide § 613.

* « West Point, N, Y., January 29, 1856.

" My dear Sir, — I have examined with much pleasure the highly interest-
ing specimens collected by Lieutenant Brooke, of the United States Navy,
which you kindly sent rne for microscopic analysis, and I will now briefly
report to you the results of general interest which I have obtained, leaving the
enimieration of the organic contents and the description of new species for a

THE BASIN AND BED OF THE ATLANTIC. 331

Carolinas that Brooke's apparatus brought up from the bottom of
the Atlantic off the Irish coast.

617. Their suggestions. — The unabraded appearance of these
shells, and the almost total absence among them of any detritus

more complete account, which I hope soon to publish. The specimens ex-
amined by me were as follows, viz. :

"No. 1. Sea bottom, 2700 fathoms; lat. 56° 46' N., long. 168° 18' E. ;
brought up July 19, 1855, by Lieutenant Brooke, with Brooke's lead.

"No. 2. Sea bottom, 1700 fathoms; lat. 60^ 15' N., long. 170^ 53' E. ;
brought up as above, July 26, 1855.

" No. 3. Sea bottom, 900 fathoms ; temperature (deep sea) 32^, Saxton ; lat.
60° 30' N., long. 175° E.

" A careful study of the above specimens gave the following results :

" 1st. All the specimens contain some mineral matter, which diminishes in
proportion to the depth, and which consists of minute angular particles of
quartz, hornblende, feldspar, and mica.

" 2nd. In the deepest soundings (No. 1 and No. 2) there is the least mmeral
matter, the organic contents, which are the same in all, predominating, while
the reverse is true of No. 3.

" 3rd. All these specimens are very rich in the silicious shells of the Diato-
maceae, which are in an admirable state of preservation, frequently with the
valves united, and even retaining the remains of the soft parts.

" 4th. Among the Diatomes the most conspicuous forms are the large and
beautiful discs of several species of coscinodiscus. There is also, besides many
others, a large number of a new species of rhizosolenia, a new syndendrium, a
curious species of cheetoceros, with furcate horns, and a beautiful species of
asteromphalus, which I propose to call Asteromphalus Brookei, in honour of
Lieutenant Brooke, to whose ingenious device for obtaining deep soundings,
and to whose industry and zeal in using it, we are indebted for these and many
other treasures of the deep.

" 5th. The specimens contain a considerable number of silicious spicules of
sponges, and of the beautiful silicious shells of the polycistinese. Among the
latter I have noticed Cornutella clathrata of Ehrenberg, a form occurring fre-
quently in the Atlantic soundings. I have also noticed in all these soundings,
and shall hereafter describe and figure, several species of eucyrtidium, hali-
calyptra, a perichlamidium, a stylodictya, and many others.

" 6th. I have not been able to detect even a fragment of any of the calca-
reous shells of the polythalamia. This is remarkable from the striking con-
trast it presents to the deep soundings of the Atlantic, which are chiefly made
up of these calcareous forms. This difference cannot be due to temperature,
as it is well known that polythalamia are abundant in the Arctic Seas.

•'7th. These deposits of microscopic organisms, in their richness, extent, and
the high latitudes at which they occur, resemble those of the antarctic regions,
whose existence has been proved by Ehrenberg, and the occurrence in these
northern soundings of species of asteromphalus and chsetoceros is another
striking point of resemblance. These genera, however, are not exclusively

3o2 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

from the sea or foreign matter, suggest most forcibly the idea of
perfect repose at the bottom of the deep sea. Some of the
specimens are as pure and as free from the sand of the sea as
the freshly fallen snow-flake is from the dust of the earth.
Indeed, these sormdings suggest the idea that the sea, like
the snow- cloud with its flakes in a calm, is always letting fall
upon its bed showers of these microscopic shells ; and we may
readily imagine that the "sunless wrecks," which strew its
bottom, are, in the process of ages, hid under this fleecy cover-
ing, presenting the rounded appearance which is seen over
the body of the traveller who has perished in the snow-storm.
The ocean, especially within and near the tropics, swarms with
life. The remains of its myriads of moving things are conveyed
by currents, and scattered and lodged in the course of time all
over its bottom. This process, continued for ages, has covered
the depths of the ocean as with a mantle, (jonsisting of organisms
as delicate as the macled frost, and as light in the water as is
down in the air.

polar forms, but, as I have recently determined, occur also in the Gulf of
Mexico and along the Gulf Stream.

" 8th. The perfect condition of the organism in these soundings, and the
fact that some of them retain their soft portions, indicate that they were very
recently in a living condition, but it does not follow that they were living when
collected at such immense depths. As among them are forms which are known
to live along the shores as parasites upon the algse, etc., it is certain th^t a por-
tion, at least, have been carried by oceanic currents, by drift ice, by animals
which have fed upon them, or by other agents, to their present position. It is
hence probable that all were removed from shallower waters, in which they
once lived. These forms are so minute, and would float so far when buoyed up
by these gases evolved during decomposition, that there would be nothing sm-
prising in tinding them in any part of the ocean, even if they were not trans-
ported, as it is certain they often are, by the agents above referred to.

" 9th. In conclusion, it is to be hoped that the example set by Lieutenant
Brooke will be followed by others, and that, in all attempts to make deep
soundings, the effort to bring up a portion of the bottom will be made. The
soundings from any part of tlie ocean are sure to yield something of interest to
microscopic analysis, and it is as yet impossible to tell what important results
may yet flow from their study.

" The above is only a preliminary notice of the soundings referred to. I
shall proceed witliout delay to describe and figure the highly interesting and
novel forms whicii 1 have detected, and I hope soon to have them ready foi
publication.

" Yours, very respectfully, " J. W. Bailey."

" Lieutenant M. F. Matjuv, National Observatory, Washington City, D. C."

THE BASIN AND BED OF THE ATLANTIC. 333

618. TJie work of re-adaptation, hoiv carried on. — The waters
of the Mississii3]Di and the Amazon, together with all the streams
and rivers of the world, both great and small, hold in solution
large quantities of lime, soda, iron, and other matter. They
discharge annually into the sea an amount of this soluble matter,
which, if precipitated and collected into one solid mass, would
no doubt surprise and astonish even the boldest speculator with
its magnitude. This soluble matter cannot be evaporated.
Once in the ocean, there it must remain ; and as the rivers are
continually pouring in fresh supplies of it, the sea, it has been
argued, must continue to become more and more salt. Now
the rivers convey to the sea this solid matter mixed with fresh
water, which, being lighter than that of the ocean, remains
for a considerable time at or near the surface. Here the micro-
scopic organisms of the deep-sea lead are continually at work,
secreting this same lime and soda, etc., and extracting from the
sea water all this solid matter as fast as the rivers bring it down
and empty it into the sea. Thus we haul up from the deep sea,
specimens of dead animals, and recognize in them the remains
of creatures which, though invisible to the naked eye, have
nevertheless assigned to them a most important office in the
physical economy of the i\ni verse, viz., that of regulating the
sal tn ess of the sea (§ 489). This view suggests many contem-
plations. Among them, one, in which the ocean is presented
as a vast chemical bath, in which the solid parts of the earth are
washed, filtered, and precipitated again as solid matter, but in
a new form, and with fresh properties. Doubtless it is only a
readaptation — though it may be in an improved form — of old,
and perhaps effete matter, to the uses and well-being of man.
These are speculations merely ; they may be fancies without
foundation, but idle they are not, I am sure ; for when we come
to consider the agents by which the j)hysical economy of this
our earth is regulated, by which this or that result is brought
about and accomplished in this beautiful system of terrestrial
arrangements, we are utterly amazed at the offices which have
been performed, the work which has been done, by the ani-
malculae of the water. But whence come the little silicious
and calcareous shells which Brooke's lead has brought up,
in proof of its sounding, from the depth of over two miles ? Did
they live in the surface waters immediately above ? or is their
habitat in some remote part of the sea, whence, at their death,

334 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

the currents were sent forth as pall-bearers, with the command
to deposit the dead corpses where the plummet found them.

619. Animalcules at the surface of the sea. — Fellow-labourers as
Foster, and Toynbee, and Piazzi Smyth, are beginning to dip
into the surface water of the sea for its animalcules. They are
making interesting discoveries, and have gone quite far enough
to show that this field is exceedingly rich, and that labourers in
it are greatly needed.*

CHAPTEE XV.

§ 621-680. — SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.

621. Practical results of jyhysical researches at sea. — Plate VIII.,
so far as the winds are concerned, is supplemental to Plate I.
The former shows the monsoon regions, and indicates the
prevailing direction of the winds in every part of the ocean ;
the latter indicates it generally for any latitude, without regard
to any particular sea. Plate VIII. also exhibits the principal
routes across the ocean. This plate indicates the great practical
lesults of all the labour connected with this vast system of
research ; its aim is the improvement of navigation ; its end,
the shortening of voyages. Other interests and other objects,
nay, the great cause of human, knowledge, have been promoted
by it; but the advancement that has been given to these do
not, in this utilitarian age, and in the mind of people so emi-
nently practical as mariners are, stand out in a relief half so
grand and imposing as do those achievements by which the
distant isles and marts of the sea have, for the convenience of
commerce, been lifted up, as it were, and brought closer together
by many days' sail.

622. Time-tables. — So to shape the course on voyages as to
make the most of the winds and currents at sea is the perfection
Df the navigator's art. How the winds blow and the currents
flow along this route or that, is no longer matter of opinion or
subject of speculation, but it is a matter of certainty determined
by actual observation. Their direction has been determined for
months and for seasons, along many of the principal routes, with
all the accuracy of which results depending on the doctrine of

* See paper " On tlic Minute Inhabitants of the Surface of the Ocean," bv
Captain Henry Toynbee, F.R.A.S. [Naut. Magazine, ISGO.]

SEA ROUTES, CALM BELTS, AND VAEIABLE WINDS. 660

chances are capable ; and farther, these results are so certain
that there is no longer any room for the mariner to be in doubt
as to the best route. When a navigator undertakes a voyage
now, he does it with the lights of experience to guide him.
The winds and the weather daily encountered by hundreds who
have sailed on the same voyage before him, with " the distance
made good " by each one from day to day, have been tabulated
in a work called Sailing Directions, and they are so arranged
that he may daily see how much he is ahead of time, or how far
he is behind time ; nay, his path has been literally blazed
through the winds for him on the sea ; mile-posts have been set
up on the waves, and finger-boards planted, and time-tables
furnished for the trackless waste, by which the ship-master, even
on his first voyage to any port, may know as well as the most
experienced trader whether he be in the right road or no.

623. Close running. — From New York to the usual crossing oi
the equator on the route to Rio, the distance, by an air line,
is about 3400 miles ; but the winds and currents are such as to
force the Rio bound vessel out of this direct line. Nevertheless,
they have been mapped down, studied, and discussed so
thoroughly that we may compute with remarkable precision the
detour that vessels attempting this route from Kew York, or any
other port, would have to make. This computation shows that,
instead of 3400 miles, the actual distance to be accomplished
through the water by vessels under canvas on this part of the
voyage is 4093 miles. More than a hundred sailing vessels have
tried it by measuring and recording the distance actually sailed
from day to day; their mean distance is 4099 miles, consequently
their actual average differs only six miles from the computed
average.*

624. A desideratum on ship-hoard. — The best navigated steam-
ships do not sail closer than this, and a better proof of the
accuracy of oiir knowledge concerning the prevailing direction
of the winds at sea could not be afibrded. Unfortunately, ane-
mometers are not used on shipboard. Had they been in common
use there, and had we been furnished with data for determining
the force of the wind as well as its direction, we could compute
the time as well as the distance required for the accomplishment
of any given voyage under canvas. Thus the average time
required to sail from New York to the equator might be

* P. 146, vol. ii., Maury's Sailing Directions.

336 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

computed within an hour, for it has been computed within
an hour's sail — six miles (§ 623).

625. How passages have been shortened. — By the knowledge thus
elaborated from old and new log-books and placed before the
nautical world, the average passage from Europe or the United
States to all ports in the southern hemisphere has been shortened
ten days, and to California a month and a half.* Between
England and her golden colony in the South Seas the time
required for the round voyage has been lessened fifty days or
more, and from Europe to India and China the outward passage
has been reduced ten days. Such are some of the achievements
that commend this beautiful system of research to the utili-
tarian spirit of the age.

626. Fast sailing. — The route that affords the bravest winds,
the fairest sweep, and the fastest running for ships, is the route
to and from Auistralia. But the route which most tries a ship's
prowess is the outward-bound voyage to California. The voyage
to Australia and back carries the clipper ship along a route which
for more than 300° of longitude runs with the " brave west winds "
of the southern hemisphere. With these winds alone, and with
the bounding seas which follow them, the modem clipper, with-
out auxiliary p?iwer, has accomplished a greater distance in a day
than any sea steamer has ever been known to reach. Eunning
before these fine winds and heaving seas those ships have per-
formed their voyages of circumnavigation in 60 days.

627. TJie longest voyage.— The sea voyage to California, Colum-
bia, and Oregon is the longest voyage in the world — longest both
as to time and distance. Before these researches were extended

* '-During the last year [1859] the 8th edition of Manry's Sailing Directions,
in tw^o quarto volumes, has been published at the Observatory in Washington.
It atfords abundant evidence of the activity, to which allusion has aheady been
made, in this field of research, and with regard to w:hich all geographers feel
the most lively interest.

" Official tables have been received from San Francisco, showing the vessels
that have arrived at tliat port during the year, with the length of passage. Of
those arriving direct via Cape Horn, 124 were from the Atlantic ports of the
United States, and 34 from Em-ope. Of these 124, 70 are known to have had
the Wind and Current Charts on board ; their average passage was 135 days,
which is 11 days less than the average of those from the United States, and 24
days less than the average of those from Europe without the Charts. When
these researches commenced, the general average was 180 days from the
United States, and 183 from Europe to California." — Journal American Geo-
graphical Society.

SEA ROUTES. CALM BELTS. AND VATlIi^BLE WINDS. 337

to the tides and currents along that route, tne average passage
both from Europe and America to our north-west coast was not less
than 180 days. It has been reduced so as to average only 135
days. This route is now so well established, and the winds of
the various climates along it so well understood, that California
bound vessels sailing about the same time from the various ports
of Europe and America are, if "they be at all of like prowess,
almost sure to fall in with and speak each other by the way.

628. Obstructions to the navigator. — The calm belts at sea, like
mountains on the land, stand mightily in the w^ay of the voyager,
but, like mountains, they have their passes and their gaps. In the
regions of light airs, of bafding winds, and deceitful currents, the
seaman finds also his marshes and his " mud-holes " on the water.
But these, these researches have taught him how best to pass or
entirely to avoid. Thus the forks to his road, its turnings, and
the crossings by the way, have been so clearly marked by the
winds that there is scarcely a chance for him who studies the
lights before him, and pays attention to directions, to miss his
w^ay.

629. Plate VIIL — The arrows of Plate VIIT. are supposed to
fly with the wind ; the half-bearded and half-feathered arrows
denote monsoons or periodic winds ; the dotted bands, the regions
of calm and baffling winds. Monsoons, properly speaking, are
winds which blow one half of the year from one direction, and the
other half from an opposite, or nearly an opposite direction. The
time of the changing of these winds, and their boundaries at the
various seasons of the year, have been discussed in such numbers,
and mapped down in such characters, that the navigator who
wishes to take advantage of them or to avoid them altogether is
no longer in any doubt as to when and where they may be
found.

630. Deserts. — Let us commence the study of the calm belts as
they are represented on Plates I. and VIII. The monsoons and
trade-winds are also represented on the latter, they often occupy
the same region. But, turning to the trade-winds for a moment,
we see that the belt or zone of the south-east trade-winds is
broader than the belt or zone of north-east trades. This pheno-
menon is explained by the fact that there is more land in the
northern hemisphere, and that most of the deserts of the earth —
as the great deserts of Asia and Africa — are situated in the rear,
or behind the north-east trades ; so that, as these deserts become

z

338 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

more or less lieated, there is a call — a pullmg back, if yoii
please — upon these trades to turn about and restore the equili-
brium which the deserts destroy. There being few or no such
regions in the rear of the south-east trades, the south-east trade-
wind force prevails, and carries them over to the northern
hemisphere.

681. Diurnal rotation. — We see by the plate that the two
opposing currents of wind called " the trades," are so unequally
balanced that the one recedes before the other, and that the cur-
rent from the southern hemisphere is larger in volume ; i. e., it
moves a greater zone or belt of air. The south-east trade-winds
discharge themselves over the equator — i. e., across a great circle
— into the region of equatorial calms, while the north-east trade-
winds discharge themselves into the same region over a parallel
of latitude, and consequently over a small circle. If, therefore,
we take what obtains in the Atlantic as the type of what obtains
entirely around the earth, as it regards the tr^ de-winds, we shall
see that the south-east trade-winds keep in motion more air than
the north-east do, by a quantity at least proportioned to the dif-
ference between the circumference of the earth at the equator
and at the parallel of latitude of 9° north. For if we suppose that
those two perpetual currents of air extend the same distance
upward from the surface of the earth, and move with the same
velocity, a greater volume from the south should, as has already
been shown (§ 343), flow across the equator in a given time than
would flow from the north over the parallel of 9° in the same
time ; the ratio between the two quantities would be as radius to
the secant of 9°. Besides this, the quantity of land lying within
and to the north of the region of the north-east trade-winds is
much greater than the quantity within and to the south of the
region of the south-east trade- winds. In consequence of this, the
mean level of the earth's surface within the region of the north-
east trade-winds is, it may reasonably be supposed, somewhat
above the mean level of that part which is within the region of the
south-east trade-winds. And as the north-east trade-winds blow
under the influence of a greater extent of land surface than the
south-east trades do, the former are more obstructed in their course
than the latter by the forests, the mountain ranges, unequally
heated surfaces, and other such like obstacles.

632. Tlie land in the northern hemisphere. — That the land of the
northern hemisphere does assist to turn these winds is rendered

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 339

still more probable from this circumstance : All the great deserts
are in the northern hemisphere, and the laud surface is also
much greater on our side of the equator. The action of the sun
upon these unequally absorbing and radiating surfaces in and
behind, or to the northward of the north-east trades, tends to
check these winds, and to draw in large volumes of the atmo-
sphere, that otherwise would be moved by them, to supply the
partial vacuum made by the heat of the sun, as it pours down its
rays upon the vast plains of burning sands and unequally heated
land surfaces in our overheated hemisphere. The north-west
winds of the southern are also, it may be inferred, stronger than
the south-west winds of the northern hemisphere.

633. Why the south-east trades are the stronger. — That the south-
east trade-winds should, as observations (§ 343) have shown, be
stronger than the north-east trade- winds, is due in part also to
the well-established fact that the southern (§ 446) is cooler than
the northern hemisphere. The isothermal lines of Dove show
that the air of the south-east is also cooler than the air of the
north-east trade-winds. Being cooler, the air from the cool side
would, for palpable causes, rush with greater velocity into the
equatorial calm belt than should the lighter air from the warmer
or northern side. The fact that the air in the lower latitudes of
the southern hemisphere is the cooler will assist to explain many
other contrasts presented by the meteorological conditions on
opposite sides of the equator. Plate XIII. shows that we have
more calms and more fogs, more rains and more gales, with more
thunder, on our side than on the other, and that the atmosphere
preserves its condition of unstable equilibrium with much more
uniformity, being subject to changes less frequent and violent on
the south side of the equator than on the north side.

634. Their uniformity of temperature. — The highest summer
temperature in the world is to be found in the extra-tropical
countries of the north. The greatest extremes of temperature are
also to be found among the valleys of the extra-tropical north.
In the extra- tropical south there is but little land, few valleys,
and much water ; consequently the temperature is more uniform,
changes are less sudden, and the consequent commotions in the
air less violent.

635. The mean place of the equatorial calm belt. — Following up
these facts with their suggestions, we discover the key to many
phenomena which before were locked up in " the chambers of

z 2

34.0 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOIiOLOGT.

the south." The belt of equatorial calms which separates the
two systems of trade-winds is, as we know (§ 295), variable as to
its position. It is also variable in breadth. Sometimes it covers
a space of several degrees of latitude, sometimes not more than
one. Its southern edge, in spring, sometimes goes down to 5° S. :
its northern edge, in autumn, often mounts up to the parallel of
15° N. The key to these phenomena has been found ; with it in
hand, let us proceed to unlock, first remarking that the mean
position of the equatorial calm belt in the Atlantic is between
the equator and 9° N., and that as it is there, so I assume it to
be in other oceans.

636. Never at rest. — This calm belt is produced by the meeting
of the two trade-winds, and it occupies strictly a medial position
between them. It is in the barometric valley, between the two
barometric ridges (§ 667), from which the trade-winds flow. If
one "trade " be stronger than the other, the stronger will pre-
vail so far as to force their place of meeting over and crowd it
back upon the weaker wind. It is evident that this place of
meeting will recede before the stronger wind, until the momen-
tum of the stronger wind is so diminished by resistance, and its
strength so reduced as exactly to be counterbalanced by the
weaker wind. Then this calm place will become stationary, and
so remain, until, from some cause, one or the other of the meeting
winds gains strength or loses force ; then the stronger will press
upon the weaker, and the calm belt will change place and adjust
itself to the new forces. The changes that are continually going
on in the strength of the winds keep the calm belt in a trembling
state, moving now to the north, now to the south, and alwaj^s
shifting its breadth or its place under the restless conditions of
our atmosphere.

637. Tlte calm belts occupy medial positions. — The southern half
of the torrid zone is cooler than the northern, and, parallel for
parallel, the south-east trade-winds are consequently cooler than
the north-east. They both blow into this calm belt, where the
air, expanding, ascends, flows off above, produces a low barometer,
and so makes room for the inflowing current below. Now if the
trade-wind air which flows in on one side of this calm belt be
heavier, whether from temperature or pressure, than the trade-
wind air which flows in on the other, the wind from the heavy
side will be the stronger. This is obvious, for it is evident that
if the difference of temperature of the ascending column and the

SEA EOUTES, CALM BELTS, AND VARIABLE WINDS. 341

inflowing air were scarcely perceptible, the difference of specific
gravity between the inflowing wind and tlie uprising air would
be scarcely perceptible, and the movement of the inflowing wind
would be ver}^ gentle ; but if the difference of temperature were
very great, the difference of specific gravity would be very great,
and the violence of the inrushing wind proportionably great.
Because the southern half of the torrid zone is the cooler, the
difference in temperature between the air of the calm belt and
the air of the trade -winds is greater, parallel for parallel, in the
south-east than in the north-east trade-winds ; consequently, the
south-east trade-winds should be — as observations show them to
be— stronger than the north-east; — and consequently, also, their
meeting should take place, not upon the equator, but upon that
side of it where the weaker winds prevail, and this is also in
accordance (§ 343) with facts.

638. Strength of the trade-ivinds varies with the seasons. — It follows
from these premises that the winter trade-winds should be
stronger than the summer. In our summer, the air which the
north-east trade-winds put in motion has its temperature raised
and brought more nearly up to that of the air in the calm belt.
At the same time, the temperature of the air which the south-
east trade-winds put in motion is proportionably lowered. Thus
they increase in strength, while the north-east diminish ; the
consequence is, they push their place of meeting with the north-
east trades far over on this side of the equator, and for two or
three months of the year maintain the polar edge of the calm belt
as high up as the parallel of 15° N. But with the change ot
seasons these influences are all transposed and brought into play
on opposite sides — only in the southern summer the strength of
the south-east and the temperature of the north-east trade-winds
are diminished so as to admit of the edge of the calm belt being
pressed down only as far as 5° instead of 15° 8. The causes which
produce this alternation of trade-wind strength are cumulative ;
consequently, the north-east trade-winds should be weakest in
August or September, strongest in February or March, after the
period of maximum heat in one case and of minimum in the
other.

639. Sailing through them in fall and winter. — ^In the other hemi-
tsphere, the period of strongest trades is coincident with that of the
minimum in this. These deductions are also confirmed by observa-
tions ; for such is the difference as to strenp-th and regularitv of

342 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the nortli-east trade-winds in September and February, that the
average passage through them from New York to the line is 26.4
days in the winter against 38.8 in the fall month.

640. A thermal adjustment. — Thus it appears that the equatorial
calm belt is made to shift its place with the seasons, not by
reason of the greater intensity of the solar ray in the latitude
where the calm belt may be at that season, but by reason of the
annual variations in the energy of each system of trades ; which
variations (§ 638) depend upon the changes in the temperature
and barometric weight of the air which each system puts in
motion. This calm zone, therefore, may be considered as a
tJiermal adjustment — the dynamical null-belt — between the trade-winds
of the two hemispheres.

641. The barometer in the trade-ivinds and equatorial calms. — The
observations on the barometer at sea (§ 858) shed light on this
subject. According to the Dutch, that instrument stands higher
by 0.055 inch in the south-east than it does in the north-east
trade-winds. According to the observations of American navi-
gators, it stands 0.050 inch higher.* The former determination
is derived from 80,873, the latter from 1899 observations ; there-
fore 0.055 inch is entitled to most weight. The trade-winds are
best developed between the parallels of 5° and 20°. The mean
barometric pressure between these parallels is 29.968 inches for
the north-east, and 30.023 inches for the south-east trade-wdnds ;
while for the calm belt it is 29.915 inches. The pressure, there-
fore, upon the air in each of the trade-winds is greater than it is
in the calm belt ; and it is this difference of pressure, from whatever
cause arising, that gives the wind in each system of trades its
velocity. The difference between the calm belt and trade-wind
pressure is 0.108 for the south-east and 0.053 for the north-east.
According to the barometer, then, the south-east should be
stronger than the north-east trade-winds, and according to actual
observations they arcf

642. Experiments in the French Navy. — Now if we liken the
equatorial calm belt with its diminished pressure to a furnace,
the north-east and the south-east trade-winds may be not inaptly
compared to a pair of double bellows that are blowing into it. In
excess of barometric pressure, the former is a bellows with a
weight of 3.8 lbs., the latter with a weight of 7.8 lbs. to the

* Maury's SaiUng Directions : " Barometric Anomalies off Cape Horn."
t Nautical Monograph, No. 1.

SEA ROUTES, CALM BELTS, AND VAEIABLE WINDS. 343

square foot. It is this pressure which, like the weight upon the
real bellows in the smithy, keeps up the steady blast ; and as the
effective weight upon the one system of trades is about double
that upon the other, the .one under the greatest pressure should
blow with nearly double the strength of the other, and this
appears, both from actual observations and calculations, as well
as from direct experiments ordered in the French brig of war
" Zebra," by Admiral Chabannes, to be the case.*

* Letter to Admhal Chabanues, with extracts from his reply thereto : —

'' Observatory, Washington, 8th April, 1859.

" My dear Admiral, — My last was dated 15th January ultimo. I hope the
charts and vol. i., 8th ed. Sailing Directions, and part of vol. ii. in the sheets,
came safely to hand. Vol. ii. is just out, and I hasten, in homage of my
respect, and as a token of good-will, to lay a copy before you.

" Permit me, if you please, to call your attention to the chapter on the ' Ave-
rage Force of the Trade-winds,' p. 857, and especially to the table of compara-
tive speed (of sailing vessels) through the north-east and south-east trade-winds
of the Atlantic, p. 865. The average speed, you observe, is nearly the same,
notwithstanding that through the south-east trades the wind is aft, through
the north-east just abaft the beam.

" In order to treat this question thoroughly, it is very desirable to know the
difference in the speed of vessels when sailing with the same wind aft, with it
quartering, with it a point or two abaft the beam, and with it close hauled.
With a good series of experiments upon this subject, we should be able to arrive
at definite conclusions with regard to the average difference in force not only of
the two systems of trade- winds, but of the winds generally in various parts of
the ocean.

" If we assume that a wind which, being dead aft, drives a vessel at the rate
of six knots, wiU, when brought nearly abeam, drive her eight knots— as in
this chapter I have supposed — and then if we apply the dynamical law of the
resistance increasing as the squares of the velocity of the ship, we should be
led to the remarkable conclusion that the average velocity of the north-east
to south-east trades of the Atlantic is as 36 to 64. Therefore, in conducting
these experiments, it would be very desirable to know the area of canvas that
fairly feels the wind when it is aft, and the area upon which the wind blows
when the ship is hauled up. Suffice it to say, that the facts which we
already have, indicate that the south-east trades, both of the Atlantic and
Indian Oceans are fresher than the north-east trades of the Atlantic. May we
infer from this that the south-east trades of the Pacific are also fresher than the
north-east trades of that ocean ? If we may so infer, and be right, then there
is another step which we may take with boldness, and pronounce the atmosphe-
rical circulation of the southern liemisphere to be much more active than that
of the northern. And having reached this round in the ladder up which I am
soUciting you to accompany me, we are prepared to pause and take a view of
some of the new physical aspects which these facts and this reasoning spread

out before us.

" That

344 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOEOLOGY.

643. Difference in tons of the harometric ^pressure upon tJie north-east
and south-east trade-ioinds. — With these barometric observations,
and the assumed fact that the mean pressure of the atmosphere is
15 lbs. upon the square inch, we ma}'' readily determine in tons
the total by which the superincumbent pressure upon the south-
east trade-winds between the parallels of 5° and 20° exceeds that
upon the north-east between corresponding parallels. For the
whole girdle of the earth, the excess of pressure upon the south-

" That the atmospherical circulation is more active in the sonthern than in
the northern hemisphere appears to be indicated also by the " brave west winds "
of the extra-tropical south,^ If the air performs its cncuit more rapidly through
one system of trade-winds than the other, then it follows that it must perform
its circuit more rapidly also along those regions through which it has to pass in
order to reach such rapid trades. Consequently, there should be a great differ-
ence between the gales of the northern and those of the southern hemisphere.
If we suppose the general chculation of the northern hemisphere to be sluggish,
the air in its circuits there would have time to tarry by the way, as it were, and
to blow gales of wind from all points of the compass. On the contrary, if the
general circulation of the southern hemisphere be brisk and active, the air in its
general circuits, like a fast train on the railway, would not have so much time to
tarry by the way, because, like the cars, it must he up to time. Hence, admit-
ting this view of the matter to be correct (and you perceive that for the want of
the experiments alluded to we are groping in the darkness of conjecture), though
we might expect gales of wind in the extra-tropical regions of the south, yet thej
would for the most part blow with the prevailing direction of the wind, and not
against it. Thus the gales on the polar side of Capricorn should, particularly at
sea, have westing in them always — almost.

" In corroboration of this view, I may mention, on the authority of a paper just
received from Lieutenant Van Gogh, of the Dutch Navy, that the gales of wind
which take place between the meridians of 14° and 32° E., and between the
parallels of 33° and 37° S., have been discussed at the Meteorological Institute
of Utrecht. For this purpose he tabulated the results for the whole jea,Y of
17,810 observations — an observation comprehending a peiiod of eight hours.
According to these observations, it is blowing a gale of wind off the Cape of
Good Hope 7'16 per cent, of the whole year, and from the following quarters;
namely, between N.N.W. and S.S.W. 6.43 per cent. : from all other quarters,
0.73 per cent.

" Perhaps you may find it convenient to institute, with some of the vessels of
your fleet, a regular series of experiments in the south-east trades upon speed,
when sailing at various angles with the course of the wind. Besides answering
our immaliate purpose, the results might enable us to convert ships into very
good anemometers for all winds except gales.

♦' Pardon me for being so tedious ui)on tliis subject. If you have felt me so.

1 See also Plate XIII. and § 6^2 and t) 633.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. cJlO

east trade-winds is 1,235,250 millions of tons. This is the super-
incumbent weight or pressure which is urging the south-east
trade-winds forwai'd faster than the north-east. It is incon-
ceivably gi-eat ; and to bring it within comprehensible terms, the
mariner will be astonished to hear that the weight of atmosphere
which is bearing down upon the deck of a first-class clipper ship
is 15 or 20 tons greater when he is sailing i-n her through the
south-east than it is when he is sailing in her through the north-
east trade-winds.

644. Why the barometer should stand higher in the south-east than in
the north-east trade-winds. — The question now suggests itself, Why
should the barometer stand higher in the south-east than it does
in the north-east trade-winds ? The theory of a crossing at the
calm belts affords the answer. The air which the north-east
trade-winds deliver into the calm belt is not as heavily laden
with moisture as that of the south-east trades. It is not as
heavily laden for two reasons ; one is, the south-east trade- wind
belt is broader than the north-east ; consequently, in the former
there is more air in contact with the evaporating surface. In the

pray ascribe it to my desire to get by actual experiment an expression in the
average speed of ships for the actual force and velocity of the winds.

" Wishing you all success and good luck in the investigation which you have
in hand, pray believe me, my dear admiral, yours very truly,

" M. F. Maury
*' Admiral C. de Chabannes, Commander-in-chief of tl:e French
Naval Division of Brazil and La Plata, Rio de Janeiro."

Extract from a letter in reply to the foregoing : —

" Montevideo, January 25, I860.

" My dear Sir, — • * * * * As you have indicated to me in your letter
of April, I have caused to be made, by a brig of my division, experiments upon
the comparative velocities, wind abaft and wind abeam witli a given force of
wind, but I have not yet been able to deduce any positive rule, the experiments
not having been sufficiently multiplied. I can, however, give as a result that
the increase of headway given by wind abeam over the headway with wind aft
«as been a little less than two knots; when the velocity with wind aft was
from 6 to 8 knots, the force of the wind aft might be expressed by 4, and of tiie
wind abeam by 6. * * * * " C. de Chabannes."

London, November 26, 1860.

Just in time for insertion here, I receive from the gallant admiral the sub-
loined very valuable and interesting series of experiments on the speed of bis
ship : — first, before the wind, i.e. sixteen points, and so on for every two points
to six, and close hauled. At eight points the wind is abeam and at right angles
with the course of the ship ; at ten it is two points abaft the beam. From these
experiments we infer that an average sailer that goes six knots before the wind,

846 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

next place, the north-east trade-wind belt includes more land
within it than the south-east ; consequently, when the two winds
arrive at the calm belt, they are, for this reason, also unequally
charged, with moisture. Now, w^hen they rise up and precipitate
this moisture, more heat is liberated from the south-east than

will, if hauled up and trimmed, go nine knots with the wind two points abaft
the beam, and 8"8 wind abeam.

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REMARKS.

The different experiments, whose results are inscribed in this Table, were made during the passage
from Bahia to France. Tliey were made in the trade-winds, or in fixed and regular winds; never-
theless, even in the trades the regularity of the wind was not always such that some results did not
appear to differ a little from the rule. On the other hand, the log itself gives rise to errors some-

tmies quite large.

In going eight knots we have thrown two logs, simultaneously, without touching the line ; the two
results differed a knot. The incomplete experiments were interrupted in consequence of the irregu-
larity of the wind, and each result is a mean result.

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SEA ROUTES, CALM BELTS, AND VARIABLE WINBS. 347

from the north-east trade-wind air; the latter, therefore, after
rising up, is the cooler and the more compact ; and as, by the
theory of the crossings, it flows off to the south as an upper
current, it presses upon the barometer with more weight than
the warmer and more moist air that feeds the current which is
above and counter to the north-east trades. There is not in the
whole range of marine meteorology a single well-established
fact that is inconsistent with the theory of a crossing at the calm
belts.

645. Cataclysms. — The geological record affords evidence that
the climates of the earth were once very different from what
they are now ; that at one time intertropical climates extended
far up towards the north ; at another time polar climates reached,
with their icebergs and their drift, far down towards the equator ;
that in remote ages most of what we now call dry land was
covered with water, for we find on the mountains and far away
in the interior of continents deposits many feet thick, con-
sisting of sea-shells, marine animals, and organic productions of
many sorts. These fossils, marks, and traces indicate that since
their day, ages inconceivably great have elapsed. Not only so :
the lines of drift, and boulders, and gashes with which the earth
is scored and strewed, afford reason for the conjecture that there
have been cataclysms, in which the waters have swept from north
to south, and again from south to north, bearing with them ice-
bergs, huge blocks of stone, rubble, drift, and sediment of various
sorts. Lieutenant Julien, M. Le Hon, and M. Adhemar have,
with much ingenuity, treated of this subject. They maintain
that our earth has a " secular " as well as an annual summer and
winter; that these "secular" seasons depend upon the pre-
cession of the equinoxes, and that the length of each is con-
sequently 10,500 of our years ; and that it is the melting of the
polar ices in the " secular" season of one hemisphere, and their
recongelation in the " secular " winter of the other, that causes a
rush of the sea from one hemisphere into the other; and so
cataclysms are produced at regular intervals of 10,500 years. In
consequence of the inclination of the axis of the earth to the
plane of its orbit, we have our change of seasons ; and in conse-
quence of the ellipticity of that orbit, the spring and summer of
our hemisphere are at present longer than those of the southern.
During; the excess of time that the sun tarries on our side of the
equator, the southern nights are prolonged, so that the night of

348 PHYSICAL GEOGRAPHY OB' THE SEA, AND ITS METEOROLOGY.

the south pole — the antarctic winter — is annually a week longer
(§ 366) than the arctic. Thus, during the period of 10,500 jears,
the antarctic regions will experience 142 j^ears of night, or
winter, in the aggregate, more than the arctic. Therefore it is
manifest, say the cataclysmatists, that though the two hemispheres
do receive annually the same amount of solar heat, yet the
amount dispensed by radiation is very much greater on one side
of the equator than the other. The total effect of the alternate
cooling down on each side of the equator causes an accumulation
of ice at the pole — when the nights are longest — sufficient, say
they, to disturb the centre of gravity of the earth, causing it to
take up its position on the icy side of the equator. As the ice
accumulates, so is the water drawn over from the opposite
hemisphere. Such, briefly stated, is the theory which has found
very ingenious and able advocates in the persons of MM. Julien*
and Adhemar."f

646. Are the climates of the earth changing? — This theory is
alluded to here, not for the purpose of discussion, but for the
purpose of directing attention to certain parts of this work
in connection with it, as Chapters VII. and XXI., for example,
and of remarking upon the stability of terrestrial climates.
Though the temperate regions be cooler in the southern than in
the northern hemisphere, it does not appear certain that the
climates of the earth are now changing. Observations upon the
subject, however, are lacking. The question is one of wide-
spread and exceeding interest ; and it may be asked if we have
not in the strength of the trade-winds a gauge, or in their
barometric weight an index, or in the equatorial calm belt a
thermometer — each one of the most delicate construction and
sensitive character — which would, within the compass of human
life, afford unerring indications of a change of climates, if any
such change were going on? If the temperature of the S.E.
trade-winds, or the barometric pressure upon tl^e N.E. (§ 641),
were to be diminished, the S.E. trades would force this calm belt
still farther to the north, and we might have a regular rainy
season in what is now the great desert of Sahara ; for where this

* Courants et Kevolutions de I'Atmosphere et de la Mer, comprenant une
Theorie nouvelle sur Its Deluges Periodiques. Par Felix Julien, Lieutenant de
Vaisseau, etc. Paris, 1860.

] Ptevolutions de la Mer. Deluges Periodiques. Par /. Adhemar. Paris,
1660.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 349

calm belt is (§ 517) there is the cloud-ring, with its constant pre-
cipitation. Therefore, if there be any indications that the
southern edge of the great desert is gradually approaching the
equator, it would favour the supposition that the southern
hemisphere is growing warmer ; but if the indications be that the
southern edge of the desert is receding from the equator, then
the fact would favour the supposition that the southern hemi-
sphere is growing still cooler. Nor are these the only latchets
which a study of this calm belt and of the winds enables us to
lift.

647. Tem^perature of the trade-winds and calm belts. — Theory sug-
gests, and observation, as far as it goes, seems to confirm the sugges-
tion, that the N.E. andS.S. trade- winds enter the equatorial calm
belt at the same temperature. I have followed 100 vessels with
their thermometer across the equatorial calm belt of the Atlantic,
and another 100 across it in the Pacific. Assuming its mean
position to be as these observations indicate it to be — viz., between
the parallels of 3^ and 9° N. — the mean temperature is 81° at
its northern, 81°.4 at its southern edge, and 82° in the middle of
it. These 200 logs were taken at random, and for all months.
The temperature of the air Avas noted also in each trade at the
distance of 5° from its edge of the calm belt. Thus the tem-
perature of the N.E. trades, 5° from the north edge of the calm
belt, or in 14° N., is 78°.2 ; at a like distance in the S.E. trades
from the equatorial edge, or in 2° S., the mean temperature is
80.°2. From this it would seem that, in traversing this belt of
5°, the temperature of the N.E. is raised twice as much as the
temperature of the S.E. trades ; which is another indication that
the velocity of the S.E. is nearly or quite double the velocity of
the N.E. trades (§ 642). For if it be supposed that it takes the
N.E. trades twice as long to traverse 6'^ of latitude as it does the
S.E., it is evident that the former would be exposed twice as
long to the solar ray, and receive twice the amount of heat that
is imparted to the S.E. trade-winds in traversing given differences
of latitude. Thus the position of the calm belt, the barometer,
the thermometer, and the rate of sailing, all indicate the S.E.
trade-wdnds to be the stronger. It appears, moreover, that the
temperature of the S.E. trade-wind is in 2° S. below the tem-
perature of the N.E. in 9° N., the latter being 81°, the former
80°.2.

648. The thermal equator. — The foregoing observations show

350 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

that after these winds enter the calm belt, the air they bring into
it continues to rise, and this also is what might well be antici-
pated, for the sun continues to pour down upon it. But while
the temperature of the surface is kept down by the rain-drops
from above, the temperature of the air in the whole belt is raised
both by the direct heat of the sun and the latent heat which is
set free by the constant (§ 515) and oftentimes heavy precipita-
tion there. This latent heat is much more effective than is the
direct heat of the sun in rarefying the air ; consequently we here
unmask the influences which place the thermal equator in the
northern hemisphere.

"649. A natural adinometer in the trade-winds. — Nor is this the
only chamber into which this calm belt key conducts us. Parallel
for parallel (§ 446), the southern hemisphere is cooler than the
northern ; that is, the mean temperature for the parallel of 40°
south, for example, is below the mean temperature for the
parallel of 40° north, and so of all corresponding parallels be-
tween 40° and the equator. It appears, moreover, that the mean
temperature of the north-east trade-winds as they cross the
parallel of 9° north, and the mean temperature of the south-east
trade-winds as they cross the equator, is about the same (§ 647).
The difference of temperature, then, between the south-east trades
as they cross the parallel of 9° south, and as they cross the equa
tor, expresses the difference in the thermal forces which give dif-
ference of energy to the dynamical power of the trade-winds.
Not only so : it expresses the difference of temperature between
the two corresponding parallels of 9° north and 9° south, and dis-
covers to us a natural actinometer on a grand scale, and of the
most delicate and beautiful kind.

650. Heat daily received hy the south-east trade-ivinds.— This acti-
nometer measures for us the heat which the south-east trade-
winds receive between the moment of crossing the parallel of 9°
south and their arrival at the equator, for the heat thus received
is just sufficient (§ 644) to bring so much of the south-east up to
the temperature which the north-east trades have as they cross
the parallel of 9° north. To complete this measurement of heat
we should know how long the south-east trade-winds are on their
march from the parallel of 9° south to the equator. According
to the estimate, it takes them about a day to accomplish this dis-
tance ; but, knowing the exact time, we should have in the band
of winds an actinometer which would disclose to us the average

SEA EOUTES, CALM BELTS, AND VARIABLE WINDS. 851

quautity of heat daily impressed by the sun upon the atmosphere
at sea between the equator and 9° south. I say it takes about a
day, and so infer from these data, viz. : The mean annual direc-
tion of the south-east trade-winds between 10° south and the line
is south 40° east* We suppos^^their average velocity to be
(§ 343) about 25 miles an hour. At this rate it would take thqm
29h. 22m. 30s. to reach the equator. During this time they
receive more heat than they radiate, and the excess is just sufiB-
cient to raise them from the normal temperature of the north-east
trades as they enter the calm belt in 9° north. A series of obsei-
vations on the temperature of the air in latitude 9° south at sea
would, for the farther study of this subject, possess great
value. I

651. Equatorial calm belt never stationary. — If these views be
correct, w^e should expect to find the equatorial calm belt chang-
ing its position with night and day, aud yielding to all those
influences, whether secular, annual, diurnal, or accidental, which
are capable of producing changes in the thermal condition of the
trade-winds. The great sun-swing of this calm belt from north
to south is annual in its occurrence ; it marks the seasons and
divides the year (§ 296) into wet and dry for all those places that
are within the arc of its majestic sweep. But there are other
subordinate and minor influences which are continually taking
place in the atmosphere, and which are also calculated to alter
the place of this calm belt, and to produce changes in the thermal
status of the air which the trade-winds move. These are, un-
usually severe winters or hot summers, remarkable spells of
weather, such as long continuous rains or droughts over areas of
considerable extent, either within or near the trade-wind belts.
It is tremblingly alive to all such influences, and they keep it in
continual agitation ; accordingly we find that such is its state
that within certain boundaries it is continually changing place
and limits. This fact is abundantly proved by the speed of ships,
for the log-books at the Observatory show that it is by no means
a rare occurrence for one vessel, after she may have been dallying
in the Doldrums for days in the vain efibrt to cross that calm belt,
to see another coming up to her, " hand over fist," with fair

* Maury's Nautical Monograph, No. 1.

t The mean temperature of sea water in the Atlantic is for 9° nortli, 80°.2G
by 565 obs. ; for equator, 79°. 63, by 269 obs. ; and for 9° south, 78°.96. 223 obs.
— Maury s Thermal Charts.

