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:,.c> . ^'

THE NEW Y;'kK

PUBLIC LIBRARY

ASTOR. L»NOK
TILBtM fOUNDATIOH*

ELEMENTARY

PHYSICAL GEOGRAPHY

WILLIAM MORRIS DAVIS

gTUBOIS-HOOPKB PBOFE880B OF GBOLOOY IN

Habyabd Uniyebsity

• . • • » • t t

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Boston, U.SA., and London

GINN & COMPANY, PUBLISHERS

QDie 3[t|)en8rttm '^xtu

1903

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THE NLVv- ij. n
PUBLIC LIBRARY

746490

A8TOR, LENOX ANO
TILDEN FOUNDATIONS

H 1916 L

Entebed at Stationebs' Hall

/I .••- *..'•:• -AV-^^OHTS RE8EBVED

• • • • V • •• • • • . • •

• • ••• •• • • • • •

• •• • •

• • • »

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• - .

• •••

• • •

- • • •

• • - • ••

• • ••

PSEFACE

The educational progress of recent years has resulted
in two profitable advaDces for the venerable subject of
Geography, A strong feeling has been developed in favor
of treating the subject as a whole more rationally than
lieretofore, and a wholesome desii^e has arisen in favor of
introducing some of its scientific aspects more generally
into the school course. A natural accompaniment of this
progress has been a demand for textrbooks that shall present
Physical Geography in its modern scientific development
as well as in an elementwy form, Tlie pi'esent book,
reduced from the author's "Physical Geography," lias been
prepared to meet this demand.

The reduction of the earlier book to tlie present volume
has been made chiefly by omitting the more aJvaiiced
problems and by simplifying and abbreviating the treat-
ment of the remainder; but the chapter on The Atmos-
phere is here given a greater length than before ; and a new
chapter is added on The Distribution of Plants, Animals,
and Man, considered from a physiographic standpoint.
Several topics of a somewhat more advanced nature than
the rest of the text, and yet of too great importance to he

^ omitted altogether, are placed in supplements to Chap-

-, ters I, II, and III.

iv PREFACE

The plan of this volume is, like that of its predecessor,
to give the problems of Physical Geography a rational
treatmeot. The object of this method is not simply to
explain physiographic facts, but through explanation to
increase the appreciation o£ the facts themselves. It is,
however, not enough that physiographic facta should be
associated with their causes ; they must also be seen in
relation to their consequences if their full importance is
to be realized. This relation must not be presented merely
as an afterthought, in a detached chapter at the end of a
book; it must accompany the presentation of the facts
themselves. As Guyot long ago said so well: "To
describe, without rising to the causes, or descending to
the consequences, is no more science than merely and
simply to relate a fact of which one has been a witness."
The ideas of cause and of consequence, one preceding,
the other following, the physiographic fact, have therefore
been held constantly in mind by the author; they should
be no less constantly rememhered by the teacher and
impressed upon the pupil.

Yet, while the causal notion is introduced as far as
possible, it must be recognized that certain facts of great
importance cannot he really accounted for in an elementary
book. Such facts must therefore be described rather than
explained. For example, the rotation of the earth and the
separation of continental masses from ocean basins are
subjects of great importance ; they must be described, and
their consequences deserve careful atteution, but their
causes involve speculative investigation of a grade that
far transcends the reach of an elementaiy text. Again, j

L J

PREPACK V

the simpler phenomena of the tides must be presented ;
their period may be correlated with the movement iif the
moon, and the moon may he thus indicated as their chief
cause ; hub the relation between lunar cause and tidal
effect cannot be demonsti-ated to young pupils. A mere
outline of theory, with the briefest conaiderfition of the
joint action of sun and moon, is introduced in the sup-
plement to Chapter III.

The general cii'culation of t!ie atmosphere is also far
beyond elementary explanation. The circulation may be
not unreasonably asserted to depend on the differences
between equatorial and polar temperatures ; but the more
intelligent the pupil, the less can he be satisfied with
a simple conventional origin of the prevailing westerly
winds. Exjilanation of this complicated problem is there-
fore touched upon lightly ; while emphasis is given to the
elements of which the circulation consists, to the correla-
tion of these elements, and to the deduction of climatic
conditions from them. The deflective effect of the earth's
rotation is almost universally misimderatood, because it
cannot he fully explained in an elementary manner. Its
quality is briefly asserted in the text, and on account of
ita importance a correct explanation in the simplest pos-
sible form is inserted in the supplement to Chapter II ;
but neither this supplement nor that on the tides should
be studied by the youngest pupils.

On the other hand, the forms of the lands have not as a
rule been sufficiently explained in text-books on Physical
Geography. Fifty years ago there was justification for
the wnpirical treatment and even for the neglect of land

forms, in the ignorance of geographers concerning their
origin ; but the investigations of the last thirty years have
thrown a flood of light on this important division of the
subject, and to-day it may be treated as rationally as any
other. Many problems, formerly obscure, are novF seen to
be essentially simple and to lie entirely within the reach
of elementary treatment. It has thus become possible to
extend the explanatory method, long familiar in the study
of the atmosphere and the ocean, to the lands as well;
and to present plains and plateaus, mountains and volca-
noes, rivers, valleys, and shore lines under a rational
system. It is believed that this division of the subject
is here treated in a manner more systematic and compre-
hensive and at the same time more simple and I'easonable
than is the case in any other elementary book. It should
however be carefully Iwrne in mind that the explanation
of the processes which are involved in the dissection of
a plateau, for example, is not introduced mei-ely that the
past history of the plateau shall become known, but
chiefly that the existing features and especially the
systematic correlation of these features shall be better
perceived and remembered.

While the list of topics ti'eated wiU, it is believed, be
found exceptionally full for an elementary book, it has
nevertheless been necessary to go somewhat against time-
honored traditions in omitting certain subjects. Elemen-
tary text-books should not present an encyclopedic richness
of contents, as if to show the learning of their authors;
they should provide a well-selected body of useful infor-
mation having disciplinary value, pertinent to their subject

PREFACE vii

and appropriate to young pupils. It has therefore been
decided to follow carefully the outline nf Physical Geog-
raphy lately prepared for and published by the National
Educational Association, and to exclude certain traditional
but irrelevant topics belonging properly to Astronomy,
Geology, and Biology. It has also been deemed expedient
tn omit, certain other relatively advanced topics ; sucli, for
example, as the distribution of atmospheric pressure, shown
by charts of isobaric lines, which have been, it may be said,
fashionable since the publication of Buchan's excellent
charts of these elements. Important as are the facts thus
shown for the more advanced study of meteorology, they
have no immediate climatic importance, and their proper
use involves so many advanced coneiderations that they are
best excluded from elementary study. Again, there is a
chart of cotidal lines, purporting to show the advance of
the tidal wave through the oceans, wliieh has been repeat-
edly copied since it was first published by Whewell in 1833 ;
* but this pleasing generalization is omitted here because it
was discredited by its very author in 1835, and because
ithaa never since then received the approval of experts in
tidal investigation. The best chart of cotidal lines, that
of Berghaus' Physical Atlas (reproduced in the United
States Coast Survey Report for 1900, Appendix No. 7,
Figure 25), leaves the open oceans blank.

The method of presentation adopted is sometimes induc-
tive, sometimes deductive, according to the subject in hand.
The inductive method ia more largely used, because young
pupils are as a ride better able to leani from direct descrip-
tion tii&a. from inferences baaed on general principles. The

Tlii PREFACE

exercises suggested for the study of weather maps, in the
supplement to Chapter II, are purely inductive ; and the sev-
eral chapters on the development of land forms are largely
inductive. But it must not be forgotten that the simpler
processes of deduction are perfectly familiar to young
pupils, and may be safely employed in teaching where
they are appropriate to tlie topic in hand. It is indeed
advisable that the pupil should gain some experience in
deduction as well as in induction, and Physical Geography
should be recognized as presenting ample ojiport unity
for the exercise and development of both these mental
processes. The relation of rainfall to tlie several mem-
bers of the atmospheric circulation may Ite instanced as
appropriately deductive, because of the systematic rela-
tions of these topics.

The illustrations in the chapters on land forms are of
two kinds. The block diagrams represent ideal types.
The views of actual landscapes in woodcuts and plates
serve as examples of the ideal types. The block diagrams
are in several respects more comprehensive than any
actual view can be. They show so large an area, from so
elevated a point of view, that the relation of the parts to
the whole is easily perceived; tliey omit numerous and
frequently irrelevant details by which the pupil's attention
might be distracted ; they present in the most elementary
manner possible the correlation of undei^round structure
and surface form ; and in this respect they are far supe-
rior to mere geological sections, in which the land surface
is represented only by a profile line which few young
pupils can translate into a topographic form. Exercises in

hd.

drawing simple outline maps from the block diagrams are
frequently suggestfid, in order to insure the recognition
of the essential features of the type. It will also be found
useful to ask the pupil to indicate the relation of a view
to its type diagram, as is done in tlie text for Figui-es 71
and 73, and for Figures 141 and 142.

The questions inserted in tlie test are intended to aid
the pupil in learning his lessons ; the questions at tlie end
of the chapters are intended for use by the teacher in tests
aad reviews after the lessons have been learned. If it is
desired to extend the time devoted to Physical Geography
by classes whose average age is somewhat above that for
which this book may be used, all of the text, as well as the
supplements to Chapters I, II, and III, may be studied in
fulL If it is desired to shoilsn the course, tlie supple-
ments may be passed over, the number of map drawings
may be decreased, and certain sections that are concerned
with relatively advanced topics (for example, Sections 99,
103, 107, 124) may be omitted.

The teacher will find it practically convenient to indi-
cate by a brief reference in the page margin the books and
maps mentioned in the Appendix, The examples there
referred to should be supplemented as far as possible by
local examples observable at or near the school. Illustra-
tions of many topics treated in Chapter II will be found
in the ordinary observation of passing weather phenomena.
Many of the activities of the lands may be illustrated by
local excursions, for which the autumn is a convenient
season; while examples of the land forms seen in the
school neighborhood should be studied in the spring.

X PREFACE

Inasmuch as land forms vary greatly from place to place,
no general guide can be of service in this division of the
subject; but teachers are advised to make themselves
familiar with their school district by frequent excursions,
and to use as far as possible all the appropriate illustra-
'tions that they discover.

The author desires to express his thanks to a number of
his correspondents who have supplied photographs from
which several of the plates have been copied, and also to
a number of teachers and others who have accepted the
fatiguing task of criticising his manuscripts and proof,
particularly to Professor J. B. Woodworth of Harvard
University, Mr. M. Grant Daniell of Boston, and Mrs.
M. A. L. Lane of Hingham. The questions at the ends
of chapters have been prepared by Mr. R. H. Cornish,
of the Girls' High School, New York, whose practical
acquaintance with school work insures their value.

W. M. D.

Harvard University,
March, 1902.

CONTENTS

CHAPTER PAOK

I. The Earth as a Globe 1

11. The Atmosphere 23

III. The Ocean 96

IV. The Lands 129

V. Plains and Plateaus 141

VI. Mountains 177

VII. Volcanoes 215

VIII. Rivers and Valleys 234

IX. Deserts and Glacuirs 278

X. Shore Lines 304

XL The Distribution of Plants, Animals, and Man 332

LIST OF PLATES

I. Grays Peak, Rocky Mountains of Colorado (photograph
by W. H. Jackson) Frontispiece

FACura PAos
II. A Sailing Vessel at Sea (by Neurdin) ....... 40

III. A. Cumulus Clouds ; B. Cirrus Clouds (by Riggenbach) . 63

IV. Waterspout over Vineyard Sound, Aug. 19, 1896 (by

J. N. Chamberlain) 67

V. The Bore, or Surf-like Flood I'ide, in an Estuary at the

Head of the Bay of Fundy, Nova Scotia 121

VI. The Great Plains (by W. D. Johnson) 168

VII. A Railroad rounding a Spur of Mt. Ouray, Colorado (by

W. H. Jackson) 190

VIII. Grandfather Mountain, North Carolina (by A. Keith) . 204
IX. A Water Gap in the Allegheny Mountains (by Maryland

Geological Survey) 211

X. Dinant on the Meuse, Belgium' (by Neurdin) 268

XI. The Braided Channels of the River Var in the Western

Alps 261

XII. Bad Lands in the Great Plains, South Dakota (by N. H.

Darton) 283

XIII. A Sand Dune rippled by the Wind (by G. K. Gilbert) . 287

XIV. The Muir Glacier, Alaska (by H. F. Reid) 292

XV. A Trough-like Glaciated Valley in the Western Alps (by

Neurdin) 299

XVI. A Land-tied Island, near Genoa, Italy (by A. Noack) . 316

XVII. A Branch of Sogne Fiord, Norway (by A. Lindahl) . . 320

XVIIL Forest in the Equatorial Rain Belt, Ceylon 348

XIX. Moab, an Irrigated Settlement in Eastern Utah (by L. M.

Prindle) 362

• •

Xll

r •

LIST or FIGURES

Eclipse of tbe Moon 2

Height uf Land and Depth of Sea 3

The Shadow of a Box, showing the Altitude of the Sun . . 8

HeridiHQH and Parallels 9

Latitude and Longitude . 0

Mariner's Coinpass 18

Globular Form of Earth shown by Vieibility of Stars ... 20

Mercurial Barometer 25

Mirage of Part ol a Schooner, formed on a Thin Layer of Air 30

The Comey Self-Recarding Thermometer 32

LluBtration of an Isothermal Line 33

Chart of Mean Annual Temperatures 34

Anemometer 38

The Planetary Circulation, of the AUnoBphere 40

Wet-Weatlier Streams of the Tarso Mountains, Sahara . . 42

Cyclonic and Anticyclonic Areas 45

Monthly Positions of the Earth witli Respect to the Sun . . 47

Chart of Mean Temperatures fur January 50.

Chart of Mean Temperatures for July 50

Chart of Annual Kange of Temperatai'e 51

Diagrams of Terrestrial Winds for January and July ... 63

Winds of January 54

Winds of July 6B

January Monsoons in Indian Ocean 57

July Monsoons in Indian Ocean 57

A Distant Thunderstorm 05

Regions of Tropical Cyclones 68

Chart of Mean Annual Raitifall 71

Annual Rainfall of the United States 73

Storm Tracks of the North Temporale Zone (after Ijoomis)
Botation of a Disk on a Rotating Globe

86 j

xiv LIST OF FIGURES

FIG. PAGE

32. Diagram of the Sun's Midday Altitude 88

33. Diagram of Sunrise and Sunset Hours .- . 89

34. Water and Land Hemispheres 97

36. An Ocean Steamship 98

36. Sounding Instrument and Water Bottle 99

37. Dredge 99

38. A Vessel beset by Pack Ice 103

39. An Iceberg 104

40. Globigerina (magnified 100 times) 105

41. Section of Continental Shelf 108

42. Orbital Movement of Water in Waves 109

43. Surf 112

44. Chart of Ocean Surface Temperatures and Currents .... 115

45. Displacement of a Vessel by Currents 116

46. Drift of Floating Objects by Currents 117

47. Low Tide in a Harbor 120

48. The Tidal Wave, or Bore, in the Seine 121

49. Jellyfish fioating in Sea Water 122

50. Deep-Sea Fish, x i 123

51. Deep-Sea Crustacean, x i 123

52. Earth and Moon ^ 125

53. Spring Tides, New Moon 125

54. Neap Tides, First Quarter 125

55. Spring Tides, Full Moon 125

56. Neap Tides, Third Quarter 125

67. Variation of Tides for Two Weeks 126

58. Height of Land and Depth of Sea 132

69. A Quarry showing Weathered Rock 135

60. Mountains bordering the Sea 142

61. Sample Map of a Mountainous Coast 142

62. Narrow Coastal Plain 144

63. . Sample Map of a Narrow Coastal Plain ........ 145

64. A Narrow Coastal Plain in Scotland 146

65. Broad Coastal Plain 147

66. Coastal Plain of the Carolinas 148

67. A Truck Farm on the North Carolina Coastal Plain . . . . 149

68. A Belted Coastal Plain 160

69. Sample Map of Part of a Belted Coastal Plain 161

LIST OF FIOL'KES

The Belted CoMtnl Plain of Soulhem New Jersey .... 153

An Embayed Coaslal Plain 164

Sample Map of an Embayed Coastal Plain 165

A Branch of CheBapenke Bay, Maryland 157

Ancient Coastal Plain of Wisconsin 1(11

A Plateau in Arizona 1(13

Diagram of a Narrow Canyon 1(J4

Diagram of a Widened C!anyun 1U5

The Allegheny Plateau 1((8

Canyon of ibe Kanawha River in Allegheny Pl.iieuu, W. Va. 160

The Enehanted Misa, New Mexico 172

Brobeu Plateaus ITS

Hurricane Ledge, a Disseoted Fault Cliff 174

A Mounlaiu Peak 178

Block Mountains 171>

Mountains of Southern Ore^n 180

A DisEected Mountain Kange, Utah 182

Diagram of the Jura, a Folded Mouiiiniii Range 184

Peaks of the Central Alps !8(l

An Alpine Peak of Slanting Layei-a 187

Path of an Ice Fall in the Alps U)2

The Landslide of Airolo, Switzerland IIH

A Landslide in the Himalayas IHo

The Himalaya Mountains 100

Alluvial Fans 108

A Filled Valley with a Flat Floor 1911

A Terraced Valley 200

Kailroad shaken by an Earthquake, Niirtheastem India , . -202

Land Surface displaced hy an Earthquake, Japmi .... 2tXS

The Piedmont Belt, Virginia 206

Map of Iho Piedmont Belt, Virginia 207

The Upland oE New England 208

Valley of the Deerlield in the New England Upland ... 200

Diagram of the Allegheny Mouiilains, Pennsylvania . . . 210

Model of Embayed Mountains 211

Vesuvius in Eruption 217

Monte NuuTO 218

Cinder Cone and Lava Flow, California 220

xvi LIST OF FIGURES

FIG. PAOS

108. Deception Island, a Volcanic Caldera (plan and section) . . 221

109. The Cone of Vesuvius in the Caldera of Monte Somma . . 221

110. Contour Map of Crater Lake in Mt. Mazama, Oregon ... 222

111. Excavations in Herculaneum 224

112. Distribution of Volcanoes and Coral Islands 226

113. Lava Flows on the Plateaus of Arizona 228

114. The Lava Plateau of Idaho, Oregon, and Washington ... 229

115. Contour Map of Mt. Shasta, California 230

116. Mt. Shasta 231

117. Map of the Lake Nicaragua District : . . 232

118. Diagram of Cavern and Sink Hole 235

119. Section showing Ground Water in Rock Crevices beneath a

Valley 237

120. Diagram of a Coastal Plain with Artesian Wells .... 238

121. A Geyser 240

122. A Dividing Ridge in the Mountains of Northwest England . 242

123. Niagara Falls 248

124. Diagram of Niagara River between Lakes Erie and Ontario . 251

125. Falls of the Yellowstone River 252

126. Diagram of Torrent, with Falls and Reaches 253

127. Valley of Yakima River, Washington 257

128. The Mohawk Valley 268

129. Outline Map of a Young Valley 269

130. Diagrams of a Widening Valley 260

131. A Meandering River, Vale of Kashmir, India 262

132. A Meandering River on the Plain of Hungary 263

133. Meandering Channel and Oxbow Lakes in the Flood Plain

of the Mississippi 264

134. The Valley of California 266

135. Torrent Fan Delta, Lake Geneva, Switzerland 267

136. The Delta of the Mississippi 268

137. Diagram of a Narrowed Spur in a Meandering Valley ... 272

138. Diagram of a Cut-OfE Spur in a Meandering Valley . . . 272

139. Intrenched Meanders of the Neckar 273

140. Transverse and Longitudinal Streams 274

141. Transverse and Longitudinal Valleys 274

142. Water Gap of the Susquehanna above Harrisburg, Pennsyl-

vania 274

LIST OF FIGURES

The Ozark Plateau, Missouri 279

fiiacialed Areas, Interior Basins and Oceao Dcpllia . . . 279

Flood in Cherry Creek, Denver, Colorado . 282

Sand Dunce in the Sahara 387

Lakes Bonneville and I^hontaii 280

Bosegg Glacier in the Alps 203

Viesoli Glacier in the Alps 204

Glacial Moraines, Sierra Nevada, California ...... 205

Glaciitlcd Area of the Norllierii Unitfd Stal<'H -'(Ki

IcB-Wom Rocks, Coast of Maine 297

Glacial Moraines, North Dakota 298

A Glacial Bowlder 298

A Drumlin, Massacliusetta 299

A Side Valley banging over the Valley of llie Ticino, Soutli-

em Alps 300

Luke in the Adirondacltd, New York 301

Sea CllHs, Grand Manan, Now Brunawick 305

Diagramof a Lowland Coast nJtii Bluff and Sand Reef . . 309

The Sea Cliffs of Normandy (iooltine southweat) .... 311

Diagram of an Irregular Shore Line 312

Diagrani of an Irregniar Shore I.,ine with Cliffed Headlands

and Beached Bays 312

Diagram of a Curved Sliore Line , . 313

A Cliffed Headland and a l^iid-Tied Island 314

Gibraltar 316

Diagram of a Group of Sea-Cut Islands 316

A Cliffed Coast in Alaska 318

The "Old Man of Hoy " 317

The Coast Platform of Norway 316

A Delta in a Norwegian Fiord 321

Deltas of the Texas Coast 322

A Mangrove Tree 324

A Fringing Reef 326

A Barrier Reef 326

Part of the Great Barrier Reef of Australia (as seen at low

tide, looking toward llie tnainland) 320

Diagrani of Part of a Barrier Reef 327

Digram of Part of an Elevated Reef witb a New Fringing Reef 327

xviii LIST OF FIGURES

FIO. PAGB

178. Diagram of an Atoll 328

179. An Atoll, or Coral Island 329

180. Beavers 341

181. Caribou 342

182. Jaguar 343

183. Kangaroo 344

184. Cassowary 347

185. Dwarfs in the Equatorial Forest 361

186. Eskimo hunting Walrus 362

187. Stunted Trees at the Tree Line on the Slope of Pikes Peak . 366

188.^ Ibex 366

189. ' The Yucca, a Desert Tree 360

190. El Kantara Oasis, Algerian Sahara 362

ELEMENTARY
PHYSICAL GEOGRAPHY

CHAPTER I
THE EARTH AS A GLOBE

1. Introduction — Physical geography treats of the
Tarious features of the earth that influence the manner in
which man lives upon it. Hence it must consider the
form of the earth as a whole, the climates of its different
parts, its oceans with their waves and tides, and the forms
of its lands.

It is the plan of this book to describe the more important
Icinds of physical features on the earth, to refer them to
their causes in natural processes, and to trace them to their
consequences as seen in the condition of mankind.

2. The Shape of the Earth. — The people of savage races,
when they think at all about the shape of the earth, gen-
erally imagine it to be a great plain, varied by hills and
mountains and surrounded by the sea; for that is the
appearance of the lands when seen from some higli point,
with mountains rising to greater heights, lowlands extend-
ing to the seashore, and the ocean stretching beyond.

The people of an ignorant race usually regard the place
where they live as the center of the great earth plain. Of

2 ELKMENTARY PHYSICAL GEOGRAl'HY

the ocean tlioy know little ; its further pMtti are invisible
and mysterious and are often thought of as much more
dangerous than those which border the solid lands.

Among the earliest observations that led to a knowledge
of the true form of the earth were thoae made by the Greeks.
The great philosopher Aristotle, who flourished alwut
the middle of the fourtli century u.c, made an ingeniouB
use of the eclipses of the
moon to deteiTuine the form
I of tiie earth. He knew that
the earth cast a great shadow
stretching away into space on
the side oppasite the sun; and
tliat whenever the moon, in
its movement around the
earth, entered this shadow
it was hidden or eclipsed,
because it then no longer
received tlie suiihght that
I, show- ordinarily makes it visible.
' He noted that the edge of
' the earth's shadow on the

moon is a curved line, and thus he knew that the earth
must have a curved surface, such as a globe has.

The moon, revolving about the earth once in twenty-
eight days, is not eclipsed every time it is opposite the.'
sun, for it usually passes a little to one side of the earth's'
tapering shadow.

Tlie famihar ai'gument for the globular form of the
earth, based on the disappearance of the lower part of

THE EARTH AS A GLOBE 3

distant vessels at sea, was not mentioned by aiicient
writers until about the beginning of the Christian era.

3. Size of the Earth. — The earliest recorded measure-
ment of the size ot the earth was made by a Greek philos-
opher in the thii-d century n.c, who found ita diameter to
be about 8000 miles. The knowledge thus gained by the
wise men of the ancient Mediterranean coiuitriea concern-
ing the size and shape of the earth was unknown to the
rest of the world and was afterwards forgotten ; but it was
i-egained about the time of Columbus.

The proof of globular form liy sailing around the earth,
orcircumnn ,,u n h is lii i , i li ! lintUsixt nth

- 1

century, when the Philippine islands were discovered.
What -can you learn about Magellan? In later centuritH
nearly all parts of the earth have been explored, and its
size and sliape have been accurately measured. Its diam-
eter is about 7912 miles.

4. Unevenness of the Earth's Surface. — The broad
depressions between the continents, iu which the oceans
are gathered, are of small dcjith compared to the diameter
of the earth, The continents have many mountains and
valleys, but the general surface of the lands does not
depart greatly from a. globular form, such as is so well
shown by the surface of the oceans. This is fortunate,

4 ELEMENTARY PHYSICAL GEOGRAPHY

for on very uneven lands the long ascents and descents
between the higher and lower parts would make travel
and transportation enormously difficult or utterly impos-
sible. It is difficult enough to cross over the existing
mountain ranges, whose highest peaks rise hardly more
than Y^^ ^^ ^^® earth's radius and whose passes are much
lower ; if their height were -j^ of the earth's radius, they
would be absolutely impassable.

Exercise. With chalk and string draw a circular curve of 4 feet
radius on a blackboard. If the chalk line is ^ inch wide, it
will represent the average depth of the oceans (2 miles) ; if it is
increased underneath here and there to -^ inch, it will indicate
the greatest known depths of the oceans (about 5 miles). Small
inequalities rising yj^ to ^ inch above the outside of the curved
line will represent the altitude of the continents and their moun-
tains above sea level. At a distance of 20 feet the departure of
the curve from a true circle will be hardly noticed. So the earth
would seem smooth and truly globular if we could see it from a
great distance.

5. Consequences of the Size and Shape of the Earth. —

The earth is so large that savage tribes, even on the same
continent, may remain in ignorance of each other for cen-
turies. Each tribe then comes to have its own way of
doing things, appropriate to its local surroundings. Thus
differences of language and customs haye originated. But
since railroads and steamships have been invented the
earth may be considered a relatively small body ; an active
traveler may now visit nearly all its larger districts in his
adult years.

The civilized nations have become well acquainted with
each other, because the earth's surface is so neaily level

THE EARTH AS A GLOBE 5

that movement over it is poasilde. They now maintain an
international postal service, hy which nearly 200,000 post
ofQces are in regular communication with each other. The
Roman alphabet is used by many nations, although tlieir
language may be different. The use of Arabic numerals
is even more extended. The metric system of weights
and measures is already widely inti-oduced and will
probably be adopted by all advanced nations during this
century.

The pioducts of remote regions are exchanged, even
from opposite sides of the earth. The wheat of one
continent furnishes flour to another. Australian wool
and meat are sold in London. The manufactures of
Europe and the United States are distnbuted all over the
vorld. On a more uneven earth it might be impossible
to develop a world-wide commerce.

6. The Earth's Attraction, or Gravity.— It is the attrac-
tion of the earth, or terrestrial gravity, that causes bodies
ta have weight and to fall when not supported. Recog-
nizing the earth to be a globe, "down" is toward its
center, or in the direction that bodies are pulled by its
attraction, as indicated by a plumb line; "up" is away
from the earth's center, or against the pull of gravity. A
level surface, like that of a quiet body of water, a calm
lake or ocean, i-epresents a part of the convex or globular
Borface of the earth ; it is everywhere at right angles to
the up-and-down, or vertical, lines.

The stems and trunks of plants grow " up" against the
force of gravity. Even on hillsides ti-ees tend to grow

6 ELEMENTARY PHYSICAL GEOGRAPHY

erect and not square out from the sloping surface. Many
parts of the skeletons of men and animals, as well as many
of their muscles, are especially adapted to bear the stram
that is exerted upon them by the downward weight of the
body. The habit of lying down to sleep has been formed
chiefly to rest the muscles that are in action whUe a per-
son is standing. The walls of buildings are built vertical,
because in that position they will stand most securely.

7. The Earth's Rotation and its Consequences. — Few

discoveries ever made by man have been more opposed to
his early beliefs than that the earth turns or rotates on its
axis once a day and that it moves or revolves around the
sun once a year; for nothing is more natural than to sup-
pose that the firm earth stands still in the center of the
universe and that all the bodies of the sky turn around it
But it has been proved that the apparent turning of the
sun and stai-s around the earth from east to west is due to
the actual rotation of the earth from west to east. One
may gain a false impression of the same kind while look-
ing from the window of a smoothly running train, when it
seems as if the landscape moved backward instead of the
train forward. The northern end of the imaginary line,
or axis, on which the earth turns is directed (almost)
toward the North Star in the sky.

A little over two centuries ago it was discovered that
the earth is not a perfect sphere, but is very slightly flat-
tened at the poles. The equatorial diameter is 7926 miles ;
the polar diameter, 7900 miles. This was explained by
Newton as a result of the earth's rotation, and it may be

THE EARTH AS A GLOBE 7

taken as one of the best proofs that tlie eartJi and not
the skj turns.

8. Day and Night. — The sun illuminates oiiu half of
the earth, leaving the other haU in shadow. As the earth
turns ai'ouud, passing from the light into the darkness, one
perceives the succession of day and night every time a
rotation is made. The time at which the sun comes in
sight over the eastern horizon is sunrise; when it disap-
pears below the western horizon, sunset.

The succession of day and night, resulting from the
rotation of the earth, hiia given man and many jinimalB
the habit of working in the light and resting in the dark-
ness. The period of the eartli's rotation furniahes a nat^
ural unit of time, easily recognized and counted, and
everywhere alike and constant. Clocks and wiitches are
regulated to keep time with the earth's turning. The
hour hand of timepieces in common use turns once for the
average duration of daylight, and once for the average
duration of darkneHS.

The rotation of the earth, causing suniise and sunset,
suggests a natural system of directions by which the rela-
tive positions of different places may be indicated. The
cardinal points, east and west, north and south, arc in a
more or less delinite way recognized by most peoples of
the world.

The sun riseB through the eastern half of the sky dur-
ing the morning and sinks through the western half in the
afternoon. Midday is the moment when the sun passes
the north and south line that divides the eastern from

ELEMENTARY PHYSICAL GEOGRAPHY

the western half of the b^. The sun then reaches its
greatest height above the horizon ; and, hence, at this
moment a vertical rod casts the shortest shadow.

EzerciAe. Set up a Terti'cal post in level ground (or & square-
cornered box on a level table). Mark the succeBsive poBitions of the .
end of the rod shadow (or of a comer of the box nhadow) every ten
or fifteen minutes for an hour or more before and after noon. Draw

a line through the marks. Find the shortest line from the base of
the post (or from the lower corner of the box) to the line through
the marks. This shortest line is a true north line, or meridian (mid-
day) line. On the following day note the moment when the shadow
falls on the meridian line ; that moment is local solar noon, or mid-
daj. A watch then set to 12 o'clock will mark local solar time.

9. Latitude and Longitude The north or meridian

line would, if followed in the direction away from the

THK EAKTII AS A GLOBE

Biin, lead to the north pole ; in the opposite direction, to the
south pole. All meridian lines therefore meet at the poles.
When prolonged aromid the eartli they are called meridian
circles. Lines drawn at right angles to the meridians will
run parallel toeach other, east and west, around the earth
and are therefore called parallels. The earth being globu-
lar, a simple system of meridians and parallels may be
imagined to form a network of circles over its surface.

Fia.i. Meridians and Pf

Fio. 5. Latitude luid LiOiigltude

It is by reference to these hnes that the relative positions
of places on the earth's surface are determined.

The parallel that lies halfway between the poles is
called the equator. It divides the earth into the northern
and Boutliem hemispheres (half-spheres). The latitude of
a place is its distance north or south of the equator. It is
measiired along the meridian of the place and is counted
in degrees, ninety to a quai'ter circle. In Figure 5 the lati-
tude of A is the number of degrees in the arc AC, or the
ftngle AOC. Whiit id the latitude of Bf

10 ELEMENTARY PHYSICAL GEOGRAPHY

Low latitudes are near the equator in either hemi-
sphere; high latitudes, near the poles; middle latitudes,
roughly midway between pole and equator in either hemi-
sphere. (See page 89.)

The longitude of a place is the number of degrees by
which its meridian is east or west of a standard or prime
meridian. The meridian of the national observatory of
Great Britain at Greenwich, a suburb of London, is now
very generally taken as the standard. The longitude of a
place is measured from the prime meridian east or west
along the equator to the meridian of the place and is
counted in degrees, 180 to half a circle, or in hours,
12 to a half circle. If NACS^ Figure 5, is taken as the
standard or prime meridian, the longitude of B is measured
by the arc CD of the equator, or by the angle (702),
l)etween the local and the prime meridians. Is B in east
or west longitude? What is the latitude oi G? What
is its longitude ?

Practical Exercise. A useful illustration of the manner in which
maps are made is given by providing a number of outline maj)?,
showing parallels and meridians (latitude and longitude lines), on
which the latitudes and longitudes of a number of points are to be
platted. The points should be selected on the boundary of some
state or country ; their positions may be taken from an atlas and
written upon a blackboard. By drawing a line through the points
thus platted each pupil will. have constructed a rough map of the
chosen boundary. Rivers and cities may be similarly located.

Land surveys, by which the boundary lines of farms
and house lots are marked out, are best made with refer-
ence to the local meridian, or north line. Navigators have

THE EARTH AS A GLOBE 11

daily occasion to determine their position with riiapecl to
the network of meridians and pai-allels, in order to follow
the desired route, to avoid ialands and headlands, and to
iKieh their intended port.

The boundaries of thinly settled parts of civilized
nations and states are often defined by meridians and
parallels, as between the weatem parta of the United
States and Canada, as well aa between many of tlie states
themselves, and between the various parts of Canada and
Australia. Thus great advantage is taken of the simple
globular form and regular rotation of the earth.

10, Relation of the Earth to the Sun The sun, glow-
ing with extreme heat, has the enormous diameter of
866,600 miles. If the eaiili were placed at the sun'a
center, and the moon were moving around the earth at its
actual distance of 240,000 miles, the sun would still reach
almost 200,000 miles beyond the moon on all sides.

So huge a body is a fitting center for the earth to move
around. Even at the great distance of 93,000,000 miles,
the brilliant sun gives abundant heat and light to the
earth. This distance is so great that an express train
traveling from the earth fifty miles an hour could not
reach the sun in less than two centuries.

The earth travels or revolves around the sun eveiy year
in a nearly circular path, called its orbit. In order to
accomplish this long Journey of over 600,000,000 miles,
our globe rushes along at a speed of 18.5 miles a second,
or over 1,500,000 miles a day. As the motion is accom-
plished with perfect smoothuesa. and as we move with the

12 ELEMENTARY PHYSICAL GEOGRAPHY

earth, we are as unconscious of this rapid movement in
the annual orbit as we are of the diurnal rotation on the
axis.

Exercise. Lay a large sheet of paper on a table; draw a line
through the middle of the sheet. Let this line represent a distance of
200,000,000 miles. On each side of the middle of the line set up a
pin, so that the distance between the pins shall represent 3,000,000
miles (^jj of the length of the line). Lay off 189,000,000 miles on
this scale on a thread and knot together the ends of this length, so
aa to make a loop. Lay the loop over the pins, stretch it tight with
a pencil point, and thus guided draw a curve around the pins. The
line thus drawn is nearly circular and represents the true form of
the earth's orbit. Take out the pins. Around one pin hole draw a
circle to scale, somewhat less than 1,000,000 miles in diameter;
this will represent the sun. On the same scale the earth would be a
small dot. The points where the orbit is crossed by the middle
line show the greatest and least distances of the earth from the sim.
AVhat are these distances? The point nearest the sun (perihelion=
"near-sun*') is passed on January 1 ; the farthest (aphelion=«far-
^un") on July 1.

The stars are distant suns, shining by their own light.
Most of them are much more than a million times as far
from the sun as the earth is. They are so exceedingly
remote that a ray of light which travels from the sun to
the earth in eight minutes would be about three and a
half years on the journey to as from the nearest star.
Many of the stars are believed to be larger than the sun.

11. Relation of the Earth to other Planets. — There are
a number of other bodies which, like the e^rth, move
around the sun. Like the earth they do not shine by
their own light, but only by sunlight that falls on them.

THE EARTH AS A GLOBE 13

At night these bodies look like stars, except that they
twinkle less. Their light is brighter or fainter accord-
ing to their size and their distance from the sun. The
telescope shows them to be of globular form, like the
earth. Their movement among the stars, easily noted
from month to month, shows that they revolve around the
sun in the same direction that the earth does. The spots
that may sometimes be seen on the sun show that it also
rotates on its axis in a little less than a month, in the same
direction that the planets move around it.

The planets that may be easily seen without a telescope
are named Mercuiy, Venus, Mars, Jupiter, and Saturn.
Mercury, Venus, and Mars are smaller than the eailh;
Jupiter and Saturn are much largei*. Mercury and Venus
are nearer to the sun than the earth is ; Mai*s, Jupitei*, and
Saturn are more distant; and two other large planets,
Uranus and Neptune, are farther away than Saturn. The
planets that are near the sun revolve around it in a shorter
time (or "year") than those further away. The small
planets, Mercury and Venus, are believed to rotate very
slowly on their axes, so that their "day" is long. The
large planets, Jupiter and Saturn, rotate rapidly, so that
their day is about half as long as ours.

The moon is a planetlike body which revolves around
the earth while the earth revolves around the sun. The
moon is therefore called a satellite (= a follower), because
it accompanies the earth. Its diameter is about a quarter
of that of the earth; its distance from the earth is about
240,000 miles. Mercury and Venus have no satellites, Mars
has two very small ones, Jupiter has five, Saturn has eight.

ELEMENTARY PHYSICAL GEOGRAPHY

It is thus found that the earth is not a solitary body,
unlike all others, but that it occupies an intermediate posi-
tion in a large family of similar bodies.

Diagrams may be constructed to represent the relative
sizes of the planets and their relative distances from the
sun by means of the following table. Diameters are given
in thousands of miles ; distances in millions of miles.

Distance

Diameter

Distance

DIAHETEB

Sun

866.

Jupiter . .

480

85.3

Mercury . .

3.0

Saturn . . .

881

70.1

Venus . . .

7.6

Uranus . .

1772

30.9

Earth ....

7.9

Neptune . .

2770

34.0

Mars ....

141

4.2

12. The Solar System. — The sun, the planets, and their
satellites form a group of bodies called the solar system.
The resemblances of form and motion among the planets
and satellites are so numerous that it is believed that they
have all had a common origin. It has been thought that
these bodies, and the sun also, have been formed by the
gathering together of materials that were once scattered
through an enormous space, like a vast cloud or nebula.
This interesting and famous theory is called the nebular
hypothesis, but it is not successful in explaining all fea-
tures of the solar system.

The stars resemble the sun in many ways. It is
believed that each star may be accompanied by a larger or
smaller family of planets ; and hence the number of earth-
like bodies in the universe is probably very large.

THE EARTH AS A GLOBE 15

13. Structure of the Earth. — Rocks of one kind or
another are often seen at the surface of the lands; or if
the surface is covered by soil, rocks may be found beneath
the soil in wells and railro'ad cuts. The deepest mines
and borings, reaching about a mile beneath the surface,
pass through similar rocky materials. Hence it is believed
that the body of the earth is composed of rock.

This great globe of rock is covered with a considerable
quantity of water and air lying upon its surface and
forming its oceans and its atmosphere. The oceans are
not continuous all over the earth, but are gathered on
the lower parts of the surface, while the higher parts rise
somewhat above the oceans and form the continents. The
atmosphere entirely incloses the oceans and the continents,
rising far above the highest mountains.

Thus the earth as a whole consists of matter in three
different states, — solid, liquid, and gaseous. The liquid
portion, or water, is also known as a solid when it freezes
and forms ice ; and as a gas when it evaporates and mixes
with the air as invisible water vapor. The solid portion,
or rock, is seen as a liquid when it comes forth from vol-
canoes at high temperatures as molten lava. The gaseous
portion, or air, is always gaseous under natural conditions,
but it may be artificially reduced to a liquid or a solid by
subjecting it to heavy pressure at extremely low tempera-
tures.

There is a certain amount of mixture of rock, water,
and air, or of the solid, liquid, and gaseous parts of the
earth. Some solid substances have been dissolved by the
action of water and are now found in the oceans. A small

16 ELEMENTARY PHYSICAL GEOGEAPIIY

amount of rack in very fine particles, or dust, is raised
from barren surfaces by the wind and carried far and
wide; the finest particles remain long in the air, slowly
settling but often lifted again'bj rising currenta. Water
and air penetrate all pores and crevices that they can find
in the rocky sphere. Water vapor is always present in
the atmosphere in siuall and variable proportion ; it becomes
visible when chilled and condensed, forming small liquid
or solid particles in cloud, rain, or snow. A small amount
of air is dissolved in the oceans ; but for this, the fish and
many other animals that live beneath the surface of the
sea could not breathe.

14. Underground Temperatures. — Temperatures n
ured in deep wells and miiies show that the earth becomes
wanner beneath the surface. The average increase of
temperature downwards is about 1° for sixty feet. At^
great depths, such as twenty or a hundred miles or more,
very high temperatures would be expected ; they are proved
to occur by the melted lavas that rise and escape in vol-
canoes. It is therefore supposed that the gi'eat interim
rocky mass of the eai'th is hot enough to be melted^
although the enormous pressure of the outer parts may
prevent the expansion that would be needed to make il
liquid. It may thus be foreed to remain solid in spite oi
I ite high temperature. The outer and cooler part of the

Garth is often called its crust.
\ Just as a hot bail of iron will cool when it is hung in

I the free air, so the earth must be slowly cooling as it

I moves through cold space. It is very probable that the.

THE EARTH AS A GLOBE 17

renneas of the geosphere, in ocean basins, continents,
i mountains, is in some way the result of a sort of setr
tending of the cmsfc, slowly caused by the long
booling of the earth.

15. Age of the Earth. — It is impossible to say what the
ige of the earth and the solar system is, but it certainly
tumid be reckoned in millions and millions of years.
niere is every reason to believe that the sun and the
tlanets existed for an indefinitely long period before the
audition of the earth's surface was such as to allow
he habitation of the planet by plants and animals. It is
veil proved by the prints or fossils of various plants and
mimals in ancient rock layers that these lower forms of
ife existed upon the earth for a vast lengt}. of time,
nilHons and millions of years before man appeared. It
eems entirely possible that other planets may have once
>aeu, may now be, or may yet come to be occupied by
idiabitautB of some kind.

16. The Earth as a Magnet. — If a magnetized bar oE steel
s balanced on a pivot and placed in the neighborhood of a
Wge magnet, the direction in which the small bar points
?ill be detei'mined by its large neighbor. This may be
mted by changing the relative positions of the two. If the
BtaU magnet is left alone, it will in most parts of the earth
Im nntal it points about north and south. This is because
96 earth acts as if it were a huge magnet and so determines

direction in which smaller magnets tend to stand.
-Tie behavior of suspended bar magnets makes them
valuable in detei'miuing directions, especially in

ELEMEi^TARY PHYSICAL GEOGRAPHY

cloudy weather at sea. A magnet mounted in a con-
venient case is called a aompaas, the bar being called a
needle. In tbe mariner's compass a card bearing the
letters indicating tbe points of tbe compass lies on the
needle and turns witli it.

Tbe needle seldom points along a true meridian toward
the pole, but somewhat to one side or the other of a
meridian, in a direction that if followed will lead, toward
the " north magnetic pole " (about twenty degrees away
fi'om the true north pole
toward Hudson bay) c
toward tbe "south maf
netic pole " (about Hm
same distance from thff
ti'ue south pole toward'.
New Zealand). The dif--
fi'ience between true'
jiorth and magnetic
north at any place may
be determined by (
paling the direction of the midday (or shortest) shadoV'
cast by a vertical pole with tbe direction of a compaw,
needle.

17. The Aurora. — During clear nights, especially in-
winter time, the northern part of the sky is sometimet
illuminated by an areb of whitish, greenish, or rosy lights
Moving streamers of ligbt, whitish or colored, i
between the arch and tbe higher parts of the sky. This
appearance is called the aurora borealis, or "northern

TUB EARTH AS A GI.OUE 19

lighta." The aurora is more freqiient and brilliant in
high northern latitudes than in temperate latitudes. A
similar appearance in far southern latitudes is known as
the aurora australis. In both cases the middle of Hie
auroral ai'ch is seen in the direction of the magnetic pole.
From the disturbance of delicate magnets during an
auroral display it is believed that the liglits are due to a
faint electric discharge controlled by the magnetic forces
of the earth.

SuppLEMEKT TO Chapter I

18. Pn»f of the Globular Form of the Earth by ObKrrationa of the
Stars. — Looking upward from the cartli, the sky seems liki: a lioUow
shell of vast size, carrying tiie sun by day and thti Btars by niglit.
The earth may be thought of as standing at the center of the great
sky shell, bo that an observer at any point bbm only lialf the aky
above him, the other half being hidden liEneatli the earth. The
lower border of the visible half of the sky is called the horizon, and
the plane that extends outward from the observer to the sky border
18 called the plane of the horizon.

By watching tliroiigii the night the Greek philosophers saw the
stars rising in the eaattrn side of the sty and deseeiidiiig in the
western; and they concluded that the aky, carrying the stars with
it, turned around the earth once a day. It is now known that the
earth turns, and not the sky.

In order to understand this clearly the pupil should learn by
observation something of the diurnal movement of the sim, moon,
and stars across tlie sky and should recognize that their paths are
parts of slanting circles.

Perception of the essential facta is greatly aided by the uae of a
"pointer," three or four feet long, tied at one end to the top of a
slake about which it may turn freely. Direct the poiiitpr toward the
BUQ at different hours of the day. Repeat this until the (apparent}

ELEMENTARY PHYSICAL GEOGRAPHY

movement of the sun becomes familiar. Then sweep the pointer
more rapidly tlirough its successive positions. Infer the directions
it would assume if the sun could be observed all night. Infer the
attitude of a line, or axis, about which the pointer turns. This line
must be parallel to the axis on which the earth turns.

The (apjiarent) diurnal rotation of the stars is best shown by home
observations. Direct a pointer toward a star at a convenient evening
hour. Watch the star for five or ten minutes and note its change of
position. The next evening begin the observation fifteen or twenty
minutes earlier. IIow can the facts thus observed be best accounted

for? The movement of
^^ ^^ ♦ .IT the stars as seen from dif-

ferent places must next
be considered.

When one travels
southward from B to C
it is found that new
groups of stars, Zf
Figure 7, not visible
before, come into sight
over the southern horizon, while other groups, X, that had before
IxMiu seen over the northern horizon are no longer visible. From
til is it is concluded that the plane of the horizon HJ at the new
point of observation is not parallel to the plane FG at the first
point, and that the surface of the earth must be convex instead of
flat. Hence the earth as a whole must be a globe or sphere.

Changes of this kind are easily recognized in traveling from the
northern to the southern border of the United States, or farther
south into Mexico or Cuba. They may be verified by correspond-
ence between different schools, several hundred miles apart north
and south. What changes would be noted in traveling northward
from BtoA'i

Fig. 7.

Globular Form of Earth shown by
Visibility of Stars

THE EARTH AS A GLOBE

QUESTIONS

Sec. 1. ^Vhat are the cLlef aubjects that axe tuught in Physical
Gei^raphy ?

2. What IB the view generally held by savage races as to the size
and shape of the earth? When were correct notioiiB first gained as
to the earth's ahape? How did Aristotle infer the earth's Hha))e?
What must be tlie relative positions of aun, earth, and moon when

he moon is eclipsed ? Why is the moon uot eclipsed every month/

3. When was the earth's size first determined? AVlien and by
whom was the earth first circumitavigated ? Name some of the
places then discovered.

4. Describe the general form of the earth. State the relation of
its mountain heights and ocean depths to ita diameter. Boes the
earth's form favor travel and transportation? How?

5. How are savage tribes affected by the size of the earth? In
vhat ways have civilized nations become associated with one
BBother?

6. What is meant by "np" and "down"? How is the surface
>f a quiet body of wafer related to the direction of gravity? How
s the position of tree trunks and house walls related to the direction

of gravity? What conseq^uencea of the action of gravity are seen in
Den and animals?

7. What is the belief of primitive man about the position of the
earth? What are the facta? What is the effect of the earth's rota-
tion on its form?

8. What is the cause of day and night? What is the most
natural unit of time? What habits of man and animals result front
the earth's rotation? How are the cardinal points related to the
earth's rotation? What is the position of the aun at midday? How
are midday and true north deternijiicd? Given a north and south
line, how can you determine east and west?

S. Define meridian line, m.eriiiian circle, poles, parallels, equator.
What ia latitude and how is it measured? What is meant by low,

22 ELEMENTARY PHYSICAL GEOGRA.PHY

middle, and high latitudes ? What is longitude and how is it meas-
ured ? State some of the practical uses of meridians and parallels.

10. Compare the sun's size with that of the moon's orbit. Calcu-
late the time needed for an express train to reach the sun. What is
the earth's orbit? What is the earth's orbital velocity? How is it
found ? What are the stars ? What can- be said of their distance
from us ?

11. How are the planets distinguished from the stars? Which
planets can be seen without a telescope ? Name the planets in order
of distance from the sun. Which are larger, which smaller, than the
earth? Compare the "day" of Jupiter and of Saturn with our day;
the " year " of Venus and of Mercury with our year. State the size
and distance of the moon.

12. What is the solar system? What features are possessed in
common by its members ? What do these common features suggest?

13. Of what is the great body of the earth believed to consist?
Why ? What is meant by the earth's crust ? What are the three
states of matter? Give examples of them. What are the chief
divisions of the earth?

14. What is known about underground temperatures? At what
rate does temperature increase downward? What is the supposed
condition of the earth's interior? What relation is suggested
between the earth's surface form and its interior temperature?

15. What may be said of the earth's age and of life on the
earth ?

16. How is a small balanced magnet affected by a large one?
How will a balanced magnet stand when alone? What is a com-
pass ? What are the magnetic poles ? Where are they ? How far
to one side of the meridian does the compass point at your school?
Does it point east or west of the true meridian ?

17. Describe the aurora borealis. How is it related to the mag-
netic pole ?

19. The Atmosphere is a light and transparent mixture
of gases, known as air. It rests upon the lands and seas,
forming the outermost part of the earth. It takes part ia
the earth's daily rotation and yearly revolution.

Many processes that take place on the lands and seas
depend on the atmosphere. The waves and currents of
the ocean are caused by the winds ; the soil that covers
so large a part of the lands results from the decay of the
underlying rocks, largely through the action of moist air.
Rainfall, bo important in many ways, is supplied by mois-
ture received from the oceans and carried about by the
movements of the atmosphere.

The atmosphere far overtops the highest mountains.
Meteors, or "falling stars," — small sci-aps of matter dash-
ing toward the earth from outer sjiaoe — are heated by
rushing through the air at enormous speed, so that they
become luminous. They are sometimes seen at heightw
of more than a himdred miles, showing that some air
reaches that great altitude.

Cloud, haze, and dust make the lower air more or less
turbid and often shut out a great part of the sun's rays ;
but when the air is clear it is so transparent that sunlight
is strong even at the bottom of the atmosphere.

24 ELEMENTARY PHYSICAL GEOGRAPHY

20. Composition of Air Air consists of a unifonn

mixture of giises in which a small and variable quantity
of water vapor is usually present. The chief gases are
nitrogen and oxygen, which constitute about four fifths
and one fifth, respectively, of the atmosphere.

Fire is the I'esult of an active combination of some bum-
able substance with the oxygen of the atmosphere. The
heat thus developed may produce light, or it may con-
vert wat«r into steam, and the expansive force of tie
steam may be used to drive engines and many kinds of
machinery.

All animals and plants breathe in air and use some of
its oxygen to combine with part of their substance in a
very slow combustion, whicli produces a slight amount o£
heat, but no fire. Thus all forms of life, animal and vege-
table, depend upon the oxygen of the air, as well as upon.
their food, to keep them alive.

Carbonic dioxide, constituting less than a thousandth.
part of the atmosphere, is nevertheless important for tha
growth of plants. The carbon taken from this gaa hf
growing plants makes a large part of their structnie^

21. Pressure of the Atmosphere. — Although tbe air is
invisible, it is attracted by the earth and exerts a pressure
of about a ton to the square foot upon the surface on
which it rests. The total pressure on a man's body
amounts to several tons; but this is not felt because the
air within the body exerts a corresponding pressure out-
ward. The air is so easily moved that little resistance ia
noticed when one walks through it ; but fasj; railroad

THR ATMOSPHKRE

tr^ns axe much impeded by tlie reBl.sUnce of the air that
they have to push mpidly aaide.

The pressure of the atmosphere is measured by the
barometer. This instrument ia of two kinds.
The mercurial barometer, Figure 8, consists of
a glass tube, somewhat more thau thirty inches
long and closed at one end. It is prepared by
filling the tube with mercury, closing the open
end with tlie finger, and inverting the tube;
the open end is then placed in a vessel of mer-
cury and the finger la withdrawn. Tlie mer-
cury ainlts a little below the closed upper end
of the tube, leaving an empty space, or vacuum,
above it. The mercury column must pi-ess
down on part of the mercury in the vessel
just as much as the air presses on any equal
part of the mercury surface. Thus the height
of the mercury column, measured by a scale,
may be taken as a measure of the pressure of
the atmosphere.

The aneroid barometer consists of a small
boi, from which the air has been exhausted.
A variation in the pressure of the atmosphere
causes a slight change in the shape of the
box. The change is magnified by a aeries of
delicate levers, by which an index is moved
on a dial. The reading indicated on the dial MiTi-urial
then shows the pressure of the atmospliere. Jiarumetar

The ordinary changes of atmospheric pressure, such as
may be seen to accompany weather changes by reading a

iig a J

26 ELEMENTARY PHYSICAL GEOGRAPHY

barometer from hour to hour and from day to day, are
seldom more than a thirtieth or a fifteenth of the total
pressure.

If a barometer is carried up a lofty mountain, leaving
much of the atmosphere beneath it, the pressure of the
overlying atmosphere is found to be much reduced. An
ascent of a thousand feet causes a lowering of about an
inch in the barometric column. Thus barometers may be
used to measure mountain heights.

Although very light, the air supports the flight of birds
and insects. The wind drives sailing vessels and wind-
mills. In dry regions, where the ground is not covered
with vegetation, the shape of the surface is changed by the
long-continued action of the wind in drifting sand and
dust from place to place.

22. Elasticity of the Air. — Air is extremely elastic,
changing its volume with every change of pressure. Its
lower part is compressed by the weight of the overlying
parts, so that much more air is contained in a cubic foot
at sea level than at a height of three miles. This is
expressed by saying that the density of the lower air is
greater than that of the upper air. A cubic foot of air at
sea level weighs about 0.075 pound, while at three miles
above sea level its weight is only about half as much, and
at an altitude of a hundred miles the air must be almost
imperceptible.

Men and animals living on high plateaus have become
accustomed to the rarity or thinness of the air around
them. There are villages on the plateau of Tibet and in

THE ATMOSPHERE 27

the higher valleys of the Andes at heights o£ frnra 12,000
to 14,000 feet, where the density of the air is hardly two
thirds of that at sea level. Mountain climbing at alti-
tudes above 20,000 feet is almost impossible, from the
difficulty of breathing the thin upper air.

It is by slight wavelike movements in the air that
sound is traasraitted. So quickly ia the wavelike dis-
turbance passed on that sound travels a mile in five
seconds. So easily is the air disturbed that a locust
(cicada) may set hundreds of tons of air vibrating per-
ceptibly to our nei-ves of hearing. When the volcano
Krakatoa, between Java and Sumatra, exploded in August,
1883, sounds were heard for 2000 miles, and atmospheric
waves, detected by slight changes of pressure in barom-
eteis, passed three times around the earth.

23, Colors of the Atmosphere.^ The clear atmosphere is
no teansparent that tlie light of faint stars can pass through
its whole thickness. In the daytime the sun lights up
the sky ao brightly that stars are not seen. The blue
color of the clear sky is due to the scattering of sunUght
on eoimtlesa numbers of extremely minute particles, tlie
scattered light being seen against the darkneas of outer
space. The red and yellow colors near the horizon at sun-
rise and sunset are due to the sifting out of other colors as
the sunlight passea obliquely through a great thickneas of
atmosphere.

As the sun sinks slowly below the western horizon
after a clear sunset, a pink or rosy arch of sunlit air^ —
the twilight arch — may be seen slowly rising over the

28 ELEMENTARY PHYSICAL GEOGRAPHY

eastern horizon ; the dull blue sky below the arch is dark-
ened by the shadow of the earth. A similar arch and
shadow may be seen sinking in the west before a clear
sunrise. Thus the shadow of night may be seen follow-
ing the sunlit air of one day and disappearing before the
sunlight of the next.

24. Temperature of the Atmosphere. — The temperature
of the land and sea surface and of the atmosphere is con-
trolled by the rays of the sun. The temperature of the
atmosphere is not much affected directly by the sun's rays,
because the air is so transparent that the rays are very little
taken in or absorbed by it; hence the upper air is every-
where cold. The temperature of the lower air is largely
controlled by the temperature of the land or sea surface on
which the air rests. The sea surface absorbs the sun's rays
somewhat more actively, and the land surface much more
actively, than the air does ; thus they become warmer than
the air. The air lying next to the heated surface is then
warmed by heat that is carried or conducted from the land
or sea to the air.

At night, when sunshine is absent, land, sea, and air cool
by radiating their own heat (giving out rays) toward outer
/^ space. Just as the air absorbs the rays of the sun very imper-
fectly in the daytime, so it gives up very little of its own
heat by radiating at night. The sea surface is somewhat
more active than the air in cooling by radiation at night,
and the land surface is much more so. Hence the lower air
is cooled at night by conduction of its heat to the cooling
surfaces on which it rests. In the upper air the ^urnal

TI[E ATMOSPHERE 29

range or the change of temperature from day to night is
very small ; it ia somewhat greater iu the lower air on the
oceans ; it is much greater in the lower air on the lautla.

The Sim's i-aya fail almost vertically on every part of the
earth's surface near the equator for several midday hours,
and there high temperatures niust prevail. The rays fall
obliquely on the polar regions, so that, each ray is there
spread over a larger sui-face than in the torrid zone, and
its noon effect is no greater than that of on early morning
or afternoon ray near the equator ; hence low temperatures
must prevail around the poles. This may be illustrated
by the difference in the heating effect of sunshine on the
two slopes of a road that runs north and south over a hill.
Between poles and equator intermediate temperatures are
maintained.

High, medium, and low temperatures are thus distrilj-
uted in belts ■ — hot, medium, and cold — roughly parallel
to the equator; the Iielts are known as the torrid, tem-
perate, and frigid zonea. Fortunately the cohi or frigid
areas occupya relatively small part of the world.

Yet even in the torrid zone lofty mountains rise into
air that is so cold that snow lies on their upper parts all
the year round. The lower Umit of the permanent snow
fields is ciflfed the snow line. It is about three miles
sea level in the mid-torrid zone; about a mile above
[tude 55" or 60° N, or S,; it descends to sea level
the frigid zone, where permanent snow may be
even on the lowlands.

Heated air expands. Hence, volume for volume, hot
lit is lighter than cold air ; the air of the torrid zone is

80 ELEMBNTARV PHYSICAL GEOGRAPHY

lighter than that of the frigid zones. This fact will be
found of great impoiUince us a cause of the winds.

25. Hirage. — A curious consequence of the strong
control of air temperature by that of the land or sea sur-
face on which the air rests is sometimes seen in the reflec-
tion of distftiit objects by the lower layer of air wiien its
temperature is distinctly unlike that of the overlying air.
A reflection of this kind is called a miragp (Frencli, mean-
ing "reflection"; pron. meerahzh). Its cause is as follows:

Tliiu Layer nl A

The surface of a level desert in a warm zone becomes
very hot under unclouded summer sunshine, and the air
close to the ground is heated by conduction, so that it
Ijecoraes much hotter than that three or four feet higher.
The upper surface of the hot air acts like a mirror aad
gives an inverted reflection of objects beyond it. The
reflecting air surface thus imitates a water surface so well
that travelera are often deceived by it and think that a J
lake exists where in reality tliere is nothing but dr
sand.

out dr m

THE ATMOSPHKRE 31

When cqld air blows over a warmer sea its lower layei
may be heated by conduction from the water, so as to
become distinctly warmer than the air at a greater height.
When warm aii' blows over a colder sea the lower part
may be cooled by conduction. In either case the lower
layer may reflect the figure of distant vessels, the reflected
image being seen upside down beneath the object itself, if
the lower layer of air is thin and the observer is above it ;
but above the object itself, if the lower layer is thicker
and the observer is within it.

The equivalent of a mirage may often be seen by look-
ing close along a brick wall that is exposed to strong sun-
shine in calm warm weather. Objects that are nearly in
line with the wall may be seen reflected on the film of hot
ail' next to it.

36. Thermometers. — The temperature of the air and
of other bodies may be meflaured by the thermometer
(temperature measure), consisting of a fine tube opening
into a bulb at its lower end and containing mercury (or
other liquid). The glass and the mercury take the tem-
perature of the suri'ounding air. If warmed, both expand,
but the liquid mercury expands more than the solid glass,
and part of the mercury is therefoi« pushed from the bulb
into the tube; if cooled, both contract and some of the
mercury is withdrawn from the tube into the bulb. Thus
the height of the inercuiy in the tube measures relative
heat and cold, or temperature.

In the United States and Great Britain it is still
oostomary to employ the Fahrenheit thermometer (P.),

32 ELEMENTARY PHYSICAL GEOGRAPHY

m&rUng 32° at the freezing point and 21*2° at the boiling
point of water. In continental Europe the Centigmde
thermometer (C.) is used, reading 0° at the freezing and
100° at the boiling point.

Some thermometers are arranged so ae to give a contiii'
uous temperature record in a curve drawn on a sheet of
paper; such instruments are called self-recording ther-
mometei-s, or thermographs,
one pattern being shown in
Figure 10. Others are
trived so as to register the
highest (maximum) and low-
est '(minimum) temperatures
of the day; this is sometime
done by placing an index
short piece of fine wire inside
the tube, so that it may
pushed up or down as tits
liquid expands or eontractK
Such instruments are called
maximum and minimum thei
mometerg.

When the thermometer is used to measure the temper*
ture of the air it should be suspended so as to be protectei
from direct sunshine and from rain and snow, hut exposed
to the wind. If placed outside of a window, the thermom
eter should be on the north side of the building, free froi
the wall and where warm air escaping from window!
cannot affect it. It is better phiced ui a special sheltei
away from buildings and trees.

Fio. 10

The Coioey 8el (-Record In g
TbermomeCer

THE ATMOSPHERE 33

27. Temperature Charts and Mean Temperatures. — Tlie
distribution of temperature is uidirated on charts by lines
drawn through places having the same temperature.

Figure 11 gives the degrees of temperature prevailing
over the middle and eastern United States nn a certain
morning. The dotted line is drawn so as to separate
all places having
higher temperatures
(wanner) than 40''
from those having
lower temperatures
(colder). Similar
liaes may be drawn
for temperatures
of 10°, 20°, 30°,
50°, and 60°. Each
of these lines is
called an isother-
mal (equal tem-
perature) line, or
isotheiTu. It is a
line of uniform temperature, separating regions of higher
and lower temperatoi-e.

In the example here given all the states northwest
of a line drawn from the southwest comer of Arkan-
sas to the western end of Lake Erie have temperatures
lower than 40°, All the states southeast of this line
have temperatures higher than 40°. Many illustrations
of this kind are afforded by the daily weather maps
issued by the national Weather Bureau. What would be

IlluBtratiuii ol ai

ELEMENTARY PHYSICAL GEOGRAPHY

the temperature of a place halfway between the isothenna
of 50= and 60"?

If records of temperature are kept at regular houis
every day for a mouth, the hours being chosen so as to
include the cooler as well as the warmer periods of the
day, the sum of all the temperatures divided by the
number of observations will give tiie average or mean

—

— T — -J

-;^-^S-7-^ji

— ^

jS5

?^"

?i.

I—

=^8

=jf=

— '

Fio. 12. Cbart of Mean Atinual Temperatnces

temperature of tlie month. Similarly, if observations are
kept up through a whole year, the mean temperature of
the year may be determined. The mean temperatures
of a place for a year usually differ by a small amount in
successive years; lience the standard mean annual tempen-
ture of a place is determined by averaging the means of
ten or twenty successive years. Observations of temper-
ature have now been made during many years at a great

THE ATMOSPHERE 36

many places, so that the distribution of temperature ull
over the world, except in the two frigid zones, is fairly
well known.

