;-'■:'. H&* m M.: M. *m fS :*i.v : JB $8 ^:J * Or ; J*?l? 3 0.9 /^h^fr^ S Si) W t 3 0.'^/^ S $ -si/ '< T1SIM '&&±LuLM ©IF MrHAO^IEAo THE ELEMENTS OP PHYSICAL GEOGKAPHY, FOE, THE USE OP Schools, Academies, and Colleges. BY EDWIN J. HOUSTON", A.M., PROFESSOR OF PHYSICAL GEOGRAPHY AND NATURAL PHILOSOPHY IN THE CENTRAL HIGH SCHOOL OF PHILADELPHIA; PROFESSOR OF PHYSICS IN THE FRANKLIN INSTITUTE OF THE STATE OF PENNSYLVANIA. REVISED EDITION. philadelphia: Published by Eldredge & Brother, No. 17 North Seventh Street. 1892. A SERIES OF TEXT-BOOKS ON THE NATURAL SCIENCES. By Prof. E. J. HOUSTON. — ii i m&fh* i ■ 1. Easy Lessons in Natural Philosophy. 2. Intermediate Lessons in Natural Philosophy. 3. Elements of Natural Philosophy. 4. Elements of Physical Geography. JWGAXIQI IIBB/ The Easy Lessons in Natural Philosophy is in- tended for children. It is arranged on the " question-and- answer" plan ; but the answers, in almost every case, con- tain in themselves a distinct statement apart from the ques- tion, thus removing the objections of those who are op- ponents of the " question-and-answer " plan of teaching; which, if properly used, is shown by experience to be one of the best methods of reaching the mind of a young child. The Intermediate Lessons in Natural Philos- ophy is designed for the use of pupils who have finished such books as Houston's " Easy Lessons in Natural Philos- ophy," Martindale's "First Lessons in Natural Philos- ophy," Swift's "First Lessons in Natural Philosophy," Hotze's "First Lessons in Physics," Parker's "Natural Philosophy," Part I., Peterson's "Familiar Science," and other similar books, but who are not sufficiently advanced to take up the larger text-books. Its publication was de- termined upon at the request of teachers in many parts of the country, who have felt the need of a book of this grade to meet the wants of their own classes. So far as we know, there is no other book in the market which fills the want here indicated. The Elements of Natural Philosophy is in- tended for High Schools, Academies, Seminaries, Normal Schools, etc. It gives the elements of the science in a concise form and in logical sequence, so that the book forms a system of Natural Philosophy, and not a mere collection of disconnected facts. It is fully "up to the times" in every respect, and gives full descriptions of the most important discoveries recently made in Physical Science. The Electric Light, the Telephone, the Micro- phone, the Phonograph, etc. are all described and illus- trated. Teachers will be well pleased with this book. It will give satisfaction wherever introduced. • o<>o. Copyright, 1891, by ELDREDGE & BROTHER. Westcott & Thomson, Mectrotypers, Philada. The George S. Ferguson Co, Printers, Philada. J Ml Preface TO THE ORIGINAL EDITION. "HD^^OO 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 unneces- sary 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 state- ments 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. Benja- min Snyder, of the Central High School, for revision of the proof-sheets of the chapter on Mathe- matical Geography. E. J. H. Central High School, Philadelphia, Pa. — - t mtmm jr^fiM m MroUojLx i5i Preface TO THE KEVISED EDITION. 5XKO rTlHE 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 school- room. The author has endeavored in the revised edition to avoid undue multiplicity either of ele- mentary principles or unimportant details. His object has been to develop forcibly the close inter- dependence 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. Eecognizing, 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, Jan., 1891. NOTE. The first chapter of this book is intended mainly for reference, containing as it does, m 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. Contents. Introductory 9 PART I. THE EARTH AS A PLANET. CHAPTER I. Mathematical Geography 10 Syllabus 21 Review Questions 21 PART II. THE LAND. Section I. THE INSIDE OF THE EARTH. I. The Heated Interior 22 II. Volcanoes • 23 III. Earthquakes 28 Syllabus 31 Eeview and Map Questions 32 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. Relief Forms of the Land 42 V. Relief Forms of the Continents ... 45 Syllabus 54 Review Questions 55 Map Questions , 56 PART III. THE WATER. Section I. CONTINENTAL. WATERS. I. Physical Properties of Water II. Drainage 57 59 CHAPTER PAGE III. Rivers 63 IV. Transporting Power of Rivers ... 65 V. Drainage Systems 67 VI. Lakes 69 Syllabus 71 Review and Map Questions 72 Section II. OCEANIC WATERS. I. The Ocean 73 II. Oceanic Movements 75 III. Ocean Currents 79 Syllabus 83 Review 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 Syllabus 98 Review Questions 99 Map Questions 100 Section II. MOISTURE OF THE ATMOSPHERE. I. Precipitation of Moisture 101 II. Hail, Snow, and Glaciers 107 III. Electrical and Optical Phenomena . 110 Syllabus 115 Review Questions 116 Map Questions 117 CONTENTS. vn PART V. ORGANIC LIFE. Section I. PLANT LIFE. CHAPTER PAGE I. Plant Geography 118 II. Cultivated Plants 124 Syllabus 127 Review and Map Questions 128 Section II. ANIMAL LIFE. I. Zoological Geography 129 II. Characteristic Fauna of the Conti- nents 133 III. The Distribution of the Human Pace 135 Syllabus 138 Review Questions 139 Map Questions 140 PART VI. THE PHYSICAL FEATURES OF THE UNITED STATESr CHAPTER PAGE I. Surface Structure 142 II. Meteorology 146 III. Vegetable and Animal Life 151 IV. Agricultural and Mineral Produc- tions 152 V. Alaska 156 Syllabus 157 Review Questions 158 Map Questions 159 GENERAL SYLLABUS 159 GENERAL REVIEW QUESTIONS .... 162 GENERAL MAP QUESTIONS 163 PRONOUNCING VOCABULARY 166 BRIEF ETYMOLOGICAL VOCABULARY 169 STATISTICAL TABLES 170 INDEX TO THE MAPS. *o>*io° 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 141 MAP SHOWING THE MEAN TRACKS OF STORM-CENTRES, AREAS OF LOW BAROMETER AND SIGNAL FLAGS 148 Physical GtEOgbaphy. 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 geog- raphy — 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 concep- tions of the laws which govern terrestrial phenomeoa. 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 2 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 inani- mate 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 five classes of objects — Land, Water, Air, Plants, and Animals. Geography deals with the inside as well as with the out- side 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 geol- ogy, 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 in 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 around the sun, and, on account of its inertia, must con- tinue so moving for eternities. There are ample 10 reasons for believing that all the heavenly bodies continue their motion solely on account of their inertia. The mutual attraction or gravitation of neighboring bodies for each other produces, as will be hereafter explained, the curved paths in which they move. Space is not absolutely empty, but is everywhere filled with a very tenuous substance called ether, which trans- mits 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. These balls of matter are called stars. All the heavenly bodies, how- ever, 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, two hundred and eighty-one smaller bodies called planetoids or asteroids, besides nu- merous 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 elliptical orbits mark the paths MATHEMATICAL GEOGRAPHY. 11 NEPTUNElifif Fig. 2. The Solar System, of the comets. The drawing shows both the relative distances of the planets and their sizes as compared with each other and with the sun, the relative size of the sun being that of the orbit of Neptune. 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 hun- dred 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. * 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. 12 PHYSICAL GEOGRAPHY. 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 thirty- six 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 satel- lite. All the planets whose orbits are beyond the orbit of the earth have moons : Jupiter has four, Uranus six, Saturn eight, and Neptune one. Be- sides 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 vol- ume 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 diam- eter 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 eventu- ally 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 inter- planetary 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 observa- tions, it is believed that the sun's heat is not being main- tained 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 prodig- ious 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 tele- scope 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's motion through space is caused solely by a projectile force imparted to it when it began its separate existence, prob- ably when first thrown off from the nebulous sun. From its inertia it would move for an indefinite time in one direction, but by the sun's attraction it is constantly changing its direction by falling toward the sun ; and thus is produced the curved shape of its orbit. Under the in- fluence of the projectile force alone the earth would move b Fig. 3. Cause of the Curved Shape of the Earth's Orbit. through space from a to 6 (Fig. 3) ; but during this time it has been continually changing its direction by an amount equivalent to a direct fall from 6 to c along the line b d ; hence its real orbit, during this time, is along the. curved line from a to 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 veloc- ity, the direction at present being toward the constella- tion 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 pro- late ; the former has the shape of an orange, the latter that of a lemon. MATHEMATICAL GEOGRAPHY. 13 The straight line that runs through the centre of a sphere or spheroid and terminates at the cir- cumference 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 diam- eter ; 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 hori- zon — or, as the word means, the boundary — is the line which limits our view when nothing inter- venes. The fact that this is always a circle fur- nishes another proof that the earth is spherical. The horizon would still he a circle if the earth were perfectly flat, for we would still see equally far in all di- rections ; 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 only see 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 dur- ing an eclipse of the moon is always circular, and as only spherical bodies cast circular shad- ows 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 the exact amount of its ob- lateness. (5.) The Shape of the Great Circle of Illumi- nation, 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 of the rotundity of the earth. 15. The Dimensions of the Eartfi. — The equa- torial diameter of the earth, or the distance through at the equator, is, approximately, 7926 14 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 ahout 55 ; that is, the average weight of all the materials that constitute it 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 por- tions 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. Fig. 7. Great Circle. The shortest distance between any two places on the earth is along the arc of a great circle. 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. 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 one-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 q , 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 there- fore 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 meridians 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 south- ern 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. 15 mines the value of its latitude. If we conceive eighty-nine equidistant parallels drawn between the equator and either pole, they 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 forty- five of these parts, its latitude is 45°. If more than eighty-nine parallels be drawn, the value ©f each part will be less than one degree. Places north of the equator are in north lati- tude ; 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 me- ridian 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 par- allels 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 Longi- tude. — As latitude is distance measured on the arc of a meridian, the value of one degree must be the -g-g-^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 -^r^h part of the earth's circumference, provided the place be situated on the equator; otherwise, it is the ^jl^th 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 longi- tude becomes equal to zero. The value of a single degree of longitude on the equator, or at lat. 0°, is equal to about 69£ miles. At latitude 45° it is equal to about 49 miles. u 60 o « « 35 » II g O « II 12 M " 90° " " " Geographical Mile.— The sy^th of the equatorial circumference, or the one-sixtieth of a degree of longitude at the equator, is called a nautical or geographical mile. The statute mile contains 1760 yards ; the geographical or nautical mile, 2028 yards. The nautical mile is sometimes called a knot. 20. Map Projections. — The term projection as applied to map-drawing means the various methods adopted for representing portions of the earth's surface on the plane of a sheet of paper. The projections in most common use are Merca- tor's, the orthographic, the stereographic, and the conical projections. Of these the stereographic is best adapted to ordinary geographical maps, and Mercator's to physical maps. All projections must be regarded as but approximations. 1. The Orthographic Projection is that by which the earth's surface is represented as it would appear to an observer viewing it from a great distance. 2. The Stereographic Projection is that by which the earth's surface is represented as it would appear to an observer whose eye is directly on the surface, if he looked through the earth as through a globe of clear glass, and drew the details of the surface as they appeared projected on a transparent sheet of paper stretched in front of his eye across the middle of the earth. There may be an almo? . infinite number of such projections, according to the position of the observer. The two stereographic pro- jections in most common use are the Equatorial and the Polar. Mercator's Projection represents the earth on a map in which all the parallels and meridians are straight lines. Mercator's charts are drawn by conceiving the earth to have the shape of a cylinder instead of that of a sphere, and to be unrolled from this cylinder so as to form a flat surface. The me- ridians, instead of meeting in points at the north and south poles, are drawn parallel to each other. This makes them as far apart in the polar regions 16 PHYSICAL GEOGRAPHY. as at the equator, and consequently any portion of the earth's surface represented on such a chart, if situated toward the poles, will be dispropor- Fig. 10. The Earth on Mercator's Projection. tionally large. In order to avoid the distortion in the shape of the land and water areas, the dis- tance between successive parallels is increased as they approach the poles. The dimensions of the land or water, however, are greatly exaggerated in these regions. The immediate polar regions are never represented on such charts, the poles being supposed to be at an infinite distance. Mercator's charts are generally employed for physical maps, on account of the facility they afford for showing direction. The distortion they produce in the relative size of land or water areas must he carefully borne in mind, or wrong ideas of the relative size of various parts of the world will be obtained. Mercator's charts make bodies of land and water situated near the poles appear much larger than they really are. In an Equatorial Projection of the entire earth the equator passes through the middle of each hemisphere, and a meridian circle forms the borders. In a Polar Projection of the entire earth the Fig. 11. The Earth on an Equatorial Projection. poles occupy the centres of each hemisphere, and the equator forms the borders. In a Conical Projection the earth's surface is represented as if drawn on the frustum of a cone and afterward unrolled. This projection is suit- able where only portions of the earth's surface, Fig. 12. The Earth on a Polar Projection. and not hemispheres, are to be represented. The cone is supposed to be placed so as to touch the earth at the central parallel of the country to be represented. In maps as ordinarily constructed it is not true that the upper part is north, the lower part south, the right hand east, and the left hand west, except in those on Merca- tor's projection. In all maps due north and south lie along the meridians, and due east and west along the parallels, since 1 MATHEMATICAL GEOGRAPHY. 17 Fig. 13. The CoDical Projection. in most maps both parallels and meridians are curved lines. Therefore, in most maps due north and south and due east and west will lie along the meridians and parallels, and not directly toward the top and bottom, or the right- and left-hand side. 21. The Hemispheres. — The equator divides the earth into a Northern and a Southern Hemisphere. The meridian of long. 20° W. from Greenwich is generally taken as the dividing-line between the Eastern and Western Hemispheres. 22. The Movements of the Earth ; Rotation. — The earth turns around or spins on an imaginary diameter called its axis. This motion is called its rotation. That the earth rotates from west to east the following consideration will show : To a person in a steam-car mov- ing rapidly in any direction, the fences and other objects along the road will appear to.be moving in the opposite direction : their motion is of course apparent, and is caused by the real motion of the car. Now, the motion of the sun and the other heavenly bodies, by which they appear to rise in the east and set in the west, is apparent, and is caused by the real motion of the earth on its axis; this motion must therefore be from west to east. The sun, the planets, and their satellites, so far as is known, also turn on their axes from west to east. The earth makes one complete rotation in about every twenty-four hours — accurately, 23 hours 56 minutes 4.09 seconds. The velocity of its rota- tion is such that any point on the equator will travel about 1042 miles every hour. The veloci- ty of course diminishes at points distant from the equator, until at the poles it becomes nothing. 23. Change of Day and Night. — The earth re- ceives its light and heat from the sun, and, being an opaque sphere, only one-half of its surface can be lighted at one time. The other half is in dark- ness, since it is turned from the sun toward por- tions of space where it only receives the dim light of the fixed stars. The boundary-line between the light and dark parts is a great circle called the Great Circle of Illumination. Had the earth 3 no motion either on its axis or in its orbit, that part of its surface turned toward the sun would have perpetual day, and the other part perpetual night; but by rotation different portions of the surface are turned successively toward and away from the sun, and thus is occasioned the change of day and night. 24. The Revolution of the Earth.— The earth has also a motion around the sun, called its revolution. The revolution of the earth is from west to east; this is also true of all the planets and asteroids, and of all their satellites, except those of Uranus, and probably of Neptune. The phrases "rotation of the earth on its axis" and "revolution in its orbit" are often used in reference to the earth's motion ; but the simple words " rotation " and " revolution " are sufficient, since the first refers only to the motion on its axis, and the second only to the motion in its orbit. The earth makes a complete revolution in 365 days 6 hours 9 minutes 9.6 seconds. This time forms what is called a sidereal year. The tropical year, or the time from one March equinox to the next, is somewhat shorter, or 365 days 5 hours 48 minutes 49.7 seconds. The latter value is the one generally given for the length of the year. It is nearly 365 J days. It will be found that the sum of the days in all the months of an ordinary year is only equal to 365, while the true length is approximately one-quarter of a day greater. This deficiency, which in every four years amounts to an entire day, is met by adding one day to February in every fourth or leap year. The exact time of one revolution, however, is some 11 minutes less than 6 hours. These eleven extra minutes are taken from the future, and are paid by omitting leap year every hundredth year, except that every 400 years leap year is counted. In other words, 1900 will not be a leap year, since it is not divisible by 400, but the year 2000 will be a leap year. The length of the orbit of the earth is about 577,000,000 miles. Its shape is that of an el- lipse which differs but little from a circle. The sun is placed at one focus of the ellipse, and, as this is not in the centre of the orbit, the earth must be nearer the sun at some parts of its revo- lution than at others. When the earth is in that part of its orbit which is near- est to the sun, it is said to be at its perihelion; when in that part farthest from the sun, at its aphelion. The peri- helion distance is about 90,259,000 miles ; the aphelion dis- tance, 93,750,000 miles. The earth reaches its perihelion about January 1st. The earth does not move with the same rapidity through all parts of its orbit, but travels more rapidly in perihelion than in aphelion. Its mean velocity is about 19 miles a second, which is nearly sixty times faster than the speed of a cannon-ball. , 18 PHYSICAL GEOGRAPHY. 25. Laplace's Nebular Hypothesis.— The uniformity in the direction of rotation and revolution of the planets has led to a very plausible supposition as to the origin of the solar system, by the celebrated French astronomer La- place. This suppositioTi, known as Laplace's nebular hy- pothesis, assumes that, origiually, all the materials of which the solar system is composed were scattered throughout space in the form of very tenuous or nebulous matter. It being granted that this matter began to accumulate around a centre, and that a motion of rotation was thereby ac- quired, it can be shown, on strict mechanical principles, that a system resembling the solar system might be evolved. As the mass contracted on cooling, the rapidity of its rotation increased. The equatorial portions bulged out through the centrifugal force, until ring-like portions separated, and, collecting in spherical masses, formed the planets. The planets in a similar manner detached their satellites. At the time of the separation of Neptune the nebulous sun must have extended beyond the orbit of this planet. The temperature requisite for so great an expan- sion must have been enormous. Although a mere hypothesis, there are many facts which tend to sustain it, and it is now generally accepted. 26. The Plane of the Earth's Orhit is a per- fectly flat surface so placed as to touch the earth's orbit at every point. It may be regarded as an imaginary plane of enormous extent on which the earth moves in its journey around the sun. 27. Causes of the Change of Seasons. — The change of the earth's seasons is caused by the revolution of the earth, together with the fol- lowing circumstances: Fig. 14. Inclination of Axis to Orbit and Ecliptic. (1.) The inclination of the earth's axis to the plane of its orbit. The inclination is equal to 66° 33'. The ecliptic is the name given to a great circle whose plane coincides with the plane of the earth's orbit. Since the earth's axis is 90° distant from the equator, the plane of the ecliptic must be inclined to the plane of the equator 90° minus 66° 33', or 23° 27'. The mere revolution of the earth would be unable to produee a change of seasons, unless the earth's axis were inclined to the plane of its orbit. If, for example, the axis of the earth stood perpendicularly on the plane of its orbit, the sun's rays would so illumine the earth that the great circle of illumination would always be bounded by some meridian circle. The days and nights would then be of equal length, and the distribution of heat the same throughout the year. Under these circumstances there could b* no change of seasons, since the sun's rays would always fall perpendicularly on the same part of the earth : on the equator. (2.) The Constant Parallelism of the Earth's Axis. — During the revolution of the earth, its axis always points to nearly the same place in the heavens: nearly to the north star. It is therefore always parallel to any former position. Unless the earth's axis were constantly parallel to any former position, the present change of seasons would not exist. On account of the spherical form of the earth, only a small part of its surface can receive the vertical rays of the sun at the same time. This part can be regarded as nearly a point ; and since only one-half of the earth is lighted at any one time, the great circle of illumination must extend 90° in all directions from the point which receives the vertical rays. By rotation all portions of the surface situated anywhere within the tropics in the same latitude, at some time or another during the day, are turned so as to receive the vertical rays of the sun, and consequently, the portion so illumined has the form of a ring or zone. Other things being equal, this zone con- tains th^ hottest portions of the surface, the heat gradually diminishing as we pass toward either pole. On account of the inclination of its axis, the earth receives the vertical rays of the sun on new portions of its surface every day during its revo- lution ; and it is because different portions of the surface are constantly being turned toward the sun that the change of seasons is to be attributed. As the earth changes its position in its orbit, the sun's rays fall vertically on different parts of the surface, so that during the year one part or an- other of the surface within 23° 27' on either side of the equator receives the vertical rays. The astronomical year begins on the 20th of March, and we shall therefore first consider the position of the earth in its orbit at that time. An inspection of Fig. 15 will show that at this time the earth is so turned toward the sun that the vertical rays fall exactly on the equator. The great circle of illumination, therefore, reaches to the poles, and the days and nights are of an equal length all over the earth. This time is called the March equinox. Spring then begins in the North- ern Hemisphere, and autumn in the Southern. This is shown more clearly in Fig. 16, which represents the relative positions of the illumined and non-illumined portions at that time. MATHEMATICAL GEOGRAPHY. 19 SEPTEMB ER- o EQUINOX DECEMBER, SOLSTICE? JUNE \SOLSTICE\ "MARCH EQUINOX April. Fig. 15. The Orbit of the Earth, showing the Change of Seasons, As the earth proceeds in its orbit, the inclina- tion of the axis causes it to turn the Northern Hemisphere more and more toward the sun. The vertical rays, therefore, fall on portions farther and farther north until, on the 21st of June, the Fig. 16. The Earth at an Equinox. vertical rays reach their farthest northern limit, and fall directly on the Tropic of Cancer, 23° 27' N., when the sun is said to be at its summer sol- stice. * Since the portions receiving the vertical rays of the sun are now on the Tropic of Cancer, the light and heat must extend in the Northern Hemisphere to 23° 27' beyond the north pole, or to the Arctic Circle ; while in the Southern Hemi- sphere they must fall short of the south pole by the same number of degrees, or reach to the Ant- Fig. 17. The Earth at the Summer Solstice. arctic Circle. The Northern Hemisphere then be- gins its summer, and the Southern its winter. The relative positions of the illumined and non-illumined portions of the earth at the sum- mer solstice are more clearly shown in Fig. 17. Here, as is shown, the great circle of illumination 20 PHYSICAL GEOGRAPHY. extends in the Northern Hemisphere as far over the pole as the Arctic Circle. After the 21st of June the Northern Hemi- sphere is turned less toward the sun, and the vertical rays continually approach the equator, all the movements of the preceding season being reversed, until on the 22d of September, the time of the September equinox, the equator again receives the vertical rays, the great circle of illumination again coinciding with the meridian circles. The earth has now moved from one equinox to an- other, and has traversed one-half of its orbit. The Southern Hemisphere then begins its spring, the Northern its autumn. ' From the 22d of September until the 20th of March, while the earth moves through the other half of its orbit, the same phenomena occur in the Southern Hemisphere that have already been noticed in the Northern. Immediately after the 22d of September the inclination of the axis causes the earth to be so turned toward the sun that its rays begin to fall south of the equator ; and, as the earth proceeds in its orbit, the South- ern Hemisphere is turned more and more toward the sun, and the vertical rays fall farther and farther toward the pole. This continues until the 21st of December, when the rays fall vertically on the Tropic of Capricorn, and the December sol- stice is reached. The great circle of illumination now extends beyond the south pole as far as the Antarctic Circle, but falls short of the north pole 23° 27', reaching only the Arctic Circle. Sum- mer then commences in the Southern Hemisphere, and winter in the Northern. After the 21st of December the Southern Hemisphere is turned less and less toward the Fig. 18. S. rFUGUJje*"^ Mathematical Climatic Zones. sun, and the part receiving the vertical rays approaches the equator, until on the 20th of March the equator again receives the vertical rays, and, with the March equinox, spring com- mences in the Northern Hemisphere, and with it a new astronomical year. 28. Mathematical Zones. — The Torrid Zone. — That belt of the earth's surface which lies be- tween the tropics is called the Torrid Zone. During one time or another throughout the year every part of its surface receives the ver- tical rays of the sun. The Temperate Zones are included between the tropics and the polar circles. The northern zone is called the North Temperate Zone, and the south- ern zone, the South Temperate Zone. The Polar Zones are included between the polar circles and the poles. The northern zone is called the North Frigid Zone, and the southern zone, the South Frigid Zone. These zones, which are separated by the parallels of lati- tude, are generally termed the astronomical or mathematical zones to distinguish them from others called physical zones, which are bounded by the lines of mean annual temper- ature. It will be noticed that the distance of the tropics from the equator and of the polar circles from the poles is 23° 27', or the value of the inclination of the plane of the ecliptic to the plane of the equator. 29. Length of Day and Night. — Whenever more than half of either the Northern or South- ern Hemisphere is illumined, the great circle of illumination will divide the parallels unequally, and the length of the daylight in that hemisphere will exceed that of the night in proportion as the length of the illumined part, measured along any of the parallels, exceeds that of the dark part. The length of daylight or darkness may exceed that of one complete rotation of the earth. The great circle of illumination may at times pass over the poles as far beyond them as 23° 27'; and places situated within this limit may remain during many rotations exposed to the rays of the sun. A little consideration will show that the longest day must occur at the poles, since the poles must continue to receive the sun's rays from the time they are first illu- mined at one equinox until the sun passes through a sol- stice and returns to the other equinox. Nowhere, outside the polar circles, will the length of daylight exceed one entire rotation of the earth. The length of the longest day at the equator, latitude 0°, is 12 hours. Of the longest day at latitude 66° 33' is 24 hours. Of the longest day at latitude 67° 20' is one month. Of the longest day at latitude 73° 6' is three months. Of the longest day at the poles, latitude 90°, is six months. MATHEMATICAL GEOGRAPHY. 21 SYLLABUS. There are three kinds of geography — Mathematical, Po- litical, and Physical. Physical Geography treats of Land, Water, Air, Plants, and Animals. Geography deals mainly with the earth as it is ; geology mainly with the earth as it was. The earth continues its motion around the sun in conse- quence of its inertia. The distant stars are balls of fire like our sun, and prob- ably have worlds resembling ours revolving around them. The sun and the bodies that revolve around it consti- tute the solar system. The sun is about 1,300,000 times larger than the earth. The sun is a body heated to luminosity, and gives out or emits light and heat like any other highly-heated body. The shape of the earth is that of an oblate spheroid whose equatorial diameter is about 26 miles longer than its polar. That the earth is round and not flat is proved — 1st, by the appearance of approaching or receding ob- jects ; 2d, by the circular shape of the horizon ; 3d, by the circular shape of the earth's shadow ; 4th, by actual meas- urement; and 5th, by the shape of the great circle of illumination. The earth's diameter is nearly 8000 miles, its circumfer- ence not quite 25,000 miles, and its area about 197,000,000 square miles. The imaginary circles used in geography are the Equa- tor, the Meridian Circles, and the Parallels. Latitude is measured on the meridians by the parallels. The greatest number of degrees of latitude a place can have is 90° ; the greatest of longitude, 180°. The latitude at the equator is 0° N. or S. The. longitude at the poles or on the prime meridian is 0° E. or W. Longitude is measured on the equator, or on the parallels, by the meridians. Maps are drawn on different projections : the Equatorial, the Polar, and Mercator's projections are in most general use. A Mercator's projection causes places near the poles to appear larger than they really are. On all maps due north and south lies along the merid- ians; due east and west, along the parallels: when these are curved lines, the top and bottom of the map will not always represent north and south, nor the right and left hand east and west. The inclination of the earth's axis to the plane of its orbit, and the constant parallelism of the axis with any former position, together with the revolution around the sun, cause the change of seasons. The astronomical year begins March 20th. On the 20th of March and on the 22d of September the days and nights are of equal length all over the earth. From the 20th of March the days increase in length in the Northern Hemisphere until the 21st of June, when they attain their greatest length ; they then decrease until the 22d of September, when they again become equal. The Torrid Zone is the hottest part of the earth, because, during one time or another throughout the year, every part of its surface receives the vertical rays of the sun. REVIEW QUESTIONS. «>XKc The Solar System. How does the principle of inertia apply to the earth's motion around the sun? What do you understand by the solar system? Describe the earth's position in the solar system. Which of the planets are between the earth and the sun ? Which are beyond the orbit of the earth ? How does the size of the sun compare with that of the earth ? Are any of the distant stars larger than our sun ? What is a satellite ? Which of the planets have satellites ? Explain the cause of the circular shape of the earth's orbit. In what part of space is the solar system ? Has our sun any motion through space? Enumerate the proofs of the rotundity of the earth. State accurately the length of the equatorial diameter of the earth ; of its polar diameter ; of its circumference. What is its area ? How many times heavier is the earth than an equally large globe of water? Imaginary Circles. Define great and small circles. Name the circles most commonly used in geography. What do you understand by latitude ? How is latitude reckoned ? Of what use is latitude in geography ? Why can the value of the latitude never exceed 90° ? Of what use are meridians and parallels in measuring latitude? What do you understand by longitude ? How is longi- tude reckoned ? Of what use is longitude in geography ? Why can its value never exceed 180° ? Of what use are meridians and parallels in measuring longitude? Where is the value of a degree of latitude the greatest ? Of a degree of longitude ? Why? What effect has a Mercator's chart on the appearance of bodies of land or water in high northern or southern lati- tude? / What is an equatorial projection? A polar projection? A conical projection? What is the position of the poles in an equatorial projection ? In a polar projection ? Movements of the Karth. Prove that the earth turns on its axis from west to east. Explain the cause of the change of day and night. Define a sidereal year ; a tropical year. Which value is generally taken for the length of the civil year ? Describe Laplace's nebular hypothesis. Enumerate the causes which produce the change of seasons. On what days of the year will the sun's rays fall verti- cally on the equator ? On what days will its rays fall ver- tically on the Tropic of Cancer? On the Tropic of Capri- corn? Part II. THE LAND. -«o>©^c Although water occupies much the larger portion of the earth's surface, yet, when compared with the entire volume of the globe, its quantity is comparatively insignificant ; for the mean depth of the ocean probably does not exceed two and one-third miles, and underneath this lies the solid crust, with its heated interior. The crust and heated interior are composed of a variety of simple and compound substances. Simple or elementary substances are those which have never been separated into components. Compound substances are those which are composed of two or more simple or elementary substances combined under the influence of the chemical force. -~-z-3-jz5ZT^>f~$ : ^-Suz — Section I. THE INSIDE OF THE EARTH. °XXc CHAPTER I. The Heated Interior. 30. The Proofs of the Earth's Original Fluidity or fused condition through heat are — (1.) Its Spherical Shape, which is the shape the earth would have taken had it been placed in space when in a melted condition. This is the shape of nearly all the heavenly bodies. 22 (2.) The fact that the rocks which were first formed give evidence by their appearance of having been greatly heated. These rocks are generally highly crystalline. (3.) The general climate of the earth during the geological past was much warmer than at present. Very little of the internal heat now reaches the surface. According to Poisson, all that escapes would raise the mean annual temperature only ^th of a degree Fahr. VOLCANOES. 23 31. Laplace's Nebular Hypothesis agrees very well with the idea of a former igneous fluidity, since, at the time of its separation from the nebulous sun, the earth must have had a temperature sufficient not only to fuse, but even to volatilize, most of its constituents. 32. Proofs of a Present Heated Interior. — The following considerations show that the inside of the earth is still highly heated: (1.) The deeper we penetrate the crust, the higher the temperature becomes. Moreover, the rate of increase, though varying in different lo- calities with the character of the materials of the crust, is nearly uniform over all parts of the sur- face, the average value of the increase being 1° Fahr. for every 55 feet of descent. This would seem to indicate that the entire inside of the earth is heated, and that the heat increases as we go toward the centre. We cannot, however, estimate the thickness of the crust from this fact — 1. Because we have never penetrated the crust more than a few thousand feet below the level of the sea, and therefore we do not know that this rate of increase of temperature continues the same: 2. Even if it did continue uniform, since the melting- point of solids increases with the pressure, we do not know what allowance should be made for this increase. (2.) In all latitudes prodigious quantities of melted rock escape from the interior through the craters of volcanoes. The interior, there- fore, must be hot enough to melt rock. 33. Condition of the Interior. — We do not know the condition of the material which fills the interior of the earth. It might be supposed, since rock escapes from the craters of volca- noes in a fluid or molten condition, that the in- terior is filled with molten matter ; but this is not necessarily so, since the enormous pressure to which the interior is subjected would prob- ably be sufficient to compress it into a viscous or pasty mass, or, possibly, even to render it solid. The lava which issues from the crater of a vol- cano is necessarily more mobile than the interior of the earth ; for, coming, as it does, from great depths, it must grow more and more liquid as it approaches the surface and is thus relieved of its pressure. Indeed, the most viscous rock conceiv- able, if highly heated when ejected from pro- found depths, would become comparatively fluid on reaching the surface. 34. Views Concerning the Condition of the Interior. — Considerable difference of opinion ex- ists as to the exact condition of the interior of the earth. The following opinions may be men- tioned : (1.) That the earth has a solid centre and crust, with a heated or pasty layer between. (2.) That the crust is solid, but the interior highly heated, so as to be in a fused or pasty condition. (3.) That the earth is solid throughout, but highly heated in the interior. Of the above views, the second is perhaps the most tenable, and will be adopted as serving in the simplest manner to explain the phenomena of the earth arising from the presence of a highly heated interior. Admitting the crust to be suf- ficiently thin, and in such a condition as to per- mit of but a small degree of warping, then all the phenomena can be satisfactorily explained. 35. Thickness of the Crust. — We cannot as- sign a definite limit to the thickness of the crust, since the portions that are solid from having cooled, most probably pass insensibly into those that are nearly solid from the combined influence of loss of heat and increasing pressure. It seems probable that the portion solidified by cooling is thin, when compared with the whole bulk of the earth ; in other words, the heated interior lies comparatively near the surface. 36. Effects of the Heated Interior. — As the crust loses its heat it shrinks or contracts, and, growing smaller, the materials of the interior are crowded into a smaller space, and an enormous force is thus exerted, both on the interior and on the crust itself, tending either to change the shape of the crust, to break it, or to force out some of the interior. The following phenomena are there- fore caused by the contraction of the crust : (1.) Volcanoes; (2.) Earthquakes; (3.) Non-volcanic igneous eruptions ; (4.) Gradual elevations or subsidences of the crust. CHAPTER II. Volcanoes. 37. Volcanoes. — One of the most striking proofs of the existence of a heated interior is the ejection of enormous quantities of melted rock through openings in the crust. A volcano is a mountain, or other elevation, through which the materials of the interior escape to the surface. The opening is called the crater, and may be either on the top or on the sides of the mountain. 24 PHYSICAL GEOGRAPHY. Fig. 19. An Eruption of Mount Vesuvius. 33. Peculiarities of Craters. — The crater, as its name indicates, is cup-shaped. The rim, though generally entire, is sometimes broken by the force of the eruption, as in Mount Vesuvius, where the eruption in 79 A. D. — the first on record — blew off the northern half of the crater. The material thus detached, together with the showers of ashes and streams of lava, completely buried the cities of Her- culaneum and Pompeii, situated near its base. The crater is often of immense size. Mauna Loa, on the island of Hawaii, has two craters — one on the summit, and the other on the mountain-side, about 4000 feet above the sea. The latter — Kilauea — is elliptical in shape, and about 7i miles in circumference ; its area is nearly 4 square miles, and its depth, from 600 to 1000 feet. Volcanic mountains are of somewhat different shapes, but near the crater the conical form pre- dominates, and serves to distinguish these moun- tains as a class. The shape of the volcanic cone is caused by the ejected materials accumulating around the mouth of the crater in more or less concentric layers. 39. The ejected materials are mainly as fol- lows : (1.) Melted Bock, or Lava. — Lava varies, not only with the nature of the materials from which it was formed, but also with the conditions under which it has cooled, and the quantity of air or vapor entangled in it. Though generally of a dark gray, it occurs of all colors ; and its texture varies from hard, compact rock to porous, spongy material that will float on water. When just emitted from the crater, ordinary lava flows about as fast as molten iron would on the same slope. On steep mountains, near the crater, the lava, when very hot, may flow faster than a horse can gallop ; but it soon cools, and becomes covered with a crust that greatly re- tards the rapidity of its flow, until its motion can only be determined by repeated observations. At Kilauea, jets of very liquid lava are sometimes thrown out, which, falling back into the crater, are drawn out by the wind into fine threads, thus producing what the natives call Pele's hair, after their mythical goddess. The volume of the ejected lava is often very great. Vol- canic islands are generally formed entirely by lava streams. Hawaii and Iceland were probably formed entirely of lava emitted from uumerous volcanic cones. (2.) Ashes or Cinders. — These consist of minute fragments of lava that are ejected violently from the crater ; at night they appear as showers of brilliant sparks. When they fall directly back on the mountain, they aid in rearing the cone. More frequently, they are carried by the wind to points far distant. The destructive effects of volcanic eruptions are caused mainly by heavy showers of ashes. The ashes, when exceedingly fine, form what is called volcanic dust At the beginning of an eruption large frag- ments of rock are sometimes violently thrown out of the crater. (3.) Vapors, or Gases. — The vapor of water often escapes in great quantities from the crater, especially at the beginning of the eruption. On cooling, it condenses and forms dense clouds, from which torrents of rain fall. These clouds, lighted by the glowing fires beneath, appear to be actually burning, and thus give rise to the erroneous belief that a volcano is a burning mountain. To the condensation of this vapor is probably to be as- cribed the lightning which often plays around the summit of the volcano during an eruption. Be- sides the vapor of water, various gases escape, of which sulphurous acid is the most common. When a large quantity of rain mingles with the ashes, torrents of mud are formed, which move with frightful velocity down the slopes of the mountain, occasioning con- siderable damage. During the eruption of Galungung, in Java, more than one hundred villages were thus destroyed. The rock that is formed by the hardening of volcanic mud is called tufa. 40. The Inclination of the Slopes of the vol- canic cones depends on the nature of the material of which they are formed. Where lava is the main ingredient, the cone is broad and flat. The inclination of a lava cone ranges from 3° to 10°, Fig. 20. Lava Cone. Inclination from 3° to 10°. according to the liquidity of the lava. A very stiff lava will form a much steeper cone. VOLCANOES. 25 Ashes and cinders form steeper cones, whose inclinations range from 30° to 45°. Fig, 21. Ash Cone. Inclination from 30° to 45°. The sides of volcanic cones are often rent dur- ing the eruption, and the fissures filled with lava, which hardens and forms rocky ribs called dykes. Sometimes the central cone becomes choked, and secondary or parasitic cones are formed. Fig. 22. Volcanic Dykes and Parasitic Cones. 41. The Cause of Volcanic Eruptions. — As the heated earth cools and the crust contracts, the ma- terials of the interior are crowded into a smaller space, and an enormous force is exerted, which causes portions of the interior to rise from profound depths and escape through openings in the crust. These openings form the craters of volcanoes. The principal agency, therefore, which brings up the heated material from great depths is the contraction of the crust on cooling. The melted rock thus brought into the volcano may escape — (1.) By the pressure of highly-heated gases or vapors, mainly that of water, which throws the lava explosively from the crater. (2.) By the pressure exerted by a column of liquid lava. Before the lava can run over the edge of the crater near the top of the mountain, the pressure caused by its weight becomes so great that the sides of the mountain are broken, and the lava escapes quietly from a lower opening. 42. Other Explanations of Volcanic Action.— The above theory of volcanic action is not accepted by all sci- entists. Instead of an originally heated globe that has not yet completely cooled, it is asserted by some that heat is now being produced either by some chemical means, such as oxidation or hydration, or by a mechanical crush- ing of deep-seated strata. These explanations assume that the seat of the lava is not the entire interior of the earth, but that it is purely local, existing in comparatively shal- low basins or reservoirs not far from the surface. The peculiarities of distribution of volcanoes would -appear to disprove the latter assumption. 43. Volcanic* Eruptions may be divided into two classes: explosive and non-explosive. Explosive eruptions are caused by the sudden formation of highly-heated vapors. In boiling water, drops are thrown from the surface by the bursting of bubbles of steam. This action is similar to that of explosive vol- canic eruptions. When the liquid is viscous, like tar, the escaping vapor accumulates in large bubbles, the bursting of which scatters the mate- rial in all directions. On account of the great viscidity of some lavas, the evolved gases accumulate until considerable force is ac- quired. At Kilauea, liquid jets are thrown upward to the height of 40 feet. With very viscid lavas, like those of Vesuvius, bubbles of enormous size are suddenly formed, which burst with almost incredible force. Cases are on record in which it is estimated the ashes were projected 10,000 feet above the mouth of the crater. Non-explosive eruptions are caused by the pressure of a column of liquid lava. In non-explosive eruptions the lava escapes quietly through a fissure which opens in the mountain's side by the pressure exerted by the column of liquid lava in the crater. Since a column of lava 500 feet high exerts a pressure of about 625 pounds to the square inch, when the moun- tain is high the pressure against the sides of the crater may be sufficient to rend the solid rock. Vesuvius is an example of an explosive eruption ; Kila- uea and Etna, of non-explosive eruptions. Volcanic mountains whose eruptions are non- explosive are generally high; the lava can thus accumulate in the crater until it forces its way through fissures below. Volcanic mountains whose eruptions are explosive are generally low. Volcanoes are of common occurrence at the bottom of the ocean. These are called submarine volcanoes. During eruptions their cones some- times project above the water; but they gene- rally soon afterward disappear. 44. Active and Extinct Volcanoes. — Volcanoes may be classified as active and extinct. Active Volcanoes are those which emit smoke, vapor, ashes, or lava from the crater. By an active volcano we do not mean one that is con- tinually in a state of eruption — ejecting ashes and lava — but one from which at least smoke or vapor is escaping. The crater may at any time become permanently choked, when the volcano becomes extinct. It may, however, open at any time, after extended intervals of rest, when the volcano again becomes active. Page 26. "W^ 3^ A* ■*"> &f $ ) -*X r«i V CQ: 3 % c a U < > 5 en | z | &H ~ ^J^ I 1 -* - s o $ Q[ fc> < L, , I ^ % )S rt VOLCANOES. 27 45. The number of volcanoes is not accurately known. The best authorities estimate it at about 672, of which 270 are active. Of the latter, 175 are on islands, and 95 are on the coasts of the con- tinents. 46. Regions of Volcanoes. — The principal vol- canic regions of the earth are — * (1.) Along the Shores of the Pacific, where an immense chain of volcanoes, with but few breaks, encircles it in a huge "Sea of Fire." On the Eastern Borders, in the Andean range, are the volcanic series of Chili, Bolivia, and Ecua- dor ; those of Central America and Mexico ; in the United States are the series of the Sierra Nevada and Cascade ranges and of Alaska ; and finally, connecting the system with Asia, the vol- canic group of the Aleutian Islands. On the Western Borders volcanoes occur in the following districts : the Kamtchatkan Peninsula, with its submerged ranges of the Kurile Islands ; the Japan, the Loo Choo, and the Philippine Islands ; the Moluccas ; the Australasian Island Chain, terminating in New Zealand ; and finally, nearly in a line with these, the volcanoes of Ere- bus and Terror on the Antarctic continent. (2.) In the Islands of the Pacific. — Volcanic activity is not wanting over the bed of the Pa- cific. The Sandwich Islands, the Society Group, the Marquesas, Friendly Islands, New Hebrides, Ladrones, and many others, are volcanic. (3.) Scattered over the Seas that divide the Northern and Southern Continents, or in their vicinity, viz. : in the neighborhood of the Carib- bean Sea, in the Mediterranean and Red Seas, and in the Pacific and Indian Oceans between Asia and Australia. In the neighborhood of the Caribbean Sea. — This region includes the two groups of the Antilles in the Caribbean Sea, and the Gallapagos Islands in the Pacific Ocean. In the neighborhood of the Mediterranean and Bed Seas. — This region includes the volcanoes of the Mediterranean and its borders, those of Italy, Sicily, the Grecian Archipelago, of Spain, Central France, and Germany, together with those near the Caspian and Red Seas. Between Asia and Australia. — This region in- cludes the Sunda Islands, Sumatra, Java, Sum- bawa, Flores, and Timor, which contain numerous craters. In Java there are nearly 50 volcanoes, 28 of which are active, and there are nearly as * We follow mainly the classification of Dana. 4 many in Sumatra., There are 109 volcanoes in the small islands near Borneo. (4.) In the Northern and Central Parts of the Atlantic Ocean. All the islands in the deep ocean which do not form a part of the continent are volcanic ; as, for example, the island of St. Helena, Ascension Island, the Cape Verdes, the Canaries, the Azores, and Iceland. The Cameroons Mountains, on the African coast near the Gulf of Guinea, together with some of the islands in the gulf, are volcanic. (5.) In the Western and Central Parts of the Indian Ocean. Volcanoes are found in Madagascar and in the adjacent islands. They also occur farther south, in the island of St. Paul and in Kerguelen Land, and in Kilimandjaro, near the eastern coast of Africa. 