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GEO GRAPH Yll

OF-THE-SEA

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MCTEOROtOeY

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1930

Gift of

Elizabeth T. Bunce
February, 1984

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TEE

PHYSICAL G^EOGEAPHY

THE SEA,

METEOROLOaY.

BY

M. F. MAUEY, LL.D., U.S.N.,

SUPERIKTEXDENT TO THE NATIONAL OBSERVATOBY, -WASHINGTO]

TENTH EDITION, REVISED,
BEING THE SECOND EDITION OF THE AUTHOR'S RECONSTRUCTION OF THE WORK.

ILLUSTRATED WITH NUMEROUS CHARTS AND DIAGRAMS.

LONDON:
SAMPSON LOW, SON & CO., 47 LUDGATE HILL.

1861.

\Tlie right of Translation is reserved.']

LONDON : PrJNTED BY WILLIAM CLOWES AND SONS, STAMFORD STREET.

In acknowledgment of tlie services rendered to tlie
cause of a universal system of Meteorological Observa-
tions at Sea,' and as a tribute of Friendship, this Volume is.
Dedicated to the Lord Wrottesley by bis

Obedient Servant,

The Authoe»

INTRODUCTION.

The Physical Geography of the Sea is a new department of hnman
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
dihgent, too ; and in proportion to that activity and that diligence
has been the advancement of om^ knowledge concerning the physical.

GEOGRAPHY OF THE SEA AND ITS METEOROLOGY. It may be doubtcd

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 reaUy 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 toucliing
the sea and an, 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

VI INTRODUCTION.

and not to be foimd in any of its predecessors. Most, if not all the
chapters contained in them, have also been enlarged, amended, and
improved.

In short, the author deshes here to state to the friends and
students of this beautiful and elevating science, that it is pro-
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 Y\^ind
and Cm^rent Charts," out of which has gTown this Treatise, was to
collect the experience of every navigator as to the winds and
ciuTcnts of the ocean, to discuss his observations upon them, and
then to present the world Vfith the results on charts for the im-
provement 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 dm^ing
all seasons, and by projecting along each track the "whids and cur-
rents daily encountered dui^ing the voyage, it was plain that navi-
gators hereafter, by consultmg 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 na^sdgator to the
given port, when his own personal experience of the mnds to be
expected, the currents to be encountered by the way, would itself be
blank. If so, there would be the wind and cmTcnt chart for refer-
ence. It would spread out before him the tracks 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 cm-rents 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 groj)ing his way along until the lights of experience
should come to him by the slow teacliings of the dearest of all
schools, would here find, at once, that he had already the experi-
ence of a thousand navigators to guide him on his voyage. He
might, therefore, set out upon his first voyage with as much confi-
dence in liis knowledge as to the viinds 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 took it

INTRODUCTION. Yll

to sea, they tried it, and to their surprise and delight they found
that, mth 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 c\raator alone was shortened
ten days. Before the commencement of this midertaking, the
average passage to California w^as 183 days ; but with these charts
for theh 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 w^hich they have
given rise, bid fah^ to bring that colony and the mother country
nearer by many days, reducing in no small measure the average
dm-ation 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 meetmg 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 com-
merce, in those waters alone, of one or tw^o millions of dollars ;t and
in all seas, of ten milhons.J

* The outward passage, it has since been ascertained, has "been reduced to
97 days on the average, and the homeward passage has been made in G3 imder
canvas alone.

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

X . . . " Now let us make a calculation of the annual saving to the commerce
of the United States effected by those charts and sailing du-ections. 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 witiiin the mark,
we will take it at 15, and include all the ports of South America, China, and tl:o
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 aggre-
gate 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 cut of the calcu-

h 2

Vm INTRODUCTION.

A system of pliilosopliical research whicli is so rich mth fruits
and abimdant %Yith promise could not fail to attract the attention
and commend itself to the consideration of the seafaring community
of the whole ci\dlized world. It was founded on observation ; it
was the result of the experience of many observant men, now brought
together for the &st time, and patiently discussed. The results
tended to increase human knowledge mth 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 atten-
tion was called to the blank spaces, and the importance of more and
better observations than were generally contained in the old sea-logs
was m-ged 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, mth a copy of the charts and sailing directions that
mioht be founded upon those observations.

The quick, practical mind of the enterprising ship-master
seized the proposition at once. To him the field was mviting,
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 navigators
engaged day and night, and in all parts of the ocean, in maldng and
recording observations according to a uniform plan, and in fur-
thering this attempt to increase om^ knowledge as to the w^nds and
currents of the sea, and other phenomena that relate 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 dhected 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

lation. Take these into consideration, and also the foct that there is a vast
amount of foreign tonnage trading between these pkices and the United States,
and it will be seen that the annnal sum saved will swell to an enormous amount."
Extract from Hunt's Merchant's Magazine, May, 1S54.

INTRODUCTION. IX

made. These attracted the attention of the commercial world, and did
not escape the notice of ^philosophers generally.

The Held was immense, the harvest was plenteous, and there was
both need and room for more labom-ers. Whatever the reapers
should gather, or the merest gleaner collect, was to insure to the
benefit of commerce and navigation — the increase of human know-
ledge— the good of all.

Therefore, all who use the sea were equally interested in the
imdertaking. The government of the United States, so considering
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, Eng-
land, and Piussia, from Sweden and Norway, Holland, Denmark,
Eelgimn, 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 then- representatives.

Prussia, Spain, Sardinia, Oldenberg and Hanover, the Holy See,
the free city of Hambm^g, the republics of Bremen and Chili, and
the empires of Austria and Brazil, have since offered their co-opera-
tion also in the same plan.

Thus the sea has been brought regularly within the domains of
philosophical 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 vmich they are conducted may
be captm^ed, the abstract log — as the jomnal which contains these
observations is called — is to be held sacred.

The illustrious Humboldt, several years before his death, expressed
the opinion that the results akeady obtained from this system of
research had given rise to a new department of science, which he
called the Physical Geography or the Sea.

Earely before has there been such a subhme spectacle presented
to the scientific w^orld : all nations agreeing to unite and co-operate
in carrying out according to the same plan, one system of philo-
sophical research with regard to the sea. Though they 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 regarded as a floating observatory, a
temple of science. The instruments used by every co-operatmg
vessel are to be compared with standards that are common to all ;

INTKODUCTION.

SO that an observation that is made anywhere and in any ship
may be referred to and compared with all similar observations by
ail other ships in all parts of the w^orid.

But these meteorological observations which tliis extensive and
admirable system includes will relate onhj 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 na^dgation have been. A series of
systematic observations, dhected 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, and valuable results.

With proper encouragement, this plan of research is capable
of gTeat expansion. With the aid of the magnetic telegTaph, and
by estabhshing 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. xVnd Admiral
Fitzroy, at the head of the Meteorological Department of the
Board of Trade in London, informs me that akeady, though the plan
went into operation only in the month of September, 18G0, yet it is
most rich with the promise of a fine harvest of practical results.

The agricultural societies of many states of America have ad-
dressed memorials to the American Congress, asldng 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 observa-
tions, time of making them, and the interchange of results are
concerned. Grreat good is to come of it — shipwi'ecks and disasters
are to be prevented by it — the pubhc 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 interest or pleasm'e in
a perusal of these passages, will lend their assistance to the carrying
out of this plan, by advocating it among their friends. These re-
searches for the land look not only to the advancement of the great
interests of sanitary and agricultm-al meteorology, but they involve
also a study of the laws which regulate the atmosphere, and call for
a careful investigation of all its phenomena.

Another beautiful feature in this system is, that it costs nothing;

INTRODUCTION. XI

additional. The instrimieiits that these observations at sea call for
are such as are already in use on board of every well- conditioned
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 accomphshed
by these researches in the way of shortening passages and lessening
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
commimity 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 hiin acquainted
mth things new and instructive. His intelligence Y^ll enable him
to appreciate the contrasts of each coimtry in its general aspect,
manners, and productions, and in modes of navigation adapted to
the character of coast, cKmate, and rivers. He vvill dwell with
interest on the phases of the ocean, the storm, the calm, and the
breeze, and v/ill look for traces of the laws which regulate them.
All this will induce a serious earnestness in his work, and teach him
to view hghtly those irksome and often ofi'ensive duties incident to
the beginner."*

And that these researches do have such an effect many noble-
hearted mariners have testified. Captain Phinney, of the American
ship " Gertrude," writing from Callao, January, 1855, thus ex-
presses himseK:

" 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 ovvn 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 famishing you with material to work out still farther
towards perfection yom^ great and glorious task, not only of pointing

* "The Log of a Merchant Officep. ; viewed witli reference to the Educa-
tion of young Officers and the Youth of the Merchant Service. By Egbert
Methrex, Commander in the Peninsular and Oriental Company, and author of
the ' Narrative of the Blenheim Hurricane of 1851.'" London: John W^eale,
59 High Holborn ; Smith, Elder & Co., Cornhill ; Ackermann & Co., Strand. 1854.

XU INTRODUCTION.

Gilt the most sj^eedy routes for ships to follow over the ocean, but
also of teaching us sailors to look about us, and see by what Vv^onder-
fiil manifestations of the wisdom and goodness of the great God we
are continually surrounded.

"For myself, lam free to confess that for many years I com-
manded a ship ; and, although never insensible to the beauties of
natm-e 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
Fkst 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 Avork, 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 dis-
pleased with, or, at least, will know how to excuse, so much of what
(in a letter of this kind) might be termed irrelevant 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 from all good men, whether ashore or afloat. Admkal
Fitz Eoy, admitting the value of the practical results abeady
derived by commerce and navigation from these researches, is of
opinion that their mfluence in improving and elevating the mind
of the British seaman also, can scarcely be of less importance.

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

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 He hidden
in its depths ; and of the phenomena that display themselves at its
siuface. In short, I shall treat of the economy of the sea and its
iidaptations — of its salts, its w^aters, its climates, and its inhabitants,

INTEODUCTION. Xlll

and of whatever there may be of general interest in its commercial
uses or industrial pui'suits ; — for all such things pertain to this de-
j)artment 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
interestmg department of science ; and the aim of the author is to
present the gleanings from this new field in a manner that may be
interestmg 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.*

The results that are embodied in Plate I. alone of this edition
would, had the data for it been collected 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

* There ia an old and very rare book wliicli treats npon some of the subjects to
which this little work relates. It is by Count L. F, Maesigli, an Italian, and is
called Natural Description of the Seas. The copy to which I refer was trans-
lated into Dutch by Boerhaave in 17SG.

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

He divides sea water into sin-f:ice and deej^-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 this acid (iodme?) is found in surface and
not in deep-sea water is, it is derived from the air ; but he supposes that the salt-
l^etre 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 tlie 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 tliis saltpetre vapour.

Donati, also, was a valuable labourer in this field. His inquiries enabled
Mr. Trembley^ to conclude that there are, " at the bottom of the water, moun-
tains, plains, valleys, and caverns, just as upon the land."

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

> Philosophical Transactions.

XIV INTEODUCTIOX.

labour. Officers here have been engaged upon tbe ^vork for many
years. This patient industry has been rewarded with the discovery
of laws and the development of truths of great value in navigation
and very precious to science.

It would be presumptuous to claim freedom from error for a
work hke this : true progTess consists in the discovery of error
as well as of truth. But I may be pardoned for saying that the
present edition of this w^ork mil 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 abun-
dant 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 con-
jecture grow and gain as truth, or fade and fall as error.

The fact seems now to be clearly estabhshed that the atmosphere
is very unequally divided on opposite sides of the equator, and that
there is a mild climate in the unkno^vn resfions of the antarctic

o

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 smface in northern latitudes. These,
and many other developments not less interesting, seemed to call
for a recast of the work. Indeed several new chapters have been
added to this edition, and many new subjects have been treated of in
it. New ^dews also have been presented, and the errors of former
views corrected wherever in them farther research has pointed out
error. These researches have gTo^sm 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 Geogba-

PHY OF THE Sea, and its METEOKOLOaY.

1 Albemarle Street, London.
20tJi November, 1860.

CONTENTS.

CHAPTER I.

THE SEA AND THE ATMOSPHERE.

The two Oceans of Air and Water, § 1.— Their Meeting, 2.— Their Depth, 3.— The
Weight of the Atmosphere, 4. — Three fourths below the Mountain-tops, 5. — Its
Height, 6.— Data conjectural, 7.— Analysis of Air, 8.— Information respecting the
Depth of the Ocean, 9.— Its probable Depth, 10.— Relation between the Depth
and the Waves of the Sea, 11.— Airy's Tables, 12.— The Earthquake of Simoda,
13.— The Propagation of its Waves, 14.— Their Breadth and Velocity, 15.— Ave-
rage Depth of the North Pacific, 16. — Specific Gx-avity of Sea-water, 17.— Ditto
of Air, 18.— Unequal Distribution of Light and Heat, of Air, Water, and Land,
19.— The Sun longer in northern Declination, 20.— England about the Pole of
the Hemisphere with most Land, 21.— Eiiects in the Terrestrial Economy of Ine-
quality in the Distribution of Land and Water, 22.— Quantity of fresh Water in
American Lakes, 23. — The southern Seas likened to the Boiler, northern Lands
to the Condenser of a Steam-engine, 24. — Oflices of the Atmosphere multitudi-
nous, 25.— Dr. Buist, 26. — The Sea and the Atmosphere contrasted, 27. — Influence
of the Sun, 28.— Of diurnal Rotation, 29.— Currents, 30.— Icebergs, 31.— Mountain
Ranges, 32.— Water, 33.— Latent Heat, 34.— Effects of, upon* the Earth, 35.— The
Tides, 36.— Hurricanes, 37.— Powers of the Air, 38.— Its Functions, 39.— The
Operations ofY/ater, 40, — Its marvellous Powers, 41. — It caters on the Land for
the Insects of the Sea, 42. — Leeching, 43.— Solid Ingredients, 44.— Quantity of
Silver in the Sea, 45. — Its Inhabitants, their Offices, 46.— Monuments of their In-
dustry, 47.— Analysis of Sea-water, 48.— Proportion of Water to the Mass of the
Earth, 49.— The three great Oceans, 50.— The Atlantic, 51.— Its Tides, 52.— Its
Depths, 53.— Contrasted with the Pacific, 54.— The Telegraphic Plateau, 55.— New
Routes for an Atlantic Telegraph, 56.— The Greenland Route, 57.— The French
Route, 58.— Their Length of Circuit, 59.— Faulty Cables, 60.— Their Iron Yv rappings,
61, — Imperfect Insulation, 62. — The Red Sea and Mediterranean Cables, 63.— A
Galvanic Battery in the Sea, 64. — Two Metals should not be used about a Sub-
marine Cable, 65. — Rogers's Cable "Jacket," 66. — Deep-sea Temperatures a
Desideratum, 67,— Specimens from the Depth of 19,800 feet, 68 . . Page 1

CHAPTER TI.

THE GULF STREAM.

Its Colour, § 70. — How caused, 71. — Speculations concerning the Gulf Stream, 72. —
Agencies concerned, 73. — Early Writers, 74. — Objection to the fresh-water Theory,
75. — Livingston's Hypothesis, 76. — Franklin's Theory, 77. — Objections to it, 78. —
Herschel's Explanation, 79. — Objections to it, 80. — The Supremacy of the Winds
disputed, 81.— The Bonifaccio Current, 82.— The Bed of the Gulf Stream an
ascending Plane, 83. — The Niagara, 84.— x^ Current Counter to the Gulf Stream,
85.— Bottle Chart, 86.— Their Drift, 87.— The Sargasso Sea, 88.— A Bifurcation,
89. — Winds exercise but little Influence upon constant Currents, SO. — Effects of
diurnal Rotation upon the Gulf Stream, 91. — The Gulf Stream jannot be accounted
for by a higher Level, 92. — Nor by the trade-wind Theory, 93. — Illustration, 94. —
The Gulf Stream the Effect of some constantly operating Power, 95.— The Pro-
duction of Currents without Wind, 96. — Warm Currents flow towards the Pole, cold
towards the Equator, 97.— The Edges of the Gulf Stream a striking Feature, 98. —
Illustrations, 99.— How the Water of the Gulf Stream differs from the littoral
Waters, 100.— Action on Copper, 101.— Saltness of the Gulf Stream, 102.— Agents

XVI CONTENTS.

concerned, 103,— Evaporation and Precipitation, 104.— Current into the Caribbean
Sea, 105.— Amount of Salt left by Evaporation, 106.— Currents created by Storms,
107.— The dynamical Force that calls forth the Gulf Stream to be found in the
Diiference as to Specific Gravity of intertropical and polar Waters, 108. — Winter
Temperature of the Gulf Stream, 109.- The Top of the Gulf Stream roof-shaped,
110.— Drift Matter sloughed off to the right. 111.— Why so sloughed off, 112.—
Illustration, 113.— Drift-wood on the Mississippi, 114.— Effect of diurnal notation
upon, 115.— Formation of the Grand Banks, 116.— Deep Water near, 117.— The
Gulf Stream describes in its Course the Path of a Trajectory, 118.— ^Its Path from
Bernini to Ireland, 119.— The Tendency of all Currents, both in the Sea and Air,
to move in Great Circles a physical Law, 120.— This Law recognized by the Gulf
Stream, 121.— The Shoals of Nantucket do not control its Course, 122.— Herschel's
Theory not consistent with known Facts, 123.— The Channel of the Gulf Stream
•shifts with the Season, 124.— The Phenomenon thermal in its Character, 125. —
Limits of the Gulf Stream in Mai'ch and September, 126. — Reluctance of Layers or
Patches to mingle, 127.— Streaks of warm and cool, 128.— Waters of theOcean kept
in Motion by thermo-dynamical Means, 129.— Fig. A, Plate VI., 130.— The high
Temperature and Drift in the western Half of the North Atlantic and Pacific
Oceans, 131. — A Gulf Stream in each, 132.— Their Connection with the Arctic
Ocean, 133. — The Sargassos show the feeble Power of the Trade-winds upon Cur-
rents, 134. — The drift Matter confined to Sargassos by Currents, 135. — Theory as
to the Formation of Sargassos, 136.— Sargassos of southern Seas to the left of the
southern, to the right of the great polar and equatoi-ial Flow and Reflow, 137. —
Their Position conforms to the Theory, 138. — The Discovery of a new Sargasso,
13 J. — One in the South Atlantic, 140. — The large Volume of warm Water outside
of the Gulf Stream, 141. — The Resemblance between the Currents in the North
Atlantic and the North Pacific, 142. — A Cushion of cool Water protects the
Bottom of the deep Sea from Abrasion by its Currents, 143. — Why should the
Oulf Stream take its Rise in the Gulf of Mexico, 144.— The Trade-Winds as a
Cause of the Gulf Stream, 145. — Gulf Stream impelled by a constantly acting
Force, 146.— The true Cause of the Gulf Stream, 147 . . . Page 21

CHAPTEK III.

INFLUENCE OF THE GULF STREAM UPON CLIMATES AND COMMERCE.

How the Washington Observatory is warmed, § 150. — An Analogy showing how the
Gulf Stream raises Temperature in Europe, 151.— Depth and Temperature, 152. —
Contrasts of Climates in the same Latitudes, 153. — Mildness of an Orkney Winter,
154. — Amount of Heat daily escaping through the Gulf Stream, 155. — Its benign
'Influences, 156.— Cold Water at the ^Bottom of the Gulf Stream, 157.— Fish and
•Currents, 158.— A Shoal of Sea-nettles, 159.— Food for Whales, 160.— Piazzi
Smyth's Description, 161. — The Waters of the Sea bring forth — oh how abundantly !
162.— Contrasts between the Climates of Land and Sea, 163.— Order and Design,
164.— Terrestrial Adaptations, \%b.—3Ieieorology of the Sea: the Gulf Stream the
Weather-breeder — its Storms— the great Hurricane of 1780, 166. — Inquiries in-
stituted by the Admiralty, 167. — The most stormy Sea, 168. — Northern Seas more
.boisterous than southern, 169.- Storms in the North Atlantic and Pacific, 170. —
Storms along their western Shores, 171. — Position of the Poles of maximum Cold,
and their Influence upon the Meteorology of these two Oceans, 172. — Climates of
England and Silver Fogs of Newfoundland, 173. — Influences upon Storms, 174. —
More observations in and about the Gulf Stream a Desideratum, 175. — Certain
Storms make for it and follow it, 176. — How aqueous Vapour assists in producing
Winds, 177. — Storms in the interior attracted by the Gulf Stream, 178.— Storms of,
dreaded by Seamen, 179. — Routes formerly governed by the Gulf Stream, 180. —
Difficulties with early Navigators, 181. — Finding Longitude by the Gulf Stream,
182.— Folger's Chart, 183.— Using the Gulf Stream in Winter, 184.— Running
.south to spend the Winter, 185. — Thermal Navigation, 186. — Commodore Truxton,
187. — The Discovery of the high Temperature of the Gulf Stream followed by a
Decline in Southern Commerce, 188.— Statistics, 189.— The Shortening of Voyages,
190. — The Scope of these Researches, 191 Page 51

CONTENTS. xyii

CHAPTEE lY.

THE ATMOSPHERE.

Likened to a Machine, § 200.— The Air and the Ocean governed by stable Laws, 201.
— Importance of observing the Works of Nature, 202. — Materials for this Chapter,
203.— Different Belts of Winds, 204.— The trade-wind Belts, 205.— The return
Current, 206. — The Effect of diurnal Rotation on the Course of the Trade-winds,
207.— Two grand Systems of Currents, 208.— From the Pole to 35O-30°, 209,—
The "Horse Latitudes," 210. — The Barometer there, 211. — The equatorial calm
Belt, 212.— The calm Belt of Capricorn, 213. — The polar Calms and the return
Current, 214. — Diagram of the Winds — Plate I., 215. — As our knowledge of the
LaAvs of Nature has increased, so have our Readings of the Bible improved, 216. —
Sloughing off from the counter Trades, 217. — The Air which supplies the south-
east Trade-wind in the Band 5° does not cross the Band 25°, 218. — Winds with
Northing and Winds with Southing in them contrasted, 219. — South-cast Trade-
winds stronger near the equatorial Limits, 220.— Speed of Vessels through the
Trade-winds, 221. — The Question. Whence are the south-east Trade-winds supplied
with Air? answered, 222. — AVhither it goes, 223. — How it is drawn down from
above, 224. — Velocity of south-east shown to be greater than north-east Trade-
winds, 225. — The Air sloughed off from the counter Trades moist Air, 226. — The
Air sloughed off from the upper Ti'ade Current dry, 227. — The meteorological
Influences of ascending Columns of- moist Air, 228. — Supposing the Air visible,
the Spectacle that would be presented between the upper and lower Currents, 229.
— The Importance of atmospherical Circulation, 230. — Its vertical Movements, how
produced, 231. — Vertical and horizontal Movements in the Air Consequents of,
and dependent upon each other, 232.— Cold Belts, 233. — The upper Currents, their
Numbers and Offices, 234. — Tendency of Air when put in Motion to move in the
Plane of a Great Circle, 235. — The Results upon its Circulation of this Tendency,
236. — Experiments by the French Academy, 237. — How Supplies of fresh Air are
brought down from the upper Sky, 23S. — Beautiful and benign Arrangements, 239.
— Their Influences upon the jMind, 240. — The Effect of downward Currents in pro-
ducing Cold, 241. — The Winter Northers of Texas, 242.— Their severe Cold, 243. —
" Cold Snaps," 244.— Anemometers to determine the Inclination of the wind wanted,
245.— The hot Winds of the Andes, 246. — Certain "Hot Spells" explained, 247.—
Reservoirs in the Sky, 248. — The warm Winds of the Andes caused by the Trade-
Winds, 249.— Dormant Powers of the Telegraph in Meteorologj', 250. — The Wind
in his Circuits, 251.~Forces which propel the Wind, 2.52. — Effect of the direct
Heat of the Sun upon the Trade-winds, 253. — The two Systems of Trade-winds un-
equal both in Force, Duration, and Stability, 254. — Effects of Heat and Vapour,
255. — Hurricanes not due to direct Heat of the Sun, 256. — The Influence of other
Agents required, 257. — Where found, 258. — Vapour as one of the Causes of the
Trade-winds, 259. — Black's Law, 260. — The latent Heat transported in Vapour,
261.— The Effect of the Deserts upon the Trade-winds, 262.— Indications of a
Crossing at the calm Belts, 263.— The counter Trades — they approach the Pole in
Spirals, 264.^They turn ivitli the Hands of a Watch about the south Pole, against
them about the north, 265. — The Arrows in the Diagram of the Winds, 266. — The
Offices of Sea and Air in the physical Economy, 267. — Powerful Machinery,
268 Page 72

CHAPTER V.

RAIXS AND RIVERS.

Rivers considered as Rain-gauges— the ten largest, § 270. — Heat required to lift Va-
pour for these Rivers, 271.— Rain-fall in the Mississippi Valley, 272.— Its Area,
and the latent Heat liberated during the Process of Condensation there, 273. —
Annual Dischai'ge of the Mississippi River, 274.— Physical Adaptations, 275. —
Whence come the Rains for the Mississippi, 276. — The north-east Trades of the
Atlantic supply Rains only for the Rivers of Central and South America, 277. —
The calm Belt of Cancer furnishes little or no Rain, 278.— The North Atlantic

XYUl CONTENTS.

insufficient to supply Rain for so large a portion of the Earth as one sixth of all
the Land, 279. — Daily Rate of Evaporation at Sea less than on Land — Observa-
tions wanted, 280.— Rivers are Gauges for the Amount of effective Evaporation,
281. — Importance of Rain and River Gauges, 282. — Hypsometry in the Korth
Atlantic peculiar, 283.^ — Limited Capacity of AVinds to take up and transjiort, for
the Rivers of Europe and America, Vapour from the North Atlantic, 284.— The
Vapour-Springs for all these Rivers not in the Atlantic Ocean, 285.— The Places in
the Sea whence come the Rivers of the North, discovered — proves the Crossing at
the calm Belts, 286.— Spirit in which the Search for Truth should be conducted,
287. — The Number of known Facts that are reconciled by the Theory of a Cross-
ing at the calm Belts, 288. — The Atmosphere to be studied, like any other Ma-
chinery, by its Operations, 289.— Arguments furnished by the Rivers, 290.— IMore
Rain in the northern than in the southern Hemisphere, 291. — The Trade-winds
the evaporating "Winds, 292. — The saltest Part of the Sea, 293. — Seeing that the
southern Hemisphere affords the largest evaporating Surface, how, unless there be
a Crossing, could we have most Rain and the great Rivers in the northern ? 294. —
The rainy Seasons, 295.— The rainy Seasons of California and Panama, 296. —
The rainless Regions, 297. — Tlie rainy side of llountains, 298.— The Regions of
greatest Precipitation, Cherraponjie and Patagonia, 2\i^.— Amount of Evaporation
greatest from the Indian Ocean, 300. — The Rivers of India, and the Measure of the
effective Evaporation from that Ocean, 301. — Physical Adjustments, 302. — Adapta-
tions, their Beauties and Sublimity, 303 Page 100

CHAPTEE \i: '

RED FOGS AND SEA BREEZES.

The Alternations of Land and Sea Breezes, § 311.— The Sea Breeze at Valparaiso,
312. — The Contrast, 313. — Land and Sea Breezes along the Shores of intertropical
Countries, 314. — Cause of Land and Sea Breezes, 315. — Lieutenant Jansen on the
Land and Sea Breezes in the Indian Archipelago, 316. — Sanitary Influences of
Land and Sea Breezes, 317. — Influences which regulate their Strength, 318. — Land
Breezes from the west Coast of Africa scorching hot, 319. — Land Breeze in Brazil
and Cuba, 320. — Night Scenes when sailing with the Land Breeze, 32L— Red Fogs
in the Mediterranean, 322. — Red Fogs near the Equator, 323. — Putting Tallies on
the Wind, 324.— They tell of a Crossing at the calm Belts, 325.— Humboldt's
Description of the Dust-whirlwinds of the Orinoco, 326.— Are the great Deserts
Centres of Circulation ? 327. — The Colour of " Sea-dust," 328. — A Clew leading into
the Chambers of the South, 329.— Red Fogs do not always occur at the same Place,
but the}^ occur on a north-east and south-west Range, 330.— Conditions requisite to
the Production of a Sea Fog, 331. — What is the Agent that guides the Air across
the calm Belts ? 332 Page 127

CHAPTER YII.

THE EASTING OF THE TRADE-WINDS, THE CROSSING AT THE CADM BELTS, AND THE
MAGNETISM OF THE ATMOSPHERE.

Halley's Theory not fully confirmed by Observations, $ 341.— Observed Course of
the Trade-winds, 342.— Velocities of the Trade-vrinds, 343.— Difference between
Observation and Theory, 344. — Faraday's Discovery of Magnetism in the Air,
345.— Lines of magnetic Force, 34G.— Tlie magnetic Influences of the Oxygen of
the Air and of the Spots on the Sun, 347.— The Needle in its diurnal A^ariations,
the Barometer in its Readings, and the Atmosphere in its electrical Tension, all
have the same hours for their Maxima and Minima, 348. — The Question raised
by modern Researches, 349.— Wet and dry Air of the calm Belts, 350.— Principles
according to which the phj-sical Machinery of our Planet should be studied, 351. —
Division into "Wind-bands, 352. —The medial Bands, 353. — The rainless Regions
and the calm Belts, 354. — The theory of the Crossings restated, and the Facts
reconciled by it, 355. — The Question, How can tAvo Currents of Air cross?

CONTENTS. XIX

answered, 356. — The Kain "Winds in the'Mississippi Valley, 357. — Ehrenberg and
his Microscope, 358. — Quetelet's Observations, 359. — At Sea in the southern Hemi-
sphere we have the Rule, on Land in the northern the Exception, as to the general
Circulation of the Atmosphere, 360. — The magnetic Poles, the Poles of the "Wind
and of Cold coincident, 361.— The Barometer in the Wind Bands, 362. — More
Atmosphere in the northern than in the southern Hemisphere, 363.^ — A Standard of
Comparison for the Barometer at Sea, 364. — South-east Trade-winds having no
Moisture traced over into rainless Regions of the northern Hemisphere, 365. — Each
Hemisphere receives from the Sun the same amount of Heat, 366. — The northern
radiates most, 367. — Another Proof of the Crossings at the calm Belts, 368. — Facts
and Pearls, 369 Page 147

CHAPTEE VIII.

CUERENTS OF THE SEA.

Obedient to Order, $ 370.— The Fauna and Flora of the Sea, 371. —Those of southern
unlike those of northern Seas, 372. — The Capacity of Water to convey Heat, 373. —
Currents of the Sea to be considered in Pairs, 374. — Marine Currents do not, like
those on Land, run of Necessity from higher to lower Levels, 375. — The Red Sea
Current, 376. — Upper and under currents through Straits explained, 377. — The
Mediterranean Current, 378.— The Suez Canal, 379. — Hydrometrical Observations
at Sea wanted, 380.— Specific Gravity of Red Sea Water, 381.— Evaporation from,
382.— The Mediterranean Currents, 383.— The " Drift" of thePha>nix, 384.— Salt-
ness of the Mediterranean, 385.— The Escape of salt and heavy Water by under
Currents, 386. — ^Vertical Circulation in the Sea a physical Necessity, 387. — The
Bars at the Mouths of the Mississippi an Illustration, 388. — Views of Admiral
Smyth and Sir C. Lyell, 389— Currents of the Indian Ocean, 390.— The Black
Stream of the Pacific contrasted Mith the Gulf Stream of the Atlantic, 391.— The
Lagulhas Current and the Storms of the Cape, 392.— The Currents and Drift of the
Indian Ocean, 393. — The ice-bearing Currents from the antarctic Regions, 394. — The
Currents of the Pacific— Drift-wood, 395.- The Black Current of the Pacific, like
the Gulf Stream, Salter than the adjacent Waters, 396. — The Current of Okotsk,
397._Humboldt's Current, 398. — The "desolate" Region, 399.— Polynesian Drift,
400. — Equatorial Currents, 401.— The Influence of Rains and Evaporation upon
Currents, 402. — Under Currents— Parker's deep-sea Sounding, 403. — the Compres-
sibility of "^Vater- Elfect of, in the oceanic Circulation, 404. — Assisted by its Salts,
405.— The Origin of Currents, 406. — Currents of the Atlantic, 407.— The St. Roque
Current, 408.— The Greenland Current, 409 Page 172

CHAPTER IX.

THE SPECIFIC GRAVITY OF THE SEA, AND THE OPEN WATER IN THE ARCTIC OCEAN.

Interesting physical Inquiries, § 420. — Voyages of Discovery to the North Pole, 421.
— The first Suggestions of an open Sea in the Arctic Ocean, 422. — Harpoons — ■
Habits of the Whales, 423. — The under Current into the Arctic Ocean— its Influ-
ences, 424. — Indications of a milder Climate, 425. — How the littoral Waters, by
being diluted from the Rivers and the Rains, serve as a Mantle for tlie Salter and
warmer Sea Water below, 426. — An under Current of warm but salt and heavy
AVater, 427. — De Haven's Water Sky, 428. — Dr. Kane, 429. — Under Currents
change Temperature slowly, 430. — Solid matter annually drifted out of the polar
Basin, 431. — Volume of '^^'ater kept in jMotion by the Arctic Flow and Reflow,
432. — The Hj'drometer at Sea, 433. — Specific Gravity of average Sea Water, 434.
■ — An Anomaly, 435. — Influence of the Trade-winds upon the Specific Gravity of
Sea Water, 436. — Compensating Influences, 437. — Nicely adjusted, 438. — A
thermal Tide, 439. — The isothermal Floor of the Ocean, 440.— Thermal Dilata-
tion of the Water, 441.— Experiments on the Freezing Point, 442.— Sea Water at
summer more expansible than Sea Water at Winter Temperature, 443. — Data for
Plate X., 444. — A thermal Tide: it ebbs and flows once a Year, 445. — Sea Yv^ater
of the southern cooler and heavier, Parallel for Parallel, than Sea Water of

X CONTENTS.

the northern Hemisphere, 446. — Testimony of the Hydrometer in favour of the
xVir Crossings at the calm Belts, 447. — Amount of Salt in, and mean specific
Gravity of Sea Yv'ater, 44S. — Light cast by Plate X, on the open Sea in the
Arctic Ocean, 449. — The heaviest Water, 450. — Chapman's Experiments, 451. —
The Hydrometer indicates the rainy Latitudes at Sea, 452. — Astronomical View,
453.-- The latent Heat of Vapour, 4:54. — Its Influence upon Climates, 455.— The
Ilesults of the marine Hydrometer, 456. — Barometric Indications of an open Sea,
457. — Polar Karefa'ction, 45S. — The Middle Ice, 459. — Position of the open Sea,
460 Pagel9S

CHAPTER X.

THE SALTS OP THE SEA.

The Brine of the Ocean, § 461.— Were the Sea of Fresh Water, 462.— Uniform
Character of Sea V/ater, 463. — Hypothesis, 464. — Arguments aftbrded by Coral-
lines in favour of, 465. — Ditto by the lied Sea, 466. — A general System of Circu-
lation required for the Ocean, 467. — Dynamical Agents, 468. — Currents without
Wind, 469.— Influence of Salts and Evaporation, 470. — The under Currents
owing entirely to the Salts of Sea Water, 471. — A Property peculiar to Seas of
saltwater, 472.— Quantity of Salt in the Sea, 473.— Deductions, 474.— Drift of
the "Resolute," 475.— De Haven's Drift, 476. — An anti-polynian View, 477. — The
Drift explained, 478. — Thickness of a \Yinter's Ice, 479. — Layers of Water of
diiferent Temperature in the Arctic Ocean, 480. — The ice-bearing Drift from
the Arctic like the ordinary Drift from the Baltic, 481.— Icebergs drifting north,
482. — Temperature of the under Current, 483. — It comes to the Surface, 434. —
Sea-shells — their Influence upon Currents, 485. — Solid Matter secreted by them
48G. — Dynamical Force derived from, 487. — Their physical Relations, 4SS. — Th
Regulators of the Sea, 489. — Whence does the Sea derives its Salts ? 490. — Their
Antiquity, 491. — Insects of the Sea — their Abundance, 492. — Ditto, calcareous
in the Pacific, silicious in the Atlantic, 493. — The Records of the Sea and of
Revelation agree, 494. —Cubic Miles of Sea-salt, 495. — The Saltness of VV'ater
retards Evaporation, 496. — The Harmonies of the Ocean, 497. — The Micro-
scope and the Telescope, 498.— Sea- shells and Animalculaj in a new Liglit,
499 Page 226

CHAPTEE XI.

THE CLOUD REGIOX, THE EQUATORIAL CLOUD-RING, AND SEA FOG?.

Clotid Region — highest in the calm Belts, § 501.— Fogless Regions, 502.— The
most stormy Latitudes, 503. — Influences of the Gulf Stream and the ice-bearing
Currents of the South, 504. — Sea Fogs rare within 20° of the Equator— Red Fogs,
505. — Cloudless Regions and Height of Clouds at Sea, 506. — Height and Velo-
city of Waves — Plan for determining, 507. — Determining the Height of Clouds
at Sea, 508. — Cloud Regions at Sea in the shape of a double-inclined Plane, 509.
— Fogs in the Harbour of Callao, 510. — The Cloudy Latitudes, 511. — Why there
should be less Atmosphere in the southern than in the northern Hemisphere,
512.— Influence of antarctic Icebergs in expelling the Air from austral Regions,
513. — The Horse Latitudes — the Doldrums, 514. — A Frigate under the Cloud-
ring, 515.— Subjects which at Sea present themselves for Contemplation, 516.—
The Barometer under the Cloud-ring, 517.— Its Motions, 518. — Meteorological
Processes, 519.— Snow-line mounts up as it crosses the Equatorial calm Belt, 520.
— Otfices of the Cloud-ring, 521.— It acts as a Regulator, 522. — The latent Heat
liberated in the Processes of Condensation from and under the Cloud-ring, true.
Cause of the Trade-winds, 523.— Imagined Appearance of the Cloud-ring to a
distant Observer. 524. — Thunder, 525. — Exceeding Interest attached to physical
Research at Sea, 526 Page 260

CONTENTS. XXI

CHAPTEE XII.

THE GEOLOGICAL AGENCY OF THE WIIQ-DS.

The Sea and Air regarded as Parts of the same Machine, § 531. — The Level of the
Dead Sea, 532, — An ancient River from it, 533. — Precipitation and Evaporation
in the Dead Sea Valley, 534.— Whence come its Rains? 535.— The Influence of
mountain Ranges, 536. — How the Level of Caspians is reduced, 537. — The For-
mation of Inland Basins— a third Process, 538.— Examples, 539.— The Influence
of the South American Continent upon the Climate of the Dead Sea, 540. — The
Path of the S.E, Trade- winds over into the northern Hemisphere, 541,— Relays
for supplying them with Vapour by the way, 542.— Adjustments in this Hj-gro-
metry of Caspians, 543. — 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, 544. — Their Situation, and the Range of dry Winds, 545. — The Medi-
terranean within it, 546.— Heavy Evaporation, 547, — The Winds that give Rains
to Siberian Rivers have to cross the Steppes of Asia, 548, — How Climates in one
Hemisphere depend upon the Arrangement of Land in the other, and upon the
Course of the Winds, 549.— Terrestrial Adaptations, 550.— The Red Sea and its
Vapours, 551. — Certain Seas and Deserts considered as Counterpoises in the Ter-
restrial Machinerj^, 552. — Hypothesis supported by Facts, 553.— How, by the Winds,
the Age of certain geological phenomena in our Hemisphere may be compared
with the Age of those in the other, 554.— The Andes older than the Dead Sea as
an inland Water, 555 Page 274

CHAPTEE XIII.

THE DEPTHS OF THE OCEAN.

Submarine Scenery, § 560.— Ignorance concerning the Depth of " Blue Water," 561.
— Early Attempts at Deep-sea Soundings — Unworthy of Reliance, 562. — Various
Methods tried or proposed, 563. — Physical Problems more difficult than that of
measuring the Depth of the Sea have been accomplished, 564, — The Deep-sea
Sounding Apparatus of Peter the Great, 565, — A Plan of Deep-sea Sounding devised
for the American Navy, 566, — The great Depths and Failures of the first Attempts,
567. — The Plan finally adopted, 568.— Discovery of Currents in the Depths of the
Sea, 569. — Evidence in favour of a regular System of Oceanic Circulation, 570. — •
Method of making a Deep-sea Sounding, 571. — The Law of the Plummet's Descent,
572. — Brooke's sounding Apparatus, 573. — The Deepest Part of the Atlantic
Ocean, 574. — Deep-sea Soundings by the English Navy, 575 . , Page 292

CHAPTEE XIV.

THE BASIN AND BED OF THE ATLANTIC.

The Wonders of the Sea, § 580. — Its Bottom and Chimborazo, 581.— An Orographic
View, .582.— Plate XL, 583.— "AVhat'sthe Use" of Deep-sea Soundings ? .584.— The
telegraphic JPlateau, 585. — The First Specimens of Deep-sea Soundings, 586. —
Bailey's Letter, 587.— Specimens from the Coral Sea, 588. — They belong to the
Animal, not to the Vegetable or Mineral Kingdom, 589.— Quiet reigns in the*
Depths of the Sea, 590. — Is there Life in them? 591. — The Ocean in a New Light,
592.— Levelling Agencies, 593.— The Offices of Animalculae, 594.— The Study of
them profitable, 595. — The Abrasion of Currents, 596.— Their Pressure on the
Bottom, .597. — Why they cannot chafe it, 598. — What it consists of, 599. — The
Causes that produce Currents in the Sea reside near its Surface, 600. — Their Depth,
601.— The Cushion of still Water— its Thickness, 602.— The Conservators of the
Sea. 603. — The anti-biotic View the most natural, 604. — The Question stated, 605.
—The Arguments of the Biotics, 606. — Ehrenberg's Statement of them, 607. — The
anti-biotic View, 608.— Their Arguments based on the Tides, 609.— On the anti-
septic Properties of Sea-water, 610. — On Pressure, 611, — Arguments from the
Bible, 612, — A Plan for solving the Question, 613. — An unexpected Solution

C

XXU CONTENTS.

afforded, 614. — A Discovery suggested by it, 615. — Specimens from the three
Oceans all tell the same Story, 616. — Their Suggestions,617. — The workof Readapt-
ation, how carried on, 618. — Animalcule at the Bottom of the Sea, 619 Page 302

CHAPTEE XY.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.

Practical Results of physical Researches at Sea, § 621. — Time-tables, 622. — Close
Running, 623. — A Desideratum on Shipboard, 624. — How Passages have been
shortened, 625. — Fast sailing, 626. — The longest Voyage, 627. — Obstructions to the
Navigator, 628.— Plate VIII., 629.— Deserts, 630.— Diurnal Rotation, 631.— The
Land in the northern Hemisphere, 632. — Why the south-east Trades are the stronger,
633. — Their Uniformity of Temperature, 634. — The mean Place of the Equatorial
calm Belt, 635. — Never at rest, 636. — The calm Belts occupy medial Positions, 637.
—Strength of the Trade-winds varies with the Seasons, 638. — Sailing through them
in Fall and AVinter, 639. — A thermal Adjustment, 640. — The Barometer in the
Trade-winds and equatorial Calms, 641. — Experiments in the French Navy, 642.—
Diifeience in Tons of the barometric Pressure upon the north-east and south-east
Trade- winds, 643.— Why the Barometer should stand higher in the south-east than
in the north-east Trade-winds, 644. ^Cataclysms, 645.^ — Are the Climates of the
Earth changing ? 646. — Temperature of the Trade-winds and calm Belts, 647.^ — The
thermal Equator, 648. — A natural Actinometer in the Trade-winds, 649.— Heat
daily received by the south-east Trade-Minds, 6.50. — Equatorial calm Belt never
stationary, 651.— It varies with the Strength of the Trade-winds, 652. — Precipita-
tion in it, 653. — The Appearance of the calm Belts from a distant Planet, 654. —
Rainy Seasons of the Tropical calm Belts, 655. — Their Position, 656. — A meteoro-
logical Law, 657. — The Barometer in the calm Belts, 658.— Winds with Northing
and Winds with Southing in them, 659. — -The barometric Ridges, 660. — They make
a Depression in the Atmosphere, 661. — The upper Surface of the Atmosphere, 662.
— Winds in the southern stronger than "Winds in the northern Hemisphere, 663. —
The Waves and Gales oflF the Cape of Good Hope, 664. — Winds blow from a high
to a low Barometer, 665. — Polar Rarefaction, 666. — The tropical calm Belts caused
by the polar and equatorial Calms, 667. — The meteorological Power of latent Heat,
668 — The low Barometer off Cape Horn, 669. — Barometric Table, 670. — Barometer
at the Poles, 671. — The "brave west Winds" — their barometric Descent, 672. —
Study of the Monsoons affords farther Information touching the calm Belts, 673. —
The south-west Winds of the Atlantic, 674.— Sailing through the Trade-wind, 675.
The Influence of the Land upon the Winds at Sea, 676.— A " Gulf-Stream" in the
Air, 677.— Counterpoises, 678. — Normal State of the Atmosphere, 679.— Rain-
winds, 680 Page 321

CHAPTEE XVI.

MONSOONS.

The Cause of, § 681.— The Region of, 682.— A low Barometer in Northern India, 683.
—The S.AV. Monsoons "backing down," 684.— How they begin, 685.— The Sun
assisted by the latent Heat of Vapour, 686.— The Rain-fall in India, 687.— Its
Influences upon the Monsoons, 688.— The March of the Monsoons, 689. — Their
Conflict— it begins at the North, 690. — The Barometric Descent of the Monsoons,
691. — The Summer Rains of Cherraponjie, 692. — Dove and the Monsoons, 693. —
The south-east Trades passing into south-west Monsoons, 694.— Lieutenant Jansen,
695. — Monsoons in the Pacific, 696. — Influence of Coral Reefs upon Winds, 697. —
Monsoons in Miniature, 698. — The Changing of the Monsoons, 699. — How the calm
Belt of Cancer is pushed to the north, 700. — The curved Form of the equatorial
calm Belt in the Indian Ocean, 701. — The Winter Monsoons, 702. — The Monsoons
of Australasia, 703. — Thunder and Lightning, 704. — Water-spouts, 705,— The east
Monsoon in the Java Sea, 706. — Currents, 707. — Marking the Seasons, 708.— Con-
flicts in the Air, 709.— Passing of the calm Belts, 710. — Where they are, there the
Changing of the Monsoons is going on, 711 Page 350

CONTENTS. XXlll

CHAPTEE XYII.

THE CLIMATES OF THE SEA.

A "Milky Way" in the Ocean, $ 720.— The Vibrations of the Gulf Stream, 721.—
Sea and Land Climates contrasted, 722.— Plate IV., 723.— The Effects of Kight and
Day upon the Temperature of Sea Water, 724. — A Belt of uniform Temperature at
Sea, 725.^ — The Avestern Half of the xltlantic warmer than the eastern, 726.— The
warmest Sides of Oceans and the coldest Shores of Continents in Juxtaposition, 727.
—The Climates of Europe influenced by the Shore-lines of Brazil, 728.— The Gulf
of Guinea and the Climate of Patagonia, 729. — Shore-lines, 730.— Sudden Changes
in the Water Thermometer, 731. — The Fogs of Newfoundland, 732.— Aqueous
isothermal Lines, 733. — The Meeting of cool and warm Waters, 734. — The Direc-
tion of aqueous Isotherms on opposite Sides of the Sea, 735 . , Page 367

CHAPTER XYIII.

TIDE-RIPS AND SEA-DRIFT.

The Glories of the Sea, $ 740.— Drift described, 741.— Plate IX., 742.— The great
Bend in the Gulf Stream, 743.— The Horse-shoe in the Japan Current, 744. — The
Animalculas of the Sea, 745.— Coloured Patches, 746. — Whence the lied Sea derives
its Name, 747. — The Escape of warm Waters from the Pacific, 748.— Ditto from
the Indian Ocean, 749.— A wide Current, 750. — Commotions in the Sea, 751. —
Humboldt's Description of Tide-rips, 752. — Horsburgh's, 753.— Tide-rips in the
Atlantic. 754. —Mock Vigias, 755. — Bores, Eagres, and the Earthquake Wave of
Lisbon, 756. — Rains at Sea, and their Effect upon its Equilibrium, 757.— Ditto of
Cloud and Sunshine, 758. — Day and Night, 759.^Logs overhauled for Kelp and
Ice, 760.— A Sargasso in the South Pacific, 761.— Seaweed about the Falkland
Islands, 762. — The African Sargasso, 763. — Icebergs, 764. — The largest Drift
farthest, 765. — The Line of Antarctic Drift, 766. — Necessity for and Advantages
of an Antarctic Expedition, 767. — Commercial Considerations, 768. — Value of
the Fisheries, 769.— Sperm Whales, 770.— A Sea of Fire to the, 771.— Right
Whales, 772 • . . Page 379

' CHAPTEE XIXl

STORMS, HURRICANES, AND TYPHOONS.

Plate v., § 781.— Typhoons, 782.— The Mauritius Hurricanes, 783.— The West India
Hurricanes, 784.— The Cyclone Theory, 785. — Puzzling Questions, 786. — Espy's
Theory, 787. — Dove's Law, 788. — Bernouilli's Formula, 789. — Predicting Storms,
790.— The Changing of the Wind in a Cyclone, 791. — The Wind stronger on one
side than the other, 792, — The rainy Quadrant of a Cyclone, 793. — Erroneous
Theories, 794.:^— The Wind in a true Cyclone blows in Spirals, 795. — An Illustration,
796. — Dust Whirlwinds and AVater-spouts, 797.— A vera Causa, 798. — Objections to
the Theory, 799.— The three Forces, 80(J.— The effect of each, 801.— A Storm within
a Storm, 802.— The Black Sea Storm of 1854, 803.— Cyclones of the North Atlantic,
804. — The Hurricane Season, 805. — Cyclones in the Mississippi Valley, 806.— Extra-
tropical Gales, 807.— Storm and Rain Charts, 808 .... Page 397

CHAPTEE XX.

THE WINDS OF THE SOUTHERN HEMISPHERE.

Repetition often necessary, § 811.— The S.E. and N.E. Trade-winds put in a Balance
812.— Observations by 2235 Vessels, 813.— Ships used as Anemometers, 814. —
Velocity of the Trade-winds, 815. — Ditto of the Counter-trades, 816— The waves
they get up, 817.— A meteorological Corollary, 818.— Facts established, 819— At-
mospherical Circulation more active in the southern than in the northern Hemi-
sphere, 820.— Gales in the two Hemispheres, 821.— Ditto Calms, 8:^2.- The pro-
pelling Power of the Winds, 823.— Lt. Van Gough's Storm and Rain Charts, 824.—

XXIY CONTENTS.

The "brave west Winds" caused by Rarefaction in the Antarctic Regions, 825. —
Relative Frequency of Rains and Gales at Sea, 826. — The Rainfall of Cape Horn
and Cherraponjie, 827. — Influence of Highlands upon Precipitation, 828. — The
latent Heat of Vapour, 829. — The cause of the boisterous Weather off Cape Horn,
830.— Offices of Icebergs in the meteorological Machinery, 831.— The Antarctic
calm Place a Region of constant Precipitation, 832. — Also of a low Barometer, 833.
Aqueous Vapour the Cause of both, 834.— The topographical Features of Antarctic
Lands, 835. — A perpetual Cyclone, 836. — Discovery of Design in the meteorological
Machinery, 837. — Indications which the Winds afford concerning the unexplored
Regions of the South, 838.— Their Extent; Plate XIV., 839.— A physical LaM^ con-
cerning the Distribution of Land and Water, 840.— Dr. Jilek, 841. — Antarctic Ex-
peditions, 842 Page 416

CHAPTER XXI.

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY.

Indications of a mild Climate about the South Pole, § 850. — The Story of the Winds,
851. — The null Belts, 852. — Extent of the polar Indraught, 853. — The Rarefaction
of the Air over polar Regions, 854. — Barometrical Observations, 855. — The low
austral Barometer, 856. — Discussion of Observations, 857.— Barometric Curve at
Sea, 858. — Ditto over the Land, 859. — Agreement of Observations at Sea, 860. —
The Question why the Barometer should stand lower about the South than the
North Pole considered, 861. — Psychrometry of polar Winds, 862. — Aerial Rarefac-
tion about the North Pole, 863.— Ditto about the South Pole, 864.— Influences
favourable to heavy Precipitation, 865. — The Climates of corresponding Shores and
Latitudes north and south, 866. — Thermal Difference between Arctic and Ant-
arctic Climates, 867. — The Influence of aqueous Vapour upon Winds and Climates,
868. — How the Temperature of Air may be raised by crossing Mountains, 869.
• — Local Variations of Climate, how caused, 870. — Aurora Australis, 871. — An
erroneous Opinion, 872.— Tropical Regions of the southern Hemisphere cooler,
extra-tropical warmer, than those of the northern, 873. — Formation of southern
Icebergs, 874.— Mild Climate in 63° S., 875.— Antarctic Ice-drift, 876.— Antarctic
Currents, 877. — Antarctic Explorations demanded, 878. — Former Expeditions, 879.
— An Appeal for others, 880 Page 436

CHAPTER XXII.

THE ACTINOMETRY OP THE SEA.

A new Field, § 881. — The warmest Waters in the Sea — where are they ? at or below
the Surface, 882. — The annual Supply of solar Heat uniform, 883. — Quantity of
Heat daily impressed upon the Earth, 884.— How far below the Surface does the
Heat of the Sun penetrate? 885. — The Stratum of warmest Water, 886.— Its
Position, 887.— The different Subjects for Observation, 888.— Expected Disco-
veries, 889.— Actinic Processes, 890.— The Reservoirs of Heat, 891. — An Office
for Waves in the Sea, 892. — The Radiating Power of Earth, Air, and Water
compared, 893— A Reflection concerning Heat, 894, — Probable Relation between
the Actinism of the Sea and its Depth, 895 Page 451

EXPLANATION OF THE PLATES.

Plate I.— 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 83,334 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 Explor-
ing Expedition, of Sir James Clark Ross, on board the " Erebus" and " Terror" 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
Town, etc., making upwards of 100,000 in all. This profile shows how unequally the
atmosphere is divided by the equator.

The arrows ivithin 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. It 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 betw^een 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 row^s 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, nqrs, 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 observa-
tions show, they also greatly increase both their duration and 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 parallels are smaller. In other
words, they diminish, as they approach the poles, the area of their vertical section ;

XXVI EXPLANATION OF THE PLATES.

consequently there is a crowding out— a sloughing off 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 Capricorn.

This dotted or shaded periphery is intended to represent a profile view of the at-
mosphere 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 distribution 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. Except-
ing 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 atmosj)here 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. More-
over, being lighter, it mounts up into the cloud region, where it is condensed either
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 ex-
pands 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
over 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 effect 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 construc-
tion 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.

PiiATES 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 connection 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 Ob-
servatory. 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 di-
vided into convenient sections, usually five degrees of latitude by five degrees of lon-
gitude. These parallelograms are then subdivided into a system of engraved squares,
the months of the year being the ordinates, and the points of tlie 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 constructed.

Plate VI. illustrates the position of the channel of the Gulf Stream (Chap. II.) for
summer and winter. The diagram A shows at h ermometrical profile presented by
cross-sections of the Gulf Stream, according to observations made by the hjdrogra-
phical 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 AVashington, 1S54. Imagine a vessel to sail from the

EXPLANi.TION OF THE PLATES. XXVU

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 dia-
gram shows the elevation and depression of the thermometer across this section as
they were actually observed by such a vessel.

The black lines r, y, z, 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
pi'ecipitation 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 VIII. shows the 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 prevailing 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 the number of arrows.

Plate IX. 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 thermometer
(§ 742). Farther researches will enable us to improve this chart. The sargasso seas
and the most favourite places of resort for the whale — right in cold, and sperm in
warm water— are also exhibited 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 Xn. speak for themselves. They are orographic for the North
Atlantic Ocean, and exhibit completely the present state of our knowledge with re-
gard 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. ex-
hibiting 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, San Domingo, and the
Cape de Verds, to the coast of Africa, marked A on Plate XI.

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

The heavy vertical lines, 5°, 10^, 15°, etc., represent parallels of latitude ; the
other vertical lines, months , - -

days in a hundred.

XXVm EXPLANATION OF THE PLATES.

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 condition 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.

Pr,ATE XIV. (§ 839) shows the limits of the unexplored 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 observa-
tions at sea, from the parallel of 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 METEOPiOLOGY.

CHAPTEE I.

1-68. THE SEA AND THE ATMOSPHERE.

§ 1 . OuE planet is invested with two great oceans ; one visible,
The two oceans of the other invisible ; one is imderfoot, the other over-
air and water. head ; 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. It is at the bottom of this lighter ocean where the forces
Their meetmg. whicli WO are about to study are brought into play.

This place of meeting is the battle-field of natm^e, the dvcolling-
place of man ; it is the scene of the greatest conflicts which he is
permitted to witness, for here rage in their utmost fiu-y the povrers
of sea, earth, and air ; therefore, in treating of the Physical Geo-
graphy 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. As to their depth, we know very little more of the one than
Their depth. of tlic othoT ; but the conjectiu^e 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, like water, non-elastic, and not more compressible than this

B

;^

Z PHYSICAL GEOGEAPHY OF THE SEA, AXD ITS METEOROLOGY.

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 ascertained 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
hmidredth part of the wdiole; consequently, by going up 300
+ 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. But the air is elastic, and very unlike water. That at the
Weight of the atmo- bottom is prosscd down by the superincumbent
^P^^^^- 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 do-^Ti, 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,
though it might have been ten feet thick when it first fell, yet with
the weight of the accumulated and superincumbent mass, it might
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 fi^om 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 atmosphere : 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 inch for eveiy successive 87 feet
upward through which he may carry it. To get it to fall a tenth
of an inch, he must cany it higher and higher for every successive
layer.

5. More than three foinths of the entire atmosphere is below
Three fourths below the Icvcl of the highost mouutains ; the other fom-th
the moimtaia tops, jg rarefied and expanded in consequence of the di-
minished pressm-e, 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.

6. At the height of 26,000 miles fi'om the earth, the centrifugal
Its height. force would counteract gravity ; consequently, all

ponderable matter that the earth carries with it in its dim'nal

THE SEA AXD THE ATMOSPHERE. 6

revolution must be within that distance, and consequently tlie at-
mospliere cannot extend beyond that. This limit, however, has
been greatly reduced, for Sir John Herschel has shown, by bal-
loon 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 somid cannot tra^^el through vacuum, it was inferred that the
explosion took place vdthin the limits of the atmosphere. Herschel
concludes that the aerial ocean is at least 50 miles deep.

7. The data from which we deduce om- estimate, both as to the
Data conjectural, mean height of the atmosphere and average depth

of the ocean are, to some extent, conjectm^al ; consequently the
estimates themselves must be regarded as approximations, but suf-
ficiently close, nevertheless, for the present purposes of this work.

8. Chemists who have made the analysis, tell us that, out of
Analysis of air. IQO parts of atmospheiic air, 99.5 consist of oxygen

and nitrogen, mixed in the proportion of 21 of oxygen to 79 of
nitrogen by voliune, and of 23 to 77 by weight. The remaining
half of a jjctvt consists of .05 of carbonic acid and .45 of aqueous
vapour.

9. The average depth of the ocean has been variously com-
infyrmation respect- pntcd by astrouomers, from such arguments as the
ocean.^ ep o e g^-^^^^g afFords, 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.! Other navies, especially the English, have done not a
little in furtherance of that object. Suffice it to say that, within
this brief period, though the undertaking has been by no means
completed — no, not even to the tenth j^art — yet more knowledge
has been gained concerning the depths and bottom of the deei^ sea,
than all the world had before acquired in all previous time.

10. The system of deep-sea somidings thus inaugurated does
Its probable depth, uot thus far authoHze tho conclusion that the average

* Those of !Mr. Welsh, in his ascent from Kew.

t '■'■ And he it furtlier enacted, T\\Q.t i\\Q Secretary of the Navy he directed to
detail three suitable vessels of the navy in testing new routes and perfecting
the discoveries made by Lieut. Maury in the course of his investigations of the
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 incompatible with the public interests."— From Naval Ap-
propriation Bill, approved March 3, 1849.

b2

4 PHYSICAL GEOGllAPHi OF THE SEA, A^W ITS METEOROLOGY.

deptli of ocean water is more tlian three or four miles (§ 3), nor
liave any reliable soundings yet been made in water over five miles
deep.

11. In very shallow pools, where the water is not more than a
Relation between its few iuchos deep, the rioples or waves, as all of us,

depta and the waves , i •! i i it n n •

oftiiesea. wiien cmlclren, nave observed, are small; tneu^ mo-

tion, also, is slow. But when the water is deep, the waves are
larger and more rapid in theii* progress, thus indicating the exist-
ence of a numerical relation between their breadth, height, and ve-
locity, and the depth of the water. It may be inferred, therefore,
that if we Imew the size and velocity of certain vraves, we could
compute the depth of the ocean.

12. Such a computation has been made, and v;e have the au-
Airy's wave tables, tliority 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.

Depth of
the Water

!

in Feet.

1

10 1 100

1000

10,000

100,000

1,000,000

10,000,000

Corresponding Velocity of Wave per Her.

• in Miles.

1

1.54

3.81

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

3o4.92

386.40

386.06

100,000

i.«

4.87

15.18

48.77

154.25

487.79

1151.11

1222.70

13. Accident has afforded us an opportunity of giving a quasi
The earthquake of practical application to Mr. iVirv's formula. On
shnoda. i-i^g 23^,^^ (^£ December, 1854, at 9^45 a.m.,! the first

shocks of an earthquake Vy-ere felt on board the Russian frigate
"Diana," as she lay at anchor in the harbour of Simoda, not far
fi:om Jeddo, in Japan. In fifteen minutes afterwards (10 o'clock),
a large wave was observed rolling into the harboiu', and the water
on the beach to be rapidly rising. The to^^^l, as seen from the
frigate, appeared to be sinking. This wave was followed by an-

* Encyclop. Metropol.

t Notes of a Russian Officer, p. 07, No. 2 (Feb. 1856), vol. xxv., Nautical
Magazine, London.

THE SEA AND THE ATMOSPHERE. O

otiier, and v^hen the two receded — wliich was at lOh. 15m. — there
was not a house, save an untinished temple, left standing in the
village. These waves contmued to come and go until 2.30 p.m.,
dming which time the frigate was thrown on her beam ends five
times. A piece of her keel 81 feet long was torn ofi", holes were
knocked in her by striking on the bottom, and she was reduced
to a wreck. In the coiu'se of five minutes the Vv'ater in the harboui*
fell, it is said, from 23 to 3 feet, and the anchors of the ship were
laid. bare. There was a great Joss of life; many houses were
washed into the sea, and many junks carried up — one tw^o miles in-
land— and dashed to pieces on the shore. The day was beautifally
line, and no warning was given of the approaching convulsion ;
the barometer standing at 29.87 in., thermometer 58°; the sea
perfectly smooth Avhen its smface was broken by the first ^vave.
It w^as calm in the morning, and the wind continued light all day.
,14. In a few hoiu's afterwards, at San Francisco and San Diego,
The propagation of the tido-gaugos showcd that several well-marked
waves by it. ^j^.] extraordinary waves had arrived off the coast

of California.* Ti:ie origin of these waves, and those which de-
stroyed the town of Simoda, in Japan, and wrecked the " Diana,"
was doubtless the same. But where was their birthplace ? Sup-
posing it to be near the coasts of Japan, w^e may, with the tide-
gauge observations in Galifomia and Mr. Airy's formulae, calculate
the average depth of the sea along the path of the v;ave from Simoda-
both to San Francisco and San Diego.

15. Supposing the weaves to have taken up their line of march
iheir bieadih and ^om some poiut aloug tlic coast of Japan, the San
velocity. 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. Admitting these premises — which are partly assumed — to
Avc>T-n-e depth of the bc corrcct, then, according to Airy's formula^, the
'N-orth"^i\icitic. average depth of the North Pacific between Japan
and California is, by the path of the San Francisco wave, 2149
fathoms, by the San Diego, 2034 (say 2-1 miles).

17. At the temperatm^e of 60'', the specific gravity of average
-P-Ti" gi-avHy of sca-wator is 1.0272,t and the weight of a cubic foot
.^^^^t::^. ' ig 64.003 lbs.

'' Ex. Doc. No. 22, Senate, 1st sess. 34tli Congrees, p. 342.
t Maiivy's Sailing Directions, vol. i. Sir John Hcrschel quotes it at i.Oily.'
for G2°.

0 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IMETEOEOLOGY.

18. Witli the barometer at 30 in. and the thermometer at 32°,
Of air. 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 j^hysical geography of the sea its charms.

19. There is in the northern hemisphere more land, less sea,
Unequal distribution more frosli watcr, more atmospheric air, and a longer
ofiight. land, and air. g^j^j^^^^l duration of siinlight, than there is in the
southern. And though the two hemispheres receive amiually the
same amount of heat directly h'om the sun, yet the northern, without
growing cooler, dispenses the greater quantity by radiation.

20. In his annual romid, the sun tarries a w^ek (7 J days) longer
The sun longer in on the nortli than he does on the south side of the

northern declina- , -. ,i ii i i • • t i i

tion. equator, and consequently tne antarctic night and

its v/inter 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 smi is in perigee, and
during the course of a diimial revolution there the southern half of
our planet receives more heat than the northern half during the
same period of oiu' summer. This difference, however. Sir John
Herschel rightfully maintains is compensated by the longer dm-ation
of the northern summer. Therefore, admitting the total quantity
of heat annually impressed 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 fi'eely — 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 fi'om growing cooler
than the southern :^ — 1. by the transfer of heat in the latent form
with the vapours fi'om the southern seas ; — 2. by the transfer of
heat in the sensible form, by ciu'rents such as the Gulf Stream, et
al., from one climate to another in our hemisphere. 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 fi'ee here by condensation.

21. Within the torrid zone the land is nearly equally divided
England about the north and south of the equator, the proportion be-
l,s°ith mJsUand.^'^^ iug as 5 to 4. In the temperate zones, however, the

THE SEA AXD THE ATMOSPHERE. 7

jiortii with its land is thirteen times in excess of the south. In-
deed, such is the inequahty in t\ie distribution of land over the
surface of the globe that the world may be divided into hemi-
spheres consisting, the one with almost all the land in it, except
Australia and a sKp 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 gTeat waters except the Atlantic Ocean ; New Zealand is the
nearest land to its centre.

22. This unequal distribution of land, light, air, and Avater is
Effects of inequaiitj' suggestive. To it we owc, in a measure, the differ-
land and water. cut climatcs of the earth. Were it different, they
would be different also ; were it not for the winds, the vapom^s
that rise from the sea would fi^om the clouds be retm-ned in showers
l)ack 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
cmTents in the sea, nor vertical moverjients m the air, the seasons
might change, but climates would be a simple affair, depending
solely on the dechnation of the sun in the sky.

23. About two-thirds of all the fresh water on the surface of the
Quantity of fresh earth is coutaiucd in the great American lakes ; and
iciiel ^" ^^^*^" ' though there be in the northern, as compared with the
southern hemisphere, so much less sea sui-face to yield vapour, so
much more land to swallow up rain, and so many more plants to
diink 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.

24. These facts have suggested the comparison in which the
Southern seas the southcm hemisphere has been likened to the boiler

boiler, and northern -i ,-, ,-i ^ , l^ i' on i

lauds the condenser, and the northcm to the condenser ot 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. The offices of the atmosphere are many, marvellous, and
Offices of the atmo- various. Thougli many of them are past finding
^i^'^^'^^- out, yet, beautiful to contemplate, they afford most
instructive and profitable themes for meditation.

26. When this system of research touching the physics of the
Dr. Buist. gea first began — when friends were timid and co-
labourers few, the excellent Dr. Buist stood up as its fiiend and

8 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

cliampion in India ; and by the services he thus rendered, entitled
himself to the gratitude of all, who with me, take delight in the
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
v/hich never fails to inspire zeal. They are apropos, and it is a
pleasure to repeat the substance of them.

27. " The weight of the atmosphere is equal to that of a solid
I'he sea and the at- oflobc 01 lead sixtv milcs in diameter. Its principal

inosphere contrast- ^-, . ^ t • , • , i i

ed. elements are oxygen and nitrogen gases, with a vast

quantity of waiter 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 substances, the ocean and
the air are increased in bulk, and, consequently, 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 mto ice, or vaporized into
steam ; the air is elastic ; it may be condensed to any extent by
pressure, or expanded to an indefinite degree of tenuity by pressure
being removed from it ; it is not liable to midergo any change in
its constitution beyond these, by any of the ordinary influences by
vviiich it is affected.

28. " These facts are few and simple enough ; let us see v;hat
Influence of the sun. results aiise from them : As the constant exposure
of the equatorial regions of the earth to the sun must necessarily
tliere engender a vast amount of heat, and as his absence from
the polar regions must in like manner promote an infinite accu-
mulation of cold, to fit the entire earth for a habitation 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 sm-pass all de-
scription. 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 cmTents from the poles toward
the equator are thus established at the smface, 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

THE SEA AND THE ATMOSPHERE . 9

thus established, constantly carrying away the heat from the tomcl
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. "Did the earth, as was long beheved, stand still while the
Of iiiiiraai rotation, gun circlcd aroimd it, we should have had directly
from north and south two sets of meridional currents blowing at
the sm-face 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 heating and cooling in-
fluences just referred to to cease, and the earth to fail in impressing
its own motion on the atmosphere, we should have a fmious hurri-
cano rushing round the globe at the rate of 1000 miles an hour —
tornadoes of ten times the speed of the most violent now knowTi to
us, sweeping everything before them. A combination of the two
iniluences, modified by the friction of the earth, which tends to draw
the au' after it, gives us the trade-winds, wdiich, at the speed of
from ten to twenty miles an hour, sw^ep round the equatorial region
of the globe unceasingly.

30. " Impressed v,'ith the motion of the air, constantly sweeping
Currents. its surfkce iu ouc dircctiou, and obeying the same

laws 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 cmTents
flowing fi'om the torrid toward the frigid zone to supply the vast
amount of vapour there drained ofi", v^'hile other w^hirlpools and
cmTents, such 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
vv'orld, is condemned to perpetual 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 w^here either
exists in excess.

31. " In obedience to these laws water warmer than ice attacks
Icebergs. the basis and saps the foundations of the icebergs —

themselves gigantic glaciers, which have faUen from the mountains
into the sea, or which have gro\ATi 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

10 PHYSICAL GEOGKAPHY OF THE SEA, AXD ITS METEOROLOGY.

tliem to sea, wliere the beautiful law wliicli 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 accu-
mulation 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 extending 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. " But these, though among the most regular and magnifi-
Mountain rarges. ccut, are but a Small number of the contrivances

by which the vast and beneficent ends of natm'e 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
torrid zone mountains reach the line of perpetual congelation at
nearly a third less altitude than the extreme elevation v/hich they
sometimes attain. At the poles snow is perpetual on the ground,
and at the different intervening latitudes reaches some intermediate
point of congelation betwixt one and 20,000 feet. In America,
from the line south to the tropics, as also, as there is now evers'
reason to believe, in Africa within similar latitudes, vast ridges of
mountains, covered with perpetual snow, run northward and south-
ward 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 Doda-
betta, and about 6000 in Ceylon. The Alps in Eiu'ope, and the
gigantic chain of the Himalayas in Asia, both far south m the
temperate zone, stretch fi'om 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 the same.

33. " Magnificent and stupendous as are the efi^ects and results
Water. qi the Water and of air acting independently on

each other, in equalizing the temperatm-e of the globe, they are
«till more so when combined. One cubic inch of water, when in-

THE SEA AND TPIE ATMOSPHERE. 11

vested with a sufficiency of heat, will form one cubic foot of steam
— the water before its evaporation, and the vapoui' which it forms,
being exactly of the same temperatm-e ; though in reality, in the
process of conversion, 1100 degrees of heat have been absorbed or
carried away fi'om the -vicinage, and rendered latent or imper-
ceptible ; this heat, is retiu^ned 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 vapom- carried off by dry air
at any temperature that may be imagined ; for, down far belovv' the
freezing-point, evaporation proceeds uninterruptedly.

34. " The ah', heated and dried as it sweeps over the aridsmface
Latent heat. of the soil, driuks up by day myriads of tons of

moistm'e fi-om the sea — as much, indeed, as w(Md, were no
moisture restored to it, depress its whole smface at the rate of eight
or ten feet annually. The quantity of heat thus converted from a
sensible or perceptible to an insensible or latent state is almost in-
credible. The action equally goes on, and with the like results,
over the surface of the earth, where there is moistm'e to be vdth-
di'awn. But night and the seasons of the year come round, and
the sm^plus temperatm'e, thus withdi-a^Mi and stored away at the
time it might have proved superfluous or inconvenient, is rendered
back so soon as it is requu'ed ; thus the cold of night and the rigour
of winter are modified by the heat given out at the point of con-
densation by dew, rain, hail, and snow.

35. '.' The earth is a bad conductor of heat ; the rays of the sun.
Effects upon the which enter its smface and raise the temperature
^^'^^- to 100^ or 150"", scarcely penetrate a fbot into the
groimd ; a few feet d.ovm, the warmth of the ground is nearly the
same night and day. The moistm-e which is there preserved free
from the influence of currents of air is never raised into vapom^ ;
so soon as the upper stratum of earth becomes thoroughb,^ dried,
capillary action, by means of which all excess of water was with-
dra^^Ti, ceases ; so that, even under the heats of the tropics, the
soil two feet doAvn wiU be found, on the approach of the rains,
sufficiently moist for the nomishment of plants. The splendid
flowers and vigorous foliage which bm'st forth in May, when the
parched soil would lead us to look for nothing but sterility, need in
no way sm-prise us ; fountains of water, bomidless in extent and
limited in depth only by the thiclmess of the soil which contains
them, have been set aside and sealed up for their use, beyond the
reach of those thirsty wmds or burning rays which are saflered to

12 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOLOGY.

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 material of clouds and dew, in
the crystal vault of the firmament, the soiu:ce, when the fitting sea-
son comes round again, of those deluges of rain which provide for
tiie wants of the year. Such are some of the examples which may
be supplied of general laws operating over nearly the whole siu'face
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. "We have not noticed the tides, which, obedient to the sun
Tiie tides. and moon, daily convey two vast masses of water

round the glebe, and which twice a month, rising to an miusual
height, visit elevations which otherwise are diy. Dming 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 tvro
differ by two or three feet irom each other. The tides simply
rise and fall, in the open ocean, to an elevation of two or three
leet 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 America, at Brest and
Mihord Haven, in Europe, to a height of from forty to sixty feet.
The tides sweep our shores from filth, and pm'ify our rivers and
inlets, affording to the residents of om- islands and continents the
benefits of a bi-dimiial ablution, and giving a health, and freshness,
and pmity Avherever they appear. Obedient to the influence of
bodies many miUions of miles removed 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 flov^^s back again to its place when the word goes forth,
' TIius far shalt thou go, and no farther ;' and that which no human
povrer or contrivance could have repelled, returns at its appointed
time so regularly and sm^ely that the hour of its approach, and
measure of its mass, may be j)redicted vfith unerring certainty cen-
tmies beforehand.

37. " The hurricanes which whirl vdth. such fearful violence
Hurricanes. ovor the surfaco, 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

THE SEA A^B THE AT:iIOSPHEEE. 13

rain, seem rec[iiisite to deflagrate the noxious gases wliicli have
accumulated, to commingle in one healthful mass the polluted ele-
ments of the air, and restore it fitted for the ends designed for it.
We have hitherto dealt vrith 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 vrorld — the means of secm'ing the interchange of these in-
estimable commodities, so that excess may be removed to where
deficiency exists, deficiency substituted for excess, to the un-
bomided advantage of all. This group of illustrations has been
selected because they are the most obvious, the most simple, and
the most intelligible and beautiful that could be chosen.

38. " We have already said that the atmosphere forms a spheri-
Towers of the air. cal shcll, smTouuding the earth to a depth which is
unknown to us, by reason of its growing tenuity, as it is released
from the pressure of its own sujjerincumbent 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 we 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 do^vn, more impalpable
than the finest gossamer, it leaves the cobweb undisturbed, and
scarcely stirs the lightest flower that feeds on the dew it supplies ;
yet it bears the fleets of nations on its wings around the v/orld,
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 tmiis the earth and the living
creatures that inhabit it. It draws up vapours from the sea and
land, retains them dissolved m itseK or suspended in cisterns of
clouds, and throws them do"wn 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 day. But for the atmosphere, sunshine would
burst on us in a moment and fail us in the t^mlding of aii eye,
removing us in an instant from midnight darkness to the blaze
of noon. We should have no tv^dlight to soften and beautify tLo

11

landscape, no clouds to sliade iis from tlie scorching heat ; but the
bald earth, as it revolyed on its axis, would tui'n its tanned and
weakened front to the full and unmitigated rays of the lord of day.

39. " The atmosphere affords the gas which vivifies and warms
Its functions, om' framcs ; 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 combustion is over.
It is the girdling encircling air that makes the whole world kin.
The carbonic acid viith which to-day om- breathing fills the au',
to-morrow seeks its way round the Avorld. The date-trees that
grow round the faUs of the Nile will drink it in by their leaves ;
the cedars of Lebanon ^oll take of it to add to their stature ; the
cocoa-nuts of Tahiti will grow rapidly upon it; and the palm-s
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 great trees that sknt the
Orinoco and the Amazon ; the giant rhododendrons of the Hima-
layas contributed to it, and the roses and myrtles of Cashmere,
the cinnamon-tree of Ceylon, and the forest, older than the flood,
that lies bmied deep in the heart of Ahica, far behind the Momi-
tains 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 tli(^
Nile, and exhaled as vapour again into the ever-present air."

40. There are processes no less interesting going on in other
The operations of parts of tliis magnificent field of research. Water
w*<^"- is natm^e's carrier. With its currents it conveys
heat away from the torrid zone and ice from the frigid ; or, bot-
tling the cfaloric avv^ay 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 rest-
less leveller from mountains, rocks, and valleys in all latitudes.
Some it washes down fi'om 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 Em-ope, or from the marble quarries of
ancient Greece and Eome. These materials, thus collected and

THE SEA AND THE ATMOSPHEEE. 15

carried over falls or down rapids, are transported 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 temperatm-e, in proper form,
and in due quantity.

41. Tjreating the rocks less gently, it grinds them into dust, or
Its marvellous pouuds tlicm into sand, or rolls and rubs them until
powers. ii^Qj ^YQ fashioucd into pebbles, rubble, or boulders :
the sand and shingle on the sea-shore are monuments of the
abrading, tritm'ating 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 wliich the everlasting hills
are established, everything on the smface of om^ planet seems to have
been removed from its original foimdation and lodged in its present
j)lace by water. Protean in shape, benignant in office, water, whether
fi^esh or salt, solid, fluid, or gaseous, is marvellous in its powers.

42. It is one of the chief agents in the manifold workshops in
It caters on land for wliicli aiid by vfhich the earth has been made a
insects of the sea. habitation fit for man. Circulating in veins below
the surface, it ]:)ervades the solid crust of the earth in the fulfil-
ment 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 sohd
matter the sea in its economy requires.

43. The waters which dash against the shore, which the run-
Leaching, ning streams pom* into the flood, or mth v/hich the

tides and cui'rents scour the bottom of their chamiel ways, have
soaked from the soil, or leached out of the disintegrated materials
which strew the beach or line the shores, portions of every sol-
uble ingi'edient knov^m in nature. Thus impregTiated, the laugh-
ing, dancing waters come dovv^i fi'om the mountams, tm-ning
wheels, dri\ang machineiy, 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. Iron, hme, silver, sulphur, and copper, silex, soda, magnesia.
Solid ingredients, potash, chloriiie, iodiuo, 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, never-
theless, are elaborated therefrom ])y physical processes the most
exquisite.

16 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

45. By examining in Yalparaiso the copper that had been a great
Quantity of silver in while on the bottom of a ship, the presence of silver,
the sea. 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 precij^itated and col-
lected into a separate mass.

46. The salts of the sea, as its solid ingredients may be called.
Its inhabitants- caii neither be precipitated on the bottom, nor taken
their offices. -^p ]jj i\^q yapours, noT returned again by the rains
to the land ; and, but for the presence in the sea of certain agents
to which has been assigned the task of collecting these ingredients
again, in the sea they would have to remain. There, accumu-
lating in its waters, they would alter the quality of the brine, in-
jure 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 machinery 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 elaborating into vegetable
tissue and fibre the impmities 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 lixi-vdated matter as fast as
the dripping streams and searching rains discharge it into the ocean.

47. As to the extent and magnitude of this endless task some
Monnmcnts of their idca may bc fomicd from the coral islands, the marl
industry. |^g(jg^ j-i^Q ^IjqH banks, the chalk cliffs, and other
marine deposits which deck the sea-shore or strew the land.

48. Fresh water is composed of oxygen and hydrogen gas in the
Analysis of sea- j^roportiou by wciglit of 1 to 8 ; and the principal
^^■'^^^i- ingredients which chemists, by treating small samples
of sea-water in the laboratory, have found in a thousand grains are.

Water 962.0 grains

Cliloride of Sodium ^I*-'- "

Chloride of Mairncsium 5.4 „

Chloride of Potassium 0.4 „

Bromide of Magnesia • . . . . 0.1 „

Sulphate of Magnesia 1-2 „

Sulphate of Lime 0.8 „

Carbonate of Lime 0.1 „

Leaving a residuum of 2.9 „ = 1000,

THE SEA AND THE AT:5I0SPIIERE. 17

consisting o± sulphuretted hydrogen gas, hydrochlorate of ammonia,
etc., etc., in various quantities and proportions, according to the
locality of the specimen.

49. If we imagine the whole mass of the earth to be divided into
Proportion of water 1786 CQual parts bv wcififht, then the weiejht of all

to the niass of the ., / • n i i t j >■ >

earth. the watcr m the sea would, according to an estimate

by Su' John Herschel, be equivalent to one of such parts. Such is
the quantity, and such some of the quahties of that dehghtful fluid
to which, in the laboratories and workshops of natm^e, such mighty
tasks, such important offices, such manifold and multitudinous
powers have been assigned.

50. This volume of w^ater, that outweighs the atmosphere (§1)
The three great about 400 timcs, is divided into thi'ee gi'eat oceans,
,.ceans. '" ^}^g Atlaiitic, the Pacific, and the Ai'ctic ; for in the
rapid siuTey 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 Ocean, with its arms, is supposed to extend
'ihe Atlantic, 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 hes between the Old World and the Nev\^ : passing
beyond the "stormy capes," there is no longer any barrier, but
only an imaginary line to separate its waters from that great southern
waste in which the tides are cradled.

52. The young tidal wave, rising in the circumpolar seas of the
Its tides. south, rolls thence into the Atlantic, and in 12 hours

after passing the parallel of Cape Horn, it is foimd pouring its flood
into the Bay of Fmidy.

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

54. The Atlantic Ocean contrasts very strikingly with the
Contrasted with the Pacific. The grcatcst length of one hes east and
i'^^'^c- west ; of the other, north and south. The currents
of the Pacific are broad and sluggish, those of the Atlantic SAvift
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 rim between

c

18 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

tlie equator and the soutliern seas. In the Atlantic the tides are
high, in the Pacific they are low. The Pacific feeds the clouds
mth vapours, and the clouds feed the Atlantic Avith rain for its
rivers. If the volume of rain which is discharged into the Pacific
and on its slopes be represented by 1, that discharged 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 shores of the most power-
ful, intelKgent, and Christian nations ; 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. Among the many valuable discoveries to which these re-
The Telegraphic searchcs touchiug the physics of the sea have led.
Plateau. ^^^^^ perhaps is more interesting than the Telegraphic
Plateau of the Atlantic, and the fact that the bottom of the deep
sea is lined wdth its own dead, whose microscopic remains are pro-
tected fi'om the abrading action of its currents and the violence of
its waves by cushions of still water.

56. The idea of a telegraph from England or Ireland along this
New routes for an platcau to America, seems after the splendid failure
Atlantic Telegraph, ^f iQ^Q ^^ ^^^^ ^^^^ abandoned, cliiefly however on

account of the electrical difficulties which stand in the way of so
long a circuit. Other routes with shorter circuits are now pro-
posed : these are engaging the attention of enlightened govern-
ments in Em'ope, and of enterprising men on both sides of the
Atlantic.

57. A line met Iceland and Greenland to Labrador, and thence
The Greenland route, ovcrland to Canada and the United States, is attract-
ing attention in England. The Admiralty have despatched Captam
McClintock in the "Fox," of Arctic renown, to run a line of deep-
sea soundings along this route.

58. Another Ime from France, via the Western Islands to St.
The French route. Pierre Miquelou, a French fishing-station ofi" New-

fomidland, and thence to the United States, is attracting the
attention of the French people. Their emperor has given his
sanction with the most liberal encom-agement.

59. The longest reach by the Greenland route may require a cir-
Their length of cir- cuit not oxcecding 400 or 500 miles in length. The
^^"'- greatest distance between the relay batteries of the
French line w^ill be a little over a thousand. These distances,

THE SEA AXD THE ATMOSPHERE. 19

witli ^vires 'properly insulated, are held to be within effectiYe
telegraphic reach.

60. One of the chief physical difficulties Yvhich seem now to
Faulty cables. stand in the way of these Imes lies with the " cables."

It so happens that all deep-sea lines have at the present Y/riting
ceased to work. The two Malta lines in the Mediterranean are out
of order ; so also are the Red Sea lines : no messages have passed
])etween Kurrachee and Aden for some time, and the line to Algiers
has been suspended, if not abandoned, for the present.

61 . All these lines had cables incased in a wrapping of iron wire ; —
Their iron wrappings, and it is a qucstioH 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 dis-
integration, like the iron fastenings of coppered ships. This
evidence of galvanic action excites suspicions 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 Ydre in this instance encom^ages the belief as to defective
insulation.

62. Such are the facts. But the facts do not prove that gutta
imperfect insula- pcTcha is au imperfcct 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
handlmgs to which the cable was afterwards subjected, and above
all by the heavy strains which v^ere brought upon it by the " brakes "
during the operation of laymg it along the plateau.