352 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOfrY.

winds, and crossing the belt after a delay in it of only a few
hours instead of days.

652. It varies with the strength of the trade-ioinds. — Hence we
infer that the position of the equatorial calm belt is determined
by the difference of strength between the north-east and south-
east trade-winds, which difference, in turn, depends upon dif-
ference of barometric pressure (§ 642), and upon difference in
temperature between them in corresponding latitudes north and
south. In it the air which they bring ascends. Now if we lil^en
this belt of calms to an immense atmospherical trough, extend-
ing, as it does, entirely around the earth, and if we liken the
north-east and south-east trade-winds to two streams discharging
themselves into it, we shall see that we have two currents per-
petually running in at the bottom, and that, therefore, we must
have as much air as these two currents bring in at the bottom to
flow out at the top. A-V hat flows out at the top is carried back
north and south by these upper currents, which are thus proved
to exist and to flow counter to the trade-winds.

653. Precipitation in it. — Captain Wilkes, of the Exploring
Expedition, when he crossed this belt in 1838, found it to extend
from 4° north to 12° north. He was ten days in crossing it, and
during those ten days rain fell to the depth of 6.15 inches, or at
the rate of eighteen feet and upwards during the year. In its
motions from south to north and back, it carries with it the rainy
seasons of the torrid zone, always arriving at certain parallels at
stated periods of the year ; consequently, by attentively consider-
ing Plate VIII., one can tell what places within the range of this
zone have, during the year, two rainy seasons, what one, and
what are the rainy months for each locality.

654. TJie ai^jpearance of the calm belts from a distant planet. — Were
the north-east and the south-east trades, with the belt of equato'
rial calms, of different colours, and visible to an astronomer in
one of the planets, he might, by the motion of these belts or gir-
dles alone, tell the seasons with us. He w^ould see them at one
season going north, then appearing stationary, and then com-
mencing their return to the south. But, though he would
observe (§ 295) that they follow the sun in his annual course, he
would remark that they do not change their latitude as much as
the sun does his declination ; he would therefore discover that
their extremes of declination are not so far asunder as the
tropics of Cancer and Capricorn, though in certain seasons the

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 3.53

changes from day to day are very great. He would observe that
tne zones of winds and calms have their tropics or stationary
nodes, about which they linger near three months at a time ; and
that they pass from one of their tropics to the other in a little less
than another three months. Thus he would obseiTe the whole
system of belts to go north from the latter part of May till some
time in August. Then they would stop and remain nearly sta-
tionary till winter, in December ; when again they would com-
mence to move rapidly over the ocean, and down towards the
south, until the last of February or the first of March ; then again
they would become stationary, and remain about this, their
southern tropic, till May again. Having completed his physical
examination of the equatorial calms and winds, if the supposed
observer should now turn his telescope towards. the poles of our
earth, he would observe a zone of calms bordering the north-east
trade-winds on the north (§ 210), and another bordering the
south-east trade-winds on the south (§ 213). These calm zones
also would be observed to vibrate up and down with the tiade-
wind zones, partaking (§296) of their motions, and following the
declination of the sun. On the polar side of each of these two
calm zones there would be a broad band extending up into the
polar regions, the prevailing winds within which are the oppo-
sites of the trade-winds, viz., south-west in the northem and
north-west in the southern hemisphere. The equatorial edge of
these calm belts is near the tropics, and their average breadth is
10° or 12°. On one side of these belts (§ 210) the wind blows
perpetually towards the equator ; on the other, its prevailing
direction is towards the poles. They are called (§ 210) the
" horse latitudes " by seamen.

655. Bainy seasons of the tropical calm belts. — Along the polar
borders of these two calm belts (§ 296) we have another region of
precipitation, though generally the rains here are not so constant
as they are in the equatorial calms. The precipitation near the
tropical calms is nevertheless sufficient to mark the seasons ; for
whenever these calm zones, as they go from north to south with
the sun, leave a given parallel, the railiy season of that parallel,
if it be in winter, is said to commence. Hence we may explain
the rainy season in Chili at the south, and in California at the
north.

656. Their position. — We can now understand why the calm
belts of Cancer and Capricorn occupy a medial position between

2 A

354 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the trades and the counter trades; why, on one side of it, the
prevailing direction of the wind should be polarward, on the
other towards the equator ; and we also discover the influences
which determine their geographical position ; for : —

657. A meteorological laio. — An accumulation of atmosphere
over one part of the earth's surface implies a depression over
some other part, precisely as the piling up of water into a wave
above the sea level involves a corresponding depression below ;
and in meteorology it may be regarded as a general law, that the
tendency of all winds on the surface is to blow from the place
where the barometer is higher to the place where the barometer
is lower. This meteorological law is only a restatement of the
dynamical traism about water seeking its own level.

658. The barometer in the calm, belts. — The mean height of the
barometer in the calm belts of the tropics is greater (Plate I.)
than it is in any other latitude. The mean height of the baro-
meter in the equatorial calm belt is less than it is on any other
parallel between the tropical and equatorial calm belts. The
difference for the calm belt of Cancer is 0.25 inch. This differ-
ence is permanent. It is sufficient to put both systems of trade-
winds in motion, and to create an indraught of air flowing per-
petually towards the equatorial calm belt from the distance of
two thousand miles on each side of it.

659. Winds with northing and winds with southing in them. — In
like manner, as we go from either tropical calm belt towards the
nearest pole, the barometric pressure becomes less and less. The
meteorological law just announced requires the prev^ailing wind
on the polar side of these calm belts to be from them and in the
direction of the poles ; and observations (Plate I.) show that such
is the case. Dividing the winds in each hemisphere into winds
with northing and winds with southing in them as has been done
in Chapter XXI. and Plate XV., actual observation shows (§ 852)
that they balance each other in the southern hemisphere between
the parallels of 35*^ and 40°, and in the northern between the
parallels of 25° and 50° ; that between these parallels the average
annual prevalence of winds with northing and of winds with
southing in them is the same, the difference (Plate XV.) being
so small as to bo apparently accidental ; that, proceeding from
the medial band towards the pole, polar-bound winds become
more and more prevalent, and proceeding from it towards the
equator, equatorial-bound winds become more and more preva

SEA KOUTES, CALM BELTS, AND VARIABLE WINDS. 355

lent. Now, in each case, the prevailing winds blow (§ 657) from
the high to the low barometer (Plate I.).

660. Tlie harometric ridges. — The fact of two barometric ridges
encircling the earth, as the high barometer of the tropical calm
belts do, and as they may be called (Plate I,), suggests a place of
low barometer on the polar side as naturally as the ascent of a
hill on one side suggests to the traveller a descent on the other ;
and, had not actual observations revealed the fact, theory should
have taught us (§ 654) the existence of a low barometer towards
the polar regions as well as towards the equatorial

661. Tliey make a depression in the atmosphere. — Let us contem-
plate for a moment this accumulation of air in the tropical belt
about the earth in each hemisphere. Because it is an accumula-
tion of atmospheric air about the calms ; — because the barometer
stands higher under the calm belt of Capricorn, for instance, than
it does on any other parallel between that calm belt and the pole
on one side, or the equator on the other, it is not to be inferred
that therefore there is a piling — a ridging up — of the atmosphere
there. On the contrary, v^ere the upper surface of our atmo-
sphere visible, and could we take a view of it from above, w^e
should discover rather a valley than a ridge over this belt of
greatest pressure ; a^d over the belt of least pressure, as the
equatorial calm belt, we should discover (§ 520), not a valley,
but a ridge, and for thes*^ reasons : In the belts of low barometer,
that is, in bo.th the eqaatorial and polar calms, the air is ex-
panded, made light, and caused to ascend chiefly by the latent
heat that is liberated by the heavy precipitation which takes
place there. This causes the air which ascends there to rise up
and swell out far above the mean level of the great aerial ocean.
This intumescence at the equatorial calm belt has been estimated.
to be several miles above the general level of the atmosphere.
This calm belt air, therefore, as it boils up and flows off through
the upper regions, north and south, to the tropical calm belts,
does not so flow by reason of any difference of barometric pres-
sure, like that which causes the surface winds to blow, but it so
flows by reason of difference as to level.

662. The upper surface of the atmosphere. — The tropical caim
belts (§ 278) are places where the mean amount of precipitation
is small. The air there is comparatively dry air. So far from
being expanded by heat, or swelled out by vapour, this air is
contracted by cold, for the chief source of its supply is through

2 A 2

356 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the upper regions, from the equatorial side, where the cross sec-
tion between any two given meridians is the larger ; and this
tipper current, while on its way from the equator, is continually
parting with the heat which it received at and near the surface,
and which caused it to rise under the equatorial cloud-ring. In
this process it is gradually contracted, thus causing the upper
surface of the air to be a sort of double inclined plane, descending
from the equator and from the poles to the place of the tropical
calm belts.

663. Winds in the southern stronger than winds in the northern
hemis'phere. — Observations show that the mean weight of the
barometer in high southern is much less (Plate I.) than it is in
corre«:ponding high northern latitudes ; consequently, we should
expect that the polar-bound winds would be much more marked
on the polar side of 40° S., than they are on the polar side of
40° N. Accordingly, observations (Plate XV.) show such to be
the case ; and they moreover show that the polar-bound winds
of the southern are much fresher than those of the northern
hemisphere.

664. Tlie imves and gales off the Cape of Good Hope. — To appre-
ciate the force and volume of these polar-bound winds in the
southern hemisphere, it is necessary that one should " run them
down " in that waste of waters beyond the parallel of 40° S.,
where " the winds howl and the seas roar." The billows there
lift themselves up in long ridges with deep hoUows between
them. They run high and fast, tossing their white caps aloft in
the air, looking like the green hills of a rolling prairie capped
with snow, and chasing each other in sport. Still, their march
is stately and their roll majestic. The scenery among them is
grand, and the Australian-bound trader, after doubling the Cape
of Good Hope, finds herself followed for weeks at a time b}^
these magnificent rolling swells, driven and lashed by the
"brave west winds" most furiously. A sailor's bride, per-
forming this voj^age with her gallant husband, thus alludes in
her " abstract log " to these rolling seas : " We had some mag-
nificent gales off the Cape, when the colouring of the waves, the
transition from gi-ay to clear brilliant green, with the milky -
white foam, struck me as most exquisite. And then in rough
weather the moral picture is so fine, the calmness and activity
required is such an exhibition of the power- of mind over the
elements, that I admired the sailors fully as much as the sea,

SEA ROUTES, CALM BELTS. AND VARIABLE WINDS. 357

and, of course, the sailor in command most of all ; indeed, a sea
voyage more than fulfils m}^ expectations."

665. Winds bloiv from a high to a low barometer. — It appears,
therefore, that the low barometer about the poles and the low
barometer of the equator cause an inrush of wind, and in each
case the rushing wind comes from the high and blows towards the
low barometer ; that in one hemisphere the calm belt of Capri-
corn, and in the other the calm belt of Cancer, occupies the
luedial line between the equatorial and polar places of low
barometer.

666. Polar rarefaction. — It appears, moreover, that the polar
refraction is greater than the equatorial, for the mean height of
the austral barometer is very much below that of the equatorial,
and, consequently, its influence in creating an indraught is felt
at a greater distance (Plate XY.)— even at the distance of 50° of
latitude from the south pole, while the influence of the equatorial
depression is felt only at the distance of 30° in the southern, and
of 25° in the northern hemisphere. The difference as to degree
of rarefaction is even greater than this statement implies, for the
influx into the equatorial calm belt is assisted also by tempera-
ture in this, that the trade-winds blow from cooler to warmer
latitudes. The reverse is the case with the counter-trades ;
therefore, while difference of thermal dilatation assists the equa-
torial, it opposes the polar influx.

667. Tlie tropical calm belts caused by the polar and equatorial
calms. — Thus we perceive that the tropical calm belts are simply
an adjustment between the polar and equatorial calms ; that the
tropical calm belts assume their position and change their lati-
tude in obedience to the energy with which the influence of the
heated and the expanding columns of air, as they ascend in the
polar and equatorial calms, is impressed upon them.

668. The meteorological power of latent heat. — This explanation of
the calm places and of the movements of the low austral ba-
rometer shows, comparatively speaking, how much the latent
heat of vapour, and how little the direct heat of the sun has to
do in causing the air to rise up and flow off from these calm
places, and consequently, how little the direct action of the solar
ray has to do either with the trades or the counter trades. It
regulates and controls them ; it can scarcely be said to create
them.

669. The low barometer off Cape Horn. — The fact of a low

358 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

barometer off Cape Horn was pointed out* as long as 1834. It
was considered an anomaly peculiar to the regions of Cape
Horn. It is now ascertained by the comparison of 6455 obser-
vations on the polar side of 40° south, and about 90,000 in all
other latitudes, that the depression is not peculiar to the Cape
Horn regions, but that it is general and alike in all parts of the
austral seas, as the following table, compiled from the log-books
of the Observatory by Lieutenants Warley and Young, shows : —

Barometric Table.
Mean Height of the Barometer as observed heticeen

the Meridians of

the Parallels of

20° W. and 140° E.

140° E. and 80° W.

Off Cape Horn.

No. of

Barom.

No. of

Barom.

No. of

Barom.

No. of

Barom.

Obs.

Inches.

Obs.

Inches.

Obs.

Inches.

Obs.

Inches.

40° S. and 43° S.

1115

29.90

210

29.84

378

29.86

1703

29.88

43 „ 45

788

.80

155

.73

237

.75

1130

.78

45 „ 48

611

.58

226

..71

337

.68

1174

.63

48 „ 50

174

.53

247

.56

250

.61

672

.62

50 „ 53

108

.35

198

.45

359

.56

665

.48

53 „ 55

6

.14

92

.35

377

.37

475

.36

7

.27

64

.42

1055

,28

1126

.29

671. Barometer at the poles. — These are the observed heights ;
for the want of data, no corrections have been applied to them ;
and for the want of numbers sufficient to give correct means, they
lack that uniformity which larger numbers would doubtless give.
They show, however, most satisfactorily, that a low barometer is
not peculiar to Cape Horn regions alone; they show that it is
common to all high southern latitudes ; and other observations
(§ 362) show that it is peculiar to these and not to northern lati-
tudes. Projecting on a diagram A, with parallels of latitude a^nd
the barometric scale as ordinates and abscissse, a curve S, which
will best represent the observations (§ 670), and continuing it to
the south pole — also projecting another curve N, which will best
represent the observations (§ 362) on the polar side of 40° N.,
and continuing it to the north pole — we discover that if the
oarometric pressure in polar la,titudes continue to decrease for

* American Journal of Science, vol. xxvi. p. 54 (1834).

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.

559

the unknown as it does for the known regions, the mean height
of the barometer would be at the north pole about 29.6, at the
south about 28 inches. These lines, N and S, represent what
may be called the barometric descent of the counter-trades.

672. The " hrave ivest winds " — their barometric descent. — The
rarefaction of the air in the polar calms is, as we have seer

LAT ^'0

Diagram A.
so! e 0"

70"

80

90

BaroTiifiter 8i).i
so.o

29.ff
.8

.7

.c

.5

.4

3

.2

.1

290

28.3

.8

.7

.6

.5

.3

.2

.1

2S.0

279

1 1

~

P>-

P

■^

1

■v.

1

r-

i.

^

(

3"

r-.

1

\

■->,

1

1

c

IN

■*-

^^

1

\

■->,,

1

\

i» n

i\

1^

\

V

«

1.

\

c

~i

'•'

\

\

1

^

\

\

\

i

\

'\

J_

!

\

i

1

\

1

1

S

1

\

1

rs

~^

^

IS

1 '

"V

l\

1

/

s

fc»

L_

_

1

(§ 667), suf&cient to create an indraught all around to the dis-
tance of fifty degrees ot latitude from the south pole; also
(§ 662) the rarefaction in the belt of equatorial calms is sufficient

360 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

to extend with its influence no farther than thirty degrees of
latitude. The fact also favours the idea suggested by the
diagram (§ 671), that the mean height of the barometer in the
polar calms is very much less than it is in the equatorial. More-
over, the counter trades of the southern hemisphere are very
much stronger (§ 626) than the counter trades of the other.
The}^ are also stronger than the trade-winds of either ; these
facts likewise favour the idea of a greater exhaustion of air
in the antarctic than in the arctic calm place ; and it is mani-
fest that actual observations also, as far as they go, indicate
such to be the case. In other words, " the brave west winds " of
the southern hemisphere have the greatest "barometric descent,"
and should therefore be, as they are, the strongest of the four
winds.

67o. Study of the monsoons affords farther information touching the
calm belts. — Farther information may be gained upon the subject of
high and low barometers, of the " barometric declivity of winds,"
and of the meteorological influence of diminished atmospheric
pressure by studying the calm belts in connection with the
monsoons.

674. The south-west ivinds of the Atlantic. — Before, however, we
proceed to these, let us take a hasty glance at the winds in cer-
tain other parts of the ocean. The winds which most prevail on
the polar side of the calm belt of Cancer, and as far as 50° N. in
the Atlantic, are the west winds. " Wind and weather in this
part of the ocean," says Jansen, " are very unreliable and change-
able ; nevertheless, in the summer months, we find permanent
north winds along the coast of Portugal. These north winds are
worthy of attention, the more so from the fact that they occur
simultaneously with the African monsoon, and because we then
find northerly winds also in the Mediterranean, and in the Eed
Sea, and farther eastward to the north of the Indian monsoon.
When, between the months of May and November, during which
the African monsoon prevails, the Dutch ships, which have lin-
gered in the calm belt of Cancer run with the north-east trade,
and direct their course for the Cape Yerd Islands, then it seems
as if they were in another world. The sombre skies and change-
able— alternately chilly and sultry — weather of our latitudes are
replaced by a regular temperature and good settled weather.
Each one rejoices in the glorious heavens, in which none save
the little tr^.de-clouds are to be seen — which clouds in the trade-

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 361

wind region make the sunset so enchanting. The dark-blue
water, in which many and strange kinds of echinas sport in the
sunlight, and, when seen at a distance, make the sea appear like
one vast field adorned with flowers ; the regular swellings of the
waves with their silvery foam, through which the flying-fishes
flutter ; the beautifully-coloured dolphins ; the diving schools of
tunnies — all these banish afar the monotony of the sea,* awake
the love of life in the youthful seaman, and attune his heart to
goodness. Everything around him fixes his attention and in-
creases his astonishment.

675. Sailing through the trade-wind. — " If all the breathings out
of heartfelt emotion which the contemplation of nature forces
from the sailor were recorded in the log-books, how much farther
should we be advanced in the knowledge of the natural state of
the sea ! Once wandering over the ocean, he begins to be im-
pressed by the grand natural tableau around him with feelings
deep and abiding. The most splendid forecastle is lost in the
viewless surface, and brings home to us the knowledge of our
nothingness; the greatest ship is a plaything for the billows, and
the slender keel seems to threaten our existence every moment.
But when the eye of the mind is permitted to wander through
space and into the depths of the ocean, and is able to form a
conception of Infinity and of Omnipotence, then it knows no
danger ; it is elevated — it comprehends itself. The distances of
the heavenly bodies are correctly estimated ; and, enlightened by
astronomy, with the aid of the art of navigation, of which Maury's
Wind. and Current Charts form an important part, the shipmaster
marks out his way over the ocean just as securely as any one can
over an extended heath. He directs his course towards the Cape
Verd Islands, and is carried there by the lively trade-wind. Yet
beyond the islands, sooner or later, according to the month, the
clear skies begin to be clouded, the trade-wind abates and
becomes unsteady, the clouds heap up, the thunder is heard,
heavy rains fall ; finally, the stillness is death-like, and we ha'Te
entered the belt of calms. This belt moves towards the north
from May to September. It is a remarkable phenomenon that
the annual movements of the trades and calm belts from south to
north, and back again, do not directly follow the sun in its

* When we, as our forefathers did, preserve in the journals all that we observe
at 8ea, then we shall have abundant material with which to keep ourselves
pleasantly occupied.

862 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

declination, but appear to wait until tlie temperature of the sea
water puts it in motion. If a ship which has come into the belt
of calms between May and September could lie still in the place
where it came into this belt — cast anchor, for example — then it
would perceive a turning of the monsoon or of the trade-wind.
It would see the belt of calms draw away to the north, and after-
wards get the south-west monsoon, or, standing more westerly,
perhaps the south-east trade. On the contrary, later than Sep-
tember, this ship lying at anchor will see the north-east gradu
ally awake. The belt of calms then moves towards the south,
and removes from the ship, which remains there anchored on the
north side."*

676. Tlie influence of the land upon the winds of the sea. — The in-
vestigations that have taken place at the Observatory show that
the influence of the land upon the normal directions of the wind
at sea is an immense influence. It is frequently traced for a
thousand miles or more out upon the ocean. For instance, the
action of the sun's rays upon the great deserts and arid plains of
Africa, in the summer and autumnal months, is such as to be felt
nearly across the Atlantic Ocean between the equator and the
parallel of 13° north. Between this parallel and the equator, the
north-east trade-winds, during these seasons, are arrested in their
course by the rainy seasons and heated plains of Africa, as- obser-
vation shows they are in India, and instead of " blowing home "
to the equator, they stop and ascend over the desert sands of the
continent. The south-east trade-winds, arriving at the equator
during this period, and finding no north-east trades there to con-
test their crossing the line, continue their course, and blow home
as a south-west monsoon, where they deposit their moisture and
ascend. These southwardly monsoons bring the rains which
divide the seasons in these parts of the African coast. The
region of the ocean embraced by these monsoons is cuneiform in
its shape, having its base resting upon Africa, and its apex
stretching over till within 10° or 1 o° of the mouth of the Amazon.
Indeed, when we come to study the eifects of South America and
Africa (as developed by the Wind and Current Chai'ts) upon the
winds at sea, we should be led to the conclusion — had the foot of
civilized man never trod the interior of these two continents —

* Natuurkiindige Beschrijving der zecen, door M. F. Maury, LL.D., Lui-
tenant der Nord-Amcrikaiinsche Marine, vertaald door M. H. Jansen, Liiitenaut
der Zee, (Bijdrage.; Dordrecht, P. K. Braat. 1855.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 363

that the climate of one is humid ; that its valleys are, for the
most part, covered with vegetation, which protects its surface
from the sun's rays ; while the plains of the other are arid and
naked, and, for the most part, act like furnaces in drawing the
winds from the sea to supply air for the ascending columns which
rise from its over-heated plains. Pushing these facts and
arguments still farther, these beautiful and interesting researches
seem already sufficient almost to justify the assertion that, were
it not for the great desert of Sahara and other arid plains of
Africa, the western shores of that continent, within the trade-
wind region, would be almost, if not altogether, as rainless and
sterile as the desert itself.

677. A *' Gulf Stream " in the air. — Lieutenant Jansen has called
my attention to a vein of wind which forms a current in the air
as remarkable as that of the Gulf Stream is in the sea. This
atmospherical Gulf Stream is in the south-east trade-winds of the
Atlantic. It extends from near the Cape of Good Hope, in
a direct line to the equator, on the meridian of Cape St. Eoque
(Plate YIII.). The homeward route from the Cape of Good
Hope lies in the middle of this vein ; in it the winds are more
steady than in any other part of the Atlantic. On the edges of
this remarkable aerial current the wind is variable and often
fitful ; the homeward-bound Indiaman resorts to and uses this
stream in the atmosphere as the European-bound American does
the Gulf Stream. It is shaded on the plate.

678. Counterpoises. — These investigations, with their beautiful
developments, eagerly captivate the mind ; giving wings to the
imagination, they teach us to regard the sand}^ deserts, and arid
plains, the mountain ranges, and the inland basins of the earth,
as compensations in the great system of atmospherical circulation.
Like counterpoises to the telescope, which the ignorant regard
as incumbrances to the instrument, these wastes serve as make-
weights, to give certainty and smoothness of motion — facility
and accuracy to the workings of the machine.

679. Normal state of the atmosphere. — When we travel out upon
the ocean, and get beyond the influence of the land upon the
winds, we find ourselves in a field particularly favourable for
studying the general laws of atmospherical circulation. Plere,
beyond the reach of the great equatorial and polar currents of
the sea, there are no unduly heated surfaces, no mountain ranges

364 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

or other obstructions to the circulation of the atmosphere-
nothing to disturb it in its normal courses. The sea, therefore,
is the field for observing the operations of the general laws which
govern the movements of the great aerial ocean. Observations
on the land will enable us to discover the exceptions, but from
the sea we shall get the rule. Each valley, every mountain
range and local district, ma}^ be said to have its own peculiar
S3^stem of calms, winds, rains, and droughts. But not so the
surface of the broad ocean ; over it the agents which are at work
are of a more uniform character.

680. Ham-ioinds. — Eain-winds are the winds which convey the
vapour from the sea, where it is taken up, to other parts of the
earth, where it is let down either as snow, hail, or rain. As a
general rule, the trade-winds (§ 293) may be regarded as the
evaporating winds ; and when, in the course of their circuit, they
are converted into monsoons, or the variables of either hemi-
sphere, they then generally become also the rain-winds —
especially the monsoons — for certain localities. Thus the south-
west monsoons of the Indian Ocean are the rain- winds for the
west coast of Hindostan (§298). In like manner, the African
monsoons of the Atlantic are the winds which feed the springs of
the Niger and the Senegal with rains. Upon every water- shed
which is drained into the sea, the precipitation, for the whole
extent of the shed so drained, may be considered as greater than
the evaporation, by the amount of water which runs off through
the rivers into the sea. In this view, all rivers may be regarded
as immense rain-gauges, and the volume of water annually
discharged by any one, may be taken as an expression of the
quantity which is annually evaporated from the sea, carried back
by the winds, and precipitated throughout the whole extent of
the valley that is drained by it. Now, if we knew the rain
winds from the dry for each locality and season generally
throughout such a basin, we should be enabled to determine,
wnth some degi^ee of probability at least, as to the part of the
ocean from which such rains were evaporated. And thus, not-
withstanding all the eddies caused by mountain chains and other
uneven surfaces, we might detect the general course of the
atmospherical circulation over the land as well as the sea, and
make the general courses of circulation in each valley as obvious
to the mind of the philosopher as in the current of the Mississippi,

MONSOONS. 3G5

or of any other great river, to his senses. The greatest move

THAT CAN NOW BE MADE FOR THE ADVANCEMENT OF METEOROLOGY IS TO
EXTEND THIS SYSTEM OF CO-OPERATION AND RESEARCH FROM THE SEA TO
THE LAND, AND TO BRING THE MAGNETIC TELEGRAPH REGULARLY
INTO THE SERVICE OF METEOROLOGY.

CHAPTER Xyi.

§ 681-711. — MONSOONS.

681 . TliG cause of. — Monsocms are, for the most part, trade-winds
deflected. When, at stated seasons of the year, a trade-wind is
turned out of its reguhvr course, as fro-m one quadrant to another,
it is regarded as a monsoon. The African monsoons of the
Atlantic (Plate VIII.), the monsoons of the gulf of Hexico, and
the Central American monsoons of the Pacific ai'e, for the most
part, formed of the trade- winds which are turned back or deflected
to restore the equilibrium which the overheated plains of Africa,
Utah, Texas, and New Mexico have disturbed; these winds,
cari-ying their fuel (§ 254) with them in vapour, have their equi-
librium still further disturbed by the heat which is liberated
when that vapour is condensed. Thus, with regard to the N.W.
and the S.W. monsoons of the Indian Ocean, for example : a force
is exerted upon the N.E. trade-winds of that sea by the dis-
turbance which the heat of summer creates in the atmosphere
over the interior plains of Asia, which is more than sufficient to
neutralize the forces which cause those winds to blow as trade-
winds ; it arrests them and turns them back ; but, were it not
for the peculiar conditions of the land about that ocean, what are
now called the N.E. monsoons would blow the year round ; there
would be no S.W. monsoons there ; and the N.E. winds, being
perpetual, would become all the year what in reality for several
months they are, viz., N.E. trade-winds.

682. The region of. — Upon India and its seas the monsoon
phenomena are developed on the grandest scale. These remark-
able winds blow over all that expanse of northern water that lies
between Africa and the Philippine Islands. Throughout this
vast expanse, the winds that are known in other parts of the
world as the N.E. trades are here called N.E. monsoons, because,

366 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS BIETEOROLOGY.

instead of blowing from that quarter for twelve months, as in other
seas, they blow only for six. During the remaining six months
they are turned back, as it were ; for, instead of blowing towards
the equator, they blow away from it, and instead of N.E. trade?
Ave have S.W. monsoons.

683. A low barometer in Northern India. — If the N.E. trade wind?
blow towards the equator by reason (§ 657) of the lower baro-
meter of the calm belt there, we should — seeing them turned
back and blowing in the opposite direction as the S.W. monsoon
— expect to find towards the north, and at the place where they
cease to blow, a lower barometer than that of the equatorial calm
belt. The circumstances which indicate the existence of a lower
summer barometer — the period of the S.W. monsoon — in the
regions about northern India are developed by the law which
(§ 657) requires the wind to blow towards that place where there
is least atmospheric pressure.

684. The S.W. monsoons " baching doion.'' — The S.W. monsoons
commence at the north, and "back down," or work their way
towards the south. Thus they set in earlier at Calcutta than they
do at Ceylon, and eailier at Ceylon than they do at the equator.
The average rate of travel, or " backing down to the south," as
seamen express it, is from fifteen to twenty miles a day. It
takes the S.W. monsoons six or eight weeks to "back down"
from the tropic of Cancer to the equator. During this period
there is a sort of barometric ridge in the air over this region,
which we may call the monsoon wave. In this time it passes
from the northern to the southern edge of the monsoon beU, and
as it rolls along in its invisible but stately march, the air beneath
its pressure flows out from under it both ways — on the polar side
as the S.W. monsoon, on the equatorial as the N.E.

685. Hoio they begin. — As the vernal equinox approaches, the
heat of the sun begins to play upon the steppes and deserts of
Asia with power enough to raref}^ the air, and cause an uprising
sufficient to produce an indraught thitherward from the surround
ing regions. The air that is now about to set ofi" to the south as
the N.E. monsoon is thus arrested, turned back, and drawn into
this place of low barometer as the S.W. monsoon. These plains
become daily more and more heated, the sun more and more
powerful, and the ascending columns more and more active ; the
area of inrushing air, like a circle on the water, is widened, and
thus the S.W. monsoons, " backing down" towards the equator,

MONSOONS.

367

drive the N.E. monsoons from the land, replace them, and
gradually extend themselves out to sea.

686. Tlie sun assisted hy the latent heat of vapour. — Coming now
from the water, they bring vapour, which, being condensed upon
the hill-sides, liberates its latent caloric, and so, adding fuel to
the flame, assists the sim (§ 648) to rarefy the air, to cause it to
rise up and flow off more rapidly, and so to depress the baro-
meter still more. It is not till the S.W. monsoons have been
extended far out to sea that the}' commence to blow strongly, or
that the rainy season begins in India. By this time the mean
daily barometric pressure in this place of ascending air, which is
also a calm place, has become less than it is in the equatorial
calm belt ; and the air which the S.E. trade-winds then bring to
the equator, instead of rising up there in the calm belt, pass over
without stopping, and flows onward to the calms of Central Asia
as the S.W. monsoon. It is drawn over to supply the place of
rarefaction over the interior of India.

687. The rain-fall in India. — The S.W. monsoon commences to
change at Calcutta, in 22° 34' N., in February, and extends
thence out to sea at the rate of fifteen or twenty miles a day : yet
these winds do not gather vapour enough for the rainy season of
Cherraponjie, in lat. 25^ 16', to commence with until the middle
or last of April, though this station, of all others in the Bengal
Presidency, seems to be most favourably situated for wringing
the clouds. Selecting from Colonel Sykes's report of the rain-fall
of India, those places which happen to be nearest the same
meridian, and about 2° of latitude apart, the following state-
ment is made, with the view of showing, as far as such data can
show, the time at which the rainy season commences in tho
interior ;

.

Lat.

Long.

March.

April.

ilay.

June.

July.

Aug. ; Sept.

Oct.

Poorie ....
Baitool ....
Saugor ....
Humeerpore
Bareilly . .
Ferozepore

Simla

Ciierraponjie

o '
19 48
2151
23 50

2G 7
28 12

30 57

31 6
25 16

85 49

77 58

78 47

79 47
79 34
74 4]
77 11
9143

n.

1

1

in.
1

28

in.
1
]

2

1
115

X

2
7
3
1
4
147

in.
14
15
15
13
17
19
18
99

in.

7

9

12

11

8

12
104

in.
4
4

13

5

2

72

in.

i

1

3
40

2

29

120

173

210

163

100

45

868 PHYSICAL GEOGRAPHY OF I'HE SEA, AND ITS METEOROLOGY.

It is June before the S.W. monsoons liave backed down as far as
the equator and have regularly set in there.

688. Its influences upon the monsoons. — These positions are
Belected without regard to elevation above the sea level. Of
course, when the S.AV. monsoon comes only from a short distance
out to sea, as in April it does, it is but lightly loaded with
moisture. The low country cannot condense it, and it then
remains for the mountain stations in the interior, such as
Cherraponjie, to get the first rains of the season ; and a most
interesting physical problem may be here put on the road to
solution by the question : — Does not the rainy season of the S.W.
monsoon commence at the high stations in the interior, as on the
sides of the Himalaya, earlier than in the flat country along the
sea-coast ?

689. The march of the monsoons. — With the view of investigat-
ing certain monsoon phenomena, recourse was had to our great
mao-azine of undigested facts, the abstract logs; and after dis-
cussino- not less than 11,697 observations on the winds at sea
between the meridians of 80° and 85° E., and from Calcutta to
the equator, results were obtained for the following table, in
which is stated in days the average monthty duration of the N.E.
and S.W. winds at sea between the parallels of —

22° and 20° N.

20° and 15°N.

15° and 10° N.

10° and 5° N.

5» and 0° N.

Days.

I'ays.

Days.

Dayi.

Days.

Days.

Days.

Days.

Days.

Days.

N.E.

S.W.

N.E.

...
S.W.

KE.

s.w.

N.E.

s.w

.N.E.

S.w.

January

17

6

21

2

23

1

20

1

19

3

February

11

11

13

6

19

3

22

1

16

2

March .

4

18*

7

15

18

5

13

0

15

2

April . .

2

24

2

22

6

12

6

11

4

14

May . .

1

26

1

24

3

21*

1

23*

0

19*

June . .

0

28

1

27

0

29

1

25

0

24

July . .

2

24

1

27

0

30

0

28

0

24

August .

0

28

1

24

0

24

1

22

0

18

September

6

14

1

18

0

23

0

26

1

18

October

9

6

12

6t

8

10

6

16

4

14

November

11

6

25

2

21

2t

10

6

5

14

December

27

0

26

1

24

1

15

3t

12

11

* Setting in of the S.W. monsoon.

f Ending of the S.W. monsoon.

It appears from this table that between Calcutta and the line
the S.W. monsoons are the prevailing winds for seven months,
the N.E. for five.

690. Their conflict— ii begins at the north. — Resorting to the

MONSOONS.

369

graphic method of engraved squares for a farther discussion of
these figures, it appears by the subjoined Diagi'am B, that in

22"

20"

Diagram

15° 1

B.

i

5°

o

Dass

1

za

1

" 1 1

n

i

^

^

20

1

„-'

u*

\

.

1

"

k.

/

.

"^

.

1

,

W

X

\

V

1

1

^y

/

f.

\l

N

ht\ 1 I.

'.'/

1

s^

V

j/i

^' /

/

1

■^

1

^v

1

^

-^

^

i/-

/

w

/

■^

/^

3D

«\

"

.i<i.

a

"*'/

V

^

\

1

/

\

/

r

'■

^

1

5

^

Oh

^\x

V^

i

.

-<

y

-

^^^

■>

^

■'v

^a

\

•^r-l-0

■^

0

|-

-4.

^,-

-^

.--

-;:

---■'

0

^

1

_

-

1

-

_^

_

-

«

_

1

February the north-east and Houth-west winds are in equal con-
flict between the parallels of 20° and 22° ; that in March the
former have been " backed down" (§ 684) as far as the parallel
of 16°-15'^ — the medial line between them from which each
monsoon is blowing — and where, again, the conflict of " back to
back" is equally divided as to time of mastery (12 days) on
either side. By the month of June they (the south-west) have
fairly gained the ascendancy, and so remain masters of the field
until October, when the bi-annual conflict is again commenced
at the north. The vanquished north-east trades now lead off in
the attack, and, as the Diagram C shows, the two combatants
have force enough about the parallel of 1 5° north to blow during
this month 9 days each. The conflict, instead of being " back to
back," is now face to face ; instead of blowing awa}^ from the
medial line, they blow towards it ; instead of being a place of
high, the medial line is now (§ 657) a place of low barometer.
By November the north-east monsoon has pushed the place of
eqnal contest as far do^^ii as the parallel of 5° north.

2 B

370 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

691. Tlie harometric descent of the monsoons.— Each, monsoon,
like the trade-winds, blows from a higher to a lower barometer.
Taking np the clew from this fact, and resorting again to the
graphic method for illustration, we may ascertain, with consider-

Diaofram 0.

22'

20"

ST.

15°

Xat

10°

f

O*

-

.

%%

"~

\

N

\

1

\

^

rfim

^

U

A

•

^

1

\

\

\

\

0

„1K

L^

,

,

,

\

''

'■^

--,

-/i\

j

— 1

:/\

J

1

^

V

^

K''

1

w

\

\^

/>

Tin

'

^

\

n-*

V

/

— c

/

V

si.'

\

/

.\.

,.'

K

Vrfl

in

\

i^-'-

---

n

-<

M

['

-®

H.

S

,^

T

r-

■>

\

V-,

^k

-^

TO

\''

-'

'

.

S

m

.»

1

_

_

able accuracy, not only the relative strength of the north-east
and south-west monsoons of the sea, but also the mean height of
the barometer in the interior of India during the south-west
monsoon, supposing that monsoon to go no farther than the
mountain range, which may be taken at a mean to be about the
parallel of 30° north. Now, taking the mean height of the
barometer at the equatorial calm belt to be (§ 362) 29.92 inches ;
the mean height in the calm belt of Cancer to be 30.21 inches,
the line N.E. of the Diagram D will represent the average baro-
metric declivity of the north-east monsoons generally. The mean
height of the barometer during the three months of June, July,

JIONSOONS.

371

and August, when the sonth-west monsoons are at their height,
is.

For Calcutta
„ Bombay
„ Madras

29.55 inches.
29.65 „
29.73 „

The line S.W. represents the mean barometric declivity of the
south-west monsoons at their height, and indicates that at their

IsT

Diagram D.
5° Xat 10° 15'

20°

25

S0°

~r~r

T

_L

.rCTC-H — — TT^

1

XtiO^^^^^^

^•——-'^

4- -

— 1 — r""

1 1 1 -^

C"" ^. "

1

-jS-

"^^-i-^

■ 1

1 ^-^

^

o

_L ^

S^^^^ i„„

_ 1 „ ^„ «- _„„

^a^..

R 1

1 1 1

^'^^"^=- (^

1 1

"^ ^"^-.^ i^^i.

_^ ^E^t-

1 ^^=a-

1 1 1

Bar.g

.1

30.0
29.9

A

.7

.6

.5
,4

northern edge, supposed to be the parallel of 30° north, the baro-
meter stands at about 29.45 inches. This barometric declivity
indicates that the south-west are stronger than the north-east
monsoons, and observations show that they are.*

692. T]ie summer rains of Cherraponjie. — These are the winds —
the south-west monsoons — which, coming from the sea, carry
into the interior rains for the great water-shed of India. They
bear with them an immense volume of vapour, as is shown by the
rivers, and confirmed by the rain-fall of Cherraponjie, and at

126 other stations. Cherraponjie is 4,500 feet above the sea
level. It reaches quite up to the cloud region, and receives a
precipitation of 537^ inches during the south-west monsoon,
from May to August inclusive. Col. Sykes reported to the
British Association, at its meeting in 1852, the rain-fall at these

127 places, which are between the parallels of 20° and 34° in
India. According to this report, the south-west monsoons pour
down during the three summer months upon this water-shed 29|
inches of rain. The latent heat that is liberated during the

* Dr. Buist.

2 B 2

372 PHYSICAL GEOGBAPHY OF THE SEA, AND ITS METEOROLOGY.

condensation of the vapour for all this rain expands the air,
causing it to boil over, flow off, and leave a low barometer — a
diminished atmospheric pressure throughout all the region south
of the Himalaya.

693. Dove and the monsoons. — As long ago as 1831, Dove
maintained that the south-west monsoon was the south-east
trade-wind rushing forward to fill the vacant places over the
northern deserts. Dove admits the proofs of this to be indirect,
and acknowledges the difficulty of finding out and demonstrating
the problem.

694. Tlie south-east trades passing into south-west monsoons. —
But any navigator who, during the summer months, has occasion
to traverse the Indian Ocean from north to south, may find that
it is so. The outward-bound Indiaman, who, when on his way
to Calcutta, crosses the equator in August, for example, will
find the south-east trades, as he approaches the line, to haul
more and more to the south. As he advances still farther north
they get to the west of south. Finally, he discovers that he has
got the regular south-west monso<ms, and that he has jDassed
from the south-east trades into them without any intervening
calm. This in summer is the rule ; it has its exceptions, but
they are rare. Examining the logs of a number of vessels taken
at random for the passage in August, we find, by 421 obser-
vations therein recorded, they had the wind thus :

Wind from S.E. between Lat. 10° and 5° S. . with . 0 calms.

S. „ 5° S. and Equator „ . 3 „

S.W. „ Equator and 5° N. . „ . 3 „

S.W. „ Lat. 5° and 10° N. . „ . 0 „

695. Lieutenant Jansen. — In like manner, and with like force,
Jansen maintains that the north-west monsoon of Australia is the
north-east trade-wind turned aside.

696. Monsoons in the Pacific. — The influence exerted upon
rainless winds by the deserts of Africa and the overheated plains
of Asia is felt at sea for a thousand miles or more. Thus, though
the desert of Gobi and the sun-burned plains of Asia are, for the
most part, north of latitude 30°, their influence in assisting to
cause monsoons (§ 692) is felt south of the equator (Plate VIII.).
So, too, with the great desert of Sahara and the African monsoons
of the Atlantic ; also with the Salt Lake countiy and the Mexican
monsoons on one side, and those of Central America in the
Pacific on the other. The influence (§ 298) of the deserts of

MONSOONS. 373

Arabia upon the winds is felt in Austria and other parts of
Europe, as the observations of Kriel, Lamont, and others show.
So, also, do the islands, such as the Society and Sandwich, that
stand far away from any extent of land, have a very singular but
marked effect upon the wind. They interfere with the trades
very often, and turn them back ; for westerly and equatorial
winds are common at both these groups in their vdnter-time.
Some hydrographers have even taken those westerly winds of the
Society Islands to be an extension of the monsoons of the Indian
Ocean.

697. Influences of coral reefs upon winds. — It is a curious thing
is this influence of islands in the trade-wind region upon the
winds in the Pacific. Every navigator who has cruised in those
parts of that ocean has often turned with wonder and delight to
admire the gorgeous piles of cumuli, heaped up and arranged in
the most delicate and exquisitely beautiful masses that it is
possible for fleecy matter to assume. Not only are these cloud-
piles found capping the hills among the islands, but they are
often seen to overhang the lowest islet of the tropics, and even
to stand above coral patches and hidden reefs, " a cloud by day,"
to serve as a beacon to the lonely mariner out there at sea, and
to warn him of shoals and dangers which no lead nor seaman's
eye has ever seen or sounded out. These clouds, under favour-
able circumstances, may be seen gathering above the low coral
island, and performing their office in preparing it for vegetation
and fruitfulness in a very striking manner. As they are con-
densed into showers, one fancies that they are a sponge of the
most delicately elaborated material, and that he can see, as they
" drop down their fatness," the invisible but bountiful hand
aloft that is pressing it out. — Maury's Sailing Directions, 7th ed.,
p. 820.