47. Submarine Volcanoes. — From the difficulty in ob- serving them, submarine volcanoes are not so well known as the others. The following regions are well marked : In the Mediterranean Sea, near Sicily and Greece. Near the island of Santorin the submarine volcanic en- ergy is intense. It has been aptly described as a region "Where isles seem to spring up like fungi in a wood." In the Atlantic Ocean ; off the coast of Iceland ; near St. Michael, in the Azores ; and over a region in the nar- rowest part of the ocean between Guinea and Brazil. In the Pacific Ocean ; near the Aleutian Islands, where two large mountain-masses have risen from the water within recent time. Near the Japan Islands, where, about twenty -one centuries ago, according to native his- torians, Fusi Yama, the highest mountain in Japan, rose from the sea in a single night. In the Indian Ocean, the island of St. Paul, in the deep ocean between Africa and Australia, exhibits signs of submarine activity. 48. Peculiarities of Distribution. — Nearly all volcanoes are found near the shores of continents or on islands. The only exceptions are found in the region south of the Caspian Sea, and in that of the Thian Shan Mountains. As volcanoes are but openings in the earth's crust which permit an es- cape of materials from the pasty interior, they will occur only where the crust is weakest. This will be on the borders of sinking oceans, in the lines of fracture formed by the gradual separa- tion of the ocean's bed from the coasts of the continent. The floor of the ocean in all latitudes is covered with a layer of quite cold water, so that the difference in the amount of the contrac- tion will in general be most marked on the bor- ders of the oceans or on the edges of the conti- nents. In most regions the volcanoes lie along lines 28 PHYSICAL GEOGRAPHY. more or less straight. Lines joining such a series may be considered as huge cracks in the crust, the volcanic phenomena occurring in their weak- est places. The frequent occurrence of volcanoes in moun- tainous districts is caused by the crust being broken and flexed, so as to admit of an easy passage for the molten rock. Where one system of fissures crosses another the crust becomes weak, the openings numerous, and the volcanic activity great. The two antipodal points of the Antilles and the Sunda Islands are excel- lent examples, and are the most active volcanic regions on the earth. Efforts have been made to show some connection be- tween certain states of the weather and periods of vol- canic activity ; but, so far, these have amounted to mere predictions of coming changes, based on observations of the direction of upper currents of air from the clouds of ashes or smoke ejected by the volcano. No law of periodicity of eruption has, as yet, been discovered. 49. Other Volcanic Phenomena : Mud Volcanoes are small hillocks that emit streams of hot mud and water from their craters, but never molten rock. They are found in vol- canic regions. Solfataras are places where sulphur vapors es- cape and form incrustations. They occur in vol- canic regions. Geysers are sometimes ranked with volcanic phe- nomena. They are described under Hot Spriugs. D^KC CHAPTER III. Earthquakes. 50. Earthquakes are shakings of the earth's crust, of degrees varying in intensity from scarcely perceptible tremors to violent agita- tions that overthrow buildings and open huge fissures in the ground. They may therefore be divided into two classes: (1.) A shaking movement without any perma- nent change in the surface ; (2.) A shaking movement accompanying an uplift or subsidence. An earthquake is sometimes called a seismic shock. ,51. Facts concerning Earthquakes. — A careful study of earthquakes appears to establish the fol- lowing facts : (1.) The place or origin of the shock is not deep-seated or far below the earth's surface, but Fig. 23, Fissures produced by the Charleston Earthquake of 1886. is near the surface, probably never deeper than thirty miles, and often much less. (2.) The area of disturbance depends not only on the energy of the shock, but also on the depth of its origin below the surface : the deeper the origin, the greater the area. (3.) The shape of the origin is generally that of a line, often many miles in length. (4.) The direction of the motion at the surface is nearly upward over the origin, and more in- clined as the distance from the origin increases. (5.) The shape of the area of disturbance de- pends on the nature of the materials through which the wave is moving. If these are of nearly uniform elasticity in all directions, the area is nearly circular; if more elastic in one direction than in another, the area is irregular in shape. 52. The Varieties of Earthquake Motion at the Earth's Surface are — (1.) A wave-like motion, in which the ground rises and falls like waves in water. (2.) An upward motion, somewhat similar to that which follows an explosion of powder below the surface. This has been known to occur with sufficient force to throw heavy bodies considerable distances up into the air. (3.) A rotary motion, which, from its destruc- tive effects, is fortunately of rare occurrence. Humboldt mentions an earthquake that happened in Chili where the ground was so shifted that three great EARTHQUAKES. 29 palm trees were twisted around one another like willow wands. There are two kinds of movement transmitted through the crust during earthquakes: these are the earthquake motion proper, and the motion that produces the accompanying sounds. 53. The Velocity of Earthquake Motion varies according to the intensity of the shock and the na- ture of the material through which it is trans- mitted. No average result can therefore be given. Various observers have estimated it at from 8 to 30 miles per minute. 54. The Sounds Accompanying Earthquakes vary both in kind and intensity. Sometimes they resemble the hissing noises heard when red- hot coals are thrown into water ; sometimes they are rumbling, but more frequently they are of greater intensity, and are then comparable to discharges of artillery or peals of thunder. The confused roaring and rattling are probably caused by the different rates of transmission of the sound through the air and rocks. 55. Duration of the Shocks. — When the area of disturbance is large, shocks of varying intensity generally follow each other at irregular intervals. Though, in general, the violence of the shock is soon passed, disturbances may occur at intervals of days, weeks, or even years. During the earthquake in Calabria in 1783, when nearly 100,000 persons perished, the destructive vibrations lasted scarcely two minutes, but the tremblings of the crust con- tinued long afterward. During the earthquake at Lisbon in 1755, when about the same number perished, the shock which caused the greatest damage continued but five or six seconds, while a series of terrible movements followed one another at intervals during the space of five minutes. 56. Cause of Earthquakes. — It is generally be- lieved that the principal cause of earthquakes is the force produced by the contraction of a cooling crust. During the cooling of the earth the crust con- tinually contracts, and the pressure so produced, slowly accumulating for years, at last rends it in vast fissures, thus producing those violent movements of its crust called earthquakes. If this theory be admitted — and it is a probable one — the earth's crust must every now and then be in such a strained condition that the slightest increase of force from within, or of diminished resistance from without, would disturb the con- ditions of equilibrium, and thus result in an earthquake. 57. Strain Caused by Contraction consequent on cooling is well exhibited in the so-called "Prince Ru- pert's Drops," which are made by allowing melted glass to fall in drops through cold water. The sudden cooling of the outside produces powerful forces, which tend to compress the drop; but, since these forces balance one another, no movement occurs until, by breaking off the long end of the drop, one set of forces is removed, when the others, no longer neutralized, tear the drop into almost countless pieces. Similar effects are produced by unequal contraction and expansion. Hot water poured into a tumbler will often crack it. The crackling sound of a stovepipe when sud- denly heated or cooled is a similar effect. 58. Other Causes of Earthquakes. — Earth- quakes may also be occasioned by — (1.) The sudden evolution of gases or vapors from the pasty interior. This is probably the cause of many of the slight shocks that occur in the neighborhood of active volcanic regions. (2.) Shocks caused by falling masses. Those who deny the existence of a pasty interior, en- deavor to explain the production of earthquakes by the shock caused by the occasional caving in of huge masses of rocks, in caverns hollowed out by the action of subter- ranean waters ; or by the gradual settling of the upturned strata in mountainous districts. There can be no doubt that even moderately severe shocks are caused by falling masses ; but such a force is utterly inadequate to produce a shock like that which destroyed Lisbon, when an area of nearly 7,500,000 square miles was shaken. 59. Periodicity of Earthquakes. — It was for- merly believed that earthquakes occurred with- out any regularity, but by a comparison of the times of occurrence of a great number it has been discovered that they occur more frequently — (1.) In winter than in summer ; (2.) At night than during the day ; (3.) During the new and full moon, when the attractive force of the sun and moon acts simul- taneously on the same parts of the earth. Earthquake shocks are more frequent in winter, and during the night, because the cooling, and consequent contraction, occur more rapidly at these times, and therefore the gradually accumu- late g force is more apt to acquire sufficient inten- sity to rend the solid crust. Earthquakes are more frequent during new and full moon, because the increased force on the earth's crust caused by the position of the sun and moon at these times, is then added to the accumulated force produced by cooling. It has been asserted that in the equatorial regions earth- quakes are especially frequent during the setting in of periodical winds called the monsoons, at the change of the rainy season or during the prevalence of hurricanes. These facts, however, are not well established. 60. Distribution of Earthquakes. — Earth- quakes may occur in any part of the world, but 30 PHYSICAL GEOGKAPHY. are most frequent in volcanic districts. They are more frequent in mountainous than in flat coun- tries. They are especially frequent in the high- est mountains. According to Huxley, fairly pro- nounced earthquake shocks occur in some part of the earth at least three times a week. There is, in many instances, an undoubted connection between volcanic eruptions and earthquakes. Humboldt relates that during the earthquake at Kiobarnba, when some 40,000 persons perished, the volcano of Pasto ceased to emit its vapor at the exact time the earthquake began. The same is related of Vesuvius at the time of the earth- quake at Lisbon. 61. Phenomena of Earthquakes. — In order to give some idea of the phenomena by which severe earthquake shocks are attended, we append a brief description of the earthquake which destroyed the city of Lisbon, on the 1st of November, 1755. The loss of life on this occasion was the more severe, since the shock occurred on a holy day, when nearly the whole population was assembled in the churches. A sound like thunder was heard, and, almost immediately afterward, a series of violent shocks threw down nearly every building in the city. Many who es- caped the falling buildings perished in the fires that soon kindled, or were murdered by lawless bands that after- ward pillaged the city. The ground rose and fell like the waves of the sea ; huge chasms were opened, into which many of the buildings were precipitated. In the ocean a huge wave, over 50 feet high, was formed, which, retreating for a moment, left the bar dry, and then rushed toward the land with frightful force. This was repeated several times, and thousands perished from this cause alone. The neighboring moun- tains, though quite large, were shaken like reeds, and were rent and split in a wonderful manner. This earthquake was especially remarkable for the im- mense area over which the shock extended. It reached as far north as Sweden. Solid mountain-ranges — as, for example, the Pyrenees and the Alps — were severely shaken. A deep fissure was opened in France. On the south, the earthquake waves crossed the Mediterranean and destroyed a number of villages in the Barbary States. On the west, the waves traversed the bed of the Atlantic, and caused unusually high tides in the West Indies. In North Amer- ica the movements were felt as far west as the Great Lakes. Feebler oscillations of the ground occurred at intervals for several weeks after the main shock. 62. Non-volcanic Igneous Eruptions. — In re- gions remote from volcanoes, melted rock has been forced up from the interior through fissures in the rocks of nearly all geological formations. On cooling, the mass forms what is called a dyke. Dykes vary in width from a few inches to several yards. They are generally much harder than the rocks through which they were forced, and, being less subject to erosion, often project considerably above the general surface. From their mode of formation, dykes are gen- erally without traces of stratification, but by cool- ing a series of transverse fractures are sometimes produced. The dykes thus obtain the appearance of a series of columns, called basaltic columns. Igneous rocks of this description are found in all parts of the continents, but are especially com- mon near the borders of mountainous districts. Fingal's Cave, in Scotland, is a noted example of basaltic columns. Fig. 24. Basaltic Columns, Fingal's Cave, Scotland, 63. Gradual Elevations and Subsidences. — Be- sides the sudden changes of level produced by earthquakes, there are others that take place slowly, but continuously, by which large portions of the surface are raised or lowered from their former positions. The rate of movement is very slow — probably never exceeding a few feet in a century. The following examples are the most noted : The Scandinavian peninsula (Norway and Swe- den) is slowly rising in the north and sinking in the soidh. The southern part of the coast of Greenland is sinking. The North American coast, from Labrador to New Jersey, is rising. The Andes Mountains, especially near Chili, are gradually rising. The Pacific Ocean, near the centre, is sinking over an area of more than 6000 miles. The cause of these movements is to be traced to the warping action caused by gradual contrac- tion of a cooling crust. SYLLABUS. 31 SYLLABUS. dXKc The earth was originally melted throughout. It after- ward cooled on the surface and formed a crust. The earth's original fluidity is rendered probable — (1.) By the spherical shape of the earth ; (2.) By the crystalline rocks underlying all others; and (3.) By the greater heat of the earth during geological time. The interior is still in a highly-heated condition. This is proved — 1st. By the increased heat of the crust as we go below the surface ; 2d. By the escape of lava from volca- noes in all latitudes. The following opinions are held concerning the condi- tion of the interior of the earth : (1.) That the earth has a solid centre and crust, with a heated layer between. (2.) That the earth has a solid crust only, and an inte- rior sufficiently heated to be in a fused or in a pasty con- dition. (3.) That the earth is solid throughout, but highly heated in the interior. The thickness of the crust is not known. It is probable that the portions solidified by cooling pass insensibly into those that are nearly solid from the combined influence of loss of heat and increasing pressure. The heated interior, however, must lie comparatively near the sur- face. The effects produced by the heated interior on the crust are — 1st. Volcanoes; 2d. Earthquakes; 3d. Non-volcanic igneous eruptions; and 4th. Gradual elevations or subsi- dences. Volcanic mountains are of a variety of shapes. Near their craters the cone shape predominates, and serves to distinguish these mountains as a class. The ejected materials of volcanoes are — 1st. Melted rock or lava; 2d. Ashes or cinders; 3d. Vapors or gases. These materials are brought up from great depths into the volcanic mountain by the force produced by a contract- ing globe. They may escape from the crater — 1st. By the pressure of highly-heated vapors; or, 2d. By the pressure of a column of melted lava. The inclination of the slopes of the volcanic cone de- pends on the materials of which it is composed. Ash- cones are steeper than those formed of lava. Eruptions are of two kinds, explosive and non-explo- sive. High volcanic mountains are, as a rule, characterized by non-explosive eruptions. Volcanoes occur both on the surface of the land and on the bed of the ocean. Those on the land occur mainly near the borders of sinking oceans, where the crust is weakest. The principal volcanic districts of the world are — 1. Along the shores of the Pacific; 2. On the islands which are scattered over the Pacific; 3. Scattered over the seas which divide the northern and southern continents; 4. In the northern and central parts of the Atlantic Ocean ; 5. In the western and central parts of the Indian Ocean. The centres of volcanic activity are found in the An- tilles and in the Sunda Islands, where several lines of fracture cross each other. Subordinate volcanic phenomena are seen in — 1. Mud volcanoes; 2. Solfataras; 3. Geysers. Earthquakes are shakings of the earth's crust ; they may occur with or without a permanent displacement. The following facts have been discovered as to earth- quakes : (1.) Their place of origin is not very deep-seated. (2.) The area of disturbance increases with the energy of the shock and the depth of the origin. (3.) The shape of the origin is that of a line, and not that of a point. (4.) The shape of the area of disturbance depends on the elasticity of the materials through which the shock moves. (5.) The earthquake motion travels through the earth as spherical waves which move outward in all directions from the origin of the disturbance. The movement at the earth's surface may be — 1st. In the form of a gentle wave ; 2d. An upward motion ; 3d. A rotary motion. The velocity with which the earthquake motion is trans- mitted varies with the intensity of the shock and the nature of the materials through which it is propagated. There are two distinct kinds of motion accompanying earthquake waves : the earthquake motion proper, and the motion producing the accompanying sounds. As a rule, the earthquake shocks which produce the greatest damage are of but short duration, generally but a few seconds or minutes, slighter disturbances may fol- low the main shock at i-iteryals of days, weeks, or even years. Earthquake shocks are more frequent — 1st. In winter than in summer; 2d. At night than during the day ; 3d. During the time of new and full moon than at any other phase. Earthquakes are mainly caused by the gradually in- creasing force produced by the contraction of the crust. Earthquakes are also to be attributed to the forces which eject the molten matter from the craters of volcanoes. Slight earthquake shocks may be occasioned by the fall- ing in of masses of rock from the roofs of subterranean caverns, or by the settling of upturned strata. Earthquakes may occur in any part of the earth, but are most frequent in volcanic and in mountainous regions. Dy ves are masses of rock formed by the gradual cooling of melted matter which has been forced up through fis- sures from the interior. Basaltic columns are formed by dykes. They owe their columnar structure to fractures produced on cooling. The crust of the earth is subject to gradual as well as to sudden changes of level. The Scandinavian peninsula is rising on the north and sinking on the south. The southern coast of Geeenland is sinking. The North American coast, from Labrador to New Jer- sey, is rising. The range of the Andes near Chili is rising. The bed of the Pacific in the neighborhood of the Poly- nesian island chain is sinking. These movements are caused by the contraction of a cooling crust. 32 PHYSICAL GEOGRAPHY. REVIEW QUESTIONS. ►o^c The Heated Interior. Enumerate the proofs that the interior of the earth is still in a highly-heated condition. Name some circumstances which render it probable that the earth was originally melted throughout. What is the average rate of increase of temperature with descent below the surface ? How can it be shown that the whole interior of the earth is filled with highly-heated matter? Why is it so difficult to assign a definite limit to the thickness of the earth's crust? Is the interior of the earth supposed to be in as fluid a condition as that of the lava which escapes from a volcano ? What four classes of effects are produced in the crust by the heated interior ? Volcanoes. What are volcanoes ? What connection have they with the interior of the earth ? How do active volcanoes differ from those which are extinct ? Explain the origin of the conical form of volcanic mountains. Which generally produces the more destructive effects, ashes or lava? Why? Enumerate the materials which are ejected from the in- terior of the earth through the craters of volcanoes. What is tufa ? How is it formed ? Which has the greater inclination, a lava-cone or an ash-cone ? Explain in full the manner in which the shrinkage, or contraction of the earth on cooling, produces a pressure both in the interior and in the crust. By what forces are volcanic eruptions produced? Into what two classes may all volcanic eruptions be di- vided ? How are those of each class caused ? Give an example of each of these classes. What is the highest volcano in the world? Under what five regions may all the volcanoes in the world be arranged? In what parts of the world are volcanoes most numer- ous? Why are volcanoes more numerous here than elsewhere ? Name some of the regions of submarine volcanoes. Why are all volcanoes found near the coasts of the con- tinents or on islands ? What are mud volcanoes? Solfataras? Earthquakes. What are earthquakes ? Into what two classes may they be divided ? Name some facts that have been discovered about earth- quakes. Name three kinds of earthquake motion. Which is the most dangerous ? Describe the sounds which accompany earthquakes. What is the main cause of earthquakes ? To what other causes may they be attributed? What facts have been discovered respecting the period- icity of earthquakes? Give a short description of the earthquake which de- stroyed the city of Lisbon. Are any portions of the earth free from earthquake shocks ? In what parts of the earth are earthquake shocks most frequent ? What are dykes ? How were they formed ? Enumerate some of the gradual changes of level which are now occurring in the crust of the earth. By what are these changes caused ? MAP QUESTIONS. Trace on the map the five principal volcanic districts of the earth. Which contains the greater number of volcanoes, the Atlantic or the Pacific shores of the continents? Does the eastern or the western border of the Indian Ocean contain the greater number of volcanoes? Name the principal volcanic islands of the Atlantic. Of the Indian. Of the Pacific. Locate the following volcanoes : Hecla, Pico, Kilauea, Sarmiento, Llullayacu, Egmont, Cosiguina, Teneriffe, Antisana, Kilimandjaro, Demavend, Peshan, Osorno, Ere- bus, and Terror. Name the principal volcanic mountains of North America. In what part of the Atlantic Ocean are submarine erup- tions especially frequent ? Name three noted volcanoes of the Mediterranean Sea. Name the portions of the earth which were shaken by the earthquake of Lisbon. When did this earthquake occur? What notec" volcanoes are found in the region visited by the earthquake of Lisbon ? In what portions of the Eastern Hemisphere are earth- quake shocks especially frequent? In what portions of the Western Hemisphere? " Section II. THE OUTSIDE OF THE EARTH. «>X* the diameter. The highest elevations of the earth are proportionally much smaller than the wrinkles on the skin of an orange. Fig, 39, Eelative Height of Mountains. If, as in Fig. 39, a sphere be drawn to represent the size of the earth, its radius will be equal to about 4000 miles. If, now, the line A B be drawn equal to the radius, it will represent a height of 4000 miles. One-half this height would be 2000 miles; one-half of this 1000, and successive halves 500 and 250 miles. An elevation of 250 miles would not therefore be very marked. Although the irregularities of the surface are comparatively insignificant, they powerfully affect the distribution of heat and moisture, and conse- quently that of animal and vegetable life. An elevation of about 350 feet reduces the tempera- ture of the air 1° Fahr. — an effect equal to a difference of about 70 miles of latitude. High mountains, therefore, though under the tropics, may support on their higher slopes a life similar to that of the temperate and the polar regions. 103. The Relief Forms of the Land are divided into two classes : Low Lands and High Lands. The boundary-line between them is taken at 1000 feet, which is the mean or average elevation of the land. Low Lands are divided into plains and hills. High Lands are divided into plateaus and mountains. If the surface is comparatively flat or level, it is called a plain when its elevation above the sea is less than 1000 feet, and a plateau when its ele- vation is 1000 feet or over. 6 If the surface is diversified, the elevations are called hills when less than 1000 feet high ; and mountains when 1000 feet or over. 104. Plains and Hills cover about one-half of the land surface of the earth. In the Eastern Continent they lie mainly in the north; in the Western, they occupy the central portions. Plains generally owe their comparatively level surface to the absence of wrinkles or folds in the crust, in which case the general level is preserved, but the surface rises and falls in long undulations : these may therefore be called undulating plains. The flat surface may also be due to the gradual settling of sedimentary matter. In this case the plains are exceedingly level. They are called marine when deposited at the bottom of a sea or ocean, and alluvial when deposited by the fresh water of a river or lake. Alluvial plains occur along the lower course of the river or near its mouth. Marine and alluvial plains, from their mode of forma- tion, are generally less elevated than undulating plains. 105. Plateaus are generally found associated with the mountain-ranges of the continents. Their connection with the adjacent plains is either ab- rupt, as where the plateau of Anahuac joins the low plains on the Mexican Gulf; or gradual, as where the plains of the Mississippi Valley join the plateaus east of the Rocky Mountains. 106. Mountains. — In a mountain-chain the crest or summit of the range separates into a num- ber of detached portions called peaks; below the peaks the entire range is united in a solid mass. The breaks in the ridge, when extensive, form mountain-passes. The influence of inaccessible mountains, like the Pyr- enees and Himalayas, in preventing the intermingling of nations living on their opposite sides, is well exemplified by history. In the past, mountains formed the boundaries of different races. Some mountains, like the Alps and the Appalachians, have numerous passes. A Mountain-System is a name given to several connected chains or ranges. Mountain-systems are often thousands of miles in length and hun- dreds of miles in breadth. The Axis of a Mountain-system is a line extend- ing in the general trend of its chains. Where several mountain-axes intersect one an- other, a complicated form occurs, called a Moun- tain-Knot. The Pamir Knot, formed by the intersection of the Karakorum, Belor, and Hindoo-Koosh Mountains, is an example. It lies on the southern border of the elevated plateau of Pamir. 44 PHYSICAL GEOGRAPHY. A Mountain-Pass, mountains and their Fig. 40 107. Orology treats of formation. The force which upheaved the crust into moun- tain-masses and plateaus had its origin in the contraction of a cooling globe. There are good reasons for believing that no extensive mountains existed during the earlier geological ages, since the crust was then very thin, and would have been fractured before sufficient force could accu- mulate to upheave it into mountain-masses. The great mountain-systems of the world are formed from sedimentary deposits that slowly ac- cumulated over extended areas until they acquired very great thickness. The deposits forming the Appalachians, according to Dana, were, in places, 40,000 feet in depth, and covered the eastern bor- der of the continent from New York to Alabama, varying from 100 to 200 miles in breadth. After the accumulation of these strata they were, through the contraction of the crust, sub- jected to the gradual effects of lateral pressure, by which they were sometimes merely flexed or folded, but more frequently crushed, fractured, or mashed together, and thus thickened and thrust upward. That side of the deposit from which the thrust came would have a steeper slope than the opposite side, which received a thrust arising from the resistance. This theory of mountain-formation, which is generally accepted, explains the following facts : (1.) All mountains have two slopes — a short steep slope, facing the ocean, and a long gentle slope, facing the interior of the continent. (2.) The strata on the short steep slope are generally highly metamorphosed; those on the long slope are in general only partially metamor- phosed, or wholly unchanged. (3.) The mountain-systems are situated on the borders of the continents where the sedimentary strata collected. (4.) Slaty cleavage, or the readiness with which so many of the rocks of mountains cleave or split in one direction, is a proof of these rocks having been subjected to intense, long-acting, lateral pres- sure, since such pressure can be made to develop slaty cleavage in plastic material. Isolated Mountains.— Nearly all high isolated moun- tains were formed by the ejection of igneous rocks from the interior ; that is, they are of volcanic origin and have been upheaved by a vertical strain or true projectile force, as in the volcanic range of Jorullo in Mexico. 108. Valleys in mountainous regions are either longitudinal or transverse. Longitudinal Valleys are those that extend in the direction of the length of the mountains. Transverse Valleys extend across the moun- tain. It is in transverse valleys that most passes occur. Although valleys, like mountains, owe their origin to the contraction of a cooling crust, yet their present shapes are modified by the operation of other forces. By the action of their water-courses, valleys are deepened in one place and filled up in another. Extensive land-slides often alter their configuration. During the Glacial Period many valleys were greatly changed by the action of huge mov- ing masses of ice. Fiord-valleys were formed in this manner. In level countries valleys generally owe their origin to the eroding power of water. 109. Peculiarities of Continental Reliefs. — The following peculiarities are noticeable in the relief forms of the continents : (1.) The continents have, in general, high bor- ders and a low interior. (2.) The highest border lies nearest the deep- est ocean; hence, the culminating point, or the highest point of land, lies out of the centre of the continent. (3.) The greatest prolongation of a continent is always that of its predominant mountain-sys- tem. (4.) The prevailing trends of the mountain- RELIEF FORMS OF THE CONTINENTS. 45 masses are the same as those of the coast lines, and are, in general, either north-east or north-west. In describing the relief forms of the continents we shall observe the following order : (1.) The Predominant System, or a system of elevations exceeding all others in height, and con- taining the culminating point of the continent. (2.) The Secondary System or Systems, inferior to the preceding in height. (3.) The Great Low Plains. Fig, 41. Orographic Chart of North America. (Light portions, mountains ; shaded portions, plains.) 1, Rocky Mountain System; 2, System of the Sierra Nevada and Cascade Ranges; 3, Sierra Madre; 4, Great Interior Plateau; 5, Wahsatch Mountains; 6, Appalachians; 7, Plateau of Labrador; 8, Height of Land; 9, Arctic Plateau; 10, Mackenzie River; 11, Nelson River; 12, St. Lawrence River; 13, Mississippi River. CHAPTER V. Relief Forms of the Continents. I. NORTH AMERICA 110. Surface Structure. — The Predominant Mountain-System lies in the west. The Secondary Systems lie in the east and north. The Great Low Plains lie in the centre. 111. The Pacific Mountain-System, the pre- dominant system, extends, in the direction of the greatest prolongation of the continent, from the Isthmus of Panama to the Arctic Ocean. It con- sists of an immense plateau, from 300 to 600 miles in breadth, crossed by two nearly parallel mountain-systems : the Rocky Mountains on the east and the system of the Sierra Nevada and Cascade ranges on the west. The eastern moun- tain-system is highest near the south ; the west- ern range is highest near the north. Between these lie numerous parallel ranges enclosing lon- gitudinal valleys, connected in places by trans- verse ranges forming basin-shaped valleys. The Rocky Mountain System. — The Rocky Mountains rise from the summits of a plateau whose elevation, in the widest part of the system, varies from 6000 to 7000 feet above the sea; therefore, although the highest peaks range from 11,000 to nearly 15,000 feet, their elevation above the general level of the plateau is comparatively inconsiderable. The plateau on the east rises by almost imperceptible slopes from the Mississippi River. The upper parts of the slopes, near the base of the mountains, form an elevated plateau called the " Plains," over which, at one time, roamed vast herds of buffalo or bison. This ani- mal is rapidly becoming extinct. Though the name " Eocky Mountains " is generally con- fined to those parts of the chain which extend through British America and the United States, yet, in connection with the Sierra Nevada Mountains, it is continued through Mexico by the Sierra Madre Mountains, and by smaller ranges to the Isthmus of Panama. 46 PHYSICAL GEOGRAPHY. Pig. 42. On the Plains. The Rocky Mountain System forms the great watershed of the continent, the eastern slopes draining mainly through the Mississippi into the Atlantic, and the western slopes draining through the Columbia and the Colorado into the Pacific. It slopes gradually upward from the Arctic Ocean toward the Mexican plateau, where it attains its greatest elevation in the volcanic peak of Popo- catepetl, 17,720 feet above the sea. The System of the Sierra Nevada and Cascade Mountains extends, in general, parallel to the Rocky Mountain System. It takes th( name of Sierra Nevada in California and Nevada, and of the Cascade Mountains in the remaining portions of the continent. It reaches its greatest eleva- tion in Mount St. Elias, in Alaska, 19,500 feet above the sea. This is the culminating point of the North American continent. In the broadest part of the plateau of the Pacific system, between the Wahsatch Mountains on the east, and the Sierra Nevada and Cascade ranges on the west, lies the plateau of the Great Basin. Its high mountain borders rob the winds of their moisture, and the rainfall, except on the mountain-slopes, is inconsiderable. The Great Basin has a true inland drainage. The heights of all mountains, except those much fre- quented, must generally be regarded as but good approxi- mations, since the methods employed for estimating heights require ■ great precautions to secure trustworthy results. Even the culminating points of all the continents have not, as yet, been accurately ascertained. 112. The Secondary Mountain-Systems of North America comprise the Appalachian system, the Plateau of Labrador, the Height of Land, and the Arctic Plateau. The last three have but an inconsiderable elevation. The Appalachian Mountain System consists of a number of nearly parallel chains extending from the St. Lawrence to Alabama and Georgia. It is high at the northern and southern ends, and slopes gradually toward the middle. The highest peaks at either end have an elevation of about 6000 feet. The Appalachian system is broken by two deep depres- sions, traversed by the Hudson and Mohawk Rivers. Be- tween the foot of the system and the ocean lies a low coast plain, whose width varies from 50 to 250 miles. 113. The Great Low Plain of North America lies between the Atlantic system on the east and the Pacific system on the west. It stretches from the Arctic Ocean to the Gulf of Mexico. Near the middle of the plain the inconsider- able elevation of the Height of Land divides it into two gentle slopes, which descend toward the Arctic Ocean and the Gulf of Mexico. A gen- tle swell extending from north-west to south-east divides the northern portion of the plain into two parts. The eastern and western basins, so formed, are connected by a break in the water- shed, through which the Nelson River empties into Hudson Bay. The southern part of the plain is traversed, in its lowest parts, by the Mississippi River. The tributaries of this river descend the long, gentle slopes of the Atlantic and Pacific systems. 114. The Relief Forms of a Continent are best understood by ideal sections, in which the base line represents the sea-level, and the scale of heights on the margin represents the elevation of the various parts. In all such sections the vertical dimensions of the land are necessarily greatly exaggerated. Fig. 43. Section of North America from East to West. 1, St. Elias; 2, Sierra Nevada; 3, Rocky Mountains; 4, Mississippi Valley ; 5, Appalachian System. 115. Approximate Dimensions of North America. Area of continent, 8,400,000 square miles. Greatest breadth from east to west, about 3100 miles. Greatest length from north to south, about 4500 miles. Coast line, 22,800 miles. Culminating point, Mount St. Elias, 19,500 feet. BELIEF FORMS OF THE CONTINENTS. 4? Fig, 44. Orographic Chart of South America. (Light portions, mountains ; shaded portions, plains.) 1, System of the Andes; 2, Plateau of Quito; 3, Plateau of Bolivia; 4, Aconcagua; 5, Plateau of Guiana; 6, Plateau of Brazil; 7, The Orinoco ; 8, The Amazon ; 9, The La Platte. II. SOUTH AMERICA. 116. Surface Structure. — The Predominant Mountain-System of South America is in the west. The Secondary Systems are in the east. The Great Low Plain lies between them. 117. The System of the Andes, which extends along the western border of the continent, is the predominant mountain-system. It is composed mainly of two approximately parallel chains separated by wide and comparatively level val- leys. On the north there are three chains, and on the south but one ; in the centre, mainly two. The chains are connected by transverse ridges, forming numerous mountain-knots. The Andes System forms a continuation of the Pacific Mountain-System. A wide depression at the Isthmus of Panama marks their separation. From this point the Andes increase in height toward the south, probably reaching their high- est point in Chili, where the volcanic peak of Aconcagua, 23,910 feet, is believed to be the cul- minating point of South America, and of the West- ern Continent. Nevada de So rata was formerly believed to be the cul- minating point of South America, but recent recalculations of the observations have resulted in a loss of nearly 4000 feet of the supposed height of Sorata. Some authorities still claim that several peaks in Bolivia reach an ele- vation of nearly 25,000 feet. The Andes Mountain-System terminates ab- ruptly in the precipitous elevations of Cape Horn. Numerous table-lands are included between the parallel ranges : the most important are— the plateau of Quito, 9543 feet; the plateau of Pasco, in North Peru, 11,000 feet; the plateau of Bolivia, from 12,000 to 14,000 feet. From most of these higher plateaus volcanic peaks arise. 118. The Secondary Mountain-Systems of South America are the plateaus of Brazil and Guiana. They both lie on the eastern border. The Plateau of Brazil is a table-land whose average height is about 2500 feet. Narrow chains or ridges separate the river-valleys. , The plateau of Brazil forms the watershed between the tributaries of the Amazon and the La Plata. Along the Atlantic a moderately continuous range descends in steep terraces to the ocean. The average altitude is more than double that of the western portion of the plateau. The highest peaks are somewhat over 8000 feet. The Plateau of Guiana, smaller than the Plateau of Brazil, but about equally elevated, forms the watershed between the Orinoco and the Amazon. Fig. 45. Amazon River Scenery. 119. The Great Low Plain of South America lies between the predominant and the secondary mountain-systems. It is mainly of alluvial origin, but slightly elevated, and is much more level than the great plain of North America. This plain is drained by the three principal river-sys- 48 PHYSICAL GEOGRAPHY. terns of the continent, by which it is divided into three parts : the Llanos of the Orinoco, the Selvas of the Amazon, and the Pampas of the La Platte. The Llanos are grassy plains which, during the rainy season, resemble our prairies, but during the dry weather are deserts. The Selvas, or forest plains, are covered by an uninter- rupted luxuriant forest. The vegetation here is so dense that in some places the broad rivers form the only ready means of crossing the country. Near the river-banks are vast stretches of swampy ground. The Pampas are grassy plains which in some respects resemble the Llanos. A coast plain lies between the Andes and the Pacific. It is widest near the Andes of Chili, Fig, 46. Section of South America from East to West, 1, Volcano Arequipa; 2, Lake Titicaca; 3, Nevada de Sorata; 4, Central Plain ; 5, Mountains of Brazil. where in some places it is 100 miles in breadth. Between the parallels of 27° and 23° the plain is an absolute desert, called the Desert of Ata- cama. Here rain never falls and vegetation is entirely absent. 120. Approximate Dimensions of South America. Area of continent, about 6,500,000 square miles. Greatest breadth from east to west, 3230 miles. Greatest length from north to south, 4800 miles. Coast line, 14,500 miles. Culminating point, Aconcagua, 23,910 feet. 121. Contrasts of the Americas. — In both North and South America the predominant system lies in the west, the secondary systems in the east, and the low plains in the centre. They differ in the following respects : In North America the predominant system is a broad plateau, having high mountain-ranges ; the principal secondary system is narrow, and formed of parallel ranges ; the low plains are character- ized by undulations, and contain several deep de- pressions occupied by extensive lake-systems. In South America the predominant system is nar- row; the secondary systems are broad ; the low plain is alluvial, extremely flat, contains no depressions, and consequently no extensive lake-systems. Fig, 47, Orographic Chart of Europe. (Light portions, mountains ; shaded portions, plains.) 1, The Alps; 2, Mont Blanc; 3, Pyrenees; 4, Cantabrian; 5, Sierra Estrella; 6, Sierra Nevada; 7, Mountains of Castile; 8, Apennines; 9, Dinaric Alps; 10, Balkan; 11, Pihdus; 12, Taurus; 13, Caucasus; 14, Cevennes; 15, Plateau of Auvergne; 16, Vosges; 17, Black Forest; 18, Jura; 19, Hartz; 20, Bohemian Plateau; 21, Carpathians; 22, Hungarian Forest; 23, Transylvanian Mountains; 24, Kiolen Mountains; 25, Urals. III. EUROPE. 122. Surface Structure. — The Predominant Mountain-System is in the south. The Secondary Systems are in the north and east. The Great Low Plain lies between the Pre- dominant and Secondary Systems. A line drawn from the Sea of Azov to the mouth of the Rhine Eiver divides Europe into two distinct physical regions. The great low plain lies on the north, and the predominant mountain-system on the south. The coun- try north of this line is sometimes called Low Europe, and that south of it, High Europe. 123. The Predominant Mountain-System of Eu- rope is composed of a highly complex series of mountain-systems extending along the northern shores of the Mediterranean in a curve, from the Straits of Gibraltar to the shores of Asia Minor. The system is highest in the centre, where the Alps form the culminating point of the continent. The average elevation of the Alps ranges from 10,000 to 12,000 feet. The highest peak, Mont Blanc, 15,787 feet, is the culminating point of the European continent. Matterhorn and Monte Rosa are but little inferior in height. On the south- west the system is continued to the Atlantic by the Cevennes and adjoining ranges in France, and the Pyrenees and Cantabrian in the northern part of the Spanish peninsula. The Pyrenees are an elevated range, with peaks over 11,000 feet high. On the east the system extends in two curves to the Black Sea by the Carpathian and Transylva- nian Mountains on the north, and the Dinaric Alps and the Balkan Mountains on the south. 124. Divisions of Predominant System. — The predominant mountain-system of Europe may be conveniently regarded as consisting of a central body or axis, the Alps, with six projections or limbs — three on the north, and three on the south. The three divisions on the north include — The Western Division, or the mountains of France, including the mountains lying west of the valleys of the Rhine and the Rhone ; The Central Division, or the mountains of Ger- many, situated between the Western Division and the upper valleys of the Oder and the Danube ; The Eastern Division, or the mountains of Austria-Hungary, situated between the Central Division and the Black Sea. These divisions contain a highly complicated system of minor elevations. Their complexity is due to the fre- quent intersection of the north-eastern and north-western trends. Basin-shaped plateaus, like the Bohemian and Transylvanian, are thus formed. The Western Division includes most of the mountains of France, as the Cevennes, the mountains of Auvergne, and the Vosges Mountains. * The Central Division includes the Jura Mountains in Switzerland, the Swiss and the Bavarian plateaus, the Black Forest Mountains, the Hartz Mountain;:.-, and the Bohemian plateau. The Eastern Division includes most of the mountains of Austria, as the Carpathians, the Hungarian Forest, and the Transylvanian Mountains. 125. The three projections on the south are the three mountainous peninsulas of Southern Eu- rope : The Iberian Peninsula, including Spain and Portugal ; The Italian Peninsula ; The Turco-Grecian Peninsula. The Iberian Peninsula. — The principal mountains are the Sierra Estrella, the mountains of Castile, and the Sierra Nevada. The Pyrenees separate the Peninsula from France. The Cantabrian Mountains extend along the northern coast. The Italian Peninsula contains the Apennines, ex- tending mainly in the direction of the north-western trend. The Turco-Grecian Peninsula.— The Dinaric Alps extend along the coast of the Adriatic ; the Balkan Moun- tains extend from east to west, through Turkey ; and the Pindus from north to south, through Turkey and Greece. 126. The Secondary Mountain-Systems of Eu- rope comprise the system of the Scandinavian peninsula, the Ural Mountains, and the Cauca- sus Mountains. The System of the Scandinavian Peninsula includes the elevations of Norway and Sweden. With the exception of the Kiolen Mountains in the north, the system does not embrace distinct mountain-ridges, but consists mainly of a series Fig. 48. Fiord on Norway Coast. of broad plateaus that descend abruptly on the west in numerous deeply-cut valleys called fiords, through which the sea penetrates nearly to the heart of the plateaus. Fiords are valleys that were deeply eroded by slowly moving masses of 50 PHYSICAL GEOGRAPHY. ice, called glaciers, and subsequently partially sub- merged. On the east the slopes are more gradual, and are occupied by numerous small lakes. The System of the Urals is composed of a moderately elevated range extending from the Arctic Ocean on the north to the plains of the Caspian on the south. The elevated island of Nova Zembla may be considered as forming a part of its northern prolongation. The Caucasus Mountains bear peaks exceeding in elevation those of the Alps. They belong, however, more properly to the elevations of Asia. 127. The Great Low Plain of Europe lies be- tween the predominant and secondary mountain- systems, and stretches north-eastwardly from the Atlantic to the Arctic. It is remarkably level, and is highest in the middle, where the Valdai Hills form the principal watershed of Europe. Westward the plain is continued under the North Sea to the British Isles, where a few inconsider- able elevations occur. South of the Alps the large plain of the Po River stretches across the northern part of Italy. 128. Approximate Dimensions of Europe. Area of continent, 3,700,000 square miles. Coast line, 19,500 miles. Greatest breadth from north to south, 2400 miles. Greatest length from north-east to south-west, 3370 miles. Culminating point, Mont Blanc, 15,787 feet. Fig. 49^ Orographic Chart of Asia^ (Light portions, mountains ; shaded portions, plains.) 1, Himalaya Mountains; 2, Karakorum; 3, Kuen-lun; 4, Belor; 5, Thian Shan; 6, Altai; 7, Great Kinghan; 8, Yablonoi; 9, Naullng; 10, Peling; 11, Vindhya; 12, Ghauts; 13, Hindoo-Koosh ; 14, Elburz; 15, Suliman; 16, Zagros; 17, Taurus; 18, Caucasus; 19, Asiatic Island Chain. IV. ASIA. 129. Surface Structure. — The Predominant Mountain-System is in the south. The Secondary Systems surround the Predomi- nant System. The Great Low Plain is on the north and west, and lies between the mountain-systems of Asia and the secondary system of the Urals. Europe and Asia are sometimes considered as geographic- ally united in one grand division called Eurasia. 130. The mountain-systems of Asia are nearly all connected in one huge mass which extends in RELIEF FORMS OF THE CONTINENTS. 51 the line of the north-east trend, from the Arctic to the Indian Ocean. Though in reality one vast system, yet they are most conveniently arranged in one predominant and several secondary systems. The Predominant System is the plateau of Thibet, the loftiest table-land in the world. It is between 15,000 and 16,000 feet high, and is crossed by three huge, nearly parallel, mountain- ranges : the Himalayas on the south, the Kuen- lun on the north, and the Karahorum between them. The Himalayas, the loftiest mountains Fig. 50. Himalaya Mountains. in the world, rise abruptly from the plains of Northern Hindostan. Like the Alps, their axis is curved, but in the opposite direction. The breadth of the system varies from 100 to 200 miles ; the length is about 1500 miles. The high- est point is Mount Everest, 29,000 feet above the sea ; it is the culminating point of the Asiatic con- tinent and of the world. Kunchinjunga and Dha- walaghiri are scarcely inferior in height. 131. The Secondary Systems lie on all sides of the predominant system, though mainly on the north and east of the predominant system. Like Europe, the Asiatic continent projects on the south in the three mountainous peninsulas of Arabia, Hindostan, and Indo-China. On the north and east of the plateau of Thibet is an extended region called the plateau of Gobi, considerably lower than the surrounding country. The Kuen-lun and Great Kinghan Mountains bound it on the south and east, and the Altai Mountains on the north. On the west lie the Thian Shan and Altai, which by their open val- leys afford ready communication with the low plains on the west. The plateau of Gobi varies in average height from 2000 to 4000 feet. The greatest depression is in the west, and is occupied by Lake Lop and the Tarim River. A small part of the region near the mountain-slopes is moderately fertile, the remainder is mainly desert. The Altai Mountains are but little known, but some of their peaks exceed 12,000 feet. They are continued east- ward by the Yablonoi Mountains. East of the plateau of Gobi a rauge extends north-easterly through Mantchooria. On the south and west of Thibet lie the pla- teaus of Iran, Armenia, and Asia Minor. The Plateau of Iran includes Persia, Afghan- istan, and Beloochistan. It is a basin-shaped region from 3000 to 5000 feet high. The Elburz and Hindoo-Koosh Mountains form its borders on the north, the Suliman on the east, and the Za- gros on the south and west. The Suliman Mountains rise abruptly from the plains of the Indus. Across these mountains occurs the only practicable inland route between Western Asia and the Indies. The Plateaus of Armenia and of Asia Minor lie west of the Plateau of Iran. Armenia is 8000 feet high, and bears elevated mountains : Mount Ararat, 16,900 feet, is an example. On the west, the peninsula of Asia Minor, or Anatolia, extends between the Black and Mediterranean Seas, and is traversed by the Taurus Mountains. The Caucasus Mountains lie north of the pla- teau of Armenia. They are an elevated range extending between the Black and Caspian Seas, and form part of the boundary-line between Eu- rope and Asia. Mount Elburz, the " Watch- Tower," the culminating peak, is 18,493 feet high. The Arabian Plateau occupies the entire penin- sula of Arabia. It is separated from the plateau jf Iran by the Persian Gulf and the valleys of the Tigris and the Euphrates. The Plateau of Deccan occupies the lower part of the peninsula of Hindostan. It is crossed on the north by the Vindhya Mountains, and along the coasts by the Eastern and Western Ghauts. The Peninsula of Indo-China is traversed by a number of mountain-ranges which diverge from the eastern extremity of the Himalayas. The Nanling and Peling extend from east to west through China. 132. The Great Low Plain is, in reality, but a continuation of the European plain. It extends from the Arctic Ocean south-westerly to the Cas- 52 PHYSICAL GEOGRAPHY. pian and Black Seas. It is hilly on the east, but level on the west. South of the 60th parallel it is comparatively fertile. Around the shores of the Arctic are the gloomy Tundras. The Tundras are vast regions which in summer are covered with occasional moss-beds, huge shallow lakes, and almost interminable swamps, and in winter with thick ice. The tundras are caused as follows : The rivers that flow over the immense plain of Asia rise in the warmer regions on the south. Their upper courses thawing while the lower courses are still ice-bound, permits large quan- tities of drift ice to accumulate at their mouths, which, damming up the water, causes it to overflow the adjoining country. Depressions of the Caspian and Sea of Aral. — Two remarkable depressions occur in the basins of the Caspian and Sea of Aral, and that of the Dead Sea. These are all considerably below the level of the ocean. The waters of the Caspian and Sea of Aral were probably once connected in a great inland sea. The Smaller Asiatic Plains are drained by several river-systems. These are the Plain of Mantchooria, drained by the Amoor; the Plain of China, drained by the Hoang-Ho and the Yang-tse-Kiang ; the Plain of India, drained by the Indus, the Ganges, the Brahmapootra, and the Irrawaddy ; and the Plain of Persia, drained by the Tigris and the Euphrates. 