63. These facts, however, do not suggest the same for the Bed
riie Red Sea and ^^^ ^^^ ' Mediterranean cables, for these cables had
iMediterraaeanca- all been dowu for somo time, and had been working
' ''■ more or less satisfactorily ; nevertheless, we are re-

mmded by these failures now, and that too from a fresh quarter,
that iron wrappmgs about a telegraphic wire are of no use in the
deep sea.*

64. Two metals, as a copper conductor and an iron wrapper,
A galvanic battery Y' ould secm uot to be dcsirable for the same cord, for
m the sea. ^^ ^^^^ q£ jg^kage a galvanic batter}^ is at once formed
m ihe sea, and brought hito play upon the cable. Not only so, the

"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
finger.' —Letter to Secretary of the Navy, November 8, 1850.

c2

20 PHYSICAL GEOGEAPKY OF THE SEA, AKD ITS METEOROLOGY.

cable itself is a long and powerful Leyden jar, the iron ^Tapping
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. But independent of these facts and views, there is another
Two metals should I'^ason why iron wrappings and two metals should
not be used about not be usod, at Icast foT doep-sca cables. Our

a submarine cable. , , ■, ■, , i . n

researches at sea have sho^n that there is no run-
ning 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 distm'b it more. Wherefore it has been held,* that the iron
^vrapping for deep-sea lines of telegraph, instead of being advan-
tageous in any aspect, are not only a hindrance, but an incum-
brance also and a waste : the weight of the cord may be adjusted to
sinking by the size of the conducting wire WTthin as well as by the
character of the non-metallic -swapprng without.

6Q. Whether the insulating material be gutta percha, india-
Rogers's cable Tubber, OT othoT matter, it requires to be protected
"jacket." fj,Qj^ 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 American!
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 rmming water. Thus one of the obstacles
vdiich have been interfering mth the progress of submarine tele-
graphy is removed out of the wa^^

67. But notwithstanding all that has been done with the sea
j).v.p.sea tempera- a^d iu the sca foT the elcctro-magnetic telegraph,
tur.^s a desideratum. ^^-^^_ f^^, human progrcss, there still remains many
agenda. There is both room and need for further research, more
exploration, and many experiments. As bearing upon the best in-
sulating 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 pheno-

* Vide Letter to Secretary of the Navy, November 8, 1856. Maurys'
Sailing Directions, chapter Submarine Telegraphy ; ditto, Physical Geo-
graphy of the Sea, chapters XIII. and XXI., Harper Brothers, New York, 1859 ;
also Journal Royal Dublin Society, numbers XII. and XIII. Letter to
John Locke, on tlie Atlantic Telegraph causes of failure and probabilities of
ultimate success. Read January, 1859.

t Henry J. Rogers of Baltimore,

THE GULF STREAM. 21

mena of tlie sea, are there none wlio will make deep-sea tempera-
tures a speciality? They would no doubt prove as instructive
and as useful too as deep-sea soundings have been and are.

68. Lieutenant Brooker, in the " Hancock," has obtained sound-
-specimeus from the I'^gs iu the North Pacific from the depth of 3300
depth of 19,800 feet, fathoms, with specimens both of the ooze and the
water at the bottom. These have been sent to Professor Ehrenberg
of Berlin, for microscopic exammation. He has not completed his
study of these treasm-es, but he already reports the discovery in
tJiem of more than one hundred new species of animalculse.

CHAPTEE II.

§ 70-147. THE GULF STREAM.

70. There is a river in the ocean: in the severest droughts
Its colour. it never fails, and in the mightiest floods it never
overflows ; its banks and its bottom are of cold water, while its
current is of warm ; it takes its rise in the G-ulf 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 CaroHna coasts, are of indigo blue. They are
so distinctly marked that their line of junction v>'ith 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 reluc-
tance, so to speak, on the part of those of the Gulf Stream to mingle
with the littoral waters of the sea.

71. At the salt-Avorks of France, and along the shores of the
now caused. Adriatic, where the "salines'' 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 crystalhzation is about to commence, when the nov/ deep-
blue Avater puts on a reddish tint. Now the water of the Gulf
Stream is Salter (§ 102) than the littoral water of the sea through

22 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOBOLOGY.

-vyIiicIi it flows, and hence we can account for tlie deep indigo
blue which all navigators observe in Gulf Stream water off the
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. What is the cause of the Gulf Stream has always puzzled
Speculations con- philoso j)hers . Many are the theories and nume-
s'iream. rous the speculatious that have been advanced with
regard to it. Modern investigations and examinations are begin-
ning to throw some light upon the subject, though all is not yet
entkely clear. But they seem to encom^age the opinion that this
stream, as well as all the constant cm^rents of the sea, is due mainly
to the constant difference produced by temperature and saltness
in the specific gravity of water in certain parts of the ocean. Such
difference of specific gravity is inconsistent with aqueous equili-
brium, and to maintain this equilibrium 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 perpetual work.

73. These agents, however, are not the sole cause of cmTents.
Agencies concerned. The wiuds liclp to make currouts by pressing 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 at-
mosphere, by pressing with more or less superincumbent force
upon different parts of the ocean at the same moment, and as in-
dicated by the changes of the barometric column. But when the
winds and the rains cease, and the barometer is stationary, the
cmTents that were the consequence cease. The currents thus
created are therefore ephemeral. But the changes of temperatm-e
and of saltness, and the work of other agents Avhich affect the
specific gravity of sea-water and derange its equilibrium, are as

THE GULF STREAM. 23

ceaseless in their operations as the siin in his course, and in their
effects they are as endless. Philosophy points to them as the chief
cause of the Griilf Stream and of all the constant currents of the sea.

74. Early writers, however, maintained that the Mississippi
Early writers. Eivcr was the father of the Grulf 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 cmxent of the
river on the land.

75. Captain Livingston overturned this h3-pothesis by showing
Objection to the that tho volume of water vrhich the Mississippi
fresh-water theory, j^^^.g^, empties iuto the Gulf of Mcxico is not equal
to the three thousandth part of that which escapes from it through
the Grulf Stream. Moreover, ih.Q 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. The above-quoted argument of Captam Livingston, however,
Livingstons hypo- was held to be conclusive; and upon the remains
*^^^^^- of the hypothesis which he had so completely over-
turned, he set up another, Avhich, 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. But the opinion that came to be most generally received and
Franklin's theory, dcep-rooted in the miud of seafaring people w^as the

one repeated by Dr. Franldin, and which held that the Gulf Stream
is the escaping of the waters that have been /orcefZ into the Carib-
bean 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. We know of instances in which the waters have been accu-
objections to it. mulatcd on one side of a lake, or in one end of a

canal, at the expense of the other. The pressm-e 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 of
water from the phores of America to the shores of Europe, that

24 PHYSICAL GEOaiiAPHY OF THE SEA, AXD ITS METEOROLOGY.

cexeeds in discliarge tlie miglity Mississippi a thousand times ?
Keason teaches and examination shoYvs that they are not. With the
"sdew 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-boolis 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 shovv- that within those lati-
tudes, 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, byblov^--
ing for less than one third of the time, cause the Gulf Stream to iim
all the time, and without varying its velocity either to their force or
their prevalence ?

79. Sii* John Herschel mamtainst that they can ; that the trade-
Hersciiei's expiana- wiuds are the sole causeX of the Gulf Stream ; not,
^^"^^^ indeed, by causing "a head of water" in the Y/est
Indian seas, but by roUmg particles of water before them somewhat
as billiard balls are rolled over the table. He denies to evaporation,
temperatm^e, salts, and sea-shells, any efiective influence vrhatever
upon the cu^culation of the waters in the ocean. According to him
the winds are the supreme current-producing power in the sea,§

80. This theory would require all the cm-rents of the sea to set
Objections to it. Yni]i the wiuds, or when deflected, to be deflected

from the shore, as billiard balls are from the cushions of the table,
making tlie littoral angles of incidence and reflection equal. Now,
so far from this being the case, not one of the constant cmTents 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
liundi^eds of miles after it enters the Atlantic, against the trade-
winds ; for a part of the way it runs right in the " v/ind's eye."
The Japan current, '' the Gulf Stream of the Pacific," does the
same. The Mozambique cmTent runs to the south, against the

* Nautical Monographs, Washington Observatory, No. 1.

t Article " Physical Geography," 8th edition Encyelopeedia Britannica.

X " The dynamics of the Gulf Stream have of late, in the work of Lieutenant
Maury, already mentioned, been made the subject of much (we cannot but think
misplaced) wonder, as if there could be any possible ground for doubting that it
owes its origin entirely to tlie trade-winds.'' — Art. 57, Phys, Geography, Stli
edition Encyc, Brit.

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

THE GULF STREAM. 25

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, flow.:;
north in spite of them. These are the main and constant currents of
the sea — the great arteries and jugulars through which its circulation
is conducted. In every instance, and regardless of winds, those cur-
rents 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
wuids, but in spite of them, and by the force of those very agencic:;
that make the Avinds to blow. They flow thus by virtue of those
efforts which the sea is continually making to restore that equili-
brium to its waters which heat and cold, the forces of evaporation,
find the secretion of its inhabitants are everlastingly destroying.

81. If the winds make the uj^joer, what makes the tmder and
The supren-:acy of couuter cmTcuts ? This qucstiou is of itseK enough
the ^iuds disputed. ^Q impeach that supremacy of the winds upon thi'
cuiTents, which tlie' renovrned philosopher, wdth whom I am so
unfortunate as to differ, travelled so far out of his way to vindicate.''
The " bottles " also dispute, in their silent way, the " supremacy oi'
the VN^inds " over the currents of the sea. The bottles that arc
throvm 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 Caril^bean Sea, where ihe trade-
winds blow, none have been fomid to drift 'with the wind : they all
drift Yvith the cmTont, and nearly at right angles to the wind.

82. That the vands do make currents in the sea no one will
The Bonifaccio cur- havo the hardihood to deny ; but cm^rents^ that are
'"^"" born of the w^inds are as unstable as the winds ; mi-
certain as to time, place, and direction, they are sporadic and ephe-
meral ; they are not the constant currents such as have been already
enumerated. Admiral Smyth, in his valuable memoir on the

* " We have, perhaps, been more diifase on the subject of oceanic cnrronts than
the nature of tiiis article may seem to justify ; but some such_ detail seemed
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 servicv
as a cause of buoyancy in the regions occupied by coral formations." — Art, G,>,
Phys. Geography, Encyc. Brit.

26 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY,

Mediterranean (p. 162), mentions that a continuance in tlie Sea
of Tuscany of ''gusty gales " from tlie south-west has been known
to raise its sm^face 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
miniatm^e 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 Bonifaccio 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 v/ater, loses
itself by broad spreading as soon as it finds sea room. As soon as
the force that begets it expends itself, the ciuTent is done.

83. Supposing with Franldin, and. those of his school, that the
ThebedoftheGuif prossuro of the v;aters that ^yq forced into the Carib-
ing plane. boau Sca by the trade-winds is the sole cause of the

GuK 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
Eemiell 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 ofl" Cape Hatteras. Their breadth
here is about seventy-five miles against thirty-two in the "Nar-
rows " of the Straits, and their mean velocity, is three knots ofl'
Hatteras against four in the "Narrows." This being the case, it
is easy to shov/ 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 smface of an inclined plane — inclined dowmvards from the north
towards the south — uj:) which plane the lower depths of the stream
onust ascend. If we assume its depth off Bemini* to be two hundred
fathoms, 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 de-
scending, are actually forced up an inclined plane, whose submarine
ascent is not less than ten inches to the mile.

* Navy officers of the United States Coast Survey liave sounded with the
deep-sea lead, and ascertained its depth here to be 370 fathoms (January, 185G).

THE GULF SlTvEAM. 27

84. The Niagara is an " immense river descending into a plain."
The Niagara. Biit instead of preserving its character in Lake On-
tario as a distinct and well-defined stream for several hundi'ed miles,
it spreads itself out, and its waters are immediately lost in those of
the lake. Why should not the Gulf Stream do the same ? It
gradually enlarges itself, it is true ; but, instead of minghng with
the ocean by broad spreading, as the " immense rivers " descending
into the northern lakes do, its v/aters, like a stream of oil in the
ocean, preserve a distinctive character for more than three thousand
miles.

85. Moreover, vv'hile the Gulf Stream is rmming to the north
A current counter to h-'om its supposod elcvatcd Icvcl at the south, there
the Gulf Stream. jg ^ qqI^ cmTcnt comiug dowu firom the north ;
meeting the vrarm waters of the Gulf midway the ocean, it divides
itself, and runs by the side of them right back into those very re-
servoirs at the south, to which theory gives an elevation siifticient
to send out entirely across the Atlantic a jet of warm water said
(§ 75) to be more than three thousand times greater in volume than
the Mississippi Eiver. This cmTent from Baffin's Bay has not only
no trade-winds to give it a head, but the prevailing Avinds are un-
favourable to it, and for a great part of the way it is below the sur-
face, and far beyond the propelling reach of any wind. And
there is every reason to believe that this, with other polar cur-
rents, is quite equal in volume to the Gulf Stream. Are they not
the efiects of like causes ? If so, what have the trade-winds to do
with the one more than the other ?

86. It is a custom often practised by seafaring people to throw
Bottle chart. a bottlc ovcrboard, with a paper, stating the time

and place at which it is done. In the absence of other informa-
tion as to currents, that afforded by these mute little navigators is
of great value. They leave no tracks behind them, it is true, and
their routes camiot 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 voj^age, 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 appears that the waters from
every quarter of the Atlantic tend toward the Gulf of Mexico and
its stream. Bottles cast into the sea midway between the Old
and the New Worlds, near the coasts of Europe, Afi^ica, and America,

28 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

at the extreme nortli or farthest south, have been found either in
the West Indies, on the British Isles, or within the well-known
range of Gruli Stream waters.

87. Of two cast out together in south latitude on the coast of
Their drift. .\frica, ouc was fouud ou 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 conclusive.
And there is reason to suppose that some of the bottles of the gal-
lant captain's chart have also performed the tour of the Gulf
Stream ; then, without being cast ashore, have retm^ned 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 YI.) Another bottle, said to be thrown over off
Cape Horn by an American ship-master in 1837, was afterwards
picked up on the coast of Ireland. An inspection of the chart,
and of the drift of the other bottles, seems to force the conclusion
that this bottle too went even from that remote region to the so-
called higlier level of the Gulf Stream reservoir.

88. Midway the Atlantic, in the triangular space between the
;rhe Sargasso Sea. AzoTos, Caiiarics, and the Cape de Verd Islands, is the
great Sargasso Sea. (Plate YI.) Covering an area equal in extent
to the Mississippi Yalley, 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 navigation, and became
alarmed. To the eye, at a little distance, it seems substantial
enough to walk upon. Patches of the vreed 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 of marine anemometer, 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 flows in a circle, going to the north on
the western side, and returniDg to the south on the east side of the

THE GULF STREAM. 29

x\tlantic — 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 YI.,
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. Nay, more; at the very season of the year when the Gulf
A bifurcation. Stream is rushing in greatest volume through the

Straits of Florida, and hastening to the north with the greatest ra-
pidity, 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 underrmis the
Gulf Stream, as is shovm by the icebergs which are carried in a
direction tending across its course. The probability is, that this
"fork" flows on tovfard the south, and runs into the Caribbean
Sea, for the temperatiu'e of the water at a little depth there has
been found far belov/ the mean temperature of the earth's crust,
and quite as cold as at a corresponding depth off" the Arctic shores
of Spitzbergen.

90. More water cannot run from the equator or the pole than
Winds exercise but to it. If Avo make the trade-winds to cause the

little influence upon r\ ir. ai. i j_ j_ i n • i ,

constant currents, (juli btrcam, we ougiit to have some other wmd 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 appear that winds have little
to do mth the general system of aqueous cuTulation in the ocean.
The other " fork " runs between our shores and the Gnilf Stream
to the south, as already described. As far as it has been traced,
it v>"arrants the belief that it, too, runs uv to seek the so-called
higher level of the Mexican Gulf.

91. The power necessary to overcome the resistance opposed
Effects of diurnal to such a bodv of Water as that of the Gulf Stream,

rotation upon the . i ji t -i • ,^ , i

Gulf siream. rmmmg 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 accuracy, the resistance which the
w^aters of this stream meet with hi their motion towards the east.

30 PHYSICAL G-EOGRAPHY OF THE SEA, AXD ITS METEOHOLOGY.

Owing to the diumal rotation, tliey are carried around with the
earth on its axis toivards the east mth an hourly velocity of one
hundred and fifty-seven* miles greater when they enter the Atlan-
tic than v;hen they arrive off the Banks of Newfoundland ; for in
consequence of the difference of latitude between the parallels of
these two places, then' rate of motion around the axis of the earth
is reduced fi^om nine hundred and fifteen! 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 ifi an horn', 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 eastwardiy 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. If therefore, in the proposed inquiry, we search for a pro-
Thc G uif stream can- pelling powcr nowlicre but in the higher level of the
byabigheTievei.*^^ Grulf, or in the "billiard-ball" rebound from its
shores, we must ad.mit, in the head of water there, the existence
of a force capable of putting in motion, and of driving over a
l^lain at the rate of four miles the hour, aU the waters, as fast as
they can be brought down by three thousand (§ 75) such streams
as the Mississippi Eiver — a power, at least sufficient to overcome
the resistance requu"ed to reduce from two miles and a haK to a
few feet per minute the velocity of a stream that keeps in perpe-
tual motion one fourth of all the waters in the Atlantic Ocean. Not
only so, we must admit the existence of an engine in the Gulf of
Mexico, which, being played upon by the gentle forces of the trade-
v\'inds, is capable of sending a stream of water from the shores o
the New World to the shores of the Old.

93. The advocates of the trade-wind theory, whether, with
Nor by the trada- Franklin (§ 77), they make the propelling power to
wii.d {heory. j^g dcrlvcd from a '' head of ivater " in the Gulf, or,
with Herschel (§ 79), from the rebound, a la billiard-balls, against

* In this calculation tlic 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 of
about one and a half mile the hour, making the true velocity to the east, and on
the axis of the eartli, about seven hundred and sixty miles an hour at the Grand
Banks.

THE GULF STREAM. 31

its shores, require that the impulse then and there comnmnicatecl
to the ^Yaters of the Grulf' 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 ex-
pended ?

94. When we inject water mto a pool, be the force never so
Illustration. 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 remem-
ber to have observed as children how soon the mill-tail loses its
current in the pool below ; or ^Ye may now see at any time, and
on a larger scale, how soon the Niagara, current and all, is swal-
lowed up in the lake below.

95. Xothing but a continually-acting power can keep currents
Gulf stream the iH the sea, any more than cannon-balls in the air or
Sn'th^lpm^^^ rivers on the land, in motion. But for the forces
power. 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. For the sake of fm^ther illustration, let us suppose a globe
The production of of the carth's size, and with a solid nucleus, to be

currents without t n -n i j i n t n n

wind. covered ail over with water two hundred lathome

deep, and that every source of heat and cause of radiation be re-
moved, so that its fluid temperature becomes constant and uni-
form throughout. On such a globe, the equilibrium remaming
undistm-bed, 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 woidd thereby be disturbed, and a gene-
ral system of ciuTents and counter currents would be immediately
commenced — the oil, in an unbroken sheet on the surface, run-
ning towards the poles, and the water, in an under ciuTent, to-
wards 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 in-
tertropical regions, and retmiiing as before. Thus, ivithout wind,
we should have a perpetual and uniform system of tropical and
polar currents, though ivitJioiit wind, Sir John Herschel main-

32 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS UIETEOEOLOGY.

tains,* we should liave no '' considerable ciiiTents " 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, imtil, 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 the 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 poles
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 miiform
system of currents just described would now be interrupted by
obstructions and local causes of various kinds, such as unequal dej)th
of water, contour of shore lines, &c. ; and we should have at cer-
tain places cm-rents greater in volume and velocity than at others.
But still there would be a system of currents and counter cmTents
to and from either pole and the equator. Now, do not the cold
waters of the north, and the v;arm waters of the gulf, made specifi-
cally lighter by tropical heat, and which we see actually preser^dng
such a system of counter currents, hold, at least in some degree,
the relation of the supposed water and oil ?

97. In obedience to the laws here hinted at, there is a constant
Warm currents flow tendencv (Plate IX.) of polar waters towards the

towards tbe pole, cold • \ n , • i j -> xi i

tovv-ards the equator, tropics and 01 tropical wators towards the poles.
Captain Wilkes, of the United States Exploring Expedition,
crossed one of these hj^perborean mider cm-rents two hundred
miles in breadth at the equator.

98. No feature of the Gulf Stream excites remark among
Edges of the Gulf seamen more frequently than the sharpness of its
feature. '"° cdgcs, 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

* '^ If there were no atmospliere, there would be no Gulf Stream or any other
considerable oceanic current (as distinguished from a mere surf;ice drift) what-
ever/'— Art. 37, Phyeical Geography, 8tli ed. Encyclop. Brit.

THE GULF STRK^M. 33

the warm ^\'aters of the stream to mix vdth 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 circumstances less calculated to attract
attention or excite remark ?

99. The water, hot and cold, as it is let into the tub for a warm
Illustrations bath, generally arranges itself in layers or sections,

according to temperatm'e ; it requu'es violent stirring to break them
up, mix, and bring the whole to an even temperature. The jet of
air from the blow-pipe, or of gas from the bm-ner, presents the
phenomenon still more familiarly ; here we have, as with the Gulf
Stream, the dividing hne between fluids in motion and 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 Missomi 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 then" statu quo fluids that have abeady arranged
themselves in layers, streaks, or aggregations.

100. In the ocean we have the continual heaving of the sea and
How the water of agitatiou of the waves to overcome this vis
fel-s fr^ilStto'lai inertia, and the marvel is, that they in their violence
waters. (Jo not, by mingling the Gulf and httoral waters
together (§ 70), sooner break up and obliterate aU marks of
a division between them. But the waters of the Gulf Stream
difier from the inshore waters not only in coloin-, transparency, and
temperature, but in specific gravity, in saltness (§ 102), and in other
properties, I conjectm-e, also. Therefore they may have a peculiar
viscosity, or molecular arrangement of then- g\mi, w^hich fiurther tends
to prevent mixtm-e, and so preserve their line of demarkation.

101. Observations made for the pm-pose in the navy show that
Action on copper, sliips cruisiug in the West Indies sufier in their cop-
per sheathing more than they do in any other seas. This would
indicate that the waters of the Caribbean Sea and Gulf of Mexico,
fi'om which the Gulf Stream is fed, have some peculiar property or
other which makes them so destructive upon the copper of cruisers.

102. The story told by the copper and the blue colour (§71) in-
siitness of tbeGuif dicatcs a higher point of saturation ^dth salts than sea
Stream. watcr generally has ; and the salometer confirms it.

D

34 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IVIETEOROLOGY.

Dr. Thomassy, a Frencli savant, who lias been extensiyely engaged
in the manufacture of salt by solar evaporation, infonns 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 J- per cent, of salt ; in the trade-wind region 4^ per
cent. ; and in the Gulf Stream, off Charleston, 4 per cent,, not-
withstanding the Amazon and the Mississippi, vnih. all the inter-
mediate rivers, and the clouds of the West Indies, had lent their
fresh water to dilute the saltness of this basin.

103. Now the question may be asked, What should make the
Asents concerned, wators of the Mcxican 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 knov\-ii to
be at work in different parts of the ocean, the 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 by sea-shells in secreting soHd
matter for their structures ; they are also heat* and radiation, eva-
poration and precipitation. In the trade-vviad regions at sea (Plate
VIII.), evaporation is generally in excess of precipitation, while in
the extra-tropical regions the reverse is the case ; that is, the clouds
let dovm more water there than the winds take up again; and
these are the regions in which the GuK 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 evapora-
tion of fifteen feet. In the process of evaporation fi'om 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 ciuTont (Plate
VI,) which often sweeps from the shores of Africa across the Atlan-
tic 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 vapom' ? If so — and it probably
does — have we not detected here the footprints of an aQ:ent that does
tend to make the waters of the Caribbean Sea Salter, and there-
fore heavier, than the average of sea-water at a given temperatm-e ?

* According to Dr. Marcet, sea'-water contracts down to 28'^ ; my own to about
25.6.

THE GULF STREAM. 35

104. It is immaterial, so far as the correctness of tlie principle
Evaporation and pre- i^pon which tliis rcasomng depcncls is concerned,
cipitation. wlietlier the annual evaporation from the trade-mnd
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 pom^ed back by the clouds upon the
same spot whence it came. But they take and poui* 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 do^n tln^ough
the soil to feed the springs, and retmTis tlirough 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 tvro inches, as the case may be, of fresli water
added to the sea in those parts, and which therefore tends to lessen
the specific gravity of sea-water there to that extent, and to produce
a double dynamical effect, for the simple reason that what is taken
fi'om one scale, by being put into the other, doubles the difference.

105. Now that we may form some idea as to the influence which
cun-ent into the ca- the salts left by the vapour that the trade-winds,
ribbean Sea. north-cast and south-east, take up from sea-water, is
calculated to exert in creating currents, let us make a partial cal-
culation to show how much salt this vapour held in solution before
it was taken up, and, of course, wdiile 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 eva-
poration 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 sufficient to cover the British islands to the depth of four-
teen feet. As this water supplies the trade-winds with vapom', it
therefore becomes salter, and as it becomes Salter, it becomes
heavier ; and therefore we may infer that the forces of aggi^egation
among its particles are increased.

106. Whatever be the cause that enables these trade-wind waters
Amount of salt left to remain on the surface, whether it be from the
by evaporation. £^^j. j^^^^ stated, and in consequence of which the
waters of the Gulf Stream are held together in their chamiel ; or
whether it be from the fact that the expansion from the heat of the
torrid zone is sufficient to compensate for this increased saltnes3 ; or
whether it be from the low temperature and high satm-ation of the

36 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

submarine waters of the intertropical ocean ; or ^Ylletller 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 fi^om the Amazon, the Orinoco, and the Mis-
sissippi, and from the clouds, and the rivers of the coasts round
about. An immense volume of fresh v\^ater is supplied from these
sources. It tends to make the sea- water, that the trade-winds have
been playing upon and dri\dng 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 Grulf 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. The dynamics of the sea confess the power of the winds in
Currents created by thoso tromendous cmTeuts which storms are some-
^*''™'- times kno^^ai to create; and that even the gentle
trade-mnds may have influence and effect upon the cm-rents 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 cmTent. Drift is confined to surface waters, and
the trade- winds of the Atlantic may assist in creatmg the Grulf
Stream by driftmg the waters which have supplied them ytiHi 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 Carib-
bean Sea, what should make it flow thence with the Gulf Stream to
the shores of Em'ope ? It is because there is room for it there ; and
there is room for it because of the difference in the specific gra^dty of
sea-water in an intertropical sea on one side, as compared v*ith the spe-
cific gravity of water in northern seas and frozen oceans on the other.

108. The dynamical forces which are expressed by the Gulf
?h^atS'^foni/°the ^^^6^^ i^ay "^th as much propriety be said to reside
Gulf Stream to be in tlioso northom waters as in the West India seas ;

found in the differ- p -t -i l^ r^ •^ ^ o T

ence as to specific lor ou ouc Side WO liavc the Caribbean bea, and
piS'and'po^'r' wa-' ^^"^ 0^ Mcxico, mth their waters of brine ; on the
^ers. other, the Great Polar basin, the Baltic, and the

North 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 Polar basin has a known water area of 3,000,000 square miles, and an
unexplored area, including land and water, of 1,500,000 square miles. Whether

THE GULF STREAM. 37

the other it is light. Between them the ocean intervenes ; but water
is bound to seek its equihbrimn as its level ; and here, therefore,
we unmask one of the agents concerned in causing the GuK Stream.
What is the power of this agent — is it greater than that of other
agents, and how much ? We camiot say how much ; we only
know it is one of the chief agents concerned. Moreover, speculate
as we may as to all the agencies concerned in collecting these waters,
that have supplied the trade-winds with vapom-, into the Caribbean
Sea, and then in driving them across the Atlantic — we are forced
to conclude that the salt which the trade-wind vapom- leaves be-
hind 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
through 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
GuK Stream in motion, theorists may place them exclusively on one
side of the ocean with as much philosophical propriety as on the
other. Its waters find their way into the K'orth Sea and the
Arctic Ocean by virtue of their specific gi'avity, while water thence,
to take their place, is, by virtue of its specific gravity and by counter
cmTents, 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. As to the temperatm-e of the Gulf Stream, there is, in a
Winter temperature wiutcr's day, off Hattcras, and even as high up as
oftheGuifsueam. ^j^g Grand Banks of Ne\N^oimdland 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 temperatm-e may more than compensate for the differ-
ence in saltness, and leave, therefore, the waters of the Gulf Stream,
though Salter, yet lighter by reason of their warmth.

110. If they be Hghter, they should therefore occupy a higher
Top of Gulf stream Isvcl than thoso through which they fiow. Assum-
roof-sbaped. ^j^g j-^^q depth off Hattcras to be one hundred and
fom'teen fathoms, and allowing the usual rates of expansion for sea

the water in this basin be more or less salt than that of the intertropical seas, we
know it is quite different in temperature, and difference of temperature will beget
currents quite as readily as difference in saltness, for change in specific gravity
follows either.

38 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOriOLOGY.

water, figures show that the middle or axis of the GuK Stream
there should be nearly two feet higher than the contiguous 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 ^vater 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 G-ulf
Stream is therefore roof-shaped, causing the waters on its smface to
flow off to either side from the middle, we have not only circum-
stantial evidence to shov\^, but observations to prove. Navigators,
while druting along with the Gulf Stream, have lowered a boat to
try the surface cmTcnt. 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 of its com'se : thus shovf ing
the existence of a shallow roof-ciu'rent from the middle towards either
edge, which would carry the boat along, but which, being superfi-
cial, does not extend deep enough to affect the drift of the vessel.

111. That such is the case (§ 110) is also indicated by the cir-
Drift matter slough- cumstauce that the sea- weed and drift-wood which
ed off to the right, ^^.g fouud 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-cm'rent 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 GuK 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 Em'ope, but rarely on the
Atlantic shores of this country.

112. AVe are treating now of the effects of physical causes. The
Vviiy so sloughed off. 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 sho^^m 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 GULF STREAM. 3^

the effects pro<^iaced upon the di'ift matter of the stream by the
dim'iial rotation of the earth.

113. Take, for iUustration, a railroad that lies north and south
Illustration. in OUT hemisphere. It is weU known to engineers
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 — i. e.,
always on the right-hand side. Y/hether the road be one mile or
one hundi^d 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 you 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 inertife and velocity being taken into the accomit,
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 Iiiver, 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 off' ; but there are no rails to restrain the
sea-weed, and nothing to prevent the diift matter of the Gulf Stream
fi-om going off in obedience to this force. The slightest impulse
tending to tm^n aside bodies moving li'eely in water is inmiediately
felt and implicitly obeyed.

114. It is in consequence of this dim-nal rotation that drift-wood
Drift-wood on the coming dowu the Mississippi is so very apt to be cast
Mississippi. 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. The effect of diurnal rotation upon the winds and upon the
Effect of diurnal ro- curreuts of the sca is admitted by all — the trade-vvinds
tation upon. dcrivo their easting from it — it must, therefore, ex-
tend to all the matter which these cmTcnts 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 impalpable particles of sea-dust.
This effect of diui-nal rotation upon di'iit will be frequently alluded
to in the pages of this w^ork.

116. In its com^se to the north, the Gulf Stream gradually trends
Formation of the moro and more to the eastward, until it arrives off

Orand Banks.

40 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the Banks of Newfoundland, wliere its course becomes nearly
due east. These banks, it has been thought, deflect it from its
proper course, and cause it to take this turn. Examination will
prove, I think, that they are an efiect, certainly not the cause.
It is here that the frigid current aheady 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, stones, and gravel
brought dowTi upon these bergs are here deposited. Captain
Scoresby, far away in the north, coimted at one time five hundred
icebergs setting out fr'om the same vicinity upon this cold current
for the south. Many of them, loaded mth 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 creatm-es " that are brought
forth so ■ abundantly in the warm waters of the Grulf Stream, and
delivered in myriads for burial where the conflict between it and
the great Polar cm-rent (§ 89) takes place, is everlastingly going
on. These agencies, with time, seem altogether adequate to the
formation of extensive bars or banks.

117. The deep-sea soundings that have been made by vessels of
Deep water near, 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 do^^ii by a precipitous descent to unknown depths —
thus indicating that the debris which forms the Grand Banks comes
fr'om the north.

118. From the Straits of Bemini the course of the Gulf Stream
The Gulf stream de- (Plate YI.) doscribes (as far as it can be traced over
Sepath'of'atrTc- ^^ward the British Islands which are in the midst of
tory. its waters) the arc of a gi'eat circle nearly. Such a
course as the Gulf Stream takes is very nearly the course that a
cannon-ball, could it be shot fr'om these straits to those islands,
would foUow.

119. If it were possible to see Ireland from Bemini, and to get
Its path from Be- a canuou that would reach that far, the person stand-
mini to Ireland. jj^g qj^ Beuiini 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 difierence of motion between marksman

THE GULF STREAM. 41

and target. Its path would lie in the plane of a gi'eat circle. But
there is diurnal rotation ; the earth does revolve on its axis ; and
since Beniini is nearer to the equator than Ireland is, the gun
would be moving in diiu-nal rotation (§91) faster than the target,
and therefore the marksman, taking aim point blank at his target,
would miss. He would find, on examination, that he had shot
south — that is, to the ri<jM (§ 108) of his mark. In other words,
that the path actually described by the ball would be a resultant
arising from this difierence in the rate of rotation and the trajectile
force. Like a ray of light from the stars, the baU would be
affected by aberration. The ball so shot presents the case of the
passenger in the raikoad 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. Hence we may assume it as a law, that the natm-al tendency
Tendency of all cur- of all currcuts in the sea, like the natural tendency

rents both in the sea ^ n •■•in t ji • • j t •^ t.

and air to move in 01 all projcctilcs througn the aiT, IS to describe eacn
^S'law.'''''^''^' its cmrve 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, the
howhng wind, running water, and all substances, whether ponde-
rable or imponderable, seek, when in motion, to obey this law.
Electricity may be tiurned aside from its course, and so may the
cannon-ball or running water ; but remove eveiy obstruction,
and leave the ciu:rent or the shot free to continue on in the
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. The waters of the Gulf Stream, as they escape fi'om the
This law recognized G-uLf, are bouud for the British Islands, to the North
by the Gulf Stream, gea, and Frozeu 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.

42 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

And tliis coui'se, as already remarked, is nearly that of the great
circle, and of the supposed cannon-ball.

122. Many philosophers have expressed the opinion — indeed,
Shoals of xantucket the hoHef (§ 116) is common among mariners — that
course. the coasts of the United States and the Shoals of
Nantucket tm-n the Grulf Stream towards the east ; but if the view
I have been endeavouring to make clear be correct, it would ap-
pear that the course of the Gulf 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 GuK Stream is boimd 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 Nan-
tucket were not in existence, it could not pm-sue a more direct
route. The Grand Banks, however, are encroaching (§ 116), and
cold cmTents from the north come do^vn upon it : they may, and
probably do, assist now and then to tm^n it aside.

123. Now if this explanation as to the course of the Guit Stream
^otTnti'^tent*iTth ^^^ ^^^ castward tendency hold good, a cm-rent set-
known facts, ting 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 resistance and for a great distance. Ac-
cordingly, and in obedience to the propelling powers derived
from the rate at which different parallels are whhled aromid in
diurnal motion (§ 91), we find the current from the north, which
meets the Gulf Stream on the Grand Banks (Plate IX.), taking a
Q0VLt}i-2vestivardIi/ dhection, as abeady 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 tm-n the Gulf Stream towards the east :
and Sh John Herschel (§79) makes the trade-winds, which blow
from the eastward, drive this stream to the eastward !

124. But there are other forces operating upon the Gulf Stream.
The Channel of the They are derived (^ 80) from the efiect of chansfes

Gulf stream shifts . .M , r }i i i j l l

with the season. m the watcTs 01 the wholc ocean, as produced by
changes in their temperatui'e and saltness fi'om time to time. As

THE GULF STREAM. 43

tlie Gulf Stream leaves the coasts of the United States, it begins to
vary its position according to the seasons ; the limit of its northern
edge, as it passes the meridian of Cape Eace (Plate YI.), being in
wnter about latitude 40-41°, and in September, when the sea is
hottest, about latitude 45-46^. The trough of the Gulf Stream,
therefore, may be supposed to waver about in the ocean not unlike
a peimon 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 BanlvS of Ne^^foundland is, as the tem-
peratm-e of the waters of the ocean changes, fii^st pressed down to-
wards the south, and then again up towards the north, accordmg to
the season of the year,

125. To appreciate the extent of the force by which it is so
The phenomenon prcsscd, Ict US imagine thc watcTS of the Gulf
ractof "^ ^ ^ '^ ' ■ Stream to extend all the way 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 sum-
mer : the waters of the sea on either hand are for the most part in
a Hquid state, and the GuK Stream, let it be supposed, has as-
sumed a normal condition between the two divisions, adjusting itself
to the pressm^e on either side so as to balance them exactly and
be in equilibriimi. Now, again, it is the dead of winter, and the
temperatm^e of the waters over an area of millions of square miles
in the North Atlantic has been changed many degrees, and this
change of temperatm^e has been folloAved likewise by a change in
volume of those waters, amounting, no doubt, in the aggregate,
to many hundi'ed miUions of tons, over the whole ocean ; for sea-
water, unlike fresh (§ 103), contracts to freezing, and below. Now
is it probable that, in passing fi'om then' summer to their winter
temperatm^e, the sea-waters to the right of the GuK Stream should
change their specific gi-avity 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 compensated 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 ah*
whenever, wherever, and by whatever it be disturbed. Therefore,
though the waters of the GuK Stream do not extend to the bottom,
and though they be not impenetrable to the waters on either hand,
yet, seeing that they have a w^aste of waters on the right and a
waste of waters on the left, to which (§ 70) they offer a sort of

44 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

resisting permeability, we are enabled to comprehend bow the
waters on either hand, as their specific gravity is increased or
diminished, will impart to the trough of this stream a vibratory
motion, pressing it now to the right, now to the left, according to
the seasons and the consequent changes of temperatm^e in the sea.

126. Plate VI. shows the limits of the GuK Stream for March
stream ?a March"^^ ^^^ September. The reason for this change of posi-
and September. tion is obvious. The bauks of the Gulf Stream
(§ 70) are cold water. In mnter the volume of cold water on the
American, or left side of the stream, is greatly increased. It must
have room, and gains it by pressing the warmer waters of the
stream farther to the south, or right. In September, the tempera-
ture of these cold waters is modified ; there is not such an extent
of them, and then the warmer waters, in tm^n, press them back,
and so the pendulum-like motion is preserved.

127. In the offings of the Balize, sometimes as far out as a hun-
Reiuctance of layers drod milcs or more from the land, puddles or patches
or patches to mingle, ^f Mississippi watcr maybe observed on the sm'-
face of the sea with little or none of its brine mixed with it. This
anti-mixing property in water has abeady (§ 98) been remarked
upon. It may be observed from the gutters in the street to the
rivers in the ocean, and everywhere, wherever two bodies of
water that differ in colour are fomid in juxtaposition. The patches
of white, black, green, yellow, and reddish waters so often met mth
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 temperature or velocity. This peculiarity is often so strik-
ingly developed in the neighbourhood of the Gulf Stream, that
persons have been led to suppose that the GuK Stream has forks in
the sea, and that these are they.

128. Now, if any vessel will take up her position a little to the
streaks of warm and uorthward of Bermuda, and steering thence for the
^^°^' Capes of Virginia, will try the water-thermometer
all the way at short intervals, she mil find its readings to be now
higher, now lower ; and the observer ^ill discover that he has
been crossing streak after streak of warm and cool water in regular
alternations. He will then cease to regard them as bifm-cations
of the Gulf Stream, and view them rather in the light of thermal
streaks of water which have, in the plan of oceanic ckculation
and in the system of imequal heating and cooling, been brought
together.

THE GULT STREAIVT. 45

129. The waters of the Gulf Stream form by no means the
Waters of the ocean onlj bodj of Warm Water that the thermo-dy-
Semi'o-d°nlmicJi ii^mical forces of the ocean keep in motion. Kearly
means. all that portion of the Atlantic which lies between
the Gulf Stream and the island of Bermuda has its surface covered
vdth. water which a tropical sun and tropical winds have played
upon — with water, the specific gravity of which has been altered
by their action, and which is now drifting to more northern climes
in the endless search after lost equilibrium. This water, more-
over, as well as that of the Gulf Stream, cools unequally. It
would be sm'prising 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 conditions ; therefore all of the
water over such a smiace cannot be heated ahke ; radiation here,
sunshine there ; clouds and rain one day, and storms the next ;
the miequal depths ; the breaking up of the foimtains below, and
the bringing then' 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 natm-al result of which would be
streaks and patches of water differing in temperature. Hence it
would be sm-prising if, in crossing this drift and stream (Plate YI.)
with the water-thermometer, the observer should find the water all
of one temperature. 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 diflerently-
tempered streaks and layers (§ 127) which are so familiar to
navigators, and which have been mistaken for "forks of the Gulf
Stream."

130. Curves showing some of these variations of temperatm-e
Fig. A, Plate VI. havo been projected by the Coast Survey on a

chart of engraved squares (Fig. A, JPlate YI.). These curves
show how these waters have sometimes arranged themselves ofi'
the Capes of Yirginia into a series of thermal elevations and
depressions.

131. In studpng the Gulf Stream, the high temperature and
drift of the waters to the east of it are worthy of consideration.

46 PHYSICAL GEOaRAPHY OF THE SEA, AND ITS SIETEOROLOGY.

The Japan current (§80) lias a like drift of warm water to tlie
The hi-h tempera- east of it also (Tlates YI. and IX.). In the west-

ture and drift in the i i r> i • r ii l j j t r^ ^n

western half of North em hall, roachmg up irom the equator to the Gruli
ociaS^:° '°' '*'''''' 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 temperatm-e is lower, the
flow is to the south — making good the remark (§ 80) that, when
the waters of the sea meet in cm-rents, the tendency of the warm
is to seek cooler latitudes, and of the cool, warmer.

132. The Gulf Stream of each ocean has its genesis on the west
A Gulf stream in sido, and iu its couTse it skirts the coast along ;
«^^^' leaving the coast, it strikes ofl" to the eastward in each
case, losing velocity and spreadhig 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 ail 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
di'ift matter cannot pass. Such are the points of resemblance
between the two oceans and in the circulation of their waters.

133. A prominent point for contrast is afforded by the chan-
Their connection ncls or water-ways between the Arctic and these
Ocean. ^ '^ '"^ two occaus. With the Atlantic they are divers and
large ; with the Pacific there is but one, and it is both narrow
and shallow. In comparison mth that of the Atlantic, the Gulf
Stream of the Pacific is sluggish, ill-defined, and irregular. Were
the water-ways between the Atlantic and the Arctic Ocean no larger
than Behring's Straits, oui' Gulf Stream would fall far below that
of the Pacific in majesty and grandem\

134. Here I am reminded to tm-n aside and caU attention to an-
The sargassos show othoT fact that militates against the vast current-
the feebie power of beofettinfi: powor that has been criven by theory to

the trad>wmds up- O & 1 x i i.1 l^ ^

on currents. the gentlc trade-^ands. In both oceans tnese weedy

seas lie partly mthin the trade-wind region ; but in neither do
these winds give rise to any current. The weeds are partly out

THE GULF STREAM. 47

of water, and the wind lias 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-^ind region, we should have here the strongest cm-rents.
Had there been currents here, these weeds would have been
borne away long ago; but so far from it, we simply know
that they have been in the Sargasso Sea (§ 88) of the Atlantic
since the first voyage of Colmnbus. But to take up the broken
thread : —

135. The water that is drifting north, on the outside of the GrJf
fiSd^o^^^-aSosT" ^^^'®^^^' turns, with the Gulf Stream, to the east
currents.' '°^ also. It camiot rcach the high latitudes (§ 80), for
it cannot cross the Gulf Stream. Two streams of w^ater 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 Vs^eed^, is too Hght to
sink. They, therefore, are cut off fi'om a passage into higher
latitudes.

136. According to this view, there ought to be a sargasso sea
Theory as to the for- somewhcre iu the sort of middle ground between
mation of sargassos. j^\^q grand equatorial flow and reflow which is per-
foiTQcd 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, woidd slough off its drift matter. The
forces of diurnal rotation would requii'e this collection of drift to be,
in the northern hemisphere, on the right-hand side of the cmTent,
and, in the southern, to be on the left. (See Chap. XVIII. and
Plate IX.)

137. Thus, with the GuK Stream of the Atlantic, and the '^ Black
Sargassos of south- Stream " of the Pacific, their sargassos are on the
oMhrJouthera/to right, as they are also on the right of the returning
JJk?anV',^uatS ^^^^ ^ooler ciuTeuts on the eastern side of each one of
flow and reflow. tliosc uorthem occaus. So, also, with the Mozam-
bique current, which runs south along the east coast of Africa from
the Indian Ocean, and with the cooler current setting to the north
on the Austrahan side of the same sea. Between these there is a
sargasso on the left ; for it is in the southern hemisphere.

138. Again, there is in the South Pacific a flow of equatorial
Their position con- watcTS to the Antarctic on the east of Austraha, and

lurms to the theory. '

48 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of Antarctic waters (Huraboldt's cuiTent) 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. To test the correctness of this ^dew, I requested Lieut.
The discoveri- of a Warlcj to ovcrhaul om' sea-joumals for notices of
new sargasso. . ^ ]j-gjp ^^^^ ^]j,^£^ matter ou the passage from Australia
to Cape Horn and the Chincha Islands. He did so, and found it
abomiding in small patches, with "many birds about," between the
parallels of 40° and 50° south, the m'eridians 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 m position than any one of the
others.

140. There is no warm cmTcnt, or if one, a very feeble one,
One in the South flomug out of the South Atlantic. Most of the diift
Atlantic. matter borne upon the ice-bearing cm-rent 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 diiit. The sargassos of
the South Atlantic are therefore small. The formations and
physical relations of sargassos v^ill be again alluded to in Chapter
XVIII.

141. Let us return (§ 129) to this great expanse of warm vrater
The large volume of whicli, comiug from the torrid zone on the south-
of\™Giif stream!^ westcm sido of the Atlantic, drifts along to the north
on the outside of the Gulf Stream. Its velocity is slow, not suffi-
cient to give it the name of cm-rent ; 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 intertropical heat: con-
sequent upon this change in temperatm-e is a change in specific
gravity also, and by reason of this change, as well as by the diffi-
culties of crossing the Gulf Stream, its progress to the north is
arrested. It now turns to the east with the Gulf Stream, and, yield-
ing to the force of the westerly winds of this latitude, is (§ 107)
by them slowhj 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 ^\ind, 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.

THE GULF STREAM. 49

142. The Thermal Charts of the North Atlantic afford for these
The resemblance be- yiews other iUiistratioiis which, when compared with
in the NorthTtkn- the charts of the North Pacific now in the process of
fIc^^ '^' ^'''^' construction, will make still more striking the re-
semblance of the two oceans in the general featm^es of their systems
of circulation. We see how, in accordance with this princijDle
(§ 132), the cmTents 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
accoimt 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. As a rule, the hottest water of the Gulf Stream is at or
A cushion of cool j^^car tho smface ; and as the deep-sea thermometer
Stom^of medeep is scut do^\Ti, it shows that thcse waters, though still
by iS'SJrreSs''*''' far Warmer than the water on either side at corre-
sponding 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 every-
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
Em'ope. Now cold water is one of the best non-conductors of heat,
and if the warm water of the Gulf Stream was sent across the
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 mth 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 bit-
terly cold.

144. That there should be in the North Atlantic Ocean a con-
\vTiy should the Gulf staut and copious flow and reflow of water between
SThTGuif'o^MS! that ocean and the Arctic is (§ 107) not so strange,
^^<^- for there are abundant channel- ways between the two
oceans. In one water is to be found nearly at blood heat, in the

50 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

other as cold as ice. A familiar experiment shows that if two basins
of such water be brought in connection by oj)ening a w^ater-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. To satisfy ourselves that the trade-winds have little or
The trade-winds as nothing to do in causiug the Gulf Stream, we may by

ji cause ol tu6 ijuii ^ . i*t' ii ti c* i i

stream. a proccss 01 rcasomug, wnicn ignores all the tacts and

circumstances abeady adduced, show that they cannot create a cm^-
rent 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. A constantly acting power, such as the force of gTavitation,
Gulf stream impelled fg as necessarv (S 95) to keep fluids as it is to keep

by a constantly act- tt • i- t -n n • l'i !>

ing force. solids in motiou. In either case the projectile lorce

is soon overcome by resistance, and unless it be renewed, the ciuTent
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 descend-
ing an inclmed plane ; there, gravity ceases to act as a propelling
force, and the stream ceases to flow on, notwithstanding the impulse it
derived from the falls and rapids above. A propelling povrer, hav-
ing its seat only in the Gulf of Mexico, or the trade-wind region,
could (§ 92) no more drive a jet of water across the ocean, than
any other single impulse could send any other trajectile 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 diflerence, however, the Mississippi runs down
hill, the GuK 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
som'ces of everlasting changes and just such constantly acting
forces as are requked (§ 108) to keep up and sustain, not only the
Gulf Stream, but the endless round of ciuTents 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 diflerence in specific
gravity between the flowing and reflowing water.

147. The waters of the GuK as they go fi'om their fountain have

GULF STPtEAM, CLIHIATES, AXD COMMEnCS. 51

their specific gravity in a state of perpetual alteration in consequence
The true cause of of tlic cliangc of saltuess, and in consequence also of
the Gulf Stream. j^i^q cliangc of temperature. In' these changes, and
not in the trade-winds, resides the power vrhich makes the great
ciuTents of the sea.

CHAPTEE III.

§ 150-191. IXFLUENCE or THE GULF STSExUI UPOK CLIMATES

AND COMMEECE.

150. Modern ingenuity has suggested a beautiful mode of
How the ^vashing- warming houses in winter. It is done by means
warmer'"'''''^ '' of hot watcr. The fm-nace and the caldron are some-
times placed at a distance from the apartments 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 of the basement rooms of the Observatory,
a distance of one hundi-ed feet. These pipes are then flared out
so as to present a large coolnig surface; after which they are
imited into one again, through which the water, being now cooled,
returns of its o\m accord to the caldron. Thus cool water is
retm-ning all the time and flowing m at the bottom of the caldron,
while hot water is continually flomng out at the top. The ven-
tilation of the Observatory is so arranged that the cii-culation of the
atmosphere through it is led from this basement room, where the
pipes are, to all other parts of the buildmg ; and in the process of
this cnculation, the warmth conveyed by &e water to the basement
is taken thence by the air and distributed over all the rooms.
Kov/, to compare small things with great, we have, in the warm
waters which are contained in the Gulf of Mexico, just such a heat-
ing apparatus for Great Britain, the North Atlantic, and Western
Eiu-ope.

151. The fm^nace is the torrid zone; the Mexican Gulf and
An anaiopry showing Caribbean Sea are the caldrons; the Gulf Stream
rl-ares teuipiratmi'^ is the couducting pipe. From the Grand Banks of
iu Europe.. Ne^\'foundiand to the shores of Em^ope is the base-

ment— the hot-air chamber — in which this pipe is flared out so as
to present a large cooling surface. Here the circulation of the

E 2

52 PHYSICAL GEOGE.iPHY OF THE SEA, AND ITS METEOROLOGY.

atmosptiere is arranged by nature ; it is from west to east ; conse-
quently 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 temperatm-e 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 temperatm-e due the latitude. Increasing its
latitude 10°, it loses but 2° of temperature; and, after having rmi
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 Em'ope the rigoiu'S of
winter. Moving now more slowly, but dispensing its genial in-
fluences 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 im-
mense 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 there.

152. We know not, except approximately in a few places,
Depth and tempera- wdiat the depth of the Under temperatm'e of the
t""^^- GuLf Stream may be ; but assuming the temperature
and velocity at the depth of two hundi'ed fathoms to be those of
the surface, and taldng the well-kno"^^i difference between the
capacity of air and of water for specific heat as the argument, a
simple calculation mil show that the quantity of heat discharged
over the Atlantic fi'om the waters of the Gulf Stream in a winter's
day would be sufiicient to raise the whole column of atmosphere
that rests upon France and the British Islands from the freezing-
point to summer heat.

153. Eveiy west A^ind that blows crosses this stream on its way
Contrasts of climates to Em'opo, and carrics with it a portion of this heat
tudes! ^^™^ ^ to temper there the northern mnds 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 xAlbion
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

GULF STREAM, CLIMATES, AND COIVrMERCE. 53

paper on cuiTents,* Mr. Bedfield states, that in 1831 the harbour
of St. John's, Newfoundland, was closed vdth. ice as late as the
month of June ; yet who ever heard of the port of Liverpool, on
the other side, though 2^ farther north, being closed with ice, even
in the dead of ^vinter ?

154. The Thermal Chart (Plate lY.) shows this. The isother-
Miidnessofanork- i^al liues of 60^, 50°, ctc, starting off fi'om the pa-
ney ^vinter. rallcl of 40° ucar the coasts of the United States, run
off in a north-eastwardly direction, sho^\dng the same oceanic tem-
peratme 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 apparatus, and to the
latent heat of the vapours from it which is liberated dming 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. Nor do the beneficial influences of this stream upon climate
Amount of heat daily end hcrc. The "West Indian ArchipelaGfo is encom-

escaping through the , • 1 "L u T, • r • l J T j.i

Gulf Stream. passcd ou onc Side by itscnam oi islands, and on the

other by the Cordilleras of the Andes, contracting with the Isthmus
of Darien, and stretching themselves out over the plains of Central
America and Mexico. Beginning on the summit of this range, Ave
leave the regions of perpetual snow, and descend first into the
tierra temijlada, and then into the terra caliente, or bm-ning land.
Descending still lower, we reach both the level and the smface of
the Mexican seas, where, were it not for this beautiful and benign
system of aqueous circulation, the peculiar features of the surround-
ing comitry assure us we should have the hottest, if not most pes-
tilential climate in the world. As the waters in these two caldrons
])ecome heated, they are boiTie off by the Gulf Stream, and are re-
placed by cooler currents through the Caribbean 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 tMs
difference in smface temperatm-e as an index of the heat accumu-
lated there, a simple calculation will show that the quantity of heat

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

t Temperature of the Caribbean Sea (from the journals of Mr. Dunsterville) :
Surface temperature: 83^ September; 84^, July; 83"-86|-\ Mosquito Coast.
Temperature in depth ; 48^ 240 fathoms ; 43^ 3*80 fathoms ; 42^, 150 fathoms :
43\ 500 lathoms.

54

daily carried off by the Grulf Stream from those regions, and dis-
charged over the Atlantic, is sufficient to raise mountains of iron
from zero to the melting-point, and to keep in fioY/ fr'om them a
molten stream of metal greater in Yolimie than the waters daily dis-
charged from the Mississij^pi Eiver.

156. Who, therefore, can calculate the benign influence of this
Its benign influences, wonderful cmTcut upou the climatc 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 Yvill not the study of
this subject fill with profitable emotions? Unchanged and un-
changing alone, of all crea^ted things, the ocean is the great emblem
of its everlasting Creator. " He treadeth upon the waves of the sea,"
and is seen in the wonders of the deep. Yea, " He calleth for
its waters, and poureth them out upon the face of the earth." In
obedience to this call, the aqueous portion of om^ planet preserves
its beautiful system of circidation. By it heat and warmth are dis-
pensed to the extra-tropical regions : clouds and rain are sent to
refresh the dry 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 and forty fathoms the temperatiu:e of the currents
setting into the Caribbean Sea has been found as low as 48°, while
that of the sm-face was 85°. Another cast with three himdi'ed and
eighty-six fathoms gave 43° below against 83° at the smface. 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 smface
portions of the cooler water below.

157. At the very bottom of the Gulf Stream, when its smface
bStom'lJf theGuif ^emperatm^e was 80°, the deep-sea thermometer of
sireani. ' tho Coast SuTvcy has recorded a temperature as low
as 35° Fahrenheit. These cold waters doubtless come do^ii from
the north to replace the warm water sent through the Gulf Stream
to moderate the cold of Spitzbergen ; for within the Arctic Cfrcle
the temperatm-e at coiTesponding 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 temperatui'e 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 lati-
tude 72°, the temperature of the air was 42° ; of the water, 34° ;
and 29° at the depth of one hundred and eighteen fathoms. He

GULP STKKiM, CLIMATES, AlU) COlTuEECE. 5D

there found a surface current setting to the south, and bearing v/ith
it this extremely cold water, with vast numbers of icebergs, whose
centres, perhaps, were far below zero. It would be cm-ious to as-
certain the routes of these under cm-rents on their way to the tropi-
cal regions, which they are intended to cool. One has been found
at the equator (§ 97) two hundred miles broad and 23^ colder than
the smface water. Unless the land or shoals intervene, it no doubt
comes down in a spiral curve (§ 96), approaching in its course the
great circle route.

158. Perhaps the best indication as to these cold cm-rents may
Fish and currents. \)q dcrivcd from the fisli cf the sea. The whales, by
avoiding its warm waters, pointed out to the fisherman the exist-
ence of the Gulf Stream. Along our own coasts, all those delicate
animals and marine productions Avhich dehght in warmer waters
are wanting ; thus indicating, by their absence, the prevalence of
the cold cm-rent from the north now knov/n to exist there. In the
genial warmth of the sea about the Bermudas on one hand, and
Africa on the other, we find, in great abundance, those delicate
sheU-fish and coral formations which are altogether wanting in the
same latitudes along the shores of South Carolina. The same ob-
tains in the west coast of South America ; for there the immense
flow of polar waters knov^m as Humboldt's CmTent almost reexdies
the hne before the first sprig of coral is found to grow. A fev^
years ago, great numbers of bonita and albercore — tropical fish —
following the GvHi Stream, entered the English Channel, and
alarmed the fishermen of Cornwall and Devonshire by the havoc
which they created among the pilchards. It may well be ques-
tioned if the Atlantic cities and towns of America do not owe their
excellent fish-markets, and the watering-places their refi-eshing sea-
bathing in summer, to this littoral strea^m of cold water. The
temperatm-e of the MediteiTanean is 4"^ or 5^ above the ocean tem-
perature of the same latitude, and the fish there are, for the most
part,, very indifferent. On the other hand, the temperature along
the American coast is several degrees below that of the ocean, and
from Maine to Florida, tables are supplied with the most excellent
of fish. The sheep's-head of this cold cmTent, so much esteemed
in Virginia and the Carolinas, loses its flavom^ 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 dehcious flavom-, and are highly esteemed ;
but when taken in the warm water on the other ecWe of the GuK

56 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Stream, tliougli but a few miles distant, their flesli is soft and unfit
for the table. The temperatm-e of the water at the Balize reaches
90°. The fish taken there are not to be comj^ared 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 cmTent of cold water
(§ 398) from the south swee2:)S the shores of Chili, Peru, and
Columbia, and reaches the Gallipagos Islands imder the equator.
Throughout this whole distance, the world does not afibrd a more
abundant or excellent supply of fish. Yet out m the Pacific, at the
Society Islands, where coral abounds, and the water preserves a
higher temperatm^e, the fish, though they vie in gorgeousness of
coloming with the birds, and plants, and insects of the tropics, are
held in no esteem as an article of food. I have kno^^Ti 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
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 tempera-
tm-e of the water ; and whether these cold and warm cm-rents of
the ocean do not constitute the gi^eat highways through which
migratory fishes travel fi'om one region to another. AYhy should
not fish be as much the creatm'es of climate as plants, or as birds
and other animals of land, sea, and ah' ? Indeed, we know that
some kinds of fish are found only in certain climates. In other
words, they hve where the temperature of the water ranges be-
tween certain degrees.

159. Navigators have often met with vast numbers of young
A shoal of sea-net- soa-nettles {medusie) drifting along mth the Gull"
"®^- Stream. They are kno"\ATi to constitute the princi-

pal 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 insj^ection in the water, 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 yellow leaf. He was boimd to Eng-
land, and was five or six days in sailing through them. In

GULF STREAM, CLIMATES, AKD COMMERCE. 57

about sixty clays afterwards, on his return, he fell in with the same
school off the Western Islands, and here he was three or foui-
days in passing them again. He recognized them as the same,
for he had never before seen any like them ; and on both occasions
he frequently hauled up buckets full and examined them.

160. Now the Western Islands is the great place of resort for
Food for whales, whales ; and at first there is something curious to

ns in the idea that the Gulf of Mexico is the harvest field, and the
Grulf Stream the gleaner which collects the fruitage planted there,
and conveys it thousands of miles off to the hungry whale at sea.
But how perfectly in unison is it with the kind and providential
care of that great and good Being that caters for the sparrow,
and feeds the young ravens when they ciy !

161. Piazzi Smyth, the Astronomer Koyal of Edinbm-gh, when
piazzi Smyth's de- bouud to Tcueriffe on his celebrated astronomical
scription. expedition of 1856, fell in with the annual harvest
of these creatm-es. They were in the form of hollow gelatinous
lobes, arranged in groups of five or nine — each lobe having an
orange vein do"\^Ti the centre. Thus each animal was formed of
an aggregation of lobes, with an orange-colom-ed vein, or stomach,
in every lobe. ^'Examining," says he, " in the microscope a por-
tion of one of the orange veins, apparently the stomach of the
creatm-e, it was found to be extraordinarily rich in diatomes, and
of the most bizaiTe forms, as stars, Maltese crosses, embossed cir-
cles, semicu'cles, and spirals. The whole stomach could hardly
have contained less than seven hundi'ed 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 countless millions of
diatomes that go to make a feast for the medusae — some of the
softest things in the world thus confoimding and devouring the
hardest — the flinty-shelled diatomacse." Each of these " sea-net-
tles," 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 then' inhabitants had
collected from the silicious matter which the rains washed out
from the valleys, and which the rivers are continually rolling down
to the sea.

162. The medusae have the power of sucking in the sea-water
brin<^fonh-ohh^^* slowly, and of ejecting it again mth more or less
abundantly! forcc. Thus they derive both food and the power

of locomotion, for, in the passage of the water, they strain it and

58 PHYSICAL GEOG-EAPHY OF THE SEA, AND ITS METEOEOLOGY.

collect tlie little diatomes. Iiiicagiue, now, how many mednsae-
moiitliMs of water there must be in the sea, which, though loaded
with diatomes, are never filtered through the stomachs of these
creatm^es ; imagine how many medusse the whale must gulp down
with every mouthful ; imagine how deep and thicldy the bottom
of the sea must, dming the process of ages, have become covered
with the flinty remams 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 povrers of the
imagination are silenced in their very impotency, and the emotions
of wonder, love, and praise take iheii place.

163. The sea has its climates as well as the land. They both

?hTciSiatesofiaud ^^^^^o® ^''^'^^'^ *^^^6 ktitudo ; but oue varies with the
and sea. "^ elcvation above, the other with the depression be-

low the sea level. The cKmates in each are regulated by circula-
tion ; but the chief regulators are, on the one hand, winds ; on the
other, cmTents.

164. The inhabitants of the ocean are as much tlie creatures
Order and design, of cHmate 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 inhabitants
are all his creatures, subjects of his laws, and agents in his eco-
nomy. The sea, therefore, we may safely infer, has its ofiices 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 per-
ceive 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. To one who has never studied the mechanism of a watch,
Terrestrial adapta- its maiu-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;
lie win recognize neither design, nor adaptation, nor relation be-

GULF STEEAil, CLI3IATES, AXD COMMENCE. 59

tween tliem ; 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 concerned, the whole piece
is of one thought, the expression of one idea. He now rightly con-
cludes 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 ffiial conclusion ^ill be, that such a piece of
mechanism could not have been produced by chance ; for the adap-
tation 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 v\^orld, he may admu^e its
lovely scenery, but his admiration can never grov/ into adoration
unless he will take the trouble to look behmd and study, in some of
its details at least, the exquisite system of machinery by which such
beautiful results are brought about. To him who does this, the
sea, with its physical geogTaphy, becomes as the main-spnng of a
watch ; its waters, and its currents, and its salt, and its inhabitants,
with their adaptations, as balance-wheels, cogs, and pinions, and
jewels in the terrestrial mechanism. Thus he perceives that they
too are accordmg to design — parts of the physical machinery
that are the expression of One Thought, — a unity, with harmonies
which 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 subhme. It elevates the
mind and ennobles the man ; for " His gentleness makes " it gTcat.
The Gulf Stream is now no longer, therefore, to be regarded by
such a one merely as an immense cmTent of warm water running
across the ocean, but as a balance-wiieel — a part of that grand
machinery by v/hich air and water are adapted to each other, and by
vrhich this earth itself is adapted to the weU-bemg of its inhabitants
— of the flora which deck, and the fauna which enliven its surface.
168. Let us now consider the Influence of the Gulf Stream
Meteorology of upon the Meteovology of the Ocecm. To use a sailor's
ifreamthewe^amer- cxpressiou, the GuK' Stream is the great "weather-
-?hf';^eSt™ril breeder" of the North Atlantic Ocean. _ The most
cane of Hso. furious gales of mnd 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,

60 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ill that cold sea, of immense volumes of warm ^vater brought by the
Gulf Stream. Sir Philij) 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 distm'bance in its bosom, w^e 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 kno^vn to spend their fm-y within or near its 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-of-war go down before them, and seldom, indeed, 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 w^orks tell
us of a West India hrn'ricane so violent that it forced the GuK
Stream back to its som'ces, and piled up the water in the Gulf to
the height of thu^ty feet. The Ledbury Snow attempted to ride it
out. When it abated, she fomid herself high up on the diy land,
and discovered that she had let go her anchor among the tree-tops
on Elliott's Key. The Florida Keys were inundated many feet,
and, it is said, the scene presented in the Gulf Stream was never
surpassed in awful sublimity on the ocean. The water thus dammed
up rushed out with frightful velocity against the fmy of the gale,
producing a sea that beggared description. The "great hmii-
cane " 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 ujDrooted, and the waves rose to
such a height that forts and castles were washed away, and their
great guns carried about in the au' like chaff ; houses were razed ;
ships T^Tecked ; and the bodies of men and beasts hfted 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 w^ere driven on
shore at the Bermudas.

167. Several years ago the British Admiralty set on foot inquiries
Inquiries instituted as to the causc of the storms in certain parts of the

by the Admiralty, ■"-

GULF STEEAM, CLIMATES, AND C0M5IERCE. 61

Atlantic, which so often rage mth 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 neighbour-
ing regions, both in the air and water.

168. The southern points of South America and Africa have won
The most stormy sea. for thcmselvcs, amoug seamon, 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 stoim-find in the wide
ocean can out-top that which rages along the Atlantic coasts of
North America. The China seas and the North Pacific may vie in
the fmy of their gales mth this part of the Atlantic, but Cape
Horn and the Cape of Grood Hope cannot equal them, certainly, in
frequency, nor do I believe in fury.

169. In the ex-tropical regions of the south we lack those con-
Northern seas more trasts which the mouutaius, the deserts, the plains,
southern. the coutinents, and the seas of the north afford for
the production of atmospherical disturbances. Neither have we
in the southern seas such contrasts of hot and cold ciuTents. The
flow of warm water towards the pole, and of polar water towards the
equator is as great — perhaps if measured according to volume, is
greater in the southern hemisphere. But in the southern hemi-
sphere 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 fm^ther investigation, we may infer southern seas
to be less boisterous than northern.

170. By a Kke reasoning we may judge the North Pacific to
storms in the North bo Icss boistcrous than the North Atlantic ; for,
Atlantic and Pacific. i^j^Q^^gli^e havo Continental climates on either side
of each, and a Gulf Stream in both, yet the Pacific is a very much
wler 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 atmospherical disturbance in that com-
pactness which is so striking in the narrow North Atlantic.

171. Nevertheless, though the North Pacific generally may not
storms along their bo SO stormy as the North Atlantic, we have reason
western shores. |q befievo that meteoTological 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

62 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

littoral ciuTents 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, mth its neighbouring
seas, is some 500 miles nearer to the pole of maximum cold than
the GuK Stream of the Atlantic is. Great prominence in the
brewing of storms is to be given to the latent heat vfhich is set free
in the air when vapom- is condensed into rain. The North Pacific
being broader than the North Atlantic, supphes its shores (§ 283)
more abundantly with vapom' than the North Atlantic does. This
no doubt assists to make fmious and more frequent the storms of
the North Pacific.

172. Some philosophers hold that there are in the northern
Position of the poles hemisphere two poles of maximum cold : the Asiatic,
aLXlrSueS near the intersection of the parallel of 80° with the
oTy of'thSe^two ^©I'iclian of 120'' E., and the American, near lat.
ocelns. 79^ and long. 100° W. The Asiatic pole is the
colder. The distance between it and the Japan CmTent 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 tlie atmo-
sphere. These commotions, as indicated by the storms, are far
more frequent and violent in vdnter, when the contrasts between
the warm and cool places are greater, than they are in summer,
when those contrasts are least. Moreover, each of these poles is to
the north-west of its ocean, the quarter whence come the most
terrific gales of winter, ^'^rbatever be the exact degTee 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 temperatm-e of
summer as far north as the Grand Banks of Newfomidland.

173. The habitual dampness of the cHmate of the British
Climates of England Jslauds, as wcll as the occasioual dampness of that
Scwfouu^andf ^ along the Atlantic coasts of the United States
vvhen easterly v/inds prevail, is attributable also to the Gulf
Stream. These winds come to us loaded mth vapom's gathered
from its warm and smoking waters. The Gulf Stream carries the
temperatm-e of summer, even in the dead of winter, as far north
as tlie Grand Banks of Newfoundland, and there maintains it in

GULF STEEAM, CLIilATES, AXD COMIilEKCE. 63

tlie midst of the severest frosts. It is the presence of this warm
water and a cold atmosphere in juxtaposition there which gives rise to
the "silver fogs" of Newfomidland, one of the most beautiful phe-
nomena to be seen any^vhere among the treasures of the fi'ost-king.

174. The influence which the Gulf Stream exercises upon the
Influences upon storms of the North Atlantic, 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 ImoTMi to visit the oflfings 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-west
until they join it, when they "recm'vate," as the phrase is, and
take up their line of march to the north-east along with it. Gales
of mnd have been traced from latitude 10° N. on the other side of
the Atlantic to the GuK Stream on this, and then with it back
again to the other side, off the shores of Em^ope. 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 T^Tecked, dismasted, or damaged.

175. Now, what should attract these storms to the Gulf Stream,
More observations in is a qucstion whicli yet remains to be satisfactorily
s?ioi'°",* !!it/^''.^^ answered. A c'ood series of simultaneous baro-
turn. metric observations within and on either side of
the Gdf Stream is a gi'eat desideratum in the meteorology of
the Atlantic. At the equator, where the trade-winds meet and
ascend, where the air is loaded with moistm^e, and where the vapour
n'om the warm waters below is condensed into the equatorial
cloud-ring above, we have a low barometer.

176. How is it with the Gulf Stream when these storms fi'om
Certain stoi-ms make right and left buTst in upou it, and, turning about,
for it and follow it. gom'se aloug mth it ? Its waters are warm ; they
give off vapour rapidly; and, were this vapom' visible to an
observer in the moon, he no doubt would, on a winter's day espe-
cially, be able to trace out by the mist in the air the path of the
Guh* Stream through the sea.

177. Let us consider the effect of vapoiu' upon winds, and then
How aqueous vapour the importance of the observations proposed (§ 175)

assists in produciDg „. -l- , i i ji • j i ■'• a

Minds. _ wiil perhaps be better appreciated. Aqueous va-

64 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

poiu' assists in at least five, perhaps 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 the au', as is manifest in the tendency
of the cooled air to flow off, and of warmer and lighter to take its
place. (2.) Excepting hydrogen and ammonia, there is no gas so
light as aqueous vapom^, 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 mnd is called for
below. (4.) Arrived in the cloud-region, this vapom^, being con-
densed, liberates the latent heat which it borrowed from the air and
water below ; which heat, being now set free and made sensible,
raises the temperature of the smTOunding au', causing it to expand
and ascend still higher ; and so winds are again called for. Ever
ready, they come ; thus we have a fourth way. (5.) Innmnerable
rain-drops now begin to fall, and in their descent, as in a heavy
shower, they displace and press the air out below with great force.
To this cause Espy ascribes the gusts of wind which are often
found to bloAV 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 atmo-
sphere, 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. These agents, singly and together, produce rarefaction,
A channel of rarefied diminish pressuro, and call for an inward rush of air
and over SSf ""^ ^^^ either sidc. Mr. Espy asserts, and quotes actual
Stream. obscrvation 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 com^se. That those w^hich have their origin at sea,
on the other side of the Gulf Stream, do (§ 174) often make right
for it, is a fact well kno^vn to seamen. The Gulf Stream from

GULF STREAIM, CLIMATES, AND COMMERCE. 65

Bernini to the Grand Banks is constantly sending up volumes
of steam; this, being lighter than air, produces a channel way
of rarefied air through the atmosphere, 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 phenomena
alluded to above, viz. ; that certain storms, both in the Atlantic
and in the United States, invariably make for the GuK Stream,
and, reaching it, turn and follow it in its course sometimes entirely
across the ocean. Hence, the interest that is attached to a jjroper
series of observations on the meteorology of the Gulf Stream.

179. Sailors dread its storms more than they do the storms in
storms of-dreaded ^uy othcr part of the ocean. It is not the fury of

^ea " which these storms raise. The cmTent of the stream run-
ning in one dfrection, and the wind blowing in another, create a sea
that is often frightful.

180. The influence of the Stream upon commerce and naviga-
iioutes formerly tioii. Fomierlv the Gulf Stream controlled com-

guverned by the j_l * xl j.- "l • i •

Gulf Stream. mcrco across the Atlantic by governmg vessels m

their routes through this ocean to a greater extent than it does
now, and simply for the reason that ships are faster, nautical in-
struments better, and navigators are more skilful now than for-
merly they were.

181. Up to the close of the last centmy, the navigator ^^tessetZ
Difficuitips with as much as he calculated the place of his ship ; ves-
eariy navigators. g^jg ^^^^ Europo to Bostou fr^cqucntly maclo Kew
York, and thought the landfall by no means bad. Chronometers,
now so accurate, were then an experiment. The Nautical Ephem-
eris itself was faulty, and gave tables which involved errors of
thirty miles in the longitude. The instruments 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 " mari-
ner'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 fr'om
port.

p

66 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

182. Though navigators had heen in the habit of crossing and
Finding longitude reci'ossing the Grulf Stream almost daily for three
by the Gulf Stream, centimes, it nover occurred to them to make use of
it as a means of gi^'ing 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 aiforded 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. When he was in London, in 1770, he happened to be con-
Foigers Chart, sultcd as to a memorial which the Board of Customs

at Boston sent to the Lords of the Treasmy, stating that the Fal-
mouth packets were generally a fortnight longer to Boston than
common traders were from London to Providence, Khode Island.
They therefore asked that the Falmouth packets might be sent to
Pro^adence instead of to Boston. This appeared strange to the doc-
tor, for London was much farther than Falmouth, and from Fal-
mouth the routes were the same, and the difference should have
been the other way. He, however, consulted Captain Folger, a
Nantucket whaler, who chanced to be in London also ; the old fisher-
man explained to the philosopher that the difference arose fi'om the
circumstance that the Pthode Island captains were acquainted with
the G-ujf 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 (§ 158). 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 cor-
rect knowledge in every respect -^dth regard to it, and to many
other new and striking features in the physical geography of the sea.

184. No part of the world affords a more difficult or dangerous

GJJLF STREAM, CLIMATES, AND COMMERCE. 67

navigation than the approaches of the North American coast in
Using the Gulf wintcr. Before the warmth of the Gulf Stream was
Stream iu wiuter. Jjnown, R vojago at this scason from Em'ope to New
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 fi'e-
quently 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 frosted 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 disappears 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 there 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-Vv'est ;
but each time that he is driven off from the contest, he comes forth
from this stream, like the ancient son of Neptune, stronger and
stronger, until after many days, his freshened strength prevails,
and he at last triumphs, and enters his haven in safety, though in
this contest he sometimes falls to rise no more, for it is terrible.
Many ships annually foimder 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 dovm. 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. Nevertheless, the presence of the warm waters of the Gulf
p.uTiTiin- south to Stream, with their summer heat in mid-winter, oif
spend the winter, ^j^g sliores of Ncw England, is a great boon to navi-
gation. At this season of the year especially, the number of
wrecks and the loss of life along the Atlantic sea-front are fright-
ful. 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 conjectm-e. Suffice
it to say, that before their temperature was known, vessels thus
distressed knew of no place of reftige short of the West Indies ;
and the newspapers of that day — Erankhn's Pennsylvania Gazette

f2

68 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

among them — inform us that it was no uncommon occurrence for
vessels bound for the Capes of the Delaware in winter to be blown off
and to go to the West Indies, and there wait for the return of spring
before they would attempt another approach to this part of the coast.

186. Accordingly, Dr. Franklin's discovery with regard to the
Thermal navigaiioii. Gulf Stream tcmpcrature was looked upon as one
of great importance, not only on accoimt of its affording 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 20,000/., which had been offered, and
partly paid, by the British government, to Harrison, the chro-
nometer 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 ther-
mometer, would enable the mariner to judge with great certainty,
and in the worst of weather, as to his position. Jonathan Wil-
liams afterwards, in speaking of the importance which the thermal
use of these warm 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. When his work on Thermometrical Navigation appeared,
Commodore Truxton. Commodoro Truxtou wroto to him : " Your pub-
lication will be of use to navigation by rendering sea voyages secure
far beyond what even you yourself will immediately 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 unac-
quainted with astronomical observations ; * * * * these particularly
stand in need of a simple method of ascertahiing their approach to
or distance from the coast, .especially in the winter season ; for it is
then that passages are often prolonged, and ships b'own off the
coast by hard westerly winds, and vessels get into the Gulf Strerm
without its being known ; on which account they are often hove to

GULF STREAM, CLIMATES, AND COMMERCE.

69

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

188. Though Dr. Franklin's discoveiy was made in 1775, yet.
The disa.veryjjnhe for political reasous, it was not generally made
the Gulf stream fui- ImowTL till 1790. Its immediate effect in navigation
soutilerrc.Smerce!' was to make tho ports of the Northern States as
accessible in mnter as in summer. What agency this circumstance
had in the dechne of the direct trade of the south, which followed
this discoveiy, would be, at least to the political economist, a sub-
ject 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 coin-
cidence, let others judge.

189. In 1769 the commerce of the two Carolinas equalled that
Statistics. of all the New England States together ; it was

more than double that of New York, and exceeded that of Pennsyl-
vania by one thiixl.* In 1792, the exports from New York

* From M'Phersons Annals of Commerce. — Exports and Imports in 1769, valued
in Sterling Money.

I EXPORl'S.

To Great Britain.

South of Europe.

"West Indies.

Afiicii.

1 Total.

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

142,775 12
113.382 8
28,112 6

405,014 13

d.
9

8
9

1

£ s. d.
81,173 16 2

50,885 13 0
203,702 11 11

76,119 12 10

£ s. d.

308,427 9 6
66.324 17 5
178,331 7 8

87,758 19 3

£ s.

17,713 0

1,313 2

560 9

691 12

d.
9
6
9

1

£ s. d.
550,089 19 2
231,9(6 1 7
410,756 16 1

569,584 17 3

IMPORTS.

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

223,695 11

75,930 19

204.979 17

327,084 8

6

7
4

6

25,405 17 9
14,927 7 0
14,249 8 4

7,C99 5 10

314.749 14 5
897,420 4 0
180,591 12 4

76,269 17 11

180 0
697 10

137,620 10

0
0

9

564,034 3 3
188.976 1 3
399,830 18 0

535,714 2 a

70 PHYSICAL GEOaEAPHY OF THE SEA, AND ITS BIETEOEOLOGY.

amounted in value to two millions and a half; from Pennsylvania,
to 53,820,000; and from Charleston alone, to ,s'3,834,00d. But
in 1795 — by which time the Gulf Stream began to be as well un-
derstood by navigators as it now is, and the average passages from
Europe to the north v>^ere shortened nearly one half, while those to
the south remained about the same — the customs at Philadelphia
alone amomited to 52,941,000,* or more than one half of those
collected in all the states together.

190. Nor did the effect of the doctor's discovery end here.
The shortening of Boforc it was made, the Gulf Stream was altogether
voyages. insidious in its effects. By it, vessels w^ere often

drifted many miles out of their com'se without knowing 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 naviga-
tors 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
Foiger to Dr. Franklin. The discovery, therefore, of its high tem-
perature assured the navigator of the presence of a current of sui'-
prising velocity, and which, novv^ turned to certain account, would
hasten, as it had retarded his voyage in a w^onderful degree. Such,
at the present day, is the degree of perfection to which nautical
tables and instruments Iiave been brought, that, the navigator may
now detect, and with great certainty, every cmTent that thwarts his
way. He makes great use of them. General Sabine, in his

*

Value of Exports in Dollars}

1791.

1792.

17:3.

1794.

1735.

1796.

llassaclinsetts .
New York . .
Pfimsj'lvat.ia .
South Carolina .

2,519,651
2,5(;'5,465
3, 436, TOO
2,693,000

2,8-^8,104
2,535,790
3,820,000
2,428,000

3,755,^47
2.9.S2 370
0,958,000
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

9,9:9,345
12,208,027
17,513,866

7,620,000

Duties on Imports in Dollars.

MasFachusetts
New York .
Pennsylvania
South Carolina

1791.

1,0(6,000

1,334,000

],1(;6,000

523,000

1792.

723,000
1,173.000
1,100,000

359,000

1793. I 1794.

1,044,000

1,204,(100

1,.S23,000

360,000

1,121,000

1,878,000

1,498,000

661,000

1795.

1,520,000

2,02-<.000

2,.'',00,000

722,000

1796.

1833.

1,4 60,000

2.187.000

2,0.j(l,000

60,000

3 ('55,000

10,713,000

2,207,000

389,000

1 Doc. No. 330, H. R., 2nd Sf^ssiun, 25th Congress. Some of its statements do not agree with thos
-taken fi-om M'Pherson, and previously quoted.

GULF STEEAM, CLIMATES, AND COMSIEKCE. 71

passage, souig ^'ears ago, from Sierra Leone to Nevv York, was
diifted one tlionsand six linndred miles of liis way by the force ot
cuiTents alone; and, since tlie application of the thermometer to
the Gulf Stream, the average passage fi^om England has been
reduced fi'om upwards of eight weeks to a little more than four.
Some political economists of Ameiica 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 thinlv these statements
and figm-es 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 — remo^dng it from its posi-
tion as a half-way house, and placing it in the category of an out-
side station.

191. The plan of om- work takes us necessarily into the air, for
The scope of these the sea dcrives from the winds some of the most
researches. striking featurcs in its physical geography ; and from

the air all of its meteorology. Without a knowledge of the ^^ands,
we can neither miderstand the navigation of the ocean, nor make
om-selves intelligently acquainted with the great highv^ays across
it. As with the land, so with, the sea ; some parts of it are as
untravelled and as unknown as the gTeat 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
Till.) is an immense waste of waters. None of the commercial
thoroughfares of the ocean lead through it ; only the adventurous
whaleman finds his vray there now and then in pm'suit of his game ;
but for all the purposes of science and navigation, it is a vast
unknown region. Now, Vv^re 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 supphes the wind vrith food for the rain which these busy
messengers convey away from the ocean to " the springs in the
valleys Vv'hich run among the hills." To the philosopher, the
places which supply the vapours are as suggestive and as interest-
ing for the instruction they afford, as the places are upon which
the vapours are showered do^Ti. Therefore, as he who studies the
physical geography of the land is expected to make himself ac-
quainted with the regions of precipitation, so he who looks into
the physical geography of the sea should search for the regions of

72 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS IVIETEOROLOGY.

evaporation, and for those springs in the ocean which supply the
reservoirs among the mountains Avith water to feed the rivers ; and,
in order to conduct this search j)roperl3^, 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 lY.

200-268. THE ATMOSPHEEE.

200. There is no employment more ennobling to man and hi»
Likened to a ma- intellect than to tracc the evidences of design and
*=^i^«' 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 atmosphere
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 smiace of the earth ; it is a sewer into
which, mth every breath we draw, we cast vast quantities of dead
animal matter ; it is a laboratory for pm-ification, in which that
matter is recompounded, and "wi'ought again into wholesome and
healthful shapes ; it is a machine for pumping up all the rivers
from the sea, and for conveying the water (§ 191) from the ocean
to their som'ces 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 sufficient 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
machine 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 constructed by an Architect
who designed it for certain purposes ; therefore the management
of it, its movements, and the performance of its offices, cannot be
left to chance. They are, we may rely upon it, guided by laws
that make all parts, functions, and movements of this machinery

THE ATMOSPHERE. 73

as obedient to order and as liarmonious as are tte planets in their
orbits.

201. Any examination into the economy of the nniverse will be
The air and t!ie sufficient to satisfy tlio wcU-balanced minds of obser-
sSrefaws!"'' ^ vant men that the laws which govern the atmo-
sphere and the laws which govern the ocean (§ 164) are 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 always 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, To one who looks abroad to contemplate the agents of
Importance of Ob- natiu-c, as ho sccs them at work upon our planet, no

serving the works . , , ^ , ,, i i 1 1 • • 1 1

of nature. cxprcssiou uttercQ OT act periormed by them is with-

out meaning. By such a one, the wind and rain, the vapour and
the cloud, the tide, the cmTent, 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
aU may be regarded as the exponent of certain physical combi-
nations, and therefore as the expression in which Nature chooses to
annoimce her own doings, or, if we please, as the language in which
she wiites 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 natm^e, every such fact is a syllable ; and it is by
patiently collecting fact after fact, and by joining together syllable
after syllable, that we may finally seek to 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. There have been examined at the Observatory more than a
Materials for this milliou of obscrvations on the force and dii'ection of
chapter. ^^le wiuds at sea.* The discussion of such a mass

of material has thrown much light upon the circulation of the

* Nautical Monograph, No. 1, 1859.

74 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS ZIETEOROLOGY.

atmospliere ; for, as in tlie ocean (§ 201), so in tlie air, there is a
regular system of circulation.