The distribution of mean annual temperatures for the
year is shown by isotherms on the chart of the world.
Figure 12, which ia therefore called a chart of annual iso-
therms. A line drawn near the earth's equator, through
the middle of the belt of greatest heat, is called the heat
equator, the average temperature of wliich is about 80".
From the heat equator the temperature decreases toward
each pole at the rate of about one degree of the Fahrenheit
thermometer scale to a degree of latitude.

In the southern hemisphere the isotherms are nearly
parallel to the latitude circles ; this is because the oceans
there are so little interrupted by land.

In the northern hemisphere the isotherms are much
more irregular, because the oceans are hei'e interrupted
by broad continents, and the temperatures on lanii.s and
seas are often unlike in the same latiUide.

Exercise. What parts of the lands and oceans have a mean
annual temperature ahove 70°? above S0°7 What is the general
path of the ieotherm of zero in the northern hemiBphere ? Estimate
from the chart the mean annual temperature of your home ; of Lon-
don; of Cape of Good Hope.

28. Circulation of the Atmosphere. — Movements of the
atmosphere are usually caused hy differences of tempera-
ture. For example, a movement of air will take place
between two rooms, one warm and the other cold, if a door
is opened between tliem. The cold air is lieavier than the
warm air. Cold air will therefore creep into the lower

36 ELEMENTARY PHYSICAL GEOGRAPHY

part of the wami room, while the light warm air spreads
into the upper part of the cold room. The movement may
1x3 shown by the drift of smoke from a smoldering matcL
If the cold air is wanned as it enters the warm room, and
the warm air is cooled as it enters the cold room, the
movement will continue indefinitely, the air going round
and round in a circuit. Such a movement is called a
circulation. It is also called a convectional circulation,
l)ecause heat and cold are conveyed by the movement that
is excited by differences of temperature.

In the same way the cold air of the polar regions, being
heavier than the warm air of the torrid zone, continually
tends to creep under it, thus forming convectional air cur-
rents in the lower atmosphere, which we know as winds.
The warm air, being slowly raised all around the equatorial
belt, tends to overflow north and south toward the poles,
forming convectional air currents at a great height in the
atmosphere.

The lower winds approaching the equator where sun-
shine is strong are warmed; thus their air is expanded
and made lighter, so that it is in turn slowly raised over
the equatorial belt to form the overflow toward the poles.
The upper currents, flowing toward the poles, where sun-
shine is weak, are slowly cooled; hence their air settles
down to lower levels and forms the currents returning
toward the equator. A permanent interchanging move-
ment or circulation is thus established between the warmer
and colder parts of the earth. It must continue as long as
the sun warms the equatorial more than the polar regions
On accoimt of the earth's rotation the air does not movi

THE ATMOSPHERE

directly north and south, but is turned obliquely towiinl
the east or west. (See page 85.)

Changes of temperature in the eirculating atmosphere are
produced not only during movements toward or from the
equatorial belt, but also during the ascent or descent of the
■air currents. As the warm air rises the pressure of the over^
lying atmosphere upon il is less and less ; the rising air
therefore expands, and in so doing it is cooled ; hence even
over the torrid zone the upper atmosphere is cold. On the
other hand, as the descending air in higher latitudes sinks
to lower levels a greater and greater amount of air rests
upon it ; it is thus compressed and warmed. The descent
of air fnwn a great altitude is therefore not a cause of cold,
warmed by compression as it comes down.
iges of temperature of this kind will later be seen
of importance in producing and in dissolving rain

luds. Illustrations of such changes may he foimd in a
small way by noting the coolness of the air tliat expands as
it flows out of a bicycle tire when the valve is opened, and
the warmth of an air pump in which air has Iwen com-
pressed in order to force it into a tire.

The most general movements of the atmosphere thus
established on a planet like the earth may be called the
pianetart/ cirmlation ; the lower membei-s of this circula-
tion are the planetary winds. The surface winds move
much slower than the upper currents, on account of fric-
tion with the earth's sui-face.

29. Observation of Winds The direction of the wind

ijt detenoined by a vane or arrow, turning easily on a

KLEMENTARY PHYSICAL GEOGRAPHY

vertical axis and freely exposed, as on a spire or high pole,
to the movement of the air. The wind is named after the
point of the compass from wliich it blows.

The strength of tlie wind nmy be described aa light, mod-
erate, strong (twenty miles an hour), fresh gale, whole gale,
Imnicane (seventy-five or more miles an hour) ; or it maybe
determined in miles
per hour by an anemo-
meter (wind measm^)
tiu:ning on a veitical
axis, as in Figure IS.
Describe the atrangt-
iiient of the cups on the
arms of this instrument.
Which way will the arma tun
when the wind blows? Wlff'

A pointer on a small dial,
connected with the axis of
the tm'ning arms by cog-
wheels, indicates the move-
ment of the wind in miles
per hour.
The surface -wind on the uneven lands seldom blows in
straight lines with uniform velocity. It usually roUs and;^
whirls, now faster, now slower.

30. Rainfall. — Witter is evaporated from the oceas'
surface, especiidly from its warmer parts, and the invisiUe '
vapor thus formed mixes with the air luid is carried abon
in the winds. When the moist air is sufficiently oo<J

THE ATMOSPHERE 39

he vapor in it is condensed into minute water di-ops or
snow crystals, and the air becomes cloudy. If tlie cooling
continues still furtlier, rain or snow may fall. The vapor
may thus be returned directly to the oceans, or it may fall
upon the lands, whence it returns to the oceans in streams
and. rivers. In this way there is a circulation of water
■through the atmosphere, from tlie ocean and back again.

The processes by which the air is cooled are nearly
always connected with its movements. Hence the general
distribution of rainfall will be referred to in the following
account of the winds, while a fuller account of clouds, rain,
and snow will be given farther on. .

31. Planetary Winds. — The most important members
of the plauetaiy winds are tlie trade T,vinds and the [ire-
vajling westerlies.

The trade winds blow with much regularity from about
latitude 28° N. and S. obliquely toward a belt of low atmos-
pberic pressure around the equator, from the northeast
in the noiUiem hemisphere, and from the southeast in
,the southern. The prevailing westerly winds blow from
a westerly source, but usually witli a slight inclination
toward the pole, over the greater part of the temperate
zones ; they form great spiral whirls around regions of low
pressure in the high latitudes of each hemisphere. These
frinds are made irregular by the occurrence of many
smaller whirls, about 1000 miles in diameter, which drift
eastward with the general movement of the atmoaphei-e
in middle latitudes. The winds of the puhir regions are

liitts known.

ELEMENTARY PHYSICAL GEOGBAPHT

Narrow lii'ltH of light vaiiable winds and frequent oalnu
lit^ tietween tlie sevcnd l>elts of steadier winds; in these
Ix'Uh of light winds the pressure of the atmosphere is bo
nfiii'ly iiiiil'onii tlmt the air is not pushed steadilj in any
direction. All these mem-
bers of the planetary circu-
lation are better defined over
tiie oceans than on the lands.

Point oot and name the semal
members of the planetaij drcnla-
tion in Figure 14. In viut
directions do their wiuda blow?
Between what latitades do thej
occur?

The trade 'winda are so

Fio. 14. Tlie Planetarv Circulation ii j i _ j.i. _.

ofibcAtmosrhen, «="!«« i™«» ™« constancy

witli which they follow their
course, the word trade formerly having meant "steady."
Tliey warm slowly as they approach the heat equator.
Tlifir velocity at eea is from ten to tliirty nules an hour.
They give fair weather, seldom interrupted by storms.

When sailing vessels enter the trade-wind belt they may
count upon making good liendway. If soling witli the
winds, extra sails ai-e often rigged out on the ends of tie
yawls, and tlius aided by a broadened stretch of canvas
the vessels speed along day and night.

Coasts upon wliich the trade winds blow are usnaUy
lieaten witli lieavy snrf, so that landing is difficult, except
in well-protected liurbors. This is the ease on the noifli-
east side of the Windwaixl islands in the Lesser Antilles-

^HYHanonend

XaOA M3M SHI

THE ATMOSPHERE 41

Lowlanda over which the trade winda blow are made

desert by the drying action of their warming air; for as
the winda become warmer they take up any moisture that
they find instead of giving up what they have. The Afri-
can Sahara and the central Australian deserts are thus
explained: it is entirely on account of tlieir dryness and
not because of the infertility of tlieir soils that these
legions are barren.

Where the trade winda encounter mountain ranges they
■are forced to asceud the side on which they approach (the
Tpindward side). As they rise the air expands and cools ;
as the air cools some of the invisible vapor that it contains
is condensed into minute drops of water ; tlms the ascend-
ing air becomes cloudy and rainy. The eastern slope of
the Andes, about the headwaters of the Amazon, the
mountains along the east coast of Brazil under the aouth-
,east trades, and the eastern slopes of the higlJands of
Mexico and Central America under the nortlieast tirades
'thus receive a good amount of rainfall (80 to 100 inches a
'year). All these mountain slopes bear heavy forests.

The further slope of the mountains, where tlie winds
descend (tlie leeward side), ia relatively diy and Uvrren,
because as the air descends it ia compressed by tlie weight
of the air that follows upon it; as it ia compressed it is
warmed, and as it warms it hoids all tlie vapor tliat it has
and eagerly takes up any vapor it can get from the gi'ound
over which it blows. This is especially noticeable on the
western side of the Peruvian Andes, where much of the
Old is a desert in spite of being near the ocean.

Even in the Sahara the few mountains tliat interrupt

ELEMENTABY PHYSICAL GEOGRAPHY

the general snrf'ice receive a sufficient rainfall to permit
tree growth, but the stremis supplied on the moimtaiQ
aides wither awaj after descendiug to the desert below.

The prevailing westerlies are much less regular than the
trades Thej may weaken to lesa than ten miles an hour,
or strengthen to gales of sixty or more miles an hour.
They often shift
from their general
course to take part
in the drifting spiral
iiio'\ ements indicated
m the temperate lati-
tudes of Figure 14.
It IS chiefly to these
great whirllike
movements that the
frequent changes of
weather in teraper-
Fio 16 Wet Weather Streims of tho Tareo ate latitudes are due.
MonutaiuB StLam Locate tl ese mouiita. as — ,, , ,

on tha chart ol meaQ annual temperatures The irea of the

Figure 12 by the latitude and longitude here United States lies
s'"™ almost entirely

within the belt of the prevailing westerlies. If the wind is
obseiTed at noon every day for a month or two, a westerly
direction will be found more common than an easterly. If
the drift of clouds is observed, the general movement of
the atmospheric currents from the western toward tiie;
eastern side of the sky is very noticeable. Variations from i
e prevalent directions are generally due to tlie drifting
t spiral movements.

^«-ML. J

THE ATMOSPHERE 43

The lands under the westerly winds are generally well
watered if they do not lie too far from the oceans ; the con-
tinental interiors are comparatively dry. Abundant rain-
fall is received on the mountainous Pacific slopes of North
and South America in middle latitudes, but the opposite
slopes are drier. In these latitudes the western (wind-
\ ward) slope of the mountains is heavily forested, while tlie
{ eastern (leeward) slope has an open tree growth or none.
i The distribution of forests over the great American moun-
tain system thus gives striking illustration of the relation
of timber supply to winds, land forms, and rainfall.

The belt of calms and light breezes in the neighborhood
of the equator, between the trade winds, is called the
equatorial calm belt ; that pai-t of the belt which lies on
the oceans is known to sailors as the doldrums. The air
in the doldrums is moist and sultry, for the warm inflow-
ing trade winds gather much water vapor as they blow
over the ocean. The sky is prevailingly cloudy ; rain
falls every day or two, especially in the late afternoon or
night. The lands are heavily forested under this warm
and moist belt, and agriculture is difficult from the very
luxuriance of vegetation.

Sailing vessels bound across the equator are frequently
becalmed for several days in the doldrums ; there they lie
idle, rocking very gently to and fro in the long flat swell
that sweeps across the glassy waters. They must then
take advantage of every light breeze to push onward and
reach the trade winds beyond. The dull sky, the sultry
air, and the glassy sea make the delay all the more
vexatious.

44 ELEMENTARY PHYSICAL GEOGRAPHY

The rain of the doldrums results from the slow ascent of
tlie warm moist air supplied by the inflowing trade winds.
Tlie lower air is mised to greater and greater height by the
inflow of more air beneath from both sides ; it expands as
it rises, and cook as it expands ; the vapor in the air is
then condensed into cloud particles, the clouds become
lieavier and lieavier and give forth plentiful rain ; the air
fi-om wliicli tlie rain has fallen continues to rise and at
last ovei-flows aloft and thus supplies the upper currents
tliat move obliquely toward the poles. Violent thunder-
storms arc frequently formed in the great cloud masses of
the calm belt.

The ill-defined belts of light breezes and occasional
calms lying between the trades and the prevailing wester-
lies in each hemisphere are known as the horse latitude»»
Theii- light winds usually blow obliquely outward on both
sides ; hence tlie air here must slowly descend from the
upper currents to supply the outflowing breezes. As the
air slowly settles down it is compressed by the weight of
that which rolls in on top of it ; as it is compressed it is
warmed, and as it is warmed any clouds that it may have
contained are dissolved ; hence clear fair weather is preva-
lent in this belt.

32. Whirls of the Westerly Winds. — The irregular
winds by which the prevailing westerlies are so often
interrupted sometimes have an inward, sometimes an out-
ward, spiraling movement, as in Figure 16. They are like
great slow-turning whirls from 500 to 1000 miles in diame-
ter ; they may be compared to eddies in streams of water.

THE ATMOSPHERE

When blowing outward the air slowly descends from
aloft ; the winds are light and the weather is fair, for the
reasons ^ready given for the fair weather of the horse
latitudes. When blowing inward the air slowly ascends,
and the weather is cloudy and wet, for the reasons given in
explaining the doldrums Here the w'nds may gain a
stormy strength fifty to eighty miles an hour on land and
sometimes over one hnn
dred miles an hour at sea

Exercise. Locate the cen
ters of the two wh rla show
in Figure 16. Deacnbe the
spiral movement of the it nds
with respect to the centers
In which whirl does the t irn
ing around the center agree
with the turning of the ha ds
of the clock Y Which whirl
should have low pressure?
Which one fair weather j,^^ j^ Inward and Outwarl Whirl.

Both classes of whirls
travel from 600 to 1000 miles a day in an easterly direc-
tion, with the general drift of the atmosphere in temperate
latitudes. Changes of weather are caused by their pas-
sage. The whirls may strengthea and increase in area for
a time, then weaken and fade away ; their duration being
from a few days to two or three weeks, and their distance
of travel from 5000 to 15,000 miles or more. The direc-
tion in which the whirls turn in the northern hemisphere
is opposite to that in the southern ; that is, the outflowing
spirals turn clockwise in the northern hemisphere, as in

46 ELEMENTARY PHYSICAL GEOGRAPHY

Figure 16, and counter-clockwise in the southern hemi-
sphere. How do the inflowing spirals turn in the two'
hemisplierea ?

The pressure of the atmosphere, as shown by the barom-
eter, is less than usual about the central part of the stormy
inward whirls, and greater than usual in the fair-weather
outward whirls. Hence they are often called low-pressure
and high-pressure areas. They have also been named
cyclonic and anticyclonic areas from the curving move-
ment of their winds. They will be further described in
the section on weather.

33. Seasons and Zones. — As the earth moves around
the Sim there are six months in each year (March 21
to September 22) in which the northern hemisphere is
inclined somewhat toward the sun, so that it has longer;
days and stronger sunshine than the southern, which is at
the same time inclined somewhat away from the sun, as in
Figure 17.

In this condition the gain of heat in the northern hemi-
sphere by the alsorption of the strong sunshine during the
long days is greater than the loss of heat by radiation dur-
ing the short nights ; hence the temperature there rises
above the mean of the year. But in the southern hemi-
sphere the loss of heat by radiation during the long
nights is greater than the gain by absorption of weak sun-
shine during the short days ; hence the temperature there
falls below the mean of the year. During these inonthB
the northern may be called the summer hemisphere, and
the southern the winter hemisphere.

THE ATMOSPHERE

During the other six months of the year (September 22
to March 21) the southern hemisphere is iiicUned toward
the sun, and the northern away from it, so that the above

Fio. IT. Mouthly Fositiona at tlie Eaiili vrhh Respect M tbe Sun

conditions are reversed. The southern is then the sum-
mer hemisphere, and the northern the winter hemisphere.

In both hemispheres t'l.s succession of higher and lower
temperatures during the year produces the cliange of

48 ELEMENTARY PHYSTCAI. GEOGRAPHY

The winter months in the northern hemisphere
are December, Jimuary, and February (these being the
summer months of the southern hemisphere) ; the spring
months are March, April, and May ; the sunamer months,
June, July, and August; the autumn or fall months,
September, October, and November.

The zones may be defined by means of Figure 17 aa fol-
lows: In the torrid zone, from 23^° N. to 23^° S., every
point receives vertical sunshine sometime in the year;
here the days do not vary much from twelve hours in
length. In the frigid zone, extending 23^° from each
pole, there is at least one day in the year when the sun
does not rise and another when it does not set ; here the
days vary greatly in length. The temperate zones occupy
the space between the torrid and the frigid zones (23^°
to 66^°), north and south latitude ; here no place has ver-
tical sunshine on any day, and no day passes without a
sunrise and a sunset.

If zones are limited by the mean annual isotherms of
70° and 30°, their bordei"s are much more irregular than
when limited by sunshine.

34. Observations of the Sun. — Records of thermometer
readings during the school year should be used to show
the general fall of temperature to midwinter, and the
general rise from midwinter to midsummer. These
changes of temperature should be connected with the
changes in the apparent movement of the sun. In late
December the sun rises south of east and sets south of
west : at midday it reaches but a moderate altitude ahovtil

THE ATMOSPHERE

the BGUthem horizon ; at this time the dumtion of daylight
is less than twelve hours and the strength of tlie sunshine
is reduced. In late June these conditions are all revcraed.
The low temperature of winter ia thus seen to dejiend on
the weak sunshine of short days, and the high temperature
of summer on the strong suashine of long days. The ris-
ing temperatiu'e through spring results from the strength-
ening of sunshine in the lengtliening days ; the falling
temperature of autumn, from the weakening sunshine in
the shortening days. (See Supplement.)

35. Change of Temperature with the Seasons. — An
observer at any one place notes the familiar succession of
the seasons during the coui^'Se of the year. A better
understanding of the meaning of the seasons may be
gained if the earth as a whole is considered, as on the
above charts. It is then seen that for a time the heat
equator moves a moderate distance from the geographic
equator into the summer hemisphere, while the high tem-
peratures of the toi'iid zone advance into the temperate
zone, and the rigor of polar cold is somewhat lessened ; in
the other hemisphere the polar cold is extreme, low tem-
peratures advance over the temperate zone, and the heat
on the border of the torrid zone is decreased.

In the next half year the heat equator moves slowly
lack and crosses the geographic equator, and all these con-
ditions are reversed. The year, or period in which the
earth revolves around the sun and in which the change of
seasons therefore take place, thus comes to be a natural
, measure of time.

50 ELEMENTARY PHYSICAL GEOGRAPHY

36. January and July Isotherms. — The general distri-
bution of mean temper atiirea for January and for July is
shown in charts of monthly isotherms, Figures 18 and 19,
on which the following exercise may be based.

Exercise. Ta wbicb. summer hemisphere does the heat equator
Btand farther from the geographic equator? Does the heat equator
stand farther from the geographic equator on the oceans or on the
lands? Where do midsummer temperatures of more than 90°
occur? In wliich hemisphere do they cover the largest area? What
ia the lowest mean temperature in January ? Where does it occur ?

About how much difference ia there between January and July
temperatures in latitude 40° S. ? Where in latitude 40° N. is there
a strong difference between January and July temperatures?

37. Mean Annual Range of Temperature. — The average
change of temperature with the seasons may be best
studied by taking the difference between the mean temper-
atures of January and July. This difference is called the
mean annual range of temperature. It ia shown for the dif-
ferent parts of the world in Figure 20. The range is gen-
erally less than 10° over the torrid oceans and less than
20" over most of the temperate oceans. On land the range
increases. Places in the interior of continents have a much
stronger range than tliose on continental borders or islands.

Central Australia and the interior of the Sahara have a
range of over 30°. Over most of the United States the
range is from 30° to 60°. Over a belt of land from Hudson
bay into Alaska the i-ange is more than 80°. Over the
greater part of Europe-Asia the range exceeds 40°.

In regions of the greatest range the winters are bo cold
that the ground is frozen to a depth of 100 feet or m

:i-^5~~J

^g " -^ss

w-^

^tS *-fe — R^?®^

a^^

IC^

""^

=^=^1

ir~

■•:d

FiQ. IS. Cluirt i)f Mean Tt-niperatiires fur Jiiiiimry

Fic. IVi. Chart of Muan Tempewtures (or July

THE WEW YC'kK

I'UBLIC LIBRARY

ASTOft. L^NOK
TNJDEN POUNDATIOrtt

TOE ATMO.SPliERE

In winter ice is so hard that the runner of a skate does
not hold upon it; wood is too hard to be chopped witli
an ax. In summer thawing reacbea only a few feet
below the surface. Trees gain only a stunted growth or
are altogether wanting.

Compare the annual range on the western and eastern
Goasta of the continents in temperate latitudes. On which

Chart of Annual Bsngd of Temperatur

coast is the range of less amount? The difference of range
is due to the prevailing westerly winds, which carry the
nearly uniform conditions of the ocean on to the western
coasts, and the changing conditions of the continental
interior out to the eastern coast.

Exercise. Where is the greatest annual range? Wlmt is its
amount? Compare tlie annual range of Labrador and England, of
Virginia and Spain, of Japan and California.

52 ELEMENTARY PHYSICAL GEOGRAPHY

The annual changes of temperature are much more dia-
tinct in the northern hemisphere, where thei-c is much
land, than in the southern, where there is much ocean.
Thia is because the land surface changes its temperature
more easily than the ocean surface, and therefore the air
over the land becomes hot in summer and cold in winter.
The change of seasons in the north temperate zone,
especially on the lands, is much stronger than in the south
temperate zone. This is because the northern continents
are broad in t«mperate latitudes, while the southern are
relatively narrow.

Bxercue. lu Figure 20 foUo-w the latitude circle of 40° or 50° N.
around tlia earth. For how many degrees of longitude doea it lie
on the continents? How many on the oceans? Do the same for
latitudes 40° or 50° S. Compare the results.

Winter and summer are not very different over the great
oceans of the south temperate zones, where the weatiier
is rather uniformly chill and damp, or inclement, all the
year round. This is because water is slow to change its
temperature ; the ocean waters and the air over them suffer
small changes of temperature during the year.

In the temperate zone tlie summer half year is the time'
of plant growth, and is therefore the season of greater
activity in all industries immediately coimected with agri-
culture. One of the most interesting consequences of the
advance of spring and summer temperatures into higher
latitudes is tiie northward passage of migratory birds,
familiar to every lover of outdoor naturae. Tlie approach
of winter is accompanied by the return of the birds to
warmer latitudes.

THE ATMOSPHERE

38. Terrestrial Winds The etrength of the planetiry

circulation and the boundaries of its wind belts vary with
the seasons. Thus modified, the winds may be called
terrestrial, aa belonging to the earth in particular with its
winters and summers, instead of to the other j»lanets which
may not have seasons like ours.

I ffio. 31. Diagrams ol Terrestrial Winrta fc

■y nnd rluly

s a general scheme of the winds for January aud
laidering the irregular winda produced by tlie

Figure 21 g

July, witliout

continenta and their mountain ranges.

the stronger winds. In whicli iiiontli

the tiortheni hemisphere? In wliat se

same queetioiis for the Runinier heiiiisphi

prevailing westerlies most interrupted by Bpiraliiig

and anticycloneB) 1

Examine the isotherms in tlie northern liemisphere for January
and Jnly, Figures 13 and IQ. In which month are the lines closer
together? How can you tell from this in which month there is the
greatest difference of tpmiierature between the torrid Bone and the
Arctic regions? In wbieh month would you expect the general

The heavier lines show
;he winds strongest in
is this? Answer the
In what season are the
nds (cyclonea

54 ELEMENTARY PHYSICAL GEOGRAPHY

circHlation in the northern hemisphere to be the stronger? Why?
Answer the same questions for the Houthern hemisphere. Compare
the results for the two liemispheres.

It 18 thus seen that in winter the difference of tempera-
ture between the equatoi' and high latitudes is strength-
ened. As the general circulation of the atmosphere
depends on this difference, the winds will generally be

F:o, 23. WiDds of Jajiuary

stronger in winter than in summer. This is especially
true of the prevailing westerlies and their spiraling
cyclonic winds in the northern hemisphere; they fre-
quently become stormy in winter, while they are rela-
tively light in summer. In the southern hemisphere
these changes are less marked. Why so ?

Examine in Figure 21 the belts of light breezes and occasionsl
ealms between the trades and the westeriies. What is the name o£
these heltfl? Compare their positions in January and July. What'

THE ATMOSPHERE

is the name of the belt of ca

winds ? How doea its poaiti

nis and light breezen betm
n change witli the seasolif

The horBe latitudes and equatorial calms are much less
regular in reality thaji they are represented in Figure 21,
on account of the irregular outline and form of the lands.
A better illustration of the prevailing winds for January
and for July is given in Figures 22 and 23.

Flo 2J Winda of July

The light and irregular winda of the horse latitudes
migrate toward the equator in the winter of their hemi-
sphere, and toward the pole in the sumnier; these hells of
migration are known as the northern and southern subtropi-
cal belts (ST, Figure 21). . Any country over which a sul>
tropical belt is stretched will have the westerlies and their
rainy stoi-ms in winter and the drying trades in summer.
This is the case with southern California and the Mediter-
ranean countries of southern Europe and northern Africa, as

56 ELEMENTARY PHYSICAL GEOGRAPHY

well as with central Chile, southern Africa, and south-
ern Australia, These countries are said to liave a sub-
tropical climate. In what months will they have their
rainy season?

As countries in the subtropical belts are dry in the
growing season, agriculture there generally requires the
aid of irrigation (watering the fields by canals led from
streams or reservoirs).

Like the calms of the horse latitudes, the calms and
lains of the doldrums also migrate north and south dur-
ing the year. The belt of winds and rainfall thus eon-
trolled forma the subequatorial belt (5^, Figure 21). The
migration of these three belts follows the migration of
the sun.

The plains of the Orinoco in Venezuela, north of
the equator, receive a plentiful rainfall in July and
August, but in December and January they are relatively
dry. In the wet season cattle find abundant pasture
on the plains, but in the diy season they are driven
into the valleys. On the plains between the headwatera
of the Amazon and the Parana, south of the equatoi', the
months of wet and dry seasons are reversed from those
of Venezuela.

The western Sahara, between the reach of the subtropical
(winter) rains on the north and the subequatorial (summer)
rains on the south, gives no important river to the Atlantio
along a thousand miles of coast line. The rise of the
Nile in Egj-pt from June to September results from the
northward advance of the equatorial rains over the uppo^
part of this river basin, as in Figure 23.

THE ATMOSPHERE

In the belt over which the equatorial
calms move north and south during the year the trade
winds change their direction in tlie warmer and cooler half
years. Winds of this kind are called monsoons.

How do the winda blow in the northern lialf of the subequato-
rial belt(Se, Figure 21)
in January? in Jtily?
how in the southern
half?

Wliat parts o:
equator are crossed bj
the extended northeaat
tradcB in Jamiarj, ]
ure 22? by the
tended southeast trades
in July, Figure 23?
Where do these ex-
tended winds cover the i
greatest area? I

Note ill Figure24 the I
change in the direetion I
of the northeast trades |
in January as they c>
tJie geographical equar ■
tor and enter the south-
em hemisphere on their |
way to tlie calm belt.
What is the direction
gf the wind in the same
part of the aoiithern hemisphere in July? Note the corresponding
tbonge in the extended southeast trades for July in Figure 35.

The reason for this change of direction as the winds cross
the equator is found in the earth's rotation, on account of

Fio. 25. July MoDsooDS Id Indi

58 ELEMENTARY PHYSICAL GEOGRAPHY

which all winds in the northern hemisphere tend to turn to
the right, and in the southern hemisphere to the left. On
account o£ the irregular distribution of land and water mon-
soons are not evenly developed all around the equator.

The monsoons of the Indian ocean are the most remark-
able of the woiid. In January a belt of northwest mon-
soon winds is developed for about ten degrees south of the
equator, as in Figure 24. In July, when the heat equator
has shifted far northward to the border of Asia, a broader
belt of southwest monsoon winda ia developed north of
the equator, as in Figure 25.

The primitive sailing vessels of the Indian ocean in
earlier centuries, poorly adapted for sailing against the
wind, made voyages only as the monsoons favored their
courses, going outward from India to Africa in one half
year and returning in the next.

The east coast of the Malay peninsula is beaten by heavy
surf under the northeast monsoon, and then the native fish-
ermen stay ashore. But under the southwest monsoon,
an offshore wind, the wat«r is comparatively smooth, and
large fleets of fishing boats put out to sea with their
palm-leaf sails.

In what months -would the eTenta doscriheii in the twn preceding
paragraphs be expected ?

40. Winds of the Continents. — As the air over the con-
tinents is wanner than that over the neighboring oceana
in summer and colder in winter, the winds tend to blow
inward toward continental centers in summei'and outward
from them in winter-

THE ATMOSPHERE 59

In the north temperate zone the cold land winds of
winter tend outward toward the aea, and the far inland
regions have much clear and dry weather. In summer
the warm and moist sea winds tend inward towai-d the
still warmer lands, and the interior parts of the large con-
tinents then have a greater abundance of clouds and rain.

The general circulation of the atmosphere is much com-
plicated by this outward and inward tendency of the winds
over the continents, as may be seen by compaiiiig the
winds of January and July over Asia, Figures 22 and 23,
with the winds of corresponding latitudes in Figure 21.
The regular belts of winds in the latter figure are much
broken up, especially in the northern hemispliere.

41. Winds on Land. — The lower winds are generally
not so fitiong or so ixigular on the uneven lands as on the
level seas, although the upper currents over the lands stiU
flow^ rapidly. In valleys the winds are much influenced
by the direction of the inclosing slopes. Hence observers
hying in deep valleys may often determine the general
direction of the winds better by watching the drift of the
clouds tlian by noting the position of their wind vanea.

The air over the lands is cooler and therefore heavier
than that over the sea at night, but warmer and ligliter by
day. Hence around the border of the lands tlie wind
tends to blow alternately offshore at night and onshore by
day for a short distance from the coast, such winds being
known as land and sea breezes.

On the coasts in the torrid zone the sea breeze is wel-
come, as it tempers the excessive heat of the day on land.

w^m

aO KLEMKNTARY PHYSICAL GEOGRAPHY ]

The same is true of suramer weatlier in the temperate
zone. On the coast of Peru the fishermen sail offshore in
the eaily morning with the land breeze, and I'eturn in the
afternoon witli the sea breeze,

42. Daytime Winds In fair, wanu weather the lower

air lying on the land becomes unduly heated by day, as
compared with tlie overlying air. Tlie warmer lower air
then rises and the cooler upper air descends, tliis being a
small example of convectioual circulation. It is like the
movement of water in a kettle that is heated at the
bottom.

The faster-moving currents from aloft are tlius brought
down to the surface. Hence on landa the winds of fair
weather in the daytime are commonly stronger than those
of the night. Tliis is prevailingly tlie case tlutjugh the
year on torrid lands ; on the temperate lands it is common
during summer weather, hut is less noticed in winter.
Why does no such daily change in the strength of the
wind occur at sea?

43. Humidity. — The condition of the atmosphere as to
the water vapor that it contains is expressed by the term
humidity. When t)ie air contains much vapor and feels
damp the humidity is said to be hig]i. When it eon-
tains little vapor and feels dry the humidity is low. The
liigher tlie temperature of the air, the greater the amount
of vapor it may contain. When as much vapor is present
aa is possible at a given temperature the air is said to be
in the state of saturation. The lower air over the ocean
is usually almost satmated ; in the doldrums the humidity

THE ATMOSPHEKE 61

is always high. Far Inland, in the desert regions of con-
tinents, the air may contain veiy little vapor; here the
humidity is [ow. Dry air is more agreeable than damp,
because it aUows active evaporation from the skin. Cold
damp air is chilly and " penetrating." * Wami damp air is
sultry and " close."

44. Dew and Frost. — Dew is a deposit nf moisture on

tlie ground, or on loose objects like leaves and stit-ks lying
on the ground. It is formed wlien the groimd is cooled
at night by radiation ; then the air near it is cliiUed by
conduction, and some of the water vapor in the air is
changed to the liquid fonn. The temperature at which
dew begins to be formed in cooling air is called tlie deto-
point.

Exercise. The dew-point iiiay be determined liy experiment as
follows: Half fill a, tin cup with water wbose teniperature is about
like that of tlie air. Then slowly pour in ice wuter, atiiriiig it with
a thermometer. As the cup is cooled the air next to it is cooled
also. As tlie air is cooled the vapor that it contains wiU more and
more nearly saturate it. When the outer surface of the cup is first
clouded by a deposit of moisture the air next to it has just passed
the condition of saturation^ and the temperature of the water gives a
close indication of the dew-]>oint. If ice is added so as to make the
water still colder, more and more vapor will be condensed on tlie
tap, the air constantly being saturated with the vapor that remains
in it a« its temperature falls.

When moisture is condensed upon the ground at tem-
peratures below the freezing pomt it fonnn frost. Thus
frost on tlie ground coiTCRponds tii snow in tint air, and
dew corresponds to rain.

62 ELEMENTARY PHYSICAL GEOGRAPIIV

Dew and fi-ost are in part supplied from water vapor in
the air that lies near the ground, in part by vapor that rises
through the soil fi'om its deeper and moister parts. In the
daytime the vapor from the soil escapes into the warm air ;
but at night, when the ground is colder at the surface than
beneath, the rising vapor is condensed.^ Dewdrops found
on the blades of grass and on the living leaves of plants
close to the ground are in large pari; supplied by the water
that the plants bring up from tlie ground through the
roots. In the daytime the moisture evaporates from the
leaves, but at night it may collect upon them in drops.

At night, when the air is calm and clear, the ground is
cooled by losing its heat to cold outer space ; the quiet
lower air is then chQled, because it lies on the cooled
ground, and dew (or frost) is formed. When the wind is
blowing the lower air is constantly changed and none of
it is much chilled; when the sky is cloudy at night the
ground cools but little ; hence on windy or cloudy nights
little or no dew (or frost) ia fonned.

45. Clouds, Fog, and Mist, — The different processes by
which water vapor is condensed^ in the atmosphere pro-
duce clouda of many diif erent forms. It has been explained
that in daytime of fair summer weather the lower air tends
to rise in convectional currents. The ascending air currents

' It should be noticed that the term condensation, when applied t(
refers to its change from the gaseous to the liquid (or eolid) attM, i
to its cotnpreaaioD, as vapor, into a smaller volume. Hence candeoaation
of vapor may take place while the air with which it is mixed is expanding,
provided that the expansion proiiiioeB sufficient cooling to lov
perature helow the dew-point

THE NEW YC?.K |

PUBLIC LIBRAR'i

TILDEN FOUNDATIONS

THE ATM(.).SP1IEKE 63

sad cool aa they rise, and, if tlieir ascent is great
eiiough, some of tlieir vapor is condensed, fomiing round-
topped clouds, brilliant white in strong sunshine, as in
Plate III, A; the air within the clouds is all saturated
by the vapor it still contains. Tlie clouds are of unequal
size, but liave their bases at about the same height {com-
monly one fourth to one half of a mile), and all drift
along with the speed of the currents in which they are
ioimed- Their rapid motion can be recognized by watch-
ing Ibeir shadows pass across a field ; they npjirly always
drift eastward in the United States, being home in tlie
prevailing westerly winds of middle latitudes.

Clouds of this kind are called cumulus (heap) clouds.
They usmdly begin to form in the wanning morning hours
of fair weather, but dissolve and disappear in tlie late
afternoon, when sunshine weakens, the ground cools, and
CMJUvection ceases.

It is usually the case that the great cyclonic storms of
(It$ -westerly winds are preceded by long filmy or feathery
strips of pale whitish cloud, as in Plate III, B. Clouds of
this kind are formed at a height of several miles, in the air
currents tliat flow out and forward from the upper part of
the storm. They are called cirrus (curl) clouds. They con-
BiBt of minute ice crystals, because the moisture foi-ming
tbein has been condensed in the cold upper air at tempei-a-
ttires below the freezing point. Sometimes the cirrus is
Bprefld out in a thin sheet called cirro-stratus. When the
Btib or moon is seen through a cirro-stratus a large ring
nintly colored with red on the inside is seen around the
luminary. Such a ring is called a halo ; it is formed by

64 ELEJIENTARY PHYSICAL GEOGRAPHY

the bending (refraction) of tte light in passing through the
ice crystals. Haloa are common and brilliant in the polar
regions.

In the central parts of the great whirling cyclonic storms
heavy dull-gray clDud sheets of gi'eat size are formed
at a moderate height above the earth's surface by the
gradual cooling of the inflowing winds. Clouds of this
kind, from which rain or snow falls, are called alto^imbus
and nimbus. A nimbus cloud is shown on the right side
of Plate IV. As with other clouds, the air within the
nimbus is constantly saturated. These clouds often cover
the area of several states at once, and they may hide
tlie sun and stars for several days at a time, yielding
plentiful rain or snow before they drift away eastward
and reveal the clear sky again in fair weather. They aiB
especially large and heavy in winter, when the westerly
winds and their storms are strongest. When the sun or
moon is seen through the fragments of nimbus clouds it ii
often closely surrounded by a brilliant glow, called a corona.

When a cloud is formed at so low a level that it rests
on the ground or on the sea surface it is called fog. This
is often the case when moist sea wuida of mild temperature
blow across a colder part of the sea or blow inland over
snow-covered hills. Fog is often foi-med in valleys among
mountains by the cooling of the lower air at night. Fog
of this kind usually disappears in the morning sunshine,
but if veiy heavy it may not be dissolved by the shoit and
weak sunsliine of a winter day.

A slight cooling of damp air may produce a faint cloudi-
ness, known aa mist, much less dense than fog.

THE ATMOSPHERE 65

46. Thunderstorms. — When the lower air is warm and

moist it ia apt to liae iind form great cumuhis clouds from
ten to fifty miles in length, whose tops may reach heights
of more than a mile. When the rising movement is active
and the cloud grows to great size it may often be seen to
spread out at the top in a cirro-stratus film, and aixiut tlie
same time rain falls from its base. If the rain becomes
heavy, lightning flashes occur, causing peals of thunder;
hence such storms are called thunderstorms.

Storms (if this kind are common in the cloudy helt of
the doldrums, where they usually occur in the afternoon

Fio. 26, A Distant TbnndeTstorm

and evening. They are also common on the lands in
periods of hot summer weather. Much of the summer
rain in the Mississippi valley falls from thunderstorms
which drift eastward in the afternoon and night at a rate
of twenty or thirty miles an hour, giving heavy rainfall for
an hour or two as they pass by. A violent blast of wind,
or timnder squall, often rushes forward from beneath the
front of the cloud mass, raismg a cloud of dust before the
tain arrives.

During the growth of a thunderstorm cloud the water
particles in it become cliarged with electricity. When the
drops become large enough to fall as rain the electricity
is diachaiged from one part of the cloud to another, or from

66 ELEMENTARY PHYSICAL GEOGRAPHY

the cloud to the ground, in a great electric spark, or light-
ning flash. Thunder is the sound caused by the violent
agitation of the air along the flash. It may be compared
to the sound caused by snapping a whip. As* sound travels
through the air at the rate of a mile in five seconds, the
distance of a flash can be determined in miles by counting
the number of seconds between the lightning and its
thunder clap and dividing the number by five. The
" rolling " of thunder is caused partly by the continuous
arrival of the sound from different parts of a long flash,
partly by the echoing from clouds or from hills and moun-
tains. At night the upper clouds of distant thunderstorms
are illuminated by flashes, commonly called heat lightning,
too far away for the thunder to be heard.

An unusually heavy and violent rain, popularly known
as a cloud-burst, sometimes falls during a thunderstorm
upon a small district. If on a hillside it may wash away
the soil, baring the rock beneath.

47. The Rainbow. — When a thunderstorm passes east-
ward in the late afternoon a rainbow is usually seen by
observers on the west of it. The bow is formed by the sun-
light that is turned back and bent (refracted) by the drops
that are falling from the rear of the cloud. The center of
the bow will be directly opposite the sun. Why will a
rainbow form a half circle at sunset? Why does a rain-
bow usually show less than a half circle ? A bow forming
a complete circle might be seen from a balloon.

48. Tornadoes and Waterspouts. — Violent whirlwinds
are occasionally formed in thunderstorms. They are seldom

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THE ATMOSPHERE

TBWe than a quarter of a mile in diameter ; they diift along
with the thunderstorm in which they are formed, usually
in an easterly direction, posing hy in a minute or two.
ThMT whirling winds are strong enough to blow down
trees aud overturn buildings. Violent local storms of this
kind are often called cycloues,- or prairie twisters, in the
Mississippi valley, but the name tornado is to l)e preferred
in order to distinguish them from the much lai^er and less
violent cyt'lonie stornis,

When violent whirlwinds of this kind- occur over a
water surface a watery column is formed iu their vortex ;
they are then called waterspouts. Plate IV" shows a water-
spout over Vineyard sound, southeastern Massachusetts,
as photographed on Aug. 19, 1896. A vessel overtaken
by Buch a wliirlwind may be suddenly liismastcd.

49. Tropical Cyclones (Hurricanes and Typhoons). —
Violent sforma known as tropical cyclones are occasionally
dereloppd in the doldrums when the heat equator stands
farthest fi'om the geographical equator. They appear to
be, like thunderstorms, due to the inflow, ascent, and out-
flow of very warm moist air. They grow to be several
haiidred miles in diameter, with violent winds, whirling in
great spirals around a center of low barometric pressure,
gr^at cloud sheets, and heavy rains.

Ab in the cyclonic storms of temperate latitudes, the
winds of tropical cyclones turn counter-clockwise in the
northern and clockwise in the southern hemisphere. As
tropical cyclones increase in size, they travel slowly (one
or two hundred miles a day) westward and towai'd the

68 ELEilESTARY PHYSICAL GEOGRAPHY

temperate zone near the western border of their ocean. In
a week or ten clan's they pass from the trade-wind belt into
the prevailing westerlies. As they enter the temperate
zone, stiU increasing in size but usually decreasing in
violence, their path curves eastn'ard, and they join the
great pzoceHsiou of cyclonic stonns of middle and higher

latitudes. The chief regions of these stonns are shown
by dotted areas in Figure 27.

In the southern hemisphere the doldrums of the Atlantic
hardly pass south of the equator, on account of the lai^e
HUpply of cooled water that comes northward west of
Africa; hence no tropical cycldnes occur on the Brazilian
coast. In the western Pacific ocean the doldrums are
farthest south in February and March, and at that -time
cyclones occur in tlie region of the Fiji islands. In the
southern Indian ocean cyclones occur in the same months
east of

THK ATMOSPHERE 69

In the northern hemisphere tlie doldrums are farthest
north in the western Atlantic and Pacific in August and Sep-
temher ; eyclouea occur in these months in the West Indies,
where theyare commonly called hurricanes, and in the region
of the Phihppines, where they are known as typhoons. In
the Indian ocean there are two seasons when the doldrums
stand over the warm seas between the equator and Asia:
one in May, as the doldrums are moving noith ; one in
October, when they are moving south ; hence in tliis ocean
alone there are two seasons when ti'opieal cyclones occui'.

Formerly much destruction was ^vrought on vessels at
sea by the furious wuids of tropical cyclones ; hut now
that the season of occurrence, the usual patli, and the
behavior of tlie winds of hurricanes have been learned, and
now that vessels are built larger and stronger, losses at sea
are much less serious tlian they were a century ago.

When hurricane winds blow over islands in the torrid
oceans they may cause much damage to vessels in the
harbore by driving them ashore, and to settlements by
destroying the houses and plantations. Cocoanut palms
may thus be stripped of their leaves, after which the trees
require a number of years of growth before again bearing
&e fruit of which so many uses are made.

The great sea floods by which Galveston, Texas, was
devastated in September, 1900, were caused by the winds
of a tropical cyclone which brushed the suiface waters
from the Gulf of Mexico into the streets of the city-
Similar sea floods liave repeatedly occurred on the low-
lands at the head of the Bay of liengid, drowning many
thousands of the people.

70 ELEMENTARY PHYSICAL GEOGRAPHY

50. Rainf aU. — Rain, snow, hail, and sleet are all included
under the general term rainfall. The explanation already
given in Section 30 has shown how closely the amount and
season of rainfall are connected with the circulation of the
atmosphere.

Snow occurs when the moisture of the air is condensed
at temperatures below the freezing point (32°). Snow
flakes are six-rayed ice crystals of various patterns. Rain
occurs when the moisture of the atmosphere is condensed
into drops at temperatures above the freezing point, or
when the snow flakes of lofty clouds descend into the
warmer lower atmosphere and melt before reaching the
groimd. Sleet is half-melted snow.

Hail is a mixture of ice and snow, usually in roimded
pellets, sometimes half an inch, rarely an inch, in diameter.
It occurs chiefly in summer, when the ascending currents
of lofty thunderstorms carry raindrops so far upward that
they are frozen and coated with snow before they fall.
Hailstorms occasionally do . much damage to crops and
buildings.

Hail should not be confounded with the little pellets of
nearly transparent ice, properly called frozen rain, caused
by the fall of raindrops from a cloud whose temperature
is above 32° through a lower stratum of freezing air.
Hail occurs chiefly in hot summer weather; frozen rain
in winter.

The amount of rain is determined by measuring the
depth of water that is collected in a cylindrical vessel
having vertical sides, called a rain gauge. The gauge
should be set in an open space, away from trees and

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THE ATMOSPHERE 71

buildings. Snow should be melted before it is m(>asured.
Eight or ten inches of snow correspond to about an inch
of rainfall. An annual total of eighteen, twenty, or more
inches is necessary for agriculture, as over the great pntirie
re^on of the Mississippi and Ohio valleys from the 95tli
meridian eastward. If the annual amount is between
eighteen and ten inches, agriculture requires irrigation, iis
on a large part of the Great plains east of tlie Rocky moun-
tains, and over large areas in tlie basins of Utah and Neva<lii ;
but scattered grass sufficient for cattle ranges may grow in
such regions. If the annual total is luider twelve or tnn
inches, there will not be water enough for irrigation, unless
it is supplied by rivers that rise in a moister climate, as in
parts of Arizona and southeastern California.

The distribution of tlie annual rainfall over tlie world,
T^resented in Figure 28, shows that the greater auiounts
(eighty inches or more) occur in the subeqnatorial belt and
on mountain slopes ascended by tlie trade winds or the pre-
vailing westerlies. Most of the dry and desert regions of
the world (twenty inches of rain or less) ai'e either low-
lands of the tnwle-wind belt, like the Sahara and central
Australia, or the slopes and lowlands to the leeward of
lofty mountains, as in Peru, or continental interioi-s crossed
by the westerly winds, as in central Asia.

Exercise. Where are the regiona of lieavieat rainfall ? How are
these tegioHH related to the belts of the tcrreatrial winds? to coast
lines? to mountain ranges? Where are the regions of light rain-
fall? Bow are these regions related to the terrestrial winds?

The heaviest rainfall in tlie world occurs on the
southern slopes of tlie Himalayas, north of tlie Bay of

72 ELEMENTARY PHYSICAL GEOGRAPHY

Bengjtl. Here the rainfall of a single year would meas-
ure t!iirty-flve or forty feet in depth, ajid much more
Uiun lialf of tltis amount falls during the summer half
year when the southerly monsoon is blowing. On the
bold southwest coast of India an annual fall of over
thirty feet occurs.

The greater parts of western Europe and of eastern
Nortli America are fortunate in receiving a plentiful but
not excessive rainfall.

In the polar regions the annual snowfall, melted, would
seldom exceed fifteen inches of water, and would^fre-
quently be less than ten. This is because cold air can-
not contain much vapor, and because when cold air is
cooled there is but little vapor condensed from it. In
the torrid zone the equatorial rains are heavier because
warm air can contain a lai^e quantity of vapor, and when
warm air is cooled it yields an abundant condensation
of moisture.

51. RainfaU of the United States. — The ramfall of the
United States may be considered under three lieadings:
the Piiciflc slope, the western interior region, the eastern
region. The Pacific slope has plentifiil rainfall in the
north (over sixty inches), where Uie storms of the west-
erlies are common ; but it has light rainfall in the south
(under thirty inches), because here tlie westerlies turn
southward to join the trades, and storms are infrequent.
The westerly winds are stronger and stormier in winter
than in snmmer ; hence the rainfall of Washington and
Oregon is heavier in the winter than in the summer

The western interior region, from the Cascade nnd Sierra
Nevada moiuitaius to tlie 100th meridian, has moderate or
plentiful rainfall on the mountains and high ptiit«au8, be-
cause the iiir is cooled and some of its moisture is con-
densed as the westerly winds rise over these elevations,
The lower lands, aa in the bEisins of Utati and Nevada
and over the Great plains that slope eastwai^d from the

74 ELEMENTARY PHYSICAL GEOGRAPHY

Rocky iiiountiiius, have light rainfall. The winds here,
already dried by losing much of their moisture in cross-
ing the ranges faither west, are seldom cooled enough to
form clouds and to yield rain. Hence much of this region
is arid, A lai^e part of Nevada, Utah, and Aiizona is too
dry to yield pastumge; elsewhere a thhi gi-nwth of grass
suffices to support cattle if they hare a lai'ge area over
whigh to range. Agricultui'i; is seldom successful in
tliis region without the aid of irrigation.

The eastern region ia not dintinetly separated from
the western; the rainfall gi'aduaUy increases eoatwaxd,
as moisture is supplied in greater quantities by south-
erly winds from the Gulf of Mexico and from the
Atlantic. Over most of this great region rainfall is
well distributed through the year (over forty or fifty
inches) ; somewhat more falls in summer than in winter
over the mid- Mississippi basin. The heaviest fall (over
sixty or eighty inches) is on the states bordering the Gulf
of Mexico (not including Texas), and ob the mountains
of North Carolina.

52, Weather Changes. — The temi weather includes all
the atmospheric conditions that an observer may feel or
see, — hot or cold, clear or eloiidy, dry or wet, windy or
calm.

In the torrid zone the weather is marked by regular-
changes from day to night ; the changes are small at eea
and greater on land, and they are seldom interrupted by
storms, except that afternoon thundei'storms are common
in the belt of equatorial rains. In the summer season of

THE ATMOSPHERE

temperate latitudes weather changes are usually of mod-
erate amount. In winter the weather of teiupemto liili-
tudes is largely controlled by tlie passage of cyclonic iuid
antieyclonic areas, which are tlien numerous and lai^e,
while the control hy the change from day to night in rela-
tively weak.

In frigid latitudes the change of weather from day t4»
night 18 always weak compared with the changes cauBe<l
by the passage of the great atmospheric whirls.

The relation of weather changes to the spiraling winds
of the prevailing westerlies msvy he simply illusti"ated hy
drawing (on an appropriate scale) the winds and clouds
nf a cyclonic and an antieyclonic area, as in Figure 16, on
tracing paper and moving the paper slowly to the right,
across a map of the United States. Let the center of the
cyclonic area he supposed to move, for example, in four
days from Colorado past Lake Micliigan and down the
St. Lawrence river. Note the changes of wuid aJid
weather at Indiaimpolis, or some other place, as the spi-
raUng wind areas advance eastward. Consider the tem-
perature of the regions whence the winds come in winter
and sununer. Figures 18 and 19, and infer the changes of
weather that they will bring. In the diagram for winter
weather the area of the spiraling winds should be larger
than in sununer ; tlie cloud sheet about the cyclonic center
should be larger and the winds stixinger.

A series of cyclonic areas sometimes pass hy at tlie rate
of two in seven days, thus causing a repetition of a certain
kind of weather on the stirae day of the week for several
weeks together.

76 ELEMENTARY PHYSICAL GEOGBAPHY

53. Summer Weatlier in the tfaited States A well-

miu'ked. spri<is »£ weather ciuvngcs over the uentral and
eastern United States in summer may open with fair
weather and bright blue sky ; the days are warm but not
oppressive ; the nights are cool and refreshing. Then, if
a eyclonie center appears a thousand miles or so to the
west, the wind chiuiges to a soutlieiiy source, so that it
comes from the warm waters of the Gulf of Mexico and
, the warmer land of the Soutliem States. The air l>ecome8
hazy and the sky pale blue ; the days are sultry and
oppressive, and the nights lose their refreshing coolness;
the ground is dried and parched, and vegetation suffers,
The great com crop of the Mississippi valley may profit
by these high temperatures if they do not last too long,
but manual labor is exhausting under the blazing sun, and
sunstrokes occur in increasing numbers.

Scattered thunderstonnB are then reported for a day or
two in the afternoon and evening. These are followed by a
more extended cloudiness as the cyclonic center approacliea,
and general rains may fall over several states near the low-
pressure center. Tbundei-storms of great size are some-
times formed in the moist southerly winds, occasionally-
giving rise to destructive tornadoes. As these local storms:
pass by, the cooler northwesterly winds in the rear of the
low-pressure center come from the far northern plains.
The clouds drift away eiiatward, the pressure slowly rises^
the temperature falls 20° or more, and damp sultry gitf
under heavy clouds is exchanged for fresh air with bright,
blue sky. Then, as tlie westerly winds weaken, a southerly
breeze springs up and all tJieae changes are repeated.

THE ATMOSPHERE 77

54. Winter Weather in the United States. — In winter the
succession of weather chajigea is controlled even nuirc (lis-
tinctly than iu summer by the passf^^e of cyclonic and anti-
cyclonic areas. A period of fine, cold, antieyelonic weather
usiially has a cloudless sky with light winds. The weak aun-
shine of a short midwinter day cannot overcome tlie stnmg
cooling by radiation during the long clear night, and the tem-
perature at dawn sinks to a low degree. But sis the anticy-
clone moves eastward Uie pressure begins to fall. Then U>Dg
filaments of lofty cirrus cloud float slowly over from the west,
announcing the approach of a cyclonic center, the wind turns
to a more southerly soui-ce, and the temperature slowly rises.

As the cyclonic center dmws near, the wind strengthens,
the sky is more heavily overcast, and the temperature rbes
more distinctly, for the source of the winds is now over
the tempered waters of the sea on the south and southeast.
The rise of temperature may continue steadily through the
night, so that midnight and dawn are warmer than tlie pre-
vious noon ; for the southerly wind may bo mure powerful
as a cause of warming tlian the cloudy night is as a cause
of cooling. The lowering clouds let fall their rain or snow ;
if rain, the snow of former storms is rapidly washed away;
if snow, the drifts of former storms are deepened and the
oountry is slmmded in white Jar and wide. It is under
the long-lasting snow cover that the "winter wheat" of
tile northern prairies, sown in November, is protected
hom the extreme cold of the winter winds, for the snow
IB an excellent non-conductor.

As the cyclonic center moves on, the northwesterly winds
follow it and the prcssm-e lises- The rain or snow ceases ;

78 ELEMENTARY PHYSICAL GEOGK.iPHY

the clouds break up and drift away to the east and reveal a
brilliantly clear sky. The cold northwesterly gale that has
come from the far northern plains, west of the cyclonic cen-
ter, now arrives as a "cold wave." These winds may be
from 30° to 50° colder than the sontheriy wintls. A fall
of temperature may thus be produced steadily through the
day, so that noon is colder tlian the previous midnight.

If the cold gale is accompanied by falling or drifting
snow, it is called a blizzard, a di'caded stonn on the plains
and prairies. Ab tlie temperature falls, furnaces must be
made hotter to keep houses warm, and destructive fires then
Ijecome more frequent tiian usual. Tlie cold winds may
sweep fax south, causing great damage to southern crops.
Then, as tlie storm center moves eastward, the winds farther
ui its rear wealien; the nights become calm and the tem-
perature falls to its lowest degree, and thus another spell
of fine and intensely cold weather is ushered in,

55. Summer and Winter Weather in Temperate Lati-
tudes. — Both in winter and summer all the changes here
described as connected with areas of high and of low
pressure are felt earlier in the west than in the east
The eastward passage of cyclonic or low-pressure areas,
illustrated in Figure 30, is controlled by the prevailing
eastward atmospheric currents in middle latitudes; and
tlie direction of the curi'ents is deteimined, as has been
stated, by the earth's rotation. In summer time the
difference of pressure between cyclonic and anticyclonio
eentera in North America is relatively small (from 0,5 to
0.8 inch); hence the spiraling winds are then relatively

THE ATMOSPHERE 79

light. Moreover, the southern and nortliern regions
whence the inflowing spiral wiuds are then dra*vn have
temperatures not gi'eatly different (about 85° and 65°);
hence the changes of temperature are moderate. The
eastward movement of the cyclonic areas is relatively

slow (500 nules a day in the United States), hent-e the
weatlier changes are gradual

All this IS changed lu winter Tlie differences of pres
sure are doubled (from 1 0 to 1 5 inches) and the winds
often gain the strength of gales; the regions whence the
southerly and northerly winds are drawn upon the Cen-
tral States have very unlike temperatures (80° and 0°),

80 ELEMENTARY PHYSICAL GEOOaATHY

and the contrast between tbe warmth in the front and
the cold in the rear of the cyclonic areas is very marked.
In tlie winter hemisphere the general winds are quick-
ened, especialiy in middle latitudes; and therefore the
centers of high and of low pressure drift eastward faster
(800 miles a day). Besides all this, the cyclonic and
antieyclonic centers are more numerous in winter than
in summer; hence weather changes in winter are frequent
as well as rapid and strong. Winter is therefore a time
of stormy changes as well as of low temperatures, thus
resembling the conditions of the frigid zone ; while sum-
mer weather ia comparatively even at a high temperature,
like that of the torrid zone.

56. Ocean Stonns. — Tlie stormy areas of the westerly-
winds drift from North America out upon the" northern
Atlantic ocean, as shown in Figure 30. Gales attend their
passage, especially in the winter season, when a voj
across this ocean is much rougher tlian in summer. The
gales caused by these storms are usually on the southern
side of the low-pressure center, and hence from a western
quarter. The general course of tlie storm centers is nortb*
eastward, so that a cyclonic center that passes over New
England or down the St. Lawrence Vidley is more likely
to affect the weather of Norway than that of Spain.
Storms from the North Pacific ocean come upon the "w
em coast of North America; they may before breaking up
pass far inland or even cross the whole breadth of the con-
tinent. The storms in the prevailing westerly winds oi
tlie southern hemisphere encounter but little land in theij

THE ATMOSl'HElti; 81

course. They are more severe iu the southern winter
{June to August) than in the summer (December to FeU
ruary). Soutli America reaches farther south than tiie
other contmeuts; hence vessels i^ouuding Cape Horn must
enter much farther into this stormy belt than iii rounding
the Cape of Good Hope, and the passage aioond Cape
Hoxn is dreaded for tliis reasou.

57. Cyclonic Winds. — The inflowing spiral wijids of
cyclonic storms are often given special names in different
parte of the world, according to tlie kind of weather they
may bring. The cold wave of our winters, sweeping over
the central and eastern United States from the far northern
plains in the rear of cyclonic centers, has already been
described. In western Europe the cold wind of winter is
tlie northeaster, because the pLiins of northeastern Europe
supply colder air tlian the ocean about Iceland. It occurs
when a cyclonic center follows a more southerly track than
nsuaL The blizzard of our plains corresponds to tlio
buran of Siberia. No special name has been given in the
United States to the sultry southerly wind that frequently
brings unseasonahly warm weather ui front of a cyclonic
center. It might he called a sirocco, after the Italian name
of a similar wind. In the snuthem hemisphere cold winds
come from the south, and hot winds from the north. In
southern Australia the wind that coiTesponds to the sirocco
18 called a brickfielder, because it bakes the fields hard
uid dry,

58. Weather Predictions.^ — Wcatiier maps from which
general character of the weather for one or two days

, 82 ELEMENTARY PHYSICAL GEOGRAPHY

may be predicted are now prepared daily in many countries.
Obaervations of tiie weather made at the same hour at
many different places are telegraphed to the central station,
- — the Weather Bureau at Washington for tlie United
States. They lU'e then promptly charted bo that the areas
uf liigh and low pressure, tlie tempeniture, tlie direction
and strength of the windH, the distribution of clear and
cloudy sky and of rain or snow are all shown. It is known,
as described on preceding pages, that cyclonic and anti-
eyclonic areas with their attending weather conditions usu-
ally move eastward; it is therefore possible to foretell with
considerable accuracy the weather tliat may be expected
for a day or two in various parts of the country from the
conditions shown on the weather map.

Predictions thus prepared are distributed by telegraph,
and published in special bulletins and in newspapers for
the benefit of the public.

No one has yet succeeded in making successful predic-
tions of the weather regularly for definite districts several
weeks or months in advance. It is true that such " long-
mnge predictions," as they are called, are frequently pub-
lished. As the weather differs in different partfl of the
country, predictions of hot weather over the central United
States in July and of cold weather in January, or rain in
March and drought in September, may be correct for one
place or another, but they must he incorrect for other
places. Such predictions cannot be depended upon.

59. Climate. — The general succession of weather
changes through the year, averaged for many years,

THE ATMOSPHERE 88

constitntea the climate of a region. The five climatic
zones into which the earth is commonly divided need
further Bubdivision in order to correspond to tlie many
well-niai'ked typea of climate on lands and seas, on coasts
and inland regions, on lowlands and higlilands,

The trade-wind belt at sea has the simplest climate in
the world, with small daily and yearly changes of tempera-
ture. The steady wind and fair weather of almost any
day give a fair sample of the year. Low lands uiidei'
the regular trade winds suffer greater daily and yeai'ly
changes of temperature, with light lainfall.

Compare the mean amiual range of temperature in the West
tndiee and in inner Africa, latitude 20" N., Figure 20 ; in Africa,
Indian ocean, and Australia, latitude 20° S.

The subequatorial l>elt has a distinct seasonal change
as the clouds of the heat equator move away and give
place to the dry trade winds. The Sudan, between the
desert of Sahara and the forest belt of equatorial Africa,
has plentiful rainfall and active plant growth when tlie
equatorial cloiid belt moves north, bringing the wet sea-
son (May to August), but it becomes parched, ban.'cn, and
dusty under the trade winds of the dry season (December
to March).

Examine Figure 21 and atate in what months you would eipect
rain on or near the geographical equator. At the head of the Gulf
of Guinea, west equutoriu! Africa, rain ia most abundant in March
and October to November. In Ceylon the rainfall is greater in May
and OctJ^ber than in the other months; at the city of Quito, Ecua-
dor, in April aod November. Huw do yuu explain ttieae double
nioy seaBons?

84 ELEMENTARY PHYSICAL GEOGRAPHY

The Boutli temperate zone is mostly an oceanic belt.
The changes of air temperature with the seasons are small,
as shown in Figure 20, because the water surface warms
and cools so little in summer and winter. Its winds are
more stormy in winter, less stormy in summer ; never
verj' hot or extremely cold, but for the most pait chill,
damp, and blustering. Islands near 50° S. are haixily
habitable, not that the winters are too severe, althougb.
cloudy and wet, but that the summers are too chilling.

The north temperate zone contains large areas of both
land and water, and the temperatures of its various parts
are therefore very unlike, as shown in Figures 18, 19, and
20. The parallel of 50° N. crosses regions whose climates
are so different that they would hai'dly have been placed
under a single zone had they been studied before being
named ; but the name was given from the truly temper-
ate climate of southern Europe, before other parts of the
world were well known.

Beginning in tlie moderate climate of the North Atlantic,
Figure 20, the parallel of 50° N, enters the favorable
climate of middle Europe, where the last thousand years
have witnessed the greatest human progress in the arta
and sciences that the world has ever known. It cro
the broad deserts of central Asia, where the scattered
population is held down in barbarism chiefly by severe
and unfavorable climatic conditions.

The broad North Pacific has in this latitude a climate
as moderate as tliat of the North Atlantic. Passing the
tempered and moist climate of the coast belt of British
Columbia, and crossing the snowy mountain ranges beyond,

THE ATMOSPHEHE

the severe interior climate of middle Canada is reached,
with extremes of temperature, summer and winter, only
less than those of inner Asia. As far as habitability is
concerned, the middle north temperate zone contains
climatic differences almost as great as those found in
passing from the equator to the pole.

Compare this account of the climate of latitude 51)° N. with the
conditioiiB iu latitude 50° S.

Supplement i

. CuAn

: n

60. Deflection of Winds by the Earth's Rotation.^ Tlace a marhla
in the center of a circular board. Set the luarlile in motion by
atriting it a light blow. It will move ^

in a straight line along b radius f roni
center to circumference. Now let the
board be given a alow movement of
rotation around a pivot at its "center.
The marble wiU now ^aiti move
diiectlj' outward, but the line that it
traces on the turning board will be
curved so as to fall behind the radius
OD which it started. If the board
tuma to the left, the marble will be \
deflected to the right of its original
path; if the board turns rapidly, the
dedectioii will be strong.

