Marine Biological Laboratory Library

Woods Hole, Massachusetts

Gift of F. R. Lillie estate - 1977

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THE

PHYSICAL GEOGRAPHY

OF

THE SEA

BY M. F. MAURY, L L. D.,

LIEUT. U. S. NAVY.

NEW YORK :

HARPER & BROTHERS, PUBLISHERS,

329 & 331 PEARL STREET,
FRANKLIN SQUARE.

1855.

Entered, according to Act of Congress, in the year one thousand eiglit
hundred and fifty-five, by

HARPER A; BROTHERS,

in the Clerk's Office of the District Court of the Southern District of
New York.

AS

A TOKEN OF FRIENDSHIP, AND A TRIBUTE TO WORTH,

€^13 f nlnmi^ is i^Mtntrt in
GEORGE MANNING,

OF NEW YORK.

Washington Observatory, December, 1854-

INTRODUCTION.

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

II. Accordingly, when this object was made known, and an ap-
peal was addressed to mariners, there was a flight up into the gar-
rets, and a ransackmg of time-honored sea-chests in all the mari-
time communities of the country for old log-books and sea journals.

III. It was supposed that the records therein contained as to
winds and weather, the sea and its currents, would afford the in-
formation requisite for such an undertaking.

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

V. Perhaps it might be the first voyage of a young navigator to
the given port, when his own personal experience of the winds to
be expected, the currents to be encountered by the way, would it-
self be blank. If so, there would be the wind and current chart.
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 currents by
the way, the temperature of the ocean, and the variation of the

VI

hNTRODUCTION.

needle. All this could be taken in at a glance, and thus the young
mariner instead of groping his way along until the lights of expe-
rience should come to him by the slow teachings of the dearest of
all schools, would here find, at once, that he had already the expe-
rience of a thousand navigators to guide him on his voyage. He
might, therefore, set out upon his first voyage with as much con-
fidence in his knowledge as to the winds and currents he might
expect to meet with, as though he himself had already been that
way a thousand times before.

VI. But, to show the tracks of these vessels on a chart, a line
had to be drawn for each one ; now this, for so many, and all in
black or blue, and on the same sheet of paper too, would present,
it was j^erceived, a mass of lines in inextricable confusion. More-
over, after these tracks were projected, there would be no room left
for the name of the month to show when each one was made,
much less for any written account of the winds and currents daily
encountered by each vessel of the multitude. After the tracks
Were projected, there would, it was found after trial, be barely
room left on the chart to write the name of the vessel, much less
the direction and set of the windi? and currents.

YIL An appeal^ it was consequently decided, should be taken to
the most comprehensive sense of the five, and it was thereupon re-
solved to address all those tracks, and winds, and currents, with
their strength, set, and direction — in short, all this experience,
knowledge, and information — to the eye, by means of colors and
symbols.

YIII. The symbols devised with this view were a comet's tail
for the wind, an arrow for currents, Arabic numerals for the tem-
perature of the sea, Roman for the variation of the needle, contin-
uous, broken, and dotted lines for the month, and colors for the
four seasons.

IX. A continuous line was used to show that the track was
made during the first month ; a broken, the second ; and a dotted
line, the last month of each season : black standing for the winter,
green for spring, red for summer, and blue for autumn.

X. The comet's tail, and the arrow, and the numerals, were also
in colors, according to the seasons. The force and direction of the
wind were indicated by the shape and position of this tail ; while

INTRODUCTION. vii

the flight and length of the arrows designated the velocity and set
of the currents.

XI. Thus the eye was successfully addressed ; for, by a mere
glance at the chart, the navigator saw in a moment from what
quarter he might expect to find the wind in any part of the sea to
prevail for any month ; and he thus had to guide him across the
pathless ocean, not theory or conjecture, nor the faint glimmerings
of any one man's experience, but the entire blaze and full flood of
light which the observations of all the navigators that had preceded
him could shed.

XII. Thus, while the young ship-master, with these charts be-
fore him, would be immediately lifted up and placed on a footing
with the oldest sea-captains in this respect, the aged might see in
these charts also the voyages made in their young days spread out
before them. There, on the chart, was the ship's name, her track,
the year ; and, by the color and fashion of the line (§ IX.), the
month might be told. There, on that day, in that latitude and
longitude, these charts would remind the old sailor that he had en-
countered a terrible gale of wind ; there, that he had been beset
with calms ; how here, with fair winds and a smooth sea, he had
made a glorious run. Here, he had first encountered the trades ;
and there, lost them. At this place, he had met with a '^ hawsing
current." Here, the winds were squally with rain ; and there, it
was he had been beset with fogs ; here, with thunder-storms. All
this was seen on paper, and so represented as to recall the reality
vividly to mind.

XIII. Such a chart could not fail to commend itself to intelli-
gent ship-masters, and such a chart was constructed for them.
They took it to sea, they tried it, and to their surprise and delight
they found that, with the knowledge it afforded, the remote corners
of the earth were brought closer together, in some instances, by
many days' sail. The passage hence to the equator alone was
shortened ten days. Before the commencement of this undertak-
ing, the average passage to California was 183 days ; but with
these charts for their guide, navigators have reduced that average,
and brought it down to 135 days.

XIV. Between England and Australia, the average time going,
without these charts, is ascertained to be 124 days, and coming,

viii INTRODUCTION.

about the same ; making the round voyage one of about 250 days
on the average.

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

XVI. At the meeting of the British Association of 1853, it was
stated by a distinguished member — and the statement was again
repeated at its meeting in 1854 — that in Bombay, whence he
came, it was estimated that this system of research, if extended
to the Indian Ocean, and embodied in a set of charts for that sea,
such as I have been describing, would produce an annual saving
to British commerce, in those waters alone, of one or two millions
of dollars ;t and in all seas, of ten miUions.$

XVII. A system of philosophical research, which is so rich with
fruits and abundant with promise, could not fail to attract the at-
tention and commend itself to the consideration of the seafaring
community of the whole civilized world. It was founded on ob-
servation ; it was the result of the experience of many observant

* The outward passage, it has since been ascertained, has been reduced to 97 days
on the average.

t . . . " Now let us make a calculation of the annual saving to the commerce of the
United States effected by those charts and sailing directions. According to Mr.
Maury, the average freight from the United States to Rio 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 cents per ton per day ; but to be within the mark, we will take it
at 15, and include all the ports of South America, China, aad the East Indies.

" The sailing directions have shortened the passages to California 30 days, to Aus-
tralia 20, to Rio Janeiro 10. The mean of this is 20, but we will take it at 15, and
also include the above-named ports of South America, China, and the East Indies.

" We estimate the tonnage of the United States engaged in trade with these places
at 1,000,000 tons per annum.

" With these data, we see that there has been effected a saving for each one of
these tons of 15 cents per day for a period of 15 days, which will give an aggregate
of $2,250,000 saved per annum. This is on the outward voyage alone, and the ton-
nage trading with all other parts of the world is also left out of the calculation.
Take these into consideration, and also the fact that there is a vast amount of foreign
tonnage trading between these places and the United States, and it will be seen that
the annual sum saved will swell to an enormous amount." — Extract from Hunt's
Merchant's Magazine, May, 1854.

t See Inaugural Address of the Earl of Harrowby, President of the British Asso-
ciation at its twenty-fourth meeting. Liverpool, 1854.

INTRODUCTION. IX

men, now brought together for the first time and patiently dis-
cussed. The results tended to increase human knowledge with
regard to the sea and its wonders, and therefore they could not be
wanting in attractions to right-minded men.

XYIII. As we went on with our labors in this field, it was
found that the flight into the garret and the dive into the sea-
chests for old logs (§11.) were not sufficient. The old records thence
turned up proved to be only outcroppings to the rich vein which
had been struck ; but the indications which they gave of hidden
treasure were unmistakable to the nautical mind of the world.
It was found necessary to go deeper, and to observe more minutely
than our ancestors of the sea had done.

XIX. Accordingly, it was deemed advisable to make an exhibit
of what had been obtained from the old sea-chests. This was
done, and presented to mariners in the shape of a set of " Track
Charts" for the North Atlantic Ocean.

XX. On those charts aU the tracks that could be collected at
that time from the old sea-journals were projected, and one was
surprised to see how they cut up and divided the ocean off into
great turnpilic-looking thoroughfares. There was the road to
China : it, and the road to South America, to the Pacific around
Cape Horn, to the East around the Cape of Good Hope, and to
Australia, were one and the same until the navigator had left the
North, crossed the equator, and passed over into the South Atlan-
tic. Here there was, in this great highway, a fork to the right,
leading to the ports of Brazil. A little farther on you came to an-
other on the left : it was the road by which the Cape of Good Hope
was to be doubled. There was no finger-board or other visible
sign to guide the wayfarer, but, nevertheless, all turned oiT at the
same place. None missed it.

XXI. This outward road to India and the gold fields of Austra-
lia was, as it passed tlii'ough the South Atlantic, a crooked one,
but the road home from the Cape was straight, for the winds along
it were fresh and fair.

XXII. But the outward-bomid route through the North Atlantic,
from the United States especially, was most curious and crooked.
It seemed, on the chart, to be as well beaten, and almost as well
defined, as any Indian trail through the wilderness. First it struck

X INTRODUCTION.

across the Atlantic until it reached the Cape de Verd Islands on
the other side ; then it took a turn, and came hack on this side
again, reaching the coast of Brazil in the vicinity of Cape St.
Roque. Here there was another turn, and another recrossing of
the broad ocean, striking this time for the Cape of Good Hope,
but bending far away to the right before that turning point was
reached.

XXni. Thus the great highway from the United States to the
Cape of Grood Hope nearly crossed the Atlantic, it was discovered,
three times. The other parts of the ocean by the wayside were
blank, untraveled spaces. All the vessels that sailed went by one
road and returned by the other. Now and then there was a sort
of a country cross-road, that was frequented by robbers and bad
men as they passed on their voyage from Africa to the West In-
dies and back. But all the rest of the ocean on the wayside, and
to the distance of hundreds of miles on either hand, was blank, and
seemed as untraveled and as much out of the way of the haunts
of civilized man as are the solitudes of the wilderness that lie broad
off from the emigrants' trail to Oregon. Such was the old route.

XXIY. Who were the engineers that laid out these highways
upon the sea, and why did traders never try short cuts across the
blank spaces ? There was neither rock, nor shoal, nor hidden dan-
ger of any sort to prevent ; why did not traders, therefore, seek to
cut off these elbows in the great thoroughfares, and, instead of
crossing the Atlantic three times on their way to the Cape of Grood
Hope (§ XXH.), cross it only once, as they did coming home ?

Who, it was repeated, were the hydrographic engineers concern-
ed in the establishing of this zigzag route ?

XXV. Inquiry was instituted, and, after diligent research, it was
traced, by tradition^ to the early navigators and the chance that
directed them. When they set sail from E urope, seeking a pas-
sage to the East via the Cape of Good Hope, they passed along
down by the Cape de Yerd Islands, and then, as they approached
the equator, the winds forced them over toward the coast of Bra-
zil. Thus a track was made, and the route to the East laid out.

XXYI. As one traveler in the wilderness follows in the trail of
another, so, it was discovered, did the trader on the high seas fol-
low in the wake of those who had led the way.

INTRODUCTION. ^j

The pioneer goes and returns : " Which way did you go ? How
Kes the route ? Grive us your saihng directions," say his followers.

XXVII. He that is questioned can speak only of the route by
which he went and came. He knows of no others ; and this,
therefore, he commends to his followers, and they to those who
come after them ; and thus, in many cases, the route from place to
place across the sea was, it was ascertained, handed down from
sailor to sailor by tradition, or as legend, and very much in the
same way that the overland route of the first emigrants to Cali-
fornia continued to be followed season after season.

XXVIII. Among other things, these legends told of the most
sweeping currents to the north of St. Roque, along the coast of
Brazil. The vessel, said they, that should fall so far to leeward of
that cape and coast as to come within the influence of these cur-
rents, was almost sure to be beset, and her crew to be cast upon
an iron-bound coast amid the horrors of shipwreck.

XXIX. INTow these investigations have proved that there is no
current there w^orth the name, and no danger to be apprehended
when it is encountered, and so mariners now allude to these cur-
rents as the " bugbear" of St. Roque.

XXX. Nevertheless, impressed with these legends and tradi-
tions, the early navigators of this country, wdien they first com-
menced to double the Cape of Good Hope on trading voyages,
thought it most prudent to make the best of their way to the route
from Europe, which had been often tried and was well known.
They aimed to fall in with this route about the Cape de Verd Isl-
ands. The winds there threw them back on this side of the At-
lantic, upon the coast of Brazil, and so they had to cross the ocean
again to reach the Cape of G-ood Hope. But every body said that
was the way, and it was so written down in the books. Hence
the zigzag route (§ XXIL), and the supposed necessity, on the out-
ward voyage to India, of crossing the Atlantic Ocean three times
instead of once.

XXXL The results of the first chart, however (§ XIII.), though
meagre and unsatisfactory, were brought to the notice of naviga-
tors ; their attention was called to the blank spaces, and the im-
portance of more and better observations than the old sea-chests
generally contained was urged upon them.

xii INTRODUCTION.

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

. XXXIII. The quick, practical mind of the American ship-mas-
ter took hold of the proposition at once. To him the field was in-
viting, for he saw in it the promise of a rich harvest and of many
useful results.

XXXIY. So, in a little while, there wxre more than a thousand
navigators engaged day and night, and in all parts of the ocean, in
making and recording observations according to a uniform plan,
and in furthering this attempt to increase our knowledge as to the
winds and currents of the sea, and other phenomena that relate to
its safe navigation and physical geography.

XXXY. To enlist the service of such a large corps of observers,
and to have the attention of so many clever and observant men di-
rected to the same subject, was a great point gained : it was a
giant stride in the advancement of knowledge, and a great step to-
ward its spread upon the w^aters.

XXXYI. Important results soon followed, and great discoveries
were made. These attracted the attention of the commercial
world, and did not escape the notice of philosophers every where.

XXXYIL The field was immense, the harvest was plenteous,
and there w^as both need and room for more laborers. Whatever
the reapers should gather, or the merest gleaner collect, was to in-
ure to the benefit of commerce and navigation — the increase of
knowledge — the good of all.

XXXYIII. Therefore, all who use the sea were equally interest-
ed in the undertaking. 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 con-
ference upon the subject.

XXXIX. This conference, consisting of representatives from
France, England and Russia, from Sw^eden and Norway, Holland,
Denmark, Belgium, Portugal, and the United States, met in Brus-
sels, August 23, 1853, and recommended a plan of observations

INTRODUCTION. xiii

which should be followed on hoard the vessels of all friendly na-
tions, and especially of those there present in the persons of their
representatives.

XL. Prussia, Spain, the free city of Hamburg, the republics of
Bremen and Chili, and the empires of Austria and Brazil, have
since offered their co-operation also in the same plan.

XL I. Thus the sea has been brought regularly within the do-
mains of philosophical research, and crowded with observers.

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

XLIIL Baron Humboldt is of opinion that the results already
obtained from this system of research are sufficient to give rise to
a new department of science, which he has called the Physical
Geography of the Sea. If so much have already been accom-
plished by one nation, what may we not expect in the course of a
few years from the joint co-operation of so many ?

XLiy. Rarely before has there been such a sublime spectacle
presented to the scientific world : all nations agreeing to unite and
co-operate in carrying out one system of philosophical 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-operating vessel are to be compared
with standards that are common to all; so that an observation
that is made any where and in any ship, may be referred to and
compared with all similar observations by all other ships in all
other parts of the world.

But these meteorological observations which this extensive and
admirable system includes will relate only to the sea. It is a pity.
The plan should include the land also, and be universal. It is now
proposed to have another and general meteorological congress ; and
the initiatory steps, by way of counsel, for calling it together, have
been taken, both in England and on the Continent. It is to be
hoped that this country will not fail to co-operate in such a hu-
mane, wise, and noble undertaking as is this. It involves a study

xiv INTRODUCTION.

of the laws which regulate the atmosphere, and a careful investi-
gation of all its phenomena.

XLY. Another heautiful feature in this system is, that it costs
nothing additional. The instruments that these observations call
for are such as are already in use on hoard of every well-condi-
tioned ship, and the observations that are required are precisely
those which are necessary for her safe and proper navigation.

XLYI. As great as is the value attached to what has been ac-
complished 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 community of the world. A very clever English ship-
master, speaking recently of the advantages of educational influ-
ences among those who intend to follow the sea, remarks :

" To the cultivated lad there is a new world spread out when
he enters on his first voyage. As his education has fitted, so will
he perceive, year by year, that his profession makes him acquaint-
ed with things new and instructive. His intelligence will enable
him to appreciate the contrasts of each country in its general aspect,
manners, and productions, and in modes of navigation, adapted to
the character of coast, climate, and rivers. He will dwell wdth in-
terest on the phases of the ocean, the storm, the calm, and the
breeze, and will look for traces of the laws which regulate them.
All this will induce a serious earnestness in his work, and teach
him to view lightly those irksome and often offensive duties inci-
dent to the beginner."* Sentiments which can not fail to meet
with a hearty response from all good men, whether ashore or afloat.

XLVn. Never before has such a corps of observers been enlist-
ed in the cause of any department of physical science as is that
which is now about to be eno^as^ed in advancino^ our knowledsje of
the physical geography of the sea, and never before have men felt
such an interest with regard to this knowledge.

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

INTRODUCTION. xv

Under this term 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 won-
ders that are hidden in its depths ; and of the phenomena that dis-
play themselves at its surface. In shorty I shall treat of the econ-
omy of the sea and its adaptations — of its salts, its waters, its
climates, and its inhabitants, and of whatever there may be of gen-
eral interest in its commercial uses or industrial pursuits, for all
such things pertain to its Physical Geography.

XLVIII. The object of this little book, 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 this interesting depart-
ment of science ; and the aim of the author is to present the glean«
ings from this new field in a manner that may be interesting and
instructive to all, w^hether old or young, ashore or afloat, who desire
a closer look into " the wonders of the great deep," or a better knowl-
edge as to its winds, its adaptations, or its Physical Geography.*

* There is an old and very rare book which treats upon some of the subjects to
which this httle work relates. It is by Count L. F. Marsigli, a Frenchman, and is
called Natural Description of the Seas. The copy to which I refer was transla-
ted into Dutch by Boerhaave in 1786.

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

He divides sea water into surface and deep-sea water ; because, when he makes
salt from surface water (not more than half a foot below the upper strata), this salt
will give a red color to blue paper ; whereas the salt from deep-sea water will not al-
ter the colors at all. The blue paper can only change its color by the action of an
acid. The reason why this acid (idoine 1) is found in surface and not in deep-sea water
can be derived from the air ; but he supposes that the saltpetre that is found in sea
water, by the action of the sun's rays and the motion of the waves, is deprived of its
coarse parts, and, by evaporation, embodied in the air, to be conveyed to beasts or
plants for their existence, or deposed upon the earth's crust, as it occurs on the plains
of Hungary, where the earth absorbs so much of this saltpetre vapor.

Donati, also, was a valuable laborer in this field. His inquiries enabled Mr. Trem-
bley^ to conclude that there are, " at the bottom of the water, mountains, plains, val-
leys, and caverns, just as upon the land."

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

* Philosophical Transactions.

CONTENTS.

CHAPTER I.

THE GULF STREAM.

The Gulf Stream, () 1.— Its Color, 2.— Its Cause, 3-7.— Dr. Franklin's Theory, 8.—
The Sargasso Sea, 13. — The Trade-wind Agency refuted, 14. — Galvanic Properties
of Gulf Stream Waters, 26. — Initial Velocity, 30. — Agents that make Water in one
part of the Sea heavier than in another, 31. — Temperature of the Gulf Stream, 37.
— It is Roof-shaped, 39. — W^hy the Drift Matter of the Gulf Stream is sloughed off
to the right of its Course, 42. — Course of the Gulf Stream, 47. — Currents run along
arcs of Great Circles, 49. — The Course of Currents counter to the Gulf Stream, 52.
— The Force derived from Changes of Temperature, 53. — Limits of the Gulf Stream
for March and September, 54. — Streaks of Warm and Cool Water in it, 55. — A
Cushion of Cold Water between the Bottom of the Sea and the Waters of the Gulf
Stream, 56. — It runs up hill, 57 Page 25

CHAPTER II.

INFLUENCE OF THE GULF STREAM UPON CLIMATES.

An Illustration, ^ 60. — Best Fish in cold Water, 65. — The Sea a Part of a grand Ma-
chine, 67. — Influence of the Gulf Stream upon the Meteorology of the Sea: It is a
"Weather Breeder," 69. — Dampness of Climate of England due to it, 70. — The Pole
of Maximum Cold, 71.— Gales of the Gulf Stream, 72.— The Wreck of the San
Francisco, 73. — Influence of the Gulf Stream upon Commerce and Navigation : Used
as a Land-mark, 77. — The first Description of it, 78. — Thermal Navigation, 81 . 47

CHAPTER III.

THE ATMOSPHERE.

The Relation of the Winds to the Physical Geography of the Sea, <$> 88. — No Expres-
sion of Nature without Meaning, 93. — The CirQulation of the Atmosphere, Plate I.,
95. — Southeast Trade-wind Region the larger, 109. — How the Winds approach the
Poles, 112. — The Offices of the Atmosphere, 114. — It is a powerful Machine, 118. —
Whence come the Rains that feed the great Rivers ] 120. — How Vapor passes
from one Hemisphere to the other, 123. — Evaporation greatest about Latitude 17'^-
20°, 127.— Explanation, 128.— The Rainy Seasons : how caused, 129.— Why there
is one Rainy Season in California, 130 — One at Panama, 131 — Two at Bogota,
132. — Rainless Regions explained, 135. — Why Australia is a Dry Country, 136. —
Why Mountains have a dry and a rainy Side, 137. — The immense Fall of Rain
upon the Western Ghauts in India: how caused, 139.— Vapor for the Patagonia
Rains comes from the North Pacific, 141. — The mean annual Fall of Rain, 144. —
Evaporation from the Indian Ocean, 146. — Evidences of Design, 148 66

B

-^yjii CONTENTS.

CHAPTER IV.

RED FOGS AND SEA DUST.

Where found, ^ 157. — Tallies on the Wind, 158. — Where taken up, 160. — Hum-
boldt's Description, 163. — Information derived from Sea Dust, 165. — Its Bearings
upon the Theory of Atmospherical Circulation, 167. — Suggests Magnetic Agency,
170 • Page 97

CHAPTER V.

ON THE PROBABLE RELATION BETWEEN MAGNETISM AND THE CIRCULATION OF THE

ATMOSPHERE.

Reasons for supposing that the Air of the Northeast and of the Southeast Trades
cross at the calm Belts, ^ 174. — What Observations have shovs^n, 184. — Physical
Agencies not left to Chance, 188. — Conjectures, 192. — Reasons for supposing that
there is a crossing of Trade-wind Air at the Equator, 194. — W^hy the extra-trop-
ical Regions of the Northern Hemisphere are likened to the Condenser of a Steam-
boiler in the South, 199.— -Illustration, 200.— A Coincidence, 202.— Proof, 203.—
Nature affords nothing in contradiction to the supposed System of Circulation, 204.
Objections answered, 205. — Why the Air brought to the Equator by the Northeast
Trades will not readily mix with that brought by the Southeast, 207. — Additional
Evidence, 209. — Rains for the Mississippi River are not supplied from the Atlan-
tic, 210.— Traced to the South Pacific, 213.— Anticipation of Light from the Polar
Regions, 216. — Received from the Microscope of Ehrenberg, 217, and the Exper-
iments of Faraday, 219. — More Light, 221. — W'hy there should be a calm Place
near each Pole, 222. — Why the Whirlwinds of the North should revolve against
the Sun, 223. — ^Vhy certain Countries should have scanty Rains, 228. — Magnetism
the Agent that causes the Atmospherical Crossings at the calm Places, 231 . . 104

CHAPTER VI.

CURRENTS OF THE SEA.

Currents of the Sea : Governed by Laws, ^ 232. — The Inhabitants of the Sea the
Creatures of Climate, 233. — The Currents of the Sea an Index to its Climates, 235.
— First Principles, 236. — Some Currents run up hill, 237. — Currents of the Red
Sea, 238. — Top of that Sea an inclined Plane, 240. — How an under Current from
it is generated, 245. — Specific Gravity of Sea Waters, 248. — Why the Red Sea is
not salting up, 251. — Mediterranean Currents : How we know there is an un-
der Current from this Sea, 252. — The sunken W^reck which drifted out, 253. — Both
Currents caused by the Salts of the Sea, 254. — Currents of the Indian Ocean :
Why immense Volumes of warm Water flow from it, 255. — A Gulf Stream
along the Coast of Chhia, 256. — Points of Resemblance between it and the Gulf
Stream of the Atlantic, 257. — A Current into Behring's Strait, 258. — Geographical
Features unfavorable to large Icebergs in the North Pacific, 260. — Necessity for
cold to restore the Waste by the warm Currents, and Evaporation, 261. — Argu-
ments in favor of return Currents, because Sea Water is salt, 262. — Currents or
the Pacific : Its Sargasso Sea, 264. — The Drift on the Aleutian Islands, 265. —
The cold China Current, 266. — Humboldt's Current, 267. — Discovery of an ini-

CONTENTS. xix

mense Body of warm Water drifting South, 268. — Currents about the Equator,
270. — Under Currents: Experiments of Lieutenants Walsh and Lee, 271. —
Proof of under Currents afibrded by Deep Sea Soundings, 272. — Currents caused
by Changes in Specific Gravity of Sea Water, 273. — Constituents of Sea Water
every where the same ; affords Evidence of a system of Oceanic Circulation, 274. —
Currents of the Atlantic : The great Equatorial Current : its Fountain-head,
275. — The Cape St. Roque Current proved to be not a constant Current, 276. —
Difficulties of understanding all the Currents of the Sea-shore of the Atlantic can
not be accounted for without the aid of under Currents, 277 Page 124

CHAPTER VIL

the open sea in the arctic ocean.

Ji'ow Whales struck on the east Side of the Continent have been taken on the west
Side, (} 278. — Right Whales can not cross the Equator, 279. — How the Existence
of a northwest Passage was proved by the Wliales, 280. — Other Evidence in Favor
of it, 281. — An under Current sets into the Arctic Ocean, 282. — Evidences of a
milder Climate near the Pole, 284. — The Water Sky of Lieutenant De Haven, 285.
— This open Sea not permanently in one Place, 286 146

CHAPTER VHL

the salts of the sea.

Wliat the Salt in the Sea Water has to do with the Currents in the Ocean, <J 289. —
Reasons for supposing the Sea to have its system of Circulation, 290. — Arguments
furnished by Coral Islands, 293. — What would be the Effect of no system of Cir-
culation for Sea Water 1 295. — Its Components, 297. — The principal Agents from
which Dynamical Force in the Sea is derived, 300. — Illustration, 302. — Sea and
Fresh Water have different Laws of Expansion, 308. — The Gulf Stream could not
exist in a Sea of fresh Water, 309. — The effect of Evaporation in producing Cur-
rents, 310. — How the Polar Sea is supplied with Salt, 323. — The Influence of this
under Current upon open Water in the Frozen Ocean, 326. — Sea Shells : The
Influence exerted by them upon Currents, 330. — Order among them, 335. — They
assist in regulating Climates, 336. — How Sea Shells and Salts act as Compensa-
tions in the Machinery by which Oceanic Circulation is conducted, 339. — Whence
come the Salts of the Sea 1 344 150

CHAPTER IX.

the equatorial cloud-ring.

Description of the Equatorial Doldrums, <^ 346. — Oppressive Weather, 348. — The Of-
fices performed by Clouds in the terrestrial Economy, 349. — The Barometer and
Thermometer under the Cloud-ring, 350. — Its Offices, 353. — How its Vapors arc
brought by the Trade-Winds, 361.— Breadth of the Cloud-ring, 363.— How it
would appear if seen from one of the Planets, 364. — Observations at Sea interest-
ing, 368 171

XX CONTENTS. -'

CHAPTER X.

ox THE GEOLOGICAL AGENCY OF THE WINDS.

To appreciate the Offices of the Winds and Waves, Nature must be regarded as a
Whole, ^ 369.— Level of the Dead Sea, 370. — Evidences that at former Geolog-
ical Periods more Rain fell than now falls upon the Dead Sea and other inland
Basins, 371. — Where Vapor for the Rains in the Basin of the American Lakes
comes from, 375. — The Effect produced by the Upheaval of Mountains across the
course of vapor-bearing Winds, 376. — The Agencies by which the Drainage of
Hydrographic Basins may be cut off from the Sea, 380. — Utah an Example, 382.
— Effect of the Andes upon vapor-bearing Winds, 383. — Geological Age of the
Andes and Dead Sea compared, 391. — Ranges of dry Countries and little Rain,
393. — Rain and Evaporation in the Mediterranean, 399. — Evaporation and Precip-
itation in the Caspian Sea equal, 404. — The Quantity of Moisture the Atmosphere
keeps in Circulation, 407. — \\liere Vapor for the Rains that feed the Nile come
from, 409.-— Lake Titicaca, 420 Page 181

CHAPTER XL

THE DEPTHS OF THE OCEAN.

The Depth of blue Water unknown, <$> 421. — Results of former Methods of Deep-sea
Soundings not entitled to Confidence, 422. — Attempts by Sound and Pressure, 423.
— The Myths of the Sea, 424. — Common Opinion as to its Depths, 425. — Interest-
ing Subject, 427. — The deepest Soundings reported, 428. — Plan adopted in the
American Navy, 429. — Soundings to be made from a Boat, 431. — Why the Sound-
ing-twine will not stop running out when the Plummet reaches Bottom, 432. — In-
dications of under Currents, 433. — Rate of Descent, 434. — Brooke's Deep-sea
Sounding Apparatus, 437. — The greatest Depths at which Bottom has been found,
438 200

CHAPTER XII.

THE BASIN OF THE ATLANTIC.

Plate XL, <} 439. — Height of Chimborazo above the Bottom of the Sea, 440. — Orog-
raphy of Oceanic Basins, 441. — The deepest Place in the Atlantic, 442. — The Bot-
tom OF the Atlantic : The Utility of Deep-sea Soundings, 445. — A telegraphic
Plateau across the Atlantic, 446. — Specimens from it, 447. — A microscopic Exam-
ination of them, 448. — Brooke's Deep-sea Lead presents the Sea in a new Light,
453. — The Agents at work upon the Bottom of the Sea, 454. — How the Ocean is
prevented from growing salter, 458. — Knowledge of our Planet to be derived from
the Bottom of the Sea, 460 308

CHAPTER XIII.

the WINDS.

Plate VIII., <$» 461. — Monsoons, 462. — Why the Belt of Southeast is broader than the
Belt of Northeast Trade-winds, 463. — Effect of Deserts upon the Trade-winds, 466.
— At Sea the Law^s of Atmospherical Circulation are better developed, 470. — Rain

CONTENTS. xxi

Winds : Precipitation on Land greater than Evaporation, 472. — The Place of Sup-
ply for the Vapors that feed the Amazon with Rains, 473. — Monsoons : How-
formed, 474. — Monsoons of the Indian Ocean, 475. — How caused, 476. — How the
Monsoon Season may be known, 478. — The Distance to which the Influence of
Deserts upon Winds may be felt at Sea, 479. — Why there are no Monsoons in the
Southern Hemisphere, 482. — Why the Trade-wind Zones are not stationary, 483.
The Calm Belts : Doldrums — a Zone of constant Precipitation, 486. — The Horse
Latitudes, 488.— The Westerly Winds, 490 Page 217

CHAPTER XIV.

THE CLIM.\^TES OF THE OCEAN.

Gulf Stream likened to the Milky Way, (} 492. — March and September the hottest
Months in the Sea, 496. — How the Isothermal Lines move up and down the Ocean,
498. — A Line of invariable Temperature, 508. — How the western Half of the At-
lantic is heated up, 509. — The Relation between a Shore-line in one part of the
World and Climates in another, 512. — The Climate of Patagonia, 516. — The Sum-
mer of the northern Hemisphere warmer than the Summer of the southern, indi-
cated by the Sea, 521. — How the cold Waters from Davis's Straits press upon the
Gulf Stream, 522. — How the different Isotherms travel from North to South with
the Seasons, 523.— The Polar and Equatorial Drift, 524 231

CHAPTER XV.

THE DRIFT OF THE SEA.

Object of Plate IX., ^ 528. — The Eastern Edge of the Gulf Stream sometimes visi-
ble, 529.— The Polar Drift aboufc Cape Horn, 533.— How the Polar AVaters drift
into the South Atlantic, and force the Equatorial aside, 535. — How this is accom-
plished, 537. — A Harbor in a Bend of the Gulf Stream for Icebergs, 539. — Why
Icebergs are not found in the North Pacific, 540. — The Womb of the Sea, 541. —
Drift of warm Waters out of the Indian Ocean, 543. — A Suggestion from LieU'
tenant Jansen, of the Dutch Navy, 544. — A Current of warm Water sixteen hund-
red Miles wide, 545.— The Pulse of the Sea, 546.— How the Gulf Stream beats
Time, 547.— The Circulation of the Sea likened to that of the Blood, 548.— The
Fish : Number of Vessels engaged in the Fisheries of the Sea, 551. — The Sperm
Whale delights in warm Water, 552. — The Torrid Zone impassable to the Right
Whale, 553 244

CHAPTER XVL

STORMS.

Typhoons, ^ 559. — Cyclones, 561. — West India Hurricanes, 562. — Extra-tropical
Gales, 563. — The San Francisco's Gale, 564. — These Gales seldom occur at cer-
tain Seasons, 565. — Most prevalent Quarter for the Gales beyond the Calm Belt of
Capricorn, 566. — Storm and Rain Charts, 567 257

xxii . CONTENTS.

CHAPTER XVII.

ROUTES.

How Passages have been shortened, ^ 568. — How closely Vessels follow each other's
Track, 570. — The Archer and the Flying Cloud, 571. — The great Race-course upon
the Ocean, 573. — Description of a Race, 575. — Present Knowledge of Winds en-
ables the Navigator to compute his Detour, 582 Page 262

CHAPTER XVIII.

A LAST WORD.

Brussels Conference, () 584. — How Navigators may obtain a Set of Maury's Wind
and Current Charts. 585.— The Abstract Log, 586 271

4

EXPLANATION OF THE PLATES.

Plate I. (p. 70) is a diagram to illustrate the circulation of the atmosphere (Chap.
III.)- The arrows and bands within the circumference of the circle are intended to
show the calm belts, and prevailing direction of the wdnd on each section of those
belts. , The arrows exterior to the periphery of the circle — which is a section of the
earth supposed to be made in the plane of the meridian — are intended to show the
direction of the upper and lower strata of winds in the general system of atmospher-
ical circulation ; and also to illustrate how the air brought by each stratum to the
calm belts there ascends or descends, as the case may be ; and then, continuing to
flow on, how it crosses over in the direction in which it was traveling when it arrived
at the calm zone.

Plates II. and III. (p. 207) are drawings of Brooke's Deep-sea Sounding Appa-
ratus, for bringing up specimens of the bottom {^ 438).

Plate IV. (p. 230) is intended to illustrate the extreme movements of the isotherms
50°, 60°, 70°, &c., 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. is a section taken from one of the manuscript charts at the Observatory.
It illustrates the method adopted there for co-ordinating for the Pilot Charts the winds
as reported in the abstract logs. For this purpose the ocean is divided into conven-
ient sections, usually five degrees of latitude by five degrees of longitude. These par-
allelograms are then subdivided into a system of engraved squares, the months of the
year being the ordinates, and the points of the compass being the abscissae. As the
wind is reported by a vessel that passes through any part of the parallelogram, so it
is assumed to have been at that time all over the parallelogram. From such investi-
gations as this the Pilot Charts (<5> 558) are constructed.

Plate VI. illustrates the position of the channel of the Gulf Stream (Chap. I.) for
summer and winter. The diagram A shows a thermometrical profile presented by
cross-sections of the Gulf Stream, according to observations made by the hydrograph-
ical parties of the United States Coast Survey. The elements for this diagram were
kindly furnished me by the superintendent of that work. They are from a paper on
the Gulf Stream, read by him before the American Association for the Advancement
of Science at its meeting in Washington, 1854. Imagine a vessel to sail from the
Capes of Virginia straight out to sea, crossing the Gulf Stream at right angles, and
taking the temperature of its waters at the surface and at various depths. This 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 x, y, z, in the Gulf Stream, show the course which those threads
of warm waters take (<J 55). The lines a, b show the computed drift route that the
unfortunate steamor Saa Francisco would take after her terrible disaster in December,
1853.

xxiv EXPLANATION OF THE PLATES.

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

Plate VIII. shows the prevailing direction of the wind during the year in all parts
of the ocean, as derived from the series of investigations illustrated on Plate VII. It
also shows the principal routes across the seas to various places. VV^here 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 perpendicular or square, that the winds
are, for the most part, fair. The figures on or near the diagrams representing the
vessels show the averagie 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 (^ 462), 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 northwest and the southwest, the idea intended
to be conveyed is, that the prevailing direction of the wind is between the northwest
and the southwest, 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
(^ 528). Further researches will enable us to improve this chart. The most favorite
places of resort for the whale — right in cold, and sperm in warm water — are also ex-
hibited on this chart.

Plate X. exhibits the actual path of a storm, which is a type (<5> 72) of the West
India hurricanes. Mr. Redfield, Colonel Reid, and others, have traced out the paths
of a number of such storms. All of this class appear to make for the Gulf Stream ;
after reaching it, they turn about and follow it in their course {^ 75).

Mr. Piddington, of Calcutta, has made the East India hurricanes, which are similar
to these, the object of special, patient, and laborious investigation. He calls them
cycloins, and has ehcited much valuable information concerning them, which may be
found embraced in his " Sailor's Horn-book," " Conversations about Hurricanes," and
numerous papers published from time to time in the Journal of the Asiatic Society.

Plates XI. and XII. speak for themselves. They are orographic for the North
Atlantic Ocean, and exhibit completely the present state of our knowledge with re-
gard to the elevations and depressions in the bed of the sea ; Plate XII. exhibiting a
vertical section of the Atlantic, and showing the contrasts of its bottom with the sea-
level in a line from Mexico across Yucatan, Cuba, San Domingo, and the Cape de
Verds, to the coast of Africa, marked A on Plate XI.

THE

PHYSICAL GEOGRAPHY OF THE SEA,

CHAPTER I.

THE GULF STREAM.

The Gulf Stream, <J 1.— Its Color, 2.— Its Cause, 3-7.— Dr. Franklin's Theory, 8.—
The Sargasso Sea, 13. — The Trade-wind Agency refuted, 14. — Galvanic Properties
of Gulf Stream Waters, 26. — Initial Velocity, 30. — Agents that make Water in one
part of the Sea heavier than in another, 31. — Temperature of the Gulf Stream, 37.
—It is Roof-shaped, 39.— Why the Drift Matter of the Gulf Stream is sloughed off
to the right of its Course, 42. — Course of the Gulf Stream, 47. — Currents run along
arcs of Great Circles, 49. — The Course of Currents counter to the Gulf Stream, 52.
— The Force derived from Changes of Temperature, 53. — Limits of the Gulf Stream
for March and September, 54. — Streaks of Warm and Cool Water in it, 55. — A
Cushion of Cold Water between the Bottom of the Sea and the Waters of the Gulf
Stream, 56. — It runs up hill, 57.

1 . There is a river in the ocean. In the severest droughts it
never fails, and in the mightiest floods it never overflows. Its
banks and its bottom are of cold water, while its current is of
warm. The Gulf of Mexico is its fountain, and its mouth is in
the Arctic Seas. It 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.

2. Its waters, as far out from the Gulf as the Carolina coasts,
are of an indigo blue. They are so distinctly marked, that their
line of junction with the common sea-water may be traced by the
eye. Often one half of the vessel may be perceived floating in
Gulf Stream water, while the other half is in common water of the
sea ; so sharp is the line, and such the want of affinity between
those waters, and the reluctance, on the part of those of the Gulf
Stream to mingle with the common water of the sea.

3. What is the cause of the Gulf Stream has always puzzled

26 THE PHYSICAL GEOGRAPHY OF THE SEA.

philosophers. Modern investigations and examinations are begin-
ning to throw some hght upon the subject, though all is not yet
clear.

4. Early writers maintained that the Mississippi River was the
father of the Gulf Stream. Its floods, they said, produce it ; for
its velocity, it was held, could be computed by the rate of the cur-
rent of the river.

5. Captain Livingston overturned this hypothesis by showing
that the volume of water which the Mississippi River empties into
the Gulf of Mexico is not equal to the one thousandth part of that
which escapes from it through the Gulf Stream.

6. Moreover, the water of the Gulf Stream is salt — of the Mis-
sissippi, fresh; and those philosophers (§ 4) 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
below — neither of which is probable — would become a fresh-water
basin.

7. The above quoted argument of Captain Livingston, however,
was held to be conclusive ; and upon the remains of the hypoth-
esis which he had so completely overturned, he set up another,
which, in turn, has 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."

8. But the opinion that came to be the most generally received
and deep-rooted in the mind of seafaring people was the one re-
peated by Dr. Franklin, and which held that the Gulf Stream is
the escaping of the waters that have been forced into the Carib-
bean Sea by the trade-winds, and that it is the pressure of those
winds upon the water which forces up into that sea a head, as it
were, for this stream.

9. We know of instances in which waters have been accumu-
lated on one side of a lake, or in one end of a canal, at the ex-
pense of the other. But they are rare, sudden, and partial, and
for the most part confined to sheets of shoal water where the rip-
ples are proportionably great. As far as they go, the pressure of
the trade-winds may assist to give the Gulf Stream its initial ve-
locity, but is it of itself adequate to such an effect ? To my mind,

THE GULF STREAM.

27

the laws of Hydrostatics, as at present expounded, appear by no
means to warrant the conclusion that it is, unless the aid of other
agents also be brought to bear.

J Admiral Smyth, in his valuable memoir on the Mediterranean
(p. 1 62), mentions, that a continuance in the Sea of Tuscany of
'•' gusty gales'^ from the southwest has been known to raise its sur-
face no less than twelve feet above its ordinary level. This, he
says, occasions a strong surface drift through the Strait of Boni-
faccio. But in this we have nothing like the Gulf Stream ; no
deep and nari'ow channel-way to conduct these waters off like a
miniature river even in the 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 water,
loses itself by broad spreading as soon as it gets to sea.

10. Supposing the pressure of the waters that are /orcec/ into
the Caribbean Sea by the trade-winds to be the sole cause of the
Gulf Stream, that sea and the Mexican Gulf should have a much
higher level than the Atlantic. Accordingly, the advocates of this
theory require for its support " a great degree of elevation." Major
Rennell likens the stream to " an immense river descending from
a higher level into a plain." Now we know very nearly the aver-
age breadth and velocity of the Gulf Stream in the Florida Pass.
We also know, with a like degree of approximation, the velocity
and breadth of the same waters off Cape Hatteras. Their breadth
here is about seventy-five miles against thirty-two in the " Nar-
rows" of the Straits, and their mean velocity is three knots off
Hatteras against four in the "Narrow^s." This being the case, it
is easy to show that the depth of the Gulf Stream off Hatteras is
not so great as it is in the " Narrows" of Bemini by nearly 50 per
cent., and that, consequently, instead of descending, its bed rep-
resents the surface of an inclined plane from the north, up which
the lower depths of the stream must 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 descending, are actually forced up

28 THE PHYSICAL GEOGRAPHY OF THE SEA.

an inclined plane, whose submarine ascent is not less than ten
inches to the mile.

The Niagara is an " immense river descending into a plain."
But instead of preserving its character in Lake Ontario as a dis-
tinct and well-defined stream for several hundred 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 en-
larges itself, it is true ; but, instead of mingling with the ocean by
broad spreading, as the " immense rivers" descending into the
northern lakes do, its w^aters, like a stream of oil in the ocean,
preserve a distinctive character for more than three thousand miles.

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

12. It is a custom often practiced by seafaring people to throw
a bottle overboard, with a paper, stating the time and place at
which it is done. In the absence of other information as to cur-
rents, that afforded by these mute little navigators is of great
value. They leave no tracks behind them, it is true, and their
routes can not 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, show-
ing the shortest distance from the beginning to the end of their
voyage, with the time elapsed. Captain Beechey, R. N., has pre-
pared a chart, representing, in this way, the tracks of more than
one hundred bottles. From it, it appears that the waters from
every quarter of the Atlantic tend toward the Gulf of Mexico and

THE GULF STREAM.

29

its stream. Bottles cast into the sea midway between the Old
and the New Worlds, near the coasts of Europe, Africa, and
America, at the extreme north or farthest south, have been found
either in the West Indies, or within the well-known range of Gulf
Stream waters.

Of two cast out together in south latitude on the coast of Africa,
one was found on the island of Trinidad ; the other on Guernsey,
in the English Channel.

In the absence of positive information on the subject, the cir-
cumstantial evidence that the latter performed the tour of the
Gulf is all but conclusive.

Another bottle, thrown over off Cape Horn by an American
master in 1837, has been recently picked up on the coast of Ire-
land. 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 highe?' level of the
Gulf Stream reservoir.

13. Midway the Atlantic, in the triangular space between the
Azores, Canaries, and the Cape de Verd Islands, is the Sargasso Sea.
(Plate VI.) Covering an area equal in extent to the Mississippi
Valley, it is so thickly matted over with Gulf weed (fucus natans),
that the speed of vessels passing through it is often much retard-
ed. 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 weed are always to be seen floating along the Gulf
Stream. Now, if bits of cork or chaff, or any floating substance,
be put into a basin, and a circular motion be given to the water,
all the light substances will be found crowding together near the
centre of the pool, where there is the least motion. Just such a
basin is the Atlantic Ocean to the Gulf Stream, and the Sargasso
Sea is the centre of the whirl. Columbus first found this weedy
sea in his voyage of discovery ; there it has remained to this day ;
and certain observations as to its hmits, extending back for fifty
years, assure us that its position has not been altered since that
time. This indication of a circular motion by the Gulf Stream is
corroborated by the bottle chart and 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 ?

30 THE PHYSICAL GEOGRAPHY OF THE SEA.

14. Nay, more ; at the very season of the year when the Gulf
Stream is rushing in greatest volume through the Straits of Flor-
ida, and hastening to the north w^ith the greatest rapidity, there is
a cold stream from Baffin's Bay, Labrador, and the coasts of the
north, running to the south with equal velocity. Where is the
trade-wind that gives the high level to Baffin's Bay, or that even
presses upon, or assists to put this current in motion ? The agen-
cy of winds in producing currents in the deep sea must be very
partial. These two currents meet off the Grand Banks, where
the latter is divided. One part of it underruns the Gulf Stream,
"as is shown by the icebergs which are carried in a direction tend-
ing across its course. The probability is, that this " fork" con-
tinues on toward the south, and runs into the Caribbean Sea, for
the temperature of the water at a little depth there has been found
far below the mean temperature of the earth, and quite as cold as
at a corresponding depth off the Arctic shores of Spitzbergen.

15. "More water can not run from the equator or the pole than
to it. If we make the trade-winds cause the former, some other
wind must produce the latter ; but these, for the most part, and
for great distances, are submarine, and therefore beyond the influ-
ence of winds. Hence it should appear that loinds have little to
do with the general system of aqueous circulation in the ocean.

The other " fork" runs between us and the Gulf Stream to the
south, as already described. As far as it has been traced, it war-
rants the belief that it, too, runs up to seek the so-called higher
level of the Mexican Gulf,

16. The power necessary to overcome the resistance opposed
to such a body of water as that of the Gulf Stream, running sev-
eral 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 con-
siderable accuracy, the resistance which the waters of this stream
meet with in their motion toward the east. Owing to the diurnal
rotation, they are carried around with the earth on its axis toward
the east with an hourly velocity of one hundred and fifty-seven*
miles greater when they enter the Atlantic than when they arrive
off the Banks of Newfoundland. In consequence of the difference

* In this calculation the earth is treated as a perfect .sphere, with a diameter of
7925-56 miles.

THE GULF STREAM. 31

of latitude between the parallels of these two places, their rate of
motion around the axis of the earth is reduced from nine hundred
and fifteen* to seven hundred and fifty-eight miles the hour.

17. Therefore this immense volume of water, in passing from
the Bahamas to the Grand Banks, meets with an opposing force
in the shape of resistance, sufficient, in the aggregate, to retard it
two miles and a half the minute, and this only in its eastwardly
rate. If this 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 eflfect assigned them ? If, therefore,
in the proposed inquiry, we search for a propelling power nowhere
but in the higher level of the Gulf, we must admit, in the head of
water there, the existence of a force capable of putting in motion,
and of driving over a plain at the rate of four miles the hour, all
the waters, as fast as they can be brought down by three thou-
sand such streams as the Mississippi River — a power, at least, suf-
ficient to overcome the resistance required to reduce from two
miles and a half to a few feet per minute the velocity of a stream
that keeps in perpetual motion one fourth of all the waters in the
Atlantic Ocean.

18. The facts, from observation on this interesting subject, af-
ford us at best but a mere glimmer of light, by no mea,iis sufficient
to make any mind clear as to a higher level of the Gulf, or as to
the sufficiency of any other of the causes assigned for this w^onder-
ful stream. If it be necessary to resort to a higher level in the
Gulf to account for the velocity oflf Hatteras, I can not perceive
why we should not, w^ith like reasoning, resort to a higher level
off Hatteras also to account for the velocity off the Grand Banks,
and thus make the Gulf Stream, throughout its circuit, a descend-
ing current, and, by the reductio ad absurdum, show that the trade-
winds are not adequate to the effect ascribed.

19. When facts' are wanting, it often happens that hypothesis
will serve, in their stead, all the purposes of illustration. Let us,
therefore, suppose a globe of the earth's size, having a solid nu-
cleus, and covered all over with water two hundred fathoms deep ;

* Or, 91.5-26 to 75860. On the latter parallel the current has an east set of about
one and a half miles the hour, making the true velocity to the east, and on the axis
of the earth, about seven hundred and sixty miles the hour at the Grand Banks.

32 THE PHYSICAL GEOGRAPHY OF THE SEA.

and that every source of heat and cause of radiation be removed,
so that its fluid temperature becomes constant and uniform through-
out. On such a globe, the equihbrium remaining undisturbed,
there w^ould be neither w^md nor current.

20. Let us now suppose that all the v^^ater v^^ithin the tropics,
to the depth of one hundred fathoms, suddenly becomes oil. The
aqueous equilibrium of the planet is thereby disturbed, and a gen-
eral system of currents and counter currents is immediately com-
menced— the oil, in an unbroken sheet on the surface, running to-
W3Lx:d. the poles, and the vi^ater, in an under current, tov^^ard the
equator. The oil is supposed, as it reaches the polar basin, to be
reconverted into v^^ater, and the water to become oil as it crosses
Cancer and Capricorn, rising to the surface and returning as before.

21. Thus, without tvind, we should have a perpetual and uni-
form system of tropical and polar currents. In consequence of
diurnal rotation of the planet on its axis, each particle of oil, were
resistance small, would approach the poles on a spiral turning to
the east, with a relative velocity greater and greater, until, finally,
it would reach the pole and whirl about it at the rate of nearly a
thousand miles the hour. Becoming water and losing its velocity,
it would approach the tropics by a similar, but inverted spiral,
turning toward 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 toward the equator a westward.

22. 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 wxll as the coast lines and con-
tinents of the earth. The uniform system of currents just de-
scribed would now be interrupted by obstructions and local causes
of various kinds, such as unequal depth of water, contour of shore-
lines, &c. ; and we should have at certain places currents greater
in volume and velocity than at others. But still there would be
a system of currents and counter currents to and from either pole
and the equator. Now do not the cold waters of the north, and
the warm waters of the Gulf, made specifically lighter by tropical
heat, which we see actually preserving such a system of counter
currents, hold, at least in some degree, the relation of the sup-
posed water and oil ?

THE GULF STREAM. 33

23. In obedience to the laws here hizited at, there is a constant
tendency of polar waters toward the tropics and of tropical waters
toward the poles. Captain Wilkes, of the United States Explor-
ing Expedition, crossed one of these hyperborean under-currents
two hundred miles in breadth at the equator.

24. Assumino- the maximum velocity of the Gulf Stream at five
knots, and its depth and breadth in the Narrows of Bemini as be-
fore (^ 10), the vertical section across w^ould present an area of
two hundred millions of square feet moving at the rate of seven
feet three inches per second. The difference of specific gravity
between the volume of Gulf water that crosses this sectional line
in one second, and an equal volume of water at the ocean temper-
ature of the latitude^ is fifteen millions of pounds. If these esti-
mated dimensions (assumed merely for the purposes of illustration)
be within limits, then the force per second operating here to pro-
pel the waters of the Gulf toward the pole is the equilibrating ten-
dency due to fifteen millions of pounds of water in the latitude of
Bemini.

25. In investigating the currents of the seas, such agencies
should be taken into account. As a cause, I doubt whether this
one is sufficient of itself to produce a stream of such great velocity
as that of the Gulf; for, assuming its estimated discharge to be
correct, the proposition is almost susceptible of mathematical dem-
onstration, that to overcome the resistance opposed in consequence
of its velocity would require a force at least sufficient to drive,
at the rate of three miles the hour, ninety thousand millions of
tons up an inclined plane having an ascent of three inches to the
mile.* Yet the very principle from which this agent is derived
is admitted to be one of the chief causes of those winds which are
said to be the sole cause of this current.

26. The chemical properties, or, if the expression be admissible,
the galvanic properties of the Gulf Stream waters, as they come
from their fountains, are different, or, rather, more intense than
they are in sea water generally.

In 1843 the Secretary of the Navy took measures for procur-
ing a series of observations and experiments w-ith regard to the
corrosive effects of sea water upon the copper sheathing of ships.
With patience, care, and labor, these researches were carried on

* SupposinjT there be no resistance from friction.

c

34 THE PHYSICAL GEOGRAPHY OF THE SEA.

for a period of ten years ; and it is said the fact has been estab-
lished, that the copper on the bottom of ships cruising in the
Caribbean Sea and Gulf of Mexico suffers more from the action
of sea water upon it than does t\ie copper of ships cruising in
any other part of the ocean. In other words, the salts of these
waters create the most powerful galvanic battery that is found in
the ocean.

27. Now it may be supposed — other things being equal — that
the strength of this galvanic battery, in the sea depends in some
measure upon the proportion of salts that the sea waters hold in
solution.

If, therefore, in the absence of better information, this sugges-
tion be taken as a probability, we may go a step farther, and draw
the inference that the waters of the Gulf Stream, as they rush out
in such volume and with such velocity into the Atlantic, have not
only chemical affinities peculiar to themselves, but, having more
salts, they are therefore specifically heavier than the sea water
through which they flow in such a clear and well-defined channel.

28. The affinities of which I speak, and which are manifested
in the reluctance of the Gulf Stream to mingle its waters with
those of the ocean (§ 2), may be the resultant of their galvanic
properties, higher temperature, and greater degree of saltness, all
combined.

29. If the story told by the copper (^ 26) be taken to mean a
higher point of saturation with salts, and, consequently, a greater
specific gravity for the waters of the Gulf and Caribbean Sea
than for the waters of the broad ocean at the same temperature,
then we should have as a source for the initial velocity of the
Gulf Stream, not, indeed, a higher level of the waters in the Gulf,
but a greater density.

30. Now a greater density, implying, of course, a greater specific
gravity, would serve, as well as a higher level, to impart an initial
velocity, but with this difference : the heavier waters would, by
reason of their greater pressure, be ejected through the most con-
venient aperture out into the ocean of lighter waters by a sort of
squirting force. But what, it may be asked, should make the
waters of the Mexican Gulf and Caribbean Sea Salter than the
waters of like temperature in those parts of the ocean through
which the Gulf Stream flows ?

THE GULF STREAM. 35

31. There are physical agents that are known 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 solid matter
for their structures, also of heat* and radiation, evaporation and
precipitation.

32. In the trade-wind 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 dow^n more
water than the winds take up again ; and these are the regions in
which the Gulf Stream enters the Atlantic.

33. Along the shores of India, where experiments have been
carefully made, the evaporation amounts 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 evap-
oration of say fifteen feet. In the process of evaporation from the
sea, fresh water only is taken up, the salts are left behind.

Now a layer of sea water fifteen feet deep, and as broad as the
trade-wind belts of the Atlantic, and reaching across the ocean,
contains an immense amount of salts.

34. The great equatorial current (Plate VL) which sweeps from
the shores of Africa across the Atlantic into the Caribbean Sea
is a surface current ; and may it not bear into that sea a large
portion of those waters that have satisfied the thirsty trade-winds
with saltless vapor ? If so — and it probably does — have we not
detected here the foot-prints of an agent that does tend to make
the waters of the Caribbean Sea Salter, and therefore heavier than
the average of sea water ?

It is immaterial, so far as the correctness of the principle upon
which this reasoning depends is concerned, whether the annual
evaporation from the trade-wind regions of the Atlantic be fifteen,
ten, or five feet. The layer of water, whatever be its thickness,
that is evaporated from this part of the ocean, is not all poured
back by the clouds in the same place w^hence it came. But they
take it and pour it down in showers upon the extra-tropical regions
of the earth — on the land as well as in the sea — where, as a rule,
more water is let down than is taken up into the clouds again.
* According to Doctor Marcet, sea water contracts down to 28^.

36 THE PHYSICAL GEOGRAPHY OF THE SEA.

Suppose the excess of precipitation in these extra-tropical regions
of the sea amounts to but twelve inches, or even to but tv^o, it is
twelve inches or two inches, as the case may be, of fresh 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
for the simple reason, that what is taken from one scale, by being
put into the other, reduplicates the difference.

35. Now, that we may form some idea as to the influence which
the salts left by the vapor that the trade-winds, northeast and south-
east, take up from sea water, is calculated to exert in creating
currents, let us make a partial calculation to show how much salt
this vapor held in solution before it was taken up, and, of course,
while yet in the state of sea water. The northeast trade-wind
regions of the Atlantic embrace an area of at least three million
square miles ; and the yearly evaporation from it is (§ 33), 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
milhon square miles in superficial extent, w^ould be sufficient to
cover the British islands to the depth of fourteen feet. As this
water supplies the trade-winds with vapor, it therefore becomes
Salter, and as it becomes salter, the forces of aggregation among
its particles are increased, as we may infer from the fact (§ 27),
that the waters of the Gulf Stream are reluctant to mix with those
of the ocean.

