Hugh Chisholm.

The Encyclopædia britannica; a dictionary of arts, sciences, literature and general information (Volume v. 20) online

. (page 157 of 353)
Online LibraryHugh ChisholmThe Encyclopædia britannica; a dictionary of arts, sciences, literature and general information (Volume v. 20) → online text (page 157 of 353)
Font size
QR-code for this ebook

developed during the southern winter; at other seasons the regular
trade-belt is cut across from north-west to south-east by a band
twenty to thirty degrees wide, in which the trades alternate with
winds from north-east and north, and with calms, the calms prevail-
ing chiefly at the boundary of the monsoon region (5° N.-i5° S.,
l6o°-i85 E.). Thisarea, in which the south-east trade is interrupted,
includes the Fiji, Navigator and Society groups, and the Paumotus.
In the Marquesas group the trade-wind is constant. Within the
southern monsoon region there is a gradual transition to the north-
west monsoon of New Guinea in low latitudes, and in higher latitudes
to the north-cast wind of the Queensland coast. The great warming
and abundant rainfall of the island regions of the western Pacific,
and the low temperature of the surface water in the east, cause a
displacement of the southern tropical maximum of pressure to the
east; hence we have a permanent "South Pacific anticyclone"
close to the coast of South America. The characteristic feature of
the south-western Pacific is therefore the relatively low pressure and
the existence of a true monsoon region in the middle of the trade-
wind belt. It is to be noted that the climate of the islands of the
Pacific becomes more and more healthy the farther they are from
the monsoon region. The island regions of the Pacific are every-
where characterized by uniform high air-temperatures; the mean
annual range varies from 1° to 9° F., with extremes of 24° to 27°,
and the diurnal range from 9° to 16°. In the monsoon region relative
humidity is high, viz. 80 to 90 °o. The rainfall is abundant; in the
western island groups there is no well-marked rainy season, but
over the whole region the greater part of the rainfall takes place
during the southern summer, even as far north as Hawaii. In the
trade-wind region we find the characteristic hea\'>' rainfall on the
weather sides of the islands, and a shorter rainy season at the season
of highest sun on the lee side. Buchan describes the island-studded
portion of the western Pacific as the most extensive region of the
globe characterized by an unusually hea\T.- rainfall. Beyond the
tropical high-pressure belt, the winds of the North Pacific are under
the control of an area of low pressure, which, however, attains neither
the size nor the intensity of the " Iceland " depression in the north



Atlantic. The result is that north-westerly winds, which in winter
are exceedingly dry and cold, blow over the western or Asiatic
area; westerly winds prevail in the centre, and south-westerly and
southerly winds off the American coast. In the southern hemisphere
there is a transition to the low-pressure belt encircling the Southern
Ocean, in which westerly and north-westerly winds continue all the
year round.

The distribution of temperature in the waters of the Pacific Ocean
has been fully investigated, so far as is possible with the existing
observations, by G. Schott. At the surface an extensive
Temperature. ^^^^ ^j maximum temperature (over 20° C.) occurs over
10° on each side of the equator to the west of the ocean. On the
eastern side temperature falls to 22° on the equator and is slightly
higher to N. and S. In the North Pacific, beyond lat. 40°, the
surface is generally warmer on the E. than on the W., but this con-
dition is, on the whole, reversed in corresponding southern latitudes.
In the intermediate levels, down to depths not exceeding 1000 metres,
a remarkable distribution appears. A narrow strip of cold water
runs along the equator, widest to the east and narrowing westward,
and separates two areas of ma.xirnum which have their greatest
intensity in the western part of the ocean, and have their central
portions in higher latitudes as depth increases, apparently tending
constantly to a position in about latitude 30° to 35° N. and S. A
comparison of this distribution with that of atmospheric pressure
is of great interest. High temperature in the depth may be taken
to mean descending water, just as high atmospheric pressure means
descending air, and hence it would seem that the slow vertical
movement of water in the Pacific reproduces to some extent the
phenomena of the " doldrums " and " horse latitudes," with this
difference, that the centres of maximum intensity lie off the east
of the land instead of the west as in the case of the continents. The
isothermal lines, in fact, suggest that in the vast area of the Pacific
something corresponding to the " planetary circulation " is estab-
lished, further investigation of which may be of extreme value in
relation to current inquiries concerning the upper air. In the greater
depths temperature is extraordinarily uniform, 8o°'o of the existing
observations falling within the limits of 1-6'' C. and 1-9° C. In the
enclosed seas of the western Pacific, temperature usually falls till
a depth corresponding to that of the summit of the barriers which
isolate them from the open ocean is reached, and below that point
temperature is uniform to the bottom. In the Sulu Sea, for example,
a temperature of 10-3° C. is reached at 400 fathoms, and this remains
constant to the bottom in 2500 fathoms.