204. Before we proceed to describe this system, let us point out
Different belts of ^^6 principal belts or bands of wind that actual ob-
^i^'i'^- servation has sho^vn 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 cahns nearly at right angles, and in the follow-
ing 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 du-ection 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 -^inds, a
region in which winds from the south-west and winds fi'om the
north-west contend for the mastery, and with nearly equal -persist-
ency. (3.) Between 35^ and 30^, she finds herself in a region of
variable winds and calms ; the winds blowing all around the com-
pass, and averaging about three months fi'om each quarter during
the year. Om' fancied ship is now in the " horse-latitudes."
Hitherto winds with westing in them have been most prevalent ;
but, crossing the cahn belt of Cancer, she reaches latitudes where
winds vfith 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 cahn belt, w^hich, like all the other v>' ind-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, w^here, as in that of Cancer (3), she again
finds herself in a region of shifting ^inds, 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-vfesfc winds contend with equal power for the mas-
tery. (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 om' observations at sea extend towards the
south pole.

Such are the most striking movements of the winds at the sur-
face of the sea. But, in order to treat of the general system of

THE ATMOSPHERE. 75

atmosplierical cii'ciilation, we sliould consider where those agents
reside which impart to that system its d^Tiamical force. They e\i-
dently reside near the equator on one side, and about the poles on
the other. Therefore, if, instead of confining our attention to the
winds at the smface, and then' relative prevalence from each one of
the four quarters, we direct" our attention to the upper and lower
cm-rents, and to the ^e;iera/ movements lach and forth betvv^een the
equator and the poles, we shall be enabled the better to understand
the general movements of this grand machine.

,205. Thus treating the subject, obseiTations show that from the
The trade-wiDd belts. parallel of *about 30^ or 35^ north and south to the
equator, we have, extending entkely around the earth, two zones
of perpetual v/inds, 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 t^^o main cmTents of air are constantly flowing
from the poles toward the equator, we are safe in assuming that
the au" 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
polar 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. This retm^n cm-rent, therefore, must be in the upper re-
The return current, gions of the atmosphero, at Icast until it passes over
those parallels between w^hich the trade-winds are usually blowing
on the sm-face. The return cm-rent must also move in the direc-
tion opposite to that wind the place of which it is intended to sup-
ply. These dii^ect and counter cmTents are also made to move in
a sort of spiral or loxodronic cmwe, turning to the WTst as they go
from the poles to the equator, and in the opposite direction as they
move from the equator towards the poles. This tm^ning is caused
by the rotation of the earth on its axis.

207. The earth, we know, moves from west to east. Now if
Effect of diurnal ro- ^e imao^iue a particle of atmosphere at the north

tation on the course -, ,o l , . i ■*■ , •

of the trade-winds, polc, wbere it IS at Tost, to DO put m motion m a
straight hne towards the equator, we can easily see how this par-
ticle of au', coming fi'om the very axis of dim'nal rotation, where
it did not partake of the dimmal motion of" the earth would, in

76 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

consequence of its vis inertia, find, as it travels south, the earth
shppiug 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 w^ords, 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, tm^n the globe on its axis
from west to east, to represent the dim^nal 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 started ; 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 north-
ward 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 inertise, be going towards the east faster than
the earth. It would therefore appear to be blowing from 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. Such is the process which is actually going on in nature ;
Two grand systems ^^d if WO take the motious of these two particles as
of currents. ^]^g ^^^ q£ ^^le motiou of all, WO shall have an illus-
tration 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 ; 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
should have, on the sm-face, 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. Let us return now to our northern particle (§ 207), and
From the Pole to follow it in a rouud froui the north pole across the
30*^-05-. equator to the south pole, and back again. Setting ofl:"
from the polar regions, this particle of air, for some reason which does
not appear, hitherto, to have been very satisfactorily explained hj

THE ATMOSPHERE. 77

philosophers, instead of travelHng (§ 208) on the surface all the
way from the pole to the equator, travels in the upper regions of
the atmosphere mitil it gets near the helt between 30^-35°. Here
it meets, also in the clouds, the hypothetical particle that is coming
from the south, and going north to take its place.

210. About this belt of 30^-35° north, then, these two particles
Thr>" horse lati- prcss agaiust each other with the whole amount of
ludjs." tjjgjj. motive power, and produce a calm and an
accumulation of atmosphere : this accumulation is sufficient to
balance the pressm'e of the two cm-rents from the north and south.
From under this bank of calms, which seamen call the " horse
latitudes," two sm'face cm-rents 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
consequentl}- the place of the air borne away in this manner must
be supplied, we may infer, by downward cmTents from the superin-
cumbent 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 dowTiward ; — so is
the motion of the air in this calm zone.

211. The barometer, in this calm region, stands higher than it
Th? barometer there, docs either to thc uortli 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 ; there-
fore, supposing we were untaught by observation as to direction of
the wind, reason would teach us to look for the prevailing winds on
each side of this calm belt to be from it.

212. Following our imaginary particle of air, however, from the
The equatorial calm uorth across this calm belt of Cancer, we now per-
^''^^- ceive it mo^ang 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 hypothetical particle, which,
starting from the south at the same time the other started from i\\Q
north pole, has blown as the south-east trade-mnd. 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

78 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

have been put in motion by the same power ; tbey meet Y^tb equal
force ; and, therefore, at their place of meeting, they are arrested
in their com'se. Here, therefore, there is a calm belt, as well as at
Capricorn and Cancer. Warmed now by the heat of the smi, and
of vapour in the process of condensation, 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. This imaginary particle then, having ascended to the upper
The calm bait of rogions of the atmosphcre again, travels there coun-
Capricoin. |.g^, ^q |]^q south-cast tradcs, 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) flov\^s on
towards the south pole as a surface wind from the north-west.

214. Entering the polar regions obliquely, it is pressed upon by
The polar calms and similar particlcs flowdug in oblique crn'rents across
the return current, evcij 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
v/hirled about the pole in a continued circular gale ; finally, reach-
ing 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 en-
comiters (§ 213) its fellow from the north (§ 207) ; they stop,
descend, and flow out as surface currents (§ 210), the one with
which the imagination is travelling, 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 cmTcnt comiter to the north-
east trades. Here (§ 210 and 209) it ceases to be an upper cur-
rent, but, descending (§ 210), travels on with the south-west
passage-winds towards the pole.

215. Now the course we have imagined an atom of air to take, as
n-agrnm of the illustratcd by the " diagram of the winds," (Plate I.)
'^"''''^- is this : an ascent in a place of calms about the north
pole, as at Y P ; an efllux thence as an upper current, A B C,
imtil 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

THE ATMOSPHERE. 79

meets the south-east trades, 0 0, in the equatorial calms, where it
ascends as E F, and travels as ¥ G with the upper cmTent to the
calms of Capricorn, thence as H J K, with the prevaihng 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 LMNOQESTUY.

216. The Bible frequently makes allusion to the laws of nature,
As our knowicdgre of their Operation and effects. But such allusions
Ss i'ncn>ai!ed!so^^ are oftcH SO Wrapped in the folds of the peculiar and
of the'nibi??m-^^ graceful drapery with which its language is occa-
proved. sioually clothed, that the meaning, though peeping
out from its thin covering all the while, yet hes in some sense
concealed, until the lights and revelations of science are thrown
upon it ; then it bursts out and strikes us with exquisite force and
beauty. As om: 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 vv^orld ;" 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 question, have thrown so much light upon
it as to show that, if ever it be answered by man, he must consult
the science of astronomy. It has been recently 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 influences ?"
And as for the general system of atmospherical circulation which I
have been so long endeavom'ing 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
retm^neth again according to his circuits." — Eccl. i. 6.

217. Of course, as the surface winds, H J K, and T U Y,
Fiongiiinc; off from approach the polcs, there must be a sloughing off, —
the counter trades, jf J ^^^ ^^ allowcd the cxprcssion,— 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 cm-rent must either extend much higher up, and blow witli

80 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

greater rapidity, or else a part of it must be sloiighed off above,
and so turn back before reaching the cahns about the poles. The
latter is probably the case. Such was the conjecture. Subsequent
investigations* have established its correctness, and in this way :
they show that the south-east trade-winds, as in the Atlantic, blow,
on the average, duiing 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 5^ S. Here
between 5^ and 10^ S. they blow on the average for 329 out of the
365 days.

218. Now the question may be asked, Where do the supplies
pUeVaie'^suuihS't which furnish air for these winds for 329 days come
trade-wind in the from ? Thc " trades " could not convey this fresh
cross the band 253. supply of air across the parallel of 25"^ S. diuring
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 across 25°. (2.) Because the girdle of the earth near the equa-
tor is 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 cir-
cumference. 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 trade-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 aU seas, we may, for the
sake of illustration, liken this belt of winds which encircles 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. Now, dividing the winds into only two classes, as winds
Winds with north- with %OTtliing and winds with southing in them,
southnVin'the'm^ actual obscrvatious show, taking the world around,
contrasted. ^-^^^^^ wiuds liaviug southiug in them blow into the
southern or smaller end of this cone for 209 days annually, and

* Nautical Monographs, No. 1, Observatory, Washington, October, 185D.

THE ATMOSPHERE. 81

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 northing in them
are blowing in at the big end, or out at the little end of i\\Q imagi-
nary 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 illus-
tration, that these winds with northing and these winds with
southing move equal volumes of air in equal times, we may sub-
tract 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 oiu* 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 quantity that is to pass through, or go
from the parallel of 25^ to 5°, the volume expressed by the trans-
porting 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. The south-east trade- winds, as they cross the parallel of
South-east trade- 5^ aud como out of this belt, appear to be strongert
Tht^equatomT ^"^^^ thau they are when they enter it. But assuming
"™'^- the velocity at each parallel to be the same, we

have (§ 219) just three times as much air with so^^^Awi^ 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

* Naniioal Monographs, No. 1, " The Winds of the Sea," Observatory, Wash-
ington, 1859.

t The force of the trade-winds, as determined by the average speed of 2235
vessels sailing through them, is greater between 5<^ and 10'-^ S. than it is between
25' and 30^ ^.—Maury's Sailing Directions, 1S59.

G

82 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

10^ S : the annual deficiency of air liere would be tlie volume re-
quired to supply the trades for 151 days (214 — 63 = 151).

221. The average speed which vessels make in sailing through
specd^of vessels ^ the tradc-wiuds in difierent parts of the ^Y0^1d has
winds" ''^ ' been laboriously investigated at the National Ob-
servatory,* 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 horn*, and 5.7 between 25" and 30^.

222. All these facts being weighed, they indicate that the
The question, Whence volumc of air whicli investigations show that the
trad2wi5?ds suppfied south-oast trado-winds of the w^orld annually v\^aft
with air? answered, ^cross the parallels of 10^-5'' S. in 285t days— for
that is their average duration for all oceans taken together — is at
least twice as great as the volume which they 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 ex-
cess ?" the reply is, it can only come from above, and m this way,
viz. : the south-east trade-winds, as they rush fi'om 25° S. towards
the equator, act upon the upper air like an under-tow. Crossing, as
they approach the equator, parallels of larger and larger circumfe-
rence, these winds draw down and tm^n back from the counter current
above air enough to supply imhidum to larger and larger, and to
stronger and stronger currents of sm-face-wind.

223. The air which the trade-winds pour into the equatorial
Whither it goes, 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 m below. They bring it from towards tlie poles
— back, therefore, towards the poles the upper cmTents must carry
it. On their jom-ney they cross parallel after parallel, each smaller
than the other in circumference. There is, therefore, a constant
tendency vdth the air that these upper currents carry polarward
to be crowded out, so to speak — to slough off and turn back.
Thus the upper cmTcnt 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. This upper air, having supplied the equatorial cloud-ring
}fow is it drawn (§ 514) with vapouT foT its clouds, and with moisture
down from above. £qj. ]^ rains, flows off pokrward as comparatively

* See "Average Force of the Trade -winds," p. 857, vol. ii., Sth ed., Maury '3
Sailing^ Directions, 1859.

t Nautical Monographs, Plate I., No. 1, "The winds at sea."

THE ATMOSPHEEE. 83

dry air. The dry est air is the heaviest. This dry and heavy air is
therefore the air most hkely 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 cm^ved arrows,
f g and/' g , r s and r s, are intended to represent, in the " dia-
gram of the wTuds " (Plate I.), this sloughing off and tmning back
of ah^ from the upper currents to the trade-mnds below.

225. According to investigations which are stated at length in
veiocitj'ofsoutii- Maury's Sailing Directions, on his Wind and Cur-
s?^L?r than north- TBut Charts, and in the Monographs of the Washing-
east trade-wind^. j^Qj^ Observatory, the average strength and annual
duration of the south-east trade-winds of the Atlantic may be thus
stated for every band or belt of 5° of latitude in breadth, fr-om 30°
to the equator. For the band between the parallels of —

Ann. duration. Force. No. ofobs.

30^ and 25^ S 124 davs. 5-6 miles.* 19,817

25^ and 20^ 157 „' 5.7 „ 20,762

20^ and 15^ 244 „ 5.9 „ 17,844

15^ and 103 295 „ 6.3 „ 14,422

lO^andS^ 329 „ 6.1 „ 13,714

S^andO^ 314 „ 6.0 „ 15,463

It thus appears 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. On the polar side of 35°-40°, and in the counter trades
The air sloughed off (^ 204 [7]), a different process of slou2;hinoj off and

irom the counter 2" . K -JV . . "•■ tt n • t ii

trades, moist air. tummg bacK IS gouig ou. ±1016 the wmcis are blow-
ing toivards the poles ; they are going from parallels of large to
parallels of smaller circumference, while the upper retm^n current is
doing the reverse ; it is widening out with the increasing circumfe-
rence of parallels, and creating room for more air, while the narrow-
ing cun-ent below is crowding out and sloughing off air for its winds.

227. In the other case (§ 224), it was the heavy dry air that
The air sloughed off ^yas sloughcd off to joiu the winds below. In this
current dry. ^ ' casc it is the moist v.iid. lightest air that is crowded
out to join the current above.

228. This is particularly the case in the southern hemisphere.
The meteorological where, entirely around the globe between the paral-
ingSnms oSs't lels of 40^ and G0° or 65^, all, or nearly aU, is water.
'*^^- In this great austral band the winds are in contact

* Distance per hour that vesseb average while sailing through it,

g2

84 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEaROLOGY.

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 liorizontal flow of air with tho
winds, numerous little ascending columns. As these columns of
air and vapour go up, the superincumbent j^ressm-e decreases, the
air expands and cools, causing precipitation or condensation of the
vapour. The heat that is set free dming this process expands the
air still fm-ther, 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, and thus we have another turning back, and a constant
mingling. The curved arrows, h j h and Ji f Jc, are intended, on
the " diagram of the Avinds " (Plate I.), to represent this rising
up from the counter trades and turnmg back with the upper
current.

229. Let us imagine the air to be visible, that we could see these
Supposing the air different strata of winds, and the air as it is sloughed
SI' would ITprr.'' off from one stratum to join the other. We can only
sented between the \[^QYi the spectaclo that would be presented between

upper and lower cur- -^1-11 l j. ^ i? li • J i.

rents. the uppor and the lower stratum oi these wmds to

the combing of a succession of long waves as they come rolhng 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. If the ordinances of natm-e requu'e a constant circulation
The importance of and coutinual mixiug up of the water in the sea^
StioT^"^"*^^ ^'^'^'^' that it become not stagnant, and that it may be kept
in a wholesome state for its inhabitants, and subserve properly the
various offices requfred 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 ; stagnation 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 cir-
culation and intermingling of its ingredients are required of it.
Personal experience teaches us this, as is manifest in the recognized
necessity of ventilation in oiu" buildings — the wholesome influences
of fresh air, and the noxious qualities of "an atmosphere that has
in circulation." Hence, continual mixing up of particles in the

THE ATMOSPHERE. . 85'

utmospiiere being required of the winds in their circuits, is it
possible for the human mind to conceive of the appointment of
"cii'cuits" for them (§ 216) which are so admirably designed and
exquisitely adapted to the pm'pose as are those which this view
suggests ?

231. As a physical necessity, the vertical circulation of the air
Its verucai move- sccms to bc uo Icss important than its horizontal
<iuced. 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 in arcs of great
cii'cles, and not in small ones * — creates a vertical circulation either
by dragging down air from the upper regions (§ 224), or by slough-
ing it off and forcing it up fi'om the lower (§ 228), according as the
wind is approaching the pole or the equator.

232. Indeed the point may be well made whether the horizontal
SnS4mH^t'S?S;circlllation of 'the air be not dependent upon and a
air consequents of, consequeut of its Vertical circulation; — so nearly

And dependent upon n • T a! J. f ' lX. • i ±- *^

each other. alliecL are the two motions m then- relations as cause

and effect. Upward and downward movements in fluids are conse-
quent upon each other, and they involve lateral movements. The
sea, mth 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 pro-
duces ascending columns in the atmos2}here. 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 p(rce'ved.
But when the ascending vapour is condensed, and its latent heat
liberated and set fi'ee in the upper air, we often have the most
terrific storms.

* The tendency of all bodies, wlien pnt in motion on the surface of the eartli,
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 tJie motion is hori-
zontal, is an arc of a great circle. If we imagine a partial vacuum to be formed at
the north pole, wo can readily enougli perceive that the wind for 5^, 10°, 20° of
polar distance, all around, would tend to rush nortli, and strive to get there along
the meridians— arcs of great circles. This would be the case whether the earth
be supposed to be Avith 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 it, and the air all around would, in rush-
ing into the vacuum, seek to reach it by these great circles. Furce may turu it
aside, but such is the tendency (§ 120j.

Ob PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS IIETEOEOLOGY.

233. Now suppose the surface from wliicli this vapour rises, or
Cold belts. on which it is condensed, be sufficiently large to

produce a rush of wind fr'om afar ; suppose it, moreover, to be an
oblong lying east and west somewhere, for example, in the tem-
perate zone of the northern hemisphere. The wind that comes
rushing 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 ; while that
fr'om the northern side, moving in the opposite direction, is, like
the trade-winds (§ 223), bringing down air from above.

234. By the motion of the clouds upper cmTents of wind are
-^ih"hMrmb^^'^"% ^^scerned in the sky. They are an-anged in layers
offices. ' 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 cur-
rents 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 machinery. We have seen (§ 230) some of
thefr 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), di-awinoj down
and sucking in air from above, or, hke the counter trades (§ 226),
crowding out and forcing it off into the upper cuiTents.

235. This tendency to move in great circles is checked by the
Tendency of air forcos of diiUTnal rotatiou, or by the pressure of the
to m(\^e1n ui'rpLme VTind whou it blows towards a common centre, as in
of a great circle. j^ cyclonc. lu uo caso is it entirely overcome in its
tendency, but in all it is diverted from the great circle path and
forced to take up its line of march either in spfrals about a point
on the sm^face of the earth, or in loxodromics about its axis. In
either case the pushing up or pulling down of the combing, cm'd-
ling air fr'om layer to layer is going on.

236. Thus the laws of motion, the force of gravity, and the
The results upon its fiorm'e of tlio caith all uuitc iu requirinsf every wind

circulation ot ihis .^ , in • ,^ i o • i- n '' p

tendency. that blows Cither to lOTce au' u]) trom tiie suriace

into the regions above, or to draw it down to the earth from the

THE ATMOSPHERE. 87'

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 hurricane to stir up and agitate, to
mix and mingle the whole in one homogeneous mass. By this
perpetual stirring up, this continual agitation, motion, mixing, and
circulation, the airy covering of the globe is kept in that state
which the well-being of the organic world requires. Every breath
we draw, every fire we kindle, every 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 sur-
rounding air. Diligent, therefore, in their offices must the agents
be which have been appointed to maintain the chemical status of
the atmosphere, to presence its proportions, to adjust its ingredi-
ents, and to keep them in that state of admixtm'e best calculated to
fit it for its pur[)oses.

237. Several years ago the French Academy sent out bottles
Experiments by the ^iid caused spccimcns of air from various parts of
Frei^ch Academy. j^]^q ^^orld to be collectcd and brought home to be
analyzed. The nicest tests Vv^hich the most skilful chemists could
apply were incapable of detecting any, the slightest, difference as
to ingredients m the specimens from either side of the equator ;
so thorough in the performance of then' office are these agents.
Nevertheless, there are a great many more demands on the atmo-
sphere by the organic world for loahuhiin in one hemisphere
than in the other ; and consequently a great many more inequali-
ties 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 om-
crops in summer, with om- 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, notmthstanding the compensations and adjust-
ments between the two kingdoms of the organic world, there are
almost in every neighbourhood causes at work which would produce
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 pro-
vided for its perfect working. The study of its mechanism is

88 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOFwOLOGY.

good and wholesome in its influences, and the contemplation of
it well calculated to excite in the bosom of right-minded philoso-
phers the deepest and best of emotions.

238. Upon the proper adjustments of the djaiamical forces
How supplies of fresh -which keep up thoso ccascless movements the life of

air are brought down . ^. ^ -, -, t/- j^i • ji j. • i xi n

from the upper sky. orgauic naturc depeuds. 11 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 au' 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 do^\ii from the
pui'e blue sky fi'esh supplies of life-giving air wherever it is
wanted, and to catch up li^om the earth wherever it may be found,
that which has become stale — to force it up, there to be deflagrated
among the clouds, pmified and. renovated by processes known
only to Him whose ministers they are. The slightest change
in the puiity of the atmosphere, though it may be too slight for
recognition 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.
No chemical tests are sensitive enough to tell us what those
changes are, but experience has taught us the necessity of ventila-
tion in om' buildings, of circulation through om* groves. The
cry in cities for fresh air from the mountains or the sea, reminds
us continually of the life-giving virtues of circulation. Experience
teaches that all air when pent up and deprived of circulation be-
comes impm-e and poisonous.

239. How minute, then, pervading, and general, benignant,
Beautiful and benign sm'c, and pcrfcct uiust bc that system of circulation
arrangements. which iuvosts the atmosplierc and makes " the whole
world kin ?" In the system of vertical circulation which I have
been endeavoming to describe, we see, as in a figure, the lither sky
filled with crystal vessels full of life-giving air continually ascend-
ing and descending between the bottom and the top of the atmo-
spherical ocean ; these buckets are let down by invisible hands fi'om
above, and, as they are taken up again, they carry off from the
smface, to be pmified in the laboratory of the skies, phials of
mephitic vapom^s and noxious gases, Avith the dank and deadly air
i)f marshes, ponds, and rivers.

240. Whenever, by study and research, we succeed in gaining

THE ATMOSPHERE. 89

an insight, though never so dim, into any one of the offices for
Their influences up- which any particular part of the physical machinery
on tiie mind. ^f Qur planet was designed by the Great Archi-

tect, the mind is enriched with the conviction that it has com-
prehended a thought that was entertained at the creation. For
this reason the beautiful compensations which philosophers have
discovered in terrestrial arrangements are som'ces of never-failing
wonder and delight. How often have we been called on to admire
the benign provision by which fi^esh water is so constituted
that it expands from a certain temperature do^^^l to freezing 1
We recognize in the formation of ice on the top instead of at the
bottom of freezing water, an arrangement which subserves, in
manifold w^ays, wise and beneficent purposes. So, too, when w^e
discern in the upper sky (§ 234) currents of wind arranged in
strata one above the other, and running hither and thither in dif-
ferent dnections, 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 dovm fresh air and taking up foul, they assist in main-
taining the world in that state in which it was made and for which
it is designed — " a habitation fit for man ?"

2-1:1. The phenomena of cold and warm *' spells" are often
The effect of down- observcd in the United States, and I suppose in other
producing cold.' 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 degTees
to the north or to the south of them. The conditions requii^ed for one
of these cold " snaps " in America appear to be a north or north-west
wind of considerable breadth from west to east. As it goes to the
south, its tendency is, if it reach high enough, to bring do^^Ti 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 wanner vreather both
to the north and the south of it. AVhile I ^mte the thermometer
is —4^ in Mississippi, lat. 32°, and they are having colder weather
there than we have either in Washington or Cinciimati, 7° farther
to the north.

242. The winter "northers " of Texas sometimes bring down the
The winter northers cold air there mtli terrific efiect. These bitter cold
^^ ^''''''''- Vvdnds are very severe at Kueces, in the coast countiy,

90 THYSICAL GEOaEAPHY OF THE SEA, AZW ITS MSTEOr.OLOGY.

or the soutli-west comer of Texas bordering tlie G-iilf 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 kno'vvn in
northern Texas goes to show that the cold they bring is not-
translated by the smiace winds from the north.

243. A correspondent in Nueces, lat. 27^ 36' N.y long. 97^ 27'
Their severe cold. ^,Y.^ bas described thoso 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 fi'om the north ; the
wind is heard seyenil minutes before it is felt ; the thermometer
begins to fall ; the cold norther bm^sts upon the people, bringing
the temperatm'e down to 28^, and sometimes 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 moistm-e therefrom, still retain enough
of strength to make themselves terrible to mariners — they are the
far-famed northers of Vera Cruz.

244. The temperatm^e of the atmosphere at the height of three or
"Cold Snaps." four milcs is Variable — observations and balloonists

tell us so. Air may be brought below the normal temperatm-e
due the height at which it may be, by radiation and other
processes. It may also be raised above that normal temperature
hj 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 condition, the people
of the district upon which it descends find themselves in a " cold
snap " or "hot term," as the case may be.

245. That our climates, especially the continental, are affected
j\nemorrieters to de- by, and that many of the changes in the weather
Sn'oTthe wS^d "'^" arc due to, the vertical circulation of the atmosphere
'^'^°^'^'^- seems clear.! We have other evidence besides that
of induction (§ 224) as to upward and do^vnward movements

* " Two men," says T.Ir. M. A. Taylor, in a letter dated January 11th, 1S69, 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 Avhen the norther is
coming, and make tlieir way from the open prairies to timber and other shelter,
startin'j; often on a run when the heat is not oppressive. Tiiis is when the change
is to bo su<lden and violent. Many cattle, horses, and sheep are frozen to death
at such times."

t Vide Chapter XXI.

THE ATSIOSPHEKE. 91

amongst the particles of aii\ In violent winds especially are these
upward and downward ciuTents made obvious by the leathers,
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. Y/e may seek in the vertical chculation of the atmosphere
The hot xMnds of for an explanation in part, not only of hot and cold
the Andes. tcrms, but iu a measm'e 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 v/inds
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. To explain one of these sudden and severe "hot spells," let
Certain "Hot Spells " i^s supposo tlio neighbouring atmosphcre to be weU
explained. loaded T\dth moisturo at the tem;^» era tore 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
hberated heat may be sufficient to raise it to 20°, and so
prevent the temperatm^e from going below that reading. Thus
this air is at least 20^ above* the normal temperature 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. Whenever and wherever air in this condition descends to the
Reservoirs in the surfacc, there will bc a longer or shorter period of
*^^" excessively warm weather. t Thus we infer the

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

t " Heated Wind Storm. — A heated wind storm passed over a portion of

92 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

existence in the upper air of reservoirs for the lieat as well as
of chambers for the cold.

249. The streaks of warm air on the Andes (§ 246) derive their
The warm winds of warmth in all probability from the liberated heat of
xhl trude^vuidL ^ tho trade-wind vapom's as they are condensed into
snow-storms.

250. Spells of wet and dry, as well as " terms " of hot and cold,
dormant powers of woathcr sometimos pass over portions of the country
meteorology. ^" like great waves. They occupy hours, or days, or weeks
in their march. The magnetic telegraph 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,* 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 foreknow-
ledge. We could foretell the coming of storms also.

251. We now see the general course of the "wind in his cir-
The wind in his cir- cuits," as WO seo the general course of the water in
*="i^- a river. There are many abrading sm'faces, 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-cmTents ; so with the atmosphere and
the variable winds which we find here in this latitude. Have I not,
therefore, very good grounds for the opinion (§ 200) that the " wind
in his circuits," though apparently to us never so wayward, is as
obedient to law and as subservient to order as were the morning
stars when fii'st they " sang together ?"

Kansas on the 7tli 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 119p, and
continued so for about an hour, and then began gradually to decrease. The 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 miles), were overtaken and perished. TJiere were
three others at Humboldt who were caught out with teams, wliich perislied, the
men alone surviving, 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 conjectm-es as to its cause are given, but all unsatisfactory."
— 'Newspajjer.

* Arrangements for so using it have already been made in Holland, France,
and England, and we liope to see them extended ere long to all otlier countries,
and wiicrever lines of telegraph may go. Tliough the plan only went into
operation in England, in Sept. 1860, Admiral Fitzroy informs me, it is already
rich with the promise of practical results the most valuable and important.
London, Nov. 14, 18G0.

THE ATMOSPHERE. 93

252. There are at least two forces concerned in drmng the
Forces T^hich propel wind throiigh its circuits. We have seen (§ 207)
the wiiKi. 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 soui'ce whence they derive their northing and
their southing. Philosophers foi-merly held that the trade-winds
are dra^Ti 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 the south ; and as the solar 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. But the direct rays of the sun, instead of being most
Effect of the direct powcrful upoH the air at the equator, is most

heat of the sun upon ■•■ r» i i j i • i • i i • p . i

the trade-winds. powertul whcre the sun is vertical; and if the
trade-winds were produced by direct heat alone ffom the sun,
the place of meeting would follow the sun in declination much
more regularly than it does. But, instead of so follo^\ang the sun,
tiie 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 (jV) than it is when she is
in aphelion, as in our midsummer. For this reason the southern
summer is really hotter than the northern ; yet, notwith-
standing 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.

254. By examining the log-books of vessels while sailing
The two sj-stems ..f tln'ough tlio uorth-cast and south-east trade-wind
b'Jthi^'force^Xr^- bclts, and Comparing their rate of sailing, it has
tion. and stability. -^^^^ asccrtaincd that ships sail faster with the
south-east than they do with the north-east trade-winds, and that

* " The Winds of the Sea," Maury's Nautical Monograplis, No. 1.

94 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS IIETEOEOLOGY.

the south-east blow more clays 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-wdnds are very
unequal both as to force and stabiHty, the south-east surpassing in
each case.

255. Moreover, the hottest place within the trade-wind regions
Effects of heat and IS not at the cquator I it is where these two winds
vapour. j^qqI- ^^ 253). Lieutenant Warley has collated fi^om

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
Ibllowing averages : In the north-east trades, 5° north of the north
edge of the equatorial calm belt, say in latitude 14° N., air 78^.69.
North edge cahn 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 extreme 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°.
According to the experiments of Gay-Lussac and Dalton, the dila-
tation of atmospheric air due a change of 12° in temperature is 2J-
per cent. ; that is, a column of atmosphere 100 feet high will, after
its temperature has been raised 12°, be 102-J feet high. However,
only about one thhd 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
temperatm'e of sea and air by conduction. The ah at the surface
of the earth receives most heat directly from ih.Q sun; as you

* See Maury's Wind and Current Charts, vol. ii., 8th edition, Sailing Directions.

THE ATMOSPHEPiE. 95

ascend, it receives less and less, and the consequent temperature
becomes more and more uniibrm ; so that the height within the
tropics to which the direct rays of the sun is not, as reason sug-
gests, and as the snow-lines of Chimborazo and other mountains
show, very great or very variable.

256. Moreover, daily observations show most conclusively that
Hurricanes not due tlic strouo; winds and the £?reat winds, the hurricanes

to direct heat of the -, ^ -, , • r- jit j_i • p

sun. and tornacioes, do not arise from the direct heat of

the sun, for they do not come in the hottest weather or in the
clearest sides. 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 simshinej — 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 v/hich it makes by
playing upon the w^ater.

257. From these facts it is made obvious that other agents be-
The influence of sidcs the diroct aiid reflected heat of the sun are

otlier agents re- -, . -, . n , i • ^ t ■

quired. coucemed m producing the trade-winds. Let us

inquire into the nature of these agents.

258. They are to be found in the unequal distribution of land
AHiere found, aud sca, aiid raiiis, as between the two hemispheres.

They derive their power from heat, it is true, but it is chiefly from
the latent heat of vapour wdiich is set free during the processes of
precipitation. The vapour itself, as it rises from the sea, is (§ 232)
no feeble agentj in the production of wind, nor is it inconsiderable
-in its influence upon the trade-winds.

259. Let us consider this influence. A cubic foot of water,
vapr.ur as one of the bein.<^ couvcrted into vapour, occupies the space of

causes of the trade- -.Qf.;? -. • o , c m- • l T i / i.i

winds. ibUU cubic icet.§ 1ms vapour is also lighter than

the 1800 cubic feet of air which it displaces. Thus, if the dis-

* Gales of the Atlantic, Observatory, Y/asliington, 185G.

t Storm and Kaiu Charts.

X I am sustained in this view by a recent paper on " tlie forces that produce
the great currents of the air, and of the ocean," recentl) read before the Eoyal
Society by Thomas Hopkins.

§ Black and Watt's Experiments on Heat.

96 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS lilETEOEOLOGY.

placed air weigh 1000 ounces, the vapour will weigh 623 ; conse-
quently, 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 dming 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 perhfips not so strong as the trades, yet owing their existence,
nevertheless, merely to the formation of aqueous vapour. But this
is not all.

260. " During the conversion of solids into liquids, or of liquids
Black's law. into vapom^s, heat is absorbed, which is again given

out on their recondensation."* In the process of converting one
measure of water into vapom-, heat enough is absorbed — i. e., ren-
dered latent, without raising the temperatm^e of the vapour in the
least — to raise the temperature of 1000 such measm-es 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, as into hail or snow, the latent heat
rendered sensible during the process of congelation would be
sufficient to raise the temperatm-e of 140 additional measm-es of
water 1°.

261. In this heat rendered latent by the processes of evapora-
Tbeiatentheat trans- tion, and transported hither and thither by the
ported ill vapour. wiuds, rcsidcs the chief source of i\\Q dpiamical
power which gives them motion. In some aspects vapom' is to the
winds what fuel is to the steam-engine : they cany it to the equa-
torial calm belt ; there it rises, entangling the air, and carrjdng 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 vapoiu: is condensed,
the latent heat of which is thus liberated ; this raises the tempera-
tiu-e of the upper air, causing it to be rarefied and to ascend still
higher. This increased rarefaction calls for increased velocity on
the part of the inpom-ing trade-winds below.

262. Thus the vapours uniting with the direct solar ray would,
* Black's law. It is an important one, and should be ieni?mb( red.

THE ATMOSPHERE. 97

were there no counteracting influences, cause the north-east and
The effect of the south-cast tradc-wiuds to rush in with equal force.
tSde-wSJ! * 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
sufficient 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. We have, in this difference as to strength and stability
croS'^rtthe^ (^ ^^^^ between the north-east and south-east trade -
calm belts. wiuds, another link in the chain of faats tending to
show that there is a crossing of the mnds at the calm belts. The
greatest amount of evaporation takes place in the southern hemi-
sphere, which is knoAMi by the simple circumstance that there is
BO 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 precipitation 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 vapour is precipitated, thus assisting to make
the northern warmer than the southern hemisphere. In those
northern latitudes where the precipitation of vapour and libera-
tion of heat take place, aerial rarefaction is produced, and the air
in the calm belt of Cancer, which is about to blow north-east
trade, is tm^ned back and called in to supply the indraught 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. On the north side of the trade- wind belt in the northern,
— ^rT^^r *™h^b ^^^ ^^ ^'^^ south side in the southern hemisphere,
pole in spirals. the prevailing direction of the winds is not towards
the equator, but exactly in the opposite direction. In the extra-
tropical region of each hemisphere 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
]K)les produce in the amount of heat set free, according to Black's

H

98 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

law (§ 260), a rarefaction in tlie upper regions, and an ascent of
air about tlie poles similar to that about tbe equator, with this dif-
ference however : the place of ascent over the equator is a Hne, or
band, or belt ; about the poles it is a disc. The air rushing in
from all sides gives rise to a vdnd, 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 spu^als from the south-
west.

265. If we draw a circle about this pole on a common terres-
Tiiey turn ^^^^^^^^ trial globo, aud iutcrscct it by spirals to represent
about the south pole, the dii'ection of the wind, we shall see that the wind
r north'!'"' '^'^' enters aU parts of this circle from the south-west,
and that, consequently, 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
consequently there they revolve about it ivith 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 pre-
vailing direction of the wind at the surface of the earth on the
polar side of these calms.

266. The arrows that are drawn about the axis of this diagram
The arrows in the aro intended to represent, by their flight, the mean
wfnds. direction of the wind, and by their length and their
feathers the mean annual dm-ation from each quadrant. Only the
arrows nearest to the axis in each belt of 5° of latitude are cLra^vsTi
with such nicety. The largest arrow 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 aiTOws
represent winds having an average dm-ation 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 dm^ation is ten months — being half an inch. Winds that
blow five months are represented by an arrow half this length, and so
on. The haK-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

THE ATMOSPHERE. 99

discs about the poles as it does in cyclones, \az., against the hands
of a watch in the northern, with them in the southern hemisphere.
267. To act and react upon each other, to distribute moisture
The offices of sea and over the surfaco of the earth, and to temper the
economy^ ^ ^"'^^ climato of different latitudes, it would seem, are two
of the many offices assigned by their Creator to the ocean and the
?iir. 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, w^e have a region of constant precipita-
tion. Old sailors tell us of such dead calms of long continuance
here, of such heavy and constant rains, that they have scooped up
fi'esh 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 moistiu-e 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 Amazon and
the Mississippi, for example. We see them day after day, and year
after year, discharging immense volumes of water into the ocean.
*' All the rivers run 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 retm-ned 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 through-
out the whole extent of valley drained by them ; and by precipita-
tion I mean the total amount of water that falls from, or is de-
posited 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 w^hich are taken up
from the sea, that " it be not full," and carried up to the mountains
tlu'ough the air. " Note the place whence the rivers come, thither
they retm-n again." Behold now the waters of the Amazon, of the
Mississippi, the St. Lawrence, and all the great rivers of America,

h2

100 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

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 conveyed one year with the
other is nearly the same : for that is the quantity which we see run-
ning 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. We now begin to conceive what a powerful machine the
Powerful machinery, atmospherc must bc ; 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 regualrity
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 intertropical 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 afibrd if
applied to machinery, is astonished at the number of figures which
are 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 maMng and lifting vapom' from each
area of one acre that is included on the surface of the earth is equal
to the power of 30 horses.

CHAPTEE Y.

270-303. RAINS AND RIVERS.

270. KrvERS are the rain-gauges of nature. The volume oi
Sn^£uges-thft?n ^^tcr annually discharged by any river into the
largest. ° sca cxpresscs the total amount by which the precipi-

tation upon the valley drained by such river exceeds the evapora-
tion fi'om the_ sam3 valley during the year. There are button

EAINS AND Bn'ERS. 101

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 mileg.

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, v;ith 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 should all
be regarded as belonging to one hydrographic basin, for a canoe
may pass inland from any one to either of the others without
portage. Of these hydrographic basins, three, including an area
of 3,916,000 square miles, are American; six, which contain 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 possess the interest
which, in the minds of men generally, is attached to the rest. The
three others of Asia drain 1,668,000 square miles, and run into
the Pacific ; while the whole American system feed with their
waters and their commerce the Atlantic Ocean. These rivers,
with their springs, give drink to man and beast, and noiu-ish with
their waters plants and reptiles, 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, hke a watch without a balance.

102 PHYSICAL GEOGBAPHY OF THE SEA, AND ITS METEOROLOGY.

271. We see these majestic streams pomiiig tlieir waters into

Mt'W^Jur'fol- the ^^® ^®^' ^^^ -^^'^^ ^^^ ^^^ ^^ know tliose waters
rivers. must come again, else the sea would be full. AYe

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 av/ay
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 ui visible, imponderable,
omnipresent, and wonderful agent called heat. This is the agent
which controls both sea" and air in their movements "and hi many
of their offices. Th© average amount of heat daily dispensed to
our planet from the som^ce of light in the heavens is enough to
melt a coating of ice completely encasing 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 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 mountains. 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
examinmg its operations here in various aspects. To assist in this
undertaking I have appealed to the ten greatest rivers for terms
and measm-es in which some definite idea may be conveyed as to
the magnitude of the work and the immense physico-mechanical
power of this imponderable and invisible agent called heat. Calcu-
lations have been made which show that the great American lakes
contain 11,000 cubic miles of water. This, according to the best
computation, is twice as much as is contaiaed in all the other fresh-
water lakes, and rivers, and cisterns of the world. The Mississippi
Eiver does not, dming a hundred years, discharge into the sea so
large a volume of water as is at this moment contamed in the great
northern lakes of this continent ; and yet this agent, whose w^orks
we are about to study, operating through the winds, has power
annually to lift up from the sea and pour down upon the earth in
grateful showers fresh water enough to fill the great American lakes
at least twenty times over.

272. That we may be enabled the better to appreciate the power
Rain-fall in the Mis- and the majcsty of the thermal forces of the sun,
sissippi Valley. ^-^^ Comprehend in detail the magnitude and gran-

* Deduced from the experiments of Pouillet.

RAINS AND RIVERS. 103

deiu' of tlieir operations, let us inquire how mucli rain falls annually
upon the water-sheds of one of these streams, as of the Mississippi ;
how much is carried off by the river; how much is taken up
by evaporation; and how much heat is evolved in hoisting up
and letting do^vn 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 evaporated by artificial heat, and if we wished
to find out how much would be required for the pm-pose, we
should learn fi:om 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 wiU be easy to tell how many
of such huge measures of heat are set free during the annual opera-
tion of condensing the rain for our hydrographic basin. And then,
if we could tell how many inches of this rain-water are again
taken up by evaporation, we should have the data for determining
the number of these monstrous measures of heat that are employed
for that operation also.

273. The area of the Mississippi Yalley is said by physical
Its area, and the la- ffeoOTaphcrs to embrace 982,000 SQuarc miles; and

tent heat liberated o o i : . i ^

during the processes upou cvcry squarc milc there IS an annual average
of condensation ^am-fall of 40 iuches. Now if we multiply 982,000
by the number of times 6 will go into 40, we shall have the
number of om' units of heat that are annually set free among the
clouds that give rain to the Mississippi Yalley. Thus the imagina-
tion 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 Yalley with water is as
much as would be set free by the combustion of 30,000 tons of
coal midtiplied 6,540,000 times. Mr. Joule, of Manchester, is our
authority for the heating power of one pound of coal ; the Army
Meteorological Eegister, compiled by Lorin Blodget, and pubhshed
by the Sm^geon General's Office at Washington in 1855, is the
authority on which we base om- 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
ui Tennessee, the annual fall of rain there to be 49 inches, the
annual evaporation 43, and the quantity of water that annually

104 PHYSICAL GEOGBAPHY OF THE SEA, AND ITS METEOROLOGY.

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. It is estimated that the tributaries which the Mississippi
Anmiai discharge of Rivcr receivos below Memphis increase the volume
the Mississippi River. Qf ^j^^ watcrs about ouo 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 v>'ater to ba
evaporated from this river-basin annually. All the coal that the
present mining force of the country could raise from its coal
measm-es in a thousand years would not, during its combustion,
give out as much heat as is rendered latent annually m evaporating-
this water. Utterly insignificant are the sources of man's mechanical
powers when compared with those employed by nature in moving
machinery which brings the seasons round and preserves the-
harmonies of creation !

275. The amount of heat required to reconvert these 513 cubic
Physical adaptations, milcs of raiu- Water iuto vapour and bear it away, had
accumulated in the Mississippi Yalley 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 preserve the harmonies of
natm^e, and how water from the sea is made to carry off by re-
evaporation from the plains and valleys of the earth their sur-
plusage of heat, which could not otherwise be got rid of without
first disturbing the terrestrial arrangements, and producing on the
land desolation and a desert. Behold now the offices of clouds and
vapom- — the adaptations of heat. Clouds and vapour do something
more than brew storms, fetch rain, and send down thunder-bolts.
The benignant vapom'S cool our climates in summer by rendering
latent the excessive heat of the noonday sun ; and they temper
them in winter, by rendering sensible and restoring again to the
air, that selfsame heat.

276. Whence came, and by what channels did they come, these
Whence come the cubic milcs of watcr which the Mississippi Eiver

rains for the Missis- n • j ji o rrn • l i-

sippi, pours annually mto the sea f The wisest ot men

has told us they come from the sea. Let us explore the sea for
their place and the air for their channel. The Gulf of Mexico-
cannot fornish rain for all the Mississippi Yalley. The Gulf lies

BAINS AND BIVERS. 105

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 Yalley
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. The north-east trade-wind region of this ocean extends
S'tSlScS^^^ (§ 210) from the paraUel of 30° to the equator,
ply rains only for the These muds carrv their vapour before them, and.

rivers oi Central and , . , , ,*<, , , \ • t 1 1 i r>

South America. mcctmg the south-cast trade-wmd, the two lorm
clouds which give rain not only to Central America, but 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 i\.frica.
So completely is the rain wi'ung 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 v/hence our rivers come, and whence Europe-
is supplied with rains, is clearly not to be found in this part of the
ocean.

«^ 278. Between the parallels of 30° and 35° N. lies the calm belt
The calm belt of of Caucor, a rcgiou where there is no jprevaili7ig
litSe or nJ'rain. wiud (sco Diagram of the Winds, Plate I.). It is a
belt of light airs and calms — of airs so baffling that they are often
insufficient to carry off the "loom," or that stratum of air, which,
being charged with vapom-, covers calm seas as with a film, a&
if to prevent fe,rther evaporation. This belt of the ocean can scarcely
be said to fm-nish any vapour to the land, for a rainless country,
both in Africa, and Asia, and America, lies ^^dthin it.

279. All Em'ope is on the north side of this calm belt. Let us
The North Atlantic cxtcud OUT scarch, thou, to that part of the Atlantic
STofJ^^ig:^;"'^ which hes between the parallels of 35° and 60° N.,
Sone"sritb'of'au^ to sce if WO havo water smface enough there to
*he land. supply raius for the 8J- milhons of square miles that

are embraced by the water-sheds under consideration. The area of

J 0.6 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOPtOLOGY.

tliis part of tlie Atlantic is not quite 5 millions of square miles, and
it does not include more than one thirtieth of the entu'e sea sm^face
of our planet, while the water-sheds under consideration contain
one sixth part of its entire land surface. The natural proportion
of land and water smface is nearly as 1 to 3. According to this
ratio, the extent of sea sm-face required to give rain for these SJ-
millions of square miles would be a little over 25, instead of a Httle
less than 5 millions of square miles.

280. The state of our knowledge concerning the actual amount
Daily rate of evapo- of evaporation that is daily going on at sea has, not-
than on land-ob- withstauduig the activity in the fields of physical
servations wanted, roscarch, becu but little improved. Kecords as to
the amount of water daily evaporated from a plate or dish on shore
iifibrd us no means of 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 evaporating 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 thh^sty
wind, and drinl^ up vapour from it greedily. Now had the same
dish been placed on the sea, the air would come to it over the water,
diinking as it comes, and arriving already quite or nearly saturated
with moistm^e; consequently, the observations of the amount of
evaporation on shore give no idea of it at sea.

281. There is no physical question of the day which is more
Kivers are gauges for worthy of attention than the amount of effective

the amount of effect- "^ . n , • -i -i • • ii i-*

ive evaporation. cvaporatiou that IS daily gomg on m the sea. 13y
effective I mean the amount of water that, in the shape of vapom-, 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 procm^ed the Mississippi to be gauged at
Memphis in 1849.

282. The monsoons supply rains to feed the rivers of India, as
Importance of rain the north-cast and south-east trade-winds of the
-and river gauges. Atlantic supply raius to feed the rivers of Central
.and South America. Now rain-gauges which wiU 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-
<jourses, would afford data for an excellent determination as to the
amount of evaporation from some parts of the ocean at least, espe-

RAIXS AND En^KS. 107

cially for the trade-wind belts of the Atlantic and the monsoon
region of the Indian Ocean. All the rain which the monsoons
of India dehver 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 volume to half the dis-
charge of the Mississippi Kiver, it would not make a ditierence 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. That part of the extra-tropical North Atlantic under con-
Hypsometiy in the sidcratiou is pcculiar as to its hypsometry. It is

North Atlantic pe- , tit -t t-t !>

cuiiar. traversed by large icebergs, v/hich are more lavour-

able to the recondensation of its vapours than so many islets would
be. Warm waters are in the middle of it, and both the east and
the west mnds, which waft its vapours to the land, have, before
reaching the shores, to cross cmTents of cool water, as the in-shore
cmTent counter to the Guh' Stream on the western side, and the cool
drift fi'om 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 temperatm'e 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 aU the time." This is
far h^om 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 icebergs and cold currents
which lie in their way ; whereas, such being absent from the North
Pacific, they arrive at the islands there literally reeking wiih.
moistm-e. Oregon in America, and France on the Bay of Biscay,
are between the same parallels of latitude; their situation ^vith
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 abundantly by rains as are those in the same
latitudes which curtain our north-west coast. The American water-
* Keith Johnston. f Army Meteorological Kegister, 1855.

108 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

slied 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 ? *

284. It may well be doubted whether the south-westerly winds
iimis\'!>'tS''up ""^ — which are the prevailing winds in this part of
and transport, lor tho Atlantic — Carry into the interior of Europe
and America, va°^^ mucli morc moisturo 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 temperatm^e varying from
60^ to 40^, according to the latitude in which they reach the shore,
and consequently with an average dew-point 7iot higher than the
mean temperature. Classifying the vrinds of this part of the ocean
according to the halves of the horizon as east and west, the mean
of 44,999 observations in the log-books of the Observatory shows
that, on the average, the Avest winds blow annually 230 and the
east v/inds 122 days.

285. Taking all these facts and circumstances into considera-
The vapour-strings for tiou, and without pretending to determine how
the A^tlanti^J^ocean"^ much of the watcr whicli the rivers of America and
Em'ope carry into this part of the ocean, comes from it again, we
may with confidence assume that the A\^nds do not get vapour
enough from this part of the ocean to give rain to Europe, to the
Mississippi Valley, to om- Atlantic slopes, and the western half
of Asiatic Eussia. We have authority for this conclusion, just as
we have authority to say that the evaporation ffom the ]\Iediter-
ranean is greater in amount than the volume of water discharged
into it again by the rivers and the rains ; only in this case the re-
verse takes place, for the rivers empty more water into the At-
lantic than the w^inds carry from it. This fact also is confirmed by
the hydrometer, for it shows that the water of the North Atlantic
is, parallel for parallel, lighter than water in the Southern Ocean.

286. The inference, then, from all this is, that the place in the
The places in the sea sca (§ 276) wlienco comc the watcrs of the Missis-
riverTonh^Vonh, sippi and other great rivers of the northern hemi-
S^crosSi^atThe^ sphoro is to be found in these southern oceans, and
calm belts. the chauuels by which they come are to be searched
out aloft, in the upper cmTents of the air. Thus we bring evi-

♦ Keith Johnston, " Physical Atlas."

The number of know-
facts that are rec(

ciled by the

BAINS AND RIVERS. 109

dence and facts whicli seem to call for a crossing of air at tlie 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 vapom-s taken up in the southern hemisphere — to
show whence come the hundreds of cubic miles of water which these
rivers annually pour into the Atlantic and the Arctic Oceans. In
finding the " place " of all this water, it is incumbent upon them
to show us the winds which bring it also, and to point out its
channels.

287. '' In the greater number of physical investigations some
Spirit in which the hypothcsis is requisite, in the fii'st instance, to aid
Ihonw b°e'^con.*'^ the imperfcctiou of om' senses ; and when the phe-
<*"^'^^'*^- nomena of nature accord with the assumption, we
are justified in believing it to be a general law."*

288. In this spirit this hypothesis has been made. Without
oj^any evidence bearing upon the subject, it would be

. ir^theory as philosopliical to maintain that there is no cross-
caim'^beus"" ^^ ^^^ iug at the calm belts as it would be to hold that
there is ; but nature suggests in several instances that there must
be a crossing. (1.) In the homogeneousness of the atmosphere
(§ 237). The vegetable kingdom takes fi'om 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 hemisphere.
iVnd is it consistent with the spirit of true philosophy to deny the
existence, because we may not comprehend the nature, of a contriv-
ance 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 om- winter over into the other hemisphere
for re-elaboration, and which conducts across the calm places and
over into this that which has been replenished from the plains and
sylvas of the south ? (2.) Most rain, notwithstanding there is
most water in the southern hemisphere, falls in this. How can
vapour thence come to us except the winds bring it, and how can
the wmds fetch it except by crossing the calm places ? (3.) The
*' sea-dust " of the southern hemisj)here, 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

* Mrs. Somcrville.

110 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Ocean. If this be so, it mnst cross one or more of the calm belts.*
(4.) Parallel for parallel, the southern hemisphere from the equator
to 40° or 45° S., is the cooler. This fact is consistent with the suppo-
sition that the heat that is rendered latent and abstracted h'om 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
jfrom the sun by the two hemispheres is, as astronomers have
shown, precisely the same.t (5.) Well-conducted observations
made with the hydrometer^ (§ 285) for every parallel of latitude
in the Atlantic Ocean from 40° S. to 40° N., show that, parallel
for parallel, and notwithstanding the difference of temperature,
the specific gravity of sea-water is greater in the southern than it

* After this liad been wTitten, I received from 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 caught
in a small sack (hoisted up above the tops) between 22^-25^ lat. N., and 380-39Jo
long, W. This piece is of the following dimensions : 14 millim, long, 1 to 1| mm.
large, i mm. thick, and weighing 1^ milligrams. Our famous microscopist and
naturalist, Professor P. Harting, at IFtrecht, told me, after an exact inquiry, ' that
this vegetable fragment issued from a leaf of the family Monocotjdedou, probably
not from a palm-tree, but from a Padanacese or Scitaminese ' — consequently, from
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 than 1200 geographical miles in the upper regions of
the atmosphere ; for the nearest coast-lines 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 Navy, dated Utrecht, Jan. 2, 1860.

t The amount of solar heat annually impressed upon the two hemispheres is
identically the same ; yet within certain latitudes the southern hemisphere is,
parallel 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 hemi-
sphere would be gradually growing cooler. There is no evidence that it is so
growing, and tlie 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 nortliern radiates
more heat than the 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 re-
conciled but upon the supposition that the southern surplusage is stowed away in
vapours, transported thence across the calm belts by the winds, and liberated by '
precipitation on our side of the equator ?

X Kodgers, in the Vincennes. Maury's Sailing Directions, 8th ed., vol. i., p. 235*

EAINS AND EIYEES. Ill

is in the nortliem hemisphere. This difference as to the average
condition of the sea on different sides of the'hne is reconciled by
the hj^othesis which reqiiires a crossing at the cahn belts. The
vapour which conveys fresh water and caloric from the southern
hemisphere to the northern will in part account for this differ-
ence both of specific gravity and temperature, and no other hypo-
thesis will. This hydrometric difference indicates the amount
of fresh water which, as vapom' in the air, as streams on the land,
and as cmTents in the sea,* is constantly in transitu between the
two hemispheres. All these facts are inconsistent with the sup-
position that there is no crossing at the calm belts, and consistent
with the hypothesis that there is. It is no argument agaiast 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 om* notions of the attributes of
the great Architect. The planets have their orbits, the stars their
com^ses, and the wind " his circuits." And in the construction
of om' 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 circumstances and others favouring
this hypothesis as to these air-crossings, are presented ia further
detail in Chaps. YII. IX. XI. and XII., also § 349.

289, In obser^dng the workings and studyiag the offices of the
The atmosphere to various parts of the physical machinery which keeps
Mhfr^'madiilferjrby the world iu ordor, we should ever remember that
its operations. [j^ jg ^}2 made for its pm-poses, 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
h}^othesis can the student expect to gain profitable knowledge con-
cerning the physics of sea, earth, or air. Eegardiag these elements
of the old philosophers as parts only of the same piece of machinery,

* The water wMcli the rivers empty into the North Atlantic has to find its
way south with the currents of the sea.

112 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

■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 yery
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 ? Ai'e 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
l)arrier ? Eather let us regard them as made for each other, as
adapted to each other, the one as an essential to the other, and
Loth as parts of the same machine. So regarding them, we
observe that all the great rivers in the world are in the northern
hemisphere, where there is less ocean to supply them. Whence,
then, are their som^ces 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 ^vithout
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 fi^om the Atlantic Ocean. Taking
the Amazon, therefore, out of the count, the Eio 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 Afiica entitled to be called great that we know of.
290. The great rivers of North America and North Africa, and
Arguments furnished all tlic rivors of Em'opo and Asia, lie wholly ■within
y I e nvere. ^-j^^ northom hemisphere. How is it, then, consider-

ing that the evaporating sm-face lies mainly in the southern hemi-
sphere— how is it, I say, that we should have the evaporation to
take place in one hemisphere and the condensation in the other ?
The total amount of rain which fall^ in the northern hemisphere
is much greater, meteorologists tell us, than that which falls in the
southern. The annual amount of rain in the north temperate
zone is half as much again as that of the south temperate. How
is it, then, that this vapour gets, as stated, from the southern into
the northern hemisphere, and comes mth. such regularity that our

RAINS AND RFV^ES. 113

rivers never go diy and our springs fail not ? It is becanse of
tliese air-crossings — these beautiful operations, and the exquisite
compensation of this grand machine, the atmosphere. It is exqui-
sitely and wonderfully counterpoised. Late in the autumn of the
north, throughout its vanter, and in early spring, the sun is pour-
ing his rays with the greatest intensity doAMi upon the seas of the
southern hemisphere, and this powerful engine which we are con-
templating is pumping 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, wath the mois-
tm-e, is carried through the upper regions of the atmosphere until
it reaches om- climates. Here the vapour is formed into clouds,
condensed, and precipitated. The heat which held this water in
the state of vapom' is set free, it becomes sensible heat, and it is
that [(4), § 288] which contributes so much to temper our winter
chmate. It clouds up in ^\inter, turns warm, and we say we are
going to have falling weather. That is because the process of con-
densation has abeady commenced, though no rain or snow may
have fallen : thus we feel this southern heat, that has been
collected fi'om 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 om' northern winter. If Plate I. fairly
represent the coui'se of the wands, the south-east trade-^ands would
enter the northern hemisphere, and, as an upper current, bear into
it aU then- moisture, except that which is precipitated m the region
of equatorial calms, and in the crossing of high momitain ranges,
such as the Cordilleras of South America.

291. The South Seas, then (§ 290), should supply mainly the
Jiore rain in the watcr for this eugiuc, whilc the northern hemisphere
thrjmhernVcmi- coudenscs it ; we should, therefore, have more rain in
^P^^""®- the northern hemisphere. The rivers teU us that

we have — the rain-gauge also. The yearly average of rain in the
north temperate zone is, according to Jolmston, thirty-seven inches..
He gives but twenty-six in the south temperate. The observations
of mariners are also corroborative of the same. Log-books, contain-
ing altogether the records for upwards of 260,000 days in the
Atlantic Ocean north and south (Plate XIII.), have been care-
fully examined for the pm-pose of ascertaining, for comparison, the
number of calms, rains, and gales therein recorded for each hemi-
sphere. Proportionally the number of each as given is decidedly
greater for the north than it is for the south. The resdt of this

114 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

examination is very instrnctiye, for it shows tlie status of tlie atmo-
sphere to be much more unstable in the northern hemisphere, ^yith its
excess of land, than in the southern, with its excess of water. Eains,
and fogs, and thunder, and calms, and storms, all occm' much more fre-
quently, and are more irregular also as to the time and place of their
occmTence on the north side, than they are on the other side of the
equator. Moistm-e is never extracted from the air by subjecting it
from a low to a higher temperatm^e, but the reverse. Thus all the
au" Avhich comes loaded with moistm'e 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 cahns
of Cancer ; here it becomes the sm'&ce "wind that prevails from the
southward and westward. As it goes north it grows cooler, and
the process of condensation commences. We may now hken it to
the wet sponge, and the decrease of temperature to the hand that
squeezes that sponge. Finally reaching the cold latitudes, all the
moistm'e that a dew-point of zero, and even far below, can extract,
is wrung from it ; and this an' then commences " to retm'n accord-
ing to his cii'cuits" as dry atmosphere. And here we can quote Scrip-
tm'e again : " The north wind driveth away rain." This is a
meterological fact of high authority, and one of great significance
too.

292. By reasoning in this manner and from such facts, we are
The trade-winds the foTced to the conclusiou that OUT rivors are supphed
evaporating winds. ^^]^ ^]^gjj, wators principally from the trade-wind
regions — the extra-tropical northern rivers fi'om the southern
trades, and the extra-tropical southern rivers from the northern
trade-mnds, for the trade-winds are the evaporating winds.

293. Taking for om- guide such faint glimmerings of Hght as
The saitest part of ^6 can catch from theso facts, and supposing these
the sea. viows to be correct, then the saitest portion of the
sea should be in the trade-wmd regions, where the water for all
the rivers is evaporated ; and there the saitest portions are found.
There, too, the rains fall less frequently (Plate XIII.). Dr. Eu-
schenberger, of the Navy, 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 —
midway 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

EAINS AND RIYERS. 115

parallels of 20° nortli and 17° south. Captain Eodgers, in the
United States ship Yincennes, found the heaviest water in 17° N.,
and between 20' and 25° S. _

291. In summing up the evidence in favour of this view of the
seeingthat the south- general sjstem of atmospherical cii^culation, it re-
fo7dsX largest''^' maius to be shown how it is, if the view be correct,
how^uniSf there'^be ^^^^'^ should be Smaller rivers and less rain in the
a crossing.^ could we southem hemisphere. The winds that are to blow as
the^^at r[ve?sTi pokr tho uorth-cast trade- winds, returning from the
the northern? rcgious, whcrc the moistm^c (§ 292) has been com-
pressed out of them, remain, as we have seen, dry winds until they
cross thecalm zone of Cancer, and are felt on the surface as the north-
east trades. About two thirds of them only can then blow over the
ocean ; the rest blow over the land, over Asia, Ahica, and North
America, where there is comparatively but a small portion of
evaj)orating 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, commencing
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 parallels, 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, illus-
trated 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 of equatorial cahns, the vapours which make
the rains that feed the rivers in the extra-tropical regions of the
southem hemisphere. Upon this supposition, then, two thirds
only of the northern trade-winds are fully charged with moisture,
and only two thu'ds of the amount of rain that falls in the northern
hemisphere should faU in the southem ; and this is just about the
proportion (§ 292) that observation gives. In like manner, the
south-east trade-winds take up the vapom^s 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-v^dnds have, we might expect, according to this hvpothesis,

/2

116 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

more rains in the northern — and, consequently, more and larger
rivers — than in the southern hemisphere. A glance at Plate YIII.
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 hemisj^heres is one which is not capable of verification by any
more than the rudest approximations ; 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 Bcmiy Seasons, Jioiv caused. — The calm and trade-wind
The raiky Seasons, rcgious or bclts movo up and down the earth, an-
nually, in latitude nearly a thousand miles. In July and August
the zone of equatorial calms is fomid 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 Ore-
gon it rains every month, but about five times more in the winter
than in the summer months. The winter there is the summer of
the southern hemisphere, when this steam-engine (§ 24) is work-
ing with the greatest pressm'e. 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, this vapour is condensed and
precipitated, during this part of the year, almost in constant showers,
and to the depth of about thirty inches in three months.

296. In the winter the calm belt of Cancer approaches the equa-

The rainy seasons of tor. Tilis wholc SVStcm of ZOnCS, viz., of tradcS,
California and Pa- , -, , i • -\ o m n t

nama. calms, and westerly wmds, lollows the sun; and

they of our hemisphere are nearer the equator in the winter and
spring months than at any other season. The south-west mnds
commence at this season to prevail as far down as the lower part
of CalifoiTiia. In winter and spring the land in California is cooler
than the sea au', and is quite cold enough to extract moisture from
it. But in summer and autumn the land is the warmer, and can-
not condense the vapours of water held by the air. So the same
* See the Trade-wind Chart.

RAINS AND Em^^RS. 117

cause T^liieli made it rain in Oregon now makes it rain in California.
As the sun returns to the north, he hrings 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, instead of
going from a warmer 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 precipi-
tate it. Proof, if proof were wanting that the prevailing winds in
the latitude of California are from the westward, is obvious to all
Avho cross the Eocky Mountains or ascend the Sierra Madi'e. 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 abra-
sion and the scorning effects of the driving sand. Those who 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 xlpril. Wliere these calms are it is always raining, and
the chart* shows that they hang over the latitude of Panama from
Jime to November ; consequently, fi'om June to November is the
rainy season at Panama. The rest of the year that place is 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 moistm-e, and leave Panama rainless and
pleasant until 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 illus-
tration : dming 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 Avas 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,

* Vide Trade-wind Chart (Maury's Wiud and Current).

118

when tlie belt of calms recrosses this 2:)arallel 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 A^ithin the bi-rainy latitudes.

297. The Bainless Piegions. — The coast of Peru is within the
The eainless ee- rogion of perpetual south-east trade-winds. Though
^^°^^- the Peruvian 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. Travelling 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 con-
tinue to bear along across the continent, depositing it as they go,
and supplying ^ith it the somxes 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
moistui^e that that very low temperature can extract. Eeaching
the summit of that range, they now tumble do^n as cool and dry
winds on the Pacific slopes beyond. Meeting with no evaporating
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 before, there-
fore, 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. Thus we see how
the top of the Andes becomes the reservoir from which are supphe^ .
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 Austraha. Now study the geographical
features of the country surrounding those regions ; see how the
mountain ranges run ; then turn to Plate YIII. to see how the
winds blow, and where the soui'ces 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 mil 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 tempera-
true ; for the air can never deposit its moisture iclien its temjjera-

EAINS AKD EIVEES. 119

ture is liiglier than its detv-jwint. We have a rainless region
about the Ked Sea, because the Eed 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 HoUand lies
within the south-east trade-wind region; so does most of inter-
tropical South America. But intertropical South America is the
land of showers. The largest rivers and most copiously watered
coimtiy 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 the trades ; in South America — east coast — it is per-
pendicular 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 aU the moisture fi'om them ; their vege-
table instincts teach them to turn their edges to his rays. In
intertropical 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 plaintain, &c. — turn their broad sides up to the sun, and court
his rays.

298. WJiy there is more rain on one side of a mountain than on
The ratxy SIDE OF the other. — We may now, from what has been said,
z^ouMAi.Ns. ggg ^^j j.^Q 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 diy side. Thus, let us take the southern
coast of Chili for illustration. In om^ summer-time, when the sim
comes north, and drags after him the belts of perpetual winds and
calms, that coast is left within the regions of the north-west vdnds
— the winds that are counter to the south-east trades — which,
cooled by the winter temperatm-e 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 California to prevent rain there, operate
in Chih ; only the dry season in one place is the rainy season of
the other. Hence we see that the weather side of all such moun-

120 PHYSICAL GEOaEAPHY OF THE SEA, AND ITS METEOEOLOGY.

tains as the Andes is the Tvet side, and the lee side the dry. The.-
same phenomenon, from a like cause, is repeated in intertropical
India, only in that comitry 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, Peru^dan-like, cool,
rainless, and dry ; wherefore that narrow strip of comitry between
the Ghauts and the Arabian Sea would, lil^e that in Peru between
the Andes and the Pacific, remain "VNdthout 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 blo^^Ti out their season, w^hich in India ends
in April, the great arid plains of Central Asia, of Tartary, Tliibet,
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, are felt by the air which
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 sum-
mer and early autumn, mto south-west monsoons. These then
come fi'om the Indian Ocean and Sea of Arabia loaded vdth.
moisture, and, striking with it perpendicularly upon the Ghauts,
precipitate upon that narrow strip of land between this range and
the Arabian Sea an amoimt 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. Accord-
ingly, when we come to consult rain gauges, and to ask meteoro-
logical observers in India about the fall of rain, they tell us that
on the western slopes of the Ghauts it sometimes reaches the enor-

BAINS AND RR^RS. 121

moiis deptli of twelve or fifteen inches in one day.* "Were the
Ancles 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 Amazon and the other majestic streams of South
America retm^n to the ocean would still be precipitated between
the sea-shore and the crest of these mountains. These winds of
India then continue theu' course to the Himalaya range as dry
winds. In crossing this range, they are subjected to a lower tem-
peratm-e than that to which they were exposed in crossing the
Ohauts. 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 coimter-
ourrents in the i2,-eneral system of atmospherical circulation. By
fitud}dng Plate YIII., where the rainless regions and inland basins,
as well as the course of the prevailing winds, are shown, these facts
will become ob^dous.

299. The Fiegions of Greatest Freciiyitation. — We shall now be
The regions of great- enabled to deteiTuiue, if the views which I have
€he?raS£^^J~ ^^^^ cndeavouriug to present be correct, w^hat parts
Patagonia. ' q£ ^j^g g^rth are subject to the greatest fall of rain.
They should be on the slopes of those mountains which the trade-
winds or monsoons first strike after having blown across an ex-
tensive tract of ocean. The more abrupt the elevation, and the
shorter the distance between the mountain top and the ocean
{§ 298), the greater the amoimt of precipitation. If, therefore, w^e
commence at the parallel of about 30^ north in the Pacific, where
the north-east trade-winds first strike that ocean, and trace them
through their circuits till they first meet high land, w^e ought to
find such a place of heavy rains. Commencing at this parallel
of 30^, therefore, in the Xorth 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
com'se in the upper stratum of winds through the southern hemi-
sphere, they, in. consequence of the rotation of the eai-th (§ 207),
are made to take a south-east course. They keep in this upper
stratmn until they reach the calms of Capricorn, between the
parallels of 30"" and 40^, after which they become the prevailing

* Keith Johnston.

122 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

nortli--west winds of the southern hemisphere, which correspond to
the south-west of the northern. Continuing on to the south-east,
they are now the surface winds ; they are going from warmer to
cooler latitudes; they become as the wet sponge (§ 292), and are
p.bruptly 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 fomid the astonishing fall of water
here of nearly thirteen feet (one hundred and fifty-one inches) in
forty-one days ; and Mr. DarT\'in 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 Cherraponjie, a mountain in India.
Colonel Sykes reports a fall there dm^ing the south-west monsoons
of 605 J inches. This is at the rate of 86 feet during the year ; but
King's Patagonia rain-fall is at the rate of 114 feet dming the
same period. Cherraponjie is not so near the coast as the Pata-
gonia range, and the monsoons lose moistm'e before they reach it.
We ought to expect a corresponding rainy region to be fomxl to
the north of Oregon ; but there the mountains are not so high,
the obstruction to the south-west winds is not so abiTipt, the high-
lands are farther from the coast, and the air which these winds
carry in their circulation to that part of the coast, though it be as
heavily charged with moistui'e as at Patagonia, has a gi'eater ex-
tent of comitry 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. — The mean annual fall of rain on
amohnt of evapo- the entire surface of the earth is estimated at about

RATION greatest from n r. , rr\ j_ i. i n i-

the Indian Ocean, iive icet. lo ovaporato Water enough annually irom
the ocean to cover the earth, on the average, five feet deep \vith
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
evaporation, 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

EAIXS AND EIYEES. 123

have, encircling the earth, a belt of ocean thi'ee 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 invisible machinery. What a
powerful engine is the atmosphere ! and how nicely adjusted must
be aU the cogs, and wheels, and springs, and com])ensations of this
exquisite piece of machinery, that it never wears out nor breaks
do^^^l, nor fails to do its w^ork 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, w^hile its Asiatic water-shed contains an area of
2,500,000. Supposing all the rivers of this water-shed to dis-
charge annually into the sea four times as much w^ater as the
Mississippi (§ 274) discharges into the Gulf, we shall have an-
nually on the average an effective evaporation (§ 282) from the
North Indian Ocean of 6.0 inches, or 0.0165 per day.

301. The rivers of India are fed by the monsoons, which have to
The rivers of ludia, do their work of distributing their moisture in about
""^Vil^^eZ'^^L. tt^ee months. Thus we obtain 0.065 inch as the
tionfrom that ocean, 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 w^hich would require rivers having
sixteen times the capacity of the Mississippi to discharge. Never-
theless, the evaporation from the North 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

* In his annual report of the Society (Transactions of the Bombay GeograpMcal
Society from May, 1849, to August, 1850, vol. ix.), the late Dr. Buist, the secretary^
stated, on the authority of Mr. Laidly, the evaporatiouat Calcutta to be " about fifteen
feet annually ; tliat between the Cape and C/alcutta it averages, in October and
November, nearly three-fourths of an inch daily ; between 10^ and 20° in the Bay
of Bengal, it was fu.und 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 evapora-
tion on shore tliat have led (§ 280) to such extravagant estimates as to the rate
at sea.

124 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

trade-wind region generally at sea, I estimate that it does not
exceed four feet.

302. We see the light breaking in upon lis, for we now begin
I'hysicai adjustments, to perceive whj it is that the proportions between
the land and w^ater 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 now, and the inhabitants, neither animal
nor vegetable, would not have been as they are. And as they
^re, 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 v/ell-being of all the inhabitants
of earth, sea, and air depends ; and which, in the beautiful adapta-
tions that we are endeavoming 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 evapo-
ration : thus the amount of w^ater borne down by every river that
runs into the sea (§ 270) may 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
Oaspian 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 whole 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 w^e find distributed over that and
-every other inhabitable inland basin, we see reservoirs or evaporat-
ing 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

RAINS AXD RIVERS. 125

precipitation takes place, and in which we find neither plant nor
animal to fit the land for man's use.

303. Adaptations. — In contemplating the system of terrestrial
ADAPTATioN-s-their adaptations, these researches teach one to regard the
limity''' ""^ ^"^ ' mountain ranges and the great deserts of the earth
as the astronomer does the counterpoises to his telescope — though
they be mere dead Vv^eights, 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 y Whenever I turn to contemplate the
works of natm-e, I am struck with the admirable system of
compensation, with the beauty and nicety with which every depart-
ment is adjusted, adapted, and regulated according to the others ;
things and principles are meted out in directions apparently the
most 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 firma-
ment, is found to come and tmnkle in its proper place at the
proper moment. Nay, philosophy teaches us that when the little
snowdrop, which in our garden walks we see raising its head at
"the singing of birds," to remind us that " the venter 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 consti-
tution 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 difierent ;
in that case, the strength of fibre in the snowdrop, as it is, v^^ould
have been too much or too little ; the plant could not bov/ or raise
its head at the right time, fecimdation could not take place, and its
family would have become extinct with the fii'st individual that
was planted, because its *' seed " would not have been " in itself,"

126 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

and therefore coiild not have reproduced itself, and its creation
would have been a failure. Now, if we see such a perfect adapta-
tion, such exquisite adjustment in the case of one of the sraallest
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 performance of which depends not only the
life of that plant, but the well-being of every individual that is
found in the entii^e vegetable and animal kingdoms of the world ?
When the east winds blow alorfg the Atlantic coast for a little
while, they bring us air saturated with moisture fi'om the Gulf
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 moistiure that it cannot take up and carry off
that which encumbers his lungs, and which nature has 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 limgs 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, an-, and water had not been
in exact counterpoise — the whole arrangement of the animal and
vegetable kingdoms would have varied from their j)"esent state.
But God, for reasons which man may never know, chose to make
those kingdoms what they are ; for this purpose it was necessary,
in his judgment, 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 have it to do all its work in obedience to law and in
subservience to order. If it were not so, why was power given to
the mnds 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 fii'st vapom*, and then fniitful showers
or gentle dews ? If the proportions and properties of land, sea,
and air were not adjusted according to the reciprocal capacities
of all to perform the fimctions required of each, why should
we be told that He " measured the waters in the hollow of his

KED FOGS AND SEA BREEZES. 127

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 was necessary 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 concerning the wonders of the deep,
the mysteries of the sky, the greatness, and the wisdom, and good-
ness of the Creator, which make us wiser and better men. The
investigations into the broad-spreading circle of phenomena con-
nected with the mnds 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.

§ 311-332. — RED FOGS AKD SEA BREEZES.

311. The inhabitants of the sea-shore in tropical countries wait
The alternations of evcry momiug with impatience the coming of the

land and sea breezes, gga brCCZe. It USUally SCts ITL about tcU o'clock.

Then the sultry heat of the oppressive morning is dissipated, and
there is a dehghtful freshness in the ah which seems to give new
life to all for their daily labours. About sunset there is again an-
other 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 rismg and setting of the
sun.

312. In extra-tropical countries, especially those on the polar
The sea breeze at sidc of the tradc-^iuds, this phenomenon is presented
Valparaiso. Qj^jy ^ summcr and fall, when the heat of the

sun is sufficiently intense to produce the requisite degree of atmo-

128 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

spherical 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 exerted with most eflfect. In such cases the
sea breeze amounts to a gale of wind. In the summer of the
southern hemisphere the sea breeze is more powerfully developed
at Valparaiso than at any other place to which my services afloat
have led me. Here regularly in the afternoon, at this season, the
sea breeze blows fm'iously ; pebbles are torn up from the walks
and whirled about the streets ; people seek shelter ; the Almen-
dral is deserted, business interrupted, and all communication fi.'om
tlie shipping to the shore is cut off. Suddenly the wwls and the
sea, as if they had again heard the voice of rebuke, are hushed,
and there is a great calm.

^_ 313. The lull that follows is delightful. The sky is -without a
The contrast, cloud ; the atmosphcro is transparency itself ; the
Andes seem to draw near ; the climate, always mild and soft, be-
comes now doubly sweet by the contrast. The evening imdtes
abroad, and the population sally forth — the ladies in ball costume,
for nov/ 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 yet the calm always seems to sur-
prise, and to come before one has time to reahze that the furious
sea vrnid could so soon be hushed. Presently the stars begin to
j)eep out, timidly at first, as if to see whether 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. Shius, or that blazing world -n Argus, may be the first
watcher to send down a feeble ray ; then follow another and an-
other, all smiling meekly ; but presently, in the short t-^^light of
the latitude, the bright leaders of the starry host blaze forth in all
their glory, and the sky is decked and spangled ^vith superb bril-
liants. In the twinkling of an eye, and faster than the admiring
gazer can tell, the stars seem to leap out from theh^ hiding-places.
By invisible hands, and in quick succession, the constellations are
hmig out ; iDut first of ail, and with dazzling glory, in the azure
depths of space appears the Great Southern Cross. That shining
symbol lends a holy grandem- to the scene, making it still more
impressive. 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, rapt. I have seen there, above the horizon at

KED FOGS AXD SEA BREEZES. 129

once, and sliining 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 hes the city on the sea-shore, wrapped in sleep. The sky
looks sohd, hke a vault of steel set with diamonds. The stillness
below is in harmony with the silence ahove, and one almost fears
•to speak, lest the harsh somid of the human voice, reverberating
through those vaulted " chambers of the south," should wake up
echo, and di'own the music that fills the soul. On looking aloft,
the fh'st emotion gives birth to a homeward thought : bright and
lovely as they are, those, to northern sons, are not the stars nor the
skies of fatherland. Alpha Lyrse, with his pure white hght, has
gone from the zenith, and only appears for one short hour above
ihe 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 daz-
zled with the splendours of the fii'mament. The moon and the
planets stand out fi^om 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 m the east are the Centaurs, Spica,
Bootes, and xintares, wiih his lovely Httle companion, which only
the best telescopes have power to unveil. These are all bright
particular stars, difiering 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 Shius, with Castor and his twin-brother,
and Procyon, t) Argus, and Kegulus — these are high up in their
com'se ; they look down with great splendour, smilmg 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 tm-moil
is done, can have no idea of its grandem', beauty, and loveliness.
„. 314. Within the tropics, however, the land and sea breezes are
!iand and sea breezes moro gcutle, and, thougli the uiglit sceucs there are
rnSiopkaUo^.^ not SO suggcstivo as those just described, yet they
^'^'- are exceedingly dehghtful and altogether lovely.

The oppressive heat of the sun and the climate of the sea-shore is

130 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOP.OLOGY.

mitigated and made botli refreshing and IiealtliM by the alterna-
tion of those mnds which invariably 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 sim
has played upon the land with sufficient intensity to raise its tem-
peratm^e above that of the water. A portion of this heat, being
imparted to the superincmnbent air, causes it to rise, when the air,
first from the beach, then from the sea, to the distance of several
miles, begins to flow in Viith a most dehghtfiil and invigorating
freshness.

315. When a fire is kindled on the hearth, we may, if we will
Cause of land and , obsorve the moats floating in the room, see that
sea breezes. tlioso ncarost to the chimncy are the fii'st to feel
the draught and to obey it — they are drawn into the blaze. The
circle of inflo^dng air is gradually enlarged, until it is scarcely
perceived in the remote parts of the room. Now the land is the
hearth, the rays of the sim the fire, and the sea, with its cool and
calm air, the room; and thus we have at ouj* fii'esides the sea
breeze in miniatm^e. When the sun goes down, the fii'o 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 temperatm^e. The atnlosphere 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. "A long residence in the Indian Archipelago, and, conse-
i.icut. jansen on the queutly, in that part of the world where the inves-
irthnndTan Archi! tigatious of the Obscrvatory at Washington have not
p^^^so. extended, has given me," sa^^s Jansen,* in his
Appendix to the Physical Geography of the Sea, " the opportunity
of stud}ang the phenomena which there occur in the atmosphere^
and to these phenomena my attention was, in the first place,

* I have been assisted in my investigations into tliese phenomena of the sea by
many thmking minds ; among those whose debtor I am stands first and foremost
the clear head and v\'-ann 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 enriclied my liumble contributions to the " Physical
Geography of the Sea" with contributions from the store-house of his knowledge^
set oif and presented in many fine pictures, and has appended them to a translation
')f tlie first edition of tins work in the Dutch language. He has added a chapter
on the land and sea breezes ; another on the changing of the monsoons in the East
Indian Arcliipelago : he has also extended his remarks to the north-we^t mon-
soon, to hurricanes, the south-east trades of the South Atlantic, and to winds and
currents generally.

RED FOGS A>:D SEA BREEZES. 131

directed. I was involuntarily led from one research to another,
and it is the result of these investigations to vfhich I would
modestly give a place at the conclusion of Maury's Physical Geo-
graphy of the Sea, mth 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 developed. There as the gor-
geous ' eye of day ' rises almost perpendicularly from the sea with
fiery ardom', in a cloudless sky, it is greeted by the volcanoes mth a
coliunn of wliite smoke, which, ascending from the conical summits
high in the fii'mament above, forms a croTSTi, 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, furnishes, with its fresh breath, so much enjoyment to the
inhabitants of that sultry belt of the earth, for, by means of it,
everything 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 commencmg everywhere the
mornmg hymn of mute natm^e, whose gesticulation is so expressive
and sublime. All that hves feels the necessity of pom^ing forth,
each in its way, and in various tones and accents, from- the depths
of inspiration, a song of praise. The ah', stiU filled with the fresh-
ness of the evening dew, bears aloft the enraptm'ed song, as,
mingled with the jubilee tones which the contemplation of natm-e
everywhere forces from the soul, it gushes forth in deep earnest-
ness to convey the daily thank-ofiermg over the sea, over hill and
dale.t As the sun ascends the sky, the azm^e vault is bathed in
dazzhng 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
stilhiess of the calm. But not so ^^ith the atmosphere : it sparkles,
and glitters, and tmnkles, becoming clear under the increasing
heat, while the gentle swelling of the now polished waves reflects,
like a thousand min^ors, the rays of light which dance and lea]) to
the tremulous but vertical movements of the atmosphere. Like
pleasant visions of the night, that pass before the mind in sleep, so

* Upon the coast of Java I saw daily, during the east monsoon, such, a column
of smoke ascending at sunrise from feromo, 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,

K 2

132 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

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 ofl&ng. All objects become distinct
and more clearly delineated,* while, upon the sea, small fishing-
boats loom up like large vessels. The seaman, drifting along the
coast, and misled by the increasing clearness and mirage, believes
that he has been driven by 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.f The planks
burn mider his feet ; in vain he spreads the a^vning to shelter him-
self 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 hght 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 vnth. a bountiful store of
building material for their pictm^esque 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 depend-
ent upon the winds, upon the clouds, and upon the sunshine ; for
upon these depend the vapour and the rains which feed the streams
that bring nourishment for them into the sea 4 Wlien the sun
reaches the zenith, and his stern eye, with bmiiing glare, is
tm'ned 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 micertain 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 movement appears to be not
easily overcome by the horizontal which we call wind. Yonder,
far out upon the sea, arises and disappears alternately a darker
tint upon the otherwise shining sea-carpet ; finally that tint

* The transparency of the atmosphere is so great that we can sometimes
discover Venus in the sky in the middle of the day. — Jaksen.

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

X The archipelngo of coral islands on the north side of the Straits of Sunda is
remarkable. 33efore 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. — Jansex.

EED FOGS AND SEA BREEZES. 133

remains and approaches ; that is the long-mshed-for sea breeze :
and yet it is sometimes one, yes, even two hours before the darker
tint is permanent, before the sea breeze has regularly set in.
Now small white clouds begin to rise above the horizon ; to the
experienced seaman they are a prelude to a fresh sea breeze. We
welcome the iu\st breath from the sea ; it is cooling, but it soon
ceases ; presently it is succeeded by other grateful puffs of air,
which continue longer; presently they settle down into the
regular sea breeze, with its coohng and refreshing breath. The
sun dechnes, and the sea wind — that is, the common trade-wdnd
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 refi'eshed uj)on the deep,
becomes gray from the vapour which envelops the promontories
in mist, and cm'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 from shore than he really is, and steers on his com-se care-
lessly, wdiile the capricious wind lashes the waters, and makes a
short and broken sea, fi'om the white caps of w^hich light cmds
are torn, with sportive hand, to float away hke party-colom'ed
streamers in the sunbeam. In the meanwhile clouds appear now
and then high in the air, yet it is too misty to see far. The sun
approaches 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 wdnd has laid down the lash, the sea, which,
chafing and fretting, had with curled mane resisted its violence,
begins to go dovni also. Presently both v/ind 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
dri^dng brine, that has made a salt-pan of the face, the short,
restless sea, the dampness — all have grovv^n wearisome, and welcome
is the calm. There is, hoAvever, a somewhat of dimness in the
air, an uncertain but threatening appearance. Presently, fi-'om

* At Buitenzorg, near Biitavia, 40 English miles from the shore, five hundred
feet above the sea, with high hills around, these thunder-storms occur betweeu
4 p. M. and 8 p. m.