698. Monsoons in miniature. — Land and sea breezes are mon-
soons in miniature, for they depend in a measure upon the same
cause. In the monsoons, the latent heat of vapour which is set
free over the land is a powerful agent. In the land and sea
breezes, the heat of the sun by day and the radiation of caloric
by night are alone concerned. In the monsoons the heat of
summer and cold of winter are also concerned. But could the
experiment be made with two barometers properly jDlaced — one
at sea and the other on land, but both within the reach of land
and sea breezes — they would show, I doubt not, regular altera-

371 PHYSICAL GEOGRAI^HY OF THE SEA, AND ITS METEOROLOGY.

tions of pressure. In the sea breeze, the land barometer would
be low and the sea high, and vice versa in the land breeze ; and
when the barometer was highest and when it was lowest it
would be calm at the barometric stations.

699. The changing of the monsoons. — It is these calm bands or
" medial belts," as the crest and trough of the barometric wave
may be called, which, with their canopy of clouds, follow the
departing and herald the coming monsoon. They move to and
fro, up and down the earth, like the sun in declination. As they
have a breadth of 200 or 300 miles, they occupy several days in
passing any given parallel, and while they overshadow it, then
the monsoons are dethroned. During the interregnum, which
lasts a week or two, the fiends of the storm hold their terrific
sway in these bands. The changing of the monsoons is marked
by storm and tempest. Becalmed in them, meanings are said
by seamen to be heard in the air — a sign of the coming storm —
a warning of impending danger to ship and crew. Then the
props and stays are taken away from the air, and the wind seems
ready to rush violently hither and thither, and whenever there
is from any cause a momentary disturbance of the equilibrium.
In such an atmosphere, the latent heat that is liberated by every
heavy rain-shower has power to brew a storm. Throughout the
monsoon region, the people know beforehand, almost to a day,
the coming of this interregnum, which they call the changing of
the monsoons, for the annual changing at the same place is very
regular.

700. Sow the calm helt of Cancer is ])ushed to the north. — Theory,
therefore, points to a place in Northern India, which is near the
northern limits of the south-west monsoon, where the mean
height of the barometer during the rainy season (§ 691) is about
29.5 inches, the mean height at the equator being 29.92 inches.
Into this monsoon place of low barometer over the land the
wind rushes from the north-east as well as the south-west. The
place of high pressure towards the north from which it rushes is
under the calm belt of Cancer. Hence this belt is also pushed
north, and made to occupy, in summer at least, the position over
.and somewhat like that assigned to it on Plate YIII In the
south-west monsoon the Malabar coast has its rainy season, so
that the air over the peninsula is permanently kept more or less
in a rarefied state, by the liberation of latent heat from vapour
'<m actual observations abundantly show.

MONSOONS. 375

701. The curved form of the equatoricl calm belt in the Indian
Ocean. — The equatorial calm belt in the Indian Ocean is a
decided curve. The peculiar form may be ascribed to the
meteorological influence of the Indian peninsula upon the calm
belt, and in this way : The north-east monsoon brings the rainy
season to the Coromandel coast and to the east coast of Ceylon.
This rainy season embraces the land rather than the sea. The
latent heat that is liberated during these rains, together with
the effect of the solar ray upon this tongue of land, has the effect
of expanding the air over it, and so " deadening " the north-east
monsoon. In the mean time, the meteorological influences from
Africa on one side, and Australia on the other, tend to draw the
wind in towards those lands and so retard the edges of the south-
east trades, thus giving the calm belt the curved form shown in
the plate.

702. TJie winter monsoons. — In the winter-time, and during the
north-east monsoon, there is in the calm belt which intervenes
between that monsoon and the south-east trades, a belt of winter
or westerly monsoons. It, too, is curved, as shown (Plate VIII.)
by the two lines drawn to represent its mean limits about
the 1st of March. This is a most remarkable phenomenon, for
which no satisfactory explanation has been suggested. It ex-
tends nearly, if not entirely, across the Pacific Ocean also, and
the winds all the way in it prevail from the westward. The
extreme breadth of this winter monsoon belt is about 9° or 10°
of latitude. In the Indian Ocean, its middle is between the
equator and 5° S. ; in the Pacific, between the equator and 5° N. ;
in the Atlantic, between 5° and 10° N. In the Atlantic it is a
summer monsoon easily to be accounted for. This belt of sub-
monsoons, considering its great length and small breadth, is one
of the most remarkable phenomena in marine meteorology.

703. Tlie monsoons of Australasia. — The north-west monsoons
of Australia come from this belt ; there it is widened, for these
winds extend far down the west coast of that continent. The
Malayan and Australasian archipelago have a complication of
monsoons and sub-monsoons. The land and sea breezes impart
to them peculiar features in many places, especially about the
changing of the monsoons, as described by Jansen in his appendix
to the Dutch edition of this work : " We have seen," says he
" that the calms which precede the sea breeze generally continue
longer, and are accompanied with &ii upwai d motion of the air^

376 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

that, on the contrary, those which precede the land-breeze are,
in the Java Sea, generally of shorter duration, accompanied by a
heavy atmosphere, and that there is also an evident diiFerence
between the conversion of the land breeze into the sea breeze,
and of the latter into the former. Even as the calms vary, so
there appears to be a marked difference between the changing of
the monsoons in the spring and in the autumn in the Java Sea.
As soon as the sun has crossed the equator, and its vertical rays
begin to play more and more perpendicularly upon the northern
hemisphere, the inland plains of Asia, North Africa, and of North
America are so heated as to give birth to the south-west mon-
soons in the China Sea, in the North Indian Ocean, in the North
Atlantic, and upon the west coast of Central America : then the
north-west monsoon disappears from the East Indian Archipelago,
and gives place to the south-east trade- wind, which is known
as the east monsoon, just as the north-west wind, which prevails
during the southern summer, is called the west monsoon. This
is the only north-west monsoon which is found in the southern
hemisphere. While in the northern hemisphere the north-east
trade-wind blows in the China Sea and in the Indian Ocean, in
the East Indian Archipelago the west monsoon prevails ; and
when here the south-east trade blows as the east monsoon, we
find the south-west monsoon in the adjacent seas of the northern
hemisphere. Generally the westerly monsoons blow during the
summer months of the hemisphere wherein they are found.

704. Thunder and lightning. — " In the Java Sea, during the
month of February, the west monsoon blows strong almost con-
tinually ; in March it blows intermittingly, and with hard
squalls ; but in April the squalls become less frequent and less
severe. Now the changing commences ; all at once gusts begin
to spring up from the east : they are often followed by calms.
The clouds which crowd themselves upon the clear sky give
warning of the combat in the upper air which the currents there
are about to wage with each other. The electricity, driven
thereby out of its natural channels, in which, unobserved, it has
been performing silently, but with the full consciousness of its
power, the mysterious task appointed to it, now displays itself
with dazzling majesty ; its sheen and its voice fill with astonish-
ment and deep reverence the mind of the sailor — so susceptible,
in the presence of storm and darkness, to impressions that inspire
teelings both of dread and anxiety, which by pretended occupa-

MONSOONS. 377

tions he strives in vain to conceal.* Day and niglit we now liave
tliunder-storms. The clouds are in continual movement, and the
darkened air, laden with vapour, flies in all directions through
the skies. The combat which the clouds seem to court and to
dread appears to make them more thirsty than ever. They
resort to extraordinary means to refresh themselves ; in tunnel
form, when time and opportunity fail to allow them to quench
their thirst from the surrounding atmosphere in the usual man-
ner, they descend near the surface of the sea, and appear to lap
the water directly up with their black mouths. Water-spouts
thus created are often seen in the changing season, especially
among small groups of islands, which appear to facilitate their
formation. I The water-spouts are not always accompanied by
strong winds ; frequently more than one is seen at a time, where-
upon the clouds whence they proceed disperse in various direc-
tions, and the ends of the water-spouts bending over finally cause
them to break in the middle, although the water which is now
seen foaming around their base has suffered little or no move-
ment laterally.

705. Water-sjiouts. — " Yet often the wind prevents the forma-
tion of water-spouts. In their stead the wind-spout shoots up
like an arrow, and the sea seems to try in vain to keep it back.
The sea, lashed into fury, marks with foam the path along which
the conflict rages, and roars with the noise of its water-spouts ;
and woe to the rash mariner who ventures therein !^ The height
of the spouts is usually somewhat less than 200 yards, and their
diameter not more than 20 feet, yet they are often taller and
thicker ; when the opportunity of correctly measuring them has
been favourable, however, as it generally was when they passed
between the islands, so that the distance of their bases could be
accurately determined, I have never found them higher than 700

* No phenomena in nature make a deeper impression upon the sailor than
a dark thunder-storm in a calm at sea. — Jansen.

t I never saw more water-spouts than in the Archipelago of Bioun Singen
during the changing. Almost daily we saw one or more. — Jansen.

X The air-spouts near the equator always appear to me to be more danger-
ous than the water-spouts. I have once had one of the latter to pass a ship's
length ahead of me, hut I perceived little else than a waterfall in which I
thought to come, yet no wind. Yet the water-spouts there also are not to be
trusted. I have seen such spouts go up out of the water upon the shore, where
they overthrew strong isolated frame houses. I have, however, never been in
a situation to observe in what direction they revolved. — Jansen.

878 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

yards, nor thicker than 50 yards. In October, in the Archipe-
lago of Eio, they travel from north-west to south-east. They
seldom last longer than five minutes ; generally they are dissi-
pated in less time. As they are going away, the bulbous tube,
which is as palpable as that of a thermometer, becomes broader
at the base, and little clouds, like steam from the pipe of a loco-
motive, are continually thrown off from the circumference of the
spout, and gradually the water is released, and the clouds whence
the spout came again closes its mouth.*

706. Tlie east monsoon in the Java Sea. — " During the changing
of the monsoons, it is mostly calm or cool, with gentle breezes,
varied with rain-storms and light gales from all points of the
compass. They are harassing to the crew, who, with burning

* Miniature water-spouts may b^s produced artificially by means of elect'-^*-
city, and those in nature are supposed to be caused by the display of electrical
phenomena. " From the conductor of an electrical machine," says Dr. Bon-
zano, of New Orleans, " suspend by a wire or chain a small metallic ball (one
of wood covered with tinfoil), and under the ball place a rather wide metallic
basin containing some oil of turpentine, at the distance of about three-quarters
of an inch. If the handle of the machine be now turned slowly, the liquid
in the basin will begin to movo in different directions, and form whirlpools.
As the electricity on the conductor accumulates, the troubled liquid will ele-
vate itself in the centre, and at last become attached to the ball. Draw off
the electricity from the conductor to let the liquid resume its position : a por-
tion of the turpentine remains attached to the ball. Turn the handle again
very slowly, and observe now the few drops adhering to the ball assume a
conical shape, with the apex downward, while the liquid under it assumes also
a conical shape, the apex upward, until both meet. As the liquid does not
accumulate on the ball, there must necessarily be as great a current downward
as upward, giving the column of liquid a rapid circular motion, which con-
tinues until the electricity from the conductor is nearly all discharged, silently,
or until it is discharged by a spark descending into the liquid. The same
phenomena take place with oil or water. Using the latter liquid, the ball
must be brought much nearer, or a much greater quantity of electricity is
necessary to raise it.

" If, in this experiment, we let the ball swing to and fro, the little water-
spout will travel over its miniature sea, carrying its whirlpools along with it.
"When it breaks up, a portion of the liquid^ and with it anything it may con-
tain, remains attaclied to the ball. The fish, seeds, leaves, etc., etc., that have
fallen to the earth in rain-squalls, may have owed their elevation to the clouds
to the same cause that attaches a few drops of the liquid, with its particles of
impurities, to the ball."

By reference to Plate XIII., we see that the phenomenon of thunder and
lightning is of much more frequent occurrence in the North than in the South
Atlantic ; and I infer tliat we have more electrical phenomena in the northern
than in the southern hemisphere. Do water-spouts occur on one side of the

MONSOONS. . 379

faces under the clouded skies,* impatiently trim the sails to the
changing winds. However, the atmosphere generally becomes
clear, and, contrary to expectation, the north-east wind comes
from a clear sky ; about the coming of the monsoon it is northerly.
Now the clouds are again packed together ; the wind dies away,
but it will soon be waked up to come again from another point.
Finally, the regular land and sea breezes gradually replace rain,
and tempests, calms, and gentle gales. The rain holds up during
the day, and in the Java Sea we have the east monsoon. It is
then May. Farther to the south than the Java Sea the east mon-
soon commences in April. f This monsoon prevails till September
or October, when it turns to become the west monsoon. It has
seemed to me that the east monsoon does not blow the same in
every month, that its direction becomes more southerly, and its
power greater after it has prevailed for some time.;};

707. Currents. — " It is sufficiently important to fix the attention,
seeing that these circumstances have great influence upon the
winds in the many straits of the Archipelago, in which strong
currents run most of the time. Especially in the straits to the
east of Java these currents are very strong. I have been unable
to stem the current with eight-mile speed. However, they do
not always flow equally strong, nor always in the same direction.
They are probably the strongest when the tidal current and the
equatorial current meet together. It is said that the currents in
the straits during the east monsoon run eighteen hours to the
north and six hours to the south, and the reverse during the west

equator more frequently than they do on the other ? I have cruised a great
deal on the southern hemisphere, and never saw a water-spout there. Accord-
ing to the log-books at the Observatory, they occur mostly on the north side
of the equator. — M.

* At sea the face and hands bum (change the skin) much quicker under a
clouded than under a clear sky. — Jansen.

t In the north-east part of the Ai'chipelago the east monsoon is the rainy
monsoon. The phenomena in the north-east part are thus wholly different
from those in the Java Sea. — Jansen.

j As is well known, the Strait of Soerabaya forms an elbow whose easterly
outlet opens to the east, while the westerly outlet opens to the north. In the
beginning of the east monsoon the sea wind (east monsoon) blows through the
westerly entrance as far as Grissee (in the elbow) ; in the latter part of this
monsoon, the sea-wind blows, on the contrary, through the easterly entrance
as far as Sambilangan (the narrow passage where the westerly outlet opens into
the sea). — Jansen.

380 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

monsoon. The passing of the meridian by the moon appears to
be the fixed point of time for the turning of the currents. It is
probable that the heated water of the Archipelago is discharged
to the north during the east monsoon, and to the south during
the west monsoon.

708. Marling the seasons. — " As the sea makes the coming of the
southern summer known to the inhabitants of the Java coast,* the
turning of the east monsoon into the west monsoon commences.
After the sun has finished its yearly task in the northern hemi-
s^Dhere, and brings its powerful influence to operate in the southern
hemisphere, a change is at once perceived in the constant fine
weather of the east monsoon of the Java Sea. As soon as it is at
its height upon the Java Sea (6° south), then the true turning of
the monsoon begins, and is accomplished much more rapidly
than the spring turning. The calms then are not so continuous.
The combat in the upper atmosphere appears to be less violent ;
the south-east trade, which has blown as the east monsoon, does
not seem to have sufficient strength to resist the aggressors, who,
with wild storms from the north-west and west, make their supe-
riority known. Upon and in the neighbourhood of the land
thunder-storms occur, but at sea they are less frequent.

709. Conflicts in the air. — " The atmosphere, alternately clear
and cloudy, moves more definitely over from the north-w:est, so
that it appears as if no combat was there waged, and the south-
east gives place without a contest. The land breezes become less
frequent, and the phenomena by day and night become, in a
certain sense, more accordant with each other. Storms of wind
and rain beneath a clouded sky alternate with severe gales and
steady winds. In the last of November the west monsoon is
peiinanent.

710. Passing of the calm belts. — " Such are the shif tings. But
what have they to do with the general system of the circulation
of the atmosphere ? Whenever we read attentively the beau-
tiful meditations of the founder of the Meteorology of the Sea,
and follow him in the development of his hypothesis, which lays
open to view the wheels whereby the atmosphere performs its
varied and comprehensive task with order and regularity, then it
will not be necessary to furnish proof that these turnings are

* In tlie Archipelago we have generally high water but once a day, and,
with the equinoxes, the tides also turn. The places which have high water
by day in one monsoon get it at night in the other. — Jansen.

MONSOONS. 381

nothing else than the passing of a belt of calms which separates
the monsoons from each other, and which, as we know, goes
annually with the sun from the south to the north, and back
over the torrid zone to and fro.

711. Where they are, there the changing of the monsoons is going on.
■ — " So also the calms, which precede the land and sea winds, are
turned back. If, at the coming of the land-wind in the hills, we
go with it to the coast — to the sea, we shall perceive that it
shoves away the calms which preceded it from the hills to the
coast, and so far upon the sea as the land-wind extends. Here,
upon the limits of the permanent monsoon, the place for the
:;alms remains for the night, to be turned back to the land and
to the hills the following day by the sea- wind. In every place
where these calms go, the land and sea-winds turn back. If
various observers, placed between the hills and the sea, and
between the coast and the farthest limit of the land-wind, noted
the moment when they perceived the calms, and that when they
perceived the land-wind, then by this means they would learn
how broad the belt of calms has been, and with what rapidity
they are pushed over the sea and over the land. And even
though the results one day should be found not to agree very
well with those of another, they would at least obtain an average
thereof which would be of value. So, on a larger scale, the belt
of calms which separates the monsoons from each other presses
in the spring from the south to the north, and in the fall from
the north to the south, and changes the monsoons in every place
where it presses."*

* Bijdrage Natuurkiindige Beschrijving der zeen, vertaald door M, H. Jansen^
Luitenant fcer zee.

382 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

CHAPTER XVII.

§ 720-735. THE CLIMATES OF THE SEA.

720. A "milky way" in the ocean. — Thermal charts, showing
the temperature of the surface of the Atlantic Ocean by actual
observations made indiscriminately all over it, and at all times
of the year, have been published by the National Observatory.
The isothermal lines which these charts enable us to draw, and a
few of which are traced on Plate IV., afford the navigator and the
jDhilosopher much valuable and interesting information touching
the circulation of the oceanic waters, including the phenomena of
their cold and warm currents ; these lines disclose a thermal tide
in the sea, which ebbs and flows but once a year ; they also cast
light upon the climatology of the sea, its h3'etographic peculia-
rities, and the climate conditions of various regions of the earth ;
they show that the profile of the coast-line of intertropical
America assists to give expression to the mild climate of Southern
Europe ; they also increase our knowledge concerning the Gulf
Stream, for they enable us to mark out, for the mariner's guid-
ance, that " milky way " in the ocean, the waters of which teem,
and sparkle, and glow with life and incipient organisms as they
flow across the Atlantic. In them are found the clusters and
nebulae of the ocean which stud and deck the great highway of
ships on their voyage between the Old World and the New ; and
these lines assist to point out for the navigator their limits and
his way. They show this via ladea to have a vibratory motion
in the sea that calls to mind the graceful wavings of a pennon as
it floats gently to the breeze. Indeed, if we imagine the head
of the Gulf Stream to be hemmed in by the land in the Straits of
Bernini, and to be stationary there, and then liken the tail of
the Stream itself to an immense pennon floating gently in the
current, such a motion as such a streamer may be imagined to
have, very much such a motion, do my researches show the tail
of the Gulf Stream to have. Eunning between banks of cold
water (§ 71), it is pressed now from the north, now from the
south, according as the great masses of sea water on either hand
may change or fluctuate in temperature.

721. Tlie vibrations of the Gulf Stream. — In September, when th^
waters in the cold regions of the north have been tempered, and
been made warm and light by the heat of summer, its limits on

THE CLDIATES OF THE SEA. 383

the left are as denoted by the line of arrows (Plate VI.) ; but,
after this great sun-swing, the waters on the left side begin to
lose their heat, grow cold, become heavy, and press the hot
waters of this stream into the channel marked out for them,
Thus it acts like a pendulum, slowly propelled by heat on one
side and repelled by cold on the other. In this view, it becomes
a chronograph for the sea, keeping time for its inhabitants, and
marking the seasons for the great whales ; and there it has been
for all time vibrating to and fro, once every year, swinging from
north to south, and from south to north again, a great self-regu-
Jating, self-compensating pendulum, beating time in the sea to
the seasons of the year.,

722. Sea and land climates contrasted. — In seeking information
concerning the climates of the ocean, it is well not to forget this
remarkable contrast between its climatology and that of the land,
namely : on the land February and August are considered the
coldest and the hottest months ; but to the inhabitants of the sea,
the annual extremes of cold and heat occur in the months of
March and September. On the dry land after the winter " is past
and gone," the solid parts of the earth continue to receive from
the sun more heat in the day than they radiate at night, con-
sequently there is an accumulation of caloric, which continues to
increase until August. The summer is now at its height ; for,
with the close of this month, the solid parts of the earth's crust
and the atmosphere above begin to dispense with their heat faster
than the rays of the sun can impart fresh supplies, and conse-
quently, the climates which they regulate grow cooler and cooler
until the dead of the winter again. But at sea a different rule
seems to prevail. Its waters are the store-houses* in which the
surplus heat of summer is stored away against the severity of
winter, and its waters continue to grow warmer for a month after
the weather on shore has begun to get cool. This brings the
highest temperature to the sea in September, the lowest in March.
Plate IV. is intended to show the extremes of heat and cold to
which the waters — not the ice — of the sea are annually subjected,
and therefore the isotherms of 40°, 50°, 60°, 70°, and 80° have been
drawn for March and September, the months of extreme heat
and extreme cold to the inhabitants of the "great deep." Cor-
responding isotherms for any other month will fall between
these, taken by pairs. Thus the isotherm 70° for July will fall
* Vide Chap. XXII., Actinometry of the Sea.

384 PHYSICAL GEOGEAPHT OF THE SEA, AND ITS METEOROLOGY.

nearly midway between tlie same isotlierms (70°) for March and
September.

723. Plate IV. — A careful study of this plate, and the con-
templation of the benign influence of the sea upon the climates
which we enjo}^ suggest many beautiful thoughts ; for by such
study we get a glimpse into the arrangements and the details of
that exquisite machinery in the ocean which enables it to perform
all its ofSces, and to answer with fidelity its marvellous adapta-
tions. How, let us inquire, does the isothermal of 80°, for
instance, get from its position in March to its position in
September ? Is it wafted along by currents, that is, by water
which, after having been heated near the equator to 80°, then
flows to the north with this temperature ? Or is it carried there
simply by the rays of the sun, as the snow-line is carried u]3 the
mountain in summer? We have reason to believe that it is
carried from one parallel to another by each of these agents
acting together, but mostly through the instrumentality of
currents, for currents are the chief agents for distributing heat to
the various parts of the ocean. The sun with its rays would,
were it not for currents, raise the water in the torrid zone to
blood heat ; but before that can be done, they run off with it
towards the poles, softening, and mitigating, and tempering
climates by the way. The provision for this is as beautiful as it
is benign ; for, to answer a physical adaptation, it is provided by
a law of nature that when the temperature of water is raised, it
shall expand ; as it expands, it must become lighter, and just in
proportion as its sjoecific gravity is altered, just in that proportion
is equilibrium in the sea destroyed. Arrived at this condition,
it is ordained that this hot water shall obey another law of
nature, which requires it to run away, and hasten to restore that
equilibrium. Were these isothermal lines moved only by the rays
of the sun, they would slide up and down the ocean like so many
parallels of latitude — at least there would be no break in them,
like that which we see in the isotherm of 80° for September. It
appears from this line that there is a part of the ocean near the
equator, and about midway the Atlantic, which, with its waters,
never does attain the temperature of 80° in September. More-
over, this isotherm of 80° will pass in the North Atlantic, from
its extreme southern to its extreme northern declination — nearty
two thousand miles — in about three months. Thus it travels at
the rate of about twenty -two miles a day. Surely, without the

THE CLIMATES OF THE SEA. 385

aid of currents, the rays of the sun could not drive it along that
fast. In this fact we have another link in the chain of proof
(Chap. XXII.), going to show that the sea receives more heat
than it radiates off again. Being now left to the gradual process
of cooling by evaporation, atmospherical contact, and radiation,
this isotherm occupies the other eight or nine months of the
year in slowly returning south to the parallel whence it com-
menced to flow northward. As it does not cool as rapidly as it
was heated, the disturbance of equilibrium by alteration of
specific gravity is not so sudden, nor the current which is
required to restore it so rapid. Hence the slow^ rate of move-
ment at which this line travels on its march south. Between
the meridians of 25° and 30° west, the isotherm of 60° in Sep-
tember ascends as high as the parallel of 56° N. In October it
reaches the parallel of 50° north. In November it is found
beneath the parallels of 45° and 47°, and by December it has
nearly reached its extreme southern descent between these meri-
dians, which it accomplishes in January, standing then near the
parallel of 40°. It is all the rest of the year in returning north-
ward to the parallel whence it commenced its flow to the south
in September. Now it will be observed that this is the season —
from September to December — immediately succeeding that in
which the heat of the sun has been playing with greatest activity
upon the polar ice. Its melted waters, which are thus put in
motion in June, July, and August, would probably occupy the
fall months in reaching the parallels indicated. These waters,
though cold, and rising gradually in temperature as they flow
south, are probably fresher, and if so, probably lighter than the
sea water ; and therefore it may well be that both the warmer
and cooler systems of these isothermal lines are made to vibrate
up and down the ocean principally by a gentle surface current in
the season of quick motion, and in the season of the slow motion
principally by a gradual process of calorific absorption on the
one hand, and by a gradual process of cooling on the other. We
have precisely such phenomena exhibited by the waters of the
Chesapeake Bay as they spread themselves over the sea in winter.
At this season of the year, the charts show that water of very
low temperature is found projecting out and overlapping the
usual limits of the Gulf Stream. The outer edge of this cold
water, though jagged, is circular in its shape, having its centre
near the mouth of the bay. The waters of the bay, being fresher

2 0

386 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

than those of the sea, are therefore, though colder, yet lighter
(§ 426) than the warmer waters of the ocean. And thus we have
repeated here, though on a smaller scale, the phenomena as to
the flow of cold waters from the north, M^hich force the surface
isotherm of 60"^ from latitude 56° to the parallel of 40° during
three or four months. Changes in the colour or depth of the
water, and the shape of the bottom, etc., are also calculated to
cause changes in the temperature of certain parts of the ocean,
by increasing or- diminishing the capacities of such parts to
absorb or radiate heat ; and this, to some extent, assists to bend
or produce irregular curves in the isothermal lines. After a
careful study of this plate, and the Thermal Charts of the
Atlantic Ocean, from which the materials for it are derived, I
am led to infer that from January to August the mean tempera-
ture of the atmosphere between the parallels of 56° and 40° north,
for instance, and over that part of the ocean in which we have
jcen considering the fluctuations of the isothermal line of 60°, is
at least 60° of Fahrenheit, and upward, and that the heat which
the waters of the ocean derive from this source — atmospherical
contact and radiation — is one of the causes which move the
isotherm of 60° from its January to its September parallel. It
is well to consider another of the causes which are at work upon
the currents in this part of the ocean, and which tend to give the
rapid southwardly motion to the isotherm of 60°. We know the
mean dew-point must always be below the mean temperature of
any given place, and that, consequently, as a general rule, at sea
the mean dew-point due the isotherm of 60° is higher than
the mean dew-point along the isotherm of 50°, and this, again,
higher than that of 40°, this than 30°, and so on. Now suppose,
merely for the sake of illustration, that the mean dew-point for
each isothei-m be 5° lower than the mean temperature, we should
then have the atmosphere which crosses the isotherm of 60°,
with a mean dew-point of 55°, gradually precipitating its vapours
until it reaches the isotherm of 50°, with a mean dew-point of
45° ; by which difference of dew-point the total amount of pre-
cipitation over the entire zone between the isotherms of 60° and
50° has exceeded the total amount of evaporation from the same
surface. The prevailing direction of the winds to the north of
the fortieth parallel of north latitude is from the southward and
westward (Plate VIII.) ; in other words, it is from the higher to
the lower isotherms. Pa,ssing, therefore, from a higher to a

THE CLIMATES OF THE SEA. 387

lower temperature over the ocean, the total amount of vapour
deposited by any given volume of atmosphere, as it is blown
from the vicinity of the tropical towards that of the j)olar regions,
is greater than that which is taken up again. This is an in-
teresting and important fact.

724. The effects of night and day upon the temperature of sea water.
— Having, therefore, more precipitation in high than in low
latitudes at sea, we should have more clouds ; and therefore it
requires a longer time for the sun, with his feeble rays, to raise
the temperature of the cold water which, from September to
January, has brought the isotherm of 60° from latitude 56° down
to the parallel of 40°, than it did for those cool surface currents
to float it down. After this southwardly motion of the isotherm
of 60° has been checked in December by the cold, and after the
sources of the current which have brought it down have been
bound in fetters of ice, it pauses in the long nights of the northern
winter, and scarcely commences its return till the sim recrosses
the equator, with increased powers both as to intensity and
duration. Thus, in studying the physical geography of the sea,
we must take cognizance of its actinometry also, for here we
have the effects of night and day, of clouds and sunshine, upon
its currents and its climates, beautifully developed. These effects
are modified by the operations of certain powerful agents which
reside upon the land ; nevertheless, feeble though those of the
former class may be, a close study of this plate will indicate that
they surely exist.

725. A belt of uniform temperature at sea, — Now, returning
towards the south : we may, on the other hand, infer that the
mean atmospherical temperature for the parallels between which
the isotherm of 80° fluctuates is below 80°, at least for the nine
months of its slow motion. This vibratory motion suggests the
idea that there is probably, somewhere between the isotherm of
80° in August and the isotherm of 60° in January, a line or belt
of invariable or nearly invariable temperature, which extends on
the surface of the ocean from one side of the Atlantic to the
other. This belt or band may have its cycles also, but they are
probably of a long and uncertain period.

726. The western half of the Atlantic warmer than the eastern. — The
fact has been pretty clearly established by the discoveries to
which the wind and current charts have led, that the western
half of the Atlantic Ocean is heated up, not by the Gulf Stream

2 c 2

388 PHYSICAL GEOGEAPHY OF .THE SEA, AND ITS METEOROLOGY.

alone, as is generally supposed, but (§ 131) by the great
equatorial caldron to the west of longitude 35°, and to the north
of Cape St. Eoque, in Brazil. The lowest reach of the 80°
isotherm for September — if we except the remarkable equatorial
flexure (Plate IV.) which actually extends from 40" north to the
line — to the west of the meridian of Cape St. Roque, is above its
liigliest reach to the east of that meridian. And, now that we
have the fact, how obvious, how beautiful, and striking is the
cause! Cape St. Eoque is in 5° 30' south. Now study the
configuration of the Southern American Continent from this cape
to the Windward Islands of the West Indies, and take into
account also certain physical conditions of these regions : the
Amazon, always at a high temperature because it runs from west
to east, is pouring an immense volume of warm water into this
part of the ocean. As this water and the heat of the sun raise
the temperature of the ocean along the equatorial sea-front of
this coast, there is no escape for the liquid element, as it grows
warmer and lighter, except to the north. The land on the south
prevents the tepid waters from sjDreading out in that direction as
they do to the east of 35° west, for here there is a space, about
18 degrees of longitude broad, in which the sea is clear both to
the north and south: they must consequently flow north. A
mere inspection of the plate is sufficient to make obvious the fact
that the warm waters which are found east of the usual limits
assigned the Gulf Stream, and between the parallels of 30° and
40° north, do not come from the Gulf Stream, but from this great
equatorial caldron, which Cape St. Eoque blocks up on the
south, and which dispenses its overheated waters up towards the
fortieth degree of north latitude, not through the Caribbean Sea
and Gulf Stream, but over the broad surface of the left bosom of
the Atlantic Ocean.

727. The warmest sides of oceans and the coldest shores of continents
in juxta-position. — Like the western half of the North Atlantic
Ocean, the western half of every one of the three great oceans is
the warmer. The great flow of warm water in the North Pacific is
with the " Black Stream of Japan," on the Asiatic side ; in the
South Pacific it is with the Polynesian drift, on the Australian
side : opposite to these warm Pacific currents and on its eastern
side, are the Humboldt current in one hemisphere, and the
California current in the other — cold currents both. In the
South Indian Ocean, the warm water is with the Mozambique

THE CLIMATES OF THE SEA. 389

current on tlie African side, and the cold drift on the Australian ;
and in the South Atlantic, Plate IV. shows that, parallel for
parallel, the littoral waters of Brazil are several degrees warmer
than those on the African side. Thus at sea the climatic conditions
of the land are reversed, for the coldest side of the ocean is next
the warmest side of the continent, and vice versa. The winds
from extra-tropical seas temper the climates of the shores upon
which they blow, not so much by the sensible heat they convey
as by the latent heat which is liberated from the vapour they
bring. This being condensed, as upon the British Islands and
Western Europe, sets free heat enough not only to soften the
climate, but to rarefy the air to such an extent as to be observed
in the mean barometric pressure.

728. The climates of Europe influenced hy the shore-lines of Brazil.
— Here we are again tempted to pause and admire the beautiful
revelations which, in the benign system of terrestrial adaptations,
these researches into the physics of the sea unfold and spread out
before us for contemplation. In doing this, we shall have a free
pardon from those at least who delight " to look through nature
up to nature's God." What two things in nature can be appa-
rently more remote in their physical relations to each other than
the climate of Western Europe and the profile of a coast-line in
South America ? Yet this plate reveals to us not only the fact
that these relations between the two are most intimate, but
makes us acquainted with the arrangements by which such
relations are established. The barrier which the South American
shore-line opposes to the escape, on the south, of the hot waters
from this great equatorial caldron of St. Eoque, causes them to
flow north, and in September, as the winter approaches, to heat
up the western half of the Atlantic Ocean, and to cover it, as far
up as the parallel of 40° N., with a mantle of warmth above
summer heat. Here heat to temper the winter climate of
Western Europe is stored away as in an air-chamber to furnace-
heated apartments ; and during the winter, when the fi]e of the
solar rays sinks down, the westwardly w^inds and eastwardly
currents are sent to perform their office in this benign arrange-
ment. Though unstable and capricious to us they seem to be,
they nevertheless " fulfil His commandments " with regularity
and perform their offices with certainty. In tempering the
climates of Europe with heat in winter that has been bottled
away in the waters of the ocean during summer, these winds and

390 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

currents are to be regarded as the flues and regulators for dis-
tributing it at the right time, and at the right places, in the right
quantities. By March, when " the winter is past and gone," the
furnace which had been started by the rays of the sun in the
previous summer, and which, by autumn, had heated up the
ocean in our hemisphere, has cooled down. The caldron of St.
Eoque, ceasing in activity, has failed in its supplies, and the
chambers of warmth upon the northern sea, having been exhausted
of their heated water (which has been expended in the manner
already explained), have contracted their limits. The surface of
heated water which, in September, was spread out over the
western half of the Atlantic, from the equator to the parallel of
40° north, and which raised this immense area to the temperature
of 80° and upward, is not to be found in early spring on this side
of the parallel of 8° north. The isotherm of 80° in March, after
quitting the Caribbean Sea, runs parallel with the South American
coast towards Cape St. Eoque, keeping some 8 or 10 degrees from
it. Therefore the heat dispensed over Europe from this caldron
falls off in March. But at this season the sun comes forth with
fresh supplies ; he then crosses the line and passes over into the
northern hemisphere; observations show that the process of
heating the water in this great caldron for the next winter is
now about to commence. In the mean time, so benign is the
system of cosmical arrangements, another process of raising the
temperature of Europe commences. The land is more readily
impressed than the sea by the heat of the solar rays; at this
season, then, the summer climate due these transatlantic latitudes
is modified b}' the action of the sun's rays directly upon the
land. The land receives heat from them, but, instead of having
the capacity of water for retaining it, it imparts it straightway
to the air ; and thus the proper climate, because it is the climate
which the Creator has, for his own wise purposes, allotted to this
portion of the earth, is maintained until the marine caldron of
( 'ape St. Eoque and the tropics is again heated and brought into
die state for supplying the vapour and the heat to maintain the
needful temperature in Europe during the absence of the sun in
the other hemisphere. Thus the equable climates of Western
Europe are accounted for,

729. Tlte Gulf of Guinea and the climate of Patagonia. — In like
irianner, the Gulf of Guinea forms a caldron and a furnace, and
spreads out over the South Atlantic an air-chamber for heating

THE CLIMATES OF THE SEA. 393

np in winter and assisting to keep warm the extra-tropical region&i
of South America. Every traveller has remarked upon the mild
climate of Patagonia and the Falkland Islands. " Temperature
in high sonthern latitudes," says a very close observer, w^ho is
co-operating with me in collecting materials, " differs greatly
from the temperature in northern. In southern latitudes there
seem to be no extremes of heat and cold, as at the north. New-
port, Khode Island, for instance, latitude 41" north, longitude
71° west, and Kio Negro, latitude 41° south, and longitude 63°
west, as a comparison : in the former, cattle have to be stabled
and fed during the winter, not being able to get a living in the
fields on account of snow and ice. In the latter, the cattle feed
in the fields all winter, there being plenty of vegetation and no
use of hay. On the Falkland Island (latitude 51-2° south),
thousands of bullocks, sheep, and horses are running wild over
the country, gathering a living all through the winter." The
water in the equatorial caldron of Guinea overflows to the south,
as that of St. Eoque does to the north ; it carries to Patagonia
and the Falkland Islands warmth, which, uniting with the heat
set free by precipitation during the passage of the vapour-laden
west winds across the Southern Andes, carries beyond latitude
50° into the other hemisphere the winter climate of South
Carolina on one side of the North "Atlantic, or of the "Emerald
Island " on the other.

730. Shore-lines. — All geographers have noticed, and philo-
sophers have frequently remarked upon the conformity as to the
shore-line profile of equatorial America and equatorial Africa.
It is true, we cannot now tell the reason, though explanations
founded upon mere conjecture have been offered, why there
should be this sort of jutting in and jutting out of the shore-line,
as at Cape St. Roque and in the Gulf of Guinea, on opposite
sides of the Atlantic ; but one of the purposes, at least, which
this peculiar configuration was intended to subserve, is without
doubt now revealed to us. We see that, by this configuration,
two cisterns of hot water are formed in this ocean, one of which
distributes heat and warmth to western Europe ; the other, at
the opposite season, helps to temper the climate of eastern Pata-
gonia. Phlegmatic must be the mind that is not impressed with
ideas of grandeur and simplicity as it contemplates that exquisite
design, those benign and beautiful arrangements, by whicli the
climate of one hemisphere is made to depend upon the curve of that

392 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

line against which the sea is made to dash its waves in the other.
Impressed with the perfection of terrestrial adaptations, he who
studies the economy of the great cosmical arrangements is re-
minded that not only is there design in giving shore-lines their
profile, the land and the water their proportions, and in placing
the desert and the pool where they are, but the conviction is
forced upon him also that every hill and valley, with the grass
upon its sides, is a part of the wonderful mechanism, each having
its offices to perform in the grand design. March is, in the
southern hemisphere, the first month of autumn, as September is
with us ; consequently, we should expect to find in the South
Atlantic as large an area of water at 80° and upwards in March,
as we should find in the Korth Atlantic for September. But do
we ? By no means. The area that is covered on this side of the
equator with water at 80° and upwards is nearly double that on
the other. Thus we have the sea as a witness to the fact which
the winds had proclaimed, viz., that summer in the northern
hemispheie is hotter than summer in the southern.

731. Sudden changes in the water thermometer. — Pursuing the
study of the climates of the sea, let us now turn to Plate VI.
Here we see at a glance how the cold waters, as they come down
from the Arctic Ocean through Davis' Straits, press upon the
warm waters of the Gulf Stream, and curve their channel into a
horse-shoe. Navigators have often been struck with the great
and sudden changes in the temperature of the water hereabouts.
In the course of a single day's sail in this part of the ocean,
changes of 15°, or 20°, and even of 30°, have been observed to
take place in the temperature of the sea. The cause has puzzled
navigators long, but how obvious is it now made to appear !
This " bend " is the great receptacle of the icebergs which drift
down from the north ; covering frequently an area of hundreds of
miles in extent, its waters differ as much as 20°, 25°, and in rare
cases even as much as 30° of temperature from those about it.
Its shape and place are variable. Sometimes it is like a peninsula,
or tongue of cold water projected far down into the waters of
the Gulf Stream. Sometimes the meridian upon which it is in-
serted into these is to the east of 40°, sometimes to the west of
50°. On my passage to England November, 1860, I passed
over this horse-shoe ; the water in it was 1 6° colder than the
water at its side. It looked as though we might have been on
soundings.

THE CLIMATES OF THE SEA. 393

732. TJiefogs of Newfoundland. — By its discovery we have clearly
unmasked the very seat of that agent which prodiices the New-
foundland fogs. It is spread out over an area frequently em-
bracing several thousand square miles in extent, covered with
cold water, and surrounded on three sides at least with an im-
mense body of warm. May it not be that the proximity to each
other of these two very unequally heated surfaces out upon the
ocean would be attended by atmospherical phenomena not unlike
those of the land and sea breezes ? These warm currents of the
sea are powerful meteorological agents. I have been enabled to
trace in thunder and lightning the influence of the Gulf Stream
in the eastern half of the Atlantic as far up as the parallel of 55°
X., for there, in the dead of winter, a thunder-storm is not un-
usual.

783. Aqueous isothermal lines. — These isothermal lines of 50°,
60°, 70°, 80°, etc., may illustrate for us the manner in which the
climates in the ocean are regulated. Like the sun in the ecliptic,
they travel up and down the sea in declination, and serve the
monsters of the deep for signs and for seasons.

734. The meeting of cool and warm waters. — It should be borne
in mind that the lines of separation, as drawn on Plate IX.,
between the cool and warm waters, or, more properly speaking,
between the channels representing the great polar and equatorial
flux and reflux, are not so sharp in nature as this plate would
represent them. In the first place, the plate represents the mean
or average limits of these constant flows — polar and equatorial ;
whereas, with almost every wind that blows, and at every change
of season, the line of meeting between their waters is shifted.
In the next place, this /ine of meeting is drawn with a free hand
on the plate, as if to represent an average ; whereas there is
reason to believe that this line in nature is variable and unstable
as to position, and as to shape rough and jagged, and oftentimes
deeply articulated. In the sea, the line of meeting between
waters of different temperatures and density is not unlike the
sutures of the skull-bone on a grand scale — very rough and
jagged ; but on the plate it is a line drawn simply with a free
hand, merely for the purpose of illustration.

735. The direction of aqueous isotherms on opposite sides of the sea.
— Now, continuing for a moment our examination of Plate IV.,
we are struck with the fact that most of the thermal lines there
drawn run from the western side of the Atlantic towards the

394 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGT.

eastern, in a nortli-eastwardly direction, and that, as they ap-
preach the shores of this ocean on the east, they again turn down
for lower latitudes and wanner climates. This feature in them
indicates, more surely than any direct observations upon the
currents can do, the presence, along the African shores in the
Korth Atlantic, of a large volume of cooler waters. These are
the waters which, having been first heated up in the caldron
(.§ 726) of St. Eoque, in the Caribbean Sea, and Gulf of Mexico,
have been made to run to the north, charged with heat and
electricity to temper and regulate climates there. Having per-
formed their offices, they have cooled down ; but, obedient still
to the "Mighty Yoice" which the winds and the waves obey,
they now return by this channel along the African shore to be
again replenished with warmth, and to keep up the system of
beneficent and wholesome circulation designed for the ocean.

CHAPTER XYIII.

§ 740-772. TIDE-PvIPS AND THE SEA DRIFT.

740. Tlie glories of the sea, and the destiny of the nautilus. — We
never tire of the sea ; like the atmosphere, it is a laboratory in
which wonders by processes the most exquisite are continually
going on. Its flora and its fauna, its waves and its tides, its currents
and its salts, all in themselves afford profitable subjects of study
and charming themes for thought. But as interesting as they are
individually, and as marvellous too, they are not half so mar-
vellous, nor nearly so wonderful as the offices which, with their
aid, the sea performs in the physical economy of our planet. In
this aspect the sea, with its insects, its salts, and its vapours, is a
machine of the most beautiful construction. Its powers are vast,
multitudinous, and varied. It is so stable and true in its work
that nothing can throw it out of gearing, and yet its compensa-
tions are so delicate that the task of preserving them is assigned
to the tiniest of its inhabitants, and to agents apparently the
most subtle and fickle. They preserve its harmonies and make
its adjustments, in beauty and sublimity of effect, to vie w^ith
the glories of the heavens. Take the tiny little nautilus, one of
the oldest families in the sea, for example. Where, inquires
M. Lucien Dubois, do they go in such fleets with their purple

TIDE-RIPS AND SEA DRIFT. 395

sails SO nicely trimmed to the breeze ? Who pilots them, and
what master hand holds the helm ? What compass, and of whose
workmanship, is that which guides these delicate and graceful
little argonauts from sea to sea? i^rriving off the "Stormy
Capes," the flotilla is separated, one division holding its way for
the Pacific, the other hauling up for the Atlantic, each bound on
its high and secret mission. They build, equip, and repair as
they go ; the fleet is imperishable, but individual life in it is
ephemeral. They die, these tiny " men o' war," one after another,
but the same watchful Providence that cared for them while
living, now provides for their burial being dead. The inanimate
shell, drawn to distant seas by under currents, descends like
autumnal leaves from depth to depth by an insensible fall. In
future times the seaman's sounding-rod may reach the bottom on
which it has fallen, and thus reveal to man the secret paths of
the sea, — or when the geological clock next strikes the hour, the
same little shell may, by some throe of nature, be brought up to
the surface, and spread out in its marl bed, to fertilize and make
fruitful unknown lands.