The surface waters of the North Pacific are relatively fresh, the
salinity being on the whole much lower than in the other great
Salinity oceans. The saltest waters are found along a belt extend-
ing westwards from the American coast on the Tropic of
Cancer to 160° E., then turning southwards to the equator. North
of this salinity diminishes steadily, especially to the north-west,
the Sea of Okhotsk showing the lowest salinity observed in any
part of the globe. South and east of the axis mentioned salinity
becomes less to just north of the equator, where it increases again,
and the saltest waters of the whole Pacific are found, as we should
expect, in the south-east trade-wind region, the ma.ximum occurring
in about 18° S. and 120° W. South of the Tropic of Capricorn the
isohalines run nearly east and west, salinity diminishing quickly to
the Southern Ocean. The bottom waters have almost uniformly a
salinity of 34-8 per mille, corresponding closely with the bottom
waters of the South Atlantic, but fresher than those of the North

The surface currents of the Pacific have not been studied in the
same detail as those of the Atlantic, and their seasonal variations
Circulation ^■'^ little known except in the monsoon regions. Speak-
' ing generally, however, it may be said that they are
for the most part under the direct control of the prevailing
winds. The North Equatorial Current is due to the action of the
north-east trades. It splits into two parts east of the Philippines,
one division flowing northwards as the Kuro Siwo or Black Stream,
the analogue of the Gulf Stream, to feed a drift circulation which
follows the winds of the North Pacific, and finally forms the Cali-
fornian Current flowing southwards along the American coast.
Part of this rejoins the North Equatorial Current, and part probably
forms the variable Mexican Current, which follows the coasts of
Mexico and California close to the land. The Equatorial Counter-
Current flowing eastwards is largely assisted during the latter half
of the year by the south-west monsoon, and from July to October
the south-west winds prevailing east of 150° E. further strengthen
the current, but later in the year the easterly winds weaken or even
destroy it. The South Equatorial Current is produced by the south-
east trades, and is more vigorous than its northern counterpart.
On reaching the western Pacific part of this current passes south-
wards, east of New Zealand, and again east of Australia, as the East
Australian Current, part northwards to join the Equatorial Counter-
Current, and during the north-east monsoon part makes its way
through the China Sea towards the Indian Ocean. During the
south-west monsoon this last branch is reversed, and the surface
waters of the China Sea probably unite with the Kuro Siwo. Between
the Kuro Siwo and the Asiatic coast a band of cold water, with a
slight movement to the southward, known as the Oya Siwo, forms
the analogue of the " Cold Wall " of the Atlantic. In the higher

latitudes of the South Pacific the surface movement forms part of
the west wind-drift of the Roaring Forties. On the west coast of
South America the cold waters of the Humboldt or Peruvian Current
corresponding to the Benguela Current of the South Atlantic, make
their way northwards, ultimately joining the South Equatorial
Current. The surface circulation of the Pacific is, on the whole,
less active than that of the Atlantic. The centres of the rotational
movement are marked by " Sargasso Seas " in the north and south
basins, but they are of small extent compared with the Sargasso Sea
of the North Atlantic. From the known peculiarities of the distri-
bution of temperature, it is probable that definite circulation of
water is in the Pacific confined to levels very near the surface, except
in the region of the Kuro Siwo, and possibly also in parts of the
Peruvian Current. The only movement in the depths is the slow
creep of ice-cold water northwards along the bottom from the
Southern Ocean; but this is more marked, and apparently penetrates
farther north, than in the Atlantic.

Seei??/)ortjof expeditions of the U.S.S. " Albatross " and " Thetis."
1888-1892; A. Agassiz, Expedition to the Tropical Pacific, 1899-1900,
1904-1905; H.M.S. "Challenger," 1873-1876; " Egeria." 1888-
1889 and 1899; " Ehsabeth," 1877; " Gazelle," 1875-1876; " Planet,"
1906; " Penguin," 1891-1903; " Tuscarora," 1873-1874; " Vettor
Pisani," 1884; " Vitraz," 1887-1888; also observations of surveying
and cable ships, and special papers in the A nnalen der Hydrographie
(for distribution of temperature see G. Schott, p. 2, 1910).

(H. N. D.)