In Figure 81 the circle. A, rest
on the earth in a northern latitude pm, 31, Roiaiionof b Disk on a
may be taken to represent a circular Botutiug Globe

board or surface of great size. A

north line drawn from the center oi Iha circle meets the prolonged
aiis of the earth at N. When the rotiitiun of the earth baa cur-
ried the circle to B the same north line haa a new direction, BN,

86 ELEMENTARY PHYSICAL GEOGRAPHY

showing that the circle has turned somewhat to the left with respect
to its own center. Hence any such circle may be taken to represent
a turning surface. A body beginning to move in any direction from
the point A will tend to turn to the right, because of the rotation of
the circle to the left. This tendency will be strongest at the pole,
because a circle there rotates with the greatest rapidity, turning
completely round in twenty-four hours. The tendency is zero at the
equator, because there a circle has no movement of rotation with
respect to its own center. In the southern hemisphere, where the
circle must turn to the right, the deflective force acts to the left.

The wind is so free to move over the earth's surface that it is
greatly affected by the deflective force arising from the earth's rota-
tion. Hence the members of the atmospheric circulation do not flow
north and south, but are always deflected to the right of these direc-
tions in the northern hemisphere, and to the left in the southern.

The lofty ovei-flow currents are deflected so as to run from the
southwest or even from the west-southwest in the northern hemi-
sphere, from the northwest or west-northwest in the southern. The
winds approaching the equator do not blow directly from the north
and the south in the two hemispheres, but are deflected so as to blow
from the northeast and southeast, forming the trade, winds. The
whirling winds of cyclonic storms, described on pages 45 and 67,
attempt to blow toward their centers of low pressure, but on account
of the earth's rotation the winds are deflected to the right in the
northern hemisphere, and to the left in the southern ; thus the storms
are given their whirling movement.

It should be noted that winds will be deflected to the right or left,
in whatever direction they begin to blow, east and west winds being
affected just as much as north and south winds. Ocean currents are
similarly affected but to a less degree, because they move more
slowly than the winds. Rivers tend to turn to the right in the
northern hemisphere and to the left in the southern; but the
tendency is practically overcome by the resistance of the banks.
Similarly a railroad train tends to be deflected, but is held to its
track by the flanges on the wheels.

THE ATMOSPHERE 87

61. Practical Hetliod of itodTing Obseiratioiis of the Sun. — Tn
Btudjiug the control of the Beasous by the Bim it ia desiralile lo
determine the length of the day and the midiiay altitude of tlip Kim
by observations aboat once a fortnight, or at least once a montli,
through the Bchool year, with a^lditionai obseryatioDg near the times
of ahorteat and longest days or of lowest and highest midday sun.

If Bunriae conies at too early an hour for convenient oliservation,
note that midday occurs at tlip middle of the iaterval between sun-
riae and sunset. Midday is determined by the method explained on
page 8. The time of sunset may be directly observed. The time
of sunrise may then be deterniiueJ Ijy counting back aa many hours
and minutes before midday as sunset occurs after midday.

The midday altitude of the sun may be determined as follows ;
Use such a bos as is shown in Figure 9, and drive a piti square into
one side of the box, close to its upper corner. With the piu aa a cen-
ter, draw an arc of a circle on the box side. Draw a horizontal and
a vertical line from the pin to the arc. The arc included between the
two lines will be a right angle, or 90°. Divide it into halves, divide
the halves into thirds, and the thirds again into thirds. The small
divisions thus fouml will bo 5° of arc. Number the divisions from
0 at the horizontal line to 90° at the vertical.

As the sun approaches the meridian, turn the side of the box so
that it is directed toward the aun. The shadow of the pin is then
seen as a slanting line, and the altitude of the sun is indicated by
the angle that the shadow line makes with the horizontal line. Con-
tinue to turn the box after the sun, until the attitude indicated by
the shadow line begins to decrease. The greatest angle thus foimd
is the midday altitude of the sun.

In Figure 39 let the horisiontal scale represent the days of the
year, and the vertical scale the angular altitude of the sun at mid-
day. Mark the sun's midday altitude by dots opposite the appro-
priate dates. At the close of the school year draw a curve through
the dote. Draw lines parallel to the base line and touching the
upper and lower yminlj* of the cui-ves. Draw a third line midway
between the last two.

88 ELEMENTARY PIIYSICAI, GEOGRAPHY

In Figiire 33 the vertical scale repreaenta the days of the year;
the horizontal scale nieaeurea hours before and after midday. Mark
dots to the right and left of the midday line and opposite to the
appropriate dates, to represent the time before and after midday at
■which Bunrise and sunset occur. Connect these dots by curved lines.
Draw two lines that shall stand six hours on either side of the mid-
day line.

Now determine from Fignre 32 the dates when the sun liae the
gTBfttcst midday altitude (or when it stands farthest north in the skj)
when it has the least midday altitode (farthest south in the sky),

70-

Fia. 32. Diagram of the Sun's Wddaj Altitude

and the two dates when its altitude is that of the mid^Lorizontal
line. Determine from Figure 33 the date when the day is longest,
when it is shortest, and the two' dates when it is twelve hours long.
Compare the dates thus found. If the observations are well made
and the diagrams accurately constructed, the four dates should ^^ree
on the two diagrams.

The dates when the days are twelve hours long, and therefore
equal to the nights, are March SI and September 2S ; these dates
are called the vernal (spring) and autumnal (fall) equinox (equal-
night). The date when the sua is farthest north, and when the day
in the northern hemisphere is consequently longest, is June 21,
This is called the summer solstice (sun-stand), because the sun, hav-
ing then finished its northward movement, stops or "stands" before
beginning its southward nioveiiient. The day when the aun is

THE ATMOSPHERE 89

farthest sonth, and nhen the day is consequently ahortest in the
northern hemisphere, ia called the winter solstice; this date U
December 21.

Between wliat dates is the sua moving northward in the sky?
Between what dates ia it moving southward? Between what dates
are the days lengthening?

At the time of the equi- ^~
noxes the sun must be on
the equator of the sky ; for,
as ia shown in Figure 17,
it ia only tlien that equal
days and nights occur in all
parte of the world. Hence
the middle horizontal line
in Figure 32 must repre-
sent the angular altitude
of the sky equator where
crosses the meridian. Tl
angular distance of the si
north or south of the sky
equator for any day of the
year maji be measured hy
the scale at the side of
the figure. The greatest
angular distance of the sun
from the sky equator gives
means of determining the p,^ 33_ Diagram of SunriBcaud

limits of the zones. (Sec Sutitiiit Hours

page 48.)

How far north of the sky equator does the sun stand at the time of
the summer solstice ? Ilow far south at the time of the winter solstice ?
How many days is it north of the sky equator? How many days south?

62. Determination of Latitude. — The sky equator passes overhead
(in the nenith) to an observer at the earth's equator ; hence the sky
eqaator will depart one degree from the zenith for every Aeffma that

90 ELEMENTARY PHYSICAL GKOGRAPIIT

the observer movea toward t]ie pole. Therefore t.Iie latitude of a
place mUEt equal the angular distance of the sky equator from the
zenith. Latitude may thus be determined on any day by mBasnring
the Bun's midday altitude and allowing for its distance from the aky
equator, as determined by Figure 32. The altitude of the aky equa-
tor subtracted from 00° ia tVie latitude. Results that are correct
within a few degrees may be obtained even hy the rough obser
vations here described.

If records of the kind indicated above are taken on different dates
in succesaiTe years, the increasing number of dota will give better and
better definition of the currea in Figures 32 and 33; but minute
accuracy of performance is not so important aa iittelligeiit e:
the application of principles.

Examples. If the midday altitude of the sun is 50° on the 22d of
September, what is the latitude of the place of observation? What
would the latitude be if the observation had been made on Decem-
ber 21 ? on March 21 ? on June 21 ?

63. Exercises on Weather Haps Many instructive exorctse.i

may be based on the daily weatiier maps. Copies of these maps for
school use may be obtained, under certain conditions, by addressing
the Chief of the Weather Bureau, Washington, D.C. Th^ exercises
here described may be performed on the original maps, or on outline
maps of the United States upon "which certain weather elements ore
copied. It is usually best to select maps on which differences of
pressure are well defined, in order to exhibit strongly marked types
of weather.

64. Distribution of Presaiue. — Flat upon a blank map of the
United States the barometer readings taken from a weather map,
and thus guided draw in lines of equal pressure, or isobars, for every
f«nth of an inch according to the method already explained for iso-
therms. The difference of pressure between the highest and lowest
readings is often six or eight tenths of an inch or more. Shade the
areas of high and low pr«SBiire, leaving the area of intermediate pres-
sure (for example, from 29.9 to 30.1 inches) blank. Describe the

U-k.

THE ATMOSPIIRRE 91

distribution of pressure tlius showu. Drnw a iiimilar map fur tliu
nest day. Deaeribe the I'lianye in. the djalribution of pressure IhuK
found. Temperature tnny be similarly treated.

65. MoTement of Winds in Aresi of Higb and Low Preasnre. —
Select several well-defiued examples of high- ami iow-presaure areas
whose centers lie in the mid-OIiio valley, bo that observations are
provided on all sides of tlieni. Plat the wind arrows (the arrow
Sies with the wind on weather maps), and let their length indicate
wind velocity (an eighth of au inch for five or ten miles) . Uraw addi-
tional lines to represent inferred wind movement between tlie points
of obaervatiou. How is the direction of the wind at any place
related to the distribution of pressure about that place? In answer-
ing this question it will be well to draw, through the point consid-
ered, a line at right angles to the neighboring isobars. This line
shows the direction of increase or decrease of pressure. Describe
the general movement of the winds (direction and velocity) with
respect to a center of high pressure ; of iow pressure.

66. Composite Portcftit of HiEh' and Low-Piessure Areas. — Ride
a Btraight line throngh the centur of a sheet of tracing paper and mark
the ends of the line N and S. Lay the center of the sheet over the
center of an area of low presBiire and turn the N-S line so that it
ahftU lie most nearly parallel to the adjacent meridians. Trace off
the mgna indicating the state of the sky (clear, fair, rain, or snow) at
various stations. Do the same for several other maps that have a
low-pressure center. Do the same on another tracing paper tor sev-
eral areas of high pressure. Compare the results as to the distribu-
tion and frequency of clear, fair, and wet weather, with respect to
centers of high and of low pressure. Winds may be similarly

67. FiD£iession of High- and Low-PresBuce Areas. — Select a series
of four or five maps on which a well-defined area of hipli or
of low pressure is represented as occupying successive jmsitiona
eastward across the country from the Rocky mountains to the
Atlantic. Chart on an outline map the path of the center of the

^^^

ELEMENTARY PHTSICAL GEOGRAPHY

aren stuilicd and determine its -velocity in miles an hour and a day.
Note the weather changes (prasBure, temperature, ■wind, sky) that
opcur at a single station as the cyclonic or anticyclonic
over it. What is the general character of these changes for a cyclonic
area? for an anticyclonic area?

Compare the sticcesaiou of weather chaoges at any place, as deter-
mined from veather maps, with the weather changes observed at
Hchool dining sevenil daya. Uow are the local weather changes
related to passing areas of high or of low pressure (anticyclonic and
cyclonic areas) ?

QDSSTIONS

Sec. 19. What proceBses depend on the atmosphere? "What is
known ol its height?

30. Wliat 13 the composition of air? How is osygen used?
carbonic dioxide?

21. What is the pressure of the atmosphere on a square foot of
surface ? Describe the mercurial barometer ; the aneroid barometer.
How can barometers be used 1« measure mountain heights?

23. How does the density of the air vary? Why? What is the
weight of a cubic foot of air at sea level? How is sound carried?

23. How are the culors of the sty produced? What is the ini-
light arch? When may it be seen?

24. How is the temperature of the air controlled? Why is tha
upper air cold? Consider the diurnal range of temperature in the
upper and lower air. How do the processes of absorption, conduc-
tion, and radiation affect the temperature of the air ? How does the
form of the earth affect the distribution of temperature ? How is
the weight of air affected by heat?

25. What is a mirage? How is it produced on level deserts?
on a water surface ?

26. Explain the construction of a, thermometer. How do the
Fahrenheit and Centigrade thermometer scales differ? What is a

THE ATMOSPHERE 93

thennagrsipb ? a maximum thermometer? a minmium thermou-
eter? How ehould a thermometer be exposed?

;7. How are temperature charts conatrueted? Wliat is an iso-
thermal line? How are mean lemperaturea determined? What
is the heat equator ? Describe its position. Compare the niean
annaal isotherms of the nortliern and soutiiern hemispheres.

28. Describe the moyements of the air between a hot and a cold
□oni. What ia a convectional circulation? Describe the general
circolation of the atmosphere between equator and poles. What
chtuigea of temperature are caused in ascending and deacendin);
cnrrenta? What is the planetary circulation?

39. How are winds named? How is their strength described?
What is an anemometer?

30. Describe the steps in the circulation of water through the
atmosphere. How is rain caused?

31. What are the chief members of the plunetiiry winds?
Describe the trade winds. Where do they occur? What is their

ctioD? What is the relation of rainfall and deserts to the
trade winds? of wet and dry mountain slopes to the trade winds?
Give esamples. Describe the prevailing westerlies. Where do they
IT? What is their direction? How is rainfall related to these
winds? What are the doldrums? the horse latitudes? Describe
and explain the weather of the doldrums ; of the horse latitudes.
12. Describe the whirls of the westerly winds. Explain their
weather. How fast do they travel 1 Compare the wiiirls o£ the
two hemispheres. Compare the atmospheric pressure at the center
of the inward and outward whirls. What names are given to these
wUrlfl?

33. Describe the movement of the eart:h around the sun. Com-
pare the attitudes of the northern and southern hemispheres with
respect to the sun in the two lialf years, Wliat are the resulting
variations of temperature? What are the months of each of the four
seasons iu the northern hemisphere ? in the southern ? What are the
Umita of the torrid none? the frigid zones? the temperate zones?

} 94 ELEMENTARY PHYSICAL GEOGRAPHY

34. What are the apparent movements of the Gun in DecemlxT
t in June? How are the teiupe-ratures of winter Had summer relato

to tiiese tnoTementB? Explain the rising temperatui'e of spring;
the falling temperature of autumn.

35, 36. How may the change of seasons be described if the earEh
as a whole is considered ? Mention the most striking facts shown on
the isntheTmal charts for January and for July.

37. Describe the most striking facts shown on the chart of main
annual temperature range. Compare the annual range of temperature
over the northern (^ntinenta and the southern oceaus ; on western ani
eastern coasts in temperate latitudes. Why are the annual chaiiges
large in the northern itemiaphere? Why small in the soutliem?

38. How do the terrestrial winds differ from the planetaiy!
Explain the differences. Descrihe and eiiplain the suhtropiul
belts. Name some countries lying in a subtropical belt and desci'ito
them as to winds and rainfall. Describe and explain the subeqii»
torial belt. Describe its migration, Figures 32, 23, on the Atlantic
ocean ; on the eastern Pai^ific ; on the Indian ocean. Give son
examples of suhequatorial rainfall in South America ; in Africa.

39. What are luonaoons? How are they caused? WJiere do they
occur, Figures '22, 23 ? Describe the monsoons of the Indian ocean.

40. 41, 42. How do the continents affect the terrestrial winds?
Give examples from Asia. What are land and sea breezes? Hof
do fair-weather winds on lands vary frora night to day? Explsia
this variation. Why does it not occur at sea?

43. What is humidity? How does it vary with temperature?
What is saturation? Compare the feeling of damp and dry air.

44, What is the dew-point? How may it be determined? Whst
are dew and frost '' I t d r what conditions are tliey produced?

45. Describe tl e chief kinds of clouds cumulus, cirrus, ciiTO-
stratus, alto-nimbus ai d nimbus Describe a halo ; a corona.

46, 47, 48 Describe a thunderstorm V, here and when do suflh
storms occui ? '\\ hat cin vou Ba> ibout hghtuing and thundeC'
What is a cloud burst? a rainbow? a tornado? a waterspoat?

THE ATMOSniERE

Where and how are tropical cyclones formed 'I How do theii
,Trindfi blow 7 How do these atomxs travel 1 In what regions do they
occur? In what months? Why are there two geuaoiiB of cycloues
^in tbe northern Indian ocean V Wbj are tropical cyclones not
formed in the South Atlantic?

j 50. What iaraeant by rainfall? Describe and explain snow; rain ;
' hail; frozen rain. How is rainfall meaaured? State the relation of
^ rainfall to agriculture. Give several examples of the relation between
tbe terrestrial winds, Figures 22, 23, and rainfall. Figure 28. Where
is the heaviest rainfall of the world? What is its amount? its cause?
Why is the i-ainf all of low latitudes liirge, and of high latitudes snaU ?
61. Describe the rainfall of the Pacific slope of the United States ;
of the interior region ; of the eastern region.

S2. What is meant by weather? Describe the prevailing weather of
the torrid Koue ; of the temperate zones in suuimer ; in winter ; of
frigid latitudes. Explain the effects of cyclonic and anticyclonic areas.
B3. Describe a period of summer -weather in the eastern United
States as a cyclonic area is approaching ; after it has passed. When
m sunstrokes and thunderstorms moat coiniuon ?

64. Describe our winter weather in front of a cyclonic area ; in
the rear. When may a warming night occur? a cooling day?
Wat is a cold wave? a blizzard?

, Describe the tracks of high- and low-pressure areas in the
north temperate zone. What changes of pressure do they cause
Q anmnier? iu winter? How fast do they travel in summer? in
"idler? Compare the changes of temperature that they produce
in Qie central part of United States in summer and in winter.

58, 57, 58, Describe the storms of the Noilh Atlantic. What is
ibutan? a sirocco? a hrickfielder? How is th w atl i dieted?
69. What ia climate? Describe the clii t f tl t de^wind
belt at sea ; of the subequatorial belt ; of the th te pe t zone ;
nf the north temperate zone on the oceans ; th 1 I Describe
the climates of latitude 50° If. ; of latitude 50 S

CHAPTER in

TH£ OCEAN

68. Form of the Ocean The ocean is a sheet of salt

water, clear and blue, covering about three quarters of the
earth's surface to an average depth of about two miles.
It lies in brontl depressions or basins between the conti-
nents, its shallow edges lapping over the margin of tha
continental masses.

The outline and distribution of the ocean are best
studied on a globe. A vast frater area, comprising the
Pacific and Antarctic oceans, covers nearly half the earth.
The water surface is broken only by Australia, the Antarc-
tic lands, and many small islands. A short Indian arm
extends from this great oceanic area into the space between
Africa and Australia, and a long, relatively narrow Atlan-
tic arm runs between the Old and New Worlds, ending in
the gulf-like Arctic ocean around the north pole.

The surface of a hemiaphere whose pole is near New
Zealand is nearly all water, as in Figure 34 ; while tlie
opposite hemisphere contains all the large land areas,
except Australia, the Antarctic lands, and the extremity
of Soutii America. It is not a little curious to note that
near the pole of the land hemisphere stands the greatest
city of the world, the capital of the empire whose colonies
are more widely spread than those of any other nation.

THE OCEAN

What lands lie entirely in tiie land hemisphere V What oceans
lie lariijelj in the land hemisphere? Trace tlie course uf the great
eirt'le which divides the land and water hemispheres.

69. The Ocean as a Highway. — The lands are widely
separdted by the oceiuis, imd navigation of tliij "high seas"
rt-quii-es great skill and is fraught with many dangers.
But the oceaus are a ready-made highway, where movement

^-■t^^^MfSPj

^^ HEM/Sp

FiQ. 34. Water snd Laud Iletaisiihe

is easy and open to all comeis ; the winds funiish free motive
power to sailing vessels, and coal is an economical fuel for
steamers. Hence ocean-gtiing vessels are used to carry
lai^ quantities of merchandise from one part of the world
to another.

Before railroads were invented the two sidea of the North
Atlantic were in more active communication by sea than the
two sides of any continent overland. Since railroads have
been extensively built inland tmnsportation hiis greatly in-
creased ; but a great part of international commerce is still
carried on across the oceans in steamships and sailing vessels-

ELEMENTAUY PHYSICAL (iEOGRAI'HY

70. Eiiploratioii of the Ocean. — The earlier exploration

of the ocean discovered ita shore lines on the continents and
isUvnds. Exjiloration in the latter part of the nineteenth
century penetrated its depths and reached its bottom.

Soundings are now made with much accuracy, even to
depths of four miles or more. Fine steel wire is uaed for

a line ; the sinker is a heavy iron ball that is automatically
detached on touching tlie bottom; then the wire is rapidly
reeled in by steam power. A sounding of 3000 fathoms
(one fathom equals six feat), or over three miles, can be
completed in about an hour.

The tflmperature of the deep water is taken by self-
registeiing theiinometers. They must be protected by an
outer glass tube against the tremendous pressure of the

THE OCEAN

Amep water. Samples of water are obtained from varioiut
d^tbs by the use of brass tubes, called water Iwttles, sent
down open but automatically closed when
reeling in Iwgiiis. Speciraeiia of tlie ixeari
bottom are gathered by dredges, or stiong
nets with an iron rim. Wire rope ia needed
to haul up the ton or more of material
tliat they take in while dragging on the
sea floor at depths of one, two, or even
three miles. Nets are sometimes attached
to the wire rope at different depths, for
the purpi>se of catching animals that hap-
pen to enter them. The host nets are
closed while sinking
and rising, being open
only while trolling at
Sounding in8truBu.nt the greatest depth
and Wnter Bottle that they reach.

71. Ocean Depths. — Soundings have
shown that the ocean basins are com-
paratively ateep sided and flat floored.
The greatest depth yet found is 31,614
feet, in the western Pacific near the
island of Guam {lat. 12° 45' N., long.
145° 45' E.). Another place of great
depth, S0,930 feet, is Jn the Pacific,
near the Fiji islands.

The deepest sounding yet made in the Atlantic
feet, or over five miles, in a local depression 100 mill

.00 ELEMENTARY I'Hi'SlOAI. OEOGRAPHY

of Porto Rieo, West Indies. The Atlantic is generally less
deep along its middle (9000 to 12,000 feet) than on either
side (15,000 to 18,000 feet), the shallower middle part
Ijeing sometimes called a ridge or ewell, (See Figure 144.)

72. Composition and Density. — The ocean contains a
great variety of substances in solution, for it haa received

everything that streams have dissolved and canied from
the lands for ages past. Common salt makes three quarters
of the dissolved substances. An important but much less
plentiful dissolved substance is limestone, of which many
sea animals make their sheila or skeletons,

A small quantity of atmospheric gases is found dis-
solved in sea water, even in its deepest parts. The gases
are taken in at the surface, especially when air is caught
in dashing waves. It is upon the oxygen thus supplied
that fish and most other marine animals depend for breath-
ing; but whales and other mammals living in the oeean
come to the surface for air.

The mineral substances dissolved in ocean water make
about three per cent of its weight; their presence makes it
a little heavier than pure water (in proportion of 1.026 to
1.000). Although water is easily moved, it can be very
little compressed. Hence, in spite of the great pressure of
the upper layers of the ocean on those beneath, the oeean
is unlike the atmosphere in being of nearly uniform density
from top to hottoni. Anything that is heavy enough to
sink at the top will sink all the way to the bottom.

73. Color and Phosphorescence. — In the open ocean, far
from land, the water is esti-aordinarily clear. It is of a

THE OCEAN 101

beantifnl deep blue, so strong that one would expect the
color to show in a bucket; but if some water is clipped up
from the sea surface, it appears perfectly ti-ansparent and
colorless. In cloudy weather the ocean is of a duller,
more leaden hue. Near the lands the blue is lighter and
turns toward a greenish shade. Opposite Urge rivers the
water may be yellowish from suspended sediment; the
Yellow sea is so named on this account What large
rivers euter it?

There are many small jellylike animals that float in the
ocean. Some of these have the power of emitting, when
disturbed, a pale light, visible in the dark. They are
found chiefly in the wai'mer parts of the ocean. Break-
ing waves and the foam in the wake of a vessel may thus
become beautifully luminous or phosphorescent at night.

74. Ocean Temperatures The surface layers of the

ocean vaiy in temperature witli latitude, reaching about
80° around the equator, and being reduced to 30° or 28°
in the polar regions (Figure 44). The great body of the
deep ocean is cold in all latitudes; its temperature is about
30° in high latitudes and 35° or 40° in the torrid zone.

When exploring vessels dredge in a torrid ocean the
sediments brought up from the bottom have a terapei-a-
ture near freezing, strangely in contrast with that of the
objects on shipboard under a hot sun.

The sun's rays have small effect on ocean water at
depths below 100 or 150 fathoms. At greater depths the
ocean must he nearly dark, with hardly perceptible dif-
ference between day and night, or between wint«r and

102 ELKMEXTAlty niYSlCAI, fiEOfillAI'HY

summer. The temperature at any point in the great IxxJy
of the deep ocean is therefore nearly constant.

ChmigL'B of tempemlure in the ocean surface through
tlio day or the year are very small, seldom more than 3°
and 15°, respi-ctively. As the tempeiatnre of the lower
air is largely controUed by that of the surface on which
it rests, the climate of ialauds in mid ocean and of conti-
nental borders where the prevailing winds blow ashore is
free from great changes of temperature between winter
and summer.

Salt water becomes heavier and heavier as it is cooled
down to its freezing point, 28°. Hence the cold surface
water of high latitudes eints to great depths and creeps
very slowly toward the eq^uator; thus the low tempera-
ture of the great body of the ocean is accounted for.

Fresh water is unlike salt water in being densest at 39",
On being warmed or cooled from this temperature it expands
and becomes lighter. Hence in winter, when all the water
of a lake has been cooled to 89°, further cooling affects only
the surface water, which may then soon freeze.

75, Ice in the Ocean. — Ice expands a little as it freezes;
it thei-efore floats, about one seventh of its volume being
ont of water. The ice formed in the polar oceans is
known as floe ice ; it may reach a thickness of from three
to seven feet in a single winter. .

Great fields of floe ice drift with the winds and currents.
They may thus be torn apart or crushed together. When
two floes collide pack ice of very irregular surface is
formed; it may reach a tliickness of over 100 feet.

THE OCEAN

103

In Greely's expeditiim to the Arctic regions in 1S83
his boats were frequently in danger of being cnished
when ice fields drifted together, closing the water passage
he had been following.

Smooth floe ice is easily crossed on sleda. The Kskimos
make winter journeys upon it. Where packed it may be

Fia. 38. A Vessel beset hj Pack Ice

impassable. It was on account of the roughness ot ridged
pack ice that Nansen had to turn back from his " dash for
the pole," in latitude 86° 13' N., longitude 96° E., on
April 8, 1895. When two large fields of pack ice diift
together a vessel between them would be crusheil, unless
of great strength and shaped so as to escape by rising.
Nanaen'a vessel, the " Frara," was especially constructed
to withstand great pressure and so survived the dangers
to which it was exposed.

(104 i:i,KMENTARY PHYSICAL GEOGKAI'HY

leebergB in the North AUantic are fragments from the
ends of great fields of ice (glaciers) that descend into the
sea £i-om Arctic lauds, chiefly Greenland ; they are of
fresh water. The tabular icebei;g8 of the Antaictic ocean
are fragments of a heavy sheet of ice around the south
pole. Some of these ice blocks measure a mile or more

on a side, and 1200 to 1500 feet in thickness. Icebergs,
being of fresh water, float with about one sixth or one
seventh of their volume above the sea surface.

Collision with an iceberg is one of the di'eaded dangers
of navigation in high latitudes. In the southern oceans
drifting icebergs reach latitude 50°, or even 40°. In the
North Atlantic they reach latitude 45°, southeast of New-
foundland, but they are absent from the northvrestem
coast of Europe, even in latitude 70°, on account of the

THE OCEAN

105

warm water there prevailing. They are wanting in the
Sorth Pacific, except in the seas of northeastern Asia.

76. The Ocean Bottom The greater part of the deep

ocean bottom is a comparatively even plain of soft ooze.
The plain rises and falls gently in broad swells, but iw not

FlO. 40. Gtnhigei

varied by hills and valleys such as occur on the lands.
A large part of the deep sea bottom is covered with a fine
deposit, called ooze, which consists of the minnte shells,
more or less decayed, of simple animal forms that live at
or near the surface. One of these, liighly magnified, is
^ovn in Figure 40. In the deepest oceans the bottom
is Qovered with a fine reddish clay. Nearer the shores

106 ELEMENTARY PHYSICAL GEOGRAPHY

the deposits become muddy with sediments derived from
the land. It is by the veiy slow but long-continued accu-
mulation of these deposits that the ocean floor haa been
made so smooth.

" The monotony, dreariness, and desolation of the deeper
partji of this submarine scenery can scarcely be realized.
The most barren terrestrial districts must seem diversified
when compared with the vast expanse of ooze which covers
the deeper parts of the ocean."

No mountain ranges with sharp peaks and ridges
separated by deep passes and valleys have yet been dis-
covered on the open ocean floor far from the conti-
nents ; but Cuba and some of the neighboring islmkds
in the West Indies seem to he the crests of a mountain
range whose we8t«m extension forms submarine ridgea
in the northern Caribbean, connecting the islands with
Central America.

Volcanic and coral islands rise with steep slopes from
the deep ocean. Volcanic cones sometimes rLse above the
ocean surface, forming lofty mountains, as in the Hawaiian
islands ; sometimes they are known only by soundings,
their summits being below sea level.

77. Uediterraneans. — Besides the open oceans thus far
considered there are several deep seas, more or less separated
from the oceans by land Ihirriera. The most important of
these is the classic Mediterranean (the sea " in the middle
of the lands ") ; its average depth is nearly as great as that
of the great oceans, but it is connected with the Atlantio
only by the narrow and shallow Strait of Gibraltar.

THE OCEAN 107

Other Bimilar meditemuuMn Beiia are th<! Caribbean niid
the Mexican (deep central ptirt o£ the (iiilf of Mexico),
adjoining tbe western Atlantic; and tliu Juptui, fliinii.
Sulu, and some smaller seaa imperfectly inclosiKJ fitim
the western Pacific by island eliaijis. The deep wat^r
of mediterraneans is wanner tluui tliat of the iii-ighlior-
mg oceans, whose cold bottiim waters cannot enter tlie
inclosed basins.

78. Continental Shelves. — The ocean often overlaps
the bordere of the continental masses in a comparatively
shallow belt of water, at whose outer edge tlie depth is
commonly about 600 feet; thence it rapidly sinks to the
deep ocean floor. These shallow bottoms are known as
contjneutal slielves. The water on the shelf is • of t«n
greenish from fine suspended sediment, imlike the clear
deep bine water of the open occiin.

A well^iefined continental shelf, from 50 to 100 or
mare miles in widtli, stretches along the eastern side of
North America from Newfoundland to Florida, and thence
around the Gulf of Mexico. The Biitish Isles stand upon
a continental slielf that borders mid-west«m Europe. The
Malayan and Australasian islands surmount broad shelves
between Asia and Aaetralia, separated by a belt of deeper
Wtter.

The gravel, sand, and clay washed from the lands into
the seas are moved about by waves, currents, and tides
on tbe continental slielves. Thus the land waste is slowly
ground finer and finer, and its finest particles are gradu-
ally moved outward to deeper water. They are seldom

108 ELKMENTARY PHYSICAL GEOGRAPHY

found ill dredgings over 200 miles from shore; for the
most piirt they are carried a lesa distance.

In the coui-ae of years, centuries, and ages the sedi-
ments thus accunmlating- on a continental shelf may
form Buceeaaive layers, each a few inches or feet in
thickness, according to the rate of supply. A layer of
setUments of this kind is cidled a bed or stratum (plural,
strata). Many strata laid down on the sea floor, one

after another, may foim a heavy deposit liuiulreds ol
feet in thickness, including many shells and other rehcs
of marine life.

As new strata are adtled, the older strata are huried
deeper and deeper, their grains are more or less cemented
together by mineral substances deposited upon them by
slowly iniiltrating watei-s, and thus they gain a firm
texture. It is chiefly in this way that layers of loose
sediments are changed into layers of solid rock.

The lowland borders of continents are often built of
layers of sand and clay frequently containing marine
fossils ; this suggests that a former continenbil shelf has
there been raised to a land surface.

The shallower waters of continental shelves are oi
great importance as the chief fishing grounds of thai

THE OCEAN

109

world. The European ports aroiuid tlie North eea send out
hundreds of fishing vessels to its shallow waters. Tlie
rich fishing grounds of the Newfoundland banks attracted
many fishermen from the Old World over three centuries
ago. They are still resorted to every year by fishermen
from New England, chiefly from Gloucester, Massachusetts.
Although far out of sight of land, the water on the Imnks

BO shallow that fishing schooners (such as the one shown
in Figure 42) may ride at anchor whQe their men go off in
small boats to fish with nets or with hook and line. Dur-
fogs, which are frequent, there is danger of collision
with transatlantic steamers, whose route leads them through
the fishing grounds.

79. Waves. — Win<l blowing over the sea forms waves that
follow the wind. The water in the waves moves only up and
iown, back and forth, with very small forward motion. The

I 110 KLEMENTAUy I'JIYSICAL GEOGRAPHY

Stronger the wiiiil, tlie higher the ereBts and the deeper the
troughs of the waves, the greater their length (distance from
crest to creat), and the faster their forward motion.
I The waving of a field of grain under the wind may be
, taken as an illustration to ehow the relation of the curved-
path movement of the particles to the forward progress of
the waves. The mdependence of wave and water move-
ment may be seen on a river surface when the wind is
blowing upstream ; or at the mouth of a harbor when the
wind is blowing on shore, while the tide is running oat.

Great waves formed in the open ocean by gales and hur-
ricanes are often called seas. Their height from trough to
crest reaches 30 or 40 feet, but seldom exceeds 50 feet
Their length varies from 300 to 1500 feet or more, and
their velocity from 20 to 60 miles an hour. The interval
between the passage of successive crests, or the period
of the wave, is seldom more than 10 or 12 seconds.

80. The Use of Oil in Storms A smnll quantity of

oil poured on the sea spreads rapidly and i-eduees the
violence of the waves in a storm. A gale ordinarily
fonus ripples and small waves on the backs of greater
waves and causes the crests of great seas to curl over,
so that they would break with destmctive force on the
deck of a vessel. At such a time a film of oil decreases
the catch of the wind on the water and prevents the large
waves from cui'ling and breaking.

Many accounts of the use of oil in storms have been
published by the United States Hydrographic OfGee,
Washington. They show that when a vessel is headed

THE OCEAN 111

'tonrard the wind (" hove to ") and heavy seas come on
board over the bow, a little oil allowed to drip fvom a
iMig will spread even. toward the wind, forming a sioootli
surface, or "slick," and the waves entering the slick will
decrease in height and cease breaking over the deck.

When a vessel is running with the wind heavy seas
sometimes come aboard over the stem; but if a little oil
us allowed to drip overboard, the slick spreads out like a
fan across the wake, iind the great seas are rounded off
as they run into it, so that the vessel rides them without
difficulty.

81. Swell and Surf Great waves, traveling twenty

to sixty nules an hour, soon run out of the storm that
forms them and swing far across tlie ocean, preser\"ing
their length and velocity, but diminishing in height. In
this reduced form a wave is called a swell.

In calm weather the ocean surface may be smooth and
glassy, but not absolutely level and quiet ; for it is never
free from the slow heaving and sinking of fading swells
from distant stonns. A vessel becalmed in tlie doldrums
always swings idly to and fro as the swell rolls by.

When the swell runs into shoaling water close to land
its velocity decreases, its crest rises and its trough sinks,
thus making its height greater; the fi'ont becomes steeper
than the back. The swell thus becomes higher and liigher
as it advances. If it arrives on a, long, smooth, gently slop-
ing beach, the water before the advancing wave becomes so
shallow that it cannot buUd up the wave front ; then the
crest curls evenly forward in long lines nearly parallel

112

ELEMENTARY PHYSICAL GEOGRAPHY

with the shore imd dashes with a roaring noise upon the
beach, in the form of surt" or breakers.

The surf is like a mill in which cobbles, gravel, and sand
on a beach are ground finer and finer. The pebbles can
be heard rattling aa they are rolled back and forth.

Exposed beachra may be beaten by a heavy surf, ten or
fifteen feet high, while tlie neighboring sea is unrufiJed by
the wind. The surf ia then derived from a bi'oad swell
which comes fixim the great waves of a storm that may be
a thousand or more miles away.

The gi'eat hurricane, of Sept. 3—12, 1889, while on its
way fi'om the West Indies to the Carolina coast, produced a
destructive surf on the long beaches of New Jersey while the
storm area was still a thousand miles distant. At St. Helena,

THE OCEAN 113

a loneuome island in tho South Atlantic, boats frnni veasels
at anchor in tlie harbor fre^iuently eamiot reach the sliore
in fair weather on account of the " rollers," or heavy surf,
cm the beach. Tlie swell tliat produces this s\ivi is hulicved
to come from stoi-ms far away in temperate latitudes of the
North Atlantic.

When waves run upon a steep and raeky sliore tJiey
dash unevenly against the ledges, foaming and fretting
as they sweep back and forth. During storms spray
may be fiimg up 50 or 100 feet into the air. These great
waves exert an enormous force, capable of moving blocks
of rock ten or more feet in diameter. Wave work is not
tJieai limited to the immediate shore line; loose materials
in depths of ten, twenty, or more fathoms are moved about
and ground smaller and smaller, and the finest grindings
are swept away to deeper, quieter water.

82> Earthquake Waves. — When an earthquake, caused
hj some diatui-bLince in the earth's crust, occui-s beneath
the sea the wliole body of the ocean above it is moved
Blightly, and tiic movement then spreads away on all sides
in long, low waves that trsivel with great speed. When
Hearing the shore the speed and lengtli of the wave are
decreased, but the height is greatly increased. The wave
may then rush far in on a lowland coast, causing gi'eat
destnietion.

The tremendous explosive eruption of the volcanic
island Krakatoa, between Java and Sumatra, ui August,
1888, produced waves tliat spi'ead far around the world.
Their average velocity of progression was nearly 400 miles

114 KLEMENTARy I'HYSICAL GEOGRAPHY

ail hum-. On distant coasts their rise and fall was slight,
but on coasts near Krakatoa the waves rushed upon the
laiid with a height of from fifty to eighty feet, flooding the
liiwlimdB, sweeping away many villages, and drowning
thousands of the inhabitants. A large vessel was carried
a mile and a half inland and sti'anded thirty feet above sea
level.

An earthquake iji tlie North Pacific produced a destruc-
tive wave, from ten to fifty or more feet high, on the coast
of northern Japan in the evening of June 15, 1896. The
coast was laid waste for 175 miles. The few persons who
saw the wave and survived it reported that the sea flist
drew back about a quarter of a mile and then came rushing
in like a black wall, gleaming with phoBphorescent light
iind overwhelming the shore. On the open coast the sea
became quiet in a few minutes after the wave broke, but
in bays the waters surged and swirled for half an hour.
The outline of the shore was changed in many places;
many villages were destroyed, and thousands of acres of
arable land were laid waste. Thousiuida of fishing boats
were crushed or carried away; 27,000 persons lost their
lives, and 60,000 survivors were left homeless,

83, Ocean Currents. - — The upper waters of the ocean,

to a depth of 50 or 100 fathoms, move slowly in the gen-
eral direction of the prevalent winds, thus forming currents
that circulate about the great oceanic areas. The general
couree of the ocean currents is such that each of the large
oceans possesses a great eddylike current that moves
slowly around it, leaving the central waters ahuost quiet.

THE NEV< VC'V:

IpUBLlC LIBRARY

A8T«I. L»HO»(
•rii B»M fOUMBATWO

THE OCEAN 115

£xErclM. How niaiiy systems of eddying currents are showa in
Figure 44? Which one is the largest? Which three umaUer ones
are of about the same size? In what ways are the eddying currents
alike ? In what different ! Compare their movementa along the west
coasts iu middle latitudes ; along east coasts. How do they move
near the equator? Note the long equatorial countercurrent in the
Pacific, separating the two great eddies, )>orth and south. Note the
connecting current hetween the two eddies of the Atlantic, Compare
the general courses of the winds, Figures 22 and 23, with the courses
of the ocean currents. Name some districts where the winds and
currents agree.

The lemarkable correspondence between the course of
the oceanic eddies, Figure 44, and the course of the pre-
vailing winds over the oceans, as shown in tlie cfaarte.
Figures 22 and 23, points to the winds as the cause of tlie
currents. Like the circulation of the atmosphere, the eddy-
ing of the upper waters of the oceans must he regarded as
a characteristic of a globe having large oceans, a niohile
atmosphere, and a warm equatorial zone.

The beUef that the winds cause the currents is confirmed
by the way in which the surface drift of the waters may be
for a time brushed to one side of its usual course, or even
reversed, during a storm.

If an observer stood in the center of an oceanic eddy in
the northern hemisphere, the currents would pass around
him from left to right, or clockwise; in the southera
hemisphere, from right to left, or counter-clockwise.

The eddying currents are the chief natural basis for sub-
dividing the great oceanic area into the six oceans; the
North and South Pacific, the North and South Atlantic,
and the Indian oceans each having its own great eddy.

116

ELEMENTARY PHYSICAL GEOGRAPHY

while the Antarctic ocean has a great eddy around the
south pole, joining the eddies of the three southern oceans.
The Arctic also has a current about the pole joining that
of the North Atlantic, somewhat like the two loops of a
figure 8 ; but the Arctic should be classified as a lai-ge sea
or gulf rather than as an ocean.

A broad and shallow current that advances at a rate of
ten or fifteen miles a day, like that which crosses the
middle North Atlantic,
shoidd be called a drift.
A narrow current, flow-
ing with a velocity of
fifty or more miles a day,
like that issuing from
the Gulf of Mexico
through the Strait of
Florida, should be called
a stream.
It is important that the niastere of vessels should be
acquainted with the movements of ocean currents. In
cloudy and foggy weather, when observations of the sun
cannot be made to determine latitude and longitude,
a vessel might be drifted out of its expected course
if no allowance were made for the movement of the
watere. Thus, if a vessel intending to follow the courae
MahcN, Figure 45, were drifted to the course MAIiCS,
it would pass dangerously near the headlands at £ and C,
and might even run ashore. Wrecks on the south-
west coast of Ireland have not infrequently been due
to this cause.

////(

A>/ -

- ■-'":?/.<:

y V'"/

THE OCEAN

In yansen's famous attempt to reach the north pole he
sailed eastward along the northern coast of Asia and
turned northward into a region of ice fields, where his
vessel was caught between two floes. He then drifted
with the ice, expecting that the Arctic current would
carry him past the pole toward Greenland. Had he gone
further east before a^yuv-
tuming north, a closer *J!f r
approach to the pole
might have been made.

The drift of aban-
doned wrecks whose
positions are noted bj
passing vessels gi\(
indications of the ,
movements of cur
rents. The angular -
lines in Figure 4 b
show the drift of sev
eral wrects. The bioken lines indicate the dnft of many
logs from a great timber rift that wis ibandcned in i
storm while on the way from the Canadian provinces to
New York, December, 1887.

Thousands of bottles have been thrown into the sea, with
record of the time and place where they have been set adrift
and request that the finder shall report the time and place
of their discovery, afloat or ashore. The dotted lines of
Figure 46 give a few inferred "bottle tracks."

The several parts of the various eddies may receive spe-
cial names. Those parts which run westward, near and

118 KLKMKNTAUY TIIYSICAI. GKOURAl'IIY

about pimdJel to the equator, are called the equatorial cur-
rents. The eastern part of the South Pacific eddy is called
the Humboldt, or Peruvian, cuiTent ; it brings a great body
of cool water from far southern latitudes.

The name Gulf Stream, in tlie Atlantic, should be lim-
ited to the uuiTow, deep, and rapid current which issues
from the Gulf of Mexico with a velocity of eighty miles
a day ; the name ia popularly, but incorrectly, extended
fai- northeast over the broad, shallow, imd slow-moving
drift on the northern side of tlie North Atlantic eddy, and
even along ita branch, past Norway. This extension of the
current is not a strejim at all, and it inchides much water
that passed outside of the West Indies and not through
the Gidf of Mexico.

Sailing vessels should tiike advantage o£ winds and cur-
rents in shaping tlieir courses. If bound from the eastern
United States to far South American ports, tliey should
cross the equivtor well to the eastward, so as to avoid being
carried backward by a strong current past the Guiana coast,
where the winds may fail in the doldrums. A ship sailing
from an Atlantic port to Australia should nnmd Cape of
Good Ho[)e and take advantage of favorable winds and
currents in the southern Indian ocean about latitude 50°.
On the homewaixl voyage favoring winds and curiBnts
would be found in the siune latitude of the South Pacific,
toward Cape Horn.

84. Currents and Temperatures. — Currents influence
the ilistribution of temperature in the uceaos and in the
winds that blow over them. In the North Atlantic, for

THE OCEAN 119

eiBmpIe, ft broad drift of rather waim water flows north-
east in middle latitudes, past the British Islea and Nor-
way ; while a cold current returning fi-om the Arctic regions
flows southward past Labrador and Newfoundland. Hence,
in the same latitude, winds from the sea are mild in noi-tli-
westem Europe and chilUng in northeastern America.

In winter tlie harbors of the Labrador and Greenland
coast are closed with ice ; harbors in the same latitude on
the eastern side of the Atlantic remain open all the year
round. In what countiies are these harbors situated?
Northern Norway has a milder climate thiui any other
country at so great a distance from the equator. Why
18 this? What land in the southern hemisphere is as
far from the equator as Norway?

The southern coast of Alaska has a comparatively mild
climate on account of the iiortheastwartl drift of the sur-
face waters in the North Pacific eddy. The cool Peruvian
current keeps the temperature so low about the Galapagos
islands (neai- the equator west of Peru) that coral reefs,
such as abound further west hi the equatorial Pacific,
are not found on their shore.

85. Tides. — Regular movements of the ocean, risuig
and falling on the shores twice in a little more than a day
(twenty-four hours, fifty-two minutes), are called tides. In
tlie open ocean tides are not perceived ; but hi many bays
the tidal change of level, or range, reiiches ten, twenty, or
more feet. The highest stage of the tide is called high tide
or high water; the lowest stage, low tide or low water,
The change of level is accompanied by currents, — flood tide

120

ELEMENTARy PHYSICAL GEOGRAPHY

running in from the ocean, ebb tide running out again. A
brief period of quiet, or " slack water," occurs when flood
changes to ebb, or ebb to flood. Tbe vessels that are aground
~at low tide in Figure 47 would be afloat at high tide.

The tidal undulations of the oceans are caused chiefly by
the attraction of the moon ; they are somewhat affected by
the attraction of the sim.

Tidal euiTcnts are beneficial in maintaining a circulation
in bays and harbors where the waters might otherwise be
almost stagnant. At high water a harbor will admit ves-
sels of a laiger size than could enter if the ocean level*
did not change; but at low water the harbor may be inac-
cessible except to much smaller vessels. The hour of
departure of ocean steamers is usually determined by the

THE NE7.' iO;:K

PUBLICU3RAK\

ABTOn. LENOX
TiLOfcN FOUNDATlONa

STHE OCEAN

121

hooriiiof high Mde, so that they may have water as deep as
possible when leaving their harbor.

In funnel-shaped bays or estuaries the tidal range
becomes large, and flood and ebb currents are veiy strong,
making navigation difficult or even dangerous. The tidal
range sometimes exceeds fifty feet in tlie estuaries at the
head of the Brist-ol channel in western England, and of
the Bay of Fundy in Nova Scotia : in the latter the flood

Fio. 4B. The Tidal Wi

icorrwit rushes in like foaming surf, sho^n in Plate V.
Tha eetuary of the Seine in iiortliwestem France has a
similar surf-like tide, shown in Figure 48. Such surf-like
tides are called borea. A bore occurs at the month of tlie
Amazon; it is so violent on the northern side of the river
near the sea that the sliore line is rapidly worn baek, and
hence no impoitant settlements have l>een made there.
, Whffl* tidal currents are thus strengthened they sweep
[the sediments of the shallow bottom back and forth,
indiug them finer and finer. The finest particles thus

122

ELEMENTARY PHYSICAL GEOGRAPHY

produced are slowly drifted offshore, where they settle in
deep water. When a gale is blowing and producing
waves in strong flood or ebb currents their work on the bot-
tom ia much increased ; for the sediments are slightly raised
from the bottom by the agitation of the waves, and thus
they are brought more into the power of the tidal currents.
Many curious tidal phe-
nomena are found on shore
Knea of different forms.
At New York a high tide
entering from the harbor
leaches the rocky narrows
of Hell Gate when a low
tide arrives through Long
Island sound; and six
hours later a low * tide
from the harbor meets a
high tide from the sound.
Thus a rapid current is
I caused to flow back and
forth in the narrow pas-
sage, which was danger-
ous to vessels until the channel was widened by blasting
away its reefs. A current of this kind ia sometimes called
a tidal race.

86. Life in the Ocean. — The surface layers of the open
ocean possess a considerable variety of animal life, from
large mammals, like whales, to minute organisms. Figure
40, whose tiny shells are so plentifully strewn over the

Jtllyfisli lioatiug ii

THE OCEAN

Dei^p-Seii

ocean floor. The formei" occur in moderate numbers; the

latter are countless. The distribution of surface life is

detennined chiefly by differences of temperature from the

torrid to the

frigid zones.

Those forms

which Bwim

or are drifted

freely by the currents are found over vast areas. In fair

weather the surface waters are sometimes alive with minute

jellylike forms.

The nearly quiet water about the central part of the
great eddying currents generally contains a considerable
quantity of floating seaweed, or »ar-
gatium ; hence these central areas are
called sargasso seas. The sargaaimm is
believed to be derived from shore
waters, where it grows on the shallow
bottom. A great variety of small ani-
mals live on the floating weed, and a
certain kind of fish uses the weed as
a "nest" for its eggs.

The intermediate depths of the
ocean, between the upper part and
the bottom, are prevailingly without
life, — a great desert space, cold, quiet,
and monotonous.
The deep ocean floors have no plants. They are inhab-
ited by a considerable variety of animals, such as fish,
crabs, sbellflsh, starEsh, etc. ; but the forms of life are

Deep-BeaCruBtocean. :

124 ELEMENTARY I'HYSICAL GEOGRAPHY

here much less varied and less numerous than in the
shallower waters near the shore.

While many deep-sea animals are blind, it is curiona
that some have well-formed eyes and are ornamented with
colors. Colors would be useless if they could not be seen,
and eyes would be of no Bervice in complete darkness.
Hence there must be some ]ight in the ocean abysses. As
sunlight cannot penetrate to great depths, the light may
be supplied by phosphorescent animals, of which there
are many kinds in the deep sea.

The shallow waters of the ocean margin teem with plants
and animals. Man}- animals, such aa sponges, corals, and
barnacles, are fixed to the bottom; they need not move
about in search of food, because the moving waters bring
it to them. Nearly all the plants of the sea are of a com-
paratively simple kind, without flowers or seeds. The
shallow waters are the fishing grounds of the sea and fur-
nish import-int supplies of food to the neighboring lands.

Supplement to Chapter III

87. The Cauae of tlie Tidea. — Note the time when the moon
passes over the south point of th« horizon on two succesBive days.
(These observations may be made in the early evening when the
moon is near its first quarter. If daytime observations arc pre-
ferred, they may be made in the early forenoon when the moon is
between third quarter and new ; or in the late afternoon between
new moon and first quarter.) How long is the interval between the
two passages 7 Compare this interval with that between two high
tides, as stated on page 110. How are the two intervals Telat«(l?

The above comparison shows that the tides in some way depend
on the moon, because two sets of tides occur in the time (24 hours

I— I.

THE OCEAN

I IS minnteB) between two RucceBHive passages of the
meridiaa. It can be shown that tim attraction of tlu
oceana tends to t-auae high tides, //'
aad H", Fignre 52, on opposite aidea
of the earth near the equator, with low
tides, 0' and 0", between them. The jr
tides tend to preserve a constant posi-
tiou with respect to the moon, some-
what as indicated in the figure. Hence

Fig, 52

the earth tiiriia round
(the axis standing at right angles to
the paper), any point in the equa-
torial oceauB must pass H', U', II",
0" in 24 hours 52 minutes, and
must therefore experience two liigli
and two low tides in that period.
The moon tends to form similar
but weaker tides around all the lati-
tude circles in the two hemispherea.
The sun also tenda to cause tides ;
but in spite of the vastly greater
size of the sun than of the moon,
the sun is so much farther away
that the solar (sun) tides have only
^ ^L^ 7^ { ^ about one third of the strength of

T S^^=-^ _ V >u^ ,....„ („„oaj tides.

y moon, when the sun and
' on the same side of the
;n Figure 53, the lunar (L)
(S) tides act together, and
hence the rise and fall of the tides,
or the tidal rangi>, is increased. At
first (quarter the line to the moon is
at right angles to that to the sun,
as in Figure 54. Here the sun tries to make a low tide where the
moon makes a high tide, L ; and the moon makes a low tide where

i TUrd Quarter

the lui

126

th«

ELEMENTARY PHYSICAL GEOGRAPHY

triea to make a high ticie, S. Ah a result, the tidal range
is wealiBned. How do the lunar and solar tidea combine at time of
full moon, Figure 55 ? at time of third quarter, Figure 56 ?

It thuB appears that in the twenty-eight days between two n
moons, or about a month, the tidal range is strong, weak, strong, and
weak. At the times of strong range the tides are called spring tides ;
at times of weak range, neap tides. The variation t)f tidal range
from new moon to full moon is shown in Figure 57. How often
does the period of spring tides occur in a month? of neap tides?

It is not possible at present to state how the tides behave in the
they cannot be observed in deep water, far from shore.

Fig. 57. Vatiatiuu \i( Tides fur Two WeekB

They are known only as they come upon the shores of islaiids and
continents. Their strength then depends not only ou the combina-
tion of lunar and solar forces, as in spring tides and neap tides, but
still more on the form of the ahidlowing sea floor and of the shore
line. Just as swell is increaited. in height as it runs ashore, so are
the tides; for the tides are in reality very long, low waves; bat
while the surf caused by the arrival of successive swells may roll in
on a beach every five or ten seconds, the high tide rolls in only every
12 hours 26 minutes. Its strength is usually less on headlands than J
in bay heads.

THE OCEAN 127

gUESTIONS

Becb. G8, 69. What ia the ocean ? Compare the Arctic iiTid Ant-
arctic oceans. Locate the poles of the land and water hemispheres.
Consider the ocean as a. highway.

70, 71. Compare the earlier and later objncts of ocean exploration.

^tanibe the method of deep sounding. What ia a water hottleV a

^Hj^Bee? How are nets used in Hounding? Where th pi ce f

H|^Heat depth in the ocejinV About how deep are th y?

^^^tS, 73. What mineral Bubstonces are dissolved oc wate ?

What is their source? What gasea are disBolvRd te !

What purpose does one of these gaaes serve? Wh t th d ty

of ocean water? What amount of dissolved sabsta ioe t

tain V Compare the ocean and the atmosphere. Describe tlie colors of

the ocean under difierent conditions. What causes phosphorescence ?

74. Describe the distribution of temperature at the ocean surface ;
at the ocean bottom. liow do ocean tenijieratures vary through the
year T How deep does sunshine penetrate the ocean ? Compare the
effect of changing temperature on the density of fresh water ; of
salt water. How is the cold water at the bottom of the e<^uatorial
oceans accounted for?

75. Why does ice float? What ia floe ice? pack ice? What are
icebergs? What sine do they roach ? How do they float? Where
are they seen? What is their source?

76. Describe the deep ocean bottom. What is the character and
source of ocean-bottom materials ? What can you say of mountains
and volcanoes in the ocean ?

77. What is a mediterranean? Name the chief examples. How
does their temperature differ from that of the oceans? j

78. What is a. continental shelf? Give some examples. What
materials are found on continental shelves? How are stratified
deposits formed? What do they include? How may lliey lie
changed to rock ? Of what value to man are the shallow waters
of contiuental shelves?

128 ELEMENTARY PHYSICAL GEOGRAPHY

79, 80. What are waves ? What size ilo they reach ? How do
they move? Illustrate the diSerence of wave movement and water
movement. What effect haa oil on wavea?

81, 82. What changes of form do waves suffer? What is swell?
Burf? Why does surf fall forward? What are "rollers"? What
work is done hy wavea? To what depth may they act? What ia
earthquake wave? Describe two examples.

83. What are ocean currents? What is their general movement?
What divisions of the ocean are suggested by its eddying currents? i
What is a drift? a stream? Of what practical importance ia
knowledge of ocean currenta? How are ocean currents determined?
What is the cause of ocean currents? How is this proved? Name
and describe some important members of the oceanic eddies. To
what should the name Gulf Stream be limited? How may sailing
vessels take advantage of winds and currents?

84. How do ocean currents influence the diatrilration of tempera-
ture? Give examples from Labrador, Great Britain, Alaska, Peru.

85. ■\Vhat are the tides? Define high tide, low tide, slack
water, flood, ebb. How are tides caused? What practical bene-
fits arise from them? What inconveniences? What is tidal range?
What may it amount to? Where does strong range occur? What
is a tidal bore ? What work ia done by tidal currents ? When is this
work most effective? What is a tidal race? Give an example.

8G. Consider the distribution of life in the ocean surface waters.
How ia it chiefly con1ro!led? What is a sargasso sea? What can
you say about the intermediate depths? the bottom? What can be
inferred from the color and eyea of deep-sea animals? Consider the
distribution of life in the shallow marginal waters.

k— k.

CHAPTKR IV

THE LANDS

88. Area of the Lands. — ■ The globular earth is uneven
enough to raise somewhat more than a quarter of its sur-
face slightly above the oceans in broad land areaa, called
continents.

The area of the globe is about 197,000,000 square miles.
The lands occupy somewhat more than 60,000,000 square
miles; their total area remains uncertain until the polar
regions are fully explored. Six sevenths of the land area
are in the land hemisphere (see Figure 34), where the
ocean occupies little more than half the surface. The
lands in the water hemisphere occupy only about one
fifteenth of the surface.

89. The Continents. — There are five large bodies of
land, known as continents. Europe and Asia together
form a single continent, often called Eurasia, the largest
of the five. On account of the great extent of this
continent, and still more because of its varied relations to
human history, it is convenient to describe both Europe
and Asia as a "grand division" of land.

The other continents are Africa, North and South
America, and Australia, the lost being the smallest of
the five. It ia possible that the lands of the Antarctic

130 ELEMENTAEY PHYSICAL GEOGRAPHY

regions may be diBcovered to be large enough to rank aa
a continent; but little is known of them at present.

The five continents differ greatly in size, outline,
arrangement of pai'ts, and degree of separation. The
most remarkable fact concerning their distrilmtion over
the earth's surface is that they cluster around the Arctic
circle, inclosing the Arctic ocean, and thence extend far
Bouthward, nai'rowing toward their ends in tlie great ocean
of the southern hemiaphere. The narrow Noi'th Atlantic
and the much narrower Bering strait occupy only about one
ninth of the Arctic circle ; the rest of its circuit crosses
the lands, with a few narrow ai^ms of the sea that separate
some of the Arctic islands from North America.

South America lies southward of North America ;
Africa lies southward of western Eurasia ; Australia lies
southward of eastern Enraaia. None of these southern
continents reach the parallel of 60° south latitude; the
whole circuit of this parallel lies on the ocean.

Another remarkable feature in the distribution of the
lands is that two land areas are seldom found opposite
to each other, on opposite sides of the earth. Opposed
to each continent is generally an ocean surface, as may be
seen by examining a globe.

A third remarkable feature regarding the distribution
of the lands is that, excepting Australia and the possible
Antarctic continent, nearly all the other lands are found
on one half of the earth's surface, known as the land hemi-
sphere. (See page 96.)

Eurasia and Afi'ica are oft«n called the Old World,
because parts of them have been known to the people of

l-Uk

THE LANDS 131

our race for more than twenty centuries ; while North and
South America are called the New World, because they
have been known to us for only a little more thaii five
centuries. But these names are sippropriate only from
the point of view of human histwry. Both the Old and
the New Worlds, so called, contain so much very ancient
land, raised aboVe tlie ocean in early stages of the earth's
history, and so many mountains and plains that have been
formed in the later stages of the earth's histoiy, that
neither world should be regarded as, on the whole, older
or younger than the other.

The greatest islands are comparatively near the conti-
nents, as in the archipelago noith of North America, the
West Indies, Newfoundland, the British Isles, Madagas-
car, the Japanese islands, the Malayan-Acstralasian archi-
pelago, and New Zealand. Most of these islands stand
npon continental shelves and are separated from the con-
tinents only by comparatively shallow water; but New
Zealand ia separated from Australia by deep water. The
Qumerous oceanic islands, distant from continents, are of
small total area (about 40,000 squai'c miles),

90. Height of the Lands. — The Mghest mountain peaks
(25,000 to 29,000 feet) do not rise above sea level so much
as the greatest ocean depths sink Ijelow it (31,600 feet).
The average elevation of the lands (2400 feet, less than
half a mile) is much less than the average depth of the
oceans (about two miles).

Figure 58 exhibits the proportion of high and low land,
and of deep and shallow ocean, the whole area of the earth

1-M

132

ELEMENTARY PHYSICAL GEOGRAPHY

being measureLl by the breadth of the figure. It is thus seen
that most of the land surfu<!e ia but little alKJve sea level,
wliile most of the sea floor hes deep below the sea surface.

91. Changes of Continental Outline. — - The foini of the

lands and the outline of their shores seem at firet sight to

be unchangeable. But the more the world ia studied, the

I certain it becomes that very slow movements are

going on in the
-rrms X,

ifiot eartns crust,

and that the out-
f,™ line of the con-
tinents is sub-
" Ject to change
as the conti-
'■"" nental masses
very slowly rise
^""' or sink. The
movements are
so slow that
they are hardly perceptible in the course of a century ;
but when continued for hundreds of centuries they cause
changes of great importance in the geography of the lands.
Observations in the last hundred years or more give
reason to believe that the coasts of Massachusetts and
New Jersey are now sinking (one or two feet a century),
and that much of the coast of Sweden is rising (greatest
rise, three feet a century). The coast of the Netherlands
is sinking a foot a century, and its fields near the shore,
fifteen to twenty feet below the sea level, are diked to keep

THE LANDS 133

tJie water ofE. Canada northeast of the Great lakes is
rising, ho that the watei-s of the lakes are slowly backing
up on their southwestern shores.

Widespread layers of rock containing fossils of sea
animals are found on various parts of the continents, show-
ing that these parts of the lands have, in some ancient
time, been beneath the sea. Many ptber proofs of change
of level will be given on later pages.

92. Varied Conditions on the Land Surface. — -The sur-
face of the continents possesses great variety of form and
composition, very uiilike the monotony of the broad and
deep sea floors. Rocks and soils, as well as mountains,
valleys, and plains, differ greatly from place to place.

Mountain ranges are characteristic of the continents
rather than of the sea floors, where plains of vast extent
prevail. But mountain ranges occasionally rise from the
sea bottom, showing their crests above the surface, as in
the West Indies. Volcanoes and their lavas are among
the few features possessed in common by tlie deep sea
and the dry lands.

The continental shelves, overlapped by some of the
oceans, have something of the variety of the lands from
whicb they receive washings of gravel, sand, and clay.

While the deep-sea floor is always wet, dark, cold, and
quiet, the land surface has many different kinds of weather
and climate. Heavy rains are followed by clear sky;
strong winds, by light winds or calms. A bare desert
surface in the torrid zone may be heated at noon above
130°. and may cool nearly to freezing the next night. In

134 ELEMENTARY PHYSICAL GBOGRAPHY

the frigid zone the frozen soil may warm and thaw at the
surface during summer, but it will be frozen f^ain, even
to 80° below zero, the next winter.

Variations of temperature, so distinct on the land sur-
face, rapidly decrease underground. At a depth of four
or five feet daily changes are hardly perceptible ; at a depth
of twenty or thirty feet there is but little variation from
the mean temperature of the year (about 80° in the torrid
zone, near zero in far northern lands).

In northeastei'n Siberia, where the ground is frozen to a
depth of 300 to 500 feet, grass and bushes grow when the
soil thaws for a few feet in summer; but large trees are
wanting. The manunoth, an ancient animal resembling a
hairy elephant, but no longer found living, has on account
of the extreme cold sometimes been preserved in the beds
of sand and gravel that border some of the Siberian rivers,
where it was buried at the time of river floods many
centuries ago, and afterward frozen.

93. Activities of the Lands. — In nothing do the conti-
nents differ more strikingly from the deep-sea floors than
in the activity of the various processes that go on upon
the lands, and in the changes that the processes prodnce.
The aui-face rocks split apart when water freezes in their
crevices, or they slowly rust and decay imder the action
of air and water. A sheet of loosened rock waste ia
thus formed over most of the land surface. The various
processes by which rock waste la produced are known
under the general term weathering. Weathering varies
greatly under different climates and with different rocks.

