The elements of physical geography : for the use of schools, academies, and colleges

Front matter

PROM A RECENT PHOTOGRAPH

THE ELEMENTS

OF

Preface

TO THE ORIGINAL EDITION.

TN the preparation of this work, an endeavor has been made to supply a concise yet comprehensive -^ text-book, suited to the wants of a majority of our schools.

The Author, in the course of his teaching, has experienced the need of a work in which unnecessary details should be suppressed, and certain subjects added, which, though usually omitted in works on Physical Geography, seem, in his judgment, to belong properly to the science. The variety of topics necessarily included under the head of Physical Geography renders it almost impossible to cover the. entire ground of the ordinary text-books during the time which most schools are able to devote to the study, and the feeling of incompleted work thus impressed on the mind of both teacher and scholar is of the most discouraging nature.

To remove these difficulties, the Author, during the past few years, has arranged for his own students a course of study, which, with a few modifications, he has at last put into book form, thinking that it may prove beneficial to others.

The division of the text into large and small print has been made with a view of meeting the wants of different grades of schools, the large type containing only the more important statements, and the small type being especially designed for the use of the teacher and the advanced student. The maps have been carefully drawn by the Author according to the standard works and the latest authorities. Neither time nor expense has been spared to insure accuracy of detail and clearness of delineation.

Throughout the work no pains have been spared to insure strict accuracy of statement. Clearness and conciseness have been particularly aimed at; for" which reason the names of authorities for statements which are now generally credited have been purposely omitted.

The Author has not hesitated to draw information from all the standard works on Geography, Physics, Geology, Astronomy, and other allied sciences ; and in the compilation of the Pronouncing Vocabulary he acknowledges his indebtedness to Lippincott's Gazetteer of the World.

Acknowledgments are due to Mr. William M. Spackman, of Philadelphia, and Prof. Elihu Thomson, of the Central High School, for critical review of the manuscript. Also to Mr. M. Benjamin Snyder, of the Central High School, for revision of the proof-sheets of the chapter on Mathematical Geography. E. J. H.

Central High School, Philadelphia, Pa.

iii

Preface

TO THE REVISED EDITION.

oXXc rnHE marked progress which has been made in most of the departments of science embraced

in the study of Physical Geography since the issue of the original edition of "The Elements of Physical Geography" has rendered the preparation of a revised edition a matter of necessity.

The study of Physical Geography, including as it does not only the crust of the earth and its heated interior, but also the distribution of its land, water, air, plants, and animals, includes, in its range, a great variety of topics, and necessitates for its proper elucidation many branches of science. Some knowledge of the elementary principles of these sciences is necessary to the proper study of Physical Geography. The number of such principles is great, and the temptation naturally exists to encumber even an elementary text-book -with such an abundance of leading principles as to render it either incomprehensible, or too extended for actual use in the schoolroom.

The author has endeavored in the revised edition to avoid undue multiplicity either of elementary principles or unimportant details. His object has been to develop forcibly the close interdependence of the inanimate features of the earth's surface, the land, water, and air, with its animate features, its flora, and fauna, and to show the marked influence which all of these exert on the development of the human race, and, therefore, on history itself.

Kecognizing, from his standpoint of a teacher, the inadvisability of crowding a book with new matter simply because it is new, the author has carefully avoided the introduction of new theories unless they have been generally accepted by the best authorities. Old theories are in all cases given the preference of new ones, unless the latter bear the stamp of general approval. At the same time the results of recent investigations have been freely given in all cases where they have been considered sufficiently authoritative.

PREFACE.

In order to avoid confusing the mind of the student, controversial matters have been carefully avoided. When, however, opinion on any subject is fairly divided, a brief statement is made of the differing views.

The favorable reception accorded by the teaching profession to the earlier editions of the book, and the flattering increase in the number of schools using it, have satisfied the author of the inadvisability of changing, to any considerable extent, the order of sequence of topics discussed, or the general manner of explanation therein adopted.

In the preparation of the revised edition the author has freely consulted the latest standard authorities in the many sciences represented.

The maps have all been re-drawn according to the best authorities, and are printed and colored by processes that in point of clearness and beauty leave little room for improvement.