Now, whatever be the cause that enables these waters to re-
main on the surface, whether it be from the fact just stated, and
in consequence of which the waters of the Gulf Stream are held
together in their channel ; or whether it be from the fact that the
expansion from the heat of the torrid zone is sufficient to com-
pensate for this increased saltness ; or whether it be from both
of these influences together that these waters are kept on the sur-
face, suffice it to say, we do know that they go into the Carib-
bean Sea (§ 34) as a surface current. The trade-winds, by their
constant force, may assist to skim them off from the Atlantic, and
push them along into the Caribbean Sea, whence, for causes un-
known, they escape by the channel of the Gulf Stream in prefer-
ence to any other.

36. In the present state of our knowledge concerning this won-
derful phenomenon — for the Gulf Stream is one of the most mar-

THE GULF STREAM. 3-y

velous things in the ocean — we can do httle more than conjec-
ture. But we have two causes in operation which we may safely
assume are among those concerned in producing the Gulf Stream.
One of these is in the increased saltness of its water after the
trade-winds have been supplied with vapor from it ; and the other
is in the diminished quantum of salt which the Baltic and the
North Sea contain. The waters of the Baltic are nearly fresh ;
they contain only about half as much salt as sea water does gen-
erally (^ 248).

Now here we have, on one side, the Caribbean Sea and Gulf of
Mexico, with their waters of brine ; on the other, the Baltic and the
North Sea, wath waters that are but little more than brackish. In
one set of these sea-basins the water is heavy ; in the other, it is
light. Between them the ocean intervenes ; but water is bound
to seek and to maintain its level ; and here, therefore, we unmask
one of the agents concerned in causing the Gulf Stream. What
is the influence of this agent — that is, how great is it, and to what
extent does it go — we can not say ; only it is at least one of the
agents concerned. Moreover, speculate as we may as to all the
agencies concerned in collecting these waters, that have supplied
the trade-winds with A^apor, into the Caribbean Sea, and then in
driving them across the Atlantic, of this we may be sure, that the
salt which the trade-w^ind vapor leaves behind in the tropics has
to be conveyed away from the trade-wind region, to be mixed up
again in due proportion with the other water of the sea — the Baltic
included — and that these are the waters w^hich we see running off
through the Gulf Stream. To convey them away is one of the
offices which, in the economy of the ocean, has been assigned to it.

37. As to the temperature of the Gulf Stream, there is, in a
Avinter's day, ofFHatteras and even as high up as the Grand Banks
in mid ocean, a difference between its waters and those of the
ocean near by of 20°, and even 30°. Water, we know, expands
by heat, and here the difference of temperature may more than
compensate for the difference of saltness, and leave, therefore, the
waters of the Gulf lighter by reason of their warmth.

38. Being lighter and adhesive, they should therefore occupy a
higher level than those through which they flow. Assuming the
depth off Hatteras to be one hundred and fourteen fathoms, and
allowing the usual rates of expansion for sea water, figures show

38 THE PHYSICAL GEOGRAPHY OF THE SEA.

that the middle or axis of the Gulf 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 water runs in at the bottom, and so raises up the
cold water bed of the Gulf Stream, and causes it to become shal-
lower and shallower as it goes north.

39. That the Gulf Stream is roof-shaped, causing the waters on
its surface to flow off to either side from the middle, we have not
only circumstantial evidence to show, but observations to prove.

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

41. That such is the case (§ 38), is also indicated by the cir-
cumstance that the sea-weed and drift-wood which are found in
such large quantities along the outer edge of the Gulf Stream, are
never, 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
stream, as it were ; that is, they would have to stem this roof-cur-
rent until they reached the middle of the stream. We never hear
of planks, or wrecks, or of any floating substance which is cast into
the sea on the other side of the Gulf Stream being found along
the coasts of the United States. Drift-wood, trees, and seeds
from the West India islands, are said to have been cast up on the
shores of Europe, but never, that I ever heard, on the Atlantic
shores of this country.

We are treating now^ of the effects of physical causes. The
question to wdiich 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 ?

42. One cause has been shown to be in its roof-shaped current ;

THE GULF STREAM. 39

but there is another which tends to produce the same effect ; and
because it is a physical agent, it should not, in a treatise of this
kind, be overlooked, be its action never so slight. I allude now to
the effects (upon the drift matter of the stream) produced by the
diurnal rotation of the earth.

43. Take, for illustration, a rail-road that runs north and south.
It is well 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.
Whether the road be one mile or one hundred miles in length, the
effect of diurnal rotation is the same, and the tendency to run off,
as you cross a given parallel at a stated rate of speed, is the same,
whether the road be long or short, the tendency to fly the track
being in proportion to the speed of the trains, and not at all in
proportion to the length of the road.

44. Now^, vis inertioi and velocity being taken into the account,
the tendency to obey the force of this diurnal rotation, and to trend
to the right, is proportionably as great in the case of a patch of
sea-weed as it drifts along the Gulf Stream, as it is in the case
of the train of cars as they speed to the north, along the iron track
of the Hudson River railway, or the Great Western railway of
England.

The rails restrain the cars and prevent them from flying off:
but there are no rads to restrain the sea-weed, and nothing to pre-
vent the drift-matter of the Gulf Stream from going off in obedi-
ence to this force. The slightest impulse tending to turn aside
bodies moving freely in water is immediately felt and imphcitly
obeyed.

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

The effect of diurnal rotation upon the winds and upon the cur-
rents of the sea is admitted by all — the trade-winds derive then-
easting from it — it must, therefore, extend to all the matter which
these currents bear with them, to the largest iceberg as well as
to the merest sprig of grass that floats upon the waters, or the

40 THE PHYSICAL GEOGRAPHY OF THE SEA.

minutest organism that the most powerful microscope can detect
among the impalpable particles of sea-dust. This effect of diur-
nal rotation will be frequently alluded to in the pages of this work.

46. In its course to the north, the Gulf Stream gradually trends
more and more to the eastward, until it arrives off the Banks of
Newfoundland, where its course becomes 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 effect, certainly not the cause. It is here that the frigid current
already spoken of (§ 11), with 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 down upon them are here de-
posited. Captain Scoresby, far away in the north, counted five
hundred icebergs setting out from the same vicinity upon this cold
current for the south. Many of them, loaded with earth, have been
seen aground on the Banks. This process of transferring deposits
for these shoals has been going on for ages ; and, with time, seems
altogether adequate to the effect described.

The deep sea soundings that have been made by vessels of the
navy (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, its depth increases by almost a precip-
itous descent for many thousand feet, thus indicating that the
debris which forms the Grand Banks comes from the north.

47. From the Straits of Bemini the course of the Gulf Stream
(Plate VL) describes (as far as it can be traced over toward the
British Islands which are in the midst of its waters) the arc of a
great circle as nearly as may be, only the thread or axis of the Gulf
Stream does not generally go quite as far north as the great circle
would. Such a course as this is the course that a cannon ball,
could it be shot from these straits to those islands, would take.

If it were possible to see Ireland from Bemini, and to get a can-
non that would reach that far, the person standing on Bemini and
taking aim, intending to shoot at Ireland as a target, would, if the
earth were at rest, sight along the plane of a great circle, for the
path of the ball would be in such a plane.

THE GULF STREAM. 41

48. But there is diurnal rotation ; the earth does revolve on its
axis ; and since Bernini is nearer than Ireland is to the equator,
the gun would be moving in diurnal rotation 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
ahead of his mark. In other words, that the path actually de-
scribed by the ball would not be an arc of a great circle, and that
the highest parallel reached by the ball in its flight would not be
as far north as the highest parallel touched by the great circle,
and that, consequently, the path of the ball would take a due east
course before the track of the great circle would.

It is the case of the passenger in the rail-road 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, par-
taking 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.

49. Hence we may assume it as a law, that the natural tenden-
cy of all currents in the sea, like the natural tendency of all pro-
jectiles through the air, is to describe their curves of flight in the
planes of great circles, departing therefrom — unless ybrce<i to de-
part by obstructioHs — only so much as the forces of diurnal rota-
tion may impel.

50. The arc of a great circle is the shortest distance between
any two points on the surface of a sphere. Light, heat, and elec-
tricity, running water, and all substances, whether ponderable or
imponderable, seek, when in motion, to pass from point to point
by the shortest lines practicable. Electricity may be turned aside
from its course, and so may the cannon-ball or running water ;
but remove every obstruction, and leave the current or the shot
free to continue on in 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 on a sphere,
in the arc of a great circle — thus showing that it has no volition
except to obey impulse, and the physical requirements to take the
shortest way to its point of destination.

The waters of the Gulf Stream, as they escape from the Gulf
{k 36), are bound over to the British Islands, to the North Sea, and

42 THE PHYSICAL GEOGRAPHY OF THE SEA.

Frozen Ocean (Plate IX.). Accordingly, they take (§ 47), in obe-
dience to this physical law, the most direct course by which na-
ture will permit them to reach their destination. And this course,
as already remarked (^ 49), is nearly that of the great circle, and
exactly that of the supposed cannon ball.

51. Many philosophers have expressed the opinion — indeed, the
belief is common among mariners (§ 46) — that the coasts of the
United States and the Shoals of Nantucket turn the Gulf Stream
toward the east ; but if the view I have been endeavoring to make
clear be correct — and I think it is — it appears 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 Nan-
tucket Shoals not in existence, the course of the Gulf Stream, in
the main, would be exactly as it is and where it is. The Gulf
Stream is bound over to the North Sea and Bay of Biscay partly
for the reason, perhaps, that the waters there are lighter than
those of the Mexican Gulf (§ 36);* and if the Shoals of Nantuck-
et were not in existence, it could not pursue a more direct route.
The Grand Banks, however, are encroaching, and cold currents
from the north come down upon it : they may, and probably do,
assist now and then to turn it aside.

52. Now if this explanation as to the course of the Gulf Stream
and its eastward tendency hold good, a current setting from the
north toward the south should have a westward tendency. It
should also move in a great circle (§ 49)? or rather in the circle of
trajection, calling thus the circle traced upon the earth which
would be described by a trajectile moving through the air without
resistance and for a great distance. Accordingly, and in obedi-
ence to the propelling powers, derived from the rate at which dif-
ferent parallels are whirled around in diurnal motion, we find the
current from the north, which meets the Gulf Stream on the Grand
Banks (Plate IX.), taking a southiv esttvardly direction, as already
described (§ 45). 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 Rennell and M. Arago make the coasts of the

* The waters of the Atlantic generally contam 5|- per cent, more of saline matter
than those of the English Channel. — M. Bouillon la Grange.

THE GULF STREAM.

43

United States and the Shoals of Nantucket to turn the Gulf Stream
toward the east.

53. But there are other forces operating upon the Gulf Stream.
They are derived from the eiFect of changes in the waters of the
whole ocean, as produced by changes in their temperature from
time to time. As the Gulf Stream leaves the coasts of the United
States, it begins to vary its position according to the seasons ; the
hmit of its northern edge, as it passes the meridian of Cape Race
(Plate VI.), being in winter about latitude 40°-41°, and in Septem-
ber, when the sea is hottest, about latitude 45°-46°. The trouirh
of the Gulf Stream, therefore, may be supposed to weaver about in
the ocean not unlike a pennon in the breeze. Its head is confined
between the shoals of the Bahamas and the Carolinas, but that
part of it w^hich stretches over toward the Grand Banks of New-
foundland is, as the temperature of the waters of the ocean changes,
first pressed down toward the south, and then again up toward
the north, according to the season of the year.

To appreciate the extent of the force by which it is so pressed,
let us imagine the waters of the Gulf Stream to extend all the way
to the bottom of the sea, so as completely to separate, by an im-
penetrable liquid w^all, if you please, the waters of the ocean on
the right from the waters in the ocean on the left of the stream.
It is the height of summer : the w^aters of the sea on either hand
are for the most part in a liquid state, and the Gulf Stream, let it
be supposed, has assumed a normal condition between the two
divisions, adjusting itself to the pressure on either side so as to
balance them exactly and be in equilibrium. Now, again, it is the
dead of winter, and the temperature of the waters over an area of
millions of square miles in the North Atlantic has been changed
many degrees, and this change of temperature has been followed
by a change in the specific gravity of those waters, amounting, no
doubt, in the aggregate, to many hundred millions of tons, over
the whole ocean ; for sea water, unlike fresh (§ 31), contracts to
freezing. Now is it probable that, in passing from their summer
to their winter temperature, the sea waters to the right of the Gulf
Stream should change their specific gravity exactly as much in
the aggregate as do the waters in the whole ocean to the left of
it? If not, the difference must be compensated by some means.
Sparks are not more prone to fly upward, nor water to seek its

44 THE PHYSICAL GEOGRAPHY OF THE SEA.

level, than Nature is sure with her efforts to restore equilibrium in
both sea and air whenever, wherever, and by whatever it be dis-
turbed. Therefore, though the waters of the Gulf 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 waste of waters
on the right and a waste of waters on the left, to which (^ 2) they
offer a sort of resisting permeability, we are enabled to compre-
hend how the waters on either hand, as their specific gravity is in-
creased or diminished, wdll impart to the trough of this stream a
vibratory motion, pressing it now to the right, now to the left, ac-
cording to the seasons and the consequent changes of temperature
in the sea.

54. Plate VI. shows the limits of the Gulf Stream for March
and September. The reason for this change of position is obvi-
ous. The banks of the Gulf Stream (§ 1) are cold water. In
winter, 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 temperature of these cold waters is
modified ; there is not such an extent of them, and then the warmer
waters, in turn, press them back, and so the pendulum-like motion
is preserved.

55. The observations made by the United States Coast Survey
indicate that there are in the Gulf Stream threads of warmer, sep-
arated by streaks of cooler water. See Plate VI., in which these
are shown. Figure A may be taken to represent a thermomet-
rical cross section of the stream opposite tne Capes of Virginia,
for instance ; the top of the curve representing the thermometer
in the threads of the warmer water, and the depressions the height
of the same instrument in the streaks of cooler water between,
thus exhibiting, as one sails from America across the Gulf Stream,
a remarkable series of thermometrical elevations and depressions
in the surface temperature of this mighty river in the sea.

56. As a rule, the hottest water of the Gulf Stream is at or near
the surface ; and as the deep sea thermometer is sent down, it
shows that these waters, though still far warmer than the water on
either side at corresponding depths, gradually become less and
less warm until the bottom of the current is reached. There is
reason to beheve that the warm waters of the Gulf Stream are no-

THE GULF STREAM. 45

where 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 sohd parts of the earth's crust. This arrangement
is suggestive, and strikingly beautiful. One of the benign oiBces
of the Gulf Stream is to convey heat from the Gulf of Mexico,
where otherwise it would become excessive, and to disperse it in
regions beyond the Atlantic for the amehoration of the climates
of the British Islands and of all Western Europe. Now cold wa-
ter is one of the best non-conductors of heat, and if the warm wa-
ter 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 with a
cold, non-conducting cushion of cool water to fend it from the
bottom, all 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 ol
Labrador, severe in the extreme, and ice-bound.

57. But to return to the streaks and reservoirs of hot Vv^ater
below. The hottest water is the hghtest ; as it rises to the top,
it is cooled both by evaporation and exposure, when the surface is
replenished by fresh supplies of hot water from below. Thus, ii?
a winter's day, the waters at the surface of the Gulf Stream off
Cape Hatteras may be at 80°, and at the depth of five hundred
fathoms — ^three thousand feet — as actual observations show, the
thermometer will stand at 57°. Following the stream thence off
the Capes of Virginia, one hundred and twenty miles, it will be
found — the water-thermometer having been carefully noted all
the way — that it now stands a degree or two less at the surface,
while all below is cooler. In other words, the stratum of water
at 57°, which was three thousand feet below the surface off Hat-
teras, has, in a course of one hundred and twenty or one hundred
and thirty miles in a horizontal direction, ascended, vertically, six
hundred feet ; that is, this stratum has run up hill with an ascent
of five or six feet to the mile.

58. In the case of boiling springs we perceive how all the as-
cending water comes up in one column ; that there is no descent
of surface w^ater through that which is boiling up, but at the side
of the bubbling. Moreover, in a cold winter's day, the water, as
it boils up, is relatively warm ; it smokes, grows cool, and the
surface thermometer will stand highest where it is boiling, lowest

46 THE PHYSICAL GEOGRAPHY OF THE SEA.

off a little way toward the verge of the fountam. Just so with
these warmer and cooler streaks in the Gulf Strearn. This warm
water, in its ascent (§ 57) of five feet to the mile — suppose we are
considering the streak which is the hottest, and is, also, the near-
est to the American shore — represents the boiling in the fountain ;
the warm, ascending water rising up in one body, and the cooler
and heavier water going off to the side in another body, to sink
and take its place with the other waters of the stream according
to gravity and temperature. See the streaks x, y, z, Plate VI.

59. Now, wdien these waters come to the top and cool, they are
traveling with the current toward the north, and the effect of di-
urnal rotation is to turn them, as it turns any other drift (§ 45), to
the eastward. They obey this influence to a certain extent, sink-
ing down as they obey, in consequence of their greater specific
gravity ; beyond this sinking — i. e., farther from the shore — is an-
other rising-up place, each thread of the hot w^ater being less and
less warm, and each stream of cooler water more and more cool.
The forces of diurnal rotation, operating upon the waters as they
are successively sloughed off from each thread and streak alter-
nately above and below, are quite enough to determine them to
the east. A rod being poised on a point at one end, so as to stand
alone, has no more tendency to fall to the east than to the west ;
but the smallest force, the slightest breath, will determine it either
way. So with the forces of diurnal rotation, and these streaks of
warm and cool water ; the water that has been to the top and is
cooled must give w^ay to warmer water that is 2^ressing up from
below ; it must flow either to the west or to the east, and diurnal
rotation assists in determining it. When it sinks and reaches its
proper level, it must again go to the east or to the west to get
into the ascending column, and rise again to the surface in its
proper turn. There is no more tendency for it to go to the west
than to the east, and diurnal rotation, like the weight of the feath-
er, is sufficient ; it again plies its forces, and they are obeyed.

Taking all these facts and views into consideration, we are led
to the conclusion with which we set out (^ 49), that it is the law
of matter in motion, and not the Shoals of Nantucket, that controls
the Gulf Stream in its course.

INFLUENCE OF THE GULF STREAM UPON CLLMATES. 47

CHAPTER 11.

INFLUENCE OF THE GULF STREAM UPON CLIMATES.

An Illustration, ^ 60. — Best Fish in cold Water, 65. — The Sea a Part of a grand Ma-
chine, 67. — Influence of the Gulf Stream upon the Meteorology of the Sea: It is a
"Weather Breeder,'' 69. — Dampness of Climate of England due to it, 70. — The Pole
of Maximum Cold, 71. — Gales of the Gulf Stream, 72. — The Wreck of the San
Francisco, 73. — Influence of the Gulf Stream upoyi Commerce and Navigation : Used
as a Land-mark, 77. — The first Description of it, 78. — Thermal Navigation, 81.

60. Modern ingenuity has suggested a beautiful mode of warm-
ing houses in winter. It is done by means of hot water. The
furnace and the caldron are sometimes placed at a distance from
the apartments to be warmed. It is so at the 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 hundred
feet. These pipes are then flared out so as to present a large cool-
ing surface ; after which they are united into one again, through
which the water, being now cooled, returns of its own accord to
the caldron. Thus cool water is returning all the time and flow-
ing in at the bottom of the caldron, while hot water is continually
flowing out at the top.

The ventilation of the Observatory is so arranged that the cir,
culation of the atmosphere through it is led from this basemem
room, where the pipes are, to all other parts of the building ; and
in the process of this circulation, the warmth conveyed by the
water to the basement is taken thence by the air and distributed
over all the rooms. Now, to compare small things with great, we
have, in the w^arm waters which are confined in the Gulf of Mex-
ico, just such a heating apparatus for Great Britain, the North
Atlantic, and Western Europe.

The furnace is the torrid zone ; the Mexican Gulf and Carib-
bean Sea are the caldrons ; the Gulf Stream is the conducting pipe.
From the Grand Banks of Newfoundland to the shores of Eu-
rope is the basement — the hot-air chamber — in which this pipe is

48 THE PHYSICAL GEOGRAPHY OF THE SEA.

flared out so as to present a large cooling surface. Here the cir-
culation of the atmosphere is arranged by nature ; and 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.

61. The maximum temperature of the water-heated air-cham-
ber of the Observatory is about 90°. The maximum temperature
of the Gulf Stream is 86°, or about 9° above the ocean temper-
ature due the latitude. Increasing it» latitude 10°, it loses but
2° of temperature ; and, after having run three thousand miles
toward 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, and covers the ocean with a mantle of warmth that serves
so much to mitigate in Europe the rigors of winter. Moving
now more slowly, but dispensing its genial influences more freely,
it finally meets the British Islands. By these it is divided (Plate
IX.), one part going into the polar basin of Spitzbergen, the other
entering the Bay of Biscay, but each with a w^armth considerably
above the ocean temperature. Such an immense volume of heat-
ed water can not fail to carry with it beyond the seas a mild and
moist atmosphere. And this it is which so much softens climate
there.

62. We know not, except approximately in one or two places,
what the depth or the under temperature of the Gulf Stream
may be ; but assuming the temperature and velocity at the depth
of two hundred fathoms to be those of the surface, and taking the
well-known diff'erence between the capacity of air and of water
for specific heat as the argument, a simple calculation will show
that the quantity of heat discharged over the Atlantic from the
waters of the Gulf Stream in a winter's day would be sufficient
to raise the whole column of atmosphere that rests upon France
and the British Islands from the freezing point to summer heat.

Every west wind that blows crosses the stream on its way to
Europe, and carries with it a portion of this heat to temper there
the northern winds of winter. It is the influence of this stream
upon climate that makes Erin the " Emerald Isle of the Sea,"

INFLUENCE OF THE GULF STREAM UPON CLIMATES. 49

and that clothes the shores of Albion in evergreen robes ; while in
the same latitude, on this side, the coasts of Labrador are fast bound
in fetters of ice. In a valuable paper on currents,* Mr. Redfield
states, that in 1831 the harbor of St. John's, Newfoundland, was
closed with ice as late as the month of June ; yet who ever heard
of the port of Liverpool, on the other side, though 2° further north,
being closed with ice, even in the dead of winter ?

63. The Thermal Chart (Plate IV.) shows this. The isother-
mal lines of 60°, 50°, &c., starting off from the parallel of 40°
near the coasts of the United States, run off in a northeastwardly
direction, showing the same oceanic temperature on the Euro-
pean 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, for drift-wood from the West In-
dies is occasionally cast ashore there by the Gulf Stream.

64. Nor do the beneficial influences of this stream upon climate
end here. The West Indian Archipelago is encompassed on one
side by its chain of islands, and on the other by the Cordilleras 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, we leave the regions of
perpetual snow, and descend first into the tierra teniplada, and
then into the tierra caliente, or burning land. Descending still
lower, we reach both the level and the surface of the Mexican
seas, where, were it not for this beautiful and benign system of
aqueous circulation, the peculiar features of the surrounding coun-
try assure us we should have the hottest, if not the most pestilen-
tial chmate in the world. As the waters in these two caldrons'
become heated, they are borne off by the Gulf Stream, and are
replaced by cooler currents through the Caribbean Sea ; the sur-
face water, as it enters here, being 3° or 4°, and that in depth 40°t
cooler than when it escapes from the Gulf. Taking only this dif-

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

t Temperature of the Caribbean Sea (from the journals of Mr. Dunster\ille) :
Surface temperature, 83° September ; 84° July ; 83°-86i-° Mosquito Coast.
Temperature in depth, 48""% 240 fathoms; 43°, 386 fathoms; 42°, 450 fathoms;
43°, 500 fathoms.

D

50 THE PHYSICAL GEOGRAPHY OF THE SEA.

ference in surface temperature as an index of the heat accumu-
lated there, a simple calculation will show that the quantity of
specific heat daily carried off by the Gulf Stream from those re-
gions, and discharged over the Atlantic, is sufficient to raise mount-
ains of iron from zero to the melting point, and to keep in flow
from them a molten stream of metal greater in volume than the
waters daily discharged from the Mississippi River. Who, there-
fore, can calculate the benign influence of this wonderful current
upon the climate of the South ? In the pursuit of this subject,
the mind is led from nature up to the Great Architect of nature ;
and w^hat mind will the study of this subject not fill with profita-
ble emotions ? Unchanged and unchanging alone, of all created
things, the ocean is the great emblem of its everlasting Creator.
" He treadeth upon the waves of the sea," and is seen in the won-
ders 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 poi'tion of our planet pre-
serves its beautiful system of circulation. By it heat and warmth
are dispensed to the extra-tropical regions ; clouds and rain are
sent to refresh the 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 temperature of the
currents setting into the Caribbean Sea has been found as low as
48°, while that of the surface was 85°. Another cast with three
hundred and eighty-six fathoms gave 43° below against 83° at the
surface. The hurricanes of those regions agitate the sea to great
depths ; that of 1780 tore rocks up from the bottom in seven
fathoms, and cast them on shore. They therefore can not fail to
bring to the surface portions of the cooler water below.

At the very bottom of the Gulf Stream, when its surface tem-
perature was 80°, the deep sea thermometer of the Coast Survey
has recorded temperatures as low as 38° Fahrenheit.

These cold waters doubtless come down from the north to re-
place the warm water sent through the Gulf Stream to moderate
the cold of Spitzbergen ; for within the Arctic Circle, the temper-
ature at corresponding depths off the shores of that island is only
one degree colder than in the Caribbean Sea, while on the coasts
of Labrador the temperature in depth is said to be 25°, or 7° be-
low the melting point of fresh water. Captain Scoresby relates,

INFLUENCE OF THE GULF STREAM UPON CLLMATES. 51

that on the coast of Greenland, in latitude 72°, the temperature
of the air was 42° ; of the water, 34° ; and 29° at the depth of
one hundred and eighteen fathoms. He there found a current set-
ting to the south, and bearing with it this extremely cold water,
with vast numbers of icebergs, whose centres, perhaps, were far
below zero. It would be curious to ascertain the routes of these
under currents on their way to the tropical regions, w^hich they are
intended to cool. One has been found at the equator two hundred
miles broad and 23° colder than the surface water. Unless the
land or shoals intervene, it no doubt comes down in a spiral curve,
approaching the great circle.

65. Perhaps the best indication as to these cold currents may
be derived from the fish of the sea. The whales first pointed out
the existence of the Gulf Stream by avoiding its warm waters.
Along our own coasts, all those delicate animals and marine pro-
ductions which delight in warmer waters are wanting ; thus indi-
cating, by their absence, the cold current from the north now
known 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 shell-fish and coral formations
which are altogether wanting in the same latitudes along the
shores of South Carolina. The same obtains in the west coast- of
South America ; for there the cold current almost reaches the line
before the first sprig of coral is found to grow.

A few years ago, great numbers of bonita and albercore — trop-
ical fish — following the Gulf Stream, entered the English Chan-
nel, and alarmed the fishermen of Cornwall and Devonshire by
the havoc which they created among the pilchards there.

It may well be questioned if our Atlantic cities and towns do not
owe their excellent fish-markets, as well as our watering-places
their refreshing sea-bathing in summer, to this stream of cold water.
The temperature of the Mediterranean is 4° or 5° above the ocean
temperature of the same latitude, and the fish there are very indif-
ferent. On the other hand, the temperature along our coast is sev-
eral degrees below that of the ocean, and from Maine to Florida our
tables are supplied with the most excellent of fish. The sheeps-
head, so much esteemed in Virginia and the Carolinas, when taken
on the warm coral banks of the Bahamas, loses its flavor, and is
held in no esteem. The same is the case with other fish : when

52 THE PHYSICAL GEOGRAPHY OF THE SEA.

taken in the cold water of that coast, they have a dehcious flavor
and are highly esteemed ; but w^hen taken in the w^arm vs' ater on
the other edge of the Gulf Stream, though but a few miles distant,
their flesh is soft and unfit for the table. The temperature of
the water at the Balize reaches 90*^. The fish taken there are
not to be compared with those of the same latitude in this cold
stream. New Orleans therefore resorts to the cool waters on the
Florida coasts for her choicest fish. The same is the case in the
Pacific. A current of cold water from the south sweeps the shores
of Chili, Peru, and Columbia, and reaches the Gallipagos Islands
under the line. Throughout this whole distance, the world does
not afford a more abundant or excellent supply of fish. Yet out
in the Pacific, at the Society Islands, where coral abounds, and the
water preserves a higher temperature, the fish, though they vie in
gorgeousness of coloring with the birds, and plants, and insects of
the tropics, are held in no esteem as an article of food. I have
known sailors, even after long voyages, still to prefer their salt
beef and pork to a mess of fish taken there. The few facts which
we have bearing upon this subject seem to suggest it as a point
of the inquiry to be made, whether the habitat of certain fish does
not indicate the temperature of the water ; and w^hether these cold
and warm currents of the ocean do not constitute the great high-
ways through which migratory fishes travel from one region to
another.

Navigators have often met with vast numbers of young sea-
nettles (medusae) driftmg along with the Gulf Stream. They are
known to constitute the principal food for the whale ; but whither
bound by this route has caused much curious speculation, for it
is well known that the habits of the right whale are averse to the
warm waters of this stream. An intelligent sea-captain informs
me that, two or three years ago, in the Gulf Stream on the coast
of Florida, he fell in with such a " school of young sea-nettles as
had never before been heard of." The sea v as covered with them
for many leagues. He likened them, in appearance on the water,
to acorns floating on a stream ; but they were so thick as to com-
pletely cover the sea. He was bound to England, and was five
or six days in sailing through them. In about sixty days after-
ward, on his return, he fell in with the same school off the West-
ern Islands, and here he was three or four days in passing them

INFLUENCE OF THE GULF STREAM UPON CLIMATES. 53

again. He recognized them as the same, for he had never before
seen any Uke them ; and on both occasions he frequently hauled
up buckets full and examined them.

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

66. The sea has its climates as well as the land. They both
change with the latitude ; but one varies with the elevation above,
the other wdth the depression below the sea level. Each is reg-
ulated by circulation ; but the regulators are, on the one hand,
winds ; on the other, currents.

67. The inhabitants of the ocean are as much the creatures of
climate as are those of the dry land ; for the same Almighty hand
which decked the lily and cares for the sparrow^ fashioned also the
pearl and feeds the great whale. Whether of the land or the sea,
they are all his" creatures, subjects of his laws, and agents in his
economy. The sea, therefore, we infer, has its offices and duties
to perform ; so may we infer, have its currents, and so, too, its
inhabitants ; consequently, he who undertakes to study its phe-
nomena, must cease to regard it as a waste of waters. He must
look upon it as a part of the 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 which
make it a most beautiful and interesting subject for contemplation.

68. To one who has never studied the mechanism of a watch,
its main-spring or the balance-wheel is a mere piece of metal.
He may have looked at the face of the watch, and, while he ad-
mires 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 char-
acter of the machinery which is concealed within. Take it to
pieces, and show him each part separately ; he will recognize
neither design, nor adaptation, nor relation between them ; but
put them together, set them to work, point out the offices of each
spring, wheel, and cog, explain their movements, and then show

54 THE PHYSICAL GEOGRAPHY OF THE SEA.

him the result ; now he perceives that it is all one design ; that,
notwithstanding the number of parts, their diverse forms and va-
rious offices, and the agents concerned, the whole piece is of one
thought, the expression of one idea. He now perceives 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 rachets on that,
&c. ; and his conclusion will be, that such a piece of mechanism
could not have been produced by chance ; the adaptation of the
parts is such as to show it to be according to design, and obedient
to the will of one intelligence. So, too, when one looks out upon
the face of this beautiful world, he may admire the lovely scene,
but his admiration can never grow into adoration unless he will
take the trouble to look behind and study, in some of its details
at least, the exquisite system of machinery by which such beauti-
ful results are accomplished. To him who does this, the sea, with
its physical geography, becomes as the main spring of a watch ;
its w^aters, and its currents, and its salts, and its inhabitants, with
their adaptations, as balance-w^heels, cogs and pinions, and jew-
els. Thus he perceives that they, too, are according to design ;
that they are the expression of One Thought, a unity with harmo-
nies which One Intelligence, and One Intelligence alone, could ut-
ter. And when he has arrived at this point, then he feels that the
study of the sea, in its physical aspect, is truly sublime. It ele-
vates the mind and ennobles the man. The Gulf Stream is now
no longer, therefore, to be regarded by such an one merely as an
immense current of w^arm water running across the ocean, but as
a balance-wheel — a part of that grand machinery by which air
and water are adapted to each other, and by which this earth
itself is adapted to the well-being of its inhabitants — of the flora
which deck, and the fauna which enliven its surface.

69. Let us therefore consider the influence of the Gulf Stream
upon the meteorology of the ocean.

To use a sailor expression, the Gulf Stream is the great " weath-
er breeder" of the North Atlantic Ocean. The most furious gales
of wind sweep along with it ; and the fogs of Newfoundland,
which so much endanger navigation in winter, doubtless owe their
existence to the presence, in that cold sea, of immense volumes
of warm water brought by the Gulf Stream. Sir Philip Brooke

INFLUENCE OF THE GULF STREAM UPON CLIMATES. 55

found 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 cur-
rent produced great irregularities in his chronometers." The ex-
cess of heat daily brought into such a region by the waters of the
Gulf Stream would, if suddenly stricken from them, be sufficient
to make the column of superincumbent atmosphere hotter than
melted iron.

. With such an element of atmospherical disturbance in its bo-
som, we might expect storms of the most violent kind to accom-
pany it in its course. Accordingly, the most terrific that rage on
the ocean have been known to spend their fury in and near its
borders.

Our nautical w^orks tell us of a storm which forced this stream
back to its sources, and piled up the water in the Gulf to the
height of thirty feet. The Ledbury Snow attempted to ride it
out. When it abated, she found herself high up on the dry 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 dam-
med up is said to have rushed out with wonderful velocity against
the fury of the gale, producing a sea that beggared description.

The "great hurricane" of 1780 commenced at 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 w^ere uprooted,
and the waves rose to such a height that forts and castles were
washed away, and their great guns carried about in the air ;
houses were blown down, ships were wrecked, and the bodies of
men and beasts lifted up above the earth and dashed to pieces in
the storm. At the diflferent islands, not less than twenty thou-
sand persons lost their lives on shore, while farther to the north,
the "Sterling Castle" and the "Dover Castle," men-of-war,
were wrecked at sea, and fifty sail driven on shore at the Bermu-
das.

Several years ago, the British Admiralty set on foot inquiries
as to the cause of the storms in certain parts of the Atlantic, which
so often rage with disastrous eflfects 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 tern-

56

THE PHYSICAL GEOGRAPHY OF THE SEA.

perature of the Gulf Stream and of the neighboring regions, both
in the air and water.

70. The habitual dampness of the climate of the British Islands,
as well as the occasional dampness of that along the Atlantic
coasts of the United States when easterly winds prevail, is attrib-
utable also to the Gulf Stream. They come to us loaded with
vapors gathered from its warm and smoking waters.

It carries the temperature of summer, even in the dead of win-
ter, as far north as the Grand Banks of Newfoundland.

71. One of the poles of maximum cold is, according to theory,
situated in latitude 80° north, longitude 100° west. It is distant
but little more than two thousand miles, in a northwestwardly
direction, from the summer-heated waters of this stream. This
proximity of extremes of greatest cold and summer heat, will, as
observations are multiplied and discussed, be probably found to
have much to do with the storms that rage with such fury on the
left side of the Gulf Stream.

72. I am not prepared to maintain that the Gulf Stream is
really the " Storm King" of the Atlantic, which has power to con-
trol the march of every gale that is raised there ; but the course
of many gales has been traced from the place of their origin di-
rectly to the Gulf Stream. Gales that take their rise on the coast
of Africa, and even as far down on that side as the parallel of 10°
or 15° north latitude, have, it has been shown by an examination
of log-books, made straight for the Gulf Stream ; joining it, they
have then been known to turn about, and, traveling with this
stream, to recross the Atlantic, and so reach the shores of Eu-
rope. In this w^ay 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 the meeting of the American Association for
the advancement of Science in 1854, Mr. Redfield mentioned one
which he had traced out, and in which no less than seventy odd
vessels had been wrecked, dismasted, or damaged.

Plate X. was prepared by Lieutenant B. S. Porter, from data
furnished by the log-books at the Observatory. It represents one
of these storms that commenced in August, 1848. It commenced
more than a thousand miles from the Gulf Stream, made a straight
course for it, and traveled with it for many days.

The dark shading shows the space covered by the gale, and

INFLUENCE OF THE GULF STREAM UPON CLIMATES. 57

the white hne in the middle shows the axis of the gale, or the line
of minimum barometric pressure. There are many other instances
of similar gales.

Now what should attract these terrific storms to the Gulf
Stream ? Sailors dread storms in the Gulf Stream more than they
do in any other part of the ocean. It is not the fury of the storm
alone that they dread, but it is the " ugly sea" which these storms
raise. The current of the stream running in one direction, and
the wind blowing in another, creates a sea that is often frightful.

In the month of December, 1853, the fine new steam-ship San
Francisco sailed from New York with a regiment of United States
troops on board, bound around Cape Horn for California. She was
overtaken, while crossing the Gulf Stream, by a gale of wind, in
which she w^as terribly crippled. Her decks were swept, and by
one single blow of those terrible seas that the storms there raise,
one hundred and seventy-nine souls, officers and soldiers, were
washed overboard and drowned.

The day after this disaster she was seen by one vessel, and
again the next day, December 26th, by another, but neither of
them could render her any assistance.

When they arrived in the United States and reported what they
had seen, the most painful apprehensions w^ere entertained by
friends for the safety of those on board. Vessels were sent out
to search for and relieve her. But which way should these ves-
sels go ? where should they look ?

An appeal was made to know what light the system of re-
searches carried on at the National Observatory concerning winds
and currents could throw upon the subject.

73. The materials that had been discussed were examined, and
a chart was prepared to show the course of the Gulf Stream at
that season of the year. (See the limits of the Gulf Stream for
March, Plate V.) Upon the supposition that the steamer had been
completely disabled, the lines a h were drawn to define the limits
of her drift. Between these two lines, it w'as said, the steamer, if
she could neither steam nor sail after the gale, had drifted.

By request, I prepared instructions for two revenue cutters that
were sent to search for her. One of them, being at New London,
was told to go along the dotted track leading to c, expecting
thereby to keep inside of the line along which the steamer had

58 THE PHYSICAL GEOGRAPHY OF THE SEA.

drifted, with the view of intercepting and speaking homeward-
bound vessels that might have seen the wreck.

The cutter was to proceed to c, where she might expect to fall
in with the line of drift taken by the steamer. The last that was
seen of that ill-fated vessel w^as when she was at o. So, if the
cutter had been in time, she had instructions that would have
taken her in sight of the object of her search.

It is true that, before the cutter sailed, the Kilby, the Three
Bells, and the Antarctic, unknown to anxious friends at home,
had fallen in with and relieved the wreck ; but that does not de-
tract from the system of observations, of the results of which,
and their practical application, it is the object of this work to
treat.

A beautiful illustration of their usefulness is the fact that, though
the bark Kilby lost sight of the wreck at night, and the next morn-
ing did not know which way to look for it, and could not find it,
yet, by a system of philosophical deduction, we on shore could
point out the whereabouts of the disabled steamer so closely, that
vessels could be directed to look for her exactly where she was to
be seen.

74. These storms, for which the Gulf Stream has such attrac-
tion, and over which it seems to exercise so much control, are
said to be, for the most part, whirlwinds. All boys are familiar
with miniature whirlwinds on shore. They are seen, especially
in the autumn, sweeping along the roads and streets, raising col-
umns of dust, leaves, &c., which rise up like inverted cones in the
air, and gyrate about the centre or axis of the storm. Thus, while
the axis, and the dust, and the leaves, and all those things which
mark the course of the whirlwind, are traveling in one direction,
it may be seen that the wind is blowing around this axis in all di-
rections.

Just so with some of these Gulf Stream storms. That repre-
sented on Plate X. is such a one. It was a rotary storm. Mr.
Piddington, an eminent meteorologist of Calcutta, calls them Cy-
cloins.

75. Now, what should make these storms travel toward the
Gulf Stream, and then, joining it, travel along with its current ?
It is the high temperature of its waters, say mariners. But why,
or wherefore, should the spirits of the storm obey in this manner

INFLUENCE OF THE GULF STREAM UPON COMMERCE. 59

the influence of these high temperatures, philosophers have not
been able to explain.

76. The influence of the Gulf Stream upon commerce and navi-
gation.

Formerly the Gulf Stream controlled commerce across the At-
lantic by governing vessels in their routes through this ocean to
a greater extent than it does now, and simply for the reason that
ships are faster, instruments better, and navigators are more skill-
ful now than formerly they were.

Up to the close of the last century, the navigator guessed as
much as he calculated the place of his ship : vessels from Europe
to Boston frequently made New York, and thought the land-fall
by no means bad. Chronometers, now so accurate, were then an
experiment. The Nautical Ephemeris 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 " mariner's bow%" had not yet given place to
the nicer sextant and circle of reflection of the present day. In-
stances are numerous of vessels navigating the Atlantic in those
times being 6°, 8°, and even 10° of longitude out of their reckon-
ing in as many days from port.

77. Though navigators had been in the habit of crossing and
recrossing the Gulf Stream almost daily for three centuries, it
never occurred to them to ftiake use of it as a means of giving
them their longitude, and of warning them of their approach to
the shores of this continent.

Dr. Franklin w^as the first to suggest this use of it. The con-
trast afforded by the temperature of its waters and that of the sea
between the Stream and the shores of America was striking. The
dividing line between the warm and the cool w^aters was sharp
(§ 2) ; and this dividing line, especially that on the western side
of the stream, never changed its position as much in longitude as
mariners erred in their reckoning.

78. When he was in London in 1770, he happened to be con-
sulted as to a memorial which the Board of Customs at Boston
sent to the Lords of the Treasury, stating that the Falmouth
packets were generally a fortnight longer to Bosfon than com-
mon traders were from London to Providence, Rhode Island-

60 THE PHYSICAL GEOGRAPHY OF THE SEA.

They therefore asked that the Falmouth packets might be sent to
Providence instead of to Boston. This appeared strange to the
doctor, for London was much farther than 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 fish-
erman explained to him that the difference arose from the circum-
stance that the Rhode Island captains were acquainted with the
Gulf Stream, while those of the English packets were not. The
latter kept in it, and were set back sixty or seventy miles a day,
while the former avoided it altogether. He had been made ac-
quainted with it by the whales which were found on either side of
it, but never in it (§ 65). At the request of the doctor, he then
traced on a chart the course of this stream from the Straits of
Florida. The doctor had it engraved at Tower Hill, and sent
copies of it to the Falmouth captains, who paid no attention to it.
The course of the Gulf Stream, as laid down by that fisherman
from his general recollection of it, has been retained and quoted
on the charts for navigation, we may say, until the present day.

But the investigations of which we are treating are beginning
to throw more light upon this subject ; they are giving us more
correct knowledge in every respect with regard to it, and to many
other new and striking features in the physical geography of the
sea.

79. No part of the world affords a more difficult or dangerous
navigation than the approaches of our northern coast in winter.
Before the warmth of the Gulf Stream was known, a voyage at
this season from Europe 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. Li making
this part of the coast, vessels are frequently met by snow-storms
and gales which mock the seaman's strength and set at naught his
skill. In a little while his bark becomes a mass of ice ; with her
crew 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 disap-
pears from her apparel ; the sailor bathes his stiffened limbs in tep-
id waters; feeling himself invigorated and refreshed with the

INFLUENCE OF THE GULF STREAM UPON COMMERCE. 61

genial warmth about him, he reaUzes, out there at sea, the fable
of Antaeus and his mother Earth. He rises up and attempts to
make his port again, and is again as rudely met and beat back
from the northwest ; 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 fresh-
ened strength prevails, and he at last triumphs and enters his ha-
ven in safety ; though in this contest he sometimes falls to rise no
more, for it is often terrible. Many ships annually founder in
these gales ; and I might name instances, for they are not uncom-
moHj in which vessels bound to Norfolk or Baltimore, with their
crews enervated in tropical climates, have encountered, as far
down as the Capes of Virginia, snow-storms that have driven them
back into the Gulf Stream time and again, and have kept them
out for forty, fifty, and even for sixty days, trying to make an an-
chorage.

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

81. Accordingly, Dr. Franklin's discovery with regard to the
Gulf Stream temperature was looked upon as one of great import-
ance, not only on account of its affording to the frosted mariner in
winter a convenient refuge from tjie 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 con-
cealed his discovery, for we were then at war with England. It
was then not uncommon for vessels to be as much as 10^ out in

62 THE PHYSICAL GEOGRAPHY OF THE SEA.

their reckoning. He himself was 5°. Therefore, in approaching
the coast, the current of warm water in the Gulf Stream, and of
cold water on this side of it, if tried with the thermometer, would
enable the mariner to judge with great certainty, and in the worst
of weather, as to his position. Jonathan Williams afterward, in
speaking of the importance which the discovery of these warm
and cold currents would prove to navigation, pertinently asked the
question, " If these stripes of water had been distinguished by the
colors of red, white, and blue, could they be more distinctly dis-
covered 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 ?

When his work on Thermometrical Navigation appeared. Com-
modore Truxton wrote to him : " Your publication 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 unacquainted with

astronomical observations ; these particularly stand in need

of a simple method of ascertaining their approach to or distance
from the coast, especially in the winter season ; for it is then that
passages are often prolonged, and ships blown off the coast by
hard westerly winds, and vessels get into the Gulf Stream with-
out its being known ; on which account they are often hove to by
the captains' supposing themselves near the coast when they are
very far off (having been drifted by the currents). On the other
hand, ships are often cast on the coast by sailing in the eddy of
the Stream, which causes them to outrun their common reckoning.
Every year produces new proofs of these facts, and of the calam-
ities incident thereto."

82. Though Dr. Franklin's discovery was made in 1775, yet, for
political reasons, it was not generally made known till 1790. Its
immediate effect in navigation was to make the ports of the North
as accessible in winter as in summer. What agency this circum-
stance had in the decline of the direct trade of the South, which
followed this discovery, would be, at least to the political econo-
mist, a subject for much curious and interesting speculation. I
have referred to the commercial tables of the time, and have com-

INFLUENCE OF THE GULF STREAM UPON COMMERCE. 63

pared 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 in-
crease in that of the North. But whether this discovery in navi-
gation and this revolution in trade stand in the relation of cause
and effect, or be merely a coincidence, let others judge.

83. In 1769, the commerce of the two Carolinas equaled that
of all the New England States together ; it was more than double
that of New York, and exceeded that of Pennsylvania by one
third.* In 1792, the exports from New York amounted in value
to two milhons and a half ; from Pennsylvania, to $3,820,000 ;
and from Charleston alone, to $3,834,000.

But in 1795, by w^hich time the Gulf Stream began to be as
w^ell understood by navigators as it now is, and the average pas-
sages from Europe to the North were shortened nearly one half,
while those to the South remained about the same, the customs at
Philadelphia alone amounted to $2,941,000,1 or more than one
half of those collected in all the states together.

Nor did the effect of the doctor's discovery end here. Before

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

EXPORTS.

To Gr. Britain. I Sou, of Europe. | West Indies.

Africa.

Total.

New England

New York

Pennsylvania

North and South Carolina.

£ s.d.\ £ s. d.\ £ s.

142,775 12 9 81,173 16 21308,427 9

113,382 8 8| 50,685 13 0] 66,324 17

28,112 6 9 203,762 11 lljl78,331 7

405,014 13 l| 76,119 12 10 87,758 19

£ s.d. £ s.d.\

17,713 0 9 550,089 19 2i

1,313 2 6 231,906 1 7l

560 9 9 410,756 16 l!

691 12 1 569,584 17 2\

IMPORTS.

New England '223,695 11 6! 25,408 17 9 314,749 14 5 180 0 0,564,034 3 8

New York ! 75,930 19 71 14,927 7 8 97,420 4 0 697 10 0 188,976 1 3

Pennsylvania 204,979 17 4^ 14,249 8 4 180,591 12 4 1399.830 18 0

North and South Carolina. .. 327,084 8 6^ 7,099 5 10 76,269 17 11 137.620 10 0 535,714 2 3

t Value of Exports in

Dollar s.X

1791.

1792.

1793. 1 1794. 1795. | 1796.

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

2,888.104
2,535,790
3,820,000
2,428,000

3,755,347! 5.292,441 7,117,907 9.949,345
2,932,370 5,442,000 10,304,000 12,208,027
6,958,000! 6.643.000111,518,000 17,513.866
3,191,0001 3,868,000 5,998,000| 7,620,000.

New York

Pennsylvania

South Carolina

Duties on Imports in Dollars.

1791.

1792.

1793.

1794.

1795.

1790.

1S33.

Massachusetts

New York

1,006,000

1,334,000

1,466,000

523,000

723,000
1,173,000
1,100,000

359,000

1,044,000

1,204,000

1,823,000

360,000

1.121,000

1,878.000

1,498,000

661.000

1.520,00(!

2,028,000

2,300,000

722,000

l,4r-0.0(.(

2.]87.00('

2,050,000

66,000

3.(1.55,000

10,713.000

2,207,000

389.000

1 Pennsylvania

South Carolina

i Doc. No. 330, 11. R., 2d Session, 25th Congress. Some of its statements do not agree with those
taken from M'Pherson, and previously quoted.

64 THE PHYSICAL GEOGRAPHY OF THE SEA.

It was made, the Gulf Stream was altogether insidious in its ef-
fects. By it, vessels wejre often drifted many miles out of their
course 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 for but a few hours during
the interval, could only be proportioned out equally among the
whole number of days. Therefore navigators could have only
very vague ideas either as to the strength or the actual limits of
the Gulf Stream, until they were marked out to the Nantucket
fishermen by the whales, or made known by Captain Folger to
Dr. Franklin. The discovery, therefore, of its high temperature,
assured the navigator of the presence of a current of surprising
velocity, and which, now turned to certain account, would hasten,
as it had retarded his voyage in a wonderful degree.

84. Such, at the present day, is the degree of perfection to
which nautical tables and instruments have been brought, that

■the navigator may now detect, and with great certainty, every
current that thwarts his way. He makes great use of them.
Colonel Sabine, in his passage, a few years ago, from Sierra Le-
one to New York, was drifted one thousand six hundred miles of
his way by the force of currents alone ; and, since the application
of the thermometer to the Gulf Stream, the average passage from
England has been reduced from upward of eight weeks to a little
more than four.

85. Some political economists of America have ascribed the
great decline of Southern commerce which followed the adoption
of the Constitution of the United States to the protection given
by legislation to Northern interests. But I think these statements
and figures show that this decline was in no small degree owing
to the Gulf Stream and the water thermometer ; for they changed
the relations of Charleston — the great Southern emporium of the
times — removing it from its position as a half-way house, and
placing it in the category of an outside station.

86. The plan of our work takes us necessarily into the air, for
the sea derives from the winds some of the most striking features
in its physical geography. Without a knowledge of the winds, w^e
can neither understand the navigation of the ocean, nor make our-
selves intelligently acquainted with the great highways across it.
As with the land, so with the sea ; some parts of it are as un-

INFLUENCE OF THE GULF STREAM UPON COMMERCE, 55

traveled and as unknown as the great Amazonian wilderness of
Brazil, or the inland basins of Central Africa. To the south of a
line extending from Cape Horn to the Cape of Good Hope (Plate
VHI.) is an immense waste of waters. None of the commercial
thoroughfares of the ocean lead through it ; only the adventurous
whaleman finds his way there now and then in pursuit of his
game ; but for all the purposes of science and navigation, it is a
vast unknown region. Now, were the prevailing winds of the
South Atlantic northerly or southerly, instead of easterly or west-
erly, this unplowed sea would be an oft-used thoroughfare.

87. Nay, more, the sea supplies the winds with food for the
rain which these busy messengers convey away from the ocean
to "the springs in the valleys which run among the hills." To
the philosopher, the places which supply the vapors are as sug-
gestive and as interesting for the instruction they afford, as the
places are upon which the vapors are showered down. There-
fore, as he who studies the physical geography of the land is ex-
pected to make himself acquainted with the regions of precipita-
tion, so he who looks into the physical geography of the sea should
search for the regions of evaporation, and for those springs in
the ocean which supply the reservoirs among the mountains with
water to feed the rivers ; and, in order to conduct this search
properly, he must consult the winds, and make himself acquainted
with their '' circuits." Hence, in a work on the Physical Geog-
raphy of the Sea, we treat also of the x^tmosphere.

E

66 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER III.

THE ATMOSPHERE.

The Relation of the Winds to the Physical Geography of the Sea, ^ 88. — No Expres-
sion of Nature without Meaning, 93. — The Circulation of the Atmosphere, Plate I.,
95. — Southeast Trade-wind Region the larger, 109. — How the Winds approach the
Poles, 112. — The Offices of the Atmosphere, 114. — It is a powerful Machine, 118. —
Whence come the Rains that feed the great Rivers 1 120. — How Vapor passes
from one Hemisphere to the other, 123. — Evaporation greatest about Latitude 17°-
20^, 127.— Explanation, 128.— The Rainy Seasons : how caused, 129.— Why there
is one Rainy Season in California, 130 — One at Panama, 131 — Two at Bogota,
132. — Rainless Regions explained, 135. — Why Australia is a Dry Country, 136, —
Why Mountains have a dry and a rainy Side, 137. — The immense Fall of Rain
upon the Western Ghauts in India : how caused, 139. — Vapor for the Patagonia
Rains comes from the North Pacific, 141. — The mean annual Fall gf Rain, 144. —
Evaporation from the Indian Ocean, 146. — Evidences of Design, 148.

88. A PHILOSOPHER of the East,* with a richness of imagery
truly Oriental, describes the atmosphere as " a spherical shell
which surrounds our planet to a depth which is unknown to us, by
reason of its growing tenuity, as it is released from the pressure
of its own superincumbent mass. Its upper surface can not 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 softest down — 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 world, and crushes the most re-
fractory substances with its weight. When in motion, its force is
suflicient to level the most stately forests and stable buildings
with the earth — to raise the waters of the ocean into ridges like
mountains, and dash the strongest ships to pieces like toys. It
warms and cools by turns the earth and the living creatures that
inhabit it. It draws up vapors from the sea and land, retains

* Dr. Buist, of Bombay.

THE ATMOSPHERE. qj

them dissolved in itself, or suspended in cisterns of clouds, and
throws them down again as rain or dew when they are required.
It bends the rays of the sun from their path, to give us the twi-
light of evening and of dawn ; it disperses and refracts their va-
rious tints to beautify the approach and the retreat of the orb of
day. But for the atmosphere, sunshine would burst on us and
fail us at once, and at once remove us from midnight darkness to
the blaze of noon. We should have no twihght to soften and
beautify the landscape ; no clouds to shade us from the scorching
heat, but the bald earth, as it revolved on its axis, would turn its
tanned and weakened front to the full and unmitigated rays of the
lord of day. It affords the gas which vivifies and warms our
frames, and receives into itself that which has been polluted by
use, and is thrown off as noxious. It feeds the flame of life ex-
actly as it does that of the fire — it is in both cases consumed, and
affords the food of consumption — in both cases it becomes com-
bined with charcoal, w^hich requires it for combustion, and is re-
moved by it when this is over."

"It is only the girdling encircling air," says another philoso-
pher,* "that flows above and around all, that makes the whole
world kin. The carbonic acid with which to-day our breathing
fills the air, to-morrow seeks its way round the world. The date-
trees that grow round the falls of the Nile will drink it in by their
leaves ; the cedars of Lebanon will take of it to add to their stat-
ure ; the cocoa-nuts of Tahiti will grow rapidly upon it, and the
palms and bananas of Japan will change it into flowers. The
oxygen we are breathing was distilled for us some short time ago
by the magnolias of the Susquehanna, and the great trees that
skirt the Orinoco and the Amazon — the giant rhododendrons of
the Himalayas contributed to it, and the roses and myrtles of
Cashmere, the cinnamon-tree of Ceylon, and the forest older than
the flood, buried deep in the heart of Africa, far behind the Mount-
ains of the Moon. The rain we see descending was thawed for
us out of the icebergs w^hich have watched the polar star for ages,
and the lotus lilies have soaked up from the Nile, and exhaled as
vapor, snows that rested on the summits of the Alps."

89. "The atmosphere," continues Maun, "which forms the outer
surface of the habitable world, is a vast reservoir, into which the

* Vide North British Review.

68 THE PHYSICAL GEOGRAPHY OF THE SEA.

supply of food designed for living creatures is thrown ; or, in one
word, it is itself the food, in its simple form, of all living crea-
tures. The animal grinds down the fibre and the tissue of the
plant, or the nutritious store that has been laid up within its cells,
and converts these into the substance of which its own organs are
composed. The plant acquires the organs and nutritious store
thus yielded up as food to the animal, from the invulnerable air
surrounding it."

" But animals are furnished with the means of locomotion and
of seizure — they can approach their food, and lay hold of and
swallow it ; plants must wait till their food comes to them. No
solid particles find access to their frames ; the restless ambient
air which rushes past them loaded with the carbon, the hydrogen,
the oxygen, the water — every thing they need in the shape of sup-
plies is constantly at hand to minister to their wants, not only to
afford them food in due season, but in the shape and fashion in
which alone it can avail them."

90. There is no more worthy or suitable employment of the
human mind than to trace the evidences of design and purpose
in the Creator, 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 some-
thing more than a shoreless ocean, at the bottom of which his
bark is wafted or driven along. It is an envelope or covering for
the dispersion of light and heat over the surface of the earth ; it
is a sew^er into which, w4th every breath we draw, w^e cast vast
quantities of dead animal matter ; it is a laboratory for purifica-
tion, in which that matter is recompounded, and wrought again
into wholesome and healthful shapes ; it is a machine (§87) for
pumping up all the rivers from the sea, and conveying the w^aters
for their fountains on the ocean to their sources in the mount-
ains.