THE LANDS

135

Every rock-ledge or quarry offers opportunity for observ-
ing the widespread process of weathering. The weiithtTing
of the older gravestones in cemeteries may frequently !«?
noticed. In cities the different amounts of weathering on
old and new stone buildings, or in buildings of different
of stone, serve to illustrate in a simple way the
B8 that occur on

scale
over the lands.
In the dry, mild,
and equable climate
of Egypt ancient
statues have been but
slightly weathered in
severiil thousand
years. A great stone
monument, sixty feet
high, known as Cleo-
patra's Needle,
brought from Egypt

A Qututy Btaowiug Weathered Bock

to New York in 1880, was so much affected by the weather
m a single winter that it became necessary to coat its sur-
face with a preservative substance. In Egypt it had stood
over 3000 years with little clmnge.

In regions of plentiful rainfall and abundant vegetation
weathering advances with comparative rapidity, and a deep
soil is formed ; solid rock may not be found for fifty or mrwe
feet below the surface. In high latitudes, where the tem-
peiature frequently rises and falls past the freezing point,
frost is active in splitting rock masses into fragments.

136 ELEMENTART PHYSICAL GEOGRAPHY

94. The Wasting of the Lands. — Surface water, supplied
by rain or melting snow, washes the finer rock waste down
the slope of the land to the valley floors or to the streams,
and the streams hear the waste along tlieii' channels, thua
sweeping it from one place and spreading it over another,
or washing it to the sea. Where streams run they rasp
their channels with the rock grains that they bear along,
and valleys are thus slowly worn in the surface of the land.
The higher the land, the deeper the valleys may be cut.

The longer the period of wasting and washing, the more
material is taken from the valley sides and the wider and
more open the valleys become.

Large valleys, receiving many smaller branching valleys
and ravines that dissect the surface of the land and lead
streams from higher to lower ground, are among the most
characteristic featui-es of the continents. Valleys !»re the
result of stream action and do not occur on the deep-sea
floor. They are sometimes found beneath sea level, extend-
ing forward from the present coast line across the shallow
continental shelf; they are then taken as proof of the
lowering of that part of the continent.

The winds act with great effect on bare surfaces, sweep-
ing finer rock waste into drifts (dunes), and raising the
dust aloft to settle far away. The waves, cuixents, and
tides of tbe ocean wear the edge o£ the land and the
shallow continental margins, cutting cliffs and building
sand reefs along the shores, and sweeping away tie finer
land waste.

The general process of wasting and washing, by which
the land surface is slowly worn down and the deeper

THE LANDS 137

stmctTires of the earth's crust are attackerl, is called denu-
dation or erosion. The movement of land waste from one
place to another by various agents (streams, currents,
winds, waves, etc.) is called transpoi"tation. The process
of layii^ down land waste on valley floors, in lake basins,
and on sea floors is called deposition. "

Illustrations of these various processes may be found
on a small scale in the neighborhood of many schools.
The wet-weather streams of roadsides and the waves in
ponds or reservoii-s exhibit in a small way the processes of
erosion and transportation in large rivers and oceans. The
strong action of winds on dusty roads and tlieir lack of
effect on the ground beneatt grass or forests illustrate the
contrast that prevails between wind action in dry and in
moist regions.

The difference between the conditions that prevail on
the land surface and on the sea floor is thus seen to be
very grea,t. The sea floor is enduringly quiet and silent.
The tides of the deep sea are very faint. The creeping
of cold polar water toward the equator must be almost
imperceptible. The gain of the bottom by the steady
shower of organic remains from the surface is very feeble,
and the change of form by this gain must be exceedingly
slow.

Although the changes caused in the form of the lauds
by weathering and washing are gradual, they have been so
long continued that marvelous results have been produced.
Not only are the lands deeply dissected where valleys have
been worn in plateaus and mountains, but whole mountain
ranges have been worn down to lowlands. The forms of

138 ELEMENTARY PHYSICAL GEOGRAPHY

tlje land to-day can be appreciated only when it is seen
that they are the present stage of a long series of changes.
The description and explanation of land forms thus con-
sidered is the object of most of the remainder of this book.

The general wasting of a land surface is slow, but local
changes are easily noted by the attentive observer. Slop-
ing fields and roads are gullied by wet-weather streams.
Much soil may be washed from a plowed hillside in a
single rain storm. Landslides produce striking changes
on mountain slopes and in the valleys I)elow. Cataracts
like Niagara wear back their cliffs more than a foot a
year.

The land waste that is washed down a valley is deposited
at the mouth of the stream in a lake or the sea, and thus
tlie land is built out, forming a delta, which may grow
forward perceptibly in a century. Ostia, once the port of
ancient Rome, is now over a mile inland from the advanc-
ing front of the Tiber delta. Sea cliffs may be cut back
by the waves ; part of the exjKwed eastern bluff of Cape
Cod, Massac liusetts, is retreating at an avenge rate of
three feet a year.

The rate of erosion on th.e lands varies greatly with rock
structure, slope, and climate. The Mississippi carries
enough land waste to lower its whole basin an inch in about
tiu-ee centuries. An inch in from one to ten centuri&s
may be taken as a rough measure of erosion, avenged
for lai^e areas.

95. Useful Products of the Lands. — The rock of the
earth's crust in the lands is of great service in building and

THE LANDS 139

road making ; hence it ia often quarried. Clay is buined
to make bricks, used in building and street paving. Lime-
stone when heated ("burned") ia changed to lime, used
in making mortar. Coal, found in layers Ijetweeu sti'Hta
of clays and sandstones, is the moat useful kind of fuel.
Rock oil, or petroleum, ia of great value as a fuel for
lamps, and in many other ways. The oi'es of many metala
are mined and smelted, to aupply man's' needs ; iron, copper,
lead, tin, and zinc are the most useful metals in manufac-
tures ; gold and silver are used as money and in the arts.
Precious stonea or gems, such as the diamond, ruby, and
emerald, are higlily prized for thek beauty and rarity.

All these products of the lands play an important part
in the advance of civilization. Spain has iron ore but no
coal. England has abundant coal and iron ore. How is
the present condition of these two countries affected I>y
the presence and absence of coal supply? The United
States possesses extensive coal fields and abundant deposits
of iron ore, as well as other mineral products in great
variety. Argentina possesses relatively little mineral
wealth. What coinpai'ison can you make between these
two countries in other respects?

QDESTIOHS

Secb. 88, 89, 90. What ia the area of the globe? of the lands?
State three remarkable facts cotic<:rning the distributioit of thti
landa. Why are the terms OliI W&rld and New World not ajipro-
priate in physical geography? State the relation of the larger
islands to the continents. Compare land heights and ocean depths.
State the proportion ofliigh land to deep ocean.

140 ELEMENTARY PHYSICAL GEOGRAPHY

91. What changea are taking place in continenlal outline? Give
Bome examples.

92. Contrast the land surface and the sea floor as to form ; as
,to changes of temperature. Contrafit the dietribution of mountain

chainB and of volcanoes. How does temperature vary uiidei^(round 7
Describe the eftecta of extreme cold in northeastern Siberia.

93. What changes take plaiie on the lands? What is weather-
ing? Give examples of it. Name some o{ iU effects. How does
frost act and where is it most effective 1

94. Describe the action of streams. How are the depth and
width of valleys determined? Why are valleys characteristic of the
lands ? How are the lands affected by the winds? by waves and
tides? Define denudation. What effects of erosion have you seen?
State the effecta of long-continued erosion. What changes have
occurred on shore lines ? Upon what does the rate of erosion
depend ? What is its average rate ?

96. What are some of the nseful products of the earth's crust?
What coinpariflon can ynu wake between England and Spain?
between the United States and Argentina?

PLAINS AND PLATEAUS

96, Introductory Example. — In ceiiain patts of the
world the hills bordering a mountain range descend directly
to the seashore. Rock waste is washed from the moun-
tain slopes and carried down the valleys by streams. The
lai^er rivers biiild deltas at their mouths, and here tlie sea
is bordered by low land. Waves beat on the coast and
cut cliffs in the headlands between the vftUeys; here the
sea is bordered by high land. The waste of the land is
spread over the neighboring sea floor by waves and currents.

Figure 60 is a picture of a model representing a region
of this kind. Mountains and ridges of varied form descend
toward the shore line. A river in a large central valley
receives the streams with their rock waste from a number
of branching valleys and has built a delta at its mouth.
This means that while the land has been eroded and
roughened by the action of weather and streams the sea
floor has been smoothed by the gain of land waste. The
depth and number of the valleys show that already mucli
waste has been carried into the neighboring sea. The
dredge bruigs up gravel, sand, and mud from the sea bot-
tom, the sediments usually being of finer grain as distance
from land and depth of water increase.

ELEMENTARY I'lIYSICAL GEOGRAPHY

Figure 01 is a mrn) of part of the mountains shown in Figure 60.
Th(! form of thu ridgea is liere indicated by short lines, called haehnre

lines, which show the direction in whieli the slopes descend. Gentle
slopes may be represented by long fine lines, steep slopes by short
heavier lines. This map may serve as a sample for a number of others
that should 1>l d awn f on the
fiffu a on la jag s

A rugge 1 Ian 1 1 ke thit
of F gure 60 aeldom sup-
ports 1 large populat o
for t a not eaaj to gim
IV ! ing on steep n n n
tai s les It is nly n
the valleys that strips of
fiat land, suitable foi easy
occupation, can be found
Moat of the population in
such a region is gatheied

PLAINS AND PLATEAUS 143

in villages near the rnoutliu of the lai'ge rivers, where the
valleys are wider and the ridges between them are lower.
Roads cannot easily follow the shore, for many of the cliffs
are washed to theii- base at every high tide. In passing
from one valley village to another the traveler must climb
over a ridge; this is hard work and it discourages settle-
ment. Many dwellers in the shore villages are seafarers
and fishermen, although there are few protected harbors,
for the shore line is comparatively straight.

The coast of California presents many stretches of this
kind. The Sierra Santa Lucia, south of Monterey, descends
boldly to the sea, its spurs being cut off in great cliffs.
The shore is harborless and thinly inhabited for a distance
of seventy miles.

97, Narrow Coastal Plains There are some regions

where the foothills of the mountains descend to a lowland,
and the lowland slopes gently forwaitl to the sea. Such a
lowland is called a coastal plain. The gentle slope of the
lowland is continued in the slowly deepening sea floor.
The form of the land is here much more favorable to
human occupation than in the previous example.

Plains of this kind are often divided into many simi-
lar strips by the shallow valleys of streams tliat flow
across them from the mountains. Each strip of the plain
is so smooth and so nearly level that a great part of the
rainfall enters the open soil, instead of running off in
streams. The plain is built of layers or strata of gravel,
aand, and clay, the uppermost layer or stratum forming
the auifaoe of the plain. The pebbles of the gravel often

144

ELEMENTARY PHYSICAL GEOGEAPHY

resemble the harder rocks of the hilly background;
clay often contains sheUs like those living in the sea.
Figure 62 shows a region of this kmd.

Trace the line between the mountainB and the coastal pl^n iq I
Figure 62. How many rtreamB are seen cioBaing the plain? Whici 1
Btream has the broadeat vallej ? Why? Compare the depth of the
valleys in the plain with that of the valleys in the luouutaina.

Fio. I!2. Narrow Coastal Plain

Draw a map to represent part of the coaatal plain of Figure 03
and some of the hills bordering its inner margin. Notice that is
the fignre the streams crossing the plain are foreshortened, while
the spaces between the streaina are on true scale. Figure 63 illu9-
trates the way in which the map should be drawn.

Little ravines have been eroded by wet-weather streams
in the side slopes of the plaia bordering the valleys. Even
the larger valleys have been slowly eroded by the rivers
that flow through them. In the future the plain will bo

PLAINS AND PLATEAUS

145

more carved or dissected m tlie pist it wis less dissected
Before any valleys were cut the difterent parts of the plain
were all united in a continuous even 'Jurfa^.e

In view of all this, it must he concluded that the eoaitil
plain in Figure 62 was once p irt of a shillow sea bottom
and that this region w u>
then like the searskirted
mountains of Figure, 60
Since then the relative
level of the land and sea
must have been altered
laying bare a part of the
smoothed sea bottom to
form the coastal plain

As the region now
stands higher than before
the rivers tend to wear
down their valleys to the
new level of the sea at
their mouths; the valley
sides waste away, and
thus the valleys slowly
become wider; but the
streams cannot wear the valleys deeper than the surface
of the sea at their mouths. The level of the sea is there-
fore called the haaeUvel of the region.

Slender belts of a very narrow coastal plain, less tlian a
mile wide, are found along parts of the western coast of Scot-
land; they are even narrower than the plain represented
in Figure 62, being wide enough for only a single row of

Coaalal Plaiu

146

ELEMENTARY PHYSICAL GEOGRAPIir

fields. The houses of the farmera are generally placed
neai" the inner margin of the plain; a few fields are cleared
on the lower slopes of the hack country; cattle pastiira
on the higher hillsides; the cultivated crops are gathered
chiefly from the smooth surface of the little plain.

Fill. ti4. A Natrow CoaaCal Plain in Scotland

A number of narrow and low coastal plains occur along
the coast of Oregon. They are one or two miles wide and
twenty or more miles long. Heavily forested mountains
rise in the background, too uneven for easy occupation;
but the even surface and gentle slope of the coastal plains
make them attractive to settlement, although they suffer
the disadviintage of having no good harbors.

The eastern coast of Mexico in the neighborhood of Vera
Cruz is bordered by a low coastal plain about fifty miles

PLAINS AND PLATEAUS

147

wide, back of which the mountains rise rather abruptly.
The plain is called the tierra ealiente, or hot couutiy.
It is sandy, malarial, and relatively infeitile. Vera Cruz,
the chief port for the interior highlands, has a poorly
protected anchorage on the open shore.

98. Broad Coastal Plains. — Figure 65 represents a
broa<Ier coastal plain tlian the preceding examples. The

^^^851

1 J 1 bG Broad Uoiuital I'ltun

outer part of this pKin i8 much like the plain in Figure 62 ;
but tbe inner part is more cut by branching valleys and
ravines, so that it presents a hilly rather than a plain sur-
face, and the lai^er livers ha\e broader valleys than before.
The unevenness, or "I'elief," of the surface increases
inward from the shore line in consequence of the greater
depth to which the valleys are cut in the higher part of
the plain. Where the uplands are much interrupted by
branching valleys the plain is said to be well dissected.

148

f;LEMENTABY PHYSICAL GEOGEAPHY

During the slow uplift of the region different kinds of
aedimente may have been laid down near the sliore, as the
sea retired fi'om the plain. Hence the soils of such plains
are commonly of different kinds in the inner, middle, and
outer parta, being arranged in belts rouglily parallel to the
length of tlie plain.

The Atlantic coastal plain of the Southern States, of
which a characteristic portion is included in South Caro-
lina, Figure 66,

Fig. OS. Co&stal Pl^

pine woods or grassy savannahs ; this division is about fifty
miles wide, rising so gently that it seems level to the eye-
Its surface is very poorly drained.

The plain slowly rises inland with gently rolling sur-
face; here tlie soil is better than in the first belt, and much
cotton is raised. Farther inland still the surface becomee
more sandy again and more hilly, giving extensive views
seaward across the lower plain. A hundred miles inland

PLAINS AND PLATEAUS

149

a belt of hilly uplands stands 600 or 700 feet above the
sea, covered with pine forests. Here the plain is well dis-
sected, its original surface being almost entirely destroyed
by the action of many streams in carving their valleys and
by the action of the weather in opening the valley slopes.
Then come the hills of the older land (the Piedmont
belt, here not mountainous, but of moderate relief), whence

the strata of the plain have received their sediments, and
where the rivers are now cutting down narrow valleys
beneath their former valley floors.

The soil belts on this pliiin exert an important control over
the industries of the people. The leSs sandy soils are occu-
pied by cotton plantations. Extensive pine forests on the
more sandy belts furnish much lumber, tar, and turpentine.

150

ELEMENTARY PHYSICAL GEOGRAPHY

The moist swampy soils near tlie coast are well adapted
to tlie cultivation of rice. The more limy layere of the
plaiu are dug up to fertilize the more sandy fields, and the
richest of these limy deposits are exported to other states
to be used as fertilizers. In North Carolina numerous
farms on the coastal plain furnish vegetables for the mar-
kets of northern cities,

99. Belted Coastal Plains. — Figure 68 exhibits a coastal
plain which maybe divided into three belts pamllel to the

shore line, each one ten, twenty, or moi-e miles wide ; the
innermost (A) is a lowland ; the middle belt (B) is an j
upland of stronger rock layers, several hundred feet above I
the lowland ; the outer belt (C) is a smooth coastal low- 1
land. The several l>elts recall the beltlike arrangement of I
soils described in the ease of a broad coastal plain, but I
here the middle belt forms an upland that runs about 1

PLAINS AND PLATEAUS

151

parallel to the shore bne ind itaiids hetween an inner
and an outer lowland The uplind descendb by a lather
steep slope to the inner lowland, ind by a long, gentle,
outlooking slope to the coastal lowland '

la Figure 68 the front
□f the digram ia diawu
to repreeent what ■would
be seen on the aide (f i
very deep cut tliat might
be imagined to ciMsa the
plain. The liije s of
ckys, Bandston s and
other strata that form
the plain are thua shown
gently slanting under the
sea. Where is the uppe
most layer of tl e ee e
that ia, the layer that waa
last deposited? What
part of the belted pan
does it cover 7 1\ a e

the nnder layera { he fi st
deposited)? fl h e do
they reach the j res t
surface of tlie b t d
plain ? Which layers
reach the surface of the upland part of the h Ited pa ?

Draw au outh e map of tl e 1 st ct shown F gu e 8 A
Minple of part of it is shown in Figure 69. Note that some smaU
streams must run inland, down the inner slope of the upland.

1 ^n upland of this kind may be called a cuesta, following a word of
Spanish origin used in New Meitioo for low ridgea of aleep deacent on one
side and gentle slope on the other.

152 ELEMENTARY PHYSICAL GEOGRAPHY

Compare the arrangement of the riyera and streams with those
shown in the map, Figure 03, drawn from Figure 82.

The reason for the arrangement of upland and lowland
may now be understood. The under layers of this coastal
plain are weaker than the middle layers ; hence the under
layers, which reach the surface of the plain near its inner
border, are already worn down to a lowland, while the more
resistant middle layers still preserve an upland height.

Trace the river first seen at D, Figure 6S, and describe the several
belts of country that it crosses on the way to the sea. Where is its
valley deep? where shallow?

A good example of this kind of coastal plain is found
in southern New Jersey, Figure 70. The Delaware riyer
below Trenton runs along the inner lowland. Here is &
belt of pottery clays, of which much crockery and earthen-
ware are made. Then comes a belt of fanning country
on rolling hilly ground, which contains layers of marl
(limy clay); the marl is dug to serve as a fertilizer on less
productive soils. The hills rise to an upland that descends
in a long gentle slope southeastward to a lowland plain
by the sea; its soil is sandy and its even surface is gen-
erally overgrown with pine foreste. Short arms of the
sea enter the lower valleys, giving harborage for small
vessels ; many fishermen live in the shore villages. A
belt of shallow salt-water lagoons with extensive marshes
of reeds borders the mainland for a breadth of about five
miles. Finally come the sand reefs, half a mile or more
wide, inclosing the lagoons. The reefs are interruptell by
inlets, connecting the lagoons with the sea.

PLAINS AND PLATEAUS 153

' 'Name the direction of the Delaware and the Schujlkill aa they
flow into the inner lowland ; of the Delaware in the inner lowland ;
of the streams that flow down the inner slope of tlie mipsta and

across the marl belt; of the streams on the outer slojie of the
cuesta. Which ia the steeper slope of the cueata? How is this
known? Compare the arrangement of all these streams with those
shown in Figare (19.

What is the averagf breadth of the clay belt? of the marl belt?
of the hiily belt? of tiie sandy plains? of the coastal lowlani]?

iw tar is it from Philadelphia to Atlantic City?

n54

ELEMENTARY PHYSICAL GEOGRAPHY

100 Embayed Coastal Plains. - — The region here figured
does not at firat siglit seem to belong to the family of
coastal plainia Long shallow arms of the sea enter
between low hilly arras of the land. Rivers from the
back country enter the heads of the long bays ; small
streimM from every little valley between the hills of the

Fiu 71 Ka Bmbijed Cuitstal Plain

land arms enter little hays or coves on the sides of the
larger bays.

This diagram i-epresents a coastal plain which has been
depressed, so that its valley floors are " drowned " beneath
the sea. Before drowning, the region must have stood
for a long time higher above l)aaelevel than now, for the
valleys evidently had been eroded and widely opened before
the depression of the region occurred. Many side valleys
had been formed, so that the uplands between the lai^er
rivers had been dissected into branching spurs. Now the
outer coastal lowland and the broad valley floore are under

PLAINS AND PLATEAUS

155

■prater, the latter being occupied by the bays that enter far
'toward the oldland while the groups of hills stand forth
«s ragged aims of the land The former simple shore line

is thus exchanged for a very

irregular shore line

Draw a map of part of the em

bayed coastal plain shown m Fig

ure 71, after the style of the outline

in Figure 72 Compare Figures 65

and 71. Point out the inner border

of the coastal plain in each one In

what respects do the two figures

^ree? Tn what do they differ?

How has the difference been pro-
duced? In each one trace a nver

from the oldland to its mouth

What difference is noted?

The relative change in the
attitude of land and sea is here
opposite to that inferred in the
previous examples. Since
the depression of the region the
land heads have been more or
less cut back by the waves, and
the bay heads have been some-
what filled by marshy deltas. But the drowning cannot
have taken place long ago, as the earth counts time, for
the changes in the land heads and bay heads are of
moderate amount.

The Atlantic coastal plain from Delaware bay to Pamlico
sound presents many examples that fall under this class.

166 ELKMENTARY PHYSICAL GEOGRAPHY

The outer shore line is for the moat part a sand reef,
ioclosing lagoons. Many branching bays extend inland,
the largest being Chesapetike bay. Navigable arms of
the sea thus alternate with dissected arms of the land.

Pai-tly drowned coastal plains exert a peculiar contnd
over the distribution and occupation of their population.
The greater part of tlie valley lowlands is lost, and the
people must make the most of the hilly land arms that
remain above sea level. The axis of each of the larger
amis la generally followed by a main road, making its waj
from village to village among the upland farma and giv-
ing foi'th side roads to villages on the smaller laud arms
or at the little bay heads. Indicate the place of BQcA
roads and villt^es on Figures 71 and 72.

Tlie shallow bays are valuable for fishing grounds.
More important centers o£ population are found either
near the heads of the larger bays, where the large rivere
come out from the Itack country and reach tide water, or
near the mouths of the bays where the outer sand reefa
are not continuous and the ocean is easily reached.
Baltimore and Norfolk are good examples of cities thus
situated. The outer shore line is inhospitable; its long
sand reefs offer no good landing place, and the narrow
tidal inlets allow entrance only to small-sized vessels.
Where would such a view as that of Figure 73 be found
in Figure 71 ?

In the early history of "tide-water Virginia" thtt'
numerous drowned valleys afforded easier communication
between the settlements than was found overland througll
the forests of the coastal plain.

PLAINS AND PLATEAUS

157

101. The Fall Line A large river whose valley is

extended across a coastal plain often haa low falls or
rapids near the inner margin of the plain, which detennine
the "head of navigation," or uppermost point that can be
reached by vessels from the river mouth. A line drawn
through the falls on successive livers is called the fall line.

.peuke Buy, Mary] an

The falls occur where the river passes from a steeper slope
on the resistant rocks of tlie older land to a nearly level
channel excavated in tlie weak strata of the plain.

On coastal plains of a considerable breadtli settlements
near the mouth and at the head of navigation of the larger
rivers often develop into important cities. Tlie lower
city is the seaport of the region. The upper city bears
closer relation to local industries and traffic; it lies in
the midst of a diversilied region, with strong water power

jtor manufacturing the varied products of rock and soil.

' In Soudi Carolina, Columbia lies on the Congaree river.

' 158 ELEMENTARY PHYSICAL GEOGRAPHY ^^^

where it passes fi-om the older land to the dissected plain.
Charleston lies at the outer edge of the coastal lowland
on the widened course of a small river where the tide
comes in from the sea.

The fall line along the inner margin of the Atlantic coastal
plain of the United States is marked by important cities on
nearly every lai'ge river that crosses it. Trenton, Philadel-
phia (at the falls of the Schuylkill), Richmond, Ealeigh,
Camden, Columbia, and Augusta are all thus located.

The origin of the forces sufficient to deform the crust
of the earth and to elevate or depress a coastal plain is not
well understood. It is necessary that the student of
physical geography should recognize that elevation and
depression have actually taken place, and should under-
stand the importance of such movements in controlling
the forms of the lands and the conditions of their inhab-
itants ; but the processes that cause such movements must
be left to the more advanced study of geology.

Coastal plains, narrow or broad, belted or embayed, occur
along parts of the border of different continents. They
resemble more or less closely the examples here g;iven.
The coastal slope of Guiana and the plains of Patagonia,
Soutli America, belong in this group of forms.

102, Inland Plains Tlie Great plains of the central

United States slope gently forward from the Rocky moun-
tains. They are formed of many layers of sands, clays,
and gravels, washed from the mountains and now lying
one over the other, many hundred feet in total thicknesB
and nearly horizontal. Some of the layeis were deposited

PLAINS AND PLATEAUS 159

'hen the region was below sea level j some were spread
over the uplifted sea bottom by rivers when the region waa
too low to he dissected.

The plains are now high enough to he more or leas
dissected by streams and rivers whose valjeys vary in
depth and width ; hut the upland spaces between the val-
leys often preserve a comparatively even surface over
large distances. In some districts, vast areas stretching
ferther than the eye can reach are monotonously even
;ftnd almost as uniform in soil as in surface. In other dis-
;tricta, valleys are deeper and closer together, and the
-spaces between (hem are made hilly by the branching
Iravines of side streams.

I Within the United States the Great plains are treeless
Ifor 500 miles east of the Rocky mountains, except on
jcertain hills and bluffs which occasionally rise above
khe general level, or in the valleys which sink below
St. The absence of trees is due to the dryness of the
jtlimate, and this in turn is due to the general course of
the westerly winds whose moistiu'e has been left on
the mountain ranges between the plains and the Pacific,
Agriculture is impossible in the drier southern parts
without irrigation. Farther north in Canada the climate
ia moister, and the plains are forested. In still higher
latitudes the surface is treeless; the warmth of summer
melts only the upper part of the soil, and vegetation is low
and stunted.

The treeless plains possess little mineral wealth, and they
' we no forests to supply lumber; henee they cannot
djecome a closely populated manufacturing legion ; but they

160 ELEMENTARY PHYSICAI, GEOGRAPHY

have a more or less abundant growth of herbage, which
once supported herds of countless buffaloes. Now that
the buffaloes have been killed off, their place is taken by
cattle which range over the plains, wandering back and
forth over the uplands between the valleys that they visit
for water. A number of railroads traverse the plains and
carry, among other things, many cattle to eastern markets.

The plains of weetern Siberia resemble the Great plains
of the central United States. They slope gently awaj
from the mountains of central Asia, They have a mod-
erate altitude above sea level and preserve a generally
even surface over hundreds of miles. Marshes and shal-
low lakes lie in faint depressions, as if the hollows in
original surface of the plains had not yet been drained by
river action. The narrow valleys ai'e few and far between;:
they can never be cut deep while the region stands low,*
and they have not yet been worn wide.

The more northeni part of these plains is treeless because
the ground is frozen. The central part is forested; but,
south of latitude 50° to 55° the plains have a light rainfall
and are again treeless ; clothed with thin grass in summer ;■
cold, barren, and wind swept in winter.

The treeless plains have long been the home of wander-
ing tribes, whose wealth is not in fixed possessions, but in
hei-da and flocks driven from place to place for pasture.
The people live in tents and move about without definite
limits to their lands. On account of their wandering
habits they are called nomads (wanderers). Every i
is necessarily a horseman, skilled in nearly all the arts of a
wandering life.

k.k^

PLAINS AND I'LATEAUS

103. Belted Inland Plains. — In Wisconsin, far inland
from the ocean, tlie northern part of the state is occupied
by ru^ed higldands of resistant rocks. Adjoijiing on the
south and east are plains and uplands arranged m belts.
their rock layers sloping gently aw.iy fmiii the highlands

and lapping one b»^^ . —- ^ y v^^ ,

over another like ^^^S. I / '-v ^ / Lj

shingles

of the
id rocks are
found in the lower
members of the over
lapping strata; nu-
merous marine fossds,
like corals and shell-
fish, occur in man\
layers. All the lab-
els are well consoli
dated ; the firmer
ones form belts of
hilly uplands, between which the weaker layers are worn
down to lower plains.

Althougli the sea may now be a thousand miles away,
the belt^ of upland and plain are easily seen to be similar
to the belted coastal plains already described, while the
rugged highlands are the older land from which the sti-ata
of the plains and uplands were long ago derived.

This is an ancient coastal plain ; that ia, a region that
began ita existence as a coastal plain ages ago in the
earth's history, and that now stands in the interior of the

Fia 74 Ancient Coastal Plain of

162 KLEMENTARY PHYSICAL CKOGRAl'UY

continent because successive uplifts have broadened tho
con'tinental surfiice.

Belted inland plains, similai' to the example in Wiscon-
sin, occur in many parts of the world, usually presenting
a succession of hilly uplands and intermediate plains
ilar to those here described. Good examples are found
in south-central England and in northeastern France.
They all enjoy the advantage that comes from diveraity of
form and products and from the resulting variety of occu-
pations that they support.

104. Plateaus When plains stand at a considerable

height above the sea level they are called plateaus. No defi»?
nite limit of height can be given to separate the two classes
of forms. In elevated regions the lower parts may be called
plains, even though they are more than 2000 or 3000 feet
above sea level; in low regions the higher parts may be called
plateaus, even though not higher than 1000 or 2000 feet-
Plateaus are sometimes traversed by deep and narrow
valleys or canyons, branching in various directions. The
canyons are cut down to a great depth by their streams
because the plateau surface stands high ahove baaeleveL
Plateaus are generally buiit of horizontal rock layers of
various kinds, whose edges are well sliown in the canyon
walls. In Figures 75, 76, and 77 a deep cut is imagined
across the front of the view, so as to show more clearly the:
rock layers that crop out in the canyon walls. The brond.
uplands between the canyons have a comparatively even
surface across which it is easy to travel, but the deep
ganyona are almost impassable.

k-L

PLAINS AND PLATEAUS

163

The walls of the narrower canyons consist of a sueeeasion
of cliffs and slopes, oft^n too steep to be climbed. The cliffs
are formed on the hai'd resistant layers, which are strong
enough to stand witli a steep face ; the slopes are formed on the
which are more easily weathered back to a slant.

The slopes are covered with coarse ^fr^
rock waste, or talus, weathered from £
the cliffs above. The rock wast* weathers and falls from
each cliff, and rolls, washes, and creeps down each slope to
the top of the cliff next below, where it f lUh a^in shatter
ing to fragments ; at last it reiches the stream where its
finer parts are rapidly washed away Tlnii the thlfn and
slopes wear back or retreat, and the can>on widens

As a canyon widens, a platform or bench is formed on
the top of the stronger cliffs ; it is then often possible to
descend into the canyon by climbing down crevices in the
cliffs, from platform to platform.

1G4

ELEMENTARY PHYSICAL GEOGRAPHY

Point out the cliffs, slopes, &ii<l platforms of the canyon irallBiii
FigUTBS 76 and 77. Where are the highest cliffs, tlie longest slopes,
the broadest platforms? Which layers, shown in the front ot the
digram, are resistant? Which are veak?

The Blow creeping of waste down the slopes of the valley
sides is caused by very slight movements of the fragments
iind particles as they wami by day and cool by night, rs'

FiQ. Tti. Diagram of a Narrow CaQ;<

they are wet by rain and dried in fair weather, or as they

are moved by the freezing and thawing of films of water
between tliem. The movement is more noticeable on ateep
slopes, but it does not cease even on the gentler slopes,

The' slow downhill creeping of weathered fi'agments,
aided by the surface washing of fine particles in wet
weather, is the cliief means of moving waste down from
the high ground to the streams in the valley bottoms.

As the canyon is erotled by the main river, ravines are cut
in the canyon walls by streams that rise on the plateau.

PLAINS AND PLATEAUS

165

The deeper the main canyon is eroded, the deeper the
side ravines are worn downt and the more the plateau is
diBsected. Yet in the stage shown in Figure 77 the great
work of wealing away the plateau is only well begun.

The lofty plateaus of northern Arizona are traversed from
east to west by the Grand canyon of the Colorado, from
4000 to 5000 feet deep. The dry climate of the plateau

W^-

5^^^^==

■I

^^^

Fia. TT. Diagram ot a Widened Cannon

makes v^etation scanty. The I'egion offers no temptation
to settlement, however marvelous it is to the explorer.
Much of it is desolate, occupied by a few Indians, who
subsist by " cultivating little patches of com, gathering
seeds, eating the fruits and fleshy stalks of cactus plants,
and catfihing a rabbit or lizard now and then; dirty,
squalid, but happy, and boasting of their rocky land as
the very Eden of the earth."

The great elevation of this plateau pennits an unusual
de^ttb of canyon cutting. The massive sti-ong luid weak

Ef.KMENTARY PHYSICAL GEOGRAPHY

Stnitii of which the plateau is built produce strong cliffs
and long talus elopes on the canyon walls. Far down in
the bottom of the great trench runs the tawny Colorado,
turbid with waste that is showered from the walla in rocky
avalanches or swept in fi-oni side canyons by cloud-burst
torrenta. The water, bearing abundant waste, is still rasp-
ing down the rocks in its falls and rapids. Deep as the
canyon is, it has been cut down only by the river. There
is no indication of clefts or fractures along the river cooise.

Unlike most great rivers whose valleys serve as paths of
travel, the Colorado is almost inaccessible along its canyon.
Only one exploiing party has successfully gone down tha
canyon, and theii' narrative is a wonderful history of sciea-
tific adventure. When their boats once entered the canyon,
retreat was impossible against the swift cun-ent. Escape
by climbing the walls was hazardous. To descend the rivet
was easy on its smooth stretches, even tliough hemmed in by
great chfEs ; but cascades plunge over ledges where the most
resistant rock layers are not yet cut through, and rooty
rapids obstruct the eliaruiel where side canyons deUver
heaps of bowlders to the main river. After many perils
the party canie out to the open lower country on the west.

Plateaus interrupteil by narrow canyons are, as a rule,
occupied only on their upland sui'face. The elevation of
the upland is an advantage in the torrid zone, where the
high temperatures at sea level are willingly exchanged by
civilized races for a more moderate temperature at altitudes
of sevcRtl thousand feet. But in the temperate zone a
high plateau is at a disadvantage from the rigor of its
winters, as well as frem its difficulty of access-

PLAINS AND PLATEAUS 167

The canyonlike valleys are obstacles to movement ; they
serve as barriers (except to birds and winged seeds) between
the uplands on each side. They are seldom inliabited,
unless by the people of a persecuted tribe, who sometimes
take refuge as "cliff dwellers" in the recesses or caves
that are often excavated between cliff base and talus top.

105. Dissected Plateaus. — The rugged uplands that
extend continuously from New York to Alabama, known
as the Catskill, Allegheny, and Cumberland plateaus, may
here be treated together under the second name. The
whole region is occupied by inountainhke hills and spurs,
built of nearly horizontal rock layers and separated by
numberless deep valleys that have been eroded by the riv-
ers and their branching streams. The hilltop view gen-
erally discloses a rather even sky line, which may be taken
to mark a plateau surface that once extended over the
whole region, before the branching valleys were carved.

The Allegheny plateau is now thoroughly dissected by
its streams. It is evidently in a more advanced stage of
cliange than a plateau that has only a few narrow canyons.
The altitude of the original upland in West Virginia
(roughly 2500 or 3500 feet) has been great enough to per-
mit the erosion of valleys 1000 feet or more in depth;
hence some of the plateau remnants fairly deserve the
popular name of " mountains," locally apphed to them.

Many resistant sandstone layers stand out in cliffs from
ten to fifty feet high. As the layers are nearly horizontal,
the cliffs run in bands around the spurs of the great
hills, but are usually hidden by the heavy forest that

168

ELEMENTARY I'HYSICAL GEOGRAPHY

covers much of this region. The weak strata occupy the
intervening slopes, covered with a thin stony soil and sup-
porting forest trees. The liilla and spurs are all very
much alike, for they have been
dissected by similar streams.
Every side valley resem-

its neighbors ;
all the members
of a local tribe
of

streams X o "tn v i " ■■ !' Y ''"'"'""*/ ff JX"""'/cascade

'down over

'the same

' number of fall

n iking strata in

"■ their de spent to tiie

1 „ei ii\ers

In contnst to the previouB

\ imple this district has nearly

everywhere loht its once continuous

''uphnd surface and is now transformed

' into % well-dissected hiH and valley country

A great part of the surface consists of hillside

slopes. Drainage is not delayed on extensive

mi. .1,' .. uplands ; but at times of rain or winter thaws
The Allegheny .

Plateau water is quickly shed from the hills, and the
main streams rise rapidly in destructive floods.

The forests retard but do not prevent the wash of waste
from the steep slopes ; a great load of waste is delivered by
the side streams to the rivers.

PLAINS AND PLATEAUS

,169

What parts of what atatea are occtipied bj the Allegheny plateau 1
Which state has the greatest part of its area in the plateau? What
cities can yon name in that state? How far is it from the Catakill
mountain district to the Cunjberlaud plateau district?

As a whole, the Allegheny plateau m so nigged that its
population is small, being geuemlly found on isolated farms

upon the disconnected uplands, in viUages and occasional
small cities in the valleys, or gathered about mines or
other industrial woi-ks. The isolated hilltop farmers can-
not afford to construct and maintain good hillside roads ;
it ia difficult to haul upland products down bad roads to
village markets or to railroad stations, and it is doubly
^fBcult to haul supplies up to the farms. Life on the
uplands is laborious.

The hillsides are generally too steep for cultivation ; if
cleared, the soil is rapidly washed away. Wild animals,

[ 170 ELEMENTARY PHYSICAL GEOGHAPHY

L aurn

Bach as deer and bear, almost exterminated from the lower
country on the east and west, still find refuge here ; smnll
game is abundant, and hunting is almost as miicli nf w
occupation to the " mountaineers " as farming.

The forests supply lumber to the more thickly settled
communities on tiie east and west. The numerous coal
seams (vegetable deposits in ancient marshes, now membera
of the great series of horizontal strata that build the
plateau) are well exposed on the sides of the deep-cut
valleys, and are now extensively mined. Iron ore occurs
in certain strata. Rock oil and natural gas are found by
boring deep wells. It is chiefly in eoimection with the
industries dependent on these impoi-tant products .that a
larger population is to-day attracted to this rough country.
In the earlier history of the United States the dissected
Allegheny plateau was (excepting the Nortli Carolina
mounbxins) the most formidable barrier between the Atlan-
tic coastal plain and the open prairies of the Ohio valley.

Intercourse and traffic are still so difficult in the districts
of stronger relief, away from the lines of travel, that the
people of the Allegheny plateau are slow in acquiring the
ways of civilization. Family feuds ivre still maintained
among the " mountjiineers " of West Vii^inia and Ken-
tucky, As the upliinds decrease in height westward, and
the valleys become more open toward the Ohio river, popu-
lation increases ; but Pittsburg is a city of exceptional size
in this region. Its growth in early years was favored by
its position with reference to the lower Ohio valley, and in
later years by the great stores of mineral wealth in the
surrounding countiy.

PLAINS AND PLATEAUS 171

106. Mesas. — Broad plains of gently rolling surface,
drained by streams in wide-open, flat-jjoored valleys, are
sometimes overlooked by flat-topped "table mountains"
of horizontal rock layers. Neigliboring«tables are of nearly
uniform height, each one being capped by the same kind
of cliff-making rock layers and flanked by a sloping talus.
In the western United States tables of moderate height are
often given the Spanish name mesa (table ; pron. may-sa);
while the smaller mesas are known by the French name
btitte (target or l^vndmark; pron. bewt).

Mesas and buttes of -this kind are all that now remain
of a plateau that once spread far and wide over the region.
The open space between the mesas has been produced
by the widening of the valleys, so that their floors now
occupy a great part of the surface. The original level of
the plateau may have been much higher than the tops of
the mesas, for the uppermost strata may now be com-
pletely washed away. A region of this kind represents an
approach to what may be called the old age of a plateau,
when even the mesas will be worn aWay, leaving an
unbroken plain. It is very unlike the youth of the plateau,
when the uplands were broad plains and the valleys were
narrow canyons.

The plains of western New Mexico are surmounted by
numerous mesas or plateau remnants. Settlement here is
chiefly limited to the lower lands. The isolated mesas and
buttes, rising several hundred feet above the plains, are
generally uninhabited.

The mesas of an old plateau are not, like the canyons of
a young plateau, serious obstacles to travel; for while

?72

ELEMENTARY PHYSICAL GEOGRAPHY

canyons continue for long distances and are uverywliere
difficult to crosfi, niesas are generally of moderate lengtli,
and miiuy broad passages are opened among them. They I
are occasionally occupied as natui'al citadels by barbnrfm I
tribes.

One of the most remarkable remnants of an old platean I
IB the 80-Ciilled Enchanted mesa of western New Meuco. I

Fiu. so. The Enchanted llesa, New Mexico

It rises more than 400 feet above the surrounding plain,
and although no longer inhabited, it was once occupied by
a small tribe of Indians, who found safety on its almost
inaccessible summit.

Other mesas in New Mexico and Arizona are atill
occupied by Indians, whose compact groups of houses on
the upland cannot, at a little distance, be distinguished
from the rock walls of the cliffs. The Indians cultivate
small patches of com on the lower ground, but they have
not ventured to IniiUl villages tliere for feai' of attack from
; more warlike tribes.

PLAINS AJJD PLATEA'

III. the interior of Britieh Guiana gigantic renin:nas <>i nn
old plateau rise above the suiroundiDg lower country. Huge
mesas are rimined round by almost inaccessible eliffa that
stand above long talus slopes. One of the higliest is Roraima,
whose broad table is more thim 2000 feet above its base. It
18 uninhabited and until ruentlj had never been ascended

!■ a 81 Broken Plateaus

107. Broken Plateaus. — The plateaus of northern Ari-
zona, of which the Sheavwits already desci'ibed is one,
stand in a curious relation to one another. East of the
Sheavwits comes the Uinkaret, presenting the same upland
(diversified by volcanic cones and lava flows), and expos-
ing the same succession of cliffs and talus slopes in the
<»nyou walls; but the Uinkaret stands about 1800 feet
liiyher than the Sheavwits. The two are separated by a
tigli and ragged cliff, or escarpment (CA, Figure 81),
sQown aa Hurricane ledge, facing westward. .

174

ELEMENTARY I'HYSICAL GEOGRAPHY

The section exposed in the cauyon (A, Figure 81)
shows that the ulift' stands on the Hue of a great noi-tii-
aiid-south fracture, which divides the whole mass of
strata into two blocks, the eajstern block (Uinkaret)
being lifted nearly 2000 feet higher than the westeni
(Sheavwits). Several other similar platean blocks arc
found in this region. The displacement of the bloeks is

,■ Ll-Jj:.

:ted Faolt Cliff

clearly represented in the section on the right front of the
diagram, Figure 81 , under the letters D, B, E.

The western boundary of the Sheavwits plateau {FD,
Figure 81) is one of these cliffs of displacement, 2000 or
3000 feet high. It is cut by gigantic ravines, from which
great volumes of rock waste are ■washed out.

Fractures of this kind, on wliioh adjacent blocks of land
are displaced, are called faults. The cliffs that originate
on the broken face of the uplifted blocks are called fault
cliffs. They are in time more or less worn back by |

■weathering and by the growth of ravines, such being the

present stage of Hurricane ledge; and they may then

be called dissected fault cliffs.

The forces by which the plateau blocks have been

broken and lifted have not been fully explained. It is
probable that violent earthquakes accompanied the produc-
tion of the fractures, and that the displacement of the
blocks was accomplished by many small movements, each
causing a moderate earthquake.

QUESTIONS
Ssc. 96. Describe the natural proceasea in operation on a moun-
i.diatrict bordering the sua. Consider the relation of such a
habitation. Give an example.
Describe a narrow coastal plain. Describe its valleys and
,Yines. Explain their origin. What can be inferred
M to the future form of such a plain? as to its past form ? How
eu the origin of such a plain he accounted for? Define baselevel,
the relation of rivers and vaUeya to baselevel. Describe
coastal plftin in Scotland ; in Oregon ; in Mexico.
Describe a broad coastal plain. Wliat is meant by relief V
the coastal plain of the South Atlantic States as to form ;
U to soil; as to industries. Why are its soils arranged In belts?
Compare it with the narrow coastal plain ot Scotland. What
products are derived from it?

99. Describe a belted coastal plain. What is the origin of ita
'wm? What is a cuesta? Describe the course of the streams with
leapect to a ciiesta. Describe the belted coastal plain of New Jersey.
100. Describe an embayed coastal plain as to hills, valleys, and
bays. Explain its origin. How has the depression ot the region
iffected the form of the coast line? Descrihe an example of this
tJusB. Describe its effects on the distribution and occupation of its
population ; oa the location of roads, villages, and cities.

176 FXEMENTARY PHYSICAL GEOGRAPHY

Where maj fulls be espected in rivers that orosa coastal
plains? What is the cause of the falls? What is the fall line?
Where are cities likely to he situated on. the rivers of coaata! plains!
What cities lie on the fall line ot the Atlantic coastal plain?

102. Describe the Great plains of the central United States aa to t
origin, form, chmate, vegetation, and industries. Describe ttie
eEtension of these plains into Canada as to climate and vegetatioi
Describe the plains of western Siberia as to form, climate, and popn- I i
lation. Why are the valleys in these plains shallow? What ie
the relation between nomads and inland plains?

103. What is a belted inland plain ? Describe an example from
Wisconsin. Explain its origin. Where may some other inland
belted plains be found?

104. Compare plains and plateaus. Describe a canyon 8
form and origin. Compare the form of the canyon walls as shown
in the diagrams of a narrow and a widened canyon. ^Explain tli^
differences. What is the relation of strong and weak rock layers to
form? Describe the movement of rock waste in a. canyon. Describe
the plateaus of northern Arizona. Describe the Colorado river
its canyon. Why is it difficult to follow the river? What is the
value of plateaus to habitation? of canyons as barriers?

105. What is a dissected plateau? Describe the Allegheny plateau
as to location, extent, altitude, and form. Describe the hillsides;
the streams; the drainage; the industries; the products of this
plateau. What is the condition of its people?

106. Describe mesas and their surroundings. How are n
formed? Compare a mesa and a canyon. Compare the plateaus of
northern Arizona, the dissected Allegheny plateau, and the mesa
district of New Mexico. Describe the Enchanted mesa; Eoralma.

107. What is meant by broken plateaus? Describe the broken
plateaus of northern Arizona. How are they separated? What is
fault? a fault cliff? a dissected fault clifl? What is the relation of

' earthquakes to broken plateaus?

■ CHAPTER VI
MOUNT AlHS

108. Mountain Ranges. — The peaks and ridges of moun-

tains are generally grouped in Lelte of mucli greater length
than breadth, called mountain mnges. When several i-anges
grouped together they constitute a mountain chain.
:e plains and plateaus, in which, aa has been stated in
preceding chapter, the rock layers are nearly horizontal,
mountain ranges are belts of disordered structure in the
earth's crust. Sometimes the strata are broken, displaced,
and tilted as if gradually disturbed by some great uplifting
force from beneath ; sometimes the strata are bent and
folded, as if slowly compressed by some irresistible crush-
ing force fi'om one side,

The origin of the forces which produce mountains is
not fully understood. One of the most ingenious and
satisfactory theories accounts for many ranges as great
disoi-derly folds formed in the crust of the earth, which
is thought to wrinkle here and there as it very grad-
ually settles down on the slowly cooling and contracting
interior.

Streams carve deep valleys in the uneven surface pro-
duced by mountain upheaval. Mountains aa we see them
are therefore the result of deforming forces which slowly

|17S

FXKMENTARY PHYSICAL GKOGRAIMIY

raise the mountain belt to great height, and of eroding
forces wliich still more slowly wear down the uplifted bell
by cai'ving valleys in it.

Mountain Peak

109. Block Mountains. — In southern Oregon and the

a<ljoining parts of California and Nevada there are many
long narrow mountain ridges, extending about north ani
south. Each ridge is a few miles wide, ten to forty miles

MOUNTAINS

ig, and 1000 or more feet high. The ridgea are steep
iff-like on one side, of gentler slope on tlie other, and
i separated by flat trough-like depressions of vaiying
idth and depth. A general view of the country shows
* the entire region was once a plain, but that it has been
idually broken into long narrow blocks, and that the
Dcks are tilted one way and the other, so that tlieir
uplifted edges form the mountain crests.

Which block mountain is completely shown in Figure 84 ? How
does it end? (Note: the space included in the figure is too sniall
lo show the whole length of most of the mountains ; the northern
part of some and the southern part of others are cut off.) Describe
tt large block mountain; its crest line, its cliff face, its back slope.
Where could it be best ascended 7

Some of the ridgea still preserve the form of the tilted
blocks, hardly changed by weathering ; their sloping backs
are smooth; their cliffed fronts have little talus at the
base. Others have shallow gullies worn down the hack,
while the cliffs are indented hy ravines, and every ravine
has a fanlike deposit of rock waste spread out beneath it ;

nso

ELEMEKTARY THYSICAL GEOGRAPHY

between the (ana the cliffs liave a distioct talus slope at
their hase. Yet the mountain blocks of Oregon are, on
the whole, BO little worn that they must have been hroten
and tilted recently in the earth's history.

Earthquakes are not infrequent in this region ; hence it
is believed that the tilting of the blocks is still in progress
from time to time ; a movement of even a few inches would
suffice to cause earth tremors, while a sudden start of a foot
or more would produce
a violent and destructive
shock for many miles
around, gradually fad-
ing away at greater dis-
tances. There is no sign
that volcanic action has
any connection with the
fractures and earth-
quakes of this region.
The drainage of the
block mountains is veiy
simple, for the streams follow the slopes produced by the
tilting of the blocks. The smaller wet-weather streams flow
down the slopes of tbe ridges. Larger streams flow along
the troughs in the direction of their slant to the deepest
depressions, and there form shallow lakes and marshes.
The finer waste from the ridges is spread evenly over the
lower parts of the troughs, concealing their rocky floor.

Certain features of the region depend on its arid climalB-
The rainfall is light (fifteen inches or less a year), for the
Sierra Nevada and Cascade ranges on the west take most

of Southern Oregon

MOUNTAINS 181

of the moisture from the Pacific winds. Few of the lakes
are filled to overflowing; Uiey dischai^e their water supply
by evaporation into the dry air. Most of the lakes are
therefore saline, and the plains of fine waste about them
are barren.

In dry seasons the lakes shrink ; some of them disappear,
leaving smooth floors of snn-baked clay. The bottom of the
troughs elsewhere and the lower slopes of the ridges are
clothed with bunch grass and sagebrush ; the ridge slopes,
receiving more rainfall than the lower lands, support
scattered cedars, and the higher crests bear forests of pine

.d spruce.

Although the ridges are of moderate height, they repel
the few settlers in the region, whose ranches are all found
in the troughs. The thin grass supports scattered herds
of cattle, and the streams suffice for a little irrigation.
Thus even in these low young ridges the effect of moim-
tains on climate, distribution of vegetation, and location
of settlements is well shown.

110. Dissected Ranges. ^ In Nevada and the adjoining
parts of California and Utah there are many north-and-
Bouth mountain ranges from twenty to eighty miles long,
and from five to twenty miles wide. Their summits rise
irom 5000 to 7000 feet above the plains. Their crests
are notched and uneven ; their slopes are varied by well-
carved spura between deep valleys. The troughs between
the ranges contain long slopes of gravelly waste that have
-spread out from the valleys when the streams are flooded.
As compared with the ridges of southern Oregon, these

lS-2

ELKMENTARY PHYSICAL GEOGRATHY

ranges ai"e larger and more dissected. They possess more
of the beauty and variety of form generally found in

raoun tains.

The ranges of Nevaila, like the ridges of Oregon, seem
to have been formed by the uplifting of long blocks of the
earth's cruHt ; hut in Nevada tiie lilocks must have

lai'ger and the uplifting greater; and the uplifting must
have begun eai'lier than in Oregon, for the work of dis-
section by streams is here much further advanced. The
ranges of Nevada are thoroughly or maturely dissected.
Yet, as in Oregon, occasional earthquakes show that the
mountains are still growing.

The higher ranges in Nevada exhibit more distinctly
than the smaller ranges of Oregon the lower temperature,

MOUNTAINS 183

with greater cloudiness and rainfall, that prevails on the
mountains as compared with the plains between them.
The rainfall on the plains is light, hut storm clouds
often gather round the peaks while the sun shines else-
where. When the clouds dissolve, the mountains have
been refreshed by rain or whitened with snow, while the
plains may be as dry as before, except where the turbid
flooded streams rush out from the mountain valleys. The
streams generally wither away on the gravelly plains.
Settlements in Nevada are therefore commonly limited to
a belt around the mountain base, where the streams may
irrigate flelds. Some of the ranges contain valuable ores ;
hence mining towns have sprung up in their valleys.

111. Folded Moimtains.. — The Jura mountains, along
the border of France and Switzerland, occupy a belt of
countiy where the rock layers, once horizontal, have been
slowly pressed into a aeries of wavelike folds. The moun-
tains consist of a number of parallel ranges and valleys
trending about northeast and southwest. Each range con-
sists of a series of rock layers bent upward like an arch ;
each valley is underlaid by the same series of layers bent
downward like a trough. Some of the uppermost layers
have been weathered off from the creat of the arches ;
the edges of the harder layers remain in flanking ridges.
Waste fpom the arches ha.s accumulated in the troughs,
flooring them with gravel and sand.

The rock layers of these mountain.s contain sea fossils ;
the layers must originally have been horizontal strata on
the floor of an ancient sea. Since then they have gi-aduallj

184

ELEMENTARY PHYSICAL GEOGRAPHY

been pressed and folded into their areh-aud-trough striic-
ture by a powerful side pressure.

The drainage of the Jura mountains is, for the most part,
like that of the Oregon ridges in following the slopes of
the deformed surface. Short streams run down the sides
of the arches, cutting ravines on the slopes, as shown in

FiQ. ST. Diagram of the Jui

the unshaded foreground of Figure 87 Latger streams
gather on the trough floors and estipe at one end or the
other as opportunity offers Here and there a stream cuts
across an arch, wearing a deep gorge from one trough
valley to the next, and exhibiting the arched striicture, as
in the middle ridge of Figure 87.

Where are the Jura mountaina ? How niony archfia sre shown io
Figure 87 ? How many troughs ? What is their trend ? How mm}
erosa valleys? If yon were tra.veliiig there, where would you go tn

MOUNTAINS 185

' Be« the arched rock layera ? Where Joes the topmost layer lap over
an arch? What forrnB result where the topmost layer has Iwen
partly worn away? Describe the course of some of the small streams
that rise on the top of an arch.

Aa in all mountains of distinct relief, the form of this
range exercises a strong control over the distribution,
occupation, and movement of the population. The valley
floors are well settled ; villages often lie near the mouths
of transveree gorges. Roads are generally limited to the
lengthwise and crosswise valleys. Byways and footpatlia
lead to the upland fields and pastures. Little villages are
sometimes found on the tops of the broader arches. The
steeper slopes are generally forested.

112. Lofty Mountains. — Lofty mountain ranges, like cer-
tain parts of the Rocky mountains, but better represented by
the Alps, the Caucasus, and the IIimalayas,exhibit a remark-
able variety of peaks, ridges, ravines, and valleys. Their
higher central peaks usually consist of the most resistant
rocks, surrounded by slanting layers that rise in great ridges.

These majestic forms usually depend aa much on the
deep erosion of great valleys by streams aa on their lofty
uplift. Unlike the simple tilted blocks of Oregon, or the
orderly folds of the Jura, the greater ranges show little or
nothing of their original form.

The discovery of marine fossils in the bedded rocks of
high Alpine ridges towaid the close of the eighteenth cen-
tury was received with great astonishment hy the scien-
tific men of the time. The occurrence of fossils in so
elevated a position was one of the first generally accepted
proofa of the changes that have gone on in the past, by

186

ELKMENTAKY THYSrCAL GEOGRAPHY

which the present form of the earth's surface has-been
fashioned. But not until the nineteenth century had well
advanced was it generally understood how much more the
form of lofty mountains depends on processes of land
sculpture than on forces of uplift.

113. Peaks and Ridges. — The height of lofty mountain
Bummita is due in great part to the uplift that the whole

oi the Central Alps

range has suffered, but in part also to the success of the
stronger rocks in resisting the attack of the weather, under
which the weaker rocks have greatly wasted away. The
waste that is shed from the peaks and ridges creeps and
washes down into the valleys, usually leaving the loftieat
summits bare and sharp. Deep valleys are eroded by the
streams between the ridges, and steep ravines are worn in
the slopes and spurs. Thus mountain forms are chiefly
due to weathering and stream carving.

MOUNTAINS

The bare rocky peaks and ridges, I'ismg into the cold
apper atmosphere, far above the limits of vegetation, are
silent deseiis. The stillness is broken only by the rush
of storm winds and the roar of rock falls and snowslides.
Not leas barren are the snow fields and the talus slopes
B higher mountain flanks, and the slanting reservoire
j- and snow in the upper valley heads, from which

Alpine Peak of Slautiug Layers

Blow-moving ice streams, or glaciers, creep down to the
lower valleys. The lower slopes are genei-ally forested.

Many suramite in the Alps are so sharp that they are
called needles or horns. They rise as almost inaccessible
peaks between the growing valley heads. Mt. Blanc, the
highest mountain of the range (nearly 16,000 feet), is of
domelike form with a heavy snoweap; it is not yet suf-
ficiently dissected by valleys to take the form of sharp
, fidges and peaks.

188 ELEMENTARY PHYSICAL GEOGRAPHY

The Selkirk range «f tbe Rocky mountains in Canada
has steep and bare sunuuite surmounting the long lower
slopes. Tlie slopes are covered with waste that is slowly
creeping and washing into the valleys, to be borne away
by the streams. Having an abundant snowfall, the range
beiira extensive snow fields and glaciers. In the Rocky
mountains of Colorado snow is less plentiful, snow fields
are small, and glaciers are wanting. Long slopes of creep-
ing waste cover the mountain flanks far up toward the
summits, as in Plate I ; craggy peaks of sharp form are
less common than in the Selkirks or the Alps.

114. Climate of Mountains. — On extensive plains the
climate — especially the temperature and rainfall — shows
little variation from place to place, being nearly uniform
for hundreds of miles together. On the average, one must
travel from thiity to sixty miles poleward to find a diffe
ence of 1° in mean annual temperature. The same differ-
ence is found on mountains by an ascent of only 300 feet
Many mountains rise so high that they receive snow
while rain falls on the surrounding lowei' lands. Lof^
mountains ai'e therefore usually clothed with enow on their
higher slopes.

Broad plains may have only a scanty rainfall over hun-
dreds of miles together. On mountains the rainfall rapidly
increases with elevation, although less may fall on very
lofty summits than at heights of from 5000 to 10,000 feet,
Not only because they are high, but also because they
receive inuoh i-ain and snow, high mountains are usually
the sources of lai'ge rivers.

MOUNTAINS 189

The small changes of form and climate over broad plains
make the conditions of life nearly the same over great
areas. A great diversity of form and climate is found in
mountains within small distances, and stroDg contrasts are
crowded close together.

115. Mountains as Barriers. — High mountains serve as
barriers separating the climates and the populations of their
opposite sides. The windwaitl (eastern) slope of the equa-
torial Andes has a moist climate because the damp winds
from the Atlantic, ascending and cooling, give forth a heavy
rainfall there ; the western slope has a dry climate because
the same winds, descending and warming by compression,
not only give forth no more rain, but eagerly take up what^
ever moisture they iind on the way. The eastern slope is
densely forested ; the western slope is for the greater part
a desert, except in valley floors watered by streams.

Moist winds from the Pacific give a plentiful rainfall
on the windward (westward) slopes of the Sierra Nevada
and the Rocky mountains of the United States. The same
winds, descending on the eastern or leeward slopes, become
in winter unseasonably warm and dry, evaporating the light
snow of the plains and laying hare the dry tufts of grass,
greatly to the advantage of the cattle feeding there. The
dry wind is called the chinook. A similar wind occurs
in the northern valleys of Switzerland, where it is called
the foehn.

The great populations of India and China, representing
different races, are separated by the lifimalayas and other
ranges in southern Asia. The two peoples are thus so

190 ELEMENTARY PHYSICAL GEOGRAPHY

well held apart that neither of them has had any important
iiiHuence on the other. Lofty mountain ranges thus rank
with the oceans in separating the inhabitants of the lands.

When low countries ou opposite sides of a high range
are occupied by different peoples the mountains commonly
serve as a natural boundary between them. The moun-
tain range as a whole may serve as a rough boundary
between uncivilized nations ; tut between civilized nations
the erest line dividing the rivers of the opposite slopes is
often accepted as a more precise boundary, as in the
Pyrenees between France and Spain, where the river
divide is generally adopted as the national divide.

When the river divide departs from the main range
that it was supposed to follow before the mountains were
explored, the boundaj^' question may give rise to dispute,
as recently between Argentina and Chile, where a number
of Pacific rivers rise on the pampas of Patagonia and cut
tlu-ougb the Andes in deep goi^es.

The difficulty of crossing lofty ranges gives great impor-
tance to the notches, or passes, in their central ridges,
through which travel and traffic may go with less effort
than over their peaks. The heavy snows of the winter
may close the passes for several months. In earlier cen-
turies, when the passes were traversed only by paths,
houses of refuge were often maintained on the summit bj
monks, as on the famous pass of St. Bernard in the Alps.

It is mostly within the last hundred years that well-
planned roads have been constructed over the chief passes
of various mountain ranges. The roads enter the moun-
tains along the larger valleys and then zigzag up the

MOCNTAINS

Bteeper slopes. They are carefully laid nut so as not to
eKceed a certain moderate grade, — about live feet iua hun-
dred. Certain passes are now crossed even by railroads,
tte ascent from the valleys being moat ingeniously made
by curves and "loops." Sometimes the last part of the
I ascent is avoided b}' tuniieling the ridge under the paas,
, it being cheaper in the long run for a railroad to bore
through than to climb higher.

When gold had been discovered in California and a new

I population was making its way there in 1849 and 1850,

the mountain ranges in the western United States were so

forruidable a barrier to travel (hat many of the emigrants

I preferred the long voyage by sailing vessel around Cape

Horn. Those who went overland suffered great hardships

in crossing the mountains by rough trails, and many died

I on the way. Since then the mountains have been care-

I ^Uy explored, the lowest passes have been found, and aev-

I ^fal railroad lines now connect the Central States with

I ''he Pacific coast,

I Mountains are often climbed for the exhilaration tliat
comes from ascending them, and for the glorious view over
the peaks and valleys that is gained from the summitp.
Clubs of mountain climbers have been formed in manj-
•Wuntries, They publish narratives of excureious in
tt'ountainoua regions. The ascent of very lofty moun-
™iii8, above 16,000 feet in height, is made difficult by the
thinness of the air so far above sea level. Fatal acci-
i^enta sometimes occur, especially when inexperienced
climbera try to make ascents of difficult peaks without
"ell-trained guides.

192

ELEMENTARY PHYSICAL GEOGRAPHY

116. Avalanches. — The heavy saowfall of winter often
overloads the snow banks on the higher slopes, and great
masses of snow slide down to lower levels. Summer melt-
ing and rainfall also cause slides, or avalanches (a-val, to tbe
valley). Sometimes the snow mass glides along the sloping
surface at a moderate speeJ. Sometimes it leaps from cliffs

Fig. no. Path of an ica Fall ir

e Alps

and falls with a terrible velocity to the valleys below; a
violent blast of air bursts outward from beneath, overturn-
ing trees hundreds nf feet beyond the reach of the snow.

Certain villages in Alpine valleys carefully preserve a
patch of forest on the slope above them as a protection
from avalanches. Roads and railways on steep mountain
slopes must here and there be covered in by long snow-
sheds, over which the snov? may slide without blocking or
injuring the road.

Heavy masses of ice are occasionally detached fro(»
glaciers that end on steep slopes, forming "ice falls-

MOUNTAINS 198

These are eyen more destructive than avalanches of snow.
An ice fall over 5,000,000 cubic yards in volume broke
from a glacier on the slope of a peak in the Alps in Sep-
tember, 1S95 (Figure 90; see Figure 89, from a photo-
graph taken before the fall). It slid down a steep slope
two and a half miles long, gathered about 1,300,000
cubic yards of rock waste on the way, and then rushed
across the valley floor, dashing far up the opposite slope
and falling back again, like a wave fvom a cliff. A bench
OQ the path of the sliding mass caused it to leap forwai-d,
clear of the ground ; then, as it fell, the air beneath was
violently driven away, blowing out fragments of ice and
rock and breaking down trees hundreds of yards distant
(shown by arrows turned to the right. Figure 90),

117. Landslides on Mountain Sides. — In deep and nar-
row valleys among mountains the side slopes are sometimes
cut so steep that great rock masses may be loosened from
the walls and slip to the bottom, forming landslides.