133. Approximate Dimensions of Asia. Area of continent, 17,500,000 miles. Coast line, 35,000 miles. Greatest length from north-east to south-west, 7500 miles. Greatest breadth from north to south, 5166 miles. Culminating point, Mount Everest, 29,000 feet. 134. Comparison of the Relief Forms of Eu- rope and Asia. — In both Europe and Asia the chief elevations are in the south and the great low plains in the north. Asia, like Europe, extends toward the south in three great peninsulas : Ara- bia, Hindostan, and Indo-China. Fig, 51. Section of Asia from North to South. 1, Cape Comorin; 2, Deccan; 3, Plain of India; 4, Himalayas; 5, Everest; 6, Kuen-lun; 7, Karakorum ; 8, Thibet; 9, Upper Tartary; 10, Ararat ; 11, Elburz ; 12, Thian Shan ; 13, Altai ; 14, Mountains of Kamtchatka ; 15, Arctic Ocean , mouth of Yenesei. Fig, 52, Orographic Chart of Africa. (Light portions represent mountains ; shaded portions, plains.) 1, Abyssinian Plateau; 2, 3, Kenia and Kilimandjaro ; 4, Lupata; 6, Dragon; 6, Nieu veldt; 7, Mocambe; 8, Crystal; 9, Cameroons; 10, Kong; 11, Atlas; 12, Lake Tchad; 13, Madagascar. V. AFRICA. 135. Surface Structure. — Nearly the entire con- tinent of Africa is a moderately elevated plateau. It therefore has no great low plains ; but the in- terior is lower than the marginal mountain-sys- tems, and in this respect the true continental type, high borders and a low interior, is preserved. 136. The Predominant Mountain-System is in the east. The Secondary Systems are in the south, west, and north. The great interior depression is in the middle, and is surrounded by the predominant and sec- ondary systems. * A narrow, low plain extends along most of the coast. It is broadest on the north-west, between the plateau of the Sahara and the Atlas Moun< tain-system. 137. The Predominant Mountain-System ex- tends along the entire eastern shore, from the Mediterranean Sea to the southern extremity of the continent. It is highest near the centre, in RELIEF FORMS OF THE CONTINENTS. 53 the plateaus of Abyssinia and Kaffa. The culmi- nating point is probably to be found in the vol- canic peaks of Kenia and Kilimandjaro, whose estimated heights are taken at about 19,000 feet. In the Abyssinian plateau, on the north, an aver- age elevation of from 6000 to 8000 feet occurs. Upon this, rising in detached groups, are peaks the highest of which are over 15,000 feet. From the Abyssinian plateau the system is con- tinued northward to the Mediterranean by a suc- cession of mountains which stretch along the western shores of the Red Sea. Some of the peaks are from 6000 to 9000 feet. South of the plateau of Kaffa the system is continued by the Zmpata and Dragon Mountains to the southern extremity of the continent. The Zambesi and Limpopo Rivers discharge their waters into the Indian Ocean through deep breaks in the system. 138. Secondary Systems. — On the south the Nieuveldt and Snow Mountains stretch from east to west, with peaks of over 10,000 feet. Table Mountain is on the south. Fig. 53. Table Mountain. On the west the Mocambe and Crystal Mountains extend from the extreme south to the Gulf of Guinea. Near the northern end of this range, but separate from it, are the volcanic peaks of the Cameroons Mountains, 13,000 feet high. The Kong Mountains extend along the north- ern shores of the Gulf of Guinea in a general east-and-west direction. Some of the peaks are snow-capped. In the extreme north of Africa are the Atlas MoHtntains, 'which rise from the summit of a moderately elevated plateau. Some of the peaks are 13,000 feet high. 139. The Great Interior Depression north of the equator is divided into two distinct regions. A straight line extending from Cape Guardafui to the northern shores of the Gulf of Guinea marks the boundary. The mountain-systems north of this line have a general east-and-west direction ; those south of it have a general north- and-south direction. The Plateau of the Sahara occupies the north- ern part of the interior depression. Its general elevation is about 1500 feet, though here and there plateaus of from 4000 to 5000 feet occur, and even short mountain-ranges with peaks of 6000 feet. The main portion of the region is cov- ered with vast sand-fields, with occasional rocky masses, and is one of the most absolute deserts in the world. ■*ju&-^^*- Fig. 54, Desert of Sahara. Near long. 14° E. from Greenwich, in the district of Fezzan, the plateau is divided from north to south by a broad valley. In this occur many remarkable depressions, some of which are several hundred feet below the level of the Mediterranean. Here fertile spots, called oases, are common. South of the Sahara is the Soudan, a remark- ably well-watered and fertile region. Lake Tchad occupies the greatest depression. The interior, which lies south of this, is but little known. It is probably a moderately elevated plateau. Ex- tensive lake-basins — Albert and Victoria Nyan- zas and Tanganyika — lie near the predominant mountain-system. 140. Approximate Dimensions of Africa. Area of continent, 12,000,000 square miles. Coast line, 16,000 miles. Greatest breadth from east to west, 4800 miles. Greatest length from north to south, 5000 miles. Culminating point, Mount Kenia, or Kilimandjaro, about 19,000 feet. 54 PHYSICAL GEOGRAPHY. Fig. 55. Orographic Chart of Australia. (White portions, mountains ; shaded portions, plains.) 1, Australian Alps; 2, Kosciusko; 3, 4, 5, Secondary Systems; 6, Murray Eiver. VI. AUSTRALIA. 141. Surface Structure. — The Predominant Mountain-System is in the east. The Secondary Systems are in the west and north-west. The Great Low Plain lies between the pre- dominant and secondary systems, and slopes gently to the southern coast. The Predominant System extends along the entire eastern shore, from Torres Straits to the southern extremity of Tasmania. It is for the most part composed of broad plateaus. The system is highest in the south-east, where the name Australian Alps is given to the range. Mount Kosciusko, 7000 feet, probably forms the culminating point of the Australian continent. The system descends abruptly on the east, but on the west it descends by gentle slopes to the low plains of the interior. 142. The Secondary Systems, on the west and north-west, are of but moderate elevation. 143. The Great Low Plain lies in the interior. Ac- curate information as to its peculiarities is yet wanting. A moderate elevation on the north connects the eastern and western systems. The south-eastern portion, which is the hest known, is well watered and remarkably fertile. Basin-shaped valleys are found in the west. The lower parts are occupied by Lake Eyre, Torrens, and Gairdner. 144. Approximate Dimensions of Australia. Area of continent, 3,000,000 square miles. Coast line, 10,000 miles. Greatest length from east to west, 2400 miles. Greatest breadth from north to south, 2000 miles. Culminating point, Mount Kosciusko, 7000 feet. 145. Contrasts of Africa and Australia. — In the north, the African continent resembles Europe and Asia in the arrangement of its forms of relief. In the south, it resembles the Americas. As a whole, the African continent resembles Australia more closely than any other. In both Fig. 56. Australian Scenery. Africa and Australia the predominant system is in the east, and extends along the entire coast. In each the secondary systems are in the west and north. But Africa terminates in a plateau which descends abruptly to the sea, while Australia is terminated by a great low plain which descends by long, gentle slopes from the interior. SYLLABUS. <*<*c Eock-masses are divided, according to their origin, into igneous, aqueous, and metamorphic. According to their con- dition, into stratified and unstratified. According to the presence or absence of organic remains, into fossiliferous and non-fossiliferous. Stratified rocks are sometimes called fragmental. Unstratified rocks are sometimes called crys- talline. Aqueous rocks are sometimes called sedimentary. Aqueous rocks are stratified. Igneous rocks are un- stratified. Metamorphic rocks were originally stratified, but lost their stratification through metamorphism. REVIEW QUESTIONS. 55 Aqueous rocks may contain fossils. Igneous rocks never contain fossils. Metamorphic rocks, in rare instances, may contain fragments of fossils. Geological time is divided into Archaean, Palseosoic, Meso- zoic, and Cenozoic. Archaean Time includes the Azoic and the Eozoic Ages. Palaeozoic Time, or, as it is sometimes called, the Pri- mary, includes the Silurian, Devonian, and Carboniferous Ages. Mesozoic Time, or the Secondary, includes the Age of Eeptiles. Cenozoic Time includes the Age of Mammals, or the Ter- tiary, and the Era of Man, or the Quaternary Age. The changes to which the earth's crust is now subject are produced by the following agencies: 1. By the winds ; 2. By the moisture of the atmosphere; 3. By the action of running water ; 4. By the action of ocean waves ; 5. By the agency of man ; 6. By the con- traction of a cooling crust. There is more water than land surface on the earth, in proportion of 25 : 9, or as 5 a : 3 a . The land-masses surround the north pole in the shape of an irregular ring. Nearly all the land-areas are collected in one hemi- sphere, and the water-areas in another. The Land Hemisphere comprises the whole of North America, Europe, and Africa, all of Asia except a small part of -the Malay Peninsula, and the greater part of South America. The Water Hemisphere comprises the whole of Australia and the southern portions of South America and the Ma- lay Peninsula. The northern continents are almost entirely in the tem- perate latitudes ; the southern are mainly in the tropics. The land-masses may be divided into three doublets, consisting of pairs of northern and southern continents, almost or entirely separated from each other. There are two great systems of trends or lines of direc- tion, along which the continents, the coast lines, the mountain-ranges, the oceanic basins, and the island chains are arranged. These trends are north-east and north-west. The northern continents are characterized by deeply in- dented coast lines ; the southern are comparatively simple and unbroken. Europe is the most, and Africa the least, deeply indented of the continents. In proportion to her area, Europe has three times as much coast line as Asia, and four times as much as Africa. One-seventeenth of the land-area is composed of islands. Islands are either continental or oceanic. There are four successive stages in the formation of a coral island or atoll : 1. The fringing reef ; 2. The barrier reef; 3. The encircling reef; 4. The coral island or atoll. The greatest elevations and depressions in the earth's surface are small when compared with its size. Low lands are either plains or hills. High lands are either plateaus or mountains. Plains are — 1. Undulating; 2. Marine; 3. Alluvial. Mountains were produced by the contraction of the crust, producing a lateral pressure on thick, extended de- posits of sedimentary rocks. Slaty cleavage was caused by this lateral pressure. Valleys are either longitudinal or transverse. All continents have high borders and a low interior. The highest border faces the deepest ocean. The greatest prolongation of a continent is that of its predominant mountain-system. The culminating point is always out of the centre. North and South America resemble each other in the arrangement of their relief forms. Their predominant systems are in the west ; their secondary systems are in the east; their great low plains are between the predomi- nant and secondary systems. The predominant system of North America is the Pa- cific mountain-system. The secondary systems are — the Appalachian system, the plateau of Labrador, the Height of Land, and the Arctic plateau. The predominant system of South America is the sys- tem of the Andes. The secondary systems are — the pla- teaus of Guiana and Brazil. The great low plains are — the Llanos of the Orinoco, the Selvas of the Amazon, and the Pampas of the La Plata. Europe and Asia resemble each other. Their predomi- nant systems are in the south ; their great low plains are north of their predominant systems. The predominant system of Europe is in the south. The secondary systems are — the mountains of the Scan- dinavian Peninsula, the Ural Mountains, and the Caucasus Mountains. The predominant mountain-system of Asia is the pla- teau of Thibet. The secondary systems are — the plateau of Gobi, the Thian-Shan and Altai Mountains, the plateau of Indo- China, the plateau of Deccan, the plateau of Iran, the pla- teau of Asia Minor, and the plateau of Arabia. Africa and Australia resemble each other. Their pre- dominant systems are in the east; their secondary systems are in the west and north ; their depressed areas are be- tween the two. The predominant mountain-system of Africa includes the mountains of the eastern coast. The secondary systems include the Nieuveldt and Snow Mountains in the south, the Mocambe, Crystal, Cameroons, and Kong Mountains in the west, and the Atlas Mountains in the north. The predominant mountain-system of Australia includes the mountains of the eastern coast. The secondary systems include those found in the south w west, and north. REVIEW QUESTIONS. o<>x*;oo What two elementary substances form the greater part by weight of the earth's crust ? Into what classes may rocks be divided according to their condition ? According to their origin ? According to the presence or absence of fossils? What is palaeontology ? Define Archaean Time, Palaeozoic Time, Mesozoic Time, and Cenozoic Time. Explain the nature of the changes which the atmo- sphere is now effecting in the earth's surface. Which the water is effecting. Which man is effecting. What must be the areas of two squares whose areas 56 PHYSICAL GEOGRAPHY. represent the relative land- and water-areas of the earth ? What are the actual areas in square miles? How would you draw a circle around the earth which will divide it into land and water hemispheres? Do the continents extend farther to the north pole or to the south pole ? What do you understand by lines of trend ? Which have the more diversified coast lines, the north- ern or the southern continents? Define continental and oceanic islands, and give exam- ples of each. Why are continental islands to be regarded as detached portions of the neighboring mainland? Name the American island chains. The Asiatic chains. Describe the Australasian island chain. The Polynesian chain. Which are the higher, volcanic islands or coral islands ? Why? Name the four principal steps or stages in the progress of formation of a coral island. Is the coral island built by the coral animalcule or by the waves? Explain your answer. What is Darwin's theory for the presence of a lagoon within the reef? What is the difference between a plain and a plateau? A mountain and a hill? Define mountain-system. A chain. A knot. What is the name of the highest plateau in the world ? Of the largest plain ? In what different ways were plains formed ? Distinguish between a longitudinal and a transverse valley. Explain the manner in which mountains were formed. Give a short account of the surface structure, or the arrangement of the high and low lands, of North America. Of South America. Of Europe. Of Asia. Of Africa, and of Australia. Which of these resemble each other? In what respect do they all resemble one another? Name the culminating points of each of the continents. Name the predominant and secondary mountain-systems of each of the continents. How many times larger is Asia than Australia? Than Europe ? Africa ? North America ? South America ? North America. Name the principal mountains of the Pacific mountain- system. Which contains the culminating point of the continent ? Where is the Great Basin ? By what mountains is it surrounded ? Name the principal mountains of the Appalachian sys- tem. Is the greater portion of the area of North America above or below 1000 feet? What rivers drain the great low plain of North Amer- ica? South America. Name the principal plateaus of the Andes. Through which does the equator pass? Which contains Lake Titi- caca? Where is the plateau of Guiana ? Of Brazil ? What three large river-systems drain the great low plain of South America ? What resemblances can you find be- tween the directions of these rivers and those which drain North America ? Europe. Describe the chain of the Alps. What river-systems divide its northern slope into three divisions ? Name the principal mountains of each division. What three peninsulas project southward from the south- ern slopes of the predominant mountain-system? Name the principal mountains of each peninsula. Name the great low plains of Europe. Asia. What mountains form the northern boundary of the plateau of Thibet? The southern boundary? The north- ern boundary of the plateau of Mongolia? The eastern boundary? What mountains extend through China? What mountains form the boundaries of the plateau of Iran ? Is Arabia a plateau or a plain ? Is the land north of the Sea of Aral high or low? In which line of trend do the mountainous elevations of Asia extend ? Africa. What portions of Africa are high ? What portions are low? Where is the predominant system? Where is the cul- minating point? What part of the interior is low? Where are the Mocambe Mountains ? The Crystal Moun- tains, the Cameroons, the Atlas, the Kong, the Lupata, and the Dragon? Australia. Where is the predominant mountain-system? The sec- ondary system ? Where is Mount Kosciusko? The Murray River? Part III. THE WATER, ►oXKc By contact of air with the water-areas, an immense quantity of invisible vapor passes into the atmosphere, from which, when sufficiently cooled, it re-appears and descends as fog, dew, rain, hail, sleet, or snow. It then, in greater part, drains through various lake- and river-systems into the ocean, where it is either again evaporated, or carried about in waves, tides, or currents. This circulation of water never ceases, and upon it depends the existence of all life on the earth. Section I. CONTINENTAL. WATERS. -ooX^c CHAPTER I. Physical Properties of Water. 146. Composition. — Water is formed by the combination of oxygen and hydrogen, in the pro- portion, by weight, of eight parts of oxygen to one part of hydrogen ; or, by volume, of one part of oxygen to two parts of hydrogen. 147. Properties. — Pure water is a colorless, transparent, tasteless, and inodorous liquid. It freezes at 32° Fahr., and, under the ordinary pressure of the atmosphere, boils at 212° Fahr. Water exists in three states : solid, liquid, and gaseous. Under ordinary circumstances it freezes at 32°. It evapo- rates, or passes off from the surface as vapor, at all tempera- tures, even at 32° ; but it is only at the boiling-point that the vapor escapes from the mass of the liquid as well as from the surface. Heated in open vessels, under the ordinary pressure of the atmosphere, its temperature cannot be raised higher than 212°, any increase of heat only causing it to boil more rap- idly. Heated in closed vessels, which prevent the escape 57 58 PHYSICAL GEOGRAPHY. of steam, its temperature can be raised very high. In such cases great pressure is exerted on the walls of the vessel. Conversely, on high mountains, where the pres- sure of the atmosphere is lower than at the level of the sea, water boils at temperatures lower than 212° Fahr. 148. Maximum Density of Water. — A pint of cold water is heavier than a pint of warm water, because as water is cooled it contracts and grows denser. The coldest pint of water, however, is not the heaviest. The heaviest pint of water is water at the temperature of 39.2° Fahr. This temperature is therefore called the temperature of the maximum density of water. If water at this temperature be heated, it becomes lighter, or expands ; if water at this temperature be cooled, it also becomes lighter or expands until ice is formed, which floats on the water. When at the temperature of its maximum density, water is 7.2° warmer than the freezing-point. 149. Effect of the Maximum Density of Water on its Freezing. — If water continued to contract indefinitely while cooling until freezing began, the ice first formed would sink to the bottom, and, this process continuing, the entire mass would soon become solid. In this manner all bodies of fresh water, in times of great cold, might freeze through- out ; when, not even the heat of a tropical sun could entirely melt them. But for this curious exception in the physical properties of water, at least three-fourths of the globe would be in- capable of sustaining its present life. The entire floor of the ocean, both in the tropics and in the temperate and the polar regions, is covered with a layer of cold, salt water at nearly the temperature of its maxi- mum density. In the tropics the surface-water is warmer and lighter than this dense layer, and in the polar re- gions it is colder and lighter. 150. Specific Heat of Water. — Another re- markable property of water — its specific heat — enables it to play an important part in the economy of the world. The specific heat of a body is the quantity of heat-energy required to produce a definite in- crease of temperature in a given weight of that body. Water has a very great specific heat ; that is, a given quantity of water requires more heat-energy to warm it, and gives out more heat-energy on cool- ing, than an equal quantity of any other common substance. The quantity of heat required to raise a pound of ice- cold water to 212°, would heat a pound of ice-cold iron to a bright red heat, or to about 1600° Fahr. ; or, conversely, a pound of boiling water cooling to the freezing-point, would give out as much heat as a pound of red-hot iron cooling to 32° Fahr. The enormous capacity of water for heat is of great value to the life of the earth. The oceanic waters are vast reservoirs of heat, storing heat in summer and giving it out in winter. The great specific heat of water prevents it from either heat- ing or cooling rapidly. Large bodies of water, therefore, prevent great extremes of heat and cold. 151. Heat Absorbed or Emitted during Change of State. — During the conversion of a solid into a liquid, or a liquid into a vapor, a large quantity of heat-energy is absorbed. This heat-energy does not increase the temperature of the body, and therefore cannot be detected by the thermometer. The heat-energy is then in the condition of stored or potential energy, sometimes called latent heat. When the vapor condenses into a liquid, or the liquid freezes, the stored heat-energy again becomes sensible as heat. In freezing, water gives out heat and raises the mean temperature of the atmosphere. In melting, ice takes in heat and lowers the mean temperature of the atmosphere. Water has a higher latent heat than any other common substance. Stored Seat-Energy of Ice- Cold Water. — In order to heat a pound of water 1° Fahr. an amount of heat called a heat-unit, or a pound degree is required. Before one pound of ice at 32° Fahr. can melt and form one pound of water at 32° Fahr., it must take in 1J$ heat units; and yet a thermometer plunged in the water from melting ice will indicate the same temperature as when entirely surrounded by lumps of the un- melted material. The great latent heat of ice-cold water has an important influence on the freezing of large bodies of water, since, after the surface-layers have reached the temperature of the freezing-point, they have still 142 heat-units to lose be- fore they can solidify. Again, when ice reaches a tempera- ture of 32° Fahr., it has still 142 heat-units to absorb before it can melt. Were it not for this fact destructive floods would often result from the rapid melting of the winter's accumulation of snow and ice. Stored Heat-Energy of Water- Vapor. — Before one pound of water can pass off as vapor, it must take in sufficient heat to raise nearly 1000 pounds of water 1° Fahr. The vapor which then escapes is still at the same temperature as the water from which it came. The 1000 heat-units, or pound-degrees of heat, have been rendered latent, and have no influence on the thermometer. When the vapor in the air is condensed as rain, snow, hail, fog, or cloud the stored heat-energy DRAINAGE. 59 again becomes sensible. Much of the vapor which is formed in the equatorial regions is car- ried by the winds to high northern latitudes, where, on condensing, it gives out its heat and moderates the intense cold which would otherwise exist. 152. Solvent Powers. — Water is one of the best solvents of all common substances. During the constant washings to which the continents are subjected by the rains, their surfaces are cleansed from decaying animal and vegetable matters, which are partly dissolved and carried by the rivers into the ocean. The atmospheric waters in the same way cleanse the air of many of its impurities. 153. Water is the Main Food of Animals and Plants. — By far the greater part of the bodies of animals and plants is composed of water. With- out large quantities of water no vigorous life can be sustained in any locality. Deserts are caused entirely by the absence of water. CHAPTER II. Drainage. 154. Drainage. — The atmospheric waters, or those which fall from the atmosphere as rain, hail, or snow, either sink through the porous strata and are drained under ground, or run directly off the surface. Thus result two kinds of drainage — Subterranean and Surface. 155. Subterranean Drainage. — The water which sinks through the porous strata continues descend- ing until it meets impervious layers, when it either runs along their surface, bursting out as springs at some lower level, where the layers outcrop, or it collects in subterranean reservoirs. The origin of all springs is to be traced to subterranean drainage. Underground streams sometimes attain considerable size. In portions of the Swiss Jura streams burst from the sides of hills in sufficient volume to turn the wheels of moder- ately large mills. In a few instances the subterranean stream can be navigated for considerable distances, as in the Mammoth Cave of Kentucky, or in the Grotto of Adelsberg, near Trieste. 156. Surface Drainage. — The water which is drained directly from the surface, either runs down the slopes in rivulets and rills, which, uniting with larger streams, are poured directly into the ocean, or it collects in the depressions of basin-shaped valleys, where, having no connection with the ocean, it can be discharged by evapora- tion only. Thus arise two kinds of surface drain- age — oceanic and inland. 157. Springs are the outpourings of subterra- nean waters. The waters, having soaked through the porous strata, again emerge at the surface, either — (1.) By running along an inclined, impervious layer of clay, hard rock, or other material until Fig, 57. Origin of Springs. they emerge at some lower level, where the strata outcrop; or, (2.) By being forced upward out of the reser- voirs into which they have collected by the pres- sure of compressed gas, highly heated steam, or, more commonly, by the pressure of a communi- cating column of water. It is in the first way that most of the springs of moun- tainous districts discharge their waters. The tilted and broken condition of the strata is such as to favor the es- cape along some of the many layers that crop out on the mountain-slopes. The springs of plains, which are at some distance from mountains, discharge their waters mainly by the methods mentioned under the second heading. When a well is dug in most porous soils, the water from the porous strata on the sides runs in and partially fills the opening. 158. Classification of Springs.— Springs are most conveniently arranged in different classes according to peculiarities in the size, shape, and depth of their reservoirs, and the nature of the mineral substances composing the strata over which the waters flow, or in which they collect. The Reservoirs of springs are the places where 60 PHYSICAL GEOGRAPHY. the waters that sink into the ground collect. Reservoirs are sometimes large subterranean basins, but more frequently are merely porous strata, such as beds of sand or gravel, which lie between impervious layers of clay or hard rock. The water collects in the spaces between the par- ticles of sand or gravel. 159. Size of Reservoir. — When the reservoir is large, the spring is constant; when small, the spring is temporary. Constant Springs are those which flow continu- ally, and are but little affected in the volume of their discharge even by long-continued droughts. Temporary Springs are those which flow only for a short time after wet weather, drying up on the appearance of even moderate droughts. The quantity of water discharged by a spring depends on the size of the orifice or outlet tube, and the depth of the outlet be- low the surface of the water in the reservoir. The flow is proportional to the square root of the depth. That is to say, if with a given depth of orifice the velocity be one foot per second, in order to make the water escape with twice the velocity the depth must be increased fourfold. The actual velocity is somewhat less than this, being di- minished by friction. Since the volume discharged by some springs is very considerable, we must infer that their reservoirs are of great size. Many springs prob- ably receive the drainage from hundreds of square miles of surface. 160. Shape of the Reservoir. — When the out- let tube of the reservoir is siphon-shaped, the dis- charge of the spring becomes periodical. The Fig. 58. A Periodical Spring. spring continues to discharge its waters for a time, and then stops flowing, even during wet weather. After a certain interval it again dis- charges. The times during which the spring con- tinues to discharge are always practically the same. Hence the spring is called a periodical spring. The cause of periodical springs is due to the siphon- shape of the outlet tube. A siphon is a tube so bent as to have two vertical arms of unequal length. When filled, it will continue to discharge as long as its shorter arm is below the water and the longer arm free. If a large cav- ernous reservoir be in connection with the surface of the earth by a tube of this shape, it will begin to discharge its water when, by infiltration, the level reaches the highest bend of the tube, as at a, in Fig. 58, since the water will then drive out the air and fill the entire tube. The discharge will then continue until the water-level falls below the mouth of the tube, or at 6, in the figure. The time of the discharge is always practically the same, since the same quantity is discharged each time under exactly similar conditions. Springs are common on the shores of the ocean. Their waters are fresh because the outflow of the fresh water prevents the inflow of the salt water. This is the case even on coral islands, where the height of the land is but ten or twelve feet above the sea. A comparatively shallow well, on such islands, generally yields fresh water, derived, of course, from the rainfall. 161. Depth of Reservoir. — According to the distance the reservoir is situated below the sur- face of the earth, springs are divided into Cold, and Hot or Thermal. Cold Springs are those whose temperature does not exceed 60° Fahr. Their waters are sometimes much colder than 60° Fahr. Very cold springs owe their low temperatures to the sources whence they draw their supplies. In mountainous districts these can generally be traced to the melting of huge snow-fields, or masses of ice called glaciers. The temperature in such cases is often nearly that of ordinary ice- water. The reservoirs of all springs the temperature of whose waters ranges from 50° to 60° are, in general, comparatively near the surface. They are colder than surface waters — (1.) Because they are shielded from the sun ; (2.) Because evaporation occurs in their cav- ernous reservoirs. The temperature of springs of this kind is, in general, but slightly affected by changes in the temperature of the outer air. Since the reservoirs of ordinary springs are shielded from the hot air in summer and from the cold air in winter, their waters are colder than river-water in summer, and warmer than river-water in winter. Their waters average, in their temperature, that of the strata over which they flow in their subterranean course. DRAINAGE. 61 The mean annual temperature of the strata over which the waters flow can, therefore, he ascertained by plunging a thermometer into the water as it comes out of the spring. Hot or Thermal Springs range in temperature from 60° Fahr. to the boiling-point. In geysers the temperature of the water far down in the tube is considerably above the boiling-point at the sur- face. Hot springs which occur in the neighborhood of active volcanoes owe their high temperature to the vicinity of their reservoir's to beds of recently- ejected lava. Hot springs, however, are common in regions distant from volcanic disturbance. In such cases their high temperature must be attributed to the dis- tance of their reservoirs from the earth's surface, the heat being derived directly from the interior. In some cases the source of the heat is to be attributed to chemical action in neighboring strata. Thermal springs, whose reservoirs are at comparatively moderate depths, may discharge their waters by ordinary hydrostatic pressure; but where, from the great depth of the reservoirs, this force would be insufficient, the waters are probably raised to the surface by the pressure of super- heated steam or compressed gas. Since the temperature rises 1° for about every 55 feet of descent, in cases where the increased temperature is due solely to depth, if the issuing waters have a tempera- ture of 149° Fahr., the reservoirs must be about one mile below the surface, or fifty-five times the difference between 149° and 60°, the temperature of ordinary springs. In many cases the waters probably rise from profound depths as columns of steam, condensing in reservoirs that are less profound. Source of Deep-seated Waters. — Deep-seated waters are probably derived by infiltration from the bed of the ocean. The natural porosity of large areas is greatly in- creased by the immense pressure of the water, which in the deep ocean is equal to thousands of pounds per square inch. Fig. 59. Artesian Well. 162. Artesian Wells differ from ordinary wells in that their waters are discharged by natural pressure on their reservoirs, so that pumping is not necessary to raise the water. Such wells are therefore true springs. The reservoirs are basin-shaped, and generally consist of several water-logged, porous strata, con- tained between two, curved, impervious strata. If the upper porous layer be pierced, the waters will flow out by reason of the pressure of the liquid in the higher parts. The reservoirs of many natural springs are of this kind, the upper im- pervious strata being broken in one or more places by some natural force. Artesian wells have been sunk to great depths, and it is a significant fact that the temperature of the issuing waters is always proportional to the depth, showing a nearly constant increase of 1° above the temperature of ordinary springs — viz. about 60° Fahr. — for every 55 feet of descent. In the case of the artesian well of Grenelle, Paris, the successful boring of which was accomplished only after many years of the most discouraging labor, and which reached a depth of nearly 1800 feet, the tem- perature of the water was 82° Fahr. A well at Neusalz- werk, Prussia, has penetrated 2200 feet; its temperature is 91° Fahr. 163. Geysers are boiling springs which, at in- tervals more or less regular, shoot out huge col- umns of water with great violence. They are Fig. 60. Geyser in Eruption. confined to the neighborhood of volcanic dis- tricts, and, by some, are classed with subordinate volcanic phenomena. The jets of water some- 62 PHYSICAL GEOGRAPHY. times reach a height of more than two hundred feet. The geyser issues from the summit of a conical hillock of silicious material deposited by the water. A broad, shallow basin generally surmounts the hillock and forms the mouth of a deep, funnel-shaped tube. The sides of both tube and basin are lined with a smooth incrustation of silica. In the Great Geyser of Iceland, the basin is 52 feet wide and the tube 75 feet deep. Both the tube and basin are the work of the spring, being deposited from the silica contained in the highly heated waters. It is only when the tube has reached a certain depth that the spring becomes a true geyser. When the depth becomes too great the geyser eruptions cease, the waters forcing their way through the walls of the tube to some lower level. Hence, in all geyser re- gions, numerous deserted geyser-tubes, and simple ther- mal springs occur. The waters of some geyser regions are calcareous. In this case the tube of the geyser is, of course, formed of limestone. 164. Bunsen's Theory of Geysers. — Bunsen explains the cause of geyser eruptions as follows : The heat of the volcanic strata, through which the geyser-tube extends, causes the water which fills it to become highly heated. The water at the bottom of the tube, having to sustain the pressure of that above it, gradually acquires a tem- perature far above the boiling-point at the surface. The temperature of the water in the tube will, therefore, de- crease from the bottom to the surface. If now, when the tube is filled, the water, near the mid- dle, is brought to its boiling temperature, the steam thus formed momentarily lifts the water in the upper part of the tube, when the water in the lower part, released from its pressure, bursts into steam and forcibly ejects the con- tents of the tube. Bunsen succeeded in lowering a thermometer into the tube of the Great Geyser in Iceland just before an erup- tion. At the depth of 72 feet he found the temperature of the water to be 261° Fahr., or 49° above the ordinary boiling-point. 165. Geyser Regions. — There are three exten- sive geyser regions : (1.) In Iceland, in the south-western part of the island, where over one hundred occur in a limited area. (2.) In New Zealand, about the centre of the northern island, where, near the active volcano Tongariro, over one thousand mud springs, hot springs, and geysers burst from the ground. (3.) In Yellowstone National Park, in Wyoming, where numerous large geysers occur, mostly near the head-waters of the Madison and Yellowstone Rivers, at heights often as great as 8000 feet above the sea-level. Here the boiling-point of the water at the surface of the geyser, owing to the diminished atmospheric pressure, is as low as about 200° Fahr. A small geyser region is found in California, near San Francisco. 166. Nature of the Mineral Substances form- ing the Reservoir. — The subterranean waters dis- solve various mineral matters either from the strata over which they flow, or from their reser- voirs ; this is especially true of thermal springs, owing to the greater solvent powers of the heated waters. The waters of mineral springs generally contain a number of mineral ingredients. Mineral springs are divided into various classes according to the predominating material. (1.) Calcareous Springs are those whose waters contain lime in solution. Thermal waters charged with carbonic acid usually con- tain large quantities of lime, which they have dissolved from subterranean strata. On reaching the surface the waters cool and part with some of their carbonic acid, and deposit layer after layer of hard limestone, called travertine. In this way immense quantities of limestone are brought to the surface from great depths, leaving huge subterra- nean caverns. In portions of Tuscany, Italy, beds of travertine occur more than 250 feet thick. (2.) Silicious Springs are those whose waters contain silicon. (3.) Sulphurous Waters are those whose waters contain sulphuretted hydrogen and various metal- lic sulphides or sulphates. Sulphurous springs are found in Baden, near Vienna, and in Virginia. (4.) Chalybeate Waters are those whose waters contain iron. (5.) Brines, or those whose waters contain com- mon salt. The springs of Halle, in the Alps of Salzburg, yield 15,000 tons of salt 'annually. The artesian well of Neu- salzwerk, Prussia, yields about 28,000 tons annually. In the United States the springs of Salina and Syracuse are among the most important. The water in the springs of Salina is ten times Salter than ocean-water. The salt is obtained from these springs by the evaporation of the water. (6.) Acidulous Springs are those whose waters contain large quantities of carbonic acid gas, as the Seltzer springs in Germany, and those of Vichy in France. 167. Petroleum and Bituminous Springs. — Be- sides the springs above mentioned, there are two others, closely connected, but which can scarcely be included in any of the above classes. These are petroleum and bituminous springs. Petroleum Springs are those containing rock- or coal- oil. They rise from large reservoirs containing oil instead of water. The oil is derived from the slow decomposition, in the presence of heat, of various animal and vegetable RIVERS. 63 matters which are found in the strata of nearly all the geological formations. The reservoirs are of the same nature as those of artesian wells, the oil being obtained by boring. Petroleum springs are numerous. The most extensive regions in the world ai - e found in the great oil districts of Western Pennsylvania and the neighboring States. Bituminous Springs, or those from which pitch or bitumen issue. Their origin is the same as that of oil springs, the decomposition, however, occurring in a some- what different way. The famous pitch lake on the island of Trinidad, north-east of South America, probably owes its origin to the large quantities of trees and other vege- table matters, which have been rolled down the Orinoco and buried in the delta formation on the eastern shores of the island. XJ^C CHAPTER III. Rivers. 168. Definitions. — The water that issues from the ground as springs, that is derived from the melting of ice or snow, or that drains directly from the surface after rainfall, runs down the slopes of the land and collects in the depressions formed by the intersection of the slopes, forming rills or rivulets, which at last combine in larger streams called rivers. The source of a river is the place where it rises ; the mouth, the place where it empties ; the channel, the depression through which it flows. Rivers generally rise in mountains, where the rainfall is greater than elsewhere, and where vast beds of snow and ice occur. In reality, all rivers have three mouths, or places where they discharge their waters : (1.) Where the river empties directly into some other body of water ; (2.) Where the river empties by evaporation into the air ; that is, its entire upper surface ; (3.) Where the river empties into the earth through the porous strata of its bed or channel. Since the downward motion of a river is caused by the inclination of its channel from the source to the mouth, a correct idea of the general inclination of any country can be obtained by a careful study of a map in which the di- rections of the rivers are represented. In studying the various river-systems the student should endeavor to ob- tain in this way clear ideas of the general directions of the tontinental slopes. The River-System is the main stream, with all its tributaries and branches. The Basin is the entire area of land which drains into the river-system. The Water-shed is the ridge or elevation which separates two opposite slopes. The streams flow in opposite directions from the water-shed. The Velocity of a river depends on the inclina- tion or pitch of the channel and the volume or depth of the water. 169. River-Courses. — The river-channel, from its source to its mouth, is, for ease of description, conveniently divided into three parts or courses : the upper, middle, and lower. The Upper Course of a river is that part which is situated in the mountainous or hilly country near its source. In this course the river has a great velocity, and its channel is characterized by sharp, sudden turns, alternating with long, straight courses. In the upper course erosion occurs almost entirely along the bottom of the channel, so that the river runs between steep, and some- times almost vertical, banks. In this way river- valleys are formed, generally with narrow and overhanging, precipitous sides. In the upper and middle courses rapids and waterfalls occur. Rapids and Waterfalls. — During the erosion of the channel, where harder rocks occur in the bed of the stream, the softer strata, immediately adjoin- ing them down stream, are rapidly worn away, and the obstruction becomes at last the head of a waterfall. The height grows rapidly from the increased force of the falling water, and continues until stopped by some similar obstruction below. \ 5y i U i i VH 2 2 -^ 3 3 4 4 Fig, 61. Erosion of Waterfall. Thus, suppose a a, Fig. 61, is the bed of a river, the di- rection of flow of which is shown by the arrow. The softer rock being worn away more rapidly, the bed reaches the level 1, 1. A fall, and consequent increase in the velocity of the river, soon causes the level of the bed to reach 2, 2, 3, 3, and 4, 4, successively. At the same time the falling water eats away the vertical wall of the precipice, causing the waterfall to move up stream. The water then cuts the precipice away in steps, as shown at 5, 6, 7, thus changing the fall into cascades. These are finally worn away, as shown at 8, changing the cascades to rapids, when, finally, the fall disappears entirely, or the erosion of the hard rock is completed. When the water falls perpendicularly — that is, when it does not slip or slide — it forms a water- fall or cataract; in all other cases of swift de- scent it forms rapids. 64 PHYSICAL GEOGRAPHY. Fig. 62. The Falls of Niagara. The grandest falls in the world are those of the Niagara, 160 feet high. Though greatly inferior to many others in height, yet their volume of water is so great that they surpass all others in grandeur. The Victoria Falls of the Zambezi in Africa nearly equal in volume those of the Niagara. Their height is 360 feet. The highest falls in the world are those of the Yosemite, in California. Two projecting ledges break the sheet into three falls, whose total height exceeds 2000 feet. One of the highest falls in Europe is the Staubbach or Dust-brook, in the valley of the Lauterbriinnen in Switzerland. The water makes one sheer fall of 959 feet, and is lost in a sheet of mist before it reaches the ground. The Middle Course extends from where the river emerges from the mountainous or hilly dis- tricts to the low plains near the mouth. The descent is comparatively slight, and the velocity small. The erosion of the bottom of the channel is insignificant, but at the sides, especially during freshets, the river undermines its banks and thus widens its valley. Here the river is divided into two distinct portions : the channel proper and the alluvial flats or flood-grounds. The Lower Course extends from the middle course to the mouth. The fall is slight, and the velocity small. 170. Changes in River-courses. — During floods, when the velocity and eroding power are greatly increased, ex- tensive changes often occur in river-courses. After the floods have subsided the water is found running through new channels, its old ones being either completely filled with deposits of mud, or occupied by slender streams. Along the Mississippi these partially deserted channels are called bayous, and, in places, widen out into large lakes. (See Fig. 63.) The Red River appears to have formerly emptied into the Mexican Gulf through a separate chan- nel. In the basins of the Amazon, the Ganges, and the Po, the old deserted channels are numerous on both banks of the streams. 171. River Mouths. — A wide, open river-mouth is called an Estuary; the accumulation of mud or sand which occurs in the mouths of certain rivers is called a Delta. 172. Inundations. — During certain seasons of the year, the amount of water drained into the river-channel is greater than it can discharge ; it then overflows its banks and inundates the sur- rounding country. Inundations of rivers are caused — (1.) By excessive rainfall ; (2.) By periodical rains ; (3.) By the melting of ice and snow. In the tropics, where the rainfall is more or less periodical, the inundations of the rivers are also periodical. The melting of the ice and snow, which occurs regularly at the beginning of the warm weather, also causes periodical inundations. The Nile rises annually on account of the period- ical rainfall of its upper sources ; the Mississippi semi-annually, once from the melting of snow, and once from the winter rainfall. When both the area of the river-basin and the rainfall in inches are known, experience permits of a calculation, by means of which the probable time and extent of rise of water in a river can be approximately predicted. In times of heavy rainfall, the Weather Bureau of the United States is enabled to predict the probable rise of the im- portant rivers. Influence of the Destruction of the Forests on In- undations. — When the forests are removed from a large portion of a river-basin, the rains are no longer absorbed quietly by the ground, but drain rapidly off its surface into the river-channels, and thus in a short time the entire precipitation is poured into the main channel, causing an overflow. It is from this cause that the disastrous effects of otherwise harmless storms are produced. The inunda- tions are most intensified by this cause in the early spring, when the ice and snow begin to melt. The destructive effects of the floods are increased by masses of floating ice, which, becoming gorged in shallow places in the stream, back up the waters above. The increased frequency of inundations in the United States is, to a great extent, to be attributed to the rapid destruction of the forests. 173. The Quantity of Water Discharged by a River depends principally — (1.) On the size of the basin ; (2.) On the amount of the rainfall. The quantity of water in a river also depends — (1.) On the climate of the basin, a dry, hot air diminish- ing the quautity by evaporation ; (2.) On the physical features of the basin, whether wooded or open ; TRANSPORTING POWER OF RIVERS. 65 (3.) On the nature of the bed or channel, whether leaky or not. It will be noticed that these three circumstances are connected with the two additional river-mouths already alluded to : the air-surface of the river, and the channel- surface. Keith Johnston estimates the daily discharge of all the rivers of the world at 229,000,000,000 cubic yards, or over 2,620,000 cubic yards per second. x>XKc CHAPTER IV. Transporting Power of Rivers. 174. Silt or Detritus. — Rivers are ceaselessly at work carrying the eroded materials, called silt or detritus, from their upper to their lower courses. Valleys are thus formed, miles in width and thou- sands of feet in depth, and lofty mountains greatly reduced in height. The amount of silt transported by rivers is almost in- credible. According to the careful estimates of Hum- phreys and Abbot, the silt brought down every year by the Mississippi and thrown into the Mexican Gulf, if collected in one place, would cover a field one square mile in area to the depth of 268 feet. According to Lyell, the deposits, in the Bay of Bengal, of the Ganges and the Brahmapootra, are nearly as great. The rivers are carrying the mountains seaward, and the continents are thus decreasing in mean height and increasing in mean breadth. 175. Deposition of Silt. — Since the silt or eroded mineral matter is heavier than water, it will settle in all parts of the river-course. It will, however, remain in those places only where the velocity of the river is comparatively small. These places are as follows : (1.) In the channel of the river ; (2.) On the banks, over the alluvial flats or flood-grounds ; (3.) At the mouth ; (4.) Along the coast near the mouth. 176. In the Channel. — In rivers that traverse great plains, the inclination near the mouth is slight, and the diminished velocity allows the ma- terial to accumulate in the channel, thus raising the general level of the stream. When the rivers traverse settled districts, the inhabitants are com- pelled to erect huge river-walls to prevent the flooding of the adjacent lands ; and, in some places, the channel has beeu filled to such an extent that the ordinary level of the river is higher than that of the plains along its banks. The levees or banks of the Mississippi are of this nature. On the level plain of Lombardy the surface of the Po, in some places, is higher than the tops of the neighboring houses. When floods occur in such districts, the breaking of a levee or river-wall is generally attended by much loss. 177. Rafts. — Drift timber, thrown into the stream by the undermining of the banks, is common in rivers that traverse wooded districts. Portions of such timber, be- coming imbedded in shallow parts of the channel, form obstructions which prevent the passage of subsequent masses. The impediment so formed checks the velocity of the stream, and mud deposits occur between the trees. Such accumulations are called rafts. The raft of the Bed Eiver, previous to its removal, was thirteen miles in length. A large raft exists near the mouth of the Mackenzie Eiver in British America. 178. On the Alluvial Flats or Flood-grounds. — The low flat plains on the sides of the river, which are formed by the erosion of the banks in the middle and lower courses, are covered by the water when the river overflows its banks. In the shallow water over these parts the velocity of the water is slight, and the silt is deposited, thus forming rich alluvial plains. In large rivers the flood-grounds often attain consider- able size. In the Mississippi at Vicksburg the width of the alluvial plain is over 60 miles. In the lower courses of a river, the velocity being small, comparatively slight obstacles suffice to turn the waters from their course. The river- channel is therefore characterized by wide bends Fig, 63. Alluvial Plats of the Mississippi, (Showing deserted courses and fluviatile islands and lakes.) or curves. At the bend of a river the main cur- rent is directed against one of the banks, where rapid erosion takes place, the eroded material ac- cumulating lower down the river, in the bed of the stream, where the velocity is small. The river is thus continually damming %k 'i^A U P portions of its old chan- X % nel and cutting new ones. The rapid excavation of these portions of the alluvial plain is favored by the loose materials which compose it. Sometimes the river cuts a new channel across the nar- row neck of a bend, part of its waters running through the old channel and part through the new. In this way jiuviatile islands are formed. One of the chan- nels is sometimes separated from the other by a deposi- tion of mud or sand. The water fills the old channel by soaking through the soil, and thus Jiuviatile lakes are formed. Numerous fluviatile lakes occur near the banks of the Lower Missis- sippi and the Red River. Fig, 64. Formation of Fluviatile Islands and Lakes. Thus, suppose the river flows in the direction of the arrow at S, Fig. 64, and its channel has the bends shown. A new channel may be formed at a, b, the river either flowing through both channels, thus converting the neck of land I, into a fluviatile island, or the old channel may fill up and form a fluviatile lake, L, by bars forming in the old channel at a and b. 179. At the Mouth. — Delta Formations.