Islands of the Pacific Ocean

Up to a certain point, the islands of the Pacific fall into an
obvious classification, partly physical, partly political. In
the west there is the great looped chain which fringes the east
coast of Asia, and with it encloses the series of seas which form
parts of the ocean. The north of the chain, from the Kuriles
to Formosa, belongs to the empire of Japan; southward it is
continued by the Philippines (belonging to the United States
of America) which link it with the vast archipelago between the
Pacific and Indian oceans, to which the name Malay Archipelago
is commonly applied. As the loop of the Kuriles depends from
the southern extremity of Kamchatka, so from the east of the
same peninsula another loop extends across the northern part
of the ocean to Alaska, and helps to demarcate the Bering Sea;
this chain is distinctly broken to the east of the Commander
Islands, but is practically continuous thereafter under the name
of the Aleutian Islands. Islands form a much less important
feature of the American Pacific coast than of the Asiatic;
between 48° N. and 38° S. there are practicaUy none, and to the
north and south of these parallels respectively the islands,
though large and numerous, are purely continental, lying close
under the mainland, enclosing no seas, and forming no separate
political units. South-eastward of the Malay Archipelago lies
" the largest island and the smallest continent," Australia;
eastward of the archipelago, New Guinea, the largest island if
Australia be regarded as a continent only. With Australia
may be associated the islands lying close under its coasts,
including Tasmania. Next foUow the two great islands and
attendant islets of New Zealand.

There now remains a vast number of small islands which lie
chiefly (but not entirely) within an area which may be defined
as extending from the Philippines, New Guinea and Australia
to 130° W., and from tropic to tropic. These islands fall
principally into a number of groups clearly enough defined to be
well seen on a map of small scale; they are moreover divided, as
will be shown, into three main divisions; but whereas they have
enough characteristics in common to render a general view of
them desirable, there is no well-recognized name to cover them
all. The name Polynesia was formerly taken to do so, but
belongs properly to one of the three main divisions, to which the
name Eastern Polynesia was otherwise given; Oceania and
Oceanica are variants of another term which has been used for
the same purpose, though by no means generally. Moreover
usage varies slightly as regards the limits of the three main
divisions, but the accompanying table shows the most usual
classification, naming the principal groups within each, and
distributing them according to the powers to which they are

The following islands may be classified as oceanic, but not with
any of the three main divisions: the Bonin Islands, north of the
Marianas, belonging to Japan; Lord Howe and Norfolk Islands (to


e a



■,,'■* 3 'Pcinafitlin

.'b'/j' 7 ''^'urA (Two 7 <

a i^'i'^*, ' -'Borodino Is. Caffm -.^isjands (to fapan)

^\^ ^fas/jinta Arzobispo, Kita-'wo-iima

.yakazhima I .ftcial. .'"'°-^'"'° -.Volcano Is. uo J*i«n) ,' «<i^m /. .

'Formosa no lapan) i '

Gangts /.




'" PhUippine




- Cojaaon //-^f^,^ ^Mindanao y ,< •„,_.""»''•"«'' \s»"'

^^- ., .V

C !■ / ? 6'.- s .„ S e a , , -i ■ _/)j„"^,a


«.* Oraluh : i,iP



i.oj Oauoo f

Pelew Js.

- -V '' '

. Snrrsercl
^ ~-Arina


£.„„,, ,»/„..y>M i d d 1

'**oVV 1< '-■'

Uajt'6ng - MentschiUouj V %r •■ SomoMOt rl roup

■ «« '^;°"1,' '< ■ Mate ft b

c r n ■ Marshall . o '

•'Veflj^i ■•■P'tgtiap \ Islands ,^^ ^„ «''^? -.'•'■'

Caroline Islanids

/T ^

.-sis- I . ,Kop'flOO.

, Namorih* .' Jaluit , ^

ffiiSj;* \ ,, 't>, Know/

Ebon' ' ,'


. Bismarck ^,f^;0" .

Arch. JHec/<ieiiiiHrg^ • * ,cti ' ,„(et ;,ckls- *^

<pa..^sv*'°'°'' Gilbert '■■.


"TZy.'rZT Islands \

Nawodo_'y .^ Ncnuti \ p^^^

i^-.Bonabe Tap'teuta -'■ • \Muliunau

Tamana' *jiro,o.



*-^ ■*. *.V*,M<./a.(ff \SantaCru2 Is.
Cr:>4 . ^- '

■teaux_: CO^ ■ ^ '■^atema ~ ::^i'~ffVrrY

_ Rcissel '■• OcHonn , S.Crutoja/.- mTupua J^ \^Anuda

, .'^ , ■■■-. 'l> „ .■:' VanihofO* ..-^ -Fataka

LoiiiSiade ■■.. \flennell

Archipelago "-■• -■'

Torres «

Is. \ 't Banks
- Group 1

.' H, 1 Neu

EUice ^Q.Eupt
Islands "'f"

.„Hebrides\ \ FW-.,-0^-


Tropic _ of Ca

''\S^^-^^'-^h.-. u s Lfr..m.?A ..:,L v^i.m

^jSa U S-T-RA;Ll A ■'. . . oodnL^mA,.-;^-'^"^-

o Y.X 'i •yit. O'VMcniKS a.m ■• ._ AUS 1 K A L. 1-»A -Vi . y Bpurto


o.-s'^-jfo^j.. ^-^:>^E-"« - t^-vpo.



