between the approaching extremities of the eastern and western
mountain-ranges ; the St. Lawrence sloping off northeastward ;
GENERAL FEATURES OF THE EARTH. 25
the Mackenzie, to the northward ; the central area of the phiin
dividing the three systems being only about 1700 feet above the
ocean, — a less elevation than about the head-waters of the Ohio in
the State of New York.
South America, like North America, has its great western range
of mountains, and its smaller eastern (fig. 19 ); and the Brazilian
Fig. 19.
A.
w a h K
line (6) is closely parallel to that of the Appalachians. As the
Andes [a] face the South Pacific, a wider and probably much
deeper ocean than the North Pacific, so they are more than twice
the height of the Rocky Mountains, and, moreover, they rise more
abruptly from the ocean, with narrow shore-plains.
Unlike North America, South America has a broad ocean on the
north, — the North Atlantic in its longest diameter ; and, accord-
ingly, this northern coast has its mountain-chain reaching along
through Venezuela and Guaiana.
The drainage of South America, as observed by Professor Guyot,
is closely parallel with that of North America. There are,Jirst, a
southern, — the La Plata, — reaching the Atlantic towards the south,
between the converging east-and-west chains, like the Mississippi ;
second, an eastern system, — that of the Amazon, — corresponding to
the St. Lawrence, reaching the same ocean just nortli of the
eastern mountain-border ; and, third, a northern system, — that of the
Orinoco, — draining the slopes or mountains north of the Amazon
system. The two Americas are thus singularly alike in system of
structure : they are built on one model.
The relation of the oceans to the mountain-borders is so exact
that the rule-of-three form of statement cannot be far from the
truth. As the size of the Appalachians to the size of the Atlantic, so is the
size of the Rocky chain to the size of the Pacific. Also, As the height of the
Rocky chain to the extent of the North Pacific, so are the height and boldness
of the Andes to the extent of the South Pacific.
30. (2.) Europe and Asia. — The land covered by Europe and
Asia is a single area or continent, only partially double in its
nature (^ 19). Unlike either of the Americas, it lies east-and-
west, with an extensive ocean facing Asia on the south ; and its
great feature-lines are in a large degree east-and-west. Tlie Arctic
is on the north ; the North Atlantic is on the west ; the North
26 PHYSIOGRAPHIC GEOLOGY.
Pacific on the east ; Africa and the Indian Ocean are on the south.
The Atlantic is the smallest ocean ; the North Pacific next, — for its
average depth is probably not over 13,000 feet (p. 12), and it is
much encumbered by islands to the west-of-south ; the Indian
Ocean next, — for it is full 5000 miles wide in front of the Asiatic
coast, and singularly free from islands. The boundary is a complex
one, and the land between the Atlantic and Pacific over 6000
miles broad.
On the side of the small North Atlantic there are the moun-
tains of Norway and the British Isles, the former having a mean
height of 4000 feet. On the Pacific side there are loftier moun-
tains, extending in several ranges from the far north to southern
China, — the Stanovoi, Jablonoi, and the Khingan Ranges ; and off
the coast there is still another series of ranges, now partly sub-
merged, — viz., those of Japan and other linear groups of islands.
These stand in front of the interior chain, very much as the
Cascade Range and Sierra Nevada of the Pacific border of America
are in advance of the summit-ridges of the Rocky Mountains,
and both are alike in being partly volcanic, with cones of great
altitude.
Facing the still greater Indian Ocean, and looking southward,
stand the Himalayas, — the loftiest of mountains, — called the Hima-
layas as far as Cashmere, and from there, where a new sweep in
the curve begins, the Hindoo Cush, — the whole over 2000 miles in
length : not so long, it is true, as the Andes, but continued as
far as the ocean in front continues. The mean height of the
Himalayas has been estimated at 16,000 feet ; over forty of the
I)eaks surpass Chimborazo. The Kuen-Luen Mountains, to the
north of the Himalayas, make another crest to the great chain,
with Thibet between the two. Going westward, the mountains
decline, though there are still ridges of great elevation.
On the north there are the great Siberian plains, backed by the
Altai, about half the Himalayas in height. The Altai thus have
Fig. 20.
the same relation to the Himalayas as the Appalachians to the
Rocky Mountains, or the Brazilian Mountains to the Andes, yet
GENERAL FEATURES OF THE EARTH. '27
with a, striking difference in the immense shore-plain hriwccn
tliem and the sea.
The sketch (fig. 20) presents the general features to tlie eye.