A landslide in the Alps in 1898 destroyed a few of
the houses on the edge of the village of Airolo, near the
Bouthern entrance to the great St. Gotthard tunnel. The
scar left by the falling mass is still distinctly visible high
lip on the mountain side ; the fallen rock, greatly shattered,
spreads forward toward the stream in the valley floor.
Had the slide taken a course a quarter of a mile farther
South, it would have destroyed much of the village.

In September, 1893, a great landslide occurred in the
deep valley of one of the upper branches of the Ganges in
t^ HimaUiyas. In three days 800,000,000 tons of rock

i;m

KLKMKNTARY PHYSICAI, UEOGRAPHY

fell with deafening Duifie. diirkeniiig tlie air with diist, leav- i
ing )i grent bare cavity wiUi steep walls seveml thousand
feet high to mark its source, aud building a dam neaily 1000
feet deep across the narrow valley floor. A lake gradu-
ally formed on tlie
upstream side of
(he dam and grew
to be four milea
lotig before it over-
flowed, aboutayeai'
after the slide.

In the meantimti
the danger that die
lake might burst
out in a great flood
being perceived bv
the British engi-
neers in cbaige of
the public works of
India, the bridges
in the lower valley
were removed;
safety marks were
set up on the vallev
sides, 100 or 200 feet above the ordinary river level, indi-
cating the height above which the flood would probably not
rise ; ajid a telegraph line was constructed down the v^ef
from the dam, to give prompt warning of the outburst

The flood occurred at midnight, August 26-27, 1894.
In four hours about 400,000,000 cubic yards of w^ter

The Laiiiislicle n[ Airolo, Switzerland

MOKNTAINS

195

were discharged, cuttiug down the dam nearly 400 feet,
flooding the valley to a depth of from 100 to 170 feet,
aud rushing forward with a velocity of 20 miles an hour.
Main- miles of valley road were washed away. Every-

vestige of habitation was destroyed in villages along the
Upper Ganges ; but so well was»the notice of danger given
that only one man lost his life, and that because he
would not heed the warning. Under a less intelligent
control, thousands of people must have perished in such a
catastrophe. The remains of many other landslides aiu
found in the valleys of the Himalayas.

196

ELEMKNTAIiV PHYSICAL GEOliRAPHV

118. Valleys among Mountains One of the strongeBt

characteristics of thoroughly dissected, lofty mountains is
the activity with which the rock waste is weathered from
the peaks and clifl's, moved down the precipitous slopes,

swept by fiooded torrents down ateep ravines, and wash*
by streams along the lai^er valleys and out upon tt
adjoining lowlands. The waste seemB everywhere to I
Btreaniing (as the long-lived mountains might say) do\«

MOUNTAINS

from the peaks and ridgea. The carving of valleys in the
mountains has been accomplished by the long duration of

these active processes for ages past.

The rock waste consista of angukr fragments as it falls
from the cliffs and creeps down the Blopea. The angles are
■worn off as the waste is rolled along in rapid Uirrent*i,
and after traveling thus for a few miles the fragmenta aj-e
well rounded, becoming smaller and smaller the farther
they are swept along the stream bed. The fine grains
that are worn off from the angles of the larger fragments
are borne along more quickly than tbe lai^r pebbles and
cobbles.

A torrent that receives much coarse waste from a steep-
sided ravine frequently sweeps so much of it into the main
ViiUey that it cannot all be carried away by the mi&ter
river. The coarser part of the waste then accumulates in
a conelike form, known as an alluvial fan, spreading with
even slope from the i-avine mouth into the main valley.

Alluvial fans have a steep slope when formed by small
torrents bearing a coarse and plentiful load. They have
a flat slope when formed by large streams with a fine-
textured load. They may grow to great size, with a
radius of five or ten miles, in large valleys.

Large fans drive the master river against the farther
side of its valley, where it undercuts the valley wall. The
fan still growing, the river may be obstructed and thus
required to spread over the valley floor upstream from
tbe fan, forming a shallow lake, while on the downstream
side the river descends in rapids over the coarsest bowlders
iM'DUght down by the torrent.

KIJCMKNTARY I'HYSJCAL GEOGRAPHY

How i.iaiiy fi.LJ« a
iiial«rinl come from?
Imve tbey ou the coil

B sliowu in Figure 947 Where has theif
Uow has it beeu brought? WbaX effect
re of the main river?

]

A torrent fi'equently changes ita course on a fan aDtl
enters the main river
at a new point. Two-
()i ean creek, a small
btieam in the Yellow*
btoiie Park, has built
a fan that formB it ■
pait of the conti-
nental divide. Some-
times the stream flows
on in eastern ladiuB
of the fan to Atlan
tic creek (Mishoiin-
Missiaaippi system)
aometmies on a west
ern radius, to Patifio
creek (Columbia bjb-
tem)

Villages ire often
built and helds are
cultivated on fans ol
laige Bi7e When the tonent of such a fan is turned on,
a new course it may flood fields and villages, causing rauca '
damage. A valley road crossing the fan is swept a\V^
where the torrent then comes upon it, while the briAS*
over the former channel is useless, now that the tont?^
has abandoned itf '

Flo 94 Alluvial Fans

hji.

!aent^ of this sort ai-e common m mountain regions.
0 ft stream entering a lake in Switzerland overHowed

with a stony flood fed by a landslip in the head

It laid waste a strip two miles long and over 300

ide at the forward end, covering it with a hiyer of

nud ten or twelve feet thick. Houses were pushe<l

place; a road and a railroad were buried The

.oftlmouri- l|K.^^VfV*r
Hxl was some- [1^ " ' i-" * \

o slow that the
in the fields in
if it was saved
y mowing. For
all travel had
jy boat on the
Che people who
n the fan had

GOiDpensation
X losses in car-

iie thousands of visitors to and fiTjm the scene of
aster.

Btimes the steep toiTential headwaters wash so much
from their ravines into the lower valley that tlie

unable to carry along all that it receives. Some
waste then gathers on the valley floor, gradually
t higher and higher, as in Figure 95. Valley floors

form are much more easily traveled upon than
he side slopes descend directly to the river bank,
r mountain waste has in this way gathered in a val-
B corisiderahle de]>th, sometimes measuring seventl

KLEMENTARY PHYSICAL GEOGRAPHY

hundred feet, there may be a decrease in the amount of
waste supplied by the headwater streams. This change
will peraiit the river to turn part of its strength to sweep-
ing away some of the waste in its bed, and thus to deepen
its channel. As more and more waste is thus removed,
a new valley cornea to be opened in the flat valley floor,
remnants of which then stand in benches or terraces above
the new level of Hie
river, as in Figure 96.
Terraced valleys of
this kind are not un-
common in the Rocky
mountain region.
Some of the inner
valleys of the Hima-
laya mountains have
gravel terraces over
/alley l^OO feet high.

119. Lengthwise and Crosswise Valleys. — When a liver
has cut down its valley floor to as moderate a slope as the
load of waste that it has to carry along will allow, it may
still wear away its banks, first on one side, then on the
other. Thus in the course of time the river broadens the
valley floor. This is especially true in a valley that is
worn down along a belt of weak rocks parallel to the gen-
eral trend of a mountain range, for these rocks weather
and wash away at a comparatively rapid rate.

The crosswise valleys, by which the rivers of the long
inner valleys find outlota through inclosing ridges, are

MOUNTAINS 201

often narrow and Bteep-walled gorges, for the ridge-
making i-ocks are resistant and weather slowly. The
floor of a crosswise or transverse valley may be hardly
wider than its stream; the walls rise steep from the
water's edge, leaving little or no room for a road or path
on either side.

It is chiefly in the broader lengthwise valleys that
tnountaiti peoples dwell. When the outlet valleys are
narrow gorges the outer world has for centuries been
i-eached only by passes over the inclosing ridges; but
modem engineering skill has sufficed to build and cut
roads and railroads through many gorges that were
impassable a century ago.

120. Earthquakes of Growing Mountain Ranges. — The

process of bending and breaking the rock structures
within a mountain mass is certainly very slow, but it
sometimes causes sudden snaps and slips of a few inches
or a few feet. Tremoi-a then spread in all directions
from the seat of disturbance, diminishing in force as they
advance. On reaching the earth's surface they are felt as
earthquakes, producing more or less destruction. Shocks
of this kind are comparatively common in and near most
d the lofty mountains of the world.

Earthquake tremors travel through the earth's crust with
great velocity, — from ten to forty mUes a minute ; but, as
in the case of water waves, the actual movement of the
leaking earth at any point may be only a few inches or a
few feet a second, backward and forward. The shocks
produced by earthquake waves are most violent at places

202

ELEMENTARY PHYSICAL GEOGRAl'HY

directly over the seat of chief disturbance, Tliey may
very faint, eaiuing no damage. They may be strong
enough to be felt violently over hundreds of squaiB
milea, less distinctly over many thousands, and very faintly
(by the aid of delicate instruments) all over the earth.

One of the greatest modern earthquakes occurred at
the base of the Himalaya mountains in northeastern
India in 1897. It was probably caused by some under-
ground movement of mountain growth. It foi-med sev-
eral fissures, displacing the land on one aide with respect
to that on tbe other, forming a step several feet high.
The vibrations of the shock loosened rock masses and
soil on steep slopes, causing many landslide.^, which left

MOUNTAINS

bhe hillsides bare and clogged the valleys. Tlimisands of
Forest trees and a great number of buildings in Uie central
irea were broken down by being swayed violently back
md fortli, although the movement was only a few inches.
Streams were obstructed and turned from their courses.

Fio. 9S. Laud Surface dUplaceiJ by hu Kurttiquake, Japun

Railroad tracks on the neighboring plains were thrown
out of line.

A violent earthquake occurred in Japan in 1891 by
which a deep fissure vras forined in the eartli's crust,
and the land on one side of it was lowered with respect
to that on the other, as shown in Figure 98.

Eai-thquakes of moderate violence are still frequent in
the Alps, occurring five or ten times a year. Five Gen-
tries ago (1348) a violent earthquake in the eastern

ELEMENTARY PHY&ICAI, GEOGRAPHY

Alps caused a great landslide by which a valley wks
barred across and a lake formed upstream from the slide.
Countless thousands of 'shocks must have been produced
during the long ages of mountain growth. The associa-
tion of earthquakes with the young tilt«d-bloek ridges of
Oregon, with the more mature mountains of Nevada, and
with vigorous ranges like the Alps and the Himalayas, is
a natural result of the continued disturbance or growth of
the mountains.

121. Human Life in Lofty Mountains. — Tlie people
who to-day dwell in the valleys of lofty mountains are
in many cases the descendants of races who formerly
occupied the adjacent lower lands, from which they
were driven by conquering invadeis. Inclosed valleys
among mountains serve as I'efuges, where pursuit is t*)0
difficult to be profitable. There the weaker race long
remains unmolested, holding little intercourse with the
outer world and preserving old foims of speech and old-
fashioned customs. The invaders occupy the neighboring
open country; they engage in traffic with other parts of
the worid and advance in new ways of living.

182. Subdued Mountains. — There are certain mountain
ranges of moderate height in which sharp peaks are aleent
and bold cliffs are rare. The slopes are of moderate steep-
ness, and rock waste covers them almost from base to
summit. Mountains of this kind do not reach upward
into a climatfi very unlike that of their base ; and if
not in a dry or a frigid region, they may be forest clad
to the top.

I earthquakes tbat are common in mountains of active
1 and the landslides that happen frequently in moun-
where the valley sides are still steep are rare or
■wn in these mountains of gentler form. Unlike
vigorous and !ofty younger forms in which uplift
rosion are still active, the rounded forma of these
ains express subdued strength, as if their Ingh
and ridges had been greatly worn away by the long-
ued attack of the weather. They may therefore be

subdued mountains,

! Blue ridge and other mountains of North Carolina
od examples of subdued mountains. No sharp peaks

into the sky. The summits generally rise dome-
. rounded outline. Heavy forests clothe their slopes,
dued mountains may still have so strong a relief
;he people living in their valleys preserve older
na than those of the more open lower country. This
a in the homespun clothing and in the primitive
ir of living of the North Carolina mountaineers.
! mountains of Wales make another group of sub-
forms, but more rugged than the mountains of North
na. Here remain some of the descendants of the
it Britons who were driven from the more open
ids of eastern and central England by Saxon and
ui invadei's, 1000 or 1500 years ago. The Welsh
ige, therefore, represents the original language of
n, while the Englisli language is a compound of the
I of the invading peoples from the continent. The
I highlanders are clannish because the clans have
ived in secluded glens among the Highlands.

206 KLKMKNTAKY PHYSICAL GEOGRAPHY

123. Worn-Down Mountains In certain parts of the

world ancient mountain i-.iugea have been almost com-
pletely worn iiway. Their disordered rocka, once rising in
lofty peaks and ridges, and perhaps beaiiug snow fields and
glaciei's, have been reduced to an almost plain surface, little
above baselevel and everywhere open to settlement. Li
lands of this kind ai'e called peneplains {pene, almost).

Pimitiiont Belt, Virgini;

The Piedmont belt of Virginia, between the Blue ridge
and the eoaatal plain, is in many respects an excellent
example of a worn-down mountain range. It is a pene-
plain, not monotonously smooth, but undulating in graceful
swells between gentle depressions. The soil is deep,
and fertile, and the district is very generally occupied by
fai-ma. The height to which the rock masses once rose
above the present surface ia reasonably estimated as at least
one mile ; it may have been two or three. The wearin]
down of these ancient mountains to the rolhng plain of
to-day hiis required an enormously long period of timi

It often happens that the plain surface of a worn-down,
mountain range is here and there surmounted by rounded'

MOUNTAINS

207

till In or low mountaina, lUUO or moie feiit liigh, composed
of the mobt rcbihtant rocks of tLe whole region. These
hills are the last remtiaDtf> of the mountains that once
toweied over the tsurface of to-day Sevenil hills of this
kind aie scatteied over the Piedmont plain of Virginia,
one bemg shown in Fii^me ^JM buch remnant hiilu and

lit, VicKinia

mountaina are often called monadnocks, after an excellent
example of their claaa in southwestern New Hampshire.

It is generally the case that old-mountain lowlands are
now uplifted above tlie position in wliich they stood when
worn down, so that they form plateauhJte uplands. Their
streams are thus revived into a new period of activity and
at once proceed to trench and dissect the upland.

The Piedmont Iwlt of Vii^nia now stands several hun-
dred feet above baselevel. It is cut across by a number
of active streams that flow in rocky, 8teei>sided valleys

208

ELESIENTARV PHYSICAL GEOGliAPUY

from 100 to 300 feet below the upland plain. It must
therefore lie supposed that this region has been somewhat
uplifted since its ancient mountains were worn down. It
is in the valley sides that the tilted rock stmctures in the
foundations of the ancient mountains are best seen.

Southern New Hampshire and Vermont, central and west-
ern Massachusetts, and all of Connecticut include many
uplands, above which occasional Iiills and low mountains

Tbe Upland ot New England, wltli Mt, Molinilnock in th>: (

IHstsncB and a Valley in the Foregronni

rise, and below which numerous open valleys are worn.
When an observer stands on the uplands the sky line is seen
to I)e comparatively even. If the valleys were in imagina-
tion filled up again to the level of the uplands, the worn-
down peneplain of the ancient mountains of New England
would be restored.

The peneplain does not now stand so low as when it was
worn down. It has been uplifted into a slanting position,
so that it slowly rises from sea level at Long Island sound
to a height of from 1400 to 1600 feet on tbe northern
boundary of central and western Massachusetts. The

MOUNTAINS

209

have been carved beciiuse the old lowland has been
lifted up. They are shallow near the coast, but deep (800
to 1000 feet) in the interior, where the upland is higher
above baselevel. They are compai-atively narrow where
the rocks are so resistant that they weather slowly, but
wide open where the rocks are weaker. The chief of
the wider valleys is that of the Connecticut liver, a

Fig. 102. VailKj

broad lowland excavated along a belt of relatively weak

The uplands have a scattered farming population, here
and there gathered iti small villages. The larger valleys
contain many villages and cities, and guide the chief roads
and raUroads. Here is gathered the more active manu-
facturing and coramereial population of New England.

!10 ELEMENTARY PHYSICAL GEOGRAPHY

124. Old Mountain Ridges. — The Allegheny mountaiiw
of I enns)l\ una and \ ij^nii consist of a number cf nearly
parallel i Iges with remarkably even ciest Imes here aud
there cut down hj the notches or water gaps of streams
and rivers The strata of the'-e mountain belts are stronglj

Dukgram uf the Allegheny

ns Penn yl 3

folded, BO that, if unworn, they would rise in great arehea,
as in the background of Figure 103.

But it is now so long since the strata were pressed
into folds that they have been worn down to a low
peneplain at the level of the dotted line AB, in the fore-
ground of Figure 103. The peneplain thus formed has
been uplifted one or two thousand feet ; the weaker
strata have been again worn down, forming open valleys
and leaving the harder strata standing in relief, a*

I— L

MOUNTAINS

211

even-crested ridges. The waste from the open valleys
lias been washed out through the notches that have been
slowly cut down wliere the streams flowed across the
harder strata.

Plate IX shows one of these ridgea in Maryland, with
a noteh cut through it by a bi'anch of the Potomac liver
How many notches are shown in Figure 103 ?

125. Embayed Mountains. — If a mountain range near a
continental border is lowered, it will be partly covered hy

the sea. The effect thus produced will be similar to that
observed in the half-drowned coastal plain already described.
The valley floors and mountain flanks wiU be submerged
I to a greater or less depth, and many long bays wiil enter
between outstretehing promontories and islands, as in
Figure 104. Islands of this kind are called continental
because of their close relation to the neighboring land.

^Kl2

ELEMENTARY PHYSICAL GEOGRAPHY

The coast of British Columbia and southern Alaska is
bordered by higlj mountains, into whose valleys the sea
now enters in long and deep passages, called fiords. Lat-
eral ridges, separated from the mainland by water chan-
nels or souiids, stand forth as islands. A navigable "inner
passage," well protected from the rough water of the open
ocean, is thus provided for steam vessels. The steep moun-
tain sides, descending rapidly beneath the sea, generally
offer no flat ground for settlement ; but most of the fiords
now contain delta plains where streams enter their heads;
here villages find convenient sites.

The coast of Maine, part of the dissected upland in the
old mountain region of New England, has been partly sub-
merged, BO that it is entered by many long arms of the
sea and fringed by many islands. Excellent harbors are
thus provided, and many of the people living near the
coast are sailors and fishermen.

QDESTIORS

Sec. 108. What is a mottntain range? u momitain system!
How do mountains differ from, plateaus? What ia the action of
mountain-making forces? State a theory of their origin. How do
streams a&ect nioimtain form ? To what two processes is mountain
form due V

109. Describe an example of block mountains. Where are good
examples of this class found? How has the form of tliese moan-
tains been produced? How do the forma of several blocks vaiy?
What can be said of the age of these mountains? Why way it be
believed that these mountainB are still growing? Describe the
drainage of these mountains. Consider the climate of the Tegion.
Describe the places of settlement.

Lji.

MOUNTAINS

110. Describe the dissei^ted ranges of NeTada.. Compare tliem
with the hlock mountaiiiB of Oregdn. Are the Nevada ranges still
growing? Compare the climate of the ranges of Nevada and of
Oregon. Describe the streatiis of the Nevada ranges. Where are
aetUements found among these ranges?

111. Where are the Jura monntaina? What is their structure?
How have these mountains been produced? How is their Btnioture
related to their form? What changes iiave been produced by erosion?
Describe the drainage of these moimtaina. Compare the side ravines
and the crossing gorgea. State the location of villagea and roads.

112. 113. Name some lofty mountain ranges. Upon what two pro-
ceaaea does the form of these mountains depend ? Compare the import-
ance of land sculpture in these ranges and in the block nioniitaina of
Oregon. Of what do the lofty peaks and ridges consist? What
becomes of the waste from tliem? What is the origin of the deep
valleys? Compare the domes and the horns of the Alpa, Compare
tbe Selkirk range of Canada and the Rocky mountains of Colorado.

114. Compare plains and mountains as to variation of tempera-
tore ; of rainfall i as to conditions of life. Why are the sources of
large rivers often found in mountains?

115. How do mountains act as hfirriers? Compare the two slopes
of the equatorial Andes as to climate and vegetation. What
influence is exerted on climate by tlia Sierra Nevada and the Rocky
mountains? What is the chinook wind? the foehn? How have
the Himalayas acted as harriers between nations 1 How do mountain
ranges serve as national boimdarioa ? Give examples. Explain the
importance of passes. How are roads and railroads built over moun-
tains? Give an illustration of mountains as an obstacle to travel.

116. 117. What are avalanches? How are they caused? How
do they move? How are villages and roads protected from them ?
Describe an ice fall in the Alps. What is a landslide? Describe
the landalide of Airolo in the Alps; of the upper Ganges in the
Himalayas. What disaster followed the latter landslide? How
were its dangeiB lessened?

1814 EI.EMf:NTARY PUVSICAI- CEOGRAPHY

118. Describe the movement of rock waste in moiintaina. I
is tlie form of the waste fragments changed? What is an alluvial
fail? IIow ia it formed? How doea the form of alluvial fans v(
How do fans affect the course of a river tu front of them? 1
does the course of a torrent vary on its fan? Describe Two-0«Bn
creek. To what dangers are villages and roads on {ana exposed!
Describe an example from Switzerland. Describe and explain a
waste-filled valley. Describe and explain a terraced valley.

119. How are valleys widened? What sort of valleys are wid-
ened most easily? Describe crosflwise valleys. Compare lengthwise
and crosswise valleys as to occupation.

120. What is an earthquake? How are earthquakes related lo
mountains? How fast do earthquake tremors travel? How mm
movement may they cause? Where are the shocks felt most v;
lently? How far may they be felt? How often do enrthqiiatea
occur in the Alps? Describe the great earthquake of India, 18:
What effect was produced by an earthquake in Japan in 1891?

121. Compare the people of mountains with those of the nei|
boring lowlands.

122. Describe subdued mountains as to height, form, rock
waste, earthquakes, landslides. Describe a.n example of this clus.
What effects have these mountains on their inhabitants ?

133. What is meant by worn-down mountains? What is a pene-
plain? Describe an example in Virginia. What is a monadnoek?
Describe and explain the valleys of the Virginia Piedmont bell.
Describe and explain the uplands and valleys of southern Ne*
England. How do they influence the distribution of populatioi

124. Describe the Allegheny ridges as to form ; as to origin ; w
to drainage. What is a water gap?

125. Describe the appearance of embayed mountains. What is
their origin? What ia a continental island? Describe the ooaatoi
Bouthern Alaska; the coast of Maine,

126. Volc&nic Eruptions Most of the processes of

nature go on without violence. The usual movements
of the winds and currents, the flow and ebb of the tides,
the rise and fall of the lands, the weathering and wash-
ing of rock waste are so placid that we gain confidence
in the earth as a safe home to live in. But sometimes
natural processes of a more violent beliavior are witnessed.
HuiTicanes and tornadoes bi'ing destructive winds and tor-
rential i-ains, flashes of lightning and peals of thunder.
Landslides rush down mountain sides, overwhelming the
valleys below. Now and then the rocky ci'ust beneath

, us quivers and trembles in earthquakes. Great waves
occasionally roll in from the sea and sweep over low
coastal lands. Here and there volcanoes burst forth
with terrible commotion. Nature then seems friglitful
and destructive. Those who are overtaken by such dis-
asters struggle against them, hopefully awaiting the return
of the more peaceful conditions under which their habits
of life have been formed, for man could not survive if
he were always battling against the wilder forces of
nature.

« Of all natural catastrophes, the explosive eruption of
a great volcano is the most terrible. The air resounds

216 KLEMENTARY PHYSICAL GEOGRAPHY

■with its roaring. The sky ia darkened and the
hidden .by clouds of dust blown from the crater. The
sea is burdened with floating ashes. Glowing streams of
molten rock, or lava, flow down the flanks of the volcano,
driving away everything that can take flight before them.
Even the eaitJi around trembles as the gases and lavas
burst out fi'ora their deep sources. No wonder that igno-
rant races of men have imagined struggling giants to be
imprisoned under active volcanoes, nor that even the moat
learned are baffled when trying to account for these ter-
rific displays of natural forces.

But violent as a volcanic eruption may be, it weakens
and in time ceases. The sky clears, the sun shines again,
and nature once more goes on with her more quiet tasks.
As the years pass by and a soil is formed on the weath-
ered lavas, plants clothe their surface and man comes to
dwell on the flanks of the volcanic mountain. The erup-
tion is forgotten ; fields and villages occupy the volcaoio
slopes ; little remains to teU. of the commotion of formei
times.

187. Young Volcanoes. — Volcanoes are fonned by the
ascent of molten lava through fraetui-ea or passages lead-
ing from unknown depths beneath the earth's crust to ita
surface, on the land or on the sea floor. Although the
lava is very hot, it is not burning or flaming. A volcano
should never he described as a burning mountain.

It is beUeved by many that the ascent of molten lava
from its deep source is chiefly caused by pressures similar
to those which cause movements in the earth's crust in

VOLCANOES

217

mountain building. As tlie lava nears the surface and meets
water in greater or less quantities, explosions of steam and
other heated gases take a violent piirt in the eruptions.

Id Eruptiou

The early growth of a volcano has occasionally been
observed. The outbui-st is preceded and accompanied by
earthquakes, which indicate the breaking of an upwani pas-
sage through the undei'ground rocks, before hot lavas make
their appearance at the surface. When the eruption is

ELEMENTARY PHYSICAL GEOGEAPHY

ffii^^^^^

^^M

n^teiwf

^r- - .

a4:-

accompanied by gaseous explosiona much of the lava
blown into fragments, of which the smaller are called
ashes or cinders. The lai^er blocks and the coarser
ashes accumulate in a conical heap, or volcano, frequently
having remarkable regularity of form, a cup-shaped hollow
or crater being kept open at the top over the vent by
the outbursting gases. The finer ashes or dust may fall
far away. When the
eruption is less vio-
lent the lava mns
forth more quietly in
a stream or flow, fol-
lowing the slopes of
Fidw. Monte Nuovo the ground. Explo-

sive and quiet ei-up-
tions may alternate in iiregular succession, and after many
eruptions the volcano may become a lofty mountain, one
or two miles high.

Monte Nuovo (new mountaiu) is a small volcano that
was formed on the north side of the Gulf of Naples
in Italy in 1538. Earthquakes occurred thereabouts
for two years before the eruption, when in a week's
time a cone was built up 440 feet high, half a mile in
diameter at the base, and with a crater over 400 feet
deep, Masses of lava " as large as an os " were shot
into the air by the bursting of great bubbles of gas or
steam that ascended through the lava in the vent. Finer
ashes fell over the country for several miles around.
The people of the neighboring \'illages fled in terror
from their homes.

VOLCANOES 219

A greater eruption took place in Mexico iii 1759, when
the volcauo JoruUo (pi'on. Ho-rul-yo) was built ou the
central plateau, burying fertile fields of sugar cane and
indigo. The outburst was preceded by earthquakes; the
eruption continued half a year, building six cones and
pouring out extensive lava flows. The highest cone,
Jorullo, rose 700 feet above the plateau. The flows
retained a perceptible heat for over twenty years.

Many examples might be given of marine eruptions.
In 1867 a shoal was discovered among the Tonga islands
of the Pacific (lat. 20° 20' S., long. 17.5° 20' W.), the
surrounding sea floor being about 1000 fathoms deep. In
1877 smoke was seen ascending from the sea surface over
the shoal. In 1885 an island had been formed two miles
long and 200 feet high. At this time a terrific eruption
was in progress, and the shocks of the explosions were felt
on neighboring islands. As the island consisted chiefly
of ashes, it has since been rapidly eroded by the waves
and will soon disappear, unless new eruptions occur.

Most volcanoes have not been observed in their early
growth, yet, even if not now in eruption, so perfectly do
they correspond in foi-m and structure with such examples
as Monte Nnovo and Jorullo that no doubt can remain as
to their origin.

lu northern California there is a cinder cone of remark-
ably perfect form. Its barren slopes of loose ashes rise
640 feet to the rim that incloses a crater 240 feet deep.
A stream of lava has issued from near the base of the cone,
flooding a neighboring valley with a lava field a mile wide
and nearly three miles long. The surface of the field is

ELEMENTARY PHYSICAL GEOGRAPHY

HO covei'ed with unweathered angular blocks of lava as to
be almost impassable. The edge of the field is a steep
and ragged slope 100 feet high. It obstructs a stream from
the south, which forms Snag lake, so called from the dead
trees still standing in it. On all sides the surface of the
country is covered with a layer of volcanic ashes and dust,
six or more feet deep near the cone, thinner and finer
farther away, yet recognizable at a distance of eight miles.

Fia. 107. Cinder Cone and Lava Flow, Calitori

From the size of trees growing on the ashes it
tiiat the cinder cone was built about 200 years ago. The
lava flow is younger, but none of the Indians or early
settlers thereabouts (1845) observed its eruption,

128. Great Volcanoes. — Many large volcanoes, whose
firat eruption must have occurred many thousands of yeara
ago, are still active. After long periods of more or less
complete rest they burst forth again for a short time,
blowing out showers of ashes, building their cones to a
height of 10,000 feet or more, and adding new lava streams
to their flanks, so as to gain a diameter of ten or twenty
miles or mora at the base. The melted lava often breaks

VOLCANOES

221

forth from the mountain aide and flows down to gentler
slopes on the flanks aud out upon the surrounding eountrj' ;
thus the cone as a whole comes
to have a rudely bedded struc-
ture of ashy and dense lavas.

It sometimes happens that |
the upper part of a volcano is
destroyed by a violent eruption
or broken in by underground
disturbance, forming a greatly
enlarged crater, or caldera.
Volcanoes of this formare some-
times called ring mountains.

Deception island, in the
South Shetland group, beyond
Cape Horn, is the high rim of
a caldera, breached on one side
by a narrow gap, which gives entrance to a quiet circular
Layers of ice
are to he seen between
beds of ashes and lava
on the caldera walls.
The cone of Vesu-
I viuB has been built in
alarge caldera of more
ancient origin. The
cone buries one side of
the caldera rim, the other side being known as Monte Somma.
map of VeBUviua and Monte Somma, liie the map of
island in Figure 108.

intheCaldt^ni

222

ELEMENTARY PHYSICAl, GEOGRAPHY

Mt. MazamH, a superb ring uiouiitain in Oregon, con-
tains a beautiful lake in its huge calilera. This volcano
must have been once several thousand feet higher thag it
is now, before its ujijier part was engulfed in tlie formation
of the caldeKi,

Figures 110 and 116 ai'c maps of Mts, Mazama and Shasta, in which
the inoantain forcn is iDdicatM by lines that curve around the slopoa
at definite heights, every line following a level course, and every pair

Fitr no. Cont

iMat

<t Crater Lake in Mt. Maznoiu, Orei

of lines differing iu height by a, fi:<ed amount. Lines of this kiriii
are called contour lines, and the maps are contour mapa. Where the.
lines are open spaced, the slopes are relatively gentle ; 'where tlie lines
are close together, the slopes are steep. Compare the inward and out-
ward slopes of the ring of Mt. Mazama; compare the upper and lower
slopes of Mt. Shasta. Determine from Figure 110 the diameter of the
caldera, and the average height of its rim above sea level and above Qa
lake surface.

VOLCANOES 223

rough classification of volcanoes groups them as
active, ■ when they are frequently in eruption; dormant
(Bleeping), when now at rest, though giving signs in hot
springs ajid sulphurous vapore that activity may be begun
again ; and extinct, when they give no sign of activity.
^t is not possible to make ceitain distinction between the
last two classes.

I Showers of ashes as they chance to fall may bury villages,
£elds, and forests. Tlie disturbance in the atmosphere dur-
ing a violent eruption often causes rainfall. The floods
jihus caused may be increased liy the water from melted
^ow on a lofty cone, and occasionally by hot water from
jOie ei"ater itself. The tremendous eruption of Galung-
ffung, Java, in 1822, jiroduced hot and muddy torrents
^-hich devastated villages and plantations on the lowlands.
\ At the eruption of Conseguina, Central America, in
|S35, ashes destroyed trees and dwellings twenty-five miles
liouth of the volcano ; thousands of cattle and innumerable
^Id animals and birds were killed. Lava blocks in frag-
loeiits five or more feet in diameter are strewn for ten or
nfteeu miles around the great cone of Cotopaxi, Ecuador.
' An explosive eruption of Mount Pelee on the island of
Jtfartinique, in the Lesser Antilles, took place in May,
1902, Clouds of dust and ashes were driven out by great
y-olumes of heated gases. The city of St, Pien-e, on the
feoast about six miles southwest of the crater, was suddenly
Overwhelmed, and nearly all of its inhabitants — probably
pver 20,000 persons — were kdled.

j The first recorded enaption of Vesuvius, a.d. 79, dark-
ened the sky with its clouds. The ancient city of Pompeii

ELEMENTARY THTSrCAL GEOGBAPHY

was buried in ashes and about 2000 persona
one fifteenth of the population) were killed. Herculaneum,
near by, was overwhelmed with toiTents of ashy mud.
After being long forgotli'ii iiiid <ivi'igrown by modem

i^'tG. 111. ExcavaUooH in HeFcnlaneain
villages, parts of these cities have been laid bare by recent
excavations, affording many illustrations of ancient archi-
tecture and of ancient modes of living. The walls in the
foreground of Figui-e 111 are the ruins of houses in ancient
Herculaneum, They were buried to the level LL.

129. Earthquakes in Volcanic Districts The shocks of a

violent eruption may shatter the volcano, breaking its sides-

VOLCANOES 225

The earthquakes thus caused are felt for many miles amund
the volcano. The exploding gases produce thundering
sotinda, sometimes audible for hundreds of miles.

In the remarkable explosion of the volcanic island of
Krakatoa, already referred to (page 27), half the island was
destroyed, leaving water more than 1000 feet deep where
high land had stood before. The iiir was shaken so vigor-
ously by the explosion that windows were broken a hun-
dred miles away. Huge sea waves rolled away from the
exploded island, causing great destmction on neighboring
ooafita. Pumice, or light spongy lava, formed a I
layer on the sea surface, obstructing the course of i
The dust blown out of the volcano darkened the air for
hundreds of miles around. As the dust was spread far
and wide by the upper atmospheric currents, it increased
thfl brilliancy of sunset and sunrise colors. The famous
"red sunsets" thus produced were visible in all parta of
the world before the end of 1883 ; then, as the dust settled,
their brilUancy gradually decreased. .

Besides the earthquakes directly produced by the explo-
sive eruptions of volcanoes, it is probable that many other
earthquakes in volcanic districts are the result of disturb-
ances within the crust of the earth not directly connected
with volcanic action. The numerous earthquakes of Japan
and Italy sometimes accompany eruptions, but are more
frequently independent of all visible eruptive action.

Great destruction is caused by eartJiquakes in regions
that are frequently shaken. In the thickly populated dis-
tricts of southern Italy many thousands of lives have been
lost in the violent earthquakes of the last three centuries.

226 ELEMENTARY PHYSICAL GEOGRAPHY

130. Distribution of Volcanoes. — Volcanoes generally
occur near the seacoast or on the sea floor, but a considerable
number of cones and flows are known far in continental
interiors. Volcanoes are more numerous on the lands bo>
dering the Pacific ocean and the mediteiTaueiui seas than
on the coasts of the Atlantic, but many volcanic islands are
known in the Atlantic, as well as in the Pacific and Indian
oceans. It is estimated that over 300 volcanoes are now
active, about 100 of these standing on the continents. All
high islands of small area, far from the continents, and many
such islands near the continents are of volcanic origin.

Extinct volcanoes are sometimes found far inland.
Cinder cones and barren lavas are known on the plateaus
of Arizona, SOO mUes from the ocean ; in Colorado, SOOor
more miles inland; in Tibet, 500 or more miles inland.
Several active volcanoes in Mexico, Central America, and
elsewhere are so far from the coast that direct connection
with sea water should not be regarded {as it has been)
necessary to eruptions.

Active volcanoes in the interior of continents are rare,
but a large one is known in central Afiica, north of Lake
Tanganyika, 700 miles from the Indian ocean.

Islands formed by the growth of volcanoes in mid ocean
are often bordered by wave-cut cliffs, so that it is almost
impossible to find a landing place on their shores. Being
of rugged form and nearly inaccessible, as well as distant
from the continents, they are all the more lonesome.

A remarkable instance of the effect of isolation on tbe
occupants of a remote volcanic island is seen in the language
of the people of Iceland. Icelandic, Norwegian, Swedish,

VOLCANOES

227

' and Danish were all one language a thousand years ago ;
but while the isolated Icelandic has preserved its ancient
form with slight change, the languages of the continental
countries iiave been much modified; that of Denmark
especially having been affected by the neighborhood of
Germany.

131. Lava Flows. ^ Great flows of lava sometimes
run beyond the base of the volcano in wliich they break
forth. Their surface is comparatively smooth if it remains

unbroken after first cooling, but extremely ragged and
angular if the first crust is repeatedly broken by con-
tinued movement. The edge of a ragged flow may
form a bluff 100 feet or more in height. On one of the
plateaus of Arizona near the Colorado canyon stands a
throng of volcanic cones, from which broad streams of
lava descend the bordering cliffs in black cascades and
,. form baiTen lava floods on a lower plateau near by.

228 ELEMENTARY PHYSICAL GEOGRAPHY

In 1783 a great flood of lava rose from a deep fissure
in Iceland, the lava issuing tranquilly for the most part,
flowing away in vast sheets on each side, and advancing
in streams far along the lower valleys. Hundreds of
small cones were built over the fissure, which was twenty
imles long. In the course of ages successive lava floods
of this kind have built up broad uplands in the plateau of
Iceland, the loose slaggy cones of earlier eruptions being
gradually buried under later sheets.

Two lava streams of the eruption of 1783 in Iceland
flowed down valleys forty-iive and fifty miles fi-om their
source, gainuig a depth of several J'undi'ed feet where the
valleys were narrow, and spreading out in lakelike plains
where the valleys wei'e open. The water of side streams
was dammed and rose in lakes. Twenty villages were
destroyed by the floods of lava or water; 9000 persons
(about one seventh of the island's population) and a great
Dumber of cattle perished, not only at the time of the
eruption, but afterwai'd during a famine caused by the
burial of the pastures and by the desertion of the coast
by fish.

The form assumed by successive lava flows in building
a plateau is sometimes imitated on a cold winter night
when trickling streams of water, supplied by daytime
thawing, are frozen as they advance. If the wafer is arti-
ficially colored, successive flows are made plainly visible.

Lava floods thousands of square miles in area have
been poured forth in Idaho, Oregon, and Washington.
where they form an extensive plateau in a broad depres-
sion among the surrounding mountains.

VOLCANOES

229

Between the Columbia and Snake rivere, in eastern
Washington, thtj plain surface of the lava flood meets the
inclosing mountains just as the sea meets a half-drowned
mountain range. The lava forms level bays between the
ridgea; the ridges stand forth like promontories; outstand-
ing peaks rise like islands over the plain. A nigged moun-
tainoTia baim his thus been con\ erted into i j lateiu Part
of the la\a plain has been uplifted in domelike form to a
gi eater height than the rest and is now deeplj di lecfed
by the canyons of Snake
n\er and ita branches
This part is called the
Blue mountams i Fig
ure 11-i

132 Dissected Volca
noes — Torrential streams
running down the slope
of volcanic cones carve
ravines on their flanks.
Many ravines are formed
during the periods of rest in the growth of great volcanoes,
only to be filled again by later eruptions of lavas and
ashes. After eruptions cease the ravines deepen more and
more, leaving sharp ridges between them, and at last dis-
secting the cone so deeply as to leave little appearance of
its original shape.

Mt. Shasta, in northern California, is furrowed on all
sides by gigantic ravines, but its conical form is still well
preBerved, Figures 115, 116, Many meadows about its

230

ELEMENTARY PHYSICAL GEOGRAPHY

base mark the sites of lakes formed by lava-flow barriers
but now filled and drained. The best agricultural land
in the region is of this origin.

A number of extinct and more or less dilapidated vol-
canic cones surmount the plateaus of Arizona and New
Mexico, Mts San Frincisco and Taylor being among the
best examples

Before the summit of Mt Mazama was destroyed by
engulfment its height was probably about equal to that

VOLCANOES

231

of Mt. Shasta to-day. Ravines like those of Shasta hati
been worn down the slopes of Mazama; their lower
courses are still seen on the outer slopes of the ring
mountain, but their upper courses are lost.

Many great volcanoes in various stages of activity and
> found in the Andes along the western side

133. Geographical Changes caused by Volcanoes. — The

construction of large volcanoes by successive eruptions
sometimes causes curious changes in the coui'se of rivers,
whose valleys are more or less blockaded by the new-built
cones.

A remarkable example of this kind is found in Central
America, where the growth of a range of volcanoes has
transformed a bay th^t once opened to the Pacific into a
Jake, known as Lake Nicaragua, The volcanoes formed so

ELEMENTARY PHYSICAL GEOGRAPHY

effective a barrier that the lake surface is now 105 feet
above sea level and its outlet flows across what used to
be the continental divide and discharges into the Carib-
bean sea. Since the outlet took this course it has eroded a

Fig. 117. Ma;) ol tlie Laku Nicnmgua District

deep gorge across the divide, and the level of the lake is
now lower tlian when the eastward overflow first took place.
This lake would form part of the proposed interoceanic
canal route across Nicaragua.

Draw a map, based on Figure 117, to show the general outUne of
the land hefore the volcanic range was built. The original outUoe
of the bay now closed by the Tolcanoes and their lava flows is shoifn
by a dotted line. Describe the changes caused hy the building of
the volcanic range.

VOLCANOES

QtTESTrons

Sec. 126. Give exampicB of the quiet procesaCB of nature; of tlie
violent procesaes. Describe the explosive eruptiou of a volcano.

127. How are volcanoes formed? What ia the moat probable
cause of the ascent of lava in volcanoes ? What ia the eHect of
steam? Describe the early gi'owth of a volcano. Give an example
from near Naples; from Mexico; in the Pacific. Deaeribe the cin-
der cone in California. How did its lava flow affect a neighboring
stream? Why ia this volcano thought to be of recent origin?

128. How ai^e great volcanoes formed? What size do they
attain? What is a caldera? Deaeribe Deception island; Vesuvius
and Monte Somma; Mt. Mazamaand its caldera. How may volcanoes
be classified? What effects may he produced by showers of ashes?
by floods? How may these floods be caused ? Describe some inci-
dents of the eruption of Galung-gting, 1R23; of Conseguina, 1R.S5;
of Cotopaxi ; of Pelee, 1W2,

129. Why are earthquakes often associated with volcanoes?
Describe the explosion of Krakatoa.

130. How are volcanoes distributed? Compare the Atlantic and
Pacific in this respect. How many active volcanoes are known?
How many of these are on the continents? Where are volcanic
islands found? What fonas have they? Wliere are extinct vol-
canoes often found? Where is an active volcano foumf far inland?
Give an histanca of the eitects of living on a remote volcanic island.

131. Describe the surface form of lava flows. Describe the lava
cascades near the Colorado canyon ; the eruption and lava flood of
1783 in Iceland; the lava floods of Idaho.

132. Describe a dissected volcano. Nanie some examples of this
class. Compare Mta. Shasta and Klozama.

133. WTiat geographical changes may be produced by volcanoes?
Describe an example of such changes in Nicaragua.

RIVERS AND VALLEYS

134. Underground Water. — The water supplied by rain
and snow is disposed of in part by evaporating from the
surface, in part by running down the slopes of the land
to the streams, and in part by smking underground. The
latter part is called underground water, or simply ground
water.

The proportions of these several parts vary under
different conditions. The greater part of a light and
long-continued rain may pass underground, especially if
failing on a plain. A very heavy rain, or " cloud-burst,"
falling on strong slopes is largely disposed of by direct
run-off, causing sudden floods.

Rain, falling on a surface having a deep soil well cov-
ered witb vegetation (gra.s8, bushes, or forest), will for the
most part soak into the ground. On arid plains a great
part of a light rain may diy off from the barren surface of
the ground, but a heavy rain will run off in a flood.

Loosely consolidated strata and deep rock waste take
iu much ground water. Finn rocks, such as granito,
allow but little water to enter beneath the weathered
waste on their surface. When the ground is frozen little
water can enter it ; hence rivers rise in floods when deep
snow is lapidly melted by a heavy i-ain.

RIVKRS AND VALLEYS

235

Underground water is essential to the growth of phmts,
whose roots must reach moist earth. Where gniBS and
trees cover the surface, much ground water taken in l>y
their roots is discharged into the air by evaporation from
their leaves.

135. Caverns. - — Most rocks are not soluble in water.
Limestone is exceptional in this respect ; it may he slowly
dissolved, especially
by ground water,
which gathers cer-
tain acids from
decomposing vege-
tation as it soaks
down through
soiL Caverns in
limestone districts

are the result of this solvent action of underground waters.
The Mammoth cave of Kentucky and the Luray cavern of
Virginia are famous examples of their class. Streams
gathering on the surface descend to underground pas-
sages by hollows, known as sink holes or swallow holes.
After flowing underground for some distance such streams
may issue in enlarged and turbid currents from the mouths
of caverns.

Where sink holes and cavern drainage prevail so much
water enters the ground that surface streams are compai'a-
tively rare. When the sink holes or the underground pas-
sages become obstructed ponds and lakes are formed in
the surface basins.

236 ELEMENTARY PHYSICAL GEOGRAPHY

Several species of animala dwelling in the complete
darkness of caverns are blind, but their senses of bearii^
and touch are highly developed.

As the cavern enlai^es, its roof may fall in more or less
completely. The beautiful Natural bridge of Virginia is
the remnant of a cavern roof.

136. Springs. — Very little ground water remains per-
manently beneath the land surface. Sooner or later, after
descending to less or greater depths, it returns to the sar-
face at a lower level than where it entered, coming ont in
the form of springs and joining the rmiKiff of streams.

The movement of ground water is comparatively slow
while percolating among the particles of rock waste or
through the pores and crevices of rocks. Where a large
part of the rainfall enters the ground, the volume of the
streams fed by springs is less variable than where the rain-
fall is mostly discharged by direct run-off during and
shortly after a storm.

It is for this reason that the springs and streams of a
forested region usually have a comparatively constant flow;
but this rule does not apply in regions of strong relief, sacb
as the dissected plateau of West Vii'ginia. When forests
are cut down, the direct run-off of the rainfall ia increased:
then the springs are likely to run dry and the streams will
vary greatly in volume between flood and drought.

Ground water slowly moves from hills and slopes,
descending to lower levels and accumulating beneath the
lower ground. It may, therefore, be generally found near
the surface in valleys, where the soil is usually damp. At

RIVERS AND VALLEYS

237

the base of a slope the ground water may issue iu a spring,
S, Figiu-e 119, supplying a small brook. Innumerable
small springs occur unnoticed in the banks of streams.

Ground water stands close to the land surface in marshes,
swamps, and bogs, rising or falling somewhat with changes
of weather and season.

In regions of sufficient rainfall and moderate relief the
ground water may be reached at almost any point except
on hilltops by sinking wells to a depth of from ten to forty

Fig. 119. Soutdoo Bhowiog Ground Water in Eoek Ci

lieneatli a Vallej

feet. The bottom of the well should be a few feet deeper
than the level at which the trickling stream of ground
water enters it, so as to accumulate water in sufScient
volume to supply ordinary domestic needs.

Ground water and spring water carry very little rock
waste {unless in solution) and are generally clear and pure.
For this reason weUs and springs generally afford a better
water supply than the surface streams that receive the
wash of fields and meadows.

In coastal regions ground water may flow forth as springs
directly into the sea, either on a sloping beach near low-tide
level, or at the bottom offshoi'e ; here they sometimes have
a current so abundant as to supply a column of fresh water
that ascends through the heavier salt water to the surface.

238 ELEMENTARY PHYSICAL GEOGRAPHY

137. Artesian Wells In maiij coastal and interior

plains a large part of the rainfall enters the more sandy
layers and follows their gentle slope deep underground,
between other layers tliat are leas open to the passage ot
water. If a deep well is sunk to the water-bearing stratum,
the water may rise and flow out of the surface like a foun-
tain. Wells of this kind are called Artesian, from Artois,
a district in France where tbey were first bored.

It is essential that the water-bearing stratum should
receive its rainfall at a Iiigher level than that of the top
of the well by which it is tapped, as shown in Figure 120.

Fid. 120. Diagram of a. Coastal Plain nltli Artesian WqUb

In what part of the plain Uoes the stratum tapped by the deeper
well reach the surface?

Charleston, Galveston, and many other coastal cities
receive much water supply from artesian weils. In east-
ern Maiyland deep wella pierce strata that reach the
surface and receive rainfall west of Chesapeake bay; the
strata lead the water beneath the nearly water-tight layers
that floor the bay, and it is atCl fresh when rising in the
wells. Southern Wisconsin and eastern Iowa have many
artesian wells, supplied by water-bearing strata that slope
gently away from the older land of northern Wisconsin.

KIVERS AND VALLKYS 239

Hot and Mineral Springs. — < jround water nome-
tiiiies descends deep beneath the surface with a slow snpijly
from a large area. While deep underground the water
acquires a high temperature and stands under a heavy
pressure. It is shown by experiment that hot water under
pressure has iuci«ased power of dissolving certain minerals,
Jlence the slowly percolating waten takes into solution
what it can dissolve of the more soluble minerals dis-
covered on its way, such as ealcite (the mineral base of
limestone), salt, and certain compounds of magnesia, u^on,
etc. If the water then rises rather rapidly along a. rock
fracture, it will appear at the surface in springs, bearing
an unusual amount of mineml substances in solution and
oft«n having a high temperature. Such springs are ffc-
quently of medicinal value.

Springs of this kind are associated with disturbed rock
structures such as occur in mountainous districts, Saratoga
^Springs, N,Y., White Sulphur Springs, W.Va,, Vichy in
central France, and Karlsbad in Bohemia ai'e examples of
settlements determined chiefly or wholly by tlie value of
their medicinal wateiB. Many other mineral springs occur
in the Appalachian and Kocky mountains.

139. Geysers. — In certain volcanic regions the tempei'ar
ture of tlie underground water may rise to or above the
boiling point. Steam then issues with the water, often in
a more or less explosive manner, and such steaming and
spouting springs are called geysers. The geysers of Ice-
|land have long been famous ; those of the Yellowstone
."Park are now the most celebrated in the world.

240 ELEMENTARY PHYSICAL GEOGRAPHY

The jet of steaming water and spray may rise for several
minutes to a. height of a hundred feet, with a loud I'oaring
noise. Then all remains quiet till the next eruption,
usually a number of hours later. Mineral substauces that
were dissolved in small quantity
by the hot water undet^round
ai'e partly deposited near
geyser's vent as the water cools
or evaporates, and thus a mound
or t«rrace of mineral deposits is
gradually formed. The terraces
around the hot spiings of
Yellowstone Park are of great
beauty.

The intermittent action of
many geysers suggests that a
certain period of time (an hour
or more) is necessary to warm
the new supply of water that
entera the crevice of discharge
after a previous supply has been
blown out by steam. Water
under pressure must be heated
above the ordinary boiling point
(212° F.) before it will change to steam. Hence in the
deeper part of the crevice the temperature of the boiling
point is higher than at the surface. When the deeper
water reaches its boiling point a great part of it is quicklT
converted into steam, which blows the rest of the wiiter out
of the vent.

Fio. 121. AGeyse:

RIVERS AND VALLKYS 241

140. Hud Volcanoes. — Certain hot springs bring a con-
siderable amount of fine rock waste to the surface with
their steaming water. The waste is then deposited as a
muddy sediment around the opeuing of the spring, where
it forms a mound with a hollow or crater in the center.
Although seldom over a few score feet in height, the
resemblance of these mounda to true volcanoes has given
them the name of mud volcanoes. A number of mad vol-
canoes occur in the Yellowstone Park, where some of them
are only a few feet high. Some of the lai^est known,
with heights up to 400 feet, are near the lower course of
the river Indus in northwest India.

141. River Systems and their Parts A river is a

stream of water bearing the i-ainfall and the waste of the
land from higher to lower ground and, as a rule, to the sea.
A trunk stream and all the branches that join it constitute
a river system.

Stream m a general term, with little relation to size.
Rill, rivulet, brook, and creek apply to streams of small
01' moderate size. River is generally applied to the trunk
or to the larger branches of a river system.

A river flows in a channel that is somewhat lower than
the adjoining land surface. Tlie floor of the channel is
the river bed; the sides of the cliannel ai'e the jiver
banks. The coarser part of the waste borne by the river
is swept along the bed ; the finer part may be carried in
the stream.

The land from which a river gathers its water and its load
of rock waste is called its basin. The crest line, or "height of

**p

ELEMENTARY PHYSICAL GEOGRAPHY

land," between the basins of neighboring streams or rivere,
or between the valleys of river branches, is called a divide,

Dividing RidRO in tho Mountains of Nortliwtat Englftn

Trace the liix'ide shown in Figure 122. Note that a divide tmj
he much higher at one point than at another. Follow soma of the
Biraple and branching divides ehowii in Figures 85 and 104.

HIVKRS AND VALLKYS ■243

The land slopes in opposite directions on the two sides
of a divide. When rain falls on the adjoining slopes it
will be shed into difEerent streams; hence a divide is
sometimes called a watershed or water parting. Certain
crest lines in the Rocky mountains separate the Imsins of
rivers wliich discharge into the Atlantic and the Pacific
oceans ; these crests constitute the " continental divide."
Name some of the rivers that are thus divided.

On smooth plains and uplands there is no well-marked
height of land or ridge separating the headwaters anil
side streams of neighboriug rivers. Such surfaces may be
described as having an undivided or imperfectly divided
drainage. Undivided drainage areas are often found on
young plains and plateaus. Compare the foreground and
hackground of Figure 62 in this respect.

When a plain or plateau or mountain region i.s well
dissected numerous sharply dt^fined subdivides are devel-
oped between the smaller rivers and their branches, as
on the Allegheny plateau. River and stream basins in
vigorous mountains are sharply divided by the crest lines
of the lofty ridges between the deeply eroded valleys. A
wom-down region may have indistinct divides, as on
the even uplands of the Piedmont belt of Virginia,
Figure 99.

Nearly all these features of river systems may be illus-
trated in a small way \yy the temporary streams on a road
surface just after a fall of i-ain. Many interesting studies
may be made of the small stream basins, divides, branches
and channels, "and of the manner in which the streams
heal" waste from higher to lower ground.

244 ELEMKNTARY PHYSICAL GEOGRAPHY

142. Floods and Droughts The volume of a river varies

with the change in the aniount of rainfall over its basin.
During and sliortly after a rain (or a thaw of snow) the
surface run-t»ff ia most active ; all the rivulets are running
with water and waste to the creeks, and the creeks run to
the rivers. The volume of all the streams is increased at
such a time, and their current is quickened. The water is
then turbid with the waste that has been washed into the
streams by the rivulets on the vallej sides and lifted from
the stream beds by the strengtiiened eurrents. As the
stream volume increases, the water may rise above the
banks of the channel and overflow the low ground or flood
plain on either side. There some of the fine river-home
waste, or silt, will be deposited as the current slackens.

When the i-ain stops and the surface run-ofE lessens and
ceases the flooded streams are drained down the valleys
toward the sea; theirvolume decreases andtheir surface sinks
t« a more ordinary level. Then the streams must depend on
ground water supplied by springs at innumerable point* in
the stream beds. Less waste is washed into the streams at
thistimeiiindtheircurrent may become nearly or quite clear.

During a drought of several weeks or months the streams
di'ain away much of the ground water. Then the discharge
of the springs ia weakened, and the streams are reduced to
.imaller volume. They may shrink so much as to be unable
to cover all the bed of their channel, especially in the head-
water branches. The streams may entirely disappear for a
time, but even if lost at the surface, ground water may gen-
erally be found slowly creeping through the sand and gravel
of the channel bed a few feet below the surface.

RIVERS AND VALLKYS 245

In regions of plentiful rainfall, like the eastern United
States, the rivers may be mucli reduced during droughts,
but they do not entirely disappear. In the drier climate
of many of the Western States the streams habitually dis-
appear and leave their channels dry during the long inter-
vals between rain storms.

143. The Work of Rivers. — Frequent reference has
already been made to the work of rival's in sculpturing
the lands. This important subject may now be con-
sidered more carefully. The higher a river lies above
baselevel, the deeper may its valley in time be worn.
The steeper the channel, the faster the river flows and
the more and the coarser rock waste it may sweep and
cany downstream. The greater the volume of a river on
a given slope, the less it is retarded by friction on the bed
and banks, and the faster it flows. Hence a river in flotxl
flows faster than at time of low wat«r, and the flooded
current transports a greatly increased load of rock waste.
Indeed, it is chiefly in time of flood that the work of a
riyer is performed.

The deepening of a valley by the erosion of rock in the
river channel is accomplished chiefly by the i-asping of the
rock surface with the innumerable fragments and particles
of i-ock waste that are swept over it. The more resistant
the rock, the slower it will be worn down. The particles
thus worn from the rock surface make part of the load of
waste borne away by the river.

As the valley bottom is worn deeper and deeper below
the surrounding country, the valley sides are attacked by

246 ELEMENTARY I'llTSICAL GEOOKAFHY

the weather, and much waste washes and creeps down
from them into the river, thus widening the valley,
decreasing the steepness of its side slopes, and adding to
the load of waste borne away by the stream. It is in this
sense that it is said that "rivers erode their valleyB."
Another portion of the river load is received from the
headwaters and side streams, which in turn receive it
chiefly from the wash of waste down the side slopes of
their valleys at times of rain or thaw.

The load of waste thus gathered is not swept along ia
a continuous movement to the sea; it stops. many times oq
the way, being laid do\vn on the bed or sides of the chan-
nel when the water is low, forming bars and banks; it is
swept forward again a greater or less distance at time of
flood.

Rivers that are beginning their work of erosion and
transportation in sculpturing a newly uplifted land may be
called young. When they have worked so long that all
the land slopes in their basin have been worn down low,
so as to fonn a surface of faint relief — a peneplain — at
a small altitude above sea level, the rivers may be called
old. Between youth and old age, when the rivers are
actively working in well-carved valleys, sweeping along
the waste received from the hills or mountains that form
the valley sides, they may be called middle-aged or mature.

144. Young Rivers. — The examples of land forms
described in earlier chapters have shown that when «
region is first raised from the sea, or wlien a former
land surface ia uplifted, tilted, or folded, the streams as

RIVERS AND VALLEYS 247

a rule follow the lead of the land slopes, uniting liere
and tliere to form rivers of larger and larger size.

Young rivers thus newly established proceed to cut
down their eliaimela where the slope is steep enough to
give them an active current; the waste that they gather
is washed along, rasping down the ledges in the river
bed; but where ihe slope is very faiut, or where rivers
enter a basin holding a lake, they lay down their load
of waste and build up the land surface.

While rivers are still young their course is often
marked by rapids and falls, not yet eroded away, and
by lakes not yet filled up with sediments or drained
away by the deepening of their outlet by the outflowing
stream. The current of such rivers is irregular, being
very fast at rapids and falls and almost wanting in lakes.
As the river grows older both the falls and the lakes dis-
appear and the cniTent becomes more uniform.

The drainage of the Laurentian highlands of Canada
north of the St. Lawrence river beare every mark of youth.
Lakes are very numerous and of irregular form. They
often have several outlets, no one stream having cut
down enough faster than tlie others to secure all the
discharge. The streams are frequently intermpted by
rapids or falls on rock ledges, in which channels are as
yet cut only to moderate depth. The rivers frequently
split into two or more channels, which reunite after wan-
dering in independent courses for ten or twenty miles
across country.

These highlands are a rugged, forested, and thinly popu-
lated wilderness without roads. All travel is by canoes

248

KI.EMENTARY PHYSICAL CEOGRAPHY

along the water rourses and the cAiioes hive to be car- |

ried past evpr\ rapid and fall The birch tree from whose \

bark portable caniies aie mide is here as ippropriate to |
the needs of the inhabitants as the camel is to the dwellera

in arid deiieitb I

The St I iwrence sjstem with its inan\ lakes, falls, I
and rapidf is a reniarktblt example rf \erv young or

undeveloped drainage. The ontlet of Lake Superior is
by a river interrupted by rapids, called the Sault Sainte
Marie (Soo St. Mary). The outlet of Lake Erie is
Niagara, with its renowned cataract and rapids. The out
let of Lake Ontario is the St. Lawrence, with numer-
ous rapids. The lakes favor navigation, but the rapids
and falls obstruct it. Canals and locks have now been

ElVERS AND VALLEYS 249

constructed, by which the rapids and falls are passed.
Nanae the great lakes r»f the St, Lawrence system.

The region of the greiit African lakes bears many mai'ks
of youthful drainage. The lake basins here indicate a break-
ing or warping of the earth's crust, like that In southern
Oregon. The inclosing plateaus are bordered by I'j^ged
clifEs, where fractures have taken place. The Nile, flowing
north from Lake Victoria Nyanza, and the Shirfi, flowing
south from Lake Nyassa, are young rivers of powerful cur-
rent, descending i>ver falls and rapids, and are very busy in
the work of deepening their valleys and draining the lakes.

By long-continued action the path of a river will in
time be everj'where worn down or built up to such a
slope that the cuiTent will be just strong enough to
carry the load of waste that it receives. Such a river
may be descriljed as passing from youth to maturity.

145. Lakes may be generallj- taken to indicate a youth-
ful drainage system, as in the examples just given. In
time they will be destroyed, partlj hy lilhng with the
waste that is brought by the inflowmtf streams partly
by the deepening of the outlet viliey 1 ikes should
therefore be regarded as only temporary features in the
long life of the river system to which they belong. The
rivers may remain long after the lakes disappear.

The depressions between the tilted lava blocks of south-
ern Oregon hold lakes because enough time has not yet
pftBsed to enable the streams to fill and drain their basins.
Lnva flows obstruct streams and for a time hold back
lakes. Lakes of other kinds will be described later.

250 ELEMENTARY PHYSICAL GEOGRAPHY

As the current of a. river decreases on entering a lake,
the stream-borne wast« settles ; thus deltas are formed at
the inlets and the lake bottom is strewn with the finest
waste or silt.

Lake Geneva in Switzerland receives the Rhone at it9
east end ; the river ia turbid with the waste that it has
received from Alpine glaciers and torrents. A delln
twenty miles long has been built into the lake. It has
grown a mile forward since Roman times, nearly 2O00
years ago. The lake bottom is a plain of fine silt. When
even tlie finest silt has settled, the lake water becomes
very clear, and the Rhone at the outlet ia wonderfully
transparent.

Lakes aeb as regulators of the discharge of their
outflowing rivers ; for the level of the lake changes
little, whether the inflowing streams are flooded or
low, and hence the outlet river has a relatively constant
volume.

The Ohio witliout lakes ami the St. Lawrence with five
great lakes are strongly contrasted in respect to flooda.
The latter has no great floods, because even a heavy
rain raises the surface of the lakes gradually and only
by a small amount ; hence the outflowing river cannot
be greatly increased in volume. The rains of the upper
Ohio basin, a hilly district, ai'e not detained in lakes, but
quickly flow down the hillsides to the streams. Floods
in the Ohio valley may rise fifty or sixty feet in a few
days, spreading to ten or twenty times the usual width
of the river and causing great damage to villages and
cities on the valley floor.

KIVERS AND VALLEYS

251

146, Falls and Rapids. — When a river begins to
wear it-s valley it rushes down any descending slope
that occurs on its course. Here a gorge is cut as the
rocks are rasped away by the gravel and sand in the
rapid current. Niagara, when first taking its present
courae, fell over the iiorth-fiicin^ bhiff of tlie upland

that separates the basin of Lake Erie from that of Lake
Ontario ; since then the river has cut back a -gorge about
seven miles long from the edge of the upland; the falls
now plunge into the head of the gorge. The larger or
Canadian fall is now retreating three or more feet a year
at its middle.

The falU of the Yellowstone river occur at the head of
■a deep canyon cut by the river in the process of deepening

252

eli:mf.,tauy physical geography

itfl c«ui-se through a lava plateau. As the falls are worn
back the gorge is lengtbened.

While a stream is engaged in deepening its valley it
often flowM from a haitler to a softer rock structure. It
will deepen the valley much more quickly in the latter
than in the former, and a rapid or fall will be formed on

Fro. V15. Falla of the Yellowstoue Bivei

the abrupt slope between the two. Falls and rajiids of
this kind are numerous, especially in dissected plateaua
and mountains.

It has long l>een the custom to build mills near falls, so
that part or all of the descending water may be used to
turn water wheels and thus to drive the machinery of tlie
mills. VUlageH have often grown up around the niilla
and factories thus located. As the work of the mills
increases it has frequently been necessaiy to add steam

RIVERS AND VALLEYS

253

power to water power; at the same time the vilhige may
grow to be a large city. In recent yeara it has been found
possible to transform the power of falling water into an
electric current, which may be earned many miles through

Diagr&m

How many falls are shown iji Figure 12GV Draw a proRIe along
the river course and coinparo its slope at and between the iaih.
Why are some of the stretches between the falls longer than others?
Wliere are the gorges deepest V

wires and then set to work to drive machinery, to run
cars, or to furnish electric light. Waterfalls in thinly
populated mountains may thus in time come to be used to
supply electric power to cities on the neighboring plains.