134 PHYSICAL GEOGRAPHY OF THE SEA, AOT) ITS METEOROLOGY.

the dark mass of clouds, wliicli hastens the change of day into
night, the thunder-storm peals forth. The rain falls in torrents in
the mountains, 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. AVhat 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 gro^vmg stronger, as usual dming the whole night. If
the land breeze meets with a squall, then it is brief, and becomes
feeble and micertain. 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 sometimes suffers itseK 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 accord-
ing to the theory which ascribes the origin of the sea and land
breezes to the heating of the soil by day, and the coohng by
means of radiation by night ; for, dming the rainy season, the
clouds extend over land and sea, interrupting the sun's rays by
day and the radiation of heat by night, thus preventing the
variations of temperature ; and from these variations, according to
this th^eory, 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. One of the causes which make the west coast of Africa so
Sanitary influences of very Unhealthy wlicu comparod with places in cor-
laud and sea breezes, responding latitudes ou the opposite side of the At-
lantic, as in Brazil, is no doubt owing to the difference in the land
and sea breezes on the two sides. On the coast of Africa the land
breeze is " universally scorcliing hot."* There the land breeze is
the trade-wind. It has traversed the continent, sucldng up by the
way disease and pestilence from the dank places of the interior.
Eeeking with miasm, it reaches the coast. Peru is also within the
trade-^vind 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

* Jansen.

EED FOGS AND SEA BEEEZES. 135

come cool and fresh from the pure snows of the Ancles. Betvreen
this range and the coast, instead of marshes and a jungle, there is
a desert — a rainless country, upon which the rays of the sun play
with sufficient force not only to counteract the trade-wind power and
produce a calm, but to tm^n the scale, and draw the air back from
the sea, and so cause the sea breeze to blow regularly.

318. On the coast of Africa, on the contrary, a rank vegetable
Influences which re- gTOwth scrcons the soil from the scorching rays of
giiiate then- strength. ^j^Q ^^j^^ ^j^^ ^--^q rarcfaction iS uot ovcry 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 fi'esh, 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 topography
of a place, but also upon its situation with regard to the prevail-
ing winds ; and also that a given difference of temperatui'e
between land and water, though it may be sufficient to produce
the phenomena of land and sea breezes at one place, v\'ill not be
adequate to the same effect at another ; and the reason is perfectly
philosophical.

319. It is easier to obstruct and turn back the current in a
Lnna breezes from sluggish tliau iu a rapid stream. So, also, in
AWca scorching hot. tiu^ning a currcut of air first upon the land, then
upon the sea — very shght alternations of temperatm^e 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 considerable 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 therefore, if this view be correct, the sea
breeze should be more feeble than the land breeze, neither should it
last so long.

136 PHYSICAL GEOGRAPHY OF THE SEA, KKD ITS METEOROLOGY.

320. But on the opposite side — on the coast of Brazil, as at Per-
and breeze in Bra- namhiico, for instanco — where the trade-wind comes-
11 and Cuba. 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 which 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
Afiica, and for the simple reason that the Gulf shores lie nearly
parallel with the prevailing direction of the winds. In Kio de Ja-
neiro, the sea breeze is the regular trade-v/ind made freshei' by tha
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. "Happy he," remarks Jansen, "who, in the Java Sea at
Nighty scenes when eveuing, scckiug tho land breeze off the coast, finds
breezl. it there, after the salt-bearing, roaring sea wind, and
can, in the magnificent nights of the tropics, breathe the refresh-
ing 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 tho
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 wholly
replaced by the sea breeze, or, rather, by the trade-:^vind. If
the land breeze continues, then the stars loom forth, as if to free
themselves from the dark vault of the heavens, but their light does
not wholly vanquish its deep blue, which causes the Coal-sacks ta
come out more distinctly near the Southern Cross, as it smiles,
consolingly upon us, while Scorpio, the emblem of the tropical cli-
mate, 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 in the un-
fathomable ocean afibrds a great contrast to the seeming quiet of
the gently-flowing, aerial current of the land breeze. But at times,,

* In the Koads of Batavia, however, they are not very agreeable. — Jansen.

KED FOGS AXD SEA BREEZES. 137

when, 30^ or 40° above the horizon, a fire-ball arises which sud-
denly illumines the whole horizon, appearing to the eye the size
of the fist, and fading :iway as suddenly as it appeared, falling into
fiery nodules, then we perceive 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 appear-
ance of which amazes the crevv-s of ships. When the slender keel
glides quicldy over the mirrored waters upon the wings of the
wind, it cuts for itself a sparkling way, and distm-bs in their sleep
the monsters of the deep, which whirl and dart quicker than an
eight-knot ship ; sweeping and tm-ning around their distm'ber,,
they suddenly clothe the dark smface of the water in brilliancy.
.A.gain, when we go beyond the hmits 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 j^O'^^'er to endm^e.
The fervent, fiery natm^e insphes the traveller with deep avve.
They who, mider the beating of the storm and terrible violence
of the ocean, look danger courageously in the face, feel, in the pre-
sence 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 sensa-
tions 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
affliction.! 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 gradually dies away as the sun
rises. The time at which it becomes calm after the land and sea
breezes is indefinite, and the calms are of unequal duration. Ge-
nerally, those which precede the sea breeze are rather longer than
those which precede the land breeze. The temperatm-e of the

* I have seen this hi a remarkable degree upon the south coast of Java ; these
sparks were then seen six feet above the deck, upon the frames of timber (Jcoussen
der hlohken), 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
Iwofdcn), which I have seen, liowever, but once dmiug all the years which I have
spent between the tropics.— Jansex.

138 PHYSICAL GEOaRAPHY OF THE SEA, AXD ITS METEOROLOGY.

land, the direction of the coast-line with respect to the preyailing
direction of the trade-wind in which the land is situated, the clear-
ness 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 aii', 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 continues uninterruptedly to blow.
The direction of land and sea winds must also be deteiTiiined by
local observations, for the idea is incorrect that they should always
blow per}3endicularly to the coast-Hne. 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, natm-e 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
display, 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 \-iolent, always strong thi^ough 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-wuid often blows so violently
that they have not sufficient power to force it beyond the coast.
Ovdng 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 only rises when it blows
hard from the south-east upon the south coast, is easily distin-
guished from the gentle land breeze. The regularity of the land
and sea breezes in the Java Sea and upon the coasts of the north-
em range of islands, Banca, Borneo, Celebes, etc., during the east
monsoon, must in part be ascribed to the hindi'ances which the
soiith-east trade-wind meets in the islands which he directly in its
way — in part to the inclination towards the east monsoon which

* Sucli is tlie case, among others, in the Strait of Madura, upon the heights of
Bezoekie.

EED FOGS AND SEA BKEEZES. 139

the trade-wind undergoes after it has come ^Yithin 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. Seamen tell us of ^' red fogs " which they sometimes en-
Eed fogs in the Medi- counter, especially in the yicinity of the Cape de
tcrratican. YeiS. Islauds. Li othcr 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 " Afiican
dust,"* because the w^inds which accompany them are supposed to
€ome from the Sii'occo desert, or some other parched land of the con-
tinent of Africa. It is of a brick-red or cinnamon colour, and it some-
times 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. Dr. Clymer, Flest-suj-geon of the African squadron, reports
Red fogs near the a red fog which was encountcred in February, 1856,
equator. I^y ^j^g U. S. ship Jamcstown. " 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 cahns 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
^outh-west cm-rent 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 powder, of a brick-dust or cinnamon colour.
The atmosphere was so dusky that we could not have seen a ship at
inidday beyond a quarter of a mile."t

324. Now the patient reader, who has had the heart to follow
Putting tallies on me in a preceding chapter (lY.) around with "the
the wind. WTiid in his circuits," will perceive that evidence in
detail is 5*et wanting to establish it as a fact that the north-east and
south-east trades, after meeting and rising up in the equatorial
■calms, do cross over and take the paths represented by K S and
F G, Plate I. Statements, and reasons, and arguments enough
have already been made and adduced (§ 288) to make it highly

* Prof. Ehrenl)er2: calls it "Sea-dnst."

t See Sailing Directions, 8th ed., vol. ii., p. 377.

140 PHYSICi\JL GEOGEAPHY OF THE SEA, AND ITS METEOPtOLOGY.

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 chamiels 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 circulation is such
as Plate I. represents it to be, might consider himself 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 smface. As diffi-
cult 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 the northern hemisphere. The
Shocco or African dust, which he has been observing so closely,
has turned out to be tallies put upon the wind m the other
hemisphere; and this beautiful instrument of his enables us to>
detect the marks on these little talhes as plainly as though those-
marks had been written upon labels of wood and tied to the wings
of the wind.

325. This dust, when subjected to microscopic examination, is.
Ji^Tuiefafm'^'^^^* ^^'^'^^ ^^ cousist of iufasoria and organisms whose
belts. habitat is not Africa, but South America, and in

the south-east trade-wind region of South 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 similarity 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 ; mdeed, they are the prevailing forms in every specimen
he has examined. It may, I think, be now regarded as an esta-
blished fact that there is a perpetual upper current of ah from

RED FOGS AND SEA BREEZES. 141

Soutli America to Nortli 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-^vinds, there can be no doubt. The "rain dust "has
been observed most fi'equently to fall in spring and autumn;
that is, the fall has occurred after the equinoxes, but at intervals
from them var3ring 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 sivimming in the atniosj^here hy continuous currents of
ah\ and lying in the region of the trade-u'inds, hut suffering j^cir-
tial and i^eriodical deviations''' It has already been shown (§ 295)
that the rain or calm belt between the trades travels up and do-\vn
the earth from north to south and back again, making the rainy
reason wherever 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 suggests,
it more 23robably 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 — everythmg 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 smface of the earth in this region,
(Strewed with impalpable and feather-light remains of animal and
vegetable organisms, is swept over by whirlwinds, gales, and tor-
nadoes of terrific force : this is the period for the general atmo-
<spheric distm^bances 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 re-
mains of dead animal and vegetable matter: these impalpable

* Humboldt.

Ii2 PIirSICAL GEOGRAPHY OF THE SEA, AND ITS IIETEOEOLOGY.

organisms, whicli each rainy season calls into being, to perisli tlie
succeeding season of drought, are perhaps distended and made
even lighter by the gases of decomposition which has been going
on in the period of drought. May not, therefore, the whirl-
winds 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. The Baron von Humboldt, in his Aspects of Nature, thus
Humboldt's descrip- coutrasts the wot and the dry seasons there :

tion of the dust- whirl- ,, txti t ji i- i r> n

wmds of the Orinoco. "When, uudcr tno vertical rays oi the never-
clouded sun, the carbonized turfy covering falls into dust, the in-
dm-ated soil cracks asunder as if from the shock of an earthquake.
If at such times two opposing currents of air, whose conflict pro-
duces a rotary motion, come in contact with the soil, the plain as-
sumes 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
cmTent, resembling the loud water-spout, dreaded by the expe-
rienced mariner. The lowering sky sheds a dim, almost straw-
coloured light on the desolate plain. The horizon di'aws suddenly
nearer, the steppe seems to contract, and mth it the heart of the
wanderer. The hot, dusty particles Avhich fill the air increase its
suffocating heat, and the east wind, blo\\dng over the long-heated
soil, brings with it no refreshment, but rather a still more bm-ning
glow. The pools which the yellow, fading branches of the fan-
palm had protected fi'om evaporation, now gradually disappear,
xis in the icy north the animals become torpid with cold, so here,
imder the influence of the parchmg drought, the crocodile and the
boa become motionless and fall asleep, deeply bmied in the dry
mud. . . . The distant palm-bush, apparently raised by the
influence of the contact of unequally heated and therefore im-
equally dense strata of air, hovers above the ground, from which
it is separated by a narrow mtervening margin. Half-concealed
by the dense clouds of dust, restless with the pain of thhst and
hunger, the horses and cattle roam around, the cattle lovang dis-
mally, and the horses stretching out their long necks and snuffing
the wind, if . haply a moist current may betray the neighbour-

EED FOGS AXD SEA EEEEZES. 143

hoocT of a not wholly dried-up pool. ... At length, after tlie 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 refi'eshing moisture, when the previously
terren 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 hght, mifold their
droopmg, 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 mornmg."

327. The arid plains and deserts, as well as high moimtain
Are the great de- rangos, havc, it mav well be supposed, an influence

serts centres of cir- n , f> n "'•■'•. • i

cuiation? upon the movements oi the great aerial ocean, as

shoals and other obstructions have upon the channels of circula-
tion in the sea. The deserts of Asia, for instance, produce (§ 299)
a disturbance upon the grand system of atmospherical chculation,
which, m summer and autunm, is felt in Europe, in Liberia, and
away out upon "^^h^ Indian Ocean, as far as the parallel of the 10th
degree of south latitude. There is an indi'aught from all these regions
towards these deserts. These indraughts are kno^Ti as monsoons at
sea ; on the land, as the prevaihng winds of the season. Imagine the
area within which this indraught is felt, and let us ask a question
or two, hoping for ansvrers. The air which the indraught brings
into the desert places, and which, being heated, rises up there,
whither does it go ? It rises up in a column a few miles high and
many in chcumference, we know, and we can imagine that it is like
a shaft many times thicker than it is tall ; but how is it crovvaied ?
Is it crooned like the stem of a mushroom, with an efilorescence
or ebulhtion of heated au' flaiing over and spreading out in all
directions, and, then gradually thinning out as an upper cmTent,
extending even unto the verge of the area whence the indi'aught
is drawn ? If so, does it then descend and return to the desert
plains as an indraught agam ? Then these desei^t places -would
constitute centres of chcidation for the monsoon period; and if
they were such centres, whence vvould these winds get the vapour
for their rains m Europe and Asia ? Or, histead of the mushroom
shape, and the flare at the top in all directions from centre to
circumference, does the uprising column, hke one of those subma-
rme fountauis which are said to be in the Guh Stream otl* the
coast of Elorida, bubble up and join in with the flow of the
upper current? The right answers and explanations to thes^

144 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 hght here. Let us hope.

328. The colour of the "rain dust," when collected in parcels
The colour of "sea- : and seut to Ehreuberg, is "brick-red," or "yellow
■^"^^•" ochre ;" when seen by Humboldt in the air, it was
less deeply shaded, and is described hy hini as imparting a " straw
•colom^ " to the atmosphere. In the search of spider-lines for the
diaphragm of my telescopes, I procui'ed 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 colom^ ; 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. It aj^pears, therefore, that we here have placed in our hands
A clew leading into a clow, which, attenuated and ejossamer-like thout^h
souLh. it at first appears, is nevertheless palpable and
strong enough to guide us along through the " circuits of the
"wind " even imto " 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 Yerd Islands, is remarked
upon with emphasis by the microscopist. It is worthy of remark,
because, in connection with the investigations at the Observatory,
it is significant. The latitudmal limits of the northern edge of
the north-east trade-wmds are variable. In the spring they are
nearest to the equator, extending sometimes at this season not far-
ther fi-om the equator than the j)arallel of 15° north. The breadth
of the calms of Cancer is also variable ; so also are then' limits.
The extreme vibration of this zone is between the parallels of 17°
and 38° north, according to the season of the year.

330. According to the hypothesis (§ 210) suggested by my
Says^oSurrihe" r^searches, this is the region in which the upper
same place, but they curreuts of atmosplicre that ascended in the equa-

occiir on a north-east , • ^ ^ -, ^n TiY'j_j_i j_i t'^t

and soutii-west range, tonal caims, anci liowecl on to tne nortnwarcl and
eastward, are supposed to descend. This, therefore, is the region
in which the atmosphere that bears the "ram dust," or "African
sand," descends 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 Yerd

RED FOGS AND SEA BREEZES. 145

Islands are situated ; tliey are in the direction wliicli theory gives
to the upper current of air from the Orinoco 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. It is true that, in the present state of our information, we
Condition rpquisite camiot tcll wliv tliis "rain dust" should not be

to the production of in • • , i ^ n n • , ^

a sea'fog. gradually precipitated irom this upper cmTcnt, and

descend into the stratum of trade-Avinds, as it passes from the
equator to higher northern latitudes ; neither can we tell why the
vapom' 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 any other atmo-
sj)herical j)henomenon to-morrow, and not to-day : all that we can
say is, that the conditions of to-day are not such as the pheno-
menon requires for its own development. Therefore, 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 occm' 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 — favom^able to its
descent, and that these conditions, as with the vapom-, may occiu'
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 by the fall of sea or rain dust, we may suppose that the
ciUTents in the upper regions of the atmosphere are remarkable ^r
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 distm^bances in the atmosphere and the occm--
rence of these shoAvers, thoucfh it does not enable us to determine
the true rate of motion in the general system of atmospherical
circulation, yet assm^es us that it is not less on the average than a
certain rate. We cannot pretend to prescribe the conditions requi-
site for bringing the dust-cloud down to the earth. The radiation
fi'om the smoke-dust — as the particles of visible smoke may be
called — has the effect of loadinsr each little atom of smoke with

146 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

dew, causing it to descend in tlie black fogs of London. Any
circumstances, 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. I do not offer these remarks as an explanation with which
What is the agent ^rg ouglit to rcst Satisfied, provided other proof can
acTosfthe^caim belts? be obtained; I rather offer them in the true philo-
so]}hical spirit of the distinguished microscopist himself, simply as
affording, as far as they are entitled to be called an explanation,
that explanation which is most in conformity wdth 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
pro^dnce, or that of any other philosopher, to dictate behef. Any
one may found hypotheses if he will state his facts and the rea-
soning by which he derives the conclusions which constitute the
hyi^othesis. 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 j^resence
has never yet been clearly recognized. When the ?jr vrliich 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 ? 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
iis 10 " the relation between magnetism and the circulation of the
atmosphere " may perhaps throw some light upon the answer to
this question.

14'

CHAPTEE YII.

§ 341-368. — THE EASTING OF THE TKADE-WIXDS, THE CROSSIKa
AT THE CALM BELTS, AND THE MAGInETISM OF THE ATMOSPHERE.

341. Halley's theory of the trade-winds, especially so mncli of it
iiaiiey'sdieorynot as ascribcs their castcrly direction to the effect of the
observSns!^ '^ diumal 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 nnited in a common system
of research concerning the physics of the sea, and occupied it with
observers, that we have been enabled to apply the exioerimentum
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 observations — each one itself being the mean of
many separate ones — upon the force and direction of the trade-
winds. It appears from these that dim^nal rotation being re-
garded as the sole cause, does not entirely account for the easting
of these winds.

342. From these observations the following table has been com-
observed course of piled. It shows the mcau annual direction of the
the trade-wiuds. tradc-wuids 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 :

Between

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

Mean . . .

N.E. Trades.

Course.

No. of Obs.

N.

51°

51° 30'
53° 30'
52° 30'
53° 30'
54° 30'

E.

N. 52° 45' E.

G8, 777
44, 527
33, 103
30, 339
36, 841
67, 829

S.E. Trades.

Course.

S. 46°
49° 20'
52°

49° 40'
51° 40'
48° 40'

S. 49° 33' E.

No. of Obs.

66, 635
66, 395
46, G04
43, 817
54, 648
72.945

Between the equator and 5° north, the annual average dm-ation of
the trades is 67 days for the north-east, and 199 for the south-east,

L 2

148 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IIETEOEOLOGT.

■with a mean direction for the latter — which are the prevaiHng
winds hetween those parallels — of S. 47° 30' E. According to the
Halleyan theory these should be south-w^est mnds.

343. In the Atlantic the average velocity of the south-east is.
Velocities of the greater than the average velocity of the north-east
trade-winds. tradcs.* I estimate one to be from 14 to 18, the

other from about 25 to 30 miles an hour. Assuming their velocity
to be 14 and 25 respectively, the following departures show the
miles of easting which the trade-winds average per horn* through
each of the above-named belts :

Hourly Eate of Depaetl-re of the Teade-winds aceoss the Belts.

Between

N.E. Trades.

S.E. Trades.

Easting per Hour.

Easting per Hour.

30^ 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. G „

5° and 0°

11.4 „

18.8 „

344. That dim-nal rotation does impart easting to these wiads
Difference between thoro is uo doubt : but the path Suggested by the

observation and iiii i e j.xlj.1' 1 T i.

theory. table docs not coniorm to that wdiicn, accorcimg to

any reasonable h3rpothesis, the trade-winds w^ould follow if left to-
obey the forces of dim^nal rotation alone, as they would do w-ere
dimiial 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 liave be-
tw^een 30^ and 25°. Nay, the south-east trades between the equa-
tor and 5° N. — where, by the Halleyan theoiy, they sJiouId 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 resistmg 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 diimial rota-
tion should not, until more numerous and accm^ate observations

* "Average Force of the Trade-^vinds," p. 857, vol. ii., Maury's Sailing Direc-
tions, 1859

EASTING OF THE TKADE- WINDS, ETC. 149

shall better satisfy the theory than those half a million and more
now do, he regarded as the sole cause of the easterly dhection of
the trade-winds. It suggests either that other agents are concerned
in gi^'ing the trade-winds theh easting, or that the effect of the
upper and counter cm-rent, when drawn down and tm^ned hack
,(§ 232), is such as to counteract their unequal turning in ohedience
to the vaiying forces of dimiial rotation. No apology is needed
for appljang the tests of actual observation to this part of the Hal-
leyan theor)^, notwithstanding the general concmTence of opinion
as to its sufficiency. With equal favom- that featm-e 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 smce Hal-
ley expounded his trade-wind theory suggested a review of that
featm-e, and it was fomid 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 vapom^
for the equatorial cloud-ring and its rains is now also (§ 252) re-
■cognized as an agent of no feeble power in this calm belt.

345. Where shall those who are disposed to search, look for this
Faraday's discovery other agcut that is supposcd to be conccmed with the
^f magnetism in t e ^^^^-j^.^^.^-^^jg jj^ ^]^g^, castiug ? I canuot Say wliore
it is to be found, but considering the recent discoveries in terres-
trial magnetism — considering the close relations between many of
its phenomena and those both of heat and electricity — the question
may be asked whether some poAver capable of guiding " the wind
in his circuits " may not Im'k there ? Oxygen comprises more than
one fifth part (two ninths) of the atmosphere, and Faraday has dis-
covered that oxygen is para-magnetic. If a bar of iron be sus-
pended between the poles of a magnet, it will arrange itself axially,
and point toAvards them ; but if, instead of iron, a bar of bismuth be
used, it will arrange itself equatorially, 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 natm-e belong to one or the other
of the two classes of which iron and bismuth are the types.

346. This eminent philosopher has also shoAMi that if you place
Lines of masnetic ^ maguctizcd bar of irou ou a smooth smface, and
force. " g-f^ £j^g ^,Qj^ filings doAvn upon it, these filings will
arrange themselves ia curved lines as in Fig. 1 ; or, if the bar be

150 PHYSICAIi GEOGBAPHY OF THE SEA, AND ITS IMETEOROLOGY.

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, are held ta

Fig. 1.

'^\J'-

llli

be just such lines as those are which surround artificial magnets ;
proceed whence they may, they are supposed to extend through the
atmosphere, and to reach even to the planetary spaces. Many
eminent men and profound thinkers, Sh 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 m.eteor-
ology of our planet, exercise a marked influence upon the magnetic
condition of the atmosphere also.

347. Now, when, referring to Dr. Faraday's discovery (§ 345),
The TBagnetic influ- and the magnetic lines of force as shown by tli&
Tthe air a^d^f^e Irou filhigs (§ 346), WO comparo the particles of oxy-
spots on the sun. ggj^ gg^g j^q tliesc miuuto bits of fcrruginous 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^
filels in comparison gross and ponderous matter; — that the entire

EASTING OF THE TRADE- WINDS, ETC. 151

mass of this air is equivalent to a sea of mercury covering the earth
aroimd and over to the depth of 30 inches, and that this very sub-
tile mass is in a state of unstable equilibrium, and in perpetual com-
motion by reason of various and incessant distm'bing 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 fomitain of magnetism, there is at least reason to suspect
a close alliance between solar and terrestrial magnetism ; — that
certain weU-known meteorological phenomena, as the aurora, come
also within the category of magnetic phenomena ; — that the mag-
netic 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 coinci-
dent mth either the terrestrial or with that which the direct solar ray
would indicate, but that it follows, and in its double curvatures con-
forms to the magnetic equator ; — moreover, vdien we reflect upon
Barlow's theory and Fox's observations, which go to show that
the direction of metallic veins of the northern hemisphere, Avhich
.generally lie north-east and south-westwardly, must have been in-
fluenced by the direction of the magnetic meridians of the earth or
vji ; — finally, I say, when we reflect upon magnetism in all its
aspects, we may well inquke whether such a mass of highly mag-
netic gas as that which surrounds our planet does not intervene, by
reason of its magnetism, in influencing the circulation of the atmo-
sphere and the com'se of the winds.

318. This magnetic sea, as the atmosphere may be called, is con-
The needle in its di- tinuallv ae^itatod I it is disturbed in its movements by

unial variations, the .«^."^^ i-i , ■ i i^ t i •

barometer in its read- various mnuences wnicu prevcut it irom adjusting
sphere'in its^eteSrkai itsclf to any permanent magnetic or other dynamical
s^mriours foTtheir status ; and its para-magnetic properties are known
maxima and minima, to Vary with cvcry chaugo of pressm'o or of tempera-
tm^e. The experiments of Faraday show that the magnetic force
of the an* changes with temperature ; that it is least near the
equator, and 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 hom's of maximum and mininum tension. Coincident with
this, and in aU parts of the world, but 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. Without other.

152 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS I^IETEOEOLOGY.

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 flomngs — the diurnal change
in the electrical t^sion — the diurnal variation of the needle, — and
the dim-nal 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 invaria-
bly puts it in motion, giving rise to gentle airs or fmious gales,
according to degree ; and here, at least, we have a relation between
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. Indeed, such is the natm^e of this imponderable called mag-
The question raised by nctism, and sucli the suggostious made by Faraday's
modern researches, discovcries, that the qucstiou 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 som^ce. Sm'ely, then, it cannot be considered as miphilo-,
sophical to inquire of magnetism for some of the anomalous move-
ments that are observed in the atmosphere. These anomalies are
many ; they are not con&ied to the easting of the trade-v^ds ;
they are to be fomid 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 ch^cumstances
which seem to favom- this belief. Our researches have enabled us,
for instance, to trace fi'om the belt of calms, near the tropic of
Cancer, which extends entirely across the seas, an efflux of ah' both
to the north and to the south. From the south side of this belt
the air flows in a steady breeze, called the north-east trade-winds,
towards the equator (Plate I.) ; on the north side of it, the prevail-
ing winds come from it also, but they go towards the north-east.
They are the well-known westerly winds w^hich prevail along the
route from this coimtry 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 Em'ope, — the
land upon which these westerly winds blow, — precipitation is in ex-
cess of evaporation, and because at sea they are going from a warmer
to a colder climate ; and therefore it may be inferred that nature
.exacts fi-'om them what v,^e know she exacts from the air under

KVSTING OF THE TLADE- WINDS, ETC. 153

similar circmnstances, but on a smaller scale, before our eyes, viz.,
more precipitation than evaporation. In other words, they pro-
bably leave in the Atlantic as much vapom- as they take up from
the Atlantic. Then Avhere, it may be asked, does the vapour which
these winds carry along, for the replenishing of the whole extra-
tropical regions of the north, come fi'om ? They did not get it as
they came along in the upper regions, as a counter-cm-rent to the •
north-east trades, unless they evaporated the trade- wind clouds, and
«o robbed those mnds of their vapom*. They certamly did not get
it h'om the surface of the sea in the calm belt of Cancer, for they
did not tariy long enough there to become satm-ated with moisture.
ThiLs circumstances again pointed to the south-east trade-wind
regions as the place of supply. This question has been fully dis-
cussed in Chapter Y., where it has been sho^vn they did not get it
from the Atlantic. Moreover, these researches afforded gTounds 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 satm^ated with vapom'
^t its exodus, is diy ; for near their polar edge, the north-east
ti'ade-winds are, for the most part, diy winds.

350. Facts seem to confirm this, and the calm belts of Cancer
Wet and dry air of and Capricom both throw a flood of hght upon the
the calm belts. subjcct. Thcse are two bands of light afrs, calms,
and baflling winds, which extend entirely around the earth. The
afr 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
oalled, an efflux of dry air on one side and of moist on the other ?
Answer : upon the supposition that the air without rain comes
fr'om one quarter, that with rain fr'om another — that, coming fr'om
opposite directions to this place of meeting, where there is a cross-
ing, they pass each other in their cfrcuits. They both meet here
BS> upper cmTents, and how could there be a crossing, v/ithout 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 dfrection ?

351. He that estabhshed the earth "created it not in vain ; He
formed it to be inhabited." And it is presumptuous, arrogant, and

154 PHYSICAL aEOaPtAPHY OF THE SEA, AND ITS METEOROLOaY.

impious to attempt tlie study of its machinery upon any other:
toSi'thfphvsl?' theory : it tvas made to he inhaUtecl. How could it
cai macbiaery of our be inhabitable but for the sending of the early and
studied! ^ the latter rain ? How can the rain be sent except by
the winds ? and how can the fickle ^Tuds do their errands miless
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 infal-
libly led into error. And so it is with the physical machinery of
the world. The theory upon which this vfork is conducted is that
the earth ivas made for man ; and I submit that no part of the
machinery by which it is maintained in a condition fit for him is
left to chance, any more than the bit of mechanism by which man
measures time is left to go by chance.

352. That I might study to better advantage the workuigs of
Division into wind the atmosphcrical 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 these bands on
^ch side of the equator that are traversed more or less frequently
by om' fleet of observers ; they extend to the parallel of 60^ in each
hemisphere. To determine the force and dnection of the v^ind 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 for each of the fom' quarters in
every band was ascertained. Considering difierence of temperatm^e
between these various bands to be one of the chief causes of move-
ment in the atmosphere ; — 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 m a path crossing these
bands more or less obliquely, and that therefore the general move-
ments in the atmosphere might be classed accordingly, as mnds
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 ma-
chinery. See Plate XV.

EASTING OF THE TRADE- WINDS, ETC.

155

353. Thus, when, after so classing them, we come to examine
The medial bands, thosc 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 move-
ments to be exactly in opposite du^ections. Observations show
that dming the year the winds in the former blow toivards the
equator 283, and from it 73 days ; and in the latter they blow
toward the j^ole for 224, and from it 132 days. These facts show
that there must be a place of rarefaction — of low barometer, an in-
draught towards the poles as well as the equator ; — and that conse-
quently, also, there must be a medial line or band somev>^here be-
tween the parallels of 10° and 65^ south, on one side of which the
prevailing direction of the wind is towards the equator, on the
other towards the j^ole. 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 table.

Winds loith Northing and Wi7ids loith Southing in each Hemisphere, expressed bp
Average Number of Days for lohich they blow annually.

Bands.

Norlhern^Hemisphere.

Southern Hemisphere.

Northing.

Southing.

No. of Obs.

Northing.

Southing.

No. ofObs.

Between

Days.

Days,

Days.

Davs.

O^andSO

78

268

67,829

84

269

72,945

o^audlO^

158

182

36,841

73

283

54.648

lO^andlo^

278

73

27,339

82

275

43,817

island 20^

272

81

33,103

91

266

46,604

20^ and 250

240

101

44,527

128

227

66,395

25^ and 30^

185

162

68,777

146

208

66,635

30^ and 350

155

195

62,514

150

204

76,254

352 and 403

173

178

41,233

178

177

107,231

40^ and 453

163

186

33,252

202

155

63,669

453 and 59^

164

188

29,461

209

148

29,132

50^ and 553

147

204

41,570

208

151

14,286

553 and 603

141

213

Total

17,874
504,320

224

132

13,617
655,233

Observati

ons 1,15c

),553

_ The wind ciuwes (Plate XY. and the table) afford a very striking
viev/ of these medial bands, as the parallels in either hemisphere
between which the winds with northinsf and the winds with south-

156 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ing are on the yearly average exactly equal. In the nortliem
hemisphere the debatable ground appears by the table to extend
pretty nearly from 25° to 50^ N. By the plate the two wmds fii'st
become equal between 25° and 30° ; the two curves then recede
and approach very closely again, but without crossing, between
35° and 40°. In the southern hemisphere, the conflict between
the polar and equatorial indraught, as expressed by winds vdth.
southing and winds with northing, is more decided. There the
tv,^o cmTes 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 condition of the atmo-
sphere is more unstable in the northern than it is in the southern
hemisphere.

354. Such, for the winds at sea, is their distribution between
The rainless regions the two halvcs of the horizoii in the several bands
»jid the calm belts., ^^^ ^^ g^ch hemisphere. Supposing a like distri-
bution to obtain on shore, we shall find it suggestive to trace the
cahn belts of the tropics across the continents (Plate YIII.), and
to examine, in connection with them, the rainless regions of the
earth, and those districts of country which, though not painless,
are nevertheless considered as " clri/ countries," by reason of the
small amount of precipitation upon them. So, tracing the calm
belt of Cancer, w^hich at sea lies between the parallels of 28° and
37° (Plate YIII.), but which, according to Su' John Herschel,*
reaches higher latitudes on shore, it will be perceived that the
winds that flow out on the north side blow over countries abomid-
ing in rivers, which countries are therefore abmidantly supplied
with rains. Hence we infer (§ 350) that those winds are rain
winds. On the other hand, the winds that flow out on the equa-
torial side blow either over deserts, rainless regions, or dry coun-
tries. Hence we infer that these winds are dry v/inds. These
'** dry " winds traverse a comitry abomiding 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 equa-
torial side give out no moistm-e, except as dew, until they reach
the sea, and are replenished with vapom^ thence in sufficient quan-
tities to make rain of; whereas the winds which come out on the
polar side leave moistiu-e enough as they come for such rivers as
the Obi, the Yenisei, the Lena, and the Amoor, in Asia ; the Mis-
Rom'i, the Sascatchawan, the Eed Eiver of the North, and others,
* § 273, p. G14, vol. xvii. (Phys. Geog.), Encyclopedia Britannica.

EASTING OF THE TEADE-WIKDS, ETC. 157

in America. Between this calm belt and the head waters of these?
rivers there are no seas or other evaporatmg smfaces, neither are
they so situated with regard to the sea-coast that they may be, as
the shores of Eastern China and the Atlantic slopes of the United
States are, sii2:»phed mth vapoiu' by the winds from the sea-board.
When we consider the table (§ 353), the situation of the rainless
regions and diy coimtries 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 au', one well charged with moisture, the other dry and thirsty
to a degree.

355. The supposition that the diy air came fi-om the north and
The theory of the the moist from the south, and both as an upper cur-
Td tSS^eco'n. i^ent, is the only hypothesis that is consistent with
ciied by it. all the known facts of the case. The dry air gave

up all its moistui'e when, as a surface wind, it played upon the
frozen summits of the northern hills ; the wet obtained its mois-
tm^e when, as the south-east trade-^rads, it swept across the bosom
of intertropical seas of the southern hemisphere. Eising up at the
equator, it did not leave all its moisture with the cloud-ring, but,
retainmg a part, conveyed 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 polar side, is clearly indicative of a crossing. Uj^on
no other supposition can we account for the barremiess on one
side, the fertility on the other. The following are also links in
the chain of facts and cncumstances which give strength to the
supposition that the rains for the Lena and the Missomi are
brought across the calm belt of Cancer by those cmTents of air
which flow thence towards the pole as the prevailing comiter-
trades or south-westerly winds of the extra-tropical north. We
have akeady 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 Vv^nds retmn as
ABC through the upper regions from the pole ; that, arriving at
the calms of Cancer, this upper current, ABC, meets another
upper current, S E, from the equator, where they neutralize each
other, produce a calm, descend, and come out as smface ^rads,
D E, or the trade-winds ; and as T U, or the counter-trades.

158 PHYSICAL GEOGBAPHY OF THE SEA, AKD ITS METEOROLOGY.

l\ow obseryations have shown that the winds represented by T IT
are rain vands ; those represented by D E, diy 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 jomiiey they parted with all their
moistm^e, and, retrnming through the upper regions of the air to the
calm belt of Cancer, they arrived there as diy winds. The winds
represented by D E are dry winds ; therefore it was supposed
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 tiuii 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 vapom- enough to feed the great 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 w^as inferred that B C and E S do come out on the
smface 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 vapom-s 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. And if this
mode of reasoning be admitted as plausible — if it be true that
E S carry the vapom* vfhich, by condensation, is to water with show-
ers the extra-tropical regions of the northern hemisphere, Nature,
we may be sm^e, has provided a guide for conducting S T across
this belt of calms, and for sending it on in the right way. Here
it was, then, at this crossing of the winds, that I thought I fii'st
saw the footprints of an agent whose character I could not com-
prehend. 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 an- should
come out on this side or on that of this calm belt, or whether the
moist air should retmn 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

EASTING OF THE TRADE-WINDS, ETC. 159

•excessive, and then again seasons of rains the most destmctive ;
but, so far fi'om this, we find for each place a mean aminal pro-
portion 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
cm-rents of air, when they meet over the calms of Cancer and Ca-
IDricorn, are tmned back to the equator, but having shovm that
there is reason for supposing that the air of each current, after
descending, continues on in the direction towards which it was tra-
velling before it descended, we may go farther, and, by a similar
train of circumstantial evidence, afforded by these researches and
other som-ces of information, show that the air, kept in motion on
the sm'face by the two systems of trade-winds, when it arrives at
the belt of equatorial calms and ascends, continues on thence, each
cmTent towards the pole which it was approaching while on the
smface. In a problem like this, demonstration in the positive
way is difficult, if not impossible. We must rely for our proot
upon philosophical deduction, guided by the lights of reason ; and
in all cases in which positive proof cannot be adduced, it is per-
mitted to bring in cii'cumstantial evidence ; and the circumstan-
tial e^ddence afforded by my investigations goes to show that the
winds represented by 0 Q, § 215, tZo become those represented by
E S T U Y A, and A B C D E F respectively. In the fii^t
place, 0 Q represents the south-east trade- winds — i. e., all the winds
of the southern 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 contrary, 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 m the two hemi-
spheres, we might imagine that the constituents of the atmosphere
in them would, in the com'se 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 trades, when arrived at the zone of equatorial

160 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOPvOLOGY.

calms, should not, after ascending, rather retimi to the south than
go on to the north ? Where and what is the agency by which its
course is decided ? Here I found circumstances which again in-
duced me to suppose it probable that it neither tm-ned back to the
south nor mingled with the air which came fi'om 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 con-
tinued over into the southern hemisphere as an upper ciu-rent,
bomid 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. Therefore it is fair to sup-
pose that much of the vapom- which is taken up on that side of the
equator is precipitated on this. The evaporating smface in the
southern hemisphere is greater, much greater, than it is in the
northern ; still, all the gi^eat rivers are in the northern hemisphere,
the Amazon being regarded as common to both ; and this fact, as
far as it goes, tends to corroborate the suggestion as to the cross-
ing of the trade-winds at the equatorial calms. Taking the laws;
and rates of evaporation into consideration, I could find (Chapter
V.) no part of the ocean of the northern hemisphere fi^om which
the sources of the Mississippi, the St. Lawrence, and the other
great rivers of om^ hemisphere could be supplied. A regular
series of meteorological observations has been carried on at the mili-
taiy posts of the United States since 1819. Kain maps of the
whole country* have been prepared from these observations by
Mr. Lorin Blodget at the sm-geon general's office, and under the
direction of Dr. Cooledge, IT. 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 diy season in
California and Oregon is the wet season in the J\rississippi Val-
ley. The winds coming from the south-west, and striking upon
the coast of California and Oregon in Vv^nter, precipitate there
copiously. They then pass over the momitains robbed in part of
their moistm^e. Of com^se, after watering the Pacific shores, they
* See Army Meteorological Observations, publislied 1835.

EASTIXG OF THE TEADE-AYINrDS, ETC. 161

have not as mucli vapour to make rains of, specially for tlie npper
Mississippi Valley, as they had in the summer-time, when they
dispensed then- moistm-e, in the shape of rains, most sparingly upon
the Pacific coasts. According to these views, the diy season on
the Pacific slopes should be the wet, especially in the upper Mis-
sissippi Yalley, and vice versa. Blodget's maps show that such is
actually the case. Meteorological observations in the " Eed Eiver
countrv " and other parts of British America would throw farther
light and give farther confirmation, I doubt not, both to these
^dews and to this interesting question. These army observations,
as exj^ressed in Blodget's maps, reveal other interesting featm-es,
also, touching the physical geography of the country. I allude
to the two isothermal lines 45° and 65° (Plate YIII.), which in-
clude between them all places that have a mean annual tempera-
tm-e between 45° and 65°. I have di-awn, for the sake of com-
parison, similar hues on the authority of Dove and Johnston (A. K.,
of Edinbm-gh), across Europe and Asia. The isothenn of 65°
skirts the northern limits of the sugar-cane, and separates the in-
tertropical from the extra-tropical plants and productions. I have
di'a^^Tx these two lines across America in order to give a practical
exemplication of the nature of the advantages which the indus-
trial pm'suits and the pohtical economy of the country would de-
rive by the systematic extension of our meteorological observa-
tions from the sea to the land. These lines show how much we
err when we reckon chmates according to parallels of latitude.
The space that these two isotherms of 45° and 65° comprehend
between the Mississippi and the Piocky Mountains, o^ving to the
singular effect of those mountains upon the climate, is larger than
the space they comprehend between the Mississippi and the At-
lantic. Hyetographically it is also different, being dryer, and pos-
sessing a pm-er atmosphere. In this grand range of climate be-
tween the meridians of 100° and 110° W-., the amount of precipi-
tation is just al)out one half of what it is between those two iso
therms east of the Mississippi. In this new country west of it,
winter is the day, and spring the rainy season. It includes the
climates of the Caspian Sea, which Humboldt regards as the most
salubrious in the world, and where he fomid the most dehcious
fruits that he saw dming his travels. Such was the pm'ity of the
air there, that pohshed steel would not tarnish even by night ex-
posiu'e. These two isotherms, mth the remarkable loop which
they make to the north-west, beyond the Mississippi, embrace the

M

162 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS lilETEOEOLOGY. '

most choice climates for tlie olive, tlie Yme, and the poppy ; for
the melon, the joeach, and almond. The finest of "wool may be
grown there ; and the j)otato, 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 sm-pass in salubrity that
of this Piedmont trans-Mississippi 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 pre-
vail from the north-west instead of the south-west, and on the equa-
torial side from the south-east instead of the north-east. Now if it
be true that the vapom- of the north-east trade--\\dnds is condensed
in the extra -tropical regions of the southern hemisj)here, the fol-
lowing path, on account of the effect of diurnal rotation of the
earth upon the com'se of the winds, would represent the mean cir-
cuit of a portion of the atmosphere moving according to the gene-
ral system of its circulation over the Pacific Ocean, viz. : coming
down from the north as an upper cm-rent, and appearmg 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
trade- winds of that region. To make this clear, see Plate YII., on
which I have marked the course of such vapom'-bearing v\^ds ; A
being a breadth or sivath of vdnds in the north-east trades ; B, the
same wuid as the upper and counter-cmTent to the south-east
trades ; and C, the same vdiid. after it has descended in the calm
belt of Capricorn, and come out on the 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-"^TQd, it sweeps
over a gTeat 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 diur-
nal 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

EASTING OF THE TEADE- WINDS, ETC. 163

ihe siirface from warmer to colder regions, it mnst, in this part of
its circuit, precipitate more than it evaporates. Now it is a coin-
cidence, 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 smface ; the route
by which all circumstances are most favoiu:able to complete satura-
tion ; and this is the route by which they can pass over into the
southern hemisphere most hea\'ily laden with vapom-s for the ex-
tra-tropical regions of that half of the globe ; and this is the sup-
posed route which the north-east trade-winds of the Pacific take to
reach the equator and to pass from it. Accordingly, if this pro-
cess of reasoning be good, that j)ortion of South America betvreen
the calms of Capricorn and Cape Horn, upon the mountain ranges
of which this part of the atmosphere, whose circuit I am consider-
ing as type, first impinges, ought to be a region of copious pre-
cipitation. Now let us turn to the works on Physical Geography,
and see what we can find upon this subject. In Berghaus and
Johnston — department Hyetography — it is stated, on the autho-
rity of Captain King, K. N., that upwards of twelve feet (one hun-
<ired and fifty-three inches) of rain fell in forty-one days on that
part of the coast of Patagonia which Hes 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 YIII.
These conditions, the direction of the prevailing -^A^nds, and the
amount of precipitation, may be regarded as evidence afforded by
natm-e, if not in favom' of, certainly not against, the conjectm-e that
such may have been the voyage of this vapom' 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 vapoiu\

356. Notwithstanding the amount of circumstantial e^adence
SJi^two?'?r ' ^% ^^^^ ^^^ already been brought to show that the air
air cross ? answered, which the uorth-cast and the south-east trade-winds
discharge into the belts of equatorial calms, does, in ascending,

M 2

164 PHYSICUl, GEOGRAPHY OF THE SK\, AND ITS METEOROLOGY.

cross — that from the southern passing over into the northern, and
that from the northern passing over into the southern hemisphere
(see 0 Q E S, and D E F Gr, § 215) — yet some have imphed
doubt by asking the question, " How are two such cm-rents of air
to pass each other ?" And, for the want of light upon this point,
the correctness of my reasoning, facts, inferences, and deductions
have been questioned. In the fii'st 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 pom- into it is only about three miles, for that is
supposed to be about the height to which the trade-wmds extend.
Thus we have the air passing into these calms by an opening on
the north side for the north-east trades, and another on the south
for the south-east trades, having a cross section of tln^ee miles ver-
tically to each opening. It then escapes by an opening upward,
the cross section of which is sixty or one himdred, or even three
hmidred miles. A very slow motion upward there will cany off
the air in that direction as fast as the two systems of trade-winds,
with their motion of twenty miles an hour, can pour it in ; and that
curds or flahes of aii' can readily cross each other and pass in
different directions without interfering 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 ciu'dles
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 smface, is caused by the
ascent and descent, at one and the same time, of flakes of air at
different temperatm^es, the cool coming dow^i, the warm going up.
They do not readily commingle, for the astronomer long after
nightfall, when he tm^ns 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 difter in
temperature (and why not ?) from that brought by the south-east
trades we have the authority of nature for saying that the two
currents would not readily commingle (§ 98). Proof is daily
afforded that they would not, and there is reason to believe that the
air of each cm-rent, in streaks, or patches, or flahes, does thread its
way through the air of the other without difliculty. Therefore we
may assume it as a postulate which natm-e concedes, that there is no
physical difficidty as to the two cm-rents of air, which come into

EASTING OF THE TRADE- WINDS, ETC. 165

those calm belts from difterent directions, crossing over, each in its
proper direction, without mingling.

357. The same process of reasoning which conducted us (§ 355)
The rain winds ill the into the tradc-wiud Tcgion of the northern hemi-
jiississippi Valley, gphero for the sources of the Patagonian rains, now
invites us into the trade-wind regions of the South Pacific Ocean
to look for the vapour siblings of the Mississippi. If the rain ^™ds
of the Mississippi Yalley 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 wmds come from the
south, then the vapom' springs might, perhaps, be in the Gulf of
Mexico ; if the rain winds come h'om the north, then the great
lakes might be supposed to feed the air with moisture for the
fountains of that river ; but if the rains come from the west, where,
short of the great Pacific Ocean, should we look for the place of
evaporation ? AVondering where, I addressed a circidar letter to
farmers and planters of the Mississippi Yalley, requesting to be
informed as to the direction of their rain mnds. I received replies
from Virginia, Mississippi, Temiessee, Missouri, Indiana, and Ohio ;
and subsequently, from Colonel W. A. Bird, Bufialo, 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, Avith the
exception of one in Missomi, said, " The south-west winds bring us
om* rains." These muds certainly cannot get their vapoiurs 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
temperatm^e ; and the winds in the Mississippi valley, not being in
contact with the ocean, or with any other evaporating surface to
supply them with moistm^e, must bring with them from some sea
or another that which they deposit. Therefore, though it may be
urged, inasmuch as the winds which brought the rains to Patagonia
(§ 355) came direct from the sea, that they therefore took up
their vapom-s as they came along, yet it cannot be so urged in this
case ; and if these winds could pass with their vapom's fi'om the
equatorial calms through the upper regions of the atmosphere to

166 PHYSICAL aEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the calms of Cancer, and then as siu-face 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 mth vapours, they must precipitate as they go,
and take up less moistm-e than they deposit. The circumstance that
the rainy season in the Mississippi Yalley (§ 355) alternates with
the dry season on the coast of California and Oregon, indicates
that the two regions derive vapom- for their rains from the same
fountains.

358. During the discussion on this subject, my friend Baron von
Ehrenberg and his Grcrolt, the Prussiau minister, had the kindness to
microscope. placc in my hand Ehrenberg's work, " Passat-Staub

und Blut-Eegen." Here I foimd another clew 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 probability that the general com'so
of atmosjDherical chculation 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 hemisj)here, after arri-vdng at
the belt of equatorial calms, ascend and continue in then' course
towards the calms of Cancer as an upper cul'rent from the south-
west, and that after passing this zone of calms, they are felt on
the surface as the prevailing south-west wuids of the extra-tropical
parts of our hemisphere ; and that for the most part, they bring
their moistm-e 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 Hne in dots denoting where it was in the upper
cm-rent, and the unbroken hne where it was wafted by a smface
cmTcnt ; also on the same plate is designated the part of the South
Pacific in which the vapour-springs for the Mississippi rains
are supposed to be. The hands ((m^) point out the dkection of
the wind. Where the shading is light the vapour is supposed to be
carried by an upper cmTent. Such is the character of the cu'cum-
stantial evidence which induced me to suspect that some agent,,
whose office in the grand system of atmospherical circulation is
neither understood nor recognized, was at work in these calm.

167

belts and other places. It may be electrical, or it maybe magnetic,
or botli conjoined.

359. The more we study the workings of the atmospherical
Queteiets observa- machinery of our planet, the more are we impressed
^^^^^- with the conviction that we as yet know very little con-
cerning its secret springs, and the httle " 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 electricity. He has shown
that there is in the upper regions of the air a great reservoir of
positive electricity, which increases as the temperatm^e diminishes.
So, too, mth the magnetism of the oxygen in the upper regions.

360. In the southern hemisphere, we may, by reason of its great
At sea in the south- aqucous area, suppose the g-eneral lavv^ of atmo-
have the rule, on sj)herical movemeuts to be better developed than it
the'exce^prion^fas^to is iQ the northcm hemisphere. We accordingly

tion^uhe^atmo"^''' ^^^ ^J ^^® ^^'^^^ (§ ^^^) ^^^* *^® movcmeuts uorth
sphere. and south between 45° and 50° correspond with the

movements south and north between 25° and 30° ; that as you
go h^om the latter band towards the equator the winds with southing
in them increase, while the mnds with northing in them increase as
you go from the former towards the pole.

361. This is the law in both hemispheres : thus indicating that
The magnetic poles, tliore must bo iu the polar resions, as in the equa-

the poles of the wind , • -, ^ i S n ii i-n

and ofcoid coincident, tonal, a calm placc, where these polar-bounci wmds
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 of 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,* andlwas^then
moved to propound it by the inductions of theoretical reasoning.
Observers, perhaps, may never reach those mhospitable regions
with their instruments to shed more light upon this subject ; but
Parry and Barrow have fomid reasons to believe in the existence
of a perpetual calm about the north pole, and later, Bellot has
reported the existence of a calm region within the frigid zone.
Professor J. H. Coffin, in an elaborate and valuable paper t on the

* Maury's Sailing Directions.

t Smithsonian Contributions to Knowledge, vol. vi., 1854.

168 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

"AViXDS OF THE Northern Hemisphere," arrives by dediiction
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
hundred 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,* in latitude 73° 35' north, longitude
95° 39' w^est. Neither of these poles is a point suscej)tible of
definite and exact position. The polar calms are no more a point
than the equatorial calms are a line ; and, considering that these
jDoles are areas or discs, not points, it is a little cmious that philo-
sophers in different parts of the world, using different data, and
following up investigation each through a separate and independent
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 physical cause ? By the latter, undoubtedly.
Here, then, we have another of those gossamer-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, w^here we pause and linger, fondly hoping that the
chambers of hidden things may be thrower open, and that w^e may
be permitted to behold and contemplate the mysteries of the wdnds,
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 temperatm^e.
Therefore we have pahpably 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. Thousands of observations, made by mariners and recorded
Thfi barometer in the in their abstract logs, have enabled us to determine
^■ind bands. approximately the mean height of the barometer

for the various bands (§ 352) at sea. Between the parallels

* Gauss.

EASTING OF THE TRADE- WINDS, ETC. 169

of 36'' S. and 50° N., Lieut. Anclimi, of the Dutch '^axj, has
collected from the abstract logs at the Meteorological Institute of
Utrecht no less than 83,334 observations on the height of the
barometer ui the following bands :

Nnmher of Ohservations and Mean He/gU of the Barometer heticeen the Parallels of
78° 37' .V. and 74° S.*

North.

Barometer.

Xo. 1

South.

Barometer.

Xo.

■ 0° and 5° C)

29.915

5114

0°and 5°

29.940

3692

■ 5° and 10°

29.922

5343

5° and 10°

29.981

3924

1U° and 15°

29.964

4496

10° and 1.0°

30.028

4166

15° and 20°

30.018

3592

15° and 20°

30.060

4248

20° and 25°

30.081

3816

20° and 25°

30.102

4536

25° and 30°

.30.149

4392

25° and 30°

30.095

4780

30° and 35°

30.210

4989

30° and 36° 0

30.052

6970

35° and 40°

30.124

5103

42° 53'

29.90 O

40° and 45°

30.077

5898

45° 0'

29.66 C)

45° and 50°

30.060

8282

49° 08'

29.47

51° 29'

29.99 (2)

1 51° 33'

29.50

59° 51'

29.88 C)

I 54°"26'

29.35

78° 37'

29.759 C)

! 55° 52'
j 60° 0'
1 6Q'^ 0'

29.36
29.11

29.08

74° 0'

28.93

the northern than iu
the southern hemi
sphere.

(1) From 50O X. to 36d S. the observations are the mean of 83,334 taken from " Jlaandelijksche
Zeilaanwijzingen van Java naar het Kanaal Koninklijk Xederlandsch Meteorologisch Iiistituut, 1850."
^2) Greenwich; mean of 4 years' observatioQs.
(3) St. Petersburg ; mean of 10 years' observations.
(*) Dr. Kane ; 12,000 observations (mean of 17 months' observations).
(5) Hobart Town ; mean of 10 years' observations. (") Sir J. C. Ross ; " Erebus and Terror."

363. The diagram of the winds (Plate I.) has been constructed
More atmosphere in SO as to show by its sliadcd bordcT tliis uncqual

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 vapom^ rising from its waste
of waters drives the air away from the austral regions, just as the
vapour that is formed 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. Admiral Fitzroy has also reduced from the abstract logs in
A standard of com- fj^e Metcorological Department of the Board of Trade
meter at sea. in Loudou a OTcat muuber of barometrical observa-

o

* Below the parallels of 50° N. and 36° S. the observations are reduced to the
Temp, of 32° Fahr.

170 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IIETEOROLOGY.

tions. He has discovered tliat near tlie parallel of 5° N. in tlie At-
lantic 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-hom'ly fluc-
tuations, the mariner may detect any error in his barometer
amounting to the two or three thousandth part of an inch.

365. According to the ^dews presented in § 358 and Plate YII.,
Enrio'moSm-?'^' ^'^^ south-cast trade-muds, which reach the shores
SfreSonso'f^the''''' ^^ ^^'^^^^ ^^^1' ^^® parallel of Kio, and which blow
northern hemisphere, thouce for the most part ovor the land, should be
the winds which, in the general com^se 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 want-
ing in moistm^e. Now, are not those portions of the Old World,
for the most part dry countries, receiving but a small amount of
precipitation ? 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 comj^rises 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.

366. The earth is nearer to the sun in the summer of the
Each hemisphere re- southcm hemisphere than it is in the summer of the
thrsamc'amounrof northcm ; 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 Su' John Herschel has sho^^n, ^.nd any one who wiU
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

EASTIKG OF THE TEADE-WIKDS, ETC. 171

makes up vatli heat for the greater intensity but shorter duration of
the southern summer. 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 oS into space by
each hemisphere again is also identically the same. There is no
reason to beheve that the earth is growing warmer or cooler, and
therefore we infer that the total amount of heat received annually
by the u'lwle earth is again annually radiated from the whole
earth. Nevertheless, the two hemispheres may radiate very
unequally.

367. Du'ect observations concerning the amount of radiation
The northern radi- ^^^m different pai^ts of the surfacc of our planet are
ates most. meagTo, and the results as to quantity by no means
conclusive ; but we have in the land and sea breezes a natm^al
index to the actinometry of sea and land, v\^hich shows that the
radiating forces of the two are very different. Notwithstanding the
temperatm^e of the land is raised so much above that of the waters
dm'ing the day, its powers of radiation are so much gTeater than
those of water that its temperature falls dm^ing 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. The question now may be well put : Since the two hemi-
Another proof of the sphcrcs Toceive annuallv the same amount of heat

crossings at the calm ^^ ,, t • ii n i '• i

belts. ' from the sun, and smce the northern nemispnere,

with its greater area of land, radiates most, whence does it derive
the sm-plus ? The theory of the crossing at the calm belts indi-
cates both the way and the means, and suggests the answer ; for it
points to the latent heat of vapom' that is taken up ia the southern
hemisphere, transported by the mnds across the calm belts, and
hberated, as the clouds drop dow^n their fatness uj^on 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 difference of cloud ia a continental and an oceanic sky must
also greatly quicken the radiatiag powers of the northern hemi-
sphere. Kadiation goes on from the upper surface of the clouds
and fi'om the atmosphere itseK, but we know that clouds in a great
measure obstruct radiation from the surface of the earth ; and as
the smiace of the earth receives more of the direct heat of the sun
than the atmosphere, the point under discussion relates to the mode
in which the surface of the earth gets rid of that heat. It gets rid

172 PPIYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOPtOLOGY.

of it cliiefly in three ways : some is carried off by convection in tlie
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 dm-ing the rainy season in intertropical countries, as on
the coast of Africa, there 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-radiating influence
of clouds. The southern hemisphere, bemg 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. Thus, by observing and discussing, by resorting to the

Facts and pearls, force of rcasou aud to the j^rocesses of induction,

we have gathered for the theory that favom^s 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.

CHAPTEK yill.

§ 370-409. — CURRENTS or the sea.

§370. We here set out with the postulate that the sea, as well
. Obedient to order, as the air, has its system of circulation, and that this
system whatever it be, and wherever its channels lie, whether in
the Avaters at or below the smiace, 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 ninnmg 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 Natm-e, we know who gave it, and that
neither chance nor accident had anything to do mth 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 cm-rent of the sea or
air has conveyed far away from imder a tropical sun. She mm'-
murs it out in the cooling current of the north ; the whales of the
sea tell of it (§ 158) ; and all its inhabitants proclaim it.

CURRENTS OF THE SEA. 173

371. The faima and the flora of the sea are as much the crea-
The fauna and flora tiu'es of cHmate (§ 161), and are as dependent for
of the sea. j^]^q[j^ woll-being upon temjDeratm^e, as are the fauna
and the flora of the dry land. Were it not so we should find
the fish and the algas, the marine insect and the coral, distributed
equally and ahke in all parts of the ocean. The arctic ^Yhale
^YOuld delight in the torrid zone, and the habitat of the pearl oyster
^yould be also under the iceberg, or in the frigid waters of polar
seas.

372. Nevertheless, though the constituents of sea water be the same
Those of southern in kind, WO must uot infer that they are the same

unlike those of north- . ■, ,, iJii inn'' on

ern seas. m degree throughout all parts oi the ocean, for there

is a peculiarity, perhaps of temperatm^e, perhaps of transparency,
which marks the inliabitants of trans-equatorial seas. MM. Peron
and Le Sueur, who haye turned their attention to the subject,
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. Water, while its capacities for heat are scarcely exceeded
The capacity of by thoso of any other substance, is one of the most
Avater to convey heat. comiDloto of nou-conductors. Heat docs uot per-
meate 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 con-
duction, but to get through water it requires to be conyeyed by a
motion, which in fluids we caU currents. Therefore the study of
the climates of the sea inyolyes a knowledge 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. Hence, in studying the system of oceanic circulation, we
Currents of the spa get out With, the vory simplo assumption, \dz., that

to be considered lu ^ , i '^ n n ^ ^ , ■ n ^

pairs. n'om wnatever part oi the ocean a current is lounci

to run, to the same part a cmTent of equal volume is bound to
retm^n ; for upon this principle is based the whole system of cm-rents
and counter-cmTcnts 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 ah^, meeting fi'om various directions, create gyrations, which
in some parts of the sea, as on the coast of Norway, assume the

174

AND ITS METEOROLOGY.

appearance of wliirlpools, as tliougli the water were drawn into a
chasm below. The celebrated Maelstrom is caused by such a con-
flict of tidal or other streams. The late Admiral Beechey, K.N.,*
gave diagrams illustrative of many " rotatory streams in the Eng-
Esh 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
actmg obliquely upon each other."

375. It is not necessary to associate with oceanic currents the
nS!^iikYthosr?/^ ^^^^ *^^* *^®y iii^st, of necessity, as on land, run
land rimofneces- from a higher to a lower level. So far fi'om this
lower levels. being the case, some currents of the sea actually run
up hill, while others run on a level. The Grulf Stream is of the
first class (§ 83).

376. The currents which nm from the Atlantic into the Medi-
The Red Sea current, tcrrancan, and from the Indian Ocean into the Ked
Sea, are the reverse of this. Here the bottom of the current is
probably a water-level, and the top an inclined plane, running
dotvii 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 reborned 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 is said to be two
feet lower than it is near the mouth. t 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 gomg 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 evaporation from this sea and the Persian Gulf
is probably greater than it is from any other arms of the ocean.
We know that the waste from canals by evaporation, in the summer-
time, is an element which the engineer, when taking the capacity

* See an interesting paper by liim on Tidal Streams^ of tlie North Sea and
Englisii Channel, p. -703; Phil. Transactions, Part ii„ 1851.
t Johnston's Physical Atlas.

CURRENTS OF THE SEA. 175

of his feeders into calculation, has to consider. With him it is an
important element : how much more so must the waste by evapora-
tion from this sea be when we consider the physical conditions
under which it is placed ! Its feeder, the Arabian. Sea, is a thou-
sand miles from its head ; its shores are bm-ning sands ; the eva-
poration is ceaseless ; it is a natm^al evaporating dish (§ 525) on a
grand scale ; none of the vapom^s which the scorching winds that
blow over it carry away are returned to it again in the shape of
rains. The Ked Sea vapom^s are carried off and precipitated else-
where. 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 fomihs of an inch to an inch daily.
Whatever it be, it is doubtless gTeater 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 cmrent 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 sm-face by evaporation 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., eva-
poration and temperatm^e ; for the temperature of that sea is
necessarily lower at Suez, in latitude 30°, than it is at Babel-
mandeb, in latitude 13°. To make it quite clear that the surface
of the Red 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 smface
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 in-
cHned plane, made so by evaporation.

377. But the salt water, which has lost so much of its freshness
Fm?entrt hrLu*S ^^^^ ovaporation, becomes Salter, and therefore heavier.
straits explained. The lighter wator at the Straits cannot balance the
heavier water at the Isthmus, and the colder and Salter, and there-

176 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

fore heavier water, must either rim out as an under ciuTent, or it
must deposit its sm-phis salt in the shape of crystals, and thus
gradually make the bottom of the Ked Sea a salt-bed, or it must
abstract all the salt from the ocean to make the Ked 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 cm-rent, as there is from the Mediterranean through the
Straits of Gibraltar, and that the sm^face 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 fr'om each of these two
seas, let us suppose the case of a vat of oil, and a vat of wine con-
nected by means of a narrow trough — the trough ])eing taken to
represent the straits connecting seas the waters 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 fr'eshness 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
rmi out as an under cmTent.

378. The rivers which discharge thefr v\'aters into the Mediter-
The Mejiterranean raucau are uot Sufficient to supply the waste of
current. cvaporatiou, and it is by a process similar to this

that the salt which is carried in from the ocean is retiu'ned to the
ocean again : were it not so, the bed of that sea would be a mass of
solid salt. The mistable equihbrium of the seas is a physical
necessity. Were it to be lost, the consequences would be as dis-
astrous as would be any derangement in the forces of gravitation.
Without doubt, the equihbrium of the sea is preserved by a system
of compensation as exquisitely adjusted as are those by w^hich the
" music of the spheres " is maintained. It is difficult to form an
adequate conception of the immense quantities of sohd matter which
the current from the Atlantic, holding in solution, carries into the
Mediterranean. In his abstract log for March 8th, 1855, Lieu-
tenant Wilham Grenville Temple, of the United states ship Levant,
homeward bound, has described the indraught there : " Weather
fine ; made 1 J pt. lee-way. At noon, stood in to Almiria Bay,
and anchored off" the village of Eogiietas. Found a great number
of vessels waiting for a chance to get to the westward, and learned

CURRENTS OF THE SEA. 177

from tliem that at least a tliousand sail are TS'eather-Lomid l^etween
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 cm^-
rent. Indeed, no vessel had been able to get out into the Atlantic
for three months past." Now suppose this cm-rent, which baffled
and beat back this fleet for so many days, ran no faster than two
knots the hom\ Assuming its depth to be 400 feet only, and its
width seven miles, and that it carried in with it the average propor-
tion of sohd matter — say one thirtieth — contained in sea water ;
and admitting these postulates into calcidation as the basis of the
computation, it appears that salts enough to make no less than 88
cubic miles of solid matter, of the density of water, were carried
into the Mediterranean dming these 90 days. Now, unless there
were some escape for all this solid matter, which has been rumiing
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. AVe have in this fact, viz., the difficulty of egress from the
The Suez Canal. Mediterranean, and the tedious character of the
na^agation, under canvas, within it, the true secret of the indif-
ference 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 rmming 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 mhabited, for the most part, by an anti-com-
mercial and thriftless people. On the northern shores the chmates
of each nation are nearly duplicates of the climates of her neigh-
bom's to the east and the west; consequently, these nations all
cultivate the same staples, and have wants that are similar : for a
commerce among themselves, therefore, they lack the main elements,
viz., difference of production, and the diversity of wants which are
the consequence of variety of chmates. To reach these, the Medi-
terranean people have had to encounter the tedious navigation and
the sometimes difficult egress — -just described — from then* sea.
Clearing the Straits of Gibraltar, their vessels do not even then
find themselves 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 cmTcnt

178 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

from the Atlantic offer to the navigation there, that vessels boimcl
to India from the United States, England, or Holland, may often
double the Cape of Good Hope before one saihng with a like desti-
nation fr'om a Mediterranean port would find herself clear of the
Straits of Gibraltar. It is therefore not sm^prising that none of
the great commercial marts of the present day are found on the
shores of this classic sea. The people who inhabit the hydro-
graphic 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 commercially pent up. A
ship-canal across the Isthmus of Suez mil 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 wiU add
largely to thefr 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. Oc-
cupying this stand-point in thefr system of commercial economy,
the people of the United States await with a Hvely interest the
completion of the Suez Canal.

380. Of all parts of the ocean, the warmest water, the saltest and
Hydrometricai obser- the hcaviost too, is Said to be fouud in the seas of
vations at sea wanted. i^l^Q Indian Occau. A good scrics 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 Ked Sea and the Mediterranean, and upon the-
mider currents that run out from these seas, let us examine results.

381. Several years ago, Mr. Morris, chief engineer of the
Specific rjravity of Oriental Company's steam-ship Ajdaha, collected
Red Sea Water. spccimcns of Eod Sca wator all the way fr'om Suez
to the Straits of Babelmandeb, which were afterwards examined by
Dr. Giraud, who reported the following results : *

Latitude.

Ivongitude.

Degrees.

Degrees.

No. 1.

Sea of Suez

9

Gulf of Suez .

.' 27.49

33.44

3.'

Red Sea . .

24.29

.36.

4.

Ditto . .

. 20.55

38.18

5.

Ditto . .

. 20.43

40.03

6.

Ditto . .

14.35

42.43

7.

Ditto . .

. 12.39

44.45

Spec. Grav.

Saline Cont.
1000 parts.

1027 41.0

1026 40.0

1024 39.2

1026 40.5

1024 39.8

1024 39.9

1023 39.2

Transact, of the Bombay Geograph. Soc. vol. ix., May 1849, to August, 1850..

CUBRENTS OF THE SEA.' 179

Tliese observations agree with tlie theoretical deductions just an-
nounced, and show that the surface waters at the head are heavier
and Salter than the surface waters at the mouth of the Bed Sea.

382. In the same paper, the temperatm-e of the an- between
Evaporation from. Suoz and Aden ofteu 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 thermometers
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." " Now assuming," says Dr. Buist, " the evaporation of
the Eed Sea to be no greater than that of Aden, a sheet of water
eight feet tliick, 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 fom^
per cent, of salt by weight — or, as salt is a liaK heavier than water,
some 2.7 per cent, in bulk — or, in round numbers, say three per
cent. In the com^se of three thousand years, on the assumptions
just made, the Eed Sea ought to have been one mass of sohd salt,
if there were no cmTent 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 cm-rents bring the
salt in at the top, the under currents carry it out at the bottom.

383. Meditereanean Currents. — With regard to an mider
The mediterrakean current from the Mediterranean, we may begin by
CuERENTs. remarking that we know that there is a current
always setting in at the smface from the Atlantic, and that this is
a salt-water cmTent, which carries an immense amomit of salt into
that sea. We know, moreover, that that sea is not salting up ; and
therefore, independently of the postulate (§ 374) and of observa-
tions, we might infer the existence of an under current, through
which this salt finds its way out into the broad ocean again.*

* Dr. Smith appears to liave been the first to conjecture this explanation, which
he did in 1673 {vide Philosophical Transactions). This continual indraught into
the Mediterranean appears to have been a vexed question among the navigators
and philosophers even of those times. Dr. Smitb 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, which,
in his own words, is, " that there is an imder current, by which as great a quan-

N 2

180 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

384. Witli regard to this outer and under current, we have ob-
The drift of the servatious telling of its existence as long ago as
Phoenix. 1712. '' In the year 1712," says Dr. Hudson, in a
paper commimicated to the Philosophical Society in 1724, " Mon-
sieiu' du L'Aigle, that fortimate and generous commander of the
privateer called the Phcenix, of Marseilles, giving chase near Ceuta
Point to a Dutch ship bomid to Holland, came up with her in the
middle of the Gut between Tariffa and Tangier, and there gave her
one broadside, which directly sunli her, all her men being saved by
Monsiem' 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 fom- leagues to the westward of the place where she sunk,
and directly against the strength of the cmTent, v^diich has per-
suaded many men that there is a recurrency in the deep water in
the middle of the Grut that sets outward to the grand ocean, which
this accident very much demonstrates ; and, possibly, a great part
of the water which rmis into the Straits retm^ns that way, and along
the two coasts before mentioned; otherwise this ship must, of
com^se, have been driven towards Ceuta, and so upwards. The water
in the Gut must be very deep ; several of the commanders of ouj'
ships of war having attempted to sound it with the longest lines
they could contrive, but could never find any bottom."

385. In 1828, Dr. Wollaston, in a paper before the Philosophi-
saitness of the cal Socicty, statcd that he fomid the specific gi^avity
Mediterranean. q£ c^ spccimcn of sca wator, fi'om a de])th of six
hmidred 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 fom' times the usual quantity of saline residuum. Hence
it is clear that an mider cuiTent outward of such denser water, if of

tity of water is carried out as comes flowing in. To confirm which, besides what
I have said above about the difierence of tides in the offing and at the sliore 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
seamen, who was at the making of the trial. He told me that, being there in one
of the kings frigates, they w^ent with their pinnace into the mid stream, and were
carried violently by the current ; 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 still 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 deei^, and that the lower the bucket was let fall, they
foimd the under current the stronger."

CUBBENTS OF THE SEA. 181

equal breadth and depth with the ciuTent invfard near the surface,
would carry out as much salt below as is brought in above, although
it moved ^vith less than one fomih part of the velocity, and would
thus prevent a perpetual 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 Enghsh Navy, who had collected it for Dr. Marcet. Dr. Mar-
cet 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 fom^ths of the sea water
which rmis into the Mediterranean, is evaporated from it, lea^dng
a brine for the under cmTent having /owr times as much salt as the
water at the smface 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 mider cmTent from the Mediterranean.
386. However that may be, these facts, and the statements of
The escape of salt the Secretary of the Geogi'aphical Society of Bombay
^der currents. (§382), secm to Icavo uo room to doubt as to the
existence of an under cmTent both fi'om the Bed Sea and Mediter-
ranean, and as to the cause of the sm-face current which flows into
them. I think it a matter of demonstration. It is accounted for
(§ 377) by the salts of the sea. Writers whose opinions are
entitled to great respect differ with me as to the conclusiveness of
this demonstration. Among those wTiters are Admiral Smyth, of
the British Navy, and Sir Charles Lyell, who also differ with each
other. In 1820, Dr. Marcet being then engaged in stud^dng the
chemical composition of sea water, the admiral, with his usual
alacrity for doing " a kind tmii," undertook to collect for the doctor
specimens of Mediterranean water from various depths, especially
in and al^out the Straits of Gibraltar. Among these was the one
(§ 385) taken fifty miles within 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 jiLst seen, no doubt in the mind of Dr. Wollaston as to the
existence of this under cmTent of brine. But the indefatigable
admiral, in the com'se of his celebrated smwey of the Mediterranean,
discovered that, while inside of the Straits the depth was upwards of
nine hmidred fathoms, yet in the Straits themselves the depth
across the shoalest section is not more than one hundred and sixty*

* " The Mediterranean."'

182 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

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 gTavity, 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."!

387. According to this reasoning, all the cavities, the hollows,
yertjcai circulation and tho vallevs at the bottom of the sea, especially

in the sea a physical - n i -^ - i • i i--

necessity. m the trade- wmd region, where evaporation is so

constant and great, ought to be salting up or fiUing up with brine.
Is it probable that such a process is actually going on ? No.
According to this reasoning, the water at the bottom of the great
American lakes ought to 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
bellow 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 Eiver
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. Consequently,
wherever the breadth of that river is no gTeater than it is at the
Falls, we should have a cm-rent 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 miU-
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 deep." Moreover, we know it is not such a skimming
cmTent as the geologist would make, which runs fr'om one lake to
another ; for wherever above the Niagara Falls the water is
deep, there we are sure to find the cmTent sluggish, in compa-

* One hundred and sixty, Smyth.

t Lyell's Prmciples of Geology, p. 334-5, ninth edition. London, 1853.

CUERENTS OF THE SEA. 183

rison witli 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. The reasoning of this celebrated geologist appears to be
The bars at the fouudcd upou the assumptiou that when water, in
Sppi^iuusua-* consequence of its specific gravity, once sinks below
*i"^"- 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 fif-
teen or sixteen feet of water on it, we have now four or five times
that depth. As new bars were successively formed seaward fi-om
the old, what dug up the sediment which formed the old, and hfted
it up fi'om where specific gravity had placed it, and carried it out to
sea over a barrier not more than a few feet fi^om the surface ? In-
deed, 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 feet t below the top of the bar which obstructs its entrance
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 th^ 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 firom 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

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

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

184 PHYSICAL CtEOGKAPHY OF THE SEA, AND ITS jyiETEOPvOLOGY.

scarcely to be ^perceptible, wbile it may dasli 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 Mediterranean has taken, even duiing
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 mtli solid matter.
Admiral Smyth brought up bottom with his briny sample of deep
sea water (six hmidi'ed and seventy fathoms), but no salt crystals.

389. The gallant adjniral — appearing to mthhold his assent
Views of Admiral both fL'om Dr. Wollastou iu liis conclusions as to
Lyeii-'^" >u . ^|_^.^ 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 specimen, according to
analysis, was of sea water, and it is not necessary to call in the
suj^position of a brine spring to account for this hea-vy specimen.
If we admit the principle assumed by Sir Charles Lyell, 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 har-
monies of the sea are gone, and we are forced to conclude they
never existed. Every particle of water that sinks below a sub-
marine ridge is, i2:>so facto, by his reasoning, stricken fi*om the
channels of circulation, to become thenceforward for ever motion-
less 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 w^ere 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 cmTcnts 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 measm'ed and the momitains 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 faihne 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 theoretical
proofs, — the proofs derived exclusively from reason and analog}^ —

CUEEEXTS OF THE SEA. 185

are as clear in favour of this mider current from the Mediterranean
as tliey 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 smface current takes into the Mediterranean find
their way out again. It would not be difficult to show, even to the
satisfaction of that eminent geologist, that this indi'aught conveys
salt away from the Atlantic faster than all the /?*es/i-water streams
empty fresh supplies of salt into the ocean. Now, besides this
drain, vast quantities of salts are extracted fi-om sea water for coral
reefs, shell banks, and marl beds ; and by such reasoning as this,
which is perfectly somid and good, we establish the existence of this
under cm-rent, or else we are forced to the very unphilosophical
concliLsion that the sea must be losing its salts, and becoming less
and less briny.

390. The Cueeents of the Indian Ocean. — By carefully
ctiRREXTs OF THE cxamimng the physical featm'es of this sea (Plates
lndiax Ocean. YIII. and IX.), and stud}dng its conditions, we are
led to look for warm cmTents that have their genesis in this
ocean, and that carry from it volmnes of overheated water, pro-
bably exceeding in quantity many times that which is discharged
by the Gulf Stream fi^om its fountains (Plate YI.). The Atlantic
Ocean is open at the north, but tropical countries bomid the
Indian Ocean in that direction. The waters of this ocean are
hotter than those of the Carii)bean Sea, and the evaporating force
there (§ 300) is much greater. That it is greater we might, with-
out observation, infer from the fact of a higher temperatm^e and a
greater amount of precipitation on the neighboming 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,
caUed at the Cape of Good Hope the Lagulhas cmTent. Another
of these warm cm-rents from the Indian Ocean makes its escape
through the Straits of Malacca, and, being joined by other warm
streams fi'om the Java and China Seas, flows out into the Pacific,
like another Gulf Stream, between the Philippines and the shores
of Asia. Thence it attempts 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. Between the physical features of this, the " Black Stream"

186

of the Pacific, and the Grnlf Stream of the Atlantic there are
Se^p^Sec cont^°^ "^ several points of resemblance. Simiatra and Ma-
trasted with the lacca corrcspond to Florida and Cuba; Borneo to
Atiantia^"^ ^ ^ 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 Ber-
mudas, the Japan Islands to ]S[e^vfoundland. As "svith the Gulf
Stream, so also here with this China current, there is a counter
cmTent of cold water between it and the shore. The chmates of
the Asiatic coast correspond with those of America along the At-
lantic, and those of Columbia, Washington, and Vancouver resemble
those of Western Europe and the British Islands ; the climate of
California (State) resembles that of Spain ; the sandy plains and
rainless regions of Lower Cahfornia reminding one 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 mth liglitning. The
Aleutian Islands are almost as renoT\Tied for fogs and mists as are
the Grand Banks of NeTsrfoundland. A smface current flows north
from Behring's Strait into the Arctic Sea ; but in the Atlantic the
current is from, not into the Ai'ctic Sea : it flows south on the
surface, north below ; Behring's Strait being too shallow to admit
of mighty under cm^rents, or to permit the introduction fi.'om 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 tm-ned down
through a sort of North Sea along the western coast of the con-
tinent toward Mexico. They appear here as a cold current. The
efiect of this body of cold water upon the littoral climate of Cali-
fornia 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 resemblance and of contrast between the cmTents and
aqueous cuTulation 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 fL^ozen ocean
and its Atlantean arms. The seas of Okotsk and Kamtschatka

CIJBBENTS OF THE SEA. 187

alone, and not the fi-ozen seas of the Arctic, cradle the icebergs for
the North Pacific.

392. The Lagulhas current, as the Mozambique is sometimes
The LagTiiiias Cur- called, sku'ts the coast of Natal as our Gulf Stream

rent aiid the storms -, ,-• i i* n • i -i • -in

of the cap.^ Qocs tlie coast 01 (jrcorgia, where it gives rise to the

most grand and terrible displays of thmider and hghtning that are
anywhere else to be witnessed. Missionaries thence report to me the
occmTence there of thunder-storms in which for hours consecutively
they have seen an uninterrupted blaze of lightning, and heard a
continuous peal of thmider. Eeaching the Lagulhas banks, the
current spreads itself out there in the midst of cooler waters, and
becomes the centre of one of the most remarkable storm-regions in the
world. My friend and fellow-labom^er, Lieut. Andrau, 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 cm-ious 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 forious 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. There is sometimes, if not always, another exit of warm
drift ^orr^ind"'^ water from the Lidian Ocean. It seems to be an
Ocean. ovcrflow of the great intertropical caldi'on of Lidia ;
— seeking to escape thence, it works its way polarvmrd 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 over-
flow finds its way south midway between Africa and Austraha, and
appears to lose itself in passing round a sort of Sargasso Sea, thinly
strewed with patches of weed. Nor need we be sm^prised at such
a vast flow of warm water as these tliree 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 fre-
quently 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.

188 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS LIETEOPvOLOGY.

394. On either side of this warm current that escapes from the
The ice-bearing cur- intertropical parts of the Indian Ocean, but espe-

rents from the Ant- . -,-, ii a j t -n • i • .

arctic regions. cially on tiie Australian side, an ice- bearing current

(Plate IX.) is found wending its way n'om 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 large and
high, are set to the eastward by the " brave west winds " of those
regions. Hence the icebergs that are so often seen to the south of
the Cape of Good Hope. They set ojBl' for the Atlantic, but are
diTven to the eastward by the west winds of these latitud.es. The
Gulf Stream seldom permits icebergs from Ai'ctic waters to reach
the parallel of 40^ in the North Atlantic, but I have Imowm the
ice-bearing cmTent 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 fr'om the intertropical basin of that
immense sea — Indian Ocean — convey along immense volumes of
water containing 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 cmTents, 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
cmTents here that keep in notion immense volumes of water.

395. The Currents of the Pacific. — The contrast has been
The currents of the draMTi (§ 391) bctweeii the Japan or " Black Stream"
Pacific-Drift-wood, ^f the North Pacific, and the Gulf Stream of the
North Atlantic. The com'se of the former has never been satis-
factorily traced out. There is (Plate IX.), along the coast of
California and Mexico, a southwardly 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 di'ift-wood and sea-weed of
the Atlantic. So, in like manner, to the west fr'om California of
this other southwardly set, lies the pool into which the di'ift-wood
and sea-weed of the North Pacific are generally gathered, but in
small quantities. The shores of Johnston's Islands (17° N., 169°
30' W.), which are near the edge of this pool, are lined ^^dth drift-
wood from the Columbia, and the red cedar of California. The

CUEEEXTS OF THE SEA. 189

immense trees that have been cast np on these gnano islands were
probably drifted down with the cool California cm-rent into the
north-east trades, and by them wafted along to the west, thus
showing that the cm-rents of the North Pacific flow in a sort of
circle, on the outer edge of which He the Japanese and Aleutian
Islands, and the north-west coast of America.

396. The natives of the Aleutian Islands, Avhere no trees grow,
SfpSc^mIeThV*^^^^P^^^^ ^^P^^^ *^^® drift-wood cast ashore there for
Gulf Stream. Salter all tho timber uscd iu the construction of their boats,
l^ateis.^ ^ ^^"^^^^ fishing-tackle, and household gear. Among this
timber, the camphor-tree, and other woods of China and Japan,
are said to be often recognized. 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 weU aware of its existence, and have given it the name
of 'Km-o-Siwo,' or Black Stream, which is midoubtedly derived
fi-om the deep blue colom- of its water, when compared vnili 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 neigh-
bouring waters of the sea.

397. TJie Cold Current of OJcotsh. — Inshore of, but counter to
The Current of the " Bkck Stream," along the eastern shores of
okotsk. ^g-^^ jg fo^-^(i (§ 391^ a streak or layer, or cm-rent
of cold water answering to that between the Gulf Stream and the
American coast. This cmrent, like its fellow in the Atlantic, is not
strong enough at all times sensibly to affect the com-se of navi-
gation ; but, like that in the Atlantic, it is the nursery (§ 158) of
most valuable fisheries. The fisheries of Japan are nearly as ex-
tensive as those of Newfoundland, and the people of each counti-y
are indebted for their valuable supplies of excellent fish to the cold
waters which the cmi-ents of the sea bring down to their shores.

398. Humholdfs Current. — The cm-rents of the Pacific are but
Humboldt's Current, little undcrstood. Amoug those about which most
is thought to be kno^m is the Humboldt Cm-rent of Peru, which
the great and good man whose name it bears was the first to dis-
cover. It has been traced on Plate IX. according to the best in-
formation— defective at best — upon the subject. This cm-rent is
felt as far as the equator, mitigatmg the rainless climate of Peru as

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

190 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. .

it goes, and making it delightful. The Andes, with their snow-
caps, on one side of the narrow Pacific slopes of this intertropical
repuhhc, and the cuiTent 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 temperatm^e that cloth
clothes are seldom felt as oppressiye during any time of the year,
especially after nightfall.

399. Between Hiunholdt's CmTent and the great equatorial
The "desolate " flow, there is an area marked as the " desolate region,"
region. ^Uts IX. It was ohscrved that this part of the
ocean was rarely visited by the whale, either sperm or right ; why,
it did not appear ; but observations asserted the fact. Foimerly,
this part of the ocean was seldom whitened by the sails of a ship,
or enlivened by the presence of man. Neither the industrial pur-
suits 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 unfrequented 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 jour-
nals of some of them it is described as a region almost void of the
signs of life in both sea and au\ In the South Pacific Ocean espe-
cially, where there is such a wide expanse of water, sea-birds often
exhibit a companionship with a vessel, and will follow and keep
company with it through storm and calm for weeks together. Even
those kinds, as the albatross and Cape pigeon, that delight in the
stormy regions of Cape Horn and the inhospitable chmates of the
Antarctic regions, not unfrequently accompany vessels into the per-
petual summer of the tropics. The sea-bkds 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 itseK is said to be singularly barren of life.

400. In the intertropical regions of the Pacific, and among the
Polynesian drift, heated watcrs of Polynesia, a warm cm-rent or drift

of immense volume has its genesis. It rather drifts than flows 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
coraUines dehght to build their atolls and their reefs. The inter-
tropical seas of the Pacific afford an immense smface for evapora-
tion. No rivers empty there ; the annual fall of raui there, except
in the " Equatorial Doldrums," is small, and the evaporation is all

CUBRENTS OF THE SEA. 191

that botli tlie north-east and the south-east trade-winds can take
up and cany off. I have marked on Plate IX. the dhection of the
supposed warm-water cuiTent which conducts these overheated and
briny waters from the tropics in mid ocean to the extra-tropical
regions where precipitation is in excess. Here, being cooled, and
agitated, and mixed up mth 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 navi-
gation.