— In sheltered parts of the ocean, where the tides are weak and the ocean-currents feeble, or in inland seas and lakes, where they are entirely absent, the eroded material accumulates at the mouth of the river in large, triangular-shaped deposits, called deltas, from their resemblance to the Greek letter (J) of that name. The Delta of the Mississippi is the largest in the Western Continent. Its entire area is about 12,300 square miles, though but two-thirds of it are permanently above the water, the remainder being a sea-marsh. It begins a little below the mouth of the Red River. The stream cuts through the delta in one main channel, but near the ex- treme end of the delta forms several mouths. On all sides of the main stream, numerous smaller streams force their way into the Gulf through the soft material. The Delta of the Nile, at its outlet into the Mediter- ranean, occupies an area of nearly 9000 square miles. A large portion of the sediment of the river is deposited over the flood-grounds during inundations. The fertility of the land is largely dependent on these deposits. Fig. 65. Delta of the Mississippi. (After Dana.) The Delta of the Ganges and the Brahmapootra, in the Bay of Bengal, is cousiderably larger than the Delta of the Nile. Between the Hoogly and the main branch of the Ganges, numerous streams force their way between countless islands, called the Sunderbunds, inhabited by tigers and crocodiles. The Po, the Rhone, the Rhine, and the Danube in Europe, the Tigris, the Euphrates, the Yang-tse- Kiang and Hoang-Ho in Asia, and the Senegal and the Zam- besi in Africa, have extensive deltas. 180. Along the Coast, near the Mouth. — Fluvio- Marine Formations are deposits of silt that form along the coast near and opposite the mouths of rivers, under the combined action of the river- current and the tides of the ocean. A sand-bar is formed at some little distance from the mouth of the river, where the outflowing river-current DRAINAGE SYSTEMS. 67 Fig. 66. Fluvio- Marine Formations. and the inflowing tide neutralize each other. The impediment so formed permits of the rapid de- position of silt, which fills up the portions of the ocean so shut off, and converts them into shallow bodies of water called sounds. These sounds, by gradual rising of the land, are afterward con- verted into river-swamps. According to Dana, the eastern and southern coasts of the United States, from Virginia to Texas, are an almost con- tinuous fluvio-marine formation. Albemarle and Pamlico Sounds and the Great Dismal, Alligator, and Okefinoke Swamps are but different stages in the formation of these deposits. CHAPTER V. Drainage Systems. 181. Continental Drainage is dependent on the position of the mountain-systems and the direc- tion of their slopes. The mountain-ridges or peaks, or the high plateaus, form the water-sheds. In some cases, from a single peak or plateau, the water drains into distinct river-systems, emptying into different oceans. 182. North America. — The central plain of North America is drained by four large river- systems : the Mackenzie into the Arctic Ocean ; the Saskatchewan and the Nelson into Hudson Bay ; the St. Lawrence into the Gulf of St. Law- rence ; and the Mississippi into the Gulf of Mex- ico. The basin of the Mississippi occupies the long slopes of the Rocky Mountains and the Appalachians. The Missouri and the Ohio are the principal tributaries of the Mississippi. Numerous streams descend the eastern slopes of the Appalachian system into the Atlantic. Owing to the position of the predominant sys- tem, the streams which empty into the Pacific are comparatively small. The principal are the Yu- kon, the Columbia, and the Colorado. There are several remarkable isolated water-sheds or drainage-centres in North America. These are — (1.) In the central part of the Rocky Mountain system, where the land drains in different directions into the sys- tems of the Mississippi, the Columbia, and the Colorado Rivers. (2.) In the northern part of the Rocky Mountains, where the drainage is received by the systems of the Yukon, the Mackenzie, and the Saskatchewan Rivers. 183. South America resembles North America in its drainage systems. The long, gentle slopes of the Andes, and those of the systems of Brazil and of Guiana, are occupied at their intersections by the three great river-systems of the continent : that of the Orinoco, in the north ; that of the Amazon, near the centre; and that of the La Plata, in the south. Nearly the entire continent is drained by these rivers and their tributaries into the basin of the Atlantic. The Pacific receives no considerable streams. Only impetuous mountain-torrents are found. The Magdalena, which drains north, corresponds to the Mackenzie; the Orinoco and the Amazon, which drain east, to the Nelson and the St. Lawrence; and the La Platte, which drains south, to the Mississippi. 184. Europe forms an exception to the other continents as regards its drainage. Though some of its large rivers rise in its predominant moun- tain-system, yet the majority rise in the incon- s \terable elevations of the Valdai Hills. The Alps are drained by four large rivers — the Phone, the Rhine, the Danube, and the Po. These all have large deltas. Although in this part of the continent the frequent in- tersection of the two lines of trend produces numerous basin-shaped valleys, yet, owing to breaks in the enclosing mountains, none of any size have an inland drainage, but discharge their waters through numerous tributaries into one or another of the principal river-systems. The Great Low Plain of Europe is drained toward the north and west by the Petchora and Dwina into the Arctic ; by the Duna, the Nie- men, the Vistida, and the Oder into the Baltic; Page. 6(9. LAKES. 69 and by the Elbe and the Weser into the North Sea. It is drained toward the south and east by the Ural and the Volga into the inland basin of the Caspian ; and by the Don, the Dnieper, and the Dniester into the Sea of Azov and the Black Sea. All the peninsulas have streams traversing them. The Seine, the Loire, and the Garonne from France, and the Douro, the Tagus, and the Gaudiana from Spain and Por- tugal, empty into the Atlantic. The Ebro from Spain, and the Po from Italy, empty into the Mediterranean. 185. Asia possesses the most extensive inland drainage of all the continents. The plateaus are surrounded by lofty mountains containing but comparatively few breaks, and their waters, there- fore, can find no passage to the sea. The outer slopes, however, are drained by some of the largest rivers in the world. The Great Northern Plain drains into the Arctic, mainly through the Lena, the Yenisei, and the Obe. The Eastern Slopes drain into the Pacific through the Amoor, the Hoang-Ho, the Yang-tse- Kiang, and the Cambodia. The Southern Slopes drain into the Indian Ocean through the Irrawaddy, the Brahmapootra, the Ganges, the Indus, the Tigris, and the Eu- phrates. The principal drainage-centre in Asia is the Plateau of Thibet, from which descend the Hoang-Ho, the Yang-tse- Kiang, the Cambodia, the Irrawaddy, the Ganges, the Brahmapootra, and the Indus. 186. Africa, being low in the interior, with high mountain-walls on her borders, is charac- terized, like the Americas, by the union of her smaller river-systems into a few large streams, which drain nearly the entire continent. These embrace the Nile, emptying into the Mediterra- nean ; the Zambezi, into the Indian Ocean ; and the Orange, the Congo, the Niger, and the Senegal, into the Atlantic. 187. Australia. — The Murray, which drains the south-eastern part of the continent into the Indian Ocean, is the only considerable stream. 188. Principal Oceanic Systems. — A careful study of the river-basins of the different oceans discloses the following fact: The Atlantic and Arctic Oceans receive the waters of nearly all the large river-systems of the world. The cause of this is as follows : The predomi- nant systems being situated nearest the deepest ocean, the long, gentle slopes descend toward the 9 smaller, shallower oceans (the Atlantic and the Arctic), which thus receive the greatest drainage. For details of the various river-systems — such as the length, area of basin, etc. — see Table, page 170. D^C CHAPTER VI. Lakes. 189. Lakes are bodies of water accumulated in depressions of the surface of the land. They are connected either with the systems of oceanic or of inland drainage. The waters of lakes draining into the ocean are fresh; those having no connection with the ocean are salt. Depth. — From their mode of formation lakes which occur in mountainous districts are, as a class, deeper than those found on the great low plains, since the former occupy the basins of nar- row but deep valleys, and the latter the depres- sions of the gentle undulations of the plain. In mountainous districts the depths of the depressions are sometimes so great that the bottom of the lake is con- siderably below the sea-level. Lake Maggiore in the Swiss Alps extends about 2000 feet below the level of the sea. Lake Superior. Lake Huron. Fig. 67. Elevations and Depressions of Lakes, One of the most remarkable series of depressions in the general land-surface of the world is that occupied by the waters of Lakes Superior, Michigan, Huron, Erie, and On- tario. Superior and Huron, though some 600 feet above the level of the ocean, reach, in their greatest depths, far below its surface ; the former being 270 feet, and the latter about 400 feet, below the general level of the Atlantic. When a lake is connected with a river-system, the place where the principal stream enters is called the head of the lake ; the place where it empties is called the foot of the lake. 190. Geographical Distribution. — The large 70 PHYSICAL GEOGRAPHY. lake-regions of the world are almost entirely confined to the northern continents. 191. Oceanic Drainage Systems. — North Amer- ica contains the most extensive lake-system in the world. The lake-region surrounds Hudson Bay, and drains into the Arctic through the Mac- kenzie; into Hudson Bay through the Sas- katchewan ; or into the Atlantic through the St. Lawrence. To it belong the Great Lakes — Superior, Michigan, Huron, Erie, and Ontario — Fig. 68. View on Lake George, N. T. embracing a combined area of nearly 100,000 square miles — and the numerous lakes of Brit- ish America'. Athabasca, Great Slave, and Great Bear Lakes drain into the Arctic through the Mackenzie ; Lake Winnepeg, into Hudson Bay through the Nelson ; and the Great Lakes, into the Atlantic through the St. Lawrence. Europe contains two extensive systems of fresh- water lakes. The larger region is in Low Europe, and surrounds the Baltic Sea and its branches ; to it belong Lakes Ladoga and Onega in Russia, Wener and Wetter in Sweden, with numerous smaller lakes. The smaller region is found in the Alps in High Europe. Africa contains an extensive system of lakes west of the predominant system. Victoria and Albert Nyanzas, which drain into the Nile, Lake Tanganyika, which drains into the Livingstone or the Congo, and Lake Nyassa, which drains into the Zambezi, are the principal lakes. The remaining continents contain but few large fresh-water lakes. In South America we find Lake Maracaybo, with brackish water from its vicinity to the sea ; and in Asia, Lake Baikal. 192. The Inland Drainage Systems are inti- mately connected with that of inland rivers. The term Steppe Lakes and Rivers is generally applied to those which have no outlet to the ocean. Cause of the Saltness of Inland Waters.— All river- water contains a small quantity of common salt and other saline substances. Since lakes which have no outlet, or, as they are generally called, inland lakes, lose their waters by evaporation only, the saline ingredients must be con- tinually increasing in quantity; the water of such lakes is therefore generally salt. The Dead Sea in Syria is remarkable for the quantity of its saline ingredients. In every one hundred pounds of its waters there are over twenty-six pounds, or more than one-fourth, of various saline ingredients. North America. — The largest inland drainage- system is in the Great Basin, containing Great Salt, Walker, Pyramid, and Owen Lakes. South America. — The largest region of inland drainage includes the plateau of Bolivia, contain- ing Lake Titicaca. The waters of this lake are fresh, but have no outlet to the sea, the river form- ing the outlet being lost in a salty, sandy plain. Europe and Asia contain a vast region of in- land drainage extending from the Valdai Hills eastward to the Great Kinghan Mountains, em- bracing most of the Asiatic plateaus. The region contains Lake Elton in Bussia, and the Cas- pian and Aral Seas. The combined area of the last two is 175,000 square miles. They receive the waters of the Volga, the Ural, the Sir, and the Amoo, all large streams. Numerous lakes occur on the plateaus. Lake Lop, in the depression north of Thibet, receives the Tarim, and Lake Hamoon, on the Iranian plateau, the Helmund Biver. Africa contains Lake Tchad in the Soudan, re- ceiving the Komadagu and the Shirwa, and Lake Ngami in Southern Africa. Australia contains Lakes Eyre, Torrens, Gaird- ner, and Amadeo near the southern coast. 193. Utility of Lakes. — By offering extended basins into which the rivers, when swollen, can disgorge them- selves, lakes greatly diminish the destructive effects of inundations, often checking them entirely. They afford extended surfaces for evaporation, and, collecting the finer sediment of the rivers when deserted by their waters, form fertile plains. SYLLABUS. Water is formed by the union of oxygen and hydrogen. The waters of the earth may be divided into two classes — the continental and the oceanic. Water is a solid at and below 32° Fahr., a liquid from 32° to 212°, and a vapor above 212°. It passes off as vapor, however, at all temperatures. A pint of water is heaviest at the temperature of 39.2° Fahr. Hence in deep lakes, covered with ice, the lower layers of water are 7.2° Fahr. above the freezing-point. Large bodies of water moderate the extremes of tem- perature, because water takes in more heat while warming and gives out more on cooling than any other common substance. During the freezing of a body of water, or the condensa- tion of a mass of vapor, considerable stored heat-energy appears, or latent heat becomes sensible and warms the surrounding air. After a body of water has been cooled to the tempera- ture of 32° Fahr., it has still 142 heat-units, or pound-de- grees, to lose before it can turn into ice. After a body of ice has been warmed to the temperature of 32° Fahr.,^t has still 142 heat-units, or pound-degrees, of heat to gain before it can turn into water. Therefore, both freezing and melting are gradual pro- cesses. The rains cleanse the surface of the earth and purify the atmosphere. Water is necessary for the existence of life. It forms the main food of both animals and plants. The atmospheric waters are drained into the ocean either by surface or subterranean drainage. Springs are the outpourings of the subterranean waters. Springs may be classified according to peculiarities in the size, shape, and depth of their reservoirs, and the nature of the mineral substances composing the strata over which the waters flow or in which they collect. According to the size of their reservoirs, springs are either constant or temporary. If their reservoirs have siphon-shaped outlet tubes, their discharges are periodical. When their reservoirs are superficial, springs are cold; when deep-seated, they are hot or thermal. Springs whose waters are moderately cold have their reservoirs near the surface. Their lower temperature is due to their waters being shielded from the sun. Springs with very cold waters have their sources in the melting of large masses of ice or snow. Hot or thermal springs owe their high temperature to the heat they receive from the interior of the earth. Geysers are boiling springs, which, at irregular intervals, shoot out huge columns of water with great violence. The most extensive geyser regions are those of Iceland, New Zealand, and Wyoming. Calcareous springs contain lime; silicious, silex; sul- phurous, sulphuretted hydrogen and metallic sulphides or sulphates ; chalybeate, iron ; brines, common salt ; acidu- lous, carbonic acid ; petroleum, coal oil ; bituminous, pitch. Eivers are fed both by surface and subterranean drain- age. The main stream with all its tributaries and branches is called the river-system. The territory drained into the river-system is called the river-basin. The ridge or ele- vation separating opposite slopes is called the water-shed. In the upper courses of rivers erosion occurs mainly on the bottom of the channel ; in the lower courses, at the sides. In the lower courses of rivers extensive flats or plains are found. They are caused by the erosion of the banks and the subsequent deposition of fine mud during inunda- tions. Eivers are constantly at work carrying the mountains toward the sea. Through their agency the mean height of the continents is decreasing, and their mean breadth increasing. The eroded material, or silt, may accumulate — 1. In the channel of the river; 2. Along the banks, on the alluvial flats or flood-grounds; 3. At the river's mouth; and 4. Aloug the coast, near the mouth. The accumulations in the channel of the lower Missis- sippi have so raised the bed of the stream as to necessitate the erection of levees or embankments along the sides. Where the tides are weak and the ocean currents absent or feeble, the eroded material, or silt, accumulates at the mouths of rivers in masses termed deltas. The Alps are drained by the Rhine, the Rhone, the Po, and the Danube ; these rivers have extensive delta-forma- tions. The plateau of Thibet is drained by the Hoang-Ho, the Yang-tse-Kiang, the Ganges, the Brahmapootra, and the Indus ; all these rivers have extensive delta-formations. Among other extensive deltas are those of the Missis- sippi, which drains the long slopes of the Pacific and Appalachian mountain-systems; the Nile, the Tigris, the Euphrates, and the Zambezi. Fluvio-marine formations occur along the coasts ; they are caused by the combined action of the river and tides. The destruction of forests, by increasing the rapidity of drainage, increases the violence of floods. Lakes along the river-courses decrease their violence, by allowing the torrents to discharge their waters. The direction of the drainage of a country is dependent on the direction of its slopes. The central plain of North America is drained north into the Arctic Ocean through the Mackenzie ; east into the Atlantic through the Nelson and the St. Lawrence; and south into the Gulf of Mexico through the Mississippi. The central plain of South America is drained north into the Caribbean Sea through the Magdalena, east, into the Atlantic through the Orinoco and the Amazon, and south, into the Atlantic through the Rio de la Plata. The rivers draining the great low plain of Europe rise either in the Valdai Hills or on the northern slopes of the predominant system. Asia possesses the most extended system of inland drainage of the continents. Extended systems are also found in North America and Europe. The Atlantic and the Arctic Oceans drain about three- fourths of the continental waters. The largest systems of fresh-water lakes occur in North America and Europe. The Great Lakes of North America occupy remarkable depressions in the continent. The beds of some of them are several hundred feet below the level of the sea. Lakes without an outlet are salt, because the waters they receive contain small quantities of saline ingredients, while the waters they lose contain none. 72 PHYSICAL GEOGRAPHY. REVIEW QUESTIONS. What is the composition of water ? Enumerate the physical properties which enable water to play so important a part in the economy of the earth. What effect has the temperature of the maximum den- sity of water on the freezing of large bodies of fresh water ? Why? How do large bodies of water moderate the extremes of heat and cold ? Why are freezing and melting necessarily gradual pro- cesses ? What effect has a heavy rainfall on the temperature of the atmosphere? Explain the cause of deserts. Define subterranean drainage. Surface drainage. Upon what does the quantity of water discharged by a spring in a given time depend? Explain the cause of periodical springs. What is the temperature of cold springs? Of hot or thermal springs? What is the probable cause of the high temperature of hot springs? How can the probable depth of the reservoir of an arte- sian spring be ascertained from the temperature of its waters ? What are geysers? Explain the cause of their erup- tion. What is the origin of the tube and basin of the geyser ? Name the three largest geyser regions of the world. What is travertine ? How is it formed? Name some of the most important springs from which large quantities of salt are obtained. What is believed to be the origin of petroleum or coal oil? How are the precipices of waterfalls caused? In what courses of a river are they most common? Name the highest waterfall in the world. The grand- est. Distinguish between an estuary and a delta. How does the destruction of the forest increase the severity of inundations? Upon what does the quantity of water in a river de- pend? In what different portions of a stream may the silt or detritus be deposited? What are rafts ? How are they caused ? Explain the formation of fluviatile islands and lakes. Name some of the most extensive delta-formations in North America. In Europe. In Asia. In Africa. What is the probable origin of the swamp-lands of the Atlantic seaboard? How may a tolerably accurate notion of the direction of the slopes of a country be obtained by a study of the direction of its rivers? In what respects do the drainage of North and South America resemble each other? Name the principal systems of inland drainage of the world. Explain the cause of the saltness of inland waters. MAP QUESTIONS. «&Kc Which ocean drains the largest areas of the continents ? Which the smallest ? Name the important rivers which drain into the Atlan- tic from North America. From South America. From Europe. From Africa. Name the important rivers which drain into the Pacific from North America. From Asia. Name the important rivers which drain into the Indian Ocean from Africa. From Asia. From Australia. What two systems of inland drainage are there in North America ? What large region in South America ? Name an important steppe lake and river in each of the continents. Describe the region of inland drainage of Europe and Asia. What large lakes and rivers belong to this region? Describe the regions of inland drainage of Africa. Of Australia. Name the important lakes found in each region. What South American river corresponds in the direction of its drainage with the St. Lawrence? With the Mac- kenzie? With the Mississippi? Name the large rivers which drain the predominant mountain-system of Asia. Of Europe. Of Africa. Of North America. Of South America. Of Australia. Describe the fresh-water lake-region of North America. Of South America. Of Europe. Of Africa. In which line of trend are most of the fresh-water lakes of North America found ? Name the Atlantic rivers which have large deltas The Pacific rivers. The Indian rivers. Section II. OCEANIC WATERS. -oXKc CHAPTER I. The Ocean. 194. Composition. — The water of the ocean contains a number of various saline ingredients, which give it a bitter taste and render it heavier than fresh water in the proportion of 1.027 to 1. Every hundred pounds of ocean-water contains about three and one-third pounds of various saline ingredients. Chloride of sodiu»a, or common salt, chloride of magne- sium, sulphates and carbonates of lime, magnesia, and potassa, and various bromides, chlorides, and iodides, are the principal saline ingredients. 195. Origin of the Saltness of the Ocean. — The rivers are constantly dissolving from their channels large quantities of mineral matters, and pouring them into the ocean. Besides this, fully three-fourths of the earth's sur- face is covered permanently by the oceanic waters. In this way immense quantities of mineral ingredients have been dissolved out from the crust. The latter cause was especially active during the geological past, when frequent convulsions brought fresh portions of the crust into con- tact with the warm waters. The ocean is salter in those parts where the evaporation exceeds the rainfall, or at about the latitude of the tropics; where the rainfall exceeds the evaporation, the water is slightly fresher than at the equator. In inland seas, like the Mediterranean or the Red Sea, which, though connected with the ocean, yet lose much more of their waters by evaporation than by outflow, the proportion of salt is slightly greater than in the ocean. In such cases a current generally flows into the sea from the ocean. In colder latitudes, inland seas, like the Bal- tic, receiving the waters of large rivers, contain rather less salt than the open sea, and a current generally flows from them into the ocean. 196. Color. — Though transparent and colorless in small quantities, yet in large masses the color of sea-water is a deep blue. The same is true of fresh water. Over limited portions of the ocean the waters are sometimes of a reddish or a greenish hue, from the presence of numberless minute organisms. Sometimes a pale light or phosphorescence, visible only at night, and due to the presence of animalcule, appears where the air comes into con- tact with the water, as in the wake of a vessel or on the crests of the waves. 197. Temperature. — The salts dissolved in ocean-water lower the temperature of its freez- ing-point. Ordinary ocean-water freezes at about 27° F. In places where the water is salter, the temperature of its freezing-point is lower. Ice formed from ocean-water is comparatively fresh, nearly all the salt being separated as the water freezes or crystallizes. The salt, thus thrown out from the frozen water, is dissolved by the water below, lowers the temperature of its freez- ing-point, and thus increases its density. In this manner the water below the ice may have a tem- perature lower than that at which the surface- water freezes, and yet remain liquid. In the polar regions the water below the sur- face is at a temperature lower than that of the freezing-point of the surface-water. This cold water, from its greater density, spreads over the floor of the ocean in all latitudes, so that, except where stirred by deep currents, the entire bottom of the ocean is covered with a layer of dense, heavy water, the temperature of which is nearly constant. The temperature of this water is about 35° F. Near the poles it is somewhat lower : about 29°, or a little higher than its maximum density of the surface-waters. The upper limit of this line of invariable temperature varies with the latitude. Near the equator, where the waters are heated to great depths, it is found at about 10,000 feet below the surface. Toward the poles, it comes nearer the surface, reaching it at about Lat. 60°, from which point it again sinks, being found at Lat. 70° at about 4500 feet below the surface. In the tropics the temperature of the surface-water is about 80° F. ; in the polar regions it is near the freezing-point. The ice which forms in the polar regions collects in vast ice-fields or floes. 198. Shape of the Bottom of the Ocean.— The bed of the ocean, though diversified like the sur- face of the land, contains fewer irregularities. Numerous soundings show that it extends for immense distances in long undulations and slopes. Its plateaus and plains, therefore, are of great size, compared with those of the continents. Submerged mountain-ranges occur both in the deep ocean and along the shores. The latter 74 PHYSICAL GEOGRAPHY. belong, properly, to the continental systems of elevations. 199. The Oceanic Areas. — The ocean is one continuous body of water, but for purposes of description and study it is generally divided into five smaller bodies : the Pacific, Atlantic, Indian, Arctic, and Antarctic Oceans. The last two are separated from the preceding by the polar circles ; the others are separated mainly by the continents. As the continents do not extend to the Antarctic Circle, the meridians of Cape Horn, Cape of Good Hope, and South Cape in Tasmania, are taken as the ocean boundaries south of these points. The following table gives the relative size of the oceanic areas : The Pacific occupies about \ the entire water-area. " Atlantic " " \ " " " Indian " " } " " " Antarctic " " fr H " " Arctic " " ■& 200. Articulation of Land and Water. — The indentations of the oceans, or the lines of junc- tion between the water and the land, may be arranged under four heads: (1.) Inland Seas, or those surrounded by a nearly continuous or unbroken land-border; as the Gulf of Mexico, Hudson Bay, the Baltic, and the Mediterranean, in the Atlantic ; the Red Sea and the Persian Gulf, in the Indian; and the Gulf of California, in the Pacific. (2.) Border Seas, or those isolated from the rest of the ocean by peninsulas and island chains ; as the Caribbean Sea, the Gulf of St. Lawrence, and the North Sea, in the Atlantic ; and Bering Sea, the Sea of Okhotsk, the Sea of Japan, and the North and South China Seas, in the Pacific. (3.) Gulfs and Bays, or broad expansions of the water extending but a short distance into the land ; as the Gulf of Guinea and the Bay of Biscay, in the Atlantic ; and the Bay of Bengal and the Arabian Sea, in the Indian. (4.) Fiords, or deep inlets, with high, rocky headlands, extending often from 50 to 100 miles into the land. One of the best instances of this form of indentation is off the Norway coast. Ac- cording to Dana, fiords are valleys that were ex- cavated by vast ice-masses called glaciers, but which have since become partially submerged by the gradual subsidence of the land. Fiord valleys occur on the Norway coast, on the coasts of Greenland, Labrador, Nova Scotia, and Maine, on the western coast of Patagonia and Chili, and on the western coast of North America north of the Straits of Fuca. On parts of the coast of Greenland the glaciers are now cutting out their partially submerged valleys, and forming what will probably become fiord valleys. The Atlantic Ocean is characterized by inland seas; the Pacific, by border seas; the Indian, by gulfs and bays; the Atlantic and the Pacific, by fiords. 201. Depth of the Ocean. — The mean depth of the ocean is about 12,000 ft., or nearly 2k miles. Recent soundings give the greatest depth of the Atlantic, in the neighborhood of the island of St. Thomas of the West Indies, as 27,000 feet. The greatest depth in the Pacific, as reported by recent careful soundings, occurs east of Japan, and is 27,930 ft. These give a depth of about 5i miles, or less than the greatest elevation of the land. It is probable, however, that some portions of the ocean are much deeper. The greater depressions of the ocean are called deeps, the shallower portions are called rises. 202. The Pacific Ocean.— The shape of the shore-line of the Pacific is that of an immense oval, nearly closed at the north, but broad and open at the south. As indicated by the island chains, a number of shallow places, or rises, extend in the direction of the north-west trend : the summits of those on the north form the Sand- wich Islands, and the summits of those on the south form the Polynesian Island chain. 203. The Atlantic Ocean. — The shape of the shore-line of the Atlantic is that of a long, trough-like valley, with nearly parallel sides. The Atlantic has a broad connection with both the polar oceans, and forms the only open chan- nel for the intermingling of the warm and cold waters. Shape of the Bed. — Recent soundings in the Atlantic show the presence of a submarine plateau extending in mid- ocean parallel to the coasts of the continents from the lati- tude of the southern point of Africa to Iceland, thus di- viding the basin into eastern and western valleys. The western valley is the deeper ; the average depths of the two being respectively 18,000 and 13,000 feet. A remarkable Feet. Level of the sea. Fig. 69. The Telegraphic Plateau. plateau extends across these valleys, from Newfoundland to Ireland. Its depth ranges from 10,000 to nearly 13,000 feet. It is called the Telegraphic Plateau, and bears a number of telegraphic cables. The eastern and western OCEANIC MOVEMENTS, 75 valleys, though less marked in this region, are still dis- tinguishable. The true bed of the ocean begins at a considerable dis- tance from the eastern coast of North America. For dis- tances of from 75 to 100 miles, the depth scarcely exceeds 600 feet ; but from this point it descends, by steep terraces, to profound depths. The British Isles are connected with the continent of Europe by a large submerged plateau, which underlies nearly the whole North Sea, and extends for considerable distances off the western and southern coasts. The depth of this part of the ocean is nowhere very great. 204. The Indian Ocean. — The shape of the shore-line is, in general, triangular. This ocean has no connection with the Arctic, but is entirely- open on the south, where it merges into the great water-area of the globe : the basins of the Ant- arctic and Pacific. Shape of the Bed. — A submarine plateau extends to the south off the western coast of Hindostan. Its summits form the Laccadive, Maldive, and Chagos Islands, and pos- sibly extends in the same direction as far as Kerguelen Island. 205. The Antarctic and Arctic Oceans.— The shore-line of the Arctic has the shape of an ir- regular ring. The shore-line of the Antarctic is probably of the same shape. But little is known concerning the beds of these oceans. From the very limited land-areas south of lat. 50° S., the bed of the Antarctic is presum- ably deeper than that of the Arctic, except toward the south pole, where it is probably shallower. 206. Ooze Deposits. — Foraminiferal Land. — The reef-forming coral polyps are not the only animalculse the accumulation of whose bodies after death add to the land-masses of the earth. Deep-sea soundings show that over extended areas Fig, 70. Foraminifera. the floor of the ocean is evenly covered with a creamy layer of mud or ooze, which, like the deposits of the coral animalculse, is composed principally of carbonate of lime. This ooze con- sists almost entirely of microscopic skeletons of a group of animalculse known as the Foraminifera, from the great number of perforations or open- ings in their hard parts. These animalculse are so small that 1,000,000 are equal in bulk to only one cubic inch. They appear to live in the layers of water near the surface, and after death to fall gradually to the bottom of the sea. Sound- ings show their presence over very extended areas. Many of the very deep parts of the ocean's bed are covered, not with foraminiferal deposits, but with a layer of red mud composed of finely-di- vided clay. Its origin is probably as follows : In very deep parts of the ocean before the fora- miniferal deposits reach the bottom their limey matters are dissolved, and the undissolved parts form the deposits of fine red mud. CHAPTER II. Oceanic Movements. 207. The Oceanic Movements can be arranged under three heads : waves, tides, and currents. Waves are swinging motions of the water, caused by the action of the wind. Their height and velocity depend on the force of the wind, and the depth of the basin in which they occur. The stronger the wind, and the deeper the ocean, the higher the waves and the greater their velocity. Fig. 71. Ocean Waves, Height of Waves. — Scoresby measured waves in the North Atlantic 43 feet above the level of the trough. Waves have been reported in the South Atlantic, off the Cape of Good Hope, between 50 and 60 feet high. Navi- 76 PHYSICAL GEOGRAPHY. gators have occasionally reported higher waves, but the accuracy of their measurements is, perhaps, to he doubted. In the open sea, with a moderate wind, the height of ordinary waves is about 6 feet. The distance between two successive crests varies from 10 to 20 times their height. Waves 4 feet high have their successive crests 40 feet apart; those 33 feet high, about 500 feet apart. 208. No Progressive Motion of Water in Waves. — In wave motion, the water seems to be moving in the direction in which the wave is ad- vancing, but this is only apparent ; light objects, floating on the water, rise and fall, but do not move forward with the wave. In shallow water, however, the water really advances. The for- ward motion of the wave is retarded, so that the waves following reach it, thus increasing its height. The motion at the bottom is lessened, and the top curls over and breaks, producing what are called breakers. On gently sloping shores, the water which runs down the beach, after it has been thrown upon it by the breakers, forms, at a little distance from the shore, the dreaded "undertow" of our bathing-resorts. Force of the Waves. — When high, and moving in the direction of the wind, the waves dash against any obstacle, such as a line of coast, with great force, and may thus cut it away and change the coast-line. This action occurs only on ex- posed, shelving coasts. The wave-motion is, in general, very feeble at 40 feet below the surface. The eroding action of the ocean waves is, there- fore, far inferior to that of the continental waters. 209. Tides are the periodical risings and fall- ings of the water, caused by the attraction of the sun and moon. The alternate risings and fallings succeed each other with great regularity, about every six hours. Unlike waves, in which the motion is confined practically to the surface waters only, tides affect the waters of the ocean from top to bottom. The rising of the water is called flood tide ; the falling, ebb tide. When the waters reach their highest and lowest points, they remain stationary for a few minutes. These points are called, re- spectively, high and low water. Corresponding high or low water, at any place, occurs fifty-two minutes later each successive day. 210. Theory of the Tides.— If the earth were uniformly covered with a layer of water, the pas- sage of the moon over any place, as at a, Fig. 72, would cause the water to lose its globular form, become bulged at a, and b, and flattened at e, and d. In other words, the water would become deeper at a, and b, at the parts of the earth near- est and farthest from the moon, and shallower in ! o Fig. 72, Lunar Tide. all places 90° or at right angles to these points, such, for example, as at c, and d. This deepening and shallowing of the water is caused by the attraction of the moon. As the moon passes over a, the water is drawn toward the moon, thus deepening the water directly under the moon, and shallowing it at c, and d. The cause of the deepening of the water at 6, on the side farthest from the moon, is as follows : the solid earth being, as a whole, nearer the moon than the water at b, but farther from it than that at a, must take a position which will be nearly midway between a, and b, leaving a protuberance at b, nearly equal to that at a. The protuberances a, and b, mark the position of high tides. At all points of the earth 90° from the protuberances, as at e, and d, the depression is greatest. These mark the position of low tides. High tides, then, occur at those points of the earth's surface which are cut by a straight line, which passes through the centre of the earth and that of the attracting body, as the sun or moon. Low tides are found at right angles to these points. Had the earth no rotation, the tidal waves, so formed, would slowly follow the moon in its mo- tion around the earth. But, by the rotation of the earth, different parts of its surface are rapidly brought under the moon, and the tidal waves, consequently, move rapidly from one part of the ocean to another. Had the moon no motion around the earth, there would be two high tides and two low tides every 24 hours. While, however, the earth is making one complete rota- tion, the moon, in its motion around the earth, has changed its position, and the earth rotates for 52 minutes longer before the same point again comes directly under the moon. Since the uniformity of the water surface is broken by the elevations of the land, the progress of the tidal wave is greatly affected by the size, shape, and depth of the oceanic basin, and the OCEANIC MOVEMENTS. 77 position of the continents. Owing to the obstruc- tions offered by the continents, and by inequalities in the bed of the ocean, a very considerable re- tardation of the tidal wave is effected, so that a high tide may not occur at a place until long after the moon has passed over it. Solar Tides. — The sun also produces a system of tidal waves, but owing to its greater distance from the earth, the tides thus produced are much smaller than those of the moon, upon which, there- fore, they exert but a modifying influence. The tide-producing power of the moon is greater than that of the sun, in about the proportion of 800 to 355. That is, the tide produced by the moon is about 24 times greater than that produced by the sun. The tidal wave moves, in general, from east to west, or in the opposite direction to the rotation of the earth. The motion of so large a mass of water thus opposed to the earth's ro- tation, must gradually diminish the axial velocity, and, eventually, entirely ■stop the rotation of the earth ; in this way an increase in the length of day and night should be produced, but so far, however, no increase has been de- tected, although astronomical observations extend back- ward for loug periods. The increased axial velocity, pro- duced by the contraction of the globe, probably balances the retarding influence of the tides. In the deep ocean, and near the mouths of rivers, the duration of the flood and ebb are about equal ; but in most rivers, at some distance from the mouth, the ebb is longer than the flood. The cause is to be found in the fact that the outflowing river current meets and temporarily neu- tralizes the inflowing flood tide, thus diminishing its dura- tion, and afterward, adding its motion to the ebb, makes the difference between the two still greater. The tidal wave often ascends a stream to a much greater elevation above the level of its mouth than the height of the tide at the river's mouth. In large rivers, like the Amazon, the tidal wave advances up the river as much as 100 feet above the sea-level. Some of the proofs of the connection between the tides and the attraction of the moon and sun are as follows : (1.) The interval between corresponding high tides at any place is the same as the interval between two succes- sive passages of the moon over that place: 24 hours, 52 minutes. (2.) The tides are higher when the moon is nearer the earth. (3.) The tides are higher when the sun and moon are simultaneously acting to cause high tides in the same places Quarter. # » : '!:■ ill Neap Tides, • flood and ebb ' moderate. \ SUN ." x Quarter. ^ Fig, 73. Cause of the Phases of the Moon, Phases of the Moon. — An inspection of Fig. 73 will show, that during new and full moon, the earth, moon, and sun are all in the same straight line, but, that during the first and last quarters, they are at right angles. The portions of the earth and moon turned toward the sun are illumined, the shaded portions are in the darkness. To an observer on the earth, the moon, at a, appears new, since the dark part is turned toward him ; at b, however, it must appear full, since the illumined portions are toward him. At c, and d, the positions of the quarters, only one- half of the illumined half, or one quarter, is seen. Spring Tides, flood and ebb excessive. Tig. 74. Position of the Earth, Moon, and Sun during Spring and Neap Tides. 211. Spring and Neap Tides. — When the sun and moon act simultaneously, on the same hemi- sphere of the earth, as shown in Fig. 74, the tidal wave is higher than usual. The flood tides are then highest, and the ebb tides lowest. These are called spring tides. They occur twice during 10 every revolution of the moon — once at full, and once at new moon. The highest spring tides oc- cur a short time before the March and the Sep- tember equinoxes, when the sun is over the equa- tor, and is nearest the earth. When, however, the sun and moon are 90° 78 PHYSICAL GEOGRAPHY. apart, or in quadrature, each produces a tide on the portion of the earth directly under it, dimin- ishing somewhat that produced by the other body. High tide, then, occurs under the moon, while the high tide caused by the sun, becomes, by compari- son, a low tide. Such tides are called neap tides. During their prevalence, the flood is not very high, nor the ebb very low. They occur twice during each revolution of the moon, but are low- est about the time of the June and December solstices. The average relative height of the spring tide to that of the neap tide is about as 7 to 4. 212. Birthplace of the Tidal Wave.— Although a tidal wave is formed in all parts of the ocean where the moon is overhead, yet the " Cradle of the Tides " may properly be located in the great southern area of the Pacific Ocean. Here the combined attraction of the sun and moon origin- ate a wave, which would travel around the earth due east and west, with its crests north and south ; but, meeting the channels of the oceans, it is forced up them toward the north. Its progress is accelerated in the deep basins, and retarded in the shallow ones. On striking the coasts of the con- tinents, deflected or secondary waves move off in different directions, thus producing great com- plexity in the form of the parent wave. 213. Co-Tidal Lines.— The progress of the tidal wave, in each of the oceans, is best understood by tracing on a map, lines connecting all places which receive the tidal wave at the same time. These are called co-tidal lines. The distance be- tween two consecutive lines represents the time, in hours, required for the progress of the tidal wave. In parts of the ocean where the wave travels rap- idly the co-tidal lines are far apart ; when its prog- ress is retarded, they are crowded together. Fig. 75. Co- Tidal Chart, Since it is only possible to take the height of the tide on the coasts of islands and of the continents, the tracks of the co-tidal lines must be to a considerable extent con- jectural. 214. The Pacific Ocean. — Twice every day a tidal wave starts in the south-eastern part of the Pacific Ocean, west of South America, somewhere between the two heavy lines marked xn on the chart. It advances rapidly toward the north- west in the deep valley of this ocean, reaching Kamtchatka in about 6 hours. Toward the west its progress is retarded by the shallower water, and by the numerous islands, so that it only reaches New Zealand in about 6 hours and enters the Indian Ocean in about 12 hours. 215. The Indian Ocean. — The 12-hour-old tidal OCEAN CURRENTS. 79 wave from the Pacific, meets and moves along with a wave started in this ocean by the moon, and advances in the direction indicated by the co-tidal lines entering the Atlantic Ocean about 12 hours afterward. 216. The Atlantic Ocean. — The tidal wave from the Indian joins two other waves, one formed by the moon in this ocean, and the other a deflected wave that has backed into the Atlantic from the Pacific. The tidal wave thus formed advances rapidly up the deep valley of the Atlantic, reach- ing Newfoundland 12 hours afterward, or 48 hours after it started in the Pacific. It then advances rather less rapidly toward the north-east, reach- ing the Loffoden Islands 12 hours afterward, or 60 hours after leaving its starting-place in the Pacific. 217. Tides in Inland Seas and Lakes are very small and, consequently, difficult to detect. In the Mediterranean Sea the tides on the coasts average about 18 inches. The tide in Lake Michigan is about If inches. 218. Height of Tidal Wave. — Ocean tides are lowest in mid-ocean, where they range from two to three feet. Off the coasts of the continents, especially when forced up narrow, shelving bays, deep gulfs, or broad river mouths, they attain great heights. The cause of these unusual heights is evident. When the progress of the tidal wave is retarded, either by the contraction of the chan- nel or by other causes, the following part of the wave overtakes the advanced part, and thus, what the ivave loses in speed it gains in height, from the heaping up of the advancing waters. Where the co-tidal lines, therefore, are crowded together on the chart, high tides are likely to occur ; for example, the Arabian Sea and Bay of Bengal, the North and South China Seas, the eastern coasts of Pata- gonia, the Bay of Fundy, the English Channel, and the Irish Sea, have very high tides. Near the heads of the Persian Gulf and China Seas, the tides sometimes rise about 36 -feet. At the mouth of the Severn, the spring tides rise from 45 to 48 feet ; on the southern coast of the English Channel, 50 feet ; and in the Bay of Fundy, near the head, the spring tides, aided by favoring winds, sometimes reach 70 feet, and, oc- casionally, even 100 feet. A strong wind, blowing in the direction in which the tidal wave is advancing, causes an increase in the height of the tide. A low barometer is attended by a higher tide than usual ; a high barometer, by a lower tide. 219. Other Tidal Phenomena. The Bore or Eager. — On entering the estuary of a river, the volume of whose discharge is considerable, the onward progress of the tidal wave is checked ; but, piling up its waters, the incoming tide at last overcomes the re- sistance of the stream, and advances rapidly, in several huge waves. The tides' of the Hoogly, the Elbe, the Weser, and the Amazon, are examples. In the latter river, the wave is said to rise from 30 to 50 feet. Races and Whirlpools. — When considerable differ- ences of level are caused by the tides, in parts of the ocean separated by narrow channels, the waters, in their effort to regain their equilibrium, move with great velocity, pro- ducing what are called races. At times, several races meet each other obliquely, thus producing whirlpools. Near the Channel Islands, and off the northern coasts of Scotland, races are numerous. The Maelstrom, off the coasts of Nor- way, is an instance of a whirlpool, though the motion of the waters is not exactly a whirling one. The main phe- nomenon is a rapid motion of the waters, alternately back- ward and forward, caused by the conflict of tidal currents off the Loffoden Islands. K>J#XXC Point out, on the map of the river-systems, the inland seas of the Atlantic ; of the Pacific ; of the Indian Ocean. Point out the border seas of the Atlantic; of the Pacific. Point out the gulfs or bays of the Atlantic ; of the In- dian Ocean. Point out the principal regions of fiords. How many hours does it take the tidal wave to progress from Tasmania to the Cape of Good Hope ? From Tasma- nia to Newfoundland? From Tasmania to the British Isles? (See map of the co-tidal lines.) In what parts of the Atlantic does the tidal influence progress most rapidly? If the velocity of any kind of wave motion in water in- creases with the depth of the basin, what parts of the At- lantic appear to be the deepest? What portions of the Pacific? What portions of the Indian Ocean? Trace on the map of the ocean currents, the motion of the Antarctic currents in each of the three central oceans. Where is the Cape Horn current? Is it hot or cold? What points of resemblance exist between the north and south equatorial currents in the Atlantic and Pacific Oceans ? Trace the progress of the Gulf Stream. What points of resemblance exist between the Gulf Stream and the Japan current? How far to the north-east do the waters of the Gulf Stream extend? What distant shores are warmed by the waters of the Gulf Stream? By those of the Japan current? Why do not the heated waters of the Gulf Stream exert a more powerful influence on the climate of the eastern sea-board of the United States? Point out the principal cold currents; the principal warm currents. Which currents would aid, and which would retard, the progress of a vessel in sailing from New York to San Fran- cisco? From America to Europe? From America to India or Australia? Part IV. THE ATMOSPHERE. o^Xc We live at the bottom of a vast ocean of air, which, like the ocean of water, is subject to three general movements — waves, tides, and currents. By means of waves, its upper surface is heaved in huge mountain-like masses in one place, and hollowed out in deep valleys in another. By means of currents, circulatory movements are set up, which effect a constant interchange between the air of the equatorial and the polar regions. By means of tides, the depth of the atmosphere is increased in some places and decreased in others. Of these three movements of the atmosphere, currents are of the greatest importance. Aerial cur- rents, or winds, are similar to oceanic currents, but are more extensive and rapid, owing to the greater mobility of air. By retaining and modifying the solar heat, absorbing and distributing moisture, supplying animals with oxygen and plants with carbonic acid, the atmosphere plays an important 'part in the economy of the earth. Meteorology is the science which treats of the atmosphere and its phenomena. Section I. THE ATMOSPHERE. >o>. Sea, in Miles. 30.00 1 1 0.0 15.00 2 i 3.4 7.50 4 i 6.8 3.75 8 i 10.2 1.87 16 irV 13.6 .93 32 £ 17.0 It appears from the above table that by far the greater part of the air by weight lies within a few miles of the surface, nearly three-fourths being below the level of the summits of the highest mountain-ranges. The height of the upper limit of the atmosphere has been variously estimated. Calculations based upon the diminution of pressure with the height, place it at from 45 to 50 miles above the level of the sea ; others, based on the duration of twilight, place it at distances varying from 35 to 200 miles. The form of the atmosphere is that of an ob- late spheroid, the oblateness of which is greater than that of the earth. CLIMATE. 87 By carefully observing the decrease in pressure with the elevation, at different altitudes, and making proper correc- tions, the heights of mountains can be readily determined by the barometer. The measurement of heights by the barometer, or similar means, is called Hypsometry. >XX.c CHAPTER II. Climate. 232. The Climate of a country is the condi- tion of its atmosphere as regards heat or cold. The climate of a country also embraces the con- dition of the air as regards moisture or dryness, and healthiness or unhealthiness, which are de- pendent on the temperature. 