91. Upon the proper working of this machine depends the well-
being of every plant and animal that inhabits the earth ; there-
fore the management of it, or its movement, or the performance
of its offices, can not be left to chance. They are, we may rely
upon it, guided by laws that make all parts, functions, and move-
ments of the machinery as obedient to order as are the planets in
their orbits.

THE ATMOSPHERE.

69

92. An examination into the economy of the universe will be
sufficient to satisfy the well-balanced minds of observant men
that the laws which govern the atmosphere and the laws which
govern the ocean (§ 67) are laws which w^ere 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
winds and sea obey the voice of rebuke ?

93. To one who looks abroad to contemplate the agents of na-
ture, as he sees them at work upon our planet, no expression ut-
tered nor act performed by them is without meaning. By such an
one, the w^ind and rain, the vapor and the cloud, the tide, the cur-
rent, the saltness, and depth, and warmth, and color of the sea, the
shade of the sky, the temperature of the air, the tint and shape of
the clouds, the height of the tree on the shore, the size of its
leaves, the brilliancy of its flowers — each and all may be regarded
as the exponent of certain physical combinations, and therefore as
the expression in which Nature chooses to announce her own do-
ings, or, if we please, as the language in which she WTites down
or chooses to make known her own laws. To understand that
language and to interpret aright those law^s is the object of the
undertaking which we now^ have in hand. No fact gathered in
such a field as the one before us can, therefore, come amiss to
those who tread the walks of inductive philosophy ; for, in the
hand-book of nature, every such fact is a syllable ; and it is by pa-
tiently 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 and the philosopher on the
mountain see spread out before them.

94. Of its Circulation. — We have seen (§31) that there are
constant currents in the ocean ; w^e shall now see that there are
also regular currents in the atmosphere.

95. From the parallel of about 30° north and south, nearly to
the equator, we have, extending entirely around the earth, two
zones of perpetual winds, viz., the zone of northeast trades on this
side, and of southeast on that. They blow perpetually, and are

70

THE PHYSICAL GEOGRAPHY OF THE SEA.

as steady and as constant as the currents of the Mississippi River

always moving in the same direction (Plate L). As these two

PLATE L

DIAGRAM OF THE WINDS.

currents of air are constantly flowin- from the poles toward the
equator, we are safe in assuming that the air which they keep m
motion must return by some channel to the place near 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 atmos-
phere, and pile it up about the equator, and then cease to blow
for the want of air to make more wind of.

THE ATMOSPHERE. 7I

96. This return current, therefore, must be in the upper regions
of the atmosphere, at least until it passes over those parallels be-
tween which the trade-winds are always blowing on the surface.
The return current must also move in the direction opposite to
that wind the place of which it is intended to supply. These di-
rect and counter currents are also made to move in a sort of spiral
or loxodromic curve, turning to the west as they go from the poles
to the equator, and in the opposite direction as they move from
the equator to the poles. This turning is caused by the rotation
of the earth on its axis.

97. The earth, we know% moves from west to east. Now if we
imagine a particle of atmosphere at the north pole, where it is at
rest, to be put in motion in a straight line toward the equator, we
can easily see how this particle of air, coming from the very axis
of the pole, where it did not partake of the diurnal motion of the
earth, would, in consequence of its vis inerticE^ find, as it travels
south, the earth slipping from under it, as it were, and thus it
would appear to be coming from the northeast and going toward
the southwest ; in other words, it would be a northeast wind.

The better to explain, let us take a common terrestrial globe
for the illustration. Bring the island of Madeira, or any other
place about the same parallel, under the brazen meridian ; put a
finger of the left hand on the place ; then, moving the finger down
along the meridian to the south, to represent the particle of air,
turn the globe on its axis from west to east, to represent the diur-
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 northward and eastw^ard.

98. 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, in consequence of
its vis inerti(2, be going toward the east faster than the earth.
It would, therefore, appear to be blowing from the southwest, and
going toward the northeast, and exactly in the opposite direction
to the other. Writing south for north, the same takes place be-
tween the south pole and the equator.

72 THE PHYSICAL GEOGRAPHY OF THE SEA.

Such is the process which is actually going on in nature ; and if
we take the motions of these two particles as the type of the mo-
tion of all, we shall have an illustration of the great currents in
the air, the equator being near one of the nodes, and there being
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 northeast trade-wind extending
from the pole to the equator would satisfy it ; and were this so,
we should have, on the surface, no winds but the northeast trade-
winds on this side, and none but southeast trade-winds on the
other side, of the equator.

99. Let us return now to our northern particle (Plate I., p. 70),
and follow it in a round from the north pole across the equator to
the south pole, and back again. Setting off from the polar re-
gions, this particle of air, for some reason which does not appear
to have been very satisfactorily explained by philosophers, instead
of traveling (^ 98) on the surface all the way from the pole to the
equator, travels in the upper regions of the atmosphere until it
gets near the parallel of 30°. Here it meets, also in the clouds,
the hypothetical particle that is coming from the south, and going
north to take its place.

100. About this parallel of 30° north, then, these two particles
press against each other with the whole amount of their motive
power, and produce a calm and an accumulation of atmosphere :
this accumulation is sufficient to balance the pressure of the two
winds from the north and south.

101. From under this bank of calms, which seamen call the
" horse latitudes" (I have called them the calms of Cancer), two
surface currents of wind are ejected ; one toward the equator, as
the northeast trades, the other toward the pole, as the southwest
passage-winds.

These winds come out at the lower surface of the calm region,
and consequently the place of the air borne away in this manner
must be supplied, we may infer, by downward currents from the
superincumbent air of the calm region. Like the case of a vessel
of water which has two streams from opposite directions running
in at the top, and two of equal capacity discharging in opposite

THE ATMOSPHERE. ^3

directions at the bottom, the motion of the water would be down-
ward, so is the motion of the air in this calm zone.

102. The barometer, in this calm region, is said to stand higher
than it does either to the north or to the south of it ; and this is
another proof as to the banking up here of the atmosphere, and
pressure from its downward motion.

103. Following our imaginary particle of air from the north
across this calm belt, we now feel it moving on the surface of the
earth as the northeast trade-wind ; and as such it continues, till it
arrives near the equator, where it meets a like hypothetical par-
ticle, which, starting from the south at the same time the other
started from the north pole, has blown as the southeast trade-wind.

104. Here, at this equatorial place of meeting, there is another
conflict of winds and another calm region, for a northeast and
southeast wind can not blow^ at the same time in the same place.
The two particles have been put in motion by the same power ;
they meet with equal force ; and, therefore, at their place of meet-
ing, are stopped in their course. Here, therefore, there is a calm
belt.

105. Warmed now by the heat of the sun, and pressed on each
side by the whole force of the northeast and southeast trades,
these two hypothetical particles, taken as the type of the whole,
cease to move onw^ard and ascend. This operation is the reverse
of that which took place at the meeting (§ 100) near the parallel
of 30°.

106. This imaginary particle then, having ascended to the up-
per regions of the atmosphere again, travels there counter to the
southeast trades, until it meets, near the calm belt of Capricorn,
another particle from the south pole ; here there is a descent as
before (§ 101) ; it then (§ 98) flows on toward the south pole as
a surface wind from the northw^est.

Entering the polar regions obliquely, it is pressed upon by sim-
ilar particles flowing in oblique currents across every meridian ;
and here again is a calm place or node ; for, as our imaginary par-
ticle approaches the parallels near the polar calms more and more
obhquely, it, with all the rest, is whirled about the pole in a con-
tinued circular gale ; finally, reaching the vortex or the calm place,
it is carried upward to the regions of atmosphere above, whence
it commences again its circuit to the north as an upper current, as

74 THE PHYSICAL GEOGRAPHY OF THE SEA.

far as the calm belt of Capricorn ; here it encounters (§ 106) its
fellow from the north (^ 98) ; they stop, descend, and flow out as
surface currents (^ 101), the one with which the imagination is
traveling, to the equatorial calms as the southeast trade-wind ;
here (§ 104) it ascends, traveling thence to the calm belt of Can-
cer as an upper current counter to the northeast trades. Here
(§ 100 and 99) it ceases to be an upper current, but, descending
(§ 101), travels on with the southwest passage-winds toward the
pole.

Now the course we have imagined an atom of air to take is this
(Plate I.) : an ascent at P, at the north pole ; an efflux thence as
an upper current (^ 99) until it meets G (also an upper current)
over the calms of Cancer. Here (^ 100) there is supposed to be
a descent, as shown by the arrows along the wavy lines which en-
velop the circle. This upper current from the pole (^ 97) now
becomes the northeast trade-wind B (^ 103), on the surface, until
it meets the southeast trades in the equatorial calms, when it
ascends and travels as C with the upper current to the calms of
Capricorn, then as D with the prevailing northwest surface cur-
rent 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 E, F, G, and H.

107. The Bible frequently makes allusions to the laws of nature,
their operation and effects. But such allusions are often so wrap-
ped in the folds of the peculiar and graceful drapery with which
its language is occasionally clothed, that the meaning, though
peeping out from its thin covering all the while, yet lies in some
sense concealed, until the lights and revelations of science are
thrown upon it ; then it bursts out and strikes us with the more
force and beauty.

As our knowledge of Nature and her laws has increased, so has
our understanding of many passages in the Bible been improved.
The Bible called the earth " the round world ;" yet for ages it was
the most damnable heresy for Christian men to say the world is
round ; and, finally, sailors circumnavigated the globe, proved the
Bible to be right, and saved Christian men of science from the
stake.

" Canst thou tell the sweet influences of the Pleiades ?"

Astronomers of the present day, if they have not answered this

THE ATMOSPHERE. 75

question, have thrown so much hght upon it as to show that, if
ever it be answered by man, he must consult the science of astron-
omy. 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 inconceiv-
ably remote, and that that point is in the direction of the star Al-
cyon, 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 endeavoring to describe, the Bible tells
it all in a single sentence : " The wind goeth toward the south,
and turneth about unto the north ; it w^hirleth about continually,
and the wind returneth again according to his circuits." — EccL,
i.,6.

108. Of course, as the surface winds H and D (Plate I.) ap-
proach the poles, there must be a sloughing off, if I may be al-
lowed the expression, of air from the surface winds, in consequence
of their approaching the poles. For as they near the poles, the
parallels become smaller and smaller, and the surface current
must either extend much higher up, and blow with greater rapid-
ity as it approaches the poles, or else a part of it must be slough-
ed off above, and so turn back before reaching the poles. The
latter is probably the case.

Our investigations show that the southeast trade-wind region is
much larger than the northeast. I speak now of its extent over
the Atlantic Ocean only ; that the southeast trades are the fresh-
er, and that they often push themselves up to 10° or 15° of north
latitude ; whereas the northeast trade-wind seldom gets south of
the equator.

The peculiar clouds of the trade-winds are formed between the
upper and lower currents of air. They are probably formed of
vapor condensed from the upper current, and evaporated as it de-
scends by the lower and dry current from the poles. It is the
same phenomenon up there which is so often observed here below ;
when a cool and dry current of air meets a warm and wet one, an
evolution of vapor or fog ensues.

We now see the general course of the " wind in his circuits,"
as we see the general course of the water in a river. There are
many abrading surfaces, irresrularitics, &c., which produce a thou-

76 THE PHYSICAL GEOGRAPHY OF THE SEA.

sand eddies in the main stream ; yet, nevertheless, the general di-
rection of the whole is not distm'bed nor affected by those counter
currents ; 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 (§ 92)
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 they " sang together ?"

109. There are at least two forces concerned in driving the
wind through its circuits. We have seen (^ 97 and § 98) whence
that force is derived which gives easting to the winds as they ap-
proach the equator, and westing as they approach the poles, and
allusion, without explanation, has been made (^ 105) to the source
whence they derive their northing and their southing. The trade-
winds are caused, it is said, by the inter-tropical heat of the sun,
which, expanding the air, causes it to rise up near the equator ;
it then flows off in the upper currents north and south, and there
is a rush of air at the surface both from the north and the south
to restore the equilibrium — hence the trade-winds. But to the
north side of the trade-wind belt in the northern, and on the south
side in the southern hemisphere, the prevailing direction of the
winds is not toward the source of heat about the equator, but ex-
actly in the opposite direction. In the extra-tropical region of
each hemisphere the prevailing winds blow from the equator to-
ward the poles. It therefore at first appears paradoxical to say
that heat makes the easterly winds of the torrid zone blow toward
the equator, and the w^esterly winds of the temperate zones to
blow toward the poles. Let us illustrate :

110, The p'imum mobile of the extra-tropical winds toward the
equator is, as just intimated, generally ascribed to heat, and in
this wise, viz. : Suppose, for the moment, the earth to have no di-
urnal rotation ; that it is at rest ; that the rays of the sun have
been cut off" from it ; that the atmosphere has assumed a mean
uniformity of temperature, the thermometer at the equator and
the thermometer at the poles giving the same reading ; that the
winds are still, and that the whole aerial ocean is in equilibrium
and at rest. Now^ imagine the screen which is supposed to have
shut off the influence of the sun to be removed, and the whole at-
mosphere to assume the various temperatures in the various parts

THE ATMOSPHERE. 77

ot the world that it actually has at this moment, what w^ould take
place, supposing the uniform temperature to be a mean between
that at the equator and that at the poles ? Why, this would take
place : a swelling up of the atmosphere about the equator by the
expansive force of inter-tropical heat, and a contraction of it about
the poles in consequence of the cold. These two forces, consid-
ering them under their most obvious effects, would disturb the
supposed atmospherical equilibrium by altering the level of the
great aerial ocean ; the expansive force of heat elevating it about
the equator, and the contracting powers of cold depressing it about
the poles. And forthwith two systems of winds would commence
to blow, viz., one in the upper regions from the equator toward
the poles, and as this warm and expanded air should flow toward
either pole, seeking its level, a wind w^ould blow on the surface
from either pole to restore the air to the equator which the upper
current had carried off.

These two winds would blow due north and south ; the effects
of heat at the equator, and cold at the poles, wo^ld cause them so
to do. Now suppose the earth to commence its diurnal rotation ;
then, instead of having these winds north and south winds, they
will, for reasons already explained (^ 97), approach the equator
on both sides with easting in them, and each pole with westing.

111. The circumference of the earth measured on the parallel
of 60° is only half what it is when measured on the equator.
Therefore, supposing velocity to be the same, only half the vol-
ume of atmosphere (^ 109) that sets off from the equator as an
upper current toward the poles can cross the parallel of 60° north
or south. The other moiety has been gradually drawn in and
carried back (^ 108) by the current which is moving in the oppo-
site direction.

Such, and such only, would be the extent of the power of the
sun to create a polar and equatorial flow of air, were its power
confined simply to a change of level. But the atmosphere has
been invested with another property w^hich increases its mobility,
and gives the heat of the sun still more power to put it in motion,
and it is this : as heat changes the atmospherical level, it changes
also the specific gravity of the air acted upon. If, therefore, the
level of the great aerial ocean were undisturbed by the sun's rays,
and if the air were adapted to a change of specific gravity alone,

78 THE PHYSICAL GEOGRAPHY OF THE SEA.

without any change in volume, this quahty would also be the
source of at least two systems of currents in the air, viz., an up-
per and a lower. The two agents combined, viz., that which
changes level or volume, and that which changes specific gravity,
give us the general currents under consideration. Hence we say
that the primum mobile of the air is derived from change of speci-
fic gravity induced by the freezing temperature of the polar re-
gions, as well as from change of specific gravity due the expand-
ing force of the sun's rays within the tropics.

112. Therefore, fairly to appreciate the extent of the influence
due the heat of the sun in causing the winds, it should be recol-
lected that w^e may with as much reason ascribe to the inter-
tropical heat of the sun the northwest winds, which are the pre-
vailing winds of the extra-tropical regions of the southern hemi-
sphere, or the southwest winds, which are the prevailing winds
of the extra-tropical regions of the northern hemisphere, as we
may the trade-winds, which blow^ in the opposite directions. Par-
adoxical, therefore, as it seems for us to say that the heat of the
sun causes the winds between the parallels of 25° or 30° north
and south to blow toward the equator, and that it also causes the
prevailing winds on the polar sides of these same parallels to blow
toward the poles, yet the paradox ceases when w^e come to rec-
ollect that by the process of equatorial heating and polar cooling
which is going on in the atmosphere, the specific gravity of the
air is changed as well as its level. Nevertheless, as Halley said,
in his paper read before the Royal Society in London in 1686,
and as we also have said (§ 99), "it is likewise very hard to con-
ceive why the limits of the trade-wind should be fixed about the
parallel of latitude 30° all around the globe, and that they should
so seldom exceed or fall short of those bounds."

113. Operated upon by the equilibrating tendency of the at-
mosphere and by diurnal rotation, the wind approaches the north
pole, for example, by a series of spirals from the southwest. If
we draw a circle about this pole on a common terrestrial globe,
and intersect it by spirals to represent the direction of the wind,
we shall see that the wind enters all parts of this circle from the
southwest, and, consequently, that a whirl ought to be created
thereby, in which the ascending column of air revolves from right
to left, or against the hands of a watch. At the south pole the

THE ATMOSPHERE. 79

winds come from the northwest (^ 106), and consequently there
they revolve about it with the hands of a watch.

That this should be so will be obvious to any one who will look
at the arrows on the polar sides of the calms of Cancer and Cap-
ricorn (Plate I., p. 70). These arrows are intended to represent
the prevailing direction of the wind at the surface of the earth on
the polar side of these calms.

114. It is a singular coincidence between these two facts thus
deduced, and other facts which have been observed, and which
have been set forth by Redfield, Reid, Piddington, and others, viz.,
that all rotary storms in the northern hemisphere revolve as do
the w^hirlwinds about the north pole, viz., from right to left, and
that all circular gales in the southern hemisphere revolve in the
opposite direction, as does the whirl about the south pole.

How can there be any connection between the rotary motion
of the wind about the pole, and the rotary motion of it in a gale
caused here by local agents ?

That there is probably such a connection has been suggested
by other facts and circumstances, and perhaps I shall be enabled
to make myself clearer when we come to treat of these facts and
circumstances, and to inquire farther, as at § 172, into the rela-
tions between magnetism and the circulation of the atmosphere ;
for, although the theory of heat satisfies many conditions of the
problem, and though heat, doubtless, is one of the chief agents in
keeping up the circulation of the atmosphere, yet it can be made
to appear that it is not the sole agent.

115. Some of its Meteorological Agencies. — So far, we see
how the atmosphere moves ; but the atmosphere, like every other
department in the economy of nature, has its offices to perform,
and they are many. I have already alluded to some of them ;
but I only propose, at this time, to consider some of the meteoro-
logical agencies at sea, which, in the grand design of creation,
have probably been assigned to this wonderful machine.

To distribute moisture over the surface of the earth, and to
temper the climate of different latitudes, it would seem, are two
great offices assigned by their Creator to the ocean and the air.

When the northeast and southeast trades meet and produce the
equatorial calms (§ 104), the air, by this time, is heavily laden
with moisture, for in each hemisphere it has traveled obliquely

80 THE PHYSICAL GEOGRAPHY OF THE SEA.

over a large space of the ocean. It has no room for escape but
in the upward direction (§ 105). It expands as it ascends, and
becomes cooler ; a portion of its vapor is thus condensed, and
comes dov^^n in the shape of rain. Therefore it is that, under
these calms, w^e have a region of constant precipitation. Old
sailors tell us of such dead calms of long continuance here, of
such heavy and constant rains, that they have scooped up fresh
w^ater from the surface of the sea.

116. The conditions to which this air is exposed here under the
equator are probably not such as to cause it to precipitate all the
moisture that it has taken up in its long sweep across the waters.
Let us see what becomes of the rest ; for Nature, in her economy,
permits nothing to be taken away from the earth which is not to
be restored to it again in some form, and at some time or other.

Consider the great rivers — the Amazon and the Mississippi, for
example. We see them day after day, and year after year, dis-
charging an immense volume of water into the ocean.

" All the rivers run into the sea, yet the sea is not full." — Ecc.
i., 7. Where do the waters so discharged go, and where do they
come from ? They come from their sources, you will say. But
whence are their sources supplied ? for, unless what the fountain
sends forth be returned to it again, it will fail and be dry.

1 17. We see simply, in the waters that are discharged by these
rivers, the amount by which the precipitation exceeds the evapor-
ation throughout the whole extent of valley drained by them ; and
by precipitation I mean the total amount of water that falls from,
or is deposited by the atmosphere, whether as dew, rain, hail, or
snow.

The springs of these rivers (§ 87) are supplied from the rains
of heaven, and these rains are formed of vapors which are taken
up from the sea, that " it be not full," and carried up to the mount-
ains through the air.

*' Note the place whence the rivers come, thither they return
again."

118. Behold now the waters of the x4.mazon, of the Mississippi,
the St. Lawrence, and all the great rivers of America, Europe,
and Asia, lifted up by the atmosphere, and flowing in invisible
streams back through the air to their sources among the hills
(§ 87), and that through channels so regular, certain, and well de-

THE ATMOSPHERE. 81

fined, that the quantity thus conveyed one year with the other is
nearly the same : for that is the quantity which we see running
down to the ocean through these rivers ; and the quantity dis-
charged annually by each river is, as far as we can judge, nearly
constant.

We now begin to conceive what a powerful machine the at-
mosphere must be ; and, though it is apparently so capricious and
wayward in its movements, here is evidence of order and arrange-
ment which we must admit, and proof which we can not deny,
that it performs this mighty office with regularity and certainty,
and is therefore as obedient to law as is the steam-engine to the
will of its builder.

119. It, too, is an engine. The South Seas themselves, in all
their vast inter-tropical extent, are the boiler for it, and the north-
ern hemisphere is its condenser.

120. Where does the vapor that makes the rains lohichfeed the
rivers of the northern heinisphere come from ?

The proportion between the land and water in the northern
hemisphere is very different from the proportion 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 w^ater than land. All the great rivers in the world are in
the northern hemisphere, where there is less ocean to supply them.
Whence, then, are their sources replenished ? Those of the Ama-
zon are supplied with rains from the equatorial calms and trade-
winds of the Atlantic. That river runs east, its branches come
from the north and south ; it is always the rainy season on one
side or the other of it ; consequently, it is a river without periodic
stages of a very marked character. It is always near its high-
water mark. For one half of the year its northern tributaries are
flooded, and its southern for the other half. It discharges under
the line, and as its tributaries come from both hemispheres, it can
not be said to belong exclusively to either. It is suppUed with
water from the Atlantic Ocean. Taking the Amazon, therefore,
out of the count, the Rio de la Plata is the only great river of the
southern hemisphere.

There is no large river in New Holland. The South Sea Isl-
ands give rise to none, nor is there one in South Africa that we
know of.

F

32 THE PHYSICAL GEOGRAPHY OF THE SEA.

121. The great rivers of North America and North Africa, and
all the rivers of Europe and Asia, he wholly w^ithin the northern
hemisphere. How is it, then, considering that the evaporating sur-
face lies mainly in the southern hemisphere — how is it, I say, that
we should have the evaporation to take place in one hemisphere
and the condensation in the other ? The total amount of rain
which falls in the northern hemisphere is much greater, meteorol-
ogists 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.

122. How is it, then, that this vapor gets, as stated ^ 119, from
the southern into the northern hemisphere, and comes with such
regularity that our rivers never go dry and our springs fail not ?
It is because of the beautiful operations and the exquisite compen-
sation of this grand machine, the atmosphere. It is exquisitely
and wonderfully counterpoised. Late in the autumn of the north,
throughout its winter, and in early spring, the sun is pouring his
rays with the greatest intensity down upon the seas of the south-
ern hemisphere, and this powerful engine which we are contem-
plating is pumping up the water there (^ 119) for our rivers with
the greatest activity. At this time, the mean temperature of the
entire southern hemisphere is said to be about 10° higher than the
northern.

123. The heat which this heavy evaporation absorbs becomes
latent, and, with the moisture, is carried through the upper regions
of the atmosphere until it reaches our climates. Here the vapor
is formed into clouds, condensed, and precipitated. The heat
which held this water in the state of vapor is set free, it becomes
sensible heat, and it is that which contributes so much to temper
our winter chmate. It clouds up in winter, turns warm, and we
say we are going to have falling weather. That is because the
process of condensation has already commenced, though no rain
or snow may have fallen : thus we feel this southern heat, that
has been collected from the rays of the sun by the sea, been bot-
tled away by the winds in the clouds of a southern summer, and
set free in the process of condensation in our northern w^inter.

124. If the Plate at page 70 fairly represent the course of the
winds, the southeast trade-winds would enter the northern hemi-
sphere, and, as an upper current, bear into it all their moisture,

THE ATMOSPHERE.

83

except that which is precipitated in the region of equatorial
calms.

The South Seas, then, according to § 119, should supply mainly
the water for this engine, while the northern hemisphere condenses
it ; w^e should, therefore, have more rain in the northern hemi-
sphere. The rivers tell us that we have — at least on the land:
for the great water-courses of the globe, and half the fresh water
in the world, are found on our side of the equator. This fact
alone is strongly corroborative of this hypothesis.

The rain gauge tells us also the same story. The yearly aver-
age of rain in the north temperate zone is, according to Johnston,
thirty-seven inches. He gives but twenty-six in the south tem-
perate.

125. Moisture is never extracted from the air by subjecting it
from a low to a higher temperature, but the reverse. Thus, all the
air which comes loaded w^ith moisture from the other hemisphere,
and is borne into this with the southeast trade-winds, travels in
the upper regions of the atmosphere (§ 100) until it reaches the
calms of Cancer ; here it becomes the surface wind that prevails
from the southward and westward. As it goes north it grows
cooler, and the process of condensation commences.

We may now liken it to the wet sponge, and the decrease of
temperature to the hand that squeezes that sponge. Finally reach-
ing the cold latitudes, all the moisture that a dew-point of zero,
and even far below, can extract, is WTung from it ; and this air
then commences " to return according to his circuits" as dry at-
mosphere. And here we can quote Scripture again : " The north
wind driveth away rain." This is a meteorological fact of high
authority and great importance in the study of the circulation of
the atmosphere.

126. By reasoning in this manner, we are led to the conclusion
that our rivers are supphed with their waters principally from the
trade-wind regions — the extra-tropical northern rivers from the
southern trades, and the extra-tropioal southern rivers from the
northern trade-winds, for the trade-winds are the evaporating
winds.

Taking for our guide such faint glimmerings of light as we can
catch from these facts, and supposing these views to be correct,
• hen the saltest portion of the sea should be in the trade-wind re-

g4 THE PHYSICAL GEOGRAPHY OF THE SEA.

gions, where the water for all the rivers is evaporated ; and there
the saltest portions are found.

127. Dr. Ruschenberger, of the Navy, on his late voyage to In-
dia, 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 parallels of 20° north and 17° south.

In summing up the evidence in favor of this view of the general
system of atmospherical circulation, it remains to be shown how-
it is, if the view be correct, there should be smaller rivers and less
rain in the southern hemisphere.

128. The Explanation. — The winds that are to blow as the
northeast trade-winds, returning from the polar regions, where
the moisture (§ 125) has been compressed out of them, remain, as
we have seen, dry winds until they cross the calm zone of Cancer,
and are felt on the surface as the northeast trades. About two
thirds of them only can then blow over the ocean ; the rest blow
over the land, over Asia, Africa, and North America, where there
is but comparatively a small portion of evaporating surface ex-
posed to their action.

The zone of the northeast 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.

According to the hypothesis, illustrated by Plate I., p. 70, as to
the circulation of the atmosphere, it is these northeast trade-winds
that take up and carry over, after they rise up in the belt of equa-
torial calms, the vapors which make the rains that feed the rivers
in the extra-tropical regions of the southern hemisphere.

Upon this supposition, then, two thirds only of the northeast
trade-winds are fully charged with moisture, and only two thirds
of the amount of rain that falls in the northern hemisphere should

THE ATMOSPHERE. 85

fall in the southern, and this is just about the proportion (^ 124)
that observation gives.

In like manner, the southeast trade-v^^inds take up the vapors
which make our rivers, and as they prevail to a much greater ex-
tent at sea, and have exposed to their action about three times as
much ocean as the northeast trade-winds have, we might expect,
according to this hypothesis, more rains in the northern — and, con-
sequently, more and larger rivers — than in the southern hemi-
sphere. A glance at Plate VIII. will show how very much larger
that part of the ocean over which the southeast trades prevail is
than that where the northeast trade-winds blow.

This estimate as to the quantity of rain in the two hemispheres
is one which is not capable of verification by any more than the
rudest approximations ; for the greater extent of southeast trades
on one side, and of high mountains on the other, must each of ne-
cessity, and independent of other agents, have their effects. Nev-
ertheless, this estimate gives as close an approximation as we can
make out from any other data.

129. The rainy seasons, how caused. — The calm and trade-wind
regions or belts move up and down the earth, annually, in latitude
nearly a thousand miles. In July and August the zone of equato-
rial calms is found between 7° north and 12° north; sometimes
higher ; in March and April, between latitude 5° south and 2° north.
With this fact and these points of view before us, it is easy to
perceive why it is that we have a rainy season in Oregon, a rainy
and dry season in California, another at Panama, two at Bogota,
none in Peru, and one in Chili.

In Oregon it rains every month, but more in the winter months.
The winter there is the summer of the southern hemisphere,
when this steam-engine is working with the greatest pressure.
The vapor that is taken up by the southeast trades is borne along
over the region of northeast trades to latitude 35° or 40° north
(§ 124), where it descends and appears on the surface with the
southwest winds of those latitudes. Driving upon the highlands
of the continent, this vapor is condensed and precipitated, during
this part of the year, almost in constant showers.

130. In the winter, the calm belt of Cancer approaches the
equator. This whole system of zones, viz., of trades, calms, and
westerly winds, follows the sun ; and they of our hemisphere are

86 THE PHYSICAL GEOGRAPHY OF THE SEA.

nearer the equator in the winter and spring months than at any
other season.

The southwest winds commence at this season to prevail as far
down as the lower part of California. In winter and spring, the
land in California is cooler than the sea air, and is quite cold
enough to extract moisture from it. But in summer and autumn
the land is the warmer, and can not condense the vapors of water
held by the air. So the same cause which made it rain in Ore-
gon now makes it rain in California. As the sun returns to the
north, he brings the calm belt of Cancer and the northeast trades
along with him ; and now, at places where, six months before, the
southwest winds were the prevailing winds, the northeast 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. Conse-
quently, they can not, if they have the moisture in them to make
rains of, precipitate it under such circumstances.

131. Panama is in the region of equatorial calms. This belt
of cahns 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 returns so as to reach its extreme
southern latitude some time in March or April. Where these
calms are it is always raining, and the chart shows that they hang
over the latitude of Panama from June to November ; consequent-
ly, from June to November is the rainy season at Panama. The
rest of the year that place is in the region of the northeast trades,
which, before they arrive there, have to cross the mountains of the
isthmus, on the cool tops of which they deposit their moisture,
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 northeast 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.

132. Take the parallel of 4° north as an illustration : during
these two months the entire belt of calms crosses this parallel, and
then leaves it in the region of the southeast trades. During these
two months it was pouring down rain on that parallel. After the

THE ATMOSPHERE.

87

calm belt passes it the rains cease, and the people in that latitude
have no more wet weather till the fall, when the belt of calms re-
crosses this parallel on its way to the south. By examining the
" Trade-wind Chart," it may be seen what the latitudes are that
have two rainy seasons, and that Bogota is within the bi-rainy
latitudes.

133. The Rainless Regions. — The coast of Peru is within the
region of perpetual southeast 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 southeast trade-winds in the Atlantic Ocean first strike the
water on the coast of Africa. Traveling to the northwest, they
blow obliquely across the ocean until they reach the coast of
Brazil. By this time they are heavily laden with vapor, which
they continue to bear along across the continent, depositing it as
they go, and supplying with it the sources of the Rio de la Plata
and the southern tributaries of the Amazon.

Finally they reach the snow-capped Andes, and here is wrung
from them the last particle of moisture that that very low temper-
ature can extract.

Reaching the summit of that range, they now tumble down 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 become charged with fresh vapor, and be-
fore, therefore, they have any which the Peruvian climate can ex-
tract. Thus we see how the top of the Andes becomes the res-
ervoir from which are supplied the rivers of Chili and Peru.

134. The other rainless or almost rainless regions are the west-
ern coasts of Mexico, the deserts of Africa, Asia, North America,
and Australia. Now study the geographical features of the coun-
try surrounding those regions ; see how the mountain ranges run ;
then turn to Plate VIII. to see how the winds blow, and where the
sources are (§ 87) which supply them with vapors. This plate
shows the prevailing direction of the wind only at sea ; but know-
ing it there, we may infer what it is on the land. Supposing it to
prevail on the land as it generally does in corresponding latitudes
at sea, then the Plate will suggest readily enough how the winds
that blow over these deserts came to be robbed of their moisture,

88 THE PHYSICAL GEOGRAPHY OF THE SEA.

or, rather, to have so much of it taken from them as to reduce their
dew-point below the Desert temperature ; for the air can never de-
posit its moisture when its temperature is higher than its dew-point.

135. We have a rainless region about the Red Sea, because the
Red Sea, for the most part, lies within the northeast 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 vapor.

136. Most of New Holland lies within the southeast trade-wind
region ; so does most of inter-tropical South America. But inter-
tropical South America is the land of showers. The largest riv-
ers and most copiously watered country in the world are to be
found there, whereas almost exactly the reverse is the case in
Australia. Whence this difference ? Examine the direction of
the winds with regard to the shore-line of these two regions, and
the explanation will at once be suggested. In Australia — east
coast — the shore-line is stretched out in the direction of the trades ;
in South America — east coast — it is perpendicular to their direc-
tion. In Australia, they fringe this shore only with their vapor,
and so stint that thirsty land w^th showers that the trees can not
aiford to spread their leaves out to the sun, for it evaporates all
the moisture from them ; their instincts, therefore, teach them to
turn their edges to his rays. In America, they blow perpendicu-
larly upon the shore, penetrating the very heart of the country
with their moisture. Here the leaves — as the plantain, &c. — turn
their broad sides up to the sun, and court his rays.

137. Why there is more rain on one side of a mountain than on
the other.

We may now, from what has been said, see why the Andes and
all other mountains which run north and south have a dry and a
rainy side, and how the prevailing winds of the latitude determine
which is the rainy and which the dry side.

Thus, let us take the southern coast of Chili for illustration.
In our summer time, when the sun comes north, and drags after
him his belts of perpetual winds and calms, that coast is left with-
in the regions of the northwest winds — the winds that are counter
to the southeast trades — which, cooled by the winter temperature
of the highlands of Chili, deposit their moisture copiously. Dur-
ing the rest of the year, the most of Chili is in the region of the

THE ATMOSPHERE.

89

southeast trades, and the same causes which operate in Cahfornia
to prevent rain there, operate in ChiU ; only the dry season in one
place is the rainy season of the other.

Hence we see that the weather side of all such mountains as
the Andes is the wet side, and the lee side the dry.

138. The same phenomenon, from a like cause, is repeated in
inter-tropical India, only in that country each side of the mountain
is made alternately the wet and the dry side by a change in the
prevailing direction of the wind. Plate VIII. shows India to be in
one of the monsoon regions : it is the most famous of them all.
From October to April the northeast trades prevail. They evap-
orate 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 (§ 133) hold to the southeast trades; it
first cools and then relieves them of their moisture, and they tum-
ble down on the western slopes of the Ghauts, Peruvian-like
(^ 137), cool, rainless, and dry; wherefore that narrow strip of
country between the Ghauts and the Arabian Sea would, like
that in Peru between the Andes and the Pacific, remain without
rain forever, 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.

139. After the northeast trades have blown out their season,
which in India ends in April (§ 138), the great arid plains of Cen-
tral Asia, of Tartary, Thibet, and Mongolia, become heated up,
react upon these northeast trades, turn them back, and convert
them, during the summer and early autumn, into southwest mon-
soons. These then come from the Indian Ocean and Sea of Ara-
bia loaded with moisture, and striking with it perpendicularly upon
the Ghauts, precipitate upon that narrow strip of land between
this range and the Arabian Sea an amount of water that is truly
astonishing. Here, then, are not only the conditions for causing
more rain, now" on the west, now on the east side of this mount-
ain range, but the conditions also for the most copious precipita-
tion. Accordingly, when we come to consult rain gauges, and
to ask meteorological observers in India about the fall of rain,
they tell us that on the western slopes of the Ghauts it some-

90 THE PHYSICAL GEOGRAPHY OF THE SEA.

times reaches the enormous depth of twelve or fifteen inches in
one day.*

140. These winds then continue their course to the Himalaya
range as dry winds. In crossing this range, they are subjected to a
lower temperature than that to which they w^ere exposed in cross-
ing the Ghauts. Here they drop more of their moisture in the
shape of snow and rain, cind then pass over into the thirsty lands
beyond with scarcely enough vapor in them to make even a cloud.
Thence they ascend into the upper air, there to become counter-
currents in the general system of atmospherical circulation. By
studying Plate VHI., where the rainless regions and irfland basins,
as well as the course of the prevailing winds, are shown, these
facts will become obvious.

141. The Regions of Greatest Precipitation. — We shall now
be enabled to determine, if the views which I have been en-
deavoring to present be correct, what parts of the earth are sub-
ject to the greatest fall of rain. They should be on the slopes of
those mountains which the trade-winds first strike, after having
blown across the greatest tract of ocean. The more abrupt the
elevation, and the shorter the distance between the mountain top
and the ocean, the greater the amount of precipitation.

If, therefore, we commence at the parallel of about 30° north
in the Pacific, where the northeast trade-winds first strike that
ocean, and trace them through their circuits till they first strike
high mountains, we ought to find such a place of heavy rains.

Commencing at this parallel of 30°, therefore, in the North Pa-
cific, and tracing thence the course of the northeast trade-winds,
we shajl find that they blow thence, and reach the region of equa-
torial calms near the Caroline Islands. Here they rise up ; but,
instead of pursuing the same course in the upper stratum of winds
through the southern hemisphere, they, in consequence of the ro-
tation of the earth (§ 98), are made to take a southeast course.
They keep in this upper stratum until they reach the calms of
Capricorn, between the parallels of 30° and 40° ; after which
they become the prevailing northwest winds of the southern hemi-
sphere, which correspond to the southwest of the northern. Con-
tinuing on to the southeast, they are now the surface winds ; they
are going from warmer to cooler latitudes ; they become as the

* Keith Johnston.

THE ATMOSPHERE. 91

wet sponge (^ 125), and are abruptly intercepted by the Andes of
Patagonia, whose cold summit compresses them, and with its low
dew-point squeezes the water out of them. Captain King found
the astonishing fall of water here of nearly thirteen feet (one
hundred and fifty-one inches) in forty-one days ; and Mr. Darwin
reports that the sea water along this part of the South American
coast is sometimes quite fresh, from the vast quantity of rain that
falls.

142. We ought to expect a corresponding rainy region to be
found to the north of Oregon ; but there the mountains are not so
high, the obstruction to the southwest winds is not so abrupt, the
highlands 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 moisture as at Patagonia, has a
greater extent of country over which to deposit its rain, and con-
sequently the fall to the square inch will not be as great.*

143. In like manner, w^e should be enabled to say in what part
of the w^orld the most equable climates are to be found. They
are to be found in the equatorial calms, w^here the northeast and
southeast trades meet fresh from the ocean, and keep the temper-
ature uniform under a canopy of perpetual clouds.

144. A?nount of Evaporation. — The mean annual fall of rain
on the entire surface of the earth is estimated at about five feet.

145. To evaporate water enough annually from the ocean to
cover the earth, on the average, five feet deep with rain ; to trans-
port 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
oflices of the grand atmospherical machine. This water is evap-
orated principally from the torrid zone. Supposing it all to come
thence, w^e shall have, encircling the earth, a belt of ocean three
thousand miles in breadth, from which this atmosphere evaporates
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

* I have since, through the kindness of A. Holbrook, Esq., United States Attorney
for Oregon, received the Oregon Spectator of February 13, 1851, containing the Rev.
G. H. Atkinson's Meteorological Journal kept in Oregon City during the month of
January, 1851. The quantity of rain and snow for that month is 13.63 inches, or
about one third the average quantity that falls at Washington during the year.

92 THE PHYSICAL GEOGRAPHY OF THE SEA.

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 all the cogs, and wheels, and springs,
and pinions of this exquisite piece of machinery, that it never wears
out nor breaks down, nor fails to do its work at the right time
and in the right way !

146. In his annual report to the Society {Transactions of the
Bombay Geographical Society from May, 1849, to August, 1850,
vol. ix.). Dr. Buist, the secretary, states, on the authority of Mr.
Laidly, the evaporation at Calcutta to be " about fifteen feet an-
nually ; that between the Cape and Calcutta it averages, in Octo-
ber and November, nearly three fourths of an inch daily ; between
10° and 20° in the Bay of Bengal, it w^as found to exceed an inch
daily. Supposing this to be double the average throughout the
year, w^e should," continues the doctor, " have eighteen feet of
evaporation annually."

147. If, in considering the direct observations upon the daily
rate of evaporation in India, it be remembered that the seasons
there are divided into wet and dry ; that in the dry season, evap-
oration in the Indian Ocean, because of its high temperature, and
also of the high temperature and dry state of the wind, probably
goes on as rapidly as it does any where else in the world ; if, more-
over, we remember that the regular trade-wind regions proper
are, for the most part, rainless regions at sea ; that evaporation is
going on from them all the year round, we shall have reason to
consider the estimate of sixteen feet annually for the trade-wind
surface of the ocean not too high.

148. We see the light beginning to break upon us, for we now
begin to perceive why it is that the proportions between the land
and water were made as we find them in nature. If there had
been more water and less land, we should have had more rain, and
vice versa ; and then climates would have been different from
what they now are, and the inhabitants, animal or vegetable,
would not have been as they are. And as they are, that wise
Being who, in his kind providence, so watches over and regards
the things of this w^orld that he takes notice 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 con-

THE ATMOSPHERE. 93

templating the physical arrangements of the earth from such points
of view as this is which we now have before us ; from it the sea,
and the air, and the land, appear each as a part of that grand
machinery upon which the well-being of all the inhabitants of
earth, sea, and air depends ; and which, in the beautiful adapta-
tions that we are pointing 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 con-
structed and arranged according to one human design.

149. In some parts of the earth the precipitation is greater than
the evaporation ; thus the amount of water borne down by every
river that runs into the sea may be considered as the excess of
the precipitation over the evaporation that takes place in the val-
ley drained by that river.

150. This excess comes from the sea; the winds convey it to
the interior ; and the forces of gravity, dashing it along in mount-
ain torrents or gentle streams, hurry it back to the sea again.

151. In other parts of the earth the evaporation and precipita-
tion are exactly equal, as in those inland basins such as that in
which the city of Mexico, Lake Titicaca, the Caspian Sea, &c.,
&CC., are situated, which basins have no ocean drainage.

152. If more rain fell in the v-alley 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, w^ould dry up, and
plants and animals there would all perish for the w^ant of water.

153. In the sheets of water which we find distributed over that
and every other inhabitable inland basin, we see reservoirs or
evaporating surfaces just sufficient for the supply of that degree
of moisture which is best adapted to the w^ell-being of the plants
and animals that people such basins.

In other parts of the earth still, we find places, as the Desert
of Sahara, in which neither evaporation nor precipitation takes
place, and in which we find neither plant nor animal.

154. Adaptations. — In contemplating the system of terrestrial
adaptations, these researches teach one to regard the mountain
ranges and the great deserts of the earth as the astronomer does
the counterpoises to his telescope — though they be mere dead
weights, they are, nevertheless, necessary to make the balance

94 THE PHYSICAL GEOGRAPHY OF THE SEA.

complete, the adjustments of this machine perfect. These coun-
terpoises give ease to the motions, stabiUty to the performance,
and accuracy to the workings of the instrument. They are com-
pensations.

155. Whenever I turn to contemplate the works of nature, I
am struck with the admirable system of compensation, with the
beauty and nicety with which every department is poised by the
others ; things and principles are meted out in directions the most
opposite, but in proportions so exactly balanced and nicely ad-
justed, 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 ad-
justed, that, at the end of a thousand years, the earth, the sun,
and moon, and every star in the firmament, is found to come to
its proper place at the proper moment.

Nay, philosophy teaches us, when the little snow-drop, which in
our garden walks we see raising its beautiful head to remind us that
spring is at hand, was created, that 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 de-
gree of strength might be given to the fibres of even this little plant.

Botanists tell us that the constitution of this plant is such as to
require that, at a certain stage of its growth, the stalk should bend,
and the flower should bow its head, that an operation may take
place which is necessary in order that the herb should produce
seed after its kind ; and that, after this, its vegetable health re-
quires 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 grav-
ity would have been different ; in that case, the strength of fibre
in the snow-drop, as it is, would have been too much or too little ;
the plant could not bow or raise its head at the right time, fecund-
ation could not take place, and its family would have become ex-
tinct with the first individual that was planted, because its *' seed"
would not have been " in itself," and therefore it could not repro-
duce itself.

Now% if we see such perfect adaptation, such exquisite adjust-
ment, in the case of one of the smallest flowers of the field, how
much more may we not expect "compensation" in the atmosphere

THE ATMOSPHERE.

95

and the ocean, upon the right adjustment and due performance of
which depends not only the hfe of that plant, but the well-being
of every individual that is found in the entire vegetable and ani-
mal kingdoms of the world ?

When the east winds blow along the Atlantic coast for a little
while, they bring us air saturated with moisture from the Gulf
Stream, and we complain of the sultry, oppressive, heavy atmos-
phere ; the invalid grows worse, and the well man feels ill, be-
cause, when he takes this atmosphere into his lungs, it is already
so charged with moisture that it can not 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 con-
veying off matter from the lungs too fast ; he realizes the idea
that it is consuming him, and he calls the sensation parching.

156. Therefore, in considering the general laws which govern
the physical agents of the universe, and 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 wa-
ter had been different — if the earth, air, and water had not been
in exact counterpoise — the whole arrangement of the animal and
vegetable kingdoms would have varied from their present state.
But God chose to make those kingdoms what they are ; for this
purpose it was necessary, in his judgment, to establish the pro-
portions 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 obe-
dience to law and in subservience to order. If it were not so,
why was power given to the winds to lift up and transport moist-
ure, or the property given to the sea by which its waters may be-
come first vapor, and then fruitful showers or gentle dew^s ? If
the proportions and properties of land, sea, and air were not ad-
justed according to the reciprocal capacities of all to perform the
functions required by each, why should we be told that he " meas-
ured the waters in the hollow^ of his hand, and comprehended the
dust in a measure, and weighed the mountains in scales, and the
hills in a balance ?" Why did he span the heavens, but that he
might mete out the atmosphere in exact proportion to all the rest,

96 THE PHYSICAL GEOGRAPHY OF THE SEA.

and impart to it those properties and powers which it was neces-
sary 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 offices, they teach us lessons
concerning the wonders of the deep, the mysteries of the sky, the
greatness, and the wisdom, and goodness of the Creator. The
investigations into the broad-spreading circle of phenomena con-
nected with the winds of heaven and the waves of the sea are sec-
ond to none for the good which they do and 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 pon-
ders 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 ?

RED FOGS AND SEA DUST.

97

CHAPTER IV.

RED FOGS AND SEA DUST.

Where found, <J 157.— Tallies on the Wind, 158.— Where taken up, 160. — Hum-
boldt's Description, 163. — Infomiation derived from Sea Dust, 165. — Its Bearings
upon the Theory of Atmospherical Circulation, 167. — Suggests Magnetic Agency,
170.

157. Seamen tell us of " red fogs" which they sometimes en-
counter, especially in the vicinity of the Cape de Verd Islands.
In other parts of the sea also they meet showers of dust. What
these showers precipitate in the Mediterranean is called " sirocco
dust," and in other parts "African dust/' because the w4nds which
accompany them are supposed to come from the Sirocco desert,
or some other parched land of the continent of Africa. It is of a
brick-red or cinnamon color, and it sometimes comes down in such
quantities as to cover the sails and rigging, though the vessel may
be hundreds of miles from the land.

Now the patient reader, who has had the heart to follow me in
the preceding chapters around with " the wind in his circuits,"
will perceive that proof is yet wanting to establish it as a fact
that the northeast and southeast trades, after meeting and rising
up in the equatorial calms, do cross over and take the tracks rep-
resented by C and G, Plate I.

Statements, and reasons, and arguments enough have already
been made and adduced to make it highly probable, according to
human reasoning, that such is the case ; and though the theoret-
ical deductions showing such to be the case be never so good, pos-
itive proof that they are true can not fail to be received with de-
light and satisfaction.

Were it possible to take a portion of this air, as it travels down
the southeast trades, representing the general course of atmos-
pherical circulation, and to put a tally on it by which we could
always recognize it again, then we might hope actually to prove,
by evidence the most positive, the channels through wdiich the air
of the trade-winds, after ascending at the equator, returns whence
it came.

G

98 THE PHYSICAL GEOGRAPHY OF THE SEA.

But the air is invisible ; and it is not easily perceived how either
marks or taUies may be put upon it, that it may be traced in its
paths through the clouds.

The skeptic, therefore, who finds it hard to believe that the gen-
eral circulation is such as Plate I. represents it to be, might con-
sider 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 again,
and those tallies, when found at other parts of the earth's surface.

As difficult 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 southeast trade-winds bring to the
equator does rise up there and pass over into the northern hemi-
sphere.

158. The Sirocco, or African dust, which he has been observ-
ing so closely, has turned out to be tallies put upon the wind in
the other hemisphere ; and this beautiful instrument of his enables
us to detect the marks on these little tallies as plainly as though
those marks had been written upon labels of wood and tied to the
wings of the wind.

This dust, when subjected to microscopic examination, is found
to consist of infusoria and organisms whose habitat is not Africa,
but South America, and in the southeast trade-wind reo-ion 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 pile. South American
forms he recognizes in all of them ; indeed, they are the prevail-
ing forms in every specimen he has examined.

It may, I think, be now regarded as an established fact, that
there is a perpetual upper current of air from South America to
North Africa ; and that the volume of air w^hich flows to the north-
ward in these upper currents is nearly equal to the volume which
flows to the southward with the northeast trade-winds, there can
be no doubt.

The " rain dust" has been observed most frequently to fall in
spring and autumn ; that is, the fall has occurred after the equi-
noxes, but at intervals from them varying from thirty to sixty

RED FOGS AND SEA DUST. gcj

days, more or less. To account for this sort of periodical occur-
rence of the falls of this dust, Ehrenberg thinks it " necessary to
suppose a dusUcloud to he held constantly sioimming in the atmos-
jphere hy continuous currents of air, and lying in the region of the
trade-winds, hut suffering partial and periodical deviations^

It has already been shown (§ 128) that the rain or calm belt
between the trades travels up and down the earth from north to
south, making the rainy season wherever it goes. The reason of
this will be explained in another place.

159. This dust is probably taken up in the dry, and not in the
w^et season ; instead, therefore, of its being *' held in clouds suf-
fering partial and periodical deviations," as Ehrenberg suggests,
it more probably comes from one place about the vernal, and from
another about the autumnal equinox ; /or places which have their
rainy season at one equinox have their dry season at the other.

160. At the time of the vernal equinox, the valley of the Lower
Oronoco is then in its dry season — every thing is parched up with
the drought ; the pools are dry, and the marshes and plains arid
wastes. All vegetation has ceased ; the great serpents and rep-
tiles 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
lakes that are dried up, and lifting motes from the brown savan-
nas, will bear them aw^ay like clouds in the air.

This is the period of the year when the surface 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 tornadoes of terrific force ; this is the period for the
general atmospheric disturbances which have made characteristic
the equinoxes. Do not these conditions appear sufficient to afford
the " rain dust" for the spring showers ?

161. At the period of the autumnal equinox, another portion of
the Amazonian basin is parched with drought, and liable to winds
that fill the air with dust, and with the remains of dead animal
and vegetable matter ; these impalpable organisms, which each
rainy season calls into being, to perish the succeeding season of
drought, are perhaps distended and made even lighter by the gases
of decomposition which has been going on in the period of drought.

* Humboldt.

iOO THE PHYSICAL GEOGRAPHY OF THE SEA.

162. May not, therefore, the whirlwinds which accompany the
vernal equinox, and sweep over the lifeless plains of the Lower
Oronoco, take up the "rain dust" which descends in the northern
hemisphere in April and May ? and may it not be the atmospher-
ical disturbances which accompany the autumnal equinox that take
up the microscopic organisms from the Upper Oronoco and the
great Amazonian basin for the showers of October ?

163. The Baron von Humboldt, in his Aspects of Nature, thus
contrasts the wet and the dry seasons there :

" When, under the vertical rays of the never-clouded sun, the
carbonized turfy covering falls into dust, the indurated soil cracks
asunder as if from the shock of an earthquake. If at such times
two opposing currents of air, whose conflict produces a rotary
motion, come in contact with the soil, the plain assumes a strange
and singular aspect. Like conical-shaped clouds, the points of
which descend to the earth, the sand rises through the rarefied air
on the electrically-charged centre of the whirling current, resem-
bling the loud water-spout, dreaded \ij the experienced mariner.
The lowering sky sheds a dim, almost straw-colored light on the
desolate plain. The horizon draws suddp.nly nearer, the steppe
seems to contract, and with it the heart of the wanderer. The
hot, dusty particles which fill the air increase its suffocating heat,
and the east wind, blowing over the long-heated soil, brings with it
no refreshment, but rather a still more burning glow. The pools
which the yellow, fading branches of the fan-palm had protected
from evaporation, now gradually disappear. As in the icy north
the animals become torpid with cold, so here, under the influence
of the parching drought, the crocodile and the boa become mo-
tionless and fall asleep, deeply buried in the dry mud

" The distant palm-bush, apparently raised by the influence of
the contact of unequally heated and therefore unequally dense
strata of air, hovers above the ground, from which it is separated
by a narrow intervening margin. Half concealed by the dense
clouds of dust, restless with the pain of thirst and hunger, the
horses and cattle roam around, the cattle lowing dismally, and
the horses stretching out their long necks and snufhng the wind,
if haply a moister current may betray the neighborhood of a not

wholly dried-up pool

" At length, after the long drought, the welcome season of the
rain arrives ; and then how suddenly is the scene changed !

RED FOGS AND SEA DUST. 101

" Hardly has the surface of the earth received the refreshmg
moisture, when the previously barren steppe begins to exhale
sweet odors, and to clothe itself with killingias, the many pani-
cles of the paspulum, and a variety of grasses. The herbaceous
mimosas, with renewed sensibility to the influence of hght, unfold
their drooping, slumbering leaves to greet the rising sun ; and the
early song of birds and the opening blossoms of the water plants
join to salute the morning."

164. The color of the "rain dust," when collected in parcels
and sent to Ehrenberg, is *' brick-red," or "yellow ochre ;" when
seen by Humboldt in the air, it was less deeply shaded, and is
described hy him as imparting a " straw color" to the atmosphere.
In the search of spider lines for the diaphragm of my telescopes, I
procured the finest and best threads from a cocoon of a mud-red
color ; but the threads of this cocoon, as seen singly in the dia-
phragm, were of a golden color ; there would seem, therefore, no
difficulty in reconciling the difference between the colors of the
rain dust, when viewed in little piles by the microscopist, and
when seen attenuated and floating in the wind by the great trav-
eler.

It appears, therefore, that we here have placed in our hands a
clew, which, attenuated and gossamer-like though it at first ap-
pears, is nevertheless palpable and strong enough to guide us
along the " circuits of the wind" till we enter "the chambers of
the south."

165. The frequency of the fall of " rain dust" between the par-
allels 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 investiga-
tions at the Observatory, it is significant.

166. The latitudinal limits of the northern edore of the north-

o

east trade-winds are variable. In the spring they are nearest to
the equator, extending sometimes at this season not farther from
the equator than the parallel of 15° north.

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

According to the hypothesis (§ 42) suggested by my researches,

102 THE PHYSICAL GEOGRAPHY OF THE SEA

this is the zone in which the upper currents of atmosphere that
ascended in the equatorial cahns, and flowed off to the northward
and eastward, are supposed to descend. This, therefore, is the
zone in which the atmosphere that bears the " rain dust," or " Af-
rican sand," descends to the surface ; and this, therefore, is the
zone, it might be supposed, which would be the most liable to
showers of this *'dust." This is the zone in which the Cape Verd
Islands are situated ; they are in the direction which theory gives
to the upper current of air from the Oronoco and Amazon with
its " rain dust," and they are in the region of the most frequent
showers of " rain dust," all of which are in striking conformity
with this theory as to the circulation of the atmosphere.

It is true that, in the present state of our information, we can
not tell why this "rain dust" should not be gradually precipitated
from this upper current, and descend into the stratum of trade-
winds, as it passes from the equator to higher northern latitudes ;
neither can we tell why the vapor 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 dis-
play of any other atmospherical phenomenon to-morrow, and not
to-day : all that w^e can say is, that the conditions of to-day are
not such as the phenomenon requires for its own development.

168. Therefore, though we can not tell why the sea dust should
not fall always in the same place, we may nevertlineless suppose
that it is not always in the atmosphere, for the storms that take it
up occur only occasionally, and that when up, and in passing the
same parallels, it does not always meet with the conditions — elec-
trical and others — favorable to its descent, and that these condi-
tions might occur now in this place, now in that. But that the
fall does occur always in the same atmospherical vein or general
direction, my investigations would suggest, and Ehrenberg's re-
searches prove.

169. Judging by the fall of sea or rain dust, we may suppose
that the currents in the upper regions of the atmosphere are re-
markable for their general regularity, as well as for their general
direction and sharpness of limits, so to speak.

We may imagine that certain electrical conditions are necessary
to a shower of " sea dust" as well as to a thunder-storm ; and
that the interval between the time of the equinoctial disturbances

RED FOGS AND SEA DUST. 103

in the atmosphere and the occurrence of these showers, though it
does not enable us to determine the true rate of motion in the gen-
eral system of atmospherical circulation, yet it assures us that it
is not less on the average than a certain rate.

I do not offer these remarks as an explanation with which we
ought to rest satisfied, provided other proof can be obtained ; I
rather offer them in the true philosophical spirit of the distin-
guished microscopist himself, simply as affording, as far as they
are entitled to be called an explanation, that explanation w^hich is
most in conformity with the facts before us, and which is sug-
gested by the results of a novel and beautiful system of philosoph-
ical research.