401. There are also about the equator in this ocean some curious
Equatorial currents. cmTonts, wliich I have Called the " Doldrimi Cur-
rents " of the Pacific, but which I do not understand, and as to
which observations are not sufficient yet to afford the proper ex-
planation or description. There are many of them, some of which
at times run with great force. On a voyage from the Society to
the Sandmch Islands I encountered one running at the rate of
ninety-six miles a day. These cm-rents 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
Sandvdch Islands. In Captain Pichon's abstract log of the French
corvette " L'Eurydice," from Honolulu to Tahiti, in August, 1857,
a " doldrum " cmTont 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
cmTents and counter-cmTents apparently the most uncertain and
comphcated ? The Pacific Ocean and the Indian Ocean may, in
the view we are about to take, be considered as one sheet of
water. This sheet of water covers an area quite equal in extent
to one half of that embraced by the whole smface 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 smface is one hundred and
eighty-six thousand two hundred and forty cubic imperial miles.
Not less than three fomihs of the vapom^ which makes this rain
comes irom this waste of waters ; but supposing that only half of this
quantity, i. e., ninety-tliree thousand one huncbed and twenty cubic
miles of rain falls upon this sea, and that that much, at least, is taken

192 PHYSICAL GEOar.APHY OF THE SEA, AND ITS 3IETE0E0L0GY.

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 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 Tsinds.

402. The better to appreciate the operation of such agencies in
The influence of ^ produciug currcuts in the sea, now here, now there,
tbn\ipon cul?mts. first this Way, and then that, let us, by way of illus-
ti'ation, imagine a district of two hundred and filty-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-fom- hom's, all the
water to the depth of one mile in this district. The machine must
not only pump up and bear ofi' this immense quantity of water, but
it must discharge it again into the sea on the same day, but at
some other place. Noav here is a force for creating cmTents that is
equivalent in its results to the eftect that would be produced by
baling up, in twenty-fom' hom'S, two hundred and fifty-five cubic
miles of water fr^om one part of the • Pacific Ocean, and emptying-
it out again upon another part. The cm-rents that would be created
by such an operation would overwhelm na^dgation and desolate
the sea ; and, happily for the human race, the great atmospherical
machine which actually does perform every day, on the average,
all this lifting up, transporting, and letting d.o^YD. 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 thi^ee hmidi^ed
thousand times as great ; yet, nevertheless, the same quantity of
water is kept in motion, and the cm-rents, in the aggregate, trans-
port as much water to restore the equilibrium as they would have
to do were all the distm-bance to take place upon our h}q3othetical
area of one mile deep over the space of two hmidred and fifty-five
square miles. Now when we come to recollect that evaporation is
lifting up, that the winds are transporting, and that the clouds are
letting down every day actually such a body of water, we are re-
minded that it is done by little and little at a place, and by 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 natm-e a force perhaps quite sufficient to give
rise to just such a system of cmTents as that which mariners find in

CURRENTS OF THE SEA. 193

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

403. Under Currents. — Lieutenant J. C. Walsh, in the U. S.
Under cuRKENTs— schooucr " Taucy," and Lieutenant S. P. Lee, in the
bmindi^ns/^^^^* U. S. brig " Dolphiu," both, while they v^ere carry-
ing on a system of observations in connection mth the ^\^ind 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 sufiicient 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 off, against wind, and sea,
and surface current, at the rate of over one knot an horn', as was
generally the case, and on one occasion as much as IJ knots. The
men in the boat could not repress exclamations of sm-prise, for it
really appeared as if some monster of the deep had hold of the
weight below, and was walking off with it."* Both ofiicers and
men were amazed at the sight. The experiments in deep-sea
soundings have also thrown much light upon the subject of imder
currents. There is reason to believe that they exist in aU, 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 v.'hat
seamen caU a simgging 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
retm^n on board. Examination proved that the ocean there, instead
of being over ten m^iles in depth, was not over three, and that the
line was swept out by the force of one or more mider currents. But
in what direction these cm^rents were running is not known.

* Lieutenant Walsh.

19-1 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

404. Vertical cii'culation is as important in the sea as it is in
The compressibility the air (§231). In striving to understand the
m S'?c7an^c dr°-^ physical machinery of om: planet and to compre-
cuiation. hend its workmgs, we miist, il we would learn, pro-

ceed 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 properties so proportioned
and so adjusted as exactly to answer its purposes in the grand
design. • And, consequently, we are entitled 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 re-
quired 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 re-
quired to reject as insufficient, any hypothesis touching the sys-
tem of aqueous circulation on our planet which ignores, even in
the profoundest depths of the ocean, an interchange of its parti-
cles between the bottom and the top. Were such interchange
not to take place — were the water in the sea which once sinks be-
low 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 beco:ne lighter and
lighter, until the one became satm*ated with salt, the other entirely
fresh. To prevent this state of things, we recognize the in-
fluences 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 of water once finds its way to the bottom of the
sea, whence — since it goes there by virtue of its ovim specific gravity,
whence is power to be derived for bringing it up again ? tor
sooner or later, according to this view, up it must come. We thus
arrive precisely at one of those points (§ 287) at which hypothesis
becomes absolutely necessary ii' we would make fui'ther progress.
Here, therefore, let us pause to search among the physics of the
sea for such a pov/er and the foundation for hypothesis. LesHe
has pointed out exactly such a power for the atmospheric ocean,
— a power which, 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

CUREENTS OF THE SEA. 195

liaiil that vrhicli is below to the top, and send that which is on the
top do^^^l into the recesses and cavities below. Suppose the en-
tire atmosphere to be, from the bottom to the top, nearly of the
same temperatm-e, and in a perfect state of the quiescent equilibrium,
and that from some cause a certain volume of air above has its
specific gra^dty so changed that it commences to descend. As it
descends the pressm-e 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 ca-
loric 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 atmospherical 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 hght from the top, and of tm-ning, in course
of time, the whole atmosphere upside dov^ii. 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 atmosphere the dynamical
force required for its system of vertical chculation 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 experiment upon water in the
gold ball, it has since been abundantly proved that Vv^ater is com-
pressible— so much so, that at the depth of ninety-three miles its
density would be doubled. Consequently, 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 compressibihty
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 povrer which is capable of
sending up to the top water fr'om the uttermost depths of the sea ?
Suppose that this cubic measure of water, by supplying vapom* 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 out heat, raising the tempera-
ture, and changing the specific gra-v^ty of hke quantities in the va-
rious thermal strata through which it has to pass. Thus heat is
conveyed from the ton to the bottom of the sea, there to be libe-

o 2

196 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOEOLOGY.

rated and impart to its waters djraamical force for their upward
movement. This is the power we paused to search for : what-
ever 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 Nature employs in the system of
vertical circulation that has been ordained for the waters of the sea.

405. Now, but for the salts of the sea, this process could not go
Assisted by its salts, on SO loug as the kws of thermal dilatation remain
as they are for sea water. Unlike fresh water, which expands as
it is cooled below 39^.5, sea water contracts until it has passed its
freezuig-point and attained the temperatm'e of 25^.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 smface. Vertical ch'culation would be confined to polar seas,
and many of the living creatures that inhabit its waters would
perish for the lack of cmTents to convey them their food.

406. If we except the tides, and the partial cmTents of the sea,
The origin of currents, such as thosc that may bc created by the wind, we
may lay it do^vn as a rule (§ 103) that all the cmTents of the ocean
owe then' origin to difference of specific gravity between sea water
at one place and sea water at another ; for wherever there if?
such a difference, whether it be owing to difference of temperature
or to difference of saltness, etc., it is a difference that disturbs equi-
librium, and currents are the consequence. The heavier water
goes towards the lighter, and the lighter whence the heavier comes ;
for two fluids differing 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 temperature, by the matter held in solution, or by any other
thing ; the effect is the same, namely, a cmTent. 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
incessant, they are not entirely 'v\Tthout salt, may be taken as evi-
dence in proof of a system of currents or of cnculation in the sea,
by which its waters are shaken up and kept mixed together as
though they were in a phial.

407. CuRREXTS OF THE ATLANTIC. — The principal currents of
the Atlantic have been described in the chapter on the Gulf

* See Prof. Hubbard's experiments, vol. i., Sailing Directions.

CURRENTS OF THE SEA. 197

Stream. Besides this, its eddies and its offsets are the equatorial cur-
(jurrents of Lhe r^nt (Plate YL), and the St. licque or Brazil Ciir-
Atiantic. j^gjj^^ Their fountain-head is the same : it is in the

warm waters about the equator, between Africa and America. The
former, recei^dng the Amazon and the Orinoco as tributaries by the
way, flows into the Caribbean Sea, and becomes, ^\dth the v/aters
(§ 103) in which the vapours of the trade-winds leave then- salts,
the feeder of the Gulf Stream. The Brazil cmTcnt, coming from
the same fountain, is supposed to be diwided by Cape St. Eo(iue,
one branch going to the south under this name (Plate IX.), the
other to the westward. This last has been a great bugbear to
navigators, principally on account of the difficulties which a few
dull vessels faUing to leeward of St. Pioque have found in beating
up against it. It was said to have caused the loss of some English
transports in the last centmy, which fell to leeward of the Cape on
a voyage to the other hemisphere ; and navigators, accordingly,
were advised to shun it as a danger.

408. This cmTent has been an object of special investigation
rii3 St. Pwoque current, duriug my rescarches connected with the Wind and
■CuiTent Charts, and the result has satisfied me that as a rule it is
neither a dangerous nor a constant current, notwithstanding older
wi'iters. Horsbm'gh, in his East India Director}^, cautions navigators
against it ; and Keith Johnston, in his great Physical Atlas, pub-
lished in 1848, thus speaks of it : " This cmTent greatly impedes the
progress of those vessels which cross the equator west of 23" west
longitude, impelling them beyond Cape St. Koque, when they are
xlrawn towards the northern coast of Brazil, and cannot regain then*
course till after weeks or months of delay and exertion." So far
fi'om 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. 30° and in three days
from that crossing they are generally clear of that cape. A few of
them repoi-t the cmTent in their favour ; most of them experience
no cmTent at all ; but, now and then, some do find a current set-
ting to the northward and westward, and operating against them
at the rate of 20 and occasionally of 50 miles a day. The inter-
tropical regions of the Atlantic, like those of the other oceans
(§ 401), abound with conflicting cmTents, which no researches yet
have enabled the mariner to imravel so that he may at aU times know

198 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

where they are and tell how they run, in order that he may he cer-
tain of their help when favourable, or sui'e of avoiding them if adverse.
409. There are other currents, such as the Greenland Current,
The Greenland the cold curreut ft'om Davis' Strait, the ice-bearing
current. cmTcut fi'om the antarctic regions, all setting into

the Atlantic and the Gulf Stream, one branch of Avhich 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 po^ax
waters into the Atlantic than of other waters from it, and I cannot
accoimt for the preservation of the equilibrium of this ocean by any
other h^Tpothesis than that which calls in the aid of under cm-rents.
They, I have no doubt, like the water-ways, the mineral veins, the
passages in the bowels of the earth, bear in then- secret ways, an
important part in the grand system of the terrestrial economy.

CHAPTER IX.

§ 420 — 460. THE SPECIFIC GRAVITY OF THE SEA, AlW THE

OPEN WATER IN THE ARCTIC OCEAN.

420. The crust of the planet upon which we live, mth the forces
Interesting physical that havc bceu and are at work upon it, is the most
inquiries. interesting subject of physical inquiry and study that

can claim the attention of diligent students. Precisely as the pro-
gress 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
upon the tablets of this thin shell are the records of all that he may
ever know concerning this his cosmical hearthstone.

421. Researches have been carried on from the bottom of the
Voyages of discovery decpcst pit to the top of the highest mountain, but
to the North Pole, ^j^ggg j^g^^g ^^j. gatisficd. Voyagcs of discovcry, with
their fascinations and their charms, have led many a noble champion
of human progress both into the torrid and frigid zones ; and not-
withstanding the hardships, sufferings, and disasters to which many
northern parties have found themselves exposed, seafaring men, as
science has advanced, have looked mth deeper and deeper longings

THE SPECIFIC GRAVITY OF THE SEA, ETC. 199

towards the mystic cii'cles of the polar regions : there icebergs are
framed and glaciers launched : there the tides have their cradle, the
whales then* nursery : there the winds complete their circuits, and
the cmTents of the sea their round in the wonderful system of
oceanic circulation : there the Am'ora Borealis is hghted 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 Avinds 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
gro"\vii 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 hoKer
motive — a deshe 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, mth 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 mth divers
objects in view, been sent from Europe and America, up into those
inhospitable regions. Whatever may have been the immediate
object of these various expeditions, whether to enlarge the fields of
commerce, to carry the Bible, to spread civihzation, to push con-
quests, or to bring back contriliutions to science, they have never lost
sight of the promise made by Colmnbus of a western route to India.
422. Like the ah', Hke the body, the ocean must have a system
The first suggestions of circulatiou for its waters. No other h-vTothesis

ot an open sea in the ^^^ i • ji o i t • ^ i /• " i

Arctic Ocean. Will cxplam the lact w^hicn observations reveal con-

cerning the saltness of the sea, the constituents of sea water, and
many other phenomena. An attentive study of the ciuTents of
the sea, and a close examination of the laws which govern the
movements of the waters in their channels of cn'culation through
the ocean, wiU lead any one irresistibly to the conclusion that
always, in simimer and winter, there must be, somevfhere within
the arctic chcle, a large body of open water. This open water
must impress a curious featm^e 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

200 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 Behr-
ing's Strait side mth harpoons in them bearing the stamp of ships
that were known to cruise on the Baffin's Bay side of the Ame-
rican 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 G-ood Hope.

423. The whale-fishing is, among the industrial pursuits of the
iTarpoons-babits of sca, ouo of HO Httlc importance ; and when the sys-
:he whales. -j^gjj^ ^f investigation out of which the " Wind and

Current Charts " have gro\NTi was commenced, the haunts of this
animal did not escape attentive examination. The log-books of
whalers were^coUected 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 fire, through which he cannot pass, and into
which he never enters. The fact was also brought out that the
same kind of whale that is foimd ofl' the shores of Greenland, in
Baffin's bay, etc., is foimd also in the North Pacific, and about
Behring's Strait, and that the right whale of the northern hemi-
sphere is a different animal from that of the southern. Thus the
fact was established that the harpooned whales did not pass aroimd
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
with circumstantial evidence affording the most irrefi'agable 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

THE SPECITIC GRAVITY OF THE SEA, ETC. 201

established the existence — the occasional existence, if you please —
of a channel through which whales had passed. Therefore we felt
bound to introduce other evidence before we could expect the reader
to admit oiu' proof, and to beheve with us in the existence of an
open sea in the Arctic Ocean.

424. There is an under current setting from the Atlantic through
The under current Davis' Strait iuto the Arctic Ocean, and there is
into the Arciic ^ surfacc cmTCut Setting out. Observations have

Ocean — its inilu- . -i • o t • ^ j.

ences. pomtcd out the existence oi this under current

there, for navigators tell of immense icebergs which they have
seen drifting rapidly to ilie north, and against a strong surface cur-
rent. These icebergs were high above the water, and their depth
below, supposing them to be parallelepipeds, 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 sui'face 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 fur-
nished neither by 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 surface, there is, it is supposed, a basin in which the
waters, as they rise to the surface, are at 30°, or whatever be the
temperature of the under current, which we know must be above
the freezing-point, for the current is of water in a fluid, not m a
solid state. An arrangement in natm-e, by which a basin of con-
siderable area in the ii'ozen ocean could be supphed by water
-coming in at the bottom and rising up at the top, with a tempe-
rature 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. And that there is a warmer climate somewhere in that in-
•indications of a hospitablc sca, the observations of many of the ex-
miider climate. plorci's who havo visitcd it indicate. Its existence may
be inferred also from the well-knoAvn fact that the birds and animals
are found at certain seasons migrating to the north, evidently in
-search of milder climates. The instincts of these dumb creatures are

202 PHYSICAL GEOGRAPHY O:^ THE SEA, AND ITS METEOROLOGY.

unerring, and we can imagine no mitigation of the climate in that
direction, unless it arise from the proximity, or the presence there
of a large body of open Avater. It is another furnace (§ 151) in
the beautiful economy of Nature for tempering climates there.

426. The hydrograj^hic basin of the Arctic Ocean is large, and
Ster^by being di- ^^ delivcrs iuto that sea annually a very copious
and thtr'Iiii?%^v7^ drainage. Such an immense volume of fresh water

mantle for the discharo'ed iuto SO Small a sea as the Arctic Ocean

Salter and warmer -^^ ^^.^^ ^^ ^^ tOWards diluting its brinO. Fig. 2,

sea water below.

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 figm^e 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 Kodgers 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 hghter, and so continued to do as he approached the shore.
The remarkable and sudden approach of the thermal and specific
gTavity curves after crossing 34^ N. can be explained by no other
hypothesis than this, viz. : the surface water of the sea v/as so
diluted with the fresh water from the Chesapeake, the Delaware,
and New York Bays, that, notwithstanding the temperature de-
creased as Eodgers approached the shore, yet the specific gravity
decreased also, because the saltness decreased by reason of the in-
creasing proportion of river v>^ater as he neared the shore. And
thus we have in our own vv^aters 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 beiov;.

427. The mean specific gravity of the Arctic Ocean water as
^f"v'"^%f"7^i"'^ ^^^®^'^®^ ^y Bodgers, and reduced to the freezing-
and heavy water, poiut (27°. 2) of soa watcr, was 1.0263. The speci-
fic gravity of the (rulf Stream water, as observed by him, and
reduced to the same temperatm-e (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 regi'etted that the hydi'ometer has not been more
frequently used in the Arctic Ocean, for a careful series of observa-

THE SPECIFIC GRAVITY OF TEE SEA, ETC. 203

tions 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,
ijut it would }aeld other highly interesting results. Now this
salt and hea\7' water, whose specific gravity at 27^.2 would have
been 1.0303, is the very water which Kodgers observed in the
Gulf Stream on its vfay 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 cmxent from the north, imtil
it enters the Arctic Ocean, there to rise up hke a boihng spring
in the centre of an open sea.

428. Eelying upon a process of reasoning like this, and the de-
De Haven'3 water ductious flowiug tlicrefrom. Lieutenant De Plaven,
^^^- when he went in command of the American expedi-

tion in search of Sir John Frankhn 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 westward. 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 proba-
bly not always in the same place, as the Gulf Stream (§ 126) is
not always in one place. It probably is always where the v^^aters
of the under currents are brought to the surface ; and this, we may
imagine, would depend upon the freedom of ingress and egress for
the currents. Their course may perhaps be modified more or less by
the ice on the surface, by changes, from whatever cause, in the
com^se or velocity of the surface cmTent, for obviously the mider
current could not bring more water into the frozen ocean than the
sm-face cm-rent would carry out again, either as ice or water. Ex-
ploring parties may have been near this open sea without perceiving
the warmth of its climate, for every winter, an example of how very
close wann water in the sea and a 'very severe climate on the land
or the ice may be to each other is aflbrded 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 ther-
mometer frequently sinks far below zero, notwithstanding that the
tepid waters of the Gulf Stream may be fomid with their summer
temperature v/ithin one day's sail of these veiy, very cold places.

204 PHYSICAL GEOGRAPHY OF THE SEA, A^^) ITS METEOROLOGY.

429. Dr. Kane reports an open sea north of the parallel of 82^.
Dr. Kane. 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 temperatm-e of - 60 \ Passing
this ice-bound region by travelling north, he stood on the shores of
iin iceless sea, extending in an mibroken 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
^'perfectly steady." These tides, therefore, must have been born
in that cold sea, having their cradle about the North Pole. If
these statements and deductions be correct, then we infer that most,
if not all the unexplored regions about the pole are covered with
"deep water ; for, were this unexplored area mostly land or shal-
low water, it could not give birth to regular tides. Indeed, the
existence of these tides, with the immense flow and drift which an-
nually 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, fol-
lowing up this train of thought, the question is prompted, Is not
the nm'sery for the 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
{§ 160) convey it there also, and in channels so far down in the
depths of the sea that no enemy may waylay 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
idashing with measui'ed tread, like the majestic billows of old ocean,
against the shore. Solitude, the cold and boimdless expanse, and
the mysterious heavings of its green waters, lend their charm to
the scene. They suggested fancied myths, and kindled the ar-

THE SPECIFIC GRAVITY OF THE SEA, ETC. 205

dent imagination of the daring mariner's many longings. The
temperatm-e 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 siu-face level. Under
this ice there was also doubtless water above the freezing-point.

430. Xor need the presence of warm water within the arctic
undei- currents clrclo cxcito sm^risc, whcu WO rccollcct that the
tio^iy. ^^^^^^ "'^^ 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 sm-face, and until the polar flov/
(§ 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 temperature 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 temperatm^e of only 3° above the
freezing-point of fresh water, why may not water leaving the tor-
rid zone at a temperatm^e of 82°, and travelling by the same hidden
ivays, reach the frigid zone without losing more than the cold cur-
rents gained in temperature, "vaz., 7° ? In 1840, Sir James C.
Eoss, being in the antarctic regions with the 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 there 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" tempera-
tures for fresh and for saltwater are very different. In September,
when the surface water of Loch Lomond and Loch Katrine — Scot-
tish lakes — which are between 500 and 600 feet deep, is 58°, that
at the bottom is uniformly 41°, which is veiy near the point of
maximum density for fresh water. Saussure has sho'^n the same
for the Italian lakes ; only, at the depth of 1000 feet in the Lake
of Geneva, it was a Httle 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,

206 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

wliich is deep enougli to have the temperature of its v^ater some-
"what influenced by pressure (§ 404), tlie la\v is uniform; as you
descend in fresh-water lakes, the temperature decreases to that of
maximum density. Saussm^e extended his experiments to the
Gulfs of Nice and Genoa — salt-water bays in the neighbourhood of
his fresh-water lakes. Here, with the surface temperatm-e of 69°,
he found even at the depth of 1720 feet, the water no cooler than
55^.8. This salt w^ater 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°. 5, grow light, and remain on the
surface to be frozen. On the contrary, sea water contracts, grows
heavy, and sinks, until the whole basin, irom 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 comparatively 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 !
431. At the very time that the doctor was gazing with longing
«o^'d matter annu- eyes upou thoso straugo groeu waters (§ 429), there
the polar basin. is kiiown to havo becu a powerful drift setting out
from another part of this Polar Sea, and carrying with it from her
moorings the English exploring ship '' Eesoiute," 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 open-
ing in the ice, but, remaining fast in the ice, she was carried along
with the whole icy field or waste. This a.t 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 j^robably many times greater than this. A quantity of water
equal in weight to these tvro masses had to go in. The basin to

THE SPECIFIC GRAVITY OF TilE SEA, ETC. 207

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 the outflowing ice and water are at the smface, the
return current must be submarme. A part of the water that it
bears probably flows in beneath Dr. Kane's barrier of ice (§ 429).

432. These two cm-rents therefore, it may be perceived, keep in
Volume of water motiou between the temperate and polar regions of
SaJSowaifd ^^^6 ^^^^^^ a volume of water, in comparison with
reflow. 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 Brussels Conference recommended the systematic use
The hydrometer at of the hydrometer at sea. Captain Eodgers, Lieu-
^''^- tenant Porter, and Dr. Euschenberger, all of the
United States Navy, with Dr. Raymond, in the American steamer
* 'Golden Age," and Captain Toynbee, of the English East Indiaman
the "Gloriana," have each returned to me valuable observations with
this instrument. Eodgers, however, has afforded the most ex-
tended series. It embraces 128^ of latitude, extending from 71°
in one hemisphere to 57° in the other. And here I beg to re-
mark, that those navigators Vfho use the hydrometer systematically
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 httle
instrument, has been discovered in the sea between its salts, the
air, and the sun. The observations made with it by Captain
EodgerSjOn board the U. S. ship " Yincennes," have shown that the
specific gravity of sea water varies but httle in the trade-wind
regions, notwithstanding the change of temperature. The tempe-
ratm-e was a little greater in the south-east trade-wind region of the
Pacific ; less in the Atlantic. But, though the sea at the equa-
torial borders of the trade-wind belt is some 20° or 25° warmer
than it is on the polar edge, yet the specific gravity of its waters
at the two places in the Atlantic difters 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 Conference had in view when the specific gravity

208 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

column was introduced into the sea-joiunal was, that liydrographers
might find in it data for computing the djiiamical force which the
sea derives for its currents from the difference in the specific gravity
of its Yv^aters in difierent chmes. The Conference held, and rightly
held, that a given difference as to specific gravity between the
v>'atcr in one part of the sea and the water in another would give
rise to certain cm'rents, and that the set and strength of these
currents would be the same, whether such difference of specific
gravity arose from difference of temperatm^e or difference of salt-
ness, or both.

434. According to Kodgers' observations, the average specific
srieriiic gravity of gravity of sca water, as it is taken from the sea on
average s.'u water, ^j^g parallels of 34° north and south, at a mean tem-
perature of 64°, is just what, according to sahne and thermal laws,
it ought to be; but its specific gravity when taken from the
equator, at a mean temperature of 81°, is much 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 ought 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 iastead of the specific gravity of equatorial
water beiag .0025 lighter — as by thermal laws it ought to be — than
sea water at the temperatm-e of 61° in latitude 34°, it is only .0015.
What makes the equatorial water of the sea so much heavier than
accordiag to thermal laws it ought to be ? Let us inquire :

435. The anomaly is ui the trade-wind region, and is best de-
An anomaly. vclopcd (Plate X., Fig. 2) ia the North Atlantic,

betvveen 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 GuK Stream in the North Atlantic — commenciag
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. It is the trade-winds, then, which prevent the thermal and
Influence of the spccific gravity cmTcs from conforming wdth each
thfiecifi?^a?uy otlicr iu intertropical seas. The w^ater they suck up
of SUV water. jg fpesh watcr, and the salt it contained, being left

THE SPECIFIC GRAVITY OF THE SEA, ETC. 209

;behind, is just sufficient to counterbalance, by its weight, the
efiect 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 con-
clusion is, the proj^ortion of salt m sea water, its expansibihty be-
tween 62" and 82"" (for its thermal dilaiahility varies with its tem-
peratm^e), and the thirst of the trade-winds for vapour, are, where
they blow, so balanced as to produce perfect compensation ; and
4X more beautiful compensation cannot, it appears to me, be found
in the mechanism of the universe than that wdiich we have here
stiunbled upon. It is a triple adjustment : the power of the sun
to expand, the power of the winds to evaporate, and the quantity
of salts in the sea — these are so proportioned and adjusted that
when both the mnd and the sun have each played with its forces
upon the intertropical waters of the ocean, the residuum of heat and
of salt should be just such as to .balance each other in their efiects,
and so the aqueous equilibrium of the torrid zone is preserved.

437. Nor are these the only adjustments efiected by this ex-
compensating in- quisito Combination of compensations. If aU the
^^"""■■^*- intertropical heat of the sun were to pass into the

seas upon which it falls, simply raising the temperature of theu^
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 haK an inch per
day. The heat required for this evaporation would raise from the
normal temperatm^e 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 fm'ther augment its dynamical power, mitil, 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 of penetrating into the depths
of the ocean to raise inordinately the temperature of its waters, is
sent ofi" by radiation or taken up by the vapour, or borne away by
under currents, or carried off by the winds, and dispensed by the

p

210 PHYSICAL GEOGEAPHi OF THE SKI, AND ITS METEOEOLOGY,

clouds in tlie Hooper air of distant lands. Nor 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 climatology, circulation, and stabihty. Now,
suppose there were no trade-winds to evaporate and to counter-
act 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 inter-
vening sea with a mantle of warmth as with a garment. The
cool and heavy water of the polar basin, coming out as under cur-
rents, would flow equatorially with equal velocity. How much, 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 futm*e time, be considered worthy of special
inquiry. We have akeady seen (§ 434) that there is something
else besides temperature that is at work in effecting changes in the
specific gravity 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, evaporation is in excess of precipitation ; at any rate,
there is but little precipitation except under the equatorial cloud-
ring (see Storm and Kain Chart, Plate ^XIII.) ; and though, as we
approach the equator on either side from these parallels, the solar
ray warms and expands the sm-face water of the sea, the winds, by
the vapour they carry off and the salt they leave behind, prevent
it from making that water hghter.

438. Thus two antagonistic forces are unmasked, and, being
Nicely adjusted, uumasked, WO discovcr in them a most exquisite
adjustment — a compensation — by which the dynamical forces
that reside in the sunbeam and the trade-wind are made to coun-
terbalance each other ; by which the climates of intertropical seas
are regulated ; and by which the set, force, and volume of oceanic
currents are measm'ed. 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 grawity, and
* See chap. XXTI. on the Actinometky of the Sea.

THE SPECIPIC GRAVITY OF THE SE^V, ETC. 211

.the strength of fibre in the flower-stalks of plants (§ 303), but how
much more exquisite is the system of counterpoises and adjust-
ments here presented betv/een the sea and its salts, the wdnds and
the heat of the smi ! 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 vapom% are all in such nice adjust-
ment the one with the other, that there is the most perfect com-
pensation. By it they make music in the sea, and the harmony
that comes peahng thence, though not of so lofty a strain, is never-
theless, like the songs of the stars, divine.

439. Suppose there were no winds to suck up fresh water from
A thermal tide, the bruic of the occau ; that its average dej)th were
3000 fathoms; that the solar ray were endowed with power to
penetrate with its heat from the top to the bottom ; and that, from
bottom to top, the seas of each hemisphere, in thermal alternation
with the seasons, were raised to summer heat and lowered to mn-
ter temperatm^e : the change of sea level from summer to winter,
and from winter to simimer, 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 ther-
mal tide that would tm-n with the sun in the ecliptic, and tell the
equinoxes by the march on the tide staff of its rising and falling
waters. But difference of level would not be all that w^ould give
strength and volmne to this tide ; difference of specific gravity
would lend its weight as so much dynamical force, which differ-
ence would create an upper and under annual tide from one
hemisphere to the other. This double distm'bance of equilibrium
would not give rise to a tidal wave — not mere motion without trans-
lation— but to a tidal flow and reflow of water from one hemi-
sphere to the other in volumes of vast magnitude, power, and
majesty. This is an exaggerated view of the dynamical force of
the simbeam ; but it is presented to show the origin of the ther-
mal tide shown on Plate lY. The difference between the actual
and the supposed thermal tides is one of degTce merely ; for the
sea water that is hable to any considerable change of temperature,
instead of reaching from the bottom to the top, is scarcely more
than a " pelhcle " to the ocean. Nevertheless, there is a regular pe-
riodical 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,

p 2

212 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

and which comes to tlie surface near the polar edge of the tem-
perate zones ; it then dips again as it recedes towards the region of
perpetual winter.

440. The ohservations of Kotzebue, Admiral Beechey, and Sir
The isothermal floor Jamcs C. Eoss first suggcstcd the oxistence in the
of the ocean. occan of this isothcrmal floor. Its temperature, ac-
cording to Kotzebue, is 36°. The depth of this bed of water of
invariable and uniform temperatm-e is 1200 fathoms at the equa-
tor. It gradually rises thence to the parallel of about 56° N. and
S., when it crops out, and there the temperature of the sea, from
top to bottom, is conjectured to be permanently at 36°. The
place of this outcrop, no doubt, shifts with the seasons, vibrating
up and down, i.e.-^ north and south, after the manner of the calm
belts. Proceeding, in our description, onward to the frigid zones,
this aqueous stratum of an unchanging 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 thi-ee great regions — two polar
basins in which the surface temperatm-e 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 statement there is nothing
repugnant to hydrostatical laws, the compressibility of water in-
suring an increase of density in descending within much wider
limits of temperature than here contemplated."

441. The temperatm-e of 39°. 5 was assigned to this floor pro-
Thprmai dilatation ' bably uudcr tlic suppositiou that sea water follows
of the ^-ater. fresli iu its laws of thermal dilatation. Not 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 :

* This remark was made by Sir John on the supposition, probably, that the maxi-
mum density of sea water was at the same temperature as that of fresh, but it is
the same 12 ' or 14^ lower.

THE SPECIFIC GRAVITY OF THE SEA, ETC.
Thermal Dilatation of Sea Water*

213

Temp.

Dilatation.

Temp.

Dilatation.

Temp.

Dilatation.

Temp.

Dilatation.

22

0.99807

o
32

0.99795

o

50

0.99895

o

110

0950

23

801

33

797

55

943

120

1218

24

798

34

800

60

1.00000

130

1506

25

795

35

803

65

1067

140

1804

2G

793

36

806

70

142

150

2118

27

792

37

810

75

221

160

2460

28

791

38

814

80

309

170

2823

29

791

39

819

85

402

180

3192

'SO

792 1

40

.99823

90

503

190

3588

31

793 1

45

0.99856

100

0716

200

1.03993

442. The dilatation of the glass tube is included in this table.
Experiments on the To determine the freezing-point of average sea water
freezing-point. J ^j^gj ^ gkss jar 18 iuches 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 exposed this jar of water,
with a standard thermometer immersed, to the out-door tempera-
ture. When the thermometer in the jar reached 27°, small crys-
tals of ice, like macles of snow, were observed to form near the
bottom, to rise, and to increase as they rose. In truth, the phe-
nomenon 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 congelation was going on. In some in-
stances the water was brought down, as in a confined vessel,

* This agrees more nearly with Despretz Tp. 245) than with Dr. Marcet. The
latter states that sea water decreases in weight to the freezing-point until actually
concealed. In four experiments Dr. Marcet cooled sea water down to between ]8 '
and 19^ Fahr., and found that it decreased in bulk till it reached 22^, after w^iich
it expanded a little, and continued to do so till the fluid was reduced to between
19^ and 18°, when it suddenly expanded, and became ice with a temperature ol*
28^. 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 4^ 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 Mediterranean from the experiments of
Dr. Wollaston, ice could not be formed there at the same temperature as it could
nearer the smface. — (Vide M. de la Beclie, Manual Geology, p. 22.)

214

PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 ther-
mal changes of the specific gravity of sea water, fresh water being
the unit :

Temperature 27^.1 Spec. grav. 1.0290

28^.3
28^.8
29^.0
290.5
30^.0
32^.0
34^.0
34^.4
350.2

89
91

885

906

885

88

88

89

89

Temperature 380.0

Spe

c. grav.

1.0287

430.5

86

540.7

2

„

775

550.5

„

77

020.5

J)

69

(J30.5

«»

675

I „ 640.5

665

8O0.5

5>

43

88^.3

30

*930.3

,,

1.0221

443. All these experiments unite in showing that sea water at
nlTr'morJexpa^' equatorial temperatui-es is many times more ex-
sibio than sea water pausible than soa water at polar temperatm-es ; that

at wmter tempera-
ture.

IS, sea water, according to its rate of dilatation
(§ 441), will expand about seventeen times as much for 5°,
is raised from 85^,

when
its temperatm-e is raised from 85"^, as it vail when raised from
28^ ; and yet, according to Plate X., the cuitos of temperature
and specific gravity are symmetrical in polar, non-spumetrical 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 existence of such an isothermal
floor all the way from pole to pole.

444. "The physical consequences of this great law, should.
Data for Plate x. it be found Completely verified by farther research,

are in the last degree important." The observations which fur-
nished the data for Fi^. 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 Fiff. 2 the southern
observations v/ere made in May and June, the northern in Jmie and
Jdy.

445. It is well to bear this difference as to season north and
Athermaitide; it ebbs south in mind, and to comparo these curves with
and flows once ; year, thoso of the thermal, cliarts ; 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 xltlantic appears to be cooler and heavier than the northern.

* Specific gravity at 2000=: 0-9908.

THE SPECIFIC GRAVITY OF THE SEA, ETC. 215

The season of observation, however, is southern fall and winter vice
northern summer. In January, Februar}^, and March, the waters
of the southern ocean are decidedly warmer, as at the opposite six
months they are decidedly cooler, parallel for parallel, than those
of the northern oceans. Thus periodically differing 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 study-
ing the laws of this thermal tide we are struck with the compensa-
tions and adjustments 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 astronomer has to deal when he is vforking out the geometry of
the heavens. He finds that 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 cnmiple
the surface of the sea by alternate expansion and contraction 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 sm-ely 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 mistaken its rate and velocity.
These movements are well represented 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 pertm'bations in the orbits
of planets ; but the physicist is no more at liberty to despise these
than the astronomer is to neglect those.

446. The problem that we now have in hand, and which is re-
sea water of the south- presented bv the diaoframs of Plate X., is to put the

era cooler and heavier, ■■- . ■> ,^ • i ^ ix '1

parallel for parallel, scas lu scaios, the occau m a balance, and to weign
norlthem hemisphere, ill the specific gra\dty bottle, the waters of the
northern with the waters of the southern hemisphere. By Figr. 2
it would appear that both the water and the air of the south At-
lantic are decidedly both cooler and heavier, parallel for parallel.

216 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS aiETEOROLOGY,

than the waters of the north Atlantic ; but this difference may be'
more apparent than real ; for the observations were made in the
northern smnmer 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 mnter tempera-
ture, and consequently the specific gra\dty of the waters of each
must change with the seasons. A diagram — had we the data foi-
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-
born tide of the ocean. By Fig. 1 the south Pacific also outweighs
the north in specific gravity ; but here again the true difference,
whatever it be, is somewhat masked by the time of year when the
observations were made. Those north were made dming the fall,,
winter, and spring ; those south, dm'ing the fall and fii'st v^inter
months of that hemisphere. Nevertheless, the weight of the
observations presented on Plate X. does, as far as they go, indicate-
that the seas 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 mth that contained in sea water north.

447. These indications, as far as they go, and this view of the
restimonyofthe subjcct, whatcver future investigations may show to
ofTheSfcros^'sing's"' ^^ i^s truo worth, scom to lean in support of the idea
at the calm belts, advauccd and maintained by facts and arguments in
Chapter lY., -vdz., that the southern seas are the boiler and the-
northern hemisphere the condenser 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 supply oiu: fountains with rains for the
great American lakes, and vdth. rains for the majestic water-courses
of Europe and Asia, Northern Africa and America, are replenished
from seas beyond the equator, then the waters of the ocean south
should be a little Salter, and therefore specifically a little heavier,
parallel for parallel, and temperatm^e for temperatm'e, than the
waters of cis-equatorial seas. We begin to find that the hydrometer

* According to Dr. Marcet, tlie southern ocean contains more salt than the
northern in the proportion of 1 .02919 to 1 .02757.

THE SPECIFIC GRAVITY OF THE SEA, ETC. 217

f

is bearing testimony in support of the evidence adduced in Chapters
lY. 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 httle instrument
could throw any light upon 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 cm-rents from restoring its equilibrium but the winds, which
are continually sucking up from the brine of trans -equatorial seas
and pouring it down as fresh water upon cis-equatorial seas and
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 measm-e for
determinmg the amount of fresh water that is always in transitu.
Certainly, if evaporation and rains were to cease, if the rivers were
to dry uj), 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, v,'ould 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 ciu:ves 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 gTavity is counter-
acted by evaporation. Now, if we knew the thickness of the
stratum which supplies the fresh water for this evaporation, we
should not only have a measm-e 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

218 PHYSICAL GEOGRAPHY OF THE SEA, A'ND ITS METEOROLOGY.

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
temperatm-e and density of sea water have for then- object to weigh
the seas, and to measm-e 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 sj'stem of research to solve. But, in
order to v/eigh 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. From these premises it would not be difficult to show that
Amount of salt in, the saltucss of the sca is a physicpJ necessity. In
gravurof Sr'^*^ 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 harmonize 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 im-
parting dynamical force to marine cmTents ; nor prevent the solar
ray fi'om miduly disturbing the aqueous equilibrium of our planet.
As evaporation goes on from a sea of fresh water, the level only,
and not the specific gravity, of the remaining water is changed.
The w^aters 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 con-
dition which, by reason of evaporation and precipitation, is almost
the very reverse of that which natm-e 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 accm-ately known. From such
data as I have, I estimate it to be about 4 per cent. (.039), and the
mean specific gravity of sea water at 60^ to be about 1.0272. Sup-
posing these conditions to be accurate — and they are based on data
which entitle them to be considered as not veiy 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

THE SPECIFIC GRAVITY OF THE SEA, ETC. 219

of sea water into -which the navigator vill take the trouble to dip
these two instruments.

449. These specific gravity and thermal curves, as they are pre-
Light cast by Plate scutcd ou this Plate (X.), throw light also on the
in The Atretic occMi. qucstion of an open sea in the Arctic Ocean. That
open sea is hke 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 v/ith waim water from the south, which, by virtue of its
saltness (see Fig. 2), is heavier than the cool and upper current
which rmis out of the polar basin, and which is knovTi as an ice-
bearing cmTent. It is the same which is felt by mariners as £ar
down as the Grand Banks of Newfomidland, and recognized by
philosophers off the coast of Florida. This upper cmi'ent, 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
o^n shores, the thermal curve loses 12^ of heat ; and what does
the specific gravity cm've gain in the same interval ? Instead of
increasing up to 1.027, accordmg 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 fi'esh-water lakes never freezes over.
XVliy ? Because of their depth and their vertical circulation.
The depths below are continually sending water above 32° to the
surface, which, before it can be cooled dovn to the freezing-point,
sinks again. Now compare the shallow somidmgs in these lakes
"^ith the great depths of the Arctic Ocean ; compute the vast ex-
tent of the hydrographic basin v;hich holds this polar sea ; gauge
the rivers that discharge themselves into it ; measure the rain,
and hail, and snow that the clouds pom' down upon it ; and then
contrast its area, and the fresh water drainage into it, mth the
like of Long Island Sound, Delaware Bay, and the Chesapeake ;
consider also the volume of diluted sea water between om' 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 o^vn fresh water streams are diluting the brine of
the sea under our own eyes. The very Gulf Stream water, vrhich
the observing vessel left as she crossed 34° and entered into those
hght httorai waters, was bound northward. Suppose it to have
flowed on as a smiace current until it, vdth its salts, was reduced

220 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

to the temperature of 40°. Its specific gi'avity at that terapera-
ture 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 cur-
rents ? If water that freezes at 32°, that grows light and remains
on the sorface as you cool it below 39°, is prevented from freezing
in our great fresh water lakes by vertical circulation, how much
more would both vertical and horizontal circulation prevent conge-
lation in the open polar sea, that is many times deeper and larger
than the lakes, and the water of which contracts aU the way down
to its freezing-point of 27°. 2.

450. The heaviest water in the sea, micorrected for the tempera-
The heaviest water, turc, as showu by the obscrvatious before us, is 1.028.
This water was found {Figs. 1 and 2) off Cape Horn. Let us ex-
amine a little more closely into the circumstances connected with

"the heaviest water on om' side of the equator. It was a specimen
of water from the Sea of Okotsk, w^hich is a sea in a riverless
region, and one where evaporation is probably in excess of precipi-
tation— thus fulfilling the physical conditions for heavy water.
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 Babelmandeb is suffi-
cient 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 Eed 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 meri-
dian of Socotra ; after which the saltness again increases as yon
approach Bombay.

451. Its waters, from the mouth of the straits for 300 or 40Q
ciiapman's experi- milcs up, havo boeu fouud as high in temperatm^o
°''^"*'- 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 sug-
gest an explanation of this, at least in part. Evaporation ought
to assist in keeping the sm-face of intertropical seas cool in the
same way that it helps to cool other wet surfaces. And if the

THE SPECIFIC GRAVITY OF THE SEA, ETC. 221

waters of the Ked 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 carr^dng 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.

452. There is another indication which this little instrument
The hydrometer in- Jias affordcd concoming the status of the sea, and
latftudes^at^sS?' which doservcs 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' observa-
tions 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 YIII. shows that the equatorial calm belt hes south of
the line where it is intersected by the homeward route from Cali-
fornia. 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 ofiings of what are called the '^ Leeward Islands " of the West
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. The most comprehensive view that we are permitted to
Astronomical view, take of cosmical or terrestrial arrangements and

adaptations is at best narrow 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 different 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 in-
dulged, are always refreshing, and the developments of the hydro-
meter which we have been studying point us to one of them. This
fancied discovery is, that a sea of &esh water instead of salt would
not afford the compensations that are required in the terrestrial
economy, and we also fancy that we have almost discovered a

222 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

relation between the orbit of the earth and the arrangement of land
and water on its surface and their bearing upon climate. Om- planet
passes its perihelion during the southern sinnmer, when it is nearer
the centre and somxe of hght 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 heat received by the earth is about
■J5- more than it receives during a day in July, when it is in aphe-
lion.* January is the midsummer month of the southern hemi-
sphere, 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. AYhat becomes
of this dim-nal excess of southern summer heat, be it in its aggre-
gate never so small, and why does it not accumulate in trans-
equatorial chmes ? So far from it the southern hemisphere is the
cooler.

454. In the southern hemisphere there is more sea and less land
The latent heat of than in the northern. But the hydrometer indicates

vapour. ^]^Q^^ j^i^Q water in the seas of the former are Salter and

heavier than the waters of seas cis-equatorial ; and man's reason-
ing faculties suggest, in explanation of this, that this difference of
saltness or specific gravity is o^ving to the excess of evaporation
in the southern half, excess of precipitation in the northern half of
our planet. "When water passes, at 212^ Fahrenheit, into steam
it absorbs 1000^ of heat, which becomes insensible to the ther-
mometer, or latent ; and conversely, when steam is condensed into
water, it gives out 1000^ of latent heat, which thus becomes free,
and affects both the thermometer and the senses. Hence steam of
212^ Fahrenheit will, in condensing heat five and a half times its
o^Ti weight of water from the fi^eezing to the boiling point." —
M'CuIIoch. Now there is in the southern a very much larger
water smface exposed to the sun than there is in the northern hemi-
sphere, and this excess of heat is employed in lifting up vapom- from
that broad smface, in transporting it across the torrid zone and
conveying it to extra-tropical northern latitudes, where the vapour
is condensed to replenish om' fountains, and where this southern
heat is set free to mitigate the severity of northern climates.

455. In order to trace a little farther, in our blind way, the evi-
its influence upon deucos of wisdom and design, which we imagine we
climates. qcj^^ dctect in the terrestrial arrangement of land and

* Sir John Herschel.

THE SPECIFIC GRAVITY OF THE SKi, ETC. ' 223

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 remaining the same. Is it not obvious to our reason
that by this change the whole system of climatology in both hemi-
spheres would be changed ? The climates of our planet are as obe-
dient to law as the hosts of heaven. They are as they were
designed to be; and all those agents w^hich are concerned in
regidating, controlling, and sustaining them are "ministers of His."
Johnston, in the chapter to Plate XYIII. of his great Physical
Atlas, thus alludes to the seas, land, and climates of the two hemi-
spheres : " The mild winter of the southern hemisphere, plus the
contemporaneous hot summer of the northern hemisphere, neces-
sarily gives a higher sum of temperatm^e 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 periodi-
cal 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 intermixtm^e of atmospheric currents of
different temperatui'es ; but the unequal distribution of land and
sea ui the northern and southern hemispheres supplies an effectual
provision, from whence it necessarily follows that the aqueous
vapour, which f^'om the autumnal to the vernal equinox is deve-
loped to an immense extent over the southern hemisphere, retui'ns
to the earth, in the other half of the year, in the form of rain or
snow\ And. thus the wonderful march of the most powerful steam-
enguie with which we are acquainted, the atmosj)here, 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 north-
ern hemisphere as the condenser in this great steam-engine, and
the southern hemisphere as its water reservoir ; that the quantity
of rain which falls ui the northern hemisphere, is, therefore, consi-
derably gi'eater than that which falls in the southern hemisphere ;
and that one reason of the high temperatm-e of the northern hemi-
sphere is that the larger quantity of heat which becomes latent in
the southern hemisphere in the formation of aqueous vapour is set
free in the north in great falls of rain and snow."

456. In this view of what our little hydrometer has developed
or suggested, we trace the principles of compensation and adjust-

224 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS aiETEOROLOGY.

ment, the marks of design, the evidence of adaptation between
The results of the tho oiHt of the oaith and the time from the vernal
marine hydrometer. ^^ ^j^g autumnal, and from the autumnal to the
vernal equinox ; between the arrangement of the land in one hemi-
sphere 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 tele-
scope and the microscope, bear in proof that the eye, in its struc-
ture, was adapted to the light of heaven. The universe is the
expression of one thought, and that it is so every new fact deve-
loped in the progress of our researches is glorious proof.

457. In the com-se of our investigations into the physics of the
Barometer indica- sea, 100,000 obscrvatious of the barometer, and
tions of an open sea. jjioro 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 ; and the inrushing air
comes from a greater distance to the cold than to the warm
calms.*

458. The question may be asked. Whence comes the heat that
Polar rarefaction, cxpauds and rarcfics the atmosphere in these polar

places ? The answer is, it comes from the condensation of vapour.
The south pole is surrounded by ^vater, 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 rare-
faction produced in the latter by the latent heat of vapour 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 barome-
ter 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
* Plate rV., Nautical Monograph No. 1.

ETC. 225

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 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. The records of arctic explorations, together with thewhale-
Tue middle ice. men'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 compact and cold " middle ice."
In our fresh- water streams it is the ^nicldle ice that first breaks up ;
that which is out of the way of the current remains longest. Not
so in this bay and strait ; there the littoral ice first gives way, leav-
ing 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, consequently 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 broken 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 " compact
and firm, so much so as to be impassable. In this fact we recognize
another circumstance favoiuring the theory of an open sea at the
north, and giving plausibility to the conjecture that this " middle
ice " drifts out from the southern edge of the open sea as fast as it

Q

226 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOKOLOGY.

is formed during the winter. According to this 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 of 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 thickness 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. The open sea, therefore, is, it may be inferred, at no great
Position of the open distaucc from the several straits, which, leading in
^'^^- a northwardly direction, connect Bafiin's Bay with

the Arctic Ocean. It is through these straits that the winter drift
takes place. The ice in which the Fox, the Kesolute, the Advance,
and the Eescue 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 Erankhn 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 brine of the ocean is the ley of the earth (§ 43).
The brine of tiie From it the sca derives dynamical power, and its
ocean. currcuts thcu' main strength. Hence, to understand

the "dynamics of the ocean, it is necessary to study the efiects 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 im-
part to its waters those curious anomalies in the laws of freezing

THE SALTS OF THE SEA. 227

and of thermal dilatation which have been described in a previous
chapter (IX.). It is the salts of the sea that assist the rays of
:beat-to penetrate its bosom;* but for these, the solar ray, instead
of heating large masses of water like the Gulf Stream, w^ould play
only at or near the surface, raising the temperature of the. waters
there, like the sand in desert places, to an inordinate degree.
The salts of the sea invest it w^th adaptations which it could not
possess were its waters fresh. Were they fresh, they would attain
their maximiun density at 39^.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 fresh and not salt, Ireland would never have
Were the sea of presented thoso ever-green shores which have won
freshwater- foj, i^^j. ^^q j^^mo of the " Emerald Islc ;" and the

climate of England would have vied with Labrador for inhospi-
tahty. 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 cer-
tain parts of the earth would have been deluged with rain. Had
the seas been of fresh water, the amount of evaporation, the quan-
tity of rain, the volume and size of our rivers, would aU 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 normal 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 contrivanjces, flashing only with such sparks as the vegetable
kingdom raight, when the juices of its plants were converted into
vapour, lend to the clouds. It might seem strange, this idea that
the thmiderbolt of the sky, the sheet-lightning of the clouds, and
the forked flashes of the «torm, 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 httle zinc can evolve
electricity enough for a thmider-clap ; therefore, were there no salts
in the waters of the ocean, the somid of thunder would scarce be

* Melloni lias sLo-svn that the power of salt water to transmit heat is very much
greater than that of fresh. ^ o

Q -^

228 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

heard in the sky* — there would be no Gulf Stream, and no open
sea in the Arctic Ocean.

463. As a general rule, the constituents of sea water are as
Uniform character coustaut iu their proportious as are the components
of sea water. q£ ^^^q atmosphcrc. It is truo that we sometimes
come across arms of the sea, or places in the ocean, where 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 Ked Sea
(§ 376), upon which it never rains, and from which the atmo-
sphere 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 mouth 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 Ked 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 con-
centrated as to brine, a moderate degree of saltness which its
waters cannot exceed. We moreover find that, though the con-
stituents 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 con-
jecture that the ocean has its system of circulation, which is well
calculated to excite our admiration, for it is as wonderful as the
circulation of the blood.

464. In order to investigate the effect of the salts of the sea
Hypotheses. upon its currcuts, and to catch a glimpse of the

laws by which the circulation of its waters is governed, hypothe-

* The great American lakes afford, it may bo supposed, a considerable portion
of the vapour which goes to make rain for the hydrographic basin in which they
are. Visiting the Lake country in 1858, I was struck with tlie 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 lightning ; and, on inquiry from the Lake Board of Underwriters, I was in-
formed that among the records of lake disasters there was not a single instance of
a vessel having been struck by lightning on the North American lakes !

THE SALTS OF THE SEA. 229

sis, 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 mth 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 ;
and in making the selection of the various hypotheses which are
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 re-
spectful consideration at least, until we discover it leading us into
some palpable absTirdity, or until some other hypothesis be sug-
gested which will account equally as well, but for a greater num-
ber 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 bo offered. With
this understaading, I venture to offer an hypothesis with regard
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 resem-
ble 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 mth sea water from aU
other parts of the world ? Agents, therefore, it would seem, are
at work, which shake up the waters of the sea as though they
were in a bottle, and which, in the com'se of time, mingle those
that are in one part of the ocean with those that are in another as
thoroughly and completely as it is possible for a man to do in a

230 PHYSICAL GEOGRAPHY OF THE SEA, AM) ITS METEOROLOGY

vessel of Ms own construction. This fact as to uniformity of coin-
ponents 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 cmTents ; and as these currents have their offices to per-
form in the terrestrial economy, they probably do not flow by
chance, but in obedience to physical laws ; they no doubt, there-
fore, assist to maintain the order and preserve the harmony which
characterize every department of God's handywork, and as such
we treat them.

465. This hypothesis about currents is based upon our faith in
b^'lo^iiiinesTn'^'^^'^ ^^® physical adaptations mth which the sea is in-
favourof. vcstcd. Take, for example, the coral islands, reefs,

beds, and atolls with which the Pacific Ocean is studded and gar-
nished. 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 obedi-
ent cmTents, 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 creatm^e. Unless
the cmTents 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, mthout the ministering aid of currents to briag it more,
it would have perished for the want of food for itself and mate-
rials 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 archi-
tect, but as a monument in attestation of the shocking mon-
strosity that there had been a failure in the sublime system of ter-
restrial adaptations — that the sea had not been adapted by its
Creator to the well-being of aU its inhabitants. Now we do know
that its adaptations are suited to aU the wants of every one of its

THE SALTS OF THE SEA. ^3l

inhabitants — 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 ice knotu that
the sea has its system of circulation, because it transports mate-
rials for the coral insect and its rock from one part of the world to
another ; because its currents receive them from the riyers, and hand
them over to the little mason for the structure of the most stupen-
dous works of solid masonry that man has ever seen — the coral
islands of the sea. Thus, and moreover, by a process of reasoning
which is perfectly philosophical, we are irresistibly led to con-
jectm-e 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 atmosphere 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 Hfted up their voice " in
chorus ; and doubtless, therefore, the harmony in the depths of the
ocean is in tune mth 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, accordingly, 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. For instance, take the Ked Sea and the Mediterranean by
Ditto by the Red Way of iUustratiou. Upon the Eed Sea there is no
^^^ precipitation; it is a rainless region; not a river

runs down 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
brought down into the Eed 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 cmTents 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-

232 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ranean^ some of which are filtered through soils and among mi-
nerals which yield one kind of salts or soluble matter, another river
runs through a limestone or volcanic region of country, and brings
down in solution solid matter — it may be common salt, sulphate
or carbonate of hme, 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 Ked Sea are quite
the same. But the waters of the Dead Sea have no coimection
with those of the ocean ; they are cut off from its channels of cir-
culation, 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 cur-
rents. 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
com'se consequently accmnulate."* They would constantly accu-
mulate, as this very shrewd author remarks, were it not for the
shells and insects of the sea and other agents mentioned.

467. How, therefore, shall we account for this sameness of com-
A general system of pouud, tliis structuTO of coral (^ 465), this stability

circulaiion required ^ . ' . i tp • .i i j n ',•

for the ocean. as to auimai liio lu tuo sca, but upon tne supposition

of a general system of circulation in the ocean, by which, in pro-
cess 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 cutting off and shutting up from the general chan-
nels of circulation any portion of sea water, as in the Dead Sea, or
of atmospheric air, as in mines or wells, we can easily charge
either -with gases or 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. The principal agents that are supposed to be concerned in
Dynamical agents, giviiig circulatioii to the atmosphcre, and in preserv-
ing the ratio among its components, are light, heat, electricity, ani

* Youman's Chemistry.

THE SALTS OF THE SEA. 233

perhaps magnetism. But with regard to the sea, it is not kiio^\Ti
what office, if any, is performed by electricity, in giving d^qiami-
cal force to its system of circulation. The chief motive power
from which marine cm-rents 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 sys-
tem of oceanic circulation is derived from the salts of the sea.
water, 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 explaining the nature of this.
force, suppose the sea in all its parts — in its depths and at the sur-
face, 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 distm^b 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 difierent densities and temperatures. Now
let us suppose the winds, for the first time since the creation, ta
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 httle way below the
sm-face, would give rise to a feeble circulation in the supposed sea.
of fresh water. The surface drift thus created — currents they
would hardly be, — would set vdth. the wind, giving rise to counter
movements in the shape of under-tows and eddies. This, then, is
one of the som'ces whence power is given to the system of oceanic
circulation; but, though a feeble one, it is one which exists in
reahty, and, therefore, need not be regarded as hypotheticaL
Some (§ 79) think it the " sole cause r Let us next call in eva-
poration and precipitation, with heat and cold — more powerful
agents still. Suppose the evaporation to commence from this-
imaginary fresh-water ocean, and to go on as it does from the sea&
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 ofi' to the extra-tropical regions, and

234 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 temperature to be sud-
denly stricken with the invisible wand of heat and cold, bringing 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 waters, which would destroy the equili-
brium of the whole ocean ; upon this a set of currents would imme-
diately 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 diflerence of specific gravity arising from differ-
ence 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,
woiffd be quite feeble in comparison ^vith those which we fimd 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 employed 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 conse-
quently 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 sur-
face currents of warm and lighter water, from the equator towards
the poles, and in another set of under currents of cooler, dense, and
heavy water from the poles towards the equator.

469. Such, keeping out of view the influence of the winds,
Currents without whicli WO 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°,*

* 390.5.

THE SALTS OF THE SEA. 235

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 distui'b 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 cm-rent in it as the GruK Stream.
So far we have been reasoning hypothetically, to show what would
be the chief agents, exclusive of the winds, in disturbing the equi-
Hbrium of the ocean were its waters fresh and not salt. And what-
ever disturbs equilibrium there may be regarded as the jprimum
mohile in any system of marine currents.

470. Let us now proceed another step in the process of ex-
influence of salts plaining and illustrating the effect of the salts of the
and evaporation. ^^^ :^ ^YiQ systcm of oceauic circulatiou. 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 temperatm^e is lowered (§ 441) tiU it reaches
25^.6. Let evaporation now commence in the trade-mnd region,
as it was supposed to do (§ 468) in the case of the fresh-water
seas, and as it actually goes on in natm^e — and what takes 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 equi-
librium is destroyed because of the saltness of the water ; for the
water that remains after the evaporation takes place is, on account
of the solid matter held iu 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 certaiu 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,

236 PHYSIC-\X. GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

is not so cool (§ 404) — from the deptlis below. This vapour, then,
which is taken up from the evaporating regions (§ 293), is carried
by the winds through their channels of circulation, and poured
back into the ocean where the regions of precipitation 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 precipitation 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, v\^hich, for illustra-
tion 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 amomit 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
cmTent 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. Thus it is to the salts of the sea that we owe that feature
The under currents in the systcm of occanic circulatiou which causes
2iTt"of sea^4ter. ^^ au uudcr currcut 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 cmTents

THE SALTS OF THE SEA. 237

carry in. We now begin to perceive 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 cur-
rents of the sea, by reason of its saltness, attain their maximum
of volume and velocity. Hence, too, we infer that the transporta-
tion of warm water from the equator tow^ards 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 cli-
mates 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. This property of saltness imparts to the waters of the
A property peculiar occau auothcr peculiarity, by which the sea is still
to seas of salt water, i^etter 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 be-
ing a good retainer, but a bad conductor of heat, this warm 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 saJt water, and the specific gravity of that
at the top ^vill soon be so changed as (§ 404) to bring that, from
the very lowest depths of the sea to the top.

473. If all the salts of the sea were precipitated and spread
Quantity of salt In out cqualty ovcr the northcm 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 wonderfully 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 centm^ies of time, move even so much as an inch this

238 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

matter which the sunbeam, the zephyr, and the infusorial insect
keep in perpetual motion and activity.

474. If these inferences as to the influence of the salts upon •
Deductions. the cmTeuts 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 cm-rents between
them, viz., a smface 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 cur-
rent 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 Na'\^,
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 dming
the nine months that he was so frozen, his vessels, hke 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 to-
wards the south.

475. The drift of these vessels is sufficient, were there no other
Drift of ttie Reso- ovideuce, to estabhsh the existence of an open sea
^^^^- in the Arctic Ocean; for this drift cannot be ac-
counted for upon any other hypothesis, as a sHght examination
of the arctic regions on a terrestrial globe, and a careful study of
the facts (§ 459), and other phenomena will show.

476. About the middle of September, 1850, being in latitude
De Haven's drift. 74° 40', and in the fair way of Wellington Channel,

De Haven found himself, with the Advance, frozen in her tracks,
as M'Chntock did the Fox,* m August, 1857, who tried to reach
the shore, but he was fast bound, and driftmg to the west. De
* A screw yaclit of 177 tons. ,

0

THE SALTS OF THE SEA. 239

Haven, after having been carried as far as 75° 25', and M'Clintock
as fer as 75° 30', say witliin nine hundred miles of the pole, found
their northerly course ^Yas arrested; then commenced 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 tvith
the ice ; for in lat, 65° 30', when De Haven was hberated on
the 9th of June, he had the same "hummocks," the same snow-
drifts, and the same icy landscape mth set out with him on
December 2nd, vdien he commenced his drift from the parallel of
75° 25'.*

477. Now, upon the theory of no open water, and upon the
An anti-poiynian supposition of an ice-covcred 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 theory, 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 distance
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 reheved here and there, perhaps, by is-
lands, capes, and promontories dotting the surface, but neverthe-
less it is now at least as cold — being winter — ^from 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 entfre sheet of ice mth which we have supposed the Arctic
Ocean to be covered, put in motion, or was that ordy put in motion

* De Haven was frozen in lat. 74^ 40', Ions;. 92° 55' ; was carried up to 75° 25'
N., and thence down to 66° 15' N., 58^ 35' W., when he was liberated. The Fox
was frozen in 75° 30' 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. The Keso-
lute was abandoned in lat 74° 40', long. 101° 20', and was picked up afloat off
Cape Mercy in 65° N.

240 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

whicli 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 agaia, 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 5^ miles a day. But
whence — on what parallel — did it commence ? Was the whole disc
in motion from the shores of Siberia over across by 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, dming the winter
and spring — the coldest period — the edge of this ice-disc nearest Wel-
lington Channel be carried by the currents a thousand miles towards
the south, the edge along the Eussian 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 any case the northerly edge of the driftiug
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 North 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 Eescue, the Fox,
and the Eesolute are witnesses of it — that a tongue of this ice 1000
miles long was in each of these mnters thrust out of the polar basin
do^Ti through Baffin's Bay into Da\ds' Straits. These ships came
do^vn upon it. It would be difficult for those who oppose the exist-
ence of an open water here in the Arctic Ocean to discover a force
there which, dming the extreme cold months of the northern night,
when the ice is making all the time, could tear from its fastenings
and move 5|- miles a day all through the mnter and spring a disc
of ice seven feet thick* and 1800 geographical 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

* De Haven fouml the ice upon which his vessel was brought out 7 feet 2 inches
thick.

THE SALTS OF THE SEA. 241

liberated there was doubtless a continuous sheet of ice between her
in lat. 65°, and WeUington Channel in lat. 75°. This tongue of
ice is what the whalemen call the " middle ice " of Baffin's Bay.
Wlien the Advance was at Wellington Channel, this thousand miles
of ice must, according to the anti-polynians, have been to the north
of her; or, 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. Upon the supposition that the ice which drifts out of the
The drift explained. AjTctic Occan 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 kno^^Ti facts which attended the
celebrated drifts of De Haven, M'Clintock,* and the Kesolute.
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 cover-
ing— 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 tow^ards 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.!

* In the Fox, 1857-1858.

t " The Fox accomplished another of those remarkable drifts which can be ex-
plained upon no other hypothesis but that of an open water in the Arctic Ocean, and
that, too, not far from the entrance into it of some of the channels which connect it
with Baffins 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 1191: miles,
which gives an average rate of five miles a day.

" This drift, the drift of the Kesolute, of the Advance, and Eescue, each upwards
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 im-
prisonment, 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 explanation of this phe-
nomenon, and they are : Either that the great body of all the winter-formed ice

242 PHYSICAL GEOaRAPHY OF THE SEA, AND ITS METEOROLOGY.

479. On the fii'st of April De Haven measured tlie ice, and
Thickness of a foiind it seven feet two inches tliick. It was formed
winter's ice. probablj mostlj of rain and river water, which, like

our o^Ti littoral waters (§ 426), protect the Salter and heavier waters
below from the cold, for De Haven invariably found the tempera-
ture of the water under the ice 28°, which is the temperatm^e that
average sea water invariably assumes during the process of congela-
tion (§ 442). Moreover, the specific gravity of the surface water
which Eodgers 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 freez-
ing-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 way 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 congela-
tion, which varies between that of fresh water and the saltest sea
water according to the degree of its saltness.

480. Kodgers tried with his hydrometer and thermometer the

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 tlu-ust 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 all 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 phenomenon be-
comes 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 Baffin'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 insensible, 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 westward, or with Baffin's Bay, the probabilities are that this
regularly occurring winter drift would have brought them down sfifely 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
Baffin'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
tlie severest winter." — Transactions of the American Geo. Society, 18G0.

THE SALTS OF THE SEA.

243

waters of tlie Arctic Ocean at the surface, below, and at the bottom,
and as often as he tried he found this arrange-
ment : warm and hght water on the top, cool in the
middle, " hot and hea\^ " at the bottom. His experi-
ments were made near Behring's Straits in August, 1855, between
the parallels of 71^-2^, and are as per example following :

Layers of water of
different tempera-
ture in the Arctic
Ocean.

Date.

Depth.

Temp.

Sp. Grav.

Aug. 13

surface

48. S

.0264

20 fath.

33.5

.0266

40 fath.i

40.5

.0266

Aug. 15

surface

42.5

.0258

12 fath.

39.8

.0264

»>

25 fath.i

40.2

.0264

Place.

Lat. 72^ 2' Long. 174° 37' W.

)> 9> >> >>

,',' 71""2r " 1750 22'

1 Near bottom.

Assuming the surface water which Eodgers used for these experi-
ments to be a fair average of arctic surface waters generally, this
table affords data that show the proportion of rain and river water
that the Arctic Ocean receives annually. The quantity may be in-
ferred from the fact that average sea water has ten per cent, more
salt than attained by Eodgers in the Arctic.

481. Eeturning now to the drift of the ice, and the drift of the
The ice-bearing drift Advauco and hcT foUowcTS, WO SCO that, so far as
from ihe Arctic like curreuts are conccmed, we have in the Arctic Ocean

the ordmarv dnit /> i o •^• i

from the Baltic. a repetition merely of the more lamiliar 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, smce there is salt alvrays 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 confirmed by theu'
observations a law of natm-e (§ 474), and afforded us proof positive
as to the fact of this other som'ce for supplying the polar seas with salt.
They tell us of an under current setting from the Atlantic towards
the polar basin. They describe huge icebergs, mth tops high up
in the air, and of course the bases of which extend far do^vn into

244 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the deptlis of the ocean, ripping and tearing their way with terrific
force and awful violence tlirough the surface ice or against a surface
current, on their way into the polar basin.

482. Passed Midshipman S. P. Griffin, who commanded the brig
Icebergs drifting Kescuo in the American searching expedition after
^°^^^' Sir John Franklin, informs me that, on one occasion/
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 ice-
berg, with its top many feet above the water, came " drifting up "
from the south, and passed by them " like a shot." Although they
were stemming a sm-face cmTent against both the berg and them-
selves, 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 counter cm-rent. They hooked on
to it, and were towed to the north by it. Captain Dimcan, master
of the English whale-ship Dundee, says, at page 76 of his interest-
ing 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 tlirough the middle of the ice." And again, at
page 92, etc. : '' Fehruarij 2Srd. Latitude 68° 37' north, longi-
tude about 63° west. The dreadful apprehensions that assailed us
yesterday by the near approach of the iceberg were this day most
awfully verified. About tliree p.m. the iceberg came in contact
with our floe, 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
hundi'ed pieces of heavy ordnance fired at the same moment. The
iceberg, mth 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 ice-
berg, as before observed, came up very near to the stem of the ship ;
the intermediate space between the berg and the vessel was filled
with heavy masses of ice, which, though they had been j^reviously
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 fom* knots, and by its force on the mass of ice
was pushing the ship before it, as it appeared, to inevitable de-

* Arstic Eep;ion3 ; Voyage to Davis' Strait, by Dorea Duncan, Master of the
ship Dundee, 182G, 1827.

THE SALTS OF THE SEA. 245

struction. Feh. 24:th. The iceberg still in sight, but drifting away
fast to the north-east. Feb. 25th. The iceberg that so lately threat-
ened our destruction had driven completely out of sight to the
north-east from us."

483. Now, then, whence, unless from the difference of specific
Temperature of the gravity duo to soa Water of different degrees of salt-
under current j^ggg ^nd temperatiu-e, can aa'o derive a motive power
in the depths of the sea, with force sufficient to give such tre-
mendous masses of ice such a velocity ? What is the temperature
of this under current ? Kodgers'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 the water of the under
cmTent, inasmuch as it comes from the south, and therefore from
warmer latitudes, is not so cold ; and if it be not so cold, its tem-
perature, before it comes out again, must be reduced to 28°, or
whatever be the average temperature of the outer but surface cm-
rent. Dr. Kane found the temperature of the open 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 chmates of the frigid zone without falling below 36° ? To
what, in the depths of the sea, can a warm cm-rent of large volume
impart its heat ? The temperatm-e of sea water from the tropics
in which ice is forming is invariably (§ 442) 28°. Does not the
<3ircumstance of De Haven's invariahly finding this to be the tem-
peratm-e beloAV the ice on which he drifted tend to confirm the
conjecture (§ 479) about the ice and the river water ?

484. This under polar current water, then, as it rises to the top,
jt comes to the and is brought to the surface by the agitation of the
surface. g^^ ^ j^^ arctic rogious, gives out its surplus heat
to wami the atmosphere there till the temperatm-e of this warm
imder 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 miti-
gate the climate there. Now is not this one of those modifications
of chmate which may be fairly traced back to the effect of the
saltness of the sea in gi^Hng energy to its circulation ? Moreover,
if there be a deep sea in the polar basin, which serves as a recep-

246 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

tacle for the -waters brought into it by this micler 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 Lieu-
tenant De Haven, in his instructions (§ 428), was directed to look
for it ; and why both he and Captain Penny, of one of the Enghsh
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 h^^othesis 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 mobihty and circulation of its waters.
Here, then, is an office which the sea performs in the economy of
the universe by virtue of its saltness, and w^hich it could not per-
form were its waters altogether fi'esh. 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, " YvTiy is the sea salt ?"

485. Sea Shells. — We find in sea water other matter (§ 48) be-
fnflueuce^fT^^^^"^ ^^^^^^ commou Salt. Lime is dissolved by the rains
curreiiti. 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 magni-
tude, have been constructed by the inhabitants of the deep. These
creatures are endowed with the power of secreting, apparently for
their own purposes only, solid matter, w^hich 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 preser^dng the purity of
the sea. The better to comprehend how such creatm-es may in-
fluence currents and climates, let us again suppose the ocean to be
perfectly at rest — that throughout, it is in a state of complete
equihbrium — 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 natui'e capable of disturbing that equi-
hbrium— and that all these fish, etc., have suspended their secre-
tions, in order that tliis 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.

THE SALTS OF THE SEA. 247

mollnsk or coralline, we will suppose, commences his secretions, and
abstracts from the sea water (§ 465) soHd matter for his cell. In
that act this animal has destroyed the equihbrium of the w^hole
ocean, for the specific gi'avity of that portion of water from w^hich
this sohd matter has been abstracted is altered. Having lost a
portion of its sohd contents, it has become specifically fighter than
it was before ; it must, therefore, give place to the pressure which
the heavier w^ater exerts to push it aside and to occupy its place,
and it must consequently travel about and mingle with the w^aters
of the other parts of the ocean until its proportion of solid matter
is retmned to it, and until it attahis the exact degree of specific
gravity due to sea water generally.

486. How much sohd matter does the whole host of marine

Solid matter secreted plants and auimals abstract from sea water daily?

by them. jg j^ ^ thousaud pouuds, or a thousand milhons of

tons ? No one can say. But, whatever be its weight, it is so

much of the power of gravity applied to ^ the 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 w^hole sea in motion, from the equator to

the poles, and from top to bottom. But we have yet to inquire

how far may cm-rents be due to the derangement of equihbrium

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 httle creatures abstract from

sea water sohd matter enough to build continents of. And, also,

we have to remember as to the extent to which equihbrium in the

sea is distm'bed by the salts which evaporation leaves behind. Thus,

w^hen we consider the salts of the sea m one point of view, w^e 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 preserve the harmonies

of the universe.

487. From another point of view, we see the sea-breeze and the
Dynamical force de- sea-shell, m performing their appointed offices, so
rived from. actiug as to givo risc to a reciprocating motion in

the waters ; and thus they impart to the ocean dynamical forces
also for its circulation. The sea-breeze plays upon the surface ;
it converts only fresh water into vapour, and leaves the solid mat-

248 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ter behind. The surface vv^ater thus becomes specifically heavier,
and sinks. On the other hand, the httle marine architect below,
as he works upon his coral edifice at the bottom, abstracts from
the water there a portion of its solid contents ; it therefore be-
comes specifically lighter, and up it goes, ascending to the top with
increased velocity, to take the place of the descending column,
Avhich, by the action of the winds, has been sent down loaded with
fresh food and materials for the busy little mason in the depths
below. Seeing, then, that the inhabitants of the sea, with their
powers of secretion, are competent to exercise at least so7ne degree
of influence in disturbing equilibrium, are not these creatures en-
titled to be regarded as agents which have their ofiices to perform
in the system of oceanic circulation, and do they not belong to its
physical geography? Their influences upon the economy of the
sea are like those outstanding quantities which the astronomer
finds in the periods of heavenly bodies. He calls them perturba-
tions ; for short, or even during considerable intervals, their efiects
may be inappreciable ; for they are pendulums that require ages for
a single vibration ; but unless there was a balance provided some-
where, they would, during the progress of time, accumulate their
small perturbations so as to produce disorder, and finally cause the
destruction of worlds. So, too, mth the salts of the sea, and
those little microscopic inhabitants of its waters. They take care
of its outstanding 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 ; for, 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. It may therefore be supposed that the arrangements in the
'Hieir physical ccouomy of nature are such as to require that the

reiatiuns. various kiuds 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 natm-e warrants throughout her
whole domain — we may conceive how the marine animals of
which we have been speaking may impress other featm-es upon
the physical relations of the sea by assisting also to regulate cK-
mates, and to adjust the temperature of certain latitudes. For in-

THE SALTS OF THE SEA. ' 249

stance, 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 been
taken from them in a state of vapoui*, 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 heayy
water, to flow off as an under current towards the polar or some
other regions of lighter water ; but these creatm'es take from it
a portion of these salts for their own purposes, and so make it
light enough to flow off 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 chmates ; neither could evaporation give dynamical
force to its circulation; its waters, ceasing to contract as their
temperature falls below SO"", would give but little impulse to its
currents, and impart no motion (§ 404) to its waters in the depths
below : thus its circidation 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 supposed salt and heavy and hot
water at 90°, there may be none such, as in a " Desolate Eegion."
This water then may go off 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 effects 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°. Notwithstanding this, after
traveUing below to certain latitudes it may 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 sm-face through the instrumentahty
of shell-fish, and various other tribes that dwell far down in the
depths of the ocean. Thus we perceive that these creatiu-es,

250 PHYSICAL GEOGRAPHY OF THE SEA, AOT) ITS METEOROLOGY.

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 wliich temper the winds, and modify, more or less, all
the marine chmates of the earth.

489. The makers of nice astronomical instruments, when they
The regulators of havo put the different parts of their machinery to-
^^^''^^- gether, 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 comjjensatioii ; 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 uni-
verse, order and regularity are maintained by a system of com-
pensations. 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 per-
fect. So, too, with the salts and shells of the sea in the ma-
chinery of the ocean; fi'om them are derived principles of com-
pensation the most perfect ; tlirough their agency the undue
effects of heat and cold, of storm and rain, in disturbing the equih-
brium and producing thereby currrents in the sea, are compensated,
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 process ; and if it
were not comijensated, the sea would finally become, as the Dead
Sea is, satm-ated with salt, and therefore unsuitable for the habita-
tion of many fish of the sea. The sea-shells and marine insects
affi)rd the required com^pensation. They are the conservators of

THE SALTS OF THE SEA. 251

the ocean. As the salts are emptied into the sea, these crea-
tures 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 dissolved by
the dews and rains, and w^ashed by the rivers away into the sea
again.

490. The question as to whence the salts of the sea were origi-
whcnce does the sea ually dorivcd, of courso has not escaped the atten-
derive its salts? i{qj^ of philosophcrs . I oucc tliought 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 com^se of the researches con-
nected with the "Wind and Current Charts," I have found evi-
dence, 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
Kature 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 the 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
conjectm-e arose that the great sea derived its salts from the same
som'ce and by the same process. But, and per contra, though
these sohd ingredients cannot be taken out of the sea by evapo-
ration, 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 sohd ingredients — is regulated. The insects of

252 PHYSICAL GEOaRAPHY OF THE SEA, AND ITS METEOROLOGY.

the sea cannot build their structures of this salt, for it ^vould dissolve
again, and as fast as they could separate it. But here the ever-
ready atmosphere comes into play, and assists the insects in regu-
lating the salts. It cannot 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 ofi, transfers it to the
clouds, and they deliver it back to the sea as fresh water, leaving
the salts it contained in a solid state behind. These are operations
that have been going on for ages ; proof that they are still going
on is continually before our eyes ; for the " hard water " of our
fountains, the marl-banks of the valleys, the salt-beds of the plains,
Albion's chalky cliflfe, and the coral islands of the sea, are monu-
ments 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. There is no proof, nor is there any reason for the belief,
Their antiquity, that the sca is gTowiug saltcT OT frcshcr. Hence
we infer that the operations of addition and extraction are re-
ciprocal and equal ; that the eflPect of rains and rivers in washing
down 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 de-
posited any of its fossil shells and infusorial remains 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 were such a time, it must have been when the rivers
were collecting and pom-ing in the salts which now make the brine
of the ocean. But while the palaeontological records of the earth,
on one hand, afford no evidence of any such fresh-water period, the
Mosaic account is far from being negative ^vith its testimony on the
other. According 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 mo\dng
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 won-
derful 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

THE SALTS OF THE SEA. 253

constitute in their myriads of multitudes one of the " wonders of the
deep."

492. It is the custom of Captain Foster, of the American ship
Insects of the sea— Grarrick, "who is one of my most patient of ob-
their abundance. gervcrs, to amuse himscK by making drawings in
his abstract log of the curious animalculse which, with the micro-
scope, he finds in the surface water alongside ; and though he has
been following the sea for many years, he never fails to express
his wonder and amazement at the immense numbers of li\'ing
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 abmidantly the waters even there bring forth.
'' January 28th, 1855. In examining animalculae in sea water, I
have," says he, " heretofore used surface water. This afternoon,
after pumping for some time from the stern pump seven feet below
the surface, I examined the water, and was sm-prised to find that
the fluid was literaUy alive with animated matter, embracing beau-
tiful varieties." Of some he says, "Numerous heads, pm-ple, red,
and variegated." There is wonderful meaning in that word abun-
dantly, 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 fmnished by Piazzi Smyth, the Astronomer Eoyal of
Edinbm-gh, dm-ing his voyage in 1856 on an astronomical expedi-
tion to TeneriSe. 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 ap-
pears that each one of these sea-nettles, as they are sometimes
called, had in his stomachs not less than five or six millions of
flinty shells, the materials for v/hich their builders had collected
from the silicious matter which the rains washed out from the
moimtains, and which the rivers bring down to the sea. The
medusae have the power of sucking in the sea water slowly, di'op 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 vrater,
they strain it, and collect the httle diatomes. Imagine, then, how
many drops of water in the sea, which, though loaded with diatomes,
never pass through the stomach of the medusae. Imagine how
many the whale must gulp down with every mouthful of medusa?.
Imagine hov/ deep and thickly the bottom of the sea must, during

254 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the process of ages, haye become covered with the flinty shells of
these httle creatm-es. And then recollect the command which v/as
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 most abimdantly even now the moving creature that hath life,
and doing it in obedience to that command.

493. In the waters of the Pacific Ocean, the calcareous matter
Ditto, calcareous in scoms to bo iu exccss, for the microscopic shells

the Pacific, silicious ,, n ji i n ji i ^ -t

in the Atlantic. 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 pabulum 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. So far the two records agree, and the evidence is clear
The records of the that the sca was Salt whou it received its command.

sea and of revelation -rxii re t i !• i -i -\- ,•

agiee. Do they anord any testimony as to its condition pre-

viously ? 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 hiUs. The water covered the earth. This is the
account of revelation ; and the account which Nature has written,
in her own peculiar characters, 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 liigh 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 bmied on the mountains
and scattered over the plains, we have as much reason to say that
the sea was salt when it covered or nearly covered the earth, as the
naturahst, 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,"

THE SALTS OF THE SEA. 255

Yy^hen " tlie waters under heaven were gathered together unto 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 geological column of her early processes, and there we
find the fossil shell and the remains of marine organisms to in-
form us that when the foundations of om- 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 creep-
ing 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 infuso-
rial deposits which astound the geologist with their magnitude
and extent, or those fossil remains of the sea which have astonished,
puzzled, and bewildered man ui all ages — whence, had not the sea
been salt when its metes and bomids 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 precisely what they were set about
when the dry land appeared, namely, preservmg the purity of the
ocean, and regulating it in the due performance of its great offices.
As fast as the rains dissolve the salts of the earth, and send them
down 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 sufficient
for the Christian philosopher to recollect that the salts of the sea,
like its waters and the granite of the hills, are composed of sub-
stances which when reduced to their simple state, are fomid 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 Avith oxygen gas. Iron, of
which there is merely a trace, is the only ingredient which, in its

256 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS STETEOROLOGY.

imcombined and simple state, is not gaseous or volatile. Now was
the feldspar of the granite originally formed in one heap, the 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 com-
posed 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 to-
gether in the original process of formation, and united in combina-
tion 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 om* present purpose. Some geologists suppose
that in the chalk period, when the ammonites, with their huge
chambered shells, lived in the sea, the carbonaceous material re-
quired 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
companion, the tiny nautilus, remains to tell us that even in that
remote period the proportion of salt in sea water was not unsuited
to its health, for it and the coral insect have lived through all the
changes that om- 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 ex-
tinct, hke 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. Did any one who maintains that the salts of the sea were
Cubic miles of sea Originally washed down into it by the rivers and the
sa't- rains ever take the trouble to compute the quantity

of solid matter that the sea holds in solution as salts ? Talnng the
average depth of the ocean at three miles, and its ^average saltness
at 3 J 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 of

THE SALTS OF THE SEA. 257

-square miles. These millions of cubic miles of crystal salt 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 by the salt it
dissolves. Here we have therefore displayed before us an economy
of si[)s.ce calculated to surprise even the learned author himself of
the " Plm-ahty of Worlds."

496. There has been another question raised which bears upon
Tb?saitness of water what has already been said concerning the offices
retards evaporatiou. -^yJiich, in the sublimc systcm of terrestrial arrange-
ments, have been assigned to the salts of the sea. On the 20th of
January, 1855, Professor Chapman, of the University College, To-
ronto, communicated to the Canadian Institute a paper on the
" Object of the salt condition of the sea," which, he maintains, is
^'mainly intended to regulate evaporation.'' To establish this
hy})othesis, he shows by a simple but carefully conducted set of
experiments that, the Salter the water, the slower the evaporation
fi'om it ; and that the evaporation which takes place in 24 hom^s
from water about as salt as the average of sea water is 0.54 per
cent, less in quantity than from fresh water. " This suggestion
tind these experiments give additional interest to om- 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 fi'esh. 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
emj)loyment to the corallines and insects of the 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 main 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 fi'om 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

s

258 PHYSICAL GEOGEAPHY OF THE SEA, AXD ITS METEOROLOGY.

prevented. But again, if the eyaporating surface were to grow
Salter and Salter, ^vlience would the winds derive vapour duly to
replenish the earth mth showers; for the Salter the surface, the
more scanty the evaporation. Here is compensation, again, the
most exquisite ; and we perceive how, hy reason of the salts of the
sea, di'ought and flood, if not prevented, may be, and probably are,
regulated and controlled ; for that compensation which assists to
regulate the amount of evaporation is sm^ely concerned 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 mnds with
moistm^e for the cloud and the rain, remain at its surface, and be-
come more niggardly in their supplies, and finally the winds would
howl 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-mnds 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 thnsty trade-'s^inds, and are carried down, because of their
weight, into the depths of the ocean ; and thus the mnds are
dieted with vapour in due and wholesome quantities." — Mauey's
SaiUngi Biredions, 7th ed., p. 862.

497. Since the offices which, in the operations of the physical
The harmonies of machinery of the earth, have been assigned to the
the ocean. ^^i^^ ^^ j^Y\Q sca, 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 to-
gether into one jolace, and pronounced his handiwork " good,"
some check or regulator had already been jirovided for the one as
well as the other — checks which should keep the sea up to its office,
preventing it from grovdng, in the process of ages, either larger or
smaller, fr-esher or Salter. As we go doTMi into the depths of the
sea, we find that we are just beginning to penetrate the chambers
of its hidden things, and to comj^rehend its wonders. The heart
of man was never rightly attuned to the music of the spheres until
he w^as permitted to stand mth 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 wiih. the harmonies of old Ocean when

THE SALTS OF THE SEA. 259

contemplated througli the microscope ; tlien every drop of water
in the sea is discovered to be in tune vith the hosts of heaven, for
each stands forth a peopled world.