Scale, 1:40,000,000
English Miles

O 100 200 JOO 40 5OQ 1000

Principal Raihuays ■"-— Cables r— n

J I United States ...



Portuguese -

■■■■■■■" 5 "'N.o.'i>J^''',„


ViV v.><^ if"

* * - .New Plytnoulh / jF Ci^' fXiUt

NEW ZEALAND '^'<a!ig'/,'7"'"'°"

M;,it>>'y*-7/-g Wellington

•'SanAs Ptmnsula

South Island


140° Longitude East 150' c' Greenwich 160° P '7°


«.4.„nj,., I • """""• •■ (no^cr'i .'_ Group ^. -i"""*,.

To^"''' a'^ V*'^"*'""" Croup


,• • Society i -.. „K,,.' •, •. , *.»',;:•„,•-..».

,•'" \ I^ranHc I .' • 'Cor/ ."e"" /•

^ _C00k I ij*„ _1 1 V'Htrrttrtli/i /Vgoml.' ""'"'""'•

i.?''"*'^ I \ re™,.,,,.: - .C™«", /> ,

A-'""- "■ *<i, ^ •'-'":'- - - -■-, T «•'""•• .,,?■ T"., •..'■>-

■■ ». it Vauitao

• \ ^ .-

'pnualci ■

■ Vavau : INiue

'a pa I ''• ■ ■... ■ ■ "

■ufcn Hichilson I

Palmtnton I.

Islands ^''" 'W""^- !

"tRarotong.^ I »




S'i(.f(/Mflys.OVauro V. V
TradSuru I ■ q ^— ^J* - ^.''""

' .o*" ,«''^A '"''"J'W. \<Jf alalia


Scale, 1:15,000.00c
Eneliih Miles


- NEW HEBRIDES \ror.« ,,^^^^^^,

and ' .Va/ua fld/i/f.s


Scale.,o<« - -, i^ruiip

English Miles ..-. ''. '



€spintu\ \j\- n

SantoV^i AobaJ\'^'"'"°

Lug-nviUe^i. ^J

Pt. Sandwich fV^P'

<3l '''-.Shtphcrd Is.

P(, Havanruh,



• Lt/«iioijy



^0: <^ £romanga^-

160 Lontjitudc W^st i5o'\>f Greenwich 140°

Poit%- Belep Is, %.-^ A'

Caledonia „„ '^

, of'""

170' "ffesi Long.




Scnlf, 1:15,000,000
Ene1i%h Miles



titit ry \V alkcr sc.



New South Wales) ; Easter Island (to Chile) ; the Galapagos Islands
(to Ecuador). In an area to be defined roughly as lying about the
Tropic of Cancer, between Hawaii and the Bonin Islands, there are
scattered a few small islands and reefs, of most of which the position,
if not the existence, is doubtful. Such are Patrocinio (about 28° 30'
N., 177° 18' E.) and Ganges (39° 47' N., 154° 15' E.), among others
which appear on most maps. Marcus Island, in 23° 10' N., 154° E.,
was annexed by Japan in 1899 with a view to its becoming a cable

The fGllowing paragraphs review the oceanic islands generally,
and are therefore concerned almost entirely with the central
and mid-western parts of the ocean. It is impossible to estimate
the total number of the islands; an atoll, for instance, which may

slate in the Marquesas, which afford a type of the extinct
volcanic islands, as does Tahiti. In other areas, however, there
is still volcanic activity, and in many cases volcanoes to which
only tradition attributes eruptions can hardly be classified as
extinct. Hawaii contains the celebrated active crater of
Kilauea. In Tonga, in the New Hebrides, and in the long chain
of the Solomons and the Bismarck Archipelago there is much
activity. Submarine vents somelimes break forth, locally
raising the level of the sea-bottom, or even forming temporary
islands or shoals. Earthquakes are not uncommon in the
volcanic areas. Most of the volcanic islands are lofty in propor-
tion to their size. The peaks or sharp cones in which they

Islands of the Pacific



sq. m.



sq. m.



sq. m.


To Great

Fiji . • .. ■
Louisiade Archip.
Santa Cruz Island
Solomon Islands
(part) . . .