233. Temperature. — The temperature of the atmosphere is determined by means of an instru- ment called a thermometer. The thermometer consists of a glass tube of very fine bore, furnished at one end with a bulb. The tube is care- fully dried and the bulb filled with pure mercury and heated in the flame of a spirit-lamp; the mercury expands, and, filling the fine capillary tube, a portion runs out from the open end, thus effectually expelling the air. A blowpipe flame is then directed against the open end and the tube hermetically sealed. As the bulb cools, the mer- cury contracts, and leaves a vacuum in the upper part of the tube. The instrument will now indicate changes in temperature; for, whenever the bulb grows warmer, the column of mercury expands and rises; and when it grows colder, it contracts and falls. In order to compare these changes of level they are referred to certain fixed or standard points: the freezing- and boiling-points of pure water. These are obtained by marking the respective heights to which the mercury rises when the thermometer is plunged into melting ice and into the steam escaping from boiling water. In Fahren- heit's scale the freezing-point is placed at 32°, the boil- ing-point at 212°, and the space between these two points divided into 180, (212 — 32) equal parts, called degrees. In the Centigrade scale the freezing- and boiling-points are re- spectively 0° and 100°. Fahrenheit's degrees are repre- sented by an F., thus, 212° F. ; Centigrade's by a C, as 100° C. 234. Astronomical and Physical Climates. — Astronomical climate is that which would result were the earth's surface entirely uniform and of but one kind : all land or all water. Physical climate is that which actually exists. Since the physical climate is only a modification of the astronomical, we shall briefly review the causes which tend to produce a regular decrease in temperature from the equator to the poles. Astronomical Climate. — The sun is practically the only source of the earth's heat. On account of the earth's spherical shape, those portions of the surface are most powerfully heated which re- ceive the vertical rays, and these are confined to a zone reaching 23° 27' on each side of the equa- tor. Beyond these the rays fall with an obliquity which increases as we approach the poles. 235. Causes of the greater heating power of the vertical rays of the sun than of the oblique rays. lb /« I Fig. 80. Causes of the Greater Heating Power of the Vertical than of the Oblique Kays, (1.) The vertical rays are spread over a smaller area. Equal areas of the sun's surface give off equal quantities of heat. If, therefore, the bun- dle of rays a b, and c d, come from equal areas, the amounts of heat they emit will be equal ; but while the heat given off from a b, the more ver- tical rays, is spread over the earth's surface from /, to g, that from c d, is spread over the greater area h i; the area / g, therefore, which receives the more vertical rays, is much warmer than h i, where the obliquity is greater. (2.) The vertical rays pass through a thinner layer of air. Only a part of the sun's heat reaches the surface of the earth ; about 28 per cent, of the vertical rays are absorbed during their passage through the atmosphere. The amount of this absorption must increase as the length of path increases. In the figure, the light shading represents the atmosphere. It is clear that the oblique rays pass through a thicker stratum of air than the more direct ones, and, therefore, are deprived of a greater amount of heat. According to Laplace, the thickness of the stratum of air traversed by the rays when the sun is at the horizon is 35.5 times greater than when it is directly overhead. A similar absorption of light affects the comparative bright- ness of daylight in different latitudes. (3.) The vertical rays strike more directly, and, therefore, produce more heat. The heating Page 88. CLIMATE. 89 power of the more nearly vertical rays is greater than that of the rays which strike obliquely. 236. Variations in Temperature. — The differ- ences in the heating power of the vertical and ob- lique rays of the sun cause the temperature of the earth's surface to decrease gradually from the equator toward the poles. The differences of tem- perature thus effected are further increased by the difference in the length of daylight and darkness. While the sun is shining on any part of the earth the air is gaining heat ; when it is not shining the air is losing heat. When the length of daylight exceeds that of the darkness, the gain exceeds the loss ; when the darkness exceeds the day- light, the loss exceeds the gain. The excessively low temperatures that would result from the oblique rays in high latitudes are prevented by the great length of daylight during the short summers, thus allowing the sun to con- tinue heating the surface during longer periods. The warmest part of the day in high latitudes sometimes equals that in the equatorial regions. During the long winters, however, the continued loss of heat makes the cold intense. Hence in the tropics we find a continual sum- mer ; in the temperate zones, a summer and winter of nearly equal length; and in the polar zones, short, hot summers, followed by long, intensely cold winters. The true temperature of the air is ascertained by hang- ing a thermometer a few feet above the ground, so as to be shielded from the direct rays of the sun, and yet be in free contact on all sides with the air. 237. Manner in which the Atmosphere re- ceives its Heat from the Sun. — The atmosphere receives its heat from the sun — . (1.) Directly. As the sun's rays pass through the air, about 28 per cent, of the vertical rays are directly absorbed, thus heating the air. The remainder pass on and either heat the earth, or are reflected from its surface. (2.) From the heated earth. The sun's rays heat the earth and the heated earth heats the air. It does this in three ways : (a.) By the air coming in contact with the heated earth. (6.) By the heated earth radiating its heat, or sending it out through the air in all directions. After the sun's heat has been absorbed by the earth and radiated from it, a change occurs which renders the rays much more readily absorbed by the air. (c.) By the heat being reflected from the earth 11 and again sent through the air. But little heat is imparted to the air in this way. It is mainly the aqueous vapor the atmosphere contains that absorbs the sun's heat. Dry air allows the greater part of the heat to pass through it ; therefore variations in the quantity of vapor in the air must necessarily produce corresponding variations in the distribution of heat. 238. Isothermal Lines are lines connecting places on the earth which have the same mean temperature. The Mean Daily Temperature of a place is ob- tained by taking the average of its temperature during twenty-four consecutive hours. The Mean Annual Temperature of a place is the average of its mean daily temperature throughout the year. If the physical climate were the same as the astronomical, the isothermal lines would coincide with the parallels of latitude. An inspection of the map of the isothermal lines shows that their deviations from the parallels, though well marked ip all parts of the earth, are greatest in the north- ern hemisphere. Wherever, from any cause, the mean tem- perature of a place is higher, the isothermal lines are found nearer the poles; ivhen lower, nearer the equator. The former effects are noticed particularly in portions of the ocean traversed by warm currents ; the latter, in crossing por- tions of the ocean traversed by cold currents. In the map of the isothermal lines the influence of elevation is re- moved by adding 1° for every 1000 feet of elevation. 239. Physical Zones.— The Physical Torrid Zone lies on both sides of the equator, between the annual isotherms of 70° Fahr. . The Physical Temperate Zones lie north and south of the Physical Torrid Zone, between the annual isotherms of 70° and 30° Fahr. The Physical Frigid Zones lie north and south of the Physical Temperate Zones, from the an- nual isotherms of 30° Fahr. to the poles. The greatest mean annual temperature in the eastern hemisphere is found in portions of North Central Africa, and in Arabia near the Red Sea, in the southern part of Hindostan, and in the northern part of New Guinea and the neighbor- ing islands; in the western hemisphere, in the northern parts of South America and in Central America. 240. Modifiers of Climate. — The principal causes which prevent the isothermal lines from coinciding with the parallels of latitude are: (1.) The Distribution of the Land and Water Areas. — Land heats or cools rapidly, absorbing or emitting but little heat. This is because the land 90 PHYSICAL GEOGRAPHY. has a small capacity for heat, and also because the heat passes through but a comparatively thin layer. Therefore, a comparatively short exposure of land to heat produces a high temperature, and a comparatively short exposure to cooling, a low temperature. Water heats or cools slowly, ab- sorbing or emitting large quantities of heat. This is because water has a great capacity for heat. The heat penetrates a comparatively deep layer, and then, too, as soon as slightly heated, the warm water is replaced by cooler water. Therefore, the water can be exposed to either long heating or long cooling without growing very hot or very cold. Hence, the land is subject to great and sudden changes of temperature; the water, to small and gradual changes. Places situated near the sea have, therefore, a more equable, uniform climate than those in the same latitude in the interior of the continent. The former are said to have an oceanic climate; the latter, a continental climate. In the polar regions, a preponderance of moder~ ately elevated land areas causes a colder climate than an equal area of water, because land loses heat more rapidly than water. In the tropics, a preponderance of land areas^ causes a warmer climate than an equal area of mUf, because land gains heat more rapidly than water. (2.) The Distribution of the Relief Forms of the Land Masses. (1.) Elevation. — The temperature of the atmo- sphere rapidly decreases with the elevation. The decrease is about 3° Fahr. for every 1000 feet. The increased cold is caused as follows : (1.) Since the air receives so much of its heat indirectly from the earth's surface, the farther we go upward from the surface, the colder it grows. (2.) In the upper regions of the atmosphere the de~ creased density and humidity of the air prevent it from ab- sorbing either the direct rays of the sun, or those reflected or radiated from the earth. The effect of elevation is so powerful that on the sides of high tropical mountains the same changes occur in the vegetation that are observed in passing from the equator to the poles. (2.) Direction of the Slopes. — That slope of an elevation which receives the sun's rays in a direction more nearly vertical than others, will be the warmest. In the northern hemisphere the southern slope of a hill is warmer in winter than the northern slope, because it receives the rays more vertically. (3.) Position of the Mountain-Ranges. — A mountain-range will make the country near it warmer if the wind from which it shields it is cold; it will make it colder if such wind is warm. The position of the mountain-ranges of a country also greatly affects the distribution of its rainfall. Thus, the tropical Andes are well watered and fertile on their east- ern slopes, but dry and barren on their western. The pre- vailing moist trade winds, forced to ascend the slopes, deposit all their moisture on them in abundant showers, and are dry and vaporless when they reach the other side. (4.) Nature of the Surface. — The temperature of a tract of land is greatly affected by the nature of its surface. If covered with abundant vege- tation, like a forest, or if wet and marshy, its sur- face heats and cools slowly, and has a compara- tively uniform temperature ; but if destitute of vegetation, and dry, sandy, or rocky, it both heats and cools rapidly, and is subject to great extremes of temperature. (3.) Distribution of Winds and Moisture. — The principal action of the winds, and their accom- panying moisture, is to moderate the extremes of temperature by the constant interchange between the heat of the equatorial and the cold of the polar regions. Both wind and vapor absorb and render latent large quantities of heat in the equa- torial regions, and give it out, in higher latitudes, on cooling. In cold countries the climate is ren- dered considerably warmer by the immense quan- tity of heat thus emitted by the condensed vapor. (4.) Ocean Currents. — Since the warm waters move to the polar regions, and the cold waters to the equatorial regions, the general effect of ocean currents on climate is to reduce the extremes of temperature. The combined effects of the action of the winds, moisture, and ocean currents are seen in the north- ern continents, whose western shores, under the in- fluence of the prevailing south-westerly winds, copious rains, and tropical currents, are consider- ably warmer than the eastern shores in the same latitude. The coasts of Great Britain are warm and fertile, while Labrador, in the same latitude, is cold and sterile. The island of Sitka, in the Pacific, is warmer than Kamtchatka from similar causes. dXKc CHAPTER III. The Winds. 241. Origin of Winds. — Winds are masses of air in motion. They resemble currents in the ocean, and result from the same causes — differ- THE WINDS. 91 ences of density caused by differences of tem- perature. d * A A b J Fig, 81. Origin of Winds. The equilibrium of the atmosphere is disturbed by differences of temperature as fonows : When any area becomes heated, as at a a, Fig. 81, the air over it, expanding and becoming lighter, is pressed upward by the colder air which rushes in from all sides. Thus result the following currents : ascending currents, b b, over the heated area ; lateral, surface currents, c c, from all sides toward the heated area; upper currents, d d, from the heated area; and descending currents, e e. It is the lateral currents which flow toward or from the heated area that are felt mainly as winds. The ascending currents rise until they reach a stratum of air of nearly the same den- sity as their own, and then spread laterally in all directions toward the areas where the air has been rarefied by the movements of the lat- eral surface currents, until they finally descend, and recommence their motion toward the heated area. These circulatory motions continue as long as the heated area remains warmer than surround- ing regions. In speaking of winds, reference is always made to the surface currents, unless otherwise stated. 242. Origin of the Atmospheric Circulation. — The hottest portions of the earth are, in general, within the tropics ; hence in the equatorial regions ascending currents continually prevail. To sup- ply the partial vacuum so created, lateral sur- face currents blow in toward the equator from the poles, while the ascending currents, after reaching a certain elevation, blow as upper cur- rents toward the poles. Thus result currents by which the entire mass of the atmosphere is kept in constant circulation, and an interchange effected between the air of the equator and the poles. The most important of these currents are the following : (1.) Polar currents, or the lateral surface cur- rents, which flow from the poles to the equator ; and (2.) Equatorial currents, or the upper currents, which flow from the equator toward the poles. It will be noticed that wherever the surface wind blows in any given direction, the upper wind blows in the opposite direction. In several instances the ashes of volcanoes have heen carried great distances in directions opposite to that in which the surface wind was blowing. The smoke from tall chim- neys at first takes the direction of the surface wind, but rising, is soon carried in the opposite direction by the upper currents. The clouds are often seen moving in a direction opposite to that indicated by vanes placed on the tops of the houses. A current of air is named according to the di- rection from which it comes; a current of water, according to the direction in which it .is going. Thus, a north-east wind comes from the north- east ; a north-east current of water goes toward the north-east. 243. Effect of the Earth's Rotation on the Direction of the Wind. — Were the earth at rest, the equatorial and polar currents would blow due north and south in each hemisphere ; but by the rotation of the earth they are turned out of their course in a manner similar to the oceanic currents already studied. The polar currents, as they approach the equa- tor, where the axial velocity toward the east is greater, are left behind by the more rapidly mov- ing earth, and thus come, as shown in Fig. 83, from the north-east in the northern hemisphere, and from the south-east in the southern. The equatorial currents, under the influence of the earth's eastward motion, are carried toward the east as they approach the poles, and thus come, as shown in Fig. 83, from the south-west in the northern hemisphere, and from the north-west in the southern. Wherever the polar winds prevail, their direc- tion, when unaffected by local disturbances, will be north-east in the northern hemisphere, and south- east in the soidhern. Near the equator their di- rection is nearly due east. Wherever the equatorial currents prevail, their direction will be south-west in the northern hemi- sphere, and north-west in the southern. In Fig. 82, the equatorial currents are repre- sented as continuing to either pole as upper cur- rents, and the polar winds as surface currents to the equator. If this were so, constant north-east- erly winds would prevail in the northern hemi- 92 PHYSICAL GEOGKAPHY. 'sa*. Fig. 82. Direction of Wind as Affected by Rotation. Fig. 83. Interchange of the Equatorial and Polar Currents. Wind Zones, sphere, and constant south-easterly winds in the southern. Several causes, however, exist to pre- vent this simple circulation of the air between the equatorial and polar regions. The equatorial currents do not continue as upper currents all the way to the poles, but fall and become surface currents, replacing the polar winds, which rise and continue for a while toward the equator as upper currents. 244. Causes of Interchange of Surface and Upper Currents. — The causes which produce this shifting of the equatorial and polar currents are : (1.) The equatorial currents become cold — (a.) By the cold of elevation ; (b.) By expansion ; (c.) By change of latitude. The equatorial currents therefore fall and are replaced by the polar currents, which have been gradually growing warmer by continuing near the surface of the earth. (2.) As the equatorial currents approach the poles they have a smaller area over which to spread, and, being thereby compressed, are caused to descend and become surface currents. This interchange between the equatorial and polar cur- rents takes place at about lat. 30°. It varies, however, with the position of the sun, moving toward the poles when the sUn is nearly overhead, and toward the equator when the sun is in the other hemisphere. The interchange in the position of the equatorial and polar currents is represented in Fig. 83. As the equatorial currrents fall, they divide, part going to the poles, and part returning to the equator. The general system of the aerial circulation thus indicated is more regular over the oceans than over the land. Over the continents the greater heat of the land during summer causes a general tendency of the wind to blow toward the land ; similarly, the greater cold of the land during winter causes a tendency of the wind to blow toward the sea. 245. Classification of Winds. — Winds are di- vided into three classes: (1.) Constant, or those whose direction remains the same throughout the year. (2.) Periodical, or those which, for regular pe- riods, blow alternately in opposite directions. (3.) Variable, or those which blow in any di- rection. 246. Wind Zones. — The principal wind jzones are the zone of calms, the zones of the trades, the zones of the calms of Cancer and Capricorn, the zones of the variable winds, and the zones of the polar winds. Zone of Calms. — In parts of the ocean near the equator the ascending currents are sufficiently powerful to neutralize entirely the inblowing polar currents, and thus produce a calm, which, however, is liable at any moment to be disturbed by powerful winds. The boundaries of the zone vary with the season ; they extend from about 2° to 11° north latitude. THE WINDS. 93 Zones of the Trades. — From the limits of the zone of calms to about 30° on each side of the equator the polar currents blow with great steadi- ness throughout the year. The constancy in their direction has caused these winds to be named " trade winds," from their great value to com- merce. Their direction is north-east in the north- ern hemisphere, and south-east in the southern. Zones of the Calms of Cancer and Capricorn. — Between the zones of the trades and the vari- ables, where the interchange takes place between the equatorial and polar currents, zones of calms occur. Their boundaries are not well defined, and are dependent on the position of the sun. Zones of the Variable Winds. — Beyond the limits of the preceding zones to near the latitude of the polar circles, the equatorial and polar cur- rents alternately prevail. Here the equatorial and polar currents are continually striving for the mastery, sometimes one and sometimes the other becoming the surface current. During these conflicts the wind may blow from any quarter ; but when either current is once estab- lished it often continues constant for some days. This is especially the case over the ocean, where the modifying influences are less marked. Though the winds in these zones are variable, still two directions predominate : south-west and north-east in the northern hemisphere, and north- west and south-east in the southern. Westerly winds, however, occur the most frequently in nearly all parts of these zones. The equatorial currents are sometimes called the Return Trades, or the Anti-trades, because they blow in the oppo- site direction to the trades. Between about lat. 25° and 40°, N. and S., over parts of the ocean, the winds are nearly periodical, blowing during the hotter portions of the year in each hemisphere from the poles, and during the remainder of the year from the equator. This zone is often called the Zone of the Sub- tropical winds. Polar. Zones. — From the limits of the zones of the variables to the poles, there are regions of pre- vailing polar winds. These winds are most fre- quently north-east in the northern hemisphere, and south-east in the southern. 247. Dove's Law of the Rotation of the Winds.— The equatorial and polar currents usually displace each other, and become surface winds in a regular order, first discovered by Prof. Dove of Berlin. In the northern hemisphere, before the polar current is permanently established from the north-east, the wind blows in regular order from the west, north-west, and north. The displacement of the polar by the equatorial currents occurs in the opposite direction : from the east, south-east, and south, before the general south-west current is perma- nently established. In the southern hemisphere these motions are reversed. This rotation of the winds, together with the effects produced on the thermometer and barometer, is indicated in the following diagram. Since the equatorial currents are warm, moist, and light, when they prevail the ther- mometer rises and the barometer falls. On the establish- ment of the polar currents, however, the thermometer falls and the barometer rises. NORTHERN HEMISPHERE N. SOUTHERN HEMISPHERE. N. Fig. 84. Rotation of the Winds (after Dove). The " warm waves " of the zones of the variable winds are caused by the prevalence of the equa- torial currents. Similarly, the " cold waves " are caused by the prevalence of the polar currents. 248. Land and Sea Breezes. — During the day the land near the coast becomes warmer than the sea. An ascending current, therefore, rises over the land, and a breeze, called the sea breeze, sets in from the sea. At night the land, from its more rapid cooling, soon becomes colder than the water ; the ascending current then rises from the Fig, 85. Land and Sea Breezes. water, and a breeze, called the land breeze, sets in from the land. The strength of these winds de- pends upon the difference in the temperature of the land and water ; they are, therefore, best de- fined in the tropical and extra-tropical regions, though they may occur in higher latitudes during the hottest parts of the year. Land and sea breezes are periodical winds. N^ 249. Monsoons are periodical winds, which dur- ing part of the year blow with great regularity in one direction, and during the remainder of the Page 94 THE WINDS. 95 year in the opposite direction. They are in real- ity huge land and sea breezes, caused by the dif- ference in temperature between the warmer and colder halves of the year. They occur mainly in the regions of the trades, and are in reality trade winds which have been turned out of their course by the unequal heating of land and water. During winter, in either hemisphere, the oceans, being warmer than the land, cause a greater regularity in the trades; but during summer, the tropical continents become intensely heated, and their powerful ascending currents cause the equa- torial currents to blow toward the heated areas as surface winds, and thus displace the trades. The interval between the two monsoons is gener- ally characterized by calms, suddenly followed by furious gales, that may blow from any quarter. 250. Monsoon Regions. — There are three well- marked regions of monsoons — the Indian Ocean, the Gulf of Guinea, and the Mexican Gulf and Caribbean Sea. The first is the largest and most distinctly marked. Monsoons of the Indian Ocean. — Here the trades are deflected by the overheating of the continents of Asia, Africa, and Australia. In the northern hemisphere the north-east trades prevail with great regularity over the Indian Ocean during the cooler half of the year : from October to April, but during the warmer half: from April to October, the heated Asiatic continent deflects the trades, and the equatorial currents prevail from the south-west. The same winds also pre- vail south of the equator, on the western border of the ocean, along the eastern coast of Africa as far south as Madagascar. In the southern hemisphere, in the south-eastern portion of the ocean, the south-east trade is similarly deflected by the Australian continent. Here the winds blow south- east during the southern winter, and north-west during its summer. Monsoons of the Gulf of Guinea. — Here the north-east trades are deflected by the intensely heated continent of Africa. The south-west sum- mer monsoon blows over the land as far inland as the Kong Mountains. Monsoons of the Mexican Gulf and Caribbean Sea. — In this region the north-east trade winds are deflected by the overheating of the Missis- sippi Valley. The Northers of Texas, which are cold winds blowing for a few days at a time over the Texan and Mexican plains, may be considered as connected with the winter monsoons. Besides the preceding well-marked regions, nearly all the coasts of the continents in and near the tropics have small monsoon regions, as, for example, the western coasts of Mexico, the eastern and western coasts of South Amer- ica, and the western and northern coasts of Africa. >t • 251. Desert Winds. — The rapid heating and cooling of deserts make them great disturbers of the regular system of winds. Currents al- ternately blow toward and from the heated area. The latter are intensely hot and dry. The Etesian Winds. — During summer the barren soil of the Desert of Sahara, becoming intensely heated, causes strong north-east winds to blow from the north over the Mediterranean Sea, These are called the Etesian winds, and continue from July to September ; they are strongest dur- ing the daytime. Hot Desert Winds. — From the Sahara a period- ical wind, called the Harmattan, blows on the soidh- west, over the coasts of Guinea ; on the north, the Solano blows over Spain, and the Sirocco blows over Southern Italy and Sicily. Though some- what tempered during their passage across the Mediterranean, these winds are still exceedingly hot and oppressive. From the deserts of Nubia and Arabia in- tensely hot, dry winds blow in all directions over the coasts of Arabia, Nubia, Persia, and Syria. These winds are known under the general name of the simoom or samiel. From their high tem- perature and the absence of moisture, they often cause death from nervous exhaustion. During the prevalence of the simoom, particles of fine sand are carried into the atmosphere and obscure the light of the sun. Becoming intensely heated, these particles, by their radiation, increase the temperature of the air, Fig. 86, Sand Storm in the Desert. which sometimes rises as high as 120° or 130° Fahr. When powerful winds prevail, dense clouds of sand are carried about in the atmosphere, producing the so-called sand storms. The sand-drifts which are thus formed constantly change their position. 96 PHYSICAL GEOGRAPHY. The Khamsin blows at irregular intervals over Egypt from the south ; but when established, generally continues for fifty days. It is intensely hot and dry, like the simoom, and is loaded with fine sand. 252. Mountain Winds. — During the day the elevated slopes of mountains heat the air over them hotter than at corresponding elevations over the valleys. Currents, therefore, ascend the val- leys toward the mountains during the day. During the night, however, the air near the summits be- comes colder than that near the base. Currents, therefore, descend the valleys from the mountains during the night. oo^oo CHAPTER IV. Storms. 253. Storms are violent disturbances of the ordinary equilibrium of the atmosphere by wind, rain, snow, hail, or thunder and lightning. During storms the wind varies in velocity from that of a scarcely perceptible breeze to upwards of 200 miles per hour. Velocity and Power op Winds. Velocity of Wind in Miles, per hour. Common Names of Winds. 1 4 to 5 Hardly Perceptible Breeze. Gentle Wind. 10 to 15 Pleasant Brisk Gale. 20 to 25 30 to 35 40 50 Very Brisk. High Wind. Very High. Storm. 60 Great Storm. 80 Hurricane. 100 Violent Hurricane. 80 to 200 Tornado. 254. Cyclones are storms of considerable ex- tent, in which the velocity of the wind is much greater than usual, and the air moves in eddies or whirls, somewhat similar to whirlwinds, but of vastly greater power and diameter. In all such storms the wind revolves around a calm centre ; over the calm centre the barometer is low, but on the sides, and especially on that side toward which the storm is moving, it is high. Besides the rotary motion of the wind, there is also a progressive motion, which causes the storm to advance bodily, moving rapidly in a parabolic path. The general term Cyclone has been ap- plied to these storms on account of their rotary motion. They have also various local names. Cyclones originate in the tropical regions, but frequently extend far into the temperate zones. Fig. 87. A Storm at Sea. 255. Regions of Cyclones. — The following are the most noted regions : The West Indies, where they are generally called hurricanes. The China Seas, where they are known as typhoons. The Indian Ocean. In each of these regions the storms occur about the time of the change of the regular winds, and have their origin in marked differences of tem- perature ; thus in the Indian Ocean and the China Seas, they generally occur at the change of the mon- soon, after the great heat of summer. They are at- tended with the condensation of moisture and in- tense electrical disturbance. 256. Cause of Cyclones. — Cyclones originate in an area of low barometer caused by the ascending current of air that follows the overheating of any region. As the air rushes in from all sides it is deflected by the earth's rotation, and assumes a rotary or whirling motion around the heated area. The centrifugal force generated by this rotation causes the barometric pressure of the area to be- come lower and the area to grow larger. Mean- while the inflowing air, ascending, is chilled by the cold of elevation and by expansion sufficiently to condense its vapor rapidly. The heat energy, previously latent in the vapor, is now disengaged, and causes the air to mount higher and condense still more of its vapor. It is to the energy thus rapidly liberated by the condensation of the vapor that the violence of the cyclone is due. Cyclones, therefore, acquire extraordinary violence only when an abundance of vapor is present in the air. STORMS. 97 As the inblowing winds come near the heated area, they must blow with increased violence in order to permit the same quantity of air to pass over the constantly narrowing path. Besides the rotary motion of the wind, the storm moves or progresses over a parabolic path, which in the tropics is generally toward the west, and in the temperate zones toward the east. This progressive motion of the storm is like the similar January Fig. 88. Chart showing Path and Direction of Cyclone, motion often noticed in a rapidly spinning top. It is due to the combined influences of the inrush of air, the earth's rotation, and centrifugal force. 257. Peculiarities of Cyclones. — Cyclones rage most furiously in the neighborhood of islands and along the coasts of continents. They are most powerful near their origin. As they advance the spiral increases in size and the fury of the wind gradually diminishes, because the amount of moist- ure in the air is less. The rotarv motion varies from 30 to 100 miles an hour. The progressive motion of the calm centre is more moderate — from 20 to 50 miles an hour. This progressive motion is least in the tropics and greatest in the temperate regions. The wind invariably rotates in the same direc- tion in each hemisphere ; in the northern, it ro- tates from right to left, or in the direction oppo- site to that of the hands of a watch ; in the south- ern, from left to right, or in the same direction as the hands of a watch. The cause of the regu- NOBTHBEN HEMISPHERE. \ I / '*I*\ 01 y^ SOUTHERN HEMISPHERE. / \ \ / V. -4--... *1{%\1 o\ / I X Fig. 89. Canse of the Rotation of the Wind. larity of rotation is seen, from an inspection of Fig. 89, to be due to the rotation of the earth. The wind, blowing in from all sides toward the heated area, is so deflected by the rotary motion of the earth as to move in vast circles, from right to left in the northern hemisphere, and from left to right in the southern. The force of the wind in these storms is tremendous. So furiously does the wind lash the water that its tem- perature is often sensibly raised by the friction. The intelligent navigator always endeavors to avoid the centre of the storm, since it is the most dangerous part. This he can do by remembering the direction of the rota- tion of the wind in the hemisphere he may be in ; for if, in the northern hemisphere, he stands so that the wind blows directly in his face, the calm centre is on his right, while in the southern hemisphere it is on his left; and in- stead of running with the storm, hoping to outsail it, he will boldly steer toward its circumference. 258. Tornadoes and Whirlwinds are the same as cyclones, except that they are more limited in area. Their violence, however, often exceeds that -# 98 PHYSICAL GEOGRAPHY. of cyclones. Tornadoes appear to be due to ro- tary motion of the air occurring above the earth's surface, which results in a rapid sucking up of the warmer surface air. 259. Water-spouts. — When tornadoes or whirl- winds occur on the water they cause a water-spout. A rapid condensation of vapor takes place, both from the different temperature of the winds and from the rarefaction produced at the centre of the revolving mass of air. Portions of the clouds are sometimes drawn down from above and whirled around in the form of an immense funnel-shaped mass ; finally the whirl reaches the water, and a column of spray is thrown up, which unites with the mass above and moves over the surface of the water as an immense pillar. Though of formidable ap- pearance, water-spouts have never been known seriously to damage large vessels. Similar phenomena are noticed on the land when tornadoes occur. Here, however, only the cloud cone is observed. 260. The North-Easters and other Storms of the United States. — The following important facts have been discovered in regard to the extended storms which occur in the United States: (1.) All our great storms are attended by an immense whirling of the wind, and are, in fact, species of cyclones. (2.) The great north-east storms of our eastern sea-board originate in the west, in an area of low barometer, somewhere between Texas and Minne- sota. In the front and rear of this area the ba- rometer is high. (3.) The calm centre of the storm, or the area of low barometer, moves toward the north-east. The shape of the calm centre is longer from north to south than from east to west. (4.) The storms begin by the winds blowing toward the area of low barometer. (5.) During the prevalence of the storm the winds are north-east, east, or south-east ; toward the end, north-west, west, and south-west. 261. Sailing Routes. — A knowledge of the di- rections of the winds and ocean currents has ma- terially diminished the time required by sailing vessels to go from one port to another. Opposing winds and currents often render it advisable for the vessel to begin its journey in a direction consider- ably out of the direct line of the desired port. Europe— America.— The Gulf Stream and prevailing westerly winds render the passage across the ocean from east to west considerably longer than from west to east. The general route, in either direction, varies with the season of the year. New York — San Francisco. — After leaving New York the course is considerably to the east, in order to clear the South American coast in the region of the trades. After doubling Cape Horn the course is westward. The zone of the north-east trades is entered about 118° W. long. America— India— Australia.— In sailing from Amer- ica to India or Australia the vessel takes the same route as between Eastern America and San Francisco. About opposite Eio Janeiro, however, the routes diverge. On entering the Indian Ocean the direction is dependent on that of the prevailing monsoon. Europe— India— Australia.— The vessels either pass through the Mediterranean Sea and the Suez Canal, or around the Cape of Good Hope. The broad expanse of ocean in the southern hemisphere, in the zone of the vari- ables, renders the westerly winds very steady. Vessels sail- ing from Atlantic ports of America or Europe generally find it preferable to go by the eastward route, around the Cape of Good Hope, and return by the westward route, around Cape Horn, thus circumnavigating the globe. California — Japan. — The southerly route, from east to west, is aided by the north-east trades and the north equa- torial current of the Pacific ; the northerly route, from west to east, is necessary in order to avoid the trade winds. The general sailing routes between some of the most important ports are traced on the map of the winds. SYLLABUS. —o^c Atmospheric air is composed mainly of a mixture of ni- trogen and oxygen, in the proportion, by weight, of about 77 parts of nitrogen to 23 of oxygen in every hundred parts. The atmosphere also contains small quantities of carbonic acid and the vapor of water. The oxygen of the air is necessary to combustion and respiration ; the carbonic acid and the vapor of water, to plant-life. At the level of the sea the atmosphere presses on every square inch of the earth's surface with a force of about 15 pounds. The upper limit of the atmosphere has been variously estimated at from 50 to 200 miles above the level of the sea. A barometer is used for measuring the pressure of the at- mosphere ; a thermometer, for measuring its temperature. The vertical rays of the sun are warmer than the oblique rays — 1. Because they are spread over a smaller area of the earth. 2. Because they pass through a thinner stratum of air, and consequently lose less of their heat by absorption. 3. Because they strike the earth more directly, and there- fore produce more heat. REVIEW QUESTIONS. 99 Continual summer is found in the tropics ; summer and winter of nearly equal length in the temperate zones; short, hot summers, followed by intensely cold winters, in the polar zones. The atmosphere is heated — 1. Either by direct absorp- tion of the rays while passing through it; or 2. By con- tact with, or by radiation and reflection from, the heated earth. Isothermal lines connect places whose mean temperature is the same. The mathematical zones are bounded by the parallels of latitude; the physical zones, by the isotherms. The mathematical and physical zon«s do not coincide — 1. Because of the unequal distribution of the land and water areas. 2. The irregularities in the surface of the land. 3. The distribution of the winds and moisture. 4. The ocean currents. 5. The difference in the rainfall. The temperature of the air decreases with the altitude — 1. Because the air receives most of its heat from the earth's surface, so that it must grow continually colder the farther we go above the surface. 2. The decreased den- sity and humidity of the air prevent it from absorbing either the direct rays of the sun or those reflected or ra- diated from the earth. Places situated near the sea have a more equable, uni- form climate than those in the same latitude in the inte- rior of the continent. Whenever any part of the earth's surface is heated more than the neighboring parts, ascending currents occur over the heated area, lateral surface currents blow in toward the heated area, and upper currents blow from the heated area. The general system of the atmospheric circulation con- sists mainly of the following currents : 1. The polar cur- rents, blowing from the poles toward the equator. 2. The equatorial currents, blowing from the equator toward the poles. The direction of these currents is modified by the rota- tion of the earth. Thus modified, the equatorial currents are south-west in the northern hemisphere, and north- west in the southern. The polar currents are north-east in the northern hemisphere, and south-east in the south- ern. When a wind at the surface blows in any direction, there is generally an upper current blowing in the opposite di- rection. The equatorial currents do not continue as upper cur- rents to the poles — 1. Because they become cooled and fall. 2. From the contracted space of the higher latitudes when compared with that of the equator. We distinguish the following wind zones: the zone of calms ; the zones of the trades ; the zones of the calms of Cancer and Capricorn ; the zones of the variables ; and th« zones of the polar winds. Land and sea breezes are caused by the unequal heating of the land and water during day and night; monsoons, by their unequal heating during summer and winter. Monsoons occur on the coasts of tropical countries within the limits of the trade zones. They are most frequent in the Indian Ocean, in the Gulf of Guinea, and in the Mex- ican Gulf and neighborhood. The Etesian Winds blow over the Mediterranean toward the Desert of Sahara. The Hot Winds caused by the deserts of Sahara and Arabia are the Harmattan, over Guinea; the Solano, over Spain ; the Sirocco, over Italy ; the Simoom, over Arabia, Nubia, and Persia; and the Khamsin, over Egypt. In most mountainous regions winds blow up the valleys toward the mountains during the day, and down the val- leys from the mountains during the night. Cyclones are caused by the wind blowing in from all sides toward an area of low barometer caused by the overheating of the area. The centrifugal force thus gen- erated increases both the size of the area and the differ- ence of pressure as compared with regions surrounding it. The fury of the storm is increased by the heat energy liberated by the condensation of the vapor in the uprush- ing air. Storms occur whenever the ordinary equilibrium of the atmosphere is violently disturbed by wind, rain, snow, hail, or thunder and lightning. Nearly all powerful storms are attended with a rotation of the wind. Such storms are known under the general names of Cyclones, Hurricanes, Typhoons, and Tornadoes. The north-easters and other great storms of the United States are species of cyclones. REVIEW QUESTIONS. -oo^c Of what use is the atmosphere in the economy of the earth ? Define meteorology. Describe the construction of a barometer. What proof have we that the greater part of the atmo- sphere, by weight, lies within a few miles of the earth's surface? Define hypsometry. Describe the construction of a thermometer. Why are the vertical rays of the sun warmer than the oblique rays? What is the characteristic climate of the tropics? Of the temperate regions? Of the polar regions? In what different ways does the atmosphere receive its heat from the sun ? State the boundaries of the mathematical torrid zone. Of the physical torrid zone. Of the mathematical and physical temperate zones. Of the mathematical and phys- ical frigid zones. 12 In what parts of the eastern hemisphere is the greatest mean annual temperature found? In what parts of the western hemisphere? What influence is produced on the climate of high lati- tudes by a preponderance of moderately elevated land masses? On the climate of the tropics? Why should the temperature of the atmosphere decrease with the altitude ? Name all the causes which prevent the mathematical climatic zones from coinciding with the physical climatic zones. What is the origin of winds? Name the currents of which the atmospheric circulation principally consists. Explain the action of the rotation of the earth on the direction of the equatorial and polar currents. Name the causes which produce the shifting of the equa- torial and polar currents. 100 PHYSICAL GEOGRAPHY. Name the principal wind zones of the earth. Explain, in full, the origin of land and sea breezes. In what respect do monsoons resemble land and sea breezes ? Name the principal monsoon regions of the earth. Describe the origin of desert winds? Name the winds which are caused by the desert of Sa- hara. By the deserts of Arabia and Nubia. What are storms ? What are cyclones? Where do they originate? In what direction does the wind rotate in the northern hemisphere? In the southern hemisphere ? In what di- rection does the storm progress in each hemisphere? Ex- plain the cause of the rotation of the wind. What are hurricanes? Typhoons? Explain the formation of a water-spout. Is the water in the upper part of a water-spout salt or fresh ? Name the important facts which have been discovered respecting the north-easters and other severe storms of the United States. MAP QUESTIONS. ->»4c Trace on the map of isothermal lines the areas of great- est heat in the eastern hemisphere. In the western hemi- sphere. Show from the map of the isothermal lines wherein the physical torrid zone differs in position from the mathematical torrid zone. In which hemisphere do the isothermal lines deviate more from the parallels of latitude, in the northern or the southern? • Trace on the map of the isothermal lines the limit of the Arctic drift ice. Of the Antarctic drift ice. What are the mean summer and winter temperatures of Sitka? Of Quebec? What causes exist to render the climate of Sitka so much warmer than that of Quebec, notwithstanding the difference of their latitudes? What are the mean summer and winter temperatures of Mexico, Madras, Singapore, Berlin, London, Philadelphia, Algiers, Melbourne, and Eio Janeiro? What instances can you find on the map of the in- crease in the mean annual temperature of places through the influence of ocean currents? Of winds? Of rain- fall? Name similar instances of places whose mean annual temperature is lowered by such causes. Trace on the map of the winds the boundaries of the various wind zones. State the direction of the wind in each of these zones. Point out the limits of the monsoon regions of the world. What hot winds blow over Arabia? Over Egypt? Over Greece and Italy ? Over Guinea? What cold wind blows over Texas? Describe the path of the West India hurricanes. How far to the north do these storms extend ? Describe the path of the Mauritius hurricanes. Where do these storms originate ? How far to the south do they extend ? Describe the region of the typhoons. Describe the route a vessel would take in sailing from America to Europe. From New York to San Francisco, From America to Australia. PRECIPITATION OF MOISTURE 101 Section II. MOISTURE OF THE ATMOSPHERE. ->oXKc CHAPTER I. Precipitation of Moisture. 262. Evaporation. — From every water surface, and even from masses of ice and snow, there is constantly arising, at all temperatures, an invisible vapor of water. Water vapor is about three-fifths as heavy as air. It diffuses readily through the air, and is borne by the winds to all parts of the earth. This giving off of vapor from the surface of water is called evaporation. It is evaporation which dries the wet earth, when the moisture is unable either to pass off the earth's surface by drainage, or to soak through the porous strata. About one-half, by weight, of the vapor of the atmo- sphere is within a little over a mile above the mean sea level. 263. The Rapidity of Evaporation is influ- enced by the following circumstances: (1.) The temperature of the atmosphere. The capacity of the air for absorbing moisture in- creases with an increase of temperature. Warm air can retain more vapor than cold air. (2.) The extent of surface exposed. Evapora- tion takes place only from the surface ; therefore, the greater the surface, the greater the evapora- tion. (3.) The quantity of vapor already in the air. Dry air absorbs moisture more rapidly than moist air. All evaporation ceases when the air is com- pletely saturated. (4.) The renewal of the air. During very calm weather, the air in contact with a water surface becomes saturated, and so prevents further evapo- ration. Gentle breezes, by renewing the air, in- crease the rapidity of evaporation. (5.) Pressure on the surface. A diminished atmospheric pressure increases the rapidity of evaporation. 264. The Dew Point. — When the air contains as much vapor as it is capable of holding, it is said to be at its dew point. The quantity of moisture necessary to saturate a given quantity of air and bring it to the dew point, varies with the temperature. Cold air requires less moisture to satu- rate it than air which is warmer, and, therefore, may feel damper than warm air, which may contain more vapor. We thus distinguish between the actual humidity, or the amount actually present in a given volume of air, and the relative humidity, or the relation between the amount present and that required to saturate the air at the given temperature. The humidity of the air is determined by means of an instrument called a hygrometer. Weight in grains of aqueous vapor in one cubic foot of satubated AIR at different temperatures. (Silliman.) Temperature, Fahr. Weight in Grains. Approximate Values. 0° « 0.545 0.6 10° 0.841 0.9 20° 1.298 1.3 7* 30° 1.969 2.0 40° 2.862 2.9 50° 4.089 4.1 60° 5.756 5.8 70° 7.992 8.0 80° 10.949 11.0 . 90° 14.810 15.0 100° 19.790 20.0 No matter how much aqueous vapor a given quantity of air contains, if its temperature be lowered, it will grow relatively moister until, if the fall of temperature be sufficient, its dew point is reached; and as soon as the temperature falls below the dew point, a deposition of moisture will begin, either in the liquid or solid state. 265. Precipitations. — The invisible vapor may be precipitated from the atmosphere and become visible, either as dew, mist, fog, cloud, rain, sleet, hail, or snow. These are called precipitations. Law of Precipitations. In order that any precipitation may occur, the air must be cooled below the temperature of its' dew point. 266. Distribution of Precipitations. — The quan- tity of moisture in the air depends on its tempera- ture, and its vicinity to the sea. The amount of precipitation regularly decreases as we pass from the equator to the poles, and from the coasts of the continents toward the interior. 267. Dew. — If, during a warm day, a dry glass be filled with cold water, the outside of the glass will soon become covered with small drops of water, derived entirely from the air. The air 102 PHYSICAL GEOGRAPHY. which comes in contact with the cool sides of the glass has its temperature lowered below the dew point, and deposits as vapor the moisture it no longer can retain. The dew which is deposited during certain sea- sons of the year on plants and other objects on the earth, has a similar origin. Objects on the earth cool more rapidly than the surrounding air, which deposits its moisture on them whenever they lower its temperature below the dew point. When the objects are colder than 32° Fahr., the dew is deposited as hoar-frost. Dew falls more heavily on some objects than on others ; this is because some objects radiate or give off their heat more rapidly than others, and thus becoming cooler, they condense more of the moisture of the air. More dew falls during a clear night than during a cloudy one, because objects cool more rapidly when the sky is clear than when it is cloudy. Thick clothing keeps the body warm, not because the clothes give any heat to the body, but because they are non- conductors, and prevent the escape of heat from the body. In like manner the clouds, acting as blankets to the earth, prevent its losing heat rapidly. More dew falls during a still night than during a vrindy one. The air must remain long enough in contact with cold objects to enable them to lower its tem- perature and collect its moisture. Powerful winds prevent this, while gentle breezes favor the depo- sition, by bringing fresh masses of air into contact with the cold objects. In the tropics, during seasons when the sky is clear, the dew is so copious that it resembles a gentle rain. In the deposition of dew, the moisture is derived from a comparatively thin stratum of air in the immediate neigh- borhood of the cool object. All other kinds of precipita- tions are produced by the cooling of a large mass of air. 268. Fogs and Clouds. — Whenever the tem- perature of a large mass of air is reduced below its dew point, its moisture begins to collect in minute drops, which diminish the transparency of the air, and form fogs or mists, when near the surface, and clouds, when in the upper regions of the atmosphere. Fogs and clouds are the same in their origin and composition, and differ only in their elevation. The minute drops of water that form clouds and fogs, though formed of a substance about eight hundred times heavier than air, are pre- vented from settling rapidly by the resistance of the air. This is rendered possible by the minute size of the drops, which are much smaller than the relatively heavier dust-particles, which are wafted about by the winds. Whenever the drops exceed a certain size, they fall as rain or snow. It was once believed that the moisture in fogs and clouds existed in the form of hollow bubbles or vesicles, filled with air, and that the clouds or fogs ascended, whenever the contained air expanded the bubbles and rendered them specifically lighter. This idea is now generally abandoned. Clouds or fogs result whenever a mass of air is cooled below the temperature of its dew point, as, for example, when two bodies of air of dif- ferent temperatures are mingled, especially if, as is generally the case, the warmer of the two is the moister. On the contrary, clouds or fogs disappear on the approach of a dry, warm wind. Clouds are higher in the tropics than in the polar regions, and generally are higher during the day than during the night. Off the banks of Newfoundland, the warm, moist air of the Gulf Stream is cooled by the cold, moist air of the Labrador ocean current. Hence result the dense fogs so frequent over this part of the ocean. 