498. Catching, as we contemplate the hosts of heaven through
The microscope and the tclcscope and the moving creatures of the sea
the telescope. througli the microscopo, the sphit 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 philosopher they are presented
through these instruments : '' one leads him to see a world in
every atom, the .other a system for eveiy star. One shows him
that this vast globe, with its mighty nations and multitudinous
inhabitants, is but a grain of sand in the immensity of space ; the
other, that every particle of clay that lies bmied in the depths of
the sea has been a living habitation, containing vdthin it the work-
shops of a busy population. One tells him of the insignificance of
the world we inhabit ; the other redeems it from that insignificance
by shoTN-ing in the leaves of the forest, in the flowers of the field,
and in every di'op of water in the sea, worlds as numberless as the
sands on its shores, all teeming -^ith life, and as radiant with glories
as the fiimament of heaven. One suggests that, beyond and above
all that is visible to man, there are fields of creation which sweep
immeasm'ably along, and carry to the remotest regions of space the
impress of the Almighty hand ; the other reminds us that, mthin
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
"VN'ithin the 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 vrorlds, filling and animating
them all mth 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 then- day the
sea was salt ; and then, when we take up the microscope again to
study the foraminiferes, the diatomes, and corallines, and examine
the structure of the most ancient inhabitants of the deep, comparing
their phvsiology with that of their kindred in the fossil state, we

s 2

200 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

are left to conjecture no longer, but are furnished ^Yitll evidence and
proof the mo3t convincing and complete that the sea is salt from a
physical necessity.

499. Thus beholding sea-shells and animalculae, may we not
Sea-shells and aiii- now ccasc to reo'ard them as beings which have little

iiialculaj in a new ,. jt* • i • • n ^ • p

light. or notnnig to do m mamtammg the harmonies oi

creation ? On the contrary, do we not see in them the principles
of the most admirable compensation in the system of oceanic circu-
lation ? 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. Sm^ely an hypo-
thesis which, being followed out, suggests so much design, such
perfect order and arrangement, and so many beauties for contempla-
tion and admiration as does this, which, for want of a better I have
ventured to ofi'er 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 altogether profitless.

CHAPTEE XI.

§ 501-526. THE CLOUD REGION, THE EQUATORIAL CLOUD-
RING, AND SEA FOGS.

501. To simplify the discussion of these phenomena, let us con-
cioud region-high- sidcr fogs at sea to be in character like clouds m the
est in the calm belts, g]^^^ g^ treating them, and confining om- attention
to them as they appear to the mariner, we discover that the cloud ^
region in the main is highest in the trade-wdnd and calm belts,
lowest in extra-tropical regions.

502. At sea, beyond "the offings," fogs are not often seen be-

Fogiess regions, twccu the parallels of 30° N. and S. Sea fogs,

therefore, may be considered a rare phenomenon over one half of

the surface of the globe. These fogless regions, though certain

parts of them are not unfrequently visited by tempests, tornadoes,

THE CLOUD REGIOX, ETC. 2C1

and linrricanes, are nevertheless mucli 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. Taking the Atlantic Ocean, north and south, as an index
The most stormy of what talvcs pkcc ou othcr watcrs, the abstract logs
latitudes. Qf ^}^Q 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 j^ol a r side ;
and that for every fog on the equatorial they encounter 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 stoimy latitudes are between the parallels
of 55° and 60°, the most foggy between 50° and 55°.

504. How suggestively do these two groups of phenomena re-
influenccsoftbeGuifHiind US, ou tho ouc hand, of the Gulf Stream and
beariJJcuiSsS" ^^® ice-bearing currents of the north, and, on tho
the south. other, of Cape Horn and the antarctic icebergs which
cluster off the Falkland Islands !*

505. Though sea fogs mthin 20° on either side of the equator
Sea fogs rare within arc SO rarely seen, yet within this distance, on the
?ed fogl^ '''^''''^"'~ north side, red fogs of "sea-dust" (§322) are not
unfrequently encountered by navigators. These can scarcely be
considered as coming within the category 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 so often observable morning and
evening in the settling smoke from neighbouring chimneys. The
fogs which at early dawni are discovered hovering over om- cities or

* Captain Chadwick reports, by letter of 30th April, 1860, an iceberg, seen first by
him 14th September, 1859, in S. lat. 52^ 25', long. 51^ 8' W. : next, on October
10th, in 47° 15' S., 59^ 30' W., by tho 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." Whetlier this were the
same "berg" or not, it shows that icebergs are not imknown to the north of the
Falkland Islands, as, indeed, the aqueous isotherm of 60'^, Plate TV., uidicates
by its sharp curve about those islands.

262 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

skirting the base of the hills near by are of the same 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 con-
ditions favom^able for radiation on occasions when the air in which
they are floating happens to have a high devf-point. Thus each one
of these innumerable 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
imder our classification of sea fogs.

506. On the polar side of 40^ at sea the weather is for the most
Cloudless retrions and part cloudy. Ou tlic equatorial side, and especially
height of clouds at sea. ^^il-l^jj^ the"^ tradc-Aviud 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;?(X?ie 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. Observations here are to be made rather under the direction
of the commander of a fleet or squadi'on than of a single ship, and
it is hoped that some of the distinguished admirals and brave old
commodores who cruise about the vv'orld, with veiling 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. Commodore Wiillerstorf, of the Austrian frigate No vara,
Slvavct-"^ kin"fo*^ made an interesting series of observations upon the
determining. height and vclocity of the waves dming his cruise
in that vessel upon his last scientific mission. These no doubt
will be published with the other important results of that admira-
hlj conducted expedition. The most simple plan for determining
the velocity of waves, and it may be homdy practised on board of
every vessel, is the plan which is followed by Captain Grinn, 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 tm-ns the glass, or notes his watch,
and marks the time it takes the wave to reach the ship. The usual

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

THE CLOUD REaiON, ETC. 263

yelocity of the waves in the Atlantic is 22-3 miles an hour, oiBf
Cape Horn 26-8.*

508. It would aiford a pleasant and agreeable diversion for a
Determining tiie sQuadrou of luen-of-war, as they pursue their voyae^e

height 'Of clouds at f- . ,-, -, ■ f • i i n • n • ^

sea. at sea, to amuse themselves and instruct then" triends

at home with observations upon all such phenomena. Those who
are willing to undertake the clouds will have no difficulty in devis-
ing a plan both for the upper and the lower strata.

509. Over the land the cloud region is thought to vary from
Cloud region at sea thrcc to fivc milcs iu height ; there the height of
douwVincfined plane, clouds is Imow to bc vcry 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 fi^om the equa-
torial cloud-ring as a sort of ridge-pole. In the balloon ascents
which have taken place h'om the Kew Observatory in England,
it has been ascertained that there the cloud region is from 2000 to
6500 feet high, with a thickness varying 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. AVe 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 Teneriffe, at the
height of 12,200 feet, dming the months of August and September,
1856.t 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

* From Captain Ginns Abstract Log: —

" Saturday, September lltli, 1858, doubling: Cape Horn, The long regular swell
during this part of the day afforded me another opportunity of trying the velocity
■of the waves. This I did by paying out the log-line enough to be equal to 13
knots with tlie 14-second glass ; then by watching the chip— to which I had fixed
ii 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 tliis 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 considerably
more, namely, 26 to 28 miles an hour. Tims the crest of a wave would pass, while
the ll-second glass ran out, from the ])lace wliere the log-chip was towing astern
(13 knots) to just ahead of the ship. The length of the sliip is equal to about 6J
knots : the ship's speed at the time was 8 knots; thus, 134-GJ-t-8 = 27|-. 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 ? Has the soundings anything to
<io with it ?"

t Teneriffe. An Astronomer's Experiment. London, 1858.

264 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS I\IETEOROLOGY.

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 at 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 overhead.
Farther to the north, in the Atlantic, however, as in the fog region
about the meeting of the cool and warm currents near the Grand
Banks, the look-out at the masthead often finds himself above the fog
or cloud in which the lower parts of the ship are enveloped. Going
stiU farther towards the north and reaching the ice, the cloud region
would again, for obvious reasons, mount up until you reached the
open sea there, when again it w^ould touch the earth with its smoke.

510. In the harbour of Callao, in Peru, which is filled Avith the
Fogs in the harbour cool watcrs of Humboldt's currcut, I have seen the^
of Callao. i^g^y 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 skimming 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 w^ith 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 fairy scene. However, there are influences exerted in
the formation of clouds and fogs over and near the land w^hicli
appear not to be felt at sea.

511. In the extra-tropical north, the cloud region is high over
The cloudy latitudes, 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 calm 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-

THE CLOUD KEGION, ETC. 265

drenclied witli rain, as he sails througli these latitudes, he is dis-
pirited imder the influences of the gloomy and mui'ky weather
which prevades 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. Such are the quantities of vapom- rising up from the en-
why there should be orirdlmo^ occau about thosc austral regions, that it

le&5 atinospheie in P j_i n n j_i ^ l'

the southern than in Jvceps permanently expelled thence a large portion
the northern hemi- ^^ ^j^^ atmospherc. The spccific 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 dra\\ai from the puny contrivances of
human device is often a feeble resort, but nevertheless we may^
m 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 vapom^ begins to form in the tea-kettle, it
expels au' thence, and itself occupies the space which the air occu-
pied. If still more heat be applied, as to the boiler of a steam-
engine, the au' will be entkely expelled, and we have nothing but
steam above the water m the boiler. Now at the south, over this,
gi'eat 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 vapom' which has proportionally precisely the same
tendency that the vapour in the tea-kettle has to drive off the ah^
above and occupy thei space it held. Nor is this all. This 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". Tliis unequal distribution of atmosphere between the two
halves of the globe is imperfectly represented in harometric profile
on Plate I. (§ 215) — the shading aroimd the periphery of the circle
being intended to represent the relative height, and the scales
standing up in it, the barometric column.

513. This part of the southern ocean where the barometer
Influence of antarctic sliows diminished prossm^c is frequented by icebergs,
ihe^aif fim^aSstniT ^^uy of them vcry large and high, and some of
regions. them scudiug 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

266 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

eye from aloft look down upon the scene, the upper side of the
cloud stratum would present somewhat the appearance of an immense
caldron, boilmg, and bubbling, and intumescing in the upper air.
These huge bergs condense the vapoiu", and the liberated heat causes
the an above them to swell out, and to stand like so many curiously-
shaped fimgi above the general cloud level. And thus, where the
icebergs are thick, the clouds are formed low dovai. Icebergs, like
islands, facihtate the formation of clouds and promote precipitation.
514. Tm-n we now to the equatorial cloud-ring. Seafaring
The horse latitudes peoplo havo, as if by common consent, divided the
—the doldrums. occan off iiito icgions, and characterized them ac-
cording 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 hght airs (§ 210)
which border the polar edge of the north-east trades. They were
so called from the cncumstance that vessels formerly bound from
New England to the West Indies, mth a deck-load of horses,
were often so delayed in this calm belt of Cancer, that, for the want
of water for then- animals, they Avere compelled to thi^ow a portion
of them overboard. The " equatorial doldrmns " is another of
these calm places (§ 212). Besides being a region of calms and
baffling ^Aonds, 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 Em-ope for Austraha have to cross it.
They are often baffled m it for two or tln'ee weeks ; then the
cliildren and the passengers who are of deHcate health suffer most.
It is a frightful graveyard on the wayside to that golden land. A
vessel bound into the southern hemisphere from Em'ope or x\merica,
after clearing the region of variable wids 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 failing 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, measm'ed
by the barometer, amounts to about one tenth (0.1) of an inch,
and it occm's daily and everj^vhere between the tropics : the maxi-
mum about lOh. 30m. a.m., the minimum between 4h. and 5h. p.m.,
with a second maximum and minimum about 10 p.m. and 5 a.m.*

* See paper on Meteorological Observations in India, by Colonel Sykes, Philo-
sopliical Transactions for 1850, part ii., page 297.

THE CLOUD REGION, ETC. 267

The cliurnal variation of the needle (§ 344) changes also with the
tiuming of ihese invisible tides. Continmng his coni'se towards the
equinoctial line, and entering the region of equatorial calms and
rams, 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. I find in the journal of the late Commodore Ai'thur Sin-
A frigate under the clair, kept ou board the United States frigate Con-
cioud-iing. gross dming a cruise to South America in 1817-18,

a pictm-e of the weather mider this doud-ring that is singularly
graphic and striking. He encountered it m the month of Janu-
ary, 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 fcAV hours after a thunder-
storm, diu:ing which time torrents of rain fall, when the air
becomes a little refreshed ; but a hot, glowmg smi soon heats it
again, and but for yom^ a^wngs, and the little air put in circu-
lation 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. 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 shipvTcck, I never spent
twelve more disagreeable days in the professional 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 romid to the south-south-east,
bringing with it a clear sky and most heavenly temperature, reno-
vating and refreshing beyond description. Nothing was now to be
seen but cheerful countenances, exchanged as by enchantment from
that sleepy sluggishness which had borne us all down for the last
two weeks."

516. One need not go to sea to perceive the grand work which
subjocts ^hich at sea the clouds perfomi in collecting moisture from the
tor contemplation, crystal vaults of tlio sky, in sprinlding 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, and I do not propose to con-

268 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

sicler it now. But the sailor at sea observes phenomena and wit-
nesses operations in the terrestrial economy which telL him that,
in the beautiful and exquisite adjustments of the grand macliinery
of the atmosphere, the clouds have other important offices to per-
form 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 philo-
sophical marmer, 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
mth 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 in-
tense 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 places
which stand in need of like offices. Familiar with clouds and
sunshine, the 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 per-
forms many important offices ; he regards it as a great moderator
of heat and cold — as a " compensation " in the atmospherical
mechanism which makes the performance perfect. Marvellous are
the offices and wonderful is the constitution of the atmosphere.
Indeed, I Imow 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 afforded by the atmosphere and
its offices. Of all parts of the physical machinery, of all the con-
trivances in the mechanism of the universe, the atmosphere, with
its offices and its adaptations, appears to me to be the most Avon-
derful, sublime, and beautiful. In its construction, the grandeur
of knowledge is displayed. 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 wis-
dom be foimd, and where is the place of understanding? The-

THE CLOUD REGION, ETC. 269

deptli 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. T\Tience, then, cometh
-svisdom, and where is the place of understanding ? Destruction
and Death say, we have heard the fame thereof ^ith om^ ears.
God miderstandeth 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 maJce the weight for the icinds ; and he
weigheth the waters by measm^e. When he made a decree for the
rain, and a way for the hghtning of the thmider, then did he see it
and declare it; he j)repared it, yea, and searched it out."* AVhen
the pimip-maker came to ask Galileo to explain how it was that
his pump would not lift water higher than thirty-two feet, the philo-
sopher thought, but was afraid to say, it was o^ving to " the weight
of the ^inds ;" and though the fact that the ah' has weight is here
so distinctly announced, philosophers never recognized the fact
imtil mthin comparatively a recent jjeriod, and then it was pro-
claimed by them as a great discovery. Nevertheless, the fact was
set forth as distinctly in the book of nature as it is in the book of
revelation ; for the infant, in availing itself of atmospherical pressure
to di'aw mdk from its mother's breast, unconsciously proclaimed it.

517. The barometert stands lower under this cloud-ring than
The barometer nn- ou either sido of it (§ 362). After havmg crossed
tier the ciuu<i-ring. j|.^ ^q attentive navigator may perceive how this
belt of clouds, by screening the parallels over wliich he may have
found it to hang from the sun's rays, not only promotes the pre-
cipitation 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 travelhng 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 cu'cida-
tion of the world, and vigour to its vegetation.

518. Having travelled with the calm belt to the north or south,
Its motions. the cloud-riug leaves a clear sky about the equator ;

the rays of the tonid sun then pour do^Mi upon the sohd crust of
the earth there, and raise its temperature to a scorching heat. The

* Job, chap, xxviii.

t Observations now show that the thermometer stands higliest under the cloud-
ring. Indeed, the indications are tliat it coincides with the thermal equator.

270 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

atmosphere dances (§ 356), and the air is seen trembling in ascend-
ing and descending cohmms, with busy eagerness to conduct the
heat off and dehver it to the regions aloft, where it is required to
give dynamical force to the air in its general channels of circula-
tion. The dry season continues ; the sun is vertical ; and finally
the earth becomes parched and dry ; the heat accmnulates 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 smi 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 smface of the clouds.

519. Eadiation from land and sea below the cloud-belt is thus
Meteorological pro- 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
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 the clouds
before it can commence the process of cooling by radiation. In
the mean time, also, the vapours which the trade-^dnds bring from
the north and the south, expanding and groTOig cooler as they
ascend, are being condensed on the loAver side of the cloud stra-
tum, and their latent heat is set free, to check precipitation and
prevent a flood. AVhile 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 doAvn mthout
intermission. Every day, and all day long, they play mth cease-
less 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 off 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, imtil 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 sufiicient to enable us to
perceive that exquisite indeed are the arrangements which Nature

THE CLOUD REGION, ETC. 271

has proyided for supi^lying tliis calm belt vdth 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
com'se back into its channels of healthful chculation. 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 dm^ing the dry season, and which cannot now
escape by radiation.

520. In the process of condensation, these rain-drops, on the
snow-iine mounts otlicr liaud, liavc sct free a vast quantity of latent
equSJiiarcaim belt, licat, which has bccu gathered up with the vapour
from the sea by the trade- winds and brought hither. The caloric
thus liberated is taken by the air and carried up aloft still farther,
to keep, at the proper distance from the earth, the line of perpetual
congelation. Were it possible to trace a thermal curve in the
upper regions of the air to represent this line, we should no doubt
find it mounting sometimes 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 rmg from the equator,
north or south, is regulated according to the seasons. If we
imagine the atmospherical 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, winch should represent the line
of perpetual congelation in the air, would be always found to stride
tliis equator; and it may be supposed that a thermometer, kept
sliding on the surface of the earth so as always to be in the midcQe
of this rain-belt, would show very nearly the same temperatm-e all
the year roimd ; and so, too, would a barometer the same pressure,
though the height of the atmosphere over this calm belt would, m
consequence of so much heat and expansion, be very much greater
than it is over the trade-winds or tropical cahns.

521. Keturning and taking up the train of contemplation as to
Offices of the cioixd- tlio oflfice v/liicli tliis 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

272 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

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. Thus this ring, or band, or belt of clouds is stretched
It acts as a regulator, aromid OUT plauct to rcgulatc tlic quantity of pre-
cipitation in the rain-belt beneath it ; to preserve the due quan-
timi 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 moistm'e. Like the balance-wheel of
an artificial machine, this cloud-ring affords the gTand atmospherical
macliine the most exquisitely-arranged seIf-com])ensatwn. If the
sun fail in his supply of heat to this region, more of its vapom's 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-surface
CIS may be requisite is then resolved into invisible vapour — for of
in-vdsible vapom- are made the vessels wherein the sm-plus heat of the
sim is stored aw^ay 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. Evaporation under this cloud-ring is suspended almost
T]ted'in''the^p?o."^^" entirely. We know that the trade- wmds encircle the
j^^ses of condensa- earth ; that they blow perpetually ; that they come
the ci.;ud-ring, true froui the uorth and the south, and meet each other
^vinds?^ ^^^ "^^^'' near the equator ; therefore we infer that this line of
meeting extends around the world. By the rainy seasons of the
torrid zone, except where it may be broken by the continents, w^e
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 wliich it rises. As the air,
with its vapom's, rises up m this calm belt and ascends, these vapours
are condensed into clouds, and this condensation is followed by a
-turgid intumescence, w^hich causes the clouds to overflow the calm
belt, as it w^ere, both to the north and the south. The air floTNTUg
oft' in the same dii'ection assumes the character of T^inds that form

THE CLOUD REGION, ETC. 273

the upper currents that are counter (Plate I.) to the trade-^inds.
These currents carry the clouds still farther to the north and south,
and thus make the cloud-rmg broader. At least we mfer such to
be the case, for the rains are foimd 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. Were this cloud-ring luminous, and could it be seen by an
Imagined appear- obscrver from ouc of the planets, it would present to
Hn*^rf,o^.[*dlsunt'^' ^^^ ^^ appcarauco not unlike the rings of Saturn
obJ^rver. do to US. Sucli an obscrver would remark that this
cloud-ring of the earth has a motion contrary 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 rise 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 therefore appear to require a longer
time to complete a revolution. But, unlike the rings of Saturn
through the telescope, the outer sm-face, or the upper side to us, of
this cloud-ring would appear exceedingly jagged, rough, and uneven.

525. The rays of the sun, playing upon this peak and then upon
Thunder. that of the uppcr 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
hberated 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 -
sm^face in a perpetual state of agitation, upheaval, and depression.
Imagine in such a cloud-stratum an electrical discharge 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 dis-
charged 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 upper surface is often hke Alpine regions, wliich echo
back and roll along with rumbling noise the mutterings of the distant
thunder.

274 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

526. It is by trains of reasoning like tliis that we are conti-
Excecding interest nually reminded of the interest wliich attaches to
research at fei!''^'^^ the observations which the mariner is called on to
make. There is no expression uttered by nature wliich is un-
worthy of our most attentive consideration — for no physical fact
is too bald for study — and marmers, 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 fiir-
nishino* facts which will throw much lio-ht on the featm-es and
character of the clouds in different latitudes and seasons. Physical
facts are the language of Natm-e, and every expression uttered by
her is worthy of our most attentive consideration, for it is the voice

of AViSDOM.

CHAPTEE XII.

§ 531-555. THE GEOLOGICAL AGENCY OF THE WINDS.

531. Properly to appreciate the various offices which the winds
The sea and air re- and tlic wavcs pcrform, we must regard nature as
the s!iim machine, a wholc, for all the departments thereof are m-
timately connected. If we attempt to study in one of them, we
often find om'selves tracing clews which insensibly lead us off mto
others, and, before we are aware, we discover ov;rselves exploring
the chambers of some other department. 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 astro-
nomer 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 principles of optics — until he has con-
sulted 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 liimself, in his researches, alongside of the navigator, the
geologist, and the meteorologist, with a host of other good fellows,

THE GEOLOaiCAL AGENCY OF THE WINDS. 275

each one hokling 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 espe-
cially for him. And thus, in imdertaking 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 in considering marine fossils, changes of ch-
mates, the effects of deserts upon the winds, or the influence of moun-
tains upon rains, or some of the many phenomena which the
inland basins of the earth — those immense indentations on its sur-
face that have no sea-drainage — present for contemplation and study.

532. Among the most interesting of these last is that of the
The level of the Dead Sca. Lieutenant Lynch, of the United States
Dead Sea. Navy, has run a level from that sea to the Mediter-
ranean, and finds the former to be about one thousand three hun-
dred feet below the general sea-level of the earth. In seeking to
account for this great difference of water-level, the geologist ex-
amines the neighbom^ing region, and calls to his aid the forces of
elevation and depression which are supposed to have resided in the
neighbom'hood ; he then points to them as the agents which did the
work. Truly they are mighty agents, and they have diversified
the sm-face 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 in-
land basins, as far removed as the other hemisphere ? 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 which my investigations have suggested. It has its seat
in the sea, and therefore I propomid it as one which, in accounting
for the formation of this or that inland basin, is worthy, at least, of
consideration.

533. Is there any evidence that the annual amount of precipita-
An ancient river tiou upoxL the watcr-shcd 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 esta-
blish the fact that the Dead Sea at a former period did send a

T 2

276 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 vapour and carry away again ; the river carried
off the excess to the ocean whence it came (§ 267).

534. In the basin of the Dead Sea, in the basin of the Caspian,,
Precipitation and of the Sca of Aral, and in the other inland basins of
Dead Sea valley. Asia, WO 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 observation does not show, nor history teU 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 difiicult to realize
the existence of subterranean channels between them and the great
ocean. Were there such 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. It may be that the question suggested by my researches
Whence come its lias uo bearing upon the Dead Sea ; that local ele-
^^*°^- vations 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 circu-
lation pass over the Dead Sea, have alone been unchanged?
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 o-wn hand upon the tablets of the rock, aU indicate
plainly enough that not only the Dead Sea, but the Caspian also,,
had upon them, in former 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 depres-
sion 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 vaUey, and which the St. Law-

THE GEOLOGICAL AGENCY OF THE WINDS. 277

rence carries off to the Atlantic Ocean, is taken up by tlie south-
east trade-^^iQ(is of the Pacific Ocean. Suppose this to be the
€ase, and that the winds which bring this vapour arrive with it in
the lake countr}' at a mean dew-point of 50". Let us also admit
the south-west ^Ninds to be the rain mnds for the lakes generally,
iis well as for the Mississippi Valley ; they are also, speakmg gene-
rally, the rain ^^inds of Europe, and, I have no doubt, of extra-
tropical Asia also.

536. Now suppose a certain mountain range, himdreds of miles
The influence of f 0 ^hc south-wcst of the lakcs, but across the path of
luuuntain ranges. ^j^ggg ^yijicls, mth their dcw-pouit at 50"", were to be
,suddenly elevated, and its crest pushed into the regions of snow,
having a mean temperature at its siunmit of 30^ Fahrenheit.
The winds, in passing that range, would be subjected to a mean
dew-point of 30^ ; and, not meeting (§ 297) with any more evapo-
rating surface between such range and the lakes, they would have
no longer any moisture to deposit at the supposed lake tempera-
•tm-e 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 "^inds 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 dr^Tiess of the atmosj)here and the want of rain, and
the lakes would sink to that level at which, as in the case of the
Caspian Sea, the precipitation and evaporation would finally become
equal.

537. There is a self-regiilating principle that would bring about
itow the level of Cas- this equality ; for as the water in the lakes becomes
plans is reduced. lowcr, 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 evapo-
rated from the sea is exactly equal to the whole amount pom-ed
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 ;
^nd finally, too, the great American lakes, in the process of ages,

* The quantity of dew in England is about five inches during a year. — Glaisher.

278 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

would become first brackish, and then briny. Now suppose the
water lasins which hold the lakes to be over a thousand fathoms,
(six thousand feet) deep. We know they are not more than four
hundred and twenty feet deep; but suppose them to be six thou-
sand feet deep. The process of evaporation, after the St. Law-
rence has gone dry, might go on until one or two thousand feet
or more were lost from the sm^face, 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. Coralhnes are
at work 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 GuJ.f Stream ; and that, in like manner, they were to connect
Cuba mth Yucatan by damming up the Yucatan Pass, so that the
waters of the Atlantic should cease to flow into the Gulf of Mexico.
"What shoidd 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 exj)osed to the air would be just sufficient to retm^n
to the atmosphere, as vapour, the amount of water discharged by
the rivers — the Mississippi and others, into the Gulf. As the
waters were lowered, the extent of evaporating surface would
grow less and less, until Natm^e should establish the proper ratio
between the abihty of the air to take up and the capacity of the
clouds to let doTSTi. 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. There is still another process, besides the one already
The formation of in- alludcd to, bv which the draiuaejo of these inland

land basins— a tlnrd ,. '/, n.i c ,^ • i i

p^oce^s. basms may, through the agency oi the \Mnas, nave

been cut off by the gi'eat 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. Now suppose that a conti-
nent should rise up in that part of the ocean, wherever it may be^
that supphes the clouds ^^ith the vapour that makes the rain for

THE GEOLOGICAL AGENOx OF THE '\YINDS. 279

the liycTrographic basin of tlie great American lakes. What would
be the result? Wtij, smely, fewer clouds and less rain, which
would involve a change of 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 smi ;
and consequently, too, there would follow a low stage for water-
com'ses, and a lowering of the lake-level vfould ensue.

539. So far, I have instanced these cases only hypothetically ;
Examples. but, both ui regard to the hydrographical basms of
the Mexican Grulf and American lakes, I have confined myself
strictly to analogies. Mountain ranges have been upheaved across
the com'se of the ^inds, 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 moistm^e brought by them
woidd produce. In the case of the Salt Lake of Utah, we have
an example of drainage that has been cut off, and an illustration
of the j)roce3S by which Nature equalizes the evaporation and pre-
cipitation. To do this, in this instance, she is saltmg 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. Supposing there
was such a time and. such a vfater-com^se, the water returned
through it to the ocean v/as the amount by which the precij^ita-
tion 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 agents
which used to bring 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 moistm^e 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 Gridf 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 south-
ward and westward of our northern lake basin ; that is the quar-
ter (§ 357) whence the rain-winds have been supposed to come.
May not the same cause which lessened the precipitation or in-

280 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

creased the eyaporation in the Salt Lake water-shed, have done the
same for the water-shed of the great 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 vdnds which
feed the Salt Lake valley with precipitation, 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 he elevated across the track of the
winds which supply the lake country with rains ; it is easy to per-
ceive how the whole country to the leeward of such range, and
now watered by the vapour which such winds bring, would be con-
verted into a ramless 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
e\ident, 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 sub-
sidence 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 ch'cuits,"
which have been interposed in some other quarter of the world,
which obstructions may prevent the winds from taking up or from
bearing off their wonted supphes of moisture for the region whose
water-level has been lowered.

540. Having therefore, I hope, made clear the meaning of the
SoutrAmerkim ^^^ q^estion proposcd, by showing the manner in which
continent upon the 'winds mav bccomo important e'eolooical accents,

climate of the Dead II.- I'll xi i • X-

Sea. and navmg explamed how the uphea\ang oi a

mountain range in one part of the world may, through the -vviads,
bear upon the physical geography of the sea, afiect 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 elevation of the South American continent, and
the upheaval of its mountains, to have had any effect upon the

THE GEOLOGICAL AGENCY OF THE WINDS. 281

water-level of those seas ? There are indications (§ 535) that they
all once had a higher water-level than they now have, and that
formerly the amount 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 be diminished (§ 538)
either by the substitution of dry land for water-surface in those
parts of the ocean wliich used to supply that vapour ; or the quan-
tity of vapom' deposited in the hydrograpliical basins of 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 mth vapour and these basins.
A chain of evidence which it would be difficult to set aside is
cantained in the chapters lY., YI., and YII., going to show that the
vapom- which supplies the extra-tropical regions of the north vdih
rains comes, in all probability, from the trade-wind regions of the
southern hemisphere.

541. Now if it be true that the trade- winds from that part of
The path of the S.E. the world take up there, water which is to be
iiuo'^the northern rained in the extra-tropical north, the path ascribed
hemisphere. to the south-cast tradcs of Africa and America, after

they descend and become the prevailing 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 blown 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 hemi-
sphere, we should be able to identify the track of these Andean
winds by the droppings of the clouds ; for the path of the Tivdnds
which depend for their moisture upon such sources of supply as
the dry land of Central South America and Africa cannot over-
shadow a country that is watered well. It is a remarkable fact
that the countries in the extra-tropical regions of the north that
are situated to the north-east of the south-east trade- winds of South
Africa and America — that these countries, over which theory

282 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 YII.),
would, after passing the tropic of Cancer, mark upon the sm-face
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 supphed with rains. Now the hyetographic
map of Em-ope, in Johnston's beautiful Fhysical Atlas, places the
region of least precipitation between these two lines (Plate YIL).

542. It would seem that Nature, as if to reclaim this " lee " land
Relays for supplying fpom the dcscrt, had stationed by the wayside of

them with vapour by , , . -. . /••it j r\

the way. thcso '^^ncis a succcssion 01 mland seas to serve them

as relays for supplying them with moisture. There is the Mediter-
ranean, 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 designed, in the grand system of aqueous arrange-
ments, to supply with fresh vapour winds that had already 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 remams of marine animals.
^Vhen they and their continent were submerged — admitting that
Em'ope in general outline was then as it now is — it cannot be
supposed, if the chculation 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 dis-
tributed, it may be supposed, among the countries situated along
the route (Plate YII.) ascribed to them.

543. If ever the Caspian Sea exposed a larger surface for evapo-
Adjustments in this ratiou than it now does — and no doubt it did; if
piaos. 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 condi-
tions there. And admittmg the vapour-sprmgs 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 moun-
tains in certain parts of America, Africa, or Spain, across the route

THE GEOLOGICAL AGENCY OF THE WINDS. 283

of the winds wliich brought the rain for the Caspian water-shed,
might have been sufficient to rob them of the moistm^e which they
were wont to carry away and precipitate upon this gTeat inland
basin. See how the Andes have made Atacama a desert, and of
Western Peru a rainless country : these regions have been made
rainless sunply by the rising up of a mountain range between
them and the vapour-springs in the ocean which feed -^ith moisture
the A^dnds that blow over those now rainless regions.

544. That part of Asia, then, which is mider the lee of southern
peTtl'zonlVnhS'"' *^^^6-Tsd^^^ AfHca, hes to the north of the tropic
hemisphere that are of Caucor, aud botweon two liuos, the ono passing
in the trade-wind re- through Capo Palmas and Medina, the other through
Srir^Voun'triS Aden and Delhi. Bebg extended to the equator,
they will include that part of it which is crossed by the conti-
nental south-east trade-Tsinds of Africa after they have traversed
the greatest extent of land sm^face (Plate YII.). The range which
lies between the two lines which represent the course of the Ameri-
can winds mth then* vapours, and the two lines which represent
the com'se of the African winds with theu' vapom's, is the range
which is under the lee of ^N-inds that have, for the most part, tra-
versed water smiace or the ocean in then' cncuit as south-east trade-
wdnds. But a bare inspection of Plate YII. wiU 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 Avater ; and the Trade-Aviud Chart * shows that it is precisely
those ANinds which, in the summer and faU, are converted into
south-west monsoons for supplying the whole extent of Guinea
with^rains to make rivers of. Those winds, therefore, it would
jseem, leave much of their moisture beliind them, and pass along
to their channels in the grand system of cnculation, for the most
part, as dry A\inds. 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 as sharply defined in
natm^e as the hues suggested, or as Plate YII. would represent them
to be.

545. The whole region of the extra-tropical Old World that is
Their situation, and included AATitliin the ran^-es marked is the region

trie r[in"'e ot dry ^ o o

T%mds. ° which has most land to windward of it in the southern

hemisphere. Kow it is a curious coincidence, at least, that all

* Series of Maiirv's Wind and Current Charts.

284 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. '

the great extra-troj^ical deserts of the earth, with those regions m
Europe and Asia which have the least amount of precipitation
upon them, should he 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 pm'pose in the terrestrial economy. Let us see,
therefore, if we can discover any other marks of that design — any
of the purposes to be subserved by such an arrangement — and
trace any connection between that arrangement and the supposi-
tion which I maintain as to the place where the w^inds that blow
over these regions derive their vapours. It will be remarked at
once that all the iuland seas of Asia, and all those of Europe ex-
-cept the semi-fresh-water gulfs of the north, are witlnn 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
imder this lee, and in the very dh'ection in w^hich theory makes
this breadth of thirsty winds to prevail ? Clearly and obviously,
one of the purposes iu 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 vapomdess because their route, in the general system of ck-
culation, 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 supphes have since been taken away
by the cool tops of mountain ranges over which these ^^dnds have
had to pass.

546. In the Mediterranean, the evaporation is greater than the
The Mediterranean prccipitatiou. Upou the Eed Sea there never falls
^""^'^ ^'- a drop of rain ; it is all evaporation. Are we not,

therefore, entitled to regard the Eed Sea as a make-weight, thrown
in to regulate the proportion of cloud and sunshine, and to dis-
pense rain to certain parts of the earth in due season and in pro-
per quantities ? Have we not, in these two facts, evidence conclu-
sive that the winds which blow over these two seas come, for the
most part, from a dry countiy — from regions which contain few
or no pools to furnish supphes of vapom' ?

THE GEOLOGICAL AGENCY OF THE AVINDS. 285

547. Indeed, so scantily supplied with vapour are the winds
Heavy evaporation, which pass lu the general channels of circulation

over the water-shed and sea-basin of the Mediterranean, that they
take up there more water as vapour than they deposit as rain. But,,
thi'owing out of the question what is taken up from the suiface 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 dis-
charge themselves into the Mediterranean ; but so thirsty are the
winds which blow across the bosom of that sea, that they 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 difierence,
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 great inland basin of Asia, which contains the Sea of
The winds that give Aral and the Caspian, is situated on the route which
rains to Siberian ^]^g Jiypothcsis rcquires thcso tliirsty winds from
the steppes of Asia, soutli-oast 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
knowledge extends, the level of each of these two seas is as per-
manent 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 permanently to lay down their load of moisture, be
it gTeat or small, until they cross the Oural Mountains. On the
steppes of Issam, after they have suppHed the Amazon and the
other great equatorial rivers of the south, we find them first be-

* V('de article "Pliysicul Geography," Encyclopaedia Britannica.

286 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY

ginning to lay clown more moisture tlian 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 m these almost hyperborean river-basins do we
find the first instance in which, throughout the entire range
assigTied these mnds, they have, after supphdng the Amazon, etc.,
left more water beliind them than they have taken up again and
carried ofi". The low temperatures of Siberian Asia are quite
sufficient to extract from these "winds the remnants of vapom- which
the cool mountain-tops and mighty rivers of the southern hemisphere
have left in them.

549. Here I may be permitted to pause, that I may call atten-
How climates in one tiou to auothor remarkable coincidence, and admire
upSffh^e'^Sm'ifge-'^ the uiarks of design, the beautiful and exquisite ad-
ment of land in the jnstments that WO liero see pro^dded, to insure the

other, and upon the «^ i • p i t

course of the winds, perfect workmgs 01 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 coim-
tries within, and the hygrometrical conditions of all the countries
^vithout, the range included mthin the lines which I have drawQ
(Plate YII.) to represent the route in the northern hemisphere of
the south-east trpxle winds after they have blown then' coui'se over
the land in South Africa and America. Both to the right and left
of this range are coimtries 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 rimning into the sea. On the one hand, there is in Em^ope
the Ehine, the Elbe, and all the great rivers that empty into the
Atlantic ; on the other hand, there are in Asia the Ganges, and all
the great Chinese rivers ; and in North 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-^vind regions of the southern
hemisphere, any considerable body of land ; they are, all of them,
under the lee of evaporating sm-faces in the trade-^iad regions of
the south. Only those countries in the extra-tropical north which
I have described as hiag under the lee of trade-TS^d South America
and Africa are scantily supplied with rains. Pray examine Plate

THE GEOLOGICAL AGEXCY OF THE WIXDS. 287

YII. in this connection. It tends to confirm the views taken in
Chapter YII. The surface of the Caspian Sea is about equal to
that of our lakes ; in it, evaporation is just equal to the precipita-
tion. 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. Lawi'ence give lis an idea of how
greatly the precipitation upon its hydrogTaphic basin is in excess of
the evaporation. To windward of the lakes, and in the trade-^vwd
regions of the southern hemisphere, is no land ; but to windward
of the Caspian Sea, and in the trade- wid region of the southern
hemisphere, there is land. Therefore, supposing the course of the
vapour-distributing mnds 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, w^here,
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 gTeat 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-"v\Tnd
regions of the other hemisphere, should be scantily supplied with
rains; and likewise that those so situated in the extra-tropical
south, with regard to land in the trade-VNind region of the north,
should also be scantily supplied with rains.

550. Having thus remarked upon these dry coincidences, let us
Terrestrial adapta- Contemplate the beautiful harmony displayed in the
*^°°^- arrangement of the land and water, as we find them

along this conjectm^al '' w^ind-road." (Plate YII.) Those who
admit design in terrestrial adaptations, or who have studied the
economy of cosmical arrangements, ^^nll not be loth to grant that
by design the atmosphere keeps in ch^culation a cei-tam amount of
moistm-e ; that the water of which this moistm'e is made is supphed
by the aqueous surface of the earth, and that it is to be retm-ned to
the seas again through rivers and the process of precipitation; for

288 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 ^vinds,
which would be followed by a corresponding change of hygrometrical
conditions, which, in turn, would draw after it permanent changes
of climate ; and permanent changes of climate would involve the
ultimate well-being of myriads of organisms, both in the vegetable
and animal kingdoms. The quantity of moisture that the atmo-
sphere 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 dependent upon the arrangement and the proportions
that we see in natm'e between the land and the water — between
mountain and desert, river and sea. If the seas and evaporating
sm'faces 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 bhght of plants, whole tribes of
animals would also perish. Under such a chance arrangement,
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 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.

551. It should be borne in mind that, by this hypothesis, the
The Red Sea and its south-cast tradc-wiuds, after they rise up at the
vapours. equatoT (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 YII.)? niore
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 YII., and
it wiU be seen that the upper half of the Ked Sea is north of the

THE GEOLOGICAL AGENCY OF THE AVINDS. 289

tropic of Cancer ; the lower half is to the south of it ; that the
latter is ^dthin the north-east trade-A\iQd region ; the former, in the
region where the south-west passage winds are the prevailing
winds. The Kiver Tigris is probably evaporated from the upper
half of this sea by these winds ; while the north-east trade-^vinds
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 " cross-
ing 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 hes, 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. Tliis is the route by
which theory would require the vapom- from the Eed Sea and
Persian Gulf to be conveyed, 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. Is it not a curious circumstance, that the winds which
Certain sea^^nd travcl the road suggcstcd from the southern hemi-
counterpoises in the sphcrc should, whcu they touch the earth on the
Snery!''^ ™'^" polar sido of thc tropic of Cancer, be so thirsty,
more thirsty, much more, than those which travel on either side
of their path, and which are supposed to have come from southern
seas, not from southern lands ? The Mediterranean has to give
those winds three times as much vapour as it receives from them
(§ 547) ; the Eed Sea gives them as much as they can take, and
receives nothing back in return but a httle dew (§ 376) ; the Per-
sian 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 them-
selves to the mind as counterpoises 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 Ame-
rica 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
mth a span, and comprehended the dust of the earth in a measure,
and weighed the mountains in scales, and the hills in a balance ;"

u

290 PHYSICAL GEOGRAPHY OF THE SEA, AlW ITS METEOKOLOGY.

and hence we know that they are arranged both according to pro-
portion and to place. Here, then, we see harmony in the winds,
design in the monntains, order in the sea, arrangement for the dust,
and form for the desert. Here are signs of beauty and works of
grandem- ; and we may now fancy that, in this exquisite system of
adai^tations and compensations, we can almost behold, in the Eed
and Mediterranean Seas, the very waters that were held m 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-sm-face 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 ^ith vapours, or to restore to them that which they have left
behind to feed the sources of the Amazon, the Niger, and the Congo.
553. The hypothesis that the winds from South Africa and
Hypothesis sup- America do take the course through Europe and
ported by facts. ^g^g^ which I havo marked out for them (Plate
YII.), is supported by so many coincidences, to say the east, that
we 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. Ketm-ning once more to a consideration of the
geological agency of the winds in accoimting 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 retm^ned to it through the rivers ; but, suppos-
ing it to be barred up : as the demand upon it for vapour would
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 v/ould be estabhshed between the evaporation and precipita-

THE GEOLOGICAL AGEXCY OF THE WINDS. 291

tion an eqnilibriiim, as in the Dead and Caspian Seas. But, for
aught we know, the water-level of the Mediterranean 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 attaming such an equilibrium. There are connected with
it the remains of a channel by which the water ran into the sea ;
but the sm^face 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. The winds, in this sense, are geological agents of great power.
How, by (he winds It is not impossiblc but that they may afford us the
the age of certain meaus of comparius:, dhectly, o-eolo^^ical events which

geological pheno- i . ^5' i • i -n i • i

mena in our hemi- navo taken placc m onc hemisphere, witn geoiogical
pSeTwitif the age'of events in another: e. g., the tops of the Andes were
those in the other. ^^^^ ^^ ^Yie bottom of the soa.— WMch 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 hygro-
metrically very different from what it now is. In regardmg the
winds as geological agents, we can no longer consider them as the
type of instability. We should rather treat them in the hght of
ancient and faithful chroniclers, which, upon being rightly con-
sulted, will reveal to us truths that Natm^e has written upon their
wings m characters as legible and endm^ing as any with which she
has ever engraved the history of geological events upon the tablet of
the rock.

555. The waters of Lake Titicaca, which receives the drainage
The Andes older of the gTcat inland basin of the Andes, are only
as an inland water, brackish, Hot Salt. Hcuce WO may 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 L^nch, 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 testily in this presence concerning
the works of Natm-e, 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.

u 2

292 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IVIETEOROLOGY.

CHAPTEE XIII.

§ 560-575. THE DEPTHS OF THE OCEAN.

560. "We dive," says Schleiden,* "iiito the liquid crystal of the
Submarine scenery. Indian Occan, and it opens to us the most wondrous
enchantments, reminding us of fairy tales in childhood's dreams.
The strangely branching thickets bear living flowers. Dense
masses of meandrinas and astraeas contrast \\dth the leafy, cup-
shaped expansions of the explanaries, the variously-ramified Madre-
pores, 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 everything ; vivid green alter-
nates with brown or yellow ; rich tints of purple, from pale red-
broMTi to the deepest blue. Brilliant rosy, yellow, or peach-
coloured Nullipores overgrow the decaying masses, and are them-
selves interwoven with the pearl-coloured plates of the Eetipores,
resembling the most delicate ivory cartings. Close by wave the
yellow and lilac fans, perforated hke trellis-work, of the Gorgonias.
The clear sand of the bottom is covered mth the thousand 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 tinmks. 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. Aromid 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, hke 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 3'ellow, 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

* «' Tl.e riant."

THE DEPTHS OF THE OCEAN. 293

(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
jamid 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 up in new splendour. Millions
-of glowing sparks, little microscopic medusas and crustaceans,
dance hke glow-worms through the gloom. The sea-feather, which
by daylight is vermilion-coloured, waves in a greenish, phospho-
rescent 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 ot
Jittle sparkling stars. The most luxmiant vegetation of a tropical
landscape cannot unfold as great wealth of form, while in the
yariety and splendour of colour it would stand far behind this
gardeir landscape, which is strangely composed exclusively of
animals, and not of plants ; for, characteristic as the luxuriant
development of vegetation of the temperate zones is of the sea
bottom, the fullness and multiphcity 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 Echino-
derms, 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 clifi's, 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 accommodate itself to
outward ch'cumstances, 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,

* Ortbagoriscus mola.

294 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

and, even from the depths to which no ray of light is callable of
penetrating, the sounding-lead brings up news at least of living
infusoria." — Schleiden's Lectures, p. 403 — 406.

561. Until the commencement of the plan of deep-sea soundings,
i^^° hTdc- Tif o7°" ^ ^^ ^^-^^y \\^YQ been conducted m the American and
" blue water." English navics, the bottom of what the sailors call
" blue water " was as unknown to us as is the interior of any of the
planets of our system. Boss and Dupetit Thouars, w4th other officers
of the Enghsh, French, and Dutch navies, had attempted to fathom
the deep sea, some mth silk threads, some mth spun-yarn (coarse
hemp threads tmsted together), and some with the common lead
and line of na\dgation. All of these attempts were made upon
the supposition that when the lead reached the bottom, either a
shock would be felt, or the hne, becoming slack, would cease to
run out. ♦

562. The series of systematic experiments recently made upon
Early attempts at this subjcct sliow that there is no reliance to be
Snwortby of ?e°it pl^ccd ou such a suppositiou, foT the shock caused
'"ice. by striking bottom cannot be communicated through
very great depths. Fuirthermore, the hghts 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 httle reliance to be placed
upon deep-sea soundings of former methods, vdien the depths reported
exceeded eight or ten thousand feet.

563. Attempts to fathom the ocean, both by sound and pres-
various methods surc, had bccn made, but out in "blue water" every
tried or proposed, ^^g^j ^j^^ Q^]y g^ 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
Vvinds V\'ere 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 sm^face, echo was
silent, and no answer was received from the bottom. Ericsson
and others constructed deep-sea leads having a column of air in
them, which, by compression, would show the aqueous j)ressm'e to
which they might be subjected. This was found to answer well
for ordmary purposes, but in the depths of the sea, where the pres-
sure would be equal to several hundred atmospheres, the trial was
more than this instrument could stand. Mr. Baur, an ingenious

t THE DEPTHS OF THE OCEAN . 29.5

mechanician of New 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 numher of revolutions made by the
Httle screw dm-ing the descent, and it ha\ing been ascertained by
experiment in shoal water that the apparatus, hi descending, would
cause the propeller to make one revolution for every fathom of per-
pendicular descent, hands provided with the power of seK-registration
were attached to a dial, and the instrument was complete. It
worked beautifully m 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 hauhng 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 experiment the rate at which the torpedo
would sink, and the rate at which the soimd or the gas would ascend,
and so, by timing the interval, to detennine the depth. Tliis plan
would aftbrd no specimens of the bottom, and its adoption was
opposed by other obstacles. One gentleman proposed to use the
magnetic telegraph. The v\ii'e properly coated, was to be laid up
in the sounding-line, and to the plummet was attached machinery,
so contrived that on the uicrease of every 100 fathoms, and by means
of the additional pressure the circuit would be restored, somewhat
after the manner of Dr. Locke's electro-chronograph, and a message
would come up to tell how many himdred fathoms up and down the
plummet had sunk. As beautiful as this idea was, it was not simple
enough in practical application to answer our purposes.

564. Greater difficulties than any presented by the prol^lem of
Physical problems dccp-sca soundings had been overcome in other
Tat'of nSsur?n" departments of physical research. These plans and

the depth of the sea attempts scrvcd to encourae;e, nor were they fruit-
have been accom- 1 tt^p i • i m.

pushed. less, though they proved barren ot practical results.

Astronomers had measured the volumes and weighed the masses of
the most distant planets, and mcreased 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 mth ancient and eloquent
legends, and suggestive of many an instructive lesson that might
be useful and profitable to man. The seal Avhich covered it was of

296 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOKOLOGY

rolling waves' many thousand feet in thickness. Could it not be
broken ? Curiosity had always been great, yet neither the enter-
prise 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 sohd matter for the
study of philosophers.

565. The honour of the first attempt to recover specimens of the
The deep-sea sound- bottom from great depths belongs to Peter the Great
STthe Great. of Eussia. That remarkable man and illustrious
monarch constructed a deep-sea sounding apparatus especially for
the Caspian Sea. It was somewhat 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 plummet would become detached, and the hook
would bring up the specimen.

566. The sea, with its myths, has suggested attractive themes
A plan of deep-sea to all pcoplo in aU agcs. Like the heavens, it

sounding devised for re t i i_ ^^ • j_ o i • i ' r

the American navy, anords an almost endlcss variety oi subjects tor
pleasing and profitable contemplation, and there has remained in
the human mind a lono^ing 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 bot-
tom 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 propitious ; but when or
how to begin, after all these failures, wth this interesting problem,
was one of the difficulties first to be overcome. It was a common
opinion, derived cliiefly from a supposed physical relation, that the
depths of the sea are about equal to the heights of the mountains.
But this conjectm-e was, at best, only a speculation. Though
plausible, it did not satisfy. There were, in the depths of the
sea, imtold wonders and inexplicable mysteries. Therefore the con-
templative 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. Neverthe-
less, the depths of the sea stiU remained as fathomless and as
mysterious as the firmament above. Indeed, telescopes of huge
proportions and of vast space-penetrating powers had been erected

THE DEPTHS OF THE OCEAN. 297

here and there hy 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
astronomical undertakings* hes in the discovery that what, through
other instrmnents of less power, appeared as clusters of stars, were,
by these of larger powers, separated into groups, and what had been
reported as nebula?, could now be resolved into clusters ; that in
certain directions, the abyss beyond these faint objects is decked
with other nebulae, which these great instruments may brmg 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 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 question 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
hght, exploration had invested the subject vdth. 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-hne, 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. Well-directed attempts to fathom the ocean began now to
The great d -pths and be made mth such a line and plummet, and the
^tiempis. " ""^ pubhc mind was astonished at the vast depths that
were at first reported. Lieutenant Walsh, of the United States
schooner " Taney," reported acastmth the deep-sea lead at thirty-
four thousand feet without bottom. His sounding-line was an
iron we more than eleven miles in length. Lieutenant Berry-
man, of the United States brig "Dolphin," reported another un-
successful attempt to fathom mid-ocean with a line thiiiy-nine
thousand feet in length. Captaui Denham, of Her Britannic
Majesty's ship " Herald," reported bottom in the South Atlantic at
the depth of forty-six thousand feet ; and Lieutenant J. P. Parker,
* See the works of Hersehel and Kosse, and their telescopes.

298 PirYSIC^\JL GEOGRAPHY OF THE SEA, AIW ITS METEOROLOGY.

of the*Umted States frigate "Congress," afterwards, in attempt-
ing to sound near the same region, let go his phimmet, and saw
it rmi 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 introduced in conformity
with a very simple plan for sounding out the depths of the ocean.
It involved for each cast only the expenditure 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 fruitM and beneficial, concerning the
winds and currents, and other phenomena of the ocean. These
researches had already received the 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 pubHc vessels to assist in
perfecting the discoveries, and in conducting the investigations con-
nected theremth.

568. The plan of deep-sea soundings finally adopted, and now
The plan finally iH practice, is this i Evory vessel of the navy, when
adopted. qIjq p^^|;g ^Q gg^^ jg^ j£ g|-^Q ^■[esires 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, v/henever he may find himself out
upon "blue water." For this purpose he is to use a cannon-ball
of 32 or 68 pomids 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 t^vine 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 pm^pose, for it was supposed there would
be no strain upon the line except the very slight one requu'ed to
drag it down, and tlie twme having nearly the specific gravity of
sea Vv^ater, this strain would, it was imagined, be very shght. More-
over, when the shot reached the bottom, the line, it vras 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 ivdne.

THE DEPTHS OF THE OCEAN. 299

569. But practical difficulties that were not expected at all
Discovery of currents AYcre lurkiiiQ; in tlic wav, and afterwards showed

in the depths of the ,^ -, , i i i i t i -j

sea. themselYes 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 do^n into
the depths of the ocean, never would cease to run out (§ 562)
and, consequently, that there was no means of knovring 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, and that, consequently, the U\me to be used
miLst be strong ; it was therefore subjected to a test which re-
quhed 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
himdred thousand fathoms of sounding-twme especially for the
pm'pose. It was small, and stood the test required, a pound of it
measuring about six hundred feet in length. The officers in-
trusted with the duty soon found that the soundings could not be
made from sailing vessels mth 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 ciUTcnts, operating upon the bight
of the hne, which caused it to continue to run out after the shot
had reached the bottom. In corroboration of this conjecture, 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 hne — for there might be several cm^rents nninmg in different
dkections, 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. A powerful train of circumstantial evidence was tliis (and
Evidence in favour of it ^yas dcrivcd froiii a sourco whoUv unexpected),

a regular system of . . , , . , /. , i , " j / •

oceanic circulation, gomg to provo tlio cxistencc 01 that systcui 01 occanic
chculation which the climates, and the offices, and the adaptations
of the sea reqmre, and which its inhabitants (§ 465) in theii* mute

300 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

way tell iis 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 prohahly continue as long as sea
water shall j^ossess the properties of saltness and fluidity.

571. In making these deep-sea soundings, the practice is to time
Method of making a the liimdrcd fathom marks (§ 568) as they successively
deep-sea sounding, g^ q^-^ . ^j^^ |^y always usiug a liuc of tlic sauic size
and " make," and a sinker of the same shape and weight, we at last
established the law of descent. Thus the mean of our experiments
gave us, for the sinker and twine used,

2 m. 21' 8. 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. Now, by aid of the law here indicated, we could tell very
The law of the nearly when the ball ceased to carry the line out, and
plummet's descent, -^j^en, of courso, it bcgau to go out in obedience to
the current and drift alone ; for currents would sweep the line out
at a imiform 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 interesting : the problem in hand was impor-
tant, and it deserved every effort that ingenuity could suggest for
reducing it to a satisfactory solution.

573. As yet no specimens of the bottom had been brought up.
Brooke's sounding The Kuo was too Small, the shot was too heavy,
apparatus. rjj^(j {^ could not bc Weighed ; and if we could reach
the bottom, why should we not know its character ? In this state
of the case. Passed ]\[idshipman J. M. Brooke, United States Navy,
who at the time was associated with me on duty at the Observa-
tory, 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 below. 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 m 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 httle soap or tallow,* called " arm-

* The harrel of a common qnill attacliod to the rod lias heen fonnd to answer
hotter.

THE DEPTHS OF THE OCEAN.

301

ing," in the cup C, at the lower end of the rod B. With tliis
contrivance specimens of the bottom have been brought up from
the depth of nearly four miles.

574. The greatest depths at which the bottom of the sea has
The deepest part of bccn rcachcd mth the plmnmet are in the North
the Atlantic Ocean. Atlantic Occan, and the places where it has been
fathomed do not show it to be deeper than twenty-five thousand
feet. The deepest place in tliis ocean (Plate XL) is probably
between the parallels of 35° and 40° north latitude, and imme-
diately to the southward of the Grand Banks of Newfoundland.
The first specimens have been received from the coral sea of the
Indian Archipelago and from the North Pacific. They were col-
lected 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.

302 PHYSICAL G-EOGrvAPHY OF THE SEA, AND ITS METEOROLOGY.

575. The friends of physical research at sea are -under obliga-
Deep-sea soundings tions to the officcrs of the EngHsh navy for much
na\T.^ °^'^^ valuable information toncliing this interesting sub-
ject. Certain officers in that service have taken up the problem
of deep-sea soundings with the most praiseworthy zeal, energy,
and intelligence. Dayman in the Atlantic, Captains Spratt and
Mansell 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, thek maps and
profiles, they have enabled physical geographers to form, vnth some
approach towards correctness, an idea as to the orography of the
basins which hold the water for these two seas. We are also in-
debted to the French for dee23-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.

CHAPTEE XIY.

§ 580-619. THE BASIN AND BED OF THE ATLANTIC.

580. The wonders of the sea are as marvellous as the glories of
The^wonders of the the hcavcns ; and they proclaim, in songs divine,
^^^- that they too are the work of holy fingers. Among

the revelations which scientific research has lately made concerning
the crust of our planet, none are more mteresting 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. The basin of the Atlantic, according to the deep-sea sound-
its bottom and Chim- i^gs made by the American and English navies,
^°'"^2o- is shown on Plate XI. This plate refers chiefly 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 separat-
ing the 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 Atlan-
tic, at the deepest place yet reached by the plummet in that ocean,
the distance, in a vertical line, is nine miles.

THE BASIN AND BED OF THE ATLANTIC. 303

582. Could the waters of the Atlantic be drawn off so as to
An orographic view, cxposc to vicw tliis great sca-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, w^ould be
brought to hght, 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, m the poet's eye, he 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 mapping 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. presents the latest attempt at such a map. It
Plate XI. relates exclusively to the bottom of that part of the

Atlantic Ocean which hes 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 fourth, or hght-
est, where it is not over twenty-four thousand feet deep. The
blank space south of Nova Scotia and the Grand Banks includes
a district within which casts showing very deep water have been
reported, but which subsequent investigation and discussion 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 may be yet 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 accuracy as the
best geographers have been enabled to show, on a map, the eleva-
tions above the sea-level of the interior either of Africa or Austraha.
584. "What is to be the use of these deep-sea soundmgs ?" is
"What's the use " of a qucstiou that often occurs ; and it is as difficult
deep-sea soundings? ^q be auswcred in catcgorical terms as Frankhn's

304 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

question, " What ls 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 purposes. Already
we are obtaining practical answers to this question as to the use of
deep-sea soundings ; for, as soon as they were announced to the
public, they forthv^ith assumed a practical bearing in the minds of
men with regard to the question of a submarine telegraph across
the Atlantic.

585. There is, at the bottom of this sea, between Cape Kace, in
Til? tpicgraphic Newfoundland, and Cape Clear, in Ireland, a re-
piateau. markablo steppe, wliich is already known as the tele-
grapliic plateau, and has already been made famous by the attempts
to rim 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 tln*ough
it, when it ceased to work. Whether messages can ever be suc-
cessfulhj sent, in a commercial sense, through such a length of con-
tinuous 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 ovvdng to the fact that the cable was constructed upon erro-
neous principles. Its projectors, in planning its construction, did
not, unfortunately, avail themselves of the hght which om- deep-sea
soimdings had cast upon the bed of the ocean.

586. It was upon this plateau that Brooke's sounding apparatus
The first specimens brouglit up its first tropMes fi'om the bottom of the
ings!^^'^^^ ^'"^°'^' sea. These specimens the ojfficers 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 Bailey, of West Point — eminent
microscopists both. The latter thus responded : —

587. "I am greatly obhged to you for the deep soundings you
Bailey's letter, scut mc last wcck, and I havc looked at them with

great interest. They are exactly what I have wanted to get hold

THE BASIN AND BED OF THE ATLANTIC. 305

of. The bottom of the ocean at the depth of more than hvo 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 de-
lighted to find that all these deep soundings are filled with micro-
scopic shells ; not a particle of sand or gravel exists in them. They
are chiefly made up of perfect httle calcareous shells (Foraminifera),
and contain, also, a number of sihcious shells (Diatomaceae). It is
mot probable that these animals hved at the depths where these
shells are found, but I rather think that they inhabit the waters
near the smface ; 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 fi'om various depths which were brought
home by the Dolphin, and any similar materials, either 'bottom,'
or water from other locahties. I shall study them carefully. . . .
The results abeady obtained are of very great interest, and have
jnany 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
iinimalculae 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. Lieutenant Brooke of the North Pacific Exploring Ex-
specimens from the jocdition, procurcd specuneus, of the bottom from the
coral sea. ^^^^^i of 2150 fathoms ui the coral sea, lat. 13^ S.,

long. 162^ E. With regard to these, the admnable and lamented
Bailey wrote in 1855, " You may be sure I was not backwards in
taking a look at the specimens you sent me, which, from their
locahty, promised to be so interesting. The sounding from 2150
fathoms, although very small in qua^itity, is not so bad in quality,
yielding representatives of most of the great groups of microscopic
organisms usually found in marine sediments. The predomi-
nant forms are sihcious spicules of sponges. Yarious forms of
these occur : some long and spindle-shaped, or acicular ; others
pin-headed ; some three-spined, etc., etc. The Diatomes (sihcious
infusoria of Ehrenberg) are very few m 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, ^\ith 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

X

806 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

indicate that various interesting species might be obtained if we
had more of the material. You ^ill see by the above that this
deep sounding differs considerably from those obtained in the At-
lantic. The Atlantic soundings were almost wholly composed of
calcareous shells of the Foraminifera ; these, on the contrary, con-
tain very few Foraminifera, and are of a sihcious rather than a
calcareous nature. Tliis only makes the condition of things in
the Northern Atlantic the more interesting."

589. The first noticeable thing the microscope gives of these
They belong to the spccimens is, that nearly all of them are of the
vegTtabiTo/minerai animal, fcw of the mineral or vegetable kmgdom.
kingdom. The occau teems with life, we know. Of the fom* ele-
ments 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 difierent famihes 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 invariably the case, yet this rule, to a
certain extent, is true, and will, therefore, answer our present pur-
poses, which are simply those of illustration. Take the elephant
and his remams, or a microscopic animal and liis, and compare
them. The contrast, as to space occupied, is as striking as the
difierence 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. We notice another practical bearing in tliis group of physi-
Quiet reigns in the cal facts that Brookc's apparatus has fished up from
depth of the sea. ^j-^g bottom of the deep sea. Bailey, with liis micro-
scope (§ 587), could detect scarcely a single particle of sand or
gravel among these httle 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 mo-
tion enough to abrade these very delicate organisms, nor current
enough to sweep them about and mix up with them a grain of
the fimest 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 whe to sink down and rest
upon, yet it is not so shallow that currents, or icebergs, or any
abrading force can derange the we after it is once lodged there.

591. As Professor Bailey remarks (§ 587), the animalculse, whose
Is there life'in them.? remains Brooke's lead has brought up from the

THE BASm AND BED OF THE ATLANTIC. 307

bottom of the deep sea, probably did not live or die there. They
YvTonld have had no hght there, and, had they hved 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 pro-
bably lived and died near the smface, where they could feel the
genial influence of both hght and heat, and were bmied in the
hchen caves below after death.

592. Brooke's lead and the microscope, therefore, it would
The oceau in a new scom, are about to toach us to regard the ocean in
^'sht- a new hght. Its bosom, which so teems ^ith ani-
mal life — its face, upon wliich 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 famihes of hving
creatures that out-number the sands on the sea shore for multi-
tude. 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. On those parts of the solid portions of the earth's crust
Levelling agencies. wMch are at the bottom of the atmosphere, various
agents are at work, levelling both upwards and downwards. Heat
and cold, rain and sunshine, the winds and the streams, ail, assisted
by the forces of gravitation, are unceasingly wasting away the
high places on the land, and as perpetual£^ filhng 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 bot-
tom of the sea, one is led, at first thought, almost to the conclusion
that these leveUing agents are powerless there. In the 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 use half its power, as on dry land, in -tearing the
overhangkig rock from the precipice and casting it down into the
valley below.

594. Hitherto we have, in imagination, been disposed to
The offices of ani- regard the waters of the sea as a great cushion,
maicuicB. placed between the air and the bottom of the ocean,

X 2

308 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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
animalculse that make the surface of the sea sparkle and glow
with life : they are secreting from its surface sohd 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 do^vvTi 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 nearly four miles (two thousand feet) below the
sea-level.* These Forayninifera, therefore, when Hving, may have
been preparing the ingredients for the fniitful 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 these "sunless treasures," recovered with so
The study of them much ingenuity from the rich bottom of the sea,
profitable. suggosts ucw ^dcws 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 ceme-
teries, and enabling us to study their economy, — but it conducts
us into the very chambers of the deep. Our investigations go to
show that the roaring waves and the mightiest billows of the
ocean repose, 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 hned 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.

* The greatest depth, from which specimens of bottom have been obtained,
ia 19,800, feet (3300 fathoms) in the North Pacific.

THE BASIN AND BED OF THE ATLANTIC, ' 309

596. The tooth of running water is very sharp. See how the
The abrasion of Hudson has gnawod through the Highlands, and the
currents. Niagara cut its way through layer after layer of the

sohd 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 pres-
sure of ocean water upon the bottom of the deep sea ? It is not so
great by contrast as the 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. Suppose
the currents which we see at and near the sm-face 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 pressm-e 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 sohd matter beneath the pile with the
weight of "1,296,000 pounds, or 648 tons.

597. The better to comprehend the amount of such a pressure.
Their pressure on let US imagine a column of water just one foot
tiie bottom. square, where the sea is 3000 fathoms deep, to be

frozen fi'om 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 pressm-e on its pedestal would be more than
a miUion and a quarter of pounds ; and if placed on a ship of 648
tons burden, it would be heavy enough to sink her. There are
cm-rents in the sea where it is 3000 fathoms deep, and some of
.them — ;as the Gulf Stream — run with a velocity of four miles 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 rubbmg, and scouring, and
chafing over it, under a continuous pressure of 648 tons. What
would the bottom of the sea have to be made of to withstand 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 ?

310 PHYSICAL GEOGRAPHY OF THE SKi, AND ITS METEOROLOGY.

Why have not its currents cut through the sohd crust in which
its hillows 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. If the currents of the sea, with this four-mile velocity at
the sui'face, and this himdreds of tons pressure on the bottom,
AVhy they cannot wcrc permitted to chafe against its bed, the Atlantic,
chaie it. instead of being tvv^o 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 vvinds, for lack of area to play upon, could not
have sucked up from the sea vapom^s for the rams, and the face of
the earth would have become as a desert without water. Now
there is a reason why such changes shoidd not take place, why the
currents shoidd not uproot nor score the deep bed of the ocean,
why they should not thi'ow out of adjustment any physical arrange-
ment whatever : because, in the presence of everlasting wisdom, a
compass was set upon the face of the deep ; because ^'fe ivaters were
measured in the holloio of the Almighty hand ; because hars and
doors tvere set to stay its proud waves ; and because, ivhen He
gave to the sea His decree that its ivaters should not pass His com-
mand, He laid the foimdaiions of the ivorld so fast that they should
not he removed for ever.

599. By bringing up specimens from the depth of the ocean,
■^vhat it consists of. and studyiug them through the microscope, it has

been ascertained that the bed of the ocean is lined Vvdth the micro-
scopic remams of its own dead, with marine feculences which lie on
the bottom as lightly as gossamer. How frail yet how strong, how
light yet how fii'm are the foundations of the sea ! Its waves
cannot fret them, its currents cannot wear them, for the bed 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 foimdations as with a gar-
ment, so that they may not be worn. If the cmTents chafe upon
it now here, now there, as in shallow seas they sometimes do, this
protectmg cushion is self-adjusting ; and the moment the un-
wonted pressure is removed the hquid cushion is restored, and there
is again compensation.

600. The discovery of this arrangement in the oceanic ma-

THE BASIN AND BED OF THE ATLANTIC. 311

-cliiiiery suggests that the streams of running water in the sea play
The causes that pro- rather about its sui'face than in its depths ; that
duce currents in the f^Q causes which procluce curreuts reside at and

sea reside near its i /> i i t • i

surface. near the surface ; that these causes are changmg heat

and alternating cold ^vith theu' powers of contraction and expansion
— winds and sea-shells ^^dth evaporation and precipitation ; and it
is certain that none of these agents appear capable of reachmg
with their influences very far down into the depths of the great and
wide sea. They go not much, if any, farther do^\Ti 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. The greatest depth at wliich running water is to be found
Their depth, in the sea 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 shows 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 tliis terrestrial globe,
is more beautiful or suggestive than some of the secrets wliich have
been fished up from the caverns of the deep, and brought to light
from the liidden paths of the sea ? ^

602. In my researches I have as yet found no marks of running
The cushion of still water impressed upon the foundations of the sea
n^s. "^ ^ ' '^ " beyond the 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 mvestigation.

603. In Chapter X. (The Salts of the Sea), I have endeavoured
The conservators of to show how soa-shells and marine uisects may, by

^''^** ^^ - reason of the ofiices which they perform, be regarded
as compensations in that exquisite system of physical machinery
by which the harmonies of nature are preserved. But the trea-
sures of the lead and revelations of the microscope present the
insects of the sea in a new and stiU more striking light . We

312 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

behold them now, serving not only as compensations by whicb
the motions of the water in its channels of circulation are regu-
lated 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 estabhshed that these
microscopic creatures live at the surface, and are only buried
at the bottom of the sea, we may then view them as con-
servators of the ocean ; for, in the offices which they performy
they assist to preserve its status by maintaining the purity of its-
waters.

604. Does any portion of the shells which Brooke's sounding-
The anti-biotic view rod briugs up froui the bottom of the deep sea live-
the mo.t natural. h^q^q .^ 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 death ? 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 ch^cumstances, I mcline to the anti-biotic
hypothesis, and chiefly because it w^ould 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 q-WlI conclusion, in the absence of positive evidence-
upon the subject, has been, that the habitat of these mites of thingR.
hauled up from the bottom of the great deep is at and near the
surface. On the contrary, others maintain, and perhaps with
equal reason, the biotic side of the question. Professor Ehren-
berg, of Berhn, is of this latter class.

605. This is an interesting question. It is a new one ; and it
The question stated, bclougs to that class of questious whicli mere dis-
cussion helps to settle. It is therefore deshable to state both
sides — present all the known facts ; and then, pro^dded ^vith such
lights as they afford, we may draw conclusions.

606. As soon as the deep-sea sjDecimens were mounted on the
The arguments of slidcs of the microscopo, the two great masters of
thebiotics. ^\^r^i^ instrument in Europe and America — Bailey o£
West Point, and Ehrenberg of Berlin — discovered the greater part
of the small calcareous caraimces to be filled mth a soft pulp, which
both admitted to be fleshy matter. From tliis fact the German

THE BASIN AND BED OF THE ATLANTIC. 313

argued that there is hfe at the bottom of the deep sea; the
American (§ 587), that there is only death and repose there.

607. " The other argmnent," says Ehrenberg, "for hfe in the
i^hrenberg's state- deep which I havo cstabhshod is the sm-prising
inentofthem. quantity of new forms which are wanting in other
parts of the sea. If the bottom were nothmg but the sedmient
of the troubled sea, like the fall of snow in the air, and if the bio-
hthic curves of the bottom were nothmg 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
pecuhar 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 per-
ceived. The great quantity of peculiar forms and of soft bodies
existing in the innumerable carapaces, accompanied by the observa-
tion of the number of unknowns, increasing with the dejjths — 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. The anti-biotics, on the other hand, quoted the observa-
The anti-biotic view, tious of Profossor Forbcs, who has shoA^Ti that, the
deeper you go m the littoral waters of the Mediterranean, the fewer
are the living forms.

609. As for the number of unkno^vns increasing with the depth
Their arguments (§ 607), they couteud that the tides, the currents, and
based on the tides, ^j^g agitatiou of the wavos all reach to the bottom iii
shallow water ; that they sweep and scour from it the feculences
of the sea, as these insects remams may be called, and bear them off
mto deep water. After reaching a certaui depth, then this sedi-
ment 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 de-
posited 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. The anti-biotics referred to the antiseptic properties of sea
oji^tj^e^^nuseptic water, and told how it is customary ^dth mariners,
vater. ^ ' especially with the masters of the saihng packets be-

3M PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

tween Europe and America, to " corn " fresh meat by sinking it to
great depths overboard. If they sink it too deep, or let it stay dovm
too long it becomes too salt. According to them, this process is so
quick and thorough, because of the pressure and the affinity wliich
not only forces the water among the fibres of the meat, but which
also induces the salt to leaye the water and strike 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 microscopist ; 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 mto the ah.

611. Thus the anti-biotics held that these httle creatures were
On pressure. preserved for a wliile 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 com-
pound, are capable of exerting only a certain mechanical 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 decomposition or vegetable decay can-
not take place. In support of this \dew, they referred to the well-
known eftects of pressure in arresting or modifying the energies
displayed by certain chemical affinities ; and in proof of the posi-
tion that great compression in the sea prevents putrefaction, they
referred to the fact weU kno^Ti to the fishermen of Nantucket and
New Bradford, viz., that when a whale that they have killed sinks
in shallovv' 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, hi the Pacific
with " fleshy parts " among them, at the depth of 3300 fathoms,
and where the pressure is nearly 700 atmospheres. We have

THE BASIN AKD BED OF THE ATLANTIC. 315

brought up fleshy matter from the deev sea as cleep doTvn as ^ve have
gone ; and ^e may infer that if we were to go to 4000 fathoms, we
should still find j)ulpy matter among the dead organisms there. At
that depth, or a httle over, common air, according to " Mariotte's
laiv,'' would be heayier than water, and an air-bubble do^n there,
if one may imagine such a thing, would be heav^^ enough to sink.
Under such conditions, and mth the antiseptic agencies of the sea,
the fleshy matter of these infusoria might be preserved at the bot-
tom of the deep sea for a great length of time.

612. Moreover (§ 604), the anti-biotics pointed to the first chap-
Arguments from the fer 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 maiine 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. This was an exceedingly interesting question, and we could
A plan for solving suggcst but ouo Way of deciding it, which was this :
the question. Many of thcse httle organisms of the sea are in the
shape of plano-convex discs ; all such, when ahve, live with the
convex side up, the flat side dowTi ; but when placed dead in the
water and allowed freely to sink, the force of gravity always, and
for ob\dous reasons, causes all such forms to sink with the convex
side do'^n. 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 hved, and he as they died, for (§ 590) there is
nothing to turn them over after death at the bottom of the deep sea,
consequently their skeletons would be brought up in the quills of
the sounding machine flat side down, convex side up ; but if they
lived near the surface, and reached the bottom after death, they
would be foimd flat side up.

614. But, before there was an opportunity of trying this plan.
An unexpected soiu- Ehrenbcrg IfimseK afibrded the solution in a most
tion afforded. unexpccted Way : — in examining soundings from a
great depth in the Mediterranean, he found many fresh-water shells
^\'ith their fleshy parts still in them, though the specimens were
taken from the middle of that sea. That savant, vdth 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

316 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 unexpected great depths of the
Mediterranean, obtained by Captain Spratt from deep-sea soundings between Malta
and Crete, in 1857, and read before the Berlin Academy, November 27, 1857,
Ehrenbcrg 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 PJiytolitharia, 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 tlie 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 eastw^ardly one. Besides, there are among the
forms some northern ones — e. g., Eunotia triodon, Campijlodiscus clypeus, and many
gallionella. This peculiarity may, perhaps, indicate a lower return current,
hitherto 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 circulation. But, on the other hand, a highly striking agree-
ment with the forms of the ' trade-wind dust ' is not to be overlooked.

" 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 wdio has the opportunity to com-
pare 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 tiic depth is not merely a collection of rubbisli of the dead suriace-like, how-
ever much there must be of fragments which naturally and undoubtedly deposii
themselves there. I have considered this final remark necessary, because the
Distinguished Sea-knower in Washington, often so kindly supplying and instiiict-
ing me with material, has recently, in a report on Sub-oceanic Geography, New
York, January 8, 1857, page 5, and yet more in detail in a late private letter, ex-
pressed a view opposite to that here laid down by me, in wbicb, lio\Yever, I can-
not coincide, for tlie reasons given above."

As tliese sheets are passing through the press (Nov. 22, 1860), a copy of
Dr. Wallaeh's " Notes on the Presence of Animal Life in Vast Depths of the
Sea,'' dated " Off Eockall, Nov. 8, 18G0," 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 soundhig," says the doctor, p. 22, "not quite midway between Capo
Farewell and Eockall, in 126 fathoms, whilst the sounding apparatus brouglit up
an ample specimen of coarse gritty-looking matter, consisting of about 95 per
cent, of clean Glohigerina-slieWs, a number of star-fishes, belonging to the genus
Ophiocoma, 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 coloured tints " being as clear and
brilliant, says the doctor, as seen in their congeners inhabiting its shallow icaters
uliere the sun's rays penetrate freely.

One of the animals was dissected, which was found to differ in no respect

THE BASIX AND BED OF THE ATLANTIC. 317

615. Having thus discoyerecl that the most frail and dehcate
A discovery sug- oi'ganisms of the sea can remain in its depths for
gesttdbyit. an indefinite length of tune -^dthont showing a
single trace of decay, we find ourselves possessed of a fact which
suggests many beautiful fancies, some toucliing thoughts, and a
few useful ideas ; and among these last are foimd reasons for the
conjecture th^t the gutta percha or other msulating material in
wliich the conducting wires of the sub-Atlantic telegraph and
other deep-sea lines are incased, becomes, when 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 aii' 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 !

616. Specimens of the " ooze and bottom of the sea " have also
Specimens fiom the })een obtained by the ingetiuity of Brooke from the
the same story. depth of 2700 fathoms in the North Pacific, and
examined by Professor Bailey.* We have now had specimens

(p. 23), as regards internal anatomy, from the species inliabiting shallow water,
He found in the alimentaiy cavity numerous Globigerina-shella, more or less
completely freed of their soft contents.

These contents, and the bringing up of these li\4ng 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 miqM have taken hold of tl)e
line near the surface as well as near the bottom. It is difficult, it is true, to
account for their being afloat so fiir out at sua ; but how often are frogs and fishes
found under circumstances and in conditions which cannot be accounted for!
Their coming out of the sea adlierent to the line proves notliing.

But the creature had Glohigerina-shcWs in its stomach ; therefore, say the
biotics, these shells must also have lived at the deptli 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 tlie anti-hiotic view quite as much as the other circumstances of the
case ])rove the hiotic.

Life in the depths of the sea is an interesting question, and the plan whicli
seems most capable of settling it has been akeady suggested, vide § 613.

" West Point, N. Y., January 29, 1856.

"My DEAR Sir,— I have examined with much pleasure the highly interesting
specimens collected by Lieutenant Brooke, of the United States Navy, which you
kindly sent me for microscopic analysis, and I will now briefly report to you the
results of general interest which I have obtained, leaving the enumeration of the
organic coatents and the description of new species for a more complete account,

318 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

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

which I hope soon to publish. The specimens examined by me were as follows,
viz. :

"No. 1. Sea bottom, 2700 fathoms ; lat. 56^46' N.;iong. 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 pro-
portion to the deptli, 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 mineral mat-
ter, tlie organic contents, which are the same in all, predominating, while the
reverse is true of No. 3.

" 3rd. All these specimens oxe'very rich in the silicious shells of the Diatomacea,
which are in an admirable state of preservation* frequently with the valves united,
and even retaining the remains of tlie soft parts.

" 4th. Among the Diatoraes the most conspicuous forms are the large and beau-
tiful 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 chpetoceros, with furcate liorns, 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 otlier treasures of the deep.

" 5th. The specimens contain a considerable number of silicious spicules of
sponges, and of the beautiful silicious shells of the polycistinea;. Among the
latter I have noticed Gornutella clathrata of Ehrenberg, a form occurring fre-
quently in the Atlantic soundings. I have also noticed in all these soundings, and
shall liereafter describe and figure, several species of eucyrtidium, halicalyptra, a
perichlamidium, a stylodictya, and many others.

" 6th. I have not been able to detect even a fragment of any of the calcareous
shells of the polythalamia. This is remarkable, from the striking contrast it pre-
sents to the deep soimdings 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. Tliese deposits of microscopic organisms, in their richness, extent, and the
high latitudes at which they occur, resemljle those of the antarctic regions, whose
existence has been proved by Ehrenberg, and the occurrence in these northern
soundings of species of asteromphalus and clisetoceros is another striking point of re-
semblance. 'Tliese genera, however, are not exclusively polar forms, but, as I have
recently determined, occur also in tlie Gulf of IMexico 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 thai 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 tliem are forms which are known to live
along the shores as parasites upon the alga?, etc., it is certain that a portion, at
least, have been caiTied by oceanic currents, by drift ice, by animals which liave
fed upon them, or by other agents, to their present position. It is hence probable

THE BASIX AKD BED OF THE ATLANTIC. 319

ocean's bed has been found everywhere, wberever Brooke's sonnd-
ing-rod has touched, to be soft, consisting -almost entirely of
the remains of infusoria. The Gulf Stream has hterally strewed
the bottom of the Atlantic -with these microscopic shells ; for
the Coast Survey has caught wp the same infusoria in the Gulf
of Mexico and at the bottom of the GuK Stream off the shores of
the Carolinas that Brooke's apparatus brought up from the bottom
of the Atlantic off the Irish coast.

617. The unabraded appearance of these shells, and the almost
Their suggestions, total abscnco amoug them of any detritus 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 pm'e and as free from the sand of the sea as the freshly fallen
snow-flake is from the dust of the earth. Indeed, these soundings
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 covering, presenting the rounded appearance wiiich 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
cm-rents, and scattered and lodged in the com'se of time all over its
bottom. This process, continued for ages, has covered the depths
of the ocean as with a mantle, consisting of organisms as de-
Hcate as the mailed frost, and as light in the water as is down in
the air.

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 surprising in finding
them in any part of the ocean, even if they were not transported, as it is certain
they often are, by the agents above referred to.

"9tli. 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 the 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 without del^ to describe and figure the highly interesting and novel
forms which I have detected, and I hope soon to have them ready for publication.
" Yours, very respectfully, " J. W. Bailey."'

" Lieutenant M. F. Mauky, National Observatory, Washington City, D, C."

320 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOHOLOGY.

618. The waters of the Mississippi and the Amazon, together
The work of re- wlth -all the stroams and rivers of the world, both
caiTied on.' '^^^ 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 sm-prise and astonish
even the boldest speculator with its magnitude. This soluble mat-
ter cannot be evaporated. Once in the ocean, there it must re-
main ; and as the rivers are continually pouring in fresh supphes
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 mat-
ter mixed with fresh water, which, being lighter than that of the
ocean, remains for a considerable tune at or near the surface.
Here the microscopic organisms of the deep-sea lead are continu-
ally at work, secreting this same hme and soda, etc., and extract-
ing 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 universe, viz., that of regulating the salt-
ness of the sea (§ 489). This view suggests many contemplations.
Among them, one, in which the ocean is presented as a vast chemi-
cal 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
physical economy of this Qur earth is regulated, by wdiich this or
that result is brought about and accomplished in this beautiful sys-
tem of terrestrial arrangements, we are utterly amazed at the offices
which have been performed, the work w^hich has been done,
by the animalculse of the water. But whence come the little sih-
cious 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 sm'face waters immediateh" above ? or is then-
habitat in some remote part of the sea, whence, at their death, the
currents were sent forth as pall-bearers, with the command to de-
posit the dead corpses where the plummet found them ?

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 321

619. Fellow-labourers as Foster, and Toynbee, and Piazzi
Animalcule at the Smyth, are beginning to dip into the sm^face water
surface of the sea. ^f ^q gea for its animalculse . They are making
interesting discoveries, ^nd have gone quite far enough to show
that this field is exceedingly rich, and that labourers in it are
greatly needed.*

CHAPTEK Xy.

§ 621-680. — SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.

621. Plate YIII., so far as the mnds are concerned, is supple-
Practical results of mental to Plate I. The former shows the monsoon

physical researches . t • t i xi -t t •• e ii

at sea. rcgious, and mdicates the prevailmg dn^ection oi the

winds in every part of the ocean ; the latter indicates it generally
for any latitude, without regard to any particular sea. Plate YIII.
also exhibits the principal routes across the ocean. Tliis plate
indicates the great practical results of aU the labour connected with
this vast system of research ; its aim is the improvement of naviga-
tion ; 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 utihtarian 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. So to shape the course on voyages as to make the most of
Time-tables. the wiuds and currents at sea is the perfection of 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 dkection has been determined for months and
for seasons, along many of the principal routes, with aU the accu-
racy of which results depending on the doctrine of 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

* See paper " On the Minute Inhabitants of the Surface of the Ocean," by
Captain Henry Toynbee, F.R.A.S. [Naut. Magazine, 1860.J

322 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IIETEOROLOGY.

with the lights of experience to guide him. The wmds and the
weather daily encountered by hundreds who have sailed on the same
voyage before liim, 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 tln'ough 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' m the right road
or no.

623. From New York to the usual crossing of the equator on
Close running, the route to Eio, the distance, by an au^ line, is about

3400 miles ; but the winds and cui'rents are such as to force the
Eio bound vessel out of this direct liue. 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 New 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. The best navigated steam-ships do not sail closer than this,
A desideratum on and a better proof of the accuracy of our knoAvledge
ship-board. Concerning the prevailing direction of the winds at
sea could not be afforded. Unfortunately, anemometers are not
used on shipboard. Had they been in common use there, and had
we been fui'nished with data for determining the force of the wind
as well as its dhection, 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 .computed within an hour, for it has
been computed within an hour's sail — six miles (§ 623).