254 ELEMENTARY PHYSICAL GEOGRAPHY

147. Graded Rivers. — A river caimot wear down its
course to a level, for there must be some slope down
which the current, bearing its load of rock waste, may
flow toward its mouth. While the alope is strong and
the cuiTent is very swift the stream ia called a torrent.
The waste is then swept along so actively that bare rock
is commonly seen in the stream bed. Torrential streams
are usually clear, because they quickly sweep away the
fine particles that they receive from time to time, leaving
coarse cobbles and bowlders lying on their rocky channels.
Such streams are still young.

As time passes and the channel is eroded deeper aud
deeper it will be worn down more nearly level, closer and
closer to baselevel. But it must always preserve a slope
snfBcient to give the water a velocity that will enable it
to wash forward the load of waste received from the head-
waters and side streams, though without either deepening
or building up the bed of the channel significantly. When
such a slope is attained the river is said to be graded. It
has reached maturity.

The current of a graded river is iisualiy deliberate
instead of torrential. Its bed aiid banks consist, for tha
most part, of deposits of rock waste ; firm ledges are seldom
seen along its course. The water is usually made some-
what turbid or muddy by the presence of line waste, with
which it is plentifully supplied by its tributaries and by
the wash from its bed and banks.

In valleys among high mountains, where an abundant
supply of ooaise waste is washed down from the steep
valley sides, graded streams: must have a slope strong

^^M RIVERS AND VALLEYS 255

rtbtragh to give them an active curi-ent ; otherwise their
coarse and abundant load could not be washed forwaid.
In lowlands where only fine-textureil waste of the land is
slowly washed into the streams, graded riveiB have a very
gentle descent.

Water moves so easily that large rivers assume very
faint slopes ; tlie lower Mississippi has a descent of only
two or three inches to the mile, yet it bears along a vast
amount of rock waste, — 6700 million cubic feet of sus-
pended silt, 750 million of silt dragged along the bottom,
and 1400 million of minerals in solution every year,

148. Reaches and Rapids.- — A longer time is requii-ed
to wear a valley down to grade where the rocks are reaist-
ant than where they are weak. If a river crosses a suc-
cession of weak and strong rocks, as in Figure 126, the
graded condition will be first attained on the weak rocks,
and each reach of the river on tlie weak rocks will be
graded with refei'ence to the sill of hard rocks next down-
stream or with reference to the lake or sea into which the
river may flow. The sills of hard rocks then serve as local
bajselevela with respect to which the stretch or reach next
upstream is graded.

Many rivers come in this way to be divided into long
smooth reaches and short plunging rapids or falls. Most
of the rivers of New England and of eastern Canada are
in this condition.

When a river system has been undisturbed for a long
period of time, even the resistant rocka are worn down.
Few falls then remain to interrupt the steady flow of the

256 elp:mentary physical geography

river current, and its graded reaches become longer and
longer. The side atreama, following the example of the
master stream, wear down the side valleys so as to join the
main valley at even grade. It is in this well-establislieil
condition that many large rivers of the world are found.
When a graded condition is reached in even the sroalter
branches of a river system the slope will be steepest in
the headwater streams and least near the river moutli;
thus the profile of a well-developed river is a curve ol
decreasing slope from head to moutJi.

149. The Development of Valleys. — While a young river
is deepening its valley, the valley sides are steep and the
valley bottom is no wider than the I'iver channel, as In Fig-
ure 127. At such a time the valley floor offers no attraction
to settlement, as it affords no level ground for roads near
the river; roads built in such a valley must perch on tLe
side slope. If the valley is deep, like the Colorado canyon,
it may act as a barrier between the uplands on either side.

Floods have Httle itiom to spread in a steep-sided valley:
lience they rise rapidly on the valley walls, even thirty
feet or more in a day or two. Thus confined in the valley.
the flood flows rapidly and sweeps away all obstacles,
gradually subsiding as its supply of water lessens.

It is for this reason difficult to maintain road bridges
across the streams of the Allegheny plateau. Figure 79:
the great expense of building strong and high bridges can-
not be borne by the scattered population. The streams
are therefore commonly crossed by fording. At time of
high water travel is inteiTupted,

illVERS AND VALLEYS

257

The continued action of the liver, wearing first on
one banit and then on the other, gradually widens the
valley floor. At the same time the sides of tlie valley are

Fia. 127. Valluy of Yakutiii River, WasliiHgt.Hi
worn back to gentler slopes, and the valley floor becomes

At this stage of development the valley is much more
available for human ueea than when young, narrow, and

251*

ELE.MKNTA1U' I'HYSICAL GEOGRAPHY

steep-walled. Villages may be built and fields may be
cultivated on the valley floor. Roads may follow it on
each side of the river. Instead of being a trenchlifce bar-
rier between two highlands, the valley has now hecoiiie a
well-gi'aded pathway for settlement and for trade between
the upper and lower parts of the river system to which it

'liH Muliawk V«iiey

The Mohawk valley in eastern New York, Fig-
ure 128, is a good example of this kind. Another is
shown in Pliitc X,

The behavior of rivers during the advance in the devel-
opment of their valleys raust now he coiisidered in greater
detail.

160. The Development of Flood Plains In a wiflding

stream the fastest current is displaced from the middle
of the channel towai-d the outer bank- Such a stream

XONil -MOXSV

RIVERS AND VALLEYS

259

I therefore teuda to cut mora on the outer bank thau on
the inner bank at every turn^ hence as it cuts down it
also cuts sideways.

When grade is reached the valley walla will be slant-
ing, but they will be steepest on the outer side of every
bend, where the stream has undercut the valley wall, as in
Figure 129, The valley walla will therefore be equally
steep on the two sides only where the valley is straight.
At each tui'n sloping spurs descend opposite abrupt cliffs,
and the belt of country occu-
pied by the turns of the river
is broader than at first.

Draw a. map of the district shon n
in Figure 130 a, following the stjle
of Figure 129, and show where thp
river ia undercutting the cbffH
The river is Bupposed to be flowing
toward tlte front of the diagram
in Figure 130.

Fia. VJit. Outlino Mup nl' a

When a river has worn down Young Valley

its valley to a gentle slope it

still wears on the outer bank of every turn, because the
strong current runs there; thus the valley floor is broad-
ened. At the same time the turns tend to become sniootli
curvea of regular form.

As the outer bank of a curving channel ia slowly cut away,
tlie inner bank, where the cuiTent runs slower, is gradually
filled up nearly to high-water level with rock waste from
farther upsti-eam. A curved strip of flat valley floor is
thus developed on the inner side of each curve, as ui

2(10 iCl.KMENTARY PHYSICAL GEOGRArHY

Figiiie 1 30 1 h"st on i ne side and then on the other side of the
river As the valley floor
IS exposed to overflow it
timen of flood, the flat
I md bordering the strcivm
IS called the flood plain.

Draw a map of the diatrict
in tigure )30i. Deacribe thf
Bliape and poaition of the
patchpe of flood plain.. VThni
difficulticB would be met in
matmg a road along the val-
ley bottom ?

With continued action
the ri\er consumes more
md more of the spurs that
enter its curved course, as
in Figure 130 c, (f. In
time the spura are all woru
awav as in Figure 130 e.
Then an open flood plain
IS formed on which the
liver freely follows sucha
L ui ve d course as best suits
il^, -volume. With still fur-
ther action of the river tlie
flood plain will be slowly
Fio. 130. Diagrams of a Widening Valley widened to greater breadth.
The valley will then be more attractive to settlement than
before, with room for villages and fields on its floor.

*MJ VOi\

THE NE\V Y

[public L13RAR\

A3TO^. L6NOX

-i: -. N FQUNJATtONt

RIVKRS AND VALLKYS 2l51

Whicli side (u( valley or downvallej) of ll p n dJIe k| r
Figure ISO t has been »or awaj I Draw ami repreae tuj.
Figure 130 d.

Deeoiibe the for f the plan 1 tl e d agrama of F gure 1 JO
Compare the for and 1 readth of the flood pla the d fF rent

digrams. Compare the sIoim-b f the alley a des C pure tl e
forms of the upland spurs that ent r the corveB of tl e valley

When a river overflows, the greatest amount of silt
is hiid down on the flood plain near the river channel.
Thus in time the plain comes to have a gentle slope
away from the river on either side, aa well as down the
valley.

If a sti'eiim has a large load of coarse rock waste, its
graded flood plain must be relatively steep (a descent of
from five to twenty feet or more in a mile). In this case
the stream does not turn far aside from a direct coiirse
along tlie flood plain to form seipentiue curves; but it
is constantly embarrassed by the formation of bars and
islands of gra,vel and sand, apUtting ita current into a
braided network of channels.

The Platte is a river of this kind. It gathers mucli
waste from the weaker i-o<.'k.s of the Great plains and
therefore requii'es a rather strong slope for its graded
valley floor. Many rivers flowing from the Alps to the
lower lands have gravel bars and islands between theii'
braided channels, as in Plate XI.

151. River Meanders. — If the waste borne by a river
is of very line tuxture, the flood plain will have a very
gentle grade. Then the river easily turns aside from a
direct course on its broadened flood plain, and in this

262

KLliMENTAUY PHYSICAL GEOGRAPHY

Avay (whatever its original path) develops a system nf
serpentine curves, m in Figure 130 d, e. Curves of this
kintl iire called meanders, after the Meander, a wimling
jriver of Asia Minor. How many turns docs the river
lake in Figure 131?

The size of the mearidei« increases with the volume nf
the stream. A meadow brook may swing around curres

i Knsbmir, Ii

measuring only forty or fifty feet across. The curves of
the lower Mississippi are fi'oni three to six miles across.
The flatter the flood plain, the greater is the meander turn-
ing. The Koroa, Figure 132, on the Plain of Hungary,
lias its meanders remarkahly developed.

Meanders are slowly changed, for the river wears away
the outer bank of each cniTe because the current runs
fastest there ; the opposite side of the channel is filled

RIVERS AND VALLEYS

_ m with waste where the current is slow. The Mississippi
below Cairo has in the courae of ages shifted itB course,
now eastward, now westward, and has thus opened a flood
plain from twenty to sixty miles wide, that is, five or six
times widei' than its meander belt. Similar changes may
be seen on a small scale in a meadow brook.

In the fine silt of a broad and fiat flood plain a large river
changes its course easily and rapidly; it takes material
from the outer bank,
where its current is
strong.and deposits it
farther downstream
on the inner bank,
where the current is
weaker.

The necks of the
flood-plain spurs be-
tween adjoining „,.,..., ^ , „,

^ ° Fin. 132, A MeamlerinB River ou Iho

meanders are often piaimif Hungary

gradually narrowed

and cut through by the river, the meander around the
spur being then deserted for a shorter and more direct
course, called a cut-off. Where are cut-offs likely to
occur in Figure 132?

Large livers, like the Mississippi, exhibit all stages
of this process. An abandoned meander is occupied
by nearly sti^ant water, more or less completely sep-
arated from the new and shorter channel by deposits
of silt in the ends of its arms; in time it becomes an
oxbow lake.

KLEMENTARY PHYSICAL GEOGRAPHY

I Draw no outline map to show the probable {MitJi of the 3rlia»iiiHi[i|>i
irheii it ran through the oxbow lakes, Figuru 13a. How Jobs tlie
ehainiel of ISSfl differ from that of 1882 7

The shifting of the channel may be checked hy pro-
tecting tlie outer bank
with Btone or wood,
))ut this is expensiTE.
Rising flootis may be
held back by dikes or
U-vees built on the
plain a little distanee
from the river banks,
When the levees are
overtopped or breached
widespread floods may
resultjSuch as occurred
on theMisaissippi flood
pKin in April, 189T,
^\hen about 13,000
M[uare mi lee of tlie
pliin {two fifths of the
entire area) wei-e under
wdter. Tlie value oE
live atock and crops
lost in this Hood was
estimated at $15,000,-

000; many thousands of people were for a time driven

from their homes.

In March, 1890, a strong flood in the lower Mississippi

broke through the levees on the left bank, forming the

Lakes in the Flood Plain of the Mibsibs
according to Surveys 1q 1SH2 and 1883

□ b; dotted line)

>f the channel »t

RIVERS AND VALLEYS 265

"Nita crevasse" (a break on the Nita plantation), flood-
ing the plain, carrying river silt into the shallow waters of
the Gulf of Mexico, and ruining the oyster beds east of
the delta.

152. Alluvial Fans of Large Rivers. — When rivers flow
from mountains or plateaus and enter open lowlands,
where no valley walls inclose them, they may build exten-
sive alluvial fans of faint slope. The Merced river of
California (see Jf, Figure 134) offers a good illustration
of this habit.

The Merced gathers much waste from its steep head-
waters in the Sierra Nevada. On issuing from its narrow
valley at the mountain base it is free to run in any direc-
tion — forward, to the right or to the left — on the broad
" valley of California," a belt of low country between the
Sierra and the Coast range. Here the river, flowing first
in one direction, then in another, has built a fan about
forty miles in radius, of gravel near the mountains, of fine
silt farther forward.

As the rain of this region falls chiefly in winter, it is
necessary to irrigate the fields for summer crops. Nothing
could be better adapted to the needs of irrigation than a
gently sloping alluvial fan; for the river may be easily
turned into various channels at the head of the fan and
led forward on different courses, and thus distributed over
thousands of acres.

One of the largest alluvial fans in the world is that of
the Hoang-Ho, in eastern China. This great river, bear-
ing a heavy load of fine silt from the basins among the

266

ELEMENTARY PHYSICAL GEOGRAPHY

inner mountains, issues from its inclosed valley 300 miles
inland from Uie present shore line, and at a height of abont
400 feet above sea level, and then flows to the sea down
the gentle slope of its extensive fan.

The great fan of the Hoang-llu
is very fertile and supporte one
of the densest populations on the
earth ; but it is subject to overflow
on a vast scale, when the river
suddenly changes its course from
one path to another and invades
fields and villages on a new course
to the sea. Overflow is prevented
I far as possible by dikes; but
the channel has repeatedly been
changed during the many cen-
turies of Chinese history.

The loss of life caused by these
overflows is very great. Not only
are many thousands of people
drowned, but the crops are de-
stroyed over large districts, eauft-
ing famines in which many more
thousands perish.

1S3. Broad Plains formed by Rivers When many

rivers flow forth from mountain valleys upon a neighboring
lowland their adjoining fans unite in a broad plain slop-
ing gently forwai-d from the mountain base- This may be
called a river-made plain. It resembles a coastal plain in

RIVERS AND VALLEYS

26T

land for a background, but it dues not neces-
<f front upon the sea, and it is generally but little
;lied by the rivers that built it. A plain of this kind
t occupies the depression between two highlands or
fitaiu ranges.

le many rivers issuing from the valleys of the Sierra
ada and the

4. Deltas. — When a river ent«i's a lake or the sea its
mt is cheeked. The finest part of the waste may be
t away by waves and tides ; the rest accumulates at
iver mouth and builds up a new land surface, called a
, in advance of the original shore line. The fans of
itain torrents form deltas in lakes at the mountain

F2G8
base.

EI.EMENTARl- rilYSIt'AL UEOGKAI'HY

Small deltas ai-e characteristic of young rivera ; the
longer the progress of river growth, the larger the delta
may become.

The land surface of a delta is built on the same slope
as that of the river flood plain farther upstream, the delta
being only the forward part of the flood plain. Uuder
water a delta slopes at a steeper angle than above water.
The great fan of
the IIoang-Ho maybe
I'egarded as its delta,
because it has been
built f or^vaixl into tlie
Yellow sea (so named
from the color given
by the river waste).

A river frequently
splits into several
channels on its delta,
the outgoing branches
being known as dit-
tributaries. These are well exhibited in the fingerlite
divisions of the Mississippi on its outer delta, Figure 136i
and in the many channels of the Ganges and the Brabma-
putra on their deltas at the head of the Bay of Bengal
How many distiibutaries are shown in Figure 136?

Great rivers may build their deltas in the face of waves
and tides. At the Mackenzie delta the tidal range is three
feet, at the Niger four feet, at the Hoang-Ho eight feet,
at the Ganges-Brahmaputra eighteen feet. The building
of deltas by small rivers is favoj-ed by the protection from

Fio. 130. The DeltH o(

KIVERS AND VALLEYS 209

ivBTes in bay heads and by the weakness or absence of
.tides. Where aiB the altove-iiamed rivers?
' The absence of deltas at the embayed mouths of certain
rivers is frequently not so much because the tidal cm'rents
aweep away aU the river silt, as because there liaa not yet
|been time enough to build a delta since the embaymenta
"were formed by the depression of the coastal lands.

The lower valleys of the Delawai'e, Susquehanna, Poto-
mac and neighboring rivers are drowned, forming bays in
the partly subniei^ed coastal plain of the Middle Atlantic
States. Whatever deltas these rivei's previously built are
JBow beneath the sea. Very little delta growth has yet
taken place at the bay heads ; hence the depression of the
^gion is relatively recent.

The deltas of large rivers consist of fine-textured waste
ci" silt, worn during the long journey from the river head-
waters and weathered during many rests in the flood plain
ten the way. In a favorable climate deltas are very fertile
Ituid attract a large population. The three densest popular
tions of the world (outside of large cities) are in eastern
China, northeastern India, and northern Italy, aU on the
lower flood plains and deltas of lai'ge rivers.

155. Mature Rivers. — When a river and its larger
'branches have destroyed their lakes and falls and reduced
-their valleys to graded slopes, when all the side valleys
join the larger valleys at grade, when the larger streams
ifaaye broadened their valley floors so that they can meander
ilreely upon flood plains in curves appropriate to their
jolume, and when a delta is built forward at the river

^olume, and wl

270 ELEMENTARY PHYSICAL GEOGRAPHY

mouth, the river system has reached the mature or full-
grown stage of its development.

Mature rivers accomplish the drainage of their basina
and the carrying of ixjck waste to the sea in the most per-
fect manner. No undivided uplands remain from « hith ii
great part of the rainfall may be returned to the dtmos
phere by evaporation. The largest possible share of the
rainfall is shed from the well-carved surface of the land
an<I runs off in the streams with no delay in lakes or haite
in falls. No hard rock ledges remain to be worn down in
the valley floors. Everywhere the waste of the land is
washed down the slopes to the streams and delivei'ed in
such quantity that the streams are kept working at their
full capacity to transport the waste toward tlie sea.

The valleys of matnre rivers are easily followed by roads
and railroads ; they are broad enough to contain eultivateil
fields as well as villages and cities, as in Plate X.

156. Old Rivers. — If no disturbance oecui-s, a maturely
developed river system passes by slow degi-ees into a quiet
old age. The hills waste away to fainter slopes and yield
less and less waste to the streams. The texture of the
waste becomes finer and finer. More of the waste is car-
ried in solution.

The extreme old age of a river system would be char-
acterized by low and ill-defined divides between faint slo[>e3
leading to broad flood plains, on which the streams would
meander with great freedom. An increasing share of the
transported waste would be dissolved. A lai'ge amount of. ,
rainfall might be lost by evaporation on the gentle slopea. |

RIVERS AND VALLEYS 271

It is unusual to find an old river system. The lower
trunks of large river systems often gain very gentle slopes
and free-swinging meanders, but before old age is attained
by all the small side branches and the headwaters move-
ments of elevation or depression generally occur in the
earth's crust, with more or less tilting and breaking ; and
in this way the rivers are made young again and set to
work at new tasks.

157. Revived Rivers. — At any stage in the erosion of
a region drained by a river, the river basin may be uplifted
to a greater height above sea level. Then the river will
at once begin to cut its valley floor deeper than it could
have done before. Such rivers may be called revived.

Old rivers flowing across low worn-down mountains are
rare, but revived rivers flowing through gorges in uplifted
lowlands of this kind are common. The rivers and their
narrow valleys in the Piedmont district of Virginia are
thus explained.

If a meandering river is revived, it will intrench itself
beneath its former flood plain ; then its new valley will be
regularly curved after the pattern of its meanders.

The north branch of the Susquehanna follows a deep
and winding valley of this kind through the Allegheny
plateau of northern Pennsylvania. The Osage has an
extremely serpentine valley in the uplands of central Mis-
souri. Both these rivers seem to have learned to meander
when the uplands were lowlands. Since these regions
were raised the rivers have cut down valleys of a meander-
ing pattern. The valleys are still narrow. The rivers are

272 ELEMENTARY PHYSICAL GEOGRAPHY

enlarging their curves by cutting away the outer bank;
here the river ia bordered by steep bluffs. Stiips of Hood
plain are beginning to form on the inside o£ the river
— ___^^^^^ curves where the hanks

, -^^^ --T^ ^^"-N. are low and flat.

Draw a map of the dLrtrict
shown in Figure 1 37 . Describe
the form and arraiigemeDt uE
the patches of flood plain.
Where are the valley Bides
steep? Wliere are their slopes
gentler?

It sometimes happens that a revived meandering river,
eroding its outer bank, may wear throtigh the neck oi the
naiTOwest upland spurs that enter its tnenclitd course; it

will then desert a round- , .

about course for a more
direct one. Figures 137,
138. Rapids will occur
for a time at the cut-off.

Draw two maps of tha dis-
trict shown in Figure 138, one
showing the path of the river
just before thu cut-off was
made, one just afterwards.
Compare the first of these maps with the one drawn from Figure 137.

The village of Lauffen (Rapids) ou the river Neckar in
HOTithem Germany gains water power from rapids fonned
at a recent cutnaff. The former course of the river is seen
in a meadow beautifully curved around an isolated hill,

RIVERS AND VALLP:YS

f end of an upland apnr, Figure 139.
Bpur IB seen near the village of Hofen.

Water Gaps. — Many rivers
nf tLe Allegheny
lins of Pennsyl-
n sharp notches,
water gaps. For
le, the Dekwnm

gathers tu.M
es from the ni > ..
of northeastern
lylvania and es-
ly a deep, narrow

called the Delar
atergap, in Kitta^
mountain, at the
'estern corner of
ersey.

t as follows. Once
lole region stood
than now and a
d spread far and

t about the level of what are the ridge crests to-day.
h the elevation of the region all the revived rivers
,0 wear down their valleys. Where a trunk river cuts
■ts new valley across the belt of hard rock that is to
;he mountain ridge, the valley remains naiTow for a
ing time ; but ekewhei* the vaileya of the trunk and

274

ELEMENTARY PHYSICAL GEOGRAPHY

branch streama widen
rapidly in the weaker
rocks, and in time all
the hilla of the weak-
rock belts are worn
away, leaving a low-
land on each side of
' the hard-rook ridge,
through which tie
water gap has been
cut, aa in Figure 141.
This explanation
applies to the Susque-
hanna, cutting gaps in

Fio. Ul, TrfmsrerSB and LongituUiual Valleys , 6 J "6 '

Figure 142, and to
the stream that has cut a deep passage in one of the Alle-
gheny ridges in Maryland, shown in Plate IX.

Where miist ona stand in Figure 141 to gain a view lite th»l
of Figure 142 ? How many water gaps are showu in Figure 103?

RIVERS AND VALLEYS

QDBSTlOnS

Sec. 134. How is the raiofall of a region disposed of? What is
ground water? Under what conditions will much of the rainfall be
evaporated into the air? discharged by streams? absorbed by the
gronnd? What ia the run-off? Of what Talue is ground water?

135. How are caverns generally formed ? What in a sinlt hole ?
What effect have sink holes on surface streams 1 Describe an under-
ground stream. Describe the animala of caverns. What is the
origin of the Natural bridge of Virginia?

1S6, What ia a spring? Upon what doaB the variation of stream
volnnae depend? Under what conditions is the variation snial!?
Describe the movement of ground water. Where is it found at a
small depth? To what depth should wells be dug or bored? Why
is spring water purer than stream water ?

137. What is an Artesian well ? How is its water supplied? Name
some districts where such wells are common. What is the relation
of certain Artesian wells in eastern Maryland to Chesapeake bay?

138. Explain hot springs. Why are they commonly chained with
mineral salts? Of what value are they? Name some examples.

1S9, 140. What is a geyser? Where are the most famous gey-
seta? Describe and explain the action of geysers ; of mud volcanoes.

141. Deflue river, river system, river basin, divide, channel, bed,
banks. What is meant by a continental divide ? by undivided
dnanttge? by subdivides? What features of a river system have
you seen illustrated in a small way?

142. Describe a. river flood. Where is the river-borne waste
laid down? How is a river supplied after a flooil subsides? How
does a drought aifect ground water? springs? streams? Comjiiire
the streams of the rainy and of the drier parts of the United States.

143. Give some examples of the work of rivers from earlier chap-
teirs. Upon what does the depth to which a valley may be cut
depend? How do Bloi)e and volume affect the velocity of a stream
and its load of sediment? Why does a river carry more sediment at

276 ELEMENTARY PUYSICAL GEOGRAPHY

lime of flood? How is erosion perfonned bj rivers? What h
source of the rock waste borne by rivers? In what aeose is it
that "rivers erode their TuUeys"? Under what conditions may t
river be called young? old? mature?

144. How is the course of a young river determined? Wh»l I
work is done by young rivera ? What are the characteristic oi
younj; rivers? Describe the St. Lawrence systera.; the drainage al
the Laurentian highlands ; that of the region of the great Afticm
lakes. What changes occur as a river paBsea from youth to raattirity!

145. How are lakes converted into rivers? Illustrate by Lak|
Geneva. In what part of the life of a river syatfira are lakes it
common? How do lakes affect the transparency and the steadina
of flow of their outflowing SitreaiaB? Corai»are the Ohio and tb
St Lawrence as to floods.

146. Where are falls and rapids formed in yonng rivers? Howu
gorges formed ? Ulustrat* by the gorge of the Niagara ; by the Yd
lovvstone canyon. How do difierences in rock structure deterrab
the occurrence of falls or rapids ? What uses are made of waterfall!

147. Describe a torrent. What determines the least slope ti
wliich a river can wear down its course? Describe a graded rivet
Where have graded atreains a relatively strong slope? Whyi
Where have they a very faint slope? Why? State the slopeund'
the load of the lower Mississippi.

148. Where are graded reaches first developed in a river ? Whsn
do rapids survive longest? What is a local baaelevel? In what
condition are the rivers of New England? What other region hii»
similar rivers? Describe a river that has long been undisturbed.
Describe the stream slopes in a well-graded river syfitem. How do
its branches Join its trunk? Why are they thus related?

149. Describe the valley of a young river. What disadvantages
does it present to occupation? How do floods act in such valiaja?
Illustrate from the Allegheny plateau. How is a valley floor will'
aned? What changes do the Talley sides suffer? What advanlagM
are presented fay a widened valley ?

RIVERS AND VALLEYS 277

160. Describe the action of a winding stream. Describe ita val-
ley when grade is reached. What changes occor after grade is
iteached ? Compare the outer and inner sides of river curves. Where
;and in what pattern is the flood plain first developed? Describe the
later changes in the valley spurs; in the flood plain. Where is the
inost silt laid down during a flood? How does this afFect the form
m aflood plain? How does a heavy load of waste affect the behavior
m a river ? Give an example.

I 161. How does a light load affect the course of a river and the
tAope of its flood plain ? What are meanders ? AVhat is the deriva-
laon of this term ? On what does the size of iiieaitders depend ?
How does their fomi vary? How hits the course of the Mississippi
j^lianged? How have these changes affected its flood plain? What
Sb an oxbow lake 7 Describe an example. How is the shifting of a
jiver channel checked V How are flooded rivers restrained ? Describe
I3ie effects of the Mississippi flood of 1897. Describe the Nitoci

152, 153. Describe the fan of the Merced river. Why is irriga-
iKon needed here? How is it favored? Describe the fan of the
Boang-Ho, and its relation to the people of China. Describe a rivcr-
luade plain. Give an illustration from California.

164. How are deltas formed? What is the relation of a delta to
A flood plain ? What are distributaries ? Describe some examples.
What is the relation of deltas to tides? Give examples. Why art;
deltas wanting at certain river mouths? Give examples. What is
the relation of large deltas to population?

155, 156. What are the features of mature rivers? Describe the
work of mature rivers ; the change from a mature to an old river ;
an old river system. Why is it unusual to find old rivers?

157. What is a revived river? Describe the rivers of the Pied-
mont belt in Virginia. Describe the valley of a revived meandering
river. Give two examples. What changes may happen in such
vaUajB? Illustrate by the Neckar.

168. What is a water gap? Give an example. Explain it, What
Ib the origin of the lowland upstream irom a water gap ?

DESERTS AND GLACIERS

159. Land Forms dependent on Climate In regions

of ordinaiy climate the snow of winter melts in the spring,

and the droughts of summer are not severe enough to niaki

I the surface barren by preventing plant growth. The form

I of such regions is determined largely by the action of

I Htreaius and rivers, whose work goes on steadily along

' branches and trunk so that, in the course of ages, the

land surface is dissected and a mature system of branch-

I ing valleys is carved. Many examples of I'egions of this

' kind have been given in tlie descriptions of plains and

plateaus, mountains and volcanoes.

An excellent illustration of a well-dissected upland ia
found in the Ozark plateau of southern Missouri, The
once even plateau has been transformed into a succession
of rounded hills and spurs of graceful form, separated by a
multitude of branching valleys. The maturely dissectedsuc-
face has much less strength of relief than the plateau of
West Virgin ia ; its slopes are usually of moderate steepness;
it is a fertile agrieultui'al district. Villages are generallj
on the uplands, for moat of the valleys are as yet too narrow
to atti'aet settlement. Many other examples might be named
in which well-established branching valley systems testify
to the long duration of an ordinary or normal climate.

'^:?;'^

DESERTS AND GLACIERS

279

In certain otJier parts of the world the climate is so dry-
that vegetation is scanty or wanting, and the surface is left
barren and desolate. Here streams flow only at rare inter-
vals, the rivers frequently fail to reach the ocean, and the
wind becomes an important means of moving land wiiate.

In still other parts of the world the mean annual tem-
perature is so low that the snowfall is not aU melted away

Fio. 1*3. TliB Oiark Plateau, Mi

in the warm season. The snow thus gathers from year to
year, and, as it thickens, the under part is slowly com-
pacted into ice. The ice has become thick enough to
behave like a viscous body and to creep slowly down the
slope of the land until it enters a warmer climate, where
it melts away. Such moving slieets or streams of ice are
called glaciera. Regions thus covered with ice and snow
are even more barren tlian arid deserts. The removal of
rock waste is there chiefly performed by ice instead of by
lain and rivers.

l280 ELEMENTARY PHYSICAL GEOGRAPHY I \

160. Deserts. — It has been explained in the paragraph!

rainfall that the arid deserts of the world occur under

the drying trade winds, on the slopes and lowlands to the
leeward of higli mountain ranges, or in inclosed continental
interiors. (See page 71.) The interior basins of Nevada
and Utah, inclosed from moist winds by the ranges o£ tiie
Pacific slope, fall under the third claas, although they are
less arid than many pai-tfi of the Sahara.

All of these deserts are hot in summer, but they may te
cool or cold in winter. They shoiild therefore be thought
of as prevailingly dry regions which may be hot or cold
accoi'ding to the season of the year. The deserts of cen-
tral Asia have a mean January temperature of only ID"
or 20° F.

Rain seldom falls, and the dry air parohes the dusty,
sandy, or stopy ground, so that plant hfe in deserts is
scanty, though it is I'arely altogether absent. Rock waate
is plentifully exposed on open spaces between the scat-
tered desert plants, instead of being covered by a close
growth of grass, bushes, or trees, as in regions of more
favorable climate.

Deserts are of all. forma, — mountains, plateaus, and
plains; but desert plains are the most extensive. The
desolate gray forma of desert mountains, like the ranges
of northvvesl Mexico (Sonora) and of northern Chile
(Atacama), are much less picturesque than mountains
with snowy sumniita and forested flanks in a moister
climate ; but the wet-weather torrents of desert moun-
tains have furrowed them with deep ravines like those of
forested mouutaina.

DESERTS AND GLACIERS 281

161. Streams of Dry Climates. — When a light rain
occurs in a region of dry climate much of the water
returns to the atmosphere by evaporation, a large part of
the remainder sinks into the thirsty soil, and the run-o£E by
streams is small. Much of tha grouud water evaporates
underground and passes out from the soil as vapor, instead
of coming out in springs. When a heavy rain occurs, as
occasionally happens, water is supplied faster than it can
soak into the ground, surface rilla form everywhere, tmd
the streams are quickly flooded ; but the floods soon run
away, leaving the channels empty and dry again.

The streams of dry regiona are, therefore, very vaiiable
in volume ; active for a while after a rain, almost or quite
disappearing in the long dry seasons ; advancing far down
their lower couraes when in flood, then dwindling and
withering away and leaving their lower charmels dry.

In the Sahara dry water conises, known as wadies, are
commonly used for ixiads, as their gorges frequently offer
graded ways through rocky uplands. Death by drown-
ing would nowhere be so little expected as in a desert;
but it sometimes happens that a caravan, following a wady
through an upland, meets a down-rushing flood, and before
the travelers can climb the steep wails of the gorge they
may be overwhelmed and drowned.

In parts of the Rocky mountain region, of generally
dry climate, heavy rains occasionally fall in summer.
Then for a few hours the dry channels are flooded with
a rushing turbid stream, which sweeps away the waste that
has been washed in by lighter rains. Camping parties,
pitching their tents too near a channel that is almost

1282

ELEMENTARY PHYSICAL GEOGRAPHY

dry in the afternoon, may be OTerwlielmed by a rusluDg
flood at nigbt. Opposite the months of canyons, streams
of coai-se waste, including bowlders weighing many tons,
are spread forward hy floods from cloud-bursta in the raoun-
tains, — "immense, sudden, deluging rainstorms, which at
rare and exceptional moments discharge their waters info

one of these mountain gorges. On such occasions bowlders |
six or eight feet in diameter are swept down the canyon
in a fearful rush, and are sometimes carried out on the
. . . slope for half a mile."

Figure 145 illustrates a sudden flood in Cherry creek,
where it passes through the city of Denver, Colorado. .
The channel of the creek was dry half an hour before
this raging torrent appeared.

DESERTS AND GLACIERS 283

Streams that are supplied by springs in arid uplands
and mouutaiuB fi-etjueutly diminisli in volume, partly by
evaporation, paitly by sinking into the gi'ound, m they
advance over desert lowlands. They may wither away
and disappear entirely from the surface ; but their flow
is usually continued as ground water for some distance
beyond their visible end. Their load of waste is spread
on the surface before them in the form of an alluvial fan.
Many such streams are known around the mountains of
Utah and Nevada. The depressions between the ranges
are floored with fans and plains of waste that has been
washed from the mountain i-avines in time of flood.

162. Bad Lands. — Arid regions of weak, fine-textured

strata are often minutely carved by the wet-weather rills
and rivulets bordering their chief vivlleys. This would not
happen in a moistei' climate, for there the abundant plant
growth wouhl protect the surface and prevent the active
run-off of the wet-weather rills ; but in an ai-id region,
where plants ai-e few or wanting, every little wet-weather
rill erodes its own little ravine in tlie barren surface.

Western Nebraska offers many examples of uplands that
have been elaborately dissected in this way. Plate XII
exhibits the delicately carved sides of a young valley in an
even upland. Sharply carved forms of this kind are known
as had lands because of tlie difBculty of crossing them.

163. Interior Basms and Salt Lates — The lai-ger rivers
of interior regions do not entirely wither away in their chan-
nels, hut continue until they reach a depression or basin be-
tween tlie uplands. There the waters spread out, forming a

|;284 ELEMENTARY PHYSICAL GEOGRAPHY

lake. Evaporation from the lake surface diechargea as much
water into the air as is received from the inflowing streams.

In regions of more abundant rainfall the streams from
a moderate drainage area suffice to fill lake basins to over-
flowing. The Great lakes o£ the St, Lawrence system
gather their water from a comparatively small area around
each basin, yet they are always full, up to the outlet notch
in their rim. In desert regions rainfall is so scanty and
evaporation is so active that the streams from a large
drainage area may form only a shallow lake, occupying
a small fraction of its drainage area.

Lakes of the latter kind arc usually salt, for all the saline
substances gathered in small quantity by their rivers accu-
mulate in the lake and may in time constitnte a fifth or
even a third, by weight, of the lake contents.

Great Salt Sake of Utah, with about eighteen per cent
of salt, is of this kind. It lies on the lowest part of the
waste plain that has been built up in the depression among
several mountain ranges. Its waters are so dentse that a
man's body will not sink beneath the surface. The Dead
sea, with twenty-four per cent of salt, is one of the most
famous salt lakes, occupying a long narrow depression in
Palestine. Lake Van, in eastern Turkey, containing thir^-
three per cent of salt, is the densest water body known.

Interior basins, from which no rivers escape to the sea,
receive the waste that the slopes of the inclosing moun-
tains lose. The floors of .the basins are in this way built
up and smoothed. By the wearing down of the moun-
tains and the filling of the basins the I'elief of the region
as a whole is decreased. (See Figure 144.)

DESERTS AND GLACIERS 285

The level of the Dead sea ia almost 1300 feet below
that of the Mediterranean, and the bottom of tha ti^ugh
occupied by this sea is about 1300 feet deeper still.
Ravines in the border of the uplifted plateaus lead
down to stony fans that are advancing into the sea.
The great depth of the wattr and the moderate esten-
Bion of the fans show tliat the l>asia contains much less
waste now than it will in the future.

A great part of Persia consists of large basins inclosed
by mountains and without outlet to the sea. Long waste
slopes stretch forward five or ten miles with a descent
of 1000 or 2000 feet, stony near the mountain flanks,
and gradually becoming finer textured and more nearly

of drifting sands, with occasional salt lakes. The popu-
'lation gathers around the margins of the basins where the
■dwindling streams are still rtmning, avoiding the rugged
and barren mountains on the one hand, and the unin-
habitable central plains on the other.

Central Asia repeats the same conditions on a still
larger scale. The basin of Eastern Turkestan includes
in its central part many low ranges that have been half
iburied with waste from the higher inclosing mountains.
Many rivers flowing fi'om the mountain rim wither on
;their way toward the chief central depression ; only the
'largest river (Tarim) reaches tt^ there spreading out in
ithe marshy Lake Lob. The chief settlements are near
;the border of the basin, where the larger rivers come out
^frora the moimtains and where their waters can be used
ior irrigation.

SIM. Wind Action in Deserts Where the land surface
IB covered with vegetation the wind has little effect on
the form of the gruiind. In arid regions where vegetation
is scanty or wanting tlie wind becomes a powerftil agent
of change. The difference of wind action on a dusty road
and on a grassy field may be taken to illustrate the con-
trast between wind action in regions of dry and of wet
climate.

Wind storms in deserta raise the finest dust high into

the air, drift along the satid at the bottom of the current,

and rasp the unmoved stones and ledges with the drifted

I sand.

Even in calm weather whirlwinds are of daily occur-
rence in deserts during the hot season. They are formed
hy the whirling ascent of air that has been heated by the
action of sunshine on the dry bare ground. Before the
whirl begins the existence of the overheated layer of sur-
face air is often indicated by a mirage.

Whirlwinds may raise dust more than a thousand feet
into the air and drift it long distances before it settles.
When violent winds blow, like the squalls which often
precede thunderstorms in a nioistfir cUmate, heavy clouds
of sand and dust are raised from the desert surface, dark-
ening the sky, and almost suffocating the traveler over-
taken by thera.

Vessels in the Atlantic west of the Sahara sometimas
have their sails reddened with dust brought by the trade
wind from the Sahara. Rain in southern Europe is occa-
sionally reddened with dust brought by storm winds from
the same source. It has been estimated that, during four

ELEMENTARY PHYSICAL GEOGRAPHY

THE NEW Y; ;

A8TCH. f_ - -c^

DESERTS AND (iLACIEaS 287

^m.of fiueb windH iu Mnvch, 1901, nearly 2,000,000 tois
of dust from the Sahara fell on central Europe ; the greater
part reached the ground south of the Alps, but some of the
dust was observed as far north as the Baltic sea. East of
the deserts of central Asia extensive deposits of wind-bome
dust have been formed ; they constitute some of the most
fertile districts in the Chinese empire.

Desert mountains and uplands are so well exposed to
sti'ong winds that the finer piirticles of rook waste are

blown from them, leaving their surface rocky and atony.
The finer particles settle chiefly in the depressions where
the winds are less violent; here the surface is sandy
or dusty.

165. Sand Dunes. — When the rocks of a desert are of
a kind, like granite, that affoi-da sand on weathering, the
wind may blow the sand grains into drifts or dunes.
Dunes sometimes gi-ow to a height of from .500 to 600
feet. Their surface may be delicately rippled, as in
Plate Xni. In a region of relatively steady winds tbe
sand is blown up the windward slope and carried over
the creet; hence the dune may slowly advance, gradually

ELEMENTARY PHYSICAL GEOGRAPHY

ohsngiug its place and fomi. Dunes of diifting sand an
usiiiilly more barren than other ports of a desert.

A group of dunes sometimes advances across a diy val-
ley, concealing its form for several miles. Wlien rain falls
the stream fi-om the upper part of the valley disappears as
it enters the loose eand of the dunes.

Sand dunes occur also on low coasts where the winds
frequently blow landward across a sandy beach. The
dunes then fonn a belt of hills a little inland from the
beach, as will be again referred to under shore forms.

166. Dry Regions, formerly Hoiet. — In some regions
now aiid, marks of a former moist climate are found.
Certain basins now almost without water have been filled
with great lakes, even to oveiflowing; the foriyer shore
lines of the lakes are marked by cliffs, beaches, and deltas,
and an outlet is sometimes traceable in a trench across the
lowest pass in the inclosing highlands.

The basin of Great Salt lake in northwestern Utah in
prehistoric times contained a much larger lake, t« which
the name of an explorer, Bonneville, has been given. Its
shore lines are still plainly recorded on the mountain sides
nearly lUOO feet above the desert plain around the present
lake ; the foreground of Figure 86 shows an extensive lieach
of this lake. The channel of an outlet leads northward
across a pass to the basin of Snake I'iver ; hence the former
lake must have been fresh. The change from the moister
climate of Lake Bonneville time to the drier climate of
to-day has caused the almost complete disappearance of the
lake waters, revealing the stidiments of the lake floor in

UESERTS ANO GLACIERS

2S9

»n arid plain. The ancient lake deltas are ni»w trenched
hy the streama that built them.

Another extensive lake (Lahontaii) of very irregular
outline and several Biualler Likes once occupied the now
desert basins of western Nevada.

Fig. 14T. Ijikes Bonneville und I^h<

Compare the area of Lake Bonneville and that of Great Salt ialte
(fine and coarae dots, Figure 147). How long is Lake Bonneville
from nortli to south? How long is Great Salt lake from, northwest
to soutJieastV (Scale of figure, 200 miles to an inch.)

The causes of climatic ehangea of this kind are little
understood, but their geogra^jhical consequences are of
great importance. Extensive lakes among forest-clad
slopes have been replaced by deseiir plains between arid
mountains.

290 KLEMENTARY niVSICAL GEOGRAPHY

167. Salinas. — Certain basins that formerly contained
salt lakes have now been more or less completely liried
out, leaving marshy or dry plains of salt, known as Salinas,
in the central depressions, avoided by all plant and animal
life.

The Bolivian table-land, a lofty waste-filled basin lying
between two great ranges of the Andes, holds Lake TiU- '
caca in its northera part at an altitude of 12,500 feet
The outflowing stream mns 100 miles southeast to a
marshy salina, fifty miles long. The water not evaporated
here flows southwest and is lost in a broad salina of daz-
zling white surface. Somewhat farther south is a more
extensive salina, 4000 square miles in area, a white aud
level plain covered with a layer of suit about four feet
thick, impassable when wet, but fiim in the dry season.

Salt lakes and salinas yield common salt and other min-
erals of eommeixiial value. Great Salt lake is estimated
to contain 400,000,000 tons of salt. These products
would be of greater utility if they did not so generally
occur in thinly populated desert regions.

168. Ice Sheets and Ice Streams. — In the polar regions
the temperature even in the lower atmosphere is so low that
snow and ice cover much of the land all the year round,
even close to sea level, cloaking the ground with ice
sheets. In the temperate and torrid zones it is only on
mountains that the temperature is low enough for snow
to be more abundant than rain, so that snow fields are
formed on the higher slopes and ice streams in the upper
valleys.

', vttimj'H.

DESEKTS AND (il.ACIERS 291

During winter in the northern United States tliere are

■ frequent examples of the formation of small shorHived

ice sheets, after a succession of snowstorms with prevalent

I cold weather and occasional thaws. Such an ice sheet is

I not thick enough to move ; but if it (ihoukl grow yew after

yaar to a thickness of 1000 or more feet, it would slowly

move outward from the region of greatest height and

thickness to lower ground in a milder climate. This is

because ice is not perfectly solid ; it moves toward its

unsupported border very much as a thick mass of paste

would move, but much more slowly.

169. Antarctic Ice Cap A few explorers of the far

southern ocean have discovered a great ice aheet ending
in cliffs that rise from 100 to 180 feet above the sea. No
land was seen back from the top of the cliffs,

Although as yet known only on one side of the south
pole, the ice sheet is thought to form a polar ice cap, per-
haps 1000 miles in diameter. There may be some land on
which the cap rests ; but it is believed that much of it lies
on the sea bottom. It must tend to thicken from snow
supply over its desert plateaulike center ; but it slowly
creeps toward the free seaward margin, where great tables
of ice break off and float away as icebergs. As far as this
desolate region has been explored it is uninhabited,

170. The Greenland Ice Sheet Greenland is covered

by a heavy sheet of ice, measuring about 1500 miles north
and south and from 300 to 600 east and west It has a
slightly convex surface and probably rises to a height

, of 9000 feet in the central part. The ice sheet conceals

l'29-i ELEMENTARY PHYSICAL GEUGRAPfIT

the hills and mountains except near the margin, where
the slieet is thinner; here occasional rocky suiumite rise
above the sui-face like Islancls in a frozen sea.

Some of the Greenland glaciem (arms of the ice sheet

descending toward or into the sea) are from ten to fiftj

I miles broad. Their forward movement is from twenty

m to fifty feet a day. Many icebergs are formed of great

P fragments broken from their front. The interior of the

ice sheet is a monotonous desert of snow and ice, nuw

melting and becoming almost impassable, now freezing

over or receiving a new layer of snow.

The only inhabitants of this great cold desei-t are a
minute worm and a simple microscopic plant that some-
times gives a red color to snow. The Eskimos of Green-
land live on the narrow belt of lantl iietwcen the ice sheet
and the shore.

171, Alpine Glaciers. — Glaciers of the Alpine type flow
slowly down in streamhke tongues from snow basins in the
valley heads between lofty peaks and ridges.

The end of a glacier, melting as the ice descends to a
milder climate than that of its gathering ground, often
reaches below the tree line. Glaciers of this kind occur in
the Alps, the Caucasus and Himalaya mountains of the
Old World, and in the mountains of Canada, Alaska,
and Patagonia in the New World. In Alaska many of
the glaciers descend to the sea. The front of the Muir
glacier. Plate XIV, breaks off in cliffs 200 feet high.

A glacier moves faster along the middle surface Une
than at its sides or bottom, thus resembling a river. Tbe

DESEKTS AND GLACnCBU

'293

movement of Alpine glaciers is on the avBrage from 100
to 500 feet a year.

Glaciers press heavily on their beds, dragging rock
waste beneath them and scouring the bed-rock clean and
smooth. Loose grains and fragments of rook, dragged along
by the ice, scratch and groove the smoothed roek surface.
The rock waste
thus scoured from
the ice floor, as
well as that torn
from projecting
ledges and that
received in rock
slides and ava-
lanches from sur-
mounting slopes,
is drag^d or car-
ried along by the
ice and laid down
around its lower
margin or at its
end, or washed
away by the stream that issues from beneath the ice.
Great bowldeia may be carried on the ice.

The ridge of rock waste that is ordinarily formed around
the end of a glacier is called a terminal moraine ; one is
shown in Figure 148. Note the momine that trails down
on the Rosegg glacier from a rocky spur between two of
its upper snow basins. It is called a medial moraine.
Why does it not follow the middle of the glacier?

Fia. 14S. RoMgg Glacier iu the Alps

294

i;i.KMENTARY PHYSICAL GEOGRAPHY

Describe the medial moraine of the Viesch (pron. feeih) gla-
cier, Figure lis. From how many snow basins is this glacier
supplied ?

Large glaciers are sometimes so heavily covered witli
rinoraines near their lower end that a plant-bearing soil is
formed upon them. Pas-
turage is found for the
flocks of the mountaineers
in the Himalayas on cer-
tain grass-covered mo-
raines overlying the ice.
Some Alaskan glaciei^
l>ear large forests on the
moraines near their ends.
Water received from
side atreams and supplied
from melting ice gathers
beneath a glacier and
issues from an ice cave
at its end. The water is
usually whitfined by fine
"rock flour" ground
"*■ '•- "• i' 111 "I I " . i>* beneath the ice.

172. The Work of Ancient Glaciers and Ice Sheets. — Cer-
tain pai'ts of the woild show the marks of ancient glaciitl
action, although the climate there to-day does not ailoff
snow to i-emain on the ground through the summer.

Ancient glaciers occupied certain valleys in the Rockj'
mountains of Colorado and in the Sieri'a Nevada of Califo^
nia. Great glaciers descending from the high Sierra into the

DESERTS AND GLACIERS

desert lowland in eastern California built strong moraines
forward from the mountain base at the mouth of the valley.

Compare the glacier that once occupied the \'alli?y id Figure 150
with the Roaegg glacier. Figure 148.

Around the border of the Alps the lower land near the out
let of the chief valleys is often inclosed for ten or twenty
miles from the mountains by a belt of hilly morainie ridges.
The ancient glaciers that descended southeast from Mt.
Blanc to the river-
nmde plain of the
Po built a huge
terminal moraine,
whose ridges rise
froml000tol500
feet above the
plain and inclose
a great amphi-
theater.

The most ex-
tensive ice sheets
of the glacial
period were those
that spread outward from the highlands of Canada across
the basins of the Great lakes upon the northern part of the
United States, and from the highlands of Scandinavia across
the Baltic upon northern Germany. (See Figure 144.)

The highlands of eastern Canada, — the Laurentian liigh-
lands, — whence the ice sheets moved out to the suiTound-
ing regions, show much bare rock, clean scoui'ed or covered

Fill, l.-jO. Glaoial Moniiripfl, Sierra Kuvaila. Calitomiii

298 KI.EMENTARY PHYSICAL GEOGRAPHY

Moi-ainic hills are fre<iueiitly dotted over with lai^
rocks or bowlders, large aiid small, brought from some

I. 15^. Gtaiiia.! Moraines,

more or less distant ledges hy the ice; the bowldei's un
frequently unlike the rock on winch the morjjiie hes

Fio. IIH. A Obudal Bowlder

Glacial bowlders are so plentiful in some parts of New
England as to make the land there almost worthlesa.

IfLoti^?'*- L^

'CiS,

^Oi

/»

Sox

'-■^ir

'o>.<

DESERTS AXD GLACIERS

209

173. DTumlins. — In some districte the rock waste hiis
been gathered beneath the ice sheet in archedj oval hilia
called drumling, commonly half a mile or more long and
from 100 to 200 feet high, easily recognized when once
known. They may be compared to sand liars in rivers or
to Band dunes under the wind.

174. Valleys, Lakes, and Waterfalls in Regions of Ancient
Glaciers. — Some of the ancient glaciers of mountain regions
were very massive, from 2000 to 5000 feet thick, and moved
with relative rapidity down cliannela of rapid descent ; here
glacial erosion was most intense. The channels thus occu-
pied are now seen lis broad troughlike valleys with steep
walla, deepened from 500 to 1000 feet or more beneath
the side valleys that once joined them at even grade. The
streams from the side valleys plunge down the rocky walls
of the deepened main valley, forming fine waterfalls. Dis-
cordaniwde valleys of this kind are called hanging valleys.

Many hanging vaUeys are found in the Alps and in the
L moimtains of Norway and Alaska; in the latter regions

the deepened main valley is UBiially occupied by an umi of
the flea, called a fiord. (See page 320.)

The rivers of a region that has been overridden by an
ice sheet me often greatly disordered. At one place a

valley floor may be scoured out, producing a rock basin.
Lakes occupying such basins have been mentioned as con*-.

mon in the rocky highlands of eastern Canada. At another'
place the irregular distribution of rock wa^te or drift may

^^H DESKRTS ANIJ GLACIERS 301

Ptn a stream to a new courae, where it ia now seen cat-
mng a steep-walled gorge with many rapids and fallB. A
■ke ia often formed upstream from the drift barrier.
I The Adu-ondaeka resemble the Black mountains of North
krolina in being disaeeted, subdued mountains, but the
L|^m group possesses numerous lakes and gorges

^^^^^ - ^^j^iSBS* --^

Fi,i. Iu7. I-ake iu tlm Ailirutidatka, New York 1

'chaBins") which are wanting in the southern group. These ,1
leculiaritiea result from glacial action, which the Adiron- '
lacks suffered in common with the other northern paiie of
ihe country, but which the southern mountains escaped.

When a river is displaced by baiTiers of glacial drift
t must carve a new channel. Before the time of tlie ice
iction the river may have had a weU-giaded course ; now
ia flow is interrupted by falls and rocky rapids. Hence
the displaced streams of glaciated regions supply much
water power for mills and factories.

302 KLEMENTARY PHYSICAL GEOGRAPHY

Many rapids aiid falls of this kind occur in the streama
of the northern United States and Canada. It must be con-
cluded that the streams have not yet had time to establish
graded courses since the ice melted away, and therefore
that the ice sheet covered the country not long ago, as
streams measure time, even though it was thousands ol
years ago, as time is counted by man.

The Merrimac is a famous river of this kind. Its falls
at Manchester, Lowell, and Laivrence have determined tlie
growth of great manufacturing cities. Rochester, Grand'
Rapids, Minneapolis, and many other important citit
have grown up at the side of falls on rivers that hava
been turned from their former channels by glacial drift

QnESTIOHS
Sec. 159. What is meant by an ordinary climate V Flow i
iorma carveiJ in regions of ordinary climate ? What are the conifr
tiona of a land surface in an arid climate ? in a cold climate 'I

160. How are arid deserts related to the wind system V Consider
their climate as to heat, cold, and dryness. Describe their surface
as to vegetation aud rock waste. What are the forma of deserts!

161. How ia rainfall disposed of in a dry climate ? Describe tlw
streams of dry regions. What is b. wady 1 What danger attenib
the use of a wady as a roadway ? Describe the floods of the dner
parts of the Rocky mountain region. Describe a flood at Denver.
How may streams end in desert lowlands? What becomes of tlieir
load of waste ? Where is their flow continaed 7

162. 163 Under what conditions are bad lands formed?
Describe Lheir form Where do they occur? What becomes of th"
larger rivers of interior basins? What is the reIa,tion of inflow tasi
evaporation m Kkea without outlets? in lakes with outlets? Com-
pare the lake area with the dra.inage area in the two cases. AVhy

DESEETS AND GLACIERS 303

e lakes without outlets usually salt ? Describe Great Salt lake ;
the Dead sea. How is the form of interior basins changed ? Describe
the basin of the Dead sea ; the basins of Persia ; of ceiilra! Asia.
164, 165. Compare wind action on plant^covered anil on barren
Burfaces. Describe the action of whirlwinds in arid regions; of
▼iolent winds. How far is duat carried by the wind? Where do

isits of wind-bome dust occur '! Describe sand dunes as to origin,
height, form, movement. Describe the dunes of coasts.

166, 167. Describe the ancient shore lines of the Great Salt lake
basin. What do they prove ? Describe another similar example in
Nevada. How do the two differ? "What is the present condition
of these two basins? What are saluias? Describe an example.

68, 169, 170. Where do ice sheets occur? When may a short-
lived ice sheet he seen ? Describe the movement of an ice sheet.
What is known and what is supposed about the Antarctic ice cap?
Describe the Greenland ice sheet. How are glaciers and icebergs
related to this ice slieet ? Where do the Eskimos of Greenland live ?

171. Describe a glacier of the Alpine type. Where do sxich
glaciers occur? How does a glacier move? What work does it
perform? Describe a terminal moraine ; u medial moraine. State
the relation of vegetation to certain moraines.

172, 173. How has the occurrence of ancient glaciers been discov-
ered ? Where have such glaciers existed 7 What remains have they

i Where did the most extensive ancient ice sheets occur? What
effect was produced by the North American ice sheet iiueastern Can-
ada? in tiie northeastern United States? ^V'hat is glacial drift?
Describe the effects of the ancient ice sheet of northwestern Europe.
Describe the terminal moraines south of the Great lakes. What are
glacial bowlders? Where are they plentiful? What are drumlinsV
174. What are hanging valleys? Explain them. Where do they
ccur? What eSect have ancient ice sheets hud on drainage?
Describe the drainage of the Laurentian highlands. Compare the
Adirondack^ and the Black mountains. What efiect have displaced
streams on industries? Name some examples.

SHORE LINES

175. The Border of the Lands — Next to the proepect
gained from a lofty mountain, the view of the sea from
the border of a highland is the most inspiring sight
that the earth offers. To the traveler from an inland
country it is as if the shore line marked the beginning
of a new kind of world. There is the mystery of tLe
distant horizon, far beyontl which strange lands are hid-
den. There is the unceasing movement of the waves as
they roll upon the beach, and of the tides as they slowly
rise and fall ; and the thought comes that thus the ocean
has been rolling in waves, rising and falling in tides,
ever since the lands and the waters were divided. With
the sight of the vast ocean comes the thought of unend-
ing time.

While the surface of tlie land has been for ages
attacked by rain and riveis, the border of the land lias
been attacked by the sea. The sun warms the air in
the torrid zone, and thus the general circulation of the'
atmosphere is established. The winds heat on the ocean
and form waves, and the waves run ashore and dash in
surf upon the lands. The border of the land is worn
back under so constant an attack, and the waste taken
from it by the surf, aa well as that washed into the sea

SHORE LINES

306

by rivers, is slowly carried away into deeper waier by the
waves, the currents, and the tides. In time the area of
the land would be greatly reduced by tlie invasion of the
sea, were it not for upheavals of the earth's crust by
which the land is now and then, here and tliere, renewed.

FiQ. 158. Sea Cliff;

176. The Work of the Sea on the Shore. — Where tlie
border or coast of the land dips under the sea the water
lies against it and marks the shore line. The waves and
other agents work upon the shore and produce changes
in its form. Hence the outline of any shore line depends,
in the first place, on the fonn that the land had when its
present attitude with respect to tlie sea was taken, and
in the second place on the clianges afterward made by
the shore processes.

J806 ELEMKNTARY PHYSICAL GEOGRAPHY

The iigitation of sea water in waves ia greatest at the
sea sui'fivce and gradually decreases downward ; but the
large waves cause st>me slight disturbance even at depths
of several Uuudred feet. The movement of wat«r in
waves is not steadily forward in the direction in which
the waves travel, but repeatedly to and fro over small
distances. The larger the waves and the shallower the
water, the greater effect their agitation has on the bottom.
Fragments of rock, lai^e and small, are thus moved back
and forth according to their size and to the strength ai
the waves. The fragments wear each other as well as
the rocky ledges on which they are rolled and thrown.
Thus the edge of the land is worn back by the sea, the
shallower parts of the sea are slowly deepened, and the
waste is slowly removed to deeper water offshore. Little
work of this kind is done in calm or fair weather; but
during storms the processes of grinding and transporta-
tion are actively at work, shaping the shore line and the
shallow sea bottom.

The currents of shore waters are chiefly of tidal origin.
but they are also sometimes parts of the general circulation
of the ocean. Except in narrow channels, they are seldom
strong enough, unaided, to move the waste that is strewn
over the bottom ; but when the waste is jostled by waves
it slowly shifts along in the direction of the current.

If deep water reaches close to the land, the waves spend
most of their strength close to the shore line, breaking vio-
lently on the headlands, whence they sweep loose material
out to the deeper bottom ; there it rests in comparative quiet.
Bare rock is abundantly exposed on shores of this kind-

SHORK LINES 307

If the land descends slowly under the sea, tlie shore is
fronted by shoal water; then much of the strengtli of the
-waves is spent on the shelving bottom before they reach
the shore line. Rock waste is so slowly removed from a
shore line of this kind that beaches of gravel and sand
axe commonly strewn along it ; the waters offshore become
Bomewhat tuibid during storms with fine waste raised by
strong waves from the shallow bottom.

177. Different Kinds of Shore Lines. — Two kinds of
shore hnea have already been described. In one tlie sea
lies upon a smooth coastal plain that was once a sea bot-
tom (page 144) ; in the other it lies on the flanks of a
depressed mountain range (page 211). These two kinds
JU'e the types for many other examples.

' Shore Hnes of the first kind are smooth and simple, and
^re bordered by shallow water. Shore lines of the second
pkind are irregular and ai'e generally bordered by deep
rwater. Those of the first kind border lowlands of weak
'strata ; they have few good harbors and hence they do not
■offer good opportunity for traffic between land and sea.
(Those of the second kind generivlly have rocky headlands
Siand islands inclosing protected bays, where harbors are
fnnmerous and trading settlements are favoi-ed.

178. Shore Lines of the First Kind. ^ The low plain of
Buenos Aires dips gently beneath the sea, whose waters
are shallow for many miles off the simple shore line.

lILai^e vessels cannot approach close to the land, except
!■ where an artificial harbor has been dredged out.

808 ELEMENTARY PHYSICAL (iEOGRAPHY

When storm winds blow from the sea they sweep the
water upon tLe low coast and eause destructive sea floods [
dikes are built along certain parts of the shore to keep
the waters off.

The waves along the shallow shores of lowlands beat
up the bottom sands and in time build offshore sand reefa
inclosing narrow lagoons. The movement of currents along
the sand i-eef forms a beach, straight or gently curved on
its seaward side. On-shore winds blow sand from the
beach and build sand bills or dunes of irregular form,
sometimes fifty or one hundred feet high, on the reef.
Flood and ebb tidal eurrenta maintain passages, called
inlets, thi'ough the reef, aa at D, Figure 159.

Sediments are brought into the lagoons by streams from
the land, and, with the aid of saltr-water plants, the shallow
lagoons are gradually filled and converted into salt marshes
at high-tide level. Sand reefs, lagoons, and marshes are
plentiful along the Atlantic and Gulf coast of the United
Stat«8.

A sand reef is slowly worn back by the action of tlie
surf on its beach. The dune sands are slowly blown back
into the nan-owing lagoon or upon the lagoon marsh. At
last the lagoon and its marsh disappear, and the mainland
is directly attacked and cut back in a low bluff. The
retreat of the sand reefs may be more rapid on one stretch
of the shore than on another ; thus one pai-t, CA, Fig-
ure 159, may have a bluff cut in the mainland, whOa
another part, AB, is still fronted by reef and lagoon.

The coast of New Jersey is fronted by long sand reelfl
inclosing lagoons and tide marshes. Farther north at

SHORE LINES

309

tong Branch, a noted seaside resort, the land is akeady
cut back in a low bluff. Severe storms cut away the base
of the bluff, sometimes undermining the houses that are
built too close to it.

The low coast of the middle Netherlands has retreated
two miles or more in historic times. A belt of dunes,
hsii a mile or more wide, lies inland from the smooth

1. ISU. Diagi

Draw an outline map iUustrating tlje feaLurea o£ Figure 15B.
Draw another map representing an earlier stage in the development
of this shore line, when the whole length of shore was fronted by a,
reef and before any bluff htid been cut. Draw a third outline show-
iag a later stage, when the retreat is great enough to produce a hluff
nearly all along the shore line, leaving only a small part fronted
with Band reef and marsh-filled lagoon.

iliarborlesB beach. The cliief ports are on the lower
courses of rivers, whose channels are broadened by the
flow and ebb of the tides.

The Uomauis buUt a castle back of the dunes, near the
mouth of the Rhine. In 1520 the dunes had blown
inland, grain by grain, and the sea had cut the shore back
close to the cattle. In 1694 the castle stood in the sea,

310 f:LP:MEXTAKY PHYSICAL GEOGRAPHY

about half a mile from land. In 1752 it disappeared,
I destroyed by the waves.

In 14G0 a cliurch that had been built inside the dunes
1 the Dutch village of Scheveningen (near The Hague]
was reached by the sea. A new church was tlien built
about a mile inland, at the east end of the village. In
1574, the outer part of the village having been gradn-
aliy consumed by the waves, new houses had been built
east of the church, so that it stood in the middle of tlie
village. In a later century the new church again stood
close to the shore, the village having moved beyond it.

In southwestern France the west winds, sweeping in
from the Bay of Biscay, have formed a belt of dunes two
or three miles wide. Formerly the sand was drifted fe^
ther and farther inland witli every westerly gale. Fieliis
and villages were invaded and buried by the advancing
drifts. Now most of the dunes have been planted with a
kind of pine tree that thrives in a sandy soil ; the wind is
lifted from the sand by the trees, and the sand drifts have
ceased advancing. The pine forests yield much resin.