170. Thus, though we have talHed 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 at-
mosphere whose functions are manifest, but whose presence has
never yet been clearly recognized.

171. When the air which the northeast trade-winds bring down
meets in the equatorial calms that which the southeast trade-
winds convey, and the two 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 as to *' the relation between
magnetism and the circulation of the atmosphere" may perhaps
throw some light upon the answer to this question.

104 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER V.

ON THE PROBABLE RELATION BETWEEN MAGNETISM AND THE
CIRCULATION OF THE ATMOSPHERE.

Reasons for supposing that the Air of the Northeast and of the Southeast Trades
cross at the calm Belts, ^ 174. — What Observations have shown, 184. — Physical
Agencies not left to Chance, 188. — Conjectures, 192. — Reasons for supposing that
there is a crossing of Trade-v^rind Air at the Equator, 194. — Why the extra-trop-
ical Regions of the Northern Hemisphere are likened to the Condenser of a Steam-
boiler in the South, 199.— Illustration, 200.— A Coincidence, 202.— Proof, 203. —
Nature affords nothing in contradiction to the supposed System of Circulation, 204.
Objections answered, 205. — Why the Air brought to the Equator by the Northeast
Trades will not readily mix with that brought by the Southeast, 207. — Additional
Evidence, 209. — Rains for the Mississippi River are not supplied from the Atlan-
tic, 210. — Traced to the South Pacific, 213. — Anticipation of Light from the Polar
Regions, 216. — Received from the Microscope of Ehrenberg, 217, and the Exper-
iments of Faraday, 219. — More Light, 221. — Why there should be a calm Place
near each Pole, 222. — Why the Whirlwinds of the North should revolve against
the Sun, 223. — Why certain Countries should have scanty Rains, 228. — Magnetism
the Agent that causes the Atmospherical Crossings at the calm Places, 231.

172. Oxygen, philosophers say, comprises one fifth part of the
atmosphere, and Faraday has discovered that it is magnetic.

This discovery presents itself to the mind as a great physical
fact, which is perhaps to serve as the keystone for some of the
grand and beautiful structures which philosophy is building up for
monuments to the genius of the age.

173. Certain facts and deductions elicited in the course of these
investigations had directed my mind to the w^orkings in the at-
mosphere of some agent, as to whose character and nature I was
ignorant. Heat, and the diurnal rotation of the earth on its axis,
were not, it appeared to m.e, sufficient to account for all the cur-
rents of both sea and air which investigation w^as bringing to light.

174. For instance, there was reason to suppose that there is a
crossing of winds at the three calm belts ; that is, that the south-
east trade-winds, when they arrive at the belt of equatorial calms
and ascend, cross over and continue their course as an upper cur-
rent to the calms of Cancer, while the air that the northeast trade-

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. iQo

winds discharge into the equatorial calm belt continues to go
south, as an upper current bound for the calms of Capricorn.
But what should cause this wind to cross over ? Why should there
not be a general mingling in this calm belt of the air brought by
the two trade-winds, and w^hy should not that which the southeast
winds convey there be left, after its ascent, to flow off either to
the north or to the south, as chance directs ?

175. In the first place, it w^as at variance with my belief in the
grand design ; fQr I could not bring myself to believe that the
operations of such an important machine as the atmosphere should
be left to chance, even for a moment. Yet I knew of no agent
which should guide the wind across these calm belts, and lead it
out always on the side opposite to that on which it entered ; nev-
ertheless, certain circumstances seemed to indicate that such a
crossing does take place.

176. Evidence in favor of it seemed to be afforded by this cir-
cumstance, viz., our researches enabled us to trace from the belt
of calms, near the tropic of Cancer, which extends entirely across
the seas, an efflux of air both to the north and to the south ; from
the south side of this belt the air flows in a never-ceasing breeze,
called the northeast trade-winds, toward the equator. (Plate I.)

On the north side of it, the prevailing winds come from it also,
but they go toward the northeast. They are the well-known
southwesterly winds which prevail along the route from this
country to England, in the ratio of two to one. But w^hy should
we suppose a crossing to take place here ?

177. We suppose so, because these last-named winds are going
from a w^armer to a colder climate ; and therefore it may be in-
ferred that nature exacts from them what w^e know she exacts
from the air under similar circumstances, but on a smaller scale,
before our eyes, viz., more precipitation than evaporation.

178. But where, it may be asked, does the vapor which these
winds carry along, for the replenishing of the whole extra-tropical
regions of the north, come from ? They did not get it as they
came along in the upper regions, a counter-current to the north-
east trades. They did not get it from the surface of the sea in
the calm belt of Cancer, for they did not tarry long enough there
to become saturated with moisture. Thus circumstances again
])ointed to the southeast trade-wind regions as the place of supply.

106 THE PHYSICAL GEOGRAPHY OF THE SEA.

179. Moreover, these researches afforded grounds for the sup-
position that the air of which the northeast trade-winds are com-
posed, and which comes out of the same zone of calms as do these
southwesterly winds, so far from being saturated with vapor at its
exodus, is dry; for near their polar edge, the northeast trade-
winds are, for the most part, dry winds. Reason suggests, and
philosophy teaches, that, going from a lower to a higher tempera-
ture, the evaporating powers of these winds are increased ; that
they have to travel, in their, oblique course toward the equator,
a distance of nearly three thousand miles ; that, as a general rule,
they evaporate all the time, and all the way, and precipitate little
or none on their route ; investigations have proved that they are
not saturated with moisture until they have arrived fully up to the
regions of equatorial calms, a zone of constant precipitation.

This calm zone of Cancer borders also, it was perceived, upon
a rainy region.

180. Where does the vapor which here, on the northern edge
of this zone of Cancer, is condensed into rains, come from? —
and where, also— was the oft-repeated question — does the vapor
which is condensed into rains for the extra-tropical regions of
the north generally come from ? By what agency is it convey-
ed across this calm belt from its birth-place between the trop-
ics ?

181. I know of no law of nature or rule of philosophy which
would forbid the supposition that the air which has been brought
along as the northeast trade-winds to the equatorial calms does,
after ascending there, return by the counter and upper currents
to the calm zone of Cancer, here descend and reappear on the
surface as the northeast trade-winds again. I know of no agent
in nature which would pr^event it from taking this circuit, nor do
I know of any which would compel it to take this circuit ; but
while I know of no agent in nature that would prevent it from
taking this circuit, I know, on the other hand, of circumstances
W'hich rendered it probable that such, in general, is not the course
of atmospherical circulation — that it does not take this circuit. I
speak of the rule, not of the exceptions ; these are infinite, and,
for the most part, are caused by the land.

182. And I moreover knew of facts which go to strengthen
the supposition that the winds which have come in the upper

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. IQ?

regions of the atmosphere from the equator, do not, after arriving
at the calms of Cancer, and descending, return to the equator on
the surface, but that they continue on the surface toward the pole.
But why should they ? What agent in nature is there that can
compel these, rather than any other winds, to take such a circuit ?

183. The following are some of the facts and circumstances
which give strength to the supposition that these winds do contin-
ue from the calm belt of Cancer toward the pole as the prevailing
southwesterly winds of the extra-tropical north :

We have seen (Plate I.) that, on the north side of this calm
zone of Cancer, the prevailing winds on the surface are from this
zone toward the pole, and that these winds return as A through
the upper regions from the pole ; that, arriving at the calms of
Cancer, this upper current A meets another upper current G from
the equator, where they neutralize each other, produce a calm,
descend, and come out as surface w^inds, viz., A as B, or the trade-
winds ; and G as H, or the variable winds.

184. Now observations have shown that the winds represented
by H are rain winds ; those represented by B, dry winds ; and it
is evident that A could not bring any vapors to these calms to
serve for H to make rains of; for the winds represented by A have
already performed the circuit of surface winds as far as the pole,
during which journey they parted with all their moisture, and, re-
turning through the upper regions of the air to the calm belt of
Cancer, they arri^^ed there as dry winds. The winds represented
by B are dry winds ; therefore it was supposed that these are but
a continuation of the winds A.

185. On the other hand, if the w^nds A, after descending, do
turn about and become the surface winds H, they would first have
to remain a long time in contact with the sea, in order to be sup-
plied with vapor 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 on the north
as well as on the south side of this zone of Cancer ; but investi-
gation shows no such region ; I speak exclusively of the ocean.

186. Hence it was inferred that A and G do come out on the
surface as represented by Plate I. But what is the agent that
should lead them out by such opposite paths ?

187. According to this mode of reasoning, the vajDors which

108 THE PHYSICAL GEOGRAPHY OF THE SEA.

supply the rains for H would be taken up in the southeast trade-
wind region by F, and conveyed thence by G, and delivered to H.
And if this mode of reasoning be admitted as plausible — if it be
true that G have the vapor which, by condensation, is to water
with showers the extra-tropical regions of the northern hemisphere,
Nature, w^e may be sure, has provided a guide for conducting G
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
first saw the foot-prints of an agent whose character I could not
comprehend. Could it be the magnetism that resides in the oxy-
gen of the air ?

188. Heat and cold, the early and the latter rain, clouds and
sunshine, are not, we may rely upon it, distributed over the earth
by chance ; they are distributed in obedience to laws that are as
certain and as sure in their operations as the seasons in their
rounds. If it depended upon chance whether the dry air should
come out on this side or on that of this calm belt, or whether
the moist air should return or not whence it came — if such were
the case in nature, we perceive that, so far from any regularity as
to seasons, we should have, or might have, years of droughts the
most excessive, and then again seasons of rains the most destruct-
ive ; but, so far from this, we find for each place a mean annual
proportion of both, and that so regulated withal, that year after
year the quantity is preserved with remarkable regularity.

189. Having thus shown that there is no reason for supposing
that the upper currents of air, when they meet over the calms of
Cancer and Capricorn, are turned back to the equator, but hav-
ing shown that there is reason for supposing that the air of each
current, after descending, continues on in the direction toward
which it was traveling before it descended, we may go farther,
and, by a similar train of circumstantial evidence, afforded by these
researches and other sources of information, show that the air,
kept in motion on the surface by the two systems of trade-winds,
when it arrives at the belt of equatorial calms, and ascends, con-
tinues on thence, each current toward the pole which it w^as ap-
proaching while on the surface.

190. In a problem like this, demonstration in the positive way
is difficult, if not impossible. We must rely for our proof upon
philosophical deduction, guided by the lights of reason ; and in all

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 109

cases in which positive proof can not be adduced, it is permitted
to bring in circumstantial evidence.

I am endeavoring, let it be borne in mind, to show cause for the
conjecture that the magnetism of the oxygen of the atmosphere is
concerned in conducting the air which has blown as the southeast
trade-winds, and after it has arrived at the belt of equatorial calms
and risen up, over into the northern hemisphere, and so on through
its channels of circulation, as traced on Plate I.

But, in order to show reasonable grounds for this conjecture, I
want to establish, by circumstantial evidence and such indirect
proof as my investigations afford, that such is the course of the
" wind in his circuits," and that the winds represented by F, Plate
I., do become those represented by G, H, A, B, and C success-
ively.

191. In the first place, F represents the southeast trade-winds —
i. e.y all the winds of the southern hemisphere as they approach
the equator ; and is there any reason for supposing that the atmos-
phere does not pass freely from one hemisphere to another 1 On
the contrary, many reasons present themselves for supposing that
it does.

192. If it did not, the proportion of land and water, and conse-
quently of plants and warm-blooded animals, being so diiferent in
the two hemispheres, we might imagine that the constituents of
the atmosphere in them would, in the course of ages, probably
become different, and that consequently, in such a case, man
could not safely pass from one hemisphere to the other.

193. Consider the manifold beauties in the whole system of
terrestrial adaptations ; remember what a perfect and wonderful
machine (§ 118) 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. Therefore
I was led to ask myself why the air of the southeast trades, when
arrived at the zone of equatorial calms, should not, after ascend-
ing, rather return to the south than go on to the north. Where
and what is the agency by which its course is decided ?

194. Here I found circumstances which again induced me to
suppose it probable that it neither turned back to the south nor
mingled with the air which came from the regions of the north-

110 THE PHYSICAL GEOGRAPHY OF THE SEA.

east trades, ascended, and then flowed indiscriminately to the
north or the south.

But I saw reasons for supposing that what came to the equato-
rial calms as the southeast trade-winds continued to the north as
an upper current, and that what had come to the same zone as
northeast trade-winds ascended and continued over into the south-
ern hemisphere as an upper current, bound for the calm zone of
Capricorn.

And these are the principal reasons and conjectures upon which
these suppositions were based :

195. At the seasons of the year when the sun is evaporating
most rapidly in the southern hemisphere, the most rain is falling
in the northern. Therefore it is fair to suppose that much of the
vapor which is taken up on that side of the equator is precipitated
on this.

The evaporating surface in the southern hemisphere is greater,
much greater, than it is in the northern ; still, all the great rivers
are in the northern hemisphere, the Amazon being regarded as
common to both ; and this fact, as far as it goes, tends to corrobo-
rate the suggestion as to the crossing of the trade-winds at the
equatorial calms.

196. Independently of other sources of information, my investi-
gations also taught me to believe that the mean temperature of the
tropical regions was higher in the northern than in the southern
hemisphere, for they show that the difference is such as to draw
the equatorial edge of the southeast trades far over on this side of
the equator, and to give them force enough to keep the northeast
trade-winds out of the southern hemisphere almost entirely.

197. Consequently, as before stated, the southeast trade-winds
being in contact with a more extended evaporating surface, and
continuing in contact with it for a longer time or through a
greater distance, they would probably arrive at the trade-wind
place of meeting more heavily laden with moisture than the others.

198. Taking the laws and rates of evaporation into considera-
tion, I could find no part of the ocean of the northern hemisphere
from which the sources of the Mississippi, the St. Lawrence, and
the other great rivers of our hemisphere could be supplied.

Hence, by this process of reasoning, I was induced to regard
the extra-tropical regions of the northern hemisphere as standing

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE.

Ill

in the relation of a condenser to a grand steam machine (^ 120),
the boiler of which is in the region of the southeast trade-winds,
and to consider the trade-winds of this hemisphere as performing
the like office for the regions beyond Capricorn.

199. The calm zone of Capricorn is the duphcate of that of
Cancer, and the winds flow from it as they do from that, both
north and south ; but with this difference : that on the polar side
of the Capricorn belt they prevail from the northwest instead of
the southwest, and on the equatorial side from the southeast in-
stead of the northeast.

Now if it be true that the vapor of the northeast trade-winds
IS condensed in the extra-tropical regions of the southern hemi-
sphere, the following path, on account of the effect of diurnal ro-
tation of the earth upon the course of the winds, would represent
the mean circuit of a portion of the atmosphere moving according
to the general system of its circulation over the Pacific Ocean,
viz., coming down from the north as an upper current, and ap-
pearing on the surface of the earth in about longitude 1 20° west,
and near the tropic of Cancer, it would here commence to blow
the northeast trade-winds of that region.

200. To make this clear, see Plate VIL, on which I have mark-
ed the course of such vapor-bearing winds ; A being a breadth or
swath of winds in the northeast trades ; B, the same wind as the
upper and counter-current to the southeast trades ; and C, the
same wind after it has descended in the calm belt of Capricorn,
and come out on the polar side thereof, as the rain wunds and pre-
vailing northwest winds of the extra-tropical regions of the south-
ern hemisphere.

This, as the northeast trades, is the evaporating wind. As the
northeast trade-wind, it sweeps over a great waste of waters lying
between the tropic of Cancer and the equator.

201. 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 northeast from the
southeast trade-winds. Here, depositing a portion of its vapor as
it ascends, it would, with the residuum, take, on account of diurnal
rotation, a course in the upper region of the atmosphere to the
southeast, as far as the calms of Capricorn. Here it descends

112 THE PHYSICAL GEOGRAPHY OF THE SEA.

and continues on toward the coast of South America, in the same
direction, appearing now as the prevaihng northwest wind of the
extra-tropical regions of the southern hemisphere. Traveling on
the surface from warmer to colder regions, it must, in this part of
its circuit, precipitate more than it evaporates.

202. Now it is a coincidence, at least, that this is the route by
which, on account of the land in the northern hemisphere, the
northeast trade-winds have the fairest sweep over that ocean.
This is the route by which they are longest in contact with an
evaporating surface ; the route by which all circumstances are
most favorable to complete saturation ; and this is the route by
w^hich they can pass over into the southern hemisphere most
heavily laden with vapors for the extra-tropical regions of that
half of the globe ; and this is the supposed route which the north-
east trade-winds of the Pacific take to reach the equator and to
pass from it.

203. Accordingly, if this process of reasoning be good, that
portion of South America between the calms of Capricorn and
Cape Horn, upon the mountain ranges of which this part of the
atmosphere, whose circuit I am considering as a type, first im-
pinges, ought, to be a region of copious precipitation.

Now let us turn to the works on Physical Geography, and see
what we can find upon this subject. In Berghaus and Johnston
— department Hyetography — it is stated, on the authority of
Captain King, R. N., that upward of twelve feet (one hundred
and fifty-three inches) of rain fell in forty-one days on that part
of the coast of Patagonia which lies within the sweep of the winds
just described. So much rain falls there, navigators say, that
they sometimes find the w^ater 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 range as a dry wind ;
as such, it traverses the almost rainless and barren regions of Cis-
Andean Patagonia and South Buenos Ayres.

204. These conditions, the direction of the prevailing winds,
and the amount of precipitation, may be regarded as evidence af-
forded by nature, if not in favor of, certainly not against, the con-
jecture that such may have been the voyage of this vapor through

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. II3

the air. At any rate, here is proof of the immense quantity of
vapor which these winds of the extra-tropical regions carry along
with them toward the poles ; and I can imagine no other place
than that suggested, whence these winds could get so much vapor.

I am not unaw^are of the theory, or of the weight attached to
it, which requires precipitation to take place in the upper regions
of the atmosphere on account of the cold there, irrespective of
proximity to mountain tops and snow-clad hills.

But the facts and conditions developed by this system of re-
search upon the high seas are in many respects irreconcilable
with that theory. With a new system of facts before me, I have,
independent of all preconceived notions and opinions, set about to
seek among them for explanations and reconciliations.

These may not in all cases be satisfactory to every one ; in-
deed, notwithstanding the amount of circumstantial evidence that
has already been brought to show that the air which the north-
east and the southeast trade-winds discharge into the belts of
equatorial calms, does, in ascending, cross — that from the southern
passing over into the northern, and that from the northern pass-
ing over into the southern hemisphere (see F and G, B and C,
Plate I.) — yet some have implied doubt by asking the question,
" How are tw^o such currents of air to pass each other ?" And,
for the w^ant of light upon this point, the correctness of reasoning,
facts, inferences, and deductions have been questioned.

205. In the first place, it may be said in reply, the belt of equa-
torial calms is often several hundred miles across, seldom less than
sixty ; whereas the depth of the volume of air that the trade-winds
pour into it is only about three miles, for that is supposed to be
about the height to w^hich the trade-winds extend.

Thus we have the air passing into these calms by an opening
on the north side for the northeast trades, and another on the south
for the southeast trades, having a cross section of three miles ver-
tically to each opening. It then escapes by an opening upward,
the cross section of which is sixty or one hundred, or even three
hundred miles. A very slow motion upw^ard there will carry 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 cu7'ds or columns of air can readily cross each other and pass
in different directions without interferinsr the one with the other,

H

114 THE PHYSICAL GEOGRAPHY OF THE SEA.

or at least to that degree which obstructs or prevents, we all
know.

206. For example, open the window of a warm room in winter,
and immediately there are two currents of air ready at once to set
through it ; viz., a current of warm air flowing out at the top, and
one of cold coming in below.

But the brown fields in summer afford evidence on a larger
scale, and in a still more striking manner, of the fact that, in na-
ture, columns, or streamlets, or curdles of air do readily move
among each other without obstruction. That tremulous motion
which we so often observe above stubble-fields, barren wastes, or
above any heated surface, is caused by the ascent and descent, at
one and the same time, of columns of air at different tempera-
tures, the cool coming down, the warm going up. They do not
readily commingle, for the astronomer, long after nightfall, when
he turns his tele&cope upon the heavens, perceives and laments
the unsteadiness they produce in the sky.

207. If the air brought down by the northeast trade-winds differ
in temperature (and why not?) from that brought by the southeast
trades, we have the authority of nature for saying that the two
currents would not readily commingle. Proof is daily afforded
that they would not, and there is reason to believe that the air of
each current, in streaks, or patches, or curdles, does thread its way
through the air of the other without difficulty. Now, if the air of
these two currents differs as to magnetism, might not that be an
additional reason for their not mixing, and for their taking the di-
rection of opposite poles after ascending ?

208. Therefore we may assume it as a postulate which nature
concedes, that there is no difficulty as to the two currents of air,
which come into those calm belts from different directions, cross-
ing over, each in its proper direction, without mingling.

209. Thus, having shown that there is nothing to p'event the
crossing of the air in these calm belts, I return to the process of
reasoning by induction, and offer additional circumstantial evi-
dence to prove that such a crossing does take place. Let us
therefore catechise, on this head, the waters which the Mississippi
pours into the sea, inquiring of them as to the channels among the
clouds through which they were brought from the ocean to the
fountains of that mighty river.

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 115

It rains more in the valley drained by that river than is evapo-
rated from it again. The difference for a year is the volume of
water annually discharged by that river into the sea (^ 117).

At the time and place that the vapor which supplies this im-
mense volume of water was lifted by the atmosphere up from the
sea, the thermometer, we may infer, stood higher than it did at
the time and place where this vapor was condensed and fell down
as rain in the Mississippi Valley.

210. I looked to the south for the springs in the Atlantic which
supply the fountains of this river with rain. But I could not find
spare evaporating surface enough for it, in the first place ; and if
the vapor, I could not find the winds which would convey it to the
right place.

The prevailing w^inds in the Caribbean Sea and southern parts
of the Gulf of Mexico are the northeast trade-winds. They have
their offices to perform in the river basins of tropical America, and
the rains which they may discharge into the Mississippi Valley
now and then are exceptions, not the rule.

211. The winds from the north can not bring vapors from the
great lakes to make rains for the Mississippi, for two reasons :
1st. The basin of the great lakes receives from the atmosphere
more water in the shape of rain than they give back in the shape
of vapor. The St. Lawrence River carries off the excess. 2d.
The mean climate of the lake country is colder than that of the
Mississippi Valley, and therefore, as a general rule, the tempera-
ture of the Mississippi Valley is unfavorable for condensing vapor
from that quarter.

212. It can not come from the Atlantic, because the greater
part of the Mississippi Valley is to the windward of the Atlantic.
The winds that blow across this ocean go to Europe with their
vapors ; and in the Pacific, from the parallels of California down
to the equator, the direction of the wind at the surface is from,
not toward the basin of the Mississippi. Therefore it seemed to
be estabhshed with some degree of probability, or, if that expres-
sion be too strong, with something like apparent plausibility, that
the rain winds of the Mississippi Valley do not, as a general rule,
get their vapors from the North Atlantic Ocean, nor from the Gulf
of Mexico, nor from the great lakes, nor from that part of the Pa-
cific Ocean over which the northeast trade-winds prevail.

116 THE PHYSICAL GEOGRAPHY OF THE SEA.

The same process of reasoning which conducted us (^ 203) into
the trade-wind region of the northern hemisphere for the sources
of the Patagonian rains, now invites us into the trade-wind regions
of the South Pacific Ocean to look for the vapor springs of the
Mississippi.

213. If the rain winds of the Mississippi Valley come from the
east, then we should have reason to suppose that their vapors
were taken up from the Atlantic Ocean and Gulf Stream ; if the
rain winds come from the south, then the vapor springs might,
perhaps, be in the Gulf of Mexico ; if the rain winds come from
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 ?

Wondering where, I addressed a circular letter to farmers and
planters of the Mississippi Valley, requesting to be informed as to
the direction of their rain winds.

214. I received replies from Virginia, Mississippi, Tennessee,
Missouri, Indiana, and Ohio ; and they all, with the exception of
one person in Missouri, said, " The southwest winds bring us our
rains."

215. These winds certainly can not get their vapors from the
Rocky Mountains, nor from the Salt Lake, for they rain quite as
much upon that basin as they evaporate from it again ; if they did
not, they would, in the process of time, have evaporated all the
water there, and the lake would now be dry.

These winds, that feed the sources of the Mississippi with rain,
like those between the same parallels upon the ocean, are going
from a higher to a lower temperature ; and these winds in the
Mississippi Valley, not being in contact with the ocean, or with
any other evaporating surface to supply them with moisture, must
bring with them from some sea or another that which they deposit.

Therefore, though it may be urged, inasmuch as the winds
which brought the rains to Patagonia came direct from the sea,
that they therefore took up their vapors as they came along, yet
it can not be so urged in this case ; and if these winds could pass
with their vapors from the equatorial calms through the upper
regions of the atmosphere to the calms of Cancer, and then as
surface winds into the Mississippi Valley, it was not perceived

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 117

why the Patagonian rain winds should not bring their moisture by
a similar route. These last are from the northwest, from warmer
to colder latitudes ; therefore, being once charged with vapors,
they must precipitate as they go, and take up less moisture than
they deposit.

216. This w^as circumstantial evidence. No fact had yet been
elicited to prove that the course of atmospherical circulation sug-
gested by my investigations is the actual course in nature. It is
a case in which I could yet hope for nothing more direct than
such conclusions as might legitimately flow from circumstances.

My friend Lieutenant De Haven was about to sail in command
of the American Arctic Expedition in search of Sir John Frank-
lin. Infusoria are sometimes found in sea-dust, rain-drops, hail-
stones, or snow-flakes ; and if by any chance it should so turn out
that the locus of any of the microscopic infusoria which might be
found descending with the precipitation of the Arctic regions should
be identified as belonging to the regions of the southeast trade-
winds, we should thus add somewhat to the strength of the many
clews by which we have been seeking to enter into the chambers
of the w^ind, and to " tell whence it cometh and whither it goeth."

It is not for man to follow the *' w^ind in his circuits ;" and all
that could be hoped was, after a close examination of all the facts
and circumstances which these researches upon the sea have
placed within my reach, to point out that course which seemed to
be most in accordance w^ith them ; and then, having established a
probability, or even a possibility, as to the true course of the at-
mospheric circulation, to make it known, and leave it for future
investigations to confirm or set aside.

217. It was at this stage' of the matter that my friend Baron
von Gerolt, the Prussian minister, had the kindness to place in my
hand Ehrenberg's work, '■'■ Passat-Staub und Blut-Regen."

Here I found the clew which I hoped, almost against hope, De
Haven would place in my hands (§ 216).

That celebrated microscopist reports that he found South Amer-
ican infusoria in the blood-rains and sea-dust of the Cape Verd
Islands — Lyons, Genoa, and other places (^ 158).

Thus confirming, as far as such evidence can, the indications
of our observations, and increasing the probability that the general
course of atmospherical circulation is in conformity with the sug-

118 THE PHYSICAL GEOGRAPHY OF THE SEA.

gestions of the facts gathered from the sea as I had interpreted
them, viz., that the trade-winds of the southern hemisphere, after
arriving at the belt of equatorial calms, ascend and continue in
their course toward the calms of Cancer as an upper current from
the southwest, and that, after passing this zone of calms, they are
felt on the surface as the prevailing southwest winds of the extra-
tropical parts of our hemisphere ; and that, for the most part, they
bring their moisture with them from the trade-wind regions of the
opposite hemisphere.

218. I have marked on Plate VII. the supposed track of the
" Passat-Staub," showing where it was taken up in South Amer-
ica, as at P, P, and where it was found, as at S, S ; the part of
the line in dots denoting w^here it was in the upper current, and
the unbroken line where it was wafted by a surface current ; also
on the same plate is designated the part of the South Pacific in
which the vapor-springs for the Mississippi rains are supposed to
be. The hands (1^^) point out the direction of the wind. Where
the shading is light, the vapor is supposed to be carried by an up-
per current.

Such is the character of the circumstantial evidence which in-
duced me to suspect that some agent, whose office in the grand
system of atmospherical circulation is neither understood nor rec-
ognized, was at work in these calm belts.

219. Dr. Faraday has shown that, as the temperature of oxygen
is raised, its paramagnetic force diminishes, being resumed as the
temperature falls again.

" These properties it carries into the atmosphere, so that the
latter is, in reality, a magnetic medium, ever varying, from the
influence of natural circumstances, in its magnetic power. If a
mass of air be cooled, it becomes more paramagnetic ; if heated,
it becomes less paramagnetic (or diamagnetic), as compared with
the air in a mean or normal condition."*

220. Now, is it not more than probable that here we have, in
the magnetism of the atmosphere, that agent which guides the
air from the south (§ 217) through the calms of Capricorn, of the
equator, and of Cancer, and conducts it into the north ; that agent
which causes the atmosphere, with its vapors and infusoria, to flow

* Philosophical Magazine and Journal of Science, 4th series, No. 1, January, 1851,
page 73.

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE, ng

above the clouds from one hemisphere into the other, and whose
footprints had become so palpable ?

221. Taking up the theory of Ampere with regard to the mag-
netic polarity induced by an electrical current, according as it
passes through wire coiled with or coiled against the sun, and ex-
panding it in conformity wuth the discoveries of Faraday and the
experiments of a Prussian philosopher,* we perceive a series of
facts and principles which, being applied to the circulation of the
atmosphere, make the conclusions to which I have been led touch-
ing these crossings in the air, and the continual "w^hirl" of the
w^ind in the Arctic regions against, and in the Antarctic with the
hands of a ivatch, very significant.

In this view of the subject, we see light springing up from va-
rious sources, by which the shadows of approaching confirma-
tion are clearly perceived. One such source of light comes from
the observations of my excellent friend Quetelet, at Brussels,
which show that the great electrical reservoir of the atmosphere
is in the upper regions of the air. It is filled with positive elec-
tricity, which increases as the temperature diminishes.

222. May we not look, therefore, to find about the north and
south magnetic poles these atmospherical nodes or calm regions
which I have theoretically pointed out there ? In other words,
are not the magnetic poles of the earth in those atmospherical
nodes, the two standing in the relation of cause and effect, the
one to the other ?

This question was first asked several years ago,t and I w^as
then moved to propound it by the inductions of theoretical rea-
soning.

Observers, perhaps, will never reach those inhospitable regions
with their instruments to shed light upon this subject ; but Parry
and Barrow have found reasons to believe in the existence of a
perpetual calm about the north pole. Professor J. H. Coffin, in
an elaborate and valuable paperj on the " Winds of the North-
ern Hemisphere," arrives at a like conclusion. In that paper he
has discussed the records at no less than five hundred and sev-
enty-nine meteorological stations, embracing a totality of observa^

* Professor Von Feilitzsch, of the University of Greifswald. Philosophical Mag.
azine, January, 1851. t Maury's Sailing Directions.

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

120 THE PHYSICAL GEOGRAPHY OF THE SEA.

tions for two thousand eight hundred and twenty-nine years. He
places his " meteorological pole" — pole of the winds — near lati-
tude 84° north, longitude 105° west. The pole of maximum cold,
by another school of philosophers, 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^ west.

223. Neither of these poles is a point susceptible of definite
and exact position. The polar calms are no more a point than
the equatorial calms are a line ; and, considering that these poles
are areas, not points, is it not a little curious that philosophers
in different parts of the w^orld, 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 posi-
tion 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 clew^s, that
sometimes seem almost palpable enough for the mind, in its hap-
piest mood, to lay hold of, and follow up to the very portals of
knowledge, where pausing to knock, we may boldly demand that
the chambers of hidden things be thrown wide open, that we may
see and understand the mysteries of the winds, the frost, and the
trembling needle.

224. In the polar calms there is (^ 113) an ascent of air ; if an
ascent, a diminution of pressure and an expansion ; and if expan-
sion, a decrease of temperature. Therefore we have palpably
enough a connecting link here between the polar calms and the
polar place of maximum cold. Thus we establish a relation be-
tween the pole of the winds and the pole of cold, with evident in-
dications that there is also a physical connection between these and
the magnetic pole. Here the outcroppings of the relation between
magnetism and the circulation of the atmosphere again appear.

May we not find in such evidence as this, threads, attenuated
and almost air drawn though they be when taken singly and alone,
yet nevertheless proving, w^hen brought together, to have a con-
sistency sufficient, with the lights of reason, to guide us as we seek
to trace the wind in his circuits? The winds (§ 106) approach

* Gauss.

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 121

these polar calms by a circular or spiral motion, traveling in the
northern hemisphere against, and in the southern with the hands
of a watch. The circular gales of the northern hemisphere are
said also to revolve in like manner against the hands of a watch,
while those in the southern hemisphere travel the other way.
Now, should not this discovery of these three poles, this coinci-
dence of revolving winds, with the other circumstances that have
been brought to light, encourage us to look to the magnetism of
the air for the key to these mysterious but striking coincidences ?
Indeed, so wide for speculation is the field presented by these
discoveries, that we may in some respects regard this great globe
itself, with its " cups" and spiral wires of air, earth, and water, as
an immense " pile" and helix, w^hich, being excited by the natural
batteries in the sea and atmosphere of the tropics, excites in turn
its oxygen, and imparts to atmospherical matter the properties of
magnetism.

225. With the lights which these discoveries cast, we see (Plate
I.) why air, which has completed its circuit to the whirl* about the
Antarctic regions, should then, according to the laws of magnet-
ism, be repelled from the south, and attracted by the opposite pole
toward the north.

And when the southeast and the northeast trade-winds meet in
the equatorial calms of the Pacific, would not these magnetic
forces be sufficient to determine the course of each current, bring-
ing the former, with its vapors of the southern hemisphere, over
into this, by the courses already suggested ?

226. This force and the heat of the sun would propel it to the
north. The diurnal rotation of the earth propels it to the east ;
consequently, its course, first through the upper regions of the
atmosphere, and then on the surface of the earth, after being
conducted by this newly-discovered agent across the calms of
Cancer, would he from the southward and westw^ard to the north-
ward and eastward.

These are the winds (§ 122) which, on their w^ay to the north
from the South Pacific, would pass over the Mississippi Valley,
and they appear (^214) to be the rain winds there. Whence, then,
if not from the trade-wind regions of the South Pacific, can the
vapors for those rains come ?

* " It whirleth about contimaally.'" — Bible.

122 THE PHYSICAL GEOGRAPHY OF THE SEA.

227. According to this view, and not taking into account any
of the exceptions produced by the land and other circumstances
upon the general circulation of the atmosphere over the ocean, the
southeast trade-winds, which reach the shores of Brazil near the
parallel of Rio, and which blow thence for the most part over the
land, should be the winds which, in the general course of circula-
tion, would be carried, after crossing the Andes and rising up in
the belt of equatorial calms, toward Northern Africa, Spain, and
the South of Europe.

They might carry with them the infusoria of Ehrenberg (§ 158),
but, according to this theory, they would be wanting in moisture.
Now, are not those portions of the Old World, for the most part
dry countries, receiving but a small amount of precipitation ?

228. 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 southeast trade-wind
region of the earth, should have a scanty supply of rain, and vice
versa.

229. Let us try this rule : The extra-tropical part of New Hol-
land comprises a portion of land thus situated in the southern hem-
isphere. Tropical India is to the northward and westward of it ;
and tropical India is in the northeast 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. Referring back to p. 79 for what has been already
said concerning the " Meteorological Agencies" {^ 115) of the
atmosphere, it will be observed that cases are there brought for-
ward which afford trials for this rule, every one of which holds
good.

230. Thus, though it be not proved as a mathematical truth
that magnetism is the power which guides the storm from right
to left and from left to right, which conducts the moist and the
dry air each in its appointed paths, and which regulates the "wind
in his circuits," yet that it is such a power is rendered very prob-
able ; for, under the supposition that there is such a crossing of the
air at the five calm places, as Plate, p. 70, represents (^ 106), we

MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 123

can reconcile a greater number of known facts and phenomena
than we can under the supposition that there is no such crossing.
The rules of scientific investigation always require us, when we
enter the domains of conjecture, to adopt that hypothesis by which
the greatest number of known facts and phenomena may be rec-
onciled ; and therefore we are entitled to assume that this cross-
ing does take place, and to hold fast to the theory so maintaining
until it is shown not to be sound.

231. That the magnetism of the atmosphere is the agent which
guides the air across the calm belts, and prevents that which en-
ters them from escaping on the side upon which it entered, we
can not, of our ow^n knowledge, positively affirm. Suffice it to
say, that we recognize in this property of the oxygen of air an
agent that, for aught we as yet know to the contrary, may serve
as such a guide ; and we do not know of the existence of any
other agent in the atmosphere that can perform the offices which
the hypothesis requires. Hence the suspicion that magnetism and
electricity are among the forces concerned in the circulation of the
atmosphere.

124 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER VI.

CURRENTS OF THE SEA.

Currents of the Sea : Governed by Laws, ^ 232.— The Inhabitants of the Sea the
Creatures of Climate, 233. — The Currents of the Sea an Index to its CUmates, 235.
— First Principles, 236. — Some Currents run up hill, 237. — Currents of the Red
Sea, 238. — Top of that Sea an inclined Plane, 240. — How an under Current from
it is generated, 245.— Specific Gravity of Sea Waters, 248.— Why the Red Sea is
not salting up, 251. — Mediterranean Current : How we know there is an un-
der Current from this Sea, 252. — The sunken Wreck which drifted out, 253. — Both
Currents caused by the Salts of the Sea, 254. — Currents of the Indian Ocean :
Why immense Volumes of warm Water flow from it, 255. — A Gulf Stream
along the Coast of China, 256. — Points of Resemblance between it and the Gulf
Stream of the Atlantic, 257. — A Current into Behring's Strait, 258. — Geographical
Features unfavorable to large Icebergs in the North Pacific, 260. — Necessity for
cold to restore the Waste by the warm Currents, and Evaporation, 261. — Argu-
ments in favor of return Currents, because Sea Water is salt, 262. — Currents of
the Pacific : Its Sargasso Sea, 264. — The Drift on the Aleutian Islands, 265. —
The cold China Current, 266. — Humboldt's Current, 267. — Discovery of an im-
mense Body of warm Water drifting South, 268. — Currents about the Equator,
270. — Under Currents: Experiments of Lieutenants Walsh and Lee, 271. —
Proof of under Currents afforded by Deep Sea Soundings, 272. — Currents caused
by Changes in Specific Gravity of Sea Water, 273. — Constituents of Sea Water
every where the same ; affords Evidence of a system of Oceanic Circulation, 274. —
Currents of the Atlantic : The great Equatorial Current : its Fountain-head,
275. — The Cape St. Roque Current proved to be not a constant Current, 276. —
Difficulties of understanding all the Currents of the Sea-shore of the Atlantic can
not be accounted for without the aid of under Currents, 277.

232. Let us, in this chapter, set out with the postulate that the
sea, as well as the air, has its system of circulation, and that this
system, whatever it be, and wherever its channels lie, whether in
the waters at or below the surface, is in obedience to physical
laws. The sea, by the circulation of its waters, has its offices to
perform in the terrestrial economy ; and when we see the currents
in the ocean running hither and thither, we feel that they were not
put in motion without a cause. On the contrary, reason assures
us that they move in obedience to some law of Nature, be it re-
corded down in the depths below, never so far beyond the reach

CURRENTS OF THE SEA. 125

of human ken ; and being a law of Nature, we know who gave it,
and that neither chance nor accident had any thing to do with its
enactment.

Nature grants us all that this postulate demands, repeating it
to us in many forms of expression ; she utters it in the blade of
green grass which she causes to grow in climates and soils made
kind and genial by warmth and moisture, that some current of the
sea or air has conveyed far away from under a tropical sun. She
murmurs it out in the cooling current of the north ; the whales of
the sea tell of it (^ 65), and all its inhabitants proclaim it.

233. The fauna and the flora of the sea are as much the crea-
tures of climate (^ 66), and are as dependent for their well-being
upon temperature as are the fauna and the flora of the dry land.
Were it not so, we should find the fish and the algae, the marine
insect and the coral, distributed equally and alike in all parts of
the ocean. The polar whale WQuld delight in the torrid zone, and
the habitat of the pearl oyster would be also under the iceberg, or
in frigid waters colder than the melting ice.

234. Now water, while its capacities for heat are scarcely ex-
ceeded by those of any other substance, is one of the most com-
plete of non-conductors. Heat does not permeate water as it does
iron, for instance, or other good conductors. Heat the top of an
iron plate, and the bottom becomes warm ; but heat the top of a
sheet of water, as in a pool or basin, and that at the bottom re-
mains cool. The heat passes through iron by conduction, but to
get through^ water it requires to be conveyed by a motion, which
in fluids we call currents.

235. Therefore the study of the climates of the sea involves 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.

236. Hence, in studying the system of oceanic circulation, we
set out with the very simple assumption, viz., that from whatever
part of the ocean a current is found to run, to the same part a cur-
rent of equal volume is obliged to return ; for upon this principle
is based the whole system of currents and counter-currents of the
air as well as of the water.

237. It is not necessary to associate with oceanic currents the
idea that they must of necessity, as on land, run from a higher to

126 THE PHYSICAL GEOGRAPHY OF THE SEA.

a lower level. So far from this being the case, some currents of
the sea actually run up hill, while others run on a level.
The Gulf Stream is of the first class (^ 10).

238. The currents which run from the Atlantic into the Medi-
terranean, and from the Indian Ocean into the Red Sea, are the
reverse of this. Here the bottom of the current is probably a
water-level, and the top an inclined plane, running down hill.
Take the Red 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 dis-
trict, the evaporation from it is immense ; none of the water thus
taken up is returned to it either by rivers or rains. It is about
one thousand miles long ; it lies nearly north and south, and ex-
tends from latitude 13° to the parallel of 30° north.

239. 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.* This
change or difference of level is ascribed to the effect of the wind,
which, prevaihng 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 sea-
son when evaporation is going on most rapidly ; and when we
consider how dry and how hot the winds are which blow upon
this sea at this season of the year, we may suppose the daily evap-
oration to be immense ; not less, certainly, than half an inch, and
probably twice that amount. We know that the waste from ca-
nals by evaporation, in the summer time, is an element which the
engineer, when taking the capacity of his feeders into calculation,
has to consider. With him it is an important element ; how much
more so must the waste by evaporation from this sea be, when we
consider the physical conditions under which it is placed. Its feed-
er, the Arabian Sea, is a thousand miles from its head ; its shores
are burning sands ; the evaporation is ceaseless ; and none of the
vapors, which the scorching winds that blow over it carry away,
are returned to it again in the shape of rains.

240. The Red Sea vapors are carried off and precipitated else-
where. The depression in the level of its head waters in the sum-
mer time, therefore, it appears, is owing quite as much to the effect
of evaporation as to that of the wind blowing the waters back.

* Johnston's Physical Atlas.

CURRENTS OF THE SEA.

127

241. The evaporation in certain parts of the Indian Ocean
(^ 33) is from three fourths of an inch to an inch daily. Suppose
it for the Red Sea in the summer time to average only half an
inch a day.

Now, if we suppose the velocity of the current which runs into
that sea to average, from tnouth to head, twenty miles a day, it
would take the water fifty days to reach the head of it. If it lose
half an inch from its surface by evaporation daily, it w^ould, by
the time it reaches the Isthmus of Suez, lose twenty-five inches
from its surface.

242. Thus the waters of the Red Sea ought to be low^er at
the Isthmus of Suez than they are at the Straits of Babelman-
deb. Independently of the waters forced out by the wind, they
ought to be lower from two other causes, viz., evaporation and
temperature, for the temperature of that sea is necessarily low-
er at Suez, in latitude 30^, than it is at Babelmandeb, in latitude
13°.

243. 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 Red 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 Babel-
mandeb, and to flow up the channel 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.

244. The top of that sea, therefore, may be regarded as an in-
clined plane, made so by evaporation.

245. But the salt water, which has lost so much of its freshness
by evaporation, becomes Salter, and therefore heavier. The fight-
er water at the Straits can not balance the heavier water at the
Isthmus,»and the colder and Salter, and therefore heavier water,
must either run out as an under current, or it must deposit its sur-
plus salt in the shape of crystals, and thus gradually make the
bottom of the Red Sea a salt-bed, or it must abstract all the salt
from the ocean to make the Red Sea brine — and we know that
■neither the one process nor the other is going on. Hence we in-
fer that there is from the Red Sea an under or outer current, as
there is from the Mediterranean throunfh the Straits of Gibraltar,

128 THE PHYSICAL GEOGRAPHY OF THE SEA.

and that the surface waters near 8uez are Salter than those near
the mouth of the Red Sea.

246. And, to show why there should be an outer and under
current from each of these two seas, let us suppose the case of a
long trough, openmg into a vat of oil, with a partition to keep the
oil from running into the trough. Now suppose the trough to be
filled up with wine on one side of the partition to the level of the
oil on the other. The oil is introduced to represent the lighter
water as it enters either of these seas from the ocean, and the wine
the same water after it has lost some of its freshness by evapora-
tion, and therefore has become salter and heavier. Now suppose
the partition to be raised, what would take place ? Why, the oil
would run in as an upper current, overflowing the wine, and the
wine would run out as an under current.

247. The rivers which discharge in the Mediterranean are not
sufficient to supply the waste of evaporation, and it is by a proc-
ess similar to this that the salt which is carried in from the ocean
is returned to the ocean again ; were it not so, the bed of that sea
would be a mass of solid salt. The equilibrium of the seas is
preserved, beyond a doubt, by a system of compensation as exqui-
sitely adjusted as are those by which the " music of the spheres"
is maintained.

248. The above about under currents is theory : Now let us see
the results of actual observation upon the density of water in the
Red Sea and the Mediterranean, and upon the under currents that
run out from these seas.

Four or five years ago, Mr. Morris, chief engineer of the Ori-
ental Company's steam-ship Ajdaha, collected specimens of Red
Sea water all the way from Suez to the Straits of Babelmandeb,
which were afterward examined by Dr. Giraud, who reported the
following results :*

No. 1.

Sea at Suez

Latitude.

Longitude.

Spec. Grav.
1027

Saline Cont.

1000 par' .

41.0

No. 2.

Gulf of Suez

27.49

33.44

1026

40.0

No. 3.

Red Sea

24.29

36.

1024

39.2

No. 4.

do.

20.55

38.18

1026

40.5

No. 5.

do.

20.43

40.03

1024

39.8

No. 6.

do.

14.34

42.43

1024

39.9

No. 7.

do.

12.39

44.45

1023

39.2

Transact, of the Bombay Geograph. Soc, vol. ix., May, 1849, to August, 1850.

CURRENTS OF THE SEA. 129

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

250. In the sailie paper, the temperature of the air between
Suez and Aden often rises, it is said, to 90°, " and probably aver-
ages little less than 75° day and night all the year round. The
surface of the sea varies in heat from 65° to 85°, and the differ-
ence 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 Red
Sea to be no greater than that of Aden, a sheet of water eight feet
thick, equal in area to the whole expanse of the sea, will be car-
ried off annually in vapor ; or, assuming the Red 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 Red Sea, throughout, contain some four per
cent, of salt by weight — or, as salt is a half heavier than water,
some 2.7 per cent, in bulk — or, in round numbers, say three per
cent. In the course of three thousand years, on the assumptions
just made, the Red Sea ought to have been one mass of solid salt,
if there were no current running out."

251. Now we know the Red Sea is more than three thousand
years old, and that it is not filled with salt ; and the reason is, that
as fast as the upper currents bring the salt in at the top, the under
currents carry it out at the bottom.

252. Mediterranean Currents. — With regard to an under
current from the Mediterranean, we may begin by remarking that
we know that there is a current always setting in at the surface
from the Atlantic, and that this is a salt-water current, which
carries an immense amount of salt into that sea. We know,
moreover, that that sea is not salting up ; and therefore, inde-
pendently of the postulate (^ 236) and of observations (^ 253), 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 have been the first to conjecture this explanation, which he
did in 1683 {vide Philosophical Transactions). This contmual indraught into the

I

130 THE PHYSICAL GEOGRAPHY OF THE SEA.

With regard to this outer and under current, we have observa-
tions telhng of its existence as long ago as 1712.

" In the year 1712," says Dr. Hudson, in a paper communicated
to the Philosophical Society in 1724, " Monsieur du L'Aigle, that
fortunate and generous commander of the privateer called the
Phoenix, of Marseilles, giving chase near Ceuta Point to a Dutch
ship bound to Holland, came up wdth her in the middle of the Gut
betvi^een Tariflfa and Tangier, and there gave her one broadside,
which directly sunk her, all her men being saved by Monsieur du
L'Aigle ; and a few days after, the Dutch ship, with her cargo of
brandy and oil, arose on the shore near Tangier, which is at least
four leagues to the westward of the place where she sunk, and di-
rectly against the strength of the current, which has persuaded
many men that there is a recurrency in the deep water in the
middle of the Gut that sets outward to the grand ocean, which this
accident very much demonstrates ; and, possibly, a great part of
the water which runs into the Straits returns that way, and along
the two coasts before mentioned ; otherwise, this ship must, of
course, have been driven toward Ceuta, and so upward. The
water in the Gut must be very deep ; several of the commanders
of our ships of war having attempted to sound it with the longest
lines they could contrive, but could never find any bottom."

In 1828, Dr. Wollaston, in a paper before the Philosophical So-
ciety, stated that he found the specific gravity of a specimen of
sea water, from a depth of six hundred and seventy fathoms, fifty
miles within the Straits, to have a " density exceeding that of dis-

Mediterranean appears to have been a vexed question among the navigators and phi-
losophers even of those times. Dr. Smith alludes to several hypotheses which had
been invented to solve these phenomena, such as subterraneous vents, cavities, exha-
lation by the sun's beams, &c., and then offers his conjecture, which, in his own
words, is, " that there is an under current, by which as great a quantity of water is
carried out as comes flowing in. To confirm which, besides what I have said above
about the difference of tides in the ofRng and at the shore in the Downs, which ne-
cessarily supposes an under current, I shall present you with an instance of the like
nature in the Baltic Sound, as I received it from an able seaman, who was at the
making of the ttial. He told me that, being there in one of the king's frigates, they
went with their plimace into the mid stream, and were carried violently by the cur-
rent ; that, soon aftei 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 alofl, as he added, not being over four or five fathoms deep, and that the
lower the bucket was let fall, they found the under current the stronger."

CURRENTS OF THE SEA. I3I

tilled water by more than four times the usual excess, and accord-
ingly leaves, upon evaporation, more than four times the usual
quantity of saline residuum. Hence it is clear that an under cur-
rent outward of such denser water, if of equal breadth and depth
with the current inward near the surface, would carry out as much
salt below as is brought in above, although it moved with less than
one fourth pari of the velocity, and would thus prevent a perpet-
ual increase of saltness in the Mediterranean Sea beyond that ex-
isting in the Atlantic."

The doctor obtained this specimen of sea water from Captain,
now Admiral Smyth, of the English navy, who had collected it
for Dr. Marcet. Dr. Marcet died before receiving it, and it had
remained in the admiral's hands some time before it came into
those of Wollaston.

It may, therefore, have lost something by evaporation ; for it is
difficult to conceive that all the river water, and three fourths of
the sea water which runs into the Mediterranean, is evaporated
from it, leaving a brine for the under current having four times
as much salt as the w^ater at the surface of the sea usually con-
tains. Very recently, M. Coupvent des Bois is said to have shown,
by actual observation, the existence of an outer and under current
from the Mediterranean.

However that may be, these facts, and the statements of the
Secretary of tlie Geographical Society of Bombay (^ 250), seem
to leave no room to doubt as to the existence of an under current
both from the Red Sea and Mediterranean, and as to the cause
of the surface current which flows into them. I think it a matter
of demonstration. It is accounted for (§ 245) by the salts of the
sea.

253, Writers whose opinions are entitled to great respect differ
with me as to the proof of this demonstration. Among these
writers are Admiral Smyth, of the British Navy, and Sir Charles
Lyell, who also differ with each other. In 1820, Dr. Marcet, be-
ing then engaged in studying the chemical composition of sea
water, the admiral, with his usual alacrity for doing " a kind turn,"
undertook to collect for the doctor specimens of Mediterranean
water from various depths, especially in and about the Straits of
Gibraltar. Among these was the one (§ 252) taken fifty miles
within the Straits from the depth of six hundred and seventy

132 THE PHYSICAL GEOGRAPHY OF THE SEA

fathoms (four thousand and twenty feet), which, being four times
Salter than common sea water, left, as we have just seen (§ 252),
no doubt in the mind of Dr. WoUaston as to the existence of this
under current of brine.

But the indefatigable admiral, in the course of his celebrated
survey of the Mediterranean, discovered that, while inside of the
Straits the depth was upward of nine hundred fathoms, yet in the
Straits themselves the depth across the shoalest section is not more
than one hundred and sixty* fathoms.

" Such being the case, w^e can now prove," exclaims Sir Charles
Lyell, " that the vast amount of salt brought into the Mediterra-
nean does 7iot pass out again by the Straits ; for it appears by Cap-
tain 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. t It is therefore evident, that if water sinks
in certain parts of the Mediterranean, in consequence of the in-
crease of its specific gravity, to greater depths than two hundred
and twenty fathoms, it can never flow out again into the Atlantic,
since it must be stopped by the submarine barrier which crosses
the shallowest part of the Straits of Gibraltar."^

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

According to this reasoning, the water at the bottom of the
great American lakes ought to be salt, for the rivers and the rains,
it is admitted, bring the salts from the land and empty them into
the sea. It is also admitted that the great lakes would, from this
cause, be salt, if they had no sea drainage. The Niagara River
passes these river salts from the upper lakes into Ontario, and the
St. LawTence conveys them thence to the sea. Now the basins
or bottoms of all these upper lakes are far below the top of the
rock over which the Niagara pitches its flood. And, were the
position assumed by this writer correct, viz., that if the water in

* " The Mediterranean." f One hundred and sixty, Smyth.

i Lyell's Principles of Geology, p. 334-5, ninth edition. London, 1853.

CURRENTS OF THE SEA. I33

any of these lakes should, in consequence of its specific gravity,
once sink below the level of the shoals in the rivers and straits
which connect them, it never could flow out again, and conse-
quently must remain there forever* — were this principle physi-
cally correct, would not the water at the bottom of the lakes grad-
ually have received salt sufficient, during the countless ages that
they have been sending it off to the sea, to make this everlasting-
ly pent-up water briny, or at least quite different in its constitu-
ents from that of the surface ? We may presume that the water
at the bottom of every extensive and quiet sheet of w^ater, whether
salt or fresh, is at the bottom by reason of specific gravity ; but
that it does not remain there forever we have abundant proof. If
so, the Niagara River would be fed by Lake Erie only from that
layer of water which is above the level of the top of the rock at
the Falls. Consequently, wherever the breadth of that river is no
greater than it is at the Falls, we should have a current as rapid
as it is at the moment of passing the top of the rock to make the
leap. To see that such is not the w^ay of Nature, we have but to
look at any common mill-pond when the water is running over
the dam. The current in the pond that feeds the overflow is
scarcely perceptible, for " still water runs deep." Moreover, we
know it is not such a skimming current as the geologist would
make, which runs from one lake to another ; for wherever above
the Niagara Falls the water is deep, there w^e are sure to find the
current sluggish, in comparison with the rate it assumes as it ap-
proaches the Falls ; and it is sluggish in deep places, rapid in shal-
low ones, because it is fed from below. The common "wastes"
in our canals teach us this fact.

The reasoning of this celebrated geologist appears to be found-
ed upon the assumption that when water, in consequence of its
specific gravity, once sinks below the bottom of a current where
it is shallowest, there is no force of traction 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.
Thus 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 vary-
ing from one hundred to twenty yards a year.

* Sec paragraph quoted (^ 253) from " Lyell's Principles of Geology."

134 THE PHYSICAL GEOGRAPHY OF THE SEA.

In the place where that bar was when it was one thousand
yards nearer to New Orleans than it now is, whether it were fif-
teen years ago or a century ago, with only fifteen or sixteen feet
of water on it, we have now four or five times that depth. As
new bars were successively formed seaward from the old, what
dug up the sediment which formed the old, and lifted it up from
where specific gravity had placed it, and carried it out to sea over
a barrier not more than a few feet from the surface ? Indeed, Sir
Charles himself makes this majestic stream to tear up its own bot-
tom to depths far below the top of the bar at its mouth. He de-
scribes 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
feett below the top of the bar which obstructs its entrance into the
sea. Could not the same power which scoops out this solid mat-
ter draw the brine up from the pool in the Mediterranean, and
pass it out across the barrier in the Straits ?

The traction of locomotives on rail-roads and the force of that
traction are well understood. Now have not currents in the deep
sea power derived from some such force ? Suppose this under
current from the Mediterranean to extend one hundred and sixty
fathoms down, so as to chafe the barrier across the Straits. Upon
the bottom of this current, then, there is a pressure of more than
fifty atmospheres. Have we not here a source of power that
would be capable of drawing up, by almost an insensibly slow mo-
tion, water from almost any depth ? At any rate, it appears that
the effect of currents by traction, or friction, or whatever force,
does extend far below the level of their beds in shallow places.
Were it not so — were the brine not drawn out again — it would be
easy to prove that this indraught into the Mediterranean has taken,
even during the period assigned by Sir Charles to the formation
of the Delta of the Mississippi — one of the newest formations —
salt enough to fill up the whole basin of the Mediterranean with

* " From near its mouth at the BaUze, a steam-boat may ascend for two thousand
miles with scarcely any perceptible difference in the width of the river." — Lycll, p. 263.

t " The Mississippi is continually shifting its course in the great alluvial plain, cut-
ting frequently to the depth of one hundred, and even sometimes to the depth of two
hundred and fifty feet." — Lyell^ p. 373.

CURRENTS OF THE SEA. I35

crystals. Admiral Smyth brought up bottom with his briny sam-
ple of deep sea water (six hundred and seventy fathoms), but no
salt crystals.

The gallant admiral — appearing to withhold his assent both from
Dr. Wollaston in his conclusions as to this under current, and
from the geologist in his inferences as to the effect of the barrier
in the Straits — suggests the probability that, in sounding for the
heavy specimen of sea water, he struck a brine spring. But the
specimen, according to analysis, was of sea water, and how did a
brine spring of sea w^ater get under the sea but through the proc-
ess of evaporation on the surface, or by parting with a portion of
its fresh water in some other way ?