741. Drift described. — There is a movement of the waters of
the ocean which, though it be a translation, yet it does not
amount to what is known to the mariner as " current," for our
nautical instruments and the art of navigation have not been
brought to that state of perfection which will enable navigators
generally to detect as currents the flow to which I allude as drift.
If an object be set afloat in the ocean, as at the equator, it would,
in the course of time, even though it should not be caught up by
any of the known currents, find its way to the icy barriers about
the poles, and again back among the tepid waters of the tropics.
Such an object would illustrate the drift of the sea, and by its
course would indicate the route which the surface-waters of the
sea follow in their general channels of circulation to and fro
between the equator and the poles.

742. Flate IX. — The object of Plate IX., therefore, is to illus-
trate, as far as the present state of my researches enable me to do,
the circulation of the ocean as influenced by heat and cold, and
to indicate, on one hand, the routes by which the overheated
waters of the torrid zone escape to cooler regions, and to point
out, on the other, the great channel-ways through which the
same waters, after having been deprived of this heat in the extra-
tropical or polar regions, return again towards the equator : it

396 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

being assnmed that the drift or flow is from the poles when the
temperature of the surface water is helow, and from the equatorial
reirions when it is above that due the latitude. Therefore, in a
mere diagram, as this plate is, the numerous eddies and local
currents which are found at sea are disregarded. Of all the
currents in the sea, the Gulf Stream is the best defined ; its limits,
especially those of the left bank, are alwa^^s well marked, and as
a rule, those of the right bank, as high as the parallel of the
thirty-fifth degree of latitude, are quite distinct, being often
visible to the eye. The Gulf Stream shifts its channel (§ 124),
but nevertheless its banks are often very distinct. Ships, in
crossing the edges of it, can sometimes know it by the colour of
the water ; at other times they find, as they pass along, the
temperature of the water to change 8° or 10° in the course of as
many minutes ; as an example of this, I quote from the abstract
log of the " Herculean," in which Captain William M. Chamber-
lain, being in latitude 33° 39' north, longitude 74° 56' west (about
one hundred and thirty miles east of Cape Fear), remarks :
" Moderate breezes, smooth sea, and fine weather. At ten o'clock
fifty minutes, entered into the southern (right) edge of the
Stream, and in eight minutes the water rose six degrees ; the
edge of the stream was visible, as far as the eye could see, by
the great rippling and large quanties of Gulf weed — more ' weed '
than I ever saw before, and I have been many times along this
route in the last twenty years." In this diagram, therefore, I
have thought it useless to attempt a delineation of any of those
currents, as the Kennell Current of the North Atlantic, the
"connecting current" of the South, "Mentor's Counter Drift,"
" Eossel's Drift of the South Pacific," etc., which run now this
way, now that, and which are frequently not felt by navigators
at all. In overhauling the log-books for data for this chart, I
have followed vessels with the water thermometer to and fro
across the seas, and taken the registrations of it exclusively for
my guide, without regard to the reported set of the currents.
When, in any latitude, the temperature of the water has appeared
too high or too low for the latitude, the inference has been that
such water was warmed or cooled, as the case may be, in other
latitudes, and that it has been conveyed to the place where found
through the great channels of oceanic circulation. If too warm,
it is supposed that it had its temperature raised in warmer
latitudes, and therefore the channel in which it is found leads

TIDE-EIPS AND SEA DRIFT. 397

from the equatorial regions. On the other hand, if the water be
too cool for the latitude, then the inference is that it has lost its
heat in colder climates, and therefore is found in channels which
lead from the polar regions. The arrow-heads point to the
direction in which the waters are supposed to flow. Their rate,
according to the best information that I have obtained, is, at a
mean, only about four knots a day — rather less than more.
Accordingly, therefore, as the immense volume of water in the
antarctic regions is cooled down, it commences to flow north.
As indicated by the arrow-heads, it strikes against Cape Horn,
and is divided by the continent, one portion going along the
west coast as Humboldt's Current (§ 398) ; the other, entering the
South Atlantic, flows up into the Gulf of Guinea, on the coast of
Africa. Now, as the waters of this polar flow approach the torrid
zone, they grow warmer and warmer, and finally themselves
become tropical in their temperature. They do not then, it may
be supposed, stop their flow ; on the contrary, they keep moving,
for the very cause which brought them from the extra- tropical
reo-ions now operates to send them back. This cause is to be
found in the difference of the specific gravity at the two places.
If, for instance, these waters, when they commence their flow
from the hyperborean regions, were at 30°, their specific gravity
will correspond to that of sea water at 30°. But when they
arrive in the Gulf of Guinea or the Bay of Panama, having risen
by the way to 80°, or perhaps 85°, their specific gravity becomes
such as is due to sea water of this temperature ; and, since fluids
differing in specific gravity can no more balance each other on
the same level than can unequal weights in the opposite scales of
a true balance, this hot water must now return to restore that
equilibrium which it has destroyed in the sea by rising from 30°
to 80° or 85°. Hence it will be perceived that these masses of
water which are marked as cold are not always cold. They
gradually pass into warm ; for in travelling from the poles to the
equator they partake of the temperature of the latitudes through
which they flow, and grow warm. Plate IX., therefore, is only
introduced to give general ideas; nevertheless, it is very in-
structive. See how the influx of cold water into the South
Atlantic appears to divide the warm water, and squeeze it out at
the sides, along the coasts of South Africa and Brazil. So, too,
in the North Indian Ocean, the cold water again compelling the
warm to escape along the land at the sides, as well as occasionally

398 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

in the middle. In the Korth Atlantic and North Pacific, on the
contrary, the warm water appears to divide the cold, and to
squeeze it out along the land at the sides. The impression made
by the cold current from Baffin's Ba}^ upon the Gulf Stream is
strikingly beautiful.

743. Ihe great hend in the Gulf Stream. — Another feature of the
sea expressed by this plate is a sort of reflection or recast of the
shore-line in the temperature of the water. This feature is most
striking in the North Pacific and Indian Oceans. The remark-
able intrusion of the cool into the volume of warm waters to the
southward of the Aleutian Islands is not unlike that (§ 731)
which the cool waters from Davis' Straits make in the Atlantic
upon the Gulf Stream. In sailing through this " horse-shoe," or
bend in the Gulf Stream (§ 731), Captain N. B. Grant, of the
American ship " Lady Arbeila," bound from Hamburgh to New
York, in May, 1854, passed, from daylight to noon, twenty-four
large " bergs," besides several small ones, "the whole ocean, as
far as the eye could reach, being literally covered with them. I
should," he continued, "judge the average height of them above
the surface of the sea to be about sixty feet ; some five or six of
them were at least twice that height, and, with their frozen peaks
jutting up in the most fantastic shapes, presented a trul}^ sublime
spectacle."

744. TJie horseshoe in the Japan current. — The " horse-shoe " of
cold in the warm water of the North Pacific, though extending
5 degrees farther towards the south, cannot be the harbour for
such icebergs. The cradle of those of the Atlantic was perhaps
in the Frozen Ocean, for they may have come thence through
Baffin's Bay. But in the Pacific there is no nursery for them.
The water in Behring's Strait is too shallow to let them pass
from that ocean into the Pacific, and the climates of Eussian
America do not favour the formation of large bergs. But,
though we do not find in the North Pacific the physical con-
ditions which generate icebergs like those of the Atlantic, we
find them as abundant with fogs. The line of separation between
the warm and cold water assures us of these conditions.

745. The animalculce of the sea. — What beautiful, grand, and
benign ideas do we not see expressed in that immense body of
warm waters which are gathered together in the middle of tlie
Pacific and Indian Oceans ! It is the womb of the sea. In it
coral islands innumerable have been fashioned, and pearls formed

TIDE-HIPS AND SEA DRIFT. 399

in " great heaps ;" there multitudes of living things, countless in
numbers and infinite in variety, are hourly conceived. With
space enough to hold the four continents and to spare, the tepid
waters of this part of the ocean teem with nascent organisms.*
They sometimes swarm so thickly there that they change the
colour of the sea, making it crimson, brown, black, or white,
according to their own hues. These patches of coloured water
sometimes extend, especially in the Indian Ocean, as far as the
eye can reach. The question, " What produces them ?" is one
that has elicited much discussion in seafaring circles. The
Brussels Conference deemed them an object worthy of attention,
and recommended special observations with regard to them.

746. Coloured patches. — Capt. W. E. Kingman, of the American
clipper ship the " Shooting Star," reports in his abstract log a
remarkable white patch, which he encountered in lat. 8° 4-6' S.,
long. 105° 30' E., and which, in a letter to me, he thus describes:
" Thursday, July 27, 1854. At 7h. 45m. p.m., my attention was
called to notice the colour of the water, which was rapidly grow-
ing white. Knowing that we were in a much frequented part of
the ocean, and having never heard of such an appearance being
observed before in this vicinity, I could not account for it. I
immediately hove the ship to and cast the lead ; had no bottom
at 60 fathoms. I then kept on our course, tried the water by
thermometer, and found it to be 78|-°, the same as at 8 a.m. "VVe
filled a tub, containing some sixty gallons, with the water, and
found that it was filled with small luminous particles, which,
when stirred, presented a most remarkable appearance. The
whole tub seemed to be active with worms and insects, and
looked like a grand display of rockets and serpents seen at a
great distance in a dark night ; some of the serpents appeared to
be six inches in length, and very luminous. We caught, and
could feel them in our hands, and they would emit light until
brought within a few feet of a lamp, when, upon looking to see
what we had, behold, nothing was visible ; but, b}^ the aid of a

* " It is the realm of reef-building corals, and of the wondrously-beautiful
assemblage of animals, vertebrate and invertebrate, that live among them or
prey npon them. The brightest and most definite arrangements of colour are
here displayed. It is the seat of maximum development of the majority of
marine genera. It has but few relations of identity with other provinces. The
Eed Sea and Persian Gulf are its offsets." — From Professor Forbes's Paper
on the " Distribution of Marine Life." Plate 31st, Johnston' Physical Atlas,
2nd ed. ; Wm. Blackwood and Sons, Edinburgh and London, 1854.

400 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

sextant's magnifier, we could plainly see a jelly-like substance
without colour. At last a specimen was obtained of about two
inches in length, and plainly visible to the naked eye ; it was
about the size of a large hair, and tapered at the ends. By
bringing one end within about one-fourth of an inch of a lighted
lamp, the flame was attracted towards it, and burned with a red
light ; the substance crisped in burning something like a hair,
or appeared of a red heat before being consumed. In a glass of
the water there were several small round substances (say j^^^th
of an inch in diameter), which had the power of expanding to
more than twice their ordinary size, and then contracting again ;
when expanded, the outer rim appeared like a circular saw, only
that the teeth pointed towards the centre. This patch of white
water was about 23 miles in length, north and south, divided
near its centre by an irregular strip of dark water half a mile
wide ; its east and west extent I can say nothing about. I have
seen what is called white water in about all the known oceans
and seas in the world, but nothing that would compare with this
in extent or whiteness. Although we were going at the rate of
nine knots, the ship made no noise either at the bow or stern.
The whole appearance of the ocean was like a plain covered
with snow. There was scarce a cloud in the heavens, yet the
sky, for about ten degrees above the horizon, appeared as black
as if a storm was raging ; the stars of the first magnitude shone
with a feeble light, and the ' Milky Way ' of the heavens was
almost entirely eclipsed by that through which we were sailing.
The scene was one of awful grandeur ; the sea having turned to
phosphorus, and the heavens being hung in blackness, and the
stars going out, seemed to indicate that all nature was preparing
for that last grand conflagration which we are taught to believe
is to annihilate this material world. After passing through the
patch, we noticed that the sky, for four or five degrees above the
horizon, was considerably illuminated, something like a faint
aurora borealis. We soon passed out of sight of the whole con-
cern, and had a fine night, without any conflagration (except
of midnight oil in trying to find out what was in the water). I
send you this because I believe you request your corps of ' one
thousand assistants ' to furnish you with all such items, and I
trust it will be acceptable. But as to its furnishing you with
much, if any, information relative to the insects or animals that
inhabit the mighty deep, time will only tell ; I cannot think it wilL"

TIDE-EIPS AND SEA DRIFT. 4(U

74-7. Whence the Bed Sea derives its name. — These discolonra-
tions are no doubt caused by organisms of the sea, but whether
wholly animal or wholly veget-able, or whether sometimes the
one and sometimes the other, has not been satisfactorily ascer-
tained. I have had specimens of the colouring matter sent to me
from the pink-stained patches of the sea. They were animalculee
well defined. The tints which have given to the Eed Sea its
name may perhaps be in some measure due to agencies similar to
those which, in the salt-makers' ponds, give a reddish cast (§ 71)
to the brine just before it reaches that point of concentration
when crystallization is to commence. Some microscopists main-
tain that this tinge is imparted by the shells and other remains
of infusoria which have perished in the growing saltness of the
water. The Eed Sea may be regarded, in a cei-tain light, as the
scene of natural salt-works on a grand scale. The process is by
solar evaporation. No rains interfere, for that sea (§ 376) is in a
riverless district, and the evaporation goes on unceasingly, day
and night, the year round. The shores are lined with incrusta-
tions of salt, and the same causes which tinge with red (§71) the
brine in the vats of the salt-makers probably impart a like hue
to the arms and ponds along the shore of this sea. Quantities,
also, of slimy, red colouring matter are, at certain seasons of the
year, washed up along the shores of the Red Sea, which Dr.
Ehrenberg, after an examination under the microscope, pro-
nounces to be a very delicate kind of sea-weed : from this matter
that sea derived its name. So also the Yellow Sea. Along the
coasts of China, yellowish-coloured spots are said not to be
•uncommon. I know of no examination of this colouring matter,
however. In the Pacific Ocean I have often observed these dis-
colourations of the sea. Eed patches of water are most frequently
met with, but I have also observed white or milky appearances,
Avhich at night I have known greatly to alarm navigators by their
being taken for shoals.

748. The escape of warm waters from the Pacific. — These teeming
waters bear off through their several channels the surplus heat
of the tropics, and disperse it among the icebergs of the Antarctic.
See the immense equatorial flow to the east of Australia, and
which I have called the Polynesian Drift. It is bound for the
icy barriers of that unknown sea, there to temper climates, grow
cool, and return again, refreshing man and beast by the way,
either as the Humboldt current, or the ice-bearing current which

2 D

402 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

enters the Atlantic around Cape Horn, and changes into warm
again as it enters the Gulf of Guinea. It was owing to this
gi'eat southern flow from the coral regions that Captain Eoss
w^as enabled to penetrate so much farther south than Captain
Wilkes on his voyage to the Antarctic. The ISorth Pacific,
except in the narrow passage between Asia and America, is closed
to the escape of these warm waters into the Arctic Ocean. The
only outlet for them is to the south. They go down towards the
antarctic regions to dispense their heat and get cool ; and the
cold of the Antarctic, therefore, it may be inferred, is not so
bitter as is the extreme cold of the Frozen Ocean of the north.

749. Ditto from the Indian Ocmw.— The warm flow to the south
from the middle of the Indian Ocean is remarkable. Masters
who return their abstract logs to me mention sea- weed, which I
suppose to be brought down by this current, as far as 45" south.
There, it is generally, but not always, about 5 degrees warmer
than the ocean along the same parallel on either side.

750. A wide current. — But the most unexpected discovery of all
is that of the warm flow along the west coast of South Africa, its
junction with the Lagulhas current, called, higher np, the Mozam-
bique, and then their starting off as one stream to the southward.
The prevalent opinion used to be that the Lagulhas current,
which has its genesis in the Eed Sea (§ 390), doubled the Cape
of Good Hope, and then joined the great equatorial current of the
Atlantic to feed the Gulf Stream. But my excellent friend,
Lieutenant Marin Jansen, of the Dutch Navj^-, suggested that
this was probably not the case. This induced a special investi-
gation, and I found as he suggested, and as is represented on
Plate IX. Captain K. B. Grant, in the admirably well-kept
abstract log of his voyage from New York to Australia, found
this current remarkably developed. He was astonished at the
temperature of its waters, and did not know how to account for
such a body of warm water in such a place. Being in longitude
14" east, and latitude 39° south, he thus writes in his abstract
log : " That there is a current setting to the eastward across the
South Atlantic and Indian Oceans is, I believe, admitted by all
navigators. The prevailing westerly winds seem to offer a suffi-
cient reason for the existence of such a current, and the almost
constant south-west swell would naturally give it a northerly
direction. But why the water should be luarmer here (38° 40'
south; than between the parallels of 35° and 37° south, is a pro-

TIDE-EIP3 AND SEA DRIFT. 403

blem that, in my mind, admits not of so easy solution, especially
if my suspicions are true in regard to the northerly set. I shall
look with much interest for a description of the ' currents ' in
this part of the ocean." In latitude 38° south, longitude 6° east,
he found the water at 56°. His course thence was a little to the
south of east, to the meridian of 41° east, at its intersection with
the parallel of 42° south. Here his water thermometer stood at
50°, but between these two places it ranged at 60° and upward,
being as high on the parallel of 39° as 73°. Here, therefore,
was a stream — a mighty " river in the ocean " — one thousand six
hundred miles across from east to west, having water in the
middle of it 23° higher than at the sides. This is truly a Gulf
Stream contrast. What an immense escape of heat from the
Indian Ocean, and what an influx of warm water into the frozen
regions of the south ! This stream is not always as broad nor
as warm as Captain Grant found it. At its mean stage it conforms
more nearly to the limits assigned it in the diagram (Plate IX.).

751. Commotions in the sea. — Instances of commotions in the
sea at uncertain intervals are not unfrequent. There are some
remarkable disturbances of the sort which I have not been able
wholly to account for. Kear the equator, and especially on this
side of it in the Atlantic, mention is made, in the "abstract log,"
by almost every observer that passes that way, of " tide-rips,"
which are a commotion in the water not unlike that produced by
a conflict of tides or of other powerful currents. These " tide-
rips " sometimes move along with a roaring noise, like rifts over
rocks in rivers, and the inexperienced navigator always expects
to find his vessel drifted by them a long way out of her course ;
but when he comes to cast up his reckoning the next day at noon,
he remarks with surprise that no current has been felt.

752. Humboldt's description of tide-rips. — Tide-rips present their
most imposing aspect in the equatorial regions. Humboldt met
some in 34° N., and thus describes them : " When the sea is per-
fectly calm, there appear on its surface narrow belts, like small
rivulets, and in which the water runs with a noise very percep-
tible to the ear of an experienced pilot. On the 15th of June, in
about 34° 36' N., we found ourselves in the midst of a great
number of these belts of currents ; we were able to determine
their direction by the compass. Some were flowing to the iN .E. ;
others E.N.E., although the general motion of the ocean, indi-
cated by a comparison of the log and the longitude by chrono-

2 D 2

404 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY

meter, continued towards the S.E." It is very common to see a
mass of motionless water crossed by ridges of water which run in
different directions. This phenomena may be observed every
day on the surface of our lakes ; but it is more rare to find par-
tial movements impressed by local causes on small portions of
water in the midst of an oceanic river occupying an immense
space, and moving in a constant direction, although with an
inconsiderable velocity. In this conflict of currents, as in the
oscillation of waves, our imagination is struck with these move-
ments, which seem to penetrate each other, and by which the
ocean is incessantly agitated.

753. Horsburgh's.—HoTshurgh, in his East India Directory,
thus remarks on them, when speaking of the north-east monsoon
about Java : " In the entrance of the Malacca Straits, near the
Nicobar and Acheen Islands, and between them and Junksey-
Ion, there are often very strong ripplings, particularly in the
south-west monsoon ; these are alarming to persons unacquainted,
for the broken water makes a great noise when the ship is pass-
ing through the ripplings in the night. In most places ripplings
are thought to be produced by strong currents, but here they are
frequently seen when there is no perceptible current. Although
there is no perceptible current experienced so as to produce an
error in the course and distance sailed, yet the surface of the
water is impelled forward by some undiscovered cause. The
ripplings are seen in calm weather approaching from a distance,
and in the night their noise is heard a considerable time before
they come near. They beat against the sides of a ship with
great violence, and pass on, the spray sometimes coming on deck ;
and a small boat could not always resist the turbulence of these
remarkable ripplings."

754. Tide-rij}S in the Atlantic. — Captain Higgins, of the " Maria,"
when bound from New York to Brazil, thus describes, in his
abstract log, one of these " tide-rips," as seen by him, 10th
October, 1855, in N. lat. 14°, W. long. 34°: "At 3 p.m. saw a
tide-rip ; in the centre, temp, air 80°, water 81°. From the
time it was seen to windward, about three to five miles, until it
had passed to leeward out of sight, it was not five minutes. I
should judge it travelled at not less than sixty miles per hour, or
as fast as the bores of India. Although we have passed through
several during the night, we do not find they have set the ship
to the westward any ; it may be that they are so soon passed

TIDE-RIPS AND SEA DRIFT. 405

that they have no influence on the ship, but they certainly beat
very hard against the ship's sides, and jarred her all over. They
are felt even when below, and will wake one out of sleep."

755. Moch vigias. — Captain Wakeman, of the "Adelaide," in
January, 1856, lat. 11° 21' N., long. 33° 33' W., encountered
" tide-rips " which broke and foamed with such violence that he
took them for breakers or a shoal. They sometimes are most
alarming. Approaching through the stillness of the night with a
roaring noise, and in the shape of tremendous rollers combing
and foaming, they seem to threaten to overwhelm vessel and
crew ; but, breaking over the deck, they pass by, and in a few
moments the sea is as smooth and as unruffled as before. Many
of the " vigias " which disfigure our charts have no other founda-
tion than the foam of a tide-rip. Captain Arquit's log of the
" Comet " gives an account of many tide-rips which he encoun-
tered also in the north-east trade- wind region of the Atlantic.
Thus, November 15, 1855, lat. 7° 34' N., long. 40° 30' W. :
" Many tide-rips, which we had a good opportunity of observing
when becalmed. They came up in ridges as long as the eye
could reach, from all parts of the compass, but mostly from the E.
I examined the ridges very closely, but could not see any fine
drift-matter of any kind, as you can on the ridges of currents in
many parts of the ocean. We have had no currents unless they
have been from different directions, and one counteracting the
other. November 16th, lat. 6° 07' N. : Light winds and plea-
sant. There has been no time since noon to midnight but there
have been tide-rips either in sight or hearing, mostly tending
N.E. and S.W. in long narrow ridges. From 8 p.m. to 9 p.m. the
ocean appeared like a boiling caldron, which we sailed through
for three miles. The bubbling made a loud noise, which we
heard for a long time after we had sailed through it. The ship
had a very singular motion, like striking her keel on a soft
muddy bottom in a short rough sea-way — the same as I have
felt in the harbour of Montevideo. The motion was noticed by
all on board. We have had a current of fifteen miles going west.
I have often noticed tide -rips in this part of the ocean before,
particularly when bound home (for I have never been where 1
am now, bound out, before), and have mentioned them in my
abstract log, but they were different from what we had last night.
The ship would come to and fall off three points without any
reirard to the rudder."

406 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

756. Sores, eagres, and the eartliquake loave of Lisbon. — But, be-
sides tide-rips, bores, and eagres,* there are the sudden dis-
ruptions in the ice which arctic voyagers tell of, the immense
icebergs which occasionally appear in groups near certain

* The bores of India, of the Bay of Fiincly, and the Amazon, are the most
celebrated. They are a tremulous tidal wave, which at stated periods comes
rolling in from the sea, threatening to overwhelm and ingulf everything that
moves on the beach. This wave is described, especially in the Bay of Fundy,
as being many feet high ; and it is said oftenthnes to overtake deer, swine, and
other wild beasts that feed or lick on the beacb, and to swallow them up before
the swiftest of foot among them have time to escape. The swine, as they feed
on mussels at low water, are said to snuff the " bore," either by sound or smell,
and sometimes to dash off to the cliffs at great speed before it rolls on.

The eagre is the bore of Tsien-Tang Kiver. It is thus described by Dr.
Macgowan, in a paper before the Eoyal Asiatic Society, 12 January, 1853, and
as seen by him from the city of Hang-chow, in 1848 : —

" At the upper part of the bay, and about the mouth of the river, the eagre
is scarcely observable ; but, owing to the very gradual descent of the shore,
and the rapidity of the great flood and ebb, the tidal phenomena even here
present a remarkable appearance. Vessels, which a few moments before were
afloat, are suddenly left high and dry on a strand nearly two miles in width,
which the returning wave as quickly floods. It is not until the tide rushes be-
yond the mouth of the river that it becomes elevated to a lofty wave consti-
tuting the eagre, which attains its greatest magnitude opposite the city of Hang-
chow. Generally there is nothing in its aspect, except on the third day of the
second month, and on the eighteenth of the eighth, or at the spring-tide about
the period of the vernal and autmnnal equinoxes, its great intensity being at
the latter season. Sometimes, however, during the prevalence of easterly
winds, on the third day after the sun and moon are in conjunction, or in oppo-
sition, the eagre courses up the river with hardly less majesty tha,n when pay-
ing its ordinary periodical visit. On one of these unusual occasions, when I
was travelling in native costume, I had an opportunity of witnessing it, on
December 14th, 1848, at about 2 p.m.

" Between the river and the city walls, which are a mile distant, dense
suburbs extend several miles along the banks. As the hour of flood-tide ap-
proached, crowds gathered in the streets running at right angles with the
Tsien-Tang, but at safe distances. My position was a terrace in front of the
Tri-Wave Temple, which afibrded a good view of the entire scene. On a
sudden, all traffic in the thronged mart was suspended, porters cleared the front
street of eveiy desci'iption of merchandize, boatmen ceased lading and unlading
their vessels, and put out in the middle of the stream, so that a few moments
sufficed to give a deserted appearance to the busiest part of one of the busiest
cities of Asia. The centre of the river teemed with craft, from small boats to
huge barges, including the gay « flower-boats.' Loud shouting from the fleet
announced the appearance of the flood, which seemed like a glittering white
cable, stretched athwart the river at its mouth, as far down as the eye could
reach. Its noise, compared by Chinese poets to that of thunder, speedily
drvsvned that of the boa'tmen; and as it advanced with prodigious velocity— at

TIDE-EIPS AND SEA DRIFT. 407

latitudes, the variable character of all the currents of the sea—
now fast, now slow (§ 401), now running this way, then that —
all of which may be taken as so many signs of the tremendous
throes which occur in the bosom of the ocean. Sometimes the
sea recedes from the shore, as if to gather strength for a great
rush against its barriers, as it did when it fled back to join with
the earthquake and overwhelm Callao in 1746, and again Lisbon
nine years afterward.

the rate, I should judge, of twenty-five miles an liour— it assumed the appear-
ance of an alabaster wall, or, rather, of a cataract four or five miles across, and
about thhty feet high, moving bodily onward. Soon it reached the advanced
guard of the immense assemblage of vessels awaiting its approach. Knowing
that the bore of the Hooghly, which scarcely deserves mention in connection
with the one before me, invariably overturned boats which were not skilfully
managed, I could not but feel apprehensive for the lives of the floating multi-
tude. As the foaming wall of water dashed impetuously onward, they were
sUenced, all being intensely occupied in keeping thek prows towards the wave
wliich tlireatened to submerge everything afloat ; but they all vaulted as it
were to the summit with perfect safety. The spectacle was of great interest
when the eagre had passed about one hah" way among the craft. On one side
they were quietly reposing on the surface of the um-uffled stream, while those
on the nether portion were pitching and heaving in tumultuous confusion on
the flood ; others were scaling with the agility of salmon the formidable cascade,
■rhis grand and exciting scene was but of a moment's duration ; it passed up
the river in an instant, but from this point with gradually diminishing force,
size, and velocity, until it ceased to be perceptible, which Chinese accounts re-
present to be eighty miles distant from the city. From ebb to flood tide the
change was almost instantaneous ; a slight flood continued after the passage of
the wave, but it soon began to ebb. Having lost my memoranda, I am obliged
to write from recollection. My impression is that the fall was about twenty
feet ; the Chinese say that the rise and fall is sometimes forty feet at Hang-chow.
The maximum rise and fall at spring-tides is probably at the mouth of the river,
or upper part of the bay, where the eagre is hardly discoverable. In the Bay of
Fundy, where the tides rush in with amazing velocity, there is at one place a
rise of seventy feet ; but there the magnificent phenomenon in question does
not appear to be known at all. It is not, therefore, where tides attain their
greatest rapidity, or maximum rise and fall, that this wave is met with, but
where a river and its estuary both present a peculiar configuration.

" Dryden's definition of an eagre, appended in a note to the verse above
quoted from the Threnodia Augustalis, is, 'a tide swelling abqve another tide,'
which he says he had himseh^ observed in the River Trent. Such, according to
Chinese oral accounts, is the character of the Tsien-Tang tides — a wave of con-
siderable height rushes suddenly in from the bay, which is soon followed by one
much larger. Other accounts represent thi-ee successive waves riding in ; hence
the name of the temple mentioned, that of the Three "Waves. Both here and
on the Hooghly I observed but one wave ; my attention, however, was not par-

408 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

757. Rains at sea and their effect upon its equilihrimn. — Few
persons have ever taken the trouble to compute (§ 402) how
much the fall of a single inch of rain over an extensive region in
the sea, or how much the change even of two or three degrees of
temperature over a few thousand square miles of surface, tends
to disturb its equilibrium, and consequently to cause an aqueous
palpitation that is felt from the equator to the poles. Let us
illustrate by an example : The surface of the Atlantic Ocean
covers an area of about twenty-five millions of square miles.
Now let us take one fifth of this area, and suppose a fall of rain
one inch deep to take place over it. This rain would weigh
three hundred and sixty thousand millions of tons ; and the salt
which, as water, it held in solution in the sea, and which, when
that water was taken up as vapour, was left behind to disturb
equilibrium, weighed sixteen millions more of tons, or nearly
twice as much as all the ships in the world could carry at a
cargo each. This rain might fall in an hour, or it might fall in
a day ; but, to occupy what time it might in falling, it is calcu-
lated to exert so much force — which is inconceivably great — in
disturbing the equilibrium of the ocean. If all the water
discharged by the Mississippi Eiver during the j^ear were taken
up in one mighty measure and cast into the ocean at one effort,
it would not make a greater disturbance in the equilibrium of
the sea, than would the supposed rain-fall. ]Sow this is for but
one fifth of the Atlantic, and the area of the Atlantic is about
one fifth of the sea area of the world ; and the estimated fall of
rain was but one inch, whereas the average for the year is
(§ 757) sixty inches ; but we will assume it for the sea to be no
more than thirty inches. In the aggregate, and on an average,
then, such a disturbance in the equilibrium of the whole ocean
as is here supposed occurs seven hundred and fifty times a year,

ticularly directed to this feature of the eaa^re. TJie term should, perhaps, be
more comprehensive, and express ' the instantaneous rise and advance of a tidal
wave ;' the Indian barbarism ' bore ' should be discarded altogether.

" A very shoEt period elapsed between the passage of the eagre and the re-
sumption of trafiic. The vessels were soon attached to the shore again ; women
and children were occupied in gathering articles which the careless or unskilful
had lost in the aquatic mele'e. The streets were drenched with spray, and a
considerable volume of water splashed over the banks into the head of the
grand canal, a few feet distant."' — Vide Transactions of Chinese JBranclt, of the
Royal Asi'tic Society.

TIDE-RIPS AND SEA DRIFT. 409

or at the rate of once in twelve hours. Moreover, when it
is recollected that these rains take place now here, now there ;
that the vapour of which they were formed was taken up at still
other places, we shall be the better enabled to appreciate the
force and effect of these irregular movements in the sea.

758. Ditto of cloud and sunshine. — Between the hottest hour
of the day and the coldest hour of the night there is frequently
a change of four degrees in the temperature of the sea.* Let us,
therefore, the more thoroughly to appreciate those agitations
of the sea which take place in consequence of the diurnal changes
in its temperature, call in the sunshine, the cloud without rain,
wdth day and night, and their heating and radiating processes.
And to make the case as strong as, with truth to nature, we may,
let us again select one fifth of the Atlantic Ocean for the scene
of operation. The day over it is clear, and the sun pours down
his rays with their greatest intensity, and raises the temperature
of the water two degrees. At night the clouds interpose, and
prevent radiation from this fifth, whereas the remaining four
fifths, which are supposed to have been screened by clouds, so as
to cut off the heat of the sun during the da}^ are now looking
up to the stars in a cloudless sky, and serve to lower the tempe-
rature of the surface waters, by radiation, two degrees. Here,
then, is a difference of four degrees, which we will suppose
extends only ten feet below the surface. The total and absolute
change made in such a mass of sea water by altering its tempe-
rature two degrees is equivalent to a change in its volume of
three hundred and ninety thousand millions of cubic feet. And
yet there be philosophers who maintain (§ 123) that evaporation
and precipitation, changes of temperature and saltness, and the
secretions of insects, are not to be reckoned among the current-
producing agents of the sea. That the gentle trade-winds do it
all!

759. Day and night. — Do not the clouds, night and day, now
present themselves to us in a new light? They are cogs, and
pinions, and wheels in that grand and exquisite machinery which
governs the sea, and which, amid all the jarring of the elements,
preserves the harmonies of the ocean.

760. Logs overhauled for help and ice.— The log-books of not
less than 1843 vessels cruising on the polar side of 35° S. have,
by the officers of the Observatory, been overhauled for kelp and

* Vide Admiral Smyth's Memoir of the Mediterranean, p. 125.

4:10 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ice. Of these, 367 (or one in five) mentioned kelp or sea-weed
east of Cape Horn ; 142 n\ention " rock-weed and drift matter "
between the previous meridian and 10° W., and chiefly between
35° and 40° S. " Long kelp " is also found by Australian traders
after passing the Cape of Good Hope ; 146 logs make mention of
it between the meridians of 40° and 120° E. It most abounds
alono' this line, however, between the meridians of 45° and 65°
E., and the parallels of 42° and 48° S. These sargassos are
sketched with a free hand on Plate IX.

761. A sargasso in the South Pacific. — Sea- weed is frequently
mentioned also b}^ the homeward-bound Australian traders on
their way to Cape Horn : this collection has (§ 139) already been
alluded to. It now appears that instead of three, as stated in
former editions of this work, there are really five true sargassos,
as shown on Plate IX.

762. Sea-iveed about the Falkland Islands. — The weedy space,
marked as such, about the Falkland Islands, is probably not a
true sargasso. The sea-weed reported there probabl}^ comes
from the Straits of Magellan, where immense masses of it grow.
These straits are so encumbered with sea-weed that steamers
find great difficulty in making their way through it. It so
encumbers their paddles as to make frequent stoppages necessary.

763. TJie African sargasso. — The sargasso to the west of the
Cape of Good Hope, though small, is perhaps the best defined
of them all. Mention is generally made of it in the logs as
*' rock-weed" and "drift matter." Now when it is recollected
that weeds have been found as frequently, nearly (§ 760), in this
small space as they have been in the large space between the
Cape and Australia, the reader will be able to form a more
correct idea as to the relative abundance of weed in these seas of
weed.

764. Icebergs. — By going far enough south, icebergs may
be foimd on any meridian ; but in searching for them, we can
only look where commerce carries our colleagues of the sea.
Out of the 1843 tracks traced on the polar side of 35° S., only
109 make mention of ice. Few of these went, except in doubling
Cape Horn, beyond the paiallel of 55° S., therefore we have
not been able to track the ice back into the " chambers of the
frost." We can only say that north of 50° antarctic icebergs
most abound between the meridians of 1 5° W. and 55° E.

765. Tlie largest drift farthest.— As a rule, the bergs which aro

TIDE-EIPS AND SEA DRIFT. 411

the largest last longest, and approach nearest to the equator.
Here, then, is the great line of antarctic drift; by studying it
we may perhaps catch a glimmer of light from south polar shores.
These icebergs, be it remembered, have drifted north through a
belt of westerly winds. Their course, therefore, was probably
not due north, but to the east of that rhomb.

766. TJie line of antarctic <in/i(. — Tracing this line of di-ift,
then, backward in a south-westerly direction, it should guide us
to that part of the southern continent where the icebergs have
their principal nursery. This would take us to the sources of
the Humboldt current, and seem to indicate that these glaciers
are launched in its waters ; but, as their motion is slow, the
winds bear the bergs to the east, while the general drift sets them
to the north.

767. Necessity for, and advantages of an antarctic expedition. —
Arrived at this point, fiords, deep bays, and capacious gulfs
loom up before the imagination, reminding us to ask the
question. Is there not embosomed in the antarctic continent a
Mediterranean, the shores of which are favourable to the growth
and the launching of icebergs of tremendous size ? and is not
the entrance to this sea near the meridian of Cape Horn, perha'ps
to the west of it ? Circumstances like these beget longings, and
we sigh for fresh antarctic explorations. Surely, when we
consider the advantages which the improvements of the age, the
lights of the day, would afford an exploring expedition there
now ; when we reflect upon the drawbacks and difficulties with
which former expeditions thither had to contend ; when we call
to mind the facilities with which one might be conducted now :
surely, I say, when we thus reflect, no one can doubt as to
the value and importance of the discoveries which a properly
equipped expedition would noio be sure to make.

768. Commercial considerations. — •In those regions there are
doubtless elements of commercial wealth in the number of seals
and abimdance of whales, if in nothing else. It seems to be a
physical law that cold-water fish are more edible than those of
warm water. Bearing this fact in mind as we study Plate IX.,
we see at a glance the places which are most favoured with good
fish-markets. Both shores of North America, the east coast of
China, with the west coasts of Europe and South America, are
all washed by cold waters, and therefi^re we may infer that their
markets abound with the most excellent fish. The fisheries of

412 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Newfoundland and Xew England, over which nations have
wrangled for centuries, are in the cold water from Davis' Strait.
The fisheries of Japan and Eastern China, which almost, if not
quite, rival these, are situated also in the cold water. Neither
India, nor the east coasts of Afiica and South America, where
the warm waters are, are celebrated for their fish.

769. Value of the fisheries. — Three thousand American vessels, it
is said, are engaged in the fisheries. If to these we add the Dutch,
French, and English, we shall have a grand total, perhaps, of
not less than six or eight thousand, of all sizes and flags, engaged
in this one pursuit. Of all the industrial pursuits of the sea,
however, the whale fishery is the most valuable. Wherefore,
in treating of the physical geography of the sea, a map for
the whales, it was thought, would be useful : it has so proved
itself.

770. Sperm whales. — The sperm whale is a warm-water fish.
The right whale delights in cold water. An immense number of
log-books of whalers have been discussed at the National Obser-
vatory with the view of detecting the parts of the ocean in
which the whales are to be found at the different seasons of
the year. Charts showing the results have been published;
they form a part of the series of Maury's Wind and Current
Charts.

771. A sea of fire to them. — In the course of these investi-
gations, the discovery was made that the torrid zone is, to the
right whale, as a sea of fire, through which he cannot pass ; that
the right whale of the northern hemisphere and that of the
southern are two different animals ; and that the sperm whale
has never been known to double the Cape of Good Hope — he
doubles Cape Horn.

772. Bight whales. — With these remarks, and the explanation
given on Plate IX., the parts of the ocean to which the right
whale most resorts, and the parts in which the sperm are found,
may be seen at a glance. The sargassos, or places of weed, are
also represented on this plate.

STORMS, HURRICANES, AND TYPHOONS. il3

CHAPTER XIX.

§ 781-808. — STORMS, HURRICANES, AND TYPHOONS.

781. Plate Y. — Plate Y. is constructed from data flirnished
by the Pilot Charts, as far as they go, that are in process of
construction at the National Observatory. For the Pilot Charts,
the whole ocean is divided off into " fields " or districts of five
degrees square, i. e. five degrees of latitude by five degrees of
longitude, as already stated in the " Explanation of the Plates."
Now, in getting out from the log-books materials for showing, in
every district of the ocean, and for every month, how navigators
have found the winds to blow, it has been assumed that, in what-
ever part of one of these districts a navigator may be when he
records the direction of the wind in his log, from that direction
the wind was blowing at that time all over that district ; and
this is the only assumption that is permitted in the whole course
of the investigation. Now if the navigator will draw, or imagine
to be drawn in any such district, twelve vertical columns for
the twelve months, and then sixteen horizontal lines through the
same for the sixteen points of the compass, i. e. for N., N.N.E.,
N.E., E.N.E., and so on, omitting the 6?/-points, he will have
before him a picture of the "Investigating Chart" out of which
the " Pilot Charts " are constructed. In this case the alternate
points of the compass only are used, because, when sailing free,
the direction of the wind is seldom given for such points as N.
hy E., W. hy S., etc. Moreover, any attempt, for the p-esent, at
greater nicety would be over-refinement, for navigators do not
always make allowance for the aberration of the wind; in
other words, they do not allow for the apparent change in the
direction of the wind caused by the rate at which the vessel may
be moving through the water, and the angle which her course
makes with the true direction of the wind. Bearing this expla-
nation in mind, the intelligent navigator will have no difficulty
in understanding the wind diagram (Plate V.) and in forming a
correct opinion as to the degree of credit due to the fidelity with
which the prevailing winds of the year are represented on
Plate VIII. As the compiler wades through log-book after log-
book, and scores down in column after column, and upon line
aftei- line, mark upon mark, he at last finds that, under the

414 PHYSIAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

month and from tlie course upon which he is about to make an
entry, he has already made four marks or scores, thus (////).
The one that he has now to enter will make the fifth, and he
" scores and tallies," and so on ruitil all the abstracts relating to
that part of the ocean upon which he is at work have been gone
over, and his materials exhausted. These " fives and tallies "
are exhibited on Plate V. Now, with this explanation, it will
be seen that in the district marked A (Plate Y.) there have been
examined the logs of vessels that, giving the direction of the
wind for every eight hours, have altogether spent days enough
to enable me to record the calms and the prevailing diiection of
the winds for eight hours, 2144 times : of these, 285 were for the
month of September ; and of these 285 observations for Septem-
ber, the wind is reported as prevailing for as much as eight
hours at a time : from N. 3 times ; from N.N.E., 1 ; N.E., 2 ;
E.X.E., 1; E., 0; E.S.E., 1; S.E., 4; S.S.E., 2 ; S., 25,-
S.S.W., 45; S.W., 93; W.S.W., 24; W., 47; W.N.W., 17,
N.W., 15; X.N.W., 1 ; Calms (the little O's), 5; total 285 for
the month in this district. The number expressed in figures
denotes the whole number of observations of calms and winds
together that are recorded for each month and district. In C,
the wind in May sets one third of the time from west. But in
A, w^hich is between the same parallels, the favourite quarter for
the same month is from S. to S.W., the wind setting one third
of the time from that quarter, and only 10 out of 221 times
from the west ; or, on the average, it blows from the west only
Ij day during the month of May. In B, notice the great "sun
swing " of the winds in September, indicating that the change
from summer to winter, in that region, is sudden and violent ;
from winter to snmmer, gentle and gradual. In some districts of
the ocean, more than a thousand observations have been dis-
cussed for a single month, whereas, with regard to others, not a
single record is to be found in any of the numerous log-books at
the National Observatory.

782. Typhoons.— The China seas are celebrated for their
furious gales of wind, known among seamen as typhoons and
white squalls. The seas are included on the plate (VIII.) as
within tlie region of the monsoons of the Indian Ocean. But the
monsoons of the China Sea are not five month monsoons (§ 681) ;
they do not prevail from the west of south more than two or
three months. Plate Y. exhibits the monsoons very clearly in a

STORMS, HURKIOANES, AND lYPHOONS. 415

part of this sea. In the square between 15° and 20° north, 110^
and 116° east, there appears to be a system of three monsoons;
that is, one from the north-east in October, November, Decem-
ber, and January; one from east in March and April, changing
in May ; and another from the southward in June, July, and
August, changing in September. The great disturber of the
atmospheric equilibrium appears to be situated among the plains
and steppes of Asia ; their influence reaches up to the clouds,
and extends to the China Seas ; it is about the changing of the
monsoons that these awful gales, called typhoons and white
squalls, are most dreaded.