EDWIN J. HOUSTON.

Central High School,

Philadelphia, Pa.

NOTE.

The first chapter of this book is intended mainly for reference, containing as it does, an abstract of the elementary principles of Mathematical Geography, with which most pupils beginning the study of Physical Geography are familiar. In many schools in which the book is used, it is customary to begin the formal study of the book with the Syllabus, page SI, which presents a comprehensive review of the chapter, and in practice and results this plan has proved satisfactory.

Section II. THE OUTSIDE OF THE EARTH

I. The Crust of the Earth 33

II. Distribution of the Land Areas ... 37

III. Islands 39

IV. Belief Forms of the Land 42

V. Belief Forms of the Continents ... 45

Eeyiew Questions 55

Part III. The Water

Section I.

CONTINENTAL. WATERS.

L Physical Properties of Water .... 57 JL Drainage 59

CHAPTER PAGE

III. Bivers 63

IV. Transporting Power of Biyers ... 65 V. Drainage Systems 67

VI. Lakes 69

Beview and Map Questions 72

Section II.

OCEANIC WATERS.

I. The Ocean 73

II. Oceanic Movements 75

III. Ocean Currents 79

Beview and Map Questions 84

Part IV. The Atmosphere

Section I.

THE ATMOSPHERE.

I. General Properties of the Atmosphere 85

II. Climate 87

III. The Winds 90

IV. Storms 96

Beview Questions 99

Section II.

MOISTURE OF THE ATMOSPHERE.

I. Precipitation of Moisture 101

II. Hail, Snow, and Glaciers 107

III. Electrical and Optical Phenomena . 110

Beview Questions 116

CONTENTS.

Part V. Plant Life, Animal Life, And Minerals

Section I.

PLANT LIFE.

CHAPTER PAGE

I. Plant Geography 118

II. Cultivated Plants 124

Review and Map Questions 128

Section II.

ANIMAL LIFE.

I. Zoological Geography 129

II. Characteristic Fauna of the Continents 133

III. The Distribution of the Human Pace 135

Section III. MINERALS

I. Minerals 141

Part VI. The Physical Features Of The United States

CHAPTEK PAGE

I. Surface Structure 146

II. Meteorology 150

III. Vegetable and Animal Life 155

IV. Agricultural and Mineral Produc-

tions 156

V. Alaska 160

GENERAL SYLLABUS 163

GENERAL REVIEW QUESTIONS .... 166

GENERAL MAP QUESTIONS 167

BRIEF ETYMOLOGICAL VOCABULARY 173

STATISTICAL TABLES 174

INDEX 176

Index To The Maps

*o>e<oo

PAGE

MAP OF VOLCANOES AND REGIONS OF EARTHQUAKES 26

MAP OF OCEANIC AREAS AND RIVER-SYSTEMS 68

MAP OF THE OCEAN CURRENTS 81

MAP OF THE ISOTHERMAL LINES 88

MAP OF THE WINDS, RAIN, AND OCEAN ROUTES 94

MAP SHOWING THE DISTRIBUTION OF VEGETATION 121

MAP SHOWING THE DISTRIBUTION OF ANIMALS 131

MAP SHOWING THE DISTRIBUTION OF THE RACES OF MEN 136

PHYSICAL MAP OF THE UNITED STATES 145

MAP SHOWING THE MEAN TRACKS OF STORM-CENTRES, AREAS OF LOW BAROM- ETER, WEATHER SIGNALS, AND STORM SIGNALS 152

Physical Geogkaphy.

Introductory.

1. Geography is a description of the earth.

The earth may be considered in three different ways:

(1.) In its relations to the solar system ;

(2.) In its relations to government and society;

(3.) In its relations to nature.

Hence arise three distinct branches of geography — Mathematical, Political, and Physical.

2. Mathematical Geography treats of the earth in its relations to the solar system.

Mathematical Geography forms the true basis for accurate geographical study, since by the view we thus obtain of the earth in its relations to the other members of the solar system, we are enabled to form clearer conceptions of the laws which govern terrestrial phenomena. Here we learn the location of the earth in space, its size, form, and movements, its division by imaginary lines, and the methods of representing portions of its surface on maps.