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
harmonies of the sea are gone, and we are forced to conclude they
never existed. Every particle of w^ater that sinks below a sub-
marine ridge is, ipso facto, by his reasoning, stricken from , the
channels of circulation, to become thenceforward forever motion-
less matter. The consequence would be " cold obstruction" in
the depths of the sea, and a system of circulation between differ-
ent seas of the waters only that float above the shoalest reefs and
barriers. I do not believe in the existence of any such imperfect
terrestrial mechanism, or in any such failures of design. To my
mind, the proofs — the theoretical proofs — the proofs derived ex-
clusively from reason and analogy — are as clear in favor of this
under current from the Mediterranean as they were in favor of
the existence of Leverrier's planet before it was seen through the
telescope at Berlin.

Now suppose, as Sir Charles Lyell maintains, that none of these
vast quantities of salt which this surface current takes into the
Mediterranean find their way out again. It would not be difficult
to show, even to the satisfaction of that eminent geologist, that
this indraught conveys salt away from the Atlantic faster than all
the/re5/i-water rivers empty fresh supplies of salt into the ocean.
Now, besides this drain, vast quantities of salts are extracted from
sea water for madrepores, coral reefs, shell banks, and marl beds ;
and by such reasoning as this, which is perfectly sound and good,
we estabhsh the existence of this under current, or else we are

136 THE PHYSICAL GEOGRAPHY OF THE SEA.

forced to the very unphilosophical conclusion that the sea must
be losing its salts, and becoming less and less briny.

255. The Currents of the Indian Ocean. — By carefully ex-
amining the physical features of this sea (Plates VIII. and IX.),
and studying its conditions, we are led to look for warm currents
that have their genesis in this ocean, and that carry from it vol-
umes of overheated water, probably exceeding in quantity many
times that which is discharged by the Gulf Stream from its fount-
ains (Plate VI.).

The Atlantic Ocean is open at the north, but tropical countries
bound the Indian Ocean in that direction. The waters of this
ocean are hotter than those of the Caribbean Sea, and the evap-
orating force there (^ 146) is much greater. That it is greater
we might, without observation, infer from the fact of a higher
temperature and a greater amount of precipitation on the neigh-
boring shores (^ 139). These two facts, taken together, tend,
it would seem, to show that large currents of warm water have
their genesis in the Indian Ocean. One of them is the well-
known Mozambique current, called at the Cape of Good Hope
the Lagullas current.

256. Another of these currents makes its escape through the
Straits of Malacca, and, being joined by other warm streams from
the Java and China Seas, flows out into the Pacific, like another
Gulf Stream, between the Philippines and the shores of Asia.
Thence it attempts the great circle route (§ 69) for the Aleutian
Islands, tempering climates, and losing itself in the sea on its
route toward the northwest coast of America.

257. Between the physical features of this current and the
Gulf Stream of the Atlantic there are several points of resem-
blance. Sumatra and Malacca correspond to Florida and Cuba ;
Borneo to the Bahamas, with the Old Providence Channel to the
south, and the Florida Pass to the west. The coasts of China
answer to those of the United States, the Philippines to the Ber-
mudas, the Japan Islands to Newfoundland. As with the Gulf
Stream, so also here with this China current, there is a counter-
current of cold water between it and the shore. The climates of
the Asiatic coast correspond with those of America along the At-
lantic, and those of Columbia, Washington, and Vancouver are
duplicates of those of Western Europe and the British Islands ;

CURRENTS OF THE SEA. I37

the climate of California (State) resembling that of Spain ; the
sandy plains and rainless regions of Lower California reminding
one of Africa, with its deserts between the same parallels, &c.

Moreover, the North Pacific, like the North Atlantic, is envel-
oped, where these warm waters go, with mists and fogs, and streak-
ed with lightning. The Aleutian Islands are as renowned for fogs
and mists as are the Grand Banks of Newfoundland.

258. A surface current flows north through Behring's Strait
into the Arctic Sea ; but in the Atlantic the current is from, not
into the Arctic Sea : it flows south on the surface, north below ;
Behring's Strait being too shallow to admit of mighty under cur-
rents, or to permit the introduction from the polar basin of anv
large icebergs into the Pacific.

259. Behring's Strait, in geographical position, answers to Da-
vis's 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, the Pacific shore-line inter-
venes, and turns them down through a sort of North Sea along the
western coast of the continent toward Mexico.

260. These contrasts show the principal points of resemblance
and of diflference between the currents and aqueous circulation in
the two oceans. The ice-bearing currents of the North Atlantic
are not repeated as to degree in the North Pacific, for there is no
nursery for icebergs like the frozen ocean and its arms. The seas
of Qkotsk and Kamtschatka alone, and not the frozen seas of the
Arctic, cradle the icebergs for the North Pacific.

There is, at times at least, another current of warm water from
the Indian Ocean. It finds its way south midway between Africa
and Australia. The whales (Plate IX.) give indications of it.
Nor need we be surprised at such a vast flow of warm water as
these three currents indicate from the Indian Ocean, when we rec-
ollect that this ocean (^ 255) is land-locked on the north, and that
the temperature of its waters is frequently as high as 90° Fahr.

261. There must, therefore, be immense volumes of w^ater flow-
ing into the Indian Ocean to supply the waste created by these
warm currents, and the fifteen or twenty feet of water that obser-
vations (^ 33) tell us are yearly carried off" from this ocean by
evaporation.

138 THE PHYSICAL GEOGRAPHY OF THE SEA.

On either side of this warm current that escapes from the inter-
tropical parts of the Indian Ocean (^ 260), midway between Africa
and Austraha, an ice-bearing current (Plate IX.) is found wending
its way from the Antarctic regions with supplies of cold water to
modify climates, and restore the aqueous equilibrium in that part
of the world. These cold currents sometimes get as far north
with their icebergs as 40° south. The Gulf Stream seldom per-
mits them to get so near the equator as that in the North Atlan-
tic, but I have known the ice-bearing current which passes east
of Cape Horn into the South Atlantic to convey its bergs as far
as the parallel of 37° south latitude. This is the nearest ap-
proach of icebergs to the equator.

262. These currents w^hich run out from the inter-tropical basin
of that immense sea — Indian Ocean — are active currents. They
convey along immense volumes of water containing vast quanti-
ties of salt, and we know that sea water enough to convey back
equal quantities of salt, and salt to keep up supplies for the out-
going currents, must flow into or return to the inter-tropical re-
gions of the same sea ; therefore, if observations were silent upon
the subject, reason would teach us to look for currents here that
keep in motion immense volumes of water.

263. The Currents of the Pacific. — The contrast has been
drawn (^ 257) between the China or " Gulf Stream" of the North
Pacific, and the Gulf Stream of the North Atlantic. The course
of the China Stream has never been 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
toward the Cape de Verd Islands.

264. In the open space west of this southwardly set along the
African coast, there is the famous Sargasso Sea (Plate IX.),
which is the general receptacle of the drift-wood and sea-weed of
the Atlantic. So, in like manner, to the west from Cahfornia of
this other southwardly set, hes the pool into which the drift-wood
and sea-weed of the North Pacific are generally gathered.

265. The natives of the Aleutian Islands, where no trees grow,
depend upon the drift-wood cast ashore there for all the timber
used in the construction of their boats, fishing-tackle, and house-
hold gear. Among this timber, the camphor-tree, and other woods
of China and Japan, are said to be often recognized. In this fact

CURRENTS OF THE SEA. I39

we have additional evidence touching this China Stream, as to
vrhich (^ 263) but Kttle, at best, is known.

266. The Cold Asiatic Current. — Inshore of, but counter to
the China current, along the eastern shores of Asia, is found
(§ 257) a streak, or layer, or current of cold water answering to
that between the Gulf Stream and the American coast. This
current, like its fellow in the Atlantic, is not strong enough at all
times sensibly to affect the course of navigation ; but, like that in
the Atlantic, it is the nursery (^ 65) of most valuable fisheries.
The fisheries of Japan are quite as extensive as those of New-
foundland, and the people of each country are indebted for their
valuable supplies of excellent fish to the cold waters which the
currents of the sea bring down to their shores.

267. Humboldt's Current. — The currents of the Pacific are
but little understood. Among those about which most is thought
to be known is the Humboldt Current of Peru, which the great
and good man whose name it bears was the first to discover. It
has been traced on Plate IX. according to the best information
— defective at best — upon the subject. This current is felt as far
as the equator.

268. I have, I believe, discovered the existence of a warm cur-
rent in the inter-tropical regions of the Pacific, midway between
the American coast and the shore-lines of Australia.

269. This region affords an immense surface for evaporation.
No rivers empty into it ; the annual fall of rain, except in the
" Equatorial Doldrums," is small, and the evaporation is all that
both the northeast and the southeast trade-w^inds can take up and
carry off". I have marked on Plate IX. the direction of the sup-
posed warm w^ater current 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 with waters that are less salt, these over-
heated and over-salted waters from the tropics may be replenish-
ed and restored to their rounds in the wonderful system of oceanic
circulation.

270. There are also about the equator in this ocean some curi-
ous currents w^hich I do not understand, and as to which obser-
vations are not sufficient yet to afford the proper explanation or
description. There are many of them, some of which, at times,

140 THE PHYSICAL GEOGRAPHY OF THE SEA.

run with great force. On a voyage from the Society to the Sand-
wich Islands, I encountered one running at the rate of ninety-six
miles a day.

And what else should we expect in this ocean but a system of
currents and counter-currents apparently the most uncertain and
complicated ? The Pacific Ocean and the Indian Ocean may, in
the view we are about to take, be considered as one sheet of wa-
ter. This sheet of water covers an area quite equal in extent to
one half of that embraced by the whole surface of the earth ; and,
according to Professor Alexander Keith Johnston, who so states
it in the new edition of his splendid Physical Atlas, the total an-
nual fall of rain on the earth's surface is one hundred and eighty-
six thousand, two hundred and forty cubic imperial miles. Not
less than three fourths of the vapor which makes this rain comes
from this w^aste of waters ; but supposing that only half of this
quantity, i. e,, ninety-three thousand, one hundred and twenty
cubic miles of rain falls upon this sea, and that that much, at
least, is taken up from it again as vapor, 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 winds.

The better to appreciate the operation of such agencies in pro-
ducing currents in the sea, now here, now there, first this way,
and then that, let us, by w- ay of illustration, imagine a district of
two hundred and fifty -five square miles in extent to be set apart,
in the midst of the Pacific Ocean, as the scene of operations for
one day. We must now conceive a machine capable of pumping
up, in the twenty-four hours, all the water to the depth of one
mile in this district. The machine must not only pump up
and bear off'this immense quantity of water, but it must discharge
it again into the sea on the same day, but at some other place.
Now here is a force for creating currents that is equivalent in its
results to the eflfects that would be produced by bailing up, in
twenty-four hours, two hundred and fifty-five cubic miles of wa-
ter from one part of the Pacific Ocean, and emptying it out again
upon another part. The currents that would be created by such an

CURRENTS OF THE SEA.

141

operation would overwhelm navigation and desolate the sea ; and,
happily for the human race, the great atmospherical machine
(§ 90), which actually does perform every day, on the average, all
this lifting up, transporting, and letting down of water upon the face
of the grand ocean, does not confine itself to an area of two hund-
red and fifty-five square miles, but to an area three hundred thou-
sand times as great ; yet, nevertheless, the same quantity of water
is kept in motion, and the currents, in the aggregate, transport as
much water to restore the equilibrium as they would have to do
were all the disturbance to take place upon our hypothetical area
of one mile deep over the space of two hundred and fifty-five
square miles. Now when we come to recollect that evaporation
is lifting up, that the winds are transporting, and that the clouds
do let down every day actually such a body of water, but that it
is done by little and little at a place, and by hair's breadths at a
time, not by parallelopipedons one mile thick — that the evapora-
tion is most rapid and the rains most copious, not always at the
same place, but now here, now there, we shall see actually existing
in nature a force sufficient to give rise to just such a system of
currents as that which mariners find in the Pacific — currents which
appear to rise in mid ocean, run at unequal rates, sometimes east,
sometimes west, but which always lose themselves where they
rise, viz., in mid ocean.

271. Under Currents. — Lieutenant J. C.Walsh, in the United
States schooner "Taney," and Lieutenant S. P. Lee, in the United
States brig " Dolphin," both, while they were carrying on a sys-
tem of observations in connection with the Wind and Current
Charts, had their attention directed to the subject of submarine
currents.

They made some interesting experiments upon the subject. A
block of wood was loaded to sinking, and, by means of a fishing-
line or a bit of twine, let down to the depth of one hundred or five
hundred fathoms (six hundred or three thousand feet). A small
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 wonderful, indeed, to
see this harrega move off*, against wind, and sea, and surface cur-
rent, at the rate of over one knot an hour, as was generally the case,
and on one occasion as much as If knots. The men in the boat

142 THE PHYSICAL GEOGRAPHY OF THE SEA.

could not repress exclamations of surprise, for it really appeared
as if some monster of the deep had hold of the weight below, and
was walking off with it."* Both officers and men were amazed
at the sight.

272. The experiments in deep-sea soundings have also thrown
much light upon the subject of under currents. There is reason
to believe that they exist in all, or almost all parts of the deep
sea, for never in any instance yet has the deep-sea line ceased to
run out, even after the plummet had reached the bottom.

If the line be held fast in the boat, it invariably parts, showing,
when two or three miles of it are out, that the under-currents are
sweeping against the bight of it with what seamen call a swig-
ging force, that no sounding twine has yet proved strong enough
tp 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 paid
out. Night coming on, he had to part the line (which he did
simply by attempting to haul it in) and return on board. Exam-
ination proved that the ocean there, instead of being over ten
miles in depth, was not over three, and that the line was swept
out by the force of one or more under currents. But in what di-
rection these currents were running is not known.

273. It may, therefore, without doing any violence to the rules
of philosophical investigation, be conjectured, that the equilibrium
of all the seas is preserved, to a greater or less extent, by this
system of currents and counter-currents at and below the surface.

If we except the tides, and the partial currents of the sea, such
as those that may be created by the wind, we may lay it down as
a rule (§ 34) that all the currents of the ocean owe their origin to
difference of specific gravity between sea water at one place and
sea water at another ; for wherever there is such a difference,
whether it be owing to difference of temperature or to difference
of saltness, &c., it is a difference that disturbs equilibrium, and
currents are the consequence. The heavier water goes toward
the lighter, and the lighter whence the heavier comes; for two
fluids differing in specific gravity (§36), and standing at the same

* Lieutenant Walsh.

CURRENTS OF THE SEA. I43

level, can not balance each other. 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 current.

27'4. That the sea, in all parts, holds in solution the same kind
of solid matter ; that its vt^aters 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 without salt,
may be taken as evidence in proof of a system of currents or of
circulation in the sea, by which its waters are shaken up and kept
mixed together as though they were in a phial. Moreover, we
may lay it down as a law in the system of oceanic circulation,
that every current in the sea has its counter current ; in other
words, that the currents of the sea are, like the nerves of the hu-
man system, arranged in pairs ; for wherever one current is found
carrying off water from this or that part of the sea, to the same
part must some other current convey an equal volume of water,
or else the first would, in the course of time, cease for the want
of water to supply it.

275. Currents of the Atlantic. — The principal currents of
the Atlantic have been described in the chapter on the Gulf Stream.
Besides this, its eddies and its offsets, are the equatorial current
(Plate VI.), and the St.Roque or Brazil Current. Their fountain-
head is the same. It is in the w^arm waters about the equator,
between Africa and America. The former, receiving the Amazon
and the Oronoco as tributaries by the w^ay, flows into the Carib-
bean Sea, and becomes, with the waters (§ 35) in which the
vapors of the trade-winds leave their salts, the feeder of the Gulf
Stream. The Brazil Current, coming from the same fountain, is
supposed to be divided by Cape St. Roque, one branch going to
the south under this name (Plate IX.), the other to the w^estward.
This last has been a great bugbear to navigators, principally on
account of the difficulties which a few dull vessels falling to lee-
ward of St. Roque have found in beating up against it. It was
said to have caused the loss of some English transports in the last
century, which fell to leeward of the Cape on a voyage to the
other hemisphere ; and navigators, accordingly, were advised to
shun it as a danarer.

276. This current has been an object of special investigation

144 THE PHYSICAL GEOGRAPHY OF THE SEA.

during my researches connected with the wind and current charts,
and the result has satisfied me that it is neither a dangerous nor a
constant current, notwithstanding older writers. Horsburgh, in
his East India Directory, cautions navigators against it ; and Keith
Johnston, in his grand Physical Atlas, published in 1848, thus
speaks of it :

" This current greatly impedes the progress of those vessels
which cross the equator west of 23° west longitude, impelling
them beyond Cape St. Roque, when they are draw^n toward the
northern coast of Brazil, and can not regain their course till after
weeks or months of delay and exertion."

So far from this being the case, my researches abundantly prove
that vessels which cross the equator five hundred miles to the west
of longitude 23° west 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 30° west, and in three days
from that crossing they are generally clear of that cape. A few
of them report the current in their favor ; most of them experience
no current 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 twenty miles a day. The inter-tropical regions of
the Atlantic, like those of the other oceans (§ 270), abound w^ith
conflicting currents, w^hich no researches yet have enabled the
mariner to unravel so that he may at all times know where they are
and tell how they run, in order that the navigator may be certain
of their help when favorable, or sure of avoiding them if adverse.

277. I may here remark, that there seems to be a larger flow
of polar waters into the Atlantic than of other waters from it, and
I can not account for the preservation of the equilibrium of this
ocean by any other hypothesis than that which calls in the aid of
under currents. They, I have no doubt, bear an important part
in the system of oceanic circulation.

Admiral Sir Francis Beaufort, the venerable hydrographer of
England, made, when in command of her Britannic majesty's
frigate Frederiksteen, in the Mediterranean, some interesting ex-
periments upon under currents, w^hich I should be glad to see re-
peated in other parts of the sea, especially between the tropics, in
the Atlantic, Pacific, and Indian Oceans, and wherever the w^ater
is remarkably transparent. That officer says :

CURRENTS OF THE SEA. 145

" The counter currents, or those which return beneath the sur-
face of the water, are also very remarkable ; in some parts of
the Archipelago they are at times so strong as to prevent the
steering of the ship ; and, in one instance, on sinking the lead,
when the sea was calm and clear, with shreds of bunting of vari-
ous colors attached to every yard of the line, they pointed in dif-
ferent directions all round the compass."

K

146 THE PHYSICAL GEOGllAPHV OF THE SEA

CHAPTER VII.

THE OPEN SEA IN THE ARCTIC OCEAN.

How Whales struck on the east Side of the Continent have been taken on the west
Side, {} 278. — Right Whales can not cross the Equator, 279. — How the Existence
of a northwest Passage was proved by the Whales, 280. — Other Evidence in Favor
of it, 281. — An under Current sets into the Arctic Ocean, 282. — Evidences of a
milder Climate near the Pole, 284. — The Water Sky of Lieutenant De Haven, 285.
— This open Sea not permanently in one Place, 286.

278. It is the custom among whalers to have their harpoons
marked with date and the name of the ship ; and Dr. Scoresby,
in his work on Arctic voyages, mentions several instances of
whales that have been taken near the Behring's Strait side with
harpoons in them bearing the stamp of ships that were known to
cruise on the Baffin's Bay side of the American continent ; and as,
in one or two instances, a very short time had elapsed between
the date of capture in the Pacific and the date when the fish must
have been struck on the Atlantic sitle, it was argued therefore
that there was a northwest 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
around either Cape Horn or the Cape of Good Hope.

The whale-fishing is, among the industrial pursuits of the sea,
one of no little importance ; and when the system of investigation
out of which the "wind and current charts" have grown was
commenced, the haunts of this animal did not escape attention or
examination. The log-books of whalers were collected in great
numbers, and patiently examined, co-ordinated, and discussed, in
order to find out what parts of the ocean are frequented by this
kind of whale, what parts by that, and what parts by neither.
(See Plate IX.)

279. Log-books containing the records by different ships for
hundreds of thousands of days were examined, and the observa-
tions in them co-ordinated for this chart. And this investigation.

THE OPEN SEA IN THE ARCTIC OCEAN 147

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 can not pass, and into which he never enters. The fact was
also brought out that the same kind of whale that is found ofi'
the shores of Greenland, in Baffin's Bay, &c., is found also in the
North Pacific, and about Behring's Strait, and that the right whale
of the northern hemisphere is a different animal from that of the
southern.

280. Thus the fact was established that the harpooned whales
did not pass around Cape Horn or the Cape of Good Hope, for
they w^ere of the class that could not cross the equator. In this
way we were furnished with circumstantial evidence affording
the most irrefragable proof that there is, at times at least, open
water communication through the Arctic Sea from one side of the
continent to the other, for it is known that the whales can not
travel under the ice for such a great distance as is that from one
side of this continent to the other.

But this did not prove the existence of an open sea there ; it
only established the existence — the occasional existence, if you
please — of a channel through which whales had passed. There-
fore we felt bound to introduce other evidence before we could
expect the reader to admit our proof, and to believe with us in the
existence of an open sea in the Arctic Ocean.

281. There is an under current setting from the Atlantic through
Davis's Strait into the Arctic Ocean, and there is a surface cur-
rent setting out. Observations have pointed out the existence of
this under current there, for navigatqrs tell of immense icebergs
w^hich they have seen drifting rapidly to the north, and against a
strong surface current. These icebergs were high above the wa-
ter, and their depth below was seven times greater than their
height above. No doubt they were drifted by a powerful under
current.

282. Now this under current comes from the south, where it is
warm, and the temperature of its waters is perhaps not below
32° ; 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 cur-
rent ; for the surface current, though its waters are mixed with
the fresh waters of the rivers and of precipitation in the polar

148 THE PHYSICAL GEOGRAPHY OF THE SEA.

basin, nevertheless bears out vast quantities of salt, which is fur-
nished neither by the rivers nor the rains.

283. These salts are supplied by the under current ; for as
much gait as one current brings in, other currents (^ 252) must take
out, else the polar basin would become a basin of salt ; and where
the under current transfers its w^aters 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 in a solid state.

An arrangement in nature, by which a basin of considerable
area in the frozen ocean could be supplied by water coming in at
the bottom and rising up at the top, with a temperature not below
30°, or even 28° — the freezing point of sea water — would go far
to mitigate the climate in the regions round about.

284. And that there is a warmer climate somewhere in that in-
hospitable sea, the observations of many of the explorers who
have visited it indicate. Its existence may be inferred also from
the well-known fact that the birds and animals are found at cer-
tain seasons migrating to the north, evidently in search of milder
climates. The instincts of these dumb creatures are 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 water. It is another furnace (§ 60) in the beauti-
ful economy of Nature for tempering climates there.

285. Relying upon a process of reasoning like this, and the de-
ductions flowing therefrom, -Lieutenant De Haven, when he went
in command of the American expedition in search of Sir John
Franklin and his companions, was told, in his letter of instruc-
tions, to look, when he should get well up into Wellington Chan-
nel, for an open sea to the northward and westward. He looked,
and saw in that direction a " water sky." Captain Penny after-
ward went there, found open water, and sailed upon it.

286. The open sea in the Arctic Ocean is probably not always
in the same place, as the Gulf Stream (^ 54) is not always in one
place. It probably is always where the waters of the under cur-
rent are brought to the surface ; and this, we may imagine, would
depend upon the freedom of ingress for the under current. Its
course may, perhaps, be modified more or less by the ice on the

THE OPEN SEA IN THE ARCTIC OCEAN.

149

surface, by changes, from whatever cause, in the course or ve-
locity of the surface current, for obviously the under current could
not bring more v^^ater into the frozen ocean than the surface cur-
rent would carry out again, either as ice or water.

287. Every winter, an example of how very close warm water
in the sea and a very severe climate on the land or the ice may
be to each other, is afforded to us in the case of the Gulf Stream,
and the Labrador-like climate of New England, Nova Scotia, and
Newfoundland. In these countries, in winter, the thermometer
frequently sinks far below zero, notwithstanding that the tepid
w^aters of the Gulf Stream may be found with their summer tem-
perature within one good day's sail of these very, very cold places.

150 '^'HE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER VIII.

THE SALTS OF THE SEA.

What the Salt in the Sea Water has to do with the Currents in the Ocean, <5> 289. —
Reasons for supposing the Sea to have its system of Circulation, 290. — Arguments
furnished by Coral Islands, 293. — W^hat would be the Effect of no system of Cir-
culation for Sea Water "? 295. — Its Components, 297. — The principal Agents from
which Dynamical Force in the Sea is derived, 300. — Illustration, 302. — Sea and
Fresh Water have different Laws of Expansion, 308. — The Gulf Stream could not
exist in a Sea of fresh Water, 309. — The effect of Evaporation in producing Cur-
rents, 310. — How the Polar Sea is supplied with Salt, 323. — The Influence of this
imder Current upon open Water in the Frozen Ocean, 326. — Sea Shells : The
Influence exerted by them upon Currents, 330. — Order among them, 335. — They
assist in regulating Climates, 336. — How Sea Shells and Salts act as Compensa-
tions in the Machinery by which Oceanic Circulation is conducted, 339. — Whence
come the Salts of the Sea 1 344.

288. In order to comprehend aright the currents of the sea, and
to study with advantage its physical adaptations, it is necessary to
understand the effects produced by the salts of the sea upon the
equilibrium of its waters ; for wherever equilibrium be destroyed,
whether in the air or water (§ 276), it is restored by motion, and
motion among fluid particles gives rise to currents, w^hich, in turn,
constitute circulation.

This chapter is therefore added as -a sort of supplement, which
will assist us in elucidating what has been advanced concerning
the currents of the sea.

289. The question is often asked, " Why is the sea salt ?" I
think it can be shown that the circulation of the ocean depends,
in a great measure, upon the salts of sea water ; certainly its in
fluences upon climate are greatly extended by reason of its salt-
ness.

As a general rule, the sea is nearly of a uniform degree of salt-
ness, and the constituents of sea water are as constant in their
proportions as are the components of the atmosphere. It is true
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

THE SALTS OF THE SEA. 15X

water is generally ; but this circumstance is due to local causes
of easy explanation. For instance : when we come to an arm of
the sea, as the Red Sea (§ 238), upon which it never rains, and
from which the atmosphere is continually abstracting, by evapor-
ation, 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 other parts where it rains
more than it evaporates. Therefore we do not find sea water
from all parts of the ocean actually of the same degree of salt-
ness, yet we do find, as in the case of the Red Sea, sea water that
is continually giving off to evaporation fresh water in large quan-
tities ; nevertheless, for such water there is a degree, and a very
moderate degree, of saltness which is a maximum ; and we more-
over find that, though the constituents of sea water, like those of
the atmosphere, are not for every place invariably the same as to
their proportions, yet they are the same, or nearly the same, as to
their character.

290. When, therefore, we take into consideration the fact that,
as a general rule, sea water is, with the exceptions above stated,
every where and always the same, and that it can only be made
so by being well shaken together, we find grounds on which to
base the conjecture that the ocean has its system of circulation,
which is probably as complete and not less wonderful than is the
circulation of blood through the human system.

In order to investigate the currents of the sea, and to catch a
glimpse of the laws by which the circulation of its waters is gov-
erned, hypothesis, in the present meagre state of absolute knowl-
edge with regard to the subject, seems to be as necessary to prog-
ress as is a corner-stone to a building. To make progress with
such investigations, we want something to build upon. In the ab-
sence 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 an one, we are entitled to claim
for it a respectful consideration at least, until we discover it lead-
ing us into some palpable absurdity, or until some other hypoth-

152 THE PHYSICAL GEOGRAPHY OF THE SEA.

esis be suggested which will account equally as well, but for a
greater number of phenomena. Then, as honest searchers after
truth, we should be ready to give up the former, adopt the latter,
and to try it until some other better than either of the two be of-
fered.

291. With this understanding, 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 do but conjecture when we say 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 ; for if we take a
sample of water w^hich shall fairly represent, in the proportion of
its constituents, the average w^ater of the Pacific Ocean, and ana-
lyze it, and if we do the same by a similar sample from the At-
lantic, w^e shall find the analysis of the one to resemble that of the
other as closely as though the two samples had been taken from
the same bottle after having been w^ell 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 into
contact and mixed up with sea water from all other parts of the
world ? Agents, therefore, it would seem, are at work, which
shake up the waters of the sea as though they were in a bottle,
and w^hich, in the course of time, mingle those that are in one part
of the ocean with those that are in another as thoroughly and com-
pletely as it is possible for man to do in a vessel of his owti con-
struction.

292. This fact, as to uniformity of components, appears to call
for the hypothesis that sea water which to-day is in one part of
the ocean, w ill, in the process of time, be found in another part
the most remote. It must, therefore, be carried about by cur-
rents ; and as these currents have their offices to perform in the
terrestrial economy, they probably do not flow by chance, but in
obedience to physical laws ; they no doubt, therefore, maintain
the order and preserve the harmony which characterize every de-

THE SALTS OF THE SEA.

153

partment of God's handiwork, upon the threshold of which man
has as yet been permitted to stand, to observe, and to compre-
hend.

293. Nay, having reached this threshold, and taken a survey of
the surrounding ocean, we are ready to assert, with all the confi-
dence of knowledge, that the sea has a system of circulation for
its waters. We rest this assertion upon our faith in the physical
adaptations wuth which the sea is invested. Take, for example, the
coral islands, reefs, beds, and atolls with which the Pacific Ocean
is studded and garnished. They were built up of materials which
a certain kind of insect quarried from the sea water. The cur-
rents of the sea ministered to this little insect — they were its liod
carriers ; when fresh supplies of solid matter were wanted for the
coral rock upon which the foundations of the Polynesian Islands
were laid, they brought them ; the obedient currents stood ready
with fresh supplies in unfailing streams of sea water from which
the solid ingredients had not been secreted. Now, unless the cur-
rents of the sea had been employed to carry off from this insect
the waters that had 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 w^ant of food long before its task w^as half
completed. But for currents, it w^ould have been impaled in a
nook of the very drop of water in which it was spawned ; for it
would have soon secreted the lime contained in this drop of wa-
ter, and then, without the ministering aid of currents to bring it
more, it w^ould have perished for the w^ant of food for itself and
materials for its edifice ; and thus, but for the benign currents
which took this exhausted water away, there we perceive this
emptied drop would have remained, not only as the grave of the
little architect, but as a monument in attestation of the shocking
monstrosity that there had been a failure in the sublime system of
terrestrial adaptations — that the sea had not been adapted by its
Creator to the well-being of all its inhaWtants. Now we do know
that its adaptations are suited to all the w^ants of every one of its
inhabitants — to the wants of the coral insect as well as to those
of the whale. Hence we say we know that the sea has its system
of circulation, for it transports materials for the coral rock from
one part of the world to another ; its currents receive them from
the rivers, and hand them over to the little mason for the struct-

154 THE PHYSICAL GEOGRAPHY OF THE SEA.

ure of the most stupendous works of solid masonry that man has
ever seen — the coral islands of the sea.

294. And thus, by a process of reasoning which is perfectly
philosophical, we are irresistibly led to conjecture that there are
regular and certain, if not appointed channels, through which the
water travels from one part of the ocean to another, and that those
channels belong to an arrangement which may make, and, for
aught we know to the contrary, which 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, " the waves
also lifted up their voice ;" and doubtless, therefore, the harmony
in the depths of the ocean is in tune with that which comes from
the spheres above. We can not 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 trav-
erse different latitudes and climates — if this were so, then the ma-
chinery of the ocean would be as incomplete as that of a watch
without a balance-wheel ; for the waters of these arms and seas
would, as to their constituents, become, in the process of time, very
diflferent from the sea waters in other parts of the world, and their
inhabitants would perish for the want of brine of the right strength
or of water of the right temperature.

295. For instance, take the Red Sea and the Mediterranean by
way of illustration. Upon the Red Sea there is no precipitation ;
it is a rainless region ; not a river runs 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 lield in solution
by rain or river water, can be brought down into the Red Sea.
Its salts come from the ocean, and the air takes up from it, in the
process of evaporation, fresh water, leaving behind all the solid
matter which this sea holds in solution (§ 239).

296. On the other hand, numerous rivers discharge into thr
Mediterranean, some of which are filtered through soils and amon.^-

THE SALTS OF THE SEA. I55

minerals 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 lime, magnesia, soda, potash, or iron —
either or all may be in its waters. Still, the constituents of sea
water from the Mediterranean and of sea water from the Red Sea
are quite the same. But the waters of the Dead Sea have no con-
nection with those of the ocean ; they are cut off from its channels
of circulation, and are therefore quite different, as to their com-
ponents, from any arm, frith, or gulf of the broad ocean. Its in-
habitants are also different from those of the high seas.

297. " The solid constituents of sea water amount to about 3^
per cent, of its weight, or nearly half an ounce to the pound. Its
saltness may be considered as a necessary result of the present
order of things. Rivers which are constantly flowing into the
ocean contain salts, varying from ten to fifty, and even one hund-
red grains per gallon. They are chiefly common salt, sulphate
and carbonate of lime, magnesia, soda, potash, and iron ; and these
are found to constitute the distinguishing characteristics of sea
water. The water w^hich 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 sea-
ward by the returning currents. The ocean, therefore, is the
great depository of every thing that water can dissolve and carry
down from the surface of the continents; and, as there is no chan-
nel for their escape, they of course consequently accumulate."*

298. "The case of the sea," says Fowner, "is but a magnified
representation of what occurs in every lake into which rivers flow,
but from which there is no outlet except by evaporation. Such
a lake is invariably a salt lake. It is impossible that it can be
otherwise ; and it is curious to observe that this condition disap-
pears when an artificial outlet is produced for the waters."

299. How^, therefore, shall wc account for this sameness of
compound, this structure of coral (§ 293), this stability as to ani-
mal life in the sea, but upon the supposition of a general system
of circulation in the ocean, by which, in process of time, water
from one part is conveyed to another part the most remote, and

* Yeomans's Chemistry.

156 THE PHYSICAL GEOGRAPHY OF THE SEA.

by which a general interchange and commingUng 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 channels of cir-
culation any portion of sea water, as in the Dead Sea, or of at-
mospheric air, as in mines or wells, we can easily fill 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.

300. The principal agents that are supposed to be concerned
in giving circulation to the atmosphere, and in preserving the ratio
among its components, are light, heat, electricity, and magnetism
(^ 231). But with regard to the sea, it is not known what office
is performed by electricity and magnetism, in giving dynamical
force to its waters in their system of circulation. The chief mo=
tive power from which marine currents derive their velocity has
been ascribed to heat ; but a close study of the agents concerned
has suggested that an important — nay, a powerful and active agen-
cy in the system 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.

301. Let us, for the sake of illustrating and explaining this
force, suppose the sea in all its parts — in its depths and at the
surface, at the equator and about the poles — to be of one uniform
temperature, and to be all of fresh water ; and, moreover, that
there be neither wind to disturb its surface, nor tides nor rains to
raise the level in this part, or to depress it in that. In this case,
there would be nothing of heat to disturb its equilibrium, and there
would be no motive power (^ 288) to beget currents, or to set the
water in motion by reason of the difference of level or of specific
gravity due to water at different densities and temperatures.

302. Now let us suppose the winds, for the first time since the
creation, to commence to blow upon this quiescent sea, and to
ruffle its surface ; they, by their force, would create partial sur-
face currents, and thus agitating the waters to a certain depth,
would give rise to a feeble and partial aqueous circulation in the
supposed sea of fresh water.

303. This, then, is one of the sources whence power is given
to the system of oceanic circulation ; but, though a feeble one, it

THE SALTS OF THE SEA.

157

is one which exists in reahty, and, therefore, need not be regard-
ed as hypothetical

304. Let us next call in evaporation and precipitation, with
heat and cold — more powerful agents. Suppose the evaporation
to commence from this imaginary fresh-water ocean, and to go on
as it does from the seas as they are. In those regions, as in the
trade-wind regions, where evaporation is in excess of precipitation
(§ 126), the general level of this supposed sea would be altered,
and, immediately, as much water as is carried oflf by evaporation
would commence to flow in from north and south toward the
trade-wind or evaporating region, to restore the level.

305. On the other hand, the winds have taken this vapor, borne
it off to the extra-tropical regions, and precipitated it (§ 129), we
will suppose, where precipitation is in excess of evaporation. Here
is another alteration of sea level by elevation instead of by depres-
sion ; and hence we have the motive power for a surface current
from each pole toward the equator, the object of which is only to
supply the demand for evaporation in the trade-wind regions — de-
mand for evaporation being taken here to mean the difference be-
tween evaporation and precipitation for any part of the sea.

306. Now imagine this sea of uniform temperature (^ 301) to
be suddenly stricken with the invisible wand of heat and cold, and
its waters brought to the various temperatures at. w^hich they at
this instant are standing. This change of temperature would
make a change of specific gravity in the waters, which Avould de-
stroy the equilibrium of the whole ocean, upon w^hich (§ 275) a
set of currents (§ 277) would immediately commence to flow, viz.,
a current of cold and heavy water to the w^arm, and a current of
warm and lighter to the cold.

The motive power of these would be difference of specific grav-
ity due to difference of temperature in fresh water.

307. We have now traced (^ 303 and 306) the effect of two
agents, which, in a sea of fresh water, would tend to create cur-
rents, and to beget a system of aqueous circulation ; but a set of
currents and a system of circulation which, it is readily perceived,
would be quite different from those which we find in the salt sea.
One of these agents would be employed (^ 305) 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

158 THE PHYSICAL GEOGRAPHY OF THE SEA.

precipitation. The other agent would be employed in restoring,
by the forces due difference of specific gravity (§ 306), the equi-
librium, which has been disturbed by heating, and of course ex-
panding, the waters of the torrid zone on one hand, and by cool-
ing, and consequently contracting, those of the frigid zone on the
other. This agency would, if it were not modified by others, find
expression in a system of currents and counter currents, or rather
in a set of surface currents of warm and light water, from the
equator toward the poles, and in another set of under currents of
cooler, dense, and heavy w^ater from the poles toward the equator.

308. Such, keeping out of view the influence of the winds, which
we may suppose would be the same, whether the sea were salt or
fresh, would be the system of oceanic circulation were the sea all
of fresh water. But fresh w^ater, in cooling, begins to expand near
the temperature of 40°, and expands more and more till it reaches
the freezing point, and ceases to be fluid. This law of expansion
by cooling would impart a peculiar feature to the system of oce-
anic circulation were the waters all fresh, w^hich it is not neces-
sary to notice further than to say it can not exist in seas of salt
water, for salt water (§ 31) contracts as its temperature is lower-
ed to its freezing point. Hence, in consequence of its salts,
changes of temperature derive increased power to disturb the equi-
librium of the ocean.

309. 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
probably have no such current in it -as the Gulf Stream.

So far we have been reasoning hypothetically, to show what
would be the chief agents, exclusive of the winds, in disturbing the
equilibrium of the ocean, were its waters fresh and not salt. And
whatever disturbs equilibrium there may be regarded as the p?7-
mum mobile in any system of marine currents.

Let us now proceed another step in the process of explaining
and illustrating the effect of the salts of the sea in the system of
oceanic circulation. To this end, let us suppose this imaginary
ocean of fresh water suddenly to become that which we have, viz.,
an ocean of salt w^ater, which contracts as its temperature is low-
ered (§ 308) till it reaches 28° or thereabout.

THE SALTS OF THE SEA. I59

310. Let evaporation now commence in the trade-wind region,
as it was supposed to do (^ 304) in the case of the fresh-water
seas, and as it actually goes on in nature — and what takes place ?
Why, a lowering of the sea level, as before. But as the vapor of
salt water is fresh, or nearly so, fresh water only is taken up from
the ocean ; that which remains behind is therefore more salt.
Thus, while the level is lowered in the salt sea, the equilibrium is
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 in solution, specifically heavier than it was be-
fore any portion of it was converted into vapor.

311. The vapor is taken from the surface water; the surface
water thereby becomes more salt, and, under certain conditions,
heavier ; when it becomes heavier, it sinks ; and hence we have,
due to the salts of the sea, a vertical circulation, viz., 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 —
from the depths below.

312. This vapor, then, which is taken up from the evaporating
regions (^ 126), 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, &c., than it
returns to the atmosphere in the shape of vapor.

313. In the precipitating regions, therefore, the level is de-
stroyed, as before explained, by elevation ; and in the evaporating
regions, by depression; which, as already stated (§ 305), gives
rise to a system of surface currents, moved by gravity alone, from
the poles toward the equator.

But we are now considering the effects of evaporation and pre-
cipitation in giving impulse to the circulation of the ocean where
its waters are salt.

314. The fresh water that has been taken from the evaporating
regions is deposited upon those of precipitation, which, for illu!<-
tration merely, we will locate in the north polar basin. Among
the sources of supply of fresh water for this basin we must in-
clude not only the precipitation which takes place over the basin
itself, but also the amount of fresh water discharged into it by the

160 THE PHYSICAL GEOGRAPHY OF THE SEA.

rivers of the great hydrographical basins of Arctic Europe, Asia,
and America.

315. 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 extends to no great depth (§ 302),
it is only the upper layer of salt water, and that to a moderate
depth, which becomes mixed with the fresh. The specific grav-
ity 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 toward the equator, and an under current
of water Salter and heavier from the equator to the poles. This
under current supplies, in a great measure, the salt which the
upper current, freighted with fresh water from the clouds and riv-
ers, carries back.

316. Thus it is to the salts of the sea that we owe that feature
in the system of oceanic circulation which causes an under cur-
rent to flow from the Mediterranean into the Atlantic (§ 252), and
another (^ 245) from the Red Sea into the Indian Ocean. And
it is evident, since neither of these seas is salting up, that just as
much, or nearly just as much salt as the under current brings out,
just so much the upper currents carry in.

317. We now begin to perceive what a powerful impulse is de-
rived from the salts of the sea in giving -effective and active cir-
culation to its waters.

318. Hence we infer that the currents of the sea, by reason of
its saltness, attain their maximum of tolume and velocity. Hence,
too, we infer that the transportation of warm water from the equa-
tor toward the frozen regions of the poles, and of cold water from
the frigid toward the torrid zone, is facilitated ; and consequently
here, in the saltness of the sea, have we not an agent by which
climates are mitigated — by which they are softened and rendered
much more salubrious than it would be possible for them to be
were the waters of the ocean deprived of their property of saltness ?

319. This property of saltness imparts to the waters of the
ocean another peculiarity, by which the sea is still better adapted
for the regulation of climates, and it is this : by evaporating fresh
water from the salt in the tropics, the surface water becomes
heavier than the average of sea water (6 127). This heavy wa-

THE SALTS OF THE SEA. jgl

ter is also warm water ; it sinks, and being a good retainer, but a
bad conductor of heat, this warm water is employed in transport-
ing 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. Let the winds take up their vapor
from a sheet of fresh w^ater, and that at the bottom is not disturb-
ed, for there is no change in the specific gravity of that at the sur-
face by which that at the bottom may be brought to the top ; but
let evaporation go on, though never so gently, from salt water,
and the specific gravity of that at the top will soon be so changed
as to bring that from the very lowest depths of the sea speedily
to the top.

320. If these inferences as to the influence of the salts upon the
currents of the sea be correct, the same cause which produces an
under current from the Mediterranean, and an under current from
the Red Sea into the ocean, should produce an under current
from the ocean into the north Polar basin. In each case, the hy-
pothesis with regard to the part performed by the salt, in giving
vigor 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 Red Sea, has been amply shown in other parts of this
work (§ 252 and 239), and abundantly proved by other observers.

321. That there is a constant current setting out of the Arctic
Ocean through Davis's and other straits thereabout, which con-
nect it with the Atlantic Ocean, is generally admitted. Lieuten-
ant De Haven, United States Navy, when in command of the
American expedition in search of Sir John Franklin, was frozen
up with his vessels in the main channel of Wellington Straits ;
and during the nine months that he was so frozen, his vessels,
holding their place in the ice, were drifted with it bodily for more
than a thousand miles toward the south.

The ice in which they were bound was of sea water, and the
currents by which they were drifted were of sea water — only, it
may be supposed, the latter were not quite so salt as the sea wa-
ter generally is. The same phenomenon is repeated in the Sound,
where (^ 252) an under current of salt water runs in, and an upper
current of brackish water (§ 36 and 51) runs out.

L

162 THE PHYSICAL GEOGRAPHY OF THE SEA.

322. -Then, since there is salt always flowing out of the north
polar basin, we infer that there must be salt always flowing into
it, else it would either become fresh, or the whole Atlantic Ocean
would 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.

323. But, fortunately, Arctic voyagers, w^ho have cruised in the
direction of Davis's Straits, have afforded us, by their observations
(§ 281), proof positive as to the fact of this other source for sup-
plying the Polar seas with salt. They tell us of an under current
setting from the Atlantic toward the Polar basin. They describe
huge icebergs, with tops high up in the air, and of course the
bases of which extend far down into the depths of the ocean, rip-
ping and tearing their way, with terrific force and awful violence,
through the surface ice or against a surface current, on their way
into the Polar basin.

Passed Midshipman S. P. Griffin, who commanded the brig
Rescue in the American searching expedition after Sir John
Franklin, informs me that, on one occasion, the two vessels were
endeavoring to warp up to the northward, in or near Wellington
Channel, against a strong surface current, which of course was
setting to the south ; and that while so engaged, an iceberg, with
its top many feet above the water, came " drifting up" from the
south, and passed by them " like a shot." Although they were
stemming a surface current against both the berg and themselves,
such was the force and velocity of the under current, that it car-
ried the berg to the northward faster than the crew could warp
the vessel against a surface but counter current.

Captain Duncan, master of the English whale-ship Dundee,
says, at page 76 of his interesting little narrative :*

'^December 18th (1826). It was awful to behold the immense
icebergs working their way to the northeast from us, and not one
drop of water to be seen ; they were working themselves right
through the middle of the ice."

And again, at page 92, &c. :

* Arctic Regions ; Voyage to Davis's Strait, by Dorea Duncan, Master of the Ship
Dundee, 1826, 1827.

THE SALTS OF THE SEA. 163

'^ February 23d. Latitude 68° 37^ north, longitude about 63^
west.

" The dreadful apprehensions that assailed us yesterday, by
the near approach of the iceberg, were this day most awfully ver-
ified. About three 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
hundred pieces of heavy ordnance fired at the same moment.
The iceberg, with awful but majestic grandeur (in height and di-
mensions resembling a vast mountain), came almost up to our
stern, and every one expected it would have run over the
ship

'' The iceberg, as before observed, came up very near to the
stern of our ship ; the intermediate space between the berg and
the vessel was filled with heavy masses of ice, which, though
they had been previously broken by the immense weight of the
berg, were again formed into a compact body by its pressure.
The berg w^as drifting at the rate of about four knots, and by its
force on the mass of ice, was pushing the ship before it, as it ap-
peared, to inevitable destruction."

" Feb. 24:th. The iceberg still in sight, but driving away fast to
the northeast."

" Feb. 25th. The iceberg that so lately threatened our destruc-
tion had driven completely out of sight to the northeast from us."

324. Now, then, whence, unless from the diff'erence of specific
gravity due sea water of different degrees of saltness, can we de-
rive a motive power with force sufficient to give such tremendous
masses of ice such a velocity ?

325. What is the temperature of this under current ? Be that
what it may, it is probably above the freezing point of sea water.
Suppose it to be at 32°. (Break through the ice in the northern
seas, and the temperature of the surface water is always 28^. At
least Lieutenant De Haven so found it in his long imprisonment,
and it may be supposed that, as it was with him, so it generally
is.) Assuming, then, the water of the surface current which runs
out with the ice to be all at 28°, we observe that it is not unreas-
onable to suppose that the water of the under current, inasmuch
us it comes from the south, and therefore from warmer latitudes.

164 THE PHYSICAL GEOGRAPHY OF THE SEA.

is probably not so cold ; and if it be not so cold, its temperature,
before it comes out again, must be reduced to 28°, or whatever
be the average temperature of the outer but surface current.

Moreover, if it be true, as some philosophers have suggested,
that there is in the depths of the ocean a line from the equator to
the poles along which the water is of the same temperature all
the way, then the question may be asked, Should we not have in
the depths of the ocean a sort of isothermal floor, as it were, on
the upper side of which all the changes of temperature are due to
agents acting from above, and on the lower side of which, the
changes, if any, are due to agents acting from below ?

326. This under Polar current water, then, as it rises to the
top, and is brought to the surface by the agitation of the sea in
the Arctic regions, gives out its surplus heat and warms the at-
mosphere there till the temperature of this warm under current
water is lowered to the requisite degree for going out on the sur-
face. Hence the water-sky of those regions.

327. And the heat that it loses in falling from its normal tem-
perature, be that what it may, till it reaches the temperature of
28°, is so much caloric set free in the Polar regions, to temper the
air and mitigate the climate there. Now is not this one of those
modifications of climate which may be fairly traced back to the
effect of the saltness of the sea in giving energy to its circula-
tion?

Moreover, if there be a deep sea in the Polar basin, which serves
as a receptacle for the w^aters brought into it by this under cur-
rent, which, because it comes from toward 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 re-
gions— why Lieutenant De Haven, in his instructions, was direct-
ed to look for it ; and why both he and Captain Penny, of one of
the English searching vessels, found it there.

328. And in accounting for this polynia, we see that its exist-
ence is not only consistent with the hypothesis with which we set
out, touching a perfect system of oceanic circulation, but that it
may be ascribed, in a great degree at least, if not wholly, to the
effect produced by the salts of the sea upon the mobility and cir-
culation of its waters.

Here, then, is an office which the sea performs in the economy

THE SALTS OF THE SEA. 165

of the universe by virtue of its saltness, and which it could not
perform were its waters altogether fresh. And thus philosophers
have a clew placed in their hands which will probably guide them '
to one of the many hidden reasons that are embraced in the true
answer to the question, " Why is the sea salt ?"

329. Sea Shells. — We find in sea water other matter besides
common salt. Lime is dissolved by the rains and the rivers, and
emptied in vast quantities into the ocean. Out of it, coral islands
and coral reefs of great extent — marl-beds, shell-banks, and in-
fusorial deposits of enormous magnitude 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, which the waters of the sea hold in solution. But
this power w^as given to them that they also might fulfill the part
assigned them in the economy of the universe. For to them,
probably, has been allotted the important office of assisting in
giving circulation to the ocean, of helping to regulate the cli-
mates of the earth, and of preserving the purity of the sea.

330. The better to comprehend how such creatures may influ-
ence currents and climates, let us suppose the ocean to be per-
fectly at rest — that throughout, it is in a state of complete equi-
librium— that, with the exception of those tenants of the deep
which have the power of extracting from it the solid matter held
in solution, there is no agent in nature capable of disturbing that
equilibrium — and that all these fish, &c., have suspended their se-
cretions, in order that this state of a perfect aqueous equilibrium
and repose throughout the sea might be attained. '

In this state of things — the waters of the sea being in perfect
equilibrium — a single mollusk or coraUine, we will suppose, com-
mences his secretions, and abstracts from the sea water (^ 293)
solid matter for his cell. In that act, this animal has destroyed
the equilibrium of the whole ocean, for the specific gravity of
that portion of water from which this solid matter has been ab-
stracted is altered. Having lost a portion of its solid contents, it
has become specifically lighter than it was before ; it must, there-
fore, give place to the pressure w^hich the heavier water 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 returned to it, and

166 THE PHYSICAL GEOGRAPHY OF THE SEA.

until it attains the exact degree of specific gravity due sea water
generally.

331. How much solid matter does the whole host of marine
plants and animals abstract from sea water daily ? Is it a thou-
sand pounds, or a thousand millions of tons ? No one can say.
But, whatever be its weight, it is so much of the power of gravity
applied to 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 whole sea
in motion, from the equator to the poles, and from top to bottom.

332. Those powerful and strange equatorial currents (^ 270),
which navigators tell us they encounter in the Pacific Ocean, to
what are they due ? Coming from sources unknown, they are
lost in the midst of the ocean. They are due, no doubt, to some
extent, to the effects of precipitation and evaporation, and the
change of heat produced thereby. But we have yet to inquire,
How far may they be due to the derangement of equilibrium aris-
ing from the change of specific gravity caused by the secretions
of the myriads of marine animals that are continually at work in
those parts of the ocean ? These abstract from sea water solid
matter enough to build continents of. And, also, we have to in-
quire as to the extent to which equilibrium in the sea is disturbed
by the salts which evaporation leaves behind.

Thus, when we consider the salts of the sea in one point of
view, we see the winds and the marine animals operating upon
the waters, and, in certain parts of the ocean, deriving from the
solid contents of the same those very principles of antagonistic
forces which hold the earth in its orbit, and preserve the harmo-
nies of the universe.

In another point of virw, we see how the sea-breeze and the
sea-shell, in performing their appointed offices, act so as to give
rise to a reciprocating motion in the waters ; and thus they impart
to the ocean dynamical forces also for its circulation.

333. The sea-breeze plays upon the surface ; it converts only
fresh water into vapor, and leaves the solid matter behind. The
surface water thus becomes specifically heavier, and sinks. On
the other hand, the little marine architect below, as he works
upon his coral edifice at the bottom, abstracts from the water

THE SALTS OF THE SEA.

167

there a portion of its solid contents ; it therefore becomes spe-
cifically lighter, and up it goes, ascending to the top with in-
creased velocity, to take the place of the descending column,
which, 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.

334. Seeing, then, that the inhabitants of the sea, with their
powers of secretion, are competent to exercise at least some de-
gree of influence in disturbing equilibrium, are not these crea-
tures entitled to be regarded as agents which have their offices to
perform in the system of oceanic circulation, and do not they be-
long to its physical geography ? It is immaterial how great or
how small that influence may be supposed to be ; for, be it great
or small, we may rest assured it is not a chance influence, but it
is an influence exercised — if exercised at all — by design, and ac-
cording to the commandment of Him whose "voice the winds and
the sea obey." Thus God speaks through sea-shells to the ocean.

335. It may therefore be supposed that the arrangements in
the economy of nature are such as to require that the various
kinds of marine animals, whose secretions are calculated to alter
the specific gravity of sea water, to destroy its equilibrium, to be-
get currents in the ocean, and to control its circulation, should
be distributed according to order.

336. Upon this supposition — the like of which nature warrants
throughout her whole domain — w^e may conceive how the marine
animals of which w^e have been speaking may impress other fea-
tures upon the physical relations of the sea by assisting also to
regulate climates, and to adjust the temperature of certain lati-
tudes. For instance, let us suppose the w^aters in a certain part
of the torrid zone to be 70°, but, by reason of the fresh water
which has been taken from them in a state of vapor, and conse-
quently by reason of the proportionate increase of salts, these wa-
ters are heavier than waters that may be cooler, but not so salt
(§ 35).

This being the case, the tendency would be for this warm, but salt
and heavy water, to flow off* as an under current toward the Polar
or some other regions of lighter water.

Now if the sea were not salt, there would be no coral islands
to beautify its landscape and give variety to its features ; sea-

168 THE PHYSICAL GEOGRAPHY OF THE SEA.

shells and marine insects could not operate upon the specific grav-
ity of its waters, nor give variety to its climates ; neither could
evaporation give dynamical force to its circulation, and they, ceas-
ing to contract as their temperature falls below 40°, would give
but little impulse to its currents, and thus its circulation would be
torpid, and its bosom lack animation.

337. This under current may be freighted with heat to temper
some hyperborean region or to soften some extra-tropical cli-
mate (§ 64), for we know that such is among the effects of ma-
rine currents. At starting, it might have been, if you please, so
loaded with solid matter, that, though its temperature were 70°,
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°.

338. Notwithstanding this, 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 surface through the instrumentality
of shell-fish, and various other tribes that dwell far down in the
depths of the ocean. Thus we perceive that these creatures,
though they are regarded as being so low in the scale of creation,
may nevertheless be regarded as agents of much importance in
the terrestrial economy ; for we perceive that they are capable of
spreading over certain parts of the ocean those benign mantles of
warmth which temper the winds, and modify, more or less, all the
marine climates of the earth.

339. The makers of nice astronomical instruments, when they
have put the diflferent parts of their machinery together, and set
it to work, find, as in the chronometer, for instance, that it is sub-
ject 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 over-
come ; and, with a beautiful display of ingenuity, they have at-
tached to the works of the instrument a contrivance which has
had the effect of correcting these irregularities, by counteracting

THE SALTS OF THE SEA.

169

the tendency of the instrument to change its performance with the
changing influences of temperature.

This contrivance is called a compensation ; and a chronometer
that is well regulated and properly compensated w^ill perform its
office with certainty, and preserve its rate under all the vicissi-
tudes of heat and cold to which it may be exposed.

340. In the clock-work of the ocean and the machinery of the
universe, order and regularity are maintained by a system of com-
pensations. A celestial body, as it revolves around its sun, flies
oflf 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 distance were adjusted. Its compensation is
perfect.

341. So, too, with the salts and the shells of the sea in the ma-
chinery of the ocean ; from them are derived principles of com-
pensation the most perfect ; through their agency the undue ef-
fects of heat and cold, of storm and rain, in disturbing the equi-
librium, and producing thereby currents in the sea, are compen-
sated, regulated, and controlled.

342. The dews, the rains, and the rivers are continually dis-
solving certain minerals of the earth, and carrying them off to the
sea. This is an accumulating process ; and if it were not com-
pensated, the sea would finally become as the Dead Sea is, sat-
urated with salt, and therefore unsuitable for the habitation of
many fish of the sea.

The sea-shells and marine insects aflford the required compensa-
tion. They are the conservators of the ocean. As the salts are
emptied into the sea, these creatures secrete them again and pile
them up in solid masses, to serve as the bases of islands and con-
tinents, to be in the process of ages upheaved into dry land, and
then again dissolved by the dews and rains, and washed by the
rivers away into the sea.

343. Darwin, many years ago, during one of those moments of
inspiration which enabled him to foreshadow the steam-boat and
the locomotive, told philosophers whence came the salts of the
sea.