783. The Mauritius hurricanes. — In like manner, the Mauritius
hurricanes, or the cyclones of the Indian Ocean, occur during
the unsettled state of the atmospheric equilibrium which takes
place at that debatable period during the contest between the
trade-wind force and the monsoon force (§ 699), and which
debatable period occurs at the changing of the monsoon, and
before either force has completely gained or lost the ascendency.
At this period of the year, the winds, breaking loose from their
controlling forces, seem to rage with a fury that would break up
the very fountains of the deejD.

784. TJie West India hurricanes. — So, too, with the West India
hurricanes of the Atlantic ; these winds are most apt to occur
during the months of August and September. There is, there-
fore, this remarkable difference between these gales and those
of the East Indies : the latter occur about the changing of
the monsoons, the former during their height. In August and
September, the south-west monsoons of Africa and the south-
east monsoons of the West Indies are at their height; the agents
of one drawing the north-east trade-winds from the Atlantic into
the interior of ISTew Mexico and Texas, the agents of the other
drawing them into the interior of Africa. These two forces,
pulling in opposite directions, assist now and then to disturb the
atmospheric equilibrium to such an extent that the most powerful
revulsions in the air are required to restore it. " The hurricane
season in the North Atlantic Ocean," says Jansen, "occurs
simultaneously with the African monsoons; and in the same
season of the year in which the monsoons prevail in the North
Indian Ocean and the China Sea, and upon the Western coast of
Central America, all the seas of the northern hemisphere have
the hurricane season. On the contrary, the South Indian Ocean

416 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

has its liurricane season in the opposite season of the year, and
when the north-west monsoon prevails in the East Indian
Archipelago."

785. Tlie cyclone theory. — Under the head of hurricanes, typhoons
and tornadoes, I include all those gales of wind which are
known as cyclones. These have been treated of by Eedfield
in America, Reid in England, Thorn of Mauritius, and Pidding-
ton of Calcutta, with marked ability, and in special works. 1
refer the reader to them. The theory of this school is, that
these are rotary storms ; that they revolve against the hands
of a watch in the northern, and with the hands of a watch in the
southern hemisphere ; that nearer the centre or vortex the more
violent the storm, while the centre itself is a calm, which travels
sometimes a mile or two an hour, and sometimes forty or fifty ;
that in the centre the barometer is low, rising as you approach
the periphery of the whirl ; that the diameter of these storms
is sometimes a thousand miles, and sometimes not more than
a few leagues ; that they have their origin somewhere betw-een
the parallels of 10° and 20° north and south, travelling to the
westward in either hemisphere, but increasing their distance
from the equator, until they reach the parallel of 25° or 30°,
w^hen they turn tow^ards the east, or " recurvate," but continue
to increase their distance from the equator — i. e., they first
travel westwardly, inclining towards the nearest pole ; they
then recurve and travel eastwardly, still inclining towards the
pole ; and that such is their path in both hemispheres, etc.

786. Puzzling questions. — The questions why these storms should
recurve, and why they should travel as they do, and why they
should turn, with the hands of a w^atch in the southern, and against
them in the northern hemisphere, are still considered by many
as puzzles, though it is thought that their course to the westward
in the trade-wind region, and to the eastward in the counter-
trades, is caused by the general movement of the atmosphere,
like the w^hirls in an angry flood, which, though they revolve,
yet they are borne do^vn stream with the currents as they do
revolve. The motion polarward is caused, the conjecture is, by
the fact that the equatorial edge of the stoi-m has, in consequence
of diurnal rotation, a greater velocity than its polar edge. There
seems, however, to be less difficult}^ with regard to their turning
than with regard to their course ; the former is now regarded as
the resultant of diurnal rotation and of those forces of translation

STORMS, HURRICANES, AND TYPHOONS. y 17

wliicli propel the winds along the surface of our planet. This
composition of the forces of the revolving storm, and the resolution
of them, are precisely such (§ 215) as to produce opposite rotation
on opposite sides of the equator.

787. Espys theory. — Many of the phenomena connected with
these storms still remain to be explained ; even the facts with
regard to them are disputed by some. The late Professor Espy,
after having discussed for many years numerous observations
that have been made chiefly on shore, maintained that the wind
does not blow around the vortex or place of low barometer, but
directly toivards it. He held that the place of low barometer,
instead of being a disc, is generally an oblong, in the shape of a
long trough, between two atmospherical waves ; that it is curved
with its convex side towards the east ; that it is sometimes nearly
straight, and generally of great length from north to south,
reaching in America, from the Gulf of Mexico to the great lakes
and beyond, and having but little breadth in proportion to its
length ; that it travels east, moving side foremost, requiring
about two da3^s to go from the Mississippi to St. John's, Xew-
foundland ; that on either side • of it, but many miles distant,
there is a ridge of high barometer ; that the wind on either side
of the line of lov7 barometer, in which there is little or no wind,
blows toward it, etc., and, in support of these positions, he
advanced this theory : "When the air in any locality acquires a
higher temperature or a higher dew-point than that of the sur-
rounding regions, it is specifically lighter, and will ascend ; in
ascending, it comes under less pressure, and expands ; in ex-
panding from diminished pressure, it grows colder about a degree
and a quarter for every hundred yards of ascent ; in cooling as
low as the dew-point (which it will do when it rises as many hun-
dred yards as the dew-point at the time is below the temperature
of the air in degrees of Fahrenheit), it will begin to condense its
vapour into cloud ; in condensing its vapour into water or cloud,
it will evolve its latent caloric ; this evolution of latent caloric
will prevent the air from cooling so fast in its farther ascent as it
did in ascending below the base of the cloud now forming ; the
current of the air, however, will continue to ascer i, and grow
colder about half as much as it would do if it had no vapour in it
to condense ; and when it has risen high enough to have con-
densed, by the cold of expansion from diminished pressure, one
hundredth of its weight of vapour, it will be about forty-eight

2 E

418 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

deoTees less cold than it would have been if it had no vaponr to
condense nor latent caloric to give out— that is, it will be about
forty-eight degrees warmer than the surrounding air at the same
heio-ht ; it will, therefore (without making any allowance for the
hio-her dew-point of the ascending current), be about one tenth
lighter than the surrounding colder air, and, of course, it will
continue to ascend to the top of the atmosphere, spreading out in
all directions above as it ascends, overlapping the air in all the
surrounding regions in the vicinity of the storm, and. thus, by
increasing the weight of the air around, cause the barometer to
rise on the outside of the storm, and fall still more under the
storm-cloud by the outspreading of air above, thus leaving less
ponderable matter near the centre of the upmovmg column to
press on the barometer below. The barometer thus standing
below the mean under cloud in the central regions, and above
the mean on the outside of the cloud, the air will blow on all
sides from without, inward, under the cloud. The air, on coming
under the cloud, being subjected to less pressure, will ascend
and carry up the vapour it contains with it, and as it ascends
will become colder by expansion from constantly diminishing
pressure, and will begin to condense its vapour in cloud at the
height indicated before, and thus the process of cloud-forming
will go on. Now it is known that the upper current of air in
the United States moves constantly, from a known cause, towards
the eastward, probably a little to the south of east ; and as the
upmoving column containing the cloud is chiefly in this upper
current of air, it follows that the storm-cloud must move in the
same direction. And over whatever region the storm-cloud
appears, to that region will the wind blow below ; thus the wind
must set in with a storm from some eastern direction, and, as the
storm-cloud passes on towards the eastward, the wind must
change to some western direction, and blow from that quarter
till the end of the storm."*

788. Doves law. — According to Dove's " Law of Eotation,"
which is said to hold good in the northern hemisphere, and is
supposed to obtain in the southern also, the wind being N.W.
and veering, it ought to veer by W. to S.W., and so on, against
the hands of a watch. This " law " is explained thus : Suppose
a ship be in S. lat. off Cape Horn as at a, with a low barometer

* Tlie Fourth Meteorological Keport of Prof. James P. Espy ; Senate Doc.
60, 34th Con.i^ress, 3rd session.

STORMS, HURRICANES, AND TYPHOONS.

419

lo the nortli of her, as at C, where the air ascends as fast as it
comes pouring in from all sides. The ship, let it be supposed, is
just on the verge of, but exterior to the vortex, or that place
where the wind commences to revolve. The first rush of the air
at a will be directly for the centre C ; consequently, a ship so

w ^v

placed would report the storm as commencing wdth the wind at
south. For the sake of illustration, we will suppose this place of
low barometer to be stationary, and the air, as it rushes in, to
ascend at the disc C. Thus the area of inrushing air will
gi-adually enlarge itself by broad spreading, like a circle on the
water, until it be compassed by a circle with a radius C S, of
indefinite length. The air then, on the meridian SON, but to
the south of a, will not blow along this meridian and pass over
the ship ; in consequence of the diurnal rotation of the earth, it
will take a direction, S a', to the westward ; and the arrow d a,
representing a S.S.E. wind, will now show the direction of the
wind at a. Thus the ship will report that the wind commenced
at south, and gradually hauled to S.S.E., i.e. against the hands of
a watch ; and so the arrows h' a' will represent the direction of
the wind at each station, a' a' a', when the storm commenced,
and the arrows d' a' the directions afterwards, thus showing it to
have veered against the hands of a watch. And this is the
direction in which the forces of diurnal rotation, when not

2 E 2

4.20 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

mastered by opposing forces, always require the wind, when not
blowing round in spirals and a whirl, to haul in the southern
hemisphere. Now, paradoxical as it may at first seem, it is also
the forces of diurnal rotation that give that same wind, when it
is blowing round in spirals, its first impulse to march round in
the contrary direction, or (§ 786) with the hands of a loatch ; but
this is as it should be — it hauls one way, and marches the other.
After passing ct, and each of the other stations, a! a\ the rush of
wind is sufficient, let us suppose, to create a whirl. The wind
at a' «'•«', continuing on with a circular motion, is represented
thenceforward in its course by the curved arrows a e, a' e'. The
wind coming from the east and the west has no direct impulse
from diurnal rotation, but the wind on either side of it has, and
hence the pnme «?erfo*caZ wind is carried around with the rest. If,
now, we imagine the disc C to be put in motion, and the storm
to become a travelling one, we shall have to consider the com-
position and resolution of other forces also, such as those of
traction, aberration, and the like, before we can resolve the
whirlwind.

789. Bernouillis formula. — But the cyclonologists do not locate
their storms in such high latitudes as the parallels of Cape Horn.
Hence we might safely infer, one would suppose, that in high
southern latitudes a north wind has a tendency to incline to the
westward and a south wind to the eastward ; and the cause of
this tendency is in operation, whether the place of low barometer
be a disc or an oblong, for it is in obedience to the trade-wind
law, as expounded by Halley, that it so operates; and it will
also be the case whether the wind be caused by an influx into
the place of low, or the efQux from the place of high barometer ;
or, as is generally the case, by both together. If the distance
between the place of high and low barometer were always the
same, then a given difference of barometric pressure would
always be followed by a wind of the same force of velocity. By
expanding Bernouilli's formula for the velocity of gas jets under
given pressures. Sir John F. W. Herschel has computed* the
velocity and the force with which currents of air or winds would
issue under certain differences of barometric pressure. Under
the most favourable conditions, i. e., when the places of high and
of low barometer are in immediate juxtaposition, as on the inside
and outside of an air pump, an efiective difference of 0.006 inch
* See article Meteorology, Encyclopsedia Britanniea, 1857.

STOEMS, HTJRRIOANES, AND TYPHOONS.

421

in the barometric pressure would create a breeze with a velocity
of seven miles the hour. Such a wind is capable of exerting a
horizontal pressure of 0.2 lb. the square foot, thus :

Diff. barometric
Pressure.

0 . 006 inch

0.010 „

0.016 „

0.0)3 „

0.14 „

0.25 „

0.41 „

Velocity of Wind.

7 miles per hour.
14
21
41
61
82
92

Horizontal Pressure.

0 . 2 lbs. per sq. ft.

0.9 „

1.9 „

7.5 „

16.7 „

30.7 „

37.9 „

Strength of Wind.

Gentle air.

Light breeze.

Good saihng breeze.

A gale.

Great storm.

Tempest.

Devastating hm-rieane.

Changes, however, in the barometer, amounting to five or six
times these differences, are observed to take place at sea without
producing winds exceeding in velocity the rates above. This is
because the places of high and low barometer at sea are far apart,
and because, also, of the obstructions of the winds afforded by
the inequalities of the earth's surface.

790. Frediding storms. — But, in this view of the subject, the
importance of a daily system of weather reports by telegraph on
shore, and across the water between Europe and America when
the sub-Atlantic cable is well laid, looms up and assumes all the
proportions of one of the great practical questions of the age.
We may conjecture, as the probable result of observation, that
the greater the distance between the place of high and low
barometer, the less the velocity of wind for a given barometric
difference would be. Professor Buys Ballot has discovered,
practically, the numerical relation between the force of the wind
and given barometric differences for certain places in Holland.
With the view of ascertaining like relations for this country, it
has been proposed to establish a cordon of meteorological stations
over the United States, each station being required to report
daily to the Observatory in Washington, by telegraph, the height
of the barometer, force of wind, etc. By such a plan, properly
organized, we might expect soon to be able to give the ships,
not only on the great lakes, but in our sea-port towns also,
timely warning of many a gale, and to send by telegraph to
Europe — when one shall be paid — warning of many a one long
before it could traverse the Atlantic. The contributions which
the magnetic telegraph is capable of making for the advancement

422 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of meteorology will enable ns to warn the ships in our Gnlf
ports, as well as those of Cuba, of the approach of every hurricane
or tornado that visits those regions.

791. The changing of the wind in a cyclone. — But, returning to the
cyclone theory : though the wind be blowing around in spirals
against the hands of the watch, yet, from the fact that the centre
about which it is blowing is also travelling along, the changes of
the wind, as observed by a vessel over which the storm is
jDassing, will not, under all circumstances, be against the sun in
the northern, or with the sun in the southern hemisphere. The
reason is obvious. This point is worth studying, and any one
who will resort to ^'■moving diagrams^'' for illustration will be

repaid with edification. Piddington's
horn cards are the best; but let those
who have them not cut a disc of paper
of any convenient diameter, say 2^
inches, and then cut out a circle of 2
inches from the middle ; this will leave a
ring half an inch broad upon which to
draw arrows representing the course of
the wind. Suppose them to be drawn
for the northern hemisphere, as in the
annexed diagram; lay the paper ring on the chart : suppose the
ship to be in the N.E. quadrant of the storm, which is travelling
north, the centre of the storm will pass to the west, but the wind
will chano-e from S.E. to S., and so on to the west, with the hands
of a watch, though it be revolving about the centre against the
hands of a watch ; still the rule for finding the direction of the
centre holds good : Face the wind, and the centre in the northern
hemisphere will be to the right ; in the southern, to the left.

792. TJie wind stronger on one side than the other. — Suppose that
in the case before us the storm is travelling to the north at the
rate of 20 miles the hour, and that the wind is revolving around
the centre also at the rate of 20 miles the hour : when the vortex
bears west of the ship, the wind will be south. It is going 20
miles to the north with the body of the storm, and 20 miles
around the centre ; total force of the wind, 40 miles an hour on
the east side. Now imagine yourself on the other side, that is,
that you are in the north-west quadrant, and that the storm is
travelling due north as before ; the vortex will pass east of you,
when the wind should have changed from N.E. to north, turning

STORMS, HURRICANES, AND TYPHOONS. 423

against the hands of a watch; but when the wind is north, it is,
in the case supposed, travelling south at the rate of 20 miles an
hour around the storm, while the progressive movement of the
storm itself is north at the rate of 20 miles an hour. One motion
exactly cancels the other, and there is, therefore, a line of calm
and light, or moderate or not so heavy winds on one side of the
centre, while on the other side there is a line of maximum
violence ; in other words, in every travelling cyclone the wind
blows harder on one side than the other. This is the case in
both hemispheres ; and by handling these moving diagrams for
illustration, the navigator will soon become familiar with the
various problems for determining theoretically the direction of
the vortex, the course it is travelling, its distance, etc. There-
fore, when it is optional with the navigator to pass the storm on
either side, he should avoid the heavy side. These remarks
apply to both hemispheres.

793. The rainy quadrant of a cyclone. Ca]3tain To^^nbee asks if
it rains more in one quarter of a cyclone than another ? In
cj^clones that travel fast, I suppose there would be most rain in
the after quarter ; with those that have little or no progressive
motion, I conjecture that the rainy quarter, if there be one,
would depend upon the quarter whence that wind comes that
brings most rain. The rain in a cyclone is supposed to come
from the moisture of that air which has blown its round and
gone up in the vortex ; then it expands, grows cool, and con-
denses its vapour, which spreads out at top like a great mushroom
in the air, the liberated heat adding fury to the storm.

794. Erroneous theories. — Such, briefly stated, are the two
theories. They appear to me, from such observation and study
as I have been able to bestow, to be neither of them wholly
right or altogether wrong. Both are instructive, and the sug-
gestions of one will, in many instances, throw light upon the
facts of the other. That rotary storms do frequently occur at
sea we know, for vessels have sometimes, while scudding before
the wind in them, sailed round and round. The United States
brig " Perry" did this a few years ago in the West Indies ; and
so did the " Charles Ileddle " in the East Indies : she went round
and round a cyclone five times.

795. The wind in a true cyclone blows in spirals. — From such ob-
servations as I have been able to obtain upon the subject, I am
induced to believe, with Thorn, that the wind in a cyclone does

424 PHYSICAL GEOGRAPHY OF THE SEA, Ai5D ITS METEOROLOGY.

not blow round in a circle, but around in spirals. Nay, I go
farther, and conjecture, that it is only within a certain distance
of the vortex that the wind gyrates, and that the gyrating column
is never hundreds of miles in diameter, as the advocates of this
theory make it : I shall allude to this again. The low barometer
at the centre is owing, in part, to two causes ; one is the con-
densation of vapour, with its liberated heat, as maintained by
Espy ; the other is the action of a real centrifugal force, which
applies to all revolving bodies. In weighing the effect of this
centrifugal force upon the low barometer, care should be taken
not to give it an undue weight. It is not sufficient to cause the
air to fly off in a tangent. The lateral atmosph-eric pressure
would prevent that, if the centrifugal force were never so great ;
and the lower the barometer in the centre, the greater would be
the pressure of the surrounding air. The proper weight, there-
fore, due to the centrifugal force I hold to be not very great,
though it is appreciable to this extent : The storm having com-
m.enced revolving, the flow of air into the vortex is retarded, not
prevented, by centi'ifugal tendency ; and this retardation assists
in causing the barometer to stand lower than it would if there
were no revolution. Any one who has watched the little whirl-
winds so often seen during summer and fall, or who can call to
mind the whirls or " sucks " in a mill pond, or at the lock in a
canal when the water is drawn off at the bottom, may appreciate
the extent to which the centrifugal tendency will help to make a
low barometer at the centre of a cyclone.

796. An illustration. — The low barometer, the revolving storm,
and the ascending column require for a postulate the approach
b}'- spirals of the wind from circumference to centre. The wind
(§665) blows towards the place of low barometer ; that is ad-
mitted by all. It can only reach that place by a direct or by a
curvilinear motion. If by the former, then there can be no revo-
lution ; but if there be revolution, then the air, while as wind it
is revolving around the centre in the gyrations of the storm, is
approaching the centre also. Hence we derive the elements of a
spiral curve ; and the physical necessity for spiral motion is
demonstrated from the fact that there is circular motion and an
uprising in the centre. This spiral movement and the uprising
may be illustrated by familiar examples : The angles and corners
of the Observatory, and its wings, are so arranged that at a
certain place there is, with westerly winds, always a whii'lwind.

STORMS, HURRICANES AND TYPHOONS. 425

This whirlwind is six to eight feet in diameter ; and when there
is snow, there is a pile of it in the centre, with a naked path, in
the shape of a ring, three or four feet broad about it. It is the
spiral motion which brings the drift-snow to the centre or vortex,
and the upward motion not being strong enough to carry the snow
up, it is left behind, forming a sort of cone, which serves as a
cast for the base of the vortex. If you throw chips or trashy
matter into the lock uf a canal and watch them, you will see that
as they come within the influence of the " suck " they will ap-
proach the whirl by a spiral until they reach the centre, when,
notwithstanding they may be lighter than the water, they will be
" sucked " down. Here we see the effects of centrifugal force
upon a fl.uid revolving within itself. The " suck " is funnel-
shaped. As it goes down, the lateral pressure of the water
increases ; it counteracts more and mere the effect of centrifugal
force, and diminishes, by its increase, the size of the " suck."

797. Dust loMrlwinds and water-spouts. — So, too, with the little
autumnal whirlwinds in the road and on the lawn : the dust,
leaves, and trash will be swept in towards the centre at the bottom,
whirl round and round, go up in the middle, and be scattered
or spread out at the top. I recollect seeing one of these whirl-
winds pass across the Potomac, raising from the river a regular
water-spout, and, when it reached the land, it appeared as a
common whirlwind, its course being marked, as usual, by a
whirling column of leaves and dust. These little whirlwinds
are, I take it, the great storms of the sea in miniature ; and a
proper study of the miniature on land may give us an idea of the
great original on the ocean.

798. A vera causa. — The unequally heated plain is thought to
be the cause of the one. But there are no unequally heated plains
at sea ; nevertheless, the primum mobile there is said, and rightly
said, to be heat. Electricity, or some other imponderable, may
be concerned in the birth of the whirlwind both ashore and afloat.
But that is conjecture ; the presence of heat is a fact. In the
middle of the cyclone there is generally rain, or hail, or snow ;
and the amount of heat set free during the process of condensing
the vapour for this rain, or hail, or snow, is sufficient to raise
from the freezing to the boiling point more than five times the
whole amount of water that falls. This vast amount of heat is
set free, not at the surface of the sea, it is true, but in the cloud-
region, and where the upward tendency of the indraught is still

426 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

farther promoted. What sets the whirlwind a-brewing is another
question ; but its elements being put in motion, there is a dimi-
nished barometric pressure, first, on account of centrifugal ten-
dency ; next, on account of the ascending column of air, which
expands and ascends, — ascends and expands on account of such
diminished pressure ; — and next, though not least, on account of
the heat which is set free by the condensation of the vapour
which forms the clouds and makes the rain. This heat expands
and joushes aside the upper air still more-

799. Objections to the theory. — After much study, I find some
difficulties about the cyclone theory that I cannot overcome.
They are of this sort : I cannot conceive it possible to have
a cyclone with a revolving and travelling disc 1000, or 500
miles in diameter, as the expounders of the theory have it.
Is it possible for a disc of such an attenuated fluid as common
air, having 1000 miles of diameter with its less than wafer-like
thickness in comparison, to go travelling over the earth's surface
and revolving about a centre with tornado violence ? With the
log-books of several vessels before me that are supposed to have
been in different parts of the same cyclone I have a number
of times attempted to project its path, but I always failed to
bring out exactly such a storm as the theory calls for.* I make a
distinction between the hauling of the wind in consequence of
diurnal rotation of the earth, and the rotation of the wind in the
cyclone in consequence of its centripetal force. For the sake of
illustrating my difficulties a little farther, let us suppose a low
barometer with a revolving storm to occur at A in the southern
hemisphere. Let the storm be travelling towards B. Let ob-
servers be at c", d, and e, and let c" and d be each several
hundred miles from A, and so far as to be clearly without the
reach of the whirl. Now, then, will not the air at c" and d
blow north and east as directly for the place of low barometer as
it would were that place an oblong, N A, instead of a disc, as
per the arrows ? And why should it be a disc in preference to

* Since this was written, I liave had the privilege of examining at the
Meteorological Department of the Board of Trade, Admiral Fitzroy's admirable
diagrams, in MS., of the "Royal Charter" storm of October, 1859. It was a
true cyclone— the best type of one, and the most perfectly developed on a
large scale that has ever fallen under my observation. Its largest diameter did
not measure less than 300 miles.

STORMS, HURRICANES. ASTD TYPHOONS. 427

an ellipse a square, an oblong, or any figure, be it never so ir-
regular ? The trade -winds an-
swer, showing the equatorial
calm belt — an oblong — as their
.V y jDlace of meeting. They neither

^^^''' revolve nor blow at right

^ " ano;les, with the line of their

/

^^

direction from the place of low
g' ^ / barometer; but they blow as

directly for it as the forces of
diurnal rotation will allow. But the cyclonologists, instead of
permitting the wind at the distance c" sometimes to blow to the
east, and at d to blow to the north, merel}^ because there is a low
barometer east of c" and north of d, require it alivays so to blow
because, by their theory, there is a low barometer east of d and
south of c" ! Thus, to reach its theoretical place of destination,
the wind must blow in a direction at right angles to that destina-
tion ! It would require a rush of inconceivable rapidity so to
deflect currents of air while they are yet several hundred miles
from the centre of gyration. Moreover, the two cyclonologists,
c" and d, would differ with each other as to the centre of the
storm. Each at first w^ould assume that the wind was blowing
about him in the direction of the curved arrow c" and d. As the
place of low barometer travels towards B, the hauling of the wind
would be according to the theory at c'', but against it at d. The
cyclonologist in d would place the centre of the storm to the
eastward of him, as in the direction of <i, but the other would
place it to the southward of him, as in Wiq direction c'. B}^ the
rule, ship cZ would be led towards the real track of the storm, i. e.,
into danger, and ship c" away from it.* From all this it would
appear that the cyclone theory is defective in this : when the
wind hauls in the storm, the sailor who is contending with it,
lacks a rule by which he may know the influence which causes it
to haul. The gyrating disc of a cyclone can never, I apprehend,
exceed a few miles in diameter. On shore we seldom find it
exceeding in breadth as many rods, in most cases not of as many
fathoms, as its advocates give it miles at sea. I think the dust-
whirl in the street is a trtie type of the tornado (cyclone) at
sea.

* See letter to Commodore Wiillerstorf, p. 457, vol. ii., 8tli ed., Maury 'a
Failing Directions.

428 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

800. Tlie three forces. — There are in the various parts of the
storm at least three forces at work in effecting a change of wind,
as observed on board ship at sea. (1.) One is diurnal rotation :
it alone can never work a change of direction exceeding 90° ;
(2.) another is the varying position or travelling motion of the
place of barometric depression : the change effected by it cannot
exceed 180° ; (3.) and the third is the whirling motion imparted
by the rush to a common centre — as the whirl of water at the
flood-gate of the mill, the whirlwind in the street, for example.

801. The effect of each. — Hence it appears that in a storm the
wind may shift from any one of three causes, and we are not
entitled to call it a cyclone unless the wind shift more than 180°.
If the change of direction . be less than 90°, the shifting may
be due to diurnal rotation alone; if it be less than 180°, the
shifting may be, and is probably, due to (1) and (2). The
sailor has therefore no proof to show that he has been in a
cyclone unless the wind during the storm changed its directions
more than 180°. Cyclones, there is reason to believe, are often
whirlwinds in a storm. This may be illustrated by referring
again to our miniature whirlwinds on the hind ; there we often
see a number of them at one time and about the same place ; and
they often appear to skip, raging here, then disappearing for a
moment, then touching the ground again, and pursuing the
former direction.

802. A storm ivithin a storm. — Observations have proved that
this is the case on land, and observations have not established
tliat this is not the case at sea ; observations are wanting upon
tliis subject. Tornadoes on the land often divide themselves,
sending out branches, as it were. It remains to be seen whether
cyclones do not do the same at sea ; and whether, in those wide-
spread and devastating storms that now and then sweep over the
ocean, there be only one vortex or several ; and if only one,
whether the whole storm partake of the cyclone character. In
other words, may there not be a storm within a storm — that is, a
cyclone travelling with the storm and revolving in it ? I ask
the question because the theory, as at present expounded, does
not satisfy all the facts observed ; and because the existence of
storms or whirlwinds within a storm would.

803. The Black Sea storm of 1854.— The celebrated Black Sea
storm of 1854, which did so much damage to the allied fleet,
is still maintained by some to be a true cyclone ; and by the

STORMS, HUREICANES, AND TYPHOONS.

429

observations of some of the vessels a cyclone may be made out.
But if we take the observations of all of them, and discuss them
upon the supposition that the whole storm was a cj^clone, it
will puzzle any one to make anything of them. Admiral Fitz-
roy, in the Meteorological Papers of the Board of Trade,
published diagrams of the winds as observed during that storm
on board of various vessels in various parts of that sea. I have
not been able to reconcile them with the cyclone theory. Espy
maintains that they confirm his theory; and his (§ 787) is anti-
cyclonic.

804. Cyclones of the North Atlantic. — The cylones of the Xorfh
Atlantic take their rise generally (§ 785) somewhere between
the parallels of 10° and 20° north. They take a westerly course
until they fall in with the Gulf Stream, when they turn about
and run along upon it until their force is expended. The atmo-
sphere over the Gulf Stream is generally well charged with
moisture, and in this fact perhaps will be found the reason why
(§ 176) the path of the storm is laid along the Gulf Stream.

805. T]ie hurricane season. — The following table is from Birt's
Handbook of Storms :

Average Number of Cyclones or Hurricanes which have occurred in different
Months of the Year, and in various Regions.

Locality.

Jan.

Feb.

Mar.

April

May: June July

Aug. Sept.

Oct.

Nov.

1
4

6
6

Dec.

2
3
6
3

Total

West Indies .
S. Indian Ocean
Mauritius .
Bay of Bengal.
China Sea .

9
9
1

1
13
15

2
10
15

1

's

8
1

i'

7

3

2

15
5

36

1
5

25
1

18

27
1

"l
10

113
53
53

30
46

806. Cyclones in the Mississijp^i Valley. — The vortex of a cyclone
is often and aptly compared to a meteor. I have often observed
the paths of such through the forests of the Mississippi Valley,
and the path of one of these "whirlwinds" as they are there
called has in no instance that has fallen under my observation
been more than a few hundred yards broad. There the track of
these tornadoes is called a " wind-road," because they make an
avenue through the wood straight along, and as clear of trees
as if the old denizens of the forest had been felled with an axe.
T have seen trees three or four feet in diameter torn up by the
roots, and the top, with its limbs, lying next the hole whence

430 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the roots came. Kevertheless, the passage of the meteor, whose
narrow path was marked by devastation, would create a great
commotion in the air, and there would be high winds raging for
several miles on either side of the " wind-road." But (§ 799) let
us consider for a moment the effect of the diurnal rotation of the
earth upon one of these revolving discs 1000 miles in diameter :
its height would scarcely be two miles, and its thickness would
not be as great, in proportion to its diameter, as half the thickness
of this leaf is to the length of an inch. Now the difference in
rate of the diurnal rotation between the northern and southern
limbs of the disc would be sufficient, irrespective of any other
power, to break it up. Suppose its southern limb to be in 20°
jS"., its northern limb would be 1000 miles, say 17°, farther
north, that is, in 37°. Diurnal rotation would carry to the east
the air in the southern limb at the rate of 845 miles an hour ;
out when this same air comes round on the northern limb,
diurnal rotation would carry it eastward at the rate only of 720
miles. Because the wind hauls in a particular way, it does
not follow, as by diagram (§ 799) it has been shown, that it
is blowing in a circle, or that the centre of the storm is at right
angles to its line of direction.

807. Extra-tropical gales. — In the extra-tropical regions of each
hemisphere furious gales of wind also occur. One of these,
remarkable for its violent effects, was encountered on the 24th of
December, 1853, about three hundred miles from Sandy Hook,
latitude 39° north, longitude 70° west, by the " San Francisco,"
steam-ship. That ship was made a complete wreck in a few
moments, and she was abandoned by the survivors, after in-
credible hardships, exertions, and sufferings. Some months'
after this disaster I received by the California mail the abstract
log of the line clipper ship " Eagle Wing " (Ebenezer H. Linnell),
from Boston to San Francisco. She encountered the ill-fated
steamer's gale, and thus describes it : " December 24tli. Latitude
39° 15' north, longitude 62° 32' west. First part threatening
weather ; shortened sail ; at 4 p.m. close-reefed the top -sails and
furled the courses. At 8 p.m. took in fore and mizen top-sails ;
hove to under close-reefed main top-sail and spencer, the ship
l^'ing with her lee rail under water, nearly on her beam-ends.
At 1 30 A.M. the fore and main top-gallant- masts went over the
fdde, it blowing a perfect hurricane. At 8 a.m., moderated ;
p. iioa took away jib-boom and bowsprit cap. In my thirty-one

THE WINDS OF THE SOUTHERN HEMISPHERE. 431

years' experience at sea, I have never seen a typhoon or hurri-
cane so severe. Lost two men overboard — saved one. Stove
skyJight, broke my barometer, etc., etc." Severe gales in this
part of the Atlantic — i. e., on the polar side of the calm belt
of Cancer — rarely occur during the months of June, Jul}-,
August, and September. This appears to be the tiwie when the
fiends of the storm are most busily at work in the West Indies.
During the remainder of the year, these extra-tropical gales,
for the most part, come from the north-west. But the winter
is the most famous season for these gales. That is the time
when the Gulf Stream has brought the heat of summer and
placed it (§ 1 72) in closest proximity to the extremest cold of
the north. And there should, therefore, it would seem, be a
conflict between these extremes ; consequently, great disturbances
in the air, and a violent rush from the cold to the warm. In
like manner, the gales that most prevail in the extra-tropics of
the southern hemisphere come from the pole and the west, i. e.,
south-west.

808. Sto7in and Rain charts. — Storm and Eain Charts for the
Atlantic Ocean have already been published by the Observatory,
and others for the other oceans are in process of construction.
The object of such charts is to show the directions and relative
frequency of calms, fogs, rain, thunder, and lightning. These
charts are very instructive. They show that that half of the
atmospherical coating of the earth which covers the northern
hemisphere — if we may take as a type of the whole what occurs
on either side of the equator in the Atlantic Ocean — is in a much
less stable condition than that which covers the southern.

CHAPTEK. XX.

§ 811-542. — THE WINDS OF THE SOUTHERN HEMISPHERE.

811. Bepetition often necessary. — A work of this sort, which is
progressive, must necessarily bear with it more or less of
repetition. It embodies the results of the most extensive system
of philosophical observations, physical investigation, and friendly
co-operation that has ever been set on foot. As facts are developed,
theories are invented or expanded to reconcile them. As soon
as this is done, or in a short time thereafter, some one or more of

432 PHYSICAL GEOGRAPHY OF TEE SEA, AND ITS METEOEOLOGY.

the fleets tliat are out reconnoitring the seas for us, returns with
additional facts for our storehouse of knowledge. Whether these
tend to" confirm or disprove the theory a restatement is often
called for; hence the repetition, of which the case before us is ah
example.

812. TJie S.E. and N.E. trade-winds 'put in a balance. — The facts
stated in Chap. XV. go to show that the south-east trade- winds
are stronger than the north-east. The barometer tells us (§ 643)
that between the parallels of 5° and 20° the south-east trade-
winds bear a superincumbent pressure upon the square foot of
nearly 4 pounds greater than that to which the north-east trades
are subjected. Such an excess of superincumbent pressure upon
a fluid so elastic and subtle as air, ought to force the south-east
trade- winds from under it more rapidly than the lighter pressure
forces the north-east. Observations showing that such is or
is not the case should not be ignored.

813. Ohservations hij 2235 vessels. — I have the separate and
independent evidence from every vessel in a fleet numbering no
less than 2235 sail to show that the S.E. are stronger than the
N.E. trades. All of these vessels passed through both systems of
trade-winds. The knots run per hour by each one of them,
as they passed through the south-east trades of the Indian Ocean
and through both systems of the Atlantic, have been measured
and discussed from crossing to crossing. The average result in
knots is expressed in the annexed table, P. 433. The comparison
is confined to the rate of sailing between the parallels of 10° and
25°, because this is the belt of steadiest trades.

814. Ships used as anemometers. — It is well to observe, that on
each of these three oceans, though the direction of the wind is
the same, the course steered by each fleet is different ; conse-
quently, these sailing anemometers are at different angles with the
wind ; through the south-east trades, the wind is nearly aft in
the Atlantic, and quartering in the Indian Ocean, giving an
average sailing speed of 7 knots an hour in the latter, and of 6
in the former ; while through the north-east trades the average
speed is 6i knots an hour one way (N.W. J W.), with the wind
just abaft the beam, and 5j the other (S.S.E.), with the wind at
a point not so favourable for speed. Indeed, most of the ships
which average a S.S.E. course through this part of the north-
east trade-wind belt are close hauled ; therefore the avei'age
strength of the trades here cannot be fairly compared with the

THE WINDS OF THE SOUTHERN HEMISPHERE.

433

Average Speed of Vessels sailing through the Trade-winds of the Nmih

Atlantic and South Indian Oceans.

Knots per Hour from

10° to 15°.

15° to 20°.

20° to 25°.

Average.

Course steered through.

Month.

.

.

1

y-^

M-^

«l

K-S

a J

:^l

M-S

N.E. Trades. 1 S.E. Trades.

^S

r^£

^£

cc >:

^' 2

^ g

r^2

(N. Atlantic.) j (I. Ocean.)

H

H

^

January

8

6J

7|

7

6

6

7

6*

N. 493 W. : S. 69^ W.

February .

n

6

6

6f

5

6

6

6

N. 46 W. j

March .

s

7

7

7

51

6i

6f

6f

N. 47 W. 1

April . .

n

7

5f

7f

4

6

6

6f

N. 48 W.

S. 70° W.

May . .

^

8

6f

7^

6*

6

7

7

N. 46 W.

»

June . .

9

7*

8

7^

51

7

7*

71

N. 43 W.

V

July . .

5^

8

8

8J

6i

7

6*

7f

N. 46 W.

„

August. .

4f

7f

6

8i

4f

7*

5

n

N. 40 W.

S. 69° W.

September.

51

8*

6

8

4

6f

5

7f

N. 50 W.

)»

October .

7^

s^

6f

8

6

5f

^

7^

N. 45 W.

>«

November .

6

8

6

7

4^

51

51

6f

N. 49 W.

December .

6

6i

6f

6f

5*

5

6

6

N. 48 W.

J'

Means .

7

n

6f

7i

51

6J

6^

7

N. 47° W.

S. 691^^ W.

Average course steered through the N.E. trades (N. Atlantic Ocean), N.W. J W.
„ „ S.E. trades (South Indian „ ), W.S.W.

Average ditto through the Trade-winds

0/ f/ie North and South Atlc

intic Oceans.

Knots per Hour from

25° to 20°.

20° to 15°.

150 to 10°.

Average.

Course steered through.

MOXTH.

M'I

^•1

mI

^1

m:^

^^

W^

^•|

S.E. Trades.

N.E. Trades.

02 2

^5

r^C

^i

r^2

^2

cc ^

?q2

(S. Atlantic.)

(N. Atlantic.)

H

H

H

H

H

H

t-i

H

January

6

5

5f

5^

5f

7*

6

6

N. 540 W.

S. 21° E.

February .

^

5

51

61

6

7

51

6

N. 55 W.

S. 25 E.

March . .

61

4f

6

61

6

71

6

6i

N. 55 W.

S. 221 E.

April .

5^

51

5*

6*

6f '

7f

6

61

N. 53 W.

S. 221 E.

May . .

^

5

5f

6^

61

7

6

6

N. 55 W.

S. 24f E.

June .

5f

6

6

6

7

5

61

5f

N. 55 W.

S. 28 E.

July . .

51

7

6

7*

61

41

6

6

N. 55 W.

S. 27 E.

August .

5

5*

5f

61

6

4

5^

5*

N. 55 W.

S. 281 E.

September .

51

31

6i

51

7

5

6i

4*

N. 55 W.

S. 221 E.

October .

5^

^

b

U

5^

4f

5*

U

N. 56 W.

S. 20 E.

November .

6J

4

61

5J

6i

5f

6*

5

N. 55 W.

S.22iE.

December .

51 4f

51

^

6J

7f

51

5

N. 55 W.

S. 23 E.

Means .

H 5

5f

6

61

6,

6

5|

N. 550W. S. 24aE.

i

Average course steered through the S.E. trades (S. Atlantic), N.W. by W.

N.E. trades (N. Atlantic;, S.S.E.
2 F

434 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

average strength where the fleet have free winds. What is the
difference in the strength of such winds, which impinging upon
the sails, each at the particular angle indicated above, imparts the
aforesaid velocities ? Moderate winds, such as these are, give a
ship her highest speed generally when they are just abaft the
beam, as they are for a north-west course through the north-east
trades of the North Atlantic. So, to treat these ships as anemo-
meters that will really enable us to measure the comparative
strength of the winds, we should reduce the average knots per
hour to the average speed of a mean ship sailing through average
" trades " in each ocean, with the wind impinging upon her sails
at the same angle for all three, as, for example, just abaft the
beam, as in the North Atlantic.

815. Velocity of the trade-winds. — Let us apply to the average speed
through the South Atlantic and Indian Oceans such a correction.
Through the former the wind is aft ; through the latter, quarter-
ing. If we allow two knots as a correction for the one and one
as a correction for the other, we shall not be greatly out. Apply-
ing such corrections, we may state the speed of a mean ship
sailing with average trades just abaft the beam to be as follows :

Through the N.E. of the N. Atlantic . . Q\ knots per hour.*
•S.E. „ S. Atlantic . . 8
S.E. „ S. Indian Ocean . 8 „

* That this correction is not too large is indicated not only by the experi-
ments Tviiich Admiral Chabannes, in command of the French fleet on the
coast of Brazil, has kindly caused to be made by the brig " Zebra," but by
experiments wliich he has subsequently made >vith the frigate "Alceste,"
as per the following extracts of a letter, just received from that distinguished
officer, dated —

" Frigate ' L' Alceste,' at Monte Video, May 10, 1860.
" Dear Sib, — I am replying to your letter of the .30th of January last, which
I have received with the duplicates of that dated January 15th, 1859, which
you have had the goodness to send me through M. de Montholon, as well as
the interesting nautical monograph No. 1, and, finally, the manuscript passage
from an article relative to the force of the winds to the height and velocity of
clouds and waves. I regret exceedingly that I have not under my orders a
squadron of sailing vessels with which I could put to sea, and devote myself
to all these researches. Unfortunately, I have only steamers in my division,
with the exception of the frigate which carries my flag, and political circum-
sta.nces have retained me almost constantly in the La Plata. I am now ap-
proaching the end of my command, and in a few days must leave Monte Video
to engage in some hydrographical works on the coast of Brazil, and afterwards
I shall return to France, where I expect to arrive in the beginning of September.
I shall not fail during this voyage to make a series of experiments such up, you

THE WINDS OF THE SOUTHERN HEMISPHERE. 435

I do not take into this comparison the force of the N.E. trades on
a S.S.E. course (§ 813), because the winds along this route are
known not to be as steady as they are farther away from the
African, coast. Thus it is clearly established that the S.E. trades
are stronger than the N.E., and so they should he if there he a cross-
ing of winds in the calm helt of Capricorn.

816. Ditto of the counter-trades.— The counter-trades of the
southern hemisphere move, as before stated, towards their pole
more steadily and briskly than do the counter-trades of the north-
ern hemisphere. To give an idea of the difference of the strength
of these two winds, I cite the fact that vessels sailing through
the latter, as from New York to England, average 150 miles a
day. Along the corresponding latitudes through the former, as
on a voyage to Australia, the average speed is upwards of 200
miles a day. Consequently, the counter-trades of the southern
hemisphere transport in given times larger volumes of air towards
the south than our counter-trades do towards the north. This
air returns to the tropical calm belts as an upper current. If,
descending there, it feeds the trade- winds, then, the supply being
more abundant for the S.E. trades than for the N.E., the S.E.
trades must be the stronger ; and so they are ; observations prove
them so to be. Thus the crossing of the air at the tropical calm
belts, though it may not be proved, yet it is shown to be so very
probable that the onus of proof is shifted. It now rests with
those who dispute the crossing to prove their theory the true one.

have indicated, in order to estabUsh the relative force of the trade-winds in the
southern and in the northern hemisphere — determining the differences of velo-
city of the frigate with wind aft and wind abeam.