At a, there is the elevated land of India ; between a and b, the low
river-plain at the base of the Himalayas ; at b, the Himalayas ; b to
c, Plains of Thibet ; e, the Kuen-Luen ridge ; ctod, Plains of Mongolia
and Desert of Gobi ; at (/, the Altai ; d to n, the Siberian plains.
The interior region of the continent in its eastern half is the
plateau of Gobi and Mongolia, which, at 4000 feet, is low compared
with the mountains in front and rear. More to the westward the
region c, d becomes intersected by the lofty Thian-chan Range.
Still farther westward the surface declines into the great depression
occupied by the Caspian and Aral, part of which is below tide-level
The interior drainage-system for Asia is without outlet. The
waters are shut up within the great basin, the Caspian and Aral
being the seas which receive those w^aters that are not lost in the
plains. The Volga and other streams, from a region of a million
of square miles, flow into the Caspian.
The Urals stand as a partial barrier between Asia and Europe,
parallel nearly with the mountains of Norway.
Europe has its separate system of elevations and interior plains ;
but it is not necessary to dwell on it here.
The great continental mass accords wath the law stated : — high
borders proportioned in the case of each to the extent of the bor-
dering oceans, and a general basin-form.
31. (3.) Africa. — Africa has the Atlantic on the w^est, the larger
Indian Ocean on the east, with Europe and the Mediterranean on
the north, and the South Atlantic and Southern Ocean on the
south. Its system of structure has been well explained by Pro-
fessor Guyot. As he has stated, the northern half has the east-
and-west position of Asia, and the southern the north-and-south
of America ; and its reliefs correspond Avith this structure. The
Guinea coast belonging to the northern half projects east in front
of the South Atlantic, and is fticed by the east-and-west Kong
Range ; and opposite, on the Mediterranean, there are the Atlas
Mountains, one peak of which is 11,000 feet high, — although the
ridges are generally much lower. The two thus oppose one
another, like the Himalayas and Altai. The southern half of the
continent has a border mountain-range the most of the way along
the west and south. On the latter, which has a length of 700
miles, there are three or four parallel ridges, and some of the
peaks are 4000 to 7000 feet high. Up the eastern coast there is
28 PHYSIOGRAPHIC GEOLOGY.
also a mountain-border, and higher than the western. By these
border-ranges the interior of Africa is mostly shut off from the sea :
— it is a shut-up continent, as Guyot calls it. The loftiest mountains
are in Abyssinia and Zanguebar, facing the Indian Ocean. Abys-
sinia is, to a great extent, an elevated plateau, GOOO to 7000 feet in
height, with ridges reaching to 11,000 and 13,500 feet ; and farther
south, in 3° 40'', stands the snowy Kilimanjaro, which, according
to report, is 20,000 feet high, and probably the source of the Nile.
The interior of the northern or east-and-west half consists of (1)
the Great Sahara region, a plateau of about 1500 feet elevation,
with its undulations and ridges ; (2) an east-and-west depression
on the north, between Sahara and the border-mountains, nearly to
the ocean's level in some parts, and being the region of the oases ;
(3) a partial east-and-west depression about the parallels 10° to
15° JS"., separating the Sahara plateau from the southern, and con-
taining Lake Tchad, at an elevation of 800 feet. The interior of
the southern half is a plateau 2000 to 2500 feet in average height :
the great lake Uniamesi, south of the equator, between the meri-
dians 25° and 35°, is stated by Livingstone to have its surface 2000
feet above the sea.
Fig. 21.
The sections figs. 21 and 22 give a general idea of these features
Fig. 21 is a section from south to north (the heights necessarily
much exaggerated in proportion to the length); a, the southern
mountains ; h, the southern plateau ; c, Lake Tchad depression ;
d, Sahara plateau ; e, oases depression ; /, mountains on the Medi-
terranean, of which there are two or three parallel ranges. Fig. 22
Fig. 22.
W E
represents the surface-outline from west to east through the
southern half of the continent. In all these sections all minor
details are omitted, in order to bring out clearly the system, or
continental model.
Africa has, therefore, the basin-form, but is a double basin ; and
its highest mountains are on the side of the largest ocean, the
Indian. The height of the mountains adjoining the Mediter-
ranean is the only exception to the relation to the oceans ; and this
is small. Moreover, the position of the head of the continent
GENERAL FEATURES OF THE EARTH, 29
against the continent of Europe with only the Mediterranean
between, instead of an ocean, is a sufficient reason for the excep-
tions. Africa has some resemblance to America, but America
turned about, with the most elevated border on the east instead of
the west.