*' Gnomes ! You then taught transuding dews to pass
Through time-faU'n woods and root-inwove morass

170 THE PHYSICAL GEOGRAPHY OF THE SEA.

Age after age ; and with filtration fine
Dispart from earths, and sulphurs, and saline.
Hence with diffusive salt old ocean steeps
His emerald shallows, and his sapphire deeps."

In every department of nature there is to be found this self-ad-
justing principle — this beautiful and exquisite system of compen-
satioUf by which the operations of the grand machinery of the uni-
verse are maintained in the most perfect order.

344. Thus we behold sea-shells and animalculse in a nevi^ light.
May we not novr cease to regard them as beings v^^hich have little
or nothing to do in maintaining the harmonies of creation ? On
the contrary, do we not see in them the principles of the most ad-
mirable compensation in the system of oceanic circulation ? We
may even regard them as regulators, to some extent, of climates
in parts of the earth far removed from their presence. There is
something suggestive, both of the grand and the beautiful, in the
idea that, while the insects of the sea are building up their coral
islands in the perpetual summer of the tropics, they are also en-
gaged in dispensing warmth to distant parts of the earth, and in
mitigating the severe cold of the Polar winter.

Surely an hypothesis which, being followed out, suggests so
much design, such perfect order and arrangement, and so many
beauties for contemplation and admiration as does this, which, for
the want of a better, I have ventured to offer with regard to the
solid matter of the sea water, its salts and its shells — surely such
an hypothesis, though it be not based entirely on the results of
actual observation, can not be regarded as wholly vain or as al-
together profitless.

THE EQUATORIAL CLOUD-RING. i^j

CHAPTER IX.

THE EQUATORIAL CLOUD-RING.

Description of the Equatorial Doldrums, ^ 346. — Oppressive Weather, 348. — The Of-
fices performed by Clouds in the terrestrial Economy, 349. — The Barometer and
Thermometer under the Cloud-ring, 350. — Its Offices, 353. — How its Vapors are
brought by the Trade- Winds, 361. — Breadth of the Cloud-ring, 363. — How it
would appear if seen from one of the Planets, 364. — Observations at Sea interest-
ing, 368.

345. Seafaring people have, as if by common consent, divided
the ocean off into regions, and characterized them according to
the winds ; e. g., there are the " trade-wind regions," the " varia-
bles," the " horse latitudes," the " doldrums," &cc. The " horse
latitudes" are the belts of calms and light airs (§ 101) w^hich bor-
der the Polar edge of the northeast trades. They were so called
from the circumstance that vessels formerly bound from New En-
gland to the West Indies, with a deck load of horses, were often
so delayed in this calm belt of Cancer, that, for the want of water
for their animals, they were compelled to throw a portion of them
overboard.

346. The " equatorial doldrums" is another of these calm places
(§ 104). Besides being a region of calms and baffling winds, it is
a region noted for its rains and clouds, which make it one of the
most oppressive and disagreeable places at sea. The emigrant
ships from Europe for Australia have to cross it. They are often
baffled in it for two or three weeks ; then the children and the
passengers who are of delicate health suffer most. It is a fright-
ful grave-yard on the way-side to that golden land.

347. A vessel bound into the southern hemisphere from Europe
or America, after clearing the region of variable winds and cross-
ing the " horse latitudes," enters the northeast trades. Here the
mariner finds the sky sometimes mottled w^th clouds, but for the
most part clear. Here, too, he finds his barometer rising and fall-
ing under the ebb and flow of a regular atmospherical tide, which
gives a high and low barometer every day with such regularity

172 THE PHYSICAL GEOGRAPHY OF THE SEA.

that the time of day withm a few minutes may be told by it. The
rise and fall of this tide, measured by the barometer^ amounts to
about one tenth (0.1) of an inch, and it occurs daily and every
where between the tropics ; the maximum 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.* The diurnal variation
of the needle changes also with the turning of these invisible tides.
Continuing his course toward the equinoctial line, he observes his
thermometer to rise higher and higher as he approaches it ; at last,
entering the region of equatorial calms and rains, he 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."

Escaping from this gloomy region, and entering the southeast
trades beyond, his spirits revive, and he turns to his log-book to
see what changes are recorded there. He is surprised to find
that, notwithstanding the oppressive weather of the rainy latitudes,
both his thermometer and barometer stood, while in them, lower
than in the clear weather on either side of them ; that just before
entering and just before leaving the rainy parallels, the mercury
of the thermometer and barometer invariably stands higher than
it does when within them, even though they include the equator.
In crossing the equatorial doldrums he has passed a ring of clouds
that encircles the earth.

348. I find in the journal of the late Commodore Arthur Sin-
clair, kept on board the United States frigate Congress during a
cruise to South America in 1817-18, a picture of the weather
under this cloud-7-ing that is singularly graphic and striking. He
encountered it in the month of January, 1818, between the paral-
lel of 4° north and the equator, and between the meridians of 19^
and 23° west. He says of it :

" This is certainly one of the most unpleasant regions in our
globe. A dense, close atmosphere, except for a few hours after a
thunder-storm, during which time torrents of rain fall, when the
air becomes a little refreshed ; but a hot, glowing sun soon heats
it again, and but for your awnings, and the little air put in circu-

* See paper on Meteorological Observations in India, by Colonel Sykes, Philosoph-
ical Transactions for 1850, part 2d, page 297.

THE EQUATORIAL CLOUD-RING. ^^3

lation by the continual flapping of the ship's sails, it would be al-
most 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 every where else proves so salutary and renovating, can
dispel. Except when in actual danger of shipwreck, I never spent
twelve more disagreeable days in the professional part of my hfe
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 difficul-
ties consequent to that event ; that the breeze continued to freshen
and draw round to the south-southeast, bringing with it a clear
sky and most heavenly temperature, renovating and refreshing be-
yond description. Nothing was now to be seen but cheerful coun-
tenances, exchanged as by enchantment from that sleepy sluggish-
ness which had borne us all down for the last two weeks."

349. One need not go to sea to perceive the grand work which
the clouds perform in collecting moisture from the crystal vaults
of the sky, in sprinkling it upon the fields, and making the hills
glad with showers of rain. Winter and summer, " the clouds drop
fatness upon the earth." This part of their office is obvious to all,
and I do not propose to consider it now. But the sailor at sea ob-
serves phenomena and witnesses operations in the terrestrial
economy which tell him that, in the beautiful and exquisite ad-
justments of the grand machinery of the atmosphere, the clouds
have other important offices to perform besides those merely of
dispensing showers, of producing the rains, and of weaving man-
tles of snow for the protection of our fields in winter. As import-
ant as are these offices, the philosophical mariner, as he changes
his sky, is reminded that the clouds have commandments to ful-
fill, which, though less obvious, are not therefore the less benign
in their influences, or the less worthy of his notice. He beholds
them at work in moderating the extremes of heat and cold, and in
mitigating climates. At one time they spread themselves out ;
they cover the earth as with a mantle ; they prevent radiation
from its crust, and keep it warm. At another time, they interpose
between it and the sun ; they screen it from his scorching rays,
and protect the tender plants from his heat, the land from the
drought ; or, like a garment, they overshadow the sea, defending its

174 THE PHYSICAL GEOGRAPHY OF THE SEA.

waters from the intense forces of evaporation. Having performed
these offices for one place, they are evaporated and given up to
the sunbeam and the winds again, to be borne on their wings away
to other places which stand in need of like offices.

Familiar with clouds and sun^shine, the storm and the calm, and
all the phenomena which find expression in the physical geogra-
phy of the sea, the right-minded mariner, as he contemplates
"the cloud without rain," ceases to regard it as an empty thing;
he perceives that it performs many important offices ; he regards
it as a great moderator of heat and cold — as a " compensation" in
the atmospherical mechanism which makes the performance of
the grand machine perfect.

350. Marvelous are the offices and wonderful is the constitu-
tion of the atmosphere. Indeed, I know of no subject more fit for
profitable thought on the part of the truth-loving, knowledge-
seeking student, be he seaman or landsman, than that afforded by
the atmosphere and its offices. Of all parts of the physical ma-
chinery, of all the contrivances in the mechanism of the universe,
the atmosphere, with its offices and its adaptations, appears to me
to be the most wonderful, sublime, and beautiful. In its construc-
tion, the perfection of knowledge is involved. The perfect man
of Uz, in a moment of inspiration, thus demands of his comfort-
ers : " But where shall wisdom be found, and where is the place
of understanding ? The depth saith, it is not in me ; and the sea
saith, it is not with me. It can not 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.

" Whence, then, cometh wisdom, and where is the place of un-
derstanding ? Destruction and Death say, we have heard the fame
thereof with our ears.

" God understandeth the w'ay thereof, and he knoweth the place
thereof ; for he looketh to the ends of the earth, and seeth un-
der the whole heaven; to make the weight for the winds; and he
weigheth the waters by measure. When he made a decree for the
rain, and a way for the lightning of the thunder ; then did he
see it, and declare it ; he prepared it, yea, and searched it out."*

When the pump-maker came to ask Galileo to explain how it
was that his pump would not lift water higher than thirty-two

* Job, chapter xxviii.

THE EQUATORIAL CLOUD-RING. 175

feet, the philosopher thought, but was afraid to say, it was owing
to the '' weight of the winds ;" and though the fact that the air
has weight is here so distinctly announced, philosophers never
knew it until within comparatively a recent period, and then it was
proclaimed 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 suck the milk from its mother's breast, unconsciously
proclaimed it.

351. Both the thermometer and the barometer (^ 347) stand
lower under this cloud-ring than they do on either side of it. Af-
ter having crossed it, and referred to the log-book to refresh his
mind as to the observations there entered with regard to it, the at-
tentive navigator may perceive how this belt of clouds, by screen-
ing the parallels over which he may have found it to hang from
the sun's rays, not only promotes the precipitation which takes
place within these parallels at certain periods, but how, also, the
rains are made to change the places upon w^hich they are to fall ;
and how, by travehng wdth 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 op-
eration, tone is given to the atmospherical circulation of the world,
and vigor to its vegetation.

Having traveled with the calm belt to the north or south, the
cloud-ring leaves the sky about the equator clear ; the rays of the
torrid sun pour down upon the crust of the earth there, and raise
its temperature to a scorching heat. The atmosphere dances
(^ 205-6), and the air is seen trembling in ascending and descend-
ing columns, with busy eagerness to conduct the heat off and de-
liver it to the regions aloft, where it is required to give momentum
to the air in its general channels of circulation. The dry season
continues ; the sun is vertical ; and finally the earth becomes
parched and dry ; the heat accumulates faster than the air can
carry it away ; the plants begin to wither, and the animals to per-
ish. Then comes the mitigating cloud-ring. The burning rays
of the sun are intercepted by it. The place for the absorption
and reflection, and the delivery to the atmosphere of the solar
heat, is changed ; it is transferred from the upper surface of the
earth to the upper surface of the clouds.

352. Kadiation from the land and the sea below the cloud-belt

176 THE PHYSICAL GEOGRAPHY OF THE SEA.

IS thus interrupted, and the excess of heat in the earth is deUvered
to the air, and by absorption carried up to the clouds, and there
transferred to their vapors to prevent excess of precipitation.

353. 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 cease-
less volumes of heated air loaded to saturation with vapor, which
has to rise above and get clear of the clouds before it can com-
mence the process of cooling by radiation. In the mean time,
also, the vapors which the trade-winds bring from the north and
the south, expanding and growing cooler as they ascend, are be-
ing condensed on the lower side of the cloud stratum, and their
latent heat is set free, to check precipitation and prevent a flood.

354. While this process and these operations are going on upon
the nether side of the cloud-ring, one not less important is going
on upon the upper side. There, from sunrise to sunset, the rays of
the sun are pouring down without intermission. Every day, and
all day long, they operate with ceaseless activity upon the upper
surface of the cloud stratum. When they become too powerful,
and convey more heat to the cloud vapors than the cloud vapors
can reflect and give off to the air above them, then, with a beau-
tiful elasticity of character, the clouds absorb the surplus heat.
They melt away, become invisible, and retain, m a latent and
harmless state, until it is wanted at some other place and on some
other occasion, the heat thus imparted.

355. We thus have an insight into Uie operations which are go-
ing on in the equatorial belt of precipitation, and this insight is
sufficient to enable us to perceive that exquisite indeed are the ar-
rangements w^hich Nature has provided for supplying this calm
belt with heat, and for pushing the snow-line there high up above
the clouds, in order that the atmosphere may have room to ex-
pand, to rise up, overflow, and course back into its channels of
healthful circulation. As the vapor is condensed and formed into
drops of rain, a twofold object is accomplished : coming from the
cooler regions of the clouds, the rain-drops are cooler than the air
and earth below ; they descend, and by absorption take up the heat
which has been accumulating in the earth's crust during the dry
season, and which can not now escape by radiation. Thus this
cloud-ring modifies the climate of all places beneath it ; overshad-
owing, at different seasons, all parallels from 5° south to 15° north.

THE EQUATORIAL CLOUD-RING. I77

356. In the process of condensation, these rain-drops, on the
other hand, have set free a vast quantity of latent heat, which has
been gathered up with the vapor from the sea by the trade-winds
and brought hither. The caloric thus hberated 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 possi-
ble to trace a thermal curve in the upper regions of the air to rep-
resent this line, we should no doubt find it mounting sometimes at
the equator, sometimes on this side, and sometimes on that of it,
but alw^ays so mounting as to overleap this cloud-ring. This
thermal line would not ascend always over the same parallels : it
would ascend over those betw^een which this ring happens to be ;
and the distance of this ring from the equator is regulated accord-
ing to the seasons.

357. If w^e imagine the atmospherical equator to be always
where the calm belt is which separates the northeast from the
southeast trade-winds, then the loop in the thermal curve, which
should represent the line of perpetual congelation in the air, w ould
be always found to stride this equator ; and it may be supposed
that a thermometer, kept sliding on the surface of the earth so as
always to be in the middle of this rain-belt, would show very nearly
the same temperature all the year round ; and so, too, would a
barometer the same pressure.

358. Its Office. — Returning and taking up the train of contem-
plation as to the office which this belt of clouds, as it encircles
the earth, performs in the system of oceanic adaptations, we may
see how the cloud-ring and calm zone which it overshadows per-
form the office both of ventricle and auricle in the immense atmos-
pherical heart, where the heat and the forces w^iich 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.

359. Thus this ring, or band, or belt of clouds is stretched
around our planet to regulate the quantity of precipitation in the
rain-belt beneath it ; to preserve the due quantum of heat on the
face of the earth ; to adjust the winds ; and send out for distribu-
tion to the four corners, vapors in proper quantities to make up to
each river-basin,, climate, and season, its quota of sunshine, cloud,
and moisture. Like the balance-wheel of a well-constructed chro-

M

178 THE PHYSICAL GEOGRAPHY OF THE SEA.

nometer, this cloud-riiig affords the grand atmospherical machine
the most exquisitely arranged self -compensation. If the sun fail
in his supply of heat to this region, more of its vapors are con-
densed, and heat is discharged from its latent store-houses in quan-
tities just sufficient to keep the machine in the most perfect com-
pensation. If, on the other hand, too much heat be found to ac-
company the rays of the sun as they impinge upon the upper cir-
cumference of this belt, then again on that side are the means of
self-compensation ready at hand ; so much of the cloud-surface
as may be requisite is then resolved into invisible vapor — for of in-
visible vapor are made the vessels v^^herein the surplus heat from
the sun is stored aw^ay and held in the latent state until it is call-
ed for, when instantly it is set free, and becomes an obvious and
active agent in the grand design.

360. That the thermometer stands invaiiahly lov^^er (§ 351) be-
neath this cloud-belt than it does on either side of it, has not, so
far as my researches are concerned, been made to appear by ac-
tual observation, for the observations in my possession have not
yet heexi fully discussed concerning the temperature of the air.
But that the temperature of the air at the surface under this cloud-
ring is lov^er, is a theoretical deduction as susceptible of demon-
stration as is the rotation of the earth on its axis. Indeed, Nature
herself has hung a thermometer under this cloud-belt that is more
perfect than any that man can construct, and its indications are
not to be mistaken.

361. Where do the vapors v^hich form this cloud-ring, and
which are here condensed and poured down into the sea as rain,
come from? They come from the trade-wind regions (^ 115);
under the cloud-ring they rise up ; as they rise up, they expand ;
and as they expand, they grow cool, form clouds, and then are con-
densed into rains ; moreover, it requires no mercurial instrument
of human device to satisfy us that the air which brings the vapor
for these clouds can not take it up and let it down at the same
temperature. Precipitation and evaporation are the converse of
each other ; and the same air can not precipitate and evaporate,
take up and let down water, at one and the same temperature.
As the temperature of the air is raised, its capacity for receiving
and retaining water in the state of vapor is increased ; as the tem-
perature of the air is lessened, its capacity for retaining that moist-

THE EQUATORIAL CLOUD-RING. I79

ure IS diminished. These are physical laws, and therefore, when
we see water dripping from the atmosphere, we need no instru-
ment to tell us that the elasticity of the vapor so condensed, and
falling in drops, is less than was its elasticity when it was taken
up from the surface of the ocean as water, and went up mto the
clouds as vapor.

362. Hence w^c infer that, when the vapors of sea water are
condensed, the heat which was necessary to sustam them in the
vapor state, and which was borrowed from the ocean, is parted
with, and that therefore they were subjected, in the act of con-
densation, to a lower temperature thcMi they were in the act of
evaporation. Ceaseless precipitation goes on under this cloud-
ring. Evaporation under it is suspended almost entirely. We
know that the trade-winds encircle the earth ; that they blow per-
petually ; that they come from the north and the south, and meet
each other near the equator ; therefore we infer that this line of
meeting extends around the world. By the rainy seasons of the
torrid zone we can trace the declination of this cloud-ring stretch-
ed like a girdle round about the earth : it travels up and down the
ocean as from north to south and back

363. It is broader than the belt of calms out of which it rises.
As the air, with its vapors, rises up in this calm belt and ascends,
these vapors are condensed into clouds (§ 361), and this condensa-
tion is followed by a turgid intumescence, which causes the clouds
to overflow the calm belt, as it were, both to the north and the
south. The air flowing off in the same direction assumes the
character of w^nds that form the upper currents that are counter
(Plate I.) to the trade-winds. These currents carry the clouds
still farther to the north and south, and thus make the cloud-ring
broader. At least, we infer such to be the case, for the rains are
found to extend out into the trade-winds, and often to a consider-
able distance both to the north and the south of the calm belt.

364. Were this cloud-ring luminous, and coukl it be seen by an
observer from one of the planets, it Avould present to him an ap-
pearance not unlike the rings of Saturn do to us. Such an ob-
server 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 the cloud-vapor to this region of calms

180 THE PHYSICAL GEOGRAPHY OF THE SEA.

rise up with it, the earth is shpping from under them ; and thus
the cloud-ring, though really moving from west to east with the
earth, goes relatively slow^er than the earth, and would therefore
appear to require a longer time to complete a revolution.

365. But, unlike the rings of Saturn through the telescope, the
outer surfa-ce, or the upper side to us, of this cloud-ring would ap-
pear exceedmgly jagged, rough, and uneven.

366. The rays of the sun, playing upon this peak and then upon
that of the upper cloud-surface, melt away one set of elevations
and create another set of depressions. The whole stratum is, it
may be imagined, in the most turgid state ; it is in continued
throes when viewed from above ; the heat which is liberated from
below in the process of condensation, the currents of warm air as-
cending from the earth, and of cool descending from the sky, all,
we may well conceive, tend to keep the upper cloud-surface in a
perpetual state of agitation, upheaval, and depression.

367. 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 thun-
der. How often do we hear the voice of the loud thunder rum-
bling and rolling away above the cloud-surface, like the echo of
artillery discharged among the hills !

Hence we perceive or infer that the clouds intercept the prog-
ress of sound, as well as of light and heat, through the atmosphere,
and that this upper surface is often like Alpine regions, which echo
back and roll along with rumbling noise the mutterings of the dis-
tant thunder.

368. It is by trains of reasoning like this that we are continu-
ally reminded of the interest which attaches to the observations
which the mariner is called on to make. There is no expression
uttered by Nature which is unworthy of our most attentive consid-
eration—for no physical fact is too bald for observation — and mar-
iners, by registering in their logs the kind of lightning, whether
sheet, forked, or streaked, and the kind of thunder, whether roll-
ing, muttering, or sharp, may be furnishing facts which will throw
much light on the features and character of the clouds in different
latitudes and seasons. Physical facts are the language of Nature,
and every expression uttered by her is worthy of our most atten-
tive consideration.

ON THE GEOLOGICAL AGENCY OF THE WINDS. ig]

CHAPTER X.

ON THE GEOLOGICAL AGENCY OF THE WINDS.

To appreciate the Offices of the Winds and Waves, Nature must be regarded as a
Whole, <J 369. — Level of the Dead Sea, 370. — Evidences that at former Geolog-
ical Periods more Rain fell than now falls upon the Dead Sea and other inland
Basins, 371. — Where Vapor for the Rains in the Basin of the American Lakes
comes from, 375. — The Effect produced by the Upheaval of Mountains across the
course of vapor-bearing Winds, 376. — The Agencies by which the Drainage of
H3-drographic Basins may be cut off from the Sea, 380. — Utah an Example, 382.
— Effect of the Andes upon vapor-bearing Winds, 383. — Geological Age of the
Andes and Dead Sea compared, 391. — Ranges of dry Countries and little Rain,
393. — Rain and Evaporation in the Mediterranean, 399. — Evaporation and Precip-
itation in the Caspian Sea equal, 404. — The Quantity of Moisture the Atmosphere
keeps in Circulation, 407. — Where Vapor for the Rains that feed the Nile come
from, 409.— Lake Titicaca, 420.

369. Properly to appreciate the various offices which the
winds and the waves perform, we must regard nature as a whole,
for all the departments thereof are intimately connected. If w^e
attempt to study in one of them, we often find ourselves tracing
clews which lead us off insensibly into others, and, before we are
aware, w^e discover ourselves exploring the chambers of some
other department.

The study of drift takes the geologist out to sea, and reminds
him that a know^ledge of waves, winds, and currents, of navigation
and hydrography, are closely and intimately connected with his
favorite pursuit.

The astronomer directs his telescope to the most remote star,
or to the nearest planet in the sky, and makes an observation upon
it. He can not reduce this observation, nor make any use of it,
until he has availed himself of certain principles of optics ; until
he has consulted the thermometer, gauged the atmosphere, and
considered the effect of heat in changing its powers of refraction.
In order to adjust the pendulum of his clock to the right length,
he has to measure the water of the sea and weigh the earth. He,
too, must therefore go into the study of the tides ; he must ex-
amine the earth's crust, and consider the matter of which it is

182 THE PHYSICAL GEOGRAPHY OF THE SEA.

composed, from pole to pole, circumference to centre ; and in
doing this, he finds himself, in his researches, right alongside of
the navigator, the geologist, and the meteorologist, with a host of
other good fellows, each one holding by the same thread, and fol-
lowing it up into the same labyrinth — all, it may be, with different
objects in view, but nevertheless, each thread will be sure to lead
them where there are stores of knowledge for all, and instruction
for each one in particular. And thus, in undertaking to explore
the physical geography of the sea, I have found myself standing
side by side with the geologist on the land, and with him, far away
from the sea-shore, engaged in considering some of the phenome-
na which the inland basins of the earth — those immense indenta-
tions on its surface that have no sea-drainage— present for con-
templation and study.

370. Among the most interesting of these is that of the Dead
Sea. Lieutenant Lynch, of the United States Navy, has run a lev-
el from that sea to the Mediterranean, and finds the former to be
about one thousand three hundred feet below the general sea-level
of the earth. In seeking to account for this great difference of
water level, the geologist examines the neighboring region, and
calls to his aid the forces of elevation and depression which are
supposed to have resided in the neighborhood ; he then points to
them as the agents which did the'w^ork. Truly they are mighty
agents, and they have diversified the surface of the earth with the
most towering monuments of their power. But is it necessary to
suppose that they resided in the vicinity of this region? May
they not have come from the sea, and been, if not in this case, at
least in the case of other inland basins, as far removed as the other
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 propound it
as one which, in accounting for the formation of this or that inland
basin, is worthy, at least, of consideration.

371. Is there any evidence that the annual amount of precipi-
tation upon the water-shed of the Dead Sea, at some former pe-
riod, was greater than the annual amount of evaporation from it
now is ? If yea, from what part of the sea did the vapor that sup-
plied the excess of that precipitation come from, and what has cut

ON THE GEOLOGICAL AGENCY OF THE WINDS. 183

off that supply ? The mere elevation and depression of the lake
basin (^ 370) would not do it.

372. If we establish the fact that the Dead Sea at a former pe-
riod did send a river to the. ocean, we carry along with it the ad-
mission 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 cbuld. convert into vapor and carry away again ;
the river carried off the excess to the ocean whence it came
(M16).

373. In the basin of the Dead Sea, in the basin of the Caspian,
of the Sea of Aral, and in the other inland basins of Asia, we are
entitled to infer that the precipitation and evaporation are at this
time exactly equal. Were it not so, the level of these seas would
be rising or sinking. If the precipitation were in excess, these
seas would be gradually becoming fuller ; and if the evaporation
were in excess, they would be gradually drying up ; but observa-
tion does not show, nor history tell us, that either is the case. As
far as we know, the level of these seas is as permanent as that of
the ocean, and it is difficult to realize the existence of subterra-
nean channels between it and the great ocean. Were there such
a channel, the Dead Sea being the lower, it would be the recipi-
ent of ocean waters ; and we can not conceive how it should be
such a recipient without ultimately rising to the level of its feeder.

374. It may be that the question suggested by my researches
has no bearing upon the Dead Sea ; that local elevations and sub-
sidences alone w^ere concerned in placmg the level of its waters
w^here it is. But is it probable that, throughout all the geological
periods, during all the changes which have taken place in the dis-
tribution of land and water surface over the earth, the winds,
which in the general channels of circulation pass over the Dead
Sea, have alone been unchanged ? Throughout all ages, periods,
and formations, is it probable that the winds have just brought us
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? Ob-
viously and clearly not. The salt-beds, the water-marks, the
geological formations, and other facts traced by Nature's own
hand upon the tablets of the rock — all indicate plainly enough that
not only the Dead Sea, but the Caspian also, had upon them, in
former periods, more abundant rains than they now have. Where

184 THE PHYSICAL GEOGRAPHY OF THE SEA.

did the vapor for those rains come from ? and what has stopped
the supply ? Surely not the elevation or depression of the Dead
Sea basin.

375. My researches w^ith regard to the winds have suggested
the probability (§ 121) that the vapor which is condensed into
rains for the lake valley, and which the St. Lawrence carries off
to the Atlantic Ocean, is taken up by the southeast trade-winds
of the Pacific Ocean. Suppose this to be the case, and that the
winds which bring this vapor arrive with it in the lake country at
a mean dew-point of 50°. This would make the southwest winds
the rain winds for the lakes generally, as well as for the Missis-
sippi Valley ; they are also, speaking generally, the rain winds of
Europe, and, I have no doubt, of extra-tropical Asia also.
■ 376. Now suppose a certain mountain range, hundreds of miles
to the southwest of the lakes, but across the path of these winds,
were to be suddenly elevated, and its crest pushed up into the re-
gions of snow, having a mean temperature of 30° Fahrenheit.
The winds, in passing that range, would be subjected to a mean
dew-point of 30° ; and, not meeting with any more evaporating
surface between such range and the lakes (§ 125), they would
have no longer any moisture to deposit at the supposed lake tem-
perature of 50° ; for they could not yield their moisture to any
thing above 30°. Consequently, the amount of precipitation in the
lake country w^ould fall off; the winds which feed the lakes w:ould
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 bed ; evaporation W"ould be increased
by reason of the dryness of the atmosphere and the w^ant 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.

377. There is a self-regulating principle that would bring about
this equality ; for as the water in the lakes becomes lower, the
area of its surface would be diminished, and the amount of vapor
taken from it would consequently become less and less as the sur-
face was low^ered, until the amount of water evaporated would
become equal to the amount rained down again, precisely in the
same way that the amount of w^ater evaporated from the sea is
exactly equal to the whole amount poured back into it by the

ON THE GEOLOGICAL AGENCY OF THE WINDS. 185

rains, the fogs, and the dews.* Thus the great lakes of this con-
tinent would remain inland seas at a permanent level ; the salt
brought from the soil by the washings of the rivers and rains
would cease to be taken off to the ocean as it now is ; and final-
ly, too, the great American lakes, in the process of ages, would
become first brackish, and then briny.

378. Now suppose the water-basins which hold the lakes to be
over a thousand fathoms (six thousand feet) deep. We know
they are not more than four hundred and twenty feet deep ; but
suppose them to be six thousand feet deep. The process of evap-
oration, after the St. Lawrence had gone dry, might go on until
one or two thousand feet or more were lost from the surface, and
we should then have another instance of the level of an inland
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.

379. Or let us take another case for illustration. Corallines
are at work about the Gulf Stream ; they have built up the Flor-
ida Reefs on one side, and the Bahama Banks on the other. Sup-
pose they should build up a dam across the Florida Pass, and ob-
struct the Gulf Stream ; and that, in like manner, they were to
connect Cuba with Yucatan, by damming up the Yucatan Pass,
so that the waters of the Atlantic should cease to flow into the
Gulf of Mexico. What should w^e have ?

The depth of the marine basin which holds the waters of that
Gulf is, in the deepest part, about a mile. The officers of the
United States ship Albany have run a line of deep-sea soundings
from west to east across the Gulf; the greatest depth they re-
ported was about six thousand feet. Subsequent experiments,
however, induce the belief that the depth is not quite so great.

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 w^ould
sink down until the surface exposed to the air would be just suffi-
cient to return to the atmosphere, as vapor, the amount of water
discharged by the rivers — the Mississippi and others — into the
Gulf. As the waters were lowered, the extent of evaporating

* The quantity of dew in England is about five inches during a year. — Glaishcr.

186 THE PHYSICAL GEOGRAPHY OF THE SEA.

surface would grow less and less, until Nature should establish
the proper ratio between the ability of the air to take up and the
capacity of the clouds to let down. Thus we might have a sea
whose level would be much farther below the water-level of the
ocean than is the Dead Sea.

380. There is still another process, besides the two already al-
luded to, by w^hich the drainage of these inland basins may,
through the agency of the winds, have been cut off from the great
salt seas, and that is by the elevation of continents from the bot-
tom 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.

381. Now suppose that a continent should rise up in that part
of the ocean, wherever it may be, that supplies the clouds with
the vapor that makes the rain for the hydrographic basin of the
great American lakes. What would be the result ? Why, surely,
fewer clouds and less rain, which would involve a change of cli-
mate in the lake country ; an increase of evaporation from it, be-
cause a decrease of precipitation upon it ; and, consequently, a
diminution of cloudy screens to protect the waters of the lakes
from being sucked up by the rays of the sun ; and consequently,
too, there would follow- a low stage for water-courses, and a low-
ering of the lake-level would ensue.

So far, I have instanced these cases only hypothetically ; but,
both in regard to the hydrographical basins of the Mexican Gulf
and American lakes, I have confined myself strictly to analogies.
Mountain ranges have been upheaved across the course of the
winds, and continents have been raised from the bottom of the
sea ; and, no doubt, the influence of such upheavals has been felt
in remote regions by means of the winds, and the effects which a
greater or less amount of moisture brought by them would produce.

382. In the case of the Salt Lake of Utah, wx have an example
of drainage that has been cut off, and an illustration of the process
by which Nature equalizes the evaporation and precipitation. To
do this, in this instance, she is salting up the basin which received
the drainage of this inland water-shed. Here we have the ap-
pearance, 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 water-course, the water returned through it to

ON THE GEOLOGICAL AGENCY OF THE WINDS. I87

the ocean was the amount by which the precipitation used to ex-
ceed the evaporation over the whole extent of country drained
through this now dry bed of a river. The winds have had some-
thing to do w^th this ; they are the agents which used to bring
more moisture from the sea to this water-shed than they took
away ; and they are the agents which now carry off from that
valley more moisture than is brought to it, and which, there-
fore, are making a salt-bed of places that vised to be covered by
water. In like manner, there is evidence that the great Amer-
ican lakes formerly had a drainage with the Gulf of Mexico.
Steamers have been actually known, in former years, and in times
of freshets, to pass from the Mississippi River over into the lakes.
At low water, the bed of a dry river can be traced between them.
Now the Salt Lake of Utah is to the southward and westward of
our northern^ lake basin; that is the quarter (§ 214) whence the
rain winds have been supposed to come. May not the same cause
which lessened the precipitation or increased the evaporation in
the Salt Lake water-shed, have done the same 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 winds which
fed the Salt Lake valley with, precipitation had, as (§ 212) I sup-
pose they have, to pass the summits of the mountains, it is easy to
perceive w^hy the winds should not convey as much vapor across
them now as they did when the summit of the range was lower
and not so cool.

383. 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 (§ 133), and consequently there is, on the
west side, a rainless region. Now suppose a range of such mount-
ains as these to be elevated across the track of the winds which
supply the lake country with rains ; it is easy to perceive how the
whole country watered by the vapor which such winds bring,
would be converted into a rainless 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 m-
land basin Ihe water-level of which, it is evident, was once higher
than it now is ; and that position is that, though the evidences of

188 THE PHYSICAL GEOGRAPHY OF THE SEA.

a higher water-level be unmistakable and conclusive, it does not
follow^, therefore, that there has been a subsidence of the lake
basin itself, or an upheaval of the water-shed drained by it.

384. 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 winds in his circuits,"
which have been interposed in some other quarter of the world,
which obstructions may prevent the winds from taking up or from
bearing off their wonted supplies of moisture for the region whose
water-level has been lowered.

385. Having therefore, I hope, made clear the meaning of the
question proposed, by showing the manner in which winds may be-
come important geological agents, and having explained how the
upheaving of a mountain range in one part of the world may,
through the winds, bear upon the physical geography of the sea,
affect climates, and produce geological phenomena in another, I
return to the Dead Sea and the great inland basins of Asia, and
ask, How far is it possible for the elevation of the South American
continent, and the upheaval of its mountains, to have had any ef-
fect upon the water-level of those seas ? There are indications
(§ 374) 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 vapor ?
What has diminished its supply ? Its supply would be diminished
(§ 381) by the substitution of dry land in those parts of the ocean
which used to supply that vapor ; or the quantity of vapor depos-
ited in the hydrographical basins of those seas would have been
lessened if a snow-capped range of mountains (§ 376) had been
elevated across the path of these winds, between the places where
they were supplied with vapor and these basins.

386. A chain of evidence which it would be difficult to set
aside is contained in the 'chapters beginning severally at p. 66,
97, and 104, going to show that the vapor which supplies the ex-
tra-tropical regions of the north with rains comes, in all probabil-
ity, from the trade-wind regions of the southern hemisphere.

387. Now if it be true that the trade-winds from that part of
the w^orld take up there the water which is to be rained in the
extra-tropical north, the path ascribed to the southeast trades of
Africa and America, after they descend and become the prevail-

ON THE GEOLOGICAL AGENCY OF THE WINDS. 189

ing southwest winds of the northern hemisphere, should pass over
a region of less precipitation generally than they would do if,
while performing the office of southeast trades, they had blown
over water instead of land. The southeast trade-winds, with their
load of vapor, whether great or small, take, after ascending in the
equatorial calms, a northeasterly 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 vapor w^hich the winds that blow over
southeast trade-wind Africa and America convey.

388. Now, if we could trace the path of the winds through the
extra-tropical regions of the northern hemisphere, we should be
able to identify the track of these Andean winds by the foot-prints
of the clouds ; for the path of the winds which depend for their
moisture upon such sources of supply as the dry land of Central
South America and Africa can not lie through a country that is
watered well.

389. It is a remarkable coincidence, at least, that the countries
in the extra-tropical regions of the north that are situated to the
northeast of the southeast trade-winds of South Africa and Amer-
ica— that these countries, over which theory makes these winds
to blow, include all the great deserts of Asia, and the districts of
least precipitation in Europe. A line from the Galapagos Islands
through Florence in Italy, another from the mouth of the Amazon
through Aleppo in Holy Land (Plate VII.), would, after passing
the tropic of Cancer, mark upon the surface of the earth the route
of these winds ; this is that " lee country" (^ 137) which, if such be
the system of atmospherical circulation, ought to be scantily sup-
plied with rains. Now the hyetographic map of Europe, in John-
ston's beautiful Physical Atlas, places the region of least precipita-
tion between these two lines (Plate VII.).

390. It would seem that Nature, as if to reclaim this " lee" land
from the desert, had stationed by the way-side of these winds a
succession of inland seas, to serve them as relays for supplying with
moisture this thirsty air. There is the Mediterranean Sea, the
Caspian Sea, and the Sea of Aral, all of which are situated ex-
actly in this direction, as though these sheets of water Avere de-
signed, in the grand system of aqueous arrangements, to supply

190 THE PHYSICAL GEOGRAPHY OF THE SEA.

with fresh vapor, winds that had ah-eady left rain enough behind
them to make an Amazon and an Oronoco of.

391. Now that there has been such an elevation of land out of
the water, we infer from the fact that the Andes were once cov-
ered by the sea, for their tops are now crowned with the remains
of marine animals. When they and their continent were sub-
merged— admitting that Europe in general outline was then as it
now is — it can not be supposed, if the circulation of vapor 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, the winds had nearly all
the waters which now make the Amazon to bring away with
them, and to distribute among the countries situated along the
route (Plate VII.) ascribed to them.

392. If ever the Caspian Sea exposed a larger surface for evap
oration than it now does — and no doubt it did ; if the precipitation
in that valley ever exceeded the evaporation from it, as it does in
all valleys drained into the open sea, then there must have been a
change of hygrometrical condition there. And admitting the va-
por-springs for that valley to be situated in the direction supposed,
the rising up of a continent from the bottom of the sea, or the up-
heaval of a range of mountains in certain parts of America, Africa,
or Spain, across the route of the winds which brought the rain for
the Caspian w^ater-shed, might haye been sufficient to rob them
of the moisture which they were wont to carry away and precip-
itate upon this great inland basin. See how the Andes have made
Atacama a desert, and of Western Peru a rainless country ; these
regions have been made rainless simply by the rising up of a
mountain range between them and the vapor-springs in the ocean
which feed with moisture the winds that blow over these now rain-
less regions.

393. That part of Asia, then, which is under the lee of south-
ern trade-wind Africa, lies to the north of the tropic of Cancer, and
between two lines, the one passing through Cape Palmas and Me-
dina, the other through Aden and Delhi. Being extended to the
equator, they will include that part of it which is crossed by the
continental southeast trade-winds of Africa, after they have trav-
ersed the greatest extent of land surface (Plate VII.).

ON THE GEOLOGICAL AGENCY OF THE WINDS. 191

394. The range which hes between the two lines that represent
the course of the American winds with their vapors, and the tw^o
hnes w^hich represent the course of the African winds with their
vapors, is the range which is under the lee of winds that have, for
the most part, traversed water-surface, or the ocean, in their cir-
cuit as southeast trade-winds. But a bare inspection of Plate VII.
will show that the southeast trade-winds which cross the equator
between longitude 15° and 50° west, and which are supposed to
blow over into this hemisphere between these two ranges, have
traversed land as well as water ; and the Trade-wind Chart* shows
that it is precisely those w^inds which, in the summer and fall, are
converted into southwest monsoons for supplying the whole extent
of Guinea with rains to make rivers of. Those winds, therefore,
it would seem, leave much of their moisture behind them, and pass
along to their channels in the grand system of circulation, for the
most part, as dry winds. Moreover, it is not to be supposed that
the channels through which the winds blow that cross the equa-
tor at the several places named, are as sharply defined in nature
as the lines suggested, or as Plate VII. would represent them to be.

395. The whole region of the extra-tropical Old World that is
included within the ranges marked, is the region which has most
land to w^indward of it in the southern hemisphere. Now it is a
curious coincidence, at least, that all the great extra-tropical des-
erts of the earth, with those regions in Europe and Asia which
have the least amount of precipitation upon them, should lie within
this range. That they are situated under the lee of the southern
continents, and have but little rain, may be a coincidence, I ad-
mit ; but that these deserts of the Old World are placed where
they are is no coincidence — no accident : they are placed where
they are, and as they are, by design ; and in being so placed, it was
intended that they should subserve some grand purpose in the ter-
restrial 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 supposition which I maintain as to the place
where the winds that blow over those regions derive their vapors,

396. It will be remarked at once that all the inland seas of
Asia, and all those of Europe except the semi-fresh-water gulfs of

* $eries of Maury's Wind and Current Charts.

192 THE PHYSICAL GEOGRAPHY OF THE SEA.

the north, are within this range. The Persian Gulf and the Red
Sea, the Mediterranean, the Black, and the Caspian, all fall within
it. And why are they planted there ? Why are they arranged to
the northeast and southwest under this lee, and in the very direc-
tion in which theory makes this breadth of thirsty winds to pre-
vail ? Clearly and obviously, one of the purposes in the divine
economy was, that they might replenish with vapor the winds
which are almost vaporless when they arrive at these regions in
the general system of circulation. And why should these winds
be almost vaporless ? They are almost vaporless because their
route, in the general system of circulation, is such, that they are
not brought into contact with a water-surface from which the need-
ful supplies of vapor are to be had ; or, being obtained, the sup-
plies have since been taken away by the cool tops of mountain
ranges over which these winds have had to pass.

397. In the Mediterranean, the evaporation is greater than the
precipitation. Upon the Red Sea there never falls a drop of rain ;
it is all evaporation. Are we not, therefore, entitled to regard the
Red Sea as a make-weight, thrown in to regulate the proportion
of cloud and sunshine, and to dispense rain to certain parts of the
earth in due season and in proper quantities ? Have we not, in
these two facts, evidence conclusive that the winds which blow over
these two seas come, for the most part, from a dry country — from
regions which contain few or no pools to furnish supplies of vapor?

398. Indeed, so scantily supplied with vapor are the winds which
pass in the general channels of circulation over the water-shed
and sea-basin of the Mediterranean, that they take up there more
water as vapor than they deposit. But, throwing out of the ques-
tion what is taken up from the surface of the Mediterranean itself,
these winds deposit more water on the water-shed whose drainage
leads into that sea than they take up from it again. The excess
is to be found in the rivers which discharge into the Mediterrane-
an ; 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 (§ 252)
to create a demand for an immense current from the Atlantic to
supply the waste.

399. It is estimated that three* times as much water as the
* Vide article " Physical Geography," Encyclopsedia Britannica.

ON THE GEOLOGICAL AGENCY OF THE WINDS. 193

Mediterranean receives from its rivers is evaporated from its sur-
face. This may be an over-estimate, but the fact that evapora-
tion from it is in excess of the precipitation, is made obvious by
the current which the Atlantic sends into it through the Straits of
Gibraltar ; and the difference, we may rest assured, whether it be
much or little, is carried off to modify climate elsewhere — to re-
fresh with showers and make fruitful some other part of the earth.

400. The great inland basin of Asia, in which are Aral and the
Caspian Seas, is situated on the route which this hypothesis re-
quires these thirsty winds from southeast trade-wind Africa and
America to take ; and so scant of vapor 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 (§ 116) 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 permanent as that of the great ocean itself. Therefore, the
volume of water discharged by rivers, the rains, and the dews, into
these two seas, is exactly equal to the volume which these two seas
give back as vapor to the atmosphere.

401. These winds, therefore, do not begin permanently to lay
down their load of moisture, be it great or small, until they cross
the Oural Mountains. On the steppes of Issam, after they have
supplied the Amazon and the other great equatorial rivers of the
south, w^e find them first beginning to lay down more moisture than
they take up again. In the Obi, the Yenesi, and the Lena, is to
be found the volume which contains the expression for the load of
water which these winds have brought from the southern hemi-
.sphere, from the Mediterranean, and the Red Sea ; for in these
almost hyperborean river-basins do we find the first instance in
which, throughout the entire range assigned these winds, they
have, after supplying the Amazon, &c., left more w^ater behind
them than they have taken up again and carried off. The low
temperatures of Siberian Asia are quite sufficient to extract from
these winds the remnants of vapor which the cool mountain-tops
and mighty rivers of the southern hemisphere have left in them.

402. Here I may be permitted to pause, that I may call atten-
tion to another remarkable coincidence, and admire the marks of

N

194 THE PHYSICAL GEOGRAPHY OF THE SEA.

design, the beautiful and exquisite adjustments that we see here
provided, to insure the perfect workings of the great aqueous and
atmospherical machine. This coincidence — may I not call it
cause and effect ? — is between the hygrometrical conditions of all
the countries within, and the hygrometrical conditions of all the
countries without, the range included within the lines which I have
drawn (Plate VII.) to represent the route in the northern hemi-
sphere of the southeast trade-winds after they have blown their
course over the land in South Africa and America. Both to the
right and left of this range are countries included between the same
parallels in which it is, yet these countries all receive more water
from the atmosphere than they give back to it again ; they all have
rivers running into the sea. On the one hand, there is in Europe
the Rhine, 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 rivers of China ; 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 magnificent.

403. It is remarkable that none of these copiously-supplied wa-
ter-sheds have, to the southwest of them in the trade-wind regions
of the southern hemisphere, any considerable body of land ; they
are, all of them, under the lee of evaporating surfaces, of ocean
waters in the trade-wind regions of the south. Only those coun-
tries in the extra-tropical north which I have described as lying
under the lee of trade-wind South America and Africa are scanti-
ly supplied with rains. Pray examine Plate VII. in this connec-
tion. It tends to confirm the views taken in Chapter V., p. 115.

404. The surface of the Caspian Sea is about equal to that of
our lakes ; in it, evaporation is just equal to the precipitation.
Our lakes are between the same parallels, and about the same
distance from the western coast of America that the Caspian Sea
is from the western coast of Europe ; and yet the waters dis-
charged by the St. Lawrence give us an idea of how greatly the
precipitation upon it is in excess of the evaporation. To wind-
ward of the lakes, and in the trade-wind regions of the southern
hemisphere, is no land ; but to windward of the Caspian Sea,
and in the trade-wind region of the southern hemisphere, there
is land. Therefore, supposing the course of the vapor-distributing

ON THE GEOLOGICAL AGENCY OF THE WINDS. 195

winds to be such as I maintain it to be, ought they not to carry-
more water from the ocean to the American lakes than it is pos-
sible for them to carry from the land — from the interior of South
Africa and America — to the valley of the Caspian Sea ?

405. In like manner (^ 228), extra-tropical New^ Holland and
South Africa have each land — not water — to the windward of them
in the trade-wind regions of the northern hemisphere, where, ac-
cording to this hypothesis, the vapor for their rains ought to be
taken up : they are both countries of little rain ; but extra-tropical
South America has, in the trade-wind region to windward of it in
the northern hemisphere, a great extent of ocean, and the amount
of precipitation (^ 141) in extra-tropical South America is wonder-
ful. The coincidence, therefore, is remarkable, that the countries
in the extra-tropical regions of this hemisphere, which lie to the
northeast of large districts of land in the trade-wind regions of the
other hemisphere, should be scantily supplied with rains ; and like-
wise, that those so situated in the extra-tropical south, with regard
to land in the trade-wind region of the north, should be scantily
supplied with rains.

Having thus remarked upon the coincidence, let us turn to the
evidences of design, and contemplate the beautiful harmony dis-
played in the arrangement of the land and water, as we find them
along this conjectural " wind-road." (Plate VH.)

406. Those who admit design among terrestrial adaptations, or
have studied the economy of cosmical arrangements, will not be
loth to grant that by design the atmosphere keeps in circulation a
certain amount of moisture ; that the water of which this moist-
ure is made is supplied by the aqueous surface of the earth, and
that it is to be returned to the seas again through rivers and the
process of precipitation ; that a permanent increase or decrease
of the quantity of water thus put and kept in circulation by the
winds would be followed by a corresponding change of hygromet-
rical conditions, which would draw after it permanent changes of
climate ; and that permanent changes of climate would involve
the ultimate well-being of myriads of organisms, both in the veg-
etable and animal kingdoms.

407. The quantity of moisture that the atmosphere keeps in
circulation is, no doubt, just that quantity which is best suited to
the well-being, and most adapted to the proper development of

196 THE PHYSICAL GEOGRAPHY OF THE SEA.

the vegetable and animal kingdoms ; and that quantity is depend-
ent upon the arrangement and the proportions that we see in na^
ture between the land and the water — between mountain and des-
ert, river and sea. If the seas and evaporating surfaces were
changed, and removed from the places they occupy to other
places, the principal places of precipitation probably would also
be changed : whole families of plants would wither and die for
want of cloud and sunshine, dry and wet, in proper proportions
and in due season ; and, with the blight of plants, whole tribes of
animals would also perish. Under such a chance 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 w^e recol-
lect who it is that " sendeth" it, we feel the conviction strong
within us that He that 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.

408. It should be borne in mind that the southeast trade-winds,
after they rise up at the equator (Plate I.), have to overleap the
northeast trade-winds. Consequently, they do not touch the earth
until near the tropic of Cancer (see the bearded arrows, Plate
Vn.) — more frequently to the north than to the south of it ; but
for a part of every year, the place where these vaulting southeast
trades first strike the earth, after leaving the other hemisphere, is
very near this tropic. On the equatorial side of it, be it remem-
bered, the northeast trade-winds blow ; on the polar side, what
were the southeast trades, and what are now the prevailing south-
westerly winds of our hemisphere, prevail. Now examine Plate
VIL, and it will be seen that the upper half of the Red Sea is
north of the tropic of Cancer ; the lower half is to the south of
it ; that the latter is within the northeast trade-wind region ; the
former, in the region where the southwest passage winds are the
prevailing winds.

409. The River Tigris is probably evaporated from the upper
half of this sea by these winds ; while the northeast trade-winds
take up from the lower half those vapors which feed the Nile with
rain, and which the clouds deliver to the cold demands of tht>

ON THE GEOLOGICAL AGENCY OF THE WINDS. 197

Mountains of the Moon. Thus there are two "wind-roads" cross-
ing this sea : to the windward of it, each road runs through a rain-
less region ; to the leeward there is, in each case, a river to cross.

410. The Persian Gulf lies, for the most part, in the track of
the southwest winds ; to the windward of the Persian Gulf is a
desert ; to the leeward, the River Indus. This is the route by
w^hich theory would require the vapor from the Red Sea and Per-
sian Gulf to be conveyed ; and Ijiis 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.

411. Is it not a curious circumstance, that the winds which
travel the road suggested from the southern hemisphere should,
when they touch the earth on the polar side of the tropic of Can-
cer, be so thirsty, more thirsty, much more, than those which trav-
el on either side of their path, and which are supposed to have
come from southern seas, not from southern lands ?

412. The Mediterranean has to give those winds three times as
much vapor as it receives from them (§ 399) ; the Red Sea gives
them as much as they can take, and receives nothing back in re-
turn but a little dew (§ 238) ; the Persian Gulf also gives more
than it receives. What becomes of the rest ? Doubtless it is
given to the winds, that they may bear it off to distant regions, and
make lands fruitful, that but for these sources of supply would be
almost rainless, if not entirely arid, waste, and barren.

413. These seas and arms of the ocean now^ present themselves
to the mind as counterpoises in the great hygrometrical machinery
of our planet. As sheets of w^ater placed where they are, to bal-
ance the land in the trade-wind region of South America and
South Africa, they now present themselves. When the founda-
tions of the earth were laid, we know who it was that "measured
the waters in the hollow of his hand, and meted out the heavens
with a span, and comprehended the dust of the earth in a meas-
ure, and weighed the mountains in scales, and the hills in a bal-
ance ;" and hence we know also that they are arranged both ac-
cording to proportion and to place.

414. Here, then, we see harmony in the winds, design in the
mountains, order in the sea, arrangement in the dust, and form for
the desert. Here are signs of beauty and works of grandeur ; and

198 THE PHYSICAL GEOGRAPHY OF THE SEA.

we may now fancy that, in this exquisite system of adaptations
and compensations, we can almost behold, in the Red and Medi-
terranean Seas, the very waters that were held in the hollow of
the Almighty hand when he weighed the Andes and balanced the
hills of Africa in his comprehensive scales.

415. In that great inland basin of Asia which holds the Caspian
Sea, and embraces an area of one million and a half of geo-
graphical square miles, we see the water-surface so exquisitely
adjusted that it is just sufficient, and no more, to return to the at-
mosphere as vapor exactly as much moisture as the atmosphere
lends in rain to the rivers of that basin.

416. Thus we are entitled to regard (^ 390) the Mediterranean,
the Red Sea, and Persian Gulf as relays, distributed along the
route of these thirsty winds from the continents of the other hemi-
sphere, to supply them with vapors, or to restore to them that which
they have left behind to feed the sources of the Amazon, the Ni-
ger, and t.he Congo.

The hypothesis that the winds from South Africa and America
do take the course through Europe and Asia which I have mark-
ed out for them (Plate VII.), is supported by so many coincidences,
to say the least, that we are entitled to regard it as probably cor-
rect, until a train of coincidences as, striking can be adduced to
show that such is not the case.

417. Returning once more to a consideration of the geological
agency of the winds in accounting for the depression of the Dead
Sea, we now see the fact most strikingly 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
is evaporated from that sea as is returned to it through the rivers.
A portion of water evaporated from it is probably rained down and
returned to it through the rivers ; but, supposing it to be barred
up, as the demand upon it for vapor 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 would be estab-
lished between the evaporation and precipitation an equilibrium,
as in the Dead and Caspian Seas ; but, for aught we know, the
water-level of the Mediterranean might, before this equiUbrium

ON THE GEOLOGICAL AGENCY OF THE WINDS. 199

were attained, have to reach a stage far below that of the Dead
Sea level.

The Lake Tadjura is now^ in the act of attaining such an equi-
librium. There are connected with it the remains of a channel by
which the water ran into the sea ; but the surface of the lake is
now five hundred feet below the sea-level, and it is salting up.
If not in the Dead Sea, do w^e 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 ?

418. The winds, in this sense, are geological agents of great
power. It is not impossible but that they may aiFord us the
means of comparing, directly, geological events which have taken
place in one hemisphere, with geological events in another : e.g.,
the tops of the Andes were ojice at the bottom of the sea. Which
is the oldest formation, that of the Dead Sea or the Andes ? If
the former be the older, then the climate of the Dead Sea must
have been hygrometrically very different from what it now is.

419. In regarding 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 consulted, will reveal to us truths that Na-
ture has written upon their wings in characters as legible and en-
during as any with which she has ever engraved the history of
geological events upon the tablet of the rock.

420. The waters of Lake Titicaca, -which receives the drain-
age of the great inland basin of the Andes, are only brackish, not
salt. Hence we 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
Lynch, informs me that, in his exploration oi the Dead Sea, he
saw what he took to be the dry bed of a river that once flowed
from it. And thus we have two more links, stout and strong, to
add to the chain of circumstantial evidence going to sustain the
testimony of this strange and fickle witness which I have called
up from the sea to testify in this presence concerning the works
of Nature, and to tell us which be the older— the Andes, watching
the stars with their hoary heads, or the Dead Sea, sleeping upon
its ancient beds of crystal salt.

200 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER XL

THE DEPTHS OF THE OCEAN.

The Depth of blue Water unknown, ^ 421. — Results of former Methods of Deep-sea
Soundings not entitled to Confidence, 422. — Attempts by Sound and Pressure, 423.
— The Myths of the Sea, 424. — Common Opinion as to its Depths, 425. — Interest-
ing Subject, 427. — The deepest Soundings reported, 428. — Plan adopted in the
American Navy, 429. — Soundings to be made from a Boat, 431. — Why the Sound-
ing-twine will not stop running out when the Plummet reaches Bottom, 432. — In-
dications of under Currents, 433. — Rate of Descent, 434. — Brooke's Deep-sea
Sounding Apparatus, 437. — The greatest Depths at which Bottom has been found,
438.

421. Until the commencement of the plan of deep-sea sound-
ings, as now conducted in the American Navy, the bottom of what
the sailors call " blue water" was as unknown to us as is the inte-
rior of any of the planets of our system. Ross and Dupetit Then-
ars, with other officers of the English, French, and Dutch navies,
had attempted to fathom the deep sea, some with silk threads,
some with spun-yarn (coarse hemp threads twisted together), and
some with the common lead and line of navigation. All of these
attempts were made upon the supposition' that when the lead
reached the bottom, either a shock would be felt, or the line, be-
coming slack, would cease to run out.

422. The series of systematic experiments recently made upon
this subject s^ows that there is no reliance to be placed on such a
supposition, for the shock caused by striking bottom can not be
communicated through very great depths, and therefore it does not
follow that the line will become slack and cease to run out when
the plummet reaches the bottom. Furthermore, the lights of ex-
perience show that, as a general rule, the under .jcurrents of the
deep sea have force enough to take the hne out long after the
plummet has ceased to do so. Consequently, there is but little re
liance to be placed upon deep-sea soundings of former methods,
when the depths reported exceeded eight or ten thousand feet.

423. Attempts to fathom the oces^n, both by sound and pressure,
had been made, but in " blue water" every trial was only a failure

THE DEPTHS OF THE OCEAN. 201

repeated. The most ingenious and beautiful contrivances for
deep-sea soundings were resorted to. By exploding heavy charges
of powder in the deep sea, when the winds were hushed and all
was still, the echo or reverberation from the bottom might, it was
held, be heard, and the depth determined from the rate at which
sound travels through water. But, though the explosion took place
many feet below the surface, 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 pressure to which they might be subject-
ed. This was found to answer well for ordinary purposes, but in
the depths of " blue water," where the pressure would be equal to
several hundred atmospheres, the trial was more than this instru-
ment could stand.

Mr. Baur, an ingenious 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
number of revolutions made by the little screw during the descent ;
and, it having been ascertained by experiment in shoal water that
the apparatus, in descending, would cause the propeller to make
one revolution for every fathom of perpendicular descent, hands
provided with the power of self-registration were attached to a
dial, and the instrument was complete. It worked beautifully in
moderate depths, but failed in blue water, from the difficulty of
hauhng 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 re-
quisite strength for hauling up.