" In my last letter, of the 25th of January, I gave you the results obtained
by the brig ' Zebra,' but they are very incomplete ; and I wish, with the
Alceste,' to determine the comparative velocities obtained with a perfectly
regular wind in the diiferent rates of going from the nearest the wind to wind
full aft. It is evident that the differences observed in this manner will be
dependent on the special qualities of each vessel used in the experiments, and
that it will be also necessary to take full account of the state of the sea ; but
by multiplying experiments, one will certainly arrive at an average in which
confidence may be placed. I think with you, that for a ship sailing 6 knots,
with wind full aft, there will be an increase of speed of 2-5 to 3 knots, with
the wind a little abaft the beam. I have already had occasion to remark that
for the ' Alceste ' this difference sometimes exceeds 3 knots. My next letter
will give you the details of tlie experiments which I shall have made in this
respect, both south and north of the Line, which will necessarily lengthen my
voyage a little. I am too anxious to co-operate in my feeble way in the great
works you are carrying on, not to sacrifice willingly some hours daily whenever
circumstances wUl permit."

2 F 2

436 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

817. Tlie loaves they get up. — Arrived at this point, another view
in the field of conjecture is presented, which it is proper we
should pause to consider. The movements of the atmosphere on
the polar side of 40° N. are, let it be repeated, by no means so
constant from the west, nor is the strength of the westerly winds
there nearly so great on the average as it is in the corresponding
regions of the south. This fact is well known among mari-
ners. Every one who has sailed in that southern girdle of
waters which belt the earth on the polar side of 40°, has been
struck with the force and trade-like regularity of the westerly
winds which prevail there. The waves driven before these winds
assume in their regularity of form, in the magnitude of their pro-
portions, and in the stateliness of their march, an aspect of
majestic grandeur that the billows of the sea never attain else-
where. No such waves are found in the trade-winds ; for,
though the S.E. trades are quite as constant, yet they have not
the force to pile the water in such heaps, nor to arrange the
waves so orderly, nor to drive them so rapidly as those " brave "
winds do. There the billows, chasing each other like skipping
hills, look, with their rounded crests and deep hollows, more like
mountains rolling over a plain than the waves which we are
accustomed to see. Many days of constant blowing over a wide
expanse of ocean are required to get up such waves. It is these
winds and waves which, on the voyage to and from Australia,
have enabled the modern clipper-ship to attain a speed, and, day
after day, to accomplish runs which at first were considered, even
by the nautical world, as fabulous, and are yet regarded by all
with wonder and admiration.

818. A meteorological corollary. — Seeing, therefore, that we can
bring in such a variety of facts and circumstances, all tending
to show that the S.E. trade-winds are stronger than the N.E., and
that the westerly winds which prevail on the polar side of 40° S.
are stronger and more constant than their antoecian fellows of
the north, we may consider it as a fact established, independently
of the conclusive proof afforded by Plate XIII., that the general
system of a.tmospherical circulation is more active in the southern
than it is in the northern hemisphere. And, seeing that it blows
with more strength and regularity from the west in the extra-
tropical regions of the southern than it does in the extra-tropical
regions of the northern hemisphere, we should deduce, by way
of corollary, that the counter -trades of the south are not so easily

THE WINDS OF THE SOUTHERN HEMISPHERE. 437

arrested in their course, or turned back in their circuits, as art
those of the north. Consequently, moreover, we should not,
either in the trades or the counter-trades of the southern hemi-
sphere, look for as many calms as in those of the northern
systems.

819. Fads established. — Wherefore, holding to this corollary,
we may consider the following as established facts in the meteor-
ology of the sea : That the S.E. trade-winds are stronger than the
N.E. ; that the N.W. passage- winds — the counter-trades of the
south — are stronger and less liable to interruption in their cir-
cuits than the S.W., the counter-trades of the north; that the
atmospherical circulation is more regular and brisk in the south-
ern than it is in the northern hemisphere ; and, to repeat : since
the wind moves in its circuit more briskly through the southern
than it does through the northern hemisphere, it consequently
has less time to tarry or dally by the way in the south than in
the north; hence the corollary just stated. But observations,
also, as well as mathematically-drawn inferences, show that calms
are much less prevalent in the southern hemisphere. For this
inference observations are ample ; they are grouped together by
thousands and tens of thousands, both on the Pilot and the Storm
and Eain Charts. These charts have not yet been completed
for all parts of the ocean, but as far as they have been constructed
the facts they utter are in perfect agreement with the terms of
this corollary.

820. Atmospherical circulation more active in the southern than in
the northern hemisphere. — These premises being admitted, we may
ascend another round on this ladder, and argue that, since the
atmosphere moves more briskly and in more constant streams
through its general channels of circulation in the southern than
it does through them in the northern hemisphere ; and that,
since it is not arrested in its courses by calms as often in the
former as it is in the latter, neither should it be turned back b}^
the way, so as to blow in gales from the direction opposite to that
in which the general circulation carries it. The atmosphere, in
its movements along its regular channels of circulation, may be
likened, that in the southern hemisphere to a fast railway train ;
that of the northern to a slow. The slow train may, when
" steam is up," run as fast as the fast train, but it is not obliged
to get through so quick ; therefore it may dally by the way, stop,
run back, and still be through in time. !N"ot so the fast ; it has not

^38 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOKOLOGY.

time to Rtop often or to run back far ; neither have the counter-
trades oi the south time to blow backward ; consequently, such
being the conditions, we should also expect to find in the extra-
tropical south a gale with easting in it much more seldom than
in the extra-tropical north.

821. Gales in the two hemispheres. — We shall appeal to observa-
tions for the correctness of this conjecture, and claim for it, also,
as presently will appear, the dignity of an established truth in
marine meteorology.

Average Number {to the 1000 Observations) of Gales, with Easting and with
Westing in them, between the corresponding Parallels in the North and South
Atlantic, as shown by the Storm and Rain Charts.

Number of Observations . .

North.

South.

17,274

8,756

Between 40° and 45°,

Gales in 1000 do., with easting

23

12

„ „ „ westing

66

82

"

Number of Observations^ .

11,425

5,548

Between 45° and 50^, <

Gales in 1000 do., with easting

24

1

„ „ „ westing

106

61

Number of Observations . .

4,816

5,169

Between 50° and 55^,

Gales in 1000 do., with easting

24

10

„ „ westing

144

97

Thus the Storm and Kain Charts show that between the parallels
of 40° and 55° there were in the northern hemisphere 33,515
observations, and that for every 1000 observations there were
24 gales with easting and 105 with westing. That in the south-
ern, there were 19,473 observations, and for every 1000 of these
there were 5 gales with easting and 80 with westing in them.
Those for the southern hemisphere are only for that part of the
ocean through which vessels pass on their way to and fro around
Cape Horn. That part of this route which lies between 40° and
65° S., is under the lee of South America ; and Patagonia, that
lies east of the Andes, is almost a rainless region ; consequently,
we might expect to find more unsteady winds and fewer rains in
that part of the ocean where the observations for the southern
part of the tables were made than we should expect to meet with
well out to sea, as at the distance of two or three thousand miles
to the eastward of Patagonia. So that the contrast presented by
the above statement would probably be much greater did our
observations extend entirely across the South, as they do across

THE WINDS OF THE SOUTHERN HEMISPHERE.

439

the Korth Atlantic. But as it is, the contrast is very striking.
In some aspects, the meteorological agents of the two hemi-
spheres, especially those forces which control the winds and the
weather, diifer very much. The difference is so wide as to sug-
gest greater regularity and rapidity of circulation on one side of
the equator than on the other.

822. Calms in the two hemispheres . — Average Number of Calms to the 1000 Ob-
servations betioeero the Parallels of 30° and 55^, in the North and South Atlantic,
and betiveen the Parallels of 30" and 60^ in the North and South Pacific Oceans,
as shown by the Pilot Charts.

Between the Parallels of

30^ and 35°, No. of Observations

Calms to the 1000 do. . .
35° and 40° No. of Observations

Calms to the 1000 do. . .
40° and 45°, No. of Observations

Calms to the 1000 do. . .
45° and 50°, No. of Observations

Calms to the 1000 do. . .
50^ and 55°, No. of Observations

Calms to the 1000 do. . .
55° and 60°, No. of Observations

Cahns to the 1000 do. . .

Total No. of Observations .
Averagre Calms to the 1000 do.

Atlantic.
North. South.

12,935

46
22,136

37
16,363

45
8,907

38
3,519

40

63,050

15,842

26
23,439

24
8,203

27
4,183

25
3,660

16

North.

22,730

34
13,939

31
12,400

53
15,897

35
32,804

32
15,470

43

41

55,327 ill3,240 166,829

24

39

25

Each one of these observations embraces a period of eight hours ;
the grand total, if arranged consecutively, with the observations
drawn out each to occupy its period separately, would be equal
to 373 years. They exhibit several curious and suggestive facts
concerning the difference of the atmospherical stability in the
two hemispheres.

823. The propelling power of the winds. — If we would discover
the seat of those forces which produce this difference in the
dynamical status of the two great aerial oceans that envelop our
planet, we should search for them in the unequal distribution of
land and water over the two hemispheres. In one the wind is
interrupted in its circuits by the continental masses, with their
wooded plains, their snowy mantles in winter, their sandy
deserts in summer, and their mountain ranges always. In the

140 THTSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

otlier tliere is but little land and less snow. On the polar side
of 40° S. especially, if we except the small remnant of this con-
tinent that protrudes beyond that parallel in the direction of
Cape Horn, there is scarcely an island. All is sea. There the
air is never dry ; it is always in contact with a vapour-giving
surface ; consequently, the winds there are loaded with moisture,
which, with every change of temperature, is either increased by
farther evaporation or diminished by temporary condensation.
The propelling power of tlie winds in the southern hemisphere resides
chiefly in the latent heat of the vapour which they suck up from the
engirdling sea on the polar side of Capricorn.

824. lAeut. Van Gough's Storm and Bain Charts. — The Storm
and Eain Charts show that within the trade-wind regions of both
hemispheres the calm and rain curves are symmetrical ; that in
the extra-tropical regions the symmetry is between the calm and
fog curves ; and also, especially in the southern hemisphere,
between the gale and rain curves. Lieutenant Yan Gough, of
the Dutch Navy, in an interesting paper on the connection be-
tween storms, near the Cape of Good Hope and the temperature
of the sea,* presents a storm and rain chart for that region. It is
founded on 17,810 observations, made by 500 ships, upon wind
and weather, between 14° and 32° E., and 33° and 37° S. By
that chart the gale and rain curves are so symmetrical that the
phenomena of rains and gales in the extra-tropical seas present
themselves suggestively as cause and effect. The general storm
and rain charts of the Atlantic Ocean, prepared at the National
Observatory, Washington, hold out the same idea. Let us
examine, expand, and explain this fact.

825. The " brave west winds" caused by rarefaction in the antarctic
regions. — We ascribe the trade-winds to the equatorial calm -belt.
But to what shall we ascribe the counter-trades, particularly of
the southern hemisphere, which blow v^th as much regularity
towards the pole as the north-east trades of the Atlantic do
towards the equator ? Shall we say that those winds are drawn
towards the south pole by heat, which causes them to expand and
ascend in the antarctic regions? It sounds somewhat para-
doxical to say that heat causes the winds to blow towards the
poles as well as towards the equator ; but, after a little explana-
tion, and the passing in review of a few facts and circumstances,

* De Stormen nabij de Kaap cle Goede Hope in verband bescbouwd met do
Temperatuur der Zee.

THE WINDS OF THE SOUTHERN HEMISPHERE. 441

perhaps the paradox may disappear. It is held as an established
fact by meteorologists that the average amount of precipitation is
greater in the northern than in the southern hemisphere ; but
this, I imagine, applies rather to the land than the sea. On the
polar side of 40° it is mostly water in the southern, mostly land
in the northern hemisphere. It is only now and then, and on
rare occasions, that ships carry rain-gauges to sea. We can
determine by qnantitive measurements the difference in amount
of precipitation on the land of the two hemispheres, and it is the
result of this determination, I imagine, that has given rise to the
general remark that the rain-fall is greater for the northern than
it is for the southern hemisphere. But we have few hyeto-
graj)hic measurements for quantity at sea ; there the determina-
tions are mostly numerical. Our observers report the " times "
of precipitation, which, whether it be in the form of rain, hail,
or snow, is called by the charts, and in this discussion, rain.
Among such a large corps of observers, rain is sometimes, no
doubt, omitted in the log ; so that, in all probability, the charts
do not show as many " times " with rain as there are " times "
actually with rain at sea. This omission, however, is as likely to
occur in one hemisphere as in the other. Still, we may safely
assume that it rains oftener in all parts of the sea than our
observations, or the rain charts that are founded on them,
indicate.

826. Relative frequency of rains and gales at sea. — With the
view of comparing the rains at sea between the parallels of 55^
and 60°, both in the Xorth and South Atlantic, we have taken
from the charts the following figures :

South Atlantic— Observations, 8410; gales, 1228
North Atlantic— „ 526; „ 135

Gales to the 1000 observations . . S.Atlantic, 146
Kains, „ „ • • S.Atlantic, 131

rains, 1105
64

N. Atlantic, 256
N. Atlantic, 121

That is, for every 10 gales, there are in the southern hemisphere
9 rains, and in the northern 4.7. In which hemisphere does
most water fall on the average during a rain at sea ? Observa-
tions do not tell, but there seems to be a philosophical reason
why it should rain not only oftener, but more copiously at sea,
especially in the extra-tropical regions, in the southern hemi-
sphere than in those of the northern. On the polar side of
40° N., for example, the land is stretched out in continental
masses, upon the thirsty besom of which, when the air drops

442 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

down its load of moisture, only a portion of it can be taken np
again ; the rest is absorbed by the earth to feed the springs. On
the polar side of 40° S. we have a water instead of a land surface,
and as fast as precipitation takes place there, the ocean re-
plenishes the air with Dioisture again. It may consequently be
assumed that a high dew-point, — at least one as high as the
ocean can maintain in contact with winds blowing over it, and
going from warmer to cooler latitudes all the time — is the
normal condition of the air on the polar side of 40° S., whereas
on the polar side of 40° N. a low dew-point prevails. The rivers
to the north of 40°, I reckon, could not, if they were all con-
verted into steam, supply vapour enough to make up this
average difference of dew-point between the two hemispheres.
The symmetry of the rain and storm curves on the polar side of
40° S. suggests that it is the condensation of this vapour which,
with the liberation of its latent heat, gives such activity and
regularity to the circulation of the atmosphere in the other
hemisphere.

827. The rain-fall of Cape Horn and Cherraponjie.— On the polar
side of 40° S., near Cape Horn, the gauge of Captains King and
Fitzroy showed a rain-fall of 153.75 inches in 41 days. There
is no other place except Cherraponjie where the precipitation
approaches this in amount. Cherraponjie (§ 299) is, it has
already been stated, a mountain station in India, 4500 feet high,
which, in latitude 25° N., acts as a condenser for the monsoons
fresh from the sea. But on the polar side of latitude 45°, in the
northern hemisphere, it is, except along the American shores of
the North Pacific, a physical impossibility that there should be a
region of such precipitation as King and Fitzroy found on the
western slopes of Patagonia — a physical impossibility, because
that peculiar combination of conditions required to produce a
Patagonian rain-fall is wanting on the polar side of 45° N.
There is in the North Atlantic, water surface enough to afford
vapour for such an amount of precipitation. In the North
Pacific the water surface may be broad and ample enough to
afford the vapour, but in neither of these two northern sheets of
water are the winds continuous enough from- the westward to
bring in the requisite quantities of vapour from the sea. More--
over, if the westerly winds of the extra-tropical north were as
steady and as strong as are those of the south, there is lacking in
the north that continental relief — mountain ranges rising ab-

THE WINDS OF THE SOUTHERN HEMISPHERE. 443

ruptly out of the sea, or separated from it only by lowlands —
that seems to be necessary to bring down the rain in such floods.
Colonel Sykes* quotes the rain-fall of Cherraponjie at 605.25
inches for the 214 days from April to October, the season of the
south-west monsoons. Computing the Cape Horn rains according
to the ratio given by King and Fitzroy for their 41 days of
observations, we should have a rain-fall in Patagonia of 825
inches in 214 days, or a yearly amount of 1368.7 inches.
Neither the Cape Horn rains, nor the rains anywhere at sea on
the polar side of 45° S., are periodical. They are continuous ;
more copious, perhaps, at some seasons of the year than at
others, but abundant at all.

828. Influence of highlands upon precipitation. — Now, considering
the extent of water surface on the polar side of the south-east
trade-wind belt, we see no reason why, on these parallels, the
engirdling air of that great watery zone of the south should not,
entirely around the earth, be as heavily charged with vapour as
was that which dropped this flood upon the Patagonian hills. If
those mountains had not been there, the condensation and the
consequent precipitation would probably not have been as great,
because the conditions at sea are less apt to produce rain ; but the
quantity of vapour in the air would have been none the less,
which vapour was being borne in the channels of circulation
towards the antarctic regions for condensation and the liberation
of its latent heat ; and we make, as we shall proceed to show, no
violent supposition, if, in attempting to explain this activity of
circulation south of the equator, we suppose a cloud region, with
a combination of conditions in the antarctic circle peculiarly
favourable to heavy and almost incessant precipitation. But,
before describing these conditions, let us turn aside to inquire
how far precipitation in the supposed cloud region of the south
may assist in giving force and regularity to the winds of the
sonthern hemisphere.

829. The latent heat of vapour. — If we take a measure, as a cubic
foot, of ice at zero, and apply heat to it by means of a steady
flame that will give off heat at a uniform rate, and in such quan-
tities that just enough heat may be imparted to the ice to raise
its temperature 1° a minute, we shall find that at the end of
32 minutes the ice will be at 32°. The ice will now begin to

* Report of the British Association for 1852, p. 256.

444 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

melt ; but it and its water, the heat being continued, will re-
main at 32° for 140 minutes, when all the ice will have become
water at 32°*. This 140° of heat, which is enough to raise the
temperature of 140 cubic feet of ice one degree from any point
below 32°, has been rendered latent in the process of liquefac-
tion. Freeze this water again, and this latent heat will become
sensible heat, for heat no more than ponderable matter can be
annihilated. But if, after the cubic foot of ice has been con-
verted into water at 32°, we continue the uniform supply of heat
as before and at the same rate, the water will, at the expiration
of 180 minutes more, reach the temperature of 212° — the boiling-
point — and at this temperature it will remain for 1030 minutes,
notwithstanding the continuous supply of heat during the in-
terval. At the expiration of this 1030 minutes of boiling heat,
the last drop of water will have been converted into steam ; but
the temperature of the steam will be that only of the boiling
water ; thus, in the evaporation of every measure of water, heat
enough is rendered latent during the process to raise the tem-
perature of 1030 such measures one degree. If this vapour be
now condensed, this latent heat will be set free and become
sensible heat again. Hence we perceive that every rain-drop
that falls from the sky has, in its process of condensation, evolved
heat enough to raise one degree the temperature of 1030 rain-
drops. But if instead of the liquid state, as rain, it come down
in the solid state, as hail or snow, then the heat of fluidity,
amounting to enough to raise the temperature of 140 additional
drops one degree, is also set free.

830. Tlie cause of the boisterous weather off Cajpe Horn. — We
have in this fact a clew to the violent wind which usually accom-
panies hail-storms. In the hail-storm congelation takes place
immediately after condensation, and so quickly that the heat
evolved during the two processes may be considered as of one
evolution. Consequently, the upper air has its temperature
raised much higher than could be done by the condensing only.
So also the storms which have made Cape Horn famous are no
doubt owing, in a great measure, to this heavy Patagonian rain-
fall The latent heat which is liberated by the vapour as it is
condensed into rain there, has the effect of producing a great in-
tumescence in the air of the upper regions round about them,

* See Espy's Philosophy of Storms.

THE WINDS OF THE SOUTHERN HEMISPHERE. 445

which in turn produces commotion in the air below. But this is
digressive. Therefore let us take up the broken thread, and
suppose, merely for illustration, such a rain-fall as King and
Fitzroy encountered in Patagonia to have taken place under the
supposed cloud region of the antarctic circle, and to have been
hail or snow instead of rain, then the total amount of caloric
set free among the clouds, in those 41 days of such a flood, would
be enough to raise from freezing to boiling six and a half times
as much water as fell. But if the supposed antarctic precipita-
tion come down in the shape of rain, then the heat set free
would be sufficient only to raise from freezing to boiliug about
5| as much water as the flood brought down. We shall have,
perhaps, a better idea of the amount of heat that would be set
free in the condensation and congelation in the antarctic regions
of a« much vapour as it took to make the Patagonian rain-fall,
if we vary the illustration by supposing this rain-fall of 153.75
inches to extend over an area of 1000 square miles, and that it
fell as snow or hail. The latent heat set free among the clouds
during these 41 days would have been sufficient to raise from the
freezing to the boiling point all the water in a lake 1000 square
miles in area and 83 i feet in depth. The unknown area of the
antarctic is eight millions of square miles. We now see how the
cold of the poles, by facilitating precipitation, is made to react
and develop heat to expand the air, and give force to the winds.

831. Offices of icehergs in the meteorological machinery. — Thus
we obtain another point of view from which we may contemplate,
in a new aspect, the icebergs which the antarctic regions send
forth in such masses and numbers. They are a part of the
raeteorological machinery of our planet. The offices which they
perform as such are most important, and oh, how exquisite !
While they are in the process of congelation the heat of fluidity
is set free, which, whether it be liberated by the freezing of
water at the* surface of the earth, or of the rain-drop in the sky,
helps in either case to give activity and energy to the southern
system of circulation by warming and expanding the air at its
jDlace of ascent. Thus the water, which by parting with its heat
of liquefaction, has expended its meteorological energy in giving
dynamical force to the air, is like the exhausted steam of the
engine ; it has exerted its power and become inert. It is,
therefore, to be got out of the way. In the grand meteorological
engine which drives the wind through his circuits, and tempers

446 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

it to beast, bird, and plant, this waste water is collected into
antarctic icebergs, and borne away by the currents to more
genial climes, where the latent heat of fluidity which they dis-
pensed to the air in the frigid zone is restored, and where they
are again resolved into water, which, approaching the torrid zone
in cooling streams, again joins in the work and helps to cool the
air of the trade- winds, to mitigate climate, and moderate the
gale. For, if the water of southem seas were warmer, evapora-
tion would be gTcater ; then the S.E. trade-winds would deliver
vapour more abundantly to the equatorial calm belts ; this would
make precipitation there more copious, and the additional quan-
tity of heat set free would give additional velocity to the in-
rushing trade winds. Thus it is, as has alread}^ been stated,
that, parallel for parallel, between 40° or 50° north and south,
trans-equatorial seas are cooler than cis- equatorial ; thus it is that
icebergs are employed to push forward the winds in the polar
regions, to hold them back in the equatorial ; and thus it is that,
in contemplating the machinery of the air, we perceive how ice-
bergs are " coupled on," and made to perform the work of
regulator, with adjustments the most beautiful, and compensa-
tions the most exquisite, in the grand machinery of the atmo-
sphere.

832. The antarctic calm place a region of constant jprecipitation. —
With this illustration concerning the dynamical force which the
winds derive, from the vapour taken up in one climate and trans-
ported to another, we may proceed to sketch those physical
features which, being found in the antarctic circle, would be
most favourable to heavy and constant precipitation, and, conse-
quently, to the development of a system of aerial circulation
peculiarly active, vigorous, and regular for the aqueous hemi-
sphere, as the southern in contrast with the northern one may
be called. These vapour -bearing winds which brought the rains
to Patagonia are — 1 wish to keep this fact in the reader's mind
— the counter-trades (§ 257) of the southern hemisphere. As
such they have to perform their round in the grand system of
aerial circulation, and as, in every system of aerial circulation
there must be some point or place at which motion ceases to be
direct and commences to be retrograde, so there must be a pla.ce
somewhere on the surface of our planet where these winds cease
to go forward, stop, and commence their return to the north;
and that jjlace is, in all probability, within the antarctic regions. Its

THE WINDS OF THE SOUTHERN HEMISPHERE. 447

precise locality has not been determined, but I suppose it to be a
band or disc — an area — within the polar circle, which, could it
be explored, would be found, like the equatorial calm belt, a
place of light airs and calms, of ascending columns of air, — a
region of clouds, of variable winds, and constant precipitation.

833. Also of a low harometer. — But, be that as it may, the air
which these vapour-bearing winds — vapour-bearing because they
blow over such an immense tract of ocean — pour into this
stopping-place has to ascend and flow off as an upper current, to
make room for that which is continually flowing in below. In
ascending it expands and grows cool, and, as it grows cool, con-
densation of its vapour commences ; with this, vast quantities of
latent heat, which converted the water out at sea into vapour for
these winds, are set free in the upper air. There it reacts by
warming the ascending columns, causing them still farther to
expand, and so to rise higher and higher, while the barometer
sinks lower and lower. This reasoning is suggested not only by
the facts and circumstances already stated as well known, but it
derives additional plausibility for correctness by the low baro-
meter of these regions. In the equatorial calm belts the mean
barometric pressure is about 0.25 inch less than it is in the
trade-winds, and this diminution of pressure is enough to create
a perpetual influx of the air from either side, and to produce the
trade-winds. Off Cape Horn the mean barometric pressure * is
0.75 inch less than in the trade- wind regions. This is for the
parallel say of 57° — 8° S. According to the mean of 2,472 baro-
metric observations made along that part only of the route to
Australia which lies between the meridians of the Cape of Good
Hope and Melbourne, the mean barometric pressure on the polar
side of 42° y. has been shown by Lieutenant Van Gough, of the
Dutch Navy, to be 0.33 inch less than it is in the trade-winds.
The mean pressure in this part of the South Indian Ocean is,
under winds with easting in them, 29.8 inches : ditto, under
winds with westing, 29.6 inches. Plate I. shows a supposed
mean pressure in the polar calms of not more than 28.75 inches.
The barometric curve, page 468, shows with a higher degree of
probability that the mean pressure there is about 28.14 inches.

834. Aqueous vapour the cause of both. — To what, if not to the

* Maury's Sailing Directions, 6th ed., 1854, p. 692; ditto, 8th ed., 1859,
vol. ii., p. 450.

448 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGT.

effects of the condensation of vapour borne by those surcharged
winds, and to the immense precipitation in the austral regions,
shall we ascribe this diminution of the atmospherical pressure in
high south latitudes? It is not so in high north latitudes,
except about the Aleutian Islands of the Pacific, where the sea
to windward is also wide, and where precipitation is frequent,
but not so heavy. The steady flow of " brave " winds towards
the south would seem to call for a combination of physical con-
ditions about their stopping-place in the antarctic regions,
exceedingly favourable to rapid, and heavy, and constant pre-
cipitation there. The rain-fall at Cherraponjie and on the slopes
of the Patagonian Andes reminds us what those conditions are.
There mountain masses seem to perform in the chambers of the
upper air the office which the jet of cold water does for the
exhausted steam in the condenser of the engine. The presence
of land, not water, about this south polar stopping-place is there-
fore suggested ; for the sea is not so favourable as the mountains
are for aqueous condensation.

835. The tojpographical features of the antarctic hands. — By the
terms in which our proposition has been stated, and by the
manner in which the demonstration has been conducted, the
presence in the antarctic regions of land in large masses is called
for ; and if we imagine this land to be relieved by high moun-
tains and lofty peaks, we shall have in the antarctic continent a
most active and powerful condenser. If, again, we tax imagina-
tion a little farther, we may, without transcending the limits of
legitimate speculation, invest that unexplored land with
numerous and active volcanoes. If we suppose this also to be
the case, then we certainly shall be at no loss for sources of
dynamical force sufficient to give that freshness and vigour to
the atmospherical circulations which observations have abun-
dantly shown to be peculiar to the southern hemisphere.
Neither under such physical aspects need it be any longer con-
sidered paradoxical to ascribe the polaf tendency of the " brave
west winds " to rarefaction by heat in the antarctic circle. This
heat is relative, and though it be imparted to air far below the
freezing-point, raising its temperature only a few degrees, its
expansive power for that change is as great when those few
degrees are low down as it is when they are high up on the
scale. If such condensation of vapour do take place, then
liberation of heat and expansion of air must follow, and con-

THE WINDS OF THE SOUTHERN HEMISPHERE 449

sequentl}'' the oblateness of the atmospherical covering of our
planet will be altered ; the flattening about the poles will be
relieved by the intumescence of the expanded and ascending air,
which, protruding above the general level of the aerial ocean,
will receive an impulse equatorially, as well from the mere de-
rangement of equilibrium as from the centrifugal forces of the
revolving globe. And so this air, having parted with its
moisture, and having received the expansive force of all the
latent heat evolved in the process of vaporous condensation, will
commence its return towards the equator as an upper current of
dry air.

836. A perpetual cyclone. — Arrived at this point of the investi-
gation, we may contemplate the whole system of these " brave
west winds " in the light of an everlasting cyclone on a gigantic
scale. The antarctic continent is in its vortex, about which the
wind, in the great atmospherical ocean all around the world,
from the pole to the edge of the calm belt of Capricorn, is re-
volving in spiral curves, continually going, with the hands of a
watch, and twisting from left to right.

837. Discovery of design in the meteorological machinery. — In
studying the workings of the various parts of the physical
machinery that surrounds our planet, it is always refreshing
and profitable to detect, even by glimmerings never so faint,
the slightest tracings of the purpose which the Omnipotent
Architect of the universe designed to accomplish by any
particular arrangement among its various parts. Thus it is
in this instance : whether the train of reasoning which we
have been endeavouring to follow up, or whether the argu-
ments which we have been adducing to sustain it be entirely
correct or not, we may, from all the facts and circumstances
that we have passed in review, find reasons sufficient for regard-
ing in an instructive, if not in a new light, that vast waste of
waters which surrounds the unexplored regions of the antarctic
circle. It is a reservoir of dj^namical force for the winds — a re
gulator in the grand meteorological machinery of the earth. The
heat w^hich is transported by the vapours with which that sea
loads its superincumbent air is the chief source of the motive
power w^hich gives to the winds of the southern hemisphere, as
they move through their channels of circulation, their high speed,
great regularity, and consistency of volume. And this insight
into the workings of the w^onderful machinery of sea and air we

2 G

450 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

obtain from comparing together the relative speed of vessels as
tliey sail to and fro upon intertropical seas !

838. Indications which the winds afford concerning the unexplored
regions of the south. — Such is the picture which, after no little
labour, much research, and some thought, the winds have enabled
us to draw of certain unexplored portions of our planet. As we
have drawn the picture, so, from the workings of the meteorolo-
gical machinery of the southern hemisphere, we judge it to be.
The evidence which has been introduced is meteorological in its
nature, circumstantial in its character, we admit ; but it shows
the idea of land in the antarctic regions — of much land, and high
land — to be plausible at least. Not only so : it suggests that a
group of active volcanoes there would by no means be incon-
sistent with the meteorological phenomena which we have been
investigating. True, volcanoes in such a place may not be a
meteorological necessity. We cannot say that they are ; yet the
force and regularity of the winds remind us that their presence
there would not be inconsistent with known laws. According
to these laws, we may as well imagine the antarctic circle to en-
compass land as to encompass water. We know, ocularly, but
little more of its topographical features than we do of those of
one of the planets ; but, if they be continental, we surely may,
without any unwarrantable stretch of the imagination, relieve
the face of nature there with suow-clad mountains, and diversify
the landscape with flaming volcanoes. None of these features
are inconsistent with the phenomena displayed by the winds.
Let us apply to other departments of physics, and seek testimony
from other sources of information. None of the evidence to be
gathered there will appear contradictory — it is rather in corrobo-
ration. Southern explorers, as far as they have penetrated
within the antarctic circle, tell us of high lands and mountains
of ice ; and Eoss, who went farthest of all, saw volcanoes burning
in the distance.

839. Their extent ; Plate XIV. — The unexplored area around
the south pole is about twice as large as Europe. This untra-
velled region is circular in shape, the circumference of which
does not measure less than 7000 miles. Its edges have been
penetrated here and there, and land, whenever seen, has been
high and rugged. Plate XIV. shows the utmost reach of antarc-
tic exploration. The unexplored area there is quite equal to
that of our entire frigid zone. Navigators on the voyage from

THE WINDS OF THE SOUTHERN HEMISPHERE. 451

the Cape of Good Hope to Melbourne, and from Melbourne to
Cape Horn, scarcely ever venture, except while passing Cape
Horn, to go on the polar side of 55° S. The fear of icebergs
deters them. These may be seen there drifting up towards the
equator in large numbers and large masses all the year lound.
I have encountered them myself as high up as the parallel of
37° — 8** S. The belt of ocean that encircles this globe on the
polar side of 55° S. is never free from icebergs. They are foimd
in all parts of it the year round. Many of them are miles in
extent and hundreds of feet thick. The area on the polar side
of the 55th parallel of south latitude comprehends a space of
17,784,600 square miles. The nursery for the bergs, to fill such
a field, must be an immense one ; such a nursery cannot be on
the sea, for icebergs require to be fastened firmly to the shore
until they attain full size. They therefore, in their mute way,
are loud with evidence in favour of antarctic shore lines of great
extent, of deep bays where they may be formed, and of lofty
cliffs whence they may be launched.

840. A ^hjsical laiv concerning the distribution of land and
water. — There is another physical circumstance which obtains
generally with regard to the distribution of land and water over
the surface of the earth, and which, as far as it goes, seems to
favour the hypothesis of much land about the south pole ; and
that circumstance is this : It seems to be a physical necessity
that land should not be antipodal to land. Except a small por-
tion of South America and Asia, land is always opposite to water.
Mr. G-ardner has called attention to the fact that only one
twenty-seventh part of the land is antipodal to land. The belief
is, that on the polar side of 70° north we have mostly water, not
land. This law of distribution, so far as it applies, is in favour
of land in the opposite zone. Finally, geographers are agreed
that, irrespective of the particularized facts and phenomena
which we have been considering, the probabilities are in favoui
of an antarctic continent rather than of an antarctic ocean.

841. Dr. Jileh. — " There is now no doubt," says Dr. Jilek, in
his Lehrbuch der Oceanographie, " that around the south pole
there is extended a great continent mainly within the polar
circle, since, although we do not know it in its whole extent, yet
the portions with which we have become acquainted, and the
investigations made, furnish sufficient evidences to infer the
existence of such with certainty. This southern or antarctie

2 G 2

452 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY,

continent advances farthest northward in a peninsula S.S.E. of
the southern end of America, reaching in Trinity Land almost to
62*^ south latitude- Outwardly these lands exhibit a naked,
rocky, partly volcanic desert, with high rocks destitute of vege-
tation, always covered with ice and snow, and so surrounded
with ice that it is difficult or impossible to examine the coast
very closely. * * *

842. Antarctic expeditions. — " The principal discoverers of
these coasts are (Wilkes), D'Urville, and Ross (the younger), of
whom the latter, in 184^, followed a coast over 100 miles between
72° and 79° south latitude, and 160° and 170° east longitude, to
which he gave the name Victoria Land, and on which he dis-
covered a volcano (Erebus) 10,200 feet high in 167° east longi-
tude and 77° south latitude, as well as another extinct one
(Terror) 10,200 feet high, and then discovered the magnetic
south pole." *

CHAPTER XXL

§ 850-880. THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY.

850. Indications of a mild climate about the south pole. — During
our investigations of the winds and currents, facts and circum-
stances have been revealed which indicate the existence of a mild
climate — mild by comparison — within the antarctic circle. These
indications plead most eloquently the course of exploration there.
The facts and circumstances which suggest mildness of climate
about the south pole are these : a low barometer, a high degree of
aerial rarefaction, and strong winds from the north.

851. The story of the winds. — The winds were the first to whisper
of this strange state of things, and to intimate to us that the
antarctic climates are in winter very unlike the arctic for rigour
and severity. In dividing the sea into wind-bands (§ 852) or
longitudinal belts 5° of latitude broad each, I excluded from
the table on the next page, observations from those parts of
the sea, such as the North Indian Ocean, the China Sea, and
others where monsoons prevail. The object of this exclusion was
to investigate the general movements of the atmosphere, hence

* Text-book of Oceanography for the Use of the Imperial Naval Academy,
by Dr. August Jilek, Vienna, 1857.

THE ANTARCTIC REGIONS AND THEIR CLTMATOLOGT.

453

the propriety of excluding all regions which are known to pre
eent exceptional cases to the general law. The grouping was not
carried beyond lat. 60° north and south, for the lack of observa-
tions on the polar side of those parallels. The number of obser-
vations thus becoming available was 1,159,353. These were
then divided simply into two classes for each belt, viz., polar
winds* and equatorial winds. They were then reduced to terms
of a year, and the average prevalence of each wind in days de-
duced therefrom, as per Plate XY., and the following table : —

Polar and Equatorial Winds.

Northern Hemisphere.

Southern Hemisphere.

Equa-

Polar.

Excess in

Polar

Equa-

Excess in

Belts

No. of

torial.

Days.

No. of
Observa-
tions.

torial.

Days.

Observa-
tions.

Days.

Days.

Equa-
torial.

Polar.

Days.

Days.

Polar.

Equa-
torial.

Between

0°and

5°

67,829

79

268

189

72,945

83

269

186

5 ,,

10

36,841

158

183

25

54,648

72

283

211

10 ,,

15

27,339

278

73

205

43,817

82

275

193

15 ,,

20

33,103

273

91

182

46,604

91

266

. .

175

20 ,,

25

44,527

246

106

140

66,395

128

227

99

25 ,,

80

68,777

185

163

22

66,635

147

208

61

30 ,,

35

62,514

155

195

40

76,254

150

204

54

35 ,,

40

41,233

173

179

6

107,231

178

178

0

0

40 ,,

45

33,252

163

186

23

63,669

202

155

47

45 ,,

50

29,461

164

189

25

29,132

209

348

61

50 ,,

55

41,570

148

203

55

14,286

208

151

57

55 ,,

60

17,874

142

213

71

13,617

224

132

92

852. TJie null belts. — This plate and table reveal a marked
difference in the atmospherical movements north, as compared
with the atmospherical movements south of the equator. The
equatorial winds of the northern hemisphere are in excess only
between the parallels of 10° and 30° ; i. e., they are the dominant
winds over a zone 20^ of lat. in breadth, while the equatorial
winds of the southern hemisphere hold the mastery from 35° S.
to 10° N. ; i. e., they are the dominant winds over a zone 45° of
lat. in breadth, while the others cover a space not half so broad.
This table, moreover, shows the debatable ground between the
winds, or what may be called the null belt, in this general move-
ment from poles towards the equator, and from equator towards

* Polar winds blow toward the pole, equatorial toward the equator.

454 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the poles, is, in tlie northern hemisphere, between the parallels
of 25° and 50°. In the southern the field of battle is narrowed
dotrn to a single belt (between 35° and 40°) ; here the two winds
exactly counterbalance each other. As the seaman proceeds from
this medial belt, the winds increase belt for belt very nearly ]pari
passu; on the polar side, the polar winds — on the equatorial,
the equatorial winds, gaining more and more in days of annual
duration, and more and more in average velocity each.

853. Extent of the polar indraught. — The fact that the influence
of the polar indraught upon the winds should extend from the
antarctic to the parallel of 40° S., while that from the arctic is so
feeble as scarcely to be felt in 50° N., is indicative enough as to
difference in degree of aerial rarefaction over the two regions.
The significance of this fact is enhanced by the " brave west
winds," which, being bound to the place of greatest rarefaction,
rush more violently and constantly along to their destination
than do the counter-trades of the northern hemisphere. Why
should these polar-bound winds of the two hemispheres differ so
much in strength and prevalence, unless there be a much more
abundant supply of caloric, and, consequently, a higher degree of
rarefaction, at one pole than the other ?

854. Tlie rarefaction of the air over polar regions. — In the
southern hemisphere — and our attention is now directed exclu-
sively to that — the polar winds on the south side of 40° are very
much stronger than are the equatorial winds on the north side of
35° : a fact indicative of a greater degree of rarefaction about the
place of polar calms than we have in the equatorial calm belt.

855. Barometrical observations. — That such is the case is also
suggested by the fact that the indraught into the antarctic calm
place is felt (§ 854) at the distance of 50° from the pole all round,
while the equatorial indraught is felt no farther than 35° from
the equator ; and that such is the case is proved by the barometer.
Lieutenant Andrau, of the Meteorological Institute of Utrecht,
has furnished us from the Dutch logs with 83,334 observations
on the height of the barometer between the parallels of 50° N.
and 36° S. at sea. Lieutenants Warley and Young have extracted
from the log-books in the Washington Observatory, taken at
random, 6,945 observations on the barometer south of the
parallels of 40° at sea. Dr. Kane has furnished us with the mean
height of the barometer in lat. 78° 37' N., according to 12,00C
Viourly observations made during his imprisonment cf 17 months

THE ANTAECTIC REGIONS AND THEIR CLIMATOLOGY.

455

in the ice there. The annals of Greenwich at St. Petersburg give
us the mean height of the barometer in lat. 51° 29' N., according
to three years' observations, and in lat. 69° 51' N., according to
ten years of observation. Such are the sources of the table.

3Iean Height of the Barometer

•

Latitude.

Barometer.

No. of
Observations.

Latitude.

Barometer.

No. of
Observations.

0° to 5° N.

29.915

5114

0° to 5°S.

29.940

3692

5 ,,10

29.922

5343

5 ,, 10

29.981

3924

10 ,, 15

29.964

4496

10 ,,15

30.028

4156

15 ,,20

30.018

3592

15 ,, 20

30.000

4248

20 ,,25

30.081

38] 6

20 ,,25

30.102

4536

25 ,,30

30.149

4392

25 ,,30

30.095

4780

30 ,, 35

30.210

4989

30 ,, 36*

30.052

6970

35 ,,40

30.124

5103

40 ,,43

29.88

1703

40 ,,45

30.077

5899

43 ,, 45

29.78

1130

45 ,, 50*

30.060

8282

45 ,, 48

29.63

1174

51° 29'

29.814t

Greenwich

48 ,,50

29.62

672

59° 51'

29.88

St. Peters-

50 ,, 53

29.48

665

burg

53 ,,55

29.36

475

78° 37

29.759

Dr. Kane

56i

29.29

1126

* Maandelijksche Zeibaanwijzingen van Java naar Het Kanaal. Als Uitkomsten Wetenschap
en Ervaring Aangaande Winden en Zeesiroomingen in Sommige Gedeetten Van Den Oceaan
Uitgegenen Door Heet Koninklijk Nederlandsch Meteorologisclie Institut. Utrecht, 1859.

f The mean height of the barometer for England generally is 29.94°. — Admiral Fitzroy.

856. The low austral barometer. — Captain Wilkes, U. S. N., and
Clarke Eoss, E.N., both, during their expeditions to the South
Seas in 1839-41, had occasion to remark upon the apparent defi-
ciency of atmosphere over the extra-tropical regions of the
southern hemisphere ; and the low barometer off Cape Horn had
attracted the attention of navigators at an early day. I observed
it in 1831 when doubling the Cape as master of the U.S.S. " Fal-
mouth," and wrote a paper on it, which was published in the
American Journal of Science in 1833-4. The more abundant
materials which the abstract logs since placed within my reach
have enabled me to go more fully into tins subject than it was
possible to do while I was cruising in the Pacific more than a
quarter of a century ago. To ascertain whether these " barometric
anomalies,'' as they are called, are peculiar to the regions about
Cape Horn, or whether they are common to high southern
latitudes in all longitudes, the observations about Cape Horn
were arranged in one group ; those between 20° VV. and 140° E.

456 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

in another ; and those between 140° E. and 80° W. in another,
with the following results : — (They are all on the polar side of
lat. 40^ S.)

Mean Height of the Barometer, as observed between

The Meridians of

20° W.

fe 140" E.

140° E. & 80° W.

Off Gape Horn.

Mean of all.

The parallels of

1

No. of

Baro-

No. of

Baro-

No. of

Baro-

No. of i Baro-

Obser-

meter

Obser-

meter

Obser-

meter

Obser- 1 meter.

vations.

Inches.

vations.

Inches.

vations.

Inches,

vations.

Inches.

40° S. and 43° S.

1115

29.90

210

29.84

378

29.86

1703

29.88

43 , , 45

738

.80

155

.73

237

.75

1130

.78

45 , , 48

611

.58

226

.71

337

.68

1174

.63

48 , , 50

175

.53

247

.56

250

.61

672

.62

50 , , 53

108

.35

198

.45

359

.56

665

.48

53 , , 55

6

.17

92

.35

377

.37

475

.36

S. of 55°

7

.27

64

.42

1055

.28

1126

.29

857. Discussion of observations. — The instruments used for
these observations were for the most part the old-fashioned
marine barometer, to which no corrections have been applied.
The discrepancies of this table evidently arise from the lack of
number sufficient to mask these sources of error, or from the in-
fluence of the land, and not from any difference as to the mean
heio-ht of the barometer along the same parallels at sea in any one
of the three divisions. In this discussion, the observations of
each group and every band were arranged according to the
month. These monthly tables are not repeated here, but they do
not indicate any decided change in the barometric pressure in
high southern latitudes according to the season. The barometer
there stands low the year round.