625. By the knowledge thus elaborated from old and new log-
How passages have books and placed before the nautical world, the
been shortened. average passago from Europe or the United States to

* P. 146, vol. ii., Maury's Sailing Directions.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 323

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 tune requked for the round
voyage has been lessened fifty days or more, and from Em-ope 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 utihtarian spirit of the age.

626. The route that affords the bravest winds, the fairest sweep,
Fast sailing. and the fastest running for ships, is the route to and

from Australia. 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 south-
em hemisphere. With these winds alone, and with the bounding
seas which follow them, the modem clipper, without auxihary
power, has accomphshed 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 performed their voyages of
circumnavigation in 60 days.

627. The sea voyage to California, Columbia, and Oregon is the
The longest voyage, lougcst voyago in the world — longest both as to
time and distance. Before these researches were extended to the
tides and currents along that route, the 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 estabhshed, and the winds of the various
climates along it so well understood, that California bound vessels
saihng about the same time from the various ports of Em-ope and
America are, if they be at all of like prowess, almost sure to fall in
with and speak each other by the way.

* " During the last year [1859] tlie 8th edition of Maury's Sailing Directions, in
two quarto volumes, has been published at the Observatory in Washington. It af-
fords abundant evidence of the activity, to which allusion has already been made,
in this field of research, and with regard to which all geographers feel the most
lively interest.

' Official tables have been received from San Francisco, showing the vessels that
have arrived at that 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 Europe. 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 com-
menced, the general average was 180 days from the United States, and 183 from
Europe to California." — Journal American Geographical Society.

Y 2

324 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

628. TKe calm belts at sea, like mountains on the land, stand
Obstructions to the mightily in the way of the voyager, but, like moun-
navigator. tains, they have their passes and their gaps. In the
regions of light airs, of baffling 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 ^vinds that
there is scarcely a chance for liim who studies the lights before him,
and pays attention to directions, to miss his way.

629. The arrows of Plate YIIL are supposed to fly with the
Plate vni. 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. Let us commence the study of the calm belts as they are
Deserts. represented on Plates I, and YIII. The monsoons

and trade-vvinds 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 phenomenon is
explained by the fact that there is more land in the northern hemi-
sphere, 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 more or less
heated, there is a call — a pulling back, if you please — upon these
trades to turn about and restore the equihbrium 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 car-
ries them over to the northern hemisphere.

631. We see by the plate that the two opposing cuiTents of

Diurnal rotation, wiud callcd " thc tradcs," are so unequally balanced

that the one recedes before the other, and that the current from the

southern hemisphere is larger in volume ; i. e., it moves a greater

zone or belt of air. The south-east trade-winds discharo^e them-

325

selves over the equator — i. e., across a great circle — into the region
of equatorial calms, while the north-east trade-winds discharge
lihemselves into the same region over a parallel of latitude, and con-
sequently over a small chicle. If, therefore, we take what obtains
in the Atlantic as the type of what obtains entirely around the
earth, as it regards the trade-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 difference between
the cu'cumference of the earth at the equator and at the parallel
of latitude of 9° north. For if we suppose that those two per-
petual 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 akeady been shown (§ 343),
flow across the equator m a given time than would flow fi*om 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 re-
gion of the north-east trade-winds is much greater than the quan-
tity 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 moun-
tain ranges, unequally heated surfaces, and other such like obstacles.
632. That the land of the northern hemisphere does assist to
The land in the tum thcso wiuds is rendered still more probable
northern hemisphere. fj.Qjj^ ^j^jg cuTcumstance I All the gi'cat dcscrts are in
the northern hemisphere, and the land surface is also much greater
on our side of the equator. The action of the sun upon these un-
equally absorbing and radiating surfaces in and behmd, or to the
northward of the north-east trades, tends to check these winds, and
to draw in large volumes of the atmosphere, 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 hemi-
sphere. The north-west winds, of the southern are also, it may be
inferred stronger, than the south-west winds of the northern hemi-
sphere.

326 PHYSICAL GEOGBAPHY OF THE SEA, AND ITS METEOROLOGY. •

633. That the south-east trade-wmds should, as observations
S^tradV-'^"re'h ^^ ^^^^ ^^^'® showii, be stioiiger than the north-
stronger. '^ 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 ak 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 meteoro-
logical conditions on opposite sides of the equator. Plate XIII.
shows that we have more calms and more fogs, more rains and more
gales, \vith more thunder, on om- side than on the other, and that
the atmosphere preserves its condition of unstable equihbrium
with much more uniformity, being subject to changes less fre-
quent and violent on the south side of the equator than on the
north side.

634. The highest summer temperature in the w^orld is to be
Theiriiniformity of fouiid in the oxtra-tropical countries of the north.
temperature. rj^j^^ greatest extrcmos of temperatm^e are also to be
found among the valleys of the extra-tropical north. In the extra-
tropical south there is but httle land, few vaUeys, and much water ;
consequently the temperatm-e is more uniform, changes are less
sudden, and the consequent commotions in the air less violent.

635. Following uj) these facts with their suggestions, we dis-

S^^e"ua"oriaTca'm ^^^^^^ ^^^ ^^J ^^ Hiany phenomena which before
belt. ' " were locked up in "the chambers of the south."
The belt of equatorial cahns which separates the two systems of
trade-Avinds 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 dovm to 5° S. ; its northern edge,
in autumn, often mounts up to the parallel of 15° N. The key to
these phenomena has been foimd ; with it in hand, let us proceed to
unlock, first remarking that the mean position of the equatorial cahn
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. This calm belt is produced by the meeting of the two
. Never at rest, trade-wdnds, and it occupies strictly a medial position

between them. It is in the barometric valley, between the two

SEA BOUTES, CALM BELTS, AND VARIABLE WINDS. 327

barometric ridges (§ 667), from wMch the trade-winds flow. If
one " trade " be stronger than the other, the stronger will preyail
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
mil recede before the stronger wind, mitil the momentmn of the
stronger wind is so diminished by resistance, and its strength so
reduced as exactly to be counterbalanced by the weaker wind.
Then tliis calm place will become stationary, and so remain, until,
from some cause, one or the other of the meeting mnds 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 wmds keep the calm belt in a trembling state,
mo\ing now to the north, now to the south, and always shilling
its breadth or its place under the restless conditions of our atmo-
sphere.

637. The southern half of the torrid zone is cooler than the
The calm belts occupy noi^thern, and, parallel for parallel, the south-east
medial positions. tradc-wiuds are consequently cooler than the north-
east. They both blow into this calm belt, where the an, expand-
ing, ascends, flows off above, produces a low barometer, and so
makes room for the inflowing ciUTent 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 ^vill be
the stronger. This is ob^sdous, for it is evident that if the difference
of temperature of the ascendiug column and the inflowing ak were
scarcely perceptible, the difference of specific gravity between the
iuflowiag wuid and the uprisiag air would be scarcely perceptible,
and the movement of the inflo^^dng wiud would be very gentle ; but
if' the difference of temperature were very great, the difference of
specific gravity would be very great, and the violence of the inrush-
iug wind proportionably great. Because the southern half of the
torrid zone is the cooler, the difference in temperature bet^veen the
air of the calm belt and the air of the trade-'^inds is greater,
parallel for parallel, iu the south-east than in the north-east trade-
winds ; consequently, the south-east trade-wiads 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) mth facts. ^

328 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

638. It follows from these premises that the winter trade-winds
strength of the should be stronsfer than the summer. In our sum-

trade-wiiids varies

with the seasons, mer, the air which the north-east trade-wiads put in
motion has its temperature raised and brought more nearly up to
that of the air in the cahn belt. At the same time, the temperature
of the air which the south-east trade-winds put in motion is pro-
portionably lowered. Thus they increase in strength, wliile the
north-east diminish ; the consequence is, they push their place
of meeting mth the north-east trades far over on tliis side of the
equator, and for two or thi'ee 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 of 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-A^^inds are diminished so as to admit of the edge of the calm
belt being pressed dovm only as far as 5° instead of 15° S. 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,
aftei' the period of maximum heat in one case and of minimum in
the other.

639. In the other hemisphere, the period of strongest trades is
Sailing through them coLQcident with that of the minimum in this. These
in fall and winter, doductious aro also Confirmed by observations; for
&uch is the difference as to strength and regularity of the north-east
trade-winds in September and February, that the average passage
thi'ough them from New York to the line is 26.4 days in the vdnter
against 38.8 in the fall month.

640. Thus it appears that the equatorial calm belt is made to
A thermal adjust- shift its placo with the seasons, not by reason of
°^^"^' the greater intensity of the solar ray in the lati-
tude 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 wliich each system puts in motion.
This calm zone, therefore, may be considered as a thermal adjust-
onent — the dynamical null-helt — between the trade-winds of the two
hemispheres.

641. The observations on the barometer at sea (§ 858) shed
The barometer in the light ou this subject. Accordiug to the Dutch, that
cqiutoriai^^tms. instrument stands higher by 0.055 inch in the south-

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 329

east than it does in the north-east trade-winds. According to tlie
observations of American na^dgators, it stands 0.050 inch higher.*
The former determination is derived from 30,873, the latter from
1899 observations; therefore 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-winds ; while for the calm belt it is 29.915 inches. The
pressure, therefore, 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 diiference 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-'s\inds, and according to
actual observations they are.j

642. Now if we liken the equatorial calm belt ^dth its diminished
Experiments in the pressuTC to a fm'naco, the north-east and the south-
French :savy. g^g^ trade- wmds may be not inaptly compared to a pair
of double beUows 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 square foot. It is this
pressm-e 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 observa-
tions and calculations, as well as from du-ect experiments ordered
in the French brig of war " Zebra," by Admiral Chabannes, to be
the case.J

* Maury's Sailing Directions : " Barometric Anomalies off Cape Horn."

t Nautical Monograph, No. 1.

X Letter to Admiral Chabannes, 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 ' Average
Force of the Trade-winds,' p. 857, and especially to the table of comparative 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, notwith-
standing that through the south-east trades the wind is aft, tlirough the north-east
just abaft the beam, [" In order

330 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

643. With these barometric observations, and the assumed fact
DiEFerence in tons of that the mean prcssuie of the atmosphere is 15 lbs.

the barometric pres- ,-, • -, i-i t i • •

sure upon the north- upon the squaro mch, we may readily determme in
Se'^"itii?r^''"''^' toils the total by which the superincumbent pres-
sure 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-east trade-winds is 1,235,250 millions of tons.

" In order to treat this question thoroughly, it is very desirable to know the dif-
ference 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 defi-
nite 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 wliich, being dead aft, drives a vessel at the rate of
six knots, will, 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 resist-
ance 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. Tlierefore, in conducting tliese experiments,
it would be very desirable to know the area of canvas that fairly feels the wind
wlien it is aft, and the area upon which the wind blows when the sliip is hauled
up. Suffice it to say, that the facts which we abeady have indicate that the
south-east trades, both of tiie 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 pronomice the atmospherical circulation of the southern hemi-
sphere to be much more active than that of the northern. And having reached
this round in the ladder up which I am solicitnig 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.

•' Tliat the atmosplierical circulation is more active in the southern than in the
northern ]>emisphere appears to be indicated also by the " brave west winds " of tlie
extra-tropical south.i If the air performs its circuit more rapidly through one
Bj^stem 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 difference between
the gales of tlie northern and those of the southern hemisphere. If we suppose the
general circulation of the northern hemispliereto 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 be up to time. Hence, admitting this view of the matter to
be correct (and you perceive that for the want of tiie experiments aUuded to we are
groping in the darkness of conjecture), though we mighi expect gales of wind in
the extra -tropical regions of the south, yet they would for the most part, blow ivith

^ See also Plate XIII. and § 632 and § 633.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 331

This is the superincumbent weight or pressure which is urging
the south-east trade-winds forward faster than the north-east. It
is inconceivably great; and to bring it witliin comprehensible
terms, the mariner will be astonished to hear that the weight
of atmosphere which is bearing dovm upon the deck of a first-
class clipper ship is 15 or 20 tons greater when he is sailing in
her through the south-east than it is when he is saihng in her
thi^ou2fh the north-east trade-winds.

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 paral-
lels of 33^ and 37° south, have been discussed at the Meteorological Institute of
Utrecht. For this purpose he tabulated the results for the whole year of 17,810
observations — an observation comprehending a period 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 tlie 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
yoiu- 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
immediate purpose, the results might enable us to convert ships into very good
anemometers for all winds except gales.

" Pardon me for being so tedious upon this subject. If you liave felt me so, pray
ascribe it to my desire to get by actual experiment an expression in tlie average-
speed of shii^s for the actual force and velocity of the Avinds.

" 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. Mauky.

" Admiral C. de Chabavnes, Commander-in-chief of the French
Naval Division of Brazil and La Plata, Kio de Janeiro."

Extract from a letter in reply to the foregoing : —

" Montevideo, January 2i, 1860.

" My dear Sir, — * * * * ^g y^^^ j-j^yg 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 with 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 has been a httle
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 the wind abeam by 6. * * *

" C. DE Chabannes."

London, November 26, 1860.
Just in time for insertion here, I receive from the gallant admiral the subjoined
veiy valuable and interesting series of experiments on the speed of his sliip : —
first, before the wind, ?. e. sixteen points, and so on for every two points to six,
and close hauled. At eiglit points the wind is abeam and at riglit angles with the
course of the ship ; at ten it is two points abaft the beam. From tliese experi-
ments we infer that an average sailer that goes six knots before the wind, will, if

332 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

644. The qnestion now suggests itself, Why should the baro-
Sid'sland^iMJer ^^^^^ ^^^^^ higher UI the south-east than it does
in the south-eart m the uoith-east trade-^vinds ? The theory of a
eas?tradV-windL^' crossiug at the calm belts affords the answer. The

hauled up and trimmed, go nine knots with the wind two points abaft the beam,
and S'S wind abeam.

C3 r1

P o

^

<D

oa

'Ti

rl

^

vJ

^^

<

W

—

H

<D

<

ns

M

J

U

g

P

«^

H

-tj

o

^

>^

_o

^

niJ

a

g
s

■5

^

K'uS

<<

^

w

•a

c

1
1

c

p

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^.

5
S

1
0

"2

3
1

Oi rH (M -*! 0
' A( Cq CM rl • ' 0 • '

IIEMAIIKS.

The different experiments, whose results are inscribed in this Table, were made during the pas-
sage from Bahia to France. They were made in the trade-^Yinds, or in fixed and regular winds ;
nevertheless, 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
sometimes quite large.

In going eight knots we have thrown two logs, simultaneously, without touching the line, the two
results differed a knot. Tiie incomplete experiments were interrupted in consequence of the irregu-
larity of the wind, and each result is a mean result.

CO t^ <M tH 10 CO

0
1

CO Ttt -+i rH tH
' Cq CO ' O^cb ' rH ' •

>5
>•

t> 0 Tfl r-l CO Cp

0

<

1

CTi i-H (M 10 10 TtH
• i-H M CO CO (M Ol ' ' '

■§

CO tXN 10 0 C- CO

' >0 CD 00 C5 00 00 ' 'lb

a

a

<

CO tH 05 00 00 0 r-l '
' rH i-H (N i-l cq M i-H ' ' 1

1
>

t^- 0 0^ CO 00 CO 0

' "^ 0 i> t> CO ci do ' '

rn

<

0 10 (>J 10 •<*< t> r-l
00 • i-l 0 0 i-l '0 '

5

0 Oi cq iO -ri^ 0 CO

CO CO ' CO CO CO 00 ' OD '

>

1

>

^ rt 0 ;

1^;

lO-^OOOOCOOSO ,

(NcoTj^ocoocbcboo

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 333

air wMcli the north-east trade-winds dehver 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-^vind belt is broader than the north-east; consequently, in
the former there is more air in contact with the evaporating sur-
face. In the 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 mth moisture. Now, when they rise up and
precipitate tliis moisture, more heat is liberated from the south-
east than 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 ^^dth more weight than the warmer
and more moist au' 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. The geological record affords evidence that the climates
Cataclysms. of the cartli wcro 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
theu' 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 in-
terior of continents deposits many feet thick, consisting 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 icebergs, huge blocks of
stone, rubble, drift, and sediment of various sorts. Lieutenant
Juhen, M. Le Hon, and M. Adhemar have, with much ingenuity,
treated of tins subject. They maintain that our earth has a " secu-
lar " as well as an annual summer and winter ; that these '' secular "
seasons depend upon the precession of the equinoxes, and that the
length of each is consequently 10,500 of our years ; and that it is
the melting of the polar ices in the " secular " season of one hemi-
sphere, and their recongelation in the " secular " winter of the other,

334 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

that causes a riisli 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 orhit, we have our change of seasons ; and in conse-
quence of the elhpticity of that orhit, the spring and summer of
our hemisphere are at present longer than those of the southern.
Durino; the excess of time that the sun tarries on our side of the
equator, the southern nights are prolonged, so that the night of
the south pole — the antarctic winter — is annually a week longer
{§ 366) than the arctic. Thus, during the period of 10,500 years,
the antarctic regions ^^ill exj)erience 142 years of night, or T^inter,
in the aggregate, more than the arctic. Therefore it is manifest,
say the catachjsmatists, that, though the two hemispheres do
receive annually the same amount of solar heat, yet the amount
dispensed hy radiation is very much greater on one side of the
equator than the other. The total effect of the alternate cooling
do^Ti on each side of the equator causes an accumulation of ice at
the pole — when the nights- are longest — sufficient, say they, to dis-
turb the centre of gravity of the earth, causing it to take up its
position on the icy side of the equator. As the ice accumu-
lates, so is the water drawn over from the opposite hemisphere.
Such, briefly stated, is the theory which has found very in-
genious and able advocates in the persons of MM. Juhen* and
Adhjmar.t

646. This theory is alluded to here, not for the piupose of dis-
Are the-ciimates of cussiou, but for tho purposo of directing attention
the earth cbangiDg? ^^ certain paxts of \kns> work in connection with it,
as Chapters YII. and XXI., for example, and of remarking upon
the stabihty of terrestrial climates. Though the temperate re-
gions 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 lackmg.
The question is one of widespread and exceeding interest ; and it
may be asked if we have not in the strength of the trade-winds a
gauge, or in then barometric weight an index, or in the equatorial
calm belt a thermometer — each one of the most delicate construc-
tion and sensitive character — which would, mthin the compass of

* Couranls et Revolutions de I'Atmospliere et de la Mer, comprenant une
theorie nouvellc siir les Deluges Periodiques. Par Felix Julien, Lieutenant do
Vaisseau, etc. Paris, 1860.

t Revolutions de la Mer. Deluges Periodiques. Vox J. Adliemar. Paris, 1860.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 335

Tnimaii 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 jDressui'e upon the N.E. (§ 641),
were to be diminished, the S.E. trades would force tliis calm belt
still farther to the north, and we might have a regular rainy sea-
son in what is now the great desert of Sahara ; for where this calm
belt is (§ 517) there is the cloud-ring, with its constant precipita-
tion. Therefore, if there be any indications that the southern edge
of the great desert is gradually apf)roachmg the equator, it would
favour the supposition that the southern hemisphere is growling
warmer ; but if the mdications be that the southern edge of the desert
is receding from the equator, then the fact would favour the sup-
position that the southern hemisphere is groT\dng still cooler. Nor
are these the only latchets which a study of tliis calm belt and of
the wuids enables us to lift.

647. Theory suggests, and observation, as far as it goes, seems
tod^windraod *^'^ ^^ confirm the suggestion, that the N.E. and S.E.
calm belts.'' tradc-Avinds enter the equatorial calm belt at the

same temperature. I have followed 100 vessels with their ther-
mometer across the equatorial calm belt of the Atlantic, and an-
other 100 across it m 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 temperatm^e 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 tempera-
ture of the air was noted also m each trade at the distance of 5°
from its edge of the calm belt. Thus the temperature of the N.E.
trades, 5° from the north edge of the calm belt, or in 14° N., is
78 .2; at a hke 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 tvdce as much as the temperatm-e 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 tvdce
as long to traverse 5° 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 traversmg given differences of latitude. Thus the
position of the cahn belt, the barometer, the thermometer, and the
rate of sailing, all mdicate the S.E. trade-wmds to be the strono-er.

336 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

It appears, moreover, that tlie temperature of the S.E. trade- wind
is in 2'S. below the temperature of the N.E. in 9^N., the latter
behig 81°, the former 80^2.

6i8. The foregoing observations show that after these winds
The thermal equator, enter the calm belt, the air they bring into it con-
tinues to rise, and this also is what might well be anticipated, for
the sun continues to pour down upon it. But while the tempera-
ture of the surface is kept down by the ram-drops from above, the
temperature of the air in the whole belt is raised botli by the
direct heat of the sun and the latent heat which is set free by the
constant (§ 515) and oftentimes heavy precipitation there. This
latent heat is much more effective than is the dnect heat of the
sun in rarefying the air ; consequently we here unmask the influ-
ences which place the thermal equator in the northern hemisphere.

649. Nor is this the only chamber into which this calm belt
A natural act ino- kov couducts US. Parallel for parallel (^ 446), the

meter in the trade- -^ . , , . ^ . -. ^-, ,i ■ /

winds. southern hemisphere is cooler than the northern j

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 between 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 equator, expresses the difference in the thermal
forces wliich give difference of energy to the dynamical power of the
trade- winds. Not only so : it expresses the difference of tempera-
ture between the two corresponding parallels of 9° north and 9°
south, and discovers to us a natural actinometer on a grand scale,
and of the most dehcate and beautiful kind.

650. This actinometer measures for us the heat ^diich the south-
Heat daily received east trade-winds receive between the moment of
trade-'A^hids."'^^^ crossing the parallel of 9° south and theu^ 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-Avinds 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 distance ; but, kno^ving the exact

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 337

time, we should have in the band of winds an actinometer which
would disclose to us the average quantity of heat daily imjDressed 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,
Tiz. : The mean annual direction of the south-east trade- winds
between 10^ south and the line is south 40^ east.* "We suppose
then average velocity to be (§ 343) about 25 miles an hour. At
this rate it would take them 29h. 22m. 30s. to reach the equator.
During this time they receive more heat than they radiate, and the
excess is just sufficient to raise them fiom the normal temperature of
the north-east trades as they enter the calm belt in 9^ north. A
series of observations on the temperature of the air in latitude 9^
south at sea would, for the farther study of this subject, possess
great value.!

651. If these views be correct, we should expect to find the
Equatorial calm belt cquatorial Calm belt changing its position with night
never stationary. ^^^ (jg^y^ ^;^^ yielding to all thosc uifluences, whether
secular, annual, diurnal, or accidental, which are capable of pro-
ducing changes in the theiTQal condition of the trade- viads. The
great sun-s"^^ng of this calm belt from north to south is annual in
its occui'rence ; it marks the seasons and divides the year (§ 296)
into wet and djy for all those places that are within the arc of its
majestic sweep. But there are other subordinate and minor in-
fluences 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 ak which the
trade-winds move. These are, unusually severe wuiters or hot
summers, remarkable spells of weather, such as long continuous
rahis or droughts over areas of considerable extent, either mthin
or near the trade- wind belts. It is tremblingly ahve 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 sliips, 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
effort to cross that cahn belt, to see another coming up to her,

* Maury's Nautical Monograph, No. 1.

t The mean temperature of sea water in the Atlantic is for 9^ north, 80^.26 by
565 obs. ; for equator, 79^.03, by 269 obs. ; and for 9^ south, 78^.96. 223 obs.—
Maury's Thermal Chads.

Z

338 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. ^

" hand over fist," with fair winds, and crossing the belt after a
delay in it of only a few hours instead of days.

652. Hence we infer that the position of the equatorial calm.
It varies with the belt is determined by the difference of strength be-
traSiads. ^ tweon the north-east and south-east trade-winds,
which difference, in turn, depends upon difierence of barometric
pressure (§ 642), and upon difierence in temperature between them;
in corresponding latitudes north and south. In it the au' which they
bring ascends. Now if we liken this belt of calms to an immense
atmospherical trough, extending, as it does, enthely around the
earth, and if we liken the north-east and south-east trade-winds to
two streams dischargmg themselves into it, we shall see that we
have two cm^rents perpetually running in at the bottom, and that,
therefore, we must have as much air as these two cm-rents bring in
at the bottom, to flow out at the top. What 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-mnds.

653. Captaui Wilkes, of the Exploring Expedition, when he
Precipitation in it. crosscd 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 considering Plate
YIII., one can teU what places within the range of this zone have,
dm-ing the year, two rainy seasons, what one, and what are the
rainy months for each locahty.

654. Were the north-east and the south-east, trades, with the
The appearance of belt of cquatorial calms, of different colom'S, and

the calm belts from • -i i , j • jy n i / i

a distant planet. A^siblo to au astrouomer m one oi the planets, he
might, by the motion of these belts or gkdles alone, teU the seasons
T^ith us. He would see them at one season going north, then ap-
pearing stationary, and then commencing then- return to the south.
But, though he would observe (§ 295) that they follow the sun in
his annual com^se, he woidd remark that they do not change their
latitude as much as the sun does his dechnation ; he would there-
fore discover that their extremes of dechnafion are not so far
asunder as the tropics of Cancer and Capricorn, though in certain
seasons the changes from day to day are very great. He would
observe that the zones of ^vinds and calms have their tropics or

SEA KOUTES, CALM BELTS, AND VARIABLE WINDS. 33^'

stationary nodes, about wliicli they linger near tkree months at a
time ; and that they pass from one of thek tropics to the other in a
little less than another three months. Thus he would observe 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
stationary till ^vinter, in December ; when again they would com-
mence to move rapidly over the ocean, and do^vn 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. Ha\iQg completed his physical examination
of the equatorial calms and wuids, if the supposed observer should
now tm-n his telescope towards the poles of our earth, he would ob-
serve a zone of calms bordering the north-east trade-winds on the
north (§ 210), and another bordermg the south-east trade-winds on
the south (§ 213). These calm zones also would be observed to vi-
brate up and down with the trade- wind zones, partaking (§ 296) of
then- motions, and following the declination of the sun. On the
polar side of each of these two calm zones tSere would be a broad
band extending up into the polar regions, the prevailing v/mds
within which are the opposites of the trade-winds, viz., south-west
in the northern 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
prevailmg direction is towards the poles. They are called (§ 210)
the " horse latitudes " by seamen.

655. Along the polar borders of these two calm belts (§ 296)
Eainy seasons of the "^^G have auothcr rcgiou of precipitation, though,
tropical calm belts, generally the rams 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 rainy season of that parallel, if it be in
winter, is said to commence. Hence we may explain the rainy
season m Chili at the south, and m California at the north.

656. We can now understand why the calm belts of Cancer and
Their position. Capricom occupy a medial position between the

trades and the counter trades ; why, on one side of it, the prevailing
direction of the wmd should be polarward, on the other towards the
equator ; and we also discover the influences which determme their
geographical position ; for :—

z 2

340 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

657. An accumulation of atmosphere over one part of the earth's
A meteorological law. surface impHos a dcpressiou over some other part,
precisely as the piling up of water into a wave ahove 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 truism about water
seeking its own level.

658. The mean height of the barometer in the calm belts of the
Thebarometerin the tropics is greater (Plate I.) than it is in any other
calm belts. latitude. The mean height of the barometer m 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 difference is permanent.
It is sufficient to put both systems of trade-mnds in motion, and
to create an mdraught of air flowing perpetually towards the equa-
torial calm belt from the distance of two thousand miles on each
side of it.

659. In like manner, as we go from either tropical calm belt
Winds with «or</ii«^ towards the nearest pole, the barometric pressure
southing Libera, bccomcs Icss and less. The meteorological law just
announced requires the prevaihng wind on the polar side of these
calm belts to be from them and m the direction of the poles ; and ob-
servations (Plate I.) show that such is the case. Di^dding the winds
in each hemisphere into winds with northing and winds with southing
in them as has been in Chapter XXI. and Plate XV., actual obser-
vation shows (§ 852) that they balance each other in the southern
hemisphere between the parallels of 35^ and 40°, and in the north-
ern between the parallels of 25° and 50° ; that between these
parallels the average annual prevalence of wmds with northing and
of winds with southing in them is the same, the difference (Plate
XY.) being so small as to be apparently accidental ; that, proceed-
ing 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 prevalent.
'Eov^, in each case, the prevaihng winds blow (§ 657) from the high
to the low barometer (Plate I.).

660. The fact of two barometric ridges encircling the earth, as
The barometic ridges, the high barometer of the tropical calm belts do,
and as they may be called (Plate I.), suggests a place of low

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 341

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. Let us contemplate for a moment this accumulation of air
They make a depres- in the tropical belt about the earth in each hemi-

sion in the atmo- ■, \^ • i • i i • o i

sphere. spliero. i^ecauso it IS an accumulation oi atmo-

spheric air about the calms ; — because the barometer stands higher
under the calm belt of Capricorn, for mstance, 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, were the upper surface of our atmosphere visible, and
could we take a view of it from above, we should discover rather-
a valley than a ridge over this belt of greatest pressure ; and over-
the belt of least pressure, as the equatorial calm belt, we should
discover (§ 520), not a valley, but a ridge, and for these reasons :
In the belts of low barometer, that is, in both the equatorial and
polar calms, the air is expanded, made light, and caused to ascend,
chiefly by the latent heat that is liberated by the heavy precipita-
tion 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
pressure, like that which causes the surface ^dnds to blow, but it so
flows by reason of difference as to level.

662. The tropical calm belts (§ 278) are places where the mean
The upper surface of amouut of procipitation is small. The air there is
the atmosphere. 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 the upper regions, from
the equatorial side, where the cross section between any two given
meridians is the larger ; and this upper 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 con-
tracted, thus causing the upper surface of the air to be a sort of

342 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

double inclined plane, descending from the equator and from the
poles to the place of the tropical calm belts.

663. Observations show that the mean weight of the barometer
winds in the southern i^ high southorn is mucli less (Plate I.) than it is in
'Snorll^ra hemi- Corresponding high northern latitudes ; consequently,
sphere. ^^6 should expoct 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 XY.)
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.

;:4, 664. To appreciate the force and volume of these polar-bound
</?thTcf e^of (foid ^^^^^ ^ *^® southern hemisphere, it is necessary
Hope. ' 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 m long ridges
v/ith deep hollows between them. They run high and fast, tossing
their white caps aloft in the air, looking lilvc the green hills of a
rolling prairie capped with snow, and chasing each other in sport.
Still, their march is stately and then roll majestic. The scenery
among them is grand, and the Australian-bomid trader, after
doubling the Cape of Good Hope, finds herself followed for weeks
at a time by these magnificent rolling swells, driven and lashed by
the " brave west mnds " most fmiously. A sailor's bride, per-
forming this voyage with her gallant husband, thus alludes in her
" abstract log " to these rolling seas : " We had some magnificent
gales off the Cape, when the coloming of the waves, the transition
from gray to clear brilhant 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 acti^dty reqimed is such
an exhibition of the power of mind over the elements, that I
admired the sailors fully as much as the sea, and, of course, the
sailor in command most of all ; indeed, a sea voyage more than
fulfils my expectations."

665. It appears, therefore, that the low barometer about the
Winds Mow from a poles and tlic low barometcr of the equator cause an

high to a low bare- i i p • n n • n ,^^ i • - -,

meter. mrusJi 01 Wind, and m eacn case tne rusmng wmd

comes from the high and blows towards the loiv barometer ; that in
one hemisphere the calm belt of Capricorn, and in the other the
calm belt of Cancer, occupies the medial fine between the equatorial
and polar places of low barometer.

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 34B

666. It appears, moreover, that the polar refraction is greater
Polar rarefaction, than the equatorial, for the mean height of the aus-
tral barometer is very much below that of the equatorial, and, con-
sequently, its influence in creating an indraught is felt at a greater
distance (Plate XY.) — even at the distance 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 difierence as to degree of rarefaction is
even greater than this statement imphes, for the influx into the
equatorial calm belt is assisted also by temperature in this, that the
trade- vinds blow from cooler to warmer latitudes. The reverse is
the case with the counter-trades ; therefore, while difference of ther-
mal dilatation assists the equatorial, it opposes the polar influx.

667. Thus we perceive that the tropical calm belts are simply an
The tropical calm adjustment between the polar and equatorial cahns ;
polSTd equ^oriai ^^^^^ ^^e tropical cahn_ belts assume theii^ position and
calms. change their latitude 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. This explanation of the calm places and of the movements
The meteorological of the low austral barometer shows, comparatively
power of latent heat, 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 ofi" 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 fact of a low barometer ofi" Cape Horn was pointed out*
The low barometer ^^ ^^ug as 1834. It was Considered an anomaly
off Cape Horn. pecuhar to the regions of Cape Horn. It is now
ascertamed by the comparison of 6455 observations on the polar side
of 40'' south, and about 90,000 in all other latitudes, that the de-
pression 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
tables, compiled from the log-books of the Observatory by Lieu-
tenants Warley and Young, show : — (See Table, page 344.)

671. These are the observed heights; for the want of data, no
Barometer at the correctious have bccu apphcd to them ; and for the
^^^^^' want of numbers sufficient to give correct means, they

* American Journal of Science, vol. xxvi., p. 54 (1834).

344 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.
Bakometic Table.
3Iean Height of the Barometer as observed between

the Meridians of

Mean of all.

the Parallels of

20^ W. and UO^E.

140 E. and 803 W-

Off Cape Horn.

No. of

Barom.

No. of

Barom.

No. of

Barom.

No. of

Barom.

Obs.

Inches.

Obs.

Inches.

Obs.

Inches.

Obs.

Jncbes-

40° S. and 43^ S.

1115

29.90

210

29.84

378

29.86

1703

29. 8&

43 „ 45

738

.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

.2^

lack tliat uniformity wliicli 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 latitudes. Project-
ing on a diagram A, with parallels of latitude and the barometric
scale as ordinates and abscissae, a cmwe S, which will best re-
present the observations (§ 670), and continuing it to the south
pole — also projecting another ciuwe N, which mil best represent
the observations (§ 362) on the polar side of 40^ N., and con-
tinuing it to the north pole — we discover that if the barometric
pressure in polar latitudes continue to decrease for the unknown
as it does for the known regions, the mean height of the baro-
meter 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
harometric descent of the counter- trades.

672. The rarefaction of the air in the polar calms is, as we have
The "brave west secii (§ 667), Sufficient to create an indraught all
mSric d^-scent. ^ °" aroiuid to the distance of fifty degTees of latitude
from the south pole ; also (§ 662) the rarefaction in the belt of
equatorial calms is sufficient to extend mth its influence no farther
than thirty degrees of latitude. The fact also favours the idea sug-
gested by the diagram (§ 671), that the mean height of the baro-
meter in the polar cahns is very much less than it is hi the equa-
torial. Moreover, the counter trades of the southern hemisphere
are very much stronger (§ 626) than the counter trades of the

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS.

345

other. They are also stronger than the trade-winds of either;
these facts hkewise favour the idea of a greater exhaustion of air
in the antarctic than in the arctic calm place ; and it is manifest
that actual observations also as far as they go, indicate such to he

LAT 4-0'

s

50'

Diagram A.
6 0-

70'

80'

so*

Barometer 80.1
30.0

.8
.7
,6

,s

.3
.2
,1
290
28,3
i>8
•,7
>6

,s

»3
.2

,1
58.0
279

^.

^

^

•^

^

■^

H

^

b

-<

1

I-

\

1

■-«.

*^

1

^

1

'

^

■*>»,

1

\

..

->

■u

S^

\r

9\

^

\

\

^

\

-

(.

H

N

N

'

,

-

-

~

1

'•i

K

\

s

\

\

.

\

h

\

\

»

i

\

—

\

N

■

\

\

\

V

\

^

__j

_

J_

_

. J...

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.

346 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOFtOLOGY.

673. Farther infonnation may be gained npon the subject of
study of the mon- high and low barometers, of the "barometric decli-
SHmSaftoudl!"' vity of winds," and of the meteorological influence of
ing the calm belts, diminished atmospheric pressm^e by studying the calm
belts in connection mth the monsoons.

674. Before, however, we proceed to these, let us take a hasty
The south-west winds glance at the T\inds in certain other parts of the
of the Atlantic. occau. The wiuds 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 v*dnds. " Wind and weather in this part of the ocean,"
says Jansen, " are very unreliable and changeable ; nevertheless, in
the summer months, we find permanent north ^dnds along the
coast of Portugal. These north winds are w^orthy 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, dm^ing wliich the African monsoon prevails, the
Dutch ships, which have lingered in the calm belt of Cancer run
with the north-east trade, and direct then' com^se for the Cape Yerd
Islands, then it seems as if they were in another world. The
sombre sides and changeable — 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 trade-clouds are to be seen — which clouds in the
trade-wind region make the sunset so enchanting. The dark-blue
w^ater, in which many and strange kinds of echinas sport m the sun-
light, 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-coloui'ed dolj)hins ; the diving schools of tunnies — all
these banish afar the monotony of the sea,* awake the loA^e of life
in the youthful seaman, and attmie his heart to goodness. Every-
thing around him fixes his attention and increases his astonishment.

675. "If all the breathings out of heartfelt emotion which the
fJaiiinp; through the Contemplation of nature forces fi'om the sailor were
trade-wind. recordcd in the log-books, how much farther should
we be advanced in the knowledge of the natui'al state of the sea !

* When we, as our forefathers did, preserve in the journals all that we observe at
sea. then we shall have abundant material with which to keep oiu-selves pleasantly
occupied.

SEA ROUTES, CALM BELTS, AND VARIABLE WIOT)S. 347

Once wandering over the ocean, he begins to be impressed 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 om' 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 compre-
hends itself. The distances of the heavenly bodies are correctly
estimated; and, enhghtened by astronomy, with the aid of the
art of navigation, of which Mamy's Wind and Current Charts
form an important part, the shipmaster marks out his way over
the ocean just as secm^ely as any one can over an extended heath.
He dhects his course towards the Caj^e Yerd 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
stilhiess is death-like, and we have entered the belt of calms. This
Mt moves towards the north from May to September. It is a re-
markable phenomenon that the annual movements of the trades
and calm belts from south to north, and back again, do not dii'ectly
follow the smi in its declination, but appear to wait until the tem-
perature 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 mto this belt — cast anchor, for
example — then it would perceive a turning of the monsoon or of
the trade-^ond. It would see the belt of calms draw away to the
north, and afterwards get the south-west monsoon, or, standing
more westerly, perhaps the south-east trade. On the contrary,
later than September, this ship lying at anchor will see the north-
east gradually awake. The belt of calms then moves towards the
south, and removes from the ship, wliich remains there anchored on
the north side."*

676. The investigations that have taken place at the Observa-
The influence of the torv show that the influence of the land upon the

land upon the winds it,- n n • t i • •

of the sea. normal dn^ections oi the wmd at sea is an immense

* Natuuikundige Besclirijving der zeeen, door M. F. Maury, LL.D., Luitenant
der Nord-Amerikaansche Marine, vertaald door M. H. Jansen, Luitenant der Zee.
(Bijdrage.) Dordrecht, P. K. Braat. 1855.

348 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. .

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 autmnnal months, is such as to he felt nearly across the At-
lantic Ocean between the equator and the parallel of 13^ north.
Between tliis parallel and the equator, the north-east trade-wiads,
during these seasons, are arrested in their course by the rainy
seasons and heated plains of Africa, as observation shows they are
in India, and instead of " blo^wg home " to the equator, they stop
and ascend over the desert sands of the continent. The south-east
trade-wmds, arriving at the equator durmg this period, and finding
no north-east trades there to contest their crossing the line, con-
tinue their course, and blow liome as a south-west monsoon, where
they deposit theh moistm-e and ascend. These southwardly mon-
soons bring the rams which divide the seasons in these parts of the
African coast. The region of the ocean embraced by these mon-
soons is cuneiform in its shape, ha\TQg its base resting upon Africa,
and its apex stretcliing over till mthin 10^ or 15° of the mouth of
the Amazon. Indeed, when we come to study the effects of South
America and Africa (as developed by the Wind and Current Charts)
upon the wiuds at sea, we should be .led to the conclusion — had the
foot of civilized man never trod the mterior of these two continents
— that the climate of one is humid ; that its valleys are, for the
most part, covered with vegetation, which protects its sm-face from
the sun's rays ; while the plains of the other are arid and naked,
and, for the most part, act hke furnaces m dra^^dng the winds from
the sea to supply au' for the ascendmg columns which rise from its
over-heated plams. 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, mthin the trade-w^ind region, would be almost, if not
altogether, as rainless and sterile as the desert itself.

677. Lieutenant Jansen has called my attention to a vein of
A "Gulf stream" in "^^'ind which forms a current in the air as remark-
the air. ^j^j^ ^g |-]^^^ q£ |.j^g Q.^ Stream is in the sea. This

atmospherical Grulf Stream is m the south-east trade-wmds of the
Atlantic. It extends from near the Cape of Good Hope, in a
dkect Ime to the equator, on the meridian of Cape St. Koque (Plate
VIII.). The homeward route fi'om the Cape of Good Hope hes
in the middle of this vein ; in it the winds are more steady than

SEA ROUTES, CALM BELTS, AND VARIABLE WINDS. 349

in any other part of the Atlantic. On the edges of this remark-
able aerial current the wind is variable and often fitful ; the home-
ward-bound Indiaman resorts to and uses this stream in the atmo-
sphere as the European-bound American does the Gulf Stream.
It is shaded on the plate.

678. These investigations, with their beautiful developments,
Counterpoises, cagcrlj captivatc the mind ; gi^'ing wings to the

imagination, they teach us to regard the sandy deserts, and arid
plains, the moimtain ranges, and the inland basins of the earth, as
compensations in the gTcat 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 workmgs of the machine.

679. When we travel out upon the ocean, and get beyond the
Normal state of the influeuce of the land upon the ^inds, we find our-
atmosphere. sclvcs in a field particularly favourable for studying
the general laws of atmospherical cnculation. Here, beyond the
reach of the great equatorial and polar currents of the sea, there are
no unduly heated surfaces, no mountain ranges, or other obstruc-
tions to the chculation of the atmosphere — nothmg to disturb it
in its normal coui'ses. The sea, therefore, is the field for ob-
serving 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 mountaui range and local
district, may be said to have its own peculiar system of calms,
winds, rains, and droughts. But not so the surface of the broaa
ocean ; over it the agents which are at work are of a more uiuform
character.

680. PiAiN-^vMiNDS are the winds which convey the vapour from
Eain--nir.ds. the sca, whcrc it is taken up, to other parts of the

earth, where it is let do^n either as snow, hail, or rain. As a
general rule, the trade-T\dnds (§ 293) may be regarded as the
evaporating miids ; and when, in the course of their chcuit, they
are converted iuto monsoons, or the variables of either hemisphere,
they then generally become also the rain-^wds — especially the
monsoons — for certain localities. Thus the south-west monsoons
of the Indian Ocean are the rain winds for the west coast of Hin-
dostan (§ 298). In like manner, the African monsoons of the
Atlantic are the winds which feed the springs of the Niger and the

350 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

Senegal witli rains. Upon every water-slied wliicli is drainecl
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 through-
out the whole extent of the valley that is drained by it. Now, if
we knew the ram winds from the dry for each locality and season
generally throughout such a basin, we should be enabled to deter-
mine, with some degree of probability at least, as to the part of the
ocean from which such rains were evaporated. And thus, not-
withstandmg all the eddies caused by mountain chains and other
uneven surfaces, we might detect the general course of the atmo-
spherical 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 cm^rent of the Mississippi, 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.

CHAPTEK XYI.

§ 681-711. — MONSOONS.

681. Monsoons are, for the most part, trade-winds deflected^,
The cause of. When, at stated seasons of the year, a trade-wind
is turned out of its regular course, as from one quadrant to an-
other, it is regarded as a monsoon. The African monsoons of
the Atlantic (Plate YIII.), the monsoons of the gulf of Mexico,
and the Central American monsoons of the Pacific are, 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,
carrying 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

MONSOONS. 351

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. Upon India and its seas the monsoon phenomena are
The region of. devclopcd ou the grandest scale. These remark-
able winds blow over all that expanse of northern w^ater 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, 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. trades ^Ye
have S.W. monsoons.

683. If the N.E. trade-winds blow towards the equator by reason
A low barometer iu (§ 657) of the lowcr baromcter of the calm belt
Northern India. thorc, WO should — scoing 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 commence at the north, and "back
The S.W. monsoons dowu," or work their way towards the south. Thus
"backing down." ^^gy gg^. [^ earlier at Calcutta than they do at
Ceylon, and earlier 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 tw^enty 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

352 PHYSICAL GEOGRAPHY OF THE SEA, AKD ITS METEOROLOGY.

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 belt, 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. mon-
soon, on the equatorial as the N.E.

685. As the vernal equinox approaches, the heat of the sun
How they begin, bogius to play upou the stoppes and deserts of Asia

with power enough to rarefy the air, and cause an uprising suffi-
cient to produce an indraught thitherward from the surrounding
regions. The air that is now about to set off 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 be-
come daily more and more heated, the sun more and more power-
ful, 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, drive
the N.E. monsoons from the land, replace them, and gradually
extend themselves out to sea.

686. Coming now from the water, they bring vapour, which,
The sun assisted by bein"" condonsed upon the hill-sides, liberates its
vapiu^* ^^'^^ ^^ latent caloric, and so, adding fuel to the flame,
assists the sun (§ 648) to rarefy the air, to cause it to rise up and
flow off more rapidly, and so to depress the barometer still more.
It is not tillthe S.W. monsoons have been extended far out to
sea that they commence to blow strongly, or that the rainy season
begins in India. By this time the mean daily barometric pres-
sure 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 S.W. monsoon commences to change at Calcutta, in
Therain-faiiinindia. 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

MONSOONS.

353

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 statement is made, with the view of
showino*, as far as such data can show, the time at which the
ramy season commences in the mterior :

Lat.

Long.

March.

April.

May.

June.

July.

Aug.

Sept.

Oct.

0 /

O '

in.

in.

in.

in.

in.

in.

in.

in.

Poorie . . . •

19 48

85 49

1

1

5

14

7

4

Baitool ....

21 51

77 58

1

4

15

9

4

..

Sanger ....

23 50

78 47

2

2

15

12

13

1

Humeerpore

26 7

79 47

..

7

13

11

5

1

BareiUy .. ..

28 12

79 34

,.

3

17

8

2

3

Ferozepore

30 57

74 41

..

1

19

..

..

Simla

31 6

77 11

1

1

4

18

12

..

,.

Cherraponjie

25 16

9143

1

28

115

147

99

104

72

40

2

29

120

173

210

103

100

45

It is June before the S.W. monsoons have backed down as far as
the equator and have regularly set in there.

688. These positions are selected without regard to elevation
Its influences upon above the soa lovel. Of course, when the S.W.
the monsoons. monsoou 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. With the view of investigating certain monsoon pheno-
The march of the moua, rocourso was had to our great magazine of
monsoons. undigested facts, the abstract logs ; and after dis-
cussing 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 monthly duration of the N.E.
and S.W. winds at sea between the parallels of —

2 A

854 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

220 and 200 N.

20° and 15^ N.

island 10° N.

10° and 50 N.

6^ and 0° X.

Days.

Days.

Days,

Days.

Days.

Days.

Days.

Days.

Days. , Days.

N.E.

S.W.

N.E.

S.W.

N.E.

S.W.

KE.

S.W.

N.E.

S.W.

January

17

6

21

2

23

1

20

1

19

3

February

11

11

18

6

19

8

22

1

W

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

0
0

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

«t

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. mousoon. t Ending of the S.W. monsoon.

It appears from this table that betw^een Calcutta and the line
the S.W. monsoons are the prevailing winds for seven months,
the N.E. for five.

690. Resorting to the graphic method of engraved squares for

Diagram B.
Z!f 20" 15' 10° 5" ^0°

20

JS

•3D

1 i 1

1 1 i

1 III

1 ! ! M 1

' ' ' 0

ill! ^\

rr T >>- \ . ii

1 1 1 crfl %~

i ' ' >^ 1 ^

^■h 1 1 1 <^/;^. L 1 \

^•4i 1 \4V / \4. [ ^^

r.^! y t - i%:7 J

5c / ifT . ^^^

^ t \r^

.xTP; r

Pr iM^

% zm.

'K ^1 '■• 1 1 '

1^3: '^

^i: ^

22^ ^^

^^--.±:m.

-^^ ^^rfw n^

1 ^-4^1 \

Vr.:-. 1 1 „

"::^A^---''^

_._ „ . . . ,. „. . Jt-r^--'' .

^ - ± -

MONSOONS.

355

a farther discussion of these figures, it appears by the sub-
Their conflict— it be- joined Diagram B, that in February the north-east
gius at the north, ^^j^^ south-wost wiuds are in equal conflict 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 ascendency, 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

23"

20°

Is

'

[Diagram C.
15° l.at lo"

5

o

i

3"

.25

f

s

\

\

\

,20

&

^

1

^

\,

1

J

\

\,

/

\

r\

.15

>

r-

1

\

-<-,

^-

_

1

rr

\

A

^%

k-

(

J

VA

N

A

\^

h

.10

' ^

k

o'

'

\

y

\

.'.''

1

\

/

1

s\-

y

K

>S1

\

N

1

^•

-^

•^"

^t

/'

, Uc

t.

o

?■

r^

}L

\

.5~^

^^- i

A

Tl

~--.

"~^

w

V,

4

y

\'

'■

S

W

-'

1

•^u

1

1

1

_

1

._L

J

about the parallel of 15° 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 away from the medial line, they blow

2 A 2*

356 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

towards it ; instead of being a place of bigh, the medial line is
now (§ 657) a place of low barometer. By November the north-
east monsoon has pushed the place of equal contest as far down
as the parallel of 5° north.

691. Each monsoon, like the trade-winds, blows from a higher
The barometric des- to a lower barometor. Taking up the clew from
centof themonsoofls.^|-^jg fg^^t, and rosorting again to the graphic method
for illustration, we may ascertain, with considerable 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 icterior of India during the south-west monsoon, sup-
posing 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 barometric decHvity of

Diagram D.
0" "K 5° Xat Iff 15°

20'

30"

Bar .2

.1
so.o

21>.0

1

h

-

-

"

■"

-r

M

__^

—

.»

.o.

^os

%^

\Aj

_-

*^g

'^ ^

— i

1 —

1

—1

^1

-,

— :m

— j

r

<r

J^

i*

,

1

^

^

>>

L

A.

o

•F

.'^

- --,

§

;:

^

"So

r>

^^1
*

^

•^

1

•^

s

^

-'^'

**^

■^^

Q

-^^

n^

L^

iV

1

kJ

J:-

\\>

t~

-1

"~^

f^

i

the north-east monsoons generally. The mean height of the
barometer during the three months of June, July, and August,
when the south-west monsoons are at their height, is.

For Calcutta 29 . 55 inclies.

„ Bombay 29.65 „

„ Madras 29.73 „

The line S.W. represents the mean barometric declivity of the
south-west monsoons at their height, and indicates that at their

MONSOONS. 857

nortliern 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. These are the winds — the south-west monsoons — which,
The summer rains comiug from the sea, Carry into the interior rains
of cherraponjie. foj, ^^^q gj^Q^^ watcr-shcd 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;g- inches during the south-west monsoon, from May to
August inclusive. Col. Sykes reported to the British Associa-
tion, at its meeting in 1852, the rain-fall at these 127 places,
which are between the parallels of 20° and 34° in India. Ac-
cording to this report, the south-west monsoons pour down
during the three summer months upon this water-shed 29f
inches of rain. The latent heat that is liberated during the
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. As long ago as 1831, Dov^ maintained that the south-
Dove and the west monsoon wa^ the south-east trade-Avind rush-
monsoons. ^^g 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. But any navigator who, during the summer months, has
The south-east trades occasion to travorsc the Indian Ocean from north
wesVmonsinr 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 mon-
soons, and that he has passed 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

* Dr. Buist.

358 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. ' "

August, we find, by 421 observations 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 „

69-5. In like manner, and with Hke force, Jansen maintains
Lieutenant Jansen. that the uorth-west monsoon of Austraha is the
north-east trade-wind turned aside.

696. The influence exerted upon rainless winds by the deserts
Monsoons in the 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 country 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
Arabia upon the winds is felt in Austria and other parts of
Europe, as the observations of Kriel, Lament, 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 eifect 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 winter-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. It is a curious thing is this influence of islands in the
Influences of coral tradc-wiud rogion upon the winds in the Pacific,
reefs upon winds. Evory 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 favourable circum-

MONSOONS. 359

stances, may be seen gathering above the low coral island, and
performing their office in preparing it for vegetation and fruitful-
ness in a very striking manner. As they are condensed 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 press-
ino" it out. — Mauky's Sailing Directions^ 7th ed., p. 820.

698. Land and sea breezes are monsoons in miniature, for they
Monsoons in minia- ^©peud in a moasuro upon the same cause. In the
ture. 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
niglit are alone concerned. In the monsoons the heat of summer
and cold of winter are also concerned. But could the experiment
be made mth two barometers properly placed — 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 alterations 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. 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 sfcorm 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

360 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the monsoons, for the annual changing at the same place is very
regular.

700. Theory, therefore, points to a place in Northern India,

?f°cL!cer h^^ii^hed "^^^^^^ ^^ ^^^^ *^^ uorthem limits of the south-west
to the north. mousoon, whoro 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 land somewhat like
that assigned to it on Plate VIII. 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 as actual observations
abundantly show.

701. The equatorial calm belt in the Indian Ocean is a
The curved form of docidcd curvo. The pcculiar form may be ascribed
beSThelnd^ai"^ *^ ^^^ moteorological influence of the Indian penin-
ocean. sula upou the calm belt, and in this way : The
north-east monsoon briugs the rainy season to the Coromandel
coast and to the east coast of Ceylon. This rainy season em-
braces 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. In the winter-time, and during the north-east monsoon,
The wintermon- 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^

MONSOONS. 361

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 J 0° 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. The north-west monsoons of Australia come from this
The monsoons of ^clt ; there it is widened, for these winds extend
Australasia. f^j- dowu the wost 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
loDger, and are accompanied with an upward motion of the air ;
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 difference
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 south-
ern hemisphere. While in the northern hemisphere the north-
east trade-v/ind 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.

362 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

704. " In the Java Sea, during the month of February, the
Thunder and west monsoon blows strong almost continually ; in
lightning. 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
feeliogs both of dread and anxiety, which by pretended occupa-
tions he strives in vain to conceal.* Day and night we now have
thunder-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.! 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 causes
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. "Yet often the wind prevents the formation of water-
Water-spouts. spouts. In their stead the wind-spout shoots up

* 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 dfiOy we siiw one or more. — Jansex.

MONSOONS. 363

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 contliet 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 lias
been favourable, how^ever, 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
yards, nor thicker than 50 yards. In October, in the Archipe-
lago of Rio, 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. t

* Tlie air-qDOuts near tlie equator always appear to me to be more dangerous
than the water-spouts. I have once had one of the latter to pass a ship's length
ahead of me, but 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.

t Miniature water-spouts may be produced artificially by means of electricity,
and those in nature are supposed to be caused by the display of electrical pheno-
mena. " From the conductor of an electrical machine," says Dr. Bonzano, 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 metalHc basin containing
some oil of tiu-pentine, 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
move in different directions, and form whirlpools. A s the electricity on tiie con-
ductor accumulates, the troubled liquid will elevate itself in the centre, and at last
become attached to the ball. Draw off the electricity from the conductor to let
the hquid resume its position : a portion of the turpentine remains attached to the
ball. Turn the handle again very slowly, and observe now the fqjv 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
continues imtil the electricity from tlie conductor is nearly all discharged, silently,
or until it is discharged by a spark descenchng into the liquid. The same pheno-
mena 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

364 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

706 " During the changing of the monsoons, it is mostly calm
The east monsoon or cool, with gentle breezBS, varied with rain-storms
in the Java Sea. ^^^^ ijg]^|^ gales from all points of the compass.
They are harassing to the crew, who, with burning 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 tem-
pests, 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 monsoon
commences in April.t 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.1:

707. " It is sufficiently important to fix the attention, seeing

Currents. that thoso circumstauccs have great influence upon

the winds in the many straits of the Archipelago, in which strong

breaks up, a portion of the liquid, and witli it anything it may contain, remains
attached 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 Xm., we see that the phenomenon of thunder and light-
ning is of much more frequent occurrence in the North than in the South Atlantic ;
and I infer that we have more electrical phenomena in the northern than in the
southern hemisphere. Do water-spouts occur on one side of the 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. According to the log-books at the
Observatory, they occur mostly on the north side of the equator. — M,

* At sea tlie face and hands burn (change the skin) much quicker under a
clouded than under a clear sky. — Jansen.

t In the north-east part of the Archipelago the east monsoon is the rainy mon-
soon. The phenomena in the north-east part are thus wholly different from those
in the Java Sea. — Jansen.

X 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 mor.'50on) blows through the
westerly entrance as far as Grissee (in the elbow) ; m 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.

MONSOONS. 365

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 monsoon. The passing of the meridian by the moon ap-
pears to be the fixed point of time for the turning of the currents.
It is probable that the heated water of the Archipelago is dis-
charcjed to the north durino^ the east monsoon, and to the south
during the west monsoon.

708. " As the sea makes the coming of the southern summer
iviarking the seasons, kuowu 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-
sphere, 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
superiority known. Upon and in the neighbourhood of the land
thunder-storms occur, but at sea they are less frequent.

709. "The atmosphere, alternately clear and cloudy, moves
Conflicts in the air. more definitely ovor from the north-west, 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
permanent.

* In the 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.

366 PHYSICAL GEOGKAPHY OP THE SEA, AND ITS METEOEOLOGY.

710. '' Such are the shiftings. But what have they to do with
Passing of the calm the general system of the circulation of the atmo-
^^^^^- sphere ? 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 regiilarity, then it
will not be necessary to furnish proof that these turnings are
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. "So also the calms, which precede the land and sea
■^vhere they are. there winds, are tumod back. If, at the coming of
monsoon! 'i?going on. the laud-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 calms remains for
the night, to be turned back to the land and to the hills the fol-
lowing day by the sea-wind. In every place where these calms
go, the land and sea-winds turn back. If various observers,
jDlaced 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 ter zee.

CHAPTEK XYII.

§ 720-735. THE CLIMATES OF THE SEA.

720. Theemal charts, shoAving the temperature of the surface
A "milky way "in of the Atlantic Ocean by actual observations made
the ocean. 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
philosopher 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 hyetographic 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 w^ith 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 highw^ay 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 Bemini, 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. Running between banks of cold
w^ater (§ 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.

368 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

721. In September, when the waters in the cold regions of the
The vibrations of north havo been tempered, and been made warm
the Gulf Stream. ^^^ ^jg^^ ]jy ^he heat of summer, its limits on 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-regulating, self-compensating
pendulum, beating time in the sea to the seasons of the year.

722. In seeking information concerning the climates of the

Sea and land climates ocean, it is Wcll UOt tO forgOt this remarkable con-
contrasted, -i^j-g^g^ 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 dryland, 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 SO'' have been
drawn for March and September, the months of extreme heat
and extreme cold to the inhabitants of the " great deep." Cor-
* Vide Chap. XXII., Actinometry of the Sea.

THE CLIMATES OF THE SEA. 369

responding isotherms for any other month will fall between these,
taken by pairs. Thus the isotherm 70*^ for July will fall nearly
midway between the same isotherms (70^) for March and Sep-
tember.

723. A careful study of this plate, and the contemplation of
Plate IV. the benign influence of the sea upon the climates
which we enjoy, 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 offices, 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 up 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
asjents for distributing heat to the various parts of the ocean.
The sun with his 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 miti-
gating, and tempering climates by the way. The provision for
this is as l)eautiful as it is benign ; for, to answer a physical adap
tation, 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 specific gravity is altered,
just in that proportion is equilibrium in the sea destroyed.
Arrived at this condition, it is ordamed 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 w ould 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. Moreover, this isotherm of 80° will pass in the
North Atlantic, from its extreme southern to its extreme northern
declination — nearlv two thousand miles — in about three months.

2 B

370 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOROLOGY.

Thus it travels at the rate of about twenty-two miles a day.

Surely, without the 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,

a,nd radiation, this isotherm occupies the other eight or nine

months of the year in slowdy returning south to the parallel

whence it commenced 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 movement at which this line travels on its march south.

Between the meridians of 25^ and 30^ west, the isotherm of 60*^

in September 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

meridians, which it accomplishes in January, standing then near

the parallel of 40°. It is all the rest of the year in returning

northward 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 prpcess of calorific absorption on the one

hand, and by a gradual process of cooling on the o^her. 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

THE CLIMATES OF THE SEA. 371

mouth of the bay. The waters of the bay, being fresher 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, which 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 temperature of the atmosphere
between the parallels of 56° and 40° north, for instance, and
over that part of the ocean in which we have been 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 south-
wardly 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 isotherm
be 5° lower than the mean temperature, we sliould 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 precipitation 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 YIII.); in other words, it is from the higher to the lower

2 B 2

372 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

isotherms. Passing, therefore, from a higher to a lower tempera-
ture 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 polar regions, is greater than that
which is taken up again. This is an interesting and important
fact

724. Having, therefore, more precipitation in high than in low
The effects of night latitudos at soa, WO should have more clouds; and
temper^it^STo{lta therefore it requires a longer time for the sun,
'«^'ater. 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 5(j^ 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 sun recrosses the equator, with
increased powers both as to intensity and duration. Thus, in
studying the physical geography of the sea, we must take cogni-
zance 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. Now, returning towards the south : we may, on the other
A belt of uniform hand, infer that the mean atmospherical tempera-
temperature at sea. ^^j.^ f^j. ^j^g 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 fact has been pretty clearly established by the dis-
The western half of covories to which the wind and current charts have
hati the'eastern. *^ led, that ilic westom half of the Atlantic Ocean is

THE CLniATES OF THE SEA. 373

heated up, not by the Gulf Stream alone, as is generally sup-
posed, but (§ 131) by the great equatorial caldron to the west of
longitude 35°, and to the north of Cape St. Roque, 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 highest 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. Roque 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 spreading out in that direc-
tion 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 flgw 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
gi^eat equatorial caldron, which Cape St. Roque 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. Like the western half of the North Atlantic Ocean, the
The warmest sides of ^vestern half of overv one of the three sjreat oceans

oceans and the . , rr^, *^ , ^ /. , •

coldest shores of IS tho Warmer. 1 he great How oi warm water m
p'osmo"''"^'""" 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 cur-
rent 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 current on the African side, and

874 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

the cold drift on the Austrahan; 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 re-
versed, 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. Here we are again tempted to pause and admire the
The climates of boautiful rovelations which, in the benign system
bySe^horeSes ^^ terrestrial adaptations, these researches into the
of Brazil. 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 apparently
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. Roque, 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 fire of the solar
rays sinks down, the westwardly winds and eastwardly currents
are sent to perform their office in this benign arrangement.
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 currents are

THE CLIMATES OF THE SEA. S75

to be regarded as the flues and regulators for distributiDg it at
the right time, and at the right places, in the right quantities.
By March, when 'Hhe 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. Eoc{ue, 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 quit-
ting the Caribbean Sea, runs parallel with the South American
coast towards Cape St. E-oque, 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 tVie solar rays ; at this
season, then, the summer climate due these transatlantic lati-
tudes is modified by 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 Cape St. Roque and the tropics is again heated
and brought into the 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. In like manner, the Gulf of Guinea forms a caldron and
TheGuif of Guinea a fumaco, and spreads out over the South Atlantic

and the climate of • i t r. i , • • • j i • i

Patagonia. an air-chamber for heating up m wmter and assist-

376 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

ing to keep warm the extra-tropical regions of South America.
Every traveller has remarked upon the mild climate of Patagonia
and the Falkland Islands. " Temperature in high southern lati-
tudes," says a very close observer, who is co-operating with me
in collecting materials, " differs greatly from the temperature in
northern. In southern latitudes there seems to be no extremes
of heat and cold, as at the north. Newport, Rhode Island, for
instance, latitude 41° north, longitude 71" west, and Eio 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. Koque
does to the north ; it carries to Patagonia and the Falkland
Islands warmth, which, uniting with the heat set free by precipi-
tation 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 Atla.ntic, or of the " Emerald Island " on the other.
730. All geographers have noticed, and philosophers have
Shore-lines. 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 w^as 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 Patagonia.
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 which the climate
of one hemisphere is made to depend upon the curve of that line
against which the sea is made to dash its waves in the other.

THE CLIMATES OF THE SEA. 377

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 ^ larch,
as we should find in the North 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
hemisphere is hotter than summer in the southern.

731. Pursuing the study of the climates of the sea, let us now
Sadden changes in tum to Plate VI. Here we see at a dance how

the water thermo- ,, , , , ,, t r .1

meter. the cold w^aters, as they come down irom 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 recepta^cle 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
inserted 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 16° colder than the
water at its side. It looked as though we might have been on
soundings.

732. By its discover}^ we have clearly unmasked the very seat

378 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of that agent which produces the Newfoundland fogs. It is
Th2 fogs of New- ■ spread out over an area frequently embracing seve-
fouud!;ind. Yed 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 he 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'^ N., for there, in the dead of winter, a thunder-storm is not
unusual.

733. These isothermal lines of 50^, 60^, 70^, 80°, etc., may
Aqueous isothermal lHustrato 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. It should be borne in mind that the lines of separation,
The meeting of cool as drawn ou Plate IX., between the cool and warm
and warm waters, wators, or, moro proporly speaking, between the
channels representing the great polar and equatorial flux and re-
flux, 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 flow^s — 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 line 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. Now, continuing for a moment our examination of Plate
The direction of aqne- IV., we are struck witli the fact that most of the

ous isotlipnns on op- ,, ,,. ,■, , /. ,-, ,

posit.' sides of tiie sea. thermal lines there drawn run from the western
side of the Atlantic towards the eastern, in a north-eastwardiy
direction, and that, as they approach the shores of this ocean on

TrDE-KIPS AND SEA DRIFT. 379

the east, they again turn down for lower latitudes and warmer
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 North Atlantic, of a large volume of
cooler waters. These are the waters which, having been first
heated up in the caldron (§ 726) of St. Roque, 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 performed their offices, they have cooled down;
but, obedient still to the " Mighty Voice " which the winds and
the waves obey, they now return by this channel along the
African shore to be again replenished wdth warmth, and to keep
up the system of beneficent and wholesome circulation designed
for the ocean.

CHAPTEE XYIII.

§ 740-772. TIDE-RIPS AND THE SEA DRIFT.

740. We never tire of the sea ; like the atmosphere, it is a labora-
The glories of the torv iu which wouders by processes the most exqui-

sea, and the destiny . *^ ,• n ■ ^ t , n i -^

of the nautilus. Site are Continually going on. its liora and its
fauna, its waves and its tides, its currents and its salts, all in them-
selves 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 marvellous, 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 compensations 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 with 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 sails so nicely trimmed to
the breeze ? Who pilots them, and what master hand holds the

380 PHYSICAL GEOGrEAPHY OF THE SEA, AlTD ITS METEOROLOGY.

helm ? What compass, and of Avhose workmanship, is that which
guides these delicate and graceful little argonauts from sea to
sea? Arriving 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 imperish-
able, 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.

7-il. There is a movement of the waters of the ocean which,
Drift described, though it bc 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. The object of Plate IX., therefore, is to illustrate, as far as
Plate IX. 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 being assumed
that the drift or flow is from the poles when the temperature of
the surface water is helow, and from the equatorial regions when

TIDE-RIPS AND SEA DRIET. 381

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 always well marked, and, as a rule, those of the
right bank, as high as the parallel of the thirty-rifth 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 Avater 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. Chamberlain, 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 quantities 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 Rennell Current of the North At-
lantic, the " connecting current " of the South, " Mentor's Counter
Drift," " Rossel's Drift of the South Pacific," etc., which run now
this way, now that, and which are frequently not felt by naviga-
tors 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 ap-
peared 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
w^arm, it is supposed that it had its temperature raised in warmer
latitudes, and therefore the channel in which it is found leads
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

382 PHYSIC^VL GEOGEAPHY OF THE SEA, AND ITS METEOEOLOGY.

lead from the polar regions. The arrow-heads point to the direc-
tion in which the waters are supposed to flow. Their rate, accord-
ing to the best information that I have obtained, is, at a mean,
only about four knots a day — rather less than more. Accord-
ingly, 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 Hum-
boldt'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 regions now
operates to send them back. This cause is to be found in the dif-
ference of the specific gravity at the two places. If, for instance^
these waters, when they commence their flow from the hyperbo-
rean 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 instructive. 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 in the middle.
In the North 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

TIDE-EIPS AND SEA DRIFT. 383

current from Baffin's Bay upon the Gulf Stream is strikingly-
beautiful .

743. Another feature of the sea expressed by this plate is a
The great bend ia sort of reflection or rccast of the shore-line in the
the Gulf Stream. temperature of the water. This feature is most
striking in the North Pacific and Indian Oceans. The remarkable
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 Arbella," 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 truly sublime
spectacle."

744. The *' horse-shoe " of cold in the warm water of the
The horse-shoe in North Pacific, though extending 5 degrees farther
the Japan current, towards the south, canuot 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 Bafiin'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 Russian America
do not favour the formation of large bergs. But, though we do
not find in the North Pacific the physical conditions 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. What beautiful, grand, and benign ideas do we not see
The animalcule of oxprcssed in that immeuso body of warm waters
the sea. which are gathered together in the middle of the
Pacific and Indian Oceans ! It is the womb of the sea. In it
coral islands innumerable have been fashioned, and pearls formed
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

384 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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. Capt. W. E. Kingman, of the American clipper ship the
Coloured patches. " Shootiug Star,'^ roports in his abstract log a
remarkable wliite patch, which he encountered in lat 8° 46' 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 Avas
rapidly growing white. Knov/ing that we were in a much fre-
quented 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. We 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, by
the aid of a 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 is the realm of reef-building corals, and of the wondrously-beautiful
assemblage of animals, vertebrate and invertebrate, that live among them or prey
upon them. Tiie brightest and most definite arrangements of colour are here dis-
played. It is the seat of maximum development of the majority of marine genera.
It has but few relations of identity with other provinces. The Red Sea and Persian
Gulf are its oflsets." — From Professor Forbes's Paper on the " Distribution of
Marine Life," Plate:^31st, Johnston's Physical Atlas, 2nd ed. ; Wm. Black'yood
and Soufi, Edinburgh "and Loudon, 1854.

TIDE-r.IPS AND SEA DRIFT. 385

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 xVth of an inch in diameter), which had the power of expand-
ing 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 concern, 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."

7-i7. These discolourations are no doubt caused by organisms

^'hence the Red Sea of the sca, but whether wholly animal or wholly

derives its name, vegetable, or whether sometimes the one and some-

2 0

386 PHYSICAL GEOOKAPHY OF THE SEA, AND ITS METEOROLOGY.

times the other, has not been satisfactorily ascertained. I have
had specimens of the colourinor matter sent to me from Ihe pink-
stained patches of the sea. They were animalculae well defined.
The tints which have given to the Red Sea its name may per-
haps 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 crystalli-
zation is to commence. Some microscopists maintain that this
tinge is imparted by the shells and other remains of infusoria
which have perished in the growing saltness of the water. The
Red Sea may be regarded, in a certain 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 unceasing^ly, 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. Red patches of water are most fre-
quently met with, but I have also observed white or milky
appearances, which at night I have known greatly to alarm navi-
gators by their being taken for shoals.

748. These teeming waters bear off through their several
The escape of warm channels the surplus heat of the tropics, and dis-
paciflc. perse 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 cmTent which
enters the Atlantic around Cape Horn, and changes into
warm again as it enters the Gulf of Guinea. It was owing to
this great southern flow from the coral regions that Captain Ross

TrDE-RiPS A^^) sea drift. 387"

was enabled to penetrate so much farther south than Captain
Wilkes on his voyage to the Antarctic. The North 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. The warm flow to the south from the middle of the
Ditto from the Indian Indian Oceau 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. But the most unexpected discovery of all is that of the
A wide current. Warm flow aloug the west coast of South Africa, its

junction with the Lagulhas current, called, higher up, the Mozam-
bique, and then their starting off as one stream to the south-
ward. The prevalent opinion used to be that the Lagulhas cur-
rent, which has its genesis in the Red 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 Navy, suggested
that this was probably not the case. This induced a special
investigation, and I found as he suggested, and as is represented
on Plate IX. Captain N. 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 warmer here (88 '^ 40'
south) than between the parallels of oo^ and 37^ south, is a pro-
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

2 c 2

388 PHYSICAL GEOGKAPHY OF THE SEA, AND ITS METEOROLOGY.

look with mucli 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 89° 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 con-
forms more nearlv to the limits assigned it in the diagram
(Plate IX.).

751. Instances of commotions in the sea at uncertain intervals
Commotions in the ^ro uot unfroquent. There are some remarkable
^^*- disturbances of the sort which I have not been able
wholly to account for. Near 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. Tide-rips present their most imposing aspect in the equa-
Humboidt'sdescrip- torial rogious. Humboldt met some in 34° N.,
tion of tide-rips. ^ud thus doscribcs 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 1 5th 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 N.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-

TIDE-RIPS AND SEA DRIFT. 389

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, in his East India Directory, thus remarks on
Horsburgh's. them, whou 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-
lon, there are often very strong ripplings, particularly in the
south-west monsoon ; these are alarming to persons unac-
quainted, for the broken water makes a great noise when the
ship is passing 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 consider-
able 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."

7oi. Captain Higgins, of the " Maria," when bound from New
j'ide-rips in the York to Brazil, thus describes, in his abstract log,
Atlantic. Q^Q q£ thcso " tldc-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

390 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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. Captain Wakeman, of the " Adelaide," in January, 1856,
Mockvigias. lat. ir 21' N., long. 33^ 33' W., encountered
'' tide-rips " which broke and foamed vnth 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 lon<x narrow ridojes. 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
ail on board. We have had a current of fifteen miles going west.
i have often noticed tide-rips in tiiis part of the ocean before,
particularly when bound home (for I have never been where I
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
recfard to the rudder."

TIDE-KIPS AND SEA DEIFT. 391

756. But, besides tide-rips, bores, and eagres,* there are the
Bores, eagres, and the sudden disFuptions in the ice which arctic voya-

^arthquake wave of ■ n /» , i • • i i • i

Lisbon. gcrs tell 01, the immense icebergs which occasion-

ally appear in groups near certain latitudes, the variable character

* The bores of India, of the Bay of Fundy, and the Amazon, are the most
celebrated. They are a tremulous tidal wave, which at stated periods comes
rolling in fi'om the sea, threatening to overwhelm and ingulf everything that
moves on the beach. Tijis wave is described, especially in the Bay of Fundy, as
being many feet high ; and it is said oftentimes to overtake deer, swine, and other
wild beasts that feed or lick on the beach, and to swallow them up before the
swiftest of foot among them have tune to escape. The swine, as they feed on
mus.sels at low water, are said to snutf the "'bore," either by sound or smell, and
sometimes to dasli off to the clifls at great speed before it rolls on.

The eagre is the bore of Tsien-Tang River. It is thus described by Dr. Mac-
;gowan, in a paper before the Royal Asiatic Society, 12 January, 1853, and as seen
by him from the city of Hang-chow, in 1848 : —

" At tlie 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 atioat, are
suddenly left high and dry on a strand nearly two miles in widtli, which the
returning wave as quickly floods. It is not until tlie tide rushes beyond tlie mouth
of the river that it becomes elevated to a lofty wave constituting the eagre, whicli
attains its greatest magnitude opposite the city of Hang-chow. Generally tliere is
nothing in its aspect, except on the third dny of the second montii, and on the
eighteenth of the eighth, or at the spring -tide about the period of the vernal and
autumnal 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 opposition, the eagre comses up the river witli
liardly less majesty than when paying its ordinary periodical visit. On one of
these unusual occasions, when I was travelling in native costume, I had an oppor-
tunity 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 suburb,-?
extend several miles along the banks. As the hour of flood-tide approached,
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-AVaye Temple, which
iifforded a good view of the entire scene. On a sudden, all traffic in tlie tlironged
mart was suspended, porters cleared the front street of every description of mer-
chandise, boatmen ceased lading and unlacUng 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, fi'om 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 ghttering white cable, stretched athwart the river at its mouth, as
tlir down as the eye could reach. Its noise, compared by Chinese poets to that of
thunder, speedily drowned that of the boatmen ; and as it advanced with prodi-
gious velocity — at the rate, I should judge, of twenty-five miles an hour — it
'.issumed the appearance of an alabaster wall, or, rather, of a cataract four or five
inQes across, and about thirty feet high, moving bodily onward. Soon it reached
the advanced guard of the immense assemblage of vessels awaiting its approach.
Knowing that the ]x>re of the Hooghly, which scarcely deserves mention in con-
nection with the one' before me, invariably overturned boats whicli were not
skilfully managed, I could not but feel apprehensive for the lives of the floating

392 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of all the currents of the sea — now fast, now slow (§ 401), now run-
ning 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.

757. Few persons have ever taken the trouble to compute
Rains at soa and their (^ 402) how uiuch the fall of B> sluffle iuch of raiu

effect upou its equi- ^"^ •',. • ' ,^ i i

librium. over an extensive region m the sea, or now much

multitude. As the foaming wall of water dashed impetuously onward, they were
silenced, all being intensely occupied in keeping their prows towards the wave
which threatened to submerge everytliing 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 half way among the craft. On one side they were
quietly reposing on the surface of the unruffled stream, while those on the netlier
portion were pitching and heaving in tumultuous confusion on the flood ; others
were scaling wutli the agility of salmon the formidable cascade. This 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 represent 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 recollec-
tion. My impression is that the fall was about twenty feet ; the Chinese say that
the rise and Ml 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 tlie Threnodia Augustalis, is, ' a tide swelling above another tide,' which he
says he had himself observed in the River Trent. Such, according to Chinese
oral accounts, is the character of the Tsien-Tang tides — a wave of considerable
height rushes suddenly in from the bay, which is soon followed by one much
larger. Other accounts represent three 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 particularly
directed to this feature of the eagre. The term should, perhaps, be more compre-
hensive, and express ' the instantaneous rise and advance of a tidal wave ;' the
Indian barbarism ' bore ' should be discarded altogether.

" A very short period elapsed between the passage of the eagre and the re-
sumption of trafflc. The vessels were soon attached to the shore again ; women
and children were occupied in gathering articles which the careless or unslcilful
had lost in the aquatic melee. The streets were drenched with spray, and a con-
siderable volume of water splashed over the banks into i^e head of the grand
canal, a few feet distant." — Vide Transactions of Chinese Branch of the Boyal
Asiatic Society.

TIDE-EIPS AND SEA DRIFT. 393

the change even of two or three degrees of temperature over a
few thousand square miles of surface, tends to disturb its equili-
brium, and consequentl}^ 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 calculated to exert so much force — which is
inconceivabl}^ great — in disturbing the equilibrium of the ocean.
If all the water discharged by the Mississippi River during the
year 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. Now
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 j 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, 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. Between the hottest hour of the day and the coldest
Ditto of cloud and hour of the night there is frequentl}^ a change of
sunshine. ^^^^ 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,
with day and night, and their heating and radiating processes.
And to make the case as strong as, with truth to nature, we may^
* Vide Admiral Smyth's Memoir of the Mediterranean, p. 125.

394 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 day, 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 temperature 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-pro-
ducing agents of the sea. That the gentle trade-winds do it all !

759. .Do not the clouds, night and day, now present themselves
Day and night, to US in a uew 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
tlie harmonies of the ocean.

760. The log-books of not less than 1843 vessels cruising on
Lo£?s overhauled for the polar sido of 35° S. havo, by the officers of the
k.^;p and ice. Observatory, been overhauled for kelp and ice. Of
tiiese, 367 (or one in five) mentioned kelp or sea-weed east of
Cape Horn ; 142 mention " rock-weed and drift matter" between
the previous meridian and lO'^ 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
along this line, however, between the meridians of 45"^ and 65^
Ju,, and the parallels of 42^ and 48^ S. These sargassos are
t^ketched with a free hand on Plate IX.

761. Sea-weed is frequently mentioned also by the homeward-
A sargasso in the bouud Australian traders on their way to Cape
Kouth Pacific. 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.

TIDE-RIPS AND SEA DRIFT. 395

762. The weedy space, marked as such, about the Falkland
sea-weed about the Islands, is probably not a true sargasso. The sea-
Faikiand Islands, weed reported there probably 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. The sargasso to the west of the Cape of Good Hope,
The African sargasso, 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. By going far enough south, icebergs maybe found on any
Icebergs. meridian ; but in searching for them, we can only

look where commerce carries our colleagues of the sea. Out of
the ISJjS tracks traced on the polar side of 35° S., only 10.9 make
mention of ice. Few of these went, except in doubling Cape
Horn, beyond the parallel of ^o° 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 io^ W. and 55° E.

765. As a rule, the bergs which are the largest last longest,
The largest drift and approach nearest to the equator. Here, then,
farthest. -g ^jj^ 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 we>terly winds. Their course, therefore, was probably
not due north, but to the east of that rhomb.

766. Tracing this line of drift, then, backward in a soulh-
The line of antarctic Westerly direction, it should guide us to that ]:)art
*^"''- 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. Arrived at this point, fiords, deep bays, and capacious

396 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

gulfs loom up before the imagination, reminding us to ask the
Necessity for, and quostion, Is there uot embosoniod in the antarctic
arcuJe^xpecUtion.^* continent a Mediterranean, the shores of which are
favourable to the growth and the launching of icebergs of tre-
mendous size ? and is not the entrance to this sea near the
meridian of Cape Horn, perhaps to the west of it ? Circum-
stances 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 noiv : 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 notv be
sure to make.

768. In those regions there are doubtless elements of commer-
Commerciai conside- cial Wealth in the number of seals and abundance
rations. of whalos, 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 therefore we may infer that their
markets abound w^ith the most excellent fish. The fisheries of
Newfoundland and New 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 watei\ Neither
India, nor the east coasts of Africa and South America, where
the warm waters are, are celebrated for their fish.

769. Three thousand American vessels, it is said, are engaged
Value of the fisheries, 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.

STORMS, HURRICANES, AND TYPHOONS. 397

770. The sperm whale is a warm-water fish. The right whale
Sperm whales, 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.
Cliarts showing the results have been published ; they form a
part of the series of Maury's AVind and Current Charts.

771. In the course of these investigations, the discovery was
A sea of fire to them, 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. With these remarks, and the explanation given on Plate
Right whales. 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.

CHAPTER XIX.

§ 781-808. — STORMS, HURRICANES, AND TYPHOONS.

781. Plate Y. is constructed from data furnished by the
Plate V. 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 de-
grees square, ^. e. five degrees of latitude by five degrees of longi-
tude, 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 whatever
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

398 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS 5IETE0R0L0GY.

the sixteen points of the compass, i. e. for N., N.N.E., N E.,
E.N.E , and so on, omitting the &?/-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 £., W. by S., etc. Moreover, any attempt, for the present, at
greater nicety w^ould 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 wnnd caused by the rate at which the vessel may
be moving^ throusfh the water, and the ansfle which her course
makes with the true direction of the wind. Bearing this expla-
nation in mind, the intelligent navigator w411 have no difficulty
in understanding the wind diagram (Plate V.), and in i'orming 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 YIII. As the compiler wades through log-book after log-
book, and scores do\vn in column after column, and upon line
after line, mark upon mark, he at last finds that, under the
month and from the 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 until 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 enahle me to record the calms and the prevailing direction 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.N.E., 1; E., 0; ESE., 1; S.E., 4; S S K, 2; S., 25
S.S.W., 45; S.W., 93; W.S.W., 24; W., 47; W.N.W., ]7
N.W., 15 ; N.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,

STORMS, HURRICANES, AND TYPHOONS. 399

tlie wind in May sets one third of the time from Avest. But in
A, which 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
IX day during the month of May. In B, notice the great " sun
swing " of the winds in September, indicating tliat the change
from summer to winter, in that region, is sudden and violent ;
from winter to summer, 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 Observator}^

782. The China seas are celebrated for their furious gales of
Typhoons. wiud, kuown among seamen as typhoons and white

squalls. The seas are included on the plate (VIII.) as within
the region of the monsoons of the Indian Ocean. But the mon-
soons 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 V. exhibits the monsoons very clearly in a
part of this sea. In the square between 15° and 20^ north, 110°
and 115° 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 equihbrium 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 t}^hoons and white
squalls, are most dreaded.

783. In like manner, the Mauritius hurricanes, or the cyclones
The Mauritius hurri- of the Indian Oceau, occur during the unsettled
c'^^s- 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 deep.

400 PHYSICAL GEOGRAPHY OF THE SKI, AND ITS METEOROLOGY.

784. So, too, with the West India hurricanes of the Atlantic ;
The West India theso winds are most apt to occur during the
hurricanes. months of August and September. There is,
therefore, 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 New 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 simul-
taneously 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 hurri-
cane season. On the contrary, the South Indian Ocean has its
hurricane season in the opposite season of the year, and when the
north-west monsoon prevails in the East Indian Archipelago."

785. Under the head of hurricanes, typhoons, and tornadoes, I
Tiie cyclone theory, iucludo all those galos of wiud whicli are known as
cyclones. These have been treated of by Red field in America,
Eeid in England, Thorn of Mauritius, and Piddington of Calcutta,
with marked ability, and in special works. I 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 iviili the hands of a watch in the southern hemisphere ; that
nearer the centre or vorte^x 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 baro-
meter 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 between the parallels of 10° and 20° north and
south, travelling to the westward in either hemisphere, but in-
creasing their distance from the equator, until they reach the
parallel of 25° or 30°, when they turn towards the east, or
*• recurvate," but continue to increase their distance from the

STORMS, HURRICANES, AND TYPHOONS. 401

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. The questions why these storms should recurve, and wh^^
Puzzling questions, they should travel as they do, and why they should
turn with the hands of a watch 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
whirls in an angry flood, which, though they revolve, yet they
are borne down 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 storm has, in consequence of diurnal rota-
tion, a greater velocity than its polar edge. There seems, how-
ever, to be less difficulty 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 which 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. Many of the phenomena connected with tliese storms still
Espy's theory, 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
towards 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 toward 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 days to
go from the Mississippi to St. John's, Newfoundland ; 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 low baro-
meter, in which there is Httle or no wind, blows tovv-p.rd it. etc.,

402 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

and, in support of these positions, he advanced this theory:
" When the air in any locality acquires a higlier temperature or
a higher dew-point than that of the sorrounding regions, it is
specifically lighter, and will ascend ; in ascending, it comes under
less pressure, and expands ; in expanding 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 hundred 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 ascend, 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
condensed, by the cold of expansion from diminished pressure, one
hundredth of its weight of vapour, it will be about forty-eight
degrees less cold than it would have been if it had no vapour 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
height ; it will, therefore (without making any allowance for the
higher dew-point of the ascending current), be about one tenth
lighter than the surrounding colder air, and, of course, it will con-
tinue 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 upmoving 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

STORMS, HURRICANES, AKD TYPHOONS.