269. Classification of Clouds. — Clouds assume such a variety of shapes, that it is difficult to classify them. Meteorologists, however, have rec- ognized the existence of four primary forms : the cirrus, the cumulus, the stratus, and the nimbus. Fig. 90. Primary Forms of Clouds. ■v Cirrus, -v -v- Cumulus. The Cirrus Cloud consists of fleecy, feathery masses of condensed vapor, deposited in the higher regions of the atmosphere. The name cirrus is derived from the resemblance the cloud bears to a lock of hair. These clouds are called PRECIPITATION OF MOISTURE. 103 by sailors cats' tails or mares' tails. From their elevation, the moisture is, probably, generally in the condition of ice-particles. Halos, or circular bands of light around the sun, are caused by light passing through cirrus clouds. The Cumulus, or Heap Cloud, is a denser cloud than the cirrus, and is formed in the lower re- gions of the air, where the quantity of vapor is greater. Cumulus clouds generally consist of rounded masses, in the shape of irregular heaps, with moderately flat bases. They are caused by ascending currents of air, which have their moist- ure condensed by the cold produced by expan- sion and elevation. Cumulus clouds occur dur- ing the hottest part of the day. Their height seldom exceeds two miles. Fig, 91. Primary Forms of Clouds. ■v Nimbus, -v -v Stratus. The Nimbus, or Storm Cloud, is any cloud from which rain falls. Any of the various forms of clouds may collect and form a nimbus cloud. The nimbus is not considered as a distinct form of cloud by some meteorologists. The Stratus, or Layer Clouds, form in long, horizontal sheets or bands. These clouds are most common in the early morning and evening, when the ascending currents are weak. They are caused by the gradual settling of cumulus and other clouds. The stratus is the lowest form of cloud ; it sometimes falls to the surface of the earth, and becomes a fog. The cirrus, stratus, and cumulus clouds assume a variety of shapes, producing various secondary forms. 270. Secondary Forms of Clouds. — The cirro- stratus, the cirro-cumulus, and the cumulo-stratus are the most prominent secondary forms of clouds. The first two are modifications of the cirrus cloud ; the latter, of the cumulus. Fig, 92. Secondary Forms of Clouds. •v-Cirro-Cumulus. -v -vCirro-Stratus. -v--v-*-Cumulo-Stratus. The Cirro-Cumulus is a cirrus cloud, arranged in little rounded masses, shaped something like cumuli. They are sometimes called " wool sacks," and indicate dry weather. The Cirro-Stratus is a cirrus cloud which has settled in bands or layers. The bands are not continuous, but are arranged in blotches or bars, and often give to the sky the speckled appear- ance of a mackerel's back, producing the so-called mackerel sky. The appearance of a mackerel sky indicates — 1. That the moisture of the upper strata of air is condensing; 2. That it is growing dense enough to arrange itself in layers. Therefore, a mackerel sky generally indicates approaching rain. The Cumulo-Stratus is the form produced by the heaping together of a mountain-like mass of cumulus clouds ; the base partakes of the nature of the stratus cloud, but the top clearly resembles cumuli. These clouds differ but little from the nimbus, or storm cloud. 271. Rain. — When, during the formation of a cloud, the condensation of moisture continues, the drops of which the cloud is composed increase in size, and, uniting, fall to the earth as rain. Rain which freezes while falling forms sleet. As 104 PHYSICAL GEOGRAPHY. the drops fall through the cloud they grow larger by the addition of other drops which unite with them. Raindrops, therefore, are larger when the clouds are thicker. They are, in general, larger in the tropics than in the polar regions, and dur- ing the day than at ni^ht. To produce rain, it is necessary that the tem- perature of a large mass of air be reduced con- siderably below its dew point There are several ways in which this cooling may be effected : (1.) By a change of latitude. A warm, moist- ure-laden wind may blow into a cold region. The equatorial currents of air deposit their moisture in the temperate and polar zones on account of the chilling experienced as they recede from the equator. (2.) By a change of altitude. By an ascending current of air, which carries the moisture of the lower strata into the upper regions, where the cold there existing, together with that produced by the rapid expansion of both air and vapor under the diminished pressure, condenses the moist- ure of the air. It is mainly in this manner that the rains of the tropical regions are caused. The rain in mountainous districts has a similar cause. A moist wind, reaching a mountain-range, is forced by the wind back of it to ascend the slopes. Contact with the cold, upper slopes causes condensation of the vapor as rain. (3.) The mingling of masses of cold and warm air. By this means heavy clouds and a moderate rainfall may be produced ; but the precipitation can never be considerable, because the cooler air will be warmed by the mixing, and, therefore, will have its capacity for moisture increased in- stead of diminished. 272. Distribution of the Rainfall.— The dis- tribution of rain may be considered both as re- gards its periodicity and its quantity. The distri- bution of the rain is dependent upon the direction of the winds. Each wind zone has a character- istic rainfall. The following simple principles determine the rainfall in any particular wind zone: (1.) The equatorial currents are rain-bearing, because they are moist, and while on their way to the poles, their temperature and consequent capacity for moisture, is constantly decreasing. (2.) The polar currents are dry, because they are constantly increasing in temperature as they approach the equator ; hence they take in, rather than give out, moisture. When they have reached the zones of the trade winds, the polar currents may bring abundant rains, provided they have previously crossed an ocean. They then dis- charge the moisture with which they are saturated, either by an ascending current, or by blowing against the ele- vations of the continent. 273. Periodical Rain Zones. The Zone of Calms. — In the zone of calms it rains nearly every day. In the early morning the sky is cloudless ; but near the middle of the day, as the heat increases, the ascending currents, rising higher, begin to condense their moisture; cumuli clouds form, and, increasing rapidly, soon cover the sky, when torrents of rain descend, ac- companied by thunder and lightning. After a few hours the rain ceases, and the sky again be- comes clear. In this zone it seldom rains at night. 274. The Zone of the Trades. — Since the trades are generally dry winds, it is only when their tem- perature is considerably decreased that they can cause rain. In the zone of the trades, except in mountainous districts and on the windward coasts of a continent, the rainfall occurs during the greatest heat of the season, when the sun is di- rectly overhead and the ascending currents are powerful. Hence, it rains during a few months in summer, when immense quantities of water fall ; the remainder of the year is dry. Copious dews, however, occur at night. The precipitation is not continuous throughout the en- tire summer. Since the rain only falls when the sun is nearly overhead, a brief interval of dry weather occurs in regions near the equator, thus dividing the season into two parts : one, during the passage of the sun over the zenith; the other, on his return to the zenith from the adjacent tropic. Near the limits of the zone, however, the two seasons are merged into one. Over the ocean, during most of the year, there is no rain in the zone of the trades, although the actual humidity of the .air is quite high. Between latitude 24° and 30°, in both the Northern and Southern Hemispheres, there are regions of comparatively scanty rains. Here the summers are not hot enough to cause rain by the ascending currents, but are sufficiently hot to prevent the equatorial current from bringing much rain. Here also the return branch of the equatorial cur- rent becomes drier on its return to the equator. 275. The Monsoon Region of the Indian Ocean. — During the prevalence of the winter monsoon, the north- east winds bathe the eastern shores of Hindostan in copious rains, while the western shores, shielded by the ranges of the Ghauts, are dry. During the summer monsoon, the south-west winds bathe the western shores and the south- ern slopes of the Himalayas in heavy rains, while the eastern shores are dry. This monsoon also brings rains to the western coasts of the peninsula of Indo-China. PRECIPITATION OF MOISTURE. 105 276. Non-Periodical Rain Zones. The Zones of the Variable Winds. — In these zones rain may occur at any season of the year, and at any hour of the day or night. Here it is the equatorial currents which bring the rain. These regions are sometimes called the zones of perennial rains, or of constant precipitation. In the greater part of these zones, the equatorial currents are more frequent in summer than in winter. The rainfall is, therefore, greatest dur- ing summer. Rainfall in the Zone of the Polar Winds. — In these zones the winters are dry, because the dry, cold polar currents then prevail ; but during the summer the equatorial currents sometimes pre- vail, and bring with them dense clouds and fogs, accompanied by drizzling rains. The snows occur mainly in spring and autumn. 277. Quantity of Rain. — The quantity of rain which falls in a given time on any area is deter- mined by means of an instrument called the rain- gauge or pluviometer. The rain-gauge is generally constructed in the form of a cylindrical vessel with a horizontal base, surmounted by a funnel-shaped top. A vertical glass tube communi- cates with the bottom of the vessel from the outside, and allows the water to mount in it to the same height as that in the inside. The rain-gauge is placed in an ex- posed position, where it is free from eddies or whirls. If, during any given time, the water in the instrument is one inch deep, then during that time the rainfall over the area equals one inch. In speaking of the rainfall of a country, the moisture which may fall as snow is always included. An inch of rain over a surface a square yard in area equals in weight 46! pounds : on the sur- face of an acre, it is nearly equal in weight to 100 tons. The annual rainfall is distributed, as regards quantity, as follows : Irrespective of the elevations of the surface, more rain falls in the tropics than in the temperate regions, and more in the temperate than in the polar regions. The quantity thus decreases with moderate regularity from the equator toward the poles. This is caused by a similar decrease in the quantities of heat and evaporation. While the amount of rain that falls decreases from the equator to the poles, the number of cloudy or rainy days increases, being greater at the poles than at the equate , More rain falls on the coasts of a continent than in the interior, since near the ocean the winds are moister. That coast of a continent which first receives the prevailing wind has the greatest rainfall. More rain falls in the Northern Hemisphere than in the Southern. This is due to the greater extent of the land-area of the Northern Hemisphere. Mountains receive a heavier rainfall than the plains below, because the moist winds, in order to cross the mountains, are forced to ascend their slopes and thus pass into a colder region of the atmosphere*. Therefore, the sources of rivers are generally found in mountainous districts. Moun- tains are among the most important causes of rain. When the mountains are high, the winds may reach the opposite slopes dry and vaporless. The tropical Andes of South America afford an excel- lent example of this. Plateaus, though higher than plains, receive, as a rule, less rain, because they are generally sur- rounded by mountain chains, which rob the winds of their moisture. Moreover, the air over a pla- teau is warmer than at a corresponding height in the atmosphere, and therefore dissolves, rather than condenses, the moisture. The rainfall of the New World, both in the tropical and temperate regions, is greater than that of the Old ; thus, in the tropics of the New World, 115 inches of rain fall yearly, while the same portions of the Old World receive but 77 inches. In the temperate zones in America the annual rainfall is 39 inches, while in Europe it is but 34 inches. The mean annual rainfall at Philadelphia, according to Prof. Kirkpatrick, is 46.93 inches. The figures are based on observations during 16 consecutive years. The preceding principles find ample illustration in the following tables : Table of Annual Eainfall (H. K. Johnston). Rainfall in the Tropics. OLD WOELD. Inches. Ceylon 91.7 Hindostan, mean of the Peninsula 117.5 Sierra Leone, Guinea 189.6 Macao, China 68.3 Canton 69.2 NEW WOELD. Inches. San Luis de Maranhao, Brazil 280.00 Cayenne, Guiana 116.27 Paramaribo, Guiana 229.20 Grenada, Lesser Antilles 103.41 Havana, Cuba 90.66 106 PHYSICAL GEOGRAPHY. Rainfall in the Temperate Zone. Inches. Madeira 29.82 Sicily 23.55 W. side of Apennines.. 35. 17 E. " " ..26.70 S. " Alps 57.57 N. " " 35.27 Inches. Southern France 23.54 Southern Germany 26.64 Netherlands 26.70 British Islands, Plain..27.00 " " Mts.... 50.00 W. Coast Scandinavia..82.12 Mean Eainfall in Europe in the Temperate Zone 34 inches. AMERICA. Inches. Key West, Florida 35.26 Charleston, S. C 47.60 Washington, D. C 36.30 Marietta, Ohio 34.16 West Chester, Penna 46.89 Cambridge, Mass 38.42 Burlington, Vt 39.44 Eastport, Maine 36.28 New York 36.28 Mean Eainfall in the United States in the Temperate Zone 39 inches. 610 ins. 600 ins. 500 " 400 " 300 " 200 " 100 " 301 ins. 167 ins. 107.6 ins. 82 ins. 46.9 ins. ins. 32 ins. Cherrapon- Mahabulesh- Vera St. Do- Bergen, Philadelphia, Cambridge, British Alexandria, gi, India. war, India. Cruz. mingo. Norway. Penna. Mass. Isles. Egypt. Fig, 93. Comparative Rainfall. (The figures represent the annual rainfall in inches.) 278. Rainless Districts. — In some parts of the world, rain is either entirely absent, or falls only in limited quantities, at long intervals. The most extensive rainless districts are found in the east- ern continent. Desert Belt of the Eastern Continent. — From the western shores of Northern Africa eastward to the Great Kinghan Mountains in Asia, extends an almost uninterrupted belt of desert lands. It includes the great desert of the Sahara, the Ara- bian and Persian Deserts, and the Desert of Mon- golia. The aridity is most absolute in the west, where, in the Sahara and in the desert of Arabia, rain seldom, if ever, falls. Toward the east, in Persia and Mongolia, scanty rains occur, but the country has the appearance of a desert. The cause of this immense desert tract is to be found in the dry trade winds, which blow over most of the region. Having previously crossed the vast continent of Asia as upper currents, they arrive at the deserts dry and vaporless. Even that portion of the region which receives the winds from the Mediterranean has no rainfall, because any clouds that may form, are soon dis- sipated by the hot air of the desert. Persia and Mongolia owe their deserts to their high mountain borders, which rob the clouds of their moisture before they cross the interior pla- teaus. The high system of the Himalayas effect- ually prevents any of the moisture of the south- west currents from penetrating the plateau of Mongolia. Arid tracts occur in the Kalahari desert, in Africa, and near the tropic of Capricorn, in Australia. Desert Belt of the Western Continent. — The desert lands of the Western Continent are more contracted in area. In North America, the largest desert is in the Great Interior Plateau. Here the mountain borders, especially the Sierra Nevada on the west, deprive the interior of rain. The aridity is not absolute, since scanty rains occur over parts of the region. Portions of the penin- sula of California and of the Mexican Plateau also resemble deserts. In South America, on the western slopes of the Andes, between the parallels of 27° and 23° S., is found the desert of Atacama. Here rain never falls, although the ground is occasionally refreshed by mists and dews. The cause of the absence of rain is to be traced to the high Andes, which con- dense all the moisture of the trades on their east- HAIL, SNOW, AND GLACIERS. 107 em slopes, the winds thus arriving dry and va- porless at the western. Cause of Deserts. — Deserts are caused entirely by the absence of moisture. Their soil, though gen- erally finely pulverized, or sand-like, does not dif- fer, save in the absence of vegetable mould, from that of other areas. Thus neither the nature of its temperature, nor its soil, is the cause of the desert of Sahara, since a vigorous vegetation al- ways follows the appearance of Avater, on the suc- cessful boring of an artesian well. It is probably true that deserts, once formed, tend to perpetuate themselves, by the influence their naked surfaces exert on the rainfall. >*k° CHAPTER II. Hail, Snow, and Glaciers. 279. Hail falls when considerable differences of temperature exist between higher and lower strata of air, and the moisture is suddenly con- densed in the presence of great cold. Generally, several layers or bands of dark, grayish clouds are seen. Hail falls most frequently in summer, near the close of an excessively warm day. Structure of the Hailstone. — If a large hailstone be placed on a hot surface until one-half is melted, the struc- ture can be readily examined. Concentric layers, similar to those of an onion, will be noticed, arranged around a central nucleus, sometimes of ice and sometimes of snow, though generally the latter. The stones are more or less oblately spheroidal in shape. Their general weight varies from a few grains to several ounces, but they have been known to weigh several pounds. Fig. 94. Structure of a Hailstone. Origin of Hail.— The cause of hail is not ex- actly understood, and several theories have been framed to account for it. One of these is the Rotary Theory. The wind i3 supposed to rotate as in a cyclone, only the axis of the whirl is horizontal instead of vertical. Two horizontal layers of cloud exist— the upper layer of snow, the lower, of rain. The snowflakes, which form the nu- clei of the hailstones, are caught in the whirl, and dipped 13 in rapid succession into the two clouds, thus receiving al- ternate coatings of ice and snow, until at last they are hurled to the ground. Fig. 95. Kotary Theory of Hail. Thunder and lightning are the invariable attendants of hailstorms, and some authorities have attributed the for- mation of the stones to successive electrical attractions and repulsions of the snowflakes between a snow and a rain cloud. Others have imagined a number of alternate layers of snow and rain, and have attributed the hail- stones to drops of rain falling through the successive clouds. 280. Snow. — When the moisture of the air is condensed at any temperature below 32° Fahr., the vapor crystallizes, and snowflakes are formed. The snowflakes grow, as they fall, by condensing addi- tional moisture from the air. They are larger in mild than in cold weather. Snow-crystals assume quite a variety of forms, but are built up by various groupings of minute rhombohedrons of ice. The star-shape is the most common. Fig. 96. Snow-Crystals. If the temperature of the air near the surface is much warmer than 32° Fahr., any snow that is formed in the upper regions will melt before reaching the ground. Hence, in the temperate zones, as a rule, snow falls only in winter, while in the tropics it never falls, except near the sum- mits of lofty mountains. It is a mistake to suppose that the fall of snow is greater in regions near the poles than elsewhere ; for in high lati- 108 PHYSICAL GEOGRAPHY. tudes there is comparatively little moisture in the air. The fall is heaviest in the cool temperate regions. 281. Snow Line. — The snow which falls on mountains is slowly pressed down the slopes by the weight of the snow above. The distance it will move down the mountain before melting de- pends on a number of circumstances. The lower limit of the line, above which the ground remains covered with snow throughout the year, is called the snow line. The height of the snow line depends — (1.) On the amount of the snowfall. The greater the fad, the farther down the mountain the snow will move before melting. (2.) On the temperature of the valley. The warmer the valley the higher the snow line. The snow line is, therefore, highest in the trop- ical regions, and lowest near the poles. (3.) On the inclination of the mountain slope. The steeper the slope, the more rapidly the snow will move down the mountain, and the farther it will go before melting, therefore, the lower the snow line. According to Guyot, the snow line, subject to variations, is about three miles above the sea in the tropics ; rather less than two miles in the temperate latitudes ; and less than a mile near the northern extremities of the conti- nents ; while still farther north, on the polar islands, the snow line is but a few hundred feet above the sea. Over the polar oceans, the winter snows are but partially melted, and help to produce the huge ice-floes of these regions. SNOW LINE. Europe.— Norway, lat. 70° N 3,400 feet. " " 60° N 5,500 " " Alps, lat. 46° N. (south side) 9,200 " " " (north side) 8,800 " Asia.— Altai Mountains, lat. 50° N 7,000 " " Himalayas, lat. 31° N 17,000 " Africa.— Kiliinandjaro, lat. 3° S 16,000 " North America. — Rocky Mountains, lat. 43° N 12,467 " South America. — Andes, Ecuador, lat. 1° S. 15,800 " lat. 54° S 3,700 " The snow line is generally lower in a moist atmosphere than in dry air, because of the greater fall of snow in the former case than in the latter. As a rule, that slope of a range which is exposed to the prevalent wind has a lower snow line than the opposite slope. The position the slope occupies in relation to the vertical rays of the sun, also exerts an influence on the height of the snow line. 282 Glaciers are immense masses of ice and snow, which move almost imperceptibly down the higher mountain valleys or slopes. Their upper parts are formed of soft snow ; their lower por- tions of clear, hard ice. Their origin is as fol- lows : The weight of the huge snow fields, which form above the snow line, presses the mass slowly down the slopes. The pressure, due to the weight of the layers, but especially the pressure which is produced when the mass is forced through a con- traction in the valley, squeezes out the confined air, to which snow, in great part, owes its white color, and the lower part of the glacier thus be- comes changed into a compact mass of pure ice. The alternate thawing and freezing to which the mass is subjected below the snow line, also con- tribute to the change from snow to ice. The change is most thorough in the lower parts of the glacier, where the ice is marvellously clear. Its color, when seen in great depths, is of a deep azure blue ; in the middle portions of the glacier the ice is coarse and white. The higher region of but partially changed snow is called the neve region. Here the snow occurs in coarse white grains. The process of formation is a continuous one. The neve region is supplied by fresh falls of snow, which replace those pressed down the slopes. 283. Drainage of Snow and Ice. — Glaciers closely resemble rivers, since they receive the drainage of their basins through the solid mate- rial which flows into them ; their motion, how- ever, is much slower. Like rivers, they have their tributaries, and their peculiarities of flow and velocity. Several glaciers often unite and flow on as one mass ; but their solid condition prevents the in- termingling which occurs in rivers, and the sepa- rate streams can generally be distinctly traced throughout the remainder of their course. Like rivers, the top and middle portions move more rapidly than the sides or bottom, owing to the diminished friction. 284. Peculiarities of Glaciers. — The surface of the glacier is often comparatively smooth ; but when irregularities occur, either in the direction of the valley, or in the slope of its bed, the glacier is broken into deep fissures, called crevasses. These are most numerous on the sides, from which they extend either obliquely up the stream, or directly across, in deep transverse fissures. The former are generally due to a bend in the valley, one side being compressed and the other extended; the latter, to steep and abrupt descents in the bed. Crevasses are, therefore, rapids in the ice stream. Crevasses vary in breadth from mere crevices, that a knife-blade can scarcely penetrate, to yawning chasms over 100 feet in width. The depth of the wider crevasses is generally profound. Their vertical walls afford a con- venient opportunity for studying many peculiarities of formation. Looking down the walls of the crevasses, the ice appears of a deep azure blue. The surface ice is a dirty white* HAIL, SNOW, AND GLACIERS. 1*09 J- The crevasses gradually disappear below the cause of disturbance, the fractures rejoining by a process called regelation. Regelation is the property which fragments of moist ice have of becoming firmly cemented together, when their surfaces are brought into contact under pressure. The water derived from the melting of the ice issues from a cavernous arch at the end of the glacier. The volume of the issuing stream, which is often considerable, is dependent on the tempera- ture, being greater during the warm months of the year. Many rivers have their origin in these glacier streams ; as, the Rhone and the Rhine, in Europe, and the Ganges, in Asia. The distance the glacier extends below the snow line depends on the mass and velocity of the ice, and the rapidity with which it is melted. When the winter snows are light, and the following sum- mer unusually warm, the end of the glacier re- treats up the mountain. On the contrary, heavy snowfalls in winter, followed by a cool summer, permit the end of the glacier to advance far into the valley below. 285. Transporting Power of Glaciers. — All along the borders of the valleys, stones and dirt roll down the declivities, and, accumulating on the surface of the moving mass, are carried with it to a lower level. These accumulations of dirt and stones are called moraines; they are most sharply marked at the sides of the glaciers, where : they are called lateral moraines. Where two gla- ciers flow into one common valley a moraine called the medial moraine marks the junction of their meeting edges.s At the end of the glacier, a ter- minal moraine extends in a wide curve across the valley. Medial moraines are sometimes over a hundred feet in height. Terminal moraines some- times attain the height of several hundred feet. The masses of stone transported by glaciers are often of great size. Some have been found 100 feet long, 50 feet wide, and 40 feet high. 286. Erosion. — Such immense masses of ice must deepen considerably the valleys through which they move. When they have deserted their former valleys, evidences of their previous existence are to be found in the long lines of unstratified rocks and mud left by their moraines and boulders, and especially in the deep grooves, or scratches, cut in the bottom or sides of the valleys by rocks imbedded in the moving ice mass. These scratches are parallel, and show the direction of the motion. The water which issues from the terminal cave is deeply charged with a fine sediment, the result of erosion. This sediment is exceedingly fertile, and, spread out by the rivers on the flood-grounds, becomes a source of agricul- tural wealth. Fiords and Glacial Lakes. — Valleys cut by glaciers are characterized by parallel sides. Gla- cial valleys, when formed on mountains that slope down to the ocean, if the region is subjected to subsequent depression and the valleys partially submerged, are penetrated by the sea, and form arms of the sea extending far into the mountains. Such valleys are called fiords. The following are the most important fiord regions : (1.) On the coasts of Norway. (2.) On the western coasts of the Dominion of Canada and Alaska. (3.) On the coasts of Greenland, where the valleys are still covered with ice masses. The numerous lakes of glacial regions owe their origin either to the erosion of softer rocks, or to the damming up of rivers by the terminal mo- raines left by a retreating glacier. 287. Geographical Distribution of Glaciers. — The best known glacial system in the world is found in Europe, in the region of the Central Alps. Here no less than 1100 glaciers are found, one hundred of which are of large size. One of the best known of the European glaciers is that of the Mer de Glace (Sea of Ice). It descends from the slopes of the range of Mont Blanc, and is formed by the confluence of three large glaciers : the Glacier du Giant, the Glacier de Lechaud, and the Glacier du Talefre. Fig. 97. The Mer de Glace. Glaciers occur also in the Pyrenees Mountains ; in the Caucasus range ; and in the Scandinavian plateau, from which they descend into the Norwegian fiords to less than 1000 feet from the level of the sea. They also occur in the Patagonian Andes 110 PHYSICAL GEOGRAPHY. In the Arctic zone glaciers are particularly- numerous and extensive. Here they generally reach down into the sea. They are found in the islands of the Arctic Archipelago, in Greenland, Iceland, Jan Mayen, and Spitzbergen. The Humboldt Glacier, in Greenland, is sixty-nine miles broad at its lower extremity in the sea. In all the Arctic glaciers, the neve region is more extended than in those of more southern latitudes. The terminal moraines are found at the bottom of the sea, near the foot of the glacier. In the lofty mountain-ranges of the Himalayas and in the Karakorum, occur other less known, though exten- sive, regions of glaciers. 288. Icebergs. — When the glacier extends into the sea, the base is undermined by the warmer waters of the ocean, and great fragments are broken off by the waves, forming floating moun- tains of ice, called icebergs. Icebergs are particu- larly numerous in the North Atlantic, into which they descend from the extensive Arctic glacial region already described. The limits of the Arctic and Antarctic drift ice are shown in the map of the isotherms. Fig. 98. Icebergs. The Ace floes of the polar seas have their origin in the snow which falls into the cold water, re- maining partially dissolved and subsequently freezing, thus adding to the thickness of the ice formed. 289. The Glacial Epoch of the Earth.— Toward the close of the Mammalian Age, a change occurred in the cli- mate of the earth, and extensive glaciers covered most of the northern continents, reaching, in many instances, far toward the south. In the United States, their southern limit appears to have been at about lat. 39° N., in Southern Pennsylvania, Ohio, Indiana, Illinois, and Iowa. In Eu- rope, they extended as far south as the 50° N. lat. In South America, they probably extended as far toward the equator as 41° S. lat. The evidences of the existence of ancient glaciers are found in the presence of accumulations of unstratified material, called the drift; in the presence of old moraines; in glacial scratches and grooves on rocky slopes ; in eroded valleys ; and in the presence of numerous large boulders, which are found at great distances from their places of origin. o-FiHc CHAPTER III. Electrical and Optical Phenomena. 290. Nature of Electricity. — Electricity is now generally believed to be due to a peculiar wave motion in the luminiferous ether, the medium which transmits the waves of light and heat. When a body is electrified it acquires a certain power of doing work, called electric potential. Electric potential is measured in units called volts. The path through which an electric dis- charge passes is called the circuit. All circuits offer a measurable resistance to the passage of an electric discharge. Electric resistance is meas- ured in units called ohms. The rate at which electricity passes through a circuit is called the current, and is measured in units called amperes. An ampere is the current which would pass in a circuit whose resistance is one ohm, under a potential of one volt. Though electricity is probably not a fluid, yet it resem- bles a fluid in many respects, and the units already re- ferred to are, to a certain extent, based on this resem- blance. The quantity of liquid that flows through a pipe in a given time depends on the pressure on the liquid, and the resistance offered by the pipe. The quantity-per-sec- ond corresponds to the amperes ; the pressure which causes the flow, to the volts ; and the resistance which limits the flow, to the ohms. Electricity may be produced in bodies by a variety of causes : such as friction, heat, chemical action, magnetism, and animal or vegetable life. There are two distinct forms of electrical excitement : the positive and the negative. A body with a high potential is generally assumed to be positively charged ; one with a low potential, negatively charged. The current is assumed to flow from the higher to the lower potential, or from the positive to the negative. Bodies charged with electricity ELECTRICAL AND OPTICAL PHENOMENA. Ill of the same kind, repel one another ; if charged with dif- ferent kinds, they attract, and if the bodies are free to move, they approach, when the opposite excitements neu- tralize each other. In case the electrical excitement is considerable, the union is accompanied by a sharp crack, and a flash of light, called the electric spark. 291. Conductors of electricity are bodies which allow its ready passage through them. Metals, charcoal, acids, aqueous solutions, and various animal and vegetable substances, are good con- ductors. Non-conductors are those which do not allow the electricity to flow freely through them. Gums, resins, glass, silk, and dry air are non-con- ductors. The higher the conducting power of a circuit the lower will be its resistance, and, consequently, the greater the current which will be sent through it by a given poten- tial. 292. Atmospheric Electricity. — Electric excite- ment is always present in the atmosphere. The electricity of the air is generally positive, although it often changes rapidly to negative on the ap- proach of clouds or fogs. It is feeblest within a few feet of the surface, and increases with the elevation above the general surface of the earth. Origin of Free Atmospheric Electricity. — The elec- tricity of the atmosphere is caused by a variety of circum- stances, the chief of which are evaporation and condensa- tion ; unequal heating of the earth by the sun's rays ; combustion ; animal and vegetable life ; and the friction of winds against each other or against the earth's sur- face. 293. Lightning occurs when the electricity of a cloud discharges to the earth or to a neighbor- ing cloud. The discharge is attended by a vivid spark, called lightning. The destructive effects of lightning are due to the discharge between the clouds and the earth. Thunder. — The heat of the spark vaporizes the rain-drops, and enormously expands the air, pro- ducing, on their subsequent cooling, a partial vacuum, which is further increased by the mo- mentary pushing aside of the air by the discharge. The surrounding air rushing violently into this vacuum produces the sound called thunder. The potential of the lightning flash is enormously higher than that produced by artificial means, and must be equal to many millions of volts. This high potential is due to the enormous decrease in the surface of a single rain-drop from the thousands of smaller drops which have coalesced to form it. 294. Varieties of Lightning.— There are five varieties of lightning : zig-zag or chain, sheet, heat, globular, and vol- canic lightning. Zig-zag Lightning probably owes its forked shape to the resistance which the air offers to its passage through it. The air-particles, being crowded together in the path of the spark, the lightning darts to one side, where the air is less dense. Sheet Lightning generally accompanies thunder- storms, and appears as an expanded flash s which illu- mines the clouds. Heat Lightning, or lightning without thunder, is gener- ally seen near the horizon, during hot weather. It is probably caused by the reflection of lightning from a storm below the horizon. Globular Lightning. On rare occasions, the lightning appears in the form of a globe of light, which remains stationary in the air or moves slowly through it. Its cause is unknown. Volcanic Lightning. During the eruption of volca- noes, vivid flashes of lightning often occur in the air near the craters. Volcanic lightning is probably caused by the rapid condensation of the vast volumes of vapor emitted with the ashes and lava. 295. Lightning Rods, invented by Franklin, protect the buildings on which they are placed, by quietly discharging the electricity from the over- hanging cloud. They generally effect this by an opposite electricity passing from the earth up the rod, and neutralizing that of the cloud. Unless the rods are placed in good metallic connection with the earth, and with all conductors near them, they are sources of danger rather than of protection. 296. St. Elmo's Fire. — When the atmosphere is highly charged with electricity, faint tongues of fire are often seen on the ends of bodies in Pig. 99. St. Elmo's Fire. connection with the earth, like the masts of ships, steeples, etc., due to an electric discharge, known as the brush-discharge. They are called St. Elmo's fire, and are harmless. 112 PHYSICAL GEOGRAPHY. 297. The Aurora Borealis, or northern light, is a phenomenon of marvellous beauty, occurring in the sky of high latitudes in both the northern and southern hemispheres. It appears in a va- riety of forms ; at times huge pillars of fire move rapidly across the heavens, or the entire northern sky is lighted as by a drifting storm of luminous snow. The commonest appearance, however, is that of an arch of fire, from which streamers flash toward the zenith. Auroras are most frequent in high latitudes, though not in the. immediate vicinity of the poles. Auroras are caused by the passage of electricity through the rare air of the upper regions. The proofs are as fol- lows : During the continuance of an aurora, the telegraph wires show the presence of an unusual electrical disturb- ance, and the magnetic needle is subject to frequent oscil- lations; moreover, the same phenomena can be produced by the passage of an electrical current through rarefied gases, as in the Geissler tubes — different colors arising from its passage through different gases. Fig. 100. Aurora Borealis. 298. Magnetism. — The recent researches of Herz leave little doubt that electro-magnetic phe- nomena are due to a wave motion in the lumi- niferous ether. Magnets are bodies which have the power of attracting particles of iron or the opposite poles of other magnets. All magnets possess an atmosphere of influence surrounding them, called the magnetic field. The magnetic field is traversed by lines of force, which come out of the magnet at one point and enter it at another, thus forming a magnetic circuit. The points where the lines come out are called poles ; the former being the positive or north pole, and the latter the negative or south pole. Magnets are either natural or artificial. Nat- ural magnets are found in lodestone, a species of iron ore composed of oxygen and iron. Pieces of hardened iron or steel may be magnetized, by rubbing them with a lodestone, or by passing electrical currents around them, thus forming what are called electro-magnets. All magnetiz- able substances become magnetized when they are brought into a magnetic field. If a magnetized bar or needle be suspended at its centre of gravity so as to move freely in a horizontal plane, after a few oscillations it will come to rest, with one of its ends pointing nearly to the geographical north pole of the earth. This end of the magnet is called its north pole, the op- posite end its south pole, and the magnet itself, a magnetic needle. Fig. 101. The Magnetic Needle. 299. Magnetic Attractions and Repulsions. — If a magnet is brought near a magnetic needle, attraction or repulsion will ensue — repulsion, when the poles are of the same name; attraction, when they are of opposite names. Thus, when a north pole is approached to a north pole, or a south pole to a south pole, they repel each other; but when a north pole is approached to a south pole, or a south pole to a north pole, they attract. If the approaching magnet is powerful, it will deflect the magnetic needle, although several feet distant from it ; and if placed per- manently in this position, the magnetic needle will n» longer point to the north, but will turn toward the disturbing magnet. 300. Cause of the Magnetic Needle pointing to the Geographical North. — The magnetic needle points to the north for the same reason that the opposite poles of magnets point to each other when they are sufficiently near. The entire earth acts as one huge magnet, with its poles in the neigh- borhood of the extremities of its axis, and the mag- netic needle points toward these poles on account of their attraction. ELECTRICAL AND OPTICAL PHENOMENA. 113 The earth, like all magnets, possesses a magnetic field. Lines of magnetic force come out of its north pole, pass around the earth through the air, and enter the earth at its south pole. A magnetic needle, placed in the earth's field, if free to move, will come to rest with the earth's lines of force passing into its south pole aud passing out of its north pole. That pole of the needle which points to the geographical north is, therefore, of opposite magnetic polarity to the earth's polarity in the Northern Hemi- sphere. In the United States, the Northern Hemisphere is regarded as possessing south magnetic polarity; in France, as possessing north magnetic polarity. 301 Origin of the Earth's Magnetism. — The exact cause of the earth's magnetism is unknown. Currents of electricity circulating around a con- ductor render it a magnet. Electrical currents are generated in nearly all substances, when they are unequally heated. The earth appears to owe its magnetism to the circulation around it of cur- rents of electricity, produced, most probably, by the unequal heating of different portions of its surface by the sun's rays. These currents would follow the sun in its apparent motion from east to west. Since the earth's magnetism appears to have its remote cause in the sun's heat, variations in the temperature should be followed by corre- sponding variations in the intensity of magnetism. This is found to be the case. Magnetic storms, or unusual variations in the earth's magnetism, have been noticed to Fig. 102. Declination Chart. (West Declination is represented by the continuous lines ; East Declination by the dotted lines ; the Agones by the heavy lines.) correspond with outbursts of solar activity, as manifested by the unusual occurrence of new spots. 302. The Declination or Variation of the Nee- dle. — The earth's magnetic poles do not corre- spond with its geographical poles. The magnetic needle, therefore, except in a few localities, does not point to the true geographical north, but to the east or to the west of it. This deviation from the true north is called the declination or vari- ation, and is east or ivest according as the needle points to the east or the west of the true or geo- graphical north. The amount of this variation differs in different parts of the earth. The position of the magnetic poles of the earth is not always the same, but cnanges slowly from year to year, thus producing corresponding changes in the declination of the needle. This change is called secular variation. The needle, at any place, points more and more to the east, following the change of the poles. At length, after a long period, it becomes stationary, and then begins to move toward the true meridian, which it at length reaches ; when, continuing its motion, the declination becomes west. Isogonal Lines. — Lines connecting places which have the same declination, are called isogonal lines. Lines connecting these places, when the needle points to the true north, are called agones, or lines of no declination. The direction of the isogonal lines is shown in the de- 114 PHYSICAL GEOGRAPHY. clination chart, the figures near the lines giving the value of the declination in degrees. The agone in each hemi- sphere is marked 0. In the New World it enters South America near Rio Janeiro, curves to the eastward around the Antilles, passes near Washington, through the western part of Hudson Bay, and enters the magnetic pole at Boothia Felix. The agone, in the Old World, passes through the west of Australia, near the western coasts of Hindostan, through Persia, the eastern part of the Cas- pian Sea, and through the White Sea, in Europe. The oval curves in Eastern Asia seem to indicate a secondary magnetic pole. In nearly all Europe, in the whole of Africa and Arabia, in eastern North and South America, and in nearly all the Atlantic and Indian Oceans, the declination is west. It is also west along part of the eastern shores of Asia, around the secondary magnetic pole. In the remainder of the world the declination is east. 303. The Inclination or Dip of the Needle. — The lines of force of the earth's magnetic field are in most places inclined to the earth's surface. The position of the needle is, therefore, horizontal in but a few localities. In most places, one of the poles is inclined to the earth. This is called the inclination or dip of the needle. In the Northern Hemisphere, it is the north pole, and in the south- ern, the south pole that is inclined. 304. Magnetic Equator. — The angle of dip is greater, the nearer we approach either magnetic pole. At the pole, the needle points vertically downward ; midway between the poles, the needle is horizontal ; the last position is called the mag- netic equator. Lines connecting places which have the same angle of dip are called isoclinal lines. They correspond in a very remarkable manner with the isothermal lines. This seems to show the dependence of the intensity of magnetism on the distribution of the sun's heat. The inclination is also subject to secular changes, like the declination. 305. Optical Phenomena are caused by changes in the direction, intensity, or composition of sun- light during its passage through the atmosphere. Sunlight, when passed through a prism, is dis- persed or separated into a great number of differ- ent colored lights. The following seven groups of colors are prominent : violet, indigo, blue, green, yellow, orange, and red. These are called the pris- matic colors, or, collectively, a spectrum. They differ in the ease with which they are refracted, or turned out of their course, in passing from one medium to another of different density. The above prismatic colors seen in the spectrum are name4 m the order of their refrangibility, begin- ning with the violet, the most refrangible, and ending with the red, the least refrangible. 306. Rainbows are arches of the prismatic colors, caused by the dispersion of the light during its passage through the falling drops of rain. The rays entering the drop, are reflected from the surfaces farthest from the sun, and emerge separated into the prismatic colors. Rainbows are seen when the observer stands with his back toward the sun. They are largest when the sun is nearly setting. A secondary bow sometimes occurs outside the primary, with the order of its colors reversed. It is caused by the light which is twice reflected from the back of the drops. 307. The Sunset Tints of the Sky are yellow, orange, and red. The rays of the setting sun are dispersed, during their passage through the clouds, or through accumulations of vapor at the horizon, and only the colors that are least turned out of their course, the yellow, the orange, and the red, pass through and light up the western sky. 308. The Blue Color of the Sky is caused by the diffusion through the air and their subsequent reflection from its particles of the more refrangi- ble rays of light : the indigo and the blue. 309. Halos and Coronae are rings of prismatic colors surrounding the sun and moon. Halos are caused by the presence in the air of small crystals of ice or snow. Parhelia, or mock suns, and Paraselenoz, or mock moons (bright spots which somewhat resemble suns and moons), are frequently seen where the complicated circles of halos intersect each other. Coronce are circles of light, seen most frequently around the moon. They are caused by the presence of a small quantity of condensed vapor in the air. They generally indicate changes in the weather. Fig. 103. Halo. 310. The Mirage is a general term applied to the appearance which objects present when viewed by means of rays of light that have passed through SYLLABUS. 115 strata of air, which gradually increase or decrease in density. In this way the objects appear either inverted or erect, but always out of their true position. Sometimes the objects are repeated, one being seen above the other. The mirage occurs both over water and land. It is caused by the turning of the rays of light out of their original direction. The Mirage of the Desert occurs over hot, arid surfaces, whenever the strata of air increase rap- idly in density from the surface upward. The rays of light from distant objects, such as trees, are reflected from one of the lower layers of air, and, entering the eye of the observer, appear to come from inverted objects, which seem to be surrounded by a sheet of water. The image of a real tree is seen, but out of its true situation, so that when the observer reaches the place he finds nothing. The mirage frequently occurs on the sea. Ves- sels that are too far below the horizon to be di- rectly visible, become visible by refraction. This phenomenon is called looming. The vessels are seen both erect and inverted, and sometimes ap- pear suspended in the clouds. Distant islands are sometimes visible from the same cause. SYLLABUS. -»4c Trace on the map showing the distribution of vegeta- tion, the parts of the world included in the tropical zone. Name the plants of the tropical zone which are charac- teristic of South America. Name those of Africa. Of India and Australia. Describe the principal region of the cocoa-nut palm, bread-fruit, sago, and yam in the eastern continent. Describe from the map the limits of the sub-tropical zones. Describe the characteristic flora of those por- tions of each of the continents which lie within these zones. Describe the limits of the warm temperate zones. Of the cold temperate zones. Of the sub-arctic zone. Of the polar zone. Trace on the map the northern limit of trees. Trace the southern limit of trees. Name some of the trees of the warm temperate zones. Of the cold temperate zones. Of the sub-arctic zones. In what parts of the world are pasture-lands found ? Name the characteristic plants of the regions which lie north of the arctic circle. Trace on the map showing the vertical distribution of vegetation, the characteristic plants found in Africa, be- tween the level of the sea and 5000 feet. In Europe. In Asia. In America. ZOOLOGICAL GEOGRAPHY. 129 Section II. ANIMAL LIFE. CHAPTER I. Zoological Geography. 339. Zoological Geography treats of the dis- tribution of animal life. The animals found in any region of country are called its fauna. Like plants, animals appear to have been originally created in certain localities, from which they have spread, more or less, over adjoining areas. Though able to move about freely from place to place, animals are, nevertheless, restricted, by conditions of food and climate, to well-defined areas. Animals derive their sustenance, either directly or indirectly, from plants. 340. Distribution of Animal Life. — The distri- bution of heat, moisture, and vegetation forms the true basis for the distribution of animal life. We distinguish a horizontal and a vertical dis- tribution of animal life. 25,000 feet. 20,000 " 15,000 " 10,000 " 5,000 " As a rule, the luxuriance and diversity of ter* restrial animal life decrease as we pass from the equator to the poles. A similar decrease is no- ticed in passing from the coasts of the continents toward the interior. Within the tropics, where the abundant heat and moisture produce a vigor- ous vegetation, all forms of terrestrial animal life, save man, attain the greatest development in size, intelligence, and activity. As we proceed toward the poles, the species are less developed, although, in the temperate regions, large and vigorous ani- mals are still numerous. In the polar zones, the reindeer and white bear are the only representa- tives of the larger land animals. In marine animal life, the law of distribution is reversed, both the number and size of the species increasing from the equator toward the poles. This is probably due to the more equable temperature of the ocean in high latitudes. 341. The Vertical Distribution of Life. — In Ta^sjsak Fig. 115. Vertical Distribution of Animal Life. (After Black.) passing from the base to the summit of a tropical mountain, the same change is noticed in the spe- cies of animals, as in passing along the surface of the earth from the equator to the poles. In the above chart, the names of the animals are placed at the greatest elevation at which they are found. The power of locomotion possessed by animals renders it extremely difficult to arrange the fauna in zones according to the altitude. In general, however, the animals found on the slopes of tropical mountains, at elevations included be- tween the sea-level and from 5000 to 7000 feet, correspond to those inhabiting the tropical zone ; between 5000 or 7000 feet and 15,000 feet, to those of the temperate zones. The condor is found in the high Andes, far above the snow line. The fauna of high mountain-ranges are often sharply 130 PHYSICAL GEOGRAPHY. marked. A particular species, at a given elevation on one range, is frequently entirely wanting on a neighboring disconnected range, even when the same conditions of heat, moisture, and vegetation exist. The temperature of the intervening lower country, through which the ani- mals would have to pass in order to reach the adjoining slopes, forms an impenetrable barrier. 