32. (4.) Australia. — Australia conforms also to the continental
model. The highest mountains are on the side of the Pacific, —
the larger of its border-oceans. The Australian Alps, in New South
Wales, fticing the southwest shores, have peaks 5000 to 6500 feet in
height. The range is continued northward in the Blue Mountains,
whicli are 3000 to 4000 feet high, with some more elevated summits,
and, beyond these, in ridges under other names, the whole range
being mostly between 2000 and 6000 feet in elevation. The interior
is regarded as a low, arid region.
The continents thus exemplify the law laid down, and not
merely as to high borders around a depressed interior, — a prin-
ciple stated by many geographers, — but also as to the highest border
being on the side of the greatest ocean.* The continents, then, are
all built on one model, and in their structures and origin have a
relation to the oceans that is of fundamental importance.
It is owing to this law that America and Europe literally stand
facing one another, and pouring their waters and the treasures of
the soil into a common channel, the Atlantic. America has her
loftier mountains, not on the east, as a barrier to intercourse with
Europe, but off in the remote west, on the broad Pacific, where
they stand open to the moist easterly winds as well as those of
the west, to gather rains and snows, and make rivers and alluvial
plains for the continent ; and the waters of all the great streams,
lakes, and seas make their way eastward to the narrow ocean that
divides the civilized world. Europe has her slopes, rivers, and
great seas opening into the same ocean; and even central Asia
has her most natural outlet westward to the Atlantic. Thus, under
this simple law, the civilized world is brought within one great
country, the centre of which is the Atlantic, uniting the land by a
convenient ferriage, and the sides the slopes of the Eocky Moun-
tains and Andes on the west, and the remote mountains of Mon-
golia, India, and Abyssinia on the east.\
This subject affords an answer to the inquiry, What is a continent
as distinct from an island ? It is a body of land so large as to have
the typical basin-form, — that is, mountain-borders about a low inte-
* First announced American Jour. Sci. [2], xvii., vols. iii. iv.. 1847, and xxii.
335, 1856. t Sec Guyot's Earth and Man.
30 PHYSIOGRAPHIC GEOLOGY.
rior. The mountain-borders of the continents vary from 500 to
1000 miles. Hence a continent cannot be less than a thousand
miles (twice five hundred) in width.
3. SYSTEM IN THE COURSES OF THE EAPtTH'S FEATURE-
LINES. .
33. The system in the courses of the earth's outlines is exhibited
alike over the oceans and continents, and all parts of the earth are
thus drawn together into even a closer relation than appears in the
principle already explained.
The principles established by the facts are as follow : That (1)
two great systems of courses or trends prevail over the world, a north-
western and a northeastern, transverse to one another ; (2) that the islands
of the oceans, the outlines and reliefs of the continents, and the
oceanic basins themselves, alike exemplify these systems; (3) that
the mean or average directions of the two systems of trends are
northwest-bj^-west and northeast-by-north ; (4) that there are wide
variations from these courses, but according to principle, and that
these variations are often along curving lines; (5) that, whatever
the variations, when the lines of the two systems meet, they meet
nearly at right angles or transversely to one another.
34. (1.) Islands of the Pacific Ocean. — The lines or ranges of
islands over the ocean are as regular and as long as the mountain-
ranges of the land. To judge correctly of the seeming irregularities,
it is necessary to consider that in chains like the Rocky Mountains,
or Andes, or Appalachians, the ridges vary their course many de-
grees as they continue on, sometimes sweeping around into some
new direction, and then returning again more or less nearly to their
former course, and that the peaks of a ridge are very far from
being in an exact line even over a short course ; again, that several
approximately parallel courses make up a chain.
A. Northwesterly system of trends. — In the southwestern Pacific,
the Neio Hebrides (fig. 23) show well this linear arrangement; and
even each island is elongated in the same direction with the group.
This direction is nearly northwest (N. 40° W,), and the length of the
chain is 500 miles. New Caledonia, more to the southwest, has
approximately the same course, — about northwest. Between New
Hebrides and New Caledonia lies another parallel line, the Loyalty
Group. The Salomon Islands, farther northwestward, are also a
linear group. The chain is mostly a double one, consisting of two
parallel ranges, and each island is linear, like the group, and with
the same trend. The course is northwest-by-west, the length
600 miles.
GENERAL FEATURES OF THE EARTH.
31
In the North Pucific, the Hawaian range has a west-nortliwest
course. The Sandwich or Ilawaian Islands (fig. 24), from Hawaii
Fig. 23.
15" S
W
20'
17Cr
LM
"T
^
■CD
to Kauai, make up the southeasterly part of the range, about 400
miles in length. Beyond this the line extends to 175° E., making
Fig. 24.