179. Sea Cliffs. - — As the margin of a plain is cut biick
by the sea, the shoi'e bluff increases in length and height,
until it may deserve the name of cliff. The cliff faca
weathers; fragments, large and small, fall from it to tbe
beach below, where they are moved about and ground to
pieces by the waves. The fine particles are drifted off-
shore to deeper water. Thus longer and longer stretches
of the ehore become barborlesa, and traffic between land
and sea is greatly hampered.

SHORE LINES

311

In northweBtem France the upland plain of Normandy
fronts the sea in a vertical sea cliff, 200 or 300 feet high,
with gently curving shore line for many miles. A large
part of the plain must have been consumed by the sea in
the development of the cliff.

The Sflft Cliffs o! NomuLddy (looking soiithwes

180. Shore Lines of the Second Kind. — Tiiese shore
lines are more varied than those thus far described. When
an uneven land siuface is depressed and partly covered by
the sea, numerous ridges and hilla stand forth as promon-
tories and continental islands, valleys are entered by arms
oi the Bea, and protected harbors are plentiful. The irreg-
ular coast of Maine offers many illustrations of this kind.
lis relief is of moderate measure.

The waves beat furiously on the exposed headlands of
irregular coasts during storms. Angular rock fragments,

312

ICI.KMENTARY THTSICAL GEOGRAPHY

IHagnini

weathered from the rocky coast, are swept about by the
[■ dashing waves and are in time rounded to cobbles and
pebbles, and
worn down to
sand. These
fragments bat
ter the shore
and erode
maTgin of the
land, gradually
forming a cliS
that rises above

sea level and a bench thut is partly bare at low tide.
Isolated rock columns or stacks stand for a time on the

rock bench. At high tide the waves roll across the bench

and sometimes

excavate sea

caves, fifty or

more feet in

length, at the

base of the cliff.

Fingal's cave,

on the island

of Staffa, west

of Scotland,

and many otlier

less famous caves have thus been eroded by the waves.
As the wave-cut bench "broadens and the cliffs increase

in height, some of the rock waste is swept alongshore

from the headlands into the little coves and bays, foiming

SHORE LINES

on the more protected parts of the coast Hue.
beaches present a smooth curve, coucave to the
sea; here the surf breaks in even rollers, quite unlike the
dashing and fretting waves on the ragged headlands.

Draw maps of selected parts of the coast shoivn in Figurea 161
and 162, on a somewhat larger seale than that of the flg-urea, and
thus il1ustr£lt« the change from the original to the later outline.

The cobbles and pebbles thrown up on the beaches dur-
ing storms may form a wall five or ten feet above Mgh
tide. A pond or
swamp is often (
inclosed behind
the wall beach
in the valley
that hatl previ-
ously opened
into the bay.
The New Eng-
land coast has

Fio. 163v Diagram uf a Carved Sliore Line
numerous beaches of this kind between its rocky headlands.

has the set

B the coast forma in Figurew 161, 1
gained on the lancf ? the land cm th

i2, and 16.3. Wliere

The promontory of Brittany in western France, beaten
by heavy waves and swept by strong tides, is in about the
stage of development represented hy Figure 162. The
headlands are dangerous on account of the rocky reefs
that rise to half-tide height on tlie rock bench that fronts
the ragged cliffs. The small bays are partly filled with
cui-ved beaches of cobbles, pebbles, and sand.

314

ELEMENTARY PHYSICAL GEOGRAPHY

As time passes, headlands are cut farther back, so that
the cliffs become higher and longer. The bays are more
and more filled with beaches and cobbles, gravel and saod,
and with deltas formed by streams entering the bay heads.
Thus the outline of the shore* becomes more regularly
curved than it was at first, and convex lines of cliffs
alternate with concave stretches of beach.

Fine examples of shores iii this stage are found in
parts of southwestern England. The cliSed headlands

are guaitled by lighthouses ; settlements ai-e usually fouud
in the river mouths of the beached bays. The coast of
western Italy and the northern coast of Califtu-nia offer
many examples of this kind.

181. Land-Tied and Sea-Cut Islands. — Irregular coasts,
formed by the depression of a mountainous region, are
often originally fi-onted by islands. Such islands not infre-
quently come to be attached to the mainland by the back-
ward growth of sand reefs that are supplied with waste
from the outer cliffs. Compare the two headlands of

lLL„

' -• v/: /»•

^iXreli

SHORE LINES

' Fi^re 164 in tLis respect A land tie 1
of Italy is shown in Plate \^ I

The fortified Rock of Gilraltii
belonging to Great Britain was
originally an island, but is now
tied to the mainland of Sptnu by
a broad siind reef. P irt of the
reef is "neutral ground occu
[lied by neither Spain nor Great
Britain.

If the eoast is of unequal
strengtii along its front, the nite
of Bea cutting may vary fi'om
place to place, and thus parts of
the eoaat may in time be cut off
from the mainland and form
islands, as in Figure 166, Many
islands in the bay of Panama are
thus formed. They are remnants

N^s pain/

^VLNoutrjl 1

JfW

G braltar %^';J

T'l

Europa Point

31H

KLKMHNTAllY I'HYSICAL (JEoGRArilY

of the maiiiliind whose extent has been much reduced hj
the attack of the sea. The width of the isthmus of
Panama Las thus heeu lessened and the length of the pro-
posed interoeeanio caniil across it hai> been coiieispoiidingly
shortened.

182. Cliffed Coasts, — <_'oasts that have been long
exjiosed to strong waves and tides may have been cut so
far back that no part of the original outline remaina. In
such eases a nearly continuous cliff, sometimes of great
height, fronts the shore, as in Figure 167. Traffic between

SHORK LINES

317

ind and sea ia practically imposwible on such a coast. A
1 wi'ecked on the ragged bench beneath the cliffs can
ie little succor while stormy weather lasts.
The Orkney and Shetland islands, north of Scotland,
lave lost much of their former area by the attack of the
The head-
^nds are cut off
hy lofty cliffs,
jbome of which are
Nearly 1000 feet
[high. An isolated
ptack, known an
lithe "Old Man of
Sloy," rises 600
neet above the sea.

1S3. Elevated
Shore Lines. —
When the devel-
opment of shore
^es is interrupt-
ed by a change in
ithe level of the
land, the work of

cliff cutting and Ijay filling must be begun again at a
Bew level, in much the same way as before.
I If the land rises, the former shore line may be found
^t a greater or less distance inland from the new shore
line. This has already been referred to in the descrip-
ion of coastal plains.

Mon of coastt

318 ELEMENTAKY PHYSICAL OEOGItAPHY

An elevated shore line, marked cliiefij by rocky cliffs and
bencliea with occasional beacbes, may be ti-aced along a
great part of the western eoaat of Scotland at a lieigkt of
from twenty to twenty-five feet above the sea level of to-day.
The narrow coastal plain that slopes forward from the old
shore line to the new one is -pictured in Figui'e 64. This
elevated shore line forms a convenient bench along which
raada may be laid near the base of the slopes that ascend
to the highland summits. Old sea caves, roughly witlled
in, sometimes serve as stables for the seaside farmers.

A low bluff, seeming to be a former shore Hue, has
been traced on the coastal plain of Virginia and Nortli
Cai'olina, a short distance inland from the present shore
line. Lines of ancient sea cliffs at several different
levels break the coastal slopes of Cuba and form steps
in the broad plains of eastern Patagonia.

The western coast of Norway is boidered for much of its
length by a belt of lowland and islands, sometimes as
much as from three to ten miles wide, from whose inner
margin an old sea cliff rises to the highlands (Figure 169).
The lowland is a broad rock bench or platform, cut hj the
sea when the land stood about 300 feet lower than now.
A large part of the population of western Norway dwellfi
on this ancient sea floor.

The former sea cliff, at the inner mai^n of the plat-
form, is from 500 to 1000 feet iiigh. A number of
rocky hills stand on the platform, representing uncon-
sumed islands of the former shore.

The withdrawal of lake waters by a change of climiito
(page 288) has an effect on the condition of shore lines

SHORE LINES

319

Bimilar to that produced by an elevation of the laud with
respect to the sea. The cliffs and beaches that contour
around the slopes of the mouutairis of Utah, where the
waves of Lake Bonneville once beat, in many ways
resemble the elevated shore Hues of western Scotland,

Well-defined ancient shore lines, consisting of cliffs and
beaches, are found in the legion of the Great lakes. The

Flo. 169. The Coast Flatlorm of Norway

shore lines are found to converge toward depressions in the
height of land to the south of the lakes, and well-defined
channels are there discovered. This indicates the former
existence of lakes much larger and deeper than those
of to-day, with outlets south westward to the Mississippi
system, instead of northeastward by the St, Lawrence.

These facta are explained by supposing that the
melting ice sheet of the glacial period obstructed the
St. Lawrence valley, so that the lake waters had to rise

ELEMKNTARY I'HYSICAL GEOGRAPHY

high enough to overflow south west ward. Many of the
beaches ai-e so distinct that they are used aB iiaLurally
graded roadways. The outlet of the expanded Lake
Erie ran past the site of Fort Wayne, Indianai to the
W abash river. Tlie outlet of the expanded Lake
Micliigan led past the site of Chicago to the Illinois
i-iver; this channel is now followed bj the artificial
drainage canal by which some of the water o£ I^ake
Michigan is again led along the line of aucient outlet.

184. Fiords. ^ The valleys in the highlands of Norway
have been deejjened by the heavy and strong-moving glaciers
that once filled tiiem. Since the glaciers disappeared the
sea has entered the deep ehaimels that the ice scoured out,
forming long, nan-ow, and deep euibaymenta, called ^fior^i,
often deeper at the middle than near the mouth. Their
depth has probably been increased by a depression of the
region, by which the border of the ice-scoured lowland has
been eonveiied into a swarm of islands.

The rock walls of the fiords are so steep that few setr
tlements can be made along them, except at their heads
or where deltas are built by side streams that cascade
from the hanging valleys (see page 299) of the high-
lands. Roads can seldom follow the shore lines ; hence
communication is chiefly by water.

An irregular coast of this kind has often favored the
development of maritime arts. Its outlying islands tempt
exploration ; its protected bays afford safe harborage even
for small boats. The people occupying the coastal lauJs
become expert sailors and fishermen.

SIKIRK LINES

321

The immerous bays of soutliern Scandinavia wei-e known
HH viks to the people who occupied them 1000 yeara ago,
and the inhabitant* were theiefore called mkintfg or bay
people They became bold marauders, invading the more
Bouthem coasts of western Europe by whose people the

bikings were called Northmen. Normandy is to this day
named after theae early sea kings. They were the first
European people to venture far out upon the ocean, and
thus almost 1000 years ago they discovered Greenland
and other parts of the western woild.

The west coast of Patagonia (southern Chile) resembles
that of Norway in the posBesaion of deep fiords among
bold mountains. The Canoo Indians dwell here, — a

32:i KLEMENTAEY PHYSICAL GEOGRAPHY

primitive people who find the steep slopes u£ the land
so inhospitable that they live almost entirely in open
canoes on the water. A small fire is kept burning on
few sods in the canoes, so that it may be carried from
place to place. These Indians have no fixed habita^
tions and make little use of the land, except when
they build temporary shelters of tree blanches, roughly
thatched, in one cove or another where they stop for a.
time to gather shellfish.

The mountainous coast of Alaska is varied by numer-
ous fiords, into some of which great glaciers descend from
snowy ranges in the background. As in Norway, much
of the coast is so steep as to be unfit for settlement
Hanging valleys frequently open on the walls of the fiords,
500 or more feet above sea level.

1B5. Delta Shore Lines. — Rivers tend to build their
deltas forward, and thus oppose the destructive action of
the sea. The Mississippi discharges a great quantity of
land wast* into the Gulf of Mexico. The waters of the
gulf are relatively shallow, and the tides are weak. Here
the outline of the delta seems to be governed entirely hj
the action of the great river (Figure 136).

The several distributaries of the Mississippi build low
and slender banks of mud on each side of their channels
faster than the waves can wear them away ; hence the
delta has several fingerlike projections into the sea. In
order to increase the depth of water in one of the channels,
or "passes," jetties (dikes of wood and stone) have Ijeen
built forward beyond the end of the delta fingers, thus

SHOHi: LINES

increasing the current and forcing it to acour the chaiiDel
to a depth safficient for seagoing vessels to enter on their
way to New Orleans.

The Rio Grande, a large river, but mucli smaller than
the Mississippi, delivers land waste to the gulf in greater
qimntity than the waves
and currents can altogether
remove; hence ita delt^i is
built forward {Figure 171).
But the waves are strong
enough to smooth the out^
line of the delta; hence it
has a gently convex curve
without linger! ike projec-
tions. The Brazos and Col-
orado rivera, about midway
between the Mississippi and
the Rin Grande, also cause
a slight forward Ixtwing
of the Texas coast. Fig. ni. MIju, rf IH. T.ira* toast

186. Effect of Climate on Shore Lines. — Slioi-e lines,
lite land forms, are affected by climate ; not only by
differences between regions of onsliore and offshore winds,
whei-e waves and currents are stronger or weaker, but even
more by diffei-enees of temperature.

In polar seas the land is often bordered liy a fringe of
ice called the ice foot. During the winter the ice foot
usually remains attached to the land, unless broken by
strong tides ; in summer it may loosen and float away.

324

KI.KMKNTARY PHYSICAL UEOGRAPHY

It is often used us a longshore roadway for sled travel by
Eakimoa and Arctio explorers,

In warm seas the shores that are not exposed to strong
surf may be invaded by certain kinds of trees, forming a
network so dense as to make landing difficult.

The mangrove is the most important tree of this kind.
It grows freely in
shallow sea water
on low and muddy
shores, and protects
the land from the
waves. Muddy sedi-
ments accumulate
in the quiet water
;iinnng the trees, and
tliiLs the land gaiiifi
'■n tlie sea. Shores
! overgrown with
.....ii^'rove swamps
are dismal as com-
pared with the clean shell-strewn beaches of sand and
pebbles beaten by trade-wind surf.

187. Coral Reefs. — The shallow waters of continental
borders or mid-ocean islands in the warmer seas an;
commonly occupied by coral reefs, composed of the
limy framework of coral animals. Living corals are
found chiefly on the outer side of the reef, where they
grow in the shallow water much in the same way that n
thicket of small hushes grows on the land. They take

FiQ. 172. Mangrove T

SHORE LINES

325

A Friugiiig Rest

the liraestone needed for their skeletons from solution in
the sea water.

When reef-building corals first take possession of the
shallow waters on a shoal or near a shore line, their growth
extends upward from
the shallow bottom and
outward into the surf.
Blocks and branches ai-e
detached from the Iwt-
tom by severe storms
and rolled about by the waves ; the larger fragments ai-e
thrown together, forming a beach a Httle above sea level ;
the finer particles are carried toward deep water and strewn
over the sloping bottom. The reef thus broadens, and if
near the land, it forms a fringe close along the shore Une.
At this stage it is called a fringing reef.

Strips of fringing reef are found on the equatorial coast
of eastern Africa, along parts of the Brazilian coast, at
various points on the coast of Cuba and elsewhere in the
West Indies, and border-
ing many islands in the
Pacific, as the Hawaiian
and other groups. The
Galapagos islands in the
eastern Pacific, close to
the equator, are free from reefs, because of the low tem-
perature of the water brought there by the sti-ong Peruvian
current. (See Figure 112.)

Draw maps of the ialaiidn and r*efs sliowii in Fiyiirt's 173 and
174. Compare tte two.

k-ns. Part of

188. Barrier Reefs. — A fringing reef broadens by the

outward growth of the corals, and the submarine slope is
built forward by the supply of coral fragments. At the
same time water supplied by rain, by streams from the land,

SHORK LINES

327

and especially by the aurf that rolls over the reef, slowly dis-
solves and washes away the inner part of the reef where liv-
ing corals are few or wanting. Thus the reef may come t^ i he
separated from the land
by a shallow lagoon a
mile or more wide : and
in this way a fringing
reef may change to a
barrier reef.

The Great Barrier reef
stretcheaalongthenoitli- j,^^ ^^ j,^

east coast of Australia Barrier Reef

for about 1000 miles,

the largest reef in the world. It is usually from twenty
to fifty miles from the mainland, mostly beneath sea level,
interrupted by numerous inlets, and bearing a lew low
islets. The sea outside
descends rapidly to great
depths the water inside
18 shallow (from ten to
forty fathoms).

1B9 Effects of Eleva-
tion — If a slow uplift
oLCUis, toraU will i;on-
tiitue to grow on the
outer face of the reef, but the body of the reef may be
raised above sea level, forming a terracelike bench above
the new shore line, outside of which new fringing reefs
grow. Compare Figiires 176 and 177.

eiliK Reef

8 ELEMENTARY I'HYSICAL llEOfJUAPIIY

An uplifted reef, forming a bench at a height of about
thirty feet, with a breadth of a mile or less, borders much
of tlie northern coast of Cuba. The sea has worn a low
cliff in the front of the bench; from the cliff top one may
look down upon the new fringing reef now growing in
the »ea.

The loose texture of uplifted reefs allows them to be
worn down again with relative rapidity. While the
uplifted reef is thus wasting away, the fringing reef may
be growing outward vigorously and changing to a barrier
reef. The uplifted reef will be in part dissolved by tiie
solvent action of rain water; and it may. after elevation
ceaaea, he reduced below sea level. A shallow body
water, or lagoon, will thus be formed within the new
baniei- reef.

190. Atolls. . — If the central island within a barrier or

fringing reef is worn away or is lost by slow submergence
as the reef grows upward
and outwai-d, the reef may
mate an irregular ring
around an oval lagouii
and the ring may slowly
increase in size by the
outward growth of the

reef, while the lagoon is dee[)ened by the dissolving action

of its waters.

Such a ring island is called an atoll. Many islands of

this kind ai'e known in the Pacific ocean.

Compare the reefs shov

1 Figures 1T3, 174, and 178.

SHORE LTNES 329

Although one of the most wonderful oLjecta in nature,
a lonely atoll afforJs little opportunity for human devel-
opment. The natives of such islands lead easy and indo-
lent lives, but their progress towai-d better conditions than
those of savagery is hindered by the small variety in their
surrounding8 and by their distance from lands of more
varied form and products.

The small height of atolls subjects them to the danger
of being overwhelmed by earthquake waves. Hurricanes
sometimes eoine upon them, unobHtnicted from the open
sea, sweeping violent aurf far up the lieaches; the storm
winds bi-eak down the coeoauut palms on which the
natives depend largely for food and for the materials for
many of their simple arts. Atolls have no streams, but
fresh water supplied by rains may Ire found not far below
the surface. The thin soil has little variety of mineral

330 ELEMENTARY PHYSICAL GEOGRAPHY

matter, but floating pumice (frothy lava) is oftea east
asbore from distant volcanic eruptions, and some of the
islanders have learned to gather and pulverize it to use
as a fertilizer for their little fields. Floating logs from.
other lands sometimes drift upon the atolls, and their
roots occasionally carry stones of firmer texture than
coral rock {for example, fragments of dense lava from
a volcanic island) ; rude whetstones, pestles, and mortars
are made from these chance supplies.

Although birds are plentiful, there were no mammais
on coral islands until rats and mice came ashore from
vessels; a few domestic quadrupeds liave occasionally
been imported by foreign residents,

QtXESTlOHS

Sec. 175. What is t)ie oriyiii of the forces by which the ocean
woiks on tile landa? How is the work done? What becomes
of the material worn away? Why are the lands not completely
worn away?

176, 177. Upon what two conditionB does the outline of anysliors
line depend? DeBcrihe the movement of waves and their action on tha
landa. How are shore cnrrenta caused ? How do waves aid the work
of currents? Compare the work of the sea in deep and in slialloiT'
shore waters. Describe the shore line of a, young coastal plain; ot
a, depressed mountain range. Contrast them as to harbors, settle
ment, and trade.

178. Describe the shore of the coastal plain of Buenos Aires.
What effects are here caused by storm winds? Ijy waves? Wimt.
are the origin and form of sand raefs? What are inlets? lugoonal
salt marshes ? Ifow are the sand reefs and lagoons changed hy tiie
action of surf? Describe the coast of New Jersey; of tlie Net^ie^
lands; of southwestern France.

SHORE LINES

179. What is the origin o£ Bea cliffs ? How are they -worn back 7
Describe the cliffed coast of northwestern France,

180. What are the features of a shore line of the seconil class?
How and on what parts of these shores do waves form cliffs ?
stacks? caTes? beaches? What are wall lieachea and where are
they common? Describe the eoaat of Brittany. Describe the shore
forms o£ later development. Whore are they fouad?

181,182. What are land-tied islands? Describe an example.
What sre sea-cut islands? Describe some aiamples. Describe a
cliffed coast. What is the relation of such a coast to human occu-
pation ? Describe an example. What is the " Old Man of Hoy " ?

183. What changes in the shore line result from a change in the
level of the land? Describe the elevated shore line of western ScoU
Itutd ; of North Carolina. Where are other examples found ? Describe
the western coast of Norway. Under what conditions were certain
abandoned shore lines formed in Utah? around the Great lakes?

184. Wlat are fiords? Explain their origin. Where do they
ocnr? How do they affect settlements? How does an irregular

shore line affect the maritime arts? Give an example from Scandi-

ia. Describe the Canoe Indians. What is the relation of hang-
ing valleys to fiords 1

L86. How do rivers tend to oppose the action of the sea?
Describe the delta of the Mississippi ; of the Rio Grande.

186. How does climate affect shore lines? What is the ice foot?
Describe a mangrove swamp. Where is such a swamp formed ?

187,188. What are coral reefs? Where are they found? (See
Figure 112.) IIow are they formed? What is a fringiug reef?
Where are fringing reefs found? AVhy are no reefs found on the
Galapagos island ? What *s a barrier reef? How is it formed?
Describe the Grea Ba f f Australia.

189, 190. Besc b an upl fted reef. What changes may such a
reef undergo? fl h t an atoll? In what ways may atolls be
formed? What ppo tu t d atolls aiford for human develop-
ment? To what dang a e atolls exposed?

THE DISTRIBUTION OF PLANTS, ANIMALS, AND MAN

191, Geographical Aid in Human Pr{^eBS. — The study
of physical geogi'aphy, or physiography, gives a knowl-
edge of the features of the earth, so that we may better
understand the relation of man and nature. This rela-
tion is of great importance, because the progress of man-
kind from the savage toward the civilized state has been
lai'gely made by taking advantage of favorable geograph-
ical conditions and by learning to make greater and better
use of the products and forces of the earth.

The winds blew over the lands and watera, carrying
rain and causing waves and enrrenta, for thousands of
years while man was an ignorant savage. When he
invented sailboats and windmills a new use was made
of the winds, and man profited greatly by his inventions.
Streams had been wearing down the falls and rapi<ls in
their valleys and spreading rock waste over their flood
plains during all the long existence of the continents.
When man cultivated food-bearing plants on the flood
plains and built flour mills by the waterfalls, he gained
much from making new and good use of these natural
forms and forces.

The magnetic forces of the earth have always lieen capa-
ble of directing a compass needle, but they were not used

THE DISTRIBUTION OF OROANIC FORMS 333

I until man discovered how a Isilanced magnetixed needle
would behave. Coal and iron ore lay untouched ui the
earth's crust for millions of years ; now the nations that
imake the fullest use of theae invaluable resources have
become the leaders of the world.

Reference has frequently Iwen made on the earlier pages
of this book to the effects of geographical surroundings
;on the growth and distribution of plants and animals and
■on man's way of living. The present chapter i-eviews
these effects and gives new examples of them,

192. Life on the Earth. — The earth is known to have

"been riccu]>ied for ages past by various kinds of plants
«nd animals, for their fossil remains are found in many
Tock layei-s of ancient origin, During all these ages
'living forms have tended to k pre ad over as large a
— gion as possible, just as they do now, .

Barriers of different kinds limit the spreading of
ganic forms. Land plants and animals are stopped by
e sea, unless thpy can ti'avel by water or air. Sea
[animals are stopped by the lands. Those forms that
need a waim climate do not spread into I'egions of cold
iiclimate. Grazing animals that need abundant grass are
stopped by deserts and by forested mountains.

Plants growing from heavy seeds, like nuts, spread
^slowly from the parent plant. Plants growing from
light seeds, especially from such as are carried by tlie
wind, like the seeds of the dandelion, the thistle, and
the fireweed, are very rapidly distrilmted. The dande-
lion is found on the northern lands all around the earth.

334 ELEMENTARY PHYSICAL GEOGRAPHY

Certain kinds of sea animals, like mussels, barnacles,
and corals, upend most of their life attached or rooted
to the sea bottom, living on fooil that is brought to
them by the moving waves and currents. Tliis reminds
one of the dependence of rooted land plants on the
ing air for moat of their sustenance. But the yonng
forma of these fixed animals are free to float about, and
are then carried far and wide by the eurrents of the
just aa light seeds are carried by the winds.

Most animals can move from place to place. They hav»
fins for swimming, legs for walking, or wings for fljing. As
they wander about in search of food, they come in time
be distributed over all parts of the earth accessible and
favorable to them. This is as true for tbe ancient history
of life on the earth as it is for the life of to-day.

Birds of strong flight ai'e widely distributed. Walking
birds and quadrupeds are more narrowly limited. The
ostrich of Africa, the emu of Australia, and the ihea of
South America are each confined to one of the southern
continents. The albatross, a. large sea bu-d, whose skill
in flying without flapping its wings is very remarkablS)
is found all around the great southern oceans.

Occasional examples of some fifty kinds of North
Amerid&n birds are found in western Europe ; but no
stragglers fi'om Europe are found in Noi'th America.
This is because the prevailing westerly winds blow from
North America toward Europe. The course of tbe winds
is determined by the direction of the earth's rotation, and
thus the I'otation of the earth has an influence on animal
distribution.

TIIK DISTRIBUTION OF ORGANIC FORMS

193. Geographical Factors in the Struggle for Existence.

— The niiiiiber of plante anil animals in a given regiun is
usually about as great as can be supported there. WLere
food is plenty the number of individmiis is lai^e; tliia is
usually the case in the shallow borders of the seas and
on the lands of the temperate and torrid zones. The
luxuriant plant growth of the forests under the equa-
torial rains illustrates this rule. Where food is scarce,
as in very dry and in very cold regions, the number of
individuals is small; and some of the cold, snow-covered
deserts ai-e almost uninhabited, as in central Greenland.
f Man frequently causes great changes in the numbers
of plants and animals, as when he cuts down the trees
of a forest and plants grain in the new-eleai-ed fields,
OP when he kills the wild animals of a region and inti-o-
ducea domestic animals in their place. But apart from
changes of this kind, the plants and animals of a region
remain at about the same number for centuries.

It is, however, well known that every kind of plant
and animal tends to increase in numbers, for the seeds
of plants and the offspring of animals are always more
numerous than the individuals that produce them. A
single grain of corn may grow to a stalk bearing several
ears, each of which may bear over a hundred grains.
Many thousand eggs are contained in the roe of a single
salmon. If all the young plants and animals reached
maturity and produced other young forms in their turn,
the number of individuals would increase enormously.

The reason that the number of plants and animals
in a district does not greatly increase is that, in spite of

1 in the c

■L

336 ELEMENTARY I'HISICAL GEOGRAPUV

the pi-oduction of numerous young individuals, many of
them pei'isb in the severe competition for an opportmiitj
to Hve. Many seeda fail to genninate because they fall
on unfit soil, or because tliey are eaten by animala.
Many young animals are devoured by other animals,
Ab a rule, those individuals aui'vive which have some
advantage over their fellows and are therefore more lit
to succeed in the "struggle for existence." The success
of these individuals is often called the "survival of the
fittest"; and the survivors are said to be chosen from
those which peiish by "natural selection."

The chances of survival in the struggle for existence
are increased for those plants and anhnals which are best
adapted to their geographical surrouuduigs. Fish have
gained a shape that enables them to move easily through
the water ; this is an advantage in getting their food and
in escaping from pursuit. Many of tlie smaller animalu
of the open ocean move slowly; but they imitate the
transparence of sea water and so make themselves almost
invisible and more likely to escape their enemies.

As the earth is lighted from the sky, many animals
whose backs are dark have lighter coloi-s underneath,
so as to counteract the effect of shade; they are thiia
less easily seen and so have a better chance of approach
to their prey or of escape from their enemies. Animals
inhabiting deserts are usually gray or tawny, imitating '
the color of the bare ground. In the snow-covered
Arctic regions many animals are white.

Some animals gain protection by living in caverns or
in the crevices of talus slopes ; others burrow in fine

THE DISTRIBUTION OF ORGANIC TORMS 337

rock waste or soil. Name some animals of these kinds.
Some animals choose steep cliffs and liigh peaks for their
home, so that they slmll not be easily pursued. Eagles
build theii' nests on inaccessible pinnacles, sucb as those
of the spurs that separate the hiige side ravines of the
canyon of the Colorado in Arizona, What can jou tell
about the home of the Rocky mountain sheep (the bighorn)
and of the chamois of the Alps ?

194. Variation of Plants and Animals. — All the many

existing kinds of plant and animal life are the descendants
of a smaller number of more ancient kinds. But when
the ancient forms, preserved as fossils, are compared with
living forms, it is found that they are not alike. Through
the millions and millions of years during which the earth
has been inhabited there have been slow variations in tlie
kinds of plants and animals living on it, so that those now
hving differ from their remote ancestors. The forms of
life to-day are, as a rule, very unlike those whose fossils
are found in the oldest fossil-bearing rocks.

Among the many causes which have combined to pro-
duce variations in plants and animals, none have been
more important than changes in their geographical sur-
roundings. While part of a sea bottom is slowly raised
to form a coastal plain, the kinds of animals that once
occupied this part of the sea floor must seek some other
home; at the same time the plants and animals of the
neighboring older land have opportunity of taking pos-
' session of the young plain. As lofty mountains are
L slowly worn down to lowland peneplains, the forms of

■J

838 ELEMENTARY PHYSICAL GEOGRAPHY

life that once occupied the higher mountains must adapt
themselves to their new surroundings or pei-ish. During
the slow change of climate which caused the gradual
advance and retreat of the great ice sheets that ouce
covered eastern Canada and the northeastern United
States, plants and animals were first driven away from
these regions and later allowed to return to them.

Changes of these kinds- have repeatedly taken place
in the earth's history, and it is probable that every one
of them has caused aome variation in the plants and
animals of their regions. The plants and animals that
we now find distributed over the world represent the
present stage in the long series of varying forms.

195. Life in the Seas and on the Lands. — The different
parts of the earth are so unlike that it is natural to find
striking differences among the plants and animals which
have become fitted to occupy unlike regions. No geo-
graphical contrast is greater than that between the sea
floors covered by the oceans and the lands covered by the
air. The kinds of plants and animals that have made their
home on the lands have come to differ greatly from those
that have for ages lived in the oceans. Hence continents
and oceans must have existed for long ^es because their
plants and animals are now very unlike.

A remarkable difference between land and sea hfe
results from the much greater density of water than of
air. Even the largest sea plante do not need strong
trunks, but are supported by the water. Many sea ani-
mals are no heavier than the water they live in ; hence

Bi^

THE DISTRIBUTION OF ORGANIC FORMS 339

they can float without exertion and all their strength can
be given to awimming. The kinds of fish that sometimes ■
rest on the water bottom lie upon it so lightly that they
have no need of legs ; all their members are tins. Many
kinds of fish and other marine forms spend their lives in the
open ocean without approaching the shores or the bottom.

Birds, on the other hand, are much heavier than the air
thi'ough which they fly ; hence much of their strength must
be used to prevent falling. Even the best flyers spend
some of their time on the ground or on trees. When they
alight the air gives them so little support that they need
legs on which to walk about.

It has been explained in earlier chapters that the deep
ocean is monotonously cold, dark, and quiet, without
changes of weather or seasous, and that the ocean bottom
is usually a gently undulating plain covered with ooze or
mud for thousands of miles together. The lands, on the
other hand, are the seat of varied conditions. They pos-
sess a great variety of form and material ; they experience
changes from day to night, from summer to winter; they
suffer many changes of weather from warm to cold, from
calm to stormy, from clear to cloudy, from dry to wet. The
development of the higher forms of life, such as are com-
monly found on the lands, should be regarded as a conse-
quence of the great variety of geographical conditions
found there, in contrast to the monotony of the deep ocean,
where the forms of life are of a much simpler order.

Nearly all the flowering plants live on the lands. Water
plants, especially those of the sea, are of a simpler kind.
No plants live on the dark ocean floor, for plants cannot

340 ELEMENTARY PHYSICAL GEOGRAPHT

grow without sunlight. Many aiiinialH of the sea are
attached, plantlike, to the bottom. Others move slowly,
like starfish and shellfish; still others float with the drifting
waters, having little movement of their own, like jellyfish.
Only the more highly organized, like many of the fishes,
move rapidly; but nearly all land animals move about
actively, walking, running, or flying.

The larger and more important land animals (mammala
and birds)" are warm-blooded. Most sea animals are cold-
blooded, like the lower animals of the land. The only
warm-blooded animals of the sea (whales, porpoises, seals,
etc.) are believed to be the descendants of ancient land
ancestors, gradually modified for the marine life which they
have adopted. The reason for this belief is that the sea
mammals still resemble in many ways the mammals of the
lands. They bear their young alive and nourish them with
milk from the breast ; they must come to the surface of
the sea to breathe, for unlike fish they have no gilla by
which they can make use of the air that is dissolved in sea
water. They differ from land mammals only in ways that
make them better suited for life in the sea; their legs liave
been modified into flippers for swimming ; and those forms
which, like the whales, live altogether in the sea no longer
have fur, like the land animals of a cold climate, but are
protected from the cold of sea water by a layer of fat or
"blubber" under their skin.

Many land animals have developed organs for ihe pro-
duction of sound, the most remarkable sounds being ihe
song of birds and the speech of man. The animals of the
sea are, with hardly an exception, silent.

]

DISTRIBUTION OP ORGANIC FORMS 84"

The greater intelligence of many land animals than o^i
animals should also he regarded as a result of the develop-
ment of land animals amid a greater variety of geographical
conditions than is found in the seas. The claas of insects,
almost limited to the lands, furnishes many examples of
extraordinary instincts, such as those of bees and ants.
Nest building by birds, house building by beavers, " hom-
ing" of pigeons, and
trailing(by scent) of dogs
are examples of highly
developed instincts
among land animals that
have no parallel among
the animals of the sea.

The wonderful intel-
ligence of man has been
developed on the lands, because only on the lands is to he
found the great variety of form, climate, and products
which can stimulate the development of high intelligence.
It would have been as impossible for man to develop as an
inhabitant of the dark and monotonous ocean floor as it
has been for civilization to arise on the frozen and lone-
some lands of the Antarctic regions.

196. Life on the Continents. — The arrangement of the
continents has exei^ted a great influence on the distribution
of land plants and animals. It has been stated that the north-
em continents , are nearly united around the Arctic eii-cle,
and that three great extensions of this northern land belt
stretch southward; Africa being most closely associated

Fia. 180. Btiavers

342

ELEMENTARY PHYSICAL GEOGRAPHY

with the Dorthern lands of the Old World, South America
heiiig less closely associated with Nortli America, while
Australia is cut off from Asia by the sea. It is there-
fore natural to fiud many resemblances among plauts
and animals in high northern latitudes, and to find that
differences amcuig them become greater and gi-eater as
middle and low latitudes arc
passed and far southern lati-
tudes are entered.

The lichens and mosses of the
frozen northern lands are similar
all around the Arctic circle.
The animals of the same region
include the polar bear, rein-
deer (called caribou in Nortli
America), lynx, musk ox, and
Arctic hare, which are of the
same kind on all . the lands
around the north frigid zone. The northern lands muat
therefore have once been connected, and their eounection
must have occurred at so late a period in the history of tiie
earth that there has not since then been time enough for
these Arctic animals to become unlike in their now some-
what disconnected homes.

In the lower latitudes of the northern hemisphere the
plants and animals of the lands possess certain resemblances
that prove their descent from a common ancestry, but they
also show certain marked differences that prove the separar-
tion of the continents in these latitudes for a very long
period of time.

Fig. 181. Caribou

THE DISTRIBUTION OF ORGANIC FORMS

Fia. 183. Jaguar

The puma and jaguar of the New World are catlike
animals that resemble in many ways the lion and leopard
of the Old World. The resemblance is so strong Uiat it
must be believed they are descended from a common stock ;
hence in some former time the Old and New Worlds must
have been connected in latitudes where the ancestors of
these animals could pass from
one region to the other ; but this
connection ceased so long ago
that distinct differences have
since then arisen between the
two groups of catlike animals.

The long separation of the .
Old and New Worlds is con-
firmed by finding certain plants
and animals peculiar to each region. Horses, cattle, and
other domestic animals, as well as tea, coffee, and wheat,
originated in the Old World, while humming birds and
rattlesnakes, as well as maize (corn), potatoes, and cactus
plants, are peculiar to the New World.

The differences among the animals of the three southern
continents are strongly marked. The giraffe, hippopotamus,
and many kinds of antelopes are found only in Africa ; but
that continent shares with the adjacent lands of southern
Asia the lion, elephant, rhinoceros, and the manlike apes.

South America stands more alone ; here are found mon-
keys with prehensile tails, tapirs, llamas, sloths, and arma-
dillos, none of which are found in the Old World,

In Australia, the most isolated of the southern conti-
nents, nearly all the quadrupeds belong to the peculiar

.344

ELEMENTARY PHYSICAL GEOGRAPHY

group of marsupials or pouched mammala, which carry the
young in a pouch on the breast of the mother. The best
known marsupial is the kangaroo. Australia contains also
the lowest kind of quadruped, the water mole (or duckbill),
which resembles birds in laying eggs from which its young
are hatched.

It is not because Australia is unfitted for mammals that
they are not native there.
, Rabbits have been carried
from Europe to southern
Australia, where they
have become so numerous
as to be a nuisance. Sheep
are now raised there in
great numbers, so that
Australia has become an
important wool-growing
Fio.m Kangaroo country. The absence of

mammals in Australia must therefore be explained by the
long separation of that land from the continents on which
mammals were developed. In the same way, the alweuM
of Australian forms in other parts of the world is not due
to differences of food supply or of climate, but to the long
separation of the island-continent from the other lands.
The eucalyptus, a large A\astralian tree, thrives in the mild
climate of California and southern Europe. So horses and
cattle, brought from Europe to the New World, have
become numerous on the prairies and plains of North
America, and on the llanos and pampas of South America.
Potatoes, native to America, have become an important

THK DlSTRIBirnON OF OHGANIC FORM.S 345

food supply ill Europe. What can you tell about the
English sparrow?

197. Races of Mankind. — It is not only in the distri-
bution of the lower animals that the grouping of the con-
tinents has had a controlling influence. The several races
of mankind, differing in lungu&ge, religion, and foi'm of
government as well as in color, originally occupied regions
that correspond in a general way to the grand divisions of
the lands. Hence it may he believed that the separatiou
of tbe continents by the oceans, aided by certain mountain
rand desert barriers, has been the chief cause of the division
■ of niankiud into races.

Tbe greatest of the continents, Eurasia, contains two
races. The European race, generally light colored but
with some dark-skinned families, has its home in Europe,
Africa north of the Sahara, and southwestern Asia. The
leading nations of this race are tbe most advanced peoples
of the world, Tliey have developed liberal governments
in which the rights of the people are considered, and have
advanced greatly in the cultivation of the arts and sciences.

The Asian race is found chiefty in eastern, central, and
northern Asia; it is often called the Yellow race. China
contains the greatest number of this race, the Chinese
being separated from the Hindus of India {a branch of
the European race) by the lofty mountains of the liim^
iayBn system. Although comparatively advanced in many
arts, the Asians have acquired little knowledge of the
sciences, and their governments are usually despotic. The
Japanese are to-day their most advanced nation.

346 ELEMENTARY PHYSICAL GEOGRAPHY

^^H America is the borne of the American or Red race ; ite
^^^1 native inhabitants are divided into manj tribes, each led
^^^r by a chief. Africa, south of the Sahara, is the home of the
I African or Black race, governed by despotic kings or

I chiefs. Australasia and the peninsulas and islands of

Boutheastem Asia include certain black and brown races.
Few nations among these races have made important
advances toward civilization.

Within the last few centuries the means of travel over
land iind sea have greatly increased, and to-day the races
of mankind are by no means limited to the continents
named above as their homes. People of European anceatty
now make the chief part of the population in North and
South America, southern Africa, Australia, and Ne\r
Zealand, as well as in Europe. The Chinese are not
limited to China alone, but are found as merchants and
laborera in the islands of southeastern Asia, Austraha,
and elsewhere. Many descendants of the African race
are now liviJig in Nori:h and South America.

It should be noticed that, while the people of the Euro-
pean race are now widely distributed over all parts of the
world, and while Asians and Africans are found in large
numbers in other lands than their homes, few of the less
advanced races have entered Europe, the chief of these
being members of the Asian race, the Turks in the south-
east and the Finns and Lapps in the north.

19S. Life on Islands. - — Islands that rise from conti-
nental shelves are occupied by many plants and animals
similar to those of the neighboring mainland- It is inferred

THE DISTRIBUTION OF OUGANIC FORMS 347

large ostrichlike birds

I from this that the coiitineiital mass once stood higher than
I now and that the continental shelf was then a lowland on
which the present islands rose as hills or mountains. The
forms of life that were then widespread have become sepa-
rated by the submergence of the lowlands and the division
of the islands from the continent.

Various species of caasc
unable to fly or swim, are found in
Australia and on the hilly islands
to the north, each land area having
its own species. From this it is
supposed that the ancestral family
of all these species occupied the
region when the continental misi
stood higher and the mainland and
islands were connected by the low
land now under water in the cun
tinental shelf Since then it 11
believed that the region has been
depressed and the lowland flooded
■ by the sea, while the higher parts
remain as islands separated from Australia and from each
other. The differences between the various species of
cassowaries must have arisen since their family was divided
by the drowning of the lowlands.

Many of the islands near Australia resemble tliat con-
tinent in possessing marsupials. The islands nearer Asia
have no marsupials, but possess many mammals similar to
those of the mainland to which they are related. A belt
of deep water divides tlie two groups of islands.

848 DLEMENTARY PIIV.SICAL GEOGRAPHY

Islands that rise from the deep ocean floor far from the
continents have no lai^e Jiative animals, but are occupied
by such forma of animab and plants as might have reachixi
them tlirough the air or the water from the nearest larger
land.

I The Azoi-es, a group of mid-ocean volcanic islands iu

^^H the North Atlantic, are so called from the hawka tliat

^^^P were common there when the islands were discovered by

^^^ voyagers from Kurope. The Galapagos islands of siniilsr

origin in the Pacific west of Peru are named from the

large tortoises that abound on them.

199. Climate as a Control of the Distribution of Plasts
I and Animals. — Differences of temperature resulting from

the globular form of the earth are of great importance ia
limiting the distribution of plants and animals. Planti
I like palm trees, that flourish in the torrid zone, spread inW

I lands of higher latitudes on both sides of the equator until

they reach regions where the summers are too cool fca
them to mature their fmit. Plants that occupy the tem-
perate zones are hmited to belts on whose polar side the
summer is too brief and cool and on whose equatorial side
the summer is too hot for their seeds to ripen. Thus in
the central United States cotton is limited to the soathera
I states, corn flourishes best near the middle of the conniij

' from the Ohio to the lower Missouri, and wheat is pro-

duced most abundantly in the northern states. In these
northern latitudes there are great forests of pines and
other cone-bearing trees. Still farther north, where thiS
ground is frozen all the year round, except for a littl«

L ^

THE HEW vrS'-
■UBUCUBP.Al;'i

THE DISTKIBUTION Of OllUASlC FORMS 349

melting during the short summer, trees are wanting and
vegetation is reduced to stunted and herbaceous fonns,
with many niosBcs and lichens. (See Figure 112.)

The various kinds of animals are, like plants, limited to
regions in which the summein are long aud warm enough
— but not too warm — for them to rear their young. But
unlike plants, which live on mineral food derived from the
soil and the air, animals subsist either on animal or vege-
table food ; and flesh-eating animals, like the lion, often
devour plant-eating animals, like the antelope. Thus in
the end all animals depend for food directly or indirectly
on plants ; hence the distribution of animals depends in
part on the distribution of plants, and this in turn depends
on climate.

Examples of the distribution of animals according to
zones of temperature are found in the limitation of the
caribou, moose, and elk to the northern parts of America;
of the alligator, tapir, and sloth to low latitudes; and of
the rhea to far southern America.

200. Climate as a Control over the Customs of Savage
Tribes. — The customs of mankind are influenced in many
ways by climate. Some of the climatic influences are
direct, as with regard to clothing and shelter. Some influ-
ences are indirect, as with regard to food supply, which in
turn is affected by the distribution of plants and animals.
Climatic influences are less apparent on civilized people
than on savage tribes; for the former have developed
world-wide commerce, and thus gather supplies from all
parts of the earth; while the latter know little or nothing

350 ELEMENTARY PHYSICAL GEOGRAPHY

of regions away from their own home. Two examples are
given in the following paragraphs.

The equatorial belt of Africa is in large part a densely
forested wilderness, because of its plentiful rainfall. Tall
trees spread their branches aloft, shading the ground all the
year with their heavy foliage. Vines and creepera climb the
trees and hang from bough to bough in great festoons, and
the shady and damp ground is covered with a thick growth
of bushes with stems and branches so closely interlaced that
it is almost impossible to make one's way through them
without cutting a passage. Even the wild animals of the
forest go and come by paths that they keep open by fre-
quent passing. Objects near at hand are hidden from sight;
tbe explorer cannot tell what is ahead of him in the gloom
of the forest until he is close upon it. Vegetation is here
80 luxuriant that it is a burden upon the people who live
amid its abundant growth.

Some of the savages of this great forest are Dwarfs, from
three to four and a half feet in height. They wear little
clothing, for the air about them is always warm. They do
not try to make clearings and to cultivate fields, but search
out the more open parts of the forest and build their
Tillages where the undergrowth is least dense. They have
some trade with other tribes, but live chiefly by hunting
wild game, which is plentiful. Although entirely ignorant
of many simple arts pi^acticed by people of more opea
countries, the Dwarfs are expert in all the ways of forest
life. They can travel quickly through the woods, know-
ing aU the paths and open places. They protect their
viUagea from the attack of neighboring tribes by planting

THE DISTRIBUTION OF ORGANIC FORMS

351

sharpened stakes in the paths of approach. They dig pit^
falls in the narrow forest paths, covering them with sticks
and leaves, and in this way capture even the larger "wild
animals. They prepare a poisuii finm certain plants and

FiQ. 185. Dwarfs In the Equatorij

tip their spears and arrows with it. In spite of their small
size they are formidable enemies to invaders of their forest
home.

The desolate shores of Greenland pi-esent conditions of
an entirely different kind. Extreme cold prevails there
during the long dark winter, and most of the land is
covered all the year round with iee and snow, — a vast cold

352

ELEMENTAllV PHYSICAL GtlOGRAPHY

desert. A narrow belt along the coast is free from s
in auramer, and here live a few tribes of Eskimos; but
the ground is so barren that they get little support from
it. The only treelike plants are of stunted growth,
dom over two or three feet high. The herbage consists
chiefly of mosses and lichens, which grow for a time in
r when the fiu/.en ground is thawed for a few inches
below the surface. A
small supply of wood
comes from the trunks of
trees that are occasion-
ally drifted by ocean cur-
rents to the Arctic shorea
from warmer regions j
but there in so little of it
that many articles which
might Ije made of wood elsewhere are here made from the
bones of sea animals.

The Eskimos wear heavy fur clothing. They travel in
sleds drawn by dogs over the snow-covered land or the
frozen sea. They make slender canoes, called kayaks,
which they paddle veiy skillfully when hunting seals and
walnisea. Until visited by Europeans and Americans, the
Eskimos were as ignoi-aut of the rest of the world as were
the African Dwarfs; yet so well have they learned to take
every advantage of their frigid surroundings that they sur-
vive where men from a naore civilized nation, unused to
living in so barren a region, might perish.

These brief accounts of the Dwarfs and the Eskimos show
very clearly that, as a rule, the climate and the other local

10 liuiitiug Walrus

THE DISTRIBUTION OF ORGANIC FORMS 35^

features of the re^ons in which they live exercise a strong
control over their manner of living. The Eiskimos know
nothing of forests, thickets, and pitfalla. The Dwarfs
know nothing of snow and ice, sleds, kayaks, and har-
poons. But each of these groups of people has become well
practiced in certain habits and customs that enable them
to secure food, shelter, and reasonable safety of life; and
l^ese habits and customs are closely related to the surround-
ings in which they have been acquired. The further the
world is examined, the more general this rule is found to be.

201. Effects of Change of Seasons on Plants and Animals.

— In the torrid zone the chief seasonal couti^asts ,of the
year are between the dry (hot) and wet seasons. During
the diy season vegetation withers, but with the coming
of the-wet season all forms of plant life grow actively.
This is particularly marked on the desert boixiers of the
subequatorial rain belt, where the ground may be bare and
dusty in the dry season and covered with vegetation in
the wet season, as on the llanos of Venezuela.

In higher latitudes the chief seasonal contrasts are
between the cold and warm seasons, or winter and sum-
mer. In winter vegetable growth is almost or quite sus-
pended, but with the approach of summer growth begins.
Some trees, like the pines, bear the winter with little vis-
ible change. Others, like the oaks, drop their leaves in the
autumn, and hence this season is often called fall. Trees
of this kind pass the winter with Imre branches. Still other
plants are killed by the coming of cold weather, and only
their seeds survive the winter ; these are called annuals.

S54 ELEMENTARY PHYSICAL GEOGRAPHY

" Animals also have many devices for surviving the
winter. Some are hardy enough to bear all sorts
weather, and may be seen searching for food through
winter cold as well as summer heat; wolves and foxes are
of this kind. Others retreat into cavema and crevices
and lie torpid during the cold montlis, coming forth leau
and hungry in the spring ; bears and snakes have this
habit. Many insects are like the annual plants in being
Itilled by cold weather, leaving their eggs to be hatched
on the return of higher temperatures in the spring. Many
birds escape winter weather by migrating to a warmer region
in the autumn and returning poleward in the spring-
All these peculiar habits result from the oblique position
of the earth's axis with respect to the plane of its orbit, by
which the change of seasons ia caused.

Changes in habit of hfe with changes ot season are
not limited to plants and the lower animals. Man also
responds in many ways to seasonal changes from heat to
cold, from dryness to rainfall. In continental interiors
of temperate latitudes, where most of the rainfall is in
summer, the wandering of nomadic tribes is largely con-
trolled by search for pasture for their flocks ; as on the
plains or steppes north of the Caspian sea. Again, in
Algeria, on the northern border of the Sahara, summer
pasture is found chiefly on the mountain slopes ; but when
the winter rains begin (subtropical rains) the herdsmen
drive their flocks down to the lower lands, that were dusty
and barren deserts a few months before.

Planting and harvesting are characteristic occupations
of the warmer months among the more advanced peoples

THE DISTRIBUTION OF ORGANIC FORMS 355

in all temperate climates ; during the colder months agri-
cultural labor ia in less demand. In the north temperate
zone there is the great advantage of an abundant land area
with a winter that is cold enough to require the storage of
food and a summer that ia warm enough to provide the
food to be stored. The leading nations of the world have
arisen in this zone, and tbei-e can be little doubt that the
habits of industry and thrift here made necessary, but
not too difficult, by geographical conditions have been of
great importance in bringing civilization out of savagery,

202. Plant and Animal Life on Lofty Hoimtains. —

Climate varies not only from equator to pole, but also from
lowlands to mountains. On account of the lower tempera-
ture and the heavier rainfall and snowfall of high mountains,
their plants and animals are unlike those living on the sur-
rounding lowlands. On lofty mountain flanks in the tem-
perate zone, hardy cone-bearing trees usually succeed trees
that need a milder climate. As the limit of tree growth, or
the "tree line," ia approached only stunted and deformed
trees survive. Then comes a belt in which the slopes bear
grass and Alpine flowers. (Alpine ia used to refer not only
to the European Alps, but also to the animala and plants of
any lofty mountain.) Following thia is the lower limit of
summer snow banks, or the " snow line," above which some
of the snow of one winter lasts over the following summer,
thus excluding plant life. It is remarkable that many plants
found near the snow line on mountains in the warmer zones
are also found near sea level in the frigid zone, although
they are wanting on the low ground between the two.

ELEMENTARY PHYSICAL GEOGRAPHY

Maiiy animals survive in mountains after diBappearing I
fnim tlie surrounding lower ground. Varinns kinds nf

]peariiig I

Fin. 187. Slumeil TreeH BC ilie Tree line

ibex (mountain goat) are found on the mountains of
Eurasia, eacli range having its own peculiar species. All
are derived from a common ancestry
on the intermediate lower lands; but
since they have been limited to moun-
tain homes, the imimals in each
range have varied in their own way,
independently of the others, and have
thus come to be unlike. This is a
remarkable illustration of the effect
of mountains in keeping their inhab-
itants apart from the rest of the world; it may be com-
pared with the effect of isolation on islands.

Fig. 188. Ibex

T^IE DISTRIBUTION OF ORGANIC P'ORMS 357

A species of butterfly living on the Wliite mountain
Buminits, in New Hampshire, is unlike the species of the
surrounding lower ground, but resembles th<ise of more
northern lands. The top of Mt. Katahdin, an isolated
mountain in northern Maine, possesses a similar butterfly,
but it varies Bomewhat from the one on the White moun-
tains, the varintion having taken place since the butterflies
of the two districts were isolated on their mountain homes.

203. The Effect of Mountains on their Human Inhab-
itants.— ^It has already been stated that the deep valleys
of lofty mountains have often been used as retreats by the
people of a nation that has been driven from the neigh-
boring lower land by the invasion of a sti-onger nation.
The following examples may be cited.

The Basques live in the northern valleys of the Pyrenees,
near the angle of the Bay of Biscay. They are probably
descendants of the Iberians, an ancient people who occu-
pied a large part of Spain and France, from which they
had been driven by invadere even before Cffisar made
those countries subject to Rome, nearly 2000 years ago.
The Basque language is the only surviving form of Iberian,
and is entirely unlike other European languages.

The Svanetians occupy deep inner valleys in the Cau-
casus mountains, witli difficulty accessible from the outer
country. They are the descendants of an ancient people
who occupied a much more extensive territory, fj-om wliich
they were driven back to the mountains many centuries
ago. There ancient customs and a peculiar language are
preserved ; there the people still live entirely apart from

868 ELEMENTARY PHYSICAL GEOGRAPHY

the ways of modern times. Although daring and patri-
otic, they are ignorant and superstitious. Their wretched
houses are dark and dirty; their roads are only rough
tracks. Arts and industries are of the simplest order;
trade is only by barter.

The people who live in deep valleys among lofty momir
tains find life more difficult than do those who live on open
plains. The difference between the two cases is in large
part due to the action of gravity on the mountain sides.
The peculiar dangers of avalanches and landslides are
directly the result of gravity. The finer waste on the
steep slopes is rapidly washed down by active rivulets.
The stony soil that remains cannot be easily cultivated,
and if it is spaded or plowed, much of it will be washed
away by the next heavy rain.

The valley floors are narrow, giving little room for fields.
The streams flow swiftly down their sloping channels;
their torrential current is too strong to be navigated ; their
floods are frequent and destructive. It is diiEcuIt to pass
from one valley over the dividing ridge to the next valley
because of the labor of climbing up and down the slopes.
Hence, although mountaineers are active and hardy, they
are not, as a rule, great travelers or traders. The people of
one valley know little of those a few score miles away,
a distance that would be considered a trifle by a horse-
man on a plain. The people of neighboring valleys are
often distinguished by slight differences in their common
language.

During winter mountain valleys may receive a heavy
snowfall. Then for a season the people and their flocks

I THE DISTRIBUTION OF ORGANIC FORMS 359

' are gathered in the lower villages, living on supplies stored
up from the previous summer. In summer, when the snows
are melted from the mountain sides, cattle, sheep, and goats
are driven up from the valleys to pasture on the grassy
slopes of the ridges. Hay is carried, often on the backs
of the mountaineers, down to the villages for winter need.

I 804. Life in Deserts Climate exerts a powerful con-
trol over the distribution of life through differences of rain-
fall. This control is well illustrated by the conditions of
those I'egions where rainfall is deficient. Plant and animal
life is scanty in deserts because of the difiiculty of secur-
ing food and water. The dryness of the soil ia unfavorable
to plant growth. Leaves are small or wanting, for thus
the loss of water by evaporation from the leaf surfaces is
diminished. Thorns are commonly developed, Uke so many
signs, "keep off," as if to lessen the chance of injury to
the plant in a region where living is so difficult that every
aid must he summoned to protect life.

During long droughts an arid region may seem almost
free from vegetation. If rain falls, small plants spring up
everywhere, refreshing the surface with their green color,
but soon withering away in the succeeding dry period.
On the desert slopes of Peru, where droughts may last
four or five years, plants soon spring up after a shower.
These examples show that the plants of arid regions
possess great vitality.

The larger plants of arid regions are thinly scattered,
leaving much bare surface. There is no striving for space,
such as commonly occurs in well-watered regions, where

ELEMENTARY IMIYSICAL GEOGRAPHY

plante of more active growth may crowd out the weaker
forms. Dry regions seldom produce useful plants. Trees
are small, and their wood is hard and knotted ; they cast
little shade on the dry, bare ground. The sagebrush, so
abundant on the arid
western plains of the
United States, finds
no use except as an
inferior firewood.

The animals of des-
erts are generally of
dull or gray color, not
easily seen on the bar-
ren surface. Many
of them are fleet
movement, like the
antelope, or of great
endurance under a
small supply of food
and water, like the
are often
the rattlesnake.

Desert Tree

camel. Tliose which are sluggish
like the tarantula, the scorpion, and

205. The People of Deserts. — The human inhabitants of

arid deserts are few and miserable as compared with the
more favored races of the world. Their food supply is
scanty and of little variety. Their arts are primitive, for
raw materials are of few kinds. They possess strength and
endurance, without which life would be impossible under
the dif&eultiea around them ; they have a keen intelligence

THE DISTRIBUTION OF ORGANIC FORMS 361

every advantage that their desert home affords, Ijut
Y cannot rise above a low stage of development.

Many of the wandering tribes of the Sahara find the
struggle for existence so severe that they and their
animals are often on the verge of starvation. They must
move from place to place to secure food ; hence they do nut
build houses, but live in tents that can be easily carried
about as they wander from one pasture ground to another.
As a result of their wandering habits, they have come to
be excellent horsemen and show great endurance in sur-
viving tlie hardships that they must often suffer. But, on
account of being nearly destitute, they have the habit of
taking what they want from any passing travelers whom
they can plunder. They have thus preserved into modern
times a rude manner of life which must have been universal
in the early history of raankintl, but which has been given
up in recent centuries by the people of more advanced |

nations, among whom theft is now punished as a crime.

The Papago Indians of the Sonoran region, south of
the Gila river (southwesteni United States, northwestern
Mexico), move from place to place with the failing and
flowing of springs. They are noted for strength, speed, i

endurance, and abstinence. The Seri Indians, living in I

the desert on the border of the Gulf of California, have no
horses and are noted as runners.

206. Oases. — Fixed settlements in desert regions are
controlled by the presence of water. They are commonly
I made where springs or streams flow upon the open country
I at the base of uplands and mountains; or neai' the ends of I

362 KUIMKNTAUY PHYSICAL GEOGR^LPHY

Buch Btreamsi where the water C£in be distributed in irri-
gating canals; or at points where ground water maj be
found in the neaiiy dry channels of withei-ed streams.
Such settlements are called oase» in the Sahara, and the
same name may be used elsewhere.

El Kuutara OasU, Algerian Saliitra

Tlie barrenness of many deserts is due simply to their
dryness and not to an unfavorable composition of rock or
soil. Where springs or streams moisten the soil, grass
and trees may grow naturally. If the surface can be
irrigated, its productiveness may be increased so as to
support permanent settlements.

The contrast between a habitable spot and the surround-
ing barrenness is so grateful that " an oasis in the desert "
has come to serve as a poetic figure. But oases are only
relatively delightfuL Their water supply is often limited
and impure; their products are few in variety and small

THE DISTRIBUTION OP ORGANIC FORMS 363

lin quantity; their industries are primitive; their inhaU-
itants have to suffer the diBadvantages of isohition aH
completely as do the people of islands.

The oasis of Siwa, in the Sahara, 350 miles west of
Cairo, " the iirst halting place ou the gi-eat desert highroad
to the west," is still little changed from its condition iu
ancient times. Seclusion seems to have bred mistrust, for
strangers are looked on as intruders. They and their
modern ways of doing things are unwelcome.

It sometimes happens that a river rising in well-watered
regions flows across a desert on its way to the sea. If the
river has developed an open and accessible valley, nearly
all the population of the region is gathered on its flood
plain.

The most famous river of tliis kind is the Nile, which
flows 1000 miles through the desert without receiving a
branch, except a few small wet-weather streams. Its flood
plain, several hundred feet below the desert uplands
that inclose it, ia about 500 miles long and from 5 to 15
miles wide, broadening on the delta to over 100 miles.
Here most of the milUons of Egyptians dwell. Their
resources are almost wholly agricultural and, as such,
depend on the annual inundation of the Nile, caused by
the northward movement of the belt of equatorial rains
over the upper branches of the river in summer. The flood
begins in June, usually rising twenty-five feet or more at
Cairo in late summer or early autumn. For thousands of
years the fertility of the flood plain has been maintained
by the annual additions of river silt, estimated to amoimt
to four and a half inches a century. StUl better use of

1 id

364 ELEMENTARY PHYSICAL CEOGRAPHY'

natural conditions is alwut to be made by building a strong
dam acrost! the Nile on a i-eef of racks that forms the first
cataract, at Assouan, and thus storing in a reservoir a
large volume of water for irrigation that would otherwise
run to the sea unused.

207. Geographical Factors in the Life of Civilized Peoples.

— It has already been shciwn tliat the simplest examples
of the relations of man and nature are to be found in the
life of savages, who know few arts and have little inter-
course with other peoples and who are therefore directly
dependent on the simplest home products. What can yoa
Bay in this connection about the natives of coral islands?

Civilized nations offer much more complicated exam-
ples of these relations. Here the people are engaged in
agriculture, manufactures, and commerce. Arts and trades
are highly developed ; the products of many parts of the .
world are gathered and skillfully manufactured into a
great variety of articles for use at home and abroad. It
might at first seem as if such a people had overcome
geographical controls ; but closer study will always show
that they are influenced by them on all sides, and that
their progress is less dependent on overcoming geograph-
ical obstacles than on taking advantage of geographical aids.

In savage tribes there are so few things to do that every
man is well practiced in nearly all the duties of a man's
life. In civilized nations man's work has become greatly
diversified, and " a jack of all trades is master of none."
Many occupations are immediately dependent on geograph-
ical factors, and the skill needed in them is so great that

THE DISTRIBUTION OF ORGAXIC FORMS

S65

persona are successful in more than one. A miner, a
ir, a sailor, each knows liia own work but would be
in the work of liis ueiglibors.

Some of the ways in which men gain a living require a
very close acquaintance with geographical details. A river
pilot must kuow all the bends and shoals in a river channel
and must learn how they are changed by the action of the
river in scouring away or building up the banks and in
sweeping waste along the bed.

Certain peculiar occupations are dependent on a variety
of geographical conditions. For example, in stormy
weather the schooners that sail between our Atlantic
porta sometimes anchor in shallow water near the shore.
In very severe etorma the cables may break and the
anchors are then lost. But anchors are valuable; hence
men, known as "anchor draggers," make a busines.'i of
searching for them. They sail in pairs and drag a strong
tope between their vessels over the sea bottom in fre-
quented anchorage grounds, and they know their curious
trade so well that they make a living by selling the
anchors that they find. Can you give some other examples
o£ this kind?

A member of an isolated savage tribe depends for food,
clothing, weapons, and dwelling upon what he finds close
to his home ; if work is needed in building a hut, in secur-
ing food, in making clothing or weapons, it is usually done
by each family separately. There are no mills where flour
ia ground wholesale; there are no factories where cloth is
woven; there are no shops where household supplies can
be bought.

366 KI.EMEKTAliY PHYSICAL GKOGRAPHY

In a civilized country a family may occupy a house whit
they had no share in building and which required for
construction the labor of many men in many trades,
masons, carpenters, plumbers, plasterers, and painters, M^
The materials used in building the house may have been
brought fi-om hundreds of miles away. The stone for tie
foundation, the lime for mortar, the cement for the cellai
floor, the clay for bricks in the chimney, the plaster for tlie
walls are producte of quarries and pita in different dis- ,f
triets. The beams for the frame, the hoards for the walls y
and floora, the shingles for the roof have probably come
from different forests.

Tlie furniture may be made from various kinds of wood,
metal, and cloth, gathered from far and wide, put together
in great factories, and distributed for sale. The caipets
are very likely spun from wool from the pampas of South
America. The iron in the kitchen utensils probably comes
from iron ore in the old worn-down mountain region west
of Lake Superior, smelted with coal from the dissected
plateau of western Pennsylvania ; the tin of tinware prob-
ably comes from the Malay peninsula southeast of Asia.
The crockery may be from the lowland clay belt of the.
New Jersey coaatal plain.