Gilbert Island



America Islands
Cook Islands'.
EUice Islands .
Manihiki Islands
Niue . . .
Phoenix Islands

Tokelau Islands
Tonga Islands.










1 ,000






Total, British







To United
States of

Guam ....




Samoa (part) .




Total, U.S.A





To France .

Loyalty Island
New Caledonia .



Marquesas Islands
Paumotu Archip.
Society Islands
Tubuai Islands
Wallis Archip. .








Total, French





To Germany.

Bismarck Archip.
Solomon Islands
(part) . . .



Caroline Islands .
Mariana Islands

(excl. Guam)
Marshall Islands .
Pelew Islands . .








Samoa (part) .



Total, German







New Hebrides ^ .



Total . .

Melanesia .






Polynesia .



The above figures give a total land area for the whole region of 69,561 sq. m., with a population of 978,130; but they are for the most

part merely approximate.

be divided into a large number of islets, often bears a single
name. The number of names of islands and separate groups in
the Index to the Islands of the Pacific (W. T. Brigham), which
covers the limited area under notice, is about 2650, exclusive
of alternative names. Of these, it may be mentioned, there is a
vast number, owing in some cases to divergence of spelling in
the representation of native names, in others to European dis-
coverers naming islands (sometimes twice or thrice successively)
of which the native names subsequently came into use also.

The islands may be divided broadly into volcanic and coral
islands, though the physiography of many islands is imperfectly
known. There are ancient rocks, however, in New Caledonia,
which has a geological affinity with New Zealand; old sedimen-
tary rocks are known in New Pomerania, besides granite and
porphyry, and slates, sandstone and chalk occur in Fiji, as weU
as young volcanic rocks. Along with these, similarly, hornblende
and diabase occur in the Pelew Islands and gneiss and mica

' These are dependencies of New Zealand, as are also the follow-
ing islands and groups which lie apart from the main Polynesian
clusters, nearer New Zealand itself: Antipodes Islands, Auckland
Islands, Bounty Islands, Campbell Islands, Chatham Islands,
Kermadec Islands.

^ Under British and French influence jointly.

frequently culminate, combined with the rich characteristic
vegetation, are the principal features which have led all travellers
to extol the beauty of the islands.

In the central and western Pacific the northern and southern
limits of the occurrence of reef-forming corals are approximately
30° N. and 30° S. It may be added that this belt narrows
greatly towards the east, mainly from the south, in sympathy
with the northward flow of cold water off the coast of South
America. But apart from this the limits are seen to accord
fairly closely with the geographical definition of the area under
consideration. Here the broad distinction has been drawn
between volcanic and coral islands; but this requires amplifica-
tion, both because the coral islands follow more than one type,
and because the work of corals is in many cases associated with
the volcanic islands in the form of fringing or barrier reefs. As
to the distribution of coral reefs within the Pacific area, in
Micronesia the northern Marianas (volcanic) are without reefs,
which, however, are well developed in the south. The Pelew
islands have extensive reefs, and the Carohne, MarshaU and
Gilbert islands are almost entirely coral. In Melanesia, as has
been seen, the volcanic type predominates. Coral reefs occur
round many of the islands (e.g. the Louisiade and Admiralty



groups, New Caledonia and Fiji), but in some cases they are
wholly absent or nearly so {e.g. the eastern Solomon Islands and
the New Hebrides). Of the Polynesian Islands, the Hawaiian
chain presents the type of a volcanic group through which coral
reefs are not equally distributed. The main island of Hawaii
and Maui at the east end are practically without reefs; which,
however, are abundant farther west. Round the volcanic
Marquesas Islands, again, coral is scanty, but the Society
Islands, Samoa and Tonga have extensive reefs. The various
minor groups to the north of these (Ellice, Phoenix, Union,
Manihiki and the America Islands) are coral islands. Christmas,
one of the last-named, is reputed to be the largest lagoon island
in the Pacific. The Paumotu Archipelago is the most extensive
of the coral groups.

The coral islands are generally of the form well known under
the name of atoU, rising but sHghtly above sea-level, flat, and
generally of annular form, enclosing a lagoon. Often, as has
been said, the atoU is divided into a number of islets, but in some
smaller atolls the ring is complete, and the sea-water gains access
beneath the surface of the reef to the lagoon within, where it is
sometimes seen to spout up at the rise of the tide. Besides the
atolls there is a type of island which has been called the elevated
coral island. The Loyalty Islands e.xhibit this type, in which

Online LibraryHugh ChisholmThe Encyclopædia britannica; a dictionary of arts, sciences, literature and general information (Volume v. 20) → online text (page 157 of 353)