155
0^
>
II, Hawaii; M, Maui; 3, Kahoolawe; 4, Lauai ;
C, Mololvai; 0, Oalm; K, Kauai.
a total length of nearly 2000 miles, — a distance as great as from
Boston to the Great Salt Lake in the Rocky Mountains, or from
London to Alexandria. Moreover, in this chain there are on
32
PHYSIOGRAPHIC GEOLOGY
Hawaii two summits nearly 14,000 feet in altitude ; and if the
ocean around is 15,000 feet deep, the whole height of these peaks
is just that of Mount Everest in the Himalayas.
between these groups lie the islands of the ocean, all nearly
parallel in their courses. Figs. 25, 26 are examples.
Fig. 25.
,
Go
140
Fig. 26.
16-''-^
-ISO^W-
b
^ty. o
'^N
The following table gives the courses of the principal chains of the ocean :-
Course.
Hawaian range ^'. 64° W.
Marquesas Islands X. 60° W.
Paumotu Archipelago X. 60° W.
Tahitian or Society X. 62° W.
Hervey Islands N. 65° W.
Samoan or Navigator Islands N, 68° W.
Tarawan or Kingsmill Islands N. 34° W.
Ralick group K 37° W.
Radack group X. 30° W.
Xew Hebrides X. 40° AY.
New Caledonia X. 44° W.
North extremity of Xew Zealand N. 50° W.
Salomon Islands X. 57° W.
Louisiade group X. 56° W.
New Ireland N. 65° W.
B. Northeasterly system of trends. — The body of New Zealand
has a northeast-by-north course. The line is continued to the south,
through the Auckland and Macquarie Islands, to 58° S. To the
north, in the same line, near 30° 8., lie the Kermadec Islands, and
farther north, near 20° S., the Tonga or Friendly Islands.
The Ladrones, north of the equator, follow the same general
course. It also occurs in many groups of the northwesterly system
characterizing subordinate parts of those groups. Thus, the west-
ernmost of the Hawaian Islands, Nihau, lies in a north-northwest
line, and the two lofty peaks of Hawaii have almost the same
bearing.
GENERAL FEATURES OF THE EARTH.
33
35. Pacific island-chains. — The groups of Pacific islands, with a
few exceptions, are not independent lines, but subordinate parts of
island-chains. There are three great island-chains in the ocean
which belong to the northwesterly system, — the Hawaian, the Poli/-
vcsian, and the Australasian, — and, excluding the Ladrones, which
belong to the western Pacific, one belonging to the northeasterly
system, viz. : the Tongan or New Zealand chain.
(1.) Haiuaian chain. — This chain has already been described.
(2.) Pol)/7iesian chain. — This chain sweeps through the centre of
the ocean, and has a length of 5500 miles, or nearly one-fourth the
circumference of the globe. The Paumotu Archipelago and the
Tahitian and Hervey Islands are parallel lines in the chain, forming
its eastern extremity ; westward there are the Samoan and Tara-
wan groups and others intermediate ; still northwestward there
are the Eadack and Ralick groups, and in 20° N., on the same line,
Wakes Island.
Fig. 27.
1 to 10, the Polynesian chain : 1, Paumotu group ; 2, Tahitian ; 3, Rurutu group ; 4, Hervey
group ; 5, Samoan or Navigators' ; 6, Vakaafo group ; 7, Vaitupu group ; 8, Kingsmill group ;
9, Ralick; 10, Radack; 11, Carolines; 12, Marquesas ; 13, Fanning group; 14, Hawaian.
a to /(.part of the Australasian chain: a, New Caledonia; b. Loyalty group; c, New Hebri-
des; d, Santa Cruz group ; e, Salomon Islands; /, Louisiade group; g, New Ireland; h, Ad-
miralty group.
In fig. 27 the positions and trends of the various groups in this
Polynesian chain are indicated, by lines numbered from 1 to 10,
34 THYSIOGRAPHIC GEOLOGY.
(a.) The chain, as is seen, consists of a series of parallel ranges
succeeding and overlapping along the general course, in the manner
illustrated on page 19, when speaking of mountains, {b.) It varies
its course gradually from west-northwest at the eastern extremity to
north-northwest at the western, (c.) Its mean trend is northwest-
by-west (N. 56° W.), the mean trend of all the groups of the north-
westerly system in the ocean, {d.) The chain is a curving chain,
convex to the southward, and marks the position of a great central
elliptical basin of the Pacific having the same northwesterly trend.
The Hawaian is on the opposite side of it, slightly convex to the north.