The daily food may include bread from flour ground by
the water power of a displaced river in Minnesota from
wheat grown in the rich diift soils of the northern prairies
or in the deep-weathered soils of the lava plains of Washing-
ton, beef from the cattle ranches of the Great plains, tea
from China, coffee from Brazil, sugar from Cuba, and salt
from New York. The production of all these materials

THE DISTRIBUTION OF ORGANIC FORMS

wnda on such geographical factors as rock, soil, and
r climate. Their preparation has required skilled labor of •
iny kinds, in which natural forces are usually employed.
mr transportation has been over lands and seas, along
s influenced by geographical conditions at every turn.
lie family for whose comfort all these threads of activity
jet in a single house may be that of a typesetter, skillful
I his own work, but unprepared to take part in any one
of the many arts and trades on which his home comforts
depend. He would be almost helpless alone; but if he
and every one else works faithfully and well, each one doing
his chosen task to the best of his ability, the whole nation
thrives. Yet civilized life is so complicated that, until
attention is directed to its separata items, one might fail to
notice how largely they are determined by geographicid
controls.

How many kinds of materials can you name that were used in
the Louse you live in ? How many of these materials can you trace
back to their sources ? From how many different states or countries
did they come ? What natural fomea have been employed in pre-
paring the materials for use 1 How have the materials been brought
to their place of use? Similar (luestiona may be asked concerning
furniture, food, and clothing.

208. The Influence of Geographical Factors on History.^

The progress of history has been i^epeatedly influenced by
geographical factors. It is fortunate for the modem his-
tory of America that the Atlantic is narrower than the
Pacific; it is chiefly for this reason that the New World
has been peopled by emigrants from the leading races in the
western part of Europe, instead of from the less advanced

368 ELEMENTARY PHYSICAL GEOGRAPHY

peoples of eastern Asia. The eastern coast of North Americi
has abundant harbors where the newcomers found safe
refuge for their vessels. All the early settlements, manj
of which have now become important seaboard cities, wera
located on these protected embayments of the coast line;
Done of them were estabUshed on exposed headlands.

The boundaries of the several colonies founded bj the
immigrants were in most cases established with regard to
tiie harbors on which the more important settlements had
been made. The small size of several of the colonies, and
of the states that now represent them, was determined by
the occurrence of bays or rivera to the west, where otlier
colonies were formed. Rhode Island, founded by settle-
ments on the drowned valley known as Xarragansett bay,
was limited on the west by the colony which took p<
sion of the lower Connecticut valley; and Connecticut was
in turn limited by New York, whose inland growth from
its excellent harbor was guided northward by the drowned
valley of the Hudson. New Jersey was cut off from west-
ward growth by Pennsylvania, whose chief city was estab-
lished near the head of the drowned lower part of a valley,
known as Delaware bay. The small state of Delaware wbs
limited on the west by Maryland, founded on Chesapeake
hay, the drowned lower valley of the Susquehanna; and
Maryland was in turn limited by Virginia, to whose teni-
tory the Potomac embayment of the partly drowned coastal
plain gave easy access weat of Maryland. Farther south
there are no important bays or rivers along the Atlantic
coast with a north and south trend, and there are no more
small states.

H M(

THE DISTRIBUTION OF ORGANIC FORMS

Mention Boma geographical factors on which the importance of
Hew York city d^ends; of Chica-go; of San Francisco, Mention
some factors on which the small population of the Appalachian
highlands and the great population of the prairie states depend.

Success in warfare has often been influenced directly or
indirectly by geographical factors. The size of an army is
largely the consequence of such factors as the area, form,
climate, and fertility of the country to which it belongs;
the strength of the less civilized nations has therefore often
been measured by the number of their warriors. The
character of soldiers is largely dependent on the habits of
the community from which they are enlisted. Regiments
of infantry recruited from among mountaineers have always
famed as fighting men, for they have learned endur-
and courage from the severe conditions of life in

sir rugged homes. Regiments of cavalry recruited fi-om
dwellers on grassy plains are famous aa "rough-riders,"
whether they are Russian Cossacks or American cowboys ;
their skiU and endurance as horsemen are a natural result
of habits developed in an open country of large distances,
where riding is as appropriate a means of going about as
walking is in a mountainous district.

Wliat emmiile can you give of a people whose home favored their
becoming skillful sailors, and who therehy became invaders and con-
querors of other lands? (Sea page 821.)

The fate of battle fields lias been many a time determined
by the arrangement of high and low ground ; hence an
intimate knowledge of land forms and of local geography
is of great importance to militaiy commanders. During
the recent war in South Africa the Boers, having an

370 ELEMENTARY PHYSICAL GEOGRAPHY

accurate acqoaintance with their country, often occupied
the crests of hills, and thus gained advantage over the
British soldiers, who had to make attack while climbing up
a slope from lower ground.

What can you learn about the Spartans at Therm ojijl se ? What
can you tell of Braddock'a defeat?

209. Geographical Factors favoring the Development of
Great Biitain. — The progress and prosperity of a nation
are even more dependent in peace than in war on the
advantage that its people have learned to take of their
surroundings.

West o£ continental Europe, in the latitude of Labrador,
there is an island whose climate is remarkably mUd, because
it is on the leeward side of an ocean across which the sur-
face watera and the winds move obliquely poleward from
warmer latitudes. The island is therefore fertile and
long been noted for its agricultural products. The narrow
strait by which it is separated from the continent has served
as a natural fortification against the armies of neighboring
nations; nearly a tliousand years have passed since the
island has been successfully invaded. It has rich mines of
coal and iron, and these natural products have been skill-
fully used in promoting manufactures of the most diversi-
fied kinds. It has excellent harbors, and many of its people
have therefore been fishermen andsailors ; ite navigators have
crossed the most distant oceans and have developed a world-
wide commerce. As the population of the island increased
under all these favoring conditions, many of its people
emigrated to the new lands discovered by its explorers

THE DISTRIBUTION OF ORGANIC FOKMS 371

and founded oolonie 8 in them; and to-day tlie sun never sets

on the island's poasessions. The empire thua established
is the moat widespread that the world has ever seen.

310. The United States. — A more modern instance of
the dependence of prosperity on geogiaphical elements is
seen in the rapid growth, as a world power, of a young
nation whose center of population now lies in a region
where the winter is so severe that provision must be made
for it, yet where the summer warms a fertile soil from
which industry secures provision in plenty and to spare ;
where open plains and great rivers made it easy for new
settlers to enter the country, and where the small lelief of
the surface favored the construction of the numerous rail-
roads demanded by growing traffic, yet where the variety
of form is sufBcient to promote divereified industries; where
the products of forest and mine are added to those of the
farm, and where these excellent conditions are spread over
so extensive an area that abundant opportunity is offered
for a vast population.

Yet these favoring conditions have not been in them-
selves sufficient for the growth of a powerful nation. The
aboriginal inhabitants of this great land were savages who
did not know how to develop its riches. The entke
territory remained a wilderness until it was entered by the
descendants of a race that had, by long occupation of
another highly favored region, gained a leading position
among the peoples of the 01<1 World.

But these members of the leading race of the Old World
would not have left their homes for a new country, however

372 ELEMENTARY rHYSICAL GEOGRAPHY

favorable its geographical features, i£ its government
had been tyrannical and oppressive. It is therefore cot
local geographical factors alone that have so soon given
this young nation a giant's strength, but three higlily
favoring conditions corabinecl: a land well situated, of
great extent, and rich in many forms of natural wealth
numerous immigrants from the leading race of the Old
World ; and a libera! form of government under which
the highest opportunity is open to every citizen. Let ub
remember that " it ia excellent to have a giant's strength,
but tyrannous to use it like a giant."

QUESTIONS

Sec, 191. How have geogra.phical conditiona afEected man's prog^
ress? Illustrate this by the use that haa been raaiie of the winds;
of waterfalls; of fiood plains; of terrestrial magnetism; of coal
iron. Give some eiamplea of the effects of geographioal conditions
on the distribution of plants ; of animals ; on man's way of living.

198. How is it known that the earth has long been inhabitedT
What barriers prevent the spread of organic forms? Contrast tha
spreading of plants having heavy and light seeds. In what way do
corals and mussels resemble certain land plants? How have free-
moving animals been distributed? Contrast the distribution of
walking and of flying birds. How ia the rotation of the earth
shown to be a factor in the distribution oE certain birds?

193. How is the number of plants or animals in a region limited?
How does man sometimes cause a change in these numbers? Why
do plants and animals tend to increase in number? Why doea'
their number not increase? Explain the phrases "struggle for
existence"; "survival of the fittest"; "natural selection." Upoa
■what does the chauce of survival depend? Illustrate by examples
from sea animals. What effects follow from tlie illumination <^

THE DISTRIBUTION OF ORGANIC FORMS 373

the earth from the sky 7 Give some eiamples of protection gained
by liring in out-of-the-waj places.

194. CoiTiporo ancient and moilem plants and animala. How
have variations iu plants and animals been caused? Illuatrate by
chants in a coastal plain ; in mountaitia ; in climate.

195. Name one of the strongcBt contrasts of geographical con-
ditioua. What proof can be given of tlie great age of the continents
and oceans? What consequences follow from the greater density of
water than of air? Contraat the conditions of the sea bottom with
those of the lands. Stat« some resiilta of these oontrasted conditions.
What can you tell about the warm-blooded animals of the sea?
Why are they believed to be deaceiided from land animals? Give
examples of the remarkable instincts of certain land animals,

19fi, How are the several continents arranged ? Over what region
are rimilar land plania and aniinala found? Name some examples.
Name some of the animals and plants of the lower northern lati-
tudes in the Old and in the New Worlds. What is inferred from
their differences? Name some of tlie animals of the three southern
continents. Why are mammals not found in Australia? Name some
animals and plants native to one part of the world and thriving in
wiother part.

197. How has mankind been divided iii1« race.i? In what ways
do the races differ? Describe the races of Eurasia; of America;
of Africa ; of Australia. How are the races now distributed 7

198. What forma of life are found on continental islands? Wliat
is inferred from this? How have these islands been separated from
the mainland? Xllustrate by the cassowaries; by mammals and
marsupials on the islands between Asia and Australia. What forms
are found on oceanic islands? What is the origin of the names
Azores and Galapagos?

199. How does climate control the distribution of plants? Elus-
trate by the palm (see Figure 112), by cotton, corn, and wheat. What
is the vegetation of the northern treeles.'* belt? How does climate
control the distribution of animals? Give examples. How does the

874 ELEMENTARY PHYSICAL GEOGRAPHY

dittlributkin of plaiiU control that of animals? Give exampleB from

North and South America,

200. Name some direct and some indirect effects of climate oB
man. Why are climatic influences more apparent on savage tribe*
than on civilized peoples? Describe the conditions prevailing in
the forests of equatorial Africa. Describe the lite of the Dwarfs of
these foreats. Explain the relation between thdr lite and their
environment. Do the same for Greenland and the Eatimoa. Whal
general truth do these examples illustrate?

201. Give an example of the effects of the change of seasons o'
plants in the torrid zone ; in the north temperate zone. What ar
annual plants? Name several ways in which animals survive th
winter. IIow does the oblique position of the earth's axis affect th«
life of plants and ttnuiials? How does change of season affect n
way of living? Give examples froni the Caspian steppes; from
Algeria. Of what advantage has winter been in the development
of civilization?

202. How does climate vary onmountaina? Describe the changM
of vegetation seen on ascending a mountain. What is the tree line?
the snow line? What are Alpine plants? In what lowland region
are the plants of high mountains found? AVhat may be learned
from the distribution of the ibex? Give a similar example from
the mountains of New England.

203. How have mountain valleys been used by defeated peoplesS
Give an example from the Pyrenees; from the Caucasus. Why is
life more difficult in mountaina than on plains? Name some of tha
customs of mountaineers.

204. Mention some of the features of desert vegetation. What
is the effect of rain in a desert? Describe the conditions of growth
of desert plants. What can you say of desert animals?

205. Describe the inhabitants of deserts ; the conditions of lifs
in the Sahara ; the Indiana of the Sonoran repon.

206. What are oases? What controls their location? Why aw
deserts barren? Describe the oasis of Siwa. Describe the Nih

THE DISTRIBUTION OF ORGANIC FORMS 375

valley. To what are its floods due ? Of what value are they ? How
B their value to be increased?

207. Where are the simplest examples of the relation of man
md nature found? Why are civilized people leas dependent than
savagea on natural conditions? How have civilized people been
affected by geographical conditions? Give esainplcB. What are
lehor draggera? Show that savages are dependent on immediate
surroundings and on individual wort. Show that civilized people
are often dependent on distant supplies and on the work of many
men in many trades.

208,- What geographical factors have affected tlie historical
development of North America? How were the boundaries of the
smaller northeastern states determined? Show that the character
ot soldiers and their success in warfare are dependent on geographical
conditions.

209, 210. Describe the geographical factors that have favored
ths development of Great Britain. What favorable factors are
found in the United States? What other factors have contributed
to onr national growth ?

REFERENCES FOE SUPPLEMENTARY READING

I Tub titleB in the following list liave been selected with eBpecial
j reference to their aecesBihilitj in public libraries. Mention ia made

of the publications of the U. S. Geological Survey because of their

great value to the geographer as weU as of their wide distribution.

Numbert! preceding certain references indicate the page of thia book

to which the articles cited pertilin.

GEHERAL REFEKEHCES

Gankett, The United States, Stanford's Compendium o£ Geography,
Edward Stanford, 18fl8.
■ The International Geography. D. Appleton & Co., 1890.

Annual Reports, Bulletins, Monographs, and Geological Folios of
the U. S. Geological Survey. Some of the more geographical
essays are referred to below (abbrev., G. S. Ann. Rep., etc.).

The following geographical periodicals contain much material
serviceable in teaching :

National Geographic Magazine, Washington, D. C. (abbrev., N. G. M.).
' Bulletin of the American Geographical Society, New York (B. A. G. S.).
i.Joumal of School Geography, Ijancaater, Pa. (J. S. G.),
Bulletin of the American Bureau of Geography, Winona, Minn.
(B. A. B. G.).

Geographical Journal, Londoi
Scottish Geographical Magazi

(G.J-).
le, Edidburfili (S. G. M.).

■ 878 KLEMENTARY PHYSICAL GEOGRAPHY ^^

Platt, The Better Books in School Geography, J. S. G., II, '03, 181.

(AH S>e twuka ineattonal <n the above arlicli^ would be found sorTicubli
in aobool llbrarle*,)

Mill, Ilinta to Teachera and Studenta on tlie Choice of Geographical

Brioks. Longmans, Green & Co.
Davis, The Equipment of a Geographical Laboratory, J, S. G., II,

'08, 170.
Cornish, Laboratory Wort in Elementary Physiography, J, S. G.

I, '97, 172, 204.
National Geograpliic Monographs, American Book Co., 189i

(N. G. Mon.).
PreliminaryReport of Committee on. Physical Geography of N. E. A.

J. S. G., II, '1)8, 248.

CHAPTER I. THE EARTH AS A GLOBE

TonuG, Astronomy, Ginn & Company, 1888.
Todd, Astronomy. American Book Co., 1807.
ScHOTT, The Earth's Shape and Size, N. G. M., XII, '01, 36.

CHAPTER IT. THE ATMOSPHERE

Waldo, Elementary Meteorology. American Book Co., 1896.

Davis, Elementary Meteorology. Ginn & Company, 188i.

Jameson, Elementary Meteorology, J. S. G., IT, '93, 2.

Greely, American Weather. Dodd, Mead 8c Co., I8S8.

Ward, Practical Exercises in Elementary Meteorology. Ginn &

Company, 1809.
Ward, Equipment of a Metftorologieal Laboratory, J, S, G., HI,

'90, 241.
Bahtholomew, Physical Atlas, Vol. Ill, Meteorology. Lippincott,

63. Illufltrated Cloud Forma, U. S. Hjdrographio Office, Washing-
ton, D.C.
67. Garriott, West Indian IIurricaneB, N. G. M., X, '99, 17, 343 j

XI, '00, 384.

APPENDIX

72. Grkely, Rainfall Types of the United States, N. G, M., V,

■03, 45.
72. Harrinqtok, Rainfall of the United States, U. S. Weather

Bureau, Bulletin 0, 18!)4.
72, Gannett, Reiiwood Forest of the Pacific Coast, N, G. M., X,

'!19, 145.
84. Davis, The Temperate Zones, J. S. G., I, '07, 139.
84. Ward, Climatic Control of Occupationa in Chile, J. S. G., I,

■97, 28S. .
87. Davis, Practical Exercisea in Geography, N. G. M., XI, ■00, 62.

CHAPTER III. THE OCEAH

The Depths of the Sea. Maoniillan & Co., 1874.
Thomson, The Voyage of the Challenger ; The Atlantic. Macniillan

&Co., 1877.
SiGSBEE, Deep Sea Sounding and Dredging, Washington, 1880.
Takner, Deep Sea Exploration, U. S. Fish Commisaion (Washington.
Agassiz, Three CrutBes of the Blake, Cambridge, 1886.
Monthly Pilot Charts of the North Atlantic and tho North Pacific

Oceans, U. 8. Hydrographic Office, Washington.
Sbmple, The Atlantic and Paoiflo Oceans, J. S. G., Ill, '99, 121, 172.

109. Davis, Waves and Tides, J. S. G., II, '98, 122.

113. SciDMORE, Earthquake Wave, Japan, N. G. M., Til, '95, 285.

114. Davis, Winds and Ocean Currents, S. G. M., XHI, '97, 55,

and ,T. 8. G., II, '98, 10.

118. PiLLflBtiBY, The Gulf stream, Ann. Eep. U. S. Coast Survey,

1890.

119. Tide Tables, published annually by U. S. Coast Survey.

121. Jefferson, Atlantic Bstuarine Tides, N. G. M., IX, '08, 400 ;

ELEMENTARY PHYSICAL GEOGRAPHY

CHAPTER IV. THE LANDS

StiALCR, Aspects of thr Earth. Charles ScribDer's Sons, 1S80.

J. Geikib, Earth SciiJpture. G. T. Putnam's Sons.

Text-books on Elementary Geology, by Dana, Gellde, Leconte,

Scott, Tarr, and Brigham.
Shaler, Origin and Nature of SoUb, G. S. 12th Ann. Rep., Pt. 1, 21fl.
Patterson, Work of the Water Giant, J. S. G., Ill, '90, 5.

CBAPTES T. FXAmS AKD PLATEAUS

142. Davis, Description of the Harvard Geographical Models, pub-
lished by the Boston Society of Natural History, Berkelej
Street, Boston. Figures 60, 62, aiid 104 are taken from
these models.

148. Glenn, South Carolina, J. S. G., II, '98, 9, B5.

148. Cobb, North Carolina, J". S. G., I, '97, 256, 300.

156. Abbe, Maryland, B. A. B. G., I, '00, 151, 242.

156. McGee, Chesapeake Bay, G. S. 7th Ann. Rep., 546.

157. McGek (Pall Line), G. S. 12th Ann. Rep., 360.

158. Hatcher, Patagonia, N. G. M., XI, '00, 41.

158. JoHNBOs, High Plains, N. G. M., IX, '08, 493 ; G. S. 2l8t An".

Rep., 601.

159. Fenneman, Climate of the Great Plains, J. S. G., Ill, '99, l,i8.
161. Collie, Physiography of Wiaconain, B, A. B. G., II, '01, 270.
166. PowsLL, Exploration of the Colorado River of the West^

Washington, 1875. See pp. 08-102, 130, 131.

106. Powell, Canyons of the Colorado. Flood & Vincent, Mead-
ville. Pa.

186. Ddtton, Colorado Canyon, G. S. 2d Ann. Rep., 4fl ;
Monogr. II.

168. Campbell and Mendenhall (Plateau of West Virgini»)>
G. S. 17th Ann. Rep., 480.

188. Roosevelt, Winning of the West, I. 101 ; III, 13. G. P. Put-
nam's Sons, 1894.

APPENDIX 381

168. Semple, Influence of the Appalachian Barrier upon Colonial
History, J. S. G., I, '97, 33.
. 172. Hodge, The Enchanted Mesa, N. G. M., VIII, '97, 273.

CHAPTSR VI. MOUNTAINS

178. Russell, Southern Oregon, G. S. 4th Ann. Rep., 435.

181. Russell, Mountains of Nevada, G. 8. Monogr. XI, 38.

185. Fay, Canadian Alps, J. S. G., I, '97, 160.

185. WiLLCOx, Canadian Rockies, J. S. G., I, '97, 293 ; also N. G. M.,
X, '99, 113.

197. Lubbock, Scenery of Switzerland. MacmiUan & Co., 1896
(p. 124).

201. Milne, Earthquakes. D. Appleton & Co., 1883.
, 205. Willis, Round about Asheville, N.C., N. G. M., I, '89, 291.

205. A. Geikie, Scenery of Scotland, 2d ed. (chapters on High-
lands). MacmiUan & Co., 1887.

205. Herbertson, Geography of Scotland, J. S. G., II, '98, 161.

206. McGee, Geographical History of the Piedmont Plateau,

N. G. M., VII, '96, 261.
206. Keith, Piedmont Plateau, G. S. 14th Ann. Rep., 366.
208. Davis, Southern New England, N. G. Mon.
208. Davis, Geographical Illustrations (Southern New England),

published by Harvard University, Cambridge, Mass.
210. Willis, Northern Appalachians, N. G. Mon. See also

B. A. B. G., I, '00, 342-355.
210. Hayes, Southern Appalachians, N. G. Mon.
210. Hayes, Physiography of the Chattanooga District, G. S. 19th

Ann. Rep., Pt. H, 1.
210. Davis, Rivers and Valleys of Pennsylvania, N. G. M., I, 183.

CHAPTER VII. VOLCANOES

Russell, Volcanoes of North America. MacmiUan, 1897.
Dana, Characteristics of Volcanoes. Dodd, Mead & Co., 1890.

2 ELEMENTARY PHYSICAL GEOGRAPHY

on, Volcanoes, li. Appletoii & Co., 1881.
DouGg, Volcanoes, J. S. G., 1, '97, 179 ; IV, '00, 350.

S18. Lybll, Principles of Geology (Monte Nuovo, I, 607; JoniUo,

I, 5»5). D. AH>leton & Co., 187^.
I. DiLLEU, A Late Volcanic Eruption in BTortbern California,

G. S. Bull. No. 79.
221. Phillips, Vesuriiw. Macmillan & Co., 1869.

221. Milne, Eartliquakea. D. Appleton & Co., 1883.
I 3sa. biLLER, Crater Lake, N. G. M., VIH, 33.

222. DiLtER, Crater Lake, J. S. G., I, "97, 36S.
I. Moore, The Aetive Volcanoes North of Kivu (Central Afriia),

G. J., XVII, '01. n.

227. DrTTON (Lava Flows), G. S. Monogr. II.
827. DcTTON, Hawaiian Volcanoes, G. S. 4th Ann. Rep., 81.
229. DiLLKR, Mt.ghaBta,N. G.Mon. Seealao B. A. B. G., I,'l)0,Sfln.
231. Haves, Physiography of the Nicaragua Canal Route, N. G. M.,
X, '99, 233.

CHAPTER Vin. RIVEHS AND VALLEYS
Russell, Rivers o£ North America. G. P. Putnam's Sons, I89H.

235. HovEV, Celebrated American Caverns. Clarke, Cincinnati-

235. HOVEY, Mammoth Cave, J. S. G., 1, '97, 133.

236. Walcott, Natural Bridge of Vii^inia, N. G. M., V, 'Sa, 58.

238. Chamberlis, Artesian Wells, G. S. 5th Ann. Rep., 125.

239. Weed, Hot Springs, G. S. 9th Ann. Rep., 613.
247. Bell, The Labrador Peninsula, S. G. M., XI, 335.
251. Gilbert, Niagara, N. G. Mon.

260. Davis, Seine, Meuse, and Moselle, N. G. M., VII, '97, 189, 228.
264. Gannett, The Flood of April, 1897, in the Lower Missisaippi,

8. G. M., XIII, '07, 419.
266. Fairbanks, Physiography of California, B. A. B. G., II, '01,

232, 329.

CHAPTEK IX. DESERTS AUD GLACIEHS

. Marbut, Missouri, J. S. G., I, '07, 110, U4.

. Platt, The Sahara, J. S. G., IV, '00, 235.

. King, Geological Surrey, 40th Parallel, Washington, I, 460,

484 ; II, 470.
. McGek, Seriland, N. G. M., VII, 'ill, 123.
. Rdbbell, Paat and Present Lakes of Nevada, N. G. Mon.
. Davis, A Temporary Sahara, J. S. G., I\', 'OO, 171.
. GrLBERT, Lake Bonneville, G. S. Sii Ann. Rep., IIJI).
. Gilbert, Lake Bonneville, G. S. Monogr. I.
. Russell, Lake Lahontan, G. S. 3d Ann. Rep., Iflj.
. Holder, A Remarkable Salt Deposit, N. G. M., XII, '01, 391.
. Russell, Glaciers of North America,. Ginn & Company, 1897.
, Shalbr and Davis, Glaciers. Houghton, Mifflin & Co., 1881.
. Tyndall, Forms of Water. D. Appleton & Co., 1872.
. J. Geikib, Great Ice Age, 3ded. D. Appleton & Co., 1895.
, Wright, Ice Age in North America. D. Appleton & Co., ISBO.
. AKCTowSKt, Explonttiun of Antarctic Lands, G. J., XVII,

'01, 50.
, Nansen, First Crossing of Greenland, 1800. Longmans,
Green & Co., 1800.
Peaky, Northward over the Great Ice. Frederick A. Stokes

Co., 1808.
BussELL, Glaciers of Aliiska, G. S. 13th Ann. Rep., 7.
Russell, Mt. St. Eliaa, Alaska, N. G. M., Ill, 53.
Reid, Muir Glacier, Alaska, N. G. M., IV, Ifi.
Reid, Glacier Bay and ita Glaciers, G. S. ICtli Ann. Rep., Pt. I,

415.
Russell, Existing Glaciers of the United States, G. S. 5th

Ann. Rep., 303.
Russell, Mono Lake Region, G. S. 8th Ann. Rep., Pt, I, 321.
Bell, The Labrador Peninsula, S. G. M., XI, 335.
A. Geikib, Scenery of Scotland, 2d ed. (chapters on Glacial
Action). Macmillan & Co., 1887.

384 ELEMENTARY PHYSICAL GEOGRAPHY

295. Russell, Geography of the Lanrentian Baain, B. A. G. )

XXX, '98, 220.
298. McGkb, Drift PlaiaB of Iowa, G. S. lltt Ann. Rep., 383.

296. Taylor, Studies in Indiana Geography, Terre Haute, 1897.

("Short History of the Great Lakes.")

296. Gilbert, Modification of Great Lakes by Earth Movement,

N. G. M., VIII, 233.
2S7. Chambeklin, Rock Scorings, G. S. Tth Add. Rep., 155.

297. Chamberlin, Termiual Moraines, G. S. 3d Ann. Rep., 295.
297. Todd, Terminal Moraines in Dakota, G. S. Bull. No. 144,

IB.
297. Dkybb, Studies in Indiana Geography, Terre Haute, 1897.

The Morainic Lakes of Indiana.
297. Leverett, The Illinois Glacial Lobe, G. S. Mon., XXXVIIL
290. Upham, Glacial Lake Agaasiz, G. S. Monogr. XXV.
300. Gannett, Lake Chelan, N. G. M., IX, '98, 417.
300. Tarb, Lakes and Swamps of New York, B. A. G. S., XXXI,

CHAPTER X. SHOSB LUfES

304. Shaler, Sea and Land. Cliarles Scribner's Sons, 1804.

308. SuALER, Seacoast Swamps of Eastern United States, G. S,

6th Ann. Rep., 93.

308. Shaleh, Beaches and Tidal Marshes, N. G. Mod.

310, Gilbert, Features of Lake Shores, G. S. 5th Ann. Rep., 75,

311. Shaler, Natural History of Harbors, G. S. 13th Ann. Rep., flS.
317. A. Geikie, Scenery of Scotland, 2d ed. (chapter on Shore

Features). Macmilian k Co., 1887.
824. Darwin, Coral Reefs. D. Appleton & Co., 1881).
324. Dana, Corals and Coral Islands. Dodd, Mead & Go., 1801
324. A. AoASBiz, Letter in Am. Joum. Science, Feb., 1898.

IHAPTER XI. DISTRIBDTION OF PLANTS, ANIMALS,
AHD MAN

333, Heilprin, Diatribution of Animals. D. Appleton & Co., 1886.

333. Beddard, Zoogeography. University Press, Cambridge, 189.T.

333. MacMillan, Geographical Distribution of Plants, J. S. G.,
April, -97.

345. Brinton, Races and Peoples.

346. Wallace, Island Life. Macmillan & Co., 1801.

347. Wallace, Travels in the Malay Archipelago. Macmillan

& Co., 9th ed.

348. Merriam, Geographical Distribution of Terrestrial Animals

and Plants, N. G. M., VI, 229.
355. Gannett, The Timber Line, B. A. G.|S., XXXI, '09, 118.
363. JENNinca-BKAMLEY, A Journey to Sino, G. J., X, '87, 507.

386 ELEMEKTARY THTSICAL GEOGRAPHY

REFERENCES FOR MAPS

The following list of map Bheets, selected chiefly from those plll^
lished by the U. 8. Geological Survey and the U. S. Coaat and Geo- ,
detic Survey, will be found of semee in iUuBtrating various exampits
of land forms referred to in Chapters V to X. Complete lists of maps
published by these Surveys can be had, free of charge, oa application. |
The sheeta here named might be supplemented by many others in
illustration of Epecial localities. Some account of the cost and of tb»
method of ordering and nsing the maps is given in the Jouriml of
School Geography, September, 1807, and October, 1898. Coast Sur-
vey maps are here marked " C S." The others, unless specially dea-
ignated, are published bythe Gaological Survey. Numbera preceding
the names iudicate the pagey of this book to which the maps refer, i

CHAPTER V. FLAIRS AIID PLATEAUS
152. Relief Map of New Jersey, published by the Ktate GeologiMl

Survey, Trenton, N.J.; price, 25 cents.
154, Nomini, Md.
159. Topographic Atlas of the United States, folio 1, Physiographic

Types, Pis. I-III.
164. Mt. Trumbull, Diamond Creek, Ariz.
168. Kanawha Falls, Nicholas, W. Va.
172. Watrous, Corazon, N.M.; Abilene, Brownwood, Tei.
174. Mt Trumbull, Kaibab, Echo Cliffs, Ariz.

CHAPTER VL HOUNTAHfS

181, Disaster, Nev.; Alturas, Cal.
188. Platte Canyon, Huerfano Park, Col.
204. Asheville, Mt. Mitchell, Pisgah, N.C.

207. Atlanta, Ga. (Stone mountain is a fine example of a monad-
nock on the uplands of Georgia.)

APPENDIX 387

PAOB

208. Chesterfield, Granville, Mass.; Winsted, Derby, Bridgeport,
Conn.

210. Harrisburg, Hummelstown, Lykens, Pa.

211. C. S. No. 710.

CHAPTER Vn. VOLCANOES

222. Crater Lake (special sheet), Oregon.

230. Shasta, Cal. ; San Francisco Mountain, Ariz.

CHAPTER VIII. RIVERS AND VALLEYS

247. Citra, Fla.

251. Niagara Falls (special map).

256. Mesa de Maya, Col.

261. Donaldsonville, La.

264. 8-Sheet Map of the Alluvial Valley of the Mississippi River,

published by the Mississippi River Commission, St. Louis, Mo.
264. Preliminary Maps of the Mississippi River, published by the

Mississippi River Commission, St. Louis, Mo. Edition of

1900.
268. C. S. No. 194, Mississippi Delta.
271. Versailles, Tuscumbia, Mo.
273. Delaware Water Gap, Pa. ; Harpers Ferry, Va.

CHAPTER IX. DESERTS AND GLACIERS

281. Disaster, Granite Range, Long Valley, Nev.

299. Oconomowoc, Sun Prairie, Wis.

301. Elizabethtown, Mt. Marcy, N.Y.

302. Rochester, N.Y. ; Miimeapolis, Minn.

ELEMENTARY PHYSICAL GEOGRAPHY

CHAPTER X. SHOBB LIKES

308. C. S. Nos. 121, 122, 123 (New Jersey cooatj.

311. C. S. Noa. 103, 104, 105 (Maine coast).

313. C. S. No8. 108, 109 (MaasachuseUa coast).

316. C. 8. No. 674 (California coast).

322. C. S. NoH. 8100, 706 (Alaska coast).

323. C. a No. 21 (Texas coast).

^^^^^^^INDEX ^H

^Srondacka, 301.

Africa, 65, 325, 343, 346, 350.

Arctic ocean, 96, 116, 130.

Agriculture, 43, 62, 169, 230, 207,

— regions. 103, 336, 342.

330, 354, 364, 370, 371.

Argentina, 130, 100.

and irrigation, 56, 71, 159,

Arid regions, 180, 280, see Deserta.

362.

Ariatotie, 2.

and soil, 150, 206, 269, 278,

Arizona, climate, 71, 74. .

287, 296, 363.

Air, 15, 23, 24, see Atmosphere.

YOicanoes, 226. 230.

Alabama, 167.

Artesian nclls, S38.

Alaska, 119, 212, 202, 260, 310.

Asia. 129, 343, 345, 346.

Atlantic ocean, 80, 84, 96, 100,

plateau, 167, 243, 256, 271.

104, 115, 130, 226, 367.

Alluvial fans, »ee Fana.

Alps, 186, 192, 203, 261, 200.

circniation, 35, 40, 60, 304,

glaciers of, 292, 205.

coior, 27, 76, 225.

Amazoa, 41, 56, 121.

Andes, 27, 41, 189, 190, 231.

conTeotion, 36, 60, 63.

Anemometer, 38.

currents, 36, 62, 67.

Animals, in caves, 236.

density, 26, 27.

and climate, 335.

eiasticily, 20.

on deserts, 360.

Iieight, 15, 23.

distribution, 332, 348.

Immidity, 60.

ou islands, 330, 346.

pressure, 24, 90.

on monnlainfi, 26, 169, 355.

properties, 15, 23, 29.

in ocean, 100, 105, 122, 124,

saturation, 01, 83,64.

338.

weight, 26.

Antarctic ocean, 96, 104, 110.

Atolls, 328, see Roets.

regions, 96, 120, 291.

Augusta, 158.

Anticyclones. 46, 75, 77, 78, 80.

Aurora, IB. ^^^H

Apiielion, 12.

Austraiasia. 131. 346. fll^H

^^^H

B^.

■»U-J.

ELEMENTARY PHYSICAL GEOGRAPHY

), 343, 34«. Biimn. 81.

B&rumeter. S6.

Bttrriots, 167, 170, 189, 258, 333.

Btwelevel, U5, '256.

Batin, interior. S83, 28g.

river, 241.

tiK'k, 298, 300, tee Lalies.

WBS(«-filled, 284, *ee Waste.

Basques, 367.

Ba;e. 119, 121, 166,211,314.

Beacli, 112, 307, 308, 313, 320.

BeaverH, 341.

Bench, 200, 313, 827.

Bengal, Baj of, 69, 72, 268.

Bering Strait, 180.

Birds, 52, 334, 339, 341, 354.

Blaclt mountains, 301.

Blizzard, 78, 81.

Blue Ridge, 205.

Bluff, 308, see Cliff.

Boers, 3liB.

Bolivia, 290.

Bore, 121.

Boundaries, 11, 190, 368.

Bowlders, 298.

Brahmaputra, 268.

Brazil, 41, 68, 325, 366.

Brickfieiders, 81.

Bristol channel, 121.

Brilisl) Columbia, 84, 212,

British Isles, 107, 110, 370.

Buenos Aires, 307.

Buffaloes, 160.

Batt«, 171.

Cairo, Sfl3, 363.
Caldera, 221.
Calitomia, climate, 5!
— -coast, 143, 314.
fans, 267.

178, 181.

valley, 265. 260.

voicajic>eB, 219.

Calms, 43, 44, 54, 5(1, 57.

Camden, 158.

Camel, 248, 360.

Canada, 86, 133, 255. 292, 295.

Canals, 232, 248, 320.

Canoes, 248, 322, S52,

Canjons, 162, 164, 166, 38S.

Cape Cod, 138.

Cape Horn, 81, 118, 191.

Cape of Good Hope, 81, 118.

Carbon, 24.

Carbonic dioxide, 24.

Cardinal points, 7.

Caribbean sea, 106.

Caribou, 342.

Cascade mountains, 73.

Cassowary, 347.

Catsiiiii mountains, 167.

Caucasus, 185, 202.

Caverns, 235.

Central America, 106, 226, 2

Ceylon, 83.

Charleston, 158, 238.

Cbesapeahe bay, 156, 238, 36

Ciiicago, 369.

Chile, 56,' 100, 280.

295.

INDEX 891 ^H

, 1B9, S6fl, 287, 345.

Coasta, 107, 141, Sll, 288, 304, 306, ^^M

Be, 345, 348.

308, 316, 325, 368. ^M

■ok wind, 189.

Cold wave, 78, 81. ^H

r cone, 210.

Colorado, 188, 226, 282, 294. ^H

8,8.

Colorado canyon and river, 165, ^^M

i, 63.

, 166, 167, 15S, 200, 253,

270.

Columbia, 157, 158. ^H

, 302, 808.

Columbia rtver, 108, 229. ^H

sation, 4, 84, 139, 170,

332,

Commerce, 5, 07, 340, 864, 370. ^H

, 355, 364, 370, 371.

Compass, 18. ^^M

138, 152, 366.

CoudoiisaUon of vapor, 16, 30. 62. ^^

atra'B Needle, 135.

ConducCinn, 28, 31, 61.

IweUere, 167.

Conea, 219, 220, see Volcanoes.

IBS, 166, 167, 171, 17.^,

174.

ConnecUcut, 208, 368.

lea, 306, 310, 314, 316, 318.

Connecticut river, 209.

,te, 56, 59, 82, 102, 135.

Conseguina, 223.

Lnd anintals, 348, 364.

md land forms, 278, 283.

Continental shelf, 107, 133.

ind toan, &i, 349.

ContlnenlB, 58, 120, 132, 341, 345.

md plants, 83, 348, 363.

Contours, 222.

ind abore lines, 323.

ihangea of, 288, 31B, .<i38.

Coral reefs, see Heefs.

iiy, 135, 169, 180, 281,

360,

Corn, 76, 343, 348.
Corona, 64.

glacial, 200.

Cotopaxi. 223.

>i lands, 88, 138, 284.

Cotton, 148, 149, 348.

188,

Crater, 218, 221.

,353.

Cuba, 106, 318, 325, 328, 366.

if oceans, 62, 83, 84, 102.

Ciiesta, 163.

>f plains, 71, 188, 180.

Cumberland plateau, 167.

>f plateaus, 165.

Cumulus, 63.

borete, 66, 10fl. 234, 282.

Currents, 114, 116, 118, 119, 120,

B, 87, 39, 44, 62.

122, 306, 308.

189, 170, 366.

Cjclones, 46, d^i, 67, 76, 80, 81.

al plains, 143, 147, 168.

indent, 161.

Day and night, 7, 13, 28, 48.

\tlfintic, 148, 165, 158,

170,

Dead sea, 284, 285.

wlted, 150.

Deception island, 221.

unbflfed, 154.

Deerfteld river, 209.

ELEMENTARY PHYSICAL GEOGRAPHY

Degrees, 0. 10.

Delaware, 30B.

Delaware bay and river, 152, 155,

289. 273. 368.
DellAB, 138, 212, 267. 20I>, 321, 322.

ill lakes, a50. 267. 289.

DenudikUon, 137, »ee Erosion.

Denver, 282.

Deposition of waale. 108, 137, 2fi5,

267, 283, 287.
Deserts, 3D, 41, 71, 133, 278, 280,

286, 288, 359.
Dew, 81, 62.

Dikes, 132, 266, 308, 322.
Distribatsries, 268, S22.
Distribution of life, 332.
Divides, 190. 198, 242, 243.
DoidruiDB, 43, 44, 56, 80, OS, 67, 68.
Drainage, 168, 180, 234, 243, 248,

270, 284.
Drift, glacial, 296, 300, 302.

of ocean, 116, 117.

Drought, 76, 236, 244, 350.
Drumlins, £0».
Dimes, 136, 287, 308, 309.
Dust, 286, 287.
Dwarfs, 350.

Earth, rotation, 6, 7, 19,36,67,86.
shape and siie, 1, 3, 4, 0.

Earthquakes, 176, ISO, 182,201,217,

218, 224.
Earthquake waves, 113, 114.
Eclipse, 2.
Ecuador, 223.
Eddies, 116, 117.
Egypt, 135, 363.
Electricity, 19, 85, 253,
Enchaiilcd tnesa, 172.
England, 139, 162, 242, 314.
Equator, 9. 29, 30, 102.
heal, 35, 40, 49, 67, 83.

Equatorial oaluis, 43, 65, 57.
rains, 64, 56. 72, 74, 83.

Erosion, 137, 1S5, 245. 308, SU.

glacial, 294, 299, 320.

Eruptions, 219, 223, 225, 228, 231.
Escarpment, 173.
EBkimos, 103, 202, 324, 352.
Estuaries, 121.
Eurs.sia, 50, 129, 345, 356.
Europe, 55, 72, 81, 84, IW, l^e,
345, 846.

Earth. 1, 332.

Exercises, 4, 8, 10, 12, 35, 42. 46,

^age. 17.

50, 51, 53, 01, 75, 83, 85, 87, 90,

area, 120.

115, 259, 280, 201, 264.

astronomic relations, 11, 12.

14, 46,

Fall line, 157, 158.

attraction. 6, 17,24.

Falls, 157, 247, 248, 251, 291), 302,

asis, 6, 36*.

Famines, 268.

cmst, 16, 132. 137, 177.

Fans, 170, 197, 266, 267, 268, 283.

— ~ interior, lo, 16.

FaullB, 174.

proofs of shape. 2, 3, 19.

Fertilizers. 150. 152, 330.

revolution, 11, 46, 48, 49. 87.

INDEX

893

^Fingal'B cave, 312.

Glacier, Alpine, 187, 260, 292

295.

Fiords, 212, 320, 322.

-ancient, 204, 209.

Fire, 24.

— continental, 200, 206.

FiBh, 16, 100, 335, 380, 330.

Laurentian, 205.

Fisheries, 109, 121, 15fi, 212, 320.

Floe ice, 102, 117.

valley, 292, 294.

Flood plalna, 258, 281, 2(M, 268, 270.

Glens, 205.

363.

GloliigGrina, 105.

Floods, liM, 244, 260, 250, 264, 2I!6,

Glouceator, 109.

281, 282.

Gold, 139, 191,

and lakes, 104,250.

Got^es, 184, 201, 251, 301.

sea, 60, 308.

Grand canyon, 165.

Foehn wind, 180.

Grand Rapids, 302.

Fog. 64.

Granite, 234.

Forests, 149, 150, 168, 170, 348.

Grayity, 5, 24, 358.

-effects of, 236, 310, 350.

Graiing, 66, 71, 74, 160, 181

204,

— on mountaioB, 41, 43, 187, 180,

354, 359.

192, 204, 205, 355,

Great Barrier reef, 327.

Fort Wayne, 320.

Great Britain, 870,

Fossils, 108, 133, 161, \m. 185, 333,

Great lakes, 248, 284, 205, 319. |

337,

Greatplatoa, 71, 73, 158, 308.

Prance, 310,311,313.

Greek philosophera, 3, 19.

Frigid zone, 29, 75, 80.

Greely, 103.

.ProHt,61,62, 135.

Greenland, 104, 201, 321, 335

S6I.

FuDdy, Bay of, 121.

Oreenwicii, meridian of, 10.

Ground water, 234, 230, 230,

283.

Chdapagos, 119, 325, 348.

302.

Galea, 38, 80.

Guam, 00.

Galimg-gung, 223.

Guiajm, 118. 158, 173.

Oalveston, 69, 236.

Gulf Stream, 110. 118.

Ganges, 196, 208.

Oases, 15, 23, 24, 100, 210, 218.

Hail, 70.

Geology, 158.

Halo, 03.

Gwsphere, 17.

Harbors, 40, 110, 120, 143, 147

152,

Germany, 272. 205.

212. 307, 311, 320, .368.

Geysers, 230.

Harrisburg, 274.

Gibraltar, 106, 315.

Hawaiian islands, 106. 326.

Glacialperiod, 206, 310.

Hnadlands, 311, 314, 317.

Glacier, 104, 188, 270, 292, 204, 322.

Heat, 24, 28, 80, 46.

394 ELKMENTARY

rllYSlCAI. GEOGRAPHY

BfliKhtori»n.l.241,.111).

Ireland, 118.

lUlI Gale, 123.

Iron ore, 139, 170. SOS.

Heo.l«ph«rM, 0, 40, 62, M, H

. ftil.

IttigAtioD, 56, 71, 159. 266

lloiculuwuin, S34,

Islands, 60, 131. 3U,320,i

EltKhlanda ol Scotland. 206. 318.

continental, 211, 212,'

Illim.liiyu. 71, 1»6, 189, 103,

200,

coral, 100, 325, 32^ 1

202. 2M.

- — -oceanic, 106, 131.

Illilorj and nnWre, 170, 205,

.131.

volcanic, 106, 219, 2

367. 301. 307.

348.

HonnK.IIo, 26!,, 2&S.

Isobars, m.

IIcHluii, 1«,

Isothermal lines, 33, 35, 48

IIc>r» lotiludra, M, 16, 6^.

Italy, 225, 206, 314.

FIol springs, M3».

Hudson bay, 50.

Jaguar, 343.

Hudson river, 308.

Japan, 114, 203, 22ii, 346^

Humboldt current, Uf,

Java, 223.

Humidity, 00.

Jetties, 322.

Hangflry, 262.

Joriillo, 219.

Hurricane ledge, ITS, 17f..

Jura, 183, 184.

Ibei, 3W(.

Ice, 15, 63, 102, 117, 270, 201, 323.

falls, 192.

sheets, 290, 201, 204, 310.

See Glaciers.
Icebergs, 104, 201, 202.
Iceland, 220, 228, 230.
Idaho, 220,
Illinois, 320.
India, 72, IBB, 104, 2lift.
Indiana, 320.
Indian ocean, 08, 68, 00, 90, 115,

226.
Indiana, 172. 321, 361.
Inlets, 162, 308.
Instinct, 341.
Intelligence, 341.
Iowa, 288,

Kanawlia river, 1
Kangaroo, 344.
Kaiahdin, Mt., 357.
Kentucky, 170, 235.
Kittatinny Mountain, 273.
Ki'akatoa, 27, 113, 225.

Labrador, 61, 110, 370.

Lagoons, 308, 328.

Lake Bonneville, 288, 310.

^ Crater, 222.

Erie, 248, 251, 320.

Geneva, 250, 2fi7.

Great Salt, 281, 288, 2

Lahontan, 280.

Lob, 285.

Michigan, 320.

Hicaragua, 231.

Nyassa, 249.

W INDEX 395

1 Lake Ontario, 248, 261.

Llanos, 344, 353.

I Saperior, 248, 3fl6.

London, 06.

1 Titioaca, 290,

Long Branch, 300.

I Vau, 284.

Long Island sound, 208.

1 Victoria Nyanza, 248.

Longitude, 8.

1 Lakes, 160, 230, 235, 247, 240, 203,

Lowell, 302.

ft 284, 389, 3ie.

Luray cavern, 235.

^H^ African, 240.

^^■-glacial, 206, 300.

Magellan. 3.

^^P-ln mouBtaioB, 107.

Magnetic poles, 18, 19.

H^aalt, 181, 283.

shore lines, 133,288, 318.

Maine, 212, 207, 311, 357.

Malay r'ei'ii'aula, 58, 366.

volcanic, 222, 228, 240.

Mammals, 340.

Land and sea breezes, 50.

Mammoth, 134.

Land hemisphere, 00, 129, 341.

Mammoth cave, 235.

Lands, 129.

Man. 1, 189, 204, 346.

altitude, 4, 131,132.

and nature, 332, see Nature.

area, 120.

civilized, 364, see Civilization.

distribution, ISO.

in deserts, 360.

features, 138, 141, 177, 256.

life on, 338.

savage, 329, 340, 365, 371.

products, 138.

warfare, 369.

surface, 26, 133, 134, 130.

Manchester, 302.

winds on, 50.

Manufactures, 139, 157, 158, 208,

Landslides, 138, 193, 202.

252, 301, 364, 870, 371.

Language, 4, 205, 226, 357.

Maps, 386.

Latitude, 8, 10, 54, 80, 342.

MaraheB, 152, 100, 170, 308.

Marsupials, 344, 347.

Lava, 16, 16, 216, 225, 330.

Maryland. 211, 238, 274, 868.

flows, 210, 227, 230. 240.

■ plateaus, 227, 228, 220.

Meander belt, 263.

Lawrence, 302.

Meanders, 261, 271,273.

Ledges, 135, 247, 286, 306.

Mediterranean, 106, 226.

Levees, 264.

Merced river, 265.

Life, 17, 24, 122, 332.

Meridians, 8, 0, 10, 11. "

Light, 24, 27, 64, 60, 124.

Merrimac, 302. |

Limestone, 13B, 235.

Mesa, 171, 172.

396 ELEMENTARY

PHYSICAL GEOGRAPHY ^^H

MBieore, 28.

Mt. Blanc, 187, 296. ^^H

Mexico. 41, HO, 226, 280.

ML Mazama, 222, 230. ^^H

Gulf of, 74, lOT, 118, 322

Mud volcanoes, 241. ^^H

Minuig, 139. 170, 183, 333.

^^H

MUmeapoliH, 302.

Nansen, 103, 117. 1

Narragansett bay, 368,

Mirage, 30, 230.

Natural bridge, 236.

Mississippi river and valley, 06, 67,

Nature and man, 170, 204, 206, 321,

71, 74, 70, 138, 255, 202, 204

310.

332, 357, 301, 364, 307.

delta, 208, 322.

Navigation, 10, 18, 40, 43, 58,88.81,

.flood plain, 264.

97,104,116, 118, 120, 248, aWt.

-^ meandera, 202, 203, 2C4.

river, 157, 306. ^HH

Missouri, 271, 278.

Nebraska, 283. ^^H

^ river, 198.

Nebular hypothesis, 14. ^^H

Mist, 64.

Neckar river, 273. ^^

Mohawk, 258.

Netheriands, 132, 300, 310. '

Nevada, 73, 178, 181, 204, 280, 2B3.

Monsoons, 57, 58, 72.

New England, 80, 109, 209, 21?,

Monte Nuovo, -218.

255, 298, 313.

Monthfi, 47, 48, 50.

Newfoundland, 104, 100, 119.

Moon, 2, 13, 124.

Moraines, 293, 296, 297.

Now Jersey, 112, 132, 152, 308. am. t

Mouiitaine, 43, 133, 177.

m. ^BM

airon, 26, 29.

New Mexico, 171, 172, SSOci^^^l

block, 178.

New Orleans, 323. ^^^H

buried, 285.

Newton, fl. ^^

climaWof, 188.

New York, 239, 258, 301. 300, 3G8.

dissected, 181, ISO, 301.

city, 122, 360.

^effecla of, 170, 180, 185,

189,

New Zealand, 06, 1 3 1 , j

350, 357, 300.

Niagara, 138, 248, 251. ^^M

-embayed, 211.

Nile, 66, 249, 363. ^^H

folded, 183, 210.

NinibuB, 04. ^^H

— ^growing, 201,204.

Nitrogen, 24. ^^^|

lofty, 27, 185, 188, 196,

204,

Nomads, 160. ^^^H

355.

8, 88. ^^^H

^old, 196, 206,210.

Norfolk, 166. ^^^|

sabdued, 204, 301.

Normandy, 311, 321.

worn-down, 206.

North America, 43, 72, 78, 80, 107,

young, 180,204,205.

344, 34B.

^^H INDEX

1^ Carolina, 74, 148, ISO. S05,

Pacific ocean, 68, 80, Hi, 96, 99,

S18.

106, 115, 110, 226, 328.

tfonb Dakota, 298.

Pacific slope, 43, 72.

HoTthent lights, 18.

Pamlico sound, 155.

Horthmen, 321.

Pampas, 100, 344, 366.

Horth pole, S, 18, 36.

Fanama, 315, 316.

North Star, 6.

Parallels, 9, 10.

Norway, 119, 226, 299, 318, 320.

Parana, 56.

I'afiS, 190.

Oases, 361.

Patagonia, 190, 292, 318, 321.

Peaks, 178, 185, 186, 191, 356.

185, 208, 268, 358, 364. 366, 306,

Pelee, 223.

370, 371.

Peneplain, 206, 208, 210, 246.

Ocean, 96, 304.

PennBylvania, 210, 271, 273, 366.

acUon, 107, 112, 121, 305.

Perihelion, 12.

air, 60, 100.

Persia, 285.

laottom, 98, 105, 123.

Peru, 00, 71, 359.

color, 100.

Feruviaii current, 118, 325.

composition, 100.

cnrrenta, 114, 116, 118.

Philippine islands, 3, 60.

denaily, 100.

Piedmont bell, 149, 206, 243, 271.

depUi, 96, 99, 132.

PikcB peak, 356.

diBtribuUon, 15, 90, 129, 130.

Pittsburg, 170.

exploratioDB, 3, 98, 103.

Plains, 141, 158, 101, 369.

torm, 90.

coastal, 143, 147, 160, 154, 200,

life in, 100, 106, 122, 338.

307, 318,

- — -phosphoreBcence, 100, 124.

. glacial, 200.

storms, 80.

river-made, 2C(), see Flood

- — -temperature, 28, 98, 101, 107,

plains.

waves, 100, 111, 113.

Planetary circulation, 37, 40.

Ohio, 168, 170.

Planetary winds, 30.

Ohio river and vaUey, 71, 170, 250.

Planetfl, 12, 13, 14, 17, 19.

OoM, 105.

distance and diameter, 14.

Oregon, 146, 1T8, 182, 204, 22H,

Plants, 24, 52, 83, 235, 341, 346,

240.

363.

Osage river, 271.

distribution, 332, 337, 348.

0»-bow lake, 2H3.

in oceans, 123, 124, 338.

Oxygen, 24.*

— on deserts, 359, 302.

Ozark plateau, 27B.

on mountains, 355.

—^i

898

ELEMENTARY PHYSICAL GEOGRAPHY

IIbuU ui

II plMteaoi, 166.
l>Uu»iu. 103, l(t&. i:i, 173.

-diage<-U'd, JflT, 278.

I'lttUonaii, 1«3, 318.

Platle river. 2rtl.

po, 2J»5.

Polar region*, 28, IM, 72, 75, 290.

Poles, B, IB, •m

Pompeii, 223.

Populaiion, 1(111, 170, 180, 370, 371.

~ of mouiilaiuit, SOI, SIM, 357.

o( river-mndo ploiiw, 258. 20O,

269, 270, 363,
See SetlleineoU.
Porto Rioo, 100.

Porte, 147, 167, 300, tee Harbora.
Potomac river, 211, 269, .568.
Pr^ries, 71, 170, 206, 366.
Prevailing westerly winds, tee

WlndH.
Prime meridiaD, 10.
Problems, 0, 10, 35, 50, 90.
Products, 138.

Promontories, 211, 311, 313.
I'yrenees, 100, 357.

Race, tidal, 122.

Races of men, 189, 204, 205, 345.

Radiation, 28,46, 61.

Railroads, 97, 160, 191, 201, 371,

Rainbow, 66.

Rainfall, 38, 44, 05, 70, -72, 2S4.

and trade winds, 41, 44, 56.

and westerly winds, 43, 55,

\PHY I

lical, 55, 6a, 351 1

Rainfall, subtropical, f

Rain gauge, 70.

Raleigh, 168.

Rapids, 166, 247, 251, 255.

Reaclies, 266.

ReefB, coral, 324, 326, 327,

sand, 152, 158, 308, 313,311

Refraction, 64, 66.

Reindeer, 342.

Relief, 147, 186, 210, 284,

Hliine, 300,

Rhode Island, 368.

Rhone, 260.

Richmond, 169.

Ridges, 186, ISO, 100.

Rio Grande, 323. .

Rivera, 241, 245, 261, 205, affl, |

802. I

— graded, 264. ^^B

mature, 246, 254, 26». ^^|

old, 346, 270. ^H

revived, 271.

withering, 281, 283, 285.

young, 246, 257, 271.

Roads, 143, 156, 169, 185, 190,

209, 247, 250, 258, 318, 320.
Rochester, 302.
Rock basing, 206, 300.
Rock waste, see Waste.
Rocks, 16, 308, 134, 136, 138, 235
Rocky mountaina, 71, 74, 185, 1S8,

200, 239, 243, 281, 294.
R oral ma, 173.
RotaUon of earth, 8, 7, 36, 57, 85.

distribution of, 41, 4.?, 56, 59, Sahara, 41, 42, 50, 56, 71, 83,280,

71, 72, 180, 18.3, 189, 280, 359. 286, 354, 3B1, 362.

equatorial, 56, 72, 74, 83. Salinas, 200.

subequatorial, 56, 353. Salt, 200, lee Lakes.

INDEX

399

IS6, 308, 310.

efs, see Reefs.

Dne, 167, 209.

ancisco, 369.

;SL Springs, 239.

ium, 123.

es, 13.

:ion, 60.

te. Marie, 248.

ahs, 148.

lavia, 296, 321.

kill, 163, 158.

d, 145, 206, 317, 318.

06.

3, 46, 49, 50, 56, 76, 77, 78,
53.

d, 123.

nt, 101, 106, 108, 121, 148.
121.

mountains, 188.
lents on coasts, 143, 156,
314, 318, 320, 368.
iserts, 285, 361, 363.
ountains, 181, 183, 185, 216.
ains, 146, 159, 206, 297.
ateaus, 165, 166, 171, 278.
srers, 209, 262, 258, 302, 303.
?e Population.
, Mt., 222, 229, 231.
nts plateau, 173, 174.

4, 40, 69, 98, 103, 120, 212.
iver, 249.

ines, 132, 155, 304,307, 311,
323.

deltas, 322.

lakes, 133, 288, 318.
, 81, 134, 160.
Nevada, 73, 189, 295.
15, 263, 265, 269.

Sink holes, 235.

Sirocco, 81.

Siwa, 363.

Sky, 19, 27, 62, 76, 78, 89.

Snake river, 229, 288.

Snow, 70, 77, 187, 190, 192, 290.

line, 29, 365.

Soil, 23, 135, 148, 162, 158, 296,

362.
Solar system, 14, 17.
Solstice, 88.
Sound, 27, 66, 340.
Sounding, 98.
Sounds, 212.

South America, 343, 344, 346, 366.
South Carolina, 148, 157.
Spain, 139.

Springs, 236, 239, 361.
St. Bernard pass, 190.
St. Gotthard, 19^'.
St. Helena, 112.
St. Lawrence, 80, 247, 248, 250,

284, 319.
Stacks, 312, 317.
Stars, 12, 19.
Steppes, 354.

Storms, 64, 65, 66, 67, 79, 80.
Streams, 235, 236, 241, 281.
Subequatorial belts, 56, 71, 83, 353.
Subtropical belts, 55, 56, 73.
Sudan, 83.
Sulu sea, 107.

Sun, 7, 11, 14, 46, 48, 87, 125.
Sunrise and sunset, 7, 27, 89, 225.
Surf, 40, 58, 111, 304, 313.
Susquehanna, 269, 271, 274, 368.
Svanetians, 357.
Swamps, 150, 296, 313, 324.
Sweden, 132.

400 ELEMENTARY PHYSICAL (iEUGRAPHY 1

SweU, 111.

Turks. 346. ^M

Switierlsiid, 180, 11)9, aec Alja.

I'jpboons, 6T, 69. ^^M

Uinkaret plateau. 173. ^

Talua, 163, 106. 173, 180.

United States, 158, 170, 191, S38,

Tarim river, 386.

371.

Temperate toae, 69, 75, 78, 80, &4.

boimdariea, 11, 368.

Temperaluro of atmostpheri:, :!^,

coaslB, 148, 168, 308.

33, 3*, 37, 46, 49, «1.

-development, 371.

:ii.d currentt, IIB.

glai:iai action in, 295, 296,

ch:irts, 33.

302.

— - mean auimal, 33, 34, 50.

products, 76, 139, 348, 371.

of earth, 16, 134.

rainfall, 72.

of lakM, 102.

w.alher, 75, 76. 77, 82, 291.

of oceans, 28, B8, 101, 118.

-winds, 42. 63, 79,81,

Terraces, 200.

Ste Rivers, Lakes, Plains, etc.

Ta^aa, 74, 323.

Utah, 71, 73, 181, 280, 283, 319.

Thermograpb, 33.

Thennonieter, 31j 32.

Valleys, 136, 209, 258, 269, 270.

Tlmnderawrius, 44, 66.

oroeavtise, 200.

Tiber, I.IS.

drowned, 154, 156, 269, 368.

Tibet, 26, 226.

, filled, 109.

Tides, lis, 122, 126, 268, 304.

hanging, 299, 300, 322.

cause of, 120, 124.

Time, 7, 11, 46, 48.

in plains, 143, 146, 154, 169.

TiQ, 366.

in plateaus, 162.

Tonga islands, 219.

lengthwise, 200.

Tornadoes, 66.

terraced, 200.

Torrenls, 197, 253, 254, 280.

Vapor, 38, 41, 60, 62.

Torrid zone, 29, 48, 59, 60, 74,

Variation of plants and animals,

80.

337, 338.

Trade winds, 39, 40, 56, 57, 71.

Vegetation, 43, 159. 181, 187, 235,

Transport al ion of waste, 137, 164,

350, 353, 355, 359.

168, 188. 106, 246, 270.

Venezuela, 56, 353.

Tree line, 355.

Vera Cruz, 147.

Trenton, 158,

Vermont, 208.

Tributaries, 168, 254.

Vesuvius, 221, 223.

Tunnels, 191, 193.

Vikings, 321.

Turkestan, 285.

Vineyard sound, 67.

INDEX

401

a, 156, 206, 210, 318, 368.
oes, 16, 106, 113, 133, 215,
220, 223, 226, 229, 231.

s, 281.
205.

igton, 72, 229, 366.
of the land, 134, 136, 163,
254.

id climate, 136, 323.
position of, 108, 137, 265,
283, 287.

icial, 279, 293, 296.
basins, 284, 209.
valleys, 183, 197, 199, 284.
I shores, 107, 112, 141, 304.
insportation of, 137, 164,
188, 196, 246, 270.

15, 38, 96, 102, 136, 234.
rculation of, 39.
imisphere, 96, 129.
wer, 252, 301, 302.
alls, see Falls,
gaps, 210, 273.
ihed, see Divide,
ipouts, 06.
vapor, see Vapor, Kainfall.

109, 111, 304, 306, 308,
316.

rthquake, 113.
jr, 42, 69, 74, 76, 77, 78.
ireau, 82, 90.
aps, 33, 81, 90.
edictioD, 81.

iring, 134, 163, 183, 186,
205, 206, 209, 312.
237, 238.

West Indies, 69, 106, 133, 325.
West Virginia, 167, 170, 236, 278.
Wheat, 77, 348.
Whirlwinds, 66, 286.
White mountains, 357.
White Sulphur Springs, 239.
Winds, 36, 37, 39, 79, 85, 91, 189.
and currents, 115.

^ and denudation, 136, 286.

— anticyclonic, 46, 76, 78, 80.
cyclonic, 46, 63, 67, 75, 78,

80, 81.

— daytime, 60.

— land and sea breezes, 59.

— of continents, 58.

— planetary, 37, 39.

— prevailing westerly, 39, 42,
44, 51, 54, 63, 72, 75, 80, 334.

— terrestrial, 53, 76, 77, 79.

— trade, 39, 40, 44, 55, 57, 71.

— velocity, 38.

— westerly, see prevailing wes-

terly.

— whirls, 39, 40, 42, 44.

Windward islands, 40.
Wisconsin, 161, 238.
World, Old and New, 130, 343,
367, 371.

Yakima river, 257.
Yellow sea, 101, 268.
Yellowstone park, 198, 239, 240.
Yellowstone river, 251.
Yucca, 360.

Zenith, 89.

Zones, 29, 46, 48, 52, 348.

Plate A
RELIEF MAP OF THE UNITED STATES

Plate B

THE CHIEF PHYSICAL DIVISIONS OF
THE UNITED STATES

Platk C
UNITED STATES

Plate D
NORTH AMERICA

Plate E
SOUTH AMERICA

Plate B*
EUROPE

f^m

/ *

-'-'-'■d

Platk G
ASIA

Plate ^
EUROPE

— /^S-i

■ --J

Plate G
ASIA

Platk (y
UNITED STATES

fHDE 11 / PHILIPPINE. \

ll.,rfThr°'\ ASIA.

'.nr-

Plate D
NORTH AMERICA

Plate H
AFRICA

i>. *>■ . -'• • -

'<;-'...

Plate I

AUSTRALASIA, MALAY ARCHIPELAGO
AND MICRONESIA

I
I ,

\ ■

■ <

< •■ : (•

1 1

> .1 J

'->'

Platk G

ASIA

Plate H
AFRICA

^- .V, /

Plate I

AUSTRALASIA, MALAY ARCHIPELAGO
AND MICRONESIA

mni

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