342. Natural Boundaries of Zones of Animal Life. — Large bodies of water, deserts, or moun- tain-ranges, mark the boundaries of regions of animals as well as of plants ; but the influence of temperature is so important, that even when these natural barriers are wanting, the horizontal range of animals is sharply marked by the iso- thermal lines. In North America, there are well-marked zones of ani- mals, which extend from east to west across the continent. Here, although no natural barriers exist to limit the wider range of the animals, yet they seem unable to permanently pass the limits of the isotherms, which mark the climatic conditions necessary to their vigorous growth. This in- ability doubtless arises from the distribution of the flora, on which, directly or indirectly, they are dependent for their food. 343. Acclimation. — The power of becoming acclimated, or being able to live in a climate dif- fering from that in which they were first created, appears to be possessed by animals, as a class, to an exceedingly limited extent. Man, and his faithful friend, the dog, form an exception to most other animals in this respect. They are able to endure both the severe heat of the tropics, and the rigor of the Arctic regions. The reindeer thrives amid the snows of Lapland or Greenland, but perishes from the heat of St. Petersburg. Monkeys are indigenous to the tropics, but die with consumption, even in the compara- tively mild climate of the north temperate zones. 344. Horizontal Distribution of Animal Life. — The vast number of species of animals, the pe- culiar laws of their growth, and their power of adaptation to change of circumstances, render their accurate distribution into zones or regions a task far beyond the scope of an elementary book. It will be sufficient for our purpose to divide the fauna of the earth into those found, in general, in the three mathematical climatic zones : the Torrid, the Temperate, and the Polar. The accurate limits of these zones would be found in the isotherms, but in a general description, little difference would be noticed. On the map, the actual limits of some of the more important ani- mals are given. These limits, it will be noticed, in most cases follow the general direction of the isotherms. 345. Characteristic Fauna. — A careful study of the map of the distribution of animal life, will show that each continent possesses a fauna pecu- liar to itself. This arises, generally, from some clearly traceable peculiarity in the distribution of the heat and moisture, or in the nature of the vegetation. Some of these peculiarities will be discussed in a brief review of the characteristic fauna of each of the continents. The following are the characteristic tropical, temperate, and arc- tic fauna. 346. Tropical Fauna. — The abundance of heat, moisture, and vegetation of the torrid zone causes its fauna to excel all the others in the number and diversity of terrestrial species, as well as in their size, strength, and sagacity. The following animals are found mainly within the regions of the earth included between the Tropics of Cancer and Capricorn. Mammalia are represented as follows : Monkeys, by the man-like orang-outang, the chimpanzee, gorilla, baboon, and other species. Tig. 116. Lion, Carnivora, or flesh-eating mammals, by the lion, tiger, panther, and puma. Herbivora, or plant-eating mammals, by the ele~ phant, rhinoceros, tapir, and hippopotamus, the horse-like zebra and quagga, the giraffe or camel- opard, and the camel. Cetacea, or whales, by the sperm whale, found only in tropical or temperate waters. Cheiroptera, or bats, by a number of species. Marsupials, by the kangaroo of Australia. Birds are represented, in tropical regions, by Page 131. 132 PHYSICAL GEOGRAPHY. species noted for their great size and strength, or for the brilliant colors of their plumage. Among those noted for their size may be mentioned the condor, ostrich, eagle, ibis, flamingo, and cassowary ; among those especially noted for their plumage, the birds of paradise, peacock, and parrots, and the humming-birds of South America, which lat- ter, though in less brilliantly-colored plumage, extend nearly to the extreme limits of the north and south temperate zones. Fig. 117. Alligator. Reptiles are represented by the crocodile, alli- gator, iguana, gigantic lizards, and turtles ; among serpents, the enormous boa-constrictor, and num- bers of hooded and other venomous serpents. The Fish of tropical waters, though large and brightly colored, are not so well adapted for food as the more sombre varieties of the temperate or colder waters. \*^ 347. Temperate Fauna. — The following ani- mals are found mainly between the tropics and polar circles. Though fewer of the higher spe- cies of animals are found in the temperate zone than in the torrid zone, yet many of the fauna are of large size, and among them are found ani- mals most useful to man. The physical tropical zone, as will be seen from an in- spection of the map of plant life, actually extends, in the eastern continent, far into the mathematical north tem- perate zone, and in these portions the corresponding trop- ical species occur. Thus, in Northern Africa and South- ern Asia, are found the ape, tiger, lion, panther, camel, and rhinoceros. Mammalia are represented as follows : Flesh-eating mammals, by the lynx, hyena, wolf, jackal, dog, fox, raccoon, bear, seal, and walrus. Plant-eating mammals, by the wild boar and hog, the horse, ass, ox, sheep, goat, and chamois, many of which have been domesticated, as the moose, elk, reindeer, stag, antelope, buffalo, camel, llama, and numerous others. Cetacea, or whales, by the sperm and white whales. Rodentia, or gnawing mammals, by the beavers, squirrels, rats, and porcupines. Marsupials, by the kangaroo of Australia. The birds of the temperate zones are repre- sented by the condor, vulture, hawk, eagle, owl, Fig. 118. Eagles. and parrot (near the southern limit of the zone). The turkey, pheasant, and our common domesti- cated fowls also are natives of this zone. Here occur numerous birds which are noted for the sweetness of their song, as the wren, thrush, robin, nightingale, and lark; the pelican, albatross, and the cassowary are found in this zone. Reptiles are represented by the alligator, croco- dile, and lizard, and the rattlesnake, copperhead, and various other serpents, both poisonous and harmless. 348. Arctic Fauna. — The following animals are found mainly between the polar circles and the poles. The south arctic fauna is but little known ; the following description, therefore, re- fers mainly to the northern hemisphere: In the arctic regions of the world, the large land animals are, with a few exceptions, replaced by numerous smaller furry species. Throughout CHARACTERISTIC FAUNA OF THE CONTINENTS. 13< the northern portions of the north temperate zone, and the southern portions of the arctic, fur-bearing animals are especially numerous and valuable. The white polar bear, the reindeer, moose, and the musk-ox, are among the largest of the land species ; but in warmer regions of the oceans, nu- merous species exist, among which are individuals as large as any in the animal world. The Greenland whale, which sometimes attains the length of seventy feet, and is covered with blubber to a thick- ness of two or three feet, is found only in this zone. A similar, though smaller, species occurs in the southern waters. The seal and walrus are also found in this zone. Fig, 119, Seals and Walrus. Besides the larger animals, numerous smaller species, such as minute zoophytes, mollusks, and crustaceans, which form the food of the whale, and which, in some places, exist in immense numbers, inhabit the waters. Among birds, in- numerable water-fowl occur. 3^0^0-f CHAPTER II. Characteristic Fauna of the Conti- nents. 349. Characteristic Fauna of the Continents. — Each of the continents is characterized by some peculiarity in its fauna. This peculiarity arises either from the nature of the vegetation, or the distribution of the heat and moisture, and affords an excellent example of the intimate connection between the physical features of a country, and its flora and fauna. Only the general character- istics of the fauna will be given. For the particular animals inhabiting each continent, the student is referred to the map of the distribution of animal life. 350. North American Fauna. — The chief cha- racteristic of the North American fauna is found in the preponderance of plant-eating mammals. This feature is due to the abundance of pasture- lands, and their luxuriant vegetation. From its extensive lake and river systems, North America is peculiarly fitted to sustain aquatic life ; hence, its numerous water-fowl and beaver. 351. Fur-bearing animals are particularly nu- merous and valuable. Three natural districts of fur-bearing animals exist : the forest region, the prairie region, and the barren regions of the north, each of which is characterized by a pecu- liar fauna. Forest Region — Here, among carnivora, are found the black bear, marten, ermine, mink, otter, the silver fox, the black fox, and the lynx; among the rodentia, the beaver and musk-rat ; and among the ruminants, the moose and rein- deer. The wolverine and wolf are found both in the for- est region and the barren grounds. Barren Grounds. — The brown and polar bears, the polar fox, and the polar hare are characteristic. Prairie Region. — The grizzly bear, the most formidable animal of the continent ; the prairie wolf, and the gray fox are also found here. The puma, or the American lion, which is found also over the greater part of South America, is the most powerful representative of the lion and tiger tribe of the East. 352. South American Fauna. — The chief cha- racteristics of the South American fauna arise from the extreme luxuriance of its vegetation, due to the abundance of its moisture. In vast districts, as the Selvas of the Amazon, the vege- table world usurps the ground nearly to the ex- clusion of the higher forms of animal life. The fauna is, therefore, as a rule, characterized by its fitness for existing in connection with either an abundance of water or of vegetation. Insect Life is peculiarly characteristic of the continent. Nowhere else are the species so nu- merous, so brilliantly colored, or so large. Here are found the largest of the beetles, and the most beautiful of the butterflies. Reptiles are largely represented. They find, in the tepid, sluggish waters of the huge rivers, conditions most favorable to rapid growth. Here 134 PHYSICAL GEOGRAPHY. live the crocodile, gigantic lizards, and many venomous serpents. Among Birds, the water species are in the as- cendance. Humming-birds, which occur also in North America, are found in great abundance in the southern continent. The condor is found on the higher slopes throughout the Andes ; the os- trich, toucan, and parrot are also characteristic. Among the Mammalia, the ant-eaters and sloths peculiarly characterize the continent. The tapir and peccary are the only representatives of the elephant, rhinoceros, and hippopotamus of the Eastern continents. The llama, puma, and the prehensile-tailed monkeys are also characteristic of the region. The South American district of fur-bearing animals ex- tends through parts of Chili and the Argentine Eepublic. The marsh heaver is the principal animal. 353. Asiatic Fauna. — From the great mass of land within the tropics, the fauna of Asia, besides its numerous arctic and temperate species, contains a great variety of tropical forms. Taken in connection with Northern Africa, Asia is essentially the region of extensive dry plains and arid tracts. The vegetation through- Fig. 120. Elephant. out its temperate climes is greatly inferior to that of America, but its animal life is marked by a much greater variety in the higher forms. Fore- most among these are the man-like monkeys, the orang-outang, the elephant, the royal tiger, and others, fur-bearing animals are also numerous. Among birds, those with bright, gay-colored plumage abound. Reptiles also are repre- sented, though not to such an extent as in South America. When we bear in mind that in Asia, the horse, ass, goat, sheep, camel, swine, elephant, buffalo, and ox are found in great numbers, it will be seen that Asia, the home of primitive man, is also peculiarly the home of domesticated animals; that is, of the animals which man has trained to labor for him. The Asiatic district of fur-bearing animals includes Si- beria, Kamtchatka, and the basin of the Amoor River in Mantchooria. The following animals are characteristic: the brown bear, badger, weasel, ermine, sable, otter, marten, and many others. The furs of the sable, black fox, otter, and the ermine, are considered the most valuable. 354. African Fauna. — The peculiarities of the northern portion of the continent have been al- ready pointed out in connection with Asia. It is a fact worthy of notice, that the great deserts of the world, like the Sahara, though nearly desti- tute of any vegetation, are able to sustain many of the highest species of animals. Over these tracts are found the lordly lion, the leopard, and the panther, and the numerous ani- mals on which they prey, such as the antelope, the zebra, the quagga, and others. All these possess powers of rapid locomotion, which pe- culiarly fit them for the arid plains over which they roam. In the remaining portions of Africa, the luxu- riant vegetation is capable of sustaining animals of a larger growth. Here occur the largest of the Mammalia, such as the elephant, rhinoceros, and hippopotamus ; here also is found the giraffe, the largest of the ruminantia ; man-like monkeys are also characteristic. 355. Australian Fauna. — The more nearly per- fect isolation of Australia than any of the other continents, together with the peculiar distribu- tion of its heat and moisture, causes its fauna and flora to differ markedly from those of all the other continents. Australia is essentially the home of the marsu- pials. These are both carnivorous and herbivor- ous. The kangaroo is, perhaps, the most cha- racteristic of the marsupials. Large and power- ful animals are entirely absent; in this respect the continent offers a sharp contrast to Africa. DISTRIBUTION OF THE HUMAN RACE. 135 The birds are also of peculiar species, such as the emu, cassowary, dodo, and apterix. o&ic CHAPTER III. The Distribution of the Race. Human 356. Ethnography is that department of phys- ical geography which treats of the varieties of the human race, and their distribution. The range of the distribution of man is much greater than that of the lower animals, which, as we have already seen, with the trifling exception of a few that have been domesticated, are confined to certain limited localities. Man has far greater powers of adapting himself to a change of cir- cumstances, and is found in nearly all the climatic zones, from the equator to the poles, and at all elevations, from the level of the sea to the edge of the snow line. 357. Unity of the Human Race. — Although the different races of men vary greatly in color, size, stature, and intelligence, still a number of circumstances point to their descent from a single family or species. (1.) The Anatomical Structure is invariably the same in all races. (2.) Gradual Modification of Types presented by the different races. The more marked out- ward peculiarities, which serve as the basis for classification, pass into each other, by almost in- sensible gradations, from the highest race to the lowest. This points to a gradual modification of a single, original race by changes in external cir- cumstances, thus producing the present varieties. It would appear that all the varieties of the race have descended from the Caucasians, or whites. (3.) Similarity of Earlier Myths and Legends. Since the earlier myths and legends of nearly all nations resemble each other, it is fair to infer that their remote ancestors originally dwelt together. (4.) Close Resemblance of Language of Widely Separated Races. This may be regarded as the strongest proof of unity. If we examine the words used in different na- tions to express the most common ideas, we will find a remarkable similarity between many of them. For example, our word father is pita in Sanscrit, pater in Latin, pater in Greek, voter in German, and pere in French. The same similar- ity is noticeable in the words for mother, sister, brother, daughter, God, and many others. The only rational explanation for the resemblance is, that the words were derived from the same parent language, the present differences having been gradually acquired, as the descendants of this earlier people wandered farther and farther from their common home. An extended comparison made in this way between dif- ferent languages, has shown the common origin of the lan- guages of Europe and a large part of Asia. It has been conclusively proved that these tongues owe their origin to one parent nation, which dwelt, during pre-historic times, in the neighborhood of Mt. Ararat and Mesopotamia. Other families of languages, such as the Chinese and Semitic, have been studied, but thus far the connection between the different families has not been certainly es- tablished. NEGRO. MONGOLIAN. Fig. 121. Primary Races of Men, 358. The Races of Men. — Among the varieties of + he human race, three strongly-marked types are found : the Caucasian, the Mongolian, and the Negro. These, which may be regarded as the primary races, are grouped around three geograph- ical centres, which correspond nearly to the cen- tres of the three divisions of the Old World. The Caucasian type is found in most of Europe and in South-western Asia ; the Mongolian type, in those parts of Europe and Asia not occupied by the Caucasian ; the Negro type, in Africa. The other parts of the world are peopled mainly by three other races, which, in general, bear close resemblances to the preceding. These are the Malay, the American, and the Australian. They Page 136. DISTRIBUTION OF THE HUMAN RACE. 137 are called the secondary races, and appear to be modifications of the Mongolian. 359. Cranial Characteristics. — The primary races are sharply distinguished by the following types of skull : Caucasian. The skull is nearly oval, and the arch of the cheek-bones moderate. Mongolian. The skull is nearly round, the occipito- frontal diameter, or the distance from the forehead to the back of the head, is slightly greater than the parietal diameter, or that between the temples. Negro. The skull is elongated from the back of the head to the forehead ; that is, the occipitofrontal diam- eter greatly exceeds the parietal. The cheek-bones are large and projecting. 360. The Caucasian, or White Race is charac- terized by a round or oval head ; symmetrical features ; vertical teeth ; round or oval face ; arched forehead ; fair complexion, and ample beard. The Caucasian race inhabits South-western Asia (Hindostan, Persia, and Arabia), Northern Africa, and nearly the whole of Europe. The descendants of the race now people large portions of America, Australia, and Southern Africa. 361. Divisions of the Caucasian Race. — The Caucasian race may be divided into three branches : the Hamitic, the Semitic, and the Japhetic. (1.) The Hamitic Races originally inhabited Palestine, the shores of the Arabian Peninsula, and the valley of the Nile. They are now, how- ever, scarcely distinguishable from the other branches of the Caucasian race, with whom they have intermarried. (2.) The Semitic, or Syro-Arabian Races, com- prise the modern Syrians, the Jews or Hebrews, the inhabitants of Arabia and Abyssinia, and the greater part of Northern Africa. Among the ancient peoples belonging to this branch of the Caucasian race, are the Assyrians and Babylonians, the Israelites, Moabites, Ammonites, Edomites, Ishmael- ites, and Phoenicians. (3.) The Indo- Europeans, or the Aryan Race, comprise the Japhetic race. They are the most civilized peoples of the world, and include the following nations: (1.) Celtic Nations, including the Irish, Welsh, Scots, and the Bretons of France. (2.) Romanic Nations, comprising the Italians, Spaniards, Portuguese, and the French. (3.) The ancient Greeks. (4.) Germanic Nations, comprising the Germans, Anglo- Saxons (English), Dutch, Flemish, Danes, Swedes, and the Norwegians. (5.) Slavonic Nations, comprising the Russians, Poles, Croats, and Czechs. (6.) Nations of the Iranian Plateau, comprising the Per- sians, Belooches, and the Afghans. (7.) The Hindoos. 16 362. The Mongolian, or Yellow Race.— The chief characteristics of the Mongolian race are : broad head ; angular face ; high cheek-bones ; small, obliquely-set eyes ; straight, coarse, black hair ; scanty beard, and short stature. The color of the skin varies from pale lemon to brownish yellow. The Mongolian race includes the inhabitants of all of Asia, except a small part of the Malay Peninsula, and those portions of the continent occupied by the Caucasians. It also includes the Lapps and Finns, inhabiting the northern por- tions of Europe, the Turks of Europe, and the Magyars of Hungary, In America, the race is represented by the Esquimaux, who inhabit Greenland and the northern borders of the North American continent. In Central Asia, the race is represented by the Thibetans, Chinese, Indo-Chinese, and others. In Northern Asia, by the Samoides, inhabiting the shores of the Arctic Ocean, from the Petchora to the Yenisei, and south to the Altai Mountains ; the Ugrian, or Finnic races, inhabiting the upper valley of the Obe, and a part of Northern Europe ; the Tchooktchees, the Tungusians, and the Yakuts, of North-eastern Asia. Other branches of the race, are the Coreans, Japanese, Kamtchatdales, Koriaks, and the Mongols. 363. The Negro, or Black Race— The chief characteristics of this race are : narrow and elon- gated head ; crisp and curly hair ; projecting jaws; thick lips; soft and silky skin; color black or dusky ; scanty beard, especially on upper lip ; broad feet, and projecting heel-bones. The race inhabits the entire continent of Africa, excepting those parts occupied by the Caucasians. The following are the most important varieties of the race : the Jaloffs, Mandingoes, and Ashantis, in the west- ern part ; the Tibboos, in the north central ; the Gallas, in the eastern ; the Congo Negroes, in the south central ; and the Hottentots and Kaffirs, in the extreme south. The Negro tribes differ greatly in their civili- zation : the Gallas, though cruel and vindictive, are a handsome, gifted race ; the Hottentots, on the contrary, are among the most debased creat- ures in existence. 364. The Secondary Races. — The Malay, or Brown Race; the Australian; and the American, or Copper-colored Race, are modifications of the Mongolian Race. 365. The Malay, or Brown Race. — The princi- pal characteristics of this race are the same as those which distinguish the Mongolian ; the eyes, however, are horizontal, the face flat, and the hair 138 PHYSICAL GEOGRAPHY. less coarse and straight. The color of the skin varies from a clear brown to a dark olive. In the Papuans, it is dark brown, and even black. AUSTRALIAN. Fig. 122. AMERICAN INDIAN. Races of Men. This race inhabits the southern part of the Malay Peninsula, the island of Madagascar, and the islands of the Indian and Pacific Oceans. The different peoples included under the Malay race present the most strongly marked contrasts. The Papuans, for example, differ widely in their appearance from the normal Malay. They are, perhaps, allied more closely to the Aiistralians than to any others. 366. The Australian Race is to be regarded as a sub-variety of the Papuan branch of the Ma- lays. It inhabits all the continent of Australia not settled by the whites. The Australian race possesses the following characteristics : the head is large ; eyes deep-set ; nose broad ; hair dark ; beard abundant. The color of the skin varies from dark brown to deep black. The Australians are almost wholly desti- tute of civilization. 367. The American, or Copper-colored Race, though containing many widely differing varie- ties, yet possesses, in some respects, many com- mon features. Its general resemblance to the Mongolian is evident, but the top of the skull is more rounded, and the sides less angular. This race, though once numerous and powerful, is now rapidly disappearing before the whites. In Lower California, Mexico, Peru, and Bra- zil, the old races have become mixed with Span- ish and other elements. The ruins of temples, and once populous cities, are com- mon on the high Andean plateaus. These parts of the earth were inhabited at the time of the discovery of the continent by a people who had made considerable progress in the art of working metals, and who were probably of Asiatic origin. The plateaus of Central America contain the traces of a still higher, though more ancient civilization, the origin of which is unknown, though some trace it to a Semitic or an Egyptian source. SYLLABUS. The animals of any section of country are called its fauna. Notwithstanding their powers of locomotion, animals are restricted, by conditions of food and climate, to well- defined areas. Since animals are dependent for their existence upon plants, the heat and moisture of any given section of country form the true basis for the distribution of its fauna. We distinguish a horizontal and vertical distribution of animal life. The same change is noticed, in the species of animals, in passing from the base to the summit of high tropical mountains, as in passing along the surface of the earth from the equator to the poles. Terrestrial animal life attains its greatest development, both as regards luxuriance and diversity, . within the tropics. Marine animal life attains its greatest development in the colder waters of the polar regions and vicinity. Man attains his greatest mental development in the temperate zone. As regards the vertical distribution of life, the fauna of regions between the sea level and 5000 or 7000 feet, resem- bles, in general, that of the tropics ; between the preced- ing and 15,000 feet, that of the temperate zones. The boundaries of animal regions are, in general, to be found in the isothermal lines. As a class, animals appear to possess to but a limited de- gree the power of living in a climate differing greatly from that in which they were first created. The fauna of the earth may be conveniently arranged under three heads: the tropical, temperate, and arctic. The tropical fauna are characterized by the number and diversity of terrestrial species, as well as their size, strength, and sagacity. KEVIEW QUESTIONS. 139 In tropical fauna, the mammalia are represented as fol- lows: Monkeys, by the orang-outang, chimpanzee, gorilla, and baboon. Flesh-eating mammals, by the lion, tiger, panther, and puma. Plant-eating mammals, by the elephant, rhinoceros, ta- pir, hippopotamus, zebra, quagga, giraffe, and camel. Marsupials, by the kangaroo. Birds are represented by the condor, ostrich, eagle, ibis, flamingo, cassowary, bird of paradise, peacock, and parrot. Reptiles, by the crocodile, alligator, iguana, and turtles. The temperate fauna, though characterized by fewer of the higher species of animals, yet contain many of large size, and among them animals of great use to man. In temperate fauna, the carnivorous mammalia are rep- resented by the lynx, hyena, wolf, jackal, dog, fox, rac- coon, bear, seal, and walrus. The herbivorous mammalia, by the wild boar, hog, horse, ass, ox, sheep, goat, chamois, moose, elk, reindeer, stag, antelope, buffalo, camel, and llama. The gnawing mammals, by the beaver, squirrel, rat, and porcupine. The whale, by the sperm and white whale. The marsupials, by the kangaroo. Birds, by the condor, vulture, hawk, eagle, owl, parrot, turkey, pheasant, wren, thrush, robin, nightingale, lark, pelican, and albatross. The arctic fauna contain but comparatively few large land species; the chief characteristics are numerous smaller furry species. In the marine arctic fauna numerous species are found, some of which, as the whale, are among the largest in the animal world. The terrestrial arctic fauna are characterized by the fol- lowing animals: the white polar bear, the reindeer, the moose, and the musk-ox. The marine fauna, by the Greenland whale, the seal, and the walrus. The peculiar distribution of the vegetation of the con- tinents produces corresponding peculiarities in their cha- racteristic fauna. The North American continent is characterized by the preponderance of its plant-eating mammals. The cause of this peculiarity is to be found in the abundance of its pasture lands. Fur-bearing animals particularly characterize the north- ern and central portions of North America. There are three natural districts of fur-bearing animals in North America: 1. The forest region; 2. The barren grounds; 3. The prairie regions. The South American continent is especially character- ized by the predominance of reptilian life, aquatic birds, and insects. The cause of the peculiarity is traceable to the predominance of the vegetable life over the animal. The Asiatic continent is especially characterized as being the original home of most of the animals which man has domesticated. The cause of this peculiarity is traceable to the fact that Asia was the primitive home of man himself. The great deserts of Africa are characterized by the presence of animals which are peculiarly noted for their swiftness of locomotion. In the remaining portions of Africa, the luxuriant vege- tation sustains animals of a larger, bulkier growth; as, for example, the elephant, rhinoceros, hippopotamus, and the giraffe. Australia is peculiarly characterized by the presence of the marsupials. It is the home of the kangaroo, the most important of the marsupials. Ethnography treats of the varieties of the human race, and their distribution. Man has a wider range of distribution than any other animal. It is believed by most that all the varieties of the hu- man race were originally descended from one family. Though greatly different in color, size, stature, and in- telligence, the general anatomical structure, the basis on which all other animals are classified, is invariably the same, even in the most widely differing races. The languages of Europe and of a large portion of Asia, appear to owe their origin to one parent nation, which dwelt, during pre-historic time, in the neighborhood of Mount Ararat and Mesopotamia. The primary races are the Caucasian, the Mongolian, and the Negro. The secondary races are modifications of the Mongolian : they are the Malay, the American, and the Australian. The Caucasian race inhabits South-western Asia, North- ern Africa, and nearly the whole of Europe. The Caucasian race may be divided into three branches : the Hamitic, the Semitic, and the Japhetic, or the Indo- Europeaus. The Mongolian race inhabits all of Asia, except a small part of the Malay Peninsula and those portions of the continent occupied by the Caucasians. The Chinese, Japanese, Esquimaux, Lapps, Finns, Turks, and Magyars, are among the most important of the Mon- golians. The Negro race inhabits all the continent of Africa not occupied by the Caucasians. The Malay race inhabits the southern part of the Malay Peninsula, Madagascar, and the islands of the Indian and Pacific Oceans. The Australian race inhabits all the continent of Aus- tralia not settled by the whites. REVIEW QUESTIONS. ►oJ*Kc Define zoological geography. Fauna. Why should the distribution of heat and moisture form the true basis for the distribution of animal life? Distinguish between the horizontal and the vertical dis- tribution of animals. What difference exists between terrestrial tropical fauna and marine tropical fauna ? Between what limits, in the vertical distribution of ani- mals, do the fauna of a tropical mountain-range resemble that of the tropical horizontal zone ? Of the temperate zone? What lines generally form the boundaries of animal regions? Which possesses the greater power of acclimation, man or the inferior animals? State the characteristics of the tropical fauna, naming 140 PHYSICAL GEOGRAPHY. the principal carnivora, herbivora, cetacea, cheiroptera, marsupials, birds, and reptiles. State the characteristics of tbe temperate fauna, naming the principal carnivora, herbivora, rodentia, cetacea, mar- supials, birds, and reptiles. State the characteristics of the arctic fauna, naming the characteristic terrestrial and marine species. What peculiarities characterize the fauna of North America? What is the cause of these peculiarities? What are the peculiarities of the fauna of the South American continent? What is the cause of these pecu- liarities? What is the main peculiarity of the Asiatic fauna? Describe the districts of fur-bearing animals of North America. Of Asia. For what peculiarity are the animals of the deserts of Africa and Arabia noted ? What is the main characteristic of the Australian fauna ? Define ethnography. What arguments can be adduced to show the probable unity of the human race ? Name the primary races. Name the secondary races. Into what three branches may the Caucasian race be divided? What peoples have descended from the Aryans, or the Indo- Europeans ? Name the principal Celtic nations. What nations have sprung from the ancient Eomans? What nations have descended from the Germans ? Name the Slavonic nations. The Iranians. Name the parts of the world inhabited by each of the primary and secondary races. Describe the peculiarities of each of these races. Name a few of the peoples which belong to each of the races. MAP QUESTIONS. x^Kc Trace on the map of the Vertical Distribution of Ani- mal Life, the characteristic fauna in those parts of each of the continents, lying between the level of the sea and 5000 feet. Between 5000 and 10,000 feet. Between 10,000 and 15,000 feet. Between 15,000 and 20,000 feet. Name from the map of the Distribution of Animals, the tropical species of the Americas. Of Africa. Of Asia. Of Australia. Name, in a similar manner, the temperate and arctic species of the Americas. Of Europe. Africa. Asia. Aus- tralia. In what portions of the world is the seal found ? The walrus? The whale? Trace on the map the southern limit of the polar bear. Of the reindeer. Of monkeys. Of the elephant and rhi- noceros. The northern limit of the camel. Of monkeys. Locate the chief districts of venomous serpents in the eastern and western hemispheres. Describe the region of the musk-ox. Of the grizzly bear. Of the buffalo. State, from the Ethnographic Map, the portions of the world inhabited by the Caucasian race. The Mongolian race. The Ethiopian race. The Malay race. The Amer- ican race. The Australian race. What different peoples dwell north of the arctic circle? South of the tropic of Capricorn ? Trace on the map the northern limit of permanent habitation. The southern limit. What race inhabits Hindostan ? What people ? What race inhabits Abyssinia? What people? Greenland? Patagonia? China? Mexico? France and Spain ? North- ern Norway and Sweden ? Arabia? Madagascar? Page 141 Part VI. THE PHYSICAL FEATURES OF THE UNITED STATES, ►o^c The civilization and development of a country are dependent, in a marked degree, on the pecu- liarities of its physical features. The soil and climate exert their influence on the vegetable and animal life, and these, in turn, react on man. If proper soil and climate exist ; if the peculiarities of the surface structure permit of ready intercommunication, and if extensive deposits of coal and valuable metals occur, the future development of the country is assured. The physical features of the magnificent domain of the United States are such as seem to destine it to become the theatre of the civilization of the future. The peculiarities of its position and extent, the nature of its soil, the climate, and rainfall, the size and constancy of its navigable rivers, and the extent and variety of its valuable mineral deposits, eminently fit it to sustain a very high order of civilization. CHAPTER I. Surface Structure of the United States, exclusive of Alaska. 368. Situation and Extent.— The United States occupies the entire breadth of the North American continent, between lat. 49° K, and 24° 30' K and extends from long. 66° 50' W. from Greenwich, to 124° 31' W. The total area, exclusive of Alaska, is 3,026,500 square miles. 142 369. Coast Line. — The coast line is compara- tively simple and unbroken. On the east, the Atlantic Ocean extends into the land in three wide curves ; on the south, is the deep indenta- tion of the Mexican Gulf; on the west, the land is thrust out into the Pacific in an almost unbroken curve. The total coast line, exclusive of the ad- joining islands and Alaska, is about 12,609 miles. 370. Gulfs and Bays. — The principal indenta- tions on the eastern coast are Long Island Sound, Delaware and Chesapeake Bays, and Albemarle SURFACE STRUCTURE OF THE UNITED STATES. 143 and Pamlico Sounds. On the western coast are the Gulf of Georgia and the fine harbor of the Bay of San Francisco. The Atlantic shores slope gently toward the ocean ; the Pacific shores are abrupt. 371. Islands. — The islands of the Atlantic coast are of three distinct classes : those north of Cape Cod are, for the most part, rocky, and are de- tached portions of the mainland ; those south of Cape Cod are generally low and sandy, and are, for the most part, of fluvio-marine formation ; those off the coast of Florida are of mangrove forma- tion. On the Pacific coast are the Santa Barbara Islands, a rocky group south-west of California; and Vancouver Island, north-west of Washington. Fig. 123. View on the Coast of Mount Desert Island, Maine. 372. Mangrove Islands. — Mangrove trees grow in dense jungles, on low muddy shores, in tropical regions. From both trunks and branches the trees throw out air-roots, which spread so as to cover the adjoining spaces in an almost intermin- able network of roots and branches. The area of surface covered by the trees is still further in- creased by the curious property which the seeds possess of sprouting while on the tree, subse- quently floating away, and afterward affixing themselves to the bottom of the jungle, to form new growths. In this way, the trees form man- grove islands, which at first are not true islands, the trees simply standing above the water by means of their intertwined roots. In course of time, however, sediment, collecting between the roots of the trees, forms islands. These islands are common in the shallow water off the coasts of Florida. 373. Coral Reefs of Florida. — The peninsula of Florida, south of the northern extremity of the Everglades, and probably as far north on the eastern coast as St. Augustine, is, according to Agassiz, a species of coral formation, formed, however, under different conditions than are the coral islands of the Pacific. Fig. 124. Florida Reefs and Keys, (LeOonte.) Fig. 125. Everglades, Reefs, and Keys of Florida, (LeOonte.) Figure 124 is a map of Florida with its reefs and keys. Figure 125, is a section along the line A. A. In Fig. 124 the line a a, shows what was at one time the limit of the southern coast of Florida. 6 b, is the present limit of the southern coast, cc, are the keys, which are low islands. dd, is the growing coral reef, e, is the Everglades, dotted with islands, called hummocks. Between c c, and d d, is the ship channel. Outside the growing coral reef dd, are the profound depths of the Gulf Stream G. S. The growth of the reef-formations is explained hy LeConte as follows (Fig. 125) : a, was at one time the limit of the southern coast of Florida. 6, is the present southern coast, which at one time was a coral reef like d. Upon b, a line of coral islands gradually formed connecting it with the old southern coast a. The ship channel between a, and b, gradually filled up and formed the Everglades e. Meanwhile, another reef formed, in the position of the present keys, c, the ship channel being between 6, and c. This reef has now grown to be a line of coral islands, and the ship channel, between 6, and c, converted into shoals and mud flats, /. The present ship channel is between c, and d. In course of time the southern coast will extend to the present line of keys, c, and the shoal water /, will become another Everglades. Outside the present keys c, another coral reef d, is growing, to which the coast will ultimately extend, and which will mark the limit of the formation, owing to the deep waters 144 PHYSICAL GEOGRAPHY. of the Gulf Stream, immediately beyond it. In Figure 125, the dotted lines show the successive steps of the formation. 374. Forms of Relief. — The United States is traversed by two distinct mountain-systems : the Pacific System — the predominant system— on the west, and the Appalachian System — the secondary system — on the east. 375. The Pacific System, consists of a broad plateau, traversed by two distinct mountain-sys- tems: the Rocky Mountains, and the Pacific mountain-chains. It embraces about one-third of the entire territory of the United States proper. 376. The Rocky Mountain System, consists of a number of parallel chains connected by numer- ous cross ranges. They rise from the summits of an elevated plateau, which in some places is fully 7000 feet above the sea. The chains are broken in several places by transverse valleys or passes, traversed by important rivers. The most import- ant of these passes is South Pass, in Wyoming, traversed by the Sweet Water River, a tributary of the Platte. The Missouri, Rio Grande, and other rivers also flow through similar depressions. The chains are separated into northern and southern sections by a gap occupied by an elevated plateau, over which the Union Pacific Railroad passes. Among the many lofty peaks of this mountain- system are Long's Peak, 14,050 feet ; Pike's Peak, 14,216 feet ; and Fremont's Peak, 13,570 feet high. A remarkable feature of these mountains is the basin- shaped valleys, called parks, formed by transverse ranges connecting the parallel ranges. The most important of these parks are North, South, and Middle Parks. They are nearly rectangular in outline, and are hemmed in by huge mountain-ranges. Each parfi; gives rise to an im- portant river. The rich verdure of these deeply-sunken basins is rendered the more striking by contrast with the desolate mountains surrounding them. The Yellowstone National Park, in the north-western part of Wyoming, is traversed by some of the head-waters of the Yellowstone Eiver. It is a region of hot springs, deep gorges, high mountain-peaks, and magnificent scenery. It has been set apart by the government for the purposes of a public park. The Great Plains, an elevated plateau, lie along the eastern side of the Rocky Mountains. They are undulating plains, which slope by almost imperceptible gradations, to the valley of the Mississippi. They are treeless, and near the base of the mountains have but a scanty vegetation. Near the lower part of the slope they merge into prairies, covered with a luxuri- ant growth of grass. 377. The Pacific Mountain-Chains extend through California, Oregon, and Washington, and, in general, are parallel to the Rocky Moun- tains. They comprise the Cascade Mountains in Oregon and Washington, and the Sierra Nevada and the Coast Mountains in California. The famous gold regions of California lie mainly west of the Sierra Nevada and the Coast Mountains. The loftiest peaks of the Pacific Mountain- chain exceed those of the Rocky Mountains in height. The highest peaks are Mt. Rainier in the Cascade Range, 14,444 feet high ; and in the Sierra Nevada Range, Mt. Shasta, 14,482 feet high, and Mt. Whitney, 14,800 feet high. The culminating point of the Pacific Mountain- chains is Mount St. Elias, in Alaska, which is es- timated to be 19,500 feet high. The Cascade Mountains contain numerous ex- tinct volcanoes. The Great Basin lies between the Wahsatch on the east, and the Sierra Nevada and Cascade ranges on the west, Fig. 126. The Great OaSon of Colorado. It possesses a true inland drainage. East of the Wahsatch Mountains and the western flanks of the elevated peaks SURFACE STRUCTURE OF THE UNITED STATES. 145 and ranges of Colorado, lies a region drained by the head- waters of the Colorado. This region, together with the country lying in the middle courses of the river, is a won- derful section of country, traversed by streams that have eroded their valleys and flow through deep canons, some of which are over 6000 feet deep. A view of a part of one of the most noted of these canons is shown in Fig. 126. 378. The Appalachian System, sometimes called the Alleghany Mountains, extends from Georgia to Maine, nearly parallel to the Atlantic. The chain varies in breadth from 150 to 200 miles. The system consists of an elevated plateau, bearing several mountain-chains, separated by wide valleys. In the northern and southern parts of the chain, where the elevation is the greatest, the system is formed of irregular groups, without any definite direction. In the centre, low parallel chains occur separated by, fertile val- leys. These valleys generally take the names of the rivers which flow through them. The system is highest in North Carolina, where Mt. Mitchell, 6707 feet high, forms its culminat- ing point. Beginning in the north, the system includes the White Mountains in New Hampshire, with Mount Fig. 127. The Natural Bridge (Virginia). Washington, 6294 feet high ; the Green Mountains, in Vermont ; the Adirondacks, in New York, with the culminating peak of Mount Marcy, 5379 feet high ; the Catskill Mountains, the Blue Mountains, the Alleghanies, the Blue Ridge, the Cumberland Mountains, and others. The Natural Bridge, in Bockbridge County, Virginia, is, from its peculiar formation, an object of interest to tourists. 379. Plains. — There are two great low plains in the United States: the Atlantic Coast Plain and the Plain of the Mississippi Valley. The Atlantic Coast Plain lies along the eastern flanks of the Appalachian Mountains. It varies in width from 50 to 250 miles. Along the coast the soil is comparatively sandy, and has been formed by the combined action of the rivers and ocean. The extensive swamps which occur in this region — such as Cypress Swamp, in Delaware, Dismal Swamp, north of Albemarle Sound, Alligator Swamp, between Albemarle and Pamlico Sounds, and Okefinokee Swamp, in Southern Georgia — are of fluvio-marine origin. The Everglades, in Florida, are the result of a coral formation. Farther from the coast, the plain is more elevated ; long valleys occur, which are very fertile, particularly near the river bottoms. The Mississippi Valley lies between the predomi- nant and the secondary mountain-systems. It is over 300,000 square miles in area, and includes some of the most fertile land in the country. Much of it is covered with forests or prairies. 380. River- and Lake-Systems. — The United States is particularly noted for the number and extent of its navigable rivers. Oceanic Drainage — Atlantic System. —Among the important rivers emptying directly into the Atlantic Ocean are the Penobscot, Merrimac, Connecticut, Hudson, Delaware, Susquehanna, Fig, 128. Scene on the Mississippi. Roanoke, Cape Fear, Santee, Savannah, Alta- maha, and the St. John's. 146 PHYSICAL GEOGRAPHY. Of the rivers flowing into the Mexican Gulf, the Appalachicola, Alabama, Mississippi, Sabine, Trinity, Brazos, Colorado, and the Rio Grande are the most important. The Mississippi, faking its origin in the head-waters of the Missouri — which is the true parent stream — is the long- est river in the world, its length being 4490 miles. Its tributaries are, in general, navigable for great distances, and thus afford ready communication with different parts of the basin. The important tributaries of the Mississippi on the west are the Minnesota, the Missouri, the Arkansas, and the Eed. On the east, the Wisconsin, the Illinois, and the Ohio. The Pacific System. — The principal rivers emp- tying into the Pacific Ocean are the Columbia, Sacramento, San Joaquin, and the Colorado. 381. Inland Drainage. — The rivers and lakes of the Great Basin have no outlet to the ocean, and therefore form true steppe systems. Great Salt and Humboldt lakes are the principal lakes, and the Humboldt and the Reese, the principal rivers. There are two regions in the United States below the mean level of the sea: (1.) In the southern part of California, in Soda Valley, 200 feet below the sea. (2.) Death Valley in Eastern California. These regions are extremely arid.' 382. Lake-Systems. — The most important lake- system of the United States lies in the northern part. It includes, among numerous others, five of the largest fresh-water lakes in the world: Superior, Michigan, Huron, Erie, and Ontario. From their immense extent, they resemble great inland seas. Numerous fluviatile or river lakes occur near the borders of the middle and lower courses of the Mississippi and its tributaries. They are nearly all found in the States west of the Mississippi. -~oJ«0>©<J*JC The area of the United States, exclusive of Alaska, is about 3,000,000 square miles. The coast line is comparatively simple and unbroken. The principal indentations on the east are Long Island Sound, Delaware and Chesapeake Bays, and Albemarle and Pamlico Sounds ; on the west, the Gulf of Georgia and the Bay of San Francisco. The slope of the Atlantic shores is gradual ; that of the Pacific shores is abrupt. On the Atlantic coast, the islands north of Cape Cod are for the most part rocky ; those south of Cape Cod are gen- erally low and sandy. Mangrove islands are formed by sediment collecting around the closely intertwined roots of mangrove trees. These islands occur in the shallow waters off the coast of Florida. Nearly all of Florida, south of the Everglades, and probably as far north on the eastern coast as St. Augus- tine, consists of a peculiar variety of coral formation. The Pacific system is the predominant mountain-system ; the Appalachian system is the secondary system. The Pacific system consists of the Rocky Mountains, the Sierra Nevada, the Cascade, and the Coast Mountains. The highest peaks are found in the Cascade Mountains. Portions of the Pacific Mountain ranges contain extinct volcanoes. The Appalachian system, or the system of the Allegha- nies, includes the White Mountains, the Green Mountains, the Adirondacks, the Catskills, the Blue Ridge, and the Cumberland Mountains. There are two great low plains in the United States : the Atlantic Coast Plain and the Plain of the Mississippi Valley. The principal rivers draining into the Atlantic Ocean are the Penobscot, Merrimac, Connecticut, Hudson, Dela- ware, Susquehanna, Roanoke, Cape Fear, Santee, Savan- nah, Altamaha, and St. John's. 18 The principal rivers draining into the Mexican Gulf are the Appalachicola, Alabama, Mississippi, Sabine, Trinity, Brazos, Colorado, and the Rio Grande. The principal rivers draining into the Pacific Ocean are the Columbia, Sacramento, San Joaquin, and the Colorado. The Great Basin, between the Wahsatch and the Sierra Nevada Mountains, has an inland drainage. Soda Valley, in Southern California, and Death Valley, in Eastern California, are below the level of the sea. The Great Lakes, Superior, Michigan, Huron, Erie, and Ontario, form the largest system of fresh-water lakes in the world. The United States extends from the isotherm of 40° Fahr. to 77° Fahr., and therefore lies in the physical north tem- perate and the- torrid zones. A marked contrast exists between the temperature of the eastern and the western coasts of the northern half of the country. The eastern coasts are colder than the western. The greater warmth of the western coasts is caused by warm ocean currents, westerly winds, and heavy rainfalls. The Atlantic seaboard is colder than corresponding lati- tudes on the western shores of Europe or on the western shores of the United States. From observations dating back to the year 1738 it ap- pears that from that time the climate of the United States has undergone no decided change. The United States lies in the zone of the variable winds; westerly winds predominate. The heaviest annual rainfall is 65 inches. It occurs near the borders of the Gulf States and along the Pacific sea- board in Washington and Oregon. The smallest annual rainfall is found in the Great Basin , it varies from 5 to 10 inches. East of the 100th meridian from Greenwich the average fall is 40 inches. On the Atlantic coast rain is especially abundant during spring ; on most of the Pacific coast, during winter. 