858. Barometric curve at sea. — Eesorting to the graphic method
and using the table (above) for the purpose, the barometric curve
of the diagram (Plate XVI.) has been projected from pole to
pole.

859. Ditto over the Zaw(i.— Professor Schouw has given us the
mean height of the barometer for 32 places on the land between
the parallels of 33° S. and 75° 30' N. They afford materials
for the annexed diagram, and show the exceptional character
of the meteorological influences which rule on shore when com-

THE ANTARCTIC KEGIONS AND THEIR CLIMATOLOGY.

457

pared with those which rule at sea. There is barely a resemblance
between this profile of the atmosphere
over the land and the profile of it (Plate
XVI.) over the sea, so difi'erent are these
influences. The irregularities over the
land are chiefly owing to the diiference in
the amount of precipitation at one station
as compared with the amount at another.
Those islands, as the Sandwich and Society,
which are so situated as to bring down a
heavy precipitation, seem to serve as chim-
neys to the atmosphere. The latent heat
which is liberated by the vapour they
condense has the effect of bringing down
the barometer, and of causing, during the
rainy season, an indraught thitherward
from many miles at sea. Such is the rare-
faction produced by the liberation of this
heat, that its effects are, as the pilot
charts show, felt and confessed by the
winds at the distance out to sea of^more
than a thousand miles from the Sandwich
Islands. Thus the land and the islands
give us in the circulation of the atmo-
sphere systems within system. In the
Mississippi and all great rivers, the general
movement of the waters, notwithstanding
the eddies and the whirlpools, is down
stream with the current. So with the
atmosphere : its general movements are
indicated by observations at sea ; its
eddies and whirlpools are created by the
mountains, and the islands, and other in-
equalities, which obstruct its flow in the
regular channels. The mean reading of
the barometer when the rainy season in
India is at its height is 0*4 inch less than
it is in the midst of the dry.

860. Agreement of observations at sea. —
The diagram (Plate XYI.) shows the ob-
servations in the southern hemisphere to

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accordant, and

458 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the curve itself so regular, that we feel no hesitation about pio-
jecting this curve into the unexplored spaces of the south,
and asserting, with all the boldness consistent with the true
spirit of philosophical deduction, that, whether the actual
barometric pressure at the south pole be as low as 28.14 or not,
it is nevertheless very much lower in the antarctic than in the
arctic regions.

861. The question wliy the barometer should stand lower about the
south than the north pole considered. — The question now arises,
Whence this unequal distribution of atmosphere between the two
hemispheres, and why should the mean height of the barometer
in circumpolar regions be so much less for the austral than for
the boreal? No one, it is submitted, will attempt to account for
this difference by reason of any displacement of the geometrical
centre of the earth with regard to its centre of attraction, in
consequence of the great continental masses of the northern
hemisphere ; neither can it be ascribed to any difference in the
forces of gravitation arising from the oblateness of our globe;
neither can it be accounted for by the effects of diurnal rotation
after the Halleyan theory : that would create as low a barometer
at one pole as the other. The air, in its motions to the east and
in its motions to the west, is in equipoise between the parallels
of 35^ and 40° N., 25° and 30° S. There is near each pole and
about the equator a place of permanently low barometer. The
air from all sides is continually seeking to restore the equilibrium
by rushing into those places of rarefaction and reduced pressure ;
consequently there ought to be between each pole and the equator
a place of high barometer from which the air on one side flows
towards the equator, on the other towards the pole. Observation
(p. 455) shows this high place to be between the parallels of 25°
and 40° in the north, and of 20° and 80° in the southern hemi-
sphere : thus the barometer as well as the winds, Plate XV., are
both indicative of a greater degree of rarefaction about the south
than about the north pole. Were there no friction, and were the
atmosphere ordained to move without resistance, the air from
these null belts would carry with it to the polar calms the easterly
motion which it had acquired from the earth in its motion around
its axis at these null belts. Were this motion so impressed, the
wind would arrive, rushing with an hourly velocity about the
polar calm places of 700 miles in the arctic, and 800 in the
antarctic Such a velocity would impart a centrifugal force

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 459

BTifficient to keep the air away from the poles and produce almost
a vacuum there. In this state of things, the same air would
continue to revolve about the poles were not some other agent,
such as heat, brought in to expand and drive it away. Beino*
expanded and puffed out above the general atmospherical level,
but retaining its velocity — for the supposition is that it moves
without friction — and returning through the upper regions, it
would flow back as it went, viz., as a westerly wind, and arrive
at its null belt in the direction of the meridian. But the wind
has friction, and is resisted in every movement ; the atmosphere
partakes of the spheroidal form, which has been impressed upon
the earth itself by its axial rotation. That form is to it the form
of stability. The water at the pole is about 13 miles nearer to
the centre of the earth than the water at the equator ; but there
is not on that account any tendency in the sea to flow back from
the equator towards the poles ; neither is there any tendency to
motion one way or the other in the atmospherical ocean by
reason of the oblateness of its surface. To produce the polar and
equatorial movements of the air, there must be an agent both at
the equator and the poles to prevent such stability by constantly
disturbing equilibrium there, and that agent is heat ; therefore,
whatever be the degree of depression due the polar barometer in
consequence of axial rotation, such depression could, of itself,
produce neither trade nor counter-trade wind ; it could no more
produce currents in the air than in the sea, nor could axial rota-
tion produce a high barometer at one pole, a low barometer at
the other ; consequently, the difference in the pressure of the
atmosphere about the two poles, as shown by the diagram (Plate
XVI.), cannot be ascribed to the influence of axial rotation. It
is doubtless due to the excess in antarctic regions of aqueous
vapour and its latent heat.

862. Psychrometry of polar winds. — The arctic circle lies chiefly
on the land, the antarctic on the water. As the winds enter one,
they are loaded with vapour ; but on their way to the other they
are desiccated (§ 826). Northern mountains and the hills wring
from them water for the great rivers of Siberia and Arctic
America. These winds, then, sweep comparatively dry air across
the arctic circle ; and when they arrive at the calm disc — the
place of ascent there — the vapour which is condensed in the act
of ascending does not liberate heat enough to produce a rarefac-
tion sufScient to call forth a decided indraught from a greater

460 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGT.

distance in the surrounding regions than 40'' (§ 852)— 2400 miles ;
and the rarefaction being not so great, the barometer is not so
low there as in antarctic regions.*

863. Aerial rarefaction about the wor^^ poZe.— Nevertheless, there
is rarefaction in the arctic regions. The winds show it, the
barometer attests it, and the fact is consistent with the Enssian
theory of a polynia in polar waters. The presence within the
arctic circle of a considerable body of comparatively warm water,
which observation has detected going into it as an under current
— which induction shows must rise up and flow out as a surface
cuirent — would give forth vapour most freely. This vapour,
being lighter than air, displaces a certain quantity of atmo-
sphere. Eising up and being condensed, it liberates its latent
heat in the cloud region, and so, by raising temperature, causes
the moderate degree of rarefaction which the barometer at sea, at
Greenwich, at St. Petersburg, and in the arctic ice indicates.

864. Ditto about the south pole. — "Within the antarctic circle, on
the contrary, the winds bring air which has come over the water
for the distance of hundreds of leagues all around ; consequently,
a large portion of atmospheric air is driven away from the austral
regions by the force of vapour, which fills the atmosphere there.
Now there must be a place — an immense disc, with irregular
outlines, it may be, and probably is — where these polar winds
(§ 855) cease to go forward, rise up, and commence to flow back
as an upper current. If the physical aspects — the topographical
features in and about this calm place — be such as to produce
rapid condensation and heavy precipitation (Chap. XX.), then
we shall have, in the latent heat liberated from all this vapour,
an agent sufficient not only to produce a low barometer and a
powerful indraught, but quite adequate also to the mitigation of
climate there.

865. Influences favourable to heavy precipitation. — Mere altitude,
with its consequent refrigeration, does not seem as favourable as
mountain peaks and solid surfaces to the condensation and pre-
cipitation of vapour in the air. In the trade-wind regions out at
sea it seldom raius ; but let an island rise never so little above
the water, and the precipitation upon it becomes copious. In
Colonel Sykes' (§ 299) rain-fall at Cherraponjie. we have an

* Captain M'Clintock, during his northern explorations in the schooner
Fox," records the arctic baromt- ter as high as 31 inches.

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 461

annual precipitation* at tlie rate of 577.6 inches during the six
months of S.W. monsoons — from May to October. Surely no one
will maintain that this vapour, after rising from the sea, reached
the height of 4500 feet for the first time when it was blown upon
the peaks of Cherraponjie. Islands in the South Sea are ever-
lastingly cloud-capped. If it be mere refrigeration that condenses
this vapour, why, one might ask, should not the clouds form at
the same height above the sea whether there be an island below
or not, and why should not these clouds precipitate as copiously
upon the water, as they do upon the land ? "We only know that
they do not.

866. The climates of corresponding shores and latitudes north and
south. — Captains King and Fitzroy exposed their rain gauge on
the western slopes of the Patagonian Andes, and it collected
153.75 inches in forty-one days ; that is, at the rate, as already
(§ 827) stated, of 1368.7 inches in the year. The latent heat that
is liberated during these rains gives to Eastern Patagonia its mild
climate. It is this latent heat which causes the irregularity in
the barometric curve (§ 858) between the parallels of 50°-55° S.
Here the westerly winds prevail ; they carry over to the eastern
coasts the air that, in passing the mountains, is warmed by this
liberated heat ; and thus, as I have already (§ 729) endeavoured
to show, we have an exception to the rule under which meteoro-
logists ascribe cold and severe climates to the windward or
western, soft and mild to the leeward or eastern, shores of
extra-tropical oceans. Labrador and the Falkland Islands "j* are
in corresponding latitudes north and south. They are both on
the windward shore of the Atlantic ; they occupy relatively the
same position with regard to the wind. Labrador is almost
uninhabitable on account of the severity of its climate ; but in
the Falkland Islands and their neighbouring shores the cattle
find pasturage throughout the winter. The thermometrical differ-
ence of climate at these two places, north and south, may bo
taken as a sort of index to the relative difierence between the
arctic and antarctic climates of our planet.

867. Tliermal difference hetween arctic and antarctic climates. —
Along the eastern base of the Eocky Mountains the isotherms

* Eeport of the twenty-second meeting of the British Association for the
Advancement of Science, held at Belfast in September, 1852.
t Maury's Saihng Directions, sixth edition, p. 553.

462 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

mount up* towards the nortli in consequence of the heavy winter
precipitation upon the western slopes of these mountains. The
heat which is required to convert the water of the Columbia and
other rivers into vapour is set free on the mountain range, and
the upper Missouri is by this heat kept open for navigation long
after the lower and more southern portion of it is frozen up.

868. Tlie influence of aqueous vapour upon winds and climates. —
The average evaporation of water from sea and land is estimated
to be from one third to one half as much daily as is contained in
the great chain of American lakes. The average precipitation
equals the evaporation. The heat that is absorbed and evolved
in the process of lifting up and letting down such a body of
water has a powerful influence upon climates as well as upon
winds ; it is the chief source of that motive power which gives
to the winds their force, to the storm its violence. Six hundred
and twenty pounds of aqueous vapour occupy in the open air the
space which it takes one thousand pounds of dry air at the same
temperature to fill. Now to appreciate the wind -begetting power
of this vapour, and its heat, let us imagine the air over an area
of considerable extent to be saturated with vapour from the sea,
and that from some cause, as in a thunder-storm, this vapour is
suddenly, or even rapidly, condensed : — The aerial rarefaction
over such an area, and consequently the wind-begetting power
within it, would be immense, merely on account of the con-
densation of this vapour ; but if we take into the account the
rarefying effect of the heat that is set free during the process of
condensation and precipitation, we may cease to marvel either
at the force of the wind, or the violence of the rain which marks
the hurricane; nor need we wonder at the low range of the
barometer or the mildness of temperature in all rainy latitudes.

869. Hoio the temperature of air may he raised hy crossing moun-
tains.— In the preceding chapter the circumstances have been
considered which favour the idea that most of the unknown sur-
face of the antarctic circle is not only land, but that its coasts
are probably highlands ; that in its topographical features it
presents all the conditions that are required for the rapid con-
densation of the vapour with which the impinging air from the
sea is loaded, and that in the valleys beyond mild climates may
be expected. The aqueous vapour which the air carries along is

Blodget's Climatology of the United States.

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 463

one of the most powerful modifiers of climates. It is to the
winds precisely what coals are to the steam-ship at sea — the
source of motive power. The condensation of vapour is for one
what the consumption of fuel is for the other ; only with the
winds the same heat may be used over and over again, and for
many purposes. By simply sending moist air to the top of
snow-capped mountains, condensing its moisture, and bringing
it down to the surface again, it is made hot. Though by going
up the air be cooled, it is expanded, and receives as sensible
heat the latent heat of its vapour ; being brought down to the
surface again, and compressed by the whole weight of the baro-
metric column, it is hotter than it was before by the amount of
heat received from its vapour. That we may form some idea as
to the modifying influences upon climate which miglit arise from
this source, let us imagine the air as it impinges upon the ant-
arctic continent to be charged with vapour at the temperature of
of 40°. In order to arrive at the place of polar calms, it has to
cross a mountain range, we will suppose, the summits of which
are pushed high up into the regions of perpetual snow. As this
air, with its moisture, rises, it expands, cools, and liberates the
latent heat of its vapour, which the air receives in the sensible
form. Now suppose the expansion due the height of the moun-
tain-top to be sufficient to lower the temperature of dry air to
— 50°, but, on account of the latent heat which is liberated from
the vapour of the moist air, the temperature of the air that has
ascended, instead of falling as it crosses the mountain to — 50°, as
dry air would do, falls, in consequence of the condensation of its
vapour, no lower than ~ 30°. Thus, in the case supposed, heat
enough has been set free to raise the temperature of the newly-
arrived air 20°. Consequently, when this air, which, at the
temperature of 40°, came from the sea loaded with vapour, passes
the mountain, it loses vapour, but receives heat; descending
into the valleys beyond, it is again compressed by the weight of
the barometric column, which, let us assume, is the same in the
valley as at the sea level on the other side of the mountain. The
temperature of this air now, instead of being 40°, will be 60°. A
powerful modifier of climate is the latent heat of vapour in the
air.

870. Local variations of climate, how caused. — At one time, as
has been shown in Chap. lY., this heat is brought down from
the cloud region to scorch the earth ; at another time it causes

464 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

tlie warm air to ascend, and cooling currents to come down from
the upper sky. To this cause Dr. Franklin ascribed the cold
summer gusts in America that come from the west. To the
effect of this vapour and its heat, with the constant vertical cir-
culation imparted to the atmosphere, we owe those variations of
our climates which make any given day of one year to differ
from its corresponding day of another. Were it not for those
vertical movements, our days would gradually grow cooler from
midsummer to midwinter ; as the sun recedes in the ecliptic,
each day, after he reached a certain degree of south declination,
would grow cooler and cooler until his return towards the north
again ; so that were it not for this vertical circulation the tem-
perature of the day of the month, like the rising and the setting
of the sun, or the changes of the moon, might be foretold in a
calendar.

871. — Aurora australis. — There is not only reason to suppose
that the topographical features and the climates of the antarctic
regions differ greatly from the topographical features and cli-
mates of the arctic, but there is reason to suppose a difference
in other physical aspects also. The aurora points to these.
"On the morning of the second of September last," says Capt.
B. P. Howes, in his abstract log of the " Southern Cross," lat.
58° S., long. 70° W., " at about half-past one o'clock, the rare
phenomenon of the aurora australis manifested itself in a most
magnificent manner. Our ship was off Cape Horn in a violent
gale, plunging furiously into a heavy sea, flooding her decks,
and sometimes burying her whole bows beneath the waves. The
heavens were black as death : not a star was to be seen when
the brilliant spectacle first appeared. I cannot describe the
awful grandeur of the scene ; the heavens gradually changed
from murky blackness till they became like vivid fire, reflecting
a lurid, glowing brilliancy over everything. The ocean appeared
like a sea of vermilion lashed into fury by the storm ; the waves,
dashing furiously over our sides, ever and anon rushed to lee-
ward in crimson torrents. Our whole ship, sails, spars, and all,
seemed to partake of the same ruddy hues. They were as if
lighted up by some terrible conflagration. Taking all together,
the howling, shrieking storm, the noble ship plunging fearlessly
beneath the crimson-crested waves, the furious squalls of hail,
snow, and sleet driving over the vessel and falling to leeward in
ruddy showers, the mysterious balls of electric fire resting on

THE ANTARCTIC EEGIONS AND THEIR CLIMATOLOGY. 465

our mast-lieads, yard-arms, etc., and above all, tlie awful sub-
limity of the heavens, through which co]'uscations of auroral
light would often shoot in spiral streaks and with meteoric bril-
liancy, altogether presented a scene of terrible grandeur and
awful sublimity surpassing the wildest dreams of fancy. Words
fail to convey any just idea of the magnificence it presented.
One must see it and feel it in order to realize it. I have written
this because I believe it an unusual occurrence to see the
' southern lights ' at all, and also because this was far superior,
and, in fact, altogether diiferent from our northern lights, as
seen from the latitude of Boston."

872. — An erroneous opinion. — Some objections to these views
respecting the comparative mildness of antarctic climates are
suggested by common opinion. It is an opinion which is generally
received among sailors and physicists that the southern is colder
than the northern hemisphere, and that the austral are more
severe than the boreal climates, and that the antarctic icebergs,
in the silent evidence afforded by their size and numbers, are
witnesses of the fact. These objections have an apparent weight ;
they deserve consideration.

873. — Tro]^ical regions of the southern hemisphere cooler^ extra-
tropic^l imrmer, than those of the northern. — The answer to them is
as follows : Between lat. 40° or lat. 45° and the equator, and
parallel for parallel, the southern hemisphere is cooler than the
northern. Eeason teaches, and observations show that it is so.
But beyond 45° S. observations are wanting, and we are left to
reason and conjecture. That the southern hemisphere should,
till within a certain distance of the pole, be warmer in winter
and cooler in summer, may be explained by the fact that the
southern hemisphei'e has more water ; that water being more
equable than land in its temperature, produces more equable
climates ; that the vapour which is taken up from trans-equatorial
seas and condensed into rains for cis- equatorial rivers conveys
with it a vast amount of heat which the southern hemisphere
receives from the sun. It is rendered latent by evaporation on
one side of the equator, and made sensible by precipitation on the
other. Much of it is set free in the equatorial calm belt, and it
is this liberated heat which assists mightily to maintain the
thermal equator in its northern position.

8.74. Formation of southern icebergs. — So, in like manner, the
vapour that is borne to the antarctic regions by the polar-bound

2 H

466 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

winds transports immense volumes of heat from the more tem-
perate latitudes of the south, and sets it free again in the polar
regions there. And as for the southern icebergs, they are rather
of fresh than of salt water ; and they are the channels through
which the water that the winds carry there as vapour finds its
way back again. Being fresh water, and falling on the antarctic
declivities of the land, it is by rills, and streams, and rains brought
together, and by constant accretions formed into glaciers of a size
and thickness that are almost impossible to be formed out of sea
watei unless it be dashed up as spray. Moreover, on the arctic
ocean the rains are not so copious, and for that reason, though
the climate be more severe, icebergs, or rather glaciers, are not
formed on so grand a scale. Southern icebergs are true glaciers
afloat. Arctic winds are dry enough to evaporate much of the
ice and snow that fall and form in the north polar basin. As
compared with arctic climates, antarctic are marine, arctic con-
tinental ; and for the very reason that the English climate is
cooler in summer and warmer in winter than the Canadian, so is
winter at the south pole much less severe than winter at the
north. The relative difference between the two polar climates
is, as the barometer indicates, even greater than is the difference
between a Canadian and an English winter.

875. Mild climate in 63° >S^. — As tending to confirm these views
touching the mildness of unknown antarctic climates, the state-
ment of Captain Smyley, an American sealer, may be mentioned.
He planted a self-registering thermometer on the South Shetlands,
lat. 63° S., and left it for several winters, during which time it
went no lower than — 6° Fahr.*

876. Antarctic ice-drift. — The low barometer and the implied
heavy precipitation in the antarctic regions are not the only wit-
nesses that may be called up in favour of bluffs and bold shores
to the antarctic continent. The icebergs, in their mute way, tell
that the physical features of that unexplored land are such, in its
northern slopes, as to favour the formation of glaciers on the
shore, thence to be launched and become the huge icebergs that,
on their journey to the milder climates of the north, are encoun-
tered far away at sea. After a somewhat attentive, but by no
means a thorough, examination and study of antarctic icebergs
as they endanger the routes of navigation, the idea suggested

* Maury's Sailing Directions.

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 467

itself that information might be gathered from them concerning
antarctic regions which would be highly useful to any future
expedition thitherward.

877. Antarctic currents. — The conditions required for Gulf-
Stream like currents, or a rapid flow and reflow of equatorial
and polar waters between the torrid and the frigid zones, as in
the northern hemisphere, are not to be found about the antarctic
regions. Of all the currents that come from those regions,
Humboldt's current is by far the most majestic. It is believed
also to be the least sluggish of them all. It certainly conveys the
coldest water thence to the torrid zone ; and yet it appears not
to come from a nursery of icebergs, for in its line of march fewer
icebergs are found than are encountered on the same parallels
between other meridians, but where feebler currents flow. From
the arctic regions the strongest currents bring down the most
icebergs ; not so from the antarctic. Hence the inference that,
though icebergs have been encountered off the shores of the
antarctic continent wherever they have been approached, yet it
is only those which have been launched from particular points of
that frost-bound coast which are stout enough to bear transporta-
tion to the parallel of 40° south. In Humboldt's current it is
rare to see an iceberg as far from the pole as the parallel of the
fifty-fifth degree of south latitude; but off the Cape of Good
Hope on one side of the Atlantic, and Cape Corrientes on the
other, antarctic icebergs are sometimes seen as far as the parallel
of 35°, often as far as 40°. Lieutenants Warley and Young, after
having examined the logs of 1843 ships cruising on the polar
side of 35° S., report the great antarctic ice-drift to be towards
the Falkland Islands on one hand, and the Cape of Good Hope
on the other.

878. Antarctic explorations demanded. — These facts and the
stories of the icebergs are very suggestive. In mute eloquence
and with great power they plead the cause of antarctic explora-
tion. Within the periphery of that circle is included an area
equal in extent to one-sixth part of the entire land surface of our
planet.* Most of this immense area is as unknown to the in-
habitants of the earth as is the interior of one of Jupiter's satel-
lites. With the appliances of steam to aid us, with the lights
of science to guide us, it would be a reproach to the world to

The area of the antarctic circle is 8,155.600 square miles.

2h 2

468 PHYSICAL GEOGRAPHY OF THE SEA. AND ITS METEOROLOGY.

permit such a large portion of its surface any longer to remain
unexplored. For the last 200 years the Arctic Ocean has been
a theatre for exploration ; but as for the antarctic, no expedition
has attempted to make any persistent exploration, or even to
winter there.

879. Former expeditions. — England through Cook and Eoss;
Eussia through Billingshausen ; France through D'Urville ; and
the United States through Wilkes, have sent expeditions to the
South Sea. They sighted and sailed along the icy barrier, but
none of them spent the winter or essayed to travel across and
look beyond the first impediment. The expeditions which have
been sent to explore unknown seas have contributed largely to
the stock of human knowledge, and they have added renown to
nations, lustre to diadems. Navies are not all for war. Peace
has its conquests, science its glories ; and no navy can boast of
brighter chaplets than those which have been gathered in the
fields of geographical exploration and physical research.

880. An appeal for others. — The great nations of the earth
have all, with more or less spirit, undertaken to investigate cer-
tain phenomena touching the sea, and, to make the plan more
effectual, they have agreed to observe according to a prescribed
formula. The observations thus made have brought to light
most of the facts and circumstances which indicate the existence
within the antarctic circle of a mild climate — mild by compari-
son. The observations which have led to this conclusion were
made by fellow-labourers under all flags. It is hoped that this
circumstance may vindicate, in the eyes of all, the propriety of
an appeal in this place for antarctic exploration, and plead for it
favourable consideration among all nations.

CHAPTEE XXII.

§ 881-895. THE ACTIXOMETRY OF ffHE SEA.

881. A new field. — One of the columns in the m^n-of-war log
of the Brussels Conference calls for the temperature of the water
below as well as at the surface of the sea. Olily a few entries
have been made in this column ; but these, as far as they go,
seem to indicate that the warmest water, especially in tropical

THE ACTINOMETRY OF THE SEA. 469

seas, is not to be found at the top, but in a stratum a little way
down. What is the depth of this stratum, and what may be the
thermal difference between its waters and those of the surface,
are questions for future observations to settle. Indeed, this sub-
ject opens a new field of inquiry ; it is one from which much
useful and instructive information is doubtless to be obtained by
any one of our co-operators who wdll enter upon the investiga-
tion patiently and with diligence.*

882. The warmest ivaters in the sea — ivliere are they ? at or below the
surface f — The observations that we possess do not prove that the
warmest water of intertropical seas is not at the surface : they
go no farther than to show that it is sometimes not at the surface,
and to suggest that, in all probability, it is generally below,
especially in "blue water." Keason suggests it also. Supposing
that, as a rule, the hottest water is below the surface, we may, in
order to stimulate research, encourage investigation, and insure
true progress, propound a theory in explanation of the phe-
nomenon, looking to future observations to show how far it may
hold good.

* On the 26th of March, 1852, the late Passed Midshipman A. C. Jackson,
U. S. N., being in the Gulf Stream, lat. 34° 55' N., long. 74° 8' W., found the
temperature of the water 74.5^ at the surface, 79° at the depth of six feet, and
86.5° at the depth of 16^ feet. Again, on the 30th, in lat. 24° 10' N., long.
80° 11' W. (near the edge of the Gulf Stream), he tried the temperature of the
water by another carefully conducted set of observations, and found it 78° at
the surface, and 79.5° at the depth of 16J feet. The sea was rough, and he did
not, for that reason, observe the temperature at six feet. The temperature of
the air in the shade was 69.5" on the 26th, and 79° on the 30th. (Vide p. 59,
5th ed., Maury's Sailing Directions, 1853.)

Extract of a Letter from J. Bermingham. Chief Engineer of the American

Steamer " Golden Age," dated Bay of Panama, June 29, 1860, and addressed

to Lieut. John M. Brooke, U. S. N.
" On our late trip from San Francisco (5th June) to this port we experienced
the most remarkably fine weather and smooth sea that I have ever witnessed on
the Pacific, or anywhere else,

" On the 14th, while crossing the Gulf of Tehuantepec, we found the tempe-
rature of the sea water on the surface (where it had not been disturbed by the
progress of the vessel) 88°, and upon taking the temperature at the same time
ten feet below the surface the mean of three thermometers gave 90°. Tempera-
tiu-e of atmosphere 93°.

" I do not exactly understand why the temperature of the sea water should
be so much greater at a distance of ten feet from the surface than it was im-
mediately upon the surface.

" Mr. Agassiz (a son of Professor Agassiz) was on board, and he and myself
made repeated tests of the temperature of the water during the four hours we
were running through it — the warm belt.

" Ninety degrees is tlie highest temperature that I have ever known the
water of the ocean to attain."

47 1 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

883. The annual siqyply of solar heat uniform. — The flow of heat
from the sun is held to be uniform, and the quantity that is
annually impressed upon the earth is considered as a constant.
The sun spots may make this " constant " a variable, but the
amount annually received by the earth is so nearly uniform, that
our best instruments have not been able to show us any variation
in its uniformity. Some maintain that climates are undergoing
a gradual change as to temperature. However this may be as to
certain localities, Baron Fourier, after a long and laborious cal-
culation, claims to have shown that if the earth had been once
heated, and after having been brought to any given temperature,
if it had then been plunged into a colder medium, it would not
in the space of 1,280,000 years be reduced in temperature more
than would a 12-inch globe of like materials in one second of
time if placed under like conditions. It may be assumed that
for the whole earth, there has not been since the invention of the
thermometer any appreciable change in the temperature of the
crust of our planet.

884. Quantity of heat daily impressed upon the earth. — The earth
receives from the sun heat enough daily, it has been said (§ 271),
to melt a quantity of ice sufficient to incase it in a film 1-J inch
thick. What becomes of this heat after it is so impressed,
how is it dispersed by the land? how by the sea? Let us
inquire.

885. How far helow the surface does the heat of the sun penetrate f —
The solar ray penetrates the solid parts of the earth's crust only
to the depth of a few inches, but striking its fluid parts with its
light and heat, it penetrates the sea to depths more or less pro-
found, according to the transparency of the waters. Let us, in
imagination^ divide these depths, whatever they may be, into
any number of stratifications or layers of equal thickness. The
direct heat of the sun is supposed to be extinguished in the lowest
layer; the bottom layer, then, will receive and absorb the
minimum amount of heat, the top the maximum ; consequently,
each layer, as we go from the top to the bottom, will receive lesa
and less of the sun's heat.

886. The stratum of warmest ivater. — Now, which will retain
most heat and leach the highest temperature? Not the top
layer, or that to which most heat is imparted, because by eva-
poration heat is carried off from the surface of the sea almost as
fa.st as by the sun it is impressed upon the surface of the sea ;

THE ACTINOMETRY OF THE SEA. 471

not the bottom layer, because that receives a minimum, which,
though it cannot escape by evaporation, may nevertheless fail to
ake any marked change in temperature — fail, not by reason of
no evaporation, but by the ever-changing movements which, con-
sidering the length of time required to heat the lower stratum
by such slow and gradual accumulation of heat, would alter its
place and vary its condition, and indeed removing it beyond the
reach of the observer.

887. Its position. — The layer, therefore, which accumulates
most heat and becomes warmest, should be neither at the bottom
nor at the top, but intermediate, the exact temperature and depth
of which it is for observation to determine. , To encourage such
determination and the investigations which it suggests is the
main object of this chapter.

888. The different subjects for observation. — In conducting such
investigations, several questions are to be considered, such as the
transparency and specific gravity of the water, its phosphorescence ;
the face of the sky, whether clear or cloudy ; the state of the sea,
whether rough or smooth ; the condition of the weather, whether
calm or windy. Then the temperature should be tried, at
various depths and at various hours of the night and day, in
order to ascertain not only the maximum temperature and
average depth of the warmest stratum in the day, but the dif-
ference in its temperature and position by day and by night.
These observations will afford the data, also, for computing the
amount of solar heat that penetrates the bosom of the sea, as well
as the amount that is radiated then(;e again. They will reveal
to us knowledge concerning its actinometry in other aspects.
We shall learn how absorption by, as well as radiation from, the
under strata is affected by a rough sea, as when the waves are
leaping and tossing their white caps, and how by its glassy
surface, as when the winds are hushed and the sea smooth.

889. Expected discoveries. — Here we are reminded, also, to
anticipate the discovery of new beauties and fresh charms among
the wonders of the sea. We have seen (§ 366) that while the
heat of the sun is impressed alike upon sea and land, never-
theless the solid part of the earth's crust radiates much more
freely than the fluid. On the land the direct heat of the sun
operates only upon a mere shell a few inches in thickness; at
sea it penetrates into the depths below, and operates upon a
layer of water many feet thick. The solid land-crust has its

4/2 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS BIETEOROLOGY.

temperature raised high by day and cooled low down by night ;
but the most powerful sun, after beating down all day with its
fiercest intensity upon this liquid covering, has not power to
raise its temperature more than three or four degrees. This
covering serves as a reservoir for the solar heat. In the depths
below it is concealed from the powers of intense radiation, and
held by the obedient ocean in readiness to be brought to the sur-
face from time to time, and as the winds and the clouds call for
it. Here it is rendered latent by the forces of evaporation, and
in this form, having fulfilled its office in the economy of the
ocean, it passes off into the air, there to enter, in mysterious
waj^s, upon the performance of its manifold tasks.

890. Actinic p'occsses. — As evaporation goes on by day or night,
the upper stratum is rendered heavier by reason of both the heat
and the fresh water borne away by evaporation ; the upper water
having been thus rendered both Salter and cooler, has its specific
gravity increased so much the more. On the other hand, the
strata below, receiving more heat by day than they dispense again
by radiation day and night, grow actually warmer and speci-
fically lighter; and thus, by unseen hands and the "clapping of
the waves," the waters below are brought to the surface, and
those on the surface carried doT^n to unknown depths ; and thus,
also, we discover new and strange processes which have been
ordained for the waters of the ocean in their system of vertical
circulation.

891. Tlie reservoirs of heat. — Thus we arrive at the conclusion
that the ocean is the great reservoir of sensible as the clouds are
of latent heat. That in those two chambers it is innocuously
stored, thence to be dispensed by processes as marvellous as they
are benignant and wise, to perform its manifold offices in the
economy of our planet ; it is this heat which gives " his circuits "
to the winds and circulation to the sea ; it is it that fetches from
the ocean the clouds that make " the earth soft with showers."
Stored away in the depths of inter-tropical seas, it is conveyed
along by " secret paths " to northern climes, there to be brought
to the surface in due season, given to the winds, and ])orne away
to temper the climates of western Europe, clothing the British
Islands as they go, in green, and causing them to smib under the
genial warmth even in the dead of winter.

892. An office for waves in the sea. — Thus perhaps -ve discover
a new office for the waves in the physical economy of the ocean.

THE ACTINOMETEY OF THE SEA. 473

Is it not to tliem that has been assigned the task of bringing up
by their agitation of the surface the layers of warm water that
are spread out below; and are they not concerned also, as they
draw up the genial waters, in regulating the supply of heat for
the winds by night, as well as in cold or cloudy days, for the
purposes of evaporation ? Thus even the waves of the sea are
made b}^ this beautiful study to present themselves as parts, im-
portant parts, in the terrestrial machinery. We now view them
as it were, like balance-wheels in the complicated system of
mechanism by which the climates of the earth are governed. If
the waves did not stir up the heated waters from below (§ 881),
the winds would evaporate slowly by night, for the want of ade-
quate supplies of caloric ; the consequence would be less precipi-
tation and a more scanty supply of latent heat for liberation in
the cloud region. As a consequence of this, the winds would
have less motive power, and the whole climatic arrangements of
our planet would be different from M^hat they are.

893. The radiating jpowers of earth, air, and water compared. — We
may note also another peculiarity as to the difference in the
direct heat-absorbing and radiating properties of sea, land, and
air : it is one which presents the atmosphere in the light of a
regulator between the land on one hand, and the heating powers
of the sun on the other. It is suggestive also of other benign
compensations and lovely offices in the physical machinery of our
planet: both land and water receive more heat from the sun than
they radiate again ; but the atmosphere receives less heat direct
from the sun than it radiates off again into space : as the heat
comes from the sun, part of it is absorbed by the atmosphere ;
but the largest portion of it is impressed upon the land and water;
from them a portion passes off into the atmosphere by conduction,
while another portion is radiated directly off into the realms of
space. What becomes of the remainder ? Let us inquire, for
there is a remainder, and unless means for its escape were pro-
vided, the land and water, especially the latter, would continue
to grow warmer and warmer, and so produce confusion in the
terrestrial economy. The remainder of this heat, being that
which is neither radiated by sea and land directly off into space,
nor imparted to the air by conduction from them, is absorbed in the
processes of evaporation ; it is then delivered to the atmosphere
latent in the vesicles of vapour, to be set free in the cloud region,
rendered sensible and imparted to the upper air, whence it is senl

474 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

off by radiation into the " emptiness of space." Thus the air
with its actinometry presents itself in the light of a thermal
adjustment, by which the land and sea are prevented from be-
coming seething hot ; and by which they are enabled to perform
their wonderful offices with certainty and regularity.

894. A reflection concerning heat. — It is curious to think that
this heat which we have been contemplating, now as latent in
the clouds above, now as sensible in the waters below, comes
from the same source whence originall}^ came the heat which has
been packed away in seams of coal and stored in the bowels of
the earth for ages and ages, to be called forth by man at will for
his own comfort, pleasure, and convenience; that this protean
thing is the agent which controls sea and winds, and they it ;
that it is it which has lifted up the mountains ; which clothes the
world with beauty, and keeps the stupendous fabric of the uni-
verse in motion ; and that after all, this mighty agent is only
that gentle thing that "warms in the sun !"

895. Probable relation between the actinism of the sea and its
dentil. — Pursuing this subject, the philosophical mariner, as he
sails along and records observations for these purposes, may fancy
— and perhaps rightly — that he has traced to the actinometry of
the sea one of the physical conditions which, when the depths
of the ocean were laid, had its weight with the Almighty

AUCHITECT.

476

INDEX

Actinism of the sea, probable relation
between it and depth, 474.

Actinometer, a natural, in the trade
winds, 350.

Actinometry of the sea, 468, 472, 474.

Adhe'mar's cataclysm theory, 347.

Advance, drift of the, 247, 251.

Africa, hot land breezes from the west
coast of, 141.

'♦ African dust," 145 ; sargasso, 410.

Air, relative weights of ocean of water
and that of, 1 ; their depths, 1 ; their
mutual action, 11 ; phenomena at
their meeting, 1, 323; analysis of, 3;
its specific gravity, 6 ; its powers, 13 ;
its functions, 14; its tendency to
move in the plane of a great circle,
90 ; results of this tendency upon its
circulation, 90 ; experiments of the
French Academy on, 91 ; its offices
in the physical economy, 103 ; of the
calm belts, wet and dry, 159 ; crossing
of two currents explained, 170 ; a
" gulf stream" in the, 363 ; rarefaction
of, over polar regions, 454.

Air-spouts, 377.

Airj-'s wave tables, 4.

American lakes, quantity of fresh water
in, 7 ; reasonings founded on the state
of the water in, 190.

American navy, plan of deep-sea sound-
ing devised for the. 308.

Andes, hot winds of the, 95 ; caused
by the trade-winds, 96 ; older than the
Dead Sea as an inland water, 303.

Andrau, Lieut., on the "sea-dust" of
the Atlantic, 114: on the height of
the barometer in the wind bands, 175,
176 : on the storms of the Cape, 195 ;
barometrical observations in the an-
tarctic regions, 454.

Anemometers, want of, on shipboard,
3tS5 ; ships used as, 432.

Animal life in vast depths, 325, 328,
329.

Animalculse, their offices, 320, 333 ; a
profitable study, 320, 398 ; at the
surface of the sea, 334.

Antarctic bands, topographical features
of the, 448.

Antarctic circle, aerial rarefaction about
the, 460.

Antarctic climates, thermal difference
between arctic and, 461, 466 ; their
mildness, 466.

Antarctic currents, 467.

Antarctic drift, the line of, 411.

Antarctic expeditions, necessity for
411, 467; the principal, 452.

Antarctic icebergs, their influences in
expelling the air from austral regions,
276.

Antarctic ice-drift, 466.

Antarctic Ocean, Captain Eoss and
Capta'n Wilkes's voyages to the, 402.

Antarctic regions, ice-bearing currents
from the, 195 ; the " brave west
winds " caused by rarefaction in the,
440 ; calm place of, a region of con-
stant precipitation, 446 ; also of a low
barometer, 447 ; aqueous vapour the
cause of both, 447 ; probabihty of land
and volcanoes in the, 450, 451, 452 ;
indications of a mild climate in the,
452 ; mean height of the barometer in
the, 454.

Anti-biotics, argument? of the, 324;
from the Bible, 327 : solution of the
question, 328.

Anti-polynian school, views of the, 248.

Antiseptic properties of sea-water, 326.

Aqueous isothermal lines, 393.

Arctic climates, thermal difference be-
tween antarctic and, 461, 466.

Arctic Ocean, waterways between it and
the Atlantic and Pacific contrasted.

476

INDEX.

48; indications of a milder climate
in the, 210; specific gravity of its
water, 211; volume of water kept in
motion by its flow and reflow, 215;
layers of water of different tempera-
ture in the, 252 ; ice-bearing drift from
the, like the ordinary drift from the
Baltic. 253.

Arctic Ocean, open sea in the, first sug-
gestion of an, 207 ; the question ex-
amined, 227 ; barometer indications,
233 ; its position, 235, 250 ; its tem-
perature, 255.

Arctic Ocean, under-current, its in-
fluences, 209 ; its temperature, 254.

Arctic regions, aerial rarefaction in the,
460.

Arquit's, Capt., account of tide -rips,
405.

Asia, deserts of, are they centres of at-
mospherical circulation ? 149.

Astronomical view of climate, 2?0.

Atlantic Gulf stream, 48 ; contrasted
with the Black stream of the Pacific,
192.

At'antic Ocean, 18 ; its telegraphic
plateau, 19; evaporation and precipi-
tation from the, 36 ; its red fogs, 114 ;
its currents, 205 ; its sea-sht-lls sili-
ceous, 264; its deepest part, 313; its
bottom, 314 ; an orographic view of
the, 315 ; its south-west winds, 360 ;
its western half warmer than the
eastern, 387 ; tide-rips in the, 404.

Atlantic, North, high temperature of its
western half, 48 ; sargasso in the, 50 ;
resemblance of its current to that of
the North Pacific, 51 ; its storms, 64;
rain afforded by t lie, 1 1 0 ; its hypsome-
try peculiar. 111 ; its cyclones, 429.

Atlantic, South, sarga^-so in the, 50.

Atmos|)here, its weight 2, 8 ; its height,
3 ; its oiSces, 8 ; contrasted with sea,
8 : its powers, 13 ; its functions, 14 ;
likened to a machine, 75, 97, 104 ;
governed by stable laws, 76, 1 66 ; im-
poii;ance of its circulation, 88 ; how
its vertical movements are produced,
88 ; Faraday's discovery of magnet-
ism in the, 155 ; its electrical tension,
157 ; Quetelet's observations on the
electricity of the, 173; its general
circulation, 174 : more in the north-
ern than the southern hemisphere,
175; why, 275; its important offices,
278 ; its depression by the barometric

ridges, 355 ; its upper surface, 355 ;
counterpoises in the. 363; its nor
mal state, 363 ; its circidation more
active in the southern than the
northern hemisphere, 437.

Aurora australis, 464.

Australasia, monsoons of, 375.

Babelmandeb, straits of, 182, 183.

Baffin's Bay, current from, 28.

Bailey's examination of deep-sea sound-
ings, 317; his disbelief in life in the
depths of the sea, 325 ; his analysis
of the ooze and bottom of the sea,
330.

Baltic sound, under-current in the, 187,
253.

Barlow's magnetic theory, 157.

Barlocci on the temperature of the Lago
Sabatino, 214.

Barometer, its height at and above
level of sea, 2 : in the " horse lati-
tudes," 80 ; reading of the. 157 ; in
the wind bands, 175; standard of
comparison at sea, 176 ; its indica-
tions of an open sea in the Arctic
Ocean, 233 ; under the cloud-ring,
280 ; in the trade- winds and equato-
rial calms, 342 ; difference of its pres-
sure upon the north-east and south-
east trade-winds, 344, 352; why it
stands higher in the latter, 345 ; in
the calm belts, 354 ; its depression
off Cape Horn, 357; its height at
the poles, 358 ; great descent of, in
the " brave west winds," 360 ; low in
Northern India, 366, 374 ; its descent
during the monsoons, 370 ; low in the
antarctic calm place, 447 ; its pressure
off Cape Horn, 447 ; its mean height
in the antarctic regions, 454 ; why it
should stand lower about the South
Pole, 458.

Barometric ridges, 355, 366; make a
depression in the atmosphere, 355.

Baurs deep-sea sounding apparatus
306.

Becher's, Capt., bottle chart, 29.

Beechey, Admiral, on tidal streams,
181 ; isothermal floor in the ocean
suggested by, 220.

Bellot's belief in a calm region within
the frigid zone, 174.

Belts, calm — see Cfdm Beits.

Belts, cold, 89.

Bent, Lieut., on tlie China stream, 197.

INLtEX.

477

Bermingham on the temperature of sea-
water, 469.

Bernouilli's formula, 420.

Berryman, Lieut., his deep-sea sound-
ing, 309.

Bible, our readings clearer as science
advances, 82.

Biotics, arguments of the, 325 ; solu-
tions of the question, 327.

Black Sea storm of 1854, 428.

" Black stream " of the Pacific, 49 ;
contrasted with the Gulf stream of
the Atlantic, 193 ; Salter than ad-
jacent waters, 196.

Black's law, 100, 102.

Blodget's, Mr., rain maps, 167.

" Blue water," ignorance concerning the
depth of the, 305.

Bonifaccio current, 27.