424. But, notwithstanding these failures, there was encourage-
ment, for greater difficulties had been overcome in other depart-
ments of physical research. Astronomers had measured the vol-
umes and weighed the masses of the most distant planets, and in-
creased thereby the stock of human knowledge. Was it credita-
ble to the age that the depths of the sea should remain in the cat-
egory of an unsolved problem ? It was a sealed volume, abounding
in knowdedge and instruction that might be both useful and profit-
able to man. The seal which covered it was of rolling waves
many thousand feet in thickness. Could it not be broken ? Cu-
riosity had always been great, yet neither the enterprise nor the

202 THE PHYSICAL GEOGRAPHY OF THE SEA.

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 cover-
ing of the earth, any specimens of solid matter for the study of phi-
losophers.

The sea, w^ith its myths, has suggested attractive themes to all
people in all ages. Like the heavens, it affords an almost endless
variety of subjects for pleasing and profitable contemplation, and
there has remained in the human mind a longing to learn more of
its wonders and to understand its mysteries. The Bible often al-
ludes to them. Are they past finding out ? How deep is it ? and
what is at the bottom of it ? Could not the ingenuity and appli-
ances 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, with
this interesting problem, was one of the difficulties first to be over-
come.

425. It was a common opinion, derived chiefly from a supposed
physical relation, that the depths of the sea are about equal to the
heights of the mountains. But this conjecture was, at best, only
a speculation. Though plausible, it did not satisfy. There were,
in the depths of the sea, untold wonders and inexplicable myste-
ries. Therefore the contemplative mariner, as in mid ocean he
looked down upon the gentle bosom of the sea, continued to expe-
rience 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.

426. Nevertheless, the depths of the sea still remained as fath-
omless and as mysterious as the firmament above. Indeed, tele-
scopes of huge proportions and of vast space-penetrating powers
had been erected here and there by the munificence of individuals,
and attempts made with them to gauge the heavens and sound out
the regions of space. Could it be more difficult to sound out the
sea than to gauge the blue ether and fathom the vaults of the sky?
The result of the astronomical undertakings* lies in the discovery
that what, through other instruments of less power, appeared as
clusters of stars, were, by these of larger powers, separated into
groups, and what had been reported as nebulse could now be re-

* See the works of Herschel and Ross, and their telescopes.

THE DEPTHS OF THE OCEAN. 208

solved into clusters ; that, in certain directions, the abyss beyond
these faint objects is decked with other nebulae, which these great
instruments may bring to light, but can not resolve ; and that there
are still regions and realms beyond, w^hich the rays of tht) bright-
est sun in the sky have neither the intensity nor the force to reach,
much less to penetrate.

427. So, too, with the bottom of the sea, and the knowledge-
seeking mariner. Though nothing thence had been brought to
light, exploration had invested the subject with additional inter-
est, 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 con-
ception ; for, besides its simplicity, it had in its favor the greatest
of recommendations — it could be readily put into practice.

Well-directed attempts to fathom the ocean began now to be
made, and the public mind was astonished at the vast depths that
were at first reported.

428. Lieutenant Walsh, of the United States schooner " Taney,"
reported a cast with, the deep-sea lead at thirty-four thousand feet
without bottom. His sounding-line w^as an iron wire more than
eleven miles in length. Lieutenant Berryman, of the United
States brig '' Dolphin," reported another unsuccessful attempt to
fathom mid ocean with a line thirty-nine thousand feet in length.
Captain Denham, of her Britannic majesty's ship " Herald," re-
ported bottom in the South Atlantic at the depth of forty-six thou-
sand feet ; and Lieutenant J. P. Parker, of the United States frig-
ate " Congress," afterward, in attempting to sound near the same
region, let go his plummet, and saw a line fifty thousand feet long
run out after it as though the bottom had not been reached.

The three last-named attempts were made with the sounding
twine of the American Navy, which has been introduced in con-
formity 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 in-
troduced as a part of the researches conducted at the National Ob-
servatory, and which have proved so fruitful and beneficial, con-
cerning the winds and currents, and other phenomena of the ocean.
These researches had already received the approbation of the Con-
gress of the United States ; for that body, in a spirit worthy of the

204 THE PHYSICAL GEOGRAPHY OF THE SEA.

representatives of a free and enlightened people, had authorized
the Secretary of the Navy to employ three public vessels to assist
in perfecting the discoveries, and in conducting the investigations
connected therewith.

429. The plan of deep-sea soundings finally adopted, and novv^
in practice, is this : Every vessel of the Navy that will, when she
puts to sea, is, if she desires it, furnished with a sufficient quantity
of sounding-twine, carefully marked at every length of one hun-
dred fathoms — six hundred feet — and w^ound on reels of ten thou-
sand fathoms each. It is made the duty of the commander to
avail himself of every favorable opportunity to try the depth of
the ocean, whenever he may find himself out upon " blue water."
For this purpose he is to use a cannon ball of thirty-two pounds as
a plummet. Having one end of the twine attached to it, the can-
non ball is to be thrown overboard from a boat, and suffered to
take the twine from the reel as fast as it will.

The reel is made to turn easily. A silk thread, or the common
wrapping-twine of the shops would, it was thought, be strong
enough for this purpose ; for it was supposed there would be no
strain upon the line, except the very slight one required to drag it
down, and the twine having nearly the specific gravity of sea wa-
ter, this strain would, it was imagined, be very slight. Moreover,
when the shot reached the bottom, the line, it was thought (§ 421),
would cease to run out ; then breaking it off, and seeing how
much remained upon the reel, the depth of the sea could be ascer-
tained at any 2:>lace and time, simply at the expense of one cannon
ball and a few pounds of common twine.

430. But practical difficulties that were not suspected at all
were lurking in the way, and afterward showed themselves at ev-
ery attempt to sound ; and it was before these practical difficul-
ties had been fairly overcome that the great soundings (§ 428)
were reported. In the first place, it was discovered that the line,
once started and dragged down into the depths of the ocean, never
would cease to run out (§ 422), and, consequently, that there was
no means of knowing when, if ever, the shot had reached the bot-
tom. And, in the next place, it was ascertained that the ordinary
twine (§ 427) would not do ; that the sounding-line, in going down,
was really subjected to quite a heavy strain, and that, consequent-
ly, the twine to be used must be strong ; it must be subjected to

THE DEPTHS OF THE OCEAN. 205

a test which required it to bear a weight of at least sixty pounds
freely suspended in the air. So we had to go to work anew, and
make several hundred thousand fathoms of sounding-twine espe-
cially for the purpose. It was small, and stood the test required,
a pound of it measuring about six hundred feet in length.

431. The officers intrusted with the duty soon found that the
soundings could not be made from the vessel with any certainty
as to the depth. It was necessary that a boat should be lowered,
and the trial be made from it ; the men with their oars keeping
the boat from drifting, and maintaining it in such a position that
the line should be " up and down" the while.

432. That the line would continue to run out after the cannon
ball had reached bottom, was explained by the conjecture that
there is in the ocean, as in the air, a system of currents and counter
currents one above the other, and that it was one or more of
these submarine currents, operating upon the bight of the line,
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 line — for
there might be several currents running in different directions, and
operating upon it at the same time — which caused it to part when-
ever the reel was stopped and the line held fast in the boat.

433. A powerful train of circumstantial evidence w^as this (and
it was derived from a source wholly unexpected), going to prove
the existence of that system of oceanic circulation which the cli-
mates, and the offices, and the adaptations of the sea require, and
which its inhabitants (^ 293) in their mute way tell us of.

This system of circulation commenced on the third day of cre-
ation, with the "gathering together of the waters," which were
*' called seas," and doubtless will continue as long as sea water
shall possess the properties of saltness and fluidity.

434. In making these deep-sea soundings, the practice is to
time the hundred fathom marks as they successively go out ; and
by always using a line of the same 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 sink-
er and twine used,

206 THE PHYSICAL GEOGRAPHY OF THE SEA.

2 m. 21 s. as the average time of descent from 400 to 500 fathoms.
3in. 26 s. " •' " 1000 to 1100

4 m. 29 s. " " " 1800 to 1900

435. Now, by aid of the law here indicated, we could tell very
nearly when the ball ceased to carry the line out, and when, of
course, it began to go out in obedience to the current and drift
alone ; for currents would sweep the line out at a uniform rate,
while the cannon ball would drag it out at a decreasing rate.

436. The development of this law certainly was an achieve-
ment, for it enabled us to show that the depth of the sea at the
places named (§ 428) was not as great as reports made it. These
researches were interesting ; the problem in hand was important,
and it deserved every effort that ingenuity could suggest for re-
ducing it to a satisfactory solution.

437. As yet, no specimens of the bottom had been brought up.
The line was too small, the shot was too heavy, and it could not
be weighed. In this state of the case, Passed Midshipman J. M.
Brooke, United States Navy, who, at the time, was associated
with me on duty at the Observatory, proposed a contrivance by
which the shot, on striking the bottom, would detach itself from
the line, and send up a specimen of the bottom. This beautiful
contrivance, called Brooke's Deep-sea Sounding Apparatus, is
represented in Plates II. and III. opposite.

A is a cannon ball, having a hole through it for the rod B.
Plate II. represents the rod, B ; the slings, D D, with the shot
slung, and in the act of being lowered down. Plate III. repre-
sents the apparatus in the act of striking the bottom, and shows
how the shot is detached, and how specimens of the bottom are
brought up, by adhering to a little soap or tallow,* called '' arm-
ing," in the cup, C, at the lower end of the rod, B. With this con-
trivance specimens of the bottom have been brought up from the
depth of more than two miles.

438. The greatest depths at which the bottom of the sea has
been reached with the plummet are in the North Atlantic Ocean,
and the places where it has been fathomed do not show it to be
deeper than twenty-five thousand feet.

The deepest place in this ocean (Plate XI.) is probarbly between
the parallels of 35° and 40° north latitude, and immediately to the

* A Stellwagen cup is found to answer better.

THE DEPTHS OF THE OCEAN.

207

PLATE HI.

PLATE TI

BROOKE'S DEEP-SEA SOUNDING APPARATUS.

southward of the Gr^nd Banks of Newfoundland. No satisfactory-
deep-sea soundmgs, either in the Pacific or Indian Oceans, have
as yet been made by those who are co-operating in this admirable
plan of research.* A few have been made in the South Atlantic,
but not enough to justify deduction as to its depths or the shape
of its floor.

* Since the above was written, I have received a letter from Captain Ringgold,
commanding the Surveying Expedition in the Pacific, informing me that, on his way
out, he had obtained, in the southern hemisphere, a deep-sea sounding, with bottom
at the depth of eight thousand fathoms. The notes and details of this cast have not
yet been received.

208 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER XII.

THE BASIN OF THE ATLANTIC.

Plate XL, ^ 439. — Height of Chimborazo above the Bottom of the Sea, 440.— Orog-
raphy of Oceanic Basins, 441.— The deepest Place in the Atlantic, 442.— The Bot-
tom OF THE Atlantic : The UtiUty of Deep-sea Soundings, 445.— A telegraphic
Plateau across the Atlantic, 446.— Specimens from it, 447.— A microscopic Exam-
ination of them, 448. — Brooke's Deep-sea Lead presents the Sea in a new Light,
453. — The Agents at work upon the Bottom of the Sea, 454. — How the Ocean is
prevented from growing salter, 458. — Knowledge of our Planet to be derived from
the Bottom of the Sea, 460.

439. The Basin of the Atlantic, according to the deep-sea
soundings made by the American Navy, in the manner described
in the foregoing chapter, is shown on Plate XI. This plate refers
chiefly to that part of the Atlantic which is included within our
hemisphere.

440. In its entire length, the basin of this sea is a long trough,
separating the Old World from the New, and extending probably
from pole to pole.

This ocean-furrow was scored into the solid crust of our planet
by the Almighty hand, that there the waters which " he called
seas" might be gathered together, so as to " let the dry land ap-
pear," and fit the earth for the habitation of man.

From the top of Chimborazo to the bottom of the Atlantic, at
the deepest place yet reached by the plummet in the North At-
lantic, the distance, in a vertical line, is nine miles.

Could the waters of the Atlantic be drawn off, so as to expose
to view this great sea-gash, which separates continents, and extends
from the Arctic to the Antarctic, it would present a scene the most
rugged, grand, and imposing. The very ribs of the solid earth,
with the foundations of the sea, would be brought to light, and we
should have presented to us at one view, in the empty cradle of
the ocean, " a thousand fearful wrecks," with that dreadful array
of dead men's skulls, great anchors, heaps of pearl and inestima-
ble stones, which, in the poet's eye, lie scattered in the bottom of
the sea, making it hideous with siirhts of ugly death.

THE BASIN OF THE ATLANTIC. 209

441. To measure the elevation of the mountain-top above the
sea, and to lay down upon our maps the mountain 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 wuthin the domains of science, to present its
orography, 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.

442. Plate XL presents the second attempt at such a map. It
relates exclusively to the bottom of that part of the Atlantic Ocean
which lies north of 10° south. It is stippled with four shades ; the
darkest (that which is nearest the shore-line) shows where the wa-
ter is less than six thousand feet deep ; the next, where it is less
than twelve thousand feet ; the third, where it is less than eighteen
thousand ; and the fourth, or lightest, where it is not over twenty-
four thousand feet deep. The blank space south of Nova Scotia
and the Grand Banks includes a district w^ithin which very deep
water has been reported, but from casts of the deep-sea lead which
upon discussion do not appear satisfactory.

The deepest part of the North Atlantic (§ 438) is probably some-
w^here between the Bermudas and the Grand Banks, but how deep
it may be yet remains for the cannon ball and sounding-twine to
determine.

443. The waters of the Gulf of Mexico are held in a basin about
a mile deep in the deepest part.

444. The Bottom of the Atlantic, or its depressions below
the sea-level, are given, perhaps, on this plate with as much accu-
racy as the best geographers have been enabled to show on a map
the elevations above the sea-level of the interior either of Africa
or Australia.

445. " What is to be the use of these deep-sea soundings ?" is
a question that often occurs ; and it is as difficult to be answered
in categorical terms as Franklin's question, " What is the use of
a new-born babe ?" Every physical fact, every expression of na-
ture, 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

O

210 THE PHYSICAL GEOGRAPHY OF THE SEA.

precious jewels, which science or the expert hand of philosophy
will not fail to bring out, polished, and bright, and beautifully
adapted to man's purposes. Already w^e are obtaining practical
answ^ers to this question as to the use of deep-sea soundings ; for
as soon as they were announced to the public, they forthwith as-
sumed a practical bearing in the minds of men with regard to the
question of a submarine telegraph across the Atlantic.

446. There is at the bottom of this sea, between Cape Race in
Newfoundland and Cape Clear in Ireland, a remarkable steppe,
which is already known as the telegraphic plateau. A company
is now engaged wath the project of a submarine telegraph across
the Atlantic. It is proposed to carry the wires along this plateau
from the eastern shores of Newfoundland to the western shores
of Ireland. The great circle distance between these two shore-
lines is one thousand six hundred miles, and the sea along the
route IS probably nowhere more than ten thousand feet deep.
This company, it is understood, consists of men of enterprise and
wealth, who, should the mquiries that they are now making prove
satisfactory, are prepared to undertake the establishment forth-
with of a submarine telegraph across the Atlantic.

447. It was upon this plateau that Brooke's soundmg apparatus
(§ 437) brought up its first trophies from the bottom of the sea.
These specimens Lieutenant Berryman and his officers 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
Professor Bailey, of West Point — eminent microscopists both. I
have not heard from the former, but the latter, in November, 1853,
thus responded :

448-. " I am greatly obliged to you for the deep soundings you
sent me last week, and I have looked at them w^ith great mterest.
They are exactly what I have wanted to get hold of. The bottom
of the ocean at the depth of more than tivo miles I hardly hoped
ever to have a chance of examining ; yet, thanks to Brooke's con-
trivance, we have it clean and free from grease, so that it can at
once be put under the microscope. I was greatly delighted to
find that all these deep soundings are filled with microscopic
shells ; not a particle of sand or gravel exists in them. They are

THE BASIN OF THE ATLANTIC. 211

chiefly made up of perfect little calcareous shells {Forami7iiferce),
and contain, also, a small number of silicious shells {BiatomacecB).

" It is not probable that these animals lived at the depths where
these shells are found, but I rather thmk that they inhabit the wa-
ters near the surface ; and when they die, their shells settle to the
bottom. With reference to this point, I shall be very glad to ex-
amine bottles of water from various depths which were brought
home by the Dolphin, and any similar materials, either ' bottom,'

or water from other localities. I shall study them carefully

The results already obtained are of very great interest, and have
many important bearings on geology and zoology

^' I hope you will induce as many as possible to collect sound-
ings with Brooke's lead, in all parts of the world, so that we can
map out the animalcula? as you have the whales. Get your wha-
lers also to collect mud from pancake ice, &c., in the Polar re-
gions: this is always full of interesting microscopic forms.''

449. These little mites of shells seem to form but a slender
clew indeed by which the chambers of the deep are to be thread-
ed, and mysteries of the ocean revealed ; yet the results are sug-
gestive ; in right hands and to right minds, they are guides to
both light and knowledge.

The first noticeable thing the microscope gives of these speci-
mens is, that all of them are of the animal, not one of the mineral
kingdom.

450. The ocean teems with liie, we know. Of the four ele-
ments of the old philosophers— fire, earth, air, and water— perhaps
the sea most of all abounds with living creatures. The space oc-
cupied on the surface of our planet by the different families of
animals and their remains is inversely as the size of the individ-
ual. The smaller the animal, the greater the space occupied by
his remains. Though not invariably the case, yet this rule, to
a certam extent, is true, and will, therefore, answer our present
purposes, which are simply those of illustration. Take the ele-
phant and his remains, or a microscopic animal and his, and com-
pare them. The contrast, as to space occupied, is as striking as
that of the coral reef or island with the dimensions of the whale.
The grave-yard that would hold the corallines is larger than the
grave-yard that would hold the elephants.

451. We notice another practical bearing in this group ofphys-

212 THE PHYSICAL GEOGRAPHY OF THE SEA.

ical facts that Brooke's apparatus fished up from the bottom of the
deep sea. Bailey, with his microscope (§ 448), could not detect
a single particle of sand or gravel among these little mites of
shells. They were from the great telegraphic plateau (§ 446),
and the inference is that there, if any where, the w^aters of the sea
are at rest. There was not motion enough there to abrade these
very delicate organisms, nor current enough to sweep them about
and mix up wdth them a grain of the finest sand, nor the smallest
particle of gravel torn from the loose beds of debris that here and
there strew the bottom of the sea. This plateau is not too deep
for the wire to sink down and rest upon, yet it is not so shallow
that currents, or icebergs, or any abrading force can derange the
wire after it is once lodged.

452. As Professor Bailey remarks, the animalculse, whose re-
mains Brooke's lead has brought up from the bottom of the deep
sea, probably did not live or die there. They would have had no
light there, and, had they liA^ed there, their frail little textures would
have been subjected in their growth to a pressure upon them of a
column of w^ater twelve thousand feet high, equal to the weight of
four hundred atmospheres. They probably lived and died near
the surface, where they could feel the genial influences of both
light and heat, and were buried in the lichen caves below after
death.

453. Brooke's lead and the microscope, therefore, it would
seem, are about to teach us to regard the ocean in a new light.
Its bosom, which so teems with animal life ; its face, upon which
time writes no wrinkles — makes no impression — are, it would now
seem, as obedient to the great law of change as is any department
whatever, either of the animal or the vegetable kingdom. It is
now suggested that, henceforward, we should view the surface of
the sea as a nursery teeming with nascent organisms, its depths as
the cemetery for families of living creatures that outnumber the
sands on the sea-shore for multitude.

Where there is a nursery, hard by there will be found also a
grave-yard — 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.

454. On those parts of the Solid portions of the earth's crust

THE BASIN OF THE ATLANTIC. 213

which are at the bottom of the atmosphere, various agents are at
work, levehng both upward and downward. Heat and cold, rahi
and sunshine, the winds and the streams, all assisted by the forces
of gravitation, are unceasingly wasting away the high places on
the land, and as perpetually filling up the low.

But in contemplating the leveling agencies that are at work
upon the solid portions of the crust of our planet which are at the
bottom of the sea, one is led, at first thought, almost to the con-
clusion that these leveling agents are powerless there.

455. 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 down there that it can not use half its power, as
on the dry land, in tearing the overhanging rock from the preci-
pice and casting it down into the valley below.

When considering the bottom of the ocean, we have, in the ini^
agination, been disposed to regard the waters of the sea as a great
cushion, placed between the air and the bottom of the ocean to pro-
tect and defend it from these abrading agencies of the atmosphere.

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 bold, ragged, and grand. Nothing can fill up the
hollows there ; no agent now at work, that we know of, can de-
scend into its depths, and level off the floors of the sea.

456. But it now seems that we forgot these oceans of animalcu-
Ice, that make the surface of the sea sparkle and glow with life.
They are secreting from its surface sohd matter for the very pur-
pose of filling up those cavities below. These little marine insects
are building their habitations at the surface, and when they die,
their remains, in vast multitudes, sink down and settle upon the
bottom. They are the atoms of which mountains are formed —
plains spread out. Our marl-beds, the clay in our river-bottoms,
large portions of many of the great basins of the earth, are com-
posed of the remains of just such little creatures as these, which
the ingenuity of Brooke and the industry of Berryman have ena-
bled us to fish up from the depth of more than two miles (twelve
thousand feet) below the sea-level.

These foraminiferce, therefore, when living, may have been pre-

214 THE PHYSICAL GEOGRAPHY OF THE SEA.

paring the ingredients for the fruitful soil of a land that some
earthquake or upheaval, in ages far away in the future, may be
sent to cast up from the bottom of the sea for man's use.

The study of these "sunless treasures," recovered w^ith so much
ingenuity from the rich bottom of the sea, suggests nev7 vievrs
concerning the physical economy of the ocean.

457. In the chapter on the Salts of the Sea, p. 150, I endeav-
ored to show how sea-shells and marine insects may, by reason
of the offices which they perform, be regarded as compensations
in that exquisite system of physical machinery by which the har-
monies of nature are preserved.

But the treasures of the lead and revelations of the microscope
present the insects of the sea in a new and still more striking light.
We behold them now serving not only as compensations by w^hich
the motions of the water in its channels of circulation are regu-
lated and climates softened, but acting also as checks and bal-
ances by which the equipoise between the sohd and the fluid
matter of the earth is preserved.

Should it be established that these microscopic creatures live
at the surface, and are only buried at the bottom of the sea, we
may then view them as conservators of the ocean ; for, in the of-
fices which they perform, they assist to preserve its status by
maintaining the purity of its waters.

It is admitted (^ 343) that the salts of the sea come from the
land, and that they consist of the soluble matter which the rains
wash out from the fields, and which the rivers bring down to the
sea.

The waters of the Mississippi and the Amazon, together with
all the streams and rivers of the world, both great and small, hold
in solution large quantities of lime, soda, iron, and other matter.
They discharge annually into the sea an amount of this soluble
matter which, if precipitated and collected into one solid mass,
would no doubt surprise and astonish the boldest speculator with
its magnitude.

458. This soluble matter can not be evaporated. Once in the
ocean, there it must remain ; and as the rivers are continuallv
pouring in fresh supplies of it, the sea, it has been argued, must
continue to become more and more salt.

Now the rivers convey to the sea this solid matter mixed with

THE BASIN OF THE ATLANTIC. 215

fresh water, which, being hghter than that of the ocean, remains
for a considerable time at or near the surface. Here the micro-
scopic organisms of the deep-sea lead are continually at work, se-
creting this same lime and soda, &c., and extracting from the sea
water all this solid matter as fast as the rivers bring it down and
empty it into the sea.

Thus w^e haul up from the deep sea specimens of dead animals,
and recognize in them the remains of creatures which, though invis-
ible 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 saltness of the sea (^ 342).

This view suggests many contemplations. Among them, one
in w^hich the ocean is presented as a vast chemical bath, in which
the solid parts of the earth are w^ashed, filtered, and precipitated
again as solid matter, but in a new form, and with fresh properties.

Doubtless it is only a re-adaptation, though it may be in an im-
proved form, of old, and, perhaps, elFete 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 our
earth is regulated, by w^hich this or that result is brought about
and accomplished in this beautiful system of terrestrial arrange-
ments, we are utterly amazed at the offices which have been per-
formed, the work which has been done, by the animalculae of the
water.

459. But whence come the little calcareous shells which
Brooke's lead has brought up, in proof of its sounding, from the
depth of two miles and a quarter ? Did they live in the surface
waters immediately above ? or is their habitat in some remote part
of the sea, whence, at their death, the currents were sent forth as
pall-bearers, with the command to deposit their remains where
the plummet found them ?

460. In this view, these little organisms become doubly inter-
esting. When dead, the descent of the shell to its final resting-
place would not, it may be supposed, be very rapid. Il would
partake of the motion of the sea water in which it lived and died,
and probably be carried along with it in its channels of circula-
tion for many a long mile.

216 THE PHYSICAL GEOGRAPHY OF THE SEA.

The microscope, under the eye of Ehrenberg, has enabled us
(§ 158) to put talhes on the wings of the wind, to learn of them
somewhat concerning its " circuits."

Now, may not these shells, which were so fine and impalpable
that the officers of the Dolphin took them to be a mass of unctu-
ous clay — may not, I say, these, with other specimens of sound-
ings yet to be collected, be all converted by the microscope into
tallies for the waters of the different parts of the sea, by which
the channels through which the circulation of the ocean is car-
ried on are to be revealed ?

Suppose, for instance, that the dwelling-place of the little shells
which compose this specimen from that part of the ocean be ascer-
tained, by referring to living types, to be the Gulf of Mexico or
some other remote region ; that the habitat and the burial-place,
in every instance, be far removed from each other — by what agen-
cy, except through that of currents, can we suppose these little
creatures — themselves not having the powers of locomotion — to
come from the place of their birth, or to travel to that of their
burial ?

Man can never see — he can only touch the bottom of the deep
sea, and then only with the plummet. Whatever it brings up
thence is to the philosopher matter of powerful interest ; for by
such information alone as he may gather from a most careful ex-
amination of such matter, the amount of human knowledge con-
cerning nearly all that portion of our planet which is covered by
the sea must depend.

Every specimen of bottom from the deep sea is, therefore, tc
be regarded as probabl}^ containing something precious in the wa}-
of contribution to the sources of human knowledge.

THE WINDS. 217

CHAPTER XIIL

THE WINDS.

Plate YIIL, ^ 461. — Monsoons, 462.— Why the Belt of Southeast is broader than the
Belt of Northeast Trade-winds, 463. — Effect of Deserts upon the Trade-winds, 466.
— At Sea the Laws of Atmospherical Circulation are better developed, 470. — R.vin
WixDs : Precipitation on Land greater than Evaporation, 472. — The Place of Sup-
ply for the Vapors that feed the Amazon with Rains, 473. — Monsoons : How
formed, 474. — Monsoons of the Indian Ocean, 475. — How caused, 476. — How the
Monsoon Season may be known, 478, — The Distance to which the Influence of
Deserts upon Winds may be felt at Sea, 479. — "VVTiy there are no Monsoons in the
Southern Hemisphere, 482. — Why the Trade-wind Zones are not stationary, 483.
Thk Calm Belts : Doldrums — a Zone of constant Precipitation, 486. — The Horse
Latitudes, 488.— The Westerly Winds, 490.

461. Plate YIIL is a chart of the wmds, based on information
derived from the Pilot Charts, one of the series of Maury's Wind
and Current Charts. The object of this chart is to make the stu-
dent acquainted with the prevailing direction of the wind in every
part of the ocean.

The arrows of the plate are supposed to fly with the wind ; the
half bearded and half feathered arrows denoting monsoons or pe-
riodic winds ; the dotted bands, the regions of calm and baffling
winds.

462. 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.

Let us commence the study of Plate VIII. by examining the
trade-wind region ; that, also, is the region in which monsoons are
most apt to be found.

463. The belt or zone of the southeast trade-winds is broader,
it will be observed, than the belt or zone of northeast trades.
This phenomenon is explained by the fact that there is more land
in the northern hemisphere, and that most of the deserts of the
earth — as the great deserts of Asia and Africa — are situated in the
rear, or behind the northeast trades ; so that, as these deserts be-
come more or less heated, there is a call — a pulling back, if you

218 THE PHYSICAL GEOGRAPHY OF THE SEA.

please — upon these trades to turn about and restore the equilib-
rium which the deserts destroy. There being no, or few such re-
gions in the rear of the southeast trades, they obey the first im-
pulse, push and press over into the northern hemisphere.

464. By resolving the forces which it is supposed are the prin-
cipal forces that put these winds in motion, viz., calorific action
of the sun and diurnal rotation of the earth, we are led to the con-
clusion that the latter is much the greater of the two in its effects
upon those of the northern hemisphere. But not to such an ex-
tent is it greater in its effects upon those of the southern. We see
by the plate that those tw^o opposing currents of wind are so une-
qually 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 southeast trade-winds
discharge themselves over the equator — i. e., across a great circle
— into the region of equatorial calms, while the northeast trade-
winds discharge themselves into the same region over a parallel
of latitude, and consequently over a small circle. If, therefore,
we take what obtains in the Atlantic as the type of what obtains
entirely around the earth, as it regards the trade-winds, we shall
see that the southeast trade-winds keep in motion more air than
the northeast do, by a quantity at least proportioned to the differ-
ence between the circumference of the earth at the equator and
at the parallel of latitude of 9° north. For if we suppose that
those two perpetual currents of air extend the same distance from
the surface of the earth, and move with the same velocity, a
greater volume from the south would flow across the equator in a
given time than would flow from the north over the parallel of 9°
in the same time ; the ratio between the two quantities would be
as radius to the secant of 9°. Besides this, the quantity of land
lying within and to the north of the region of the northeast trade-
winds is much greater than the quantity within and to the south
of the region of the southeast trade-winds. In consequence of
this, the mean level of the earth's surface within the region of the
northeast trade-winds is, it may reasonably be supposed, somewhat
above the mean level of that part which is within the region of the
southeast trade-winds. And as the northeast trade-winds blow-
under the influence of a greater extent of land surface than the
southeast trades do, the former are more obstructed in their course

THE WINDS. 219

than the latter by the forests, the mountain ranges, unequally
heated surfaces, and other such like inequalities.

465. As already stated, the investigations show that the mo-
mentum of the southeast trade-winds is sufficient to push the equa-
torial limits of their northern congeners back into the northern
hemisphere, and to keep them, at a mean, as far north as the ninth
parallel of north latitude. Besides this fact, they also indicate
that while the northeast trade-winds, so called, make an angle in
their general course of about 23° with the equator (east-north-
east), those of the southeast make an angle of 30° or more with
the equator (southeast by east). I speak of those in the Atlantic,
thus indicating that the latter approach the equator more directly
in their course than do the others, and that, consequently, the ef-
fect of the diurnal rotation of the earth being the same for like
parallels, north and south, the calorific influence of the sun exerts
more power in giving motion to the southern than to the northern
system of Atlantic trade-winds.

466. That such is actually the case is rendered still more prob-
able from this consideration : All the great deserts are in the north-
ern hemisphere, and the land surface is also much greater on our
side of the equator. The action of the sun upon these unequally
absorbing and radiating surfaces in and behind, or to the north-
ward of the northeast trades, tends to retard these winds, and to
draw large volumes of the atmosphere, that otherwise would be
moved by them, back 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 over-
heated hemisphere. The northwest winds of the southern are also
and consequently stronger than the southAvest winds of the north-
ern hemisphere.

467. The investigations that have taken place show that the in-
fluence of the land upon the normal directions of the Avind at sea
is an immense influence. It is frequently traced for a thousand
miles or more out upon the ocean. For instance, the action of
the sun's rays upon the great deserts and arid plains of Africa, in
the summer and autumnal months, is such as to be felt nearly
across the Atlantic Ocean between the equator and the parallel of
13° north. Between this parallel and the equator, the trade- winds
are turned back by the heated plains of Africa, and are caused to

220 THE PHYSICAL GEOGRAPHY OF THE SEA.

blow a regular southwardly monsoon for several months. They
bring the rains which divide the season in these parts of the African
coast. The region of the ocean embraced by the monsoons is cu-
neiform in its shape, having its base resting upon Africa, and its
apex stretching over till within 10° or 15° of the mouth of the
Amazon.

468. Indeed, when we come to study the effects of South Amer-
ica and Africa (as developed by the Wind and Current Charts)
upon the winds at sea, we should be led to the conclusion — had
the foot of civilized man never trod the interior of these two con-
tinents— that the chmate of one is humid ; that its valleys are,
for the most part, covered with vegetation, which protects its sur-
face from the sun's rays ; while the plains of the other are arid
and naked, and, for the most part, act like furnaces in drawing the
winds from the sea to supply air for the ascending columns w^hich
rise from its overheated plains.

469. Pushing these facts and arguments still farther, these
beautiful and interesting researches seem already sufficient almost
to justify the assertion that, were it not for the Great Desert of
Sahara, and other arid plains of Africa, the western shores of that
continent, within the trade-wind region, would be almost, if not
altogether, as rainless and sterile as the desert itself.

These investigations, with their beautiful developments, eagerly
captivate the mind ; giving wings to the imagination, they teach
us to regard the sandy deserts, and arid plains, and the inland ba-
sins of the earth, as compensations in the great system of atmos-
pherical circulation. Like counterpoises to the telescope, which
the astronomer regards as incumbrances to his instrument, these
wastes serve as make-weights, to give certainty and smoothness
of motion — facility and accuracy to the workings of the machine.

470. When we travel out upon the ocean, and get beyond the
influence of the land upon the winds, we find ourselves in a field
particularly favorable for studying the general laws of atmospher-
ical circulation. 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 obstructions to the circulation of the
atmosphere — nothing to disturb it in its natural courses. The sea,
therefore, is the field for observing the operations of the general
laws which govern the movements of the great aerial ocean. Ob-

THE WINDS,

221

servations on the land will enable us to discover the exceptions.
But from the sea we shall get the rule. Each valley, every mount-
ain range and local district, may be said to have its own peculiar
system of calms, winds, rains, and droughts. But not so the sur-
face of the broad ocean ; over it the agents which are at work are
of a uniform character.

471. Rain-avinds are the winds which convey the vapor from
the sea, where it is taken up, to other parts of the earth, where it
is let down either as snow, hail, or rain. As a general rule, the
trade-winds (^ 126) may be regarded as the evaporating winds;
and when, in the course of their circuit, they become monsoons,
or the variables of either hemisphere, they then generally become
also the rain-winds — especially the monsoons — for certain locali-
ties. Thus the southwest monsoons of the Indian Ocean are the
rain- winds for the west coast of the Peninsula (^ 139), In like
manner, the African monsoons of the Atlantic are the winds which
feed the springs of the Niger and the Senegal with rams.

472. Upon every water-shed which is drained into the sea, the
precipitation may be considered as greater than the evaporation,
for the whole extent of the shed so drained, by the amount of wa-
ter which runs off through the river 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, as an expression of the
quantity which is annually evaporated from the sea, carried back
by the winds, and precipitated throughout the whole extent of the
valley that is drained by it. Now, if we knew the rain-winds from
the dry, for each locality and season generally throughout such a
basin, we should be enabled to determine, with some degree of
probability at least, as to the part of the ocean from which such
rains were evaporated. And thus, notwithstanding all the eddies
caused by mountain chains, and other uneven surfaces, we might
detect the general course of the atmospherical circulation over the
land as well as the sea, and make the general courses of circula-
tion in each valley as obvious to the mind of the philosopher as is
the current of the Mississippi, or of any other great river, to his
senses.

473. These investigations as to the rain-winds at sea indicate
that the vapors which supply the sources of the Amazon willi rain
are taken up from the Atlantic Ocean by the northeast and south-

222 THE PHYSICAL GEOGRAPHY OF THE SEA.

east trade-winds ; and many circumstances, some of which have
already been detailed (^ 226), tend to show that the winds which
feed the Mississippi with rains get their vapor in the southeast
trade-wind region of the other hemisphere. For instance, we know
from observation that the trade-wind regions of the ocean, beyond
the immediate vicinity of the land, are, for the most part, rainless
regions, and that the trade-wind zones may be described, in a hy-
etographic sense, as the evaporating regions (§ 32). They also
show, or rather indicate as a general rule, that, leaving the polar
limits of the two trade-wind systems, and approaching the nearest
pole, the precipitation is greater than the evaporation until the
point of maximum cold is reached.

And we know, also, that, as a general rule, the southeast and
northeast trade-winds which come from a lower and go to a higher
temperature are the evaporating winds, i. e., they evaporate more
than they precipitate ; while those winds which come from a high-
er and go to a lower temperature are the rain-winds, ^. e., they
precipitate more than they evaporate. That such is the case, not
only do researches indicate, but reason teaches, and philosophy
tells.

These views, therefore, suggest the inquiry as to the sufficiency
of the Atlantic, after supplying the sources of the Amazon and its
tributaries with their waters, to supply also the sources of the Mis-
sissippi and the St. Lawrence, and of all the rivers, great and small,
of North America and Europe.

A careful study of the rain- winds (^ 32), in connection with the
Wind and Current Charts, will probably indicate to us the " springs
in the ocean" which supply the vapors for the rains that are car-
ried off by those great rivers. " All the rivers run into the sea ;
yet the sea is not full ; unto the place from whence the rivers come,
thither they return again."

474. Monsoons (^ 462) are, for the most part, formed of trade-
winds. When a trade-wind is turned back or diverted by over-
heated districts from its regular course at stated seasons of the
year, it is regarded as a monsoon. Thus the African monsoons
of the Atlantic (Plate VIII.), the monsoons of the Gulf of Mexico,
and the Central American monsoons of the Pacific, are, for the
most part, formed of the northeast trade-winds, which are turned
back to restore the equilibrium which the overheated plains of

THE WINDS. 223

Africa, Utah, Texas, and New Mexico have disturbed. When
the monsoons prevail for five months at a time, for it takes about
a month for them to change and become settled, then both thev
and the trade-M^inds, of which they are formed, are called mon-
soons.

475. The northeast and the southwest monsoons of the Indian
Ocean afford an example of this kind. A force is exerted upon
the northeast trade-winds of that sea by the disturbance 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-w^inds ; it turns them back ; and
were it not for the peculiar conditions of the land about that ocean,
w^hat are now^ called the northeast monsoons would blow the year
round ; there would be no southwest monsoons ; and the northeast
winds, being perpetual, would become all the year, what in reality
for five months (§ 474) they are, viz., northeast trade-winds.

476. The agents which produce monsoons reside (§ 475) on the
land. These wdnds are caused by the rarefaction of the air over
large districts of country situated on the polar edge, or near the
polar edge of the trade- winds. Thus the monsoons of the Indian
Ocean are caused by the intense heat which the rays of a cloud-
less sun produce during the summer time upon the Desert of Gobi
and the burning plains of Central Asia. When the sun is north
of the equator, the force of his rays, beating down upon these wide
and thirsty plains, is such as to cause the vast superincumbent
body of air to expand and ascend. There is, consequently, a rush
of air, especially from toward the equator, to restore the equilib-
rium ; and in this case, the force which tends to draw the north-
east trade-winds back becomes greater than the force which is
acting to propel them forward. Consequently, they obey the
stronger power, turn back, and become the famous southwest
monsoons of the Indian Ocean, which blow from May to Septem-
ber inclusive.

477. Of course, the vast plains of Asia are not brought up to
monsoon heat per saltum, or in a day. They require time both to
be heated up to this point .and to be cooled down again. Hence
there is a conflict for a few weeks about the change of the mon-
soon, when neither the trade-wind nor the monsoon force has
fairly lost or gained the ascendency. This debatable period

224 THE PHYSICAL GEOGRAPHY OF THE SEA.

amounts to about a month at each change. So that the mon-
soons of the Indian Ocean prevail really for about five months
each vv^ay, viz., from May to September from the south w^est, in
obedience to the influence of the overheated plains, and from
November to March inclusive from the northeast, in obedience to
the trade-w^ind force,

478. The monsoon season may be alvrays knov^^n by referring
to the cause vi^hich produces these winds. Thus, by recollecting
where the thirsty and overheated plains are which cause the
monsoons, we know at once that these winds are rushing with
greatest force toward these plains at the time that is the hottest
season of the year upon them.

479. The influence of these heated plains upon the winds at
sea is felt for a thousand miles and more. Thus, though the Des-
ert of Gobi and the sun-burnt plains of Asia are, for the most
part, north of latitude 30°, their influence in making monsoons 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 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.

480. It would appear, therefore, that these desert countries ex-
ercise a powerful influence in checking, and consequently in weak-
ening, the force of the northeast trade-winds. There are no such
extensive influences at work checking the southeast trades. On
the contrary, these are accelerated ; for the same forces that serve
to draw the northeast trade-winds back, or retard them, tend also to
draw the southeast trade-winds on, or to accelerate them. Hence
the ability of the southeast trade-winds to push themselves over
into the northern hemisphere.

481. Hence, also, we infer that, between certain parallels of
latitude in the northern hemisphere, the sun's rays, by reason of
the great extent of land surface, operate with much more intensity
than they do between corresponding parallels in the southern ;
and that, consequently, the mean summer temperature on shore,
north of the equator, is higher than it is south : a beautiful phys-
ical fact which the winds have revealed, in corroboration of what

THE WINDS. 225

observations with the thermometer heid abeady induced meteorol-
ogists to suspect.

482. It appears, from what has been said (§ 474), that it is the
rays of the sun operating upon the land, not upon the water, which
causes the monsoons. Now let us turn to Plate VIIL, and exam-
ine into this view. The monsoon regions are marked with half-
bearded and half-feathered arrows ; and we perceive, looking at
the northern hemisphere, that all of Europe, some of Africa, most
of Asia, and nearly the whole of North America, are to the north,
or on the polar side of the northeast trade-wind zone ; whereas but
a small part of Australia, less of South America, and still less of
South Africa, are situated on the polar side of the zone of south-
east trade-winds. In other words, there are no great plains on
the polar side of the southeast trade-winds upon which the rays
of the sun, in the summer of the other hemisphere, can play with
force enough to rarefy the air sufficiently to materially interrupt
these winds in their course. But, besides the vast area of such
plains in the northern hemisphere, on the polar side of its trade-
wind belt, the heat of which is sufficient (§ 479) to draw these
trade-winds back, there are numerous other districts in the extra-
tropical regions of our hemisphere the summer heat of which,
though it be not sufficient to turn the northeast trade-winds back,
and make a monsoon of them, yet may be sufficient to weaken
them in their force, and, by retarding them (§ 480), draw the south-
east trade- winds over into the northern hemisphere.

483. Now, as this interference from the land takes place in the
summer only, we might infer, without appealing to actual observa-
tion, that the position of these trade-wind zones is variable ; that
is, that the equatorial edge of the southeast trade-wind zones is
farther' to the north in our summer, when the northeast trades are
most feeble, than it is in winter, when they are strongest.

484. We have here, then, at work upon these trade-wind zones,
a force now weak, now strong, which, of course, would cause these
zones to vibrate up and down the ocean, and within certain limits,
according to the season of the year. These limits are given on
Plate VIIL for spring and autumn. During the latter season
these zones reach their extreme northern declination, and in our
spring their utmost limits toward the south.

485. The Calm Belts. — There is between the two systems of

P

226 THE PHYSICAL GEOGRAPHY OF THE SEA.

trade-winds a region of calms, known as the equatorial calms. It
has a mean average breadth of about six degrees of latitude. In
this region, the air which is brought to the equator by the north-
east and southeast trades ascends. This belt of calms always
separates these two trade-wind zones, and travels up and down
with them. If we liken this belt of equatorial calms to an im-
mense atmospherical trough, extending, as it does, entirely around
the earth, and if w^e liken the northeast and southeast trade-winds
to two streams discharging themselves into it, we shall see that
we have two currents perpetually running in at the bottom, and
that, therefore, we must have as much air as the two currents 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-winds.

Using still farther this mode of illustration : if we liken the calm
belt of Cancer and the calm belt of Capricorn each to a great
atmospherical trough extending around the earth also, we shall see
that in this case the currents are running in at the top and out at
the bottom (§ 101).

486. The belt of equatorial calms is a belt of constant precipi-
tation. Captain Wilkes, of the Exploring Expedition, when he
crossed it 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 up-
ward during the year. In the summer months this belt of calms
is found between the parallels of 8° and 1 4° of north latitude, and
in the spring between 5° south and 4° north. (Vide Plate VIII.)

487. This calm belt carries w^ith it the rainy seasons of the tor-
rid zone, always, in its motions from south to north and back, ar-
riving at certain parallels at stated periods of the year ;' conse-
quently, by attentively considering Plate VIII., one can tell what
places within the range of this zone have, during the year, two
rainy seasons, what one, and what are the rainy months for each
locality.

Were the northeast and the southeast trades, W'ith the belt of
equatorial calms, of different colors, and visible to an astronomer
in one of the planets, he might, by the motion of these belts or
girdles alone, tell the seasons with us. He would see them at one
season going north, then appearing stationary, and then commenc-

THE WINDS. 227

ing their return to the south. But, though he Avould observe
(^ 131) that they follow the sun in his annual course, he would
remark that they do not change their latitude as much as the sun
does his declination ; he would, therefore, discover that their ex-
tremes of declination are not so far asunder as the tropics of Can-
cer and Capricorn, though in certain seasons the changes from day
to day are very great. He would observe that these zones of
winds and calms have their tropics or stationary nodes, about
w^hich they linger near three months at a time ; and that they pass
from one of their tropics to the other in a little less than another
three months. Thus he would observe the w^hole system of belts
to go north from the latter part of May till some time in August.
Then they w^ould stop and remain stationary till winter, in Decem-
ber ; when again they would commence to move rapidly over the
ocean, and down toward 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.

488. The Horse Latitudes. — Having completed the physical
examination of the equatorial calms and winds, if the supposed ob-
server should now turn his telescope toward the poles of our earth,
he would observe a zone of calms bordering the northeast trade-
winds on the north (§ 100), and another bordering the southeast
trade-w4nds on the south (§ 106). These calm zones also w^ould
be observed to vibrate up and down with the trade-wind zones,
partaking (§ 130) of their motions, and following the declination
of the sun.

On the polar side of each of these two calm zones there w^ould
be a broad band extending up into the polar regions, the prevail-
ing winds within w-hich are the opposites of the trade-winds, viz.,
southwest in the northern and northwest in the southern hemi-
sphere.

489. 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 (^ 101) the winds blow perpetually toward the equator; on
the other, their prevailing direction is toward the poles. They are
called (§ 101) the "horse latitudes" by seamen.

490. Along the polar borders of these two calm belts (^ 129)
we have another region of precipitation, though generally the rains
Ifcre are not so constant as they are in the equatorial calms. The ^

228 THE PHYSICAL GEOGRAPHY OF THE SEA.

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 sea-
son of that parallel, if it be in winter, is said to commence. Hence
we may explain the rainy season in Chili at the south, and in Cal-
ifornia at the north.

491, The Westerly Winds. — To complete the physical ex-
amination of the earth's atmosphere, which we have supposed an
astronomer in one of the planets to have undertaken according to
the facts developed by the Wind and Current Charts, it remains
for him to turn his telescope upon the southwest passage winds of
the northern hemisphere, pursue them into the arctic regions, and
see theoretically how they get there, and, being there, what be-
comes of them.

From the parallel of 40° up toward the north pole, the prevail-
ing winds, as already remarked, are the southw^est passage winds
(Plate VIIL), or, as they are more generally called by mariners,
the " westerly" winds ; these, in the Atlantic, prevail over the
" easterly" winds in the ratio of about two to one.

Now if we suppose, and such is probably the case, these "west-
erly" winds to convey in two days a greater volume of atmosphere
toward the arctic circle than those " easterly" winds can bring
back in one, we establish the necessity for an upper current by
which this difference may be returned to the tropical calms of our
hemisphere (^ 109). Therefore there must be some place in the
polar regions (§ 112) at which these southw^est winds cease to go
north, and from which they commence their return to the south,
and this locality must be in a region pecuharly liable to calms.
It is another atmospherical node in which the motion of the air is
upward, with a decrease of barometric pressure. It is marked P,
Plate I.

If we now return to the calm belt of the northern tropic, and
trace theoretically a portion of air that, in its circuit, shall fairly
represent the average course of these southwest passage winds, we
shall see (§ 113) that it approaches the pole in a loxodromic curve ;
that as it approaches the pole, it acquires, from the spiral convolu-
tions of this curve which represents its path, a w^hirling motion, in
a direction contrary to that of the hands of a watch ; and that the
portion of atmosphere whose path we are following would grad-^

THE WINDS.

229

ually contract its gyrations, until it would finally ascend, turning
against the hands of a watch as it whirls around.

In the southern hemisphere a like process is going on ; only
there, the northwest passage wind would, as it arrives near the
antarctic calms, acquire a motion with the sun, or in the direction
of the hands of a watch.

230 THE PHYSICAL GEOGRAPHY OF THE SEA.

PLATE IV.

THE CLIMATES OF THE OCEAN. 231

CHAPTER XIV.

THE CLIMATES OF THE OCEAN.

Gulf Stream likened to the Milky Way, <J 492. — March and September the hottest
Months in the Sea, 496. — How the Isothermal Lines move up and down the Ocean,
498. — A Line of invariable Temperature, 508. — How the western Half of the At-
lantic is heated up, 509. — The Relation between a Shore-line in one part of the
World and Climates in another, 512. — The Climate of Patagonia, 516.— The Sum-
mer of the northern Hemisphere warmer than the Summer of the southern, indi-
cated by the Sea, 521. — How the cold Waters from Davis's Straits press upon the
Gulf Stream, 522. — How the different Isotherms travel from North to South wit^
the Seasons, 523.— The Polar and Equatorial Drift, 524.

492. Thermal charts, showing the temperature of the surface
of the Atlantic Ocean by actual observations made indiscrimin-
ately 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 some of w^hich are traced on Plate
IV., afford the navigator and the philosopher much valuable and
interesting information touching the circulation of the oceanic wa-
ters, including the phenomena of the cold and warm sea currents ;
they also cast light upon the climatology of the sea, its hyeto-
graphic peculiarities, and the climatic conditions of various regions
of the earth ; they show that the profile of the coast-line of inter-
tropical America assists to give expression to the mild climate of
Southern Europe ; they also increase our knowledge concerning
the Gulf Stream, for it enables us to mark out, for the mariner's
guidance, the " Milky Way" in the ocean, the waters of which
teem, and sparkle, and glow with life and incipient organisms as
they run across the Atlantic. In them are found the clusters and
nebulae of the sea which stud and deck the great highway of ships
on their voyage between the Old World and the New^ ; and these
lines assist to point out for the navigator their hmits and his way.
They show this via lactea to have a vibratory motion that calls to
mind the graceful w^avings 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 sta-
tionary there, and then liken the tail of the Stream itself to an im-

232 THE PHYSICAL GEOGRAPHY OF THE SEA.

mense 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. Run-
ning between banks of cold water (^ 1), it is pressed now from
the north, now from the south, according as the great masses of
sea matter on either hand may change or fluctuate in temperature.

493. In September, when the w^aters in the cold regions of the
north have been tempered, and made warm and light by the heat
of summer, its limits on the left (Plate VI ) are as denoted by the
line of arrows ; 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 within the channel marked out
for them.

494. Thus it acts like a pendulum, slowly propelled by heat on
one side and repelled by cold on the other. In this view, it be-
comes the chronograph of 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, swinging from north to south
and from south to north, a great self-regulating, self-compensating
pendulum.

495. In seeking information concerning the climates of the
ocean, it is well not to forget this remarkable contrast between its
climatology and that of the land, viz. : on the land, February and
August are considered the coldest and the hottest months ; but to
the inhabitants of the sea, the annual extremes of cold and heat
occur in the months of March and September. On the dry land,
after the winter " is past and gone," the solid parts of the earth
continue to receive from the sun more heat in the day than they
radiate at night, consequently there is an accumulation of caloric,
which continues to increase until August. The summer is noAv
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 w4th
their heat faster than the rays of the sun can impart fresh sup-
plies, and, consequently, the climates which they regulate grow
cooler and cooler until the dead of winter again.

496. But at sea a diff'erent 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
sfrow warmer for a month after the weather on shore has besrun

THE CLIMATES OF THE OCEAN. 233

to get cool. This brings the highest temperature to the sea in
September, the lowest in March. Plate IV. is intended to show
the extremes of heat and cold to which the waters — not the ice —
of the sea are annually subjected, and therefore the isotherms of
40°, 50°, 60°, 70°, and 80° have been drawn for March and Sep-
tember, the months of extreme heat and extreme cold to the in-
habitants of the "great deep." Corresponding isotherms for an}^
other month will fall between these, taken by pairs. Thus the
isotherm of 70° for July will fall nearly between the same iso-
therms (70°) for March and September.

497. A. careful study of this plate, and the contemplation of the
benign influences 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 answ^er with fidelity its marvelous adaptations.

498 How, let us inquire, does the isotherm 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 flow^s 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 agents
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 to the poles, softening, and mitigating, and temper-
ing chmates by the w^ay. The provision for this is as beautiful
as it is benign ; for, to answer a physical adaptation, it is provided
by a law of nature that when the temperature of water is raised,
it shall expand ; as it expands, it must become lighter, and just in
proportion as its specific gravity is altered, just in that proportion
is equilibrium in the sea destroyed. Arrived at this condition, it
is ordained that this hot w^ater shall obey another law^ of nature,
which requires it to run away, and hasten to restore that equilib-
rium. Were these isothermal lines moved only by the rays of the
sun, they w^ould slide up and down the ocean hke so many paral-

234 THE PHYSICAL GEOGRAPHY OF THE SEA.

lels of latitude — at least there would be no breaks in them, like that
which w^e 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, w^ith its waters, never does
attain the temperature of 80° in September. Moreover, this iso-
therm of 80° will pass, in the North Atlantic, from its extreme
southern to its extreme northern declination — nearly two thou-
sand miles — in about three months. Thus it travels at the rate
of about twenty-two miles a day. Surely, w^ithout the aid of cur-
rents, the rays of the sun could not drive it along that fast.

499. Being now left to the gradual process of cooling by evap-
oration, atmospherical contact, and radiation, it occupies the other
eight or nine months of the year in slowly 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 move-
ment at which this line travels on its march south.

500. Between the meridians of 25° and 30° west, the isotherm
of 60° in September ascends as high as the parallel of 56°. In
October it reaches the parallel of 50° north. In November it is
found between the parallels of 45° and 47°, and by December it
has nearly reached its extreme southern descent between these
meridians, w^hich 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.

501. 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 there-
fore 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 mo-
tion, and in the season of the slow motion principally by a grad-

THE CLIMATES OF THE OCEAN 335

ual process of calorific absorption on the one hand, and by a grad-
ual process of cooling on the other.

502. We have precisely such phenomena exhibited by the wa-
ters 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 over-
lapping the usual limits of the Gulf Stream. The outer edge of
this cold water, though jagged, is circular in its shape, having its
centre near the mouth of the Bay. The waters of the Bay, being
fresher than those of the sea, may, therefore, though colder, be
lighter than the warmer waters of the ocean. And thus we have
repeated here, though on a smaller scale, the phenomenon as to the
flow of cold waters from the north, which force the surface iso-
therm of 60° from latitude 56° to 40° during three or four months.

503. Changes in. the color or depth of the water, and the shape
of the bottom, &:c., would also cause changes in the temperature
of certain parts of the ocean, by increasing or diminishing the ca-
pacities of such parts to absorb or radiate heat ; and this, to some
extent, would cause a bending, or produce irregular curves in the
isothermal lines.

504. After a careful study of this plate, and the Thermal Charts
of the Atlantic Ocean, from which the materials for this plate were
derived, I am led to infer that the mean temperature of the atmos-
phere 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 Fah-
renheit, and upward, from January to August, and that the heat
which the waters of the ocean derive from this source — atmos-
pherical contact and radiation — is one of the causes which move
the isotherm of 60° from its January to its September parallel.

505. It is wxll to consider another of the causes Avhich are at
work upon the currents in this part of the ocean, and which tend
to give the rapid southwardly motion to the isotherm of 60°. We
know the mean dew-point must always be below the mean tem-
perature 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

236 THE PHYSICAL GEOGRAPHY OF THE SEA.

each isotherm be 5° lower than the mean temperature, we should
then have the atmosphere which crosses the isotherm of 60°, with
a mean dew-point of 55°, gradually precipitating its vapors 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 VIII.) ; in other words, it is from the higher to the lower
isotherms. Passing, therefore, from a higher to a lower tempera-
ture over the ocean, the total amount of vapor deposited by any
given volume of atmosphere, as it is blown from the vicinity of
the tropical toward that of the polar regions, is greater than that
which is taken up again.

506. The area comprehended on Plate VIII. between the iso-
therms of 40° and 50° Fahrenheit is less than the area compre-
hended between the isotherms 50° and 60°, and this, again, less
than the area between this last and 70°, for the same reason that
the area between the parallels of latitude 50° and 60° is less than
the area between the parallels of latitude 40° and 50° ; therefore,
more rain to the square inch ought to fall upon the ocean between
the colder isotherriis of 10° diiference, than between the warmer
isotherms of the same difference. This is an interesting and an
important view, therefore let me make myself clear : the aqueous
isotherm of 50°, in its extreme northern reach, touches the paral-
lel of 60° north. Now between this and the equator there are
but three isotherms, 60°, 70°, and 80°, with the common differ-
ence of 10°. But between the isotherm of 40° and the pole, there
are at least five others, viz., 40°, 30°, 20°, 10°, 0°, with a com-
mon difference of 10°. Thus, to the north of the isotherm 50°,
the vapor which would saturate the atmosphere from zero, and
perhaps far below, to near 40°, is deposited, while to the south of
50° the vapor which would saturate it from the temperature of
50° up to that of 80° can only be deposited. At least, such would
be the case if there were no irregularities of heated plains, mount-
ain ranges, land, &c., to disturb the laws ^of atmospherical circu-
lation as they apply to the ocean.

507. Having therefore, theoretically, at sea more rain in high

THE CLIMATES OF THE OCEAA. 237

latitudes, we should have more clouds ; and therefore it would re-
quire a longer time for the sun, with his feeble rays, to raise the
temperature of the cold water, which, from September to January,
has brought the isotherm of 60° from latitude 56° to 40°, than it
did for these cool surface currents to float it down. After this
southward motion of the isotherm of 60° has been checked in De-
cember by the cold, and after the sources of the current which
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, and increases its power
as well in intensity as in duration.