3. Political Geography treats of the earth in its relations to the governments and societies of men, of the manner of life of a people, and of their civilization and government.

4. Physical Geography treats of the earth in its relations to nature and to the natural laws by which it is governed. It treats especially of the systematic distribution of all animate and inanimate objects found on the earth's surface. It not only tells of their presence in a given locality, but it also endeavors to discover the causes and results of their existence.

Physical Geography, therefore, treats of the distribution of six classes of objects — Land, Water, Air, Plants, Animals, and Minerals.

Geography deals with the inside as well as with the outside of the earth. It encroaches here on the province of geology. Both treat of the earth : geography mainly with the earth's present condition ; geology with its condition both in the past and present, though mainly during the past.

Some authors make physical geography a branch of geology, and call it physiographic geology, but we prefer the word "physical," or as the etymology would make it, "natural" geography.

Part I. THE EARTH AS A PLANET

Fig. 1. The Earth ia Space.

CHAPTER I. Mathematical Geography

5. The Earth moves through empty space around the sun. The old idea of the earth resting on, or being supported by something, is erroneous. The earth rests on nothing.

A book or other inanimate object placed on a support will remain at rest until something or somebody moves it, because it has no power of self-motion. This property is called inertia.

Inertia is not confined to bodies at rest. If the book be thrown up through the air, it ought to keep on moving upward for ever, because it has no more power to stop moving than to begin to move. We know, however, that in reality it stops very soon, and falls to the earth ; because —

(1.) The earth draws or attracts it ;

(2.) The falling body gives some of its motion to the air through which it moves.

Were the book thrown in any direction through the empty space in which the stars move, it would continue moving in that direction for ever, unless it came near enough to some other body which would attract it and cause it to change its motion.

Our earth moves through empty space on account of its inertia, and must continue so moving for eternities. There are ample reasons for believing that all heavenly bodies continue their motion solely on account of their inertia. The curved paths in which the earth and the other planets move are resultant paths produced in a manner that will be explained hereafter.

Space is not absolutely empty, but is everywhere filled with a very tenuous substance called ether, which transmits to us the light and heat of the heavenly bodies. Wherever the telescope reveals the presence of stars we must believe the ether also extends.

6. The Stars. — The innumerable points of light that dot the skies are immense balls of matter which, like our earth, are moving through empty space. Most of them are heated so intensely that they give off heat and light in all directions. They are so far from the earth that they would not be visible but for their immense size. Beyond them are other balls, also self-luminous, but too far off to be visible except through a telescope. Beyond these, again, we have reason to believe that there are still others. Tliese balls of matter are called stars.

All the heavenly bodies, however, do not shine by their own light. A few — those nearest the earth- — shine by reflecting the light of the sun. These are called planets, and move with the earth around the sun.

7. The Solar System comprises the sun, eight large bodies called planets, and, as far as now known, three hundred and eighty-four smaller bodies called planetoids or asteroids, besides numerous comets and meteors. Some of the planets have bodies called moons or satellites moving around them. These also belong to the solar system.

Fig. 2 represents the solar system. In the centre is the sun. , The circles drawn around the sun show the paths or orbits of the planets. These orbits are represented as circular, but in reality they are slightly flattened or elliptical. The elongated orbits mark the paths of the comets.

MATHEMATICAL GEOGRAPHY.

Fig. 2. The Solar System.

The drawing shows the order of the planets from the sun their common centre, together with the satellites or moons of some of the planets, and the rings of Saturn.

8. Names of the Planets. — The planets, named in their regular order from the sun, beginning with the nearest, are as follows — viz. : Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The first four — Mercury, Venus, Earth, and Mars — are comparatively small ; the second four — Jupiter, Saturn, Uranus, and Neptune — are very large, Jupiter being nearly fourteen hundred times larger than the earth. The initial letters of the last three planets, Saturn, Uranus, and Neptune, taken in their order from the sun : s, u, and n — spell the name of their common centre.

s Mercury has a mean or average distance of 36,000,000 of miles from the sun ; Venus, 67,200,000 ; Earth, 92,900,000 ; and Mars, 141,500,000.