Bonzano, Dr., on the production of
water-spouts by electricity, 378.

Bores of India, 406.

Bottle chart, 28.

" Brave west winds" a perpetual
cyclone, 449.

Brazil current, 205.

Brazil, land breeze in, 142 ; climates of
Europe influenced by the shore-lines
of, 389.

Breezes, land and sea, alternations of,
133 ; along the shores of intertropical
coimtries, 135; cause of, 136; in the
Indian Archipelago, 137 ; their sani-
tary influences, 140; influences which
regulate their strength, 141 ; from
the west coast of Africa, 141 ; in
Brazil and Chili, 142 ; monsoons in
miniature, 373.

Brewster, Sir D., atmosphere supposed
by, to be the seat of terrestrial mag-
netism, 156 ; on the pole of maximum
cold, 174.

Brine of the ocean, 235.

Brooker's, Lieut., soundings, 22.

Brooke's deep-sea sounding apparatus,
312, 316, 330.

Brussels Conference, use of hydrometer
recommended by the, 215 ; on patches
of coloured water, 399.

Buist's, Dr., researches, on the physics
of the sea, 8 ; on evaporation in
India, 129 ; from the Bed Sea, 186.

Buys-Ballot, Prof., on predicting storms,
421.

California, rainy season of, 122, 172.

Callao, fogs iu the harbour of, 274.

Calm belt, equatorial — see Equatorial
Calm Belt.

Calm belt of Cancer, 81, 151, 168 ;
supplies little or no rain, 110.

Calm belt of Capricorn, 81, 168.

Calm belts, indications of a crossing of
winds at the, 101, 113, 158, 163;
facts reconciled by the theory, 114,
120 ; agent that guides the air across
the, 152 ; wet and dry air of the, 159 ;
examination of the, 162; proofs of
the crossing of winds at the, 146,
178 ; testimony of the hydrometer in
favour of crossings, 225 ; cloud region
highest in the, 270 ; oi)structions to
the navigator, 337 ; occupy medial
positions, 340; their temperature,
349 ; their appearance from a distant
planet, 352 ; the barometer in the,
354 ; information touching, afforded by
monsoons, 360 ; passing of the, 380 ;
changing of the monsoons going on
where tliey are, 381.

Calm belt, tropical, rainy seasons of
the, 353 ; their position, 353 ; caused
by the polar and equatorial calms,
357.

Calms in the two hemispheres, average
number of, 439 ; polar, 81, 174.

Cancer, calm belt of, 81, 110, 151, 158
276 ; how it is pushed to the north
374.

Cape Horn, precipitation at, 169, 443
heaviest water found ofl", 229 ; low
barometer off, 357 ; kelp east of, 410
its rainfall, 442 ; cause of the boisterous
weather off, 444; mean barometric
pressure off, 447.

Cape St. Eoque, 388.

Cape of Good Hope, its terrible storms»
1 94 ; waves and gales off the, 356.

Capricorn, calm belt of, 81, 168 ; cross-
ing of winds in the, 435.

Caribbean Sea, cause of its saltness, 35 ;
current into the, 37 ; its teiupera-
ture, 56.

Caspian Sea, salubrity of its climates,
168 ; how its level is reduced, 288 ;
adjustments in its hygrometry, 293.

Catacl^'sms, 347.

Chabannes, Admiral, correspondence
with, on the force of the trade-winds,
343 ; experiments on the speed of
his ship, 345, 346 ; on the velocity of
trade-winds, 434.

478

INDEX.

Chadwick's, Capt., iceberg observations,

271.
Chamberlain, Capt., his experience of

the Gulf stream, 396.
Chapman's experiments on the water
of the Ked Sea, 229 ; on the object of
the salt condition of the sea, 267.

Charts, storm and min, 431.

Cherraponjie, rainfall on the sides of,
127, 367, 371, 442, 448, 460, 461.

China stream, 197.

Climate, cause of difference in, 7, 464; as-
tronomical view of. 230; sea-shells and
animalculse as affecting, 270 ; of the
Dead Sea, 291 ; of Patagonia, 390 ; of
the Falkland Islands, 391 ; indications
about the south pole of a mild, 452 ;
local variations of, how caused, 463.

Climates, contrasts of, due to the Gulf
stream, 55 ; contrasts between those of
land and sea, 60, 383 ; salubrity of
those of the Caspian Sea, 168; in-
fluence of vapom- upon, 231 ; upon
what dependent, 297 ; are they
changing ? 248 ; those of Europe in-
fluenced by the shore-lines of Brazil,
389 ; those of Labrador and the
Falkland Islands compared, 461 ;
thermal difference betweeu arctic and
antarctic, 461 ; influence of aqueous
vapour on, 462 ; arctic, 466 ; antarc-
tic, 466.

Close running, 335.

Cloud region highest in the calm belts,
270 ; its shape at sea, 273.

Cloud-ring, a frigate under the, 277 ;
the barometer under the, 280 ;
motions of the, 280 ; meteorological
processes around the, 280 ; its offices,
282 ; acts as a regulator, 282 ; latent
heat liberated from, the true cause of
trade-winds, 283 ; its imagined ap-
pearance to a distant observer, 283.

Cloudless regions, 272.

Clouds, height of, at sea, 272 ; how to
determine, 273 ; important parts
played by, 278; gorgeous in the
Pacific, 373 ; their effect on the
equilibrium of the sea, 409.

Cloudy latitudes, 275.

Clymer, Dr., his description of a red
fog near the equator, 145.

Coffin's, Prof., belief in a calm region
witiiin the frigid zone, 174.

Cold, effect of downward currents in
producing, 93 ; pole of, 174.

Cold belts, 89.

" Cold snaps," 94.

Coloured patches, 399.

C )oledge's, Dr., rain maps, 167.

Commerce, influence of Gulf stream on,
68, 72.

Copper, action of Gulf stream upon, 35.

Coral reefs, their influences upon winds,
373.

Coral sea, Brooke's deep-sea soundings
from the, 317.

Corallines, arguments afforded by, in
favour of cm-rents, 239, 256 ; the
work of, 259, 289, 324, 333 ; their
testimony to the ancient saltness of
the sea, 266.

Counter trade- winds, 77, 78, 81, 83 ; air
sloughed off from, moist, 87; ap-
proach the pole in spirals, 102 ; their
velocity, 435.

Coupvent des Bois, M., on an outer and
under current from the Mediter^
ranean, 188.

Cuba, land breeze in, 142.

Current, cold, of Okotsk, 197 ; Hum-
boldt's— see Humboldf s current ; Red
Sea, 181; Mediterranean, 183;
Mozambique, 193, 402; equatorial,
199; Greenland, 206; Lagulhas,
402.

Cui-rents, 9 ; difference in, 18; causes
of, 23, 26 ; effects of winds upon, 24-
27 ; production of, without winds, 32 ;
com-se of warm and cold, 34 ; created
by storms, 37 ; their tendency to move
in circles, 43 ; feeble power of trade
winds upon, 48, 49 ; drift-matter con-
fined to sargassos by, 49 ; resemblance
between those of the North Atlantic
and Pacific, 51 ; indications of, de-
rived from the fish of the sea, 57 ; two
grand systems of, 79; obedient to
order, 179 ; to be considered in pairs,
180; upper and under, 183; of the
Indian Ocean, 193 ; ice-bearing, from
the antarctic regions, 195 ; Paciftc,
196; equatorial, 199; influence of
rains and evaporation upon, 200;
origin of, 204 ; 'Atlantic, 205 : argu-
ments afforded by corallines in favour
of, 239; without wind, 244 ; influence
of sea-shells on, 256 ; discovery of, in
the depths of the sea, 310 ; abrasion
of, 321 ; their pressure on the bottom,
32 1 ; what it consists of, 322 ; why they
cannot chafe it, 322 ; ca^jses of, reside

INDEX.

479

near the surface of the sea, 323 ; their
depth, 323; in the Java sea, 379 ; their
influence on climate, 384 ; antarctic,
467.

Currents of wind, 90.

Cuttle-fish, the, 266.

Cyclone, theory of the, 416; objections
to the theory, 426 ; changing of the
wind in a, 422 ; the latter stronger on
one sidethanthe otner, 422 ; the rainy
quadrant of a, 423; erroneous theories
respecting, 423 ; the wind in a true,
blows in spirals, 423 ; an illustration,
424.

Cyclones in the Mississippi Valley, 429 ;
in the North Atlantic, 429.

Darwin's explanation of the saltness of
the sea, 261. 266.

De Haven's water sky, 211,255; his
drift, 212, 215, 247, 248 ; his observa-
tions of a winters ice, 251, 254.

Dead Sea, level of the, 286, 302; an
ancient river from the, 286, 303 ;
precipitation and evaporation in its
valley, 286 ; whence its rains, 287 ;
influence of the South American con-
tinent upon its climate, 291.

Deep-sea soundings, early attempts, 305 ;
various methods, 306; apparatus of
Peter tiie Great, 307 ; plan of, for
the American navy, 308 ; great depths
and failures of first attempts, 309 ;
plan finally adopted, 310 ; method of
making, 311 ; Brooke's apparatus for,
312; observations by the English
navy, 313 ; use of, 316 ; first speci-
mens of, 316 ; specimens from the
coral sea, 317 ; specimens belong to
the animal kingdom, 318 ; is there
life in them ? 319, 324,

Denham, Capt., his deep-sea sounding,
309.

Depth of the air and water oceans, 1,3;
of the North Pacific, 5 ; of the Atlan-
tic, 18 ; of the Gulf stream, 54 ; of
the sea, probable relation between its
actinism and, 474,

Deserts, their efiects upon the trade-
winds, 101, 337, 372; their use in
nature, 130 ; are those of Asia centres
of atmospherical circulation ? 149 ;
considered as counterpoises in the
terrestrial machinery, 300.

"Desolate region," the, 198.

Dew-point, the, 386.

Diana, Kussian frigate, earthquake felt
by, 5.

Diurnal rotation, 9, 49, 338 ; its efl'ect
on the course of winds, 168 ; on the
I Gulf stream, 31, 42 ; on the drift of
the Gulf stream, 40 ; on that of the
Mississippi, 41 ; on the trade- winds,
79, 90, 154, 426, 430.

Doldrum currents, 199 ; why so called,
276.

Dove and the monsoons, 372 ; his law
of rotation, 418.

Drift of the sea, 38 ; of the Mississippi,
41; of the Indian Ocean, 195; of
the Atlantic, 196; Polynesian, 198,
401; of the Fhoenix, 187; of ihe
Advance, 247, 251; of the Rescue,
247, 251 ; of the Resolute, 248, 251 ;
of the Fox, 248, 250 ; explained, 250j
described, 395.

Drift matter confined to sargassos by
currents, 49; the largest farthest,
410; the line of antarctic, 411.

Dry winds, range of, 295; the Medi-
terranean within it, 295.

Dryden's definition of an eagre, 407.

Duncan, Capt., his iceberg adventures,
254.

Dust whirlwinds, 425.

Eagle Wing in an extra-tropical gale, 430.

Eagres, 406; Dryden's definition of,
407.

Earth, efiects of heat upon the, 12.

Earthquake of Simoda, 4 ; propagation
of waves by it, 5 ; their breadth and
velocity, 5.

Earthquake wave of Lisbon, 407.

Ehrenberg, Prof., on rain dust, 147 ; his
microscope, 172, 177 ; his arguments
based on the tides, 325 ; believes in
life in the depths of the sea, 325 ; his
paper on organic life forms from great
depths, 328 ; his examination of Ked
Sea colouring matter, 401.

Electricity, Quetelet's observations ob
atmospherical, 173; office of, in
oceanic circulation, 242 ; water spouts
due to, 378.

England the centre of the dry hemi-
sphere, 7 ; climates of, 65.

Equator, red fogs near the, 145.

Equatorial calm belt, 81 ; snow line
mounts up as it crosses it, 281 ; mean
place of the, 339 ; never at rest, 340 ;
the barometer in the, 342 ; considered

480

INDEX.

as a thermal adjustment, 342 ; varies
with the strength of the trade-winds,
352 ; precipitation in it, 352 •, rainy
Seasons of tlie, 353 ; its curved form
in the Indian Ocean, 375.

Equatorial currents, 199.

Equatorial winds, 453.

Erebus and Terror volcanoes, 452.

Ericsson's deep-sea leads, 306.

Espy's theory of storms, 417, 429.

Evaporation from the Atlantic, 36 ;
amount of salt left by, 37 ; effect of
heat in producing, 106 ; less ut sea
than on land, 110; rivers gauges for
amount of. 111 ; from the Ked Sea,
181, 186 ; from the Persian Gulf, 181 ;
in parts of the Indian Ocean, 182 ;
its influence upon currents, 200 ;
annual amount of, from the trade-
wind regi(m, 218 ; its influence on
oceanic circulation, 244 ; retarded by
the saltness of water, 267.

Expeditions, antarctic, 467.

Falkland Islands, climate of, 391 ; sea-
weed about the, 410 ; comparison be-
tween climates of Labrador and, 461.

Faraday's discovery of magnetism in
the air, 155.

Fast sailing, 336.

Fauna of the sea, 179, 303.

Fish, 57, 6!).

Fisheries, value of various, 412.

Fitzroy, Admiral, his barometric obser-
vations. 176 ; on the cyclone of Oct.
1859, 426 ; on the Black Sea storm
of 1854, 429; on the rainfall near
Cape Horn and Patagonia, 442, 461.

Flora of the sea, 179.

Fogless regions, 270.

Fogs in the harbour of Oallao, 274 ; of
Newfoundland, 393.

Fogs, red, in the Mediterranean, 145 ;
near the equator, 145 ; not always at
the same place, 151 ; condition re-
quisite for their production, 151 ; of
sea-dust, 271.

Fogs, sea. 270.

Folger's chart, 69.

Forbes, Prof, scarcity of living forms
observed by, in deep sea, 325.

Forks of the Gulf streani, 47.

Foster's, Capt., observations on sea ani-
malculse, 262.

Fourier, Barr)n, on tlie temperature of
the earth, 470.

Fox, drift of the, 248, 250, note.

Fox's magnetic observations, 157.

France, rainfall of, 112.

Franklin, Dr., his theory of the 3rulf
stream, 24 ; objections, 24 ; his sug-
gestion of Gulf stream as a means of
finding longitude, 69 ; on the cause
of variations in climate, 464.

French Academy, its experiments on
air, 91.

Fresh water in American lakes, 7.

Frigid zone, calm region within the, 174.

Gales off the Cape of Good Hope, 356 ;
extra-tropical, 430; in the two he-
mispheres, 438 ; relative frequency
at sea of rains and, 441.

Gardner on the distribution of land
and water, 451.

Geological agencies of winds, 122.

Geologiciil records, their agreement with
those of revelation, 264.

Giraud, Dr., his analysis of Ked Sea
water, 186, 229.

Grant, Capt., his sail through the bend
of the Gulf stream, 398 ; on the
Lagulhas current, 402.

Ginn's, Capt., plan for determining the
velocity of waves. 273.

Greenland current, 206.

Guinea, Gulf of, and the climate of
Patagonia, 390.

Gulf stream, its colour, 22 ; speculations
concerning the, 23; views of early
writers, 24 ; Capt. Livingstone's hy-
pothesis, 24 ; Franklin's theory, 24 ;
objections to it, 24; Herschels ex-
planation of the, 25 ; objections to it,
25, 44; bed of an ascending plane,
27, 181 ; current counter to the, 28 ;
effects of diurnal rotation upon the,
31, 42 ; not to be accounted for by a
higher level, 31 ; nor by the trade-
wind theory, 3;^, 52 ; the effect of some
constantly-operating power, 32, 52 ;
sharpness of its edges, 34 ; difference
of its water from littoral waters,
34, 46 ; its action on copper, 35 ; its
saltness, 35 ; dynamical force which
calls it forth due to difference iu
specific gravity, 38, 53 ; its winter
temperature, 39 ; its top roof-shaped,
j 39 ; proof of this, 40 ; drift matter
sloughed off to its right, 40 ; reasons,
40 ; its course, 42 ; its channel shifts
with the season, 44 ; its limits in

INDEX.

481

March and September, 46 ; large
volume of warm water outside, 50 ;
how temperatm-e in Europe is raised
by the, 54; its depth and tempera-
ture, 54 ; contrasts of cHmates due to
the, 55; amount of heat daily es-
caping through the, 55 ; its benign
influences, 56; cold water at its
bottom, 57 ; its influence on the
meteorology of the ocean, 62 ; storms
accompanying it, 62, 66, 67; damp-
ness of English climate, and the fogs
of Newfoundland, caused by the, 65 ;
its influences upon storms, 65 ; its
storms the terror of seamen, 68 ; its
influence on commerce and naviga-
tion, 68, 72 ; finding longitude by
it, 68 ; its use in winter, 69 ; voyages
shortened by it, 73 ; contrasted with
the Black stream of the Pacific, 193 ;
its influences, 271 ; its vibrations,
382 ; Capt. Chamberlain's experience
of it, 396 ; the great bend in it, 398.

" Gulf stream " of the Pacific, 26 ; in
the air, 363.

Gulf- weed {Fucus natans), 29.

Hailstorms, 444.

Halley's theory of the trade-winds not
fully confirmed by observations, 153.

Harpoons, 208.

Heat, 11 ; its effects upon the earth, 12 ;
effects of vapour and, 98 ; its im-
mense evaporating powers, 106 ;
capacity of water to convey, 180 ; of
vapour, 231 ; velocity of marine cur-
rents ascribed to, 242 ; amount daily
received by south-east trade-winds,
350 ; its meteorological power, 357 ;
the reservoirs of, 472 ; a reflection
concerning, 474.

Herschel's, Sir J., balloon observations,
8; his explanation of the Gulf
stream, 25 ; objections, 25, 44 ; on
the solar heat, 177 ; on the isother-
mal floor in the ocean, 221 ; on the
velocity of winds under barometric
pressure, 420.

Higgins', Capt., description of a tide-
rip, 404.

Highlands, influence of, upon precipita-
tion, 443.

Horseburgh's description of tide-rips,
404.

"Horse latitudes," 80, 353; why so
called, 276.

" Hot spells " explained, 95.

Hot water, warming by means of, 53.

Hot winds of the Andes, 95 ; caused by
the trade-winds, 96.

Howes, Capt., on the Aurora Australis,
464.

Hubbard, Prof., on the thermal dilata-
tion of sea-water, 221.

Hudson, Dr., on the drift of the Phcenix,
187.

Humboldt, his description of the dust-
whirlwinds of the Orinoco, 148 ;
on the salubrious climates' of the
Caspian Sea, 168 ; his description ol
tide-rips, 403.

Humboldt's current, 50. 58, 197, 397,
401, 411, 467.

Hurricanes, 13; not due to direct
heat of the sun, 99 ; Mauritius, 415 ;
West India, 415 ; the season of, 429.

Hydrometer, the, at sea, 215 ; its testi-
mony in favour of the air crosvsing
at the calm belts, 225 ; indicates the
rainy latitudes at sea, 230 ; its results,
232.

Hygrometry of the Caspians, 293.

Hypsometry, peculiar, in the North
Atlantic, 111.

Ice, middle, 234, 250; He Haven's
observations of a winter's, 251, 254.

Icebergs, 10, 195, 271, 410; drifting
north, 253 ; influence of antarctic, in
expelling the air from austral regions,
276; ofiices of, 445; near the equa-
tor, 451 ; formation of southern, 465.

Ice-drift, antarctic, 466.

India, rivers of, 129 ; rainfall in, 367 ;
bores of, 406.

India, Northern, barometer low in, 366,
374.

Indian Archipelago, the land and sea
breezes in the, 136.

Indian Ocean, greatest evaporation from
the, 128, 193; its currents, 193; its
drift, 195 ; curved form of the equa-
torial calm belt in the, 375, escape
of warm waters from the, 402.

Inhabitants of the sea, 16 ; monuments
of their industry, 17.

Inland basins, formation of, 289.

Insects of the sea, 262, 333.

Isothermal floor of the ocean, 220;
aqueous lines, 393.

Jackson on the temperature of sea-
watur at difierent depths, 469.
2 I

482

INDEX.

Jan sen, Lieut., on the land and sea
breezes in the Indian Archipelago,
136 ; on the south-west winds of the
Atlantic, 360; a " gulf stream " in
the air indicated by, 363; on the
monsoons, 372, 375 ; on the Lagulhas
cm-rent, 402 ; on hurricane seasons,
415.

Japan current, 26, 48; the horse-shoe
in the, 398.

Java Sea, land breeze off the coast of
the, 142 ; storms in the, 376 ; the
east monsoon in the, 378 ; currents
in the, 379 ; marking the seasons in
the, 380 ; conflicts in the air in the,
380.

Jilek, Dr., on the existence of an an-
tai'ctic continent, 451.

Johnston, Prof. A. K., on the St. Koque
current, 205 ; on the influence- of
vapour upon climates, 232.

Julien's, Lieut., cataclysm theory, 347.

Kane's, Dr., open sea, 212, 215, 255 ;
barometrical observations, 454.

Kansas, heated wind-storm at, 96.

Kelp east of Cape Horn, 410.

King, Capt., on the rainfall near Cape
Horn and Patagonia, 442, 461.

Kingman, Capt., his description of a
white patch of water, 399.

Kotzebue's suggestions of an isother-
mal floor in the ocean, 220.

L'Aigle, M., 187.

Labrador and the Falkland Islands,
comparison of their climates, 461.

Lagulhas or Mozambique current,
opinions respecting, 193, 402 ; grand
storms produced by it, 194.

Land, its influence upon the winds of
the sea, 362 ; a physical law concern-
ing tlie distribution of water and, 451.

Le Hou's cataclysm theory, 347.

Leaching, 16.

Lee, Lieut., his experiments on sub-
marine cun-ents, 201.

Levelling agencies, 319.

Life at great depths, Ehrenberg's paper
upon, 328.

Lightning, 236 ; in the Java Sea, 376.

Lisbon, eartliquake wave of, 407.

Livingston, Capt., on the Gulf stream,
24.

Longitude found by means of the Gulf
stream, 68.

Lyell, Sir C, on the salt of the Mediter-
ranean, 189.

Lynch, Lieut., on the level of the Dead
Sea, 286 ; his discovery of a supposed
bed of a river in the, 303.

M'Clintock's, Capt., soundings, 19 ; his
drift in the Fox, 248; living star-
fish brought up from great depth by,
329 ; on the arctic barometer, 460.

Macgowan's, Dr., description of the
eagre, 406.

Maelstrom, cause of the, 181.

Magnetism, Faraday's discovery of, in
the air, 155 ; its seat suspected by
Sir D. Brewster to reside therein,
156.

Magnetic needle, its diurnal variations,
157.

Magnetic poles, 174.

Marcet, Dr., 188, 189 ; on the thermal
dilatation of sea-water, 221.

Mauritius liurricanes, 415.

Mediterranean telegraph, 20 ; red fogs
in the, 145; its currents, 183, 186;
its saltness, 188; heavy evaporation
from the, 295.

Medusse, 263.

Meteorological law, 354.

Meteorological power of latent heat , 357.

Meteorological machinery, design in, 449.

Meteorology, the telegraph in, 96 ;
of the sea, 62; facts established in
the, 437.

Mexican Gulf, cause of its saltness, 35,

IMicroscope, evidence of the, 269.

Middle ice, 284, 250.

" Milky way ' in the ocean, 382.

Mississippi river once supposed to be
the father of Gulf stream, 24; drift
wood on the, 41 ; bars at the mouths
of the, 190; Delta of the, 191.

Mississippi Valley, rainfall in the, 107 ;
its area, and latent iieat liberated
in the processes of condensation
tliere, 108 ; annual discharge of its
waters, 108 ; whence derived, 109 ;
its rain winds, 171 ; its cyclones, 427.

Monsoons, 337 ; information afibrded
by, touching the calm belts, 360;
cause of, 365 ; region of, 365 ; south-
west " backing down," 366 ; how
they begin, 366 ; influences of the
rainfall in India upon the, 368;
march of the, 3G8 ; conflict of, begins
at the north, 368; the barometrio

INDEX.

descent of the, 370 ; Dove's tlieoiy
of the, 372; Lieut. Jansen's, 372;
in the Pacific, 372; in miniature,
373 ; changing of the, in the calm
belts, 374, 381 ; winter, 375 ; Jansen's
observations on those of Australasia,
375 ; also on those in the Java Sea,
376, 414.

Morris, Mr., analysis of his specimens
of Eed Sea water, 185.

Mountain ranges, 10 ; their use in
nature, 130 ; their influence, 288, 290.

Mountains, rainy side of, 125; how the
temperature of air may be raised by
crossing, 462.

Mozambique or Lagulhas current, 18,
26, 193.

Nantucket, shoals of, 43.

Nautilus, the, 266 ; its destiny, 394.

Navigation, influence of Gulf stream on,
68 ; thermal, 71 ; obstructions in, 337.

New Zealand, 7.

Newfoundland, formation of the Grand
Bank of, 41 ; cause of its fogs, 62,
65, 393.

Niagara, the, 28 ; falls of, 190.

North pole, voyages of discovery to the,
207; aerial rarefaction about the, 460.

Northern hemisphere, effect on trade-
winds of the land in the, 338.

Null belts, the, 453, 458.

Ocean, depth of the. 3, 4 ; kept in
motion by thermo-dynamical means,
47 ; governed by stable laws, 76 ;
isothermal floor of the, 220 ; a
general system of circulation required
for the, 241 ; its harmonies, 268 ; a
" milky way " in the, 382 — vide Sea.

Oceanic circulation, evidence in favour
of a regular system of, 311.

Okotsk, Sea of, its cold current, 197 ; its
heavy water, 229.

Open sea in the Arctic Ocean, barometer
indications of an, 233.

Oregon, rainfall of, 112.

Orinoco, Humboldt's description of the
dust- whirl winds of the, 148.

Orkney winter, mildness of, 55.

Oxygen of the air, its magnetic in-
fluences, 156, 165, 173.

Pacific contrasted with the Atlantic,
18 ; Gulf stream of the, 26, 48 ; Black
stream of the, 40; contrasted with

the Gulf stream of the Atlantic, 193 ;
Salter than adjacent waters, 1 96 ; its
currents, 196; its sea-shells calca-
reous, 264 ; its monsoons, 372 ; its
gorgeous clouds, 373 ; escape of warm
waters from the, 401.

Pacific, North, average depth of the, 5 ;
high temperature of its western Jialf,
48 ; resemblance of its current to
that of the North Atlantic, 51 ; its
storms, 64.

Pacific, South, a sargasso in the, 410.

Panama, rainy season of, ] 22.

Parkers deep-sea sounding, 201, 309.

Patagonia, its rainfall, 127, 444, 448,
461 ; its climate, 390.

Peru. Humboldt's current of — see Hum
boldt's current.

Peter the Great's deep-sea sounding
apparatus, 307.

Phoenix, drift of the, 187.

Pichon, Capt., his encounter with a
doldrum current, 199.

Plummet, law of its descent, 312.

Polar calms, 81, 174; rarefaction, 233,
357, 454 ; winds, 453 ; their psychro-
metry, 459.

Polar Sea, solid matter annually drifted
out of the, 215.

Polynesian drift, 198, 401.

Precipitation from the Atlantic, 36 ;
influence of highlands on, 443 ; in-
fluences favourable to heavy, 460.

Pressure of the sea, arguments of the
anti-biotics from the, 326.

Psychrometry of polar winds, 459.

Quetelet's observations on atmospherical
electricity, 173.

Eadiating powers of earth, air, and
water compared, 473.

Eain, whence the supply required for
the Mississippi, 109 ; supply from the
Atlantic, 109 ; amount furnished by
the calm belt of Cancer, 110 ; more in
the northern than the southern
hemisphere, 118.

Eain charts, 431 ; Van Gough's, 440.

"Eain dust," 147 ; its colour, 150.

Eainfall in the Mississippi Valley, 107 ;
of France, 112; of Oregon, 112; in
India, 127, 367, 443 ; its influences
upon the monsoons, 368 ; of Cape
Horn and Cherraponjie, 442, 461 ; of
Patagonia, 444, 448.

2 I 2

484

INDEX.

Rain-gauges, rivers considered as, 105 ;
tlieir importance, 111.

Rain maps, 1G7.

Rain winds, 364.

Rainless regions, 123, 162.

Rains, rivers and, 105 ; their influence
upon currents, 200; summer, of
Cherraponjie, 371 ; their effect on the
equilibrium of the sea, 408 ; relative
frequency at sea of gales and, 441.

Rainy latitudes at sea indicated by the
hydrometer, 230.

Rainy seasons, how caused, 121 ; of
California, 122, 172 ; of the tropical
calm belts, 353.

Rarefaction, polar, 233, 357, 454 ; in the
antarctic regions, the " brave west
winds " caused by, 440 ; about the
north and south pole, 460.

Red fogs, 271.

Red Sea telegraph, 20 ; its current, 181 ;
specific gravity of its water, 185, 229 ;
evaporation from the, 186, 295 ;
Chapman's and Ritchie's experiments
on its water, 229 ; its arguments in
favour of currents, 240 ; its vapours,
300 ; whence it derives its name,
401.

Rescue, drift of the, 247, 251.

Resolute, drift of the, 248, 251.

Ritchie's analysis of Red Sea water, 229.

River gauges, importance of, 111.

Rivers considered as rain-gauges, 105 ;
as gauges of effective evaporation,
111; of India, 129; rains and, 105,
264.

Rodgers, Capt., his observations with
the hydrometer, 216, 230, 252, 254.

Rogers' cable-jacket, 21.

Ross, Sir James, on the temperature of
under-currents, 214; isothermal floor
in the ocean suggested by, 220.

Ross. Capt., voyage to the antarctic,
402 ; volcanoes seen by, within the
antarctic circle, 450.

Sabine, General, effect of a current on
his passage, 74 ; his magnetic dis-
coveries, 157.

Sailing, fast, 336.

St. Roque current, 205.

Salt, amount of, in the Gulf stream,
Caribbean Sea, and Mexican Gulf,
35 ; amount left by evaporation, 37 ;
amount in the IMediterranean, 188 ;
amount of, and physical necessity for,

in sea-water, 227, 247 ; cubic milea
of, 266.

Salt Lake of Utah, 290.

Salts of the sea, 188, 235; their effects,
201 ; powerful agents in oceanic
circulation, 242, 244 ; the sole cause
of under-currents, 246; deductions,
247 ; whence derived, 260 ; their
antiquity, 262 ; retard evaporation,
267.

Sandwich Islands, their efiect on winds,
373 ; precipitation in the, 457.

Sargasso, theory as to formation of, 49 ;
discovery of a new, 50 ; African, 410 ;
South Pacific, 410.

Sargasso Sea, 29, 196.

Saussure on the temperature of under-
currents, 214.

Scenery, submarine, 303.

Schleiden on submarine scenery, 303.

Schouw's, Prof., barometrical observa-
tions, 456.

Sea contrasted with atmosphere, 8,
242; its inhabitants, 16; drift of the,
38 ; evidences of design in the, 61 ;
its meteorology, 62 ; its oflices in the
physical economy, 103; its saltest
part, 119 ; its currents obedient to
order, 179 ; its fauna and flora, 179 ;
its currents to be considered in pairs,
180 ; salts of the, 188. 204, 235. 242,
244, 246, 247, 260, 262, 267 ; vertical
circulation in the, a physical neces-
sity, 189 ; heaviest water in the,
229 ; what if its water had been fresh,
236, 242, 259; dynamical agents of
the, 242 ; quantity of salt in the, 247 ;
shell-fish the regulators of the, 259,,
333 ; whence its salts are derived,
260, 265 ; insects of the, 262, 333 ;
agreement between its records and
those of , revelation, 264 ; subjects
for contemplation at, 278 ; interest of
physical research at, 284 ; it and air
regarded as parts of the same machine,
285 ; its wonders, 314 ; its orology,
315 ; quiet reigning in its depths,
318; arguments based on its pres-
sure, 326 ; practical results of phy-
sical researches at, 334 ; its climate
contrasted with that of the land,
383 ; a belt of uniform temperature
at, 387 ; meeting of cool and warm
waters in the, 393 ; glories of the,
394 ; drift of the, 395, 410 ; phospho-
rescent appearance of the, 400, 471 ;

INDEX.

485

commotionB in the, 403 ; effect of j
rains on its equilibrium, 408 ; effect |
of cloud and sunshine, 409 ; facts in |
its meteorology, 437 ; actinometry of |
the, 468, 472 ; an office for waves in |
the, 472 ; probable relation between
its actinism and depth, 474.

"Sea-dust," 114, 271 ; its colour, 150.

Sea-fogs, 151, 270.

Sea-nettles {medusse), 59, 263.

Sea-routes, 334.

Sea-salt, cubic miles of. 266.

Sea-shells, their influence upon currents,
256, 257 ; the regulators of the sea,
259, 324, 333 ; calcareous in the
Pacific, silicious in the Atlantic, 264.

Sea-water, its specific gravity, 6, 115,
120, 216, 219, 227 ; solid ingredients
in, 16 ; analysis of, 17 ; its proportion
to the mass of the eartli, 17 ; influence
of trade-winds upon its specific
gravity, 217; thermal dilatation of,
221 ; experiments on its freezing
point, 222 ; more expansible at

- summer than at winter temperature,
223 ; thajt of the southern cooler and
heavier than that of the northern
hemisphere, 224, 339 ; amount of salt
in, 227 ; the heaviest, 229 ; uniform
character of, 237 ; its antiseptic pro-
perties, 326 ; effects of night and day
upon, 387; its temperature at dif-
ferent depths, 469 ; stratum of
warmest, 470 ; its position, 471.

Seaweed east of Cape Horn, 410 ;
about the Falkland Islands, 410.

Seas considered as counterpoises in the
terrestrial machinery, 300.

Seasons, their influence on the Gulf
stream, 44 ; strength of trade-winds
varies with the, 341.

Shell- fish, solid matter seereted by,
257 ; dynamical force derived from,
257 ; their physical relations, 258 ;
the regulators of the sea, 259, 324,
333 ; as affecting climate, 270.

Ships used as anemometers, 432 ; their
avernge speed through the trade-
winds, 433.

Shore-lines, 391.

Siberian rivers, cause of winds that
give rains to the, 296.

Silver, quantity of, in the sea, 16.

Simoda, earthquake of, 4 ; propagation
of wavee by it, 5 ; their breadth and
velocity, 5.

Sinclair, Commodore, his picture of the
weather under the cloud-ring, 277.

" Sirocco dust," 145.

Smith, Dr., his conjecture of an under-
current from the Mediterranean, 187.

Smyley, Capt., on the mildness of an-
tarctic climates, 466.

Smyth, Admiral, on the " gusty gales "
in the Sea of Tuscany, 27 ; his Medi-
terranean soundings, 189, 191.

Smyth, Piazzi, his description of sea-
nettles, 59 ; on whales, 263 ; his cloud-
region observations, 274.

Snow line, 281.

Society Islands, their effect upon the
winds, 373 ; precipitation in the, 457.

Soundings, deep-sea, 305.

South American continent, its influence
upon the climate of the Dead Sea, 291.

South pole, indications of a mild climate
about the, 452 ; aerial rarefaction
about the, 460.

South Sea expedition, 468.

Specific gravity of air, 6 ; of sea-water,
6, 115, 120, 216, 219, 227 ; influence
of trade-winds upon the, 217; ocean
currents due to difference of, 204 ;
of Red Sea water, 185 ; of the water
of the Arctic Ocean, 211.

Spots of the sun, their magnetic in-
fluences, 156.

Star-fish, living, found at great depths,
329.

Storm charts, 431 ; Van Gough's, 440.

Storms, currents created by, 37 ; ac-
companying the Gulf stream, 62, 66,
67 ; in the North Atlantic and Paci-
fic, 64 ; influences of Gulf stream on,
65 ; those of the Gulf stream the
terror of seamen, 68 ; those of the
Cape, 194; latitudes of, 271 ; in the
Java Sea, 376 ; prediction of, 421 ;
the three forces at work in, 428 ; tlie
effect of each, 428 ; one storm within
another, 428.

Submarine telegraphy, 19, 21 ; scenery,
303.

Suez, isthmus of, 182, 183.

Suez canal. 184.

Sun longer in northern declination, 6 ;
influence of the, 8 ; effect of its direct
heat upon the trade-winds, 97 ; hur-
ricanes not due to the direct heat of
the, 99 ; power of its thernjal forces,
106 ; its direct heat, 155 ; magnetic
influences of its spots 156; assisted

486

INDEX.

by the latent heat of vapour, 367 ;
its eflect' on the eqiuHbrium of the
sea, 409 ; quantity of its heat daily
impressed upon the earth, 470 ; how
far it penetrates below the surface,
470 ; its annual supjjly of heat uni-
form, 470.
Sykes, Col., his report on the rainfall in
India, 367, 371, 443, 460.

Tadjura, Lake of. 302.

Tallies put upon the wind. 145.

Telegraph, Atlantic, 19 ; Red Sea, 20 ;
Mediterranean, 20 ; its dormant
powers in meteorology, 96.

Telegraphic plateau, 316.

Telescope, evidence of the, 269.

Temperature of the North Atlantic and
North Pacific Oceans, 48 ; of Europe,
how raised by the Gulf stream, 54 ;
of the Carribean Sea, 56 ; of sea-
water, efiects of night and day upon
the, 387 ; a belt of uniform, at sea,
387 ; of sea- water at different depths,
469 ; of the earth, Baron Fourier on
the, 470.

Temple, Lieut., on the indraught of
the Mediterranean, 184.

Teneriffe, Peak of, cloud observations
from the, 274.

Terrestrial adaptations, 299.

Texas, the winter northers of, 93 ; their
severe cold, 94.

Thermal navigation, 71 ; tide, 219, 223 ;
dilatation, 221 ; equator, 349.

Thermometer, water, sudden changes
in the, 392.

Thomassy's, Dr., salometric observa-
tions, 35.

Thunder, 284 ; in the Java Sea, 376.

Tide-lips, 403 ; in the Atlantic, 404.

Tides, 12; of the Atlantic, 18; argu-
ments based on, 325.

Time tables, 334 ; how passages have
been shortened by help of, 336.

Tornadoes not due to direct heat of the
sun, 99.

Trade-wind belts, 78.

Trade-winds, 9; supposed by Dr. Frank-
lin to be the cause of the Gulf stream,
24; objections, 24, 26; their feeble
power upon currents, 48, 49; as a
cause of the Gulf stream, 52; effect
of diurnal rotation on their course,
79 ; their duration and strength, 83,
85; speed of vessels through, 85;

whence the south-east are supplied
with air, 85 ; whither it goes, 86 ;
how drawn from above, 86 ; velocity
of south-east greater tljan north-east,
86, 339 ; warm winds of the Andes
caused by, 96 ; eflect of the direct
heat of the sun upon, 97 ; the two
systems of, unequal, 98 ; vapour one
of the causes of, 100; effects of the
deserts upon, 101 ; these the evapo-
rating winds, 119; Halley's theory
of, not fully confirmed by observations,
153 ; observed course of tiie, 153 ;
velocities of the, 154, 343 ; difference
between observation and theory, 154 ;
their influence upon the specific
gravity of sea- water, 217; true cause
of the, 283 ; path of the south-east,
over into the northern hemisphere,
292 ; relays for supplying them with
vapour by the way, 293, 301 ; uni-
formity of temperature of the south-
east, 339 ; their strength varies with
the seasons, 341 ; sailing through in
fall and winter, 341 ; barometer iu
the, 342, 344 ; their average force,
343, 434 ; difference in barometric
pressure upon the north-east and
south-east, 344, 432 ; temperature of,
349 ; a natural actinometer in the,
350 ; heat daily received by the south-
east, 350 ; equatorial calm belt varies
with their strength, 352 ; sailing
through, 361, 433 ; south-east and
north-east put in a balance, 432;
average speed of vessels sailing
through, 433.

Tropical calm belts, 357.

Truxton, Commodore, on thermal navi-
gation, 71.

Tuscany, Sea of, 27.

Typhoons,»414.

Under-current in the Arctic Ocean, its
temperature, 254 ; comes to the sur-
face, 255.

Under-currents, escape of salt and
heavy water from Mediterranean
and Ked Sea by, 188 ; experiments
upon, 201 ; change temperature
slowly, 213; entirely due to the
salts of sea-water, 246.

Utah, the Salt Lake of, 290.

Valparaiso, sea-breeze at, 133 ; the suc-
ceeding lull, 134.

INDEX.

487

Van Gougb, Lieut., his storm charts,
440 ; on barometric pressure, 447.

Vapour, its effect in producing winds,
66 ; effects of heat and, 98 ; one of
the causes of the trade-winds, 100;
its influence upon climates, 231 ;
latent heat of, 231, 233, 443; the
sun assisted by the latent heat of,
367; its influence upon winds and
climates, 462.

Vapours of the Eed Sea, 300.

Vigias, mock, 405.

Volcanoes in the antarctic regions, 450,
452.

Voyage, longest, 336.

Wakeman's, Capt., encounter with tide-
rips, 405,

Wallach, Dr., on animal life in vast
depths, 329.

Walsh, Lieut., his experiments on sub-
marine currents, 201 ; his deep-sea
sounding, 309.

Warley, Lieut., on the antarctic ice-
drifts, 467.

Warming by hot water, 53.

Washington Observatory, how warmed,
53.

Water, phenomena at the meeting of
the oceans of air and, 1, 323 ; their
depths, 1 ; their relative weights, 1 ;
their mutual action, 11 ; its opera-
tions, 15 ; its marvellous power, 15 ;
purveyor of food to insects of the
sea, 16 ; its capacity to convey heat,
180 ; effect of its compressibility in
the oceanic circulation, 202 ; assisted
by its salts, 204 ; its thermal dilata-
tion, 221 ; a physical law concerning
the distribution of land and, 451.

Water-spouts in the Java Sea, 377 ;
how produced, 378 ; in the Potomac,
425.

Wave-tables, Airy's, 4.

Waves of sea in relation to its depth, 4 ;
plan for determining their height
and velocity, 272 ; those off the Cape
of Good Hope, 356 ; got up by the
westerly winds on the polar side of
40°, 436 : a new oface for the, 472.

Welsh's, Mr., balloon observations, 3.

West India hurricanes, 415,

Whales, food for, 59, 263 ; avoid the
Gulf stream, 69; tiieir habits, 208, 213.

Whales, sperm, 412 ; right, 412.

Whiriwinds, 425.

Wilkes, Capt., his <\rossing of the equa-

torial calm belt, 352 ; his voyage to
the Antarctic, 402.

Williams, Jonathan, on thermal navi-
gation, 71,

Wind, currents of, 90 ; circuits of, 96 ;
forces by which it is propelled, 97;
putting tallies on the, 145 ; currents
without, 32, 244.

Wind bands, 160 ; the barometer in the,
175, 176.

Winds, their effects upon currents, 24-27,
30 ; exercise little influence upon
constant currents, 30 ; production of
currents without, 32, 244 ; effect of
vapour in producing, 66; different
belts of, 77 ; diagram of, 82 ; crossing
of, at the calm belts, 101, 113, 114,
158; their geological agencies, 122,
285, 302 ; effect of diurnal rotation
on, 168, 426, 430 ; pole of the, 174 ;
course of those that give rise to the
Siberian rivers, 296 ; how climates de-
pend upon the course of, 297 ; with
northing and southing in them, 354 ;
in the southern stronger than in the
northern hemisphere, 356 ; blow from
a high to a low barometer, 357 ; south-
west, of the Atlantic, 360 ; influence
of land upon, 362 ; influence of deserts
upon, 372 ; influences of coral reefs
upon, 373 ; propelling power of the,
439; the "brave west," caused by
rarefaction in the arctic regions, 440 ;
their indications concerning the un-
explored regions of the south, 450 ;
average prevalence of polar and equa-
torial, 453 ; influence of the polar in-
draught upon the, 454 ; influence of
aqueous vapour on, 462 ; dry, range of,
295 ; the Mediterranean within it, 295.

Winds, hot, of the Andes, 95 ; caused by
the trade-winds, 96.

Winds, polar, psychrometiy of, 459.

Winds, trade— see Trade Winds.

Winter, using the Gulf stream in, 69 ;
monsoons, 375 ; northers of Texas,
93 ; their severe cold, 94,

Wo Hasten, Dr., on the salt of the
Mediterranean, 188.

Wiillerstorf s, Commodore, observations
on the height and velocity of waves,
272.

Yellow Sea, whence it derives its name,
401.

Young, Lieut., on the antarctic ice-
drift, 467.

LONDON :

PETNTED BY WILLIAM CLOWES AND SONS,

STAMFORD STREET AND CHARING CROSS.

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