403

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. According to Dove's " Law of Rotation," which is said to
Dove's law. hold good in the northern hemisphere, and is sup-
posed 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

•w-

be in S. lat. off Cape Horn as at a, with a low barometer to the
north 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
he directly for the centre C ; consequently, a ship so placed

* The Fourth Meteorological Eeport of Prof. James P. Espy ; Senate Doc. 65,
3-lth Congress, 3rd session.

2 D 2

404 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

would report the storm as commencing with the wind at south.
For the sake of ilhistration, 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 gradually en-
large itself by broad spreading, like a circle on the water, until
it be compassed by a circle with a radius CS, 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, Sa', to the westward ; and the arrow (^ a, representing
a S.S.E. Avind, 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 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 ivatch ; but this is as it
should be — it hauls one way, and marches the other. After pass-
ing a, 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 a a,
continuing on with a circular motion, is represented thencefor-
ward in its course by the curved aiTows 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 prime vertical 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 composi-
tion and resolution of other forces also, such as those of traction,
aberration, and the like, before we can resolve the whirlwind.

789. But the cyclonologists do not locate their storms in such
r.eniouiiii's formula, 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

STORMS, HURRICANES, AND TYPHOONS.

405

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 efflux 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 difiference of barometric pressure would always be fol-
lowed by a wind of the same force of velocity. By expanding
Bernouilli's formula for the velocity of gas jets under given pres-
sures, 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 effective difference of 0.006 inch 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.

Velocity of Wind.

Horizontal Pressure.

Strength of Wind.

0.006 in

0.010

0.016

0,06

O.U

0.2.5

0.41

ch

7 miles per hour.
14 „
21 „
41 „
61 „
82 „
92 „

0 . 2 lbs. per sq. foot.

0.9 „

1.9 „

7.5 „
16.7 „
30.7 „
37.9 „

Gentle air.
Light breeze.
Good sailing breeze.
A gale.
Great storm.
Tempest.
Devastating hurricane.

Changes, however, in the barometer, amounting to five or six
times these differences, are observed to take place at sea without
producing v/inds 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. But, in this view of the subject, the importance of a daily
Predicting storms, systoui of wcather roports 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 propor-
tions of one of the great practical questions of the age. We may
* See article Meteorologj', Encyclopaedia Britannica, 1857.

406 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS iMETEOEGLOGY.

conjecture, as the probable result of observation, that the greater
tlie 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 nume-
rical relation between the force of the wind and given barometric
differences for certain places in Holland. ' With the vievv of
ascertaining like relations for this country, it has been proposed
to establish a cordon of meteoroloorical stations over the United
States, each station being required to report daily to the Obser-
vatory 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 tm-
verse the Atlantic. Tlie contributions which the magnetic tele-
graph is capable of making for the advancement of meteorolog}'-
will enable us to warn the ships in our Gulf ports, as well as
those of Cuba, of the approach of every hurricane or tornado that
visits those res^ions.

791. But, returning to the cyclone theory: though the wind
The changing of the be blowing around in spirals against the hands of
wind in a cyclone, ^i^q watch, yet, from the fact that the centre about
which it is blowino^ is also travelling: alons^, the chano^es of the
wind, as observed by a vessel over which the storm is passing,
will not, under all circumstances, be against the sun in tlie
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 diagrarns " 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 con-
venient diameter, say 2J 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 tlieni 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

STORMS, HURRICANES, AND TYPHOONS. 407

will pass to the west, but the wind will change from S.E. to
S., and so on to the west, with the hands of a ivatch, though
it be revolving about the centre against the hands of a icatcli ;
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. Suppose that in the case before us tiie storm is travelling
The wind stronger to tlio north at the rate of 20 miles the hour, and
cther.^ 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 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 can-
cels the other, and there is, therefore, aline 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 wdnd blows harder on one
side than tlie other. This is the case in both liemispheres ; and
by handling these moving diagrams for illustration, the navigator
wall soon become familiar with the various problems for de-
termining theoretically the direction of the vortex, the course
it is travelling, its distance, etc. Therefore, when it is optional
with the navigator to pass the storrn on either side, he
should avoid the heavy side. These remarks apply to both
hemispheres.

793. Captain Toynbee asks if it rains more in one quarter of
The rainy quadrant a cycloue than another? In cyclones that travel
of a cyclone. ^^^^^ J supposo 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
brmgs most rain. The rain in a cyclone is supposed to come
from the moisture of that air which has blown its round and oone

408 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

up in the vortex ; then it expands, grows cool, and condenses its
vapour, which spreads out at top like a great mushroom in the
air, the liberated heat adding fury to the storm.

7.94). Such, briefly stated, are the two theories. They appear
Erroneous theories, 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 suggestions 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 arid round. The United States brig " Perry "
did this a few years ago in the West Indies ; and so did the
"Charles Heddle" in the East Indies: she went round and
round a cyclone five times.

795. From such observations as I have been able to obtain
The wind in a true upou the subject, I am iuduced to believe, with
spfrais! ^"^^ ^^ Thom, that the wind in a cyclone does not blow
round in a circle, but around in spirals. Nay, I go farther, and
conjecture that it is only w^ithin a certain distance of the vortex
that the wind gyrates, and that the gyrating column is never
liundreds 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 condensation 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 atmospheric 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, therefore, due to the
centrifugal force I hold to be not very great, though it is appre-
ciable to this extent : The storm having commenced revolving,
the flow of air into the vortex is retarded, not prevented, by cen-
trifugal tendency ; and this retardation assists in causing the
barometer to stand lower than it would if there were no revolu-
tion. Any one who has watched the little wliirlwinds 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

STORMS, HURRICANES, AND TYPHOONS. 409

which the centrifugal tendency will help to make a low barometer
at the centre of a cyclone.

796. The low barometer, the revolving storm, and the ascend-
An illustration, ing column roquiro for a postulate the approach by

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 l}y 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 whirlwind. 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 of a canal and watch them, you will see that
as they come within the influence of the "suck" they will
approach 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 fluid revolving within itself. The "suck" is funnel-
shaped. As it goes down, the lateral pressure of the water
increases ; it counteracts more and more the effect of centrifugal
force, and diminishes, by its increase, the size of the " suck."

797. So, too, with the little autumnal whirlwinds in the road
Dust whirlwinds and and ou the lawu : the dust, leaves, and trash will
water-spouts. ]^q swopt iu 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 whirlwinds pass
across the Potomac, raising from the river a regular water-spout,
and, when it reached- the land, it appeared as a common whirl-
wind, its course being marked, as usual, by a whirling column of

410 PHYSICAL GEOGPtAPHY OF THE SEA, AND ITS METEOROLOGY.

leaves and dust. These little whirlwinds are, I take it, the great
storms of the sea in miniature ; and a proper study of the minia-
ture on land may give us an idea of the great original on the ocean.

798. The unequally heated plain is thought to be the cause of
A vera causa, the ouo. But there are no unequally heated plains

at sea; nevertheless, the prmw??i mohile 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
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 pushes aside the upper air still more.

799. After much study, I find some difficulties about the
Objections to the cyclono thcor}^ that I cannot overcome. They are
^^""■y- of this sort: I cannot conceive it possible to have
a cyclone with a revolving and travelling disc 1000, or oOO
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 w^afer-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

* Since this was written, I liave had the privilege of examining at the Meteor.o
logical Department of the Board of Trade, Admiral Fitzroys admirable diagranis,

STOKMS, HL-ERICANES, AND TYPHOONS. 411

diurnal rotatioD 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
baronieter 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
himdred miles from A, and so far as to be clearly without the
reach of the whirl. Now, then, will not the air at e" 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 an
ellipse, a square, an oblong, or any figure, be it never so irregular?
d ^^~e^ ^' The trade-winds answer, showing

/['g^ r 77 — --— \ — the equatorial calm belt — an

\ — y-\^=..-~J. J:- oblong — as their place of meet-

(5-/ ing. They neither revolve nor

4^0:/ blow at right angles, with the

/ Aff^'''' \d\ ■^i'^^ ^^ their direction from the

^v' * '^ place of lotv barometer ; but

, B /' '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, merely because there is a low baro-
meter east of c" and north of d, require it always so to blow be-
cause, 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 destination ! 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, w^ould
differ with each other as to the centre of the storm. Each at
first would 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 ])e
according to the theory at c", but against it at d. The cyclono-
iogist in d would place the centre of the storm to the eastward

in MS., of the " Koyal Charter " storm of Octolx^r, 1859. It was a true cyclone — the
best type of one, and the most perfectly developed on a large scale that has ever
fallen nnder my observation. Its largest diameter did not measure less than 300
miles.

412 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

of him, as in the direction of d, but the other would place it to
the southward of him, as in the direction c . By the rule, ship
d 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 true type of the tornado (cyclone) at sea.

800. There are in the various parts of the storm at least
The three forces, throo forcos at work iu 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.) und 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. Hence it appears that in a storm the wind may shift from
The effect of each, any ouo of throo causos, 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°. Cy-
clones, there is reason to believe, are often whirlwinds in a storm.
This may be illustrated by referring again to our miniature
whirlwinds on the land ; 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 touch-
ing the ground again, and pursuing the former direction.

802. Observations have proved that this is the case on land,
A storm within a storm, and obsorvations have not established that this is
not the case at sea ; observations are wantmg upon this subject.
Tornadoes on the land often divide themselves, sending out

* See letter to Commodore Wiillerstorf, p. 457, vol. ii., 8th eJ., Maury's Sailing
Directions.

STORIJ

HURRICANES, AXD TYPHOONS.

413

branches, as it were. It remains to be seen whether cyclones do
not do the same at sea ; and whether, in those widespread 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 celebrated Black Sea storm of 1854, which did so
The Black Sea storm Hiuch damage to the allied fleet, is still maintained
**^^''^^*' by some to be a true cyclone ; and by the observa-
tions 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 cyclone, it will puzzle
any one to make anything of them. Admiral Fitzroy, 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. The cyclones of the North Atlantic take their rise gene-
Cyciones of the rally (§ 785) somowhero between the parallels of
North Atlantic. IQ^ and 20' uorth. 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.

The hurricane

se.sou. ^qq]^ of Storms

805. The following table is from Birt's Hand-

Average Numher 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.

Dec.

Tot:a

West Indies .

1

2

4

15

36

25

27

1

2

113

S. ladian Ocean

9

13

10

8

4

..

..

• •

1

1

4

3

53

Mauritius . .

9

15

lo

8

..

6

53

Buy of Bengal .

1

1

1

7

3

1

7

6

3

30

China Sea . .

*"

••

••

2

5

5

18

10

6

46

414 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. '

806. The vortex of a cyclone is often and aptly compared to a
Cyclones in the Mis- Hieteor. I liavo often observcd the paths of such
sissippi Valley. 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. I
hcve seen trees three or four feet in diameter torn up by the
roots, and the top, with its limbs, lying next the hole whence the
roots came. Nevertheless, the passage of the meteor, whose nar-
row path was marked by devastation, would create a great com-
motion 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° N., 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 ; but 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. In the extra-tropical regions of each hemisphere furious
Kxtra-tropicai gales, galcs of wiud also occur. Ouo of tliose, 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 incredible hardships, exer-
tions, and sufferings. Some months after this disaster I received
by the California mail the abstract log of the fine clipper ship
" Eagle Wing " (Ebenezer H. Linnell), from Boston to San Fran-

STORMS, HUERICANES, AND TYPHOONS. 415

CISCO. She encountered the ill-fated steamer's gale, and thus
describes it: '^December 24:th. 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 lying with her lee rail under
w^ater, nearly on her beam-ends. At 1 30 A.M. the fore and
main top-gallant-masts went over the side, it blowing a perfect
hurricane. At 8 A.M., moderated ; a sea took away jib-boom
and bowsprit cap. In my thirty- one years' experience at sea, I
have never seen a typhoon or hurricane so severe. Lost two men
overboard — saved one. Stove skylight, 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, July, August, and September. This appears to
be the time 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 (§ 172) 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, ^. e.,
south-west.

808. Storm and Kain Charts for the Atlantic Ocean have
Storm and Rain Charts, already boou 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 fre-
quency of calms, fogs, rain, thunder, and lightning. These charts
are very instructive. They show that that half of the atmo-
spherical coating of the earth which covers the northern hemi-
sphere— 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.

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

CHAPTEE XX.

§ 811-842. THE WINDS OF THE SOUTHERN HEMISPHERE.

811. A WORK of this sort, which is progressive, must necessarily
Repetition often ne- hear with it more or less of repetition. It em-
cessary. hodies 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
the fleets that 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 an example.

812. The facts stated ui Chap. XY. go to show that the south-
The S.E. and N.E. gast tradc-'svinds are stronger than the north-east,
a batauce. " ^"* ^"^ The baromctcr tells us (§ 643) that between the
parallels of 5° and 20° the south-east trade-winds bear a super-
incumbent 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 ah', ought to force the south-east trade-winds from under
it more rapidly than the hghter pressure forces the north-east.
Observations showing that such is or is not the case should not be
ignored.

813. I have the separate and independent e\ddence from every
Observations by 2235 vcsscl in a fleet numbering no less than 2235 sail to
vessels. qJiqw that the S.E. are stronger than the N.E. trades.
AU of these vessels passed through both systems of trade-winds.
The Imots run per horn* 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. 417. The comparison is confined to the rate of sailing
between the parallels of 10° and 25°. because this is the^belt of
steadiest trades.

THE yvmDS OF THE SOUTHEEN HEMISPHERE.

417

Average

S2)eed of

FesseZs sen'

Ze'rjr/ throuqh the Trade-winds of the North

Atlantic and South Indian Oceans.

Knots

per Hour from

10° to 150.

150 to 20^.

20° to 250.

Average.

Course steered through

ui

Mpi

it

-1

^ 2

N.E. Trades.
(N. Atlantic.)

S.E. Trades.
(I. Ocean.)

tH

Ch

H

r^

H

f^

Ch

6i

January

8

6i

7*

7

6

6

7

N. 49° W.

S. 69° W.

February .

7*

6

6

6f

5

6

6

6

N. 46 W.

»>

March . ,

8

7

7

7

5i

6^

6f

6f

N. 47 W.

„

April . .

7i

7

5f

7f

4

6

6

6f

N. 48 W.

S. 70° W.

May. . .

8i

8

6f

7*

6*

6

7

7

N. 46 W.

,,

June. . .

9

7*

8

7f

5i

7

7*

7^

N. 43 W.

,,

July. . .

5i

8

8

8J

6i

7

6*

7f

N. 46 W.

„

August . .

4f

7f

6

8i

4f

7*

5

7f

N. 40 W.

S. 69^ W.

September .

5*

8i

6

8

4

6f

5

7^

N. 50 W.

,,

October

7*

8i

6f

8

6

5f

6f

7i

N. 45 W.

,,

November .

6

8

6

7

4*

5}

5*

6f

N. 49 W.

,,

December .

6

7

61
7f

61
6f

6f
7-^

51 ,
5i

5

6i

6

6

N. 48 W.

"

Means .

6.^

7

N. 47° W.

S. 691° w.

Ayerage course steered through the N.E. trades ^N. Atlantic Ocean), N.W. ^ W.

S.E. trades (South Indian „ ), W.S.W.

Average ditto through

f/ie Trade-windi

of the North and South Atlantic Oceans.

Knots

per Hour from

MOKTH.

25° to 20='.

20° to 15=5.

15^ to 1(P.

Average.

Course steered through

i^ 2

^1

02 .=5

^'1
^2

S.E. Trades.
(S. Atlantic.)

N.E. Trades.
(X. Atlantic.)

^

H

H

f-l

^

H

January .

6

5

5f

54

5f

7*

6

6

N. 54° W.

S. 21° E.

February .

4^

5

51

6*

6

7

5i

6

N. 55 W.

S. 25 E.

March . .

64

4f

6

64

6

74

6

6i

N. 55 W.

S. 224 E.

April . .

51

5^

5*

6^

6f

7f

6

6J

N. 53 W.

S. 224 E.

May . . .

5f

5

5f

64

64

7

6

6

N. 55 W.

S. 24f E.

June . .

5?

6

6

6

7

5

6^

5f

N. 55 W.

S. 28 E.

July. . .

5i

7

6

74

c^

44

6

6

N. 55 W.

S. 27 E.

August . .

5

5i

5f

64

6

4

5f

H

N. 55 W.

S. 284 E.

September .

5i

3J

6^

54

7

5

6}

4*

N. 5.5 W.

S. 22i E.

October

5^

4}

6

44

51

4f

54

4*

N. 56 W.

S. 20 E.

Noyember .

64

4

64

5i

6J

5f

64

5

N. 55 W.

S. 22i E.

December .

5J
5|

4f
5

5f

of

6

6i

7f

51

0

N. 55 W.

S. 23 E.

Means .

6

6i

6

6

51

N. 55° W.

S. 24° E.

Ayerage course steered through the S.E. trades (S. Atlantic), N.W. by W.

X.E. trades (N. Atlantic), S.S.E.
2 E

418 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

814. It is well to observe, that on each of these three oceans,
Ships used as anemo- 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 quartermg 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 6 J
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 average strength of the trades here
cannot be fairly compared with the 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 afores^d 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 anemometers that wiU reaUy 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, T\dth 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. Let us apply to the average speed through the South Atlan-
veiocity of the trade- tic and Indian Occans such a correction. Through
^^•^s- the former the wind is aft ; through the latter, quar-
tering. K we aUow two knots as a correction for the one and one
as a correction for the other, we shall not be greatly out. Applying
such corrections, we may state the speed of a mean ship saihiig with
average trades just abaft the beam to be as foUows :

Through the N.E. of the N. Atlantic . . 6 J 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 experiments
(note pp. 343-5) which Admiral Chabannes, in command of the French fleet on
the coast of BrazO, has kindly caused to be made by the brig " Zebra," but by
experiments whichjhe has subsequently made with the frigate *' Alceste," as per

THE WINDS OF THE SOUTHERN HEMISPHEEE. 419'

I do not take into this comparison the force of the N.E. trades on
a S.S.E. course (§ 813), because the vnnds 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 ^M.,and so tlieij should he if there he a
crossing of winds in the calm helt of Capricorn.

816. The counter- trades of the southern hemisphere move, as
Ditto of the counter- beforo statcd, towards their pole more steadily and
tra^ies. briskly than do the counter-trades of the northern

hemisphere. To give an idea of the difference of the strength of
these two winds, I cite the fact that vessels saihng 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

the following extracts of a letter, just received from that distinguished officer,
dated —

"Frigate 'L'Alceste,' at Monte Video, May 10, 1860.

" Dear Sik, — 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 j^assage 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 squadi'on of sailing vessels
witii which I could put to sea, and devote myself to all these researches. _ Un-
fortunately, I have only steamers in my division, with the exception of the frigate
which carries my flag, "and political circumstances have retained me almost con-
stantly in the La Plata. I am now approaching 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 dming this voyage to make
a series of experiments such as you have indicated, in order to establish the rela-
tive force of the trade-winds in the southern and in the northern hemisphere-
determining the difierences of velocity of the frigate with wind aft and wind abeam.

" In my last letter, of tlie 25th of January, I gave you the results obtamed 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
difterent 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 sailmg 6 knots, with wind fidl 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 the experiments which
I shall have made in this respect, Ixith 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 soma
hours daily whenever circumstances will permit."

2 E 2

420 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOEOLOGY.

day. Consequently, the counter-trades of the southern hemi-
sphere transport in given times larger volumes of air towards the
south than our counter- trades do towards the north. This air re-
turns to the tropical calm belts as an upper current. If, descend-
ing 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,

817. Arrived at this point, another view in the field of conjec-
Tbe waves they get up. ture 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 con-
stant 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 mariners.
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 pre-
vail there. The waves driven before these winds assume in their
regularity of form^ in the magnitude of their proportions, and in
the stateliness of their march, an aspect of majestic grandeur that
the billows of the sea never attain elsewhere. 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" mnds do. There the billow^s, chasing
each other like skipping hills, look, with their rounded crests
and deep hollows, more like mountains rollmg over a plain than
the waves which we are accustomed to see. Many days of con-
stant blowing over a wide expanse of ocean are reqmred to get
up such waves. It is these winds and waves which, on the voy-
age to and from Australia, have enabled the modern chpper-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, Seeing, therefore, that we can bring in such a variety of
A meteorological f^cts and circumstauces, all tending to show that the
corouary. gjg^ trade-winds are stronger than the N.E., and

THE WINDS OF THE SOUTHERN HEMISPHERE. 421

that the westerly winds which prevail on the polar side of 40° S.
are stronger and more constant than then- 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
atmospherical 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 arrested in
their course, or turned back in their circuits, as are those of the
north. Consequently, moreover, we should not, either in the
trades or the counter-trades of the southern hemisphere, look for as
many calms as in those of the northern systems.

819. AVherefore, holding to this corollary, we may consider the
Facts established, followiug as cstabHshed facts in the meteorology 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 hable to interruption in their circuits than the
S.W., the counter- trades of the north ; that the atmospherical cumu-
lation is more regular and brisk in the southern 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 coroUary just
stated. But observations, also, as weU as mathematically-drawn
mferences, 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. These premises being admitted, we may ascend another
Atmospherical cir- rouud ou this ladder, and arsfue that, since the atmo-
iQ the southern than sphcro movos moro briskly and in more constant
sphere?'''''"""'''™" streams through its general channels of circulation
in the southern than it does through them in the northern hemi-
sphere ; 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 by the way, so as to blow in gales from the direc-

422 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

tion opposite to that in which the general circulation carries it.
The atmosphere, in its movements along its regular channels of
circulation, may be hkened, 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. Not so the fast ;
it has not time to stop often or to run back far ; neither have the
counter-trades of 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. We shall appeal to observations for the correctness of this
Gales in the two Qoujecture, and claim for it, also, as presently vvill
hemispheres. appear, tho dignity of an established truth in marine

meteorology.

Average Number (to the 1000 Observations) of Gales, with Easting and with Westing
in them, betioeen the corresponding Parallels in the North and South Atlantic, as
shown by the Storm and Bain Charts.

Between 40° and 45°,
Between 45° and 50°,
Between 50° and 55°

Number of Observations . .
Gales in 1000 do., with easting .

„ „ „ westing

Number of Observations . .
Gales in 1000 do., with easting .

„ „ „ westing

Number of Observations . .

Gales in 1000 do., with easting

westing

North.

South.

17,274

8,756

23

12

66

82

11,425

5,548

24

1

106

61

4,816

5,169

24

10

144

97

Thus the Storm and Rain 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 southern,
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 aroimd Cape Horn.
That part of this route which hes between 40^ and 55° S., is under
the lee of South America; and Patagonia, that hes east of the
Andes, is almost a rainless region ; consequently, we might expect

THE Wns'BS OF THE SOUTHERN HEMISPHESE.

423

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 state-
ment would probably be much greater did our observations extend
entirely across the South, as they do across the North Atlantic.
But as it is, the contrast is very striMng. In some aspects, the
meteorological agents of the two hemispheres, especially those
forces which control the winds and the weather, diSer veiy much.
The difference is so wide as to suggest greater regularity and
rapidity of circulation on one side of the equator than on the
other.

822. Average Number of Calms to the 1000 Ohservatiom between the Parallels of
Calms in the two 30° and 55^, 171 the North and South Atlantic, and between the
hemispheres. Parallels of 30^ and 60*^ in the North and South Pacific Oceans,

as shown by the Pilot Charts.

Atlantic.

Pacific.

Between the Parallels of

North.

South.

North.

South.

30° and 35° No. of observations
Calms to the 1000 do

12,935

46
22,136

37
16,363

45
8,907

38
3,519

40

15,842

26
23,439

24
8,203

27
4,183

25
3,660

16

22,730

34
13,939

31
12,400

53
15,897

35
32,804

32
15,470

43

44,846
35

35° and 40°, No. of observations
Cahns to the 1000 do . . .

66,275
23

40° and 45°, No. of observations
Calms to the 1000 do. . . .

31,889
23

45° and 50° No, of observations
Calms to the 1000 do. , . .

4,940
21

50° and 55° No. of observations
Calms to the 1000 do. . . .

9,728
17

55° and 60°, No. of observations
Calms to the 1000 do. . . .

9,111
21

Total No. of observations . . .

63.050

55,327

113,240

166,829

Average calms to the 1000 do.

41

24

39

25

Each one of these observations embraces a period of eight hom'S ; 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 dif-
ference of the atmospherical stabihty in the two hemispheres.

823. If we would discover the seat of those forces which produce
The propelling power this difference in the dynamical status of the tvro
of the winds. . ., ^Q^^ aerial oceans that envelop our planet, we should

424 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

search for them in the unequal distribution of land and water over
the two heniispheres. 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 moun-
tain ranges always. In the other there is but httle land and less
snow. On the polar side of 40° S. especially, if we except the
smaU remnant of this continent that protrudes beyond that parallel
in the dhection of Cape Horn, there is scarcely an island. AU 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 moistm-e, which, with every change of temperature, is either
increased by farther evaporation or diminished by temporary conden-
sation. The loropelling i^ower of the winds in the southern hemi-
sjphere resides chiefly in the laient heat of the vapour which they
such up from the engirdling sea 07i the polar side of Capricorn.

824. The Storm and Eain Charts show that within the trade-
stom aiS^S^ ™^^ regions of both hemispheres the calm and rain
Charts. curvcs are symmetrical; that in the extra-tropical
regions the symmetry is between the cahn and fog curves; and
also, especially in the southern hemisphere, between the gale and
rain cmwes. Lieutenant Van Gough, of the Dutch Navy, in an
interesting paper on the connection between storms near the Cape
of Grood Hope and the temperature of the sea,* presents a storm
and rain chart for that region. It is founded on 17,810 observa-
tions, 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, Washmgton, hold
out the same idea. Let us examine, expand, and explain this fact.

825. We ascribe the trade-winds to the equatorial calm-belt.
The "brave west But to what sliall WO ascribo the counter-ti'ades, par-
^"efecu^rTin^he ticularly of the southern hemisphere, which blow
antarctic regions. wi\h as much regularity towards the pole as the
north-east trades of the Atlantic do towards the equator ? Shall wo
say that those winds are dra^n towards the south pole by heat^
which causes them to exj^and and ascend in the antarctic regions ?
It sounds somewhat paradoxical to say that heat causes the winds

* De Stormen nabij de Kaap de Goede Hope in verband beschouwd met de
Temperatuur der Zee.

THE WIKDS OF THE SOUTHERN HE3IISPHERE. 425

to blow towards tlie poles as well as towards the equator ; but, after
a little explanation, and the passing in re\'iew of a few facts and
circumstances, 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 hemi-
sphere ; 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 quantitive 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 hyetographic
measm'ements for quantity at sea ; there the determinations are
mostly numerical. Our observers report the " times " of precipita-
tion, 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. With the view of comparing the rains at sea between the
Relative frequency of parallels of 55° and 60°, both in the North and
rains and gales at sea. gouth 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

rains, 1105
64

N. Atlantic, 256

Kains, „ „ . . S.Atlantic, 131 ; 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 ? Observations do-
not tell, but there seems to be a philosopliical reason why it should
rain not only oftener, but more copiously at sea, especially in the
extra-tropical regions, in the southern hemisphere than in those of
the northern. Ou the polar side of 40° N., for example, the land_

426 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

is stretched out in continental masses, upon the thirsty bosom of
which, when the air drops do"\vn its load of moisture, only a portion
of it can be taken up 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 replenishes the air with moisture 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-pouit prevails. The rivers to
the north of 40°, I reckon, could not, if they were all converted
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 m the other hemisphere.

827. On the polar side of 40° S., near Cape Horn, the gauge of
The rain-fall of Cape Captaius King and Fitzroy showed a rain-fall of
po^iij'i'e!"^ ^"^' 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 m 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
impossibihty 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 smface
enough to afford vapour for such an amount of precipitation. In
the North Pacific the water sm-face 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 fi'om the sea. More-
over, if the westerly ^wls 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 abruptly out of the
sea, or separated from it only by lowlands — that seems to be neces-

THE WIXDS OF THE SOUTHERIT HEMISPHEBE. 427

sary to bring clo^^vn tlie 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. Com-
puting 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 any-
where 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. Now, considering the extent of water surface on the polar
Influence of highlands side of the south-cast trado-wiud belt, we see no
upon precipitation, reasou why, ou tlicse parallels, the engirdling air of
that great watery zone of the south should not, entirely around the
earth, be as heavily charged with vapom* as was that which di'opped
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 condensa-
tion and the liberation of its latent heat ; and we make, as we shall
proceed to show, no violent supposition, if, in attempting to explahi
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 in-
quu'e how far precipitation in the supposed cloud region of the
south may assist in giving force and regularity to the winds of the
southern hemisphere.

829. If we take a measure, as a cubic foot, of ice at zero, and
The latent heat of ^pply heat to it by mcaus of a steady flame that will
vapour. gj^g Qg- ]^g^^ ^^ ^ uniform rate, and in such quantities
that just enough heat may be impai'ted to the ice to raise its tem-
peratm-e 1° a minute, we shall find that at the end of 32 minutes
the ice wiU be at 32^. The ice will now begin to melt ; but it
and its water, the heat being continued, will remain at 32° for
140 minutes, when all the ice mil have become water at 32°.t
This 140° of heat, which is enough to raise the temperature of 140

* Eeport of the British Association for 1852, p. 256.
t See Espy's Philosophy of Storms.

428 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS ]METEOROLOGY.

cubic feet of ice one degree from any point below 32^, bas been
rendered latent in tbe process of liquefaction. Freeze tbis water
again, and tbis latent beat will become sensible beat, for beat no
more tban ponderable matter can be annibilated. But if, after tbe
cubic foot of ice bas been converted into water at 32°, we continue
tbe uniform supply of beat as before and at tbe same rate, tbe water
will, at the expiration of 180 minutes more, reacb tbe temperature
of 212^ — tbe boiling-point — and at tbis temperature it will remain
for 1030 minutes, notwithstanding the continuous supply of heat
during tbe interval. At the expiration of this 1030 minutes of
boiling beat, tbe last drop of water will have been converted into
steam ; but the temperature of the steam will be that only of the
boibng water ; thus, in the evaporation of every measure of water,
heat enough is rendered latent dming tbe process to raise tbe tem-
perature of 1030 such measures one degree. If this vapour be now
condensed, tbis latent heat will be set free and become sensible
heat again. Hence we perceive that eveiy rain-drop that falls
from tbe sky has, in its process of condensation, evolved beat enough
to raise one degree tbe temperatm'e of 1030 rain-drops. But if
instead of the liquid state, as rain, it come down in tbe solid state,
as bail or snow, then the beat of fluidity, amounting to enough to
raise tbe temperatm-e of 140 additional drops one degree, is also
set free.

830. We have in tbis fact a clew to the violent wind which
The cause of the usuallv accompanics hail-storms. In the bail-storm

boisterous weather f , . , \ -, . t i ^ o, j

off Cape Horn. cougelation takcs place immediately aiter condensa-
tion, and so quickly that the heat evolved dm^uig the two processes
may be considered as of one evolution. Consequently, tbe upper
an 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 osving, in a great measm^e, to tbis heavy Pata-
gonian rain-fall. The latent heat which is liberated by tbe vapour
as it is condensed into rain there, has the effect of producing a
great intumescence in the air of the upper regions round about
them, which in tmTi produces commotion in the air below. But
this is digressive. Therefore let us take up tbe broken thread, and
suppose, merely for illustration, such a rain-fall as King and Fitz-
roy encountered in Patagonia to have taken place under the sup-
posed cloud region of the antarctic circle, and to have been bail 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

THE WINDS OF THE SOUTHERN HEMISPHERE. 429

from freezing to boiling six and a half times as much water as fell.
But if the supposed antarctic precipitation come down in the shape
of rain, then the heat set free would be sufficient only to raise from
freezing to boiling about 5J 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 as much vapour as it took to make the Pata-
gonian 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 feU as snow or hail. The latent heat set free among the
clouds dm'ing 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 J feet in depth. The unknown area of the ant-
arctic is eight millions of square miles. We now see how the cold
of the poles, by facihtating precipitation, is made to react and develop
heat to expand the air, and give force to the winds.

831, Thus we obtain another point of view fi'om which we may
Offices of icebergs in contemplate, in a new aspect, the icebergs which the

the meteorological .^ '. t r> ii • i -i

machinery. autarctic rcgious seuQ lorth m such masses and num-

bers. They are a part of the meteorological machinery of our
planet. The offices which they perform as such are most im-
portant, 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
energ}^ to the southern system of circulation by warming and
expanding the air at its place of ascent. Thus the water, which
by parting with its heat of hquefaction, has expended its meteoro-
logical energy in giving dynamical force to the air, is hke 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 gi^and
meteorological engine which drives the v^ind through his circuits,
and tempers 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 dispensed
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 chmate, and moderate the gale. For, if
the water of southern seas were warmer, evaporation would be
greater; then the S.E. trade-winds would defiver vapour more

430 PHYSICAL geoctRaphy of the sea, and its meteorology.

abundantly to the equatorial calm belts ; tliis would make precipi-
tation there more copious, and the additional quantity of beat
set free would give additional velocity to the inrusliing trade -winds.
Thus it is, as has already 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 -^dnds 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 icebergs are " coupled on," and made to
perform the work of regulator, with adjustments the most beauti-
ful, and compensations the most exquisite, in the grand machinery
of the atmosphere.

832. With this illustration concerning the dynamical force which
The antarctic calm thc wiuds derivo, froui thc vapom" taken up in one

place a region of con- -,., -, , ' xTj. m i

stant precipitation, climato aud transported to another, we may proceed
to sketch those physical featm^es which, being found in the antarctic
circle, would be most favom-able to heavy and constant precipitation,
and, consequently, to the development of a system of aerial circula-
tion 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 — I 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 romid in the grand system of aerial circula-
tion, and as, in every system of aerial cumulation there must be
some point or place at wliich motion ceases to be direct and com-
mences to be retrograde, so there must be a place somewhere on
the sm^face of our planet where these winds cease to go forward,
stop, and commence their retm'n to the north ; and that place is, in
all probahilitij , within the antarctic regions. Its precise locality
has not been determined, but I suppose it to be a band or disc — an
area — within the polar cu'cle, which, could it be explored, would be
found, like the equatorial calm belt, a place of light airs and calms,
of ascending columns of au% — a region of clouds, of variable winds,
and constant precipitation.

833. But, be that as it may, the an- which these vapour-bearing
Also of a low bare- winds — vapour-bcaring 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, condensation of its

THE WINDS OF THE SOUTHERN HEMISPHEKE. 431

vapour commences ; witli tliis, 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 hiQ:her, 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 bai'ometer 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
pressm-e 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 barometric 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° S. 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 probabihty that the mean pressure there is about 28.14
inches.

834. To what, if not to the effects of the condensation of vapour
Aqueous vapour the bomo by thoso Surcharged winds, and to the immense
cause of both. precipitation in the austral regions, shall we ascribe

this diminution of the atmospherical pressm-e in high south lati-
tudes ? It is not BO 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 conditions about their stopping-place
in the antarctic regions, exceedingly favourable to rapid, and heavy,
and constant precipitation 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

* Maury's Sailing Directions, 6th ed., 1854, p. 692 ; ditto, Sth ed., 1859, vol. ii.,
p. 450.

432 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

chambers of tlie upper air the office which the jet of cold water does
for the exhausted steam in the condenser of the engine. The pre-
sence of land, not water, about this south polar stopping-place is
therefore suggested ; for the sea is not so favourable as the moun-
tains are for aqueous condensation.

835. By the terms in which our proposition has been stated, and
The topographical bv the manner in which the demonstration has been

features of the aat- titii -ji l f • n

arctic bands. couductod, the prcscnce m the antarctic regions oi

land in large masses is called for ; and if we imagine this land to be
relieved by high mountains and lofty peaks, we shall have in the
antarctic continent a most active and powerful condenser. If,
again, we tax imagination a little farther, we may, vnthout trans-
cending 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 cu'culations which observations have abundantly
shown to be peculiar to the southern hemisphere. Neither under
such physical aspects need it be any longer considered paradoxical
to ascribe the polar tendency of the " brave west winds " to rare-
faction 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 hberation of heat and expansion of air must follow, and
consequently the oblateness of the atmospherical covering of our
planet will be altered ; the flattening about the poles wiU be reheved
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 derangement of
equihbrium as h'om the centrifugal forces of the revolving globe.
And so this air, having parted with its moisture, and having re-
ceived the expansive force of aU the latent heat evolved in the process
of vaporous condensation, wiU commence its return towards the
equator as an upper current of dry air.

836. Arrived at this point of the investigation, we may con-
A perpetual cyclone, template the wholc 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

THE WINDS OF THE SOUTHERN HEMISPHERE. 433

to the edge of tlie calm belt of Capricorn, is revohing in spiral
curves, continually going with the hands of a watch, and twisting
from left to right.

837. In studying the workings of the various parts of the
Discovery of design physical machinery that smTounds oiu' planet, it is

111 the meteorological -^ , -^ pi- i hl i i i t l i ^

machinery. always reiresnmg and prontable to detect, even by

glimmerings never so faint, the slightest tracings of the purpose
which .the Omnipotent Architect of the universe designed to ac-
complish, by any particular arrangement among its various parts.
Thus it is in tliis instance : whether the train of reasoning which
we have been endeavouring to follow up, or whether the argu-
ments which we I have been adducing to sustain it be entirely
correct or not, we may, from all the facts and cu^cumstances
that we have passed in review, find reasons sufficient for regard-
ing in an instructive, if not in a new hght, that vast waste of
waters which surrounds the imexplored regions of the antarctic
circle. It is a reservou- of d}Tiamical force for the winds, — a regu-
lator in the gi'and meteorological machinery of the earth. The
heat which is transported by the vapours with which that sea loads
its superincumbent ah' is the chief source of the motive power
which gives to the winds of the southern hemisphere, as they move
through then' channels of circulation, their high speed, great regu-
larity, and consistency of volume. And this insight into the work-
ings of the wonderful machinery of sea and air we obtain from com-
parmg together the relative speed of vessels as they sail to and fro
upon intertropical seas !

838. Such is the picture which, after no little labour, much re-
indications which the search, and some thought, the winds have enabled
i^g the unexpZ'eT" "^^ ^^ draw of Certain unexplored portions of our
regions of the south, pknct. As WO havo dra^-n the picture, so, from
the workings of the meteorological machinery of the southern
hemisphere, we judge it to be. The evidence which has been in-
troduced is meteorological in its nature, ckcumstantial in its cha-
racter, 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 inconsistent with the meteorological phe-
nomena 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

2 r

434 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

with kno^Ti laws. According tx) these laws, we may as well ima-
gine the antarctic circle to encompass land as to encompass water.
We know, ocularly, but Httle more of its topographical features
than we do of those of one of the planets ; but, if they be conti-
nental, we surely may, without any unwarrantable stretch of the
imagination, relieve the face of nature there with snow-clad
mountams, and diyersify the landscape with flaming volcanoes.
None of these features are inconsistent with the phenomena dis-
played 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 contra-
dictory— it is rather in corroboration. Southern explorers, as &r
as they have penetrated within the antarctic circle, tell us of high
lands and mountains of ice ; and Koss, who went farthest of all,
saw volcanoes burning in the distance.

839. The unexplored area around the south pole is about twice
Their extent ; Hate as large as EuTopo. This untravellcd region is cir-
^^' • cular 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 Xiy. shows the utmost reach of antarctic exploration. The
unexplored area there is quite equal to that of our entire frigid
zone. Navigators on the voyage from the Cape of Good Hope to
Melbourne, and from Melbourne to Cape Horn, scarcely ever
ventm-e, 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 round. I have encountered them myself as
high up as the parallel of 37°— 8^ S. The belt of ocean that en-
circles this globe on the polar side of 55° S. is never free from ice-
bergs. They are found 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 iu 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. There is another physical circumstance which obtaias

THE WINDS OF THE SOUTHERN HEMISPHERE. 435

generally with regard to the distribution of land and water oyer
AT.hysicaiiawcon- the siu'face of the earth, and which, as far as it goes,
biiSorfof ilnd^and soems to favour the hypothesis of much land about the
^•=itei- 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 portion of South America and Asia, land is always
opposite to water. Mr. Gardner has called attention to the fact
that only one twenty-seventh part of the land is antipodal to land.
The behef is, that on the polar side of 70^ north we have mostly
water, not land. This law of distribution, so far as it apphes, is in
favour of land in the opposite zone. Einally, geographers are agreed
that, uTespective of the particularized facts and phenomena which
we have been considering, the probabilities are in favour of an ant-
arctic continent rather than of an antarctic ocean.

841. " There is now no doubt," says Dr. Jilek, in his Lehrbuch
Dr. jiiek. dcr Oceauographie, "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 por-
tions with which Vv'e have become acquainted, and the investiga-
tions made, furnish sufficient evidences to infer the existence of
such with certainty. This southern or antarctic continent ad-
vances 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 vegetation, always covered with ice and
snow, and so surrounded with ice that it is difficult or impossible to
examine the coast very closely. * * *

842. " The principal discoverers of these coasts are (Wilkes),
Antarctic expeditions. D'Urville, and Eoss (the youuger), of whom the
latter, in 1842, 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 discovered a volcano
(Erebus) 10,200 feet high in 167° east longitude and 77° south
latitude, as well as another extinct one (Terror) 10,200 feet high,
and then discovered the magnetic south pole."*

* Text-book of Oceanography for the Use of the Imperial Naval Academy, by
Dr. Augiist Jilek, Vienna, 1857.

2 P 2

436 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

CHAPTEK XXI.

§ 850-880. — THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. '

850. During our investigations of the ^vinds and currents, facts
Indications of a mild and circumstances have been revealed which indicate

climate about the , . „ -i t t i -i t i

south pole. the existence oi a mild climate — mild by comparison

— within the antarctic circle. These indications plead most elo-
quently the course of exploration there. The facts and circum-
stances 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 winds were the first to whisper of this strange state
The story of the winds, of thiugs, 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 (§ 352) or longitudinal belts 5°
of latitude broad each, I excluded from the table at the head of 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 the propriety of excluding
all regions which are known to present exceptional cases to the
general law. The grouping was not carried beyond lat. 60^ north
and south, for the lack of observations on the polar side of those
parallels. The number of observations 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 deduced therefrom, as per Plate XY., and table on the
next page.

852. This plate and table reveal a marked difference in the atmo-
Th&niaihKits. spherical movements north, as compared with the

atmospherical movements south of the equator. The equatorial

* Polar winds blow toicard the pole, equatorial toward tlie equator.

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY.
Polar and Equatorial Winds.

437

Northern Hemisphere,

Southern Hemisphere.

Equa-

Excess in

Polar.

Equa-

Excess in

Belts.

No. of
Observa-
tions.

torial.

Days.

No. of
Observa-
tions.

torial.

Days.

Days.

Days.

Equa-
torial.

Polar.

Days.

Days.

Polar.

Equa-
torial.

Between

0^ and 50

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

,, 30

68,777

185

163

22

, .

66,635

147

208

61

30

, 35

62,514

155

195

40

76,254

1.50

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

148

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

••

winds of the northern hemisphere are in excess only hetween 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 that
the debatable ground between the winds, or what may be called the
oiull belt, in tliis general movement from poles towards the equator,
and from equator towards the poles, is, in the northern hemisphere,
between the parallels of 25° and 50°. In the southern the field
of battle is narrowed down 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 jjaW j)<^ssu ; 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. The fact that the influence of the polar indraught upon
Extent of the polar the winds should cxtcnd from the antarctic to the
indraught. 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^fbeing bound to the place of greatest rarefaction, rush more

488 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

violently and constantly along to their destination tlian do tlie
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 liigher degi^ee of rarefaction, at "^one
pole than the other ?

854. In the southern hemisphere — and om- attention is now
The rarefaction of the directed oxclusively to that — the polar winds on the
airoverpoiarregions. gQ^^h sido 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. That such is the case is also suggested by the fact that the
Barometrical obsei-va- indraught into the autarctic 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 equa-
tor ; and that such is the case is proved by the barometer. Lieu-
tenant Andi'au, of the Meteorological Institute of Utrecht, has
fm-nished 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 Y/ashington Observatory, taken at ran-
dom, 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 m lat. 78° 37' N., accordmg to 12,000 hourly observa-
tions made during his imprisonment of 17 months in the ice there.
The annals of Greenmch and St. Petersbm-g give us the mean
height of the barometer in lat. 51° 29' N. according to three years'
observations, and in lat. 59° 51' N. according to ten years of ob-
servation. Such are the sources of the table, p. 466.

856. Captains Wilkes, U. S. N., and Clarke Boss, E.N., both,
The low austral ba- duriug their cxpeditious to the South Seas in 1839-41,
rometer. ]^g^^ occasiou to remark upon the apparent defici-
ency 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 IT. S. S. " Falmouth,"
and wrote a paper on it, which was published in the American
Joui'nal of Science in 1833-4. The more abundant materials which
the abstract lo,^s since placed within my reach have enabled me to go
more fully into this subject than it was possible to do while I was

THE ANTABCTIC REGIONS AND THEIR CLIMATOLOGY. 439

Mean Height of the Barometer.

Latitude.

Barometer.

No. of
Observations.

Latitude.

Barometer.

No. of
Obbeivaiions.

CO to 5° North

29.915

5114

0=^to 50 South

29.940

3692

5 to 10 „

29.922

5343

5

to 10

29.981

3924

10 to 15 „

29.964

4496

10

to 15

.80.028

4156

15 to 20 „

30.018

3592

15

to 20

30.060

4248

20 to 25 „

30.081

3816

20

to 25

30.102

4536

25 to 30 „

30.149

4392

25

to 30

30 095

4780-

30 to 35 „

30.210

4989

30

to 36* „

30.052

6970

35 to 40 „

30.124

5103

40

to 43

29.88

1703

40 to 45 „

30.077

5899

43

to 45

29.78

1130

45 to 50* „

30.060

8282

45

to 48

29.63

1174

51° 29'

29.814t

Greenwich

48

to 50

29.62

672

593 51'

29.88

St. Peters-

50

to 53

29.48

665

burg

53

to 55

29.36

475

78^ 37'

29.759

Dr. Kane

56^

29.29

1126

* Maandelijksche Zeibaanwijzingen van Java naar Het Kanaal. Als Uitkomstea Wetenschap en
Ervaring Aaugaande Winden en Zeestroomingen in Sommige Gedeetten Van Den Oceaau Uitgegenen
Door Heet Koninklijk Nederlandsch Meteorologische Institut. Utrecht, 1859.

t Tlie mean height of the barometer for England generally is 29.94-. — Atlmiral Fitzroy.

craising in the Pacific more than a quarter of a century ago.
To ascertain whether these " harometric cmomalies,'' as they are
called, are pecuhar 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^ W. and 140^ E. in another ; and those between 140°
E. and 80° W. in another, mth the following results : — (They are
all on the polar side of lat. 40° S.)

Mean He

ight of the Barometer, as

observed hetween

The Meridians of

20° W. & 14(P E.

140° E. & 803 W.

Ofif Cape Horn.

Mean of all

The parallels of

No. of

Barom.

No. of

Barom.

No. of

Barom.

No. of Barom.

Obs'ns.

Inches.

Obs'ns.

Inches.

Obs'ns.

Inches.

Obs'ns. Inches.

403S.'ancl43^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

440 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

857. The instruments used for these observations were
Discussion of observa- niost part the old-fasliionecl
^'^^^^- marine barometer, to which
no corrections have been apphed. The dis-
crepancies of this table evidently arise from
the lack of number sufficient to mask these
sources of error, or from the influence of the
land, and not from any difference as to the
mean height of the barometer along the
same parallels at sea in any one of the three
divisions. In this discussion, the observa-
tions 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. Eesorting to the graphic method.
Barometric curve at and usmg the table (p. 439) for
^^^- the pm^pose, the barometric
curve of the diagram (Plate XYI.) has been
projected fi^om pole to pole.

859. Professor Schouw has given us the
Ditto over the land, mcau height of the barometer

for 32 places on the land between the paral-
lels of 33'^ S. and 75° 30' N. They afford
materials for the annexed diagram, and show
the exceptional character of the meteorolo-
gical influences which rule on shore v/hen
compared 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 XYI.) over the sea, so
different are these influences. The UTegu-
larities over the land are chiefly owing to
the difference in the amount of precipita-
tion at one station as compared with the
amount at another. Those islands, as the
Sand^\dch and Society, which are so situated
as to biing down a heavy precipitation.

for the

?

in

a> VI

»>b

0 H

t»

r

70°

■'

'

5

/

\

60»

v_

\

■

N,

^

\

'\

■

'

L_

:

4o°*

■

,

' V:

\

\

^ *

3 0"

/

/

/

/

/

■'

20»

[

xo^sr

. '

^1

I^qUfttcT-

1

lO'S

20'

\

1

■

ao"

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 441

seem to serve as cliimneys to the atmosi:>Jiere. The latent heat
which is hberated by the vapour they condense has the effect
of bringing down the barometer, and of causing, dm^ing the
rainy season, an indraught thitherward from many miles at sea.
Such is the rarefaction produced by the hberation 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 atmosphere systems within system. In the
Mississippi and aU 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 whnlpools are
created by the mountains, and the islands, and other inequalities
which obstruct its flow in the regular channels. The mean read-
ing 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. The diagram (Plate XYI.) shows the observations in the
Agreement of obser- southcm hemisphere to be so accordant, and the cm-ve
vaiions at sea. itself SO regular, that we feel no hesitation about pro-
jecting this curve into the unexplored spaces of the south, and assert-
ing, with all the boldness consistent with the true spirit of philoso-
phical deduction, that, whether the actual barometric pressm-e 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 now arises. Whence tliis unequal distribu-
The question why tiou of atmosphcro betwcen the two hemispheres,

the barometer should ^ , iitii i*ii/^n i l

stand lower about the auQ why shouid the mean height 01 the barometer
poi?considercd°°'^^^' iH chcumpolar regions be so much less for the
austral than for the boreal ? No one, it is submitted, will attempt
to account for tliis difference by reason of any displacement of
the geometrical centre of the earth with regard to its centre of at-
traction, 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 Avould create as low a
barometer at one pole as the other. The air, m its motions to the
east and in its motions to the west, ls in equipoise between the paral-
lels of 35^ and 40° N., 25° and 30° S. There is near each pole
and about the equator a place of permanently low barometer.

442 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS IVIETEOROLOGY.

The air from all sides is continually seeking to restore tlie equi-
librium 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 ak on one
side flows towards the equator, on the other towards the pole. Ob-
servation (p. 439) shows this high place to be between the parallels
of 25^^ and 40^ in the north, and of 20^ and 30° in the southern
hemisphere : thus the barometer as well as the winds, Plate XY.,
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 mthout resistance, the air from
these null belts would cajry with it to the polar calms the easterly
motion which it had acquired from the earth in its motion aromid
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 sufficient 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 m to
expand and drive it away. Being expanded and puffed out above
the general atmospherical level, but retaimng its velocity — ^for the
supposition is that it moves without friction — and returnuig through
the upper regions, it would flow back as it went, -sdz., as a westerly
wind, and arrive at its null belt in the dii'ection of the meridian.
But the wind lias friction, and is resisted in every movement ; the
atmosphere partakes of the spheroidal form, which has been im-
pressed upon the earth itseK by its axial rotation. That' form is to it
the form of stabihty. 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 sm-face. To produce the polar and equato-
rial movements of the air, there must be an agent both at the equa-
tor and the poles to prevent such stability by constantly disturbing
equihbrium 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 hi the
air than m the sea, nor could axial rotation produce a high baro-

THE ANTARCTIC REGIONS A2TD THEIR CLIMATOLOGY. 443

meter at one pole, a low barometer at the other ; consequently, the
difference in the pressm-e of the atmosphere ahoiit the two poles, as
shown by the diagram (Plate XYI.), cannot be ascribed to the influ-
ence of axial rotation. It is doubtless due to the excess in antarctic
regions of aqueous vapour and its latent heat.

862. The arctic ch^le hes chiefly on the land, the antarctic on
PsychrometTT of tho Water. As tho wmds enter one, they are loaded
polar winds. ^^-^ vapouT ; but ou their way to the other they are
desiccated (§ 826). Northern mountains and the hills wring from
tliem 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 va-
pour which is condensed in the act of ascending does not hberate heat
enough to produce a rarefaction sufficient to call forth a decided in-
draught from a greater distance in the sm-rounding regions than
40"^ (§ 852) — 2400 miles ; and the rarefaction bemg not so gxeat,
the barometer is not so low there as in antarctic regions.*

863. Nevertheless, there is rarefaction in the arctic regions.
Aerial rarefaction The wiuds show it, the baromctor attests it, and the
about the north pole, f^^t is consistont with the Kussian theory of a
polynia in polar waters. The presence within the arctic chicle of
a considerable body of comparatively warm water, which observa-
tion has detected going into it as an under cmTcnt — which induc-
tion shows must rise up and flow out as a surface current — would
give forth vapour most freely. This vapour, being hghter than air,
displaces a certain quantity of atmosphere. Eising up and being
condensed, it hberates 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. Within the antarctic circle, on the contrary, the winds bring
Ditto about the south ^ir which has come over the water for the distance
P^^^- of hundreds of leagues all around ; consequently, a
large portion of atmospheric air is driven away from the austral re-
gions by the force of vapour, which fills the atmosphere there. Now
there must be a place — an immense disc, with irregular outhnes, 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 featm-es in and about

* Captain M'Clintoek, during liis northern explorations in the schooner "Fox,"
records the arctic barometer as hio:h as 31 inches.

444 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS IMETEOROLOGY.

tins calm place — be sucli as to produce rapid condensation and
heavy precipitation (Chap. XX.), then we shall have, in the latent
heat hberated from all this vapom^, an agent sufficient not only to
produce a low barometer and a powerful indi'aught, but quite ade-
quate also to the mitigation of chmate there.

865. Mere altitude, with its consequent refrigeration, does not
influences favourable scom as favourable as mouutain peaks and sohd sur-
to heavy precipitation. £^ggg ^q ^j^g condcusation and prccipitation of vapouT
in the air. In the trade-mnd regions out at sea it seldom rains ;
but let an island rise never so little above the water, and the preci-
pitation upon it becomes copious. In Colonel Sykes' (§ 299)
rain-faU at Cherraponjie, we have an annual precipitation* at
the rate of 577.6 inches during the six months of S.W. monsoons
— from May to October. Sm'ely no one wiU 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 everlastingly 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. Captains King and Fitzroy exposed their rain gauge on
The climates of cor- tho westom slopcs of the Patagouian Andes, and
ISiiSSortrand^'^it coUected 153.75 mches in forty-one days; that
«o^th. is^ at the rate, as aheady (§ 827) stated, of 1368.7
inches in the year. The latent heat that is liberated during these
Tains gives to Eastern Patagonia its mdd chmate. It is this latent
heat which causes the hregularity 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 moun-
tains, is waiTQed by this liberated heat ; and thus, as I have already
(§ 729) endeavoured to show, we have an exception to the rule
under which meteorologists ascribe cold and severe chmates to the
windward or western, soft and mild to the leeward or eastern, shores
of extra-tropical oceans. Labrador and the Falkland Islands t are
in corresponding latitudes north and south. They are both on
the windward shore of the Atlantic ; they occupy relatively the

* Keport of tlie twenty-secoufl meetings of the British Association for the
Advancement of Science, held at Belfast in September, 1852.
t Maury's Sailing Directions, sixth edition, p. 553.

THE ANTArXTIC EEGIOI^S AXD THEIR CLIICATOLOGY. 445

same position "svitli regard to the wind. Labrador is almost imin-
habitable on accomit of the seventy of its cHmate, but in the Falk-
land Islands and their neighbouring shores the cattle find pasturage
throughout the winter. The the rmometr iced difierence of chmate at
these two places, north and south, may be taken as a sort of index
to the relative difference between the arctic and antarctic chmates
of our planet.

867. Along the eastern base of the Eocky Mountains the iso-
TTiermai difference thorms moimt up * towards the north in consequence
antarctic climates, of the heavj wiutcr precipitation upon the western
slopes of these mountains. The heat which is reqiured 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 fi'ozen up.

868. The average evaporation of water from sea and land is
The influeuce of estimated to be from one third to one half as much

aqueous vapour upon -, .-, . l • 2 • l^ j. i • p a

winds and climates, daily as IS contamed m the great cham oi 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
ak the space w^hich it takes one thousand pounds of dry air at the
same temperatui'e 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 condensation of
this vapour; but if we take iuto the account the rarefy iug 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 ^dolence of the raiu which marks the hm-ricane ; nor
need we wonder at the low range of the barometer or the mildness
of temperature iu all rainy latitudes.

869. In the preceding chapter the circumstances have been
considered which favour the idea that most of the unknown sm'-

* Blodget's Climatology of the United States.

446 PHYSICAL GEOGRAPHY OF THE SEA, AXD ITS METEOROLOGY.

face of the antarctic circle is not only land, but that its coasts
How the tempera- are probablj biglilands ; that in its topographical
SiTed b^'^crosJacf features it presents all the conditions that are re-
mountains. ° qnired for the rapid condensation 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 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 con-
densation 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 pui'poses. 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 barometric column, it is hotter than it was before
by the amount of heat received from its vapom*. That we may
form some idea as to the modifying influences upon climate which
might arise from this source, let us imagine the air as it impinges
upon the antarctic continent to be charged with vapour at the
temperatm-e of 40°. In order to arrive at the place of polar
calms, it has to cross a mountain range, we wiU suppose, the sum-
mits 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 vapom% which the ah' receives in the
sensible form. Now suppose the expansion due the height of the
mountain-top to be sufficient to lower the temperature of dry air
to — 50 , but, on account of the latent heat which is hberated from
the vapour of the moist air, the temperatm*e of the air that has
ascended, instead of falling as it crosses the mountain to —50°, as
dry air would do, falls, iu 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 temperatm^e of the newly-
arrived air 20°. Consequently, when this au', which, at the tempera-
tm-e of 40°, came from the sea loaded with vapour, passes the moun-
tam, it loses vapour, but receives heat ; descendiog 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

THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 447

this air now, instead of being 40°, ^dll be 60°. A powerful modifier
of climate is the latent heat of vapour in the air.

870. At one time, as has been shown in Chap. lY., this heat is
Local variations of broiight dowTL fuom the cloud region to scorch the earth ;
climate, how caused, g^^ another time it causes the 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, mth the
constant vertical circulation imparted to the atmosphere, we owe those
variations of our climates wiuch 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 gi'adually 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 chculation the tempe-
rature of the day of the month, hke the rising and the setting
of the sun, or the changes of the moon, might be foretold in a
calendar.

871. There is not only reason to suppose that the topogra-
Aurora anstraus. phical fcaturcs and thc cHmates of the antarctic re-
gions differ greatly fr'om the topographical features and climates
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 austrahs manifested itseK in a most magnificent man-
ner. Our ship was off' Cape Horn in a violent gale, plunging fu-
riously into a heavy sea, flooding her decks, and sometimes bm-y-
ing 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 tiU
they became like vivid fire, reflecting a lurid, glowing brilliancy
over everything. The ocean appeared like a sea of vermihon
lashed into fury by the storm ; the waves, dashing furiously over
om- sides, ever and anon rushed to leeward 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, shiiekiiLg storm,

44 S PHYSICAL GEOGRAPIIY OF THE SEA, AND ITS IMETEOROLOQY.

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 myste-
rious balls of electric fire resting on our mast-heads, yard-arms,
etc., and above all, the awful sublimity of the heavens, through
which coruscations of auroral light would often shoot in spiral
streaks and with meteoric brilliancy, 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 magnifi-
cence it presented. One must see it and feel it in order to realize it.
I have written this because I beheve it an unusual occm-rence to see
the ' southern lights ' at all, and also because this was far superior,
and, in fact, altogether different from our northern lights, as seen
from the latitude of Boston."

872. Some objections to these views respecting the comparative
Anerroneoas mildncss of antarctic climates are suggested by
opinion. common opinion. It is an opinion which is gene-
rally 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 con-
sideration.

873. The answer to them is as follows : Between lat. 40° or
Tropical regions of lat 45° and the equator, and parallel for parallel, the
sphiTcooS-Sra- southern hemisphere is cooler than the northern.
tropical warmer, KcasoH tcachcs, and obsorvations show that it is so.

than those of the -t-»t t ai^d n ^

nortiiern. But bcyoud 45 JS. obscrvations are wantmg, and

we are left to reason and conjecture. That the southern hemi-
sphere 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 hemisphere has more water ; that water being more
equable than land in its temperature, produces more equable cH-
mates; 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 sim. 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.

THE ANTARCTIC EEGIONS AKD THEIR CLIMATOLOGY. 449

S74. So, in like manner, the vapour that is borne to the ant-
Formation of south- arctic regions by the polar-bonnd winds transports
ern icebergs. immense volumes of heat from, the more temperate

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 vapoiu: finds its way back again.
Being fi'esh water, and falhng 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 water 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 continental; and for the very reason
that the Enghsh 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. As tending to confirm these views touching the mildness of
Mild climate in 63^.8. unknown autarctic climates, the statement 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, dui'ing which time it went no lower
than-5°Fahi\*

876. The low barometer and the imphed heavy precipitation in
Antarctic ice-drift, tho autarctic rcgious are not the only witnesses that

may be called up in favom- 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 jomney to the milder
climates of the north, are encountered 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 itself that information might be

* Maury's Sailing Directions,

2 G

450 PHYSICAL GEOGEAPHY OF THE SEA, AXD ITS METEOPvOLOGY.

gathered from them concerning antarctic regions which would be
higlily useM to any future expedition thitherward.

877. The conditions required for Grulf-Stream Kke currents, or a
Antarctic currents, rapid flow and reflow of equatorial and polar waters
between the torrid and the frigid zones, as in the northern hemi-
sphere, are not to be found about the antarctic regions. Of all the
currents that come from those regions, Humboldt's cm-rent is by far
the most majestic. It is beheved 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 Kne 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
cmTcnts 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 transportation 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 G-ood 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 exammed 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. These facts and the stories of the icebergs are very sug-
Antarctic expiora- gostivo. In muto cloquencc and with great power
tioos demanded. ^]^gy plead the causc of antarctic exploration. Within
the periphery of that circle is included an area equal in extent to
the one sixth part of the enthe land surface of our planet.* Most
of this immense area is as unknown to the inhabitants of the earth
as is the interior of one of Jupiter's satellites. With the apphances
of steam to aid us, with the lights of science to guide us, it would
be a reproach to the world to permit such a large portion of its sm--
face any longer to remain unexplored. For the last 200 years the
Arctic Ocean has been a theatre for exploration ; but as for the ant-
arctic, no expedition has attempted to make any persistent explora-
tion, or even to winter there.

* The area of tlie antarctic circle is 8,155,600 square miles.

THE ACTINOMETPvY OF THE SEA. 451

879. England tkroiigli Cook and Eoss; Eussia througli Bil-
Former expeditions. Imgshaiisen ; FrancG tlirougli D'Umlle; and the
United States throiigli 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 impediraent. The expeditions which have been sent to
explore unimo^Yn seas have contributed largely to the stock of
human knowledge, and they have added reno^Yn to nations, lustre to
diadems. Na^des are not all for war. Peace has its conquests,
science its glories ; and no nav}^ can boast of brighter chaplets than
those which have been gathered in the fields of geographical explo-
ration and physical research.

880. The great nations of the earth have all, with more or less
An appeal for others. Spirit, Undertaken to investigate certain phenomena
touchmg the sea, and, to make the plan more efi'ectual, they have
agreed to observe according to a prescribed formula. The observa-
tions thus made have brought to light most of the facts and
circumstances which indicate the existence withm the antarctic
circle of a mild climate — mild by comparison. The observations
which have led to this conclusion were made by fellow-labom^ers
under all flags. It is hoped that this cu'cumstance may \dndicate,
in the eyes of all, the propriety of an appeal in this place for
antarctic exploration, and plead for it favom^able consideration among
all nations.

CHAPTEE XXII.

§ 881-895. THE ACTINOMETRY OF THE SEA.

881. One of the columns in the man-of-war log of the Brus-
A new field. scls Conference calls for the temperatm-e of the
water below as well as at the surface of the sea. Only a few
entries have been made in this column ; but these, as far as they
go, seem to indicate that the w^armest water, especially in tropical
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 siu-face, are
questions for future observations to settle. Indeed, this subject
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

2 G 2

452 PHYSICAL GEOGEAPHY OF THE SEA, AND ITS METEOPtOLOGY.

our co-operators "wiio will enter upon the investigation patiently and
■^'ith diligence.*

882. The observations that we possess do not prove that the
The warmest waters warmcst watcr of intertropical seas is not at the
i'Jc'Sev?Tto''rbSow^"-'^^^ce: thoj go no farther than to show that it
the surface ? is somctimes not at the surface, and to suggest that,
in all probabihty, it is generally below, especially in "blue water."
Eeason suggests it also. Supposing that, as a rule, the hottest
water is below the surface, we may, in order to stimulate research,
encom-age investigation, and insure true progress, propound a theory
in explanation of the phenomenon, looking to futm-e observations to
show how far it may hold good : —

883. The flow of heat from the sun is held to be uniform, and
The annual supply of tlic quantity that is annually impressed upon the earth
solar heat uniform, jg 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

* On the 26th of March, 1852, the late Passed Midshipman A. C. Jackson,
U. S. N., bein.o: in the Gulf Stream, lat. 84° 55' N., long. 74° 8' W., found the
temjjerature of tlie 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 oOth, in lat. 24^ ]0' 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 795^ at the depth of 16J feet. The sea was rough, and he did not, for that
reason, observe the temperature at six feet. The temj^erature of the air in the
shade was 69-53 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.

*'0n- our late trip from San Francisco (June 5tli) 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 14tl), wliile crossing the Gulf of Tehuantepec, we found the tempera-
ture 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 tlie surface the mean of three thermometers gave 90^^. Tempera-
ture 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 immediately
upon the surface,

••Mr. Agassiz (a son of Professor Agassiz) was on board, and he and myself
made repeated tests of the temperature of tlie water during the four hours we
were running through it — the warm belt,

♦• Ninety degrees is the highest temperature that I have ever known the water of
the ocean to attain."

THE ACTINOMETRY OF THE SEA. 453

that climates are imdergoing a gradual change as to temperature.
However tliis may be as to certain locahties, Baron Fomier, after
a long and laborious calculation, claims to have sIioami that if the
earth had been once heated, and after having been brought to any
given temperatiu-e, 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 ther-
mometer any appreciable change in the temperature of the crust of
our planet.

. 884. The earth receives from the sun heat enough daily, it has
Sr^inT rested ^ becu Said (§ 271), to melt a quantity of ice sufficient
upon the earth. to iucasc it iu a film 1;^- incli tliick. 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. The solar ray penetrates the sohd parts of the earth's crust
How far below the sur- onlv to the dcptli of a fow inchcs, but strikinsr its

TilCG Q06S tllO llP'lt or ». X ^ O

tiie sun penetrate ? fluid parts witli its light and heat, it penetrates the
sea to depths more or less profound, according to the transparency
of the waters. Let us, in imagination, divide these depths, whatever
they may be, into any niunber of stratifications or layers of equal
tliickness. The dnect heat of the sun is supposed to be extinguished
in the lowest layer ; the bottom layer, then, mil receive and absorb
the minimum amount of heat, the top the maximum ; consequently,
each layer, as w^e go from the top to the bottom, will receive less
and less of the smi's heat.

886. Now, which will retain most heat and reach the highest
The stratum of temperatm'e ? Not the top layer, or that to which
warmest water. niost licat is imparted, because by evaporation heat is
carried off from the surface of the sea almost as fast as by the sun
it is impressed upon the surface of the sea ; not the bottom layer,
because that receives a minimum, which, though it cannot escape
by evaporation, may nevertheless fail to make any marked change in
temperature — fail, not by reason of no evaporation, but by the ever-
changing movements which, considering the length of time requh-ed
to heat the lower stratimi by such slow and gradual accumulation of
heat, would alter its place and vary its condition, and indeed re-
moving it beyond the reach of the observer.

887. The layer, therefore, which accumulates most heat and
Its position. becomes waiTaest, should be neither at the bottom

454 PHYSICAL GEOGRAPHY OP THE SEA, AND ITS METEOROLOGY.

nor at the top, but intermediate, the exact temperature and depth
of Yfhich it is for observation to determine. To encourage such
determination and the investigations which it suggests is the main
object of this chapter.

888. In conducting such investigations, several questions are
The diiferent subjects to bo considcrcd, such as the transparency and
for observation. spccific gTavitj of the Water, its i:>]iosioliorescence ;
the face of the sky, whether clear or cloudy ; the state of the sea,
whether smooth or rough ; the condition of the weather, whether
calm or mndy. Then the temperature should be tried, at various
depths and at various liom's of the night and day, in order to ascer-
tain not only the maximum temperature and average depth of the
warmest stratum in the day, but the difference 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 thence
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. Here we are reminded, also, to anticipate the discovery-
Expected discoveries, of uew bcautics 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, nevertheless 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 temperature raised high by day and cooled low
doTMi 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 temperatme 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 sm-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 an*, there to enter, in mysterious ways, upon the perform-
ance of its manifold tasks.

THE ACTINOMETRY OF THE SEA. 455

890. As evaporation goes on by day or night, tlie upper stratum
Actinic processes, is rendered heayier 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, recei\dng more heat by day than they dispense again by
radiation day and night, grow actually warmer and specifically
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 down 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. Thus we arrive at the conclusion that the ocean is the
The reservoirs of gTcat rescrvoir of seusiblc as the clouds are of latent
^^^^- heat. That in these 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 " liis circuits "
to the winds and chculation to the sea ; it is it that fetches from the
ocean the clouds that make " the earth soft mth 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 sm^-
face in due season, given to the winds, and borne away to temper
the climates of western Em'ope, clothing the British Islands as they
go, in green, and causing them to smile under the genial warmth
even in the dead of winter.

892. Thus perhaps we discover a new office for the waves in
An office for waves tlio physical ccouomy of the ocean. Is it not to
in the sea. thcui that has been assigTied the task of bringing up
by their agitation of the smface 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 pm-poses of
evaporation ? Thus even the waves of the sea are made by this
beautiful study to present themselves as parts, important parts, in
the terrestrial machinery. We now view them as it were, like
balance-wheels in the comphcated 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 adequate supphes of
caloric ; the consequence would be less precipitation and a more

456 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY.

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 what they are.

893. We may note also another peculiarity as to the difference

The radiating in the dii^cct hcat-absorbinff and radiating proper-
powers or eaitn, air, .. p ,-, •]• -J- 1-ii
and water compared, tics 01 sca, land, and air : it IS one wnicn 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 oiu' planet : both land and water receive
more heat from the sun than they radiate again ; but the atmo-
sjDhere 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 im-
pressed 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
remaiuder ? Let us inquire, for there is a remainder, and unless
means for its escape were provided, 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 tlien de-
livered 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 sent 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 pre-
vented from becoming seething hot ; and by which they are enabled
to perform their wonderful offices with certainty and regularity.

894. It is cm^ious to think that this heat which we have been
A reflection concern- Contemplating, now as latent in the clouds above, now
iug heat. as scnsiblo in the waters below, comes from the same
source whence originally came the heat which has been packed away
in seams of coal and stored in the bowels of tlie earth for ages and
ages, to be called forth by man at will for his o^vn comfort, pleasure,
and convenience ; that this protean thing is the agent which con-
trols 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

THE ACTINOMETRY OF THE SEA. 457

stupendons fabric of the nniverse in motion ; and that after all, this
mighty agent is only that gentle thing that " vrarms in the sun !"

895. l^u'suing this subject, the philosophical mariner, as he
Probable relation be- gails alonoj and rocords observations for these pin-poses,

tween the actinism of „"=• , , -iii n , t i , -i

the sea and its" depth, may lancy — and pcrhaps 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 w^eight with the
Almighty Architect.

LONDON:

PRINTED Br WILLIAM CLOWES AND SONS, STAMFOKD STREET
AND CHARING CROSS.

DIAGBAM OF THE WrJV1> ,S.

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47 Ludgate Hill.

1st June, 1861.

SAMPSON LOW, SON<^- CO.,

HAVE RECENTLY PUBLISHED THE FOLLOWIXG I

The Boy's Own Book of Boats ; including Vessels of every rig and

size to be found Floating on the Waters in all parts of the World. By W. H. G.
Kingston, Esq., Author of " Peter the Whaler," &c. With numerous Illustrations
by Edwin AVeedon ; Engraved by W. J. Linton. Fcp. 8vo, 5s. handsomely
bound in cloth.
" This well-written, well-wrought book." — Athenceum.

" This is something better than a play-book, and it would be difficult to find a more compendious
and intelligible manual about all that relates to the variety and rig of vessels, and nautical imple-
ments, and gear generally."— ^afurtZa^ Review.

The Prairie and Overland Traveller ; a Companion for Emigrants,

Traders, Travellers, Hunters, and Soldiers, traversing Great Plains and Prairies. By
Captain B. B. ilARCEY. Illustrated. Fcap. 8vo, cloth, 3s. 6d.
"This is a real, carefully executed collection of information and experiences, the which every one

■who takes up will hardly lay down imtil he has read from A to Z It is not only valuable to

the special traveller, but fascinating to the general reader The author is as full of matter as

any old sailor who has sailed four times round the -world." — Athenaum.

Eailway Practice, European and American : comprising the Econo-
mical Generation of Steam ; including the Materials and Construction of Coal-burning
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REFERENCE.

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SCIENCE AND DISCOVERY.

HYSICAL Geogi-aphy of the Sea ; or, the Economy
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its Inhabitants, and whatever there may be of general interest
in its Commercial Uses or Industrial Pursuits. By M. F.
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and cheaper Edition, with important additions, with Illustrative Charts

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" We err greatly if Lieut. Manrj-'s
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displays in a remarkable degree, like
the ' AdA-ancement of Learning,' and
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The Physical Geographj^ of the Sea and its Meteorology. By
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condensed in this one volume as will be required by the general student." —
Athenaeum.

List of Publications.

The Kecent Progress of Astronomy, by Elias Loomis, LL.D.
3rd Edition. Post 8vo. 7s. M.

An Introduction to Practical Astronomy, by the Same. 8vo.
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HISTORY of Coal, Coke, Coal Fields, the Winning

and Working of Collieries, Varieties of Coal, Mine Surveying,
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Manufacture throughout Great Britain, France, Belgium, &c.
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History of the Rise and Progress of the Iron Trade of the United

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at the present moment — ' The Trade
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" We quote a favourable pa.%sage
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The Midland Florist and Suburban Horticulturist, a Hand-book
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10

Sampson Lotv, Son, and Co.^s

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ARCHITECTURE AND DRA'WING.

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Compositions in Outline. By Felix O. C Darley. From Judd's

Margaret. Folio. Originally published at Three Guineas. U. Is.

TKEOIiOGY.

^ HE Land and the Book, or Biblical Illustrations drawn
from the Manners and Customs, the Scenes and the Scenery
of the Holy Land, by W. M. Thomson, M.D., twenty-five
years a Missionary in Syria and Palestine. With 3 Maps and
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Thoughts on the Services; or, Meditations before Worship.
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By Rev. A. Cleveland Coxe, Rector of Christchurch, Baltimore, Author
of " Impi'essions of England." Revised for the use of the Church of
England, by the Rev. Leopold John Bernays, M.A. Printed by Whit-
tingham. Fcp. Svo. cloth, red edges. 3s. 6d.

"A warm-hearted suggestive icork."

English Churchman.
" We have been struck icith the

great amoxmt of really useful informa-
tion conveyed, and the pious and de-
votional spirit ichich breathes through
the whole, and we think the volume icill
be found a most usefid one to introduce
into our parishes." — Clerical Journal.
"Any. one icho is acquainted with
Mr. Cleveland Coxe's icorks will anti-
cipate the character of his ' Thoughts
on the Services.' Though by no means
deficient in ritualistic informatiuii, the

book aims rather at presenting the de-
votional aspect of the services of the
Christian year. This object itfidfls
by its simple and affectionate tone!"
Guardian.
" The name of this author has been
so often before the English public, and
generally in association icith works of
considerable merit, that a very brief
mention on our part icill suffice to
make our readers anxious to obtain
this, his last and very best book."
Literary Churchman.

List of PuhUcatlons.

11

A Short Method of Prayer ; an Analysis of a Work so entitled
by Madame de la Mothe-Guyon ; by Thomas C. Upham, Professor of
Mental and Moral Philosophy in Bowdoin College,U.S. America. Printed
by Whittingham. 12mo. cloth. Is.

Prevailing Prayer. With Introduction by Norman Macleod,
D.D., Author of " The Earnest Student," &c. Fcap. cloth. Is. M.

The Higher Christian Life.
Fcap. cloth. Is. M.

By the Eev. W. E. Boardman.

Crown 8vo. cloth.

By r. D. Huntington, D.D.

The New Life. By Horace Bushnell, D.D.

4s. M. ; cheap edit. 2s.

" A volume of profound thought and splendid eloquence. It displays
the author's great powers in their happiest and most useful exercise." — Edin-
burgh Courant.

Christian Believing and Living.

Crown 8vo. cloth, 4s. M.

" For freshness of thought, power of illustration, and evangelical ear-
nestness, these wTiters [Dr. Huntington and Dr. Bushnell] are not surpassed
by the ablest theologians in the palmiest days of the Church." — Caledonian
Mercury.

The Power of Prayer, Illustrated by the wonderful Displays of
Divine Grace during the American Revival in 1857 and 1858, by Samuel J.
Prime, Author of " Travels in Europe and the East." 12mo. cloth. 2s.
Cheap edition. Is.

The Bible in the Levant ; or, the Life and Letters of the Rev.

C. N. Righter, Missionary in Egypt, Greece, Turkey, and the Crimea.
By the Rev. Samuel Ii'enseus Prime, D. D., Author of " The Power of
Prayer." Fcap. 8vo. cloth. 2s. M.

" Mr. Righter was the agent of the
American Bible Society in the Levant,
and, while there, engaged in much mis-
sionary enterprise in Egypt, Greece,
Turkey, and the Crimea. Death over-
took him in the prosecution of his
labours. His journey to Jordan and
Jerusalem, as recorded in these pages,
is well deserving of attention. He
seems to have been well acquainted
with the countries over which he
travelled, and his letters bear traces
of single-mindedness and devotion."
Literary Churchman.

" We have read this volume with
much interest. In addition to its being

God in the Dwelling ; or, the Eeligious Training of a Household.
By the Rev. Dudley A. Tyng. Fcap. 8vo. limp cloth, Is.,

Life Thoughts. By the Rev. Henry Ward Beecher. Two Series,

complete in one volume, well printed and well bound. 2s. 6rf. Superior
edition, illustrated with ornamented borders. Sm. 4to. cloth extra. 7s. 6rf.

a monument to the memory of a pious,
devoted, and successful labourer in
the diffusion of God's Holy Word —
suddenly called from his work to his
reward — it contains lively descrip-
tions of the countries and peoples of
Paris, Switzerland, Italy, Greece, the
Crimea, Turkey, Palestine, &c. But
they are evidently descriptions given
by a Christian man, who, while he ob-
served and noted down much that was
interesting, never for a moment forgot
or neglected the great and important
objects of his mission."

Wesleyan Times.

12 Sampson Low, Son, and Co.^s

Summer in the Soul; or, Views and Experiences of Religious
Subjects. By the Rev. Henry Ward Beecher, Author of" Life Thoughts."
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Communings upon Daily Texts, tending to a Life of Practical

Holiness. " Commune with your own heart." — Psalm ir. 4. Post 8to.
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Life Scenes from Mission Fields ; edited by the Eev. Hubbard
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Motives for Missions ; Addresses by the Bishops of Carlisle and
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The Bible in England ; by the Eev. C D. Bell, Incumbent of St.
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The Miner's Sons ; Martin Luther and Henry Martyn, by the
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A Complete Analysis of the Holy Bible, based on the Works of
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Twelve Aspects of Christ ; or, Christ All in All, by the Rev.
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The Rich Kinsman ; or, the History of Ruth the Moabitess, by
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The Life of the Apostle Peter ; by the Rev. Dr. Lee, Bishop of
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History of the Old Himdredth Psalm : by H. W. Havergall. 8vo.
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Presbyterian Looking for the Church. Fcp. 8vo. cloth. 6s. 6d.

Sermons for all Seasons ; by the Rev. Charles B. Tayler, M. A.
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Sermons for Boys ; or, the Church in the Schoolroom, b}^ the Rev.
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ProfessorUpham's Life ofFaith, and Interior Life. 2 vols. 5s. 6d.
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Life and Experience of Madame de la Mothe Guyon. By Pro-
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Life of Madame Catherine Adorna; 12mo. cloth. 4s, 6d.

&lh

List of Publications. 13

LAW AND JURISPRUDENCE.

UMMARY of the Law of Copyright and International
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Elements of International Law; by Henry Wheaton,
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History of the Law of Nations ; by the Same. Eoyal 8vo. cloth.
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Commentaries on American Law ; by Chancellor Kent. Ninth
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Lectures on the Constitutional Jurisprudence of the United States,
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Principles of Political Economy ; by Francis Bowen. 8vo. cl. 1 4s.

Treatise on the Law of Evidence ; by Simon Greenleaf, LL.D.

3 vols. 8vo. calf. 4Z. 4s.

A Treatise on the Measure of Damages ; or, An Enquiry into
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Justice. By Theodore Sedgwick. Third revised Edition, enlarged.
Imperial Svo. cloth. 31s. 6d.

Mr. Justice Story's and his Son W. W. Story's Works,

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Familiar Exposition of the Law of Agency. Calf. 30s.

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Law of Conti-act^. 2 vols, cloth. 63s.

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Equity Pleadings. Calf. 32s.

Equity Precedents, Companion to " Pleadings;" by G. I. Curtis. Svo.

calf. 30s.
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Law of Partnership. 30s.
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MEDICAIi.

UMAN Physiology, Statical and Dynamical; by Dr.

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14 Sampson Loiu, Son, and Co.^s

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Lectures on the Diseases of Women and Children. By Dr. G. S.

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Principles and Practice of Dental Surgery ; by C. A. Harris. 6th

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Chemical and Pharmaceutical Manipulations ; by C. and C. Morfit.

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POETRY.

NGLISH and Scotch Ballads, &c. An extensive Col-

M!n lection. Designed as a Complement to the Works of the British
Poets, and embracing nearly all the Ancient and Traditionary
Ballads both of England and Scotland, in all the important
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Saul : a Drama, in Three Parts. Second Edition, post 8vo.
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The Painted Window; a Poem, by M. E. Arnold. Second

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Adventures of a Summer Eve ; by W. G. T. Barter. 12mo. €«.

Lee Shore and other Poems ; by James M. Share. 12mo. 2s. 6d.

Poets and Poetry of Europe; by Henry W.Longfellow. 8vo. 21s.

Poetry of the East ; by W. R. Alger. 8vo. 6s.

Codrus ; a Tragedy, by Richard Neal. Fcap. 8vo. cloth. 2s. 6d.

Shakespeare's Tragedy of Hamlet : 1603-1604. Being the first and
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POPULAR BOOKS AT POPULAR. PRICES.

[LICE CAREY'S Pictures of Country Life. Is. 6cL
Angel over the Right Shoulder. Is.
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List of Publications. 15

Dred; by Mrs. H. B. Stowe. (160th thousand.) Is. 6d.

Fools' Pence, and other Tales ; by C B. Tayler, M. A. 2s. 6cL,

Life Thoughts. By the Eev. Henry Ward Beecher. 2s.

Lights and Shades of Australian Life. Is. 6d.

Mabel Vaughan ; by the Author of " The Lamplighter." Is. 6d.

Nothing to Wear, and Two Millions, by William Allen Butler. Is.

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Eifle, Axe, and Saddlebags. Is. 6c?.

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Wolfert's Eoost, and other Tales ; by Washington Irving. Is.

FICTION.

HE Professor at the Breakfast Table. By Oliver Wen-
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^^ Types of Womanhood; in Four Stories. Eeprinted
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The 160th Thousand of Mrs. Beecher Stowe's " Dred." 2s. 6d.
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Eight at Last, and other Tales. By Mrs. Gaskell, Author of
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The Woman in White. By Wilkie Collins, Author of " The
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16 Sampson Low, Son, and Co.^s List of Publications.

Fiction — continued.

The Cruise of the " Frolic 5" or, the Yachting Adventures of
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When the Snow Falls. By W. Moy Thomas. A Book for Christ-
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" A story book that will not quickly
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poetical, and the carefulness of their
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Round The Sofa, by the Author of " Mary Barton," " Life of
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Mabel Vaughan ; by Miss Cummins, Author of " The Lamp-
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" Had we our will, the women of
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of ■ Mabel Vaughan.' " — Wesleyan
Times.

" We wish it success for the sake of
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written. Mabel is a charming cha-

*^* In ordering this book, specify Mrs. Gaskell's Edition, as the Author
has no interest in any other.

racter, and one which may be safely
held up for admiration." — Saturday
Bevieic.

" ' Mabel Vaughan ' is a quiet and
intensely good story — the book is care-
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El Fureidis : a Tale of Mount Lebanon and the Christian Set-
tlements in SjTia. By Maria S. Cummins, Author of " The Lamp-
lighter." Fcap. 8vo. 2s. 6d. — Also, Library Edition, Second Thousand,
2 vols, crown 8vo. cloth gilt, 10s. 6d.

•' One of the best novels of modern
times : a novel as rich in pure senti-
ment as it is in Christian philosophy,
and as glowing in its portraiture of
Oriental life as in its description of
scenery." — City Press.

" The author has made good use of
her material, and has shown both
skill and industry : she has evidently
taken great pains with her work." —
AthencBum,

" A thoroughly good book." — Moi-n-
ing Star.

" The best novels, of which ' El
Fureidis ' is one." — Glasgoic Herald.

" Not only has Miss Cummins en-
hanced her reputation by her present
production, but literature has gained
a Aaluable acquisition in this spirited
and heart-stirring romance of ' El
Fureidis.' " — Leader.

Chiswick Press :— Whittingham and Wilkins, Tooks Court, Chancery Lane.