Jupiter is 483,000,000: Saturn, 886,000,000; Uranus, 1,781,900,000; Neptune, 2,791,600,000. The asteroids move around the sun in the space between the orbits of Mars and Jupiter.

* Calculated in round numbers for the mean solar distance of 92,897,000 miles.

PHYSICAL GEOGKAPHY.

It is difficult to obtain clear conceptions of distances that are represented by millions of miles. We may learn the numbers, but in general they convey no definite ideas. Should a man travel forty times around the earth at the equator, he would only have gone over about 1,000,000 miles. Now, Mercury, the nearest of the planets, is thirtysix times farther from the sun than the entire distance the man would have travelled, while Neptune is nearly three thousand times the distance he would have travelled.

9. The Satellites. — A satellite is a body that revolves around another body: the planets are satellites of the sun ; the moon is a satellite of the earth. Mars has two moons. So far as is known, neither Mercury nor Venus has a satellite. All the planets whose orbits are beyond the orbit of the earth have moons : Jupiter has five, Uranus six, Saturn eight, and Neptune one. Besides its moons, Saturn has a number of curious ring-like accumulations of separate solid or liquid particles revolving around it. The earth's moon is about 240,000 miles from the earth. Its volume is about one-forty-ninth that of the earth's.

10. The Sun is the great central body of the solar system. Around it move the planets with their satellites, receiving their light and heat from it. The sun is a huge heated mass about 1,300,000 times the size of the earth. Its diameter is about 866,500 miles. It appears the largest self-luminous body in the heavens because it is comparatively near the earth. Many stars which appear as mere dots of light are much larger than the sun.

The sun is a body heated to luminosity, and gives out or emits light and heat like any other highly-heated body. If no causes exist to maintain its heat, it will eventually cool and fail to emit light. The sun's heat is partly kept up by a variety of causes, the principal of which is the heat developed by meteoric showers that fall on its surface. If a meteor fall toward the sun from interplanetary space, it will reach the surface with enormous velocity, and its motion will there be converted into heat. Since, however, the increase of the sun's mass so necessitated is not confirmed by astronomical observations, it is believed that the sun's heat is not being maintained in this way, and that the sun must eventually cool — an event, however, so remote in time that the life of the solar system may be regarded as practically infinite.

Size of the Sun. — Were the sun hollow and the earth placed at its centre, there would not only be sufficient room to enable the moon to revolve at its present actual distance around the earth, but it would still, in all parts of its orbit, be nearly 200,000 miles below the surface of the sun.

All the fixed stars are distant suns, and probably have worlds like our own moving around them.

From the enormous distances of the fixed stars, we are obliged, in estimating their distances, to use for our unit of measurement the velocity of light. Any other common unit would be too small. Light moves through space at the rate of about 186,000 miles a second, which is over

11,000,000 miles a minute. Notwithstanding this prodigious velocity, it would take over three thousand years for light to reach the earth from some of the stars that are visible to the naked eye. But beyond these stars the telescope reveals myriads of others, whose number is limited only by the power of the instrument. We may conclude that the universe is as boundless as space; that is, light can never reach its extreme limits.

11. Cause of the Earth's Revolution. — The earth continues its motion through space solely on account of its inertia. Its curved path around the sun is a resultant caused by the constant action of two forces : one, a projectile force probably imparted to it when it began its separate existence; the other, the sun's attraction, which causes the earth to fall toward the sun. Under the influence of the projectile force alone the earth would, in a given time, move from a to b (Fig. 3) ; but during this time

b

Fig. 3, Cause of the Carved Shape of the Earth's Orbit,

it has been continually changing its direction by an amount equivalent to a direct fall from b to c along b d ; hence its real orbit, during this time, is along the curved line a c.

12. Position of the Solar System in Space. — The sun, with all the bodies which move around it, is in that portion of the heavens called the Milky Way. The sun is an insignificant star among the millions of other stars the telescope has revealed to us.

It was formerly believed that the sun was stationary, for it was not then known that the positions of the fixed stars were undergoing slight variations as regards the earth. It is now generally conceded that the sun, with all the planets, is moving through space with tremendous velocity, the direction at present being toward the constellation Hercules. The astronomer Maedler, however, believes that the grand centre around which the solar system is moving is Alcyone, the brightest star in the constellation of the Pleiades. The estimated velocity of the sun in its immense orbit is 1,382,000,000 miles per year. As the earth is carried along with the sun in its orbit, it is continually entering new realms of space.