Thus, in studying the physical geography of the sea, we have
the effects of night and day, of clouds and sunshine, upon its cur-
rents and its climates, beautifully developed. These effects are
modified by the operations of certain powerful agents which re-
side upon the land ; nevertheless, feeble though those of the for-
mer class may be, a close study of this plate will indicate that they
surely exist.

508. Now^, returning toward the south : we may, on the other
hand, infer that the mean atmospherical temperature for the par-
allels 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 be-
tween the isotherm of 80° in August and the isotherm of 60° in
January, a line or belt of invariable or nearly invariable temper-
ature, which extends on the surface of the ocean from one side of
the Atlantic to the other. This line or band may have its cycles
also, but they are probably of long and uncertain periods.

509. The fact has been pretty clearly established by the dis-
coveries to which the wind and current charts have led, that the
western half of the Atlantic Ocean is heated up, not by the Gulf
Stream alone, as is generally supposed, but by the great equato-
rial 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 hne — to the
west of the meridian of Cape St. Roque, is above its highest reach
to the cast of that meridian. And now that we have the fact, how
obvious, beautiful, and striking is the cause !

238 THE PHYSICAL GEOGRAPHY OF THE SEA.

Cape St. Roque is in 5° south. Now study the configuration
of the Southern American Continent from this Cape to the Wind-
ward Islands of the West Indies, and take into account also cer-
tain 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 es-
cape 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 direction as they do to the east of 35°
west, for here there is a space, about 18 degrees of longitude
broad, in which the sea is clear both to the north and south.

510. They must consequently flow north. A mere inspection
of the plate is sufficient to make obvious the fact that the warm
waters which are found east of the usual limits assigned the Gulf
Stream, and between the parallels of 30° and 40° north, do not
come from the Gulf Stream, but from this great equatorial cal-
dron, which Cape St. Roque blocks up on the south, and which
forces its overheated w^aters up to the fortieth degree of north lat-
itude, not through the Caribbean Sea and Gulf Stream, but over
the broad surface of the left bosom of the Atlantic Ocean.

511. Here we are again tempted to pause and admire the beau-
tiful revelations which, in the benign system of terrestrial adapta-
tion, these researches into the physics of the sea unfold and spread
out before us for contemplation. In doing this, we shall have a
free pardon from those at least who delight '' to look through na-
ture up to nature's God."

What tw^o 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 be-
tween the tw^o are the most intimate, but makes us acquainted
with the arrangements by which such relations are established.

512. The barrier which the South American shore-line opposes
to the escape, on the south, of the hot waters from this great equa-
torial 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 with a mantle of w^armth

THE CLIMATES OF THE OCEAN. 239

above summer heat as far up as the parallel of 40°. 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 west-
wardly winds and eastwardly currents are sent to perform their
office in this benign arrangement. Though unstable and capri-
cious to us they seem to be, they nevertheless " fulfill His com-
mandments" with regularity and perform their offices with cer-
tainty. In tempering the climates of Europe with heat in winter
that has been bottled away in the waters of the ocean during sum-
mer, they are to be regarded as the flues and the regulators for
distributing at the right time, and at the right places, in the right
quantities.

513. By March, when "the winter is past and gone," the fur-
nace which had been started by the rays of the sun in the pre-
vious summer, and which, by autumn, had heated up the ocean
in our hemisphere, has gone down. The caldron of St. Roque,
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 ex-
plained, have contracted their limits. The surface of heated wa-
ter 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 up-
ward, is not to be found in early spring on this side of the parallel
of 8° north.

514. The isotherm of 80° in March, after quitting the Caribbean
Sea, runs parallel with the South American coast toward Cape
St. Roque, 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 hemi-
sphere ; observations show that the process of heating the water
in this great caldron for the next winter is now about to commence.

515. In the mean time, so benign is the system of cosmical ar-
rangements, another process of raising the temperature of Europe
commences. The land is more readily impressed than the sea by
the heat of the solar rays ; at this season, then, the summer cli-
mate due these transatlantic latitudes is modified by the action of

240 THE PHYSICAL GEOGRAPHY OF THE SEA.

the sun's rays directly upon the land. The land receives heat
from them, but, instead of having the capacity of water for retain-
ing it, it imparts it straightvv^ay to the air ; and thus the proper cli-
mate, 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 is again heated and
brought into the state for supplying the means of maintaining the
needful temperature in Europe during the absence of the sun in
the other hemisphere.

516. In like manner, the Gulf of Guinea forms a caldron and a
furnace, and spreads out over the South Atlantic an air-chamber
for heating up in winter and keeping w^arm the extra-tropical re-
gions of South America. Every traveler has remarked upon the
mild climate of Patagonia and the Falkland Islands.

" Temperature in high southern latitudes," 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 seem to be no extremes of heat and cold, as at the
north. Newport, R. L, for instance, latitude 41° north, longitude
71° west, and Rio 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 Islands (latitude 51-2° south), thou-
sands of bullocks, sheep, and horses are running wild over the
country, gathering a living all through the winter."

517. The water in the equatorial caldron of Guinea can not
escape north — the shore-line w^ill not permit it. It must, there-
fore, overflow to the south, as that of St. Roque does to the north,
carrying to Patagonia and the Falkland Islands, beyond 50° south,
the winter climate of Charleston, South Carohna, on our side of
the North Atlantic, or of the " Emerald Island" on the other.

All geographers have noticed, and philosophers have frequently
remarked upon the conformity, as to the shore-line profile, of equa-
torial America and equatorial Africa.

518. It is true, we can not now tell the reason, though explana-
tions founded upon mere conjecture have been offered, why there
should be this sort of jutting in and jutting out of the shore-line, as

THE CLIMATES OF THE OCEAN. 241

at Cape St. Roque and the Gulf of Guinea, on opjoosite sides of the
Atlantic ; but one of the purposes, at least, which this peculiar con-
figuration was intended to subserve, is without doubt now revealed
to us.

519. 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,
tempers 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 de-
sign, those benign and beautiful arrangements, by which the cli-
mate 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.
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 m placing
the desert and the pool w^here they are, but the conviction is
forced upon him also, that every hill and valley, with the grass-
upon its sides, have each its office to perform in the grand design.

520. March is, in the southern hemisphere, the first month of
autumn, as September is with us ; consequently, we should ex-
pect to find in the South Atlantic as large an area of water of 80-^
and upward in March, as w^e should find in the North Atlantic for
September. But do Ave ? By no means. The area on this side
of the equator is nearly double that on the other.

521. Thus we have the sea as a witness to the fact that the
w^inds (^ 196) had proclaimed, viz., that summer in the northern
hemisphere is hotter than summer in the southern, for the rays of
the sun raise on this side of the equator double the quantity of sea
surface to a given temperature that they do on the other side ; at
least this is the case in the Atlantic. Perhaps the breadth of the
Pacific Ocean, the absence of large islands in the temperate re-
gions north, the presence of New Holland, with Polynesia in the
South Pacific, may make a diff'erence there. But of this I can
not now speak, for thermal charts of that ocean have not yet been
prepared.

522.* Pursuing the study of the climates of the sea, let us now
turn to Plate VI. Here we see at a glance how the cold waters.

Q

242 THE PHYSICAL GEOGRAPHY OF THE SEA.

as they come down from the Arctic Ocean through Davis's Straits,
press upon the warm waters of the Gulf Stream, and curve then-
channel into a horse-shoe. Navigators have often been struck
with the great and sudden changes in the temperature of the wa-
ter 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 not now made to
appear ! This " bend" is the great receptacle of the icebergs which
drift down from the north ; covering frequently an area of hund-
reds 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 pen-
insula, or tongue of cold w^ater 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° longitude. By its discovery we have clearly unmasked
the very seat of that agent which produces the Newfoundland fogs.
It is spread out over an area frequently embracing several thou-
sand square miles in extent, covered with cold water, and sur-
rounded on three sides, ^t least, with an immense body of w^arm.
May it not be that the proximity to each other of these two very
unequally heated surfaces out upon the ocean would be attended
by atmospherical phenomena not unlike those of the land and sea
breezes ? These warm currents of the sea are pow^erful meteoro-
logical agents. I have been enabled to trace, in thunder and light-
ning, the influence of the Gulf Stream in the eastern half of the
xitlantic, as far north as the parallel of 55° north ; for there, in
the dead of winter, a thunder-storm is not unusual.

523. These isothermal lines of 50°, 60°, 70°, 80°, &c., may
illustrate for us the manner in which the climates in the ocean are
regulated. Like the sun in the ecliptic, they travel up and down
the sea in declination, and serve the monsters of the deep for signs
and for seasons.

524. It should be borne in mind that the lines of separation, as
drawn on Plate IX., between the cool and warm waters, or, more
properly speaking, between the channels representing the great
polar and equatorial flux and reflux, are not so sharp in nature as
this plate would represent them. In the first place, the plate rep-

THE CLIMATES OF THE OCEAN.

243

resents the mean or average limits of these constant flows — poUir
and equatorial ; whereas, with almost every w^ind that blows, and
at every change of season, the line of meeting between their wa-
ters 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 vari-
able and unstable as to position, and as to shape rough and jag-
ged, and oftentimes deeply articulated. In the sea, the hne 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 with a free
hand, for the purpose of showing the general direction and po-
sition of the channels in the sea, through which its great polar and
equatorial circulation is carried on.

525. Now% continuing for a moment our examination of Plate
IV., w^e are struck with the fact that most of the thermal lines there
drawn run from the western side of the Atlantic toward the east-
ern, in a northeastwardly direction, and that, as they approach the
shores of this ocean on the east, they again turn down for lower
latitudes and w^armer 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 (^ 509) 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 reg-
ulate 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 with warmth, and to
keep up the system of beneficent and wholesome circulation de-
signed for the ocean.

244 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER XV.

THE DRIFT OF THE SEA.

Object of Plate IX., ^ 528. — The Eastern Edge of the Gulf Stream sometimes visi-
ble, 529. — The Polar Drift about Cape Horn, 533. — How the Polar Waters drift
into the South Atlantic, and force the Equatorial aside, 535. — How this is accom-
plished, 537. — A Harbor in a Bend of the Gulf Stream for Icebergs, 539. — Why
Icebergs are not found in the North Pacific, 540. — The Womb of the Sea, 541. —
Drift of warm Waters out of the Indian Ocean, 543. — A Suggestion from Lieu-
tenant Jansen, of the Dutch Navy, 544. — A Current of warm Water sixteen hund-
red Miles wide, 545. — The Pulse of the Sea, 546. — How the Gulf Stream beats
Time, 547.— The Circulation of the Sea likened to that of the Blood, 548.— The
Fisij : Number of Vessels engaged in the Fisheries of the Sea, 551. — The Sperm
Whale delights in warm Water, 552. — The Torrid Zone impassable to the Right
Whale, 553.

526. There is a movement of the waters of the ocean which,
though it be a translation, yet does not amount to what is know"n
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.

527. If we imagine an object to be set adrift in the ocean at the
equator, and if we suppose that it be of such a nature that it would
obey only the influence of sea water, and not of the winds, this
object, I imagine, would, in the course of time, find its way to the
icy barriers aboyt the poles, and again back among the tepid wa-
ters of the tropics. Such an object would illustrate the drift of
the sea, and by its course would indicate the route which the sur-
face waters of the sea follow in their general channels of circula-
tion to and fro between the equator and the poles.

528. The object of Plate IX., therefore, is to illustrate, as far
as the present state of my researches enables me to do, the cir-
culation of the ocean, as influenced by lieat and cold, and to in-
dicate the routes by which the overheated waters of the torrid
zone escape to cooler regions, on one hand, and on the other, the
great channel ways through which the same waters, after havins"

THE DRIFT OF THE SEA. 245

been deprived of this heat in the extra-tropical or polar reoions,
return again toward the equator ; it being assumed that the drift
or flow is from the poles when the temperature of the surface
water is heloio, and from the equatorial regions when it is above
that due the latitude. Therefore, in a mere diagram, as this plate
is, the numerous eddies and local currents which are found at sea
are disregarded.

529. Of all the currents in the sea, the Gulf Stream is the best
defined ; its hmits, 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-fifth degree of latitude, are quite distinct, be-
ing often visible to the eye. The Gulf Stream shifts its channel
(§ 53), but nevertheless its banks are often very distinct. As I
write these remarks, the abstract log of the ship Herculean (Will-
iam M. Chamberlain), from Callao to Hampton Roads, in May,
1854, is received. On the eleventh of that month, being in latitude
33° 39^ north, longitude 74"^ 56^ west (about one hundred and thirty
miles east of Cape Fear), he remarks :

" Moderate breezes, smooth sea, and fine v^eather. 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."

530. In this diagram, therefore, I have thought it useless to at-
tempt a delineation of any of those currents, as the Rennell Cur-
rent of the North Atlantic, the " connecting current" of the South,
" Mentor's Counter Drift," Rossel's Drift of the South Pacific, &c.,
which run now this way, now that, and w^hich are frequently not
felt by navigators at all.

531. In overhauling the log-books for data for this chart, I have
followed, vessels with the w^ater thermometer to and fro across the
seas, and. taken the registrations of it exclusively for my guide,
without regard to the reported set of the currents. When, in any
latitude, the temperature of the water has appeared too high or too
low for that latitude, the inference has been that sucli 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

246 THE PHYSICAL GEOGRAPHY OF THE SEA.

channels of circulation in the ocean. If too warm, it is supposed
(§ 528) that it had its temperature raised in warmer latitudes, and
therefore the channel in which it is found leads from the equato-
rial regions.

532. On the other hand, if the water be too cool for the latitude,
then the inference is that it has lost its heat in colder climates, and
therefore is found in channels which lead from the polar regions.

The arrow-beards point to the direction in which the waters are
supposed to flow. Their rate, according to the best information
that I have obtained, is, at a mean, only cibout four knots a day —
rather less than more.

533. Accordingly, therefore, as the immense volume of water in
the Antarctic regions is cooled down, it commences to flow north.
As indicated by the arrow-heads, it strikes against Cape Horn, and
is divided by the continent, one portion going along the west coast
as Humboldt's Current (§ 267) ; the other, entering the South At-
lantic, 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 w^armer 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 diff'erence of
the specific gravity at the two places. If, for instance, these wa-
ters, when they commence their flow from the hyperborean re-
gions, 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 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 opposite scales, this hot water must now return to re-
store that equilibrium which it has destro3^ed in the sea by rising
from 30° to 80° or 85°.

534. 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 traveling from the poles to the equator they
partake of the temperature of the latitudes through which they
flow, and grow warm.

THE DRIFT OF THE SEA. 247

535. 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 compeUing the warm to escape along the land at the
sides, as well as occasionally in the middle.

536. 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
current from Baffin's Bay upon the Gulf Stream is strikingly beau-
tiful.

537. Why is it that these polar and equatorial waters should
appear now to divide and now to be divided ? The Gulf Stream
has revealed to us a fact in which the answer is involved. We
learn from that stream that cold and warm sea waters are, in a
measure (§ 53), like oil and vinegar ; that is, there is among the
particles of sea water at a high temperature, and among the par-
ticles of sea water at a low temperature, a peculiar molecular ar-
rangement that is antagonistic to the free mixing up of cold and
hot together. At any rate, that salt waters of different tempera-
tures do not readily intermingle at sea is obvious.

538. Does not this same repugnance exist, at least in degree, be-
tween these bodies of cold and warm water of the plate ? And if
so, does net the phenomenon we are considering resolve itself into
a question of masses ? The volume of w^arm water in the North
Atlantic is greater than the volume of cold water that meets and
opposes it ; consequently, the warm thrusts the cold aside, divid-
ing and compelling it to go round. The same thing is repeated
in the North Pacific, whereas the converse obtains in the South
Atlantic. Here the great polar flow, after having been divided
by the American Continent, enters the Atlantic, and filling up
nearly the whole of the immense space between South America
and Africa, seems to press the warm waters of the tropics aside,
compelling them to drift along the coast on either hand.

539. Another feature of the sea expressed by this plate is a
sort of reflection or recast of the shore-line in the temperature of
the water. This feature is most striking in the North Pacific and
Indian Ocean. The remarkable intrusion of the cool into the vol-

248 THE PHYSICAL GEOGRAPHY OF THE SEA.

ume of warm waters to the southward of the Aleutian Islands, is
not unlike that which the cool waters from Davis's Straits make
in the Atlantic upon the Gulf Stream. As I write, I receive from
Captain N. B. Grant the abstract log of ihe American ship Lady
Arbella, bound from Hamburg to New York, in May, 1854. In
sailing through this "horse-shoe," or bend in the Gulf Stream
(^ 522), he 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 continues, "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."

540. This " horse-shoe" of cold in the warm water of the North
Pacific, though extending 5 degrees farther toward the south, can
not be the harbor for such icebergs. The cradle of those of the
Atlantic was perhaps in the Frozen Ocean, for they may have
come thence through Baffin's Bay. But in the Pacific there is no
nursery for them. The w^ater 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 favor the formation of large bergs.
But, though we do not find in the North Pacific the physical con-
ditions which generate icebergs like those of the Atlantic, we find
them as abundant with fogs. The line of separation betw^een the
warm and cold water assures us of these conditions.

541. What beautiful, grand, and benign ideas do we not see ex-
pressed in that immense body of warm waters 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 conti-
nents and to spare, its tepid waters teem with nascent organ-
isms.* They sometimes swarm so thickly there that they change

* " It is the realm of reef-building corals, and of the wondrously-beautiful assem-
blage of animals, vertebrate and invertebrate, that live among them or prey upon them.
The brightest and most definite arrangements of color are here displayed. It is the
seat of maximum development of the majority of marine genera. It has but few re-

THE DRIFT OF THE SEA. 249

the color of the sea, making it crimson, brown, black, or white,
according to their own hues. These patches of colored 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 Brus-
sels Conference deemed them an object worthy of attention, and
recommended special observations with regard to them.

The discolorations of which I speak are no doubt caused by
organisms of the sea, but whether w^holly animal or wholly vege-
table, or whether sometimes the one and sometimes the other, has
not been satisfactorily ascertained. I have had specimens of the
coloring matter sent to me from the pink-stained patches of the
sea. They were animalculse well defined. Quantities of slimy,
red coloring matter are, at certain seasons of the year, washed
up along the shores of the Red Sea, w^hich Dr. Ehrenberg, after an
examination under the microscope, pronounces to be a very deli-
cate kind of sea weed : from this matter that sea derives its name.
So also the Yellow Sea. Along the coasts of China, yellowish col-
ored spots are said not to be uncommon. I know^ of no examina-
tion of this coloring matter, however. In the Pacific Ocean I have
often observed these discolorations of the sea. Red patches of
water are most frequently met wdth, but I have also observed white
or milky appearances, which at night I have known greatly to
alarm navigators, they taking them for shoals.

542. These teeming waters bear off through their several chan-
nels the surplus heat of the tropics, and disperse it among the
icebergs of the Antarctic. See the immense equatorial flow to
the east of New Holland. 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 Hum-
boldt Current, or the ice-bearing current 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 was enabled to penetrate so
much farther south than Captain Wilkes, on his voyage to the

lations of identity with other provinces. The Red Sea and Persian Gulf are its off-
sets."— From Professor Forbes's Paper on the '' Distribution of Marine Life." Plate
31st, Johnston's Physical Atlas, 2d ed. : Win. Blackwood & Sons, Edinburgh aiul
London, 18.54.

250 THE PHYSICAL GEOGRAPHY OF THE SEA.

Antarctic, and it is upon these waters that that sea is to be pene-
trated, if ever. 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 tow^ard 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.

543. The warm flow to the south from the middle of the In-
dian Ocean is remarkable. Masters who return their abstract logs
to me mention sea weed, which I suppose to be brought down by
this current, as far as 45° south. There it is generally, but not
always, about 5 degrees warmer than the ocean along the same
parallel on either side.

544. But the most unexpected discovery of all is that of the
warm flow along the west coast of South Africa, its junction with
the Lagullas current, called, higher up, the Mozambique, and then
their starting off as one stream to the southward. The prevalent
opinion used to be that the Lagullas current, which has its genesis
in the Red Sea (§ 55), 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 to me a few months ago 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. Cap-
tain N. B. Grant, in the admirably well-kept abstract log of his
voyage from New York to Australia, found this current remarka-
bly developed. He w^as astonished at the temperature of its wa-
ters, 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 southwest swell would naturally give it a northerly direc-
tion. But why the water should be loarmer here (38° 40^ south)
than between the parallels of 35° and 37° south is a problem that,
in my mind, admits not of so easy solution, especially if my sus-

, THE DRIFT OF THE SEA. 251

picions are true in regard to the northerly set. I shall look with
much interest for a description of the ' currents' in this part of the
ocean."

545. In latitude 38° south, longitude 6° east, he found the wa-
ter at 56°. His course thence was a little to the south of east, to
the meridian of 41° east, at its intersection with the parallel of 42°
south. Here his water thermometer stood at 50°, but between
these two places it ranged at 60° and upward, being as high on the
parallel of 39° as 73°. Here, therefore, was a stream — a mighty
"river in the ocean" — one thousand six hundred miles across from
east to west, having water in the middle of it 23° higher than at
the sides. This is truly a Gulf Stream contrast. What an im-
mense escape of heat from the Indian Ocean, and what an influx
of warm w^ater into the frozen regions of the south ! This stream
is not always as broad nor as w^arm as Captain Grant found it.
At its mean stage it conforms more nearly to the limits assigned
it in the diagram (Plate IX.).

546. We have, in the volume of heated water reported by Cap-
tain Grant, who is a close and accurate observer, an illustration of
the sort of spasmodic efforts — the heaves and throes — which the
sea, in the performance of its ceaseless task, has sometimes to
make. By some means, the equilibrium of its w^aters, at the time
of Captain Grant's passage, December — the southern summer —
1852, appears to have been disturbed to an unusual extent ; hence
this mighty rush of overheated waters from the great inter-tropical
caldron of the two oceans down toward the south.

Instances of commotion in the sea at uncertain intervals — the
making, as it were, of efforts by fits and starts to keep up to time
in the performance of its manifold oflEices — are not unfrequent, nor
are they inaptly likened to spasms. The sudden disruption of the
ice which arctic voyagers tell of, the immense bergs which occa-
sionally appear in groups near certain latitudes, the variable char-
acter of all the currents of the sea — now fast, now slow, now run-
ning this way, then that — may be taken as so many signs of the
tremendous throes which occur in the bosom of the ocean. Some-
times the sea recedes from the shore, as if to gather strengtli 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 Lis-
bon nine years afterward. The tide-rips in mid ocean, the waves

252 THE PHYSICAL GEOGRAPHY OF THE SEA.

clashing against the shore, the ebb and flow of the tides, may be re-
garded, m some sense, as the throbbings of the great sea pulse.

547. The motions of the Gulf Stream (^ 53), beating time for
the ocean and telling the seasons for the whales, also suggest the
idea of a pulse in the sea, which may assist us in explaining some
of its phenomena. At one beat there is a rush of warm water from
the equator toward the poles, at the next beat a flow from the
poles toward the equator. This sort of pulsation is heard also in
the bowlings of the storm and the whistling of the wind ; the nee-
dle trembles unceasingly to it, and tells us of magnetic storms of
great violence, which at times extend over large portions of the
earth's surface ; and when we come to consult the records of those
exquisitely sensitive anemometers, w^hich the science and ingenu-
ity of the age have placed at the service of philosophers, we find
there that the pulse of the atmosphere is never still : in what ap-
pears to us the most perfect calm, the recording pens are moving
to the pulses of the air.

548. Now if we may be permitted to apply to the Gulf Stream
and to the warm flows of water from the Indian Ocean an idea
suggested by the functions of the human heart in the circulation
of the blood, we perceive how these pulsations of the great sea-
heart may perhaps assist in giving circulation to its waters through
the immense system of aqueous veins and arteries that run betw een
the equatorial and polar regions. The waters of the Gulf Stream,
moving together in a body (§1) through such an extent of ocean,
and being almost impenetrable to the cold waters on either side —
which are, indeed, the banks of this mighty river — may be com-
pared to a wedge-shaped cushion placed between a wall of waters
on the right and a wall of waters on the left. If now w^e imagine
the equilibrium of the -sea to be disturbed by the heating or cool-
ing of its waters to the right or the left of this stream, or the freez-
ing or thawing of them in any part, or if we imagine the disturb-
ance to take place by the action of any of those agencies which
give rise to the motions which we have called the pulsations of
the sea, we may conceive how it might be possible for them to
force the wall of waters on the left to press this cushion down to-
ward the south, and then again for the wall on the right to press
it back again to the north, as (^ 54) we have seen that it is.

Now the Gulf Stream, with its head in the Straits of Florida,

THE DRIFT OF THE SEA. 253

and its tail in the midst of the ocean (^ 492), is wedge-shaped ;
its waters chng together {^ 28), and are pushed to and fro —
squeezed, if you please — by a pressure (§ 53), now from the right,
then from the left, so as to work the whole wedge along between
the cold liquid walls which contain it. May not the velocity of
this stream, therefore, be in some sort the result of this workinjr
and twisting, this peristaltic force in the sea ?

549. In carrying out the views suggested by the idea of pulsa-
tions in the sea, and their effects in giving dynamical force to the
circulation of its waters, attention may be called to the two lobes
of polar waters that stretch up from the south into the Indian
Ocean, and which are separated by a feeble flow of tropical wa-
ters. Icebergs are sometimes met with in these polar waters as
high up as the parallel of the fortieth degree of latitude. Now,
considering that this tropical flow in mid ocean is not constant —
that many navigators cross the path assigned to it in the plate
without finding their thermometer to indicate any increase of heat
in the sea ; and considering, therefore, that any unusual flow of
polar waters, any sudden and extensive disruption of the ice there,
sufficient to cause a rush of waters thence, would have the effect
of closing for the time this mid-ocean flow of tropical waters, we
are entitled to infer that there is a sort of conflict, at times, go-
ing on in this ocean between its polar and equatorial flows of wa-
ter. For instance, a rush of waters takes place from the poles
toward the equator. The two lobes close, cut off" the equatorial
flow between them, and crowd the Indian Ocean with polar wa-
ters. They press out the overheated waters ; hence the great
equatorial flow encountered by Captain Grant.

Thus this opening between the cold-water lobes appears to
hold to the chambers of the Indian Ocean, with their heated wa-
ters, the relations which the valves and the ventricles of the hu-
man heart hold to the circulation of the blood. The closing of
these lobes at certain times prevents regurgitation of the warm
waters, and compels them to pass through their appointed chan-
nels.

550. From this point of view, how many new beauties do not
now begin to present themselves in the machinery of the ocean !
its great heart not only beating time to the seasons, but palpitat-
ing also to the winds and the rains, to the cloud and the sun-

254 THE PHYSICAL GEOGRAPHY OF THE SEA.

»

shine, to day and night (^ 507). Few persons have ever taken the
trouble to compute how much the fall of a single inch of rain over
an extensive region in the sea, or how much the change even of two
or three degrees of temperature over a few thousand square miles
of its surface, tends to disturb its equilibrium, and consequently to
cause an aqueous palpitation that is felt from the equator to the
poles. Let us illustrate by an example : The surface of the At-
Ictntic Ocean covers an area of about twenty-five millions of
square miles. Now, let us take one fifth of this area, and sup-
pose a fall of rain one inch deep to take place over it. This rain
would wxigh three hundred and sixty thousand millions of tons ;
and the salt w^hich, as water, it held in solution in the sea, and
which, when that water was taken up as vapor, w^as left behind to
disturb equilibrium, weighed sixteen millions more of tons, or near-
ly twice as much as all the ships in the world could carry at a car-
go each. It might fall in an hour, or it might fall in a day ; but,
occupy what time it might in falling, this rain is calculated to exert
so much force — which is inconceivably great — in disturbing the
equilibrium of the ocean. If all the water discharged by the Mis-
sissippi River during the year were taken up in one mighty meas-
ure, and cast into the ocean at one effort, it would not make a
greater disturbance in the equilibrium of the sea than would the
fall of rain supposed. Now this is for but one fifth of the At-
lantic, 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 (§144) 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 wdiole 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 vapor of which they
were formed was taken up at still other places, we shall be en-
abled to appreciate the better the force and the effect of these
pulsations in the sea.

551. Between the hottest hour of the day and the coldest hour
of the night there is frequently a change of four degrees in the tem-
perature of the sea.* Let us, therefore, to appreciate the throb-

* Vide Admiral Smyth's Memoir of the Mediterranean, p. 125.

THE DRIFT OF THE SEA. 255

bings of the sea-heart, which take place in consequence of the di-
urnal 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 to be true to na-
ture we may, let us again select one fifth of the Atlantic Ocean
for the scene of operation. The day over it is clear, and the sun
pours down his rays with their greatest intensity, and raises the
temperature two degrees. At night the clouds interpose, and pre-
vent 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 from the sun during the day, are now looking up to the
stars in a cloudless sky, and serve to lower the temperature of the
surface waters, by radiation, two degrees. Here, then, is a differ-
ence 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 four degrees is
equivalent to a change in its volume of three hundred and ninety
thousand millions of cubic feet.

552. Do not the clouds, night and day, now present themselves
to us in a new light ? They are cogs, and rachets, and wheels in
that grand and exquisite machinery which governs the sea, and
which, amid all the jarrings of the elements, preserves in harmo-
ny the exquisite adaptations of the ocean.

553. 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 arc
most favored 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 with 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's Strait. The fisheries of Japan and Eastern China,
which almost, if not quite, rival these, are situated also in the cold
water.

Neither India, nor the east coasts of Africa and South ximcrica,
where the warm waters are, are celebrated for their fish.

554. Three thousand American vessels, it is said, are engaged
in the fisheries. If to these we add the Dutch, French, and En-

256 THE PHYSICAL GEOGRAPHY OF THE SEA.

glish, 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 fish-
ery is the most valuable. Wherefore, in treating of the physical
geography of the sea, a map for the whales would be useful.

555. The sperm whale is a warm-water fish. The right whale
delights in cold water. An immense number of log-books of
whalers have been discussed at the National Observatory, with the
view of detecting the parts of the ocean in which the whales are
to be found at the different seasons of the year. Charts showing
the result have been published ; they form a part of the series of
Maury's Wind and Current Charts.

556. In the course of these investigations, the discovery was
made that the torrid zone is to the right whale as a sea of fire,
through w^hich he can not pass ; that the right whale of the north-
ern hemisphere and that of the southern are two different ani-
mals ; and that the sperm whale has never been known to double
the Cape of Good Hope — he doubles Cape Horn.

557. With these remarks, and the explanations given on Plate
IX., the parts of the ocean to which the right whale most resorts,
and the parts in which the sperm are found, may be seen at a
glance.

STORMS.

257

CHAPTER XVL

STORMS.

Typhoons, ^ 559. — Cyclones, 561. — West India Hurricanes, 562.— Extra-tropical
Gales, 563. — The San Francisco's Gale, 564. — These Gales seldom occur at cer-
tain Seasons, 565. — Most prevalent Quarter for the Gales beyond the Calm Belt of
Capricorn, 566. — Storm and Rain Charts, 567 257

558. Plate V. is constructed from data furnished by the Pilot
Charts, as far as they go, that are in process of construction at the
National Observatory. For the Pilot Charts, the whole ocean is
divided off into districts of five degrees square, i. e., five degrees of
latitude by five degrees of longitude, as already explained on page
23. Now, in getting out from the log-books materials for show-
ing, in every district of the ocean, and for every month, how nav-
igators 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 direc-
tion 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 investigation.

Now if the navigator will draw, or imagine to be drawn in any
such district, twelve vertical columns for the twelve months, and
then sixteen horizontal lines through the same for the sixteen
points of the compass, i. e., for N., N.N.E., N.E., E.N.E., and so
on, omitting the 6y-points, he w^ill 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. hij E., W. hi/ S., &c.
Moreover, any attempt, for the present, at greater nicety, would be
over-refinement ; for navigators do not always make allowance
for the aberration of the wind ; in other words, they do not allow
for the apparent change in the direction of the wind caused by the
rate at which the vessel may be moving through the water, and
the angle which her course makes with the true direction of the

R

258 THE PHYSICAL GEOGRAPHY OF THE SEA.

wind. Bearing this explanation in mind, the intelhgent navigator
will have no difficulty in understanding the wind diagram (Plate
v.), and in forming a correct opinion as to the degree of credit due
to the fidelity with which the prevailing winds of the year are rep-
resented on Plate VIII .

As the compiler wades through log-book after log-book, and
scores down in column after column, and upon line after line,
mark after mark, he at last finds that, under the month and from
the course upon which he is about to make an entry, he has al-
ready made four marks or scores, thus (1 1 1 1). 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 w^hich 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 V.) there have been examined the logs of vessels
that, giving the direction of the wind for every eight hours, have
altogether spent days enough to enable me to record the calms
and the prevailing direction of the winds for eight hours, 2,144
times : of these, 285 were for the month of August ; and of these
285 observations for August, 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; E.S.E, 1; S.E., 4 ; S.S.E., 2;
S., 24; S.S.W.,45; S.W., 93 ; W.S.W., 24; W., 47 ; W.N.W.,
17; N.W., 15; N.N.W., 1 ; Calms (the little O's), 5; total, 285
for this month in this district.

The number expressed in figures denotes the whole number of
observations of calms and winds together that are recorded for
each month and district.

In C, the wind in May sets one third of the time from west.
But in A, which is betw^een the same parallels, the favorite quar-
ter 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
1^ day during the month of May.

In B, notice the great " Sun Swing" of the winds in September,
indicating that the change from summer to winter, in that region,
is sudden and violent ; from winter to summer, gentle and gradual.

In some districts of the ocean, more than a thousand observa-

STORMS. 259

tions have been discussed for a single month, whereas, with regard
to others, not a single record is to be found in any of the numer-
ous log-books at the National Observatory.

559. Typhoons. — The China Seas are celebrated for their furi-
ous gales of wind, known among seamen as typhoons and white
squalls. These 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 Seas are not five-month monsoons (^ 475) ;
they do not prevail from the west of south for more than two or
three months.

560. Plate V. exhibits the monsoons very clearly in a part of this
sea. In the square between 15° and 20° north, 110° and 11 5°
east, there appears to be a system of three monsoons ; that is, from
northeast in October, November, December, and January ; from
east in March and April, changing in May ; from the southward in
June, July, and August, and changing in September. The great
disturber of the atmospheric equilibrium is situated among the arid
plains of Asia ; their influence extends to the China Seas, and
about the changes of the monsoons these awful gales are experi-
enced.

561. In like manner, the Mauritius hurricanes, or the cyclones
of the Indian Ocean, occur during the unsettled state of the at-
mospheric equilibrium which takes place at that debatable period
during the contest between the trade-wind force and the monsoon
force (^ 477), 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, break-
ing loose from their controlling forces, seem to rage with a fury
that would break up the very fountains of the deep.

562. So, too, with the West India hurricanes of the Atlantic.
These winds are most apt to occur during the months of August
and September. There is, 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 southwest monsoons of Africa
(§ 479) and the southeast monsoons of the West Indies (^ 474) are
at their height ; the agent of one drawing the northeast trade-
winds from the Atlantic into the interior of New Mexico and Tex-
as, the agent of the other drawing them into the interior of Africa.

260 THE PHYSICAL GEOGRAPHY OF THE SEA.

Its 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.

563. Extra-tropical Gales. — In the extra-tropical regions of
each hemisphere furious gales of wdnd also occur. One of these,
remarkable for its violent effects, was encountered on the 24th of
December, 1853, about three hundred miles from Sandy Hook,
latitude 39° north, longitude 70° west, by the San Francisco,
steam-ship (^ 72). That ship was made a complete wreck in a
few moments, and she was abandoned by the survivors, after in-
credible hardships, exertions, and sufferings. Some months after
this disaster, I received by the California mail the abstract log of
the fine clipper ship " Eagle Wing" (Ebenezer H. Linnell), from
Boston to San Francisco. She encountered the ill-fated steam-
er's gale, and thus describes it :

564. ''December 24:th, 1853. 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 water,
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 bow^sprit-
cap. In my thirty-one years' experience at sea, I have never seen
a typhoon or hurricane so severe. Lost tw^o men overboard —
saved one. Stove sky-light, broke my barometer, (fee, &c."

565. 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-trop-
ical gales, for the most part, come from the northwest. 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 (§ 71) in closest proximity to the extremest cold of the
north. And there would, 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.

566. In like manner, the gales that most prevail in the extra-

STORMS. 261

tropics of the southern hemisphere come from the pole and the
west, i. e., southwest.

567. Storm and Rain Charts for the Atlantic Ocean have al-
ready been published by the Observatory, and others for the whole
seas are in process of construction. The object of such charts is
to show the directions and relative frequency of gales in all parts
of the sea, the relative frequency of calms, fogs, rain, thunder, and
lightning.

These charts are very instructive.

262 THE PHYSICAL GEOGRAPHY OF THE SEA.

CHAPTER XVII.

ROUTES.

How Passages have been shortened, § 568. — How closely Vessels follow each other's
Track, 570. — The Archer and the Flying Cloud, 571. — The great Race-course upon
the Ocean, 573. — Description of a Race, 575. — Present Knowledge of Winds en-
ables the Navigator to compute his Detour, 582.

568. The principal routes across the ocean are exhibited on
Plate VIII. ; the great end and aim of all this labor and research
are in these, and consist in the shortening of passages — the im-
provement of navigation. Other interests and other objects are
promoted thereby, but these, in the mind of a practical people,
who, by their habits of thought and modes of action, mark the
age in which we live as eminently utilitarian, do not stand out in
relief half so grand and imposing as do those achievements by
which the distant isles and marts of the sea have been lifted up,
as it were, and brought closer together, for the convenience of
commerce, by many days' sail.

569. We have been told in the foregoing pages how the winds
blow and the currents flow in all parts of the ocean. These con-
trol the mariner in his course ; and to know how to steer his ship
on this or that voyage so as always to make the most of them,
is the perfection of navigation. The figures representing the ves-
sels are so marked as to show whether the prevailing direction of
the wind be adverse or fair.

570. When one looks seaward from the shore, and sees a ship
disappear in the horizon as she gains an offing on a voyage to In-
dia, or the Antipodes perhaps, the common idea is that she is
bound over a trackless waste, and the chances of another ship,
sailing with the same destination the next day, or the next week,
coming up and speaking with her on the '' pathless ocean," would,
to most minds, seem slender indeed. Yet the truth is, the winds
and the currents are now becoming to be so well understood, that
the navigator, like the backwoodsman in the wilderness, is enabled
literally " to blaze his way" across the ocean ; not, indeed, upon
trees, as in the wilderness, but upon the wings of the wind. The

ROUTES. 263

results of scientific inquiry have so taught him how to use these
invisible couriers, that they, with the calm belts of the air, serve
as sign-boards to indicate to him the turnings, and forks, and cross-
ings by the way.

571. Let a ship sail from New York to California, and the next
week let a faster one follow after : they will cross each other's
path many times, and are almost sure to see each other by the
way. Thus a case in point happens to be before me. It is the
case of the "Archer" and the "Flying Cloud" on their last voy-
age to California. They are both fine clipper ships, ably com-
manded. But it was not until the ninth day after the " Archer"
had sailed from New York that the " Flying Cloud" put to sea,
California bound also. She was running against time, and so was
the " Archer," but without reference to each other. The " Archer,"
with "Wind and Current Charts" in hand, went blazing her way
across the calms of Cancer, and along the new route, down through
the northeast trades to the equator ; the " Cloud" followed after,
crossing the equator upon the trail of Thomas of the " Archer."
Off Cape Horn she came up with him, spoke him, handed him
the latest New York dates, and invited him to dine on board the
"Cloud," which invitation, says he of the "Archer," "I was re-
luctantly compelled to decline."

572. The " Flying Cloud" finally ranged ahead, made her adieus,
and disappeared among the clouds that lowered upon the western
horizon, being destined to reach her port a week or more in ad-
vance of her Cape Horn consort. Though sighting no land from
the time of their separation until they gained the ofiing of San
Francisco — some six or eight thousand miles off — the tracks of
the two vessels were so nearly the same, that, being projected on
the Plate IX., they would appear almost as one.

573. This is the great race-course of the ocean ; it is fifteen
thousand miles in length. Some of the most glorious trials of
speed and of prowess that the world ever witnessed have taken
place over it. Here the modern clipper ship — the noblest work
that has ever come from the hands of man — has been sent, guided
by the lights of science, to contend with the elements, to outstrip
steam, and astonish the w^orld.

574. The most celebrated and famous race that has ever been
run came off upon this course : it was in the autumn of 1852,

264 THE PHYSICAL GEOGRAPHY OF THE SEA.

when navigators were beginning fully to reap the benefits of these
researches with regard to the winds and currents, and other facts
connected with the Physical Geography of the Sea, that four
splendid new clipper ships put to sea from New York, bound for
California. They were ably commanded, and, as they passed the
bar at Sandy Hook, one by one, and at various intervals of time,
they presented really a most magnificent spectacle. The names
of these ships and their masters were, the "Wild Pigeon," Cap-
tain Putnam; the "John Gilpin," Captain Doane — alas! now
no more ; the " Flying Fish," Captain Nickels, and the " Trade
Wind," Captain Webber. Like steeds that know their riders,
they were handled with the most exquisite skill and judgment,
and in such hands they bounded out upon the "glad waters" most
gracefully. Each, being put upon her mettle from the start, was
driven, under the seaman's whip and spur, at full speed over a
course that it would take them three long months to run.

575. The "Wild Pigeon" -sailed October 12; the "John Gil-
pin," October 29 ; the " Flying Fish," November 1 ; and the
" Trade Wind," November 14. It was the season for the best
passages. Each one was provided with the Wind and Cu7'rent
Charts. Each one had evidently studied them attentively ; and
each one vv^as resolved to make the most of them, and do his best.
All ran against time ; but the " John Gilpin" and the " Flying Fish"
for the whole course, and the " Wild Pigeon" for part of it, ran
neck and neck, the one against the other, and each against all. It
was a sweepstake with these ships around Cape Horn and through
both hemispheres.

576. Wild Pigeon led the other two out of New York, the one
by seventeen, the other by twenty days. But luck and chances of
the winds seem to have been against her from the start. As soon
as she had taken her departure, she fell into a streak of baffling
winds, and then into a gale, which she fought against and con-
tended with for a w^eek, making but little progress the while ; she
then had a time of it in crossing the horse latitudes. After hav-
ing been nineteen days out, she had logged no less than thirteen
of them as days of calms and baffling winds ; these had brought
her no farther on her way than the parallel of 26° north in the At-
lantic. Thence she had a fine run to the equator, crossing it be-
tween 33° and 34° west, the thirty-second day out. She was un-

ROUTES. 265

avoidably forced to cross it so far west ; for only two days before,
she crossed 5° north in 30° — an excellent position.

In proof that the Pigeon had accomplished all that skill could
do and the chances against her would permit, we have the testi-
mony of the barque Hazard, Captain Pollard. This vessel, being
bound to Rio at the same time, followed close after the Pigeon.
The Hazard is an old hand with the Charts ; she had already made
six voyages to Rio with them for her guide. This was the long-
est of the six, the mean of which was twenty-six and a half days.
She crossed the line this time in 34° 30', also by co«ipulsion, hav-
ing crossed 5° north in 31°. But, the fourth day after crossing
the equator, she was clear of Cape St. Roque, while the Pigeon
cleared it in three days.*

577. So far, therefore, chances had turned up against the Pig-
eon, in spite of the skill displayed by Putnam as a navigator, for
the Gilpin and the Fish came booming along, not under better
management, indeed, but with a better run of luck and fairer
courses before them. In this stretch they gained upon her — the
Gilpin seven and the Fish ten days ; so that now the abstract logs
show the Pigeon to be but ten days ahead.

Evidently the Fish was most confident that she had the heels
of her competitors ; she felt her strength, and was proud of it ;
she was most anxious for a quick run, and eager withal for a trial.
She dashed down southwardly from Sandy Hook, looking occa-
sionally at the Charts ; but, feeling strong in her sweep of wing,
and trusting confidently in the judgment of her master, she kept,
on the average, two hundred miles to leeward of the right track.
Rejoicing in her many noble and fine qualities, she crowded on
her canvas to its utmost stretch, trusting quite as much to her
heels as to the Charts, and performed the extraordinary feat of
crossing, the sixteenth day out from New York, the parallel of 5°
north.

The next day she was well south of 4° north, and in the Dol-
drums, longitude 34° west.

Now her heels became paralyzed, for Fortune seems to have de-
serted her a while — at least her master, as the winds failed him,
feared so ; they gave him his motive power ; they were fickle, and
he was helplessly bafiled by them. The bugbear of a northwest

* According to the received opinion, this was impossible. Vide ^ 276.

266 THE PHYSICAL GEOGRAPHY OF THE SEA.

current off Cape St. Roque (§ 276) began to loom up in his im-
agination, and to look alarming ; then the dread of falling to lee-
ward came upon him ; chances and luck seemed to conspire against
him, and the mere possibility of finding his fine ship back-strapped
filled the mind of Nickels with evil forebodings, and shook his
faith in his guide. He doubted the Charts, and committed the
mistake of the passage.

578. The Sailing Directions had cautioned the navigator, again
and again, not to aitempt to fan along to the eastward in the equa-
torial doldrums ; for, by so doing, he would himself engage in a
fruitless strife with baffling airs, sometimes re-enforced in their
weakness by westerly currents. But the winds had failed, and so
too, the smart captain of the Flying Fish evidently thought, had
the Saili?ig Directions. They advise the navigator, in all such
cases, to dash right across this calm streak, stand boldly on, take
advantage of slants in the wind, and, by this device, make easting
enough to clear the land. So, forgetting that the Charts are
founded on the experience of great numbers who had gone before
him. Nickels, being tempted, turned a deaf ear to the caution, and
flung away three whole days, and more, of most precious time,
dallying in the doldrums.

He spent four days about the parallel of 3° north, and his ship
left the doldrums, after this waste of time, nearly upon the same
meridian at which she entered them.

She was still in 34°, the current keeping her back just as fast
as she could fan east. After so great a loss, her very clever mas-
ter, doubting his own judgment, became sensible of his error.
Leaving the spell-bound calms behind him, where he had under-
gone such trials, he wrote in his log as follows : " I now regret
that, after making so fine a run to 5° north, I did not dash on, and
work my way to windward to the northward of St. Roque, as I
have experienced little or no westerly set since passing the equa-
tor, while three or four days have been lost in working to the east-
ward, between the latitude of 5° and 3° north, against a strong
westerly set ;" and he might have added, "with little or no wind."

In three days after this he was clear of St. Roque. Just five
days before him, the Hazard had passed exactly in the same place,
and gained two days on the Fish by cutting straight across the
doldrums, as the Sailing Directions advised him to do.

ROUTES. 267

The Wild Pigeon, crossing the equator also in 33°, had passed
along there ten days before, as did also the Trade Wind twelve
days after. The latter also crossed the line to the west of 34°,
and in four days after had cleared St. Roque.

But, notwithstanding this loss of three days by the Fish, who so
regretted it, and who afterward so handsomely retrieved it, she
found herself, on the 24th of November, alongside of the Gilpin,
her competitor. They were then both on the parallel of 5° south,
the Gilpin being thirty-seven miles to the eastward, and of course
in a better position, for the Fish had yet to take advantage of
slants, and stand off shore to clear the land. They had not seen
each other.

579. The Charts show^ed the Gilpin now to be in the best po-
sition, and the subsequent events proved the Charts to be right,
for thence to 53° south the Gilpin gained on the Pigeon tw^o days,
and the Pigeon on the Fish one.

By dashing through the Straits of Le Maire, the Fish gained
three days on the Gilpin ; but here Fortune again deserted the
Pigeon, or rather the winds turned against her; for as she ap-
peared upon the parallel of Cape Horn, and was about to double
round, a westerly gale struck her and kept her at bay for ten days,
making little or no way, except alternately fighting in a calm or
buffeting with a gale, while her pursuers were coming up " hand
over fist," with fine winds and flowing sheets.

They finally overtook her, bringing along with them propitious
gales, when all three swept past the Cape, and crossed the paral-
lel of 51° south on the other side of the " Horn," the Fish and the
Pigeon one day each ahead of the Gilpin,

The Pigeon was now, according to the Charts, in the best po-
sition, the Gilpin next, and the Fish last ; but all were doing well.

From this parallel to the southeast trades, of the Pacific the
prevailing winds are from the northwest. The position of the
Fish, therefore, did not seem as good as the others, because she
did not have the sea-room in case of an obstinate northwest gale.

But the winds favored her. On the 30th of December the three
ships crossed the parallel of 35° south, the Fish recognizing the
Pigeon ; th6 Pigeon saw only a " clipper ship," for she could not
conceive how the ship in sight could possibly be the Flying Fish,
as that vessel was not to leave New York for some three weeks

268 THE PHYSICAL GEOGRAPHY OF THE SEA. .

after she did ; the Gilpin was only thirty or forty miles off at the
same time.

The race was now wing and wing, and had become exciting.
With fair winds and an open sea, the competitors had now a clear
stretch to the equator of two thousand five hundred miles before
them.

The Flying Fish led the way, the Wild Pigeon pressing her
hard, and both dropping the Gilpin quite rapidly, who was edging
off to the westward.

The two foremost reached the equator on the 13th of January,
the Fish leading just twenty-five miles in latitude, and crossing in
112° \T f the Pigeon forty miles farther to the east. At this
time the John Gilpin had dropped two hundred and sixty miles
astern, and had sagged off several degrees to the westward.

580. Here Putnam, of the Pigeon, again displayed his tact as
a navigator, and again the fickle winds deceived him : the belt of
northeast trades had yet to be passed ; it was winter ; and, by
crossing w^here she did, she would have an opportunity of making
a fair wind of them, without being much to the west of her port
when she should lose them. Moreover, it was exactly one year
since she had passed this way before ; she then crossed in 109°,
and had a capital run thence of seventeen days to San Francisco.

Why should she not cross here again ? She saw that the 4th
edition of Sailing Dii^ections, which she had on board, did not dis-
countenance it, and her own experience approved it. Could she
have imagined that, in consequence of this difference of forty miles
in the crossing of the equator, and of the two hours' time behind
her competitor, she would fall into a streak of w^ind which would
enable the Fish to lead her into port one whole week ? Certainly
it was nothing but what sailors call " a streak of ill luck" that
could have made such a difference.

But by this time "John Gilpin" had got his mettle up again.
He crossed the line in 116° — exactly two days after the other two
— and made the glorious run of fifteen days thence to the pilot
grounds of San Francisco.

Thus end the abstract logs of this exciting race and these re-
markable passages,

* Twenty-five days after that, the Trade Wind clipper came along, crossed in 112°,
and had a passage of sixteen days thence into San Francisco.

ROUTES. 269

The Flying Fish beat : she made the passage in 92 days and 4
hours from port to anchor ; the Gilpin in 93 days and 20 hours
from port to pilot ;* the Wild Pigeon had 118. The Trade Wind
followed, with 102 days, having taken fire, and burned for eight
hours on the way.

The result of this race may be taken as an illustration as to
how well navigators are now- brought to understand the winds and
the currents of the sea.

581. Here are three ships sailing on different days, bound over
a trackless waste of ocean for some fifteen thousand miles or more,
and depending alone on the fickle winds of heaven, as they are
called, to waft them along ; yet, like travelers on the land, bound
upon the same journey, they pass and repass, fall in with and
recognize each other by the way ; and what, perhaps, is still more
remarkable, is the fact that these ships should each, throughout
that great distance, and under the wonderful vicissitudes of cli-
mates, winds, and currents which they encountered, have been so
skillfully navigated, that, in looking back at their management,
now that w^hat is past is before me, I do not find a single occa-
sion, except the one already mentioned, on which they could have
been better handled.

There is another circumstance which is worthy of notice in this
connection, as illustrative of the accuracy of the knowledge which
these investigations afford concerning the force, set, and direction
both of winds and currents, and it is this :

582. I had computed the detour which these vessels would have
to make, on account of adverse winds, betw^een New York and
their place of crossing the equator. The whole distance, includ-
ing detour to be sailed to reach this crossing at that season of the
year, was, according to calculation, 4115 miles. The "Gilpin"
and the " Hazard" only kept an account of the distance actually
sailed ; the former reaching the equator after sailing 4099 miles,
the latter, 4077 ; thus accomplishing that part of the voyage by
sailing, the one within thirty-eight, the other within sixteen miles
of the detour which calculation showed they would be compelled
to make on account of head-w4nds. With his way blazed through
the forest, the most experienced backwoodsman would have to
make a detour greater than this on account of floods in the rivers.

* The abstract log of the Gilpin is silent after the pilot came on board.

270 THE PHYSICAL GEOGRAPHY OF THE SEA.

Am I far wrong, therefore, when I say that the present state of
our knowledge with regard to the physical geography of the sea
has enabled the navigator to blaze his way among the winds and
currents of the sea, and so mark his path that others, using his
signs as finger-boards, may follow in the same track ?

A LAST WORD.

271

CHAPTER XVIII.

A LAST WORD.

Brussels Conference, ^ 584. — How Navigators may obtain a Set of Maury's Wind
and Current Charts, 585. — The Abstract Log, 586.

583. I HAVE, I am aware, not done more in this little book than
given only a table or two of contents from the interesting volume
which the Physical Geography of the Sea is destined some day
to open up to us. The subject is a comprehensive one : there is
room for more laborers, and help is wanted.

Nations, no less than individuals ; " stay-at-home travelers," as
well as those who " go down to the sea in ships," are concerned
in the successful prosecution of the labors we have in hand.

We are now about to turn over a new leaf in navigation, on
which we may confidently expect to see recorded much informa-
tion that will tend to lessen the dangers of the sea, and to shorten
the passages of vessels trading upon it.

We are about to open in the volume of Nature a new chapter,
under the head of Marine Meteorology. In it are WTitten the
laws that govern those agents which "the winds and the sea
obey." In the true interpretation of these laws, and the correct
reading of this chapter, the planter as well as the merchant, the
husbandman as well as the mariner, and states as well as indi-
viduals, are concerned. All have a deep interest in these laws ;
for with the hygrometrical conditions of the atmosphere, the well-
being of plants and animals is involved. The health of the invalid
is often dependent upon a dry or a damp atmosphere, a cold blast
or a warm wind.

The atmosphere pumps up our rivers from the sea, and trans-
ports them through the clouds to their sources among the hills ;
and upon the regularity with which this machine, whose motions,
parts, and offices we now wish to study, lets down that moisture,
and the seasonable supply of rain which it furnishes to each region

272 THE PHYSICAL GEOGRAPHY OF THE SEA.

of country, to every planter, and upon all cultivated fields, depend
the fruitfulness of this country, the sterility of that.

The principal maritime nations, therefore, have done well by
agreeing to unite upon one plan of observation, and to co-operate
with their ships upon the high seas with the view of finding out
all that patient research, systematic, laborious investigation, may
reveal to us concerning the winds and the waves ; and philosoph-
ical travelers, and every sailor that has a ship under his foot, may
do even better by joining in this system.

584. By the reconftnendations of the Brussels Conference, ev-
ery one who uses the sea is commanded or invited to make cer-
tain observations ; or, in other words,J;o propound certain queries
to Nature, and to give us a faithful statement of the replies she
may make.

Now, unless we have accurate instruments, instruments that
will themselves tell the truth, it is evident that we can not get at
the real meaning of the answers that Nature may give us.

An incorrect observation is not only useless of itself, but, when
it passes undetected among others that are correct, it becomes
worse than useless ; nay, it is mischievous there, for it vitiates
results that are accurate, places before us wrong premises, and
thus renders the good of no value.

585. Those ship-masters who, entering this field as fellow-la-
borers, will co-operate in the mode and manner recommended by
the Brussels Conference, and keep, voyage after voyage, and as
long as required, a journal of observations and results according to
a prescribed form — and which form is annexed, under the title of
Abstract Log — are entitled, by sending the same, at the end of
the voyage, to the Superintendent of the National Observatory, to
a copy of my Sailing Directions, and such sheets of the Charts as
relate to the cruising-ground of the co-operator.

586. There are two forms of abstract logs : one, the more elab-
orate, for men-of-war ; the other for merchantmen. The observa-
tions called for by the latter are a minimum, the least which will
entitle the co-operator to claim the proffered bounty. It must
give, at least, the latitude and longitude of the ship daily ; the
height of the barometer, and the readings of both the air and the
water thermometer, at least once a day ; the direction and force
of the wind three times a day — first, middle, and latter part — at the

A LAST WORD.

27,

hours eight P.M., four A.M., and noon ; the variation of the com-
pass occasionally ; and the set of the current whenever encounter-
ed. These observations, to be w^orth having, must be accurately
made ; and as every thermometer and every barometer has its
sources of error, consequently, every ship-master who undertakes
hereafter to co-operate with us, and keep an abstract log, should
have his barometer and thermometer accurately compared with
standard instruments, the errors of which have been accurately
determined.

These errors the master should enter in the log ; the instru-
ments should be numbered, and he should so keep the log as to
show what instrument is in use. For instance, a master goes to
sea with thermometers Nos. 4719, 1, 12, &c., their errors having
been ascertained and entered on the blank page for the purpose
in the abstract log. He first uses No. 12. Let it be so stated in
the column of Remarks, when the first observation is recorded,
thus : Thermometer No. 12. Durmg the voyage, No. 12 gets bro-
ken, or for some reason is laid aside, and another, say 4719, is
brought into use. So state when the first observation with it is
recorded, and quote in the column of Remarks the errors both of
Nos. 12 and 4719. Now, with such a statement of errors given in
the log for each of the instruments, according to the number, the
observations may be properly corrected when they come up here
for discussion.

It is rare to find a barometer or a thermometer that has no er-
ror, as it is to find a chronometer without error. A good ther-
mometer, the error of which the maker should guarantee not to
exceed in any part of the scale one degree, will cost, in the United
States, not less than $2, perhaps $2 50.

The errors of thermometers sometimes are owing to inequali-
ties in the bore of the tube, sometimes to errors of division on the
scale, &c. Therefore, in comparing thermometers with a stand-
ard, they should be compared, at least, for every degree between
melting ice and blood heal.

274

PHYSICAL GEOGRAPHY OF THE SEA

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