The Marquesan range lies in the same line with the Fanning group to the
northwest, just north of the equator; and, if a connection exists, another great
chain is indicated, — a Marquesan chain.
(3.) Australasian chain. — New Hebrides and New Caledonia belong
to the Australasian island-chain. The line of New Hebrides is
continued northwestward in the Salomon group and New Ireland,
though bending a little more to the westward, and terminates in
Admiralty Land, near 145° E., where it becomes very nearly east-
and-west: the length of the range is about 2000 miles. Taking another
range in the chain, New Caledonia, the course is continued in the
Louisiade group ; then the north side of New Guinea, which con-
tinues bending gradually till it becomes east-and-west, near 135° E. :
and in the southeast, belonging to the same general line, there is the
foot of the New Zealand boot. The coral islands between New
Caledonia and Australia appear also to be other lines in the chain.
From New Guinea the east-and-west course is taken up by Ceram,
and again, more to the south, in the Java line of islands ; and from
Java the chain again begins to rise northward, becoming northwest
finally in Sumatra and Malacca.
The several ranges make up one grand island-chain, with a
double curvature, the whole nearly GOOO miles long. The relation
of the parts in the system is shown in figure 28, in which a line
stands for each group and indicates its course.
The composite nature of the chain is here apparent ; as also the
curving course, in connection with a prevailing conformity to a
northwesterly trend.
(4.) Blending of the Australasian and Polynesian island-chains. — The
two chains blend with one another in the region of the Carolines.
This large archipelago properly includes the Ralick and Radack
groups. At the Tarawan group, just south, the Polynesian chain
divides into two parts, — the Ralick and Radack ranges. But the
main body of the archinelairo f '^ee ficr. 27 and the chart) trends off to
GENERAL FEATURES OF THE EARTH.
35
the westward, and is a third branch, conforming in direction to
the Australasian system.
Fig. 28.
/ „
A. B, C, Sumatra and Java line of islands; D, Ceram; E, nortli coast
of New Guinea; F, South New Guinea; G, Admiralty Islands; 11,
Louisiade group; I, Salomon ; J, Santa Cruz group; K, New He-
brides; L, Loj-alty grouj); M, New Caledonia; N, high lands of
northeast Australia ; 0, New Zealand ; a b, northwest shore of Bor-
neo; cd, east Borneo; ef, west coast of Celebes; g h, west coast of
Gilolo.
The Caroline Archipelago forks at its southeastern extremity, —
one portion, the Tarawan, Radack, and Ralick Islands, conforming
to the Polynesian system (8, 9, 10 in fig. 27), while the great body
of the Caroline Islands trend off more to the westward (No. II),
parallel with New Zealand and the Admiralty group {g, A of the
same cut) and others of the Australasian system.
(5.) New Zealand chain. — The ranges in this chain are mentioned
in § 34. The whole length, from Macquarie Island, on the south,
to Vavau, a volcanic island terminating the Tonga range, on the
north, is 2500 miles. To the east of New Zealand lie Chatham Island,
Beverly, Campbell, and Emerald, which correspond to another range
in the chain.
This transverse chain is at right angles with the Polynesian system
at the point where the two meet. Moreover, it is nearly central
to the ocean ; and in its course farther north lie the Samoan
and Hawaian Islands, two of the largest groups in the Polynesian
system.
The central position, great length, and rectangularity to the
northwest ranges give great significance to this New Zealand or
northeasterly system of the ocean.
36 PHYSIOGRAPHIC GEOLOGY.
The large Feejee group lies near the intersection of the three Pacific chains ;
and hence its numerous islands do not conform to either one, though the larger
islands approximate most nearly to the last in direction.
36. (2.) Pacific and Atlantic Oceans. — The trend of the Pacific
Ocean as a whole corresponds with that of its central chain of
islands, and very nearly with the mean trend of the whole. It is a
vast channel, elongated to the northeast. The range of heights along
northeastern Australia runs from the eastern coast northwesterly,
by the head of the great gulf (Carpentaria) on the north ; and the
opposite side of the ocean along North America, or its bordering
mountain-chain, has a similar mean trend. A straight line drawn
from northern Japan through the eastern Paumotus to a point a
little south of Cape Horn may be called the axis of the ocean.
This axial line is nearly half the circumference of the sphere, and
the transverse diameter of the ocean full one-fourth the circum-
ference: so that the facts relating to the Pacific chains must have
a universal importance.
The North Atlantic Ocean trends to the northwest, — or at right angles,
nearly, to the Pacific : this is the course of the coasts, and therefore