13. The Earth. — The shape of the earth is that of a round ball or sphere slightly flattened at two opposite sides. Such a body is termed a spheroid. There are two kinds of spheroids — oblate and prolate; the former has the shape of an orange, the latter that of a lemon.

MATHEMATICAL GEOGRAPHY.

The straight line that runs through the centre of a sphere or spheroid and terminates at the circumference is called the diameter. If the sphere rotates — that is, moves around like a top — the

Fig, 4. Oblate Spheroid, Pig. 5, Prolate Spheroid.

diameter on which it turns is called its axis. In the oblate spheroid the axis is the shorter diameter ; in the prolate spheroid the axis is the longer diameter.

Fig. 6. Curvature of the Earth's Surface.

The shape of our earth is that of an oblate spheroid. The polar diameter is 26.47 miles shorter than the equatorial diameter.

14. Proofs of the Rotundity of the Earth.—

The earth is so large a sphere that its surface everywhere appears flat. The following simple considerations will prove, however, that its form is nearly spherical :

(1.) Appearance of Approaching Objects, — If the earth were flat, as soon as an object appeared on the horizon we would see the upper and lower parts at the same time ; but if it were curved, the top parts would first be seen. Now, when a ship is coming into port we see first the topmasts, then the sails, and finally the hull ; hence the earth must be curved ; and, since the appearance is the same no matter from what direction the ship is approaching, we infer that the earth is evenly curved, or spherical.

(2.) Circular Shape of the Horizon. — The horizon — or, as the word means, the boundary — is the line which limits our view when nothing intervenes. The fact that this is always a circle furnishes another proof that the earth is spherical.

The horizon would still be a circle if the earth were perfectly flat, for we would still see equally far in all directions ; but it would not everywhere be so, since to an observer near the edges some other shape would appear. It is on account of the spherical form of the earth that our field of view on a plain is so soon limited by the apparent meeting of the earth and sky. As we can see only in straight lines, objects continue visible until they reach such a distance as to sink below the horizon, so that a straight line from the eye will pass above them, meeting the sky far beyond, on which, as a background, the objects on the horizon are projected.

(3.) Shape of the Earth's Shadow. — We can obtain correct ideas of the shape of a body by the shape of the shadow it casts. Now, the shadow which the earth casts on the moon during an eclipse of the moon is always circular, and as only spherical bodies cast circular shadows in all positions, we infer that the earth is spherical.

(4.) Measurement. — The shape of the earth has been accurately ascertained by calculations based on the measurement of an arc of a meridian. We therefore not only know that the earth is oblately spheroidal, but also approximately the amount of its oblateness.

(5.) The Shape of the Great Circle of Illumination, or the line separating the portions of the earth's surface lighted by the sun's rays from those in the shadow, is another evidence cf the rotundity of the earth.

15. The Dimensions of the Earth.— The equatorial diameter of the earth, or the distance through at the equator, is, approximately, 7926

PHYSICAL GEOGRAPHY.

miles ; its polar diameter, or the length of its axis, is 7899 miles. The circumference is 24,899 miles. The entire surface is equal to nearly 197,000,000 square miles.

The specific gravity of the earth is about 5§ ; that is, the average weight of all its matter is five and two-third times heavier than an equal volume of water.

16. Imaginary Circles. — In order to locate places on the earth, as well as to represent portions of its surface on maps, we imagine the earth to be encircled by a number of curved lines called great and small circles.

A great circle is one which would be formed on the earth's surface by a plane passing through the earth's centre, hence dividing it into two equal parts. All great circles, therefore, divide the earth into hemispheres.

The formation of a great circle on a sphere by cutting it into two equal parts is shown in Fig. 7.

lik

Fig. 7. Great Circle,

The shortest distance between any two places on the earth is along the arc of a great circle.

All planes passing through the earth's centre form approximately great circles on its surface.

A small circle is one formed by a plane which does not cut the earth into two equal parts.