158 PHYSICAL GEOGRAPHY. The Weather Bureau was established for the observation of the meteorological conditions of the country. There are four characteristic plant regions in the United States: the Forest, the Prairie, the Steppe, and the Pacific. The forest region lies mainly east of the Mississippi ; the characteristic trees are the pine, spruce, hemlock, fir, juni- per, beech, maple, birch, alder, oak, and poplar. The principal large animals of the United States are those which have been domesticated, as the horse, ox, cow, sheep, mule, goat, and dog. Among wild animals are the black bear, panther, deer, grizzly bear, wolf, and manatee or sea-cow. The principal agricultural productions are wheat, corn, rye, oats, barley, buckwheat, hay, hops, flax, tobacco, rice, cotton, and sugar. . The principal metals are gold, silver, platinum, iron, copper, zinc, lead, tin, mercury, chromium, nickel, cobalt, antimony, bismuth, and manganese. Deposits of coal, rock-salt, marble, coal oil, and natural gas are found, and many varieties of durable building- stone. Extensive peat-bogs occur in Massachusetts and Virginia. The Territory of Alaska has an area of about 530,000 square miles and is nearly one-sixth that of the area of the rest of the domain of the United States. The coast line of Alaska is very irregular, and has a length of at least 8000 miles. Behring Sea on the west, and the Gulf of Alaska on the south, are the principal indentations of the coast. Norton Sound and Kuskovitch and Bristol Bays are among the most important of the smaller indentations. The principal islands are St. Lawrence Island, Nunivak, the Aleutian Islands, Afognak, Kadiak, Baranoff, Chicha- gof, and Prince of Wales. The northern portions of Alaska are low and flat, and are covered by tundras or frozen moor-lands. The rest of the country is generally mountainous, and is traversed by prolongations of the Pacific Mountain system of North America. Mts. St. Elias, Fairweather, and Crillon are the principal peaks. The principal river of Alaska is the Yukon, which is some 2000 miles long, and is one of the largest rivers of the North American Continent. The Kuskovim is the only other important river. The Yukon has a delta mouth — the Kuskovim, an estuary. The climate of Alaska is cold and wet, though, under the combined influences of the Japan current, the rains, and the warm south-westerly winds, the climate is less severe than at corresponding latitudes in the interior, or on the Atlantic coast. Dense growths of grasses abound during the brief sum- mer. Forests of yellow cedar and spruce occur. The chief animals are the polar and brown bears, the mink, black or silver fox, the moose, and the reindeer. The whale is found in the waters off the northern shores, and the walrus, the seal, and the sea-otter are sources of wealth by reason of their valuable furs. Salmon, hali- but, cod, and herring, are the principal food-fish. Deposits of coal, silver, gold, lead, and cinnabar occur in different parts of the country. The inhabitants consist of various elements, the princi- pal of which are the Esquimaux, the Indians, the Aleuts, the Creoles, and the people of the archipelagoes of the southern and south-eastern coast. Sitka, on Baranoff Island, is the principal settlement. REVIEW QUESTIONS. oJO{c State the geographical position of the United States. Describe the peculiarities of its coast lines. Name the principal indentations of the eastern coast. Of the western coast. In what respect do the islands which lie north of Cape Cod differ from those which lie south of it? What is the origin of the islands off the southern coast of Florida? Describe the Pacific Mountain system. Locate the Great Plains. The Great Basin. Describe the Appalachian Mountain system. Name the great low plains of the United States. Name the important rivers which drain directly into the Atlantic ; name those which drain into the Atlantic through the Gulf of Mexico ; name those which drain into the Pacific. What system of inland drainage is found in the United States? Describe the lake-systems of the United States. In what mathematical zone is the United States situated ? In what physical zones? Between what isothermal lines does the United States extend ? Describe the general direction of the isotherm of 40° Fahr. Of 55° Fahr. Of 60° Fahr. What difference exists between the climate of the eastern and western coasts ? What are the causes of this difference ? Has the climate of the United States undergone any de- cided change during the last hundred years ? In what wind zone does the United States lie? In what parts of the country does the heaviest annual rainfall occur? The smallest annual rainfall? What is the rainfall of the upper Mississippi Valley? Of the lower Mississippi ? At what season of the year do the heaviest rains occur on the Atlantic coast ? On the Pacific coast ? For what was the Weather Bureau established ? What are tornadoes ? Under what four characteristic plant regions may the vegetation of the United States be arranged? Describe the location of each of these regions. Name the principal forest trees of the United States. Name the principal domesticated and wild animals of the United States. Enumerate the principal agricultural productions. Name the principal corn-producing States. The prin- cipal wheat-producing States. Name the principal cotton-producing States. The prin- cipal rice-producing States. The principal sugar-producing States. What valuable metals are found in the United States? What other valuable mineral substances occur? What are the limits of the Territory of Alaska? State its boundaries. What is its area? What sum was paid for Alaska by the United States Government ? Name the principal indentations of the coast of Alaska. What is the extent of its coast line ? Name the principal islands of the western coast. Of the southern coast. Describe the surface structure of Alaska. To what gen- eral system of mountains do its elevations belong? Name some of the principal peaks. Are any of them volcanic? Describe the river-system of the Yukon. Where is the Kuskovim Eiver? Which of these rivers has a delta mouth? Which has an estuary? What is the general climate of Alaska ? How does the climate compare with that of corresponding latitudes in the interior of the country or on the Atlantic coast ? Why is this ? Describe the vegetation of Alaska. What are the prin- cipal trees? Name the principal food-fish of Alaska. Name the prin- cipal fur-bearing animals. What other large animals are found in the country ? Which is the principal settlement? Name some of the different people who inhabit Alaska. MAP QUESTIONS. °*Kc Describe from the Physical Map of the United States the surface structure of the country, giving the relative position of the High Lands and Low Lands. Describe the Pacific Mountain System. Describe the Appalachian Mountain System. Locate the following : the Black Hills ; the Wahsatch Mountains ; the Sierra Madre ; San Louis Park ; Pike's Peak ; Long's Peak ; Fremont's Peak. Describe the drainage of the Great Lakes. Name the principal rivers which empty into the Atlantic. Into the Gulf of Mexico. Into the Pacific. Name the principal tributaries of the Mississippi. Where are the Santa Barbara Islands? The Bahama Islands? Vancouver's Island? Trace on the map the isothermal line of 45°. What is the cause of the southward deflection of the isothermal lines 'in the western part of the United States ? Prove from the isotherms that the climate of the northern half of the Atlantic coast is colder than the southern half. In what portions of* the United States is the lowest mean annual temperature found? The highest? Name the swamps and sounds of the Atlantic sea- board whose formation is to be traced to fluvio-marine deposits. What swamp is due to coral formations? *HSH« GENERAL SYLLABUS. >j<«o< Physical Geography treats of the distribution of the land, water, air, animals, and plants of the earth. The earth moves through empty space around the sun. It is kept in motion in its orbit by its inertia and the attraction of the sun. The rotundity of the earth is proved — 1. By the ap- pearance of approaching or receding objects ; 2. By the cir- cular shape of the horizon ; 3. By the shape of the earth's shadow ; 4. By the great circle of illumination ; 5. By actual measurement. Exact geographical position is determined by reference to certain imaginary lines called parallels and meridians. Representations of the whole or of parts of the earth's surface are made by means of maps. Maps are drawn on different projections : the Equa- torial, the Polar, and Mercator's projection are in the most general use. The length of daylight in either hemisphere depends on the extent to which that hemisphere is inclined towards the sun ; the longest day in the northern hemisphere occur- ring June 21st, when the sun is vertical over the Tropic of Cancer. The change of seasons is occasioned by the revolution of the earth, together with the inclination of the earth's axis at an angle of 66° 33' to the plane of its orbit, and the constant parallelism of the axis with any former position. The Torrid Zone is the hottest part of the earth, because, at one time or another throughout the year, every part of its surface receives the vertical rays of the sun. The following different opinions are held concerning the condition of the interior of the earth : (1.) That the earth has a solid centre and crust, with a neated layer between. (2.) That the crust only is solid, and the remainder suf- ficiently heated to be in a fused or pasty condition. (3.) That the earth is solid throughout, but highly heated in the interior. The proofs of the present highly-heated condition of the interior of the earth are as follows : 1. In all parts of the earth, the deeper we penetrate the crust, the higher the temperature becomes ; that is t© say, the entire interior is heated. 2. The presence of volcanoes, which, in all latitudes, eject melted rock from the inside of the earth ; that is to say, the entire interior is filled with matter sufficiently hot to melt rock at ordinary pressures. 3. The occurrence of earthquake shocks in all parts of the earth. 160 PHYSICAL GEOGRAPHY. The original fluidity of the earth is rendered probable by the following circumstances : (1.) By the spherical shape of the earth. (2.) The crystalline rocks, or those formed in the presence of great heat, underlying all others. (3.) The warmer climate of the earth during the geolog- ical past. Volcanoes eject from the interior of the earth — 1. Melted rock or lava; 2. Showers of ashes or cinders; 3. Vapors or gases. These materials are brought up from great depths into the volcanic mountain by the force caused by a contract- ing globe. They may escape from the crater — 1. By the pressure of highly-heated vapors; 2. By the pressure exerted by a column of liquid lava. All volcanoes are found near the coasts of the continents, or on islands. The movements of the earth's crust produced by earth- quake shocks are — 1. A wave-like motion around the centre of disturbance ; 2. An upward motion ; 3. A rotary motion. The following facts have been discovered as regards earthquakes : (1.) Their place of origin is not very deep seated. (2.) The area of disturbance increases with the energy of the shock and the depth of its origin. (3.) The shape of its origin is that of a line and not that of a point. (4.) The shape of the area of disturbance varies with the elasticity of the materials through which the shock moves. (5.) The earthquake motion travels as spherical waves, which move outward in all directions from their point of origin. The most violent earthquake shocks continue but for a short time. Earthquakes are generally caused by the strain produced by the contraction of the crust. Earthquake shocks are of more frequent occurrence — 1. In winter than in summer ; 2. At night than during the day ; 3. During the new and full moon, than during any other phase. Earthquake shocks may occur in any part of the world, but are of most frequent occurrence in the neighborhood of volcanoes. Bocks may be divided, according to their origin, into three classes: 1. Igneous; 2. Aqueous; 3. Metamorphic. They may be divided according to their condition, into — 1. Stratified ; 2. Unstratified. Unstratified rocks are either igneous or metamorphic. Bocks which contain organic remains are said to be fossiliferous ; if destitute of these remains, non-fossil- iferous. Stratified rocks are sometimes called fragmental. Un- stratified rocks are sometimes called fragmental. Aqueous rocks are sometimes called sedimentary. During the geological past extensive changes occurred in the land and water surface of the earth, and in the plants and animals inhabiting it. The changes now occurring in the earth's crust are caused — 1. By the winds; 2. By the moisture of the atmosphere; 3. By the action of running water; 4. By the agency of man ; 5. By the action of the heated in- terior. Of the 197,000,000 square miles of the earth's surface, 144,000,000 square miles are covered by water, and 53,000,000 by land. The proportion between the land and water is very nearly as the square of three is to the square of five. The continents extend farther to the north than to the south ; they are crowded together near the north pole. Their southern projections are separated from each other by extensive oceans. Nearly all the land masses are collected in one hemi- sphere, and a large part of the water in another. There are two great systems of trends or lines of direc- tion, along which the shores of the continents, the moun- tain-ranges, the oceanic basins, and the island chains extend. The main prolongation of the eastern continent is in the direction of the north-eastern trend ; the western, in that of the north-western trend. The coast lines of the northern continents are very irreg- ular, the shores being deeply indented with gulfs and bays, while those of the southern continents are comparatively simple and unbroken. Of the 53,000,000 square miles of the land, 3,000,000, or about one-seventeenth, is composed of islands. Islands are either continental or oceanic. Continental islands are detached portions of the neigh- boring continents. Oceanic islands are the summits of submarine mountain- chains. They are either high or low : the high oceanic islands are generally of volcanic formation ; the low islands are of coral formation. Mangrove islands occur off the coasts of Florida. There are four varieties of coral formations : 1. Fringing reefs; 2. Barrier reefs ; 3. Encircling reefs ; 4. Atolls. A peculiar variety of coral reef occurs off the coasts of Florida. The subsidence of the ocean's bed is proved — 1. By the exclusive occurrence of volcanoes on the shores of the con- tinents or on islands; 2. By the occurrence of atolls or coral islands; 3. By the general direction of the continen- tal island chains. The earth's surface is composed of high lands and low lands. The dividing line is 1000 feet above the level of the sea. High lands are either mountainous or plateaus. Low lands are either hills or plains. About one-half of the land surface of the earth is occu- pied by plains. Plains are 1. Undulating ; 2. Marine; 3. Alluvial. Mountains were formed by the contraction of the earth's crust, producing a lateral pressure on extended, thick de- posits of sedimentary rocks. Slaty cleavage was caused by this lateral pressure. The following peculiarities are noticeable in the relief forms of the continents : 1. The continents have, in general, high borders and a low interior. 2. The highest border lies nearest the deepest ocean ; hence, the culminating point, or the highest point of land, lies out of the centre of the continent. 3. The greatest prolongation of a continent is always that of its predominant mountain-system. 4. The prevailing trends of the mountain masses are the same as those of the coast lines, and are, in general, either north-east or north-west. Water acquires its maximum density at about the tem- perature of 39.2° Fahr. Water requires more heat to warm it, and gives out more on cooling, than any other common substance. During the constant washings to which the continents GENERAL SYLLABUS. 161 are subjected by the rains, their surfaces are cleansed of the decaying animal and vegetable matters which cover them. The drainage of the laud is of two kinds : subterranean and surface, drainage. Surface drainage is either oceanic or inland. According to the size of their reservoirs, springs are either constant or temporary ; according to the depth of the reservoirs, they are either cold or hot ; according to the nature of the mineral substances lining their reservoirs, they become charged with various mineral substances ; if their reservoirs discharge through a siphon-shaped tube, they are periodical ; if their reservoirs are formed of con- cave layers, they are called artesian springs. The quantity of water discharged by a river depends— 1. On the size of its basin. 2. On the amount of its rain- fall. 3. On the climate of its basiu, a dry, hot air dimin- ishing the quantity by evaporation. 4. On the nature of its bed or channel, whether leaky or not. 5. On the features of its basin, whether wooded or open. The material eroded by a river is deposited— 1. In the channel of the river. 2. On the alluvial flats or flood- grounds. 3. At the mouth. 4. Along the coast near the mouth. In the upper courses of rivers erosion occurs mainly on the bottom of the channel ; in the lower courses, at the sides. The Atlantic and Arctic Oceans receive the waters of nearly all the large river systems of the world. Lakes connected with the system of oceanic drainage are generally fresh ; those connected with the inland drainage are generally salt. The bed of the ocean is less diversified than the surface of the land. The greatest depth of the ocean is probably greater than the greatest elevation of the land. The articulation of land and water assumes four dis- tinct forms, — inland seas, border seas, gulfs aud bays, and fiords. Inland seas characterize the Atlantic ; border seas, the Pacific ; gulfs and bays, the Indian ; fiords, the Atlantic aud Pacific. A deposit of fine calcareous mud or ooze, formed of the hard parts of minute animalcule, occurs over extended areas of the floor of the ocean. Tides are caused by the attraction of the sun and moon ; spring tides by their combined attractions ; neap tides, by their opposite attractions. Constant ocean currents are occasioned by the heat of the sun and the rotation of the earth. The vertical rays of the sun are warmer than the oblique rays — 1. Because they have a less depth of air to pass through. 2. Because they are spread over a smaller area. 3. Because, striking the surface more directly, they produce greater heat. Continual summer characterizes the tropics ; summer and winter of nearly equal duration, the temperate zones ; and short, hot summers, followed by long, intensely cold win- ters, the frigid zones. The irregular distribution of heat over the earth is caused — 1. By the irregularities of the surface. 2. By pecu- liarities in the distribution of the land- and water-areas. 3. By the influence of the winds and ocean currents. 4. By the nature of the surface. Winds are caused by the disturbance of the equilibrium of the atmosphere by heat. The general motion of the surface winds is towards an area of greatest heat; of the upper currents, towards an area of least heat. The general atmospheric circulation is from the equator to the poles, and from the poles to the equator. In storms, the wind has a rotary motion around an area of low barometer, which, at the same time, progresses along the surface. In the northern hemisphere, the rotary motion is in an opposite direction to the hands of a clock ; in the southern hemisphere, in the same direction as the hands of a clock. Moisture may be precipitated from the air in the form of dew, mist, fog, cloud, rain, hail, sleet, or snow. In order that any form of precipitation may occur, the air must be reduced below the temperature of its dew- point. Glaciers are immense masses of ice and snow, which move with extreme slowness down the higher valleys of mountain-ranges. They resemble rivers in that they re- ceive through the drainage of their basins, the solid material which flows into them. The snow line is the distance above the sea where the snow remains throughout the year. The height of its lower level above the sea depends (1.) On the amount of the snowfall. (2.) On the temperature of the valley. (3.) On the inclination of the slope. The unit of electric potential is called a volt; the unit of current an ampere; the unit of resistance an ohm. Comparing the flow of electricity to a current of water in a pipe, the volt corresponds to the pressure causing the flow, the ohm to the resistance, or friction, opposing it, and the ampere to the quantity of flow per second. The principal electrical phenomena of the atmosphere are thunder and lightning, St. Elmo's fire, and the aurora. The principal optical phenomena are the rainbow, the mirage, halos, and coronse. The earth acts like a huge magnet. Its magnetism is probably due to the circulation around it of electrical cur- rents, generated by the sun's heat. The true basis for the distribution of vegetation is the distribution of the light, heat, and moisture, upon which its existence mainly depends. The variety and luxuriance of vegetation decrease as we pass from the equator to the poles, or from the base of a mountain to the summit. The principal food-plants of the tropical regions are rice, bananas, plantains, dates, cocoa-nuts, cassava, bread-fruit, sago, and yams. Coffee, tea, cocoa, pepper, cloves, nutmegs, and vanilla are also products of the tropics. The principal food-plants of the temperate zones are barley, rye, wheat, oats, maize or Indian corn, buckwheat, and the potato. Animals are restricted, by conditions of food and climate, to certain regions of the earth. They are dependent for their continued existence upon plants, the distribution of which therefore forms an excel lent basis for the distribution of animals. With a few exceptions, animals possess but little power of becoming acclimated, or living in a climate differing greatly from that in which they were created. The grassy meadows and prairies in North America cause the fauna of the continent to be characterized by a pre- ponderance of plant-eating mammals. Its extensive lake- and river-systems harbor a great number and variety of waterfowl. South America is characterized by the predominance of its reptiles and insects. Birds are also numerous. 162 PHYSICAL GEOGRAPHY. Asia is the home of domesticated animals. Australia is the home of the marsupials. The luxuriant vegetation of the south of Africa sustains some of the largest of the mammalia, such as the elephant, rhinoceros, hippopotamus, and giraffe. The entire human family has descended from a single pair or species. The primary races of rueii are the Caucasian, the Mongo- lian, and the Negro. The secondary races are the Malay, the American, and the Australian. The coast line of the United States is comparatively simple and unbroken. The predominant mountains are in the west ; the second- ary mountains are in the east. The great low plains of the United States are the Atlantic coast plain and the plain of the Mississippi Valley. The United States lies in the physical north temperate and the physical torrid zone. The climate of the northern half of the Atlantic coast is much colder than that of the northern half of the Pacific. The United States lies in the zone of the variable winds. The heaviest rainfall is on the Pacific coast and near the borders of the Gulf States. There are four distinct plant regions: the forest, the prairie, the steppe, and the Pacific. The Territory of Alaska occupies an area of 550,000 square miles. The Territory of Alaska is mainly mountainous. The shore lands of the Arctic are frozen moor-lands like the tundra? of Asia. The Yukon and Kuskovim are the principal rivers. Myriads of salmon visit the rivers during the breeding season. Valuable food-fish are found in the waters off the coasts. Numerous fur-bearing animals are found in Alaska. GENERAL REVIEW QUESTIONS. Mathematical Geography. What is the earth's position in the solar system ? How much larger is the sun than the earth? Of what use are latitude and longitude ? Distinguish between a map of the earth on a Mercator's projection, and maps on equatorial aud polar and conical projections. Explain the cause of the change of day and night. Explain the causes of the change of seasons. The Land. Enumerate the proofs of the present heated condition of the interior of the earth. What is the theory for the exclusive occurrence of vol- canoes near the borders of the ocean ? Why is it unnecessary to consider the interior of the earth as in a fluid condition like that of the lava ejected from volcanoes ? Name the principal regions of active volcanoes. What facts have been discovered respecting earthquake shocks ? Why should the shocks occur more frequently at night than during the day, or during winter than summer ? Into what two classes may unstratified rocks be divided ? Explain the origin of coal. Enumerate some of the changes which are now taking place in the crust of the earth. What are the relative land- and water-areas of the earth ? Describe the land hemisphere. The water hemisphere. What do you understand by lines of trend? Which of the continents contains, in proportion to its area, the greatest length of coast line ? Which the least ? Distinguish between continental and oceanic islands; between coral and volcanic islands. Why does the presence of an atoll in any part of the ocean prove the subsidence of its bed at that point? Ex- plain the nature of the coral formations off the southern coast 6f Florida. What do you understand by the forms of relief of the land? Distinguish between a mountain and a hill. A plateau and a plain. What peculiarities are noticeable in the general relief forms of the continents? Which of the continents resemble each other in the gen- eral arrangement of their relief forms ? In what respect do they all resemble one another ? The Water. Enumerate the principal uses of water in the economy of the earth. What effect has the high specific heat of water on the climate of maritime countries? What is the cause of the heat developed during the con- densation of a mass of vapor ? Distinguish between subterranean and surface drainage. Explain in general the origin of springs. Into what different classes may springs be divided ac- cording to the size of their reservoirs? According to the shape? The location? The shape of the outlet tube? Define calcareous, silicious, sulphurous, chalybeate, brine, and acidulous springs. Define river-system, basin, water-shed, source, channel, and mouth. Explain the origin of waterfalls. By what are the inundations of rivers caused? What is silt? In what different parts of a river-system may silt be deposited ? Define fluvio-marine formations. In what respects do the drainage-systems of North and South America resemble each other? In what respects do the river-systems of Africa resemble those of the Americas? Why are the waters of lakes with no outlets generally salt? Name the great fresh-water lake-systems of the world. State the composition of ocean-water. What is its density? Its boiling-point? Its color? How do the five oceans compare with one another in area? Distinguish between inland seas, border seas, and gulfs and bays, and fiords. What facts are known respecting the shape of the bed of GENERAL REVIEW AND MAP QUESTIONS 163 the Atlantic Ocean ? Of the Indian Ocean ? Explain the origin of the ooze-deposits on the ocean's beds. By what are waves caused? Upon what does their height depend? How are tides caused ? Distinguish between ebb, flood, spring, and neap tides. Where does the parent tidal wave originate? In what part of the ocean are tides the highest? Why? What are the main causes of constant oceanic currents? In what respects do the currents in the three central oceans resemble one another? The Atmosphere. What is the composition of the atmosphere ? By what instrument is the pressure of the atmosphere measured? What proof have we that the greater weight of the at- mosphere lies within a few miles of the earth's surface? Define climate. Enumerate the circumstances which influence the climate of a country. Why are the vertical rays of the sun warmer than the oblique rays? In what different ways does the atmosphere receive its heat from the sun ? Explain the origin of winds. Why should the general direction of the atmospheric circulation be between the equator and the poles? Name the different wind zones of the earth. What is the origin of laud and sea breezes? What resemblance do land and sea breezes bear to monsoons ? Describe some of the peculiarities of cyclones. What facts have been discovered in regard to the great storms of the United States ? Enumerate the circumstances upon which the rapidity of evaporation depends. State the general law for the occurrence of precipi- tations. Under what circumstances will a heavy deposition of dew occur? Name the primary forms of clouds. The secondary forms. Explain the peculiarities of the rainfall in each of the wind zones. Why is the rainfall on mountains heavier than that on plains? Define snow line. On what three circumstances does the height of the snow line depend ? Describe the formation of a glacier. Enumerate the principal electrical and optical phenom- ena of the atmosphere. What is the probable cause of the earth's magnetism ? Define volt, ohm, ampere. What analogies exist between the flow of water in a pipe and an electric current ? Organic Life. Why should the distribution of light, heat, and moisture form the best basis for the distribution of vegetation ? Define flora. Distinguish between the horizontal and the vertical distribution of vegetation. State the limits of each of the horizontal zones of vegetation. What is the characteristic feature of the flora of each of these zones? State the conditions requisite for the existence of forests ; of prairies ; of steppes ; of deserts. Enumerate the principal cultivated plants of the torrid, temperate, and polar zones. Define fauna. Upon what is the existence of animal life dependent? What is the cause of the change noticed in the fauna in passing from the equatbr to the poles, or from the base to the summit of a high tropical mountain? Enumerate the characteristic tropical fauna ; the temper- ate fauna ; the arctic fauna. What is the characteristic peculiarity of the fauna of each of the continents? Enumerate the proofs of the probable unity of the human race. Name the portions of the world inhabited by each of the primary and secondary races. Physical Features of the United States. What is the area of the United States, exclusive of Alaska ? Describe the surface structure of the United States. Describe the drainage-systems of the United States. What are the causes of the difference in the temperature of the eastern and western coasts? Between what extremes of mean annual temperature are the United States included? In what wind zone is the United States situated? Name the four principal regions of vegetation. Enumerate the chief agricultural productions of the country. What large animals are found in the United States? Name the chief mineral productions. What is the area of Alaska ? What are the principal indentations of its coast? Name the principal islands of Alaska. Describe the river-system of the Yukon. Name the principal trees of Alaska. Name its principal fur-bearing animals. Its principal food-fishes. GENERAL MAP QUESTIONS. °i*ic Volcanoes and Earthquakes. Describe the volcanic districts of the Pacific Ocean. In what portions of these districts are volcanoes most numerous ? Describe the volcanic districts of the Indian Ocean. In what direction do most of the lines of fracture in this ocean extend? Describe the volcanic districts of the Atlantic. Where are submarine eruptions most numerous in this ocean ? Describe the earthquake dfstrict of the Mediterranean Sea and Central Asia. What other portions of the world are especially liable to earthquake shocks? 164 PHYSICAL GEOGRAPHY. Name the parts of the world shaken by the great earth- quake of Lisbon, in 1755. Oceanic Areas and River-Systems. What two oceans receive the drainage of the greatest areas of the continents'' State, from a careful inspection of the direction in which the principal river-systems flow, the direction of inclina- tion of the principal slopes of the continents. Observe that in most of the continents there is a long gentle slope and a short abrupt slope; state the general direction of each of these slopes. Locate the principal systems of inland drainage in each of the continents. Name the principal lakes and rivers belonging to the larger of these systems. Describe in general the river-systems of the Atlantic, or the rivers draining into the Atlantic. Describe the river- systems of the Pacific. Of the Indian. Of the Arctic. Enumerate the five largest rivers belonging to each of these river-systems. Name the principal rivers of the world which have delta mouths. What are the land and water boundaries of each of the five oceans ? Ocean Currents. What is the general direction of the equatorial ocean currents? Explain the cause of this general direction. What exception can you find to it ? What is the general direction of the Arctic currents ? Of the Antarctic currents ? What are the causes of these general directions ? Describe the principal currents of the Atlantic ; of the Pacific; of the Indian Ocean. Locate the principal grassy seas. Explain the cause of these seas. Name the principal warm ocean currents ; the principal cold ocean currents. Name some cold currents which powerfully affect the climate of different parts of the earth ? Name some warm currents which powerfully affect the climate. In what respects do the general directions of the cur- rents in each of the central oceans resemble one another ? Name the points of resemblance between the Gulf Stream and the Japan Current. Isothermal Lines and Physical Zones. Point out the most striking deviations in the directions of the isothermal lines from the parallels of latitude. Explain in each case the main cause of these deviations. In what part of the world do the isothermal lines coin- cide most nearly with the parallels ? Trace on the map the isothermal line of 79° Fahr. Of 32° Fahr. Of 40° Fahr. In what parts of the world is the highest temperature found during the month of July ? What is the temperature of the greatest cold of Jannary ? Where is it found? What is the mean temperature of London for January ? For July ? What other large cities have nearly the same mean July or January temperature as London ? What is the mean temperature of Bombay for January? For July? What other large cities have nearly the same mean July or January temperature as Bombay? Point out the northern limit of drift ice. The southern limit. Why is it advantageous for a vessel sailing from England or America via, the Cape of Good Hope to maintain an easterly direction both going and returning? Describe the boundaries of the physical torrid, tem- perate, and frigid zones. Name the principal countries which lie wholly or in part in each of these zones. Winds, Rain, and Ocean-Routes. State the boundaries of each of the wind zones. What is the general direction of the wind in each of these zones? Name the principal monsoon regions of the world. Enumerate the principal mountain and desert winds. What is the direction of the rotation of the wind in the cyclonic storms of the northern hemisphere ? Of the south- ern hemisphere ? Name the principal storm-regions of the world. Describe the characteristic rainfall in each of the princi- pal wind zones. What would be the general route of a vessel in sailing from America to Europe, and back again ? From Europe to San Francisco? What two sailing routes are there from Europe to Aus- tralia or India ? Vegetation. Give the boundaries of each of the plant zones. State the countries or portions of countries which lie in each of these zones. Name some of the useful plants of each of these zones. Point out on the map the northern limit of trees. The southern limit. Name the portions of the world from which valuable timber is obtained. What are the principal tea- and coffee-growing countries of the world ? Where are the principal forests ? Animals. What limits are assumed as the boundaries of the tropi- cal, temperate, and arctic fauna? Name the principal tropical, temperate, and arctic fauna ? What domesticated animals are found in the tropical and temperate zones? Trace on the map the northern limit of the camel and of the reindeer ; of monkeys. The southern limit of the camel ; of monkeys ; of the polar bear, and of the elephant and rhinoceros. In what parts of the world are the whale, seal, and wal- rus found ? Describe the limits of the grizzly bear. Of the musk-ox. What are the characteristic animals of the New World ? Of the Old World? State the characteristic fauna of North America. Of South America. Of Europe, Asia, Africa, and Australia. The Races of Men. Trace on the map the northern and southern limits of permanent habitation. Name all the countries of the world inhabited by the Caucasian race. GENERAL MAP QUESTIONS, 165 In what parts of the world are the Caucasians mixed with other races ? Name the different countries of the world inhabited by the Mongolian race. Name some of the different peoples belonging to this race. What parts of the world are peopled by the Ethiopian, or Negro race ? Name some of the different tribes belonging to this race. Name the different countries of the world inhabited by the secondary races of men ? Give the names of the principal tribes of each of the secondary races. What different races of men inhabit North America? South America? Europe? Asia? Africa? Australia? 19 Physical Map of the United States. Describe from the map the forms of relief of the United States. Name the principal mountain-ranges belonging to the predominant and secondary mountain-systems. Describe the drainage-systems of the United States. What large lake-system is situated in the north-eastern part of the United States ? Trace on the map the general directions of the principal isothermal lines, showing the hottest and coldest portions of the country. Name the principal islands which lie near the coasts of the United States. Name the fluvio-marine formations of the eastern coast. Pronouncing Vocabulary. =-*«= SOUNDS OF THE LETTERS. Vowels. Fate, fir, fall, fit, a (obscure), as in organ, oval ; ah, inter- mediate between a and a, as in al-a-bah'-ma ; aa or a long ; me, m§t, e, as in berth, ravel ; pine or pine, pin, i, as in firm, evil ; no, not, 9, as in sermon, harbor ; 00, as in moon ; 55, as in good; ow, as in now; ii, as in tube; fl, as in tub; ii, the French eu, nearly like u in tub, or fur ; y and ey, at end of unaccented syllable, like e in me; ai and ay, like a in fate; au and aw, as a in fall ; eS, as i in pit ; 5w or au, as now or our. Consonants. Th as in thin ; th, as in this ; d, as th, in this ; G and K, sound of the German ch, somewhat like our h, strongly aspirated. 3 indicates a blending of the sounds of n and y ; I, a blending of 1 and y ; m and n and n°, nasal, like our ng ; R, like rr in terror ; w, like our v. Pronounce all other letters as in English. The primary or principal accent is marked thus ('); the secondary, thus (*). In determining the correct pronunciation of a word, first sound the separate syllables distinctly, repeating the process several times ; afterward pronounce the whole word smoothly and continuously, being careful to mark the accents; e.g. Nevada, ni-va'-da, nay-vah'-dah ; Apache, l-pa'-cha, ah- pah'-chay; Canada, kan'-a-da, kan'-uh-duh. A. Abyssinia, ab-is-sin'-e-a. Aconcagua, a-kon-ka'-gwa. Adelsberg, a'-dels-berg\ Adriatic, ad v -re-at'-ic. Afghanistan, af-gan v -is-tan'. Agulhas, a-gool'-yas. Alabama, al-a-bah'-ma. Alaska, al-as'-ka. Albemarle, al-be-marl'. Aleutian, a-lu'-she-an. Algiers, al-jeerz'. Alleghanies, al-le-ga'-nees. Altamaha, al-ta-ma-haw'. Amazon, am'-a-zon. Amboyna, am-boi'-nl. Amoo, a-moo'. Amoor, a-moor'. Anahuac, an-a-wack'. Anatolia, an-a-to'-le-a. Antioosti, an-te-kos'-tee. Antilles, anMeel'. Antisana, In-te-sa'-na. Appalachicola, ap^-pa-lah^-che-ko'-la. Apennines, ap'-en-ninz v . Appalachian, ap-pa-la'-che-an. Apsheron, ap-sha-ron'. Ararat, ar'-a-rat\ Archangel, ark-an'-jel. Arequipa, a-ra-kee'-pa. Arizona, ar v -i-zo'-na. Arkansas, ar-kan'-sas. Armenia, ar-mee'-ne-a. Arveiron, aiO-vI-ron\ Asia, a'-she-a, not a'-zhe-a. Atacama, a-ta-ka'-ma. Athabasca, ath'-a-bas'-ka. Auckland, awk'-land. Auvergne, o v -vairfl'. Azores, az'-ors, or az-orz'. Azov, az'-ov v , or 1-zov'. B. Babylonian, bab-e-lo'-ne-an. Bahamas, ba-ha'-ma. Baikal, bi'-kal. Baku, ba v -koo\ Balkan, bal-kan'. Balkash, bar-kash'. Baltimore, bawl'-te-moce, or bawlt'-e- mpr. Banda, ban'-da. Barbadoes, bar-ba'-dpz. Batavia, ba-ta'-ve-a. Baton Bonge, bat'-9n-roozh. Bedouins, bed'-oo-inz. Beled-el-Jerid, bel'-ed-el-jer-eed'. Beloochistan, bel-oo v -chis-tan'. Belor, or Bolor, b6-lor'. Bengal, ben-gawl\ Berlin, ber'-lin. Bermudas, ber-moo'-daz. Ber&ina, ber-nee'-ni. Bohemian, bo-hee'-me-an. Bolivia, bo-liv'-e-a. (Spanish pron., bo-lee'-ve-a.) Bombay, bom-ba'. Boothia Felix, boo'-the-a fe'-liks. Bourbon, bfir'-b9n. Brahmapootra, brah v -ma-poo'-tra. BrazOS, brah'-zos. Buenos Ayres, bo'-n9s a'-riz, or bo'- nos airz. (Spanish pron., bwa'-noce I'-rSs.) c. Cairo, ki'-ro. Calabria, ka-la'-bre-q,. Calcutta, kal-kut'-ta. Cambodia, kam-b6'-de-a. 166 fate, far, fall, fat, me, met, pine, pin, no, not, organ, b§rth, firm, serm9n, tube, tub, thin, thIs. PRONOUNCING VOCABULARY. 167 Cambridge, kame-brij'. F. J. Cameroons, cam-er-oons'. Cantabrian, kan-ta'-bre-an. Falkland, frwk'-land. Jamaica, ja-ma'-ka. Canton, kan-ton'. Fayal, fill'. Jan Mayen, yan-mi'-en. Cape Verde, verd'. Feejee, fee'-jee. Japan, ja-pan'. Caribbean, kar v -rib-bee'-an. Fezzan, feV-zan'. Java, ja'-va, or jah'-va. Carpathian, kar-pa'-the-an. Finsteraarhorn, fins'-ter-aar-horn. Jorullo, bo-rool'-yo, or ho-roo'-yo. Castile, kas-teel'. Flores, flo'-r£s. Cauca, kow'-ka. Formosa, for-mo'-sa. Caucasus, kaw'-ka-sus. Fusi Tama, fu-si-ya-ma'. K. Cayenne, ka-y3nn', or kr-Snn'. Celebes, seT-e-bes. Kaffa, kaf'-fa. Ceram, se-rani'. G. Kalahari, kal-a-ha'-re. Cevennes, sa'-venn'. Kamtchatka, kam-chat'-ka. Ceylon, see'-lon, or sil-on'. Gairdner, gard'-ner. Karakorum, ka v -ra-ko'-rum. Chagos, cha'-g6s. Gallapagos, ga-la'-pa-goce. Kenia, ke'-ni-a. Chamouni, sha v -moo-nee' (or Chamo- Ganges, gan'-gez. Kentucky, ken-tuk'-ee. nix, sha x -mo-nee'). Gardafui, gar'-da-fwee'. Kerguelen, kerg'-e-len. Champlain, sham-plane'. Garonne, ga v -ronn\ Keweenaw, ke-wee'-naw. Charleston, charlz'-ton. Gaudaloupe, gwa-da-loo'-pa. Kilauea, ke v -16'-a-a. Chelyuskin, chel-yus'-kin. Ghauts, gawts. Kilimandjaro, kir-e-man v ja-ro\ Chicago, she-kaw'-go. Gila, heel'-a. Kinghan, kin-gan'. Chili, chil'-lee. Gilolo, je-lo'-lo. Kiolen, ky-6'-len, or cho'-len. Colima, ko-lee'-ma. Greenwich, grin'-idge. Kodiak, ko'-de-ak. Colorado, kol-o-rah'-do. Grenada, gren-a'-da. Kong, k6ng. Como, ko'-mo. Grenelle, greh'-nfill'. Kosciusko, kos-se-us'-ko. Comorin, com'-o-rin. Guadeloupe, gaw v -da-loop', or ga-deh- Kuen-lun, kwSnMoon'. Comoro, kom'-o-ro. loop'. Kunchinj unga, koon -chin-j ung'-gl. Congo, kong'-go. Guadiana, gwa-de-a'-na. Kuvile, koo'-ril. Constance, kon-stants'. Guardafui, gwar-da-fwee'. Cosiguina, ko-se-ghee'-na. Guiana, ghe-a'-ni. Guinea, ghin'-nee. L. Laocadive, lak'-ka-dlv\ D. H. Ladoga, la'-do-ga. Ladrones, lad-r6nz\ Dakota, da-ko'-ta. Halle, bal'-leta. Lapland, lap'-land. Danube, dan'-Qbe. Hartz, haRts. La Puebla, 11 pweV-ll. Deocan, dfik'-kan. Havana, ha-van'-a. Lauterbrunnen, 16w'-ter-brS5n x -nen. Demavend, deW-a-vSnd'. Hawaii, ha-wi'-ee. Lima, lee'-ma. Detroit, de-troit'. Hayti, ba'-tee. Limpopo, lim-po'-p6. Dhawalaghire, da-w&T-a-gheV-ree. Hecla, hek'-li. Llanos, l'ya'-n&s. Dinario, de-nar'-ic. Himalaya, him-a-la'-ya, or him-a'-la- Llullayacu, l'yoo-ryi-l'ya'-k6. Dnieper, nee'-pr. y§» Loffoden, lof-fo'-den. Dniester, nees'-tgr. Hindoo-Koosh, hin'-d5d'-koosh. Loire, lwar. Dra, dra. Hindostan, hinMo-stan'. Lombardy, lom'-bar-de. Duna, dii'-na. Hoang-Ho, ho-ang v -ho', nearly wbang x - Loo Choo, loo^-chew'. Dwina, dwi'-na, or hwee'-ni. ho'. Louisiana, loo-ee-ze-ah'-na. Hoogly, hoog'-lee. Louisville, loo'-is-vil, or loo'-e-vil. Humber, hum'-ber. Lowell, lo'-el. Hungarian, hung-ga'-re-an. Lupata, lu-pa'-ta. E. Ecuador, 8k-wa-dor'. I. M. Edgecumbe, ej'-kum. Edinburgh, Sd'-in-bur-ruh. Iberian, i-bee'-re-an. Hacao, ma-k5w', or ma-ka-o. Elbe, 51b. (Ger. pron., eT-beh.) Ilaman, or Illimani, eer-ya-ma'-ne. Mackenzie, mak-ken'-zee. Elbruz, eT-brooz'. Illinois, ir-lin-oi'. Madagascar, mad^-a-gas'-kar. Elton, eT-ton'. Indiana, in v -de-an'-a, or in-de-ah'-na. Madeira, ma-dee'-ra, or ma-da' -ra. Euphrates, u-fri'-tez. Indianapolis, in-de-an-ap'-o-lis. Madrid, mi-drid'. (Spanish pron., ma- Everest, eV-fir-4st. Iowa, i'-o-wa. dreed'.) Eyre, air. Irrawaddy, ir s -ra-wad'-de. Magdalena, mag-da-lee'-na. fate, far, fall, fat, me, m St, pine, pin, n&, not, organ, berth, firm, sern ion, tube, tub, thin, this. 168 PRONOUNCING VOCABULARY. Maggiore, mad-jo'-ra. P. San Joaquin, san Ho-a-keen', almost Malacca, ma-lak'-ka. wah-keen'. Malay, ma-la'. Pamir, pa-meer'. Santa Barbara, san'-ta baR-ba-ra. Maldive, inal'-div. Pamlico, pam'-lee-ko. Santa Cruz, san'-ta kroos. Manitoba, man-e-to'-ba. « Pampas, pain'-pas. Santorini, san-to-ree'-nee. Mantchooria, inan-choo'-re-a. Panama, pan-a-ma'. Sarmiento, saR-me-en'-to. Maracaybo, ma-ra-ki'-bo. Papua, pap'-oo-a, or pa^-poo'-a. Saskatchewan, sas-katch'-e-w&n. Marietta, ma-re-et'-ta. Paraguay, pa-ra-gwa', or pa-ra-gwi'. Scandinavian, skan-de-na'-ve-an. Marquesas, maR-ka'-sas.) Paramaribo, par^-a-mar'-e-bo. Seine, san, or s3n. Marseilles, mar-salz'. Pasco, pas'-ko. Senegal, sen v -e-gawl\ Mauna Loa, mow'-na lo'-a. Patagonian, pa-ta-go'-ne-an. Shasta, shas'-ta. Mauritius, maw-rish'-e-us. Paumotu, pow-m6-too'. Siam, si-am', or se-am\ Mediterranean, m3d v -e-ter-ra'-ne-an. Peling, pa* -ling'. Sicily, sis'-il-e. Melbourne, meT-burn. Persian, per'-she-an. Sierra Estrella, se-eR'-Ra gs-trel'-ya. Mesopotamia, meV-o-po-ta'-me-a. Petchora, petch'-o-ra. Sierra Leone, se-er'-ra le-o'-nee. Michigan, mish'-e-gan, formerly mish- Philippine, fil'-ip-pin. Sierra Madre, se-en'-Ra ma'-nra. e-gan'. Platte, platt. Sierra Nevada, se-er'-ra na-va'-Da. Mississippi, mis v -sis-sip'-pee. Polynesia, por-e-nee'-she-a. Singapore, sing v -ga-pore\ Missouri, mis-soo'-ree. Pompeii, pom-pa'-yee. Sir, or Sihon, sir, or seer, see^-hon'. Mobile, mo-beel'. Pontchartrain, pont-char-tran'. Sitka, sit'-ka. Moluccas, mo-lfik'-kaz. Popocatepetl, po-po-ka-ta-petl'. Spitzbergen, spits-berg'-en. Monte Rosa, mon v -ta-r6s'-sl. Prussia, priish'-ya, or proo'-she-a. Steppes, steps. Mont Blanc, mon8-bl6nB\ Pyrenees, plr'-en-eez. St. Louis, sent loo'-is, or sent loo'-ee. Moosehead, inoos x -hed\ St. Petersburg, sent pee'-terz-burg. Moscow, mos'-ko. St. Roque, sent rok\ Q. St. Thomas, sent tom'-as. Stromboli, strom'-bo-le. N. Quebec, kwe-beV. Quito, kee'-to. Sumatra, soo-ma'-tra. Sumbawa, soom-baw'-wa. Nanling, nan v -ling\ Suez, soo'-fiz. Natchez, natch'-iz. Suliman, or Suleiman, soo-la-man'. Netherlands, neTH'-er-landz. R. Syracuse, slr'ra-kiiz. Neusalzwerk, noi'-salts-verk. Syria, slr'-e-a,. Nevada de Sorata, ne-vah'-da da so- rl'-ta. Radack, ra'-dak. Ralick, ra'-lik. T. Newfoundland, nu' -fond-land'. Ngami, n'ga'-mee. Reading, red'-ing. Rhine, rin. Tahitian, ta-hee'-tee-an. Niagara, ni-ag'-a-rah, originally ne- a-ga'-ra. Rhone, ron. Tanganyika, tan-gan-ye'-ka. Riobamba, re-o-bam'-ba. Tarim, ta'-rem. Nicaragua, nik-ar-a'-gwa. Rio de la Plata, ree'-o da la pla'-ta. Rio Grande, ree'-o gran'-da. Tasmania, taz-ma-ne-a. Niemen, nee'-men. Taurus, taw'-rus. Nieuveldt, nyuw'-velt. Rio Janeiro, ri'o ja-nee'-ro. Tchad, chid. Niger, ni'-ger. Norfolk, nor'-fok. Nova Scotia, no'-va sko'-she-a. Nova Zembla, no'-va zem'-bla. Nubia, nu'-be-a. Roanoke, ro v -an-ok\ Teneriffe, t5n v -er-iff'. Rodriguez, ro x -dreeg\ Russia, rush'-i-a, or roo'-she-a. Thames, temz. Thian-Shan, tee v -an'-shan. Russian America, roo'-shan a-mer'- Thibet, tib'-et, or tib-et'. e-ka. Timor, te-mor'. N'yassa, or Nyassi, ne-as'-see. Titicaca, te-te-ka'-ka. Tocantins, to-kan-teens'. s. Toledo, to-lee'-do. (Spanish pron., to- o. la'-Do.) Sabine, sa-been'. Tongan, tong'-gan. Obe, o'-bee. Saghalien, sa-ga-lee'-an, or sa-ga- Torrens, tor'-rens. Okefinokee, o v -ke-fin-o'-kee. leen'. Torres, toR'-Res. Okhotsk, o-Kotsk'. (Russian pron., Sahara, sa-ha'-ra, or sa'-ha-ra. Transylvanian, tran-sil-va'-ne-an. o-Hotsk'.) Saint Helena, sant hel-ee'-na. Trieste, tre-est'. Onega, o-na'-ga. Salina, sa-li'-na. Trinidad, trin v -e-dad\ Onimak, oo-ne-mak'. Salzburg, s<s'-bfirg. Tristan d' Acunha,tris'-tan da-kun'-ya. Ontario, on-ta'-re-o. Samoan, sam-o'-an. Tundras, toon'-dra. Oregon, or'-e-gon. Sandwich, sand'-wich, or sand'-wij. Tunis, tu'-niss, or too'-niss. Orinoco, or-e-no'-ko. San Francisco, san fran-sis'-ko. Turkestan, tooR v -kis-tan'. fate, far, fall, fat, me, m 5t, pine, pin, nd, not, organ, berth, firm, sern ion, tube, tub, thin, THis. PRONOUNCING VOCABULARY. 169 u. w. Yaktusk, ya v -kootsh'. Yang-tse-Kiang, yang x -tse-ke-ang\ Urumiyah, oo-roo-mee' -ya. Wabash, waw'-bash. Wasatch, wa v -saoh. Wener, wa'-ner. Yeddo, y8d'-do. Yellowstone, yel'-lo v -stone. Yenisei, yfin v -e-sa'-e, or yeV-e-say'. Weser, we v -zer. (Ger. pron., wa'-zer.) Yosemite, yo-sem'-e-te. V. West Indies, west in'-deez. Yucatan, yoo-ka-tln'. Wetter, wSt'-ter. Yukon, yu'-kon. Valdai, val'-dl. Winnebago, win v -ne-ba' -go. Vancouvers, van-koo'-vers. Winnipeg, win'-e-peg. Venezuela, v5n v -8z-wee '-la. Wisconsin, wis-kon'-sin Vesuvius, ve-su'-vi-us. Worcester, woos'-ter. z. Vichy, vee^-shee'. Vienna, vS-en'-na. Zagros, za'-gros\ Vindhya, vlnd'-ya. y. Zambezi, zam-ba'-zee. Volga, vol'-ga. Zealand,ze'-land. Vosges, vozh. Yabloni, ya-blo-noi'. Zurrah, zur'-ra. =^= BRIEF ETYMOLOGICAL VOCABULARY. Amazon, " Boat destroyer." Arabia, " The land of the sunset." Brahmapootra, " The son of Brahma." Cameroons, "A shrimp." Deccan, " The south." Ecuador, " The equator." Elton, "Golden lake." Formosa, " Beautiful " (island). Gallapagos, " Islands of the tortoises." Ganges, " Heavenward flowing." Himalaya, " The abode of snow." Hindostan, "The country of the Hindoos," or "Negro- land." Hoang-Ho, " Yellow river." Holland, " Muddy or marshy land." Irrawaddy, " The great river." Java, " Bice." Labrador, " Cultivable." Ladrones, " Islands of the thieves." Lauterbriinnen, " Nothing but springs." Maldives, " Thousand islands." Mantchooria, " Country of the Mantchoos." Mer de glace, " Sea of ice." Mesopotamia, " Between the rivers." Mississippi, " The great water." Missouri, " Muddy water." Netherlands, " The low countries." Niphon, " Fountain or source of light." Nova Scotia, " New Scotland." Nyassa, "The sea." Orinoco, " The coiled serpent." Papua, " Frizzled hair." Patagonians, " Men with large feet." Polynesia, " Many islands." Popocatepetl, " Smoking mountain." Saskatchewan, " Swift current." Sierra Nevada, " Snow-clad mountain." Singapore, " City of the lion." Staubbach, " Dust or mist brook." Thian-Shan, " The celestial mountain." W ! nnipiseogee, "The smile of the great Spirit." Yang-tse-Kiang, " Son of the great water." Statistical Tables. ►o^c Hydrographie Table of the Rivers of the World (from A. K. Johnston). Name of River. Rhine Vistula . . • < Elbe Oder Niemen . . . . Seine Nile Danube . . . . Dnieper . . . . Obi Yenisei . . . . Lena Volga Sir or Sihon . . Amoor Yang-tse-Kiang Hoang-Ho . . . Ganges Indus Euphrates . . . Irrawaddy . . . Area of basin in geographical square miles. 65,280 56,640 41,860 39,040 32,180 22,620 520,200 (?) 234,080 169,680 924,800 784,530 594,400 397,460 237,920 (?) 582,880 547,800 537,400 432,480 312,000 (?) 195,680 331,200 Length of stream includ- ing windings. NEW WORLD. St. Lawrence and Great Lakes Delaware Orinoco Amazon Tocantins San Francisco La Plata Mississippi Rio del Norte Mackenzie . Saskatchewan Columbia Colorado 297,600 1,800 8,700 265 252,000 1,352 (?) 1,512,000 3,080 284,480 1,120 187,200 1,400 886,400 1,920 982,400 3,560 180,000 1,840 (?) 441,600 2,120 360,000 1,664 194,400 1,360 170,000 800 (?) 600 520 684 480 460 340 2,240 (?) 1,496 1,080 2,320 2,800 2,400 2,400 1,208 (?) 2,380 2,880 2,280 1,680 1,960 1,492 2,200 Areas of the Principal Lakes of the Earth. (In English square miles.) America. Area sq. m. Superior 28,600 Michigan 26,000 Huron 20,400 Great Slave 12,800 Erie 9,600 Winnipeg 9,600 Georgian Bay .... 8,000 Great Bear 8,000 Ontario 6,300 Maracaibo 4,900 Titicaca 4,200 Athabasca 3,000 Nicaragua 2,800 Great Salt 2,200 Green Bay 2,000 Champlain 480 Pontchartrain . . . . 440 Pyramid 360 Moosehead 240 Winnebago 212 Europe. Ladoga 6,330 Onega 3,280 Wener 2,136 Wetter 839 Malar 763 Area, sq. m. Geneva 326 Constance 290 Maggiore 152 Asia. Caspian Sea .... 160,000 Aral Sea 88,000 Baikal 13,000 Balkash 8,600 Zurrah(Afghanistan) 4,000 Wan 2,200 Urumiyah 1,800 Lop 560 Dead Sea 400 Tiberias 200 Africa. Victoria Nyanza . . 28,000 Albert Nyanza . . . 26,000 Tchad 15,000 Tanganyika .... 13,000 Nyassa 5,000 Australia. Eyre 3,000 Torrens 2,600 Gairdner 2,400 Population of the Earth. (From Bradley's Atlas.) America 100,415,400 Europe 327,743,414 Asia 795,591,000 Africa 205,823,260 Pacific Islands _. 4, 232,000 Total 1,433,805,074 170 STATISTICAL TABLES, 171 Tables showing the Area and Product of some of the Cereals, etc., in the United States. (From the Census Reports of 1880.) INDIAN COEN. Acres. Bushels. 9,011,602 327,796,895 6,616,364 276,093,295 5,588,357 203,464,620 3,679,247 117,121,915 Stale. Illinois Iowa Missouri .... Indiana .... Ohio 3,297,342 112,681,046 Kansas 3,417,700 106,791,482 Kentucky 3,021,350 ..... 73,977,829 Nebraska 1,631,840 65,785,572 Tennessee 2,905,038 62,833,017 Pennsylvania. . . . 1,374,241 47,970,987 WHEAT. Illinois 3,218,963 Indiana 2,619,307 Ohio 2,556,134 Michigan 1,822,752 Minnesota 3,046,821 Iowa 3,049,347 California 1,837,322 Missouri 2,074,314 Wisconsin 1,948,036 Pennsylvania . . . 51,136,455 . . . 47,288,989 . . . 46,014,869 . . . 35,537,097 . . . 34,625,657 . . . 31,177,225 . . . 28.787,132 . . . 24,971,727 . . . 24,884.689 1,445,384 19,462,405 OATS. Illinois 1,959,853 Iowa 1,507,490 New York 1,261,171 Pennsylvania .... 1,237,593 Wisconsin 955,276 Ohio 910,388 Minnesota 617,427 Missouri 968,473 Michigan 536,167 Indiana 623,600 California New York Wisconsin Iowa . . . Minnesota Nebraska . Ohio . . . Illinois . . Michigan . Oregon . . Pennsylvania Illinois . . . New York . Wisconsin . Iowa .... New Jersey . Kentucky . Missouri . . Nebraska . . Kansas . . . New York . . Pennsylvania . New Jersey . . Michigan . . . Maine . . . . Vermont . . . Wisconsin . . West Virginia Ohio Illinois . . . . BAELEY. 586,045 . 356,556 . 204,323 . 198,885 . 116,024 . 115,288 . 57,485 . 55,278 . 54,509 . 29,311 . EYE. 398,465 . 192,138 . 244,894 . 169,693 . 102,580 . 106,029 . 89,579 . 46,488 . 34.372 . 34,628 . BUCKWHEAT. 291,228 . 246,199 . 35.373 . 33,955 . 20,135 . 17,630 . 34,119 . 30,334 . 22,130 . 16,464 . 63,206,250 50,612,141 37,575,506 33,847,439 32,911,246 28,664,505 23,372,752 20,673,458 18,190,493 15,606,721 12,578,486 7,788,749 5,043,202 4,021,473 2,973,061 1,744,711 1,707,164 1,229,693 1,204,523 920,977 3,683,621 3,121,682 2,634,390 2,298,544 1,518,307 949,104 676,245 535,458 424,693 413,181 4,461,200 3,593,328 466.414 413,180 382,701 356,618 299,150 285,298 280,229 178,964 Slate. Kentucky . . Virginia, . . . Pennsylvania . Ohio Tennessee . . North Carolina Maryland . . Connecticut . Missouri . . . Wisconsin . . TOBACCO. Acres. Pounds. 226,127 171,121,134 139,423 80,099,838 27,567 36,957,772 34,679 34,725,405 41,532 29,365,052 57,215 26,986,448 38,174 26,082,147 8,666 ..... 14,044,652 15,500 11,994,077 8,811 10,878,463 Population of the United States. (From the Census of 1890.) North Atlantic States 17,401,545 Maine 661,086 New Hampshire 376,530 Vermont 332,422 Massachusetts 2,238,943 Ehode Island 345,506 Connecticut 746,258 New York 5,997,853 New Jersey 1,444,933 Pennsylvania 5,258,014 South Atlantic States 8,857,920 Delaware 168,493 Maryland 1,042,390 District of Columbia 230,392 Virginia 1,655,980 West Virginia 762,794 North Carolina 1,617,947 South Carolina . ., 1,151,149 Georgia 1,837,353 Florida 391,422 North Central States 22,362,279 Ohio 3,672,316 Indiana ! 2,192,404 Illinois 3,826,351 Michigan 2,093,889 Wisconsin 1,686,880 Minnesota 1,301,826 Iowa 1,911,896 Missouri 2,679,184 North Dakota 182,719 South Dakota 328,808 Nebraska 1,058,910 Kansas 1,427,096 South Central States 10,972,893 Kentucky 1,858,635 Tennessee 1,767,518 Alabama 1,513,017 Mississippi 1,289,600 Lf .isiana 1,118,587 Texas 2,235,523 Indian Territory Oklahoma . . . . 61,834 Arkansas 1,128,179 Western States 3,027,613 Montana 132,159 Wvoming 60,705 Colorado 412,198 New Mexico 153,593 Arizona 59,620 Utah 207,905 Nevada 45,761 Idaho 84,385 Al'Lskji • ••••••• — Washington ........ 349,390 Oregon 313,767 California 1,208,130 Total population of the United States .... 62,622,250 172 STATISTICAL TABLES. Cities of the United States having a Pop- ulation over 30,000, in order of Pop- ulation. (From the Census of 1890.) NO. CITIES. POPULATION. 1. New York City, N. Y 1,513,501 2. Chicago, 111 1,098,576 3. Philadelphia, Pa 1,044,894 4. Brooklyn, N. Y 804,377 5. St. Louis, Mo 460,357 6. Boston, Mass 446,507 7. Baltimore, Md 434,151 8. San Francisco, Cal 297,990 9. Cincinnati, 296,309 10. Cleveland, 261,546 11. Buffalo, N. Y 254,457 12. New Orleans, La 241,995 13. Pittsburgh, Pa 238,473 14. Washington, D. C • . . . 229,796 15. Detroit, Mich 205,669 16. Milwaukee, Wis 204,150 17. Newark, N. J 181,518 18. Minneapolis, Minn 164,738 19. Jersey City, N. J 163.987 20. Louisville, Ky 161,005 21. Omaha, Neb 139,526 22. Rochester, N.Y 138,327 23. St. Paul, Minn 133,156 24. Kansas City, Mo 132,416 25. Providence, E. 1 132,043 26. Indianapolis, Ind 107,445 27. Denver, Cal » . . . . 106,670 NO. CITIES. POPULATION. 28. Allegheny City, Pa. 104,967 29. Albany, N. Y 94,640 30. Columbus, 90,398 31. 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