The formation of a small circle by cutting a sphere into unequal parts is shown in Fig. 8.

■M

Fig, 8. Small Circle,

The great circles employed most frequently in geography are the equator and the meridian circles. The small circles are the parallels.

If we divide the circumference of any circle, whether great or small, into three hundred and sixty equal parts, each part is called a degree. The oue-sixtieth part of a degree is a minute; the one-sixtieth part of a minute is a second. These divisions are represented as follows : 34°, 12', 38'' ; which reads, thirty-four degrees twelve minutes and thirty-eight seconds.

The Equator is that great circle of the earth which is equidistant from the poles.

Meridian Circles are great circles of the earth which pass through both poles.

The Meridian of any given place is that half of the meridian circle which passes through that place and both poles. A meridian of any place reaches from that place to both poles, and therefore is equal to one-half of a great circle, and, with the meridian directly opposite to it, forms a great circle called a meridian circle. There are as many meridian circles as there are places on the equator or on any parallel.

In large cities the meridian is generally assumed to pass through the principal observatory.

Fig, 9. Meridians and Parallels,

Parallels are small circles which pass around the earth parallel to the equator.

The meridians extend due north and south, and are everywhere of the same length ; the parallels extend due east and west, and decrease in length as they approach the poles.

The Tropics are parallels which lie 23° 27' north and south of the equator: the northern tropic is called the Tropic of Cancer, the southern tropic is called the Tropic of Capricorn.

The Polar Circles are parallels which lie 23° 27' from each pole. The circle in the Northern Hemisphere is called the Arctic Circle; that in the Southern Hemisphere, the Antarctic Circle.

17. Latitude is distance north or south from the equator toward the poles, measured along the meridians. It is reckoned in degrees.

The meridian circles are divided into nearly equal parts by the parallels, and it is the number of these parts that occur on the meridian of any place between it and the equator which deter-

MATHEMATICAL GEOGRAPHY.

mines the value of its latitude. If we conceive eighty-nine equidistant parallels drawn between the equator and either pole, the) r will divide all the meridians into ninety nearly equal parts ; the value of each of these parts will be one degree of latitude. Therefore, if the parallel running through a place is distant from the equator fortyfive of these parts, its latitude is 45°. If more than eighty-nine parallels be drawn, the value of each part will be less than one degree.

Places north of the equator are in north latitude ; those south of it are in south latitude.

Since the distance from the equator to the poles is one-fourth of an entire circle, and there are only 360° in any circle, 90° is the greatest value of latitude a place can have. Latitude 90° N. therefore corresponds to the north pole.

To recapitulate : Latitude is measured on the meridians by the parallels.

18. Longitude is distance east or west of any given meridian.

Places on the equator have their longitude measured along it ; everywhere else longitude is measured along the parallels.

The meridian from which longitude is reckoned is called the Prime Meridian. Most nations take the meridians of their own capitals for their prime meridian. The English reckon from the meridian which runs through the observatory at Greenwich ; the French from Paris. In the United States we reckon from Washington.

Any prime meridian circle divides all the parallels into two equal parts. A place situated east of the prime meridian is in east longitude ; west of it is in west longitude.

Since there are only 180° in half a circle, the greatest value the longitude can have is 180° ; for a place 181° east of any meridian would not fall within the eastern half of the parallel on which it is situated, but in the western half; and its distance, computed from the prime meridian, would be 179° west.

It is the meridians that divide the parallels into degrees ; therefore longitude is measured on the parallels by the meridians.

19. Value of Degrees of Latitude and Longitude. — As latitude is distance measured on the arc of a meridian, the value of one degree must be the -g^-p-th part of the circumference along that meridian, since there are only 360° in all. This makes the value of a single degree approximately equal to 69£ miles. Near the poles the flattening of the earth causes the value of a degree slightly to exceed that of one near the equator.

The value of a degree of longitude is subject to great variation. It is equal to the -youth p ar t of the earth's circumference, provided the place be situated on the equator; otherwise, it is the 3^-jth part of the parallel passing through the place that is taken ; and as the parallels decrease in size as we approach the poles, the value of a degree of longitude must likewise decrease as the latitude increases, until at either pole the longitude becomes equal to zero.